JPH03156402A - Production of light control plate - Google Patents

Abstract

PURPOSE:To produce the light control plate having both of a high degree of scattering and the dependency thereof on the angle of incident light even in a thin film by adding a trace amt. of UV absorbent to a photopolymerizable compd. CONSTITUTION:Laminar microstructural bodies which are periodically formed and vary in refractive index are formed from the extreme neighborhood of the surface irradiated with UV rays if the UV absorbent is added to a compsn. for the light control plate. The UV absorbent is exemplified by 2-hydroxy-4- methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-(2'-hydroxy-5'-methyl phenyl)benzothiazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methyl phenyl)-5- chlorobenzothiazole, etc. The amt. of this UV absorbent to be used is usually in a 50 to 500ppm range, more preferably 100 to 1,000ppm. The light control plate which selectively scatters only the incident light having a specific angle and has uniform film quality and which has both of the high degree of scattering and the dependency thereof on the angle of the incident light even in the thin film is produced by the simple method in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a light control plate that selectively scatters only incident light from a specific angle.

<Conventional technology> Conventional transparent bodies made of plastic or glass were only transparent to light from any angle. Therefore, as a material that only transmits light from a specific angle, there is an alignment film cut out from a plastic block made by laminating plastic transparent sheets and opaque sheets alternately, and a checkered or striped film made of photosensitive resin on a transparent substrate. A so-called "shading plate", which had a relief pattern like this on it and a transparent substrate etc., was used for boat fishing. As this light shielding plate, for example, there is one shown in Japanese Patent Laid-Open No. 189439/1983.

<Problems to be Solved by the Invention> However, these conventional alignment films and light shielding plates have problems in that they are expensive due to complicated manufacturing methods, and the film quality is not uniform. In contrast, by curing polymerizable compounds with different refractive indexes under specific ultraviolet curing conditions, it is extremely easy to create a light control plate with a uniform film quality that selectively scatters only incident light from a specific angle. A manufacturing method has been proposed.

This control plate requires high scattering, for example, 80% or more in terms of haze value, for incident light from a specific angle, and high transparency for incident light from other angles.

In these films, layered microstructures are formed relatively regularly arranged at intervals of several to tens of micrometers along the depth direction. The incidence angle-dependent haze value is caused by this specific layered microstructure. Moreover, this layered microstructure is not visible within several tens to hundreds of micrometers (depending on the resin composition) from the film surface (the surface directly irradiated with external light during curing).

The thickness of the non-layered portion in the film has a large effect on the development of haze value. In other words, the thinner the layerless part is, the thinner the film is and the higher the haze value. However, for example, JP-A-63-30
In the composition for a light control board disclosed in Publication No. 9902, the thickness of this non-layered portion is approximately 50 μm, and the maximum haze value is 80%.
In order to exceed this, a film thickness of 300 μm or more is required.

On the other hand, when trying to improve the haze value by changing the irradiation conditions, for example, increasing the distance between the curing rod lamp and the surface of the cured sample, making the irradiation light parallel light, or using a point light source, etc. Although the haze value is improved, the dependence of the haze value on the angle of incident light is significantly impaired, and problems remain in transparency in areas that should be transparent. Even in such a case, although there is some change in the layer structure in the film, the thickness of the layer-free portion on the film surface remains unchanged.

In other words, it is very difficult to develop a sufficient function in a thin film, and furthermore, in order to develop a sufficient function in a thin film, it is necessary to make the thickness of the non-layered part of the film as thin as possible.

In the current situation where it is important to add functionality to optical materials of this type, thinning the material has been highly desired as it not only greatly contributes to the development of high functionality but also has great cost advantages.

The present inventors have developed a method for manufacturing a light control plate having uniform film quality that selectively scatters and transmits only incident light at a specific angle, and which is capable of achieving high scattering and its dependence on the incident light angle even in a thin film. As a result of studying to find a manufacturing method that has both,
The invention has been completed.

Means for Solving the Problems> That is, the present invention manufactures a light control plate that selectively scatters and transmits only incident light within a specific angle range by curing a photopolymerizable composition by irradiating it with ultraviolet rays from a specific direction. The present invention provides a method for producing a light control board, which comprises adding a trace amount of an ultraviolet absorber to the composition.

By adding an ultraviolet absorber to the composition for a light control board, the present invention enables the formation of periodically formed layered microstructures with different refractive indexes from closer to the ultraviolet irradiation surface, and in the form of a thin film. We have also discovered that it is possible to manufacture a light control plate that has both a high degree of scattering and its dependence on the angle of incident light.

The present invention will be explained in detail below.

Examples of the composition for a light control plate used in the present invention include Japanese Patent Application Laid-Open No. 63-309902 and Japanese Patent Application No. 1-247414.
The photopolymerizable composition for the light control plate described in Japanese Patent No. 1-247415 and the like can be used. That is, examples thereof include (I) a combination of two or more (A) monomers having polymerizable double bonds or (B) oligomers having different refractive indexes, or (II) curing with these monomers or oligomers before and after curing. those with different refractive indexes, or (II[)
A composition of these (A) or (B) and a compound having a different refractive index and not having photopolymerizability can be used. In particular, a combination of the above refractive index differences of 0.01 or more is preferred.

