JP2005187562A - Polyester film for insert molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for insert molding which is excellent in moldability at the time of heat molding and gives a molded item exhibiting excellent rigidity and shape stability (heat shrinkage characteristics and thickness unevenness) when used in an ordinary temperature atmosphere and being improved in finish properties. <P>SOLUTION: The polyester film for insert molding comprises a copolyester composed of an aromatic dicarboxylic acid component and a glycol component comprising ethylene glycol, and a branched aliphatic glycol and/or an alicyclic glycol, where the film has stress at 100% elongation, each in the longitudinal direction and in the width direction, of 180-1,000 MPa at 25°C and 1-100 MPa at 100°C and a melting point of 220-245°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester film for insert molding. More specifically, the present invention relates to a support film such as a transfer type printing film loaded in a mold in injection molding or the like, and relates to a polyester film for insert molding having improved moldability and finish.

  Conventionally, as a sheet for processing, a polyvinyl chloride film is typical and has been preferably used in terms of workability. On the other hand, the film has problems such as generation of toxic gas when the film burns due to fire and the like, and problems such as bleed out of the plasticizer, and new materials have been demanded according to recent needs for environmental resistance.

  Such materials having excellent environmental resistance include copolymer components such as a long-chain linear aliphatic dicarboxylic acid component and / or a long-chain linear aliphatic glycol component having 3 or more carbon atoms. Many studies have been made to improve moldability by using polymerized polyester as a film raw material. However, since the polyester resin is softened by these copolymerization components, it is inferior in rigidity, strength and shape stability (heat shrinkage characteristics, thickness unevenness, etc.) not only at the time of molding but also when actually used as a molded product. There was a drawback. On the other hand, if the composition ratio of the copolymer component is decreased in order to increase the form stability, the moldability is lowered, and it is difficult to achieve both moldability, strength and rigidity.

  Furthermore, the heat resistance is also insufficient, and when used for insert molding, the so-called finish quality is not good, such as when the pattern of the molded product is distorted, or the molded product surface is roughened to cause poor appearance. There was a case.

On the other hand, a polyester film made of polyester having neopentyl glycol or 1,4-cyclohexanedimethanol as a copolymerization component is known as the copolymer polyester (see, for example, Patent Documents 1 and 2). Since the copolymer polyester films described in these conventional techniques have a thickness of 50 μm or less, the film formation is relatively easy.
JP-A-1-252658 Japanese Unexamined Patent Publication No. 1-445699

  However, when the thickness of the film exceeds 50 μm, the co-polyester inherently has a tendency of insufficient control of molecular orientation from the viewpoint of stress reduction during stretching and crystallinity, and rigidity. And form stability may be insufficient. Therefore, when using the obtained molded product in a room temperature atmosphere while maintaining moldability, a polyester film excellent in rigidity and shape stability (heat shrinkage characteristics, thickness unevenness) has been desired.

  The object of the present invention is to solve the problems of the prior art, have excellent moldability at the time of heat molding, and when used as a molded product in a room temperature atmosphere, rigidity and shape stability (heat shrinkage characteristics, thickness unevenness) It is in providing the polyester film for insert molding which is excellent in heat resistance.

  That is, the present invention is a polyester film comprising a copolymer polyester composed of an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol and / or an alicyclic glycol, The film has a stress at 100% elongation in the longitudinal and width directions of 180 to 1000 MPa at 25 ° C. and 1 to 100 MPa at 100 ° C., and a melting point of 220 to 245 ° C. It is.

  In the polyester film for insert molding of the present invention, by controlling the stress at 100% elongation in the longitudinal and width directions of the film independently at 25 ° C. and 100 ° C., the moldability during heating and the use as a molded product Excellent rigidity and shape stability (thickness variation, heat shrinkage characteristics). Moreover, since the melting point of the film is 220 to 245 ° C. and excellent in heat resistance, even if it is used for insert molding, the pattern of the molded product is distorted, the surface of the molded product is roughened, and the appearance is poor. It is possible to prevent so-called poor finish.

