JP2005120144A - Polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base film which can eliminate troubles caused by oligomers deposited from the polyester film in uses utilizing the flatness of the film, such as a transfer material and a casting material. <P>SOLUTION: This polyester film is characterized that the central surface average roughness (SRa) of one side of the film is ≤0.020μm, preferably ≤0.015μm, and the surface oligomer content of at least side of the film is ≤2.1 mg/m<SP>2</SP>, after the film is thermally treated at 180°C for 10 min. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester film that is flat and has a small amount of oligomer precipitation.

  A polyester film is conventionally used as a base film for a transfer material, a casting material, and the like, for example, taking advantage of strong mechanical strength, high heat resistance, and a flat film surface. In recent years, with the development of liquid crystal displays and plasma displays, glossiness of the transfer surface and transparency and flatness of the cast sheet are required, and a polyester film having a lower surface roughness is used. It tends to be. Further, in such applications, a plurality of coating processes are performed, but since a flat polyester film is used, yield reduction due to foreign matters is likely to occur in the processing process and the final use process. One of the factors of these foreign matters is an oligomer contained in the polyester film. Oligomer precipitates due to the solvent and heat during processing, adheres to the surface to be used, adheres to the roll in the processing step, and deforms the transfer surface and the sheet obtained by casting, or foreign matter itself In many cases, the original performance cannot be exhibited and the yield is lowered.

  For example, the transfer material is generally formed by sequentially laminating transfer layers such as a release layer, a design layer, and an adhesive layer on one surface of a base polyester film. Depending on the purpose, a hard coat layer, an antireflection layer, and a metal vapor deposition layer are laminated as a transfer layer. Furthermore, a functional agent such as an antistatic agent or an antibacterial agent is added to these release layer and transfer layer to give the function.

  As a transfer method of these transfer materials, a transfer device is used to transfer to a transfer object with a heating roll, so-called hot stamping method, and an adhesive layer is in contact with a mold resin of an injection molding machine or a blow molding machine. A so-called simultaneous molding and transfer method is generally known in which after setting a transfer material, a molding resin is injected or blown, transferred simultaneously with molding, and a molded product is taken out from a mold after cooling.

  In the process of manufacturing these transfer materials, if oligomers are precipitated from the polyester film of the base material, not only the inside of the processing process becomes dirty, but also the heating roll during transfer and the mold during simultaneous transfer are on the polyester film surface. As it is soiled by the oligomer of polyester and the number of transfer is repeated, it accumulates in the heating roll and mold. These oligomers eventually leave a mark on the transfer surface that has been transferred to the transfer target, or deteriorate the gloss of the transfer surface. In severe cases, the transfer target is distorted. In the case of the simultaneous molding transfer method, this tendency is strong because the flowing resin and the transfer material are in contact with each other. For this reason, the transfer surface of the transfer target, the heating roll, and the mold are monitored and the heating roll and the mold are appropriately cleaned, but this is a factor that reduces the processing efficiency.

  Further, when used as a casting material, recently, there is a strong tendency to use a polyester film having a low roughness in order to obtain a highly transparent sheet or a very glossy sheet. In such a case, since the surface of the sheet surface itself is very flat, even a very small foreign object may be defective. Heat is applied to the film during processing and use, and oligomers are precipitated from the film, but this may be a foreign matter.

JP-A-8-333461

  The present invention has been made in view of the above circumstances, and the problem to be solved is, for example, in the use of the flatness of a polyester film, such as a transfer material or a casting material, to eliminate troubles caused by oligomers precipitated from the film. It is to provide a base film that can be used.

  As a result of intensive studies in view of the above situation, the present inventors have found that a film having a specific configuration can easily solve the above problems, and have completed the present invention.

That is, the gist of the present invention is that the average surface roughness (SRa) of one surface is 0.020 μm or less, and the amount of oligomer on the film surface on at least one surface after heating at 180 ° C. for 10 minutes is 2.1 mg / It exists in the polyester film characterized by being ² or less.

Hereinafter, the present invention will be described in detail.
Examples of the polyester used in the polyester film of the present invention include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, and 1,4-cyclohexyldicarboxylic acid. Manufactured by melt polycondensation of dicarboxylic acid or its ester with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol Polyester. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method. For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

In these polyesters, the surface on which the transfer layer and the casting layer are provided (hereinafter referred to as the utilization surface) does not substantially contain particles, or even if particles are contained, the center surface average roughness (SRa) is 0. Within the range of 020 μm or less, preferably 0.015 μm or less, the film can be contained for the purpose of securing the runnability of the film or preventing scratches.
In the present invention, in order to make better use of the flat surface, the maximum projection height (Rmax) of the utilization surface is preferably 0.50 μm or less, and more preferably 0.30 μm or less.

