JPH09258272A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a bright and distinct color display by incorporating a liquid crystal material, a fluorescent material having dichromaticity of a first type and having fluorescence of a blue region and a dichromatic dye having dichromaticity of a second type into a liquid crystal layer. SOLUTION: The liquid crystal material into which liquid crystal molecules 8, dichromatic dye molecules 9 of magenta and a blue fluorescent material 10 having the blue fluorescence without having absorption in a visible light region are incorporated is injected into the cell furthest from a reflection plate 4. A guest-host layer 5 of magenta is formed. The liquid crystal material into which the liquid crystal molecules 8 and the dichromatic dye molecules 9 of cyan are incorporated is injected into the cell apart next from the reflection plate 4 and a guest-host layer 6 of cyan is formed. The liquid crystal material into which the liquid crystal molecules 8 and the dichromatic dye molecules 9 of yellow are incorporated is injected into the cell nearest the reflection plate 4 and a guesthost layer 7 of yellow is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a guest-host type reflective liquid crystal display device.

[0002]

2. Description of the Related Art The guest-host method using a liquid crystal material in which a dye having a large dichroic ratio is dissolved in liquid crystal has advantages such as a wide viewing angle and is one of the display methods expected in the future. Is. In recent years, the demand for color displays has increased, and guest-host type color displays have been actively developed. An example of such a color display is (T.Uchida: Proc.3rd.Display Re
s.Conf., p202, 1983), a combination of guest host cells of three colors of yellow, cyan and magenta.

However, in this system, the number of transparent electrodes and alignment films is three times that of a normal single-layer cell because it has a structure in which cells are stacked in three layers. in this way,
When the number of transparent electrodes and alignment films is large, absorption of incident light due to them cannot be ignored, and as a result, light utilization efficiency is reduced and the display becomes dark. In particular, absorption on the short wavelength side in the visible light region becomes a problem. In order to solve this problem, many studies such as improvement of transparency of transparent electrodes and alignment films and reduction of film thickness have been earnestly conducted, but the present situation is that satisfactory characteristics have not yet been obtained.

The present invention has been made in view of the above points, and an object of the present invention is to provide a liquid crystal display device capable of realizing a bright and clear color display by improving the reflectance in the case of display, particularly white display. .

[0005]

Means for Solving the Problems A first invention of the present invention is:
A pair of substrates and a liquid crystal layer sandwiched between the pair of substrates, wherein the liquid crystal layer has a liquid crystal material, a first type of dichroism, and fluorescence having fluorescence in a blue region. Material and second
And a dichroic dye having a dichroic property of the above type. This fluorescent substance preferably has no absorption in the visible light region.

The first invention of the present invention comprises a pair of substrates and a liquid crystal layer sandwiched between the pair of substrates,
The liquid crystal layer, a liquid crystal material, a fluorescent light dichroic dye in which the transition moment in the visible light region is in the molecular major axis direction and the transition moment in the ultraviolet light region is in the direction orthogonal to the molecular major axis, or in the visible light region. And a fluorescent dichroic dye whose transition moment in the ultraviolet region is in the direction of the long axis of the molecule are contained in the liquid crystal display device.

Further, a second invention of the present invention comprises a pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and a reflection plate arranged outside the pair of substrates, The liquid crystal display device is characterized in that the reflection plate has a layer made of a colorless and fluorescent substance having blue fluorescence on the liquid crystal layer side surface.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. Usually, ITO (Indium Tin Oxide) forming the transparent electrode absorbs light on the short wavelength side. Therefore, in a guest-host type liquid crystal display device having a three-layer superposition structure, a short wavelength light (blue) is insufficient in a device having a large number of transparent electrodes and alignment films. The present inventors have conducted intensive studies in consideration of this problem, and as a result, found that bright and clear color display can be realized in a reflective liquid crystal display device by utilizing fluorescence in the blue region, Came to do.

That is, in the liquid crystal display device of the present invention, a liquid crystal material, a phosphor material having a first type of dichroism, and a fluorescent substance having fluorescence in a blue region, and a second type dichroism are provided. And a liquid crystal layer containing the dichroic dye. This fluorescent substance absorbs light in the ultraviolet light region and emits it as blue fluorescence of visible light having a wavelength longer than that in the ultraviolet light region, so that it supplements light on the short wavelength side (blue) absorbed by the transparent electrode or the like. As a result, light utilization efficiency is improved, and bright and clear color display, particularly white display close to paper white, can be realized. Particularly, in the reflective liquid crystal display element, the reflectance is improved by improving the light utilization efficiency, which is preferable.

