JPH09211496A - Reflection type guest-host liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the display contrast and lightness and to realize the paper- white appearance of a reflection type guest-host liquid crystal display device contg. a light reflection layer and a quarter-wave plate layer. SOLUTION: This reflection type guest-host liquid crystal display device is composed of a first substrate 2 on which incident light 1 is made incident from front and a second substrate 3 which is arranged behind the substrate via a prescribed spacing therefrom. A guest-host liquid layer 4 is arranged in the spacing on the first substrate 2 side an the guarter-wave plate layer 7 is arranged on the second substrate 3 side. The device is provided with a light reflection layer 9 integrally with the electrode layer 8 on the second substrate 3 side. The reflection layer converts the incident light to reflected light 11 by approximately mirror finished surface reflection. A light scattering layer 10 is interposed between the first substrate 2 and the guest-host liquid crystal layer 4. This light scattering layer 10 consists of a transparent material formed by dispersing particulates into a resin and converts the reflected light 11 from backward by scattering or diffusion the light forward to the outgoing light 12. In some cases, a microlens array may be used as the light scattering layer 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a reflection type guest-host liquid crystal display device. More specifically, the present invention relates to a technology for improving the efficiency of using incident light by incorporating a quarter-wave plate layer and a light reflection layer in a device. More specifically, the present invention relates to a technique for efficiently diffusing and emitting reflected light to increase display brightness.

[0002]

2. Description of the Related Art A liquid crystal display device has various modes.
At present, a TN mode or an STN mode using a nematic liquid crystal which is twist-oriented or super-twist-oriented is mainly used. However, these modes require a pair of polarizing plates in terms of operation principle, and because of their light absorption, a low transmittance and a bright display screen cannot be obtained. In addition to these modes, a guest-host mode using a dichroic dye has also been developed. The guest-host mode liquid crystal display device performs display using the anisotropy of the absorption coefficient of the dichroic dye added to the liquid crystal. When a dichroic dye having a rod-like structure is used, the dye molecules have a property of being arranged in parallel to the liquid crystal molecules. Therefore, when an electric field is applied to change the molecular alignment of the liquid crystal, the alignment direction of the dye also changes. Since this dye is colored or not depending on the direction, it is possible to switch between coloration and colorlessness of the liquid crystal display device by applying a voltage.

FIG. 6 is a schematic diagram of HEILMEIE.
2 shows the structure of an R) type guest-host liquid crystal display device,
(A) shows a state where no voltage is applied, and (B) shows a state where a voltage is applied. The liquid crystal display device is p-type dye and dielectric anisotropy are using positive nematic liquid crystal (N _p LCD). The p-type dichroic dye has an absorption axis substantially parallel to the molecular axis, strongly absorbs a polarized component Lx parallel to the molecular axis, and hardly absorbs a polarized component Ly perpendicular thereto. In the state in which no voltage is applied as shown in (A), the polarization component Lx contained in the incident light.
Is strongly absorbed by the p-type dye, and the liquid crystal display device is colored. In contrast, in the voltage application state (B), the dielectric anisotropy rises in response positive N _p liquid crystal in an electric field, p-type dye is also vertically aligned accordingly. Therefore,
The polarization component Lx is only slightly absorbed, and the liquid crystal display device is substantially colorless. The other polarization component Ly included in the incident light
Is hardly absorbed by the dichroic dye regardless of whether the voltage is applied or not applied. Therefore,
In the Heilmeier guest-host liquid crystal display device, one polarizing plate is interposed in advance and the other polarization component Ly is removed to improve the contrast.

In a guest-host liquid crystal display device using a nematic liquid crystal, a dichroic dye added as a guest is aligned similarly to the nematic liquid crystal. A polarized component parallel to the alignment direction of the liquid crystal is absorbed, but a polarized component orthogonal to this is hardly absorbed. Therefore, in order to obtain a sufficient contrast, one polarizing plate is arranged on the incident side of the liquid crystal display device so that the polarization direction of the incident light coincides with the alignment direction of the liquid crystal. However, in this case, in principle, 50% (actually, about 40%) of the incident light is lost due to the polarizing plate,
The display becomes dark as in the TN mode. As a method for solving this problem, simply removing the polarizing plate is not appropriate because the on / off ratio of absorbance is remarkably reduced, and various measures have been proposed. For example, as shown in FIG. 7, there has been proposed a reflective guest-host liquid crystal display device in which a polarizing plate is removed from the incident side and a quarter-wave plate and a reflective plate are attached to the outgoing side. In this method, two polarization components Lx and Ly orthogonal to each other are rotated by 90 ° in the forward and backward directions by a quarter wavelength plate,
The polarization components are exchanged. Therefore, in the off state (absorption state) shown in (A), each of the polarization components Lx and Ly is absorbed in either the incident optical path or the reflected optical path. Further, in the ON state (transmission state) shown in (B), almost no polarized components Lx and Ly are absorbed. As a result, the utilization efficiency of incident light can be significantly improved and the display device becomes brighter.

