JP2009069517A - Reflective type liquid crystal display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective type liquid crystal display medium having satisfactory reflection characteristics even when a cholesteric liquid crystal is used as a liquid crystal layer and a resin substrate is used as a substrate. <P>SOLUTION: In the reflective type liquid crystal display medium constituted by layering a plurality of optical reflection panels each having a liquid crystal layer between a pair of resin substrates, the liquid crystal layer includes the cholesteric liquid crystal, spirally twisted directions of the liquid crystal are different at least for every liquid crystal layer whose reflection wavelength regions are adjacent to each other and all of the resin substrates except the resin substrates to be both end surfaces in the layered direction at least after being layered are constituted of one or more kinds selected from a polyether sulfone, a polycarbonate, a polyvinyl chloride, a polyvinylidene chloride and a cyclic polyolefin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflective liquid crystal display medium.

  Cholesteric liquid crystal has a helical structure composed of rod-like molecules, and selectively reflects visible light near a specific wavelength when the helical pitch is in the optical wavelength order. This phenomenon is known as selective reflection of cholesteric liquid crystals. The reflectivity of the selective reflection can be changed by controlling the direction of the helical axis by electricity, magnetism, light, heat, stress, etc., or by destroying / generating the helical structure itself. In this way, the reflective liquid crystal display medium using cholesteric liquid crystal controls the on / off of the reflected light.

  Since the reflective liquid crystal display medium using cholesteric liquid crystal is a display element that performs display using external light as illumination, it does not require illumination power and has low power consumption. In addition, it has a memory property that can hold a display without a power source, and therefore, an expensive active matrix substrate such as a thin film transistor is not required for driving, a flexible substrate such as a resin substrate can be used, and a reflective plate is not used. It has features such as a relatively high rate and vivid display.

  In this case, for example, monochrome display can be performed using a cholesteric liquid crystal layer that selectively reflects monochromatic light, but three cholesteric liquid crystal layers that selectively reflect the three primary colors of blue light, green light, and red light are provided. When stacked, a reflective liquid crystal display medium with multicolor display can be obtained. In this reflective liquid crystal display medium, one of each cholesteric liquid crystal layer that selectively reflects blue light, green light, and red light is brought into a reflective state, and the other two are brought into a colorless state, whereby blue, green, Or a red display is obtained. In addition, two of the cholesteric liquid crystal layers that selectively reflect blue light, green light, and red light are in a reflective state, and the other one is in a colorless state, thereby obtaining a display of cyan, magenta, or yellow. It is done. Furthermore, white display can be obtained by making all of the cholesteric liquid crystal layers that selectively reflect blue light, green light, and red light into a reflective state. A black display is obtained by the light absorption layer.

However, in the reflective display device using the cholesteric liquid crystal layer, only one side of circularly polarized light can be used because selective reflection of cholesteric liquid crystal is used, and the reflection intensity does not exceed 50% at the maximum, so the display quality is poor and there are fields of application. It was limited.
On the other hand, in monochrome display, it has been shown that the reflectance can be improved by laminating two cholesteric liquid crystal dispersion films having different chiralities (for example, see Patent Document 1).

Further, even in the reflective color liquid crystal display device in which a plurality of the cholesteric liquid crystal layers are laminated, there is a problem with the white reflection intensity, but by reversing the chirality of the liquid crystal of the adjacent layers in the selective reflection wavelength region, Since it is not affected by the adjacent selective reflection in the region where the selective reflection wavelength region overlaps, the reflectance of each layer is effectively used, and the reflectance of white is greatly improved (for example, see Patent Document 2).
Furthermore, it is disclosed that a filter that absorbs light in a shorter wavelength region than the reflected color is inserted on the viewer side of each color layer for the purpose of improving the color purity of the liquid crystal layer of each color and preventing color shift due to the viewing angle. (For example, refer to Patent Documents 3 to 6).
Japanese Patent No. 3209254 Japanese Patent No. 3700756 Japanese Patent No. 3599089 Japanese Patent No. 3480428 Japanese Patent No. 3493454 Japanese Patent No. 3716935

  An object of the present invention is to provide a reflective liquid crystal display medium having good reflection characteristics even when a cholesteric liquid crystal is used for a liquid crystal layer and a substrate is a resin substrate.

The above-mentioned subject is achieved by the following present invention.
That is, the invention according to claim 1 of the present invention is configured by laminating a plurality of light reflecting panels having a liquid crystal layer between a pair of resin substrates,
The liquid crystal layer includes cholesteric liquid crystal, and the spiral twist direction of the liquid crystal is different for each liquid crystal layer in which at least the reflection wavelength region is adjacent,
Of the resin substrates, at least all of the resin substrates other than the resin substrates that become both end surfaces in the laminating direction are composed of one or more selected from polyethersulfone, polycarbonate, polyvinyl chloride, polyvinylidene chloride, and cyclic polyolefin. A reflective liquid crystal display medium.

  The invention according to claim 2 is the reflective liquid crystal display medium according to claim 1, wherein everything except the resin substrate which becomes both end faces in the laminating direction is made of polyethersulfone.

  The invention according to claim 3 is configured by laminating a plurality of light reflecting panels having a liquid crystal layer between a pair of resin substrates, the liquid crystal layer includes cholesteric liquid crystal, and the spiral twist direction of all the liquid crystals is the same, Of the resin substrates, at least all of the resin substrates other than the resin substrates that become both end surfaces in the laminating direction are composed of one or more selected from polyethersulfone, polycarbonate, polyvinyl chloride, polyvinylidene chloride, and cyclic polyolefin, A reflection type liquid crystal display medium in which a phase compensation layer is provided between the plurality of light reflection panels.

According to the first aspect of the present invention, even when a cholesteric liquid crystal is used for the liquid crystal layer and the substrate is a resin substrate, a reflective liquid crystal display medium having good reflection characteristics can be provided.
According to the second aspect of the present invention, it is possible to provide a reflective liquid crystal display medium having excellent heat resistance and durability and high resolution.
According to the third aspect of the present invention, it is possible to provide a reflective liquid crystal display medium having excellent reflection characteristics without laminating liquid crystals having opposite chirality.

Hereinafter, the present invention will be described in detail.
The reflective liquid crystal display medium of the present invention is formed by laminating a plurality of light reflecting panels having a liquid crystal layer between a pair of resin substrates, the liquid crystal layer includes cholesteric liquid crystal, and at least the liquid crystal layers having adjacent reflection wavelength ranges. The twisted direction of the liquid crystal is different, and at least all of the resin substrates other than the resin substrate serving as the end surface in the laminating direction are selected from polyethersulfone, polycarbonate, polyvinyl chloride, polyvinylidene chloride, and polycyclic olefin. It is comprised by 1 or more types, It is characterized by the above-mentioned.

