JP6406537B2 - Method for producing phenol novolac resin, method for producing insulating cured product, and method for producing resist material - Google Patents

Description

The present invention relates to a process for producing a preparation and the resist material of the phenolic novolak resin preparation and the insulating cured product using the phenol novolak resins obtained by the production method.

  Various techniques for improving the weight average molecular weight of a phenol novolac resin, which is a thermoplastic resin, have been reported. For example, a synthesis method that reduces phenol dimer while increasing the weight average molecular weight by carrying out a two-stage reaction can be mentioned (see Patent Document 1). In addition, a report for producing a triazine-modified phenol novolak resin that reduces unreacted phenols while increasing the weight average molecular weight is disclosed (see Patent Document 2).

  However, in these reports, it is a limited technique that requires the polymerization with phosphoric acids when synthesizing the first-stage phenol novolac resin, and it is difficult to say that the versatility is high. In addition, in order to reduce phenol dimers or unreacted phenols, the pH is controlled and the addition of aldehydes is required during the second stage reaction, which is a method with many restrictions in time. Therefore, it cannot be said that the molecular weight of the phenol novolac resin is simply increased. Moreover, the manufacturing method which makes high molecular weight the molecular weight of the phenol novolak resin containing 50 mass% or more of p-cresol is disclosed (refer patent document 3). This method is a limited method in which the resin skeleton is limited, and the high molecular weight effect is not sufficient.

  On the other hand, in the resol type phenol resin which is a thermosetting resin, the manufacturing method of the cocondensate with a melamine has been reported (refer patent document 4). However, since the synthesis method of the phenol resin used as the raw resin is different between the novolak type and the resole type, it is difficult to apply this method to the phenol novolak resin.

JP-A-2005-306987 JP 2004-292791 A JP2013-108056A JP-A-3-243613

The present invention aims to solve the above problems. That is, the conveniently high molecular weight phenolic novolak resin, a high heat resistance have, and phenol novolak tree method for producing fats which can be used as a photoresist material, and the insulating cured product using the phenol novolak resin and to provide a manufacturing method of preparation and the resist material.

  As a result of intensive studies to solve the above problems, the present inventors have used 1,4-bis (methoxymethyl) benzene as an additive, and after the addition condensation reaction process of phenols and aldehydes, The phenol novolak resin produced by adding the second catalyst before heating and vacuum distillation is found to have a high molecular weight, high heat resistance, and can be used as a phenolic resin for photoresist. Invented the invention.

The present invention relates to the following.
(1) A phenol containing m-cresol, 1,4-bis (methoxymethyl) benzene, an aldehyde, and a first catalyst are mixed, and an addition condensation reaction of the phenol and the aldehyde is performed. A step of adding a second catalyst after the step of performing the addition condensation reaction and before performing the heating and vacuum distillation, wherein the second catalyst has an acid dissociation constant (pKa) of −2 or less. The catalyst is added in an amount of 0.001 to 0.005 equivalents, where the molar amount of the whole raw material is 1 equivalent, and the weight average molecular weight of the phenol novolac resin obtained by performing the heating and vacuum distillation is 20,000 or more. A method for producing a phenol novolac resin.
(2) The manufacturing method of the phenol novolak resin as described in said (1) whose compounding ratio (molar ratio) of the phenols containing the said m-cresol and the said aldehydes is 0.6 or more .
( 3 ) A method for producing an insulating cured product , wherein a curable resin composition containing a phenol novolac resin obtained by the method for producing a phenol novolac resin according to (1) or (2) is cured.
(4) The method of producing a resist material including a method of manufacturing an insulating cured product according to (3).

  According to the present invention, a phenol novolac resin is easily made to have a high molecular weight, has a high heat resistance and can be used as a photoresist material, a method for producing the same, and insulating curing using the phenol novolac resin. And a resist material can be provided.

  The method for producing a phenol novolac resin of the present invention comprises mixing phenols containing m-cresol, 1,4-bis (methoxymethyl) benzene, aldehydes, and a first catalyst, and the phenols and the above After the step of performing an addition condensation reaction of aldehydes, the step of performing the above addition condensation reaction, and the step of adding a second catalyst before performing heating and vacuum distillation, the second catalyst has an acid dissociation constant ( pKa) is an acidic catalyst of -2 or less. The phenol novolac resin of the present invention is obtained by the above-described method for producing a phenol novolac resin.

