JP2023166827A - Lens portion, laminate, display body, method for manufacturing display body, and display method - Google Patents

Abstract

To provide a lens portion capable of achieving weight reduction and high definition of a VR goggle.SOLUTION: A lens portion is used for a display system that displays an image to a user. The lens portion comprises: a reflection portion that reflects light, which is emitted forward from a display surface of a display element representing the image and passes through a polarization member and a first λ/4 member, and that includes a reflection type polarization member and an absorption type polarization member disposed in front of the reflection type polarization member; a first lens portion disposed on an optical path between the display element and the reflection portion; a half mirror that is disposed between the display element and the first lens portion, transmits the light emitted from the display element, and reflects the light reflected by the reflection portion toward the reflection portion; and a second λ/4 member disposed on an optical path between the half mirror and the reflection portion. A thickness of an absorption type polarizing film constituting the absorption type polarization member is 8 μm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lens part, a laminate, a display body, a method for manufacturing a display body, and a display method.

Image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (eg, organic EL display devices) are rapidly becoming popular. In image display devices, optical members such as polarizing members and retardation members are generally used to realize image display and improve image display performance (see, for example, Patent Document 1).

In recent years, new uses for image display devices have been developed. For example, goggles with a display (VR goggles) for realizing Virtual Reality (VR) have begun to be commercialized. Since VR goggles are being considered for use in a variety of situations, it is desired that they be lighter and have higher definition. Weight reduction can be achieved, for example, by making the lenses used in VR goggles thinner. On the other hand, there is also a desire for the development of optical members suitable for display systems using thin lenses.

JP2021-103286A

In view of the above, the main object of the present invention is to provide a lens section that can realize weight reduction and high definition of VR goggles.

1. The lens unit according to the embodiment of the present invention is a lens unit used in a display system that displays an image to a user, and is a lens unit that emits light forward from a display surface of a display element that represents an image, and includes a polarizing member and a first a reflective part that reflects the light that has passed through the λ/4 member and includes a reflective polarizing member and an absorbing polarizing member disposed in front of the reflective polarizing member; and a reflective part between the display element and the reflective part. A first lens section disposed on the optical path is disposed between the display element and the first lens section, and transmits the light emitted from the display element and transmits the light reflected by the reflection section. An absorptive polarizing member comprising a half mirror that reflects the light toward a reflecting section, and a second λ/4 member disposed on an optical path between the half mirror and the reflecting section, and constituting the absorptive polarizing member. The thickness of the polarizing film is 8 μm or less.
2. In the lens portion described in 1 above, the reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member may be arranged parallel to each other.
3. In the lens section described in 1 or 2 above, the first lens section and the half mirror may be integrated.
4. In the lens section according to any one of 1 to 3 above, the lens section may include a second lens section disposed in front of the reflecting section.
5. In the lens portion according to any one of 1 to 4 above, the angle between the absorption axis of the polarizing member included in the display element and the slow axis of the first λ/4 member is 40° to 50°. The angle between the absorption axis of the polarizing member included in the display element and the slow axis of the second λ/4 member may be 40° to 50°.
6. In the lens portion according to any one of 1 to 5 above, the ratio of the thickness of the absorptive polarizing film to the thickness of the reflective polarizing member may be 15% or less.

7. The laminate according to the embodiment of the present invention is used in the reflective section of the lens section described in any one of 1 to 6 above, and includes the reflective polarizing member and the absorptive polarizing member.
8. In the laminate described in 7 above, the reflective polarizing member and the absorptive polarizing member may be laminated with an adhesive layer interposed therebetween.

9. A display body according to an embodiment of the present invention has the lens portion described in any one of 1 to 6 above.
10. The present invention provides a method for manufacturing a display body according to an embodiment of the present invention, and a method for manufacturing a display body having a lens portion according to any one of items 1 to 6 above.

11. A display method according to an embodiment of the present invention includes a step of causing light representing an image emitted through a polarizing member and a first λ/4 member to pass through a half mirror and a first lens portion; a step of causing the light that has passed through the first lens section to pass through a second λ/4 member; and a step of directing the light that has passed through the second λ/4 member to the half mirror using a reflecting section that includes a reflective polarizing member. a step of allowing the light reflected by the reflecting section and the half mirror to pass through the reflective polarizing member of the reflecting section by the second λ/4 member; and transmitting the light transmitted through the polarizing member through an absorbing polarizing member, and the thickness of the absorbing polarizing film constituting the absorbing polarizing member is 8 μm or less.

12. A method for manufacturing an absorption polarizing film for a lens portion according to an embodiment of the present invention includes forming a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of a long thermoplastic resin base material. A laminate is formed, and the laminate is subjected to an auxiliary stretching treatment in the air, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in which the laminate is contracted by 2% or more in the width direction by heating while conveying in the longitudinal direction. , in this order.
13. In the manufacturing method described in 12 above, the content of the halide in the polyvinyl alcohol resin layer is 5 parts by weight to 20 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin.
14. In the manufacturing method described in 12 or 13 above, the stretching ratio in the aerial auxiliary stretching treatment is 2.0 times or more.
15. In the manufacturing method according to any one of 12 to 14 above, the drying shrinkage treatment step is a step of heating using a heating roll.
16. In the manufacturing method described in 15 above, the temperature of the heating roll is 60° C. to 120° C., and the shrinkage rate of the laminate in the width direction by the drying shrinkage treatment is 2% or more.

According to the lens portion according to the embodiment of the present invention, it is possible to realize lightweight VR goggles and high definition.

1 is a schematic diagram showing a general configuration of a display system according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a laminate used in a reflective section of the display system shown in FIG. 1. FIG. FIG. 2 is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film. FIG. 2 is a schematic diagram showing an example of dry shrinkage treatment using a heating roll. This is an observation photograph showing optical unevenness.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, in order to make the explanation more clear, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the embodiment, but this is just an example, and the interpretation of the present invention is It is not limited.

