JPH0759702B2 - Guest-host liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a guest-host liquid crystal composition having high contrast and high-speed response, in particular, a color filter is arranged on one of the glass substrates constituting a display cell, and a transparent film facing each other. Used for a display that provides a good color display by interposing a liquid crystal composition having a positive dielectric anisotropy with a dichroic dye having different absorbance depending on the orientation direction of molecules between the glass substrate having an electrode. The present invention relates to a guest / host liquid crystal composition.

[Conventional technology]

Display devices using liquid crystals are widely used for clocks, calculators, etc., but most of them were still images in black and white.
Recently, it has been attempted to display moving images such as television images in full color. However, when such a color display is performed by the conventional twist-nematic (TN) system,
A phenomenon that changes depending on the viewing angle direction and the unevenness of the cell thickness occurs. For this reason, the TN method is not suitable for a large screen display or a display that requires a wide viewing angle.

Also, when displaying a moving image in full color, gradation control becomes a problem, but in the TN method, the voltage and contrast characteristics change sharply with the voltage of the contrast, and the adjustment of the voltage for controlling the gradation becomes extremely delicate. Further, the voltage-contrast characteristic is susceptible to temperature changes, which makes it more difficult to obtain an appropriate gradation.

On the other hand, in the case of the guest-host liquid crystal composition, two polarizing plates are used as in the case of the TN method by using a dichroic dye having different absorbances on the long axis and the short axis of the dye molecule as the guest molecule. Since the display can be performed without doing so, display unevenness due to the viewing angle and the cell thickness is reduced. In addition, the voltage-contrast characteristic shows a gentler characteristic than that of the TN method because it depends on the relative direction between the absorption transition moment of the dye and the incident light, which are oriented according to the liquid crystal molecular arrangement.

[Problems to be solved by the invention]

As described above, the guest-host liquid crystal has excellent features when performing full-color display, but the conventional guest-host liquid crystal has the following problems.

Since the dye has a low solubility in the host liquid crystal, it does not sufficiently function as an optical shutter.

Since the orientation of the dye with respect to the host liquid crystal (order parameter: hereinafter abbreviated as S) is low, the contrast is low.

 The light resistance of the dye is weak and it easily deteriorates.

Addition of dye increases viscosity and decreases responsiveness.

Regarding the above-mentioned solubility, when the conventional dye and host liquid crystal were used, the limit was 6 to 7% by weight. This is a case where materials of three primary colors of red, blue, and yellow are used for the pigment, and the mixture is mixed to obtain black. However, such a degree of solubility causes a problem in the black level as a display. That is, when the voltage is off, the transmittance of the display body is 1% or more, the contrast is low, and only a blurred image can be obtained. The contrast is determined by the ratio of the OFF and ON levels, with a small transmittance of OFF and a large transmittance of O.
N is required. In this case, OFF corresponds to the black level, and if you try to obtain a good black level, the transmittance when off is 0.3%.
You need the following: Regarding the value of the contrast ratio, a contrast of 50 or more is necessary to obtain a good image. In order to obtain a good contrast ratio, it is important at the same time to exhibit a high transmittance at the time of ON. Therefore, by using a guest / host liquid crystal composition having a high S, the transmittance at the time of applying a voltage is increased. Therefore, a display with high contrast can be obtained.

S will be described. S represents the order of arrangement of dye molecules in liquid crystal molecules, and is generally represented by the following formula.

Here, A ″ and A ′ represent the absorbance of the dye molecules with respect to light polarized parallel and perpendicular to the alignment direction of the host liquid crystal, respectively. When liquid crystal having a positive dielectric anisotropy is used as a host, This means that a display with good contrast can be obtained if S is close to 1. This S value is
It is also shown in JP-A-57-190071 that it depends not only on the molecular structure of the dye but also on the molecular structure of the host liquid crystal. Conventionally, even if the value of S is large, it is 0.70
However, a guest-host liquid crystal composition that overcomes all of these problems has not yet been obtained.

In addition, it has been difficult to satisfy a high contrast, a long lifetime, stability at low temperature, solubility, and various hues at the same time in a display device using a guest-host effect by adding a dichroic dye to liquid crystal. Met. One of the reasons for this is that, in addition to the small number of dichroic dyes that are excellent in dichroism, light resistance and solubility, when different dyes are blended, photodegradation of either dye, Deterioration is often accelerated and the light resistance is lower than that when the dyes are used alone, and this phenomenon is remarkable when the azo dye and the anthraquinone dye are blended.

