JP2678761B2 - Image forming method - Google Patents

Description

TECHNICAL FIELD The present invention uses a dry film to form an image by directly contacting a pattern mask on the photosensitive resin composition layer,
Furthermore, the present invention relates to an image forming method of performing alkali development.

Conventional technology A laminated film in which a photosensitive resin composition is layered on a base film (usually a polyethylene terephthalate film is used) and a protective film (usually a polyethylene film is used) is laminated thereon is
Generally called a dry film, it is widely used for manufacturing printed wiring boards and precision processing of metals.

In that use, first peel off the protective film from the dry film and affix the photosensitive resin composition layer side to the copper surface of the copper-clad substrate, and then expose with a pattern mask on the base film, Then, the base film is peeled off and provided for development.

Various types of photosensitive resin compositions are known for this purpose, and the developing method after exposure includes a solvent developing type and an alkali developing type.

Japanese Unexamined Patent Publication No. 61-201237 discloses a technique in which a negative film is directly placed on a photosensitive resin composition to perform exposure, and development after exposure is performed in an alkaline aqueous solution. A composition comprising a linear polymer compound having an acid value of 80 to 200, a carboxyl group and a glass transition temperature of 40 ° C or higher, an epoxy ester resin, a photopolymerizable vinyl monomer and a sensitizer. Is proposed.

Although the type and usage of the polymer component is different from that of the present invention, JP-A-60-225149 and JP-A-60-225841 use a compound containing the ethylenically unsaturated compound component of the present invention. The previously described photosensitive resin composition is shown.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional dry film, the exposure was performed with the pattern mask applied on the base film, that is, the base film was interposed between the pattern mask and the photosensitive resin composition layer. Do in the state. This is because when the base film is peeled off and the pattern mask is brought into direct contact with the photosensitive resin composition layer, the pattern mask adheres to the photosensitive resin composition layer and becomes difficult to peel off. This is because the mask may be contaminated or damaged.

However, in this case, since there is a slight distance between the pattern mask and the photosensitive resin composition layer, the resolution is lowered by that amount, which is an obstacle to increasing the density of the printed wiring board. In order to increase the resolution, it is sufficient to make the thickness of the base film as thin as possible, but since the base film is required to have strength, it is naturally limited in its thinning.

The contact-exposure type photosensitive resin composition disclosed in Japanese Patent Laid-Open No. 61-201237 discloses a specific resin component (a novolac epoxy resin and a monounsaturated carboxylic acid with an epoxy equivalent of 0.4 to 0.4). The composition of the epoxy ester resin having a softening point of 50 ° C. or higher (obtained by reacting at a ratio of 1.1) is made to have no tackiness so as to enable direct contact between the pattern mask and the photosensitive resin composition layer. It is something that gets done and gets attention. However, in the invention of this publication, the tackiness is prevented by improving the base polymer component, so that the polymer / monomer ratio (P / M ratio) is higher than that of the conventional photosensitive resin composition. As a result, it may not be possible to adopt the conventional coating conditions for the photosensitive resin composition, which are technically established. In addition, since the photosensitive resin composition layer is hard, it has poor adhesion to the base film or the protective film, and air bubbles are mixed in during production of the dry film, resulting in poor workability during lamination with a substrate. When a dry film is manufactured into a roll, the film may crack due to lack of flexibility.

The photosensitive resin compositions disclosed in JP-A-60-225149 and JP-A-60-225841 use an ethylenically unsaturated compound including a dipentaerythritol derivative (B ') described below. In the examples, the derivative (B ') is not used because it is not preferable, and the type of the polymer component is different, and it is considered that the support film is interposed during the exposure of the photosensitive resin. The development is carried out in a solvent system and is not intended for alkali development, and the problem to be solved, the constitution and the effects are different from those of the present invention.

Under such a background, the present invention provides an image forming method in which a dry film is used to form an image by directly contacting a pattern mask on the photosensitive resin composition layer, and further alkali development is performed. It is intended.