  As particles to be used, inorganic particles such as calcium carbonate, kaolin, silica, aluminum oxide, titanium oxide, alumina, and barium sulfate, organic particles such as acrylic resin and guanamine resin, and precipitated particles obtained by atomizing catalyst residue are included. be able to. The particle size and amount of these particles can be appropriately determined according to the purpose. In addition, various stabilizers, lubricants, antistatic agents, and the like can be added as appropriate.

  On the usage side of the present invention, a primer layer for improving adhesiveness may be provided according to the purpose, and conversely, a primer layer for improving releasability may be provided.

  The polyester film of the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the roughness of the surface opposite to the use surface can be made rougher than the use surface, and workability can be further improved. In the case of a multi-layer structure, ordinary polyethylene terephthalate may be used for the inner layer, and when used for simultaneous molding transfer, isophthalic acid and terephthalic acid are used as a copolymer component for the purpose of improving moldability. Copolyester or polybutylene terephthalate may be used.

  The film forming method of the present invention may be a generally known film forming method and is not particularly limited. For example, the film is first stretched 2 to 6 times at 60 to 120 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then 2 to 80 to 130 ° C. in a direction perpendicular to the previous stretching direction in the tenter. The film can be produced by stretching 6 times and further performing heat treatment at 150 to 250 ° C. for 1 to 600 seconds.

As for the thickness of the polyester film of this invention, 12-188 micrometers is preferable.
As a method for suppressing the surface oligomer to be 2.1 mg / m ² or less, a polyester raw material having a low oligomer content can be used. Such a raw material is obtained by solid-phase polymerization in which a polyester chip obtained by a normal melt polycondensation reaction is kept at 180 ° C. to 240 ° C. for about 1 to 20 hours under reduced pressure or under the flow of an inert gas. be able to. A single layer polyester film may be formed by mixing this raw material alone or this raw material with a normal raw material, or it may have a multilayer structure of two or more layers and may be used on both sides. You may use this raw material only for a surface layer.

  As a method for inhibiting surface oligomers, a coat layer for inhibiting oligomer precipitation can be provided on the surface layer. Examples of the coating layer include a layer containing a silane coupling agent, an acrylic resin, or polyvinyl alcohol. These coating layers may be coated on a biaxially stretched film by a conventional technique, or may be coated by a conventional technique in the process of producing a polyester film. For example, in the sequential biaxial stretching method, there are a method of coating a film after longitudinal uniaxial stretching and then stretching laterally, or a method of coating and drying after a biaxially stretched film. Although the method is not limited, the method of coating a uniaxially stretched film, then laterally stretching, and heat-treating is preferable because it has a feature that the coat layer can be uniformly thinned.

  As a method for coating the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  According to the present invention, for example, in applications using the flatness of a polyester film such as a transfer material or a casting material, problems associated with oligomer precipitation can be eliminated, and the industrial value thereof is high.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method and the processing method of a sample in an Example and a comparative example are as follows. Further, “parts” in Examples and Comparative Examples represents “parts by weight”.

(1) Measuring method of center plane average roughness (SRa) Non-contact type three-dimensional roughness meter using Al phase deposition on the surface of a 3 cm square film sample and using direct phase detection interferometry, so-called two-beam interferometry ( Under the conditions of a measurement wavelength: 554 nm and objective lens magnification: 20 times under the conditions of Micromap 512), 50 points of the center surface average roughness SRa of the film surface in the measurement region of 232 μm × 177 μm from the projection height distribution curve The average surface roughness (SRa) of the film was determined by averaging the 50 SRa values.

(2) Measuring method of maximum protrusion height (Rmax) Non-contact type three-dimensional roughness meter (micro) using a direct phase detection interference method, so-called two-beam interference method, by depositing Al on the surface of a 3 cm square film sample. 512) manufactured by Map Inc., and measured the PV value of the film surface in a measurement region of 232 μm × 177 μm over 50 points under the conditions of measurement wavelength: 554 nm and objective lens magnification: 20 times. The values were averaged to obtain the maximum protrusion height (Rmax) of the film.

