JP2003291291A - Polyester film for release film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for a release film which makes an improvement in disadvantages caused by the release film, such as blocking, a fault of carrying properties, repellence of slurry on the occasion of applying the slurry, occurrence of a pinhole and a break of a green sheet on the occasion of peeling the green sheet. <P>SOLUTION: The maximum projection height (Rmax (A)) of one surface (surface A) of the polyester film for the release film is 200 nm or less and the central surface average roughness (SRa (A)) of the surface A is 10 nm or less. The layer constituting the surface A contains aluminum oxide particles. <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 base film for a release film, and more particularly to a base film for a release film used for molding a green sheet when manufacturing a laminated ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a monolithic ceramic capacitor, a release film having a polyester film as a base material has been used as a carrier film for forming a green sheet. In recent years, with the miniaturization of capacitors accompanying the miniaturization of electronic devices, the ceramic green sheets themselves have become thinner, and under such circumstances, release film causes blocking, poor transportability, and ceramic slurry coating. Repulsion of slurry during work, pinholes,
Since problems such as breakage of the green sheet may occur when the green sheet is peeled off, improvement is required.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the problems to be solved are the occurrence of blocking, poor transportability, repelling of slurry during coating of ceramic slurry, and pinhole formation. Another object of the present invention is to provide a polyester film for a release film, in which problems caused by the release film, such as breakage of the green sheet when peeling the green sheet, are improved.

[0004]

As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific structure, and has completed the present invention. I arrived.

That is, the gist of the present invention is that one side (A
The maximum protrusion height (Rmax (A)) of the surface) is 200 nm or less, and the center plane average roughness (SRa (A)) of the A surface is 1
A polyester film having a thickness of 0 nm or less, wherein the layer constituting the A-side contains aluminum oxide particles, which is a polyester film for a release film.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The polyester referred to in the present invention refers to a polymer containing an ester group obtained from a polycarboxylic acid and a diol or a polycarboxylic acid from 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, and the like. Glycol, 1,3-Propanediol, 1,6-
Hexanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and hydroxycarboxylic acids include p-hydroxybenzoic acid and 6-hydroxy-2. −
Examples thereof include naphthoic acid and the like. Typical of such polymers are polyethylene terephthalate, polybutylene terephthalate, polyethylene-
2,6-naphthalate and the like are exemplified. These polymers may be homopolymers or may be copolymers of a third component.

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 can also be used. In the polyester film of the present invention, it is important that one side (A side) has Rmax of 200 nm or less and SRa (A) of 10 nm or less, and particularly Rmax of 100 nm.
The following is desirable. Usually, the A surface is the surface on which the release layer is installed. However, when the Rmax of the A surface is larger than 200 nm and SRa (A) is larger than 10 nm, the ceramic layer is formed when the release layer and the ceramic layer are installed. It is not practically preferable because a missing hole (pinhole) or coating unevenness occurs. Further, the layer (A layer) constituting the A-side needs to contain aluminum oxide particles (alumina particles), and the aluminum oxide particles (alumina particles) having an average primary particle diameter of 5 to 100 nm are 0.01. It is preferable to contain 10 to 10% by weight. The average primary particle diameter is more preferably in the range of 30 to 80 nm, and the addition amount is 0.3 to 3.0.
It is desirable that the content is 0.7% by weight, more preferably 0.7 to 3.0% by weight. When the average primary particle size is larger than 100 nm, the surface A may be roughened, and the average primary particle size is 5n.
If it is smaller than m, the alumina particles often form very strong agglomerates, and the agglomerates are not easily loosened during melt extrusion or stretching, and as a result, the surface A may be roughened. .

When the content of the alumina particles is less than 0.01% by weight, the scratch resistance of the surface A is lowered, and when the base film is conveyed, the film surface may be significantly scratched. The use of such a film is not preferable because it may cause pinholes when the release layer is installed or when the ceramic slurry is applied. Further, if the content of alumina particles is more than 10% by weight, the alumina particles may fall off from the polyester film, which may undesirably contaminate the step of producing a release film or a ceramic capacitor. Further, the alumina particles used in the present invention are preferably at least one selected from the crystal types of γ, δ and θ. α-
The use of alumina tends to roughen the surface.

