JPH0940964A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a guest/host liquid crystal display element having excellent light resistance, dichroic ratio and hue and the capability of an active-matrix drive and also having high voltage retention and high contrast. SOLUTION: This liquid crystal display element is composed of the first and second spaced and opposed substrates at least either of which has a transparent electrode and a liquid crystal layer sandwiched therebetween. The liquid crystal layer comprises a liquid crystal composition containing a liquid crystal compound and a plurality of dichroic anthraquinone colorants, and these colorants can afford the steric possibility for all of the hydrogen atoms of the hydrogen bonding substituents to form intramolecular hydrogen bonds.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device containing a liquid crystal composition containing a plurality of anthraquinone dyes.

[0002]

2. Description of the Related Art In an active matrix driving liquid crystal display element used for a thin film transistor or the like, since a liquid crystal material must hold a charge accumulated between frame frequencies, a material having a high voltage holding ratio should be used as the liquid crystal material. It is mandatory. Among these liquid crystal materials, a fluorine-based liquid crystal material having a fluorine atom or a fluoromethyl group such as a trifluoromethyl group or a fluoro atom such as a trifluoromethoxy group or a fluorine atom that does not easily contain an ionic impurity. However, they are being used in place of conventional liquid crystal materials containing a cyano group.

However, when a dichroic dye is added to such a liquid crystal material, there has been a problem that the voltage holding ratio characteristic of the host liquid crystal material is greatly impaired (for example, coloring material, Vol. 61). , No. 4, 227, 19
1988). In particular, when a plurality of dichroic dyes are contained for the purpose of displaying black or obtaining a predetermined spectral characteristic, the voltage holding characteristic is often greatly impaired. In the case of anthraquinone dyes, such a decrease in voltage holding ratio is generally smaller than that of azo dyes, but in many cases a satisfactory voltage holding ratio cannot be obtained.

When a plurality of liquid crystal cells obtained by encapsulating a liquid crystal composition between a pair of electrodes arranged to face each other are laminated to form a laminated liquid crystal cell, a dichroic dye is contained. When the retention characteristic of one liquid crystal layer is deteriorated, there is a problem that the voltage retention characteristic of the entire laminated liquid crystal cell is deteriorated.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a guest-host liquid crystal display device having excellent light resistance, dichroic ratio and color tone, capable of active matrix driving, high voltage holding ratio and high contrast. The purpose is to do.

[0006]

In order to solve the above-mentioned problems, the first invention is a first and a second invention which have transparent electrodes on at least one substrate and which are spaced apart and face each other. A substrate and a liquid crystal layer sandwiched between the substrates, wherein the liquid crystal layer contains a liquid crystal composition containing a liquid crystal compound and a plurality of anthraquinone dichroic dyes, and the dichroic dye is Provided is a liquid crystal display device characterized in that all hydrogen atoms of a hydrogen-bonding substituent can form an intramolecular hydrogen bond sterically.

The first invention is a multilayer liquid crystal display device in which a plurality of liquid crystal cells each having a pair of substrates arranged apart from each other and a liquid crystal layer sandwiched between the substrates are laminated, Contains a liquid crystal composition containing a liquid crystal compound and a dichroic dye, the entire liquid crystal layer contains a plurality of anthraquinone dichroic dye, and the anthraquinone dichroic dye is a hydrogen bond. Provided is a liquid crystal display device characterized in that all hydrogen atoms of the ionic substituent are sterically capable of forming an intramolecular hydrogen bond.

According to a second aspect of the invention, transparent electrodes are provided on at least one substrate, and the first and second substrates are separated and opposed to each other, and the liquid crystal layer is sandwiched between the substrates. The liquid crystal layer contains a liquid crystal composition containing a liquid crystal compound and a plurality of anthraquinone dichroic dyes, and all the anthraquinone dichroic dyes have a sum of Hammett sigma values of the substituents of −2 or more 0. Provided is a liquid crystal display device characterized by being in the following range.

Further, the second invention is a multi-layer liquid crystal display device in which a plurality of liquid crystal cells each having a pair of substrates arranged apart from each other and a liquid crystal layer sandwiched between the substrates are laminated, The contains a liquid crystal composition containing a liquid crystal compound and a dichroic dye, contains a plurality of anthraquinone dichroic dyes as a whole liquid crystal layer, and all the anthraquinone dichroic dyes, Provided is a liquid crystal display device characterized in that the sum of Hammett sigma values of the substituents is in the range of -2 to 0.