Means for Solving the Problems The image forming method of the present invention comprises: an acrylic resin (A) having an acid value of 100 to 200 mgKOH / g; (However, R is H or CH ₃ ) An ethylenically unsaturated compound (B) partially containing a dipentaerythritol derivative (B ′) represented by: and a photopolymerization initiator (C) are contained, and an acrylic resin ( The weight ratio of A) to the ethylenically unsaturated compound (B) is 75:25 to 55:45, and the ratio of the dipentaerythritol derivative (B ') to 5 parts by weight relative to 100 parts by weight of the acrylic resin (A) is 5 to 20. The photosensitive resin composition, which is part by weight, is laminated on a base film, and a dry film having a layer structure in which a protective film is coated on the base film is used, and the photosensitive resin composition layer is formed from the dry film. After peeling off the film with the weaker adhesive strength, stick the side of the photosensitive resin composition layer to the target metal surface, and peel off the remaining film, then attach the pattern mask to the photosensitive resin composition layer. Directly to Exposing in a state of being touched, after exposure, it is alkali development with dilute aqueous solution of an alkali, and is characterized in.

<Acrylic Resin (A)> In the photosensitive resin composition of the present invention, an acrylic resin (A) having an acid value of 100 to 200 mgKOH / g is used as the base polymer.

The acrylic resin (A) can be obtained by copolymerizing an acrylic ester or / and a methacrylic ester with a styrenic unsaturated carboxylic acid.

Here, as the acrylic ester, methyl acrylate, ethylene acrylate, propyl acrylate,
Examples thereof include butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethylaminoethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, glycidyl acrylate, and the like. Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl. Methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate and the like can be exemplified.

As the ethylenically unsaturated carboxylic acid, acrylic acid,
Monocarboxylic acids such as methacrylic acid and crotonic acid are preferably used, and dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, or anhydrides and half esters thereof can also be used. Of these, acrylic acid and methacrylic acid are of particular importance.

In addition to these monomer components, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, alkyl vinyl ether, etc. may be used in combination in a small amount.

The acrylic resin (A) has an acid value of 100 to 200 mgKOH / g
When the acid value is less than 100 mgKOH / g, the developing time becomes long and the tackiness increases (B ').
The effects of the present invention due to the use of the components are not sufficiently exerted, and on the other hand, when the acid value exceeds 200 mgKOH / g, the resistance of the cured product to the developing solution may be deteriorated and the image may be distorted.

In the acrylic resin (A), taking into consideration the balance of physical properties, (1) an acrylate ester having 2 or more carbon atoms of an alkyl group or / and a methacrylic acid ester having 4 or more carbon atoms of an alkyl group, and (2) an alkyl group Acrylic ester having 1 carbon atom and / or 1 to 3 carbon atoms of alkyl group
(1), (2), which each contain a monomer belonging to each group of methacrylic acid ester of (3) acrylic acid and / or methacrylic acid of (3) and occupy in the copolymer.
(3) The proportion of each component is 40 to 70% by weight, 15 to 55% by weight, and 5 to 35% by weight (however, the acid value is 100 to 200 mg KO.
H / g), and molecular weight of 50,000-15
Those in the range of 10,000 are most preferable.

<Ethylene unsaturated compound (B)> As the ethylenically unsaturated compound (B), (However, R is H or CH ₃ ) An ethylenically unsaturated compound containing at least a part of the ethylenically unsaturated compound (B) containing a part of the dipentaerythritol derivative (B ′) represented by the formula (B) is used.

A commercially available product of the dipentaerythritol derivative (B ′) represented by the above formula is, for example, “DPCA-120” manufactured by Nippon Kayaku Co., Ltd.

The DPCA series manufactured by the company has the formula [X is R ¹ and R ² are H or HC ₃ ], and “DPCA-20” in which m = 1, a = 2, b = 4, m = 1, a = 3, b = 3 "DPCA
-30 ", m = 1, a = 6, b = 0, there is also" DPCA-60 ", but" DPCA-20 "and" DPCA-30 "lack sufficient tack prevention effect, and" DPCA-60 " Also, the effect of preventing tack is insufficient.

The dipentaerythritol derivative (B ′) of the formula (i) used in the present invention has the formula (ii) in which m = 2 and a =
6, b = 0, but it is far superior to "DPCA-20" and "DPCA-30" in terms of tack (adhesive) prevention,
It is superior to "DPCA-60".

