JP5072032B2 - Laminated polyester film for transfer foil - Google Patents

Description

  The present invention relates to a laminated polyester film for transfer foil that is excellent in high gloss on the processed surface after transfer and is suitable for stabilizing the winding quality when producing a polyester film as a substrate.

  Biaxially stretched polyester film represented by polyethylene terephthalate film has good mechanical strength, thermal characteristics, humidity characteristics and many other excellent characteristics, so it can be used in a wide range of fields such as industrial materials, magnetic recording materials and packaging materials. in use.

  The base film for transfer foil used in this field is useful as a base polyester film. The transfer foil is processed by sequentially laminating a transfer layer such as a release layer, a design layer and an adhesive layer on one side, and a hard coat layer or a metal vapor deposition layer is laminated on the transfer layer according to the purpose. Further, a functional agent such as an antistatic agent or an antibacterial agent is added to the release layer or the transfer layer to give a function as a transfer foil.

  In these transfer foil transfer methods, a transfer device is used to transfer a design to a transfer object with a heating roll, a so-called hot stamping method or a transfer foil is set in an injection mold and a resin molded product is molded. At the same time, a transfer foil sheet is integrated and bonded to the surface, and the design is transferred to the resin molded product for decoration. A so-called simultaneous molding transfer method (in-mold transfer) is widely known (Patent Documents 1 to 5).

  Such a transfer method is a method of transferring to a transfer object via an adhesive layer using a plurality of laminated transfer foils including an adhesive layer on the surface of a polyester base material. It is used in a wide range of applications for the purpose of surface treatment such as decoration and surface protection on the surface of various plastic processed products such as automobile parts, cosmetic containers, and toys, and resin molded products.

  The surface of the object to be decorated decorated by the transfer method has a large effect on the gloss of the decorated pattern because the particle protrusions formed on the surface of the polyester base film transfer the shape. The transfer surface obtained by the above method has a problem that a desired glossiness cannot be obtained and a high-grade feeling is lacking.

  In recent years, there has been a growing need for a glossy surface that has a processed surface after transfer similar to that of a glass surface, and flattening of the surface of the base polyester film to achieve this has been strongly demanded. .

  The particles formed on the surface of the polyester film contain organic particles having a specific particle diameter or inorganic particles in the film. Or the method etc. which contain a micro silica etc. in the coat layer on a base film are mentioned.

Examples of inert inorganic particles used as a general lubricant for forming surface protrusions in the film include calcium carbonate, kaolin, talc, carbon black, molybdenum sulfide, gypsum, barium sulfate, lithium fluoride. , Calcium fluoride, zeolite, calcium phosphate, silicon dioxide, titanium dioxide and the like. In the organic particles, for example, crosslinked polystyrene, crosslinked acrylic resin, melamine resin or the like is used.
The surface of a biaxially stretched film can be obtained by combining the laminated structure of the film and the selection of particle types to be added to the outer layer and the appropriate average particle diameter and content in order to achieve a high gloss film surface property using these lubricant particles. It is desirable to establish a design.

  In order to obtain high glossiness on the decorative surface after transfer, the substrate is further reduced by a method of reducing the amount of particles contained on the film surface or a method of applying a coat with fine particles added to a non-particle film on the film surface. The desired planarization of the polyester film surface can be achieved. However, just flattening by simply reducing the amount of particles present on the surface of the film or applying a coating of fine particle additive ensures sufficient winding quality in the winding process of the polyester film manufacturing process. There is a disadvantage that the yield of a product that becomes a non-defective product is significantly reduced. On the other hand, in recent years, in addition to the trend of increasing the roll size of raw fabric products, the value of products with even higher glossiness has further increased, and advanced levels that satisfy both flattening of the film surface and stabilization of the winding quality in production. The film surface properties have been demanded.

Conventionally, as a means of improving the high glossiness of the polyester film, a method of appropriately flattening the film surface by making inert fine particles present in the film has been known, and some improvements have been made. Sufficient results have not been obtained.
Japanese Patent Laid-Open No. 7-196821 JP 7-237283 A JP 2007-181978 A JP 2004-9596 A JP 2006-187949 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is the surface property of the polyester film in which the decorative surface of the molded product after transfer satisfies a high degree of glossiness, and the stabilization of the winding quality. It is to provide a film that satisfies both at the same time.