The thickness unevenness of the film of the present invention is 5%.
It is desirable that it is 3% or less, particularly 1% or less. When the thickness unevenness exceeds 5%, a release layer and a ceramic dielectric layer are installed to create a green sheet for a ceramic capacitor, and then a positional deviation occurs when the sheets are laminated, or a local pressure is applied in a subsequent pressing step. In some cases, such stress concentration may occur, resulting in nonuniform capacitance, which is not preferable in practical use. Further, the center surface average roughness SRa of the surface (C surface) opposite to the release layer installation surface
(C) is preferably 10 to 50 nm, and particularly preferably 15 to 30 nm. When SRa (C) is less than 10 nm, problems such as occurrence of blocking and deterioration of transportability of the release film may occur when the release film is formed. Also,
When SRa (C) exceeds 50 nm, transfer of surface protrusions to the release layer installation surface, so-called show-through may occur.

Rm for C side of polyester film
In order to set ax and SRa within the above range, inert fine particles,
For example, silica, calcium carbonate, kaolin, titanium oxide, aluminum oxide, barium sulfate, inorganic particles such as zeolite, or silicone resin, crosslinked polystyrene,
It is preferable to mix organic particles such as acrylic resin in the film alone or as 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 without departing from the gist of the present invention, but the average particle size is usually 0.1 to 4.0 μm. The addition amount is usually 0.01 to 3.0% by weight, and the particle size distribution is preferably such that the dispersion is small.

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, which is an obstacle to a pinhole inspection of the green sheet by visual inspection using transmitted light. May be. The polyester film of the present invention may be a single-layer film or a multi-layer film in which a plurality of layers are laminated, as long as it does not exceed the gist of the present invention, but it is a constitution of a coextrusion laminate of at least two layers. It is preferable. That is, when one surface is made extremely smooth and the number of pinholes and coating unevenness are reduced, and at the same time, the opposite surface of the smooth surface is roughened to keep the blocking resistance, for example, two kinds of two layers It is desirable that the surface has different roughness on the front and back in a structure of 3 layers of 3 types
Furthermore, for example, by forming a film structure in which an intermediate layer such as 3 layers of 3 layers and 2 surface layers can be mixed with different raw materials, even if the intermediate layer does not contain fine particles, only the surface layer contains fine particles. In some cases, the essence of the present invention may be satisfied simply by adding, and it is more desirable because it is possible to reduce foreign matters caused by fine particles and to reduce production costs.

The method for producing the film of the present invention will be specifically described below, but as long as the constitution 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, as long as it does not impair the gist of the present invention, the required properties according to the required properties,
For example, in order to improve antistatic property, weather resistance and surface hardness, so-called in-line coating may be carried out, if necessary, after completion of the longitudinal stretching and before the entrance of the tenter for transverse stretching and drying in the tenter. Further, 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.

Further, the polyester film of the present invention may 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 release layer is usually provided on the A surface side (specifically, the flat surface side). The material forming the release layer is not particularly limited as long as it has releasability, and may be a type containing a curable silicone resin as a main component, or an organic material such as urethane resin, epoxy resin, alkyd resin. A modified silicone type by graft polymerization with a resin or the like may be used. Among them, the case where the curable silicone resin is the main component is preferable because the releasability is good. The types of curable silicone resin include solvent addition type, solvent condensation type, solvent UV curing type,
Any curing reaction type such as a solventless addition type, a solventless condensation type, a solventless ultraviolet ray curing type and a solventless electron beam curing type can be used.

[0015]

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 maximum protrusion height (Rmax) Non-contact type three-dimensional roughness meter using direct phase detection interferometry, so-called two-beam interferometry, by depositing 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.

(2) Measurement of center plane average roughness Al vapor deposition was performed on the surface of a 3 cm square film sample, and a non-contact type three-dimensional roughness meter (micrometer) using direct phase detection interferometry, so-called two-beam interferometry 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.

(3) Measurement of Thickness Unevenness A continuous film thickness measuring instrument (using an electronic micrometer) manufactured by Anritsu Denki Co., Ltd. was used to measure along the machine direction and the transverse direction of the biaxially stretched film (for a length of 3 m). It was calculated by the following formula. Thickness unevenness (%) = (maximum thickness−minimum thickness) × 100 / average thickness ...

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

(5) Evaluation of Slurry Coatability On the film surface, 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 comprising 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 Criteria> ◎: Slurry coatability is very good ○: Slurry coatability is good △: Fine repellency of slurry is seen ×: Slurry repellent in the above criteria, ◎ and ○ are practical There is no problem.