The liquid crystal composition used in the first invention will be described in detail below. The present inventors have found that among many dichroic dyes, when a dichroic dye having a hydrogen-bonding substituent is added to a host liquid crystal material, the voltage holding characteristic is significantly impaired. . The first invention is based on the following findings. That is, a hydrogen atom of a hydrogen-bonding substituent such as a hydroxyl group or an amino group forms a hydrogen bond with a carbonyl group or the like, and the hydrogen atom thus forming a hydrogen bond is easily dissociated as a proton. When a hydrogen bond occurs between dichroic dye molecules, the motion of the molecules causes the protons to diffuse in the liquid crystal according to the potential gradient,
As a result, the voltage holding ratio is lowered.

Moreover, since such a dichroic dye having a hydrogen-bonding substituent has high hydrophilicity, it is difficult to dissolve in a fluorine-based liquid crystal material having high hydrophobicity. Therefore, the color density cannot be increased and sufficient contrast cannot be obtained.

If only a dye compound having no hydrogen-bonding substituent is added to the liquid crystal material, problems such as a decrease in voltage holding ratio can be avoided, but sufficient light resistance and dichroic ratio are obtained, and color tone is also improved. By far the most commonly used dye compounds are of the anthraquinone type, most of which carry hydrogen-bonding substituents. Further, in a liquid crystal display element in which a plurality of dichroic dyes are used, when only dichroic dyes having no hydrogen bonding substituent are used in order to avoid a decrease in voltage holding ratio, light resistance, etc. It is practically difficult to obtain the desired characteristics in terms of

Therefore, in order to prevent the voltage holding ratio from being lowered while maintaining the properties such as light resistance, in the present invention, hydrogen bonds between dichroic dye molecules are completely prevented, and hydrogen-bonding substitution is performed. A dichroic dye was used in which all hydrogen atoms bonded to the group were capable of forming intramolecular hydrogen bonds.

That is, since the dichroic dye molecule has a hydrogen-bonding substituent, properties such as light resistance and dichroic ratio can be maintained. Furthermore, by creating hydrogen bonds within the dye molecule, protons are retained in the molecule,
Since the electrical neutrality of the molecule as a whole is maintained, the voltage holding ratio can be increased. Further, by maintaining the electrical neutrality of the entire dye molecule, the polarity of the dye molecule is also lowered and the solubility in the highly hydrophobic host liquid crystal is improved.

Whether or not the substituent bonded to the dichroic dye molecule is capable of sterically forming an intramolecular hydrogen bond is examined by a CPK molecular model or an analysis using a computer based on molecular mechanics. It is possible. Whether or not a hydrogen bond is actually formed can be examined by an infrared absorption spectrum, an NMR spectrum, or the like (for example, Takashi Araki,
Yoichiro Masuko, translated "Spectral identification of organic compounds", Tokyo Kagaku Dojin, 3rd edition, 1978).

Examples of the anthraquinone dichroic dye that can be used in the first invention include compounds represented by the formulas (1) to (9) shown in the following chemical formulas 1 and 2.

[0017]

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[0018]

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Furthermore, in addition to the anthraquinone type dichroic dyes shown in the above Chemical Formulas 1 and 2, an azo type dichroic dye represented by the following formula (10) is also used. Good.

[0020]

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As the liquid crystal compound (host liquid crystal material) to which the above-mentioned dichroic dye is added, the fluorine-based liquid crystal is most effective, but even if the cyano-based liquid crystal or the ester-based liquid crystal is used, the voltage holding ratio is high. And the solubility can be improved. Specifically, for example, a compound represented by the structural formula shown in Chemical Formula 4 below can be mentioned. These compounds may be used alone or in combination of two or more.

[0022]

Embedded image (In the above formula, R'and X are each independently an alkyl group, an alkoxy group, an alkylphenyl group, an alkoxyalkylphenyl group, an alkoxyphenyl group, an alkcyclohexyl group, an alkoxyalkylcyclohexyl group,
Alkylcyclohexylphenyl group, cyanophenyl group, cyano group, halogen atom, fluoromethyl group, phyllomethoxy group, alkylphenylalkyl group, alkoxyalkylphenylalkyl group, alkoxyalkylcyclohexylalkyl group, alkylcyclohexylalkyl group, alkoxyalkoxycyclohexylalkyl Group, an alkoxyphenylalkyl group, an alkylcyclohexylphenylalkyl group, Y is a hydrogen atom,
It represents a halogen atom and may have an optically active center in these alkyl chain and alkoxy chain. The phenyl group or phenoxy group in R'and X may be substituted with a halogen atom such as a fluorine atom or a chlorine atom. The phenyl group in each formula may be substituted with one or two fluorine atoms and halogen atoms such as chlorine atoms. The liquid crystal compound represented by the structural formula shown in Chemical Formula 4 has a positive dielectric anisotropy, but the compound that can be used in the first invention is not limited thereto. For example,
A known liquid crystal compound having a negative dielectric anisotropy can be mixed with a liquid crystal compound having a positive dielectric anisotropy to use the positive dielectric anisotropy as a whole. Further, even a liquid crystal compound having a negative dielectric anisotropy can be used as it is by using an appropriate element structure and driving method.

