JPS6034999B2 - Curing method for UV-curable adhesive tapes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultraviolet curing method for ultraviolet curable adhesive tapes.

Conventionally, UV-curable adhesive tapes are produced by coating a UV-curing adhesive on a base material made of plastic film, paper, fiber, etc. made of polyethylene, vinyl chloride, polypropylene, polyester, etc., and curing it by irradiating it with ultraviolet light. , manufactured.

Furthermore, since the above-mentioned ultraviolet curable adhesives generally undergo radical polymerization due to irradiation with ultraviolet rays, the reaction is significantly inhibited by oxygen in the atmosphere.For this reason, the surface of the ultraviolet curable adhesive has traditionally been used as a means of blocking oxygen. , - A method of covering the adhesive surface with a plastic film such as polyethylene or polyester, or a method of performing it under an inert gas atmosphere, etc., has been proposed. The stress applied to the laminate film is released before the UV-curable adhesive hardens, causing the UV-curable paper adhesive to flow, which causes air bubbles to easily enter the laminate film due to variations in thickness and unstable retention of the laminate film. This causes unevenness on the coated surface.

Furthermore, it takes time to peel off the laminate film after curing.
It has drawbacks such as poor workability. In addition, in the method of irradiating under an inert gas atmosphere, the surface of the UV-curable adhesive is cured with streaks remaining after coating, resulting in an uneven coated surface, requiring a large amount of inert gas, and requiring equipment. The larger the scale, the higher the cost. This poses difficulties in terms of the working environment, including danger. On the other hand, other methods have been proposed, such as a method of impregnating wax into an ultraviolet curable paper adhesive and a method of immersing it in a liquid and irradiating it, but these methods are undesirable because they cause deterioration of the coating film.

The present invention has been made in order to solve such drawbacks.In a method of curing an ultraviolet curable adhesive applied to a tape substrate, the adhesive-coated surface of a tape base coated with an ultraviolet curable adhesive is The adhesive is cured by being conveyed while being brought into close contact with the surface of a rotating transparent cylinder roll equipped with an ultraviolet lamp inside.

In other words, the UV-curable adhesive surface of the UV-curable adhesive tapes being transported is made of a transparent material with good UV transmittance.
For example, quartz glass has excellent transmittance at wavelengths of 30 or more.
A rotatable cylinder roll made of shelf silicate glass (ordinary soda lime glass cannot pass through it due to its transmittance) is closely attached to it using an auxiliary pressure roll to block oxygen and at the same time smooth the coated surface. To provide a method for curing ultraviolet curable adhesive tapes that is industrially simple and forms a clean coating film by irradiating ultraviolet rays from the ultraviolet curable adhesive side using one or more ultraviolet lamps installed inside a rear cylinder roll. It is.

To explain a specific example of the present invention with reference to the drawings, in FIG. It is brought into close contact with a part of the rotatable transparent cylinder roll 3 using auxiliary pressure rolls 7, 7'.

Shielding plates 5 and 5' are provided at the front and rear of the cylinder roll 3 to prevent ultraviolet rays from irradiating areas other than those in close contact with each other.
A reflecting mirror 6 is provided on the top of the screen to converge ultraviolet rays to the contact area. The reflecting mirror 6 is preferably one in which aluminum is vapor-deposited on a base material with good heat dissipation properties. In this specific example, the ultraviolet curable adhesive tape 1 that is continuously conveyed is pressed into the cylinder by auxiliary pressure rolls 7 and 7'.

Since it is in close contact with the coating roll 3, oxygen is blocked without introducing air bubbles, and at the same time, uneven coating and streaks on the coating roll are smoothed out. After that, ultraviolet rays are emitted from one or more lamps 4 inside the cylinder roll 3 and converged by a reflecting mirror 6, and the ultraviolet rays are irradiated from the side of the ultraviolet curable adhesive to cure the ultraviolet curable adhesive, so that it has a smooth coating surface. Type adhesive tapes are obtained.

Adhesive tapes cured by ultraviolet light are easily peeled off from the cylinder roll 3. Here, the cylinder roll preferably has a diameter of 100 mm to 100 mm, and the length of the portion in close contact between the ultraviolet curable adhesive tape and the roll in the conveying direction is preferably 1'2 or less of the circumference of the roll. is 1/6 to 1/3.

