JP2017189924A - Method for manufacturing laminate and method for manufacturing transparent conductive substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent electrode substrate that includes a fine patterned electrode having high uniformity of wiring width and a low resistance on a transparent substrate.SOLUTION: A receptive release layer comprising solid particles, an organic resin and a polymerizing agent is formed on a surface of a release film; a patterned electrode is formed by screen printing using a conductive paste comprising a conductive powder on the receptive release layer; a transparent resin layer and a transparent substrate are formed thereon; the release film and the receptive release layer are removed; and then a transparent electrode is formed. By printing the patterned electrode on the receptive release layer, a conductive substrate having an embedded electrode having a good shape and no bleeding can be obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transparent conductive film that can be used for an organic thin film solar cell, a dye-sensitized solar cell, an organic EL element, and the like, and a method for producing the same.

  Transparent electrodes are used on the light-receiving surface side of photoelectric conversion elements such as organic thin-film solar cells (OPV) and dye-sensitized solar cells (DSC), and on the light-emitting surface side of light-emitting elements such as organic EL elements (OLED). Organic thin-film solar cells are expected to be applied in various fields due to the advantages of low power generation efficiency, low manufacturing cost, light weight and bendability. Therefore, it is necessary for the transparent electrode not to impair these advantages.

  For example, as shown in FIG. 6, the organic thin film solar cell is a light-receiving surface in which a functional layer having a stacked structure of a hole transport layer 101, an active layer 102, and an electron transport layer 103 is formed on a transparent substrate 104. It has a structure sandwiched between a transparent electrode 105 and an aluminum electrode 106 which is the counter electrode. In recent years, an organic thin film solar cell having an inverted structure in which the stacking order of the hole transport layer 101 and the electron transport layer 103 is reversed has been developed.

  The transparent electrode requires high light transmittance (80% or more) and low sheet resistance (5Ω / □ or less), so indium tin oxide (ITO) is often used, but the resistance of the transparent electrode is lowered. Therefore, it is necessary to set the film thickness of ITO to 300 to 400 nm. However, since expensive indium is used, there is a problem that the manufacturing cost is increased and the ITO film is hard, so that the flexibility is lowered and the advantages of the organic thin film solar cell are impaired. Therefore, in place of the thick ITO film, an electrode in which a thin ITO film is laminated as a collecting electrode on a grid-like (lattice-like) metal pattern electrode has been developed.

  In many cases, a transparent electrode substrate used in an organic thin film solar cell or the like forms a collecting electrode on a flexible transparent substrate. Inexpensive and flexible materials for this transparent substrate are often those having a heat resistance of about 150 ° C. such as PET. Therefore, the pattern electrode formed on the current collecting electrode is preferably formed by a low temperature process of 150 ° C. or lower. This is because if it can be formed at a low temperature, a wide variety of materials can be selected as the transparent substrate, and it can be used for various applications.

  In order to reduce the manufacturing cost of products such as organic thin-film solar cells, it is important to pattern the pattern electrodes at a low cost, and screen printing can be used as a patterning method. Screen printing is a printing method in which a conductive paste (metal paste) containing conductive powder such as metal is attached to a transparent substrate that is a printing object through an opening pattern portion drawn on a screen printing plate. It is.

  However, since the ITO film formed on the pattern electrode is usually formed by the PVD method, the ITO film is interrupted at the step portion of the grid-like pattern electrode, and a continuous ITO film may not be formed. Therefore, Patent Document 1 and Patent Document 2 disclose a method for eliminating the level difference of the grid-shaped pattern electrode.

Special table 2013-524536 gazette JP2013-102055A

  In recent years, energy conservation has been promoted. Low-temperature process technology that achieves both improvement of light transmittance of transparent electrode and reduction of sheet resistance in a flexible substrate to improve power generation efficiency of organic thin-film solar cells. Development is underway. In particular, many flexible and low-cost materials have poor heat resistance as described above, and it is difficult to perform high-temperature heat treatment (firing) at about 500 ° C. for the purpose of reducing wiring resistance. It is important to realize both the thinning of the electric electrode and the low resistance by a low temperature process.

  Although Patent Document 1 describes that a metal electrode is dispersed in a solvent and a grid electrode is formed by coating, an electrode wiring having a certain width and a specific resistance (volume resistivity) are realized. It is unclear whether it can be done or under what conditions.

  Although Patent Document 2 discloses a specific method of forming a pattern electrode wiring using a screen printing method, the minimum wiring width of the pattern electrode (grid electrode) is about 50 [μm], and further fine wiring No technology has been disclosed up to forming with low resistance and good reproducibility.

  The present invention has been made in consideration of these points. By ensuring the aspect ratio and making the line width uniform, a pattern electrode wiring having a low resistance can be obtained even in a fine line width of 50 [μm] or less. It aims at providing the manufacturing method which can manufacture the transparent conductive base material provided, and the transparent conductive base material with a low-temperature process at low cost.

  The transparent conductive substrate according to the present invention can be effectively used for, for example, a photoelectric conversion device such as an organic solar cell or a display device, but its use is not limited and can be used for a wide variety of other purposes. Is possible. In addition, the present invention can find particularly superiority on a flexible transparent substrate having poor heat resistance, but it goes without saying that the present invention can also be applied to a substrate having high heat resistance.

The transparent conductive substrate according to the present invention is
A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
The specific resistance is 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm] on the surface of the transparent resin layer opposite to the transparent substrate, and the aspect ratio is 0 when the wiring width is 15 to 50 μm. A printed pattern electrode that is 15-0.5;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the current collecting electrode is flat.

The transparent conductive substrate according to the present invention is
A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
On the surface of the transparent resin layer opposite to the transparent substrate, the specific resistance is 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm], and the wiring width is 15 to 50 [μm]. A saddle-shaped cross-sectional shape,
Printed pattern electrodes;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the current collecting electrode is flat.

  The uniformity of the wiring width of the pattern electrode of the transparent conductive substrate according to the present invention is 25% or less when the wiring width is 15 to 50 [μm].

Furthermore, the transparent conductive substrate according to the present invention is:
The patterned electrode comprises a granular conductive powder having an average particle size in the range of 0.1 to 10 [μm], a flaky conductive powder in the range of 2 to 20 [μm], and a thermosetting resin. It is an electrode formed by screen printing the conductive paste contained. In addition, it is clear that it is impossible or difficult to specify the transparent conductive base material based on this invention, without using the above manufacturing methods.

  In addition, the ratio of the conductive powder of the conductive paste and the thermosetting resin is 90:10 to 96: 4 by weight.

  By adopting such a configuration, a pattern electrode having a low resistance and a good uniformity of the wiring width can be formed at a low cost by a screen printing method even in a pattern electrode wiring having a line width of 50 μm or less. It is possible to provide a transparent electrode capable of preventing a decrease in light transmittance and realizing a low sheet resistance. In addition, since the pattern electrode can be formed by a low-temperature process, it is possible to form a pattern on a flexible, low-cost, inferior heat-resistant film, increasing the choice of film, and various types of organic solar cells, etc. Application to products is possible at low cost. Furthermore, by setting the weight ratio of the conductive paste particles and flaky conductive powder to the thermosetting resin such as epoxy resin to 90:10 to 96: 4, a low resistance pattern electrode is formed by screen printing. can do.

The method for producing a transparent conductive substrate according to the present invention includes:
Forming a receptive release layer containing solid particles on the surface of the release film;
A step of printing a pattern electrode using a conductive paste;
Forming a transparent resin layer on the surface of the receptive release layer and the pattern electrode;
Laminating a transparent substrate on the transparent resin layer;
Peeling the release film and the receptive release layer;
And forming a transparent current collecting electrode on the surface of the transparent resin layer and the pattern electrode.

  The average particle size of the solid particles is 1/10 to 1/100 of the average particle size of the conductive powder.

  With such a manufacturing method, a pattern electrode wiring having a low resistance, a narrow line width, good wiring width uniformity, and no bleeding is obtained, for example, even for a substrate that does not allow high temperature heat treatment such as PET. It is possible to provide a method for manufacturing a transparent conductive substrate that can be formed by a low-temperature process of less than or equal to ° C. and can be applied to various products. The conductive paste is a conductive powder selected from Ag (silver), Cu (copper), Al (aluminum), Au (gold), Pt (platinum), W (tungsten), C (carbon), and the like. The solid particles are selected from inorganic particles such as silica and alumina, and organic particles formed from a polymer, and the average particle diameter of both is the above relationship, so that the solvent of the conductive paste can be quickly received. The layer absorbs and a patterned electrode having a good shape and a low specific resistance can be formed.

