WO2013069478A1

WO2013069478A1 - Film-forming method

Info

Publication number: WO2013069478A1
Application number: PCT/JP2012/077733
Authority: WO
Inventors: 公明宮本
Original assignee: 富士フイルム株式会社
Priority date: 2011-11-11
Filing date: 2012-10-26
Publication date: 2013-05-16
Also published as: JP2013103152A; TW201332667A

Abstract

A film-forming method for forming a film by coating a substrate with a dispersion containing a tabular grain, and drying the dispersion. The tabular grain has an aspect ratio of 1:10 or more, and has a contact angle in relation to the dispersion of 20° or less. The dispersion includes the tabular grain in a quantity such that the ratio of the sum of the total grain projected area of all the tabular grain to the area of the substrate region coated with the dispersion is 0.5 or less. The drying speed of the dispersion is 2cm/s or less in terms of the rate of change of the film thickness.

Description

Deposition method

The present invention relates to a film forming method in which a plurality of tabular grains are arranged on a substrate while suppressing overlapping of each other, and in particular, an optical function, a photoelectric conversion function, or a filter function in which tabular grains select or absorb or reflect wavelengths. The present invention relates to a film forming method for forming a functional film having various functions.

Currently, various functional films that exhibit a predetermined function using flat particles have been formed (see Patent Documents 1 and 2).
For example, Patent Document 1 discloses an EL element provided with an optical sheet having a configuration in which flat particles having an average aspect ratio of 2 or more are dispersed in a transparent resin.
In patent document 1, mica (mica) such as mascobite (muscovite), phlogopite (phlogopite), biotite (biotite), sericite (sericite), fluorine phlogopite (artificial mica), etc. In addition to kaolin (clay), talc (talc), montmorillonite, etc., flaky aluminum oxide / titanium oxide / zinc oxide / silicon oxide, a composite of these, and flat calcium carbonate are exemplified. Patent Document 1 discloses that silver halides such as silver chloride, silver bromide, silver iodide, silver iodobromide, silver bromochloride, silver iodochloride and silver iodobromochloride whose shape is controlled in a flat shape as flat grains. Etc. are also disclosed.

Patent Document 2 discloses a hydrophilic film provided on a substrate, and the hydrophilic film is formed from fine particles containing a phyllosilicate dispersed in a film and a binder, and the binder is formed of a fine particle and a base. The material and the fine particles are joined together. The phyllosilicate fine particles are flat particles having an aspect ratio of 3 or more. In Patent Document 2, since the flat particles are arranged and arranged in parallel with each other and in parallel with the substrate, the arrangement in which the hydroxyl groups are arranged on the surface can be maintained, so that hydrophilicity is maintained. It is disclosed.

JP 2010-1114026 A JP 2010-90461 A JP 2011-192862 A

Patent Documents 1 and 2 disclose that flat particles are used, but only flat particles are used, and these flat particles are arranged on the substrate without overlapping, and have a predetermined function. It does not form a functional film that develops. In recent years, attempts have been made to develop a predetermined function by uniformly arranging flat particles or tabular particles on a substrate so that they are not heavy. For example, Patent Document 3 discloses that a photoelectric conversion semiconductor layer is formed by a coating method using a dispersion containing tabular grains of CIS, CIGS, and CAIS. In Patent Document 3, it is estimated that the photoelectric conversion semiconductor layer is a film in which the photoelectric conversion semiconductor layer is densely packed and the photoelectric conversion efficiency is increased.

However, although there is a method of aligning particles on the liquid surface and pulling up like a LB film, a functional film that directly coats on the substrate and arranges the particles on the substrate without overlapping to express a predetermined function. The technology to obtain is not established.
In addition, in order to obtain a sufficient coverage with spherical particles, the number of particles must be increased, and there is a problem that a uniform film cannot be obtained by aggregation. In addition, spherical particles are less likely to aggregate when the particle size is increased, but there is a problem that the film becomes thick and cannot be thinned.

