JP2008274127A - Pressure-sensitive adhesive film or sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive film or sheet (surface protective film) which is useful for the surface protection of an article including the surface protection of a synthetic resin sheet, a decorative sheet, a metallic plate and a coated steel plate, the protection of the surface of window glass and the surface protection on baking coating of an automobile and on dipping of a printed circuit board in solder and is particularly suitably used in the surface protection of precision electronic parts such as liquid crystal panels, reflecting plates, polarizing plates, plasma display panel plates, organic phosphor thin film layers, and transparent electrode layers which are constituting parts of liquid crystal displays, plasma displays, and organic thin film EL devices, and semiconductor chips and printed circuit substrates. <P>SOLUTION: The pressure-sensitive adhesive film or sheet comprises (A) a polypropylene resin base material layer and (B) a pressure-sensitive adhesive layer composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of not more than 7.0 wt.% and a melt flow rate (MFR) at 190°C under a load of 2,160 g of 0.1-6.5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an adhesive film or sheet, and more specifically, has an appropriate adhesive force, and has mechanical properties such as tensile strength, impact resistance, and stiffness (rigidity), and optical properties such as haze, gloss, and light transmittance. In addition, the surface is smooth and the appearance is very good, such as almost no occurrence of fish eyes, etc., so that the surface of the article is protected, in particular, a liquid crystal panel that is a constituent member of a liquid crystal display device, a plasma display device or an organic thin film EL device The present invention relates to a pressure-sensitive adhesive film or sheet suitable for protecting the surface of precision electronic components such as plates, reflectors, polarizing plates, plasma display panel plates, organic phosphor thin films, and transparent electrodes.

  The adhesive film or sheet has conventionally been used as a surface protective film for protecting the surface of products such as synthetic resin plates, decorative plates, metal plates, and coated steel plates from dust adhesion, dirt and scratches, and window glass. As a protective film for the surface, as a protective film for surface protection during the baking coating of automobiles or when soldering printed circuit boards, and further as a component of liquid crystal display devices, plasma display devices and organic thin film EL devices It is widely used for surface protection of precision electronic parts such as reflectors, polarizing plates, plasma display panel plates, organic phosphor thin films, transparent electrodes and the like.

In general, the adhesive film or sheet has strong adhesion between the base material layer and the adhesive layer, while the surface of the article to be protected and the adhesive layer are naturally self-peeling or extremely light vibration or It does not drop off due to impact, but it is required to have an appropriate adhesive strength with the surface so that it can be peeled smoothly without leaving an adhesive substance on the surface of the protected article during opening and peeling. .
Conventionally, an ethylene-based resin such as polyethylene is generally used for the base material layer and an ethylene / vinyl acetate copolymer resin is generally used for the adhesive layer as materials satisfying such requirements.
In particular, films and sheets comprising a polyethylene resin substrate layer and an ethylene / vinyl acetate copolymer adhesive layer laminated by a coextrusion method that does not use an organic solvent at the time of production are frequently used.

  For example, Patent Document 1 discloses a surface protective film in which an adhesive layer made of an ethylene / vinyl acetate copolymer having a vinyl acetate content of 18 to 26% is laminated on one side of a base material layer made of high density polyethylene. ing.

However, ethylene polymer resins such as polyethylene used for the base material layer have thermal properties such as softening point and melting point, mechanical properties such as tensile strength, impact resistance, stiffness, haze, gloss, light transmittance, etc. The optical properties may not always be sufficient depending on the application in which it is used.
In addition, the polyethylene resin film has a problem that fish eyes are often generated during molding and processing.

Fisheye refers to a foreign object or defect in a transparent or translucent plastic such as a film or sheet that appears as a small spherical mass.
It is said that one of the causes of fish eyes is that the lump and the surrounding resin are not well mixed, but polyethylene, especially high-pressure low-density polyethylene, is extremely small in the polymerization process. A homogeneous part is often generated and mixed in the resin, and when processed into a film, the frequency of generating fish eyes is said to be higher than that of other types of resins.

  The occurrence of fish eyes not only significantly deteriorates the appearance of the film, but also has an adverse effect on the performance of the target electronic components to be protected, especially when the application is used for manufacturing and processing electronic components or protecting the surface of products. There is.

