JP2012140498A - Biaxially oriented polyester film for concurrent deep drawing and transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film for concurrent deep drawing and transfer, which is used for decorating the surface of a resin molding having a curved and slightly complicate shape, such as electric appliances and car parts, to a matte tone having little gloss unevenness, and is excellent in deep drawing.SOLUTION: The biaxially oriented polyester film for concurrent deep drawing and transfer includes a copolymerized polyester containing an isophthalic acid unit, wherein the average value of longitudinal and lateral elongations at break of the film in a tensile test at 100°C is ≥250%, and the average roughness (Ra) of the film surface is in the range of 0.10 to 0.50 μm.

Description

  The present invention is a deep drawing molding suitable as a base film for a simultaneous molding decorative sheet used to decorate the surface of a resin molded product having a curved surface, such as an electric product or an automobile part, with a slightly complicated shape. The present invention relates to a biaxially stretched polyester film for simultaneous transfer.

  As one method for decorating plastic molded products having curved surfaces such as electrical appliances, a so-called in-mold molding method in which transfer printing is performed simultaneously with molding is widely used. The in-mold molding method uses a heat and pressure during plastic injection molding to create a transfer sheet in which a printing layer consisting of a release layer, an ink layer, an adhesive layer, etc. is laminated on the base film in advance. Transfer printing.

  The surface of the base film in contact with the release layer usually has fine irregularities on the surface in order to transfer the matte appearance to the molded product. As a method for providing fine irregularities on the surface of the base film, there are a method of embossing and coating a coating liquid containing fine particles, but there is a problem that the manufacturing process of the base film increases.

  Moreover, although the film which added the particle | grain relatively large at the time of polyester film manufacture and the surface was roughened is disclosed by patent document 1, it cannot be said that the glossiness of a molded article is low enough.

  On the other hand, if the particle concentration in the film is increased in order to increase the film surface roughness, there arises a problem that the film is broken at the time of molding simultaneous transfer processing.

  Further, according to Patent Document 2, a polyester film suitable for deep drawing in which particles are added to the surface layer of a co-extrusion laminated structure is proposed, but there is a problem that glossiness changes between a flat portion and a curved portion of a molded product. . Further, when the difference in particle concentration between the surface layer and the intermediate layer is large, there is a problem that the film is peeled off at the interface between the surface layer and the intermediate layer in the step of removing the film after transfer.

JP 2007-268708 A JP 2008-163275 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation, and its solution is to decorate the surface of a resin molded product having a curved surface and a slightly complicated shape such as an electric product or an automobile part in a matte tone with less gloss unevenness. Another object of the present invention is to provide a biaxially stretched polyester film for simultaneous molding and transfer that is excellent in deep drawing moldability.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is a film made of a copolyester containing an isophthalic acid unit, and the average value of the film length and width of the elongation at break in a tensile test at 100 ° C. is 250% or more. It exists in the biaxially-stretched polyether film for deep drawing simultaneous transfer characterized by the roughness (Ra) being in the range of 0.10 to 0.50 μm.

  According to the present invention, for molding simultaneous transfer excellent in deep drawability, which is used to decorate the surface of a resin molded product having a curved surface and a slightly complicated shape such as an electric product or an automobile part in a matte tone with less gloss unevenness. A biaxially stretched polyether film can be provided, and the industrial value of the present invention is high.

  The polyester used in the present invention consists of a copolyester containing an isophthalic acid unit usually in a concentration of 5 to 25 mol%, preferably 7 to 22 mol%, more preferably 10 to 20 mol%. A copolymer polyester containing 5 to 25 mol% of isophthalic acid unit is a mixture of an aromatic dicarboxylic acid such as terephthalic acid or naphthalene-2,6-dicarboxylic acid and 5 to 25 mol% of isophthalic acid, ethylene glycol, It is a polyester made by condensation polymerization of diethylene glycol or tetramethylene glycol. When the isophthalic acid unit is 5 mol% or less, the film elongation tends to be small. On the other hand, if the concentration exceeds 25 mol%, film shrinkage during simultaneous film transfer processing of the film may increase, making it difficult to perform the forming process. Alternatively, if the heat treatment temperature is raised in order to reduce the shrinkage rate, the film may be broken during film formation.

  Examples of the polymerization catalyst include antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds, and titanium compounds. Titanium compounds include, for example, tetraalkyl titanates, tetraaryl titanates, titanyl oxalate salts, titanyl oxalate, chelate compounds containing titanium, titanium tetracarboxylates, and specifically tetraethyl titanate, tetrapropyl titanate, tetraphenyl Examples thereof include titanate or a partial hydrolyzate thereof, titanyl ammonium oxalate, potassium titanyl oxalate, titanium triacetylacetonate and the like.

