JPH0553100A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the display of a direct viewing type having good image quality of a high contrast ratio by using a light scattering type liquid crystal. CONSTITUTION:This electrode display device is formed by laminating a liquid crystal display part 10 consisting of a light source 30, a 1st transparent substrate 11 provided with 1st driving electrodes 13, a light scattering type liquid crystal layer 15, and a 2nd transparent substrate 12 provided with 2nd driving electrodes 14 and a scattering display means 40 for diffusing the light transmitted through the liquid crystal layer 15 and is constituted to impress the voltage controlling the orientation of the light scattering type liquid crystal layer 15 between the 1st driving transparent electrodes 13 and the 2nd driving transparent electrodes 14 from a driving control means 20. A 1st irradiation angle limiting means 50 for limiting the irradiation angle of the light from the light source 30 is provided between the liquid crystal display part 10 and the light source 30 of the above-mentioned device and a 2nd irradiation angle limiting means 60 for limiting the irradiation angle of the light from the light source 30 is provided between the liquid crystal display part 10 and the diffusion display means 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct-view display device using a light-dispersive liquid crystal.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, a display device using a nematic liquid crystal has been known. However, in the display using the nematic liquid crystal, since the polarizing plate is used, the light transmittance is 10%.
It is low as below and the energy efficiency of the backlight is poor. Therefore, the contrast is also low. Further, there is a problem that a polarizing plate is required in front of and behind the liquid crystal panel and an alignment film for aligning the liquid crystal is required, and the structure is complicated.

On the other hand, a light-scattering liquid crystal which does not require a polarizing plate has been studied. The light-scattering type liquid crystal has a light transmittance of 80 to 90%, and thus has high light utilization efficiency. An example of this light scattering type liquid crystal is a liquid crystal dispersion polymer in which a nematic liquid crystal is dispersed in a polymer. When an electric field is applied to this element to turn it on, the liquid crystal is uniformly aligned.
The incident light goes straight without being scattered. On the other hand, in the OFF state where no electric field is applied to the device, the liquid crystal is randomly aligned,
Incident light is scattered. This light-scattering type liquid crystal has been used only as a projection type display having a diaphragm for blocking light scattered by an optical system due to its light-scattering property. This projection display can obtain a high contrast ratio because the light incident on the liquid crystal in the OFF state and scattered is blocked by the diaphragm and does not reach the screen. However, in order to realize a direct-view display using this light-scattering liquid crystal, we created a direct-view display with a backlight and a liquid crystal panel that had the same structure as a conventional nematic direct-view liquid crystal display. However, since scattered light in the OFF state of the liquid crystal is observed, an image having a high contrast ratio could not be obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a direct-view display having a high contrast ratio and good image quality, using the light-scattering liquid crystal.

[0005]

In the present invention, the following means are used to realize a direct-view display using a light-scattering type liquid crystal. First, an incident angle of light incident on the liquid crystal panel is restricted by providing an irradiation angle restriction means for restricting an irradiation angle of the light between a light source for irradiating the light from the back surface of the liquid crystal display unit and the liquid crystal panel. On the other hand, a second irradiation angle limiting means for limiting the irradiation angle of the light from the light source is provided between the liquid crystal panel and the diffusion display plate to limit the emission angle of the light that exits the liquid crystal panel and reaches the diffusion display plate. An incident angle limiting grating and an emitting angle limiting grating can be used as the irradiation angle limiting means having the above configuration. Further, as the irradiation angle limiting means, an incident angle limiting fiber bundle and an output angle limiting fiber bundle made of transparent glass or plastic may be used.
By using these irradiation angle limiting means, it has become possible to manufacture a direct-view display using a light-scattering liquid crystal having a high contrast ratio and good image quality.

[0006]

【Example】

[Embodiment 1] A first embodiment of the present invention will be described with reference to FIG. Example 1 is an example in which the first and second irradiation angle limiting means are respectively configured by an incident angle limiting grating and an emitting angle limiting grating.

