JP5204358B2 - Transparent film for display - Google Patents

Description

  The present invention relates to a transparent polymer film used for a flat panel display such as a liquid crystal display element, an electroluminescence (EL) display element, particularly an organic EL display.

  In recent years, in the field of flat panel displays such as liquid crystal display devices and organic EL display devices, investigations to replace plastic films made of transparent polymers with conventional glass substrates have continued due to demands for improved breakage resistance, weight reduction, and thickness reduction. It has been. However, plastics generally have optical anisotropy due to distortion during molding, and easily pass through gas and water vapor.

  Plastic films for liquid crystal display elements are required to have resistance to various chemicals used in the manufacturing process of the liquid crystal panel, baking of alignment films and sealants, and heat resistance required in the connection process of the drive circuit. For this reason, a plastic molded body excellent in optical isotropy is used as a base material, and a gas barrier layer, a chemical resistance layer, and a transparent conductive layer are laminated. Furthermore, in recent years, in order to improve the display quality of a liquid crystal display, studies have been made on high definition, high capacity and multi-tone color display. For the former, use a high-temperature fired alignment film to obtain a high pretilt angle, use a high-temperature pressure-bonded anisotropic conductive film that provides fine pitch and good connection reliability, and the latter use fine pixel electrodes and color filters. Processing is one of the elemental technologies. Therefore, in addition to the above-mentioned required characteristics, the plastic film of the base material is required to further minimize the heat resistance and dimensional stability, particularly the dimensional change after high temperature heating.

  In addition, the plastic film for organic EL display elements requires extremely smoothness and excellent gas barrier properties on the surface on which the EL layer is formed. Excellent performance is required for the difference. In addition, resistance to various chemicals used in the panel manufacturing process, baking of the cathode partition walls and seals, and heat resistance required in the connection process of the drive circuit are required.

  On the other hand, Japanese Patent Application Laid-Open No. 59-158015 describes a transparent conductive film for a display in which an indium oxide film is laminated on a polyethersulfone film having a small birefringence. Although it is excellent in heat shrinkage, the dimensional change due to water absorption is remarkable, and the film is produced by heat-melt extrusion, so there are many defects such as die lines, gelled products, and fish eyes on the film surface. It is difficult to realize a display with excellent quality. JP-A-7-246661 discloses a 1,1-bis (4-hydroxyphenyl) -alkylcycloalkane having a phase difference adjusted within a range of 10 to 2000 nm and a polycarbonate or polyester carbonate comprising a substituted product thereof. Although there is a description that it is used for a substrate for a display, although the film has excellent heat resistance, the dimensional change after high-temperature heating is large and the water vapor barrier property is poor. Have difficulty.

Problems to be solved by the invention

  The present invention has been made in view of the current situation, and realizes a flat panel display excellent in display quality such as high definition, high capacity, multi-tone, and color display, and has excellent optical isotropy, heat resistance, and dimensional stability. In particular, it has excellent surface smoothness and water vapor barrier properties, has very little dimensional change after high-temperature heating, and uses a connection material containing conductive particles such as heat seal connectors and anisotropic conductive films to make printed wiring boards. An object of the present invention is to provide a transparent film for a display which is excellent in reliability when connected.

Means for solving the problem

  In order to solve the above problems, the present inventors have intensively studied a polymer material for a display such as a liquid crystal, and as a result, the polymer material having a specific molecular structure is used to form a three-dimensional refractive index by a highly accurate film formation technique. By controlling the above, a transparent film for display with extremely excellent heat resistance, optical isotropy, dimensional stability, in particular, dimensional change after heating at high temperature and extremely good surface smoothness was found.

That is, the present invention is as follows.
1. A transparent film formed by a solution casting method of a polycarbonate having a glass transition temperature of 170 ° C. or more having a repeating unit having a fluorene skeleton as a (copolymerization) component, and (i) a three-dimensional refractive index is represented by the following formula (A ) And (B) at the same time, (ii) dimensional change after heat treatment at 150 ° C. for 2 hours is 0.05% or less, (iii) saturated water absorption is 0.4% or less, and ( iv) A transparent film for display having a water vapor transmission coefficient at 40 ° C. and 90% RH of 35 g · 100 μm / m ² / day or less.
| R (550) | ≦ 20 (nm) (A)
K = | [nz− (nx + ny) / 2] × d | ≦ 100 (nm) (B)

[In the above formula (A), R (550) is the in-plane retardation of the film with respect to light having a wavelength of 550 nm. In the above formula (B), nx, ny, and nz are x with the thickness direction of the film as the z axis. It is a three-dimensional refractive index for light having a wavelength of 550 nm in the axial, y-axis, and z-axis directions, and d is a film thickness. ]
2. The transparent film for display as described above, wherein at least one surface has a surface smoothness of SRa of 10 nm or less.
3 . Polycarbonate is represented by the following formula (1)

[In the above formula (1), R ₁ to R ₈ are each independently at least one selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms. ]
A repeating unit represented by the following formula (2):

