JP2001081422A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet which is excellent in transparency and has a capability for accepting a thermally transferred dye by laminating a pressure-sensitive layer and a release sheet successively in this order on a surface substrate and by using, as the surface substrate, a transparent vinyl chloride film containing no plasticizer or containing it in a content lower than specified wt.% based on the resin content. SOLUTION: A transparent vinyl chloride film which contains no plasticizer or contains it in a content lower than 5 wt.% based on the resin content is used as the surface substrate. The average center-line roughness (Ra) of the release side of the release sheet is preferably 1 μm or lower. Preferably, the pressure-sensitive adhesive layer is an acrylic one, contains a cross-linker selected from among aliphatic isocyanate compounds and metal chelate compounds, and, when applied, exhibits a viscosity of 5,000 cP or higher. When the plasticizer content is high, a plasticizer component in the pressure-sensitive adhesive layer diffuses with time and thus remarkably reduces the cohesive force of the pressure-sensitive adhesive, causing troubles such as bulging of the pressure-sensitive adhesive during cutting or punching of the pressure- sensitive adhesive sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer and a release sheet are sequentially laminated on one surface of a surface substrate, and a dye which migrates from an ink sheet by heat supplied from a thermal head or the like. The present invention relates to a pressure-sensitive adhesive sheet having thermal transfer receptivity of a dye, which can transfer a full-color image or the like in continuous gradation, and then peel off the imaged surface base material from a release sheet and attach it to various objects.

[0002]

2. Description of the Related Art In recent years, as a full-color image recording system,
Electrophotographic recording, inkjet recording, melt heat transfer recording,
There are various recording systems such as sublimation thermal transfer recording and thermal recording.
Among them, a sublimation thermal transfer system capable of printing with excellent image gradation has been particularly noted.

[0003] In the printing by the sublimation thermal transfer system, an ink sheet having a sublimable dye layer and a dye thermal transfer receiving sheet having a dye-dyeing receiving layer are overlapped, and the ink sheet is heated by heat supplied from a thermal head of a printer. Three colors of yellow, magenta and cyan at a desired portion of
Alternatively, an image is formed by sequentially transferring the four color dyes obtained by adding black to the receiving layer at a predetermined density.
A full-color image can be obtained by repeatedly transferring the dyes of each color of the ink sheet to the receiving sheet in order.

A dye thermal transfer receiving sheet is a resin having a high affinity for a dye such as a polyester resin, a polycarbonate resin, or a cellulose derivative on the surface side of a sheet-like base material, and is used to prevent a thermal head from being fused to an ink sheet during printing. A dye receiving layer containing a release agent, a cross-linking agent, a lubricant, etc. as main components is provided.On the other hand, on the back surface side of the sheet-like substrate,
In order to provide printer runnability by preventing static electricity charge and optimizing the friction coefficient, a backside coating layer is generally provided.

[0005] As a type of the dye thermal transfer receiving sheet, a character or the like can be arbitrarily written on a surface of the sheet-like substrate opposite to the surface of the dye receiving layer with a writing instrument such as a pencil, a ball-point pen, a water-based pen, an oil-based pen, and a fountain pen. Provided with a backside coating layer that can be attached, a so-called postcard type, or, on a release sheet provided with a backside coating layer and a release agent layer in advance, an adhesive layer, a sheet-like substrate, and There is a seal type (hereinafter, also referred to as a receiving pressure-sensitive adhesive sheet) in which a dye receiving layer is sequentially laminated and a receiving sheet portion after thermal transfer recording can be freely attached to various articles.

The technique relating to the receiving pressure-sensitive adhesive sheet includes a release sheet having a release agent layer, a pressure-sensitive adhesive layer, a sheet-like substrate, and a dye receiving layer described in JP-A-64-82988. And the like, which have been subjected to half-cut treatment on the receiving sheet portion.

