TW201437022A - Cover lay film and copper-clad laminate using the same - Google Patents

Abstract

To provide a cover lay film which has excellent transparency and thermal resistance, and is significantly controlled from being milky caused by bleed-out of oligomer under high temperature, and also provide a copper-clad laminate using the same film. The cover lay film includes a transparent film layer having a first surface and a second surface, a hard coat layer, and an adhesive layer, wherein the hard coat layer is laminated on the first surface of the transparent film layer, the adhesive layer is laminated on the second surface of the transparent film layer, and the overall light transmittance is 85% or higher.

Description

Cover film and copper clad laminate using the cover film

The present invention is mainly directed to a cover film and a copper clad laminate which are used in a flexible printed wiring board.

The polyimide film has many properties required for electronic materials such as high heat resistance and high strength, and is widely used in the field of flexible printed wiring boards (hereinafter also referred to as "FPC"). In the field of FPC, for example, in applications where a high pattern design is required for cosmetic fascination, it is required to use the FPC itself to transmit light efficiently to transmit light. Specifically, a case where a transparent FPC is used in a mobile phone or the like can be cited. However, the use of a film of polyimine (PI) is difficult because the film itself is yellow, which satisfies the above requirements.

In order to satisfy the above-mentioned required characteristics, a colorless transparent film such as a polyethylene terephthalate (PET) film or a polyethylene naphthalate (PEN) film has been developed. For example, Patent Document 1 discloses a flexible substrate formed using PET or PEN as a plastic film.

Prior technical literature [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 5-259591

However, compared with PI, the film using PET and PEN is inferior in heat resistance and strength, and in the high-temperature drying, solder reflow treatment, and the like in the production step, deformation due to heat occurs and defects occur. Further, when a PET film is used, white turbidity may occur due to bleed out of the oligomer component, and transparency may be impaired.

In view of the above circumstances, an object of the present invention is to provide a cover film and a copper clad laminate using the cover film, which has excellent transparency and heat resistance, and can significantly suppress oligomerization in a high temperature environment. White turbidity caused by exudation of components.

In order to solve the above problems, the inventors of the present invention have found that the above problems can be solved by providing a hard coat layer on a transparent film contained in a cover film, and the present invention has been completed.

That is, the present invention is as follows.

[1] A cover film comprising a transparent film layer having a first surface and a second surface, and a coating layer having the first surface and the second surface; wherein the hard coat layer is laminated on the transparency The first surface of the film layer is laminated on the second surface of the transparent film layer, and the total light transmittance is 85% or more.

[2] The cover film according to the above [1], wherein the transparent film layer contains a resin selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and The polycarbonate resin is a resin of any one or more of the group consisting of.

[3] The cover film according to [1] or [2] above, wherein the transparent film layer has a thickness of 10 to 200 μm.

[4] The cover film according to any one of the above [1], wherein the hard coat layer is composed of a main component containing at least one selected from the group consisting of photosensitive compounds of an acrylate type. It is composed of a resin composition.

[5] The cover film according to any one of the above [1] to [4] wherein the hard coat layer has a thickness of 0.5 to 5 μm.

[6] The cover film according to any one of the above [1] to [5] wherein the glass transition temperature of the hard coat layer is higher than the glass transition temperature of the transparent film layer.

[7] The cover film according to any one of [1] to [6] wherein the glass transition temperature of the hard coat layer is 200 to 400 ° C, and the glass transition temperature of the transparent film layer is 50 to 180 °C.

[8] The cover film according to any one of [1] to [7] wherein the adhesive layer contains a group selected from the group consisting of an acrylic resin, a urethane resin, and a polyester resin. Any one or more of the resins.

[9] The cover film according to any one of the above [1] to [8] wherein the thickness of the adhesive layer is 10 to 50 μm.

[10] The cover film according to any one of the above [1] to [9] wherein the adhesive layer has a melt viscosity of from 100 to 100,000 poise in a range of from 100 ° C to 160 ° C.

[11] A copper-clad laminate comprising the above-mentioned adhesive layer contained in the cover film according to any one of the above [1] to [9], and a surface on which the transparent film layer is laminated The surface of the opposite side is further laminated with a copper foil layer.

[12] The copper clad laminate according to [11] above, wherein the adhesive layer has a melt viscosity of 10,000 poise or more in a range of from 100 ° C to 160 ° C.

[13] A flexible printed wiring board comprising the above-mentioned cover film according to any one of the above [1] to [10], and the copper-clad laminate according to the above [11] or [12]; After the circuit is formed on the copper foil layer contained in the copper-clad laminate, the adhesive layer of the cover film is adhered to the circuit formation surface of the copper-clad laminate.

[14] The flexible printed wiring board according to the above [13], wherein a difference between a refractive index of the adhesive contained in the cover film and an adhesive contained in the copper-clad laminate is 0 to 0.1.

According to the present invention, it is possible to provide a cover film and a copper clad laminate using the cover film, which has excellent transparency and heat resistance, and can remarkably suppress oozing out of oligomer components in a high temperature environment. White turbidity.

