JPS60258280A - Releasing paper - Google Patents

Abstract

PURPOSE:To provide a releasing paper for a pressure-senstive adhesive sheet, having excellent surface smoothness and releasability and high dimensional stability to temperature, and resistance to internal peeling, by applying a radiation-curing silicon resion layer to a double-coated paper composed of a moisture-controlled paper and having a water-vapor barrier layer. CONSTITUTION:The water-content of a paper substrate is adjusted to 5-10%, and both faces of the paper substrate are coated with a film having a moisture-permeability of <=80g/m<2>.24hr.atm. One or both surfaces of the double- coated paper are coated with a radiation-curing silicon resin, and the resin is cured with ultraviolet radiation or electron ray to obtain the objective releasing paper. The coating film is preferably a synthetic resin layer (e.g. low-density polyethylene, etc.), a metallic foil laminate layer (e.g. Al foil, etc.) or a pigment-coated layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a release paper used for adhesive sheets and adhesive tapes, and particularly to a release paper that has good dimensional stability when absorbing moisture.

Conventionally, solution-type and emulsion-type release agents of silicone resins have been used as release agents for release paper used in adhesive tapes, labels, and the like.

These require high-temperature heating of 120° C. to 180° C. during curing, and in the case of release paper based on paper, there is a drawback that the paper tends to wrinkle or curl due to the dissipation of moisture accompanying the heating. In order to eliminate this drawback, paper can be extruded and coated with low-density polyethylene on both sides and then treated with a release agent, or one side is coated with low-density polyethylene and the back side is coated with polyvinylidene chloride, etc. Types coated with a single layer of barrier are known. However, in release paper with such a structure, polyethylene (PE) softens or melts at high temperatures, so the high temperature during release treatment causes the moisture in the paper to evaporate and the air in the paper to expand, causing P[ etc.'1
! A is graded - Leveling of O7 - [] The disadvantage is that the peeling layer becomes non-uniform and it is difficult to obtain good peeling performance because pinholes are generated as well as the roughness of the layer. have.

Furthermore, one side is coated with low density polyethylene, etc., and the back side is coated with A.
1 foil or other metal foils, or A1 on both sides.
When performing release treatment on release paper with a structure in which metal foil such as foil is bonded, and on double-sided coated release paper with a pigment-coated decoy on one or both sides, dissipation of moisture from the base paper due to high-temperature heat curing of the silicone occurs. This may cause pinholes in the coating layer, making the release layer non-uniform, or peeling may occur at the interface between the coating layer and the base paper or within the base paper layer, resulting in a puncture state and impairing its performance as a release paper. It has some drawbacks. Therefore, attempts were made to lower the curing temperature of silicone to below 100°C to eliminate the above drawbacks, but essentially
For silicones that require temperatures of .degree. C. or higher, such low-temperature curing often causes insufficient curing of the silicone, resulting in poor peeling.

In order to improve these shortcomings, the inventors of the present invention have conducted intensive research and have used radiation-curable release paper to reduce the water content of the paper from 5 to 10.
The inventors have discovered that the problems of poor peeling, pinholes, interfacial and/or internal peeling as described above can be solved by adjusting the amount within the above range, and have accomplished the present invention.

i.e. polyethylene, polyvinylidene chloride, metal foil.

Water vapor permeability of pigment-coated areas, etc.: 801 J/m2
・A single layer of water vapor barrier of 24 hr/atm or less is placed on one side of the paper, and the moisture content of the paper is adjusted to within the range of 5 to 10%, and the other side of the base paper is coated with polyethylene and polychloride. Double-sided processed paper is obtained by disposing vinylidene, metal foil, etc.

Furthermore, a radiation-curable silicone release agent is coated on at least one side of this double-sided treated paper, and the silicone is cured using ultraviolet rays or electron beams.

In the release paper according to the present invention, a sufficiently crosslinked release layer is formed by using ultraviolet rays or electron beams without high temperature treatment. Therefore, it does not exhibit peeling at the interface or inside (puncture state), has excellent surface smoothness, and can have both releasability and dimensional stability against humidity (curl resistance).

