JPH05339573A - Liquid crystal material - Google Patents

Abstract

PURPOSE: To improve the contract and the retention with a low driving voltage by incorporating specific two compounds.

CONSTITUTION: 50 to 100 wt.% of a mixture of 99 to 20 wt.% of a compound represented by formula I [wherein A_1-2 denote a benzene ring, a cyclohexane ring, a pyridine ring, or a trans-1,3-dioxane ring; X_1-6, and Y each are H, F, Cl; Z_1-2 denote a single bond, -CH₂-, -CH₂CH₂-, -CH=CH-, -C≡C-, -COO-, or -OCO-; Q denotes a single bond, -CH₂-, -CH₂CH₂-, -CF₂-, -OCF₂-, -C₂F₄-, -CCl₂-, or -C₂Cl₄; R denotes C_nH_2n+1-, C_nH_2n+1O-, C_nH_2n+1CH=CH- (wherein n denotes 2 to 10); and m denotes 0 to 2] and 1 to 80 wt.% of a compound represented by formula II (wherein B, C denote C_nH_2n+1-, C_nH_2n+1O-, C_nH_2n+1CH=CH-, or C_nH_2n+1.C₆H₁₀-; and L denotes H or F) is incorporated.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal material, and more particularly to a liquid crystal material for a polymer dispersion type liquid crystal display device. More specifically, it is used for a liquid crystal display device using a display mode in which the difference in refractive index between a liquid crystal droplet or a continuous liquid crystal droplet and a polymer is changed by an external voltage to control light scattering occurring at the interface between the liquid crystal and the polymer. Related liquid crystal material. Specifically, it can be used for a liquid crystal display device, a projection television, a flat display device such as a personal computer, a display plate utilizing a shutter effect, a window, a door or a wall.

[0002]

2. Description of the Related Art Conventionally, as a display element utilizing the electro-optical effect, a TN type using a nematic liquid crystal or an STN type has been put into practical use. Also, a liquid crystal using a ferroelectric liquid crystal has been proposed. These require a polarizing plate and require an alignment treatment. on the other hand,
There is a dynamic scattering (DS) effect and a phase transition (PC) effect that utilizes the scattering of liquid crystal without requiring a polarizing plate.

Recently, there has been proposed a method of electrically controlling a transparent or opaque state by utilizing the birefringence of a liquid crystal, which does not require a polarizing plate and does not require an alignment treatment. This method basically matches the ordinary refractive index of the liquid crystal molecules with the refractive index of the support medium, displays a transparent state when a liquid crystal is aligned by applying a voltage, and displays a transparent state when no voltage is applied. The light scattering state due to the disordered orientation is displayed.

A proposed method is Japanese Patent Laid-Open No. 58-58.
No. 501631 discloses a method of encapsulating a liquid crystal in a polymer capsule, and JP-A No. 61-502128 discloses a method of mixing a liquid crystal and a light or thermosetting resin and curing the resin to precipitate a liquid crystal compound, thereby precipitating a liquid crystal in the resin. A method of forming droplets is disclosed in JP-A-59-226322, in which a phase separation state of a liquid crystal and a polymer is formed by removing the solvent from a mixture of a polymer and a liquid crystal and a solvent which dissolves the mixture. A featured method is disclosed.

Most of the liquid crystal compounds used in the polymer-dispersed liquid crystal display devices produced by these inventions are cyanobiphenyl compounds and cyanopyrimidine compounds having a --CN group at the molecular end. Examples of these liquid crystal compounds include JP-A-2-272422 to 272424, JP-A-2-75688, JP-A-2-28284, and JP-A-2-72824.
It is disclosed in Japanese Patent Publication No. 85822.

[0006]

However, the liquid crystal compound having a --CN group at the terminal, which is conventionally used in a polymer-dispersed liquid crystal display element, has a strong polarization of the --CN group.
It is highly reactive and easily incorporates impurities from the entire system.
Therefore, a high retention rate is obtained through the manufacturing process of polymer-dispersed liquid crystal display devices that often come into contact with other substances.
(90% or more) (Retention rate is 16.5 ms after voltage application.
The ratio of the retained charge) (for example, S. Mat
sumoto et al., Liq. Cryst. 5 , 1320 (1989))
It was difficult to manufacture a polymer dispersion type liquid crystal display device capable of maintaining the above.

Further, in the method of curing the curable compound from the mixture of the liquid crystal compound and the curable compound and phase-separating the liquid crystal from the cured product, the liquid crystal compound and the polymerization reaction active substance coexist in the cell. During curing of the curable compound, the liquid crystal compound was damaged due to its high reactivity,
The retention rate of the obtained liquid crystal element is extremely low.

