JPH1150020A - Method for producing heat-sensitive adhesive sheet and heat-sensitive adhesive sheet - Google Patents

Abstract

(57) [Abstract] (with correction) [Problem] To provide a method for producing an excellent heat-sensitive adhesive sheet which has excellent strength of a heat-sensitive adhesive layer and is free from powder dropping and cutter stains in a cutting step. . A heat-sensitive adhesive sheet obtained by applying a heat-sensitive adhesive mainly composed of a thermoplastic resin and a solid plasticizer to a sheet-like substrate and drying the same is used.
The temperature of the heat-sensitive adhesive layer, which is increased by the heating with warm air of 0 ° C. or more, is lower than the melting point of the solid plasticizer by 5 ° C. or more, and is 1.07 of the glass transition temperature (absolute temperature) of the thermoplastic resin. A time from application of the heat-sensitive adhesive to completion of drying of the heat-sensitive adhesive is 40 seconds or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heat-sensitive adhesive sheet obtained by applying a heat-sensitive adhesive which is non-adhesive at room temperature, but which becomes tacky when heated, on one surface of a substrate and then drying. It relates to a manufacturing method. Specifically, the present invention relates to a method for drying a heat-sensitive adhesive capable of obtaining a heat-sensitive adhesive layer having excellent strength.

[0002]

2. Description of the Related Art Conventionally, labels are applied 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 will curl if the water-soluble adhesive is applied to the back of the base material,
After sticking to a glass bottle, there is a problem that wrinkles and floating are generated on the label, resulting in a defective label and impairing the appearance. Use of a water-soluble pressure-sensitive adhesive may be unfavorable in terms of work environment hygiene.

[0003] On the other hand, a label of an adhesive sheet 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 in most cases, is disposed of. I have. 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.

In general, a heat-sensitive adhesive sheet is obtained by applying a heat-sensitive adhesive to one surface of a substrate, and is usually used as a label by printing the other surface of the substrate. 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. Usually, the heating temperature is from 50C to 150C,
The solid plasticizer in the heat-sensitive adhesive melts when heated to a temperature equal to or higher than its melting point, plasticizes the thermoplastic resin, and develops adhesiveness. Since the molten solid plasticizer crystallizes slowly, the adhesiveness lasts for a long time and can be used by sticking to a glass bottle or the like while having the adhesiveness.

[0005] Even if the heat-sensitive adhesive sheet is continuously attached to the 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.

[0006] However, the heat-sensitive adhesive sheet is often stored in a wound state or in a state in which several sheets are stacked, and in this case, there is a problem that blocking occurs unless stored at a low temperature.

To solve this problem, for example, there is a method of increasing the glass transition temperature of a thermoplastic resin.
Simply increasing the glass transition temperature will decrease the strength of the heat-sensitive adhesive layer, and the heat-sensitive adhesive layer will peel off from the cut into powder during the cutting process for use as a label. Would.

[0008] The powder dropping in this case is a phenomenon in which the heat-sensitive adhesive layer is cracked and falls off from the substrate, which is generally called dusting due to the falling off of fine particles such as pigments on the surface of the coating layer. Is a completely different phenomenon. In addition, cutter dirt is a phenomenon in which the cutter is heated by continuous cutting for a long time, and the powder of the adhesive layer that has fallen off the base material exhibits adhesiveness due to the heat of the cutter, and adheres and accumulates at the tip of the cutter. . When the amount of accumulated matter increases, it may transfer to the separated label and impair the appearance of the label, or on the contrary, the label may stick through the adhesive accumulated on the cutter and hinder continuous cutting.

On the other hand, in order to solve the problem of blocking, a method of using fine particles having no tackiness, such as inorganic pigments and organic pigments (JP-A-2-282050, JP-A-6-282050).
JP-179855, JP-A-6-179856) have been proposed, but the mere addition of ordinary pigments is insufficient in the blocking resistance and tends to deteriorate the adhesive strength and dusting. It is in. In addition, when the solid plasticizer is protected by fine particles and activated by heating the heat-sensitive adhesive at a relatively low temperature, the solid plasticizer melts and takes a long time to diffuse, making it difficult for the adhesive to appear as a heat-sensitive adhesive. In addition, there is a problem that the adhesive function of the heat-sensitive pressure-sensitive adhesive sheet is deteriorated, which is not practically sufficient.

