JPH06180446A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the bright reflection type light scattering liquid crystal display device by constituting a light reflection element in such a manner as to reflect incident light only in the specific angle direction mainly with the incident angle of the light and providing an illuminating means for irradiating the liquid crystal display device mainly from only the one direction on an observer side at need. CONSTITUTION:The incident light 10 on a picture element 8 is scattered while the light passes the picture element 8 when the light reflection element 7 is formed to have specular surface reflectivity. This light is specular-reflected by the surface of the reflection element 7 and is further scattered and emitted while the light passes the picture element 8 therefor, the light is visible brightly and to the reflected light to the observer direction 12. On the other hand, the incident light 11 on the light transmitable picture element 9 is emitted by general refraction and specular reflection and, therefore, the reflection angle is equal to the incident angle and the light does not progress to the observer direction. The picture element 9 is thus observed dark. The display is not visible from the specular reflection direction from the illuminating means in the case of use of a mirror surface reflection plate as the light reflection element 7. Then, the illuminating means is eventually necessitated to be merely provided in the directions exclusive of the specular reflection direction when viewed from the observer direction 12.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reflective light-scattering liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, the most common liquid crystal mode is TN (t
Wisted nematic mode and STN (su
Although it is a per twisted nematic mode, in these modes, the display becomes dark due to insufficient steepness in electro-optical characteristics and the necessity of using two polarizers. When a dichroic dye is added to the liquid crystal to form a guest-host (GH) type, it becomes possible to display even one sheet of the polarizer, which makes it somewhat brighter, but in this case, the contrast is remarkably lowered. Resulting in. When performing color display, it is impossible to adopt the TN type or the STN mode GH type because a large contrast is required.
In order to construct a color liquid crystal display device using these birefringence modes including the DAP type (or VAN type) and the ECB type, it is necessary to make the backlight extremely bright for the reasons described above. The liquid crystal display itself consumes very little power, but the provision of a bright illuminating means significantly impairs its remarkable features. Further, although the liquid crystal element originally has a thin flat type structure, the provision of such an illumination means impairs the thin structure. Even when performing monochrome display, the display quality cannot be said to be sufficient due to the darkness of the display when the backlight is not used. In the so-called active matrix type configuration in which elements such as TFTs and MIMs are provided for each pixel, the active matrix is not used because the insufficient steepness in electro-optical characteristics in the TN mode can be covered. A display much brighter than that of the above-mentioned simple matrix type liquid crystal element is possible, but it is still impossible to obtain sufficient brightness without using a backlight by using two polarizers. Further, since the polarizer is expensive, it is considerably disadvantageous in cost to use two polarizers. The process of attaching the polarizer (polarizing plate) to the liquid crystal element is not easy either, and it is difficult to attach it so as not to entrap air bubbles or generate wrinkles. The yield reduction due to this cannot be ignored. Further, since a general polarizing plate is made by including iodine in stretched polyvinyl alcohol (PVA) or stretching PVA containing iodine, it is significantly inferior in heat resistance and moisture resistance. Therefore, it is no exaggeration to say that the reliability of current liquid crystal elements is determined by the polarizing plate. On the other hand, in recent years, a polymer-dispersed liquid crystal in which small spheres of liquid crystal are dispersed in a polymer matrix has been proposed (Ferguson: Tokushusho 58-501631), which is not easily affected by the thickness of the liquid crystal layer and has a large area. However, it is attracting attention because it has features such as that it does not require a polarizing plate. Further, in Japanese Patent Laid-Open No. 1-1198725 of Dainippon Ink and Chemicals, a polymer network type liquid crystal in which a liquid crystal is dispersed in a three-dimensional network structure formed by a photocurable resin is used for a liquid crystal layer of a display device. In addition to features similar to dispersed liquid crystal, low voltage drive,
It has been shown that advantages such as excellent steepness can be obtained. Since these liquid crystal elements perform light modulation and display by utilizing the light scattering property of the liquid crystal layer, it is very difficult to construct a direct-view display element other than the guest-host type, and a projection display Has been actively developed. However, if it is used as a projection type, in addition to a powerful lamp, a projection optical system is also required, which is far from the original thin structure of the liquid crystal element than when a backlight is used. In addition, the guest-host type is often inferior in reliability due to impurities contained in the dichroic dye and products generated by photolysis, and a dispersion structure of a polymer and a liquid crystal is formed using a photocurable resin. When trying to do so, the dye may hinder the photo-curing reaction, which greatly limits the material system.

