JPH09248890A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the stability with time of a release layer by forming a primer layer of a specified wall thickness crosslinked with a specified compound at least on one face of a polyester film and also forming a silicone release layer at least on one face of the primer layer. SOLUTION: A primer layer of thickness of 0.02-2μm crosslinked with a compound represented by formula I is formed at least on one face of a polyester film, and a silicone release layer is formed at least on one face of the primer layer. The tensile break strength S and the tensile elongation at break E of the silicone release layer are in the range represented by formula II. In formula I, X represents an alkoxy group, Y represents an reactive organic functional group containing an epoxy, amino, vinyl, methacryl, mercapto or alkoxy group. In formula II, S represents the tensile strength at break [gf/mm<2> ] of the silicone layer and E represents the tensile elongation at break [-] of the silicone release layer.

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, it is useful as a carrier film for molding resin sheets, resin coatings, and ceramic sheets molded using a solvent-based solution or slurry, or solvent-based. The present invention relates to a release film useful as a protective film for a pressure-sensitive adhesive film that is applied using the coating liquid.

[0002]

A release film is used as a carrier film when molding a resin sheet, a resin coating, a ceramic sheet or the like. For example, for a vinyl chloride resin sheet, after coating (casting) a release film (carrier film) with a coating liquid consisting of a vinyl chloride resin and a solvent,
The solvent is removed by heating to form a vinyl chloride sheet (for marking sheet, for example). The resin film is formed by applying a coating solution composed of a resin (such as an adhesive) and a solvent to the surface of the carrier film and then heating to remove the solvent.

The ceramic sheet is formed as a ceramic green sheet (ceramic green sheet) by, for example, applying a slurry prepared by dispersing ceramic powder and a binder agent in a solvent onto a carrier film and then removing the solvent by heating. To be done. The above-mentioned ceramic green sheet, resin sheet and the like are peeled and separated from the carrier film and subjected to cutting, printing and the like and then used for various purposes.

However, when a conventional release film is used as a carrier film to form the above ceramic green sheet or resin sheet, the release film is released by contact with various rolls while being conveyed in the process. A part of the layer (for example, a silicone-based release layer) is chipped off to cause the following problems.

[0005] 1. The releasability of the part of the release film where the release layer is missing disappears, and it becomes difficult to peel and separate the ceramic green sheet, the resin sheet or the like from the release film.

[0006] 2. The powdery release layer missing due to scraping adheres to the surface of the release layer of the release sheet, and this is transferred to the ceramic green sheet or resin sheet, resulting in uneven defects on the sheet, or in extreme cases. Through-hole defects occur in the sheet. This kind of defect is fatal to the ceramic green sheet, and even if a few pinholes are generated, the electrical characteristics are extremely deteriorated, and a capacitor or the like cannot be used as a product.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the drawbacks of the prior art, and to peel off various kinds of pressure-sensitive adhesive coatings, resin sheets, resin coatings, ceramic sheets, etc. with an appropriate force (mold release). And a release film having a release layer excellent in stability over time.

[0008]

The object of the present invention is, according to the invention, to at least one side of a polyester film,
0.02 to which a compound represented by the following formula (I) is crosslinked
A release film comprising a primer layer having a thickness of 2 μm, and a silicone release layer provided on at least one surface of the primer layer, the tensile release strength (S) and the tensile rupture of the silicone release layer. It is achieved by a release film having an elongation (E) in the range represented by the following formula (A).

[0009]

Embedded image Y—Si—X ₃ ... Formula (I) [wherein X is an alkoxy group, Y is an epoxy group, an amino group, a vinyl group, a methacryl group, a mercapto group or an alkoxy group] Shows a functional organic functional group. ]

[0010]

[Equation 2] 2 [mm ² / gf] ≦ 1 / (S × E) ≦ 50 [mm ² / gf] …… Formula (A) [In formula (A), S is the tensile breaking strength of the silicone release layer. [Gf / mm ² ] and E represent the tensile breaking elongation [-] of the silicone release layer. Hereinafter, the present invention will be described in detail.

