JPH10273640A - Heat sensitive adhesive and heat sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat sensitive adhesive having sufficient adhesion, good in blocking resistance, having no dusting and excellent in printing properties, and further to obtain a heat sensitive adhesive sheet. SOLUTION: This heat sensitive adhesive consisting essentially of a thermoplastic resin and a solid plasticizer includes the thermoplastic resin containing a thermoplastic resin M having 60-150 deg.C glass transition temperature and a thermoplastic resin N having (-30) to 30 deg.C glass transition temperature regulated so that the solid weight ratio of the thermoplastic resins M/N may be (55/45) to (98/2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive adhesive which is non-tacky at room temperature, but which becomes tacky when heated, and which is coated on a surface of a substrate and dried. It relates to the obtained heat-sensitive adhesive sheet.

[0002]

2. Description of the Related Art Conventionally, labels have been attached to glass bottles such as soft drinks, alcoholic beverages, and chemical bottles by attaching a label provided with a water-soluble adhesive such as casein or starch on the back surface of a base material by an automatic labeler or the like. A method of attaching, or a method of attaching a label of a general adhesive sheet having a configuration in which a top paper, an adhesive layer, and a release sheet are sequentially laminated using an automatic labeler or the like is adopted. However, a label provided with a water-soluble adhesive, when the water-soluble adhesive is applied to the back of the base material, the label curls, and after sticking to a glass bottle, the label is wrinkled or floated, the label becomes defective and the appearance is impaired. There was a problem. On the other hand, a pressure-sensitive adhesive sheet label having a general configuration is usually used by peeling off a release sheet. However, the peeled-off release sheet is difficult to be recovered and reused, and is almost always disposed of. In recent years, attention has been paid to resource saving and environmental issues, and heat-sensitive adhesive sheets that do not require a release sheet have been attracting attention.

Generally, a heat-sensitive adhesive sheet has a structure in which a heat-sensitive adhesive is applied to the surface of a base material, and is usually used as a label by printing the other surface of the base material. The heat-sensitive adhesive is non-adhesive at room temperature, but is activated when heated by a labeler or an oven provided with a heating device to exhibit adhesiveness. Typically, the stick activation temperature is 50-150
° C, and in this temperature range, the solid plasticizer in the heat-sensitive adhesive starts to melt to give the thermoplastic resin tackiness.
Since the molten solid plasticizer slowly crystallizes, the stickiness is maintained for a long time. Therefore, the solid plasticizer is used while being adhered to a glass bottle or the like while having the stickiness.

[0004] Even if the heat-sensitive adhesive sheet is continuously adhered to a glass bottle by a labeler or the like provided with a heating device, a water-soluble adhesive is applied to the back surface of the label and the method is applied to the glass bottle. There is no problem of poor labeling. In addition, there is an advantage that it can be produced at a low cost because a release sheet is not used like the general adhesive sheet,
It is also advantageous from the viewpoint of resource saving and environmental problems.

However, the heat-sensitive adhesive sheet is often stored in a wound state or in a state in which several sheets are stacked, and a conventional general heat-sensitive adhesive sheet causes blocking when the ambient temperature becomes higher than room temperature. There is a problem that arises. In order to solve this problem, for example, there is a method of increasing the glass transition temperature of the thermoplastic resin, but if the glass transition temperature is too high, the strength of the heat-sensitive adhesive layer is reduced,
Dusting occurs in processes such as printing and cutting. Dusting can be prevented by applying a heat-sensitive adhesive and drying at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin.However, since the drying temperature must be lower than the melting point of the solid plasticizer, it is generally thermoplastic. The upper limit of the glass transition temperature of the resin is about 50 ° C.

A method of adding and mixing non-tacky fine particles such as inorganic pigments and organic pigments (Japanese Patent Laid-Open No. 2-282)
050, JP-A-6-179855 and JP-A-6-179856) have been proposed, but simply adding a normal pigment is insufficient in the blocking resistance and the adhesive strength and the like. Dusting tends to worsen. Also, when the solid plasticizer is protected by fine particles, the heat-sensitive adhesive is not heated to a temperature higher than the melting point of the solid plasticizer by 20 ° C. or more. It takes a long time for melting and diffusion of the heat-sensitive adhesive, it is difficult for the heat-sensitive adhesive to exhibit adhesiveness, and the adhesive performance of the heat-sensitive adhesive sheet is lowered.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive adhesive having a sufficient adhesive strength, good blocking resistance, no dusting and excellent printability.