Generally, when an adhesive film is attached to a double-sided coated release paper, the relationship between the moisture content in the paper and the curl height is as shown in FIG. Here, the solid line is relative humidity 85% and temperature 20℃
The dashed line shows an example when left at 20% relative humidity
, an example when left at a temperature of 20°C is shown. Further, curling may occur with the film surface on the inside, or may occur with the paper base (release paper surface) on the inside, and in both cases, the larger the value, the greater the curl. As is clear from FIG. 1, the paper moisture content of the release paper base paper of the present invention, which can minimize curling (curl height close to O), is 5 to 50% regardless of the atmospheric humidity conditions. It is essential that it be within the range of 10%. If the moisture content in the paper is less than 5%, the moisture absorption of the base paper in a high humidity atmosphere is significant.
As a result, the dimensions of the base paper increase significantly compared to when the moisture content in the paper is 5 to 10%, and this causes curling and edge waving (unevenness due to moisture absorption), and conversely, curling occurs due to dehumidification at low humidity. At the same time, even if the curing temperature is low, foaming occurs at the interface between the base paper and the barrier layer when the silicone is cured, making it difficult to obtain good peeling performance.

According to the principle of the radiation curing method using ultraviolet rays or electron beams, the surface temperature of the substrate to be cured is maintained at approximately room temperature or at a maximum of 60°C even if incidental thermal radiation is present. This was done based on the knowledge that the time required for curing is also very short. The technical problem of curing silicone without dissipating the water content in the paper, which was previously maintained at 5 to 10%, could only be solved by this radiation curing method. With the conventional heat curing method, which requires a curing temperature of 120°C or higher, it was impossible to apply a barrier coat to the back of the release paper to prevent curling, but with the radiation curing method, the paper on the release paper It is possible to maintain the medium moisture content at 5 to 10% and also maintain the barrier properties of the back surface, so the curl resistance is significantly improved.

It is an essential condition that the following is the following: baby-alternate bait 8 odada + + n 7th appearance table visit 5 wing curve t → q ha g / m2・24hr・ata+.

If the treated layer exceeds this value, the barrier effect against the external atmosphere (humidity) will be significantly reduced, and the base paper will easily absorb and desorb moisture, resulting in a loss of curl resistance of the release paper. Radiation in the present invention refers to ultraviolet rays, electron beams, etc. The ultraviolet ray or electron beam curable silicone resin used in the present invention includes, for example, a radical addition polymerization reaction or bipartization reaction initiated by ultraviolet ray or electron beam irradiation. 1) Mercapto group-containing organopolysiloxane and vinyl group Mixed composition with organopolysiloxane containing 2) Organopolysiloxane composition containing acrylic group, methacrylic group, or cinnamoyl group 3) Organopolysiloxane composition containing maleimide group or phenylmaleimide group 4) Organopolysiloxane containing azide group and vinyl Mixed composition with group-containing organopolysiloxane 5) Organopolysiloxane composition containing thioacrylic group, thiomethacrylic group, or thiocinnamoyl group 6) Organopolysiloxane composition containing one acrylamide group, one methacrylamide group, or cinnamoylamide group, etc. It is also possible to use a mixed composition of an epoxy group-containing organopolysiloxane using ultraviolet ray-initiated cationic polymerization and a photodegradable initiator such as diazoni or umlewisate.

In the case of ultraviolet curing, known curing initiators such as benzoyl alkyl ether and its derivatives, acetophenone and its derivatives, benzophenone and its derivatives, and thioxanthone and its derivatives are used.

In the case of electron beam curing, no curing initiator is required.

23,). □, ioo□. . ,. 1. A diluted solution using a solvent such as ethyl acetate, hexane, etc. can also be used. The amount of radiation-curable release agent applied is 0.1
tx/m2 to 1.5 g/m2 (solid content) is effective, and Mayer bar, roll coating, gravure coating, and other known coating methods can be applied.

As a film that functions as a water vapor barrier,
Low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, polymethylpentene, and copolymers thereof, ethylene/α-olefin copolymers, polyester, synthetic resin coating layers such as polyvinylidene chloride, AI foil, Included are metal foil bonding layers, such as Fe foil, or coatings consisting of pigment-coated kidneys.

Note that the release paper according to the present invention is a prepreg sheet.

It can also be fully applied to release paper for manufacturing ceramic green sheets, synthetic leather, etc. For example, for the production of synthetic leather, a release paper may be used in which a polyethylene coating having a predetermined surface profile is formed on one side of a paper base, and a release treatment is performed using a heat-curable silicone resin.

In a release paper having such a structure, the polyethylene softens at high temperatures, so the surface profile is damaged by the high temperatures during the release treatment, and the release paper loses its properties as a release paper for synthetic leather production.

