JP2012094618A - Light confining film for solar cell, manufacturing method of the same, and solar cell - Google Patents

Abstract

A method for producing a light confinement film capable of producing a light confinement film containing a thermoplastic resin simply, efficiently and on a mass production scale is provided. Moreover, the optical confinement film which improves the efficiency of photovoltaic power generation manufactured by the said manufacturing method is provided. Furthermore, the solar cell provided with the said light confinement film is provided.
A method for producing a light confinement film for a solar cell having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, wherein the film substrate containing the thermoplastic resin is mixed with a poor solvent The manufacturing method of the light confinement film for solar cells characterized by including the process of applying a solvent, and the process of drying the film base material which apply | coated the said mixed solvent.
[Selection figure] None

Description

  The present invention relates to a light confinement film for a solar cell, a method for producing the same, and a solar cell provided with the light confinement film.

  Conventionally, in solar cells, in order to improve power generation efficiency, attempts have been made to increase the amount of light incident on the photoelectric conversion layer, in addition to improving the photoelectric conversion efficiency of the photoelectric conversion layer itself.

  Factors that hinder the high efficiency of solar cells include (1) loss due to reflection of sunlight on the surface of the photoelectric conversion layer, and (2) loss due to incomplete collection of light incident on the photoelectric conversion layer.

  Optical confinement is one of the important technologies for realizing a solar cell having high photoelectric conversion efficiency. “Light confinement” means that the surface of the transparent conductive film or metal layer in contact with the photoelectric conversion layer is made uneven, and light is scattered at the interface to extend the optical path length and increase the amount of light absorption in the photoelectric conversion layer. It is something to be made.

  The improvement of the photoelectric conversion efficiency by this light confinement brings about the effect of reducing the film thickness of the photoelectric conversion layer. Thereby, in the case of an amorphous silicon solar cell, the optical deterioration resulting from the Staebler-Wronski effect will be suppressed.

  Furthermore, the crystalline silicon solar cell is required to have a thickness on the order of several μm, which is several to tens of times that of amorphous silicon, due to light absorption characteristics. However, when the photoelectric conversion efficiency is increased by utilizing the light confinement effect, even if it is a crystalline silicon solar cell, the film forming time is significantly reduced.

  That is, optical confinement is an essential technique as a means for solving all of the high efficiency, stabilization, and cost reduction, which are major issues for practical use of thin film solar cells.

  As a technique for improving the photoelectric conversion efficiency by light confinement, specifically, a technique for providing a so-called texture structure showing a light diffusion effect on a surface of the substrate facing the photoelectric conversion layer has been proposed.

  The factor (1) is improved by the texture structure of the light incident side surface of the photoelectric conversion layer, and the factor (2) is improved by the texture structure of the lower electrode surface and the photoelectric conversion layer surface.

  For example, when fine pyramidal irregularities are formed as a texture structure on the substrate surface, the irregularities are reflected in the surface properties of the lower electrode and the photoelectric conversion layer. Therefore, the light that reaches the uneven surface of the photoelectric conversion layer from the outside and is reflected by the inclined surface of the unevenness strikes the other inclined surface of the unevenness, enters the photoelectric conversion layer, and is absorbed by the photoelectric conversion layer. In addition, incident light that reaches the back surface of the photoelectric conversion layer without being absorbed by the photoelectric conversion layer is scattered and reflected at the concavo-convex interface between the lower electrode and the photoelectric conversion layer, and returns to the photoelectric conversion layer in an oblique direction. The distance that the reflected light travels in the photoelectric conversion layer becomes longer and is efficiently absorbed. Furthermore, of the light that has returned into the photoelectric conversion layer, the light that has reached the surface of the photoelectric conversion layer again without being absorbed is reflected again in an oblique direction on the uneven surface of the photoelectric conversion layer. By such repeated reflection, light is efficiently absorbed in the photoelectric conversion layer, and the efficiency of the battery is increased.

Examples of conventional texture production methods include the following. In the case of a crystalline silicon solar cell, a quadrangular pyramid is obtained by adding isopropyl alcohol to a heated aqueous solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH) and immersing a Si (100) wafer in the resulting mixture. A texture structure having a protrusion in the shape is obtained. In addition, a method has been proposed in which a sodium carbonate (Na ₂ CO ₃ ) aqueous solution is used as an etchant and a silicon substrate is immersed in the aqueous solution to form a fine uneven shape on the surface of the silicon substrate (see Patent Document 1). .

  On the other hand, in the case of a thin-film solar cell, an aluminum target containing 0.1 to 6.0% by mass of silicon is used as the lower electrode, and the substrate is heated to 50 to 200 ° C. and sputtered, thereby forming a texture structure. Proposals have been made to obtain an aluminum film (see Patent Document 2). In addition, by coating a metal substrate with a heat-resistant resin having an electrical insulating property blended with pigments such as titanium oxide, alumina, and silica, a substrate having irregularities with a surface roughness Rmax of 0.3 to 1.5 μm is obtained. The proposal to form is also made (refer patent document 3).

  However, the above-described conventional texture structure forming method has various problems due to production and texture structure state, and a method that can be easily, efficiently, and manufactured on a mass production scale has not yet been obtained. The present situation is that rapid development is desired (see Patent Document 4).

JP 2000-183378 A Japanese Patent Laid-Open No. 9-69642 Japanese Patent Laid-Open No. 11-177111 JP 2010-123759 A

  The present invention has been made in view of the above problems and situations, and the solution is to provide a light confinement film that can easily and efficiently produce a light confinement film containing a thermoplastic resin on a mass production scale. It is to provide a manufacturing method. Moreover, it is providing the light confinement film which improves the efficiency of photovoltaic power generation manufactured by the said manufacturing method. Furthermore, it is providing the solar cell equipped with the said light confinement film.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. A method for producing a solar cell light confinement film having a concavo-convex structure on a surface of a film substrate containing a thermoplastic resin, wherein a mixed solvent containing a poor solvent is applied to the film substrate containing the thermoplastic resin And a method for producing a light confinement film for solar cells, comprising: a step of drying, and a step of drying a film substrate coated with the mixed solvent.

  2. The average pitch of the unevenness in the uneven shape structure is in the range of 50 nm to 3 μm, and the average value of the difference between the highest point of the convex part and the lowest point of the concave part is in the range of 5 nm to 5 μm. The manufacturing method of the optical confinement film for solar cells of said 1st term | claim.

  3. 3. The method for producing an optical confinement film for solar cells according to item 1 or 2, wherein the poor solvent is a mixed solvent of water and alcohols.

  4). The method for producing a light confinement film for solar cells according to any one of items 1 to 3, wherein the poor solvent is a mixed solvent of water and ketones.

  5. A solar cell light confinement film having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, wherein the concavo-convex structure is formed by the action of a mixed solvent containing a poor solvent. A light confinement film for solar cells.

  6). A solar cell comprising a solar cell light confinement film manufactured by the method for manufacturing a solar cell light confinement film according to any one of items 1 to 4.

  By the above means of the present invention, it is possible to provide a method for producing a light confinement film capable of producing a light confinement film containing a thermoplastic resin simply, efficiently and on a mass production scale. Moreover, the light confinement film which improves the efficiency of photovoltaic power generation manufactured by the said manufacturing method can be provided. Furthermore, the solar cell provided with the said light confinement film can be provided.

  Although the mechanism of action of the mixed solvent according to the present invention is unclear, in a poor solvent containing water, the interaction between a number of hydroxyl groups (OH groups) of the cellulose ester, which is a component of the film substrate, and solvent molecules For this reason, it is presumed that the concavo-convex structure was formed on the surface by the solvent molecules penetrating / dissolving in the voids of the fine structure near the surface containing the cellulose ester.