The display device 1 uses a light-scattering type liquid crystal panel using a liquid crystal dispersion polymer 15 in which a nematic liquid crystal is dispersed in a well-known polymer as a liquid crystal display unit 10, and includes a light source 30, an incident angle limiting grating 50, The light-scattering liquid crystal display unit 10, the emission angle limiting grating 60, and the diffusion display plate 40 are stacked in this order. As the light source 30 for irradiating light from the back surface of the liquid crystal display unit, an EL panel of a surface light emitter or a light source of a cold cathode tube which is made into a plane by using a reflector is used. As the irradiation angle limiting means 50, 60, a lattice structure having a cross-sectional shape such as a square, a triangle, a hexagon, or a circle and having a predetermined length is used. This lattice is composed of thin metal plates assembled in a square, triangular or hexagonal lattice, or a bundle of thin tubes. In order to impart strength to the lattice, it is possible to embed the lattice in a transparent resin and harden it. The inner surface of the grid is processed to a black non-glossy surface that does not cause reflection.

The operation of the irradiation angle limiting means will be described below with reference to FIG. As shown in the figure, when the diameter of the grating is h and the length is L, the maximum incident angle a of the light incident on the liquid crystal after passing through the grating is a = arc tan (h / L). .. (1), the light emitted from the light source 30 passes through the incident angle limiting grating 50, so that the incident angle to the liquid crystal is limited to a. The diameter h of the grid is determined based on the pixel pitch of the display and is a fraction of the pixel pitch (usually about 0.3 mm) (0.1 mm) to several tens of minutes (about 0.03 mm).
Is decided. The length L of the grating is determined by the above equation (1) so that the incident angle a of the light passing through this grating is about several degrees to about 10 degrees so that a desired contrast can be obtained.

FIG. 3 shows a specific structural example of the irradiation angle limiting means using a grating. In this example, the grating 51 is a thin aluminum plate 52 formed in a honeycomb core shape, and its inner wall is blackened to prevent reflection of light with a large incident angle that causes a reduction in contrast. Further, the transparent resin 53 is filled inside the core to give strength to the lattice. A liquid crystal dispersed polymer is used as the light-scattering liquid crystal. The liquid crystal dispersion polymer 15 is injected between the glass substrates 11 and 12 on which the transparent electrodes 13 and 14 are deposited, as in the case of a normal nematic liquid crystal, to form the light scattering type liquid crystal panel 10. As the diffusion display means 40, a glass plate or a plastic plate processed into a ground glass shape or a lenticular lens shape is used. The light that has passed through the incident angle limiting grating 51 enters the liquid crystal display unit 10. The light-scattering liquid crystal has different light-scattering characteristics depending on whether or not a voltage is applied to the pixel. As shown in the lower half of FIG. 1, in the ON-state pixel in which a voltage is applied,
Since the liquid crystal is aligned in a certain direction, the incident light does not scatter and goes straight. As shown in the upper half of FIG. 1, in the pixel in the OFF state where no voltage is applied, the liquid crystal faces a random direction, so the incident light is scattered. Liquid crystal 1
The light passing through 0 enters the emission angle limiting grating 60. Liquid crystal ON
The light passing through the pixel portion in the state goes straight without being scattered, passes through the emission angle limiting grating 60, and reaches the diffusion display plate 40. The light scattered through the pixel portion in the OFF state of the liquid crystal has a large incident angle to the emission angle limiting grating, and therefore most of the light cannot pass through the emission angle limiting grating. Therefore, the light does not reach the diffusion display plate at the position corresponding to the pixel in the OFF state. In this way, the contrast between the ON state and the OFF state can be obtained.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
Will be explained. The second embodiment is an example in which the first and second irradiation angle limiting means are respectively constituted by an incident angle limiting fiber bundle and an output angle limiting fiber bundle, and the other configurations are the same as those of the first embodiment.

The display according to the invention has the following structure. Light scattering type liquid crystal panel 1 as a liquid crystal display unit
0, the light source 30, the incident angle limiting fiber bundle 55,
Light-scattering type liquid crystal panel 10, emission angle limiting fiber bundle 6
5 and the diffusion display plate 40 are stacked in this order. Light source 30
For this, an EL panel of a surface light emitter or a light emitting device of a cold cathode tube which has been made into a planar light emission by using a reflector is used. The incident and exit angle limiting fiber bundles 55, 65 are made of glass or transparent plastic material. The specific structure of the fiber bundle is shown in FIG. The fiber bundle 55 is a bundle of fibers 56 made of glass or transparent plastic, and a fiber peripheral material 5 having a smaller refractive index and a larger light absorption rate than the fiber material between the fibers.
It is filled with 7 and fixed, and is provided with intensity, and light with an incident angle larger than ψ TH is sufficiently attenuated. The diameter r of the fiber used for the fiber bundle is
From a fraction (about 100 microns) of the pixel pitch of the display (usually about 0.3 mm) to a few tenths of minutes (10
It can be decided. The length L of the fiber is set to a length necessary for sufficiently attenuating the light having an incident angle larger than ψTH among the lights passing through the fiber. The fiber peripheral material 57 is made of glass or plastic material, and its refractive index is slightly lower than that of the fiber. A coloring material is used for these materials so that the light absorption is increased.

