JPH10111523A - Guest host liquid crystal display - Google Patents

Abstract

(57) [Problem] To provide a composite black dichroic dye useful for a guest-host liquid crystal display device. SOLUTION: A guest host liquid crystal display device includes a pair of substrates 1 and 2 bonded to each other via a predetermined gap, and a guest containing a composite type dichroic dye 3 and held in the gap between the two substrates 1 and 2. A host liquid crystal 4 and electrodes 5 and 6 formed on each of the substrates 1 and 2 for applying a voltage to the guest host liquid crystal 4 are provided. The dichroic dye 3 is an orange dye having an absorption maximum at least around 450 nm, a red dye having an absorption maximum in the range of 500 nm to 560 nm, a magenta / blue dye having an absorption maximum in the range of 580 nm to 600 nm, and 630 nm to 660 nm. And a mixture containing a blue dye having an absorption maximum in the range described above, so that when added to the guest-host liquid crystal 4, it is compounded so as to exhibit a black color as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a guest-host liquid crystal display device. More specifically, the present invention relates to a composition of a dichroic dye added as a guest to a nematic liquid crystal serving as a host.

[0002]

2. Description of the Related Art In a guest-host liquid crystal display device, a dichroic dye is dissolved in a nematic liquid crystal, and the orientation of the dichroic dye is controlled together with the nematic liquid crystal molecules by the action of an electric field. The dichroic dye has anisotropy in light absorption, and uses this to control the transmitted light of the liquid crystal display device. This guest-host liquid crystal display device includes a transmission type and a reflection type. In any case, a black dichroic dye is used for black and white display. Further, when this is combined with a micro color filter, a full-color guest-host liquid crystal display device can be obtained. Therefore, the dichroic dye must first be a black dye suitable for monochrome display. However, it is difficult to achieve black with a single color dye. Usually, several types of monochromatic dyes are blended to prepare a composite black dye.

[0003]

In general, dichroic dyes are required to have the following characteristics. (1) The dichroic ratio is high, (2) the extinction coefficient is high, and (3) the compatibility or solubility with the liquid crystal is high. That is, the higher the dichroic ratio, the greater the anisotropy of light absorption, and the higher the contrast. Also, as the extinction coefficient increases, a sufficient contrast can be obtained with a small amount of addition. Furthermore, the higher the solubility in the liquid crystal, the lower the deposition at low temperatures and the higher the desired contrast. By the way, for a black pigment, 400 nm to 700 nm
It is necessary to have a large absorption in a wide visible light wavelength region and a high dichroic ratio. Therefore, it is necessary that a plurality of monochromatic dyes constituting the black dye body satisfy the above conditions (1) to (3). However, it is not easy to prepare dyes satisfying the above conditions in all wavelength ranges. Even if such a dye is prepared, it is not easy to prepare a sufficient black dye by blending. In particular, as a blue dye having an absorption maximum at 600 nm or more, an anthraquinone dye having good light resistance has been used. However, this type of dye had to be added in large amounts in order to increase the contrast because of its low extinction coefficient. Addition of a large amount not only tends to cause low-temperature precipitation of the dye, but also deteriorates the operation characteristics of the liquid crystal because the dye, which is essentially an impurity, is mixed. In particular, recently, as active matrix type liquid crystal display devices using thin film transistors for pixel switching have become mainstream, it is necessary to maintain normal operation characteristics of liquid crystals.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a guest-host liquid crystal display device using a composite black dye having high dichroic ratio, extinction coefficient and high compatibility with liquid crystal. The purpose is to provide. The following measures were taken to achieve this purpose. That is, the guest-host liquid crystal display device according to the present invention has a basic configuration,
A pair of substrates joined to each other via a predetermined gap, a guest-host liquid crystal containing a complex type dichroic dye and held in the gap, and an electrode formed on each substrate and applying a voltage to the guest-host liquid crystal And Characteristically, the dichroic dye is an orange dye having an absorption maximum at least around 450 nm, a red dye having an absorption maximum in the range of 500 nm to 560 nm, and a magenta / blue dye having an absorption maximum in the range of 580 nm to 600 nm. And a mixture containing a blue dye having an absorption maximum in the range of 630 nm to 660 nm, and is blended so as to exhibit a black color as a whole when added to the guest-host liquid crystal. Preferably, the dichroic dye further comprises a mixture containing a yellow dye having an absorption maximum near 400 nm and a blue dye having an absorption maximum near 700 nm.
It has a substantially flat absorption in the visible light wavelength region from 00 nm to 700 nm. The dichroic dye is 400
500 nm to 620 in the visible light wavelength region of 500 nm to 700 nm.
Absorption is relatively large in the wavelength range of nm, and relatively small in the wavelength range of 500 nm or less and 620 nm or more. For example, when the dichroic dye is added to a guest host liquid crystal having a thickness of 5 μm, the absorbance at 400 nm to 500 nm is 0.8 μm.
~ 1.0, absorbance at 500nm ~ 650nm is 1.0 ~
At 1.5, the absorbance at 650-700 nm is 1.0-1.
It is gradually falling from 5. Preferably, the dichroic dye is added to the guest-host liquid crystal at a ratio of 1.0% by weight to 5.0% by weight. Further, the dichroic dye is preferably added to the guest-host liquid crystal at a ratio of 2.0% by weight to 4.0% by weight. Preferably, the guest-host liquid crystal display device is mainly composed of nematic liquid crystal molecules having negative dielectric anisotropy, and has a molecular orientation perpendicular to upper and lower substrates.
Preferably, one substrate is transparent and located on the incident side, and the other substrate is located on the reflecting side and has a reflecting layer and a quarter-wave plate layer formed in order from the bottom.

