JPH06258638A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which uses a scatter type liquid crystal display mode, has a high contrast, and makes a uniform display of large area, and is driven with a low voltage and fast in response. CONSTITUTION:The reflection type liquid crystal display device, which has a couple of transparent substrates 11a and 11b that have transparent pixel electrodes 12a and 12b on their internal surfaces and arranged oppositly to each other with a distance, has a liquid crystal layer 13 sandwiched between the substrates 11a and 11b, and utilizes a change between a light transmission state and a light scattering state depending on whether or not a voltage is impressed to the liquid crystal layer 13, is provided with a selective light reflecting means or light diffusing means 30, which has angle selectivity for transmitting light made incident from a view direction at an angle of incidence within a specific range and reflecting light made incident on other incidence angle ranges, on the reverse side of the liquid crystal layer 13 to an observer and a light absorbing means 20 on the reverse side of the reflecting means or light diffusing means 30.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a light-scattering type liquid crystal display device, and in particular, a reflection type display using a so-called polymer dispersion type liquid crystal display device having a liquid crystal dispersion film formed of a three-dimensional fine structure such as polymer and liquid crystal. Regarding the device.

[0002]

2. Description of the Related Art Conventionally, the most common liquid crystal mode is TN (tw
isted nematic) mode and STN (super twisted nemat)
ic) mode, but in these modes, the display becomes dark due to insufficient steepness in electro-optical characteristics and the need to use two polarizers. A guest-host (G
In the case of the H) type, it is possible to display even one sheet of the polarizer, so that it becomes bright to some extent, but in this case, the contrast is significantly lowered. 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 configure a color liquid crystal display device using these birefringence modes including the DAP type (or VAN type) and the ECB type using a horizontal alignment cell, it is necessary to make the backlight extremely bright for the above-mentioned reasons. is there. Although the liquid crystal element itself consumes less power than other display elements, 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, if the backlight is not used,
The display quality is not sufficient due to the darkness of the display. In a 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 dispersion type liquid crystal in which small spheres of liquid crystal are dispersed in a polymer matrix has been proposed (Ferguson: JP-A-58-501631), which has a large area and is not easily affected by the thickness of the liquid crystal layer. It is attracting attention because it has the advantages of being able to be made into a new type and not requiring a polarizing plate. Further, in JP-A-1-198725, 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 element, and the same characteristics as the polymer dispersion type liquid crystal are obtained. Besides, it has been shown that advantages such as low voltage driving and excellent steepness can be obtained. These liquid crystal elements use the light scattering property of the liquid crystal layer to perform light modulation and display,
It is very difficult to construct a direct-view type display device other than the guest-host type, and development as a projection type display has been actively conducted. 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]

An object of the present invention is to solve the above-mentioned problems of the prior art. The object of the present invention is high contrast and low voltage driving using a scattering type liquid crystal display mode, and over a large area. A uniform display is possible,
Moreover, it is to provide a liquid crystal display device having a high-speed response.

[0004]