Since the selective reflection of the cholesteric liquid crystal occurs due to the helical structure, it exhibits a remarkable circular dichroism depending on the twist direction of the spiral. That is, the left-twisted cholesteric liquid crystal reflects left circularly polarized light and transmits right circularly polarized light. Conversely, right-twisted cholesteric liquid crystal reflects right circularly polarized light and transmits left circularly polarized light. For this reason, in the reflective liquid crystal display medium using the cholesteric liquid crystal as a liquid crystal layer, only a maximum reflectance of 50% can be obtained under general non-polarized illumination such as sunlight, incandescent lamp and fluorescent lamp. There is a problem that the reflectance is insufficient.
In particular, for example, when multi-color display is performed by laminating a plurality of liquid crystal layers that selectively reflect blue light, green light, and red light, respectively, saturation and brightness are insufficient, and a bright and bright display is obtained. There is a problem that can not be.

For the liquid crystal layer laminated as described above, the reflectance can be improved by reversing the spiral twist direction of the liquid crystal for each liquid crystal layer having an adjacent reflection wavelength range. When a resin substrate is used as the substrate of the light reflecting panel having the liquid crystal layer, the whiteness (reflectance) may not be sufficiently improved in a display medium in which these are laminated.
The reason for this is not clear, but since the resin generally has birefringence, it is considered that some change occurs in the polarization state of the transmitted light due to the birefringence of the resin substrate between the laminated cholesteric liquid crystals.

Furthermore, as a result of the study by the present inventors, there are those that have a large decrease in reflectance and those that do not decrease so much depending on the material constituting the resin substrate, and even in the case of a resin substrate made of a material that has a large decrease in reflectance, It has been found that the reflectance is not affected depending on the position where the resin substrate is disposed.
That is, first, regarding the resin material, compared to polyethylene terephthalate (hereinafter sometimes referred to as “PET”) that is generally used as a resin substrate, polyethersulfone (hereinafter sometimes referred to as “PES”). Polycarbonate (hereinafter sometimes referred to as “PC”), cyclic polyolefin (hereinafter sometimes referred to as “COP”), polyvinyl chloride (hereinafter sometimes referred to as “PVC”), and polyvinylidene chloride ( Hereinafter, it has been found that any of the “PVDC” may be effective in reducing the reflectance (hereinafter, resin substrates composed of PES, PC, COP, PVC, and PVDC are collectively referred to as “ Sometimes referred to as “specific resin substrate”).

On the other hand, with respect to the position where the resin substrate is disposed, at least all but the resin substrate that becomes both end surfaces in the stacking direction after stacking need to be made of a resin that is effective in reducing the reflectance. all right.
That is, as will be described later, even in the case of a resin substrate (PET resin substrate) made of PET with a relatively large reduction in reflectance, it becomes the outermost surface and the outermost surface in the stacking direction of the display medium after the light reflecting panel is stacked. In the case where the PET resin substrate is disposed at the position, if all the other resin substrates inside are used as the specific resin substrate, the reflectance is not affected and hardly causes a problem. On the contrary, when one of the internal resin substrates other than the outermost surface and the outermost surface is a PET resin substrate, the reflectance is lowered, which may cause a problem in practice.

  In other words, the specific resin substrate must be disposed at a position where light that has passed through even one layer of the liquid crystal layer in the laminated display medium is incident, and the PET resin substrate must not be disposed. On the other hand, a PET resin substrate can be used as a substrate on which external light that has not yet passed through the liquid crystal layer is incident. Of course, at least the resin substrate other than both end surfaces may be a specific resin substrate, and the outermost and rearmost resin substrates may be specific resin substrates.

From the above, in the PET resin substrate unsuitable for the present invention, there is no problem with non-polarized light, but the polarization state is changed with respect to circularly polarized light, and the effect of laminating the liquid crystals of different chirality May not be able to fully demonstrate.
Therefore, the details of the specific resin substrate used in the present invention are not clear, but the optical characteristics are not changed with respect to general unpolarized light or coherent light, but with respect to circularly polarized light that has passed through a liquid crystal layer or the like. It is considered that it is desirable to transmit light without passing through. More specifically, it is expected that the resin substrate has a characteristic that allows the transmitted circularly polarized light to pass through almost without rotation.

  In the present invention, regarding “the spiral twist direction of the liquid crystal is different for each adjacent liquid crystal layer in at least the reflection wavelength range”, at least the above condition is satisfied when the reflection wavelength range of the plurality of liquid crystal layers to be stacked is different. In other words, when two liquid crystal layers having the same reflection wavelength region are stacked, the spiral twist directions of the two must be different.

Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic cross-sectional view of a reflective liquid crystal display medium according to the first embodiment. The reflective liquid crystal display medium of this embodiment is a reflective liquid crystal display medium for full color display in which a light reflective panel having a liquid crystal layer that selectively reflects four lights of blue, yellow, green, and red is laminated. 1 (A) and 1 (B) are liquid crystal layers that reflect yellow light and green light between liquid crystal layers that reflect blue light and red light, and are configured by changing the stacking order.

In the reflective liquid crystal display medium shown in FIG. 1A, a blue light reflecting panel 40, a green light reflecting panel 60, and a red light reflecting panel 70 are stacked in this order from the observation side indicated by the arrows in the figure. The yellow light reflection panel 50 is provided between the green light reflection panel 60 and the green light reflection panel 60.
In addition, the black light-shielding layer 35 is formed on the back surface (lower side of the drawing) of the red light reflection panel 70, the red filter 32 is formed on the observation side, and the yellow filter 31 is formed on the observation side of the yellow light reflection panel 50. is doing.

The blue light, green light, yellow light, and red light mean colored light having peaks in the wavelength ranges of 400 to 500 nm, 500 to 600 nm, 550 to 650 nm, and 600 to 700 nm, respectively. However, in the above description, the positions of the peak wavelengths of the respective colors are always in the above order, and these peak wavelengths do not overlap.
Also, in the figure, reference numerals 11 to 18 are transparent resin substrates, and electrodes provided on the liquid crystal layer side of each resin substrate (disposed on both surfaces of each liquid crystal layer) are omitted. This point is the same in other embodiments described below.

The blue light reflecting panel 40 is formed by forming a liquid crystal layer 21 (LB) made of right-twisted cholesteric liquid crystal that selectively reflects blue light between two resin substrates 11 and 12 each having a transparent electrode. The green light reflection panel 60 is formed by forming a liquid crystal layer 23 (LG) made of left-handed cholesteric liquid crystal that selectively reflects green light between two resin substrates 15 and 16 each having a transparent electrode formed thereon. In the red light reflecting panel 70, a liquid crystal layer 24 (LR) made of a left-handed cholesteric liquid crystal that selectively reflects red light is formed between two resin substrates 17 and 18 each having a transparent electrode.
And the yellow light reflection panel 50 arrange | positioned between the blue light reflection panel 40 and the green light reflection panel 60 selectively reflects yellow light between the two resin substrates 13 and 14 which each formed the transparent electrode. A liquid crystal layer 22 (LY) made of right-twisted cholesteric liquid crystal is formed.

