JPH11348186A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film having a release layer surface not generating a defect such as a pinhole in a product even when an org. solvent type coating soln. is used for molding various coating films or sheets and having a (well releasable) release surface capable of releasing various self-adhesive coatings or sheets by proper force. SOLUTION: In a release film wherein a silicon release layer is provided on at least the single surface of a polyester film, foreign matter with a long diameter of 25 μm is not present in the polyester film, silicone release layer and silicon release layer surface per an area of 2 m<2> of the release film and the foreign matter with a long diameter of 5-below 25 μm is 10 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film, and more particularly, to a resin film or a ceramic slurry, which is useful for a protective film for a solvent-based pressure-sensitive adhesive film, or a resin-based solution such as a solvent-based pressure-sensitive adhesive solution. The present invention relates to a release film useful as a carrier film used for forming a ceramic sheet.

[0002]

2. Description of the Related Art Release films are currently widely used as protective films for various pressure-sensitive adhesive films or as carrier films used for forming various sheets and films. Natural rubber-based resin, synthetic rubber-based resin, acryl-based resin and the like are used for the various pressure-sensitive adhesive films. Examples of various sheets and coatings include vinyl chloride sheets, ceramic raw sheets, and adhesive coatings.
Release films have been used as carrier films when forming these sheets and coatings. For example, a vinyl chloride sheet for a marking sheet or the like can be formed by casting (coating) a vinyl chloride solution on a carrier film (release film) and then removing the solvent by heating. Further, after a slurry in which ceramic powder and a binder agent are dispersed in a liquid medium is cast (coated) on a carrier film, the liquid medium is removed by heating to form a green ceramic sheet.

[0003] Organic solvents have been used as solvents for the above-mentioned solutions and slurries, but aqueous solvents are mainly used at present from the viewpoint of safety against fire accidents and environmental problems.

However, resin sheets and ceramic sheets manufactured using carrier sheets, for example, are becoming increasingly thinner and the coating method is extremely precise. In many cases, an organic solvent is still used as a diluent from the viewpoint of ensuring the wettability.

However, even if an adhesive resin solution or a ceramic slurry containing an organic solvent having good wettability is used, if foreign matter is present in the film or on the film surface, the convex shape of the film surface due to the foreign matter will cause the resin sheet or the ceramic to have a convex shape. It is transferred to the green sheet in a concave shape. Then, the portion transferred in the concave shape becomes a shape defect of the resin sheet or the ceramic green sheet. In particular, in the case of a ceramic green sheet having a small film thickness, it is not limited to a simple recess but becomes a penetrated pinhole, which is a disadvantage that various defects occur in subsequent steps.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the disadvantages of the prior art, and to produce defects such as pinholes in products even when an organic solvent-based coating solution is used for forming various coatings and sheets. An object of the present invention is to provide a release film having a release layer surface having no release layer, and further having a release layer surface (having good releasability) which can be peeled off with an appropriate force to various pressure-sensitive adhesive films and sheets. .

[0007]

According to the present invention, there is provided a release film having a silicone release layer provided on at least one surface of a polyester film, wherein the release film has an area of 2 m ² per area. No foreign substance having a major axis of 25 μm or more is present in any portion of the inside of the polyester film, inside of the silicone release layer and on the surface of the silicone release layer, and foreign substances having a major axis of 5 μm to less than 25 μm are present.
This is achieved by a release film characterized in that the number is less than or equal to the number.

In the present invention, a polyester film is used as a film substrate. However, for applications requiring transparency, a polyester film having good transparency is preferably used, and a biaxially stretched polyester film is particularly preferred. For applications requiring light-shielding properties, it is preferable to use a polyester film containing an inorganic pigment, and a biaxially stretched polyester film containing a pigment such as TiO ₂ or SiO ₂ is particularly preferable.

The polyester constituting such a polyester film is preferably a crystalline linear saturated polyester comprising an aromatic dibasic acid component and a diol component, such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and the like.
Examples thereof include polyethylene-2,6-naphthalate.

The above-mentioned polyester has an average particle size of 0.1 as a lubricant in order to improve the slipperiness of the film.
About 01 to 25 μm, more preferably 0.01 to 2 μm
Organic or inorganic fine particles can be contained in an amount of, for example, 0.005 to 2% by weight, and more preferably 0.05 to 0.5% by weight. Specific examples of such fine particles include inorganic particles such as calcium carbonate, kaolin, silicon oxide, and barium sulfate, and organic particles such as cross-linked polystyrene resin particles, cross-linked silicone resin particles, and cross-linked acrylic resin particles. Alternatively, fine irregularities can be formed on the film surface by depositing fine particles from the catalyst residue used in the polyester synthesis reaction, and the film can have good sliding properties.

