JPH05269843A - In-mold transferring substrate film - Google Patents

Abstract

PURPOSE:To produce in-mold transferring substrate film by a method wherein the film concerned is turned to be made of polybutylene terephthalate, which has the predetermined heat of crystalline melting or higher and is biaxially stretched so as to bring its coefficient of planar orientation within a certain range and finally thermoset, in order to have smooth surface and improved strength, heat resistance, transparency, nonstaining properties and the like. CONSTITUTION:The film concerned is made of polybutylene terephthalate and has the heat of crystalline melting of 8cal/g or more, preferably 9cal/g or more and is biaxially stretched so as to have the coefficient of planar orientation of 0.07-0.16, preferably 0.09-0.15 and finally thermoset. As the biaxially stretching method, progressive or simultaneous biaxial stretching method with a tenter or tubular simultaneous biaxial stretching method is employed. The preferable intrinsic viscosity of polybutylene terephthalate used for the tubular simultaneous biaxial stretching is 0.7 or more.

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 in-mold transfer, that is, a base film for a transfer foil used for pattern printing on the surface of a molded product simultaneously with injection molding.

[0002]

2. Description of the Related Art In recent years, household appliances, automobile interior parts,
Plastic products used for kitchen utensils, cosmetic containers, toys, etc. tend to require a surface finish with a three-dimensional curved structure with a high degree of deep drawing due to the diversification of consumer needs regarding their design and habitability. It's getting stronger.

Among these, as a method for printing a pattern on the surface of a plastic molded article having a high deep drawing degree, a printing layer such as a release layer, a pattern layer or an adhesive layer is formed on the surface of the base film 4 as shown in FIG. A so-called in-mold transfer method is generally used, in which the transfer foil 3 on which 5 is sequentially coated is preliminarily positioned between the molds 1, and then a resin is press-fitted by the injection molding machine 2 to print a pattern simultaneously with molding. Has been adopted by many. According to this in-mold transfer method, the substrate film after transfer can be peeled from the molded product or can be left as it is and integrated with the molded product. Compared with the method of printing after molding, it is possible to greatly reduce costs by simplifying the process, and it is also possible to print on a curved surface such as two-dimensional or three-dimensional with extremely high accuracy. It is a thing.

By the way, as such a substrate film for in-mold transfer, a biaxially stretched polyethylene terephthalate film is disclosed in JP-A-64-45699, JP-A-3-253317 and JP-A-3-288699. Further, JP-A-3-288700 proposes a method using a polyvinyl chloride film.

Among them, the polyethylene terephthalate biaxially stretched film is widely used as a film of this type because it has excellent properties such as strength, heat resistance, surface smoothness and non-staining property. Since terephthalate is highly crystallized by stretching and heat setting, its elongation at break is small, and when it has a complicated shape with a deep drawing degree of 8R or less, the film breaks during in-mold molding and cannot function as a transfer foil. Had a problem.

On the other hand, a polyvinyl chloride film can be increased in elongation at break by adding a plasticizer and can relatively well follow a complicated shape having a high deep drawing degree, but on the other hand, it has a high heat resistance. This film was also unsatisfactory, because it had a serious problem that the plasticizer bleeded out to contaminate the transfer surface.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention that even a molded article having a high deep-drawing degree may be broken or wrinkled during in-mold molding. It is another object of the present invention to provide a base film for in-mold transfer, which is most suitable for obtaining a resin molded product having a beautiful appearance with less distortion such as a pattern.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have studied earnestly from a comprehensive point of view, regarding various heat resistant resins, the relationship between inherent film characteristics and deep drawing formability. As a result, the polybutylene terephthalate film biaxially stretched under specific conditions has an excellent surface smoothness, excellent transparency and non-staining properties, and excellent strength based on a unique crystal structure in which α-type crystals and β-type crystals coexist. Then, paying attention to the fact that it also has a relatively large elongation at break, which was not found in conventional polyethylene terephthalate films, and if the base film of the in-mold transfer foil is made of such a specific film, a high deep drawing degree of about 3R is achieved. However, they found that the film follows extremely well without tearing, and completed the present invention.

That is, the present invention is characterized by comprising a polybutylene terephthalate film having a heat of crystal fusion of more than 8 cal / g and a plane orientation coefficient of 0.07 to 0.16, which is biaxially stretched and heat-set. The present invention relates to a substrate film for mold transfer.

The in-mold transfer substrate film of the present invention will be described in detail below.

