JPH07199158A - Polymer liquid crystal combined film and its production and liquid crystal optical element using the same - Google Patents

Abstract

PURPOSE:To provide a porous polymer thin film which has a high degree of freedom in selection of liquid crystal materials and high polymer materials, is lessened in the change of electro-optic characteristics with lapse of time and has an excellent contrast when made into a guest-host type by forming the porous polymer thin film of a structural body in which polymer microparticles having a diameter smaller than the wavelength of incident light are linked like chains. CONSTITUTION:This novel polymer liquid crystal combined film is composed of the structural body in which the polymer microparticles having the diameter smaller than the wavelength of the incident light are linked like the chains as the porous polymer thin film 1 of a liquid crystal optical element formed by filling the liquid crystal materials 2 into the holes of the porous polymer thin film 1. This process is for production of such film. The process for production comprises eluting the inert liquid to a polymn. reaction after execution the polymn. reaction of a polymer precursor. At this time, the unreacted polymer precursors and polymn. initiators which are the cause for the deterioration in the electro-optic characteristics and the change thereof with lapse of time are removed as well. Then, the display characteristics of the liquid crystal optical element obtd. by filling the liquid crystal materials into the porous high polymer thin film 1 are good and are lessened in the change with lapse of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer liquid crystal composite film used for display devices for displaying characters, figures, dimming windows for controlling transmission / scattering or transmission / blocking of incident light, optical shutters, etc. And a manufacturing method thereof and a liquid crystal optical element using the same.

[0002]

2. Description of the Related Art Conventionally, liquid crystal optical elements of TN type or STN type using nematic liquid crystals have been put into practical use. However, since these require polarizing plates, they have the drawback of being limited in brightness and contrast. As a liquid crystal optical element that does not require a polarizing plate
There is a liquid crystal element disclosed in Japanese Patent Laid-Open No. 501631 in which a liquid crystal material is contained in a capsule-shaped accommodating means having a curved surface. In the disclosed technology, the fact that the refractive index of the liquid crystal material changes depending on the presence or absence of an electric field is used to make the refractive index of the polymer substance forming the capsule-shaped accommodating means equal to that of the liquid crystal material when a voltage is applied. With such settings, a liquid crystal element is obtained which is transparent under voltage application and becomes opaque by scattering incident light when the voltage is removed. However, in the method for producing a liquid crystal element disclosed in Japanese Patent Publication No. 58-501631, the polymer liquid crystal composite film is produced using an emulsion of an aqueous polymer solution and a liquid crystal material. A small amount of water remains.
This residual moisture causes a change in electro-optical characteristics with time.
The following operating principle is proposed, which has the same operating principle as Japanese Patent Publication No. 58-501631, but does not utilize water during production.

(I) In the manufacturing method disclosed in Japanese Patent Publication No. 61-502128, a liquid crystal material is dispersed in a thermosetting resin, and the liquid crystal material and a polymer precursor are uniformly mixed in advance. After that, the polymer precursor is polymerized to phase-separate the liquid crystal material to obtain liquid crystal droplets.

(II) The production method disclosed in Japanese Patent Laid-Open No. 62-2231 is a method in which a liquid crystal material is dispersed in an ultraviolet curable resin, and after the liquid crystal material and the polymer precursor are uniformly mixed in advance. , The polymer precursor is polymerized, and the liquid crystal material is phase-separated to obtain liquid crystal droplets.

(III) The manufacturing method disclosed in Japanese Patent Laid-Open No. 40418/1992 is a method in which a liquid crystal material is filled in a porous thin film having substantially uniform pores, and a substantially uniform particle is contained in a polymer material. A thin film is prepared with a solution in which fine particles having a diameter are dispersed, and only the fine particles are dissolved and removed to fill the porous polymer thin film with a liquid crystal material.

[0006]

[Problems to be Solved by the Invention] Tokushusho Sho 61-5021
According to the production methods of JP-A No. 28 and JP-A No. 62-2231, a liquid crystal material and a polymer precursor are uniformly mixed in advance, and then the polymer precursor is polymerized to phase-separate the liquid crystal material to obtain liquid crystal droplets. . Therefore, it is necessary to uniformly mix the liquid crystal material and the polymer precursor, and the degree of freedom in selecting the liquid crystal material and the polymer substance is limited. Further, when a guest-host type liquid crystal optical element in which a dye is contained in a liquid crystal material is produced, the dye is taken into a polymer, which causes a problem of lowering contrast. In addition, JP-A-4-
In the manufacturing method disclosed in Japanese Patent No. 401418, in order to obtain uniform characteristics of a liquid crystal optical element, first, fine particles are uniformly dispersed in a polymer material without agglomeration, and removal of the fine particles and liquid crystal material. It is necessary that each of them be sufficiently filled, and advanced technology is required.