Conventionally, the receiving pressure-sensitive adhesive sheet has a sheet-like base material such as a base material based on paper manufactured from wood pulp, waste paper pulp, or the like; a laminated paper obtained by laminating paper such as polyethylene; , A white opaque substrate such as polypropylene synthetic paper containing an inorganic pigment such as Yupo, a white PET film, a foamed PET film, etc. is used, and a dye-dyeable resin is coated on the surface of the sheet-shaped substrate on which the adhesive is not formed. It has a configuration in which a receiving layer as a main component is laminated on another surface with an adhesive layer and a release sheet. The receiving pressure-sensitive adhesive sheet is widely used in recent amusement applications and the like.

[0008]

With the spread of mobile phones and personal computers in recent years, there has been a demand in the market for a new receiving adhesive sheet having a sheet-like substrate made of a transparent film for applications such as decoration of a liquid crystal transparent portion. . SUMMARY OF THE INVENTION The present invention provides a pressure-sensitive adhesive sheet having excellent transparency and dye thermal transfer receptivity.

[0009]

Means for Solving the Problems The present inventors first conducted intensive studies on a surface substrate to be used. There are many kinds and many kinds of films having transparency. Among them, the present inventors have found that a transparent vinyl chloride film containing no plasticizer or containing less than 5% by weight based on the resin content has a dye thermal transfer receptivity without forming a receptor layer. And
It has been found that an adhesive layer having excellent transparency and high holding power can be formed. (1). That is, the present invention provides a pressure-sensitive adhesive sheet obtained by sequentially laminating a pressure-sensitive adhesive layer and a release sheet on one surface of a sheet-shaped substrate, wherein the sheet-shaped substrate does not contain a plasticizer or contains a plasticizer with respect to a resin component. A transparent vinyl chloride film having a dye thermal transfer receptivity of less than 5% by weight.

Next, the inventors of the present invention have conducted intensive studies on the transparency of the pressure-sensitive adhesive layer, and found that a decrease in the smoothness of the pressure-sensitive adhesive layer over time affects the transparency. . In order to prevent the smoothness of the pressure-sensitive adhesive layer from decreasing over time, the present inventors have found that it can be avoided by defining the release agent surface of the release sheet to specific physical properties. (2). That is, in the above (1), it is preferable that the center line average roughness (Ra) of the release agent surface of the release sheet is 1 μm or less.

Further, the present inventors have conducted intensive studies on the pressure-sensitive adhesive, and as a result, applied a cross-linked acrylic type as the pressure-sensitive adhesive and combined an aliphatic isocyanate compound and / or a metal chelate compound as the cross-linking agent. It has been found that discoloration over time of the pressure-sensitive adhesive layer can be improved by this. (3). That is, in the above (1) and (2), it is preferable that the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive and contains a crosslinking agent selected from an aliphatic isocyanate compound and a metal chelate compound.

Further, in order to enhance the suitability of the pressure-sensitive adhesive sheet for printers such as antistatic, if a backside coating layer is previously provided on the backside of the release sheet, the release sheet is usually stored in a wound state. Transfer to the release agent layer surface (or the surface to which the release agent is applied if the backside coating layer is formed before the release agent layer is formed), and streaks, repels, etc. A new problem in which a pressure-sensitive adhesive coating defect occurs was found. The inventors have found that the problem can be solved by setting the viscosity of the pressure-sensitive adhesive at the time of application to be higher than usual. (4). That is, in the above (1), (2), and (3),
It is preferable that the viscosity at the time of applying the pressure-sensitive adhesive is 5000 cps or more.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a surface substrate will be described.
The present invention uses a transparent vinyl chloride film as the surface substrate. Generally, a transparent vinyl chloride film is made of 100% vinyl chloride monomer or 85 to 95 vinyl chloride monomers.
% Of a vinyl acetate monomer and 5 to 25% of a vinyl acetate monomer are copolymerized with a phthalate ester such as dioctyl phthalate (DOP) or dioctyl adipate (DO).
A), a plasticizer represented by an aliphatic dibasic acid ester such as an aliphatic ester such as butyl oleate (BO), a stabilizer such as an inorganic acid salt, a lubricant such as a metal soap, and the like. After blending, the mixture was melted and kneaded with a mixer to form a film. In addition, the film formation processing method includes a method of extrusion molding (T-die method, circular die method), a method of roll-forming with calender rolls (calender method),
A method of forming a solution once dissolved in tetrahydrofuran, methylene chloride, or the like (solution casting method) is generally performed.