  On the other hand, when a good solvent such as methylene chloride is used, since the compatibility with water is low and the dissolving action on the cellulose ester is large, the cellulose ester as a constituent component of the film base material is uniformly dissolved as a whole. Only the concavo-convex structure is not formed.

Conceptual diagram showing an example of an uneven structure based on an observation image obtained by measuring the uneven structure with a 3D measurement laser microscope, and the difference between the uneven pitch and the highest point of the protrusion and the lowest point of the recess ( Conceptual diagram showing the definition of depth Schematic which shows an example of embodiment of the manufacturing apparatus of a light confinement film Conceptual diagram showing an example of a solar cell provided with a light confinement film

  The method for producing a light confinement film for solar cells of the present invention is a method for producing a light confinement film for solar cells having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, which contains the thermoplastic resin. It has the process of applying the mixed solvent containing a poor solvent to the film base material to perform, and the process of drying the film base material which applied the said mixed solvent. This feature is a technical feature common to the inventions according to claims 1 to 6.

  As an embodiment of the present invention, from the viewpoint of manifesting the effect of the present invention, the average pitch of the unevenness in the uneven structure is in the range of 50 nm to 3 μm, and the difference between the highest point of the convex part and the lowest point of the concave part Is preferably in the range of 5 nm to 5 μm. Furthermore, the poor solvent is preferably a mixed solvent of water and alcohols or a mixed solvent of water and ketones.

  As described above, the light confinement film for solar cells of the present invention is a light confinement film for solar cells having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, and the concavo-convex structure includes a poor solvent. It is formed by the action of a mixed solvent.

  The light confinement film for solar cells produced by the method for producing a light confinement film for solar cells of the present invention can be suitably used for solar cells.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

(Outline of manufacturing method of optical confinement film)
The method for producing a light confinement film of the present invention is a method for producing a light confinement film having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, which is poor in the film substrate containing the thermoplastic resin. It has the process of coating the mixed solvent containing a solvent, and the process of drying the film base material which coated the said mixed solvent.

  That is, the present invention is characterized in that a mixed solvent containing a poor solvent is applied as a means for forming and imparting a concavo-convex structure on the surface. The pH of the poor solvent is lower than the pH of the treatment liquid used in the alkaline saponification treatment such as cellulose ester film, and is preferably in the region of pH 5.5 to 7.5 at 25 ° C., for example.

  In addition, it is preferable to adjust so that surface roughness Ra of the film which performed mixed solvent coating and surface roughness Ra of the film which does not perform the said mixed solvent coating may differ 3 nm or more. As a method for the adjustment, a method based on selection of solvent chemical species of the mixed solvent to be applied, amount, mixed composition, temperature of solvent, optimization of conditions such as drying temperature, and the like are preferable.

  For example, when a mixture of an acrylic resin and a cellulose ester resin is used as a resin film substrate, a mixed solvent of ethanol and pure water heated to 40 to 60 ° C. in a ratio of 50:50 to 80:20 Vol% is applied to the film surface. It is preferable to spray-coat and then dry while transporting in a drying zone of 110 to 150 ° C.

  Details of the method for manufacturing the light confinement film will be described later.

(Poor solvent)
The manufacturing method of the light confinement film of this invention has the process of applying the mixed solvent containing a poor solvent to the film base material containing a thermoplastic resin, and the process of drying.

  Here, the poor solvent means that when a solvent whose solubility is to be measured is added in an amount corresponding to 3 g of the solid content of the following thermoplastic resin so that the total amount becomes 20 g and stirred at a temperature of 25 ° C., dust is recognized. If the sample is thickened or separated, it is considered to be a poor solvent for the sample.

  When the thermoplastic resin is, for example, a polyester resin or a polyester urethane resin, examples of the poor solvent include xylene, ethyl cellosolve, propylene glycol monomethyl ether, isobutanol, isopropanol, ethanol, methanol, hexane, and purified water. be able to.

  Further, when the thermoplastic resin is an acrylic resin, examples of the poor solvent include ethyl cellosolve, propylene glycol monomethyl ether, isobutanol, isopropanol, ethanol, methanol, hexane, and purified water.

  In the present invention, the poor solvent is preferably used by mixing two or more of the above solvents with respect to the thermoplastic resin. In particular, a mixed solvent of water and alcohols (methanol, ethanol, isopropanol, etc.) is preferable. Further, it may be a mixed solvent of water and ketones (acetone, propanone, butanone, etc.).

(Characteristics of optical confinement film)
The light confinement film according to the present invention has a concavo-convex shape structure on at least one surface of the light confinement film, the average pitch of the concavo-convex shape in the concavo-convex shape structure is in the range of 50 nm to 3 μm, and the highest convex portion. It is preferable from a light-scattering viewpoint that the average value of the difference (depth) between a point and the lowest point of a recessed part exists in the range of 5 nm-5 micrometers.

  In addition, it is preferable that the average pitch of the said unevenness | corrugation exists in the range of 100 nm-1 micrometer. The average value of the difference (depth) between the highest point of the convex part and the lowest point of the concave part is preferably in the range of 10 nm to 1 μm.

  Here, the pitch of the unevenness according to the present invention and the difference (depth) between the highest point of the convex portion and the lowest point of the concave portion are values measured by the following method (see FIG. 1).

  First, five areas of 130 μm × 130 μm squares are extracted at random on the surface of the light confining film where the concavo-convex structure exists, and an observation image measured with a 3D measurement laser microscope is obtained for each.

  The condition for measurement with a laser microscope is that the magnification is 350 times. Note that the observation image is acquired from a direction in which the surface of the light confinement film is viewed vertically.

  Then, the pitch of the projections and depressions and the difference (depth) between the highest point of the projections and the lowest point of the depressions were measured based on the projection / recess structure profile obtained for the five observation images.

  In the present application, in the concavo-convex structure profile, a portion below the horizontal line that includes the midpoint of each concavo-convex shape is referred to as “concave portion”, and a portion above the horizontal plane is referred to as “convex portion”.

  Here, “the highest point of the convex portion” refers to the highest point (the point at which the height is a maximum value) of the convex portion in each concavo-convex shape. In addition, “the lowest point of the concave portion” refers to the lowest point (the point at which the height is a minimum value) of the concave portion in each uneven shape.

  The “concave / convex pitch” refers to an interval between the highest points (peaks) between adjacent convex portions. The “average pitch of unevenness” is the average value of values obtained by dividing 130 μm by the number of highest points (peaks) of convex portions existing in the measurement area of 130 μm for each of the five observation images. Say.

  The “difference (depth) between the highest point of the convex portion and the lowest point of the concave portion” refers to the difference between the lowest point between the adjacent convex portion and the highest point of the concave portion. The average value of the difference (depth) is an average value of values obtained by measuring each unevenness existing in the measurement region of 130 μm for each of the five observation images.

  In addition, as a method of controlling the pitch of the unevenness and the difference (depth) between the highest point of the convex portion and the lowest point of the concave portion within the predetermined range, manufacturing conditions are optimized in the following manufacturing method. Can be done.

  In addition, by adding highly refractive particles to the light confinement film of the present invention, the interface reflection between the conductive layers can be reduced, and the power generation efficiency can be further improved.

(Film base material containing thermoplastic resin)
The light confinement film according to the present invention is characterized by having an uneven structure on the surface of a film substrate containing a thermoplastic resin.

  Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or the melting point and can be molded into a desired shape.

