JP3486692B2 - Base film for in-mold transfer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base film for in-mold transfer, that is, a transfer foil used for pattern printing on the surface of a molded product simultaneously with injection molding. The present invention relates to a base film. [0002] In recent years, household appliances, automobile interior parts,
Plastic products used in kitchenware, cosmetic containers, toys, etc. tend to require a surface finish with a three-dimensional curved surface structure with a high degree of deep drawing due to diversification of consumer needs related to design and livability. It is getting stronger. Under these circumstances, as a method of printing a pattern on the surface of a plastic molded product having a high degree of deep drawing, a printing layer such as a release layer, a pattern layer, and 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 a transfer foil 3 coated sequentially with 5 is pre-positioned between the molds 1, and thereafter, a resin is press-fitted by an injection molding machine 2 to perform pattern printing simultaneously with molding. Many are adopted. According to this in-mold transfer method, the base film after transfer can be peeled off from the molded product or can be left as it is to be integrated with the molded product, so that excellent surface characteristics are exhibited, and the conventional Compared to the method of printing after molding, various advantages are obtained, such as drastic cost reduction by simplification of the process and further, extremely accurate printing on a two-dimensional or three-dimensional curved surface. Things. Japanese Patent Application Laid-Open Nos. 64-45699, 3-253317, and 3-288699 disclose a biaxially stretched polyethylene terephthalate film as a substrate film for in-mold transfer. Japanese Patent Application Laid-Open No. 3-288700 proposes a method using a polyvinyl chloride film. [0005] Of these, polyethylene terephthalate biaxially stretched film is widely used as this kind of film because it has excellent properties such as strength, heat resistance, surface smoothness, and non-staining property. Terephthalate is highly crystallized by stretching and heat setting, etc., so its elongation at break is small, and when it becomes a complicated shape with a high degree of deep drawing of 8R or less, the film breaks during in-mold molding and cannot function as a transfer foil. Had the problem that On the other hand, a polyvinyl chloride film can increase the elongation at break by adding a plasticizer, and can follow a complicated shape having a high degree of deep drawing relatively well. This film was also unsatisfactory because of the serious problem that the plasticizer bleed out and stained the transfer surface. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. It is an object of the present invention to form a film having a high degree of deep drawing such that a film is torn or wrinkled during in-mold molding. An object of the present invention is to provide a base film for in-mold transfer which is most suitable for obtaining a resin molded product having a beautiful appearance with no distortion and little distortion such as a design. Means for Solving the Problems To achieve the above object, the present inventors have studied the relationship between the inherent film properties and the deep drawability of various heat-resistant resins in a comprehensive manner. As a result of diligent studies, polybutylene terephthalate film biaxially stretched under specific conditions has a smooth surface, excellent transparency and non-staining properties, and is excellent based on a unique crystal structure in which α-type crystals and β-type crystals coexist. The strength and the relatively high elongation at break, which were not found in conventional polyethylene terephthalate films. If the specific film is used as the base film for the in-mold transfer foil, it is as high as about 3R. It has been found that the film follows the film very well without breaking even at a deep drawing degree, and the present invention has been completed. [0009] That is, the present invention relates to a polymer having an intrinsic viscosity of 0.7 or more.
1.5 to 1.5 times each of rib-butylene terephthalate
Simultaneous simultaneous by the tubular method so that 3.8 times
Axial stretched and heat-set base material for in-mold transfer
A beam, crystal fusion heat of 8.5 to 11.1Cal /
g and a poly (butylene terephthalate) film having a plane orientation coefficient of 0.07 to 0.16. Hereinafter, the base film for in-mold transfer of the present invention will be described in detail. In the present invention, polybutylene terephthalate is a polyester having 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 It is a homo- or copolyester obtained by condensing terephthalic acid or an ester-forming derivative thereof as a main component. The polybutylene terephthalate of the present invention may contain other polyesters such as polyethylene terephthalate, poly (ethylene terephthalate / ethylene isophthalate), polycarbonate and the like as long as the properties are not impaired. And, if necessary, suitable lubricants, anti-blocking agents, inorganic extenders, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, plasticizers, coloring agents, crystallization inhibitors, crystallization accelerators, etc. Additives can be added. The substrate film for in-mold transfer of the present invention is a film made of such polybutylene terephthalate and having 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 accompanying the crystal melting when the sample is heated at a heating rate of 20 ° C./min using a differential scanning calorimeter. Since the higher the value is, the higher the crystallinity tends to be and the higher the heat resistance tends to be. When the heat of crystal fusion is 8 cal / g or less, the crystallinity is reduced and the heat resistance is poor, and the thermal dimensional stability is good. A film cannot be obtained, and the film shrinks in the coating step of the pattern layer or the like or the in-mold forming step, and the pattern is distorted, so that precise transfer printing becomes difficult. Although there is no particular upper limit for the heat of crystal fusion, the heat of crystal fusion of a polybutylene terephthalate homopolymer composed of 1,4-butanediol and terephthalic acid is generally about 13 cal / g, and therefore, less than about 13 cal / g is generally used. It is a target. Further, the substrate film for in-mold transfer of the present invention has a biaxially stretched and heat-set poly film having 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 constituted by such a specific biaxially stretched and heat-fixed film is that the film simply has a higher strength and a higher Young's modulus to improve printability. In addition to this, considering the unique properties of polybutylene terephthalate that the glass transition temperature is as low as about 40 ° C. and the crystallization rate is high, heat resistance is poor as it is in an unstretched film, and ordinary inflation film Because of the disadvantage of whitening and loss of transparency during molding, biaxial stretching is required to combine the excellent heat resistance and transparency while maintaining the strength and deep drawability required for in-mold transfer. And the conclusion that heat fixation is essential. Here, the plane orientation coefficient ΔP is defined as the refractive index in the length direction, width direction and thickness direction in the film plane, respectively.