[0003]

[Object] An object of the present invention is to provide a bright reflective light-scattering liquid crystal display device.

[0004]

In the liquid crystal device of the present invention, a light-scattering liquid crystal layer is sandwiched between a pair of substrates provided with liquid crystal driving electrodes, a light reflecting element is provided outside the liquid crystal layer, and an electric field applied to the electrodes is applied. In a liquid crystal device that controls the light scattering property of the liquid crystal layer to perform light modulation, the liquid crystal layer is in a light scattering mode, and the light reflecting element is mainly specified with respect to an incident angle of incident light. Is configured to reflect light only in the angular direction of. The configuration of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically showing a cross section of a liquid crystal device according to the present invention. In the configuration of the present invention,
It comprises a light scattering liquid crystal element 1 and a light reflecting element 2. For the sake of explanation, it is assumed that the pixel 3 is in the light scattering state and the pixel 4 is in the light transmitting state. When the light reflection element 2 is a diffuse reflection element used in a general reflection type display, regardless of whether the pixel is light transmissive or light scattering, the light is reflected toward the observer by diffuse reflection by the reflection element. Therefore, the contrast cannot be obtained. Further, as far as is known so far, since the light-scattering liquid crystal element has a large forward scattering efficiency, even if a black (or dark color) colored plate is arranged in place of the light reflecting element 2, the pixel scatters light. However, the color of the colored plate on the back side was visually recognized when it was a sex, and it was not possible to obtain a sufficient contrast. In the present invention, since the light reflecting element 2 reflects the reflected light only in a specific direction with respect to the incident angle, the light incident on the pixel 4 in the light transmissive state is reflected in the observer direction. Therefore, it is possible to obtain contrast without using a dichroic dye. FIG. 2 shows how light is scattered when the reflective element 7 has specular reflectivity (reflection angle = incident angle). In the liquid crystal element 6, the pixels 8 and 9 are in a light scattering state and a light transmitting state, respectively. The light 10 incident on the pixel 8 is scattered while passing through the pixel 8, specularly reflected on the surface of the reflecting element 7, and further scattered while passing through the pixel 8 to be emitted, so that the light 10 is reflected toward the observer 12. Visible brightly due to the light. On the other hand, the light 11 incident on the light-transmissive pixel 9 is emitted by general refraction and specular reflection, so that the reflection angle becomes equal to the incident angle, and the light does not travel toward the observer direction 12.
Therefore, the pixel 9 is visually recognized as dark. FIG. 3 shows a state of light reflection when the diffuse reflection plate 14 is used as the reflection element as in the prior art. In the liquid crystal element 13, the pixel 1
5 and 16 are in a light scattering state and a light transmitting state, respectively. Light 1 incident on the pixel 15 in the light scattering state
7 is scattered while passing through the pixels, and is also diffused and reflected on the surface of the diffuse reflection plate 14, so that the observer direction 1
The reflected light reaches 9 and is visually recognized brightly. On the other hand, the light 18 incident on the pixel 16 in the light transmissive state is not scattered within the pixel but is diffusely reflected on the surface of the diffuse reflection plate 14, so that the reflected light also reaches the observer direction 19, The pixel 16 was also brightly viewed. Therefore, when the liquid crystal element in the light scattering mode and the conventional diffuse reflection plate are combined, almost no contrast can be obtained. FIG. 4 shows the light reflecting element 2 according to the present invention.
1 (corresponding to the element 2 in FIG. 1), the state of light reflection when a reflector that reflects incident light in the incident direction (reflection angle = −incident angle) is used is shown. In the liquid crystal element 20, the pixels 22 and 23 are in a light-scattering state and a light-transmitting state, respectively. The light 24 incident on the pixel 22 is scattered as it passes through the pixel, and the incident angle on the reflection plate 21 becomes various. The light reflected by the reflection plate 21 is emitted while being further scattered in the pixel, so that the observer direction 26
The reflected light also reaches and is visible brightly. On the other hand, the pixel 23
Since the light 25 incident on the incident light is incident on the reflecting element 21 without being scattered and is reflected in the incident direction,
The reflected light does not reach, and it is visible dark.

