JP2012135951A - Polyester film for double-sided adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film for a double-sided adhesive tape, which is capable of highly enhancing winding property and workability of the biaxially oriented polyester film, and also which is suitable as an adhering member used in an application in which extremely thin clearance of ≤10 μm is required.SOLUTION: The biaxially oriented polyester film for the double-sided adhesive tape is characterized in that a plane orientation degree is 0.170 to 0.190, contracion ratio at 120°C for 3 min. is ≤2.0% in both of a film longitudinal direction and a width direction, and the thickness is 1 to 4 μm.

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape, more specifically, a double-sided pressure-sensitive adhesive suitable for fixing a mobile terminal device such as a mobile phone or a PDA, a member of a thin film display, a substrate for an optical disk, a polarizing plate, and the like. The present invention relates to a biaxially oriented polyester film for double-sided pressure-sensitive adhesive tape used as a base material for a tape.

  In recent years, in mobile terminal devices such as mobile phones and PDAs, electronic and optical parts such as digital cameras and digital video cameras, etc., in parallel with higher functionality, thinner and lighter, and further, paper for display bodies, etc. Is planned. For example, in a mobile phone, in order to improve display enlargement and portability, each major component that is configured tends to be thin.

  For fixing parts of these parts, in some applications, tapes that transfer the adhesive material layer are used to support thinning, but in this case, there is no core material, so there is a problem of poor durability Arise. Accordingly, many ultra-thin double-sided tapes have been developed, and Patent Documents 1 and 2 disclose pressure-sensitive adhesive tapes having pressure-sensitive adhesive layers on both sides of a 2 to 6 μm polyester film as a base material.

  However, the above document discloses the thickness structure and breaking strength of the pressure-sensitive adhesive tape and the structure of the pressure-sensitive adhesive layer, but does not specifically describe the base polyester film.

  Particularly in recent years, the clearance between parts has become narrower, and for an adhesive tape of less than 10 μm required for an extremely narrow clearance of 10 μm or less, an extremely thin polyester film of 4 μm or less is used as a base material in order to exhibit sufficient adhesive force. Must be used as

  Further, as the clearance becomes narrower, the adhesive tape having a small thickness fluctuation is required, but the thickness fluctuation of the base material particularly affects the thickness fluctuation of the adhesive tape. Therefore, a base film having a better thickness swing than the conventional ultra-thin base film has been required.

  That is, there is a demand for further thinning of the adhesive tape for fixing components in electronic and optical parts such as mobile terminal devices such as mobile phones and PDAs, digital cameras, and digital video cameras. The problem remains that the tape exceeds the clearance allowed for the adhesive member due to the thickness fluctuation of the base film.

JP 2005-105212 A JP 2007-169327 A

  The present invention is intended to solve the above-mentioned conventional problems, and not only improves winding properties and workability, but also a double-sided pressure-sensitive adhesive tape suitable as an adhesive member that requires an extremely thin clearance of 10 μm or less. It is to provide a biaxially oriented polyester film.

  As a result of intensive studies on the above problems, the present inventors have developed the films described below.

  That is, the gist of the present invention is that the degree of plane orientation is 0.170 to 0.190, the shrinkage ratio at 120 ° C. for 3 minutes is 2.0% or less in both the film longitudinal direction and the width direction, and the thickness is 1 It exists in the biaxially-oriented polyester film for double-sided adhesive tapes characterized by being -4micrometer.

  The biaxially oriented polyester film for double-sided pressure-sensitive adhesive tape of the present invention is an adhesive tape that is also used for extremely thin clearance for fixing members of electronic and optical components such as mobile terminal devices such as mobile phones and PDAs, digital cameras, and digital video cameras. Therefore, the industrial value of the present invention is high.

  The polyester film of the present invention is a film stretched as necessary after cooling a melted polyester sheet extruded by a so-called extrusion method that is melt-extruded from an extrusion die.

  The polyester constituting the film of the present invention refers to a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol or from a hydroxycarboxylic acid. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and diols include ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. As the production method, for example, a transesterification reaction is carried out between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or an aromatic dicarboxylic acid and a glycol are directly esterified to form a substantially aromatic compound. A method is employed in which a bisglycol ester of a dicarboxylic acid or a low polymer thereof is formed and then polycondensed by heating under reduced pressure.

  Typical examples of such polymers include polyethylene terephthalate and polyethylene-2, 6 naphthalate. These polymers may be homopolymers or may be a copolymer of the third component.

  The polyester film in the present invention is provided with an appropriate slipperiness by roughening the surface in order to improve the winding process at the time of film formation and the workability at the time of production and use of the adhesive tape.

