JP3041654B2 - Removable adhesive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removable adhesive sheet, and more particularly to a removable adhesive sheet having excellent suitability as an adhesive sheet for a floppy disk.

[0002]

2. Description of the Related Art Adhesive sheets have been used in a wide variety of applications such as labels, seals, stickers, patches and the like for commercial, office and home use. A general configuration of the pressure-sensitive adhesive sheet is one in which a pressure-sensitive adhesive layer is provided between a surface substrate and a release sheet, and paper, a film, a metal foil, or the like is usually used as the surface substrate. On the other hand, as the release sheet, a high-density base paper such as glassine paper, clay-coated paper, polyethylene laminate base paper or the like coated with a release agent such as a silicone compound or a fluorine compound is used.

[0003] As the pressure-sensitive adhesive, various types of pressure-sensitive adhesives such as rubber-based, acrylic-based, vinyl ether-based emulsions, solvents and non-solvents are used. Such an adhesive sheet is
Permanent adhesive type that can be used permanently while being adhered to the adherend after being attached to the product, etc. There are sex types.

In recent years, with the spread of personal computers, word processors, and the like, floppy disks have been widely used. 2. Description of the Related Art Removable pressure-sensitive adhesive sheets have been frequently used for floppy disk applications in which recording can be repeatedly performed. In the case of a pressure-sensitive adhesive sheet for such a purpose, unnecessary lifting of labels easily occurs in a device such as a personal computer and a word processor. Therefore, it is required that the label of the OA device be free of unnecessary lifting during the sticking period. Furthermore, when the recorded contents in the floppy disk are changed, the label before the change is peeled off and discarded, but at that time, there is no tear of the surface base material and no residue of the adhesive on the surface of the floppy disk as the adherend, and It is important that it can be easily peeled off.

[0005] However, most of the removable adhesive sheets used for floppy disk applications have excellent removability, but the adhesive sheet label is folded over the front and back surfaces of a thin floppy disk. For applications where the label is used by sticking it to the label, the label may be lifted or peeled off from the folded part, which in turn causes a problem of mechanical failure, and it is not always satisfactory. It is a fact.

[0006]

DISCLOSURE OF THE INVENTION The present invention has excellent removability especially for a floppy disk and, once the adhesive label has been stuck on the disk, does not cause unnecessary lifting of the label. The present invention provides a pressure-sensitive adhesive sheet.

[0007]

The present invention provides a release sheet,
In a removable adhesive sheet obtained by laminating an adhesive layer and a surface substrate, Clark A conforming to JIS P8143 of the surface substrate is used.
And the stiffness of law is 200 (cm ^3/100) or less, the pressure-sensitive adhesive layer is formed from two-pack crosslinking type pressure-sensitive adhesive emulsion systems or solvent-based, and conforming to JIS Z0237 of pressure-sensitive adhesive layer, relative to polystyrene plates 180-adhesive strength pulling speed 5
A removable pressure-sensitive adhesive sheet having a range of 200 to 1000 g / 25 mm under a condition of 0 mm / min. Also,
The present invention is to laminate the release sheet, the pressure-sensitive adhesive layer, the surface substrate
The removable pressure-sensitive adhesive sheet,
When attaching to an adherend, the adhesive sheet is folded back and attached.
Or affixed to an adherend that is a polystyrene molded product.
Clark A conforming to JIS P8143 for the surface substrate
Stiffness of law is at 200 (cm ^3/100) or less, the adhesive
Whether the agent layer is an emulsion-based or solvent-based two-component crosslinkable pressure-sensitive adhesive
Formed according to JIS Z0237 of the pressure-sensitive adhesive layer,
180 - adhesion strength to polystyrene board is 50mm
In the range of 200 to 1000 g / 25 mm under the condition of
Is a removable adhesive sheet.

