JPH0321585B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a release paper used for adhesive sheets, adhesive tapes, adhesive sheets, adhesive tapes, synthetic resin film castings, etc., and a method for manufacturing the same. [Prior art and problems] Conventionally, release paper has been prepared by adding clay binder, polyvinyl alcohol,
It is well known that a starch or polyethylene resin layer is provided, and a release agent layer such as silicone is provided on at least one surface of the filler layer. However, when using the above-mentioned release paper to produce adhesive sheets, adhesive tapes, adhesive tapes, and adhesive sheets, or when producing synthetic resin films by casting, the following problems tend to occur. In other words, a clay binder is used as a general sealant layer.
Release paper using polyvinyl alcohol or starch has excellent heat resistance, but since a water-based material such as clay binder or starch is applied to the base paper and then air-dried, the dimensional stability against moisture is poor. It is significantly lower than the base paper before coating. Further, in a release paper coated with the above filler and further coated with a release agent, the surface of the release paper has insufficient gloss and smoothness. In addition, with release paper coated with polyethylene resin as a filler layer by melt extrusion lamination, the gloss and smoothness of the release paper surface can be maintained at a somewhat high level by making the surface of the cooling roll mirror-finished during lamination. However, it is insufficient in terms of moisture absorption curl and heat resistance. If the moisture absorption and dimensional stability of the release paper is poor, moisture absorption and desorption will occur in the release paper depending on the humidity of the atmosphere, causing curling of the product or causing problems between the release paper and the surface base laminated on it. In some cases, the product floats up during the process, causing so-called tunneling, which reduces the commercial value and even makes it impossible to put it to practical use. In addition, if the surface of the release paper is poor in gloss or smoothness, use an adhesive film,
The shape of the surface of the release paper is transferred to the adhesive of the adhesive sheet, and even after the release paper is removed, the gloss and smoothness of the adhesive surface deteriorates, resulting in product defects. In addition, if a filler with poor heat resistance (for example, polyethylene) is used, a release agent such as silicone may be applied, and when it is heated and cured, a foaming phenomenon will appear between the paper and the filler layer, resulting in a good condition. This will not provide a clear release paper surface. As a result, the release performance, which is the most important function of release paper, becomes uneven and inadequate. Among the properties required of the above-mentioned release paper, curl resistance and dimensional stability against moisture are important as an element to prevent tunneling between the release paper and the surface base material. In order to improve this moisture absorption dimensional stability, various proposals have been made as shown below. (a) A paper mixed with a material that exhibits little or no expansion and contraction due to moisture, such as water-resistant mechanical pulp containing a large amount of lignin, glass fiber, or synthetic fiber, is used as the base paper. (b) Use paper with a material that does not expand or contract at all due to moisture, such as aluminum foil, attached to at least one side of the base paper or between the base papers. (c) Apply a moisture-proof film to the back side of the release paper. (d) Humidify the release paper in advance, or apply humidification appropriate to the atmosphere during the manufacturing process. However, mechanical pulp, glass fiber,
Paper containing synthetic fibers has a significantly reduced surface quality. Therefore, in order to coat the surface of the base paper with a uniform release agent layer, it is necessary to use a method such as increasing the thickness of the sealant layer, which creates new problems in terms of operation and cost. Furthermore, blending glass fibers, synthetic fibers, etc., laminating aluminum foil, etc., or coating a moisture-proof film on the back side of the release paper results in a significant increase in cost. Furthermore, when humidifying the paper, controlling the moisture in the release paper becomes complicated, and the dimensional stability is significantly reduced due to repeated moisture absorption and desorption. Furthermore, in recent years, there has been a demand for release papers that have very good moisture absorption dimensional stability, high gloss, high smoothness, and excellent heat resistance. However, as mentioned above, it has been difficult to satisfy these characteristics with conventional release paper. [Means and effects for solving the problems] The present inventors have developed a paper that has moisture absorption dimensional stability, high gloss and high smoothness, and has excellent heat resistance, which was difficult to achieve with the conventional release paper mentioned above. We conducted various studies in order to produce a release paper. As a result, we used tension-drying paper, which is a paper with excellent moisture absorption and dimensional stability, as the base paper for the release paper, and added a "filling agent mainly composed of pigments and adhesives" to the base paper.
