JPH06324310A - Liquid crystal display element and optical system - Google Patents

Abstract

PURPOSE:To improve the contrast while the luminance on a screen is maintained as it is a conventional element. CONSTITUTION:A liquid crystal layer 33 is electrically controlled into a scattering state or a transparent state. When the liquid crystal layer 33 is in a transparent state, incident light to projections 35 transmits so that the luminance of the element is same as that of a conventional liquid crystal element. On the other hand, when the liquid crystal layer 33 is in a scattering state, direction of the light incident to the projections 35 is changed by the projections 35. Thus, the scattering intensity is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for projectors and an optical system. More specifically, when a liquid crystal display element that performs display by electrically controlling a transparent state and a scattered state is used as a projector, the projector aims to enhance the effect of separating transparent light and scattered light. The present invention relates to a liquid crystal display device and an optical system. The liquid crystal display device and the optical system of the present invention can be applied to front type, rear projection, and OHP displays.

[0002]

2. Description of the Related Art As a liquid crystal display device for a projector,
A TN (twisted nematic) type liquid crystal display device has already been put to practical use. The TN type liquid crystal display element has a cell structure in which a liquid crystal layer is disposed between a pair of substrates, and it is necessary to provide a polarizing plate on the cell surface. Therefore, in this liquid crystal display element, 1/2 of the incident light is cut by the polarizing plate in principle, so that it is difficult to realize a bright and high-contrast projector.

Recently, there has been proposed a liquid crystal display element which does not require a polarizing plate and which does not require an alignment treatment on the surface of the substrate on the liquid crystal layer side, and is particularly attracting attention for a projector.

The above-mentioned proposed liquid crystal display element employs a method of electrically controlling the transparent state or scattering state (white turbid state) of the cell by utilizing the birefringence of liquid crystal molecules.
The birefringence Δn is given by n _e −n _o when the refractive index of ordinary light is n _o and the refractive index of extraordinary light is n _e . In this liquid crystal display element, the liquid crystal layer contains liquid crystal droplets composed of liquid crystal molecules and a polymer material as a support medium for the liquid crystal droplets, and is called a polymer dispersion type liquid crystal display element.

Control of the transparent state and the scattering state of the cell in such a liquid crystal display device is performed as follows. When the cell is made transparent, a voltage is applied to the liquid crystal layer to align the liquid crystal molecules. The refractive index of the liquid crystal droplets at this time is the refractive index n _o of the ordinary light of the liquid crystal molecules. As a supporting medium, if selecting a polymeric material having a normal light refractive index approximately equal to the refractive index n _o of the liquid crystal molecules,
When a voltage is applied, the refractive index of the liquid crystal droplets and the refractive index of the support medium substantially match, and the cell becomes transparent. In this way, when the cell is in the transparent state, the light that passes through the cell is hereinafter referred to as transmitted light. On the other hand, when the cell is in the scattering state, no voltage is applied to the liquid crystal layer. If no voltage is applied to the liquid crystal layer, the alignment of the liquid crystal molecules is not uniform and disturbed, and the light incident on the cell is scattered. The light scattered by the cell when the cell is in the scattered state is referred to as scattered light hereinafter.

The following methods have been proposed as a method for manufacturing a polymer dispersed liquid crystal display device. Tokusho Sho-501
Japanese Patent No. 631 discloses a method of forming liquid crystal droplets by including liquid crystal in a polymer capsule.
However, since the liquid crystal droplets thus formed are independent cells, the driving voltage required to change the alignment of the liquid crystal becomes high. Therefore, the liquid crystal display device obtained by this method has a narrow application range.

In Japanese Patent Publication No. 61-502128, etc.,
There is disclosed a method of forming a liquid crystal droplet in a resin by precipitating the liquid crystal by curing the resin in a mixture of the liquid crystal and a photocurable resin or a thermosetting resin.

In the case of the liquid crystal display element by any of the above methods, if the driving voltage is set to 5 V or less in accordance with the withstand voltage of the current IC, the liquid crystal droplet must be large. As a result, there is a problem that the scattering intensity of the cell is lowered when no voltage is applied.

To solve this problem, birefringence Δ
A liquid crystal material having a large n may be selected. However, considering the physical properties of the liquid crystal material comprehensively, the selectable birefringence Δn
There is a limit to the value of.

As a liquid crystal display device with further improved responsiveness, a device having a polymer dispersion layer and a liquid crystal layer between transparent electrode substrates has been reported on page 306 of the 17th liquid crystal debate. However, when this liquid crystal display device is used in a projector, it is equivalent to the conventional polymer dispersed liquid crystal display device in terms of function, particularly in terms of the contrast of the image projected on the screen, and no improvement can be seen. I can't.

