JP2982398B2 - New photosensitive resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photopolymerizable composition,
More particularly, the present invention relates to a photopolymerizable composition suitable for producing a printed circuit board and capable of being alkali-developable.

[0002]

2. Description of the Related Art Conventionally, a so-called dry film resist (hereinafter abbreviated as DFR) comprising a support layer and a photopolymerized layer has been used as a resist for producing a printed circuit board.
The DFR is generally prepared by laminating a photopolymerizable layer composed of a photopolymerizable composition on a support layer, and in many cases, further laminating a protective film on the composition.

In order to manufacture a printed circuit board using a DFR, first, a protective film is peeled off, and then a DFR is laminated on a substrate for producing a permanent circuit such as a copper-clad laminate. Next, if necessary, the support layer is peeled off, and exposure is performed through a wiring pattern mask film or the like. If there is a support layer after exposure, the support layer is peeled off as necessary, and the unexposed portion of the photopolymerized layer is dissolved or dispersed and removed with a developing solution to form a cured resist image on the substrate. As the photopolymerizable layer, an alkali developing type using an aqueous alkali solution as a developing solution and a solvent developing type using an organic solvent are known. In recent years, the demand for an alkali developing type DFR has been growing from an environmental problem or an economic viewpoint. .

[0004] If the flexibility of the DFR is not sufficient when the DFR is laminated on the substrate, the DFR cannot follow the unevenness due to the uniform surface on the substrate, the dents and groove-like scratches made during the work, and the substrate and the DFR do not follow each other. Air bubbles are taken in between the DFR and the DFR, and as a result, inconveniences such as disconnection or short circuit of the circuit occur in the subsequent etching or plating process. Also, if the DFR flexibility on the substrate after exposure is low, the DFR may crack or peel off from the substrate when a shock is applied by a work even if the substrate is a flexible substrate or a rigid substrate. May cause disconnection or short circuit. In order to avoid these problems, a DFR having excellent flexibility at the time of non-exposure and after curing is required.

[0005] Processes for forming a circuit after development are roughly classified into two methods for both the alkali development type and the solvent development type. The first method is to further remove the resist after etching and removing the copper surface that is not covered with the cured resist, and the second method is to perform a plating treatment of copper and solder on the copper surface. After that, the resist is removed, and the exposed copper surface is etched.

[0006] In a printed circuit board manufactured by using the DFR, one side of a permanent image forming substrate is provided by a conductive circuit forming material layer, for example, a copper thin film layer attached to the inner peripheral surface of the through hole. Most are electrically connected to the other surface. As a method for manufacturing this type of printed circuit board, a solder through hole method is generally used.

[0007] The solder through-hole method is a method in which an inner peripheral surface of a through-hole is covered with a conductive circuit constituent material, for example, an etching-resistant metal for protecting a copper thin film layer, for example, solder plating, and then unnecessary portions on the substrate surface are etched. is there. In various plating processes such as the above-described copper plating and solder plating, a plating solution permeates between the resist and the base material, and if the plating gets loose, it causes a short circuit. Therefore, a DFR having excellent plating resistance is required.

The photopolymerizable layer of DFR widely used at present is (1) an unsaturated compound having at least one ethylenic group and capable of forming a polymer by a photopolymerization initiator;
(2) a thermoplastic organic polymer binder, (3) a photopolymerization initiator, and (4) other additives.
0-9177, JP-B-57-21697).

As the unsaturated compound, acrylic acid and methacrylic acid esters of aliphatic polyhydric alcohols are most common, and trimethylolpropane triacrylate,
Pentaerythritol triacrylate, polyethylene glycol diacrylate, and the like are known.

Particularly, polyethylene glycol di (meth) acrylate has a great effect of imparting flexibility to the DFR, so that excellent properties can be obtained, which have good followability to the substrate and flexible physical properties of the cured film. However, the DFR containing the compound has poor plating resistance, and remarkable penetration of the plating solution between the resist and the base material.

In the case of increasing the hydrophobicity of the compound by changing the ethylene glycol chain of polyethylene glycol di (meth) acrylate to a propylene glycol chain, good plating resistance can be obtained, but the composition is separated and stable quality is obtained. At the same time, the flexibility of the cured resist is lost.