The liquid crystal composition used in the first invention can be prepared by dissolving the dichroic dye described above in the liquid crystal compound. The amount of the dye used is preferably 0.1 to 20% by weight, more preferably 0.3 to 3% by weight, based on the liquid crystal material.

The type of the dichroic dye added to the liquid crystal compound can be selected according to the desired constitution of the liquid crystal display device. For example, when used in a liquid crystal display device of a single layer cell, a liquid crystal composition is prepared by using a plurality of anthraquinone dichroic dyes. On the other hand, in the case of a laminated liquid crystal cell, it is necessary that the entire liquid crystal layer contains a plurality of anthraquinone dyes. Therefore, in some cases, the anthraquinone dye contained in the liquid crystal composition of each liquid crystal layer. May be one type.

The liquid crystal composition further comprises an optically active substance such as cholesteryl nonanoate, an ultraviolet absorber,
And additives such as antioxidants may be contained as necessary. The content of these additives can be appropriately selected.

Next, the liquid crystal composition used in the second invention will be described in detail. The present inventors have noticed that the azo dye has a voltage holding characteristic inferior to that of the anthraquinone dye and that the voltage holding characteristic is deteriorated even when the dye is mixed with a liquid crystal compound. The second invention has been reached based on the hypothesis that the electron level of the dye, that is, the HOMO and LUMO levels are involved.

Among various substances existing in the atmosphere, oxygen acts as an electron acceptor and amines act as an electron donor, so that a dye having a large donor property and a dye having a large acceptor property are respectively oxygen and amine. Cause charge transfer interaction with the class. As a result of such interaction, impurity carriers are generated in the liquid crystal, which causes deterioration of voltage holding ratio characteristics.

Since the interaction between substances such as oxygen and amines and the dye is large, they cannot be completely removed by applying a vacuum. In the case of a dichroic dye, it is considered that the reason why the azo dye is generally inferior in the voltage holding ratio characteristic due to the strong influence of oxygen is that the dye has a large donor property.

On the other hand, the anthraquinone dye is
Since the donor property is smaller than that of the azo dye and the interaction with oxygen is generally small, the voltage holding ratio characteristics are relatively excellent. However, depending on the type and number of the substituents bonded to the anthraquinone dye, the donor property or the acceptor property becomes large, and the voltage holding ratio characteristic deteriorates.

When a plurality of dichroic dyes are mixed and used, photosensitizing interaction occurs between the dyes having different electronic levels, which makes them more susceptible to oxygen and the like.
It is considered that the voltage holding ratio characteristics are deteriorated.

The electronic level of the anthraquinone type dichroic dye is determined by the substituent, and the most quantitative expression of the electronic property of the substituent is Hammett sigma (σ).
Known as the value. The σ value is an empirical parameter used in the Hammett's rule, and the Hammett's rule is used to quantify the effect of a substituent on the reaction rate or equilibrium of meta- and para-substituted benzene derivatives. P. H
This is a rule of thumb proposed by ammett. The standard of σ value is a hydrogen atom (σ = 0.00), the electron donating group is a negative value,
The electron-withdrawing group shows a positive value. This σ value is
´S HANDBOOK OF CHEMISTRY,
12th EDITION (3-134 to 3-137
Page, 1978). For substituents not listed, the σ values of the substituents with the most similar substituent structure away from the dye skeleton can be used. Table 1 below shows σ values of typical substituents.

[0032]

[Table 1]

For the anthraquinone dyes, the two σ values shown in Table 1 above are α with respect to the quinone carbonyl group.
The position is σ _para and the β position corresponds to σ _meta . With respect to the anthraquinone-based dichroic dyes having the substituents shown in Table 1, the reduction of the voltage holding ratio was examined, and the present inventors have found that the sum of the Hammett sigma (σ) values of the substituents bonded to the dye molecules is the sum. However, it has been found that the voltage holding ratio characteristic is less deteriorated in the range of −2 to 0. Further, with respect to the anthraquinone dye having a σ value within such a range, even if a plurality of kinds of them are mixed and used, the voltage holding ratio characteristic is less deteriorated. In addition, preferably, the total sum of the Hammett sigma values of the substituents is in the range of -1.5 to -0.5.

In the second invention, the dichroic dye that can be used is an anthraquinone-based dichroic dye represented by the formulas (1) to (9) shown in Chemical formulas 1 and 2 of the first invention. Is mentioned. Further, compounds represented by the formulas (11) to (14) shown in the following chemical formula 5 may be used.