Therefore, many studies on this countermeasure have already been proposed. For example, Patent Document 2 discloses that the in-pipe linear velocity of the gas-liquid mixed fluid transferred from the polymerization vessel outlet to the unreacted gas separator in the production of high-pressure polyethylene is within a certain speed range. Thus, there is disclosed an invention that suppresses the occurrence of fouling in the piping, thereby preventing the generation of fish eyes when the foreign matter is peeled off and mixed into the polyethylene resin to form a film.
Patent Document 3 uses a resin material having a specific melt flow rate (MFR), a specific density, and a specific haze obtained by specifically adjusting polymerization conditions such as polymerization pressure in the production of high-pressure polyethylene. An invention of a polyethylene film in which the number of fish eyes per unit area of the film is reduced as compared with conventional products is disclosed.

However, up to now, the frequency of fish eye occurrence of polyethylene film has not been reduced to a satisfactory level, and in particular for use as a protective film used in the electronic / information field, for the base material layer that replaces polyethylene. The resin material was demanded.
Furthermore, recently, in addition to that, even after heating to the article to be protected after sticking to the article to be protected, temperature rise, there is little change in the adhesion strength and the adhesion state between the article to be protected and the adhesion layer, that is, A pressure-sensitive adhesive film or sheet excellent in heat resistance and thermal history stability tends to be more strongly demanded than ever before.

JP-A-8-170056 JP 2004-161878 A JP 2002-273203 A

  The present inventors have almost no generation of fish eyes, excellent surface smoothness, good appearance, and excellent heat resistance and thermal history stability that do not change their adhesive properties even when heated to some extent. As a result of earnest research to develop an adhesive film or sheet, a combination of a polypropylene base layer and an adhesive layer made of specific ethylene / vinyl acetate having a relatively low vinyl acetate content and a low melt flow rate (MFR) Knowing that the above problems can be solved, the present invention has been completed based on this finding.

  Therefore, the object of the present invention is to have an appropriate adhesive force to the article to be adhered, and have thermal properties such as heat resistance and thermal history stability, tensile strength, impact resistance, stiffness, abrasion resistance, etc. Excellent optical properties such as mechanical properties, haze, gloss, and light transmittance, plus little generation of fish eyes, smooth surface and very good appearance, for surface protection of articles, especially liquid crystal display devices, plasma displays Adhesive film or sheet suitable for surface protection of precision electronic components such as liquid crystal panel plates, reflectors, polarizing plates, plasma display panel plates, organic phosphor thin films, transparent electrodes, etc. In offer.

  According to the present invention, the polypropylene resin base layer (A) and the vinyl acetate unit content are 7.0% by weight or less and the melt flow rate (MFR) at 190 ° C. under a load of 2160 g (according to JIS K7210-1999). A pressure-sensitive adhesive film or sheet comprising the pressure-sensitive adhesive layer (B) made of an ethylene / vinyl acetate copolymer of 0.1 to 6.5 g / 10 min is provided.

  In particular, an embodiment in which the adhesive layer (B) is laminated on one side of a polypropylene resin base film is suitable.

  The base material layer (A) and the adhesive layer (B) are preferably formed by coextrusion.

  Moreover, it is preferable that the said adhesion layer (B) contains a tackifier further.

  Moreover, it is preferable that the said base material layer (A) consists of a polypropylene homopolymer or a random copolymer propylene resin.

  The pressure-sensitive adhesive film or sheet of the present invention is suitable as a surface protective film for articles and members, particularly as a surface protective film for precision electronic components, and particularly for liquid crystal display devices, plasma display devices or organic thin film EL devices. It is suitably used for surface protection of members.

