JP5423013B2 - Plastic sheet - Google Patents

Description

  The present invention relates to a plastic sheet for solar cells, and particularly to a plastic sheet having a small linear expansion coefficient and excellent dimensional stability, which is suitable for forming a flexible thin film solar cell having excellent photoelectric conversion efficiency. .

  Solar cells include a rigid type using glass as a substrate and a flexible type solar cell using a plastic sheet as a substrate. In particular, flexible solar cells are becoming more and more used as auxiliary power sources for mobile communication devices such as watches and portable terminals, taking advantage of their light weight, and further integrated into the roof of automobiles, etc. Is also under review. The conventional rigid type has higher photoelectric conversion efficiency of solar cells than the flexible type, but there are limits to the reduction in thickness and weight, and the solar cell module may be damaged when subjected to an impact. .

  For this reason, solar cells using plastic sheets have been actively developed. For example, a thin-film solar cell is being formed on aramid and polyimide, and a flexible solar cell module is disclosed (Patent Document 1). Here, considering the formation of amorphous silicon, which is a photoelectric conversion layer, on a plastic sheet, plastic has a high coefficient of thermal expansion, unlike glass substrates. In order not to cause damage, a plastic sheet having a low coefficient of thermal expansion is desired.

  In addition, thin film solar cells typified by amorphous silicon solar cells, which use less silicon raw materials, are attracting attention as a next-generation solar cell because of the demand for lowering the cost of solar cells. Since silicon which is a photoelectric conversion layer is thinner than a crystalline silicon solar cell, it is necessary to improve the light utilization efficiency by introducing a light confinement structure in order to obtain a sufficient photocurrent value. Therefore, for the purpose of increasing light utilization efficiency, the surface of the solar cell substrate with the thin film silicon layer is made to have a rough surface, that is, a rough surface, thereby providing light scattering performance and increasing the amount of absorption of sunlight. Consideration is being made to increase.

  For example, by forming tin oxide with controlled crystal orientation on a glass substrate and providing an appropriate concavo-convex structure, a low-resistance transparent conductive film having a surface feature required for an amorphous silicon solar cell is formed ( Patent Document 2). In addition, for the purpose of forming a flexible sheet having surface irregularities useful for flexible thin-film solar cells, a solar cell substrate (Patent Document 3) in which a polyimide resin layer in which insulating fine particles are dispersed in a polyimide film is laminated, A thermoplastic crystalline resin base material containing inert particles (Patent Document 4) is disclosed. However, in order to provide a light confinement effect in a wavelength range of 400 to 800 nm effective for conversion of the amorphous silicon layer, particularly in a long wavelength range, it is necessary to increase the uneven shape. In this case, in forming irregularities with the transparent electrode, it is necessary to increase the film thickness in order to enlarge the crystal grains, and the transparency of the transparent electrode is lowered and the light transmittance is lowered. Moreover, it is thought that the transparent electrode performance formed in the film surface falls in the unevenness | corrugation formed on the resin film. In addition, the photoelectric conversion layer has an i-type intrinsic semiconductor sandwiched between p-type and n-type conductive semiconductors of several tens of nanometers to generate an internal electric field in the i-layer. The value is controlled. Therefore, when the unevenness on the surface of the film substrate is large, the thickness change of the p-type or n-type conductive semiconductor layer occurs, and as a result, the internal electric field becomes non-uniform in the direction along the thickness direction of the photoelectric conversion layer. Solar cell performance may be affected by weak areas.

  Further, as a method for further improving the photoelectric conversion efficiency of the thin film solar cell, a tandem thin film solar cell in which an amorphous silicon layer and microcrystalline silicon are stacked has been studied (Patent Document 5), but a crystalline silicon film is stacked. In thin-film solar cells, when the substrate surface has a large uneven shape, crystal grain boundaries are likely to be generated due to collisions between the crystal grains grown on the microcrystalline silicon, and the crystal grain boundary portion is the path of leakage current generation and carrier recombination. Since it becomes an area | region, it is described that the problem which causes the fall of a solar cell characteristic arises.

JP-A-8-306943 JP-A 61-227945 Japanese Patent Laid-Open No. 2001-15778 JP 2008-41684 A JP 2003-179241 A

  An object of the present invention is to provide a plastic sheet having a light scattering performance for obtaining a light confinement effect, having a high degree of freedom in surface shape and excellent in thermal dimensional stability, by solving the above technical problems. It is in.

