JPH11337923A - Hologram optical control film for polymer dispersed type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram optical control film capable of realizing a reflection type polymer dispersed liquid crystal display device high in brightness and visibility by arranging the film in front of a reflecting layer on the opposite side of an observer side, and diffracting incident light made incident from a predetermined direction of the observer's side in other directions other than the specular reflection direction. SOLUTION: A liquid crystal display panel holds a color filter consisting of an array of R-transmission filter 15R, G-transmission filter 15G, and B- transmission filter 15B between a observer's side transparent substrate 11 arranged on the surface of PD liquid crystal 10 side and a transparent substrate 21 on the opposite side of the observer. Holograms 23R, 23G, 23B diffract the light of R, G, B wavelengths, which have been made incident from outside at a predetermined incident angle θ, in the reflecting or transmitting direction at a critical angle or above. In such a manner, the problem is prevented, that illumination light of picture elements in the transparent state is reflected in the specular reflection direction to enter the eyes, and does not look black but looks rather black-and-white inverted to remarkably reduce visibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram light control film for a polymer-dispersed liquid crystal display device, and more particularly to a hologram light control film that enables a bright and highly visible polymer-dispersed liquid crystal display device. is there.

[0002]

2. Description of the Related Art Conventionally, polymer-dispersed liquid crystal display devices have been receiving attention. The principle of the polymer dispersed liquid crystal will be described with reference to FIG. 5A shows the case where no electric field is applied to the polymer dispersed liquid crystal, and FIG. 5B shows the case where the electric field is applied. The liquid crystal 1 is dispersed in the polymer matrix 2 and the refraction of the polymer matrix 2 is shown. The index is set so as to substantially match the ordinary light refractive index of the liquid crystal 1. In a state in which the switch from FIG. 5A is opened and the voltage from the power supply 3 is not applied between the transparent electrodes 4, the liquid crystal 1 is in a random state, so that a spatial difference in the refractive index occurs and the incident light is changed. 5 is scattered by forward scattered light (forward scattered light) 6 and backward scattered light (backward scattered light) 7. In the state where a voltage is applied between the transparent electrodes 4 and 4 in FIG. 5B, the liquid crystal 1 is arranged in the direction of the electric field, and as a result, the difference in the refractive index between the liquid crystal 1 and the polymer matrix 2 is reduced. Is transmitted as straight light 8 without being scattered, and thus becomes transparent.

A liquid crystal display device using such a polymer dispersed liquid crystal (hereinafter referred to as a PD liquid crystal display device) has been proposed. The PD liquid crystal display device does not need to use a polarizing plate due to its principle, and the liquid crystal changes to a transparent state or a scattering state depending on whether an electric field is applied or not. Therefore, the PD liquid crystal display is very bright. By doing so, substantially paper white display is possible.

FIG. 6 shows a schematic structure of a conventional monochrome reflective PD liquid crystal display device. However, the pixel electrode and the counter electrode are not shown. The polymer-dispersed liquid crystal (hereinafter referred to as PD liquid crystal) 10 as described above includes a transparent substrate 11 and a substrate 12.
A mirror 13 is disposed on the surface of the substrate 12 opposite to the observation side of the PD liquid crystal 10 and sandwiched between them. And
This reflective PD liquid crystal display device typically has three pixels X,
It is assumed to be composed of Y and Z. Now, assuming that no voltage is applied to the pixels X and Z and a voltage is applied to the pixel Y, the pixels X and Z are in the scattering state and the pixel Y is in the transparent state. When external light (surrounding ambient light) 14 is incident on the reflective PD liquid crystal display device, the pixels X and Z are in a scattering state. It looks almost white in the eyes of an observer located in front of the reflective PD liquid crystal display device. Since the pixel Y is in a transparent state, the external light 14
Since the light is specularly reflected at 3 and does not travel in the front direction of the reflective PD liquid crystal display device, it looks almost black.

