KR20190111005A - Coverlay film - Google Patents

Abstract

The present invention provides a coverlay film having good processability and workability even in a thin film and excellent followability to a flexible printed board (FPC). The coverlay film is formed by sequentially laminating a first insulating layer (12), a second insulating layer (13), and a thermosetting adhesive layer (14) on one surface of a support body film (11), wherein the first insulating layer (12) contains a flame retardant, and the tensile strength of a laminated body (15) consisting of the first insulating layer (12) from which the support body film (11) is removed, the second insulating layer (13), and the thermosetting adhesive layer (14) is 100% or more.

Description

Coverlay film {COVERLAY FILM}

The present invention relates to a coverlay film. More specifically, the present invention relates to a coverlay film of a thin film having good workability and bonding workability in a step of producing a base material and excellent followability to irregularities and steps of a flexible printed substrate (hereinafter referred to as FPC). .

In portable electronic devices such as mobile phones, electronic components are integrated on a printed board in order to reduce the external dimensions of the case and to make it thin and easy to carry. In addition, in order to reduce the external dimensions of the case, the printed circuit board is divided into a plurality of pieces, and folding or sliding the printed circuit board is performed by using an FPC having flexibility in connection wiring between the divided printed boards.

In addition, recent portable information terminals (smartphones, tablets, etc.) consume more power than conventional portable telephones, and thus the maintenance of the battery becomes worse. For this reason, it is necessary to enlarge the capacity and capacity of a battery which can be possible, and the size of a member other than a battery, components, and thickness reduction are strongly requested | required, for example, the thinning of the whole FPC which bonded the coverlay film is calculated | required. . Moreover, in recent years, light-shielding property and designability are made much important, and coloring of the coverlay film is calculated | required.

Conventionally, what apply | coated the adhesive agent to the thin polyimide film is used as a coverlay film used for the thinning of the whole FPC (patent document 1). However, the thin polyimide film had a problem that workability in a manufacturing process was inferior, and workability was inferior when affixing on FPC.

In addition, in the conventional coverlay film, since it is difficult to make the thickness thin, lack of flexibility, the followability to the step of the FPC is not sufficient, a gap is formed, which causes the occurrence of defects such as expansion in the heating process. there was. For this reason, sufficient thickness reduction of the whole FPC which bonded the coverlay film was difficult.

Japanese Patent Laid-Open No. 9-135067

SUMMARY OF THE INVENTION In view of the background art, the present invention provides a coverlay film having good processing aptitude and workability at the time of FPC production and excellent followability to a step of FPC even in the case of a thin film.

In order to improve the workability at the time of bonding a coverlay film to FPC, in the coverlay film of this invention, an insulating layer and a thermosetting adhesive bond layer are laminated one by one on the support film. In addition, the coverlay film can be transferred from the support film to the FPC by peeling the support film after the coverlay film of the present invention is overlaid and thermally pressed through the adhesive layer on the FPC.

In addition, in order to withstand severe bending and to improve the followability to FPC, in the present invention, the tensile elongation of the laminate composed of the insulating layer and the adhesive layer is increased.

In addition, the present invention, in order to solve the above problems, the first insulating layer, the second insulating layer, the thermosetting adhesive layer is sequentially laminated on one side of the support film, the first insulating layer contains a flame retardant, It provides a coverlay film characterized in that the tensile elongation of the laminate comprising the first insulating layer, the second insulating layer, the thermosetting adhesive layer from which the support film is removed is 100% or more.

It is preferable that the second insulating layer contains a flame retardant having a lower concentration than the first insulating layer, or do not contain a flame retardant.

It is preferable that the thickness of the first insulating layer is thinner than the thickness of the second insulating layer.

It is preferable that the said thermosetting adhesive layer contains a polyurethane resin and an epoxy resin.

It is preferable that the said polyurethane resin is phosphorus containing polyurethane resin.

It is preferable that at least any one of the said 1st insulating layer, the said 2nd insulating layer, and the said thermosetting adhesive bond layer contains a light absorber.

Moreover, this invention provides the mobile telephone in which the said coverlay film is used as an FPC protection member.

Moreover, this invention provides the electronic device by which the said coverlay film is used as an FPC protection member.

