JP4676232B2 - Pattern formation method - Google Patents

Description

  The present invention relates to a pattern forming method, and more specifically, electrode portions of electronic elements such as solar cell elements, liquid crystal display elements, electrochromic display elements (ECD), semiconductor packaging such as IC cards, and portable information terminals. The present invention relates to a pattern forming method particularly suitable for manufacturing a printed circuit board (wiring board) constituting a printed circuit board (component mounting board) incorporated in an electronic device such as a portable terminal (PDA).

  Printed circuit boards are broadly classified into hard plate-shaped rigid printed circuit boards and flexible film-shaped flexible printed circuit boards (hereinafter referred to as FPCs) that have been widely used, and the demand for these is the expansion of the market for electronic devices. It continues to increase with sophistication. In particular, the use of FPCs that are lightweight and have a high degree of freedom of handling has been rapidly increasing recently, and they have been incorporated into folding hinges of portable cellular phones and notebook personal computers, taking advantage of their flexible characteristics.

  In recent years, electronic devices such as mobile phones and digital cameras have been accelerating the shortening of various types of products along with the increase in functionality and miniaturization, and there are many printed circuit boards used as wiring inside these electronic devices. It is required to develop and market in as short a time as possible in order to cope with small-quantity production.

A printed circuit board is manufactured by transferring a circuit for an electronic device to a laminated board in which a conductive film such as a copper foil is bonded to an insulator, and performing etching to form a required distribution pattern. Etching in the process of manufacturing a substrate, for example, FPC, as described in Patent Document 1, for example,
(1) A photo-etching resist ink mainly composed of a photosensitive acrylic polymer resin and acrylic ester or a photosensitive epoxy polymer resin is applied to the entire surface of the copper coating formed on the surface of the flexible insulating film. Coating and drying process of coating and drying for a predetermined time at a predetermined temperature;
(2) An ultraviolet exposure step of placing a photomask having a predetermined pattern on the coated surface after the coating / drying step (1) and curing the desired pattern portion by performing ultraviolet exposure;
(3) The uncured portion of the photoetching resist coating film that has undergone the ultraviolet exposure step (2) is washed and removed using a developer, and dried at a predetermined temperature to form a desired shape on the photoetching resist coating film. Forming a pattern;
(4) Etching away all exposed copper portions on the film after step (3), then washing with water and then drying at a predetermined temperature; and (5) on the copper circuit after step (4). The remaining photoetching resist was washed and removed with a weak alkaline aqueous solution and dried at a predetermined temperature.

  However, according to such a conventional method, as a general procedure, after designing a circuit pattern by CAD or the like, a mask is manufactured by outsourcing, etc., and a prototype of the circuit board is made using the completed mask. The mask had to be designed and remanufactured. Since a considerable amount of time is spent on the mask production, the production efficiency is very low. In particular, waste of time and materials in the research and development stage has been a problem. In addition, such a conventional method is suitable for small-quantity mass production, but it is not suitable for large-variety small-volume production because the above procedure must be repeated every time the design is changed. Furthermore, since it is necessary to coat the entire surface of the copper coating with an expensive photo-etching resist itself, and then remove the resist deposited on the portion other than the desired portion, the expensive material is wasted and the cost is reduced. There was a problem. In addition, there has been a problem that a large amount of capital investment is required with the increase in the size of the exposure and development apparatus, and further, a lot of developer is wasted.

  In order to solve the problems of the conventional method, it has recently been proposed to directly form a resist film in a desired pattern using an ink jet printer. Specifically, for example, Non-Patent Document 1 discloses that a droplet of a photoresist is ejected in a desired pattern using an inkjet head on the surface of a copper foil of an FPC board in which a copper foil is bonded to an insulating substrate, and heating is performed. It is disclosed that the steps (1) to (3) are performed in one step by curing by ultraviolet irradiation or the like.

Japanese Patent No. 2562273 JP-A-8-80670 JP-T-2004-504964 Japanese Patent Laid-Open No. 5-16533 IS & T's NIP19: 2003 International Conference on Digital Printing Technologies, thermal manufacturing Printed Circuit Boards Using Ink Jet Technology

  According to the method disclosed in Non-Patent Document 1, when the resist droplets ejected from the nozzles of the ink jet printer land on the copper foil, the ink is repelled on the copper foil and the resist film does not need to be formed. There has been a problem that a so-called satellite is formed by landing.

  Furthermore, in order to control the shape of the resist droplets that land on the copper foil as desired, the ink must be ejected with a low ink viscosity, the amount of resist ejected from the nozzle (nozzle diameter), and the ejection speed. There are many parameters that need to be taken into consideration when forming a pattern, such as the surface state of a conductive film such as copper foil. For this reason, a predetermined pattern shape cannot be formed satisfactorily, and defects such as voids are generated in the formed resist pattern, particularly when such a method is applied to high-mix low-volume production. This problem has become prominent.

  The present invention solves the problems of the conventional methods described above, and easily and accurately forms a resist film having a fine pattern using a simple apparatus without requiring many complicated parameter settings. An object of the present invention is to provide a pattern forming method that can be used.

  Such an object of the present invention is achieved by a pattern forming method including forming a resist film having a predetermined pattern by thermal transfer on a conductive film provided on at least one surface of an insulating substrate.

  According to the present invention, it is possible to form a pattern by an on-demand method without using a mask or a screen. Therefore, the production efficiency is high, there is no waste of time, resources and energy, and an exposure developing device or the like. Large capital investment is not required. In addition, when the design is changed, it can be easily and quickly handled by simply changing the thermal transfer pattern of the thermal transfer device.

  In particular, in the above-described ink jet method, since the adherend is a liquid repellent material such as a copper foil that does not allow the resist liquid to penetrate, unlike the paper that is a recording medium of a general ink jet printer, It is very difficult to control the shape and size of the dots, and satellites are likely to be generated due to scattering of the resist solution upon landing. In contrast, in the method of the present invention, high-viscosity melt transfer is performed by using a high-viscosity dry dry thermal transfer medium instead of a resist solution, so that a high-definition pattern (50 μm or less, preferably 20 μm or less) can be clearly and accurately displayed. Of course, there is no scattering. In addition, in the ink jet system, a resist coating film is formed by landing of a small volume of resist droplets of 2 picoliters, so that it is necessary to repeat drawing in order to obtain a predetermined resist thickness. Since the resist film having the above pattern can be formed by a single transfer, the writing time can be drastically shortened. Furthermore, the use of a solvent is essential in the inkjet method because a resist solution is used, and labor for securing the working environment and reducing the environmental burden, equipment, and maintenance to prevent clogging of the discharge nozzle are required. In contrast, the method of the present invention is essentially solvent free and does not require such labor, equipment and maintenance.