[In the above formula (2), R _{9 to} R ₁₆ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms, and X is a hydrocarbon group having 1 to 15 carbon atoms. ]
The said transparent film for a display which consists of 10 to 90 mol% of the whole repeating unit represented by the said Formula (1).
4 . The transparent film for display as described above, wherein the repeating unit represented by the formula (1) is derived from fluorene-9,9-di (3-methyl - 4-phenol).
5 . The transparent film for display as described above, wherein X in the formula (2) is a 2,2-propylene group.
6 . The transparent film for display as described above, which has a dimensional change rate of 0.1% or less after heat treatment at 180 ° C for 2 hours.
7 . R (450) / R (550) ≦ 1.06 where R (450) is the in-plane retardation for light with a wavelength of 450 nm and R (550) is the in-plane retardation for light with a wavelength of 550 nm. Transparent film for display.
8 . Said display transparent film whose K value of said Formula (B) is 50 nm or less.
9. The amount of solvent remaining in the transparency film in the above-mentioned transparent film for display is not more than 1 wt% relative to the transparent film total weight.
10 . The transparent film for display as described above, wherein a gas barrier layer made of an inorganic material is laminated on a surface having a surface smoothness of SRa of 10 nm or less.
11 . The transparent film for display as described above, wherein a gas barrier layer and a chemical resistant layer are laminated on at least one side.
12 . The transparent film for display as described above, wherein a transparent conductive layer is laminated on at least one surface.
13 . The transparent film for display as described above, having a hardness of 18 or more and a plastic deformation rate of 50% or less when measured with an ultra-micro hardness meter
14 . 14. An organic EL display element substrate or a liquid crystal display element substrate using the transparent film according to any one of 1 to 13 above.

  In the process of searching for a plastic film substrate that gives an ideal liquid crystal display with extremely high display quality, the present invention has only high glass transition temperature, low water absorption, water vapor barrier property, and excellent optical isotropy. In addition, the present invention has provided a transparent film for a display that is excellent in surface smoothness, has very little dimensional change after high-temperature heating, and has excellent connection reliability with a drive circuit.

In the present invention, excellent optical isotropy means the following formulas (A) and (B):
| R (550) | ≦ 20 (nm) (A)
K = | [nz− (nx + ny) / 2] × d | ≦ 100 (nm) (B)
Satisfying. In the above formula (A), R (550) is the in-plane retardation of the film with respect to light having a wavelength of 550 nm, and in the above formula (B), nx, ny, and nz are x axes with the thickness direction of the film as the z axis. , Y-axis, and z-axis directions are three-dimensional refractive indexes with respect to light having a wavelength of 550 nm, and d is a film thickness.

The transparent film of the present invention preferably has the following formulas (A ′) and (B ′):
| R (550) | ≦ 15 (nm) (A ′)
K = | [nz− (nx + ny) / 2] × d | ≦ 50 (nm) (B ′)
More preferably, the following formulas (A ″) and (B ″):
| R (550) | ≦ 13 (nm) (A ″)
K = | [nz− (nx + ny) / 2] × d | ≦ 30 (nm) (B ″)
Satisfied.

  The in-plane retardation of the film is the product of the difference Δn in the refractive index between the film orientation direction and the direction perpendicular to the film orientation direction when light passes through the film of thickness d and the film thickness d Δn · d ( nm). This phase difference can also be expressed as an angle, and the conversion formula between the phase difference R1 expressed in angle and the phase difference R2 in units of nm is expressed as R1 (degree) = (R2 (nm) / λ) × 360. (Λ is the phase difference measurement wavelength).

  The transparent film of the present invention has very high heat resistance, has very little dimensional change after high-temperature heating, and the dimensional change rate in the flow direction of the transparent film after heat treatment at 150 ° C. for 2 hours is 0.05% or less. There is provided a display having excellent display quality. More preferably, the dimensional change rate after the heat treatment at 180 ° C. for 2 hours in the flow direction is 0.1% or less.

  The thermoplastic polymer constituting the transparent film of the present invention is only required to satisfy the above conditions, has excellent heat resistance, has a glass transition temperature of 170 ° C. or higher, preferably 190 ° C. or higher, and has good optical properties. Those capable of forming a solution film are preferred.

  By solution casting, a transparent polymer film for display having an excellent surface smoothness with SRa of 10 nm or less is obtained. Here, SRa is a three-dimensional center plane average roughness, a portion of area Sm is extracted from the roughness surface onto the center plane, and an axis orthogonal to the center plane of the extracted portion is represented by the Z axis. The value obtained in is expressed in μm.

(However, Lx x Ly = Sm)
However, the transparent film of the present invention has a low water absorption rate and is important for displays that require very high quality. The water absorption is selected to be 0.4% or less, preferably 0.2% or less in terms of water absorption after 24 hours in water measured by a method according to ASTM D570. Further, it is important that the transparent film of the present invention is excellent in water vapor barrier properties. It is important to select one having a water vapor transmission coefficient at 40 ° C. and 90% RH of 50 g · 100 μm / m ² / day or less, preferably 35 g · 100 μm / m ² / day or less. By having such a high water vapor barrier property, it is possible to suppress deterioration of the element due to the influence of water when used as a substrate such as a liquid crystal panel or an organic EL panel. Some organic EL panels use a low molecular weight material and a high molecular weight material for the light emitting layer. In each system, a transparent conductive film, a hole transport layer, an RGB light emitting layer, an electron transport layer are formed on the substrate. A method called bottom emission that forms a film in the order of metal cathode and a method called top emission that forms a film on the substrate in the order of metal anode, hole transport layer, RGB light emitting layer, electron transport layer, and cathode are proposed. However, the film of the present invention is useful for all of these systems, and is also useful as a sealing film used by sandwiching the light emitting layer and the substrate on which the light emitting layer is formed in each system.

The thermoplastic polymer is not particularly limited, but polycarbonate, polyester, polyester carbonate having a good balance of heat resistance, film-forming property by solution casting method, transparency, handleability, barrier properties, mechanical properties, etc. Is preferable.
These polymers have the formula

Those having a repeating unit having a fluorene skeleton represented by formula (copolymerization) as a component are particularly excellent in the above properties and particularly excellent in gas barrier properties. You may use these in mixture of 2 or more types. In said formula, R < ₁ > -R < ₈ > is at least 1 type chosen from a hydrogen atom, a halogen atom, and a C1-C6 hydrocarbon group each independently.