[0035]

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In addition to these dyes, the azo type dichroic dye represented by the formula (10) shown in the chemical formula 3 may be used at the same time as in the first invention. Second
As the liquid crystal compound (host liquid crystal material) used in the present invention, a fluorine-based liquid crystal is most effective, but even if a cyano-based liquid crystal or an ester-based liquid crystal is used, it is possible to improve the voltage holding ratio and the solubility. it can. That is, a compound represented by the structural formula shown in Chemical Formula 4 above can be mentioned. These compounds may be used alone or in combination of two or more.

As in the case of the first invention, also in the second invention, for example, a known liquid crystal compound having a negative dielectric anisotropy is mixed with a liquid crystal compound having a positive dielectric anisotropy, and the whole is mixed. Can be used as positive. Also,
A liquid crystal compound having a negative dielectric anisotropy can be used as it is by using an appropriate element structure and driving method.

The liquid crystal composition used in the second invention can be prepared by dissolving the above-mentioned dichroic dye in the liquid crystal material, as in the case of the first invention. The amount of the dye used is preferably 0.1 to the liquid crystal material.
It is 20% by weight, and more preferably 0.3 to 3% by weight.

The type of the dichroic dye added to the liquid crystal compound can be selected according to the desired constitution of the liquid crystal display element, as described above. For example, when used in a liquid crystal display device of a single layer cell, a liquid crystal composition is prepared by using a plurality of anthraquinone dichroic dyes. On the other hand, in the case of a laminated liquid crystal cell, it is necessary that the entire liquid crystal layer contains a plurality of anthraquinone dyes. Therefore, in some cases, the anthraquinone dye contained in the liquid crystal composition of each liquid crystal layer. May be one type.

The liquid crystal composition further includes an optically active substance such as cholesteryl nonanoate, an ultraviolet absorber,
And additives such as antioxidants can be contained as necessary.

The present invention using a dichroic dye having a specific substituent as described above, or a liquid crystal composition containing a dichroic dye having a sum of Hammett sigma values of the substituents within a specific range is used. The liquid crystal display element can be configured as shown in FIG. 1, for example. As shown in FIG. 1, the liquid crystal display element 10 has substrates 11 and 12 which are spaced apart and face each other, and which are formed of a light transmissive material such as glass or a plastic film. Transparent substrates 11 and 12
Usually has a thickness of about 0.5 to 2 mm.

Inside the substrates 11 and 12, transparent electrodes 13 and 14 such as ITO are provided, respectively. An insulating layer may be formed on the inside of these electrodes, and in this case, it is preferable to perform an orientation treatment. Further, a gap (not shown) having an appropriate thickness is arranged between the substrates 11 and 12 to provide a gap for enclosing the liquid crystal composition 16.
The size of the gap is usually 50 μm or less, preferably 5 to 10 μm.

Both ends of the gap containing the liquid crystal composition 16 are sealed with a sealant 15 made of epoxy resin. The liquid crystal composition described above is a guest-
It can be applied to various liquid crystal display devices that apply the host effect. For example, "Liquid Crystal Device Handbook"
(No. 315 to 329, published by Nikkan Kogyo Shimbun, edited by 142nd Committee of Japan Society for the Promotion of Science)
meier type guest-host, phase transition type guest-host, and "liquid crystal device handbook" (edited by Japan Society for the Promotion of Science, 142nd Committee, published by Nikkan Kogyo Shimbun, Inc., 367-3).
70), polymer-dispersed guest-host, and the like.

Further, such a liquid crystal composition may be used as a so-called polymer dispersion type liquid crystal or a microcapsulated liquid crystal, in addition to the above-mentioned use form in which only the guest-host liquid crystal composition is sandwiched between the electrodes. it can. Also in this case, similarly to the above, maintaining characteristics such as light resistance,
It is possible to obtain the effect of preventing the reduction of the voltage holding ratio.

Further, the liquid crystal display element of the present invention may be a laminated liquid crystal cell in which a plurality of liquid crystal cells are laminated. In Figure 2,
The sectional view which represented typically an example of a multilayer liquid crystal cell is shown.
As shown in FIG. 2, the liquid crystal display element 20 has a transparent substrate 21 and a transparent thin plate 23 that are spaced apart and face each other. These substrates and the like can be made of the same glass or plastic as described above. The transparent thin plate 23 preferably has a thickness of 0.1 to 0.7 mm.

Transparent electrodes 22 made of ITO or the like are formed on the surfaces of the substrate 21 and the thin plate 23 that face each other. An insulating layer may be formed on the inside of these electrodes, and in this case, it is preferable to perform an orientation treatment. Further, a spacer 24 having an appropriate thickness is arranged between the substrates to form a gap for injecting the liquid crystal composition. The size of the gap is usually 50 μm or less, preferably 5 to 10 μm.

In the multilayer liquid crystal cell shown in FIG. 2, the glass thin plate 23 having the transparent electrodes 22 formed on the two opposing surfaces is used, but the invention is not limited to this, and only one surface is transparent. It is also possible to bond glass substrates having electrodes formed thereon and use the same structure.