  The polyester film of the present invention preferably contains inorganic particles, organic salt particles, and crosslinked polymer particles.

  Inorganic particles used include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, lithium fluoride. Etc.

  Examples of the organic salt particles to be used include calcium oxalate, terephthalate such as calcium, barium, zinc, manganese and magnesium.

  Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers of divinylbenzene, styrene, acrylic acid, methacrylic acid, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin may be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles used in the present invention is usually preferably 3 to 8 μm. If the average particle size is less than 3 μm, the ability to form protrusions on the surface may be insufficient, which does not meet the object of the present invention. On the other hand, if the average particle size exceeds 8 μm, the film breaks when stretched. Etc. occur frequently and products cannot be collected stably.

  Furthermore, the particle content in the polyester is usually 0.1 to 5% by weight, preferably 0.2 to 3% by weight. When the particle content is less than 0.1% by weight, the number of protrusions on the film is not sufficient, and the appearance of the molded product with low gloss tends to be rough, whereas it exceeds 5% by weight. When the film is added, there is a tendency that breakage or the like tends to occur when the film is stretched, and the product may not be collected stably. In addition, there is a risk of tearing during deep drawing.

  The average roughness Ra of the polyester film of the present invention needs to be in the range of 0.10 to 0.50 μm. If Ra is less than 0.10 μm, the low glossiness of the molded product is insufficient, and the object of the present invention to obtain a film excellent in low glossiness cannot be achieved. Moreover, in order to make Ra larger than 0.50 μm, it is necessary to mix a large amount of coarse particles. When the film is stretched, breakage and the like occur frequently, and the product cannot be collected stably.

  The method for adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, heat stabilizers, lubricants, antistatic agents, fluorescent brighteners, dyes, pigments, and the like are added to the polyester film in the present invention as necessary. be able to. Depending on the application, an ultraviolet absorber, particularly a benzoxazinone-based ultraviolet absorber, may be contained.

  The polyester film of this invention can use the polyester raw material with little oligomer content as a method of suppressing a surface oligomer. Such a raw material is obtained by solid-state polymerization in which a polyester chip obtained by a usual melt polycondensation reaction is kept at 180 ° C. to 240 ° C. for about 1 hour to 20 hours under reduced pressure or under the flow of an inert gas. Can do. A single-layer polyester film may be formed by mixing only this raw material or this raw material and a normal raw material, or a multilayer structure of two or more layers, and this raw material is used only for the surface layer opposite to the transfer layer. May be. In the case of a multilayer structure, if the components of the inner layer and the outer layer are significantly different, care must be taken because peeling may occur at the interface between the two layers during molding.

  The total thickness of the polyester film for transfer foil of the present invention is not particularly limited because it is appropriately selected depending on the use for which the polyester film for transfer foil of the present invention is used, but it has points such as mechanical strength, handling properties and productivity. Therefore, it is preferably 12 to 100 μm.

  In the present invention, from the viewpoint of heat resistance, molding processability, and dimensional stability, the melting peak temperature Tm measured with a differential scanning calorimeter is preferably 190 to 230 ° C, and preferably 200 to 220 ° C. When Tm is less than 190 ° C., heat resistance and dimensional stability are inferior, and thus wrinkles are generated in the printing process, and the film surface after molding is swollen, so that the design of the design pattern is impaired. Problems may occur. On the other hand, when Tm exceeds 230 ° C., moldability and productivity tend to be deteriorated and may not be used in deep drawing applications.

  From the viewpoint of moldability at a high temperature, the film of the present invention needs to have an average value of 250% or more of the elongation and elongation at break in a tensile test at 100 ° C. When the elongation is less than 250%, the film is torn at a portion where the shape change of the mold is large. In addition, the grounds for adopting the tensile test at 100 ° C. are that the general molding temperature is 100 ° C. or higher and the temperature that can be measured stably without progressing crystallization.

  In general, it is known that the elongation at break is reduced in a sample having a large surface roughness as in the present invention. In order to increase the elongation at break to 250% or more, it is effective to reduce voids formed around the particles that cause breakage. It is known that voids can be formed by stretching a resin containing particles, but can be reduced by heat treatment at a temperature close to the melting point. Relaxing at a portion where the heat treatment temperature is high is also effective in reducing voids. Moreover, when the component of each layer of a laminated film differs greatly, the interface may become easy to fracture | rupture.