[0012]

SUMMARY OF THE INVENTION Alkali developable D
In the FR field, the plating process has become particularly important in recent years as fine patterning has progressed, and a performance that has sufficient resistance in the plating process while maintaining the flexibility of the cured film has been required. . It is an object of the present invention to develop a monomer having sufficient plating resistance while maintaining the excellent flexibility characteristic of the above-mentioned polyethylene glycol di (meth) acrylate.

[0013]

As a result of intensive studies to solve the above problems, a compound containing both an ethylene glycol chain and a propylene glycol chain in a molecule is used as a photopolymerizable unsaturated compound. And the DF above
The R characteristics were simultaneously satisfied, and the present invention was achieved. That is, the present invention relates to (a) a carboxyl group content of 100 to 600 in acid equivalent.
A polymer having a weight average molecular weight of 20,000 to 500,000,
Represented by 93 wt% and (b) the general formula (I) (of _2), -CH 2 CH 2 O- and -CH (CH ₃₎ as a repeating unit C
An oligomer composed of H ₂ O—, which is a photopolymerizable unsaturated compound having an acrylate or methacrylate terminal, 93 to 5% by weight;

[0014]

Embedded image [Wherein l, m, and n are integers of 3 to 20; R, R '
Is a hydrogen or methyl group] (c) a photopolymerization initiator, and 0.01 to 30% by weight.

When the compound represented by the general formula (I) is used as a photopolymerizable unsaturated compound, the cured resist shows sufficient resistance especially in the plating step and the cured film is rich in flexibility. It shows the characteristic. It also has the effect of improving the dispersibility of the resist component in the developer.

In the formula (I), when only ethylene glycol chains are used, plating resistance is impaired. When only a propylene glycol chain is used, if the length of the side chain is increased in order to improve the releasability, the compatibility with the binder becomes poor, and phase separation occurs. As a result, uniform performance cannot be maintained. Further, the dispersibility of the resist component in the developing solution is deteriorated, which hinders the steady operation of the developing machine.

In the formula (I), when l, m, and n are smaller than 3, the boiling point of the compound is lowered, so that the odor of the resist becomes strong and the use becomes extremely difficult. Also, l,
If m and m exceed 20, the concentration of photoreactive sites per unit weight becomes low, so that practical sensitivity cannot be obtained.

The photopolymerizable composition of the present invention comprises:
(I) 5 to 9 photopolymerizable unsaturated compounds represented by the formula
Although 3% by weight is contained, the range of 20 to 60% by weight is more preferable. When the amount of the photopolymerizable unsaturated compound is 93% by weight or more, the film imparting property and tackiness are deteriorated. When the amount is less than 5% by weight, a sufficiently cured image is not formed by exposure, and properties as a resist, such as tenting, etching, It cannot have resistance to various plating processes.

The unsaturated compound in the present invention is commercially available, or the product obtained by reacting propylene oxide with ethylene oxide is esterified with acrylic acid or methacrylic acid in the presence of a suitable acid catalyst. Can be synthesized.

In the present invention, one or more photopolymerizable unsaturated compounds other than the photopolymerizable unsaturated compound represented by the formula (I) may be used simultaneously. Examples of the photopolymerizable unsaturated compound other than the formula (I) used at the same time include 2-hydroxy-3-phenoxypropyl acrylate, phenoxytetraethylene glycol acrylate, β-hydroxypropyl-β ′-(acryloyloxy) propyl phthalate , 1,4-tetramethylene glycol di (meth) acrylate (which represents methacrylate and acrylate; the same applies hereinafter). 1,6-
Hexanediol (meth) acrylate, 1,4-cyclohexanediol (meth) acrylate, octapropylene glycol di (meth) acrylate, glycerol (meth) acrylate, 2-di (p-hydroxyphenyl) propanedi (meth) acrylate, glycerol tri (Meth) acrylate, trimethylolpropane tri (meth) acrylate, polyoxypropyltrimethylolpropane tri (meth) acrylate, polyoxyethyltrimethylolpropane tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol Hexa (meth) acrylate, trimethylolpropane triglycidyl ether tri (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate ) Acrylate, diallyl phthalate.