  The phenol novolac resin of the present embodiment uses 1,4-bis (methoxymethyl) benzene in addition to a known phenol novolac synthesis method in which phenols and aldehydes are used as raw materials and addition condensation is performed using an acidic catalyst as a first catalyst. Can be produced by adding a second catalyst after the addition condensation reaction process of phenols and aldehydes and before heating and vacuum distillation. That is, by carrying out the method for producing a phenol novolak resin of this embodiment, a high molecular weight phenol novolac resin having a weight average molecular weight of 20,000 or more can be easily synthesized, and heat resistance useful as a phenol resin for photoresists. A phenol novolac resin having a high molecular weight can be obtained. The molecular weight is measured by GPC (gel permeation chromatography) and indicates a weight average molecular weight corrected based on a calibration curve prepared with a styrene standard sample.

  As phenols to be used, substituted or unsubstituted phenol compounds containing m-cresol can be used. Specifically, xylenol such as m-cresol, o-cresol, p-cresol, phenol, 2-allylphenol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol, 3,4-xylenol, etc. M-ethylphenol, p-ethylphenol, o-ethylphenol, 2,3,5-trimethylphenol, 2,3,5-triethylphenol, 4-tert-butylphenol, 3-tert-butylphenol, 2-tert Alkylphenols such as butylphenol, 2-tert-butyl-4-methylphenol, 2-tert-butyl-5-methylphenol, 6-tert-butyl-3-methylphenol, p-methoxyphenol, m-methoxyphenol, p-ethoxyphenol, m-eth Alkoxyphenols such as siphenol, p-propoxyphenol, m-propoxyphenol, o-isopropenylphenol, p-isopropenylphenol, 2-methyl-4-isopropenylphenol, 2-ethyl-4-isopropenylphenol, etc. And polyhydroxyphenols such as 4,4′-dihydroxybiphenyl, bisphenol A, phenylphenol, resorcinol, hydroquinone, pyrogallol, α-naphthol, β-naphthol, and dihydroxynaphthalene.

  In this case, phenols contain m-cresol and may use 1 type, or 2 or more types of mixtures. At this time, it is preferable to use bifunctional phenols and trifunctional phenols as a mixture of two or more phenols. As a method for charging phenols, a method suitable for the purpose, such as a method of charging together with raw materials or a method of adding by dividing as the reaction proceeds, may be adopted.

  On the other hand, known aldehydes can be used for obtaining the phenol novolac resin. Specific examples include formaldehyde, paraformaldehyde, chloroacetaldehyde, dichloroacetaldehyde, bromoacetaldehyde, trioxane, acetaldehyde, glyoxal, acrolein, methacrolein and the like, and formaldehyde and paraformaldehyde are particularly preferable. In this case, aldehydes may be used alone or as a mixture of two or more. As the charging method for aldehydes and the like, a method suitable for the purpose, such as a method of charging together with the raw material or a method of adding by dividing with the progress of the reaction may be adopted.

  The blending ratio of phenols and aldehydes (aldehydes / phenols / phenols) is not particularly limited, but is preferably 0.6 or more on a molar basis, more preferably 0.7 to 0.8. is there. If the blending ratio is 0.6 or more, it becomes easy to reduce the content of components below the phenol dimer, and there is no extreme increase in unreacted aldehydes, etc., in terms of production efficiency. Is preferred. On the other hand, when the addition amount exceeds 0.8, there is a possibility that the reaction of the resin proceeds so much that gelation may occur.

  The first catalyst used in the present invention is usually an acidic catalyst. As the acidic catalyst as the first catalyst, inorganic acids such as hydrochloric acid, sulfuric acid, boric acid, oxalic acid, acetic acid, benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, methanesulfonic acid, Organic acids such as ethanesulfonic acid can be mentioned, and one or more can be used in combination. In addition, about the addition amount of an acidic catalyst (1st catalyst), the molar amount of the whole raw material should just be 0.001-0.005 equivalent, Preferably it is 0.015-0.025 equivalent. . At this time, as an addition method of the acidic catalyst (first catalyst), a method suitable for the purpose, such as a method of charging all together with the raw material, a method of adding in a divided manner as the reaction proceeds may be adopted. Further, the temperature at the time of addition is preferably 40 ° C. or less in consideration of safety.