  The polyester film for insert molding of the present invention includes a copolyester composed of an aromatic dicarboxylic acid component and ethylene glycol and a glycol component containing a branched aliphatic glycol and / or an alicyclic glycol. The branched aliphatic glycol and / or alicyclic glycol has a side chain or cyclic structure that suppresses mobility such as free rotation of the molecule, and glass is obtained by copolymerizing such monomers. The melting point (Tm) can be lowered and the elongation at break can be increased without lowering the transition temperature (Tg).

  The polyester film for insert molding of the present invention using such a copolymer polyester as a film raw material has excellent moldability in a high temperature atmosphere during molding, and rigidity and shape stability in a normal temperature atmosphere used as a molded product. It is a polyester film that has a feature of being excellent in (heat shrinkage characteristics and thickness unevenness) and is suitable for molding applications.

  The above-mentioned features can be expressed by physical properties of stress at 100% elongation in the longitudinal direction and width direction of 180 to 1000 MPa at 25 ° C. and 1 to 100 MPa at 100 ° C.

  The stress at 100% elongation in a 25 ° C. atmosphere in the longitudinal direction and the width direction of the film is 180 to 1000 MPa from the viewpoint of achieving both rigidity and form stability (thickness variation, thermal shrinkage at 150 ° C.) and moldability. It is important that

  The lower limit value of the stress at 100% elongation at 25 ° C. is preferably 210 MPa, particularly preferably 220 MPa, from the viewpoint of elasticity and thickness unevenness in a normal temperature atmosphere when using a molded product.

  On the other hand, in the case of a highly elastic film having a stress at 100% elongation in the atmosphere of 25 ° C. exceeding 1000 MPa, the moldability during heat molding tends to deteriorate.

  It is important that the stress at 100% elongation in a 100 ° C. atmosphere in the longitudinal direction and the width direction of the film is 1 to 100 MPa from the viewpoint of moldability.

  The lower limit value of the stress at 100% elongation in the 100 ° C. atmosphere is preferably 5 MPa, particularly preferably 10 MPa. In a field where high deformability is required, a low stress at 100% elongation in an atmosphere of 100 ° C. is a desirable direction from the viewpoint of formability. However, when the stress at 100% elongation in a 100 ° C. atmosphere decreases, the stress at 100% elongation at 25 ° C. also decreases, and the elasticity and thickness unevenness in a normal temperature atmosphere tend to deteriorate.

  On the other hand, the stress at 100% elongation at 100 ° C. is preferably 90 MPa, particularly preferably 80 MPa, from the viewpoint of moldability during heat molding.

  From the viewpoint of moldability, the breaking elongation at 100 ° C. is preferably 150% or more, more preferably 170% or more, and particularly preferably 200% or more.

  From the viewpoint of shape stability, the elongation at break at 25 ° C. is preferably 130% or more, more preferably 150% or more, and particularly preferably 170% or more.

  Furthermore, from the point of balance of formability in the vertical direction and the horizontal direction, the stress ratio at 100% elongation in the longitudinal direction and the width direction at 100 ° C. (the higher numerical value / the lower numerical value) is 1.05-1. .60 is preferred. The upper limit is particularly preferably 1.40. When the upper limit value exceeds 1.60, dimensional stability at the time of molding, printing deviation, and the like are likely to deteriorate.

  In the present invention, the change rate of the stress at 100% elongation in the longitudinal direction and the width direction at 100 ° C. as the temporal stability of workability ((after 1 month of film formation-immediately after film formation) × 100 / immediately after film formation) However, it is preferable that both are ± 20% or less. More preferably, it is ± 10% or less, and particularly preferably ± 5% or less.

  The thickness of the polyester film of the present invention is preferably 50 to 500 μm from the viewpoints of moldability, film surface protection, and design properties. The lower limit of the film thickness is preferably 60 μm, particularly preferably 70 μm. On the other hand, the upper limit value of the film thickness is preferably 300 μm, particularly preferably 200 μm.

