JP2012113065A - Photomask protective film and method for manufacturing circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask protective film suitably used in manufacturing a circuit board required to have high definition such as a printed wiring board, and to provide a photomask protective film with a small environmental load that may be provided with a degradable property such as a biodegradable property and may be disposed of through an alkaline treatment.SOLUTION: A photomask protective film comprises at least one layer of a film containing polyglycolic acid including 70 mol% or more of a glycolic acid repeating unit represented by a formula, -(O-CH-CO)-. Alternatively, a photomask protective film comprises a laminated film composed of a film including polyglycolic acid and a film including another thermoplastic resin. In a method for manufacturing a circuit board, any of these photomask protective films is used.

Description

  The present invention relates to a protective film for a photomask used in the production of a circuit board such as a semiconductor, a liquid crystal display, or a printed wiring board, or etching of a metal foil.

  2. Description of the Related Art Conventionally, photolithography that optically transfers a mask pattern has been widely used in the manufacture of circuit boards such as semiconductors, liquid crystal displays, and printed wiring boards, and the etching of metal foils. In this technique, a photoresist method using a photosensitive resin is used.

  For example, in the production of a circuit board, a photosensitive resin composition is laminated on a base material provided with a metal layer such as copper foil to form a photoresist layer, and exposure of a circuit pattern or the like on the surface of an optically transparent base material A photomask (negative film) on which a pattern for use is formed is brought into close contact with the photoresist layer, irradiated with actinic rays such as ultraviolet rays, and exposed through a photomask. Next, after the photomask is peeled off, a solvent (developer) is applied by spraying or the like, and a resist image is formed (developed) by removing the uncured resist corresponding to the unexposed portion. Thereafter, etching is performed using a cupric chloride aqueous solution or the like to remove a metal layer such as a copper foil that was under the uncured resist when irradiated with actinic rays. Subsequently, a method of forming a circuit having a predetermined pattern with a metal such as a copper foil by removing the cured resist with a solvent and performing a plating process as necessary is generally performed.

  In particular, in recent years, from the viewpoint of environmental problems and the like, there have been increasing use of a weak alkaline aqueous solution as a developer for removing an uncured resist. Further, a strong alkaline aqueous solution is often used to remove the cured resist.

  In order to cure the resist layer in a predetermined pattern, actinic rays such as ultraviolet rays are irradiated through the photomask. When the transparency of the photomask is low, the resist layer is not sufficiently exposed or light is scattered, resulting in a problem that the resolution is deteriorated. A photomask is prepared by providing a silver halide emulsion layer on an optically transparent substrate, exposing it to a predetermined pattern by irradiation with a HeCd laser, argon laser, etc., and then developing and fixing it. To do.

  Conventionally, glass such as soda lime glass or quartz glass having a thickness of about 1.6 to 5.0 mm has been used as an optically transparent substrate. The glass substrate has high flatness and little dimensional change due to changes in temperature and humidity, etc., but it is heavy and easy to break, so there are problems such as reduced workability and securing a storage location.

  Therefore, as a photomask, a film mask based on a resin film that is hard to break and has excellent handleability and high transparency has come to be used. As a base material for the film mask, a polyester film, particularly polyethylene terephthalate (hereinafter referred to as “PET”), which has excellent transparency to actinic rays such as ultraviolet rays, is highly transparent and has a low haze value, is used. A biaxially stretched polyester film, particularly a biaxially stretched PET film is used because of its excellent mechanical properties.

  Photomasks are used in close contact with the photoresist layer, so photosensitive resin may adhere to them, and repeated use may cause surface contamination or damage. Is done. Since photomasks are expensive, it is required to reduce the replacement frequency by preventing contamination and damage.

  A photomask protective film made of a plastic film (hereinafter sometimes simply referred to as “protective film”) is laminated on the photomask to prevent contamination or damage due to adhesion of the photosensitive resin to the photomask. It is done to use. Since this protective film is required to be transparent, to have a uniform film thickness, to be optically homogeneous, and to be chemically stable, films such as PET, polyethylene, polystyrene, and polycarbonate are generally used. In particular, biaxially stretched PET films have been widely used. For example, a photomask protective film in which a transparent support having a thickness of about 3 to 25 μm is used as a base material, an adhesive layer is provided on one side of the base material, and a release layer is provided on the other side so that a photoresist does not adhere. It is known (see Patent Document 1). When the protective film is dirty or damaged, the protective film may be peeled off and replaced, so that the photomask replacement frequency can be greatly reduced.

  Further, the photomask adheres foreign matters floating around during exposure, storage, or transportation. Since the foreign matter on the photomask is not accurately drawn at the time of exposure, defects appear in the product. In order to prevent such poor resolution due to foreign matter adhering to the surface of the photomask, a pellicle is mounted on the surface of the photomask as a dust-proof cover having translucency (see Patent Document 2). A film made of a crystalline fluororesin, a cyclic olefin polymer, a cellulose polymer, or the like is used as a pellicle material.

  In recent years, with the progress of pattern refinement in the field of photolithography, there has been a demand for pattern formation with higher resolution and faithful to the original image, and the protective film and pellicle are made thinner and the light transmittance is further improved. It is illustrated. However, for example, a PET film contains fine particles for imparting slipperiness and the like, and since the fine particles scatter light inside the film, haze is inevitable. For this reason, when PET is used as a protective film or pellicle, light is scattered not only on the transparent portion of the photomask but also acts on the photoresist layer under a predetermined pattern which is opaque. However, it becomes thicker than the width of the original image (the line width change amount becomes large), and reproducibility of the original image width cannot be obtained. On the other hand, in the case of low exposure, the width of the hardened resist becomes narrow due to haze, and problems such as reproducibility arise. In order to reduce this effect, for example, the protective film and pellicle have been thinned. However, if the thickness is too thin, the protective film or pellicle has insufficient rigidity, and when the protective film is laminated on the photomask. In addition, since the workability when the pellicle is mounted on the photoresist is hindered, a protective film or pellicle having better performance is required.