According to the coverlay film of the present invention, when a wiring board having a step or the like is coated without a gap, defects due to expansion or penetration of a plating solution are generated in a subsequent step such as a solder reflow step or a plating step. A thin film coverlay film can be produced.

Moreover, specific coloring is attained on one surface side of a coverlay film because an insulating layer or an adhesive bond layer contains a light absorber.

In view of the above, according to the present invention, in a heating step such as a solder reflow step after coating a wiring board or the like, the flexibility due to expansion and the occurrence of a defect due to penetration of the plating liquid is rich and thin, and The coverlay film excellent in the bending characteristic which does not produce the fall of FPC protection performance even if a severe bending operation | movement is performed repeatedly can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows embodiment of the coverlay film of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, preferable embodiment of this invention is described. This invention is not limited to this embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

As shown in FIG. 1, the 1st insulating layer 12, the 2nd insulating layer 13, and the thermosetting adhesive bond layer 14 are laminated | stacked on one surface of the support film 11 one by one. The laminated body 15 which consists of the 1st insulating layer 12, the 2nd insulating layer 13, and the thermosetting adhesive bond layer 14 can be peeled integrally from the support film 11, and can be bonded to an FPC etc ..

When the coverlay film 10 of this embodiment is bonded to FPC etc. which are to-be-adhered bodies, the outer surface is a dielectric material and can electrically protect the wiring, circuit components, etc. of an FPC. In addition, the coverlay film of this embodiment can thin the whole thickness in order to improve the bending characteristic with respect to a bending operation | movement.

(Support film)

As a base material of the support film 11 used for the coverlay film 10 of this embodiment, For example, polyester films, such as polyethylene terephthalate, a polybutylene terephthalate, and a polyethylene naphthalate, polypropylene, and polyethylene Polyolefin films, such as these, are mentioned.

When the base material of the support film 11 has some peelability to the base material itself, such as polyethylene terephthalate, for example, the laminated body 15 is directly performed without performing peeling process on the support film 11. May be laminated | stacked, and the peeling process for making it easy to peel the laminated body 15 from the support film 11 may be performed on the surface of the support film 11.

In addition, when the base film used as the said support film 11 does not have peelability, peeling process is performed by apply | coating peeling agents, such as an amino alkyd resin and a silicone resin, and heat-drying. When the coverlay film 10 of this embodiment is used for FPC, it is preferable that a silicone resin is not used for this peeling agent. When a silicone resin is used as a peeling agent, a part of silicone resin will transfer to the surface of the insulating layers 12 and 13 which contacted the surface of the support film 11, and the thermosetting adhesive bond layer is further made through the inside of the laminated body 15. There is a fear of shifting to the surface of (14). There is a concern that the silicone resin transferred to the surface of the thermosetting adhesive layer 14 may weaken the adhesive force of the thermosetting adhesive layer 14.

Although the thickness of the support film 11 is excluded from the total thickness of the laminated body 15 at the time of coating and using FPC, it is although it does not specifically limit, Usually, it is about 12-150 micrometers. By using the support film 11, the workability at the time of forming the insulating layers 12 and 13 and the thermosetting adhesive bond layer 14 and the workability at the time of bonding to FPC can be improved.

Color of the support film 11 may be colorless (colorless) or may be colored. When coloring on the support film 11, it is preferable that the index with a large contrast with respect to the color of the laminated body 15 from which the support film 11 was removed. For example, when the laminated body 15 is a dark index, such as black, it is preferable that the support film 11 has a bright index, such as white and yellow. Thereby, the handleability, such as peeling the laminated body 15 from the support film 11, and the checkability of whether the support film 11 is peeling off can be improved. Coloring of the support film 11 can be performed using a well-known pigment, dye, etc. As the support film 11, the white PET film whose thickness is 30 micrometers or more and 60 micrometers or less is mentioned, for example.

(Insulation layer)

The insulating layers 12 and 13 of the coverlay film 10 are insulating layers made of a dielectric thin film resin layer and the like. Since the thin film resin film of the polyimide film formed using solvent-soluble polyimide has high mechanical strength, heat resistance, insulation, and solvent resistance which are the characteristics of polyimide resin, it is considered to be chemically stable until about 260 degreeC, and is an insulating layer It is preferable as (12, 13).

Examples of the polyimide include thermosetting polyimide produced by the dehydration condensation reaction by heating the polyamic acid, and a solvent-soluble polyimide soluble in a non-dehydrated condensation solvent.