  The film thickness unevenness is preferably 5.5% or less. If the thickness unevenness exceeds 5.5%, the printability and dimensional stability tend to deteriorate.

  Furthermore, it is preferable that the thermal shrinkage in the longitudinal direction and the width direction at 150 ° C. of the film is 6.0% or less from the viewpoint of reducing printing deviation after providing a printing layer on the polyester film in order to enhance the design. .

  The film preferably has a haze H (%) ratio (H / d) to a thickness d (μm) of 0.030 or less from the viewpoint of transparency and print sharpness. The H / d is more than 0 and preferably 0.025 or less, particularly preferably 0.015 or less.

  The lower limit of the H / d is preferably closer to zero, but if the necessary minimum unevenness is not formed on the film surface, handling properties such as slipperiness and rollability deteriorate, and the film surface is damaged, Productivity may deteriorate. In the case of a translucent nameplate using a backlight or the like, a high degree of transparency is required. Therefore, the H / d is preferably closer to zero.

  Since the polyester film for insert molding of the present invention has a melting point of 220 to 245 ° C., in addition to the above-described characteristics, even if it is used for insert molding, the pattern of the molded product is distorted or molded product In such a case, it is possible to prevent the occurrence of so-called finish defects, such as the occurrence of surface roughness that may cause poor appearance. The melting point is preferably higher from the viewpoint of heat resistance, but conversely the moldability deteriorates, so the upper limit is more preferably 240 ° C.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The polyester in the present invention means a general term for high molecular weight substances constituted by ester bonds.

  In the polyester film of the present invention, a copolymer polyester composed of an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol and / or an alicyclic glycol as a part of the film raw material, Or use 100%.

  In the copolymerized polyester, the aromatic dicarboxylic acid component is mainly composed of terephthalic acid or an ester-forming derivative thereof. The amount of the terephthalic acid component with respect to the total dicarboxylic acid component is 70 mol% or more, preferably 85 mol% or more, particularly preferably. Is 95 mol% or more, and particularly preferably 100 mol%.

  Examples of the branched aliphatic glycol include neopentyl glycol, 1,2-propanediol, and 1,2-butanediol. Examples of the alicyclic glycol include 1,4-cyclohexanedimethanol and tricyclodecane dimethylol.

  Among these, neopentyl glycol and 1,4-cyclohexanedimethanol are particularly preferable, and the stress at 100% elongation in the longitudinal direction and the width direction of the film defined in the present invention is 180 to 1000 MPa at 25 ° C. and 100 ° C. It is effective for satisfying 1 to 100 MPa. Furthermore, the use of the above monomer as a copolymerization component of polyester is preferable not only because it is excellent in moldability and transparency, but also because it is excellent in heat resistance and improves adhesion to a coating layer such as a printing layer.

  Furthermore, you may use together the following dicarboxylic acid component and / or glycol component as a copolymerization component in the said copolyester as needed, if necessary.

  Other dicarboxylic acid components that can be used in combination with terephthalic acid or its ester-forming derivatives include (1) isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid Aromatic dicarboxylic acids such as acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid or their ester-forming derivatives, (2) oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid Aliphatic dicarboxylic acids such as fumaric acid and glutaric acid or ester-forming derivatives thereof; (3) alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or ester-forming derivatives thereof; (4) p-oxybenzoic acid; Oxycarboxylic acids such as oxycaproic acid or their esthetics Forming derivatives, and the like.

  On the other hand, as other glycol components that can be used together with ethylene glycol and branched aliphatic glycol and / or alicyclic glycol, for example, 1,3-propanediol, 1,4-butanediol, pentanediol, hexane Examples include aliphatic glycols such as diols, aromatic glycols such as bisphenol A and bisphenol S, and ethylene oxide adducts thereof, diethylene glycol, and triethylene glycol.