[0008]

The heat-sensitive adhesive of the present invention is a heat-sensitive adhesive mainly comprising a thermoplastic resin and a solid plasticizer, wherein the thermoplastic resin has a glass transition temperature of 6%.
A thermoplastic resin M of 0 to 150 ° C. and a glass transition temperature of −3;
It is characterized by containing a thermoplastic resin N at 0 to 30 ° C. and a solid content weight ratio of the thermoplastic resin M to N being 55/45 to 98/2. In the heat-sensitive adhesive of the present invention, the thermoplastic resins M and N are each an acrylate polymer, a methacrylate polymer, a vinyl acetate polymer, a styrene polymer, and a (meth) acrylate copolymer. Copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-ethylene-vinyl chloride copolymer, vinyl acetate- (meth) acrylate copolymer, ethylene-
At least one selected from a (meth) acrylate copolymer, an ethylene-vinyl chloride copolymer, a styrene-ethylene copolymer, a styrene-isoprene copolymer, a styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer One type is preferred. In the heat-sensitive adhesive of the present invention, the solid plasticizer preferably has a melting point of 50 to 100 ° C. Further, the heat-sensitive adhesive sheet of the present invention preferably has a pressure-sensitive adhesive layer containing the above-mentioned heat-sensitive adhesive as a main component formed on the surface of the substrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on heat-sensitive adhesives and found that a thermoplastic resin having a sufficiently high glass transition temperature and a thermoplastic resin having a relatively low glass transition temperature have a specific ratio. It has been found that the combined use of (1) and (2) makes it possible to achieve both blocking resistance and dusting. Conventionally, the heat-sensitive adhesive sheet is stored at around room temperature, and even if the temperature is lower than the melting start temperature of the solid plasticizer being used, the blocking phenomenon occurs in the normal heat-sensitive adhesive sheet because of the heat-sensitive adhesive. It is considered that the thermoplastic resin in the adhesive is plasticized by heat and pressure.

In the present invention, the glass transition temperature is 60 to 15
A thermoplastic resin M of 0 ° C. and a glass transition temperature of −30 to 3;
By using the thermoplastic resin N at 0 ° C. in combination, the blocking resistance can be significantly improved without deteriorating the adhesive strength and dusting of the heat-sensitive adhesive sheet.
The reason is considered as follows. That is, since the thermoplastic resin M itself having a sufficiently high glass transition temperature acts as an antiblocking agent, the blocking resistance is significantly improved. Further, by using the thermoplastic resin N having a relatively low glass transition temperature as a binder, it is possible to prevent the dusting from being deteriorated.

The glass transition temperature of the thermoplastic resin M used in the present invention is from 60 to 150 ° C., preferably from 70 to 150 ° C.
100 ° C. If the temperature is lower than 60 ° C., the blocking resistance becomes insufficient. On the other hand, when the temperature exceeds 150 ° C., even if a solid plasticizer is present, it is difficult to be plasticized, and the adhesive strength tends to decrease. The glass transition temperature of the thermoplastic resin N is -3.
It is 0-30 degreeC, Preferably it is 0-30 degreeC. If the glass transition temperature is lower than −30 ° C., the blocking resistance is inferior.

The solid content weight ratio (M / N) of the thermoplastic resin M to the thermoplastic resin N must be 55/45 to 98/2, preferably 55/45 to 95/5. , More preferably 70/30 to 90/10. If the weight ratio (M / N) is greater than 98/2, the pressure-sensitive adhesive sheet tends to cause dusting, which is not suitable for practical use. When the solid content weight ratio (M / N) is less than 55/45, the adhesive sheet tends to cause a blocking phenomenon in a wound state or when several sheets are left standing. Also, in order to obtain the desired quality as a heat-sensitive adhesive sheet,
It is of course possible to appropriately use commonly known thermoplastic resins other than those specified in the present invention. Thermoplastic resins M and N
Is preferably 80 to 100% by weight of the total thermoplastic resin, and if less than 80% by weight, the original effect of the thermoplastic resin may not be sufficiently obtained.