[0010]

The present invention relates to a method for producing an excellent heat-sensitive adhesive sheet which is excellent in strength of a heat-sensitive adhesive layer and does not cause powder dropping or cutter stain in a cutting step. is there.

[0011]

Means for Solving the Problems The present inventors have conducted intensive research on a method of applying and drying a heat-sensitive adhesive, and as a result,
Elucidate the unique relationship between heat-sensitive adhesives that is established between the drying temperature at which the strength of the heat-sensitive adhesive layer begins to rapidly increase and the glass transition temperature of the thermoplastic resin used in the heat-sensitive adhesive Succeeded.

That is, when applying and drying the heat-sensitive adhesive, the temperature of the heat-sensitive adhesive layer in the drying step is adjusted to a specific temperature related to the glass transition temperature of the thermoplastic resin used in the heat-sensitive adhesive. It has been found that when the temperature is higher than the temperature, the strength of the heat-sensitive adhesive layer can be remarkably improved, and the present invention has been completed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a heat-sensitive adhesive sheet obtained by applying a heat-sensitive adhesive mainly composed of a thermoplastic resin and a solid plasticizer to a sheet-like substrate and drying the same. The drying process involves heating in an atmosphere of 50 ° C. or more, and the temperature of the heat-sensitive adhesive layer that rises by the heating is 5 ° C. or more lower than the melting point of the solid plasticizer, and the glass transition temperature or average glass transition of the thermoplastic resin 1. Temperature (absolute temperature)
A method of producing a heat-sensitive adhesive sheet, wherein the time from application of the heat-sensitive adhesive to drying is 40 seconds or less, and a heat-sensitive adhesive sheet produced by the method. It is a sheet.

The average glass transition temperature of the present invention is as follows.
In the case of using a heat-sensitive adhesive mainly composed of a plurality of thermoplastic resins having different glass transition temperatures, it is obtained by summing the products of the respective glass transition temperatures and weight fractions (sum of 1). It is an average value of the glass transition temperature, and its meaning in terms of physical properties in a mixed composition of each thermoplastic resin is unknown.

In the present invention, if the temperature of the heat-sensitive adhesive layer in the drying step is set to be not less than 1.07 times the (average) glass transition temperature of the thermoplastic resin used for the heat-sensitive adhesive, The reason why the strength of the layer can be significantly improved can be explained as follows.

That is, the strength of the heat-sensitive adhesive layer is determined by the bonding strength of the thermoplastic resin used. The thermoplastic resin in the heat-sensitive adhesive can be bonded by drying at a temperature close to the glass transition temperature, and in some cases, at a temperature lower than the glass transition temperature, but it is sufficient because the fusion of the thermoplastic resin particles is incomplete. High bond strength cannot be obtained. On the other hand, at around 1.07 times the glass transition temperature, the fusion between the resin particles starts to become strong. From experience, if the resin particles are dried at a higher temperature, sufficient bonding strength can be obtained. As a result, a strong heat-sensitive adhesive is obtained. An agent layer is formed. In addition, if dried at a temperature of 1.08 times or more the glass transition temperature, the fusion of the resin particles becomes almost complete, and a very favorable result is obtained.

When a resin layer is formed of a thermoplastic resin alone, it is generally known that increasing the drying temperature above the minimum film forming temperature sharply increases the film strength. In a composition containing a large amount of a component such as a solid plasticizer having no resin, the relationship between the minimum film formation temperature of the thermoplastic resin and the tendency of the strength of the composition layer to be improved by increasing the drying temperature is low.