  Furthermore, a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane can be further copolymerized with the copolymerized polyester as necessary.

  Examples of the catalyst used for producing the copolymer polyester include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. . Among these, titanium compounds, antimony compounds, and germanium compounds are preferable from the viewpoint of catalytic activity.

  When producing the copolymer polyester, it is preferable to add a phosphorus compound as a heat stabilizer. As said phosphorus compound, phosphoric acid, phosphorous acid, etc. are preferable, for example.

  The copolyester preferably has an intrinsic viscosity of 0.50 dl / g or more, more preferably 0.55 dl / g or more, and particularly preferably 0.00 from the viewpoint of moldability, adhesiveness, and film-forming stability. 60 dl / g or more. If the intrinsic viscosity is less than 0.50 dl / g, the moldability tends to decrease.

  In the polyester film of the present invention, the copolymer polyester may be used as a film raw material as it is, or a copolymer polyester having a large amount of copolymer components may be blended with a homopolyester to adjust the amount of copolymer components.

  Moreover, it is preferable from the point of a moldability to blend 2 or more types of the said copolyester, and to use as a raw material of the polyester film of this invention. Among these, a mixed polymer obtained by blending polyethylene terephthalate with polyneopentyl terephthalate and / or polycyclohexanedimethylene terephthalate is particularly preferable from the viewpoint of flexibility and moldability.

  The melting point of the polyester film in the present invention is preferably 220 to 245 ° C. from the viewpoint of heat resistance and moldability. The lower limit of the melting point is more preferably 223 ° C., particularly preferably 225 ° C. If the melting point is less than 220 ° C, the heat resistance tends to deteriorate. Therefore, it may become a problem when exposed to high temperature during molding or use of a molded product. Here, the melting point of the polyester film is an endothermic peak temperature at the time of melting detected at the time of primary temperature rise in so-called differential scanning calorimetry (DSC).

  Further, it is preferable to form irregularities on the film surface in order to improve handling properties such as slipperiness and winding property of the film. As a method for forming irregularities on the film surface, a method of incorporating particles in the film is generally used.

  Examples of the particles include known internal particles having an average particle diameter of 0.01 to 10 μm, external particles such as inorganic particles and / or organic particles. When particles having an average particle diameter exceeding 10 μm are used, defects in the film are liable to occur and the design properties tend to deteriorate. On the other hand, in the case of particles having an average particle diameter of less than 0.01 μm, handling properties such as film slipperiness and winding property tend to be lowered. The average particle diameter is an equivalent circle diameter determined by an electron microscope.

  Examples of the external particles include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, hydroxyapatite, and styrene, silicone, acrylic acids. The organic particle etc. which use these as a structural component can be used. Among these, inorganic particles such as dry, wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components are preferably used. Two or more of these internal particles, inorganic particles and / or organic particles may be used in combination as long as the properties are not impaired.

  Furthermore, the content of the particles in the film is preferably in the range of 0.001 to 10% by mass. When the amount is less than 0.001% by mass, the handling property is likely to be deteriorated, for example, the slipperiness of the film is deteriorated or winding becomes difficult. On the other hand, if it exceeds 10% by mass, it tends to cause coarse protrusions and deterioration of film forming properties.

  The polyester film of the present invention is preferably an unstretched film for applications that require severe formability. From the viewpoint of heat resistance and dimensional stability, a biaxially stretched polyester film is preferred. Such a biaxial stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching.

  The polyester film of the present invention can be made into a laminated structure by a known method using different types of polyester. The form of such a laminated film is not particularly limited. For example, a laminated form of a two-layer structure of A / B, a three-layer structure of B / A / B, and a three-layer structure of C / A / B. Is mentioned.

  Although it does not specifically limit as a manufacturing method of the polyester film of this invention, For example, after drying polyester as needed, it supplies to a well-known melt extruder, it extrudes in a sheet form from a slit-shaped die, an electrostatic application etc. The method of sticking to a casting drum by this method, cooling and solidifying to obtain an unstretched sheet, and then biaxially stretching the unstretched sheet is exemplified.