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the direction perpendicular to the slow axis in the plane (i.e., fast axis direction) "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is an in-plane retardation measured with light having a wavelength of λnm at 23°C. For example, "Re(550)" is an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is determined by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in thickness direction (Rth)
"Rth (λ)" is a retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth (550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is determined by Nz=Rth/Re.
(5) Angle When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°.

FIG. 1 is a schematic diagram showing the general configuration of a display system according to one embodiment of the present invention. FIG. 1 schematically shows the arrangement, shape, etc. of each component of the display system 2. As shown in FIG. The display system 2 includes a display element 12, a reflection section 14, a first lens section 16, a half mirror 18, a first retardation member 20, a second retardation member 22, and a second lens section 24. We are prepared. The reflecting section 14 is arranged at the front of the display element 12 on the display surface 12a side, and can reflect the light emitted from the display element 12. The first lens section 16 is arranged on the optical path between the display element 12 and the reflection section 14, and the half mirror 18 is arranged between the display element 12 and the first lens section 16. The first retardation member 20 is arranged on the optical path between the display element 12 and the half mirror 18, and the second retardation member 22 is arranged on the optical path between the half mirror 18 and the reflection section 14.

The components disposed in front of the half mirror (in the illustrated example, the half mirror 18, the first lens section 16, the second retardation member 22, the reflection section 14, and the second lens section 24) are collectively called a lens section (lens section). 4).

The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12a for displaying images. The light emitted from the display surface 12a passes through a polarizing member (typically, a polarizing film) that may be included in the display element 12, and is emitted as first linearly polarized light.

The first retardation member 20 is a λ/4 member that can convert the first linearly polarized light incident on the first retardation member 20 into first circularly polarized light (hereinafter, the first retardation member is referred to as the first (sometimes referred to as a λ/4 member). Note that the first retardation member 20 may be provided integrally with the display element 12.

The half mirror 18 transmits the light emitted from the display element 12 and reflects the light reflected by the reflection section 14 toward the reflection section 14 . The half mirror 18 is provided integrally with the first lens section 16.

The second retardation member 22 is a λ/4 member that can transmit the light reflected by the reflection part 14 and the half mirror 18 through the reflection part 14 including a reflective polarizing member (hereinafter referred to as the second retardation member). (sometimes referred to as the second λ/4 member). Note that the second retardation member 22 may be provided integrally with the first lens portion 16 or may be provided integrally with the reflective polarizing member included in the reflecting portion 14.

The first circularly polarized light emitted from the first λ/4 member 20 passes through the half mirror 18 and the first lens section 16, and is converted into second linearly polarized light by the second λ/4 member 22. . The second linearly polarized light emitted from the second λ/4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member included in the reflecting section 14 . At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member included in the reflecting section 14 is the same direction as the reflection axis of the reflective polarizing member. Therefore, the second linearly polarized light incident on the reflection section is reflected by the reflective polarizing member.

The second linearly polarized light reflected by the reflection section 14 is converted into second circularly polarized light by the second λ/4 member 22, and the second circularly polarized light emitted from the second λ/4 member 22 is converted into second circularly polarized light by the second λ/4 member 22. The light passes through one lens section 16 and is reflected by a half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens section 16 and is converted into third linearly polarized light by the second λ/4 member 22. The third linearly polarized light passes through the reflective polarizing member included in the reflecting section 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing member included in the reflecting section 14 is the same direction as the transmission axis of the reflective polarizing member. Therefore, the third linearly polarized light that has entered the reflecting section 14 is transmitted through the reflective polarizing member.

The light that has passed through the reflection section 14 passes through the second lens section 24 and enters the user's eyes 26 .

For example, the absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member included in the reflecting section 14 may be arranged substantially parallel to each other, or may be arranged substantially perpendicular to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the first retardation member 20 is, for example, 40° to 50°, may be 42° to 48°, and is about 45°. It may be °. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second retardation member 22 is, for example, 40° to 50°, may be 42° to 48°, and is about 45°. It may be °.

The in-plane retardation Re (550) of the first retardation member 20 is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. .

The first retardation member 20 preferably exhibits inverse dispersion wavelength characteristics in which the retardation value increases depending on the wavelength of the measurement light. Re(450)/Re(550) of the first retardation member 20 is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

The in-plane retardation Re (550) of the second retardation member 22 is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. .

The second retardation member 22 preferably exhibits inverse dispersion wavelength characteristics in which the retardation value increases depending on the wavelength of the measurement light. Re(450)/Re(550) of the second retardation member 22 is, for example, 0.75 or more and less than 1, and may be 0.8 or more and 0.95 or less.

Each retardation member is formed of any suitable material. For example, it may be a resin film (typically a stretched film) or may be formed from a liquid crystal compound. When the retardation member is a resin film, its thickness is, for example, 10 μm to 100 μm.

The resins contained in the above resin film include polycarbonate resin, polyester carbonate resin, polyester resin, polyvinyl acetal resin, polyarylate resin, cyclic olefin resin, cellulose resin, polyvinyl alcohol resin, and polyamide resin. , polyimide resin, polyether resin, polystyrene resin, acrylic resin, and the like. These resins may be used alone or in combination (for example, blended or copolymerized). For example, a resin film containing a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be suitably used. By using such a resin, for example, the above-mentioned inverse dispersion wavelength characteristic can be exhibited.

Any suitable polycarbonate resin can be used as the polycarbonate resin. For example, polycarbonate resins contain structural units derived from fluorene-based dihydroxy compounds, structural units derived from isosorbide-based dihydroxy compounds, alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene-based dihydroxy compounds. a structural unit derived from at least one dihydroxy compound selected from the group consisting of glycol or spiroglycol. Preferably, the polycarbonate resin contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from an alicyclic dimethanol, and/or a di, tri, or polyethylene glycol. More preferably, it contains a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, and a structural unit derived from di, tri or polyethylene glycol. . The polycarbonate resin may contain structural units derived from other dihydroxy compounds as necessary. In addition, details of the polycarbonate resin that can be suitably used for the retardation member and the method for forming the retardation member can be found, for example, in JP-A No. 2014-10291, JP-A No. 2014-26266, and JP-A No. 2015-212816. , JP 2015-212817A and JP 2015-212818A, and the descriptions of these publications are incorporated herein by reference.