  Thermoplastic resins include cellulose derivatives such as hydroxymethylcellulose and methylcellulose, polymers of acrylic acid, methacrylic acid or maleic acid containing hydroxyalkyl groups such as 2-hydroxyethyl group and 2-hydroxypropyl group, Polyacrylics such as polymers or cross-linked products thereof, polyacrylamide or copolymers thereof, acrylonitrile polymers or hydrolysates of cross-linked polymers, polymers of acrylic acid or methacrylic acid, copolymers thereof or cross-linked products thereof. Resins, polyvinyl pyrrolidone resins, polyvinyl alcohol and modified products thereof, such as cationized polyvinyl alcohol, silanolated polyvinyl alcohol, sulfonated polyvinyl alcohol, polyvinyl acetal resins, polyvinyl butyral resins, Hydrolysis products of powder-acrylonitrile polymer, maleic anhydride copolymer, polyacrylamide resin, polyethylene polyamide resin, polyamide polyamine resin, polyethylene oxide, polyethylene oxide-polypropylene oxide copolymer, etc. , Polyester resins, polyurethane resins and the like.

  In addition, in this invention, it is required to contain said thermoplastic resin.

  Hereinafter, a thermoplastic resin that can be suitably used in the present invention will be described in detail.

<Cellulose ester resin>
The cellulose ester resin that can be used in the present invention is selected from cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. It is preferable that there is at least one.

  Among these, particularly preferable cellulose esters include cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  As a substitution degree of the mixed fatty acid ester, when having an acyl group having 2 to 4 carbon atoms as a substituent, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, A cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II) is preferable.

Formula (I) 2.0 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Furthermore, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, Preferably it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

  In the present invention, 1 g of cellulose ester resin is added to 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and the pH is 6 when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. It is preferable that the electric conductivity is 1 to 100 μS / cm.

<acrylic resin>
The acrylic resin that can be used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These may be used alone or in combination of two or more.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable, and methyl acrylate and n-butyl acrylate are particularly preferably used.

  A commercially available thing can also be used as an acrylic resin. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. .

<Cyclic olefin resin>
In the present invention, it is also preferable to use a cyclic olefin resin. Examples of the cyclic olefin resin include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. An addition polymer of a monomer having a monomer, an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof.

  Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene. (Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0. 1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. In addition, these substituents may be the same or different and a plurality may be bonded to the ring. Monomers having a norbornene structure can be used singly or in combination of two or more.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group.

  Other monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof, cyclic conjugated dienes such as cyclohexadiene, cycloheptadiene, and the like. And derivatives thereof.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer of a monomer having a norbornene structure and another monomer copolymerizable with the monomer have a known ring-opening polymerization catalyst. It can be obtained by (co) polymerization in the presence.

  Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, Cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of another monomer copolymerizable with a monomer having a norbornene structure can be used in the presence of a known addition polymerization catalyst. It can be obtained by polymerization.

  A hydrogenated product of a ring-opening polymer of a monomer having a norbornene structure, a hydrogenated product of a ring-opening copolymer of a monomer having a norbornene structure and another monomer capable of ring-opening copolymerization thereof, Hydrogenated products of addition polymers of monomers having a norbornene structure, and hydrogenated products of addition copolymers of monomers having a norbornene structure and other monomers capable of addition copolymerization with these A known hydrogenation catalyst containing a transition metal such as nickel or palladium is added to the polymer solution, and the carbon-carbon unsaturated bond is preferably hydrogenated by 90% or more.

Among norbornene-based resins, as repeating units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure, the content of these repeating units is 90% by mass or more based on the entire repeating units of the norbornene resin, and the content ratio of X and the content ratio of Y The ratio of X: Y is preferably 100: 0 to 40:60. By using such a resin, it is possible to obtain a light confinement film that has no dimensional change in the long term and is excellent in stability of optical characteristics.

  The molecular weight of the cyclic olefin resin used in the present invention is appropriately selected according to the purpose of use. Polyisoprene or polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography using cyclohexane (toluene if the polymer resin does not dissolve) as a solvent, usually 20,000 to 150,000. . Preferably it is 25,000-100,000, More preferably, it is 30,000-80,000. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the film are highly balanced and suitable.

  The glass transition temperature of the cyclic olefin resin may be appropriately selected according to the purpose of use. From the viewpoint of durability and stretchability, it is preferably in the range of 130 to 160 ° C, more preferably 135 to 150 ° C.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the cyclic olefin resin is 1.2 to 3.5, preferably 1.5 to 3.0, from the viewpoint of relaxation time, productivity, and the like. More preferably, it is 1.8 to 2.7.

The cyclic olefin resin used in the present invention preferably has an absolute value of photoelastic coefficient of 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less, and more preferably 4 × 10. It is particularly preferably ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient C is a value represented by C = Δn / σ where birefringence is Δn and stress is σ.

  In the present invention, it is preferable that the cyclic olefin resin does not substantially contain particles. Here, “substantially free of particles” means that even if particles are added to a film made of a cyclic olefin resin, the amount of increase in haze from the non-added state is allowed to be in the range of 0.05% or less. Means you can. In particular, the alicyclic polyolefin resin lacks affinity with many organic particles and inorganic particles. Therefore, when a cyclic olefin resin film to which particles exceeding the above range are added is stretched, voids are easily generated, and as a result, There is a risk that a significant decrease in haze occurs.

<Polycarbonate resin>
In the present invention, various known polycarbonate resins can also be used. In the present invention, it is particularly preferable to use an aromatic polycarbonate. There is no restriction | limiting in particular about the said aromatic polycarbonate, and there will be no restriction | limiting in particular if it is an aromatic polycarbonate from which the various characteristics of a desired film are acquired.

  In general, a polymer material collectively referred to as polycarbonate is a generic term for a polymer material in which a polycondensation reaction is used in its synthesis method and the main chain is linked by a carbonic acid bond. , Phosgene, diphenyl carbonate and the like obtained by polycondensation. Usually, an aromatic polycarbonate represented by a repeating unit having 2,2-bis (4-hydroxyphenyl) propane called bisphenol-A as a bisphenol component is preferably selected, and various bisphenol derivatives should be appropriately selected. Thus, an aromatic polycarbonate copolymer can be constituted.

  In addition to this bisphenol-A, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 1,1 -Bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) -2-phenyl Ethane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane, bis (4-hydroxyphenyl) diphenylmethane, bis (4-hydroxyphenyl) sulfide, bis ( 4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) -3,3,5-tri Mention may be made of a chill cyclohexane, and the like.

  It is also possible to use an aromatic polyester carbonate partially containing terephthalic acid and / or isophthalic acid components. By using such a structural unit as a part of the structural component of the aromatic polycarbonate composed of bisphenol-A, the properties of the aromatic polycarbonate, such as heat resistance and solubility, can be improved. The present invention is also effective for coalescence.

  If the aromatic polycarbonate used here has a viscosity average molecular weight of 10,000 or more and 200,000 or less, it is suitably used. A viscosity average molecular weight of 20,000 to 120,000 is particularly preferred. If a resin having a viscosity average molecular weight lower than 10,000 is used, the mechanical strength of the resulting film may be insufficient, and if it has a high molecular weight of 400000 or more, the viscosity of the dope becomes too large, causing problems in handling. The viscosity average molecular weight can be measured by commercially available high performance liquid chromatography.

  The glass transition temperature of the aromatic polycarbonate according to the present invention is preferably 200 ° C. or higher in order to obtain a highly heat-resistant film, and more preferably 230 ° C. or higher. These can be obtained by appropriately selecting the copolymerization component. The glass transition temperature can be measured with a DSC apparatus (differential scanning calorimetric analyzer). For example, the baseline is unevenly determined by a temperature rising condition of 10 ° C./min with RDC220 manufactured by Seiko Instruments Inc. It is the temperature that begins to do.