  The pressure-sensitive adhesive film or sheet of the present invention has high interlayer adhesion strength between the base material layer and the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer has an appropriate pressure-sensitive adhesive force on the surface of the article to be adhered. The adhesive strength and the adhesive state hardly change even when subjected to, and the base material layer has thermal characteristics such as softening point, heat distortion temperature, mechanical properties such as tensile strength, impact resistance, stiffness, haze, Excellent optical properties such as gloss and light transmittance, plus almost no fish eye, smooth surface and very good appearance. For example, surface protection for synthetic resin plates, decorative plates, metal plates, painted steel plates, etc. It is useful for surface protection of articles, such as protection of window glass surfaces, surface protection of automobiles by baking coating or soldering of printed circuit boards, especially for liquid crystal display devices, plasma display devices and organic thin film EL devices. Liquid crystal panel plates and reflectors as constituent members Polarizing plate, plasma display panel board, organic fluorescent thin film layer, is suitable for surface protection of precision electronic parts such as a transparent electrode layer and a semiconductor chip or a printed circuit board.

Embodiments according to the present invention will be described in detail and specifically below.
In the pressure-sensitive adhesive film or sheet of the present invention, the polypropylene resin that is a constituent resin of the base material layer is mainly composed of propylene homopolymer (polypropylene homopolymer), propylene, and a small amount of ethylene and 1-butene. , 1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene, 1-octadecene, etc. Polypropylene copolymer resins such as olefin copolymers can be mentioned. As the copolymer, either a random copolymer or a block copolymer can be used, but a random polymer is preferred.

  When a propylene copolymer is used in the present invention, the content of other monomer (eg, α-olefin) component other than propylene in the propylene copolymer is usually 10 mol% or less, preferably less than 8 mol%. It is.

  The melt flow rate (MFR) of this propylene polymer is usually 0.1 to 100 g / 10 minutes (ASTM D1238 230 ° C., 2160 g load), preferably 1 to 20 g / 10 minutes.

Moreover, as long as the characteristics of the propylene polymer (or copolymer) are not impaired, a resin composition containing a small amount of other resin components compatible with the polymer (copolymer) may be used. it can.
Examples of other resin components blended in combination with the propylene polymer or copolymer include polyolefin resins such as polyethylene, polybutene, poly-4-methyl-1-pentene, and ethylene / α-olefin copolymer. be able to.

As a preferred embodiment of the polypropylene resin material used for the base material layer in the present invention, a so-called soft material having a latent heat amount of 80 KJ / Kg or less, more preferably 30 to 79 KJ / Kg, in thermal analysis using a differential scanning calorimeter (DSC). A soft propylene copolymer containing a small amount of polypropylene or other α-olefin unit, for example, 0.01 to 10 mol% or less can be mentioned.
The above resin is preferable because it is rich in processability as a film material, and the obtained film is flexible and relatively excellent in low-temperature embrittlement resistance.

  In the present invention, a resin made of ethylene / vinyl acetate copolymer (EVA) is used as a constituent resin of the adhesive layer laminated on the base material layer.

The ethylene-vinyl acetate copolymer used in the present invention has a vinyl acetate component unit content of 7% by weight or less, more preferably 3-7% by weight, most preferably 5-7% by weight, and 190 It is protected that the melt flow rate (MFR) (according to JIS K7210-1999) at a load of 2160 g at 0.1 ° C. is in the range of 0.1 to 6.5 g / 10 minutes, particularly 1 to 5 g / 10 minutes. It is preferable from the viewpoints of appropriate adhesive strength with the article and stability of thermal history.
When the vinyl acetate component unit content is in the above range, even when subjected to heat treatment or other thermal history after adhesion to the surface of the article to be protected, an increase in interlayer adhesion is suppressed and smooth peeling is possible. . Further, when the MFR is in the above range, it has an appropriate melt viscosity, so that when the heat treatment or other heat history is received, the adhesive resin that has melted flows out from the interlayer and contaminates the article to be protected. . In the present invention, not only the ethylene / vinyl acetate copolymer but also a resin composition in which a tackifier or the like is blended with the ethylene / vinyl acetate copolymer can be used as the resin constituting the adhesive layer.
The blending amount of the tackifier is preferably 0 to 10 parts by weight with respect to 100 parts by weight of the ethylene / vinyl acetate copolymer.

Examples of the tackifier added to the adhesive layer as needed include rosin derivatives, terpene resins, petroleum resins, and the like.
The adhesive layer may be further blended with other types of resins as long as the properties of the layer are not impaired.