The composite dichroic dyes according to the present invention are black, ie have a high absorption and a dichroic ratio in the entire wavelength range from 400 nm to 700 nm. Ideally, the composite dichroic dye should be 40
Yellow dye with absorption maximum (λmax) near 0 nm, 450 nm
Orange dye having λmax in the vicinity, red dye having λmax in the vicinity of 500 nm to 560 nm, λ in the vicinity of 580 nm to 620 nm
magenta / blue dye with max, 630nm-660nm
Blue dye with λmax near λmax and λmax near 700 nm
Is a composition in which six kinds of blue pigments having the following formulas are mixed, and has a flat absorption in the entire wavelength region of visible light. In addition, even if a yellow dye having an absorption maximum near 400 nm and a blue dye having an absorption maximum near 700 nm are excluded from the relationship of human visibility,
It is possible to realize a black color that is apparently enough for practical use. In this case, the number of added dyes can be reduced from six to four. Further, if the absorption coefficients of the remaining four kinds of dyes to be added are high, there is an advantage that a high contrast can be obtained by adding a small amount of the whole mixture. Considering the visibility, the absorption around 500 nm to 620 nm is large, and the absorption is slightly smaller in other wavelength ranges. As a measure of absorption, for example, in a guest-host liquid crystal cell having a thickness of 5 μm, the absorbance at 400 nm to 500 nm is 0.8 to
1.0, absorbance at 500 nm to 650 nm is 1.0 to 1.5
It is preferred that On the longer wavelength side than 650 nm, 5
The absorbance may be reduced as the wavelength becomes longer on the extension of the absorber of 00 nm to 650 nm. Preferably, the concentration of the dichroic dye is 1% by weight to 5% by weight based on the liquid crystal. More preferably, the dichroic dye is from 2% by weight to
Add 4% by weight. If the amount is more than this, precipitation at a low temperature is large, and the electro-optical characteristics are adversely affected. If it is less than this, the absorption is low and the contrast cannot be sufficiently obtained.
The guest host liquid crystal mainly uses nematic liquid crystal molecules having negative dielectric anisotropy, and the liquid crystal molecules are vertically aligned. In this case, a white state easily appears and the contrast is increased.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a basic configuration of a guest-host liquid crystal display device according to the present invention. (A) shows a voltage non-applied state (off state),
(B) shows a voltage application state (ON state). As shown in the drawing, the guest-host liquid crystal display device has a basic configuration in which a pair of substrates 1 and 2 bonded to each other with a predetermined gap therebetween and a composite type dichroic dye 3
The liquid crystal display includes a guest-host liquid crystal 4 held in a gap between the two, and a counter electrode 5 and a reflection electrode 6 formed on each of the substrates 1 and 2 for applying a voltage to the guest-host liquid crystal 4. As a characteristic feature, the dichroic dye is an orange dye having an absorption maximum at least around 450 nm (hereinafter referred to as dye B), 500 nm to 560.
red dye having an absorption maximum in the range of nm (hereinafter referred to as Dye C), magenta / blue dye (hereinafter referred to as Dye D) having an absorption maximum in the range of 580 nm to 600 nm, and 630 nm to
Blue dye having an absorption maximum in the range of 660 nm (hereinafter referred to as dye E
) Is added to the guest-host liquid crystal 4 so as to exhibit a black color as a whole. In some cases, the dichroic dye 3 is a mixture further containing a yellow dye having an absorption maximum around 400 nm (hereinafter referred to as dye A) and a blue dye having an absorption maximum near 700 nm (hereinafter referred to as dye F). Is also good. In this case 40
It has a substantially flat absorption in the visible light wavelength region of 0 nm to 700 nm. When the dichroic dye 3 according to the present invention contains four essential dyes B, C, D and E, the mixture as a whole has a relatively high luminosity in the visible light wavelength region of 400 nm to 700 nm. The absorption is relatively large in the high wavelength range of 500 nm to 620 nm, and the visibility is relatively low at 500 nm.
Absorption is relatively small below and in the wavelength range above 620 nm. For example, the dichroic dye 3 according to the present invention has a thickness of 5 μm.
400 nm to 50 nm
The absorbance at 0 nm is 0.8-1.0, and 500 nm-650 nm
Has an absorbance of 1.0 to 1.5, and the absorbance at 650 nm to 700 nm gradually decreases from 1.0 to 1.5. The dichroic dye 3 is added to the guest-host liquid crystal 4 at a ratio of 1.0% by weight to 5.0% by weight. More preferably, 2.0
% By weight to 4.0% by weight. If the addition amount is larger than this, precipitation at a low temperature is large, and the electro-optical characteristics of the guest-host liquid crystal 4 are adversely affected. If the amount is less than this, the absorption is low and the contrast cannot be sufficiently obtained. Guest Host LCD 4
Are mainly composed of nematic liquid crystal molecules 7 having a negative dielectric anisotropy, and are vertically oriented with respect to the upper and lower substrates 1 and 2. In the vertical alignment, a white state is more likely to appear and the contrast is higher than in the horizontal alignment. The present guest host liquid crystal display device is of a reflection type. One substrate 1 is transparent and located on the incident side, and the other substrate 2 is located on the reflecting side and has a reflective layer and a quarter-wave plate layer 8 formed in order from the bottom. In this example, the reflection layer also serves as the reflection electrode 6.