The present invention relates to a novel liquid crystal material, particularly a liquid crystal satisfying all of the low driving voltage, high contrast and high holding ratio, which are considered to be the most important of the required performances when it is used for a polymer dispersion type liquid crystal display device. Intended to provide material.

The object is to provide a liquid crystal compound having a structure different from the conventional one, that is, a liquid crystal material group (functional material, Vol2) having a functional group whose main constituent atom is an atom such as F or Cl which is a chemically stable polar group. , No. 2, p. 5-12), the refractive index anisotropy (Δn), which is said to be closely related to the contrast of the polymer dispersion type liquid crystal display element, is large, This is achieved by optimizing the resin composition by using a liquid crystal material characterized in that the clearing point (nematic phase-isotropic liquid transition temperature) of the important liquid crystal material is 60 to 100 ° C.

[0010]

That is, the present invention is selected from the group consisting of the compound represented by the following "Chemical formula 3" and the group consisting of the compound represented by the following "Chemical formula 4". A liquid crystal material containing the compound in an amount of 50% by weight to 100% by weight;

[Chemical 3]

[Chemical 4] In "Chemical Formula 3", A ₁ and A ₂ are each independently a benzene ring,
It represents a cyclohexane ring, a pyrimidine ring, a pyridine ring or a trans-1,3-dioxane ring. X ₁ , X ₂ , X ₃ ,
X ₄ , X ₅ and X ₆ each independently represent H, F or C1. Z ₁ and Z ₂ are each independently a single bond, —CH ₂ —, —
_{CH 2 CH 2 -, - CH} = CH -, - C≡C -, - COO
-Or -OCO- is shown. Q is a single bond, -CH ₂ -,
_{-CH 2 CH 2 -, - CF} 2 -, - OCF 2 -, - C 2 F
₄ -, - CCl ₂ - or -C ₂ Cl ₄ - represents a. Y is H,
Represents F or Cl. R is, C _n H _{2n + 1} - or, C _n H
_{2n + 1 O-, C n H} 2n + 1 CH = CH- ( wherein, n 2-10
Is shown as an integer). m represents 0, 1, or 2. In “Chemical Formula 4”, B and C are independently C _n H _{2n + 1} −, C _n H _{2n + 1
O-, C n H 2n + 1} CH = CH- or _{C n H 2n + 1 · C} 6 H
₁₀ − (in the formula, n has the same meaning as described above). L represents H or F.

The liquid crystal compound represented by "Chemical Formula 3" is particularly excellent in chemical stability, and the higher the content thereof, the more chemically stable it is. However, with this compound alone, the refractive index anisotropy (Δn), which is said to be closely related to the contrast of the polymer dispersion type liquid crystal display element, is small. In order to increase the refractive index anisotropy (Δn) of the liquid crystal material of the present invention, it has no strong polar group, is excellent in chemical stability, and has an effect of increasing the refractive index anisotropy (Δn). A liquid crystal compound as shown in Chemical formula 4 ”is added. This compound has a large effect of increasing the refractive index anisotropy (Δn), but decreases the dielectric anisotropy (Δε), and when B and C are the same, the clearing point is increased to increase the liquid crystal. 3 for all materials
It is preferably 0% by weight or less.

In the present invention, the content is particularly important. In the present invention, other liquid crystal materials may be mixed, but in this case, in order to prevent the chemical stability of the entire liquid crystal material from being significantly reduced and the retention rate of the polymer dispersion type liquid crystal display element from being lowered. The content of the liquid crystal compounds represented by the above "Chemical formula 3" and "Chemical formula 4" in the whole liquid crystal material is 50 to 10
It is 0% by weight, and more preferably 70 to 100% by weight.

The compounds represented by "Chemical Formula 3" and "Chemical Formula 4" are in the range of 99: 1 to 20:80 ((Chemical Formula 3) :( Chemical Formula 4)), preferably 97: 3. It is used in a ratio range of ˜50: 50, more preferably in a ratio range of 95: 5 to 75:25. When the ratio is larger than 99: 1, Δn is not large, and when it is smaller than 20:80, Δε is small,
Moreover, the driving voltage becomes high, which is not suitable.

As liquid crystal compounds other than the liquid crystal compounds represented by "Chemical Formula 3" and "Chemical Formula 4", liquid crystal materials generally used for polymer dispersion type liquid crystal display devices such as cyanobiphenyl compounds and cyanopyrimidine compounds are used. be able to.

The liquid crystal material used must be sufficiently purified, and the specific resistance after mixing the liquid crystal material is 10 ¹² Ω.
-Cm or more, preferably 10 ¹³ Ω-cm or more.

