JP2005106938A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element which attains a display in a reflective display mode and also in a transmissive display mode. <P>SOLUTION: The display element is provided with a light scattering modulation layer 11 having a function to modulate a light scattering state and an optical intensity modulation layer 12 having a function to modulate light intensity. Preferably, the light scattering modulation layer 11 is a polymer dispersed liquid crystal layer comprising a liquid crystal material dispersed in a polymer material and the optical intensity modulation layer 12 is a guest-host liquid crystal layer including a host liquid crystal and a dichroic dye, being composed of two layers laminated with each other, which comprises an upper layer with three primary color pixels of R, G, B arranged in proximity to one another and a lower layer with three primary color pixels of C, M, Y arranged in proximity to one another, wherein pixels of the upper layer and pixels of the lower layer, seen two-dimensionally, are in the same positions, and further being constructed by lamination in such a way that the color of the upper layer pixel is a complementary color of the color of the directly below lower layer pixel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display element whose display form is variable.

In recent years, with the spread of mobile computing, there has been a demand for a display that is lighter, thinner, and consumes less power. In particular, there is an increasing interest in displays that do not require a backlight. As such a display, a reflective display that uses external light as reflected light, or a transmissive display that uses transmitted light (for example, a transmissive display is used for a head-mounted display used in the field of virtual reality). (See Non-Patent Document 1)) and the like. However, there is no known display capable of both reflective and transmissive display modes.
Namerikawa, two others, Proceedings of the 5th Annual Conference of the Virtual Reality Society of Japan, 2000, September

  An object of the present invention is to provide a display element capable of displaying in either a reflective display or a transmissive display.

  The above object of the present invention is a display element capable of displaying in any of a reflective display and a transmissive display, and has a light scattering modulation layer having a function of modulating the light scattering state and a function of modulating the light intensity. It is achieved by a display element comprising: a light intensity modulation layer having:

  In the display element of the present invention having the above structure, the display mode of the reflective display and the transmissive display can be switched by modulating the light scattering state of the light scattering modulation layer. That is, in the case of reflection type display, the light scattering modulation layer is increased in light scattering degree, and the display is performed with the reflected light reflected by the light scattering modulation layer. In the case of transmission type display, the light scattering modulation layer light scattering is performed. The display is performed with the transmitted light transmitted through the light-scattering modulation layer to a lesser extent. In any of the display modes of the reflection type display and the transmission type display, black and white or full color display can be performed by modulating the light intensity from the light scattering modulation layer with the light intensity modulation layer.

  The light scattering modulation layer is a layer having a function of modulating the light scattering state, and a preferable form thereof includes, for example, a polymer dispersed liquid crystal layer in which a liquid crystal material is dispersed in a polymer material. In the polymer dispersed liquid crystal, the light scattering state of the layer can be changed by controlling the alignment state of the liquid crystal molecules.

  The light intensity modulation layer is a layer having a function of modulating the light intensity, and preferred examples thereof include a guest host liquid crystal layer containing a host liquid crystal and a dichroic dye. In the guest-host liquid crystal, the intensity of light absorbed by the dichroic dye can be changed by controlling the orientation of the dichroic dye having different absorbance in the major axis direction and the minor axis direction of the molecule. .

  ADVANTAGE OF THE INVENTION According to this invention, the display element which can be displayed with the display form of both a reflection type display and a transmission type display can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a schematic view showing an embodiment of the display element of the present invention.
The display element of the present embodiment is schematically configured by a pair of transparent or opaque layers 13a and 13b, and a light scattering modulation layer 11 and a light intensity modulation layer 12 laminated between the pair of transparent or opaque layers 13a and 13b. Has been. In the display element of the present embodiment, the side of the light intensity modulation layer 12 in contact with the transparent or opaque layer 13a serves as the display surface, and incident light Lr (incident from the display surface side) emitted from an external light source according to the display mode. Light) and Lt (incident light from the back side) are used properly for display. In the display element of this embodiment, the light scattering modulation layer 11 is a polymer dispersed liquid crystal layer in which a liquid crystal material is dispersed in a polymer material, and the light intensity modulation layer 12 is a guest containing a host liquid crystal and a dichroic dye. It is a host liquid crystal layer.
The transparent or opaque layers 13a and 13b are a substrate, a protective film, an optical film, and the like, and each may have a driving element for driving the element including electrodes. The opaque layer is a layer that can scatter light to the extent that display visibility is not hindered, and means a layer that is provided with antiglare properties in order to prevent reflection due to reflection of external light. To do.

FIG. 2 is a diagram for explaining the display forms of the reflective display and the transmissive display in the display element of this embodiment. FIG. 2A is a diagram showing a reflective display, and FIG. 2B is a diagram showing a transmissive display. In the reflective display, as shown in FIG. 2 (a), the incident light Lr from the display surface side is reflected by the light scattering modulation layer 11 by increasing the light scattering degree of the light scattering modulation layer 11, and the reflection thereof. Display is performed by modulating the light intensity by the light intensity modulation layer 12. On the other hand, in the transmissive display, as shown in FIG. 2 (b), the incident light Lt from the back side is transmitted through the light scattering modulation layer 11 by weakening the light scattering degree of the light scattering modulation layer 11. Display is performed by modulating the transmitted light intensity by the light intensity modulation layer 12.
The light scattering modulation layer 11 is provided with a driving element (not shown) capable of applying a voltage, and the alignment state of liquid crystal molecules dispersed in the polymer material constituting the light scattering modulation layer 11 is controlled by the applied voltage. be able to. By changing the alignment state of the liquid crystal molecules according to the applied voltage, the light scattering degree of the light scattering modulation layer 11 is modulated according to the display form.