However, current dichroic dyes are generally yellow-based,
Red-based azo dyes are excellent, and blue-based anthraquinone-based dyes are excellent.Therefore, especially for hues that need to be mixed with yellow-based, red-based, and blue-based dyes such as black, brown, and dark blue, There is a problem that it is difficult to realize contrast, long life, and stability at low temperatures.

In order to eliminate the above problems, an object of the present invention is to provide a guest / host liquid crystal composition having a large S in a dye, excellent light resistance and solubility and having a low viscosity.

[Means for solving problems]

The present invention provides a guest / host liquid crystal composition represented by the general formula: (In the formula, R ¹ represents a linear alkyl group having 2 to 8 carbon atoms)
30% to 60% by weight of the first component represented by the general formula 5 to 40% by weight of the second component represented by the formula (wherein R ² and R ³ represent a linear alkyl group having 2 to 5 carbon atoms), 5 to 30% by weight of the third component represented by the formula (wherein R ⁴ and R ⁵ represent a linear alkyl group having 2 to 8 carbon atoms), (Wherein R ⁶ and R ⁷ represent a linear alkyl group having 2 to 8 carbon atoms), 1 to 20% by weight of the fourth component represented by the general formula 5 to 20% by weight of the fifth component represented by the formula (wherein R ⁸ and R ⁹ represent a linear alkyl group having 2 to 8 carbon atoms), 5 to 10% by weight of the sixth component represented by the formula (wherein R ¹⁰ and R ¹¹ represent a linear alkyl group having 2 to 5 carbon atoms), and (Wherein R ¹² and R ¹³ represent a linear alkyl group having 2 to 8 carbon atoms), the liquid crystal composition containing 1 to 20% by weight of the seventh component is used as a host liquid crystal, (In the formula, R ¹⁴ represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group, and R ¹⁵ represents an alkyl group, an alkoxyalkyl group, or an arylmethyl group). One type contains 17 to 23% by weight based on the total amount of dye, and has the general formula (Wherein R ¹⁶ and R ¹⁷ represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and at least one of the azo dichroic dyes represented by 7 to 7
Contains 10 wt% and general formula (Wherein R ¹⁸ and R ¹⁹ represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and at least one kind of anthraquinone dichroic dye is contained in an amount of 24 to 30% by weight based on the total amount of the dye. , And general formula (Wherein R ²⁰ represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and contains at least one dichroic dye of 22 to 27% by weight based on the total amount of the dye, and the general formula (Wherein R ²¹ and R ²² represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and contains at least one kind of anthraquinone-based dichroic dye in an amount of 17 to 21% by weight based on the total amount of the dye. The total pigment concentration is 9% by weight or more, and it exhibits a black color.

As the host liquid crystal used in the present invention, various nematic liquid crystal materials represented by the general formulas (I) to (VII) can be considered, but the reliability of the liquid crystal material and the orientation of the dye must be taken into consideration. In the above-mentioned JP-A-57-190071,
It is said that the liquid crystal materials shown in Table 1 hinder the orientation of the dye, but the No. 1 and No. 2 materials are effective components for lowering the viscosity of the liquid crystal material, and No. 3, No. Nos. 4 and 5 have large dielectric anisotropy and are effective for low voltage driving. Therefore, these components can be used together with those of the general formulas (I) to (VII), and in that case, the ratio to the whole is reduced as much as possible, or a substitute material is used to suppress the deterioration of the orientation. And to take advantage of its characteristics.

(In the formula, R and R'represent a linear alkyl group having 2 to 8 carbon atoms.) Next, the dyes of the general formulas (VIII) to (XII) are dichroic dyes having different absorbances depending on the molecular orientation. And the characteristics are shown in Table 2.

The first component of the general formula (I) that constitutes the host liquid crystal composition in the guest-host liquid crystal composition of the present invention is a material having a positive dielectric anisotropy and a large value thereof. Be the subject. Also, since it has a low viscosity, high-speed response is possible.

The second and sixth components of the general formulas (II) and (VI) are very low viscosity components. However, since the sixth component has poor orientation with respect to the dye, it is necessary to minimize the amount used and reduce the overall viscosity. Therefore, the amount of the sixth component used is limited to 10% by weight or less.