The present invention is as follows.
(1) A plastic sheet containing a transparent resin (a) and a glass filler (b), wherein the transparent resin (a) includes a cured product of a resin composition mainly composed of an epoxy resin, and the cured The product contains a crosslinked product cured with an acid anhydride curing agent or a crosslinked product cured with a cationic curing catalyst as a constituent, and the epoxy resin comprises an alicyclic epoxy resin and / or a bisphenol A type epoxy resin. includes as components, a total light transmittance of 80% or more, and a haze value of 17 to 75%, and parallel linear expansion coefficient at 30 to 150 ° C. is Ri der less 40 ppm, the refraction of the transparent resin (a) refractive index of the plastic sheet difference between the refractive index of rate as the glass filler (b) is 0.01 to 0.2 (2) wherein the glass filler (b) is 1.45 to 1.60 (1 Plastic sheet according to.
( 3 ) The plastic sheet according to any one of (1) to ( 2 ), wherein the glass filler (b) is a glass fiber cloth.
( 4 ) The cured layer is formed by laminating an ultraviolet curable resin composition comprising an acrylate monomer or an epoxy ultraviolet curable resin composition on both surfaces of the plastic sheet, according to any one of (1) to ( 3 ). Plastic sheet.
( 5 ) The plastic sheet according to ( 4 ), wherein the epoxy-based ultraviolet curable resin composition contains an alicyclic epoxy.
( 6 ) On at least one side of the plastic sheet, Si, Ta, Nb, Al, In, W, Sn, Zn, Ti, Cu, Ce, Ca, Na, B, Pb, Mg, P, Ba, Ge, Li The plastic sheet in any one of (1)-( 5 ) which laminated | stacked the inorganic composition layer of the oxide, nitride, or oxynitride containing 1 or more types chosen from K, Z, and Zr.
( 7 ) A plastic sheet in which a transparent conductive layer is formed on one side of the plastic sheet according to any one of (1) to ( 6 ), and the total light transmittance is 70% or more.
( 8 ) A solar cell substrate comprising the plastic sheet according to any one of (1) to ( 7 ).
( 9 ) A substrate for a thin film silicon solar cell comprising the plastic sheet according to any one of (1) to ( 7 ).
( 10 ) A substrate for an organic solar cell comprising the plastic sheet according to any one of (1) to ( 7 ).

  According to the present invention, a plastic sheet having light scattering performance for obtaining a light confinement effect, having a high degree of freedom in surface shape and excellent in thermal dimensional stability can be obtained. For this reason, when used as a flexible type solar cell substrate such as a thin film silicon solar cell, a compound thin film solar cell, and an organic solar cell, the performance deterioration of the solar cell generated on the solar cell substrate having a conventional surface uneven shape is improved. Therefore, a solar cell having excellent photoelectric conversion efficiency can be obtained.

Spectral haze ratio of plastic sheets of Examples and Comparative Examples

  The plastic sheet of the present invention contains a transparent resin (a) and a glass filler (b). About the transparent resin (a), it is possible to achieve both excellent heat resistance and good transparency by including an epoxy resin cured product of an epoxy resin composition mainly containing an epoxy resin.

  The plastic sheet of the present invention increases the total light transmittance by adjusting the difference in refractive index between the transparent resin (a) and the glass filler (b), and the ratio of the diffuse transmitted light amount component in the transmitted light component, It has a high haze ratio. The total light transmittance of the plastic sheet of the present invention needs to be 80% or more. By increasing the total light transmittance, sunlight incident from the plastic sheet side can be efficiently irradiated to the photoelectric conversion layer. Further, the haze ratio needs to be 15 to 95%. By increasing the haze ratio, not only the optical path length of sunlight passing through the photoelectric conversion layer is increased, but also the ratio of sunlight that is totally reflected at the photoelectric conversion layer and the transparent electrode interface and confined in the power generation layer is increased. This leads to an improvement in the photoelectric conversion efficiency of the battery. When the haze ratio is less than the lower limit, the light diffusibility is lowered, and the light confinement performance in the power generation layer is lowered. When the upper limit is exceeded, backscattering of incident light and light confinement inside the plastic sheet occur, and the amount of incident light on the power generation layer decreases.