Sectional drawing of the main manufacturing process of the transparent conductive base material which concerns on this invention. The surface SEM image photograph which shows the composition dependence of a receptive release layer surface state. The surface photograph which shows the release layer existence dependence of the wiring shape of a pattern electrode. Sectional drawing of the main manufacturing process of the transparent conductive base material which concerns on this invention. Sectional drawing of the transparent conductive base material which concerns on this invention. Sectional drawing of an organic thin-film solar cell.

FIG. 1 shows a cross section of a main manufacturing process of a transparent conductive substrate according to an embodiment of the present invention.
As shown in FIG. 1 (a), a receptive release layer 2 is applied to the surface of a release film 1, for example, a flexible substrate such as a cyclic polyolefin having a thickness of 50 [μm] or PET film, such as gravure coating or die coating. For example, 1 [μm] is formed by a coating technique, dried by hot air, for example, 50 ° C. to 120 ° C., blown, or the like, and then cured by UV irradiation.

  The material for forming the receptive release layer 2 is a polyfunctional acrylic monomer (TMPTA, DPHA, PETA, etc.) that is an acrylic resin and solid particles such as inorganic particles such as silica and alumina, and polymers such as polystyrene. Containing formed organic particles. When using inorganic particles, it is desirable to add polymethylphenylsilane (PMPS) in order to adhere the acrylic resin and the inorganic particles. In this case, PMPS also works as a photopolymerization initiator, but a photopolymerization initiator may be added separately. Furthermore, in order to improve the releasability described later, a silane coupling agent (for example, FOTES) having a fluorine functional group and polymerized with silane or acrylic, a surfactant, or an acrylic monomer may be added.

  Moreover, in order to improve the compatibility between PMPS and the acrylic monomer, a solvent such as toluene or PGMEA may be added.

  The receptive release layer 2 formed by the above method is a porous film containing solid particles as a main component, and has a mechanical strength that can withstand a peeling process described later.

  When polymethylphenylsilane is used as a photopolymerization initiator, silica particles can be preferably used as the solid particles to be added. This is because polymethylphenylsilane is cured to form a silicon oxide and thus has an effect of bonding silica particles and an acrylic resin. As the silica particles, for example, PL-1 (average particle size 15 nm) or PL-7 (average particle size 70 nm) manufactured by Fuso Chemical Industry Co., Ltd., which is a silica dispersion using a commercially available organic solvent, can be used.

  As the solid particle diameter, a size of the order of 10 nanometers is preferably used as in the above specific example. The average particle size of the solid particles is preferably sufficiently smaller than the average particle size of the conductive powder (metal powder or the like) contained in the conductive paste and is about 1/10 to 1/100.

  By setting the relationship between the average particle size of such solid particles and conductive powder, the conductive powder is not absorbed in the porous receptive release layer 2 as described later, and is contained in the conductive paste. This is because the low-viscosity solvent that is used is absorbed by capillary action.

  The filling rate of the solid particles of the receptive release layer 2 depends on the size of the solid particles contained in the material and the content of the solid particles, and the size and density of the pores formed in accordance with the size are determined accordingly. To do.

  Next, as shown in FIG. 1 (b), a conductive paste in which conductive powder is dispersed, for example, a silver paste, is screen-printed on the receptive release layer 2 by a screen printing method, dried by heat treatment, and patterned. The electrode 3 is formed. As a printing plate used for screen printing, for example, a stainless steel mesh formed with a photosensitive resin and having a pattern shape corresponding to the pattern electrode 3, for example, a grid shape, is used. As an example, a pattern shape corresponding to the pattern electrode 3, such as a grid shape, is formed with a photosensitive resin on a stainless steel mesh having a wire diameter of 16 [μm] and a pitch of 51 [μm] (# 500 mesh). Is used.

  Note that the pattern is not limited to a grid shape, and other patterns such as a stripe shape, an arc shape, a honeycomb shape, and a random pattern can be used according to customer applications.

  Drying conditions by heat treatment of the conductive paste after screen printing are, for example, 100 ° C. to 300 ° C., 30 to 60 minutes, and the specific resistance of the conductive wiring (pattern electrode 3) formed at a high temperature for a long time becomes low. Tend. However, when heat treatment at 150 ° C. or higher is performed, a film or substrate material that does not have heat resistance against these heat treatment conditions cannot be used. Therefore, by using a conductive paste that can be dried at a lower temperature, choices of types of films and base materials that can be adopted as the release film 1 are greatly expanded.

  Moreover, the higher the heat treatment temperature, the stronger the adhesion between the pattern electrode 3 and the receptive release layer 2, and the problem that the peeling characteristics deteriorate may occur. By shortening the drying process at a lower temperature and in a shorter time, the processing time of the heat treatment process including the temperature rise / fall time is shortened, thereby improving the processing capability of the heat treatment apparatus and reducing the manufacturing cost. .

  The low-resistance conductive paste that can be used in the present invention needs to be highly filled with conductive powder (conductive powder) / (conductive powder + epoxy resin component) × 100 ≧ 90 [wt. %]. In order to obtain such a highly filled composition, as the conductive powder, for example, a spherical powder having an average particle diameter of 0.1 to 10 [μm] and a size having an average particle diameter of 2 to 20 [μm] are used. A conductive powder that can be filled with a tap density of 5.0 to 5.5 [g / cc] is used. Examples of the material of the conductive powder (particles) include Ag (silver), Cu (copper), Al (aluminum), Au (gold), Pt (platinum), W (tungsten), and C (carbon). .

  Furthermore, the resin can be composed of two different types of resins (for example, a combination of liquid epoxy resins having different viscosities, a combination of a solid epoxy resin and a liquid epoxy resin at room temperature), a curing agent, and a solvent.

  By optimizing the blend and tap density of the flaky powder and the spherical powder of the conductive powder contained in the conductive paste, such as the silver paste, and the blend of the epoxy resin composition and the curing agent having different viscosities, 120 The pattern electrode 3 having a low specific resistance can be formed even under heat treatment conditions at 15 ° C. for 15 minutes.

  A particularly suitable conductive paste for forming (printing) the low-resistance pattern electrode 3 is, for example, a spherical conductive powder having an average particle size of 0.1 to 10 [μm] and an average particle size of 2 to 20 As a mixed powder with a flaky conductive powder having a size of [μm], the conductive powder having a tap density of 5.0 to 5.5 [g / cc], and a resin (thermosetting resin), Using an epoxy resin blend in which the epoxy equivalent of the mixture is 130-800, or a mixture of two or more types of epoxy resins, the blending ratio of conductive powder and epoxy resin [(conductive powder) / (Conductive powder + epoxy resin component) × 100] is 90 to 96 [wt. %]. The average particle size of the powder referred to here is obtained by measurement by microtrack measurement (microtrack particle size distribution measuring device). The particle size measurement is not limited to the microtrack measurement, and a method capable of measuring the equivalent particle size may be used.

  In addition, flake-shaped powder is a shape having a two-dimensional spread, it can be paraphrased in the form of flakes or scales, even when partially uneven and seen deformation, when viewed as a whole, It is sufficient that the powder has a shape close to a flat plate or thin rectangular parallelepiped, and a spherical powder has a three-dimensional shape that is closer to a cube than a rectangular parallelepiped when viewed as a whole, even if there are irregularities and deformation is seen partially. Any powder may be used. Moreover, the resin, the hardening | curing agent, and the solvent can utilize the well-known thing used for the electrically conductive paste.

Furthermore, the blending ratio of the two different types of resins affects the mechanical strength of the printed pattern electrode and the contact (electric resistance) between conductive powders (metal powders, etc.) due to curing shrinkage of the resin. Therefore, by optimizing the mixing ratio of these two kinds, low specific resistance (volume specific resistivity) as described later even by thermal drying at low temperature (100 to 150 ° C.) and short time (15 to 30 minutes) Can be realized.
In addition, specific resistance (rho) can be measured by a normal method. That is, the resistance value R at both ends of the rectangular pattern is measured at a temperature of 25 ° C., and the width W, the length L, and the film thickness T measured by the step meter can be calculated from the relational expression of ρ = RWT / L.

As shown in Table 1, the specific resistance of the conductive wiring formed by curing the optimal conductive paste (silver paste) realizes a low value of 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm]. be able to. In Table 1, paste examples 1 to 6 are conductive pastes that satisfy the conditions for the conductive paste, while comparative example 1 has a lower tap density than the above conditions, and comparative example 2 has a lower blending ratio than the above conditions. It is a paste. The paste examples 1-6 have a specific resistance lower than the comparative examples 1 and 2, and it can be understood that the value is 8 * 10 < ^-6 > ^-5 * 10 < ^-5 > [ohmcm].