In the display element of this embodiment, a plurality of picture elements are formed in the light intensity modulation layer 12, and display is performed by modulating the light intensity for each picture element.
FIG. 3 is a schematic diagram showing a configuration example of one picture element formed by the light intensity modulation layer 12 when full color display is performed. As shown in FIG. 3, the light intensity modulation layer 12 is formed by laminating two layers of an upper layer in which three primary color pixels composed of R, G, and B are juxtaposed and a lower layer in which three primary color pixels composed of C, M, and Y are juxtaposed. Thus, the upper layer pixel and the lower layer pixel are arranged at the same position, and the upper layer pixel and the lower layer pixel are superimposed so as to have a complementary color relationship with each other. Here, R, G, and B are additive primary colors of red (R), green (G), and blue (B), and C, M, and Y are subtractive primary colors of cyan (C) and magenta. (M), yellow (Y). Further, the complementary color relationship is a relationship between colors that become neutral gray (neutral color) by mixing colors. For example, R, C, G, M, B, and Y are complementary to each other.

Each pixel is a guest-host liquid crystal layer containing a host liquid crystal and a dichroic dye, and the color of each pixel can be selected by appropriately selecting one or more dichroic dyes. In each pixel, the orientation of the dichroic dye contained in the host liquid crystal is changed by the applied voltage, the light absorbance is changed, and display / non-display of the display color of the pixel is controlled. By controlling the display color of each pixel, color display can be performed for each pixel unit.
Drive elements (not shown) are provided for both the upper layer and the lower layer, and these drive elements can be independently driven and controlled, so that a voltage can be applied independently for each pixel. Here, as the driving method, for example, a general driving method such as a simple matrix driving method or an active matrix driving method using a thin film transistor (TFT) or the like can be used.

A color display method using the picture elements having the configuration shown in FIG. 3 will be described with reference to FIG. For example, in the case of displaying red (R), in the upper layer, the pixel R is in a color ON state and the pixels G and B are in a color OFF state. Further, in the lower layer, the pixel M and the pixel Y are turned on, and the pixel C is turned off. In this way, red (R) is colored by the pixel R in the upper layer. In the lower layer, magenta (M) is colored by the pixel M, and yellow (Y) is colored by the pixel Y. However, red (R) is colored as a whole lower layer due to the juxtaposed color mixture of both, and the upper and lower layers are combined. As a result, red (R) is displayed as the picture element. In FIG. 4, pixels in which the display color appears are indicated by hatching.
In the picture element having the configuration shown in FIG. 3, when focusing on a specific pixel in one layer, the specific pixel and a pixel in the same position as the specific pixel in the other layer are complementary colors. It is configured to be in. Therefore, when the color of a specific pixel in one layer is developed as described above (red (R) in the above example), the other two layers not located at the same position as the specific pixel in the other layer Since the display colors of the pixels (pixel M and pixel Y in the above example) are mixed in parallel, the display color of the specific pixel can be developed, so that the same color display from the entire picture element is possible. Can ensure sufficient brightness.

One picture element formed by the light intensity modulation layer 12 can take a known configuration in addition to the configuration shown in FIG. For example, as shown in FIG. 5, it may be configured by only one layer in which pixels of three primary colors composed of R, G, and B are juxtaposed (FIG. 5A), or pixels of three primary colors composed of C, M, and Y. The structure which laminated | stacked these may be sufficient (FIG.5 (b)). Further, even when two layers in which pixels of three primary colors are juxtaposed are stacked as shown in FIG. 3, the upper and lower layers are layers in which pixels of three primary colors composed of, for example, R, G, and B are juxtaposed. A configuration in which pixels of the same color are not overlapped can also be employed.
In order to ensure color reproducibility and sufficient brightness (luminance), the configuration shown in FIG. 3 is preferable. From the viewpoint of color reproducibility, a configuration in which three or more layers in which pixels of three primary colors are juxtaposed is preferable, but two layers are appropriate at present in consideration of cost and manufacturing suitability.

  Hereinafter, the display element of the present invention will be further described. The display element of the present invention is not limited to the above-described embodiment, and appropriate modifications and improvements can be made.