In this embodiment, a reflection type guest-host liquid crystal display device is obtained without using a polarizing plate by incorporating the quarter-wave plate layer 8 and the reflection layer (reflection electrode) 6. In order to obtain a black-and-white contrast, the nematic liquid crystal molecules 7 are vertically aligned in the state (A) where the applied voltage is off. Following this, the dichroic dye 3 is also vertically aligned,
High reflectance is obtained without absorbing incident light. On the other hand, when the voltage is applied as shown in FIG. 3B, the dichroic dye 3 moves in the horizontal direction together with the nematic liquid crystal molecules 7, so that the light absorption increases and the reflectance decreases. Therefore, a black display is obtained. This change in absorption is further accentuated by the provision of the quarter-wave plate layer 8. The present guest host liquid crystal display device is of a reflection type and can perform monochrome display. In some cases, full-color image display can be performed by inserting a micro color filter. In this configuration, the most important thing is that the dichroic dye 3 exhibits a neat black color. In view of this point, in the present invention, by mixing at least four types of monochromatic dyes B, C, D, and E having different absorption maximums, a composite black dichroic dye having a high absorption and a dichroic ratio can be obtained. Has been realized. Further, by adding two types of monochromatic dyes A and F, an ideal black dye having flat absorption in almost the entire wavelength region can be obtained. However, the dyes A and F are not necessarily essential. 400 due to human visibility
Even if the dye A having an absorption maximum near nm and the dye F having an absorption maximum near 700 nm are excluded, it is possible to realize a black color apparently enduring practical use. In this case, there is an advantage that a high contrast can be obtained by adding a small amount of the dye if only a small number of dyes are required and the absorption coefficient of these dyes is high. Thereby, adverse effects on the electro-optical characteristics of the guest-host liquid crystal are reduced.

