JPH04322217A - High-polymer/liquid crystal composite film - Google Patents

Abstract

PURPOSE:To provide the above film which exhibits a high contrast and high- speed response on a low driving voltage and has a high specific resistance by forming a high-polymer compd. by using divinyl ester dicarboxylate. CONSTITUTION:This film consists of the high-polymer compd. copolymerized with plural copolymn. components and a low-molecular liquid crystal component and exhibits functions in the state in which these components are held separated in phase. The high-polymer compd. in such a case is a copolymer of a monofunctional polymerizable component and a multifunctional polymerizable component. The divinyl ester dicarboxylate is used as the component essential for exhibiting the functions of the composite film. The divinyl ester dicarboxylate is adequately in a range from 5.0 to 0.01 for 1 monofunctional polymerizable component. The desired functions are thereby developed and the control of the functions of the composite film by the adjustment of the copolymn. ratio is possible.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a display element, a light control element,
This invention relates to a novel polymer/liquid crystal composite film that can be widely applied as light modulators, optical shutters, memories, etc.

0002

[Prior Art] Low-molecular liquid crystals are the most typical display material for flat panel displays, and include TN-type liquid crystal display elements for clock faces, STN-type liquid crystal display elements for portable computers and portable word processors, etc. It is widely applied as However, since these conventional techniques require the use of a polarizing plate, the light transmittance thereof is extremely low and the viewing angle is also small. In addition, technology for controlling the alignment of liquid crystals, technology for uniformly adjusting the gap between two electrodes over a wide range, etc. are essential, which are obstacles to improving productivity and increasing the display area. Furthermore, with these techniques, it is virtually impossible to make the display material itself have memory properties.

On the other hand, US Pat. No. 4,435,047 and Japanese Patent Publication No. 58-501631 disclose polymer films in which liquid crystal droplets encapsulated with polyvinyl alcohol, gelatin, gum arabic, etc. are dispersed. In this technique, by controlling the light scattering properties of a polymer film by the voltage applied to the film, a functional film having dimming ability can be produced without the need for a polarizing plate.

[0004] Furthermore, Japanese Patent Publication No. 61-502128 proposes a device in which liquid crystal is dispersed in an epoxy resin. Furthermore, a technique is also known in which a liquid crystal dispersion film is obtained by drying the solvent from a coating film of a liquid in which polymers and liquid crystal molecules are simultaneously dissolved. Furthermore, a technique for obtaining a film having memory properties by using a photopolymerization initiator for a mixture of monomers or oligomers and liquid crystals (Japanese Unexamined Patent Publication No. 1-312
No. 527) Alternatively, a technique for obtaining a film having dimming ability with a low driving voltage is also known. (Collection of materials for the 23rd Electrochemistry Seminar in Boundary Regions (1990))

0
005]

[Problems to be solved by the invention] In order to use a polymer/liquid crystal composite film as a display element, a light control element, a light modulation element, an optical shutter, etc., it is necessary to (i) have a low driving voltage and (ii) have a high contrast. , and (iii) fast response speed;
This is very important. In addition, in order to use it as a member of a liquid crystal display element using thin film transistors that have been put into practical use in recent years, it is important that (iv) it has high electrical resistance.

[0006] However, conventionally known techniques cannot satisfy all of the above requirements, and there is a demand for composite membranes with higher performance and functionality. In addition, composite films known to have memory properties utilize the property that the light scattering ability decreased by voltage application is difficult to recover even after the voltage is removed (Japanese Patent Application Laid-Open No. 1-31
2527), in this case, it is impossible to control the light transmittance (reflection) of the written part by the applied voltage, and there is a problem that its application is limited to a narrow range such as read-only memory. .

[0007] Accordingly, an object of the present invention is to provide a polymer/liquid crystal composite film that exhibits high contrast and high-speed response at low driving voltage and has high specific resistance. Another object of the present invention is to provide a polymer/liquid crystal composite film whose memory function can be controlled.

[0008]

[Means for solving the problem] A polymer compound formed by copolymerizing multiple copolymerization components and a low molecular liquid crystal component,
In a polymer/liquid crystal composite film that functions in a phase-separated state, the above polymer compound is one of the copolymer components.
One of the features is that it is formed using one or more dicarboxylic acid divinyl esters.

The structure of the polymer/liquid crystal composite film of the present invention will be described in detail below. The polymer compound, which is one of the constituent components of the polymer/liquid crystal composite film of the present invention, is formed by copolymerizing multiple copolymerization components, and includes a monofunctional polymerizable substance and a polyfunctional polymerizable substance. It is a copolymer of

The monofunctional polymerizable component is preferably one whose polymer is transparent after polymerization, such as alkyl esters of (meth)acrylic acid, such as ethyl (meth)acrylate, n-butyl (meth)acrylate, etc. ester, (meth)acrylic acid isobutyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid methyl ester, (meth)acrylic acid dodecyl ester, (meth)acrylic acid glycidyl ester, etc. They can be used alone or in combination. Further, chemical resistance etc. can be adjusted by adding styrene, acrylonitrile, etc. at a ratio of 10% or less.

