JPH10140104A - Production of self-adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a self-adhesive sheet which has no surface undulation and has a feeling of a high-quality product by using a base release paper of which the backside has a specified water absorbency and by specifying the ratio of the surface speed of a gravure roll for watering to the line speed. SOLUTION: Glassine paper which has a polyethylene layer formed on its one side to be subjected to a release treatment is used as the base release paper. On the baser release paper a release agent layer and a self-adhesive layer are successivle formed; then the backside of the release paper is watered with a gravure roll to correct curl; and a film as the surface substrate is stuck to the self-adhesive layer to give the objective self-adhesive sheet. In the above process, the base release paper the side to be watered of which has a water absorbency (coff test, according to JIS P8140, during a water absorption time of 60sec) of 10-35g/m<2> is used and the surface speed of a gravure roll for watering is set at 50% or lower of the line speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet using a film as a surface substrate, using, as a release base paper, glassine paper in which only a surface on which a release agent layer is provided is polyethylene-laminated.

[0002]

2. Description of the Related Art Conventionally, pressure-sensitive adhesive sheets have been used for a wide range of applications such as commercial use, office use, home use, and the like for labels, seals, stickers, patches, overlamps, and the like. This pressure-sensitive adhesive sheet is generally formed by laminating a surface substrate, a pressure-sensitive adhesive, and release paper. As the pressure-sensitive adhesive, a solvent-type pressure-sensitive adhesive, an emulsion-type pressure-sensitive adhesive, a hot-melt-type pressure-sensitive adhesive, or the like is used.

[0003] Surface base materials include high-quality paper, kraft paper, art paper, coated paper, cast coated paper, general paper such as thermal recording paper, coated paper, aluminum foil laminated paper, aluminum-deposited paper, and resin-impregnated paper. And special papers such as synthetic paper, and films such as PET, polypropylene, and polyvinyl chloride.

[0004] Among these, films have higher durability than papers for other surface base materials, so they are used for pressure-sensitive adhesive sheets for overlaminating or outdoor use, and have extremely high gloss. Used for high-grade adhesive sheets.

On the other hand, as release paper, polyethylene laminate type, glassine type, clay coat type,
It can be classified into aqueous resin coat type and film base type, among which polyethylene laminate type,
Glassine type is widely used.

Particularly, a polyethylene laminate type release paper is often used for an adhesive sheet using a film as a surface substrate. However, in this combination, since the surface substrate is a film, there is no dimensional change due to humidity change,
Since a part of the release paper is paper, the dimensional change accompanying the humidity change is remarkable.

As a result, since the dimensional changes of the surface substrate and the release paper are different, curling of the pressure-sensitive adhesive sheet accompanying a change in humidity becomes a problem.

[0008] The polyethylene laminate type is usually applied to the surface of the base paper in order to prevent the release agent such as silicone from seeping into the inside of the base paper such as high quality paper or kraft paper, or to exhibit the release performance effectively. It is obtained by laminating polyethylene and providing a release agent layer thereon.

Further, when a film is used as the surface base material of the pressure-sensitive adhesive sheet, the back surface of the release paper may be subjected to polyethylene lamination to prevent curling. As the polyethylene to be laminated, a high-pressure low-density polyethylene is typically used.

[0010] Such polyethylene laminate type is
Since the silicone (release agent) is completely retained on the polyethylene layer formed on the high-quality paper or kraft paper with a lot of voids, there is an advantage that the release performance is effectively exhibited.

However, since high-quality paper or kraft paper is used as the base paper for the release paper, light transmission is poor, and there is a problem in label position detection by a labeler having a transmission type position detector. In addition, when the adhesive sheet is used in the form of a roll, the polyethylene laminate type uses thick paper such as high-quality paper or kraft paper, so the roll diameter increases and the processing efficiency decreases. Has the disadvantage of

On the other hand, the glassine type usually has a beating degree of 2
30-350ml CSF (Canadian Standard Freeness) range. Highly beaten chemical pulp in the range of raw material is used to make paper, and then compressed and densified by a finishing machine such as a super calender. An agent is provided. For this reason, the glassine type release paper has an advantage that it has excellent light transmittance and does not cause a problem in label position detection by a labeler having a transmission type position detector.