The amount of the carboxyl group contained in the polymer used in the present invention is from 100 to 600 in acid equivalent,
~ 400 is preferred. The molecular weight is 20,000 to 500,000,
Preferably it is 50,000 to 200,000. Here, the acid equivalent refers to the weight of a polymer having one equivalent of a carboxyl group therein. The carboxyl group in the polymer is necessary to have developability and releasability with respect to the aqueous alkali solution, but when the acid equivalent is 100 or less, the compatibility with the coating solvent or other composition, for example, the monomer is reduced. If it is more than 600, the developability and the releasability deteriorate. When the molecular weight is 500,000 or more, the developability decreases, and when the molecular weight is 20,000 or less, it becomes difficult to maintain a uniform thickness of the photopolymerizable layer of the photopolymerizable laminate. The measurement of the acid equivalent is performed by a potentiometric titration method. The molecular weight is determined as a weight average molecular weight by gel permeation chromatography (GPC).

The polymer can be obtained by copolymerizing one or more of each of the following two types of monomers. The first monomer is a carboxylic acid or acid anhydride having one polymerizable unsaturated group such as a carbon-carbon double bond in the molecule. For example, (meth) acrylic acid, fumaric acid, cinnamic acid, crotonic acid, itaconic acid, maleic anhydride,
Maleic acid half ester and the like.

The second monomer is selected so as to maintain various properties such as developability of the photopolymerized layer, resistance in etching and plating steps, and flexibility of the cured film. For example, methyl (meth) acrylate, butyl (meth) acrylate,
There are alkyl (meth) acrylates such as 2-ethylhexyl (meth) acrylate. Further, there are esters of vinyl alcohol such as vinyl acetate, and styrene or a polymerizable styrene derivative. It can also be obtained by polymerization of only a carboxylic acid or acid anhydride having one polymerizable unsaturated group in the molecule.

The amount of the polymer containing the photopolymerizable composition is 5 to 5.
93% by weight, preferably 30-70% by weight
It is. The amount of polymer is less than 5% by weight or 93
When the content is more than 10% by weight, the cured image formed by the exposure has sufficient properties as a resist, for example, tenting,
It cannot have sufficient resistance in etching and various plating processes.

The photopolymerizable composition disclosed in the present invention contains a photopolymerization initiator as an essential component. The photopolymerization initiator here is any known compound that is activated by various actinic rays, for example, ultraviolet rays, and starts polymerization. For example, 2-ethylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone,
2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 2-methyl-1,4-naphthoquinone, 2,
Quinones such as 3-dimethylanthraquinone and 3-chloro-2-methylanthraquinone; aromatic ketones such as benzophenone and Michler's ketone [4,4'-bis (dimethylamino) benzophenone] and 4,4'-bis (diethylamino) benzophenone Benzoin ethers such as benzoin, benzoin ethyl ether, benzoin phenyl ether, methyl benzoin, and ethyl benzoin; combinations of thioxanthone compounds and tertiary amine compounds such as a combination of dimethylthioxanthone and dimethylaminobenzoic acid; and imidazole dimer There is also a body.

The amount of the photopolymerization initiator contained in the photopolymerizable composition of the present invention is 0.01 to 30% by weight, preferably 0.05 to 10% by weight. Here, when the photopolymerization initiator is 30% by weight or more, the active ray absorptivity of the photopolymerizable composition becomes high, and the curing by polymerization of the bottom portion of the photopolymerizable layer when the photopolymerizable laminate is formed is insufficient. Become. If it is less than 0.01, sufficient sensitivity cannot be obtained.

In order to improve the thermal stability and storage stability of the photopolymerizable composition, it is preferable that the photopolymerizable layer contains a radical polymerization inhibitor. For example, p-methoxyphenol, hydroquinone, pyrogallol, naphthylamine, tert-butylcatechol, cuprous chloride,
2,6-di-tert-butyl-p-cresol, 2,
2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol) and the like.