(Light scattering modulation layer)
In the display element of the present invention, the light scattering modulation layer is preferably a polymer dispersed liquid crystal layer in which a liquid crystal material is dispersed in a polymer material.
A polymer-dispersed liquid crystal layer is a layer in which a liquid crystal material is dispersed in the form of a droplet in a medium made of a polymer material, and the orientation state of liquid crystal molecules in the droplet is changed by an applied voltage. The light scattering state can be changed. A liquid crystal display element using this polymer dispersion type liquid crystal as a general liquid crystal display element has features such as being capable of a large area and not requiring a polarizing plate. Examples include reports such as JP-A-8-21986, JP-A-7-181454, JP-A-2002-287126, JP-A-2003-107438, JP-A-2000-206514, and the like. . Also in the display element of the present invention, the polymer dispersed liquid crystal described in these documents can be used.

(Liquid crystal material)
In the polymer dispersed liquid crystal layer of the display element of the present invention, the liquid crystal material dispersed in the polymer material is not particularly limited, and examples thereof include a liquid crystal compound exhibiting a nematic phase or a smectic phase. Specific examples thereof include azomethine compounds, cyanobiphenyl compounds, cyanophenyl esters, fluorine-substituted phenyl esters, cyclohexanecarboxylic acid phenyl esters, fluorine-substituted cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane, fluorine-substituted phenylcyclohexanes, cyano-substituted phenylpyrimidines, Fluorine-substituted phenylpyrimidine, alkoxy-substituted phenylpyrimidine, fluorine-substituted alkoxy-substituted phenylpyrimidine, phenyldioxane, tolan compounds, fluorine-substituted tolane compounds, alkenylcyclohexylbenzonitrile, and the like.
In addition, the liquid crystal compounds described in pages 154 to 192 and pages 715 to 722 of “Liquid Crystal Device Handbook” (Japan Society for the Promotion of Science 142nd edition, Nikkan Kogyo Shimbun, 1989) can be used.
Further, a fluorine-substituted liquid crystal compound suitable for TFT driving can also be used. For example, a liquid crystal manufactured by Mark Co. (ZLI-4692, MLC-6267, 6284, 6287, 6288, 6406, 6422, 6423, 6425, 6435, 6437, 7700, 7800, 9000, 9100, 9200, 9300, 10000, etc.) Liquid crystal (LIXON 5036xx, 5037xx, 5039xx, 5040xx, 5041xx, etc.).

As the liquid crystal material, a liquid crystal having a negative dielectric anisotropy can be used. By combining a liquid crystal having a negative dielectric anisotropy and a vertical alignment film described below, the light transmission state and the light scattering state can be switched as described below. That is, when no voltage is applied, the liquid crystal molecules are aligned vertically, so that light is transmitted without being absorbed. On the other hand, when a voltage is applied, the liquid crystal molecules are inclined horizontally, so that a difference in refractive index from the polymer material occurs, and light is scattered. That is, it is transparent and light transmissive when no voltage is applied, and is in a light scattering state when voltage is applied.
In order to become a liquid crystal having a negative dielectric anisotropy, it is necessary to have a structure in which the dielectric anisotropy increases along the short axis of the liquid crystal molecule. For example, “Monthly Display” (April 2000) No.), pages 4 to 9, and Synlett, Vol. 4, pages 389 to 396, 1999. Among these, from the viewpoint of voltage holding ratio, a liquid crystal having a fluorine-containing substituent and having a negative dielectric anisotropy is preferable. For example, the liquid crystal (MLC-6608, 6609, 6610 etc.) of Mark company is mentioned.

  In addition to the liquid crystal compound, the liquid crystal material is a compound that does not exhibit liquid crystallinity for the purpose of changing the physical properties of the liquid crystal to a desired range (for example, for the purpose of setting the temperature range of the liquid crystal phase to a desired range). May be added to the liquid crystal composition. The liquid crystal composition may further contain a compound such as a chiral compound, an ultraviolet absorber, or an antioxidant as an additive. Examples of such additives include chiral agents for TN and STN described in pages 199 to 202 of “Liquid Crystal Device Handbook” (edited by the Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989). It is done.

(Polymer dispersion)
Examples of the method for dispersing the liquid crystal material in the polymer material include the following methods.
(1) A solution in which a liquid crystal composition is dissolved in a polymerizable monomer or oligomer or a mixture thereof (hereinafter collectively referred to as a prepolymer) is coated on a substrate to form a prepolymer layer. The polymer layer is cured by ultraviolet or electron beam irradiation or heat polymerization to form a polymer medium layer, and the liquid crystal composition dissolved in the prepolymer in the polymer medium layer is deposited as a droplet. How to make.
(2) A method in which after the liquid crystal composition is dissolved in the polymer by heating, the liquid crystal composition is cooled to lower the compatibility to precipitate the liquid crystal composition as a droplet.
(3) A method in which after the liquid crystal composition and the polymer are dissolved in a common solvent, the solvent is evaporated to deposit the liquid crystal composition as a droplet.
(4) A method in which a liquid crystal composition and a polymer are mixed in a general-purpose solvent to form an emulsified state, and then the solvent is evaporated to deposit a liquid crystal component as a droplet.
(5) A method in which a liquid crystal composition is crystallized at a low temperature, pulverized and dispersed in a polymer solvent, and then coated on a substrate.