[0013] Further, since the glassine paper is subjected to a compression treatment by a finishing facility such as a super calender, the paper thickness is extremely thin as compared with ordinary high quality paper or kraft paper. As a result, when the adhesive sheet using glassine paper as the release paper is used in the form of a roll, the sheet thickness becomes thinner and the winding diameter becomes smaller than the adhesive sheet using fine paper or kraft paper as the release paper. If they are the same, the sheet can be wound up for a longer time, so that there is an advantage that the efficiency at the time of processing is improved.

However, as mentioned above, glassine paper is made from chemical pulp which has been subjected to a high degree of beating treatment in the range of 230 to 350 ml CSF as a raw material, and is further densified by finishing equipment such as a super calender.
Glassine paper has the disadvantage that the dimensional stability with humidity changes is very poor.

Due to the poor dimensional stability, when the glassine type is used as the release paper, the pressure-sensitive adhesive sheet is not adhered to the surface substrate due to dehumidification by drying of the pressure-sensitive adhesive at the time of pressure-sensitive adhesive processing and moisture absorption after laminating the surface substrate. Curls greatly. In order to suppress such curl, it is common to apply a water treatment to the back surface of the release paper before or after laminating the surface base material to correct the curl.

If the surface substrate is a pressure-sensitive adhesive sheet, which is a film, usually a glassine type is subjected to polyethylene lamination on both sides. However, when polyethylene laminate is applied to both sides, even a glassine paper which has been subjected to a compression treatment results in a considerable paper thickness. In the case of winding, the advantage of a glassine type having a small winding diameter cannot be used. In addition, although there are many pressure-sensitive adhesive sheets used by printing on the back surface, when the back surface is provided with a polyethylene laminate, the printability is significantly reduced.

For this reason, when it is necessary to reduce the winding diameter or when the pressure-sensitive adhesive sheet needs to be printed on the back surface, it is inevitable to use a glassine-type release paper that has been subjected to single-sided polyethylene lamination on only the pressure-treated side. However, the single-sided polyethylene lamination does not make the dimensional stability accompanying a change in humidity equal to that of a film.

In particular, when the film is bonded to a film as a surface substrate without any treatment, the dimensional change accompanying thermal drying during the adhesive processing is large, and the film curls greatly on the surface substrate, making it unusable for use. In order to suppress the curl generated during such processing as much as possible, before or after laminating the surface substrate, it is general to correct the curl by applying a watering treatment to the back surface of the release paper with a gravure roll or the like. .

However, the adhesive sheet using a glassine-type release paper coated with a single-sided polyethylene laminate manufactured as described above and using a film as a surface base material has a further problem. In other words, in the case of watering with a gravure roll before or after laminating the surface substrate for curl correction on the back surface of the glassine paper that is a release paper, in order to correct the curl so that it will be in the most appropriate state , It is necessary to always add a fixed amount of water to the release paper, but this is only when the moisture of the release paper before the watering treatment is constant.

When watering treatment is performed after bonding the surface substrate,
Depending on the season or weather, the amount of moisture absorbed by the release paper varies, and even if a certain amount of water is applied, the degree of curl correction differs, etc. It is not preferable because it becomes difficult to obtain a high quality adhesive sheet.

On the other hand, when watering is performed before laminating the surface base material, that is, immediately after the adhesive is dried, the water content of the release paper is almost constant, the watering amount for curl correction is constant, and the adhesive of stable quality is obtained. A sheet can be obtained, and it can be said that it is the most preferable production method as a curl correction method for a pressure-sensitive adhesive sheet using a film as a surface base material on a glassine type release paper having a single-sided polyethylene laminate.