Here, as a specific example of the monomer used for introducing the (copolymerization) component of the above formula into the polymer, fluorene-9,9-di (4-phenol) and / or fluorene-9, 9-di (3-methyl-4-phenol). It is preferable that the copolymerization component represented by the said formula is 10-90 mol% of the whole, More preferably, it is 30-80 mol%. When the amount is less than 10 mol%, sufficient isotropic and heat resistance, which will be described later, cannot be obtained, the dimensional change before and after high-temperature heating increases, and when it exceeds 90 mol%, the light transmittance decreases and the film Is not preferable because it becomes brittle.
Furthermore, as a polymer material constituting the transparent film of the present invention, the following formula (1)

A repeating unit represented by the following formula (2):

A polycarbonate in which the repeating unit represented by the formula (1) is a copolymerization component and the repeating unit represented by the above formula (1) is 10 to 90 mol% of the whole is preferable.

In said formula (1), R < ₁ > -R < ₈ > is at least 1 type chosen from a hydrogen atom, a halogen atom, and a C1-C6 hydrocarbon group each independently. Examples of the hydrocarbon group having 1 to 6 carbon atoms include alkyl groups such as a methyl group and an ethyl group, and aryl groups such as a phenyl group.

In the above formula (2), R _{9 to} R ₁₆ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms, and X is a hydrocarbon group having 1 to 15 carbon atoms. Specific examples of X include methylene, 1,1-ethylene, 2,2-propylene, 2,2-butylene, 2,2- (4-methyl) pentylene, 1,1-cyclohexylene, 1,1- ( 3,3,5-trimethyl) cyclohexylene, norbornane-2,2-diyl, tricyclo [5.2.1.0 ^2,6 ] decane-8,8'-diyl, phenylmethylene, diphenylmethylene, 1,1 -(1-Phenyl) ethylene, 2,2-hexafluoropropylene, 2,2- (1,1,3,3-tetrafluoro-1,3-dichloro) propylene and the like.

Particularly preferred polycarbonates include repeating units represented by the above formula (1) derived from fluorene-9,9-di (3-methyl-4-phenol) (in the above formula (1), R _{1 to} R ₈ Corresponds to a hydrogen atom (provided that one of R ₂ and R ₃ is a methyl group and one of R ₅ and R ₈ is a methyl group), X is 2,2-propylene, R ₉ and a repeating unit represented by formula (2) to R ₁₆ are all hydrogen atoms is a polycarbonate and a copolymer component. Here, the repeating unit represented by the above formula (1) is preferably 10 to 90 mol%, more preferably 30 to 80 mol% of the whole. By making the repeating unit represented by the above formula (1) 10 mol% or more, the glass transition temperature becomes 170 ° C. or more, and excellent heat resistance is obtained, and the water absorption rate and water vapor permeability are small. In addition, the surface hardness that can be evaluated by pencil hardness or the like is remarkably improved, and particularly, the dimensional change after high-temperature heating is extremely small, so that it exhibits preferable characteristics as a display substrate. In addition, since resistance to various cyano liquid crystals is improved, it is particularly useful for liquid crystal display applications. Further, as the number of repeating units represented by the above formula (1) increases, the optical isotropy of the film increases. When polycarbonate larger than 30 mol% is used, the in-plane retardation R for light having a wavelength of 450 nm is used. (450) and the in-plane retardation R (550) for light having a wavelength of 550 nm can be reduced, and further, R (450) / R (550) ≦ 1.06. The film is extremely excellent in isotropy. In particular, when a film is formed using a polycarbonate containing 50 mol% or more of the repeating unit represented by the above formula (1), when the film is formed by the solution casting method described later, the above formulas (A) and (B) Can be satisfied at the same time, and a transparent polymer film for display having a very small surface dimensional change with a very low SRa of 10 nm or less can be obtained after heat treatment at 180 ° C. for 2 hours.

  Further, as the number of repeating units represented by the above formula (1) is increased, the value of R (450) / R (550) decreases, and when it is about 55 mol% or more, R (450) / R (550) < 1 characteristic is exhibited. This characteristic is very useful for compensating the viewing angle characteristic and optical rotation dispersion of the liquid crystal display, particularly when the transparent film for display of the present invention is used for the liquid crystal display. However, when the repeating unit represented by the above formula (1) is 90 mol% or more, the light transmittance is lowered and the film becomes brittle.

  Carbonic acid, aliphatic dicarboxylic acid, and aromatic dicarboxylic acid can be used as the acid component in the polyester and polyester carbonate mentioned as the polymer material constituting the transparent film of the present invention. As the aromatic dicarboxylic acid, terephthalic acid and isophthalic acid are preferable.

  In addition, you may use the said polycarbonate, polyester, and polyester carbonate in mixture of 2 or more types.

  The molecular weight of these polycarbonates, polyesters, and polyester carbonates is preferably 30,000 to 300,000 in terms of number average molecular weight. A polymer having a higher molecular weight improves mechanical properties and heat resistance, but if it is too large, molding becomes difficult.