In the present invention, the critical temperature at which sufficient strength can be obtained when the drying temperature of the heat-sensitive adhesive is changed can be derived from the glass transition temperature. In the present invention,
The temperature of the heat-sensitive adhesive layer in the drying step, during drying,
Alternatively, the surface temperature of the heat-sensitive adhesive layer immediately after the completion of drying is measured, and is the temperature at which the surface temperature becomes highest due to drying heat.

On the other hand, when the temperature of the heat-sensitive adhesive layer is close to the melting point of the solid plasticizer in the heat-sensitive adhesive, the performance of the heat-sensitive adhesive is reduced, and after a few days, a powder called chalk is formed on the surface of the heat-sensitive adhesive. In some cases, a wiping phenomenon may occur, or the solid plasticizer may start to partially melt and the heat-sensitive adhesive may exhibit adhesiveness. In particular, when the substrate of the heat-sensitive adhesive sheet is a substrate that is easily torn, such as paper, if the heat-sensitive adhesive sheet exhibiting a slight adhesiveness is wound up, it cannot be unwound due to blocking and cannot be used. To prevent this, the temperature of the heat-sensitive adhesive layer may be set to a temperature lower than the melting point of the solid plasticizer by 5 ° C. or more, preferably 10 ° C. or more.

The melting point of the solid plasticizer in the present invention means the absorption when a heat-sensitive adhesive dried at a sufficiently low temperature is used as a sample and measured at a heating rate of 10 ° C./min with a differential scanning calorimeter. This is the temperature at which the heat has a maximum value. In the present invention, DS
The measured value using C22 (manufactured by Seiko Electronics Industry Co., Ltd.) was adopted.

It was also found that the strength of the heat-sensitive adhesive layer was affected by the drying speed. That is, the heat-sensitive adhesive contains a large amount of a solid plasticizer and therefore has very low water retention, and if the drying takes time, the resin particles move with moisture, so that the resin component becomes non-uniform, and the heat-sensitive adhesive layer It was found that unevenness in strength was caused, and as a result, the heat-sensitive pressure-sensitive adhesive layer was cracked and easily dropped from the substrate. In addition, as a result of the non-uniform resin content, the performance of the heat-sensitive adhesive decreases.

In order to prevent this phenomenon, the time from application of the heat-sensitive adhesive to drying must be 40 seconds or less, preferably 20 seconds or less. Here, the term “drying” refers to a state in which the moisture content of the heat-sensitive adhesive layer is 10% or less.

The heating method for drying the heat-sensitive adhesive is not particularly limited. However, even if the temperature of the heat-sensitive adhesive applied to the substrate is increased after drying, the strength of the heat-sensitive adhesive layer does not improve. Therefore, it is necessary to heat immediately after the application of the heat-sensitive adhesive to increase the temperature of the heat-sensitive adhesive before drying proceeds.

Conventionally, drying of the heat-sensitive adhesive is generally carried out in an atmosphere at a temperature of about 40 ° C. or lower, but the above-mentioned object cannot be achieved at such a relatively low temperature. That is, in the present invention, the heat-sensitive adhesive may be heated as quickly as possible in an atmosphere of 50 ° C. or higher and dried as it is.

It should be noted that even if the heat-sensitive adhesive comes into contact with air at a relatively high temperature, it takes away heat when water contained in the heat-sensitive adhesive evaporates. It is hard to be. In the present invention, before the drying of the heat-sensitive adhesive proceeds, it is easier to obtain the effect of the present invention if the temperature is increased as soon as possible, so that the initial stage of the drying step may be set to a higher temperature condition than thereafter. preferable.

Specifically, the initial stage of the drying step is set to an atmosphere of 55 ° C. or higher, preferably 60 ° C. or higher, more preferably 65 ° C. or higher, and the temperature of the heat-sensitive adhesive is rapidly increased. It is very preferable that the heat-sensitive adhesive layer be extremely dried if it is gently dried by heating to such an extent that the temperature of the heat-sensitive adhesive is maintained.