As the polyfunctional polymerizable component, divinyl dicarboxylic acid ester is used as an essential component for exhibiting the functions of the composite membrane. The dicarboxylic acid divinyl ester used in the present invention has the general formula CH2=CH-OCO-A-COO-CH=CH2
(In the formula, A represents a hydrocarbon group having 2 or more carbon atoms.)
Specifically, adipic acid divinyl ester,
Examples include divinyl succinate, divinyl suberate, divinyl azelate, divinyl sebacate, divinyl terephthalate, divinyl fumarate, and divinyl maleate.

[0012] The copolymerization ratio (weight ratio) of the monofunctional polymerizable component and divinyl dicarboxylate is suitably in the range of 5.0 to 0.01 of divinyl dicarboxylate to 1 monofunctional polymerizable component. Thereby, the desired function is expressed. By adjusting this copolymerization ratio, it is possible to control the function of the composite membrane. Taking the light transmittance (reflection) rate of a composite film as an example of applied voltage history (memory property) dependent on applied voltage, the higher the copolymerization ratio of dicarboxylic acid divinyl ester, the more remarkable the memory property becomes.

In the present invention, it is also possible to use other polyfunctional polymerizable components in addition to the above divinyl dicarboxylic acid ester. Other polyfunctional polymerizable components include, for example, ethylene glycol dimethacrylate, vinyl methacrylate, vinyl cinnamate, and the like. By using these polyfunctional polymerizable components in combination, functions can be controlled. Taking memory properties as an example, the memory properties are most noticeable when only divinyl adipic acid ester is used, and the memory properties decrease as the amount of other polyfunctional polymerizable components increases. In this case, if the ratio of the other polyfunctional polymerizable components is between 0 and 100 to 1 part divinyl adibate, it is possible to change only the memory properties while maintaining other good properties. can. At the same time, by appropriately adjusting the ratio of the monofunctional polymerizable component to the polyfunctional polymerizable component, composite films with high memory properties and composite films with no memory properties at all can be produced with other properties such as low performance. This can be achieved while maintaining voltage, high contrast, etc.

As the low-molecular liquid crystal component, which is another component of the liquid crystal composite film, it is desirable to use a liquid crystal mixture whose main component is nematic liquid crystal molecules having positive dielectric anisotropy. Additives may be added to this low molecular weight liquid crystal component. For example, it is possible to improve the light resistance of the composite film by adding an ultraviolet absorber, or to improve the contrast by adding a pleochroic dye, or to add wavelength selection to transmitted light. . The low-molecular liquid crystal component may be contained in the composite film in a proportion ranging from 40 to 95% by weight, thereby achieving the desired function. Preferably, it is in the range of 75 to 90% by weight.

Next, the production of the polymer/liquid crystal composite film of the present invention will be explained. Functional expression of the composite membrane with the above structure is not limited by its manufacturing method, and techniques used in conventional polymer polymerization such as heat, light, electron beam, etc. can be employed as the polymerization method. However, in the case of photopolymerization, the liquid crystal component or polymerizable component is mainly decomposed by ultraviolet light, which may adversely affect photoelectric properties such as resistance value, so thermal polymerization is preferable. An example is shown below.

First, a polymerizable component mixture, a low-molecular liquid crystal component, and a polymerization initiator are mixed in a predetermined ratio. As the polymerization initiator, those used in general polymer thermal polymerization reactions can be used as long as they are compatible with the mixture of the polymerizable component and the low-molecular liquid crystal component. Examples of thermal polymerization initiators include peroxide-based initiators such as benzoyl peroxide, ditertiary butyl peroxide, and lauroyl peroxide.
Azobisisobutyronitrile 1,1'-azobis(cyclohexane-1-carbonitrile) 2,2'-azobis(2-methylbutyronitrile) 2,
Examples include azobis-based initiators such as 2'-azobis(2,4-dimethylvaleronitrile) and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile).

[0017] The composite membrane can be obtained by injecting the above-mentioned solution between substrates that are faced to each other at an appropriate interval, and then heating the solution to polymerize the polymer. When producing a composite membrane, preliminary polymerization may be carried out within a polymerization rate range in which an increase in the viscosity of the solution does not interfere with injection, which is effective in preventing membrane defects due to volumetric shrinkage as the polymerization progresses. For prepolymerization, the solution and the inside of the container are degassed using a container that can be sealed, or replaced with an inert gas (nitrogen, argon, etc.), and then heated to the appropriate operating temperature range of the thermal polymerization initiator used. Let's do it. The polymerization rate is controlled by adjusting the temperature within the appropriate operating temperature range of the thermal polymerization initiator and the heating time. In addition, it is preferable to adjust the mixing ratio of the solution so that all the thermal polymerization initiator is consumed at this stage, thereby
The solution is kept stable until the next step. Moreover, a thermal polymerization initiator may be newly added immediately before the next step. In addition, if the solution is to be stored for a long time, 1000 ppm
Polymerization inhibitors may be added at the following concentrations.