In the present invention, these fine particles are preferably subjected to particle size adjustment and coarse particle removal by a purification process before being added to the polyester. Industrial means of the purification process include, for example, a dry or wet centrifugation method, an air classification method and the like. It is particularly preferable to use two or more of these means in combination and to purify them stepwise.

Further, other modifiers can be added to the polyester. For example, a compound having a sulfonate group such as sodium dodecylbenzene sulfonate can be contained as an antistatic agent. Polyesters without these modifiers can also be used.

The polyester film of the present invention comprises:
It can be manufactured by a conventionally known method. For example, a biaxially stretched polyester film is obtained by drying a polyester, melting it with an extruder, and forming a die (for example, a T-die,
(I-die or the like), extruded onto a rotary cooling drum, quenched to obtain an unstretched film, and then stretched in the biaxial direction, and heat-fixed if necessary. The thickness of the film is not particularly limited, but is preferably 5 to 250 μm.

Further, the polyester film of the present invention has no foreign matter having a major axis of 25 μm or more per 2 m ² in area and has a foreign matter having a major axis of 5 μm or more and less than 25 μm.
Not more than

If a foreign material having a major axis of 25 μm or more per 2 m ^{2 of the} polyester film area is present, when the release film is used as a carrier film, a concave shape defect occurs in the obtained resin sheet or ceramic green sheet, or a pinhole occurs. , The quality of the resin sheet or the ceramic green sheet becomes poor, and the yield is significantly reduced.

Although a foreign substance having a size of 5 μm or more and less than 25 μm is allowed to some extent, depending on the state of existence in the film, a projection having a large projection height is formed on the surface of the film. May occur.
Therefore, it is preferable to eliminate as much as possible even 25μm less foreign matter than 5 [mu] m, is required to be less than 10 area 2m ² per polyester film is preferably 3 or less. When the number of foreign substances having a size of 5 μm or more and less than 25 μm is 10 or less per 2 m ^{2 of the} polyester film, when a release film is used as a carrier film, a probability that a pinhole is generated in the obtained resin sheet or ceramic green sheet is 10%. And this level of occurrence is acceptable.

Here, the foreign material in the present invention is a foreign material that can be optically detected by a visual inspection by the cross Nicol method. For example, inorganic or organic fine particles blended when producing a polyester film are aggregated. And coarse substances, and foreign substances generated or mixed in the process of producing the polyester film.

The size of the foreign matter in the present invention is measured as follows. That is, a foreign substance in the polyester film optically detected in the visual inspection by the cross Nicol method is separately observed with transmitted light using an optical microscope, and the maximum diameter of a portion observed as an optically abnormal range is determined. The size of the foreign matter. In addition, for example, when a film is stretched, a void (void) is formed around a foreign substance or the like which is agglomerated by agglomeration of fine particles. If the void is observed as an optically abnormal range, the size of the foreign substance is reduced. Include in. The number of foreign substances was measured by measuring the sample film in a size (210 mm length ×
The film was cut into a size of 148 mm in width and 310.8 cm ^{2 in} area, and the number of foreign substances in the entire area of the film was measured.

In the present invention, the silicone resin constituting the release layer is, for example, a polydimethylsiloxane having a vinyl group represented by the following formula (A) and a hydrogen silane-based compound represented by the following formula (B): It can be obtained by addition polymerization using a system compound as a catalyst.

[0020]

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In the above formula (A), m and n are numbers of 1 or more, where m is 1 to 100, n is 20 to 5000, and m + n
Is in the range of 30 to 5000, since the crosslinking reaction proceeds favorably and the layer becomes durable. Note that, in the above formula (A),

[0022]

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It is to be understood that does not mean block connection, but merely indicates that the sum of the respective units is m, n. Therefore,
Each unit in the above formula (A) may be randomly bonded, or may be block-bonded.

[0024]

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In the above formula (B), a and b are 1 or more, and a is 3 to 200, b is 1 to 20, and 5 ≦ a + b ≦
When it is in the range of 200, the crosslinking reaction proceeds favorably, and a durable layer is formed. Note that, in the above equation (B),

[0026]

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It should be understood that does not mean block connection, but merely indicates that the sum of the respective units is a and b. Therefore,
Each unit in the formula (B) may be randomly bonded, or may be block-bonded.