An object of the present invention is to provide a film forming method capable of solving the problems based on the prior art and arranging a plurality of tabular grains on a substrate while suppressing overlapping of each other.

In order to achieve the above object, the present invention is a film forming method in which a dispersion liquid containing tabular grains is applied to a substrate, and the dispersion liquid is dried to form a film, wherein the tabular grains have an aspect ratio of 1: The contact angle with respect to the dispersion is 20 ° or less, and the ratio of the sum of the maximum projected areas of all tabular grains to the area of the substrate region coated with the dispersion is 0.5. The following amounts of tabular grains are contained, and the dispersion provides a film forming method characterized in that the drying rate is 2 cm / s or less in terms of the change rate of the film thickness.

When the thickness of the tabular grains is δ (cm) and the drying speed of the dispersion is V (cm / s), the ratio is δ / V between the thickness δ of the tabular grains and the drying speed V of the dispersion. The time T is preferably T> 2.5 × 10 ⁻⁷ (s).

According to the present invention, it is possible to form on the substrate a film in which a plurality of tabular grains having an aspect ratio of 1:10 or more are arranged in a state where they are suppressed from overlapping each other.

(A) is a schematic diagram for demonstrating a board | substrate area | region, (b) is a schematic diagram which shows the liquid film formed with a dispersion liquid. It is a typical perspective view which shows an example of the film formed with the film-forming method of embodiment of this invention. (A) is a schematic perspective view for demonstrating the force which acts on square tabular grain, (b) is a schematic diagram for demonstrating the force which acts on the end surface of square tabular grain, (C) is a schematic view for demonstrating the force which acts on the upper surface of a square tabular grain. It is a graph which shows the relationship between the contact angle in case a tabular grain is a square, and the acting force. (A), (b) is a schematic diagram which shows the overlap of the tabular grain at the time of changing a contact angle. (A) to (c) are schematic diagrams showing the overlap of tabular grains when the coverage is changed. (A) to (c) are schematic views showing the overlap of tabular grains when the drying speed is changed.

Hereinafter, a film forming method of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
The film forming method of the present invention is a method in which a dispersion containing tabular grains is used, and after coating this dispersion on a substrate, the dispersion is dried to form a film.
In the film forming method of the present invention, the tabular grains are randomly oriented in the dispersion before coating, and after the dispersion, coating, and after the drying, the capillary force acting on the tabular grains is within a certain range. It prevents particles from overlapping and becoming non-parallel to the substrate surface, and creates a highly regular layered structure.
The method for applying the dispersion is not particularly limited. For example, the spin coating method, the casting method, the roll coating method, the flow coating method, the printing method, the dip coating method, the casting film forming method, and the bar coating method. A gravure printing method or the like can be used.

In the present invention, the tabular grains have an aspect ratio of 1:10 or more. The tabular grains have a contact angle with respect to the dispersion of 20 ° or less. Further, the tabular grains are contained in the dispersion in such an amount that the ratio of the sum of the maximum projected areas of all the tabular grains and the area of the substrate region coated with the dispersion is 0.5 or less.
In the present invention, the dispersion liquid preferably has a drying rate of 2 cm / s or less in terms of a change rate of the film thickness. The method for drying the dispersion is not particularly limited as long as the rate of change in film thickness is preferably 2 cm / s or less, and natural drying, known drying methods, and the like can be used as appropriate. .

The aspect ratio of the tabular grains is defined by the thickness of the tabular grains: the representative diameter of the tabular grains. The representative diameter of the tabular grains is the diameter of the inscribed circle. Tabular grains do not include acicular grains.
If the aspect ratio of the tabular grains is less than 1:10, the tabular grains become heavy, and the acceleration necessary for moving the tabular grains in the dispersion cannot be obtained. Further, it is difficult to produce tabular grains having an aspect ratio of 1:30 or more. For this reason, the upper limit of the aspect ratio is 1:30.
The thickness of the tabular grain is preferably 5 to 50 nm.