In the liquid crystal display element shown in FIG. 2, the first liquid crystal layer 2 is provided between the glass substrates arranged opposite to each other.
5, three liquid crystal layers of the second liquid crystal layer 26 and the third liquid crystal layer 27 are formed, and a liquid crystal composition containing a liquid crystal compound and a dichroic dye is injected into each liquid crystal layer.

When a multilayer liquid crystal cell is formed in this way,
The liquid crystal layer is not particularly limited as long as it contains a plurality of anthraquinone-based dichroic dyes. For example, a liquid crystal compound injected into one liquid crystal cell may contain a plurality of anthraquinone dichroic dyes, or a liquid crystal compound containing one kind of anthraquinone dichroic dye may be mixed with a plurality of liquid crystal compounds. It can also be injected into the cell. A liquid crystal composition containing an azo dye or the like other than the anthraquinone dichroic dye may be injected into another liquid crystal cell as long as the constitution is satisfied.

In the case of a liquid crystal display device having three liquid crystal layers as shown in FIG. 2, the dichroic dye of the liquid crystal composition contained in each liquid crystal layer is yellow,
It can be a cyan and magenta dichroic dye. For example, a yellow dichroic dye is represented by the formula (1)
And a compound represented by the formula (11). Examples of the magenta dichroic dye include the formula (2) and the formula (12).
The compound represented by these is mentioned. Further, as the cyan dichroic dye, there are formula (3), formula (9) and formula (14).
The compound represented by these is mentioned.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of the present invention, but the present invention is not limited thereto unless it exceeds the gist thereof. (Example I) (Example I-1) Anthraquinone-based dichroic dyes represented by the formulas (1), (2) and (3) were mixed under the trade name ZLI-
A liquid crystal composition was prepared by mixing and dissolving a liquid crystal mixture containing a fluorine-based liquid crystal material commercially available as 4792 (manufactured by E. MERCK) at a concentration of 1% by weight.

The hydrogen-bonding substituents bonded to the compounds represented by the formulas (1), (2) and (3) all have a steric structure capable of forming an intramolecular hydrogen bond. A liquid crystal display element was manufactured as follows using the obtained liquid crystal composition. That is, first, a transparent electrode was formed on one surface of each of two glass substrates (thickness: 1 mm), and then a polyimide resin was applied. Then, a rubbing treatment was performed, and the glass substrates were arranged in parallel so as to be opposed to each other so that the transparent electrode sides of the glass substrates face each other, and cells having a gap of 9 μm were produced. The liquid crystal composition described above was sealed in this gap, and the gap was sealed with a sealant to obtain a liquid crystal display element of the present invention.

The device was baked at a constant temperature of 110 ° C. for 1 hour, and the voltage holding ratio of the liquid crystal composition at 100 ° C. was measured. The voltage holding ratio of the host liquid crystal only is 100
The specific voltage holding ratio was 96%. In addition,
The solubility of the dichroic dyes represented by the formulas (1) and (2) in the host liquid crystal was 3.2% by weight and 4.5% by weight at 20 ° C., respectively.

(Comparative Example I-1) The above-described procedure was carried out except that an anthraquinone type dichroic dye represented by the following formula (15) was used instead of the dichroic dye of the formula (1). A liquid crystal display device was manufactured in the same manner as in Example (I-1).

[0055]

[Chemical 6]

It should be noted that one of the hydrogen atoms of the hydrogen-bonding substituent contained in the dichroic dye represented by the formula (15) is sterically incapable of intramolecular hydrogen bonding. This device was baked under the same conditions as in Example (I-1), and the voltage holding ratio was measured in the same manner. The specific voltage holding ratio when the voltage holding ratio of the host liquid crystal alone was 100%. Was 60%. The solubility of the dichroic dye represented by the formula (15) in the host liquid crystal was 1.5% by weight at 20 ° C.

As described above, the dichroic dye having a substituent in which intramolecular hydrogen bonding is sterically impossible is poor in solubility in the host liquid crystal, and even when a small amount thereof is mixed with the host liquid crystal, The voltage holding ratio has dropped significantly.

Example I-2 Anthraquinone type dichroic dyes represented by formulas (4) and (5) were used in place of the dichroic dyes represented by formulas (1) and (2). A liquid crystal display device was manufactured in the same manner as in Example (I-1).

This device was baked under the same conditions as in Example (I-1) and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 98%. Further, the solubility of the dichroic dyes represented by the formulas (4) and (5) in the host liquid crystal is 3.6 at 20 ° C., respectively.
By weight and 4.5% by weight.

Example I-3 Anthraquinone type dichroic dyes represented by formulas (6) and (7) were used in place of the dichroic dyes represented by formulas (1) and (2). A liquid crystal display device was manufactured in the same manner as in Example (I-1).