The alignment state of the liquid crystal molecules when no voltage is applied can be performed by an alignment process performed on the substrate on which the polymer dispersed liquid crystal layer is provided. The alignment when no voltage is applied is preferably vertical alignment or horizontal alignment.
There is no restriction | limiting in particular as a method of orientation processing, Various methods, such as a rubbing process, light irradiation, and vapor deposition, are mentioned. Among these, an alignment film is formed on at least one of the opposing surfaces of a pair of substrates, and the alignment film is subjected to rubbing treatment, light irradiation, etc. under various conditions, so that liquid crystal molecules can be arranged at an arbitrary angle with respect to the substrate. It is preferable in that it can be easily oriented.
The material for the alignment film is not particularly limited. For example, the materials described in pages 240 to 256 of “Liquid Crystal Device Handbook” (Japan Society for the Promotion of Science 142nd edition, Nikkan Kogyo Shimbun, 1989) Can be mentioned. Of these, polyimide-based materials are preferable. Examples of the alignment film using the polyimide material include, for example, “Monthly Display” (2000, August, pages 13 to 18), “Liquid Crystal Handbook” (Liquid Crystal Handbook Editorial Committee, Maruzen, 2000). Alignment films described on pages 253 to 258 of the year).
The rubbing treatment is not particularly limited, and examples thereof include a general method for forming fine grooves by rubbing the surface of the alignment film in a certain direction with a buff.
As the alignment film to be formed, a vertical alignment film for vertically aligning liquid crystal molecules is preferably a vertical alignment film having a pretilt angle of preferably 60 ° to 90 °, more preferably 80 ° to 90 °. In the horizontal alignment film for horizontally aligning liquid crystal molecules, a horizontal alignment film having a pretilt angle of preferably 0 ° to 30 °, more preferably 0 ° to 10 ° is desirable.

(Polymer material)
There is no particular limitation on the polymer material used in the polymer-dispersed liquid crystal layer of the display element of the present invention. Water-soluble polymers such as methyl cellulose, polyvinyl alcohol, polyoxyethylene, polyvinyl butyral, gelatin, polyacrylates, polyesters, polycarbonates, cellulose derivatives such as vinyl acetate and triacetyl cellulose, polyurethanes, styrenes, etc. A water-insoluble polymer is mentioned.

[Light intensity modulation layer]
In the display element of the present invention, the light intensity modulation layer is a layer that modulates the light intensity, and is a layer in which substantial pixels are formed. A guest host liquid crystal layer containing a host liquid crystal and a dichroic dye is preferred, and the guest host liquid crystal layer is excellent in reducing power consumption of the display element.
In addition to the guest-host liquid crystal layer, for example, it is only necessary to be able to reversibly modulate light (decoloring and coloring) by stimulating electric fields, heat, and magnetic fields. For example, by electrochemical redox reaction An electrochromic coloring layer formed by an electrochromic dye that reversibly develops and decolors, an electrolyte, and the like.

<Guest host type liquid crystal layer>
The guest-host type liquid crystal layer contains other components as necessary in addition to the host liquid crystal and the dichroic dye.

(Dichroic dye)
The dichroic dye is not particularly limited and may be any dye having any chromophore. For example, azo dyes, anthraquinone dyes, perylene dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, Examples include azulene dyes, dioxazine dyes, and polythiophene dyes. Specific examples include dyes described in “Dichroic Dies for Liquid Crystal Display” (A. V. Ivashcenko, CRC, 1994). These may be used alone or in combination of two or more. Among these, azo dyes, anthraquinone dyes, perylene dyes, and the like are preferable, and azo dyes, anthraquinone dyes, and the like are particularly preferable. The dichroic dye is selected from, for example, dichroic dyes described in Liquid Crystal Device Handbook (edited by the Japan Society for the Promotion of Science 142nd Committee: 1989) p192 to p196, p724 to p730. These may be used alone or in combination of two or more.

  Among the dichroic dyes, examples of dichroic dyes used in the guest-host type liquid crystal layer include the following azo dyes, anthraquinone dyes, and perylene dyes. These dyes can also be used.

  Examples of the azo dye include JP-A-53-26783, JP-A-53-75180, JP-A-54-68780, JP-A-55-52375, JP-A-58-79077, 59-24783, JP-A-60-184564, JP-A-61-123667, JP-A-62-252461, JP-A-5-59292, JP-A-5-59293, JP-A-5-59294, JP-A-6-157927, JP-A-6-256675, JP-A-7-224281, JP-A-8-143865, JP-A-9-143471, JP-A-10-95980, and JP-A-11-172252. And azo dyes described in each of the above publications. These may be used alone or in combination of two or more.

  Examples of the anthraquinone dye include JP-A-56-38376, JP-A-57-96075, JP-A-57-190048, JP-A-57-198777, JP-A-57-198778, JP-A-57-1987. 57-205448, JP 58-185678, JP 62-64887, JP 62-64888, JP 2-67394, JP 2-69591, JP 2-178390, Examples include anthraquinone dyes described in JP-A-7-76659, JP-A-7-247480, JP-A-7-252423, and JP-A-8-67822. These may be used alone or in combination of two or more.

  Examples of the perylene dye include perylene dyes described in JP-A No. 62-129380. These may be used alone or in combination of two or more.