When a radiation-curable release agent is used as a release agent, as mentioned above, a sufficiently crosslinked release layer is formed without using high temperatures, so the surface properties of equivalent polyethylene are not impaired. None. Therefore, it has become possible to produce a release paper that maintains optimal surface properties and release properties as a release paper for the production of synthetic leather.

Specific examples of the present invention will be shown below to clarify the effects of the present invention, but these examples are not intended to limit the scope of the present invention.

Example 1 Low-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name 30) was extruded on one side of high-quality paper with a basis weight of 116 g/m2 to a thickness of 20 μm and laminated onto the high-quality paper, reducing the moisture content in the paper to approximately 8%. Adjusted to. The water vapor permeability of the obtained laminated paper was 48'J
/m'・24hr・atm. Next, low-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name LK30) was extruded on the back side of the laminated paper to a thickness of 20 μm, and the laminated paper was further laminated to obtain a double-sided laminated paper. 0.4 g of ultraviolet curing silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: X-62-783) was placed on one side of the double-sided laminated paper.
/m' amount fl cloth L, 160W/Cl1l.

It was cured at a curing rate of 20 m/min. The ultraviolet curing device is manufactured by Ushio Electric Co., Ltd., and the product name is Conicure U■4.
000 was used. Table 1 shows the peel resistance value, residual adhesion rate, rub-off, smoothness of the peeled surface, and pinhole results for the resulting release paper.

Example 2 Polynylidene chloride emulsion (manufactured by Kureha Chemical Co., Ltd., trade name NR-1804) was applied to one side of high-quality paper with a basis weight of 116 q/m2.
) was applied so that the dry weight was 14g/l112,
It was dried and solidified at 100°C for 1 minute. The water vapor permeability of the obtained coated paper was 12 g/m2·24 hr-atlR.

After adjusting the water content of the coated paper to approximately 8%, one side was coated with low-density polyethylene (manufactured by Showa Denko, trade name L-171).
> was extruded to a thickness of 20 μm and laminated onto the above single-sided coated paper to obtain double-sided resin-treated paper. As in Example 1, this processed paper was coated with ultraviolet curable silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: X-62-783) on the polyethylene side and cured. Table 1 shows the results of the release paper obtained, including the peel resistance value against the adhesive.

Example 3 Electron beam curing type silicone (Go
lcl Schmidt AG, product name RC-30
0) was applied at a rate of 1.1 g/m2 and cured under the conditions of an electron beam irradiation dose of 3 Mrad. As the electron beam curing device, an electron curtain type CB-150 manufactured by ESI was used. Table 1 shows the results of the release paper obtained, including the peel resistance value against the adhesive.

Comparative Example 1 Low-density polyethylene (manufactured by Showa Denko, trade name L-171) was coated on one side of high-quality paper with a basis weight of 116 g/m2 to a thickness of 2011 g/m2.
It was extruded into μ and laminated onto high-quality paper. The water vapor permeability of the obtained laminated paper was 47g/m2・24hr・at
It was m. This laminated paper was not particularly subjected to moisture adjustment, and low-density polyethylene (manufactured by Showa Denko K.K., trade name L-171) was extruded to a thickness of 20 μm and further laminated onto the above laminated paper. The moisture content of the obtained double-sided laminated paper was measured and found to be 3.5%. One side of this double-sided laminated paper is coated with ultraviolet curing silicone (
Shin-Etsu Chemical Co., Ltd., trade name X-62-783) at 0.4 (+
/Il+2 and cured under conditions of 160 w/cm and curing rate of 201 /min.

Comparative Example 2 A thermosetting silicone (manufactured by Toray Silicone Co., Ltd., trade name 5RX) with a dry weight of 0.61 J was applied to one side of a double-sided laminated paper with a water content of 8% in the paper obtained in the same manner as in Example 1.
/llI2 and 180℃.

It was dried and cured for 60 seconds. The resulting release paper had a low water content of 4.1%, and foaming occurred on the polyethylene surface.

Comparative Example 3 Thermosetting silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KS) was added to one side of a double-sided laminated paper with a paper moisture content of 8% obtained in the same manner as in Comparative Example 2 to a dry weight of 0.6 g/+++2. Under low temperature conditions, i.e. 100°C, where there is no risk of foaming on the polyethylene surface.