This device was baked under the same conditions as in Example (I-1) and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 94%. Further, the solubility of the dichroic dyes represented by the formulas (6) and (7) in the host liquid crystal is 4.2 at 20 ° C., respectively.
% And 3.5% by weight.

(Comparative Example I-2) The dichroic dye represented by the formula (2) was replaced with the anthraquinone type dichroic dye represented by the formula (16) shown in the chemical formula 6 above. A liquid crystal display device was produced in the same manner as in Example (I-1) described above.

One of the hydrogen atoms of the hydrogen-bonding substituent contained in the dichroic dye represented by the formula (16) is sterically incapable of intramolecular hydrogen bonding. This device was baked under the same conditions as in Example (I-1), and the voltage holding ratio was measured in the same manner. The specific voltage holding ratio when the voltage holding ratio of the host liquid crystal alone was 100%. Is 55%
Met. The solubility of the dichroic dye represented by formula (16) in the host liquid crystal was 1.2% by weight at 20 ° C.

As described above, the dichroic dye having a substituent in which intramolecular hydrogen bonding is sterically impossible is poor in solubility in the host liquid crystal, and even when a small amount of it is mixed with the host liquid crystal, the voltage The retention rate has dropped significantly.

(Example I-4) The above-mentioned Example (I) was repeated except that the anthraquinone type dichroic dye represented by the formula (8) was used in place of the dichroic dye represented by the formula (3). −
A liquid crystal display device was produced in the same manner as 1).

This device was baked under the same conditions as in Example (I-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 97%. The solubility of the dichroic dye represented by the formula (8) in the host liquid crystal was 3.1% by weight at 20 ° C.

(Example I-5) The above-mentioned Example (I) was repeated except that the azo type dichroic dye represented by the formula (10) was used in place of the dichroic dye represented by the formula (1). A liquid crystal display device was produced in the same manner as in -1).

This device was baked under the same conditions as in Example (I-1) and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 90%. Equation (1)
The solubility of the dichroic dye represented by 0) in the host liquid crystal was 2.4% by weight at 20 ° C.

Example I-6 A yellow dichroic dye represented by the formula (1) was mixed with a liquid crystal mixture (ZLI-479).
The first liquid crystal composition was dissolved in 2) at a concentration of 1.5% by weight, and the magenta dichroic dye represented by the formula (2) was added to the liquid crystal mixture (ZLI-4792) in an amount of 1.5% by weight. The second liquid crystal composition was obtained by dissolving at a concentration of%. further,
The cyan dichroic dye represented by the formula (3) and the cyan dichroic dye represented by the formula (9) are mixed in a liquid crystal mixture (ZL
I-4792) was dissolved at a concentration of 1.0% by weight to prepare a third liquid crystal composition.

Using the obtained three kinds of liquid crystal compositions, a three-layer laminated liquid crystal cell as shown in FIG. 2 was manufactured. In addition,
This laminated liquid crystal cell was produced as follows. That is, the ITO electrodes are formed on both surfaces of the glass plate 23 having a thickness of 0.5 mm, and the ITO electrodes are formed on one surface of the glass plate 21 having a thickness of 1 mm.
The electrode was formed. After applying a polyimide film on this electrode, rubbing treatment was performed. Furthermore, after spraying 9 μm spacers, cells were assembled as shown in FIG.

The above-mentioned first, second and third liquid crystal compositions were sealed in the first layer, the second layer and the third layer of the three-layer cell, and the gaps were sealed with a sealant. A liquid crystal display device of the present invention was manufactured.

The device was baked at a constant temperature of 110 ° C. for 1 hour, and then the voltage holding ratio at 100 ° C. was measured. When the voltage holding ratio of only the host liquid crystal was set to 100%, the specific voltage holding ratio of all three layers was 95%.

(Example I-7) The above-mentioned Example (I) was repeated except that the azo type dichroic dye represented by the formula (10) was used in place of the dichroic dye represented by the formula (1). A liquid crystal display device was produced in the same manner as in (6).

This device was baked under the same conditions as in Example (I-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 90% for all three layers.

(Comparative Example I-3) The above-mentioned Example (I-6) was carried out except that the dichroic dye represented by the formula (15) was used in place of the dichroic dye represented by the formula (1). A liquid crystal display device was manufactured in the same manner as in (1).

This device was baked under the same conditions as in Example (I-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 95% or more in the second and third layers. However, the specific voltage holding ratio of the first layer containing a dichroic dye having a substituent in which intramolecular hydrogen bonding is impossible sterically was 50%, which was extremely low. Therefore, it was found that the liquid crystal display element as a whole is not suitable for driving a TFT.

