JPH0431477A - Pressure-sensitive filmy adhesive - Google Patents

Abstract

PURPOSE:To improve resistance to repulsion and maintenance of heat resistance by providing a pressure-sensitive adhesive layer, which comprises a crosslinked structure divided into a plurality of blocks in the direction of the base surface, on the surface of a (non)peelable film base. CONSTITUTION:A pressure-sensitive adhesive comprising a solvent-based or (non)aqueous emulsion containing a crosslinking agent is applied to the surface of a (non)peelable film base 5-100mum thick in such a manner that it may have striped, network, dotted or other patterns 2-200mum thick and each block has a mirror axis diameter below 10 times the thickness. Then, the adhesive is crosslinked at room temp. or with heating so as to divide the adhesive layer in a plurality of blocks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a film-like pressure-sensitive adhesive having a peelable or non-peelable base material.

[Conventional technology]

When pressure-sensitive adhesives are used to fix nameplates or molded products with strong repulsion, they may partially peel off due to the repulsion of the adherend, and film (tape) adhesives with a base material may not adhere properly. The end may peel off when wrapped around the body.

Conventionally, this kind of peeling was prevented, and the temperature at 40℃ such as in summer was
In order to maintain the adhesive fixing purpose for a long time even when exposed to nearby high temperatures, that is, to provide good repulsion resistance and good heat resistance retention, pressure-sensitive adhesives can be used by appropriate means. It is common practice to perform crosslinking treatment to increase the cohesive force.

[Problem to be solved by the invention]

However, with the method of simply cross-linking pressure-sensitive adhesives, even if it is possible to satisfy the heat resistance retention property by increasing the degree of cross-linking, sufficient effects cannot be obtained in terms of repulsion resistance. However, if the degree of crosslinking is adjusted to an appropriate degree in consideration of the balance between cohesive force and adhesive force, there is a problem that sufficient heat resistance retention cannot be obtained.

An object of the present invention is to overcome these problems and provide a pressure-sensitive adhesive that has excellent repulsion resistance and heat-resistant retention.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors have developed a method of forming a layer of pressure-sensitive adhesive on the surface of a peelable or non-peelable film-like base material into a sushi-like or a mesh-like shape. Either the entire adhesive layer is cross-linked, or the adhesive layer is formed on the entire surface of the base material and then a part of it is cross-linked into the same shape as above, so that the adhesive layer forms a cross-linked structure on the base material surface. When designed to be divided into blocks in the direction, heat resistance retention can be improved by increasing the degree of crosslinking of the structure, and at the same time good results can be obtained in terms of repulsion resistance, and the repulsion of the adherend can be improved. The present invention was completed based on the knowledge that partial peeling and terminal peeling due to force can be greatly suppressed.

That is, the present invention provides a film-like material in which a pressure-sensitive adhesive layer provided on the surface of a peelable or non-peelable film-like base material is divided into a plurality of blocks in the direction of the surface of the base material as a crosslinked structure. This relates to pressure-sensitive adhesives.

[Structure and operation of the invention]

The film-like substrate used in the present invention may be either removable or non-releasable; releasable ones can be peeled off and removed when adhesive is used, and non-releasable ones can be used together with the adhesive layer. Served. As releasable base materials, there are used various base materials such as paper and polyester films whose surfaces have been subjected to release treatment.As non-releasable base materials, in addition to synthetic resin films such as the above-mentioned polyester films, non-woven fabrics and A porous base material such as cloth is used. The thickness of these film-like base materials is generally about 5 to 100 μm.

Furthermore, as the pressure-sensitive adhesive provided on one side or the entire surface of such a film-like base material, a wide variety of conventionally known adhesives such as acrylic, rubber, or silicone adhesives can be used, and the type thereof is not particularly limited. The layer thickness of the adhesive on the base material is usually 2 to 200 mm. czm (one side).

The present invention is characterized in that such a pressure-sensitive adhesive layer is divided into a plurality of blocks in the direction of the substrate surface as a crosslinked structure. The reason why it is possible to achieve both repulsion resistance and heat resistance retention by dividing into such blocks is not necessarily clear, but it is presumed as follows.

Generally, in areas where peeling such as terminal peeling occurs, shrinkage force is generated in the plane direction of the base material as the adhesive layer stretches in the thickness direction, and stress is also applied in the plane direction, which promotes the peeling phenomenon. Here, if the degree of crosslinking of the adhesive layer is lowered, the elongation increases and can be made to follow the changes in the bonded area, but since its strength is small, sufficient repulsion resistance cannot be obtained, and of course, good heat resistance cannot be obtained. Retention properties cannot be expected either. On the other hand, if the degree of crosslinking is high enough to improve heat resistance retention, the strength will increase, but the elongation will be significantly reduced, so that it will not be able to follow the changes in the bonded area, and the repulsion resistance will decrease.

