JP5536524B2 - Biaxially stretched polyester film for window pasting - Google Patents

Description

  The present invention is a polyester base film that is used by being attached to glass through an adhesive layer used for prevention of glass scattering and crime prevention such as windows of buildings and automobiles, and adhesion between the base film and the adhesive layer The present invention relates to an excellent polyester film.

  The polyester film is a film having excellent mechanical properties and is widely used in various fields. For example, Patent Document 1 discloses an effective film for preventing glass scattering as a window pasting film. In order to adhere to glass, it is common to provide an adhesive layer on one side of the base film. In a glass window that comes in contact with the outside air, the temperature between the base film and the adhesive layer decreases as the temperature decreases. Decrease in adhesion at the interface is a problem. However, Patent Document 1 does not disclose a technique related to adhesiveness with the pressure-sensitive adhesive layer. Further, Patent Document 2 discloses a CRT protective film laminate having a pressure-sensitive adhesive layer and a coating layer effective in adhesion, but does not consider adhesion at low temperatures.

JP 2000-33681 A JP-A-9-254325

  An object of the present invention is to provide a biaxially stretched polyester film that is excellent in adhesiveness between a pressure-sensitive adhesive layer and a substrate film even at low temperatures and is suitable as a window pasting film having light shielding properties.

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

That is, the gist of the present invention is a co-extruded laminated polyester film comprising at least three polyester layers containing a dye in the intermediate layer, and has a coating layer containing a polycarbonate-based polyurethane on at least one surface of the film. and consists in the window biaxially oriented polyester film for bonding, which comprises chromatic an acrylic adhesive layer on the coating layer.

  According to the present invention, it is possible to provide a biaxially stretched polyester film that is excellent in adhesiveness between the pressure-sensitive adhesive layer and the substrate film even at low temperatures, and is suitable as a window pasting film having light shielding properties. Target value is high.

Hereinafter, the present invention will be described in detail.
Polyesters used in the present invention are polyethylene terephthalate (PET) produced from ethylene glycol and terephthalic acid, polyethylene-2,6-naphthalate (PEN) produced from ethylene glycol and naphthalene-2,6-dicarboxylic acid, 1, Poly (1,4-cyclohexanedimethylene terephthalate) (PCDT) produced from 4-bishydroxymethylcyclohexane and terephthalic acid, from ethylene glycol, naphthalene-2,6-dicarboxylic acid and biphenyl-4,4′-dicarboxylic acid The poly (ethylene 2,6-naphthalate bibenzoate) (PENBB) produced is exemplified. Among them, it is preferable to contain an ethylene terephthalate unit composed of ethylene glycol and terephthalic acid and / or an ethylene-2,6-naphthalate unit composed of ethylene glycol and naphthalene-2,6-dicarboxylic acid, and these units are 90% or more. A polyester containing 95% or more is preferable.

  The film of the present invention comprises at least three or more polyester layers that are so-called co-extrusion laminated and melt extruded from an extrusion die. When the polyester layer is a double layer or a single layer, there is a phenomenon that the added dye springs up on the surface (so-called bleed out), and there is a problem that the dye is sublimated to contaminate the film production process, and hard coating on the film surface. It also adversely affects the workability and the quality of the coating layer during the layer coating process and the adhesive coating process.

  The film of the present invention contains a dye in at least one of the intermediate layers of the film (a layer excluding the surface layer and may be abbreviated as B layer hereinafter). By adding a combination of the concentration of the dye to be added and a plurality of types of dyes, the visible color of the film and the visible light transmittance of the entire film can be controlled. The visible light transmittance is preferably 3 to 80%, more preferably 5 to 70%.

  It is preferable that the dye used for the film of the present invention is not easily decomposed at the melting temperature of the polyester and is dissolved in the polyester. If the dye is easily decomposed, gas may be generated and film production may be difficult. Further, poor solubility in polyester may adversely affect the appearance quality of the film.

  Preferable dyes include anthraquinone, perinone, perylene, azomethine, and heterocyclic dyes.

  The content of the dye in the film is usually 0.01 to 5.0% by weight, preferably 0.05 to 3.0% by weight.

  The polyester film of the present invention may contain additives such as pigments, ultraviolet absorbers, antistatic agents, antioxidants, and optical brighteners as necessary.