In the present invention, examples of the dichroic dye include the following. Examples of the yellow dichroic dye (which absorbs blue light) include G-232 manufactured by Nihon Photosensitizing Co., Ltd., SI-209 manufactured by Aussie, and M-36.
1 or the like can be used. Further, as a cyan dichroic dye (which absorbs red color), SI-made by Aussie
501, SI-497, M-403, G-472 manufactured by Nippon Senshoku Co., Ltd. and the like can be used. Examples of magenta dichroic dyes (those that absorb green color) include G-239, G-471, and G-202 manufactured by Nippon Senshoku Co., Ltd., SI-512, M-618, and M-370 manufactured by Aussie. Can be used.

In the present invention, the fluorescent substance having fluorescence in the blue region has dichroism when dissolved in liquid crystal. Examples of the fluorescent substance include coumarins and stilbenes. This fluorescent substance preferably has no absorption in the visible light region. This is because it is more appropriate to adjust the hue only with the dye.

In the above-mentioned dichroic dye and fluorescent substance, the dichroic type means p-type and n-type, and p-type has an absorption axis in the long axis of the molecule, and n-type means a molecule. It has an absorption axis on the axis (short axis) orthogonal to the long axis. In the present invention, the dichroic type of the dichroic dye and the dichroic type of the fluorescent substance are set to be different. When a p-type liquid crystal material is used, when the dichroic dye is p-type (the absorption axis is the long axis of the molecule) and the fluorescent substance is n-type (the absorption axis is the axis orthogonal to the long axis of the molecule), When a voltage is applied (transmission state), the molecular long axes are aligned in the voltage application direction, absorption does not occur in the dichroic dye, and absorption / fluorescence occurs in the fluorescent substance.
On the contrary, when the dichroic dye is n-type (the absorption axis is orthogonal to the molecular long axis) and the fluorescent substance is p-type (the absorption axis is the long molecular axis), a state in which a voltage is applied to the cell ( In the transparent state, the dichroic dye absorbs and the fluorescent substance does not absorb or fluoresce.

In the present invention, as the liquid crystal, TC-4368XX and ZLI-4281 / manufactured by Merck Japan KK
2, ZLI-3889, ZLI-5500-000, M
LC-6041-000, ZLI-4620, ZLI-
5100-000, ZLI-1840, ZLI-211
6-000, LIXON4033-made by Chisso Chemical Co., Ltd.
000XX, LIXON4034-000XX, ZLI
-2293 etc. can be used. The dielectric anisotropy of the liquid crystal may be p-type or n-type, but it is preferably p-type considering the contrast of the liquid crystal display element.

Further, the liquid crystal display device of the present invention comprises a liquid crystal material and a fluorescent liquid having a transition moment in the visible light region in the direction of the long axis of the molecule and a transition moment in the ultraviolet light region in the direction perpendicular to the long axis of the molecule. A liquid crystal layer containing a chromatic dye or a fluorescent dichroic dye whose transition moment in the visible light region is in the direction orthogonal to the long axis of the molecule and whose transition moment in the ultraviolet light region is in the long axis direction of the molecule. It is characterized by that.

As described above, by using the fluorescent dichroic dye in which the transition moment directions of the ultraviolet light region and the visible light region are substantially orthogonal to each other, the dichroic dye and the fluorescent substance each having a different dichroic type are used. It is possible to obtain almost the same effect as that of adding to the liquid crystal. That is, the fluorescent dichroic dye has both the functions of the dichroic dye and the fluorescent substance, and can separate the fluorescence and the visible light absorption mode.

Further, the liquid crystal display element of the present invention is characterized by comprising a reflector having a layer made of the above-mentioned fluorescent substance which is colorless and has blue fluorescence on the surface of the liquid crystal layer side. In this case, the guest host layer closest to the reflector is preferably the yellow guest host layer. This is because the yellow dye absorbs light in the blue region. That is, the yellow guest host layer is
By adjusting the concentration in advance in consideration of the influence of fluorescence, it is possible to prevent the hue from shifting due to the fluorescence. Also in this case, blue fluorescence supplements light on the short wavelength side of visible light. As a method for forming the layer made of the fluorescent substance on the reflection plate, a coating method, a vapor deposition method, or the like can be used.

Further, in the liquid crystal display element of the present invention,
It can also be realized by making the dichroic dye itself contained in the liquid crystal layer have blue fluorescence. For example, replace the guest host layer closest to the reflector with the yellow guest
Even when a fluorescent dichroic dye having blue fluorescence is used as a guest in the host layer, the same effect as above can be obtained. Also in this case, when white is displayed, a bright display is obtained due to the effect of fluorescence, and the contrast is also increased. It should be noted that it is desirable to adjust the concentrations of the upper cyan guest host layer and the magenta guest host layer in advance in consideration of the influence of fluorescence.