According to the present invention, a pair of transparent substrates having transparent pixel electrodes on the inner surface and arranged facing each other and a liquid crystal layer is sandwiched between the substrates, and a voltage is applied to the liquid crystal layer. In a reflective liquid crystal display device that utilizes the change between a state of transmitting light and a state of scattering light depending on whether the light is applied or not, the light is incident from the viewing direction on the back side of the liquid crystal layer with respect to the viewer direction. Selective reflection or selective light diffusing means having angle selectivity for transmitting light having an incident angle in a specific range and reflecting or scattering light incident in other incident angle ranges, and a light on the back side of the reflecting means. The above object has been achieved by providing a liquid crystal display device characterized by being provided with an absorbing means. The selective light reflection or selective light diffusing means in the present invention transmits light having an incident angle in a specific range which is incident from the viewing direction as described above, and reflects or diffuses light incident in other incident angle ranges. It is preferable that it has angle selectivity, and in particular, when the liquid crystal layer is in a transparent state, it reflects or diffuses the reflected light in an angle range in which the reflected light is emitted from the liquid crystal display device in a direction that is not visually recognized by an observer. The liquid crystal display device of the present invention will be described in detail with reference to a constitutional example, using a polymer dispersion type liquid crystal cell as an example. FIG. 1 shows an example of a conventional polymer-dispersed reflective liquid crystal display device. The liquid crystal dispersion layer 13 is sandwiched between the translucent substrates 11a and 11b having the transparent electrodes 12a and 12b on the inner surface thereof to form the liquid crystal cell 10. Liquid crystal dispersion layer 13
Is composed of a liquid crystal 13a and a support 13b which is formed so as to divide the liquid crystal portion into fine regions and is made of a polymer material or the like. A light absorbing means 20 such as a black film is provided below the liquid crystal cell 10. When no voltage is applied to the liquid crystal cell 10, the liquid crystal dispersion layer 13 is in a state in which the orientation of the liquid crystal dispersion layer 13 is disturbed by the wall surface of the support, which causes a slight fluctuation in the refractive index in the liquid crystal dispersion layer 13. In this state, incident light 50 from the outside is scattered by the liquid crystal dispersion layer 13 as shown in FIG.
A part 501 of the backscattered component of the incident light 50 travels in the viewing direction and enters the eyes 40 of the observer, resulting in white display. When a voltage is applied to the liquid crystal layer, the liquid crystal is aligned parallel to the direction of the electric field (thickness direction of the liquid crystal layer), and fluctuations in the refractive index are reduced.
As shown in (1), the incident light 50 travels with almost no scattering, reaches the light absorption layer 20, is absorbed, and is observed as a black display. However, in the case of this configuration, FIG.
As shown in, even if the liquid crystal layer is in the light scattering state, the proportion of the forward scattering component 502 is large, and more than half of the light is absorbed by the light absorbing layer. As a result, sufficient white cannot be obtained, resulting in low contrast display. 4 and 5 show the structure of the liquid crystal display device of the present invention.
The liquid crystal cell 10 is the same as the conventional example, except that
In this example, on the lower side of the liquid crystal cell, light having an incident angle in a specific range including the observer direction is transmitted between the light absorbing means 20,
Reflects or scatters light incident at other incident angles,
There is preferably provided a selective light reflection or selective light scattering means 30 having an angle selectivity that reflects or scatters in a direction that is not visually recognized by an observer. FIGS. 6, 7 and 8 explain the operation of the selective light reflecting means used in the present invention. Reference numerals 61 and 62 denote boundaries of incident angles when incident light is transmitted and reflected. Selective light reflecting means 30
As shown in FIG. 6, incident light 51 having an incident angle i smaller than ic1 and ic2 is transmitted, and incident light 52 from an angle larger than that is reflected. FIG. 7 is a diagram for explaining the action when a voltage is applied to the device to bring the liquid crystal layer into a transparent state. Incident light 51 having an incident angle of ic or less on the selective light reflecting means 30 is transmitted through the liquid crystal dispersion layer 13 in the transparent state and is incident on the selective light reflecting means 30. The light also passes through the selective light reflecting means 30 and reaches the light absorbing means 20, and is absorbed and does not reach the observer 40. On the other hand, the incident angle is ic
The larger incident light 52 is reflected by the selective light reflecting means 30 and returns to the observer side, but does not reach the observer 40 if the reflection angle r is large as shown in the figure. Therefore, the element is observed black in this state. FIG. 8 schematically shows an optical path when the liquid crystal layer is in a scattering state. Incident light 51
Are scattered by the liquid crystal dispersion layer 13, and a part 511 of the backscattered component reaches the observer 40. The component 512, which is a part of the forward scattering component and has an incident angle with respect to the selective light reflecting means 30 of ic or less, is transmitted through the selective light reflecting means and absorbed by the absorbing means 20. Ingredient 513
Is reflected, again enters the liquid crystal dispersion layer 13, and is scattered again, and a part of the forward scattered component reaches the observer. On the other hand, the incident light 52 is also scattered by the liquid crystal dispersion layer 13, and a part 521 of the backscattered component reaches the observer. In addition, most of the forward-scattering components with strong light intensity (for example, 522, 52
In 3), since the incident angle with respect to the selective light reflection means is ic or more, it is reflected by the selective light reflection means 30 and again enters the liquid crystal dispersion layer 13, is scattered again, and is a forward scattering component having a relatively high light intensity. As a part of it reaches the observer 40. After all, for the observer, the backscattered component 521 of the incident light,
In addition to 511, a part of the light of the component that is reflected by the selective light reflecting means among the forward scattering components that are first scattered by the liquid crystal layer also arrives. The latter is a component that is wastedly absorbed by the light absorbing means in the conventional method described in FIG. 1, and the liquid crystal display device of the present invention can perform extremely bright white display by effectively utilizing such incident light. it can. In the present invention, when a general reflection element such as a diffuse reflection plate or a mirror that reflects light having any incident angle is used, the liquid crystal layer has a light-scattering state and a transparent state. The light is reflected toward the observer even if it changes between the two, and there is no difference in brightness and darkness, or when using a mirror, the difference in brightness and darkness is limited only when the direction of illumination light is limited to a specific narrow direction. Occurs. FIG. 9 illustrates the operation of the selective light diffusing means used in the present invention. The selective light diffusing means 302 has an incident angle i of ic as shown in the figure.
Incident angle light smaller than 11, ic22 (eg 51 in the figure)
Is transmitted, and incident light from other angles (for example, 5 in the figure
2) has the property of scattering. Reference numerals 61 and 62 denote boundaries of incident angles when incident light is transmitted and reflected. Figure 1
0 is a diagram for explaining the action when a voltage is applied to the element to bring the liquid crystal dispersion layer 15 into a transparent state. Incident light 51 having an incident angle to the selective diffusion means ic (= ic11 = ic22) or less is transmitted through the liquid crystal dispersion layer 13 in the transparent state and is incident on the selective light diffusion means 302. The light also passes through the selective light diffusing means 302, reaches the light absorbing means 20, and is absorbed and does not reach the observer 40. On the other hand, if the incident angle is i
The incident light 52 larger than c is scattered by the selective light diffusing means 302, and a small part returns to the observer side, but the intensity thereof is extremely weak because it is a backscattering component and hardly reaches the observer 40. Therefore, the element is observed black in this state. FIG. 11 schematically shows the optical path when the liquid crystal layer is in the scattering state. The incident light 51 is scattered by the liquid crystal layer, and a part 511 of the backscattering component is observed by the observer 40.
To reach. The component 512, which is a part of the forward scattering component and has an incident angle with respect to the selective light diffusing means 302 of ic or less,
Although transmitted through the selective light diffusing means and absorbed by the absorbing means 20, the component 513 having an incident angle of ic or more is scattered and a part of the component 513 is again incident on the liquid crystal layer 13 and is scattered again, A part of the scattered component reaches the observer 40. On the other hand, the incident light 52 is also scattered by the liquid crystal dispersion layer 13, and a part 521 of the backscattered component reaches the observer. Further, most of the forward scattering components having a high light intensity (for example, 522) are scattered by the selective light diffusing means 30 because the incident angle with respect to the selective light diffusing means is ic or more, and a part of them is again reflected in the liquid crystal layer. It is incident on the laser beam 13, is scattered again, and a part thereof reaches the observer 40. After all, in addition to the backscattered components 521 and 511 of the incident light, the observer also has a part of the light that is backscattered from the selective diffusing means among the forward scattered components that are first scattered by the liquid crystal layer. Will arrive. The latter is
In the conventional method described with reference to FIG. 1, all the components are wastefully absorbed by the light absorbing means, and even when the selective light diffusing means 302 is used by effectively using such incident light, the liquid crystal display of the present invention is used. The device can provide a very bright white display. As described above, the selective light reflection and selective light diffusion means used in the present invention transmits the incident light from the angle range including at least the observer direction and reflects the light in the other incident angle range. Or, it is necessary to have a property of scattering. Examples of such selective light reflecting means include various prism array sheets, and examples of the selective light scattering means include field-selecting glass commercially available from Nippon Sheet Glass under the trade name of Angle 21. . Further, the selective light reflection or light diffusing means 30 and the light absorbing means 20 used in the present invention may be sequentially provided by contacting at least some of them, or may be provided separately. If the two are separated,
Ambient light or light from an illumination light source can be allowed to enter between the both.