  The surface layer of the polyester film of the present invention preferably contains 0.001 to 1% by weight of inorganic or organic particles having an average particle size of 0.1 to 2.5 μm. By adding particles to the surface layer, minute protrusions can be formed on the film surface, and the running property and winding property of the film can be improved.

  Specific examples of the particles include inorganic fine particles such as calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, and glass, and organic particles such as melamine resin, polystyrene, organic silicone resin, and acrylic-styrene copolymer. It is done.

  The thickness of the surface layer of the polyester film of the present invention is preferably in the range of 0.2 to 10.0 μm, more preferably in the range of 0.5 to 5.0 μm. If the thickness of one surface layer is less than 0.2 μm, the effect of preventing the bleed out of the dye may be insufficient, and if it exceeds 10 μm, the haze of the film tends to increase.

  The film of the present invention has a coating layer on which at least one surface is coated with a coating solution containing a polycarbonate-based polyurethane aqueous dispersion.

  The polycarbonate-based polyurethane in the present invention uses polycarbonate polyols as one of the polyols which are main constituent components of polyurethane. Polycarbonate polyols can be obtained, for example, by reacting a carbonate and a diol. Examples of carbonate esters include ethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, dicyclohexyl carbonate, etc. Examples of diols include 1,6-one hexanediol, 1,4-one cyclohexanediol, 1, Examples include 4-1-cyclohexanedistudent diol, 3-1-methyl-1,5-pentanediol, polyethylene glycol, polypropylene glycol, polycaprolactone diol, trimethylhexanediol, and 1,4-monobutanediol. Moreover, the polyester polycarbonate obtained by reaction with polycarbonate diol, dicarboxylic acid, or polyester may be sufficient.

  The proportion of the polycarbonate-based polyurethane contained in the coating layer of the present invention is preferably 5% by weight or more. When the proportion of the polycarbonate-based polyurethane is less than 5% by weight, the adhesion with the pressure-sensitive adhesive layer tends to be lowered.

  10-100 nm is preferable, as for the thickness of the application layer of the film of this invention, More preferably, it is 12-80 nm, Most preferably, it is 15-45 nm. If the thickness is less than 10 nm, coating defects tend to occur in the coating layer. Moreover, even if it coats with thickness exceeding 100 nm, it may not contribute to the adhesive improvement with an adhesive layer.

  Moreover, aqueous polyester, aqueous polyurethane, aqueous acrylic, a crosslinking agent, a coating property improving agent, inorganic particles, and organic particles can be added to the coating layer as necessary.

For example, Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method”, as shown in “Coating Method”, Reverse Roll Co., Gravure Co., Rod Co. Co., Air A doctor or overnight or other coating device can be used. The coating layer may be formed only on one side of the polyester film or on both sides.
When formed only on one side, other characteristics can be imparted by forming a coating layer different from the above-mentioned coating layer on the opposite surface as necessary. In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may perform a chemical process and an electrical discharge process to a film before application | coating. Further, in order to further improve the surface characteristics, a discharge treatment may be performed after the coating layer is formed.

  The 120 ° C. heat shrinkage ratio of the film of the present invention is preferably 1.0% or less, more preferably 0.5% or less. If the 120 ° C. heat shrinkage rate exceeds 1.0%, the shrinkage stress may act on the film and the film may peel off when the outside air temperature is high.

  The surface roughness Ra of the film of the present invention is preferably 5 to 50 nm, more preferably 8 to 40 nm. If the surface roughness is less than 5 nm, the film runnability in the pressure-sensitive adhesive layer coating process tends to deteriorate. On the other hand, if the surface roughness exceeds 50 nm, the haze of the film increases, and the visibility of the object through the glass tends to deteriorate. In order to obtain an appropriate film surface roughness, the film preferably contains 0.001 to 1% by weight of inorganic or organic particles having an average particle size of 0.1 to 2.0 μm.

  Specific examples of the particles include inorganic fine particles such as calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, and glass, and organic particles such as melamine resin, polystyrene, organic silicone resin, and acrylic-styrene copolymer. It is done.

  Moreover, in the film of this invention, you may contain additives, such as an antiblocking agent, a ultraviolet absorber, an antistatic agent, antioxidant, and a fluorescent whitening agent, as needed.