  Specifically, in order to appropriately roughen the surface of the film, particles having an average particle diameter of 0.4 to 2.0 [mu] m, preferably 0.8 to 1.5 [mu] m are usually 0.1 to 5. 0% by weight, preferably 0.1-3.0% by weight, more preferably 0.2-2.0% by weight.

  Examples of such particles include inorganic particles such as calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide, silicon oxide, titanium oxide, kaolin, acrylic resin, Although organic particles, such as a guanamine resin and a crosslinked polymer fine powder, can be mentioned, it is not limited to these. Two or more components may be used simultaneously. When two or more components are used, it is preferable that the average particle diameter and content thereof are in the above-described range.

  When the average particle size is less than 0.4 μm or the particle content is less than 0.1% by weight, the film surface is insufficiently roughened and sufficient winding workability cannot be obtained. Sometimes. When the average particle size exceeds 2.0 μm, the protrusions due to the particles are too large, the thickness around the protrusions is increased, and there may be a problem that the clearance allowed for the adhesive member is exceeded. If the content exceeds 5.0% by weight, the film surface may become too rough and it may be difficult to uniformly apply the pressure-sensitive adhesive.

  In the present invention, a film having an appropriately roughened surface is obtained by the method as described above. In consideration of workability and workability, the average roughness (Ra) of the film surface is usually 0.03 to 0.2 μm. For convenience, the conditions are selected to be in the range of 0.04 to 0.16 μm. The method for adding the above-described particles to the polyester film in the present invention is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  The intrinsic viscosity of the polyester used in the present invention is preferably 0.40 to 0.75 dl / g, more preferably 0.50 to 0.70 dl / g when formed into a film. If the intrinsic viscosity of the film is less than 0.40 dl / g, the mechanical strength of the film tends to be weakened. If the intrinsic viscosity exceeds 0.75, the melt viscosity becomes high, and the extruder is loaded. In addition to manufacturing costs, the thickness fluctuation tends to deteriorate.

  The polyester in the present invention is melted by supplying the above-described polyester raw material to a known melt-extrusion apparatus represented by an extruder, and heating to a temperature equal to or higher than the melting point of the polymer. Next, while extruding the molten polymer from the slit-shaped die, it is rapidly cooled and solidified so that it is in the form of a rotary cooling drum or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. This sheet is obtained by stretching in a biaxial direction to form a film and heat-setting. In this case, the stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. Moreover, you may extend | stretch longitudinally and / or a horizontal direction again before or after performing heat setting as needed.

  In the present invention, in order to obtain sufficient dimensional stability, the film has a plane orientation of 0.170 to 0.190, preferably 0.170 to 0.185, and a draw ratio of 16 to 25 times as an area ratio. , Preferably 18 to 24 times. Also, if the degree of surface orientation of the film is less than 0.170, a film with little thickness fluctuation that can be used sufficiently as a base material for a double-sided pressure-sensitive adhesive sheet requiring thin clearance cannot be obtained, and the surface orientation of the film is not good. If it exceeds 0.190, the film will break during transverse stretching, making film formation difficult.

  The thickness of the polyester film of the present invention is 1 to 4 μm, preferably 1.5 to 3 μm. If the thickness exceeds 4 μm, the object of the present invention for providing a thin film double-sided tape cannot be achieved when an adhesive layer having sufficient adhesive force is applied. When the thickness is less than 1 μm, the waist of the film is damaged, handling becomes difficult, and workability deteriorates.

  The shrinkage rate of the polyester film of the present invention is 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less at 120 ° C. When it exceeds 2.0%, when used as an adhesive substrate, the member may be displaced due to shrinkage of the film, or the high temperature holding power of the adhesive may be impaired.

  The breaking strength in the longitudinal direction and the width direction of the polyester film of the present invention is usually 200 MPa or more, preferably 250 MPa or more. An adhesive tape having excellent strength can be obtained.

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. 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) Method for measuring intrinsic viscosity 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed and dissolved by adding 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio). And measured at 30 ° C.
(2) Average particle diameter (d50)
The particle size was measured by a sedimentation method based on the resistance value of the stock using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation.
(3) Measuring method of average roughness Ra Ra was measured according to the method of JIS-B-0601-1994 using the surface roughness measuring machine SE3500 by Kosaka Laboratory. The cut-off value was measured as 80 μm.
(4) Method for measuring the thickness of the base polyester film The thickness was measured by the following formula from the weight, length, width and density of the sample.