  The pattern forming method of the present invention is characterized in that a resist film having a predetermined pattern is formed by thermal transfer on a conductive film provided on at least one surface of an insulating substrate.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating an embodiment when the pattern forming method according to the present invention is applied to the production of a printed circuit board (wiring board).
In the present invention, first, as shown in FIG. 1A, a laminate 4 is prepared in which a conductive film 3 is provided on an insulating substrate 1 with an adhesive 2 interposed therebetween.
Next, as shown in FIG. 1B, a resist film 5 having a predetermined pattern is attached on the conductive film 3 of the laminated body 4 by thermal transfer.
Thereafter, as shown in FIG. 1C, the resist film 5 is cured by applying heat energy or light energy (indicated by an arrow in the figure).

Next, as shown in FIG. 1 (d), the laminate 4 having the cured resist film 5 on the surface is immersed in an etching solution (not shown) and covered with the resist film 5 on the substrate 1 of the laminate 4. Undissolved parts are dissolved and removed, then washed with water and dried.
Thereafter, as shown in FIG. 1E, the resist film 5 remaining on the conductive film 3 is washed and removed with a weak alkaline aqueous solution, and then dried.

  Here, as the material of the insulating substrate 1, in the case of a rigid printed circuit board, a material in which a thermosetting resin such as phenol resin, epoxy resin, polyimide (PI) or the like is impregnated into paper or glass cloth is preferable. Although it can mention as a thing, it is not limited to these.

  In the case of a flexible printed circuit board, preferred materials for the substrate 1 include, but are not limited to, polyimide, polyester, aramid, polycarbonate, polyparabanic acid, and aramid. The thickness of such a film is usually about 25 μm or 50 μm.

  As the material of the conductive film 3, a metal film, preferably a copper thin film, for example, a copper foil is mainly used, and in particular, an electrolytic copper foil or a roll copper foil is used.

  As the adhesive 2, in the case of a rigid printed circuit board, a mixture of a thermoplastic resin such as a butyral resin and a thermosetting resin such as a phenol resin, an epoxy resin, or a melamine resin is used.

  In the case of flexible printed circuit boards, the adhesive 2 is a liquid adhesive mainly composed of polyester-isocyanate, phenol resin-butyral, phenol resin-nitrolyl rubber, modified epoxy resin, etc., and phenol resin-butyral as the main material. Preferred examples thereof include, but are not limited to, a dry film, or an adhesive mainly containing a modified epoxy resin, epoxy-nylon, modified polyethylene, FEP-Teflon (registered trademark).

  Then, for example, a conductive film 3 such as a copper foil is superposed on the base body 1 with the adhesive 2, and heated and pressurized to obtain a laminate 4. As a representative example of such a laminate 4, a so-called copper-clad plate bonded to a copper foil using an adhesive with a polyester or polyimide having excellent dimensional stability as a base material is available on the market.

  In the present embodiment, the laminate 4 is not limited to the above-described one. For example, a metal film such as copper is formed on a film such as polyimide by vapor deposition, or treatment with an organic compound or plasma is used. A flexible substrate or the like in which a copper thin film having a thickness of several μm to several tens of μm is formed by performing other adhesion improving treatment thereon, and sputtering, vapor deposition, electrolytic plating, or the like can be suitably used.

  Next, in the present embodiment, it is preferable to use a thermal transfer medium as means for forming a resist film having a predetermined pattern by thermal transfer on a conductive film provided on at least one surface of the insulating substrate.

  Further, it is preferable to use a heating resistor or a laser as a heat source for such thermal transfer.

  Here, the thermal transfer medium refers to a laminated body in which a thermal transfer layer that is melted or softened by heating and released from the base material and is thermally transferred to the surface of the transfer target is laminated on the base material. It has been widely used as an ink ribbon for a thermal recording printer. However, the application of the thermal transfer medium is not limited to the ink ribbon, and the present inventors have (1) that the thermal transfer medium can be thermally transferred to the surface of a transfer medium made of various materials such as metal and plastic, and (2). In the field of electronic devices, paying attention to the fact that various excellent resistances can be given to the transferred layer by selecting the material of the thermal transfer layer, and (3) a layer having an arbitrary thickness can be formed by transfer. In the present study, the use of a thermal transfer medium to form a resist pattern that has been formed by photolithography using a photosensitive resin has been studied.

  As a result, as a material for the thermal transfer layer, a thermal transfer property that is thermally transferred by being melted or softened by heating, and also a photocrosslinkable property that is crosslinked by irradiation with light such as ultraviolet rays after thermal transfer is used. It has been found that, by crosslinking the subsequent transfer layer by light irradiation, the transferability is improved and the etching solution resistance is improved so that it can be effectively applied as an etching resist material.

  The material having thermal transferability and photocrosslinking property is a material mainly comprising a photopolymerizable resin and a photopolymerization initiator. Examples of such photopolymerizable resins include conventionally known monofunctional photopolymerizable resins such as epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, polyacrylate, 2-ethylhexyl acrylate, and 2-hydroxypropyl acrylate; dicyclopentenyl Bifunctional photopolymerizable resins such as acrylate, dicyclopentenyloxyethyl acrylate, 1,4-butanediol acrylate, and diethylene glycol diacrylate; Photopolymerizable more than trifunctional such as pentaerythritol triacrylate and trimethylolpropane triacrylate Resin is used. Moreover, as said photoinitiator, well-known photoinitiators, such as an acetophenone type, a thiuram type, a benzophenone type, a benzyl type, a benzoin type, an azo compound type, are used.

  Conventionally, a transfer material containing a photopolymerizable resin and a photopolymerization initiator has been known. For example, Patent Document 2 discloses a transfer material including a photopolymerizable resin (epoxy acrylate) obtained by modifying a functional group of a thermosetting resin with (meth) acrylate, a photopolymerization initiator, and a thermoplastic resin. Patent Document 3 discloses a transfer material containing a monomer such as tris (2-hydroxyethyl) isocyanurate triacrylate and a photopolymerization initiator.

  However, these conventional transfer materials have various problems. That is, all of the conventional photocrosslinkable compounds such as epoxy acrylate as shown in Patent Document 2 have a thermosetting resin as a basic skeleton and thus have a low molecular weight and are difficult to be further polymerized due to their structure. Therefore, when applied to a heat-sensitive transfer sheet, there is a problem that so-called blocking that adheres to the back side tends to occur. Further, in the material disclosed in Patent Document 3, as described in claim 7, in order to maintain good transferability, the monomer and oligomer are kept in an uncured state until the end of thermal transfer. Since it is necessary, there is a problem that blocking is likely to occur similarly. Therefore, when the material shown in Patent Document 2 is selected and used, blocking can be suppressed by using a high molecular weight thermoplastic resin, but attention must be paid to the fact that resistance to the etching solution is reduced. It was. Moreover, when using the material shown by patent document 3, it had to preserve | save on predetermined conditions.