  Therefore, the photomask protective film has a high light transmittance, that the adhesiveness of the adhesive layer does not change by irradiation with actinic rays such as ultraviolet rays, can be peeled without leaving an adhesive on the photomask, and is released from the mold. Conditions such as high durability of the layer are required, and as disclosed in Patent Documents 3 and 4, selection of the base material, improvement of the adhesive layer and the release layer, etc. have been performed, Similarly, the pellicle has been required to have a high light transmittance and that its physical properties do not change by irradiation with actinic rays such as ultraviolet rays.

JP-A-4-355759 JP 7-168345 A Japanese Patent Laid-Open No. 9-230580 Japanese Patent Laid-Open No. 5-45865

  An object of the present invention is to provide a photomask protective film or pellicle suitable for the production of a circuit board such as a printed wiring board for which higher resolution is required, and further, biodegradability and the like can be decomposed. It is another object of the present invention to provide a photomask protective film or pellicle that has a low environmental impact and can be disposed of by alkali treatment.

  Another object of the present invention is to provide an efficient method of manufacturing a circuit board that can achieve higher resolution by using the photomask protective film or pellicle.

  Since the photomask protective film and the pellicle have the same problems and the same materials are used, in this specification, the photomask protective film is hereinafter described as including a pellicle. Yes.

As a result of diligent research to solve the above-mentioned problems, the present inventors have used, as a base material, a polyglycolic acid having 70 mol% or more of a glycolic acid repeating unit represented by the formula — (O · CH ₂ · CO) — ( Hereinafter, the present invention was conceived by finding that the problem can be solved by using a film for protecting a photomask comprising at least one film containing “PGA”).

That is, according to the present invention, there is provided a photomask protection comprising at least one film containing PGA having a glycolic acid repeating unit represented by the formula — (O · CH ₂ · CO) — of 70 mol% or more. Films are provided.

  Moreover, according to this invention, the film for photomask protection of the following (1)-(5) is provided as an embodiment.

(1) The film for protecting a photomask described above, wherein the film containing the PGA is a film further containing polylactic acid.
(2) The film for protecting a photomask, comprising a laminated film of a film containing the PGA and a film containing another thermoplastic resin.
(3) The film for protecting a photomask, wherein the film containing the other thermoplastic resin is a film containing at least one selected from the group consisting of polylactic acid, PET, and a cyclic olefin polymer.
(4) The film for protecting a photomask described above, comprising an adhesive layer on one surface.
(5) The film for protecting a photomask described above, comprising an adhesive layer on one side and a release layer on the other side.

  Furthermore, according to this invention, the manufacturing method of the circuit board which uses the said film for photomask protection is provided.

  According to the present invention, there is an effect that a photomask protective film suitable for manufacturing a circuit board such as a printed wiring board for which higher resolution is required is provided. In addition, according to the present invention, by using the photomask protective film, an effect is provided that a circuit board manufacturing method realizing higher resolution is provided. Since the circuit pattern can be formed by irradiating the actinic ray, there is an effect that a finer circuit pattern can be formed. In addition, according to the present invention, a photomask protective film that can be decomposed, such as biodegradation, can be obtained.

1. Polyglycolic acid The film for protecting a photomask of the present invention comprises at least one film containing PGA having 70 mol% or more of a glycolic acid repeating unit represented by the formula — (O · CH ₂ · CO) —. .

The content ratio of the repeating unit represented by the formula-(O.CH ₂ .CO)-in the PGA contained in the film needs to be 70 mol% or more when the total monomer unit of PGA is 100 mol%. Yes, preferably 85 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, particularly preferably 99 mol% or more, and the upper limit is 100 mol%. Therefore, PGA includes a homopolymer of glycolic acid composed only of glycolic acid repeating units represented by the formula-(O.CH ₂ .CO)-(a ring-opening polymer of glycolide which is a bimolecular cyclic ester of glycolic acid). And a PGA copolymer containing 70 mol% or more of the glycolic acid repeating unit.

When the content of the repeating unit represented by the formula-(O.CH ₂ .CO)-of PGA contained in the film is less than 70 mol%, excellent transparency cannot be obtained, and biodegradability is reduced. . If the content ratio of the repeating unit is 70 mol% or more, it is possible to control the crystallinity of PGA by introducing a small amount of a copolymerization component as other components, thereby lowering the extrusion temperature and improving stretchability. It becomes. In addition, when a small amount of a copolymerization component is introduced into PGA, the adhesiveness at the lamination interface is reduced when forming a photomask protective film, which is a laminated film including a film containing the PGA and a film containing another thermoplastic resin. It is also preferable from the viewpoint that the extrusion temperature of coextrusion can be adjusted.

  Examples of comonomers that give a PGA copolymer together with glycolic acid monomers such as glycolide include ethylene oxalate (ie, 1,4-dioxane-2,3-dione), lactides, lactones, carbonates, and ethers. , Ether esters, amides and other cyclic monomers; lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid and other hydroxycarboxylic acids or alkyl esters thereof; ethylene glycol A substantially equimolar mixture of an aliphatic diol such as 1,4-butanediol and an aliphatic dicarboxylic acid such as succinic acid or adipic acid or an alkyl ester thereof; or two or more of these Can do. Among these, cyclic compounds such as lactide, caprolactone and trimethylene carbonate; hydroxycarboxylic acids such as lactic acid, and the like are preferably used because they are easy to copolymerize and easily obtain a copolymer having excellent physical properties. These comonomers can be used as a starting material for giving a PGA copolymer together with the glycolic acid monomer such as glycolide.

  PGA can be synthesized by dehydration polycondensation of glycolic acid, dealcoholization polycondensation of glycolic acid alkyl ester, ring-opening polymerization of glycolide, and the like. Among these, glycolide is heated to a temperature of about 120 ° C. to about 250 ° C. in the presence of a small amount of a catalyst (for example, a cationic catalyst such as tin organic carboxylate, tin halide, antimony halide, etc.) to open a ring. A method of synthesizing PGA by a polymerization method is preferred.