  In the above reflective liquid crystal display medium, only the liquid crystal layers 21, 23, or 24 that reflect blue light, green light, or red light are reflected when displaying blue, green, or red, and blue light and green are displayed when displaying cyan. The liquid crystal layers 21 and 23 that reflect light are set in a reflection state, and the liquid crystal layers 21 and 24 that reflect blue light and red light are set in a reflection state during magenta display. During yellow display, (1) only the liquid crystal layer 22 that reflects yellow light, or (2) the liquid crystal layers 23 and 24 that reflect green light and red light, or (3) yellow light, green light, and red light are displayed. The liquid crystal layers 22, 23 and 24 to be reflected are in a reflective state, but (3) is desirable for obtaining a high reflectance.

  Further, at the time of white display, all of the liquid crystal layers 21, 22, 23, and 24 that reflect blue light, yellow light, green light, and red light are brought into a reflection state. Further, if all of the liquid crystal layers are made colorless, a black display can be obtained by the light shielding layer 35.

  In this case, since the liquid crystal layer on the side opposite to the observation side (the lower side of the drawing) receives a larger light loss, the reflection of the liquid crystal layers 21, 22, 23, and 24 that reflects blue light, yellow light, green light, and red light, respectively. The spectrum (spectral reflectance) decreases in the order of the liquid crystal layers 21, 22, 23, and 24, as shown in FIG. 3 as blue 101, yellow 104, green 102, and red 103 reflection spectra.

  Since all of the liquid crystal layers 21, 22, 23, and 24 are in a reflective state at the time of white display, the reflection spectrum at the time of white display has a liquid crystal layer 21, 22, 23, as shown by 105 in FIG. The reflection spectrum of 24 is synthesized and becomes a substantially flat reflection spectrum from about 470 to 630 nm. In this case, since the reflectance decreases in the order of blue 101, green 102, and red 103 as described above, the liquid crystal layer that reflects yellow light is reduced by the decrease in reflectance in the wavelength range from green to red as a whole. 22 is supplemented by a reflection spectrum 104 based on.

On the other hand, in the reflective liquid crystal display medium shown in FIG. 1B, a blue light reflecting panel 40, a green light reflecting panel 60, and a red light reflecting panel 70 are stacked in this order from the observation side indicated by the arrows in the figure. The yellow light reflecting panel 50 is provided between the reflecting panel 60 and the red light reflecting panel 70.
In addition, a black light-shielding layer 35 is formed on the back surface of the red light reflection panel 70, a red filter 32 is formed on the observation side, and a yellow filter 31 is formed on the observation side of the green light reflection panel 60.

  Also in the reflection type liquid crystal display medium shown in FIG. 1B, the optical rotation in the opposite direction is used for each color light in which the wavelength range of the selective reflection is adjacent. Specifically, in this configuration, the liquid crystal layer 21 (LB) of the blue light reflection panel 40 is twisted to the right, the liquid crystal layer 23 (LG) of the green light reflection panel 60 is twisted to the left, and the liquid crystal layer 22 (LY) of the yellow light reflection panel 50. ) Is right-twisted, and the liquid crystal layer 24 (LR) of the red light reflecting panel 70 is made of left-twisted cholesteric liquid crystal.

  In the reflective liquid crystal display medium, the liquid crystal layer 21 that reflects blue light, the liquid crystal layer 23 that reflects green light, the liquid crystal layer 23 that reflects green light, the liquid crystal layer 22 that reflects yellow light, and yellow light are reflected. Since the liquid crystal layer 22 and the liquid crystal layer 24 that reflects red light have different spiral twist directions of the cholesteric liquid crystal, the reflectance increases in the wavelength band of blue and green, green and yellow, and yellow and red where the reflection spectra overlap. Thus, the saturation or lightness is improved when cyan, yellow, and white are displayed, particularly when yellow and white are displayed. Further, when displaying red and magenta, unnecessary short wavelength components reflected from the liquid crystal layer 24 that reflects red light are cut by the red filter 32, so that the saturation of red and magenta is improved.

  In addition, in this reflection type liquid crystal display medium, the reflection peak wavelength of the liquid crystal layer 22 that reflects yellow light is the same as that in the reflection type liquid crystal display medium shown in FIG. Since it is set in consideration of the reflection peak wavelength of the layer 23 and the reflection peak wavelength of the liquid crystal layer 24 that reflects red light, it is possible to obtain a white display having excellent white balance and good white reflectance during white display.

In the reflective liquid crystal display medium of the present embodiment in which the liquid crystal layer 22 that reflects yellow light is set in this way, it is desirable that the saturation during white display is in the range of 10 to 30, A range of 24 is more preferable. The lightness is preferably in the range of 50 to 75, and more preferably in the range of 55 to 70.
The saturation and lightness are lightness L ^* and saturation c ^* (= √ (a ^{* 2} + b ^{* 2} )) in L ^* a ^* b ^* chromaticity coordinates, and a spectrophotometer CM2002 manufactured by Minolta is used. Can be measured.

  In the present embodiment, the spiral twist direction of the liquid crystal layers 21 to 24 is such that the optical rotation of the opposite direction is used for each light of adjacent colors in the wavelength range of the selective reflection. That is, from the low wavelength side, the liquid crystal layer 21 that reflects blue light and the liquid crystal layer 23 that reflects green light, the liquid crystal layer 23 that reflects green light, the liquid crystal layer 22 that reflects yellow light, and the yellow light are reflected. Each of the liquid crystal layer 22 and the liquid crystal layer 24 that reflects red light has opposite spiral twist directions.

  This is because the cholesteric liquid crystal has circular dichroism that reflects only the circularly polarized component in the same direction as the helical twist direction as described above, and the reflection spectrum is only 50% in principle. This is because, in the wavelength band in which the rotation directions of the circularly polarized light are different from each other, the direction of rotation of the circularly polarized light is different from that of the same rotation direction, and the reflectance is not affected by the reflection layer laminated thereon.

  Examples of the cholesteric liquid crystal used for the liquid crystal layers 21 to 24 include liquid crystalline asymmetric carbon compounds such as cholesterol derivatives such as cholesteryl chloride and cholesteryl nonanoate, benzylidene aniline, azobenzene, azoxybenzene, cyanobiphenyl, and cyanoter. The known nematic liquid crystalline compounds containing chemical structures such as phenyl, phenylcyclohexane, phenylbenzoate, cyclohexylcyclohexane, cyclohexylcarboxylic acid ester, phenylpyrimidine, phenyldioxane, cyclohexylcyclohexane ester, cyclohexylethane, cyclohexene, and tolane are substituted with 2-methyl- A composition to which an asymmetric carbon compound called a chiral agent such as n-butylcyanobiphenyl is added can be used. These compounds may be low molecular compounds or high molecular compounds.

The liquid crystal layers 21 to 24 may contain components other than those described above, for example, a polymer or an inorganic compound dispersed in a cholesteric liquid crystal in a gel, matrix or fine particle form, or conversely in a polymer matrix. A so-called polymer having a functional group called mesogen that induces liquid crystallinity in the main chain or side chain of the polymer may be used, in which cholesteric liquid crystal is dispersed in the form of droplets or in the form of microcapsules. It may be a liquid crystal.
Furthermore, in order to control the alignment state of the cholesteric liquid crystal, an alignment layer may be provided in contact with each of the liquid crystal layers 21 to 24.