The present invention has been made in order to solve the above-mentioned problems, and has a high degree of freedom in selecting a liquid crystal material and a polymer material, reduces changes in electro-optical characteristics over time, and is a guest-host type. In this case, the object is to provide a liquid crystal optical element which has excellent contrast and does not require a high manufacturing technology.

[0008]

In order to solve the above-mentioned problems, the present invention provides a liquid crystal optical element in which pores of a porous polymer thin film are filled with a liquid crystal material, the porous polymer thin film is The present invention provides a novel polymer liquid crystal composite film composed of a structure in which polymer microparticles having a diameter smaller than the wavelength are connected in a chain, and a method for producing the same.

Further, in the production method according to the present invention, after the polymerizing reaction of the polymer precursor is carried out, the liquid inert to the polymerizing reaction is eluted. At this time, unreacted polymer precursors and polymerization initiators that cause deterioration of electro-optical characteristics and deterioration with time are also removed. Therefore, the display characteristics of the liquid crystal optical element obtained by filling the porous polymer thin film according to the present invention with the liquid crystal material are good and the change with time can be reduced. Further, it is not necessary to uniformly mix the liquid crystal material and the polymer precursor,
High degree of freedom in selecting liquid crystal materials and polymer materials. further,
When a guest-host type liquid crystal optical element is prepared by mixing a polychromatic dye into a liquid crystal material, the liquid crystal optical element that has excellent contrast and does not require a high manufacturing technology because the dye is not incorporated into the polymer substance. can get.

The electro-optical characteristics of the liquid crystal optical element are not only the material characteristics of the liquid crystal material used and the polymer substance constituting the encapsulation means, but also the aggregate of the liquid crystal materials defined by the encapsulation means ( The shape and size (liquid crystal droplet diameter) of the liquid crystal droplets, the interaction between the liquid crystal material and the polymer material, and the like have an influence. If the liquid crystal droplet size is much smaller than 1 μm, the driving voltage tends to increase. Therefore, the liquid crystal droplet diameter is 1 μm
Greater than desired. However, if the liquid crystal droplet size is too large, the response time tends to be long. this is,
This is because the influence of the interaction between the liquid crystal material and the polymer substance, which is closely related to the orientation of the liquid crystal material, does not reach the inside of the large liquid crystal droplet.

The pores of the porous polymer thin film containing a liquid crystal material according to the present invention have an average diameter of about 1 to 5 μm, and the surface thereof is composed of fine particles shorter than the wavelength of visible light ( Confirm with electron microscope). Therefore, the contact area between the liquid crystal material and the polymer material is wider than that of a conventional device having a smooth surface. That is, the influence of the interaction between the liquid crystal material and the polymer substance on the liquid crystal droplets of the same volume becomes stronger. Therefore, in the manufacturing method according to the present invention, the liquid crystal droplet diameter is 1 μm.
While keeping the above, it is possible to strengthen the influence of the interaction between the liquid crystal material and the polymer substance. As a result, it becomes possible to manufacture an optical element with an improved response speed of the element. In addition, in a polymer liquid crystal composite film including a liquid crystal material that exhibits a refractive index anisotropy when a voltage is applied and a polymer material that does not have a refractive index anisotropy that includes the liquid crystal material, the polymer material is Since there is a difference in refractive index between the liquid crystal material and the liquid crystal material, the transmittance of incident light depends on the incident angle. However, in the liquid crystal optical element according to the present invention, the porous polymer thin film is composed of a structure in which polymer fine particles shorter than the wavelength of incident light are connected in a chain. Therefore, most of the incident light passes through the porous polymer thin film without depending on the refractive index of the polymer substance that is the raw material of the polymer fine particles. Therefore, the porous polymer thin film of the present invention causes almost no difference in refractive index between the liquid crystal material and the liquid crystal material.
Therefore, the transmittance of incident light does not depend on the incident angle, and a liquid crystal element having a wider viewing angle can be obtained.

The function of the porous polymer thin film of the present invention when no voltage is applied is not to cause a difference in the refractive index with the liquid crystal material to scatter the incident light, but rather to disturb the orientation of the liquid crystal material to cause the incident light to flow. It is to scatter.

The diameter of the fine particles constituting the porous polymer thin film of the present invention may be any number as long as it is smaller than the wavelength of incident light and can maintain a structure in which they are connected in a chain. Considering use in display panels, the wavelength is below the wavelength of visible light, specifically 10
nm to 350 nm, preferably 200 nm
It is above 300 nm.

The polymer precursor may be any UV curable resin, epoxy resin, electron beam curable resin or the like as long as it can form a porous polymer thin film composed of polymer fine particles connected in a chain. Anything is fine. Further, the polymer fine particles are not necessarily required to be colorless and transparent, and may be made of an opaque or light-reflecting substance. It is preferably colorless and transparent and has a refractive index in the range of 1.3 to 1.7.