When the transparent-scattering control type liquid crystal display device is used in a projector, it is necessary to efficiently separate scattered light and transmitted light from the viewpoint of improving contrast. Therefore, the Schlieren optical system shown in FIG. 4 is used.

As shown in FIG. 4, this Schlieren optical system includes a light source 1, a lens 2 for making the light from the light source 1 parallel light, and the liquid crystal display element on which the parallel light from the lens 2 is incident. 3, a lens 4 for converging light from the liquid crystal display element 3, a schlieren diaphragm 5 having an opening 5a near the focal point of the lens 4, and light passing through the opening 5a of the schlieren diaphragm 5 on the screen 7. And a projection lens 6 for projecting.

In the Schlieren optical system having the above structure, the light from the liquid crystal display element 3 is focused by the lens 4, and the focused light is applied to the Schlieren diaphragm 5 arranged at the minimum diameter. . The light from the liquid crystal display element 3 includes the scattered light and the transmitted light described above. The transmitted light is
Since the light is emitted from the liquid crystal display element in parallel with the optical axis 8 of this optical system, it can pass through the opening 5a of the schlieren diaphragm 5. On the other hand, most of the components of the scattered light have an angle with respect to the optical axis 8. The component having an angle with respect to the optical axis 8 is not condensed by the lens 4 at the opening 5 a of the Schlieren diaphragm 5 and cannot pass through the Schlieren diaphragm 5. As a result, the scattered light and the transmitted light are separated by the Schlieren diaphragm 5.

A schlieren optical system projector using the above polymer dispersed liquid crystal display element has a brightness twice as high as that of a conventional projector in principle. ing. Here, the reason why the brightness is expected to be doubled will be described. The liquid crystal display element used in the conventional projector is an element that requires a polarizing plate. Of the incident light, the polarizing plate
Only the linearly polarized light component in one direction is transmitted, and the linearly polarized light component in the direction orthogonal to that direction is blocked. Therefore, the light actually contributing to the display is half of the light emitted to the liquid crystal display element. On the other hand, the polymer dispersion type liquid crystal display device described above does not require a polarizing plate. Therefore, all the light emitted to the liquid crystal display element can be used for display. As a result, it is expected that the projector using the polymer-dispersed liquid crystal display device will have twice the brightness as the conventional projector.

[0015]

Since the conventional transparent-scattering control type liquid crystal display device has a low scattering intensity as described above, even in the scattered state, the straight-traveling light of the scattered light passing through the cell, that is, The intensity of light parallel to the optical axis 8 is strongest. As described above, the Schlieren optical system can remove light that is not parallel to the optical axis 8 but cannot remove straight-ahead light, so that there is light that passes through the opening 5a even in a scattered state. As a result, the contrast between the transmission state and the scattering state cannot be sufficiently increased.

In order to increase the contrast, it can be considered to reduce the area of the opening 5a of the schlieren diaphragm 5. In this case, the scattered light is sufficiently removed,
Volatility decreases for the following reasons.

When the light source 1 is a point having no area,
Since all the transmitted light passes through the focal point of the lens 4, the opening 5
Even when the area of a is reduced, it can pass through the opening 5a of the schlieren diaphragm 5 and does not affect the volatility on the screen 7. However, since the light source 1 actually has a finite size, if the aperture 5a is made smaller than the image of the light source 1 which can be located at the position of the Schlieren diaphragm 5, the aperture 5 is originally formed.
Some of the transmitted light that should pass through a cannot pass through. As a result, the brightness on the screen 7 is greatly reduced,
The advantage that high brightness can be expected without using a polarizing plate cannot be obtained.

The problem of contrast and the problem of volatility are in a trade-off relationship. In order to solve this trade-off relationship between contrast and brightness, it is conceivable to reduce the size of the bright spot of the light source 1 and to improve the scattering intensity of the liquid crystal display element 3.
However, reducing the size of the bright spots of the light source 1 shortens the life of the light source 1, and therefore its development is extremely difficult. Further, to improve the scattering intensity of the liquid crystal display element 3 with the conventional structure, that is, to improve the contrast, the scattering intensity depends on the birefringence Δn of the liquid crystal material.
It is not practical because it is almost decided by the size of.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and a liquid crystal display device for a projector and an optical system capable of improving the contrast while keeping the brightness on the screen as it is. The purpose is to provide.

[0020]

A liquid crystal display device of the present invention is arranged between two substrates, at least one of which is transparent, and is electrically disposed between a scattering state and a transparent state. The liquid crystal layer to be controlled and the light transmitted through the liquid crystal layer are incident, the light incident when the liquid crystal layer is in the transparent state is directly transmitted, and the traveling direction of the light incident when the liquid crystal layer is in the scattered state is changed. And a changing means for changing the same, thereby achieving the above object.

The changing means is a refraction means formed on one of the two substrates, and the refraction means forms an angle with respect to a plane whose normal direction is the traveling direction of the incident light beam. The liquid crystal layer may be made of a transparent solid substance having a surface having a refractive index substantially equal to the refractive index of the liquid crystal layer when the liquid crystal layer is in a transparent state.

The refractive index of the refraction means is (n _e + n _o ) / 2, where n _e is the refractive index of extraordinary light and n _o is the refractive index of ordinary light of the liquid crystal layer, and Refractive index (n _e +2
It may have a difference of at least 0.05 from the refractive index of any of n _o ) / 3.

The refracting means may be formed in units of picture elements.

The surface of the refracting means that has an angle with respect to a plane whose normal direction is the traveling direction of the incident light beam may have an angle equal to or greater than the total reflection angle that reflects all the incident light.

The liquid crystal layer side surface of at least one of the two substrates may be subjected to an alignment treatment.

A polarizing plate is provided on the outer surface of at least one of the two substrates, and the polarization axis of the polarizing plate is perpendicular to the alignment direction of the major axis of liquid crystal molecules constituting the liquid crystal layer. It may match the direction.

The optical system of the present invention comprises two substrates, at least one of which is transparent, and a liquid crystal layer which is disposed between the two substrates and whose scattering state and transparent state are electrically controlled. The light transmitted through the liquid crystal layer is incident, the light incident when the liquid crystal layer is in the transparent state is transmitted as it is, and the changing means that changes the traveling direction of the light incident when the liquid crystal layer is in the scattering state is provided. Among the light emitted from the liquid crystal display element, the light source for illuminating the liquid crystal display element, and the light source, when the liquid crystal layer is in a transparent state, light that passes through the liquid crystal display element is allowed to pass through, and the liquid crystal layer is It has a separating means for blocking the light that passes through the liquid crystal display element in the scattering state, and thereby achieves the above object.

[0028]

In the liquid crystal display element of the present invention, the scattering state and the transparent state in the liquid crystal layer are electrically controlled. When the liquid crystal layer is in the transparent state, the light incident on the changing means from the liquid crystal layer is
Since the light is transmitted as it is, the brightness is the same as that of the conventional liquid crystal display element. On the other hand, when the liquid crystal layer is in the scattering state, the light incident on the changing means from the liquid crystal layer has its traveling direction changed by the changing means, so that the scattering intensity is improved. As a result, when the liquid crystal display device of the present invention is used in a projector, the contrast on the screen is improved.

[0029]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1 shows a sectional view of a liquid crystal display device which is one embodiment of the present invention. 1A shows a liquid crystal display element when no voltage is applied, and FIG. 1B shows a liquid crystal display element when voltage is applied.

This liquid crystal display device has a pixel electrode substrate 31.
And a counter electrode substrate 32 arranged to face the pixel electrode substrate 31, and a liquid crystal layer 33 sealed between the pixel electrode substrate 31 and the counter electrode substrate 32. The pixel electrode substrate 31 includes a substrate 36 having a protrusion 35 formed on the counter electrode substrate 32 side, and a plurality of pixel electrodes 37 formed so as to cover the surface of the protrusion 35. Counter electrode substrate 32
Includes a flat substrate 38 and a counter electrode 39 formed so as to cover the entire surface of the substrate 38 on the pixel electrode substrate 31 side. For the liquid crystal layer 33, a polymer dispersed liquid crystal material in which liquid crystal droplets 34 are dispersed in a polymer is used.

FIG. 2 shows the pixel electrode substrate 31. Figure 2
2A is a sectional view of the pixel electrode substrate 31, and FIG.
Is a plan view. As shown in the figure, the protrusion 35 has a saw-like cross section having a constant angle with respect to a plane whose normal direction is the traveling direction of the incident light L, and has a linear structure.

On the other hand, with respect to the inclined surface of the projection 35 on the pixel electrode substrate 31, the liquid crystal molecules in the liquid crystal droplets near the surface of the projection 35 in the liquid crystal layer 33 are aligned, for example, horizontally. To do. In addition, the refractive index n of the normal light of this liquid crystal molecule is
_{The o} and the refractive index n _p of the protrusion 35 are set to be substantially equal.

Light is incident on the liquid crystal display element from the counter electrode substrate 32 side. When light is incident from the pixel electrode substrate 31 side, a protrusion may be formed on the counter electrode substrate 32 side.

The operation principle of the liquid crystal display device having the above structure will be described.

The transparent state and the scattered state in the liquid crystal layer 33 are controlled by applying / not applying a voltage to the liquid crystal layer 33 by the picture element electrode 37 and the counter electrode 39.
That is, when the liquid crystal layer 33 is in the transparent state, the liquid crystal layer 3
By applying a voltage to the liquid crystal molecules 3, the liquid crystal molecules are aligned so that the traveling direction of the incident light L and the long axis direction of the liquid crystal molecules in the liquid crystal droplets 34 coincide with each other, as shown in FIG. As a result, the incident light L passes through this liquid crystal display element. on the other hand,
When bringing the liquid crystal layer 33 into the scattering state, no voltage is applied to the liquid crystal layer 33. In this case, as shown in FIG. 1A, the liquid crystal molecules in the liquid crystal droplet 34 near the surface of the protrusion 35 are aligned perpendicular to the traveling direction of the incident light L, and the liquid crystal of the other portion is aligned. The liquid crystal molecules in the droplet 34 are randomly oriented. As a result, the incident light L is scattered by the liquid crystal molecules.

The operation of the projection 35 in the transparent state and the scattering state will be described.

In order to make the liquid crystal layer 33 transparent, the liquid crystal layer 3
When a voltage is applied to the liquid crystal molecules 3, the liquid crystal molecules in the liquid crystal droplets 34 are aligned parallel to the incident light L, as described above. The refractive index of the liquid crystal layer 33 at this time, since substantially equal to the refractive index n _o of the ordinary light of the liquid crystal molecules, and the refractive index n _p of the protrusions 35 of the picture element electrode substrate 31 substantially coincides, the liquid crystal layer 33 Protrusion 3
This is equal to the state in which there is no slope between the liquid crystal layer 33 and the liquid crystal layer 33, and the transmitted light of the liquid crystal layer 33 passes through the pixel electrode substrate 31. Since the refraction at the interface between the liquid crystal layer 33 and the pixel electrode 37 is canceled by the refraction at the interface between the pixel electrode 37 and the protrusion 35, the refractive index of the pixel electrode 37 can be freely selected. it can.

On the other hand, if a voltage is not applied to the liquid crystal layer 33 in order to bring the liquid crystal layer 33 into the scattering state, the liquid crystal molecules in the liquid crystal droplets 34 remain in the alignment state shown in FIG. Is. At this time, the liquid crystal layer 33 has a refractive index
Usually refractive index of the liquid crystal molecules in n _o and the extraordinary light refractive index n _e
And (n _e + n _o ) / 2, which is the average value of Therefore, since the refractive index of the liquid crystal layer 33 and the refractive index n _p of the protrusions 35 do not match, the liquid crystal layer 33 which is the incident light at this time.
The scattered light of is refracted at the slope between the liquid crystal layer 33 and the protrusion 35. As a result, the proportion of straight-ahead light in the scattered light is reduced, and the scattering intensity of the liquid crystal display element is improved.

The alignment state of the liquid crystal molecules of the liquid crystal layer 33 when no voltage is applied is not limited to the alignment state shown in FIG. 1 (a) but may be a random alignment state. In this case, the liquid crystal layer 33 has a refractive index of (n _e + 2n _o ) / 3. In any case, the difference between the refractive index and the refractive index n _p of the protrusion 35 is preferably 0.05 or more. When the difference in refractive index is less than 0.05, the liquid crystal layer 3 is in the scattering state.
The scattered light is not sufficiently refracted at the slope between the projection 3 and the projection 35, and the effect of improving the scattering intensity cannot be sufficiently obtained.

As a report utilizing such a principle, Japanese Patent Laid-Open Nos. 62-194223 and 3-6518 are available.
In the publication, there is reported a liquid crystal lens in which one of the substrates of the liquid crystal cell is a Fresnel lens. However, these reports are aimed at electrically changing the focal length of the lens, and do not change the traveling direction of the light ray for each picture element.

Hereinafter, modified examples of each part applied to this embodiment will be described.

The liquid crystal material used for the liquid crystal layer 33 is preferably a liquid crystal material having a large birefringence Δn in order to increase the scattering intensity in the scattering state, and nematic, cholesteric, ferroelectric liquid crystal material, two-frequency driving liquid crystal material and the like. Can be used.
Specifically, E8 and E7 (both manufactured by Merck), which are liquid crystal materials having a CN group at a molecular terminal, and chemically stable F
-Based or Cl-based liquid crystal material, ZLI-4792, ZLI
-4801-000, and ZLI-4801-001
(Both manufactured by Merck).

Regarding the substrate on which the protrusion is formed, that is, the pixel electrode substrate 31 in the above embodiment, the interface with the liquid crystal layer 33 forms an angle with respect to the plane whose normal direction is the traveling direction of the incident light L. Any curved surface or plane having The angle of these surfaces may be any angle at which the straight light is refracted by 5 degrees or more on the slope between the liquid crystal layer 33 and the protrusions 35 when the liquid crystal layer 33 is in the scattering state, and total reflection of light rays is possible. When the angle is larger than the angle, all the light is completely refracted, so that the contrast is increased without lowering the brightness, which is more preferable. If the angle of refraction of the straight light is less than 5 degrees, the effect of improving the contrast is not sufficient.

3 (a) to 3 (d) show examples of the cross-sectional shape of the substrate on the side where the projections applicable to this embodiment are formed.

In the above-described embodiment, as shown in FIG. 3A, the projection 3 integrally formed with the substrate 36 and having a saw-shaped cross section.
5 and the picture element electrode 37 formed on the protrusion 35 by coating.
The picture element electrode substrate 31 having In addition, as shown in FIG. 3B, a flat substrate 36b, a pixel electrode 37b formed on the substrate 36b, and a protrusion having a saw-shaped cross section formed on the pixel electrode 37b. You may use the pixel electrode board | substrate 31b which has 35b.

In addition to the protrusion having a saw-like cross section, FIG.
As shown in (c) and FIG. 3 (d), it may be a protrusion having a roof-shaped cross section. The protrusions shown in FIG.
a protrusion 35c having a roof-shaped cross section integrally formed with c,
It has a picture element electrode 37c formed on the projection 35c. The protrusion shown in FIG. 3D is a flat substrate 36.
d and the pixel electrode 37d formed on the substrate 36d
And a projection 35d having a roof-shaped cross section formed on the pixel electrode 37d.

Further, not only when the cross section of the projection in one direction is a saw-like cross section or a roof cross section, for example, one unit of the projection pattern may be a conical shape. It is preferable that the pattern of the protrusions is made to coincide with one unit of the pixel electrode, and the portion where the inclination angle of the slope changes is located outside the opening of the pixel. By doing so, it is possible to prevent the incident light from being scattered at the portion where the inclination angle of the slope changes and affecting the transmitted light.

In the above description, the projection is formed on the pixel electrode substrate side. When the projection is formed on the counter electrode substrate side, the pixel electrode 37,
37b, 37c, 37d are replaced with counter electrodes.

Regarding the transparent solid substance used for the protrusions, those having a refractive index of about 1.5 include styrene, polymethylmethacrylate, PVA, polycarbonate, cured products of acrylic acid derivatives, epoxy resins, silicone resins, And compounds such as urethane resin can be used. As the resin material having a refractive index of 1.5 or more, a resin material containing S element can be used.

As a method for producing the protrusions, the following methods can be mentioned.

A method for producing a substrate having protrusions by pouring (press-fitting) molten plastic into the protrusion mold having the shape to be produced, and cooling the protrusion protrusion mold having the shape to be produced with a compound such as an adhesive. To form a soft resin layer on the substrate, and then to form protrusions by pressing a mold against the resin layer, and to form a soft resin layer on the substrate. A method of applying a rubbing treatment to the resin layer to form protrusions can be used.

Japanese Patent Laid-Open No. 4-273213 discloses a liquid crystal optical element in which a sawtoothed transparent solid is placed on a substrate to electrically control refraction / transmission of incident light. Since this liquid crystal optical element does not intentionally manipulate the orientation of liquid crystal molecules, it has a structure in which liquid crystal domains exist in random directions. Considering each domain, the liquid crystal molecules in the domain face in one direction. Therefore, if the domain is not sufficiently small with respect to the wavelength of the incident light, the incident light is scattered in the direction in which each domain is difficult to pass, and passes only in the direction in which it is easy to pass. That is, when the incident light is viewed for each linearly polarized light component, one polarized light component is refracted on the slope of the transparent solid by the action of the extraordinary light refractive index n _e of the liquid crystal molecule, and the other polarized light component is the normal light refractive index of the liquid crystal molecule. would it passes through the element by the action of n _o. As a result, the scattering efficiency is halved,
When used as a display element, the contrast is not sufficient.

The following two methods can be considered for such a problem.

As the first method, there is a method of cutting the polarized light passing through the device with a polarizing plate. In this method, a polarizing plate is provided on the outside of at least one substrate of the device. At this time, the polarization axis direction of the polarizing plate is set to be perpendicular to the alignment direction of the long axis of the liquid crystal molecules when no voltage is applied.

A second method is to improve the light bending effect by using a transparent-scattering control type liquid crystal material as a liquid crystal layer together with a transparent solid slope structure.

The transparent-scattering control type liquid crystal material used in the second method may be any one which can electrically control the transparent state and the scattering state. Specifically, the liquid crystal material is a polymer. The dispersed polymer-dispersed liquid crystal material is preferable from the viewpoint that a polarizing plate is not required when used in a projector. The transparent-scattering control type liquid crystal material may be used in combination with a normal liquid crystal material. In that case, the layer made of a normal liquid crystal material should be on the protrusion side.