  The reflection wavelength range (display color wavelength range) of the liquid crystal layers 21 to 24 is adjusted by the helical pitch of the cholesteric liquid crystal. The helical pitch of the cholesteric liquid crystal can be adjusted by the amount of chiral agent added to the nematic liquid crystal. For example, when the display colors are blue, green, and red, the center wavelengths of selective reflection are 400 nm to 500 nm, The range is 500 nm to 600 nm and 600 nm to 700 nm. Further, in order to compensate for the temperature dependence of the helical pitch of the cholesteric liquid crystal, a known method of adding a plurality of chiral agents having different twist directions or opposite temperature dependence may be used.

  As the chiral agent, cholesterol derivatives such as cholesteryl nonanoate, compounds having an optically active group such as 2-methylbutyl group, and the like can be used. The helical pitch of the cholesteric liquid crystal can be changed depending on the type and amount of the chiral agent and the material of the liquid crystal.

As the resin substrates 11 to 18, at least all the resin substrates (internal resin substrates) other than the resin substrates 11 and 18 that become both end surfaces in the laminating direction after lamination are selected from PES, PC, PVC, PVCD, and COP 1 It shall consist of more than seeds. In this case, all the internal resin substrates may be made of the same material or different ones.
Further, the resin substrates 11 and 18 serving as the both end surfaces may be the specific resin substrate.

PES is a resin synthesized by polycondensation reaction using dichlorodiphenylsulfone and bisphenol S as raw materials. Since it has a glass transition temperature of 220 ° C. or higher, excellent heat resistance, and excellent solvent resistance, it is suitable as a resin substrate in this embodiment from the viewpoint of durability in addition to the above optical characteristics.
PC is a general engineering plastic, and its heat resistance is inferior to that of PES, but is effective because of its excellent transparency and dimensional stability. In particular, even when the resin substrate is thick, it is preferable because the decrease in reflectance is small.

  COP is a resin obtained by polymerizing cyclic olefins such as cyclopentene, 2-norbornene, and tetracyclododecene. However, homopolymerization is difficult sterically, so that it can be obtained by addition polymerization with α-olefin or ring-opening polymerization. Specifically, ZEONEX (manufactured by Nippon Zeon Co., Ltd.) obtained by synthesizing cyclopentane from raw material dicyclopentadiene (DCP) and reacting with olefins to synthesize norbornene as a monomer and ring-opening polymerization, Arton (manufactured by JSR) that has undergone addition polymerization may be used as a raw material.

PVC is an amorphous thermoplastic resin obtained by polymerizing a vinyl chloride group, is flexible, is easy to process, and has little deterioration over time.
PVDC is an amorphous thermoplastic resin obtained by polymerizing vinylidene groups, and is excellent in moldability and solvent resistance. Although heat resistance is not sufficient, it has a barrier property against oxygen and moisture, which is preferable in terms of environmental resistance in addition to the above optical characteristics.

The refractive index of the resin used for the specific resin substrate is desirably 1.4 or more and 1.7 or less, and more desirably 1.45 or more and 1.65 or less. The retardation per 100 μm of the resin is preferably 1 nm or more and 50 nm or less, and more preferably 3 nm or more and 30 nm or less. The haze value of the resin is desirably 2% or less, and more desirably 1.5% or less. Furthermore, the glass transition temperature is desirably 90 ° C. or higher, and more desirably 140 ° C. or higher.
Among these specific resin substrates, it is more preferable to use PES having excellent heat resistance, and it is preferable that all internal resin substrates are PES resin substrates to suppress a decrease in reflectance with respect to long-term use of a display medium. This is the most suitable. In this case, the resin substrates on the outermost surface and the outermost surface may be made of PES. However, since PES has a yellowish color as compared with PET, the reflectance of blue is lowered. Moreover, since the haze value of PES is 1.4 and is larger than the haze value 0.6 of PET, the reflectance of green and red is also lowered. From the above points, it is desirable to use a PET resin substrate.

  The thickness of the resin substrate in this embodiment is preferably 5 μm or more and 150 μm or less, and more preferably 10 μm or more and 100 μm or less. Further, the transmittance in the visible light region is desirably 85% or more, and more preferably 90% or more.

  For the electrode formed on the resin substrate, a light-transmitting conductive material such as indium tin oxide, tin oxide, or aluminum-added zinc oxide is used. These materials are formed into a thin film on a substrate by a sputtering method, a vapor deposition method, a sol-gel method, or the like, and processed into a desired shape by a photoetching method or the like to form an electrode.

  As the light shielding layer 35, a black color material that absorbs the entire visible wavelength range (400 to 700 nm), for example, a paint containing a black pigment such as carbon black or aniline black or a black dye, or an inorganic material such as chromium oxide is used. . The light shielding layer 35 may be provided below the liquid crystal layer 24 that reflects red light, and may also serve as an electrode or substrate below the liquid crystal layer 24.

As will be described later, in manufacturing the reflective liquid crystal display medium of the present embodiment, it is desirable to provide an adhesive layer when the color light reflecting panels are laminated.
For the adhesive layer, UV curable or thermosetting adhesives such as acrylic resin and epoxy resin, hot melt adhesives such as polyester and polyethylene-polyvinyl alcohol copolymer, adhesives such as polyvinyl acetate, etc. A known optical adhesive or pressure-sensitive adhesive can be used. However, the adhesive layer needs to have translucency. The adhesive layer not only bonds the panels to each other but also has an effect of reducing the surface reflection of the substrate and increasing the contrast, so that the refractive index is preferably close to that of the resin substrate material.

  The yellow filter 31 and the red filter 32 are formed by a known method such as applying a colored paint containing a pigment or a dye on the substrate, or providing an acrylic resin or gelatin film on the substrate and dyeing with a dye. be able to.

The yellow filter 31 may be provided between the liquid crystal layer 21 that reflects blue light and the liquid crystal layer 22 that reflects yellow light, and is formed on the upper surface of the yellow light reflecting panel 50 or the lower surface of the blue light reflecting panel 40. Alternatively, the electrode 13 or the substrate 13 serving as an adhesive layer between the blue light reflecting panel 40 and the yellow light reflecting panel 50 or directly below the liquid crystal layer 21 reflecting blue light or directly above the liquid crystal layer 22 reflecting yellow light is used. You may also serve. The same applies to the red filter 32.
By providing these filters, the display saturation can be improved and the change in display hue due to the viewing angle can be suppressed.

  The yellow filter 31 absorbs blue light and transmits green light and red light. The yellow filter 31 has a cutoff wavelength near 460 nm, absorbs blue light having a shorter wavelength, and has longer wavelengths of green and red. It is a filter that transmits the colored light. On the other hand, the red filter 32 has a cutoff wavelength near 570 nm, absorbs blue and green color lights having shorter wavelengths, and transmits red color light having longer wavelengths.

