JPS61170704A - Production of optical filter - Google Patents

Abstract

PURPOSE:To reduce polymn. time by sandwiching a cholesteric liquid crystal by two sheets of substrates having light transmittability and subjecting the liquid crystal to a planar orientation them irradiating light from both sides of the substrates to effect photopolymn. CONSTITUTION:The cholesteric liquid crystal consisting of a soln. mixture composed of a polypeptide compd. and photopolymerizable monomer is sandwiched by two sheets of the substrate consisting of glass, polymer films, etc. and having light transmittability and after the liquid crystal is subjected to the planar orientation, the light is irradiated thereto from both sides of the substrate to accelerate the photopolymn. from the two sides of the substrate. The polymn. velocity is lower the further in the thickness direction of the film. The polymn. time is longer than twice when the thickness of the film is double- fold. If the light is irradiated from both sides of the substrates, the thickness at which the arrival of the light is required is 1/2 the thickness required when the light is irradiated from one substrate side. The time required for the production of the film is thus made shorter by as much as the decreased quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing optical filters used in displays, optoelectronics, and the like.

[Prior Art] It has been well known that Lesteric liquid crystals exhibit optical properties such as selective light scattering, optical rotation, and 9-circular dichroism. By applying the optical properties of cholesteric liquid crystal, a method for manufacturing a cholesteric liquid crystal film that can withstand practical use was invented (Japanese Patent Application Laid-Open No. 139506/1983). This cholesteric liquid crystal film is a solid polymer film in which a cholesteric liquid crystal structure is fixed by photopolymerizing a lyotropic liquid crystal consisting of a liquid mixture of a cholesteric liquid crystal component and a compound having a polymerizable unsaturated group.

Photopolymerization is used in the production of photoresists and surface coatings. In this case, the film thickness was several μm, and it was possible to polymerize in a short time by irradiating light from one side.

Problems to be Solved by the Invention In order for a cholesteric liquid crystal film to have the optical properties necessary as an optical filter, it must have a thickness of several tens of micrometers to several hundreds of micrometers.
thickness is required. When producing a film by polymerizing by irradiating light from one substrate side, polymerization starts sequentially from near the substrate surface on the side irradiated with light. The polymerized and unpolymerized portions each have the property of absorbing light. As photopolymerization progresses, the polymerized portion absorbs the irradiated light, the amount of light reaching the unpolymerized portion decreases, and the polymerization rate slows down, resulting in a longer polymerization time.

The longer the polymerization time, the more the already polymerized portions are irradiated with light, which accelerates the deterioration caused by light. Therefore, a long polymerization time will affect the optical properties and durability of the film.

6゜In order to solve the above-mentioned problems, the present invention sandwiches a cholesteric liquid crystal made of a mixed solution of a polypeptide compound and a photopolymerizable monomer between two light-transmitting substrates such as glass or polymer film, After planar orientation, light is irradiated from both sides of the substrate to promote photopolymerization from both sides of the substrate, increasing the efficiency of light irradiation and shortening the polymerization time required for film production.

The working polymerization time varies depending on the intensity of irradiation light, material, film thickness, etc. If light is irradiated from one substrate side, it will be farther away from the substrate on the light source side. In other words, the polymerization rate becomes slower as the distance increases in the film thickness direction. Therefore, if the thickness of the film is doubled, the polymerization time will be more than doubled. On the other hand, when light is irradiated from both sides of the substrate, the thickness that the light needs to reach is % of the thickness when irradiated from one substrate side.
, and the time required for film production can be shortened to the extent that the amount of light decreases less.
1. It is also believed that by shortening the polymerization time, deterioration during film production can be prevented and an optically stable film can be provided.

Example 1 Weighed 60% by weight of poly-L-glutamic acid n-butyl ester as a liquid crystal material and 60% by weight of triethylene glycol dimethacrylate as a photopolymerizable monomer.
Both were sufficiently stirred while maintaining the temperature at 6 to 40"C. The homogeneous liquid crystal solution thus obtained was sandwiched between two glass substrates via a 200 μm thick spacer, and heated at 30"C.
The temperature was maintained at a constant temperature for 3 hours. After that, continue to 30″
1 k simultaneously from both sides of the substrate while holding at a temperature of 1 k
UV irradiation was performed for 1 hour using an ultra-high-pressure mercury lamp placed 1 m apart to polymerize the 7-mer to obtain a film.

Next, for comparison, a similarly uniformly mixed liquid crystal solution was sandwiched between two glass plates via a 200 μm thick spacer, and held at a constant temperature of 30° C. for 3 hours. after that,
The monomers were subsequently polymerized at a constant temperature of 30°C. Since this product had unpolymerized portions, it lacked strength as a film and was insufficient for use as an optical filter.

Sandwiched between two glass substrates via a thick spacer,
A constant temperature of °C was maintained for 3 hours. After that, continue to 3
The substrate was rotated every 10 minutes while being maintained at a temperature of 2°C, and ultraviolet rays were irradiated for 2 hours using a 1 kW ultra-high pressure mercury lamp at a distance of 0.8 m to polymerize the monomer and obtain a film.

Next, for comparison, a similar liquid crystal solution was sandwiched between two glass substrates via a 200 μm thick spacer, and heated at 32°C.
3 hours at a constant temperature of 32°C.
While holding the substrate at
The monomer was polymerized. Since this product had unpolymerized portions, it lacked strength as a film and was insufficient for use as an optical filter.

Effects of the Invention According to the present invention, it is possible to increase the efficiency of light irradiation, prevent deterioration during polymerization, and provide a stable film.

Claims (4)

[Claims] (1) A cholesteric liquid crystal made of a mixed solution of a polypeptide compound and a photopolymerizable monomer is sandwiched between two light-transmitting substrates, planarly oriented, and then photopolymerized by irradiating light from both sides of the substrates. A method for manufacturing an optical filter, characterized by: (2) The method for manufacturing an optical filter according to claim 1, wherein in the step of photopolymerizing the liquid crystal by irradiating light from both sides of the substrate, light is irradiated from both sides of the substrate simultaneously. (3) The method for manufacturing an optical filter according to claim 1, wherein the substrate is rotated in the step of photopolymerizing the liquid crystal by irradiating light from both sides of the substrate. (4) The polypeptide compound is polyglutamic acid n-
The method for producing an optical filter according to claim 1, wherein the photopolymerizable monomer is a butyl ester and the photopolymerizable monomer is triethylene glycol dimethacrylate.