[0008]

The removable pressure-sensitive adhesive sheet of the present invention is, as described above, a JIS P8143
The stiffness according to the Clark A method conforming to the standard is 200 (cm ³ /
100) or less, preferably selective use of facestock or less 150 (cm ^3/100). Incidentally, if the stiffness of the surface substrate using pasted 200 adhesive labels more than (cm ^3/100) to a floppy disk, liable unwanted blistering and lifting turning over from the folded portion of the label, in order that , Which may cause failure of machines such as personal computers and word processors.

As long as the above range of stiffness is satisfied, high-quality paper, art paper, coated paper, cast-coated paper and other papers, synthetic paper, resin films and the like can be appropriately used as the surface substrate. is there. In the present invention, a case where papers, which are most frequently used practically and economically inexpensive, are used as the surface substrate will be described in detail below.

As a method for obtaining a surface base material (paper base) having a stiffness in the specific range as described above,
For example, adjustment of pulp beating degree, adjustment of internal paper strength agent and filler (ash content) at the time of mixing paper stock, change of rice tsubo, adjustment of starch coating amount by size press at the time of paper making, etc., or calendering conditions in pressure treatment The desired stiffness can be obtained by, for example, changing. When adjusting or changing the filler (ash content), rice tsubo, or the like, a decrease in paper strength may accompany the paper strength. Therefore, it is necessary to appropriately take measures to increase the paper strength by using an internal paper strength agent or the like. Therefore, one or two of the above-mentioned countermeasures can be used.
By appropriately combining one or more conditions, it is possible to take measures suitable for the purpose of use of the surface substrate.

On the other hand, it is strongly desired that the re-peelable pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a pressure-sensitive adhesive with little adhesive residue on the adherend when the pressure-sensitive adhesive label is peeled from the adherend. For this purpose, in the present invention, a polyisocyanate compound or a polyepoxide compound is blended as a crosslinking agent into the carboxyl group and / or hydroxyl group-containing acrylic copolymer, and the carboxyl group and / or the hydroxyl group is crosslinked with the epoxy group. A two-part crosslinking type pressure-sensitive adhesive is used.

Incidentally, the above-mentioned carboxyl group- and / or hydroxyl group-containing acrylic copolymer includes an ethylenically unsaturated carboxylic acid-containing monomer and C _{4 of} (meth) acrylic acid.
To ₁₈ alkyl ester monomers, and acrylate copolymers containing other monomers copolymerizable with these monomers as constituent monomers. Examples of the crosslinking agent include polyglycol diglycidyl ether compounds such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether.

Next, regarding the requirement for suppressing the lifting phenomenon of the pressure-sensitive adhesive sheet (label), particularly regarding the relationship between the lifting phenomenon and the adhesive force of the pressure-sensitive adhesive, the present invention mainly relates to a floppy disk and an adherend. Is described.
The present inventors have intensively studied the relationship between the lifting phenomenon of an adhesive label and the adhesive strength of an adhesive. As a result, it was found that the phenomenon that the pressure-sensitive adhesive label was lifted up from the floppy disk was greatly related to the adhesive force of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet. Here, the adhesive force is a value measured by a method based on the measuring method of 180 ° adhesive force specified in JIS Z0237.

That is, in the present invention, in order to prevent the pressure-sensitive adhesive label from being lifted up from the folded portion, the pressure-sensitive adhesive layer to be used conforms to JIS Z0237 for a polystyrene plate under the condition of a pulling speed of 50 mm / min. ° Adhesive strength is 2
100 to 1000 g / 25 mm, preferably 300 to 800 g / 25 mm
Wherein the pressure-sensitive adhesive layer in the range of (1) is used. By the way, in the case of less than 200 g / 25 mm, even if the stiffness of the surface substrate by the Clark A method satisfies the specified value, when the adhesive label is used by sticking it to a floppy disk, the label may not be folded. Swelling and lifting occur, and the effect desired by the present invention cannot be obtained. On the other hand, when it exceeds 1000 g / 25 mm, the label is not lifted up when used by sticking it to a floppy disk, but the surface substrate is easily broken at the time of re-peeling.