  Therefore, in the reflective liquid crystal display medium shown in FIG. 1, even if the reflection wavelength band of the liquid crystal layer 23 is shifted from the green wavelength band to the blue wavelength band due to, for example, a large incident angle of external light, the yellow filter 31 Therefore, the blue light is not reflected by the liquid crystal layer 23. Further, even if the reflection wavelength band of the liquid crystal layer 24 is shifted from the red wavelength band to the green wavelength band due to the large incident angle of the external light, the green light and the blue light are absorbed by the red filter 32. The liquid crystal layer 24 does not reflect green light or blue light.

  That is, in the reflection type liquid crystal display medium of the present embodiment, in addition to the above-described decrease in reflectance, even when the incident angle of external light is large, as a result, the reflection wavelength band in the liquid crystal layer 23 is the original. Only shifting to the shorter wavelength side and narrowing within the green wavelength band does not shift to the shorter wavelength side than the original green wavelength band. Further, in the liquid crystal layer 24, even when the incident angle of the external light is large, as a result, the reflection wavelength band is shifted to the short wavelength side within the original red wavelength band and becomes narrower. There is no shift to the shorter wavelength side than the band. Therefore, the display color does not change depending on the viewing angle, and the color purity does not decrease.

The reflection characteristics of the reflective liquid crystal display medium can be evaluated by measuring the spectral reflectance in a state where the reflectance of all the liquid crystal layers is maximized. As the reflection characteristics of the reflective liquid crystal display medium of this embodiment, the reflectance is desirably 20% or more and 60% or less in the wavelength region of 420 nm or more and 650 nm or less in the above evaluation, and is 25% or more and 55% or less. Is more preferred.
Note that “maximizing the reflectance of the liquid crystal layer” means that, for example, in the case of cholesteric liquid crystal, the liquid crystal is in a planar state and is in a reflective state. The spectral reflectance was measured with an ultraviolet-visible spectrophotometer U-4000 (manufactured by Hitachi).

Next, an example of a manufacturing method of the reflective liquid crystal display medium of this embodiment will be described.
First, an adhesive is applied to an end portion of one resin substrate on which an electrode is formed, and the other substrate on which an electrode is similarly formed is adhered at a constant interval so that both electrodes face each other via a spacer. Four of these are produced for each color. Next, a cholesteric liquid crystal capable of reflecting blue light, yellow light, green light, and red light is injected between a pair of substrates in each of them, and the edge of the substrate is sealed. The light reflection panel 50, the green light reflection panel 60, and the red light reflection panel 70 are produced. The thickness of the liquid crystal layers 21, 22, 23, and 24 in each panel is set to a range of 2 to 20 μm.

  Next, the yellow filter 31 is formed on the upper surface of the yellow light reflecting panel 50, the red filter 32 is formed on the upper surface of the red light reflecting panel 70, and the light shielding layer 35 is formed on the lower surface. Finally, the blue light reflecting panel 40, the yellow light reflecting panel 50 with the yellow filter 31 formed thereon, the green light reflecting panel 60, the red filter 32, and the red light reflecting panel 70 with the light shielding layer 35 formed thereon are bonded to each other. Glue through.

  In order to improve the display characteristics and display uniformity of the display medium, an alignment film may be provided at the interface between the electrode formed on each resin substrate surface and the liquid crystal layers 21, 22, 23, and 24. . As the alignment film, resins such as polyimide and polyvinyl alcohol, low molecular surface modifiers such as alkyl ammonium compounds and alkyl silane compounds, inorganic thin films such as SiO, and the like can be used. As the alignment film, a vertical alignment film is particularly preferable.

  It should be noted that members provided between adjacent liquid crystal layers such as a resin substrate, an electrode, and an alignment film need not disturb the polarization state. Therefore, it is desirable that these members have less light scattering.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of a reflective liquid crystal display medium according to the second embodiment. The reflective liquid crystal display medium of the present embodiment is obtained by inserting a λ / 2 wavelength plate (phase compensation layer) into the configuration of the display medium shown in FIG. 1, and other configurations are the same as those of the first embodiment. The same as described.
In the reflective liquid crystal display medium shown in FIG. 2A, a blue light reflecting panel 40, a green light reflecting panel 60, and a red light reflecting panel 70 are stacked in this order from the observation side indicated by the arrows in the figure. The yellow light reflecting panel 50 is provided between the green light reflecting panel 60 and the phase compensation layer 36 is further provided between the yellow light reflecting panel 50 and the green light reflecting panel 60.
Further, the black light-shielding layer 35 is formed on the back surface of the red light reflection panel 70, the red filter 32 is formed on the observation side, and the yellow filter 31 is formed on the observation side of the yellow light reflection panel 50.

  Also in the reflection type liquid crystal display medium, the optical rotation in the reverse direction is used for each color light in which the wavelength range of the selective reflection is adjacent. Specifically, in this configuration, the liquid crystal layer 21 (LB) of the blue light reflection panel 40, the liquid crystal layer 23 (LG) of the green light reflection panel 60, the liquid crystal layer 22 (LY) of the yellow light reflection panel 50, and the red light reflection. The spiral twist directions of the cholesteric liquid crystals of the liquid crystal layer 24 (LR) of the panel 70 are all the same, for example, right twist.

The phase compensation layer 36 changes circularly polarized light in the reverse direction, and uses a birefringent member called a ½ wavelength plate that sets the phase difference between ordinary light and extraordinary light to ½ wavelength. As such a birefringent member, a birefringent crystal such as mica or quartz, or a polymer film in which a polymer such as polyester, polyvinyl alcohol, polycarbonate, or polyether sulfone is molecularly oriented by stretching is used. Can do.
Further, instead of providing the phase compensation layer 36 as a layer separate from the reflected light panel in this way, the resin substrate 15 on the observer side of the green light reflecting panel 60, an electrode or an alignment film between the electrode and the liquid crystal layer 23, etc. The member constituting the reflected light panel may serve as the phase compensation layer 36 as a birefringent member.

  The light passing through the phase compensation layer 36 has its optical rotation reversed. For this reason, even if all the liquid crystal layers have the same spiral twist direction of the cholesteric liquid crystals, the spiral twist directions of the cholesteric liquid crystals of the liquid crystal layer are alternately reversed in the order of blue, green, yellow, and red as in the first embodiment. In the same way as in the case of blue, green, green and yellow, and yellow and red, the reflectance increases in the wavelength band where the reflection spectrum overlaps, and when displaying cyan, yellow and white, especially yellow and white The saturation or brightness of the hour is improved, and a bright and bright multicolor display can be obtained.

  In addition to this, also in the present embodiment, the reflection peak wavelength of the liquid crystal layer 22 that reflects yellow light is set to the reflection peak wavelength of the liquid crystal layer 23 that reflects green light, and the red light is reflected as in the first embodiment. Since the reflection peak wavelength of the liquid crystal layer 24 to be reflected is set in consideration, it is possible to obtain a white display having excellent white balance and a good white reflectance during white display. Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

(Third embodiment)
FIG. 4 is a schematic cross-sectional view of a reflective liquid crystal display medium according to the third embodiment. The reflective liquid crystal display medium of the present embodiment is a reflective liquid crystal display medium for full-color display in which a light reflective panel having a liquid crystal layer that selectively reflects three light beams of blue, green, and red is laminated. The configuration of B) is obtained by inserting a half-wave plate into the configuration of FIG.