  As described above, the present inventors use a transfer material having the above thermal transfer property and photocrosslinkability as an etching resist material, and a thermal transfer medium having a thermal transfer layer containing such a material on a substrate. It has been found that an etching resist film having a predetermined pattern can be formed by thermal transfer on a conductive film provided on at least one surface of the above insulating substrate. As a result of further research and investigation based on such knowledge, the present inventors will explain the transfer material having the above-mentioned thermal transfer property and photocrosslinkability in order to form an etching resist film by transfer. It has been found that it is optimal to use a material (hereinafter referred to as “transfer material X”).

The transfer material X is characterized in that it contains a (meth) acrylate modified product of an acrylic polymer containing at least a repeating unit derived from glycidyl (meth) acrylate, an epoxy resin, and a photopolymerization initiator.
Here, it is desirable that the epoxy resin is a bisphenol type epoxy resin.
Moreover, it is desirable that the thermal transfer layer contains the acrylic polymer (meth) acrylate modified product A and the epoxy resin E at a weight ratio A / E = 95/5 to 60/40.

  In the (meth) acrylate modified product, by changing the proportion of the repeating unit derived from glycidyl (meth) acrylate contained in the acrylic polymer that is the basic skeleton, the glycidyl group portion of the repeating unit is changed. The number of (meth) acrylates as a photocrosslinkable functional group to be bonded can be arbitrarily changed. Therefore, the crosslink density of the transfer layer after crosslinking and the etching resistance of the transfer layer, and characteristics such as chemical resistance, scratch resistance, solvent resistance, and heat resistance can be freely designed.

  In addition, since the thermal transfer layer is used in combination with an epoxy resin that causes the thermal transfer layer to have an adhesive force to the transferred object at the time of thermal transfer, it is sensitively heated on the surface of the transferred object by heating to a predetermined thermal transfer temperature. Thermal transfer can be performed. In addition, the epoxy resin reacts with the hydroxyl group contained in the side chain of the (meth) acrylate modified product by the heat generated by the light irradiation when the (meth) acrylate modified product is crosslinked by light irradiation. Since it is taken in, the transfer layer after thermal transfer can be more firmly adhered to the surface of the transfer target body by crosslinking by light irradiation. For this reason, in particular, even on the surface of a material to be transferred such as polyimide, polyethylene terephthalate, etc. with a small surface energy, the thermal transfer layer can be thermally transferred with high sensitivity and the transfer layer after thermal transfer can be cross-linked to be strong with high adhesive strength. It becomes possible to adhere to.

  In addition, in the transfer material X, each component of the (meth) acrylate modified product, the epoxy resin, and the photopolymerization initiator is subjected to a cross-linking reaction by a photopolymerization reaction by light irradiation, and thus has a three-dimensional network structure and a large molecular weight. Since a crosslinked product is formed, chemical resistance, scratch resistance, solvent resistance, heat resistance and the like can be improved in addition to the etching resistance of the transfer layer after crosslinking. In addition, by changing the proportion of the epoxy resin, the sensitivity of the thermal transfer layer during thermal transfer can be adjusted, and the adhesive strength of the transfer layer after thermal transfer can be adjusted. Etching resistance and chemical resistance, scratch resistance, solvent resistance, heat resistance, and other characteristics can be freely designed.

  In addition, when a bisphenol type epoxy resin is used as the epoxy resin in the transfer material X, the bisphenol type epoxy resin contains a hydroxyl group in the molecule and is particularly excellent in adhesion to the transfer target. The thermal transfer layer is thermally transferred to the surface of the transfer target with higher sensitivity, and the transfer layer after the thermal transfer is cross-linked so that it can be more firmly adhered to the surface of the transfer target.

  The ratio of the epoxy resin is preferably in the range of 95/5 to 60/40, expressed as a weight ratio A / E between the (meth) acrylate modified product A of the acrylic polymer and the epoxy resin E. When the ratio of the epoxy resin E is less than this range, the thermal transfer layer by using the epoxy resin together is thermally transferred to the surface of the transfer target with high sensitivity, and the transfer layer after the thermal transfer is crosslinked, There is a possibility that the effect of firmly adhering to the surface of the transfer object may not be obtained. In addition, when the proportion of the (meth) acrylate modified product A is less than this range, in addition to the etching resistance of the transfer layer after crosslinking, chemical resistance, scratch resistance, solvent resistance, heat resistance, etc. may decrease. , Transparency may be reduced. On the other hand, if the weight ratio A / E is in the range of 95/5 to 60/40, the etching resistance of the transfer layer after crosslinking, as well as chemical resistance, scratch resistance, solvent resistance, heat resistance, While maintaining the effect of improving the transparency, the thermal transfer layer is further thermally transferred to the surface of the transfer target body, and the transfer layer after the thermal transfer is cross-linked to further increase the surface of the transfer target body. It is possible to bond firmly. In addition, by adjusting the weight ratio A / E within the above range, the sensitivity of the thermal transfer layer during thermal transfer can be adjusted, and the adhesive strength of the transfer layer after thermal transfer can be adjusted. It is also possible to freely design the crosslink density and the etching resistance as well as the chemical resistance, scratch resistance, solvent resistance, heat resistance and other characteristics.

As described above, the transfer material X is characterized in that it contains a modified (meth) acrylate of an acrylic polymer containing at least a repeating unit derived from glycidyl (meth) acrylate, an epoxy resin, and a photopolymerization initiator. .
Among them, the acrylic polymer which is the basic skeleton of the (meth) acrylate modified product is composed of only glycidyl (meth) acrylate, that is, glycidyl acrylate homopolymer, glycidyl methacrylate homopolymer, glycidyl acrylate and glycidyl methacrylate. In addition, a copolymer of glycidyl (meth) acrylate and another monomer can also be used.

  Other monomers that can form copolymers with glycidyl (meth) acrylate include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-butyl acrylate, cyclohexyl Xyl acrylate, octyl acrylate, dodecyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, dodecyl methacrylate, etc. An alkyl (meth) acrylate monomer having 1 to 18 carbon atoms, Styrene, one or more of styrene-based monomers such as α- methyl styrene.

  When the acrylic polymer is a copolymer of glycidyl (meth) acrylate and another monomer, the content of glycidyl (meth) acrylate in the copolymer is preferably 50% by weight or more, and preferably 60% by weight or more. It is particularly preferred. If the content is less than this range, the number of (meth) acrylates as photocrosslinkable functional groups bonded to the glycidyl group portion of the copolymer is too small, and the crosslinking density of the transfer layer after crosslinking is insufficient. Therefore, in addition to the etching resistance of the transfer layer, chemical resistance, scratch resistance, solvent resistance, heat resistance and the like may be reduced.