  Such a stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching. In short, the unstretched sheet is stretched and heat-treated in the longitudinal direction (MD) and the width direction (TD) of the film, and the intended surface. A method of obtaining a biaxially stretched film having an internal orientation degree is employed. Among these methods, in terms of film quality, the MD / TD method in which the film is stretched in the longitudinal direction and then stretched in the width direction, or the TD / MD method in which the film is stretched in the width direction and then stretched in the longitudinal direction. An axial stretching method and a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are stretched almost simultaneously are desirable. Furthermore, if necessary, a multistage stretching method in which stretching in the same direction is performed in multiple stages may be used.

  The film stretching ratio when biaxially stretching is preferably 1.6 to 4.2 times in the longitudinal direction and the width direction, particularly preferably 1.7 to 4.0 times. In this case, the stretching ratio in the longitudinal direction and the width direction may be either larger or the same ratio.

  In the polyester film of the present invention, (1) a copolymer polyester comprising terephthalic acid and ethylene glycol or neopentyl glycol, or (2) a copolymer polyester comprising terephthalic acid, ethylene glycol or 1,4-cyclohexanedimethanol is used. In this case, in order for the stress at 100% elongation in the longitudinal direction and the width direction to be 180 to 1000 MPa at 25 ° C. and 1 to 100 MPa at 100 ° C., the stretching ratio in the longitudinal direction is 2.8 to 4.0 times, the width The stretching ratio in the direction is preferably 3.0 to 4.5 times.

  The stretching conditions for producing the polyester film of the present invention are not particularly limited. However, in order to satisfy the range of stress at 100% elongation at 25 ° C. and 100 ° C. defined in the present invention, it is preferable to adopt the following conditions, for example.

  In the longitudinal stretching, the stretching temperature is preferably 50 to 110 ° C. and the stretching ratio is preferably 1.5 to 4.0 times so that the subsequent lateral stretching can be performed smoothly.

  In transverse stretching, stress at 100% elongation in the longitudinal direction and the width direction is particularly important because the stress at 25 ° C. is 180 to 1000 MPa and 100 ° C. is 1 to 100 MPa.

  Usually, when stretching the polyethylene terephthalate, if the stretching temperature is lower than the appropriate conditions, the yield stress increases rapidly at the beginning of the lateral stretching, and therefore stretching cannot be performed. Moreover, even if it can extend | stretch, since thickness and a draw ratio become easy to become nonuniform, it is unpreferable.

  In addition, when the stretching temperature is higher than appropriate conditions, the initial stress is low, but the stress does not increase even when the stretch ratio is high. Therefore, the film has a small stress at 100% elongation at 25 ° C. Therefore, by taking the optimum stretching temperature, a highly oriented film can be obtained while ensuring stretchability.

  However, when the copolymerized polyester contains 1 to 40 mol% of a copolymer component, the stretching stress rapidly decreases as the stretching temperature is increased so as to eliminate the yield stress. In particular, since the stress does not increase even in the latter half of the stretching, the orientation does not increase and the stress at 100% elongation at 25 ° C. decreases.

  Such a phenomenon is likely to occur when the thickness of the film is 60 to 500 μm, and is particularly noticeable in a film having a thickness of 100 to 300 μm. Therefore, for example, in the case of a film using polyester copolymerized with neopentyl glycol or 1,4-cyclohexanedimethanol, the stretching temperature in the transverse direction is preferably set as follows.

  First, the preheating temperature is 90 to 120 ° C., and the preheating temperature is preferably +5 to 25 ° C. in the first half of the transverse stretching, and the first half is preferably −15 to −40 ° C. in the second half of the transverse stretching. By adopting such conditions, the first half of the transverse stretching is easy to stretch because the yield stress is small, and the second half is easily oriented. In addition, it is preferable that the draw ratio of a horizontal direction shall be 22.5-5.0 times. As a result, it is possible to obtain a film in which the stress at 100% elongation in the longitudinal direction and the width direction satisfies 180 to 1000 MPa at 25 ° C. and 1 to 100 MPa at 100 ° C.