The type of the thermoplastic resin used in the present invention includes vinyl acetate-ethylene-styrene copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-ethylene-
Vinyl chloride copolymer, vinyl acetate-acrylate copolymer, vinyl acetate-ethylene-acrylate copolymer, ethylene-vinyl chloride copolymer, (meth) acrylate copolymer, styrene-isoprene copolymer Examples include aqueous solutions and aqueous dispersions of polymers, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, vinyl acetate polymers, styrene polymers, acrylate polymers, and the like. These resins are used alone or in combination.

The glass transition temperature of the thermoplastic resin is usually -3.
Those having a temperature of 0 ° C to 70 ° C, preferably about -10 ° C to 60 ° C are used. Incidentally, those below -30 ° C tend to be inferior in blocking resistance, and those above 70 ° C tend to be inferior in dusting and heat-sensitive adhesive layer strength,
Not very preferably used. When a plurality of thermoplastic resins are used, the balance between blocking resistance and dusting can be improved by combining a resin having a relatively low glass transition temperature and a resin having a relatively high glass transition temperature. In addition, in order to obtain a heat-sensitive adhesive sheet having particularly excellent heat-sensitive adhesive layer strength as in the present invention, a thermoplastic resin having a glass transition temperature or an average glass transition temperature of −10 ° C. to 45 ° C. is used. Is particularly preferred.

The type of the solid plasticizer used in the heat-sensitive adhesive of the present invention includes dihexyl phthalate (melting point: 65).
° C), dicyclohexyl phthalate (melting point 65 ° C), dihydroabiethyl phthalate (melting point 65 ° C), dimethyl isophthalate (melting point 66 ° C), di-2-phenoxyethyl isophthalate (melting point 77 ° C), N-cyclohexyl-p -Toluenesulfonamide (melting point 86 ° C.), 1,4-bishydroxyethoxybenzene di-m-toluate (melting point 97
° 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), sucrose octaacetate (Melting point 89
C), and an aqueous dispersion of a plasticizer having a melting point of 50 to 100 ° C, such as tricyclohexyl citrate (melting point 57 ° C), is preferably used. Incidentally, if the melting point is less than 50 ° C., the blocking resistance is poor, and if it exceeds 100 ° C., there is a problem that it is difficult to activate by heating.

The solid plasticizer melts at a temperature higher than its melting point when activated by heat and plasticizes the thermoplastic resin, so that the solid plasticizer provides tackiness as a heat-sensitive adhesive, but the duration of the tackiness varies depending on the solid plasticizer. The solid plasticizer may be used alone or in combination. Further, when the time during which the adhesiveness is maintained is increased, it is preferable to use dicyclohexyl phthalate. The melting point of dicyclohexyl phthalate is 65 ° C, but the melting point is 62 ° C to 64 ° C depending on the purity.
Are commonly used. When it is desired to raise the drying temperature of the heat-sensitive adhesive as much as possible, a material having particularly high purity and a melting point of 65 ° C. can be used.

In addition to the thermoplastic resin and the solid plasticizer, the heat-sensitive pressure-sensitive adhesive includes water-soluble resins such as rosin-based resins, phenol-based resins, terpene-based resins, xylene-based resins, and petroleum-based hydrocarbon resins as tackifiers. The adhesive function may be adjusted by incorporating a dispersion.

The mixing ratio of the thermoplastic resin and the solid plasticizer in the heat-sensitive adhesive of the present invention is 10% in total of the thermoplastic resin.
The solid plasticizer is 50 to 300 parts by weight of solids per 0 parts by weight of solids. By the way, when the amount of the solid plasticizer is less than 50 parts by weight of solid content, the adhesiveness as the heat-sensitive adhesive is hard to appear.
When the amount of the solid plasticizer exceeds 300 parts by weight, the duration of adhesiveness tends to be short as a heat-sensitive adhesive. When a tackifier is contained, the thermoplastic resin 10
It is preferable to add 10 to 150 solid parts by weight of a tackifier to 0 solid parts by weight. 10 tackifiers
When the amount is less than the solid content part by weight, the effect of enhancing the adhesive function is poor, and when it exceeds 150 solid parts by weight, there is a problem that the blocking resistance is poor.

