JP2001192627A - Adhesive sheet for electronic photographic recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet for an electronic photographic recording free from the failures in label releasability, stacking and the like attributable to curling generated by the heat shrinkage of a surface base material, and the troubles of appearance defect of flapping and the like caused by the heat shrinkage of the surface base material. SOLUTION: This adhesive sheet for electronic photographic recording has the following features: an adhesive sheet prepared by serially laminating a surface base material containing a heat-shrinking film having a heat shrinkage factor of >2.0% determined in one minute at 150 deg.C as base material, an adhesive layer and a release sheet; in the adhesive sheet, the heat shrinkage factor A of the larger one between the heat shrinkage factors in the MD and CD directions of the surface base material and the heat shrinkage factor B of the release sheet in the direction same as in the heat shrinkage factor A have the relations of A>B and 1.0<=A-B<=3.5%; and further, in the adhesive sheet, the relation between the Gurlay stiffness a of the surface base material and the Gurlay stiffness b of the release sheet (they are each determined in an environment of 23 deg.C and 50% RH, and in the same direction as the measuring direction of the heat shrinkage factor A) is 0.01<=a/b<=0.06.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive sheet for electrophotographic recording, and more particularly to an adhesive sheet for electrophotographic recording using a heat-shrinkable film as a surface substrate.

[0002]

2. Description of the Related Art A general pressure-sensitive adhesive sheet has a structure in which a surface substrate, a pressure-sensitive adhesive, and a release sheet are sequentially laminated, and a solvent-type pressure-sensitive adhesive such as a rubber-based, acrylic, or vinyl ether-based pressure-sensitive adhesive is used. Emulsion type adhesives, hot melt type adhesives and the like are used.

Examples of the surface substrate include general papers such as high quality paper, kraft paper, art paper, coated paper, cast coated paper, etc., thermal recording materials, thermal transfer image receiving sheets, recording sheets such as ink jet recording sheets, and aluminum foil. Lami paper, aluminum evaporated paper,
Special papers such as resin-impregnated paper and synthetic paper, and films such as PET, polypropylene, and polyvinyl chloride are used.
Among them, films have higher durability than papers and have a texture not found in papers, so that they are appropriately selected and used according to the purpose. As the release sheet substrate, polyethylene laminated paper, glassine paper, clay-coated paper, water-based resin-coated paper and a film such as PET or polypropylene are used as the release base paper, and a silicone compound or a fluorine compound or the like is provided on the side in contact with the adhesive. A release agent is applied and used.

As described above, the pressure-sensitive adhesive sheet has a structure in which a surface substrate and a release sheet are laminated with a pressure-sensitive adhesive layer interposed therebetween. Therefore, when a change in dimension occurs between the surface substrate and the release sheet, the pressure-sensitive adhesive sheet is deformed. For example, if the shrinkage of the surface substrate is greater than the shrinkage of the release sheet, curl occurs due to the dimensional difference (the curl direction in this case is called top curl, and the curl direction under the reverse condition is called back curl). The causes of the dimensional change include expansion and contraction mainly due to a change in environmental humidity for a paper base, and expansion and contraction due to heat for a film base.

[0005] The pressure-sensitive adhesive sheet is used as a label, a sticker, a sticker, an emblem, etc., for a wide range of uses such as commercial use, office use, home use, etc., by performing desired printing according to the purpose. Especially in the field of printing, digitalization has recently been newly digitized. Digital printing, in which digital images taken by a digital camera or the like are output by a printer of various recording methods via a personal computer, has been used in small lots and other types. As a printing method that matches the adhesive label industry in Japan, it is easy to create a favorite label easily at home, and it is in the spotlight for personal consumption. As these recording methods, there are an ink jet method such as a bubble jet method, a thermal method such as a melting heat transfer method and a sublimation heat transfer method, and an electrophotographic method such as a laser beam method and an electron beam method. Among them, the electrophotographic method is excellent in terms of clarity and storability of an obtained image, maintenance, and the like, and is one of the recording methods expected in the future.

The recording method of the electrophotographic system will be briefly described. Toner of several microns in diameter is finally transferred to the surface of a recording sheet, and the toner is melted by a fixing roll having heat and pressure to be fixed on the recording sheet. Things. This fixing method differs depending on the manufacturer of the printer or copier, the processing capacity, and the specifications such as image reproducibility.
Heat of about 00C to 200C is applied to the fixing roll.