However, this method also has a major problem.
In other words, the surface (the opposite side of the water-treated surface) is covered with the adhesive to perform the watering treatment immediately after drying the adhesive,
As a result, the only way to control the adhesion amount is to use a gravure roll as a watering method, and even if a gravure roll is used, a holding roll cannot be installed on the opposite side of the gravure roll. As a result, if water is applied with a gravure roll without a holding roll, flapping or the like may occur, or water may not be uniformly applied to the back surface of the release paper, resulting in unevenness due to fine streaks of the release paper. Occur.

When a surface substrate composed of a normal paper or a kraft paper is used, such irregularity of the release paper does not appear on the surface substrate side, and there is no problem in quality. When a film is used as the material, the film itself is highly smooth and high-gloss, and as a result, the streaks of the release paper generated by the watering process are increased, and such a release paper is used as a surface base material. Although a pressure-sensitive adhesive sheet using a film has high gloss, a streaky unevenness or gloss unevenness on the surface of the pressure-sensitive adhesive sheet which is given to an eye is generated, and it is difficult to obtain a high-quality pressure-sensitive adhesive sheet.

Further, the pressure-sensitive adhesive sheet having such a streaky unevenness or gloss unevenness not only has a poor appearance as a product, but also has a highly smooth and air-impermeable adherend such as glass,
When affixed to a metal or plastic solid, it causes air to enter between the adherend and the adherend, and the surface of the pressure-sensitive adhesive sheet gives an apparent appearance, which hinders a sense of quality.

[0025]

Accordingly, the present invention provides curling correction under almost constant conditions even when using glassine paper in which a single-sided polyethylene laminate is applied to a release base paper and using a film as a surface base material. The present invention relates to a method for producing a pressure-sensitive adhesive sheet which facilitates quality control and does not cause streaks on the surface of the pressure-sensitive adhesive sheet.

[0026]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the streak generated by the gravure roll watering process is affected by the line speed and the surface of the gravure roll. If the speed ratio depends on the speed ratio between the speed and the speed ratio, the bumping becomes worse as the speed ratio increases, and the speed ratio with respect to the surface speed and the line speed of the gravure roll is the same. The reason is that if the water absorption measured by the Cobb method under the condition of JIS P8140 of 60 seconds (Cobb method) (hereinafter simply referred to as Cobb water absorption) is low, the amount of water absorption increases conversely. However, it was found that a phenomenon that resulted in seemingly contradictory results was found. .5% (approximately 2 by weight of the total weight of the release paper
When 5% is the weight of the polylaminate), the pressure-sensitive adhesive sheet becomes flat without curling under an atmosphere of 20 ° C./65% RH], the quality is easily controlled, and the pressure-sensitive adhesive sheet surface They have found that an excellent pressure-sensitive adhesive sheet full of luxurious feeling can be produced without generating streak-like bumps, and the present invention has been completed.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a gravure roll installed immediately after a dryer for drying an adhesive applied to the surface of a release paper, and curls the back surface of the release paper immediately after the adhesive is dried. By performing the watering process for correction, the watering process is performed under almost constant conditions. If the watering treatment is not performed immediately after drying, the release paper absorbs moisture in the atmosphere and changes the moisture. The amount of moisture absorption varies depending on the weather at the time of processing. As a result, the amount of water applied for curl correction also varies, and it is necessary to adjust the moisture content of release paper to 6% or more depending on the day. Is difficult to obtain.

Therefore, in the present invention, a gravure roll for watering is installed immediately after the dryer for drying the pressure-sensitive adhesive, and the watering treatment is performed. The amount of water used for this is always constant, and quality control becomes easy. However, as described above, since the surface of the release paper is coated with an adhesive, there is no watering method other than a gravure roll, and a holding roll cannot be provided on the opposite side of the gravure roll. For this reason, flapping occurs, and streaky rattling, which is considered to be caused by uneven water, is generated.