The second catalyst used in the present invention is an acidic catalyst having an acid dissociation constant (pKa) of −2 or less. Specific examples include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as benzenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, methanesulfonic acid, and ethanesulfonic acid. Two or more kinds can be used in combination. Then, an acid catalyst having an acid dissociation constant (pKa) of −2 or less is added after the addition condensation reaction and before the heating and vacuum distillation to obtain a phenol novolak resin having a weight average molecular weight of 20,000 or more. it can. Note that the amount of acid catalyst (second catalyst), the molar amount of the entire raw material may be a 0.001 to 0.005 equivalents as 1 equivalent, it is preferably from 0.0015 to 0.0025 equivalents . At this time, as an addition method of the acidic catalyst (second catalyst), a method suitable for the purpose, such as a method of charging the raw material at once or a method of adding the catalyst in a divided manner as the reaction proceeds, may be employed. Further, the temperature at the time of addition is preferably 40 ° C. or less in consideration of safety.

  In a known method for synthesizing a phenol novolac resin, a reaction kettle charged with raw materials is heated to a reaction temperature to cause an addition condensation reaction of phenols and aldehydes, followed by heating under reduced pressure. In the heating and vacuum distillation process, addition condensation reaction further proceeds, and water and unreacted monomers are removed. In the present invention, after the addition condensation reaction process is completed and the second catalyst is added, heating and vacuum distillation are performed. Regarding the temperature during the addition condensation reaction before the addition of the second catalyst, the reaction time can be shortened as the temperature is increased. However, if the temperature is extremely increased, the reaction becomes difficult to control. It is preferable to carry out the reaction at a temperature of 0 ° C. or lower. The reaction time is determined in consideration of the reaction temperature, the water content of the reaction system, the condensation state of the product, etc., but is generally about 1 to 20 hours. In addition, after addition condensation reaction of phenols and aldehydes, after cooling to 20-60 degreeC as needed, you may add a 2nd catalyst. Moreover, as conditions of the heat | fever vacuum distillation after adding a 2nd catalyst, they are 100-200 degreeC and about 1 to 10 hours, for example.

  The phenol novolac resin obtained by the present invention can be made into a curable resin composition by blending a known crosslinking agent, polymerization initiator, solvent, additive and the like. For example, a curable resin composition containing a thermal polymerization initiator can be suitably used for a prepreg material or an adhesive material, and a curable resin composition containing a photopolymerization initiator can be suitably used for a resist material. Alternatively, the curable resin composition containing the phenol novolac resin of the present invention may be cured to form an insulating cured product, and the insulating cured product may be used as a resist material.

  The cross-linking agent is a compound having two or more functional groups that react with the hydroxy group in the phenol novolac resin in one molecule, and examples thereof include polyfunctional epoxy compounds and oxetane compounds, and the use of polyfunctional epoxy compounds. Is preferred.

  The polyfunctional epoxy compound is not particularly limited as long as it is a compound having two or more glycidyl groups in one molecule, for example, bisphenol A type epoxy, biphenyl type epoxy, naphthalene type epoxy, bisphenol F type epoxy, phosphorus-containing Epoxy, bisphenol S type epoxy, cycloaliphatic epoxy, aliphatic chain epoxy, phenol novolak type epoxy, cresol novolak type epoxy, bisphenol A novolak type epoxy, diglycidyl etherified product of bisphenol, diglycidyl etherified product of naphthalenediol, phenol Diglycidyl etherification products of alcohols, diglycidyl etherification products of alcohols, and alkyl-substituted products, halides, hydrogenated products thereof, and high molecular weight compounds containing one or more of these. Shows possible, these epoxy compounds may be used alone or in combination of two or more.

  Although the addition amount of a polyfunctional epoxy compound changes with the efficiency of hardening, 0.1-80 mass% is preferable with respect to the solid content of a curable resin composition, and 1-60 mass% is more preferable. If it exceeds 80% by mass, it tends to be governed by the properties of the curing agent.

