JPH06102525A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device that can display an image which is easy for the human eye to see and similar to a printer output by obtaining both a high-speed display and resolution almost as high as the printer output. CONSTITUTION:The liquid crystal display device is equipped with an image writing means 1 which writes an image digitally according to moving picture information, an optical modulator 2 which holds the written image as changes in optical state, an optical image irradiating means 3 which reading the image out of the optical modulator 2 as an analog image with light and enlarges and projects the optical image, and a liquid crystal cell 4 which is formed by laminating a photoconductive layer 4a irradiated with the enlarged optical image from the optical image irradiating means 3 and a liquid crystal high polymer compound film 4b wherein liquid crystal is dispersed in high polymer resin and has the orientation of the liquid crystal controlled according to an electric field pattern from the photoconductive layer 4a.

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 used as a display device for workstations and personal computers, and more particularly, it is a light-receiving type display device having a high reflection contrast, high resolution and high speed image display. The present invention relates to a new liquid crystal display device that can be manufactured.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for an electronic display device that is easy for human eyes to see and handle, and that can display an image equivalent to a printer output. CR
Although a conventional light emitting display device represented by T can obtain a high contrast, eyes are more likely to be tired than a reflected image such as a character on paper. Further, the characters and the like seen on the electronic display device often have different images from those actually printed because the resolution of the display device is not sufficient as compared with the printer.

To avoid these problems, a display device having a high reflection contrast and capable of displaying a high-definition image at high speed is desired. In these demands, a technique utilizing a light scattering mode of liquid crystal has attracted attention as a display material capable of obtaining high reflection contrast. A light scattering mode display device mixes a liquid crystal and a transparent material having a refractive index substantially equal to that of the liquid crystal at the time of vertical alignment, and controls the alignment of the liquid crystal by heat or an electric field to transmit light at the time of vertical alignment. This is a display technology that utilizes the fact that light is scattered and becomes opaque due to the difference in refractive index during random orientation. Since this display device does not need to use a polarizing plate, a bright and high reflection contrast display can be obtained.

As a material technology used for such a light scattering mode display device, a method is known in which encapsulated liquid crystals are dispersed as liquid crystal droplets in a polymer to form a film (Japanese Patent Publication No. 58-501631). Gazette, U.S. Pat. No. 4,435,047). In this technology, Nematic Curvilear Ali
The liquid crystal encapsulated in gned phase (NCAP) exhibits a nematic phase with a positive dielectric anisotropy at the operating environment temperature, and when it is placed in an electric field, its orientation vector is aligned in the direction of the electric field and the refractive index of the liquid crystal. When n0 is equal to the refractive index np of the polymer, the film becomes transparent. On the other hand, when the electric field is removed, the liquid crystal becomes a random arrangement, and the light is scattered at the boundary surface of the liquid crystal droplets in the film and the transmitted light. Is cut off, and the film becomes cloudy and the recorded information is displayed. In addition, special table Sho 63
JP-A-501512 and JP-A-63-155022 disclose that a liquid crystal exhibiting a smectic phase at room temperature is used to impart a memory property to light modulation of a film.

Furthermore, the following methods are known as image writing methods for liquid crystal display devices using these liquid crystal materials. For example, as disclosed in Japanese Patent Application Laid-Open No. 63-155022, a voltage is applied to a binder layer containing microcapsules containing numectic liquid crystals and heated by a thermal head driven according to image information. It is known to control the transmission and non-transmission of light by changing the orientation of. In addition, Japanese Patent Laid-Open No. 2-93432
As disclosed in the publication, a layer in which a nematic liquid crystal is irregularly dispersed in a polymer is sandwiched between matrix electrodes, and an electric field is applied to the layer to control the alignment of the liquid crystal to prevent transmission or non-transmission of light. There is also a method of switching. Also,
As an image writing method of a liquid crystal display device using a liquid crystal material, as shown in FIG. 5, a laser beam from a semiconductor laser 100 is collimated through a collimator lens 101, and then two-dimensionally by a polygon mirror 102 and a galvano mirror 103. That is optically polarized and scanned to form an image on the photoconductive layer 106 of the liquid crystal cell 105 through the projection lens 104 (for example, Japanese Patent Laid-Open No. 2-39018).
No.) etc. are known.