By coating the coating liquid while it is in a fluidized plastic state and drying it while bringing the coated surface into close contact with a heated surface that has a specular gloss, the moisture absorption and dimensional stability is higher than that of the paper before applying the filler. I found it to be even better. Furthermore, since the filler layer had specular gloss, the release agent could be applied uniformly, so that a release paper with a high gloss and high smoothness on the surface of the paper was obtained. In addition, since the main component of the eye blocker is an inorganic pigment,
A release paper was obtained which also had high heat resistance. Note that the tension-dried paper described here is paper that shrinks significantly in the horizontal direction in the drying section during paper making, and is dried by applying tension in the horizontal direction to suppress the shrinkage of the paper. For example, a wet paper web is tightly attached to the surface of a large diameter dryer cylinder with a highly polished surface, such as a Yankee dryer, using a pressure roll.
This is paper whose shrinkage in the horizontal direction is suppressed by drying, and includes so-called single-gloss paper. Furthermore, when single-gloss paper is used as the base paper, the difference in unevenness between the front and back surfaces becomes a drawback. This means that when a release paper is rolled up together with a surface substrate in the production of adhesive sheets, adhesive tapes, adhesive sheets, adhesive tapes, or film casting products, the unevenness on the back side of the release paper may affect the quality of the product. This may cause adverse effects. However, it has been found that the problem can be solved by providing the above-mentioned filler layer on the non-glossy surface (non-smooth surface) of the glossy paper. That is, the present invention applies 5g of "filling agent coating liquid mainly composed of pigment and adhesive" to the non-glossy surface (non-smooth surface) or both sides of tension-dried paper with a water immersion elongation of 2.0% or less in terms of solid content. /m ² or more, and after drying while the coated surface is brought into close contact with a surface with specular gloss, a release agent layer is provided on the upper surface of the coated surface, and the surface of the release agent layer has a 20 degree specular gloss. 10% or more, and the maximum height of surface roughness is 0.8 μ (standard length 0.25 mm) or less, and a method for producing the same, which is difficult to achieve with conventional release paper according to the present invention. It is possible to obtain a release paper having moisture absorption dimensional stability, high gloss, high smoothness, surface properties, and excellent heat resistance. The present invention will be explained in more detail below using the drawings. 1 and 2 are cross-sectional configuration diagrams of a typical release paper of the present invention, and FIGS. 3 and 4 are cross-sectional configuration diagrams showing a modification of FIG. 1 using the present invention. . In the figure, 1 is a release paper base material, 2 is a filler layer containing pigment and adhesive as main components and dried while adhering to a mirror-glossy surface, 3 is a release agent layer, and 4 is a polyolefin resin or The other filler resin layers, 5, indicate the back resin layer. Tension-dried paper is used as the base paper in the present invention. That is, in paper making, paper is used which is manufactured by applying tension to suppress the contraction of the wet paper web in the horizontal direction during drying and drying it. Good hygroscopic dimensional stability cannot be obtained unless strain-dried paper is used. In order to obtain even better moisture absorption dimensional stability, the water immersion elongation in the horizontal direction of the tension-dried paper should be
Must be 2.0% or less. Preferably 1.0%
The following water immersion elongation is good. On the other hand, when tension-dried paper with a water immersion elongation in the horizontal direction exceeding 2.0% is used as a base paper, the non-glossy surface (non-smooth surface) or both sides of the base paper may contain pigments and adhesives as main components. Even if, after coating the filler layer 2'', the coated surface is brought into close contact with a mirror-glossy surface and allowed to dry, the moisture absorption dimensional stability of the release paper will become insufficient. The strain-dried paper is a so-called single-gloss paper in which a wet paper web is brought into close contact with the surface of a large-diameter dryer cylinder with a highly polished surface using a pressure roll, and tension-dried paper is produced by suppressing the horizontal shrinkage of the paper web. Paper is used. In addition, the large diameter dryer cylinder mentioned above is