(6) Evaluation of Thickness Unevenness of Ceramic Green Sheets 100 parts of a curable silicone resin (“KS-779H” manufactured by Shin-Etsu Chemical) and 1 part of a curing agent (“CAT-PL-8” manufactured by Shin-Etsu Chemical) on the surface of the film. , Methyl ethyl ketone (M
A release film comprising 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 layer having the following composition is coated on the release surface by a known method so that the thickness becomes 12 μm in a wet state, a ceramic green sheet is prepared, and the thickness of the ceramic green sheet is set to a non-contact type. The thickness of the ceramic layer in the vertical and horizontal directions on the film was measured by a β-ray thickness meter, and based on the results, the judgment was made according to 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 in the above criteria, Δ, ○ The marks ⊚ and ⊚ are practically acceptable.

(7) 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 ○: Little scratches Δ: Slight scratches ×: Very many scratches In the above criteria, Δ, ○ and ◎ are practically acceptable levels.

(8) Evaluation of Blocking Property of Release Film 100 parts of 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 occurrence of blocking 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, and methanol was distilled off to transesterify. 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 producing the polyester A, 20,000 ppm of calcium carbonate having an average primary particle size of 0.7 μm was added to obtain a polyester B. Further, when producing the polyester A, 20,000 ppm of amorphous silica having an average primary particle size of 2.4 μm was added to obtain a polyester C.
Further, when the polyester A is manufactured, 20,000 pp of δ-type aluminum oxide having an average primary particle size of 60 nm is added.
m was added to obtain polyester D.

(Production of Polyester Film) Polyester A and C are prepared by using the mixed raw material 1 in which the above polyesters A and D are mixed at a ratio of 50% and 50%, respectively, as a raw material for the A layer.
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. Then, after stretching 3 times in the machine direction at 90 ° C., a preheating process was performed in a tenter to stretch 4 times horizontally at 100 ° C., 23
Heat treatment is performed at 0 ° C for 10 seconds, the thickness of the film just before winding is measured laterally with a non-contact type online thickness gauge, and the thickness unevenness is actually measured. Was adjusted to obtain a 38 μm polyester film with controlled thickness unevenness. still,
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.

Examples 2 to 3 In Example 1, the raw material composition was changed as shown in Table 1, and the thickness unevenness was controlled in the same manner as in Example 1 to give Table 1.
Except that the thickness unevenness is set to 38 in the same manner as in Example 1.
A μm polyester film was obtained. The obtained polyester films had the results shown in Table 1, and were all highly practical films.

Examples 4 to 7 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 3 Polyester films were obtained in the same manner as in Example 4, except that the raw material composition of the A layer, B layer, and C layer and the thickness unevenness were as shown in Table 2 below. The obtained polyester films had the properties shown in Table 2 and were films lacking in practicality.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

EFFECTS OF THE INVENTION According to the present invention, the release film is caused by blocking, poor transportability, repelling of the slurry when coating the ceramic slurry, pinholes, breakage of the green sheet when peeling the green sheet, etc. It is possible to provide a polyester film for a release film with improved defects, and its industrial value is high.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4F100 AA19A AA19B AK41A AK41B                       AR00C BA02 BA03 BA07                       BA10A BA10C BA16 DE01A                       DE01B EH20A EH20B GB90                       JK14A JK14B JL14 JL14C                       JN01A JN01B YY00A YY00B                 4J002 CF031 CF041 CF051 CF061                       CF071 CF081 CF091 CF101                       CF181 DE146 FD166 GQ00

Claims (7)

[Claims] 1. A maximum protrusion height (Rma) on one surface (A surface).
x (A)) is 200 nm or less, and the center plane average roughness (SRa (A)) of the A surface is 10 nm or less, and the layer constituting the A surface contains aluminum oxide particles. Characteristic polyester film for release film. 2. The polyester film for a release film according to claim 1, wherein the thickness unevenness of the film is 5% or less. 3. The polyester film for a release film according to claim 1, wherein the center surface average roughness (SRa (C)) of the surface opposite to the A surface (C surface) is 10 to 50 nm. . 4. The polyester film for release film according to claim 1, wherein the aluminum oxide particles are at least one selected from γ type, δ type and θ type. 5. The polyester film for a release film according to claim 1, wherein the film haze is 20% or less. 6. The polyester film is a coextruded laminate of at least two layers, wherein the polyester film is a coextruded laminate.
A polyester film for a release film according to any one of 1. 7. A release film for a green sheet, which has a release layer on the surface A of the polyester film according to any one of claims 1 to 6.