  That is, as PGA contained in the photomask protective film of the present invention, in order to efficiently produce a desired high molecular weight polymer, 70 to 100% by mass of glycolide and 30 to 0% by mass of other cyclic monomers are opened. PGA obtained by ring polymerization is preferred. Another comonomer may be a cyclic monomer between two molecules, or may be a mixture of both instead of a cyclic monomer, but a cyclic monomer is preferred for the photomask of the present invention.

  Hereinafter, PGA obtained by ring-opening polymerization of 70 to 100% by mass of glycolide and 30 to 0% by mass of other cyclic monomers will be described in detail.

[Glycolide]
Glycolide that forms PGA by ring-opening polymerization is a bimolecular cyclic ester of glycolic acid, which is a kind of hydroxycarboxylic acid. Although the manufacturing method of glycolide is not specifically limited, Generally, it can obtain by thermally depolymerizing a glycolic acid oligomer. As a depolymerization method for glycolic acid oligomers, for example, a melt depolymerization method, a solid phase depolymerization method, a solution depolymerization method, etc. can be adopted, and glycolide obtained as a cyclic condensate of chloroacetate should also be used. Can do. If desired, glycolide containing glycolic acid can be used up to 20% by mass of the glycolide amount.

  The PGA contained in the photomask protective film of the present invention may be formed by ring-opening polymerization of only glycolide, but a ring-opening polymerization is simultaneously performed using another cyclic monomer as a copolymerization component to form a copolymer. May be. In the case of forming a copolymer, the proportion of glycolide is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass. % Or more, most preferably 99% by weight or more of a substantially PGA homopolymer.

[Cyclic monomer]
Other cyclic monomers that can be used as a copolymerization component with glycolide include lactones (for example, β-propiolactone, β-butyrolactone, in addition to bimolecular cyclic esters of other hydroxycarboxylic acids such as lactide). Cyclic monomers such as pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε-caprolactone, trimethylene carbonate, 1,3-dioxane and the like can be used. Other preferable cyclic monomers are bimolecular cyclic esters of other hydroxycarboxylic acids. Examples of hydroxycarboxylic acids include L-lactic acid, D-lactic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α- Hydroxyvaleric acid, α-hydroxycaproic acid, α-hydroxyisocaproic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid, and these Examples include alkyl-substituted products. Another particularly preferable cyclic monomer is lactide, which is a bimolecular cyclic ester of lactic acid, and may be any of L-form, D-form, racemate, and a mixture thereof.

  The other cyclic monomer is 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less, particularly preferably 2% by mass or less, and most preferably 1% by mass or less. Used in proportions. By ring-opening copolymerization of glycolide and other cyclic monomers, the melting point of PGA (copolymer) is lowered to lower the molding temperature, and the crystallization rate is controlled to improve extrusion processability and stretch processability. can do. However, if the use ratio of these cyclic monomers is too large, the crystallinity of the formed PGA (copolymer) may be impaired, and heat resistance, mechanical strength, and the like may be reduced. In addition, when PGA is formed from glycolide 100 mass%, another cyclic monomer is 0 mass%, and this PGA is also included in the scope of the present invention.

(Ring-opening polymerization reaction)
The ring-opening polymerization or ring-opening copolymerization of glycolide (hereinafter sometimes collectively referred to as “ring-opening (co) polymerization”) is preferably carried out in the presence of a small amount of a catalyst. Although the catalyst is not particularly limited, for example, a tin-based compound such as tin halide (for example, tin dichloride, tin tetrachloride, etc.) or organic carboxylate (for example, tin octoate such as tin 2-ethylhexanoate). A titanium compound such as alkoxy titanate; an aluminum compound such as alkoxyaluminum; a zirconium compound such as zirconium acetylacetone; an antimony compound such as antimony halide and antimony oxide; The usage-amount of a catalyst is a mass ratio with respect to cyclic ester, Preferably it is 1-1000 ppm, More preferably, it is about 3-300 ppm.

  Glycolide usually contains a trace amount of water and a hydroxycarboxylic acid compound composed of glycolic acid and a linear glycolic acid oligomer as impurities. By adjusting the total proton concentration of these impurities to preferably 0.01 to 0.5 mol%, more preferably 0.02 to 0.4 mol%, particularly preferably 0.03 to 0.35 mol%. The physical properties such as melt viscosity and molecular weight of the produced PGA can be controlled. Adjustment of the total proton concentration can also be performed by adding water to the purified glycolide.

  The ring-opening (co) polymerization of glycolide may be bulk polymerization or solution polymerization, but in many cases, bulk polymerization is employed. In order to adjust the molecular weight, a higher alcohol such as lauryl alcohol or water can be used as the molecular weight regulator. Moreover, you may add polyhydric alcohols, such as glycerol, for a physical property improvement. There are various types of polymerization equipment for bulk polymerization, such as an extruder type, a vertical type with paddle blades, a vertical type with helical ribbon blades, a horizontal type such as an extruder type and a kneader type, an ampoule type, a plate type and a tubular type. The device can be selected as appropriate. Moreover, various reaction tanks can be used for solution polymerization.

  The polymerization temperature can be appropriately set according to the purpose within a range from 120 ° C. to 300 ° C. which is a substantial polymerization start temperature. The polymerization temperature is preferably 130 to 270 ° C, more preferably 140 to 260 ° C, and particularly preferably 150 to 250 ° C. If the polymerization temperature is too low, the molecular weight distribution of the produced PGA tends to be wide. If the polymerization temperature is too high, the produced PGA is susceptible to thermal decomposition. The polymerization time is in the range of 3 minutes to 20 hours, preferably 5 minutes to 18 hours. If the polymerization time is too short, the polymerization does not proceed sufficiently and a predetermined weight average molecular weight cannot be realized. If the polymerization time is too long, the produced PGA tends to be colored.

