JP2013014729A - Transparent film, method for manufacturing the same and method of using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent film which is flexible and can suppress the occurrence of yellow shift.SOLUTION: The transparent film containing an acyclic olefin-cyclic olefin copolymer elastomer, a blue inorganic pigment and a non-amide based lubricant is prepared. The olefin based elastomer can be noncrystalline. The acyclic olefin-cyclic olefin copolymer includes α-acyclic 2-4C olefin and polycyclic olefin as polymerizable components, and the molar ratio of both may be α-acyclic 2-4C olefin/polycyclic olefin=about 80/20-99/1. The content of the blue inorganic pigment may be 10-50 ppm with respect to the total amount of film.

Description

  The present invention relates to a transparent film that is used in electrical / electronic equipment or optical equipment and requires flexibility, and a method for producing and using the transparent film.

  With the recent miniaturization and advancement of portable devices, home appliances, control devices, etc., as a switch member used for the input part of electrical / electronic devices or optical devices, a sheet-like switch member formed of a thin film sheet, For example, key top sheets and light guide sheets for forming push button switches, membrane switches, sensor switches, touch panels and the like are widely used. These sheet-like switch members have light guiding properties (transparency to transmit light), moldability, operability (click feeling, etc.), mechanical strength (durability against repeated operations, etc.), durability (light resistance) , Heat resistance, water resistance, hydrolysis resistance, etc.), printability (printability for use as an operation panel, etc.) are required. Since elasticity and flexibility for bending by being pressed by a hand or the like are required, a transparent film mainly made of plastic or elastomer is used.

  Silicone elastomers and thermoplastic polyurethane elastomers are known as such transparent films. Among the thermoplastic polyurethane elastomers, the non-yellowing thermoplastic polyurethane elastomer is expensive in raw material resin and has low film economics. On the other hand, the hard yellowing thermoplastic polyurethane elastomer is relatively inexpensive, but has low light resistance and large discoloration. Further, a curable non-yellowing polyurethane elastomer has been studied, but the economic efficiency has not been overcome.

  On the other hand, inexpensive thermoplastic polyolefin-based elastomers have been used as impact modifiers for polypropylene and polyethylene, but have low heat resistance when used for key top sheets and the like. Cyclic olefin elastomers are known as olefin elastomers with high heat resistance, and Patent No. 3274702 (Patent Document 1) contains a cyclic olefin copolymer having a glass transition temperature of 30 ° C. or lower. A multilayer material comprising a layer to be formed and a layer or a molded body made of at least one material selected from synthetic polymers, natural polymers, metals, metal oxides, and mixtures thereof has been proposed. This document describes that multilayer materials can be used in various fields such as films, sheets, containers, packaging materials, automobile parts, electrical / electronic parts, building materials, civil engineering materials, and the like.

  However, when the cyclic olefin-based elastomer described in this document is used as a key top sheet or a light guide sheet, a yellow shift (yellow discoloration, sunset) in which the hue of light from a white light source changes and yellowish appears. Occur. In particular, as a result of investigations by the present inventors, even when no yellow shift occurs in light transmitted in the thickness direction, yellow shift occurs in light incident along the surface direction of the film. For example, when used as the key top sheet or the light guide sheet, when light enters from the film end face (cross section) and passes through the optical path length (80 mm), a yellow shift occurs in the light of the white LED. Required. As a cause of the yellow shift, the cyclic olefin elastomer contains a chain olefin unit in addition to the cyclic olefin unit, and it is presumed that the microcrystalline property of the chain olefin unit has an influence.

  As a method for suppressing yellow shift, a method using a bluing agent is known. For example, in JP 2009-59583 A (Patent Document 2), a fluorescent light brightening agent or a bluing agent is contained in a sheet-like light guide formed of a polycarbonate-based resin, and the absorbed ultraviolet energy is visible. A method for improving the color tone of the emitted light to white or bluish white by radiating to the part is disclosed. In this document, the polycarbonate resin contains a benzene ring structure in its molecular structure, so when irradiated with light, it absorbs light in the ultraviolet region (blue) and the yellow color that is its complementary color is clearly visible (Yellow shift) is observed. In addition, organic dyes such as quinacdrine compounds and anthraquinone compounds are described as bluing agents.

  However, since the polycarbonate-based resin is hard, if a click feeling is given by the key top sheet, it must be thinned to give the key top sheet a click feeling. Furthermore, when the polycarbonate is thinned, it becomes easy to break, so that the mechanical properties are not sufficient.

  JP-A-2004-131661 (Patent Document 3) discloses a method for producing a bluing masterbatch for emphasizing the whiteness of a white film, 30 to 70% by weight of titanium dioxide, ultramarine violet as ultramarine, One or more kinds selected from ultramarine pink 1 to 5.5% by weight, zinc stearate 1 to 5% by weight, and a mixture containing at least a thermoplastic resin, a reduced pressure of −0.09 MPa or less and a resin temperature of 180 to 250 ° C. The manufacturing method which melt-kneads and shape | molds on conditions and makes a water content 900 ppm or less is disclosed. This document describes polyolefin resins such as polyethylene, polypropylene, polybutene-1, polymethylpentene, and polystyrene as thermoplastic resins.

  However, this document does not disclose a transparent sheet such as a light guide sheet. The bluing agent is commercially available as a colorant for melt-processed resins, and its form is commercially available in the form of a mixture of an amide-based lubricant such as ethylene bisstearyl amide in addition to the dispersant.