The photopolymerizable composition of the present invention may contain coloring substances such as dyes and pigments. For example, fuchsin, phthalocyanine green, auramine base, chalcoxide green S, paramagenta, crystal violet,
Methyl orange, Nile Blue 2B, Victoria Blue, Malachite Green, Basic Blue 20, Diamond Green and the like.

Further, a coloring dye which develops color upon irradiation with light may be contained. As a color-forming dye, a combination of a leuco dye and a halogen compound is well known. As the leuco dye, for example, tris (4-dimethylamino-
2-methylphenyl) methane [leuco crystal violet], tris (4-dimethylamino-2-methylphenyl) methane [leucomalachite green] and the like. On the other hand, examples of the halogen compound include amyl bromide, isoamyl bromide, isobutylene bromide, ethylene bromide, diphenylmethyl bromide, benzal bromide, methylene bromide, tribromomethylphenylsulfone, carbon tetrabromide, and tris (2,3 -Dibromopropyl) phosphate, trichloroacetamide, amyl iodide, isobutyl iodide,
There are 1,1-trichloro-2,2-bis (p-chlorophenyl) ethane, hexachloroethane, and the like.

Further, the photopolymerizable composition may contain additives such as a plasticizer, if necessary. For example, phthalic esters such as diethyl phthalate can be exemplified. The second invention of the present invention comprises a photopolymerizable layer comprising the above photopolymerizable composition and a support layer. The support layer of the photopolymerization layer is desirably a transparent layer that transmits active light.

Examples of the support layer that transmits the active light include polyethylene terephthalate film, polyvinyl alcohol film, polyvinyl chloride film, vinyl chloride copolymer film, polyvinylidene chloride film, vinylidene chloride copolymer film, and polymethyl methacrylate copolymer. Examples thereof include a polymer film, a polystyrene film, a polyacrylonitrile film, a styrene copolymer film, a polyamide film, and a cellulose derivative film. These films may be stretched if necessary.

In addition to the photopolymerized layer laminated with the support layer, a protective layer is laminated on the surface of the photopolymerized layer, if necessary. An important characteristic of this protective layer is that the protective layer is sufficiently small and easily peelable from the support layer in terms of adhesion to the photopolymerizable layer. For example, there are a polyethylene film and a polypropylene film. Further, a film having excellent releasability as disclosed in JP-A-59-202457 can also be used. Although the thickness of the photopolymerized layer varies depending on the application, it is 5 to 100 μm, preferably 5 to 70 μm for producing a printed circuit board.
μm, and the thinner the film, the higher the resolution. Further, the film strength increases as the thickness increases.

Next, the process for producing a printed circuit board using the photopolymerizable laminate of the present invention is in accordance with the prior art.
Briefly stated. First, if there is a protective layer, the protective layer is peeled off, and then the photopolymerization layer is laminated on the metal surface of the printed circuit board substrate by heating and pressing. The heating temperature at this time is generally 40 to 16
0 ° C. Next, if necessary, the support layer is peeled off, and image exposure is performed with actinic light through a mask film. Next, if there is a support layer on the photopolymerized layer after exposure, the support layer is removed if necessary, and then the unexposed portion is developed and removed using an aqueous alkali solution. As the alkaline aqueous solution, an aqueous solution of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or the like is used. These can be selected according to the characteristics of the photopolymerization layer, but a 0.5% to 3% aqueous solution of sodium carbonate is generally used.

Next, an image pattern of a metal is formed on the exposed metal surface by development using an etching method or a plating method, whichever is known. Thereafter, the cured resist image is generally stripped off with an aqueous alkaline solution that is stronger than the aqueous alkaline solution used for development. The alkaline aqueous solution for peeling is not particularly limited, but an aqueous solution of 1% to 5% of sodium hydroxide or potassium hydroxide is generally used. Further, it is possible to add a small amount of a water-soluble organic solvent to a developer or a stripper.