Drying/curing was performed for 2 minutes. The moisture content of the release paper obtained was 7.5%.

Examples 1, 2, 3. Table 1 shows the physical properties of the release paper obtained in Comparative Example 1.2.3, and Table 2 shows the relationship between the water content in the paper and the curl height after film lamination.

From Table 1, the release paper obtained in Example 1.2.3 has a low peel resistance value to adhesives and a residual adhesion rate of 88 to 9.
It is high at 0%. Furthermore, it is clear that it has excellent properties such as high smoothness and no pinholes. On the other hand, in the release paper of Comparative Example 2, foaming occurred on the polyethylene surface due to high temperature curing at 180° C., the peel resistance to the adhesive was high, many pinholes were observed, and the peelability was impaired.

In addition, in the release paper of Comparative Example 3, crosslinking of the silicone resin was insufficient due to low temperature curing, and the peel resistance value against adhesive was 140 g/15 mm, which was ~10 times higher than that of the release paper of Example 1.2°3. It was found to lack removability, as changes were observed in the rub-off test.

Next, based on Table 2, the superiority of the present invention will be clarified.

In the release paper obtained in Example 1.2.3, there was almost no change in the moisture content in the paper before and after silicone curing, and the moisture content in the paper was maintained at approximately 8%. The curl height was also kept to an extremely low value of 6 to 7 m111.

On the other hand, the release paper of Comparative Example 1 has a low moisture content of approximately 3% before and after silicone curing, so
), the curl height was 20 mm, which was a much larger value than in the example. In addition, the release paper of Comparative Example 2 also has a large dissipation of moisture in the paper due to silicone curing, and the moisture content in the paper after curing is as low as 4.1%. showed a large value of 18 mm. Since Comparative Example 3 was cured at a low temperature, there was very little change in the moisture content in the paper before and after curing, and the moisture content in the paper after curing could be maintained at a high value of 7.5%. Therefore, the curl height was approximately between that of the release paper obtained in the example. However, as shown in Table 1 above, the release properties were lost due to insufficient crosslinking due to low temperature curing.

As described above, the release paper of the present invention is obtained by achieving high degree of crosslinking of silicone resin at a low curing temperature, and has excellent release properties and curl resistance.

Margin below 1.・ Table 1 Physical properties of each paper Adhesive A is BPS! 1127 Manufactured by Toyo Ink Co., Ltd.

As adhesive B, SK Dyne 801B manufactured by Soken Chemical Co., Ltd. was used.

Love-off test; O...No change △・・・Slight change Pinhole: ○・・・No penetration of test staining solution ×・・・There is penetration The temperature for measuring the curl height of the film bonded product is 20°C.

The curl axis is the longitudinal direction (T D l) and occurs with the curl film surface facing inside.

In addition, each physical property value described in the present invention was measured by the method described below.

0 water vapor permeability, 1 cup method based on monthly S 1-0708. The measurements are conducted using a coated paper with a barrier coating formed on the paper base.

Based on the original 31'-8127, the water content in paper is measured using a coated paper with a barrier coating formed on the paper base, and the measured value is expressed as a percentage of the water content based on the paper base weight. .

The release paper obtained with a peel resistance value of 0 was left for 24 hours in an atmosphere of a temperature of 2+l'G and a relative humidity of [1+%], and then an adhesive was applied to the silicone surface to a thickness of 125μ (100μ). °G, dry in a hot air dryer for 1 minute.
A piece of high-quality paper (15 rql) was pasted on this surface and pressed with a 2M tape roller.
l'C, Peeling speed: soo, 1110f1mn+,'
The force required for peeling when peeled off under the conditions of m111 was examined, and this was taken as the peeling resistance value.

After leaving the release paper with a residual adhesion rate of 0 in an atmosphere at a temperature of 2 (1'C) and a relative humidity of 659A for 744 hours, a heavy adhesive tape (manufactured by Nitto Denko Corporation, trade name: Lumirror 31B) was applied to the silicone. Arrived, 'IOC, 1%R11, pressure 0.1k
After applying pressure for 24 hours under the conditions of q and 'rJ', the tape was removed and the stain was affixed to a stainless steel plate, and after being crimped using a 2klJ roller from the same city, 2(lC,fuj)%l( Place the adhesive tape at a peel angle of 1.
80"C, peeling speed: l (l I) mm r' m
f l'l and pull it, check the force required for peeling at this time,
Let this be the resistance value Q.