  When using the plastic sheet of this invention as a board | substrate for solar cells, it is preferable that the average linear expansion coefficient in 30-150 degreeC is 40 ppm or less, More preferably, it is 30 ppm or less, Most preferably, it is 20 ppm or less. For example, when this plastic sheet is used for amorphous silicon solar, if this upper limit is exceeded, there is a risk that device defects such as warping, peeling of the silicon thin film, or crack destruction may occur in the manufacturing process.

  As the transparent resin (a) used in the present invention, various resins can be used and are not particularly limited. However, cationic polymerization is possible, for example, a compound having an epoxy group, a compound having an oxetanyl group. Or a cured product of a resin composition containing a compound having a vinyl ether group.

  Examples of the compound having an epoxy group include a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, or a hydrogenated product thereof, an epoxy resin having a dicyclopentadiene skeleton, and a triglycidyl isocyanurate skeleton. Examples of epoxy resins, epoxy resins having a cardo skeleton, and alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl 3 ′, 4′-epoxycyclohexylcarboxylate, 1,8,9, diepoxy limonene, dicyclopentadiene diene. 3,4-epoxycyclohexylmethanol and 3,4-epoxycyclohexylcarboxylic acid are attached to both ends of oxide, cyclooctene dioxide, acetal diepoxyside, and ε-caprolactone oligomer, respectively. Tellurium-bonded ones, epoxidized hexahydrobenzyl alcohol, alicyclic polyfunctional epoxy resins, alicyclic epoxy resins having a hydrogenated biphenyl skeleton, alicyclic epoxy resins having a hydrogenated bisphenol A skeleton, etc. It is done.

Examples of the compound having an oxetanyl group include 1,4-bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene (Aron oxetane OXT-121 (XDO)), di [2- (3-oxetanyl) butyl]. Ether (Aron oxetane OXT-221 (DOX)), 1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene (HQOX), 1,3-bis [(3-ethyloxetane-3-yl ) Methoxy] benzene (RSOX), 1,2-bis [(3-ethyloxetane-3-yl) methoxy] benzene (CTOX), 4,4′-bis [(3-ethyloxetane-3-yl) methoxy] Biphenyl (4,4′-BPOX), 2,2′-bis [(3-ethyl-3-oxetanyl) methoxy] biphenyl (2,2′-BPOX), 3,3 ′, 5,5′-tetramethyl [4,4′-bis (3-ethyloxetane-3-yl) methoxy] biphenyl (TM-BPOX), 2,7-bis [(3-ethyloxetane- 3-yl) methoxy] naphthalene (2,7-NpDOX), 1,6-bis [(3-ethyloxetane-3-yl) methoxy] -2,2,3,3,4,4,5,5- Octafluorohexane (OFH-DOX), 3 (4), 8 (9) -bis [(1-ethyl-3-oxetanyl) methoxymethyl] -tricyclo [5.2.1.0 ^2.6 ] decane, 1,2 -Bis [2-{(1-ethyl-3-oxetanyl) methoxy} ethylthio] ethane, 4,4'-bis [(1-ethyl-3-oxetanyl) methyl] thiodibenzenethioether, 2,3-bis [ (3-ethyloxetane-3- L) Methoxymethyl] norbornane (NDMOX), 2-ethyl-2-[(3-ethyloxetane-3-yl) methoxymethyl] -1,3-O-bis [(1-ethyl-3-oxetanyl) methyl] -Propane-1,3-diol (TMPTOX), 2,2-dimethyl-1,3-O-bis [(3-ethyloxetane-3-yl) methyl] -propane-1,3-diol (NPGOX), 2-butyl-2-ethyl-1,3-O-bis [(3-ethyloxetane-3-yl) methyl] -propane-1,3-diol, 1,4-O-bis [(3-ethyloxetane -3-yl) methyl] -butane-1,4-diol, 2,4,6-O-tris [(3-ethyloxetane-3-yl) methyl] cyanuric acid, bisphenol A and 3-ethyl-3- Chloro Etherified product of tiloxetane (abbreviated as OXC) (BisAOX), etherified product of bisphenol F and OXC (BisFOX), etherified product of phenol novolac and OXC (PNOX), etherified product of cresol novolac and OXC (CNOX), oxetanylsilsesqui Oxane (OX-SQ), 3-ethyl-3-hydroxymethyloxetane silicon alkoxide (OX-SC) 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane (Aron oxetane OXT-212 (EHOX )), 3-ethyl-3- (dodecyloxymethyl) oxetane (OXR-12), 3-ethyl-3- (octadecyloxymethyl) oxetane (OXR-18), 3-ethyl-3- (phenoxymethyl) ) Oxetane (Aron Oxetane OX T-211 (POX)), 3-ethyl-3-hydroxymethyloxetane (OXA), 3- (cyclohexyloxy) methyl-3-ethyloxetane (CHOX) and the like. Here, the above parentheses are product names or abbreviations of Toagosei Co., Ltd.