In contrast, in the present invention, the adhesive layer, which is a crosslinked structure, is divided into blocks in the direction of the substrate surface, so that stress caused by shrinkage force in the direction of the substrate surface due to elongation in the thickness direction The peeling force will be reduced accordingly. For this reason, it is thought that when the degree of crosslinking of the adhesive is increased to improve heat resistance retention, a decrease in repulsion resistance is suppressed, and as a result, it becomes possible to satisfy both of the above characteristics.

In the present invention, the following method may be employed to divide the pressure-sensitive adhesive layer into blocks as described above as a crosslinked structure.

The first method is to form a pressure-sensitive adhesive layer in various pattern shapes such as sushi-like, mesh-like, and dot-like shapes on the surface of a film-like base material, and make the entire layer a crosslinked structure. In addition, the second method involves forming a layer of pressure-sensitive adhesive on the surface of a film-like base material, and then cross-linking a part of it into a pattern similar to the above, so that only that part becomes a cross-linked structure. This is the way to do it.

The first method includes (a) applying a pressure-sensitive adhesive in the form of a solution, aqueous or non-aqueous emulsion containing a crosslinking component such as a crosslinking agent to gravure coating, screen coating,
A method in which layers are formed in various patterns by reverse coating, etc., and then crosslinked at room temperature or under heat; A method of forming layers into various patterns by coating; c) A method of forming layers in various patterns by applying an aqueous or non-aqueous adhesive emulsion containing cross-linked structured polymer particles to a single layer of the polymer particles by reverse coating or electrostatic coating. There is a method of forming a dot-like adhesive layer by applying the adhesive so that it is separated and arranged in the same state.

In the second method, a) an adhesive containing a crosslinkable monomer or crosslinkable polymer is applied all over the base material by reverse coating or extrusion coating, and then active energy such as ultraviolet rays or laser light is applied. A method of partially polymerizing and cross-linking by irradiating lines in an arbitrary pattern, b) A method of undercoating a migratable cross-linking component in various patterns on the base material in advance, and then applying a cross-linkable adhesive over the entire surface of the base material. There are methods such as applying the agent all over.

In the block-shaped crosslinked structure formed in this way, the minor axis diameter of each block is 10 times or less the layer thickness,
It is preferably 7 times or less, and usually up to about 5 times. When set to such a size, the stress based on the shrinkage force in the plane direction is effectively reduced, and a particularly favorable result can be obtained in improving the anti-reflection T8 property. The above-mentioned short axis diameter refers to the width of the sushi block in the case of a sushi-shaped block, but refers to the minimum width or diameter of the block in other shapes such as rectangular, circular, and needle-like.

On the other hand, the distance between each block is preferably as small as possible in order to secure the adhesion holding area, and is usually less than twice the short axis diameter, and generally less than 1.ON. , when dividing into blocks such as the above-mentioned dots, some of them may touch each other, that is, the distance between the blocks may be partially 01n, but even in this case, the effects of the present invention can be achieved. be.

〔Effect of the invention〕

As described above, the present invention has a simple configuration in which the pressure-sensitive adhesive layer is used as a crosslinked structure and is divided into blocks in the direction of the substrate surface, thereby achieving repulsion resistance and heat resistance retention that were difficult to achieve in the past. It is possible to provide a film-like pressure-sensitive adhesive that can achieve both of the following.

〔Example〕

Next, examples of the present invention will be described in more detail. In addition, in the following, parts mean parts by weight. Example 1 85 parts of 2-ethylhexyl acrylate, 10 parts of vinyl acetate
A polyfunctional epoxy crosslinking agent (trade name: Tetrarad
0.05 part of was added to prepare a pressure-sensitive adhesive solution.

This adhesive solution is screen-coated onto a polyester film with a thickness of 25 μm in the shape of a slit, and dried to create a cross-linked structure with a thickness of 30 μm, a slit width of 200 μm, and a distance between slits of 20 parts 1 m. A film-like pressure-sensitive adhesive having an adhesive layer was prepared.

Comparative Example 1 A film-like pressure-sensitive adhesive was produced in the same manner as in Example 1, except that an adhesive layer with a thickness of 30 μm was coated on the entire surface of the base film.

Example 2 A mixed solution consisting of 85 parts of isononyl acrylate, 15 parts of acrylic acid, 0.2 parts of trimethylolpropane triacrylate, and 0.3 parts of benzophenone was mixed into a 25 μm thick liquid mixture.
A polyester film having a thickness of 75 μm and a peel-treated polyester film was superimposed thereon.

In this condition, IKW's low-pressure mercury lamp was used from a distance of 30 countries to
After irradiating ultraviolet rays for minutes through a photomask with a wire mesh pattern, the peel-treated polyester film was removed and dried by heating at 120° C. for 30 minutes.