  In the present invention, a coating layer such as a release layer, an antistatic layer, and an easy adhesion layer may be provided on the film surface as necessary, or chemical treatment or discharge treatment may be performed. When providing a coating layer, it is preferable to provide by an in-line coating. In-line coating is a method of coating within the process of producing a polyester film. Specifically, it is a method of coating at any stage from melt-extrusion of polyester to biaxial stretching, heat setting and winding. is there. Usually applied to either a substantially amorphous unstretched sheet obtained by melting and quenching, a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In these, the method of extending | stretching to a horizontal direction after apply | coating to a uniaxially stretched film is excellent. According to such a method, since film formation and coating / drying can be performed at the same time, there is a merit in manufacturing cost, and it is easy to apply a thin film to perform stretching after coating. Since the high temperature is not achieved by the method, the coating film and the polyester film are firmly adhered.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

(1) Melting peak temperature (Tm)
Accompanied by melting obtained when a temperature difference of about 5 mg of polyester resin is raised from 0 ° C. to 300 ° C. at a rate of 20 ° C./minute using a differential scanning calorimeter “MDSC 2920 type” manufactured by TA Instruments The temperature of the endothermic peak was Tm.

(2) Elongation at break at 100 ° C. Sample film having a distance between chucks of 50 mm and a width of 15 mm taken in the vertical and horizontal directions in a tank adjusted to a temperature of 100 ° C. using Shimadzu Corporation AG-I Is pulled at a speed of 200 mm / min, each N = 3 times, and the average value is taken as the elongation at break of the sample. For samples whose flow direction is known, the average value of the flow direction and its orthogonal direction is adopted, and for samples whose flow direction is unknown, an arbitrary direction and its average value of its orthogonal direction are adopted.

(3) Surface roughness (Ra)
The center line average roughness Ra (nm) is defined as the surface roughness. It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [nm]. The centerline average roughness was expressed as an average value of the centerline average roughness of the extracted portion obtained from 10 cross-sectional curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = (1 / L) ∫ 0 L | f (x) | dx

(4) Heat resistance A release layer, a printing layer, and an adhesive layer are formed on a polyester film. A mold having a length of 35 cm, a width of 25 cm, and a maximum depth of 3.0 cm is used, preheated with an IR heater, and then inside the mold. Preliminary molding was performed by vacuum or pneumatic molding. The heat resistance was evaluated according to the following criteria based on the state of melting of the film by preheating.
○: Can withstand processing temperatures and can be used for preforming. △: Can be used for preforming, but rarely expands due to film softening. ×: Frequent expansion due to film melting or softening occurs.

(5) Formability When preforming was performed by the method of (4) above, the formability was evaluated according to the following criteria based on the frequency of film breakage caused by the molding.
○: There is no film breakage, crack generation, etc., and the film is molded with a uniform thickness. Δ: The film is not broken, but there is a local area where the film is extremely thin. X: The film breaks frequently.

(6) Low gloss feeling of transfer molded product In accordance with the method of JIS Z-8741, using Nippon Denshoku Co., Ltd. Grosmeter VG-107 type at the bottom of the film obtained in (4) above. The glossiness was measured. The reflectance of the sample was obtained based on the reflectance of the black standard plate at an incident angle and a reflection angle of 60 degrees, and the gloss was determined.
◎: 0 or more and less than 20 ○: 20 or more and less than 50

(7) Interfacial delamination The fractured pieces after the tensile test by the method (2) were determined according to the following criteria.
○: No peeling occurred between the surface layer and the inner layer of the film.
X: Peeling occurs between the surface layer and the inner layer of the film.

Next, the polyester raw material used for an Example is demonstrated.
<Polyester 1>
Using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the polyhydric alcohol component, a polyester chip containing no lubricant particle size and having an intrinsic viscosity of 0.66 dl / g by a conventional melt polymerization method was produced.

<Polyester 2>
By using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the polyhydric alcohol component, and using an alkyl methacrylate-styrene copolymer having an intrinsic viscosity of 0.66 dl / g and an average particle size of 4.5 μm by a conventional melt polymerization method. A polyester chip containing 10 parts of organic particles was produced.

<Polyester 3>
Using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the polyhydric alcohol component, 0.60 part of amorphous silica having an intrinsic viscosity of 0.66 dl / g and an average particle diameter of 2.5 μm by a conventional melt polymerization method A polyester chip was produced.