In the heat-sensitive adhesive of the present invention, mineral pigments such as silicate, aluminosilicate, carbonate, silica, alumina, magnesium oxide, carbon black, polystyrene resin, urea resin, acrylic Known or used pigments such as resins, melamine resins, benzoguanamine resins, and other organic pigments, and starch, flour, synthetic resin fine particles, and the like can also be added. In addition, as a binder, polyvinyl alcohol, starch and the like, a resin other than a thermoplastic resin may be used as an auxiliary, or a surfactant, a thickener, an organic solvent, a wax, a dye, or 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, when the coating amount is less than 3 g / m ^2, it is difficult to obtain a sufficient adhesive function when used as a label. On the other hand, if it exceeds 30 g / m ² , the blocking resistance is reduced, it takes time to heat-activate the heat-sensitive adhesive, and the adhesive function is saturated and the economy is poor.

The method for 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 at the time of application must be lower than the melting point of the solid plasticizer used by 5 ° C. or more. When the temperature of the heat-sensitive adhesive is raised to a higher temperature, the performance of the heat-sensitive adhesive decreases, or the solid plasticizer starts to partially melt, and the heat-sensitive adhesive layer has a slight tackiness. It is.

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, the surface of these substrates may be provided with 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, a pigment coating layer, or a heat-sensitive adhesive is applied. A barrier layer may be provided on the surface to reinforce the strength or to prevent the heat-sensitive adhesive from penetrating into the base material and preventing the adhesive function from deteriorating.

When used as a label, excellent printability is required. In particular, when used as a label to be attached to a glass bottle containing a liquid such as soft drinks, alcoholic beverages, chemical bottles, etc., water resistance is required. It is preferable to use a base material excellent in quality.

[0039]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should be understood that the present invention is not limited thereto. In the examples, “parts” means “parts by weight of solid content” unless otherwise specified.

The glass transition temperature was measured using a scanning calorimeter (DSC22, manufactured by Seiko Denshi Kogyo Co., Ltd.) under the conditions of a heating rate of 10 ° C./min and a starting temperature of −100 ° C.

[Preparation of Thermosensitive Adhesive] An aqueous dispersion of a vinyl acetate-ethylene-vinyl chloride resin having a glass transition temperature of 20 ° C. (absolute temperature 293 ° K.) as a thermoplastic resin (trade name “Sumikaflex 830” Sumitomo) 100 parts of Chemical Co., Ltd.) and 250 parts of an aqueous dispersion of dicyclohexyl phthalate as a solid plasticizer having a melting point of 65 ° C. were mixed to adjust the solid content concentration to 50%, thereby preparing a heat-sensitive adhesive A. .
At this time, the temperature range of the heat-sensitive adhesive layer which rises by heating according to claim 1 is 40.5 ° C or more and 60 ° C or less.

Next, an aqueous dispersion of a vinyl acetate-ethylene-vinyl chloride resin having a glass transition temperature of 30 ° C. (absolute temperature of 303 ° K) as a thermoplastic resin (trade name “SUMICA FLEX 850” manufactured by Sumitomo Chemical Co., Ltd.) ) 80 parts, an aqueous dispersion of vinyl acetate-ethylene resin having a glass transition temperature of -15 ° C (absolute temperature 258 ° K) (trade name “SUMICA FLEX 751” manufactured by Sumitomo Chemical Co., Ltd.), and a melting point of 6
250 parts of an aqueous dispersion of dicyclohexyl phthalate as a solid plasticizer at 5 ° C., and an aqueous dispersion of a rosin-based resin having a softening temperature of 100 ° C. as a tackifier (trade name “Superester E
-720 "(Arakawa Chemical Industry Co., Ltd.) was mixed to adjust the solid content concentration to 50% to prepare a heat-sensitive adhesive B. At this time, the temperature range of the heat-sensitive adhesive layer which is increased by heating according to claim 2 is 41.5 ° C. or more and 60 ° C. or less.