The contrast when the liquid crystal display device of the present invention is used is determined by the ratio of the brightness in the illumination direction to the brightness in the observer direction. Therefore, the visibility is highest when strongly illuminated only from one direction. On the other hand, when the illumination is extremely diffuse, the brightness of the illumination light and the brightness in the direction of the observer become almost equal, and the visibility is poor. Therefore, as shown in FIG. By providing, it is possible to secure a certain level of visibility. In FIG. 5, an illuminating unit 28 is provided so that the illuminating light is not emitted in the observer direction 30, and illuminates the display surface of the display device 27 including a liquid crystal element and a light reflecting element. When a specular reflector is used as the light reflection element, the illumination means 2
The display cannot be visually recognized from the regular reflection direction 29 from 8. Therefore, the illuminating means 28 may be provided in a direction other than the regular reflection direction when viewed from the observer direction. Generally, since the display device is not observed from the illumination direction, when a reflection plate that reflects reflected light in the incident direction is used as the light reflection element as shown in FIG. 4, the direction of the illumination means 28 is restricted. However, if the specular reflection on the surface of the liquid crystal display device 27 is directed toward the observer, this specularly reflected light interferes with the display of any display element, so that the specular reflection is seen by the observer. It is better not to arrange the illumination means 28 in the direction.