Thickness = (sample weight) ÷ ((sample length) x (sample width) x (sample density))
(5) Method of measuring degree of plane orientation Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., the maximum refractive index nγ in the film plane, the refractive index nβ in the direction perpendicular to it, and the refractive index nα in the thickness direction of the film And the degree of plane orientation was calculated from the following equation. The refractive index was measured at 23 ° C. using sodium D line.

Plane orientation degree (ΔP) = (nγ + nβ) ÷ 2-nα
(6) Measuring method of shrinkage rate The sample was heat treated for 3 minutes in an oven maintained at a predetermined temperature (120 ° C.) in a tensionless state, and the length of the sample before and after that was measured and calculated by the following formula. In addition, it measured about each of the vertical direction (MD) and width direction (TD) of a film.

Shrinkage rate = {(sample length before heat treatment) − (sample length after heat treatment)} / (sample length before heat treatment) × 100
(7) Measuring method of breaking strength Using a tensile tester model 2001 type manufactured by Intesco Corporation, a sample sample having a length (between chucks) of 50 mm and a width of 15 mm in a room adjusted to a temperature of 23 ° C. and a humidity of 50% RH is 200 mm. The film was pulled at a strain rate of / min, the load at the time of film breakage was measured, and the break strength was determined by the following formula. In addition, it measured about each of the vertical direction (MD) and width direction (TD) of a film.

Breaking strength (MPa) = Load at cutting (N) / Cross-sectional area of sample film (mm ² )
(8) Measuring method of film thickness fluctuation With a continuous thickness measuring machine manufactured by Anritsu Electric Co., Ltd., measuring 3 m in the longitudinal direction, measuring the maximum, minimum and average thicknesses, measuring the thickness unevenness by the following formula, The average value of 10 measurements was defined as thickness fluctuation.

Thickness unevenness = 100 × (maximum film thickness−minimum film thickness) / average film thickness (9) Measuring method of adhesive strength The adhesive tape obtained in Examples and Comparative Examples was JIS with a 25 mm wide sample. Measured according to Z 1528. That is, after pasting a 25 mm long part of one adhesive surface of a test piece to a stainless steel metal plate, the release film on the other side was peeled off, and JIS C having the same size as the test piece was removed. A polyethylene terephthalate film having a thickness of 25 μm specified in 2318 was bonded and pressure-bonded, and the adhesive strength was determined by peeling 180 ° from the test plate (stainless steel metal plate) according to 10 (adhesive strength) of JIS Z 0237.
(10) Pressure-sensitive adhesive layer thickness Double-sided tape (peeling film A / pressure-sensitive adhesive layer A / base polyester film / pressure-sensitive adhesive layer B / peeling film B) is taken with an electron microscope and a cross-sectional photograph of the tape is taken. The thickness of was measured. The measurement was carried out 10 times, and the average value of 10 times was taken as the thickness of the pressure-sensitive adhesive layer.
(11) Peeling force of peeling film With a 50 mm width sample, the peeling film on the side opposite to the side to be measured is peeled off, the exposed pressure-sensitive adhesive surface is stuck on a glass plate, and the peeling film on the side to be measured is tension tester Was used to measure the resistance at the time of peeling in the direction of 180 ° at a speed of 300 mm / min.
(12) compatibility;
Apply double-sided adhesive tape to the part where the clearance between parts is 10 μm or less, and judge whether the part can be fitted to the clearance without any deviation. It was set as “x”.

The polyester raw materials used in the following examples and comparative examples were produced by the following method.
<Manufacture of polyester>
Starting with 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is taken in the reactor, the reaction start temperature is 150 ° C., and methanol is distilled off. The reaction temperature was gradually 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 the reaction mixture, 0.5 part by weight of spherical organic crosslinked particles having an average particle size of 1.1 μm and 0.03 part of antimony trioxide were added, and polycondensation was performed for 4 hours. Reaction was performed. 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 0.65 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (A1) chip. The intrinsic viscosity of this polyester was 0.65.
Example 1:
<Manufacture of film>
A polyester (A1) chip is melt-extruded at 290 ° C. with a vented twin-screw extruder, and cooled and solidified on a cooling roll set at a surface temperature of 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. It was. Next, after stretching 3.0 times in the longitudinal direction at 90 ° C, further stretching 1.4 times at 83 ° C, leading to a tenter, stretching 4.5 times in the transverse direction at 110 ° C, and further heat treating at 225 ° C. The substrate polyester film having a thickness of 2.0 μm was obtained.