The vinyl chloride resin, which is the main component, has a high affinity for the sublimation type heat transfer dye and has excellent dyeing performance. Need not be formed. When a receiving layer is present on the surface substrate, the transparency is reduced by itself, and the resin of the receiving layer is colored with time by the influence of heat or ultraviolet rays. This is excellent not only in terms of cost but also in terms of transparency.

The vinyl chloride film is soft (plasticizer amount to resin: 30 to 5) depending on the amount of plasticizer contained.
0% by weight), semi-rigid (plasticizer amount to resin: 10 to 10% by weight)
20% by weight), hard (amount of plasticizer based on resin: 0 to 1)
The transparent vinyl chloride film used in the pressure-sensitive adhesive sheet of the present invention contains no plasticizer at all, or contains a plasticizer even if it contains a plasticizer. Less than 5% by weight in minutes.

When the content of the plasticizer is 5% by weight or more, the plasticizer component diffuses with time into the pressure-sensitive adhesive layer provided on the back surface of the film, and the cohesive force of the pressure-sensitive adhesive is significantly reduced. As a result, when the adhesive sheet is cut and punched with a guillotine, cutter, die roll, or the like, problems such as the occurrence of oozing of the adhesive and poor printer runnability caused by the sticking adhesive may occur. appear. In particular, the use of a vinyl chloride film containing no plasticizer is preferable because the plasticizer does not affect the adhesive.

In the transparent vinyl chloride film used in the present invention, auxiliary agents such as inorganic / organic pigments and modifiers can be used in combination as long as the desired substrate transparency can be satisfied. Further, in order to prevent occurrence of trouble in printer running (double feeding) due to electrostatic charging of the adhesive sheet, a coating layer mainly composed of an antistatic agent may be provided on at least one surface of the transparent vinyl chloride film.

Next, the release sheet will be described. As the release sheet, a known release sheet including a release agent layer and a substrate for a release sheet (hereinafter, also referred to as a release substrate) can be used. The release agent layer may optionally use a non-silicone type release agent represented by a silicone-based or long-chain alkyl acrylate polymer that causes addition / condensation reaction of vinyl group or hydroxyl group-containing polydimethylsiloxane with methylhydroxysiloxane. be able to.

The coating of the release agent can be performed by known equipment such as a gravure coater and a bar coater. The coating amount of the release agent is suitably from 0.05 to 1.5 g / m ² .
Incidentally, it is less than 0.05 g / m ^2, variations in release performance is large, whereas, of little practical use in terms of economy in 1.5 g / m ² or more.

Examples of the release substrate include a PET film, a foamed PET film, a polycarbonate film,
Examples thereof include polypropylene film, synthetic paper, coated paper, laminated paper, glassine paper, and the like, and the type thereof is not particularly limited. In particular, the center line average roughness (Ra) of the release agent surface when processed into a release sheet is preferably 1 μm or less.

The roughness of the release agent surface of the release sheet affects the surface properties of the pressure-sensitive adhesive layer. Incidentally, when the center line average roughness (Ra) is larger than 1 μm, fine irregularities on the surface of the release sheet are transferred to the pressure-sensitive adhesive layer with time while the pressure-sensitive adhesive layer is in contact with the release sheet. As a result, the surface of the pressure-sensitive adhesive layer becomes uneven, and as a result, the transparency of the pressure-sensitive adhesive sheet is reduced.

