JP2012224489A - Colored multilayer biaxially-drawn polyester film for laminated glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially-drawn polyester film causing suppressed deposition of a coloring agent to the film surface in heating, having transparency and a light-shielding property, and free from generation of optical distortion even by laminating it on a curved glass.SOLUTION: The colored multilayer biaxially-drawn polyester film for laminated glass is a coextruded multilayer biaxially-drawn polyester film composed of at least three layers including an intermediate layer containing the coloring agent and both outermost layers essentially free from coloring agent and having a thickness of 3.0-30 μm. The film has film haze of ≤5.0%, and the absolute value of the difference of thermal shrinkage ratios between the film flow direction (MD) and transverse direction (TD) measured at 180°C for 5 min is ≤1.0%.

Description

  The present invention relates to a biaxially stretched polyester film substrate that can be suitably used for laminated glass that is useful for light shielding, glass scattering prevention and crime prevention for buildings and automobile windows.

  Films that are bonded to automobile windows and building windows for the purpose of privacy protection, design, sunlight adjustment, glass scattering prevention, crime prevention, etc., have transparency, light resistance, water resistance, heat resistance, Biaxial polyester film with excellent chemicals is used. For example, according to Patent Documents 1 and 2 as a colored laminated film for pasting a window, a laminated film composed of at least three layers containing a colorant as an inner layer is proposed in order to prevent the colorant from being deposited on the surface.

  However, it cannot be said that the prevention of colorant deposition at the time of heating is sufficient. For example, after heat treatment in a film production line, there is a problem that the colorant adheres to a roll in contact with the film and adversely affects film productivity.

  Further, as biaxially stretched polyester films for laminated glass, for example, Patent Documents 3 and 4 disclose a transparent laminated polyester film, but a laminated polyester film containing a colorant in an intermediate layer is not disclosed.

JP-A-63-94850 Japanese Patent Laid-Open No. 10-157040 JP 2005-186613 A JP 2010-138024 A

  The present invention has been made in view of the above-mentioned actual situation, and the problem to be solved is that it has a transparent feeling and a light shielding property in which precipitation of a colorant on the film surface is suppressed during heating, and is laminated on a curved glass. An object of the present invention is to provide a biaxially stretched polyester film in which no optical distortion occurs.

  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-extrusion laminated biaxial structure comprising at least three layers including an intermediate layer containing a colorant and both outermost layers having a thickness of 3.0 to 30 μm which substantially do not contain the colorant. It is a stretched polyester film, has a film haze of 5.0% or less, and an absolute value of a difference in heat shrinkage rate at 180 ° C. for 5 minutes in the film flow direction (MD) and the film width direction (TD) is 1.0%. The present invention resides in a colored laminated biaxially stretched polyester film for laminated glass characterized by:

  According to the present invention, it is useful for light shielding and prevention of glass scattering and crime prevention for windows of buildings and automobiles, etc., for excellent production of film and prevention of coloring agent deposition during film heating, and productivity that does not adversely affect the handling of the film processing line. An excellent colored laminated biaxially stretched polyester film for laminated glass can be provided, and the industrial value of the present invention is high.

  Hereinafter, the present invention will be described in detail.

  The polyester used for each layer laminated in the biaxially oriented polyester film of the present invention is obtained by polycondensation of aromatic dicarboxylic acid and aliphatic glucose. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glucose include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalene carboxylate (PEN) and the like. Among these, PET has a good balance between physical properties and cost, and is the most frequently used polyester.

  Further, the polyester used in the present invention may be a copolymer containing a third component as long as the total is within 10 mol%, preferably within 5 mol%. Examples of the dicarboxylic acid component of the copolyester include one or two of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenecarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  The laminated polyester film of the present invention is required to be a film in which at least three polyester film layers are laminated. More specifically, all layers are melt-extruded together from an extrusion die, so-called coextrusion method. Extruded by the film. Further, the film is not an unstretched state or a uniaxially stretched film, but needs to be a film that is stretched and oriented in the biaxial directions of the longitudinal direction and the transverse direction and then heat-set.

  Such a laminated film has a coextruded surface layer on both sides and a coextruded intermediate layer therebetween, but the coextruded intermediate layer itself may have a laminated structure.

  The outermost layers on both sides (hereinafter sometimes abbreviated as A layer) contain substantially no colorant, and the intermediate layer excluding the A layer (hereinafter sometimes abbreviated as B layer) contains the colorant. contains. In the case where the outermost layer is a film composed of a polyester layer containing a colorant, a phenomenon that the added colorant is deposited on the surface (so-called bleed out) occurs, and the film manufacturing process is contaminated. In addition, the meaning of "it does not contain substantially" is that it does not contain the quantity exceeding 100 ppm.