[0006]

However, in the type disclosed in Japanese Patent Laid-Open No. 63-155022, for example, an image is written by using a thermal head, so that a hard copy of up to about 400 lines per inch is required. Although a high resolution can be obtained, the display speed is limited by the heat transfer speed of the thermal head, and for two-dimensional writing, the head or display medium must be mechanically scanned in one direction. Therefore, there is a technical problem that it is not possible to switch the display at high speed unlike a normal display device.

Further, in the type disclosed in Japanese Patent Application Laid-Open No. 2-93432, since the alignment of the liquid crystal is controlled not by heat but by the electric field, it is possible to rewrite the image at a high speed, but it is possible to rewrite the pixel beforehand. It is necessary to form the electrode parts for individually driving each one by fine processing, which leads to a complicated structure and there is a limit in improving resolution in manufacturing.

Further, as shown in FIG. 5, in the method of two-dimensionally exposing and scanning the photoconductive layer of the liquid crystal cell by the laser beam, although the writing can be performed with high resolution, the scanning range is wide. There is a limit to the writing speed.

As described above, the above-mentioned liquid crystal display technologies achieve either high-speed display or high resolution comparable to printer output. Even if they are combined, the structures of the respective liquid crystal display devices cannot be used at the same time, so it has been practically difficult to simultaneously achieve both high-speed display and high resolution comparable to printer output.

The present invention has been made in order to solve the above technical problems, and provides a high-speed display and a printer in a light-receiving display device using the light scattering mode of liquid crystal capable of obtaining high reflection contrast. The present invention provides a liquid crystal display device that provides an image writing technology that achieves both high resolution comparable to output, is easy for the human eye to see, and is capable of displaying an image equivalent to a printer output.

[0011]

That is, the liquid crystal display device according to the present invention, as shown in FIG. 1, is an image writing means 1 for writing an image digitally according to moving image information.
And an optical modulator 2 for holding the written image as a change in the optical state, and an optical image irradiating means 3 for reading the image on the optical modulator 2 by light in an analog manner and enlarging and projecting the optical image. And a photoconductive layer 4a irradiated with the magnified optical image from the optical image irradiation means 3 and a liquid crystal-polymer composite film 4b in which a liquid crystal is dispersed in a polymer resin are laminated to form a photoconductive layer 4a.
And a liquid crystal cell 4 in which the alignment of the liquid crystal is controlled according to the electric field pattern from 1.

In such a technical aspect, if the liquid crystal cell 4 is constructed so that an electric field is applied according to the optical image from the optical image irradiation means 3, a transparent electrode is provided on the inner surface. A photoelectric conversion device in which a transparent film in which a photoconductive layer 4a, a light blocking layer, and a liquid crystal-polymer composite film 4b are sequentially laminated is sandwiched, or a charge is generated by receiving light and the charge is transported. A layer (corresponding to the photoconductive layer 4a), a liquid crystal-polymer composite film 4b, and a transparent electrode may be laminated.

From the viewpoint of simplifying the drive circuit of the liquid crystal cell 4, for example, the liquid crystal-polymer composite film 4b exhibits a nematic phase having a positive dielectric anisotropy at the ambient temperature. It is preferable to use a composite film in which liquid crystal is irregularly dispersed in a polymer resin and to control light transmission and non-transmission (scattering) only by applying an electric field.

Further, from the viewpoint of facilitating image retention in the liquid crystal cell 4, for example, the liquid crystal-polymer composite film 4b of the liquid crystal cell 4 exhibits a smectic phase at room temperature and nematic at room temperature or higher. It is preferable to use a composite film in which a liquid crystal exhibiting a phase is dispersed in a polymer resin so that the alignment state of the liquid crystal has a memory property at room temperature after writing and an image can be held without a power source.