On the back side of the release sheet, to prevent static electricity charge and to optimize the friction coefficient, to provide printer runnability, ink sheet fusion prevention performance when the front and back sides are erroneously printed, and further to provide writability. It is preferable to provide a back coating layer.

The back coating layer may be made of inorganic or organic pigments such as kaolin, calcium carbonate, titanium oxide, talc, barium sulfate, urea resin filler, acrylic resin, SBR resin, polyester resin, PVA, starch, CMC, etc. Coating a component appropriately blended with a natural binder, a cationic, anionic, nonionic polymer antistatic agent, a conductive inorganic pigment such as zinc oxide, a lubricant such as silicone oil, metal soap, or an aliphatic wax. Form.

The backside coating layer is coated by a gravure coater,
Bar coater, roll coater, air knife coater,
It can be carried out arbitrarily by a known equipment such as a blade coater, and the coating amount is suitably from 1 to 10 g / m ² . By the way, if it is less than 1 g / m ² , the desired various properties are likely to be insufficient, while if it is more than 10 g / m ² , it is not economically practical. In addition, coating of the backside coating layer can be performed after processing into an adhesive sheet,
Since vinyl chloride, which is a surface substrate, has poor heat resistance, it is preferable to form a backside coating layer first and then process it into an adhesive sheet.

Next, the pressure-sensitive adhesive layer will be described. As the pressure-sensitive adhesive, those having various compositions such as acrylic, synthetic rubber, and natural rubber can be arbitrarily selected and used according to the desired quality, but use of a cross-linkable acrylic pressure-sensitive adhesive is particularly preferable. Incidentally, the rubber-based pressure-sensitive adhesive is not suitable because the material resin itself is slightly colored from the beginning, and the coloring becomes remarkable with time due to the influence of heat or ultraviolet rays, and the transparency is significantly reduced.

Acrylic pressure-sensitive adhesives are roughly classified into a solvent type and an aqueous emulsion type. In general, the emulsion type is inferior in water resistance and moisture resistance. When water enters the pressure-sensitive adhesive layer, the pressure-sensitive adhesive becomes cloudy. Therefore, it is preferable to use a solvent type since the transparency is lowered.

In addition, various tackifiers composed of natural resins such as rosin and terpene and synthetic resins such as petroleum, phenol and xylene can be used in combination with the acrylic pressure-sensitive adhesive in order to improve adhesiveness. Many tackifiers are colored over time under the influence of heat or ultraviolet rays, and cause a decrease in transparency. Therefore, it is preferable not to use the tackifier, and it is desirable to use only a small amount even when used.

In the present invention, it is preferable to use a cross-linkable pressure-sensitive adhesive among acrylic pressure-sensitive adhesives. The cross-linkable pressure-sensitive adhesive is a low-cohesive pressure-sensitive adhesive base composed of a low-molecular-weight polymer before cross-linking, and a functional group such as a carboxyl group, a hydroxyl group, or an epoxy group present in the acrylic polymer in the pressure-sensitive adhesive. The added crosslinking agent reacts to increase the molecular weight and express desired adhesive strength and cohesive strength.

The crosslinking reaction has not yet proceeded sufficiently during coating and drying, and the pressure-sensitive adhesive layer is very soft and rich in fluidity. Even if a defect occurs, an effect is produced in which the adhesive is gradually creeped during the subsequent winding and preservation so that the defect disappears. Therefore, even if a little streak or repelling occurs during the coating, a pressure-sensitive adhesive layer having excellent transparency can be obtained. Therefore, it is preferable to use a cross-linkable acrylic pressure-sensitive adhesive.

As the crosslinking agent, known crosslinking agents can be used. For example, aliphatic isocyanate compounds, aromatic isocyanate compounds, epoxy compounds, metal chelate compounds and the like can be used. Above all, aliphatic isocyanate compounds and metal chelate compounds are particularly preferable because they are less colored by ultraviolet rays. Specifically, aliphatic isocyanate compounds such as hexamethylene diisocyanate (HMDI) and derivatives thereof, aluminum chelate compounds such as aluminum-isopropylate, aluminum-sec butyrate, and aluminum acetylacetonate; tetraisopropyl titanate; −
Metal chelate compounds such as titanium chelate compounds such as ethylhexoxy) titanate can be exemplified, but not limited to these examples. In addition, it is also possible to use 2 or more types together.