Formula (III), (IV), third (V), the fourth, fifth component is effective to raise the nematic liquid crystal upper limit temperature of the whole liquid crystal composition (hereinafter referred to as T _NI). By increasing T _NI , S is also improved, and the contrast is not impaired even if the temperature of the liquid crystal cell rises due to the light source of the backlight.
In addition, these compounds can increase T _NI without significantly increasing the viscosity of the entire composition, and are useful for high-speed response. Furthermore, the composition containing fluorine has the effect of lowering the minimum temperature (hereinafter abbreviated as T _SN ) of the nematic liquid crystal, and can prevent the appearance of a smectic phase. Moreover, the orientation with respect to the dye is also high.

The seventh component of the general formula (VII) has a function of strengthening the bond between the liquid crystal and the interface of the substrate, and is effective in enhancing the orientation of the liquid crystal.

In the present invention, by adding the above-mentioned dye to the host liquid crystal material in which these respective components are combined, a low dielectric anisotropy is positive, S of the dye is large, and light resistance and solubility are excellent. A viscous guest-host liquid crystal composition is obtained. In order to form a display body from the guest-host liquid crystal composition of the present invention, a color filter is arranged on one of the glass substrates constituting the display cell, and the liquid crystal composition is formed between the glass substrate having the transparent electrodes facing each other. An object is made to exist and an image is displayed by controlling the voltage of each display pixel. This gives a quick response,
In addition, a display having high contrast and excellent light resistance can be obtained.

〔Example〕

 Hereinafter, the present invention will be described according to examples.

Table 3 shows combinations of liquid crystal components of the host liquid crystal composition used in the examples and respective addition amounts.

Example 1 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
2.21 g of the dye represented by ₁₅ (n)], the general formula (IX) [wherein R ¹⁶ : C ₄ H ₉ (n), R ¹⁷ : OC ₄ H
₉ (n)] dye 0.81 g, general formula (X) [however, R ¹⁸ : C ₄ H ₉ (n), R ¹⁹ : CH ₃ ] 3.11 g, general formula (XI) [however R ²⁰ : C ₄ H ₉ (n)]
2.82g and general formula (XII) [dashi R ²¹ : C ₄ H ₉ (n), R ²² : C ₄ H
2.16 g of the dye represented by ₉ (n)] was dissolved in 100 g of the host liquid crystal having the composition shown in Formulation Example 1 in Table 3 to prepare a liquid crystal composition I.

Example 2 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
2.21 g of the dye represented by ₁₅ (n)], the general formula (IX) [wherein R ¹⁶ : C ₄ H ₉ (n), R ¹⁷ : OC ₄ H
₉ (n)] dye 0.81 g, general formula (X) [provided that R ¹⁸ : C ₄ H ₉ (n), R ¹⁹ : CH ₃ ] dye 0.62 g, general formula (X) [provided Dye represented by R ¹⁸ : C ₇ H ₁₅ (n), R ¹⁹ : CH ₃ ], 1.34 g, represented by the general formula (X) [wherein R ¹⁸ : CH ₈ H ₁₇ (n), R ¹⁹ : CH ₃ ]. Dye 1.38 g, a dye represented by the general formula (XI) [wherein R ²⁰ : C ₄ H ₉ (n)]
2.82g and general formula (XII) [dashi R ²¹ : C ₄ H ₉ (n), R ²² : C ₄ H
2.16 g of the dye represented by the formula ( ₉ (n)] was dissolved in 100 g of the host liquid crystal having the composition shown in Formulation Example 2 in Table 3 to prepare a liquid crystal composition II.

Example 3 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
2.60 g of the dye represented by ₁₅ (n)], the general formula (IX) [wherein R ¹⁶ : C ₄ H ₉ (n), R ¹⁷ : OC ₄ H
₉ (n)] dye 1.11 g, general formula (X) [provided that R ¹⁸ : C ₄ H ₉ (n), R ¹⁹ : CH ₃ ] 3.30 g, general formula (XI) [provided that R ²⁰ : C ₄ H ₉ (n)]
3.00 g and general formula (XII) [dashi D R ²¹ : C ₄ H ₉ (n), R ²² : C ₄ H
2.30 g of the dye represented by ₉ (n)] was dissolved in 100 g of the host liquid crystal having the composition shown in Formulation Example 1 in Table 3 to prepare a liquid crystal composition III.