In the present invention, polybutylene terephthalate is a polyester containing butylene terephthalate as a main repeating unit, and specifically, 1,4-butanediol as a glycol component or an ester-forming derivative thereof and a dibasic acid. A homo- or copolyester obtained by condensing terephthalic acid or its ester-forming derivative as a main component and condensing them.

In the case of such a copolyester mainly composed of polybutylene terephthalate, there is an advantage that the elongation at break becomes large and the deep drawability is improved although the heat resistance is slightly lowered. The copolyester mainly composed of polybutylene terephthalate means that a part of the terephthalic acid component as a dibasic acid component is a dibasic acid component such as isophthalic acid, phthalic acid, adipic acid or sebacic acid. And / or a part of the 1,4-butanediol component as a glycol component is replaced with another glycol component such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, cyclohexanedimethanol, etc. It is a polyester obtained by condensing styrene with a butylene terephthalate unit of 70% or more.

The polybutylene terephthalate of the present invention may be added with other polyesters such as polyethylene terephthalate, poly (ethylene terephthalate / ethylene isophthalate), polycarbonate, etc. within a range that does not impair the properties thereof. Further, if necessary, appropriate lubricant, antiblocking agent, inorganic extender, antioxidant, ultraviolet absorber, antistatic agent, flame retardant, plasticizer, colorant, crystallization inhibitor, crystallization accelerator, etc. It does not matter if you add additives.

The substrate film for in-mold transfer of the present invention is a film made of such polybutylene terephthalate and has a heat of crystal fusion of more than 8 cal / g, preferably 9 cal / g or more.

Here, the heat of crystal fusion is obtained from the area of the heat absorption peak associated with crystal melting when the sample is heated at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter, and is generally The higher the value, the more the crystallinity and the better the heat resistance. Therefore, when the heat of fusion of crystal is 8 cal / g or less, the crystallinity decreases and the heat resistance becomes poor, and the thermal dimensional stability is good. Such a film cannot be obtained, and the film shrinks in the coating process of the pattern layer or the like or the in-mold forming process to cause distortion in the pattern, making it difficult to perform delicate transfer printing. Although there is no particular upper limit to the heat of crystal fusion, the heat of crystal fusion of a polybutylene terephthalate homopolymer consisting of 1,4-butanediol and terephthalic acid is usually about 13 cal / g, and therefore, the heat of fusion is generally less than that. Target.

The base film for in-mold transfer of the present invention is a biaxially stretched and heat-fixed poly film which has a plane orientation coefficient of 0.07 to 0.16, preferably 0.09 to 0.15. It is composed of a butylene terephthalate film.

In the present invention, the reason why the base film for in-mold transfer is made of such a specific biaxially stretched and heat-fixed film is to simply increase the strength and Young's modulus of the film to improve printability. Not only because of this, but considering the properties peculiar to polybutylene terephthalate, which has a low glass transition temperature of about 40 ° C. and a high crystallization rate, the unstretched film is poor in heat resistance, and a normal inflation film is Since the disadvantage of whitening and loss of transparency occurs during molding, biaxial stretching is required to combine excellent heat resistance and transparency while maintaining the strength and deep drawability required for in-mold transfer. This is because it was concluded that heat fixation is essential.

Here, the plane orientation coefficient ΔP is the refractive index in the length direction, the width direction, and the thickness direction in the film plane, respectively.
When x, Ny, and Nz, ΔP = (Nx + Ny) / 2
When the surface orientation coefficient is less than 0.07, the thickness unevenness is large due to insufficient stretching, and due to insufficient heat resistance and Young's modulus, a release layer, a pattern layer, an adhesive layer, etc. In the coating process, the film is easily stretched, and so-called print misalignment occurs. On the other hand, if the plane orientation coefficient is larger than 0.16, it is necessary to stretch at a high magnification, so if the film is made thick, the transparency is lost, and if the transparency is improved, the elongation becomes too small. Therefore, it becomes difficult to achieve both transparency and deep-drawing formability, for example, the deep-drawing formability is lowered and the film is easily broken during in-mold forming.

In the film of the present invention, the birefringence index determined from the difference in the refractive index in the length direction and the width direction is preferably 0.05 or less, and when it exceeds 0.05, the anisotropy of the film is increased. Becomes large, and the deep drawability decreases.