The manufacturing method of a general polyimide film synthesize | combines the polyamic acid which is an imide precursor by making diamine and carboxylic dianhydride react in a polar solvent, and converts a polyamic acid to polyimide by dehydration cyclization. However, the temperature of the heat treatment in this imidation step is considered to be preferably in the temperature range of 200 ° C to 300 ° C, and if the heating temperature is lower than this temperature, imidization may not proceed, which is not preferable. In addition, when the heating temperature is higher than the above temperature, thermal decomposition of the compound may occur, which is not preferable.

The coverlay film 10 of the present embodiment is intended to further improve the flexibility of the insulating layers 12 and 13, and an extremely thin polyimide film having a total thickness of the insulating layers 12 and 13 of less than 10 µm. Can be used. When the thickness of the polyimide film used is thinner than about 7 micrometers, it is preferable to laminate | stack and form a thin polyimide film on one side of the support film 11 used as a reinforcement material on strength. For example, the coating liquid containing a polyamic acid can be casted on one side of the support film 11, and heated, and a polyimide can be formed into a film.

However, the polyimide film itself has heat resistance to heat treatment at a heating temperature of 200 ° C. to 250 ° C., but is a general-purpose heat resistant resin film in view of the balance between price and heat resistance temperature performance as the support film 11. For example, when using films with low heat resistance, such as a polyethylene terephthalate (PET) resin film, the method of forming a polyimide from the polyamic acid which is a conventional imide precursor cannot be employ | adopted.

Since the solvent-soluble polyimide has completed imidation of this polyimide, and is soluble in a solvent, it can form into a film by apply | coating the coating liquid dissolved in the solvent, and volatilizing a solvent at low temperature below 200 degreeC. For this reason, after apply | coating the coating liquid of solvent-soluble polyimide which is a non-dehydration condensation type on one surface of the support film 11, the insulating layers 12 and 13 are dried at the heating temperature below 200 degreeC, and a polyimide resin is applied. It is preferable to form a thin film. By doing in this way, the ultrathin polyimide film whose thickness is 1-9 micrometers can be laminated | stacked on one surface of the support film 11 which consists of a general-purpose heat resistant resin film. Similarly to the thermosetting adhesive layer 14, by forming the insulating layers 12 and 13 by coating (coating), the insulating layers 12 and 13 and the thermosetting on the support film 11 are transported along the longitudinal direction thereof. Since the adhesive bond layer 14 etc. can be formed continuously, production by roll-to-roll is also possible and is excellent in workability and productivity.

Although the solvent-soluble polyimide which is a non-dehydration condensation type which can be used for the insulating layers 12 and 13 of this embodiment is not specifically limited, It is possible to use the coating liquid of the commercially available solvent-soluble polyimide. As a coating liquid of commercially available solvent-soluble polyimide, specifically, Sorrup 6,6-PI (Sorrup Industries), Q-IP-0895D (Pia Giken), PIQ (Hitachi Chemical Industry), SPI-200N (Shinnet) Tetsu Chemical), Rika coat SN-20, Rika coat PN-20 (Shin-Nippon Chemical), etc. are mentioned. The method of apply | coating the coating liquid of solvent soluble polyimide on the support film 11 is not specifically limited, For example, it can apply | coat with a coater, such as a die coater, a knife coater, a lip coater.

It is preferable that the thickness (for example, thickness of a polyimide film) of the sum total of the insulating layers 12 and 13 of this embodiment is 1-9 micrometers. It is technically difficult to form the thickness of a polyimide film below 0.8 micrometer in the point that the mechanical strength of the film formed into a film is weak. Moreover, when the thickness of insulating layers 12 and 13, such as a polyimide film, exceeds 10 micrometers, it will become difficult to obtain the laminated body 15 which is thin and has the outstanding bending performance. In addition, when the thickness of the total of the insulating layers 12 and 13 is thinner than about 7 µm, the tension adjustment at the time of winding on the roll is difficult, so it is preferable to use the support film 11 as a reinforcing material on strength.