  As such a resin, for example, ethylene / unsaturated carboxylic acid, which is a copolymer of ethylene and unsaturated carboxylic acid such as (meth) acrylic acid, ethacrylic acid, fumaric acid, maleic acid, monomethyl maleate, maleic anhydride, etc. An acid copolymer resin, a copolymer of ethylene and an alkyl ester of the unsaturated carboxylic acid, such as ethylene methyl (meth) acrylate, ethylene ethyl ethyl (meth) acrylate, ethylene isobutyl (meth) acrylate, etc. Certain ethylene / unsaturated carboxylic acid ester copolymer resins, ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer resins such as ethylene / acrylic acid / isobutyl methacrylate, low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), metallocene touch Polyethylenes such as polymerized polyethylene, ethylene and propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, etc., and α-olefins having 3 to 20 carbon atoms Examples thereof include ethylene-based resins, propylene-based resins such as polypropylene, butene-based resins such as polybutene, and olefin-based resins such as 4-methyl-1-pentene.

Two or more of these resins may be blended.
Among these, ethylene / unsaturated carboxylic acid copolymer resin such as ethylene / (meth) acrylic acid copolymer, ethylene / unsaturated carboxylic acid ester copolymer such as ethylene / (meth) acrylic acid isobutyl copolymer, etc. Copolymer resin, ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer resin such as ethylene / acrylic acid / isobutyl methacrylate copolymer, low density polyethylene, linear low density polyethylene, metallocene catalyzed polyethylene, etc. -Ethylene / α-olefin copolymer resin such as 1-butene copolymer is preferable.
These other types of resins can be added in a range not impairing the physical properties of the adhesive layer, for example, about 0 to 30 parts by weight with respect to 100 parts by weight of the ethylene / vinyl acetate copolymer.

  In the present invention, when the adhesive layer is a resin composition in which an tackifier or other resin is blended with an ethylene / vinyl acetate copolymer, the surface layer of the protected article is PET (polyethylene terephthalate) or OPP. Considering the case of (stretch-oriented polypropylene) film, polyether film, and polycarbonate film, the vinyl acetate unit content per unit amount of the resin composition and its MFR are the same for the ethylene / vinyl acetate copolymer from the viewpoint of adhesiveness. It is preferable to be in the same range as the specified range in the polymer.

  The ethylene / vinyl acetate copolymer constituting the adhesive layer can be obtained by direct copolymerization by high-pressure free radical polymerization according to a known method for producing this type of copolymer resin.

  The copolymer or resin composition further includes, for example, an antioxidant such as phenyl-α-naphthylamine, 4,4′-dioctylphenylamine, alkylated diphenylamine, lead carbonate, lead orthosilicate, barium stearate, Various additives such as heat stabilizers such as calcium laurate and dibutyltin dilaurate, conventionally known phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants and the like are blended to about 0 to 5% by weight, for example. be able to.

Next, the manufacturing method of the adhesive film or sheet | seat of this invention is demonstrated.
As a method for forming a laminated film, sheet, etc., there are a casting method, an inflation method, a dry laminating method, a wet laminating method, an extrusion laminating method, a coextrusion molding method, etc. A coextrusion method that is excellent in terms of production cost and production efficiency is preferred.

  More specifically, as a coextrusion molding method, more specifically, a so-called multilayer coextrusion casting method in which a polypropylene resin melt and an ethylene / vinyl acetate copolymer melt are extruded from a multilayer coextrusion T-die and cooled by a cooling roll. Can be mentioned.

  The polypropylene resin film layer (base material layer) of the laminated film or sheet to be formed is usually used in an unstretched state, but may be uniaxially or biaxially stretched. The film is fed from the feeding section at a constant speed, led to the laminating section, where the laminating section is heated and melted at a predetermined temperature in the cylinder, and continuously extruded into a thin film from a T-die. The polypropylene film and the ethylene / vinyl acetate copolymer laminate resin are compressed and cooled between the cooling roll and the compression roll, and then wound as a laminated film product at the winding portion.