[0015]

According to the above-mentioned technical means, the image writing means 1 writes an image on the light modulator 2, and the scanning width on the light modulator 2 is the liquid crystal cell 4 which becomes the final display screen. Since it can be made smaller than that, the scanning time is short, and an image is written in the optical modulator 2 at high speed. Then, the image written on the light modulator 2 is instantaneously read as light by the optical image irradiation means 3 in an analog manner, and the optical image is enlarged and projected on the liquid crystal cell 4. At this time, the liquid crystal cell 4
Is a laminate of a liquid crystal-polymer composite film 4b in which a liquid crystal is dispersed in a polymer resin and a photoconductive layer 4a, and an electric field corresponding to a projected optical pattern is generated via the photoconductive layer 4a. Since it is applied to the polymer composite film 4b, the alignment of the liquid crystal is controlled according to the strength of the electric field. That is, a portion of the liquid crystal that causes vertical alignment transmits light, and a portion of the liquid crystal that does not align becomes opaque.
As a result, the liquid crystal cell 4 has a high reflection contrast,
Moreover, a high-resolution image is written at high speed.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the accompanying drawings. Example 1 FIG. 2 is an example of a liquid crystal display device to which the present invention is applied. In the figure, reference numeral 21 is the image signal generation circuit 10.
A semiconductor laser that emits light in accordance with an image signal generated from the emitted beam is collimated by a collimator lens 22 and is then two-dimensionally deflected by a polygon mirror 23 and a galvanometer mirror 24. Is focused as a beam spot. Here, the polygon mirror 23 is used for horizontal scanning, for example, a rotation speed of 360.
The one having 80 planes at 00 rpm is used, and the galvanometer mirror 24 used for vertical scanning vibrates at a frequency (indicating a frame frequency of display) of 20 Hz, for example.

In this embodiment, the optical modulator 30 has a structure similar to that used as a normal reflection type liquid crystal light valve, and has a liquid crystal layer 31 showing a nematic phase at room temperature and a dielectric. ZnS / Mg as a mirror
An F2 multilayer reflective film 32, a CdTe light-shielding layer 33, and a photoconductive layer 34 made of CdS, which are sequentially laminated, are I
The TO transparent electrode is sandwiched by a pair of vapor-deposited glasses 35. A power supply 36 is connected to the transparent electrode so that an AC voltage is applied. At this time, the laser beam that is the writing light of the image is the light modulator 3
0 is irradiated to the photoconductive layer 34 side, and the size of the light modulator 30 is 21 mm in width and 30 mm in length, and the size of the A4 size screen on which an image is finally displayed is 10 mm. It is about one-third. Further, the spot diameter of the beam focused on the optical modulator 30 is 25 μm, and the writing pitch is about 12 μm, and the resolution at this point is 2 μm.
It is equivalent to 000 DPI (Dots Per Inch). When writing an image in the light modulator 30, it is sufficient to expose the photoconductive layer 34 with a laser beam while applying an AC voltage from the power supply 36, and the image corresponding to the laser beam is displayed on the liquid crystal. The layer 31 is written with high resolution and high speed.

Further, reference numeral 40 is an optical image irradiation system, and in this embodiment, a light from a high-intensity lamp (for example, a metal halide lamp in this embodiment) 41 is used as a condenser lens 4.
2. Photoconduction of the optical modulator 30 via the heat ray cut filter 43 and the half mirror 44 that prevent the light modulator 30 and the liquid crystal cell 50 from being heated by the heat rays (infrared rays) from the high-intensity lamp 41 and rising in temperature. By irradiating from the opposite side of the layer 34, the image held in the light modulator 30 is read out as reflected light, and after the reflected light is projected 10 times enlarged by the projection lens 45, it is displayed on the liquid crystal cell 50 to be a display screen. The image is formed with a resolution equivalent to 200 DPI.

In this embodiment, the liquid crystal cell 50 is also used.
Is a liquid crystal obtained by mixing 1 part of an acrylic photopolymerizable resin, 4 parts of a smectic A liquid crystal composition (“S2” manufactured by BDH), and 0.2 parts of a polymerization initiator (“Darocur 1116” manufactured by Merck) -high. The molecular composite film 53 is uniformly applied on a PET film 51 with an ITO transparent electrode (also used as a heating electrode in this embodiment) and then UV-cured, and a light-shielding layer 54 made of CdTe is laminated on the PET film 51. A photoconductive layer 55 made of silicon is laminated, and another PET film 52 with an ITO transparent electrode is laminated thereon. The size of the liquid crystal cell 50 is 210 mm.
It is about 300 mm in size and about A4 size.