100 parts of an aqueous dispersion of a styrene-butadiene resin having a glass transition temperature of 35 ° C. (absolute temperature 308 ° K.) (trade name “P-6522” manufactured by Sumika ABS Latex Co., Ltd.) as a thermoplastic resin And melting point 65
The solid content concentration was adjusted to 50% by mixing 250 parts of an aqueous dispersion of dicyclohexyl phthalate as a solid plasticizer at 50 ° C.,
A heat-sensitive adhesive C was prepared. At this time, the temperature range of the heat-sensitive adhesive layer which is increased by heating according to claim 1 is 5
6.5 ° C. or higher and 60 ° C. or lower.

Further, 100 parts of an aqueous dispersion of a styrene-butadiene resin having a glass transition temperature of 35 ° C. (absolute temperature: 308 ° K.) (trade name “P-6522” manufactured by Sumika ABS Latex Co., Ltd.) as a thermoplastic resin And melting point 7
250 parts of an aqueous dispersion of di-2-phenoxyethyl isophthalate as a solid plasticizer at 7 ° C., and an aqueous dispersion of a rosin-based resin having a softening temperature of 100 ° C. as a tackifier (trade name “Super Ester E-720”, Arakawa Chemical) (Industry Co., Ltd.) 50 parts were mixed to adjust the solid content concentration to 50% to prepare a heat-sensitive adhesive D. At this time, the temperature range of the heat-sensitive adhesive layer which rises by heating according to claim 1 is 56.5 ° C. or more and 7 ° C.
2 ° C. or less.

[Preparation of Heat-Sensitive Adhesive Sheet] Example 1 A heat-sensitive adhesive A was applied to one side of a double-sided coated paper (trade name “OK Topcoat” manufactured by Oji Paper Co., Ltd.) having a rice area of 84.9 g / m ^2. 8 g / dry weight using a bar coater
m ^2, and immediately warm air at 70 ° C. to 7.2
Subsequently, hot air at 55 ° C. was blown for 10.8 seconds, and the heat-sensitive adhesive layer was dried so that the water content of the heat-sensitive adhesive layer became about 8%, to obtain a heat-sensitive adhesive sheet. At this time, the temperature of the heat-sensitive adhesive layer rose to 49 ° C.

Example 2 A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that heat-sensitive adhesive B was used instead of heat-sensitive adhesive A.

Example 3 The temperature of the drying step of the heat-sensitive adhesive sheet was changed to 80 ° C.
Was heated in the same manner as in Example 1 except that the hot air was blown for 7.2 seconds, followed by hot air at 65 ° C. for 10.8 seconds, and dried so that the water content of the heat-sensitive adhesive layer became about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 59 ° C.

Example 4 A heat-sensitive adhesive sheet was obtained in the same manner as in Example 3, except that the heat-sensitive adhesive C was used instead of the heat-sensitive adhesive A.

Example 5 A heat-sensitive adhesive sheet was obtained in the same manner as in Example 3, except that the heat-sensitive adhesive D was used instead of the heat-sensitive adhesive A.

Example 6 The temperature of the drying step of the heat-sensitive adhesive sheet was changed to 85 ° C.
In the same manner as in Example 5 except that the hot air was blown for 7.2 seconds, followed by 70 ° C. hot air for 10.8 seconds, and dried so that the moisture of the heat-sensitive adhesive layer became about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 64 ° C.

Example 7 The temperature of the drying step of the heat-sensitive adhesive sheet was changed to 65 ° C.
Was blown for 7.2 seconds, followed by 48 ° C. hot air for 10.8 seconds, and dried in the same manner as in Example 2 except that the heat-sensitive adhesive layer was dried so that the moisture content of the layer was about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 43 ° C.