Japanese Patent No. 3274702 (claims, paragraphs [0019] [0057], Examples) JP 2009-59583 A (Claim 1, paragraphs [0014] [0018] [0019] [0026]) JP 2004-131661 A (Claim 1, paragraph [0023], Example)

  Accordingly, an object of the present invention is to provide a transparent film that is flexible and can suppress the occurrence of yellow shift, and a method for producing and using the transparent film.

  Another object of the present invention is to provide a transparent film excellent in durability such as heat resistance and light resistance, and a method for producing and using the same.

  Another object of the present invention is to provide a transparent film that can easily suppress yellow shift and can suppress deterioration in appearance due to bleeding out of a blueing agent or additive, and a method for producing and using the same.

  In order to achieve the above object, the present inventors first selected a chain olefin-cyclic olefin copolymer elastomer having excellent heat resistance and flexibility as a resin for forming a transparent film, and prepared a light guide sheet. An attempt was made, but as described above, a yellow shift occurred due to Rayleigh scattering due to the microcrystalline nature of the chain olefin units. Therefore, the film forming conditions of the cyclic olefin-based elastomer were examined, and the film was rapidly cooled after forming the film, thereby suppressing the microcrystals and succeeding in improving the yellow shift and light loss due to Rayleigh scattering. However, since the transmitted light is not completely white, we next considered the addition of a bluing agent and blended a blue dye with a coloring power, but there was no bleed-out that was not compatible with olefinic materials and damaged the appearance. Occurred. Moreover, although phthalocyanine blue was blended as an organic pigment, the coloring power was too strong, and toning was difficult. Furthermore, as a result of blending commercially available colorants for melt-processed resins as inorganic pigments, fatty acid metal salts and amide-based lubricants included as dispersants in the colorants bleed out, but the appearance is impaired by including amide-based lubricants. It turned out to be only the colorant.

  Therefore, as a result of intensive studies, the present inventors have found that a transparent film prepared by dispersing a blue inorganic pigment with a non-amide lubricant in a chain olefin-cyclic olefin copolymer elastomer is flexible and has a yellow shift. As a result, the present invention was completed.

That is, the transparent film of the present invention includes a chain olefin-cyclic olefin copolymer elastomer having a chain olefin and a cyclic olefin as polymerization components, a blue inorganic pigment, and a non-amide lubricant. The chain olefin-cyclic olefin copolymer elastomer may have a crystallinity of about 20 to 30%. The chain olefin-cyclic olefin copolymer elastomer is composed of an α-chain C _2-4 olefin and a polyolefin. It is a copolymer having a cyclic olefin as a polymerization component, and the molar ratio between them may be about α-chain C _2-4 olefin / polycyclic olefin = 80/20 to 99/1. The blue inorganic pigment may be ultramarine blue and / or cobalt blue. The non-amide lubricant may be at least one selected from the group consisting of higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, higher alcohols and waxes. The ratio of the blue inorganic pigment may be about 10 to 50 ppm with respect to the total amount of the chain olefin-cyclic olefin copolymer elastomer, the blue inorganic pigment and the non-amide lubricant. The ratio of the non-amide lubricant may be about 1 to 1000 ppm with respect to the total amount of the chain olefin-cyclic olefin copolymer elastomer, the blue inorganic pigment, and the non-amide lubricant. The transparent film of the present invention may have a haze of 10% or less. The transparent film of the present invention may be a key top sheet or a light guide sheet.

  The present invention also includes a method for producing the transparent film, in which a resin composition containing a chain olefin-cyclic olefin copolymer elastomer, a blue inorganic pigment, and a non-amide lubricant is formed into a film. In the production method of the present invention, the resin composition may be cooled at 50 ° C. or lower after extrusion. In the production method of the present invention, a masterbatch containing a chain olefin-cyclic olefin copolymer elastomer, a blue inorganic pigment and a non-amide lubricant, a chain olefin-cyclic olefin copolymer elastomer and a non-amide lubricant is included. The resin composition may be mixed and extruded. In the master batch, the ratio of the non-amide lubricant is about 10 to 100 parts by weight with respect to 100 parts by weight of the blue inorganic pigment, and in the resin composition, the ratio of the non-amide lubricant is a chain olefin. -About 1-1000 ppm may be sufficient with respect to 100 weight part of cyclic olefin copolymer elastomers.

  The present invention includes a method of using the transparent film as a key top sheet or a light guide sheet.

  In the present invention, since the blue inorganic pigment is dispersed with the non-amide lubricant in the chain olefin-cyclic olefin copolymer elastomer, it is flexible and can suppress the occurrence of yellow shift. Moreover, since it is formed of an olefin elastomer composed of a chain olefin-cyclic olefin copolymer, durability such as heat resistance and light resistance can be improved as compared with a chain olefin elastomer mainly composed of polyethylene. In addition, since the blue inorganic pigment is dispersed using a dispersant, yellow shift can be easily suppressed, and because it is dispersed using a non-amide lubricant, the appearance of bleeding out of blueing agents and additives Can be suppressed.

[Transparent film]
The transparent film of the present invention contains a chain olefin-cyclic olefin copolymer elastomer having a chain olefin and a cyclic olefin as polymerization components, a blue inorganic pigment, and a non-amide lubricant.

(Chain olefin-cyclic olefin copolymer elastomer)
The chain olefin-cyclic olefin copolymer elastomer is a copolymer containing a chain olefin and a cyclic olefin as a polymerization component, and has appropriate flexibility and elasticity, and has a cyclic olefin skeleton and polyethylene as a main component. Compared to general-purpose olefin resin, it has high heat resistance.

Examples of the chain olefin include chain C such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. _2-10 olefins etc. are mentioned. These chain olefins can be used alone or in combination of two or more. Among these chain olefins, α-chain C _2-8 olefins are preferable, and α-chain C _2-4 olefins (particularly ethylene) are more preferable.