  In the present invention, the solvent used for the dope composition containing the aromatic polycarbonate is a mixed solvent containing 4 to 14 parts by mass of methylene chloride and a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. It is preferable.

  The mixing amount of the linear or branched aliphatic alcohol having 1 to 6 carbon atoms is preferably 4 to 12 parts by mass. By using such a mixed solvent, the web is peeled off at a higher residual solvent concentration than before, thereby suppressing the generation of strong static electricity when the web is peeled off, thereby causing damage to the belt, film streaks, unevenness, Scratches can be prevented from occurring.

  The type of alcohol added is limited by the solvent used. It is a necessary condition that the alcohol and the solvent are compatible. These may be added alone or in combination of two or more. The alcohol in the present invention is preferably a linear or branched aliphatic alcohol having 1 to 6, preferably 1 to 4, more preferably 2 to 4 carbon atoms. Specific examples include methanol, ethanol, isopropanol, and tert-butanol. Of these, ethanol, isopropanol, and tertiary-butanol can achieve almost the same effect, but methanol has a slightly lower effect. Although the reason is not clear, it is presumed that the boiling point of the solvent, that is, the ease of flying during drying is related. Higher alcohols higher than that are not preferred because they have a high boiling point and are likely to remain after film formation.

  The amount of alcohol added must be carefully selected. These alcohols are completely poor in solubility in aromatic polycarbonate and are completely poor solvents. Therefore, it cannot be added too much, and should be the minimum amount that provides satisfactory peelability. As mentioned above, it is 4-14 mass parts with respect to a methylene chloride, Preferably it is 4-12 mass parts. When the addition amount is in the range of 4 to 14 parts by mass with respect to the amount of methylene chloride, the solubility of the solvent in the polymer and the dope stability are improved, and the effect of improving the peelability is increased.

  The present invention comprises the above methylene chloride and aliphatic alcohol in the dope composition, but other solvents can also be used. The remaining solvent is not particularly limited as long as it dissolves the aromatic polycarbonate at a high concentration and is compatible with alcohol, and is a low-boiling solvent. For example, as a solvent having a solubility in an aromatic polycarbonate, in addition to methylene chloride, halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, 1,3-dioxolane, 1, Examples include cyclic ether solvents such as 4-dioxane and tetrahydrofuran, and ketone solvents such as cyclohexanone.

  When using other solvent, there is no limitation in particular and it may use it in consideration of an effect. The effects here include mixing the solvent without sacrificing solubility and stability, for example, improving the surface properties of the film formed by the solution casting method (leveling effect), evaporation rate and system These include viscosity adjustment and crystallization suppression effects. What is necessary is just to determine the kind and addition amount of the solvent to mix by the degree of these effects, and you may use 1 type, or 2 or more types as a solvent to mix.

  Other solvents preferably used include halogen solvents such as chloroform and 1,2-dichloroethane, hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, and ethyl acetate and butyl acetate. Examples include ester solvents, ether solvents such as ethylene glycol dimethyl ether and methoxyethyl acetate.

  The dope composition according to the present invention may be prepared by any method as long as a transparent solution having a low haze is obtained as a result. A predetermined amount of alcohol may be added to the aromatic polycarbonate solution dissolved in a certain solvent in advance, or the aromatic polycarbonate may be dissolved in a mixed solvent containing alcohol. However, as described above, since alcohol is a poor solvent, the method of adding the latter after the former may cause clouding of the dope due to the precipitation of the polymer. Therefore, the method of dissolving in the latter mixed solvent is preferable.

<Polyester resin>
The polyester resin that can be used in the present invention is obtained by polymerizing a dicarboxylic acid and a diol, and 70% or more of dicarboxylic acid structural units (constituent units derived from dicarboxylic acid) are derived from aromatic dicarboxylic acid, and 70% or more of the diol constituent units (constituent units derived from the diol) are derived from the aliphatic diol.

  The proportion of the structural unit derived from the aromatic dicarboxylic acid is 70% or more, preferably 80% or more, more preferably 90% or more.

  The proportion of the structural unit derived from the aliphatic diol is 70% or more, preferably 80% or more, and more preferably 90% or more. Two or more polyester resins may be used in combination.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid such as 2,7-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. 3,4'-biphenyldicarboxylic acid and the like and ester-forming derivatives thereof.

  As the polyester resin, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, and sebacic acid, and monocarboxylic acids such as benzoic acid, propionic acid, and butyric acid can be used without departing from the object of the present invention.

  Examples of the aliphatic diol include ethylene glycol, 1,3-propylene diol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, and the like, and ester-forming derivatives thereof.

  As the polyester resin, monoalcohols such as butyl alcohol, hexyl alcohol, and octyl alcohol, and polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol can be used as long as the object of the present invention is not impaired.

  A known esterification method or transesterification method can be applied to the production of the polyester resin. Examples of the polycondensation catalyst used in the production of the polyester resin include known antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds such as germanium oxide, titanium compounds such as titanium acetate, and aluminum compounds such as aluminum chloride. Although it can, it is not limited to these.

  Preferred polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polyethylene-2,6-naphthalene dicarboxylate resin, polyethylene-2, 6-naphthalene dicarboxylate-terephthalate copolymer resin, polyethylene-terephthalate-4,4'-biphenyldicarboxylate resin, poly-1,3-propylene-terephthalate resin, polybutylene terephthalate resin, polybutylene-2,6-naphthalene There are dicarboxylate resins and the like.

  More preferable polyester resins include polyethylene terephthalate resin, polyethylene terephthalate-isophthalate copolymer resin, polyethylene-1,4-cyclohexanedimethylene-terephthalate copolymer resin, polybutylene terephthalate resin, and polyethylene-2,6-naphthalene dicarboxylate. Resin.

  The intrinsic viscosity of the polyester resin (phenol / 1,1,2,2-tetrachloroethane = value measured at 25 ° C. in a 60/40 mass ratio mixed solvent) is preferably 0.7 to 2.0 dl / g, more Preferably it is 0.8-1.5 dl / g. Since the molecular weight of the polyester resin is sufficiently high when the intrinsic viscosity is 0.7 or more, the molded product comprising the polyester resin composition obtained by using the polyester resin has mechanical properties necessary for the molded product and is transparent. Property is improved. When the intrinsic viscosity is 2.0 or less, the moldability is good.

<Other additives>
The thermoplastic resin substrate according to the present invention and various functional layers provided on the substrate can contain various compounds as additives depending on the purpose. For example, a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, an ultraviolet absorber, an optical anisotropy control agent, a matting agent, an antistatic agent, a release agent, and the like can be contained.

  Among the additives, it is an optical anisotropy control agent that effectively contributes to the present invention, and in particular, the retardation increasing agent makes it easy to optically exhibit birefringence obliquely from the plane of the present application. Therefore, it is preferable. The retardation increasing agent is preferably an aromatic compound having at least two aromatic rings. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the resin. And it is preferable to use in 0.05-15 mass parts, and it is still more preferable to use in 0.1-10 mass parts. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. Details of these are described in JP-A No. 2004-109410, JP-A No. 2003-344655, JP-A No. 2000-275434, JP-A No. 2000-1111914, JP-A No. 12-275434, and the like.

  In the light confinement film according to the present invention, fine particles may be added as a matting agent in order to prevent the produced film from being scratched or being deteriorated in transportability when handled.

