JPH10292004A - Production of photocured product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for inexpensively producing a photocured product which does not absorb light such as ultraviolet rays, is transparent thereto and reduced in influences such as dissolution in an uncured substance by curing a non-liquid-crystal photopolymerizable substance in the form of a film having a specified thickness and in the state immersed in water by light irradiation and thereby effectively excluding oxygen. SOLUTION: The photopolymerizable substance is a non-liquid-crystal photopolymerizable substance, the curing of which proceeds by a radical reaction, is exemplified by a water-insoluble compound having an olefinic unsaturation such as acrylic or methacrylic or a composition essentially consisting of it and includes an oligomer and a polymer. The thickness of the film of the phtocurable substance should be 10 μm or below. For example, a photocurable substance layer/polycarbonate sample 1 prepared by applying a photocurable substance being a protective coating mateal (e.g. acrylic monomer/oligomer mixture) in a thickness of 2 μm on a polycarbonate film having a thickness of 100 μm is immersed in water 2, irradiated with light from a high-pressure mercury vapor lamp and dried to obtain a stable cured substance layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a photocured product utilizing a photoradical reaction.

[0002]

2. Description of the Related Art An acrylic resin can be obtained by a radical reaction of a monomer as a raw material. The reaction starts by generation of radicals from the initiator, and the reaction proceeds in a chain. Initiators include those that generate radicals by heat and those that generate radicals by light.

[0003] One of the major problems in this reaction is the so-called oxygen inhibition, in which the radicals responsible for the reaction are trapped by oxygen in the air, thereby stopping the reaction or greatly reducing the reaction rate. In the case where the object to be cured is a thin film, the area of contact with oxygen is large, so that oxygen inhibition is a problem. Also, comparing the case where the radical reaction is initiated by heat and the case where it is initiated by light, the latter is characterized by rapid curing, and the problem of oxygen inhibition is more important.

Conventional measures against oxygen inhibition in the photoradical reaction include increasing the amount of initiator, increasing the amount of exposure, increasing the film thickness, and covering the surface of the object to be cured with an oxygen barrier film. Have been.

In the first case, the properties of the cured resin may deteriorate due to an increase in the amount of the non-curable initiator. There is also a possibility that a decomposition product of the initiator contributes to coloring of the cured product. The other method requires a large-sized lamp and cooling equipment, and greatly increases running costs. Further, if the process speed is reduced in order to increase the irradiation efficiency per area, the productivity is reduced. In many cases, even if these problems are ignored, sufficient curability cannot be sufficiently improved.

The above method is not a general method because the types of products from which the film thickness can be selected are limited. Is a method in which the surface of the object to be cured is covered with a film such as polyvinyl alcohol as a barrier film to block oxygen. The method comprises:
It can be said that the effect is the largest among the above measures. However, a process for forming the blocking film and a process for removing the blocking film after curing are required, which leads to a large increase in cost. Further, in the process of forming the barrier film, the material to be cured may be degraded, so that it cannot be used as a method for coping with excellent oxygen inhibition.

[0007]

DISCLOSURE OF THE INVENTION In view of the above problems, the present inventors have been able to block oxygen, have no absorption with respect to irradiation light such as ultraviolet rays, are transparent, and have been subjected to ordinary photocuring. As a result of examining a material having little influence on the cured product such as dissolution, it was found that an inexpensive substance such as water could be used very effectively, and the present invention was completed.

[0008]

That is, the present invention is characterized in that a thin film non-liquid crystal photopolymerizable material having a film thickness of 10 μm or less is irradiated with light in a state of being immersed in water and cured. The present invention relates to a method for producing a photocured product.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below. The photopolymerizable material to be used in the method of the present invention is not particularly limited as long as it is a non-liquid crystalline photopolymerizable substance which cures by a radical reaction and is insoluble in water. There are photopolymerizable substances conventionally used for photocuring, for example, a compound having an olefinic double bond such as an acryl group or a methacryl group or a composition containing the compound as an essential component. Here, the compound includes not only a monomer but also an oligomer or a polymer as in a general photocurable resin.

Specific examples of these compounds include the following compounds. For example, ethyl acrylate,
Butyl acrylate, hydroxyethyl acrylate,
Esters of acrylic or methacrylic acid of monohydric or polyhydric alcohols such as hydroxyethyl methacrylate, ethylene glycol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, etc. Classification: Polyester (meth) acrylate obtained by reacting (meth) acrylic acid with polyester prepolymer obtained by condensation of polyhydric alcohol and monobasic acid or polybasic acid; having polyol group and two isocyanate groups Polyurethane (meth) acrylate obtained by reacting a compound and then reacting with (meth) acrylic acid; bisphenol A epoxy resin, bisphenol F epoxy resin, novolak epoxy resin Carboxymethyl resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, fatty acid or alicyclic epoxy resin, amine epoxy resin, triphenolmethane type epoxy resins, and epoxy resins such as dihydroxybenzene type epoxy resin (meth)
Examples include ordinary photopolymerizable resins such as epoxy (meth) acrylate obtained by reacting acrylic acid.