1‧‧‧hard coating

2‧‧‧Transparent film

3‧‧‧ adhesive layer

3'‧‧‧ adhesive layer

4‧‧‧copper layer

10‧‧‧ Cover film

20‧‧‧Copper laminate

30‧‧‧Soft printed wiring board

Fig. 1 is a view showing an example of a cross-sectional view of a cover film of the present embodiment.

Fig. 2 is a view showing an example of a cross-sectional view of the copper clad laminate of the embodiment.

Fig. 3 is a view showing an example of a cross-sectional view of the flexible printed wiring board of the embodiment.

Hereinafter, the form for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail. The present invention is not limited to the embodiments described below, and various modifications can be made without departing from the spirit and scope of the invention.

[cover film]

The cover film of the present embodiment includes a transparent film layer having a first surface and a second surface, and a hard coat layer laminated on the transparent film layer. In the first surface, the adhesive layer is laminated on the second surface of the transparent film layer, and the total light transmittance is 85% or more.

As shown in Fig. 1, the cover film 10 of the present embodiment has a structure in which a hard coat layer 1 is laminated on one surface of the transparent film layer 2, and an adhesive layer 3 is laminated on the other surface. In the cover film of the present embodiment, since the total light transmittance of the entire cover film is set to 85% or more and has excellent transparency, it can be suitably used as a skeleton for pattern design which is mainly required height (transparent ) A component of an FPC used in electronic equipment, components, and the like. The total light transmittance of the cover film of the present embodiment is preferably 86% or more, preferably 88% or more. Further, the cover film system is provided with a separation film, and the measurement of the total light transmittance is performed on the cover film in a state in which the separation film is peeled off. Hereinafter, each layer will be described.

[Transparent film layer]

When the cover film is used as a member of a flexible printed wiring board, the transparent film layer has a task of protecting a circuit or the like formed on the wiring board. The resin constituting the transparent film layer is not particularly limited as long as it is a transparent resin, and examples thereof include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and poly Any one or more of a group consisting of ethylene naphthalate (PEN) and a polycarbonate resin. Among the above, PET is preferred from the viewpoint of cost and transparency.

The thickness of the transparent film layer is preferably from 10 to 200 μm, preferably from 25 to 100 μm. When the thickness of the transparent film layer is 10 μm or more, the protective effect of the circuit or the like tends to be good, and when it is 200 μm or less, the transparency is improved and the bending property tends to be good.

[hard coating]

In the cover film of the present embodiment, by providing a hard coat layer on the transparent film, the thermal and mechanical effects exerted on the transparent film layer can be minimized. As a result, the heat resistance of the cover film is improved and the heating deformation start temperature can be increased. Moreover, the dimensional change in the high temperature environment in the manufacturing process can be suppressed. Specifically, although the PET film which is a transparent film has a property of largely shrinking in the longitudinal direction (M D) at more than 100 ° C, this can be reduced by providing a hard coat layer.

Moreover, by providing a hard coat layer, it is possible to suppress bleed out of the oligomer contained in the transparent film layer. In general, when the PET film is placed in a high temperature environment of 100 ° C or higher, white turbidity is generated, but the hard coat layer can be physically closed and suppressed.

Further, by providing a hard coat layer, the scratch resistance of the cover film can be improved. Generally, the pencil hardness of the PET film is about 2B, and the hardness is increased to HB by providing a hard coat layer. Thereby, it is possible to suppress scratches which are likely to occur in the FPC processing steps such as copper foil etching and CL pressing.

As described above, in the cover film of the present embodiment, by providing a hard coat layer on the transparent film layer, in addition to imparting excellent heat resistance, it is possible to suppress bleed out of the oligomer in a high-temperature environment and also to be resistant to damage. The performance is improved, and the transparency and pattern design are also excellent.

The hard coat layer is composed of a resin composition containing at least one main component selected from the group consisting of acrylate-based photosensitive compounds.

Examples of the acrylate-based photosensitive compound include polytetramethylene glycol di(meth)acrylate and ethoxylated 2-methyl-1,3-propanediol di(meth)acrylate. 1,6-hexanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-nonanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated iso-cyanuric acid tris(methyl) Acrylate, ethoxylated Tris(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, pentaerythritol lanthanum (meth) acrylate, ethoxylate Base group pentaerythritol oxime (meth) acrylate, propoxylated pentaerythritol ruthenium (meth) acrylate, ditrimethylolpropane oxime (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like. The acrylate-based photosensitive compound preferably has a weight average molecular weight of from 150 to 3,000, more preferably from 150 to 2,000, and preferably has two or more functional groups as a functional group. The (meth)acrylic group is preferred, and it is preferably 4 or more.

The hard coat layer is formed of a resin composition obtained by blending a polymerization initiator, other additives, and the like in addition to the above-mentioned main component. The polymerization initiator can be mainly classified into a photoradical polymerization initiator; and a thermal radical polymerization initiator which generates a radical by heat.

