JPH031989A - Pressure sensitive adhesive sheet - Google Patents

Abstract

PURPOSE:To realize both the strong adhering property and the anti-blocking property by including hollow microcapsules in a layer of an adhesive agent. CONSTITUTION:When the confronting surfaces of adheseve layers of this pres sure sensitive adhesive sheet on which an adhesive agent is apllied are added with pressure, the adhesive sheets are bonded with each other. Hollow microcapsules are included in the layer of the adhesie agent of the pressure sensitive adhesive sheet. For the adhesive agent of the layer, for example, ethylene-polyvinyl acetate resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, synthetic rubber resin, natural rubber resin etc. are usable. On the other hand, for the hollow microcapsules, foam microcapsules using a thermoelastic resin mainly composed of a (metha)acrylic ester such as polyvinylidene chloride, acrylonitrile or methyl methacrylate, or an aromatic vinyl compound such as styrene as a wall film material of the capsule and including hydrocarbons having a low boiling point such as n-butane, i-butane, pentane or neopentane as a core substane are employed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pressure-sensitive adhesive sheet, and more specifically, the present invention relates to a pressure-sensitive adhesive sheet, and more specifically, it exhibits good adhesion only when the adhesive-coated surfaces are opposed to each other and are particularly pressed with strong pressure. The present invention relates to a pressure-sensitive adhesive sheet showing the following characteristics.

[Conventional technology]

In recent years, there has been an increase in demand for pressure-sensitive adhesive sheets that can be processed into postcards, envelopes, slips, etc. by applying adhesive to the sheets, placing the coated surfaces facing each other, and joining them under strong pressure. These types of pressure sensitive adhesive sheets are usually printed prior to bonding.

However, when Z-folding a pressure-sensitive adhesive sheet and using it as form paper, depending on the weight of the stacked papers,
So-called blocking, where the adhesive layers are bonded to each other, is likely to occur.

When such sheets are run through a printer, a plurality of blocked sheets enter the machine in an overlapping state, resulting in sheet loss and printer failure. For such problems, Japanese Patent Application Laid-open No. 61-34550,
JP-A-61-34552 and JP-A-34-S53 propose a method of adding so-called anti-blocking agents such as inorganic or organic pigments, lubricants, and mold release agents to adhesives, but this method is not completely effective. The current situation is that the problem has not been resolved.

[Problem to be solved by the invention]

An object of the present invention is to provide a pressure-sensitive adhesive sheet that exhibits excellent adhesive properties under strong pressure and does not cause any troubles due to blocking, especially when used as a form paper after Z-folding.

[Means to solve problems]

The present invention is a pressure-sensitive adhesive sheet that can be bonded by applying pressure to the coated surfaces of the adhesive layers, characterized in that the adhesive layer contains hollow microcapsules. .

[Effect]

Examples of the adhesive that can be used to form the adhesive layer of the present invention include ethylene-vinyl acetate resin, acrylic resin, vinyl chloride resin, vinyllindene chloride resin, synthetic rubber resin, and natural rubber resin. Among them, those having a glass transition point of 170°C to 30°C are preferably used.

The hollow microcapsules used in the present invention include, for example, n-butane, i-butane, pentane,
Contains low-boiling hydrocarbons such as neopentane, and uses vinylidene chloride, acrylonitrile, etc. as the capsule wall material.
Examples include foamable microcapsules using thermoplastic resins whose main components are (meth)acrylic acid esters such as methyl methacrylate and aromatic vinyl compounds such as styrene. Commercially available products include Matsumoto Microsphere F-
30, F-50, F-80 (Matsumoto Oil Source), :L Kusuba:/Se) IyWU-642, WU-551, WU-46
1 (manufactured by Nippon Philite), etc.

By incorporating such hollow microcapsules into the adhesive layer of the pressure-sensitive adhesive sheet of the present invention, fine irregularities can be formed on the surface of the layer.

Therefore, even if the adhesive layer surfaces are left facing each other for a long time as in the Z-fold state, the contact area between the adhesive layers on the opposing surfaces is significantly reduced compared to when hollow microcapsules are not added. Therefore, the blocking phenomenon does not occur. On the other hand, under the strong pressure used for normal lamination, this capsule is completely destroyed and the adhesives come into sufficient contact with each other, thus exhibiting strong adhesive properties.