  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 adopting a specific configuration, and the present invention has been completed.

  That is, the gist of the present invention is that at least one side of the polyester layer (B) substantially free of particles has a cross-linking height of 2.0 to 5.0 and a mean particle size of 0.2 to 1.0 μm. It has a polyester layer (A) containing 0.01 to 0.15% by weight of molecular particles, and the thickness of the polyester layer (A) is in the range of 1 to 30% of the total film thickness. It exists in the laminated polyester film for transfer foil.

Hereinafter, the present invention will be described in detail.
Since the polyester film may confirm the printing color (color matching) from the opposite side of the printing layer of the transfer foil, it is preferable that the polyester film has high transparency. Further, the film of the present invention may be provided with a primer layer for improving adhesiveness, and conversely, a primer layer for improving releasability may be provided. Further, in order to improve the performance of the transfer foil, a coating agent having antistatic performance may be applied to the back side of the transfer surface.

  The laminated film of the present invention refers to a film obtained by stretching and heat-treating a film extruded by a so-called coextrusion method in which all layers are co-melt extruded from a die of an extruder. Hereinafter, although a 2 type 3 layer film is demonstrated as a laminated | multilayer film, unless it exceeds the summary of this invention, it is not limited to a 2 type 3 layer film, The multilayer beyond it may be sufficient.

  In the present invention, the polyester constituting each layer of the laminated film is a polyester obtained using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 80% or more of the repeating structural units are ethylene terephthalate. Polyester having ethylene unit or ethylene-2,6-naphthalate unit. And you may contain other 3rd components on the conditions which do not deviate from said range. As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid, etc.) ) Etc. can be used. As the glycol component, in addition to ethylene glycol, for example, one or more of diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like can be used. Can be used.

  In addition, stabilizers, colorants, antistatic agents, and the like may be appropriately added to the polyester constituting each of these layers, and the requirements of the present invention are satisfied even if these layers are subjected to such treatment. If it is, there is no problem.

  In the present invention, the polyester substantially free of particles is a polyester as described above, and a method of preventing particles formed by precipitation of a catalyst during the production of the polyester as much as possible (for example, Japanese Patent Laid-Open No. Hei 8). -Method described in JP-A-198960) or synthesized without particles added for purposes other than the purpose of the polymerization catalyst. Since this polyester does not contain or has few insoluble particles that absorb light or scatters, it can be made into a film having high transparency.

  In the present invention, the polyester layer (A) containing specific particles is laminated on at least one side of the layer (B) made of polyester substantially free of particles. In the polyester (A) layer, specific crosslinked polymer particles are used in order to improve the winding quality stability within a range not impairing the flatness of the film surface. In the present invention, the crosslinked polymer particles used for improving the winding quality stability of the film needs to have a particle size distribution within a specific range.

  The particle size distribution (defined later) of the crosslinked polymer particles used in the present invention is 2.0 to 5.0, preferably 2.5 to 4.0. When this value is less than 2.0, it means that the presence of single particles increases, and it is difficult to ensure winding quality and high glossiness. On the other hand, if the particle size distribution exceeds 5.0, it means that the presence of large particles increases, the gloss (flattening) of the film surface is impaired, and dent defects occur on the surface appearance of the molded product after transfer. The desired glossiness cannot be obtained.

  The average particle diameter of the crosslinked polymer particles used in the present invention is 0.2 to 1.0 μm, preferably 0.3 to 0.7 μm. Particles having an average particle size of less than 0.2 μm are not preferable because the winding quality stability of the film is lowered. On the other hand, when the average particle size exceeds 1.0 μm, large protrusions are formed and the film surface glossiness is impaired.

  The addition amount of the crosslinked polymer particles of the present invention is in the range of 0.01 to 0.15% by weight, preferably 0.03 to 0.10% by weight. When the addition amount is less than 0.01% by weight, the number of particle protrusions formed on the film surface is small, so that it does not contribute to stabilizing the winding quality. On the other hand, if it exceeds 0.15% by weight, the film surface flatness and film transparency are impaired, which is not preferable. In addition, even if the film surface is flat, if the transparency deteriorates, the printing color (color matching) viewed from the opposite side of the base film is hindered.