In the present invention, the ratio of the sum of the maximum projected areas of tabular grains and all tabular grains contained in the dispersion and the area of the substrate region coated with the dispersion is defined as the coverage. As described above, the tabular grains are contained in the dispersion so that the coverage is 0.5 or less. If the coverage exceeds 0.5, the tabular grains are in a very dense state, so that even if the other definition of the film forming method of the present invention is satisfied, the overlap of the tabular grains cannot be avoided. For example, when the tabular grains in the dispersion liquid remain in the arrangement state and the dispersion liquid shrinks in the thickness direction, there are cases where overlap occurs due to the randomness of the arrangement.

Here, as shown in FIG. 1A, when the dispersion liquid is applied to the substrate 10, the application area 12 to which the dispersion liquid is applied is called a substrate area. When the dispersion liquid is applied to the entire surface of the substrate 10, the entire surface of the substrate 10 becomes the application region 12, that is, the substrate region.
In addition, when the coverage is 0.05 or less, as long as the dispersion is well dispersed in the dispersion, no overlap due to randomness occurs. For this reason, the lower limit of the coverage is set to 0.05.
If the shape of the tabular grains is triangular, quadrangular, or hexagonal, the ratio of the sum of the maximum projected areas of all tabular grains to the substrate region coated with the dispersion is 100% in a single layer without overlapping. Is the theoretical maximum. If the shape of the tabular grains is circular, the ratio of the sum of the maximum projected areas of all tabular grains to the substrate region coated with the dispersion is the theoretical maximum of 83% in a single layer with no overlap.

The dispersion is applied to the surface 10a of the substrate 10 to form a liquid film 14 as shown in FIG. The liquid film 14 is preferably 2 cm / s or less at the rate of change of the film thickness d. The changing speed of the film thickness d is the drying speed. The film thickness d is the distance from the surface 10a of the substrate 10 to the surface of the liquid film 14 (liquid surface 14a).

In the present invention, for example, as shown in FIG. 1B, the above-mentioned prescribed dispersion liquid is applied to the surface 10a of the substrate 10 to form a liquid film 14, and then the liquid film 14 composed of the dispersion liquid. Dry. At this time, the tabular grains 16 are randomly oriented in the liquid film 14. By using the above-mentioned prescribed dispersion and tabular grains, when the liquid surface 14a is lowered with time from the application to the end of drying, a force acts on each tabular grain 16 in the direction in which the overlap is removed, It is suppressed that the tabular grains 16 overlap and become non-parallel to the surface 10 a of the substrate 10. Thereby, for example, as shown in FIG. 2, a coating film 20 having one layer disposed on the surface 10 a of the substrate 10 can be formed without a plurality of tabular grains 16 overlapping each other.
In the present invention, when tabular grains are overlapped, the area of the overlapping portion is treated as not overlapping tabular grains up to 5% of the sum of the maximum projected areas of all tabular grains. The ratio at which the tabular grains overlap is called the stack rate. That is, when the stack rate is up to 5%, tabular grains are treated as not overlapping.

Hereinafter, the reason for limiting the numerical value of the present invention will be described in detail.
First, the reason for limiting the numerical value of the contact angle will be described in detail.
As shown in FIG. 3A, for example, two square tabular grains 16 overlap in the liquid film 14, and the upper tabular grains 16 partially protrude from the liquid surface 14a of the liquid film 14. In this state, the relationship between the force acting on the upper tabular grains 16 and the contact angle was examined. As shown in FIG. 3A, the upper tabular grains 16 are inclined obliquely.