[0005]

However, in this structure, since the quarter-wave plate and the reflection plate are externally mounted, the liquid crystal display device itself needs to be of a transmission type. In particular, when an active matrix type structure is adopted to enable high definition and moving picture display, a thin film transistor for driving a pixel electrode is integrated on a substrate. A considerable part is cut off. Therefore, even if the polarizing plate is removed, the screen of the display device cannot be significantly brightened. In view of this point, a structure in which a quarter-wave plate and a reflection plate are built in the display device has been proposed, which is shown in FIG. In this specification, a structure having a quarter-wave plate and a reflection plate built therein is referred to as an "integrated polarization conversion guest-host liquid crystal display device". As shown in the figure, the integrated polarization conversion guest-host liquid crystal display device includes a first substrate 101 located on the incident light 101 side, and a second substrate 102 arranged behind the first substrate 101 with a predetermined gap therebetween. It is composed of. In this gap, a guest-host liquid crystal layer 103 located on the first substrate 101 side and a quarter-wave plate layer 104 located on the second substrate 102 side are formed. or,
Electrode layers 105 and 106 are formed on both the first substrate 101 side and the second substrate 102 side, and a voltage is applied to the guest-host liquid crystal layer 103. Further, a light reflection layer 107 is provided integrally with the electrode layer 106 on the second substrate 102 side.
The light reflecting layer 107 is interposed between the second substrate 102 and the quarter-wave plate layer 104 to substantially specularly reflect the incident light 101 and emit reflected light 108. A passivation layer 109 is interposed between the liquid crystal layer 103 and the quarter-wave plate layer 104.

In a reflection type guest-host liquid crystal display device, in order to obtain a bright display, it is common to use a reflection electrode such as an aluminum metal film in which the light reflection layer 107 and the electrode layer 106 are integrated and the aperture ratio is maximized. However, a flat metal film electrode causes specular reflection, so that the viewing angle is extremely limited, and the display becomes metallic rather than paper white. In order to prevent this, it has been proposed to form fine irregularities on the surface of the light reflection layer of the metal film to have a wide distribution of reflection angles. However, a problem with this method is that a process for forming irregularities is required.
Further, in the integrated polarization conversion guest-host liquid crystal display device, it is necessary to accurately control the quarter-wave plate layer 104 so as to have a uniform film thickness by following the irregularities. However, this is extremely difficult in reality. Further, it is necessary to set the optimum viewing angle range by controlling the inclination angle distribution of the unevenness, but this is also extremely difficult in practice. As described above, providing irregularities on the surface of the light reflecting layer made of a metal film has many difficulties in device manufacturing.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide an integrated polarization conversion guest-host liquid crystal display device having a bright and wide viewing angle. The following measures were taken to achieve this purpose. That is, the reflective guest-host liquid crystal display device according to the present invention has, as a basic configuration, a first substrate on which light is incident from the front side, and a second substrate disposed on the rear side with a predetermined gap from the first substrate. Is equipped with. A guest-host liquid crystal layer located on the first substrate side and a quarter-wave plate layer located on the second substrate side are provided in this gap. Further, electrode layers are formed on the first substrate side and the second substrate side, and a voltage is applied to the guest-host liquid crystal layer. In addition, a light reflection layer is provided integrally with or separately from the electrode layer on the second substrate side. The light reflecting layer substantially specularly reflects the light that has entered between the second substrate and the quarter-wave plate layer. As a feature, the light scattering layer is interposed between the first substrate and the guest-host liquid crystal layer. This light scattering layer is made of a transparent material in which fine particles are dispersed in a resin, and scatters and emits light reflected from the rear toward the front. Preferably, the electrode layer on the first substrate side is formed on the light-scattering layer whose surface is flattened, and is in contact with the guest-host liquid crystal layer.