(3) Measuring method of intrinsic viscosity [η] (dl / g) of polymer 1 g of polymer is dissolved in 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio), and 30 ° C. using an Ubbelohde viscometer. Measured with

(4) Method for measuring oligomer in polyester raw material After dissolving a predetermined amount of polyester raw material in o-chlorophenol, reprecipitation with tetrahydrofuran and filtering to remove linear polyethylene terephthalate, the filtrate obtained was It supplies to a liquid chromatography (Shimadzu LC-7A), the oligomer amount contained in polyester is calculated | required, and this value is divided by the polyester amount used for the measurement, and it is set as the oligomer amount contained in polyester. The amount of oligomer determined by liquid chromatography was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing a preliminarily prepared cyclic trimer of polyethylene terephthalate and dissolving it in DMF (dimethylformamide) accurately measured. The conditions of the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(5) Polyester film heat treatment and oligomer measurement method Overlay the polyester film on the A4 size Kent paper so that the surface to measure the amount of oligomer is on the outside, clip the four corners, and stop the Kent paper and the polyester film . In this state, the sample was placed in an oven at 180 ° C. under a nitrogen atmosphere, left to stand for 10 minutes, and then taken out. Next, create a box by folding the four sides so that the bottom of the polyester film oligomer measurement surface faces inward (12.5 cm x 20 cm), and put about 10 ml of dimethylformamide (DMF) in this box. Then, the amount of oligomer dissolved in DMF was quantitatively determined. In quantification, the amount of oligomer in the solution finally made to 10 ml was determined from the peak area ratio between the standard sample peak area and the measured sample peak area using liquid romatography (Shimadzu LC-7A) (absolute calibration curve method). ). The standard sample was prepared by accurately weighing a preliminarily prepared cyclic trimer of polyethylene terephthalate and dissolving it in DMF (dimethylformamide) accurately measured. The unit is shown in mg / ² . The liquid chromatograph measurement conditions were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(6) Substitute evaluation method for roll dirt and mold dirt at the time of transfer As a means of evaluating roll dirt and mold dirt at the time of transfer, the surface of the film opposite to the transfer layer is made of 150 ° C. stainless steel. The plate was hot pressed and the degree of metal contamination was visually determined. The press thickness was 5 kg / cm ² and was performed 200 times in 30 seconds. Evaluation was determined as follows.
○: No stain was seen on the stainless steel plate.
Δ: Slight dirt was seen on the stainless steel plate, but it was practically satisfactory.
X: White stains were clearly visible on the stainless steel plate.

The polyester raw materials used in the examples and comparative examples were produced by the following method.
<Polyester 1>
Polyester 1 having an intrinsic viscosity of 0.66 and containing substantially no particles was produced by a general melt-in polymerization method. The amount of oligomers contained was 0.83% by weight.

<Polyester 2>
A polyester having an intrinsic viscosity of 0.58, which does not substantially contain particles, is produced by a normal melt-in polymerization method, and then heated at 220 ° C. for 10 hours in a nitrogen stream to produce polyester 2 having a low oligomer content. did. The amount of oligomer contained was 0.24% by weight.
<Polyester 3>
Polyester 3 having an intrinsic viscosity of 0.66 containing 0.3 part of amorphous silica having an average particle size of 2.5 μm was produced by an ordinary melt polymerization method. The amount of the oligomer contained was 0.83% by weight.

<Polyester 4>
In the same manner as for polyester 2, polyester 4 having an oligomer content of 0.24% by weight containing 0.03 part of organic particles having a particle size of 0.37 μm was produced.

<Polyester 5>
In the same manner as for polyester 2, polyester 5 having an oligomer content of 0.24% by weight containing 1.0 part of alumina particles having a particle size of 0.20 μm was produced.

<Polyester 6>
Polyester 6 was prepared by blending 96 parts of polyester 2 and 4 parts of polyester 3.
These chips were sufficiently dried and used after the water content was reduced to 50 ppm or less.

(Comparative Example 1)
73 parts of polyester 1 and 27 parts of polyester 3 are blended in a blender, dried and melted at 295 ° C., melt-extruded onto a cooled drum to obtain an amorphous sheet, and then vertically at 85 ° C. to 100 ° C. The film was stretched 3.5 times to obtain a longitudinally uniaxially stretched film. This film was stretched 4.0 times horizontally in an atmosphere of 85 ° C. to 110 ° C. and then heat treated at 235 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm. The film of Comparative Example 1 had an SRa of 0.035 μm, an Rmax of 0.68 μm, and a surface oligomer amount of 3.0 mg / m ² . When this was used as a glossy transfer foil, a haze-like turbidity occurred on the transfer surface and the appearance was not good. Moreover, the evaluation of dirt by a press machine was x.