  Preferred dichroic dyes include the dyes described in JP-A No. 2003-138262.

The order parameter of the dichroic dye is preferably 0.65 to 0.95, more preferably 0.75 to 0.95, and the higher the order parameter, the more preferable.
The use of a dichroic dye having an order parameter within the above numerical range is preferable for achieving both sufficient contrast and brightness.

Here, the order parameter is defined by the following mathematical formula (1) when the molecular long axis of the dichroic dye molecule that is thermally fluctuated is inclined with respect to the director by the shift angle θ in terms of time average. .
Order parameter (S) = (3 cos 2θ−1) / 2 Expression (1)

  In the above formula (1), when the order parameter (S) = 0.0, it indicates that the molecule has no order at all, and when the order parameter (S) = 1.0, the molecule has a molecular long axis. It shows that it is in a state of being aligned in the direction of the director.

Although there is no restriction | limiting in particular as content in a guest host liquid crystal layer of a dichroic dye, 0.1-15 mass% is preferable with respect to a host liquid crystal for every area | region of a pixel, 0.5-6 mass% Is more preferable.
It should be noted that the additive mixed three primary colors (R, G, B) pixels described in the above-described embodiment are provided by mixing two subtractive mixed three primary colors (C, M, Y). Can do. Specifically, red (R) is a mixture of magenta (M) dye and yellow (Y) dye, green (G) is a mixture of Y dye and cyan (C) dye, and blue (B) is C dye and M dye. Is a mixture of Specific examples of the dichroic dyes of the three subtractive primary colors include the dyes described in the Liquid Crystal Device Handbook (Japan Society for the Promotion of Science 142nd Committee Edition: 1989) p489, liquid crystals having an optically active center, etc. These optically active substances may be added. Usually, the Y dye has a maximum absorption wavelength in the range of 430 to 490 nm, the M dye has a range of 500 to 580 nm, and the C dye has a maximum absorption wavelength in the range of 600 to 700 nm.

(Host LCD)
The host liquid crystal is not particularly limited as long as it can coexist with the dichroic dye, and examples thereof include a liquid crystal compound exhibiting a nematic phase or a smectic phase.
Specifically, azomethine compounds, cyanobiphenyl compounds, cyanophenyl esters, fluorine-substituted phenyl esters, cyclohexanecarboxylic acid phenyl esters, fluorine-substituted cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane, fluorine-substituted phenylcyclohexane, cyano-substituted phenylpyrimidines, fluorine Examples thereof include substituted phenylpyrimidine, alkoxy-substituted phenylpyrimidine, fluorine-substituted alkoxy-substituted phenylpyrimidine, phenyldioxane, tolan compounds, fluorine-substituted tolan compounds, and alkenylcyclohexylbenzonitrile. Moreover, it has a cyano group, a fluorine atom, a chloro atom, etc. which have P type or N type dielectric anisotropy of p116-p192 description of liquid crystal device handbook (Japan Society for the Promotion of Science 142nd committee edition: 1989) In addition to various nematic liquid crystals and smectic liquid crystals having a skeleton of biphenyl, phenylcyclohexane, etc., side chain type polymer liquid crystals having polyacrylates or polysiloxanes described in the Handbook p641-p653 as the main chain can be used. In this case, the side chain may have a dichroic dye.
Preferred host liquid crystals include liquid crystal compounds described in JP-A No. 2003-138262.

  The operation mode of the liquid crystal is particularly preferably a nematic-cholesteric phase transition, but is not particularly limited to this, and any mode can be used as long as the orientation direction of the dichroic dye can be controlled basically according to the orientation of the liquid crystal molecules. A liquid crystal in such an operation mode may be used. Examples include a reflective liquid crystal display, a transmissive liquid crystal display, and a transflective liquid crystal display. More specifically, “Liquid Crystal Device Handbook” (edited by the 142th Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun) 1989)), “homogeneous alignment”, “homeotropic alignment”, White-Taylor type (phase transition type), “focal conic alignment” and “homeo alignment”. Combination with “tropic alignment”, “Super Twisted Nematic (STN) system”, combination with “ferroelectric liquid crystal (FLC)”, and the like. Heilmeier type GH described in Chapters 2-1 (GH mode reflective type color LCD), pages 15 to 16 of "Reflective type color LCD integrated technology" (supervised by Tatsuo Uchida, CMC, 1999). Mode, λ / 4 plate type GH mode, two-layer type GH mode, phase transition type GH mode, polymer dispersed liquid crystal (PDLC) type GH mode, and the like. Among these, a liquid crystal display having a homeotropic alignment in the λ / 4 plate type GH mode is particularly preferable in that sufficient contrast can be realized.

(Other components contained in the guest-host liquid crystal layer)
In the guest-host liquid crystal layer, for example, a compound that does not exhibit liquid crystal properties for the purpose of setting the physical properties of the host liquid crystal in a desired range, such as setting the temperature range of the liquid crystal phase within a desired range, You may make it contain as another component. Moreover, you may contain compounds, such as a chiral compound, a ultraviolet absorber, and antioxidant, as another compound. Examples of such other components include TN and STN chiral agents described on pages 199 to 202 of “Liquid Crystal Device Handbook” (edited by Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989). Etc.