An example of such a selective light reflecting means is a prism array sheet having prisms formed on the surface of a plate-like transparent substrate. The prism array sheet 29 shown in FIG. 12 shows one specific example of the preferable selective light reflecting means of the present invention. The prism array sheet 29 in the figure is composed of a plurality of rows of prisms having a shape elongated in one direction, and the rows of the prisms are substantially the same in the longitudinal direction. is there. In FIG. 12, each prism array has a substantially triangular cross section. For the sake of explanation, the definitions of the three directions are shown in the lower part of FIG. The thickness direction of the light reflecting element is z, the longitudinal direction of the prism array is y, and the direction perpendicular to these is x. The light reflection (transmission) characteristics of this reflective element will be described by taking as an example the case where the apex angle α of each prism is 90 ° and the refractive index of the material is 1.586. FIG. 13 shows an optical path of the light 80 which is vertically incident on the prism array sheet 29 in which the apex angle α of each prism is 90 °. The light 80 incident perpendicularly to the sheet surface is refracted at an incident point 90 on the prism and an emitting point 100 from the prism, and is emitted as an emitted light 110 having an angle of 30 °. That is, the light that is perpendicularly incident on the sheet surface passes through the prism array sheet. The direction of the incident light is the direction (x
Direction, the output angle increases rapidly,
When the incident angle is 36 ° or more with respect to the sheet surface, total reflection occurs at the interface from the sheet to the air, and the incident light is reflected by the sheet. FIG. 14 shows a state in which total reflection occurs. When the incident angle A becomes 36 ° or more, the light 130 incident on the ridge surface 120 side of the prism is totally reflected by the interface 150 between the prism and the air, and is reflected as the emitted light 140 having the same angle A as the incident angle. It As described above, when a prism array sheet made of polycarbonate having an apex angle α of 90 ° and a refractive index of 1.586 is taken as an example, light is mainly emitted when the incident angle is less than 36 ° in the x direction from 0 °. It transmits and is reflected at 36 ° or more. When the incident light is tilted in the y direction, the above-mentioned special thing does not occur.
When tilted in the intermediate direction of x and y, the characteristics become intermediate when tilted in the respective directions of x and y. When the cross section of each prism is approximately triangular, the characteristics slightly differ from the above depending on the size of the refractive index, the size of the prism apex angle α, and the symmetry of the triangle. Light with a small incident angle is mainly transmitted, and light with a large incident angle is mainly reflected. FIG. 15 shows the relationship between the reflectance and the incident angle in the case of a prism array sheet having a vertex angle of 90 ° and a material refractive index of 1.41. The characteristic is that the incident light from the front direction is transmitted and the oblique incident light is reflected. In general, it is preferable to design the direction of the observer in the normal direction of the display of the device or in the direction inclined at an angle within 30 ° from the normal direction.
Since it becomes the switching angle of reflection, the reflected light does not reach the direction of the observer. In the configuration of this example, incident angles ic1 and ic2 at which transmission / reflection or diffusion are switched.
Is determined from the viewing angle range required for the device. ic
Is small, the light intensity from the reflection or diffusion portion of the device is high, and high contrast is obtained, but there is a problem that the viewing angle is narrowed. On the contrary, when ic is increased, the viewing angle is widened, but the above-described effect of using the selective reflection or diffusion means is weakened, and the contrast is lowered. Further, in the configuration of this example, the incident angles ic1 and ic2 at which transmission / reflection is switched can be adjusted by changing the structure of the prism. Specifically, ic can be adjusted by changing the apex angle α of the prism, the inclination angle β of the prism bottom surface, and the inclination angle γ of the prism shown in FIG. By decreasing the apex angle, the angular range of transmitted light (Δic = ic1−ic2) becomes smaller, and by increasing the apex angle, Δic can be increased. The lower limit of ic varies depending on the device in which the element is mounted, the method of use, the size of the element and the distance from the observer, but it can be used at 20 ° or more for general direct-view display elements used in word processors, etc. Is. The preferred ic range is 25
The range is from ° to 55 °, and the range from 35 to 50 ° is more preferable. In order to obtain such ic, the apex angle of the prism is set in the range of 30 ° to 150 ° in consideration of the refractive index range (1.4 to 2.0) of glass or plastic that can be used as the prism. Preferably 4
The range of 0 ° to 140 ° is more preferable. The preferable apex angle range depends on the refractive index of the prism material used, and has a relatively small refractive index (1.4 to 1.5) like polysiloxane.
In the case of a material, the range of 30 ° to 130 ° is preferable, and in the case of a material having a relatively large refractive index (1.5 to 2.0), it is 60 °.
The range of up to 150 ° is preferred. The smaller the apex angle α, the greater the brightness of the display device, but the angle range in which the reflective element causes total reflection is too wide, and the brightness when the liquid crystal element is in the transparent state does not decrease. The range becomes narrow. When α is too large, the brightness when the liquid crystal element is in the light scattering state is reduced, resulting in a dark display. Both the tilt angle of the bottom surface and the tilt angle of the prism make the selective transmission angle range asymmetric with respect to the normal line. Considering a preferable observation direction (within 30 ° from the normal line), the inclination angle of the bottom surface is preferably within 20 °, and the inclination angle of the prism is preferably within 30 °. In the above description, the prisms arranged one-dimensionally are described, but it is also possible to use prisms arranged two-dimensionally as shown in FIG. 18 to 21
Shows a schematic example of a sectional structure of another selective light reflecting means. The prism cross section is not limited to the shape of an isosceles triangle as in the above example, and the effect is exhibited as long as it is an aggregate of structures having a surface inclined with respect to the display surface of the element. In these cases, it is desirable that the angle α formed by the two inclined surfaces is within the above preferable range. In addition, FIG.
As described above, a structure in which a plurality of types of structures are mixed may be used.
Each of the five structural examples shown here has a surface parallel to the display surface of the device or having a different tilt angle. Therefore, the above-mentioned ic becomes unclear, but on the contrary, there is also an advantage that this feeling reduces discomfort in the visual sense. When the cross-sectional shape of the prism is an isosceles triangle, the optical characteristics of the prism are symmetrical in the x-axis direction with the z-axis as the center in FIG. 12 or FIG. Therefore, when a liquid crystal element having an isotropic optical characteristic in the cell plane, such as a polymer dispersion mode or a dynamic scattering mode, is used, the characteristics of the display device as a whole are also in contrast. If the shape of the prism is not an isosceles triangle, such symmetry of optical characteristics is broken. The shape of the prism is not limited to the isosceles triangle because it is not necessarily considered that such symmetry is necessary for the display device. 24 and 25 show a configuration example in which the prism is tilted, a prism bottom surface is tilted, and optical paths 71 and 72 of light rays at the critical angle δc of total reflection.
Is shown. In these examples, the angle range of the transmitted light can be made asymmetric with respect to the normal direction, and thus it is particularly suitable for applications where the element is observed from an oblique direction. FIG. 26 shows the optical path in the lens when the lenticular lens array sheet in which the cross-sectional shape of each prism is not a triangle but a substantially semicircular shape is used. Incident light 26 and 27 have the same angle of incidence B with respect to the surface of the sheet, but depending on which part of the lens they are incident on, it is either reflected by the sheet or transmitted through the sheet. The larger the incident angle B is, the easier total reflection is, as in the case of the prism array sheet, but in FIG. 26, the light incident on the lower part of the lens is more likely to be totally reflected. Therefore, unlike the prism array sheet, the characteristics do not suddenly change from a certain angle. FIG. 27 shows another configuration example of the selective light reflecting means according to the present invention. In this example,
Another layer 32 is provided on the prism array sheet 29 of the selective light reflecting means. 32 is formed for the purpose of protecting the prism structure and controlling the refraction angle. In order to provide the above-mentioned incident angle selectivity, 32 needs to be formed of a material having a refractive index smaller than that of the prism structure 31. As described above, the selective light reflecting means according to the present invention may be formed at any place on the plate-shaped transparent substrate. As a material for forming the selective light reflection means, inorganic materials such as glass, polystyrene, polyester, polycarbonate, polyolefins, polyarylate, polysulfone, polyether sulfone, polyacrylate, epoxy resin, polysilicone, polyvinyl alcohol, acetyl cellulose Most transparent materials such as resins can be used. The refractive index of the material used is generally in the range of 1.4 to 1.7, but there are some materials such as glass for optical use which have a refractive index of about 2.0. As a selective light reflecting means, a pitch of a prism structure composed of a plurality of rows of prisms having a shape elongated in one direction, and a prism array sheet in which the directions of the rows of the prisms are substantially the same in the longitudinal direction. d (see FIG. 28) is 0.
The range of 01 mm to 1 mm is preferable, and the range of 0.02 mm to 0.5 mm is more preferable. If the pitch is too short, it becomes difficult to form the prism structure itself and the cost becomes high. Further, if it is too large, the prism structure is visually recognized by an observer, which is not preferable in view of display quality. The pitch of the prism array sheet 29 is d, the pitch of the pixels of the liquid crystal dispersion layer 13 in the x direction is 1, and the sheet 29 and the liquid crystal dispersion layer 1 are
When the distance of 3 is h, and when d and h are too large with respect to 1, even if a pixel is in a light scattering state and the light passing through the pixel and entering the prism is totally reflected,
The light does not always pass through the original pixel, and the pixel does not show sufficient brightness, especially when the surrounding pixels are in the light transmitting state. Therefore, the pitch d of the prism array sheet 29, the liquid crystal dispersion layer 13, and the prism array sheet 2
The distance h of 9 is preferably not so large as compared with the pixel pitch 1 of the liquid crystal cell 10. The preferable size of the pitch d of the array sheet 29 is within 2 times of 1, and more preferably within 1 time of 1. Also, in general, the liquid crystal dispersion layer 1
The preferable range of the distance h between 3 and the light reflecting element or the light scattering element is within 5 times 1 and more preferably within 2 times 1. As the light absorbing means arranged on the back side of the light reflecting element or the light scattering element, any material such as colored glass, metal, or plastic that absorbs light can be used. Generally, those colored black are preferably used,
In this case, the element is displayed in black and white. When it has a color, it is colored / white. It is also possible to form the light absorbing means on the lower surface of the prism by a method such as coating, but in this case, the light is made of a material whose refractive index is sufficiently smaller than that of the prism so that total reflection at the bottom surface of the prism occurs. It is necessary to configure the absorption layer. As described above, the present invention improves the contrast of the scattering type liquid crystal display device by utilizing the incident angle selectivity of the selective light reflecting means or the light scattering means,
Although bright display is possible, this may cause the following problems. In the example used in FIGS. 13 and 14, when the pixel is in the transparent state, the light inclined at the critical angle of 36 ° or more in the x direction is almost totally reflected by the prism array sheet. When viewed from above, transparent pixels are also visually recognized brightly, and the contrast is significantly reduced. Generally, the display element is not observed from the direction of specular reflection with respect to the illumination light, but it has been confirmed that the illumination from the x direction significantly reduces the contrast even when observed from the front. Figure 2
9 shows the illumination direction dependence of the contrast when the prism array sheet 29 having the apex angle α of 100 ° is used. Figure 2
3 shows the definition of the direction at this time. The measurement direction is perpendicular (z direction) to the display device surface (the same applies to the prism array sheet surface and the liquid crystal element surface). The incident angle of the illumination light 22 is θ, and the azimuth angle φ is the angle formed by the longitudinal direction y of the prism and the projection vector of the incident light on the xy plane. The results shown in FIG. 26 are obtained when the incident angle θ of the illumination is 30 °.
As can be seen from FIG. 29, although the good contrast is maintained from 0 ° to nearly 80 °, φ is 80 °
After that, the contrast decreases rapidly. When a dynamic scattering mode or polymer dispersion mode is used as a liquid crystal element,
Since the optical characteristics of the liquid crystal cell are isotropic in the cell plane, it is presumed that the contrast decreases only when φ is in the vicinity of 90 ° and 180 °. The present invention proposes a configuration in which φ is not in the vicinity of 90 ° or 180 ° in a general use state of the display element. That is, the prism array is arranged so that the longitudinal direction y is not in the left-right direction when viewed from the observer. If y is in the left-right direction, the position of the observer will be in the xz plane, and the azimuth angle of the illumination light from the overhead illuminator will be 90 ° or 180 °, and the contrast will be remarkably poor. Be seen. At this time,
The position of the luminaire has a similar result regardless of where it is on the plane including the observer and z, which is a frequent occurrence under general illumination environment. At this time, in order to avoid a decrease in contrast, the display device surface must be viewed from the lateral direction, which makes it extremely difficult to use. On the other hand, when the longitudinal direction y of the prism array is up and down, or front and back when viewed from the observer, φ is 90 ° or 180 ° only when the luminaire is on a plane that cuts the display device surface vertically and right next to it.
Becomes Such a situation is unlikely to occur in a general lighting environment, and even if it occurs, it can be escaped by slightly changing the elevation angle of the display device surface. In another configuration of the invention, FIG.
Alternatively, a configuration may be adopted in which the selective light reflecting means 30 or the prism array sheet 29 in FIG. 23 is not fixed in the arrangement direction but is rotated in the plane according to the illumination environment and can be adjusted to the most convenient direction. it can. Also,
When the element has a large area and the observer and the element are relatively close to each other, or when the transmitted incident light range of the selective light reflecting means is set to be extremely narrow, there is a problem that the contrast around the element is lowered. There is. This will be described with reference to FIG. In the figure, Δic1, Δic2, and Δic3 represent angular ranges in which reflected light from the upper end, the center, and the lower end of the display unit is not observed during non-scattering. It should be noted that the liquid crystal cell is omitted in this figure for simplification of description. If the observer's position is within the shaded area, the reflected light from the non-scattering portion does not reach the observer's eyes, so that high contrast can be obtained over the entire area of the element.
When there is 0, the reflected light 571, 581 from the non-scattering pixels from the upper and lower ends of the element is visually recognized by the observer, and the contrast at the end is significantly reduced.