Furthermore, in this embodiment, the liquid crystal-polymer composite film 53 of the liquid crystal cell 50 is heated by supplying a heating current pulse (heating pulse) 61 to one of the ITO electrodes attached to the PET film. It has become. Further, a liquid crystal phase detection sensor 62 for detecting the phase state of the liquid crystal in a part of the non-image part of the liquid crystal cell 50 to which no electric field is applied.
Is attached. In this embodiment, the liquid crystal phase detection sensor 62 is provided with a light emitting element 62a and a light receiving element 62b sandwiching the liquid crystal cell 50. The operation of the liquid crystal phase detection sensor 62 will be briefly described below. Once the liquid crystal of the liquid crystal cell 50 is liquefied by heating, the liquid crystal phase detection sensor 62 causes the light receiving element 62b to constantly receive the light from the light emitting element 62a while the liquid crystal of the liquid crystal cell 50 is in the liquid phase and transparent state. ing. On the other hand, when the liquid crystal undergoes a phase transition from the liquid phase to the nematic phase due to natural cooling, the electric field is not applied to the region of the liquid crystal cell between the liquid crystal phase detection sensors 62, so that the alignment of the liquid crystal is disturbed and light is scattered. Light receiving element 62b
The light is blocked, and this change becomes a signal indicating a change in phase.

Further, the timing control circuit 70 determines the generation timing of the heating pulse 61, and also determines the writing scanning timing of the optical image based on the phase change signal from the liquid crystal phase detection sensor 62.

Next, the image rewriting operation in the liquid crystal display device according to this embodiment will be described with reference to the timing chart of FIG. First, immediately before the rewriting of an image in the liquid crystal cell 50 on the basis of the image signal occurs, the timing control circuit 70 issues an image preparation signal S1 for notifying it. Upon receiving this signal S1, a DC heating pulse 61 is supplied to the heating electrode, which is the heating means, from an external power source (not shown). The width of this heating pulse 61 is about 10 ms.

In parallel with this operation, a power source 56 is connected to the transparent electrode (also serving as a heating electrode) of the liquid crystal cell 50 via a changeover switch 57, which is sufficient for orienting the liquid crystal. A voltage (here, 50 V) is applied. However, this voltage is not applied to the liquid crystal cell 50 until the photoconductive layer 55 is exposed. The liquid crystal is once made into a liquid phase by Joule heat generated by the heating current pulse 61, and then is naturally cooled to change into a nematic phase. When the liquid crystal phase detection sensor 62 detects that the liquid crystal has changed from the liquid phase to the nematic phase, it receives the signal S2, and Δt
The semiconductor laser 2 is slightly delayed (for example, about 1 ms).
Writing of an image to the light modulator 30 by 1 is started,
The optical image irradiation system 40 reads out an image from the light modulator 30,
An image is irradiated to the photoconductive layer 55 side of the liquid crystal cell 50. At this time, since the voltage is applied to the electrodes of the liquid crystal cell 50 in advance, the electric field pattern according to the optical image is immediately given to the liquid crystal cell 50 by the exposure by the optical image irradiation system 40, and according to the optical image. The liquid crystal is aligned. That is,
When the image is rewritten periodically, the above-described operation is continuously performed, and the image is rewritten according to the moving image information. It should be noted that the exposure and the application of the voltage are preset so that the liquid crystal is completed in sufficient time before the phase transition from the nematic phase to the smectic phase. Particularly, in this embodiment, since the image writing operation is performed slightly after the detection signal S2 is output from the liquid crystal phase detection sensor 62, the phase change of the liquid crystal in the liquid crystal cell 50 is stable. The image writing is assured as much as the image writing is performed in this state, but the image writing operation is designed to be performed immediately in synchronization with the detection signal S2 from the liquid crystal phase detection sensor 62. It doesn't matter.

