JP2010180324A - Photo-setting composition, its use as sealing material for wet organic solar cell, and wet organic solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photo-setting composition which is very less in the amount of gas emission during photo-setting, is excellent in sealing property, adhesiveness, chemical resistance or the like, and is suitable for sealing an electrolyte of a wet organic solar cell. <P>SOLUTION: The photo-setting composition contains a monofunctional (meth)acrylate, a saturated thermoplastic elastomer and a photopolymerization initiator, characterized in that: the monofunctional (meth)acrylate is an alicyclic or aliphatic monofunctional (meth)acrylate having 15 to 26 carbon atoms; the saturated thermoplastic elastomer contains a styrene-isobutylene diblock copolymer by not less than 40 mass%; the content proportion of the saturated thermoplastic elastomer ranges from 30 to 80 parts by mass with respect to 100 parts by mass of the monomfunctional (meth)acrylate; and the composition exhibits specified viscoelastic characteristics. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photocurable composition, and more particularly to a photocurable composition exhibiting excellent characteristics as a sealing material for an electrolyte solution, particularly in wet organic solar cells. The present invention also relates to the use of the photocurable composition as a sealing material for wet organic solar cells. Furthermore, this invention relates to the wet organic solar cell which uses the photocured material layer formed from this photocurable composition as a sealing layer.

  The wet organic solar cell is a new solar cell that takes out electricity from sunlight using an organic compound such as an organic dye as a photoelectric conversion layer without using a silicon semiconductor film unlike a conventional solar cell. In addition to being able to be manufactured at low cost, dye-sensitized solar cells, which are representative of wet organic solar cells, can be made thin and flexible by using a plastic film substrate, and various dye molecules It has a variety of features, such as the ability to produce colorful solar cells, and the ease of mounting on automobiles, clothing, curtains, and the like.

  In recent years, research and development related to improving energy conversion efficiency has been promoted toward the practical application of wet-type organic solar cells such as dye-sensitized solar cells. Development of a sealing material suitable for this is one of the most important issues. A wet organic solar cell generally has a structure in which an electrolytic solution is sealed between two conductive substrates. Since a sealing material is used to enclose the electrolytic solution, it is essential to improve the sealing property of the sealing material and the resistance to the electrolytic solution in order to improve the reliability and durability of the wet organic solar cell.

  More specifically, a dye-sensitized solar cell representative as a wet organic solar cell has, for example, the structure shown in FIG. FIG. 1 is a cross-sectional view showing the basic structure of an example of a dye-sensitized solar cell. A transparent conductive film 2 is formed on one side of a transparent substrate 1 made of glass or plastic film, and a metal oxide semiconductor layer in which metal oxide semiconductor particles such as titanium dioxide particles are baked on the transparent conductive film 2 4 is formed. The metal oxide semiconductor layer 4 usually has a porous structure, and a large number of dyes 3 are adsorbed on the surface and inside the porous structure.

  Opposite to the first conductive substrate (working electrode substrate) having the layer configuration of “transparent substrate / transparent conductive film / metal adsorbed metal oxide semiconductor film”, a conductive film (conductive layer) is formed on the substrate 8. A second conductive substrate (counter electrode substrate) having a layer configuration of “conductive film / substrate” in which 7 is formed is disposed. Both conductive substrates face each other on the side of each conductive film, and are arranged via a sealing layer 6 provided in a frame shape on the periphery of these conductive substrates.

  In the case where the conductive film (conductive layer) 7 itself plays a role as the second conductive substrate, the substrate 8 can be omitted. When the dye-sensitized solar cell is a monolithic type in which series cells are formed on one transparent substrate, a second substrate having no conductive film can be used instead of the second conductive substrate. . The second substrate used in the monolithic type may be transparent or opaque.

  The sealing layer is generally formed of a sealing material, but a solid spacer may be used, or a solid spacer and an adhesive may be used in combination. The electrolyte solution 5 is sealed in a gap between the two conductive substrates formed by the sealing layer 6 by various methods. As the electrolytic solution 5, a solution in which an electrolyte is dissolved in an organic solvent is generally used. A typical example of such an electrolytic solution is an acetonitrile / ethylene carbonate mixed solution containing iodine and lithium iodide.

When light is applied to the dye-sensitized solar cell, first, the dye 3 absorbs light and emits electrons. The electrons quickly move to the metal oxide semiconductor layer 4, travel from there to the transparent conductive film 2, and further to the counter conductive film 7 via the circuits 9 and 11. Electrons transmitted to the conductive film 7 of the counter electrode reduce triiodide ions (I ₃ ⁻ ) in the electrolytic solution and convert them into iodide ions (I ⁻ ). The iodide ions are oxidized again on the dye 3 to become triiodide ions. Thus, the oxidation-reduction reaction cycle is repeated in the dye-sensitized solar cell.

  By repeating this cycle, current flows in the circuits 9 and 11. If the circuits 9 and 11 are connected to a load (for example, a motor or a lighting device) 10, electric energy can be extracted from the dye-sensitized solar cell. In addition to the iodine / iodine compound combination, various redox systems can be used as the electrolyte involved in charge transport in the charge / discharge process. In this case, the same oxidation-reduction reaction cycle is repeated. .

  If the sealing property of the sealing layer 6 is poor, the electrolyte solution tends to leak. Even if the initial sealing property is good, if the resistance of the sealing layer 6 to the electrolytic solution is insufficient, the sealing layer 6 swells with the electrolytic solution over time or deteriorates due to a reaction with the electrolyte. As a result, the electrolyte solution leaks or the electrolyte concentration decreases, so that the reliability and durability of the dye-sensitized solar cell are significantly reduced.

  When the sealing layer 6 is formed using a reactive sealing material such as a photocurable composition containing a monofunctional (meth) acrylate, there is a problem that gas is easily released during a reaction such as photocuring. found. When the amount of gas released from the reactive sealing material is large, the reliability of the sealing layer is impaired, and the emitted gas component adversely affects the performance of the dye-sensitized solar cell.

  The basic principle and structure of the dye-sensitized solar cell are disclosed in detail in, for example, Japanese Patent No. 2664194 (Patent Document 1) and Japanese Patent Publication No. 8-15097 (Patent Document 2). Regarding the method for sealing the electrolytic solution, Patent Document 1 describes a method of sealing using a frame made of an electrically insulating material such as synthetic resin or glass. Patent Document 2 describes using a silicone adhesive, polyethylene, and an epoxy resin as a sealant.

  Japanese Patent Laid-Open No. 2000-30767 (Patent Document 3) describes a method of sealing an opening for injecting an electrolyte solution of a dye-sensitized solar cell with a silicon resin or an epoxy resin. In JP 2000-150005 A (Patent Document 4), a titanium substrate on which a dye-sensitized semiconductor electrode is formed, a glass substrate with an ITO thin film on which platinum is deposited, and a spacer (polyester film) are used. A dye-sensitized solar cell having a structure in which an iodine electrolyte is put in the gap and an epoxy resin is applied and cured around the gap is described. In JP 2000-294814 A (Patent Document 5), a spacer (polytetrafluoroethylene sheet) is sandwiched between the ends of the four sides between the electrodes of the dye-sensitized solar cell, leaving two injection ports and surroundings. A dye-sensitized solar cell having a structure sealed with an epoxy adhesive is described.

  However, since the solid spacer is disposed in a compressed state between the two conductive substrates, the elasticity is lost over time, and the reliability as a seal tends to be lowered. Sealants such as silicone resins and epoxy resins are easily eroded by the electrolyte solution of dye-sensitized solar cells, and will swell or deteriorate due to contact with the electrolyte solution for a long period of time, causing the electrolyte solution to leak. There is.