The present invention also relates to the improvement of such problems. That is, according to the present invention, by making the angle selectivity of the selective light reflecting means different depending on the location of the element, for any location of the display portion of the element,
Provided is a liquid crystal display device in which reflected light corresponding to non-scattering pixels does not reach an observation position. As a means for adjusting the angle selectivity of the selective light reflecting means, a method of changing the prism structure depending on the position of the element is preferably used. FIG. 31 is a sectional view showing a particularly preferable configuration example and operation of the selective light reflecting means. In this figure, the cross section of the prism corresponding to the center of the element has an isosceles triangular shape.
Light in the angle range indicated by ic5 is selectively transmitted. On the other hand, the triangle formed by the prism cross section of the selective light reflection means corresponding to the end of the element is inclined, and the angular ranges Δic4 and Δic6 of the transmitted light in this part are directed toward the observer 40. As a result, the observer does not see the reflected light 571, 581 from the non-scattering portion over the entire display screen,
A uniform and high-contrast display can be performed. In this example, the prism structure of the selective light reflecting means is roughly divided into three parts in order to simplify the description, but it is possible to divide the prism structure into smaller parts or to change the structure continuously. It is more preferable from the viewpoint of viewing angle and uniformity.
Although the prism structure is also mirror-symmetrical, it may be asymmetrical depending on the position of the observer. Another preferred configuration example of the selective light reflecting means with reduced viewing angle dependency is provided by making the inclination angle of the bottom surface of the prism different within the element. FIG. 32 is a cross-sectional view showing a preferable configuration example thereof. In this example, a part of the bottom surface of the prism, for example, the upper end and the lower end of the display unit are inclined in a saw-tooth shape to change the angle selectivity. The bottom surface is preferably inclined so as to face the viewer. In this example, the case where the sawtooth-shaped pitch on the bottom surface is the same as that on the upper prism is described, but the two may be different. Further, the inclination angle of the bottom surface can be continuously changed, which is more preferable from the viewpoint of viewing angle and uniformity. FIG. 33 shows another preferred configuration example of the selective light reflecting means with reduced viewing angle dependency. In this case, the selective light reflecting means 30 is arranged so as to be curved with the observer direction facing inward. Since the transmission angle range also faces inward with the curvature, it is possible to provide a uniform light contrast display to an observer at a short distance. Another structure of the liquid crystal display device having the selective light reflection means and the improved viewing angle dependency according to the present invention is provided by providing the optical path changing means between the observer and the selective light reflection means. It The optical path changing means functions to change the selective reflection / transmission angle of the selective light reflection means and bend the angular range of the transmitted light toward the observer. FIG. 34 shows a preferred configuration example thereof. For the observer of the liquid crystal cell (omitted), the optical path changing means 70 including a Fresnel lens is provided on the lower surface, and the selective light reflecting means 30 as described above is provided on the lower surface. Light absorbing means (omitted) is provided on the lower surface of the selective light reflecting means. In this example, the case where the transmission angles of the selective light reflecting means are uniform will be described. Transmission angle range in the center △
Since ic2 'is hardly affected by the Fresnel lens, when the pixel is non-scattering, the reflected light does not reach the observer, resulting in a black display. At the edge of the element, the optical path is bent inward by the effect of the wedge-shaped Fresnel lens,
The transmission angle range now includes the observation direction (Δic
1 ', Δic3'), it is possible to obtain a black display similar to that of the front pixel.