When x, Ny, and Nz are set, ΔP = (Nx + Ny) / 2
When the plane orientation coefficient is less than 0.07, the thickness unevenness is large due to insufficient stretching, and the release layer, the pattern layer, the adhesive layer, etc. due to insufficient heat resistance and Young's modulus. In the coating step, the film is easily stretched, and so-called printing misregistration occurs. On the other hand, when the plane orientation coefficient is larger than 0.16, stretching at a high magnification is required. Therefore, the transparency is lost when trying to thicken the film, and the elongation is too small when trying to improve the transparency. Thus, it is difficult to achieve both transparency and deep drawability, for example, the deep drawability is reduced and the film is easily broken during in-mold formation. In the film of the present invention, the birefringence determined from the difference between the refractive indices in the length direction and the width direction is preferably 0.05 or less. And the deep drawability decreases. In order to produce the polybutylene terephthalate film of the present invention, first, 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 a transparent unstretched film is formed at a temperature of 40 ° C. to obtain a transparent unstretched film, followed by a biaxial stretching and heat setting through a preheating step of 40 ° C. or less.
At that time, Ji Yubura simultaneous biaxial stretching method is used as a method of biaxial stretching. In a resin having a high crystallization rate such as polybutylene terephthalate, the stretching rate is high,
Moreover, the tubular stretching method in which stretching is performed simultaneously in the longitudinal and transverse directions is preferable in that oriented crystallization in the stretching process is suppressed and uniform and stable stretching can be performed. Here, specific examples of 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, The film 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 vertical and horizontal magnification of 1.5 to 3.8 times according to the degree of chemical conversion. In the case of polybutylene terephthalate, it is also important to keep the preheating temperature at 40 ° C or less before leading to the stretching zone. If the preheating temperature is higher than 40 ° C, stretching in the vertical and horizontal directions becomes unbalanced or uniform stretching is difficult. become. The intrinsic viscosity of polybutylene terephthalate subjected to such tubular simultaneous biaxial stretching is 0.7
Are those described above, except that the shape retention during extrusion makes it easier to draw down low melt viscosity is difficult is less than 0.7, no matter how rapid cooling after melt extrusion for crystallization rate is significantly faster spherulites Cannot suppress the whitening phenomenon due to the formation of, and not only the transparency is impaired, but also the strength, the deep draw formability and the like are reduced. In the present invention, the heat setting conditions for producing a polybutylene terephthalate film include:
When the temperature is low, the increase in crystallinity is small, and it is difficult to obtain a film with a large heat of crystal fusion, which inevitably deteriorates the thermal dimensional stability. Ordinarily, when the melting point of polybutylene terephthalate is Tm, (Tm−6)
It is preferable to set the temperature at 0) to (Tm-10) ° C. and heat-set at a relaxation rate of about 5 to 30%. In the present invention, the thickness of the polybutylene terephthalate film varies depending on the required degree of deep drawing, but it is usually 10 to 100 μm, preferably about 20 to 80 μm, and the film strength, elongation at break, printability, It is suitable from the viewpoint of deep drawing formability and the like. In addition, as the resin for injection molding to be printed by using the substrate film for in-mold transfer of the present invention, basically any resin can be 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. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating physical properties performed in the present invention are as follows. (1) Heat of crystal fusion (unit: cal / g) Differential scanning calorimeter DSC22 manufactured by Seiko Electronic Industry Co., Ltd.
