JP3185287B2 - Liquid crystal device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal device and a method for manufacturing the same. More specifically, it is possible to increase the area,
The present invention relates to a liquid crystal device capable of electrically controlling light transmission / scattering and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, research on applying a liquid crystal exhibiting a chiral smectic C phase, that is, a ferroelectric liquid crystal, to a display material has been actively conducted. It is a typical example, and in 1980, N.C.
A. Clark and S.M. T. Surface-stabilized ferroelectric liquid crystal display (hereinafter referred to as SSF) proposed by Lagerwall
It is called LCD. ).

[0003] However, there are many problems that must be solved in order to put SSFLCD into practical use. One such issue is the development of methods or materials to obtain a sufficient contrast ratio without sacrificing brightness. Therefore, it is necessary to minimize light leakage in a dark state. Causes of light leakage in the dark state include a chevron structure in which the smectic layer is bent at the center of the cell and a twisted state. One of the reasons that SSFLCD has not been put into practical use at present is this chevron structure,
This was a structure that could not be predicted at all when the concept of FLCD was announced. Efforts have been made actively to eliminate the chevron structure and realize the original bookshelf structure or the inclined bookshelf structure in terms of the liquid crystal material and the orientation control. However, at present, it is very difficult to control the orientation of these molecules in the ferroelectric liquid crystal phase. Further, the thickness of the ferroelectric liquid crystal compound or composition and the thermoplastic resin is 1.
Kajiyama et al. Have proposed a ferroelectric composite thin film of about 2 μm. (JP-A-62-260841). However, the purpose of this composite film is to produce a ferroelectric film capable of forming a ferroelectric phase that is thermodynamically stable at around room temperature, and the above-mentioned problem is not necessarily solved.

On the other hand, when a ferroelectric liquid crystal is sealed in a sufficiently thick cell, the ferroelectric liquid crystal becomes chiral smectic C
In the phase (hereinafter referred to as Sc *), the azimuthal angle of the molecule changes little by little in each layer in order to cancel spontaneous polarization, and there is a property that the entire system has a helical structure.

Yoshino et al. Report that a ferroelectric liquid crystal is sealed in a relatively thick cell which has been subjected to horizontal alignment treatment, and that the amount of transmitted light changes when an electric field is applied to this cell [Japanese Journal of Art. Applied Physics (J
pn. J. Appl. Phys. ) 17 (1978) 5
97]. It is said that this is due to the fact that light scattering due to the helical structure disappears due to disappearance of the helical structure due to application of a voltage. Yoshino et al.
Decyl-oxybenzylidene-p'-amino-2-methylbutyl-cinnamate [p-decyl-oxybe
nzylidene-p'-amino-2-meth
ylbutyl cinnamate] (hereinafter referred to as DOBA
Abbreviated as MBC. ) Achieves a contrast ratio of about 60 in a cell having a thickness of 250 μm. However, in this case, since the applied voltage is as high as about 100 V, it is not always practical. In a similar study using DOBAMBC, a contrast ratio of about 20 (at a voltage of 30 V) was achieved with a cell thickness of 30 μm. In this case, since the operating temperature was close to the lower limit of the temperature range showing the Sc * phase, the rise response was low. Time has increased significantly.

[0006] However, the operation mode as described above is transparent /
Although a display device using a scattering type liquid crystal device has various problems, a polarizing plate is not required, and a bright screen can be expected. Also, unlike the above-mentioned surface-stabilized ferroelectric liquid crystal display device which is often studied as a display device using a ferroelectric liquid crystal, the molecular orientation does not need to be perfect. Therefore, it is possible to more easily create a cell having a large area.

[0007]

However, in the transmission / scattering type liquid crystal device described above, it is necessary to increase the cell thickness in order to increase the light scattering when no voltage is applied and to increase the contrast ratio. Requires a high driving voltage. When the temperature is lowered within the Sc * phase temperature range,
Although the contrast ratio is improved, in this case, there is a problem that the rising response time increases. As for the response time, the rising response time can be shortened by increasing the applied voltage, but in this case, the falling response time increases. Since the function as a liquid crystal device is regulated by the longer response time of rising or falling, the problem still remains.