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

The polyester constituting the polyester film is preferably a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene- 2,6-naphthalate and the like can be mentioned.

The above polyester has a mean particle size of 0.1 as a lubricant in order to make the film slippery.
Organic or inorganic fine particles of about 01 to 20 μm can be contained at a blending ratio of, for example, 0.005 to 20% 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 crosslinked polystyrene resin particles, crosslinked silicone resin particles and crosslinked acrylic resin particles. Alternatively, by depositing fine particles from the catalyst residue used in the polyester synthesis reaction, fine irregularities can be formed on the film surface, and the film can have good slipperiness.

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

The polyester film of the present invention is
It can be manufactured by a conventionally known method. For example, in a biaxially stretched polyester film, after drying polyester, it is melted in an extruder, and a die (for example, T-die,
(I-die, etc.) onto a rotary cooling drum, rapidly cooled to give an unstretched film, and then the unstretched film is stretched biaxially and optionally heat-set. The thickness of the film is not particularly limited, but is preferably 5 to 250 μm.

[Primer layer] In the present invention, the following formula (I) is provided on at least one side of the polyester film in order to enhance the adhesion between the polyester film and the release layer.
A primer layer having a wall thickness of 0.02 to 2 μm, which is obtained by crosslinking the compound represented by

[0017]

## STR3 ## Y-Si-X ₃ ...... formula (I)

In the above formula (I), X represents an alkoxy group, Y represents an epoxy group, an amino group, a vinyl group, a methacryl group, a mercapto group or a reactive organic functional group having an alkoxy group.

In the compound represented by the above formula (I),
X is an alkoxy group, but is preferably a methoxy group or an ethoxy group. It is particularly preferable that X is a methoxy group because the compound of formula (I) has a high rate of cross-linking and polymerizing when the primer layer is applied.

In the compound represented by the above formula (I), Y is preferably an epoxy group or a reactive organic functional group having an amino group, and particularly Y is a reactive organic functional group having an epoxy group. It is preferable that the adhesion between the primer layer and the polyester film is good and the effect of suppressing impurities in the polyester from migrating to the surface of the release layer is good. Examples of such a reactive organic functional group include a 3-glycidoxypropyl group and 3,4-
An epoxy cyclohexyl group etc. can be mentioned.

As the compound represented by the above formula (I),
For example, compounds represented by the following formula (II) and the following formula (III) are particularly preferable.

[0022]

Embedded image

[0023]

Embedded image

The primer layer in the present invention is prepared by, for example, dissolving or dispersing the compound represented by the formula (I) in water, and then coating it on at least one side of the polyester film,
For example, it can be applied by heating at a temperature of 120 to 150 [deg.] C. for 10 to 60 seconds to dry and remove water, and crosslinking and curing.

The thickness of the primer layer in the present invention is 0.02 to 2 μm. When the thickness is within this range, the adhesion between the polyester film and the release layer is good,
Further, since the polyester film provided with the primer layer is difficult to block, no trouble occurs in handling.

If a release layer is laminated on the surface of the polyester film without providing such a primer layer, even if the cohesive force of the silicone resin itself constituting the release layer is strong, P
Adhesion with ET is poor, and scraping occurs due to uprooting abrasive wear from the interface between PET and the release layer.

[Release Layer] In the present invention, a release layer containing a silicone resin as a main component is provided on at least one surface of the primer layer. As the silicone resin, a generally used silicone resin (for example, addition polymerization type silicone resin) is used as long as the tensile breaking strength (S) and the tensile breaking elongation (E) of the release layer are in the ranges represented by the following formula (A). , Polycondensation type silicone resin).

[0028]

[Equation 3] 2 [mm ² / gf] ≦ 1 / (S × E) ≦ 50 [mm ² / gf] …… Equation (A)

In the formula (A), S is the tensile breaking strength [gf / mm ² ] of the silicone release layer, and E is the tensile breaking elongation [-] of the silicone release layer.