  After making the produced PGA into a solid state, solid phase polymerization may be further carried out if desired. The solid-phase polymerization means an operation of performing heat treatment while maintaining a solid state by heating at a temperature lower than the melting point (Tm) of PGA. By this solid phase polymerization, low molecular weight components such as unreacted monomers and oligomers are volatilized and removed. The solid phase polymerization is preferably performed for 1 to 100 hours, more preferably 2 to 50 hours, and particularly preferably 3 to 30 hours.

  Further, the crystallinity may be controlled by giving a thermal history to the solid PGA by a step of melting and kneading the PGA in a melting point Tm + 38 ° C. or higher, preferably within a temperature range from Tm + 38 ° C. to Tm + 100 ° C.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) of PGA obtained by these polymerization methods is in the range of 25,000 to 800,000, preferably 50,000 to 700,000, more preferably 80,000 to 600, 000, more preferably 120,000 to 500,000, particularly preferably 150,000 to 400,000.

[Melting point (Tm)]
The PGA melting point (Tm) of the film contained in the photomask protective film of the present invention is 197 to 245 ° C., and can be adjusted by the type and content ratio of the copolymerization component. Preferably it is 200-243 degreeC, More preferably, it is 205-238 degreeC, Most preferably, it is 210-235 degreeC. The melting point of the homopolymer of PGA is usually about 220 ° C. If the melting point is too low, the mechanical strength is insufficient, or the temperature control when performing the molding process becomes difficult. If the melting point is too high, the processability may be insufficient or the flexibility of the film may be insufficient. On the other hand, if the melting point is too high, the molding temperature becomes high, so that PGA and other additive components may be thermally decomposed and oxidized.

[Crystallization temperature (TC ₁ )]
The crystallization temperature (TC ₁ ) of PGA contained in the photomask protective film of the present invention is usually 75 to 100 ° C., preferably 80 to 97 ° C., more preferably 85 to 95 ° C., and particularly preferably 88. ~ 93 ° C. The crystallization temperature (TC ₁ ) of PGA is such that sample PGA is heated from 50 ° C. to about 250 ° C. at a heating rate of 10 ° C./min, held at this temperature for 2 minutes, and then rapidly (about 100 The amorphous sample obtained by cooling to ° C / min) was detected in the process of reheating using a differential scanning calorimeter (DSC) in a nitrogen atmosphere from around room temperature at a heating rate of 10 ° C / min. It means the temperature of the exothermic peak due to crystallization. If the crystallization temperature (TC ₁ ) is too high, crystallization starts early in the production process of the photomask protection film of the present invention, an unstretched film cannot be obtained, and the mechanical strength due to subsequent stretching operations, etc. And surface properties cannot be controlled. When the crystallization temperature (TC ₁ ) is too low, coarse PGA crystals are formed, and the mechanical strength may be lowered. The crystallization temperature (TC ₁ ) can be adjusted by appropriately selecting the molecular weight of PGA and the type and amount of the polymerization component.

[Melt viscosity]
The melt viscosity of PGA contained in the photomask protective film of the present invention is preferably 100 to 2,000 Pa · s, more preferably 200, as measured at a temperature of 270 ° C. and a shear rate of 122 sec ^−1. ˜1,500 Pa · s, more preferably 250 to 1,000 Pa · s. When the melt viscosity of PGA at 270 ° C. and 122 sec ⁻¹ is less than 100 Pa · s, the molecular weight of PGA is low, and there is a risk of decomposition during use. Also, when the melt viscosity exceeds 2,000 Pa · s, there is a problem that the load on the extruder and the filtration pressure increase in the polymer extrusion process, or lamination by coextrusion with a film containing another thermoplastic resin. May become difficult.

2. Photomask protective film (film containing PGA)
The film for protecting a photomask of the present invention is a film containing PGA having 70 mol% or more of a glycolic acid repeating unit represented by the formula — (O · CH ₂ · CO) — (hereinafter, simply “PGA-containing film”). At least one layer.

  Therefore, the photomask protective film of the present invention contains a photomask protective film consisting of only a single layer or a plurality of layers containing the PGA, a film containing the PGA, and other thermoplastic resins. Any of the films for protecting a photomask made of a laminated film provided with a film is included.

[Other resins and additives]
The PGA-containing film can be blended with other thermoplastic resins in addition to PGA within a range that does not impair the object of the present invention.

  For example, aliphatic polyesters such as polylactic acid (hereinafter sometimes referred to as “PLA”), polybutylene succinate, polyethylene succinate, poly β-propiolactone, polycaprolactone, and the like; Other thermoplastic resins such as glycols; modified polyvinyl alcohol; polyurethane; polyamides such as poly L-lysine; From the viewpoint of adjusting the degradability such as biodegradability, it is preferable to add PLA.

  Since these contents are within a range in which the transmission of actinic rays such as ultraviolet rays is not inhibited and the light transmittance is maintained, 30% by mass when all the components of the film containing PGA are 100% by mass. % Or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.

  In addition, for PGA-containing films, inorganic fillers, plasticizers, heat stabilizers, light stabilizers, moisture proofing agents, waterproofing agents, water repellents, lubricants, mold release agents, coupling agents, oxygen as necessary Various additives usually blended such as an absorbent can be contained.

  These contents are within a range that does not hinder the object of the present invention as described above, and in particular, are within a range that does not hinder the transmission of actinic rays such as ultraviolet rays and can maintain light transmittance. Specifically, when the total component of the film containing PGA is 100% by mass, it is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 2% by mass or less.

[Laminated film photomask protection film]
The film for protecting a photomask of the present invention may be composed of a single film layer containing the PGA, but may be composed of a plurality of layers of a film containing the PGA. It may include a plurality of layers of PGA-containing films and a layer of PGA-containing films having different monomer compositions, or a layer of PGA-containing films having different average molecular weights, melt viscosities, etc. It may be a thing, and the other resin and additive to mix | blend may contain the layer of the film from which another differs.