An absorptive polarizing member may be provided in front of the reflective polarizing member. Typically, an absorptive polarizing member can be provided between the reflective polarizing member and the second lens portion 24. The reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member may be arranged substantially parallel to each other, and the transmission axis of the reflective polarizing member and the transmission axis of the absorptive polarizing member may be arranged substantially parallel to each other. The absorbing polarizing member may be included in the reflecting section 14. When the reflecting section 14 includes an absorption type polarizing member, the reflecting section 14 may include a laminate having a reflective polarizing member and an absorbing polarizing member.

FIG. 2 is a schematic cross-sectional view showing an example of a laminate used in the reflective section of the display system shown in FIG. The laminate 30 includes a reflective polarizing member 32 and an absorbing polarizing member 34, and the reflective polarizing member 32 and the absorbing polarizing member 34 are laminated with an adhesive layer 36 in between. By using the adhesive layer, the reflective polarizing member 32 and the absorbing polarizing member 34 are fixed, and it is possible to prevent misalignment of the axis arrangement between the reflective axis and the absorption axis (the transmission axis and the transmission axis). Further, it is possible to suppress the adverse effects of an air layer that may be formed between the reflective polarizing member 32 and the absorbing polarizing member 34. The adhesive layer 36 may be formed of an adhesive or a pressure-sensitive adhesive. The thickness of the adhesive layer 36 is, for example, 0.05 μm to 30 μm, preferably 3 μm to 20 μm, and more preferably 5 μm to 15 μm. Although not shown, the second retardation member 22 may be provided integrally with the reflective polarizing member 32, so the laminate 30 may include the second retardation member 22. In this case, the second retardation member 22 may be laminated on the reflective polarizing member 32 via an adhesive layer.

The reflective polarizing member can transmit polarized light parallel to its transmission axis (typically, linearly polarized light) while maintaining its polarized state, and can reflect light in other polarized states. The reflective polarizing member is typically composed of a film having a multilayer structure (sometimes referred to as a reflective polarizing film). In this case, the thickness of the reflective polarizing member is, for example, 10 μm to 150 μm, preferably 20 μm to 100 μm, and more preferably 30 μm to 60 μm.

FIG. 3 is a schematic perspective view showing an example of a multilayer structure included in a reflective polarizing film. The multilayer structure 32a has layers A having birefringence and layers B having substantially no birefringence alternating. The total number of layers making up the multilayer structure may be between 50 and 1000. For example, the refractive index nx in the x-axis direction of the A layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of the B layer are substantially the same, The refractive index difference between layer A and layer B is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction can become the reflection axis, and the y-axis direction can become the transmission axis. The refractive index difference between layer A and layer B in the x-axis direction is preferably 0.2 to 0.3.

The layer A is typically made of a material that exhibits birefringence when stretched. Such materials include, for example, naphthalene dicarboxylic acid polyesters (eg, polyethylene naphthalate), polycarbonates, and acrylic resins (eg, polymethyl methacrylate). The B layer is typically made of a material that does not substantially exhibit birefringence even when stretched. Examples of such materials include copolyesters of naphthalene dicarboxylic acid and terephthalic acid. The multilayer structure may be formed by a combination of coextrusion and stretching. For example, after extruding the material constituting layer A and the material constituting layer B, they are multilayered (for example, using a multiplier). The obtained multilayer laminate is then stretched. The x-axis direction in the illustrated example may correspond to the stretching direction.

Commercially available reflective polarizing films include, for example, 3M's product names "DBEF" and "APF" and Nitto Denko's product name "APCF".

The cross transmittance (Tc) of the reflective polarizing member (reflective polarizing film) may be, for example, 0.01% to 3%. The single transmittance (Ts) of the reflective polarizing member (reflective polarizing film) is, for example, 43% to 49%, preferably 45% to 47%. The degree of polarization (P) of the reflective polarizing member (reflective polarizing film) can be, for example, 92% to 99.99%.

The single transmittance (Ts) is typically measured using an ultraviolet-visible spectrophotometer. The degree of polarization (P) is typically measured using an ultraviolet-visible spectrophotometer, and is calculated based on the parallel transmittance (Tp) and cross transmittance (Tc) obtained by correcting visibility. It is determined by the formula. Ts, Tp, and Tc are Y values measured using a 2-degree visual field (C light source) according to JIS Z8701 and subjected to visibility correction.
Polarization degree (P) = {(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

The absorption type polarizing member may typically include a resin film (sometimes referred to as an absorption type polarizing film or simply a polarizing film) containing a dichroic substance. Preferably, a polyvinyl alcohol (PVA) film containing iodine is included. The thickness of the absorption type polarizing film is preferably 1 μm or more and 8 μm or less, more preferably 7 μm or less, and still more preferably 5 μm or less. By using an absorptive polarizing film having such a thickness, shrinkage that may occur due to environmental changes (for example, temperature changes) can be suppressed, and excellent display characteristics can be maintained. Specifically, in the display system mentioned above, slight contraction of the member can cause image distortion, so by using an absorbing polarizing film with such a thickness, distortion of the displayed image can be extremely suppressed. can be suppressed.

The ratio of the thickness of the absorptive polarizing film to the thickness of the reflective polarizing member is preferably 15% or less, more preferably 10% or less. The ratio of the thickness of the absorptive polarizing film to the sum of the thickness of the second retardation member, the thickness of the reflective polarizing member, and the thickness of the absorptive polarizing member is preferably 10% or less, more preferably 5% or less. It is.