  Furthermore, the film is heat-treated after biaxial stretching, and this heat treatment can be performed by a conventionally known method such as in an oven or on a heated roll. Further, the heat treatment temperature and the heat treatment time can be arbitrarily set according to the required level of heat shrinkage. The heat treatment temperature is preferably in the range of 120 to 245 ° C, particularly preferably 150 to 230 ° C. The heat treatment time is preferably 1 to 60 seconds. In addition, you may perform this heat processing, relaxing a film to the longitudinal direction and / or the width direction. In order to reduce the thermal shrinkage in the longitudinal direction and the lateral direction at 150 ° C., it is preferable to increase the heat treatment temperature, lengthen the heat treatment time, and perform relaxation treatment. It is difficult to lengthen the line and increase the heat treatment time due to equipment limitations. Further, when the film feeding speed is slowed, productivity is lowered.

  In order to set the heat shrinkage rate in the longitudinal direction and the width direction at 150 ° C. to 6.0% or less, the heat treatment temperature is preferably 200 to 220 ° C. and relaxed at a relaxation rate of 1 to 8%. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

  Hereinafter, the present invention will be described in detail by way of examples. The film properties obtained in each example were measured and evaluated by the following methods.

(1) Intrinsic viscosity 0.1 g of the chip sample was precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 6/4 (mass ratio), and measured at 30 ° C. using an Ostwald viscometer. In addition, the measurement was performed 3 times and the average value was calculated | required.

(2) Thickness unevenness A continuous tape-like sample having a length of 3 m in the transverse stretching direction and a length of 5 cm in the longitudinal stretching direction is taken up, and the thickness of the film is measured with a continuous film thickness measuring machine (manufactured by Anritsu Corporation). To record. From the chart, the maximum value (dmax), minimum value (dmin), and average value (d) of the thickness were obtained, and the thickness unevenness (%) was calculated by the following formula. In addition, the measurement was performed 3 times and the average value was calculated | required. Moreover, when the length of a horizontal extending direction is less than 3 m, it joins and performs. The connecting part is deleted from the data.
Unevenness of thickness (%) = ((dmax−dmin) / d) × 100

(3) Haze Based on JIS-K7136, it measured using the haze meter (Nippon Denshoku Industries Co., Ltd. make, 300A). In addition, the measurement was performed twice and the average value was calculated | required.

(4) Film Thickness Using a millitron, a total of 15 points were measured, 5 points per sheet, and the average value was determined.

(5) Stress at 100% elongation, elongation at break With respect to the longitudinal direction and the width direction of the biaxially stretched film, a sample was cut into a strip shape having a length of 180 mm and a width of 10 mm, respectively, with a single-blade razor. Next, the sample was pulled using a tensile tester (manufactured by Toyo Seiki Co., Ltd.), and the stress at 100% elongation (MPa) and elongation at break (%) in each direction were determined from the obtained load-strain curve.

  The measurement was performed in an atmosphere of 25 ° C. under the conditions of an initial length of 40 mm, a distance between chucks of 100 mm, a crosshead speed of 100 mm / min, a recorder chart speed of 200 mm / min, and a load cell of 25 kg. The measurement was performed 10 times and the average value was used.

  In addition, a tensile test was performed under the same conditions as described above even in an atmosphere at 100 ° C. At this time, the sample was held for 30 seconds in an atmosphere at 100 ° C. and then measured. The measurement was performed 10 times and the average value was used.