In order to produce the polybutylene terephthalate film of the present invention, as a general rule, a polybutylene terephthalate raw material having a heat of crystal fusion of more than 8 cal / g is melt-extruded at a temperature of 240 to 290 ° C., and then 30 ° C. or less. It is obtained by a series of methods in which a transparent unstretched film is formed by quenching at the temperature of 1., followed by biaxial stretching and heat setting through a preheating step of 40 ° C. or less.
At that time, any method such as a sequential or simultaneous biaxial stretching method using a tenter and a tubular simultaneous biaxial stretching method may be used as the biaxial stretching method, but in a resin having a high crystallization rate such as polybutylene terephthalate, the stretching rate is high. The tubular stretching method, in which the stretching is fast and the stretching is carried out simultaneously in the longitudinal and lateral directions, is preferable in that oriented crystallization in the stretching process is suppressed and uniform and stable stretching is possible.

Specific examples of the stretching conditions in the tubular simultaneous biaxial stretching method include a stretching zone designed so that the time from the start to the end of stretching is within 5 seconds, the thickness of the unstretched film and the crystal. Polybutylene is stretched so that the plane orientation coefficient becomes 0.07 to 0.16 under the conditions of a temperature of 50 to 140 ° C. and a magnification of 1.5 to 3.8 depending on the degree of chemical conversion. In the case of terephthalate, it is important to keep the preheating temperature up to 40 ° C until it reaches the stretching zone. If the preheating temperature is higher than 40 ° C, stretching in the longitudinal and transverse directions becomes unbalanced and uniform stretching becomes difficult. ..
The intrinsic viscosity of polybutylene terephthalate to be subjected to such tubular simultaneous biaxial stretching is preferably 0.7 or more. If it is less than 0.7, the melt viscosity is low and drawdown easily occurs, so that the shape retention during extrusion is low. In addition to being difficult, the crystallization rate will be significantly faster, so no matter how quickly it is cooled after melt extrusion, the whitening phenomenon due to the formation of spherulites cannot be suppressed, the transparency is impaired, and the strength and deep drawing formability also deteriorate. To do.

The heat setting conditions for producing the polybutylene terephthalate film in the present invention include:
When the temperature is low, the increase in crystallinity is small, so it is difficult to obtain a film with a large heat of fusion of crystals, and the thermal dimensional stability is inevitably deteriorated. When the melting point of polybutylene terephthalate is usually set to Tm because the heat of crystal fusion and the plane orientation coefficient cannot be maintained due to a decrease in orientation, (Tm-6
It is preferable that the temperature is set to 0) to (Tm-10) ° C., and the heat setting is performed at a relaxation rate of about 5 to 30%.

In the present invention, the thickness of the polybutylene terephthalate film is usually 10 to 100 μm, preferably 20 to 80 μm, though it depends on the required deep drawing degree and the like. It is suitable in view of deep drawability. Further, as the resin for injection molding which is printed with the pattern using the in-mold transfer base material film of the present invention, any resin can be basically used as long as it is an injection moldable resin, but it is usually acrylonitrile / butadiene. / Styrene copolymer resin, acrylonitrile / styrene copolymer resin,
Polypropylene, polystyrene, polyamide, polycarbonate, polyethylene and the like are common.

[0024]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

The methods of measuring and evaluating the physical properties used in the present invention are as follows. (1) Heat of fusion of crystal (unit: cal / g) Differential scanning calorimeter DSC22 manufactured by Seiko Instruments Inc.
It was calculated by the following formula from the area of the endothermic peak accompanying crystal melting when the sample was heated at a temperature rising rate of 20 ° C./min using 0 C. Heat of fusion of crystal = H · S / M where H: heat of fusion per unit area when indium is measured under the same conditions (cal / cm ² ) S; peak area of crystal melting of sample (cm ² ) M; of sample Weight (g) (2) Plane orientation coefficient Calculated as ΔP from the refractive index in the length direction, width direction and thickness direction in the film plane. The refractive index was measured using an Appe refractometer manufactured by Atago Co., Ltd. under a sodium light source. (3) Tensile strength (unit: kg / mm ² ) and elongation at break (unit:%) Measured by a method according to JIS C2318. (4) Thermal dimensional stability (unit:%) 100 mm in length and width to be parallel to the length direction of the film
Sample film sampled in a square of 3
It was hung for 0 minutes and left to stand, and the thermal dimensional stability in the vertical and horizontal directions was calculated by the following formula. Thermal dimensional stability = [(100−A) / 100] × 100 where A: length in the vertical or horizontal direction after leaving in hot air for 30 minutes (mm) (5) Printability Base material using a gravure printing machine A release layer, a pattern layer, an adhesive layer and the like were sequentially coated on the film surface. The coating conditions were such that the film tension in each printing machine was 15 to 25 kg / cm ² and the drying temperature was 60 to 80 ° C., respectively. As a result, the printability of the film was rated as good (○), and that when the film was slightly shrunk or stretched and the pattern was distorted or misaligned was defined as (x). (6) Deep drawing formability As shown in FIG. 1, using a mold in which the transfer foil is positioned in advance so that the printing surface comes into contact with the resin side, a tray with a size of 10 cm square, a rise of 10 mm, and a corner R of 3 mm is used. The molded article was injection molded. At that time, ABS is used as the molding resin.
Molding conditions are: resin temperature 220 ° C, mold temperature 55
The resin pressure was about 300 kg / cm ² . In this evaluation method, those having no problem in deep drawing formability (◯) were evaluated, and those in which the pattern was distorted due to the transfer foil being torn or contracted were evaluated as (x).