The orthogonal transmittance (Tc) of the absorption type polarizing member (absorption type polarizing film) is preferably 0.5% or less, more preferably 0.1% or less, and still more preferably 0.05% or less. be. The single transmittance (Ts) of the absorption type polarizing member (absorption type polarizing film) is, for example, 41.0% to 45.0%, preferably 42.0% or more. The degree of polarization (P) of the absorption type polarizing member (absorption type polarizing film) is, for example, 99.0% to 99.997%, preferably 99.9% or more. Excellent display characteristics can be achieved by combining a reflective polarizing member with an absorptive polarizing member. For example, visual recognition of afterimages (ghosts) by the user can be suppressed.

The method for producing an absorption type polarizing film according to one embodiment includes forming a polyvinyl alcohol resin layer (PVA resin) containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long thermoplastic resin base material. system resin layer) to form a laminate, and the laminate is subjected to aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and heating while conveying in the longitudinal direction to reduce the width by 2%. This includes performing the above-described drying and shrinking treatment in this order. The content of the halide in the PVA resin layer is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin. The stretching ratio in the aerial auxiliary stretching process is preferably 2.0 times or more. The drying shrinkage treatment is preferably carried out using a heating roll, and the temperature of the heating roll is preferably 60°C to 120°C. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 2% or more. A laminate including a PVA resin layer containing a halide is produced, the laminate is stretched in multiple stages including auxiliary stretching in the air and stretching in water, and the laminate after stretching is heated with a heating roll. It is possible to obtain a polarizing film that has excellent optical properties (typically, single transmittance and degree of polarization) and suppresses variations in optical properties. Specifically, by using a heating roll in the drying shrinkage process, the entire laminate can be uniformly shrunk while being transported. This not only makes it possible to improve the optical properties of the resulting polarizing film, but also allows stable production of polarizing films with excellent optical properties, and suppresses variations in the optical properties (especially single transmittance) of the polarizing film. can do.

Any suitable method may be adopted as a method for producing a laminate of a thermoplastic resin base material and a PVA-based resin layer. Preferably, a coating liquid containing a halide and a PVA resin is applied to the surface of the thermoplastic resin base material and dried to form a PVA resin layer on the thermoplastic resin base material. As mentioned above, the content of the halide in the PVA resin layer is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin.

Any suitable method can be adopted as a method for applying the coating liquid. Examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.). The coating and drying temperature of the coating liquid is preferably 50° C. or higher.

The thickness of the PVA resin layer is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

Before forming the PVA-based resin layer, the thermoplastic resin base material may be subjected to surface treatment (for example, corona treatment, etc.), or an easily adhesive layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA resin layer can be improved.

The thickness of the thermoplastic resin base material is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it exceeds 300 μm, for example, it may take a long time for the thermoplastic resin base material to absorb water in the underwater stretching treatment described below, and an excessive load may be required for stretching.

The thermoplastic resin base material preferably has a water absorption rate of 0.2% or more, more preferably 0.3% or more. The thermoplastic resin base material absorbs water and can be plasticized by the water acting as a plasticizer. As a result, stretching stress can be significantly reduced and stretching can be performed at a high magnification. On the other hand, the water absorption rate of the thermoplastic resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a thermoplastic resin base material, it is possible to prevent problems such as a significant decrease in the dimensional stability of the thermoplastic resin base material during production, resulting in deterioration of the appearance of the resulting polarizing film. Furthermore, it is possible to prevent the base material from breaking during underwater stretching or from peeling off the PVA resin layer from the thermoplastic resin base material. Note that the water absorption rate of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material. The water absorption rate is a value determined according to JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin base material is preferably 120°C or lower. By using such a thermoplastic resin base material, it is possible to sufficiently ensure the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. Furthermore, in consideration of plasticizing the thermoplastic resin base material with water and performing underwater stretching satisfactorily, the temperature is preferably 100° C. or lower, and more preferably 90° C. or lower. On the other hand, the glass transition temperature of the thermoplastic resin base material is preferably 60°C or higher. By using such a thermoplastic resin base material, the thermoplastic resin base material may be deformed (e.g., unevenness, sagging, wrinkles, etc.) when applying and drying a coating solution containing the above-mentioned PVA-based resin. It is possible to prevent this problem and produce a good laminate. Further, the PVA resin layer can be stretched well at a suitable temperature (for example, about 60° C.). Note that the glass transition temperature of the thermoplastic resin base material can be adjusted by, for example, heating using a crystallizing material that introduces a modifying group into the constituent material. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

Any suitable thermoplastic resin may be employed as the constituent material of the thermoplastic resin base material. Examples of thermoplastic resins include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. can be mentioned. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred.

In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among these, amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include copolymers further containing isophthalic acid and/or cyclohexane dicarboxylic acid as a dicarboxylic acid, and copolymers further containing cyclohexanedimethanol or diethylene glycol as a glycol.

In a preferred embodiment, the thermoplastic resin base material is comprised of a polyethylene terephthalate-based resin having isophthalic acid units. This is because such a thermoplastic resin base material has extremely excellent stretchability and can suppress crystallization during stretching. This is thought to be due to the fact that the introduction of the isophthalic acid unit imparts a large bend to the main chain. Polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content of the isophthalic acid unit is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all repeating units. This is because a thermoplastic resin base material with extremely excellent stretchability can be obtained. On the other hand, the content of the isophthalic acid unit is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. By setting the content to such a content ratio, the degree of crystallinity can be favorably increased in the drying shrinkage treatment described below.

The thermoplastic resin base material may be stretched in advance (before forming the PVA-based resin layer). In one embodiment, the elongated thermoplastic resin base material is stretched in the lateral direction. The lateral direction is preferably a direction perpendicular to the stretching direction of the laminate described below. In addition, in this specification, "orthogonal" also includes a case where they are substantially orthogonal. Here, "substantially orthogonal" includes a case where the angle is 90°±5.0°, preferably 90°±3.0°, and more preferably 90°±1.0°.