Using 0C, the following equation was used to calculate the area of the endothermic peak accompanying the crystal melting when the sample was heated at a heating rate of 20 ° C./min. Heat of crystal fusion = H · S / M where H: Heat of fusion per unit area when measuring indium under the same conditions (cal / cm ² ) S: Crystal melting peak area of sample (cm ² ) M: Sample Weight (g) (2) Plane orientation coefficient ΔP was calculated from the refractive index in the length direction, width direction and thickness direction in the plane of the film. The refractive index was measured under a sodium light source using an Atpe refractometer. (3) Tensile strength (unit: kg / mm ² ), elongation at break (unit:%) Measured by a method according to JIS C2318. (4) Thermal dimensional stability (unit:%) 100 mm vertically and horizontally so as to be parallel to the length direction of the film
The sample film sampled in a square of
The sample was suspended for 0 minutes and allowed to stand, and the thermal dimensional stability in the vertical and horizontal directions was calculated by the following equation. Thermal dimensional stability = [(100−A) / 100] × 100 where A is the length in the vertical or horizontal direction (mm) after being left in hot air for 30 minutes (5) Printability Substrate using gravure printing machine A release layer, a design layer, an adhesive layer, and the like were sequentially applied to 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 film which could be applied without any trouble as the printability of the film was evaluated as (）), and the film which contracted or expanded slightly due to the film shrinking or expanding was evaluated as (×). (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 is in contact with the resin side, a tray having a size of 10 cm square, a rise of 10 mm, and a corner radius of 3 mm. The molded article was injection molded. At that time, ABS for molding resin
The molding conditions were set at a resin temperature of 220 ° C. and a mold temperature of 55.
C. and a resin pressure of about 300 kg / cm ² . In this evaluation method, a pattern having no problem in deep drawing formability was indicated by (）), and a pattern in which the transfer foil was torn or shrunk to cause distortion in the design was indicated as (x). Example 1 A polybutylene terephthalate raw material (melting point: 225 ° C.) having an intrinsic viscosity of 1.4, comprising terephthalic acid as a dibasic acid component and 1,4-butanediol as a glycol component,
Using a 65 mm diameter extruder equipped with an annular die at the tip, melt extrusion was performed under each condition of a screw rotation speed of about 40 rpm, a cylinder and a die temperature of 240 to 280 ° C, and then immediately cooled with water at a temperature of 5 ° C and folded. About 300mm in diameter,
A tubular unstretched film having a thickness of about 245 μm was produced. The unstretched film is guided to a pair of upper and lower nip rolls having different peripheral speeds while being preheated at a temperature of 25 ° C., and is supplied with pressurized air at a stretching temperature of 60 to 90 ° C. to have a stretching ratio of 2.5 times in length and 3 times in width. Tubular simultaneous biaxial stretching was performed so as to be 0.0 times. Subsequently, the tube shape was maintained at 200 ° C. for 3 seconds while giving 15 to 20% relaxation 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
1 / g and a biaxially stretched polybutylene terephthalate film having a plane orientation coefficient of 0.13 were produced. A release layer, a pattern layer, an adhesive layer, and the like were sequentially applied to the surface of the obtained film, and the deep drawability was evaluated by an in-mold molding 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 oriented polyethylene terephthalate film (thickness: 38 μm) was used as the base film for in-mold transfer. . [Table 1] From the results shown in Table 1, when the biaxially stretched and heat-set polybutylene terephthalate film of the present invention is used as a base film for in-mold transfer, the elongation at break is lower than that of a conventional polyethylene terephthalate film. It can be seen that they are large and have excellent deep drawability. Example 2 Same as Example 1 except that a polybutylene terephthalate raw material having an intrinsic viscosity of 1.0 (melting point: 224 ° C.) comprising terephthalic acid as a dibasic acid component and 1,4-butanediol as a glycol component was used. 45 μm thick by the method of
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 tensile strength, elongation at break, thermal dimensional stability, printability, deep drawability, and the like of this film. Example 3 Except that the heat-setting temperature was 210 ° C., the heat of crystal fusion was 8.5 cal / g and the plane orientation coefficient was 0.
Ten biaxially stretched polybutylene terephthalate films were prepared. Table 2 shows tensile strength, elongation at break, thermal dimensional stability, printability, deep drawability, and the like of this film. Comparative Example 2 87.5 mol% of terephthalic acid and 12.5 mol% of isophthalic acid as dibasic acid components and 1,4 as a glycol component
A copolyester raw material comprising butanediol (melting point;
205 ° C.) with cylinder and die temperatures of 230 to 260
C. and extruded at a temperature of 180.degree. C. in the same manner as in Example 2, except that the heat of crystal fusion was 7.4.
