JP2005179487A - Biaxially oriented polyester film for transfer foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate film for a transfer foil, excellent in the processability on complicated deep drawing. <P>SOLUTION: The biaxially oriented polyester film for an in-mold transfer foil is a film containing a polyester whose glycol component is 1,4-cyclohexane dimethanol. Its degree of orientation on the plane (ΔP) is ≤90×10<SP>-3</SP>, and the heat shrinkage after the heat treatment of 170°C and 1 min is ≤25%. It is preferable that the film strength at 200% elongation at 100°C is ≤110 MPa. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transfer foil polyester film having excellent moldability, heat resistance, processability, and good thickness unevenness, and more specifically, for in-mold molding transfer for transfer printing simultaneously with molding in injection molding or the like. The present invention relates to a polyester film for transfer foil useful as a base film for transfer foil.

  Conventionally, a polyester foil such as polyethylene terephthalate or a film of vinyl chloride resin is used as a base film as a transfer foil for in-mold molding and transfer printing simultaneously with molding in injection molding, etc., and a release layer on the surface of the base film Is used, and a laminated film provided with a printed layer thereon is used.

  The laminated film used for in-mold molding transfer is separated between the release layer surface and the printing layer surface after the molding transfer. That is, after molding transfer, the printed layer is adhered to the surface of the molded product and taken out as a product, and the release layer is taken out while being laminated on the base film.

  Such a transfer method is used for plastic molded products used for household appliances, automobile interior products, kitchenware, cosmetic containers, toys and the like. In particular, a transfer foil using a polyester film as a base film has been proposed, and a polyester film having a specific refractive index and plane orientation, which is made of a polyester film having a specific heat of fusion copolymerized with isophthalic acid at a specific ratio, is used. What is known is known (Patent Document 1).

  However, in recent years, consumer needs related to the design properties and comfortability of the above plastic molded products have diversified, and there is a strong tendency that a surface finish with a large-sized and deeply drawn three-dimensional curved surface structure is particularly desired. Yes.

  If a transfer foil for in-mold molding transfer using polyester as a base film as described above is used for a molded product having a high deep drawing degree, since the elongation of the polyester film is extremely small, the film is not torn in the molding process. Frequent and transcription is virtually impossible. For this reason, the transfer foil using a polyester film is currently used only in molding transfer using a mold having a shallow bottom and a simple shape.

  In order to solve this problem, a polyester film containing isophthalic acid and 1,4-cyclohexanedimethanol in a specific ratio and having a specific secondary transition temperature, a heat shrinkage rate, and a film strength has been proposed. However, since this method does not lower the plane orientation, a deeply drawn molded product having a complicated structure may cause partial film breakage in the molding process or to solve the film breakage. However, if the surface orientation is to be lowered, the heat shrinkage rate becomes very large, and there remains a problem that wrinkles are generated in the molding process.

In addition, a polyelter film in which polybutylene terephthalate and polyethylene terephthalate are mixed and melted and a polyester film having a specific crystallization temperature, secondary transition temperature, heat of fusion, plane orientation, and film strength has been proposed ( In this method, since the plane orientation is still high even in this method, the problem of partial film breakage in the molding process remains in a molded article having a complex structure and a large deep drawing.
Japanese Patent Laid-Open No. 1-40400 Japanese Unexamined Patent Publication No. 07-198621 Japanese Patent Laid-Open No. 10-17683

  The present invention is intended to solve the above-mentioned conventional problems, and the problem to be solved is to provide a base film for a transfer foil that is excellent in complex deep drawing workability.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be easily solved by a film having a specific configuration, and have completed the present invention.

That is, the gist of the present invention is a film containing a polyester having 1,4-cyclohexanedimethanol as a glycol component, having a plane orientation degree (ΔP) of 90 × 10 ⁻³ or less, and at 170 ° C. for 1 minute. It exists in the biaxially-oriented polyester film for shaping | molding transfer foil characterized by the heat shrinkage rate after heat processing being 25% or less.

Hereinafter, the present invention will be described in detail.
The present invention is a polyester film containing a polyester copolymerized with 1,4-cyclohexanedimethanol (hereinafter sometimes abbreviated as CHDM) as an alcohol component. The CHDM content in the polyester film is preferably 10 mol% or more, more preferably 20 mol% or more.