An object of the present invention is to provide a liquid crystal device in which the operation mode utilizing the change in the helical structure of a ferroelectric liquid crystal (hereinafter, referred to as a helical distortion effect) is a transmission / scattering type liquid crystal device. By compounding the compound, the property is to be improved as compared with the case where the ferroelectric liquid crystal is used alone. That is, the present invention provides a novel liquid crystal device exhibiting a faster fall time and a higher contrast ratio at a lower driving voltage by utilizing the transmission / scattering phenomenon of a liquid crystal-containing composite film having an Sc * phase, and a method for manufacturing the same. It is in.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a pair of transparent substrates having at least one electrode layer, and a liquid crystal-containing layer sandwiched between the electrode layers of the substrate. Liquid crystal 60-9 which becomes smectic C phase
A composite consisting of 8% by weight and 40 to 2% by weight of polymer;
It is an object of the present invention to provide a liquid crystal device whose operation mode is of a transmission / scattering type. As a result of research on ferroelectric liquid crystal compositions exhibiting good helical distortion characteristics, the present invention has found and achieved a system in which various physical properties are improved by mixing a polymer with a ferroelectric liquid crystal compared to before mixing. It is a thing.

The liquid crystal used in the present invention is not particularly limited as long as it is a compound or a composition which becomes a ferroelectric Sc * liquid crystal. As a compound to be a ferroelectric Sc * liquid crystal, a compound showing a ferroelectric Sc * liquid crystal such as an azomethine compound, a Schiff base compound, an azo and azoxy compound, a biphenyl compound, an aromatic ester compound and a phenylpyrimidine compound can be used alone or in combination. Mixtures of more than one species. Further, as a composition to be a ferroelectric Sc * liquid crystal, a composition exhibiting a ferroelectric Sc * liquid crystal obtained by adding an improver to the above compound or a smectic liquid crystal compound as a base liquid crystal and a chiral compound added thereto to obtain a ferroelectric Sc * liquid crystal * Examples of the composition include liquid crystal.

Specifically, for example, Japanese Patent Application Laid-Open No. 62-26084
Azomethine-based ferroelectric Sc * exemplified in JP-A-1
Liquid crystal compounds and compositions, phenylpyrimidine-based ferroelectric S exemplified in JP-A-3-12487 and the like.
c * liquid crystal compounds and liquid crystal compositions containing them, optically active biphenyl-based ferroelectric Sc * liquid crystal compounds exemplified in JP-A-3-83949 and liquid crystal compositions containing the same, 98051 and 60-
Schiff base ferroelectric Sc * liquid crystal compounds and compositions containing the same as exemplified in JP-A-98865, and azoxy ferroelectric Sc * liquid-crystal compounds as exemplified in JP-A-61-183256 and the same. A composition comprising
Aromatic ester-based ferroelectric liquid crystal compounds exemplified in JP-A-2-167251 and compositions containing the same, phenylpyrimidine-based compounds exhibiting smectic liquid crystals exemplified in JP-A-3-207790, A ferroelectric Sc * liquid crystal composition in which a phenylpyridine compound, a biphenyl compound or an aromatic ester compound is used as a base liquid crystal and a chiral compound is added thereto, and a smectic liquid crystal compound exemplified in JP-A-3-62885. A ferroelectric Sc * liquid crystal composition to which an aromatic ester-based chiral compound is added is exemplified.