As the ethylenically unsaturated compound (B) other than the above dipentaerythritol derivative (B '), ethylene glycol diacrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, propylene glycol diacrylate, polypropylene glycol diacrylate, butylene glycol Diacrylate, neopentyl glycol diacrylate, 1,6
-Hexane glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,
Dipentaerythritol pentaacrylate, 2,2-bis [4-acryloxy (diethoxy) phenyl] propane, 2,2-bis [4-acryloxy (polyethoxy) phenyl] propane, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol Dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butylene glycol dimethacrylate,
Neopentyl glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol pentametallylate, 2,2
-Bis [4-methacryloxy (diethoxy) phenyl]
Examples thereof include polyfunctional monomers such as propane and 2,2-bis [4-methacryloxy (polyethoxy) phenyl] propane. An appropriate amount of monofunctional monomer may be used in combination with these polyfunctional monomers.

<Photopolymerization Initiator (C)> Examples of the photopolymerization initiator (C) include benzoin and
Benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-
Butyl ether, benzoin phenyl ether, benzyl diphenyl disulfide, azobisisobutyronitrile, dibenzyl, diacetyl, anthraquinone, naphthoquinone, benzophenone, pivaloin ethyl ether,
Benzoyl peroxide, benzyl ketal, 1,1-
Dichloroacetophenone, para-t-butyldichloroaetophenone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,2-diethoxyacetophenone, 2,2
-Dimethoxy-2-phenylacetophenone, 2,2-dichloro-4-phenoxyacetophenone, Michler's ketone, phenylglyoxylate, α-hydroxyisobutylphenone, dibezosparone, benzophenone amine system, 1- (4-isopropylphenyl) -2-hydroxy 2-methyl-1-propanone, 2-methyl- [4
-(Methylthio) phenyl] -2-morpholino-1-
Examples include propanone, leuco crystal violet, tribromophenyl sulfone, and tribromomethylphenyl sulfone.

<Blending Ratio> Next, the ratio of each component constituting the photosensitive resin composition will be described.

The weight ratio of the acrylic resin (A) and the ethylenically unsaturated compound (B) is set in the range of 75:25 to 55:45. If the ratio of the acrylic resin (A) is higher than this range, the polymer / monomer (P / M ratio) ratio becomes too large and the crosslinkability at the time of exposure is poor, and at the time of coating and further after drying. There is a possibility that restrictions may occur in that the photosensitive resin composition layer is hard and poor in flexibility. On the other hand, when the proportion of the ethylenically unsaturated compound (B) is higher than this range, the composition becomes tacky.

The ratio of the dipentaerythritol derivative (B ') to 100 parts by weight of the acrylic resin (A) is set in the range of 5 to 20 parts by weight. When the proportion of the dipentaerythritol derivative (B ') is less than this range, the composition remains tacky, while when it is more than this range, the adhesion to the copper surface becomes poor.

The mixing ratio of the photopolymerization initiator (C) is appropriately about 0.5 to 10% by weight based on the total amount of the acrylic resin (A) and the ethylenically unsaturated compound (B).

In addition to the above components, known additives such as a plasticizer, a colorant, a surface tension modifier, a stabilizer and an antifoaming agent can be added.

<Layering method> The dry film is obtained by coating the above-mentioned photosensitive resin composition on the base film surface (after further drying when a solvent is used), and then coating the protective film on the coated surface. It is obtained by

A polyethylene terephthalate film is most suitable as the base film. When the untreated polyethylene terephthalate surface is applied, when the protective film is peeled off so as to be attached to the copper surface of the copper clad substrate, it may be peeled off from the interface between the polyethylene terephthalate and the photosensitive resin composition layer. So in this case,
A photosensitive resin composition layer can be formed on the corona discharge treated surface of the polyethylene terephthalate film treated by corona discharge.

A polyethylene film is usually used as the protective film, but it is also advantageous to use a vinyl alcohol-based resin film such as polyvinyl alcohol or ethylene-vinyl alcohol copolymer.