As shown in FIG. 3 (b), and the meniscus M ₁ on the end face 16a of the upper tabular grains 16 occurs, the portion in contact with the liquid surface 14a in the end face 16a, the force F ₁ along the contact angle φ is acting To do. The component force F ₁₁ of the force F ₁ acts in the direction of pulling the tabular grains 16, and the component force F ₁₂ acts in the direction of lowering the tabular grains 16.
Further, as shown in FIG. 3C, a meniscus M ₂ is formed on the upper surface 16b of the upper tabular grain 16, and the force F ₂ along the contact angle φ is applied to the portion of the upper surface 16b in contact with the liquid surface 14a. Act. Component force _{F 21} of the force _{F 2} acts in a direction to raise the tabular grains 16, the component force _{F 22} acts in the direction along the tabular grains 16 in the upper surface 16b. The component force F ₁₁ and the component force F ₂₂ are forces acting in the direction in which the overlap of the tabular grains 16 is removed.
As described above, various forces act on the upper tabular grains 16, and as a sum of these, a tensile force acts on the tabular grains 16 so that the overlap is removed. The tensile force F acting on the upper tabular grains 16 is expressed by the following mathematical formula 1. In the following formula 1, l (el) is the wet side length, σ is the surface tension, and φ is the contact angle.

In Formula 1 above, if the tensile force F is divided by σl to make it dimensionless, the force acting on the upper tabular grains 16 depends on the contact angle φ. The result is shown in FIG. As shown in FIG. 4, when the contact angle φ is 45 ° or less, a force acts in a direction in which the tabular grains 16 are not overlapped. When the contact angle is 20 ° or less, the force acts more in the direction in which the tabular grains 16 are separated from each other. For this reason, in this invention, the contact angle with the liquid film 14 of the tabular grain 16, ie, a dispersion liquid, shall be 20 degrees or less. Thus, by setting the contact angle to 20 ° or less, the force for moving the tabular grains 16 works more, and the overlap of the tabular grains 16 can be avoided.

The contact angle can be adjusted by a combination of the tabular grain composition and the dispersion composition.
When the dispersion is water, PVA (polyvinyl alcohol), PVP (polyvinyl pyrrolidone) or the like is adsorbed on the surface in order to reduce the contact angle. When the dispersion is a solvent, it is preferable to select an olefin having a small contact angle.

Here, as shown in FIG. 3 (a), the upper tabular grains 16 are inclined obliquely, and the lower tabular grains as described above are formed by the meniscus M ₁ (see FIG. 3 (b)) formed on the end face 16a. A force that pulls the tabular grains 16 acts in the direction overlapping the grains 16, and acts in a direction to separate the tabular grains 16 from the lower tabular grains 16 by the meniscus M ₂ (see FIG. 3C) formed on the upper surface 16 b of the tabular grains 16. The power to do works. The force acting in the direction away from the tabular grains 16 on the lower side is such that the liquid film 14 acts at a position that is 1 to 2 times the thickness of the tabular grains 16, so the tabular grains on the upper side of the liquid film 14 only during the thickness. A force is applied to 16 in the direction away from the lower tabular grains 16.
Accordingly, when the thickness of the tabular grains 16 is δ (cm) and the drying speed of the liquid film 14 (dispersion) is V (cm / s), the thickness δ of the tabular grains 16 and the liquid film 14 (dispersion) The time T (s) represented by the ratio δ / V with the drying speed V of) is a preferable drying speed of 2 cm / s or less when the thickness δ of the tabular grains 16 is 10 nm. The limit is (nm) / (2 cm / s) = 5 × 10 ⁻⁷ (s). Therefore, time T> 5 × 10 ⁻⁷ (s), that is, time T> 50 (μs).

The upper and lower limits of time T (s) are defined by the upper and lower limits of the thickness of tabular grain 16.
Here, the thickness of the tabular grains 16 is preferably 5 to 50 nm as described above. If the thickness of the tabular grain 16 is less than 5 nm, no meniscus is formed.
On the other hand, when the thickness of the tabular grains exceeds 50 nm, the aspect ratio of the tabular grains is 1:10 or more, so that the grain diameter becomes large exceeding 500 nm. At this time, in the initial state in which the liquid film 14 is formed on the surface 10a of the substrate 10 as shown in FIG. 1B, a part of the tabular grains is in contact with the surface 10a of the substrate 10 and a part protrudes from the liquid film 14. In such an upright state, the liquid film 14 may dry without being tilted obliquely by Brownian motion and dragged by capillary force. In such a case, the overlap of tabular grains is difficult to be eliminated.
Thus, the upper limit (maximum value) of the thickness of the tabular grains 16 is 50 nm, and the time T = 25 × 10 ⁻⁷ (s), that is, the time T = 250 (μs) is the upper limit.
On the other hand, the lower limit (minimum value) of the thickness of the tabular grain 16 is 5 nm, and the time T = 2.5 × 10 ⁻⁷ (s), that is, the time T = 25 (μs) is the lower limit.