For this reason, in the case of an electrophotographic recording system requiring high heat, various problems occur when an adhesive sheet having a complicated layer structure is used as recording paper as described above. In particular, when the surface substrate is a heat-shrinkable film stretched at the time of film forming, the surface substrate contracts due to the heat of the fixing roll, and the pressure-sensitive adhesive sheet curls, causing the following problems. If the curl height after printing on the printer exceeds about 60 mm (evaluate the average of the curl heights at the four corners after placing the adhesive sheet on a flat table after printing on the printer), the stacking (sheet stacking) failure at the discharge section of the printer Becomes About 80m
If it exceeds m, the curled sheet may be erroneously detected as a full stack, and continuous printing may not be performed. In addition, it becomes very difficult to peel off the label if it is cylindrical. Therefore, it is necessary to suppress the curl height to 60 mm or less.

To solve these problems, Japanese Patent Laid-Open No. 11-30 / 1999
In JP-A-0898, the heat shrinkage at 130 ° C. for 30 minutes is 2% for the purpose of improving the difficulty of peeling from the release sheet.
An adhesive sheet using the following substrate has been devised. However, in the technical range, curling can be reduced by a printer having a relatively low-temperature fixing roll, but curling cannot be suppressed by a latest printer having a relatively high-temperature fixing roll by colorization. is not. Further, even if curl can be suppressed, deformation of the base material alone (hereinafter, waving) due to shrinkage of the base material occurs, so that the requirements for an adhesive sheet suitable for an electrophotographic printer or the like are not satisfied.

Japanese Patent Application Laid-Open No. 5-287242 discloses a pressure-sensitive adhesive sheet having a small curl against heat.
A pressure-sensitive adhesive sheet using a release sheet having a heat shrinkage of 1.5% or less at 2 ° C. for 2 minutes and an absolute value of a difference in heat shrinkage of the surface substrate and the release sheet of 0.7% has been proposed. However, in order to satisfy the numerical value, the film is limited to a film made of a material having low shrinkage and a high softening point such as polyester. In addition, even when this technique is applied, a wave occurs due to the contraction of the base material as described above.

[0010]

SUMMARY OF THE INVENTION In the present invention, when printing and copying are performed by an electrophotographic printer or a copying machine having a high-temperature fixing roll, curling caused by thermal shrinkage of a surface substrate is caused. Poor label peelability,
An object of the present invention is to provide an electrophotographic recording pressure-sensitive adhesive sheet free from stacking defects and the like, and free from problems of appearance defects such as waving due to thermal shrinkage of a surface substrate.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted various studies on the surface base material, release sheet, and pressure-sensitive adhesive which constitute the pressure-sensitive adhesive sheet. The present inventors have found that there are various conditions, and have completed the present invention.

[0012] It is clear that the smaller the difference in shrinkage between the surface base material and the release sheet due to heat, the better the curl generated during printing in the electrophotographic recording system. However, the heat shrinkage rate at 150 ° C. for 1 minute, which is the range of the present invention, is 2.0%.
In the case of a pressure-sensitive adhesive sheet having a heat-shrinkable film as a base material, a heat-shrinkable surface substrate is inevitable during electrophotographic printing, thereby controlling curling and waving. That is the primary purpose.

Therefore, in the first invention, in order to reduce curling, the difference in heat shrinkage between the surface substrate and the release sheet is reduced. However, it was found that the difference in shrinkage had a large effect on the undulation of the base material, and curling and undulation were simultaneously solved by controlling the difference in shrinkage to an appropriate range. More specifically, by providing a specific range of shrinkage difference between the surface base material and the release sheet, an appropriate tension is generated when the surface base material shrinks, and thus a state of uniform tension. There is no undulation because it keeps shrinking. Therefore, if the difference in shrinkage is too small, the emphasis is placed on curl reduction, the generated tension will be small, and as a result, undulation will occur. Furthermore, in order to control the curl after printing within a practically usable range within the heat shrinkage difference range necessary for eliminating waving, it is effective to set the rigidity of the surface base material and the release sheet to an appropriate relationship. Thus, the present invention was completed.

In the second invention, the effect of the first invention is more effectively exhibited by setting the conditions at the interface between the pressure-sensitive adhesive on which the surface base material is laminated and the release sheet interface in an appropriate range. The curling of the generated pressure-sensitive adhesive sheet is reduced within a short time.