[0013] The gel content of the thermoplastic resin M used in the present invention is preferably in the range of 5 to 40%. By the way, when the gel content exceeds 40%, the solid plasticizer is less likely to be plasticized due to melting, and the adhesive strength tends to decrease. On the other hand, when a thermoplastic resin having a gel content of less than 5% is used, In some cases, the blocking resistance may be reduced, or a required adhesive function may not be obtained. Although not particularly limited, a gel content of the thermoplastic resin N of about 10 to 90% is preferably used.

The gel content of the present invention refers to the ratio of the organic solvent insoluble content in the thermoplastic resin, and is the insoluble content excluding residual monomers, oligomers and resin components having a relatively low polymerization degree in the entire resin solid content. Represents the proportion occupied by the high molecular weight component. That is, as a sample for measuring the gel content, a thickness of 0.3 to 0.3 mm after drying on a Teflon sheet at 50 ° C for 24 hours.
Using 0.5mm thermoplastic resin film (3cm square)
This is immersed in toluene for 24 hours and then dried at 105 ° C. for 3 hours to completely evaporate the solvent. The weight change of the sample before and after immersion in toluene is measured, and the gel content is calculated by the following equation. Gel content (%) = [weight after immersion (g) / weight before immersion (g)] × 100

As the thermoplastic resin used in the present invention, for example, methyl acrylate, ethyl acrylate,
(Meth) acrylates such as butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and butyl methacrylate, homopolymers such as vinyl acetate, styrene, acrylonitrile, ethylene and vinyl chloride or copolymers thereof, and styrene and acrylonitrile Copolymers with isoprene and butadiene are shown. Further, it is also possible to copolymerize by appropriately using maleic acid, fumaric acid, itaconic acid or the like in order to adjust the adhesive properties.

Specific examples include acrylic ester polymers, methacrylic ester polymers, vinyl acetate polymers,
Styrene polymer, (meth) acrylate copolymer, vinyl acetate-ethylene copolymer, vinyl acetate- (meth) acrylate copolymer, ethylene-vinyl chloride copolymer, styrene-isoprene copolymer, Styrene-butadiene copolymer, acrylonitrile-butadiene copolymer and the like can be mentioned. These polymers indicate the monomers used as the main component, and may optionally contain other monomer components according to quality requirements.For example, in the case of a vinyl acetate-ethylene copolymer, And vinyl acetate-ethylene-vinyl chloride copolymers and vinyl acetate-ethylene- (meth) acrylate copolymers. The above-mentioned polymer is used alone or in combination of two or more as the thermoplastic resin M or the thermoplastic resin N, and is generally used in the form of an aqueous solution or an aqueous dispersion.

The glass transition temperature of the thermoplastic resin is related to the type of the monomer, the composition ratio of the copolymerized monomer, the degree of polymerization, the degree of cross-linking, and the like, and can be easily adjusted particularly by the composition ratio of the copolymerized monomer. For example, in the case of a styrene-butadiene copolymer resin, the glass transition temperature is changed from -85 ° C. to 10% by changing the styrene content from 0 to 100%.
It can be varied almost linearly up to 0 ° C. Also,
The gel content of the thermoplastic resin is related to the degree of polymerization and the degree of crosslinking of the thermoplastic resin, and the degree of polymerization is determined by the polymerization solvent, polymerization temperature, monomer concentration, initiator concentration, chain transfer agent, or Can be adjusted by changing the emulsifier concentration or the like. Further, the degree of crosslinking is adjusted by the type and amount of the crosslinking agent used, and the like.

When the heat-sensitive adhesive sheet of the heat-sensitive adhesive sheet is preliminarily printed, the heat-sensitive adhesive of the present invention is printed on the surface of the heat-sensitive adhesive sheet coated with the heat-sensitive adhesive in comparison with the conventional heat-sensitive adhesive sheet. It was found that suitability (ink drying property) was improved.
Although the reason for this is not necessarily clear, the use of a thermoplastic resin having a sufficiently high glass transition temperature partially reduces the film forming property of the pressure-sensitive adhesive layer, and forms a void structure for ink penetration. It is thought to be.

The heat-sensitive adhesive of the present invention comprises a thermoplastic resin and a solid plasticizer as main components, and generally has a melting point of the thermoplastic resin M (glass transition temperature of 60 to 15).
(0 ° C.). Therefore, the heat-sensitive adhesive sheet of the present invention has an extremely excellent adhesive function by melting the solid plasticizer first and bonding the thermoplastic resin to the plasticizer to exhibit adhesiveness when the adhesive sheet is heated and adhered. .