  The outermost layer (A layer) thickness in the film of the present invention is 3.0 to 20 μm, preferably 3.5 to 18 μm, more preferably 4.0 to 15 μm, and particularly preferably 5.0 to 15 μm. . If the thickness of the outermost layer is less than 3.0 μm, leaching of the colorant during heating cannot be sufficiently prevented. On the other hand, when the thickness of the outermost layer exceeds 20 μm, the haze of the film due to particles usually added to the A layer for improving the film running property and winding property is increased, and the visibility through the window of the film is lowered, resulting in transparency. Inferior to

  The intermediate layer (B layer) of the film of the present invention contains a colorant. By adding a combination of the concentration of the colorant to be added and a plurality of kinds of colorants, the visible color of the film and the visible light transmittance of the entire film can be controlled by absorbing visible light.

  The colorant used in the film of the present invention is preferably not easily decomposed at the melting temperature of the polyester and is preferably dissolved in the polyester. If the colorant is easily decomposed, gas is generated and film production may be difficult. Further, poor solubility in polyester may adversely affect the appearance quality of the film. Preferable colorants include anthraquinone, perinone, perylene, azomethine, and heterocyclic colorants.

  The content of the colorant in the film is usually 0.002 to 2.0% by weight, preferably 0.005 to 1.0% by weight. The colorant is added to the intermediate layer (B layer) so that the visible light transmittance of the film is usually 3 to 80%, preferably 5 to 70%.

  The intermediate layer (B layer) of the film of the present invention may contain additives such as pigments, ultraviolet absorbers, antistatic agents, antioxidants, and optical brighteners as necessary.

  The outermost layer (A layer) of the polyester film of the present invention preferably contains 0.0005 to 0.5% by weight of inorganic or organic particles having an average particle size of 0.1 to 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 difference (absolute value) in heat shrinkage rate at 180 ° C. for 5 minutes between the film flow direction (MD) and the film width direction (TD) of the film of the present invention is 1.0% or less, preferably 0.7% or less. More preferably, it is 0.5% or less, particularly preferably 0.3% or less. When the absolute value of the difference between the heat shrinkage ratios exceeds 1.0%, when laminated on a glass having a curved surface, the polyester film cannot follow the curved surface of the glass and optical distortion occurs. In order to make the difference (absolute value) of the heat shrinkage ratio 1.0% or less, for example, it is achieved by not relaxing at the time of heat treatment in the film forming process, or by keeping the relaxation ratio within 2% even if it is carried out. it can.

  The haze of the film of the present invention is 5.0% or less, preferably 4.0% or less, more preferably 3.0% or less. If the haze exceeds 5.0%, the visibility through the window is adversely affected.

  The film of the present invention is generally adhered to glass through a transparent resin. As the transparent resin, for example, polyvinyl butyral (PVB) or ethylene-vinyl acetate copolymer (EVA) is used. In order to improve the adhesion with these transparent resins, the film surface of the present invention may be subjected to corona treatment. preferable. The wetting index of the corona-treated film surface is preferably 52 dyne / cm or more.

  Although the film thickness of this invention is not specifically limited, Usually, it is 30-300 micrometers, Preferably it is 50-200 micrometers. When the film thickness is less than 30 μm, there is a tendency for wrinkles or the like to easily enter when making a laminated glass. When the film thickness is greater than 300 μm, the haze of the film becomes high, and the transparency of the laminated glass is There is a tendency to decrease.

  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. 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-100 ° 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, relaxation in the film width direction within 2% may be performed on the biaxially stretched film.

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

(3) Thickness of outermost layer (A 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. The particles added to the A layer were observed, and the thickness of the A layer was measured. However, the acceleration voltage was set to 300 kV, and the magnification was set in the range of 10,000 to 100,000 times according to the outermost layer thickness. Thickness measurement was performed at 50 points, and 10 points from the thicker measurement values and 10 points from the thinner ones were deleted, and 30 points were averaged.

(4) VLT (%) of colorant deposition solution
A square box is made by folding an evaluation film which is left in an oven at 180 ° C. for 10 minutes under a nitrogen atmosphere and heat-treated with A4 size Kent paper so that the area of the bottom surface is 250 cm ² . Next, 10 ml of DMF (N, N-dimethylformaldehyde) is placed in the box and left for 3 minutes. Next, the solution was diluted 50% with xylene, put in a quartz cell having an optical axis distance of 10 mm, and the visible light rate was measured using a color difference meter (Ultra Scan VIS) manufactured by Hunter Lab.