From the above results, the anthraquinone type dichroic dye in which all the hydrogen atoms have a substituent capable of sterically forming an intramolecular hydrogen bond has a large solubility in the fluorine type host liquid crystal, and after addition, It was found that the decrease in the voltage holding ratio was extremely small. Furthermore, even if an azo dichroic dye is used in addition to a plurality of anthraquinone dichroic dyes, this effect is not affected at all. (Example II) (Example II-1) The anthraquinone-based dichroic dyes represented by the formulas (11), (12) and (3) were used under the trade name ZL.
I-4792 (manufactured by E. MERCK) was mixed and dissolved in a liquid crystal mixture containing a fluorine-based liquid crystal material as a main component at a concentration of 1% by weight to prepare a liquid crystal composition.

Note that equations (11), (12) and (3)
The total Hammett sigma value of the dichroic dye represented by
They are -0.68, -1.32 and -1.18, respectively. A liquid crystal display element was manufactured as follows using the obtained liquid crystal composition. That is, first, a transparent electrode was formed on one surface of each of two glass substrates (thickness: 1 mm), and then a polyimide resin was applied. Then
A rubbing process was performed, and the cells were arranged in parallel and spaced apart so that the transparent electrode sides of the glass substrates face each other, and a cell having a gap of 9 μm was produced. The liquid crystal composition described above was sealed in this gap, and the gap was sealed with a sealant to obtain a liquid crystal display element of the present invention.

The device was baked at a constant temperature of 110 ° C. for 1 hour, and the voltage holding ratio of the liquid crystal composition at 100 ° C. was measured. The specific voltage holding ratio was 97% when the voltage holding ratio of the host liquid crystal was 100%.

(Comparative Example II-1) An anthraquinone type dichroic dye represented by the formula (17) shown in the chemical formula 6 was used in place of the dichroic dye represented by the formula (3).
A liquid crystal display device was produced in the same manner as in Example (II-1) described above.

The total Hammett sigma value of the compound represented by the formula (17) is -2.02. This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The specific voltage holding ratio when the voltage holding ratio of the host liquid crystal alone was 100%. Was 68%. (Example II-2) Except that anthraquinone-based dichroic dyes represented by formulas (5) and (13) were used instead of the dichroic dyes represented by formulas (11) and (12).
A liquid crystal display device was manufactured in the same manner as in Example (II-1) described above. The sum of the Hammett sigma values of the compounds represented by formulas (5) and (13) is -0.34 and -0.52, respectively.

This device was baked under the same conditions as in Example (II-1) and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 95%.

(Example II-3) The above-mentioned Example (II) except that the anthraquinone-based dichroic dye represented by the formula (7) was used in place of the dichroic dye represented by the formula (12).
A liquid crystal display device was produced in the same manner as in -1). Equation (7)
The sum of the Hammett sigma values of the compounds represented by
It is 0.71.

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio was 100% when only the host liquid crystal was used. The voltage holding ratio was 97%.

(Comparative Example II-2) The above-mentioned Example (II) was repeated except that the anthraquinone dichroic dye represented by the formula (18) was used in place of the dichroic dye represented by the formula (11). A liquid crystal display device was produced in the same manner as in -1). The sum of the Hammett sigma values of the compound represented by the formula (18) is 0.1.

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100%. The voltage holding ratio was 59%.

As described above, it can be seen that the dichroic dye having the sum of the Hammett sigma values of the substituents larger than 0 significantly reduces the voltage holding ratio even when mixed in a small amount in the host liquid crystal.

(Example II-4) The above-mentioned example (except that the anthraquinone type dichroic dye represented by the formula (8) was used in place of the dichroic dye represented by the structural formula (3). A liquid crystal display device was produced in the same manner as in II-1). The sum of the Hammett sigma values of the compound represented by the formula (8) is −1.32.

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio was 100% when only the host liquid crystal was used. The voltage holding ratio was 94%.

(Example II-5) The above-mentioned Example (II) except that the azo type dichroic dye represented by the formula (10) was used in place of the dichroic dye represented by the formula (11). A liquid crystal display device was produced in the same manner as in -1).

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio was 100% when the host liquid crystal alone was used. The voltage holding ratio was 90%.

Example II-6 A yellow dichroic dye represented by the formula (11) was mixed with a liquid crystal mixture (ZLI-479).
The first liquid crystal composition was dissolved in 2) at a concentration of 1.5% by weight, and the magenta dichroic dye represented by the formula (12) was added to the liquid crystal mixture (ZLI-4792) in an amount of 1.5% by weight. The second liquid crystal composition was obtained by dissolving at a concentration of%. further,
The cyan dichroic dye represented by the formula (3) and the formula (14)
And a cyan dichroic dye represented by
LI-4792) was dissolved at a concentration of 1.0% by weight to prepare a third liquid crystal composition. Note that equation (14)
The sum of the Hammett sigma values of the compounds represented by
It is 0.76.