The solid plasticizer used in the heat-sensitive adhesive of the present invention preferably has a melting point of 50 to 100 ° C., for example, dihexyl phthalate (melting point 65 ° C.), dicyclohexyl phthalate (melting point 65 ° C.) Dihydroabiethyl phthalate (melting point 65 ° C), dimethyl isophthalate (melting point 66 ° C), N-cyclohexyl-p-toluenesulfonamide (melting point 86 ° C), sucrose benzoate (melting point 98 ° C), ethylene glycol dibenzoate (Melting point 70
° C), trimethylolethane tribenzoate (melting point 73
° C), pentaerythritol tetrabenzoate (melting point 95 ° C),
And sucrose octaacetate (melting point 89 ° C.) and tricyclohexyl citrate (melting point 57 ° C.). The solid plasticizer is generally used as an aqueous dispersion, and may be used alone or in combination.

The higher the melting point of the solid plasticizer, the better the blocking resistance. However, if it exceeds 100 ° C., it is difficult to activate by heating, and sufficient tackiness may not be obtained. If the melting point of the solid plasticizer is less than 50 ° C., the blocking resistance may be poor. Among the above-mentioned solid plasticizers, dicyclohexyl phthalate is preferably used, and the adhesiveness can be maintained for a long time. When a plurality of solid plasticizers are used in combination, the melting start temperature of the solid plasticizer having the lowest melting point has the greatest influence on the bonding temperature of the heat-sensitive adhesive.

The heat-sensitive adhesive of the present invention further comprises a rosin-based tackifier, a phenol resin-based tackifier, a terpene resin-based tackifier, and a xylene-based tackifier in addition to the thermoplastic resin and the solid plasticizer. Alternatively, the adhesive function may be adjusted by adding a tackifier such as a petroleum resin-based tackifier.

The mixing ratio of the thermoplastic resin and the solid plasticizer in the heat-sensitive adhesive of the present invention is preferably 50 to 300 parts by weight of the solid plasticizer based on 100 parts by weight of the total solid content of the thermoplastic resin. By the way, when the amount of the solid plasticizer is less than 50 parts by weight, tackiness as a heat-sensitive adhesive is hard to appear, and the adhesive performance may be poor. On the other hand, if the amount of the solid plasticizer exceeds 300 parts by weight, the duration of adhesiveness may be shortened as a heat-sensitive adhesive. When the tackifier is added, it is preferable to add 10 to 150 parts by weight of the tackifier to 100 parts by weight of the solid content of the thermoplastic resin. When the amount of the tackifier is less than 10 parts by weight, the effect of enhancing the adhesive performance is poor, and when the amount exceeds 150 parts by weight, the blocking resistance may decrease.

In the heat-sensitive adhesive of the present invention, kaolin, calcined kaolin, calcium carbonate, calcium silicate, talc, silica, alumina,
Diatomaceous earth, calcined diatomaceous earth, mica, magnesium oxide, magnesium carbonate, aluminosilicate, activated clay, montmorillonite, mineral pigments such as zeolite, porous pigments, carbon black, polystyrene resin, urea resin,
Acrylic resin, melamine resin, benzoguanamine resin,
In addition, known and used pigments such as organic pigments, starch, flour, polyolefin fine particles, and the like can be added and used. In addition, as a binder, polyvinyl alcohol, starch, etc., other resins other than thermoplastic resins may be used as an auxiliary, or as a surfactant, a surfactant, a thickener, an organic solvent,
Waxes, dyes and the like may be added.

The amount of the heat-sensitive adhesive applied is preferably 3 to 30 g / m ² in terms of dry weight. More preferably 7 to
20 g / m ² . By the way, if the coating amount is less than 3 g / m ² , sufficient adhesive performance may not be obtained when used as a label. On the other hand, when the amount exceeds 30 g / m ² , it takes time to heat-activate the heat-sensitive adhesive, and the adhesive performance is saturated, resulting in poor economy.

The method of applying the heat-sensitive adhesive on a substrate includes brush coating, spray coating, screen printing, gravure printing, offset printing, letterpress printing, a Meyer bar coater, a kiss roll coater, a lip coater, and a direct roll coater. This is performed by various coating apparatuses such as an offset roll coater, a gravure roll coater, a reverse roll coater, a rod coater, a blade coater, and an air knife coater.