Examples of the pressure-sensitive adhesive having an adhesive force in such a range that the pressure-sensitive adhesive layer has such an adhesive force include X.
−388 −429 E, X−390−456 E, X−387 −486
E, AE224 and AE260 manufactured by Nippon Synthetic Rubber Co., Ltd., and BPS-5130 manufactured by Toyo Ink Mfg. Co., Ltd.

By the way, it is specified in the official JIS Z0237.
As a measuring method of 180 ° adhesive strength, pulling speed is 300m
At m / min, a stainless steel plate is used as the adherend. However, the main adherend targeted by the pressure-sensitive adhesive sheet of the present invention is a floppy disk, and most of the floppy disk is a polystyrene molded product.
It has been found that the adhesive strength is greatly affected by the type of adherend.

In the present invention, various experiments were repeated in setting the conditions of the adhesive force. As a result, although the reason is not clear, the phenomenon that the label is lifted up is less than the conventional JIS Z0237.
It was found that the adhesive force obtained at a lower pulling speed, that is, an adhesive force measured at 50 mm / min, was extremely highly correlated with the adhesive force at 300 mm / min specified in the above.

For the reasons described above, a 180 ° adhesive force conforming to JIS Z0237 to a polystyrene plate is employed under a condition of a pulling speed of 50 mm / min. By this method, sufficiently reproducible results could be obtained.

The method for forming the pressure-sensitive adhesive sheet is not particularly limited, and a pressure-sensitive adhesive is applied on the release layer surface of the release sheet according to a conventional method, and the pressure-sensitive adhesive layer is formed by drying. It can be finished by bonding a surface substrate on the agent layer. The release sheet may be a high-density base paper such as glassine paper, clay-coated paper, or a poly-laminated paper obtained by laminating polyethylene or the like on kraft paper or woodfree paper, or the like.
Those having a release agent layer formed by coating about m ² and heat curing or ionizing radiation curing are used.

The pressure-sensitive adhesive is coated on a release sheet usually by adjusting the viscosity to about 3,000 to 8,000 centipoise by controlling the molecular weight of the acrylate, diluting with water or a solvent, or increasing the viscosity. However, as a coating device in this case, for example, a roll coater, a knife coater, a bar coater, a slot die coater, or the like is used, and the coating amount is adjusted in a range of about 5 to 50 g / m ² by dry weight.

In the removable pressure-sensitive adhesive sheet of the present invention, it is preferable to provide an undercoating layer containing a pigment between the surface substrate and the pressure-sensitive adhesive layer, since adhesive residue on the adherend is further suppressed. This is one of the embodiments. As the pigment to be contained in the undercoat layer, an inorganic or organic pigment generally used in the coated paper field can be used. Examples of such pigments include oxides, hydroxides, sulfides, carbonates, sulfates or silicates of various metals such as magnesium, calcium, zinc, barium, titanium, aluminum, antimony, and lead, and polystyrene, Solid polymer fine powders such as polyethylene and polyvinyl chloride are mentioned.

Among them, kaolin, talc, silica, gypsum, barite powder, alumina white, gloss white,
When an inorganic pigment such as satin white, titanium oxide, calcium carbonate, acid clay, and activated clay is used, an ionic interaction is added with the pressure-sensitive adhesive layer, and the anchoring effect is more effectively exerted. is there.

The amount of the pigment contained in the undercoat layer is desirably 90% by weight or less, preferably 80% by weight or less of the total solids constituting the undercoat layer. By the way, if it exceeds 90% by weight, the bonding strength between the undercoat layer and the surface substrate becomes insufficient, and the pigment may fall off.