The crosslinked polymer particles used in the present invention can be usually obtained as follows. That is, a compound (a) having only one aliphatic unsaturated bond in the molecule is copolymerized with a compound (b) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent. It is obtained. Examples of the compound (a) which is one component of the copolymer include acrylic acid, crotonic acid, methacrylic acid, and lower alkyl esters such as methyl ester and ethyl ester, or glycidyl ester, maleic anhydride and alkyl thereof. Derivatives, vinyl glycidyl ether, vinyl acetate, acrylonitrile, styrene and substituted products thereof. Examples of the compound (b) include divinylbenzene, ethylene glycol dimethacrylate, butylene glycol acrylate and the like.
Typical examples of these copolymers include copolymers of methacrylic acid and divinylbenzene, styrene and divinylbenzene, and methacrylic acid and ethylene glycol dimethacrylate. In the present invention, the compound (a ) And (b) may be used to obtain crosslinked polymer particles.

  A characteristic point of the present invention is a cross-linked polymer particle having an average particle diameter of 0.2 to 1.0 μm and a particle size distribution in a specific range of 2.0 to 5.0. . That is, by using particles having a particle size distribution in this range for the outer layer of the polyester film, stress dispersion greatly contributes between each particle under the influence of stretching stress at the time of film production, and swell components existing on the film surface are present. By reducing the appearance of the particle protrusions necessary for the winding quality of the present invention and adding the surface properties and scratch resistance of the film having high glossiness, a polyester film suitable for transfer foil can be realized. It is a thing.

  Furthermore, it is preferable that the base material used in the present invention adopts a composite polyester film structure (multilayer structure) and is designed according to the thickness of the outer layer and the average particle diameter of particles added to the outer layer. By bringing the thickness of the outer layer close to the average particle diameter, the surface undulation component can be removed, and a smoother surface can be achieved. In addition, by using cross-linked polymer particles having an average particle size of 0.2 to 1.0 μm and a particle size distribution of 2.0 to 5.0, it is possible to contain appropriate small particles and large particles on the film surface. By having appropriate small and large protrusions on the surface, high protrusions that cause moderate air bleed between the film layers when the film is rolled up and small protrusions that exhibit slipperiness act. Thus, it is possible to obtain a good base film that improves the stabilization of the winding quality and further increases the high glossiness of the film surface.

  In the present invention, in order to obtain particles having a specific particle size distribution and average particle size, those obtained directly by suspension polymerization or emulsion polymerization may be blended, but they are easily obtained particularly in the case of suspension polymerization. It is preferable to obtain by pulverizing and classifying a crosslinked polymer having a size of several tens μm to several hundreds μm.

  One of the features of the present invention is that the thickness of the polyester (A) layer is in the range of 1 to 30% of the total film thickness. When the thickness of the A layer is less than 1%, the particles are likely to fall off from the film, the film winding appearance quality becomes inferior, and defects such as coating missing at the time of coating the transfer foil are caused. . On the other hand, when the thickness of the A layer exceeds 30%, the winding quality of the film is deteriorated, and the transparency of the film is also deteriorated.

  If necessary, the polyester (A) layer of the film of the present invention may contain additives such as an antistatic agent, an antioxidant, an antifoaming agent, and a fluorescent whitening agent as long as the properties as a transfer foil are not impaired. It may be contained. The thickness of the laminated polyester film of the present invention is usually in the range of 12 to 100 μm, preferably 20 to 75 μm.

  Next, a method for producing a polyester film will be described. That is, the polyester is co-melt extruded from the die of the extruder and the polyester (A) layer and the polyester (B) layer so that the film after manufacture falls within the scope of the present invention, and is cooled and solidified with a casting drum to form an amorphous unstretched film. And stretched in the longitudinal and transverse directions. Stretching in the machine direction is, for example, at a temperature of 70 to 130 ° C. and 3.0 to 5.0 times, preferably 5.5 to 4.5 times. Stretching in the transverse direction is, for example, at a temperature of 70 to 150 ° C., preferably 90 to 140 ° C., and is stretched 3.0 to 5.0 times, preferably 3.5 to 4.5 times in the transverse direction.