The temperature of the heat-sensitive adhesive coating solution in the coating step must be lower than the melting point of the solid plasticizer contained. If the temperature of the coating liquid is higher than the melting point of the solid plasticizer, the solid plasticizer may melt and the heat-sensitive adhesive may have tackiness. Generally, the temperature of the pressure-sensitive adhesive coating liquid is preferably 50 ° C. or less. In addition, drying can be performed by a known method combined with the above-described device used in the coating step, and for the same reason as described above, it is necessary to perform drying at a temperature lower than the melting point of the solid plasticizer contained therein, Generally, the drying is preferably performed at a temperature of 50 ° C. or lower.

Examples of the material of the substrate on which the heat-sensitive adhesive of the present invention is applied include papers, synthetic papers, films, metal foils, nonwoven fabrics, woven fabrics and the like, and sheets obtained by appropriately laminating these. Of course, various layers such as a heat-sensitive recording layer, a pressure-sensitive recording layer, a thermal transfer image-receiving layer, an ink-jet recording layer, and a pigment coating layer may be provided on the surface of these substrates. Further, a barrier layer may be provided on the surface to which the heat-sensitive adhesive is applied to reinforce the strength or to prevent the heat-sensitive adhesive from penetrating into the base material and preventing the adhesion function from deteriorating.
When used as a label, printability and the like are required. In particular, when used as a label to be affixed to a glass bottle containing a liquid such as soft drink, alcoholic beverage, drug bottle or the like, it is preferable to use a substrate having excellent water resistance. In addition, the heat-sensitive adhesive layer can be formed on both sides of the base material if necessary.

[0029]

The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is by no means restricted to such specific examples.
In the examples, “parts” and “%” indicate “parts by weight of solid content” and “% by weight”, respectively, unless otherwise specified.

Example 1 [Preparation of heat-sensitive adhesive] Thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C, gel content:
25 parts) and 28 parts of a thermoplastic resin B (styrene-methyl methacrylate-2-ethylhexyl acrylate resin, Tg: 25 ° C., gel content: 52%) in a mixed dispersion of 28 parts, dicyclohexyl phthalate as a solid plasticizer 150 parts of a dispersion (mp: 65 ° C.) were mixed to adjust the solid content concentration to 50% to prepare a heat-sensitive adhesive. [Preparation of Heat-Sensitive Adhesive Sheet] The heat-sensitive adhesive obtained above was obtained by using a Meyer bar coater on the surface of a double-sided art paper (brand name: Kinto both sides, manufactured by Oji Paper Co., Ltd.) of 84.9 g / m ^{2 in} rice tsubo. The pressure-sensitive adhesive was applied to a dry weight of 16 g / m ² and dried to obtain a heat-sensitive pressure-sensitive adhesive sheet.

Example 2 The thermoplastic resin of Example 1 was composed of 85 parts of thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25%) and thermoplastic resin C (styrene-ethyl acrylate). A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the butadiene resin (Tg: 5 ° C, gel content: 70%) was changed to 15 parts.

Example 3 The procedure of Example 2 was repeated except that 80 parts of a rosin ester-based tackifier dispersion (softening temperature: 150 ° C.) having a solid content of 50% was added as a tackifier to the heat-sensitive adhesive of Example 2. A heat-sensitive adhesive sheet was obtained in the same manner as in Example 2.

Example 4 Thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25%) of Example 2 was replaced with thermoplastic resin D (styrene-ethylene-vinyl acetate resin, T
g: 65 ° C., gel content: 28%)
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 2.

Example 5 The thermoplastic resin C (styrene-butadiene resin, Tg: 5 ° C., gel content: 70%) of Example 4 was replaced with the thermoplastic resin E (ethylene-vinyl acetate resin, Tg: 20 ° C.). , Gel content: 65%) to obtain a heat-sensitive adhesive sheet in the same manner as in Example 4.

Example 6 Thermoplastic resin C (styrene-butadiene resin, Tg: 5 ° C., gel content: 70%) of Example 4 was replaced with thermoplastic resin F (butyl methacrylate resin, Tg: 10 ° C., gel) Except that the content was changed to 57%), a heat-sensitive adhesive sheet was obtained in the same manner as in Example 4.