  As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable. The content of these fine particles in the light confinement film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a light confinement film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available under the trade names of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the light confinement film low. In the light confinement film of the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

(Method for producing optical confinement film)
As a method for producing the resin film substrate according to the present invention as a film, production methods such as a normal inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. However, the solution casting method and the melt casting method by a casting method are preferable from the viewpoints of suppressing coloring, suppressing defects of foreign matters, and suppressing optical defects such as die lines.

  Hereafter, the manufacturing method in the case of producing the light confinement film concerning this invention is explained in full detail.

<Method for producing optical confinement film by solution casting method>
《Organic solvent》
When the optical confinement film according to the present invention is produced by the solution casting method, an organic solvent useful for forming the dope can be used without limitation as long as it dissolves a thermoplastic resin such as a cellulose ester resin. .

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, ethyl lactate, lactic acid , Diacetone alcohol and the like, methylene chloride, methyl acetate, ethyl acetate, acetone, ethyl lactate and the like are preferably used. That.

  In addition to the organic solvent, the dope may contain 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, facilitating peeling from the metal support, and when the proportion of alcohol is small, the dissolution of the thermoplastic resin in a non-chlorine organic solvent system is promoted. There is also a role.

  In particular, the thermoplastic resin should be a dope composition in which at least a total of 10 to 45 mass% is dissolved in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. preferable.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, a preferable film forming method of the light confinement film (hereinafter also simply referred to as “film”) according to the present invention will be described.

1) Dissolution Step In this step, a thermoplastic resin and other additives are dissolved in an organic solvent mainly composed of a good solvent for the thermoplastic resin while stirring to form a dope.

  For the dissolution of the thermoplastic resin, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557 Alternatively, various dissolution methods such as a cooling dissolution method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. The method of pressurizing at a boiling point or higher is preferred.

  Recycled material is a finely pulverized film, which is generated when the film is formed, cut off on both sides of the film, or the original film that has been speculated out due to scratches, etc. Reused.

2) Casting process An endless metal belt, such as a stainless steel belt or a rotating metal drum, which supports the dope is fed to a pressure die through a liquid feed pump (for example, a pressurized metering gear pump) and supported infinitely. This is a step of casting a dope from a pressure die slit to a casting position on the body.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, etc. High efficiency and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. If the web is peeled off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 100 N / m.

  In the present invention, the temperature at the peeling position on the metal support is preferably -50 to 40 ° C, more preferably 10 to 40 ° C, and most preferably 15 to 30 ° C.

5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through rolls arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout the drying is generally carried out at 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  In addition, extending | stretching operation may be divided | segmented and implemented in multiple steps, and it is also preferable to implement biaxial stretching in a casting direction and a width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and it is preferable to perform drying while applying the tenter until the residual solvent amount of the web becomes 10% by mass or less. More preferably, it is 5% by mass or less.

  30-160 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-150 degreeC is more preferable, and 70-140 degreeC is the most preferable.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C Is more preferable, and within ± 1 ° C. is most preferable.

6) Winding process This is a process in which the amount of residual solvent in the web becomes 2% by mass or less, and is taken up by the winder 37 as a film, and the dimensional stability is achieved by setting the residual solvent amount to 0.4% by mass or less. Can be obtained. It is particularly preferable to wind up at 0.00 to 0.10% by mass.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The film according to the present invention is preferably a long film. Specifically, the film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  Although there is no restriction | limiting in particular in the film thickness of the film concerning this invention, It is preferable that it is 20-200 micrometers, It is more preferable that it is 25-150 micrometers, It is especially preferable that it is 30-120 micrometers.

<Method for producing optical confinement film by melt casting method>
The method in the case of manufacturing the resin film base material which concerns on this invention as a light confinement film by the melt casting film forming method is demonstrated.

<Melted pellet manufacturing process>
The composition constituting the thermoplastic resin film used for melt extrusion is usually preferably kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, a dry thermoplastic resin and an additive depending on the purpose are supplied to an extruder with a feeder, and kneaded using a single-screw or twin-screw extruder. Extruded into a shape, water-cooled or air-cooled and cut.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  Additives may be fed into the extruder and fed into the extruder, or may be fed by individual feeders. In order to mix a small amount of additives such as an antioxidant uniformly, it is preferable to mix them in advance.

  The antioxidant may be mixed with each other, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with a thermoplastic resin and mixed, or mixed by spraying. May be.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. It is also possible to feed the raw material powder directly to the extruder with a feeder and form a film as it is without pelletization.

<Process for extruding molten mixture from die to cooling roll>
First, using a single-screw or twin-screw type extruder, the melt temperature Tm during extrusion is set to about 200 to 300 ° C., and filtered with a leaf disk type filter or the like to remove foreign matter, and then the T-die The film is coextruded into a film, solidified on a cooling roll, and cast while pressing with an elastic touch roll.

  When introducing into the extruder from the supply hopper, it is preferable to prevent oxidative decomposition and the like under vacuum, reduced pressure, or inert gas atmosphere. Tm is the temperature of the die exit portion of the extruder.

  When foreign matter such as scratches or plasticizer aggregates adheres to the die, streak-like defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  In the present invention, there is no particular limitation on the cooling roll, but it is a roll having a structure in which a heat medium or a coolant that can be controlled in temperature flows with a highly rigid metal roll, and the size is not limited. It is sufficient that the film is large enough to cool the film, and the diameter of the cooling roll is usually about 100 mm to 1 m.

  Examples of the surface material of the cooling roll include carbon steel, stainless steel, aluminum, and titanium. Further, in order to increase the hardness of the surface or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, or ceramic spraying.

  The surface roughness of the chill roll surface is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable that the surface processed is further polished to have the above-described surface roughness.

  In the present invention, as an elastic touch roll, JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97 / 028950, JP-A-11-235747, A thin-film metal sleeve-covered silicon rubber roll having a surface as described in JP-A No. 2002-36332, JP-A No. 2005-172940 and JP-A No. 2005-280217 can be used.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

<Extension process>
In the present invention, the film obtained as described above can be further stretched 1.01 to 3.0 times in at least one direction after passing through the step of contacting the cooling roll.

  Preferably, the film is stretched 1.1 to 2.0 times in both the longitudinal (film transport direction) and lateral (width direction) directions.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used. In particular, when the light confinement film also serves as a polarizing plate protective film, it is preferable to make the stretching direction the width direction because lamination with the polarizing film can be performed in a roll form.

  By stretching in the width direction, the slow axis of the light confinement film becomes the width direction.

  Usually, the draw ratio is 1.1 to 3.0 times, preferably 1.2 to 1.5 times, and the draw temperature is usually Tg to Tg + 50 ° C. of the resin constituting the film, preferably Tg to Tg + 50 ° C. In the temperature range.

  The stretching is preferably performed under a uniform temperature distribution controlled in the longitudinal direction or the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  When the film-like resin film produced by the above method is used as a light confinement film, the film may be contracted in the longitudinal direction or the width direction for the purpose of reducing the retardation of the light confinement film and reducing the dimensional change rate. .

  In order to shrink in the longitudinal direction, for example, there is a method in which the film is shrunk by temporarily clipping out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  The uniformity in the slow axis direction is also important, and the angle is preferably −5 to + 5 ° with respect to the film width direction, more preferably in the range of −1 to + 1 °, and particularly −0. It is preferably in the range of 5 to + 0.5 °, particularly preferably in the range of −0.1 to + 0.1 °. These variations can be achieved by optimizing the stretching conditions.