Example 4 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
2.60 g of the dye represented by ₁₅ (n)], the general formula (IX) [wherein R ¹⁶ : C ₄ H ₉ (n), R ¹⁷ : OC ₄ H
₉ (n)] dye 1.11 g, general formula (X) [provided that R ¹⁸ : C ₄ H ₉ (n), R ¹⁹ : CH ₃ ] 3.30 g, general formula (XI) [provided that R ²⁰ : C ₄ H ₉ (n)]
1.29g Dye 0.46g represented by the general formula (XI) [where R ²⁰ : C ₆ H ₁₃ (n)], 1.45g Dye 1.45 represented by the general formula (XI) [where R ²⁰ : C ₈ H ₁₇ (n)] g and general formula (XII) [dashi R ²¹ : C ₄ H ₉ (n), R ²² : C ₄ H
2.30 g of the dye represented by the formula ( ₉ (n)] was dissolved in 100 g of the host liquid crystal having the composition shown in Formulation Example 2 in Table 3 to prepare a liquid crystal composition IV.

Comparative Example 1 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
Dye ( ₁₅ (n)] 1.60 g, the following general formula (XIII) [wherein R ²³ : C ₄ H ₉ (n), R ²⁴ : C ₄ H ₉
2.50 g of the dye represented by (n)], Dye represented by general formula (XI) [wherein R ²⁰ : C ₄ H ₉ (n)]
1.40 g and general formula (XII) [however, R ²¹ : C ₄ H ₉ (n), R ²² : C ₄ H
₉ (n)], and 2.50 g of the dye represented by Comparative Formulation Example 1 in Table 3 was used.
A liquid crystal composition V was prepared by dissolving it in 0 g.

Comparative Example 2 General formula (VIII) [wherein R ¹⁴ : C ₄ H ₉ (n), R ¹⁵ : OC ₇ H
Dye ( ₁₅ (n)] 1.60 g, the following general formula (XIV) [wherein R ²⁵ : C ₄ H ₉ (n), R ²⁶ : CH ₃ ,
R ²⁷ : C ₆ H ₁₃ (n)] 0.80 g and Dye represented by general formula (XI) [wherein R ²⁰ : C ₄ H ₉ (n)]
3.60 g of the host liquid crystal 10 having the composition shown in Comparative Formulation Example 2 in Table 3 was used.
Liquid crystal composition VI was prepared by dissolving it in 0 g.

These liquid crystal compositions were applied to a cell in which a polyimide film was formed on the surface of a glass substrate and subjected to a rubbing treatment, and the cell thickness was 6 to 12
It was injected to have a thickness of μm. The electro-optical characteristics of these cells are shown in Table 4.

In Table 4, T _NI indicates the transition point from the nematic liquid crystal phase to the isotropic liquid. The viscosity was measured by an E-type rotational viscometer, and the viscosity value at 20 ° C was shown. τ _r and τ _d are rising and falling response times at 25 ° C., respectively, and were measured by switching between applying and not applying a rectangular wave of 10 V and 64 Hz. V ₁₀ and V ₉₀ are applied voltages at 10% and 90% change, respectively, assuming that the optical change of the liquid crystal display is 100% when 30 V is applied. T _OFF , T _ON
Indicates the transmittances when OV and 10 V were applied, respectively. CR is the contrast ratio and is calculated by T _ON / T _OFF . Each measurement was performed at 25 ° C.

In Examples 1 and 2, S is improved as compared with Comparative Example 1. This is because in the case of Examples 1 and 2, the components I and L were added and the addition of the components F and G was suppressed as much as possible. Further, it is understood that the component P contributes to lowering the viscosity, and as a result, the fall time (τ _d ) at 20 ° C. is about 40 ms, which is faster than that of Comparative Example 2.

In Examples 3 and 4, the constituent ratios and concentrations of the component dyes were changed from those in Examples 1 and 2, so that the viscosity was increased,
Although the response time was slightly longer, S was improved and the drive voltage could be lowered.