  The polymerization initiator is a compound that initiates or accelerates the reaction between a hydroxy group, a glycidyl group, and a glycidyl group. Photopolymerization initiators that exhibit an initiating function can be broadly classified.

  The thermal polymerization initiator is not particularly limited as long as it exhibits or accelerates the polymerization function by heat, but an imidazole compound, a tertiary amine compound, an organic phosphine compound, a complex of an organic phosphine compound and an organic boron compound, or the like. The imidazole compound, the organic phosphine compound, and the complex of the organic phosphine compound and the organic boron compound are preferable in that there are many types on the market and it is easy to select the efficiency and the starting temperature.

  Examples of imidazoles include imidazole, 2-methylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-imidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl. 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazoline , Naphthimidazole, pyrazole, triazole, tetrazole, indazole, pyridine, pyrazine, pyridazine, pyrimidine, benzotriazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl -4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate Tate etc. can be illustrated.

  Examples of organic phosphine compounds include triphenylphosphine, diphenyl (p-tolyl) phosphine, tris (alkylphenyl) phosphine, tris (alkoxyphenyl) phosphine, tris (alkylalkoxyphenyl) phosphine, tris (dialkylphenyl) phosphine, tris ( Trialkylphenyl) phosphine, tris (tetraalkylphenyl) phosphine, tris (dialkoxyphenyl) phosphine, tris (trialkoxyphenyl) phosphine, tris (tetraalkoxyphenyl) phosphine, trialkylphosphine, dialkylarylphosphine, alkyldiarylphosphine, etc. Can be illustrated.

  Examples of the complex of an organic phosphine compound and an organic boron compound include tetraphenylphosphonium / tetraphenylborate, tetraphenylphosphonium / tetra-p-tolylborate, tetrabutylphosphonium / tetraphenylborate, tetraphenylphosphonium / n-butyltriphenylborate And butyltriphenylphosphonium / tetraphenylborate and methyltributylphosphonium / tetraphenylborate.

  One thermal polymerization initiator may be used alone, or two or more thermal polymerization initiators may be used in combination. As a method for efficiently producing a semi-cured epoxy resin composition and a cured epoxy resin composition described later, two types of curing accelerators having different reaction start temperatures and reaction rates between an epoxy resin monomer and a phenol novolac resin are used in combination. A method is mentioned.

  In addition, although the content rate in particular of the thermopolymerization initiator of a curable resin composition is not restrict | limited, from a viewpoint of a sensitivity and the transmittance | permeability, 0.1-5 in total 100 mass% of solid content of a thermosetting resin composition. It is preferably 0.0% by mass, more preferably 0.2 to 3.0% by mass, and even more preferably 0.5 to 2.0% by mass.

  The photopolymerization initiator is not particularly limited as long as it exhibits a polymerization function by irradiation with light of a specific wavelength, but there are many commercially available types of photocationic polymerization initiators, which are efficient. It is preferable in that it is easy to select the wavelength of light. For example, as the cationic photopolymerization initiator that initiates polymerization in the ultraviolet region, any of the initiators shown in the known literature can be used, and aromatic iodonium salts, aromatic sulfonium salts, aromatic onium salts can be used. Is preferable from the viewpoint of ease of handling and efficiency. The photocationic polymerization initiator is preferably 0.1 to 5.0% by mass, and preferably 0.2 to 3.0% by mass, out of a total of 100% by mass of the solid content of the curable resin composition. More preferably, it is more preferable that it is 0.5-2.0 mass%.

  Further, additives can be freely added as long as they do not hinder the curability of the curable resin composition. For example, sensitizers, dissolution accelerators, adhesion improvers, dyes, pigments, surfactants, leveling agents, difficulty A flame retardant, rubber-based elastomer, ion trapping agent, antifoaming agent, conductive particles, filler, and the like can be added.

  For example, it is effective to add a sensitizer for efficient light absorption. The sensitizer is selected according to the wavelength of the light source to be irradiated. The addition amount of the sensitizer is not particularly limited, but is preferably 0.01 to 20% by mass with respect to the solid content of the resin in order to efficiently form an image while maintaining the properties of the resin. Mass% is particularly preferred.