  The light confinement film of the present invention is preferably a long film. Specifically, the light confinement film is about 100 m to 5000 m, and is usually in the form of a roll. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

  There is no restriction | limiting in particular in the film thickness of the film-form resin film which concerns on this invention, It is preferable to change according to the objective. For example, when using for a polarizing plate protective film, it is preferable that it is 20-200 micrometers, It is more preferable that it is 25-150 micrometers, It is especially preferable that it is 30-120 micrometers.

<Production equipment for optical confinement film>
FIG. 1 is a schematic flow sheet showing the overall configuration of an example of the light confinement film manufacturing apparatus of the present invention. In FIG. 1, the light confinement film is produced by mixing a film material such as a thermoplastic resin and then extruding it from a casting die 4 onto a first cooling roll 5 using an extruder 1. 5, and further circumscribed in order with a total of three cooling rolls, that is, the second cooling roll 7 and the third cooling roll 8, and cooled and solidified to form a film 10. Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12 and then wound by the winding device 16. In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5.

  In the present invention, it is preferable to add an apparatus for automatically cleaning the belt and the roll to the manufacturing apparatus. There is no particular limitation on the cleaning device. For example, there are a method of niping a brush roll, a water absorbing roll, an adhesive roll, a wiping roll, an air blowing method for spraying clean air, a laser incinerator, or a combination thereof. is there.

  In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

(Functional layer)
Functionality of curable resin layer, antistatic layer, antireflection layer, slippery layer, easy adhesion layer, antiglare layer, barrier layer, optical compensation layer, etc. before and / or after stretching in the production of light confinement film A layer may be applied. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

  In the present invention, a curable resin layer is preferably provided particularly from the viewpoint of imparting mechanical strength.

(Curable resin layer)
The curable resin layer according to the present invention contains an actinic radiation curable resin or a thermosetting resin as a binder component. In the present invention, an actinic radiation curable resin is preferable. Here, “active ray curable resin” refers to a resin whose main component is a resin that is cured through a crosslinking reaction upon irradiation with active rays such as ultraviolet rays or electron beams (also referred to as “active energy rays”).

<Actinic radiation curable resin>
As the actinic radiation curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used, and an actinic radiation curable resin layer is formed by curing by irradiation with actinic radiation such as ultraviolet rays or electron beams. The Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but the resin that is cured by ultraviolet irradiation is excellent in mechanical film strength (abrasion resistance, pencil hardness). preferable. As the ultraviolet curable resin, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. Of these, ultraviolet curable acrylate resins are preferred. As the ultraviolet curable acrylate resin, a polyfunctional acrylate is preferable. The polyfunctional acrylate is preferably selected from the group consisting of pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate, and dipentaerythritol polyfunctional methacrylate. Here, the polyfunctional acrylate is a compound having two or more acryloyloxy groups or methacryloyloxy groups in the molecule. Examples of the polyfunctional acrylate monomer include ethylene glycol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate. , Tetramethylolmethane tetraacrylate, pentaglycerol triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerol triacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol Lithol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, Tetramethylol methane trimethacrylate, tetramethylol methane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate Acrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate, isobornyl acrylate and the like preferably. These compounds are used alone or in combination of two or more. Moreover, oligomers, such as a dimer and a trimer of the said monomer, may be sufficient.

  The curable resin layer preferably contains a photopolymerization initiator to accelerate the curing of the actinic radiation curable resin. The amount of the photopolymerization initiator is preferably contained in a mass ratio of photopolymerization initiator: active ray curable resin = 20: 100 to 0.01: 100.

  Specific examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto.

<solvent>
In the coating composition when the curable resin layer according to the present invention is applied and formed, a mixed solvent composed of a good solvent for the thermoplastic resin and a poor solvent for the thermoplastic resin is used as a solvent. preferable. Here, the good solvent and the poor solvent refer to solvents having solubility measured by the following method.

  When a solvent whose solubility is to be measured is added to a solid content of 3 g corresponding to 3 g of the thermoplastic resin so that the total amount is 20 g and stirred at a temperature of 25 ° C., it is uniform and transparent and has a viscosity change. Those that are compatible with each other are considered to be good solvents for the sample, while those that are found to be dusty, thickened, or separated are considered to be poor solvents for the sample.

  When the thermoplastic resin is, for example, a polyester resin or a polyester urethane resin, examples of the good solvent include toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone, ethyl acetate, and tetrahydrofuran. On the other hand, examples of the poor solvent include xylene, ethyl cellosolve, propylene glycol monomethyl ether, isobutanol, isopropanol, ethanol, methanol, hexane, and purified water. When the thermoplastic resin is an acrylic resin, examples of the good solvent include toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone, ethyl acetate, tetrahydrofuran, xylene, and the like. On the other hand, examples of the poor solvent include ethyl cellosolve, propylene glycol monomethyl ether, isobutanol, isopropanol, ethanol, methanol, hexane, and purified water. The good solvent and the poor solvent other than purified water are good solvents for the commonly used actinic radiation curable resins.

  In the present invention, the good solvent and the poor solvent may be used alone or in combination of two or more with respect to the thermoplastic resin.

  Moreover, the curable resin layer according to the present invention may contain fine particles of an inorganic compound or an organic compound.

(Fine particles)
As inorganic fine particles, silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silicic acid Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

  These inorganic fine particles are preferably coated with an organic component having a reactive functional group on a part of the surface because the scratch resistance is improved while maintaining the transparency of the film. As a method for coating an organic component having a reactive functional group on a part of the surface, for example, a compound containing an organic component such as a silane coupling agent reacts with a hydroxyl group present on the surface of the metal oxide fine particles, and the surface A mode in which an organic component is bonded to a part of the metal particle, a mode in which an organic component is attached to a hydroxyl group present on the surface of a metal oxide fine particle by an interaction such as a hydrogen bond, or one or more inorganic particles in a polymer particle The aspect containing microparticles | fine-particles etc. are mentioned.

  Organic particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, and melamine resin. Powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyfluoroethylene resin powder, or the like can be added.

  Preferred fine particles include crosslinked polystyrene particles (for example, SX-130H, SX-200H, SX-350H manufactured by Soken Chemical), polymethyl methacrylate-based particles (for example, MX150, MX300 manufactured by Soken Chemical), and fluorine-containing acrylic resin fine particles. . Examples of the fluorine-containing acrylic resin fine particles include commercial products such as FS-701 manufactured by Nippon Paint. Examples of the acrylic particles include Nippon Paint: S-4000, and examples of the acrylic-styrene particles include Nippon Paint: S-1200, MG-251.

  The average particle size of these fine particle powders is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.01 to 1.0 μm. Moreover, you may contain 2 or more types of microparticles | fine-particles from which a particle size differs. The average particle diameter of the fine particles can be measured by, for example, a laser diffraction particle size distribution measuring device.

  The proportion of the ultraviolet curable resin composition and the fine particles is desirably blended so as to be 1 to 400 parts by mass, and more desirably 50 to 200 parts by mass with respect to 100 parts by mass of the resin composition.

  The curable resin layer according to the present invention is applied by applying a coating composition for forming a hard coat layer using a known method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, or an inkjet method. Thereafter, it can be formed by heat drying and UV curing.

  The coating amount is suitably 0.1 to 40 μm, preferably 0.5 to 30 μm, as the wet layer thickness. The dry layer thickness is an average layer thickness of 0.1 to 30 μm, preferably 1 to 20 μm, particularly preferably 6 to 15 μm.

  As a light source for UV curing treatment, any light source that generates ultraviolet rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 200 mJ / cm ² .