  The compound having a vinyl ether group is not particularly limited, but 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol vinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, Examples thereof include tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol type tetravinyl ether, and the like.

In order to cure these resins and compounds, in the case of curing alone, they can be cured using a cationic catalyst or an anionic catalyst, and can also be cured using various curing agents. For example, in the case of an epoxy resin, it can be cured using an acid anhydride or an aliphatic amine.
As the cationic curing catalyst, for example, a thermal cationic curing catalyst (for example, an onium salt cationic curing catalyst or an aluminum chelate cationic curing catalyst) that releases a substance that initiates cationic polymerization by heating, or cationic polymerization using active energy rays. (For example, an onium salt-based cationic curing catalyst) that releases a substance that initiates the reaction. Among these, a thermal cationic curing catalyst is preferable. Thereby, the hardened | cured material which is more excellent in heat resistance can be obtained.
Examples of the thermal cationic curing catalyst include aromatic sulfonium salts, aromatic iodonium salts, ammonium salts, aluminum chelates, and boron trifluoride amine complexes. Specifically, examples of aromatic sulfonium salts include hexafluoroantimonate salts such as SI-60L, SI-80L, SI-100L manufactured by Sanshin Chemical Industries, and SP-66 and SP-77 manufactured by Asahi Denka Kogyo. Examples of the aluminum chelate include ethyl acetoacetate aluminum diisopropylate and aluminum tris (ethyl acetoacetate). Examples of the boron trifluoride amine complex include boron trifluoride monoethylamine complex, boron trifluoride imidazole complex, and trifluoride. Examples thereof include boron bromide piperidine complexes.

  The difference between the refractive index of the transparent resin (a) and the refractive index of the glass filler (b) in the present invention is preferably 0.01 or more in order to increase the haze ratio, more preferably 0.01 to 0.2. Preferably, 0.01 to 0.1 is more preferable. When the difference in refractive index is less than the lower limit, the total light transmittance of the obtained plastic substrate is high, but the amount of diffused light component is reduced, so that the haze ratio may be reduced. Moreover, when the refractive index difference exceeds the upper limit value, the backscattered light component increases, and the amount of light incident on the power generation layer may decrease.

  The refractive index of the glass filler (b) used in the present invention is preferably 1.45 to 1.60 in order to obtain an excellent transparent composite. The Abbe number of the glass filler (b) and the Abbe number of the transparent resin (a) are preferably relatively close. When the Abbe number between the transparent resin and the glass is relatively close, the wavelength dependency of the amount of diffused light is reduced, so that the wavelength used for solar power generation can be used without waste. However, the Abbe number can be adjusted by arbitrarily adjusting the wavelength dependence of the diffused light depending on the wavelength band used for power generation of the photoelectric conversion layer.

Examples of the glass filler (b) used in the present invention include glass fiber cloths such as glass fiber, glass cloth and glass nonwoven fabric, glass beads, glass flakes, glass powder, and milled glass. Since it is high, glass fiber, glass cloth and glass nonwoven fabric are preferable, and glass cloth is most preferable.
Examples of the glass include E glass, C glass, A glass, S glass, D glass, NE glass, T glass, quartz, low dielectric constant glass, and high dielectric constant glass. E glass, S glass, T glass, and NE glass, which have few impurities and are easily available, are preferred.
The blending amount of the glass filler (b) is preferably 1 to 90% by weight, more preferably 10 to 80% by weight, and still more preferably 30 to 70% by weight. If the blending amount of the glass filler (b) is within this range, molding is easy, and the effect of reducing linear expansion due to compounding is recognized.