As the liquid crystal display system which can be used in the present invention, any liquid crystal display system can be used as long as the light scattering property is changed by application of a voltage, and the conventionally known dynamic scattering system, phase transition system, polymer A method using a nematic liquid crystal such as a dispersion method, a method using a thermoelectro-optical effect of a smectic liquid crystal, a method using light scattering of a ferroelectric liquid crystal, or the like can be used. These display methods generally have a problem that the operating voltage rises when trying to obtain a high contrast by increasing the light scattering property. For example, increasing the liquid crystal layer thickness, decreasing the cholesteric pitch in the phase transition method, and miniaturizing the liquid crystal droplets in the polymer dispersion method all have the effect of increasing the scattering property, but both increase the driving voltage. There is an adverse effect. When the present invention is applied to these methods, when the same liquid crystal cell as the conventional one is used, the contrast is improved by improving the scattering property, and when the contrast is the same as the conventional one, the driving voltage can be increased. . Among these methods, in a so-called polymer dispersion type liquid crystal display device in which the liquid crystal layer is composed of a liquid crystal region and a support configured to divide the liquid crystal region into fine parts, low voltage driving and light scattering Since it is particularly difficult to satisfy both requirements, the above advantages are particularly remarkable when the present invention is applied. The internal structure of the polymer dispersion layer that can be used is not particularly limited, and a droplet structure in which a liquid crystal represented by a dispersion film produced by an emulsion method or the like is dispersed in a support as substantially spherical droplets, It is easy to form in the photopolymerization method, the support may form a network structure, the network structure in which the liquid crystals in the network communicate with each other, such as a polymer support or some other structure that divides the liquid crystal part into fine regions Can be used. The term “fine” as used herein means a size in the range of approximately 0.2 μm to 10 μm. The thickness of the liquid crystal dispersion layer may be the same as that of a conventionally known polymer dispersion type liquid crystal display device, and may be 3 μm to 30 μm.
The range of μm is common. Further, the ratio of the liquid crystal to the support may be the same as that in the conventionally known polymer dispersion type display device, and the liquid crystal is generally in the range of 40% to 90% with respect to the entire film. Several methods have been reported as methods for forming such a dispersed structure. For example, a method of applying and drying an emulsion of an aqueous solution of a water-soluble polymer such as polyvinyl alcohol and liquid crystal (emulsion method), dissolving the soluble polymer and liquid crystal in a solvent to prepare a uniform solution, coating and drying the solution, and drying. Sometimes a polymer and liquid crystal are phase-separated (solvent evaporation method), a photopolymerizable substance such as an acrylic monomer, a liquid crystal and a photopolymerization initiator are enclosed in a space between upper and lower substrates, and ultraviolet rays are irradiated to the photopolymerizable substance. And a phase-separation method (photopolymerization method), a method in which a mixture of a thermopolymerizable substance-for example, an epoxy compound and its curing agent-and liquid crystal is sealed between the upper and lower substrates and then polymerized by heating to cause phase separation ( Thermal polymerization method) and the like.

[0008]

The present invention will be described in more detail with reference to the following examples.

Example 1 Prepolymer KAYARAD HX62 manufactured by Nippon Kayaku Co., Ltd.
Photopolymerization initiator Darocurll73 manufactured by Merck & Co.
Was added in an amount of 3% by weight to prepare a photocurable resin composition.
A glass substrate having a transparent conductive film was overlaid with a 6 μm spacer interposed therebetween to produce a liquid crystal cell having a cell gap of 6 μm. A liquid crystal composition BL036 manufactured by Merck & Co., Inc. and a photocurable resin composition were mixed so that the ratio of the liquid crystal composition was 70% by weight, heated to a temperature at which the liquid became uniform, and injected into a liquid crystal cell. This was irradiated with light from a high-pressure mercury lamp to polymerize the prepolymer so that the liquid crystal and the polymer were phase-separated to prepare a liquid crystal cell 1 having a polymer-dispersed liquid crystal layer. Directly below the liquid crystal cell 1, a field selection glass angle 21-c type (ic1 = 26.5 °, made by Nippon Sheet Glass,
ic2 = -26.5 °) was placed parallel to the cell. Further, a light absorbing means made of a black film having a roughened surface was provided immediately below the selective reflection plate to prepare a reflection type liquid crystal display element A of the present invention having the structure shown in FIG. As a reference sample, a reflective liquid crystal display element R1 having the structure shown in FIG. 1 was prepared without providing a selective diffusion means. When these liquid crystal display elements were observed from the front under a fluorescent lamp in the room, a good black display was obtained for all the elements when a voltage of 20 V was applied.
Regarding the intensity of scattered light when no voltage was applied, A of the present invention was clearly superior.

Second Embodiment In the first embodiment, ic1 = + is used as the selective light diffusing means.
A liquid crystal display device B was produced in the same manner by using a selective diffusion plate having a scattering characteristic of only 26.5 ° in one direction.
When the liquid crystal display devices B and R1 were observed from the front under a fluorescent lamp in the room, all the devices exhibited a good black display when a voltage of 20 V was applied, but the scattered light intensity when no voltage was applied was obviously the present invention. B was excellent.

Example 3 Prepolymer KAYARAD HX62 manufactured by Nippon Kayaku Co., Ltd.
Photopolymerization initiator Darocurll73 manufactured by Merck & Co.
Was added in an amount of 3% by weight to prepare a photocurable resin composition.
A glass substrate having a transparent conductive film was overlaid with a 6 μm spacer interposed therebetween to produce a liquid crystal cell having a cell gap of 6 μm. A liquid crystal composition BL036 manufactured by Merck & Co., Inc. and a photocurable resin composition were mixed so that the ratio of the liquid crystal composition was 70% by weight, heated to a temperature at which the liquid became uniform, and injected into a liquid crystal cell. A liquid crystal cell 1 having a polymer-dispersed liquid crystal layer by subjecting this to light irradiation with a high-pressure mercury lamp to polymerize the prepolymer to phase-separate the liquid crystal and the polymer.
Was produced. Directly below the liquid crystal cell 1, a selective light reflection plate made of polycarbonate (refractive index 1.58) having a prism array having an apex angle of 90 ° and a pitch of 0.3 mm in FIG. 12 was arranged in parallel. The selective transmitted light range of this reflector is
It was symmetrical with respect to the normal to the display surface and was in the range of ± 36 °, and it functioned as a reflector for incident light with a larger incident angle. Further, a light absorbing means made of a black film having a roughened surface was provided directly below the selective light reflecting plate, and a reflection type liquid crystal display device of the present invention having the structure shown in FIG. 5 was produced. As a reference sample, a reflective liquid crystal display device having the structure shown in FIG. 1 was prepared without providing a selective light reflecting means. When these liquid crystal display devices were observed from the front under a fluorescent lamp indoors, 2
When a voltage of 0 V was applied, all the devices displayed a good black display, but the scattered light intensity when no voltage was applied was clearly superior to the display device of the present invention.