  In addition, since an acrylic polymer may be formed only with glycidyl (meth) acrylate as above-mentioned, the upper limit of the content rate is not limited, and reaches to 100 weight%. However, the cross-linking density of the transfer layer after cross-linking by copolymerizing other monomers and the characteristics such as etching resistance, chemical resistance, scratch resistance, solvent resistance, heat resistance, etc. are free. In order to exhibit the design effect satisfactorily, the content ratio of glycidyl (meth) acrylate is preferably 95% by weight or less.

  As a polymer containing only glycidyl (meth) acrylate, the content ratio is set to 100% by weight, or other monomers are copolymerized so that the content ratio of glycidyl (meth) acrylate is within the range of 50% by weight or more. By adjusting the above, it is possible to freely design the cross-linking density of the transfer layer after cross-linking and the resulting etching resistance, and chemical resistance, scratch resistance, solvent resistance, heat resistance and other characteristics.

  The acrylic polymer (meth) acrylate modified product used as the photocrosslinkable compound has a structure in which (meth) acrylate is bonded to the glycidyl group portion of the acrylic polymer. Specifically, in addition to a compound in which an acrylate is bonded to a plurality of glycidyl groups in one acrylic polymer, a compound in which a methacrylate is bonded, or a compound in which an acrylate and a methacrylate are mixed and bonded. It is done.

  The (meth) acrylate modified product of the acrylic polymer preferably has a glass transition temperature of 40 to 80 ° C, particularly preferably 40 to 70 ° C. If the glass transition temperature is less than this range, the thermal transfer layer tends to melt and soften even below the thermal transfer temperature, and may be easily blocked due to, for example, a thermal history during storage. If the glass transition temperature exceeds this range, the melting and softening temperature of the thermal transfer layer rises, so that even if heated to a predetermined thermal transfer temperature, it may not be possible to transfer the heat to the surface of the transfer target with high sensitivity. There is.

In addition, in order to adjust the glass transition temperature of the (meth) acrylate modified product of acrylic polymer,
(1) Change the type of glycidyl (meth) acrylate constituting the acrylic polymer,
(2) Raising the copolymerization of two glycidyl (meth) acrylates changes the ratio,
(3) When copolymerizing other monomers, change the type or change the ratio,
(4) Change the type of (meth) acrylate to be bonded to the glycidyl group.
(5) When two types of (meth) acrylates are mixed and bonded, a method of changing the ratio may be adopted.

As the (meth) acrylate modified product of the acrylic polymer, one of the various compounds may be used alone, or two or more may be used in combination.
As an epoxy resin, it is possible to generate an adhesive force to a transferred material in a thermal transfer layer at the time of thermal transfer, and to react with a (meth) acrylate modified product of an acrylic polymer to form a cross-linked product by heat by light irradiation. Any of various epoxy resins that can be used can be used, and bisphenol type epoxy resins are particularly preferable. Bisphenol-type epoxy resins contain hydroxyl groups in the molecule and are particularly excellent in adhesion to the transfer target, so that the thermal transfer layer can be thermally transferred to the surface of the transfer target with higher sensitivity, and the transfer layer after thermal transfer Can be bonded to the surface of the transfer target body more firmly.

  Moreover, as an epoxy resin, it is preferable to use the thing whose number average molecular weight is 1000-3000, especially 1000-2000. A thermal transfer layer containing an epoxy resin having a number average molecular weight less than this range tends to easily generate an adhesive force even at a predetermined thermal transfer temperature or lower. Therefore, for example, the thermal transfer layer may be easily blocked due to a thermal history during storage. In addition, when a thermal transfer layer is partially heated by a thermal head or the like in correspondence with a pattern to be formed and thermally transferred to the surface of the transfer target, the area of the unheated area around the heated area Even in the thermal transfer layer, an adhesive force is easily generated. At the time of thermal transfer, even the thermal transfer layer in the region is thermally transferred to the surface of the transfer target, and the reproducibility and sharpness of the pattern formed by the transfer layer may be reduced.

  On the other hand, a thermal transfer layer containing an epoxy resin having a number average molecular weight exceeding the above range tends to hardly cause adhesiveness even when heated to a predetermined thermal transfer temperature. Therefore, even when heated to a predetermined thermal transfer temperature, there is a possibility that the thermal transfer layer cannot be thermally transferred to the surface of the transfer target with high sensitivity.

  As the epoxy resin, it is preferable to use an epoxy resin having an epoxy equivalent of 1500 g / eq or less, particularly 600 to 1000 g / eq. An epoxy resin having an epoxy equivalent exceeding this range has a low reactivity with the (meth) acrylate modified product of the acrylic polymer and may not be able to form a strong cross-linked product upon light irradiation. Therefore, in addition to the etching resistance of the transfer layer, chemical resistance, scratch resistance, solvent resistance, heat resistance and the like may be reduced.

  Specific examples of the bisphenol type epoxy resin that satisfies the above-mentioned conditions are not limited to these, but, for example, among the Epicoat (registered trademark) series manufactured by Japan Epoxy Resin Co., Ltd., all are bisphenol A type epoxy resins. Epicoat 1002 [epoxy equivalent: 600 to 700 g / eq, softening point: 78 ° C., number average molecular weight: about 1060], Epicoat 1003 [epoxy equivalent: 670 to 770 g / eq, softening point: 89 ° C., number average molecular weight: About 1200], Epicoat 1055 [epoxy equivalent: 800 to 900 g / eq, softening point: 93 ° C., number average molecular weight: about 1350], Epicoat 1004 [epoxy equivalent: 875 to 975 g / eq, softening point: 97 ° C., number average Molecular weight: about 1600], Epicoat 1004AF [Epoxy equivalent: 875] ˜975 g / eq, softening point: 97 ° C., number average molecular weight: about 1600] and the like.

  In the thermal transfer layer, the acrylic polymer (meth) acrylate-modified product A and the epoxy resin E are in a weight ratio A / E = 95 / 5-60 / 40, particularly A / E = 90 / 10-70 / 30. It is preferable to contain. If the weight ratio A / E is within this range, the thermal transfer layer can be maintained while maintaining the effects of improving the etching resistance and chemical resistance, scratch resistance, solvent resistance, and heat resistance of the transfer layer after crosslinking. Furthermore, it is possible to more firmly adhere to the surface of the transferred body by thermally transferring the surface to the transferred body with high sensitivity and crosslinking the transfer layer after the thermal transfer. In addition, by adjusting the weight ratio A / E within the above range, the sensitivity of the thermal transfer layer during thermal transfer can be adjusted, and the adhesive strength of the transfer layer after thermal transfer can be adjusted. It is also possible to freely design the crosslink density and the etching resistance as well as the chemical resistance, scratch resistance, solvent resistance, heat resistance and other characteristics.