Further, regarding the contact angle, square tabular grains were used, and the overlap at the time of film formation was examined by numerical analysis using Sample 100 and Sample 101 in which the contact angles of the square tabular grains were changed. The results are shown in FIGS. 5 (a) and 5 (b).
For the numerical analysis, a simulator called “SNAP-Lver 2.2.1” distributed by the “Meso Simulation Consortium” was used. Naviestokes' formula with the addition of thermal fluctuation term as shown in the following formula 2 and equations of motion by viscoelastic contact force, torque, capillary force, electrostatic force, intermolecular force, and viscous resistance acting on each particle. Solved by combining. The following formula 2 (Naviestokes formula) is a time partial differential equation, and the calculation time step is 10 ⁻¹² seconds.

The particle was a metal flat plate having a size of 10 nm (thickness) × 110 nm (side length) × 110 nm (side length) and a specific gravity of 10. This metal flat plate has an aspect ratio of 11. In addition, for calculation visualization, it is expressed as a combination of particles.
The calculation area of the numerical analysis was set to 550 nm × 550 nm × 100 nm (depth). That is, the volume of the dispersion is 550 nm × 550 nm × 100 nm (depth). The drying rate was the rate of change of the height of the calculation area.

The dispersion had a specific gravity of 1, a surface tension of 20 mN / m, a viscosity of 1 mPa · s, and a zeta potential of 80 mV.
Of the numerical analysis conditions, the coverage, drying speed, contact angle, and friction coefficient were as shown in Table 1 below.
The number of particles contained in the dispersion is proportional to the coverage, and is 11 when the coverage is 0.5. Under the initial conditions, the calculation starts from the same three-dimensional arrangement. When the coverage is 0.3, the number of particles is 6, and when the coverage is 0.7, the number of particles is 15.

FIG. 5A shows the result when the contact angle is 45 °, and FIG. 5B shows the result when the contact angle is 20 °.
As shown in FIG. 5A, when the contact angle is 45 °, the tabular grains overlap. On the other hand, as shown in FIG. 5B, the tabular grains do not overlap when the contact angle is 20 °. Thus, the overlap of the tabular grains is avoided by setting the contact angle to 20 °.

Next, the reason for limiting the numerical value of the coverage will be described in detail.
In the present invention, the coverage is 0.5 or less. Therefore, for the samples 110 to 112 using square tabular grains and changing the coverage of the square tabular grains, the overlap at the time of film formation was examined by numerical analysis. The results are shown in FIGS. 6 (a) to (c).
For the numerical analysis, the same analysis method as the numerical analysis of the contact angle described above was used, and the same analysis conditions were used. For this reason, the detailed description about numerical analysis is abbreviate | omitted. Of the numerical analysis conditions, the coverage, drying speed, contact angle, and friction coefficient were as shown in Table 2 below.

FIG. 6A shows the result when the coverage is 0.3, FIG. 6B shows the result when the coverage is 0.5, and FIG. 6C shows the result when the coverage is 0.7. As shown in FIGS. 6A to 6C, when the coverage is 0.7, there is much overlap. On the other hand, when the coverage is 0.5, the overlap is significantly improved as compared with the coverage of 0.7. Furthermore, when the coverage is 0.3, the tabular grains do not overlap. Thus, the overlap of tabular grains can be improved by setting the coverage to 0.5 or less.
As shown in Table 2 above, since the contact angle is 45 °, the force for moving the tabular grains hardly works according to FIG. For this reason, it is thought that it overlapped when the coverage was 0.5.