The value of 1 / (S × E) of the release layer is 2 [mm ² /
If it is less than gf], the release layer is too soft to cause blocking when the release film is wound and cannot be wound into a roll, and blocking of the release film when wound into a roll is not possible. Therefore, unwinding becomes difficult, or unreacted substances existing in the release layer are transferred to the surface of the film adjacent to the release layer while the release film wound in a roll is stored, and then When using the release film, problems such as a serious defect occur.

Further, the value of 1 / (S × E) of the release layer is 50.
When it exceeds [mm ² / gf], the release layer is apt to undergo abrasive wear, and there arises a problem that the release layer is missing due to minute projections of the roll.

The release layer having a value of 1 / (S × E) within the range of the present invention can be obtained, for example, by the following method.

(1) A silicone resin that constitutes the release layer has a low crosslink density and does not lose its behavior as a linear molecule if possible.

(2) A low molecular weight compound (for example, silicone oil) that behaves as a plasticizing substance is added to the silicone resin constituting the release layer.

In the method (2), the plasticizing substance such as silicone oil is easily transferred from the release layer to the surface of the adjacent film, resulting in a problem when printing or the like on the surface of the film. There is. Therefore, it is usually preferable to use the method (1).

[Other compounding agents] Various known additives may be compounded in the release layer of the present invention within a range not impairing the object of the present invention. Examples of this additive include an ultraviolet absorber, a pigment, a defoaming agent, a pot life extender, and a cross-linking agent.

[0037]

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. Peeling strength A polyester adhesive tape (Knit-31B) is attached to the release layer surface of a polyester film, and the pressure is applied with a 5 kg pressure roller and left for 20 hours, after which the peeling force (R _f0 ) between the release layer and the adhesive tape is tested by a tensile tester. It was measured at.

The preferred range of peel strength is 2 to 30 g.
/ In, 2 to 10 g / in, especially 2 to 10 g
/ In. If the peel strength is less than 2 g / in, the resin sheet or the like may peel off from the release film when the laminated sheet in which the resin sheet or the like is laminated on the release film is wound up. The peel strength is 3
When it exceeds 0 g / in, peeling may be difficult when the resin sheet or the like is peeled off from the laminated sheet and used, which is not preferable.

2. Residual Adhesion Rate Polyester adhesive tape (Knit-31B) JIS /
Cold rolled stainless steel sheet (SUS3
The peeling force after sticking to 04) is measured, and the basic adhesive force (f
₀ ). Further, the polyester adhesive tape is pressure-bonded to the surface of the sample film coated with the release layer with a pressure roller of 5 kg, and left for 30 seconds, and then the pressure-sensitive adhesive tape is peeled off. Then, the peeled adhesive tape is stuck on the above stainless steel plate, and the peeling force of the stuck portion is measured, and is defined as a residual adhesive force (f). From the obtained basic adhesive strength (f ₀ ) and residual adhesive strength (f), the residual adhesive rate is determined using the following equation.

[0041]

## EQU4 ## Residual adhesion rate (%) = (f / f ₀ ) × 100

It should be noted that the higher the residual adhesion rate is, the more preferable.
A preferable range is 85% or more, and particularly 90% or more. When the residual adhesion ratio is less than 85%, for example, when the release film is wound into a roll and stored, the components constituting the release layer are transferred to the surface of the adjacent film (so-called back surface transfer).
However, this is not preferable because the release layer may have poor properties or the adhesive property of the surface of the adjacent film may be poor.

3. Tensile breaking strength / elongation of release layer The same silicone compound or silicone resin used for coating the release layer of Examples or Comparative Examples was applied to the surface of the polyester film so that the thickness of the film was 250 μm. Then, the coating film was peeled and separated from the polyester film to prepare a sample having a width of 10 mm, a length of 150 mm and a thickness of 250 μm. Then, using an Instron type tensile tester, a tensile load / tensile elongation curve of this sample was measured with a chuck interval of 100 mm, a tensile speed of 10 mm / min, and a chart speed of 10
The tensile strength at break and the tensile elongation at break were determined from the obtained results under the condition of 0 mm / min. The tensile breaking elongation is
It is a value obtained by dividing the elongation [mm] at break by the chuck interval (100 mm).

4. Abrasion resistance 100 with rubbing tester (Otsubo Rika Kogyo Co., Ltd.)
A load of g / cm ² was applied and after 300 reciprocating operations, the peeling load on the rubbing surface was measured.

Example 1 Polyethylene terephthalate (having an inherent viscosity of 0.65 di / g measured in O-chlorophenol at 25 ° C. and containing SiO ₂ particles having an average particle size of 0.17 μm in an amount of 0.05% by weight) was used. It is melt extruded onto a rotary cooling drum maintained at 20 ° C. to obtain an unstretched film having a thickness of 950 μm, and then the unstretched film is machined in the machine axial direction (longitudinal direction).
Was stretched 3.5 times to give a uniaxially stretched film, and then a 5 wt% aqueous solution of 3-glycidoxypropyltrimethoxysilane was applied to one side of the uniaxially stretched film by a kiss coating method, and the temperature was 105 ° C. for 10 seconds. It was dried under the conditions. The average coating amount at this time was 100 mg / m ² in terms of solid content.
Then stretched laterally 3.9 times at 105 ℃, 220 ℃
To obtain a biaxially stretched polyester film having a base film having a thickness of 75 μm coated with a primer layer having a thickness of 0.025 μm on one surface.

Next, a toluene solution (solid content concentration: 3% by weight) of an addition polymerization type silicone compound (TPR-6712 manufactured by Toshiba Silicone Co., Ltd.) was applied to the surface of the biaxially stretched polyester film coated with the primer layer. Pt catalyst (manufactured by Toshiba Silicone Co., Ltd. CM-670) was used as TPR-6712.
1 part by weight per 100 parts by weight of the solid content of the coating solution was applied at a coating amount (wet) of 6 g / m ² and dried at 140 ° C. for 1 minute to carry out an addition polymerization reaction. A release film having a mold layer thickness of 0.2 μm was obtained. The characteristics of this release film are shown in Table 1.

Comparative Example 1 A release film was prepared in the same manner as in Example 1 except that the primer layer was not provided. The characteristics of this release film are shown in Table 1.

[Comparative Example 2] Mold release was carried out in the same manner as in Example 1 except that a silicone resin having a branched main chain (KS-839 manufactured by Shin-Etsu Silicone Co., Ltd.) was used in place of the addition polymerization type silicone compound. I made a film. The characteristics of this release film are shown in Table 1.

[0049]

[Table 1]

As is clear from Table 1, the release film of the present invention shown in Example 1 was excellent in peel strength, residual adhesiveness and abrasion resistance of the release layer.

[0051]

The release film of the present invention comprises a polyester film having a specific primer layer on at least one surface thereof, and further having at least one surface of the primer layer provided with a specific release layer. It has excellent wettability when using a water-based coating liquid for sheet and sheet molding, and excellent releasability from various resin sheets, resin coatings, ceramic sheets, etc., so it is a protective film for adhesive coatings, resin sheets, resin coatings, ceramic sheets. It is useful for a carrier film for molding such as.

Claims (1)

[Claims] 1. A compound of the following formula (I) is crosslinked on at least one side of a polyester film.
A release film comprising a primer layer having a thickness of 2 to 2 μm, and a silicone release layer provided on at least one surface of the primer layer, wherein the silicone release layer has a tensile breaking strength (S) and Tensile breaking elongation (E) is the following formula (A)
A release film characterized by having a range shown by. Embedded image Y—Si—X ₃ ... Formula (I) [wherein X is an alkoxy group, Y is an epoxy group, an amino group, a vinyl group, a methacryl group, a mercapto group or an alkoxy group] Shows a functional organic functional group. ] [Equation 1] 2 [mm ² / gf] ≤ 1 / (S × E) ≤ 50 [mm ² / gf] ... Formula (A) [In Formula (A), S is the tensile rupture of the silicone release layer. The strength [gf / mm ² ] and E indicate the tensile elongation at break [-] of the silicone release layer. ]