[0035]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the present invention. In addition,
Measurement of acid equivalent is Hiranuma reporting titrator COM
This was performed by potentiometric titration with 0.1 N sodium hydroxide using TITE-7. The molecular weight is determined by gel permeation chromatography manufactured by JASCO (pump: TRI RO
TAR-V, column; Shodex A-80M x 2 in series, mobile phase solvent: THF, using a calibration curve with a polystyrene standard sample) as the weight average molecular weight.

Example 1 A 30% solution of a copolymer of 70% methyl methacrylate and 30% methacrylic acid (weight average molecular weight = 100,000) in 30% methyl ethyl ketone is used as a binder solution.

Compatibility test: 1 g of a binder solution was added to 10 g of the monomers shown in Table 1, and the mixture was allowed to stand overnight. The state of the mixture after standing was visually observed, and the compatibility between the monomer and the binder was evaluated based on the following criteria. ：: Uniformly mixed. X: The state was uneven.

Into 167 g of the binder solution, 40 g of the monomers shown in Table 1 and an initiator and other components were added, and the mixture was stirred at room temperature for 15 hours. Next, this mixed solution was added to a thickness of 25 μm.
m was uniformly applied to a polyethylene terephthalate film using a bar coater and dried in a drier at 90 ° C. for 5 minutes to produce a photopolymerizable laminate having a photopolymer layer thickness of 50 μm. A 35 μm polyethylene film was laminated on the surface of the photopolymerization layer on which the polyethylene terephthalate film was not laminated to obtain a laminated film. The surface of the copper-clad laminate on which the 35 μm rolled copper foil is laminated is wet-buffered (3M, Scotch Bright HD # 600, passed twice), and the photopolymerized layer is peeled off by a hot roll laminator while peeling off the polyethylene film of the laminated film. Lamination was performed at 105 ° C. to obtain a laminate.

The photopolymer layer was exposed at 80 mJ / cm ² by an ultra-high pressure mercury lamp (HMW-201KB, manufactured by Oak Manufacturing Co., Ltd.) through a mask film through the laminate. Subsequently, after peeling off the polyethylene terephthalate film, a 1% aqueous solution of sodium carbonate at 30 ° C. was sprayed for about 70 seconds to dissolve and remove unexposed portions, thereby obtaining a good cured image.

Next, after the photopolymerization layer is laminated on the copper-clad laminate substrate by the above method, a step tablet (manufactured by KODAK,
21 step tablet) and exposed to 80 mJ / cm ² by the above-mentioned ultra-high pressure mercury lamp. Then, after peeling off the polyethylene terephthalate film, 1% of 30 ° C.
An aqueous solution of sodium carbonate was sprayed for about 70 seconds to dissolve and remove unexposed portions, washed with water and dried. At this time, the maximum number of steps on the step tablet where the film was completely left was 6 steps. (Hereinafter, this test is referred to as a sensitivity test. The greater the number of steps in a step tablet, the lower the light transmittance. Therefore, the higher the number of steps, the higher the number of determination steps.)

The laminate laminated on the copper-clad laminate in the manner described above was exposed at 60 mJ / cm ² using an ultra-high pressure mercury lamp. Next, after peeling off the polyethylene terephthalate film, a 1% aqueous solution of sodium carbonate was sprayed for about 70 seconds and developed. The following two tests were performed using the developed substrate.

Cross cut test: Ten cuts were made on the cured film on the substrate at 1 mm intervals in vertical and horizontal directions.
When 00 pieces of grids were made and the cellophane tape was strongly pressed and peeled off, 0 pieces out of 100 pieces were completely peeled off. The evaluation criteria are as follows. ：: No peeling was observed at all measurement points. Δ: Peeling was observed at 1 to 20 points out of 100 measurement points. ×: Peeling was observed at 21 or more points out of 100 measurement points. Since the cross-cut test can be empirically used as a measure of the flexibility of the cured film, a rank of ○ indicates the highest flexibility.

Plating resistance test: The laminate laminated on the copper-clad laminate in the manner described above was irradiated with 80 mJ / cm ² ultraviolet light from an ultra-high pressure mercury lamp through a positive pattern mask film. Next, after peeling off the polyethylene terephthalate film, development was carried out with a 1% aqueous solution of sodium carbonate, and pretreatment, copper sulfate plating and solder plating were performed under the following conditions. A cellophane tape was applied to the thin line portion of the obtained image, and after sufficiently press-bonding, the tape was peeled off, but no resist was peeled off.