The operation of the guest-host liquid crystal display device shown in FIG. 1 will be described in detail with reference to FIG. (A) is a state in which no voltage is applied, the display device is in a transmissive state, and white is displayed. (B) shows a voltage applied state, and the display device is in an absorbing state, and black is displayed. First, consider a case where light is incident from the outside in the state of (A) where no voltage is applied. The incident light can be considered separately as a first vibration component X and a second vibration component Y, which are polarization components orthogonal to each other. The vibration component X is linearly polarized light parallel to the paper surface, and the other vibration component Y is linearly polarized light perpendicular to the paper surface. When no voltage is applied, the nematic liquid crystal molecules 7 are vertically aligned. In accordance with this, the dichroic dye 3 is also vertically aligned. Therefore, both the vibration component X and the vibration component Y are completely transmitted through the guest-host liquid crystal layer 4. In the reflected light, only the vibration component X and the vibration component Y are interchanged, and no light modulation is performed. On the other hand, in the voltage application state (B), the nematic liquid crystal molecules 7 having negative dielectric anisotropy shift from vertical alignment to horizontal alignment. Along with this, the dichroic dye 3 also shifts from vertical alignment to horizontal alignment. Since one vibration component X is the same as the horizontal alignment direction of the liquid crystal molecules 7, it is absorbed by the black dichroic dye 3 aligned in the same direction. However, the other vibration component Y is not absorbed at all because it is orthogonal to the horizontal orientation direction of the dye molecule. Therefore, the vibration component Y is the guest host liquid crystal 4
And further enters the quarter-wave plate layer 8. Thereafter, the light is reflected by the reflection electrode 6 and again passes through the quarter-wave plate layer 8. The vibration component Y has passed through the quarter-wave plate layer 8 twice in a reciprocating manner, and the polarization direction is rotated by 90 °. Then, since this time coincides with the horizontal alignment direction of the dichroic dye 3,
Light is absorbed. In this manner, all the vibration components included in the incident light are absorbed in either the outward path or the return path, so that a contrast equivalent to that of a transmission type guest-host liquid crystal display device with a polarizing plate can be obtained without a polarizing plate.