In the undercoat layer, a binder is used as a material for fixing the pigments or the undercoat layer and the surface substrate. Examples of such a binder include casein, dextrin, starch, carboxymethylcellulose, methylcellulose, and ethylcellulose. , Hydroxyethyl cellulose, polyvinyl alcohol, styrene
Natural or synthetic such as butadiene copolymer, methyl methacrylate / butadiene copolymer, ethylene / vinyl chloride copolymer, ethylene / vinylidene chloride copolymer, acrylate ester copolymer, ethylene / vinyl acetate copolymer The resin binder is used in the form of an aqueous solution or an aqueous dispersion. In addition, various auxiliary agents such as an antifoaming agent and a dispersing agent can be added to the undercoat layer, if necessary, as long as the properties are not impaired, in addition to the pigment.

With respect to the method of applying the coating liquid for the undercoat layer to the surface substrate, the coating liquid can be applied by a usual coating apparatus, for example, an air knife coater, a blade coater, a roll coater, a bar coater or the like. 2 g / m ² or more by dry weight,
Preferably it is adjusted in the range of 5 to 10 g / m ² .

Thus, the removable pressure-sensitive adhesive sheet obtained by combining the surface base material and the pressure-sensitive adhesive specified in the present invention, even when the sheet is folded back on a thin plate such as a floppy disk, does not need to be lifted. It has excellent re-peeling properties with very little glue residue without turning over.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the scope of the present invention.

Example 1 A silicone release agent (trade name: KS-770, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to glassine paper of 85 g / m ² in terms of dry weight of 0.9 g on a dry basis.
g / m ² was applied with a bar coater and dried to obtain a release sheet. A two-part crosslinkable acrylic pressure-sensitive adhesive (trade name: X-388-429E / manufactured by Seiden Chemical Co., Ltd .; adhesive strength 300 g / 25 mm) was applied on the release agent layer surface of the release sheet at a dry weight of 25 g / m ² . It was coated with a roll coater and dried to obtain an adhesive layer. Next, a rice tsubo is placed on this adhesive layer
Quality paper of 64 g / m ² [Clark stiffness: 50 (cm ^3/10
0)] and laminated with a press roll to obtain a removable pressure-sensitive adhesive sheet.

[0029] In Example 1, rice coated paper having a basis 82 g / m ² as a surface base material: except for using [Clark stiffness 45 (cm ^3/100)] was prepared in analogy to Example 1 again A peelable pressure-sensitive adhesive sheet was obtained.

[0030] In Example 3 Example 1, basis weight 89 g / m ² cast coated paper as a surface substrate [Clark stiffness: 73 (cm ^3/100
)] Was used in the same manner as in Example 1 to obtain a removable pressure-sensitive adhesive sheet.

[0031] Example 4 In Example 1, rice quality paper having a basis 64 g / m ² as a surface substrate [Clark stiffness: 50 (cm ^3/100)] on the back of, 60 parts of kaolin, 25 parts of precipitated calcium carbonate A pigment dispersion composed of 15 parts of acrylic acid / butadiene / methyl methacrylate copolymer latex (parts are parts by weight of solid content) is coated with an air knife coater so as to have a dry weight of 5 g / m ² and dried. A removable adhesive sheet was obtained in the same manner as in Example 1 except that high-quality paper provided with an undercoat layer was used.

Example 5 In Example 1, a two-part crosslinkable acrylic pressure-sensitive adhesive was used.
Adhesive (trade name: AE 224 / Nippon Synthetic Rubber Co., Ltd.)
20g / m by dry weight ^TwoWhen
Coat with a roll coater and dry to obtain an adhesive layer
Except for this, a removable adhesive sheet was prepared in the same manner as in Example 1.
Obtained.

Example 6 In Example 1, as a two-part crosslinkable acrylic pressure-sensitive adhesive, a pressure-sensitive adhesive (trade name: BPS-5130 / Toyo Ink Mfg. Co., Ltd .; adhesive strength: 500 g / 25 mm), 20 g in dry weight /
A removable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive layer was obtained by coating with a roll coater and drying so as to obtain a pressure-sensitive adhesive layer of m ² .

[0034] In Comparative Example 1 Example 1, rice quality paper having a basis 97 g / m ² as a surface base material: Except for using [Clark stiffness 230 (cm ^3/100)], in the same manner as in Example 1 again A peelable pressure-sensitive adhesive sheet was obtained.