Example 7 The thermoplastic resin of Example 1 was 65 parts of thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25%), and thermoplastic resin B (styrene-ethyl acrylate). Methyl methacrylate-2-ethylhexyl acrylate resin, Tg: 25 ° C., gel content: 52%)
Part, thermoplastic resin G (ethylene-vinyl acetate resin, Tg:-
(35 ° C., gel content: 68%) was changed to 10 parts to obtain a heat-sensitive adhesive sheet in the same manner as in Example 1.

Example 8 In Example 1, a thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25)
%), Thermoplastic resin B (styrene-methyl methacrylate-2-ethylhexyl acrylate resin),
(Tg: 25 ° C., gel content: 52%) was changed to 7 parts to obtain a heat-sensitive adhesive sheet in the same manner as in Example 1.

Example 9 In Example 4, thermoplastic resin D (styrene-ethylene-vinyl acetate resin, Tg: 65 ° C., gel content: 28%)
Was changed to 65 parts and thermoplastic resin C (styrene-butadiene resin, Tg: 5 ° C., gel content: 70%) was changed to 35 parts to obtain a heat-sensitive adhesive sheet in the same manner as in Example 4. .

Example 10 The thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25%) of Example 1 was replaced with the thermoplastic resin H (styrene-ethylene resin, Tg: 90).
C., gel content: 3%) to obtain a heat-sensitive adhesive sheet in the same manner as in Example 1.

Example 11 Thermoplastic resin D (styrene-ethylene-vinyl acetate resin, Tg: 65 ° C., gel content: 28%) of Example 4 was replaced with thermoplastic resin I (styrene-butadiene resin, Tg: 65
C., gel content: 56%).
In the same manner as in the above, a heat-sensitive adhesive sheet was obtained.

Example 12 In Example 1, the thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25)
%) Of a thermoplastic resin B (styrene-methyl methacrylate-2-ethylhexyl acrylate-based resin,
(Tg: 25 ° C., gel content: 52%) was changed to 2 parts to obtain a heat-sensitive adhesive sheet in the same manner as in Example 1.

Example 13 In Example 7, a thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25)
%), Thermoplastic resin B (styrene-methyl methacrylate-2-ethylhexyl acrylate-based resin,
Tg: 25 ° C., gel content: 52%) was changed to 20 parts, and thermoplastic resin G (ethylene-vinyl acetate resin, Tg: −35 ° C., gel content: 68%) was changed to 28 parts, A heat-sensitive adhesive sheet was obtained in the same manner as in Example 7.

Comparative Example 1 In Example 4, a thermoplastic resin D (styrene-ethylene-vinyl acetate resin, Tg: 65 ° C., gel content: 28%)
Was changed to 50 parts and the thermoplastic resin C (styrene-butadiene resin, Tg: 5 ° C., gel content: 70%) was changed to 50 parts to obtain a heat-sensitive adhesive sheet in the same manner as in Example 4. .

Comparative Example 2 Thermoplastic resin A (styrene-ethyl acrylate resin, Tg: 70 ° C., gel content: 25%) of Example 1 was replaced with thermoplastic resin J (styrene-butadiene resin, Tg: 4).
A thermosensitive adhesive sheet was obtained in the same manner as in Example 1 except that the temperature was changed to 0 ° C. and the gel content: 19%.

Comparative Example 3 The thermoplastic resin B of Example 1 (styrene-methyl methacrylate-2-ethylhexyl acrylate resin, T
g: 25 ° C., gel content: 52%)
(Styrene-butadiene resin, Tg: 40 ° C., gel content: 19%), except that a heat-sensitive adhesive sheet was obtained in the same manner as in Example 1.

Evaluation The adhesive strength, blocking resistance, dusting, and printability of the pressure-sensitive adhesive-coated surface of the heat-sensitive adhesive sheets obtained in the above Examples and Comparative Examples were evaluated, and the results are shown in Table 1. [Adhesion Function] The heat-sensitive adhesive sheet was heat-activated in an oven heated to 120 ° C. for 15 seconds, and immediately adhered to a glass plate after heat activation. Two hours after sticking, the adhesive strength was measured at an angle of 180 ° at a speed of 0.3 m / min, and judged based on the following criteria. A: The adhesive strength is 800 gf / 25 mm or more, and the adhesive strength is excellent. ：: Adhesion force of 500 gf / 25 mm or more, 800 gf /
It is less than 25 mm, which is practically good. Δ: Adhesive strength of 300 gf / 25 mm or more, 500 gf /
It is less than 25 mm, and practical use is possible. ×: Adhesive strength is less than 300 gf / 25 mm, which has a practical problem.