FIG. 7 shows a schematic configuration of a conventional color reflective PD liquid crystal display device. Also in this case, the pixel electrode and the counter electrode are not shown. This configuration basically includes an R (red) transmission R filter 15R and a G (green) transmission G filter 15 on the surface of the transparent substrate 11 on the observation side of the PD liquid crystal 10 in FIG.
A color filter 15 composed of an array of G, B (blue) transmission B filters 15B is arranged, and also in this case, it is assumed that the color filter 15 is typically composed of three pixels R, G, B. Now, assuming that no voltage is applied to the pixels R and B and a voltage is applied to the pixel G, the pixels R and B are in the scattering state and the pixel G is in the transparent state. When external light (surrounding ambient light) 14 is incident on the color reflective PD liquid crystal display device, the pixels R and B are in a scattering state.
The back scattered light of the R light and B light transmitted through the R transmission R filter 15R and the B transmission B filter 15B, respectively, is left as it is, and the forward scattered light is once reflected by the mirror 13 and is located in front of the reflective PD liquid crystal display device. It enters the observer's eyes and looks red and blue, respectively. Since the pixel G is in a transparent state, the external light 14 is specularly reflected by the mirror 13 and does not proceed in the front direction of the reflective PD liquid crystal display device, so that it looks almost black.

[0006]

However, in the case of such a conventional reflection type PD liquid crystal display device, when a mirror is arranged on the back surface of the PD liquid crystal, a portion (pixel) in a transparent state is provided.
In the specular reflection direction of the illumination light (external light), the specular reflection light enters the eyes, and does not look black, but rather reverses black and white, significantly lowering the visibility.

In view of this, it is conceivable to arrange a black member on the back surface and make the transparent portion a black display portion.
The portion in the scattering state does not become paper white. This is because the forward scattered light is absorbed by this black member and does not return to the observation side, so that it becomes gray.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a hologram light control film which enables a reflective polymer dispersed liquid crystal display device which is bright and has good visibility. To provide.

[0009]

The hologram light control film for a polymer-dispersed liquid crystal display device of the present invention, which achieves the above object, comprises a reflective layer on the opposite side of the reflective polymer-dispersed liquid crystal display device from the observation side. And diffracts incident light incident from a predetermined direction on the observation side in a direction other than the regular reflection direction.

In this case, the incident light incident from the oblique front of the observation side may be diffracted in the front direction of the reflection direction or the front direction of the transmission direction, or may be incident in a predetermined direction on the observation side. The incident light may be diffracted in the reflection direction or the transmission direction at an angle at which the incident light is totally reflected inside the hologram layer including the protective layer provided on the surface.

In the latter case, the reflection type polymer dispersion type liquid crystal display device is provided with an absorption type color filter which transmits light of different wavelength bands for each pixel, and the hologram light control film is provided for each pixel of the absorption type color filter. It is preferable that the pattern is arranged so as to be aligned, and that at a position corresponding to each pixel of the absorption type color filter, at least one wavelength band of the transmission wavelength band of the corresponding pixel is diffracted at the angle of total reflection.

The reflection type polymer dispersion type liquid crystal display device includes an absorption type color filter which transmits light of different wavelength bands for each pixel, and the hologram light control film includes:
Uniform holograms for diffracting at least one wavelength band of each wavelength band at the angle of total reflection are laminated by the number of layers corresponding to the number of the different wavelength bands, or are multiplex-recorded in one hologram layer. It is desirable to be made.

In these, the absorption type color filter is composed of, for example, R, G, B three color pixels.

The present invention also includes a reflection type polymer dispersion type liquid crystal display device provided with any one of the above-mentioned hologram light control films for a polymer dispersion type liquid crystal display device.