Example 8 The temperature of the drying step of the heat-sensitive adhesive sheet was changed to 65 ° C.
Hot air of 15.6 seconds followed by 50 ° C. hot air for 23.4 seconds.
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the heat-sensitive adhesive layer was sprayed for 2 seconds and dried so that the moisture content of the heat-sensitive adhesive layer was about 8%. At this time, the temperature of the heat-sensitive adhesive layer rose to 46 ° C.

Comparative Example 1 In Example 1, the temperature in the drying step was changed to 27 ° C.
Is blown for 18 seconds, and the moisture of the heat-sensitive adhesive layer is about 9
%, And a heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the heat-sensitive adhesive sheet was dried. At this time, the temperature of the heat-sensitive adhesive layer was 25 ° C.

Comparative Example 2 The temperature of the drying step of the heat-sensitive adhesive sheet was changed to 85 ° C.
In the same manner as in Example 4 except that the hot air was blown for 7.2 seconds, followed by 70 ° C. hot air for 10.8 seconds, and dried so that the moisture of the heat-sensitive adhesive layer became about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 64 ° C.

Comparative Example 3 In Example 1, the temperature and time of the drying step were changed.
55 ° C hot air for 15.6 seconds followed by 40 ° C hot air for 2 seconds
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the heat-sensitive adhesive layer was sprayed for 3.4 seconds and dried so that the moisture content of the heat-sensitive adhesive layer was about 8%. At this time, the temperature of the heat-sensitive adhesive layer was 3
6 ° C.

Comparative Example 4 In Example 2, the temperature and time of the drying step were changed.
55 ° C hot air for 15.6 seconds followed by 40 ° C hot air for 2 seconds
A heat-sensitive adhesive sheet was obtained in the same manner as in Example 2 except that the heat-sensitive adhesive layer was sprayed for 3.4 seconds and dried so that the moisture content of the heat-sensitive adhesive layer became about 8%. At this time, the temperature of the heat-sensitive adhesive layer was 3
6 ° C.

Comparative Example 5 In Example 4, the temperature in the drying step was changed to 60 ° C.
In the same manner as in Example 4, except that the hot air was blown for 7.2 seconds, followed by 45 ° C. hot air for 10.8 seconds, and dried so that the moisture content of the heat-sensitive adhesive layer was about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 38 ° C.

Comparative Example 6 In Example 5, the temperature in the drying step was changed to 60 ° C.
Was blown for 7.2 seconds, followed by 45 ° C. hot air for 10.8 seconds, and dried in the same manner as in Example 5 except that the heat-sensitive adhesive layer was dried so that the moisture content of the layer became about 8%. An adhesive sheet was obtained. At this time, the temperature of the heat-sensitive adhesive layer rose to 38 ° C.

Comparative Example 7 The temperature, time, and air volume of the drying step of the heat-sensitive adhesive sheet were changed, and 52 ° C. warm air was blown lightly for 96 seconds to dry the heat-sensitive adhesive layer so that the moisture content of the heat-sensitive adhesive layer was about 8%. A heat-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the procedure was repeated. At this time, the temperature of the heat-sensitive adhesive layer rose to 51 ° C.

[Evaluation] The obtained heat-sensitive adhesive sheet was evaluated for adhesive strength, blocking resistance and strength of the heat-sensitive adhesive layer. The results are shown in Table 1.

[Adhesive Strength] 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 the heat activation. Two hours after sticking, the adhesive force was measured at an angle of 180 ° at a speed of 0.3 m / min, and judged according to the following criteria. A: The adhesive strength is 800 gf / 25 mm or more, and the adhesive strength is excellent. ：: Adhesive strength is 500 to 800 gf / 25 mm, and there is no practical problem. C: Adhesive strength is 300 to 500 gf / 25 mm, which is slightly inferior in practical use. ×: Adhesive strength is less than 300 gf / 25 mm, which has a practical problem.

[Blocking resistance] The heat-sensitive adhesive sheet was treated in a wound state at 40 ° C. and 90% RH for 7 days, and the occurrence of blocking was evaluated. A: No blocking at all and extremely excellent in practical use. ：: Slight blocking, but no problem in practical use. Δ: Due to partial blocking, storage in summer has some problems. X: Blocking is severe, and storage at a low temperature is required.