  Moreover, when irradiating actinic radiation, it is preferable to carry out while applying tension | tensile_strength in the conveyance direction of a film, More preferably, it is performing applying tension | tensile_strength also in the width direction. The tension to be applied is preferably 30 to 300 N / m. The method for applying the tension is not particularly limited, and the tension may be applied in the conveying direction on the back roll, or the tension may be applied in the width direction or biaxial direction by a tenter. This makes it possible to obtain a film having further excellent flatness.

  The curable resin layer may contain a conductive agent in order to impart antistatic properties, and preferred conductive agents include metal oxide particles or π-conjugated conductive polymers. An ionic liquid is also preferably used as the conductive compound.

  In addition, the curable resin layer has a nonionic surfactant such as a silicone surfactant, a fluorosurfactant or a polyoxyether, an anion from the viewpoint of coating properties and the uniform dispersibility of fine particles. A surfactant or the like can also be contained. These enhance the applicability. Moreover, it is preferable to add these components in 0.01-3 mass% with respect to the solid content component in a coating liquid.

(Application to solar cells)
The light confinement film for solar cell of the present invention is placed on the sunlight incident side, that is, the front surface side and the back surface side of various types of solar cells such as crystalline or amorphous silicon type solar cells, or organic thin film type solar cells. It can function as a film (see FIG. 3).

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

[Production of optical confinement film]
<Example 1: Production of light confinement film 1>
(Dope solution composition 1)
Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000 ) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Film formation)
The produced dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

  The web in which the mixture of the peeled acrylic resin and cellulose ester resin is compatible is evaporated at 35 ° C., slit to 1.6 m width, and then stretched 1.1 times in the width direction with a tenter, 135 ° C. It dried at the drying temperature of. At this time, the residual solvent amount when starting stretching with a tenter was 10%.

  After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then a mixed solvent of ethanol and pure water heated to 65 ° C. in a ratio of 80:20 Vol% was spray-coated on the film surface. Drying was completed while transporting the drying zones at 120 ° C and 140 ° C with a number of rolls, slitting to a width of 1.5 m, and knurling of 10 mm width to 5 µm was applied to both ends of the film, with an initial tension of 220 N / m. The core was wound around a core having an inner diameter of 15.24 cm at a tension of 110 N / m, and a mixture of an acrylic resin and a cellulose ester resin was compatible with each other to obtain a light confinement film 1 which is a surface fine uneven resin film.

  The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

  The residual solvent amount of the light confinement film 1 shown in Table 1 was 0.1%, the film thickness was 60 μm, and the winding length was 5000 m.

(Example 2: Production of light confinement film 2)
<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.46, acetyl group substitution degree 1.58, propionyl group substitution degree 0.88, Mw = 200000)
100 parts by mass Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.) 10 parts by mass TTO-51 (C) 20 parts by mass The above was put into a sealed container and dissolved while stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 50 ° C.

  On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 70 N / m.

  Immediately after peeling, a mixed solvent of ethanol and pure water heated to 67 ° C. in a ratio of 75:25 Vol% was spray-coated on the film surface.

  A cellulose ester film coated with a poor solvent mixture was stretched 37% in the width direction using a tenter while applying heat at 155 ° C. The residual solvent at the start of stretching was 15%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 120 ° C. and the transport tension was 90 N / m.

  As described above, a cellulose ester film having a dry film thickness of 50 μm was obtained.

(Example 3: Production of light confinement film 3)
Cellulose ester A (cellulose triacetate synthesized from linter cotton, acetyl group substitution degree 2.92, Mw = 290000) 100 parts by mass Additive AC1 ((meth) acrylic copolymer) 10 parts by mass Methylene chloride 430 parts by mass Ethanol 40 parts by mass or more was put into a closed container, heated, and completely dissolved while stirring.

  Next, the belt was cast uniformly on a stainless steel band support at a temperature of 35 ° C. and a width of 2.0 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support 101 was peeled off. The web of the peeled cellulose ester film was evaporated at 35 ° C., slit to 1.80 m width, and then stretched 1.4 times in the TD direction (direction perpendicular to the film transport direction) with a tenter, It was dried at a drying temperature of 135 ° C. At this time, the residual solvent amount when starting stretching with a tenter was 20%. The maximum stress during TD stretching was 10 MPa.

  Then, after spray-coating a mixed solvent with a ratio of 70:30 Vol% of acetone and pure water heated to 64 ° C. on the film surface, the mixture was dried for 15 minutes while being transported in a drying device at 120 ° C. by a number of rolls. Thereafter, the film was slit to a width of 1.7 m, a knurling process having a width of 15 mm and a height of 10 μm was applied to both ends of the film, and the film was wound around a core to obtain a light confinement film 3. The residual solvent amount of the optical confinement film was 0.2%, the film thickness was 60 μm, and the winding number was 6000 m.

(Example 4: Production of light confinement film 4)
The light confinement film 4 was produced in the same manner as the light confinement film 3 except that the substitution degree of the cellulose ester was changed to 2.4 and the acetone / water mixed solvent was applied before stretching into the tenter. The residual solvent amount of the light diffusion film was 0.2%, the film thickness was 40 μm, and the winding number was 7000 m.

(Example 5: Production of light confinement film 5)
A film was prepared by melting and casting Dianar BR85 (manufactured by Mitsubishi Rayon Co., Ltd.).

  After the film was produced, a light confinement film 5 was produced by applying a mixed solvent of ethanol and pure water heated to 58 ° C. in a ratio of 60:40 Vol% to the film surface.

(Example 6)
The light confinement film produced in Example 3 was subjected to alkali saponification treatment with a 1N KOH solution under saponification conditions at 45 ° C. for 30 seconds. The solid content of the reducing polypyrrole fine particles was prepared by preparing an acetone dispersion liquid of about 1.3%, followed by coating and drying.

  The produced film was immersed in a 0.02% palladium chloride-0.01% hydrochloric acid aqueous solution at 35 ° C. for 5 minutes and then washed with tap water. Next, the film was immersed in an electroless silver plating bath ATS add copper IW bath (Okuno Pharmaceutical Co., Ltd.), and then immersed at 35 ° C. for 10 minutes for silver plating.

(Preparation of HC layer)
<Preparation of Curable Resin Layer Coating Supports 1-6>
The following curable resin layer coating solution is applied by reverse coating on the film surfaces of the substrates 1 to 6 prepared above by reverse coating, dried at 100 ° C. for 1 minute, and then collected in a nitrogen atmosphere at 120 W / cm. Ultraviolet irradiation (irradiation distance: 10 cm, irradiation time: 30 seconds) was performed with one optical high-pressure mercury lamp, the coating film was cured, and a curable resin layer having a thickness of 5 μm was formed.

[Preparation of curable resin layer coating solution 1]
Polybasic acid consisting of isophthalic acid and adipic acid and neopentyl glycol are reacted to produce a polyester resin having a weight average molecular weight of 65,000, an acid value of 7 mgKOH / g, a non-volatile content of 60%, 7 parts by weight of dipentaerythritol tetraacrylate 1.8 parts by mass, 57.2 parts by mass of a mixed solvent having a mass ratio of n-butanol / xylene of 4/6, and 0.2 parts by mass of a photopolymerization initiator (trade name: Irgacure 907, manufactured by Ciba Geigy) A curable resin layer coating solution 1 was prepared by mixing and stirring.

<Evaluation>
(Surface shape measurement)
On the surface where the uneven structure of the light confinement film exists, five square regions of 130 μm × 130 μm were randomly extracted and observed with a 3D measurement laser microscope (3D measurement laser microscope LEXT OLS4000 manufactured by Olympus) for each. I got a statue.

  The condition for measurement with a laser microscope was a magnification of 350 times. In addition, the image was acquired from the direction which looks at the surface of a light-diffusion film perpendicularly | vertically.