The operation of the irradiation angle limiting fiber will be described below with reference to FIGS. 5 and 6. Since the incident angle limiting fiber bundle 55 and the output angle limiting fiber bundle 65 have the same structure and principle, these two will be referred to as irradiation angle limiting fibers. FIG. 5 shows a case where the light incident on the irradiation angle limiting fiber is totally reflected on the fiber wall surface. From the left side of the figure, when a light ray passes through the air having a refractive index N ₁ (N ₁ = 1.0) and is incident on a fiber portion having a refractive index N _{2 at} an incident angle θ ₁ , the light is refracted on the fiber surface and the incident angle θ Proceed through the fiber at ₂ . The relationship between each refractive index and the incident angle is represented by N ₁ · sin θ ₁ = N ₂ · sin θ ₂ ... (2). Incident light traveling through the fiber at an angle θ ₂ has an incident angle ψ in the relationship of θ ₂ + ψ ₁ = π / 2 ... (3) It is incident on the fiber wall at ₁ .
The refractive index N ₃ around the fiber is lower than the refractive index N _{2 of the} fiber. It is surrounded by a fiber peripheral material 57 having N ₂ > N ₃ (4). The light ray incident on the fiber wall surface is totally reflected by the fiber wall surface, enters the other end surface of the fiber at an incident angle θ ₂ , is refracted at the fiber end surface, and goes out into the air at an exit angle θ ₁ . During this period, the light ray is repeatedly reflected on the wall surface of the fiber, but the light ray is not attenuated because it is totally reflected. The condition for the ray incident on the fiber wall surface to be totally reflected on the wall surface is expressed by N ₂ · sin ψ ₁ ≧ N ₃ · sin (π / 2) ... (5) Therefore, the incident angle ψTH on the wall surface when total reflection occurs is ψTH = arc sin (N ₃ / N ₂ ) ... (6). FIG. 6 shows the case where the light incident on the incident angle limiting fiber is not totally reflected by the fiber wall surface. Similar to FIG. 5, from the left side of the figure, the light beam has a refractive index N ₁ (N ₁ = 1.
It passes through the air of (0) and enters the fiber portion having a refractive index N _{2 at} an incident angle θ ₃ . Light is refracted on the fiber surface and the incident angle is θ ₄
And proceed through the fiber. The relationship between each refractive index and the incident angle is expressed by the following formula: N ₁ · sin θ ₃ = N ₂ · sin θ ₄ ........ Incident light is incident on the fiber wall surface at an incident angle ψ ₃ having a relationship of θ ₄ + ψ ₃ = π / 2 ... (8).
The condition that light rays are not totally reflected on the fiber wall surface is expressed as N ₂ · sin ψ ₃ <N ₃ · sin (π / 2) ・ ・ ・ ・ ・ ・ ・ ・ (9) The light that has entered the fiber wall surface is not totally reflected but is partially refracted and enters the fiber peripheral material 57 at the exit angle ψ ₄ . N ₂ · sin ψ ₃ = N ₃ · sin ψ ₄ ············· (10) Light that does not enter the peripheral material is reflected by the fiber wall surface and continues to travel in the fiber. The light entering the fiber peripheral material 57 is attenuated because the peripheral material absorbs a large amount of light, and does not enter the fiber 56 again. The light partially reflected on the wall surface is attenuated as the light is reflected repeatedly while part of the light enters the fiber peripheral agent 57 on the wall surface, and the light intensity becomes extremely weak when it exits from the end surface of the fiber where light is extracted. ing.