  Further, for example, by adding filler, the expansion coefficient and electrical characteristics can be improved. Examples of the filler include silica, alumina, titania, zirconia and the like. The maximum particle size of the filler is preferably 500 nm or less. If the particle diameter is larger than 500 nm, the possibility of causing defects when a cured film is formed is not preferable. The filler content is preferably 1 to 90% by mass in 100% by mass of the resin. If the amount is less than 1% by mass, the effect of the particles is small, and if it exceeds 90% by mass, the reliability is lowered due to generation of defects and the like, which is not preferable.

  The solvent is not particularly limited as long as the above materials can be uniformly dissolved or dispersed, but the boiling point of the solvent is preferably lower than the polymerization initiation temperature of the polymerization initiator from the viewpoint of workability when forming a film or the like. Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, aromatic solvents such as toluene, xylene, nitrobenzene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether , 3-methoxy-3-methyl-1-butanol, ethylene glycol monomethyl ether acetate, PMA (propylene glycol monomethyl ether acetate), diethylene glycol It can be exemplified glycol solvents such as mono butyl ether acetate and diethylene glycol monoethyl ether acetate.

  Moreover, it can be applied to a positive resist or the like by blending a dissolution inhibitor instead of the polymerization initiator in blending the curable resin composition.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
The GPC measurement was performed under the following conditions.
Measuring apparatus: “HPLC-L7000 series” manufactured by Hitachi, Ltd.
Column: Shodex “GPC KD-806M”
Detector: RI detector “I-7490” manufactured by Hitachi, Ltd.
Data processing: “D7000G” manufactured by Hitachi, Ltd.
Measurement conditions: Column temperature 30 ° C
Developing solvent NMP (N-methyl-pyrrolidone) lithium phosphate bromide solution Flow rate 1.0 ml / min, used polystyrene TOSOH standard polystyrene
Sample 1% by mass of NMP solution in terms of resin solid content filtered through a microfilter

[Example 1]
In a flask equipped with a thermometer, condenser, and stirrer, 44.8 g of m-cresol and 29.9 g of p-cresol as phenols, 15.8 g of paraformaldehyde as aldehydes and 1,4-bis (methoxymethyl). ) 4.6 g of benzene (0.017 equivalent when the total amount of raw materials is 1 equivalent), 0.44 g of oxalic acid (pKa = 1.27) as the first catalyst (when the total amount of raw materials is 1 equivalent) 0.002 equivalent) and 14.2 g of methanol were mixed and stirred at 90 ° C. for 4 hours while blowing nitrogen. Then, it cooled to 40 degrees C or less, added 0.66g (0.002 equivalent when the total amount of a raw material is 1 equivalent) p-toluenesulfonic acid (pKa = -2.8) as a 2nd catalyst, Distillation under reduced pressure was performed at 180 ° C. for 2 hours. When the obtained resin was measured by GPC, a resin having a weight average molecular weight of 120,000 was obtained.

[Example 2]
In the composition of Example 1, 12.4 g of paraformaldehyde and 13.8 g of 1,4-bis (methoxymethyl) benzene (0.053 equivalent when the total amount of raw materials is 1 equivalent) were changed as aldehydes. Except for the above, a phenol novolac resin was obtained in the same manner as in Example 1. When the obtained resin was measured by GPC, a resin having a weight average molecular weight of 28,000 was obtained.

[Comparative Example 1]
In a flask equipped with a thermometer, condenser, and stirrer, 49.7 g of m-cresol and 33.1 g of p-cresol as phenols, 18.3 g of paraformaldehyde as aldehydes, and 0 oxalic acid as an acidic catalyst .48 g (0.002 equivalent when the total amount of raw materials was 1 equivalent) and 14.7 g of methanol were mixed and stirred at 90 ° C. for 4 hours while blowing nitrogen. Thereafter, vacuum distillation was performed at 180 ° C. for 2 hours. When the obtained resin was measured by GPC, a resin having a weight average molecular weight of 11,000 was obtained.