It is also possible to use paper produced by strain drying with a paper machine having a drying section combined with this combination or a drying section combined with a multi-barrel dryer. Furthermore, it is also possible to use paper manufactured by so-called press drying, which is a method of drying the paper web in a high moisture range of 40 to 70% at a temperature of 100° C. or higher by applying external pressure. Furthermore, glass fiber, synthetic fiber, synthetic pulp, etc. may be mixed as the base paper raw material. Further, during the manufacturing process of the base paper, chemicals such as a water resistance agent, a paper strength agent, a heat resistance agent, or a dye can be added internally, or the surface can be treated with chemicals using a device such as a size press. In addition, in the present invention, a "filler layer 2 mainly composed of pigment and adhesive" is coated on the non-glossy surface (non-smooth surface) or both sides of the tension-dried paper, and the coated surface is further converted into a mirror-glossy surface. It must be allowed to dry while keeping it in close contact with the surface. By the above method, a surface with high gloss and high smoothness can be obtained, and furthermore, better moisture absorption dimensional stability can be obtained than with the base paper. On the other hand, even if a filler with a composition similar to that of the present invention is used, if the coated surface is dried by a method that does not depend on the surface having specular gloss, both gloss and smoothness may become insufficient. cormorant. Furthermore, the moisture absorption dimensional stability of the paper coated with the filler is significantly lower than that of the base paper. In addition, tension-dried paper has superior moisture absorption and dimensional stability compared to general high-quality paper, but it is also possible to improve the glossiness of the surface simply by drying it while bringing the filler-coated surface into close contact with a mirror-glossy surface. Not only the smoothness is increased, but also the moisture absorption dimension and stability of the tension-dried paper are improved. Examples of pigments that are one component of the filler in the present invention include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate, zinc white, and satin white. These may be used alone or in combination. Adhesives that are other components of fillers include casein, protein adhesives, conjugated diene polymer latexes such as styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers, other synthetic resin latexes, and starch. , carboxymethylcellulose, hydroxyethylcellulose, and other cellulose derivatives may be used alone or in combination. In addition, the above filler may contain an internal mold release agent (oil, fat, silicone resin, etc.) or
Waterproofing agents, ultraviolet absorbers, dyes, etc. may be added. In addition, in order to obtain good gloss, smoothness, and barrier properties, the coating amount of the "filler layer 2 whose main components are pigments and adhesives" should be calculated in terms of solid content.
Must be 5g/m2 or ^more . The coating amount is preferably 15 to 40 g/m ² in terms of solid content. on the other hand,
If the coating amount is less than 5 g/m ² , good gloss, smoothness and barrier properties cannot be obtained. In addition, the release agent used in the present invention may be a silicone-based release agent that is used as a conventional release agent.
Alkyd-based strippers can be used. Of the silicone types, addition reaction silicones are most desirable. Condensation reaction type silicones may result in insufficient curing properties of the silicone coating. In order to obtain a release paper with even better gloss and smoothness, the 20 degree specular gloss of the release layer surface should be 10%.
As shown in Figure 5, the maximum height of the surface roughness is 0.8μ.
(Standard length 0.25mm) or less. Preferably 20 degree specular gloss of 15% or more, maximum height 0.5μ
(Reference length 0.25mm) or less is preferable on the surface of the release agent layer.
On the other hand, the 20 degree specular gloss is less than 10% and the maximum height is
If it exceeds 0.8μ (standard length 0.25mm), a release layer surface with good gloss and smoothness cannot be obtained. As a result, the gloss and smoothness of the adhesive surface of the adhesive film sheet deteriorates. To obtain the release paper of the present invention, first, a paper machine having at least one large-diameter dryer cylinder, such as a Yankee dryer, is used to produce tension-dried paper in which drying shrinkage in the horizontal direction of the paper web is suppressed. Furthermore, the base paper may be subjected to super calendering to make the paper surface smooth and dense. Thereafter, a "filling agent mainly composed of pigments and adhesives" is applied to the non-glossy surface (non-smooth surface) or both sides of the above-mentioned tension-dried paper, and while the coated surface is in a fluid plastic state, it becomes mirror-like. Dry while adhering to a glossy surface heated to 80°C to 150°C. In this case, after applying the filler coating solution, the coated surface is immersed in a coagulant solution or the coated layer is brought into a semi-solidified state by UV irradiation, and then the mirror-glossy surface is coated. It is also possible to improve the releasability of the coating layer from a surface with specular gloss by drying it in close contact with the coating layer. In addition, when using tension-dried paper with a large difference in surface smoothness between the two sides, such as single-gloss paper, as a base paper, apply the filler on the rough surface (non-glossy side in the case of single-gloss paper) using the method described above. It is desirable to do so. Next, a release agent is applied onto the filler layer 2 and thermally cured to form release paper. Furthermore, in the release paper of the present invention, as shown in Fig. 1, the "blocking agent layer 2 mainly composed of pigment and adhesive" and the release agent layer are dried while being brought into close contact with a mirror-glossy surface. It may be provided on either side or on both sides as shown in FIG. Further, as shown in Fig. 3, the above-mentioned layer is provided on one side of the tension-dried paper, and on the other side, a polyolefin resin layer as a sealing layer 4 