<Electrochromic colored layer>
There is no restriction | limiting in particular as an electrochromic coloring layer, A normally well-known electrochromic pigment | dye, electrolyte, etc. can be used.

(Electrochromic dye)
The electrochromic dye is not particularly limited as long as it exhibits an action of coloring or decoloring by at least one of an electrochemical oxidation reaction and a reduction reaction, and can be appropriately selected according to the purpose. For example, an organic compound, a metal Complexes and the like are preferred. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the metal complex that is an electrochromic dye include Prussian blue, metal-bipyridyl complex, metal phenanthroline complex, metal-phthalocyanine complex, metaferricyanide, and derivatives thereof.

  Examples of the organic compound that is an electrochromic dye include (1) pyridine compounds, (2) conductive polymers, (3) styryl compounds, (4) donor / acceptor type compounds, and (5) other organic compounds. Pigments, and the like.

  Examples of (1) pyridine compounds include viologen, heptyl viologen (such as diheptyl viologen dibromide), methylene bispyridinium, phenanthroline, azobipyridinium, 2,2-bipyridinium complex, and quinoline / isoquinoline.

  Examples of the conductive polymer (2) include polypyrrole, polythiophene, polyaniline, polyphenylenediamine, polyaminophenol, polyvinylcarbazole, polymer viologen polyion complex, TTF, and derivatives thereof.

  Examples of the (3) styryl compounds include 2- [2- [4- (dimethylamino) phenyl] ethenyl] -3,3-dimethylindolino [2,1-b] oxazolidine, 2- [4- [4- (Dimethylamino) phenyl] -1,3-butadienyl] -3,3-dimethylindolino [2,1-b] oxazolidine, 2- [2- [4- (dimethylamino) phenyl] ethenyl]- 3,3-dimethyl-5-methylsulfonylindolino [2,1-b] oxazolidine, 2- [4- [4- (dimethylamino) phenyl] -1,3-butadienyl] -3,3-dimethyl-5 -Sulfonylindolino [2,1-b] oxazolidine, 3,3-dimethyl-2- [2- (9-ethyl-3-carbazolyl) ethenyl] indolino [2,1-b] oxazolidine 2- [2- [4- (acetylamino) phenyl] ethenyl] -3,3-dimethyl-indolino [2,1-b] oxazolidine, and the like.

  Examples of the (4) donor / acceptor type compounds include tetracyanoquinodimethane and tetrathiafulvalene.

  Examples of (5) other organic dyes include carbazole, methoxybiphenyl, anthraquinone, quinone, diphenylamine, aminophenol, tris-aminophenylamine, phenylacetylene, cyclopentyl compound, benzodithiolium compound, squalium salt, cyanine, rare earth Examples include phthalocyanine complexes, ruthenium diphthalocyanines, merocyanines, phenanthroline complexes, pyrazolines, redox indicators, pH indicators, and derivatives thereof.

  Among these, viologen dyes such as viologen and heptyl viologen (such as diheptyl viologen dibromide) are preferable.

  The combination when two or more electrochromic dyes are used in combination is not particularly limited and can be appropriately selected according to the purpose. For example, a combination of viologen and polyaniline, a combination of polypyrrole and polymethylthiophene, Examples include a combination of polyaniline and Prussian blue.

(Electrolytes)
As the electrolyte, for example, iodine, bromine, LiI, NaI, KI, CsI , CaI 2, LiBr, NaBr, KBr, CsBr, metal halides such as CaBr _2, tetraethylammonium iodide, tetrapropyl ammonium iodide, iodide Halogenated salts of ammonium compounds such as tetrabutylammonium, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide, alkyl viologens such as methyl viologen chloride and hexyl viologen bromide, polyhydroxybenzenes such as hydroquinone and naphthohydroquinone At least one of iron complexes such as ferrocene and ferrocyanate can be used, but is not limited thereto.

(Other)
In the light intensity modulation layer, in order to prevent a pigment component or the like from mixing with pixels of other colors, a boundary region may be provided in the shape of a partition at the boundary between adjacent pixels. It may also serve as a cover for the pixel periphery. The boundary region and the pixel peripheral cover are preferably achromatic, and may be provided on the substrate.

  The thickness of the light intensity modulation layer is preferably 1 μm to 100 μm, and more preferably 1 μm to 50 μm.

(Method for forming light intensity modulation layer)
Examples of the method for forming the light intensity modulation layer of the present invention include the following methods.
For example, in the case of a guest host liquid crystal layer, any primary color guest host liquid crystal composition containing an optically active substance is microencapsulated by a known method such as a coacervation method and mixed with a polymer binder. The primary color ink prepared in this way is formed on a substrate or the like by a printing method so that the pixels of the three primary colors are repeated, unnecessary portions are sequentially covered with a resist, and each primary color ink is sequentially applied, etc. Among the known methods for manufacturing color filters for liquid crystals, a method known as a printing method or a pigment dispersion method is used, and microcapsules containing guest-host liquid crystals are used instead of pigments, and three primary colors are formed on the substrate. The method of forming so that it may have a repeating unit of, etc. are mentioned.