In the present invention, the reflection type polymer-dispersed liquid crystal display device is disposed on the front surface of the reflection layer on the side opposite to the observation side, so that incident light from a predetermined direction on the observation side is directed in a direction other than the regular reflection direction. In this way, the problem that the illumination light of the pixel in the transparent state is reflected in the specular reflection direction and the light enters the eyes, and does not look black but rather inverts black and white and significantly lowers the visibility, and can be brightened. , High contrast,
A reflective polymer dispersed liquid crystal display device having high chromaticity and good visibility is made possible.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hologram light control film of the present invention and a reflection type polymer dispersion type liquid crystal display device using the same (hereinafter referred to as a reflection type PD liquid crystal display device) will be described based on examples. I do. FIG. 1 is a diagram showing a schematic configuration of an embodiment of a first type reflection type PD liquid crystal display device capable of performing color display according to the present invention. However, the pixel electrode and the counter electrode are not shown. The polymer-dispersed liquid crystal (hereinafter, referred to as PD liquid crystal) 10 as described above has R (red).
The observation-side transparent substrate 11 in which a color filter 15 composed of an array of a transmission R filter 15R, a G (green) transmission G filter 15G, and a B (blue) transmission B filter 15B is arranged on the surface of the PD liquid crystal 10 and the opposite side to the observation side. A liquid crystal display panel is sandwiched between the transparent substrate 21 and
A hologram layer 23 according to the present invention and a mirror 13 are arranged on the back surface of the hologram layer 23 with a slight gap on the transparent substrate 21 side. The mirror 13 and the hologram layer 23
Specifically, are stacked on the substrate 22 in that order. Note that a transparent protective layer is generally provided on the surface of the hologram layer 23.

Here, the hologram layer 23 is made of a volume hologram made of photopolymer or the like, and the R filter 15R, the G filter 15G,
An array of R diffraction holograms 23R, G diffraction holograms 23G, and B diffraction holograms 23B is arranged in each of the B filters 15B.
3R, 23G, and 23B reflect light of R, G, and B wavelengths, which are incident from the outside at a predetermined incident angle θ, in a reflection direction (in the case of FIG. 1) or a transmission direction at an angle greater than the critical angle (including the protective layer). (The angle of total reflection inside the hologram layer 23).

The reflection type PD liquid crystal display device of the embodiment shown in FIG. 1 has an R filter 15R for easy understanding.
, A pixel R configured at the position of the G filter 15G, and a representative pixel R, G, B of a pixel B configured at the position of the B filter 15B. In fact, it is composed of a repeating pattern of pixels R, G and B.

As shown in FIG. 1, assuming that no voltage is applied to the pixels R and B and a voltage is applied to the pixel G, the pixels R and B are in a scattering state, and the pixel G is transparent. In the state, external light (ambient ambient light) 1 at an appropriate incident angle θ
4 enters this color reflection type PD liquid crystal display device,
Since the pixels R and B are in the scattering state, the backscattered light 24 of the R light and the B light transmitted through the R transmission R filter 15R and the B transmission B filter 15B respectively is used as is in the reflection type PD.
The forward scattered light 25 almost passes through the hologram layer 23 and is once reflected by the mirror 13 to return to the observer's eyes located in front of the liquid crystal display device. , Looks blue. It is to be noted that the forward scattered light 25 almost transmits through the hologram layer 23 because the hologram layer 23 is formed of a volume hologram, and the forward scattered light incident at an angle other than the incident angle θ due to its diffraction angle selectivity. This is because 25 does not receive diffraction.

On the other hand, since the pixel G is in a transparent state, the R light and the B light in the external light 14 are absorbed by the G filter 15G.
The G light transmitted through the G filter 15G travels straight and enters the G diffraction hologram 23G of the hologram layer 23, and is diffracted at an angle greater than the critical angle in the reflection direction (in the case of FIG. 1) or the transmission direction. The light is guided to the end while repeating multiple reflections between the surface or the surface of the protective layer provided thereon and the mirror 13, and does not return to the observer side. Therefore, the pixel G looks almost black. Other pixels R, B
The same applies to the case where a voltage is applied to.