Table 1. Dependence of resistivity on conductive paste

  The viscosity of the conductive paste can be adjusted by the solvent to be added. In screen printing, the conductive paste is printed on the receptive release layer 2 through the openings in the plate mesh. If the viscosity of the conductive paste is too high, the fluidity decreases and the conductive paste does not completely enter the opening of the printing plate, and the conductive paste is interrupted by the stainless steel wire constituting the mesh. It is necessary to add as much solvent as possible.

  However, when the fluidity is increased, the conductive paste spreads on the surface of the substrate to be printed, and the bleeding phenomenon occurs, making it difficult to control the thin line width, and the resulting wiring width is uneven, uneven surface and A cross-sectional shape is obtained, and the film thickness of the pattern electrode wiring also decreases.

  Therefore, it has been difficult to form a thin line width of 50 [μm] or less, particularly 30 [μm] or less, and it is difficult to form a pattern with a uniform line width. ), The shape of the non-uniform line width was repeated, and a thin line as designed could not be formed. That is, the boundary lines on both side surfaces of the wiring do not become two parallel straight lines, and the printing performance is low. Further, since the line width becomes narrower and the film thickness becomes thinner at the constricted portion, the resistance value of the pattern electrode 3 increases, and at the swollen portion, the aperture ratio of the pattern electrode 3 decreases, and the transparent conductive base material transmits light. The rate will be reduced.

  However, in the present invention, since the pattern electrode can be formed on the receptive release layer 2 by the screen printing method using the conductive paste, it is possible to use the conductive paste with improved fluidity. Become.

  FIG. 2 shows, by screen printing using a conductive paste (silver paste), (a) a patterned electrode formed on a release film on which the receptive release layer 2 is not formed, and (b) the receptive release layer 2. It compares and shows the shape of the pattern electrode formed on the release film 1 provided with. Screen printing is performed using a printing plate in which a groove opening pattern having a width of 24 [μm] is formed of a photosensitive resin, and the mesh of the printing plate is a wire diameter of 16 μm and a pitch of 51 [μm] (# 500 mesh). A stainless steel mesh was used. The line width of the pattern electrode was 34.4 [μm] when the receptive release layer 2 was not provided, but 22.3 [μm] on the release film having the receptive release layer 2 was almost printed. The value was equal to the line width of the plate, and it was confirmed that a pattern electrode having a good shape as designed could be printed. The line width is defined by the maximum width of the formed pattern electrode.

  Further, it can be understood that when the receptive release layer 2 is provided on the release film 1, the wiring pattern shape is clearly improved and the non-uniformity of the wiring width can be eliminated. As an index for evaluating the uniformity of the pattern wiring width, a value obtained by dividing the difference between the maximum line width and the minimum line width by the printing plate line width was used. It can be seen that the value of the conventional pattern electrode is 50 to 100 [%] for a line width of 50 [mu] m or less, but is reduced to 25 [%] or less in the present invention, which is greatly improved.

The reason why bleeding is eliminated in this way is considered as follows.
By setting the average particle size of the solid particles contained in the receptive release layer 2 to a value sufficiently smaller than the average particle size of the conductive powder contained in the conductive paste, that is, a value two orders of magnitude smaller, Only the solvent content is sucked into the receptive release layer 2. As a result, the elasticity of the conductive paste (resin and conductive powder) remaining without being absorbed in the receptive release layer 2 is increased and the wet paste does not spread.

  Therefore, if the occurrence of bleeding cannot be prevented in the profile of the wiring end, the cross section of the printed wiring side (from the boundary with the substrate to the point of the maximum film thickness) has a tail shape, By preventing the occurrence, the printed wiring can realize a shape without a tail. According to this embodiment, it is possible to form for the first time an electrode wiring having a fluidity that can pass through a narrow screen mesh and having a cross-sectional shape that does not skirt.

  In the present specification, the skirting is a portion where the portion connected to the substrate at the wiring end portion is connected with a gentle inclination, and the shape without the skirting is specifically 20 [% of the maximum thickness of the wiring. ] Means that the area (width) with a thickness less than] is 20% or less with respect to the line width.

  Further, as described above, since the skirting is caused by the bleeding phenomenon, the profile of the wiring cross section changes greatly at the boundary portion between the bleeding portion and the other portion, and the sign of the curvature radius changes.

Thus, the cross-sectional shape of the pattern electrode 3 formed on the receptive release layer 2 is a saddle shape, the aspect ratio is 0.15 to 0.5 when the wiring width is 15 to 50 [μm], The aspect ratio in a width of 15 to 30 [μm] is 0.15 to 0.20, and the aspect ratio in a line width of 30 to 50 [μm] is 0.20 to 0.50. Therefore, compared with the pattern electrode formed by the conventional method, a thick pattern electrode can be formed, the resistance of the pattern electrode 3 can be lowered, and the light transmittance can be improved.
Note that the saddle type is a straight line at the interface between the transparent electrode, which will be described later, and the pattern electrode, and the width of the pattern electrode parallel to this interface is the maximum at the interface part, and gradually increases as the distance from the interface increases. The shape of the pattern electrode and the transparent resin layer does not have a sharp point, and this shape avoids stress concentration when bending products such as organic thin-film solar cells. Damage to the layer and pattern electrode can be prevented.

Thus, the pattern electrode formed by the process which used the electroconductive paste which can obtain the low specific resistance of 8 * 10 < ^-6 > ^-5 * 10 < ^-5 > [ohmcm], and prevented the bleeding by adoption of the receptive release layer 2 A transparent conductive film having a low surface resistance of 5 [Ω / □] or less can be obtained.

  Further, in the present invention, since the receptive release layer 2 is configured to be finally removed, a material having sufficient solvent absorption characteristics and having an effect of preventing bleeding without being restricted by the light transmittance. You can choose.

  That is, even if irregular reflection occurs due to the solid particles contained in the receptive release layer 2 or the light transmittance of the solid particles themselves is low, the solid particles are formed on the pattern electrode 3 and the transparent resin layer together with the receptive release layer 2. Therefore, solid particles of a level that does not affect the light transmittance of the transparent conductive substrate or cause an increase in resistance due to a decrease in contact area with the transparent electrode do not remain. The state of removal of the solid particles may be confirmed by optical means such as a microscope, and the remaining solid particles that are detected only by microanalysis such as TEM do not affect these characteristics.

  FIG. 3 is an SEM image of the surface of the receptive release layer formed by changing the content of silica particles in the composition of the material forming the receptive release layer. As a dispersion of silica particles, PL-1-Tol (silica particle diameter: 10 to 15 nm, concentration: 20 [Wt%], organic solvent: toluene) manufactured by Fuso Chemical Industry Co., Ltd. was used as an example. FIG. 3A shows a material (release layer condition 1) in which 100 [mg] each of PMPS (polysilane) and TMPTA (acrylic resin) is added to the amount of PL-1-Tol of 2.5 [g]. FIG. 3B is a surface SEM photograph of a receptive release layer formed of a material (release layer condition 2) in which 150 [mg] each of PMPS (polysilane) and TMPTA (acrylic resin) are blended.

  Clearly, there is a difference in the surface morphology between the two, and in FIG. 3 (a) where the content of silica particles is larger, the number of voids observed on the surface is larger, and the higher the content of silica particles, the more porous It can be understood that it becomes a film. Thus, although there exists a tendency which becomes cloudy by the light scattering resulting from a void, since the receptive release layer 2 is removed, it is not necessary to worry about the influence.

  On the receptive release layer 2 formed under these release layer conditions 1 and 2, a thin line pattern was printed using a conductive paste, and the shapes were compared. As a result, the wiring on the receptive release layer 2 formed under the release layer condition 1 has a uniform wiring width and no constriction or swelling, and exhibits a good wiring shape, but the receptive release layer formed according to the release layer condition 2 The wiring on No. 2 was not uniform in width, and constriction and swelling were observed. It is considered that the uniformity of the line width of the wiring is improved because the larger amount of holes on the surface of the receptive release layer 2 absorbs the solvent of the silver paste more efficiently. The photograph shown in FIG. 2 (b) is one using the receptive release layer of FIG. 3 (a).