On the basis of the above principle, when the light beam is passed through the fiber bundle, the angle ψ
Only the light incident at an angle of TH or more emerges from the end face of the fiber on the light extraction side. This fiber bundle 55,6
5 is placed between the light source 30 and the light-scattering liquid crystal 10 and between the light-scattering liquid crystal 10 and the diffusion display plate 40 to turn off.
The scattered light from the liquid crystal in the state can be prevented from reaching the diffusion display plate, and a direct-view type display can be realized. The light that has passed through the incident angle limiting fiber bundle 55 enters the liquid crystal display unit 10. The light-scattering liquid crystal has different light-scattering characteristics depending on whether or not a voltage is applied to the pixel. As shown in the lower half of FIG. 4, in the pixel in the ON state where a voltage is applied, the liquid crystals are aligned in a certain direction, so that the incident light does not scatter and goes straight. As shown in the upper half of FIG. 4, in the pixel in the OFF state where no voltage is applied, the liquid crystal faces a random direction, so the incident light is scattered. The light passing through the liquid crystal 10 enters the exit angle limiting fiber bundle 65. The light passing through the pixel portion in the ON state of the liquid crystal goes straight without being scattered, and the output angle limiting fiber bundle 65
To the diffusion display panel 40. The light scattered through the pixel portion of the liquid crystal in the OFF state has a large incident angle to the output angle limiting fiber bundle, and therefore most of the light cannot pass through the output angle limiting fiber bundle. Therefore, the light does not reach the diffusion display plate at the position corresponding to the pixel in the OFF state. In this way, the contrast between the ON state and the OFF state can be obtained.

[0014]

INDUSTRIAL APPLICABILITY According to the present invention, the incident light to the light-dispersion liquid crystal is limited by using the irradiation angle limiting means, and the light passing through the light-dispersion liquid crystal is limited to a specific angle by using the irradiation angle limiting means. Since the light is incident on the diffusion display plate, it is possible to realize a direct-view display using a light-dispersion liquid crystal.
Since this display does not require a polarizing plate, the light utilization efficiency is high and a high contrast image quality can be obtained. Further, in manufacturing, there is no need for a process such as alignment film deposition and rubbing, and the process can be simplified, and therefore the cost can be reduced. In addition, since the system in which the light from which the liquid crystal is projected is applied to the diffusion display plate, an image that does not depend on the viewing angle in principle can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a liquid crystal display device according to the present invention.

FIG. 2 is a diagram showing the relationship between the diameter (h) and length (L) of the grating and the maximum incident angle (a).

FIG. 3 is a view showing a structure of an irradiation angle limiting grating according to the present invention (example of honeycomb structure).

FIG. 4 is a view showing a structure of a liquid crystal display device according to the present invention using an irradiation angle limiting fiber.

FIG. 5 is a diagram showing a case of light having an incident angle θ ₁ which is totally reflected by the fiber wall surface and propagates.

FIG. 6 is a diagram showing a case of light having an incident angle θ ₃ which is gradually attenuated without being totally reflected by the fiber wall surface.

FIG. 7 is a diagram showing the structure of an irradiation angle limited fiber bundle according to the present invention.

[Explanation of symbols]

1 liquid crystal display, 10 liquid crystal display section, 11, 12
Transparent substrate, 13, 14 drive electrodes, 15 light-scattering type liquid crystal layer, 20 drive control means, 30 light source, 40 diffusion display plate, 50 incident angle limiting means, 51 irradiation angle limiting grating, 5
2 honeycomb core, 53 transparent resin, 55 irradiation angle limiting fiber, 56 fiber, 57 peripheral material, 60
Output angle limiting means

Claims (1)

[Claims] 1. A first transparent substrate provided with a first driving transparent electrode, and a second transparent substrate provided with a second driving transparent electrode arranged to face the first driving transparent electrode of the first transparent substrate. Of the transparent substrate, and a liquid crystal display section having a light-scattering liquid crystal layer provided between the first transparent substrate and the second transparent substrate, and a voltage for controlling the alignment of the light-scattering liquid crystal layer Drive control means for applying between the drive transparent electrode and the second drive transparent electrode, and a light source for irradiating light from one of the liquid crystal display section,
In a liquid crystal display device having a diffusion display unit that scatters light transmitted through a liquid crystal display unit provided on the side opposite to the light source of the liquid crystal display unit, an irradiation angle of light from the light source between the liquid crystal display unit and the light source. And a second irradiation angle limiting means for limiting the irradiation angle of light from the light source between the liquid crystal display section and the diffusion display means. Liquid crystal display device.