Therefore, the present inventors have conducted intensive studies and found that the surface speed of the gravure roll was 50% of the line speed.
It has been found that streaking may not occur in the following watering. However, it is difficult to apply the amount of water required for straightening the curl only when the surface speed of the roll is 50% or less of the line speed. To apply the amount of water necessary for straightening the curl, the surface speed of the roll must be reduced. It is necessary to increase the line speed to more than 50%, but in this case, streaks are generated. Of course, it is also possible to reduce the surface speed of the roll to 50% or less of the line speed by changing the roll speed to a gravure roll having a different gravure mesh.

Therefore, the inventors have conducted intensive studies on the cause of such a difference, and as a result, it was found that the Cobb water absorption measured on the surface of the release paper subjected to water treatment with the roll under the water absorption time of 60 seconds was low. For example, it was found that the amount of water absorption increased, although the reason was not clear, but seemingly contradictory results. That is, if the Cobb water absorption measured under the condition of water absorption time of 60 seconds is 10 to 35 g / m ² , the surface speed of the roll is 50% or less of the line speed, and the amount of water necessary for straightening can be applied. It was found that the present invention was completed.

In the present invention, the back side of the base paper for release paper is
The water absorption measured under the condition of the water absorption time of 60 seconds specified by JIS P8140 (Cobb method) is 10 to 35 g / m ^2.
In order to obtain a base paper for release paper,
A rosin-based sizing agent, a petroleum-resin-based sizing agent, and other synthetic sizing agents are used for paper pulp made from wood pulp as a main raw material and blended with various chemicals such as dyes and adhesives as needed. It can be obtained by appropriately setting the type and addition amount of the internal sizing agent represented by the above.

The coated base paper is coated with polystyrene / polystyrene by a coating unit such as a size press or a gate roll coating machine.
A surface sizing agent typified by a maleic acid copolymer resin and a polystyrene / acrylic copolymer resin or a surface sizing treatment of an aqueous resin aqueous solution such as polyvinyl alcohol may be performed.

Although examples of the means for obtaining the desired degree of water absorption have been described above, the present invention is not limited to these means.
As a result, if the back surface of the release paper has a water absorption of 10 to 35 g / m ² measured under the condition (Cobb method) of a water absorption time of 60 seconds specified in JIS P8140, the surface speed of the gravure roll is changed to a line. It is possible to apply the amount of water required for curl correction at 50% or less of the speed. 10 g water absorption
If it is less than / m ² , repelling or the like occurs, it is difficult to uniformly apply water, and the amount of water is absolutely insufficient. Conversely, if it exceeds 35 g / m ² , curl and unevenness cannot be balanced.

The base paper for release paper in the present invention uses a polyethylene laminate laminated on the surface to which the release agent is applied before applying the release agent. Is not specifically stipulated,
For example, ethylene-based resins include homopolymers of ethylene and copolymers mainly composed of ethylene. Specific examples of those produced by a high-pressure method include medium-density polyethylene, low-density polyethylene, and ethylene-vinyl acetate copolymer. Polymer, ethylene- (meth) acrylate copolymer,
Ethylene- (meth) acrylic acid copolymers and their ionomers are mentioned, and ethylene-propylene copolymers, ethylene-1
-Linear low-density polyethylene such as butene copolymer. However, the present invention is not limited to these.

As the method of laminating the ethylene resin, extrusion lamination, film lamination and the like are suitable. An adhesive is used on the surface of the base paper for release paper to improve the adhesion with the polyethylene laminate layer. Coating, ozone treatment, or corona discharge treatment may be applied.

[0036]

EXAMPLES 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 the examples, "parts" and "%" indicate "parts by weight of solid content" and "% by weight of solid content", respectively, unless otherwise specified.