  Moreover, the laminated film of the film containing the said PGA and the film containing another thermoplastic resin may be sufficient as the film for photomask protection of this invention. The film containing the other thermoplastic resin is not limited as long as the laminated film can maintain light transmittance, and aromatic polyolefin, aliphatic polyester, acrylic resin, polyolefin such as polyethylene and polypropylene, Alternatively, a cyclic olefin polymer or the like can be used, but as the other thermoplastic resin, at least one selected from the group consisting of PLA as an aliphatic polyester, PET as an aromatic polyester, and a cyclic olefin polymer. Preferably it is a seed.

  When the other thermoplastic resin is PLA, the entire photomask protective film can be made highly degradable. The PLA may be a copolymer containing other monomer units other than lactic acid in addition to PLA polymerized using L-lactic acid and / or D-lactic acid as main constituent components. Other monomer units include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A. Glycol compounds such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid , Naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, Dicarboxylic acids such as 5-sodium sulfoisophthalic acid and 5-tetrabutylphosphonium isophthalic acid; hydroxycarboxylic acids such as glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid; caprolactone, valerolactone , Lactones such as propiolactone, undecalactone, 1,5-oxepan-2-one; and the like.

  As the film containing PLA provided in the photomask protective film of the present invention, a film formed into a sheet or the like by PLA, inflation molding or the like using PLA is used. The film may be unstretched or uniaxially or biaxially stretched, but is preferably a stretched film from the viewpoint of ensuring transparency and strength.

  When the other thermoplastic resin is PET, a photomask protective film having required mechanical strength can be obtained at a low cost. As PET, in addition to the PET homopolymer, a copolymer in which 80 mol% or more of all dicarboxylic acid components are terephthalic acid and 80 mol% or more of all glycol components is ethylene glycol can be used. That is, 20 mol% or less of the total acid component is aromatic such as isophthalic acid, naphthalene dicarboxylic acid, diphenylethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid Dicarboxylic acid; aliphatic dicarboxylic acid such as adipic acid and sebacic acid; alicyclic carboxylic acid such as cyclohexane-1,4-dicarboxylic acid; and the like. In addition, 20 mol% or less of the total glycol component is glycol such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol; hydroquinone, resorcin, 2,2-bis (4-hydroxydiphenyl) An aromatic diol such as propane; an aliphatic diol having an aromatic ring such as 1,4-dihydroxymethylbenzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; Can do. From the viewpoint of adhesiveness with a film containing PGA and transparency, a copolymer is preferably used.

  As the film containing PET included in the photomask protective film of the present invention, a film formed into a sheet or the like by using PET, extrusion molding, inflation molding or the like is used. The film may be unstretched or uniaxially or biaxially stretched, but is preferably a stretched film from the viewpoint of ensuring transparency and strength.

  When the other thermoplastic resin is a cyclic olefin polymer, the dimensional stability and heat resistance of the photomask protective film are improved. As the cyclic olefin polymer, a polymer derived from a structural unit derived from a cyclic olefin alone, or a structural unit derived from a linear or branched α-olefin, a structural unit derived from an aromatic vinyl compound, and Examples thereof include a copolymer of at least one structural unit derived from an alkyl acrylate or alkyl methacrylate and a structural unit derived from a cyclic olefin. The combination of each structural unit may be a block or random.

Cyclic olefins include bicyclo-2-heptene derivatives (bicyclohept-2-ene derivatives), tricyclo-3-decene derivatives, tricyclo-3-undecene derivatives, tetracyclo-3-dodecene derivatives, pentacyclo-4-pentadecene derivatives, pentacyclo Pentadecadiene derivative, pentacyclo-3-pentadecene derivative, pentacyclo-3-hexadecene derivative, pentacyclo-4-hexadecene derivative, hexacyclo-4-heptadecene derivative, heptacyclo-5-eicosene derivative, heptacyclo-4-eicosene derivative, heptacyclo-5 -Heneecocene derivative, octacyclo-5-docosene derivative, nonacyclo-5-pentacocene derivative, nonacyclo-6-hexacocene derivative, cyclopentadiene-acenaphthylene Products having a norbornene ring such as 1,4-methano-1,4,4a, 9a-tetrahydrofluorene derivatives, 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene derivatives can give. Specifically, a ZEONOR film manufactured by Nippon Zeon Co., Ltd., an ARTON film manufactured by JSR Corporation, or the like can be used. By using a laminated film of these cyclic olefin polymer film and a film containing PGA as a photomask protective film, the photomask protective film is applied to a photomask and exposed 500 times (one time Even if the exposure amount is 50 mJ / cm ² ), only a 20 μm shrinkage can be generated at a rating of a distance of 450 mm.

  The cyclic olefin polymer has a glass transition point (Tg) of 50 to 220 ° C., preferably 80 to 170 ° C., a water absorption of 0.3% or less, preferably 0.1% or less, and light transmission. A highly transparent material with a rate of 88 to 95% is suitable.

  The film containing the cyclic olefin polymer provided in the photomask protective film of the present invention is a film formed into a sheet or the like by extrusion molding, inflation molding or the like using the cyclic olefin polymer. The film may be unstretched or uniaxially or biaxially stretched, but is preferably a stretched film from the viewpoint of ensuring transparency and strength.

  The content of at least one selected from the group consisting of PLA, PET and a cyclic olefin polymer in a film containing another thermoplastic resin is 100 masses of all components of the film containing the other thermoplastic resin. % Is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

  In the film containing other thermoplastic polymer, within the range which does not inhibit the object of the present invention, in addition to PGA, inorganic filler, other thermoplastic resin, plasticizer, heat stabilizer, light stabilizer, moisture-proof agent Various additives usually blended such as waterproofing agent, water repellent agent, lubricant, mold release agent, coupling agent, oxygen absorber, pigment, dye and the like can be blended.

  The content of these various additives is within a range that does not hinder the purpose of the present invention as described above, and is particularly within a range that does not inhibit the transmission of actinic rays such as ultraviolet rays and can maintain light transmittance. Therefore, specifically, when all the components of the film containing another thermoplastic polymer are 100% by mass, it is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2%. It is below mass%.