The stretching temperature of the thermoplastic resin base material is preferably Tg-10°C to Tg+50°C relative to the glass transition temperature (Tg). The stretching ratio of the thermoplastic resin base material is preferably 1.5 times to 3.0 times.

Any suitable method may be employed as a method for stretching the thermoplastic resin base material. Specifically, fixed end stretching or free end stretching may be used. The stretching method may be a dry method or a wet method. The thermoplastic resin base material may be stretched in one step or in multiple steps. In the case of multi-stage stretching, the above-mentioned stretching ratio is the product of the stretching ratios of each stage.

As described above, the coating liquid contains a halide and a PVA-based resin. The coating liquid is typically a solution in which the halide and the PVA resin are dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferred. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film that adheres to the thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin.

Additives may be added to the coating liquid. Examples of additives include plasticizers, surfactants, and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These may be used for the purpose of further improving the uniformity, dyeability, and stretchability of the resulting PVA-based resin layer.

Any suitable resin may be employed as the PVA resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA resin having such a degree of saponification, a polarizing film with excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. Note that the average degree of polymerization can be determined according to JIS K 6726-1994.

Any suitable halide may be employed as the halide. Examples include iodide and sodium chloride. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred.

The amount of halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of PVA resin, more preferably 10 parts by weight to 15 parts by weight based on 100 parts by weight of PVA resin. Department. If the amount of halide exceeds 20 parts by weight per 100 parts by weight of the PVA-based resin, the halide may bleed out and the polarizing film finally obtained may become cloudy.

Generally, by stretching the PVA resin layer, the orientation of the polyvinyl alcohol molecules in the PVA resin increases. However, when the stretched PVA resin layer is immersed in a liquid containing water, the orientation of the polyvinyl alcohol molecules increases. The orientation may be disturbed and the orientation may be deteriorated. In particular, when stretching a laminate of a thermoplastic resin and a PVA resin layer in boric acid water, when stretching the laminate in boric acid water at a relatively high temperature to stabilize the stretching of the thermoplastic resin, The tendency of the degree of orientation to decrease is remarkable. For example, while it is common for a PVA film alone to be stretched in boric acid water at 60°C, a laminate of A-PET (thermoplastic resin base material) and a PVA resin layer is stretched. It is carried out at a high temperature of around 70°C, and in this case, the orientation of PVA at the initial stage of stretching may decrease before it increases due to underwater stretching. In contrast, by producing a laminate of a PVA resin layer containing a halide and a thermoplastic resin base material, and stretching the laminate at high temperature in air (auxiliary stretching) before stretching it in boric acid water. , crystallization of the PVA resin in the PVA resin layer of the laminate after auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, disturbance in the orientation of polyvinyl alcohol molecules and deterioration of orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizing film obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment.

In particular, in order to obtain high optical properties, a two-stage stretching method is selected in which dry stretching (auxiliary stretching) and stretching in boric acid water are combined. By introducing auxiliary stretching as in two-stage stretching, it is possible to stretch while suppressing crystallization of the thermoplastic resin base material, and prevent excessive crystallization of the thermoplastic resin base material during subsequent stretching in boric acid water. This solves the problem that the stretchability is lowered due to this, and the laminate can be stretched to a higher magnification. Furthermore, in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material, when applying PVA resin on a thermoplastic resin base material, compared to the case where PVA resin is applied on a normal metal drum, As a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical properties cannot be obtained. On the other hand, by introducing auxiliary stretching, it is possible to increase the crystallinity of PVA-based resin even when applying PVA-based resin onto thermoplastic resin, making it possible to achieve high optical properties. Become. At the same time, by increasing the orientation of the PVA resin in advance, it is possible to prevent problems such as a decrease in orientation and dissolution of the PVA resin when it is immersed in water during the subsequent dyeing and stretching processes. , it becomes possible to achieve high optical properties.

The stretching method for aerial auxiliary stretching may be fixed end stretching (for example, stretching using a tenter stretching machine) or free end stretching (for example, uniaxial stretching by passing the laminate between rolls with different circumferential speeds). However, in order to obtain high optical properties, free end stretching may be actively employed. In one embodiment, the aerial stretching process includes a heating roll stretching step of stretching the laminate using a difference in peripheral speed between heating rolls while conveying the laminate in its longitudinal direction. The aerial stretching process typically includes a zone stretching process and a heated roll stretching process. Note that the order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heated roll stretching step are performed in this order. In another embodiment, the film is stretched in a tenter stretching machine by gripping the end portion of the film and widening the distance between the tenters in the machine direction (the widening of the distance between the tenters becomes the stretching ratio). At this time, the distance of the tenter in the width direction (direction perpendicular to the flow direction) is set to be arbitrarily close. Preferably, the stretching ratio in the machine direction can be set to be closer to free end stretching. In the case of free end stretching, the shrinkage rate in the width direction is calculated as (1/stretching ratio) ^1/2 .

Aerial assisted stretching may be performed in one step or in multiple steps. In the case of multi-stage stretching, the stretching ratio is the product of the stretching ratios of each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The stretching ratio in the aerial auxiliary stretching is preferably 2.0 times to 3.5 times. The maximum stretching ratio when the aerial auxiliary stretching and underwater stretching are combined is preferably 5.0 times or more, more preferably 5.5 times or more, and even more preferably 6.0 times the original length of the laminate. That's all. In this specification, the "maximum stretching ratio" refers to the stretching ratio immediately before the laminate breaks, and the stretching ratio at which the laminate breaks is separately confirmed, and it refers to a value 0.2 lower than that value.