The present invention includes not only a reflective guest-host liquid crystal display device but also a general reflective display device. That is, the reflective display device according to the present invention has, as a basic configuration, a first substrate on which light is incident from the front side, and a second substrate arranged on the rear side with a predetermined gap from the first substrate. There is. The electro-optical material layer is held in this gap.
An electrode layer is formed on the first substrate side and the second substrate side, and a voltage is applied to the electro-optical material layer. Further, a light reflection layer is provided integrally with or separately from the electrode layer on the second substrate side, and reflects light incident from the first substrate side substantially specularly. As a feature, the light scattering layer is interposed between the first substrate and the electro-optical material layer. This light scattering layer is made of a transparent material in which fine particles are dispersed in a resin, and scatters and emits light reflected from the rear toward the front.

The present invention further includes a reflective guest-host liquid crystal display device in which surface reflection due to the light scattering layer is suppressed.
That is, the present reflection type guest-host liquid crystal display device has, as a basic configuration, a first substrate on which light is incident from the front side, and a second substrate disposed on the rear side with a predetermined gap from the first substrate. There is. A guest-host liquid crystal layer located on the first substrate side and a quarter-wave plate layer located on the second substrate side are provided in this gap. Further, electrode layers are formed on the first substrate side and the second substrate side, and a voltage is applied to the guest-host liquid crystal layer. In addition, a light reflection layer is provided integrally with or separately from the electrode layer on the second substrate side. The light reflecting layer is interposed between the second substrate and the quarter-wave plate layer to substantially specularly reflect the incident light. Then, the light scattering layer is interposed between the first substrate and the guest-host liquid crystal layer. Characteristically, the light-scattering layer is composed of a microlens array that scatters and outputs the light reflected from the back toward the front. Preferably, the first microlens array is made of glass.
It is a transparent resin that fills innumerable recesses formed by etching on the inner surface of the substrate and has a refractive index different from that of glass. Alternatively, the microlens array is filled on a transparent plastic layer formed on the inner surface of a first substrate made of glass and having a refractive index substantially equal to that of glass, and innumerable recesses formed by stamping on the surface of the transparent plastic layer. And a transparent resin having a refractive index different from that of glass.

According to the present invention, the light-scattering layer is provided on the first substrate on the incident side and the emitting side, and the light-reflecting layer having a mirror surface is provided on the second substrate on the reflecting side. The light reflected from the rear second substrate side is diffused and emitted by the front light scattering layer.
For this reason, the angle distribution of the emitted light is widened, the viewing angle can be improved, and a display having a paper-white appearance instead of a metallic appearance can be obtained. Further, the light scattering layer is provided on the inner side of the first substrate rather than on the outer side, and the distance between the light scattering layer and the specular light reflecting layer is shortened. Therefore, light is hardly diffused in the lateral direction between the light reflecting layer and the light scattering layer, and a display with high contrast and high brightness can be obtained. Further, when the microlens array is used as the light scattering layer, the light reflected from the rear second substrate side is efficiently diffused and emitted forward, while the ineffective component of the incident light reflected on the surface by the light scattering layer is suppressed. It is possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic partial sectional view showing a basic structure of a reflection type guest-host liquid crystal display device according to the present invention. This device is a so-called integrated polarization conversion guest-host liquid crystal display device, and incorporates a light reflection layer and a quarter-wave plate layer. The present apparatus is composed of a first substrate 2 on which incident light 1 is incident from the front, and a second substrate 3 arranged behind the first substrate 2 with a predetermined gap therebetween. The guest host liquid crystal layer 4 is disposed in the gap on the first substrate 2 side. The guest host liquid crystal layer 4 is made of, for example, a mixture of a nematic liquid crystal 5 and a dichroic dye 6. In the same gap, the quarter-wave plate layer 7 is provided on the second substrate 3 side.
Is located. Further, the electrode layers 8 are formed on both the first substrate 2 side and the second substrate 3 side, respectively, and a voltage is applied to the guest-host liquid crystal layer 4. Further, the light reflection layer 9 is provided integrally with or separately from the electrode layer 8 on the second substrate 3 side.
Incident light 1 is interposed between the substrate 3 and the quarter-wave plate layer 7.
Is almost mirror-reflected. In this embodiment, the light reflecting layer 9 and the electrode layer 8 are integrated. As a feature, the first substrate 2
The light scattering layer 10 is interposed between the guest-host liquid crystal layer 4 and the guest-host liquid crystal layer 4. The light scattering layer 10 is made of a transparent material in which fine particles are dispersed in a resin, and the reflected light 11 reflected from the back is scattered and emitted toward the front. Therefore, the emitted light 12 scattered over a wide range is emitted from the first substrate 2. The first
The electrode layer 8 on the substrate 2 side is a light-scattering layer 10 whose surface is flattened.
And is in contact with the guest-host liquid crystal layer 4.
A passivation layer 13 is interposed between the guest-host liquid crystal layer 4 and the quarter-wave plate layer 7. The surfaces of the upper electrode layer 8 and the passivation layer 13 are subjected to an alignment treatment, and the guest-host liquid crystal layer 4 is aligned homogeneously, for example. The present invention can be applied not only to a guest-host liquid crystal display device but also to a general reflection type display device using an electro-optical material layer.