(6) Thermal contraction rate at 150 ° C. A strip sample having a length of 250 mm and a width of 20 mm is cut out in the longitudinal direction and the width direction of the film, respectively. Two marks are marked at intervals of 200 mm in the length direction of each sample, and the distance A between the two marks is measured under a constant tension (tension in the length direction) of 5 g. Subsequently, one side of each strip-shaped sample is hung with a clip on a basket under no load, and placed in a gear oven under an atmosphere of 150 ° C., and time is taken. After 30 minutes, the basket is removed from the gear oven and left at room temperature for 30 minutes. Next, for each sample, the distance B between the two marks is read with a gold finger in units of 0.25 mm under a constant tension of 5 gf (longitudinal tension). From the read intervals A and B, the thermal shrinkage rate at 150 ° C. of each sample is calculated by the following formula.
Thermal contraction rate (%) = ((A−B) / A) × 100

(7) Insert moldability After printing on the film, the film was heated at 130 ° C. for 5 seconds, and then press molded at a mold temperature of 80 ° C. and a pressure holding time of 5 seconds. The obtained press-molded product was subjected to insert molding in which an ABS resin having a resin temperature of 210 ° C. was poured with an injection molding machine, and a key top having a height of 3.0 mm covered with a film was produced. Printing deviations were measured for the 10 created, and the molding state was visually observed and ranked according to the following criteria. In addition, (double-circle) and (circle) were set as the pass, and x was set as the disqualification.

A: Printing deviation is 0.1 mm or less, and the appearance is very good.
◯: The printing misalignment is 0.1 mm or more and 0.2 mm or less, and some wrinkles can be seen, but it is a level that causes no problem in practical use.
X: Printing deviation exceeds 0.2 mm. Or, the film is broken. Or, large wrinkles enter and the appearance is very bad.

Example 1
Containing 100 mol% terephthalic acid unit as the aromatic dicarboxylic acid component, 92 mol% ethylene glycol unit and 8 mol% neopentylglycol unit as the diol component, containing 400 ppm of amorphous silica having an average particle size of 1.5 μm, A copolyester having an intrinsic viscosity of 0.69 dl / g is pre-crystallized, then dried, melt-extruded at 280 ° C. using an extruder having a T-die, rapidly cooled and solidified on a drum having a surface temperature of 40 ° C., and amorphous. A sheet was obtained.

  The obtained sheet was stretched 3.5 times at 80 ° C. in the longitudinal direction between the heating roll and the cooling roll, and then the uniaxially stretched sheet was led to a tenter. Next, preheating was performed at 100 ° C. for 15 seconds, the first half of the transverse stretching was 115 ° C., the latter half was stretched 3.6 times at 95 ° C., and heat treatment was performed at 205 ° C. while performing 7% transverse relaxation. A biaxially stretched polyester film having a thickness of 188 μm was obtained. The melting point of the obtained film was 232 ° C.

Comparative Example 1
In Example 1, polyethylene terephthalate containing 400 ppm of amorphous silica having an average particle diameter of 1.5 μm and having an intrinsic viscosity of 0.69 dl / g was longitudinally stretched 3.7 times at 90 ° C., and then 4 times at 120 ° C. A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the film was stretched by 0.times. And then heat-treated at 230.degree. C. while relaxing 10% in the transverse direction. The melting point of the obtained film was 260 ° C.

Comparative Example 2
In Example 1, the film was longitudinally stretched 3.5 times at 125 ° C., then transversely stretched 3.5 times at 130 ° C., and then heat treated at 220 ° C. An axially stretched polyester film was obtained.

Comparative Example 3
In the method of Example 1, the composition ratio of ethylene glycol and neopentyl glycol in the polyester composition is 85 mol% and 15 mol%, respectively, except that the heat treatment temperature after transverse stretching is 190 ° C. Thus, a biaxially stretched polyester film was obtained. The melting point of the obtained film was 210 ° C.

Example 2
In Example 1, a biaxially stretched polyester film was obtained in the same manner as in Example 1 except that the thickness was 100 μm.