  The polyester referred to in the present invention refers to a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol or from a hydroxycarboxylic acid. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and diols include ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. As the production method, for example, a transesterification reaction is carried out between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or an aromatic dicarboxylic acid and a glycol are directly esterified to form a substantially aromatic compound. A method is employed in which a bisglycol ester of a dicarboxylic acid or a low polymer thereof is formed and then polycondensed by heating under reduced pressure.

  Typical examples of such polymers include polyethylene terephthalate and polyethylene-2, 6 naphthalate. These polymers may be homopolymers or may be a copolymer of the third component.

  In order to improve workability in the film winding process, coating process, vapor deposition process, and the like, it is desirable that the polyester film in the present invention contains fine particles. These fine particles include inorganic particles such as calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide, silicon oxide, kaolin, acrylic resin, guanamine resin, etc. Although there may be mentioned organic particles and precipitated particles obtained by making catalyst residuals into particles, the present invention is not limited to these. The particle size and amount of these particles can be appropriately determined according to the purpose. The fine particles to be contained may be a single component, or two or more components may be used simultaneously.

  The method of blending each particle with the raw material polyester is not particularly limited, and for example, a method of adding each particle to the polyester polymerization step or a method of melt-kneading the raw material polyester and each particle is suitable. In addition, various stabilizers, lubricants, antistatic agents, and the like can be added as appropriate.

  The polyester film of the present invention is melted by supplying the above-described polyester raw material to a known melt-extrusion apparatus represented by an extruder, and heating to a temperature equal to or higher than the melting point of the polymer. Next, while extruding the molten polymer from the slit-shaped die, it is rapidly cooled and solidified so that it is in the form of a rotary cooling drum or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. This sheet is obtained by stretching in a biaxial direction to form a film and heat-setting. In this case, the stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. Moreover, you may extend | stretch longitudinally and / or a horizontal direction again before or after performing heat setting as needed. In the present invention, in order to obtain sufficient dimensional stability, the draw ratio is preferably 8 times or more, more preferably 10 times or more, as the area ratio.

  The heat treatment temperature after stretching in the present invention is not particularly limited, but it is preferable to perform the heat treatment at 170 ° C. or higher. Heat treatment at a temperature lower than 170 ° C. increases the heat shrinkage rate, which may cause wrinkles in the film during molding.

The plane orientation degree (ΔP) of the polyester film of the present invention is 90 × 10 ⁻³ or less, preferably 70 × 10 ⁻³ or less. If the degree of plane orientation (ΔP) is greater than 90 × 10 ⁻³ , film breakage occurs in the molding process.

  The heat shrinkage ratio after heat treatment at 170 ° C. for 1 minute of the polyester film of the present invention is 25% or less, preferably 20% or less. If the heat shrinkage rate is greater than 25%, the film is wrinkled during the printing process and molding process.

  The film strength of the polyester film of the present invention at 200% elongation at 100 ° C. is preferably 110 MPa or less, more preferably 70 MPa or less.

  According to the film of this invention, the base film of the transfer foil excellent in the complicated deep drawing workability can be provided, and the industrial value of this invention is high.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example, unless the summary is exceeded. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows. Further, “parts” in Examples and Comparative Examples represents “parts by weight”.

(1) Method for measuring the degree of plane orientation (ΔP) of a film Using an Abbe refractive index type manufactured by Atago Co., Ltd., using a sodium lamp as a light source, the refractive index of the film is measured. Calculated.
ΔP = 1/2 (nγ + nβ) −nα
In the above formula, nγ and nβ respectively represent the maximum refractive index in the film plane and the refractive index in the film plane orthogonal to the film plane, and nα represents the refractive index in the thickness direction of the film.