[Blocking Resistance] The rolled-up heat-sensitive adhesive sheet was treated for 7 days at 45 ° C., and the occurrence of blocking was visually observed and evaluated according to the following criteria. ：: No blocking at all, very good. ：: Very slight blocking, but practically good. Δ: Slight blocking, but practically no problem. X: Blocking is remarkable and there is a practical problem.

[Dusting] An ink for sheet offset (trade name: G) using an RI-1 type printing test machine (manufactured by Meiji Seisakusho)
(raf-G black, manufactured by Dainippon Ink and Chemicals, Inc.) The surface of the heat-sensitive adhesive sheet was printed three times using 0.3 ml of the heat-sensitive adhesive sheet, and the state of the heat-sensitive adhesive applied surface was observed. From the evaluation of the surface strength, the tendency of dusting to occur was determined. ：: Excellent surface strength and no peeling of heat-sensitive adhesive applied surface. ：: Peeling of the heat-sensitive adhesive applied surface is very slight,
Practically good. Δ: There is some peeling of the heat-sensitive adhesive applied surface, but there is almost no problem in practical use. X: The peeling of the heat-sensitive adhesive applied surface is remarkable, and there is a practical problem.

[Printability] Ink for sheet offset (Gra manufactured by Dainippon Ink and Chemicals, Inc.) using an RI-1 type printing test machine.
f-G black) Print on the heat-sensitive adhesive applied surface of the heat-sensitive adhesive sheet using 0.5 ml, immediately after printing, 5 minutes after printing,
After 10 minutes from printing, high-quality paper was superimposed on the printing surface and pressed at a constant pressure, and the density of the ink transferred to the high-quality paper was evaluated according to the following criteria. A: Almost no ink transfer after 5 minutes. ：: Almost no ink transfer after 10 minutes. Δ: The transfer density after 10 minutes is about half the transfer density of the ink immediately after printing. X: The transfer density of the ink immediately after printing and the transfer density after 10 minutes hardly change.

[Comprehensive Evaluation] From the results of the above evaluations of the adhesive function, blocking resistance, dusting, and printability of the heat-sensitive adhesive sheet, five ranks of 5 to 1 are given in the order of excellent overall quality. The results are shown in Table 1. 5 is the most practically practical and 1 is practically problematic.

[0051]

[Table 1]

[0052]

The heat-sensitive adhesive of the present invention provides a heat-sensitive adhesive sheet having sufficient adhesive strength, excellent blocking resistance, no dusting, and excellent printability. Became possible.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09J 133/04 C09J 133/04 155/00 155/00

Claims (4)

[Claims] 1. A heat-sensitive adhesive mainly comprising a thermoplastic resin and a solid plasticizer, wherein the thermoplastic resin comprises a thermoplastic resin M having a glass transition temperature of 60 to 150 ° C., and a glass transition temperature of -30 to 30. ° C thermoplastic resin N, and the solid content weight ratio of said thermoplastic resin M and N is 55 / 45-98.
/ 2, which is a heat-sensitive adhesive. 2. The method according to claim 1, wherein the thermoplastic resins M and N are each an acrylate polymer, a methacrylate polymer, a vinyl acetate polymer, a styrene polymer, a (meth) acrylate copolymer, and a vinyl acetate polymer. Ethylene copolymer, vinyl acetate-ethylene-vinyl chloride copolymer, vinyl acetate- (meth) acrylate copolymer, ethylene- (meth) acrylate copolymer, ethylene-
The heat-sensitive adhesive according to claim 1, which is at least one member selected from a vinyl chloride copolymer, a styrene-ethylene copolymer, a styrene-isoprene copolymer, a styrene-butadiene copolymer, and an acrylonitrile-butadiene copolymer. Sheet. 3. The solid plasticizer has a melting point of 50 to 100 ° C.
The heat-sensitive adhesive according to claim 1, which is: 4. A heat-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer comprising the heat-sensitive pressure-sensitive adhesive according to claim 1 as a main component.