The cyclic olefin may be a polymerizable cyclic olefin having an ethylenic double bond in the ring, and may be a monocyclic olefin (for example, cyclic C _4-12 cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, etc. However, polycyclic olefins are preferred.

  Examples of typical polycyclic olefins include norbornene, norbornene having a substituent (2-norbornene), a multimer of cyclopentadiene, a multimer of cyclopentadiene having a substituent, and the like. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a cyano group, an amide group, and a halogen atom. These substituents may be used alone or in combination of two or more.

  Specifically, examples of the polycyclic olefin include 2-norbornene; 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl-2-norbornene. Norbornenes having an alkyl group such as: norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; alkoxycarbonyls such as 5-methoxycarbonyl-2-norbornene and 5-methyl-5-methoxycarbonyl-2-norbornene Norbornenes having a group; norbornenes having a cyano group such as 5-cyano-2-norbornene; norbornenes having an aryl group such as 5-phenyl-2-norbornene and 5-phenyl-5-methyl-2-norbornene; Dicyclopentadiene; 2,3-dihydrodi Derivatives such as clopentadiene, methanooctahydrofluorene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, methanooctahydrocyclopentadienonaphthalene; derivatives having substituents such as 6-ethyl-octahydronaphthalene; cyclo Examples thereof include adducts of pentadiene and tetrahydroindene, 3-pentamers of cyclopentadiene, and the like.

  These cyclic olefins can be used alone or in combination of two or more. Of these cyclic olefins, polycyclic olefins such as norbornenes are preferred.

In the chain olefin-cyclic olefin copolymer, a chain olefin (especially α-chain C _2-4 olefin such as ethylene) and a cyclic olefin (particularly norbornene, etc.) from the viewpoint of achieving both transparency and flexibility. The ratio (molar ratio) to the polycyclic olefin) is, for example, the former / the latter = 80/20 to 99/1 (for example, 82/18 to 97/3), preferably 85/15 to 95/5, More preferably, it is about 88/12 to 94/6 (particularly 90/10 to 93/7).

  Other copolymerizable monomers include, for example, vinyl ester monomers (eg, vinyl acetate, vinyl propionate, etc.); diene monomers (eg, butadiene, isoprene, etc.); (meth) acrylic monomers Monomer [for example, (meth) acrylic acid or derivatives thereof ((meth) acrylic acid ester etc.)] etc. can be illustrated. These other copolymerizable monomers may be used alone or in combination of two or more. The content of these other copolymerizable monomers is, for example, 5 mol% or less, preferably 1 mol% or less, based on the copolymer. In particular, when a polymer is formed with a monomer having no aromatic ring or polar group, light resistance can be improved.

  The chain olefin-cyclic olefin copolymer elastomer may be an elastomer obtained by addition polymerization or an elastomer obtained by ring-opening polymerization (ring-opening metathesis polymerization or the like). The polymer elastomer obtained by ring-opening metathesis polymerization may be a hydrogenated hydrogenated product. The chain olefin-cyclic olefin copolymer elastomer may be polymerized by a conventional method, for example, ring-opening metathesis polymerization using a metathesis polymerization catalyst, addition polymerization using a Ziegler type catalyst, or addition polymerization using a metallocene catalyst ( Usually, ring-opening metathesis polymerization using a metathesis polymerization catalyst) can be used.

  The chain olefin-cyclic olefin copolymer elastomer exhibits moderate crystallinity, and the crystallinity (crystallinity after film forming) can be selected from the range of 20-30%, preferably about 20-25%. . If the degree of crystallinity is too small, the heat resistance of the film tends to decrease, and if the degree of crystallinity is too large, the film becomes clouded and yellow shift is likely to occur. In the present invention, by controlling the degree of crystallinity, light scattering at a short wavelength (near 450 nm) can be suppressed, and light guide properties in the surface direction of the film (light guide from one end surface of the film to the other end surface facing each other). Property) and the hue of the emitted light can be improved. The degree of crystallinity can be obtained by dividing the heat of fusion measured using a differential scanning calorimeter by the heat of fusion of the complete crystal, and specifically, obtained by the method described in the examples described later. Can do.

  The glass transition temperature (glass transition temperature before film forming) (Tg) of the chain olefin-cyclic olefin copolymer elastomer can be selected from a range of about 30 ° C. or less, for example, −25 ° C. to 30 ° C., preferably −20. It is about -20 degreeC, More preferably, it is about -15 degreeC-10 degreeC.

  The melting point (melting point before film forming) (Tm) of the chain olefin-cyclic olefin copolymer elastomer can be selected from the range of about 50 ° C. or higher, for example, 50 to 200 ° C., preferably 60 to 150 ° C., more preferably. It is about 70-120 degreeC (especially 75-100 degreeC).

  The glass transition temperature and the melting point can be controlled by adjusting the ratio of the monomer, the substituent of the monomer, the molecular weight of the polymer, and the like.

  The number average molecular weight of the chain olefin-cyclic olefin copolymer elastomer is, for example, about 15,000 to 200,000, preferably 20,000 to 100,000, more preferably about 30,000 to 80,000 (particularly 40,000 to 70,000).

(Blue inorganic pigment)
In the present invention, a blue inorganic pigment is used as the bluing agent. By using a blue inorganic pigment, it is possible to suppress a decrease in appearance due to bleed-out and to improve light resistance. Further, since it has an appropriate coloring power, it is possible to finely adjust the transparent film by fine adjustment of the addition amount. Furthermore, it is possible to uniformly disperse in the copolymer elastomer only with a non-amide lubricant without using an amide lubricant that causes a decrease in appearance due to bleeding out.

