JPH0695097A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which can simultaneously improve the contrast and brightness on the screen of a liquid crystal display cell without using a diaphragm of Schlieren system. CONSTITUTION:This liquid crystal display device is constituted to include the liquid crystal cell 1 having a high polymer dispersion type liquid crystal display element which is formed by dispersing liquid crystals into the high polymer sealed between electrodes and is electrically controlled in a scattering state and a transparent state and a light control plate 3 which is mounted to the liquid crystal cell 1 and allows the transmission of light in such a manner that the transmission intensity of light in the case of 30 deg. incident angle of light attains <=80% transmission intensity of the light in the case of 0 deg. incident angle.

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, and more particularly to a liquid crystal display device including a liquid crystal cell having a polymer dispersed liquid crystal element and a light control plate for transmitting light.

[0002]

2. Description of the Related Art As a liquid crystal element for electrically controlling a scattering state and a transparent state, a dynamic scattering (DS) effect and a phase transfer (PC) are used.
The effect is known. Recently, a method of electrically controlling a transparent or cloudy state by utilizing the birefringence of a liquid crystal has been proposed as a method that does not require a polarizing plate and does not require an alignment treatment. It is attracting attention for use.

In this method, basically, when a voltage is applied to align the liquid crystals, the ordinary refractive index of the liquid crystal molecules and the refractive index of the supporting medium (polymer) are matched to display a transparent state,
When no voltage is applied, the light scattering state due to the disordered orientation of the liquid crystal molecules is used for display.

As a proposal, there is a special table Sho 58-5.
[0163] Although a method in which a liquid crystal is included in a polymer capsule is disclosed in JP-A-2004-26498, since the liquid crystal droplets are independent cells, the driving voltage causing a change in the liquid crystal alignment is high and the application range is narrow.

Further, Japanese Patent Publication No. 61-502128 discloses a method in which liquid crystal is mixed with a light or thermosetting resin and the resin is cured to precipitate the liquid crystal to form liquid crystal droplets in the resin.

In any of the 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 droplets must be made large, and the scattering intensity when no voltage is applied has a drawback. In order to solve this, it has been considered to increase the birefringence (Δn) depending on the electric field of the liquid crystal material, but there is a limit when considering the overall physical properties of the liquid crystal material.

When a liquid crystal element that electrically controls the scattering state and the transparent state is used as a projector, it is necessary to efficiently separate the scattering state and the transparent state. Therefore, the light passing through the liquid crystal cell is lensed. A Schlieren optical system has been used in which a diaphragm is installed at a position where the diameter becomes the smallest and a scattered light and a transmitted light are separated. Projector combining the above liquid crystal element and Schlieren optical system
Is, in principle, 2 because a polarizing plate is not used for the liquid crystal element.
It is expected that doubled brightness can be obtained brightly, and it is regarded as promising.

Further, when a liquid crystal display panel of DS (dynamic scattering) mode is used for a projector, by installing a fiber plate from the light source side to the opposite side, the light scattered by the cell is JP-A-56-155924 discloses that the contrast is improved by efficiently blocking the light.

However, the fiber plate is a bundle of circular fibers, a dead space is formed between these aggregates, and the total light transmittance is only 50 to 70%. However, the effect of improving the contrast is great, but there is a drawback that the overall transmittance is lowered.

[0010]

In a Schlieren optical system when a conventional transparent-scattering control type liquid crystal display element is used in a projector, since the light source has a finite size, the aperture is reduced. If the aperture is smaller than the image of the light source formed at the aperture position, the brightness on the screen is greatly reduced, and the feature that high brightness can be expected is destroyed without using a polarizing plate.

Further, when the aperture is widened, the transparent-scattering control type liquid crystal display element has a low scattering intensity, so that the contrast on the screen is lowered.

In order to solve the relationship between the contrast and the brightness in the trade-off, it is conceivable to reduce the size of the bright spot of the light source and improve the scattering intensity (contrast) of the liquid crystal display element. .

However, reducing the size of the bright spot of the light source shortens the life of the light source, and its development is extremely difficult. Further, improving the scattering intensity (contrast) of the liquid crystal display element is also not practical because it is almost determined by Δn of the liquid crystal material.

An object of the present invention is to screen a liquid crystal display cell.
It is an object of the present invention to provide a liquid crystal display device capable of simultaneously improving the contrast and the brightness on the screen without using a Schlieren diaphragm.