Examples of the UV curable resin include fluorine-containing resins such as Optodyne UV-3000 and Optodyne UV-2000, ethylene glycol diacrylate, 1,
4-butanediol diacrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate,
Bifunctional acrylates such as ethylene oxide-modified bisphenol A diacrylate and their methacrylate compounds, polyfunctional acrylates such as trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and their methacrylate compounds, And so on.

If necessary, a polymerization initiator may be added to the polymer precursor. Examples of the polymerization initiator include acetophenone compounds such as diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone-1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, benzoin, benzoin methyl ether, and benzoin. Benzoin compounds such as isobutyl ether, benzophenone, 4-phenylbenzophenone-3,3'-dimethyl-4-methoxybenzophenone, 3,3 ', 4,4'-
Benzophenone compounds such as tetra (t-butylperoxycarbonyl) benzophenone, thioxanthone, 2-chlorothioxanthone, isopropylthioxanthone-2,
Examples thereof include thioxanthone compounds such as 4-diisopropylthioxanthone. The addition amount thereof is preferably 0.005 to 15% by weight with respect to the polymer precursor.

The liquid which is inert to the polymer reaction used in the present invention is inert to the polymerizing reaction and can be used in a general solvent such as an aliphatic hydrocarbon or an aromatic hydrocarbon such as hexane or toluene. Any solvent may be used as long as it dissolves, and aliphatic saturated and unsaturated hydrocarbons such as silicone oil, liquid paraffin, and dodecane, and cyclic saturated hydrocarbons may be used. The molecular weight may be in the range of liquid at room temperature, or may be a mixture.

Any combination of the polymer precursor and the liquid inert to the polymerizing reaction may be used as long as it becomes a saturated solution of the polymer precursor when the polymerizing reaction is performed.

The mixing ratio of the polymer precursor and the liquid inert to the polymer reaction may be any as long as the structure of the obtained porous polymer thin film can be maintained. When the amount of the liquid inert to the polymer reaction exceeds 95% of the total volume of the mixed solution, the mechanical strength is remarkably lowered because the volume fraction of the obtained porous polymer thin film is lowered. Therefore, it is difficult to maintain the structure of the porous polymer thin film when the liquid inert to the polymer reaction is eluted. On the other hand, if it is less than 30%, when the liquid crystal material is filled, the drive voltage increases due to the small volume fraction of the liquid crystal material, and the scattering characteristic of the incident light deteriorates. Therefore, the proportion of the liquid inert to the polymer reaction is preferably 60% to 85%.

The coating of the film on the substrate is carried out by a dip coater,
It can be performed by using a general coating method such as a spin coater, a bar coater, a roll coater, and a printing method.

As a method for producing a liquid crystal optical element in which a polymer liquid crystal composite film is sandwiched between a pair of electrodes-attached substrates, for example, a polymer liquid crystal composite film is cast in advance on one substrate and then another substrate is prepared. A method of making by sandwiching between substrates can be used. Further, it may be peeled from the substrate and sandwiched between two other substrates.

The substrate used in the present invention has a highly transparent electrode layer such as ITO (indium tin oxide) on the surface, at least one of which is transparent, and is made of glass,
Plastic, metal, etc. can be used. The two substrates are placed so that the electrodes are on the polymer liquid crystal composite film side. The electrode layer may be formed uniformly on the substrate, but a simple matrix configuration in which strip-shaped electrodes are arranged between the opposing substrates so as to be orthogonal to each other, or an active matrix in which active elements are added in pixel units It may be configured.
The liquid crystal material used in the present invention is not particularly limited as long as it is a liquid crystal material, and any of nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal and the like and a mixture thereof can be used. Further, a guest-host liquid crystal mixed with a single or a plurality of dyes can be used for colorization.

[0023]