Hereinafter, specific examples of the composite dichroic dye according to the present invention will be described in detail. As described above, it is difficult to realize a black pigment with a single pigment, and in the present invention, a black pigment is prepared by mixing at least four or more monochromatic pigments. An ideal black color can be realized by mixing six types of dyes having absorption maximums at different wavelengths in the wavelength range of 400 nm to 700 nm. In the first embodiment, six kinds of dyes A, B and D having different absorption maximums in the visible light wavelength region are used.
An ideal composite black dichroic dye is obtained by mixing all of C, D, E, and F. FIGS. 10 to 13 show the molecular structural formulas of the respective dyes. As the yellow dye A having an absorption maximum (λmax) near 400 nm, dyes Nos. 1 and 2 shown in FIG. 10 can be mentioned. Further, as the orange dye B having λmax at around 450 nm, dye numbers 3 and 4 shown in FIG.
Dyes. Λmax around 500 nm to 560 nm
Dye numbers 5 to 5 shown in FIG.
8 dyes. Λma around 580 nm to 600 nm
As the magenta / blue dye D having x, the dyes of dye Nos. 9 to 12 shown in FIG. 12 and the dye of dye No. 14 shown in FIG. Λ around 630 nm to 660 nm
As the blue dye E having max, there are dyes of dye numbers 13 and 15 shown in FIG. Finally, as the blue F having a λmax near 700 nm, the dye of dye No. 16 shown in FIG. 13 can be mentioned. All of these dyes have high dichroism and high light absorption, and also have excellent compatibility with nematic liquid crystals. If a dye material is selected according to the absorption wavelength, and the mixing ratio is set in consideration of the respective extinction coefficients, a black dye having flat absorption can be realized.

FIG. 3 shows an absorption spectrum of a composite black dichroic dye obtained by mixing all six dyes A to F at an appropriate ratio. The horizontal axis represents the wavelength and the vertical axis represents the absorbance. This graph was measured using a cell in which a guest-host liquid crystal to which a dichroic dye was added was horizontally aligned. The cell thickness is 4.4 μm. By switching the polarizing plate between parallel and perpendicular to the horizontal alignment direction, an absorption state and a transmission state are realized. As is clear from the graph,
In the absorption state, the composite black dichroic dye according to this example has a flat absorption distribution over almost the entire visible light wavelength region.

The first embodiment described above is an ideal case. In practice, it is necessary to prepare a plurality of dyes having different absorption wavelengths and a high dichroic ratio, and to mix a large number of dyes. As a result, the total amount added to the liquid crystal increases. In some cases, it is not preferable in terms of low-temperature crystal precipitation and influence on the electro-optical characteristics of the liquid crystal display device. In view of human luminosity, the dyes A and F are not necessarily indispensable and can be omitted because the luminosity is low in this wavelength range. For example, dyes A, B, C, D, and E were mixed to obtain a composite black dichroic dye having an absorption spectrum as shown in FIG. 4 as a second example. Compared with the first embodiment, only the dye F is missing. As is clear from the graph shown in FIG. 4, the absorption of the composite black dye according to the second embodiment is not necessarily flat in the wavelength region of visible light, but a black color that is practically satisfactory is realized. is made of. Considering the visibility, the absorption around 500 nm to 620 nm is large, and the absorption at other wavelengths may be slightly smaller. As a measure of absorption, a cell with a thickness of 5 μm, 400 nm
Absorbance at ~ 500 nm is 0.8-1.0, 500 nm-65
The absorbance at 0 nm is preferably 1.0 to 1.5.
If the wavelength is longer than 650 nm, the wavelength may be reduced as the wavelength becomes longer in the extension of 500 nm to 650 nm.

Next, the mixture of dichroic dyes according to the second embodiment described above was actually applied to a cell to examine electro-optical characteristics. First, a mixture of dichroic dyes was dissolved in a total of 3% by weight in a nematic liquid crystal having a negative dielectric anisotropy (dielectric anisotropy Δε = −4.6). 5 μm to evaluate this
A liquid crystal cell of a transmission type having a gap of was formed. A vertical alignment film was applied on the transparent electrodes provided on both substrates and rubbed. The guest-host liquid crystal was injected into this, and electro-optical characteristics were examined using one polarizing plate. An AC electric field having a frequency of 60 Hz is applied to this cell,
FIG. 5 shows the result of measuring the change in transmittance with respect to the applied voltage. The measurement wavelength at this time was 560 nm. As is clear from the graph of FIG. 5, the guest-host liquid crystal exhibits a steep threshold characteristic, and changes between an absorption state and a transmission state according to an applied voltage. The threshold voltage is approximately 3V. FIG. 6 shows a change in transmittance of the liquid crystal cell using the applied voltage as a parameter. As is clear from the graph, a high transmittance change was observed according to the applied voltage. When 5 V is applied, the polarizing plate 1
Almost black was realized in a state where the sheets were used.