In addition, it is preferable that the insulating layers 12 and 13 of this embodiment have a large tensile elongation in order to improve the followability to the step | step of FPC. It is preferable that the tensile elongation of one or both of the insulating layers 12 and 13 is 100% or more, and 250% or less is preferable. Here, although the tensile elongation shows the elongation at the time when a film is cut | disconnected by constant speed tension in%, the larger this tensile elongation is a flexible film with respect to a tensile force. For this reason, it is preferable that the said tensile elongation is 100% or more in order for the said laminated body 15 to have sufficient flexibility, and to express the outstanding followability with respect to the unevenness | corrugation and the step | step of an FPC.

In the case where the insulating layers 12 and 13 having high tensile elongation are constituted by a polyimide film, it is preferable to use a polyimide material having, for example, an aliphatic unit having three or more carbon atoms in between aliphatic units. Furthermore, it is preferable that an aliphatic unit contains the polyalkyleneoxy group which has a C1-C10 alkylene group.

Moreover, it is preferable that the water vapor transmission rate of the polyimide film which can be used for the insulating layers 12 and 13 of this embodiment is 500 g / m <2> * day or more. In the case where the water vapor transmission rate is lower than this, in the heating process such as solder reflow after coating the FPC, the outgassing from the residual solvent of each layer, the adhesive from the adhesive, and the moisture generated in the film are caused by the water vapor generated rapidly. There is a possibility that the interlayer is peeled off. Although no upper limit is specifically set for the water vapor permeability, as long as the same material is used, the water vapor permeability is inversely proportional to the thickness. Therefore, when the thickness is made thin and the water vapor permeability is increased, it is preferable to be within the above-described thickness.

(Flame retardant)

In order to ensure the flame retardancy of the laminated body 15, the insulating layers 12 and 13 may contain a flame retardant. Examples of the flame retardant include inorganic flame retardants such as metal hydroxides, antimony and red phosphorus, organic flame retardants such as halogens (chlorine and bromine), phosphorus and guanidine. Organic flame retardants, such as phosphorus and bromine, are preferable at the point which is excellent in dispersibility with insulating resins, such as a polyimide. Examples of the phosphorus flame retardant include aliphatic phosphate esters, aromatic phosphate esters, aromatic condensed phosphate esters, bisphenol phosphate esters, halogen-containing phosphate esters, halogen-containing condensed phosphate esters, and phosphogen compounds.

When the flame retardant is an additive type flame retardant that does not react with the resin, there is a possibility that the tensile elongation of the insulating layers 12 and 13 may decrease depending on the amount of the flame retardant added. For this reason, when the laminated body 15 is bonded to an FPC etc., the 1st insulating layer 12 used as outermost layer contains a flame retardant, and the 2nd insulating layer 13 has a lower concentration than the 1st insulating layer 12. It is preferable that a flame retardant is included or that the 2nd insulating layer 13 does not contain a flame retardant. In addition, the thickness of the first insulating layer 12 is preferably thinner than the thickness of the second insulating layer 13. As thickness of the 1st insulating layer 12, 0.5-5 micrometers is mentioned, for example. As thickness of the 2nd insulating layer 13, 2-9 micrometers is mentioned, for example.

The ratio of resin and flame retardant contained in the insulating layers 12 and 13 can be set suitably. In the 1st insulating layer 12, 20-200 weight part of flame retardants are preferable with respect to 100 weight part of resin. In the 2nd insulating layer 13, 0-100 weight part of flame retardants with respect to 100 weight part of resin is preferable. Here, 0 weight part of flame retardants with respect to 100 weight part of resin means that a flame retardant is not included. The flame retardant may have a concentration distribution in the thickness direction of the insulating layer.

When the interface between the 1st insulating layer 12 and the 2nd insulating layer 13 differs, such as a composition of resin or an additive, may show an interface, and when it does not show a clear interface by continuous change of a composition, etc. There is also.

The first insulating layer 12 may be a flame retardant layer in which an electrically insulating flame retardant is separated from the second insulating layer 13 by coating, agglomeration, precipitation, or the like. In this case, the structure which does not contain resin may be sufficient as the 1st insulating layer 12, and the structure which contains resin etc. as a binder of a flame retardant may be sufficient.