The conveying speed is from 1/min to 50 min;
The diameter of the transparent roll is determined depending on the curability of the ultraviolet curable adhesive and the length of the contact portion in the conveying direction. Further, the term "ultraviolet lamp" refers to, for example, a high-pressure mercury lamp having a wavelength of 25 mm to 50 mm, and one or more UV lamps are provided inside the roll depending on the diameter and length of the roll.

Alternatively, the apparatus may include a plurality of sets of the above-mentioned odor bodies. In the present invention, an ultraviolet curable adhesive is a mixture of monomers having an ethylenically unsaturated bond such as alkyl ester acrylate or alkyl methacrylate and can be copolymerized in a liquid state without a solvent, or a corresponding polymer. It refers to a composition in which a photosensitizer is mixed into a polymer or a mixture of a monomer and a prepolymer, but a solvent may be used in the coating process.

Further, the prepolymer has one or more reactive unsaturated bonds or the like per molecule at the terminal or side chain.

In addition to adding a tackifier to the above composition, a softener, an antioxidant, a filler, a pigment, etc. may also be mixed as necessary.

The present invention is also extremely useful as a method for curing adhesives that are easy to peel off after curing, especially among photocurable paints, adhesives, and pressure-sensitive adhesives.

This will be explained below using examples.

However, all parts below refer to parts by weight. Example 2 - Ethylhexyl acrylate 9 base part An ultraviolet curable copolymer prepared by adding 5 parts of glycidyl methacrylate to a copolymer consisting of 1 part of acrylic acid, and a sensitizing agent of 2 parts.
6 parts of an adhesive composition containing 5 parts of monoethyl anthraquinone
Adhesive tape coated on a polyethylene film with a coating thickness of 3.0 cm to assist in crimping a Pyrex glass roll with a diameter of 30 cm and a silicone rubber fence with a diameter of 50 cm, containing 4 high-pressure mercury lamps of 80 W' skin inside. As a result of continuous photocuring at a transport speed of 4/min using the apparatus shown in the above specific example, in which the length of the adhesion part of the ultraviolet curable adhesive tape in the transport direction is 300 ribs, the auxiliary adhesive tape is There are no air bubbles in the adhesion area crimped with a roll, the coated surface is smooth, and an adhesive tape with a uniform coating film is obtained.It also shows moderate adhesion and cohesive force to the stainless steel surface and remains strong even after peeling. The adhesive did not transfer to the stainless steel surface, and a good adhesive tape could be manufactured.

Comparative Example The adhesive tape shown in the above example was laminated with a 40% polyethylene film, and as a result of irradiating ultraviolet rays of the same intensity as in the example from the adhesive side for the same time, the stress applied to the laminate film was released. None, the adhesive flows and hardens with uneven coating, and the curing is not completed in the air bubbles that are not completely degassed and the pressure is removed. Transferred to the steel surface.

As shown in the Examples and Comparative Examples above, the present invention eliminates the disadvantages of uneven coating due to the flow of the adhesive mold and poor curing in the air bubbles that occur in the lamination method when producing ultraviolet curable adhesive tapes, and also eliminates the disadvantages of curing failure in the air bubbles. There are many problems such as residual streaks after coating due to removal using adhesives, high costs, and dangers in the working environment, as well as damage to the paint film that occurs when wax is mixed into the adhesive or when it is immersed in a liquid and irradiated. It is possible to provide a curing method that does not cause the drawback of deterioration and can safely and quickly obtain good ultraviolet curable pressure-sensitive adhesive tapes having a smooth and uniform coating film using compact equipment.

[Brief explanation of drawings]

The drawing is a side view showing an embodiment of the invention.

Claims (1)

[Claims] 1. In a method of curing an ultraviolet curable adhesive applied to a tape base material, the adhesive-coated surface of the tape base material coated with an ultraviolet curable adhesive is placed in a rotating transparent cylinder roll equipped with an ultraviolet lamp inside. A method for curing ultraviolet curable adhesive tapes, which is characterized by curing the adhesive by transporting it in close contact with a surface.