  In the plastic sheet of the present invention, the closer the glass filler (b) and the resin are, the better the transparency of the composite composition such as the plastic substrate for display elements. It is preferable to treat with a known surface treating agent such as an agent. Preferred silane coupling agents include epoxy silane and oxetanyl silane because they react with the resin with a cationic curing catalyst.

  If necessary, the plastic sheet of the present invention may be used in combination with a thermoplastic or thermosetting oligomer or polymer as long as the properties such as transparency, solvent resistance and heat resistance are not impaired. In addition, in the plastic sheet of the present invention, a small amount of antioxidant, ultraviolet absorber, dye / pigment, and other inorganic substances are added as necessary, as long as the properties such as transparency, solvent resistance, and heat resistance are not impaired. It may contain a filler such as a filler.

There is no limitation on the molding method of the plastic sheet of the present invention, for example, a method in which an uncured resin composition and a glass filler (b) are directly mixed, cast into a required mold, and then crosslinked to form a sheet, A method in which an uncured resin composition is dissolved in a solvent and the glass filler (b) is dispersed and cast, and then crosslinked to form a sheet, etc., and a glass cloth or glass nonwoven fabric is impregnated with an uncured resin composition and then crosslinked. For example, a sheet or the like.
When using the plastic sheet of this invention as a solar cell board | substrate, the thickness of a board | substrate becomes like this. Preferably it is 50-2000 micrometers, More preferably, it is 50-1000 micrometers. When the thickness of the substrate is within this range, the flatness is excellent, and the weight of the substrate can be reduced as compared with the glass substrate.

  On both surfaces of the plastic sheet of the present invention, a cured layer is formed by laminating a resin composition having excellent transparency, heat resistance, and chemical resistance in order to enhance adhesion with an inorganic substance layer to be laminated such as a transparent electrode. May be formed. As the resin composition, an ultraviolet curable resin composition comprising an acrylate monomer or an epoxy ultraviolet curable resin composition is preferable. More specifically, a composition containing at least one of alicyclic epoxy, epoxy acrylate, urethane acrylate, isocyanuric acid triacrylate, neopentyl acrylate, pentaerythritol acrylate, trimethylolpropane acrylate, ethylene glycol acrylate, polyester acrylate, and the like. Can be used. The thickness of the cured layer of the resin composition is preferably 0.1 to 50 μm.

An inorganic substance layer may be formed on at least one side of the plastic sheet of the present invention. The inorganic material layer is selected from Si, Ta, Nb, Al, In, W, Sn, Zn, Ti, Cu, Ce, Ca, Na, B, Pb, Mg, P, Ba, Ge, Li, K, and Zr. It is preferable that the main component is an oxide, nitride, or oxynitride containing one or more of the above. These substances achieve both good gas water vapor barrier properties and transparency. The thickness of the inorganic material layer is not particularly limited, but a thickness of 10 to 500 nm is preferable. If it is this range, favorable light transmittance, water vapor | steam barrier property, and the crack tolerance by bending will be obtained. About the formation method of a silicon oxynitride layer, it implement | achieves by means, such as vacuum evaporation, ion plating, CVD, sputtering. In particular, sputtering and CVD, which have good composition controllability and can form a dense film, are preferable. For sputtering, raw materials are selected from Si, Ta, Nb, Al, In, W, Sn, Zn, Ti, Cu, Ce, Ca, Na, B, Pb, Mg, P, Ba, Ge, Li, K, and Zr There is an RF sputtering method in which an oxide, a nitride, or an oxynitride containing one or more of the above is used. 1 selected from Si, Ta, Nb, Al, In, W, Sn, Zn, Ti, Cu, Ce, Ca, Na, B, Pb, Mg, P, Ba, Ge, Li, K, and Zr There is a DC sputtering method in which O ₂ or N ₂ is introduced as a reactive gas during the process using a target containing more than seeds. In this case, an RF sputtering method can also be selected.

A transparent conductive layer may be formed on one side of the plastic sheet of the present invention. As a material for the transparent conductive layer, known materials such as SnO ₂ , ITO, ZnO can be used. However, when forming a silicon film, the transparent conductive layer is exposed to a hydrogen gas atmosphere due to the use of SiH ₄ and H _2. Therefore, it is desirable to form a ZnO film having excellent reduction resistance at least as the final surface. As a film forming method, a known technique such as a CVD method, a vapor deposition method, an ion plating method, or a sputtering method can be used.