(Thermosetting adhesive layer)

As the adhesive layer used for bonding the laminate 15 of the coverlay film 10 to the FPC, the thermosetting adhesive layer 14 is preferable. The thermosetting adhesive used for the thermosetting adhesive layer 14 may be an electrically insulating adhesive layer, and specific examples thereof include thermosetting adhesives generally used such as acrylic adhesives, polyurethane adhesives, epoxy adhesives, rubber adhesives, and silicone adhesives. Can be mentioned. In addition, a thermosetting adhesive obtained by mixing flame retardants such as phosphorus and bromine and the like with flame retardancy is preferably used, but is not particularly limited. Phosphorus-containing compounds may be used as polyol compounds or polyisocyanate compounds serving as polyurethane raw materials, and polyurethane resins containing phosphorus may be used as the thermosetting adhesive in the molecular structure of the resin. It is preferable that the thermosetting adhesive layer 14 contains a polyurethane resin and an epoxy resin, and it is more preferable that a polyurethane resin is a phosphorus containing polyurethane resin.

As for the thickness of the thermosetting adhesive layer 14, 1-8 micrometers is preferable, for example. The thermosetting adhesive layer 14 can be formed by application | coating, for example.

Although the adhesive force of the thermosetting adhesive layer 14 is not specifically limited, The measuring method is 5-30 N in the method A (90 degree-direction peeling) of 8.1.1 of JIS-C-6471 "The copper clad laminated board test method for flexible printed wiring boards". A range of / inch is preferred. If the adhesive force is less than 5 N / inch, for example, the laminate 15 bonded to the FPC may peel off or float due to heat or bending.

If the thermosetting adhesive layer 14 is not an adhesive which shows pressure-sensitive adhesiveness at normal temperature but an adhesive layer which shows adhesiveness by heating and pressing, adhesive force will hardly fall with respect to repetitive bending, and it is preferable. Although the heat-pressure adhesion | attachment conditions with respect to FPC are not specifically limited, For example, the conditions which heat-press for 60 minutes can be illustrated at the temperature of 160 degreeC, and a pressing force of 4.5 Mpa.

When heat-pressurizing the laminated body 15 with respect to FPC, the support film 11 may be peeled off from the laminated body 15 previously. Moreover, it is also possible to heat-press with respect to FPC with the support film 11 laminated | stacked on the laminated body 15. FIG. In this case, you may peel off the support body film 11 from the laminated body 15 after the process of the heat press adhesion with respect to FPC.

(Anchor layer)

Anchor between the second insulating layer 13 and the thermosetting adhesive layer 14 in order to improve the adhesion between the insulating layers 12 and 13 serving as the base material of the laminate 15 and the thermosetting adhesive layer 14. You may form a layer (not shown). Since the anchor layer can withstand the adhesive temperature by heat-pressing the thermosetting adhesive layer 14 even if it is 150-250 degreeC, it is preferable to use the adhesive excellent in heat resistance. Moreover, the anchor layer which is excellent in the adhesive force with respect to the insulating layers 12 and 13 and the thermosetting adhesive bond layer 14 is preferable. On the other hand, when sufficient adhesive force is sufficient, the anchor layer may be abbreviate | omitted and the 2nd insulating layer 13 and the thermosetting adhesive bond layer 14 may directly contact.

As the adhesive resin composition used for the anchor layer, thermoplastic resins such as polyester resins, polyurethane resins, (meth) acrylic resins, polyethylene resins, polystyrene resins, and polyamide resins are preferably used. Moreover, thermosetting types, such as an epoxy resin, an amino resin, a polyimide resin, and a (meth) acrylic resin, may be sufficient.

Especially preferable as adhesive resin composition of an anchor layer is the adhesive resin composition which crosslinks the polyester resin composition which has an epoxy group, and the adhesive resin composition which mixed epoxy resin as a hardening | curing agent to polyurethane resin. For this reason, an anchor layer has harder physical properties than the insulating layers 12 and 13 which consist of thin films, such as a polyimide film. Although the polyester resin composition which has an epoxy group is not specifically limited, For example, the epoxy resin (its uncured resin) which has 2 or more epoxy groups in 1 molecule, the polyhydric carboxylic acid which has 2 or more carboxyl groups in 1 molecule, and Reaction can be obtained. As a crosslinking of the polyester resin composition which has an epoxy group, the crosslinking agent for epoxy resins which react with an epoxy group can be used.