As the photopolymerizable crosslinking agent, any of various compounds capable of forming a crosslinked product by taking an epoxy resin and photopolymerizing an acrylic polymer (meth) acrylate-modified product by irradiation with light such as ultraviolet rays can be used. is there.
Examples of the photopolymerizable crosslinking agent include biacetyl, acetophenone, benzophenone, 4,4-bis (diethylamino) benzophenone, phenanthraquinone, azobisisobutylnitrile, Michler's ketone, benzyl, benzoin, benzoin isobutyl ether, and benzyldimethyl ketal. Tetramethylthiuram sulfide, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4- Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, methylbenzoylformate, and the like.

  The photopolymerizable crosslinking agent is preferably contained in the thermal transfer layer in a ratio of 1 to 10 parts by weight with respect to 100 parts by weight as a total of the (meth) acrylate modified product of the acrylic polymer and the epoxy resin. In addition to the above-described components, the thermal transfer layer further includes a colorant for coloring the thermal transfer layer, a dispersant for dispersing the pigment, a sensitizer, an ultraviolet absorber, a leveling agent, a viscoelastic modifier. Various additives such as a quality agent can be contained in an arbitrary ratio. In the use of a resist pattern, it is usually not necessary to contain a colorant, but it may be colored for the purpose of identification or the like.

  The above-described thermal transfer medium is manufactured by applying a coating liquid containing each of the above-described components and a solvent to one side of a substrate and drying to form a thermal transfer layer. The coating agent can be applied to the surface of the substrate by a conventional method such as a roll coater, an air knife coater, a blade coater, a rod coater, a bar coater, a comma coater, or a gravure coater. As the base material, any of conventionally known films and sheets made of various materials can be used as the base material of the thermal transfer medium. Examples of such a substrate include a film or sheet made of a resin such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyamide, and capacitor paper.

  On the surface of the base material on the side where the thermal transfer layer is to be formed, a release layer such as those mainly composed of waxes may be formed. In addition, when the thermal transfer medium is used in a thermal recording printer equipped with a thermal head, the surface of the substrate opposite to the above, on the side where the thermal head abuts, is coated with silicone resin, fluorine. A stick prevention layer made of a resin, a nitrocellulose resin, a silicone-modified urethane resin, a silicone-modified acrylic resin, or the like and having a lubricant dispersed therein may be formed as necessary.

  The above-described thermal transfer medium is obtained by heating the thermal transfer layer using a thermal head, laser, infrared flash, thermal pen, etc., thermally transferring it to the surface of the transfer object, and then irradiating with ultraviolet rays or the like to crosslink. It is excellent in etching resistance, chemical resistance, scratch resistance, solvent resistance, heat resistance and the like, and can form a robust resist layer suitable for the above applications.

  In particular, by using a laser for thermal transfer, it is generally possible to obtain a higher definition and higher resolution image than a thermal head. In the case of performing laser thermal transfer, generally a layer that contains an infrared absorbing dye or the like between the above-mentioned substrate of the thermal transfer medium and the thermal transfer layer and converts infrared laser light into heat (photothermal conversion). A layer further provided with a layer) is prepared, the thermal transfer medium and the transfer target are brought into close contact with each other, and exposed, for example, with a laser beam having an absorption peak near 830 nm, and then peeled off. The infrared absorbing dye in the photothermal conversion layer in the thermal transfer medium converts the laser light into heat and heats the thermal transfer layer. The heat-transferred thermal transfer layer is transferred to the transfer target.

  Furthermore, the present inventors have found that a thermosetting material that is a material different from the transfer material X described above can be used as the material of the thermal transfer layer. Examples of such a thermosetting material include a material containing a compound having two or more epoxy groups and a latent crosslinking agent (amine compound) of an epoxy resin as disclosed in Patent Document 4. However, since these materials themselves have problems in storage stability at high temperatures, the present inventors have conducted intensive studies. As a result, in order to form an etching resist film by transfer, the following will be described as a thermosetting material. It has been found that it is optimal to use a material (hereinafter referred to as “transfer material Y”).

  In the present embodiment, instead of the transfer material X described above, the transfer material Y is used as an etching resist material, and a thermal transfer medium having a thermal transfer layer including the transfer material Y on a base material is used. An etching resist film having a predetermined pattern can be formed by thermal transfer on a conductive film provided on at least one surface of the substrate.

  The transfer material Y includes an epoxy resin and a carboxyl group-containing polymer having a weight average molecular weight (hereinafter simply referred to as “molecular weight”) of 3,000 to 30,000.

  In the transfer material Y, the epoxy resin is used because it is excellent in transferability to a transfer material during thermal transfer, and in etching resistance and scratch resistance after transfer. Among epoxy resins, a combination of glycidyl (meth) acrylate or a copolymer thereof and a non-acrylic epoxy resin is preferable.

  The film strength can be improved by using glycidyl (meth) acrylate or a copolymer thereof. However, if only glycidyl (meth) acrylate or a copolymer thereof is blended, the hardness is high even in an uncured state, and the sensitivity during thermal transfer may be insufficient. For this reason, sensitivity can be supplemented by using a combination of non-acrylic epoxy resins. In addition, when this non-acrylic epoxy resin contains a hydroxyl group, it reacts not only with the polymer as a crosslinking agent but also with glycidyl (meth) acrylate or a copolymer thereof at the time of curing, so that it is stronger after curing. A film can be obtained.

  The glycidyl (meth) acrylate copolymer used in the transfer material Y is an acrylic copolymer containing at least a structural unit derived from glycidyl (meth) acrylate (hereinafter sometimes referred to as glycidyl (meth) acrylate unit). Glycidyl (meth) acrylate and / or glycidyl acrylate and other copolymerizable monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, Isobutyl (meth) acrylate, tert-butyl (meth) acrylate, n-butyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate Rate, etc., alkyl (meth) acrylates of carbon atoms in the alkyl group 1 to 18, styrene, a copolymer of one or more such styrenic monomers such as α- methyl styrene. These glycidyl group-containing acrylic copolymers may be used alone or in combination of two or more.

  The glycidyl group-containing acrylic copolymer preferably has a molecular weight of 3,000 to 500,000, more preferably 5,000 to 200,000. Of these, those having a glycidyl (meth) acrylate unit content of 5 to 90% by weight are preferred. If the molecular weight is less than 3,000, a sufficient cured state of a three-dimensional network structure cannot be obtained, and the etchant resistance and heat resistance of the cured product are not sufficient. On the other hand, if it exceeds 50,000, the transferability tends to decrease. Furthermore, if the content of the glycidyl (meth) acrylate unit is less than 5% by weight, a sufficient cured state cannot be obtained, and the etching solution and heat resistance of the cured product tend to be insufficient. There is a tendency for transferability to decrease. Further, from the viewpoint of transferability, those having a glass transition point of 40 to 130 ° C are preferable.