Next, the reason for limiting the numerical value of the drying speed will be described in detail.
In the present invention, the drying speed (change speed of the film thickness d of the liquid film 14 shown in FIG. 1B) is set to 2 cm / s or less. Therefore, for the samples 120 to 122 in which square tabular grains were used and the coverage of the square tabular grains was changed, the overlap at the time of film formation was examined by numerical analysis. The results are shown in FIGS. 7 (a) to (c).
For the numerical analysis, the same analysis method as the numerical analysis of the contact angle described above was used, and the same analysis conditions were used. For this reason, the detailed description about numerical analysis is abbreviate | omitted. Of the numerical analysis conditions, the coverage, drying speed, contact angle, and friction coefficient were as shown in Table 3 below.

FIG. 7A shows the result when the drying speed is 10 cm / s, FIG. 7B shows the result when the drying speed is 5 cm / s, and FIG. 7C shows the result when the drying speed is 2 cm / s. As shown in FIGS. 7 (a) to 7 (c), the tabular grain overlap is large when the drying speed is 5 cm / s and 10 cm / s. On the other hand, when the drying speed is 2 cm / s, the tabular grains do not overlap. Thus, the overlap of tabular grains can be improved by setting the drying rate to 2 cm / s or less.

According to the film forming method of the present invention, it is possible to form a single-layered film in which a plurality of tabular grains are arranged on a substrate while being prevented from overlapping each other. For this coating, the composition of the tabular grains and the like according to the function of the functional film are selected as appropriate so that the wavelength can be selected and absorbed or reflected, and the photoelectric conversion has the function of generating charges by optical absorption. It can be set as the functional film or functional layer which has a function or a filter function and has various functions. Examples of the filter function include a color filter, an infrared reflection filter, and a projection screen.

For example, a magnetic recording medium layer can be formed by the film forming method of the present invention. In this case, a tabular magnetic body is used as the tabular grain, and hexagonal ferrite is used as the tabular magnetic body. Examples of the hexagonal ferrite include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitutes, and Co substitutes. Specific examples include magnetoplumbite-type barium ferrite and strontium ferrite, magnetoplumbite-type ferrite whose particle surface is coated with spinel, and magnetoplumbite-type barium ferrite and strontium ferrite partially containing a spinel phase. Other than the predetermined atoms, Al, Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta, W, Re, Au, Hg , Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, B, Ge, Nb, and Zr may be included. In general, an element such as Co—Zn, Co—Ti, Co—Ti—Zr, Co—Ti—Zn, Ni—Ti—Zn, Nb—Zn—Co, Sb—Zn—Co, or Nb—Zn is added. Things can be used. Some raw materials and manufacturing methods contain specific impurities.

In the flat magnetic layer, a nonmagnetic support is used for the substrate. Examples of the nonmagnetic support include known ones such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyamideimide, and aromatic polyamide. Among these, polyethylene terephthalate, polyethylene naphthalate, or polyamide is used.

Moreover, the tabular grain used for the film-forming method of this invention can be comprised with a metal compound. Examples of the metal compound include a metal salt, a metal complex, and an organometallic compound.
Examples of the metal in the metal compound include silver, gold, platinum, palladium, copper, nickel, and cobalt, and among these, silver or gold is particularly preferable. The acid that forms the metal salt may be either an inorganic acid or an organic acid. There is no restriction | limiting in particular as an inorganic acid, According to the objective, it can select suitably, For example, hydrohalic acids, such as nitric acid; hydrochloric acid, hydrobromic acid, hydroiodic acid, etc. are mentioned. There is no restriction | limiting in particular as an organic acid, According to the objective, it can select suitably, For example, carboxylic acid, a sulfonic acid, etc. are mentioned.

Examples of the carboxylic acid include acetic acid, butyric acid, oxalic acid, stearic acid, behenic acid, lauric acid, and benzoic acid.
Examples of the sulfonic acid include methyl sulfonic acid. Examples of the metal salt include silver nitrate, chloroauric acid, and chloroplatinic acid.
There is no restriction | limiting in particular as a chelating agent which forms a metal complex, According to the objective, it can select suitably, For example, acetylacetonate, EDTA, etc. are mentioned. Moreover, you may form a complex with said metal salt and a ligand, and examples of this ligand include imidazole, pyridine, and phenylmethyl sulfide.
In addition, the metal compound includes an acid of a halogenated complex of a metal ion (for example, chloroauric acid, chloroplatinic acid, etc.) and an alkali metal salt (for example, sodium chloroaurate, sodium tetrachloropalladate, etc.). .