  In the above example, when a material containing 100 [mg] of PMPS and TMPTA is used for forming a receptive release layer for a PL-1-Tol amount of 2.5 [g], a good wiring shape is obtained. Although it could be obtained, the blending amount also depends on the silica particle diameter. When a silica dispersion having a large silica particle diameter is used, the amount of PMPS and TMPTA can be increased. By increasing the amount of resin, the bond between the solid particles of the receptive release layer 2 is strengthened, and the mechanical strength against peeling is also improved. What is necessary is just to optimize the compounding of each resin corresponding to a silica particle diameter and it.

  Further, in order to adjust the release characteristics, it is possible to adjust the peel strength by adding a fluorine additive to the receptive release layer 2. Examples of the fluorine additive include FOTES, but are not limited thereto.

  The receptive release layer 2 needs to have a peeling property in a subsequent process, but can be applied at a low heat drying temperature by optimizing the composition of the conductive paste, thus preventing deterioration of the peeling property. Can do.

  In the above description, the example in which the pattern electrode is formed on the release film 1 having poor heat resistance by low-temperature drying of the conductive paste has been described. However, the release film 1 is made of a heat-resistant material such as glass. Using a film, the conductive paste (eg, silver paste) may be dried at a high heat treatment temperature (eg, 150 ° C. to 300 ° C.), and may be further baked (eg, 400 to 600 ° C.) in some cases. This is because heat-resistant silica or alumina can be used as the solid particles of the receptive release layer 2 and the silica component derived from PMPS binds the particles.

  As the conductive material used for the conductive powder of the conductive paste, other metals such as copper, gold, aluminum, platinum, tungsten, and carbon may be used.

  Next, as shown in FIG. 1 (c), the transparent resin layer 4 is, for example, 15 [μm] by coating the receptive release layer 2 and the pattern electrode 3 with an acrylic ultraviolet (UV) curable resin. Form. The transparent resin layer 4 can be made of an acrylic resin or a transparent resin such as an ester resin, a silicone resin, or an epoxy resin. Moreover, the surface of the pattern electrode 3 can be covered by making the film thickness thicker than the pattern electrode 3. The pattern electrode 3 has a structure covered with the transparent resin layer 4 except for the contact surface with the receptive release layer 2, but the surface of the pattern electrode 3 is flat (the cross section is linear, ie, transparent resin) due to the fluidity of the transparent resin layer 4. Shape without a step with the layer).

  The resin used for forming the transparent resin layer 4 is preferably a UV curable resin. The transparent resin layer 4 may be a single layer or may be composed of a plurality of layers.

  Further, an adhesive layer may be formed on the transparent resin layer 4 by coating or printing.

  In addition, when the transparent resin layer 4 is formed by printing, since the transparent resin layer 4 is formed only immediately above the area where the pattern electrode 3 is printed, there is an advantage that the material cost is reduced.

  Next, as shown in FIG. 1D, a base material 5 made of a PET film having a thickness of 50 to 250 μm is laminated (laminated). The base material 5 is PET, PEN, COP, PC (polycarbonate), PMMA (acrylic), PI (polyimide), LCP (liquid crystal polymer) and other flexible plastic films, and a flexible film of 200 μm or less. A certain glass substrate (so-called glass film) can be used. As described above, since the transparent resin layer 4 has fluidity, the interface between the transparent resin layer 4 and the substrate 5 is flat.

  Moreover, you may form a 1-10 micrometers abrasion-resistant layer (hard coat), a 100-150 nm antireflection layer, and a gas barrier layer on the base material 5. FIG. This improves the abrasion resistance, total light transmittance, and gas barrier properties of the transparent electrode substrate. Further, the transparent substrate 2, the wear-resistant layer, and the antireflection layer may contain an ultraviolet (UV) absorber.

  Thereafter, the transparent resin layer 4 is cured. When a UV curable resin is used as the transparent resin layer 4, ultraviolet rays (UV) are irradiated from the substrate 5 side toward the transparent resin layer 4. Since the transparent resin layer 4 is cured after the base material 5 is formed, the influence of deformation due to the shrinkage of the transparent resin layer 4 during the curing process is reduced, and a step between the pattern electrode 3 and the transparent resin layer 4 is less likely to occur.

  Next, as shown in FIG. 4 (a), the release film 1 and the receptive release layer 2 are peeled off at the interface between the transparent resin layer 4 and the pattern electrode 3 and the receptive release layer 2 to obtain a transparent resin. The layer 4 and the pattern electrode 3 are exposed.

  The exposed surfaces of the pattern electrode 3 and the transparent resin layer 4 are flush. Moreover, the surface other than the exposed surface of the pattern electrode 3 is surrounded by the transparent resin layer 4. Therefore, the pattern electrode 3 is embedded in the transparent resin layer 4.

  The receptive release layer 2 has sufficient mechanical strength against peeling as described above, and does not break in the peeling process. Moreover, you may adjust the intensity | strength required for peeling with a fluorine additive.

  Next, as shown in FIG. 4B, a transparent conductive film 6, for example, an ITO film is formed as a collecting electrode on the exposed surfaces of the transparent resin layer 4 and the pattern electrode 3. The transparent conductive film 6 only needs to be transparent and conductive. In addition to the ITO-based film, the ZnO-based, SnO2-based, TiO2-based, conductive polymer (PEDOT / PSS), metal nanowire (MNW), carbon nanotube ( CNT), graphene, and the like, or a combination thereof can be used. The transparent conductive film 6 may be composed of a single layer or a plurality of layers.

  If the ITO film thickness of the transparent conductive film 6 is too thin, the resistance will be high, and if it is too thick, the manufacturing cost will increase and the flexibility will be impaired, so it is preferably 10 to 150 nm, and preferably 10 to 30 nm. More preferably.

FIG. 5 is a cross-sectional structure diagram of the transparent conductive substrate at the stage of the process of FIG. 4B when the transparent resin layer 4 is formed by a printing method. Since the transparent resin layer 4 is formed only on the pattern electrode 2 formation region by printing, the transparent resin layer 4 is partially formed on the substrate 5. When the conductive substrate is transferred to a final product, for example, a light-receiving surface of an organic solar cell or a light-emitting surface of an organic EL element, a region where the pattern electrode 2 and the transparent resin layer 4 are laminated is used.
Therefore, when the transparent conductive film 6 is formed on the entire surface by vapor deposition or the like, there is a step at the boundary between the region where the pattern electrode 2 and the transparent resin layer 4 are laminated and the other region, but there is a problem in actual use. There is no.

DESCRIPTION OF SYMBOLS 1 Release film 2 Receptive release layer 3 Pattern electrode 4 Transparent resin 5 Base material 6 Transparent electrically conductive film 101 Hole transport layer 102 Active layer 103 Electron transport layer 104 Transparent base material 105 Transparent electrode 106 Aluminum electrode

  The present invention relates to a transparent conductive film that can be used for an organic thin film solar cell, a dye-sensitized solar cell, an organic EL element, and the like, and a method for producing the same.

  Transparent electrodes are used on the light-receiving surface side of photoelectric conversion elements such as organic thin-film solar cells (OPV) and dye-sensitized solar cells (DSC), and on the light-emitting surface side of light-emitting elements such as organic EL elements (OLED). Organic thin-film solar cells are expected to be applied in various fields due to the advantages of low power generation efficiency, low manufacturing cost, light weight and bendability. Therefore, it is necessary for the transparent electrode not to impair these advantages.

  For example, as shown in FIG. 6, the organic thin film solar cell is a light-receiving surface in which a functional layer having a stacked structure of a hole transport layer 101, an active layer 102, and an electron transport layer 103 is formed on a transparent substrate 104. It has a structure sandwiched between a transparent electrode 105 and an aluminum electrode 106 which is the counter electrode. In recent years, an organic thin film solar cell having an inverted structure in which the stacking order of the hole transport layer 101 and the electron transport layer 103 is reversed has been developed.

  The transparent electrode requires high light transmittance (80% or more) and low sheet resistance (5Ω / □ or less), so indium tin oxide (ITO) is often used, but the resistance of the transparent electrode is lowered. Therefore, it is necessary to set the film thickness of ITO to 300 to 400 nm. However, since expensive indium is used, there is a problem that the manufacturing cost is increased and the ITO film is hard, so that the flexibility is lowered and the advantages of the organic thin film solar cell are impaired. Therefore, in place of the thick ITO film, an electrode in which a thin ITO film is laminated as a collecting electrode on a grid-like (lattice-like) metal pattern electrode has been developed.