<Pretreatment conditions> 50 ° C. PC-455 (manufactured by Meltec) 25% immersion for 3 minutes → water washing → 20% ammonium persulfate aqueous solution for 1 minute → 10% sulfuric acid aqueous solution → water washing.

<Conditions for Copper Sulfate Plating> In a plating solution obtained by diluting “copper sulfate conc” manufactured by Meltex Co., Ltd. with 3.6% of 19% sulfuric acid, plating was performed at room temperature for 30 minutes at a current density of 2.5 A / dm ^2. Do.

<Solder Plating Conditions> Using a solder plating solution (tin / lead = 6/4) manufactured by McDermid, 2.0 A / dm ²
Plating at room temperature for 10 minutes.

<Evaluation Criteria for Tape Peeling> a. There is no peeling of the resist. b. A portion having a width of 100 μm or less and a length of 1 mm or less was gradually peeled off on both sides of the image. c. On both sides of the image, portions having a width of 100 μm or more and a length of 1 mm or more peeled off gradually. d. Almost all the resist was peeled off. Further, after removing polyethylene terephthalate from the laminate obtained by laminating the DFR on the copper-clad laminate, spraying a 1% aqueous solution of sodium carbonate for about 70 seconds was carried out. ² /
Continued until it became 1. Thereafter, the presence or absence of deposits and deposits inside the developing machine was observed.

Examples 2 to 4 The compositions shown in Table 1 were evaluated in the same manner as in Example 1. Table 2 shows the evaluation results.

Comparative Examples 1 to 3 The compositions shown in Table 1 were evaluated in the same manner as in Example 1. Table 2 shows the evaluation results. As can be seen from these results, the examples had better results in each test than the comparative examples.

[0050]

[Table 1]

(Note) (Binder): B-1: Copolymer of 70% methyl methacrylate and 30% methacrylic acid (weight average molecular weight =
100,000) (monomer): M-1: bis (triethylene glycol methacrylate) polypropylene glycol

[0052]

Embedded image M-2: Nonaethylene glycol diacrylate

[0053]

Embedded image M-3: Nonaethylene glycol dimethacrylate

[0054]

Embedded image M-4: Nonapropylene glycol dimethacrylate

[0055]

Embedded image M-5: bis (tetraethylene glycol methacrylate) polypropylene glycol

[0056]

Embedded image M-6: phenoxytetraethylene glycol acrylate

[0057]

Embedded image (Initiator) K-1: benzophenone K-2: 4,4'-bis (dimethylamino) benzophenone K-3: imidazole dimer (dye) S-1: malachite green

[0058]

[Table 2]

[0059]

The photopolymerizable composition and the photopolymerizable laminate of the present invention have sufficient durability in each of the steps of etching, tenting, and plating, and have excellent durability especially in the plating step. Is shown. The compatibility with the binder is good, and the cured film is rich in flexibility. As described above, the photopolymerizable composition and the photopolymerizable laminate of the present invention have characteristics necessary for alkali development, and are useful as a resist for producing a printed circuit board.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-184744 (JP, A) JP-A-62-208044 (JP, A) JP-A-2-105155 (JP, A) JP-A-3-3 6202 (JP, A) JP-A-2-269721 (JP, A) JP-A-60-28493 (JP, A) JP-A-1-168703 (JP, A) JP-A-2-208305 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) G03F 7/027 G03F 7/004 G03F 7/033

Claims (1)

(57) [Claims] 1. A polymer having a carboxyl group content of 100 to 600 in acid equivalent and a weight average molecular weight of 20,000 to 500,000, 5 to 93% by weight, and (b) a polymer represented by the following general formula (I): ) 93 to 5% by weight of a photopolymerizable unsaturated compound represented by the following formula (I): [Wherein l, m, and n are integers of 3 to 20; R, R '
Is a hydrogen or methyl group] (c) a photopolymerization initiator, comprising 0.01 to 30% by weight.