  The blue inorganic pigment (blue-green inorganic pigment) of the present invention includes a green inorganic pigment in addition to a blue inorganic pigment.

  Examples of blue inorganic pigments include, for example, bitumen (miloli blue, Prussian blue, iron blue, etc.) composed of iron and cyan complex, and ultramarine blue, ultramarine violet, ultramarine composed of sulfur-containing sodium aluminosilicate complex. Marine pink and the like, and complex oxide blue (cobalt blue and the like) composed of a complex oxide of cobalt and aluminum. These blue inorganic pigments can be used alone or in combination of two or more.

  Examples of the green inorganic pigment include a composite oxide such as chromium oxide green (chromium oxide green) composed of pure chromium oxide (III), Co—Zn—Ni—Ti, and Co—Al—Cr. Examples thereof include complex oxide green (such as cobalt green). These green inorganic pigments can be used alone or in combination of two or more.

  Of these blue inorganic pigments, blue inorganic pigments, particularly ultramarine blue and cobalt blue, are preferable from the viewpoint of having appropriate coloring power.

  The average particle size of the blue inorganic pigment is, for example, about 0.01 to 10 μm, preferably about 0.03 to 5 μm, more preferably about 0.05 to 3 μm (particularly about 0.1 to 2 μm).

  The proportion of the blue inorganic pigment is, for example, 10 to 50 ppm, preferably 12 to 40 ppm, based on the entire film (total amount of chain olefin-cyclic olefin copolymer elastomer, blue inorganic pigment and non-amide lubricant). More preferably, it is about 15-35 ppm (especially 20-30 ppm). If the ratio of the blue inorganic pigment is too small, yellow remains and yellow shift cannot be suppressed. If the ratio is too large, the transparency is lowered and the light loss is increased.

(Non-amide lubricant)
In the present invention, a non-amide lubricant is used as a dispersant because it is excellent in dispersing action, can uniformly disperse the blue inorganic pigment in the copolymer elastomer, and can suppress deterioration in appearance even when bleeded out. Use.

  The non-amide lubricant may be any lubricant that does not have an amide unit (amide group and / or amide bond), and examples thereof include higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, higher alcohols, and waxes. . These non-amide lubricants can be used alone or in combination of two or more.

The higher fatty acid may be saturated or unsaturated, and usually a saturated higher fatty acid is used. Examples of the higher fatty acid include 8 to 30 (for example, 10 to 30) carbon atoms such as octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, preferably 12 to 30 (for example, 12 to 12). 28), more preferably about 14 to 24 (for example, 16 to 22) saturated aliphatic monocarboxylic acid, oleic acid, linoleic acid, linolenic acid, eleostearic acid and other C _8-30 unsaturated higher monocarboxylic acids (Preferably C _14-30 unsaturated monocarboxylic acid, more preferably C _16-22 unsaturated monocarboxylic acid), aliphatic saturated or unsaturated hydroxycarboxylic acid such as ricinoleic acid and sabinic acid, cyclic group such as naphthenic acid ( Branched aliphatic saturated such as aliphatic saturated or unsaturated monocarboxylic acid, 2-ethylhexenoic acid having cycloalkyl group) Etc. unsaturated monocarboxylic acids can be exemplified. These higher fatty acids can be used alone or in combination of two or more. Of these, saturated aliphatic monocarboxylic acids (eg, stearic acid and behenic acid) having 12 to 28 carbon atoms, preferably 14 to 24, and particularly about 16 to 22 carbon atoms such as stearic acid and behenic acid are preferable. In addition, these higher fatty acids can be illustrated also as a fatty acid which comprises higher fatty acid metal salt and higher fatty acid ester.

  The types of metal salts in the higher fatty acid metal salts include various metal salts such as Group Ia of the periodic table (for example, sodium, potassium, rubidium, cesium), Group IIa (for example, beryllium, magnesium, calcium, strontium, barium). ), Group VIII (for example, iron, nickel, cobalt), Group Ib (for example, copper, silver, gold), Group IIb (for example, zinc, cadmium), Group IIIb (for example, aluminum, gallium, indium), Group IVb Examples of the metal salt include (eg, germanium, tin, lead). Among these, polyvalent metal salts (for example, IIa group such as magnesium, calcium and barium, Ib group such as copper, IIb group such as zinc, IIIb group such as aluminum, and IVb group metal salt such as lead) preferable.

Examples of higher fatty acid esters include C _1-24 monoalcohols such as methanol, ethanol and hexanol, (poly) C _2-6 alkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol, (poly) glycerin, trimethylolpropane, Examples thereof include esters with alcohols such as polyvalent (for example, 3 to 8) alcohols such as pentaerythritol and sorbitan. Among these, esters with alcohols having 3 or more (for example, 3-6, preferably 3-4) hydroxyl groups such as (poly) glycerin and pentaerythritol are widely used.

  As the higher alcohol, a higher alcohol having an aliphatic skeleton similar to the aliphatic skeleton of the higher fatty acid can be used.

As the wax, aliphatic hydrocarbon wax (for example, poly C _2-4 olefin wax such as polyethylene wax, ethylene copolymer wax, polypropylene wax, paraffin wax such as natural paraffin and synthetic paraffin, microcrystalline wax, etc. ), Vegetable or animal waxes (for example, carnauba wax, beeswax, shellac wax, montan wax, etc.).