【Example】

(Example 1) Optodyne UV-3 as a polymer precursor
1 part by weight of 000 (manufactured by Daikin Chemical Industries) and 4 parts by weight of silicon oil WF-30 (manufactured by Wako Pure Chemical Industries, Ltd.), and stirred sufficiently while heating to 70 ° C. in an oil bath bath to obtain a mixed solution. Was prepared. After the mixed solution was dropped onto one glass substrate with an ITO (indium tin oxide) electrode, a film was formed by a spin coating method. The glass substrate was irradiated with ultraviolet rays for 3 minutes with a high pressure mercury lamp having an ultraviolet irradiation intensity of 15 mW / cm (365 nm) in an inert gas atmosphere to cure the resin. The substrate was immersed in a hexane bath for 1 minute and only silicone oil was eluted to obtain a porous polymer thin film. It was confirmed by SEM observation that a porous polymer thin film having a structure in which fine particles having a diameter of about 200 nm were connected in a chain was formed. The thickness of the obtained porous polymer thin film was 9 μm. This porous polymer thin film is immersed in a liquid crystal material RDP-71120-1 (manufactured by RODIC Co., Ltd.) in a vacuum for each substrate to fill the pores with the liquid crystal material, as schematically shown in FIG. A polymer substance 1 filled with a liquid crystal material 2 was obtained. After that, it was superposed on another glass substrate with an electrode, and a liquid crystal material 2 filled in a polymer substance 1 was sandwiched from both sides by a transparent substrate 4 having a transparent electrode 3 as shown in FIG. A liquid crystal optical element was produced. The light transmittance (wavelength 632.8 nm) of the obtained liquid crystal optical element was 0.7%. When this liquid crystal optical element was kept at 20 ° C. and a rectangular wave AC voltage of 100 Hz and 30 V was applied, the light transmittance was 84% (however, the air transmittance was 100%). When the voltage was removed, the light transmittance returned to 0.7% (see FIG. 3).
The response time of this element was 8 ms when the voltage was turned off → on (30 V) and 15 ms when the voltage was turned on → off (see FIG. 3). Repeating this operation showed similar results.

(Embodiment 2) As a liquid crystal material, E-8 (ME
A liquid crystal optical element was produced in the same manner as in Example 1 except that a mixture of 4 parts by weight of RCK) and 0.08 parts by weight of the black dye S-344 (made by Mitsui Toatsu Co., Ltd.) was used. The light transmittance of the obtained liquid crystal optical element was 0.3%. When the liquid crystal optical element was kept at 20 ° C. and a rectangular wave AC voltage of 100 Hz and 35 V was applied, the light transmittance was 63% (however, the air transmittance was 100%). When the voltage was not applied, the light transmittance returned to 0.3%. Moreover, the response time of the element is 10 m when the voltage is turned off → on (30 V).
It was 18 ms when the voltage was on and off.

(Comparative Example) 1 part by weight of Optodyne UV-3000 (manufactured by Daikin Chemical Industries) as a polymer precursor,
As a liquid crystal material, 4 parts by weight of E-8 (manufactured by MERCK) and 0.08 part by weight of black dye S-344 (manufactured by Mitsui Toatsu Co., Ltd.) were sufficiently mixed. The mixture was vacuum-injected into an empty cell having a cell gap of 9 μm consisting of two glass substrates with transparent electrodes, and then the ultraviolet irradiation intensity was 15 mW at the phase separation temperature.
/ Cm (365 nm) high pressure mercury lamp, the glass substrate was irradiated with ultraviolet rays for 3 minutes to cure the resin to obtain a liquid crystal optical element. Keep this liquid crystal optical element at 20 ° C.
Even if a rectangular wave AC voltage of 0 Hz and 30 V is applied, light (6
The transmittance at 32.8 nm was 51% (provided that the transmittance of air is 100%). Moreover, the response time of the element is 20 ms when the voltage is turned off → on (30 V), and the voltage is turned on.
→ It was 35 ms when off.

[0026]

According to the present invention, there is a high degree of freedom in selection of a liquid crystal material and a polymer material, a change in electro-optical characteristics over time is reduced, and when a guest-host type is used, it has excellent contrast and a high degree of contrast. It is possible to provide a liquid crystal optical element that does not require various manufacturing techniques. Further, it becomes possible to manufacture a liquid crystal element having an improved response speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a polymer liquid crystal composite film according to the present invention.

FIG. 2 is a sectional view showing a liquid crystal optical element according to the present invention.

FIG. 3 is a graph showing a rectangular AC voltage applied to the liquid crystal optical element of the present invention and a light transmittance of the liquid crystal optical element.

[Explanation of symbols]

 1 Porous Polymer Thin Film 2 Liquid Crystal Material 3 Transparent Electrode 4 Transparent Substrate

Claims (3)

[Claims] 1. In a liquid crystal optical element in which the pores of a porous polymer thin film are filled with a liquid crystal material, the porous polymer thin film has polymer microparticles having a diameter smaller than the wavelength of incident light connected in a chain. A polymer liquid crystal composite film, which is composed of a structure. 2. A mixture of a polymer precursor and a liquid inert to the polymerizing reaction is applied on a substrate with a transparent electrode, the polymerizing reaction is performed, and then the liquid inert to the polymerizing reaction. A porous polymer thin film composed of a structure in which polymer microparticles having a diameter smaller than the wavelength of incident light is connected in a chain is prepared by eluting only the A method for producing a polymer-liquid crystal composite film, which comprises filling a liquid crystal material. 3. A liquid crystal optical element in which the polymer liquid crystal composite film according to claim 1 is sandwiched between a pair of substrates with electrodes.