(5) Colorant precipitation evaluation during film heating The colorant precipitation tendency during film heating was as follows.
○: Visible light transmittance of the solution is 95 %% or more, and there is almost no tendency to precipitate the colorant, and there is no adverse effect on film productivity. Δ: Slight colorant precipitation tendency when the visible light transmittance of the solution is 90 to 95%. There is a slight adverse effect on film production. ×: The visible light transmittance of the solution is less than 90%, and there is a tendency for the colorant to be precipitated. descend

(6) Optical distortion of laminated glass A polyvinyl butyral film and a polyester film are sandwiched between two glass plates having a curved surface, pre-pressed at a glass temperature of 80 to 100 ° C. and a degree of vacuum of 650 mmHg or more, and then a temperature of 120 to 150 ° C. Laminated glass was obtained by performing main bonding for 20 to 40 minutes in an autoclave at a pressure of 10 to 15 kg / cm ² . The appearance of the prepared laminated glass was observed, and optical distortion in the laminated glass was evaluated according to the following criteria. ○: Wrinkled due to the polyester film in the laminated glass and excellent appearance without any optical distortion ×: Wrinkled due to the polyester film in the laminated glass, the transparency is lowered and there is a practical problem.

The raw materials used in the following examples and comparative examples were prepared as follows.
(Raw material adjustment)
・ Polyester a
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used 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 gradually distilled off. 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 had 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, and the temperature is raised while heating and methanol is distilled off. 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 2.5 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.

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 91/9 (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 3.6 times at a film temperature of 90 ° C., then led to a tenter and stretched 4.0 times laterally at 95 ° C. to obtain a biaxially oriented film. It was. Next, the obtained biaxially oriented film was guided to a heat setting zone and heat-treated at 220 ° C., and polyester films described in Table 1 below were obtained. The thermal relaxation in the width direction was not performed.

Example 2:
A mixture of polyester a and polyester b forming the surface layer (A layer) in a ratio of 95/5 (weight ratio) is supplied to a vented twin-screw extruder (sub), and the polyester a and polyester c constituting the intermediate layer Example: A mixture having a ratio of 91/9 (weight ratio) was supplied to another twin-screw extruder with a vent (main), the heat treatment temperature was set to 215 ° C., and a film having the thickness structure shown in Table 1 was obtained. 1 and the same conditions.

Example 3:
A mixture in which the ratio of polyester a and polyester c constituting the intermediate layer (B layer) is 96/4 (weight ratio) is supplied to another twin-screw extruder with a vent (main), and the thickness composition described in Table 1 is used. The conditions were the same as in Example 2 except that a film was obtained.

Comparative Example 1:
The conditions were the same as in Example 1 except that the thickness of the outer layer (A layer) was 1.5 μm and a film having a thickness structure described in Table 2 below was obtained.

Comparative Example 2:
The conditions were the same as in Example 2 except that the film was relaxed in the film width direction by 5% after the heat treatment, and the films listed in Table 2 were obtained.

Comparative Example 3:
The thickness of the re-outer layer (A layer) was 30 μm, and the same conditions as in Example 1 were obtained except that a film having a thickness structure shown in Table 2 was obtained. The haze of the obtained film was high, the visibility through the film was lowered, and the transparency was inferior.

  In Examples 1 to 3, since the thickness of the outermost layer (A layer) of co-extrusion is in an appropriate range, it is excellent in prevention of colorant precipitation and film transparency during heating. On the other hand, in Comparative Example 1, since the thickness of the outermost layer (A layer) was small, the colorant deposition preventing property during heating was inferior. Comparative Example 2 had a large difference (absolute value) in heat shrinkage, wrinkles due to the polyester film in the laminated glass, and transparency was lowered. In Comparative Example 3, the haze of the film was high, the visibility through the film was lowered, and the transparency was inferior.

  The film of the present invention can be suitably used as a base film for laminated glass that requires light shielding properties.

Claims (1)

A co-extrusion laminated biaxially stretched polyester film comprising at least three layers, comprising an intermediate layer containing a colorant and both outermost layers having a thickness of 3.0 to 30 μm substantially not containing a colorant, and film haze Is 5.0% or less, and the absolute value of the difference between the heat shrinkage ratios at 180 ° C. for 5 minutes in the film flow direction (MD) and the film width direction (TD) is 1.0% or less. Colored laminated biaxially stretched polyester film for laminated glass.