Next, a third embodiment will be described. As described above, in the present invention, dyes having the molecular structural formulas shown in FIGS. 10 to 13 are classified into A to F according to their absorption wavelengths,
By mixing each, at least 4 in the visible wavelength range
Almost flat light absorption can be realized in the wavelength range of 50 nm to 650 nm, and black can be expressed. Ideally, all six dyes A to F are used, but it is also possible to produce black efficiently with fewer dyes. In other words, utilizing the difference in luminosity factor with respect to human colors,
-500 nm and 650 nm-700 nm
By increasing the absorption between 00 nm and 650 nm,
C, D, and E can be reduced to four types, and apparent black can be expressed. FIG. 7 shows the absorption spectrum. However,
The data in FIG. 7 was evaluated in a horizontal alignment cell as in FIG. In this embodiment, the dye B is selected from the dye No. 3, the dye C is selected from the dye No. 7, the dye D is selected from the dye No. 14, and the dye E is selected from the dye No. 13. did. A guest-host liquid crystal composition having the absorption spectrum shown in FIG. 7 was obtained from these four components. The total amount of the dye added to the guest-host liquid crystal composition was 3% by weight. FIG. 8 shows a change in the transmission spectrum with respect to the applied voltage. As is evident from this graph, sufficient black was able to be expressed at a practical level. Note that the types and mixing ratios of the dyes B to E are not limited to those in the above-described embodiment, and various changes can be made.

Finally, a specific configuration example of the guest-host liquid crystal display device according to the present invention will be described with reference to FIG.
This embodiment is of a reflection type, employs an active matrix system, and incorporates a micro color filter to enable full color display. As shown in the figure, the present display device is configured using a pair of upper and lower substrates 101 and 102 bonded to each other via a predetermined gap (5 μm). Upper substrate 1
Numeral 01 is located on the incident side and is made of a transparent base material such as glass. On the other hand, the lower substrate 102 is located on the reflection side, and it is not always necessary to use a transparent material. A guest-host liquid crystal 103 is held in a gap between the pair of substrates 101 and 102. The guest-host liquid crystal 103 mainly includes nematic liquid crystal molecules 104 having negative dielectric anisotropy, and contains a complex type dichroic dye 105 at a predetermined ratio according to the present invention. On the inner surface of the upper substrate 101, a micro color filter 150, a counter electrode 106, and an alignment layer 107 are formed. The counter electrode 106 is made of a transparent conductive film such as ITO. The alignment layer 107 is made of, for example, a polyimide film, and vertically aligns the guest-host liquid crystal 103. still,
The present invention is not limited to this, and the guest-host liquid crystal may be horizontally aligned. In this embodiment, the guest-host liquid crystal 103 is vertically aligned when no voltage is applied, and shifts to horizontal alignment when a voltage is applied. On the lower substrate 102, at least a switching element including a thin film transistor 108, a reflective layer 109, a quarter-wave plate layer 110, and a pixel electrode 11
1 are formed. As a basic configuration, the pixel electrode 111 is patterned on the thin film transistor 108 and the reflective layer 109. Therefore, it is possible to apply a sufficient electric field to the guest host liquid crystal 103 between the pixel electrode 111 and the counter electrode 106. This pixel electrode 111 has a contact hole 1 opened in the quarter-wave plate layer 110.
12 and electrically connected to the thin film transistor 108.