In the present invention, a so-called photoinitiator for generating radicals is usually contained in the object to be cured, in order to initiate the curing reaction of the object comprising the non-liquid crystalline photopolymerizable substance by light. Coexist. As the photoinitiator, a well-known photoinitiator can be appropriately used. Specific examples include the following compounds.

For example, benzyl, benzoyl ether, benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, benzyl methyl ketal, dimethylaminomethyl benzoate, 2- n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-
Methoxybenzophenone, methyllobenzoylformate, 2-methyl-1- (4-methylthio) phenyl
-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2 -Methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2
-Hydroxy-2-methyl-1-phenylpropane-1
-One, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone 2,4
-Diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone and the like. These photoinitiators are usually 0.5 to 30% by weight, preferably 2 to 30% by weight, based on the photopolymerizable compound contained in the object to be cured.
Used in the range of 15% by weight. The photoinitiators may be used alone or in combination of two or more.

Further, an appropriate sensitizer may be coexistent on the object to be cured according to the wavelength of the light source for irradiation. The object to be cured described above can exert its effect on the object to be cured having any shape in the method of the present invention,
The effect is remarkable for a thin film, particularly a thin film having a thickness of 10 μm or less, preferably 6 μm or less.

As means for forming the object to be cured into a thin film, a coating method on a plate is usually used. In this case, the object to be cured may be applied to an appropriate substrate, for example, a glass plate, a plastic film, a plastic sheet, or the like, or may be once dissolved in a solvent and applied, and then the solvent may be removed. As a coating method, for example, a bar coating method, a roll coating method, a spin coating method, a die coating method,
Dipping method, gravure printing method, screen printing method,
A spray coating method can be given.

According to the present invention, a thin film of a material to be cured is formed on a substrate by the above-mentioned method, and then the thin film together with the substrate is poured into water to perform a photocuring reaction. Generally, the amount of dissolved oxygen in water is as low as about 8 ppm at room temperature, which is suitable for eliminating the influence of oxygen inhibition. Regarding the low dissolved oxygen content in water, the Bunsen absorption coefficient (Bunse
n's aboaction coefficie
nt). That is, the coefficient of oxygen to water is 0.028 at 20 ° C., which means the amount of oxygen (weight or moles) in a given volume.
However, if the value in the air is 1, the value is only 0.028 in the water in contact with the air.

The water used is not particularly limited.
For example, distilled water, ion-exchanged water, tap water, or the like can be used as appropriate. If there is no possibility that the effects of the present invention are impaired, an organic solvent or the like may coexist in the water, or an organic or inorganic substance may be dissolved in the water.

The oxygen inhibition in water is much smaller than that in a normal air atmosphere. However, in order to eliminate the influence of dissolved oxygen in water and obtain better curing conditions, it is necessary to use nitrogen or argon. It is preferable to bubble water with an inert gas such as. It is desirable to perform bubbling with nitrogen gas in terms of cost. The flow rate of the inert gas cannot be said because it depends on the production scale, but as a guide, it is usually 10 ml / min to 1000 m / liter of water.
1 / min, preferably in the range of 50 ml / min to 500 ml / min. If the flow rate is less than 20 ml / min, the effect of lowering the dissolved oxygen concentration in water may be insufficient, and the merit of bubbling is small. On the other hand, if it is more than 1000 ml / min, the water surface is difficult to stabilize, so that light from the light source is likely to be irregularly reflected on the water surface, which may lower the irradiation efficiency.

The temperature of the water is not particularly limited. Usually, water temperature at room temperature may be used, but it may be controlled in accordance with the properties of the object to be cured or the cured product of the reaction system.

When the object to be cured is immersed in water, the distance from the surface of the object to be cured is not particularly limited, since the water has high transparency, but is usually from 1 mm to 50 cc, preferably 5 mm. Not less than 20 cm. In general, if the depth is smaller than 1 mm, the surface of the object to be cured may be exposed from the water surface, which is not desirable. On the other hand, if it is deeper than 50 cm, the intensity of light applied to the object to be cured may be weak, which is not desirable.

The wavelength of the light to be subsequently irradiated is not particularly limited, and ultraviolet light, visible light, and infrared light (heat ray) can be used as needed. Usually, ultraviolet light is used. Light sources include low-pressure mercury lamps (germicidal lamps, fluorescent chemical lamps, black lights), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), short arc discharge lamps (ultra-high-pressure mercury lamps, xenon lamps, mercury xenon lamps), etc. Is mentioned. Among them, ultraviolet light from a high-pressure mercury lamp is the most common and can be preferably used in the present invention. When an appropriate sensitizer is contained in the object to be cured or when the object to be cured itself has a sensitizing effect, it is of course possible to use a light source in the visible light region.

The amount of light emitted from the light source as described above cannot be determined unconditionally because it depends on the type of the object to be cured and the amount of the initiator added, but is usually from 1 to 5000 mJ / cm ² , preferably from 20 to 5000 mJ / cm ² . 3000 mJ / cm ² , more preferably 5
The range is from 0 to 2000 mJ / cm ² . Note that water shows high transmittance with respect to light from the light source, so that there is almost no loss of light due to absorption.

After the light irradiation, the cured product is taken out of the water,
Remove water droplets on the surface. The removing method may be blowing off with air or the like, or drying with heat or wind. In addition, after removing water, the unreacted site is further reacted,
Aging by so-called heat treatment may be performed.

When photocuring is carried out by the method of the present invention described above, a cured product can be obtained with little influence of oxygen inhibition by a photoradical reaction.

[0024]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. FIG. 1 schematically shows a light irradiation apparatus used in the examples. (Example 1) Protective coating material UV-3 manufactured by Toagosei Co., Ltd.
810 (acrylic monomer / oligomer mixture) was used as a material to be cured, and was applied to a 30 cm square, 100 μm thick polycarbonate film by a gravure coating method to a thickness of 2 μm. A sample 1 of a cured material layer / polycarbonate film obtained by coating was applied to a 40 cm square, 15 c depth.
tap water at 30 ° C to a depth of 10cm
Sample 1 was submerged with the surface of the layer to be cured facing upward. Next, the surface of the layer to be cured was irradiated with light from a high-pressure mercury lamp. After irradiating 400 mJ of light per 1 cm ² ,
Sample 1 was taken out and water droplets on the surface were blown off with an air gun. Next, it was dried on a hot plate at 60 ° C. for 10 minutes. The cured material layer on the polycarbonate had no stickiness and rubbing with a cotton swab soaked in toluene did not change anything.

Comparative Example 1 Sample 1 prepared in Example 1
Was irradiated with light on the surface of the layer to be cured in an air atmosphere. 40
At a light amount of 0 mJ / cm ² , the surface of the layer to be cured was sticky and was not completely cured. When light was further applied and irradiation was performed for a total of 2000 mJ / cm ² , no stickiness was found, but it was found that the layer of the material to be cured was whitened by toluene and curing was insufficient. 400 more light
When irradiated with 0 mJ / cm ² , whitening was finally stopped by toluene. The curing was about 10 times slower than that of Example 1.

Example 2 Tripropylene glycol diacrylate (50 parts), hexanediol triacrylate (20 parts), trimethylolpropane triacrylate (10 parts), butyl methacrylate (10 parts),
A cured object was prepared containing polyvinylpyrrolidone (10 parts) and benzoin isobutyl ether (2.5 parts) as an initiator. The object to be cured was 30 cm square and 10 cm thick.
A 4 μm thick film was applied on a 0 μm polyethylene terephthalate film using a gravure coating method, and the obtained cured material layer / polyethylene terephthalate film sample 2 was placed in a saturated saline solution at 25 ° C. The layer surface was irradiated with light from a high pressure mercury lamp. The sample 2 was irradiated with light in a state where the sample 2 was submerged at a depth of about 2 cm from the water surface.
After irradiating 600 mJ of light per 1 cm ² , the sample 2
After being taken out and washed with fresh water, water drops on the surface were blown off with an air gun and dried on a hot plate at 60 ° C. for 10 minutes. The hardened material layer on the polyethylene terephthalate film had no stickiness, and there was no change when rubbing with a cotton swab soaked in toluene.

Comparative Example 2 Sample 2 prepared in Example 2
Was irradiated with light on the surface of the layer to be cured in an air atmosphere. At least about 8,000 mJ until the layer to be cured is no longer sticky and no longer dissolved by toluene.
/ Cm ² . In addition, the temperature of Sample 1 immediately after the end of the light irradiation rose to 80 ° C., and curling was observed around the polyethylene terephthalate film.

[0028]

According to the method of the present invention, by irradiating light in water, the effect of oxygen inhibition can be greatly reduced, and rapid photocuring can be achieved. Therefore, less irradiation energy is required, and the cost can be reduced. Furthermore, since the irradiation device is simplified, the industrial value is high.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a light irradiation device used in an embodiment.

[Explanation of symbols]

 1 sample 2 water 3 vat 4 lamp 5 quartz plate 10 exhaust

Claims (1)

[Claims] 1. A method for producing a photocured product, comprising irradiating a non-liquid crystalline photopolymerizable material having a thickness of 10 μm or less with light in a state of being immersed in water and curing the photocured product.