The polymer-dispersed liquid crystal material may be a material obtained by a conventional method, and as an example of a method for producing the polymer-dispersed liquid crystal material, the method disclosed in Japanese Patent Publication No. 58-501631 mentioned above, And Special Table Sho 61-5021
In addition to the method disclosed in Japanese Patent No. 28, etc., the following method can be mentioned.

A liquid crystal material, a polymer material, and a mixture of solvents common to both materials disclosed in JP-A-59-226322 and JP-A-1-250925 are used on a pixel electrode substrate or A method in which a liquid crystal material and a polymer material are phase-separated into a polymer dispersion-type material by evaporating a solvent after coating on a counter electrode substrate, and a fibrous polymer material or beads in the liquid crystal material. A method of suspending a polymer to obtain a polymer-dispersed material.

The following method may be mentioned as a method for producing the cell.

First, on the counter electrode substrate 32 having the counter electrode 39, a transparent-scattering control layer made of a polymer dispersed liquid crystal element thinner than the entire cell thickness is formed in advance, and then the pixel electrode having the protrusions 35. The substrate 31 is bonded to the counter electrode substrate 32 with a spacer (not shown) interposed therebetween to form a cell structure. After that, the transparent-scattering control layer 34
A liquid crystal material to be a liquid crystal layer is poured between the substrate and the pixel electrode substrate 31 to form a cell. After forming a thin film containing a polymerization initiator on a counter electrode substrate 32 having a counter electrode 39, a pixel electrode substrate 31 having protrusions 35 is attached with a spacer (not shown) interposed between the counter electrode substrate 32 and the counter electrode substrate 32. Combined into a cell structure. After that, a mixture of the liquid crystal material and the resin material is injected between the pixel electrode substrate 31 and the counter electrode substrate 32, and the resin component is polymerized from the direction of the counter electrode substrate 32, so that the liquid crystal droplets and the polymer material. And are phase-separated to form a transparent-scattering control layer, and a liquid crystal layer is formed near the protrusion 35.

Counter Electrode Substrate 3 Having Counter Electrode 39
2 and the pixel electrode substrate 31 having the protrusions 35 are bonded in advance with a spacer (not shown) interposed therebetween to form a cell structure. After injecting a mixture of a liquid crystal material, a polymerizable resin material, and a polymerization initiator into this cell, the counter electrode substrate 3
By curing the polymerizable resin material from the 2 side, the liquid crystal droplets and the polymer material are phase-separated to form the transparent-scattering control layer, and the liquid crystal layer is formed near the protrusions 35.

Counter Electrode Substrate 3 Having Counter Electrode 39
2 and the pixel electrode substrate 31 having the protrusions 35,
After a fibrous or bead-shaped polymer material to be the polymer material 41 is put in advance, both substrates 31 and 32 are bonded together with a spacer (not shown) interposed therebetween. After that, both boards 3
A liquid crystal droplet and a liquid crystal material to be a liquid crystal layer are injected between 1 and 32.

The driving method of the liquid crystal display device of the present invention may be a simple matrix system, an active matrix system using a thin film transistor (TFT) device, a metal-insulator-metal (MIM) device, etc., depending on the application. It is not particularly limited.

A case where such a liquid crystal display device is used in a projector of the Schlieren optical system shown in FIG. 4 will be described.

When the liquid crystal layer 33 of the liquid crystal display element is in a transparent state, as described above, the liquid crystal layer 33 and the protrusions 35 are formed.
Equivalent to the absence of a slope between and. Therefore,
The transmitted light passes through the opening 5a of the schlieren diaphragm 5,
Its strength is almost conventional. On the other hand, when the liquid crystal layer 33 is in the scattering state, as described above, the scattered light is refracted at the slope between the liquid crystal layer 33 and the protrusion 35, and the traveling method is distorted. Therefore, of the scattered light, the light parallel to the optical axis 8 is reduced, and the intensity of the light passing through the opening 5a of the schlieren diaphragm 5 is reduced. As a result, a very high contrast is obtained on the screen 7.

When a transparent-scattering control type liquid crystal material is used for the liquid crystal layer 33, since the brightness is maintained as it is, the brightness is high in addition to the high contrast, which is an advantage of not using a polarizing plate. A projected image is obtained.

Specific examples of the present invention will be shown below, but the present invention is not limited thereto.

<First Embodiment> As the counter electrode substrate 32,
Glass with ITO (a mixture of indium oxide and tin oxide) serving as the counter electrode 39 (made by Nippon Sheet Glass: thickness 5)
Using a 00 angstrom ITO flint glass substrate, and as the pixel electrode substrate 31, the linear projections 35 (width in the slope direction × height of 2 μm × 6 μ) shown in FIG.
A substrate provided with ITO serving as the pixel electrode 37 on PMMA (polymethylmethacrylate) having m) on the surface was used. The ITO surfaces of both substrates 31 and 32 were subjected to orientation treatment by randomly rubbing with a nylon cloth. Both the substrates 31 and 32 that have been subjected to the alignment treatment are placed as spacers with the side on which the ITO is formed facing inward.
μm plastic beads (made by Sekisui Fine Chemical:
A cell was created by bonding with micro pearls).