Example 1 A polybutylene terephthalate raw material (melting point: 225 ° C.) having an intrinsic viscosity of 1.4, which comprises terephthalic acid as a dibasic acid component and 1,4-butanediol as a glycol component,
Using an extruder with a diameter of 65 mm equipped with an annular die at its tip, melt-extrude under each condition of screw rotation speed of about 40 rpm, cylinder and die temperature of 240 to 280 ° C, and immediately chill with water at 5 ° C and fold. Diameter about 300mm,
A tubular unstretched film having a thickness of about 245 μm was produced. While preheating this unstretched film at a temperature of 25 ° C., it is guided to a pair of upper and lower nip rolls with different peripheral speeds, and pressurized air is fed at a stretching temperature of 60 to 90 ° C. to obtain a stretching ratio of 2.5 times the length and 3 times the width. Tubular simultaneous biaxial stretching was carried out so that the magnification was 0.0 times. Then, while maintaining the tube shape, heat fixation was carried out at 200 ° C. for 3 seconds while giving a relaxation of 15 to 20% in each of the vertical and horizontal directions, and then both ends were cut to a thickness of 45 μm, a width of 750 mm, and a heat of crystal fusion of 10 .8ca
A biaxially stretched polybutylene terephthalate film having a surface orientation coefficient of 1 / g was prepared. A release layer, a pattern layer, an adhesive layer, etc. were sequentially coated on the surface of the film thus obtained, and the deep drawing formability was evaluated by an in-mold forming test. The results were tensile strength, elongation at break, and thermal dimensional stability. Table 1 shows the physical properties of the film.

Comparative Example 1 Table 1 shows the results of a test conducted in the same manner as in Example 1 except that a commercially available biaxially stretched polyethylene terephthalate film (thickness 38 μm) was used as a substrate film for in-mold transfer. ..

[0028]

[Table 1]

From the results shown in Table 1, when the biaxially stretched and heat-fixed polybutylene terephthalate film of the present invention was used as a base film for in-mold transfer, the elongation at break was higher than that of the conventional polyethylene terephthalate film. It can be seen that it is large and has excellent deep drawability.

Example 2 The same as Example 1 except that a polybutylene terephthalate raw material (melting point: 224 ° C.) having an intrinsic viscosity of 1.0 and containing terephthalic acid as a dibasic acid component and 1,4-butanediol as a glycol component was used. Thickness of 45 μm,
A biaxially stretched polybutylene terephthalate film having a width of 750 mm, a heat of crystal fusion of 11.1 cal / g and a plane orientation coefficient of 0.14 was produced. Table 2 shows the tensile strength, elongation at break, thermal dimensional stability, printability, and deep drawability of this film.

Example 3 The heat of crystal fusion was 8.5 cal / g and the plane orientation coefficient was 0. 1 in the same manner as in Example 2 except that the heat setting temperature was 210 ° C.
Ten biaxially oriented polybutylene terephthalate films were produced. Table 2 shows the tensile strength, elongation at break, thermal dimensional stability, printability, and deep drawability of this film.

Comparative Example 2 87.5 mol% of terephthalic acid as a dibasic acid component and 12.5 mol% of isophthalic acid, and 1,4 as a glycol component.
A copolyester raw material consisting of butanediol (melting point;
205 ℃) Cylinder and die temperature 230 to 260
The heat of crystal fusion was 7.4 by the same method as in Example 2 except that the temperature was 180 ° C. at the time of heat setting.
A biaxially stretched film having a cal / g and a plane orientation coefficient of 0.13 was produced. Table 2 shows the tensile strength, elongation at break, thermal dimensional stability, printability, and deep drawability of this film.