Therefore, according to this structure, unlike the conventional case of FIG. 7, specular reflection from a portion (pixel) in a transparent state when viewed from any direction on the viewing side of the reflective PD liquid crystal display device. Light does not enter the eyes and looks black, so color visibility P with good visibility and contrast
A D liquid crystal display device is obtained.

FIG. 2 shows a method of forming the hologram layer 23. FIG. 2A shows a case where the holograms 23R, 23G, and 23B are configured as a reflection type (diffraction in a reflection direction).
FIG. 2B shows a case of a transmission type (diffraction in the transmission direction). First, the case of FIG. 2A will be described. An angle θ corresponding to the incident angle θ of the external light 14 when used from the front side of the volume hologram photosensitive material 30 such as a photopolymer.
A light 32 having a central wavelength of R is made incident on the position of the R pixel, and a prism 31 having a refractive index substantially the same as that of the photosensitive material 30 is brought into close contact with the back surface of the photosensitive material 30 via a refractive index matching liquid,
Light 33 of the same wavelength is applied to the position of the R pixel at an angle α that is greater than the critical angle.
And the two lights interfere with each other in the photosensitive material 30 to form an R diffraction hologram 23R in the photosensitive material 30. By changing the wavelength to the center wavelength of G and the center wavelength of B and repeating the same exposure by changing the incident position to the position of the G pixel and the position of the B pixel, the G diffraction holograms 23G and B
By also forming the diffraction hologram 23B, the hologram layer 23 composed of an array of the reflection holograms 23R, 23G, 23B is produced.

Next, a description will be given of the case of FIG. 2B. A deformable prism 3 having a refractive index substantially the same as that of the photosensitive material 30 and having a refractive index similar to that of the photosensitive material 30 is provided on one side of the same volume hologram photosensitive material 30.
1 ′ is brought into close contact with the refractive index matching liquid,
At the angle θ ′ (derived from Snell's law) when the external light 14 having an incident angle θ is refracted and incident on the photosensitive material 30 through one surface 1 ′, the light 32 ′ having the central wavelength of R is obtained. At the position of the R pixel and the deformed prism 3 from the same side.
Light 33 ′ of the same wavelength is incident on the position of the R pixel at an angle α that is equal to or greater than the critical angle through another surface of the photosensitive material 3 ′, and the light 33 3
By causing the interference in 0, an R diffraction hologram 23R is formed in the photosensitive material 30. The wavelength is the central wavelength of G,
By repeating the same exposure by changing the incident position to the position of the G pixel and the position of the B pixel instead of the center wavelength of B, thereby forming the G diffraction hologram 23G and the B diffraction hologram 23B, the transmission hologram 23R, 23G, 23
The hologram layer 23 made of the B array is manufactured.

In FIG. 2, selective exposure to each pixel position is performed by, for example, using a pattern plate provided with an opening corresponding to a pixel pattern of any one of R, G, and B pixels on the photosensitive material 30. It can be performed by exposing through both sides.

FIG. 3 shows a modification of the color reflection type PD liquid crystal display device of FIG. In the case of FIG. 1, the hologram layer 23 arranged on the front surface of the mirror 13 is composed of the diffraction hologram 2 aligned with each of the color filters 15R, 15G, and 15B.
Since it is an array of 3R, 23G, and 23B, the diffraction hologram 23R, 23
G and 23B were necessary, but in the case of FIG. 3, instead of the hologram layer 23, three uniform volume hologram layers 26R, 26G, and 2 without patterning were used.
A hologram layer 26 formed by laminating 6B is used. Others are the same as those in FIG. Here, the volume hologram layers 26R, 26G, 26B are formed by the diffraction holograms 23R,
Similarly to 23G and 23B, R light, G light and B light incident at an incident angle θ are diffracted in a reflection direction (in the case of FIG. 3) or a transmission direction at an angle equal to or greater than the critical angle. The reflected light is guided to the end while repeating multiple reflections between the surface of the hologram layer 26 or the surface of the protective layer provided thereon and the mirror 13, and does not return to the observer side. Also in this case, as in the case of FIG. 1, the R, G, and B pixels to which no voltage is applied appear red, green, and blue, respectively, and the pixels to which voltage is applied are substantially visible when viewed from any direction on the observation side. Looks black.