The ratio of the polydimethylsiloxane having a vinyl group and the hydrogensilane-based compound used in the above addition polymerization is such that the ratio of the hydrogensilane-based compound is 1.0 mol of the vinyl group in the vinyl group-containing polydimethylsiloxane. It is preferable that the content of the SiH group is 1.0 to 2.0 mol. The addition polymerization referred to here is
~Si-CH = a functional group at the molecular ends or in the molecular side chains represented by CH _2, and a functional group in a molecular end or a molecular side chain represented by _{H-Si~, ~Si-CH 2} CH 2 - Si ~
It is a polymerization reaction that becomes However, “to” in the above functional group indicates that the molecule is further connected.

The release layer in the present invention may contain various known additives as long as the object of the present invention is not hindered. As this additive, for example, ultraviolet absorbers, pigments,
Examples include an antifoaming agent, a pot life extending agent, a crosslinking agent, and the like.

In the present invention, a release layer is provided on at least one side of the polyester film. The release layer may be, for example, a polydimethylsiloxane having a vinyl group represented by the formula (A) or a compound represented by the formula (B). It can be provided by applying a coating liquid containing the indicated hydrogensilane-based compound and Pt-based compound to a film and heating to cause a drying and curing reaction. The conditions for this heating are, for example, 80-160 ° C. for 10-120 seconds, especially 100-1
It is preferable to set the temperature to 50 ° C. for 15 to 60 seconds, since the drying and curing reactions become sufficient.

As a method of applying the coating liquid, any known coating method can be applied, and examples thereof include a roll coater method and a blade coater method, but are not limited to these methods. Further, the coating liquid may be a coating liquid using an organic solvent, may be an aqueous coating liquid, it is preferably a solution in which polydimethylsiloxane or hydrogen silane compound is dissolved, for example, toluene and the like The coating liquid using an organic solvent is preferable.

In the present invention, there is no foreign matter having a major axis of 25 μm or more per area of 2 m ² , and no more than 10 foreign substances having a major axis of 5 μm or more and less than 25 μm per 2 m ² in the release layer. Things.

When foreign substances having a major axis of 25 μm or more per 2 m ^{2 of the} release layer are present, when the release film is used as a carrier film, a concave shape defect occurs in the obtained resin sheet or ceramic green sheet, or a pin defect occurs. Since holes are formed, the quality of the resin sheet or the ceramic green sheet becomes poor, and the yield is significantly reduced.

Although a foreign substance having a size of 5 μm or more and less than 25 μm is allowed to some extent, depending on the state of the release layer or the surface of the release layer, a projection having a large projection height is formed on the release film surface. In some cases, the same quality failure and yield reduction may occur. Therefore, it is preferable to also remove as much as possible 25μm less foreign matter than 5 [mu] m, the area 2m ² per
The number must be 0 or less, and preferably 3 or less. When the number of foreign substances having a size of 5 μm or more and less than 25 μm is 10 or less per 2 m ² , when a release film is used as a carrier film, the probability of occurrence of pinholes in the obtained resin sheet or ceramic green sheet is less than 10%, This level of occurrence can be tolerated.

Here, the definition of the above-mentioned foreign matter and the method of measuring the size thereof are the same as those for the above-described foreign matter of the polyester film.

In order to reduce the above-mentioned foreign matter on the release layer, particularly on the surface of the release layer, it is preferable to use, for example, an adhesive roll or an ultrasonic cleaner.

In the present invention, in order to enhance the adhesion between the polyester film and the release layer, it is preferable to provide an adhesive layer on at least one side of the polyester film and provide a release layer on the adhesive layer. For this adhesive layer, for example, a silane coupling agent can be preferably used. As this silane coupling agent, a general formula YS
those can be mentioned which are represented by i-X _3. Here, Y represents a functional group represented by, for example, an amino group, an epoxy group, a vinyl group, a methacryl group, a mercapto group, and X represents a hydrolyzable functional group represented by an alkoxy group.

The preferred thickness of the adhesive layer is 0.01 to
It is about 5 μm, particularly about 0.02 to 2 μm.
When the thickness of the adhesive layer is in the above range, the adhesion between the polyester film and the release layer becomes good, and the polyester film provided with the adhesive layer is difficult to block, so that it is hard to cause trouble in handling.

[0039]

EXAMPLES The present invention will be further described below with reference to examples. In addition, each characteristic value of the film was measured by the following method.

1. Peel strength A polyester adhesive tape (Nitto 31B) was adhered to the release layer surface of the polyester film, pressed with a 5 kg pressure roller and left for 20 hours, and the peel force between the release layer and the adhesive tape was measured with a tensile tester. .