In the integrated polarization conversion guest-host liquid crystal display device according to the present invention, the light reflecting layer 9 having a mirror surface is formed on the rear side of the second substrate 3 while the diffusion is formed on the inner surface of the front side of the first substrate 2. The light-scattering layer 10 having the property is provided. The incident light 1 is diffused by the light scattering layer 10 to some extent, and then the light reflection layer 9
Is reflected by a mirror. The reflected light 11 is diffused by the light scattering layer 10 and emitted light 12 is emitted forward. Since the outgoing light 12 has a relatively wide angular distribution due to the diffusing action of the light scattering layer 10, the viewing angle is improved. Further, since the reflected light 11 is converted into the scattered outgoing light 12 via the light scattering layer 10, the display is not metallic but has a paper white appearance. Furthermore, since the light scattering layer 10 is provided inside the first substrate 2 instead of outside, the distance from the light reflecting layer 9 is extremely short. Therefore, the guest-host liquid crystal layer 4
Lateral diffusion of the reflected light 11 that passes through is suppressed as much as possible, and a high-contrast display can be obtained without impairing the resolution.

Now, referring to FIG. 1, the second substrate 3 will be described.
The film forming process on the side will be described in detail. First, the second substrate 3 made of glass or the like is washed, and then a metal film is formed on the surface of the second substrate 3 by a sputtering method or a vacuum evaporation method to form the light reflection layer 9. This metal film is patterned into a predetermined shape to be processed into an electrode layer. The reflective electrode thus obtained is covered with a base alignment film. This rubbing alignment film is rubbed along a predetermined shape. Further, a polymer liquid crystal material is applied on the underlying alignment film. This polymer liquid crystal is, for example, a side-chain polymer liquid crystal having a benzoate ester mesogen as a pendant. This polymer liquid crystal is dissolved in a solution in which cyclohexanone and methyl ethyl ketone are mixed in a ratio of 8: 2 by 3 to 5% by weight. This solution is spin-coated at a rotation speed of, for example, 1000 rpm to form a polymer liquid crystal film on the second substrate 3. Thereafter, the substrate is heated, and the polymer liquid crystal is once heated to an optically isotropic state. Then, the heating temperature is gradually lowered to return to room temperature through the nematic phase. In the nematic phase, the polymer liquid crystals are aligned along the rubbing direction of the underlying alignment film, and the desired uniaxial alignment is obtained.
This uniaxial orientation is fixed by returning the second substrate 3 to room temperature. By such annealing treatment, the liquid crystal molecules contained in the polymer liquid crystal material are uniaxially oriented, and the desired quarter-wave plate layer 7 is obtained. Furthermore, this quarter wave plate layer 7
A passivation layer 13 is formed on the above. The passivation layer 13 is made of, for example, a PVA film. By rubbing the passivation layer 13 along a predetermined direction, a homogeneous alignment (horizontal alignment) of the guest-host liquid crystal layer 4 in contact therewith can be realized.
The passivation layer 13 is interposed between the polymer liquid crystal material forming the quarter-wave plate layer 7 and the guest-host liquid crystal layer 4 and functions as a blocking layer for both. The rubbing direction of the passivation layer 13 and the rubbing direction of the underlying alignment film intersect each other at an angle of 45 °. It is to be noted that a color filter can be configured by dispersing the dyes of the three primary colors of red, blue and green in the quarter wave plate layer 7 in a region-divided manner.