(Comparative Example 2)
97 parts of polyester 1 and 3 parts of polyester 3 are blended in a blender, dried and melted at 295 ° C., melt extruded on a cooled drum to obtain an amorphous sheet, and then vertically at 85 ° C. to 100 ° C. The film was stretched 3.5 times to obtain a longitudinally uniaxially stretched film. This film was stretched 4.0 times horizontally in an atmosphere of 85 ° C. to 110 ° C. and then heat treated at 235 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm. The film of Comparative Example 2 had an SRa of 0.013 μm, an Rmax of 0.42 μm, and a surface oligomer amount of 3.0 mg / m ² . The evaluation of dirt by a press was x.

97 parts of polyester 2 and 3 parts of polyester 3 were blended in a blender, and a biaxially stretched polyester film having a thickness of 38 μm was obtained in the same manner as in Comparative Example 1. The film of Example 1 had an SRa of 0.013 μm, an Rmax of 0.42 μm, and a surface oligomer amount of 0.1 mg / m ² . The evaluation of dirt by the press machine was ○.

A biaxially stretched polyester film having a thickness of 38 μm was obtained in the same manner as in the comparative example by blending 67 parts of polyester 1, 30 parts of polyester 2, and 3 parts of polyester 3. The film of Example 2 had an SRa of 0.013 μm, an Rmax of 0.42 μm, and a surface oligomer amount of 2.0 mg / m ² . The evaluation of dirt by the press was Δ.

Polyester 4 and polyester 1 are melted in separate extruders, and two types and three layers of a configuration of polyester 4 (layer A) / polyester 1 (layer B) / polyester 4 (layer A) are used using a laminated die. A laminated polyester resin was obtained, and then melt-extruded on a cooled drum to obtain an amorphous sheet, and then stretched 3.5 times vertically at 85 ° C. to 100 ° C. to obtain a longitudinally uniaxially stretched film. This film was stretched 4.0 times horizontally in an atmosphere of 90 ° C. to 120 ° C., and then heat treated at 235 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm. The thickness configuration of A layer / B layer / A layer was 4 μm / 30 μm / 4 μm. SRa of the obtained film was 0.008 μm, Rmax was 0.28 μm, and the amount of surface oligomer was 0.3 mg / m ² . The evaluation of dirt by the press machine was ○.

  A 10% by weight methylene chloride solution of polycarbonate resin was applied to the polyester film surface of Example 3, dried until the residual solvent amount of the coating film was 1% by weight or less, and then the carbonate was peeled off from the polyester film. A polycarbonate sheet having a thickness of 80 μm was obtained. The surface of the polycarbonate sheet that was in contact with the polyester film was a polycarbonate sheet having very good specularity, and could be uniaxially stretched to form a good retardation plate.

Polyester 5, polyester 1 and polyester 6 are melted in separate extruders, and three types of constitution of polyester 5 (A layer) / polyester 1 (B layer) / polyester 6 (C layer) using a laminated die are used. A three-layer laminated polyester resin was obtained, then melt-extruded on a cooled drum to obtain an amorphous sheet, and then stretched 3.5 times vertically at 85 ° C. to 100 ° C. to obtain a longitudinally uniaxially stretched film. In the same manner as in Example 3, transverse stretching and heat treatment were performed to obtain a biaxially stretched polyester film having a thickness of 38 μm. The thickness structure of the A layer / B layer / C layer was 4 μm / 30 μm / 4 μm. In the obtained film, Ra on the A layer side was 0.003 μm, Rmax was 0.20 μm, SRa on the C layer side was 0.013 μm, and the amount of surface oligomer on the C layer side was 0.3 mg / m ² . The evaluation of dirt by the press on the C layer side was “good”.

One side of the longitudinally uniaxially stretched film of Comparative Example 1 was coated with 5 μm of a 2% aqueous solution of N-β (aminoethyl) γ-aminopropyltrimethoxysilane with a gravure coater, and 4.0 sideways in an atmosphere of 90 to 120 ° C. The film was stretched twice and then heat treated at 235 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm. The obtained film had an uncoated surface with an SRa of 0.013 μm, an Rmax of 0.42 μm, and a surface oligomer amount of 0.3 mg / m ^{2 on the} coated surface. The evaluation of the dirt by the press on the coated surface was “good”.
The obtained results are summarized in Table 1 below.

  The film of the present invention can be suitably used as a base film for transfer materials, casting materials and the like.

Claims (1)

The center surface average roughness (SRa) of one surface is 0.020 μm or less, and the film surface oligomer amount on at least one surface after heat treatment at 180 ° C. for 10 minutes is 2.1 mg / ² or less. Polyester film.