As a photoradical polymerization initiator, for example, three can be used. Department, benzoin, acetophenone, imidazole, A compound such as a xanthone or an oxime ester. As a specific example, 2,4-bistrichloromethyl-6-p-methoxystyryl-s-three can be mentioned. 2-p-methoxystyryl-4,6-bistrichloromethyl-s-three 2,4-trichloromethyl-6-three 2,4-trichloromethyl-4-methylnaphthyl-6-three , diphenyl ketone, p-(diethylamino)diphenyl ketone, 2,2-dichloro-4-phenoxyacetophenone, 2,2-diethoxyacetophenone, 2-12 Alkylthio Ketone, 2,4-dimethylthio Ketone, 2,4-diethylthio Ketone, 2,2-bis-2-chlorophenyl-4,5,4,5-tetraphenyl-2-1,2-diimidazole, Ciba Specialty Chemicals Co., Ltd. Irgacure 369, Irgacure 651, Irgacure 907, Darocur TPO, Irgacure 819, OXE-01, OXE-02, N-1919 of ADEKA Co., Ltd., NCI-831, etc. These compounds can be used alone or in combination of two or more.

As the thermal radical polymerization initiator, a diazo compound or a peroxide compound can be used. Specific examples include azobisisobutyronitrile manufactured by Tokyo Chemical Industry Co., Ltd., and Naiber BW manufactured by Nippon Oil & Fats Co., Ltd., and the like. These compounds may be used singly or in combination of two or more.

As other additives, for example, an antioxidant such as a hindered phenol type, a phosphorus type or a sulfur type; a stabilizer for a light stabilizer, a weather stabilizer, a heat stabilizer, or the like; a phosphoric acid (dibromopropyl) can be used. Flame retardant such as ester, triallyl phosphate, cerium oxide; anionic, cationic, nonionic surfactant; antistatic agent; resin modifier for organic fillers, inorganic fillers, etc.; organic filler; Various well-known additives such as inorganic fillers; plasticizers; slip agents and the like. The blending amount of the additive can be appropriately adjusted according to the purpose within the range not impairing the effects of the invention.

The thickness of the hard coat layer is preferably 0.5 to 5 μm, preferably 0.8 to 2 μm. When the thickness of the hard coat layer is 0.5 μm or more, the effect of heat resistance tends to be better, and when it is 5 μm or less, the bendability tends to be good.

The glass transition temperature of the hard coat layer is preferably higher than the glass transition temperature of the transparent film layer. The glass transition temperature of the hard coat layer is preferably 200 to 400 ° C, preferably 250 to 350 ° C, more preferably 300 to 350 ° C. When the glass transition temperature of the hard coat layer is 200 ° C or more, the effect of heat resistance tends to be more favorable. Further, when the glass transition temperature of the hard coat layer is 250 ° C or more, the adhesion can be suppressed, and the workability tends to be improved. On the other hand, the glass transition temperature of the transparent film layer is preferably from 50 to 180 ° C, preferably from 80 to 160 ° C, more preferably from 80 to 110 ° C.

[adhesive layer]

The subsequent layer is a layer in which the transparent film layer is bonded to an adherend such as a circuit. The resin constituting the adhesive layer is not particularly limited as long as it has transparency. For example, one or more selected from the group consisting of an acrylic resin, a urethane resin, and a polyester resin may be used. Resin. Among the above, from the viewpoint of transparency, an acrylic resin or a polyester resin is preferred.

The acrylic resin is a polymer obtained by polymerizing (meth)acrylic acid alkyl ester or (meth)acrylic acid, and is not particularly limited as the (meth)acrylic acid alkyl ester, and examples thereof include ( Methyl)methyl acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate And 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and the like.

The acrylic resin is not particularly limited, and for example, it can be exemplified by A solvent-soluble urethane resin obtained by polymerizing a polyhydric alcohol with a polyisocyanate. The polyester polyol is not particularly limited, and may be obtained by subjecting a polybasic acid to a polyhydric alcohol esterification reaction. For example, a compound having two or more hydroxyl groups in one molecule can be used.

The polybasic acid which is a starting material for the production of the polyester polyol is not particularly limited, and examples thereof include a polyvalent carboxylic acid having two or more carboxyl groups in one molecule. Examples of the polyvalent carboxylic acid include aliphatic dibasic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, sebacic acid, and dodecanedicarboxylic acid; An aromatic polybasic acid such as citric acid, p-citric acid, 1,2,4-benzenetricarboxylic acid, pyromic acid or the like; and butane tricarboxylic acid, 1,2,3-propane tricarboxylic acid (tricarballylic acid), lemon An aliphatic polybasic acid such as an acid. In the present embodiment, only an aliphatic dibasic acid may be used as the polybasic acid, and an aliphatic dibasic acid may be used as a main component, and a small proportion of an aromatic polybasic acid or an aliphatic polybasic acid may be blended therein. In addition, these dibasic acids or polybasic acids may be used alone or in combination of two or more.