That is, the heat shrinkage at 150 ° C. for one minute is 2.
A surface substrate having a heat-shrinkable film exceeding 0% as a substrate,
In a pressure-sensitive adhesive sheet obtained by sequentially laminating a pressure-sensitive adhesive layer and a release sheet, the larger the heat shrinkage A in the MD or CD direction of the surface substrate, the more the heat shrinkage of the release sheet in the same direction as the surface substrate heat shrinkage A The ratio B is A> B, and 1.0 ≦ AB ≦
3.5%, and the Gurley stiffness a of the surface substrate
And the Gurley stiffness b of the release sheet (23 ° C.
% RH environment, the relationship of Girley stiffness in the same direction as the heat shrinkage A measurement direction is 0.01 ≦ a / b ≦ 0.06.
An electrophotographic recording pressure-sensitive adhesive sheet according to the first aspect of the present invention.

According to the shear adhesion test described in JIS-Z-0237, the release sheet was used in place of the test plate, and when the adhesive was pulled at a rate of 0.5 mm / min, the adhesive and the release were removed. Slip occurs between the sheets. More preferably, a sheet from which the release sheet substrate of the pressure-sensitive adhesive sheet has been removed is used as a test piece according to a shear adhesion test (3 in Reference column of JIS-Z-0237), When the test piece is pulled at a rate of 0.5 mm / min using a peeling sheet substrate removed as a test plate and the test piece is pulled at a rate of 0.5 mm / min, the shear adhesive force (S) expressed by the following formula is 0.5 to 2. An electrophotographic recording pressure-sensitive adhesive sheet having a pressure of 5 N / cm ^2, which is the second and third inventions described above. S = P / W In the formula, S: shear adhesive strength (N / cm ² ) P: maximum load (N) W: shear area (cm ² ) of test piece (specifically, heat shrinkage of the surface substrate) Pull in the same direction as the rate A measurement direction,
The test piece shearing area was 5.0 cm in the same direction and 1.5 cm in the direction perpendicular thereto. Therefore, W = 7.5 cm ²
It is. The thickness of the pressure-sensitive adhesive layer at this time differs depending on the thickness of the pressure-sensitive adhesive layer to be tested, and need not be specified.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first invention of the present invention is to adjust the heat shrinkage difference and the rigidity ratio of the surface substrate and the release sheet to appropriate ranges as described above, and thereby to generate the electrophotographic recording system at the time of printing. It simultaneously solves the problem of curling and waving. That is, the heat shrinkage rate at 150 ° C. for 1 minute is 2.0%.
In a pressure-sensitive adhesive sheet obtained by sequentially laminating a surface substrate, a pressure-sensitive adhesive layer, and a release sheet, each having a heat-shrinkable film having a thickness of more than The heat shrinkage B of the release sheet in the same direction as the substrate heat shrinkage A is A> B, and 1.0 ≦ AB ≦ 3.5.
(%), And the Gurley stiffness a of the surface substrate and the Gurley stiffness b of the release sheet (23 ° C., 50% RH, respectively)
The relationship of Girley stiffness in the same direction as the measurement direction of the thermal shrinkage A under the environment is 0.01 ≦ a / b ≦ 0.06, preferably 0.01 ≦ a / b ≦ 0.04.

In the case of AB <1.0 (%), the curl is good, but the undulation is large and there is a problem in practical use.
On the other hand, when AB> 3.5 (%), there is no waving but the curl is large and there is a practical problem. In the case of A <B, the pressure-sensitive adhesive layer may protrude at the time of heat shrinkage, thereby contaminating the inside of the printer. When a / b <0.01, there is a problem in the label peelability, and when a / b> 0.06, the curl after printing becomes large.

Next, the heat shrinkage and Gurley stiffness used in the present invention will be described. Regarding the heat shrinkage, the maximum heat shrinkage direction of the surface substrate is defined as the heat shrinkage A, and the Gurley stiffness in the same direction as the direction is defined as the Gurley stiffness a. During the production of the pressure-sensitive adhesive sheet, the surface substrate and the release sheet are bonded in the same direction, that is, in the MD direction (generally, the flow (long) direction in paper and film production is the MD direction, and the perpendicular direction is the C direction).
D direction). Accordingly, the heat shrinkage B and the Gurley stiffness b of the release sheet are measured in the same direction as the surface substrate. For example, if the maximum heat shrinkage direction of the surface base material is the MD direction, both the surface base material and the release sheet have a heat shrinkage rate in the MD direction,
The Gurley stiffness can be measured to obtain the heat shrinkage A, the heat shrinkage B, the Gurley stiffness a, and the Gurley stiffness b.