BL0, which is a liquid crystal material, is placed in the prepared cell.
01 (manufactured by Merck & Co., Inc.: Normal refractive index of the light n _o = 1.521,
Refractive index of extraordinary light n _e = 1.746) 4 g, bifunctional acrylate R684 (manufactured by Nippon Kayaku Co., Ltd.) 0.2
A mixture of 0.8 g of LA, which is n-lauryl acrylate (Shin Nakamura Chemical Co., Ltd.), and 0.015 g of a photopolymerization initiator is injected. The photocurable compound (R684 and n-lauryl acrylate) was solidified by irradiating with ultraviolet light having an intensity of 45 mW / cm ² (measured at a wavelength of 365 nm) using a high pressure mercury lamp in a state where this mixture was made uniform. Then, a polymer dispersed liquid crystal display device of this example was prepared.

The inclination angle of the projection 35 of this embodiment is 72 degrees. Since the liquid crystal material in this embodiment when no voltage is applied has a random orientation, the refractive index as a whole is (n _e + 2n _o ).
/3=1.596. On the other hand, the refractive index n _p of the material of the protrusion 35, n _p = 1.49. From the total reflection condition given by the following equation, the critical angle i _{c of} total reflection is 6
Since it is 6 degrees, the inclination angle of the protrusion 35 satisfies the condition of total reflection.

[0072]

[Equation 1]

<First Comparative Example> In place of the pixel electrode substrate 31 having the protrusions 35 of the first embodiment, a flat substrate with ITO similar to the counter electrode substrate 32 is used, and the same procedure as in the first embodiment is performed. A polymer dispersed liquid crystal display device having a cell thickness of 12 μm was prepared.

<Second Embodiment> The pixel electrode substrate 31 having the protrusions 35 of the first embodiment was rubbed with a nylon cloth in the groove direction of the protrusions 35. Using the pixel electrode substrate 31 and the counter electrode substrate 32 that have been subjected to this rubbing treatment, a cell was created in the same manner as in the first embodiment, and then the same liquid crystal material as in the first embodiment was injected. A liquid crystal display device was completed by bonding a polarizing plate on the outer surface of the prepared cell so that the polarization axis was aligned with the direction perpendicular to the groove direction of the protrusion 35.

The liquid crystal display elements of the first embodiment, the first comparative example, and the second embodiment are used in the Schlieren optical system (converging angle 6 °) shown in FIG. An experiment was conducted. Table 1 shows the voltage applied (20V, 60
Hz rectangular wave) and the results of measuring the luminance on the screen 7 when no voltage is applied. In the optical system, a metal halide lamp having a light source 1 of 150 W and an arc length of 5 mm was used.

[0076]

[Table 1]

As can be seen from Table 1, the liquid crystal display element of the first example has a smaller luminance when no voltage is applied, that is, in the scattering state, as compared with the first comparative example. In the liquid crystal display element of the second embodiment, the brightness when voltage is applied is slightly reduced by providing the polarizing plate, but the brightness when no voltage is applied is
It was drastically reduced as compared with the comparative example.

<Third Example> First, 0.7 g of a liquid crystal material (E8 manufactured by Merck & Co.) and PMMA (manufactured by Asahi Kasei Kogyo KK:
Delpet) (0.3 g) was mixed with chloroform to prepare a solution having a uniform solute concentration of 15 wt%. This uniform solution is applied to the counter electrode substrate 3 using an applicator.
2 glass with ITO (Nippon Sheet Glass: film thickness 50
It was coated on a 0 angstrom ITO flint glass substrate to have a thickness of 9 μm after removing the solvent.

Next, a liquid crystal material (manufactured by Merck & Co., Inc.) was placed on a PMMA substrate (2 mm thick) serving as a pixel electrode substrate 31 provided with ITO having a sectional shape similar to that of the protrusions 35 of the first embodiment. : E8) was applied by spin coating.

Finally, the counter electrode substrate 32 and the pixel electrode substrate 31 were bonded to each other with a fiber having a diameter of 8 μm serving as a spacer interposed therebetween to produce a liquid crystal display element. The liquid crystal layer 33 of the liquid crystal display element of this embodiment has a two-layer structure including a layer made of a transparent-scattering control type liquid crystal material (polymer dispersion type liquid crystal material) and a layer made of a normal liquid crystal material. .