  Japanese Unexamined Patent Publication No. 2000-186114 (Patent Document 6) proposes a method of using an ethylene-unsaturated carboxylic acid copolymer or its ionomer as a solar cell element sealing material. Similarly, Japanese Patent Laid-Open No. 2001-144313 (Patent Document 7) proposes a method of using, as a solar cell element sealing material, a resin composition in which a coupling agent is blended with an ethylene-polar monomer copolymer. Yes.

  In the sealing methods disclosed in Patent Documents 6 and 7, a resin material is formed into a sheet by extrusion molding or press molding, the sheet is punched into a predetermined shape, and then the punched product is melted at the melting temperature of the resin material. It is heated and pressed to the substrate. Patent Documents 6 and 7 only disclose a solar cell module using a semiconductor such as silicon, gallium-arsenic, copper-indium-selenium, etc., and is a wet solar cell using an electrolytic solution. The dye-sensitized solar cell is not described.

  In order to use a resin material such as an ionomer disclosed in Patent Documents 6 and 7 as a sealing material, it is necessary to punch into a predetermined shape in advance. Since the resin material is solid and hardly soluble in a solvent, it cannot be applied to a conductive substrate by a pattern printing technique such as screen printing to form a sealing pattern. Therefore, the method of using the resin material has many manufacturing steps, and there is a decrease in yield due to punching.

  Moreover, in order to bond the punched product of the resin material to the substrate, it is necessary to heat the punched product to the melting temperature of the resin material. Sealing of the conductive substrate in the dye-sensitized solar cell is performed on the conductive film side of each conductive substrate, but the metal oxide semiconductor film adsorbing the dye exists on the conductive film of the working electrode substrate. ing. Since the dye used in the dye-sensitized solar cell is not necessarily only one having a high heat resistance, it is necessary to prevent the dye from being deteriorated or destroyed by heating during the sealing process. Therefore, it is difficult to actually apply a method of sealing using a punched product of a resin material.

  In dye-sensitized solar cells, a combination of iodine / iodine compounds is often used as an electrolyte. Iodine is present in the form of iodine ions in the electrolyte, but ionomers crosslinked with metal ions react with iodine ions. Therefore, when an ionomer is used as a sealing material, the iodine ion concentration in the electrolytic solution may decrease with time.

  Japanese Patent Application Laid-Open No. 2004-311036 (Patent Document 8) discloses a dye-sensitized solar cell encapsulating composition mainly composed of an isoprene polymer having at least one (meth) acrylate group. Patent Document 8 describes that isobornyl acrylate or a photopolymerization initiator is added as a diluent to the sealing composition. Therefore, the sealing composition can be applied to a desired shape on a conductive substrate and photocured. However, since the carbon-carbon double bond derived from isoprene exists in the main chain even after photocuring, the sealing composition reacts with iodine in the electrolytic solution, so that the iodine concentration There is a possibility that the performance of the dye-sensitized solar cell and the adhesiveness of the sealing layer are lowered due to the decrease in the thickness. Furthermore, it was found that isobornyl acrylate used as a diluent is easily vaporized as a gas during photocuring.

  JP-A-2005-154528 (Patent Document 9) discloses that a chain aliphatic monofunctional (meth) acrylate having 18 to 25 carbon atoms is 100 parts by weight, isobornyl (meth) acrylate is 5 to 10 parts by weight, styrene-isobutylene- A curable composition comprising 5 to 30 parts by weight of a styrene block copolymer and 1 to 10 parts by weight of a radical initiator is disclosed. Patent Document 9 describes that the curable composition is applied to a sealant such as a dye-sensitized solar cell. However, since the curable composition has a high viscosity and it is difficult to add a thixotropic agent, a pattern printing technique such as screen printing is applied to form a sealing pattern of a desired shape on the conductive substrate. It is difficult to form. In addition, isobornyl acrylate used in the examples of Patent Document 9 tends to vaporize as a gas during photocuring.

  Japanese Patent Application Laid-Open No. 2005-302564 (Patent Document 10) discloses 100 parts by weight of (meth) acrylate having a linear aliphatic hydrocarbon having 10 to 20 carbon atoms in the molecule, and 5 to 15 alicyclic (meth) acrylates. A photocurable dye-sensitized solar cell sealing agent containing parts by weight, 10 parts by weight or more of a maleic anhydride-modified hydrogenated styrene-butadiene-styrene block copolymer, and a photopolymerization initiator is disclosed. In the examples of Patent Document 10, isobornyl acrylate and cyclohexyl acrylate are used as the alicyclic (meth) acrylate, but it has been found that both of them are easily vaporized as a gas during photocuring.

  JP-A 2007-106822 (Patent Document 11) discloses a monomer component containing isobornyl acrylate and an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms, a saturated thermoplastic elastomer, and photopolymerization initiation. A photocurable composition containing an agent is disclosed. Patent Document 11 describes that the photocurable composition is used as a sealing material for a dye-sensitized solar cell. However, it was found that the isobornyl acrylate contained in the photocurable composition of Patent Document 11 is easily vaporized as a gas during photocuring.

Japanese Patent No. 2664194 Japanese Patent Publication No. 8-15097 JP 2000-30767 A JP 2000-150005 A JP 2000-294814 A JP 2000-186114 A JP 2001-144313 A JP 2004-311036 A JP 2005-154528 A JP 2005-302564 A JP 2007-106822 A

  The subject of this invention is providing the photocurable composition excellent in sealing property, the adhesiveness with respect to a to-be-adhered body, chemical-resistance, etc. More specifically, the subject of this invention is providing the photocurable composition suitable for sealing the electrolyte solution of the wet organic solar cell represented by the dye-sensitized solar cell. In particular, the object of the present invention is to provide a photocurable composition that, in addition to having excellent adhesion to a substrate, emits very little gas during photocuring and does not adversely affect the performance of wet organic solar cells. Is to provide. Depending on the type of wet organic solar cell such as a dye-sensitized solar cell, the substrate includes a conductive substrate on which a conductive film is formed, a substrate made of a conductive film alone, and a substrate without a conductive film.

  Another object of the present invention is to provide use of a photocurable composition having such excellent characteristics as a sealing material for wet organic solar cells. Still another object of the present invention is to provide a wet organic solar cell provided with a photocured material layer formed from the photocurable composition as a sealing layer.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a specific ratio of an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms and a styrene-isobutylene diblock copolymer. A sealing material suitable for sealing an electrolyte of a wet organic solar cell, wherein the photocurable composition containing a saturated thermoplastic elastomer and a photopolymerization initiator and having a specific viscoelastic property I found out that it could be. The photocurable composition of the present invention has an adverse effect on the performance of the wet organic solar cell because the photocured product has excellent adhesion to the substrate, and the amount of gas released during photocuring is extremely small. There is no.

  Although the photocurable composition containing an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms as a photopolymerizable monomer has a small amount of gas release during photocuring, the photocured product is Resistance to electrolytes and solvents such as iodine contained in the electrolyte is not sufficient. When isobornyl acrylate is included in this photocurable composition, a photocurable composition capable of forming a cured product having excellent resistance to an electrolyte and a solvent can be obtained, but a large amount of gas is released during photocuring. This adversely affects the performance of wet organic solar cells. When the content ratio of isobornyl acrylate is increased, the cured product becomes hard and brittle, and the adhesion to the substrate decreases.

  On the other hand, it is strongly desired from the viewpoint of workability and productivity that the photocurable composition can be applied on a substrate by screen printing. With only the photopolymerizable monomer component, the viscosity is too low to obtain a photocurable composition excellent in screen printing suitability. By incorporating a saturated thermoplastic elastomer into a photocurable composition containing a photopolymerizable monomer and a photopolymerization initiator, the viscosity can be adjusted to impart screen printing suitability. However, by simply adding a saturated thermoplastic elastomer, it is a photo-curable composition with a high balance of properties such as screen printability, adhesion to substrates, resistance to electrolytes and solvents, and suppression of outgassing during photocuring. It is difficult to get things.