The reflective liquid crystal display medium shown in FIG. 4A has a configuration in which a blue light reflecting panel 40, a green light reflecting panel 60, and a red light reflecting panel 70 are stacked in order from the observation side indicated by the arrows in the figure. Further, the black light-shielding layer 35 is formed on the back surface (lower side of the drawing) of the red light reflection panel 70, the red filter 32 is formed on the observation side, and the yellow filter 31 is formed on the observation side of the green light reflection panel 60. is doing.
That is, this configuration is obtained by extracting the yellow light reflecting panel from the configuration of the display medium shown in FIG. 1, and other configurations are the same as those described in the first embodiment.

  The blue light reflecting panel 40 is formed by forming a liquid crystal layer 21 (LB) made of right-twisted cholesteric liquid crystal that selectively reflects blue light between two resin substrates 11 and 12 each having a transparent electrode. The green light reflection panel 60 is formed by forming a liquid crystal layer 23 (LG) made of left-handed cholesteric liquid crystal that selectively reflects green light between two resin substrates 15 and 16 each having a transparent electrode formed thereon. In the red light reflecting panel 70, a liquid crystal layer 24 (LR) made of right-twisted cholesteric liquid crystal that selectively reflects red light is formed between two resin substrates 17 and 18 each having a transparent electrode.

  In the reflective liquid crystal display medium having the above configuration, the display method is basically the same as that of the reflective liquid crystal display medium having the structure shown in FIG. In this case, white color may be slightly bluish white during white display with all liquid crystal layers in a reflective state, but sufficient full color display can be performed. Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

The reflective liquid crystal display medium shown in FIG. 4B is obtained by inserting a λ / 2 wavelength plate (phase compensation layer) into the structure of the display medium shown in FIG. Is the same as that of the reflective liquid crystal display medium shown in FIG.
In the reflection type liquid crystal display medium shown in FIG. 4B, a blue light reflection panel 40, a green light reflection panel 60, and a red light reflection panel 70 are stacked in this order from the observation side indicated by the arrows in the figure, and further, the green light reflection is performed. The phase compensation layer 36 is provided below the red filter 32 between the panel 60 and the red light reflection panel 70.

  Also in the reflection type liquid crystal display medium, the selective reflection wavelength range uses reverse rotation for each color light adjacent to each other. However, in this configuration, the phase compensation layer 36 is inserted as described above. Therefore, the spiral twist directions of the cholesteric liquid crystals of the liquid crystal layer 21 (LB) of the blue light reflection panel 40, the liquid crystal layer 23 (LG) of the green light reflection panel 60, and the liquid crystal layer 24 (LR) of the red light reflection panel 70 are all Similarly, it can be a right-handed twist, for example.

  Further, the display method of this configuration is exactly the same as that of the display medium shown in FIG. 4A, and a sufficient full color display can be performed. Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

(Fourth embodiment)
FIG. 5 is a schematic cross-sectional view of a reflective liquid crystal display medium according to the fourth embodiment. The reflective liquid crystal display medium of the present embodiment is a reflective liquid crystal display medium for two-color display in which two light reflective panels each having a liquid crystal layer that selectively reflects yellow light are stacked. The configuration of FIG. Is a structure in which a half-wave plate is inserted in the configuration of FIG.

The reflective liquid crystal display medium shown in FIG. 5A has a configuration in which a first yellow light reflecting panel 52 and a second yellow light reflecting panel 54 are laminated in order from the observation side indicated by the arrow in the figure. A blue light shielding layer 39 is formed on the back surface (lower side of the drawing) of the second yellow light reflecting panel 54.
The first yellow light reflecting panel 52 is formed by forming a liquid crystal layer 25 made of right-twisted cholesteric liquid crystal that selectively reflects yellow light between two resin substrates 1 and 2 each having a transparent electrode formed thereon. The second yellow light reflecting panel 54 is formed by forming a liquid crystal layer 26 made of left-handed cholesteric liquid crystal that selectively reflects yellow light between two resin substrates 3 and 4 each having a transparent electrode.

In the reflective liquid crystal display medium having the above-described configuration, at least the internal resin substrates (resin substrates 2 and 3) must be the specific resin substrate. Other configurations and the like are the same as those described in the first embodiment.
The first yellow light reflecting panel 52 and the second yellow light reflecting panel 54 may have the same or different configurations, but the configurations of the liquid crystal layers 25 and 26 and the reflection wavelength range are the same. It is desirable.

In the reflective liquid crystal display medium, both of the two liquid crystal layers 25 and 26 that reflect yellow light are in a reflective state during white display. Further, if the two liquid crystal layers are made colorless, a blue display can be obtained by the light shielding layer 39. Therefore, according to the reflective liquid crystal display medium, for example, blue characters can be displayed on a white background.
Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

The reflective liquid crystal display medium shown in FIG. 5B is obtained by inserting a λ / 2 wavelength plate (phase compensation layer) into the structure of the display medium shown in FIG. Is similar to the reflective liquid crystal display medium shown in FIG.
In the reflective liquid crystal display medium shown in FIG. 5B, the first yellow light reflecting panel 52 and the second yellow light reflecting panel 54 are laminated in order from the observation side indicated by the arrows in the figure, and further the first yellow light reflecting panel is laminated. The phase compensation layer 36 is provided between the light reflection panel 52 and the second yellow light reflection panel 54.

  Also in the reflection type liquid crystal display medium, the selective reflection wavelength range uses reverse rotation for each color light adjacent to each other. However, in this configuration, the phase compensation layer 36 is inserted as described above. Therefore, the spiral twist directions of the cholesteric liquid crystals of the liquid crystal layer 25 of the first yellow light reflection panel 52 and the liquid crystal layer 26 of the second yellow light reflection panel 54 can all be the same, for example, right twist.

  The display method of this configuration is exactly the same as that of the display medium shown in FIG. 5A, and clear two-color display can be performed. Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

(Fifth embodiment)
FIG. 6 is a schematic cross-sectional view of a reflective liquid crystal display medium according to the fifth embodiment. The reflective liquid crystal display medium of the present embodiment is a reflective liquid crystal display medium for four-color display in which a light reflective panel having a liquid crystal layer that selectively reflects two lights of blue and yellow is laminated. FIG. In this configuration, a half-wave plate is inserted into the configuration of FIG.

The reflective liquid crystal display medium shown in FIG. 6A has a configuration in which a blue light reflecting panel 42 and a yellow light reflecting panel 56 are laminated in order from the observation side indicated by the arrows in the figure. A black light shielding layer 35 is formed on the back surface (lower side of the drawing) of the yellow light reflection panel 56.
The blue light reflection panel 42 is formed by forming a liquid crystal layer 27 made of right-twisted cholesteric liquid crystal that selectively reflects blue light between two resin substrates 5 and 6 each having a transparent electrode, and reflects yellow light. In the panel 56, a liquid crystal layer 28 made of left-handed cholesteric liquid crystal that selectively reflects yellow light is formed between two resin substrates 7 and 8 each having a transparent electrode.