[Photomask protective film thickness]
The thickness of the photomask protective film of the present invention is usually in the range of 0.5 to 25 μm, preferably 1 to 20 μm, more preferably 2 to 18 μm, and particularly preferably 3 to 16 μm. If the thickness is less than 0.5 μm, the strength of the photomask protective film is lowered and handling becomes difficult, and wrinkles and distortion may occur. If the thickness exceeds 25 μm, the light transmittance of the photomask protective film may be insufficient.

  When the film for protecting a photomask of the present invention is a laminated film of a film containing PGA and a film containing another thermoplastic resin, the thickness of the film containing PGA is relative to the thickness of the whole laminated film. In general, it is in the range of 1 to 95%, preferably 5 to 90%, more preferably 10 to 85%, particularly preferably 20 to 80%, and most preferably 30 to 75%. When the ratio of the thickness of the film containing PGA is less than 1%, the transparency of the photomask protection film may be insufficient and the resolution may be lowered. When the thickness ratio of the film containing PGA exceeds 95%, the cost increases.

(Adhesive layer)
The photomask protective film of the present invention is used by being laminated on one side or both sides of a photomask. Since an adhesive is usually used for this lamination, the photomask protection film of the present invention preferably includes an adhesive layer made of an adhesive.

  As the pressure-sensitive adhesive, known acrylic adhesives, rubber-based adhesives, urethane-based adhesives and the like can be used, and the thickness of the pressure-sensitive adhesive layer is usually 0.1 to 1 μm, preferably 0.2 to 0.00. It is 7 μm, more preferably in the range of 0.2 to 0.5 μm. The film for protecting a photomask of the present invention may be obtained by laminating a cover film for protecting the adhesive layer on the adhesive layer. When the photomask protective film having a cover film laminated on the adhesive layer is laminated on the photomask, the cover film is peeled off to adhere the photomask protective film to the photomask.

  The film for protecting a photomask of the present invention may be formed by performing a surface treatment with a corona treatment, a plasma treatment or a surface treatment agent in order to adjust the adhesive force with the adhesive.

[Release layer]
In addition, the photomask protective film of the present invention has a release layer on the surface opposite to the adhesive layer because the protective film needs to be cleaned or replaced when the photoresist adheres to the surface. It is preferable that The release layer is composed of a mixture of resin and release agent. As the resin contained in the release layer, urethane resin, acrylic resin, vinyl chloride resin, vinylidene chloride resin, chlorinated rubber, chlorinated polyolefin, alkyd resin, polyester resin, amino resin, melamine resin, etc. are used. These can be used alone or in combination. As the release agent, it is preferable to use a silicone release agent. The mixing ratio of the resin and the silicone-based release agent is preferably such that the ratio of the silicone-based release agent to the resin is in the range of 2 to 15% by mass. If it is less than 2% by mass, the mold release effect is low, and photoresist adhesion may occur after several uses. When the content exceeds 15% by mass, the release effect is good, but the release layer becomes cloudy and the transparency may be lowered, which is not preferable. An antistatic agent may be added to impart an antistatic function to the release layer. The antistatic agent may be appropriately selected depending on the compatibility with the resin to be used, transparency, etc., such as a surfactant, a conductive resin, and a metal fine powder. The thickness of the release layer is preferably thinner because it affects the resolution of the photoresist, but is preferably 0.1 to 1 μm, more preferably 0.2 to 0. 7 μm.

[Other layers]
The photomask protective film of the present invention may further include other layers. For example, a transparent conductive thin film can be provided inside the release layer. As the transparent conductive thin film, a thin film of an oxide of at least one metal such as In, Ga, Tl, Sn, Ti, V, Cr, Mo, and W can be used. In particular, ITO (indium, tin oxide) is preferable because of its light transmittance, surface electrical characteristics, and their little change with time.

[Pellicle]
When the photomask protective film of the present invention is a pellicle, the pellicle is made of aluminum, stainless steel, polyethylene, or the like via a known acrylic adhesive, rubber adhesive, urethane adhesive, or the like. The pellicle frame is adhered to the upper portion of the pellicle frame, and the pellicle frame is adhered to the photomask via an adhesive.

The pellicle may be provided with an antireflection film made of MgF ₂ , CaF _2, or the like to enhance light transmission. In addition, an adhesive layer or an adhesive layer may be provided on the side facing the photomask to capture dust adhering to the inside of the pellicle.

  Since the pellicle is mounted several mm away from the photomask, dust adhering to the inside of the pellicle deviates from the focal position of actinic rays such as ultraviolet rays and does not affect the pattern formation of the photoresist.

3. Production of Photomask Protection Film The film containing the PGA provided in the photomask protection film of the present invention is formed by melt-forming the PGA, uniaxially or biaxially stretched as desired, and further heat-treated. The As methods and conditions for these steps, known methods and conditions can be employed. For example, using an extrusion molding machine equipped with a slit-shaped die, PGA is melt-kneaded at a temperature of melting point Tm to 300 ° C. and extruded into a sheet shape, which is lower than the crystallization temperature (TC ₁ ), usually 5 to 70 ° C. In many cases, an unstretched sheet is formed by quenching and solidifying with a cooling drum maintained at a surface temperature in the range of 10 to 50 ° C., and the unstretched sheet has a stretching temperature of 30 to 70 ° C., preferably 33 to 68. Uniaxial stretching, or sequential or simultaneous biaxial stretching at a temperature of 35 ° C., more preferably 35 to 65 ° C., and an area magnification of 2 to 100 times, preferably 4 to 60 times, more preferably 6 to 30 times. , 130-210 ° C., preferably 140-200 ° C., under tension or under 20% relaxation. In order to produce a stretched film, a method in which a stretching roll and a tenter stretching machine are combined is employed. When performing sequential biaxial stretching, after stretching uniaxially in the machine direction (MD) using a stretching roll, After performing cooling or heat treatment as necessary, it is preferable to stretch in the transverse direction (TD) using a tenter stretching machine.