  In many cases, a transparent electrode substrate used in an organic thin film solar cell or the like forms a collecting electrode on a flexible transparent substrate. Inexpensive and flexible materials for this transparent substrate are often those having a heat resistance of about 150 ° C. such as PET. Therefore, the pattern electrode formed on the current collecting electrode is preferably formed by a low temperature process of 150 ° C. or lower. This is because if it can be formed at a low temperature, a wide variety of materials can be selected as the transparent substrate, and it can be used for various applications.

  In order to reduce the manufacturing cost of products such as organic thin-film solar cells, it is important to pattern the pattern electrodes at a low cost, and screen printing can be used as a patterning method. Screen printing is a printing method in which a conductive paste (metal paste) containing conductive powder such as metal is attached to a transparent substrate that is a printing object through an opening pattern portion drawn on a screen printing plate. It is.

  However, since the ITO film formed on the pattern electrode is usually formed by the PVD method, the ITO film is interrupted at the step portion of the grid-like pattern electrode, and a continuous ITO film may not be formed. Therefore, Patent Document 1 and Patent Document 2 disclose a method for eliminating the level difference of the grid-shaped pattern electrode.

Special table 2013-524536 gazette JP2013-102055A

  In recent years, energy conservation has been promoted. Low-temperature process technology that achieves both improvement of light transmittance of transparent electrode and reduction of sheet resistance in a flexible substrate to improve power generation efficiency of organic thin-film solar cells. Development is underway. In particular, many flexible and low-cost materials have poor heat resistance as described above, and it is difficult to perform high-temperature heat treatment (firing) at about 500 ° C. for the purpose of reducing wiring resistance. It is important to realize both the thinning of the electric electrode and the low resistance by a low temperature process.

  Although Patent Document 1 describes that a metal electrode is dispersed in a solvent and a grid electrode is formed by coating, an electrode wiring having a certain width and a specific resistance (volume resistivity) are realized. It is unclear whether it can be done or under what conditions.

  Although Patent Document 2 discloses a specific method of forming a pattern electrode wiring using a screen printing method, the minimum wiring width of the pattern electrode (grid electrode) is about 50 [μm], and further fine wiring No technology has been disclosed up to forming with low resistance and good reproducibility.

The present invention has been made in consideration of these points. By ensuring the aspect ratio and making the line width uniform, the present invention is low even at a fine line width of 50 [μm] or less , particularly 30 [μm]. It aims at providing the manufacturing method which can manufacture a transparent conductive base material provided with the resistive pattern electrode wiring, and the transparent conductive base material with a low-temperature process cheaply.

  The transparent conductive substrate according to the present invention can be effectively used for, for example, a photoelectric conversion device such as an organic solar cell or a display device, but its use is not limited and can be used for a wide variety of other purposes. Is possible. In addition, the present invention can find particularly superiority on a flexible transparent substrate having poor heat resistance, but it goes without saying that the present invention can also be applied to a substrate having high heat resistance.

One aspect of the method for producing a laminate according to the present invention includes a step of forming a receptive release layer containing solid particles on the surface of a release film, a step of printing a pattern electrode using a conductive paste,
Forming a transparent resin layer on the surface of the receptive release layer and the pattern electrode;
And laminating a transparent substrate on the transparent resin layer.

  In the above manufacturing method,
The solid particles may be composed of at least one selected from inorganic particles, polymers, and organic particles. For example, the solid particles may be composed of at least one selected from silica, alumina, and polystyrene.

  In the above manufacturing method,
The step of forming the receptive release layer may include a step of adding acrylic resin, the solid particles composed of inorganic particles, and polymethylphenylsilane (PMPS). The step of forming the receptive release layer may further include a step of adding a photopolymerization initiator.

  In the above manufacturing method,
The step of forming the receptive release layer may further include the step of adding a solvent.

  In the above manufacturing method,
The step of forming the receptive release layer may further include a step of adding a silane coupling agent having a fluorine functional group. The silane coupling agent may be, for example, FOTES.

In the above manufacturing method,
The step of printing the pattern electrode may include a step of screen printing a conductive paste in which conductive powder is dispersed and a drying step. Moreover, this drying process is a drying process by heat treatment, and the conditions may be configured to be 100 ° C. to 300 ° C., 30 to 60 minutes, or for a substrate having lower heat resistance. You may comprise so that it may be 100 to 150 degreeC and 30 to 60 minutes. In this case, the conductive powder may be configured to be a conductive powder that can be filled with a tap density of 5.0 to 5.55 [g / cc]. The conductive powder is configured to be a mixed powder of a spherical powder having an average particle size of 0.1 to 10 [μm] and a flaky powder having an average particle size of 2 to 20 [μm]. Also good. The material of the conductive powder is any one selected from Ag (silver), Cu (copper), Al (aluminum), Au (gold), Pt (platinum), W (tungsten), and C (carbon). You may comprise so that it may contain.

One aspect of a method for producing a transparent conductive substrate according to the present invention is a step of preparing a laminate obtained by the method for producing a laminate,
Forming a transparent resin layer on the surface of the receptive release layer and the pattern electrode;
  Laminating a transparent substrate on the transparent resin layer;
  Peeling the release film and the receptive release layer;
  And forming a transparent current collecting electrode on the surface of the transparent resin layer and the pattern electrode.

  With such a manufacturing method, a pattern electrode wiring having a low resistance, a narrow line width, good wiring width uniformity, and no bleeding is obtained, for example, even for a substrate that does not allow high temperature heat treatment such as PET. It is possible to provide a method for manufacturing a transparent conductive substrate that can be formed by a low-temperature process of less than or equal to ° C. and can be applied to various products. The conductive paste is a conductive powder selected from Ag (silver), Cu (copper), Al (aluminum), Au (gold), Pt (platinum), W (tungsten), C (carbon), and the like. The solid particles are selected from inorganic particles such as silica and alumina, and organic particles formed from a polymer, and the average particle diameter of both is the above relationship, so that the solvent of the conductive paste can be quickly received. The layer absorbs and a patterned electrode having a good shape and a low specific resistance can be formed.

One aspect of the transparent conductive substrate obtained by the above production method is:
A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
A printed pattern electrode having a wiring width of 15 to 30 [μm] and an aspect ratio of 0.15 to 0.5 on the surface of the transparent resin layer opposite to the transparent substrate;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the current collecting electrode is flat.

One aspect of the transparent conductive substrate obtained by the above production method is:
A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
On the surface of the transparent resin layer opposite to the transparent substrate, the wiring width is 15 to 30 [μm], and has a saddle-shaped cross-sectional shape without skirting.
Printed pattern electrodes;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the current collecting electrode is flat.

In the above production method, the average particle diameter of the solid particles is preferably 1/10 to 1/100 of the average particle diameter of the conductive powder.

According to the transparent conductive substrate obtained by the above manufacturing method, the specific resistance of the pattern electrode is 8 × 10 8. ^-6 ~ 5x10 ^-5 [Ωcm] can be realized.

Further, according to the transparent conductive substrate obtained by the above manufacturing method, the uniformity of the line width of the pattern electrodes, the wiring width is in the 15 30 [μm], it is possible to realize a 25% or less.

Furthermore, according to the transparent conductive base material obtained by the said manufacturing method , the average particle diameter of a pattern electrode is a granular conductive powder in the range of 0.1-10 [micrometers], 2-20 [micrometers]. It can be composed of an electrode formed by screen printing a conductive paste containing a flaky conductive powder and a thermosetting resin within the range. In addition, it is clear that it is impossible or difficult to specify the transparent conductive base material based on this invention, without using the above manufacturing methods.

Moreover, it is preferable that the ratio of the electroconductive powder of the said electroconductive paste and thermosetting resin is 90: 10-96: 4 by weight ratio .

With such a configuration, a pattern electrode having a low resistance and a good uniformity in the wiring width can be formed at low cost by a screen printing method even in a pattern electrode wiring having a line width of 50 μm or less , particularly 30 μm or less. Thus, it is possible to provide a transparent electrode that can prevent a decrease in light transmittance and realize a low sheet resistance. In addition, since the pattern electrode can be formed by a low-temperature process, it is possible to form a pattern on a flexible, low-cost, inferior heat-resistant film, increasing the choice of film, and various types of organic solar cells, etc. Application to products is possible at low cost. Furthermore, by setting the weight ratio of the conductive paste particles and flaky conductive powder to the thermosetting resin such as epoxy resin to 90:10 to 96: 4, a low resistance pattern electrode is formed by screen printing. can do.

