JPH06167697A - Image display device - Google Patents

Abstract

(57) [Abstract] [Purpose] High-contrast, small-sized, lightweight, direct-view image display device [Configuration] A plurality of light-scattering states and non-scattering states (transmission states) that can be electrically controlled A parnet having pixels, and an optical layer provided with a condensing optical system corresponding to each pixel,
An image display device having a structure in which a light shielding layer having an opening and a light transmitting / scattering layer are laminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device having a plurality of pixels used for a display panel of a measuring instrument, a computer image display device, a television and the like.

[0002]

SUMMARY OF THE INVENTION According to the present invention, in a parnet having a plurality of pixels capable of electrically controlling the scattering state and the non-scattering state of light, a light beam condensed by a condensing optical system corresponding to each pixel is , The light ray arrives by using the fact that the ratio of the light ray passing through the opening of the light shielding layer provided on the light emitting surface side of the panel greatly changes depending on whether the light is scattered or not when passing through the panel. This enables a display having a high contrast on the light transmission / scattering layer.

[0003]

2. Description of the Related Art A thin film transistor (TF) is currently used as a high-definition image display device which is compact, lightweight, and power-saving.
Twisted nematic (TN) liquid crystal panels by the active matrix driving method and super-twisted nematic (STN) liquid crystal panel by the simple matrix driving have been put into practical use. However, in the image display using these liquid crystal panels, it is necessary to dispose polarizing plates on the entrance surface and the exit surface of the panel and convert the light into linearly polarized light for use, resulting in low light utilization efficiency and dark images. It has disadvantages that it is difficult to see and that it is difficult to display an image having a high viewing angle characteristic.

[0004]

In an image display device having a plurality of pixels capable of electrically controlling the scattering state and non-scattering state of light, a high transmittance can be obtained in the non-scattering state, but Since it is difficult to obtain a sufficient light shielding property in the scattering state, a high contrast has not been obtained on the panel. Therefore, there has been devised a method of obtaining a high contrast by projecting a display image on a panel through a Schlieren optical system and then projecting it on a screen. However, in the above method, it is necessary to provide a large optical system on the light emitting surface side of the panel, and it is difficult to reduce the size and weight.

Therefore, in the present invention, a display image having a high contrast can be obtained on the light transmissive scatterer by providing an optical layer having a condensing optical system corresponding to each pixel and a light shielding layer having an opening. It is possible to realize a small-sized, lightweight direct-view type image display device by utilizing the above.

[0006]

In order to solve the above problems and to realize that a small-sized, lightweight direct-view type image display device can be realized, a microlens is used as a condensing optical system to An active matrix liquid crystal display device using a polymer dispersed liquid crystal (hereinafter sometimes referred to as PDLC) as a panel layer having a large number of pixels for electrically controlling the scattering state and the non-scattering state will be described as an example. still,
The pixel referred to here means one section on the panel which is composed of one pixel electrode 4, the pixel drive element 2, and the black matrix 5 as a set, as described in FIG.

In FIG. 1, a parallel light beam is made incident from the left side, and is condensed by the microlens 1 to the same size as the pixel electrode 4 and made incident on the panel surface. At this time, in the light-shielding layer 6 provided on the light emitting surface side of the panel, the light that can pass through the small opening 8 formed in the vicinity of the focal point of the microlens 1 and reach the light transmitting / scattering layer 7 is scattered when passing through the panel. It is limited to the light that received almost no light. Therefore, when the PDLC layer 3 in the panel is electrically controlled to be in a scattering state, the amount of light reaching the light transmitting / scattering layer 7 becomes very small,
On the contrary, in the non-scattering state, the amount of light reaching the light transmitting / scattering layer 7 becomes very large. The arriving light is scattered and emitted by the light transmitting / scattering layer 7 in a wide angle in the direction in which the observer is located (right side in the drawing). As a result, when viewed from the right side of the light transmitting / scattering layer 7, that is, from the light emitting surface side, the light transmitting / scattering layer 7 becomes dark when the amount of light reaching the panel is very small, and conversely becomes bright when the amount of light reaching is large. If the right side surface of the light shielding layer 6, that is, the light emitting side surface is made to have light absorbing properties, external light that reaches the light shielding layer 6 after being transmitted through the light transmitting / scattering layer 7 from the right side is absorbed. Therefore, it is possible to prevent the interference of the “dark” display due to the reflection of the external light to the light emitting side, and it is possible to improve the display contrast.