As the polyol which is a starting material for the production of the polyester polyol, for example, a compound having two or more hydroxyl groups in one molecule such as a divalent alcohol or a trihydric or higher polyhydric alcohol can be used. Specific examples of the divalent alcohol include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, and 2,2- Dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2, Examples of the trivalent or higher polyhydric alcohol include 2,4-trimethyl-1,3-pentanediol, and the like, and specific examples thereof include aliphatic diol, glycerin, trimethylolpropane, and trimethylol. Ethane, pentaerythritol, and the like. In this embodiment, only a glycol may be used as the polyol, and a glycol such as an aliphatic diol may be used as a main component and a small proportion of the polyol may be blended therein, particularly an aliphatic diol. As a main component, it is better. These divalent alcohols or polyhydric alcohols may be used alone or in combination of two or more. Further, a polyester polyol compound obtained by a ring-opening reaction of caprolactone may also be used as the polyester polyol.

On the other hand, the polyisocyanate compound which reacts with the above-mentioned polyester polyol is a compound which has two or more free isocyanate groups in one molecule, and specifically, hexamethylene diisocyanate, and three Methylhexamethylene diisocyanate, diazonic acid diisocyanate and three Aliphatic diisocyanate such as methylene diisocyanate; isophorone diisocyanate; alicyclic diisocyanate such as methylene bis(cyclohexyl isocyanate) and cyclohexane diisocyanate; benzene dimethylene diisocyanate, toluene An aromatic diisocyanate such as diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate or biphenyl diisocyanate. These may be used alone or in combination of two or more.

In the reaction between the above polyester polyol and the polyisocyanate compound, the reaction conditions of the usual urethanation reaction can be widely applied.

The polyester resin is not particularly limited, and examples thereof include those obtained by polycondensing a carboxylic acid (dicarboxylic acid) and a polyhydric alcohol (diol). Examples of the dicarboxylic acid component include p-citric acid, isophthalic acid, o-nonanoic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, oxalic acid, succinic acid, succinic anhydride, adipic acid, and sebacic acid. Azelaic acid, dodecanedioic acid, hydrogenated dimer acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, two Polyacid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornene dicarboxylic acid and anhydride thereof, Tetrahydrofurfuric acid and its anhydride. Further, a small amount of sodium 5-sulfonate isophthalic acid or 5-hydroxyisophthalic acid or the like can be used as an acid component as long as it does not impair the water resistance of the coating film as necessary. In particular, it is particularly preferable for citric acid, and may also contain a trifunctional or higher polybasic acid. Examples of the diol component include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, and 1,5-pentane. Alcohol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, 1,4 - cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, etc., and may also contain a trifunctional or more polyhydric alcohol.

Further, the polyester resin may contain lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid or the like by copolymerization as necessary. High-boiling monocarboxylic acid, stearyl alcohol, 2-phenoxy group such as fatty acid, ester-forming derivative thereof, benzoic acid, p-t-butylbenzoic acid, cyclohexane acid, 4-hydroxyphenyl stearic acid A high-boiling monohydric alcohol such as ethanol, ε-caprolactone, lactic acid, β-hydroxybutyric acid, a hydroxycarboxylic acid such as p-hydroxybenzoic acid, or an ester-forming derivative thereof.

The method for producing the above resin is not particularly limited, and it can be produced by a conventionally known method.

The subsequent layer may be composed of a resin composition obtained by blending a curing agent, a curing accelerator, and other additives in addition to the above resin. The curing agent and the curing accelerator are not particularly limited, and various well-known materials can be appropriately selected and used.

The curing agent is not particularly limited, and examples thereof include an epoxy resin, an isocyanate curing agent, and an imidazole curing agent. The blending amount of the curing agent is preferably 0.5 to 200 parts by mass, more preferably 5 to 80 parts by mass, per 100 parts by mass of the resin constituting the adhesive layer.

The epoxy resin is not particularly limited, and examples thereof include a bisphenol type epoxy resin such as a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a bisphenol S type epoxy resin; and a phenol novolak type; Epoxy resin, cresol novolak type epoxy resin, etc. / novolac type epoxy resin; biphenyl type epoxy resin; naphthalene ring containing epoxy resin; alicyclic epoxy resin.

The isocyanate curing agent is not particularly limited, and examples thereof include TDI-TMP (toluene diisocyanate-trimethylpropane adduct), HMDI-biuret type, HMDI-isocyanurate, and HMDI-. An isocyanate compound such as a TMP adduct (hexamethylene diisocyanate-trimethylpropane adduct) or an XDI-TMP adduct (benzodimethyl diisocyanate-trimethylpropane adduct).

The imidazole-based curing agent is not particularly limited, and examples thereof include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole. Imidazole compound.