As for the thickness of an anchor layer, about 0.05-1 micrometer is preferable, and if it is this thickness, sufficient adhesive force with the thermosetting adhesive bond layer 14 is obtained. When the thickness of an anchor layer is 0.05 micrometers or less, there exists a possibility that the adhesive force of the insulating layers 12 and 13 and the thermosetting adhesive bond layer 14 may fall. Moreover, even if the thickness of an anchor layer exceeds 1 micrometer, since it is ineffective in the increase of the adhesive force of the insulating layers 12 and 13 and the thermosetting adhesive bond layer 14, since the thickness and cost of the laminated body 15 increase, it is preferable. Not. The anchor layer can be formed, for example, by application.

(Light absorber)

In order to provide light-shielding property to the laminated body 15 in the state bonded together to FPC, or to improve designability, you may contain the light absorbing agent in any layer which comprises the laminated body 15. FIG. For this purpose, a layer which may include a light absorber is formed between one or both of the insulating layers 12 and 13, the thermosetting adhesive layer 14, or between the insulating layers 12 and 13 and the thermosetting adhesive layer 14. It is arbitrary layers which can be made, For example, at least any one layer or two or more layers, such as the insulating layers 12 and 13, for example, the thermosetting adhesive layer 14, an anchor layer, etc. are mentioned. The thermosetting adhesive layer 14 may contain a light absorber, and the insulating layers 12 and 13 which consist of solvent soluble polyimide may contain a light absorber. When the layer (light absorbing layer) containing the light absorbing agent also serves as at least one layer of the insulating layers 12 and 13 or the thermosetting adhesive layer 14, the layer 15 of the laminate 15 as compared to the case where the light absorbing layer is laminated separately It is preferable because the increase in thickness can be suppressed.

The light absorbing agent may include at least one black pigment or colored pigment selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, and manganese oxide. It is preferable that the kind, compounding quantity, etc. of a light absorber are chosen so that a light absorption layer may maintain electrical insulation.

It is preferable to contain the light absorbing agent which consists of a black pigment or a coloring pigment in 0.1-30 weight% in any layer. It is preferable that the black pigment or colored pigment is about 0.02-0.1 micrometer in average particle diameter of the primary particle by SEM observation. The thickness of the light absorbing layer is preferably thicker than the particle size of the light absorbing agent so that the fine particles of the light absorbing agent are not exposed.

As for the light transmittance of the laminated body 15 from which the support film 11 was removed, 5% or less is preferable. Examples of the light transmittance include visible light transmittance and total light transmittance.

In order to reduce light transmittance effectively and to improve light-shielding property, black pigments, such as carbon black, are preferable among light absorbers. As a black pigment, only a surface layer part may be made black by immersing a silica particle etc. in a black color material, and you may make it black over the whole by forming with black coloring resin etc. In addition to the dark black, the black pigment may be used as long as it contains a particle having a color approximating black such as gray, blackish brown, or blackish green, and which is difficult to reflect light.

(Peel film)

The coverlay film 10 may bond the release film 19 onto the thermosetting adhesive layer 14 in order to protect the thermosetting adhesive layer 14. As a base material of the release film 19, polyester films, such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefin films, such as polypropylene and polyethylene, are mentioned, for example. After apply | coating peeling agents, such as an amino alkyd resin and silicone resin, to these base films, a peeling process is performed by heat-drying. Since the coverlay film 10 of this embodiment is bonded to FPC in the state which removed the peeling film 19, it is preferable that a silicone resin is not used for this peeling agent. If the silicone resin is used as the release agent, a part of the silicone resin may migrate to the surface of the thermosetting adhesive layer 14 in contact with the surface of the release film 19, which may weaken the adhesive force of the thermosetting adhesive layer 14. Because.

Although the thickness of the peeling film 19 is excluded from the thickness of the whole laminated body 15 at the time of coating and using FPC, although it does not specifically limit, it is about 12-150 micrometers normally.

(Coverlay film)

The coverlay film 10 of the present embodiment can be suitably used as a coverlay film having excellent bending characteristics that can be bonded to an FPC subjected to repeated bending operation. Moreover, FPC which bonded the coverlay film of this embodiment can be used for various electronic devices, such as a mobile telephone, a notebook computer, and a portable terminal.

In the method for manufacturing the coverlay film 10 of the present embodiment, the insulating layers 12 and 13 and the thermosetting adhesive layer 14 are sequentially placed on the support film 11 from the side close to the support film 11. The method of laminating | stacking by application | coating is mentioned. In addition, as described above, the release film 19 may be bonded onto the thermosetting adhesive layer 14.