In general, the coating viscosity of the pressure-sensitive adhesive when producing the pressure-sensitive adhesive sheet is in the range of about 2000 to 4000 cps, preferably in the range of 2500 to 3500 cps. But,
In this viscosity range, when applying the pressure-sensitive adhesive, contamination of foreign matter such as fine dust, or transfer of the back surface coating layer treatment agent applied to the non-peeling surface side of the release sheet to the release agent layer surface, etc. Adhesive coating defects such as streaks and repelling tend to occur. Once these coating defects occur, the surface base material is transparent, and as a result, it becomes quite noticeable, and the appearance is significantly reduced, making it impossible to put to practical use. Even when the viscosity of the pressure-sensitive adhesive is high, streaks occur due to the entry of foreign matter such as dust, but the streak width becomes considerably narrower than in the case where the viscosity is low, so that the appearance is not significantly affected.

Therefore, in the present invention, the viscosity of the pressure-sensitive adhesive is 50
It is preferable to apply a high-viscosity adhesive of 00 cps or more. In general, there are three types of viscosity measuring methods: capillary viscometer, rotational viscometer, and dropping viscometer. The viscosity of the adhesive used in the present invention is determined by a rotational viscometer, specifically a Brookfield viscometer. (B-type viscometer). The viscosity greatly depends on the temperature and the adhesive concentration,
Within the above range, the temperature and the pressure-sensitive adhesive concentration can be finely adjusted as appropriate, and are not limited.

As a method for applying the pressure-sensitive adhesive, any known method suitable for applying a high-viscosity material such as a comma coater, a die coater, a lip coater, a roll coater, and a blade coater can be used. Adhesive coating is applied to the surface base material, dried and then laminated with a release sheet (so-called direct method), or applied to the release layer surface of the release sheet, dried and then laminated to the surface substrate Any of the methods (so-called transfer method) can be adopted, but the latter transfer method is preferable because the polyvinyl chloride film as the surface substrate generally has poor heat resistance.

The coating amount of the pressure-sensitive adhesive layer can be arbitrarily adjusted according to the desired quality, but is preferably 10 to 30 g.
/ M ² . By the way, when the coating amount exceeds 30 g / m ² , the transparency is lowered and the adhesive is protruded (wheat).
On the other hand, if it is less than 10 g / m ² , the adhesive strength will be extremely low.

The total thickness of the adhesive sheet is 20 to 300 μm
Is preferably within the range. By the way, the thickness is 20μm
If the thickness is thinner, the physical strength, hardness, and repulsion of the pressure-sensitive adhesive sheet against deformation become insufficient, and curling that occurs during printing cannot be sufficiently prevented. On the other hand, when the thickness exceeds 300 μm, problems such as a decrease in the number of sheets to be stored when the pressure-sensitive adhesive sheet is stored in a printer having a predetermined volume or an increase in the volume of the printer are caused.

[0036]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is, of course, not limited thereto. In Examples, “%” and “parts” all indicate “% by weight” and “parts by weight” unless otherwise specified.

Example 1 <Manufacture of Release Sheet> A 100 μm thick foamed PET film (trade name: W900E100, made of Diafoil) was used as a release substrate, and the following coating material for the backside coating layer was applied on one side thereof by dry-dry coating. Coating and drying were performed with a bar coater so that the amount was 1 g / m ² . "Coating for backside coating layer" Component Parts by weight Acrylic resin (trademark: SAR-615A, manufactured by Chuo Rika) 100 parts Epoxy crosslinking agent (trademark: SAR-615B, manufactured by Chuo Rika) 5 parts Cationic antistatic agent (trademark) ST2000H, manufactured by Mitsubishi Yuka) 75 parts Silica (trademark: P78A, manufactured by Mizusawa Chemical) 30 parts Diluted with IPA / toluene

Next, on the surface of the release substrate on which the back coating layer is not formed, the following release agent layer paint is applied in an amount of 0.
Coating was performed with a bar coater so as to have a weight of 15 g / m ² , followed by drying to obtain a release sheet. "Coating for release agent layer" Component Parts by weight Release agent (trade name: LTC750A, manufactured by Toray Dow Corning Silicone) 100 parts Release control agent (trade name: BY24-843, manufactured by Tore Dow Corning Silicone) 10 parts Catalyst (Trademark: SRX212, manufactured by Toray Dow Corning Silicone) 1.5 parts Diluted with toluene / n-hexane.

The center line average roughness (Ra) of the release agent surface of this release sheet was 0.25 μm. The center line average roughness is measured using a universal surface profiler (trade name: MODEL SE-
3C, manufactured by Kosaka Laboratory Co., Ltd.) according to JIS B0601, with a cutoff of 0.25 mm and a measurement length of 4 mm.

<Production of pressure-sensitive adhesive sheet> On the release agent surface of the release sheet, a two-part crosslinkable acrylic pressure-sensitive adhesive paint composed of the following components was applied in a comma-separated manner so that the absolute dry coating amount was 20 g / m ^2. After coating with a coater and drying, a transparent vinyl chloride film (trade name: Alphan AL, manufactured by Myprotech, plasticizer content: 0) as a surface substrate by a nip roll
%). This was aged at 22 ° C. for 7 days to obtain a pressure-sensitive adhesive sheet. "Adhesive paint" component parts by weight Acrylic adhesive (trade name: BPS5673, manufactured by Toyo Ink) 100 parts Aliphatic isocyanate cross-linking agent (trade name: BHS8515, manufactured by Toyo Ink) 3 parts The viscosity was 5500 cps without dilution. Was.

Example 2 As a release substrate, a transparent PET (trade name: 100 μm) was used.
K1585, manufactured by Toyobo Co., Ltd.), and a release sheet was prepared in the same manner as in Example 1. The center line average roughness (Ra) of the release agent surface of this release sheet was 0.2 μm. An adhesive sheet was obtained in the same manner as in Example 1, except that this release sheet was used.

Example 3 Example 1 except that the following adhesive paint was used as the adhesive.
The adhesive sheet was obtained in the same manner as described above. "Adhesive paint" component parts by weight Acrylic adhesive (trade name: BPS5904, manufactured by Toyo Ink) 100 parts Aliphatic isocyanate crosslinking agent (trade name: BHS8515, manufactured by Toyo Ink) 3 parts Diluted with toluene and had a viscosity of 7000 cps. Was.

Example 4 Example 1 except that the following pressure-sensitive adhesive paint was used as the pressure-sensitive adhesive.
The adhesive sheet was obtained in the same manner as described above. "Adhesive paint" component parts by weight Acrylic adhesive (trademark: MD-1, manufactured by Soken Chemical) 100 parts Aluminum chelate cross-linking agent (trademark: M5A, manufactured by Soken Chemical) 2 parts Not diluted, viscosity is 6000 cps there were.

Comparative Example 1 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that a transparent vinyl chloride film (manufactured by Riken Vinyl Industry, plasticizer content: 24%) was used as a surface substrate.

Comparative Example 2 An adhesive sheet was obtained in the same manner as in Example 1 except that a transparent vinyl chloride film (manufactured by Riken Vinyl Industry, plasticizer content: 10%) was used as a surface substrate.

Reference Example 1 As a release substrate, polyethylene was added to 85 μm high quality paper.
A release sheet was prepared in the same manner as in Example 1 except that a laminate having a thickness of 5 μm was used (a release agent was applied to the surface on which the laminate was applied). The center line average roughness (Ra) of the release agent surface of this release sheet was 2.5 μm. An adhesive sheet was obtained in the same manner as in Example 1, except that this release sheet was used.

Reference Example 2 A release sheet was prepared in the same manner as in Example 1 except that 55 μm glassine paper was used as a release substrate. The center line average roughness (Ra) of the release agent surface of this release sheet is 1.5
μm. An adhesive sheet was obtained in the same manner as in Example 1, except that this release sheet was used.

Reference Example 3 One-pack type rubber-based pressure-sensitive adhesive (trade name: SCC,
An adhesive sheet was obtained in the same manner as in Example 1, except that Seiden Chemical Co., Ltd.) was used.

Reference Example 4 Example 1 except that the following pressure-sensitive adhesive paint was used as the pressure-sensitive adhesive.
The adhesive sheet was obtained in the same manner as described above. "Adhesive paint" component parts by weight Acrylic adhesive (trademark: PE115E, manufactured by Nippon Carbide) 100 parts Aromatic isocyanate crosslinking agent (trademark: Coronate L, manufactured by Nippon Polyurethane) 1 part It was 200 cps.

Reference Example 5 Example 1 except that the following pressure-sensitive adhesive paint was used as the pressure-sensitive adhesive.
The adhesive sheet was obtained in the same manner as described above. "Adhesive paint" component parts by weight Acrylic adhesive (trademark: BPS5673, manufactured by Toyo Ink) 100 parts Aliphatic isocyanate cross-linking agent (trademark: BHS8515, manufactured by Toyo Ink) 3 parts Diluted with toluene, viscosity 3000 cps Met.

With respect to the pressure-sensitive adhesive sheet prepared as described above,
The following evaluations were performed, and the evaluation results are shown in Table 1. In each of the obtained pressure-sensitive adhesive sheets, an image could be recorded by a sublimation-type thermal transfer printer. <Evaluation method> (1) Transparency The receiving sheet part of the receiving pressure-sensitive adhesive sheet which was not treated and treated at 70 ° C. for 3 days was visually observed, and the transparency was evaluated according to the following criteria. ：: good transparency △: poor transparency due to fine surface irregularities, causing some practical problems. Δ △: Slightly colored and has some practical problems. X: There is a practical problem because the transparency is considerably poor due to large surface irregularities. XX: Significant coloring, practically problematic.

(2) Coating Defects The appearance of the coated surface was visually observed to confirm the presence or absence of streaks and repelling, and evaluated according to the following criteria. ：: No defect is observed. Alternatively, the defect is extremely small and poses no practical problem. Δ: The defect is small but present on one side, and there is some problem in practical use. ×: There is a problem in practical use because the defective portion is noticeable and the appearance is inferior.

(3) Holding power The holding power of the pressure-sensitive adhesive sheet treated at 70 ° C. for 3 days was measured according to JIS.
Evaluation was performed according to Z0237. The sample affixed area was 25 mm square and 60 days after crimping on SUS304 steel plate
In an environment at a temperature of 1 ° C., a load of 1 kg was applied, and the time until the sample dropped off was measured.

(4) Extrusion of pressure-sensitive adhesive (cutting ability against guillotine) Twenty pressure-sensitive adhesive sheets treated at 70 ° C. for 3 days are stacked and cut using a guillotine cutting machine, and the pressure-sensitive adhesive on the cut surface after cutting is exposed. The state of sticking of the sample was evaluated according to the following criteria. ：: Very little sticking out of the adhesive and no sticking. X: The sticking out of the adhesive is remarkable, and there is sticking.

(5) Printer runnability The adhesive sheet cut in guillotine in (4) is sublimated to a thermal transfer printer (trade name: NV-MP50, manufactured by Matsushita Electric Industrial Co., Ltd.).
Was used to continuously print 50 sheets of solid black, and the running property of the pressure-sensitive adhesive sheet was evaluated according to the following criteria. ：: There is no problem in running property. ×: Paper jams and double feeding occurred, and there was a problem in running performance.

[0056]

[Table 1]

First, each embodiment is compared with each comparative example. Although the transparency is excellent in all pressure-sensitive adhesive sheets, the comparative example using a film containing a plasticizer in an amount of 5% by weight or more based on the resin component has poor holding power, pressure-sensitive adhesive, poor printer runnability, and is not suitable as a pressure-sensitive adhesive sheet. . On the other hand, each example containing no plasticizer has excellent properties as an adhesive sheet. This is because the plasticizer component in the vinyl chloride migrated into the pressure-sensitive adhesive layer and reduced the cohesive force of the pressure-sensitive adhesive.

Next, Examples 1 and 2 and Reference Examples 1 and 2 will be compared. These are examples in which the same material is used for the surface substrate and the adhesive, and the type of the release sheet is different. Example 1 in which the center line average roughness (Ra) of the release agent surface is 1 μm or less.
Sample No. 2 has an excellent evaluation of transparency, but in Reference Examples 1 (2.5 μm) and Reference Example 2 (1.5 μm) exceeding 1 μm, the pressure-sensitive adhesive layer has irregularities, resulting in poor transparency. Becomes It can be seen that it is preferable to use a release sheet having a center line average roughness (Ra) of 1 μm or less on the release agent surface.

Example 1 and Reference Example 3 will be compared. These are examples in which the same material is used for the surface substrate and the release sheet, and the type of the adhesive is different. Example 1 uses a two-component cross-linkable acrylic pressure-sensitive adhesive, and Reference Example 3 uses a one-component rubber pressure-sensitive adhesive. In the case of a rubber-based pressure-sensitive adhesive, the pressure-sensitive adhesive is colored, so that it is understood that the use of an acrylic-based pressure-sensitive adhesive is preferable.

Examples 1, 3, 4 and Reference Example 4 will be compared.
These use the same material for the surface substrate and the release sheet,
This is an example in which the crosslinking agent of the acrylic pressure-sensitive adhesive is different. Examples 1 and 3 use an aliphatic isocyanate compound as a crosslinking agent,
Example 4 is an example using a metal chelate compound as a cross-linking agent, and Reference Example 4 is an example using an aromatic isocyanate compound as a cross-linking agent. Reference Example 4 is inferior in transparency after being treated at 70 ° C. for 3 days, while Examples 1, 3, and 4 are excellent in transparency. It is understood that the use of an aliphatic isocyanate compound or a metal chelate compound as the crosslinking agent is preferred.

Examples 1, 3, and 4 are compared with Reference Examples 4 and 5. In these, the same material is used for the surface substrate and the release sheet, and a crosslinked acrylic pressure-sensitive adhesive is used, but the viscosity at the time of applying the pressure-sensitive adhesive is different. That is, the viscosity of the adhesive paint is 5500 cps in Example 1, 7000 cps in Example 3, 6000 cps in Example 4, 200 cps in Reference Example 4, and 3000 cps in Reference Example 5. It can be seen that when the coating is performed at a viscosity of 5000 cps or more, streaking or repelling that affects the appearance does not occur, which is preferable.

[0062]

The pressure-sensitive adhesive sheet of the present invention is excellent in transparency both in the initial stage and in the passage of time, and has no sticking out of the pressure-sensitive adhesive due to the change with time of the plasticizer and no trouble in running the printer. Is high.

Claims (4)

[Claims] 1. A pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer and a release sheet are sequentially laminated on one surface of a surface base material, wherein the surface base material does not contain a plasticizer, or even if it contains a plasticizer, 5 wt. %, Which is a transparent vinyl chloride film having a dye transferability of less than 0.1%. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the center line average roughness (Ra) of the release agent surface of the release sheet is 1 μm or less. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive and contains a crosslinking agent selected from an aliphatic isocyanate compound and a metal chelate compound. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive has a viscosity of 5000 cps or more.