In general, the film forming method includes a melt extrusion film forming method and a solution casting film forming method, but the optical isotropy satisfying the above formulas (A) and (B) is excellent. A suitable molding method for obtaining the transparent film is a solution casting method. The solution casting method is inferior to the melt extrusion method in terms of productivity, but has few defects such as die lines, gelled products, and fish eyes, and the surface smoothness is far superior to the melt extrusion method. Also, in the solution casting method, even a high molecular weight resin that is too high in melt viscosity or easily colored by melt extrusion or cannot be molded can be molded if it is soluble in the solvent used. A film having excellent heat resistance can be obtained. In the solution casting method, the three-dimensional refractive index of the film can be controlled by adjusting the characteristics of the die, the state of the casting belt, the drying conditions, the film tension and the conveying conditions, and the like. In order to satisfy the above formulas (A) and (B), it is particularly important to adjust the amount of solvent contained in the film in the molding step, the drying temperature, and the tension applied to the film. Film Although determines the apparent Tg of the film by the solvent content of the zinc, the drying temperature is preferably set to below Tg on the apparent. In addition, the tension applied to the film tends to increase the tension in the film transport direction when, for example, the roll winding method is used, but a device that can apply tension also in the direction perpendicular to the film transport direction is used. It is also effective to perform molding under the condition that the difference between the two tensions is not generated as much as possible and the tension is suppressed as much as possible.

  In the solution casting method, the solvent used for film formation may remain in the film. The residual solvent plasticizes the film, resulting in a decrease in glass transition temperature and a decrease in mechanical properties. For this reason, it is preferable to remove the residual solvent completely, and it is preferable to make it 1 wt% or less, more preferably 0.5 wt% or less. When a plasticizer or a surfactant is added to the film, the residual amount is not included in the residual solvent amount.

  By the way, although the method for reducing the residual solvent amount is mainly heat treatment, it is preferable to use a low boiling point solvent such as dichloromethane as the main solvent for the solution casting method in consideration of the effect and economy. Note that the solvent is not limited to a low boiling point solvent, and a solvent such as dioxolane can also be used.

  The thickness of the transparent film of the present invention is the display quality when processed into various displays, the ease of handling in the process of forming a substrate, the ease of handling in the process of assembling the display, and the solution casting film forming process. From the viewpoint of film forming efficiency, the thickness is 20 to 500 μm, preferably 50 to 400 μm, and more preferably 70 to 200 μm. When the transparent film of the present invention is provided with an electrode made of a transparent conductive layer and used as an electrode for a liquid crystal display, the gap in the liquid crystal cell deteriorates the display quality, so the thickness unevenness of the film is ± 5% or less. More preferably, it is preferably ± 2.5% or less.

  The transparent film for display of the present invention has a low water vapor transmission coefficient and high water vapor barrier properties, but if necessary, at least one surface of the transparent film protects oxygen and moisture from entering a gas barrier layer, a hard coat layer, etc. It is possible to form a chemical resistant layer having a cross-linked structure, a transparent conductive layer, and the like. In particular, when an inorganic material described later is laminated as a gas barrier layer on the surface having excellent surface smoothness with SRa of less than 10 nm, more preferably less than 5 nm, the gas barrier property can be further improved.

  Examples of the gas barrier layer include known polyvinyl alcohol polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, polyacrylonitrile copolymers such as polyacrylonitrile and styrene-acrylonitrile copolymers, and polyvinylidene chloride. And at least one metal selected from Si, Al, Ti, Mg, Zr, etc., or an oxide, fluoride, nitride or oxynitride inorganic material of a mixture of two or more metals. Can be mentioned. Of these, inorganic materials mainly composed of Si oxides, nitrides, and oxynitrides are preferable because of their excellent transparency and gas barrier properties. In addition, a silicon oxide containing silicon and oxygen as main components, or a thin film containing silicon and oxygen as main components, containing at least fluorine and magnesium, and having silicon and fluorine chemically bonded has gas barrier properties, transparency, It is preferable in terms of surface smoothness and low film stress. Here, the ratio of oxygen atoms to silicon atoms is preferably 1.5 or more and less than 2. Depending on this ratio, the transparency and gas barrier properties of the thin film change due to a tradeoff, and if it is less than 1.5, the transparency required for display applications may not be obtained. Furthermore, the fluorine atom is chemically bonded to silicon and magnesium, and the ratio of the fluorine atom-silicon atom bond (A) and the fluorine atom-magnesium bond (B) is preferably (A)> (B). And the ratio of magnesium contained in the gas barrier layer is preferably in the range of 2.5 to 20 atom% in terms of element ratio with respect to coexisting silicon. By making such ratios, it is estimated that not only good gas barrier properties and transparency, but especially film stress can be reduced. Therefore, even if the film thickness of the gas barrier layer is increased, the transparent film for display is not deformed. Less. The chemical bonding state of the fluorine element present in the gas barrier film is analyzed and determined by, for example, X-ray photoelectron spectroscopy. In X-ray photoelectron spectroscopy, when the K-ray of Al is used as the X-ray source and the horizontal axis is corrected with 284.6 eV of neutral carbon C1s, the chemical bond state of fluorine is fluorine and silicon observed in the vicinity of 687 eV. Is determined by the presence of the F1s peak (A) derived from the bond of F1s and the F1s peak (B) derived from the bond of fluorine and magnesium observed on the lower binding energy side by about 1.5 eV, and the intensity ratio thereof. .

  Examples of the method for forming the gas barrier layer include a vapor deposition method in which a film is formed by depositing a material in a vapor phase, such as a sputtering method, a vacuum deposition method, an ion plating method, and a plasma CVD method. These gas barrier layers are used singly or in combination of two or more, and set to a thickness that allows the target performance to be exhibited. In particular, the film thickness when an inorganic thin film material is used as the gas barrier layer is preferably in the range of 2 nm to 1 μm. If the thickness of the gas barrier layer is less than 2 nm, it is difficult to form a film uniformly, and a portion where no film is formed is generated, resulting in an increase in gas permeability. On the other hand, when it is thicker than 1 μm, not only the transparency is lost, but also when the substrate is bent, a crack is generated in the gas barrier layer and the gas permeability is increased.