  In addition, it is preferable that the heat setting process after extending | stretching of a film is heat-set at the temperature of 150-250 degreeC for the time for 2 to 30 second within the temperature below melting | fusing point higher than final drawing temperature.

  In addition, in order to impart adhesiveness, antistatic ability, and releasability to the film during or after the stretching process, a coating layer is formed on one or both surfaces of the film, or a discharge treatment such as corona treatment is performed. You can also.

  The film of the present invention has particularly good winding quality, high product yield, stable production, and is extremely useful as a base film for obtaining high gloss on the transfer surface, and its industrial value is Very expensive.

  EXAMPLES Hereinafter, although the Example of this invention is given and demonstrated in detail, this invention is not limited by the following Examples, unless the summary is exceeded. In addition, the measurement methods and definitions of various physical properties and characteristics in the examples are as follows.

(1) Average particle diameter of crosslinked polymer particles (d)
It was measured with a centrifugal sedimentation type particle size distribution analyzer (SP-CP3 type) manufactured by Shimadzu Corporation.
In the present invention, the average particle size is defined as the average particle size (d), which is a particle size with an integrated volume fraction of 50% regardless of the shape.

(2) Size distribution of crosslinked polymer particles (r)
The particle size distribution was determined in the same manner as the average particle size measurement method. Integration was performed from the large particle side in the equivalent sphere distribution, and the particle size distribution ratio (r) was calculated from the following equation.
(R) = particle diameter when particle cumulative weight is 25% / particle diameter when particle cumulative weight is 75%

(3) Thickness of film layer It was performed by observing a film cross section with a transmission electron microscope (TEM). That is, a small piece of the film sample was embedded in a resin in which an epoxy resin was mixed with a curing agent and an accelerator, and a section having a thickness of about 200 nm was prepared with an ultramicrotome to obtain an observation sample. The obtained sample was taken with a transmission electron microscope (H-9000) manufactured by Hitachi, Ltd., and a cross-sectional photomicrograph was taken, and the thickness of the surface layer was measured. However, the acceleration voltage was set to 300 KV, and the magnification was set in the range of 10,000 times to 100,000 times according to the surface layer thickness. Thickness measurement was performed at 50 points, and 10 points from the thicker measurement value and 10 points from the thinner one were deleted, and 30 points were averaged to obtain a measurement value.

(4) Stability of film winding quality In the production of a polyester film, the roll quality of the final product was taken into consideration and the defect rate of the product appearance was taken into consideration, and the following criteria were used.
◎: The occurrence rate of defective products is extremely small, and there is no problem in manufacturing. ○: There are some defective products, but there is no major problem in manufacturing. ×: Many defective products are generated, which greatly affects manufacturing.

(5) Gloss on the surface of the molded product after transfer (appearance quality)
A layer consisting of a release layer, a printing layer and an adhesive layer was formed on a polyester film to prepare a transfer foil. The transfer foil was continuously molded at a rate of 100 pieces / min into a cylindrical shape having a bottom diameter of 50 mm and a depth of 5 mm using a male and female mold. The surface of the obtained molded product was visually observed and judged according to the following criteria.
A: There is sufficient glossiness, and no defects such as irregularities were observed on the surface of the processed product. ○: Glossiness is slightly inferior but there is no practical problem. Defects such as irregularities were found on the surface of the material (failed)

(6) Transparency (haze)
In accordance with JIS K 7136, total light transmittance Tt (%) and scattered light transmittance Td (%) were determined, haze ((Td / Tt) × 100) (%) was calculated, and judged according to the following criteria.
◎: Good when haze is 2.0% or less ○: Haze is 2.1 to 4.5%, but at a level where there is no practical problem ×: 4.6% or more and hinders color matching and the like ( failure)