  Examples of the non-acrylic epoxy resin used in the transfer material Y include bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol S type, cresol novolac type, and phenol novolac type epoxy resins. These epoxy resins may be used alone or in combination of two or more.

  Among the above-mentioned non-acrylic epoxy resins, a hydroxyl group-containing epoxy resin is preferable because it reacts with glycidyl (meth) acrylate or a copolymer thereof to obtain a stronger film after curing. Furthermore, bisphenol A type, bisphenol F type, bisphenol AD type, and bisphenol S type epoxy resins are particularly preferred from the viewpoint of obtaining a cured product having excellent transferability, etching solution resistance and heat resistance.

  The hydroxyl group-containing epoxy resin preferably has a molecular weight of 500 to 30,000, more preferably 500 to 10,000. Among them, those having an epoxy equivalent of 180 to 1,000 (g / eq) are preferable. If the molecular weight is less than 500, a sufficient cured state cannot be obtained, and the cured product has insufficient etching resistance and heat resistance. On the other hand, when the molecular weight exceeds 30,000, the transferability tends to decrease. On the other hand, when the epoxy equivalent is less than 180 (g / eq), a sufficient cured state cannot be obtained, and there is a tendency that the etching solution resistance and heat resistance of the cured product are not sufficient, while 1,000 (g / eq). If it exceeds 1, there is a tendency that a sufficient cured state cannot be obtained. Furthermore, from the viewpoint of transferability, those having a softening point of 60 to 150 ° C. are preferred.

  The weight blending ratio of glycidyl (meth) acrylate or a copolymer thereof and a hydroxyl group-containing epoxy resin is preferably 7: 3 to 3: 7. When there is too much glycidyl (meth) acrylate or its copolymer from this range, there exists a possibility that a sensitivity may be insufficient. On the other hand, if the hydroxyl group-containing epoxy resin is too much, the etching solution resistance and scratch resistance tend to be slightly inferior.

  Usually, a low molecular compound is used for the crosslinking agent so as to facilitate crosslinking. However, although low molecular weight compounds are easily cross-linked, there is a problem that cross-linking proceeds when stored at a high temperature, resulting in poor sensitivity during thermal transfer. Therefore, in the transfer material Y, a polymer having a molecular weight of 3,000 to 30,000 is used as a cross-linking agent, so that preservability is improved by suppressing cross-linking when stored at a high temperature. When the molecular weight is less than 3,000, crosslinking during storage at high temperatures tends to proceed, and the sensitivity during thermal transfer is poor. On the other hand, if the molecular weight is greater than 30,000, curing may be insufficient. In addition, in this material, since the crosslinking agent itself is a polymer, it can maintain a certain strength of the coating film even if it is uncured.

  Furthermore, if an amino group is contained in the cross-linking agent, cross-linking occurs even at a relatively low temperature, which causes a problem when stored at a high temperature. For this reason, in the transfer material Y, the storability at high temperature is improved by using a carboxyl group-containing polymer as a crosslinking agent instead of a crosslinking agent having an amino group with respect to the epoxy resin.

  The carboxyl group-containing polymer is preferably a methacrylic acid homopolymer. Because of the high carboxyl group content, it does not cure when stored at a temperature of about 50 to 60 ° C., but can be easily cured at a temperature of about 100 to 150 ° C., and can be stored and cured at high temperatures. And the balance is the best. Use of an acrylic crosslinking agent is advantageous because the crosslinking agent itself can improve the strength of the film.

  The content of the carboxyl group-containing polymer is preferably 30 to 70 parts by weight with respect to 100 parts by weight of the epoxy resin. This is because if it is out of this range, the etching solution resistance, scratch resistance, etc. are poor.

  In the transfer material Y, when a colorant is added for the purpose of identification or the like, it may be appropriately selected from conventionally used materials such as carbon black, organic pigments, inorganic pigments and dyes. As for content of a coloring agent, 10 to 50 weight% is preferable with respect to the total solid of all the compounding agents.

  In addition to the epoxy resin, the carboxyl group-containing polymer and the colorant, it is preferable to blend a urethane resin. Since the urethane resin itself becomes a part of the cured product, the urethane resin has an advantage that it does not inhibit curing while being excellent in adhesiveness that does not select a transfer target. The urethane resin is preferably contained in an amount of 1 to 10% by weight, preferably 2 to 8% by weight, based on the total solid content of all compounding agents. If it is less than this range, the effect cannot be obtained. On the other hand, if the amount is too large, the etching solution resistance, scratch resistance and the like are adversely affected.

  The thermal transfer layer containing the transfer material Y is heated with a thermal head, a laser, an infrared flash, a thermal pen, or the like in the same manner as the thermal transfer layer containing the transfer material X described above, so that the surface of the transfer object is fine. Thermal transfer can be performed with high accuracy. In particular, by using a laser for thermal transfer, it is generally possible to obtain a higher definition and higher resolution image than a thermal head.

  In the present embodiment, the resist film 5 is then cured by applying thermal energy, light energy such as ultraviolet rays, etc., as shown by arrows in FIG.

As a method for curing the transfer material X, ultraviolet exposure can be mentioned as a preferable method. For example, an ultraviolet light emitting lamp such as a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, or a xenon lamp can be appropriately selected and used. The effective wavelength for curing the ultraviolet curable resin is generally in the vicinity of 320 to 400 nm, and is also on the long wavelength side in the ultraviolet region, so it is also preferable to use a metal halide lamp that emits a large amount of light on the long wavelength side. As an example of a metal halide lamp, LH-6 (UV output: 187 W / cm) manufactured by Fusion Ubuy Systems Japan is preferable. The irradiation light amount, depending on the composition of the transfer material X, in general is preferably in the range of 100~2500mj / cm ^2, for example 1500 mJ / cm ² is used as the integrated quantity of light. If the integrated light quantity is less than 100 mj / cm ² , an uncured part may remain, and conversely if it exceeds 2500 mj / cm ² , overcuring may occur.

  As the method for curing the transfer material Y, any conventional heating means such as a heater or a high frequency can be used. As a specific apparatus, for example, a drying oven D0-600FPA manufactured by AS ONE is preferably used. As curing conditions, generally, heating at 80 to 150 ° C. for about 20 to 80 minutes is preferable, and examples include 130 ° C. × 30 minutes, 100 ° C. × 60 minutes, and the like.