  Then, when the present inventors further researched, the ratio of C15-26 alicyclic or aliphatic monofunctional (meth) acrylate and a styrene-isobutylene diblock copolymer is 40 mass% or more. In combination with a saturated thermoplastic elastomer contained in a specific ratio, a photocured layer having excellent screen printing suitability and excellent resistance to electrolytes and solvents such as iodine can be formed. It has been found that a photocurable composition can be obtained that has sufficient adhesion to the substrate and that has a very small amount of outgassing during photocuring.

  The photocurable composition of the present invention has viscoelasticity suitable for screen printing and can be easily applied as a sealing material to a substrate. Since the photocurable composition of the present invention can be cured without heating by irradiating with ionizing radiation such as an electron beam, it can degrade organic compounds such as dyes of dye-sensitized solar cells. Absent. The photocurable composition of the present invention does not adversely affect battery performance because it emits less gas when applied as a sealing material. The present invention has been completed based on these findings.

According to the present invention, a photocurable composition comprising a monofunctional (meth) acrylate, a saturated thermoplastic elastomer, and a photopolymerization initiator,
(A) The monofunctional (meth) acrylate is an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms,
(B) The saturated thermoplastic elastomer contains a styrene-isobutylene diblock copolymer in a proportion of 40% by mass or more based on the total mass of the saturated thermoplastic elastomer,
(C) The content ratio of the saturated thermoplastic elastomer is in the range of 30 to 80 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate,
(D) The content ratio of the photopolymerization initiator is in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate,
(E) Using a viscoelasticity measuring apparatus equipped with a cone plate having a diameter of 25 mm as a measuring jig, the viscosity (V) of the photocurable composition measured under conditions of a temperature of 23 ° C. and a rotation speed of the cone plate of 2 rpm. ₂ ) is in the range of 30 to 300 Pa · s, and
(F) Ratio of the viscosity (V ₂ ) to the viscosity (V ₂₀ ) of the photocurable composition measured using the viscoelasticity measuring device at a temperature of 23 ° C. and a rotation speed of the cone plate of 20 rpm. _(V 2 _{/ V 20)} is a photocurable composition, characterized in that in the range of 1.3 to 20 is provided.

  Moreover, according to this invention, use as a sealing material for wet organic solar cells of this photocurable composition is provided.

  Furthermore, according to the present invention, in a wet organic solar cell having a structure in which a photoelectric conversion layer made of an organic compound is disposed in an electrolytic solution sealed between two substrates via a sealing layer, the sealing layer includes: There is provided a wet organic solar cell characterized by being a photocured material layer formed from the photocurable composition.

  ADVANTAGE OF THE INVENTION According to this invention, the photocurable composition excellent in sealing performance, the adhesiveness with respect to a to-be-adhered body, chemical resistance, etc. is provided. ADVANTAGE OF THE INVENTION According to this invention, the photocurable composition suitable for sealing the electrolyte solution of a wet organic solar cell is provided. The photocurable composition of the present invention has a high balance of various properties such as screen printing suitability, adhesion to a substrate, resistance to an electrolytic solution, and suppression of gas emission during photocuring.

  The photocurable composition of the present invention can be applied onto a substrate by screen printing and has excellent adhesion to various substrates including a conductive substrate. The photocurable composition of the present invention has an extremely small amount of gas released during photocuring, can form a highly reliable sealing layer, and the released gas component has an adverse effect on the performance of the wet organic solar cell. There is no effect.

  By using the photocurable composition of the present invention as a sealing material for a wet organic solar cell, a sealing layer excellent in sealing property and resistance to an electrolytic solution while suppressing deterioration in battery performance due to outgassing during photocuring A wet organic solar cell having the following can be provided.

1 is a schematic cross-sectional view showing an example of the basic structure of a dye-sensitized solar cell.

  In the present invention, an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms is used as the photopolymerizable monomer. The photocurable composition of the present invention does not contain a photopolymerizable monomer that has a relatively low boiling point, such as isobornyl acrylate and cyclohexyl acrylate, and easily releases gas.

  The alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms means an alicyclic or aliphatic acrylate or methacrylate having 15 to 26 carbon atoms or a mixture of both. That is, in the present invention, (meth) acrylate means acrylate and / or methacrylate. Monofunctional means that the number of photopolymerizable carbon-carbon double bonds is one, in other words, that there is one (meth) acryloyl group. An alicyclic or aliphatic monofunctional (meth) acrylate means a (meth) acrylate in which the ester residue [R of —C (═O) OR] is an alicyclic group or an aliphatic group. An alicyclic group or an aliphatic group is a hydrocarbon group having no polar group such as a carboxyl group.

  When the carbon number of the monofunctional (meth) acrylate is too small, the boiling point is lowered, so that the manufacturing process of the photocurable composition and the manufacturing process of the wet organic solar cell including the coating of the photocurable composition are performed at a low temperature. These manufacturing conditions are limited. If a monofunctional (meth) acrylate having too few carbon atoms is used, the amount of gas released may increase during photocuring of the photocurable composition. On the other hand, when a monofunctional (meth) acrylate having too many carbon atoms is used, the adhesiveness of the photocurable composition to the substrate is lowered.

  The carbon number of the monofunctional (meth) acrylate is in the range of 15 to 26, preferably 16 to 25, and more preferably 17 to 22. When the number of carbon atoms of the monofunctional (meth) acrylate is within the above range, combined with the combination with other components, the adhesiveness of the photopolymerizable composition to the substrate and sufficient reliability as a sealing material are sufficient. Can be.

  Examples of the alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms include n-lauryl acrylate (carbon number 15), isomyristyl acrylate (carbon number 17), and n-stearyl acrylate (carbon number 21). ), Acrylates such as isostearyl acrylate (carbon number 21), behenyl acrylate (carbon number 25); n-lauryl methacrylate (carbon number 16), isomyristyl methacrylate (carbon number 18), n-stearyl methacrylate (carbon number 22) ), Methacrylates such as isostearyl methacrylate (carbon number 22), behenyl methacrylate (carbon number 26), and the like.

  Of the alicyclic or aliphatic monofunctional (meth) acrylates, aliphatic (meth) acrylates are preferred. Among the monofunctional (meth) acrylates, the above acrylates are preferable. Among the acrylates, isostearyl acrylate and isomyristyl acrylate are preferable, and isostearyl acrylate is particularly preferable from the viewpoint of adhesion to the substrate.

  In addition to the alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms, the photocurable composition of the present invention may contain a small amount of polyfunctional (meth) acrylate if desired. . By containing polyfunctional (meth) acrylate, the solvent resistance of the sealing layer formed from the photocurable composition is further improved. The polyfunctional (meth) acrylate means a bifunctional or higher polyfunctional acrylate and / or methacrylate. The bifunctional or higher polyfunctional (meth) acrylate means a (meth) acrylate having two or more (meth) acryloyl groups.

  Examples of the polyfunctional (meth) acrylate include 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1, Diacrylates such as 9-nonanediol diacrylate, 1,10-decanediol diacrylate, dimethylol-tricyclodecane diacrylate, tripropylene glycol diacrylate; 1,4-butanediol dimethacrylate, 1,3-butanediol Dimethacrylate, diethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,1 -Dimethacrylates such as decanediol dimethacrylate, dimethylol-tricyclodecane dimethacrylate, tripropylene glycol dimethacrylate; triacrylates such as trimethylolpropane triacrylate, pentaerythritol triacrylate; trimethylolethane trimethacrylate, trimethylolpropane And trimethacrylates such as trimethacrylate; tetrafunctional or higher acrylates such as dipentaerythritol hexaacrylate and polymethylolpropane polyacrylate. Among these polyfunctional (meth) acrylates, difunctional (meth) acrylates such as diacrylates and dimethacrylates are preferable.