The surface substrate used in the present invention is not particularly limited as long as it satisfies the above conditions. For example, polyethylene (PE), ethylene vinyl acetate (EVA), PE-
EVA, linear low density PE (LLDPE), high density PE
(HDPE), polypropylene (PP), unstretched PP
(CPP), stretched PP (OPP), polyvinyl alcohol (PVA), ethylene vinyl alcohol (EVO)
H), transparent films such as polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polystyrene (PS), polyester (PET), etc., and white films such as foamed types of the various films and kneaded white pigments; Synthetic paper or the like based on materials such as PE, PP, PET, PVC, and PS can be used. Above all, synthetic paper YUPO (manufactured by Oji Yuka Kasei Co., Ltd.) obtained by a biaxially stretched film forming method using PP and an inorganic filler as main raw materials has various durability and is suitable for an adherend required as an adhesive label. It is one of the preferable surface base materials because of good followability, curved surface adhesion and the like. Applicable YUPO grades include FPG, FGS, GF
G, SGS, KPK and the like.

The thickness of the surface substrate is 10 to 150 μm
Some degree can be used. Above all, the thickness is preferably about 20 to 100 μm from the viewpoint of ease of use as an adhesive label and practicality in an electrophotographic recording printer or the same copying machine.

The Gurley stiffness a of the surface substrate is not particularly limited as long as the relationship with the release sheet stiffness b is within the scope of the present invention as described above, but is preferably 0.05 to 1 mN, more preferably 0.1 to 1 mN. 0.5 mN. By the way, 0.05
If it is less than mN, the label peeling property and the handling property of the pressure-sensitive adhesive label are inferior, and if it exceeds 1 mN, adherence followability at the time of label application is inferior.

The above-mentioned film is heat-treated (for example,
Heat treatment at a temperature of 95 ° C. for 3 days can reduce the heat shrinkage and improve curling and waving, which is one of the preferred embodiments. The effect of heat shrinkage reduction by heat treatment is as follows:
Although the number of processing days is related, generally, the conditions can be set and processed within a range that does not cause any other problem within each condition of low tension, a temperature below the softening point of the film, and several days. .

Laminating an electrophotographic recording image-receiving layer on the surface of the above-mentioned film substrate is also one of the preferred embodiments for improving the quality of the obtained image. Known techniques can be applied to the image receiving layer for electrophotographic recording. For example, in order to optimize the surface electric resistance of the obtained coating layer, known conductive agents such as anionic, cationic, and amphoteric synthetic polymers, and kaolin, calcium carbonate, clay, talc, calcined kaolin, Delamikaolin, titanium dioxide,
Aluminum hydroxide, silica, inorganic pigments such as white carbon, or organic synthetic pigments such as polystyrene resin fine particles, urea-formalin resin fine particles, fine hollow particles, and casein, dextrin, starch, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, Polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, a binder of natural or synthetic resin such as acrylate ester copolymer, A desired electrophotographic recording image-receiving layer can be obtained by coating and drying the above-mentioned surface substrate at a coating amount of about 0.1 to 10 g / m ² . The preferable surface electric resistance is about 10 6 to 11 (Ω / cm ² ).

In addition, an anchor layer may be provided on the back surface of the front substrate for the purpose of imparting close contact with the adhesive. Known techniques can be applied as the anchoring agent, and a one- or two-part commercially available material such as polyisocyanate, polyethyleneimine, polyamide, polyacrylamine, polyester, polyurethane, and polybutadiene is coated on the back surface of the front substrate in a coating amount of 0.1%. A desired anchor layer can be obtained by coating and drying in the range of about 01 to 5 g / m ² .

The release sheet used in the present invention is not particularly limited as long as it satisfies the above-mentioned conditions. As the release sheet base material, general polyethylene laminated paper, glassine paper, inorganic pigments such as calcium carbonate, clay, talc, calcined kaolin, delamikaolin, titanium dioxide, aluminum hydroxide, silica, white carbon, or polystyrene resin Organic synthetic pigments such as fine particles, urea-formalin resin fine particles, fine hollow particles, and casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer Pigments coated with a binder of a natural or synthetic resin such as a copolymer, an ethylene-vinyl chloride copolymer, an ethylene-vinyl acetate copolymer, an acrylate ester copolymer as a main component. Paper, a clear resin-coated paper containing the above-mentioned barrier component as a main component, and a polyethylene resin-laminated paper, a pigment-coated paper, and a clear resin-coated paper on the back surface of which is laminated with a moisture-proof resin (for example, PE laminate) or coated (for example, , Polyvinylidene chloride resin,
Acrylic resin, SBR resin, acrylic-styrene resin)
There is also a type that did. Further, various film substrates as described above can be applied to the surface substrate. Above all, a release paper substrate having a moisture-proof resin coating on the back surface is preferable in terms of printing conditions at a high temperature, such as an electrophotographic recording printer, and the curling and waving of the pressure-sensitive adhesive sheet. The thickness of the release sheet substrate is 50 to 2
It is about 50 μm, preferably about 70 to 180 μm. When the thickness is less than 50 μm, the curl of the pressure-sensitive adhesive sheet is inferior.