[0033]

[Table 2] In the table, ΔP is a plane orientation coefficient.

From the results shown in Table 2, those having a heat of fusion of crystal outside the range of the present invention were poor in thermal dimensional stability and were inferior in printability and deep drawing formability such as distortion of pattern printing.

Examples 4 to 6 and Comparative Examples 3 to 4 Example 1 except that the screw rotation speed during melt extrusion was changed.
By the same method as in, the folding diameter is about 300 mm and the thickness is about 6
Various tubular unstretched films having different thicknesses of 5, 105, 170, 295 and 490 μm were produced. This unstretched film is introduced into a pair of upper and lower nip rolls having different peripheral speeds while being preheated at a temperature of 20 ° C., and pressurized air is sent under a stretching temperature of 50 to 100 ° C. to obtain a stretching ratio of the thickness of the unstretched film. From the thin order to 1.4 and 1.8, respectively
Tubular simultaneous biaxial stretching was carried out so that the ratio was 2.3, 3.0 and 3.9 times. Continuously, after cutting both ends of the tubular stretched film, about 7% in the lateral direction using a tenter.
Of 5 kinds of biaxially stretched polybutylene terephthalate having a thickness of 35 μm and a plane orientation coefficient of 0.06 to 0.17 by heat setting for 10 seconds at 180 to 210 ° C. A film was made. After subjecting the surface of the film thus obtained to corona discharge treatment, a release layer, a pattern layer, an adhesive layer and the like are sequentially applied to the treated surface, and the result of deep drawing forming evaluation by an in-mold forming test Is shown in Table 3 together with film properties such as tensile strength, elongation at break, and thermal dimensional stability.

[0036]

[Table 3] In the table, ΔP is a plane orientation coefficient.

As is clear from Table 3, when the surface orientation coefficient is less than 0.07, slight elongation was observed in the film in the coating process of the pattern layer and the like, and print misalignment occurred. Of 0.16 or more was a film that broke during in-mold molding and did not function as a transfer foil.

[0038]

The substrate film for in-mold transfer of the present invention as described above is biaxially stretched and heat-treated so that the heat of crystal fusion is larger than 8 cal / g and the plane orientation coefficient is 0.07 to 0.16. Since it is composed of fixed polybutylene terephthalate film, it has not only smooth surface but also excellent strength, heat resistance, transparency, non-staining property, etc., and it is not found in conventional base film made of polyethylene terephthalate. It also has excellent deep drawing formability, making it particularly suitable as a base film for in-mold transfer of plastic molded products with a high degree of deep drawing,
At the same time, the simplification of such transfer printing greatly contributes to cost reduction.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of an in-mold transfer method.

[Explanation of symbols]

 1 Mold 2 Injection Molding Machine 3 Transfer Foil 4 Base Film 5 Printing Layer

[Procedure amendment]

[Submission date] June 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

In the case of such a copolyester mainly composed of polybutylene terephthalate, there is an advantage that the elongation at break becomes large and the deep drawability is improved although the heat resistance is slightly lowered. The copolyester mainly composed of polybutylene terephthalate means that a part of the terephthalic acid component as a dibasic acid component is a dibasic acid component such as isophthalic acid, phthalic acid, adipic acid or sebacic acid. And / or a part of the 1,4-butanediol component as a glycol component is replaced with another glycol component such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, cyclohexanedimethanol, etc. It is a polyester obtained by condensing styrene with a butylene terephthalate unit content of 70 mol % or more.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B29K 67:00 B29L 7:00 4F (72) Inventor Sumitori Tanaka Michifuku, Tadotsu Town, Nakatado-gun, Kagawa Prefecture Temple 200-37 (72) Inventor Hideki Fukunaga 1210 Ejiri-cho, Sakaide-shi, Kagawa (72) Inventor Masato Mito 231 Utazu-cho, Ayaka-gun, Kagawa (72) Inventor Masafumi Shirai 738-1 Tsumori-cho, Marugame-shi, Kagawa

Claims (2)

[Claims] 1. The heat of fusion of crystal is larger than 8 cal / g,
A base film for in-mold transfer, comprising a polybutylene terephthalate film which has a plane orientation coefficient of 0.07 to 0.16 and is biaxially stretched and heat-set. 2. The in-mold transfer substrate according to claim 1, wherein the polybutylene terephthalate film is obtained by simultaneously biaxially stretching polybutylene terephthalate having an intrinsic viscosity of 0.7 or more by a tubular method. Wood film.