By combining with a method of electrically controlling the scattering state or non-scattering state of light separately in a plurality of pixels based on the above principle, a light-transmissive direct-view type display which is small, lightweight, bright and has high display contrast Is feasible.

Further, after the incident light beam is condensed by the microlens 1 to the same size as the pixel electrode 4 provided in each pixel, it is passed through the pixel electrode 4 and the PDLC layer 3 so that the pixel electrode 4 is formed. Other than the light incident surface, that is, the amount of incident light on the PDLC layer portion where the scattered state and the non-scattered state of light cannot be controlled depending on the presence or absence of an applied voltage, can be suppressed to a very small level, and the utilization efficiency of the incident light can be improved. Can be raised.

More specifically, it is preferable that the surface of the light-shielding layer 6 on the light emitting surface side has as high light absorption as possible, but the surface on the light incident surface side does not necessarily have light absorption. The pixel electrode 4 and the pixel driving element 2 are preferably formed on the light emitting surface side of the panel, but may be formed on the light incident surface side of the panel. Also, the pixel drive element 2
A black matrix is formed on the light incident side of the panel for the purpose of protecting the above and the like from an incident light beam, but it is not necessary to provide it in some cases.

The microlens optical system may be manufactured by using glass or an optically transparent polymer resin, and may be formed on the panel substrate or on another substrate. You may use what was formed in 2 and laminated. Furthermore, the microlens can be manufactured by an injection method or a lithography method, and may have a concave shape or a convex shape as long as it can collect light.
The shape does not necessarily have to be the shape shown in FIG.

However, when a concave lens is used, the refractive index of the lens must be lower than that of the surrounding portion, and conversely, when a convex lens is used, the refractive index of the lens must be higher. Further, as the condensing optical system, a lens other than the microlens can be used and, for example, a Fresnel lens or the like can be used. The focal lengths of these condensing optical systems are determined in consideration of the brightness and contrast of the display image, the size of the device, and the like. Further, it is desirable that the optical layer provided with these condensing optical systems is arranged at the position shown in claim (3) of the present specification, but it is not limited to this position and the light on the panel or the panel It may be arranged on the emission surface side.

The panel substrate 9 may be either a glass substrate or a polymer resin substrate as long as it is optically transparent.

The panel may be driven by either a simple matrix method or an active matrix method, and the method used for ordinary liquid crystal panels is used. still,
When the simple matrix driving method is used, the pixel electrode 4 portion in this description corresponds to the area of the intersection of the row electrode and the column electrode.

Further, similarly to a normal liquid crystal display device, it is possible to colorize a display image by providing three kinds of color filters of red, green and blue corresponding to pixels.

In this description, a polymer dispersed liquid crystal (PDL) is used as a method for electrically controlling the light scattering state and the non-scattering state.
C) is mentioned as an example. PDLC is a polymer resin matrix in which a liquid crystal phase having a positive dielectric anisotropy is dispersed in a droplet form or in a three-dimensional network form so that the difference in refractive index between the resin matrix phase and the liquid crystal phase and the long axis of the liquid crystal molecule It refers to a liquid crystal polymer composite that exhibits remarkable light scattering ability due to strain in the alignment direction. When an external electric field is applied to this PDLC, the liquid crystal molecules are aligned in the external electric field. At this time, if the refractive index of the liquid crystal molecules in the electric field direction and the refractive index of the resin matrix are matched, the PDLC loses its light scattering ability and becomes in a light transmitting state. As described above, the PDLC panel can reversibly control the light scattering state and the non-scattering state (transmission state) depending on the presence or absence of an applied electric field, and thus can be preferably used in this application.