Hereinafter, the contents of the present invention will be described in detail by way of examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Evaluation was performed by the following method.
(A) Average linear expansion coefficient After increasing the temperature from 30 ° C. to 150 ° C. at a rate of 5 ° C. per minute in a nitrogen atmosphere using a TMA / SS120C type thermal stress strain measuring device manufactured by Seiko Electronics Co., Ltd. Once cooled to 0 ° C., the temperature was increased again at a rate of 5 ° C. per minute, and the value at 30 ° C. to 150 ° C. was measured and determined. The load was 5 g and the measurement was performed in the tensile mode.
(B) Refractive index Only the resin composition used in the example was cured under the curing conditions of the example, and the refractive index at a wavelength of 589 nm was measured with an Abbe refractometer.
(C) Total light transmittance, haze ratio Using a haze meter (NDH2000: manufactured by Nippon Denshoku Industries Co., Ltd.), total light transmittance Tt (%) and diffuse transmittance Dt (%) were measured with a D65 light source.
The haze ratio was calculated by Dt / Ttx100 (%).
(D) Spectral haze ratio The light transmittance was measured in a wavelength band of 300 to 800 nm using a spectrophotometer (UV-2400PC: manufactured by Shimadzu Corporation). The total light transmittance (Tt (λ)) was measured as a transmittance measurement value with an integrating sphere, and the parallel light transmittance (Pt (λ)) was measured as a transmittance measurement value without an integrating sphere. The spectral haze ratio was calculated using the following formula at each wavelength.
Spectral haze ratio (λ) = (Tt (λ) −Pt (λ)) / Tt (λ) × 100 [%]
(E) Surface unevenness measurement The root mean square roughness Rms of the 40 μm square region was measured in a tapping mode using an atomic force microscope (NanoScope IIIa: manufactured by Digital Instruments).
(F) Water vapor barrier property Water vapor permeability was measured according to JIS K 7129B method 40 ° C 90%.

NE glass cloth (thickness 100 μm, refractive index 1.510, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Cel8000 manufactured by Daicel Chemical Industries), 100 parts by weight of aromatic sulfonium-based thermal cation catalyst (three SI-100L (manufactured by Shin Chemical Co., Ltd.) was impregnated with a resin composition (refractive index after curing of 1.520) in which 1 part by weight was melt-mixed and defoamed. The glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a sheet having a thickness of 0.1 mm. Next, 80 parts by weight of hydrogenated biphenyl type alicyclic epoxy, 17 parts by weight of silsesquioxane having an oxetanyl group, and 3 parts by weight of a photocation initiator (SP-170 manufactured by Adeka) are uniformly mixed, and a sheet is obtained. After coating with a wire bar on one side, 1100 mJ / cm ² of ultraviolet light was irradiated with a high-pressure mercury lamp, and the other side was coated and cured in the same manner, and then heated at 250 ° C. for 2 hours to obtain a thickness of 5 μm. The cured resin layer was laminated on both sides of the plastic sheet.
The produced plastic sheet had a thermal expansion coefficient of 11 ppm / ° C., a total light transmittance of 90%, and a haze ratio of 36%. The unevenness of the sheet surface was 1.2 nm as measured by Rms. The spectral haze ratio of the obtained plastic sheet is shown in FIG. The obtained plastic sheet was a plastic sheet having excellent surface flatness, high total light transmittance, and high haze ratio.