Adhesive Day 7 (same as above) (Lumirror 3 above) on a stainless steel plate
111> was applied for 24 hours under the conditions of 0'C, l Tsumugi %tilt, pressure 0.1 kq, 'rllll (after -, the pressure was removed and left for 1 hour, peel angle 180 'C, Peeling speed: The force required for peeling when peeled off with an ioOmmznl group was investigated, and this was taken as the peeling resistance value Q.

The ratio between the peeling resistance 0 and Q is determined, and this is taken as the residual adhesion rate.

Q Love A-7 Rub the silicone surface with your finger (10 rubs).

Observe the condition of the silicone surface with the naked eye.

0 smoothness The smoothness of the silicone is measured using an Oken type smoothness meter.

The dye was dissolved and a luene solution was applied to the surface, and the penetration rate to the back surface was evaluated as 1 dB 17.

Apply 12J/g of adhesive to the silicone side of the release paper with a zero curl height (
Wet) and dry it in a hot air dryer for 1 minute to a thickness of 10 (1"). After cooling to room temperature, attach a P):l film of 0μ thickness to this side. and press it with a tape roller (2 klJσ).The obtained adhesive-film set is
After cutting to a size of 0 CIll x 10 cm and leaving it in a predetermined atmosphere for 3 hours, the heights of the four corners were measured, and the average value was expressed as the curl height (-7).

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the relationship between paper moisture and curl height. Procedures Amendment Document July 9, 1980 Manabu Shiga, Commissioner of the Patent Office1, Special Application No. 1981-1110142, Name of the invention Release paper6, Person making the amendment Relationship to the case Patent Applicant address 1-4-5 Marunouchi, Chiyoda-ku, Tokyo Name (23
4) Sanyo Kokusaku Pulp Co., Ltd. President Tadami Nasu 4, Agent 100 Address 264 Suiraku Building, 1-4-5 Marunouchi, Chiyoda-ku, Tokyo
Room No. G214-286.1 (1st 6, Detailed explanation of the invention in the specification subject to amendment Z) Contents of amendment The following points in the specification will be amended. (1) Page 4, No. 1 The line ``Use radiation-curable release paper'' is corrected to ``Use radiation-curable release agent.'' (2) Page 6, line 15 [In the case of heat-curing method, release The text "K" on the back of the paper has been corrected to "In the case of the heat curing method, the release paper is placed on the back before the silicone cures." (3) On the 2nd page, line 12, the text "The release paper is used" has been changed to " (4) On page 15, lines 7 to 8, ``No moisture in the paper detected'' should be changed to ``No moisture in the paper detected''. (5) Page 18, line 8 from the bottom), ・Correct the phrase "curl film surface" to "curl is the film surface." (6) On the second line from the bottom of page 18, the phrase "Measurement is based on paper" has been corrected to "Measurement is based on paper." (7) On page 19, lines 2 and 6, the words "paper base" will be corrected to "paper base." (8) On page 20, lines 6 to 4, the phrase “Using a roller of 2Ky” was replaced with “Load of 2K
Correct it using the y roller. (9) On page 20, lines 7 and 8, "Peel resistance value ○" and "b" will be corrected to "Peel resistance value ■". OQ Page 20, line 14, "Peel resistance value ○" has been corrected to "Peel resistance value ■". (b) On page 20, line 15, replace the phrase ``Measure the ratio between peel resistance ○ and ○'' with ``peel resistance ■
Based on the ratio between and ■, we will correct it as follows. (2) Page 21, lines 15 to 16, ``Display as curl height.j'' will be corrected to ``Display as curl height.''

Claims (1)

[Claims] 1. Water vapor permeability on both sides of the paper base is 80q/m2.24
It is made of double-sided treated paper with a coating of hr/atl or less and whose moisture content is adjusted to a range of 5 to 10%, and a radiation-curable silicone resin layer is provided on one or both sides. A release paper characterized by: 2 Water vapor permeability 80 g/m2・24hr-at
2. The release paper according to claim 1, wherein the coating having a length of m or less is a synthetic resin treated layer. 3 Water vapor permeability 80 g/m2=24hr-at
Claim 1, wherein the coating of m or less is a metal foil bonding layer.
Release paper as described in section. 4 Water vapor permeability 809/m2・24hr-atm
The release paper according to claim 1, wherein the following coating is a pigment-coated layer.