  The polyfunctional (meth) acrylate is added at a ratio of up to 10 parts by mass with respect to 100 parts by mass of the alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms. When polyfunctional (meth) acrylate is used, the addition ratio is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate. Part by mass, particularly preferably 0.5 to 5 parts by mass. When the addition ratio of the polyfunctional (meth) acrylate is too small, the effect of improving the solvent resistance is small, and when it is excessive, the adhesive strength is lowered or the flexibility of the photocured product is lowered. The photopolymerizable composition of the present invention can usually exhibit various properties without containing a polyfunctional (meth) acrylate.

  In addition to the alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms, the photocurable composition of the present invention may optionally contain a carboxyl group-containing (meth) acrylate in a small proportion. Also good. By including the carboxyl group-containing (meth) acrylate, the adhesion of the sealing layer formed from the photocurable composition to the substrate is further improved. The carboxyl group-containing (meth) acrylate means an acrylate and / or methacrylate having a carboxyl group in the molecule.

  Examples of the carboxyl group-containing (meth) acrylate include 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, ω-carboxy-polycaprolactone (n≈ 2) Acrylates such as monoacrylate; and methacrylates such as 2-methacryloyloxyethyl succinic acid and 2-methacryloyloxyethyl hexahydrophthalic acid. Among these (meth) acrylates containing a carboxyl group, acrylates are preferable.

  The carboxyl group-containing (meth) acrylate is added at a ratio of up to 10 parts by mass with respect to 100 parts by mass of the alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms. When the carboxyl group-containing (meth) acrylate is used, the addition ratio is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 8 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate. Parts, particularly preferably 1 to 7 parts by mass. If the addition ratio of the carboxyl group-containing (meth) acrylate is too small, the effect of improving the adhesion to the substrate is small, and if it is too large, the resistance to the electrolytic solution tends to decrease. The photopolymerizable composition of the present invention can usually exhibit various properties without containing a carboxyl group-containing (meth) acrylate.

  The saturated thermoplastic elastomer used in the present invention means an uncrosslinked thermoplastic elastomer that substantially does not contain a radical-reactive unsaturated bond such as a carbon-carbon double bond in the main chain and side chain. The saturated thermoplastic elastomer may have an aromatic ring. By containing the saturated thermoplastic elastomer in the photocurable composition of the present invention, the viscosity can be adjusted to be suitable for screen printing.

  Since only the photopolymerizable monomer component has a viscosity that is too low, a photocurable composition having screen printing suitability cannot be obtained. As a result of investigations by the present inventors, by adding a saturated thermoplastic elastomer, screen printing suitability is imparted, and further, a saturated thermoplastic elastomer containing a styrene-isobutylene diblock copolymer in a proportion of 40% by mass or more. It was found that a photocurable composition serving as a sealing material exhibiting excellent adhesiveness to a substrate can be obtained by using.

  The saturated thermoplastic elastomer used in the present invention is a solid polymer at room temperature (23 ± 2 ° C.). The saturated thermoplastic elastomer includes a hydrogenated styrene-based thermoplastic elastomer, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-acrylic acid copolymer. At least one kind of saturated thermoplastic elastomer selected from the above is preferred.

  Among these, hydrogenated styrene-based thermoplastic elastomers, ethylene-ethyl acrylate copolymers, and ethylene-butyl acrylate copolymers are preferable. Examples of the hydrogenated styrene thermoplastic elastomer include hydrogenated styrene butadiene rubber, hydrogenated styrene-butadiene-olefin crystal block copolymer, and hydrogenated styrene-butadiene-styrene block copolymer.

  The saturated thermoplastic elastomer used in the present invention contains a styrene-isobutylene diblock copolymer. The styrene-isobutylene diblock copolymer is used in a proportion of 40% by mass or more, preferably 43% by mass or more, particularly preferably 45% by mass or more, based on the total mass of the saturated thermoplastic elastomer. If the ratio of the styrene-isobutylene diblock copolymer in the saturated thermoplastic elastomer is too small, adhesion to the substrate is insufficient, and it is difficult to highly balance other properties.

  The total amount (100% by mass) of the saturated thermoplastic elastomer can be made into a styrene-isobutylene diblock copolymer, but the viscoelasticity of the photocurable composition can be adjusted to improve screen printing suitability, electrolytes and solvents. In order to improve various resistances by improving the resistance to water, the content of the styrene-isobutylene diblock copolymer in the saturated thermoplastic elastomer is preferably 40 to 90% by mass, more preferably 43%. It is desirable that the content be in the range of ˜80% by mass, particularly preferably 45 to 70% by mass.

  The saturated thermoplastic elastomer is 30 to 80 parts by mass, preferably 35 to 75 parts by mass, more preferably 40 to 70 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate having 15 to 26 carbon atoms. use. If the ratio of the saturated thermoplastic elastomer is too small, the cured product will have insufficient flexibility, and if it is excessive, the viscosity of the photocurable composition will be too high, and pattern printing technology such as screen printing will be applied. It becomes difficult.

  In the present invention, a photopolymerization initiator is used to cure the monofunctional (meth) acrylate by photopolymerization. Specific examples of the photopolymerization initiator used in the present invention include acetophenones such as acetophenone, 2,2-diethoxyacetophenone, m-chloroacetophenone, p-tert-butyltrichloroacetophenone, 4-dialkylacetophenone; benzophenone, etc. Benzophenones; Michler ketones such as Michler ketone; benzyls such as benzyl and benzyl methyl ether; benzoins such as benzoin and 2-methylbenzoin; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether; Benzyl dimethyl ketals such as benzyl dimethyl ketal; thioxanthones such as thioxanthone; propiophenone, anthraquinone, It can be mentioned carbonyl compounds, such as Setoin, butyroin, Toruoin, benzoyl benzoate, alpha-acyloxime esters.

  As photopolymerization initiators, in addition to the above carbonyl compounds, sulfur compounds such as tetramethylthiuram disulfide, tetramethylthiuram monosulfide, thioxanthone, 2-chlorothioxanthone, diphenyldisulfide; azobisisobutyronitrile, azobis-2,4 -Azo compounds such as dimethylvaleronitrile; peroxides such as benzoyl peroxide and di-tert-butyl peroxide. Furthermore, examples of the photopolymerization initiator include phenyl glyoxylates; acylphosphine oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; organic dye compounds, iron-phthalocyanine compounds, and the like. .

  These photopolymerization initiators can be used alone or in combination of two or more. Of these, benzoins, acetophenones, and acylphosphine oxides are preferable as the photopolymerization initiator, and acylphosphine oxides are particularly preferable.

  A transparent conductive film (also referred to as “transparent electrode”) formed on a working electrode substrate of a wet organic solar cell such as a dye-sensitized solar cell may cut ultraviolet rays. In order to use as a sealing material for a sensitized solar cell, it is desirable to use a photopolymerization initiator that absorbs light in the wavelength region of preferably around 400 nm or 400 nm or more. As such a photopolymerization initiator, acylphosphine oxides are preferable.

  The photopolymerization initiator is added in an amount of 0.1 to 100 parts by mass of an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms. 1 to 10 parts by weight, preferably 0.3 to 5 parts by weight, more preferably 0.5 to 4 parts by weight. If the ratio of the photopolymerization initiator is too small, it takes time for curing, and if it is too large, the adhesive strength of the cured product is reduced.

The photocurable composition of the present invention was measured using a viscoelasticity measuring device equipped with a cone plate having a diameter of 25 mm as a measuring jig under the conditions of a temperature (V) measured at a temperature of 23 ° C. and a rotation speed of the cone plate of 2 rpm. ₂ ) is in the range of 30 to 300 Pa · s. The viscosity (V ₂ ) is preferably in the range of 40 to 280 Pa · s, more preferably 45 to 250 Pa · s, and particularly preferably 50 to 220 Pa · s.