  Various methods are known for encapsulating and printing the guest-host liquid crystal. Specific examples include the methods described in JP-A-62-2502780 and JP-A-6-34949. In addition, the guest host liquid crystal and the polymer matrix or the encapsulated guest host liquid crystal and the polymer matrix are electrodeposited and coated by the method described as the electrodeposition coating method in JP-A-6-34949. The method of forming so that it may have a repeating unit of, etc. are mentioned.

When two guest-host liquid crystal layers are stacked as in the display element shown in FIG. 3, after forming a lower layer to be stacked, a transparent layer may be provided thereon to form an intermediate transparent layer. Further, a stripe-shaped partition wall may be provided in advance between the substrate and the intermediate transparent layer, and the primary-color guest-host liquid crystal may be sandwiched so as to have the repeating units of the three primary colors. Examples of the primary color repeating pattern include stripes and mosaics. The upper layer to be laminated can be formed on the lower layer by the same method as described above. Further, a transparent layer may be formed thereon. The upper layer and lower layer pixels may be formed in advance on a transparent layer and bonded together to form a two-layer guest-host liquid crystal layer.
Further, the orientation of the host liquid crystal in the guest-host liquid crystal layer can be adjusted by subjecting the substrate on which the guest-host liquid crystal layer is provided, the transparent layer, or the like, in the same manner as the polymer dispersed liquid crystal layer described above.

[Other components and components]
Examples of other components and members in the display element of the present invention include a transparent or opaque layer such as a pair of substrates that protect or grip the light scattering modulation layer and the light intensity modulation layer. May be provided with an optical film such as a protective film or an antireflection film. Examples of other components and members include an organic interlayer insulating film, a phase difference plate, an alignment film, a light diffusion plate, a backlight, and a front light. These may be used alone or in combination of two or more.

  The display element of the present invention can be used as an electro-optical element by forming a pair of electrodes on other members including a transparent or opaque layer so as to sandwich the light scattering modulation layer and the light intensity modulation layer, respectively. it can. In particular, the light intensity modulation layer is a guest-host type liquid crystal layer containing a dichroic dye and a host liquid crystal, or an electrochromic dye and an electrolyte that are reversibly developed and decolored by an electrochemical oxidation-reduction reaction. In the case of a chromic colored layer, a light intensity modulation layer is provided between a pair of electrodes, and the light intensity can be reversibly developed and decolored by controlling the applied voltage, which is preferable. Furthermore, when the light scattering modulation layer is a polymer-dispersed liquid crystal layer in which a liquid crystal material is dispersed in a polymer material, the light scattering state is reversibly changed by an applied voltage by being provided between a pair of electrodes. This is preferable because it can be adjusted.

The transparent or opaque layer is not particularly limited and may have a relatively low mechanical strength for the purpose of protecting or flattening the display element. At least one of the pair of transparent or opaque layers is It preferably has a function as a substrate or a base paper.
The layer having an electrode including the transparent or opaque layer is preferably an electrode substrate in which an electrode layer is usually formed on a substrate made of glass, plastic, paper, metal, or the like.
Examples of the material of the plastic substrate include acrylic resin, polycarbonate resin, and epoxy resin. As these substrates, for example, the substrates described on pages 218 to 231 of “Liquid Crystal Device Handbook” (Japan Society for the Promotion of Science 142nd edition, Nikkan Kogyo Shimbun, 1989) can be used.
As the electrode layer, a transparent electrode layer is preferable. The electrode layer can be formed of, for example, indium oxide, indium tin oxide (ITO), tin oxide, or the like. As the transparent electrode layer, for example, the electrode layers described on pages 232 to 239 of “Liquid Crystal Device Handbook” (edited by the 142th Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, 1989) are used.

  The display element of the present invention is provided with a diffusion plate, a backlight, etc. on the side opposite to the side having the light intensity modulation layer with respect to the light scattering modulation layer. May be used as illumination light. Further, a front light or the like may be provided on the side opposite to the side having the light scattering modulation layer with respect to the light intensity modulation layer, and light from the front light may be used as illumination light in the case of reflective display.

  In the display element of the present invention, the size of the picture element is not particularly limited, and a normal size (about 0.35 mm × 0.35 mm) is preferable. Further, the shape of the picture element is not particularly limited, but a generally known shape such as a square is exemplified. The number of picture elements varies depending on the application of the display element, and is not particularly limited as long as it is a range known as the number of picture elements of the normal display element.

  Hereinafter, the display element of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Formation of light scattering modulation layer>
(Example 1) (Method in which a light confusion mode is set when a voltage is applied)
The following liquid crystal composition was applied to the glass plate (thickness 0.7 mm) on which the ITO transparent electrode layer and the polyimide vertical alignment film (JALS2021 manufactured by JSR) were formed using an applicator, and the ITO transparent electrode layer And a glass plate on which a polyimide vertical alignment film (JALS2021 made by JSR) was formed was laminated to prepare a liquid crystal element.