Among these non-amide type lubricants, a lubricant which is solid at room temperature is preferable, for example, a melting point of 40 ° C or higher (for example, 60 to 250 ° C), preferably 80 to 200 ° C, more preferably 100 to 180 ° C (particularly 120 to 180 ° C). It may be about 160 ° C. Specifically, higher fatty acid metal salts and poly C _2-4 olefin waxes (polyethylene wax and the like) are widely used, and higher fatty acid metal salts, particularly those having 12 to 28 carbon atoms (particularly 16 to 22) such as stearic acid. A salt of a saturated aliphatic monocarboxylic acid and a polyvalent metal (an alkaline earth metal such as magnesium or calcium, or a group IIb metal such as zinc) can be produced by an inexpensive method and is preferable from the viewpoint of high productivity. The weight average molecular weight of the poly C _2-4 olefin wax is, for example, 1000 to 30000, preferably 2000 to 20000, more preferably 3000 to 15000 (particularly 5000 to 10,000) in terms of polystyrene in gel permeation chromatography (GPC). ) Degree.

  The ratio of the non-amide lubricant can be selected from a range of, for example, about 1 to 1000 ppm with respect to the entire film (the total amount of the chain olefin-cyclic olefin copolymer elastomer, the blue inorganic pigment, and the non-amide lubricant). From the viewpoint of improving moldability in addition to the dispersibility of the inorganic pigment, it may be, for example, about 100 to 1000 ppm, preferably about 200 to 800 ppm, and more preferably about 300 to 700 ppm. If the proportion of the non-amide lubricant is too small, the inorganic pigment cannot be uniformly dispersed and the moldability cannot be improved. On the other hand, when there are too many non-amide type lubricants, transparency will fall.

(Other additives)
The transparent film of the present invention is a conventional additive, for example, other dyes, pigments, other dispersants, flame retardants, fillers, stabilizers (antioxidants, ultraviolet absorptions) as long as transparency and flexibility are not impaired. Agents, heat stabilizers, etc.), antistatic agents and the like. These additives can be used alone or in combination of two or more.

  In the transparent film of the present invention, since the blue inorganic pigment can be uniformly dispersed in the copolymer elastomer by using the aliphatic metal salt, other dispersants are substantially added from the viewpoint of suppressing bleed out. It is preferable not to contain. In particular, the transparent film of the present invention preferably contains substantially no amide-based lubricant (for example, alkylene bis fatty acid amides such as methylene bis stearic acid amide, ethylene bis stearic acid amide, ethylene bishydroxy stearic acid amide). .

(Characteristics of transparent film)
The transparent film of the present invention is excellent in transparency, and the haze (cloudiness value) may be, for example, 10% or less, for example, 0.1 to 10%, preferably in the method according to JIS K7105. Is about 0.2 to 5%, more preferably about 0.3 to 3% (particularly 0.5 to 2%). The transparent film of the present invention is excellent in durability and has a small haze after the durability test described in Examples, for example, 0.1 to 10%, preferably 0.5 to 8%, more preferably 1 to 5%. It may be a degree.

  The total light transmittance is, for example, about 84 to 94%, preferably 86 to 93%, and more preferably about 88 to 92%.

  The transparent film of the present invention is excellent in elasticity and flexibility, and the loss elastic modulus E ′ at 25 ° C. is, for example, 30 to 300 MPa, preferably 50 to 200 MPa, more preferably 60 to 180 MPa (particularly 80 to 150 MPa). Degree. Therefore, mechanical stress during processing and use, and dimensional changes due to changes in temperature and humidity can be alleviated.

  Further, in a tensile test (film having a thickness of 100 μm) based on JIS K7127, the elongation at break may be about 500% or more, for example, 500 to 2500%, preferably 600 to 2000%, more preferably 800 to It may be about 1800% (particularly 1000 to 1500%). Furthermore, since the transparent film of the present invention exhibits elastic deformability, it is excellent in clickability (operability and durability) when used for a key top sheet, and preferably does not exhibit a yield point in the tensile test.

  The thickness of the transparent film can be selected from the range of about 1 to 1000 μm depending on the application, and is, for example, 10 to 500 μm, preferably 30 to 400 μm, and more preferably about 50 to 300 μm.

  The transparent film may be formed by laminating a plurality of transparent films, and may be laminated with other layers (for example, functional layers such as a protective layer, a hard coat layer, and a light scattering layer).

[Method for producing transparent film]
The method for producing the transparent film of the present invention is not particularly limited, and conventional methods such as extrusion molding, injection molding, press molding, blow molding, compression molding and the like can be used. Extrusion methods such as extrusion methods [die (flat, T-shaped, T-die), cylindrical (circular die), etc.), inflation methods, etc.], stretching methods such as tenter method, tube method, inflation method, etc. Preferably, an extrusion method is particularly preferable.

  In the extrusion molding method, the elastomer component, the blue inorganic pigment, and the non-amide lubricant may be subjected to extrusion molding as they are, but the elastomer component and the blue pigment are easy to knead uniformly in the elastomer component. It is preferable to prepare in advance a masterbatch containing an inorganic pigment (and a masterbatch containing a non-amide lubricant).

  In the preparation method of the masterbatch, the melt-kneading can be performed using a conventional method, that is, a conventional melt-kneader, for example, a single screw or a vent type twin screw extruder. Prior to melt kneading, the elastomer component and the blue inorganic material are mixed using a conventional method such as a mixer (such as a tumbler, V-type blender, Henschel mixer, Nauta mixer, ribbon mixer, mechanochemical apparatus, extrusion mixer). A pigment and a non-amide lubricant may be premixed. The melt kneading temperature can be selected from a range of about 100 to 300 ° C. depending on the type of the elastomer component, for example, 120 to 250 ° C., preferably 150 to 220 ° C., more preferably about 160 to 210 ° C. May be.