When the FPC performs the bending operation, the coverlay film 10 of the present embodiment is preferably bonded to the FPC in the state of the laminate 15. Here, when the coverlay film 10 has the peeling film 19, the laminated body 15 is a laminated body which removed the support film 11 and the peeling film 19 from the coverlay film 10, and covers When the ray film 10 does not have the peeling film 19, it is a laminated body from which the support film 11 was removed. The laminated body 15 may also contain the anchor layer, light absorption layer, etc. which were mentioned above.

15 micrometers or less are preferable and, as for the total thickness of the laminated body 15, 5-15 micrometers and 12 micrometers or less are mentioned, for example. The tensile elongation of the laminate 15 is preferably 100% or more, and may be 150% or more or 150% or less.

Example

Hereinafter, an Example is given and this invention is demonstrated concretely.

(Example 1)

The 50-micrometer-thick polyethylene terephthalate (PET) film which performed the peeling process to one side was used as the support film 11. As shown in FIG.

The coating liquid of the solvent-soluble polyimide resin containing 50 weight part of phosphorus flame retardant with respect to 100 weight part of resin on one side of the support film 11 is cast-flexively applied, and dried so that the thickness after drying may be set to 1 micrometer, and the 1st insulating layer ( 12) was formed.

The coating liquid of the solvent-soluble polyimide resin whose tensile elongation after drying does not contain a flame-retardant on the 1st insulating layer 12, and is 170%, is cast-softened and dried so that thickness after drying may be 3 micrometers, and the 2nd insulating layer 13 ) Was formed.

2.4 parts by weight of polyfunctional epoxy resin (Toyobo: HY-30), 100 parts by weight of a phosphorus-containing polyurethane resin solution (Toyobo manufactured: UR3575) on the second insulating layer 13, fumed silica (manufactured by Nihon Aerosil: R972) 4.7 parts by weight was added sequentially and stirred to apply the resulting thermosetting adhesive to a thickness of 8 占 퐉 after drying and dried to form a thermosetting adhesive layer 14 to obtain a coverlay film of Example 1.

(Examples 2 and 3)

The coverlay films of Examples 2 and 3 were the same as in Example 1 except that the proportion of the phosphorous flame retardant included in the first insulating layer 12 was 100 parts by weight in Example 2 and 150 parts by weight in Example 3. Got.

(Examples 4 to 6)

In the same manner as in Examples 1 to 3, except that the coating liquid for forming the second insulating layer 13 was a coating liquid of a solvent-soluble polyimide resin containing 20 parts by weight of a phosphorus-based flame retardant based on 100 parts by weight of the resin. The coverlay films of Examples 4 to 6 were obtained.

(Example 7)

The coverlay film of Example 7 was obtained like Example 2 except having set the thickness of the 1st insulating layer 12 to 2 micrometers, and the thickness of the 2nd insulating layer 13 to 7 micrometers.

(Comparative Example 1)

The coating liquid for forming the first insulating layer 12 is a coating liquid of a solvent-soluble polyimide resin not containing a flame retardant, and the coating liquid for forming the second insulating layer 13 with respect to 100 parts by weight of the resin. The coverlay film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the coating liquid of the solvent-soluble polyimide resin containing 100 parts by weight of a phosphorus-based flame retardant was used.

(Comparative Example 2)

A cover of Comparative Example 2 in the same manner as in Example 2 except that a solvent-soluble polyimide resin having a lower tensile elongation after coating drying was used as the solvent-soluble polyimide resin used to form the insulating layers 12 and 13. A ray film was obtained.

(Measurement of tensile elongation)

According to IPC-TM-650 2.4.19, the sample size was measured at 15 mm in width, the distance between the chucks at 100 mm, and the measurement speed at 50 mm / min (the measurement was performed at the number of samples N = 5, and the average value was taken).

The tensile elongation of the laminated body was measured using the laminated body which removed the support film as a sample.

The tensile elongation of a 2nd insulating layer apply | coats the coating liquid for forming a 2nd insulating layer to one side of the same peeling film as a support film, and removes the peeling film after drying, and uses the sample as the sample. It was measured by.