Sectional drawing of the main manufacturing process of the transparent conductive base material which concerns on this invention. The surface SEM image photograph which shows the composition dependence of a receptive release layer surface state. The surface photograph which shows the release layer existence dependence of the wiring shape of a pattern electrode. Sectional drawing of the main manufacturing process of the transparent conductive base material which concerns on this invention. Sectional drawing of the transparent conductive base material which concerns on this invention. Sectional drawing of an organic thin-film solar cell.

FIG. 1 shows a cross section of a main manufacturing process of a transparent conductive substrate according to an embodiment of the present invention.
As shown in FIG. 1 (a), a receptive release layer 2 is applied to the surface of a release film 1, for example, a flexible substrate such as a cyclic polyolefin having a thickness of 50 [μm] or PET film, such as gravure coating or die coating. For example, 1 [μm] is formed by a coating technique, dried by hot air, for example, 50 ° C. to 120 ° C., blown, or the like, and then cured by UV irradiation.

  The material for forming the receptive release layer 2 is a polyfunctional acrylic monomer (TMPTA, DPHA, PETA, etc.) that is an acrylic resin and solid particles such as inorganic particles such as silica and alumina, and polymers such as polystyrene. Containing formed organic particles. When using inorganic particles, it is desirable to add polymethylphenylsilane (PMPS) in order to adhere the acrylic resin and the inorganic particles. In this case, PMPS also works as a photopolymerization initiator, but a photopolymerization initiator may be added separately. Furthermore, in order to improve the releasability described later, a silane coupling agent (for example, FOTES) having a fluorine functional group and polymerized with silane or acrylic, a surfactant, or an acrylic monomer may be added.

  Moreover, in order to improve the compatibility between PMPS and the acrylic monomer, a solvent such as toluene or PGMEA may be added.

  The receptive release layer 2 formed by the above method is a porous film containing solid particles as a main component, and has a mechanical strength that can withstand a peeling process described later.

  When polymethylphenylsilane is used as a photopolymerization initiator, silica particles can be preferably used as the solid particles to be added. This is because polymethylphenylsilane is cured to form a silicon oxide and thus has an effect of bonding silica particles and an acrylic resin. As the silica particles, for example, PL-1 (average particle size 15 nm) or PL-7 (average particle size 70 nm) manufactured by Fuso Chemical Industry Co., Ltd., which is a silica dispersion using a commercially available organic solvent, can be used.

  As the solid particle diameter, a size of the order of 10 nanometers is preferably used as in the above specific example. The average particle size of the solid particles is preferably sufficiently smaller than the average particle size of the conductive powder (metal powder or the like) contained in the conductive paste and is about 1/10 to 1/100.

  By setting the relationship between the average particle size of such solid particles and conductive powder, the conductive powder is not absorbed in the porous receptive release layer 2 as described later, and is contained in the conductive paste. This is because the low-viscosity solvent that is used is absorbed by capillary action.

  The filling rate of the solid particles of the receptive release layer 2 depends on the size of the solid particles contained in the material and the content of the solid particles, and the size and density of the pores formed in accordance with the size are determined accordingly. To do.

  Next, as shown in FIG. 1 (b), a conductive paste in which conductive powder is dispersed, for example, a silver paste, is screen-printed on the receptive release layer 2 by a screen printing method, dried by heat treatment, and patterned. The electrode 3 is formed. As a printing plate used for screen printing, for example, a stainless steel mesh formed with a photosensitive resin and having a pattern shape corresponding to the pattern electrode 3, for example, a grid shape, is used. As an example, a pattern shape corresponding to the pattern electrode 3, such as a grid shape, is formed with a photosensitive resin on a stainless steel mesh having a wire diameter of 16 [μm] and a pitch of 51 [μm] (# 500 mesh). Is used.

  Note that the pattern is not limited to a grid shape, and other patterns such as a stripe shape, an arc shape, a honeycomb shape, and a random pattern can be used according to customer applications.

  Drying conditions by heat treatment of the conductive paste after screen printing are, for example, 100 ° C. to 300 ° C., 30 to 60 minutes, and the specific resistance of the conductive wiring (pattern electrode 3) formed at a high temperature for a long time becomes low. Tend. However, when heat treatment at 150 ° C. or higher is performed, a film or substrate material that does not have heat resistance against these heat treatment conditions cannot be used. Therefore, by using a conductive paste that can be dried at a lower temperature, choices of types of films and base materials that can be adopted as the release film 1 are greatly expanded.

  Moreover, the higher the heat treatment temperature, the stronger the adhesion between the pattern electrode 3 and the receptive release layer 2, and the problem that the peeling characteristics deteriorate may occur. By shortening the drying process at a lower temperature and in a shorter time, the processing time of the heat treatment process including the temperature rise / fall time is shortened, thereby improving the processing capability of the heat treatment apparatus and reducing the manufacturing cost. .

  The low-resistance conductive paste that can be used in the present invention needs to be highly filled with conductive powder (conductive powder) / (conductive powder + epoxy resin component) × 100 ≧ 90 [wt. %]. In order to obtain such a highly filled composition, as the conductive powder, for example, a spherical powder having an average particle diameter of 0.1 to 10 [μm] and a size having an average particle diameter of 2 to 20 [μm] are used. A conductive powder that can be filled with a tap density of 5.0 to 5.5 [g / cc] is used. Examples of the material of the conductive powder (particles) include Ag (silver), Cu (copper), Al (aluminum), Au (gold), Pt (platinum), W (tungsten), and C (carbon). .

  Furthermore, the resin can be composed of two different types of resins (for example, a combination of liquid epoxy resins having different viscosities, a combination of a solid epoxy resin and a liquid epoxy resin at room temperature), a curing agent, and a solvent.

  By optimizing the blend and tap density of the flaky powder and the spherical powder of the conductive powder contained in the conductive paste, such as the silver paste, and the blend of the epoxy resin composition and the curing agent having different viscosities, 120 The pattern electrode 3 having a low specific resistance can be formed even under heat treatment conditions at 15 ° C. for 15 minutes.

  A particularly suitable conductive paste for forming (printing) the low-resistance pattern electrode 3 is, for example, a spherical conductive powder having an average particle size of 0.1 to 10 [μm] and an average particle size of 2 to 20 As a mixed powder with a flaky conductive powder having a size of [μm], the conductive powder having a tap density of 5.0 to 5.5 [g / cc], and a resin (thermosetting resin), Using an epoxy resin blend in which the epoxy equivalent of the mixture is 130-800, or a mixture of two or more types of epoxy resins, the blending ratio of conductive powder and epoxy resin [(conductive powder) / (Conductive powder + epoxy resin component) × 100] is 90 to 96 [wt. %]. The average particle size of the powder referred to here is obtained by measurement by microtrack measurement (microtrack particle size distribution measuring device). The particle size measurement is not limited to the microtrack measurement, and a method capable of measuring the equivalent particle size may be used.

  In addition, flake-shaped powder is a shape having a two-dimensional spread, it can be paraphrased in the form of flakes or scales, even when partially uneven and seen deformation, when viewed as a whole, It is sufficient that the powder has a shape close to a flat plate or thin rectangular parallelepiped, and a spherical powder has a three-dimensional shape that is closer to a cube than a rectangular parallelepiped when viewed as a whole, even if there are irregularities and deformation is seen partially. Any powder may be used. Moreover, the resin, the hardening | curing agent, and the solvent can utilize the well-known thing used for the electrically conductive paste.

Furthermore, the blending ratio of the two different types of resins affects the mechanical strength of the printed pattern electrode and the contact (electric resistance) between conductive powders (metal powders, etc.) due to curing shrinkage of the resin. Therefore, by optimizing the mixing ratio of these two kinds, low specific resistance (volume specific resistivity) as described later even by thermal drying at low temperature (100 to 150 ° C.) and short time (15 to 30 minutes) Can be realized.
In addition, specific resistance (rho) can be measured by a normal method. That is, the resistance value R at both ends of the rectangular pattern is measured at a temperature of 25 ° C., and the width W, the length L, and the film thickness T measured by the step meter can be calculated from the relational expression of ρ = RWT / L.

As shown in Table 1, the specific resistance of the conductive wiring formed by curing the optimal conductive paste (silver paste) realizes a low value of 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm]. be able to. In Table 1, paste examples 1 to 6 are conductive pastes that satisfy the conditions for the conductive paste, while comparative example 1 has a lower tap density than the above conditions, and comparative example 2 has a lower blending ratio than the above conditions. It is a paste. The paste examples 1-6 have a specific resistance lower than the comparative examples 1 and 2, and it can be understood that the value is 8 * 10 < ^-6 > ^-5 * 10 < ^-5 > [ohmcm].