Examples 4 to 11 Liquid crystal display devices were produced in the same manner as in Example 3, except that selective light reflecting plates having different prism structures as shown in Table 1 were used. The preferred vertical range differs depending on the material used,
It was possible to perform high-contrast display by selecting the apex angle within the range of 30 ° to 150 °.

[0013]

[Table 1]

Example 12 In Example 3, a selective light reflection plate having a bottom inclined by 7 ° (= β) as shown in FIG. 25 was used as the selective light reflection plate. The angle was 50 °, which was asymmetric with respect to the element normal. When this device was observed from the direction inclined by 15 °, a very good contrast was obtained.

Example 13 In Example 1, a selective light reflecting plate having a prism structure inclined (γ = 15 °) as shown in FIG. 24 was used.
The viewing angle range was −20 ° to 50 °, which was asymmetric with respect to the element normal. When this device was observed from the direction inclined by 15 °, a very good contrast was obtained.

Example 14 In the liquid crystal display element of Example 3, as shown in FIG. 31, the prism in the central portion of the element is not inclined, but the prism is inclined outward in proportion to the distance toward the end. A liquid crystal display device was manufactured using the selective light reflection plate. The size of the element was 200 mm × 200 mm. The inclination angle at the outermost end was 10 °. Even when this device was observed from the front of the device at a close distance of 120 mm, no unevenness was observed in the display.
On the other hand, in the device of Example 3, in order to obtain a uniform display, 15
A distance of 0 mm or more was required.

Example 15 In the liquid crystal display element of Example 3, as shown in FIG. 32, the bottom surface of the prism in the central portion of the element is not inclined, and the bottom surface of the prism is inwardly proportional to the distance toward the end. A liquid crystal display device was produced by using a selective light reflection plate tilted to the right. The size of the element was 200 mm × 200 mm, and the inclination angle of the bottom face of the prism at the end was 5 °. Even when this device was observed from the front of the device at a close distance of 120 mm, no unevenness was observed in the display. On the other hand, the device of Example 3 required a distance of 150 mm or more to obtain a uniform display.

Example 16 A liquid crystal display similar to Example 1 except that in the liquid crystal display element of Example 3, the selective light reflecting plate was curved with a radius of curvature of 600 mm as shown in FIG. A device was produced. The size of the element was 200 mm × 200 mm. Even when this device was observed from the front of the device at a close distance of 120 mm, no unevenness was observed in the display. On the other hand, the device of Example 3 required a distance of 150 mm or more to obtain a uniform display.

Example 17 In the liquid crystal display element of Example 3, a Fresnel lens (focal length 400 mm) as shown in FIG. 34 was inserted between the selective light reflection plate and the liquid crystal cell. The size of the element is 200m
It was set to m × 200 mm. Even in the case of this element, no unevenness was observed in the display even when observed at a close distance of 120 mm.

Example 18 A liquid crystal composition was prepared by adding 8% by weight of S811 which induces a counterclockwise twisted structure to a nematic liquid crystal, which is a liquid crystal optically active substance manufactured by Merck and added to liquid crystal BL007 manufactured by Merck. A glass substrate with a transparent electrode, which had been subjected to a vertical alignment treatment with a silane-based aligning agent, was attached via a 6 μm spacer, and the liquid crystal composition was injected into the formed voids to prepare a phase transition type liquid crystal cell. A reflective liquid crystal display device was produced in the same manner as in Example 3 except that this phase transition type liquid crystal cell was used instead of the polymer dispersed liquid crystal cell of Example 3. When the phase transition type liquid crystal display element produced without providing the selective light reflection means and this element were observed from the front under a fluorescent lamp in the room, both elements showed good black display by voltage application. Regarding the intensity of scattered light when no voltage was applied, the liquid crystal display element of this example provided with the selective light reflecting means was clearly superior.

Example 19 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 10 in FIG. 1 was used. 3M 90 ° prism array sheet SO on black paper
When LF (α = 90 ° in FIG. 12) was placed and the above light-scattering liquid crystal element was further stacked thereon, the brightness of the cell was increased as compared with the case without the sheet. This was the same whether the prism array surface was on the top or bottom. Next, when a drive voltage was applied to the ITO of the light scattering liquid crystal element, the cell became transparent. At this time, if the prism-side surface of the prism sheet faces the upper side (liquid crystal element side), the black paper at the bottom can be seen to give good contrast, but the sheet is upside down and the prism side When the surface faces the lower side (black paper side), the light reflectivity of the sheet is emphasized and gives almost no contrast. Cell O
When observed from various directions while turning N and OFF, the contrast was remarkably reduced when viewed obliquely from the direction perpendicular to the groove of the prism sheet, but from a position quite low from other directions, such a phenomenon would occur. I didn't get up.
Next, the display surface is illuminated obliquely (θ = 3 in FIG. 23).
(0 °) When observing from the front of the display surface and rotating the illumination direction (changing φ in FIG. 23), the contrast decreases only when the illumination direction almost coincides with the direction perpendicular to the groove of the prism sheet. did. This state is shown in FIG. When the display element of the present invention was observed in the direction of the groove of the prism sheet in the front and back under general illumination, it was possible to display with good contrast from a wide range.

Example 20 A 70 ° prism array sheet TRAF (α = 70 ° in FIG. 12) manufactured by 3M was placed on black paper, and the same cells as in Example 1 were further stacked thereon. The upper and lower sides of the prism array sheet are the prism-side surface (the liquid crystal element side).
And The display surface is illuminated obliquely (θ =
(30 °) When observing from the front of the display surface and rotating the illumination direction (changing φ in FIG. 23), the contrast deteriorates only when the illumination direction almost coincides with the direction perpendicular to the groove of the prism sheet. did. This state is shown in FIG. When the azimuth angle of the illumination is small, the contrast is higher than that in the first embodiment, but the contrast gradually decreases as the illumination direction approaches 90 °, and in the vicinity of 90 °, the contrast becomes smaller than that in the first embodiment. Will end up. However, even if the azimuth angle is 80 °, the contrast is 5 or more, and it can be seen that only the direction of 90 ° is necessary. Assuming a word processor or computer display,
The black paper, the prism sheet, and the liquid crystal cell were laid on top of each other, and the prism grooves were oriented vertically. In this way, the illumination direction from above the head cannot be perpendicular to the groove, so that the cell display can be visually recognized from a wide range.

Example 21 In Examples 19 and 20, a sheet having a prism array having a triangular cross section was used, but in this Example, a lenticular lens array sheet having a semicircular cross section was used.
The other points are the same as those in the second embodiment. When the groove direction of the sheet was set to the vertical direction, a display with high contrast could be visually recognized in a wide range.

Comparative Example 1 In Example 20, by rotating only the prism sheet,
When the cell was in a transparent state when the grooves were oriented horizontally, the illumination light overhead was reflected brightly and the contrast was significantly reduced.