and a release agent layer, or a polyvinyl alcohol or starch layer as a sealing agent layer 4 are provided on the opposite side. , SBR and/or a clay layer and a release agent layer may be provided. Further, as shown in Fig. 4, a layer as shown in Fig. 1 is provided on one side of the tension-dried paper, and a layer made of polyvinylidene chloride, polystyrene, styrene-butadiene copolymer, cellulose derivative, and/or polyolefin resin is provided on the other side. A back resin layer 5 may be provided. As the polyolefin resin, high-pressure low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, etc. are used alone or in a mixed system. [Example] Next, the present invention will be explained in more detail with reference to Examples. Example 1 A filler consisting of clay: protein adhesive: synthetic resin latex (mixing ratio 100:5:15) was applied to ^one side of tension-dried paper with a water immersion elongation of 0.9% in the horizontal direction and a basis weight of 100 g/m2. Apply the liquid at 30g/ ^m2 in terms of solid content,
It was dried while being brought into close contact with a mirror-glossy surface heated to 100 to 110°C. Furthermore, addition reaction silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KS772) is added to the above coating layer.
is coated and heat cured to form a release agent layer, resulting in a 20 degree specular gloss of 28%, maximum height of 0.3μ (standard length 0.25mm)
A release paper having the following properties was obtained. Furthermore, when a pressure-sensitive adhesive sheet was prepared using this release paper, the gloss and smoothness of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet were very good as shown in the table. Further, the curling resistance, which indicates moisture absorption dimensional stability, was also good, and the heat resistance was also excellent. Example 2 The same filler coating solution as in Example 1 was applied to one side of a tension-dried paper with a water immersion elongation of 1.0% in the horizontal direction and a basis weight of 60 g/m ² at a solid content of 30 g/m ² . It was dried while being brought into close contact with a mirror-glossy surface heated to ~110°C. Furthermore, an addition-reactive silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KS772) is applied to the above coating layer, and heat cured to form a release agent layer. A release paper having a diameter of 0.25 mm was obtained. When tested under the same conditions as in Example 1, the adhesive surface of the adhesive sheet always had good gloss and smoothness.
Furthermore, similar to Example 1, the curl resistance and heat resistance were excellent. Comparative Example 1 A polyethylene resin was laminated to a thickness of 20μ by melt extrusion lamination on one side of general high-quality paper with a water immersion elongation in the horizontal direction of 2.6% and a basis weight of 100g/ ^m2 , and then an addition reaction type silicone ( A release paper was prepared by applying KS772 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) and heat curing to form a release agent layer. In a test conducted under the same conditions as in Example 1, the gloss and smoothness of the peeled surface were insufficient, and therefore the surface properties of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet were poor. Note that curl resistance and heat resistance were significantly inferior. Comparative Example 2 A release paper was prepared by performing the same treatment as in Comparative Example 1 on one side of a strain-dried paper having a water immersion elongation in the horizontal direction of 0.9% and a basis weight of 100 g/m ² . In a test conducted under the same conditions as in Example 1, the gloss and smoothness of the peeled surface were significantly inferior, and therefore the surface properties of the adhesive surface were significantly inferior. It also has poor curl resistance,
Heat resistance was also significantly inferior. Comparative Example 3 Clay:polyvinyl alcohol (compounding ratio 100:30) was applied as a filler on both sides of mechanical pulp-compounded paper with a water immersion elongation of 1.8% in the horizontal direction and a basis weight of 90 g/ ^m2 , and the paper was dried with air. After that, the surface quality was improved through a supercan render. Furthermore, addition reaction silicone (manufactured by Shin-Etsu Chemical Co., Ltd.,
A release paper was prepared by applying a release agent (trade name: KS772) and forming a heat-cured release agent layer. In a test conducted under the same conditions as in Example 1, the heat resistance was good, but the curl resistance was poor, and the surface properties of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet were significantly poor. Comparative Example 4 A release paper was prepared by performing the same treatment as in Example 1 on ordinary high-quality paper having a water immersion elongation of 2.6% in the horizontal direction and a basis weight of 100 g/m ² . In a test conducted under the same conditions as in Example 1, the surface properties and heat resistance of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet were good, but the curl resistance was significantly poor. Regarding the evaluation measurement method in the present invention,
A brief explanation is given below. The measurement of water immersion elongation in the present invention is conducted by JAPA
According to method A of TAPPI Paper Pulp Test Method No. 27 "Water immersion elongation test method for paper and paperboard". The test piece was immersed in water for 1 hour. The 20 degree specular gloss was measured in accordance with JIS Z8741 "Glossiness measurement method".