Table 1. Dependence of resistivity on conductive paste

  The viscosity of the conductive paste can be adjusted by the solvent to be added. In screen printing, the conductive paste is printed on the receptive release layer 2 through the openings in the plate mesh. If the viscosity of the conductive paste is too high, the fluidity decreases and the conductive paste does not completely enter the opening of the printing plate, and the conductive paste is interrupted by the stainless steel wire constituting the mesh. It is necessary to add as much solvent as possible.

  However, when the fluidity is increased, the conductive paste spreads on the surface of the substrate to be printed, and the bleeding phenomenon occurs, making it difficult to control the thin line width, and the resulting wiring width is uneven, uneven surface and A cross-sectional shape is obtained, and the film thickness of the pattern electrode wiring also decreases.

  Therefore, it has been difficult to form a thin line width of 50 [μm] or less, particularly 30 [μm] or less, and it is difficult to form a pattern with a uniform line width. ), The shape of the non-uniform line width was repeated, and a thin line as designed could not be formed. That is, the boundary lines on both side surfaces of the wiring do not become two parallel straight lines, and the printing performance is low. Further, since the line width becomes narrower and the film thickness becomes thinner at the constricted portion, the resistance value of the pattern electrode 3 increases, and at the swollen portion, the aperture ratio of the pattern electrode 3 decreases, and the transparent conductive base material transmits light. The rate will be reduced.

  However, in the present invention, since the pattern electrode can be formed on the receptive release layer 2 by the screen printing method using the conductive paste, it is possible to use the conductive paste with improved fluidity. Become.

  FIG. 2 shows, by screen printing using a conductive paste (silver paste), (a) a patterned electrode formed on a release film on which the receptive release layer 2 is not formed, and (b) the receptive release layer 2. It compares and shows the shape of the pattern electrode formed on the release film 1 provided with. Screen printing is performed using a printing plate in which a groove opening pattern having a width of 24 [μm] is formed of a photosensitive resin, and the mesh of the printing plate is a wire diameter of 16 μm and a pitch of 51 [μm] (# 500 mesh). A stainless steel mesh was used. The line width of the pattern electrode was 34.4 [μm] when the receptive release layer 2 was not provided, but 22.3 [μm] on the release film having the receptive release layer 2 was almost printed. The value was equal to the line width of the plate, and it was confirmed that a pattern electrode having a good shape as designed could be printed. The line width is defined by the maximum width of the formed pattern electrode.

  Further, it can be understood that when the receptive release layer 2 is provided on the release film 1, the wiring pattern shape is clearly improved and the non-uniformity of the wiring width can be eliminated. As an index for evaluating the uniformity of the pattern wiring width, a value obtained by dividing the difference between the maximum line width and the minimum line width by the printing plate line width was used. It can be seen that the value of the conventional pattern electrode is 50 to 100 [%] for a line width of 50 [mu] m or less, but is reduced to 25 [%] or less in the present invention, which is greatly improved.

The reason why bleeding is eliminated in this way is considered as follows.
By setting the average particle size of the solid particles contained in the receptive release layer 2 to a value sufficiently smaller than the average particle size of the conductive powder contained in the conductive paste, that is, a value two orders of magnitude smaller, Only the solvent content is sucked into the receptive release layer 2. As a result, the elasticity of the conductive paste (resin and conductive powder) remaining without being absorbed in the receptive release layer 2 is increased and the wet paste does not spread.

  Therefore, if the occurrence of bleeding cannot be prevented in the profile of the wiring end, the cross section of the printed wiring side (from the boundary with the substrate to the point of the maximum film thickness) has a tail shape, By preventing the occurrence, the printed wiring can realize a shape without a tail. According to this embodiment, it is possible to form for the first time an electrode wiring having a fluidity that can pass through a narrow screen mesh and having a cross-sectional shape that does not skirt.

  In the present specification, the skirting is a portion where the portion connected to the substrate at the wiring end portion is connected with a gentle inclination, and the shape without the skirting is specifically 20 [% of the maximum thickness of the wiring. ] Means that the area (width) with a thickness less than] is 20% or less with respect to the line width.

  Further, as described above, since the skirting is caused by the bleeding phenomenon, the profile of the wiring cross section changes greatly at the boundary portion between the bleeding portion and the other portion, and the sign of the curvature radius changes.

Thus, the cross-sectional shape of the pattern electrode 3 formed on the receptive release layer 2 is a saddle shape, the aspect ratio is 0.15 to 0.5 when the wiring width is 15 to 50 [μm], The aspect ratio in a width of 15 to 30 [μm] is 0.15 to 0.20, and the aspect ratio in a line width of 30 to 50 [μm] is 0.20 to 0.50. Therefore, compared with the pattern electrode formed by the conventional method, a thick pattern electrode can be formed, the resistance of the pattern electrode 3 can be lowered, and the light transmittance can be improved.
Note that the saddle type is a straight line at the interface between the transparent electrode, which will be described later, and the pattern electrode, and the width of the pattern electrode parallel to this interface is the maximum at the interface part, and gradually increases as the distance from the interface increases. The shape of the pattern electrode and the transparent resin layer does not have a sharp point, and this shape avoids stress concentration when bending products such as organic thin-film solar cells. Damage to the layer and pattern electrode can be prevented.

Thus, the pattern electrode formed by the process which used the electroconductive paste which can obtain the low specific resistance of 8 * 10 < ^-6 > ^-5 * 10 < ^-5 > [ohmcm], and prevented the bleeding by adoption of the receptive release layer 2 A transparent conductive film having a low surface resistance of 5 [Ω / □] or less can be obtained.

  Further, in the present invention, since the receptive release layer 2 is configured to be finally removed, a material having sufficient solvent absorption characteristics and having an effect of preventing bleeding without being restricted by the light transmittance. You can choose.

  That is, even if irregular reflection occurs due to the solid particles contained in the receptive release layer 2 or the light transmittance of the solid particles themselves is low, the solid particles are formed on the pattern electrode 3 and the transparent resin layer together with the receptive release layer 2. Therefore, solid particles of a level that does not affect the light transmittance of the transparent conductive substrate or cause an increase in resistance due to a decrease in contact area with the transparent electrode do not remain. The state of removal of the solid particles may be confirmed by optical means such as a microscope, and the remaining solid particles that are detected only by microanalysis such as TEM do not affect these characteristics.

  FIG. 3 is an SEM image of the surface of the receptive release layer formed by changing the content of silica particles in the composition of the material forming the receptive release layer. As a dispersion of silica particles, PL-1-Tol (silica particle diameter: 10 to 15 nm, concentration: 20 [Wt%], organic solvent: toluene) manufactured by Fuso Chemical Industry Co., Ltd. was used as an example. FIG. 3A shows a material (release layer condition 1) in which 100 [mg] each of PMPS (polysilane) and TMPTA (acrylic resin) is added to the amount of PL-1-Tol of 2.5 [g]. FIG. 3B is a surface SEM photograph of a receptive release layer formed of a material (release layer condition 2) in which 150 [mg] each of PMPS (polysilane) and TMPTA (acrylic resin) are blended.

  Clearly, there is a difference in the surface morphology between the two, and in FIG. 3 (a) where the content of silica particles is larger, the number of voids observed on the surface is larger, and the higher the content of silica particles, the more porous It can be understood that it becomes a film. Thus, although there exists a tendency which becomes cloudy by the light scattering resulting from a void, since the receptive release layer 2 is removed, it is not necessary to worry about the influence.

  On the receptive release layer 2 formed under these release layer conditions 1 and 2, a thin line pattern was printed using a conductive paste, and the shapes were compared. As a result, the wiring on the receptive release layer 2 formed under the release layer condition 1 has a uniform wiring width and no constriction or swelling, and exhibits a good wiring shape, but the receptive release layer formed according to the release layer condition 2 The wiring on No. 2 was not uniform in width, and constriction and swelling were observed. It is considered that the uniformity of the line width of the wiring is improved because the larger amount of holes on the surface of the receptive release layer 2 absorbs the solvent of the silver paste more efficiently. The photograph shown in FIG. 2 (b) is one using the receptive release layer of FIG. 3 (a).

  In the above example, when a material containing 100 [mg] of PMPS and TMPTA is used for forming a receptive release layer for a PL-1-Tol amount of 2.5 [g], a good wiring shape is obtained. Although it could be obtained, the blending amount also depends on the silica particle diameter. When a silica dispersion having a large silica particle diameter is used, the amount of PMPS and TMPTA can be increased. By increasing the amount of resin, the bond between the solid particles of the receptive release layer 2 is strengthened, and the mechanical strength against peeling is also improved. What is necessary is just to optimize the compounding of each resin corresponding to a silica particle diameter and it.