In addition to hollow microcapsules, creating irregularities on the surface of the adhesive layer can also be achieved by adding starch particles, glass beads, inorganic pigments, solvent microcapsules, adhesive microcapsules, etc. When particles, glass beads, or inorganic pigments are used, their adhesion under strong pressure is poor because they are insufficiently broken under strong pressure.

On the other hand, when a solvent microcapsule or an adhesive microcapsule is used, the capsule breaks down at the perforation or the location where the marginal is inserted, and the core substance is released, making blocking more likely to occur at that location.

The average particle diameter of the hollow microcapsules used in the present invention is preferably 1.5 times or more the thickness of the adhesive layer (thickness of the part where no microcapsules are present); In the case of capsules that do not meet the requirements, the anti-blocking effect is extremely small. On the other hand, if capsules with an average particle diameter exceeding 100 times the thickness of the coated layer are used, the smoothness of the layer will be greatly reduced, causing various problems during printing. Cheap.

The adhesive layer in the present invention contains an adhesive and hollow microcapsules as essential components, and is formed by coating it on a support as an aqueous, solvent-based, or solvent-free coating solution. It is preferable to further add a pigment and/or polyolefin resin fine particles to the coating liquid.

Examples of pigments include silica, colloidal silica, zeolite, bentonite, kaolin, calcined kaolin, calcium phosphate, calcium carbonate, magnesium carbonate, calcium sulfate, aluminum hydroxide, zinc oxide, titanium oxide, melamine resin particles, urea resin particles, and polystyrene resin. Examples include inorganic and organic pigments known in the art, such as particles, benzoguanamine resin particles, and starch particles. Examples of the polyolefin resin fine particles include resin fine particles such as polyethylene and polypropylene.

The mixing ratio of hollow microcapsules and adhesive is usually 0.1 to 100 parts of hollow microcapsules to 100 parts of adhesive.
The amount is 100 parts by weight, preferably 0.5 to 50 parts by weight.

The amount of pigment and polyolefin resin fine particles to be blended is usually 0 to 300 parts by weight, preferably 30 to 200 parts by weight, based on 100 parts by weight of the adhesive. In addition, the adhesive layer may further contain tackifiers such as rosin resins and their derivatives, terpene resins, coumaron indene resins, xylene resins, alkylphenol resins, C3 to C9 petroleum resins, metal soaps, and silicones, if necessary. Even if additives such as mold release agents, adhesive-containing capsules or oil capsules to improve adhesion, antistatic agents, thickeners, dispersants, preservatives, antioxidants, antifoaming agents, etc. are added. good.

The support for the pressure-sensitive adhesive sheet in the present invention is not particularly limited, but conventionally used high-quality papers, various synthetic papers, various films, etc. can be used. The coating amount of the above coating liquid is usually 2 to 30 g/m', preferably 4 to 17 g/rd.

Incidentally, if it is less than 2 g/rtr, the adhesion under strong pressure is weak, and if it is more than 30 glrd, there is no economic advantage.

As the pressure-sensitive adhesive coating and printing method, conventionally known methods such as air knife coater, blade coater, bar coater, screen printing, and flexo printing can be used. In addition, when foamable microcapsules are used as the hollow microcapsules, foaming is usually performed during the drying step or reheating step when applying the coating liquid to the support.

When the pressure-sensitive adhesive sheet thus obtained is processed into postcards, envelopes, slips, etc., the surfaces coated with the adhesive can be bonded to each other when a strong pressure of 40 kg/am or more is applied.

Examples of the present invention will be described below, but it goes without saying that the present invention is not limited only to these Examples. In the examples, unless otherwise specified, parts are parts by weight and %.
% means weight %.

Example 1 Acrylic acid ester emulsion (product name: AE-9
23, manufactured by Japan Synthetic Rubber Co., Ltd.) 100 parts (dry type f), 100 parts of synthetic silica (product name: Mizukasil P832, manufactured by Mizusawa Chemical Industry Co., Ltd.), foamable microcapsules (product name: Expancel WO461, Nippon Ferrite Co., Ltd.) After adding 5 parts of the same product, the solid content concentration was adjusted to 35% to obtain a pressure-sensitive adhesive composition. This composition was applied to 80 g/cd of high-quality paper and treated at 130°C for 1 minute, resulting in a dry coating amount of 8 g/rd.
A pressure-sensitive adhesive sheet was obtained.