The response time of these examples is 50 ms or less for any τ _d . The response time of 50 ms or less is a minimum requirement for displaying a moving image, and thus the afterimage phenomenon can be suppressed. In terms of gradation, the conventional TN method uses V ₁₀
= 2.3V, V ₉₀ = 3.5V, the difference between V ₁₀ and V ₉₀ is very small,
It is difficult to perform gradation control during this period, and even if it becomes possible under certain conditions, gradation changes due to changes in temperature and viewing angle. However, in the guest-host system, the difference between V ₁₀ and V ₉₀ is large as shown in the embodiment, and gradation control becomes easy.

Regarding the contrast, it is generally considered that the optimum value is 50 or more, but for that purpose, it is necessary to reduce T _OFF . In the examples, by increasing the dye concentration, T
All _OFF is below 0.2%, so the contrast ratio is 10%.
It is 0 or more, which is a significant improvement over the comparative example.

The solubility of the dye was examined based on whether or not precipitation of the dye was observed after leaving it at -20 ° C for 50 hours. As a result, no precipitation was observed in any of the Examples, but in Comparative Example 1, when the addition amount exceeded 10% by weight, and in Comparative Example 2, when the addition amount was 8% by weight, crystal precipitation was observed. Was recognized.

The light fastness test was performed by the color change after 200 hours of carbon arc irradiation. In Examples 1, 2, 3, and 4, the color change was ΔEab * = 1.1, whereas in Comparative Example 2, ΔEab * = 1.1.
A large color change of Eab * = 2.8 is recognized.

〔The invention's effect〕

As described above, according to the guest-host liquid crystal composition of the present invention, it is possible to obtain a liquid crystal display device having a high display contrast, a high-speed response, and an easy gradation display.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location // C09K 19/30 9279-4H G02F 1/13 500 (72) Inventor Mikio Murakami Amagasaki City, Hyogo Prefecture 8-1, 1-1 Tsukaguchihonmachi Sanryo Electric Co., Ltd. Materials Research Laboratory (72) Inventor Tatsuo Masumi 8-1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Prefecture Sanryo Electric Co., Ltd. Materials Research Institute (72) Inventor Ando Torahiko 8-1-1 Tsukaguchihonmachi, Amagasaki-shi, Hyogo Sanryo Electric Co., Ltd. Materials Research Laboratory

Claims (1)

[Claims] 1. A general formula (In the formula, R ¹ represents a linear alkyl group having 2 to 8 carbon atoms)
30% to 60% by weight of the first component represented by the general formula 5 to 40% by weight of the second component represented by the formula (wherein R ² and R ³ represent a linear alkyl group having 2 to 5 carbon atoms), 5 to 30% by weight of the third component represented by the formula (wherein R ⁴ and R ⁵ represent a linear alkyl group having 2 to 8 carbon atoms), (Wherein R ⁶ and R ⁷ represent a linear alkyl group having 2 to 8 carbon atoms), 1 to 20% by weight of the fourth component represented by the general formula 5 to 20% by weight of the fifth component represented by the formula (wherein R ⁸ and R ⁹ represent a linear alkyl group having 2 to 8 carbon atoms), 5 to 10% by weight of the sixth component represented by the formula (wherein R ¹⁰ and R ¹¹ represent a linear alkyl group having 2 to 5 carbon atoms), and A liquid crystal composition containing 1 to 20% by weight of a seventh component represented by the formula (wherein R ¹² and R ¹³ represent a linear alkyl group having 2 to 8 carbon atoms) as a host liquid crystal, (In the formula, R ¹⁴ represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group, and R ¹⁵ represents an alkyl group, an alkoxyalkyl group, or an arylmethyl group). One type contains 17 to 23% by weight based on the total amount of dye, and has the general formula (Wherein R ¹⁶ and R ¹⁷ represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and at least one of the azo dichroic dyes represented by 7 to 7
Contains 10 wt% and general formula (Wherein R ¹⁸ and R ¹⁹ represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and at least one kind of anthraquinone dichroic dye is contained in an amount of 24 to 30% by weight based on the total amount of the dye. , And general formula (Wherein R ²⁰ represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and contains at least one dichroic dye of 22 to 27% by weight based on the total amount of the dye, and the general formula (Wherein R ²¹ and R ²² represent a hydrogen atom, an alkyl group, an alkoxyalkyl group, or an alkoxy group), and contains at least one kind of anthraquinone-based dichroic dye in an amount of 17 to 21% by weight based on the total amount of the dye. A guest-host liquid crystal composition having a total dye concentration of 9% by weight or more and exhibiting a black color.