The stretching temperature of the in-air auxiliary stretching can be set to any appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, etc. The stretching temperature is preferably at least the glass transition temperature (Tg) of the thermoplastic resin base material, more preferably at least the glass transition temperature (Tg) of the thermoplastic resin base material +10°C, particularly preferably at least Tg +15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and to suppress defects caused by the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). can. The crystallization index of the PVA-based resin after in-air assisted stretching is preferably 1.3 to 1.8, more preferably 1.4 to 1.7. The crystallization index of the PVA-based resin can be measured by the ATR method using a Fourier transform infrared spectrophotometer. Specifically, measurements are performed using polarized light as measurement light, and the crystallization index is calculated according to the following formula using the intensities at 1141 cm ^-1 and 1440 cm ^-1 of the obtained spectrum.
Crystallization index = (I _C /I _R )
however,
I _C : Intensity of 1141 cm ⁻¹ when measured with measurement light incident. I _R : Intensity of 1440 cm ⁻¹ when measured with measurement light incident.

If necessary, an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The above-mentioned insolubilization treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent a decrease in orientation of PVA when immersed in water. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilizing bath (boric acid aqueous solution) is preferably 20°C to 50°C.

The dyeing process is typically performed by dyeing the PVA resin layer with iodine. Specifically, this is carried out by adsorbing iodine to the PVA resin layer. The adsorption method includes, for example, immersing the PVA resin layer (laminate) in a dye containing iodine, applying the dye to the PVA resin layer, and applying the dye to the PVA resin layer. Examples include a method of spraying. Preferably, the method involves immersing the laminate in a dyeing solution (dyeing bath). This is because iodine can be adsorbed well.

The staining solution is preferably an aqueous iodine solution. The amount of iodine blended is preferably 0.05 part by weight to 0.5 part by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the iodine aqueous solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. etc. Among these, potassium iodide is preferred. The amount of iodide to be blended is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0.3 parts by weight to 5 parts by weight, based on 100 parts by weight of water. The temperature of the dyeing solution during dyeing is preferably 20° C. to 50° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the dyeing liquid, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA resin layer.

The dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the single transmittance and degree of polarization of the finally obtained polarizing film fall within the above-mentioned ranges. As for such staining conditions, preferably, an iodine aqueous solution is used as the staining liquid, and the ratio of the contents of iodine and potassium iodide in the iodine aqueous solution is 1:5 to 1:20. The content ratio of iodine and potassium iodide in the iodine aqueous solution is preferably 1:5 to 1:10. Thereby, a polarizing film having the optical properties as described above can be obtained.

When dyeing is performed continuously after immersing the laminate in a treatment bath containing boric acid (typically, insolubilization treatment), the boric acid contained in the treatment bath may mix into the dyeing bath. The boric acid concentration in the dye bath may change over time, resulting in unstable dyeing properties. In order to suppress the destabilization of dyeability as described above, the upper limit of the concentration of boric acid in the dyeing bath is preferably 4 parts by weight, more preferably 2 parts by weight, based on 100 parts by weight of water. be adjusted. On the other hand, the lower limit of the concentration of boric acid in the dyeing bath is preferably 0.1 part by weight, more preferably 0.2 part by weight, and still more preferably 0.5 part by weight, based on 100 parts by weight of water. It is. In one embodiment, the dyeing process is carried out using a dye bath pre-blended with boric acid. This can reduce the rate of change in boric acid concentration when boric acid in the treatment bath is mixed into the dyeing bath. The amount of boric acid added to the dyeing bath in advance (that is, the content of boric acid not derived from the treatment bath) is preferably 0.1 parts by weight to 2 parts by weight based on 100 parts by weight of water. , more preferably 0.5 parts by weight to 1.5 parts by weight.

If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The above crosslinking treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing the crosslinking treatment, water resistance is imparted to the PVA-based resin layer, and in the subsequent underwater stretching, it is possible to prevent a decrease in the orientation of PVA when immersed in high-temperature water. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight per 100 parts by weight of water. Moreover, when crosslinking treatment is performed after the above-mentioned dyeing treatment, it is preferable to further include an iodide. By blending iodide, it is possible to suppress elution of iodine adsorbed to the PVA-based resin layer. The amount of iodide to be blended is preferably 1 to 5 parts by weight per 100 parts by weight of water. Specific examples of iodides are as described above. The temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20°C to 50°C.

The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80° C.) of the thermoplastic resin base material or the PVA resin layer, and the PVA resin layer can be It is possible to stretch to a high magnification while suppressing the As a result, a polarizing film having excellent optical properties can be manufactured.

Any suitable method can be used to stretch the laminate. Specifically, fixed-end stretching or free-end stretching (for example, a method in which the laminate is passed between rolls having different circumferential speeds and uniaxially stretched) may be used. Preferably, free end stretching is chosen. The laminate may be stretched in one step or in multiple steps. When performing multi-stage stretching, the stretching ratio (maximum stretching ratio) of the laminate described below is the product of the stretching ratios of each stage.

Stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand tension applied during stretching, and water resistance that does not dissolve in water. Specifically, boric acid can generate a tetrahydroxyborate anion in an aqueous solution and crosslink with the PVA-based resin through hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, which can be stretched well, and a polarizing film having excellent optical properties can be manufactured.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate salt in water, which is a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 3.5 to 7 parts by weight, particularly preferably 4 to 6 parts by weight, based on 100 parts by weight of water. It is. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher characteristics can be manufactured. In addition to boric acid or a borate salt, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

Preferably, iodide is added to the stretching bath (boric acid aqueous solution). By blending iodide, it is possible to suppress elution of iodine adsorbed to the PVA-based resin layer. Specific examples of iodides are as described above. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, based on 100 parts by weight of water.

The stretching temperature (the liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such a temperature, it is possible to stretch to a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40° C., there is a possibility that the stretching cannot be performed satisfactorily even if the plasticization of the thermoplastic resin base material by water is taken into account. On the other hand, as the temperature of the stretching bath increases, the solubility of the PVA-based resin layer increases, and there is a possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by underwater stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretching ratio of the laminate is preferably 5.0 times or more, more preferably 5.5 times or more, relative to the original length of the laminate. By achieving such a high stretching ratio, a polarizing film with extremely excellent optical properties can be manufactured. Such a high stretching ratio can be achieved by employing an underwater stretching method (boric acid underwater stretching).

The drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or by heating a conveyance roll (using a so-called heating roll) (heated roll drying method). Preferably, both are used. By drying using a heating roll, heating curl of the laminate can be efficiently suppressed, and a polarizing film with excellent appearance can be manufactured. Specifically, by drying the laminate along a heating roll, it is possible to efficiently promote crystallization of the thermoplastic resin base material and increase the degree of crystallinity, which is relatively low. Even at drying temperatures, the degree of crystallinity of the thermoplastic resin base material can be increased favorably. As a result, the thermoplastic resin base material has increased rigidity and is in a state where it can withstand shrinkage of the PVA resin layer due to drying, thereby suppressing curling. Furthermore, by using a heating roll, the laminate can be dried while maintaining it in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the optical properties of the laminate can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, particularly preferably 4% to 6%. By using a heating roll, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be achieved.

FIG. 4 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage process, the laminate 200 is dried while being transported by transport rolls R1 to R6 heated to a predetermined temperature and guide rolls G1 to G4. In the illustrated example, transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin base material surface).

The drying conditions can be controlled by adjusting the heating temperature of the conveying roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, etc. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, particularly preferably 70°C to 80°C. The degree of crystallinity of the thermoplastic resin can be increased favorably, curling can be favorably suppressed, and extremely excellent durability can be imparted to the laminate. Note that the temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six conveyance rolls are provided, but there is no particular restriction on the number of conveyance rolls as long as there is a plurality of conveyance rolls. Usually 2 to 40 conveyance rolls, preferably 4 to 30 conveyance rolls are provided. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

The heating roll may be provided within a heating furnace (for example, an oven) or may be provided on a normal production line (at room temperature). Preferably, it is provided in a heating furnace equipped with air blowing means. By using both heating roll drying and hot air drying, a sharp temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30°C to 100°C. Further, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m/s to 30 m/s. Note that the wind speed is the wind speed within the heating furnace, and can be measured with a mini-vane digital anemometer.

Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The above cleaning treatment is typically performed by immersing the PVA resin layer in an aqueous potassium iodide solution.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. Note that the thickness is a value measured by the following measuring method.
<Thickness>
The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name “JSM-7100F”). Thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name “KC-351C”).

[Example 1]
As the thermoplastic resin base material, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. One side of the resin base material was subjected to corona treatment.
Iodine was added to 100 parts by weight of a PVA resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Mitsubishi Chemical Corporation, product name "Gosenex Z410") in a ratio of 9:1. A PVA aqueous solution (coating liquid) was prepared by dissolving 13 parts by weight of potassium chloride in water.
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched free end to 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed for 30 seconds in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. (insolubilization treatment).
Next, the final polarizing film was added to a dyeing bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 to 100 parts by weight of water) at a liquid temperature of 30°C. It was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 43.0% (staining treatment).
Next, it was immersed for 30 seconds in a crosslinking bath (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C. (Crosslinking treatment).
Thereafter, while immersing the laminate in a boric acid aqueous solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, the laminate was completely rolled in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds. Uniaxial stretching was performed so that the stretching ratio was 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a SUS heating roll whose surface temperature was maintained at 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment was 5.2%.
In this way, a 5 μm thick polarizing film (absorption type polarizing film) was formed on the resin base material.

A cycloolefin resin film having a thickness of 25 μm was bonded as a protective layer to the surface of the obtained polarizing film (the surface on the polarizing film side of the laminate) via an ultraviolet curable adhesive. Specifically, the adhesive layer was coated so that the thickness of the cured adhesive layer was approximately 1 μm, and the adhesive layers were bonded together using a roll machine. Thereafter, UV light was irradiated from the cycloolefin resin film side to cure the adhesive. Next, the resin base material was peeled off to obtain a polarizing film (absorbing polarizing film) having a structure of cycloolefin resin film/absorbing polarizing film.

[Example 2]
A polarizing film containing a 7 μm thick polarizing film was obtained in the same manner as in Example 1 except that a 18 μm thick PVA resin layer was formed on the resin base material.

[Comparative example 1]
A long roll of polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, trade name "PE3000") with a thickness of 30 μm was simultaneously uniaxially stretched in the longitudinal direction so as to be 5.9 times larger in the longitudinal direction using a roll stretching machine. After performing swelling, dyeing, crosslinking, and washing treatments in this order, a drying treatment was finally performed to produce a polarizing film (absorption type polarizing film) with a thickness of 12 μm.
In the above swelling treatment, the film was stretched 2.2 times while being treated with pure water at 20°C. Next, the dyeing process was carried out in an aqueous solution at 30°C in which the weight ratio of iodine and potassium iodide was 1:7, and the iodine concentration was adjusted so that the single transmittance of the polarizing film obtained was 45.0%. However, it was stretched 1.4 times. Next, a two-stage crosslinking treatment was adopted for the crosslinking treatment, and the first crosslinking treatment was performed in an aqueous solution containing boric acid and potassium iodide at 40° C. and stretched to 1.2 times. The boric acid content of the aqueous solution for the first stage crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage of crosslinking treatment, the film was stretched to 1.6 times while being treated in an aqueous solution containing boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution for the second stage crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Next, washing treatment was performed with a potassium iodide aqueous solution at 20°C. The potassium iodide content of the aqueous solution for cleaning treatment was 2.6% by weight. Finally, a polarizing film was obtained by drying at 70° C. for 5 minutes.

A cycloolefin resin film with a thickness of 25 μm was bonded to the obtained polarizing film as a protective layer using a 3% aqueous solution of PVA adhesive (manufactured by Mitsubishi Chemical Corporation, trade name "Gohsenol Z200"), and the polarizing film was attached. Obtained.