  The thickness of the film of the present invention is preferably 10 to 75 μm. If it is less than 10 μm, the film processability is inferior. On the other hand, if it exceeds 75 μm, the workability to curved glass such as an automobile rear glass becomes difficult.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, it is not specifically limited to the following illustrations.

  When the film of the present invention is produced, the polyester is supplied to at least two extruders, heated to a temperature equal to or higher than the melting point of each polyester, and melted. Next, the molten polymer from each extruder is merged with a feed block through a gear pump and a filter and extruded from a die as a molten sheet. Subsequently, the molten sheet is rapidly cooled to below the glass transition temperature on a rotary cooling drum to obtain an amorphous unstretched film. At this time, in order to improve the flatness of the unstretched film, the adhesion between the unstretched film and the rotating cooling drum may be improved by an electrostatic application adhesion method, a liquid application adhesion method, or the like. And a uniaxially stretched film is obtained by extending | stretching an unstretched film in the longitudinal direction (longitudinal stretching) using a roll stretching machine. The stretching temperature at this time is stretched in a temperature range of minus 10 ° C. to plus 40 ° C. of the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 1.5 to 6.0 times, more preferably 2.0 to 5.0 times. Furthermore, longitudinal stretching may be performed in only one stage, or may be performed in two or more stages. Next, an aqueous coating agent is applied by a coater in order to provide a coating layer having excellent adhesion to the pressure-sensitive adhesive layer. Thereafter, the film is guided to a tenter and a biaxially stretched film is obtained by stretching (laterally stretching) the uniaxially stretched film in the width direction using a tenter stretching machine. The stretching temperature at this time is stretched in a temperature range of + 50 ° C. from the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.0 times. Further, the transverse stretching may be performed only in one stage, or may be performed in two or more stages. Moreover, you may perform simultaneous biaxial stretching which performs vertical and horizontal simultaneously. And a laminated film is manufactured by heat-processing a biaxially stretched film. The heat treatment temperature at this time is Tm-6 to Tm-30 ° C., where Tm is the melting point of the polyester used for the surface layer (A layer) of the coextrusion lamination. The heat setting time is 1.5 to 10 seconds. Moreover, when heat-treating a biaxially stretched film, the biaxially stretched film may be relaxed within 20%.

  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. The measurement methods and terms used in the examples and the present invention are defined as follows.

(1) Visible light transmittance The light transmittance of each wavelength was measured with a D65 light source using a spectrophotometer SE-2000 (manufactured by Nippon Denshoku Co., Ltd.), and the visible light transmittance was calculated according to JIS-S3107. did.

(2) Turbidity of film (haze)
The turbidity of the film was measured using a turbidimeter NDH300A (manufactured by Nippon Denshoku Co., Ltd.).

(3) Coating layer thickness 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. After the obtained sample was electron-stained, a cross-sectional photomicrograph was taken using a transmission electron microscope H-900 manufactured by Hitachi, Ltd., and the thickness of the coating layer was measured.

(4) Adhesiveness with pressure-sensitive adhesive layer An acrylic pressure-sensitive adhesive having a glass transition temperature of −12 ° C. is applied to the surface of the coated surface so as to have a thickness of 6 μm and affixed to a glass plate. A cross cut was made so that it became a piece. A rapid peel test using cellophane tape (registered trademark) was performed in a room at a temperature of 5 ° C. The judgment criteria are as follows.
○: not peeled off at the adhesive / film interface Δ: peeled off at 1-30 cross-cuts, adhesive / film interface ×: peeled off at 31 cross-cuts, adhesive / film interface

(5) Coat appearance The number of defects visible in reflected light was observed by illuminating the coated surface with a halogen lamp in a dark room. The criteria for judging the appearance of the coat are as follows.
○: The number of defects is 5 or less per square mail. Δ: The number of defects is 6 to 30 per square mail. X: The number of defects is 31 or more per square mail.

(Raw material adjustment)
・ Polyester a
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The obtained polyester a has an intrinsic viscosity of 0.70 and a melting point of 253 ° C.