[0015]

DISCLOSURE OF THE INVENTION The present invention comprises a polymer dispersion type liquid crystal display device dispersed in a polymer sealed between electrodes and electrically controlled in a scattering state and a transparent state. And the liquid crystal cell attached to the liquid crystal cell so that the light transmission intensity when the incident angle of light is 30 ° is 80% or less of the light transmission intensity when the incident angle is 0 °. And a light control plate for transmitting the light.

[0016]

[Operation] The light control plate attached to the liquid crystal cell has a transmission intensity of a light beam at an incident angle of 30 ° and an incident angle of 0 °.
Since it is configured to be 80% or less of the transmission intensity of light rays at °, the scattered light can be efficiently cut without reducing the transmission intensity of the light and the contrast on the screen of the liquid crystal display cell can be improved. And brightness can be improved at the same time without using a Schlieren diaphragm.

[0017]

Embodiments of the liquid crystal display device of the present invention will be described with reference to the drawings.

The feature of the embodiment of the present invention is that when a light control plate including a light transmitting member and a light absorber is attached to the opposite side of the light source with respect to the cell, the scattered light is efficiently cut by the light control plate and the light is nearly parallel. In addition, when the light control plate is attached to the same side as the light source with respect to the cell, in the light of the light source,
Either the light other than the parallel component is efficiently cut so that the diaphragm in the Schlieren system can be narrowed, or the diaphragm is not used. In both cases, the ability of the light control plate becomes a problem.

He-Ne laser light, which is an ideal parallel light beam, is used to change the incident angle of the light, and the transmitted light is measured,
When a light control plate with a transmission intensity of light with an incident angle of 30 ° was 80% or more with respect to a transmission intensity of light with an incident angle of 0 °, the effect of improving contrast was small and inefficient.

Therefore, as the capability of the light control plate, the transmission intensity of light at an incident angle of 30 ° is set to 80% or less with respect to the transmission intensity of light at an incident angle of 0 °, and more preferably 50%.
It is the following.

In the case of using a light control plate in which a structure in which an optically transparent medium such as a fiber is covered with a light absorber is bundled,
The cross section of the structure is important. The cross-section of the structure is preferably a cross-section that covers at least 80% of the flat surface by at least one type of shape, and when the cross-section is 80% or less, the remaining cross-section becomes a dead space due to an adhesive agent, etc. I will let you.

Specifically, when one type of structure is used,
Triangle (regular triangle, isosceles triangle), quadrangle (square,
Rectangles, diamonds, trapezoids), hexagons and the like. When two or more types are combined, the shape obtained by adding a pentagon or the like may be selected so as to cover a plane by 80% or more.

Particularly, a hexagonal cross section can be easily prepared by bundling fibers having a circular cross section, and then raising the temperature above the softening point of the fibers and compressing the whole, and it is manufactured. It is preferable because it is easy. Further, the cross section of the structure may be an amorphous shape constituted by a curved line and / or a straight line.

In the structure of this structure, if it is larger than the picture element, the distance from the wall of the structure is greatly different within the picture element, and the effect of blocking scattered light is uneven in one direction, which is effective. Therefore, it is preferably smaller than the picture element.

Furthermore, the thickness of the structure is related to the ability to cut scattered light in the case of other than the optical fiber, and is preferably 10 times the length of the longest part of the cross section of the single fiber.

The material of the structure is not particularly limited as long as it is an optically transparent material such as glass, quartz, transparent polymer, transparent solvent, gas, etc., but transparent polymer is particularly preferable in view of price and processability. .

In order to enhance the scattered light cutting effect of the assembly of the structures, the wall of the structure is coated or coated with an absorber that absorbs at least the light incident on the control plate. Good

A light control polymer film having at least one regularly arranged micro domain and having angle selectivity of incident light is defined by the method described in Japanese Patent Application No. Sho 61-302500 and Japanese Patent Application Laid-Open No. 64-40903. It was made.

That is, at least 2 having a difference in refractive index
More than one kind of photopolymerizable oligomer, or a resin composition containing a monomer is developed into a film, and by irradiating and curing with UV light from a predetermined direction, microdomains are formed in the incident direction of UV light. The light control plate grows and transmits the incident light in the incident direction and scatters the incident light in the other directions.

The light control plate preferably has directivity only in the vicinity of the direction perpendicular to the plane, and in the case of the light control plate which controls the transparent-scattering only in the plane perpendicular to the one direction control plate, 2 An embodiment of the light control plate according to the present invention is manufactured by stacking a plurality of light control plates so that the surfaces for controlling the transparent-scattering are orthogonal to each other.