The liquid crystal display device of the present invention can realize color display with a three-layered structure of guest and host layers. In this case, the order of colors of the three guest / host layers may be arbitrary. However, in the case of being used in the reflection type, it is preferable that the guest-host layer containing the fluorescent substance is arranged in the layer farthest from the reflection plate (uppermost layer) in order to increase the fluorescence intensity.

In the present invention, a glass substrate, a transparent plastic substrate or the like can be used as the substrate, and aluminum, silver, magnesium oxide, barium sulfate or the like can be used as the material of the reflector.

As described above, in the guest-host liquid crystal display device of the present invention, a colorless fluorescent substance having dichroism having fluorescence in the blue region is contained in the liquid crystal together with the dichroic dye as a guest. Therefore, blue fluorescence is generated in the guest / host layer. Specifically, when an n-type fluorescent substance and a p-type dichroic dye are used, blue fluorescence can be generated when the guest / host layer is decolored (transmitted). Due to the effect of this blue fluorescence (whitening effect), light on the short wavelength side of visible light absorbed by the alignment film and the transparent electrode is supplemented, and a bright and clear color display can be obtained.

The following is a description of examples made to clarify the effects of the present invention, but the present invention is not limited thereto. (Embodiment 1) FIG. 1 is a schematic view showing an embodiment of the liquid crystal display device of the present invention. In the figure, 1a and 1b represent glass substrates. The transparent electrode 2 is formed on one surface of the glass substrate 1a by depositing ITO by sputtering. An alignment film 3 is formed on the transparent electrode 2 by applying polyimide. Further, the transparent electrode 2 and the alignment film 3 are sequentially formed on both surfaces of the glass substrate 1b in the same manner as described above.

A cell having a three-layer structure is formed by arranging the glass substrate 1a outside and the glass substrate 1b inside in parallel. Further, the reflection plate 4 is arranged outside one of the cells. Liquid crystal molecules 8, magenta dichroic dye molecules 9, and a blue fluorescent substance 10 which does not absorb in the visible light region and has blue fluorescence are contained in the cell farthest from the reflection plate 4. A liquid crystal material is injected, and a magenta guest / host layer 5 is formed. Further, a liquid crystal material containing liquid crystal molecules 8 and cyan dichroic dye molecules 9 is injected into the cell that is the second distance from the reflection plate 4, and the cyan guest-host layer 6 is formed. Has been formed. Further, a liquid crystal material containing liquid crystal molecules 8 and yellow dichroic dye molecules 9 is injected into the cell closest to the reflection plate 4 to form a yellow guest / host layer 7. ing.
The colors of the guest / host layers 5 to 7 may be in any order. The peripheral portion of the cell is sealed with a sealing material (not shown). In this way, a phase transition type reflective three-layer guest-host liquid crystal display element composed of yellow, cyan and magenta is constituted.

Here, yellow dichroic dye (p-type)
Is G-232 made by Nippon Sensitive Dye Co., Ltd., and the cyan dichroic dye (p-type) is SI-497 made by Aussie.
As the magenta dichroic dye (p-type), G-239 manufactured by Nippon Senshoku Co., Ltd. was used. In addition, liquid crystal material (p
Type) as LIXON4033-made by Chisso Chemical Co., Ltd.
000XX was used. As the blue fluorescent substance (n-type) 10 contained in the magenta guest / host layer 5, a substance represented by the following chemical formula 1 was used. That is, the dichroic dye absorbs each complementary color when voltage is applied and transmits light when no voltage is applied. On the other hand, the blue fluorescent substance does not generate fluorescence when a voltage is applied, but emits fluorescence when no voltage is applied.

[0024]

Embedded image

When white is displayed in this liquid crystal display element, a voltage is applied to all the guest / host layers 5 to 7 to bring them into a transmissive state. At this time, the magenta guest
In the host layer 5, since blue fluorescence appears due to the blue fluorescent material 10, the reflectance becomes 70% due to the effect of this fluorescence,
A bright display was obtained and the contrast was increased to 20.
When displaying blue, a voltage is applied to the yellow guest-host layer 7 (transmission state), and no voltage is applied to the cyan guest-host layer 6 and the magenta guest-host layer 5 (coloring state). . In this case, the guest-host layer 6 for cyan absorbs red, and the guest-host layer 5 for magenta absorbs green. As a result, blue is displayed. At this time, since the magenta guest / host layer 5 is in a colored state, no fluorescence is observed.