  As a viscoelasticity measuring device, Physica MCR301 (registered trademark) manufactured by Anton Paar was used. As the measuring jig, a cone plate capable of giving a uniform shearing force in the radial direction was used. When the viscosity of the photocurable composition is too low, screen printing suitability becomes insufficient, and it becomes difficult to form a sealing pattern having a desired thickness on the substrate by screen printing. If the viscosity of the photocurable composition is too high, screen printing itself becomes difficult or impossible.

The photopolymerizable composition of the present invention was measured using a viscoelasticity measuring apparatus equipped with a cone plate having a diameter of 25 mm as a measuring jig under the conditions of a temperature measured at a temperature of 23 ° C. and a rotation speed of the cone plate of 20 rpm (V the ratio of the viscosity versus _{20) (V 2) (V} 2 / V 20) is within the range of 1.3 to 20. The ratio _(V 2 _/ V ₂₀₎ is preferably 1.4 to 18, more preferably in the range of 1.5 to 15. When the value of this ratio (V ₂ / V ₂₀ ) is too high, the fluidity of the photocurable composition is lowered and screen printing suitability is liable to be lowered.

The photocurable composition of the present invention forms a circular coating film having a thickness of 100 μm and a diameter of 50 mm on a plastic film, and is irradiated with ultraviolet rays having an energy flux density of 270 mW / cm ² for 5 seconds from a high-pressure mercury lamp. When photocured, it is preferable that the reduction rate of the mass of the coating film after photocuring with respect to the mass of the coating film before ultraviolet irradiation is 1.50% or less. The mass reduction rate is more preferably 1.40% or less, and particularly preferably 1.35% or less. The lower limit of the mass reduction rate is usually 0.50% and in many cases 0.7%. This mass reduction rate is an indicator of the amount of gas released during photocuring. That is, the larger the decrease rate, the greater the amount of gas released during photocuring.

  The photocurable composition of the present invention has two “transparent substrates / transparent conductive films” facing each other on the transparent conductive film side, and a photocured material layer having a thickness of 100 μm formed from the photocurable composition. It is preferable that the T-peel adhesive strength measured for the sample bonded together at a temperature of 23 ° C., a relative humidity of 50%, and a speed of 50 mm / min is 0.65 N / 10 mm or more. The T-peel adhesive strength is preferably 0.70 N / 10 mm or more, more preferably 0.80 N / 10 mm or more, and particularly preferably 0.90 N / 10 mm or more. The upper limit of the T-peel adhesive strength is usually 7.00 N / 10 mm, and in many cases 6.5 N / 10 mm. When this T-peel adhesive force is too low, the adhesiveness with respect to the board | substrate of the photocured material of a photocurable composition will fall.

  The photocurable composition of the present invention can contain various additives (other additives) as necessary within the range not impairing the object of the present invention. Other additives include, for example, plasticizers such as phthalates to impart low temperature flexibility; various fillers such as calcium carbonate, talc, silica, and carbon black to reduce the linear expansion coefficient; Surfactants, oil-absorbing resins, organic pigments, inorganic pigments, stabilizers, silane coupling agents, spacer particles, and the like can be used in appropriate amounts.

  In order to adjust the viscosity of the photocurable composition of the present invention, a filler capable of imparting thixotropy can be contained. A filler capable of imparting thixotropic properties can act as a thixotropic agent, thereby adjusting the viscosity of the photocurable composition. Examples of the filler capable of imparting thixotropic properties include organic gelling agents such as stearic acid amide; inorganic thixotropic agents such as fumed silica, aerosil silica, precipitated calcium carbonate, and bentonite; It is not limited to these. The photocurable composition of the present invention can have a desired viscoelasticity without adding such a thixotropic agent.

  When the photocurable composition is applied to a site where light is difficult to reach or is thickly applied, heat such as an organic peroxide is applied to the photocurable composition in order to sufficiently advance the curing reaction. A polymerization initiator can be added. When a thermal polymerization initiator is added, it is preferable to arrange a heating step at the time of irradiation with ionizing radiation, after irradiation, or before and after irradiation.

  In many cases, the photocurable composition of the present invention can exhibit various excellent properties without including the various additive components (other additives) described above. When other additives are used, an appropriate amount is appropriately used according to the purpose of use.

  The photocurable composition of the present invention can be prepared by stirring and dispersing each component with a mixing apparatus such as a sand mill, a disper, or a colloid mill. Since the photocurable composition of the present invention has an appropriate viscosity, it can be applied to a desired location by a coating method. A screen printing method can be applied to apply the photocurable composition of the present invention in a pattern. Since the photocurable composition of the present invention is excellent in adhesiveness to plastic films and conductive films, it is suitable as a sealing material for wet organic solar cells such as dye-sensitized solar cells using a plastic film substrate.

  The photocurable composition of the present invention can be cured by irradiating the obtained coating film with ionizing radiation after being applied to an adherend. As the ionizing radiation, ultraviolet rays, electron beams (beta rays), gamma rays and alpha rays are preferable, and ultraviolet rays and electron beams are more preferable. In order to irradiate ionizing radiation, an apparatus that generates each radiation source may be used. For example, in order to irradiate an electron beam, an accelerating electron beam extracted from an electron beam accelerator of 20 to 2000 kV is usually irradiated. The penetration depth of the electron beam varies depending on the acceleration voltage. The electron beam penetrates deeper into the coating film as the acceleration voltage is higher. The irradiation dose of the electron beam is usually 1 to 300 kGy, preferably about 5 to 200 kGy, but is not limited to this range as long as a cured coating film is obtained.

To irradiate ultraviolet rays (UV), use UV irradiation equipment such as germicidal lamps, fluorescent lamps for ultraviolet rays, carbon arc, xenon lamps, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and electrodeless lamps. Used to irradiate light including a wavelength of 200 to 400 nm. The lamp output of the UV irradiation device is displayed as an output wattage (W / cm) per 1 cm of emission length. As the wattage per unit length increases, the intensity of the generated ultraviolet light increases. The lamp output is usually selected from the range of 30 to 300 W / cm. The light emission length is usually selected from the range of 40 to 2500 mm. The irradiation energy of ultraviolet rays is usually 0.1 to 10 J / cm ² , preferably 0.5 to 5 J / cm ² , but is not limited to this range as long as a cured coating film is obtained.

  When it is necessary to remove the polymerization inhibition effect due to oxygen when forming a cured coating film, it is preferable that the irradiation treatment with ionizing radiation is performed under an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, or rare gas. .

  The photocurable composition of the present invention has various properties preferable as a sealing material for wet organic solar cells. The wet organic solar cell has a structure in which a photoelectric conversion layer made of an organic compound is disposed in an electrolytic solution sealed between two substrates via a sealing layer. A typical dye-sensitized solar cell as a wet organic solar cell has a structure in which a photoelectric conversion layer made of an organic dye is disposed in an electrolytic solution sealed between two substrates via a sealing layer. Yes. More specifically, the dye-sensitized solar cell has, for example, the basic structure shown in FIG.

  A glass plate or a plastic film is used as the transparent substrate. Typical examples of the plastic film include thermoplastic polyester films such as polyethylene terephthalate (PET) film and polyethylene naphthalate (PEN), but other films having transparency and heat resistance can also be used. A typical example of the transparent conductive film (transparent electrode) is an ITO film obtained by thinly baking a compound composed of 95% indium oxide and 5% tin oxide on a substrate. In addition, a film (FTO) in which tin oxide is doped with fluorine is known as a transparent conductive film. As the counter electrode substrate, a conductive substrate similar to this can be used, but is not limited thereto. For example, even if a transparent substrate such as glass is used as the counter electrode substrate, if the conductive film is formed by vapor deposition of platinum on the substrate, the transparency of the entire conductive substrate may be lowered.