In the compounds represented by "Chemical Formula 3" and "Chemical Formula 4", the larger the number (N) of benzene rings and / or cyclohexane rings in the molecule, the larger the refractive index anisotropy (Δn). .. However, when a compound having a ring number (N) of N ≧ 4 is added, the clearing point of the entire liquid crystal is pushed up. In particular, in the case of a method that utilizes phase separation by curing a mixture of liquid crystal and a curable resin, the processing temperature becomes high, and the speed of the phase separation increases accordingly, resulting in liquid crystal droplet droplets. As a result, the driving voltage of the liquid crystal display element increases. From this point of view, it is not possible to add many compounds with N ≧ 4. In addition, a compound having a ring number (N) of N ≦ 2 or less lowers the refractive index anisotropy (Δn) of the liquid crystal as a whole, and in this case too, the compound cannot be added in a large amount. Therefore, among the liquid crystal compounds represented by "Chemical Formula 3" and "Chemical Formula 4", a compound having three benzene rings and / or cyclohexane rings in the molecule is 60 wt% or more, preferably 90 wt% of the total amount of both compounds. It is desirable to include the above.

Further, compounds such as dopants, cholesteric liquid crystals and dyes may be added to such an extent that the chemical stability of the liquid crystal material of the present invention is not impaired.

When these liquid crystal materials are used for a polymer dispersion type liquid crystal display device or the like, known techniques can be used for the amount of the materials used and the production method, and the invention is not particularly limited. For example, a method of encapsulating a liquid crystal material in a polymer capsule, a method of mixing a liquid crystal material and a light or thermosetting resin and curing the resin to precipitate liquid crystals to form liquid crystal droplets in the resin, a polymer and a liquid crystal material. It can be used in a method characterized by forming a phase-separated state of a liquid crystal material and a polymer by removing the solvent from a mixture of the mixture of 1) and a solvent which dissolves these mixtures. Among these methods, it is a method of forming a liquid crystal droplet in the resin by precipitating a liquid crystal by mixing a liquid crystal material and a light or thermosetting resin and curing the resin.
For the method in which the liquid crystal directly contacts the reaction active point, in particular,
The effect of the present invention is great.

The prepolymer (solvent-containing) used in the production of the polymer-dispersed liquid crystal display element is in direct contact with the above-mentioned liquid crystal and therefore must have a high purity. In particular, unreacted raw materials, synthesis catalyst, prepolymer decomposition products, water and the like during the synthesis of the prepolymer must be sufficiently removed. Specifically, in order to fully bring out the characteristics of the liquid crystal material used in the present invention, the resistance value of the prepolymer is 10 ¹¹ Ω · cm or more, preferably 10 ¹² Ω · cm or more.

Further, the liquid crystal compound of the present invention has a low solubility parameter (SP value) of the liquid crystal material because it contains fluorine and chlorine elements in the molecule, and in the case of a production method utilizing phase separation between the liquid crystal material and the polymer, Before the phase separation, the liquid crystal material and the prepolymer material must be a uniform solution, and the solubility parameter (SP) value of the prepolymer material must be low. The SP value of the prepolymer material is the S value of the liquid crystal material.
Since the P value is around 9, it is 8 to 11, and more preferably 8.5 to 9.5. Furthermore, when the homogenization temperature of the liquid crystal material and the prepolymer is lowered and the phase separation by light or thermal polymerization is utilized, the prepolymer material is used for the purpose of decreasing the phase separation speed and producing uniform liquid crystal droplets. The lower the average molecular weight of, the more preferable. However, considering the strength of the polymer matrix, it is difficult to fabricate a cell only with a monofunctional monomer. Therefore, the average molecular weight of the prepolymer material is 100 to 300.
0 is preferred.

[0021]

EXAMPLES The present invention will be further described below with reference to examples. However, the scope of the invention is not limited to these examples.

Example 1 A resin mixture of 0.4 g of 2-ethylhexyl acrylate, 0.05 g of neopentyl glycol diacrylate and 0.05 g of urethane acrylate oligomer was added to Table 1.
2 g of the liquid crystal compound shown in 1) was added, and 0.02 g of a photo-curing agent (manufactured by Ciba Geigy; Irgacure 184) was mixed,
Homogenized at 0 ° C. Glass with ITO (a mixture of indium oxide and tin oxide) (ITO-made by Nippon Sheet Glass Co., Ltd.)
A cell was constructed between two sheets of flint glass with 500Å) with a 12 μm spacer, and the above mixture was injected.
Then, at room temperature, under a high pressure mercury lamp, 30 mW / cm ² (365n
(UV irradiation intensity at m) was irradiated with ultraviolet rays for 2 minutes to cure the resin.