As the performance of the light control plate, the polymer dispersion type liquid crystal is used when the direction θ ₈₀ is within 20 °, which is 80% or less of the transmission amount of light incident in the direction perpendicular to the surface of the light control plate. It has an effect of increasing the scattering ability of the device, and is preferably within 10 °.

The manufacturing method of the embodiment of the liquid crystal display device of the present invention will be described below.

Two ITO (a mixture of indium oxide and tin oxide) glass (Nippon Sheet Glass ITO-500 flint glass with angstrom) substrates were used and 12 μm
A cell was prepared through the fiber. Add 0.1 g of trimethylolpropantonomethacrylate to the prepared cell and 2
-Ethylhexyl acrylate 0.9 g and ZLI-4792 (Merck) 4 g, photocurable catalyst Irgacure 184 (Ciba-Geigy-
0.03 g of the mixture was homogeneously mixed and injected, and then the resin was cured by irradiating it with ultraviolet rays at 20 mw / cm ² under a high pressure mercury lamp for 2 minutes to prepare a polymer dispersed liquid crystal cell. FIG. 1 is a schematic sectional view of this embodiment, and FIG. 2 is a line AA of FIG.
Figure 3 shows a schematic cross-sectional view of the light control plate taken along.

In FIG. 1, 1 is a polymer-dispersed liquid crystal cell, 2 is a pixel electrode, 3 is a light control plate, 4 is a polymer dispersed liquid crystal material (scattering-transparent control liquid crystal display element), and 5 is a transparent electrode. Attached substrate, 6 in FIG. 2 is a light transmitting (transparent) member, 7
Is a light absorber.

Θ ₈₀ = 17 was added to the prepared polymer-dispersed liquid crystal cell.
A light control plate having a temperature of 90 ° was attached, and the angle dependence of the light transmittance was measured.

FIG. 3 shows the evaluation system used for the measurement. 1 is a polymer dispersion type liquid crystal cell, 3 is a light control plate, 10 is a He-Ne laser light source, 11 is an optical detector, and 12 is a computer for data analysis. For He-Ne laser light incident perpendicular to the cell surface, the scattered light was measured perpendicularly to the cell with a direction of 0 ° and an angle from there measured as θ.

FIG. 4 is a diagram for explaining the angle dependence of the light transmittance when the voltage is OFF. 15 is a polymer-dispersed liquid crystal cell alone without a light control plate attached, and 16 is the present embodiment. Each case is shown.

In the figure, the light transmittance decreases in the range of 0 to 20 °, and when the voltage is on (20V, 60Hz), the light transmittance is 75%.
% (81% in the case of polymer-dispersed liquid crystal cell alone), it was found that the light transmittance was hardly reduced.

[0039]

The light control plate attached to the liquid crystal cell is
Since the light is transmitted so that the light transmission intensity when the incident angle is 30 ° is 80% or less of the light transmission intensity when the incident angle is 0 °, the light transmittance is not reduced. By efficiently cutting scattered light, the contrast and brightness on the screen of the liquid crystal display cell can be improved at the same time without using a Schlieren diaphragm.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic cross-sectional view of the light control plate taken along the line AA of FIG.

FIG. 3 is a diagram showing an evaluation system used for measurement of angle dependency of light transmittance.

FIG. 4 is a diagram illustrating the angle dependency of light transmittance when the voltage is OFF.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymer-dispersed liquid crystal cell 3 Light control plate 6 Light transmitting member 7 Light absorber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Ohnishi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. Within the corporation

Claims (3)

[Claims] 1. A liquid crystal cell comprising a polymer-dispersed liquid crystal display element dispersed in a polymer sealed between electrodes and electrically controlled in a scattering state and a transparent state, and the liquid crystal cell. Of the light transmission intensity when the incident angle of light is 30 ° and the transmission intensity of the light when the incident angle is 0 °.
A liquid crystal display device, comprising: a light control plate that allows light to pass through at 80% or less. 2. The light control plate is formed of either an optical fiber or an optically transparent medium and has a honeycomb structure having at least one kind of polygonal cross section and amorphous cross section. The liquid crystal display device according to claim 1, further comprising a light transmitting member formed as described above, and a light absorber that covers the light transmitting member. 3. The light control plate is formed of a light control polymer film having at least one regularly arranged micro domain and having angle selectivity of incident light. The described liquid crystal display device.