Of course, the panel is not limited to this PDLC panel, and any panel can be used as long as it can control the light scattering state and the non-scattering state. For example, a reverse mode PDLC using a liquid crystal having a negative dielectric anisotropy, a cholesteric-nematic phase transition type liquid crystal, a dynamic scattering mode of a liquid crystal, or the like can be used.

Further, the light shielding layer 6 preferably has high thermal conductivity. Further, the opening of the light shielding layer 6 needs to be optically transparent, and the size of the opening is determined in consideration of the brightness and contrast of the image displayed on the light transmitting / scattering layer 7.

Further, as the light transmission / scattering layer 7, it is possible to use a material in which the surface of an optical transparent body is subjected to a light scattering ability, and for example, a frosted glass plate or the like can be used, but not limited to this. Any optically transparent material having a scattering ability can be used.

Further, if the optical layer provided with the condensing optical system has a higher refractive index than the surroundings, the angle of the traveling direction of the incident light beam due to the refraction effect when the light is incident on the optical layer. It is possible to reduce the direction, which has the effect of increasing the contrast of the displayed image.

The optical transparent layer 10 may be made of glass, polymer resin, or a gas layer such as air.

[0022]

As described above, according to the present invention,
In a panel having a plurality of pixels capable of electrically controlling the scattering state and the non-scattering state of light, an optical layer provided with a condensing optical system corresponding to each pixel, a light-shielding layer having an opening, and light transmission By using a structure in which scattering layers are laminated, it is possible to obtain a very bright and high-contrast image display while being compact and lightweight, and to obtain a great social effect such as being able to supply a direct-view type image display device. You can

[Brief description of drawings]

FIG. 1 illustrates one embodiment of the present invention.

[Explanation of symbols]

 1: Microlens 2: Pixel driving element 3: Polymer dispersed liquid crystal (PDLC) 4: Pixel electrode 5: Black matrix 6: Light-shielding layer 7: Light transmission / scattering layer 8: Opening 9: Panel substrate 10: Optical transparent layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Nakatani 4-3-2 Asahigaoka, Hino-shi, Tokyo Inside Teijin Ltd. Tokyo Research Center

Claims (9)

[Claims] 1. Light scattering state and non-scattering state (transmission state)
A laminate having a plurality of pixels that can be electrically controlled, an optical layer having a condensing optical system corresponding to each pixel, a light shielding layer having an opening, and a light transmission / scattering layer. Image display device having a structure formed by. 2. The electronic control of the scattering state and the non-scattering state of light according to claim 1, using a polymer-dispersed liquid crystal in which liquid crystal molecules are dispersed in a polymer matrix in a droplet form or a three-dimensional network form. Image display device characterized by 3. The pixel electrode according to claim 1, wherein the optical layer provided with the condensing optical system is on the light incident surface side of the panel, and the incident light beam passing through the collective optical system is provided in each pixel. An image display device characterized by being arranged so as to pass through a pixel electrode and a polymer-dispersed liquid crystal layer after being condensed until the incident cross-sectional area is approximately the same as the area. 4. The image display device according to claim 1, wherein the condensing optical system has an optical layer that is a microlens array or a Rephnel lens array. 5. The image display device according to claim 1, wherein a light-shielding layer having an opening smaller than the area of each pixel is arranged on the light emission surface side of the panel. 6. The image display device according to claim 1, wherein the light shielding layer is arranged so that the center of the opening is located near the position of the focal point of the condensing optical system. 7. An image display device according to claim 1, wherein the light-shielding layer having an opening has a light-absorbing property at least on the light-emitting surface side. 8. The image display device according to claim 1, wherein a color filter is provided corresponding to each pixel, and a color display image is displayed on the light transmission / scattering layer. 9. The dichroic dye molecule having different light absorption depending on the direction of the molecular axis is added to the polymer-dispersed liquid crystal dispersed in the polymer matrix in a droplet form or a three-dimensional network form according to claim 2. Image display device featuring