As other additives, for example, an antioxidant such as a hindered amine system, a phosphorus system or a sulfur system; a stabilizer such as a light stabilizer, a weather stabilizer, or a heat stabilizer; a dibromopropyl phosphate or a phosphoric acid phosphate can be used. a flame retardant such as allyl ester or cerium oxide; an anionic, cationic or nonionic surfactant; an antistatic agent; a resin modifier such as an organic filler or an inorganic filler; an organic filler; an inorganic filler; Various well-known additives such as plasticizers; slip agents. The blending amount of the additive can be appropriately adjusted according to the purpose as long as the effect of the present invention is not impaired.

The thickness of the adhesive layer contained in the cover film is preferably 10 to 50 μm, preferably 15 to 30 μm. When the thickness of the coating layer is 10 μm or more, the adhesion between the transparent film layer and the object to be bonded tends to be good, and when it is 50 μm or less, the bending property tends to be good.

[separation membrane layer]

In the adhesive layer included in the cover film of the present embodiment, the separation film layer may be further laminated on the surface opposite to the surface on which the transparent film layer is laminated. When a cover film having a separation membrane layer is used, the separation membrane layer is peeled off, and then the adhesive layer is adhered to the adherend. The resin forming the separation membrane layer is not particularly limited, and examples thereof include those selected from the group consisting of polyethylene terephthalate resin, polyethylene naphthalate resin, polypropylene resin polyethylene resin, and polybutyl phthalate. One or more resins selected from the group consisting of a diester resin, in particular, one or more selected from the group consisting of a polypropylene resin polyethylene resin and a polyethylene terephthalate resin, from the viewpoint of reducing the production cost. The resin is better. The total light transmittance in the present embodiment is the total light transmittance of the entire cover film after removing the separation film layer.

The thickness of the separation membrane layer is preferably from 12 to 150 μm, preferably from 25 to 75 μm. When the thickness of the separation membrane layer is 12 μm or more, the separation membrane tends to be easily peeled off, and when it is 150 μm or less, the adhesion to the transparent membrane layer tends to be stable.

In the separation film layer, a mold release treatment may be performed on the surface on which the adhesive layer is laminated. Since the release film is subjected to the release treatment in the separation film layer, the separation film can be easily peeled off from the transparent film, and the handleability of the cover film is improved. The mold release treatment is not particularly limited, and for example, a release agent such as an anthrone-based release agent, a fluorine-based release agent, a long-chain alkyl graft polymer-based release agent, or a plasma treatment can be used. Surface treatment methods, etc.

[Copper-clad laminate]

Next, the copper-clad laminate of this embodiment will be described.

In the copper-clad laminate of the present embodiment, the adhesive layer included in the cover film is further laminated on the surface opposite to the surface on which the transparent film layer is laminated, and the copper foil layer is further laminated. Adult. As shown in Fig. 2, in the copper clad laminate 20 of the present embodiment, the hard coat layer 1 is laminated on one surface of the transparent film layer 2, and the adhesive layer 3' is laminated on the other surface. Further, a structure in which a copper foil layer 4 for forming a circuit is formed is laminated on the outer side of the adhesive layer 3'.

The copper clad laminate has the same structure as the cover film except that a copper foil layer for forming a circuit is further provided, but the hardened state of the adhesive layer is different from that of the cover film. Specifically, the cured state of the adhesive layer contained in the cover film is B-stage, whereas the hardened state of the adhesive layer contained in the copper-clad laminate is C-stage. The cover film is bonded to the circuit-clad laminate after the circuit layer is formed, and the adhesive layer is further cured to the C stage. Here, the B-stage means that the melt viscosity in the range of 100 ° C to 160 ° C is 100 to 100,000 poises, preferably 1,000 to 50,000 poises, preferably 1,000 to 40,000 poises; and the C stage is expressed at 100 ° C to 160 ° C. The range has a melt viscosity of 10,000 poise or more, more preferably 50,000 or more, and more preferably 100,000 poise or more. In the B-stage, when heating at 100 ° C or higher and pressing at 0.5 MPa or higher, the adhesive (layer) is melted and can fill the state between the circuits. In contrast, the C-stage is heated at 100 ° C or higher. When the pressure is 0.5 MPa or more, the adhesive (layer) is in a state in which the curing is not melted. Moreover, the B-stage and the C-stage are not clearly distinguishable, and a part thereof is a repetition.

The thickness of the adhesive layer contained in the copper clad laminate is preferably 5 to 50 μm, preferably 10 to 25 μm. When the thickness of the coating layer is 5 μm or more, the adhesion between the transparent film layer and the object to be bonded tends to be good, and when it is 50 μm or less, the bending property tends to be good.

The total light transmittance of the entire copper foil layer of the copper clad laminate after etching (after etching the copper foil layer with an acid) is preferably 80% or more, preferably 85% or more, more preferably 88%. the above.

[Soft printed wiring board]

The flexible printed wiring board of the present embodiment includes the cover film and the copper-clad laminate as described above, and the adhesive for the cover film can be formed by forming a circuit on the copper foil layer contained in the copper-clad laminate. The layer is adhered to the circuit forming surface of the copper clad laminate.