  Examples of metal oxide semiconductors include oxides such as titanium, zirconium, hafnium, strontium, zinc, indium, yttrium, lanthanum, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. Among these, titanium dioxide is representative. It is a typical one. The titanium dioxide is preferably ultrafine particles having a diameter of, for example, 10 to 30 nm, whereby a titanium dioxide film having a large specific surface area suitable for adsorbing the dye can be formed.

Examples of the dye include ruthenium complex [RuL ₂ (NCS) ₂ , L = 4,4′-dicarboxy-2,2′-bipyridine], porphyrin dye, cyanine dye, C ⁶⁰ derivative, styrylbenzothiazolium propyl. Examples thereof include sulfonate (BTS) and plant pigments.

  The electrolytic solution is generally a solution obtained by dissolving an electrolyte in an organic solvent. A typical example of such an electrolytic solution is an acetonitrile / ethylene carbonate solution containing iodine and lithium iodide. As the electrolyte, an oxidation-reduction pair (redox system) such as iodine / iodine compound and bromine / bromine compound is used. Among these, a combination of iodine / iodine compounds is widely used.

  As an organic solvent for dissolving or dispersing the electrolyte, ethylene carbonate, propylene carbonate, polyethylene glycol (for example, PEG # 220), acetonitrile, 3-methoxypropionitrile, a mixture of two or more thereof, and the like are used. In addition to the electrolyte, the electrolyte includes a thickener (eg, PEG # 600), a room temperature molten salt (1-propyl-2,3-dimethylimidazolium iodide) that lowers viscosity and facilitates ion diffusion. Various additives such as 4-tert-butylpyridine which prevent reverse current and increase open electromotive force may be contained.

In order to produce a dye-sensitized solar cell using the photocurable composition of the present invention, the following steps 1 to 4:
(1) A first conductive substrate having a layer configuration of “transparent substrate / transparent conductive film / metal oxide semiconductor film adsorbing a dye” and a second conductive substrate having a layer configuration of “conductive film / substrate” Step 1 of applying the photocurable composition of the present invention to the peripheral portion on the conductive film side of any one of the conductive substrates (A) by screen printing to form a frame-shaped photocurable composition layer;
(2) Step 2 of disposing the other conductive substrate (B) on the conductive substrate (A) with the other conductive substrate (B) facing each other through the photocurable composition layer;
(3) Step 3 of irradiating ionizing radiation to cure the photocurable composition; and (4) A gap between the two conductive substrates formed by a sealing layer made of a cured product of the photocurable composition. Step 4 of encapsulating the electrolyte in
Can be adopted.

  As the second substrate, instead of the second conductive substrate having the layer structure of “conductive film / substrate”, a conductive substrate made of “conductive film” or a substrate having no conductive film can be used. The structure of the first conductive substrate and the type of the second substrate can be selected according to the type of the dye-sensitized solar cell.

  The coating thickness of the photocurable composition can be appropriately adjusted according to the desired thickness of the electrolytic solution, but is usually in the range of 5 to 200 μm, preferably 10 to 150 μm, and in many cases 15 to 50 μm. . The pattern for applying the photocurable composition on the conductive substrate is set to match the shape of the dye-sensitized solar cell, such as a ring, a rectangle, or a rectangle.

  When injecting the electrolyte into the gap between the two conductive substrates, an opening is provided in a part of the cured or uncured sealing layer, or an opening is provided in a part of the substrate, and the sealing layer is formed. A method of injecting an electrolytic solution into the gap between both conductive substrates can be employed. The opening (electrolyte injection hole) is sealed using the same photocurable composition or other room temperature curable adhesive. As a result, the electrolytic solution can be sealed between the two conductive substrates. In the case of a glass substrate, an electrolytic solution reservoir is provided at the end (inside the sealing layer), and the electrolytic solution is placed therein, and the gap between the two conductive substrates formed by the sealing layer is provided. Alternatively, the electrolytic solution may be injected using capillary action.

  According to the present invention, in a wet organic solar cell having a structure in which a photoelectric conversion layer made of an organic compound is disposed in an electrolytic solution sealed between two substrates via a sealing layer, the sealing layer includes the sealing layer, There is provided a wet organic solar cell which is a photocured material layer formed from a photocurable composition.

  The wet organic solar cell includes a dye-sensitized solar cell having a structure in which a photoelectric conversion layer made of an organic dye is disposed in an electrolytic solution sealed between two substrates via a sealing layer. Specifically, the dye-sensitized solar cell includes a first conductive substrate having a layer configuration of “transparent substrate / transparent conductive film / metal oxide semiconductor film adsorbing a dye” and the first conductive substrate. The opposing second substrate has a structure in which a peripheral portion of both the substrates is disposed through a sealing layer provided in a frame shape, and an electrolytic solution is sealed in a gap between the two substrates formed by the sealing layer. Is.

  The second substrate is usually a second conductive substrate having a layer configuration of “conductive film / substrate” or “conductive film”. When the dye-sensitized solar cell is a monolithic type, a substrate without a conductive film can be used as the second substrate.

  The sealing layer (photocured material layer) made of the photocurable composition of the present invention is sufficiently resistant to the electrolytic solution, and does not swell with the electrolytic solution over time or deteriorate due to a reaction with the electrolyte. .

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. The measuring method of various characteristics is as follows.

(1) Viscosity The viscosity of the photocurable composition was measured using a viscoelasticity measuring apparatus (Physica MCR301 manufactured by Anton Paar, registered trademark) equipped with a cone plate having a diameter of 25 mm as a measuring jig, at a temperature of 23 ° C., a rotational speed of 2 rpm, and The measurement was performed under the condition of 20 rpm. The ratio (V ₂ / V ₂₀ ) was determined from these measured values when the viscosity measured at ₂ rpm was V ₂ and the viscosity measured at 20 rpm was V ₂₀ .

(2) Mass reduction rate before and after UV irradiation A photocurable composition was coated on a PET film with a thickness of 25 μm in a circular shape with a thickness of 100 μm and a diameter of 50 mm, and irradiated with ultraviolet rays for 5 seconds with a high-pressure mercury lamp (270 mW / cm ² ). The mass of the coating film before and after UV curing was measured, and the mass reduction rate before and after UV irradiation was determined. That is, the decreasing rate of the mass (m ₁ ) of the coating film after photocuring with respect to the mass (m ₀ ) of the coating film before ultraviolet irradiation is represented by the following formula [(m ₀ -m ₁ ) / m ₀ ] × 100
Determined by

(3) T-Peel Adhesive Force Two “transparent substrates / transparent conductive films” face each other on the side of each transparent conductive film, and are bonded together via a 100 μm-thick photocured material layer formed from a photocurable composition. The T-peel adhesive strength was measured for the sample under the conditions of a temperature of 23 ° C., a relative humidity of 50%, and a speed of 50 mm / min.

More specifically, the ITO-PEN film [Tobe OTEC113B-N125N (base material thickness: 125 μm)] is coated on the ITO surface with a thickness of 100 μm, and the other ITO-PEN film (same as above). ) Were bonded so that the ITO surfaces face each other, and ultraviolet rays were irradiated for 5 seconds with a high-pressure mercury lamp (270 mW / cm ² ) to photocure the coating film of the photocurable composition. Using this as a sample, the T-peel adhesive strength was measured using an Instron type tensile tester (RTM-100, manufactured by Orientec Co., Ltd.) at a temperature of 23 ° C., a relative humidity of 50%, and a speed of 50 mm / min.