Example 1 [Production of base paper for release paper] First, a stock having the following composition was prepared. -Degree of beating: 50 parts of 230 ml CSF (softwood kraft pulp)-Degree of beating: 50 parts of 230 ml CSF (hardwood kraft pulp)-30% reinforced rosin sizing agent (trade name: SPE, Arakawa Chemical Industries) 1.2 parts-30% sulfuric acid Aluminum 2 parts Note) CSF: Measured in accordance with JIS P8121. This stock is fed by a fourdrinier multi-cylinder paper machine to a rice basis weight of 73 g / m.
² of the base paper and papermaking, the dried size press apparatus, polyvinyl alcohol resin (trade name: NH20, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was applied an aqueous solution of 5% concentration, and dried again. The coating amount at this time was 1.2 g / m ² .
Then, it was compressed with a super calender and finished into glassine paper. The water absorption measured under the condition of a water absorption time of 60 seconds specified by JIS P8140 on the back surface of the base paper was 30.0 g / m ² .

After performing corona discharge treatment on the side of the obtained glassine paper on which the release agent layer is provided, low-density polyethylene is laminated at a resin temperature of 330 ° C. by a melt extrusion coating method so that the film thickness becomes 25 μm. A surface coating layer was formed.

[Production of Release Paper] A silicone solution having the following composition was prepared. -Addition reaction type silicone (trade name: SD7220, manufactured by Toray) 4.5 parts-Platinum catalyst (trade name: SRX212, manufactured by Toray) 0.5 parts-Toluene 95 parts The obtained base paper for release paper was obtained. The resulting solution was applied on a film using a Meyer bar so that the weight after drying was 2.0 g / m ² to obtain a release paper.

[Production of pressure-sensitive adhesive sheet] An acrylic solvent-type pressure-sensitive adhesive (trade name: Nissetsu KP-1954,
100 parts of Nippon Carbide Co., Ltd. and 1.5 parts of a curing agent (trade name: Nissetsu D-201) were applied and dried using a reverse roll coater at a line speed of 50 m / min and a coating amount of 25 g / m ^2. After that, the surface speed of the gravure roll (100 mesh) set immediately behind the dryer is set to 23 m / min which is 46% of the line speed of 50 m / min, and the back surface is wetted. Was. At this time, the moisture content of the release paper measured by a moisture meter was 5.5% (the value including the weight of the laminate, the same applies hereinafter). Then, an aluminum-deposited PET (trade name: MSN # 25, manufactured by Toray Industries, Inc.) was adhered as a surface substrate to obtain an adhesive sheet.

Example 2 In the production of the base paper for release paper of Example 1, except that the amount of the polyvinyl alcohol-based resin to be applied by the size press after drying was 2.0 g / m ^2. In the same manner as in Example 1, a base paper for release paper and a release paper were obtained. At this time, the water absorption measured under the condition of water absorption time 60 seconds specified in JIS P8140 on the back surface of the base paper is 2
It was 1.5 g / m ² . Next, when producing a pressure-sensitive adhesive sheet using this release paper, the surface speed of the gravure roll when applying water to the back surface is set to 36% of the line speed.
Was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet was changed to 1. At this time, the moisture content of the release paper measured by a moisture meter was 5.3%.

Comparative Example 1 In the manufacture of the base paper for release paper of Example 1, except that the amount of the polyvinyl alcohol-based resin applied by the size press after drying was applied to be 0.5 g / m ^2. In the same manner as in Example 1, a base paper for release paper, a release paper and an adhesive sheet were obtained. At this time, JIS P81 on the back of the base paper
The water absorption measured at a water absorption time of 60 seconds, defined as 40, was 45 g / m ² . At this time, the moisture content of the release paper measured by a moisture meter was 4.5%.

Comparative Example 2 In the same manner as in Example 1 except that the surface speed of the gravure roll was changed to 60% of the line speed when water was applied to the back surface when the pressure-sensitive adhesive sheet of Example 1 was produced. To obtain a pressure-sensitive adhesive sheet. At this time, the moisture content of the release paper measured by a moisture meter was 7.2%.

Comparative Example 3 In the same manner as in Comparative Example 1, except that the surface speed of the gravure roll was changed to 60% of the line speed when water was applied to the back surface when producing the pressure-sensitive adhesive sheet of Comparative Example 1. To obtain a pressure-sensitive adhesive sheet. At this time, the moisture content of the release paper measured by a moisture meter was 5.4%.

