JPH06269726A - Method for curing photosetting material - Google Patents

Abstract

PURPOSE:To effectively cure a photosetting material on the surface of a plastic substrate without damaging the substrate by printing or coating the photosetting material on the surface of low heat-resistant plastics and curing the material layer by ultraviolet rays from a dielectric barrier discharge lamp. CONSTITUTION:A photosetting material is previously printed or coated on the surface of a plastics substrate 1 having a melting point of <=280 deg.C and the material layer 3 is cured by ultraviolet rays from a dielectric barrier discharge lamp 4. By the fact that the dielectric barrier discharge lamp 4 originally operates even when it is not made at a high temperature, that is easy to cool, that its radiation wavelength region is not changed even if power load is made large, or the like, the material is irradiated with strong ultraviolet rays without raising its temperature. Particularly when the lamp 4 is used close to the material to be irradiated with the cooling being intensified and with the temperature rise of its thermal radiation part of the lamp 4 being controlled, the photosetting material layer 3 on the plastics substrate 1 of low heat-resistance is effectively cured by ultraviolet rays without damaging the substrate 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for curing a photocurable substance.

[0002]

2. Description of the Related Art Conventionally, surface modification by graft polymerization on the surface of plastics having poor heat resistance, ultraviolet drying of printing ink on a substrate of plastics having low heat resistance, curing of a coating layer of a photocurable substance, etc. For this purpose, ultraviolet rays emitted from lamps such as a high pressure mercury lamp and a metal halide lamp are used, or electron beam irradiation is used. In the case of an electron beam, it is not generally used for a wide range of fields because the irradiation device is expensive and the operation and maintenance are complicated. Further, in the case of the above-mentioned lamp, it is necessary that the metal encapsulated in order to radiate light in a predetermined wavelength range from the lamp keep a predetermined vapor pressure in the lamp bulb. Therefore, the surface temperature of the valve cannot be lowered freely. Moreover, these lamps also emit light in the wavelength range which is not necessary for UV curing. As a result, the temperature of the object to be treated rises, the bases of the surface-modified surface, the printing surface, and the coating surface of the plastics having low heat resistance are thermally deformed and cannot be used for the original purpose. For example,
This includes weakening of polyethylene bags and “warping” of plastic cards. Conventionally, these drawbacks have been solved by the following two methods.

(1) One is a method of adopting water cooling and a water filter. This is to enclose the lamp with a water jacket to cool the lamp to a level that does not depend on the vapor pressure of the metal used to fill the lamp, and at the same time absorb some of the unwanted radiation wavelength range with water to irradiate the object. To suppress the temperature rise. However, in order to suppress the temperature rise sufficiently, great cost is required. In addition, there is a risk of water leakage during maintenance, which may contaminate the illumination lamp.

(2) The other one is a method of using an optical filter. This uses an optical filter that passes through a wavelength range necessary for processing an object to be irradiated, and cuts light in an unnecessary wavelength range. However, in reality, the light in the required wavelength range is also cut to some extent, which is problematic in terms of power saving. Further, there is a drawback that the illumination lamp incorporating the lamp becomes complicated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to provide a photocurable substance on the surface of a plastic substrate having low heat resistance. Another object of the present invention is to provide a novel method for efficiently curing a substrate without thermally damaging it.

[0006]

In order to achieve this object, in the present invention, a layer of a photocurable substance preprinted or applied on the surface of plastics having a low heat resistance such as a melting point of 280 ° C. or lower. In the case of UV curing, UV light emitted from a dielectric barrier discharge lamp is used as a UV light source.

[0007]

[Function] A discharge lamp using a dielectric barrier discharge (also known as an ozonizer discharge; see the revised edition "Discharge Handpook" published by the Institute of Electrical Engineers of Japan, June 1993, 7th edition, page 263), that is, a dielectric barrier discharge lamp has already been used. , "Mode
ling and Applications of Silent Discharge Plasmas
(IEEE TRANSACTIONS ON PLASMA SCIENCE. VOL.19,
NO.2 APRIL 1991, pp. 309-)
As described in 60 “High-power radiator” and the like, its characteristic is that the efficiency of conversion from electric power to ultraviolet rays is as high as about 20% by only emitting a single spectral line. Since the spectral line is determined by selecting the filling material of the lamp, the optimum one can be selected depending on the irradiation application.

Since the optimum photosensitizing wavelength range in which each photocurable substance reacts is determined, the lamp enclosure should be selected according to it. When photo-curing a substance containing two or more photo-curable substances or photo-initiators, a plurality of optimum wavelength bands may exist. In this case, a plurality of types that emit light of different wavelengths should be used. Use the lamp.

Specifically, as a light emission enclosure of a lamp,
If a mixed gas of krypton and fluorine is selected, the emission wavelength range is 240 nm to 255 n with the main wavelength of 248 nm.
m ultraviolet light is obtained, and if a mixed gas of xenon and chlorine is selected, 300 nm to 320 nm with 308 nm as the main wavelength is selected.
nm is 35 if you select a mixed gas of xenon and fluorine.
Ultraviolet light having a wavelength of 340 nm to 360 nm with a main wavelength of 1 nm and 200 nm to 240 nm having a main wavelength of 222 nm can be obtained by selecting a mixed gas of krypton and chlorine.

By the way, this dielectric barrier discharge lamp is originally capable of operating without being heated to a high temperature.
Because of the ease of cooling and the fact that the radiation wavelength range does not change even when the electric power load is increased, strong ultraviolet light can be emitted without raising the temperature of the irradiation target. In particular, since the cooling can be strengthened and the temperature rise of the heat radiating part of the lamp can be controlled to be used close to the object to be irradiated, the layer of the photocurable substance on the plastic substrate having low heat resistance can be efficiently and efficiently formed. The layer can be UV cured without damaging the substrate.

[0011]

EXAMPLE FIG. 1 is an explanatory diagram of a first example, and is an explanatory diagram of a method of curing an ultraviolet curable printing ink. In the figure, reference numeral 1 is a substrate made of polyethylene foil having a thickness of 15 μm, which is carried by a belt conveyor 2. 3 is
A layer of a UV-curable printing ink, to which 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 was added as a photoinitiator, from a dielectric barrier discharge lamp 4 together with a polyethylene foil 1. Receive the emitted ultraviolet light.

A schematic view of the coaxial cylindrical dielectric barrier discharge lamp used in the first embodiment is shown in FIG. Discharge vessel 13
Is made of quartz glass and has an inner tube 14 and an outer tube 15 coaxially arranged to form a hollow cylinder. The inner tube 14 and the outer tube 15 also serve as a dielectric barrier for a dielectric barrier discharge and a light extraction window member, and electrodes 16 and 17 made of a metal net that transmits light are provided on the outer surfaces of the inner and outer tubes 14 and 15, respectively. A ring-shaped getter 18 is provided at one end of the discharge space 19. A discharge gas that forms excimer molecules by a dielectric barrier discharge is enclosed in a discharge space 19 formed in an airtight manner, and an alternating current is applied to the transparent electrodes 16 and 17 made of a metal mesh provided on the surfaces of the dielectrics 14 and 15. When a voltage is applied by the power supply 26, so-called dielectric barrier discharge, which is also called ozonizer discharge or silent discharge, occurs in the discharge space 19,
Ultraviolet rays are radiated with high efficiency through the dielectrics 14 and 15 and the transparent electrodes 16 and 17. Although not shown in the drawing, the surfaces of the transparent electrodes 16 and 17 are covered with an ultraviolet-transparent resin or glass to electrically insulate them, if necessary. In addition, the outer electrode 17 that directly contacts the object to be processed or the processing fluid.
Is preferably used at ground potential. Hollow part 12
The lamp can be sufficiently cooled by returning cooling water to the lamp. If a mixed gas of xenon and chlorine is used as the discharge gas, the wavelength range from the lamp will be 300 nm.
Ultraviolet light spanning from 320 nm to 320 nm is emitted, and the above work can be efficiently performed.

The electric input is 150 W per cm in the axial direction of the lamp, and six lamps are arranged on the same plane so that the lamp axis is perpendicular to the traveling direction of the belt conveyor. As the cooling condition, the surface temperature of the outer pipe 15 is 430 at the maximum.
If you use this lamp after air cooling to below ℃,
The temperature rise of the polyethylene foil is about 10 ° C. above room temperature, and the ink can be efficiently dried without damaging the foil.

In the second embodiment, the irradiation object on the belt conveyor in the first embodiment is as follows. That is, the irradiated object is a 1 mm thick polyamide card,
An epoxy acrylate UV-curable resin to which 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 was added as a photoinitiator was applied. Also in this case, if the maximum lamp surface temperature is set to 430 ° C. or lower as the lamp cooling condition, the card can be covered with resin when the “warpage” of the card is ± 0.1 mm or less.

In the third embodiment, the irradiation object on the belt conveyor in the first embodiment is as follows,
The lamp fill gas was a mixed gas of krypton and chlorine. That is, the object to be irradiated is a polyethylene foil having a thickness of 15 μm, on which a symbol is printed with an ultraviolet curable printing ink to which benzyl methyl ketal is added as a photoinitiator. Ultraviolet light in the wavelength range of 220 nm to 240 nm is emitted from the lamp, but if the lamp is used with the maximum lamp surface temperature of 450 ° C or less as the cooling condition, the surface temperature of the polyethylene foil is The rise can dry the sign without exceeding 10 ° C from room temperature. Therefore, there is no thermal deformation of the polyethylene foil.

FIG. 3 is an explanatory view of the fourth embodiment,
It is explanatory drawing of the adhesion method of a lens. In the figure, 4 is
It is the same as the lamp used in the first embodiment and is used under the same cooling condition. 5 is a convex lens made of polymethylmethacrylate, and 6 is 2-methyl-1- (4-methylthiophenyl) -2 as a photoinitiator.
-A thin layer of UV-curable epoxy acrylate resin with morpholinopropane-1 added, and 7 is a glass lens. In this state, even if ultraviolet rays are irradiated from the convex lens 5 side, both lenses can be satisfactorily adhered to each other without thermal deformation of the convex lens 5. The adhesive strength endured a pulling force of about 10N.

The fifth embodiment is the drying of UV-curable printing ink. As the substrate, a polyethylene foil having a thickness of 15 μm, and as the ink, a UV-curable printing ink containing benzyl dimethyl ketal added as a photoinitiator,
As the lamp, in the lamp having the structure used in the first embodiment, a mixed gas of krypton and fluorine is used as a filling gas, and a radiation wavelength range of 240 nm to 255 n.
The thing which can obtain the ultraviolet light of m is used. The electric input is 150 W per 1 cm in the axial direction of the lamp, and 6 lamps are arranged in parallel in a plane parallel to the substrate with the axes aligned in parallel and densely arranged to form a surface light source as a whole. As for the cooling conditions, the maximum surface temperature of all the lamps was 450 ° C, and when the drying operation was performed in this way, the temperature rise of the polyethylene foil was 10 ° C at the maximum, and the efficiency was improved without thermal deformation. The ink can be dried well.

The sixth embodiment is drying of the UV-curable printing ink using another lamp having a different emission wavelength range. As the substrate, a polyethylene foil with a thickness of 15 μm,
As the ink, 2-methyl-1- (4
-Methylthiophenyl) -2-morpholinopropane-
The UV-curable printing ink containing 1 added, the lamp having the structure used in the first embodiment, a mixed gas of xenon and fluorine is used as a filling gas, and an ultraviolet ray having a radiation wavelength range of 340 nm to 360 nm is used. Use a light source. Electric input is 1 in the axial direction of the lamp
150 W per cm, 6 in a plane parallel to the substrate,
The axes should be parallel and closely arranged so that they are like a surface light source as a whole. As for the cooling conditions, the maximum surface temperature of all the lamps was 430 ° C., and when the drying operation was performed in this way, the temperature rise of the polyethylene foil was 10 ° C. at the maximum, and thermal deformation and deterioration were also caused. In addition, the ink can be dried sufficiently efficiently.

FIG. 4 is an explanatory view of the seventh embodiment,
It is explanatory drawing of the drying method of the ink which uses two types of lamps. In the figure, 4a and 4b are dielectric barrier discharge lamps of the structure used in the first embodiment, and 4a is
A mixed gas of krypton and chlorine is used as the lamp filling gas, and 4b is a mixed gas of xenon and chlorine as the lamp filling gas. 1 is a polyethylene foil having a thickness of about 15 μm, 2 is a belt conveyor, and 3 is printing ink. The printing ink 3 contains 2-methyl-1- (4-methylthiophenyl)-as a photoinitiator.
It is a UV-curable printing ink to which 2-morpholinopropane-1 and 1-hydroxy-cyclohexyl-phenylketone are added.

As shown in the drawing, four lamps of two kinds are alternately arranged and the lamps are densely arranged with their axes in parallel. The axis of the lamp is orthogonal to the traveling direction of the belt conveyor. As for the cooling conditions, the maximum surface temperature of any of the lamps was 420 ° C., and when the drying operation was performed in this way, the surface temperature rise of the polyethylene foil became a maximum of 9 ° C., and thermal deformation and deterioration were also caused. In addition, the ink can be dried sufficiently efficiently.

The eighth embodiment is the same as the seventh embodiment, except that
The irradiation target is a polyamide plate having a thickness of 1 mm. Epoxy acrylate added with benzyl dimethyl ketal as a photoinitiator was applied to this plate, and the same experiment as in the seventh example was carried out. The board could be coated.

[0022]

As can be understood from the above description of the embodiments, a photocurable substance is printed or applied on the surface of a plastic substrate having a low heat resistance such as a melting point of 280 ° C. or lower. When curing the layer with ultraviolet rays, it was possible to cure it because it used a lamp with a high bulb surface temperature, such as a metal halide lamp or a high-pressure mercury lamp, and it was a lamp that emitted light unnecessary for curing. In the present invention, when the substrate is thermally deformed or deteriorated, or a complicated irradiation lamp is configured to eliminate this defect, the substrate is cured in a state where the substrate is hardly thermally deformed or deteriorated. Has the advantage that work can be performed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method for curing an ultraviolet curable printing ink according to the present invention.

FIG. 2 is an explanatory diagram of a dielectric barrier discharge lamp used in the present invention.

FIG. 3 is an explanatory diagram of a lens bonding method according to the present invention.

FIG. 4 is an explanatory diagram of another ink drying method according to the present invention.

[Explanation of symbols]

 1 Substrate 2 Belt Conveyor 3 Layer of UV Curing Printing Ink 4 Dielectric Barrier Discharge Lamp 5 Convex Lens 7 Glass Lens 14 Inner Tube 15 Outer Tube 16 Electrode 17 Electrode 19 Discharge Space

Claims (5)

[Claims] 1. A plastic material having a melting point of 280 ° C. or lower is preliminarily printed or coated with a photocurable substance, and the substance layer is cured by ultraviolet light emitted from a dielectric barrier discharge lamp. A method for curing a photocurable substance. 2. The method for curing a photocurable substance according to claim 1, wherein the photocurable substance contains a photoinitiator. 3. In the spectral distribution of the emission wavelength from the dielectric barrier discharge lamp, 2 is the main component of the emission wavelength.
22 nm or 248 nm, and the photocurable substance contains at least one of benzyl dimethyl ketal or 1-hydroxy-cyclohexyl-phenyl ketone as a photoinitiator. A method for curing a photocurable substance. 4. In the spectral distribution of the radiation wavelength from the dielectric barrier discharge lamp, the main component of the radiation wavelength is 3
08-nm or 351 nm, and the photo-curable substance is 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1, or 2 as a photoinitiator.
The method for curing a photocurable substance according to claim 1, which comprises at least one of -benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1. 5. Ultraviolet light has 222n as a main component.
m, 248 nm, 308 nm, or at least two of 351 nm are included.
A method for curing a photocurable substance as described above.