Next, the film forming process on the first substrate 2 side will be described with reference to FIG. As illustrated, the light scattering layer 10 is formed on the inner surface of the transparent first substrate 2 made of glass or the like. The light scattering layer 10 is made of a transparent material in which fine particles 15 are dispersed in a resin 16. The surface of this transparent material is flattened, and the electrode layer 8 is formed thereon. The electrode layer 8 is made of a transparent conductive film such as ITO and is formed by sputtering or the like. Further, the surface of this transparent electrode layer 8 is subjected to a rubbing treatment. The light-scattering layer 10 is made of, for example, a film of a transparent material in which fine particles 15 made of polymer beads are fixed in a resin (polymer matrix) 16 having a different refractive index, and is laminated on the surface of the first substrate 2 made of glass or a polymer sheet. To be done. In some cases,
The thickness of the film itself may be increased to form the first substrate 2 itself. The fine particles 15 have a refractive index of 1.0 to 1.9.
In the range. The particle size is about 1 to 10 μm. On the other hand, the resin (polymer matrix) 16 is made of, for example, a photosensitive acrylic resin and has a refractive index of 1.5. After coating the first substrate 2 with a resin material in which the fine particles 15 are dispersed in the photosensitive resin 16, ultraviolet rays are applied and cured while being pressed by a press. As a result, the light scattering layer 10 whose surface is flattened can be formed.

FIG. 3 is a schematic partial sectional view showing a reference example of a reflective guest-host liquid crystal display device. In this reference example, the light scattering plate 10 a is attached to the outside of the first substrate 2. Generally, in a reflective liquid crystal display device, a light reflection layer 9 is provided inside a cell for the purpose of achieving a high aperture ratio and preventing resolution deterioration due to parallax. Since the light reflecting layer 9 is made of a metal film such as aluminum and causes specular reflection, the display contrast and the brightness change greatly depending on the viewing angle. Also, the display is metallic and the visibility is poor. Therefore, in this reference example, the light scattering plate 10a is attached to the outer surface of the first substrate 2 on the incident side. In this way, after the incident light 1 is converted into the reflected light 11 by the light reflection layer 9, this is diffused by the light scattering plate 10a and the emitted light 12 is directed forward.
Emits in a wide angle range.

However, the light scattering plate 10 shown in FIG.
The structure in which a is externally attached has a problem in that display contrast and resolution are deteriorated. This will be described with reference to FIG. In addition, in order to facilitate understanding in FIG.
On the second substrate 3 side, a light reflection layer 9, a quarter-wave plate layer 7 and a passivation layer 13 are provided for each pixel. Here, only two pixels A and B are shown. Incident light 1
When passing through the light scattering plate 10a, it undergoes backscattering and is divided into, for example, incident lights 1x and 1y. One incident light component 1x is specularly reflected at the pixel A and is converted into reflected light 11x. This reflected light 11x is again scattered by the light scattering plate 10a located above the pixel A and becomes diffused emitted light 12x. Now, assuming that the pixel A transmits light and the pixel B does not transmit light, one of the incident light components 1x can be normally visually recognized. However, the other incident light component 1y is specularly reflected by the pixel A, and then enters the light scattering plate 10a in the portion located above the pixel B. Here, the light is diffused and the emitted light 12y is emitted forward. In this case, the pixel B is originally selected so as not to transmit light, and the outgoing light 12y leaks though it should exhibit black. Therefore, the contrast between the black level and the white level deteriorates. In order to prevent this reduction in contrast, the distance d between the light scattering plate 10a and the light reflecting layers 9A and 9B may be made as small as possible. Therefore, in the present invention, as shown in FIG. 1, the light scattering layer 10 is formed inside the first substrate 2. As a result, the size of the space between the light scattering layer and the light reflecting layer is reduced, light leakage is eliminated, and sufficient contrast can be realized.

FIG. 5 is a schematic partial sectional view showing another reference example of a reflective guest-host liquid crystal display device. In this reference example, the light reflection layer 9 on the second substrate 3 side is provided with fine irregularities. Incident light 1 is diffused by these irregularities and emitted light 1
Since it is converted to 2, it is possible to widen the viewing angle and obtain a display appearance close to paper white. However, a process of making unevenness on the light reflection layer 9 made of a metal film is required, and the base film 20 is usually required. In order to make the base film 20 uneven, for example, a photolithography process is added. Furthermore, in order to optimize the display brightness, it is necessary to control the inclination distribution of fine unevenness, and the manufacturing conditions are actually extremely difficult. Further, it is difficult to accurately form the quarter-wave plate layer 7 along the uneven surface of the light reflection layer 9.