In FIG. 3, the hologram layer 26
Represents three stacked volume hologram layers 26R, 26G,
Although it is composed of 26B, a volume hologram having three characteristics as described above may be multiplexed and recorded in a single volume hologram layer.

Next, FIG. 4 is a diagram showing a schematic configuration of an embodiment in which a mono-color pattern can be displayed on a white background by a reflection type PD liquid crystal display device of the second type according to the present invention. However, the pixel electrode and the counter electrode are not shown. This example is
The PD liquid crystal 10 is sandwiched between a transparent substrate 11 and a substrate 12, and a mirror 13 and a mirror 13 are provided on the surface of the substrate 12 opposite to the observation side of the PD liquid crystal 10. A hologram layer 27 is provided. This reflective PD liquid crystal display device typically has three pixels X, Y,
Although it is assumed to be composed of Z, a large number of pixels similar to the pixels X, Y and Z are actually arranged on the array.

Here, the hologram layer 27 is a uniform volume hologram made of a photopolymer or the like. If the hologram layer 27 diffuses, for example, green light incident at an appropriate incident angle θ, it is diffracted in the front direction of the reflection direction. Alternatively, it has a characteristic of diffracting in the front direction of the transmission direction. In such a diffuse reflection type or diffusion transmission type volume hologram, one of the two halves of the diffraction wavelength light is opposed to a volume hologram photosensitive material such as a photopolymer by directing the other through a light diffusion plate. (In the case of a reflective hologram) or from the same side and interfere with each other.

As shown in FIG. 4, assuming that no voltage is applied to pixels X and Z and a voltage is applied to pixel Y, pixels X and Z are in a scattering state and pixel Y is transparent. In the state, external light (ambient ambient light) 1 at an appropriate incident angle θ
4 enters this reflective PD liquid crystal display device, the pixels X and Z are in a scattering state, and the incident light is backscattered light 24.
And the forward scattered light 25, the back scattered light 24 enters the eyes of an observer located in front of the reflective PD liquid crystal display device, and the forward scattered light 25 is scattered by the hologram layer 2.
7 are transmitted through the mirror 13 and are once reflected by the mirror 13 to return to the observer's eyes.

On the other hand, since the pixel Y is in a transparent state, the external light 14 goes straight and enters the hologram layer 27, and the green component of the external light 14 is substantially perpendicular to the liquid crystal display panel in the reflection or transmission direction. The light is diffracted so as to diffuse with directivity in the direction. When the hologram layer 27 is a reflection type, the diffracted light enters the eyes of an observer located in front of the reflection type PD liquid crystal display device as it is, and when the hologram layer 27 is a transmission type, the diffracted light is once reflected by the mirror 13. It is reflected back and enters the observer's eyes as well, and appears green. The components other than green in the external light 14 almost pass through the hologram layer 27 and
And is reflected in the regular reflection direction. Accordingly, when viewed from the specular reflection direction, the pixels X and Z appear to be paper white, and the pixel Y appears to be a complementary color of green, magenta.

Although the hologram light control film for a polymer-dispersed liquid crystal display device of the present invention has been described based on the embodiments, the present invention is not limited to these embodiments and can be variously modified.

[0032]

As is apparent from the above description, according to the hologram light control film for a polymer-dispersed liquid crystal display device of the present invention, the reflection on the side opposite to the observation side of the reflective polymer-dispersed liquid crystal display device. It is arranged on the front side of the layer and diffracts incident light entering from a predetermined direction on the observation side in a direction other than the specular reflection direction, so that the illumination light of the pixels in the transparent state is reflected in the specular reflection direction and the light enters the eyes. In addition, it is possible to prevent the problem that the visibility is significantly lowered due to the inversion of black and white rather than the appearance of black, and a bright polymer, a high contrast, a high chromaticity, and a highly visible reflective polymer-dispersed liquid crystal display device. I do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a first type of color reflection type polymer dispersion type liquid crystal display device according to the present invention.