  Based on the concavo-convex shape profile for the five observed images, the concavo-convex pitch and the difference between the highest point of the convex part and the lowest point of the concave part were measured.

  The average pitch of the irregularities in the irregular shape structure on the surface of the light confinement films 1 to 5 produced in Examples 1 to 5 above is in the range of 50 nm to 3 μm, and the highest point of the convex part and the lowest of the concave part The average value of the difference from the point was in the range of 5 nm to 5 μm.

<Production of solar cell>
An organic thin film solar cell was produced according to the following method.

(Preparation of transparent electrode)
Using a plasma-generated sputter roll coater on the uneven surface side of the surface uneven film produced in Examples 1 to 5 above, DC magnetron sputtering, using Ti as a target, forming a film at a temperature of 180 ° C., and using argon as a process gas A hard layer of SiO _x (x = 1.8, based on XPS) having a thickness of 70 nm was formed by reactive sputtering with introduction of gas and oxygen gas. The film thickness of the hard layer was adjusted by the reaction time. Next, a 100 nm conductive layer was prepared by sputtering an ITO transparent conductive film to prepare a surface film.

(Transparent electrode (first electrode), formation of electron prevention layer)
As the substrate electrode, a film (hereinafter referred to as ITO substrate) in which an ITO (indium tin oxide) thin film, which is a transparent conductor film, was deposited on the uneven surface of the produced film was used. The ITO substrate was subjected to ultrasonic cleaning for 10 to 15 minutes using acetone and ethanol solutions. Thereafter, it was washed with pure water or ultrapure water and dried with nitrogen gas.

  Next, hydrophilic treatment is performed to facilitate deposition of the organic semiconductor layer by forming a hydrophilic group on the surface of the ITO substrate (surface of the ITO thin film) by performing ultraviolet ozone treatment using an ozone cleaner (ultraviolet (UV) irradiation device). Processed.

  An aqueous dispersion of PEDOT-PSS (poly (3,4-ethylenedithiophene) -poly (stylensulfonate)) serving as an electron-preventing layer was applied onto the surface of the ITO thin film subjected to hydrophilic treatment with a spin coater. The spin coating was performed by spinning on an initial speed of 400 rpm for 10 seconds and a final speed of 5000 rpm for 100 seconds to deposit a film having a thickness of about 70 nm. Then, heat treatment baking was performed at 140 ° C. for 10 minutes in an air atmosphere / atmospheric pressure to obtain an electron blocking layer.

(Formation of photoelectric conversion layer)
As the photoelectric conversion layer, P3HT (manufactured by Plextronics: regioregular poly-3-hexylthiophene) (Mw = 52000, high molecular p-type semiconductor material) and PCBM (Mw = 911, low molecular n-type semiconductor material) (frontier) carbon: 6,6-phenyl _{-C 61} - with butyric acid mixed material of methyl ester). The mass ratio of both was adjusted to 1: 0.8 and dissolved in o-dichlorobenzene. After sufficient stirring with an ultrasonic stirrer, a solution that passed through a filter with an aperture of 0.45 μm was applied by spin coating. The spin coating was performed by spinning on at an initial speed of 400 rpm for 10 seconds and an final speed of 1500 rpm for 40 seconds to deposit a film having a thickness of about 50 nm. Then, room temperature drying was performed in vacuum to obtain a bulk heterojunction thin film.

(Formation of electron transport layer)
Next, the substrate on which the series of functional layers is formed is moved into a vacuum deposition apparatus chamber, the inside of the vacuum deposition apparatus is depressurized to 1 × 10 ⁻⁴ Pa or less, and then fluorinated at a deposition rate of 0.01 nm / second. Lithium was laminated to 0.6 nm to form an electron transport layer.

(Formation of second electrode)
Next, as the second electrode formation, an aluminum thin film was formed by a vacuum deposition method. Place an appropriate amount of aluminum wire on a tungsten boat, a high vacuum of about 2 × 10 −6 Torr, a deposition rate of 2-3 [Å / s] (0.2-0.3 nm / s), and a substrate temperature of room temperature. The organic thin film solar cell was fabricated by forming an aluminum thin film having a thickness of 50 nm at a substrate rotation speed of 30 rpm.

  The film produced in Examples 1-5 was used for the organic thin-film solar cell obtained above as a surface uneven | corrugated film, the film produced in Example 6 was used as a back surface uneven | corrugated film, and the solar cell shown in FIG. 3 was produced.

  In Example 1, except that the mixed solvent was not spray-coated, a solar cell using the film produced in the same manner as the surface film and the back film of the solar cell should be used as the reference solar cell. Produced.

<Evaluation>
(Power generation efficiency)
About the solar cell obtained by the said method, the output was measured under the light source of Am-1.5,100mW / cm < ² > using the solar simulator made from Yamashita Denso. In addition, the improvement rate of power generation efficiency was relatively evaluated based on the power generation efficiency of the reference solar cell.

  The above evaluation results are summarized in Table 1.

  As is clear from the results shown in Table 1, the power generation efficiency equivalent to that of the light confinement film for solar cells (glass) obtained by the conventional unevenness (texture structure) forming technique is obtained by the very simple means of the present invention. You can see that

  That is, according to the present invention, a light confinement film having a concavo-convex structure using a thermoplastic resin can be manufactured easily, efficiently, and on a large-scale production scale as compared with the prior art, such as a crack in the concavo-convex structure or a leak of a conductive layer. It can be seen that a new method for producing a light confinement film can be provided. Moreover, it turns out that the solar cell which has high electric power generation efficiency can be provided using the optical confinement film manufactured by the said manufacturing method.

a Maximum point of convex part b Minimum point of concave part h Difference (depth) between the highest point of convex part and the lowest point of concave part
p pitch 1 extruder 2 filter 3 static mixer 4 casting die 5 rotating support (first cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
DESCRIPTION OF SYMBOLS 9 Peeling roll 10 Film 11, 13, 14 Conveyance roll 12 Stretching machine 15 Slitter 16 Winding machine F Resin film 20 Solar cell 21 Surface uneven | corrugated film 22 1st electrode (ITO transparent conductive film)
23 Electron prevention layer 24 Photoelectric conversion layer 25 Electron transport layer (lithium fluoride film)
26 Second electrode (aluminum thin film)
27 Back side uneven film

Claims (6)

  A method for producing a solar cell light confinement film having a concavo-convex structure on a surface of a film substrate containing a thermoplastic resin, wherein a mixed solvent containing a poor solvent is applied to the film substrate containing the thermoplastic resin And a method for producing a light confinement film for solar cells, comprising: a step of drying, and a step of drying a film substrate coated with the mixed solvent.   The average pitch of the unevenness in the uneven shape structure is in the range of 50 nm to 3 μm, and the average value of the difference between the highest point of the convex part and the lowest point of the concave part is in the range of 5 nm to 5 μm. The manufacturing method of the optical confinement film for solar cells of Claim 1.   The said poor solvent is a mixed solvent of water and alcohol, The manufacturing method of the optical confinement film for solar cells of Claim 1 or Claim 2 characterized by the above-mentioned.   The said poor solvent is a mixed solvent of water and ketones, The manufacturing method of the light confinement film for solar cells as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.   A solar cell light confinement film having a concavo-convex structure on the surface of a film substrate containing a thermoplastic resin, wherein the concavo-convex structure is formed by the action of a mixed solvent containing a poor solvent. A light confinement film for solar cells.   A solar cell comprising a solar cell light confinement film produced by the method for producing a solar cell light confinement film according to any one of claims 1 to 4.

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