The above-mentioned first, second and third liquid crystal compositions were each enclosed in a first layer, a second layer and a third layer of a three-layer laminated liquid crystal cell as shown in FIG. The liquid crystal display device of the present invention was manufactured by sealing the gap with a sealant.

This device was baked under the same conditions as in Example (II-1) and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 94% for all three layers.

Example II-7 The above-mentioned Example (II) except that the azo type dichroic dye represented by the formula (10) was used in place of the dichroic dye represented by the formula (11). A liquid crystal display device was produced in the same manner as in (6).

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio was 90% or more in all three layers.

(Comparative Example II-3) The above-mentioned Example (except that the anthraquinone type dichroic dye represented by the structural formula (17) was used in place of the dichroic dye represented by the formula (3). A liquid crystal display device was produced in the same manner as II-6).

This device was baked under the same conditions as in Example (II-1), and the voltage holding ratio was measured in the same manner. The ratio when the voltage holding ratio of the host liquid crystal alone was 100% was obtained. The voltage holding ratio is 90% for the first and second layers
That was all. However, the third layer containing the dichroic dye of the formula (17) having a total Hammett sigma value of −2.02 is 75%, and as a whole liquid crystal display device, T
It turned out that it was not suitable for FT drive.

From the above results, the anthraquinone type dichroic dye having the sum of Hammett sigma values of the substituents in the range of -2 to 0 has a large solubility in the fluorine type host liquid crystal and, moreover, after addition, It was found that the decrease in voltage holding ratio was extremely small. Furthermore, in addition to multiple anthraquinone-based dichroic dyes, the use of azo-based dichroic dyes
It has no effect on this effect.

[0100]

As described above, according to the present invention,
Provided is a guest-host liquid crystal display device having excellent light resistance, dichroic ratio, and color tone, capable of active matrix driving, and having a high voltage holding ratio. Such a liquid crystal display device has a high solubility in a hydrophobic liquid crystal material, and its industrial value is enormous.

[Brief description of drawings]

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display element, 11 ... Transparent substrate, 12 ... Transparent substrate, 13 ... Transparent electrode 14 ... Transparent electrode, 15 ... Sealing agent, 16 ... Liquid crystal layer, 20
Liquid crystal display element 21 ... Glass substrate, 22 ... Transparent electrode, 23 ... Glass thin plate, 24 ... Spacer 25 ... First liquid crystal layer, 26 ... Second liquid crystal layer, 23 ... Third
Liquid crystal layer.

Claims (5)

[Claims] 1. A transparent electrode is provided on at least one substrate, and first and second substrates are arranged at a distance from each other and are opposed to each other, and a liquid crystal layer sandwiched between the substrates. The liquid crystal layer contains a liquid crystal composition containing a liquid crystal compound and a plurality of anthraquinone-based dichroic dyes, the anthraquinone-based dichroic dye, all hydrogen atoms of the hydrogen-bonding substituents, the intramolecular hydrogen. A liquid crystal display device characterized in that a bond can be three-dimensionally formed. 2. A multi-layer liquid crystal display device comprising a plurality of liquid crystal cells having a pair of substrates arranged apart from each other and a liquid crystal layer sandwiched between the substrates, wherein each liquid crystal layer contains a liquid crystal compound. A liquid crystal composition containing a dichroic dye is contained, and the entire liquid crystal layer contains a plurality of anthraquinone dichroic dyes, and the anthraquinone dichroic dye has all hydrogen-bonding substituents. A liquid crystal display device characterized in that a hydrogen atom is capable of forming an intramolecular hydrogen bond in three dimensions. 3. A liquid crystal layer having transparent electrodes on at least one substrate, spaced apart and opposed first and second substrates, and a liquid crystal layer sandwiched between the substrates. Contains a liquid crystal composition containing a liquid crystal compound and a plurality of anthraquinone-based dichroic dyes, and all the anthraquinone-based dichroic dyes have a sum of Hammett sigma values of substituents in the range of -2 or more and 0 or less. A liquid crystal display device characterized by being present. 4. A multi-layer liquid crystal display device comprising a plurality of liquid crystal cells having a pair of substrates arranged apart from each other and a liquid crystal layer sandwiched between the substrates, wherein each liquid crystal layer contains a liquid crystal compound. A liquid crystal composition containing a dichroic dye is contained, and the entire liquid crystal layer contains a plurality of anthraquinone dichroic dyes, and all the anthraquinone dichroic dyes have a Hammett sigma value of a substituent. Is in the range of -2 to 0, a liquid crystal display device. 5. The liquid crystal display according to claim 2, which has three liquid crystal layers, and the dichroic dye contained in the liquid crystal composition contained in each liquid crystal layer is yellow, cyan and magenta, respectively. element.