As shown in Fig. 3, the flexible printed wiring board 30 of the present embodiment has the following knots. The circuit formed of the copper foil layer 4 is interposed between the adhesive layers 3 and 3', and the laminate including the transparent film layer 1 and the hard coat layer 2 is sandwiched from both sides.

In the flexible printed wiring board of the present embodiment, the difference in refractive index between the adhesive layer contained in the cover film and the adhesive layer contained in the copper clad laminate is preferably 0 to 0.1, more preferably 0 to 0.05. . When the difference in refractive index is within the above range, the transparency of the flexible printed wiring board tends to be further improved.

The total light transmittance of the entire circuit portion of the flexible printed wiring board after removal is preferably 85% or more, preferably 88% or more.

The cover film, the copper-clad laminate, and the flexible printed wiring board of the present embodiment may contain other layers as appropriate in addition to the above-described respective layers.

[Production method]

The method for producing the cover film of the present embodiment is not particularly limited, and for example, it can be produced by a method having the following steps (a) and (b).

(a) a step of applying a varnish of a resin composition forming a hard coat layer on one surface of a film constituting the transparent film layer, and drying and UV hardening;

(b) A step of applying a varnish of a resin composition forming the adhesive layer to the surface opposite to the surface on which the hard coat layer is provided on the transparent film layer, and drying it to the B stage.

When the cover film contains a separation membrane layer, for example, the following step (c) is further included.

(c) a step of bonding the separation membranes to each other in the surface of the laminated film obtained in the above step (b), in which the adhesive layer is provided.

In the method for producing a copper-clad laminate according to the present embodiment, for example, in addition to the above steps (a) and (b), the following step (d) is further carried out.

(d) a step of drying the adhesive layer to the C stage after laminating the copper foil in the surface of the laminated film obtained in the above step (b), in which the adhesive layer is provided.

The flexible printed wiring board of the present embodiment can be produced, for example, by using the above-described cover film and copper-clad laminate, and the following step (e).

(e) After the copper foil layer included in the copper clad laminate is formed into a circuit, the adhesive layer of the cover film is adhered to the circuit forming surface of the copper clad laminate.

Examples of the solvent used in the varnish include acetone, toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, propylene glycol monomethyl ether, and dimethyl acetamide.

As a method of applying the varnish, a comma coater, a die coater, a gravure coater, or the like can be suitably used depending on the coating thickness.

The drying of the varnish can be carried out by using an in-line dryer or the like, and the drying conditions in this case can be appropriately adjusted depending on the type and amount of the resin or the curing agent.

The UV curing is performed by, for example, using a usual UV irradiator such as a high pressure mercury lamp. The amount of the UV irradiation can be appropriately adjusted depending on the type and amount of the photosensitive compound and the polymerization initiator contained in the resin composition.

As a method of bonding the films, a method by pressing, a lamination method using a hot roll, or the like can be used. The bonding conditions can be carried out, for example, at a temperature of 40 to 120 ° C and a pressure of 0.1 to 3 MPa.

The measurement and evaluation of each physical property in the present specification can be carried out according to the methods described in the following examples unless otherwise specified.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to the examples.

In the examples and comparative examples, the measurement and evaluation of each physical property were carried out by the following methods.

(1) Thickness

The measurement was carried out using a micrometer specified in JIS B 7502.

(2) Glass transition temperature

The dynamic viscoelasticity at a temperature of 10 ° C /min was measured using a dynamic viscoelasticity measuring apparatus RSAII manufactured by Rhemetric Sciectific Co., Ltd., and Tg was obtained from the maximum value of tan δ.

(3) Melt viscosity

Using a Rheosol-G3000 manufactured by UBM Co., Ltd., the sample was heated at 10 ° C /min to measure the dynamic viscosity ratio in the range of 100 ° C to 160 ° C. Here, the dynamic viscosity ratio is a viscosity at which a shear vibration strain in a rotational direction is applied to a sample. Further, the melt viscosity represented by the examples and the like is a dynamic viscosity ratio at 130 °C.

(4) Heat resistance (heat distortion temperature)

The test was carried out using a reflow soldering apparatus RF-630 manufactured by the Japan PULSE Technology Research Institute. As a sample, a soft printed wiring board was cut into 5 cm squares, and this was put into a reflow apparatus and exposed to a predetermined temperature for 1 minute under far infrared rays, and then judged from the warpage of the wiring board.

Specifically, it is determined that the sample is warped when the reflow temperature is set to 100° C., and then, the warpage of the sample at 110° C. is determined, and thereafter, for each sample at a temperature of 10° C. The warpage is made and the judgment is made. In the determination method, the treated sample was placed flat on a flat table, and the reflow temperature at which the end portion was floated from the table by 5 mm or more was set as heat resistance (heat deformation temperature).

(5) Transparency (total light transmittance)

The total light transmittance was measured in accordance with JIS Z 8722. As a measuring machine, a spectrophotometer U-4100 manufactured by Hitachi, Ltd. was used.