[0035] In Comparative Example 2 Example 1, rice quality paper having a basis 105 g / m ² as a surface base material: Except for using [Clark stiffness 350 (cm ^3/100)], in the same manner as in Example 1 again A peelable pressure-sensitive adhesive sheet was obtained.

Comparative Example 3 In Example 1, a two-part crosslinkable acrylic pressure-sensitive adhesive was used.
Adhesive (trade name: AE 245 / Nippon Synthetic Rubber Co., Ltd.)
20 g / m in dry weight. ^TwoWhen
Coat with a roll coater and dry to obtain an adhesive layer
Except for this, a removable adhesive sheet was prepared in the same manner as in Example 1.
Obtained.

Comparative Example 4 In Example 1, a one-component acrylic pressure-sensitive adhesive (trade name: L-122, manufactured by Nippon Carbide Industry Co., Ltd .; adhesive strength 1200 g / An adhesive sheet was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive layer was coated with a roll coater and dried to obtain a pressure-sensitive adhesive layer so as to have a dry weight of 20 g / m ² .

The following evaluation tests were performed on the ten types of pressure-sensitive adhesive sheets thus obtained, and the results obtained are shown in Table 1.
It was shown to. In addition, each measurement item and evaluation are as follows.

[Adhesive strength] In accordance with JIS Z 0237,
180m adhesive strength to polystyrene board, pulling speed 50m
It was measured in m / min. (Unit: g / 25mm)

[Removability] An adhesive sheet sample of 30 mm × 70 mm was stuck on a commercially available floppy disk,
, And the test piece was peeled off at a speed of 10 m / min. ◎: No breakage of surface substrate and no adhesive residue on adherend
It was easily peeled off. ：: Substantially no tear of the surface substrate and no adhesive residue on the adherend
It was easily peeled off. X: The surface substrate was torn, adhesive residue on the adherend was remarkable, and re-peeling was difficult.

[Floating] A 30 mm × 70 mm adhesive sheet sample was stuck on a commercially available floppy disk,
After treatment at 3 ° C. for 3 days, lifting of the test piece was visually determined. ：: no lifting is observed. ×: Lifting is observed, which is a practical problem.

[0042]

[Table 1]

[0043]

As is clear from Table 1, the removable pressure-sensitive adhesive sheet obtained according to the embodiment of the present invention has no unnecessary lifting when sticking to a floppy disk and has excellent re-peelability. It was a removable adhesive sheet having adhesive properties.

Claims (2)

(57) [Claims] 1. A re-peelable pressure-sensitive adhesive sheet obtained by laminating a release sheet, a pressure-sensitive adhesive layer, and a surface substrate.
The stiffness according to Clark A method according to 143 is 200 (cm
^3/100) or less, the pressure-sensitive adhesive layer is formed from two-pack crosslinking type pressure-sensitive adhesive emulsion systems or solvent-based, and conforming to JIS Z0237 of pressure-sensitive adhesive layer, 1 vs. polystyrene plate
80 ° adhesive strength is 200 ~ 10 under the condition of pulling speed 50mm / min
A removable pressure-sensitive adhesive sheet characterized by being in the range of 00 g / 25 mm. 2. A laminate comprising a release sheet, an adhesive layer and a surface substrate.
The removable pressure-sensitive adhesive sheet
When attaching to an adherend, the adhesive sheet is folded back and attached.
Or affix to an adherend that is a polystyrene molded product
Clark compliant with JIS P8143
Stiffness by Method A is 200 (cm ^Three / 100) or less
Adhesive layer is an emulsion-based or solvent-based two-pack cross-linkable pressure-sensitive adhesive
And according to JIS Z0237 of the pressure-sensitive adhesive layer.
180 against polystyrene plate ー Adhesive strength pulling speed 50
in the range of 200-1000g / 25mm under the condition of mm / min
A removable pressure-sensitive adhesive sheet, comprising: