JP2003301051A - Polyester film for releasing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film which is useful as the base film for a releasing film and has excellent properties such that, when a ceramic slurry is placed on the releasing film, the irregularities in the thickness of the placed ceramic layer are remarkably reduced and, simultaneously, the formation of pinholes in the ceramic slurry layer can be inhibited. <P>SOLUTION: The polyester film for a releasing film is characterized in that it has a tensile modulus (EMD) in the film lengthwise direction of ≥4.0 GPa. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film base film, and more particularly to a release film base film used for molding a green sheet used in a ceramic multilayer capacitor.

[0002]

2. Description of the Related Art Conventionally, a release film having a polyester film as a base material has been used as a carrier film for forming a green sheet for a ceramic laminated capacitor, and in recent years, with the miniaturization of capacitors accompanying the miniaturization of electronic devices. The ceramic green sheet itself is thinned. In such a situation, when there is a large variation in the thickness of the ceramic layer on the ceramic green sheet coated with the ceramic slurry on the release film, the variation in the capacitance when a multilayer ceramic capacitor is formed using such a ceramic green sheet. It may cause it and is a real harm. Therefore, it is necessary to provide a polyester film for a release film that reduces the variation in thickness of the ceramic layer.

Further, when the height of the coarse projections on the surface of the release layer is high in the release film, there are problems such as repelling of the slurry at the time of coating the ceramic slurry, generation of pinholes, and breakage of the green sheet when peeling the green sheet. This may occur, and it may be necessary to take measures such as reducing the height of coarse protrusions of the release film, particularly reducing the height of coarse protrusions of the base film. Furthermore, if the height of the coarse protrusions of the base film is significantly reduced, or if the average roughness of the base film is significantly reduced, blocking occurs when the release layer is installed and wound, and the release film is conveyed. Problems such as sexual deterioration may occur.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the problem to be solved is, for example,
When the ceramic slurry is placed on the release film,
It is an object of the present invention to provide a polyester film capable of reducing the thickness unevenness of a ceramic layer and suppressing pinholes in the ceramic slurry layer.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a film having a specific constitution can easily solve the above-mentioned problems, It came to completion.

That is, the gist of the present invention resides in a polyester film for a release film, which has a tensile elastic modulus (E _MD ) in the longitudinal direction of the film of 4.0 GPa or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester in the present invention refers to a polymer containing an ester group obtained by polycondensation of a dicarboxylic acid and a diol or a hydroxycarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, succinic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2,6-naphthalenedicarboxylic acid, 1,4-
Cyclohexanedicarboxylic acid, etc. as the diol,
Ethylene glycol, 1,3-propanediol, 1,6
-Hexanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol,
Examples of hydroxycarboxylic acids such as polyethylene glycol include p-hydroxybenzoic acid and 6-hydroxy-2.
-Naphthoic acid etc. can be illustrated respectively.

Typical examples of such polymers include polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. These polymers may be homopolymers,
Moreover, what copolymerized the 3rd component may be sufficient. As the film of the present invention, a biaxially stretched film is preferably used from the viewpoint of excellent strength and dimensional stability, but an unstretched or at least one stretched polyester film is used unless it exceeds the gist of the present invention. You can also The polyester film of the present invention needs to have a tensile elastic modulus (E _MD ) in the longitudinal direction of the film of 4.0 GPa or more. When the tensile elastic modulus is less than 4.0 GPa, the gap between the slot die generally used when applying the ceramic slurry and the polyester film provided with the release layer as the base material varies. This may cause variations in the thickness of the ceramic layer as a result, which is not preferable.

Further, it is desirable that Rmax of the film surface (A side), which is the surface on which the release layer is usually placed, is 500 nm or less and SRa (A) is 30 nm or less, and Rmax is 200 nm or less. Is particularly desirable. When Rmax of the release layer installation surface is larger than 500 nm, or when SRa (A) is larger than 30 nm,
When the release layer is installed, the release layer may be missing (pinhole) or coating unevenness may occur, which may not be practically preferable. Further, the center surface average roughness SRa (C) of the film surface (C surface) opposite to the A surface is 10 to 50 nm, particularly 15 to 30 n.
It is preferably m. When SRa (C) is less than 10 nm, problems such as blocking and deterioration of transportability of the release film may occur when the release film is formed, which is not preferable. Also, SRa (C) is 50
If it exceeds nm, transfer of surface protrusions to the release layer installation surface,
So-called show-through may occur, which is not preferable. Furthermore, even if the film surface is significantly scratched, it may cause the pinholes described above, and it is desirable that the film has high scratch resistance.

Rmax of such polyester film,
In order to make SRa within the above range, inert fine particles, for example, inorganic particles such as silica, calcium carbonate, kaolin, titanium oxide, aluminum oxide, barium sulfate and zeolite, or organic particles such as silicone resin, crosslinked polystyrene and acrylic resin. It is preferable to mix the above in the film alone or in the form of a mixture. In this case, the average particle size, the addition amount, and the particle size distribution of the particles used are not particularly limited as long as they do not depart from the gist of the present invention, but the average particle size is 0.1 to 4.0 μm, Addition amount is 0.01 to 3.0
It is preferable that the weight% and the particle size distribution have smaller dispersions. In particular, in order to bring the Rmax and Ra of the A surface into the above-mentioned ranges, it is preferable to add aluminum oxide, and when the addition concentration is within the range of 0.3 to 3.0% by weight, the scratch resistance is improved. However, it is particularly preferable.

The film haze of the polyester film of the present invention is preferably 20% or less, more preferably 10% or less. When the film haze is 20% or more, when the film is used as a green sheet, it is widely used as an inspection of the green sheet,
This may be unfavorable because it may be an obstacle in the visual inspection of the pinholes of the green sheet using transmitted light. Further, the polyester film of the present invention may be a multilayer film in which a plurality of layers are laminated even if it is a single-layer film as long as it does not exceed the gist of the present invention, but one surface is made extremely smooth and the number of pinholes and coating unevenness are When it is attempted to maintain the anti-blocking property by reducing the surface resistance and simultaneously roughening the surface opposite to the smooth surface, for example, type 2 layer 2 or type 3 layer 3
It is desirable that the layers have a different roughness on the front and back sides. Furthermore, by providing a film configuration that allows different raw material formulations for the intermediate layer and the two surface layers, for example, 3 layers of 3 types, 3 Even if the fine particles are not added to the layer, the fine particles may be added only to the surface layer to satisfy the gist of the present invention, and it is possible to reduce foreign substances caused by the fine particles and reduce the production cost, which is more preferable.

The method for producing the film of the present invention will be specifically described below, but as long as the gist of the present invention is satisfied,
The present invention is not particularly limited to the following examples. The polyester chips dried by a known method are supplied to a melt extrusion device, and heated to a temperature higher than the melting point of each polymer to be melted. Next, the melted polymer is extruded from a die and rapidly cooled and solidified on a rotating cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to enhance the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method is preferably adopted.

In the present invention, the sheet thus obtained is biaxially stretched to form a film. Specifically, the unstretched sheet is preferably stretched 2 to 6 times in the longitudinal direction at 70 to 145 ° C. to form a uniaxially stretched film, and then stretched in the transverse direction at 90 to 160 ° C. for 2 times. It is preferable to perform stretching 6 times to 6 times and to perform heat treatment at 150 to 240 ° C. for 1 to 600 seconds. Further, in this case, in the maximum temperature zone of the heat treatment and / or the cooling zone of the heat treatment outlet, the longitudinal direction and / or the lateral direction of 0.
A method of relaxing by 1 to 20% is preferable. Further, it is also possible to add re-longitudinal stretching and re-transverse stretching if necessary.

The polyester film of the present invention is required in order to improve necessary properties, for example, antistatic property, weather resistance and surface hardness, as long as the gist of the present invention is not impaired. Accordingly, after completion of the longitudinal stretching, a so-called in-line coating may be performed in which coating is performed before the entrance of the tenter for transverse stretching and drying is performed in the tenter. Also,
Various coatings may be performed by off-line coating after the film is manufactured. Such a coat may be either single-sided or double-sided. The coating material may be either water-based and / or solvent-based in the case of off-line coating, but is preferably water-based or water-dispersed in the case of in-line coating. The polyester film of the present invention can be mixed with other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate as long as the gist of the present invention is not impaired. Further, an ultraviolet absorber, an antioxidant, a surfactant, a pigment, a fluorescent whitening agent and the like can be mixed.

When a release layer is provided on the polyester film of the present invention, the material constituting the release layer is not particularly limited as long as it has releasability, and a curable silicone resin is the main component. Type, or a modified silicone type by graft polymerization with an organic resin such as urethane resin, epoxy resin or alkyd resin may be used. Among them, when the curable silicone resin is the main component, the mold releasability is good. The types of curable silicone resins include solvent addition type, solvent condensation type,
Any curing reaction type such as solvent ultraviolet curing type, solventless addition type, solventless condensation type, solventless ultraviolet curing type, solventless electron beam curing type can be used.

[0016]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In addition, various physical properties,
The characteristics are measured or defined as follows. In the examples, "%" means "% by weight".

(1) Measurement of tensile elastic modulus Intesco Model 20 tensile tester manufactured by Intesco Co., Ltd.
Using the 01 type, a sample film having a length of 300 mm and a width of 20 mm was pulled at a strain rate of 10% / min in a room controlled at a temperature of 23 ° C. and a humidity of 50% RH, and the first straight line of the tensile stress-strain curve was drawn. The following formula (1) using the part
Calculate by E = (Δσ / Δε) × 9.807 (1) (In the above formula, E is the tensile elastic modulus (MPa), Δσ is the stress difference due to the original average cross-sectional area between two points on the straight line, and Δε is the same. Two
Means the difference in strain between points)

(2) Measurement of maximum projection height (Rmax) Non-contact type three-dimensional roughness meter using direct phase detection interferometry, so-called two-beam interferometry, by vapor deposition of Al on the surface of a film sample of 3 cm square. (512 by Micromap Co., Ltd.), the P-V value of the film surface in the measurement area of 232 μm × 177 μm was measured at 50 points under the conditions of measurement wavelength: 554 nm and objective lens magnification: 20 times, and P of 50 points was measured.
The -V value was averaged to obtain the maximum protrusion height (Rmax) of the sample.

(3) Measurement of center-plane average roughness A non-contact type three-dimensional roughness meter (micrometer) using direct phase detection interferometry, so-called two-beam interferometry, by performing Al vapor deposition on the surface of a 3 cm square film sample. 512) manufactured by Map Co., Ltd., with a measurement wavelength of 554 nm and an objective lens magnification of 20 times, from the projection height distribution curve, the center surface average roughness SRa of the film surface in the measurement area of 232 μm × 177 μm.
Was measured over 50 points, and SRa values at 50 points were averaged to calculate SRa of the film.

(4) Measurement of Thickness Unevenness A continuous film thickness measuring instrument (using an electronic micrometer) manufactured by Anritsu Electric Co., Ltd. was used to measure along the machine direction and the transverse direction of the biaxially stretched film. It was calculated by the formula (2). Thickness unevenness (%) = (maximum thickness-minimum thickness) × 100 / average thickness (2)

(5) Measurement of film haze According to JIS-K6714, the haze of the film was measured with a sphere turbidimeter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.

(6) Evaluation of Slurry Coatability On the surface of the film, 100 parts of a curable silicone resin (“KS-779H” manufactured by Shin-Etsu Chemical), 1 part of a curing agent (“CAT-PL-8” manufactured by Shin-Etsu Chemical), Methyl ethyl ketone (M
A release film composed of 2200 parts of EK) / toluene mixed solvent system was applied at a coating amount of 0.1 g / mm ² to obtain a release film. After that, a ceramic slurry having the following composition was applied onto the release surface so as to have a thickness of 5 μm in a wet state, and the slurry coatability at that time was evaluated according to the following evaluation criteria. <Ceramic slurry composition> Ceramic powder (barium titanate) 100 parts Binder (polyvinyl butyral resin) 5 parts Plasticizer (dioctyl phthalate) 1 part Toluene / MEK mixed solvent (1: 1 mixing ratio) 10 parts <slurry Coatability Judgment Criterion> ◎: Slurry coatability is very good ○: Slurry coatability is good △: Fine repellency of slurry is seen ×: Slurry repellent in the above criteria, ◎, ○ and △ are There is no problem in practical use.