E glass cloth (thickness 100 μm, refractive index 1.558, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Cel8000 manufactured by Daicel Chemical Industries), 100 parts by weight of aromatic sulfonium-based thermal cation catalyst (three SI-100L (manufactured by Shin Chemical Co., Ltd.) was impregnated with a resin composition (refractive index after curing of 1.520) in which 1 part by weight was melt-mixed and defoamed. The glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a sheet having a thickness of 0.1 mm. Next, 100 parts by mass of hydrogenated biphenyl type alicyclic epoxy (Cel8000), 200 parts by mass of silica sol (manufactured by Fuso Chemical Industries, solid content 25% by mass, secondary particle size 80 nm, dispersion medium methyl ethyl ketone (MEK)), light After mixing 3 parts by mass of a cationic polymerization catalyst (Asahi Denka Co., Ltd., SP170), the solvent was removed at 25 ° C. and 13 mmHg, and the solid content was 33% by mass, the secondary particle size was 80 nm, and the viscosity was 900 Pa · s (40 ° C.). A filler-dispersed resin varnish was obtained. The obtained filler-dispersed resin varnish was applied to both surfaces of the sheet with a wire bar while adjusting the count so that the thickness after drying was 5 μm, and then irradiated with UV light, and further at 250 ° C. in a nitrogen atmosphere. Heated for 2 hours, a cured resin layer was formed, and a plastic sheet was produced.
The produced plastic sheet had a thermal expansion coefficient of 14 ppm / ° C., a total light transmittance of 93%, and a haze ratio of 75%. Further, the roughness of the sheet surface was 1.5 nm as measured by Rms. The spectral haze ratio of the obtained plastic sheet is shown in FIG. The obtained plastic sheet was a plastic sheet having excellent surface flatness, high total light transmittance, and high haze ratio.

E glass cloth (thickness 100 μm, refractive index 1.558, manufactured by Nittobo), 80 parts by weight of alicyclic epoxy resin (trade name CFL-2021P), bisphenol A type epoxy resin (trade name Epicoat 828, JER ( Co., Ltd.) impregnated with 20 parts by weight of a resin composition (refractive index 1.522 after curing) obtained by melting and mixing 1 part by weight of an aromatic sulfonium-based thermal cation catalyst (SI-100L, Sanshin Chemical) did. The glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a sheet having a thickness of 0.1 mm. Next, on one side of the obtained sheet, 30 parts by weight of isocyanuric acid EO-modified triacrylate (M-315 manufactured by Toagosei Co., Ltd.), 10 parts by weight of bisphenol A type epoxy acrylate (VR-77 manufactured by Showa Polymer Co., Ltd.), light Stir and dissolve in 2.0 parts by weight of initiator (IRG-907 manufactured by Chiba Gakie), 9.0 parts by weight of methyl cellosolve acetate, 30 parts by weight of butyl acetate, 6.0 parts by weight of butyl cellosolve, and RC = 48.3 wt% A uniform solution was applied with a bar coater coater, and the solvent was removed by heating at 90 ° C. for 2 minutes and then at 120 ° C. for 3 minutes in a heat dryer. The resin layer after drying was irradiated with ultraviolet rays of 350 mJ / cm ² with a high-pressure mercury lamp to produce a 4 μm thick cured resin layer on the sheet. Further, on the other side, the resin layer was applied and cured in the same manner to produce a plastic sheet.
The produced plastic sheet had a thermal expansion coefficient of 15 ppm / ° C., a total light transmittance of 90%, and a haze ratio of 60%. Further, the roughness of the sheet surface was 0.7 nm as measured by Rms. The spectral haze ratio of the obtained plastic sheet is shown in FIG. The obtained plastic sheet was a plastic sheet having excellent surface flatness, high total light transmittance, and high haze ratio.

(Comparative Example 1)
T glass cloth (thickness 100 μm, refractive index 1.523, manufactured by Nittobo), hydrogenated biphenyl type alicyclic epoxy resin (Cel8000 manufactured by Daicel Chemical Industries), 100 parts by weight of aromatic sulfonium-based thermal cation catalyst (three SI-100L (manufactured by Shin Chemical Co., Ltd.) was impregnated with a resin composition (refractive index after curing of 1.520) in which 1 part by weight was melt-mixed and defoamed. The glass cloth was sandwiched between release-molded glass plates, heated in an oven at 80 ° C. for 2 hours, and further heated at 200 ° C. for 2 hours to obtain a sheet having a thickness of 0.1 mm. Next, 80 parts by weight of hydrogenated biphenyl type alicyclic epoxy, 17 parts by weight of silsesquioxane having an oxetanyl group, and 3 parts by weight of a photocation initiator (SP-170 manufactured by Adeka) are uniformly mixed, and a sheet is obtained. After coating with a wire bar on one side, 1100 mJ / cm ² of ultraviolet light was irradiated with a high-pressure mercury lamp, and the other side was coated and cured in the same manner, and then heated at 250 ° C. for 2 hours to obtain a thickness of 5 μm. The cured resin layer was laminated on both sides of the plastic sheet.
The produced plastic sheet had a thermal expansion coefficient of 9 ppm / ° C., a total light transmittance of 92%, and a haze ratio of 0.8%. The unevenness of the sheet surface was 1.2 nm as measured by Rms. The spectral haze ratio of the obtained plastic sheet is shown in FIG. The obtained plastic sheet was a plastic sheet having excellent surface flatness and a high total light transmittance but a low haze ratio.