FIG. 2 is a diagram for explaining a method of manufacturing the hologram layer in FIG.

FIG. 3 is a diagram showing a schematic configuration of a modification of FIG. 1;

FIG. 4 is a diagram showing a schematic configuration of an example of a second type monocolor reflective polymer dispersed liquid crystal display device according to the present invention.

FIG. 5 is a diagram illustrating the principle of a polymer-dispersed liquid crystal.

FIG. 6 is a diagram showing a schematic configuration of a conventional monochrome reflective polymer dispersed liquid crystal display device.

FIG. 7 is a diagram showing a schematic configuration of a conventional color reflection type polymer dispersion type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 10: PD liquid crystal (polymer-dispersed liquid crystal) 11: Observation side transparent substrate 12: Substrate 13: Mirror 14: External light (ambient ambient light) 15: Color filter 15R: R transmission R filter 15G: G transmission G filter 15B ... B transmission R filter 21 ... transparent substrate 22 ... substrate 23 ... hologram layer 23R ... R diffraction hologram 23G ... G diffraction hologram 23B ... B diffraction hologram 24 ... back scattered light 25 ... forward scattered light 26 ... hologram layer 26R ... R diffraction volume -Type hologram layer 26G ... G-diffraction volume hologram layer 26B ... B-diffraction volume hologram layer 27 ... Hologram layer 30 ... Volume hologram photosensitive material 31 ... Prism 32,33 ... R light at the center wavelength of R 31 '... Deformed prism 32' , 33 '... Light having a central wavelength of R, R, G, B, X, Y, Z.

Claims (7)

[Claims] 1. A reflection type polymer dispersion type liquid crystal display device, which is disposed on the front surface of a reflection layer opposite to the observation side and diffracts incident light incident from a predetermined direction on the observation side in directions other than the regular reflection direction. A hologram light control film for a polymer-dispersed liquid crystal display device, comprising: 2. A polymer-dispersed liquid crystal display according to claim 1, wherein incident light incident from an oblique front side on the observation side is diffracted in a front direction in a reflection direction or in a front direction in a transmission direction. Hologram light control film for equipment. 3. The method according to claim 1, wherein the incident light incident from a predetermined direction on the observation side is diffracted in a reflection direction or a transmission direction at an angle at which the incident light is totally reflected inside the hologram layer including the protective layer provided on the surface. Characteristic hologram light control film for polymer dispersed liquid crystal display. 4. The reflection type polymer dispersion type liquid crystal display device according to claim 3, further comprising an absorption type color filter which transmits light of a different wavelength band for each pixel, wherein the hologram light control film is formed of an absorption type color filter. It is patterned so as to be aligned with the pixel, and diffracts at least one wavelength band of the transmission wavelength band of the corresponding pixel at the angle corresponding to the total reflection at a position corresponding to each pixel of the absorption type color filter. Hologram light control film for polymer dispersed liquid crystal display. 5. The liquid crystal display device according to claim 3, wherein the reflection type polymer dispersion type liquid crystal display device includes an absorption type color filter which transmits light of different wavelength bands for each pixel, and wherein the hologram light control film has at least one of each wavelength band. It is required that uniform holograms that diffract one wavelength band at the angle of total reflection are stacked in a number corresponding to the number of the different wavelength bands or multiplex-recorded in one hologram layer. Characteristic hologram light control film for polymer dispersed liquid crystal display. 6. The hologram light control film for a polymer dispersed liquid crystal display device according to claim 4, wherein the absorption type color filter is composed of R, G, and B color pixels. 7. A reflective polymer-dispersed liquid crystal display device, comprising the hologram light control film for a polymer-dispersed liquid crystal display device according to claim 1.