  The master batch is prepared so as to have a content of about 5 to 100 times, preferably 10 to 50 times, and more preferably about 10 to 30 times the content of the blue inorganic pigment in the target transparent film. Also good.

  In the master batch, the ratio of the non-amide lubricant can be selected from the range of about 1 to 100 parts by weight with respect to 100 parts by weight of the blue inorganic pigment, for example, 10 to 100 parts by weight, preferably 20 to 80 parts by weight. More preferably, it is about 30 to 70 parts by weight (particularly 40 to 60 parts by weight).

  In the present invention, the elastomer component for diluting the masterbatch preferably contains a non-amide lubricant as a molding aid. The ratio of the non-amide lubricant is about 1 to 1000 ppm, preferably about 10 to 800 ppm, and more preferably about 100 to 700 ppm with respect to the elastomer component. As a blending method of the non-amide lubricant, the blender may be used.

  A resin composition for forming a transparent film (for example, a mixed pellet of the master batch and a resin composition for diluting the master batch) is an extrusion molding machine (for example, a single screw or a vent type twin screw extruder) In general, pellets are melt-kneaded in an extruder and extruded from a slit of a die (die) at the tip of the extruder. The die (die) may be a ring die used for inflation molding, but usually a T die such as a multi-manifold die or a flat die can be used. Further, the extruded sheet can be cooled by a cooling roll and wound on a sheet winder.

  The conditions for extrusion molding can be selected according to the type of the extrusion molding machine or the crystalline resin, and the molding temperature can usually be selected from a range of about 100 to 300 ° C. according to the type of the elastomer component. It may be about -250 ° C, preferably 150-220 ° C, more preferably about 160-210 ° C.

  In the present invention, in order to suppress the microcrystallization of the transparent film, it is preferable to call the cooling temperature with a cooling roll. In particular, it is preferable to suppress microcrystallization by lowering the cooling temperature by the cooling roll and quenching rapidly. For example, the cooling temperature by the cooling roll may be 60 ° C. or less, for example, 50 ° C. It is below (for example, 0-50 degreeC), Preferably it is 0-40 degreeC, More preferably, it is about 0-30 degreeC, The temperature near normal temperature, for example, about 10-35 degreeC, may be sufficient.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The glass transition temperature and melting point of the elastomer, the appearance of the transparent film, the hue of the emitted light (ultraviolet-visible absorption spectrum and evaluation), the durability test, and the haze were measured by the following methods.

(Glass-transition temperature)
Using a differential scanning calorimeter (“DSC6200” manufactured by Seiko Denshi Kogyo Co., Ltd.), the measurement was performed under a nitrogen stream at a heating rate of 10 ° C./min.

(Haze)
About the film-form test piece obtained by the Example and the comparative example, based on JISK7136, the haze was measured using the haze meter (Nippon Denshoku Industries Co., Ltd. product, NDH-500).

(Hue of emitted light)
Thickness: 200 μm, width: 20 mm, 80 mm long 80 mm long edge combined with a blue LED and YAG phosphor (manufactured by Nichia Corporation, trade name “NSPB500S”, 460 nm blue center wavelength 454 nm, White light with a phosphor center wavelength of 550 nm is incident, transmitted through the film (optical path length: 80 mm), and the emitted light from the opposite end is a fiberscope type spectrophotometer (manufactured by Hamamatsu Photonics Co., Ltd. The UV-visible spectrum was measured using a channel spectrometer PMA-11). The spectral data of the spectrophotometer was evaluated for the degree of discoloration (white) by the spectral ratio of the blue peak spectrum (454 nm) with large attenuation to the complementary orange spectrum (605 nm). If the spectral ratio is in the range of 220 to 440, it can be regarded as white light. Furthermore, the result of visual observation is also shown.

(durability)
Using an oven (“Electric Low Temperature Dryer” manufactured by Tanaka Chemical Machinery Co., Ltd.), an endurance test of 85 ° C. × dry × 1000 hr was performed to evaluate the film appearance after the endurance test and measure haze.

(Crystallinity)
Using a differential scanning calorimeter (“DSC6200” manufactured by Seiko Denshi Kogyo Co., Ltd.), the measurement was performed under a nitrogen stream at a heating rate of 10 ° C./min. The degree of crystallinity was calculated based on the following equation from the measured heat of fusion and the heat of fusion of the complete crystal. The complete crystal body heat of fusion is the theoretical value of the heat of fusion when there is no crystal defect and all crystallizes into an array of crystal lattices.

Crystallinity (%) = [(measured heat of fusion) / (complete crystal heat of fusion)] × 100
HDPE complete crystal melting heat amount: 294 J / g: cited from TA Instrument, literature value.

(Elastomer component)
Production Example 1 (Ethylene-Norbornene Copolymer Elastomer 1, COE1)
In a nitrogen atmosphere at room temperature, a 30 liter autoclave was charged with 15 liters of toluene, 15 mmol of triisobutylaluminum (TIBA), 0.75 mmol of zirconium tetrachloride, and 0.75 mmol of tetrakis (pentafluorophenyl) anilinium borate in this order. Subsequently, 1.5 liters of a toluene solution containing 70% by weight of norbornene was added. After raising the temperature to 50 ° C., the reaction was carried out for 60 minutes while continuously introducing ethylene so that the ethylene partial pressure was 5 kgf / cm ² . After completion of the reaction, the polymer solution was put into 15 liters of methanol to precipitate a polymer. The polymer was separated by filtration and dried to obtain an ethylene-norbornene copolymer 1. The yield was 3.58 kg, and the polymerization activity was 52 kg / gZr (yield per gram of zirconium).