When displaying red, the guest of cyan
By applying a voltage to the host layer 6 (transmission state), the yellow guest host layer 7 and the magenta guest host layer 5
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the magenta guest-host layer 5 absorbs green. As a result, red color is displayed. At this time, since the magenta guest / host layer 5 is in a colored state, no fluorescence is observed.

When displaying green, a voltage is applied to the guest host layer 5 of magenta (transmission state), and the guest host layer 7 of yellow and the guest host layer 6 of cyan are displayed.
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the cyan guest-host layer 6 absorbs red. As a result, green is displayed. At this time, the magenta guest host layer 5
Is transparent, so fluorescence is observed. At this time, the luminous reflectance Y was 80%, and bright green display could be realized. (Embodiment 2) FIG. 2 is a schematic view showing another embodiment of the liquid crystal display device of the present invention. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the phase transition type reflection type three-layer guest-host liquid crystal display element shown in FIG. 2, a reflection plate 4 made of aluminum is arranged outside one glass substrate 1a, and the reflection plate 4 on the liquid crystal cell side. A blue fluorescent layer 11 made of a blue fluorescent substance is provided on the surface. Further, the magenta guest / host layer 5 does not contain the blue fluorescent material 10. In this case, the layer closest to the reflector 4 needs to be the yellow guest-host layer 7. At this time, it is more desirable to adjust the concentration of the yellow guest / host layer 7 in advance in consideration of the influence of fluorescence.

Here, the same dichroic dyes as yellow, cyan, and magenta and the liquid crystal material used in Example 1 are used, and the blue fluorescent substance (n-type) is the substance represented by the following chemical formula 2. Using. The blue fluorescent layer 11 was formed by applying the blue fluorescent substance.

[0030]

Embedded image

When displaying white in this liquid crystal display device, a voltage is applied to all the guest / host layers 5 to 7 to bring them into a transmissive state. At this time, since blue fluorescent light appears from the blue fluorescent layer 11, the reflectance becomes 65% due to the effect of this fluorescent light, a bright display is obtained, and the contrast is increased to 18.

When displaying blue, a voltage is applied to the guest host layer 7 for yellow (transmission state), and the guest host layer 6 for cyan and the guest host layer 5 for magenta are applied.
Is no voltage applied (colored state). In this case, the guest-host layer 6 for cyan absorbs red, and the guest-host layer 5 for magenta absorbs green. As a result, blue is displayed. Also in this case, the luminous reflectance Y was 30% due to the blue fluorescence, and a bright and clear blue display could be realized.

When displaying red, the guest of cyan
By applying a voltage to the host layer 6 (transmission state), the yellow guest host layer 7 and the magenta guest host layer 5
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the magenta guest-host layer 5 absorbs green. As a result, red color is displayed. At this time, since the yellow guest / host layer 7 is in a colored state, the fluorescence from the blue fluorescent layer 11 is absorbed by the yellow guest / host layer 7, and the hue of the display color is not shifted.

When displaying green, a voltage is applied to the magenta guest host layer 5 (transmission state), and the yellow guest host layer 7 and the cyan guest host layer 6 are applied.
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the cyan guest-host layer 6 absorbs red. As a result, green is displayed. At this time, the yellow guest host layer 7
In the colored state, the fluorescence from the blue fluorescent layer 11 was absorbed by the yellow guest / host layer 7, and the hue of the display color did not shift. The luminous reflectance Y at this time is 75%.
Therefore, bright green display could be realized. (Example 3) The magenta guest-host layer 5 does not contain the blue fluorescent substance 10, the layer closest to the reflector 4 is the yellow guest-host layer 7, and the yellow guest-host layer 7 As a yellow dichroic dye to be included in the above, a phase transition type reflective three-layer guest-host liquid crystal display device having the structure shown in FIG. 1 is prepared except that a blue fluorescent substance having blue fluorescence shown in Chemical formula 2 above is used. did. The liquid crystal material and the dichroic dyes of yellow, cyan, and magenta used were the same as in Example 1.

When displaying white in this liquid crystal display device, a voltage is applied to all the guest / host layers 5 to 7 to bring them into a transmissive state. At this time, the yellow guest
Since blue fluorescence appears from the blue fluorescent substance of the host layer 7, the reflectance was 65% due to the effect of this fluorescence, a bright display was obtained, and the contrast was increased to 18.