When the image is not rewritten, the heating pulse 61 is not applied after the photoconductive layer 55 is irradiated with the last image to be written while applying the voltage of the power source 56 in the nematic phase. Well, in this case, since the liquid crystal phase undergoes a phase transition to the smectic phase (having a memory property at room temperature) while maintaining the alignment state according to the image, the last written image is applied with the power supply 56 voltage. It will be retained without it.

Embodiment 2 FIG. 4 shows another embodiment to which the present invention is applied. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted here. In the figure, since the area for writing an image in the light modulator 30, that is, the scanning width is narrow, it is possible to replace the mechanical scanning device used in the first embodiment with two ultrasonic deflectors (X-Y). Direction) 81,82
Is used to write an image of the output light from the ultrasonic deflectors 81 and 82 to the optical modulator 30 via the reflection mirror 83. In this embodiment, as the ultrasonic deflectors 81 and 82, for example, an element in which TiNbO3 is bonded to a TeO2 single crystal as a transducer (Paper 154 No99 / '71 of the Institute of Electrical Communication, "Commentary / Recent Progress of Optical Deflection Technology") P1266) and the like can be used. According to this type, the scanning speed is higher than that of the mechanical scanning, and the reliability is higher than that of the first embodiment because no mechanical parts are used.

[0026]

As described above, according to the first aspect of the invention, in the light receiving type display device utilizing the light scattering mode of liquid crystal capable of obtaining high reflection contrast, an image is once displayed on the light modulator. Since the image is written at high speed and this image is enlarged and projected on the liquid crystal cell to be displayed, the image can be displayed and rewritten at the same high speed as the electronic display device, and the display can be performed in the same manner as the printer output. High resolution will be obtained. Therefore, it is possible to provide an image writing technology that achieves both high-speed display and high resolution comparable to printer output, and it is possible to realize image display that is easy for human eyes to see and that is equivalent to printer output. . According to the second aspect of the invention, light is transmitted at room temperature only by applying an electric field.
Since it becomes possible to control opacity (scattering), the device configuration, in applications that require only the display of moving images,
The driving method can be simplified. Further, according to the invention of claim 3, after the image is written, the image can be held at room temperature without a power source, so that the displayed image can be picked up and grasped without restriction of electrical connection, Since it is possible to arrange them side by side, a display device that can be handled like a paper document can be realized.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a first embodiment of a liquid crystal display device to which the present invention is applied.

FIG. 3 is a timing chart showing an image rewriting operation according to the first embodiment.

FIG. 4 is an explanatory diagram showing a second embodiment of a liquid crystal display device to which the present invention is applied.

FIG. 5 is an explanatory diagram showing an example of a conventional liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image writing means, 2 ... Optical modulator, 3 ... Optical image irradiation means, 4 ... Liquid crystal cell, 4a ... Photoconductive layer, 4b ... Liquid crystal-polymer composite film

Claims (3)

[Claims] 1. An image writing unit (1) for digitally writing an image according to moving image information, and an optical modulator (2) for holding the written image as a change in optical state.
And an optical image irradiating means (3) for reading out an image on the light modulator (2) with light in an analog manner and enlarging and projecting the optical image, and an enlarged optical image from the optical image irradiating means (3) A photoconductive layer (4a) to be irradiated and a liquid crystal-polymer composite film (4b) in which liquid crystal is dispersed in a polymer resin are laminated, and the alignment of the liquid crystal is controlled according to the electric field pattern from the photoconductive layer (4a). A liquid crystal display device comprising a liquid crystal cell (4). 2. The liquid crystal cell-polymer composite film (4b) according to claim 1, wherein the liquid crystal exhibiting a nematic phase at room temperature is dispersed in a polymer resin. A liquid crystal display device characterized by the above. 3. The liquid crystal-polymer composite film (4b) of the liquid crystal cell (4) according to claim 1, wherein the liquid crystal exhibiting a smectic phase at room temperature and a nematic phase at room temperature or higher is in a polymer resin. A liquid crystal display device, which is a composite film dispersed in a liquid crystal display device.