<Exposure> When using a dry film, the protective film or the base film, whichever has the weaker adhesion to the photosensitive resin composition layer, is peeled off, and then the photosensitive resin composition layer side is placed on the copper clad substrate. After being attached to a metal surface such as the copper surface, the remaining film is peeled off, and then the pattern mask is brought into direct contact with the photosensitive resin composition layer for exposure.

For example, in the case of a polyethylene terephthalate film / photosensitive resin composition layer / polyethylene film type dry film, first, the polyethylene film is peeled off, laminated on a copper surface, and then the polyethylene terephthalate film is peeled off. Polyethylene terephthalate film /
In the case of the photosensitive resin composition layer / vinyl alcohol resin film type dry film, first, the polyethylene terephthalate film is peeled off, laminated on the copper surface, and then the vinyl alcohol resin film is peeled off.

Exposure is usually performed by ultraviolet irradiation, and as a light source at that time, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, or the like is used. Exposure amount is 40 ~ 1000mJ
/ cm ² or so, especially often with 50 to 500 mJ / cm ² or so.
After the ultraviolet irradiation, heating can be performed as necessary to complete the curing.

<Development> Since the above-mentioned photosensitive resin composition is an alkali development type, development after exposure is performed using a dilute aqueous solution of alkali such as sodium carbonate, potassium carbonate, sodium hydroxide.

<Etching> Etching is performed according to a conventional method using a ferric chloride aqueous solution or a cupric chloride aqueous solution.

<Use> The image forming method of the present invention is for producing a printed wiring board,
It can be applied to various uses including precision machining of metals.

Action and Effect of the Invention The alkali-developable photosensitive resin composition used in the present invention has no adhesiveness to the pattern mask, even though it adheres to the target metal surface. It is possible to expose with the pattern mask in direct contact with the layer.

In this way, since exposure can be performed without interposing a film between the pattern mask and the photosensitive resin composition layer, the resolution is remarkably improved and the density of the printed wiring board can be increased.

Further, in the present invention, the polymer / monomer ratio (P / M
Since the adhesiveness to the pattern mask can be eliminated even if the ratio is not increased, there is also an advantage that the conventional coating conditions which have been technically established can be used as they are.

EXAMPLES Next, the present invention will be further described with reference to examples. Hereinafter, “parts” and “%” are expressed on a weight basis.

 The following materials were prepared for the experiment.

<Acrylic resin (A)> A-1 Methyl methacrylate / n having a molecular weight of 100,000 and an acid value of 150 mgKOH / g
-Butyl acrylate / methacrylic acid (weight ratio 55/20/2
5) Copolymer A-2 Methyl methacrylate / n having a molecular weight of 60,000 and an acid value of 100 mgKOH / g
-Butyl methacrylate / n-butyl acrylate / methacrylic acid (weight ratio 55/20/10/15) copolymer A-3 Methyl methacrylate / n having a molecular weight of 80,000 and an acid value of 200 mgKOH / g
-Butyl acrylate / 2-ethylhexyl acrylate / methacrylic acid (weight ratio 50/10/10/30) copolymer <dipentaerythritol derivative (B ')>B'-1 DPCA-120 (Nippon Kayaku Co., Ltd.) B'-2 DPCA-60 manufactured by Nippon Kayaku Co., Ltd. (the above-mentioned formula (ii))
In which m = 1, a = 6, b = 0) <Ethylenically unsaturated compound (B) other than the above (B ′)> B-1 trimethylolpropane triacrylate B-2 polyethylene glycol (molecular weight 600) di Methacrylate B-3 2,2-bis [4-methacryloxy (polyethoxy) phenyl] propane (BPE-5 manufactured by Shin Nakamura Chemical Co., Ltd.
00) <Photopolymerization initiator (C)> C-1 Mixtures of Examples 1 and 2 A photosensitive resin composition having a formulation shown in Table 1 below was prepared.

This composition was applied to a polyethylene terephthalate film having a thickness of 25 μm and dried at a temperature of 100 ° C. A polyethylene film having a thickness of 30 μm was coated on the dried photosensitive resin composition layer.