Specific examples of the monomer (A) include tetrahydrofurfuryl acrylate, ethylcalcyl acrylate,
Dicyclopentenyloxyethyl acrylate, phenylcarpitol acrylate, nonylphenoxyethyl acrylate, 2-hydroxy-8-phenoxypropyl acrylate, ω-hydroxyhexanoyloxyethyl acrylate, acryloyloxyethyl succinate, acryloyloxyethyl phthalate, tribromphenoxy Ethyl acrylate, isobornyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2,2.3.3-tetrafluoropropyl acrylate, and methacrylates corresponding to these acrylates, and N-hinylpyrrolidone, N
Examples include acryloylmorpholine. These monomers can be used alone or in combination as long as they satisfy the above conditions.

Examples of the oligomer (B) include polyol polyacrylate, modified polyol polyacrylate, isocyanuric acid skeleton polyacrylate, melamine acrylate,
Examples include hydantoin skeleton polyacrylate, polybutadiene acrylate, epoxy acrylate, and urethane acrylate. These oligomers are (A)
Similarly, if the above conditions are met, they can be used alone or in combination.

Furthermore, as ultraviolet absorbers, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-(2°-hydroxy-5′-methylphenyl)benzothiazole, 2-(2′-hydroxy-3 °-tert-butyl-5'methylphenyl)-5
- Examples include chlorobenzothiazole. These ultraviolet absorbers can be used alone or as a mixture of two or more, and the amount used is usually 50 to 5000 ppm, preferably 100 to 5,000 ppm based on the composition.
The range is oooppm.

By curing the above composition in a photocuring device as shown in FIG. 1, a light control plate that selectively scatters incident light at a specific angle is produced. Further, a thermosetting mechanism can also be used in combination within a range that does not impede performance development. For curing, it is preferable to apply the composition onto a substrate or encapsulate it in a cell to form a film, and then to cure the composition by irradiating it with ultraviolet rays from a specific direction. By this method, it is possible to create a light control plate that selectively scatters incident light at a desired angle. Further, a photopolymerization initiator is not necessarily required when it is sealed in a cell and can block 0□, but in order to improve curability, it is preferable to add the following photopolymerization initiator.

Examples of photopolymerization initiators include benzophenone, benzyl,
Michler's ketone, 2-talolothioxanthone, 2,4
-diethylthioxanthone, benzoin ethyl ether, jetoxyacetophenone, benzyl dimethyl ketal, 2-hydroxy-2methylpropiophenone, l-
Examples include hydroxycyclohexylphenyl ketone.

The light source used in photopolymerization emits ultraviolet rays that contribute to photopolymerization, and the light source has a linear shape when viewed from the irradiated position (film surface), and a rod-shaped lamp is a preferable linear lamp. This is one type of irradiation light source.

When a linear light source is used and the irradiation conditions are adjusted, the resulting sheet-like cured material exhibits anisotropy in the long and short axis directions of the light source, and when rotated around the long axis of the light source, It only scatters light at a specific angle.

In other words, in the sheet-like (film-like) polymerized cured product that is produced, regions with different refractive indexes exist periodically in a state oriented in a certain direction, and light incident from a specific angle causes regions with different refractive indexes to exist periodically. It is thought that the light is totally reflected and scattered at the boundary.

This region with different refractive index is thought to be generated due to the difference in the degree of curing of the compound used in the present invention, and the larger the difference in refractive index due to the degree of curing, the greater the light scattering ability of the produced light control plate. is expected to increase. Therefore, even for compounds having only one polymerizable carbon-carbon double bond in the molecule and compounds having multiple polymerizable carbon-carbon double bonds in the molecule, the difference in refractive index before and after curing is 0. It is thought that compounds with a molecular weight of less than 100% have insufficient scattering ability because it is difficult to create a difference in refractive index due to a difference in degree of curing.

<Effects of the Invention> The light control film has layered microstructures arranged in a relatively regular manner along the depth direction at intervals of several to tens of micrometers. The appearance of haze value, which depends on the incident light angle, is due to this specific layered microstructure. Further, this layered microstructure is not visible within several tens to several hundreds of μm (depending on the resin composition) from the film surface (the surface directly irradiated with light during curing). The thickness of the non-layered portion in the film has a large effect on the development of haze value. In other words, the thinner the layerless part is, the thinner the film is and the higher the haze value. According to the present invention, by adding an ultraviolet absorber to the light-controlled pseudophase polymerizable composition, it is possible to produce a light-control board exhibiting a high haze value even in a thinner film.

Conventionally, for example, in the composition for a light control board disclosed in JP-A No. 63-309902, the thickness of the non-layered portion is approximately 5.
0μm, and as a result, in order for the haze value to exceed 80%, 3
A film thickness of 00 μm or more was required. In the light control plate manufactured by the manufacturing method of the present invention, the thickness of the non-layered portion in the film can be significantly reduced. Therefore, even with a film thickness of 300 μm or less, a haze value of 80% or more can be achieved.