  Further, in order to adjust the release characteristics, it is possible to adjust the peel strength by adding a fluorine additive to the receptive release layer 2. Examples of the fluorine additive include FOTES, but are not limited thereto.

  The receptive release layer 2 needs to have a peeling property in a subsequent process, but can be applied at a low heat drying temperature by optimizing the composition of the conductive paste, thus preventing deterioration of the peeling property. Can do.

  In the above description, the example in which the pattern electrode is formed on the release film 1 having poor heat resistance by low-temperature drying of the conductive paste has been described. However, the release film 1 is made of a heat-resistant material such as glass. Using a film, the conductive paste (eg, silver paste) may be dried at a high heat treatment temperature (eg, 150 ° C. to 300 ° C.), and may be further baked (eg, 400 to 600 ° C.) in some cases. This is because heat-resistant silica or alumina can be used as the solid particles of the receptive release layer 2 and the silica component derived from PMPS binds the particles.

  As the conductive material used for the conductive powder of the conductive paste, other metals such as copper, gold, aluminum, platinum, tungsten, and carbon may be used.

  Next, as shown in FIG. 1 (c), the transparent resin layer 4 is, for example, 15 [μm] by coating the receptive release layer 2 and the pattern electrode 3 with an acrylic ultraviolet (UV) curable resin. Form. The transparent resin layer 4 can be made of an acrylic resin or a transparent resin such as an ester resin, a silicone resin, or an epoxy resin. Moreover, the surface of the pattern electrode 3 can be covered by making the film thickness thicker than the pattern electrode 3. The pattern electrode 3 has a structure covered with the transparent resin layer 4 except for the contact surface with the receptive release layer 2, but the surface of the pattern electrode 3 is flat (the cross section is linear, ie, transparent resin) due to the fluidity of the transparent resin layer 4. Shape without a step with the layer).

  The resin used for forming the transparent resin layer 4 is preferably a UV curable resin. The transparent resin layer 4 may be a single layer or may be composed of a plurality of layers.

  Further, an adhesive layer may be formed on the transparent resin layer 4 by coating or printing.

  In addition, when the transparent resin layer 4 is formed by printing, since the transparent resin layer 4 is formed only immediately above the area where the pattern electrode 3 is printed, there is an advantage that the material cost is reduced.

  Next, as shown in FIG. 1D, a base material 5 made of a PET film having a thickness of 50 to 250 μm is laminated (laminated). The base material 5 is PET, PEN, COP, PC (polycarbonate), PMMA (acrylic), PI (polyimide), LCP (liquid crystal polymer) and other flexible plastic films, and a flexible film of 200 μm or less. A certain glass substrate (so-called glass film) can be used. As described above, since the transparent resin layer 4 has fluidity, the interface between the transparent resin layer 4 and the substrate 5 is flat.

  Moreover, you may form a 1-10 micrometers abrasion-resistant layer (hard coat), a 100-150 nm antireflection layer, and a gas barrier layer on the base material 5. FIG. This improves the abrasion resistance, total light transmittance, and gas barrier properties of the transparent electrode substrate. Further, the transparent substrate 2, the wear-resistant layer, and the antireflection layer may contain an ultraviolet (UV) absorber.

  Thereafter, the transparent resin layer 4 is cured. When a UV curable resin is used as the transparent resin layer 4, ultraviolet rays (UV) are irradiated from the substrate 5 side toward the transparent resin layer 4. Since the transparent resin layer 4 is cured after the base material 5 is formed, the influence of deformation due to the shrinkage of the transparent resin layer 4 during the curing process is reduced, and a step between the pattern electrode 3 and the transparent resin layer 4 is less likely to occur.

  Next, as shown in FIG. 4 (a), the release film 1 and the receptive release layer 2 are peeled off at the interface between the transparent resin layer 4 and the pattern electrode 3 and the receptive release layer 2 to obtain a transparent resin. The layer 4 and the pattern electrode 3 are exposed.

  The exposed surfaces of the pattern electrode 3 and the transparent resin layer 4 are flush. Moreover, the surface other than the exposed surface of the pattern electrode 3 is surrounded by the transparent resin layer 4. Therefore, the pattern electrode 3 is embedded in the transparent resin layer 4.

  The receptive release layer 2 has sufficient mechanical strength against peeling as described above, and does not break in the peeling process. Moreover, you may adjust the intensity | strength required for peeling with a fluorine additive.

  Next, as shown in FIG. 4B, a transparent conductive film 6, for example, an ITO film is formed as a collecting electrode on the exposed surfaces of the transparent resin layer 4 and the pattern electrode 3. The transparent conductive film 6 only needs to be transparent and conductive. In addition to the ITO-based film, the ZnO-based, SnO2-based, TiO2-based, conductive polymer (PEDOT / PSS), metal nanowire (MNW), carbon nanotube ( CNT), graphene, and the like, or a combination thereof can be used. The transparent conductive film 6 may be composed of a single layer or a plurality of layers.

  If the ITO film thickness of the transparent conductive film 6 is too thin, the resistance will be high, and if it is too thick, the manufacturing cost will increase and the flexibility will be impaired, so it is preferably 10 to 150 nm, and preferably 10 to 30 nm. More preferably.

FIG. 5 is a cross-sectional structure diagram of the transparent conductive substrate at the stage of the process of FIG. 4B when the transparent resin layer 4 is formed by a printing method. Since the transparent resin layer 4 is formed only on the pattern electrode 2 formation region by printing, the transparent resin layer 4 is partially formed on the substrate 5. When the conductive substrate is transferred to a final product, for example, a light-receiving surface of an organic solar cell or a light-emitting surface of an organic EL element, a region where the pattern electrode 2 and the transparent resin layer 4 are laminated is used.
Therefore, when the transparent conductive film 6 is formed on the entire surface by vapor deposition or the like, there is a step at the boundary between the region where the pattern electrode 2 and the transparent resin layer 4 are laminated and the other region, but there is a problem in actual use. There is no.

DESCRIPTION OF SYMBOLS 1 Release film 2 Receptive release layer 3 Pattern electrode 4 Transparent resin 5 Base material 6 Transparent electrically conductive film 101 Hole transport layer 102 Active layer 103 Electron transport layer 104 Transparent base material 105 Transparent electrode 106 Aluminum electrode

Claims (7)

A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
The specific resistance is 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm] on the surface of the transparent resin layer opposite to the transparent substrate, and the aspect ratio is 0 when the wiring width is 15 to 50 μm. A printed pattern electrode that is 15-0.5;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the said current collection electrode is flat. The transparent conductive base material characterized by the above-mentioned. A plate-shaped transparent substrate;
A transparent resin layer formed on one side of the transparent substrate;
On the surface of the transparent resin layer opposite to the transparent substrate, the specific resistance is 8 × 10 ^{−6 to} 5 × 10 ⁻⁵ [Ωcm], and the wiring width is 15 to 50 [μm]. A saddle-shaped cross-sectional shape,
Printed pattern electrodes;
A transparent current collecting electrode formed directly on the transparent resin layer and the pattern electrode;
The surface of the said current collection electrode is flat. The transparent conductive base material characterized by the above-mentioned.   3. The transparent conductive substrate according to claim 1, wherein the uniformity of the wiring width of the pattern electrode is 25% or less when the wiring width is 15 to 50 μm. 4.   The patterned electrode comprises a granular conductive powder having an average particle size in the range of 0.1 to 10 [μm], a flaky conductive powder in the range of 2 to 20 [μm], and a thermosetting resin. The transparent conductive substrate according to any one of claims 1 to 3, wherein the transparent conductive substrate is an electrode formed by screen printing a conductive paste contained therein.   The transparent conductive substrate according to claim 4, wherein a ratio of the conductive powder of the conductive paste to the thermosetting tree is 90:10 to 96: 4 by weight. Forming a receptive release layer containing solid particles on the surface of the release film;
A step of printing a pattern electrode using a conductive paste;
Forming a transparent resin layer on the surface of the receptive release layer and the pattern electrode;
Laminating a transparent substrate on the transparent resin layer;
Peeling the release film and the receptive release layer;
Forming a transparent current collecting electrode on the surface of the transparent resin layer and the patterned electrode, and a method for producing a transparent conductive substrate.   The method for producing a transparent conductive substrate according to claim 6, wherein the average particle diameter of the solid particles is 1/10 to 1/100 of the average particle diameter of the conductive powder.

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