By the way, the light scattering layer 10 shown in FIG. 2 has a function of efficiently scattering the reflected light from the rear toward the front as described above, while reflecting the light incident from the front to some extent on the surface. The contrast at the time of black display may decrease. This point will be described with reference to FIG. As described above, the light scattering layer 10 is made of a transparent material in which the fine particles 15 are dispersed in the resin 16. In this case, the incident light 1 from the front side on the observer side is scattered and back-reflected by a plurality of interfaces except the component that does not pass through the fine particles 15 such as polymer beads. Hereinafter, such a phenomenon will be referred to as retroreflection scattering. Incidentally, in general,
This back reflection scattering is sometimes called backscattering,
In this specification, the side where the light reflecting layer is located is referred to as the rear side, and thus this term is not used for avoiding misunderstanding. The term backscatter will be used instead of backscatter. Incident light 1 is retroreflected by at least four interfaces as indicated by. That is, as shown in, the incident light 1 is reflected by the interface between the polymer matrix resin 16 and the first substrate 2 made of glass or the like. Further, as shown by, the light is reflected at the interface between the polymer matrix resin 16 and the fine particles 15. Further, as shown in, fine particles 15
And is reflected at the interface between the polymer matrix resin 16.
In addition, the light is reflected at the interface between the polymer matrix resin 16 and the transparent electrode layer 8 as indicated by. In this way, in the light scattering layer 10, the incident light 1 is reflected by the four interfaces, and the reverse reflection scattering becomes remarkable. As a result, in white display, there is not much problem, but in black display, the contrast is weakened, and so-called black display floats.

FIG. 10 shows another structure of the light-scattering layer according to the present invention, which can suppress back reflection scattering.
As shown, the light scattering layer is a microlens array 30.
And is interposed between the first substrate 2 and the guest-host liquid crystal layer (not shown) to scatter and emit the light reflected from the rear toward the front. The microlens array 30 is made of a transparent resin 32 filled in a myriad of recesses 31 formed by isotropic etching on the inner surface of the first substrate 2 made of glass. This transparent resin 32 is made of epoxy, for example,
It has a refractive index n2 different from the refractive index n1 of the glass that constitutes the substrate 2. An arbitrary microlens can be formed by isotropically etching the surface of the first substrate 2 made of glass or the like and applying an epoxy resin or the like to the surface. The light scattering angle can be easily controlled by changing the refractive index of the transparent resin used as the microlens. On the other hand, with respect to the incident light 1 from the front, only the interface between the first substrate 2 and the transparent resin 32 as shown by and the interface between the transparent resin 32 and the transparent electrode layer 8 as shown by are retro-reflected. It causes scattering. As is clear from comparison between FIG. 9 and FIG. 10, when the microlens array 30 is used as the light scattering layer, the number of reflective interfaces is reduced from four to two, and it is possible to suppress the retroreflective scattering accordingly. Is.

FIG. 11 is a schematic partial sectional view showing another example of the microlens array used as the light scattering layer. Portions corresponding to those of the microlens array shown in FIG. 10 are designated by corresponding reference numerals to facilitate understanding. In this embodiment, the microlens array 30 has a composite structure of a transparent plastic layer 33 and a transparent resin 32. The transparent plastic layer 33 is formed on the inner surface of the first substrate 2 made of glass and has a refractive index n1 'which is substantially equal to the refractive index n1 of glass. On the other hand, the transparent resin 32 is filled in the innumerable recesses 31 formed by stamping on the surface of the transparent plastic layer 33 and has a refractive index n2 different from the refractive index n1 of glass. In the embodiment shown in FIG. 10, the recess 31 is formed by isotropic etching of glass through a mask.
In contrast to this, in this embodiment, the recess 31 is formed by stamping the transparent plastic layer 33, which is advantageous in the manufacturing process.

Finally, a specific application example of the microlens array shown in FIG. 10 will be described with reference to FIG. As shown in the figure, the present reflective guest-host liquid crystal display device includes a pair of upper and lower substrates 51, which are bonded to each other with a predetermined gap.
52 is used. The upper substrate 51 is located on the incident side and is made of a transparent base material such as glass. On the other hand, the lower substrate 52 is located on the reflection side, and it is not always necessary to use a transparent material. The guest-host liquid crystal 53 is held in the gap between the pair of substrates 51 and 52. This guest-host liquid crystal 53
Is mainly composed of nematic liquid crystal molecules 54 having negative dielectric anisotropy, and contains black dichroic dye 55 in a predetermined ratio. A color filter 34, a counter electrode 56, and an alignment layer 57 are formed on the inner surface of the upper substrate 51. The counter electrode 56 is made of a transparent conductive film such as ITO. The alignment layer 57 is made of, for example, a polyimide film and vertically aligns the guest-host liquid crystal 53. The present invention is not limited to this, and the guest-host liquid crystal may be horizontally aligned as shown in FIG. In this embodiment, the guest-host liquid crystal 53 is vertically aligned when no voltage is applied, and is horizontally aligned when a voltage is applied. A microlens array 30 is formed on the inner surface of the substrate 51. The microlens array 30 is composed of a transparent resin 32 filled in an infinite number of recesses 31 formed by etching on the inner surface of a substrate 51 made of glass or the like. The transparent resin 32 has a refractive index different from that of the glass forming the substrate 51. In this embodiment, the color filter 34 is interposed between the microlens array 30 and the counter electrode 56.