In the reflective liquid crystal display medium having the above-described configuration, at least the internal resin substrates (resin substrates 6 and 7) must be the specific resin substrate. Other configurations and the like are the same as those described in the first embodiment.
In order to obtain a white display with excellent color tone by the blue light reflection panel 42 and the yellow light reflection panel 56, the central wavelengths of the selective reflection in the reflection wavelength regions of the liquid crystal layers 27 and 28 are 400 nm to 500 nm and 550 nm, respectively. It is desirable that the relationship be in the range of ˜650 nm.

In the reflective liquid crystal display medium, at the time of white display, both the liquid crystal layer 27 that reflects blue light and the liquid crystal layer 28 that reflects yellow light are brought into a reflective state. Further, if the two liquid crystal layers are made colorless, a black display can be obtained by the light shielding layer 35. Further, if the liquid crystal layer 27 that reflects blue light is in the reflective state and the liquid crystal layer 28 that reflects yellow light is in the colorless state, blue display can be achieved, and the liquid crystal layer 27 that reflects blue light reflects the yellow light in the colorless state. If the layer 28 is in a reflective state, yellow display can be achieved. Therefore, according to this reflective liquid crystal display medium, for example, four-color display such as black, blue, and yellow letters on a white background can be performed.
Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

The reflective liquid crystal display medium shown in FIG. 6B is obtained by inserting a λ / 2 wavelength plate (phase compensation layer) into the structure of the display medium shown in FIG. Is the same as the reflective liquid crystal display medium shown in FIG.
In the reflective liquid crystal display medium shown in FIG. 6B, a blue light reflecting panel 42 and a yellow light reflecting panel 56 are laminated in order from the observation side indicated by the arrow in the figure, and further, the blue light reflecting panel 42 and the yellow light reflecting are laminated. The phase compensation layer 36 is provided between the panel 56 and the panel 56.

  Also in the reflection type liquid crystal display medium, the selective reflection wavelength range uses reverse rotation for each color light adjacent to each other. However, in this configuration, the phase compensation layer 36 is inserted as described above. Therefore, the spiral twist directions of the cholesteric liquid crystals of the liquid crystal layer 27 of the blue light reflection panel 42 and the liquid crystal layer 28 of the yellow light reflection panel 56 can all be the same, for example, right twist.

  Further, the display method of this configuration is exactly the same as that of the display medium shown in FIG. 6A, and clear two-color display can be performed. Also in this case, as in the first embodiment, since at least the internal resin substrate is the specific resin substrate, it is possible to prevent the reflectance from being lowered.

  The reflection type liquid crystal display medium of the present invention has been described with some embodiments. The above-described example is a case where the cholesteric liquid crystal display medium is electrically driven and the display is rewritten. However, the reflective liquid crystal display medium of the present invention is subjected to external stimuli such as magnetism, light, heat and stress other than electricity. The same can be applied to the case where the liquid crystal display medium is driven and the display is rewritten, and the same effect can be obtained.

<< Test Example >>
Below, the test example of this invention is shown. The present invention is not limited by this test example. In addition, as a reflection type liquid crystal display medium for evaluation, the thing of the structure shown to FIG. 1 (A) was used.
<Test Example 1>
In this test example, instead of manufacturing the display medium using the same type of resin substrate as the substrate, various types of resins were sandwiched between cells using glass, and the spectral reflection characteristics of each were examined.

(Production of blue light, green light, yellow light, red light reflecting panel)
-Preparation of liquid crystals for each color light-
As a cholesteric liquid crystal for blue light and a cholesteric liquid crystal for yellow light, a mixed chiral agent prepared by mixing R-811 and R-1011 of Merck's chiral agent at a mass ratio of 4: 1 was added to a nematic liquid crystal E44 made by Merck. The cholesteric liquid crystal for blue light was added to 23.0% by mass (440 nm) of the total for the cholesteric liquid crystal for blue light, and 18.8% by mass (550 nm) for the cholesteric liquid crystal for yellow light.

  Further, as a cholesteric liquid crystal for green light and a cholesteric liquid crystal for red light, a mixed chiral agent obtained by mixing S-811 and S-1011 of Merck Co. at a mass ratio of 4: 1 is used as a nematic liquid crystal E44 manufactured by Merck Co. Further, 20.2% by mass (520 nm) for the cholesteric liquid crystal for green light and 16.8% by mass (610 nm) for the cholesteric liquid crystal for red light were added to prepare left-twisted cholesteric liquid crystals.

-Board-
A pair of glass substrates (7059, 25 mm × 22 mm × 0.2 mm, manufactured by Corning) with a 10 mm × 10 mm ITO electrode patterned on the surface was prepared. A solution obtained by diluting a vertical alignment polyimide (SE7511L, manufactured by Nissan Chemical Co., Ltd.) 10-fold with ethyl cellsolve by spin coating was formed on the surface on the electrode side to form an alignment film.

  On the other hand, as a resin substrate, a 100 μm thick PET resin substrate (manufactured by Sumitomo Bakelite), a 100 μm thick PES resin substrate (manufactured by Sumitomo Bakelite), a 100 μm thick PC resin substrate (manufactured by Teijin Ltd.), and a thickness A 100 μm COP resin substrate (manufactured by Nippon Zeon Co., Ltd., ZEONOR) was prepared, and each was cut into the same size as the glass substrate.

-Cell fabrication and liquid crystal injection-
Spacer particles were sprayed on the alignment film of the glass substrate thus prepared, and a seal pattern was drawn in stripes at the edge of each substrate with a UV curable resin. Next, these pair of substrates were bonded to each other and UV-cured to produce four cells each having a cell gap of 5 μm.
Next, cholesteric liquid crystals for blue light (right twist), green light (left twist), yellow light (right twist) and red light (left twist) are dropped into the openings of the cells, Liquid crystal is injected using capillary action, and then the opening of each cell is sealed with UV adhesive, and the blue light reflecting panel, green light reflecting panel, yellow light reflecting panel, red light using the substrate as the glass substrate A reflective panel was obtained.

(Production and evaluation of reflective liquid crystal display media)
A solution in which 1% by mass of a yellow dye (Kayaset Yellow K-CL, manufactured by Nippon Kayaku Co., Ltd.) is dissolved in an acrylic resin solution is applied to the top surface of the yellow light reflecting panel and dried to form a yellow filter and acrylic. A solution in which 0.5% by mass of a red dye (PD400R • FX1, manufactured by Hitachi Chemical Co., Ltd.) was dissolved in the resin solution was applied to the upper surface of the red light reflection panel and dried to form a red filter. Furthermore, a black resin solution (BKR105, manufactured by Nippon Kayaku Co., Ltd.) was applied to the lower surface of the red light reflecting panel and dried to form a light shielding layer.

The blue light reflection panel, yellow light reflection panel, green light reflection panel, and red light reflection panel thus produced are laminated in this order and bonded with an ultraviolet curable adhesive, and each reflection as shown in FIG. A liquid crystal display medium was obtained.
L ^* a ^* b ^* chromaticity coordinates during white display were measured using a spectrophotometer CM2002 (manufactured by Minolta Co., Ltd.) with the reflectance of each liquid crystal layer maximized for the reflective liquid crystal display medium. . As a result, the saturation C ^* = ((a ^* ) ² + (b ^* ) ² ) ^1/2 defined by the distance from the origin is 20.5 (a ^* = − 14.0, b ^* = 15). 0.0) and the brightness was 69.5, and it was milky white with a slight yellowish appearance.