In order to obtain a composite membrane, the above solution may be injected between the substrates and then heated so that the temperature of the injected solution falls within the appropriate operating temperature range of the thermal polymerization initiator used. . Note that rapidly increasing the temperature of the reaction system at the end of the polymerization reaction is a well-known technique in general polymerization reactions, but it can also be applied when manufacturing the composite membrane of the present invention. . It is also effective to use multiple thermal polymerization initiators with different appropriate temperature ranges, and in particular, the thermal polymerization initiators used in prepolymerization and the thermal polymerization initiators used in post-injection polymerization have different appropriate temperature ranges. It is effective to ensure quantitative properties in the polymerization reaction at each stage.

[0019]

【Example】

Example 1 Acrylic acid n-butyl ester 9
Adipic acid divinyl ester
1 part 2,2'-azoisobutyronitrile
0.1 part is mixed and stirred to prepare solution A, and liquid crystal is added to this in the following ratio to prepare a stock solution. Solution A
3 part liquid crystal (BDH company E-
7) A cell was fabricated by bonding two sheets of conductive glass provided with 17-part ITO electrodes using a glass spacer for liquid crystal cells so that the electrode spacing was 10 μm. The above stock solution was sealed in a cell after deaerating it, and then kept at 60° C. for 16 hours to produce a composite membrane. The transmittance was measured using a halogen lamp as a light source and setting the angle of capture of scattered light to 13°. The applied voltage is a 100 Hz square wave. The transmittance was measured in two ways: the initial characteristics immediately after the sample was prepared, and the characteristics after a voltage of 200 V was once applied. In addition, the specific resistance is 4274ALCR manufactured by Hewlett-Packard.
The resistance value of the cell (100 Hz sine wave) was measured using a meter, and estimated using the values of the electrode area and spacing.

Example 2 Acrylic acid n-butyl ester 9 parts Adipate divinyl ester 1
Part ethylene glycol dimethacrylate 3 parts 2
, 2'-Azoisobutyronitrile A composite membrane was prepared in exactly the same manner as in Example 1, except that a solution obtained using 0.1 part of 2'-azoisobutyronitrile was used, and its properties were measured.

Example 3 Acrylic acid n-butyl ester 9 parts Adipate divinyl ester 3
methacrylic acid vinyl ester
1 part 2,2'-azoisobutyronitrile
Example 1, but using a solution obtained using 0.1 part
A composite membrane was prepared in exactly the same manner as described above, and its properties were measured.

Example 4 Acrylic acid n-butyl ester 9 parts Adipate divinyl ester 3
Cinnamic acid vinyl ester
1 part 2,2'-azoisobutyronitrile
A composite membrane was prepared in exactly the same manner as in Example 1, except for using a solution obtained using 0.1 part, and its properties were measured.

Comparative Example 1 Acrylic acid n-butyl ester 9
Part ethylene glycol dimethacrylate 1
Part 2,2' Azoisobutyronitrile
A composite membrane was prepared in exactly the same manner as in Example 1, except for using a solution obtained using 0.1 part, and its properties were measured.

Comparative Example 2 A composite membrane was prepared in exactly the same manner as in Comparative Example 1 except that ethylene glycol dimethacrylate was replaced with vinyl methacrylate, and its properties were measured.

Comparative Example 3 A composite membrane was prepared in exactly the same manner as in Comparative Example 1 except that ethylene glycol dimethacrylate was replaced with cinnamic acid vinyl ester, and its properties were measured.

Table 1 shows the properties of the composite membrane produced as described above.

[0027]

[Table 1]

[0028]

Effects of the Invention The polymer/liquid crystal composite film of the present invention is formed by using a polymer compound formed using divinyl dicarboxylate as a copolymerization component together with a low molecular liquid crystal component. It has the characteristics of low voltage, high contrast, fast response speed, and high electrical resistance. Therefore, the polymer/liquid crystal composite film of the present invention is useful as a display element, a light control element, a light modulation element, an optical shutter, a memory, and the like.

Claims (1)

[Claims] Claim 1: A polymer/liquid crystal composite film comprising a polymer compound obtained by copolymerizing a plurality of copolymer components and a low molecular liquid crystal component, and which exhibits functions in a phase-separated state.
A polymer/liquid crystal composite film, characterized in that the polymer compound is formed using one or more dicarboxylic acid divinyl esters as one of the copolymerization components.