  As a method for producing a film for protecting a photomask which is a laminated film, a method of adhering a film containing the PGA obtained by melt film formation and a film containing another thermoplastic resin with an adhesive, The laminated film can be produced by a known method such as a method of producing a laminated film by coextrusion or extrusion lamination, but it is preferable to obtain the laminated film by coextrusion. When adhering with an adhesive, commonly used acrylic adhesives, rubber adhesives, urethane adhesives and the like can be used, and the thickness of the adhesive layer is usually 0.1 to 1 μm, preferably Is in the range of 0.2 to 0.7 μm, more preferably 0.2 to 0.5 μm. When producing a film for protecting a photomask, which is a laminated film that has been subjected to stretching treatment, after obtaining the laminated film in advance, uniaxial or biaxial stretching treatment and heat treatment may be performed, or the stretching treatment and heat treatment are performed in advance. A laminated film may be laminated.

4). Method for producing circuit board To produce a circuit board such as a printed wiring board using the photomask protective film of the present invention, a photosensitive resin composition is applied to a metal surface such as a copper-clad board, SUS or 42 alloy. After providing a photoresist layer comprising, a photomask obtained by attaching the photomask protective film of the present invention to the photoresist layer is placed and adhered so that the protective film is in contact with the photoresist layer, It exposes with actinic rays, such as an ultraviolet-ray, and the photosensitive resin composition in a photoresist layer is hardened to a predetermined pattern. The exposure is usually performed by irradiating ultraviolet rays having a wavelength of about 193 to 400 nm. As the light source at that time, ArF excimer laser, KrF excimer laser, high pressure mercury lamp, super high pressure mercury lamp, carbon arc lamp, xenon lamp, metal halide lamp Chemical lamps and the like are used. Since the PGA film included in the photomask protective film of the present invention has a high ultraviolet transmittance even in a short wavelength region, actinic rays having a wavelength in the above range from the far ultraviolet light to the near ultraviolet light can be used. After the ultraviolet irradiation, heating can be performed as necessary to complete the curing.

  After the exposure is completed, the photomask with the photomask protection film of the present invention is removed, and then the uncured resist in the photoresist layer is removed, and development is performed to leave the cured resist in a predetermined pattern. Development is performed by removing the uncured photosensitive resin composition of the resist layer using a weak alkaline aqueous solution of about 0.5 to 5% by mass such as sodium hydroxide, sodium carbonate, potassium carbonate, etc. Expose the layer. In the alkaline aqueous solution, a surfactant, an antifoaming agent, a small amount of an organic solvent for accelerating development, and the like may be mixed.

  Subsequently, etching is performed to remove exposed metals such as copper foil. Etching is usually performed according to a conventional method using an acidic etching solution such as cupric chloride-hydrochloric acid aqueous solution or ferric chloride-hydrochloric acid aqueous solution. An ammonia-based alkaline etching solution can also be used.

  Next, the hardened resist is removed with a strong alkaline aqueous solution, a predetermined pattern is formed with a metal such as a copper foil, a plating process is performed as necessary, and a circuit with a predetermined pattern is formed with a metal such as a copper foil. Get. In the plating method, pretreatment is performed using a plating pretreatment agent such as a degreasing agent or a soft etching agent, and then plating is performed using a plating solution. As the strong alkaline aqueous solution, an alkaline aqueous solution having a concentration of about 1 to 10% by mass such as sodium hydroxide or potassium hydroxide is used.

  The photomask protective film of the present invention can be applied to photomasks used for precision metal processing, in addition to the production of printed wiring boards and lead frames.

  EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to the examples.

[Reference Example] Production of PGA biaxially stretched film PGA homopolymer was used as PGA. This PGA has a melting point of 221 ° C., a crystallization temperature (TC ₁ ) of 90 ° C., a temperature of 270 ° C. and a shear rate of 122 Pa ⁻¹ , and a melt viscosity of 600 Pa · s. AX-71 (monostearyl phosphate 50 mol% and distearyl phosphate 50 mol%) is contained at a ratio of 300 ppm.

  This PGA raw material pellet was heated and melted using a single screw extruder having a screw diameter of 35 mm so that the resin temperature was 260 to 270 ° C. The melt was cooled by casting through a 100 μm aperture filter from a T-die having a linear lip with a length of 270 mm and a gap of 0.75 mm, and cast on a metal drum whose surface was kept at 40 ° C., with a thickness of 200 μm. An unstretched sheet was prepared. The unstretched sheet was adjusted to a sheet temperature of 60 ° C., and uniaxially stretched in the machine direction (MD) at a stretching speed of 2 m / min using a stretching roll so that the stretching ratio was 4.5 times. The uniaxially stretched film is cooled using a spot cooler and a cooling roll so that the surface temperature becomes 33 ° C., and then introduced into a tenter stretching machine, and the film temperature is 38 ° C. and the draw ratio is 3.1 times. In the tenter stretching machine, the biaxially stretched film was immediately subjected to heat treatment in a dry heat atmosphere at a temperature of 145 ° C. with a 5% relaxation in the width direction, and a thickness of 15 μm. An axially stretched film was produced.

Example 1
<Preparation of photomask protective film>
An adhesive layer forming liquid having the following composition was applied to one side of a PGA biaxially stretched film produced according to the reference example with a Meyer bar so that the thickness after drying was 0.5 μm, and dried at 100 ° C. for 1 minute to form a coating film. Formed.

Adhesive layer forming liquid Acrylic acid ester copolymer (solid content concentration 40%, manufactured by Toagosei Co., Ltd.) 10 g
Toluene 10g
10 g of ethyl acetate

  A 25 μm-thick PET release film (trade name Ceraper: manufactured by Toyo Metallizing Co., Ltd.) was bonded to the adhesive layer as a cover film to prepare a photomask protective film.

<Hardening of photoresist>
While peeling off the PET release film from the photomask protective film and preventing wrinkles from entering the protective film, an exposure circuit pattern is provided on the surface as a photomask on the adhesive layer surface of the protective film. The surface on which the pattern for exposure of the silver salt film was formed was affixed.