At least a switching element composed of a thin film transistor 58, a light reflection layer 59, a quarter wavelength plate layer 60 and a pixel electrode 61 are formed on the lower substrate 52. As a basic configuration, the quarter-wave plate layer 60 is formed above the thin film transistor 58 and the light reflection layer 59, and the contact hole 62 communicating with the thin film transistor 58 is provided. The pixel electrode 61 is patterned on the quarter-wave plate layer 60. Therefore,
It is possible to apply a sufficient electric field to the guest-host liquid crystal 53 between the pixel electrode 61 and the counter electrode 56. The pixel electrode 61 is electrically connected to the thin film transistor 58 through a contact hole 62 opened in the quarter-wave plate layer 60.

In this embodiment, the quarter-wave plate layer 60 is composed of a uniaxially oriented polymer liquid crystal film. A base alignment layer 63 is used for uniaxially aligning this polymer liquid crystal film. The flattening layer 64 is interposed to fill the thin film transistor 58 and the light reflection layer 59, and the above-described base alignment layer 63 is provided.
Are formed on the flattening layer 64. The quarter-wave plate layer 60 is also formed on the surface of the flattening layer 64. In this case, the pixel electrode 61 is connected to the thin film transistor 58 through the contact hole 62 provided through the quarter-wave plate layer 60 and the flattening layer 64. The light reflecting layer 59 is subdivided corresponding to each pixel electrode 61. The individual subdivided portions are connected to the same potential as the corresponding pixel electrode 61. With this configuration, an unnecessary electric field is not applied to the quarter-wave plate layer 60 and the flattening layer 64 interposed between the light reflection layer 59 and the pixel electrode 61. The light reflecting layer 59 is made of a sputtered film of aluminum or the like and has a mirror surface. An alignment layer 65 is formed so as to cover the surface of the pixel electrode 61, and contacts the guest-host liquid crystal 53 to control the alignment. In this example, the alignment layer 65 together with the facing alignment layer 57 vertically aligns the guest-host liquid crystal 53. Finally, the thin film transistor 8 has a bottom gate structure, and has a laminated structure in which a gate electrode 66, a gate insulating film 67, and a semiconductor thin film 68 are stacked in this order from the bottom. The semiconductor thin film 68 is made of, for example, polycrystalline silicon, and the channel region matching the gate electrode 66 is protected by a stopper 69 from above. The bottom gate type thin film transistor 58 having such a configuration is covered with an interlayer insulating film 70. A pair of contact holes are opened in the interlayer insulating film 70, and the source electrode 71 and the drain electrode 72 are electrically connected to the thin film transistor 58 via these.
These electrodes 71 and 72 are formed by patterning aluminum, for example. The drain electrode 72 is the light reflection layer 5
It has the same potential as 9. The pixel electrode 61 is electrically connected to the drain electrode 72 via the contact hole 62 described above. On the other hand, a signal voltage is supplied to the source electrode 71.

[0024]

As described above, according to the present invention,
In an integrated polarization conversion guest-host liquid crystal display device, a light-reflecting layer that substantially specularly reflects incident light is provided between a reflecting-side substrate and a quarter-wave plate layer, while the incident-side first substrate and guest host are provided. A light scattering layer is interposed between the liquid crystal layer and the liquid crystal layer, and the reflected light entering from the rear is scattered and emitted toward the front.
This allows a bright, high-contrast paper-white display that remains specularly reflective without the light reflecting layer being intentionally diffusive. In some cases,
By combining with a color filter, a full-color, bright reflective liquid crystal display device can be realized. Further, by using a microlens array as the light scattering layer, it is possible to prevent back reflection scattering and suppress the floating at the time of black display and improve the contrast. In this case, the light scattering angle can be easily controlled by appropriately selecting the refractive index of the transparent resin forming the microlens array.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing a basic configuration of a reflective guest-host liquid crystal display device according to the present invention.

FIG. 2 is a schematic partial cross-sectional view showing a specific configuration example of a light scattering layer formed inside an incident side substrate of a reflective guest-host liquid crystal display device.

FIG. 3 is a partial cross-sectional view showing a reference example of a reflective guest-host liquid crystal display device.