[Strength of the heat-sensitive adhesive layer] An ink for sheet offset (Graf-G manufactured by Dainippon Ink and Chemicals, Inc.) was used using an RI-1 type printing test machine (manufactured by Mei Seisakusho Co., Ltd.).
The surface of the heat-sensitive adhesive sheet coated with the heat-sensitive adhesive was printed six times using 0.3 cc of black ink. Whether the heat-sensitive adhesive layer had fallen off was visually observed and evaluated according to the following criteria. ：: The peeling of the heat-sensitive adhesive layer was hardly observed, and the strength was extremely excellent. ：: Peeling of the heat-sensitive adhesive layer was partially observed, but there was no practical problem. C: Peeling of the heat-sensitive adhesive layer was remarkable, and there was a problem in practice. D: Almost the entire surface of the heat-sensitive adhesive layer was peeled off, and the strength was too weak, which caused a practical problem.

[0064]

[Table 1]

[0065]

As is clear from the results in Table 1, the heat-sensitive adhesive sheet produced by the production method of the present invention has excellent adhesive strength and blocking resistance, particularly excellent strength of the heat-sensitive adhesive layer. Was.

In Examples 3 and 4, the rising temperature of the heat-sensitive adhesive layer slightly approached the melting point of the solid plasticizer, so that a little choking occurred in the heat-sensitive adhesive layer, but it was at a sufficiently usable level.

In Example 8, the drying time was slightly increased.
Compared with Example 1, the strength of the heat-sensitive adhesive layer tended to decrease slightly. Further, in Comparative Example 7 in which drying was performed at a low temperature for a long time, the strength of the heat-sensitive adhesive layer was significantly reduced compared to Example 1, and the adhesive force was also reduced due to the reduced performance of the heat-sensitive adhesive, and was inferior. The result was.

In the heat-sensitive adhesive sheet obtained in Comparative Example 2, since the heat-sensitive adhesive layer exhibited a slight tackiness due to the heat of the drying step, the winding after the production caused blocking, which resulted in a clear appearance. It could not be rewound and could not be used for evaluation.

Claims (4)

[Claims] 1. A heat-sensitive adhesive sheet obtained by applying and drying a heat-sensitive adhesive mainly composed of a thermoplastic resin and a solid plasticizer to a sheet-like substrate, wherein the heat-sensitive adhesive is dried in a step of drying the heat-sensitive adhesive.
The temperature of the heat-sensitive adhesive layer, which is increased by the heating with warm air of 0 ° C. or more, is lower than the melting point of the solid plasticizer by 5 ° C. or more, and is 1.07 of the glass transition temperature (absolute temperature) of the thermoplastic resin. A time from application of the heat-sensitive adhesive to completion of drying of the heat-sensitive adhesive is 40 seconds or less. 2. A heat-sensitive adhesive sheet obtained by applying and drying a heat-sensitive adhesive using a plurality of thermoplastic resins having different glass transition temperatures on a sheet-like substrate, wherein the heat-sensitive adhesive sheet is heated by hot air at 50 ° C. or higher. The rising temperature of the heat-sensitive adhesive layer is at least 5 ° C. lower than the melting point of the solid plasticizer, and the average glass transition temperature (absolute temperature) obtained by summing the product of each glass transition temperature and the weight fraction is 1. A method for producing a heat-sensitive adhesive sheet, wherein the time from application of the heat-sensitive adhesive to completion of drying is 40 seconds or less. 3. The hot air in the initial stage of the drying step is set at 55 ° C. or higher, and thereafter, the heating is performed at a lower temperature than the initial stage.
3. The method according to claim 1, wherein the drying is performed.
The production method of the heat-sensitive adhesive sheet according to the above. 4. A heat-sensitive adhesive sheet produced by the method according to claim 1, 2 or 3.