<Second Comparative Example> In place of the picture element electrode substrate 31 having the protrusions 35 of the third embodiment, a flat substrate with ITO similar to the counter electrode substrate 32 is used in the same manner as in the third embodiment. By the solvent removal method, a liquid crystal display element having a cell thickness of 12 μm in which the entire liquid crystal layer 33 is a polymer dispersed liquid crystal material was prepared.

The liquid crystal display elements of the third embodiment and the second comparative example were used in the Schlieren optical system (convergence angle 6 °) shown in FIG. 4 to carry out a projection experiment on the screen 7. The optical system has a light source 1 of 150 W and an arc length of 5 m.
m metal halide lamp was used.

Table 2 shows the results of measuring the contrast and the brightness on the screen 7 when a voltage is applied. The contrast is defined by the ratio K _sat / K _o between the brightness K _sat on the screen 7 when a saturation voltage (30 V) is applied and the brightness K _o on the screen 7 when no voltage is applied.

[0084]

[Table 2]

As can be seen from Table 2, the liquid crystal display element of the third embodiment and the liquid crystal display element of the second comparative example do not differ much in luminance when a voltage is applied, but the contrast is the same as that of the liquid crystal display of the third embodiment. The display element is superior.

[0086]

As is apparent from the above description, according to the liquid crystal display element and the optical system of the present invention, when used in a projector, the brightness on the screen remains the same as before.
Since the contrast can be improved, it can be used even in a bright room.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an outline of a liquid crystal display element of the present invention, (a) shows a state when no voltage is applied, and (b) shows a state when voltage is applied.

2 shows a pixel electrode substrate of the liquid crystal display element shown in FIG. 1, (a) is a cross-sectional view, and (b) is a plan view.

FIG. 3 is a representative cross-sectional view of a substrate having protrusions that can be used in the present invention.

FIG. 4 is a schematic diagram of a Schlieren optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 lens 3 liquid crystal display element 4 lens 5 Schlieren diaphragm 5a opening 6 projection lens 7 screen 8 optical axis 31 picture element electrode substrate 32 counter electrode substrate 33 liquid crystal layer 34 liquid crystal droplet 35 protrusion 36 substrate 37 picture element electrode 38 substrate 39 Counter electrode L incident light

Claims (8)

[Claims] 1. Two substrates, at least one of which is transparent, a liquid crystal layer disposed between the two substrates and electrically controlling a scattering state and a transparent state, and a liquid crystal layer transmitting the liquid crystal layer. The liquid crystal display device is provided with a changing unit that allows incident light when the liquid crystal layer is in a transparent state to be transmitted therethrough and changes the traveling direction of the incident light when the liquid crystal layer is in a scattering state. 2. The changing means is a refraction means formed on one of the two substrates, and the refraction means comprises:
A transparent solid having a surface having an angle with respect to a plane whose normal direction is the traveling direction of the incident light and having a refractive index substantially equal to the refractive index of the liquid crystal layer when the liquid crystal layer is in a transparent state. The liquid crystal display element according to claim 1, which is made of a substance. 3. The refractive index of the refraction means is (n _e + n _o ) / 2, where n _e is the refractive index of extraordinary light and n _o is the refractive index of ordinary light of the liquid crystal layer. , And the refractive index (n _e +
3. The liquid crystal display device according to claim 2, which has a difference of at least 0.05 with respect to the refractive index of any of _2no ) / 3. 4. The liquid crystal display device according to claim 2, wherein the refraction means is formed in pixel units. 5. The surface of the refracting means having an angle with respect to a plane whose normal direction is the traveling direction of the incident light has an angle of not less than a total reflection angle for reflecting all the incident light.
The liquid crystal display element described. 6. The liquid crystal display element according to claim 1, wherein at least one of the two substrates has a liquid crystal layer side surface subjected to an alignment treatment. 7. A polarizing plate is provided on the outer surface of at least one of the two substrates, and the direction of the polarizing axis of the polarizing plate is the major axis alignment direction of the liquid crystal molecules constituting the liquid crystal layer. 7. The liquid crystal display element according to claim 6, which is perpendicular to. 8. Two substrates, at least one of which is transparent, a liquid crystal layer disposed between the two substrates and electrically controlling a scattering state and a transparent state, and a liquid crystal layer which transmits the liquid crystal layer. A liquid crystal display element provided with a changing means for transmitting incident light when the liquid crystal layer is in a transparent state and transmitting the incident light as it is, and changing the traveling direction of the incident light when the liquid crystal layer is in a scattering state. Of the light source for illuminating the liquid crystal display element and the light emitted from the light source, the light passing through the liquid crystal display element is passed when the liquid crystal layer is in the transparent state, and the light is transmitted when the liquid crystal layer is in the scattering state. An optical system having a separating means for blocking light transmitted through a liquid crystal display element.