<Polyester 4>
Using diphthalic acid components as isophthalic acid and terephthalic acid, and polyhydric alcohol components as ethylene glycol, raw material chips polymerized by a conventional melt polycondensation method were produced. The isophthalic acid content in the dicarboxylic acid component of this raw material was 22 mol%.

<Polyester 5>
In the process of producing polyester 4, a polyester chip containing 10 parts of organic particles of an alkyl methacrylate-styrene copolymer having an average particle size of 4.5 μm was produced.

Example 1:
Polyester 4 and polyester 2 were blended at a weight ratio of 84:16, melted in an extruder, supplied to a single-layer die, extruded into a film, cast on a cooling drum at 35 ° C. and rapidly cooled and solidified. A stretched film was prepared. Next, after preheating with a heating roll at 80 ° C., the film is stretched 3.2 times in the vertical direction between 95 ° C. rolls using an infrared heating heater and a heating roll, and then the film edge is held by a clip and guided into a tenter. While being heated at a temperature of 110 ° C., the film was stretched 4.2 times in the transverse direction, subjected to heat treatment at 195 ° C. for 10 seconds, and simultaneously relaxed by 10% in the width direction to obtain a polyester film having a thickness of 50 μm. The characteristics of the obtained film were as shown in Table 1 below. From this result, although a slight blistering phenomenon was observed, the result was excellent in moldability and low gloss, and no interfacial peeling occurred.

Example 2:
In Example 1, a polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that heat treatment was performed at 195 ° C. for 10 seconds and then 10% relaxation was performed at 170 ° C. in the width direction. Although the moldability was slightly inferior to that of Example 1, a result with no problem in use was obtained.

Example 3:
A polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the ratio of the polyester raw material in Example 1 was changed to Polyester 4: Polyester 2: Polyester 5 = 60: 20: 20.

Example 4:
In Example 2, a polyester film having a thickness of 50 μm was obtained in the same manner as in Example 2 except that the ratio of the polyester raw material was changed to polyester 4: polyester 2 = 95: 5.

Comparative Example 1:
In Example 2, a polyester film having a thickness of 50 μm was obtained in the same manner as in Example 2 except that the ratio of the polyester raw material was polyester 4: polyester 2: polyester 5 = 60: 20: 20. The obtained film was inferior in moldability and could not withstand practical use as a deep drawing film.

Comparative Example 2:
A polyester film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the ratio of the polyester raw material in Example 1 was changed to Polyester 4: Polyester 2: Polyester 5 = 40: 40: 20. The obtained film was inferior in moldability and could not withstand practical use as a deep drawing film.

Comparative Example 3:
In Example 2, a polyester film having a thickness of 50 μm was obtained in the same manner as in Example 2 except that the ratio of the polyester raw material was changed to polyester 4: polyester 3 = 90: 10. The resulting film was inferior in low gloss.

Comparative Example 4:
Polyester 4 and polyester 2 blended at a polymerization ratio of 80:20 and melted with an extruder, surface layer of multilayer die (A layer), polyester 4 and polyester 1 blended at a polymerization ratio of 80:20 Was supplied to a multilayer die as an inner layer (B) layer of the multilayer die, extruded into a film, cast on a cooling drum at 35 ° C., and rapidly cooled and solidified to produce an unstretched film. Next, after preheating with an 80 ° C. heating roll, using an infrared heater and a heating roll in combination, the film is stretched 3.0 times in the vertical direction between 85 ° C. rolls, and then the film edge is held with a clip and placed in the tenter. The film is stretched 3.5 times in the transverse direction while being heated at a temperature of 100 ° C., subjected to heat treatment at 195 ° C. for 10 seconds, relaxed 3% in the width direction at 170 ° C., and formed of a multilayer film having a thickness of 50 μm. A polyester film was obtained. The thickness of each layer of the obtained film was A / B / A = 5/40/5 μm. The obtained film was inferior in moldability, and delamination was also observed.

  The film of the present invention is suitable, for example, as a base film for a molded simultaneous decorating sheet used for decorating the surface of a resin molded product having a curved surface, such as an electric product or an automobile part, with a slightly complicated shape. Can be used.

Claims (1)

It is a film made of a copolyester containing an isophthalic acid unit, and the average value of the film longitudinal and horizontal elongation at break in a tensile test at 100 ° C. is 250% or more, and the average roughness (Ra) of the film surface is 0.00. A biaxially stretched polyether film for simultaneous deep drawing molding transfer, characterized in that it is in the range of 10 to 0.50 μm.