[0025]

【effect】

1. In the reflective liquid crystal display element according to the present invention, the forward scattering component of the light from the scattering pixel is introduced into the liquid crystal layer again by the selective light reflection or the light diffusing means without affecting the non-scattering pixel. A strong reflected light intensity is obtained, so that a reflective liquid crystal display device with high contrast can be provided. Further, since strong light scattering can be obtained without increasing the light scattering property of the liquid crystal layer, the driving voltage for obtaining the same contrast is low. 2. Further, by using the prism group formed on the plate-like transparent substrate as the selective light reflecting plate of the liquid crystal display device of the present invention, good incident angle selectivity can be obtained and higher contrast can be obtained. Further, by forming the prism structure into a specific shape, it is possible to provide a reflective liquid crystal display element having a wide viewing angle and excellent contrast. 3. When the angle selectivity of the selective light reflection plate used in the present invention is made asymmetric, a high-contrast display can be obtained even in an application where the viewing direction is oblique. 4. When the angle selectivity of the selective light reflecting means is varied depending on the location of the reflecting means, it is easy to obtain uniform and high-contrast display quality over the entire display screen even in a large area display. 5. When a polymer-dispersed liquid crystal is used for the liquid crystal layer of the liquid crystal display device of the present invention, high-speed response is obtained in addition to high contrast, and therefore, it is possible to display moving images. 6. The liquid crystal display device of the present invention employs a selective light reflecting means composed of a prism array sheet in which the directions of the rows of the prisms are substantially the same in the longitudinal direction, and the light reflecting means is used for the prisms. By arranging the longitudinal direction in a direction substantially other than the left-right direction when viewed from the observer, it is possible to display with good contrast in a wide range.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross-sectional structure of an example of a conventional light-scattering type liquid crystal display element.

FIG. 2 is a diagram showing an optical path of incident light to a conventional light-scattering liquid crystal display element in which a liquid crystal layer is in a light-scattering state.

FIG. 3 is a diagram showing an optical path of incident light to a conventional light-scattering type liquid crystal display element in which a liquid crystal layer is in a light transmitting state.

FIG. 4 is a diagram schematically showing a cross-sectional structure of an example of the liquid crystal display element of the present invention.

FIG. 5 is a diagram schematically showing a cross-sectional structure of an example of the liquid crystal display element of the present invention.

FIG. 6 is a diagram for explaining the operation of the selective light reflecting means used in the present invention.

FIG. 7 is a diagram showing an optical path in which the liquid crystal layer of the liquid crystal display element of the present invention is transparent.

FIG. 8 is a diagram showing an optical path in a scattering state of the liquid crystal display element of the present invention.

FIG. 9 is a view explaining the operation of the selective light diffusing means used in the present invention.

FIG. 10 is a diagram illustrating an optical path of a selective light diffusing unit when the liquid crystal layer of the liquid crystal display element of the present invention is in a transparent state.

FIG. 11 is a diagram illustrating an optical path when the liquid crystal layer of the liquid crystal display element of the present invention is in a scattering state and a selective light diffusing means is used.

FIG. 12 is a perspective view schematically showing a selective light reflecting means in which minute prism groups are formed on the surface of a translucent plate-like substrate (prisms with apex angle α = 90 °).

FIG. 13 is a diagram showing a cross section of a light reflecting element in which the apex angle α of each prism is 90 °, and the progression of light incident in a direction perpendicular to the element.

FIG. 14 is a cross section of a light reflecting element in which the apex angle α of each prism is 90 °, and an incident angle of 36 ° on the prism ridge surface of the element.
It is a figure which shows progress of the light which injected in.

15 is a diagram showing the relationship between the reflectance and the incident angle of the prism array sheet shown in FIGS. 10 and 11. FIG.

FIG. 16 is a diagram schematically showing a cross section of a selective light reflecting means that is a prism having an apex angle α, a bottom surface inclination angle β, and an inclination angle γ.

FIG. 17 is a perspective view showing a selective light reflecting means which is a two-dimensional array of prisms.

FIG. 18 is a view showing a cross section of another example of the selective light reflecting means used in the liquid crystal display element of the present invention.

FIG. 19 is a diagram schematically showing a cross section of another example of the selective light reflecting means used in the liquid crystal display element of the present invention.

FIG. 20 is a diagram schematically showing a cross section of another example of the selective light reflecting means used in the liquid crystal display element of the present invention.

FIG. 21 is a diagram schematically showing a cross section of another example of the selective light reflecting means used in the liquid crystal display element of the present invention.

FIG. 22 is a diagram schematically showing a cross section of another example of the selective light reflecting means used in the liquid crystal display element of the present invention.

23 is a diagram for explaining x, y, z, θ and φ when the azimuth angle φ depending on the illumination direction shown in FIG. 26 is measured.

FIG. 24 is a diagram showing a cross section of an example of a selective light reflecting means in which a prism is inclined and an optical path of a light beam incident on the means at a critical angle.

FIG. 25 is a view showing a cross section of an example of a selective light reflecting means in which a prism bottom surface is inclined and an optical path of a light ray incident on the means at a critical angle.

FIG. 26 is a cross-sectional view of a lenticular lens array sheet in which each prism has a substantially semicircular cross-sectional shape, and a diagram showing a path of light incident on the lens array sheet at an incident angle β.

FIG. 27 is a diagram schematically showing a cross section of another example of the selective light reflecting means.

FIG. 28 is a pitch d of the prism array sheet of the liquid crystal display device of the present invention, a pitch l of the pixels of the liquid crystal dispersion layer in the x direction,
Distance h between the prism array sheet and the liquid crystal dispersion layer of the liquid crystal element
FIG.

FIG. 29 shows the illumination direction dependence of the contrast when a light reflecting element in which the apex angle α of each prism is 100 ° is used.

FIG. 30 is a diagram showing that the contrast around the element is lowered depending on the position of the observer with respect to the element.

FIG. 31 is a view showing a selective light reflecting means in which the viewing angle dependency is reduced by changing the light transmission angle range in the central portion and the peripheral portion of the selective light reflecting means, and an optical path of incident light to the means. is there.

FIG. 32 is a view showing a selective light reflection means having a reduced viewing angle dependency, which is formed by changing the inclination angle of the prism bottom surface at the end of the selective light reflection means, and a light path of incident light to the means. Is.

FIG. 33 is a diagram showing a selective light reflecting means having a reduced viewing angle dependency, which is formed by being curved with the observer direction facing inward.

FIG. 34 is a view showing a selective light reflecting means provided with an optical path changing means composed of a Fresnel lens on the lower surface for an observer of the liquid crystal cell.

FIG. 35 is an azimuth angle φ of the illumination of the liquid crystal display device of Example 18.
It is a figure which shows the relationship between / degree and contrast.

36 is an azimuth angle φ of the illumination of the liquid crystal display device of Example 19. FIG.
It is a figure which shows the relationship between / degree and contrast.