(6) Damage resistance (pencil hardness)

The scratch resistance was evaluated in accordance with the pencil hardness test JIS K5600. Evaluation of damage resistance, in fact The examples were for the surface of the hard coat layer, and the comparative examples were evaluated for the surface of the transparent film layer.

(7) Size change

Evaluation was carried out in accordance with 9.6 of JIS C 6471.

Specifically, the state immediately after the copper foil layer of the copper-clad laminate was removed was used as a reference, and after heating at 140 ° C for 30 minutes, the dimensional change rate was calculated by comparison with the state after standing at room temperature of 24Hr. The dimensional change was measured in the MD direction (longitudinal direction) of the sample.

(8) Bending

The evaluation was carried out by bending a predetermined sample by 180° and applying a folding test of a load of 400 g/cm in this state. The sample was a thin rectangular shape having a length of 200 mm × 5 mm which was cut from the flexible printed wiring board in the MD direction.

(9) Production of exudation

After the flexible printed wiring board was heated at 150 ° C × 1 Hr in an oven, the haze value was measured in accordance with JIS K7105, and when the haze value was 10 or more, it was determined that bleeding occurred. As the measuring machine, the HM-150 manufactured by Murakami Color Technology Research Co., Ltd. was used.

(10) Refractive index

The measurement was carried out in accordance with JIS K-7105. As the measuring machine, an Abbe refractometer was used. As a sample for the measurement of the refractive index, a resin film (thickness: 20 μm) in a C-stage state, which was produced from a resin composition for an adhesive for a cover film and a copper-clad laminate, was used.

[Resin composition for hard coating] (Manufacturing Example 1)

100 parts by mass of methyl ethyl ketone, 5 parts by mass of a UV initiator (manufactured by Vabar Chemical Co., Ltd., Darocure TPO), and 100 parts by mass of acrylic acrylate (manufactured by DAICEL-CYTEC Co., Ltd., PETA-K) were added thereto. The resin composition 1 for hard coating was obtained by warm stirring.

(Manufacturing Example 2)

100 parts by mass of methyl ethyl ketone, 5 parts by mass of a UV initiator (manufactured by CIBA. SPECIALTY. CHEMICALS, Darocure TPO), 50 parts by mass of acrylic acrylate (manufactured by DAICEL-CYTEC Co., Ltd., PETA-K), 50 parts by mass of a different type of acrylic acrylate (manufactured by DAICEL-CYTEC Co., Ltd., PEG400DA) was stirred at room temperature to obtain a resin composition 2 for hard coating.

[Resin composition for adhesive] (Manufacturing Example 3)

BA (butyl acrylate) was added in a ratio of 75:20:5 (parts by mass) in a reaction vessel: MMA (methyl methacrylate): AA (acrylic acid), and 100 parts by mass of ethyl acetate was added. 0.3 parts by mass of azobisisobutyronitrile (AIBN) (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred at 70 ° C for 10 hours to carry out polymerization reaction to obtain an acrylic polymer. Next, 5 parts by mass of the bisphenol A type epoxy resin (manufactured by Asahi Kasei Chemicals Co., Ltd., trade name: AER260) was added to 100 parts by mass of the acrylic polymer, and the mixture was stirred at room temperature, and 50 parts by mass of methyl ethyl ketone was added until it became The resin composition 1 for an adhesive is obtained until the viscosity is predetermined.

(Manufacturing Example 4)

BA (butyl acrylate) was added in a ratio of 60:30:10 (parts by mass) in a reaction vessel: MMA (methyl methacrylate): AA (acrylic acid), and 100 parts by mass of ethyl acetate was added. 0.3 parts by mass of azobisisobutyronitrile (AIBN) (manufactured by Tokyo Chemical Industry Co., Ltd.) was stirred at 70 ° C for 10 hours to carry out polymerization reaction to obtain an acrylic polymer. Next, 10 parts by mass of the bisphenol A type epoxy resin (manufactured by Asahi Kasei Chemicals Co., Ltd., trade name: AER260) was added to 100 parts by mass of the acrylic polymer, and stirred at room temperature, and 50 parts by mass of methyl ethyl ketone was added until it became The resin composition 2 for an adhesive is obtained until the viscosity is predetermined.

(Example 1) Manufacture of cover film (CL)

By using a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., trade name: A4300, thickness: 50 μm) which is a transparent film layer, the thickness after drying and UV curing is 1 μm. After coating the resin composition 1 for hard coating with a die coater, it was dried at 100 ° C for 2 minutes, and secondly, UV hardening was performed using a high pressure mercury lamp, and a hard coat layer was provided on the polyethylene terephthalate film.

Next, after coating the adhesive resin composition 1 on the surface of the polyethylene terephthalate film on the opposite side to the surface on which the hard coat layer was provided, and using the die coater to have a thickness of 25 μm after drying, The film was dried at 120 ° C for 2 minutes and the adhesive layer was hardened to the B stage to obtain a cover film.

Further, on the adhesive application surface, the release surface of the separation membrane subjected to the release treatment is laminated by lamination.