  A photosensitive resin composition having the composition shown in Table 1 was uniformly applied to a copper-clad substrate so as to have a thickness of 50 μm after drying, and then dried at 60 ° C. for 24 hours to form a photoresist layer. The photomask on which the protective film prepared above was attached was placed so that the protective film was in contact with the photoresist layer, and an ultraviolet irradiation device manufactured by Nippon Battery Co., Ltd. was used. The photosensitive resin composition of the photoresist layer was cured by irradiating ultraviolet light having a wavelength of 365 nm at cm.

  The peel strength when the photomask with the protective film attached was peeled from the cured photoresist layer was measured. Measurement was performed using Tensilon RTC-1210A manufactured by Orientec Co., Ltd., in accordance with JIS Z0237, with a sample width of 15 mm, a tensile speed of 300 mm / min, and a photomask with a protective film attached on the tension side, a cured photoresist layer A 90 ° peel test was carried out using as a fixed side. The results are shown in Table 2. In addition, adhesion of the cured photoresist layer was not seen at all on the photomask protective film which is a film containing the peeled PGA.

(Comparative Example 1)
Photo in which a photomask protective film was pasted in the same manner as in Example 1 except that instead of the PGA film, a 15 μm thick PET biaxially stretched film (manufactured by Toray Industries, Inc.) was used as the protective film. A mask was manufactured and a 90 ° peel test was performed. The results are shown in Table 2. In some cases, the cured photoresist layer was partially attached to the peeled PET film (average area ratio of about 20%).

  From Table 2, since the film for protecting a photomask of the present invention including the layer of the film containing PGA of Example 1 is excellent in releasability from a photoresist, the production efficiency is improved and the photomask protecting film is used. Since the film is less fouled, it can be seen that the replacement frequency of the protective film and the photomask can be lowered, and the cost is excellent. On the other hand, in the conventional photomask protective film of Comparative Example 1 based on a PET film that has been widely used, a large force is required to peel the photomask protective film from the cured resist layer. I found out that

  A film for protecting a photomask comprising a layer of a film containing PGA of the present invention has a 90 ° peel strength (gf) of 15 mm width with a cured photoresist layer, and a film for protecting a photomask based on a PET film. In comparison, it is 50% or less, preferably 40% or less.

[Experimental Example 1] Ultraviolet Transmittance Test Using the spectrophotometer UV2450 manufactured by Shimadzu Corporation for the PGA film produced in the reference example and the PET film used in Comparative Example 1, the transmittance of ultraviolet rays having different wavelengths was measured for each wavelength. Measured. The results are shown in Table 3.

  From Table 3, it was found that the film containing PGA included in the photomask protective film of the present invention has a higher ultraviolet transmittance than conventional PET films that have been widely used as a photomask protective film. Moreover, the haze value was also low. Therefore, the circuit pattern can be more accurately reflected on the circuit board, and the photoresist layer can be cured with smaller irradiation energy, which is energy saving, improves the manufacturing efficiency of the circuit board and the manufacturing cost. Can be reduced.

  Moreover, it turns out that the film | membrane containing PGA with which the film for photomask protection of this invention is equipped has especially the transmittance | permeability with respect to the ultraviolet-ray of a shorter wavelength area | region of the wavelength 300nm or less which is not permeate | transmitted with a PET film. Therefore, if the photomask with the photomask protective film of the present invention is used, the photoresist layer can be cured by irradiating with shorter wavelength ultraviolet rays, so that a more detailed circuit pattern can be provided. It is possible to meet the demands for higher resolution such as miniaturization of printed circuit boards, development of application to liquid crystal display wiring, and direct mounting of semiconductors.

[Experimental Example 2] Alkali Degradability Evaluation An aqueous alkali solution having a sodium hydroxide concentration of 2 mass%, 5 mass%, and 10 mass% was prepared, 100 ml of the alkaline aqueous solution was placed in an Erlenmeyer flask, and a magnetic stirrer was used using a water bath. With stirring at 50 ° C. or 60 ° C. Samples cut into 4 cm × 4 cm from the PGA film produced in Reference Example and the PET film used in Comparative Example 1 were immersed in the Erlenmeyer flask. The time until each sample disappeared visually was measured as the time until complete decomposition. The results are shown in Table 4.

  From Table 4, it can be seen that the film containing PGA included in the photomask protective film of the present invention disappears in a short time by the alkaline aqueous solution. Since PGA is biodegradable as is well known, the film for protecting a photomask of the present invention having a film containing PGA has a wide range of disposal methods and a low environmental burden. On the other hand, the PET film that has been widely used as a photomask protective film has been substantially impossible to remove even with an alkaline aqueous solution.

  According to the photomask protective film of the present invention, it is possible to form a circuit pattern by irradiating an actinic ray having a shorter wavelength, so that a finer circuit pattern can be formed and the light transmittance is high. Therefore, exposure at a low irradiation dose contributes to energy saving, and a photomask protective film that can be decomposed such as biodegradation can be obtained, so the environmental burden can be reduced, and thus industrial applicability is high.

Claims (7)

A film for protecting a photomask, comprising at least one film containing polyglycolic acid having 70 mol% or more of a glycolic acid repeating unit represented by the formula — (O · CH ₂ · CO) —.   The film for protecting a photomask according to claim 1, wherein the film containing polyglycolic acid is a film further containing polylactic acid.   The film for protecting a photomask according to claim 1 or 2, comprising a laminated film of a film containing the polyglycolic acid and a film containing another thermoplastic resin.   The film for protecting a photomask according to claim 3, wherein the film containing the other thermoplastic resin is a film containing at least one selected from the group consisting of polylactic acid, polyethylene terephthalate, and a cyclic olefin polymer.   The photomask protective film according to any one of claims 1 to 4, further comprising an adhesive layer on one surface.   5. The photomask protective film according to any one of 1 to 4, comprising an adhesive layer on one side and a release layer on the other side.   The manufacturing method of the circuit board which uses the film for photomask protection of any one of Claims 1 thru | or 6.