Next, as shown in FIG. 1 (d), the laminate 4 having the cured resist film 5 on the surface is immersed in an etching solution (not shown) and covered with the resist film 5 on the substrate 1 of the laminate 4. Undissolved parts are dissolved and removed, then washed with water and dried.
In the present embodiment, the wet method is used as the etching method, and the substrate is immersed in an etching tank containing a chemical solution such as an aqueous ferric chloride solution, an aqueous cupric chloride solution, or an alkaline etching solution, or the substrate. The pattern is completed by removing the unnecessary copper by spraying the chemical while rotating or carrying on the conveyor.
However, dry etching represented by reactive ion etching (RIE) can also be used.

  Thereafter, as shown in FIG. 1E, the resist film 5 remaining on the conductive film 3 is washed and removed with an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide, and then dried.

  Hereinafter, although the present invention is explained based on an example, referring to drawings, these examples are illustrations and the present invention is not limited to these examples.

[Example 1]
<Preparation of thermal transfer medium>
1. Preparation of coating solution Methacrylate modification of copolymer of glycidyl methacrylate and methyl methacrylate (GMA / MMA-MA; content ratio of glycidyl methacrylate: 90% by weight; glass transition temperature: (meth) acrylate modification of acrylic polymer 46 parts by weight) and bisphenol A type epoxy resin [Epicoat 1003 manufactured by Japan Epoxy Resin Co., Ltd .; epoxy equivalent: 670-770 g / eq; softening point: 89 ° C .; number average molecular weight: about 1200] 3 parts by weight 1 part by weight of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator (Irgacure (trade name) 184 manufactured by Ciba Specialty Chemicals) and 10 parts by weight of carbon black as a pigment, 69 parts by weight of methyl ethyl ketone Mixed with the thermal transfer medium A coating solution for heat-sensitive transfer layer was prepared of.

2. Application of coating liquid As a base material, a 4.5 μm thick PET film with a stick-proof layer made of silicone-acrylic copolymer on one side and a wax release layer on the other side is prepared. did. And after apply | coating said coating liquid to the surface in which the mold release layer of this base material was formed, and making it dry, a 2 micrometer-thick thermal transfer layer was formed, and it slit to 100 mm in width, A tape-shaped thermal transfer medium suitable for a barcode printing printer [Zebra Printer 140Xi III Plus manufactured by Lintec Corporation] was manufactured. The weight ratio A / E between the (meth) acrylate modified product A of the acrylic polymer and the epoxy resin E in this heat-sensitive transfer layer was 85/15.

<Thermal transfer>
As an FPC substrate, a copper-clad plate was prepared by adhering a 35 μm thick copper foil on an insulating base material made of an epoxy resin sheet having a thickness of 25 μm via an adhesive layer having a thickness of 15 μm. The thermal transfer medium produced as described above was set in a thermal transfer printer (Thermabar IP4630V; manufactured by Tohoku Ricoh Co., Ltd .; transfer energy level: set to 13). A pattern was printed to form a resist pattern.

[Example 2]
Example 1 except that instead of GMA / MMA-MAA, a glycidyl methacrylate homopolymer methacrylate modification (GMA-MAA; glass transition temperature: 41 ° C.) was used as the (meth) acrylate modification product of the acrylic polymer. Similarly, a resist pattern was formed.

[Examples 3 to 7]
As an epoxy resin, a resist pattern was formed in the same manner as in Example 1 except that the following bisphenol A type epoxy resins manufactured by Japan Epoxy Resin Co., Ltd. were used instead of Epicoat 1003.
Example 3: Epicoat 1001 [epoxy equivalent: 450 to 500 g / eq; softening point: 64 ° C .; number average molecular weight: about 900]
Example 4: Epicoat 1002 [epoxy equivalent: 600 to 700 g / eq; softening point: 78 ° C .; number average molecular weight: about 1060]
Example 5: Epicoat 1004 [epoxy equivalent: 875-975 g / eq; softening point: 97 ° C .; number average molecular weight: about 1600]
Example 6: Epicoat 1007 [epoxy equivalent: 1750-2200 g / eq; softening point: 128 ° C .; number average molecular weight: about 2900]
Example 7: Epicoat 1009 [epoxy equivalent: 2400-3300 g / eq; softening point: none; number average molecular weight: about 3750]

[Example 8]
A resist pattern was formed in the same manner as in Example 1 except that a cresol novolac type epoxy resin [Araldite (registered trademark) ECN-1280 manufactured by Bantico Co., Ltd.] was used instead of Epicoat 1003 as the epoxy resin.

[Examples 9 to 12]
A resist pattern was formed in the same manner as in Example 1 except that the amounts used of GMA / MMA-MAA and Epicoat 1003 and the weight ratio A / E between them were set to the values shown in Table 1, respectively.

[Example 13]
In place of GMA / MMA-MAA, a resist pattern was formed in the same manner as in Example 1 except that a methacrylated product of gresol novolac polyglycidyl ether (CNEPX-MAA, glass transition temperature: 40 ° C.) as an epoxy acrylate was used. Formed.

[Example 14]
A resist pattern was formed in the same manner as in Example 1 except that the amounts used of GMA / MMA-MAA and Epicoat 1003 and the weight ratio A / E between them were set to the values shown in Table 1, respectively.

[Example 15]
<Preparation of thermal transfer medium>
A silicone resin was applied to one surface of a 5 μm thick polyethylene terephthalate film with a gravure coater so that the coating amount was 0.25 g / m ² to form a heat-resistant protective layer. A coating liquid having the following composition was applied to the other surface of the polyethylene terephthalate film with a gravure coater so as to have a coating amount of 2.0 g / m ² and dried to form a thermal transfer layer, thereby producing a thermal transfer medium. . Hereinafter, the unit is weight%.

(Coating solution composition)
GMA-MMA 5
(Copolymer of glycidyl methacrylate and methyl (meth) acrylate; 50:50; manufactured by NOF Corporation; Blemmer CP-50M)
Bisphenol A type epoxy resin 5
(Japan Epoxy Resin, Epicoat 1003)
Methacrylic acid homopolymer (molecular weight 10,000) 6
Carbon black 4
Methyl ethyl ketone 52
Methanol 28
Total 100
In the above formulation, the composition ratio of glycidyl (meth) acrylate and hydroxyl group-containing epoxy resin was 5: 5.

<Thermal transfer>
As in Example 1, as an FPC substrate, a copper-clad formed by adhering a 35 μm thick copper foil on an insulating base material made of an epoxy resin sheet having a thickness of 25 μm via an adhesive layer having a thickness of 15 μm A board was prepared. The thermal transfer medium produced as described above was set in a thermal transfer printer (Thermabar IP4630V; manufactured by Tohoku Ricoh Co., Ltd .; transfer energy level: set to 13). A pattern was printed to form a resist pattern.