To display blue, a voltage is applied to the guest host layer 7 for yellow (transmission state), and the guest host layer 6 for cyan and the guest host layer 5 for magenta are applied.
Is no voltage applied (colored state). In this case, the guest-host layer 6 for cyan absorbs red, and the guest-host layer 5 for magenta absorbs green. As a result, blue is displayed. Also in this case, the luminous reflectance Y was 35% due to the blue fluorescence from the blue fluorescent material, and a bright and clear blue display could be realized.

When displaying red, the guest of cyan
By applying a voltage to the host layer 6 (transmission state), the yellow guest host layer 7 and the magenta guest host layer 5
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the magenta guest-host layer 5 absorbs green. As a result, red color is displayed. Further, since the yellow guest / host layer 7 is in a colored state, the fluorescence from the blue fluorescent material was absorbed by the yellow guest / host layer 7, and the hue of the display color was not shifted.

When displaying green, a voltage is applied to the guest host layer 5 of magenta (transmission state), and the guest host layer 7 of yellow and the guest host layer 6 of cyan are applied.
Is no voltage applied (colored state). In this case, the yellow guest-host layer 7 absorbs blue, and the cyan guest-host layer 6 absorbs red. As a result, green is displayed. Further, since the yellow guest / host layer 7 is in a colored state, the fluorescence from the blue fluorescent material was absorbed by the yellow guest / host layer 7, and the hue of the display color was not shifted. At this time, the luminous reflectance Y was 80%, and bright green display could be realized. (Conventional Example) A conventional phase transition type reflective three-layer guest-host liquid crystal display device similar to that of Example 1 was prepared except that the magenta guest-host layer 5 did not contain the blue fluorescent material 10. The liquid crystal material and the dichroic dyes of yellow, cyan, and magenta used were the same as in Example 1.

The liquid crystal display device had a reflectance of 10% when displaying white and a contrast of 10. Further, at the time of white display, the decrease in reflectance in the blue region was conspicuous, and the hue was yellow.

In the above embodiment, the case where the dichroic dye is p-type and the fluorescent substance is n-type has been described. However, the dichroic dye is n-type and the fluorescent substance is p-type. Even in some cases, the same effect as above can be obtained. Further, in the above embodiment, the case of the reflection type is described, but the present invention can be applied to other modes such as the transmission type. Besides, the present invention can be variously modified and implemented without departing from the spirit thereof.

[0041]

As described above, the guest-host type liquid crystal display device of the present invention has a greatly improved reflectance particularly in white display due to the effect of fluorescence in the blue region, and the hue is almost achromatic. This makes it possible to eliminate the coloring (especially yellow) at the time of white display, which has been a problem in the past. Further, even when displaying blue and green colors, bright and clear display can be realized by the effect of fluorescence.

As described above, the liquid crystal display element according to the present invention can utilize ultraviolet light for display, and solves the darkness of display which is an important problem in the reflection type liquid crystal display element. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a reflective liquid crystal display element of the present invention.

FIG. 2 is a sectional view showing another embodiment of the reflective liquid crystal display element of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Transparent electrode, 3 ... Alignment film, 4 ... Reflector, 5 ... Magenta guest host layer, 6 ... Cyan guest host layer, 7 ... Yellow guest host layer, 8
... liquid crystal molecule, 9 ... dichroic dye molecule, 10 ... blue fluorescent substance, 11 ... blue fluorescent layer.

Claims (4)

[Claims] 1. A pair of substrates, and a liquid crystal layer sandwiched between the pair of substrates, the liquid crystal layer comprising a liquid crystal material,
A liquid crystal display device comprising: a phosphor material having a first type of dichroism and having fluorescence in a blue region; and a dichroic dye having a second type of dichroism. 2. The liquid crystal display device according to claim 1, wherein the fluorescent substance has no absorption in a visible light region. 3. A pair of substrates, and a liquid crystal layer sandwiched between the pair of substrates, the liquid crystal layer comprising a liquid crystal material,
Fluorescent dichroic dye whose transition moment in the visible light region is in the direction of the molecular long axis and transition moment in the ultraviolet region is in the direction orthogonal to the molecule long axis, or transition moment in the visible light region is orthogonal to the molecule long axis And a fluorescent dichroic dye whose transition moment in the ultraviolet region is in the long axis direction of the molecule. 4. A pair of substrates, a liquid crystal layer sandwiched between the pair of substrates, and a reflector disposed outside the pair of substrates, wherein the reflector is on the liquid crystal layer side. A liquid crystal display device having a layer made of a fluorescent substance which is colorless and has blue fluorescence on the surface.