FIG. 4 is a partial cross-sectional view showing a reference example of a reflective guest-host liquid crystal display device.

FIG. 5 is a partial cross-sectional view showing another reference example of the reflective guest-host liquid crystal display device.

FIG. 6 is a schematic view showing a conventional transmissive guest-host liquid crystal display device.

FIG. 7 is a schematic view showing a conventional reflective guest-host liquid crystal display device.

FIG. 8 is a partial cross-sectional view showing a reference example of a reflective guest-host liquid crystal display device.

9 is a schematic diagram showing a reverse reflection scattering phenomenon of the light scattering layer shown in FIG.

FIG. 10 is a partial cross-sectional view showing another embodiment of the light scattering layer according to the present invention.

FIG. 11 is a partial sectional view showing another embodiment of the light scattering layer according to the present invention.

FIG. 12 is a partial cross-sectional view showing a specific structural example of a reflective guest-host liquid crystal display device according to the present invention.

[Explanation of symbols]

1 ... Incident light, 2 ... First substrate, 3 ... Second substrate, 4 ... Guest-host liquid crystal layer, 5 ... Nematic liquid crystal, 6 ... Dichroic dye, 7 ... Quarter wave plate layer, 8 ... Electrode layer , 9 ... Light reflecting layer, 10 ... Light scattering layer, 11 ... Reflected light, 12 ... Emitted light, 1
3 ... passivation layer, 15 ... fine particles, 16 ... resin, 3
0 ... Microlens array, 31 ... Recess, 32 ... Transparent resin, 33 ... Transparent plastic layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G02F 1/136 500 G02F 1/136 500

Claims (6)

[Claims] 1. A first substrate on which light is incident from the front, and a second substrate which is disposed rearward from the first substrate with a predetermined gap therebetween.
A substrate, a guest-host liquid crystal layer located on the side of the first substrate in the gap, a quarter-wave plate layer located on the side of the second substrate in the gap, and on the first substrate side and the second substrate side. The formed electrode layer for applying a voltage to the guest-host liquid crystal layer and the electrode layer on the second substrate side are provided integrally or separately and are interposed between the second substrate and the quarter-wave plate layer. A light reflecting layer for substantially specularly reflecting incident light, a transparent material which is interposed between the first substrate and the guest-host liquid crystal layer and has fine particles dispersed in a resin, and reflects light reflected from the front to the front. A reflective guest-host liquid crystal display device comprising a light-scattering layer that scatters and emits toward the outside. 2. The reflection type guest-host liquid crystal display device according to claim 1, wherein the electrode layer on the side of the first substrate is formed on the light-scattering layer having a flattened surface and is in contact with the guest-host liquid crystal layer. . 3. A first substrate on which light is incident from the front, and a second substrate which is arranged rearward from the first substrate with a predetermined gap therebetween.
A substrate, an electro-optical material layer held in the gap, an electrode layer formed on the first substrate side and the second substrate side for applying a voltage to the electro-optical material layer, and an electrode layer on the second substrate side. A light reflection layer provided integrally or separately for substantially specularly reflecting the light incident from the first substrate side, and a transparent material in which fine particles are dispersed in a resin while being interposed between the first substrate and the electro-optical material layer. A reflection-type display device comprising a light-scattering layer made of a material, which scatters and emits light reflected from the rear toward the front. 4. A first substrate on which light is incident from the front, and a second substrate which is disposed rearward from the first substrate with a predetermined gap therebetween.
A substrate, a guest-host liquid crystal layer located on the side of the first substrate in the gap, a quarter-wave plate layer located on the side of the second substrate in the gap, and on the first substrate side and the second substrate side. The formed electrode layer for applying a voltage to the guest-host liquid crystal layer and the electrode layer on the second substrate side are provided integrally or separately and are interposed between the second substrate and the quarter-wave plate layer. And a microlens array interposed between the first substrate and the guest-host liquid crystal layer to scatter and emit the light reflected from the rear toward the front. Reflective guest-host liquid crystal display device. 5. The reflection type according to claim 4, wherein the microlens array is a transparent resin filled in a myriad of recesses formed by etching on an inner surface of a first substrate made of glass and having a refractive index different from that of glass. Guest-host liquid crystal display device. 6. The microlens array is formed on the inner surface of a first substrate made of glass, and has a transparent plastic layer having a refractive index substantially equal to that of glass, and a myriad of stamped layers formed on the surface of the transparent plastic layer. The reflective guest-host liquid crystal display device according to claim 4, comprising a transparent resin filled in the recesses and having a refractive index different from that of glass.