(Comparative Example 2)
The total light transmittance, haze ratio, and surface roughness of a glass plate with SnO ₂ conductive film (made by Asahi Glass, trade name: ASAHI-U) having a texture structure that is commercially available as a glass substrate for solar cells were measured. The glass substrate for a solar cell with a texture structure had a total light transmittance of 80% and a haze ratio of 10.0%. Further, the roughness of the texture surface was 44.9 nm as measured by Rms. The spectral haze ratio of the glass substrate for solar cells is shown in FIG. The glass substrate for solar cells is a glass substrate having large surface irregularities and a haze ratio lower than 15%. As a result of measuring the spectral haze ratio, the haze ratio on the long wavelength side was low in the wavelength band of 300 nm to 800 nm.

One side of the plastic sheet prepared in Example 3 was set as a deposition surface in a vacuum chamber of an RF sputtering apparatus. When a vacuum of 5 × 10 ⁻⁴ Pa was reached, 0.1 Pa of Ar gas was introduced, and 0.3 kW of RF power was applied between the plastic sheet and the raw material SiO ₂ target to start discharging. When the discharge was stabilized, the shutter disposed between the plastic sheet and the raw material was opened, and deposition of an inorganic substance layer made of SiOx on the deposition surface of the plastic sheet was started. When the inorganic material layer was deposited to 100 nm, the shutter was closed to finish the deposition, and the vacuum chamber was opened to the atmosphere to produce a plastic sheet with an inorganic material layer. The produced plastic sheet with an inorganic substance layer had a high water vapor barrier property of 0.02 g / m ² / day (below the measurement detection limit by the Mocon method).

  The plastic sheet of the present invention can be suitably used as a base material for a flexible thin film solar cell.

Claims (10)

A plastic sheet containing a transparent resin (a) and a glass filler (b), wherein the transparent resin (a) includes a cured product of a resin composition mainly composed of an epoxy resin, and the cured product is A crosslinked product cured with an acid anhydride curing agent or a crosslinked product cured with a cationic curing catalyst is included as a constituent component, and the epoxy resin includes an alicyclic epoxy resin and / or a bisphenol A type epoxy resin as a constituent component. wherein, the total light transmittance of 80% or more, a haze value is from 17 to 75%, and parallel linear expansion coefficient at 30 to 150 ° C. is Ri der less 40 ppm, the said refractive index of the transparent resin (a) A plastic sheet having a difference from the refractive index of the glass filler (b) of 0.01 to 0.2 The plastic sheet according to claim 1 , wherein the glass filler (b) has a refractive index of 1.45 to 1.60. The plastic sheet according to any one of claims 1-2 glass filler (b) is a glass fiber cloth. The plastic sheet according to any one of claims 1 to 3 , wherein a cured layer is formed by laminating an ultraviolet curable resin composition comprising an acrylate monomer or an epoxy ultraviolet curable resin composition on both surfaces of the plastic sheet. The plastic sheet according to claim 4, wherein the epoxy-based ultraviolet curable resin composition contains an alicyclic epoxy. On at least one side of the plastic sheet, Si, Ta, Nb, Al, In, W, Sn, Zn, Ti, Cu, Ce, Ca, Na, B, Pb, Mg, P, Ba, Ge, Li, K and The plastic sheet according to any one of claims 1 to 5 , wherein an inorganic composition layer of oxide, nitride or oxynitride containing one or more selected from Zr is laminated. The plastic sheet which forms a transparent conductive layer in the single side | surface of the plastic sheet in any one of Claims 1-6, and whose total light transmittance is 70% or more. The solar cell substrate composed of a plastic sheet according to any one of claims 1-7. Thin-film silicon solar cell substrate composed of a plastic sheet according to any one of claims 1-7. Organic solar battery substrate composed of a plastic sheet according to any one of claims 1-7.

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