[Evaluation of Roughness] Streaky roughness on the surface of the obtained pressure-sensitive adhesive sheet was measured by the following method. (Bumpiness) The roughness of the pressure-sensitive adhesive sheet surface was visually evaluated according to the following criteria. ◎: There is no unevenness. ○: There is slight unevenness, but there is no practical problem. △: There is unevenness. ×: Many unevenness is observed.

[Evaluation of Curl] A4 size sample was prepared from the obtained pressure-sensitive adhesive sheet, humidified in an atmosphere of 20 ° C./65% RH for 4 hours, and evaluated by the following method. (Curl) Place the curled side on a flat sample table of A4 size sample, measure how much the four corners of the sample float from the sample table, calculate the average value, and calculate the average value according to the following criteria. evaluated. ◎: 0 cm ○: 0 to less than 1.5 cm △: 1.5 cm or more to less than 3.0 cm ×: 3.0 cm or more

[0047]

[Table 1] * Cobb size: Measured under the condition that the water absorption time specified in JIS P8140 is 60 seconds. ** Speed ratio: Ratio of the surface speed of the gravure roll to the line speed.

[0048]

As is clear from the results of Examples 1 and 2 in Table 1, the surface speed of the gravure roll was set to 50 as the line speed.
% Or less, it is possible to provide a high-grade pressure-sensitive adhesive sheet having no unevenness on the surface, and the lower the surface speed, the better the unevenness. At the same time, J
By lowering the water absorption measured under the condition of water absorption time of 60 seconds specified in IS P8140, it is possible to apply a sufficient amount of water for curl correction, although the reason is unknown, but there is no problem in practical use. It can be provided.

As is clear from Comparative Examples 1 and 3, the water absorption time defined by JIS P8140 on the back of the release paper was 60 hours.
If the water absorption measured under the condition of seconds is higher than 35 g / m ^2, curling becomes severely unpractical if the surface speed of the gravure roll is set to 50% or less of the line speed in order to improve the unevenness. If the rotation speed of the gravure roll is increased to more than 50% of the line speed in order to apply the amount of water necessary for straightening, the curl will be in a range where there is no problem in practical use, but on the other hand, it will be so rough that it will not be suitable for practical use. Further, the water absorption measured on the back surface of the release paper under the condition that the water absorption specified in JIS P8140 is 60 seconds is 35 g /.
Even if it is less than m ² , if the surface speed of the gravure roll is higher than 50% of the line speed, the gravure roll will be uneven and the amount of water for correcting the curl will not be appropriate.

As is evident from the above, the water absorption can be measured by means of the existing paper machine or other equipment by the amount of the internal sizing agent added to the stock and the surface sizing agent added to the size press coating solution. It can be easily manufactured by simply setting the surface speed of the gravure roll to 10 to 35 g / m ² and setting the surface speed of the roll to 50% or less of the line speed for curl correction. It is extremely excellent in properties.

Claims (1)

[Claims] (1) Polyethylene lamination is applied only to the surface to be peeled.
By using glassine paper that has been subjected to nitrate processing as the release base paper,
A release agent layer and an adhesive layer are sequentially provided on the release base paper to correct curl.
For the back side of the release paper with a gravure roll (release agent layer,
After the watering treatment is applied to the reverse side where the adhesive layer is
Adhesive bonding of the film as the surface substrate through the adhesive layer
In the production process of the adhered sheet, the release agent layer of the release base paper is
Surface opposite to the surface to be provided (Apply water with a gravure roll
Water absorption time specified in JIS P8140
The water absorption (Cobb method) measured under the condition of seconds is 10 to 35.
g / m ^TwoIs used, and the back side of the release paper is used.
Line the surface speed of gravure roll for watering
The pressure-sensitive adhesive sheet is characterized in that the speed is 50% or less.
Production method.