The waving of the surface substrate at the time of printing on the printer can be basically solved when the difference in heat shrinkage between the surface substrate and the release sheet is within the above range. However, although the reason is not clear, the heat shrinkage B of the release sheet is preferably 0.5% or less from the viewpoint of preventing waving. If it exceeds 0.5%, the release sheet shrinks at the same time as the surface substrate at the time of printing on the printer, and as described above, the balance of the tension generated when the surface substrate shrinks becomes partially poor, and the heat shrinkage difference is reduced. Rippling may occur even if is secured.

The Gurley stiffness b of the release sheet is not particularly limited as long as the relationship with the surface substrate stiffness a is within the scope of the present invention as described above, but is preferably 3.5 to 10 mN, more preferably 5 to 10 mN. 8 mN. 3.5m by the way
If it is less than N, even if the other conditions are within an appropriate range, the occurrence of deviation is small and the curl reduction effect is small. On the other hand, if it exceeds 10 mN, the paper-passing aptitude of a printer or the like is inferior. The Gurley stiffness was determined by Japan TAPPI paper pulp test method No.
Measure according to 40.

Although a release sheet is formed by laminating a release agent layer on a release sheet substrate, known materials can be used as the release agent. For example, a solvent-based, emulsion-based or solvent-free silicone resin, fluorine resin, long-chain alkyl resin, acryl-silicone resin, long-chain alkyl-silicone resin, alkyd resin, alkyd-silicone resin, etc. in a dry mass of 0.05% After coating of about 3 g / m ^{2, the} release agent layer can be obtained by curing with heat or ionizing radiation such as UV or EB.

Known pressure-sensitive adhesives are used for the present invention.
it can. For example, alkyl (meth) acrylate
Copolymer, acrylic-styrene copolymer, acrylic-d
Acrylics such as Tylene copolymer, styrene-butadiene
Copolymer, styrene-isoprene-styrene copolymer,
Synthetic and synthetic rubbers such as isoprene and silicones
And natural resins, emulsion type, solvent type,
A solventless type is appropriately selected. Among them, isocyanate
Compound, epoxy compound, metal chelate compound, etc.
Acrylic two-part curable pressure-sensitive adhesive is the adhesive property of the pressure-sensitive adhesive sheet
And glue from the sheet edge is less protruding (wise)
preferable. Coating amount is 3 ~ 30g / m^Two, Preferably 5
20g / m^TwoCan be appropriately selected within the range. 3g / m ^Two
If less than 30 g / m, the adhesive properties are poor.^TwoCross over
Is inferior.

Although the various coatings and treatments on the surface substrate and the various coatings and treatments on the release sheet substrate have been described above, the numerical values of the heat shrinkage, the substrate rigidity and the like specified in the present invention have been described. Is
It goes without saying that the physical properties of the base material after the coating and the treatment are specified for the coating and the substrate subjected to the treatment.

In the second invention, the effects of the first invention are more effectively exhibited by setting the conditions at the interface between the pressure-sensitive adhesive on which the surface base material is laminated and the release sheet interface within an appropriate range, and furthermore, The curl of the generated pressure-sensitive adhesive sheet is reduced within a short period of time, and is achieved by causing a shift at the interface between the pressure-sensitive adhesive layer and the release sheet. That is, the factors governing the interface shift are mainly the slipperiness of the release agent layer and the pressure-sensitive adhesive interface, and also the stiffness of the release sheet, the stiffness of the surface substrate, etc., and make them an appropriate range. This is very important.

The slipperiness between the release agent layer and the pressure-sensitive adhesive interface is determined according to JIS.
According to the shear adhesive strength test described in -Z-0237 (reference column 3 of JIS-Z-0237), an adhesive sheet from which the release sheet of the adhesive sheet was removed was used as a test piece,
In addition, slipping occurs between the adhesive and the release sheet when the release sheet removed as a test plate is pulled at a speed of 0.5 mm per minute. Preferably, in the same test, the shear adhesive force (S) represented by the following formula is 0.5 to
^2.5 N / cm ² . S = P / W In the formula, S: shear adhesive strength (N / cm ² ) P: maximum load (N) W: shear area (cm ² ) of test piece (specifically, heat shrinkage of the surface substrate) Pull in the same direction as the rate A measurement direction,
The test piece shearing area was 5.0 cm in the same direction and 1.5 cm in the direction perpendicular thereto. Therefore, W = 7.5 cm ²
It is. )

More specifically, even if the heat shrinkage A, the heat shrinkage B, the Gurley stiffness a, and the Gurley stiffness b are the same, the one with the smaller shear adhesive force S has a smaller displacement of the interface immediately after printing on a printer. It occurs gradually and the curl becomes smaller. Incidentally, when S is less than 0.5 N / cm ^2, misalignment occurs simultaneously with printing on a printer or the like, and there is a possibility that the inside of the printer may be damaged. S is ^2.5 N / cm ²
Is exceeded, the occurrence of displacement is small and the curl reduction effect is small even if the other conditions, that is, the stiffness of the release sheet, the stiffness of the surface base material, etc. are within appropriate ranges.

As a method of controlling the shear adhesive force, a method of adjusting the elastic modulus by adjusting the molecular weight of the release agent, the cross-link density, the length between cross-links and the like, a method of adding an auxiliary agent such as silicone oil, and a method of controlling the pressure-sensitive adhesive Adjustment of the modulus of elasticity based on the molecular weight, crosslink density, length between crosslinks, Tg of the copolymer, etc., and a method of adding an auxiliary agent such as a tackifier, a surfactant, a wax, or a filler are exemplified.

The method for producing the electrophotographic recording pressure-sensitive adhesive sheet of the present invention is not particularly limited, and it can be produced by known means. Generally, an adhesive is applied to the release agent coated surface of the release sheet and dried,
Although it is possible by a transfer coating method of sticking to the surface substrate, a direct coating method of directly applying an adhesive to the surface substrate may be used.

As a coating device, a known coating device of a direct type and an offset type with a comma coater, a roll coater, a gravure coater, a lip coater, a die coater, a curtain coater, a bar or a rod coater, etc. can be applied.

However, it is important to adjust each tension of the surface base material and the release sheet at the time of bonding. That is, regardless of the same kind of material or different kind of material, it is preferable that both base materials are bonded together with the same elongation, and both base materials are bonded together with a small elongation. That is, when laminating an easily stretchable film base and a hardly stretchable paper base even with the same tension, apply a low tension to the film base and a high tension to the paper base to increase the elongation of both bases. It is about the same. Incidentally, if there is a difference in elongation at the time of bonding, the resulting pressure-sensitive adhesive sheet will be curled.

[0039]

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 thereto. In each example, "part" and "%"
Means "part by mass of solid content" and "% by mass of solid content", respectively, unless otherwise specified.

The “heat shrinkage” and “Gurley stiffness” described below were determined by the following methods. "Thermal shrinkage ratio" The hot air dryer was set at 150 ° C., and the surface substrate and the release sheet used in the production of each pressure-sensitive adhesive sheet were left for 1 minute. MD direction on the surface substrate and release sheet in advance,
And draw a straight line with a length of 100 mm in the CD direction.
After leaving at 0 ° C. for 1 minute, each dimension was measured, and the heat shrinkage was calculated by the following formula. Heat shrinkage = {(100- (dimension after standing at 150 ° C. for 1 minute))} (100)｝ × 100 [%] In the MD direction and CD direction of the surface base material, the heat shrinkage ratio is larger. The heat shrinkage was defined as the heat shrinkage of the surface substrate.
The heat shrinkage in the same direction was defined as the heat shrinkage of the release sheet.

"Gurley stiffness" was determined using a 1-inch × 2.5-inch test piece with a Gurley stiffness tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in an environment of 23 ° C. and 50% RH.
The Gurley stiffness in the direction in which the heat shrinkage of the surface substrate was large in the heat shrinkage test was the Gurley stiffness of the surface substrate and the Gurley stiffness of the release sheet, respectively.

Example 1 Production of Surface Substrate A biaxially stretched PP synthetic paper having a thickness of 65 μm and a density of 0.77 g / cm ³ (trade name: SGS60, manufactured by Oji Oil Chemicals Co., Ltd.) was used as the surface substrate. ) Was heat-treated at 95 ° C. for 3 days to obtain a heat shrinkage ratio of 2.5% in the MD direction and a Gurley stiffness of 0.22 mN (all measured values in the sheet MD direction). "Manufacture of release sheet" thickness 160 as release sheet substrate
μm single-sided polyethylene laminated backside resin coated release base paper, 4.5 parts of light release type addition reaction type silicone (trade name: SD7220, manufactured by Toray Co.) on the polyethylene laminate side, platinum catalyst (trade name: SRX212, Toray) (A product of KF96, Shin-Etsu Chemical Co., Ltd.) 0.5 part, toluene 95 parts, and silicone oil (trade name: KF96, Shin-Etsu Chemical Co., Ltd.).
The coating was dried so as to be 0 g / m ² . The obtained release sheet had a heat shrinkage of 0.0% and a Gurley stiffness of 5.49 mN.
(All measured values in the sheet MD direction). "Production of pressure-sensitive adhesive sheet" 100 parts of an acrylic solvent-type pressure-sensitive adhesive (trade name: OP-1, manufactured by Toyo Ink Mfg. Co., Ltd.) having a solid content of 46% on the silicone-coated side of the obtained release sheet;
A crosslinking agent having a solid content of 100% (trade name: BXX562)
7, Toyo Ink Mfg. Co., Ltd.) 2 parts of the pressure-sensitive adhesive preparation liquid was sprayed with a comma coater at a line speed of 50 m / min.
/ M ² and dried. Then, the surface substrate was bonded to obtain an electrophotographic recording pressure-sensitive adhesive sheet of the present invention.

Example 2 SGS60 heat treated at 60 ° C. for 3 days as a surface substrate
Was used in the same manner as in Example 1 to obtain an electrophotographic recording pressure-sensitive adhesive sheet of the invention. At this time, the surface base material has a large heat shrinkage of 3.3% in the MD direction and a Gurley stiffness of 0.22 m.
N (all measured values in the sheet MD direction).

Comparative Example 1 As a release sheet substrate, a thickness of 85 μm and a density of 0.98 g
/ Cm ³ biaxially stretched PP synthetic paper (trade name: KPK8
0, manufactured by Oji Yuka Synthetic Paper Co., Ltd.) to obtain an adhesive sheet in the same manner as in Example 1. At this time, the release sheet had a heat shrinkage of 1.6% and a Gurley stiffness of 0.66 mN (all measured values in the sheet MD direction).

Comparative Example 2 An adhesive sheet was obtained in the same manner as in Example 1 except that SGS60 without heat treatment was used as a surface substrate. At this time, the heat shrinkage of the surface base material in the MD direction is large, 3.6%, and the Gurley stiffness is 0.22 mN (all measured values in the sheet MD direction).
was.

Comparative Example 3 A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that a single-sided polyethylene laminated release base paper having a thickness of 115 μm was used as a release sheet substrate. At this time, the release sheet had a heat shrinkage of 0.0% and a Gurley stiffness of 2.94 mN (all measured values in the sheet MD direction).

Example 3 An electrophotographic recording pressure-sensitive adhesive sheet of the present invention was obtained in the same manner as in Example 1 except that the addition amount of the silicone oil was changed to 0.1 part.

Example 4 Example 1 was repeated except that SD7220 of Example 1 was changed to a heavy-release type addition-reaction silicone (trade name: SD7320, manufactured by Dow Corning Toray), and no silicone oil was further added. In the same manner as in the above, an adhesive sheet for electrophotographic recording of the present invention was obtained. At this time, the release sheet had a heat shrinkage of 0.0% and a Gurley stiffness of 5.49 mN (all measured values in the sheet MD direction).

The "heat shrinkage difference", "rigidity ratio" and "deviation test" of the thus obtained pressure-sensitive adhesive sheet were determined by the following methods and are shown in Table 1. “Thermal shrinkage difference” = (Thermal shrinkage of the surface substrate) − (Thermal shrinkage of the release sheet)

"Stiffness ratio" = (Gurley stiffness of surface substrate)
÷ (Gurley stiffness of release sheet)

"Shear test"
The following measurement was carried out according to the shear adhesion test method described in 3 of Reference (supplement regarding the definition of the main body) of SZ-0237 (Test method for adhesive tape / adhesive sheet). A pressure-sensitive adhesive sheet obtained by removing a release sheet from a pressure-sensitive adhesive sheet was used as a test piece, and the removed release sheet was used in place of a test plate. This was used as a tensile tester (RTC-121).
0, manufactured by Orientec) and whether or not slippage occurs between the adhesive and the release sheet substrate when pulled at a speed of 0.5 mm per minute, and the shear adhesive force (S) at that time,
It was determined from the following formula. S = P / W In the formula, S: shear adhesive strength (N / cm ² ) P: maximum load (N) W: shear area (cm ² ) of test piece (specifically, heat shrinkage of the surface substrate) Pull in the same direction as the rate A measurement direction,
The test piece shear area was 5.0 cm in the same direction and 1.5 cm in the vertical direction. Therefore, W = 7.5 cm ²
It is. The thickness of the pressure-sensitive adhesive layer varies depending on the thickness of the pressure-sensitive adhesive layer to be tested and is not specified. In addition, since slippage occurred in all of the tested pressure-sensitive adhesive sheets, only the determined shearing pressure is shown in Table 1.