Liquid crystal composition / ZLI-2806 (Merck) 79.6% by mass
・ 3,5,5-trimethylhexyl acrylate 15.0% by mass
・ Hexanediol divinyl ether 5.0% by mass
・ Irgacure 651 (Merck) 0.4% by mass

Thereafter, the liquid crystal element was irradiated with 30 mW / cm ² of ultraviolet light for 40 seconds to cure the polymerizable composition, thereby forming a light scattering modulation layer.
At this time, since the liquid crystal molecules were aligned perpendicular to the substrate, a transparent liquid crystal element was obtained. The light transmittance of the liquid crystal element when no voltage was applied was Toff = 85.1%.
Next, when the light transmittance when an AC voltage of 10 V (60 Hz) was applied to the liquid crystal element was measured, a white light scattering state was obtained, and the light transmittance was Ton = 5.2%. It was. The contrast ratio of the liquid crystal element was 16.3.

(Example 2) (Method in which light scattering mode is set when no voltage is applied)
The liquid crystal of Example 1 is changed from ZLI-2806 to ZLI-5081 (fluorine-based nematic liquid crystal for horizontal alignment, manufactured by Merck), and the vertical alignment film of Example 1 is changed to a polyimide horizontal alignment film (AL1051 manufactured by JSR) for rubbing treatment. The light transmittance at the time of voltage application was measured in the same manner for the liquid crystal element produced in the same manner as in Example 1 except that. When no voltage is applied, the light scattering state is white, the light transmittance Toff is 6.5%, and when an alternating voltage of 10 V (60 Hz) is applied, the light transmittance becomes transparent, and the light transmittance is Ton = 83.0. %Met. The contrast ratio of the liquid crystal element was 12.7.

(Example 3)
-Preparation of liquid crystal composition-
After mixing 3 mg of the compound (dichroic dye) shown in Table 1 and 97 mg of host liquid crystal (Merck, “MLC-6608”), the mixture was heated and stirred at 80 ° C., and then cooled to room temperature to obtain R, A guest-host liquid crystal composition corresponding to each pixel of G, B, C, M, and Y was prepared.
In Table 1, the mixing ratio of the dichroic dyes M and Y is as follows.

M; (Compound 2-1): (Compound 2-2) = 1: 1
Y; (Compound 1-1): (Compound 1-2): (Compound 1-3) = 1: 1: 1

  For R, G, and B, the dichroic dyes used for C, M, and Y were mixed and used, and the mixing ratio (molar ratio) is shown in Table 1. Here, for example, in the case of R, M: Y = 1: 1 means that 1 mol of dichroic dye (mixture obtained by mixing compounds 2-1 and 2-2 in the above molar ratio) used in M and Y This means that 1 mol of the dichroic dye (compound in which compounds 1-1, 1-2, 1-3 are mixed in the above molar ratio) used in 1) is mixed.

-Formation of light intensity modulation layer, production of display element-
After applying an adhesive resist to two transparent electrode substrates (a glass plate (thickness 0.7 mm) on which an ITO transparent electrode layer and a polyimide vertical alignment film (JALS2021 made by JSR) are formed), ultraviolet rays are irradiated. An intermediate substrate (a glass plate (thickness 0.7 mm) on which an ITO transparent electrode layer and a polyimide vertical alignment film (JALS2021 made by JSR) are formed) on which striped walls are formed and transparent electrodes are laid on both sides; A picture element having a configuration schematically shown in a cross-sectional view in FIG. 3 is obtained by injecting a guest-host liquid crystal composition corresponding to each pixel of R, G, B, C, M, and Y after bonding and baking. Then, a light intensity modulation layer having a plurality of layers was formed, and then the liquid crystal element produced in Example 1 and the substrate were bonded together to produce a display element schematically shown in cross-sectional view in FIG.

  When the produced display element was displayed in color, good visibility was obtained in any of the display forms of the reflective display and the transmissive display. Further, even when the liquid crystal element produced in Example 2 was used as the light scattering modulation layer, good visibility was obtained in the same manner.

It is a schematic diagram which shows one Embodiment of the display element of this invention. It is a schematic diagram explaining the display form of a reflection type display and a transmission type display in the display element of this invention. It is a schematic diagram which shows one structural example of the one picture element in the display element of this invention. It is explanatory drawing which shows an example of the color display in the display element of this invention. It is a schematic diagram which shows the structural example of one picture element in the display element of this invention.

Explanation of symbols

11 Light scattering modulation layer 12 Light intensity modulation layer 13a, 13b Transparent or opaque layer R Pixel (red)
G pixel (green)
B pixel (blue)
C pixel (cyan)
M pixel (magenta)
Y pixel (yellow)

Claims (3)

A display element capable of displaying in any of a reflective display and a transmissive display,
A display element comprising: a light scattering modulation layer having a function of modulating a light scattering state; and a light intensity modulation layer having a function of modulating light intensity.   The display element according to claim 1, wherein the light scattering modulation layer is a polymer-dispersed liquid crystal layer in which a liquid crystal material is dispersed in a polymer material.   The display element according to claim 1, wherein the light intensity modulation layer is a guest host liquid crystal layer containing a host liquid crystal and a dichroic dye.

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