The retention rate of the prepared cell was measured by the retention rate measuring system shown in FIG. This system is a switching transistor (F
ET), a drive circuit, and a circuit for measuring discharge of electric charge stored in the cell. The measurement result measured at room temperature was 98.2%.

[0024]

[Table 1]

The electro-optical characteristics of the fabricated cell are 10% of the value obtained by subtracting the light transmittance T ₀ when no voltage is applied from the saturation transmittance (Ts) when the light transmittance is set to an excessively high voltage. The applied voltage (threshold voltage) (Vth) was 2.6 V and the saturation voltage (Vs) was 5.7 V when the transmissivity of the liquid crystal was increased. The driving voltage was extremely lower than that of the conventional cell, and the characteristics were excellent steepness. Furthermore, the straight-line light transmittance of the fabricated cell is 2.0% when no voltage is applied when the light collecting portion of the Schlieren optical system has a light collection angle of 6 °, and is 50V.
It was 82.1% when an AC voltage was applied, and good contrast was obtained.

Examples 2 and 3, Comparative Examples 1 and 2 Liquid crystal materials shown in Table 2 (Example 2), liquid crystal materials shown in Table 3 (Example 3), cyanobiphenyl liquid crystal E8 (manufactured by Merck & Co., Comparative Example 1) and E44 (Comparative Example 2 manufactured by Merck & Co., Inc.) were replaced with the liquid crystal materials used in Example 1, respectively.
A polymer-dispersed liquid crystal display device was produced by the same method as described above. The retention rate of the prepared cell was measured in the same manner as in Example 1 and the results are shown in Table 4.

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4] ------------------ Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example Example 2 ----------------------------------------- Retention rate (%) 98.2 98.1 98.5 85 .2 87.4 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0030]

INDUSTRIAL APPLICABILITY According to the present invention, chemically stable F and Cl
The use of a liquid crystal material can solve the problem of low retention, which has been the most hindrance in polymer dispersion liquid crystal display. By using the liquid crystal material of the present invention, it is possible to provide a polymer dispersion type liquid crystal display device having excellent display quality and high reliability.

[Brief description of drawings]

FIG. 1 shows a circuit of a device for measuring retention rate.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Nobuaki Yamada 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Prefecture Sharp Corporation (72) Toshiyuki Hirai 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Incorporated (72) Inventor Noriaki Onishi 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka 72) Inventor David Coates UK, England, B21 21 ESD, Dorset, Winbone, Marley, Sopwith Cresent 87 (72) Inventor Bernhard Rieger Otadaira, Nara-cho, Midori-ku, Yokohama, Kanagawa Prefecture 2834 Wacore Tamagawa Gakuen B-511 (72) Inventor Sei Tanaka Atsugi City, Kanagawa Prefecture Tsumadanishi 3-22-1 Pure Heights Yoshimura 202

Claims (3)

[Claims] 1. A compound selected from the group consisting of the compounds represented by the following "Chemical formula 1" and a compound selected from the group consisting of the compounds represented by the following "Chemical formula 2" in a total amount of both 5
A liquid crystal material containing 0% to 100% by weight. [Chemical 1] (In the formula, A ₁ and A ₂ each independently represent a benzene ring, a cyclohexane ring, a pyrimidine ring, a pyridine ring, or a trans-1,3-dioxane ring; X ₁ , X ₂ , X ₃ ,
X ₄ , X ₅ and X ₆ each independently represent H, F or C ₁ ; Z ₁ and Z ₂ are each independently a single bond, —CH ₂ —, —
_{CH 2 CH 2 -, - CH} = CH -, - C≡C -, - COO
- or an -OCO-; Q is a single bond, -CH ₂ -,
_{-CH 2 CH 2 -, - CF} 2 -, - OCF 2 -, - C 2 F
₄ -, - CCl ₂ - or -C ₂ Cl ₄ - represents a; Y is, H,
F or Cl; R is, C _n H _{2n + 1} - or, C _n H
_{2n + 1 O-, C n H} 2n + 1 CH = CH- ( wherein, n 2-10
Represents an integer of 0); m represents 0, 1, or 2); (In the formula, B and C are independently C _n H _{2n + 1} −, C _n H _{2n + 1
O-, C n H 2n + 1} CH = CH- or _{C n H 2n + 1 · C} 6 H
₁₀ − (wherein n is as defined above); L represents H or F). 2. The compound represented by "Chemical Formula 1" and "Chemical Formula 2", containing 60% by weight or more of the total weight of the compounds having three benzene rings and / or cyclohexane rings in the molecule. Item 3. The liquid crystal material according to item 1. 3. The liquid crystal material according to claim 1, wherein the compound represented by "Chemical formula 1" and the compound represented by "Chemical formula 2" are contained in a weight ratio of 99: 1 to 20:80.