(7) Evaluation of Thickness Unevenness of Ceramic Green Sheet On the surface of the film, 100 parts of curable silicone resin (“KS-779H” manufactured by Shin-Etsu Chemical) and 1 part of curing agent (“CAT-PL-8” manufactured by Shin-Etsu Chemical) , Methyl ethyl ketone (M
A release film composed of 2200 parts of EK) / toluene mixed solvent system was applied at a coating amount of 0.1 g / mm ² to obtain a release film. After that, a ceramic slurry having the following composition is coated by a known method on the release surface with a slot die so as to have a thickness of 12 μm in a wet state to form a ceramic green sheet. The thickness of the ceramic layer in the vertical and horizontal directions on the film was measured by a non-contact β-ray thickness meter, and the judgment was made based on the results based on the following judgment criteria. <Ceramic slurry composition> Ceramic powder (barium titanate) 100 parts Binder (polyvinyl butyral resin) 5 parts Plasticizer (dioctyl phthalate) 1 part Toluene / MEK mixed solvent (1: 1 mixing ratio) 10 parts <Green Sheet thickness unevenness determination criteria> ◎: Thickness unevenness is less than 1% ○: Thickness unevenness is 1% or more and less than 2% △: Thickness unevenness is 2% or more and less than 3% ×: Thickness unevenness is 3% or more, among the above criteria, ◎, ○ And Δ are practically acceptable levels.

(8) Scratch resistance RUBING TESTER manufactured by Ohira Rika Kogyo Co., Ltd.
The sample surface was rubbed 10 times with a special felt. The load at this time was 200 g. The surface after rubbing was visually observed and classified into the following ranks. ⊚: No scratches or almost no scratches Δ: Little scratches ×: Many scratches In the above criteria, Δ and ◎ are practically no problem levels.

(9) Evaluation of Blocking Property of Release Film 100 parts of a curable silicone resin (“KS-779H” manufactured by Shin-Etsu Chemical) and a curing agent (“CAT-PL-8” manufactured by Shin-Etsu Chemical) on the surface of the film. Part, methyl ethyl ketone (M
A release film composed of 2200 parts of EK) / toluene mixed solvent system was applied at a coating amount of 0.1 g / mm ² to obtain a release film. Then, release film 10
Cut into 10 cm squares, stack 10 sheets so that the release surface and the surface without the release layer are aligned, 100 ° C, 1 hour, 10
After pressing under the condition of kg / cm ² , the degree of blocking occurrence during peeling was judged according to the following judgment criteria. <Judgment Criteria> A: No occurrence of blocking is observed. A: Almost no blocking occurs. Δ: Occurrence of blocking is recognized. X: Remarkable occurrence of blocking is observed. In the above criteria, ⊚, ◯, and Δ are levels that pose no practical problems.

Example 1 (Production Method of Polyester Chip) 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.07 part of calcium acetate monohydrate were placed in a reactor, heated and heated to distill off methanol, and then transesterification reaction. And then
About four and a half hours after the start of the reaction, the temperature was raised to 230 ° C., and the transesterification reaction was substantially completed. Then phosphoric acid 0.04
And 0.035 part of antimony trioxide were added, and the mixture was polymerized according to a conventional method. That is, the reaction temperature was gradually raised to 280 ° C., while the pressure was gradually reduced to 0.05 mmHg. After 4 hours, the reaction was terminated, and chips were obtained according to a conventional method to obtain polyester A. When the polyester A is produced, the average particle size is 0.
20,000 ppm of 7 μm calcium carbonate was added to obtain polyester B. Further, when the polyester A is produced, 200 parts of amorphous silica having an average particle size of 2.4 μm is used.
00 ppm was added to obtain polyester C. Further, when producing the polyester A, 20,000 ppm of aluminum oxide having an average particle diameter of 0.2 μm was added to obtain a polyester D.