The thus obtained pressure-sensitive adhesive sheet was cut into A4 size paper, and an electrophotographic recording type printer (trade name: Docu Print C41) was used in an environment of 23 ° C. and 50% RH.
1, Fuji Xerox Co., Ltd.), print in thick paper / high image quality mode, and evaluate "curl" and "curling over time" and "wavy", "stacking", and "turn-over" according to the following method and criteria. And a “comprehensive evaluation”, and the results are shown in Table 1.

A just after "curl" printout
The 4-size adhesive sheet was placed on a flat sample table with the curled side facing up, and how much the four corners of the sheet floated from the sample table was measured, and the average value was obtained. A: Less than 10 mm. ：: 10 to 40 mm. Δ: 40 to 60 mm. (Practical limit.) X: Exceeds 60 mm.

"Curl with Time" After one hour from the printout, the curl was evaluated according to the same criteria as described above.

The degree of deformation of the surface substrate of the pressure-sensitive adhesive sheet printed out "wavy" was evaluated according to the following criteria. ：: No deformation at all in appearance and no effect on print quality. X: Wavy deformation is seen in appearance.

"Stacking" A
Ten continuous 4-size adhesive sheets were printed, the stacking status on the discharge tray was observed, and the evaluation was made according to the following criteria. ：: All 10 sheets were stacked without any problem. C: Continuous printout was possible on all 10 sheets, but could not be stacked neatly. (Practical limit.) ×: The curl on the discharge tray was large, and the trouble of automatic stop or paper jam occurred.

"Flipping property" The surface substrate of the printed adhesive sheet was flipped and the degree of ease of peeling was evaluated according to the following criteria. ：: Peeled off without any problem. X: The curl was large and it was difficult to peel off.

"Comprehensive evaluation" was determined according to the following criteria. ：: No problem in practical use. X: Practically problematic.

[0059]

[Table 1]

[0060]

As is clear from Table 1, the electrophotographic recording pressure-sensitive adhesive sheet of the present invention has a small curl at the time of printing, so that there is no trouble in the printer, and there is no wavy after the printing, so that the quality is reduced in appearance. It is an excellent electrophotographic recording pressure-sensitive adhesive sheet without any.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive sheet comprising a heat-shrinkable film having a heat shrinkage rate of more than 2.0% at 150 ° C. for 1 minute, a pressure-sensitive adhesive layer, and a release sheet, which are successively laminated. The heat shrinkage A of the surface substrate in the MD or CD direction, which is larger, and the heat shrinkage B of the release sheet in the same direction as the heat shrinkage A of the surface substrate is A> B, and 1.0 ≦ A− B ≦ 3.5
(%), And the Gurley stiffness a of the surface substrate and the Gurley stiffness b of the release sheet (23 ° C., 50% RH, respectively)
An electrophotographic recording pressure-sensitive adhesive sheet characterized in that the relationship of Gurley stiffness in the same direction as the measurement direction of the thermal shrinkage A under the environment is 0.01 ≦ a / b ≦ 0.06. 2. According to a shear adhesion test described in JIS-Z-0237, the peeling sheet is used in place of a test plate, and when the adhesive is pulled at a rate of 0.5 mm per minute, the adhesive and the peeling are performed. 2. The electrophotographic recording pressure-sensitive adhesive sheet according to claim 1, wherein slippage occurs between the sheets. 3. A shear adhesion test (JIS-Z-0237)
According to 3) of the reference column, a sheet from which the release sheet substrate of the pressure-sensitive adhesive sheet was removed was used as a test piece, and the release sheet substrate removed as a test plate was used. Shear adhesive strength (S) expressed by the following formula when pulled at a speed of 0.5 mm is 0.5 to 2.5 N / cm
^{3. The} pressure-sensitive adhesive sheet for electrophotographic recording according to claim 2, wherein the pressure-sensitive adhesive sheet is 2. S = P / W In the formula, S: shear adhesive force (N / cm ² ) P: maximum load (N) W: shear area (cm ² ) of test piece (the heat shrinkage A of the surface substrate Pull in the same direction, and the shear area of the test piece is the length of the pressure-sensitive adhesive layer in the same direction × the width of the pressure-sensitive adhesive layer in the direction perpendicular thereto.)