Hereinafter, a specific description will be given for each element. In this embodiment, the quarter-wave plate layer 110 is composed of a uniaxially oriented polymer liquid crystal film. A base alignment layer 113 is used to uniaxially align the polymer liquid crystal film. A flattening layer 114 is interposed to fill the unevenness of the thin film transistor 108 and the reflective layer 109, and the above-described base alignment layer 113 is formed on the flattening layer 114.
Then, the quarter-wave plate layer 110 also has the flattening layer 114.
Is formed on the surface. In this case, the pixel electrode 111 is connected to the thin film transistor 108 via the contact hole 112 provided through the quarter-wave plate layer 110 and the flattening layer 114. The reflection layer 109 is subdivided corresponding to each pixel electrode 111. Each of the subdivided portions is connected to the same potential as the corresponding pixel electrode 111. With such a configuration, an unnecessary electric field is not applied to the quarter-wave plate layer 110 or the flattening layer 114 interposed between the reflective layer 109 and the pixel electrode 111. The reflection layer 109 is provided with a scattering reflection surface as shown in the figure, and improves the image quality by preventing the specular reflection of incident light. The alignment layer 11 is formed so as to cover the surface of the pixel electrode 111.
5 is formed, and is in contact with the guest-host liquid crystal 103 to control its orientation. In this example, the alignment layer 115
, Together with the facing alignment layer 107, vertically aligns the guest-host liquid crystal 103. Finally, the thin film transistor 108 has a bottom gate structure, and the gate electrode 116, the gate insulating film 117, and the semiconductor thin film 1
18 has a laminated structure. Semiconductor thin film 118
Is made of, for example, polycrystalline silicon, and a channel region aligned with the gate electrode 116 is protected by a stopper 119 from above. The bottom-gate thin film transistor 108 having such a configuration is covered with an interlayer insulating film 120. A pair of contact holes are opened in the interlayer insulating film 120, and the source electrode 121 is
The drain electrode 122 is electrically connected to the thin film transistor 108. These electrodes 121 and 122 are, for example, patterned aluminum. The drain electrode 122 has the same potential as the reflection layer 109. or,
The pixel electrode 111 is electrically connected to the drain electrode 122 via the contact hole 112 described above. On the other hand, a signal voltage such as a video signal is supplied to the source electrode 121. On the side of the counter electrode 106 facing the pixel electrode 111, a micro color filter 150 that is divided for each pixel and colored in different colors is formed. A video signal was input to a reflective guest-host liquid crystal display device having such a configuration to display an image. A vivid full-color video was displayed and a high-contrast screen was obtained.

[0016]

As described above, according to the present invention,
A complex type black dichroic dye is prepared by mixing a plurality of types of monochromatic dyes having different absorption maxima in the visible light wavelength region. True black can be expressed by using a guest-host liquid crystal in which this composite dichroic dye is dissolved in a nematic liquid crystal. By adjusting the dye concentration, the absorbance required to express black can be obtained, and by selecting a dye with a good dichroic ratio, white display can be maintained at a high level, and a display with good contrast can be obtained. Is now available. By using a plurality of types of dyes having a high absorbance and a high dichroic ratio, a small amount of the dye was added, and the problem of crystal precipitation at low temperatures was solved. Further, the type of the pigment can be set to the minimum and the density of the pigment can be reduced by considering human visibility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a guest-host liquid crystal display device according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the guest-host liquid crystal display device according to the present invention.

FIG. 3 is a graph showing an absorption spectrum of a guest-host liquid crystal display device according to the present invention.

FIG. 4 is a graph showing an absorption spectrum of another embodiment of a guest-host liquid crystal display device according to the present invention.

FIG. 5 is a graph showing an applied voltage / transmittance characteristic of a guest-host liquid crystal display device according to the present invention.

FIG. 6 is a graph showing a transmission spectrum change according to an applied voltage of the guest-host liquid crystal display device according to the present invention.

FIG. 7 is a graph showing an absorption spectrum of another embodiment of the guest-host liquid crystal display device according to the present invention.