The properties of this polyester film are shown in Table 1.
<Manufacture of an adhesive composition (coating liquid)>
Adhesiveness to 100 parts by weight of an ethyl acetate solution having a weight average molecular weight of 800,000 acrylate polymer (95% by weight of butyl acrylate, 2% by weight of acrylic acid and 3% by weight of methyl methacrylate) and a concentration of 30% by weight Giving agent [Arakawa Chemical Industries, trade name “Pine Crystal KE-359”, rosin ester type, softening point 94-104 ° C., acid value 10-20 mg KOH / g] 30 parts by weight, and isocyanate type cross-linking agent [Toyo Ink 1 part by weight, manufactured by the manufacturer, trade name “BHS8515”, solid concentration 37.5%] was added and diluted with toluene to produce a pressure-sensitive adhesive composition (coating solution) having a solid concentration of 20% by weight.
<Manufacture of double-sided adhesive tape>
Lightly-peelable polyethylene terephthalate (PET) release film [Mitsubishi Resin Co., Ltd., trade name “Diafoil MRF38”, film thickness: 38 μm] After coating with a knife coater and drying at 100 ° C. for 1 minute, the polyester film having a thickness of 2.0 μm was pasted to obtain a single-sided adhesive film.

  Next, the coating liquid is applied to the release-treated surface of a heavy release type PET release film [trade name “Diafoil MRX38”, film thickness: 38 μm, manufactured by Mitsubishi Plastics Co., Ltd.] so that the film thickness after drying becomes 3.5 μm. It apply | coated with the knife coater, and after drying for 1 minute at 100 degreeC, it bonded with the PET surface of the said single-sided adhesive film, and manufactured the double-sided adhesive tape.

The peel strength of the lightly peelable PET peel film of the obtained double-sided pressure-sensitive adhesive tape was 15 mN / 10 mm, and the peel strength of the heavy peelable PET film was 30 mN / 10 mm. The characteristics of this double-sided tape are shown in Table 1 below.
Example 2:
In the production of the film of Example 1, the film was stretched 3.0 times in the machine direction at 90 ° C., further stretched 1.5 times at 83 ° C., led to a tenter, and stretched 4.7 times in the transverse direction at 110 ° C. Except for the above, a polyester film was obtained in the same manner as in Example 1. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The characteristics of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 1.
Example 3:
In the production of the film of Example 1, a polyester film was obtained in the same manner as in Example 1 except that the thickness of the film was 1.5 μm. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The characteristics of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 1.
Example 4:
In the production of the film of Example 1, a polyester film was obtained in the same manner as in Example 1 except that the thickness of the film was 4.0 μm. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the obtained base film was used and the thickness of the pressure-sensitive adhesive layer was 2.5 μm.
The characteristics of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 1.
Example 5:
In the production of the film of Example 1, a polyester film was obtained in the same manner as in Example 1 except that the heat setting temperature was 210 ° C. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The characteristics of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 1.
Comparative Example 1:
In the production of the film of Example 1, the film was stretched 3.0 times in the machine direction at 90 ° C., then stretched 1.2 times at 83 ° C., led to a tenter, and stretched 4.2 times in the transverse direction at 110 ° C. Except for the above, a polyester film was obtained in the same manner as in Example 1. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The properties of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 2 below.
Comparative Example 2:
In the production of the film of Example 1, the film was stretched 3.0 times in the machine direction at 90 ° C., further stretched 1.8 times at 83 ° C., led to a tenter, and stretched 4.8 times in the transverse direction at 110 ° C. Except for the above, a polyester film was obtained in the same manner as in Example 1. However, breakage occurred frequently during transverse stretching, and it was difficult to continuously form a film. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The properties of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 2.
Comparative Example 3:
In the production of the film of Example 1, a polyester film was obtained in the same manner as in Example 1 except that the thickness of the film was 6.0 μm. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the obtained base film was used and the thickness of the pressure-sensitive adhesive layer was 1.5 μm.
The properties of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 2.
Comparative Example 4:
In the production of the film of Example 1, a polyester film was obtained in the same manner as in Example 1 except that the heat setting temperature was 190 ° C. A double-sided pressure-sensitive adhesive tape was produced in the same manner as in Example 1 using the obtained base film. The properties of this polyester film and double-sided pressure-sensitive adhesive tape are shown in Table 2.

  The film of the present invention can be suitably used, for example, in applications that require extremely thin clearance.

Claims (1)

The degree of plane orientation is 0.170 to 0.190, the shrinkage rate for 3 minutes at 120 ° C. is 2.0% or less in both the film longitudinal direction and the width direction, and the thickness is 1 to 4 μm. Biaxially oriented polyester film for double-sided adhesive tape.