[Example 16]
The methacrylic acid homopolymer of the coating liquid composition of Example 15 was replaced with a styrene / acrylic acid copolymer (molecular weight 10,000), and further, 52% by weight of methyl ethyl ketone and 28% by weight of methanol were changed to 80% by weight of methyl ethyl ketone. A resist pattern was formed in the same manner as in Example 15.

[Example 17]
A resist pattern was formed in the same manner as in Example 15 except that the methacrylic acid homopolymer having a molecular weight of 10,000 in the coating liquid composition of Example 15 was replaced with a methacrylic acid homopolymer having a molecular weight of 3,000.

[Example 18]
A resist pattern was formed in the same manner as in Example 15 except that the methacrylic acid homopolymer having a molecular weight of 10,000 in the coating liquid composition of Example 15 was replaced with a methacrylic acid homopolymer having a molecular weight of 30,000.

[Example 19]
The same procedure as in Example 15 except that 5% by weight of GMA-MMA and 5% by weight of bisphenol A type epoxy resin in the coating liquid composition of Example 15 were replaced with 7% by weight of GMA-MMA and 3% by weight of bisphenol A type epoxy resin. A resist pattern was formed.

[Example 20]
The same procedure as in Example 15 except that 5% by weight of GMA-MMA and 5% by weight of bisphenol A type epoxy resin in the coating liquid composition of Example 15 was replaced with 3% by weight of GMA-MMA and 7% by weight of bisphenol A type epoxy resin. A resist pattern was formed.

[Example 21]
A resist pattern was formed in the same manner as in Example 15 except that the bisphenol A type epoxy resin having the coating liquid composition of Example 15 was replaced with a cresol novolak type epoxy resin (manufactured by Asahi Ciba; Araldite ECN-1280).

[Example 22]
GMA-MMA 5% by weight and bisphenol A type epoxy resin 5% by weight of the coating liquid composition of Example 15 were replaced with GMA-MMA 8% by weight and bisphenol A type epoxy resin 8% by weight, and no methacrylic acid homopolymer was further blended. A resist pattern was formed in the same manner as in Example 15 except that the above was changed.

[Example 23]
A resist pattern was formed in the same manner as in Example 15 except that the coating liquid composition of Example 15 was changed as follows.
<Coating solution composition>
GMA-MMA 6
Bisphenol A type epoxy resin 6
Hexamethylenediamine (molecular weight 116) 4
Carbon black 4
Methyl ethyl ketone 52
Methanol 28
Total 100

[Example 24]
A resist pattern was formed in the same manner as in Example 15 except that the methacrylic acid homopolymer having a molecular weight of 10,000 in the coating liquid of Example 15 was replaced with a methacrylic acid homopolymer having a molecular weight of 2,000.

[Comparative Example 1]
A resist pattern was formed in the same manner as in Example 15 except that the methacrylic acid homopolymer having a molecular weight of 10,000 in the coating liquid of Example 15 was replaced with a methacrylic acid homopolymer having a molecular weight of 40,000.

  The resist patterns obtained in Examples 1 to 24 and Comparative Example 1 were evaluated for transferability, etching resistance, and transferability after storage in a high-temperature and high-humidity environment according to the following procedures and evaluation criteria. The results are shown in Tables 2 and 3.

(Transferability)
Transferability was confirmed visually and evaluated according to the following criteria.
○: Clear transfer was possible Δ: Transfer was possible at a level where there was no problem in practical use ×: Dot omission and residual peeling occurred, resulting in unclearness

(Etch resistance)
Each of the above transfer samples was immersed in (1) 20% ammonium persulfate aqueous solution and (2) 10% ammonium hydroxide aqueous solution for 2 minutes at 30 ° C., and the etching resistance as a resist of the transfer portion was evaluated according to the following criteria. .
○: The printing (resist) did not peel at all. Δ: The printing (resist) was slightly eroded, but it was at a level that was not a problem in practice. ×: The printing (resist) was not peeled off.

<Transferability after storage in high temperature and high humidity>
Each transfer medium prepared in each of the above Examples and Comparative Examples was rolled and stored in a high temperature and high humidity environment of 50 ° C. and 80% RH for 96 hours, and then at room temperature (23 ± 1 ° C.) for 24 hours. After cooling, the transferability and occurrence of blocking were visually confirmed and evaluated according to the following criteria.
○: Clear transfer was possible and no blocking occurred. Δ: Transfer was possible at a level where there was no problem in practical use. ×: Omission of dots and residual peeling occurred, resulting in unclearness or blocking.

It is sectional drawing explaining embodiment at the time of applying the pattern formation method concerning this invention to manufacture of a printed circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Adhesive 3 Conductive film 4 Laminate 5 Resist film

Claims (10)

A pattern forming method comprising:
Forming an etching resist film having a predetermined pattern on a conductive film provided on at least one surface of an insulating substrate by thermal transfer using a heat transfer medium as a heat source using a heat transfer medium or a laser;
Curing the resist film;
Etching the exposed portion of the conductive film through the cured resist film; and removing the cured resist film remaining on the conductive film after the etching ;
The thermal transfer medium has a thermal transfer layer on a substrate, the thermal transfer layer contains an ultraviolet curable resin or a thermosetting resin, and an acrylic containing at least a repeating unit derived from glycidyl (meth) acrylate. A pattern forming method comprising: a polymer (meth) acrylate-modified product, an epoxy resin, and a photopolymerization initiator . The pattern forming method according to claim 1 , wherein the epoxy resin is a bisphenol type epoxy resin. The pattern formation according to claim 1 , wherein the thermal transfer layer contains (meth) acrylate modified product A of acrylic polymer and epoxy resin E at a weight ratio of A / E = 95/5 to 60/40. Method. The pattern formation method according to claim 1 , wherein the thermal transfer layer includes an epoxy resin and a carboxyl group-containing polymer having a weight average molecular weight of 3,000 to 30,000. The pattern forming method according to claim 4 , wherein the carboxyl group-containing polymer is a methacrylic acid homopolymer. The pattern formation method according to claim 4 , wherein the epoxy resin is a combination of glycidyl (meth) acrylate or a copolymer thereof and a non-acrylic epoxy resin. The pattern forming method according to claim 6 , wherein the non-acrylic epoxy resin is a hydroxyl group-containing epoxy resin. The glycidyl (meth) acrylate or the blending ratio by weight of the copolymer and the hydroxyl group-containing epoxy resin is 7: 3 to 3: 7 The pattern forming method according to claim 7, wherein. The pattern formation method according to claim 3 , wherein the thermal transfer layer further contains a urethane resin. The pattern forming method according to claim 9 , wherein the content of the urethane resin is 1 to 10% by weight with respect to the total solid content in the thermal transfer layer.

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