  These gas barrier layers are used singly or in combination of two or more, and set to a thickness that allows the target performance to be exhibited.

  The chemical resistant layer can be formed by using a known coating method and curing method of a crosslinked structure of a polysiloxane resin, a crosslinked structure of an acrylic resin, a crosslinked structure of an epoxy resin, or the like. Here, the chemical resistance is intended to impart durability against solvents and chemicals during panel assembly, and is a material that can sufficiently ensure alkali resistance, acid resistance, and stability against organic solvents such as N-methylpyrrolidone. It is preferable to select curing conditions. When the gas barrier layer and the chemical resistant layer are laminated on each other, a primer layer can be appropriately provided for the purpose of improving the adhesion between the layers. As the primer layer, a silicon-based material containing a silane coupling agent or the like, an acrylic material, an acrylic-urethane material, or a material containing alkoxy titanium can be used. The film thickness of the chemical resistant layer can be appropriately selected from the range of generally 0.01 to 20 μm. Moreover, when using the transparent film for display of this invention for a liquid crystal display element or an organic EL display element, the surface of the chemical-resistant layer laminated | stacked on the liquid crystal layer or EL layer side of a board | substrate is the surface smoothness of the above-mentioned transparent film. It is preferable to select the coating solution conditions and the coating method conditions so that equivalent SRa can be obtained.

  The transparent film for display of the present invention can be formed into an electrode, for example, by forming a transparent conductive layer according to its use. As the transparent conductive layer, known metal films, metal oxide films, and the like can be applied. Among these, metal oxide films are preferable from the viewpoint of transparency, conductivity, and mechanical properties. For example, metal oxide films such as indium oxide, cadmium oxide and tin oxide to which tin, tellurium, cadmium, molybdenum, tungsten, fluorine, zinc, germanium and the like are added as impurities, and zinc oxide and titanium oxide to which aluminum is added as impurities. Can be mentioned. Among them, the main component is indium oxide, and it contains one or more oxides selected from the group consisting of tin oxide and zinc oxide, tin oxide being 2 to 20% by weight and / or zinc oxide being A transparent conductive layer containing 2 to 20% by weight is preferably used because of its excellent transparency and conductivity. When the film of the present invention is used for organic EL, it is selected from the group consisting of indium oxide and tin oxide and zinc oxide for the purpose of controlling the work function of the transparent conductive layer and improving the luminous efficiency. Furthermore, elements other than tin and zinc may be added to the film containing one or more oxides.

  As a method of forming the transparent conductive layer, a sputtering method is mainly used, and a direct current sputtering method, a high frequency magnetron sputtering method, an ion beam sputtering method, and the like can be applied. From the viewpoint of productivity, the magnetron sputtering method is preferable. The film thickness of the transparent conductive layer is preferably 10 to 1000 nm in order to obtain sufficient conductivity. The transparent polymer film for display of the present invention preferably has a total light transmittance of 80% or more in the visible light region, and more preferably 85% or more. If it is less than 80%, problems such as a reduction in visibility may occur.

  The hardness and plastic deformation rate of the transparent film for display in the present invention are measured with a microhardness meter such as commercially available Elionix, Shimadzu Corporation, Akashi Corporation, NEC Corporation, etc. . For example, in ENT-1100 manufactured by Elionix Co., Ltd., the measurement conditions are a maximum load of 50 mgf, a data capture step of 0.2 mgf, a data capture interval of 40 msec, a load retention time of 1 sec when the maximum load is reached, and the indenter used is a tip material of diamond. A certain triangular pyramid (115 °), which is an average when five continuous measurements are performed for each load, and the sample is fixed to a metal sample stand with a Toa Gosei Co., Ltd. instantaneous adhesive, Aron Alpha (201), The measurement is performed after being left for 24 hours in an atmosphere of 25 ° C. Although the hardness and plastic deformation rate can be measured under measurement conditions other than those described above, the hardness may vary depending on the wear state of the indenter used. Therefore, before measuring the hardness and plastic deformation rate, it is necessary to confirm that the measured value is always constant by using a material showing a certain hardness, for example, a single crystal silicon wafer. In particular, when the measurement load is other than the above, the measurement value varies even with the same sample due to the difference in the shape of the tip of the indenter. Is preferred.

The hardness is a value given by the following formula [I]. Further, the plastic deformation rate is a value given by the following formula [II].
Hardness = 3.7926 × 10 ⁻² × maximum load / (maximum displacement) ² [I]
(Hardness: kg / mm ² , maximum load: mg, maximum displacement: μm)
Plastic deformation rate = displacement after unloading / maximum displacement × 100 [II]
(Plastic deformation rate:%, displacement after unloading: μm, maximum displacement: μm)

  The transparent film for display according to the present invention having a hardness of 18 or more and a plastic deformation rate of 50% or less is a printed wiring board using, for example, HSC (heat seal connector) or ACF (anisotropic conductive film). When connected to, extremely good connection reliability can be ensured. In particular, when the transparent film for display of the present invention is applied to a liquid crystal, the amount of deformation of the substrate is reduced in the spacer disposed inside the liquid crystal panel, and a liquid crystal panel having uniform display characteristics with less spots can be obtained. It becomes possible.

Effect of the invention

  According to the present invention, by using a polycarbonate having a fluorene skeleton and molding so that the three-dimensional refractive index satisfies a specific condition, the optical isotropy and heat resistance are excellent, and the dimensional change after high-temperature heating is extremely small. In addition, it is possible to provide a transparent film capable of obtaining excellent reliability when a printed wiring board is connected using a connection material containing conductive particles such as a heat seal connector or an anisotropic conductive film.