・ Polyester b
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, heated to a temperature and methanol is distilled off to conduct a transesterification reaction, which takes 4 hours from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, an ethylene glycol slurry containing 2.0 parts of silica particles having an average particle diameter of 1.4 μm was added to the reaction system, and further 0.04 parts of ethyl acid phosphate and 0.04 parts of antimony trioxide were added. In 100 minutes, the temperature was 280 ° C. and the pressure was 15 mmHg, and thereafter the pressure was gradually reduced to finally 0.3 mmHg. Four hours later, the system was returned to normal pressure to obtain polyester b. The resulting polyester b had a silica particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

・ Polyester c
Polyester a is subjected to a twin screw extruder with a vent so that the concentration of dialresin red HS 3.0 wt%, blue H3G 5.5 wt%, and yellow F 1.5 wt% manufactured by Mitsubishi Chemical Corporation will be obtained. The mixture was added to the mixture, melt-kneaded to form chips, and polyester c as a dye master batch was prepared.

(Adjustment of aqueous dispersion coating solution)
Water dispersion coating liquids A to F having the composition shown in Table 1 below were prepared.

Polycarbonate polyurethane: Polyester polyol (polyester polyol comprising 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4 monobutanediol, 447 parts of neopentyl glycol, 321 parts of adipic acid, 268 parts of dimethylolpropionic acid A polyester polyol containing a pendant carboxyl group) and 1860 parts of tolylene diisocyanate.

Polyester polyurethane: Polyester polyol (polyester polyol comprising 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4-monobutanediol, 447 parts of neopentyl glycol, 321 parts of adipic acid, 268 parts of dimethylolpropionic acid Polyester poly-regulation number containing pendant carboxyl groups = 970732 (25) All) 1880 parts and 160 parts of tolylene diisocyanate.

・ Crosslinking agent: Water-soluble melamine compound (hexamethoxymethylmelamine)

Example 1:
A mixture of polyester a and polyester b forming the surface layer (A layer) having a ratio of 93/7 (weight ratio) is supplied to a vented twin-screw extruder (sub), and the polyester a and polyester c constituting the intermediate layer are supplied. A mixture having a ratio of 78/22 (weight ratio) was supplied to another twin-screw extruder with a vent (main) and melted at a melting temperature of 280 ° C., and then the molten polymer from each extruder was passed through a gear pump and a filter. They were merged in a feed block, taken up on a casting drum through a die, and two types and three layers of unstretched films were obtained. The unstretched film thus obtained was fed into a longitudinal stretching roll, first stretched 3.0 times at a film temperature of 83 ° C., then coated with an aqueous coating solution A using a bar coater and led to a tenter in the transverse direction at 95 ° C. The film was stretched 3.6 times to obtain a biaxially oriented film. Subsequently, the obtained biaxially oriented film was guided to a heat setting zone and heat-treated at 225 ° C. to obtain a polyester film described in Table 2 below.

Example 2:
The same procedure as in Example 1 was conducted except that a mixture of polyester a and polyester c forming the intermediate layer (B layer) was 95.5 / 4.5 (weight ratio) and the aqueous dispersion coating solution B was used. To obtain a film.

Example 3:
A film was obtained in the same manner as in Example 1 except that the aqueous dispersion coating liquid C was used.

Example 4:
A film was obtained in the same manner as in Example 2 except that the aqueous dispersion coating liquid D was used.

Example 5:
A film was obtained in the same manner as in Example 2 except that the aqueous dispersion coating liquid E was used.

Comparative Example 1:
A film was obtained in the same manner as in Example 3 except that the polyester forming the intermediate layer (B layer) was 100% polyester a.

Comparative Example 2:
A film was obtained in the same manner as in Example 1 except that the aqueous dispersion coating liquid F was used.
The evaluation results of the obtained film are summarized in Table 2 below.

  In Examples 1 to 5, since the intermediate layer contains a dye, the light shielding property is excellent. In addition, since the coating agent contains polycarbonate-based polyurethane, it has excellent low-temperature adhesion to the pressure-sensitive adhesive layer. On the other hand, Comparative Example 1 is inferior in light-shielding properties because it does not contain a dye, and Comparative Example 2 is inferior in low-temperature adhesion to the pressure-sensitive adhesive layer because the coating layer does not contain polycarbonate-based polyurethane.

  The film of the present invention can be suitably used as, for example, a window pasting film that requires light shielding properties.

Claims (1)

A coextruded multilayer polyester film comprising at least three polyester layer containing a dye in the intermediate layer, on at least one surface of the film, have a coating layer containing a polycarbonate-based polyurethane, acrylic on the coating layer biaxially oriented polyester film for laminated windows, characterized in that have a system pressure-sensitive adhesive layer.