The polyethylene film is peeled and removed from the dry film thus obtained, the photosensitive resin composition layer side is attached to the copper surface of the copper-clad substrate, and then the polyethylene terephthalate film is peeled and removed. The composition layer was directly exposed to a pattern mask for exposure.

A 3KW ultra-high pressure mercury lamp is used for exposure, and the irradiation dose is 120mJ / c.
It was m ^2.

After completion of the exposure, development was performed using a 1% sodium carbonate aqueous solution at a temperature of 30 ° C. and a spray pressure of 1.0 kg / cm ² . Then, according to a conventional method, etching with a ferric chloride solution and peeling of the photosensitive resin composition layer with an aqueous sodium hydroxide solution were carried out to obtain a printed wiring board.

Table 1 shows the presence or absence of tackiness (tack) between the photosensitive resin composition layer and the pattern mask, and the results of the resolution of the obtained printed wiring board.

Example 3 A photosensitive resin composition having the formulation shown in Table 1 below was prepared.

This composition was applied to a polyethylene terephthalate film having a thickness of 23 μm and dried at a temperature of 100 ° C. A polyvinyl alcohol film having a thickness of 24 μm was coated on the dried photosensitive resin composition layer.

The polyethylene terephthalate film was peeled off from the dry film thus obtained, and the photosensitive resin composition layer side was attached to the copper surface of the copper-clad substrate,
Then, after peeling off the polyvinyl alcohol film,
The photosensitive resin composition layer was directly exposed to a pattern mask for exposure.

 The steps after the exposure were the same as those in Examples 1 and 2.

Table 1 also shows the presence / absence of tackiness between the photosensitive resin composition layer and the pattern mask, and the results of the resolution of the obtained printed wiring board.

Comparative Examples 1 and 2 A photosensitive resin composition having a formulation shown in Table 1 below was prepared,
Dry films were produced in the same manner as in Examples 1 and 2.

Polyethylenefium is peeled off from the obtained dry film, and the photosensitive resin composition layer side is attached to the copper surface of the copper clad substrate, and a pattern mask is adhered onto it without peeling off the polyethylene terephthalate film. Exposure was performed.

Table 1 also shows the presence / absence of tackiness between the photosensitive resin composition layer and the pattern mask, and the results of the resolution of the obtained printed wiring board.

Further, in the formulation of Example 1, only the thickness of the photosensitive resin composition layer was changed, and the presence or absence of tackiness between the photosensitive resin composition layer and the pattern mask, and the resolution of the obtained printed wiring board were examined. It was The results are shown in Table 2.

Furthermore, in the formulations of Example 1 and Comparative Example 1, the polymer / monomer ratio (P / M ratio) was changed, and the presence or absence of tackiness between the photosensitive resin composition layer and the pattern mask was examined.

 The results are shown in Table 3.

Comparative Example 3 When Example 1 was repeated except that B′-2 was used instead of B′-1, the resolution was 50 μm, but the tack was small to medium and still unsatisfactory.

Examples 4 to 5 In order to see the effect of the base polymer component, A-2 and A-3 were used instead of A-1 in the formulation of Example 1. The results for each case are shown in Table 4.

Claims (1)

(57) [Claims] 1. An acrylic resin (A) having an acid value of 100 to 200 mg KOH / g, (However, R is H or CH ₃ ) An ethylenically unsaturated compound (B) partially containing a dipentaerythritol derivative (B ′) represented by: and a photopolymerization initiator (C) are contained, and an acrylic resin ( The weight ratio of A) to the ethylenically unsaturated compound (B) is 75:25 to 55:45, and the ratio of the dipentaerythritol derivative (B ') to 5 parts by weight relative to 100 parts by weight of the acrylic resin (A) is 5 to 20. The photosensitive resin composition, which is part by weight, is laminated on a base film, and a dry film having a layer structure in which a protective film is coated on the base film is used, and the photosensitive resin composition layer is formed from the dry film. After peeling off the film with the weaker adhesive strength, stick the side of the photosensitive resin composition layer to the target metal surface, and peel off the remaining film, then attach the pattern mask to the photosensitive resin composition layer. Directly to Exposing in a state of being touched, after exposure, an image forming method, characterized in that, the alkali development using dilute aqueous solution of an alkali.