Each evaluation of the obtained cover film was performed and the results are shown in Table 1.

Manufacture of copper clad laminates (CCL)

The PET film provided with the hard coat layer obtained in Example 1 was coated with a resin using a die coater on a surface opposite to the surface on which the hard coat layer was provided, and having a thickness of 10 μm after drying. After the object 2, it was dried at 120 ° C for 2 minutes to provide an adhesive layer on the polyethylene terephthalate film.

Next, on the adhesive-coated surface, a mat surface of a copper foil laminated with a hot roll at 60 ° C was used. Further, the laminate film laminated with the copper foil was heat-treated at 100 ° C for 48 hours to cure the adhesive layer to the C stage to obtain a copper-clad laminate.

Each evaluation of the obtained copper-clad laminate was performed and the results are shown in Table 1.

Manufacture of flexible printed wiring boards (CL/CCL)

The copper foil layer of the copper clad laminate obtained in Example 2 was formed into a predetermined circuit pattern. Next, the separation film is peeled off from the cover film obtained in Example 1, and the surface on which the circuit pattern is formed on the copper-clad laminate is bonded to the surface of the cover film on which the adhesive layer is provided, and Press molding was carried out under the conditions of 120 ° C × 3 MPa × 60 minutes to obtain a flexible printed wiring board.

Each evaluation of the obtained flexible printed wiring board was performed, and the result is shown in Table 1.

(Example 2)

A cover film, a copper-clad laminate, and a flexible printed wiring board were produced in the same manner as in Example 1 except that the thickness of the hard coat layer was changed from 1 μm to 6 μm, and each evaluation was performed and the results are shown in Table 1. .

(Example 3)

A cover film, a copper-clad laminate, and a flexible printed wiring board were produced in the same manner as in Example 1 except that the resin composition 2 for hard coating was used, and each evaluation was performed, and the results are shown in Table 1.

(Example 4)

A cover film, a copper-clad laminate, and a flexible printed wiring board were produced in the same manner as in Example 1 except that the thickness of the hard coat layer was changed from 1 μm to 0.3 μm, and each evaluation was performed and the results were shown in the table. 1.

(Comparative Example 1)

A cover film, a copper-clad laminate, and a flexible printed wiring board were produced in the same manner as in Example 1 except that the hard coat layer was not provided, and each evaluation was performed, and the results are shown in Table 1.

[Industrial Availability]

According to the present invention, it is possible to provide a cover film and a copper clad laminate using the cover film, which has excellent transparency and heat resistance, and can remarkably suppress oozing out of oligomer components in a high temperature environment. White turbidity.

Claims (14)

A cover film comprising a transparent film layer, a hard coat layer and an adhesive layer, wherein the transparent film layer has a first surface and a second surface; and the hard coat layer is laminated on the transparent film layer In the first surface, the adhesive layer is laminated on the second surface of the transparent film layer, and the total light transmittance is 85% or more. The cover film of claim 1, wherein the transparent film layer is selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, and poly The carbonate resin is a resin of any one or more of the group formed. The cover film of claim 1 or 2, wherein the transparent film layer has a thickness of 10 to 200 μm. The cover film according to any one of claims 1 to 3, wherein the hard coat layer is a resin composition containing a main component selected from the group consisting of acrylate-based photosensitive compounds. Composition. The cover film according to any one of claims 1 to 4, wherein the hard coat layer has a thickness of 0.5 to 5 μm. The cover film according to any one of claims 1 to 5, wherein the glass transition temperature of the hard coat layer is higher than the glass transition temperature of the transparent film layer. The cover film according to any one of claims 1 to 6, wherein the glass transition temperature of the hard coat layer is 200 to 400 ° C, and the glass transition temperature of the transparent film layer is 50 to 180 ° C. The cover film according to any one of claims 1 to 7, wherein the adhesive layer contains at least one selected from the group consisting of an acrylic resin, an urethane resin, and a polyester resin. Resin. The cover film according to any one of claims 1 to 8, wherein the adhesive layer has a thickness of 10 to 50 μm. The cover film according to any one of claims 1 to 9, wherein the adhesive layer has a melt viscosity in the range of 100 ° C to 160 ° C of 100 to 100,000 poise. A copper-clad laminate comprising the adhesive layer contained in the cover film according to any one of claims 1 to 9 on the opposite side to the surface on which the transparent film layer is laminated The surface is further laminated with a copper foil layer. A copper clad laminate according to claim 11 wherein the adhesive layer is at 100 ° C The melt viscosity in the range of ~160 ° C is 10,000 poise or more. A flexible printed wiring board comprising the cover film according to any one of claims 1 to 10, and the copper clad laminate according to any one of the above claims 1 to 10 After the circuit is formed on the copper foil layer contained in the copper clad laminate, the adhesive layer of the cover film is adhered to the circuit forming surface of the copper clad laminate. The flexible printed wiring board of claim 13, wherein a difference between a refractive index of the adhesive contained in the cover film and an adhesive contained in the copper-clad laminate is 0 to 0.1.