(Evaluation method of followability)

The thermosetting adhesive surface of the coverlay film was superimposed on the Tess pattern which formed the copper wiring pattern of thickness 75micrometer and L / S = 75micrometer / 75micrometer on the polyimide film whose thickness is 12.5micrometer, and the temperature is 140 degreeC, and the speed Laminated by thermal lamination at 1 m / min. After peeling the support film 11, it hot-pressed on the conditions of 160 degreeC, 4.5 Mpa, and 65 minutes, and obtained the followability evaluation sample.

When the cross section of the obtained sample was observed and followed the wiring pattern very well and the appearance was good, it was followed by "◎" and the wiring pattern well, but when the wiring edge became thin, "○" was not followed, but it floated from the wiring pattern. The case and the case where the coating film of the wiring edge part were cut | disconnected were made into "x".

(Evaluation method of flame retardancy)

The obtained coverlay film was heat-pressed to the polyimide film whose thickness is 12.5 micrometers by the method (refer to the evaluation method of followability) mentioned above, and the sample for evaluation of flame retardance was obtained. When flame retardancy is evaluated according to the method of UL-94's clap material vertical combustion test (ASTM D4804), and when flame retardation is performed such that a flame does not rise, "◎" is used. ", When the combustion to the mark grade is represented," (triangle | delta) "was burned to more than a mark and it is set as" x "when it does not have flame retardancy.

(Test result)

In Example 1-7 and Comparative Examples 1-2, the evaluation result obtained by evaluating a coverlay film by said evaluation method is shown in Table 1.

In the columns of the first insulating layer and the second insulating layer, "parts by weight" means parts by weight of a flame retardant based on 100 parts by weight of the resin. "PI1" means the solvent-soluble polyimide resin used in Example 1, and "PI2" means the solvent-soluble polyimide resin used in the comparative example 2.

In the material column of the heat adhesive adhesive layer, "PU1" means the heat adhesive adhesive containing the flame-retardant polyurethane used in Example 1.

The thickness of a laminated body means the thickness of the whole coverlay film from which the support film was removed, and "thickness of the sum" means the thickness of the whole coverlay film containing a support film.

On the other hand, as a phosphorus flame retardant, an aromatic condensed phosphate ester [(CH ₃ ) ₂ C ₆ H ₃ O] ₂ P (O) OC ₆ H ₄ OP (O) [OC ₆ H ₃ (CH ₃ ) ₂ ] ₂ was used. It was.

According to the evaluation result shown in Table 1, when a tensile elongation of a laminated body is 100% or more, it turns out that a followability becomes favorable. In other words, when the tensile elongation of the laminate was low, the followability to the step was deteriorated. When the tensile elongation of the 2nd insulating layer was low, the tensile elongation of the laminated body also tended to fall.

In addition, in Comparative Example 1 in which the flame retardant was added to the second insulating layer without adding a flame retardant to the first insulating layer, the total amount of the flame retardants included in the first and second insulating layers was greater than those in Examples 1 to 7, Since the flame retardance of the 1st insulating layer used as the outermost layer in the sample which peeled off the support film was low, flame retardance also deteriorated also as the whole laminated body.

10... Coverlay film, 11... Support film, 12... First insulating layer, 13... Second insulating layer, 14... Thermosetting adhesive layer, 15... Laminate, 19... Release film.

Claims (5)

The first insulating layer, the second insulating layer, the thermosetting adhesive layer are sequentially laminated on one side of the support film,
The first insulating layer contains a flame retardant,
The thermosetting adhesive layer contains a phosphorus-containing polyurethane resin, an epoxy resin, and silica,
The tensile elongation of the laminated body which consists of the said 1st insulating layer, the said 2nd insulating layer, and the said thermosetting adhesive bond layer which removed the said support film is 100% or more, The coverlay film characterized by the above-mentioned. The method of claim 1,
The coverlay film of claim 2, wherein the second insulating layer contains a flame retardant having a lower concentration than the first insulating layer, or does not contain a flame retardant. The method according to claim 1 or 2,
The thickness of the first insulating layer is thinner than the thickness of the second insulating layer, the coverlay film. The mobile telephone in which the coverlay film of Claim 1 or 2 is used as an FPC protection member. The electronic device in which the coverlay film of Claim 1 or 2 is used as an FPC protection member.

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