[Comparative example 2]
A polarizing film containing a polarizing film with a thickness of 17 μm was obtained in the same manner as in Comparative Example 1 except that a PVA-based resin film with a thickness of 45 μm was used.

[Comparative example 3]
A polarizing film including a polarizing film with a thickness of 23 μm was obtained in the same manner as in Comparative Example 1 except that a PVA-based resin film with a thickness of 60 μm was used.

[Comparative example 4]
A polarizing film containing a polarizing film with a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a PVA-based resin film with a thickness of 75 μm was used.

The following evaluations were performed for the Examples and Comparative Examples. The evaluation results are summarized in Table 1.
<Evaluation>
1. Dimensional change rate (%)
A test piece with a size of 100 mm x 100 mm was cut out from the obtained polarizing film along the stretching direction and a direction perpendicular thereto, and was bonded to a glass plate via a 20 μm thick acrylic adhesive layer. This was heated by placing it in an oven at 80° C. for 500 hours, the size before and after heating was measured, and the dimensional change rate before and after heating was calculated.
2. Shrinkage stress (N/4mm)
A test piece of 20 mm x 4 mm in size was cut out from the obtained polarizing film (before the protective film was attached) along the stretching direction and the direction perpendicular thereto. I set it. While maintaining this state, the test piece was heated at 50° C. for 30 minutes, and the shrinkage stress generated from the test piece was measured.
3. Optical unevenness The obtained polarizing film was cut into a size of 200 mm x 150 mm, and the sample obtained by bonding it to a glass plate via a 20 μm acrylic adhesive layer was placed in a heating tester at 80° C. for 120 hours. After that, another standard polarizing plate (manufactured by Nitto Denko Corporation, "CRT1794") was placed on top of the taken sample so that their absorption axes were perpendicular to each other, and this was placed on the backlight. We confirmed the unevenness within the area.

In the comparative example, optical unevenness (particularly at the corners) was observed as shown in FIG.

The present invention is not limited to the above embodiments, and various modifications are possible. For example, it can be replaced with a configuration that is substantially the same as the configuration shown in the above embodiment, a configuration that has the same effect, or a configuration that can achieve the same purpose.

The lens unit according to the embodiment of the present invention can be used, for example, in a display body such as VR goggles.

2 Display system 4 Lens section 12 Display element 14 Reflection section 16 First lens section 18 Half mirror 20 First retardation member 22 Second retardation member 24 Second lens section 30 Laminated body 32 Reflective polarizing member 34 Absorptive polarizing member 36 Adhesive layer

Claims (16)

A lens unit used in a display system that displays images to a user, the lens unit comprising:
A reflective polarizing member is arranged in front of a reflective polarizing member and the reflective polarizing member, and reflects light that is emitted forward from a display surface of a display element that represents an image and has passed through a polarizing member and a first λ/4 member. a reflective section including an absorptive polarizing member;
a first lens section disposed on an optical path between the display element and the reflection section;
a half mirror disposed between the display element and the first lens part, which transmits the light emitted from the display element and reflects the light reflected by the reflection part toward the reflection part;
a second λ/4 member disposed on the optical path between the half mirror and the reflection section,
The thickness of the absorption type polarizing film constituting the absorption type polarizing member is 8 μm or less,
lens section. The lens portion according to claim 1, wherein the reflection axis of the reflective polarizing member and the absorption axis of the absorptive polarizing member are arranged parallel to each other. The lens section according to claim 1, wherein the first lens section and the half mirror are integrated. The lens section according to claim 1, further comprising a second lens section disposed in front of the reflecting section. The angle between the absorption axis of the polarizing member included in the display element and the slow axis of the first λ/4 member is 40° to 50°,
The lens portion according to claim 1, wherein the angle between the absorption axis of the polarizing member included in the display element and the slow axis of the second λ/4 member is 40° to 50°. The lens portion according to claim 1, wherein the ratio of the thickness of the absorptive polarizing film to the thickness of the reflective polarizing member is 15% or less. Used in the reflective part of the lens part according to any one of claims 1 to 6,
comprising the reflective polarizing member and the absorbing polarizing member,
laminate. The laminate according to claim 7, wherein the reflective polarizing member and the absorptive polarizing member are laminated with an adhesive layer interposed therebetween. A display body comprising the lens portion according to any one of claims 1 to 6. A method for manufacturing a display body having a lens portion according to any one of claims 1 to 6. A step of passing the light representing the image emitted through the polarizing member and the first λ/4 member through the half mirror and the first lens part;
passing the light that has passed through the half mirror and the first lens section through a second λ/4 member;
reflecting the light that has passed through the second λ/4 member toward the half mirror by a reflecting section including a reflective polarizing member;
a step of allowing the light reflected by the reflection part and the half mirror to pass through the reflective polarizing member of the reflection part by the second λ/4 member;
a step of transmitting the light transmitted through the reflective polarizing member through an absorbing polarizing member,
The thickness of the absorption type polarizing film constituting the absorption type polarizing member is 8 μm or less,
Display method. A method for manufacturing an absorption type polarizing film for a lens portion according to any one of claims 1 to 6, comprising:
forming a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin on one side of a long thermoplastic resin base material to form a laminate;
The method includes subjecting the laminate to, in this order, an auxiliary stretching process in the air, a dyeing process, a stretching process in water, and a drying shrinkage process in which the laminate is shrunk by 2% or more in the width direction by heating while conveying in the longitudinal direction. ,Production method. The manufacturing method according to claim 12, wherein the content of the halide in the polyvinyl alcohol resin layer is 5 parts by weight to 20 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin. The manufacturing method according to claim 12, wherein the stretching ratio in the aerial auxiliary stretching treatment is 2.0 times or more. The manufacturing method according to claim 12, wherein the drying shrinkage treatment step is a heating step using a heating roll. The manufacturing method according to claim 15, wherein the temperature of the heating roll is 60° C. to 120° C., and the shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is 2% or more.

Images