The tabular grains composed of the above-described metal compound have absorption derived from surface plasmon resonance from the visible range to the near infrared range, and exhibit a vivid color development. Therefore, a coloring material or a colorant such as an inkjet or a color filter, It can be used as an infrared absorbing material or an electromagnetic shielding material.

Furthermore, for example, a photoelectric conversion layer can be formed by the film forming method of the present invention. In this case, as the tabular grains, those having a CuAu type structure and having elements of Group Ib, Group IIIb and Group VIb of the short period type periodic table as components are used.
As a specific element of Group Ib, for example, at least one element selected from Cu and Ag is used. The group IIIb element is, for example, at least one element selected from In, Ga, and Al. The group VIb element is, for example, at least one element selected from S, Se, and Te. Among these, Cu—In—S, Cu—In—Ga—S, Cu—In—Al—S, Cu—In—Ga—Se, Cu—In—Al—Se, and Ag—In— are preferable. A combination of S, Ag—In—Se, Ag—In—Ga—Se, Ag—In—Al—Se, Ag—Ga—Te, and Ag—Ga—Al—Te.

As the organic solvent for coating the tabular grains, hydrophobic alkanes, alkenes, cycloalkanes, benzenes, amines, alcohols and the like are used. Preferably, those having a boiling point of 100 ° C. to 180 ° C. are difficult to dry during coating and are relatively easy to dry after coating. Specifically, octane, nonane, decane, dimethylcyclohexane, isopropylcyclohexane, cycloheptane, cyclooctane, toluene, xylene, p-ethyltoluene, ethylbenzene, 2-octaneamine, 1-butanol, 1-hexanol, 2-hexanol , 3-hexanol, 2-amino-1-butanol, and the like can be used.

As a substrate on which a coating agent containing tabular grains is applied, a glass substrate, a stainless steel substrate, or the like can be used. In addition, a flexible substrate is used. The substrate is preferably a flexible substrate in order to enable roll-to-roll manufacturing. In this case, a polyimide base that can withstand temperatures up to about 400 ° C., and thin aluminum that can withstand temperatures up to about 500 ° C. An anodized substrate made of a metal base material mainly composed of bismuth is used.
A photoelectric conversion semiconductor layer is formed by applying a coating agent containing tabular grains on a substrate, performing heat treatment at 200 ° C. to 470 ° C. in an inert gas atmosphere, and pressing at 5 MPa to 20 MPa.

The present invention is basically configured as described above. The film forming method of the present invention has been described in detail above. However, the present invention is not limited to the above-described embodiment, and various modifications or changes may be made without departing from the spirit of the present invention. is there.

10 substrate 12 substrate region 14 liquid film 16 tabular grain

Claims

A film forming method in which a dispersion containing tabular grains is applied to a substrate, and the dispersion is dried to form a film,
The tabular grains have an aspect ratio of 1:10 or more and a contact angle with respect to the dispersion of 20 ° or less.
The dispersion includes the tabular grains in an amount of a ratio of the sum of the maximum projected areas of all the tabular grains and the area of the substrate region coated with the dispersion of 0.5 or less,
The film forming method, wherein the dispersion liquid has a drying rate of 2 cm / s or less as a change rate of the film thickness.
When the thickness of the tabular grains is δ (cm) and the drying speed of the dispersion is V (cm / s), the ratio of the thickness δ of the tabular grains and the drying speed V of the dispersion δ / 2. The film forming method according to claim 1, wherein the time T represented by V is T> 2.5 × 10 −7 (s).
The film forming method according to claim 1, wherein the tabular grain has a triangular, quadrangular, or hexagonal shape.