(Production of Polyester Film) The mixed raw material 1 in which the above polyesters A and D are mixed at a ratio of 50% and 50%, respectively, is used as a raw material for the A layer, and polyesters A and C are used.
As a raw material for the layer C, which was a mixture of 95% and 5%, respectively.
After melting at 85 ° C, layers A and C are the outermost layers (surface layers)
A non-oriented sheet was obtained by co-extruding and solidifying by cooling on a casting drum cooled to 20 ° C. in a layer structure of 2 layers of 2 types. Next, after stretching at 90 ° C. in the longitudinal direction at a longitudinal stretching ratio of 4.6 times, a preheating step was performed in a tenter to stretch at a transverse stretching ratio of 3.8 times at 100 ° C. and 230 ° C. for 10 seconds. Heat treatment was performed to obtain a 38 μm polyester film.
The thickness of each layer was as shown in Table 1 below. The obtained polyester film had a good green sheet thickness unevenness level, was excellent in slurry coatability, blocking resistance, and transparency, and was a highly practical film.

Example 2 In Example 1, the longitudinal stretching ratio and the lateral stretching ratio were 3.2.
A 38 μm polyester film was obtained in the same manner as in Example 1 except that the polyester film was stretched at a draw ratio of 4.2 times. The obtained polyester films had the results shown in Table 1, and were all highly practical films.

Example 3 In Example 1, the longitudinal stretching ratio and the lateral stretching ratio were 5.2, respectively.
A 38 μm polyester film was obtained in the same manner as in Example 1, except that the film was stretched at a stretching ratio of 4.3 times. The obtained polyester films had the results shown in Table 1, and were all highly practical films.

Examples 4 to 6 Mixed raw materials for each layer were prepared according to the raw material formulations shown in Table 1, each was fed to three extruders, and each was melted at 285 ° C.
A layer and a layer C are outermost layers (surface layers), and a layer B is an intermediate layer, and a non-oriented sheet is obtained by co-extruding and solidifying by cooling on a casting drum cooled to 20 ° C. in a layer structure of 3 layers of 3 types. A polyester film was obtained in the same manner as in Example 1. The thickness of each layer of the polyester film was as shown in Table 2. The obtained polyester film had a good green sheet thickness unevenness level, was excellent in slurry coatability, blocking resistance, and transparency, and was a highly practical film.

Comparative Examples 1 to 4 Same as Example 4 except that the raw material composition of the A layer, the B layer and the C layer was as shown in Table 2 and the longitudinal stretching ratio and the lateral stretching ratio were both 4.0 times. To produce a polyester film. The obtained polyester films had the properties shown in Table 2 and were films lacking in practicality.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

According to the present invention, there is provided a polyester film capable of reducing the thickness unevenness of the ceramic layer and suppressing the pinholes in the ceramic slurry layer when the ceramic slurry is placed on the release film. It has a high industrial value.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F071 AA44 AF20 AH12 BB08 BC01                       BC15 BC16                 4F100 AK41A AK41B AR00C BA02                       BA03 BA05 BA10A BA10C                       DD07 EH202 EJ383 JK07                       JL14C JN01 YY00                 5E082 AB03 BC38 FG06 FG26 FG46                       MM13 PP04

Claims (6)

[Claims] 1. A polyester film for a release film, which has a tensile elastic modulus (E _MD ) in the longitudinal direction of the film of 4.0 GPa or more. 2. The maximum protrusion height (Rma) on one surface (A surface).
x (A)) is 500 nm or less and center plane average roughness (SRa (A)) is 30 nm or less, The polyester film for release films of Claim 1 characterized by the above-mentioned. 3. A center line average roughness S of the surface opposite to the A surface (C surface).
Ra (C) is 10-50 nm, The polyester film for release films of Claim 1 or 2 characterized by the above-mentioned. 4. The polyester film for a release film according to claim 1, which has a film haze of 20% or less. 5. The polyester film for a release film according to claim 1, which has a coextrusion laminated structure of at least two layers. 6. A release film for a green sheet, characterized in that a release layer is provided on the A side of the polyester film according to any one of claims 1 to 5.