FIG. 8 is a graph showing a transmission spectrum change according to an applied voltage in another embodiment of the guest-host liquid crystal display device according to the present invention.

FIG. 9 is a schematic partial cross-sectional view showing a specific configuration example of a guest-host liquid crystal display device according to the present invention.

FIG. 10 is a chemical structural diagram showing an example of a dye used in a guest-host liquid crystal display device according to the present invention.

FIG. 11 is a chemical structural formula of the dye.

FIG. 12 is a chemical structural formula of the same dye.

FIG. 13 is a chemical structural formula of the same dye.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Substrate, 3 ... Dichroic dye, 4 ... Guest host liquid crystal, 5 ... Counter electrode, 6 ... Reflection electrode, 7 ... Nematic liquid crystal molecule, 8 ... Quarter wave plate layer

Claims (8)

[Claims] 1. A pair of substrates joined to each other via a predetermined gap, a guest-host liquid crystal containing a complex type dichroic dye and held in the gap, and a guest-host liquid crystal formed on each substrate. A guest-host liquid crystal display device comprising an electrode for applying a voltage, wherein the dichroic dye is an orange dye having an absorption maximum at least around 450 nm, a red dye having an absorption maximum in the range of 500 nm to 560 nm, and 580 nm A mixture comprising a magenta / blue dye having an absorption maximum in the range of -600 nm and a blue dye having an absorption maximum in the range of 630 nm to 660 nm, and formulated so as to exhibit a black color as a whole when added to the guest-host liquid crystal. A guest-host liquid crystal display device. 2. The dichroic dye further comprises a mixture containing a yellow dye having an absorption maximum near 400 nm and a blue dye having an absorption maximum near 700 nm.
2. The guest-host liquid crystal display device according to claim 1, wherein the liquid crystal display device has a substantially flat absorption in a visible light wavelength region of nm. 3. The dichroic dye as a whole as a mixture of 4
500 nm to 6 out of the visible light wavelength range of 00 nm to 700 nm
2. The guest-host liquid crystal display device according to claim 1, wherein absorption is relatively large in a wavelength range of 20 nm and relatively small in a wavelength range of 500 nm or less and 620 nm or more. 4. When the dichroic dye is added to a guest-host liquid crystal having a thickness of 5 μm, the absorbance at 400 nm to 500 nm is 0.8 to 1.0, and the absorbance at 500 nm to 650 nm is 1.0 to 1.0. 5, the absorbance at 650 nm to 700 nm is 1.
4. The guest-host liquid crystal display device according to claim 3, wherein the temperature gradually decreases from 0 to 1.5. 5. The method according to claim 1, wherein the dichroic dye is 1.0% by weight to 5.0% by weight.
2. The guest-host liquid crystal display according to claim 1, wherein the liquid crystal is added to the guest-host liquid crystal at a ratio of% by weight. 6. The guest-host liquid crystal according to claim 1, wherein the guest-host liquid crystal is mainly composed of nematic liquid crystal molecules having negative dielectric anisotropy, and has a molecular orientation perpendicular to upper and lower substrates. Display device. 7. One of the substrates is transparent and located on the incident side, and the other substrate is located on the reflecting side and has a reflecting layer and a quarter-wave plate layer formed in order from the bottom. Item 1
2. The guest-host liquid crystal display device according to claim 1. 8. A pair of substrates joined to each other via a predetermined gap, a guest-host liquid crystal containing a complex type dichroic dye and held in the gap, and a guest-host liquid crystal formed on each substrate. A guest-host liquid crystal display device comprising an electrode for applying a voltage, wherein the dichroic dye comprises a mixture of monochromatic dichroic dyes having different absorption maxima in a visible light wavelength region of 400 nm to 700 nm, and as a whole A guest-host liquid crystal display device having a relatively large absorption in a wavelength range of 500 nm to 620 nm and a relatively small absorption in a wavelength range of 500 nm or less and 620 nm or more.