  Next, for each reflective liquid crystal display medium, the spectral reflectance was measured with an ultraviolet-visible spectrophotometer U-4000 (manufactured by Hitachi) with the reflectance of each liquid crystal layer maximized (white display state). . FIG. 7 shows the result when two sheets of PET, PC, and PES resin are sandwiched between the total reflection panels, and FIG. 8 shows the result when six sheets of COP resin are sandwiched between the total reflection panels. In addition, the results are shown together with the results of the case where the resin used as a reference is not sandwiched (in the figure, the resin sandwiched by each is shown as “substrate: PET” or the like).

  As shown in FIGS. 7 to 8, when a resin made of PC, PES, COP, and PVDC is sandwiched between the substrates, the visible light region (450 nm or more and 650 nm or less) is compared with the case where the resin is not sandwiched. Although the reflectance was the same, it can be seen that the reflectance in the region is greatly reduced when a PET resin is sandwiched.

<Test Example 2>
In this test example, the influence of the arrangement position in the display medium was examined for the PET resin substrate in which the reflectance decrease was greatest in Test Example 1.
Specifically, in the same manner as in Test Example 1, measurement samples in which the position where one sheet of PET resin is arranged were changed to the outermost surface, the yellow reflective panel, and the green reflective panel were prepared (each “ (Displayed as “PET 1 sheet placed on the surface” and “PET 1 sheet placed between YG”) Changes in reflectance were examined.
FIG. 9 is shown together with the case where no resin is sandwiched with reference to the measurement result.

  As shown in FIG. 9, when the PET resin is disposed between the liquid crystal layers, the reflectance in the visible light region is greatly reduced as in the case of sandwiching the PET resin shown in FIG. As shown in FIG. Therefore, it can be said that a PET resin substrate can also be used as a resin substrate on the end face of the display medium.

<Test Example 3>
In this test example, in the same manner as in <Test example 1>, instead of producing a display medium using the same type of resin substrate as the substrate, various resins are sandwiched between cells using glass, and the spectral reflection characteristics of each are measured. Examined.
-Preparation of liquid crystal-
As a cholesteric liquid crystal for green right-twisted light, a mixed chiral agent obtained by mixing R-811 and R-1011 of Merck's chiral agent at a mass ratio of 4: 1 was added to Merck's nematic liquid crystal E44 at 20.2% by mass. (520 nm) was added to prepare.
As a cholesteric liquid crystal for green left-twisted light, a mixed chiral agent in which S-811 and S-1011 of Merck Corp. were mixed at a mass ratio of 4: 1 was added to Merck Nematic Liquid Crystal E44 at 20.2 mass%. (520 nm) was added to prepare.

-Cell fabrication and liquid crystal injection-
In the same manner as in <Test Example 1>, an alignment film is formed by spin coating on a pair of glass substrate surfaces patterned with ITO electrodes, spacer particles are dispersed, and then a test cell is bonded by using a UV curable resin. Obtained.
The right twisted and left twisted green light cholesteric liquid crystals are dropped into the openings of the cells, respectively, and liquid crystals are injected using a capillary phenomenon, and then the openings of the cells are sealed with a UV adhesive. A green right twist light reflection panel and a green left twist light reflection panel were obtained.

-Evaluation of resin by reflectance measurement-
As the resin substrate, a 12 μm thick PVDC resin substrate (Asahi Kasei Corp., Saran Wrap), a 12 μm thick PVC resin substrate (Riken Technos Corp., Riken Wrap) and a 5 μm thick PET resin substrate (Toray Industries, Lumirror), respectively These were prepared and each cut into the same size as the glass substrate.
Next, the spectral reflectance was measured with an ultraviolet-visible spectrophotometer U-4000 (manufactured by Hitachi) in a state where the reflectance of the reflective liquid crystal display medium with left and right twists was maximized. FIG. 10 shows the result of sandwiching PVDC and PVC resin between right and left twisted reflection panels together with the result of not sandwiching the resin referred to.

  As shown in FIG. 10, when the resin made of PVDC and PVC was sandwiched between the substrates, the reflectance was equivalent to that when the resin was not sandwiched. It can be seen that the reflectance at is greatly reduced. Even when the thickness of the PET resin substrate was 5 μm, the reflectance was reduced as in the case of the thickness of 100 μm.

It is a schematic cross section which shows an example of the reflection type liquid crystal display medium of this invention. It is a schematic cross section which shows another example of the reflection type liquid crystal display medium of this invention. It is a figure which shows the reflection spectrum at the time of each liquid crystal layer in a reflection type liquid crystal display medium, and white display. It is a schematic cross section which shows another example of the reflection type liquid crystal display medium of this invention. It is a schematic cross section which shows another example of the reflection type liquid crystal display medium of this invention. It is a schematic cross section which shows another example of the reflection type liquid crystal display medium of this invention. It is a figure which shows the spectral reflection spectrum of a test example. It is a figure which shows the spectral reflection spectrum of another test example. It is a figure which shows the spectral reflection spectrum of another test example. It is a figure which shows the spectral reflection spectrum of another test example.

Explanation of symbols

1-8, 11-18 Resin substrates 21-28 Liquid crystal layer 31 Yellow filter 32 Red filter 35, 39 Light blocking layer 36 Phase compensation layer 38 Amber filter 40, 42 Blue light reflection panels 50, 52, 54, 56 Yellow light reflection Panel 60 Green light reflecting panel 70 Red light reflecting panel

Claims (3)

It is configured by laminating a plurality of light reflecting panels having a liquid crystal layer between a pair of resin substrates,
The liquid crystal layer includes cholesteric liquid crystal, and the spiral twist direction of the liquid crystal is different for each liquid crystal layer in which at least the reflection wavelength region is adjacent,
Of the resin substrates, at least all of the resin substrates other than the resin substrates that become both end surfaces in the laminating direction are composed of one or more selected from polyethersulfone, polycarbonate, polyvinyl chloride, polyvinylidene chloride, and cyclic polyolefin. A reflective liquid crystal display medium characterized by the above.   2. The reflective liquid crystal display medium according to claim 1, wherein all but the resin substrate which becomes both end faces in the laminating direction are made of polyethersulfone. It is configured by laminating a plurality of light reflecting panels having a liquid crystal layer between a pair of resin substrates,
The liquid crystal layer includes cholesteric liquid crystal, and the spiral twist direction of all the liquid crystals is the same,
Of the resin substrates, at least all of the resin substrates other than the resin substrates that become both end surfaces in the laminating direction are composed of one or more selected from polyethersulfone, polycarbonate, polyvinyl chloride, polyvinylidene chloride, and cyclic polyolefin, A reflection type liquid crystal display medium, wherein a phase compensation layer is provided between the plurality of light reflection panels.

Images