The film-like pressure-sensitive adhesive thus obtained is
The thickness of the adhesive layer is 100 μm, and the width of each block (mesh part of the photomask) as a crosslinked structure is 0.43~
The distance between each block (patterned portion of the photomask) was 0.03 to 0.01 m.

Comparative Example 2 A film-like pressure-sensitive adhesive was produced in the same manner as in Example 2, except that the entire surface of the base film was irradiated with ultraviolet rays without using a photomask.

Comparative Example 3 A film-like pressure-sensitive adhesive was produced in the same manner as Comparative Example 2, except that the amount of trimethylolpropane triacrylate used in the mixed solution was changed to 0.02 parts.

Example 3 On a polyester film with a thickness of 25 μm, a trimethylolpropane adduct of toluene diisocyanate was
Undercoat was applied in dots to a thickness of 1.5 μm by gravure coating. On top of this, acrylic acid n-
Butyl 97 parts, 2-hydroxyethyl acrylate 0.5
A toluene solution of an acrylic polymer with an average molecular weight of 550,000, consisting of 1 part and 3 parts of acrylic acid, was applied and dried.
An adhesive layer having a thickness of 30 μm was formed.

Thereafter, in the film-like pressure-sensitive adhesive obtained after storage for 30 days, the width of the rectangular blocks located in the above-mentioned undercoated portion, which was made into a crosslinked structure, was 200 μm, and the distance between the blocks was 50 μm.

Comparative Example 4 A film-like pressure-sensitive adhesive was produced in the same manner as in Example 3, except that the entire surface of the base film was undercoated with a trimethylolpropane adduct of toluene diisocyanate to a thickness of 2 μm.

Comparative Example 5 Example 3 except that no subbing treatment with trimethylolpropane adduct of toluene diisocyanate was applied.
A film-like pressure-sensitive adhesive was prepared in the same manner as above.

Example 4 A heptamer mixture consisting of 92 parts of n-butyl acrylate, 3 parts of a methacrylic group-terminated styrene macromonomer with an average molecular weight of 6.000, and 5 parts of methacrylic acid was mixed with polyvinyl alcohol (solubility degree 80%) as a dispersion stabilizer. By carrying out suspension polymerization in water using 10 parts, a particulate polymer having a crosslinked structure and having an average particle diameter of 200 μm was obtained.

This particulate polymer is poured into methanol to make a non-aqueous dispersion, and this is applied to the entire surface of a 25 μm thick polyester film so that the polymer particles are separated and arranged in a single layer, dried, and then used as an adhesive. A film-like pressure-sensitive adhesive having a layer thickness of 90 μm was obtained.

Comparative Example 6 Toluene was further added to the non-aqueous dispersion obtained by pouring it into methanol to make a uniform solution, which was applied to the entire surface of the base film so that the thickness of the adhesive layer was 90 μm, and dried. Except for this, a film-like pressure-sensitive adhesive was obtained in the same manner as in Example 4.

Example 5 100 parts of styrene-isoprene-styrene triblock copolymer (styrene content 20% by weight), 50 parts of petroleum resin
By extrusion coating a mixture consisting of 10 parts of terpene resin and 10 parts of terpene resin in a sushi-like shape onto a polyester film with a thickness of 25 μm, the thickness of the sushi-like adhesive layer was 50 μm,
A film-like pressure-sensitive adhesive having a width of 0.2511 m and a distance between slits of 0.05 m was obtained.

Comparative Example 7 A film-like pressure-sensitive adhesive was produced in the same manner as in Example 5, except that extrusion coating was applied to the entire surface of the base film.

The film-like pressure sensitive adhesives of the above examples and comparative examples were examined for repulsion peeling resistance and heat resistance retention in the following manner. The results were as shown in Table 1 below.

Repulsion and Peeling Resistance> A film-like pressure-sensitive adhesive is cut into a tape shape with a width of 1011 mm, and this is cut into a tape shape with a diameter of 2 mm. Wrap it around the ON metal rod three times,
After leaving the tape at 23° C. for 48 hours, the floating length of the tape end was determined.

<Heat-resistance retention> Cut a film-like pressure-sensitive adhesive into a tape shape with a width of 10 squares, and bond it to a Bakelite board with an area of 1010 m
Paste them together so that they are 20mm thick, and put 500g on the edge of the tape.
A load was applied to the tape, the tape was left at 40°C, and the time required for the tape to fall from the Bakelite plate was determined.

Table 1 From the results shown in Table 1 above, it is clear that the film-like pressure-sensitive adhesive of the present invention has excellent repulsion resistance and heat-resistant retention.

Claims (2)

[Claims] (1) A film-like pressure-sensitive adhesive in which a layer of pressure-sensitive adhesive provided on the surface of a peelable or non-peelable film-like base material is divided into multiple blocks in the direction of the surface of the base material as a crosslinked structure. agent. (2) The film-like pressure-sensitive adhesive according to claim 1, wherein the minor axis diameter of each block as a crosslinked structure is 10 times or less the thickness.