  Such a transparent film is particularly useful for flat panel displays excellent in liquid crystal, organic EL, and other display quality such as high definition, high capacity, multi-tone, and color display.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to this Example. In the examples, parts and% are based on weight unless otherwise specified. Various measurements in the examples were performed as follows.
(1) Total light transmittance: It measured using Nippon Denshoku Industries Co., Ltd. COH-300A.

(2) Water vapor transmission coefficient: The water vapor transmission coefficient under the atmosphere of 40 ° C. and 90% RH was measured using Permatran W1A manufactured by MOCON, and the water vapor transmission coefficient was calculated from the film thickness of the sample.

(3) Retardation value, three-dimensional refractive index: The phase difference and the three-dimensional refractive index, which are the product of birefringence Δn and film thickness d of the protective film for polarizing plates, are spectroscopic ellipsometers, JASCO Corporation ) And the product name “M150” manufactured by the manufacturer. The retardation value was measured with the incident light beam and the film surface orthogonal. The three-dimensional refractive index is determined by measuring the phase difference value at each angle by changing the angle between the incident light beam having a wavelength of 550 nm and the film surface, and performing curve fitting with a known refractive index ellipsoid formula. Find nx, ny, nz which are rates,
| (Nz− (nx + ny) / 2) × 2 | was calculated.

(4) Dimensional change rate: After a size film sample having a width of 10 mm and a length of 100 mm is cut out along the flow direction (MD) and width direction (TD) of the film, and the length is accurately measured with an electronic micrometer. , Heat treatment at 150 ° C. for 2 hours and 180 ° C. for 2 hours, and precisely measure the length after standing for 1 hour or more in an environment of 25 ° C. and 50% RH, and determine the difference in length before and after heating. The value divided by the length was calculated in%.

(5) Residual solvent amount: Heated at a temperature 5 ° C. lower than the glass transition temperature of the polymer to be measured until the weight loss of the measurement sample disappeared, and the value obtained by dividing the difference from the initial sample weight by the initial sample weight. Calculated in%.

(6) Polymer molecular weight: GPC was used to measure tetrahydrofuran at a column temperature of 40 ° C. using tetrahydrofuran as a mobile phase, and polystyrene was used as a calibration curve sample to calculate the number average molecular weight.

(7) Film thickness: measured with an electronic micro manufactured by Anritsu Corporation.

(8) Glass transition temperature: Measured using “DSC2920 modulated DSC” manufactured by TA Instruments.

(9) Water absorption: Estimated from a change in weight after the film was immersed in 25 ° C. water for 24 hours by a method based on ASTM D570.

(10) Hardness measurement: The hardness of the thin film was measured using ENT-1100, an ultrafine hardness measuring device manufactured by Elionix Corporation. The measurement conditions were a maximum load of 50 mgf, a data acquisition step of 0.2 mgf, a data acquisition interval of 40 msec, a load retention time of 1 sec when the maximum load was reached, the indenter used was a triangular pyramid (115 °) with a diamond tip, and 5 consecutive times for each load It is an average when the measurement was performed, and the sample was fixed to a metal sample stand with an instant adhesive manufactured by Toa Gosei Co., Ltd., Aron Alpha (201), and allowed to stand in an atmosphere at 25 ° C. for 24 hours. To do. The hardness is a value given by the following formula [I].
Hardness = 3.7926 × 10 ⁻² × maximum load / (maximum displacement) ² [I]
(Hardness: kg / mm ² , maximum load: mg, maximum displacement: μm)
Plastic deformation rate measurement: The plastic deformation rate is the same as the hardness measurement described above, and is a value given by the following formula [II] from the displacement amount after unloading obtained by the same measurement and the maximum displacement amount.
Plastic deformation rate = displacement after unloading / maximum displacement × 100 [II]
(Plastic deformation rate:%, displacement after unloading: μm, maximum displacement: μm)

(11) ACF connection test: Using an ACF manufactured by Hitachi Chemical Co., Ltd., the transparent film for display of the present invention and a printed wiring board were connected at 150 ° C. and 30 kg / cm ² to examine the initial connection reliability. It was. Furthermore, the thermal shock test was repeated 500 times from −20 ° C. to 60 ° C., and it was examined whether or not connection failure occurred.

(12) Evaluation of surface smoothness The surface smoothness was measured using an amplification support device SE3CK manufactured by Kosaka Laboratory Co., Ltd. and an analysis device SPA-11, and the cutoff was 0.08 mm, the scanning pitch was 2 μm, and the recording pitch was 2 mm. SRa was calculated under the conditions of a measurement length of 1 mm and a scanning number of 80. Here, SRa is a three-dimensional center plane average roughness, a portion of area Sm is extracted from the roughness surface onto the center plane, and an axis orthogonal to the center plane of the extracted portion is represented by the Z axis. The value obtained in is expressed in μm.

(However, Lx x Ly = Sm)

(13) Creation of organic EL element Display electrodes were formed by photolithography on the transparent conductive layer of the transparent film for display of the present invention on which the transparent conductive layer was formed. Next, TPD (N, N′-bis (3-methylphenyl) 1,1′-biphenyl-4,4′-diamine) which is a triphenylamine derivative as a hole transport layer is formed on the transparent electrode by vacuum deposition. Next, Alq3 (tris- (8-hydroxyquinoline) aluminum) was deposited as a light emitting layer to a thickness of 50 nm. Furthermore, magnesium and silver were vapor-deposited on this to a thickness of 200 nm to form an organic EL layer as a metal electrode. Subsequently, using the same film as the display film on which the EL layer is formed before the transparent conductive layer is formed, after applying an ultraviolet curable sealant on the surface on which the transparent conductive layer is formed, Both substrates were bonded together with the organic EL surface of the above-described film on which the organic EL layer was formed facing inside, and the organic EL layer was sealed by ultraviolet irradiation. A voltage was applied to the organic EL element to confirm the presence or absence of light emission.