Example 2 100 parts of ethylene-vinyl acetate copolymer emulsion (trade name: Sumikaflex 920, manufactured by Sumitomo Chemical Co., Ltd.), 80 parts of synthetic silica (trade name: Mizukasil P-832, manufactured by Mizusawa Chemical Industries, Ltd.), foamable Microcapsule (product name: Expancel WU-6427 manufactured by Nippon Ferrite Co., Ltd.)
After adding 10 parts, the solid content concentration was adjusted to 35% to obtain a pressure sensitive adhesive composition. This composition was applied to 80 g/m high-quality paper and treated at 130° C. for 1 minute to obtain a pressure-sensitive adhesive sheet with a dry coating weight of 8 g/rd.

Example 3 Acrylic acid ester emulsion (product name: AE-9
23, manufactured by Japan Synthetic Rubber Co., Ltd.) and 50 parts of ethylene-vinyl acetate copolymer emulsion (product name: Sumikaflex 920, manufactured by Sumitomo Chemical Industries), 120 parts of calcium carbonate, and expandable microcapsules (product) After adding 5 parts of Expancel WU-642 (manufactured by Nippon Ferrite Co., Ltd.) and 10 parts of a polyethylene wax emulsion, the solid content concentration was adjusted to 35% to obtain a pressure-sensitive adhesive composition. 80g/n of this composition? Coated on high-quality paper and treated at 130℃ for 1 minute to obtain a dry coating weight of 8 g.
A pressure-sensitive adhesive sheet of /m was obtained.

Comparative Examples 1 to 3 Comparative Examples 1 to 3 were prepared in the same manner as in Examples except that no foamable microcapsules were added in the preparation of the pressure-sensitive adhesive compositions of Examples 1 to 3 (Examples 1 to 3, respectively). A pressure-sensitive adhesive sheet was obtained by preparing and coating a coating solution (corresponding to the above).

Comparative Example 4 In Example 1, instead of 5 parts of expandable microcapsules and 100 parts of synthetic silica, 25 parts of dioctyl phthalate-containing polyurethane microcapsules (average particle size of 6 μm, dioctyl phthalate/membrane material -100/8) and 80 parts of synthetic silica were used. A pressure-sensitive adhesive sheet was obtained in the same manner except that the same amount was used.

Comparative Example 5 In Example 2, instead of 10 parts of expandable microcapsules, starch particles and microbars (average particle size 25μ) were used.
A pressure-sensitive adhesive sheet was obtained in the same manner except that 10 parts of 100% of the adhesive was used.

The eight types of pressure-sensitive adhesive sheets obtained were evaluated for adhesion and blocking resistance by the following methods, and the results are shown in Table 1.

(Adhesiveness) Adhesive strength was evaluated when the adhesive-coated surfaces were placed facing each other and pressed using a super calender (pressure pressure: 100 kg/crA).

○: Adhesion is strong enough to destroy the paper layer when the bonded pressure-sensitive adhesive sheets are separated.

×: Adhesion is insufficient.

(Bronking resistance) The blocking resistance of the sheet was tested under the following two conditions, and the state of occurrence of blocking was evaluated.

Condition 1: The coated surfaces were placed facing each other and left under a pressure of 1 kg/cut for 24 hours.

Condition 2 Perforations were made in the flow direction of the pressure-sensitive adhesive sheet using a foam processing machine, the coated surfaces were placed opposite each other so that the perforations overlapped, and the sheets were left for 24 hours under a pressure of 0.5 kg/ci.

evaluation O-ni blocking did not occur at all.

× Ni blocking occurred.

Table 1 [Effects] As is clear from the examples, the pressure-sensitive adhesive sheet of the present invention can be applied with strong pressure when joining the adhesive-coated surfaces facing each other to form postcards, envelopes, slips, etc. It exhibits good adhesion only when pressed, and if this pressure-sensitive adhesive sheet is Z-folded and stacked before being bonded, the adhesive will not bond to each other, resulting in strong pressure adhesion and anti-blocking properties. Both genders are balanced. Further, even when the adhesive is stored in a state in which the surface coated with the adhesive and the surface of the support sheet are in contact with each other, blocking does not occur and there is no problem in handling operations.

Claims (1)

[Claims] 1. A pressure-sensitive adhesive sheet which can be bonded by applying pressure to the coated surfaces of adhesive layers, characterized in that the adhesive layer contains hollow microcapsules.