The one showing the highest haze value exhibits a high haze value of 80% or more even in a thin film of about 150 μm.

Further, such scattering occurs only for incident light at a specific angle, and the material has extremely high transparency at other angles. In other words, even a thin film has both a high degree of scattering and its dependence on the angle of incidence. That is, according to the present invention, it is possible to manufacture a light control plate with a uniform film quality that selectively scatters only incident light at a specific angle using a relatively simple method, and which has both a high degree of scattering and its dependence on the angle of incidence even in a thin film. became possible.

Although the light control plate manufactured according to the present invention is in the form of a plastic sheet, it can also be used by coating a glass plate or other plastic sheet. These products can be used in a variety of applications, including window materials, vehicles, displays, mirrors, and greenhouses.

<Examples> The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. In addition,
"Parts" in the examples mean "parts by weight."

Example 1 60 parts per 10 parts of polyether urethane acrylate (refractive index 1.483) obtained by the reaction of poly-1-2-ethylene glycol with an average molecular weight of 1000, hexamethylene diisocyanate and 2-hydroquine ethyl acrylate, 2-Hydroxy-2-propiophenone 1.5
2-(2°-hydroxy-
3°-tert-butyl-5°-methylphenol)-
A resin composition mixed with 160 ppm of 5-chloro-benzothiazole was coated on a glass plate to a thickness of 300 μm, and irradiated with ultraviolet rays using an apparatus as shown in FIG. That is, the irradiation was carried out using a lamp with a length of 40 cm equipped with a reflecting mirror 1.
Using a mercury rod lamp 2 with an intensity of 80 W/cm, using an apparatus equipped with a slit 3 with a slit width of 1.5 cm directly below the lamp and a slit 4 with a slit width of 3 cm on the belt conveyor 5 on the lamp shaft, the composition was prepared. The coated sample 6 was placed on the belt conveyor 5, and the irradiation distance was 50 cm
Irradiation was performed by moving the conveyor at a speed of 150 mm/min.

The dependence of the haze value of the obtained cured film on the angle of incident light was measured as shown in FIG. Furthermore, when the blind layered structure of the cross section of the membrane was observed using an optical microscope, it was found that the microlayered structure was developed at a distance of approximately 60 μm from the surface. Further, the haze value is shown in Table 1.

Example 2 60 parts of 2-hydroxy based on 40 parts of polyether urethane acrylate (refractive index 1,483) obtained by the reaction of polytetramethylene glycol with an average molecular weight of 1000, hexamethylene diisocyanate and 2-hydroxyethyl acrylate A resin mixed with 1.5 parts of -2-methyl-propiophenone and 160 ppm of 2-(2'hydroxy-3'-tert-butyl-5'-methylphenol)-5-chloro-benzothiazole as an ultraviolet absorber. The composition was applied to a thickness of 300 μm on a glass plate and cured in the same manner as in Example 1 to obtain a cured sheet, and the haze value was measured in the same manner as in Example 1. The results are shown in Table 1.

Example 3 2-hydroxy-2-methyl- to 30 parts of polyether urethane acrylate (refractive index 1.483) obtained by the reaction of polytetramethylene glycol having an average molecular weight of 1000, toluene diisocyanate and 2-hydroxyethyl acrylate. 3 parts of propiophenone and 2-(2°-hydroxy-3' as a UV absorber)
A resin composition containing 120 ppm of -tert-butyl-5'-methylphenol)5-chloro-benzothiazole was coated on a glass plate to a thickness of 150 μm, and cured in the same manner as in Example 1 to form a cured sheet. The haze value was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A cured sheet was obtained in the same manner as in Example 1, except that no ultraviolet absorber was used, and the haze value was measured in the same manner as in Example 1. In addition, when we similarly observed the cross section of the film using an optical microscope, we found that the microlayered structure was about 130 μm from the surface.
m and was expressed deeper than in Example 1. Further, the haze value is shown in Table 1.

Comparative Example 2 A cured sheet was obtained in the same manner as in Example 2, except that no ultraviolet absorber was used, and the haze value was measured in the same manner as in Example 1.

Comparative Example 3 A cured sheet was obtained in the same manner as in Example 2, except that no ultraviolet absorber was used, and the haze value was measured in the same manner as in Example 1.

Table 1

[Brief explanation of the drawing]

FIG. 1 shows a side view of an ultraviolet irradiation device used in Examples and Comparative Examples. FIG. 2 shows a method for measuring haze value in Examples and Comparative Examples.

Claims (1)

[Claims] In a method for manufacturing a light control plate that selectively scatters and transmits only incident light in a specific angle range by irradiating a film-like body of a photopolymerizable composition with ultraviolet rays from a specific direction to cure the composition,
A method for producing a light control board, which comprises adding an ultraviolet absorber to the composition.