In addition, the following abbreviations were used for the compound names described later.
BisA: 2,2-bis (4-hydroxyphenyl) propane BCF: 9,9-bis (4-hydroxy-3-methylphenyl) fluorene IP: 3,3,5-trimethyl-1,1-di (4- Phenol) cyclohexylidene ITO: indium-tin oxide ECHETMOS: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane APTMOS: 3-aminopropyltrimethoxysilane EVOH: ethylene vinyl alcohol copolymer ("Eval" manufactured by Kuraray) ")
DCPA: dimethylol tricyclodecane diacrylate (“Kyoeisha Chemical Co., Ltd.“ Light acrylate DCP-A ”)
UA: urethane acrylate (“NK Oligo U-15HA” manufactured by Shin-Nakamura Chemical)

[Example 1]
A polycarbonate resin having a bisphenol component of BisA / BCF = 70/30 and an average molecular weight of 37,000 and a Tg of 193 ° C. was dissolved in methylene chloride so as to be 20% by weight. This solution was cast on a polyester film having a thickness of 175 μm by a die coating method. Subsequently, it dried until the residual solvent density | concentration became 13 weight% with the drying furnace, and peeled from the polyester film. Then, the balance of the residual solvent in the film is adjusted in a drying oven at a temperature of 180 ° C. so that the difference in vertical and horizontal tension is as small as possible and the balance is maintained with the minimum tension that can hold the film. Dry to 0.3 wt%.

  The properties of the transparent film thus obtained are shown in Table 1. It turned out that it is useful as a base film for a display.

[Example 2]
A display film was obtained in the same manner as in Example 1 except that a transparent film having a thickness of 120 μm made of a polycarbonate copolymer having BisA / BCF = 50/50 (molar ratio) and Tg of 211 ° C. was used. The evaluation result of the obtained film was good as shown in Table 1.

[Example 3]
A transparent film for display was prepared in the same manner as in Example 1 except that a transparent polymer film (S) having a thickness of 140 μm made of a polycarbonate copolymer having BisA / BCF = 33/67 (molar ratio) and Tg of 228 ° C. was used. Obtained. The evaluation result of the obtained film was good as shown in Table 1.

[Example 4]
One side of the polycarbonate film obtained in Example 3 was coated with a coating composition that gave a polysiloxane-based resin layer, and heat-treated at 130 ° C. for 3 minutes to form a polysiloxane-based resin layer having a thickness of 0.05 μm. . The coating composition for giving the polysiloxane resin was prepared by adding 88 parts by weight of acetic acid to a mixed solvent of 720 parts by weight of water and 1080 parts by weight of 2-propanol, and then adding 640 parts by weight of ECHETMOS and 154 parts by weight of APTMOS in order. Obtained by stirring for hours. Next, a gas barrier layer made of a SiO ₂ film having a thickness of 350 mm was laminated on the polysiloxane resin layer by sputtering.

  Furthermore, a coating composition for forming a chemical resistant layer having gas barrier properties was prepared as follows.

100 parts of EVOH was dissolved by heating in a mixed solvent of 720 parts of water and 1080 parts of n-propanol to obtain a uniform solution. To this solution, 0.1 part of leveling agent (“SH30PA” manufactured by Toray Dow Corning Co., Ltd.) and 39 parts of acetic acid were added, then 211 parts of ECHETMOS were added and stirred for 10 minutes. Further, 77 parts of APTMOS was added to this solution and stirred for 3 hours. This coating composition was coated on both sides of a polycarbonate film on which a polysiloxane resin layer and a gas barrier layer made of SiO ₂ were laminated, and heat-treated at 130 ° C. for 3 minutes, A 2 μm chemical resistant layer was formed.

Next, a film for display was obtained by forming ITO with a thickness of 120 nm on the surface opposite to the surface on which the gas barrier layer (SiO ₂ ) of the film was laminated, by sputtering. The evaluation result of the obtained film was good as shown in Table 1.

[Example 5]
A transparent film for display was obtained in the same manner as in Example 4 except that a chemical-resistant layer having a thickness of 4 μm was formed directly under ITO by the following method.

20 parts by weight of DCPA, 10 parts by weight of UA, 30 parts by weight of 1-methoxy-2-propanol, and 2 parts by weight of 1-hydroxycyclohexyl phenyl ketone as an initiator were mixed to obtain a coating composition. This composition was coated, heated at 60 ° C. for 1 minute, and then photocured using a high-pressure mercury lamp at an integrated light quantity of 700 mJ / m ² to form a cured resin layer as a chemical resistant layer.

  The evaluation results of the obtained transparent film for display were good as shown in Table 1.

[Example 6]
A gas barrier layer made of a SiO ₂ film having a thickness of 500 mm was laminated on one side of the transparent film described in Example 3 by the sputtering method under the same conditions as in Example 4, and on the gas barrier layer, Example 4 and A transparent film for display was obtained by forming ITO with a thickness of 120 nm by sputtering under the same conditions. The evaluation results of the obtained film were good as shown in Table 3.