The polymer which is compounded with the liquid crystal can be used without any particular limitation. Suitable polymers include polyethylene, polypropylene, polyolefins such as polybutylene, polyaromatic vinyls such as polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylates such as polymethyl acrylate,
Polymethacrylic acid esters such as polymethyl methacrylate, polyacrylonitrile, polyvinyl ethers such as polymethyl vinyl ether, polyvinyl ketones, polypropylene oxide, polyalkylene oxides such as polyethylene oxide, polycarbonates, polyethylene terephthalate, polybutylene terephthalate etc. Polyamides such as polyesters, nylon 4, nylon 6, nylon 6,6 and nylon 6,12, diene polymers such as polyvinyl alcohol, polybutadiene, and polyisoprene; polyurethane polymers; silicone resins and rubbers; natural rubber; Modified celluloses such as ethyl cellulose, epoxy resins and the like can be mentioned. These polymers may be copolymers, and may be used alone or in an appropriate mixture.

The ratio of the liquid crystal and polymer exhibiting the Sc * phase to the liquid crystal-containing layer used in the present invention is not particularly limited as long as the liquid crystal-containing layer exhibits a helical distortion effect. %, The polymer is 40 to 2% by weight, more preferably the liquid crystal is 70 to 95% by weight, and the polymer is 30 to 5% by weight. If the ratio of the liquid crystal having the Sc * phase is less than 60% by weight, the liquid crystal-containing layer does not show a good helical distortion effect, while if it is more than 98% by weight,
The effect of compounding is not remarkable. In the device described above, the fine structure of the liquid crystal-containing layer at the operating temperature is uniform as long as the liquid crystal compound or composition exhibits the Sc * phase, the polymer is dispersed in the liquid crystal, or the polymer is dispersed. May be used as a matrix, and any state in which liquid crystals are dispersed may be used.

The method for producing the liquid crystal device of the present invention is not particularly limited, but as a preferred example, a step of mixing a predetermined amount of liquid crystal and a polymer and heating the mixture to form a liquid mixture, and the obtained liquid mixture having an electrode layer A method including a step of sealing between at least one of a pair of transparent substrates can be given. Specifically, first, a predetermined amount of the ferroelectric liquid crystal and the polymer are placed in a container, and heated and stirred to obtain a mixed liquid (molten) state. The mixture may be in a uniform solution state or a dispersion state. Next, the above-mentioned mixed solution is applied to a cell formed by bonding two transparent substrates (glass or the like) having a transparent electrode layer of indium tin oxide (ITO) or the like via a spacer by utilizing a capillary phenomenon. A device can be produced by encapsulation.

In the present invention, the thickness of the liquid crystal-containing layer depends on the transmission mode due to the generation and disappearance of the helical structure of the liquid crystal as an operation mode.
Since the scattering type is used, the thickness of the liquid crystal must be at least necessary for forming a spiral structure. Since the thickness range differs depending on the type of composite used, it cannot be uniquely defined. Therefore, an appropriate thickness may be selected by trial and error in consideration of the response time, contrast, operating voltage, and the like.

[0016]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. In the examples, "part"
Means "parts by weight".

Example 1 DOBAMBC was used as a ferroelectric Sc * liquid crystal. D
83.6 parts of OBAMBC and 16.4 parts of polystyrene (number average molecular weight 5050) powder were weighed and placed in a stainless steel container, and stirred while heating to about 150 ° C. to form a uniform solution. This was sealed between two glass substrates with ITO transparent electrodes using a polyimide film (trade name: manufactured by Kapton Dupont, thickness 26 μm) as a spacer by utilizing a capillary phenomenon. The evaluation of the electro-optical response characteristics of the obtained liquid crystal device was performed at a measurement temperature of 70 ° C. by the following method.