(4) Resistance to electrolyte solution A photocurable composition is coated on a PET film with a thickness of 25 μm in a circular shape with a thickness of 100 μm and a diameter of 50 mm, and irradiated with ultraviolet light with a high-pressure mercury lamp (270 mW / cm ² ) for 5 seconds. Cured to make a sample. An electrolyte solution was prepared by dissolving 0.5M iodine, 0.1M lithium iodide, and 0.5M 4-tert-butylpyridine in propylene carbonate. The sample was immersed in the electrolyte at 40 ° C. for 24 hours. Then, the sample was taken out and the shape, coloring state, and adhesiveness of the photocured product layer were observed.

[Example 1]
25 parts by mass of styrene-isobutylene diblock copolymer, 15 parts by mass of hydrogenated styrene-butadiene rubber, 10 parts by mass of hydrogenated styrene-butadiene-olefin crystal block copolymer, and photopolymerization with respect to 100 parts by mass of isostearyl acrylate. One part by weight of an initiator [Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals Co., Ltd.] was added, and the mixture was stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 1. As is clear from the results in Table 1, the photocurable composition had a small mass reduction rate before and after UV curing and good T-peel adhesion. The photocured material layer formed from this photocurable composition was excellent in resistance to the electrolytic solution, and there was almost no change in coloring or the like even after being immersed in the electrolytic solution.

[Example 2]
A photocurable composition was prepared and evaluated in the same manner as in Example 1 except that 1 part by mass of dimethylol tricyclododecane diacrylate was added as a polyfunctional (meth) acrylate. The results are shown in Table 1. As is clear from the results in Table 1, the photocurable composition had a small mass reduction rate before and after UV curing and good T-peel adhesion. The photocured material layer formed from this photocurable composition was excellent in resistance to the electrolytic solution, and there was almost no change in coloring or the like even after being immersed in the electrolytic solution.

[Example 3]
Except for adding 1 part by mass of dimethylol tricyclododecane diacrylate as a polyfunctional (meth) acrylate and 5 parts by mass of ω-carboxy-polycaprolactone (n≈2) monoacrylate as a carboxyl group-containing (meth) acrylate, A photocurable composition was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. As is clear from the results in Table 1, the photocurable composition had a small mass reduction rate before and after UV curing and good T-peel adhesion. The photocured material layer formed from this photocurable composition was excellent in resistance to the electrolytic solution, and there was almost no change in coloring or the like even after being immersed in the electrolytic solution.

[Example 4]
A photocurable composition was prepared and evaluated in the same manner as in Example 3 except that isostearyl acrylate was replaced with isomyristyl acrylate. The results are shown in Table 1. As is clear from the results in Table 1, the photocurable composition had a small mass reduction rate before and after UV curing and good T-peel adhesion. The photocured material layer formed from this photocurable composition was excellent in resistance to the electrolytic solution, and there was almost no change in coloring or the like even after being immersed in the electrolytic solution.

[Comparative Example 1]
A zinc ion-crosslinked ethylene-methacrylic acid copolymer (trade name “HIMILAN 1652” (registered trademark), manufactured by Mitsui DuPont Chemical), which is an ionomer, was heated by extrusion coating to produce an ionomer sheet having a thickness of 100 μm.

  The ionomer sheet cut into a circular shape with a thickness of 100 μm and a diameter of 50 mm is placed on a PET film with a thickness of 25 μm, and the mass of the ionomer sheet is measured before and after holding for 3 minutes at 120 ° C. which is the bonding condition. The mass reduction rate of was determined.

  The ionomer sheet (thickness 100 μm) is placed on the ITO-PEN film [Tobe OTEC113B-N125N (base material thickness 125 μm)], and the ITO-PEN film (same as above) is bonded to it and held at 120 ° C. for 3 minutes. Heat-adhered. Using this as a sample, the T-peel adhesive strength was measured using an Instron type tensile tester (RTM-100, manufactured by Orientec Co., Ltd.) at a temperature of 23 ° C., a relative humidity of 50%, and a speed of 50 mm / min. The results are shown in Table 2.

  When an ionomer is used, it is necessary to produce a sheet, cut it into a predetermined shape, and heat-bond it under high temperature conditions.

[Comparative Example 2]
100 parts by mass of isomyristyl acrylate, 8 parts by mass of isobornyl acrylate, 1 part by mass of a photopolymerization initiator (Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals), and maleic acid-modified hydrogenated styrene-butadiene-styrene 30 parts by mass of a block copolymer was added and stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 2. As is clear from the results in Table 2, this photocurable composition has a low viscosity and a low ratio (V ₂ / V ₂₀ ) of 1.1, so that the screen printability is insufficient. . Moreover, this photocurable composition has a large mass reduction rate before and after UV curing.

[Comparative Example 3]
70 parts by mass of isononyl acrylate, 30 parts by mass of isobornyl acrylate, 0.5 parts by mass of photopolymerization initiator [Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals Co., Ltd.], hydrogenated styrene-butadiene-styrene block copolymer 5 parts by mass of the coalescence and 15 parts by mass of Aerosil silica were stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 2. As is clear from the results in Table 2, this photocurable composition has a low viscosity and insufficient screen printability. Furthermore, since this photocurable composition uses acrylates having 14 or less carbon atoms, the mass reduction rate before and after UV curing is extremely large, and the T-peel adhesive strength is also insufficient.

[Comparative Example 4]
100 parts by mass of isostearyl acrylate, 1 part by mass of a photopolymerization initiator [Irgacure (registered trademark) 819, manufactured by Ciba Specialty Chemicals Co., Ltd.], 5 parts by mass of a styrene-isobutylene diblock copolymer, and hydrogenated styrene butadiene rubber 5 A mass part was added, and it stirred with the high-speed stirrer, and prepared the photocurable composition. The results are shown in Table 2. As is apparent from the results in Table 2, this photocurable composition has a very low viscosity due to a small content of the saturated thermoplastic elastomer, and is inferior in screen printing suitability.

[Comparative Example 5]
100 parts by mass of isostearyl acrylate, 1 part by mass of a photopolymerization initiator (Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals), 25 parts by mass of a styrene-isobutylene triblock copolymer, and 15 parts by mass of a hydrogenated styrene butadiene rubber And 10 parts by mass of hydrogenated styrene-butadiene-olefin crystal block copolymer were added and stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 2. This photocurable composition is obtained by using a styrene-isobutylene triblock copolymer in place of the styrene-isobutylene diblock copolymer in the photocurable composition of Example 1. This photocurable composition had poor compatibility between the styrene-isobutylene triblock copolymer and other components, and was not a dispersion or dissolution of each component uniformly. Therefore, the evaluation test was not performed.

[Comparative Example 6]
100 parts by mass of isostearyl acrylate, 1 part by mass of a photopolymerization initiator [Irgacure (registered trademark) 819, manufactured by Ciba Specialty Chemicals Co., Ltd.], 50 parts by mass of a styrene-isobutylene diblock copolymer, 30 parts by mass of hydrogenated styrene butadiene rubber And 20 parts by mass of a hydrogenated styrene-butadiene-olefin crystal block copolymer were added and stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 2. This photocurable composition had a very high viscosity because the content of the saturated thermoplastic elastomer was too large. Therefore, the evaluation test was not performed.

[Comparative Example 7]
40 parts by weight of lauryl acrylate, 60 parts by weight of isobornyl acrylate, 1 part by weight of dimethylol tricyclododecane diacrylate, 1 part by weight of a photopolymerization initiator (Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals), polyacrylate 15 parts by mass and 15 parts by mass of aerosil silica were stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 3. As is clear from the results in Table 3, this photocurable composition has a low viscosity and insufficient screen printability. Furthermore, since this photocurable composition uses acrylates having 14 or less carbon atoms, the mass reduction rate before and after UV curing is extremely large, and the T-peel adhesive strength is also insufficient.