[Example 7]
A gas barrier layer composed of a SiO ₂ film having a thickness of 500 mm was laminated on both surfaces of the transparent film described in Example 2 by sputtering under the same conditions as in Example 4, and on one surface of the gas barrier layer, A transparent film for display was obtained by forming ITO with a thickness of 120 nm by sputtering under the same conditions as in Example 4. The evaluation results of the obtained film were good as shown in Table 3.

[Example 8]
A transparent film for display was obtained in the same manner as in Example 4 except that a gas barrier layer made of a SiO ₂ film having a thickness of 500 mm was laminated by sputtering under the same conditions as in Example 4 before forming ITO. The evaluation results of the obtained film were good as shown in Table 3.

[Comparative Example 1]
A transparent film was obtained in the same manner as in Example 1 except that a polycarbonate having a Tg of 155 ° C. consisting only of BisA was used and the temperature of the drying furnace was changed to 145 ° C.
As shown in Table 2, the evaluation results of the obtained film are good in transparency, but inferior in heat resistance and optical isotropy, have a large water vapor transmission coefficient, and above all, have a large dimensional change after heating. It became.

[Comparative Example 2]
A transparent film was obtained in the same manner as in Example 1 except that a polycarbonate copolymer having a Tg of 205 ° C. composed of BisA / IP = 40/60 was used.

  As shown in Table 2, the evaluation results of the obtained film are good in heat resistance and transparency, but inferior in optical isotropy, large in water vapor transmission coefficient, and large in dimensional change after heating. .

[Comparative Example 3]
A transparent film for display was obtained in the same manner as in Example 7, except that a polycarbonate having a Tg of 155 ° C. composed only of BisA was used and the temperature of the drying furnace was changed to 145 ° C. As shown in Table 2, the evaluation result of the obtained transparent conductive substrate was good in transparency, but cracked in the transparent electrode, and the ACF connection reliability was poor from the beginning. Further, in the organic EL element lighting test, although initial light emission was recognized, lighting failure occurred after being left at room temperature for 24 hours.

[Comparative Example 4]
A transparent film for display was obtained in the same manner as in Example 7 except that a transparent film was obtained by the melt extrusion molding method. As shown in Table 2, the evaluation result of the obtained transparent conductive substrate was good in transparency, but cracked in the transparent electrode, and the ACF connection reliability was poor from the beginning. In the organic EL element lighting test, lighting failure occurred from the beginning.

Claims (14)

A transparent film formed by a solution casting method of a polycarbonate having a glass transition temperature of 170 ° C. or more having a repeating unit having a fluorene skeleton as a (copolymerization) component,
(I) The three-dimensional refractive index satisfies the following formulas (A) and (B) simultaneously,
(Ii) The dimensional change rate after heat treatment at 150 ° C. for 2 hours is 0.05% or less,
(Iii) A transparent film for display having a saturated water absorption of 0.4% or less and (iv) a water vapor transmission coefficient at 40 ° C. and 90% RH of 35 g · 100 μm / m ² / day or less.
| R (550) | ≦ 20 (nm) (A)
K = | [nz− (nx + ny) / 2] × d | ≦ 100 (nm) (B)
[In the above formula (A), R (550) is the in-plane retardation of the film with respect to light having a wavelength of 550 nm. In the above formula (B), nx, ny, and nz are x with the thickness direction of the film as the z axis. It is a three-dimensional refractive index for light having a wavelength of 550 nm in the axial, y-axis, and z-axis directions, and d is a film thickness. ]
The transparent film for display according to claim 1, wherein the surface smoothness of at least one surface is 10 nm or less in terms of SRa.
Polycarbonate is represented by the following formula (1)
[Chemical 1]

[In the above formula (1), R _{1 to} R ₈ are each independently at least one selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms. ]
A repeating unit represented by the following formula (2):
[Chemical 2]

[In the above formula (2), R _{9 to} R ₁₆ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms, and X is a hydrocarbon group having 1 to 15 carbon atoms. ]
The transparent film for a display according to claim 1 or 2 , wherein the transparent film is mainly composed of a polycarbonate composed of a repeating unit represented by the formula (1) and the repeating unit represented by the formula (1) is 10 to 90 mol% of the whole.
Repeating unit represented by formula (1) is 9,9-di (3-methyl-4-phenol) is derived from the transparent for claims 3 display according films.
The transparent film for display according to claim 3 or 4 , wherein X in the formula (2) is a 2,2-propylene group.
The transparent film for display according to any one of claims 1 to 5 , wherein a dimensional change rate after heat treatment at 180 ° C for 2 hours is 0.1% or less.
R (450) / R (550) ≦ 1.06, where R (450) is an in-plane phase difference for light having a wavelength of 450 nm and R (550) is an in-plane phase difference for light having a wavelength of 550 nm. The transparent film for display in any one of 1-6 .
The transparent film for display according to any one of claims 1 to 7 , wherein the value of K in the formula (B) is 50 nm or less.
The transparent film for display according to any one of claims 1 to 8 , wherein the amount of the solvent remaining in the transparent film is 1% by weight or less based on the total weight of the transparent film.
The transparent film for display according to claim 2 , wherein a gas barrier layer made of an inorganic material is laminated on a surface having a surface smoothness of SRa of 10 nm or less.
The transparent film for display according to any one of claims 1 to 10 , wherein a gas barrier layer and a chemical resistant layer are laminated on at least one side.
Transparent film for display according to any one of claims 1 to 11 at least one surface the transparent conductive layer are laminated.
The transparent film for display according to any one of claims 1 to 12 , which has a hardness of 18 or more and a plastic deformation rate of 50% or less when measured with an ultra-micro hardness meter.
The organic EL display device substrate or a substrate for liquid crystal display device using a transparent film of any of claims 1-13.