  The thickness of the polypropylene base layer in these laminated films and sheets is not particularly limited, but is about 30 to 100 μm, and the thickness of the ethylene / vinyl acetate resin layer is about 10 to 40 μm. Is preferred.

  The main use of the adhesive film or sheet of the present invention is as follows: surface protection of synthetic resin plates, decorative plates, metal plates, painted steel plates, window glass surface protection, carving coating of automobiles and solder immersion of printed circuit boards Protection, liquid crystal display device, liquid crystal panel plate, reflector plate, polarizing plate, plasma display panel plate, organic phosphor thin film layer, transparent electrode layer, semiconductor chip and printed circuit board which are constituent members of plasma display device and organic thin film EL device And surface protection of precision electronic parts such as

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

"Example 1"
Using a coextrusion multilayer cast molding apparatus (65 mmφ, 50 mmφ), polypropylene (random copolymerized propylene resin: F327 (manufactured by Prime Polymer)) and ethylene / vinyl acetate copolymer (vinyl acetate content 5% by weight, MFR (190 ° C.) 2160 g / load, based on JIS K7210-1999): 3 g / 10 min), and cut into a film of a predetermined size to obtain a sample laminated film (polypropylene resin layer thickness / ethylene / acetic acid Vinyl copolymer layer thickness = 40/20 μm).
The film performance of the following items was evaluated using this sample film.
The results are shown in Table 1.

"Evaluation items and methods"
Mechanical properties Tensile strength at break = JIS K6781 impact resistance (film impact) = ASTM D3420 compliance Rigidity value (film stiffness) = Toyo Seiki Co., Ltd. loop stiffness tester, span 100mm, width 25mm, indentation distance Measured at 15 mm and used as a measure of rigidity.
Optical properties Haze = Conforms to JIS K7136 Gloss = Conforms to JIS K7105 Transmittance (Transformer) = Conforms to ASTM D1746 Total light transmittance = Conforms to JIS K7361 Adhesive properties Adhesive to acrylic plates = Conforms to JIS Z0237

"Comparative Example 1"
A sample film was prepared in the same manner as in Example 1 except that polyethylene (Evolue SP2540 (manufactured by Prime Polymer)) was used in place of the polypropylene in Example 1, and evaluation was performed in the same manner as in Example 1 (polyethylene layer / ethylene -Vinyl acetate layer = 40/20 μm).
The results are shown in Table 1.

   From Table 1, the pressure-sensitive adhesive film of the present invention has a pressure-sensitive adhesive property to a surface-protected article (in this case, a pressure-sensitive adhesive property with respect to the acrylic plate surface) that is almost the same as that of a conventional product. It can be seen that the stiffness (film waist: shape stability), haze (cloudiness), gloss (brightness) light transmittance, and the like are remarkably superior to those of conventional products.

Claims (8)

  The polypropylene resin base layer (A) and the vinyl acetate unit content are 7.0% by weight or less, and the melt flow rate (MFR) at 190 ° C. under a load of 2160 g (conforming to JIS K7210-1999) is 0.1. A pressure-sensitive adhesive film or sheet comprising a pressure-sensitive adhesive layer (B) made of an ethylene / vinyl acetate copolymer of ˜6.5 g / 10 minutes.   The adhesive film or sheet of Claim 1 which laminated | stacked the said adhesion layer (B) on the single side | surface of a polypropylene resin base film.   The pressure-sensitive adhesive film or sheet according to claim 1 or 2, wherein the base material layer (A) and the pressure-sensitive adhesive layer (B) are formed by coextrusion.   The pressure-sensitive adhesive film or sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer (B) further contains a tackifier.   The pressure-sensitive adhesive film or sheet according to any one of claims 1 to 4, wherein the base material layer (A) comprises a polypropylene homopolymer or a random copolymerized propylene resin.   The pressure-sensitive adhesive film or sheet according to any one of claims 1 to 5, which is used as a surface protecting film for articles and members.   The pressure-sensitive adhesive film or sheet according to claim 6, which is used for surface protection of precision electronic components.   The pressure-sensitive adhesive film or sheet according to claim 7, wherein the precision electronic component is a constituent member of a liquid crystal display device, a plasma display device, or an organic thin film EL device.