[Comparative Example 2]
In a flask equipped with a thermometer, condenser, and stirrer, 59.6 g of m-cresol and 39.7 g of p-cresol as phenols, 22.0 g of paraformaldehyde as aldehydes, and oxalic acid as the first catalyst 0.58 g (0.002 equivalent when the total amount of raw materials is 1 equivalent) and 20.6 g of methanol were mixed and stirred at 90 ° C. for 4 hours while blowing nitrogen. Thereafter, the mixture is cooled to 40 ° C. or lower, 0.88 g of p-toluenesulfonic acid is added as a second catalyst (0.002 equivalent when the total amount of raw materials is 1 equivalent), and vacuum distillation is performed at 180 ° C. for 2 hours. went. When the obtained resin was measured by GPC, a resin having a weight average molecular weight of 17,000 was obtained.

[Comparative Example 3]
A flask equipped with a thermometer, a condenser, and a stirrer was charged with 44.8 g of m-cresol and 29.9 g of p-cresol as phenols, 15.7 g of paraformaldehyde as aldehydes and 1,4-bis (methoxy). Methyl) benzene 4.3 g (0.015 equivalent when the total amount of raw materials is 1 equivalent), 0.44 g of oxalic acid as the first catalyst (0.002 equivalent when the total amount of raw materials is 1 equivalent), 14.7 g of methanol was mixed and stirred at 90 ° C. for 4 hours while blowing nitrogen. Thereafter, the mixture was cooled to 40 ° C. or lower, and 1.74 g of oxalic acid (pKa = 1.27) was added as a second catalyst (0.008 equivalent when the total amount of raw materials was 1 equivalent), and 2 at 180 ° C. Vacuum distillation was performed for a period of time. When the obtained resin was measured by GPC, a resin having a weight average molecular weight of 8,100 was obtained.

  The weight average molecular weights and melting points of the resins of Examples 1-2 and Comparative Examples 1-3 are summarized and shown in Table 1.

  As shown in Table 1, the phenol novolak resins of Examples 1 and 2 using p-toluenesulfonic acid (pKa = −2.8) having an acid dissociation constant (pKa) of −2 or less as the second catalyst The weight average molecular weight was 20,000 or more. On the other hand, in Comparative Examples 1 and 2 in which no phenol compound is used and Comparative Example 3 in which oxalic acid (pKa = 1.27) having an acid dissociation constant (pKa) of more than −2 is used as the second catalyst, it is obtained. The weight average molecular weight of the phenol novolac resin was less than 20,000.

(Heat-resistant)
As shown in Table 1, in order to evaluate the heat resistance of the phenol novolac resins of Examples 1-2 and Comparative Examples 1-3, the melting points of the obtained phenol novolac resins were measured. As a result, the melting point of the phenol novolac resins of Examples 1 and 2 was generally high. The melting points of the phenol novolak resins of Comparative Examples 2 and 3 are higher than the melting point of the phenol novolak resin of Example 1 and have high heat resistance. From the results in Table 1, the phenol novolak resins of Comparative Examples 2 and 3 are The average molecular weight was small and it was insufficient as a photoresist material.

Claims (4)

a step of mixing a phenol containing m-cresol, 1,4-bis (methoxymethyl) benzene, an aldehyde, and a first catalyst, and performing an addition condensation reaction of the phenol and the aldehyde;
After the step of performing the addition condensation reaction, the step of adding a second catalyst before performing the heating and vacuum distillation,
The second catalyst is an acidic catalyst having an acid dissociation constant (pKa) of −2 or less , and the addition amount is 0.001 to 0.005 equivalents with the molar amount of the whole raw material as one equivalent, and the heating A method for producing a phenol novolac resin, wherein the weight average molecular weight of a phenol novolak resin obtained by distillation under reduced pressure is 20,000 or more .
The method for producing a phenol novolac resin according to claim 1, wherein a mixing ratio (molar ratio) of the phenols containing m-cresol and the aldehydes is 0.6 or more .
The method according to claim 1 or insulating cured product of curing a curable resin composition comprising a phenolic novolak resin obtained by the production method of phenol novolak resin according to 2. Method for producing a resist material containing a manufacturing method of the insulating cured product according to claim 3.