2. Residual adhesion rate Polyester adhesive tape (Nitto 31B)
Cold rolled stainless steel sheet (SUS3
04) was measured, and the base adhesive strength (f) was measured.
₀ ). Further, the polyester pressure-sensitive adhesive tape was pressure-bonded to the surface of the sample film on which the release layer was coated with a pressure roller of 5 kg, left for 30 seconds, and then peeled off. Then, the peeled adhesive tape was stuck on the above stainless steel plate, and the peeling force of the stuck portion was measured to obtain a residual adhesive force (f). From the obtained basic adhesive strength (f ₀ ) and residual adhesive strength (f), a residual adhesive rate was determined using the following equation. Residual adhesion rate (%) = (f / f ₀ ) × 100

3. Measurement of the number of foreign substances The film sample was sized according to the standard size A5 of Japanese Industrial Standards (209 to 210 mm in length x 148 to 1 in width).
49 mm: an area of about 310 cm ² ), and the entire area of the film was visually inspected for foreign substances by the cross Nicol method. Next, the detected foreign matter in the sample film was observed by transmitted light using an optical microscope, and the maximum diameter of a portion observed as an optically abnormal range was defined as the size of the foreign matter. When a cavity (void) existing around the foreign matter is observed as an optically abnormal range, it is included in the size of the foreign matter. Further, the size of the foreign material was divided into those having a size of 25 μm or more and those having a size of 5 μm or more and less than 25 μm, and the number of foreign materials per A5 plate was measured.

[Example 1] 25 parts of 100 parts by weight of polyethylene terephthalate were used as a lubricant by an air classifier.
Alumina particles from which aggregated particles of μm or more have been removed 0.05
The polyester composition mixed with parts by weight is supplied to an extruder (a sintered metal filter is provided between the tip of the extruder and a die), and the molten polyethylene terephthalate is extruded into a film, and is cooled at 20 ° C. by rotary cooling. Touch the drum,
It was rapidly cooled to obtain an unstretched film. Next, the unstretched film was successively biaxially stretched at the stretching ratios shown in Table 1.
Heat-fixed under the conditions shown in (3), thickness 38 μm, light transmittance 88
% Biaxially oriented polyethylene terephthalate film. Table 1 shows the results of measuring the number of foreign substances in the film of the biaxially oriented polyethylene terephthalate film.

Next, a silicone resin coating solution having the following composition was applied to one surface of the biaxially oriented polyethylene terephthalate film at a coating amount (wet) of 8 g / m ^{2, and} was applied at 130 ° C. ×
Drying and curing treatment under the condition of 30 seconds and coating thickness 0.24μ
m was obtained.

<Silicone Resin Solution> A curable silicone (KS-847 (H), manufactured by Shin-Etsu Silicone Co., Ltd.) of the type in which a platinum catalyst is added to a mixed solution of polydimethylsiloxane and dimethylhydrogensilane and subjected to an addition reaction is methyl ethyl ketone , Dissolved in a mixed solvent of methyl isobutyl ketone and toluene, the total solids concentration is 3%
Was prepared.

This solution was applied to a biaxially oriented polyethylene terephthalate film (thickness: 38 μm) at 6 g / m ² (we
t) coating temperature, heating temperature 140 ° C, heating time 1
After a drying and curing reaction was performed in minutes, a release film was prepared and dried, and then wound up while removing foreign substances from the release layer with an adhesive roll. Table 1 shows the characteristics of the release film.

Example 2 A release film was prepared in the same manner as in Example 1 except that silica was used as a lubricant in the polyester film. Table 1 shows the characteristics of the release film.

Comparative Example 1 A release film was prepared in the same manner as in Example 1, except that the aggregated particles were not removed by an air classifier. Table 1 shows the characteristics of the release film.

Comparative Example 2 A release film was prepared in the same manner as in Example 1 except that no adhesive roll was used. Table 1 shows the characteristics of the release film.

[0050]

[Table 1]

[0051]

According to the present invention, even when an organic solvent-based coating liquid is used for forming various kinds of films and sheets, the product has a release layer surface which does not cause defects such as pinholes. It is possible to obtain a release film having a release layer surface that can be peeled off with a moderate force to the pressure-sensitive adhesive film or sheet (has good releasability).

Claims (1)

[Claims] 1. A release film having a silicone release layer provided on at least one surface of a polyester film, wherein the interior of the polyester film per 2 m ² of area of the release film, the interior of the silicone release layer, and the release of the silicone No foreign matter having a major axis of 25 μm or more is present on any part of the layer surface, and foreign matter having a major axis of 5 μm or more and less than 25 μm is 1
A release film, wherein the number is zero or less.