^{In 13} C-NMR, the sum of the peak based on the ethylene unit and the peak based on the 5th and 6th position methylenes of the norbornene unit (around 30 ppm) and the peak based on the 7th position methylene group of the norbornene unit (around 32.5 ppm) The norbornene content determined from the ratio was 7.3 mol%. The glass transition temperature was 0.5 ° C. and the melting point was 90 ° C. as measured with a DSC 6200 series manufactured by Seiko Denshi at a rate of temperature increase of 10 ° C./min.

Production Example 2 (Ethylene-Norbornene Copolymer Elastomer 2, COE2)
In Production Example 1, ethylene and norbornene were copolymerized in the same manner as in Production Example 1 except that 0.75 mmol of bis (cyclopentadienyl) dichlorozirconium was used instead of zirconium tetrachloride. As a result, 3.30 kg of the obtained ethylene-norbornene copolymer 2 had a norbornene content of 10 mol%, a glass transition temperature of 2.0 ° C., a melting point of 81 ° C., and a yield of 3.30 kg.

(Master Badge)
Production Example 1 (Masterbatch PBb1)
Blue marine pigment ultramarine (Daiichi Kasei Co., Ltd. “Ultramarine Blue No. H2000”, CIName Pigment Blue 29), zinc stearate, amide lubricant (ethylenebisstearylamide), 60% by weight and 30% respectively. % And 10% by weight using a small vibration ball mill. A mixture obtained by mixing and dispersing the obtained mixed powder using a tumbler mixer so that the ratio of ultramarine to the elastomer component is 500 ppm is a twin-screw extruder ("PCM35" manufactured by Ikegai Co., Ltd.). ) And melt extruded at 190 ° C. to prepare a master batch.

Production Example 2 (Masterbatch PBb2)
Blue marine pigment Ultramarine (Daiichi Kasei Co., Ltd. “Ultramarine Blue No. H2000”, CIName Pigment Blue 29), Zinc stearate at a ratio of 65% by weight and 35% by weight, respectively, using a small vibrating ball mill Dispersed and mixed. The resulting mixed powder was mixed and dispersed using a tumbler mixer so that the ratio of ultramarine to the elastomer component was 500 ppm. A twin screw extruder ("PCM35" manufactured by Ikegai Co., Ltd.) )) And melt extruded at 190 ° C. to prepare a master batch.

Production Example 3 (Masterbatch PBb3)
A master batch was prepared in the same manner as in Production Example 2 except that calcium stearate was used instead of zinc stearate.

Production Example 4 (Master batch PBb4)
A master batch was prepared in the same manner as in Production Example 2 except that magnesium stearate was used instead of zinc stearate.

Production Example 5 (Master batch PBb5)
A master batch was prepared in the same manner as in Production Example 2 except that polyethylene wax (weight average molecular weight: 8000) was used instead of zinc stearate.

Production Example 6 (Master batch PBb6)
A master batch was prepared in the same manner as in Production Example 2 except that cobalt blue (“Daipyroxide Blue # 9453”, CIName Pigment Blue 36, manufactured by Dainichi Seika Co., Ltd.) was used instead of ultramarine.

Production Example 7 (Master batch PBb7)
Use a tumbler mixer so that the ratio of ultramarine ("Ultramarine Blue No. H2000" manufactured by Daiichi Kasei Co., Ltd., CIName Pigment Blue 29) of the blue inorganic pigment to the elastomer component is 500 ppm. Then, the mixture in which both components were mixed and dispersed was supplied to a twin-screw extruder (“PCM35” manufactured by Ikekai Co., Ltd.) and melt-extruded at 190 ° C. to prepare a master batch. Aggregation of ultramarine powder occurred in the obtained master batch.

Production Example 8 (Master batch PBb8)
A master batch was prepared in the same manner as in Production Example 2 except that iron oxide (“Sun Chemical C33-2199” manufactured by Nippon Koken Kogyo Co., Ltd.) was used instead of ultramarine.

Production Example 9 (Master batch PBb9)
A master batch was prepared in the same manner as in Production Example 2 except that titanium oxide, a white inorganic pigment (“Sun Chemical C47-051” manufactured by Nippon Koken Kogyo Co., Ltd.), was used instead of ultramarine.

  In addition, in the manufacture examples 1-9, the same elastomer component as the elastomer for diluting the masterbatch used in an Example was used as an elastomer component.

Example 1
100 parts by weight of the elastomer (COE1) obtained in Production Example 1 and 5 parts by weight of the master batch (PBb2) were mixed and dispersed using a tumbler mixer. The obtained mixture was wound at a cooling roll temperature of 30 ° C. using a 40 mmφ single-screw extruder (“PLASTIC EXTRUDUR VC40” manufactured by Chuo Kikai Seisakusho Co., Ltd.) equipped with a 400 mm wide die, and the thickness was 200 μm. A transparent film was obtained. Fish eyes were observed in the obtained transparent film.

Example 2
As an elastomer for diluting the masterbatch, the ratio of the higher fatty acid metal salt (zinc stearate, calcium stearate, or magnesium stearate) is 500 ppm with respect to the elastomer (COE1) obtained in Production Example 1. Thus, the transparent film was obtained like Example 1 except using the mixture which mix | blended the higher fatty acid metal salt as a shaping | molding adjuvant (FM). Fish eyes were not seen in the obtained transparent film.

Example 3
A transparent film was obtained in the same manner as in Example 2 except that the amount of the master batch used was changed to 3 parts by weight. Fish eyes were not seen in the obtained transparent film.