[Comparative Example 8]
40 parts by mass of isobornyl acrylate, 60 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of dimethylol tricyclododecane diacrylate, 1 part by mass of a photopolymerization initiator [Irgacure (registered trademark) 819 manufactured by Ciba Specialty Chemicals Co., Ltd.] 20 parts by mass of hydrogenated styrene butadiene rubber and 20 parts by mass of aerosil silica were stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 3. As is apparent from the results in Table 3, since this photocurable composition uses acrylates having 14 or less carbon atoms, the mass reduction rate before and after UV curing is extremely large, and the T-peel adhesive strength is extremely low. It is enough.

[Comparative Example 9]
8 parts by mass of isobornyl acrylate, 1 part by mass of photopolymerization initiator [Irgacure (registered trademark) 819] manufactured by Ciba Specialty Chemicals Co., Ltd., and styrene-isobutylene-styrene triblock co-polymer per 100 parts by mass of stearyl acrylate 30 parts by mass of the combined product was added and stirred with a high-speed stirrer to prepare a photocurable composition. The results are shown in Table 3. As is apparent from the results in Table 3, this photocurable composition had a high viscosity (V ₂ ) and a large viscosity ratio (V ₂ / V ₂₀ ), and was poor in screen printing suitability. Moreover, this photocurable composition has an adhesive strength that is too low to produce an adhesive strength evaluation sample.

(footnote)
(* 1) "NK ESTER S-1800A" (registered trademark) manufactured by Shin-Nakamura Kogyo Co., Ltd.
(* 2) "Light acrylate 1M-A" (registered trademark) manufactured by Kyoei Chemical Co., Ltd.
(* 3) "Light acrylate 1B-XA" (registered trademark) manufactured by Kyoei Chemical Co., Ltd.
(* 4) "Light acrylate DCP-A" (registered trademark) manufactured by Kyoei Chemical Co., Ltd.
(* 5) “Aronix M5300” (registered trademark) manufactured by Toagosei Co., Ltd.
(* 6) “Irgacure 819” (registered trademark) manufactured by Ciba Specialty Chemicals
(* 7) “SIBSTAR-042D” (registered trademark) manufactured by Kaneka Corporation
(* 8) "SIBSTAR-102T" (registered trademark) manufactured by Kaneka Corporation
(* 9) "DYNARON 1321P" (registered trademark) made by JSR
(* 10) "DYNARON 4600P" (registered trademark) made by JSR
(* 11) “Clayton G1657” (registered trademark) manufactured by Clayton Polymer Japan Co., Ltd.
(* 12) “Clayton FG1901X” (registered trademark) manufactured by Clayton Polymer Japan Co., Ltd.
(* 13) "High Milan 1652" (registered trademark) manufactured by Mitsui DuPont
(* 14) “Aerosil R976S” (registered trademark) manufactured by Nippon Aerosil Co., Ltd.
(* 15) Since each component was incompatible, no evaluation test was conducted.
(* 16) Since the viscosity is extremely high, no evaluation test was conducted.
(* 17) "Light acrylate SA" (registered trademark) manufactured by Kyoei Chemical Co., Ltd.
(* 18) “Light Acrylate LA” (registered trademark) manufactured by Kyoei Chemical Co., Ltd.
(* 19) Nippon Shokubai 2-ethylhexyl acrylate (* 20) Kaneka Co., Ltd. “SIBSTAR-073T” (registered trademark)
(* 21) "DYNARON 1320" (registered trademark) made by JSR
(* 22) 4580 made by No-Tape Industries
(* 23) Adhesive strength was too low to produce an adhesive strength evaluation sample.

  The photocurable composition of the present invention can be used in various applications including sealing materials that require sealing properties, adhesion to adherends, chemical resistance, and the like. The photocurable composition of the present invention can be particularly suitably used as a sealing material for wet organic solar cells. The wet organic solar cell in which the electrolytic solution is encapsulated with the photocurable composition of the present invention is excellent in reliability and durability, and can be used for a sealing layer for encapsulating a new solar cell electrolytic solution. it can.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent conductive film 3 Dye 4 Metal oxide semiconductor layer 5 Electrolytic solution 6 Sealing layer 7 Conductive film 8 Substrate 9 Circuit 10 Load 11 Circuit

Claims (9)

A photocurable composition containing a monofunctional (meth) acrylate, a saturated thermoplastic elastomer, and a photopolymerization initiator,
(A) The monofunctional (meth) acrylate is an alicyclic or aliphatic monofunctional (meth) acrylate having 15 to 26 carbon atoms,
(B) The saturated thermoplastic elastomer contains a styrene-isobutylene diblock copolymer in a proportion of 40% by mass or more based on the total mass of the saturated thermoplastic elastomer,
(C) The content ratio of the saturated thermoplastic elastomer is in the range of 30 to 80 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate,
(D) The content ratio of the photopolymerization initiator is in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate,
(E) Using a viscoelasticity measuring apparatus equipped with a cone plate having a diameter of 25 mm as a measuring jig, the viscosity (V) of the photocurable composition measured under conditions of a temperature of 23 ° C. and a rotation speed of the cone plate of 2 rpm. ₂ ) is in the range of 30 to 300 Pa · s, and
(F) Ratio of the viscosity (V ₂ ) to the viscosity (V ₂₀ ) of the photocurable composition measured using the viscoelasticity measuring device at a temperature of 23 ° C. and a rotation speed of the cone plate of 20 rpm. _(V 2 _{/ V 20)} is a photocurable composition, characterized in that in the range of 1.3 to 20.   The photocurable composition of Claim 1 which further contains a polyfunctional (meth) acrylate in the ratio to 10 mass parts with respect to 100 mass parts of this monofunctional (meth) acrylate.   The photocurable composition according to claim 1 or 2, further comprising a carboxyl group-containing (meth) acrylate at a ratio of up to 10 parts by mass with respect to 100 parts by mass of the monofunctional (meth) acrylate. A circular coating film having a thickness of 100 μm and a diameter of 50 mm made of a photocurable composition formed on a plastic film is irradiated with ultraviolet rays having an energy flux density of 270 mW / cm ² for 5 seconds from a high-pressure mercury lamp, and the coating film is photocured. The photocuring according to any one of claims 1 to 3, wherein a reduction rate of the mass of the coating film after photocuring with respect to the mass of the coating film before ultraviolet irradiation is 1.50% or less. Sex composition.   For a sample in which two “transparent substrates / transparent conductive films” face each other on the side of each transparent conductive film and bonded together via a photocured material layer having a thickness of 100 μm formed from a photocurable composition, The photocurable composition according to any one of claims 1 to 4, wherein the T-peel adhesive strength measured under conditions of a relative humidity of 50% and a speed of 50 mm / min is 0.65 N / 10 mm or more.   Use of the photocurable composition according to any one of claims 1 to 5 as a sealing material for wet organic solar cells.   A wet organic solar cell having a structure in which a photoelectric conversion layer made of an organic compound is disposed in an electrolyte solution sealed between two substrates via a sealing layer, wherein the sealing layer is any one of claims 1 to 5. A wet organic solar cell comprising a photocured material layer formed from the photocurable composition according to claim 1.   The wet-type organic solar cell is a dye-sensitized solar cell having a structure in which a photoelectric conversion layer made of an organic dye is disposed in an electrolytic solution sealed between two substrates via a sealing layer. The wet organic solar cell as described.   The dye-sensitized solar cell includes a first conductive substrate having a layer configuration of “transparent substrate / transparent conductive film / metal adsorbed metal oxide semiconductor film” and a second substrate facing the first conductive substrate Are arranged via a sealing layer provided in a frame shape around the two substrates, and a dye-sensitized solar having a structure in which an electrolyte is sealed in a gap between the two substrates formed by the sealing layer The wet organic solar cell according to claim 8, which is a battery.

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