(2) Measuring method of heat shrinkage rate of film Oven set at 170 ° C. in a tension-free state by cutting a sample into a strip of 35 mm width × 1000 mm length in the length direction (MD) and width direction (TD) Heat treatment was performed for 1 minute in a Tabei ESPEC Co., Ltd. product (hot air circulating furnace), the length before and after the heat treatment was measured with a straight scale, and the thermal shrinkage rate was obtained by the following formula.
Thermal contraction rate (%) = [(ab) / a] × 100
(During the trial production, a represents the length (mm) of the sample before heat treatment, and b represents the length (mm) of the sample after heat treatment)

(3) Measuring method of film strength (F200) at 200% elongation Using a tensile tester Intesco 2001 type with a constant temperature layer manufactured by Intesco Co., Ltd., setting the constant temperature layer to 100 ° C., and chucking a film having a width of 150 mm It was set in a testing machine so that the distance was 50 mm, and allowed to stand for 2 minutes, and then the strength at 200% elongation was measured at a tensile speed of 200 mm / min. The measurement was performed in the vertical and horizontal directions of the film, and the average value was F200.

(4) Measuring method of thickness fluctuation Using a continuous thickness measuring machine manufactured by Anritsu Electric Co., Ltd., 5 m was measured in the longitudinal direction, maximum, minimum and average thicknesses were measured, and thickness spots were measured by the following formula.
Thickness unevenness = 100 × (maximum film thickness / minimum film thickness) / average film thickness

(5) Evaluation Method of Formability as Transfer Film Using a 400 mm deep mold having the shape shown in FIG. 1, after preheating at 270 ° C., the film was molded into the mold by vacuum molding. The formability of the transfer film was evaluated as follows according to the frequency of film breakage during the molding.
○: No film breakage Δ: Sometimes film breakage occurs in one or two places ×: Film breakage occurs frequently

(6) Method for evaluating processability as a transfer film After forming a release layer, a printing layer, and an adhesive layer on the film, molding transfer was actually performed by the method of (5) above. Appropriateness as a transfer film was evaluated as ◯ when the film was not wrinkled or broken at the time of molding, and there was no pattern distortion or print omission in printing, and X when it was not.

The polyester raw materials used in the following examples and comparative examples were produced by the following method.
<Polyester 1>
PETG (Eastar 6763 manufactured by Eastman Chemical Co.) was used. The content of 1,4-cyclohexanedimethanol (CHDM) in the alcohol component of this polyester and this polyester raw material was 32 mol%.

<Polyester 2>
Isophthalic acid and terephthalic acid were used as the dicarboxylic acid component, and ethylene glycol was used as the polyhydric alcohol component, respectively, and those produced by a conventional melt polycondensation method were used. The isophthalic acid content in the dicarboxylic acid component of this raw material was 22 mol%.

<Polyester 3>
Uses terephthalic acid as the dicarboxylic acid component, ethylene glycol as the polyhydric alcohol component, and a polyester chip containing 0.18 parts of amorphous silica having an average particle size of 2.5 μm by a conventional melt polycondensation method did.

  A polyester resin obtained by melt blending polyesters 1 to 3 at a ratio shown in Table 1 below was extruded onto a cooling drum having a surface temperature of 35 ° C. and rapidly cooled to obtain an unstretched film having a thickness of about 700 μm. Next, the film was stretched 3.5 times in the longitudinal direction at 80 ° C., and then subjected to a preheating step in the tenter, 4.0 times lateral stretching at 110 ° C., and heat treatment for 3 seconds at the temperature shown in Table 1 to obtain a thickness. A 50 μm biaxially oriented polyester film was obtained. Table 2 below shows the degree of plane orientation, shrinkage, F200 value at 100 ° C, thickness fluctuation, moldability, and processability of this biaxially oriented polyester film.

  As is clear from the results shown in Table 2, the polyester films of the examples were large-scale molded with a large deep drawing, and were excellent in moldability and processability.

  The film of the present invention can be suitably used, for example, as a base film for a transfer foil that is excellent in complex deep drawing workability.

It is explanatory drawing of the metal mold | die used for the evaluation method of the moldability as a transfer film.

Claims (1)

A film containing polyester having 1,4-cyclohexanedimethanol as a glycol component, having a plane orientation degree (ΔP) of 90 × 10 ⁻³ or less, and a heat shrinkage ratio after heat treatment at 170 ° C. for 1 minute of 25 % Or less, a biaxially oriented polyester film for molded transfer foil.

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