Example 4
A transparent film was obtained in the same manner as in Example 2 except that the elastomer (COE2) obtained in Production Example 2 was used as the elastomer component. Fish eyes were not seen in the obtained transparent film.

Examples 5-8
A transparent film was obtained in the same manner as in Example 2 except that the master batch shown in Table 1 was used as the master batch. Fish eyes were not seen in the obtained transparent film.

Comparative Example 1
A mixture in which zinc stearate was blended as a molding aid so that the ratio of zinc stearate to the concentration of 500 ppm with respect to the elastomer (COE1) obtained in Production Example 1 was 40 mmφ with a 400 mm wide die attached. Using a single-screw extruder (“PLASTIC EXTRUDUR VC40” manufactured by Chuo Machinery Co., Ltd.), the film was wound at a cooling roll temperature of 70 ° C. to obtain a transparent film having a thickness of 200 μm.

Comparative Example 2
A transparent film was obtained in the same manner as in Comparative Example 1 except that the temperature of the cooling roll was 30 ° C. and the film was rapidly cooled.

Comparative Examples 3-6
A transparent film was obtained in the same manner as in Example 2 except that the master batch shown in Table 1 was used as the master batch.

  As is clear from the results in Table 1, the transparent films of the examples are transparent and no yellow shift is observed, and are transparent and retain a low haze even after the durability test.

  On the other hand, in the films of Comparative Examples 1 to 3 and 5 to 6, color unevenness and yellow shift occur in the appearance of the film.

  Further, the surfaces of Example 1, Comparative Example 2 and Comparative Example 4 before and after the durability test were analyzed by X-ray electron spectroscopy (XPS). From the surface of the sample after the endurance test of Example 1 and Comparative Example 2, it was observed that the peak of zinc derived from the zinc auxiliary stearate as a molding aid was increased from that before the endurance test. On the other hand, from the sample surface after the durability test of Comparative Example 4, it was observed that the zinc peak derived from zinc stearate and the nitrogen peak derived from the amide-based lubricant were increased from before the durability test. However, an increase in the aluminum peak and sulfur peak derived from ultramarine, which is a complex of sulfur-containing sodium silicate, was not observed. The peak of nitrogen derived from the amide lubricant was observed more strongly in the cloudy part where the haze increased to 20 than in the part with less cloudiness. From these facts, it can be confirmed that the higher fatty acid metal salt added as a dispersant and a molding aid does not affect the change in appearance even when bleeded, but the appearance decreases when the amide lubricant is bleeded out.

  The transparent film of the present invention can be used as a light guide sheet or film for various electric / electronic devices or optical devices such as portable devices, home appliances, and control devices. In particular, since yellow shift can be suppressed and flexibility is excellent, key top sheets (for example, mobile phones, game machines, mobile devices, touch panels, etc.) used for illuminated keys, etc. It can be effectively used for telephone key top sheets) and light guide sheets.

Claims (14)

  A transparent film comprising a chain olefin-cyclic olefin copolymer elastomer having a chain olefin and a cyclic olefin as polymerization components, a blue inorganic pigment, and a non-amide lubricant.   The transparent film according to claim 1, wherein the chain olefin-cyclic olefin copolymer elastomer has a crystallinity of 20 to 30%. The chain olefin-cyclic olefin copolymer elastomer is a copolymer having an α-chain C _2-4 olefin and a polycyclic olefin as polymerization components, and the molar ratio between the two is α-chain C _2. The transparent film according to claim 1 or 2, wherein _-4 olefin / polycyclic olefin = 80/20 to 99/1.   The transparent film according to claim 1, wherein the blue inorganic pigment is ultramarine blue and / or cobalt blue.   The transparent film according to any one of claims 1 to 4, wherein the non-amide lubricant is at least one selected from the group consisting of higher fatty acids, higher fatty acid metal salts, higher fatty acid esters, higher alcohols and waxes.   The ratio of the blue inorganic pigment is 10 to 50 ppm with respect to the total amount of the chain olefin-cyclic olefin copolymer elastomer, the blue inorganic pigment and the non-amide lubricant, The transparent according to any one of claims 1 to 5. the film.   The transparent composition according to any one of claims 1 to 6, wherein the ratio of the non-amide lubricant is 1-1000 ppm with respect to the total amount of the chain olefin-cyclic olefin copolymer elastomer, the blue inorganic pigment, and the non-amide lubricant. the film.   The transparent film according to claim 1, wherein the haze is 10% or less.   It is a key top sheet or a light guide sheet, The transparent film in any one of Claims 1-8.   The method for producing a transparent film according to claim 1, wherein a resin composition comprising a chain olefin-cyclic olefin copolymer elastomer, a blue inorganic pigment and a non-amide lubricant is formed into a film.   The manufacturing method of Claim 10 which cools at 50 degrees C or less after extrusion molding a resin composition.   A masterbatch containing a chain olefin-cyclic olefin copolymer elastomer, a blue inorganic pigment and a non-amide lubricant is mixed with a resin composition containing a chain olefin-cyclic olefin copolymer elastomer and a non-amide lubricant. The production method according to claim 10 or 11, wherein extrusion molding is performed.   In the master batch, the ratio of the non-amide lubricant is 10 to 100 parts by weight with respect to 100 parts by weight of the blue inorganic pigment, and in the resin composition, the ratio of the non-amide lubricant is a chain olefin-cyclic olefin. The production method according to claim 12, wherein the content is 1 to 1000 ppm with respect to 100 parts by weight of the copolymer elastomer.   The method which uses the transparent film in any one of Claims 1-8 as a key top sheet or a light guide sheet.