Example 3
Copolyester having an intrinsic viscosity of 0.71 dl / g, comprising 100 mol% of terephthalic acid units as the aromatic dicarboxylic acid component and 90 mol% of ethylene glycol units and 10 mol% of 1,4-cyclohexanedimethanol units as the diol component. After preliminary crystallization, this was dried, melt-extruded at 280 ° C. using an extruder having a T die, and rapidly cooled and solidified on a drum having a surface temperature of 40 ° C. to obtain an amorphous sheet.

  The obtained sheet was stretched 3.0 times at 75 ° C. in the longitudinal direction between the heating roll and the cooling roll, and then the uniaxially stretched sheet was led to a tenter. Next, preheating at 105 ° C. for 15 seconds, the first half of the transverse stretching is 125 ° C., the latter half is stretched 3.6 times at 98 ° C., and heat treatment is performed at 205 ° C. while relaxing 7% in the transverse direction. A biaxially stretched polyester film having a thickness of 188 μm was obtained. The melting point of the obtained film was 228 ° C.

Comparative Example 4
In the method of Example 3, except that the composition ratio of the ethylene glycol unit and 1,4-cyclohexanedimethanol unit in the polyester composition is 75 mol% and 25 mol%, respectively, and the heat treatment temperature after transverse stretching is 170 ° C. In the same manner as in Example 3, a biaxially stretched polyester film was obtained. The melting point of the obtained film was 195 ° C.

Comparative Example 5
The aromatic dicarboxylic acid component is composed of 100 mol% of terephthalic acid units, the diol component is composed of 95 mol% of ethylene glycol units, 3 mol% of 1,4-cyclohexanedimethanol units, and 2 mol% of diethylene glycol units. A copolyester having an intrinsic viscosity of 0.67 dl / g containing 2000 ppm of 6 μm aluminum silicate was pre-crystallized, then fully dried, and melt-extruded at 280 ° C. using an extruder having a T-die, and a surface temperature of 40 An amorphous sheet was obtained by rapid solidification on a ℃ drum.

  The obtained sheet was stretched 3.4 times at 96 ° C. in the longitudinal direction between the heating roll and the cooling roll, and then the uniaxially stretched sheet was led to a tenter. Next, it was preheated at 100 ° C. for 15 seconds, stretched 3.3 times in the transverse direction at 115 ° C., heat-treated at 180 ° C. while relaxing 5% in the transverse direction, and a biaxially stretched polyester film having a thickness of 188 μm Got. The melting point of the obtained film was 250 ° C.

The polyester film for insert molding of the present invention is excellent in moldability at the time of heating, rigidity and shape stability (thickness unevenness, heat shrinkage characteristics) at the time of use as a molded product, and further finished when used for insert molding. Therefore, it is suitable as a support film such as a transfer type printing film in insert molding.

Claims (7)

  A polyester film comprising a copolyester composed of an aromatic dicarboxylic acid component and ethylene glycol and a glycol component containing a branched aliphatic glycol and / or alicyclic glycol, the film having a longitudinal direction and a width. A polyester film for insert molding having a 100% elongation stress in the direction of 180 to 1000 MPa at 25 ° C and 1 to 100 MPa at 100 ° C, and a melting point of 220 to 245 ° C.   The polyester film for insert molding according to claim 1, wherein the branched aliphatic glycol is neopentyl glycol.   The polyester film for insert molding according to claim 1 or 2, wherein the alicyclic glycol is 1,4-cyclohexanedimethanol.   The polyester film for insert molding according to any one of claims 1 to 3, wherein the aromatic dicarboxylic acid component is terephthalic acid, naphthalenedicarboxylic acid, or an ester-forming derivative thereof.   The polyester film for insert molding according to any one of claims 1 to 4, wherein the film has a thickness unevenness of 5.5% or less.   The polyester film for insert molding according to any one of claims 1 to 5, wherein the film has a heat shrinkage of 6.0% or less in a longitudinal direction and a width direction at 150 ° C. The polyester film for insert molding according to any one of claims 1 to 6, wherein the film has a ratio (H / d) of haze H (%) to thickness d (µm) of 0.030 or less. .