The maximum height of surface roughness is based on JIS B0601 "Surface Roughness", and is the roughness of the part extracted by the standard length (0.25 mm) from the roughness curve recorded by the surface roughness meter as shown in Figure 5. The maximum height was determined using the curve. In addition, as a surface test of the adhesive side of the adhesive sheet, a pressure-sensitive adhesive sheet was prepared by coating a release paper with an adhesive and laminating a film sheet to the coated surface. Next, after peeling off the release paper from the adhesive sheet, the surface condition of the adhesive surface transferred to the film sheet was observed. In addition, as a test for curl resistance, an adhesive sheet was prepared using the method described above, and the adhesive sheet was heated at 20°C.
The curled state of the adhesive sheet was observed after being left at 80% RH for 24 hours. Note that this curl resistance indicates the superiority or inferiority of the moisture absorption dimensional stability of the release paper.
As for heat resistance, the release paper was heated at 160°C for 10 minutes, and the roughness of the release surface or the presence or absence of foaming was examined.

[Table] Notes ○Good △Slightly poor ×Poor

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional diagrams of a typical release paper of the present invention, and Figure 1 shows a release paper whose main components are pigments and adhesives, which are dried while being brought into close contact with a mirror-glossy surface. FIG. 2 is an enlarged sectional view illustrating the case where the filler layer/release agent layer is provided on one side of the tension-dried paper, and FIG. Figures 3 and 4
The figure is a cross-sectional configuration diagram showing a modification of the one shown in FIG. 1 using the present invention, and FIG.
Figure 4 is a cross-sectional view of a case where a coating layer as shown in Figure 2 is provided and a polyolefin resin or a filler layer/release agent layer other than polyolefin resin is provided on the opposite side. FIG. 4 is a cross-sectional view when a back resin layer is provided on the opposite surface in FIG. 3;
FIG. 5 is a diagram showing a method for determining the maximum height from a roughness curve recorded by a surface roughness meter. 1...Tension-dried paper, 2...A sealing agent layer "mainly composed of pigment and adhesive" that is dried while being in close contact with a mirror-glossy surface, 3...Addition-reactive silicone release agent, 4 ...Seal blocker layer, 5...Back resin layer.

Claims (1)

[Scope of Claims] 1. A filler coating liquid containing pigment and adhesive as main components is applied to the non-glossy surface (non-smooth surface) or both sides of tension-dried paper with a water immersion elongation of 2.0% or less in the horizontal direction. It is coated in an equivalent amount of 5 g/m ² or more, a release agent layer is provided on the coated surface, and the 20 degree specular gloss of the surface of the release agent layer is 10% or more, and the surface roughness is 10% or more. A release paper characterized by a maximum height of 0.8μ or less. 2. The release paper according to claim 1, wherein the release agent is an addition reaction silicone. 3 Apply a filler coating liquid containing pigments and adhesives as main components to the non-glossy (non-smooth) surface or both sides of tension-dried paper with a water immersion elongation of 2.0% or less in the horizontal direction, in an amount of 5 g/m in terms of solid content. ² or more are coated, a release layer is provided on the coated surface, and the surface of the release agent layer is
A method for producing a release paper characterized by having a 20 degree specular gloss of 10% or more and a maximum surface roughness of 0.8μ or less. 4. The method for producing a release paper according to claim 3, characterized in that an addition reaction silicone is used as the release agent.