[Explanation of symbols]

10 liquid crystal cell 11a translucent substrate 11b translucent substrate 12a transparent electrode 12b transparent electrode 13 liquid crystal dispersion layer 13a liquid crystal 13b support (polymer phase) 14 outer peripheral seal layer 20 light absorbing means (black film) 22 illumination light 26 incident Light 27 Incident light 29 Prism array sheet 30 Selective light-reflecting means or selective light-diffusing means 301 Selective light-reflecting means 302 Selective light-diffusing means 32 Light-reflecting means in which another layer is provided on the prism structure 40 Observer 50 Incident light 501 Backscattering component 502 Forward-scattering component 51 Incident light 511 Backscattering component of incident light traveling in the observer direction 512 Forward-scattering component of incident light whose incident angle to the selective light reflecting means is ic or less 513 Selective light reflecting means Forward-scattering component of incident light with an incident angle of ic or more 52 Incident light 521 Back-scattering component of incident light traveling in the observer direction 522 Forward-scattering component with an incident angle of ic or more to 523 Selective light-reflecting means Forward scattered component with an incident angle of ic or more 57 Incident light 571 Reflected light from a non-scattering pixel 58 Incident light 581 Reflected light from a non-scattering pixel 61 Boundary between transmission and reflection of incident light 62 Incident light Boundary between transmission and reflection of light 70 Optical path changing means (Fresnel lens) 71 Incident light 72 Emission light 80 Light incident perpendicularly to the prism array sheet with an apex angle of 90 ° 90 Incident point 100 Emission point 110 Emission light 120 Prism ridge 130 Incoming light 140 Outgoing light 150 Interface between prism and air ic Boundary angle between incident light to the light scattering means and reflection or diffusion ic1 When incident light to the light scattering means is transmitted Boundary angle when reflected by ic11 Boundary angle when incident light to the light scattering means is transmitted or diffused ic2 Boundary angle when incident light is transmitted or reflected to the light scattering means ic22 To light scattering means Incidence of Boundary angle when light is transmitted and diffused ic3 Boundary angle when light incident on the light scattering means is transmitted and reflected i i Incident angle r Reflection angle α Apex angle of prism α1 Apex angle of prism α2 Apex of prism Angle α3 Vertical angle of prism β Angle of inclination of prism bottom γ Angle of prism inclination δc Critical angle of total reflection A Incident angle B Incident angle N Normal line z Thickness direction of prism array y Longitudinal direction of prism array x In the above y and z Direction perpendicular to the direction θ Incident angle of illumination light 22 φ Azimuth angle (longitudinal direction y of prism and angle formed by projection vector of incident light on zy plane) d Pitch h Liquid crystal dispersion layer and selective light reflection or light diffusion Distance from the means l Pixel pitch △ ic1 Angular range where reflected light from the top edge of the display is not observed when non-scattering △ ic1 'Angular range where reflected light from top edge of the display is not observed when non-scattering △ ic2 non Angular range in which reflected light from the center of the display is not observed when disturbed △ ic2 ′ Angular range in which reflected light from the center of the display is not observed when non-scattered △ ic3 Angular range in which reflected light from the bottom of the display is not observed when non-scattered △ ic3 ′ Angular range where reflected light from the bottom of the display is not observed when not scattered △ ic4 Transmission angle range at the top of the display △ ic5 Transmission angle range at the end of the display △ ic6 Transmission angle range at the bottom of the display

Claims (18)

[Claims] 1. A pair of transparent substrates having transparent pixel electrodes on the inner surface and arranged facing each other at a distance, and a liquid crystal layer sandwiched between the substrates, and no voltage is applied to the liquid crystal layer. In some cases, in a reflective liquid crystal display device that utilizes the change between a state that transmits light and a state that scatters light, on the back side of the liquid crystal layer with respect to the viewer direction, a specific range of incident light from the viewing direction Selective light diffusing means having an angle selectivity for transmitting light of an incident angle and scattering light incident in other incident angle ranges, and a light absorbing means on the back side of the diffusing means. Liquid crystal display device. 2. A pair of transparent substrates having transparent pixel electrodes on the inner surface and arranged facing each other at a distance, and a liquid crystal layer sandwiched between the substrates, and a voltage is applied to the liquid crystal layer and not applied. In some cases, in a reflective liquid crystal display device that utilizes the change between a state that transmits light and a state that scatters light, on the back side of the liquid crystal layer with respect to the viewer direction, a specific range of incident light from the viewing direction A selective light reflecting means having angle selectivity for transmitting light of an incident angle and reflecting light incident in a range of incident angles other than that, and a light absorbing means on the back side of the reflecting means. Liquid crystal display device. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is composed of a liquid crystal region and a support configured to divide the liquid crystal region into minute portions. 4. The selective light diffusing means, when the liquid crystal layer is in a transparent state, reflects the reflected light in an angle range in which the reflected light is emitted from the liquid crystal display device in a direction invisible to an observer. The described liquid crystal display device. 5. The selective light reflecting means, when the liquid crystal layer is in a transparent state, reflects the reflected light in an angle range in which the reflected light is emitted from the liquid crystal display device in a direction invisible to an observer. The described liquid crystal display device. 6. The liquid crystal display device according to claim 2, wherein the selective light reflecting means is a prism array sheet in which prism groups are formed on the surface of a plate-like transparent substrate. 7. The prism array sheet has prisms each having a substantially triangular cross section and an apex angle range of 30 to 1.
The liquid crystal display device according to claim 6, wherein the liquid crystal display device has an angle of 50 °. 8. The liquid crystal display device according to claim 6, wherein the size of the pitch of the prisms of the prism array sheet is within twice the pixel pitch of the liquid crystal layer. 9. The liquid crystal display device according to claim 6, wherein the distance between the liquid crystal layer of the liquid crystal element and the prism array sheet is within 5 times the pixel pitch of the liquid crystal element. 10. The prism array sheet comprises a plurality of rows of prisms each having a shape elongated in one direction, and the rows of the prisms have substantially the same direction in the longitudinal direction. 10. The liquid crystal display device according to claim 6, wherein the prism is arranged so that a longitudinal direction of the prism is substantially a direction other than a left-right direction when viewed from an observer. 11. The liquid crystal display device according to claim 10, wherein the prism array sheet is arranged such that the longitudinal direction of the prism is substantially the vertical direction or the front-back direction when viewed by an observer. 12. The liquid crystal display device according to claim 8, wherein the prism array sheet is configured to be rotatable so that the longitudinal direction of the prism can be arranged in a suitable direction according to the illumination environment. 13. The liquid crystal display device according to claim 6, wherein the angle selectivity of the prism array sheet is different depending on the constituent portion of the sheet. 14. The angle selectivity of the prism array sheet is brought about by the difference in the structure of the prisms, 6, 7, 8, 9, 10, 11, 12 or 13.
The described liquid crystal display device. 15. The liquid crystal display device according to claim 14, wherein the difference in the structure of the prisms is caused by the inclination of the triangular prism structure and / or the inclination of the prism floor surface. 16. A lenticular lens array sheet having prisms each having a substantially semi-circular cross section in each prism of the selective light reflecting means.
The liquid crystal display device according to 3, 5, 6, 13 or 14. 17. The selective light reflecting means is composed of prisms arranged two-dimensionally.
The liquid crystal display device according to 8, 13, 14, 15 or 16. 18. The refractive index range of the selective light reflecting means comprises:
1.4-2.0, Claims 2, 3, 4, 5, 6, 7,
8. The liquid crystal display device according to 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17.