Example 1:
[Production of crosslinked polymer fine powder]
A homogeneous solution of 100 parts of methyl methacrylate, 25 parts of divinylbenzene, 22 parts of ethylvinylbenzene, 1 part of benzoyl peroxide and 100 parts of toluene was dispersed in 700 parts of water. Next, it superposed | polymerized by heating to 80 degreeC, stirring for 8 hours in nitrogen atmosphere. The average particle diameter of the obtained crosslinked polymer granules having ester groups was about 0.1 mm. The granules were washed with demineralized water and extracted three times with 500 parts of toluene to remove a small amount of unreacted monomer and linear polymer. Next, the polymer particles were pulverized with an attritor for 2 hours and further with a sand grinder manufactured by Igarashi Machine Co., Ltd. for 5 hours to obtain a crosslinked polymer fine powder having an average particle size of 0.6 μm. Next, after removing large particles with a super decanter, a crosslinked polymer fine powder having a particle size distribution (r) of 3.1 and an average particle size of 0.5 μm was obtained using a 2400 mesh filter.

[Production of polyester raw materials]
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.06 part of magnesium acetate were placed in a reactor to carry out a transesterification reaction. After 4 hours, 0.030 part of phosphoric acid, 0.04 part of antimony trioxide and 0.20 part of the crosslinked polymer fine powder obtained by the above method were added to the reaction product which had been substantially transesterified. In addition, polymerization was performed according to a conventional method to obtain polyethylene terephthalate (A) having an intrinsic viscosity of 0.65 after 4 hours. Moreover, the polyester (B) was obtained as a polyethylene terephthalate which does not contain the addition particle | grains obtained by the method similar to the above.

[Production of polyester film]
After these polyethylene terephthalate raw material chips are dried at 170 ° C. for 3 hours, the polyester (A) containing crosslinked polymer particles and the polyester (B) containing no added particles are used as the raw material chips for the polyester (A) layer. A predetermined amount is blended so that the content of the polyester becomes 0.05% by weight, and the polyester (B) is supplied to the main extruder as a raw material chip of the polyester (B) layer in the sub-extruder and melted at a melting temperature of 280 to 300 ° C. The melted polymer of the sub-extruder is branched into two layers, the front and back layers of the film, and then split through the gear pump filter with the molten polymer from the main extruder by a feed block, taken through a die to a casting drum, and unstretched film did. The two types and three layers of the laminated unstretched film thus obtained were fed into a longitudinal stretching roll, first stretched 3.1 times at a roll temperature of 100 ° C., then led to a tenter and stretched 4.2 times in the transverse direction at 130 ° C. Thus, a biaxially oriented film was obtained. Subsequently, the obtained biaxially oriented film was guided to a heat setting zone and heat fixed at 235 ° C. The thickness of the polyester A layer was controlled by adjusting the discharge amount of the gear pump of the sub-extruder. The total thickness of the obtained laminated film was 38 μm, the thickness of the polyester (A) layer was 4.6 μm, and the ratio (R) of the total thickness was 0.12.

Examples 2, 3 and Comparative Examples 1-6:
The particle size distribution (r), the average particle size (d), the content of the polyester layer (A) and the thickness of the polyester layer (A) of the crosslinked polymer particles are changed as shown in Table 1 as the total film thickness ratio. It was. Others were carried out similarly to Example 1, and manufactured the polyester film.

Comparative Example 7:
In Example 1, calcium carbonate particles having a particle size distribution of 2.7 and an average particle size of 0.7 μm were used instead of using a crosslinked polymer having a particle size distribution of 3.1 and an average particle size of 0.5 μm. Others were carried out similarly to Example 1, and obtained the polyester film. Table 1 shows the properties of the film thus obtained and the properties after transfer.

Comparative Example 8:
Using amorphous silica particles having an average particle size of 2.5 μm and a particle size distribution of 7.5, a polyester film was obtained by producing the polyester film. The properties of the film obtained and the properties after transfer are shown in 1.

  The film of the present invention can be suitably used, for example, as a polyester film for transfer foil.

Claims (1)

Crosslinked polymer particles having a particle size distribution of 2.0 to 5.0 and an average particle size of 0.2 to 1.0 μm are added to 0.01 to 0 on at least one surface of the polyester layer (B) substantially free of particles. A laminated polyester film for transfer foil, which has a polyester layer (A) containing 15% by weight, and the thickness of the polyester layer (A) is in the range of 1 to 30% of the total film thickness.