Evaluation was performed in the following manner using the apparatus shown in the block diagram of FIG. A rectangular wave (minimum voltage 0 V, maximum voltage 50 V) is generated by the arbitrary waveform generator 1, and a voltage is applied between the electrodes of the liquid crystal device 3 via the amplifier 2, that is, a DC voltage is applied to the liquid crystal device 3 (ON). ) Or shut off (OFF). On the other hand, the liquid crystal device 3 is irradiated with light having a wavelength of 632.8 nm from the He-Ne laser 4,
The change in the amount of transmitted light was detected by the photodiode 5 and output by the oscilloscope 7 via the amplifier 6. From the output waveform of the oscilloscope 7, that is, the change in the voltage shown in FIG. 2, the rise and fall response times and the contrast ratio were obtained. Referring to FIG. 2, V ₁₀₀ is the transmitted light amount when no device is placed, V _ON is the steady transmitted light amount when voltage is applied (ON), V _OFF is the steady transmitted light amount when no voltage is applied (OFF), and ΔV is V _ON −V _OFF , τ _R is the time from the ON time until the difference in the transmitted light amount becomes 90% of ΔV (rise response time), and τ _D is the difference in the transmitted light amount from the OFF state when the difference in ΔV is 1
This is the time (fall response time) until it reaches 0%.
The contrast ratio was determined by the following equation. Contrast ratio = Transmittance (ON) / Transmittance (OFF) Here, the transmittance (ON) is ΔV _ON / V ₁₀₀ (%), and the transmittance (OFF) is ΔV _OFF / V ₁₀₀ (%). Table 1 shows the evaluation results of the obtained liquid crystal devices.

Example 2 90.9 parts of DOBAMBC and 9.1 parts of polystyrene (number average molecular weight 9000) powder were weighed and placed in a stainless steel container and stirred while heating to about 150 ° C. to form a uniform solution. Using this solution, a liquid crystal device was prepared and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained liquid crystal devices.

Example 3 83.8 parts of DOBAMBC and an epoxy resin (trade name: Sumiepoxy ESA017, manufactured by Sumitomo Chemical Co., Ltd.)
Two parts were weighed in a stainless steel container, stirred while heating to about 150 ° C. to form a uniform solution, and a liquid crystal device was prepared and evaluated in the same manner as in Example 1 using this solution. Table 1 shows the evaluation results of the obtained liquid crystal devices.

Comparative Example 1 A liquid crystal device was prepared and evaluated in the same manner as in Example 1 except that DOBAMBC 100% was used. Table 1 shows the evaluation results of the obtained liquid crystal devices.

Comparative Example 2 50.0 parts of DOBAMBC and epoxy resin (trade name Sumiepoxy ESA017, manufactured by Sumitomo Chemical Co., Ltd.)
0 parts were weighed in a stainless steel container and stirred while heating to about 150 ° C. to form a uniform solution. Using this solution, a liquid crystal device was prepared and evaluated in the same manner as in Example 1.
Table 1 shows the evaluation results of the obtained liquid crystal devices.

[0023]

[Table 1]

[0024]

The liquid crystal device of the present invention is capable of electrically controlling the transmission / scattering of light, and is more simply a transmission / scattering type which exhibits a fast fall time and a high contrast ratio at a low driving voltage. In addition, a liquid crystal device used for a light control glass, a display device, or the like can be provided, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a block diagram of a liquid crystal device evaluation apparatus.

FIG. 2 shows the amount of transmitted light (vertical axis) in the evaluation of a liquid crystal device.
FIG. 4 is a diagram showing a relationship between the time and the time (horizontal axis).

[Explanation of symbols]

 1. 2. Arbitrary waveform generator Liquid crystal device 4, He-Ne laser 5. Photodiode 7. oscilloscope

Continuation of the front page (56) References JP-A-2-36299 (JP, A) JP-A-4-140718 (JP, A) Tables JP-A-2-503360 (JP, A) No. 3, p. 579 (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1334 G02F 1/137

Claims (2)

(57) [Claims] A ferroelectric material comprising a pair of transparent substrates having at least one electrode layer and a liquid crystal-containing layer sandwiched between electrode layers of the substrate, wherein the liquid crystal-containing layer has a chiral smectic C phase. A composite composed of 60 to 98% by weight of liquid crystal and 40 to 2% by weight of a polymer, and has an operation mode of transmission /
A liquid crystal device characterized by a scattering type. 2. A process in which a predetermined amount of a ferroelectric liquid crystal and a polymer are mixed and heated to form a mixed solution, and the obtained mixed solution is sealed between a pair of substrates having at least one transparent electrode layer. 2. The method for manufacturing a liquid crystal device according to claim 1, comprising a step.