A configuration example of the liquid crystal element used in the present invention is shown in FIG. Substrate 3 having liquid crystal driving electrodes 33, 34
A light-scattering liquid crystal layer 35 is sandwiched between 1 and 32. In principle, the liquid crystal layer 35 can be used in any mode as long as it is a light scattering mode, but it is particularly preferable to use a dispersion film made of a liquid crystal and a polymer in view of response speed, driving voltage and the like. As a method for producing a dispersed film composed of a liquid crystal and a polymer, a solvent evaporation method for obtaining a phase separation structure of the liquid crystal and the polymer by evaporating a solvent from a solution or suspension of the liquid crystal and the polymer, an ultraviolet curable resin or a thermosetting resin Known is a curable resin method in which a phase-separated structure is obtained by polymerizing a prepolymer from a mixed solution of the prepolymer and liquid crystal. The most general casting method among the former and the ultraviolet curing method typical of the latter will be specifically described below. In the casting method, both a polymer and a liquid crystal are dissolved in a suitable solvent or a mixed solvent, this solution is applied onto a substrate, and the solvent is evaporated to obtain a dispersed film. Polymer materials that can be used in the casting method include acrylic resins such as polymethylmethacrylate (PMMA), polystyrene, polycarbonate, polyvinyl alcohol, polyarylate, polyether sulfone, siloxane resins, etc., which are soluble in various solvents. Although it is preferable because it is easy, epoxy resin, polyamide resin, polyvinylidene fluoride, polyethylene and their copolymers can be used by devising the solvent system. Examples of the liquid crystal material include general biphenyl-based, terphenyl-based, phenylpyrimidine-based, phenylcyclohexane-based, phenylester-based, and the like, and liquid crystal compositions composed of a mixture thereof. Common solvents for liquid crystal and polymer include diethyl ether, ethers such as tetrahydrofuran (THF), ketones such as acetone, aromatic solvents such as toluene and chlorobenzene, γ-butyrolactone, trichloroethane, N, N-
Examples thereof include dimethylformamide, dimethylformamide, N-methylpyrrolidone, cellosolve type, and carbitol type. The composition ratio of the solution consisting of polymer, liquid crystal and solvent applied to the substrate varies depending on the composition ratio of the polymer and liquid crystal in the prepared dispersion film, the thickness of the dispersion film, and the solubility of both components in the solvent. When the total concentration is approximately 5% (all% are% by weight) or less, the thickness of the dispersion film is too thin and sufficient light scattering properties cannot be obtained. On the contrary, when the concentration is too high, the film thickness is too thick and the electric field strength applied to the liquid crystal becomes small, so that the liquid crystal does not show a sufficient response. The composition ratio of polymer and liquid crystal is 10: 9.
The range of 0 to 60:40 is preferable. About 10% polymer
In the following, it is difficult to obtain a stable dispersion structure, and the liquid crystal does not change much from the bulk state, and the light scattering property and high-speed response that are characteristic of the dispersion film are lost.
On the other hand, when the content of the polymer is 60% or more, the volume ratio of the liquid crystal in the dispersion film becomes too small, and the change in light transmittance (light scattering property) when a voltage is applied becomes small.
Examples of methods for applying a solution containing a liquid crystal, a polymer, and a solvent to a substrate include spin coating, bar coater coating, dipping, and blade coating. Examples of the photocurable resin that can be used in the present invention include unsaturated polyester / styrene type, polyene / thiol type, epoxy / Lewis acid type, and acrylate type resins. When it is necessary to adjust the polymerization rate or viscosity, different materials may be mixed, or monomers or oligomers having different degrees of polymerization may be added. Examples of the compound that can be used as the photopolymerization initiator include acetophenone, benzophenone, benzyl, benzoin, thioxanthone and their derivatives, and tetramethylthiuram monosulfide (T
MS) etc. The concentration of the polymerization initiator is 0.3 to 5.0% with respect to the polymer, and more preferably 0.5 to 3.0.
% Is good. If the concentration is lower than this, sufficient polymerization reaction does not occur, and if the concentration is too high, the adverse effect of impurities caused by the photodecomposition of the polymerization initiator becomes large. As the liquid crystal material when the dispersion film of the liquid crystal and the polymer is prepared by using the photocurable resin, the same material as in the case of the casting method can be exemplified. The light irradiation intensity depends on the light absorption wavelength of the polymerization initiator to be used, the concentration thereof, and the irradiation device, but when using a general ultraviolet irradiation device, it is approximately 5 mW / cm ² or more, preferably 10 mW / cm ^2.
It is better to use a device of cm ² or more. If it is weaker than this, it is inefficient because it requires irradiation for a long time. When the irradiation intensity is high, it is sufficient to shorten the irradiation time, but when the polymerization rate is too fast, it becomes difficult to control the shape and size of the dispersion structure, so it is necessary to adjust the irradiation intensity appropriately. . In the dispersion film of polymer and liquid crystal, whether the liquid crystal is dispersed in the polymer in the form of liquid droplets or is contained in the gap of the polymer structure having a sponge shape or a three-dimensional network structure is determined. Although it depends on the manufacturing method, it depends on the combination of the polymer and the liquid crystal and the composition ratio of the liquid crystal. In general, when the film is formed by the same method and material, the former structure tends to occur when the composition ratio of the liquid crystal is small, and the latter structure tends to occur when the composition ratio of the liquid crystal is large. Both structures may be formed in the film.

The simplest reflecting element that can be used in the present invention is a general mirror. Since a general mirror has a specular reflection characteristic, it is possible to display as shown in FIG. Another type of light reflecting element that can be used in the present invention is one in which incident light is reflected substantially in the incident direction. For the sake of simplicity, first, a two-dimensional structure will be described. FIG. 7 illustrates an element in which two mirrors are attached so as to form an angle of 90 °. As can be seen from the figure, when the incident light 36 is parallel to the paper surface, the reflected light 37 is emitted in the same direction as the incident light. When the incident light 36 is not parallel to the paper surface, the reflected light 37 is deviated toward the front side or the back side of the paper surface and reflected. Even if the incident light is not parallel to the paper surface, in order to make the reflected light parallel to the incident direction, the three mirrors 38, 39, which form the apex angle of the cube as shown in FIG. 40 combined, c
A ube corner mirror may be used (the three mirrors make an angle of 90 ° with each other). The mirror surface of each mirror faces the inside of the apex angle, and the incident light 41 from the inside of the apex angle is reflected in the incident direction regardless of the incident angle. The same effect can be obtained with a total reflection prism. Similar to FIG. 7, first, a two-dimensional case is shown in FIG. As is apparent from the figure, the reflected light 43 is parallel to the incident light when the incident light 42 is parallel to the paper surface. When the incident light 42 is not parallel to the paper surface, the reflected light 43 is displaced toward the front or the back of the paper surface as in the case of the mirror in FIG.
In order for the incident direction and the reflection direction to coincide with each other regardless of the incident direction, as shown in FIG. 10, a total reflection prism (cube corner prism) having the shape of the apex angle portion of the cube is used.
rism) may be used. In this case, the three surfaces forming the apex angle form 90 ° with each other, and the light 44 incident from the other surface is reflected parallel to the incident direction regardless of the incident angle. In FIG. 8 and FIG. 10, the cube cor
ner mirror and cubecorner pri
Although the sm having the most recognizable shape is shown, there are many optical elements having the same function and name even in other shapes. In the above description of the function of the cube corner mirror or the cube corner prism, only one element is shown in each of FIGS.
0) It is desirable to manufacture a minute element having a size of about 1 mm to 0.1 mm by stamper molding or the like, and in this case, it can be applied to a display device of a general size having a diagonal of about 15 inches or less. cube corner mir
When each light reflecting element that functions as a ror or cube corner prism is large, the pixel of the liquid crystal element must be large, and in this case, it is desirable to apply it to a large outdoor display element. As the element that mainly reflects the incident light in the incident direction, the element having the structure shown in FIG. 11 can also be used. This element has a structure in which a substantially spherical lens 45 is partially embedded in a sheet-shaped carrier 46, and the interface between the lens and the carrier is subjected to a treatment for improving the light reflectivity. There is. Such a structure can be prepared by previously adhering a material having a high reflectance such as aluminum to the surface of the carrier by vapor deposition or the like, press-bonding the spherical lens, and then removing the portion not in contact with the lens. This is an example of one manufacturing method of the configuration of the present invention, and is not limited to this.
By further improving the structure shown in FIG. 11 and coloring a part 49 of the upper end portion of the spherical lens 47 by a method such as dyeing or printing as shown in FIG. It is possible to obtain a liquid crystal device in which light reflection is reduced and visibility is further improved. An enlarged view of one lens is shown in FIG. By using such a lens, the illumination is diffuse and a contrast can be obtained even when a certain intensity of light is incident from the viewer's direction. The reason will be described below. Light incident on the light shielding portion 50 from the observer direction is absorbed and thus is not reflected in any direction. The light 51 incident on the outside of the sphere with respect to the light shielding portion 50 is reflected in the lens and is reflected in the direction of the observer, but a part thereof is reflected at the point of incidence on the lens and is lost as reflected light 52. Be seen. Therefore, the brightness when viewed from the direction normal to the reflective element surface is darker than the apparent area ratio of the light shielding portion 50 and other portions. On the other hand, when the incident direction is deviated from the normal line of the reflective element surface like most of the illumination light, the apparent area ratio between the light-shielding portion 50 and the other portions is small, so that the reflection efficiency is high. It will be big. Therefore, when the liquid crystal element arranged on the front surface of the reflecting element is in the light transmitting state, the reflected light in the observer direction is shielded by the light shielding portion 5.
It becomes smaller than that when there is no 0, and when it is in the light-scattering state, it does not become so dark that a large contrast can be obtained. The size of the light-shielding portion can be expressed by the size of the angle θ formed between the center 53 of the sphere and the end of the light-shielding portion. However, if θ ₁ is too small, the contrast cannot be improved. It also becomes dark when it is light-scattering. The size of θ ₁ is in the range of 10 to 120 °, preferably 20 to 100 °. The size of the substantially spherical lenses 45 and 47 is preferably 0.1 to 1 mm or less in the case of a display of a personal device used indoors. A large screen display device used outdoors or a lens larger than this can be used when fine pixels are not required even when used indoors. It is also possible to reduce the light reflection toward the observer by deforming the shape of the lens from a substantially spherical shape instead of the colored light shielding portions 49 and 50 in FIGS. An example is shown in FIG. In this example, a wedge-shaped recess 55 is provided at the upper end of the substantially spherical lens 54. Similar to the case of FIG. 13, when the size is represented by the angle θ ₂ formed by the center 56 of the sphere and the end of the deformed portion, when θ ₂ is too large, the function as a substantially spherical lens is lost, and conversely. If it is too small, the effect of deformation is lost, so the range of θ ₂ is 10 to 120 °, preferably 20 to 100 °. θ
_{If 3} is too large, the portion 55 becomes flat and the light flux from the main line direction cannot be bent sufficiently. On the contrary, if it is too small, it is difficult to manufacture, and the optical path in the lens is blocked, which is not preferable. The magnitude of θ ₃ is 30 to 160 °, preferably 40 to 150 °.

Example 1 Acrylic prepolymer HX620 manufactured by Nippon Kayaku Co.,
E. Photopolymerization initiator Darocur11 manufactured by Merck
About 73% of 73 was added and mixed with liquid crystal BL007 manufactured by the same company. The ratio of liquid crystal to polymer was 3: 1. IT this
It was applied on a glass substrate with O by a bar coater, put in a glass container, and the inside of the container was replaced with nitrogen. In this state, irradiation with an ultraviolet irradiation device having an irradiation intensity of 50 mW / cm ² was performed for 30 seconds, and a light-scattering dispersion film was obtained. This film thickness was about 6 microns. 1PET with ITO (uniaxially stretched polyethylene terephthalate) was attached to the surface on the side of the dispersion film so that the ITO surface was in contact with the dispersion film.
A light-scattering liquid crystal element corresponding to FIG. 6 was used. On the other hand, aluminum was vapor-deposited on a glass substrate, and the above liquid crystal element was attached so that 1PET was in contact with the vapor deposition surface to obtain a liquid crystal device. When a voltage was applied to the electrodes and a pixel with a liquid crystal element was changed between a transparent state and a light scattering state, the pixel was dark when the liquid crystal element was transparent and white when the liquid crystal element was light scattering. However, although it was not possible to visually recognize the display from the direction of regular reflection with respect to the illumination direction, on the contrary, in the environment where the liquid crystal device was strongly illuminated only from one direction, the display had high contrast.

Example 2 When the liquid crystal device obtained in Example 1 was observed in a place where the incident light from the observer's direction was strong because the illumination light was emitted from various places in the room, a sufficient contrast was obtained. I can no longer get it. This was combined with a luminaire in an arrangement as shown in FIG. The direction of illumination was 60 ° above the normal to the display surface. The display was clearly visible when observed at an angle of about 50 ° from the normal direction. The display was visible even below the normal line, but the display could not be seen from below about 50 °, but it was visible in a sufficiently wide range. The display unit 27 is changed to the illumination 2
If the light is shielded so that light from other than 8 does not enter, the contrast is further improved, but this is not preferable because the configuration of 27 becomes large. The luminaire 28 does not have to be a special one, and an ordinary lamp such as a desk lamp has been sufficiently effective. The configuration of this embodiment is most effective for display in a dim place such as a movie theater. In particular, since the display device main body 27 does not need to have a heating element such as a backlight, it is very excellent in safety. It is also possible to change the display color by changing the color of the lighting fixture 28 to change the atmosphere, or to change the color according to the display content.

Example 3 A liquid crystal cell was prepared by dispersing a gap material made of plastic beads on a 1PET substrate with ITO and bonding them so that the ITO surfaces face each other. Pixel size is 1
It was 0 mm square. To this, acrylic prepolymer HX620 manufactured by Nippon Kayaku Co., E. Photopolymerization initiator Darocur 1173, manufactured by Merck, E.I. A mixture of liquid crystal BL007 manufactured by Merck Co., Ltd. was sealed and irradiated with ultraviolet rays to prepare a light-scattering liquid crystal element. Then, follow the procedure below
The ube corner mirror was created. First, a mold having a surface shape as shown in FIG. 15 was made. Figure 15
Indicates a part of the mold, and such a triangular pyramid is formed on the entire surface. The vertices of each triangular pyramid consist of three faces of 90 ° to each other, and the bottom face is an equilateral triangle. The length of one base was 1 mm. This was contacted with a thermosetting resin and heated to cure and peel off the resin. On the resin surface,
Corresponding to the triangular pyramid of 5, a triangular pyramidal recess remains. Aluminum is vapor-deposited on this surface, and many cube corners are
A reflection plate made of er mirror was produced. When this reflection plate was placed on the back surface of the above-mentioned liquid crystal element and observed, it became bright white. Next, when a voltage was applied to the upper and lower transparent electrodes, the pixels to which the voltage was applied became dark and sufficient contrast was obtained. In this case, unlike the first embodiment, the display can be visually recognized even from the regular reflection direction of the illumination, but the reflection of the illumination light on the surface of the display device becomes an obstacle and the contrast is lowered.

Example 4 When the liquid crystal display device of Example 3 was observed under diffuse illumination, the visibility was remarkably low. Therefore, when the display was illuminated from the direction of 50 ° above the normal to the display surface as in Example 2, the visibility was improved. In this case, unlike the case of the second embodiment, the display can be visually recognized even in the regular reflection direction, that is, from about 50 ° below the normal line, but the display surface is considerably closer to 50 °. The specular reflection light from was strong and it was practically difficult to visually recognize.

Example 5 A plastic prism having a shape similar to that shown in FIG. 15 was produced. The size of the base of one prism is 1 mm.
Since each prism functions as a cube corner prism, the incident light from the bottom direction of the triangular pyramid in FIG. 15 is reflected in the same direction as the incident direction. The same light-scattering liquid crystal element as that of Example 3 was produced, and a reflecting plate made of the above cube corner prism was arranged on the back surface of the liquid crystal element so that the bottom surface of each prism faced the liquid crystal element side. Pixels to which no voltage was applied were white, and pixels to which voltage was applied were dark, and clear contrast was obtained.

Example 6 In the same manner as in Example 3, a 1PET substrate was used to fabricate a light-scattering liquid crystal element having a pixel pitch of 0.3 mm. As the light reflection plate, there was prepared one in which a large number of minute spherical lenses of about 0.1 mm were embedded on a plastic sheet as shown in FIG. When this reflective plate was arranged on the back surface of the liquid crystal element and observed, the portion where the pixels of the liquid crystal element were in the transparent state was dark and the portion in which the light scattering state was white was visually recognized. This device is also difficult to see because it is reflected on the surface of the device when viewed from the direction of regular reflection with respect to the illumination direction, but the light reflecting element and the liquid crystal element are curved together, and the surface is slightly concave with respect to the observer direction. By deforming so that the regular reflection light was reduced, it became easier to visually recognize.

Example 7 In Example 6, the upper end portion of the spherical lens was colored black. The size of the colored portion is about 45 ° when expressed by the size of θ ₁ in FIG. Although the liquid crystal device is slightly gray as a whole and the background is dark, the display can be visually recognized even under diffused illumination.

Example 8 In Example 7, instead of coloring the lens, the upper end of the lens was deformed as shown in FIG. The degree of deformation is
In FIG. 14, θ ₂ is about 45 ° and θ ₃ is about 90 °.
Also in this case, the display can be visually recognized even under the diffused illumination.

[0016]

According to the present invention, a bright reflective liquid crystal display device is provided without using a dichroic dye or the like.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross section of a liquid crystal device of the present invention.

FIG. 2 is a diagram showing how light is scattered by the liquid crystal device of the present invention when the reflective element has specular reflectivity (reflection angle = incident angle).

FIG. 3 is a diagram showing how light is scattered in the liquid crystal device when the reflection element is a conventional diffuse reflection plate.

FIG. 4 shows that incident light is reflected in the incident direction (reflection angle =
FIG. 7 is a diagram showing how light is scattered by the liquid crystal device when a (incident angle) reflector is used.

FIG. 5 is a diagram schematically showing how light is scattered in the liquid crystal device of the present invention when an illuminating unit that does not illuminate the observer is provided.

FIG. 6 is a diagram schematically showing a cross-sectional structure of an example of the liquid crystal element of the present invention.

FIG. 7 is a view showing a light reflecting element in which two mirrors are attached to each other so as to form an angle of 90 °.

FIG. 8: Three mirrors 38, 39 forming the apex angle of a cube
Cube corner m combining 40 and 40
It is a figure which shows the light reflection element which used error.

FIG. 9 is a diagram showing a light reflecting element using a total reflection prism.

FIG. 10 is a diagram showing a light reflecting element using a cube corner prism in which three surfaces forming an apex angle are 90 ° to each other.

FIG. 11 is a diagram showing a light reflection element using a sheet-shaped carrier in which a substantially spherical lens is partially embedded.

12 is a diagram showing a light reflecting element in which the upper portion of the spherical lens shown in FIG. 11 is colored.

FIG. 13 is an enlarged view of one spherical lens shown in FIG.

FIG. 14 is an enlarged view of one lens in which a part of the spherical lens shown in FIG. 11 is cut out and deformed.

FIG. 15: Multiple cube corner mirro
It is a figure which shows the reflecting plate which consists of.

[Explanation of symbols]

 1 Light-scattering liquid crystal element 2 Light-reflecting element 3 Pixel in light-scattering state 4 Pixel in light-transmitting state 5 Incident light 6 Liquid crystal element 7 Reflecting element 8 Pixel in light-scattering state 9 Light-transmitting state Pixel 10 Incident light 11 Incident light 12 Observer direction 13 Liquid crystal element 14 Diffuse reflection plate 15 Light scattering pixel 16 Light transmissive pixel 17 Incident light 18 Incident light 19 Observer direction 20 Liquid crystal element 21 Incident light Reflector for reflecting light in the incident direction 22 Pixel 23 Pixel 24 Incident light 25 Incident light 26 Observer direction 27 Display device composed of liquid crystal element and light reflection element 28 Illuminating means 29 Regular reflection direction 30 Observer direction 31 Substrate 32 Substrate 33 Electrode 34 electrode 35 liquid crystal layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroyuki Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (5)

[Claims] 1. A liquid crystal layer and a light reflection element on the outer side of the liquid crystal layer opposite to the observer side are provided between a pair of substrates provided with liquid crystal driving electrodes, and light is scattered by an electric field applied to the electrodes. In a reflection type liquid crystal display device that reversibly changes between an opaque state and a transparent state and controls the magnitude of light transmission to perform light modulation, the light reflection element has an angle of incidence of incident light with respect to an incident angle. A liquid crystal display device, which mainly reflects light only in one direction, and has an illuminating means for illuminating the liquid crystal display device mainly from one direction on the observer side if necessary. 2. The liquid crystal display device according to claim 1, wherein the light reflecting element has specular reflectance (reflection angle = incident angle) or light reflectance similar to specular reflectance. 3. The liquid crystal display device according to claim 1, wherein the light reflecting element reflects the incident light in the incident direction or in the vicinity thereof. 4. The liquid crystal display device according to claim 1, wherein the illumination means is provided in a direction other than the specular reflection direction when viewed from the observer side. 5. A reflector in which a light reflecting element is formed by combining three mirror surfaces so as to form one corner of a cube.
A corner reflector (a), a cubic prism (b), and a spherical lens are partially embedded in a sheet-shaped support so that the interface between the embedded lens and the support has a high light reflectance. (C) provided with various means, and a part of a substantially spherical lens partially embedded in the sheet-like support is deformed or colored by a coloring means to obtain a light reflectance in a specific direction. 5. At least one reflector selected from the group consisting of reduced ones (d).
The described liquid crystal display device.