A biaxially stretched film having a cal / g of 0.13 and a plane orientation coefficient of 0.13 was produced. Table 2 shows tensile strength, elongation at break, thermal dimensional stability, printability, deep drawability, and the like of this film. [Table 2] In the table, ΔP is a plane orientation coefficient. From the results shown in Table 2, those having a heat of crystal fusion outside the range of the present invention were inferior in printability and deep drawability, such as poor thermal dimensional stability and distortion in pattern printing. Examples 4 to 6 and Comparative Examples 3 and 4 Example 1 except that the screw speed during melt extrusion was changed.
By the same method as described above, the folded diameter is about 300 mm and the thickness is about 6 mm.
5 (Comparative Example 3) , 105 (Example 4) , 170 (Example
5) 295 (Example 6) , 490 μm (Comparative Example 4), and various different tubular unstretched films were produced. The unstretched film is guided to a pair of upper and lower nip rolls having different peripheral speeds while being preheated at a temperature of 20 ° C., and is supplied with pressurized air at a stretching temperature of 50 to 100 ° C., so that the stretching ratio is equal to the thickness of the unstretched film. At the same magnification in the vertical and horizontal directions from the thinner order , 1.4 times (Comparative Example 3) , 1.8 times (Example 4) ,
2.3 times (Example 5) , 3.0 times (Example 6) , 3.9
The tube was simultaneously biaxially stretched so as to be twice (Comparative Example 4) . Subsequently, after cutting both ends of the tubular stretched film, the film is heat-set at a temperature of 180 to 210 ° C. for 10 seconds while giving about 7% relaxation in the transverse direction using a tenter, so that the thickness of the film is constant at 35 μm, Coefficient is 0.0
Five different types of biaxially stretched polybutylene terephthalate films in the range of 6 to 0.17 were produced. 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 deep drawing is evaluated by an in-mold molding test. The results are shown in Table 3. [Table 3] In the table, ΔP is a plane orientation coefficient. As is clear from Table 3, in the case where the plane orientation coefficient was less than 0.07, slight elongation was observed in the film in the coating step of the design layer and the like, and printing displacement occurred. In the case where is larger than 0.16, the film was broken during in-mold molding and did not function as a transfer foil. As described above, the base film for in-mold transfer of the present invention has a polybutylene having an intrinsic viscosity of 0.7 or more.
1.5 to 3.8 times the height and width of phthalate
As described above, simultaneous biaxial stretching and heat-setting
A constant has been in-mold transfer base material film, crystal fusion heat is 8.5 to 11.1cal / g, and plane orientation coefficient is constituted by a polybutylene terephthalate film is 0.07 to 0.16 It has excellent surface smoothness and excellent strength, heat resistance, transparency, non-staining properties, etc., as well as excellent deep drawability not found in conventional base films made of polyethylene terephthalate. Since it is also used, it is particularly suitable as a base film for in-mold transfer of a plastic molded article having a high degree of deep drawing, and greatly contributes to cost reduction by simplifying such transfer printing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an outline of an in-mold transfer method. [Description of Signs] 1 Mold 2 Injection molding machine 3 Transfer foil 4 Base film 5 Print layer

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁷ Identification code FI C08J 5/18 CFD C08J 5/18 CFD (72) Inventor Suminori Tanaka 200-37, Dopukuji, Tadotsu-cho, Nakatado-gun, Kagawa Prefecture (72) Inventor Hideki Fukunaga 1210 Ejiri-cho, Sakaide-shi, Kagawa (72) Inventor Masato Mito 231 (72) Inventor Masafumi Shirai 738-1 Tsumori-cho, Marugame-shi, Kagawa (56) References JP JP-A-1-297287 (JP, A) JP-A-2-248300 (JP, A) JP-A-3-92319 (JP, A) JP-A-3-96321 (JP, A) JP-A-3-182321 (JP) JP-A-3-247427 (JP, A) JP-A-4-113900 (JP, A) JP-A-53-79969 (JP, A) JP-A-60-155427 (JP, A) JP-A-60-155427 64-40400 (JP, A) JP-A-64-45699 (JP, A) (58) Field (Int.Cl. ^7, DB name) B29C 55/00 - 55/30 B29C 45/00 - 45/84 B44C 1/00 - 7/08 B32B 27/00 - 35/00 C08J 5/18

Claims (1)

(57) [Claims] [Claim 1] Polybutylene tele having an intrinsic viscosity of 0.7 or more
The phthalate will be 1.5 to 3.8 times each in the vertical and horizontal directions
As described above, simultaneous biaxial stretching and heat setting by the tubular method
A base film for in-mold transfer , comprising a polybutylene terephthalate film having a heat of crystal fusion of 8.5 to 11.1 cal / g and a plane orientation coefficient of 0.07 to 0.16. Characteristic base film for in-mold transfer.