JP2017126735A - Coverlay film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coverlay film which is satisfactory in processing suitability and workability and superior in followability to a flexible printed circuit board (FPC) despite being shaped in a thin film.SOLUTION: To solve the above problem, a coverlay film 10 is provided. The coverlay film is arranged by laminating, on a support body film 11, a base material 12 composed of a dielectric thin film resin layer, which is coated on one face of the support body film, and a thermosetting adhesive layer 13 in turn. The base material 12 is 100% or more in tensile elongation according to a method prescribed in JIS-K-7127.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coverlay film. More specifically, it can cover and protect a flexible printed circuit board (hereinafter referred to as FPC) that repeatedly receives a bending action, and has good workability in the process of manufacturing a base material and good workability of bonding. It relates to a thin coverlay film.

  In portable electronic devices such as cellular phones, electronic components are integrated on a printed circuit board in order to keep the outer dimensions of the housing small and thin so that it can be easily carried. Furthermore, in order to reduce the outer dimensions of the housing, the printed circuit board is divided into a plurality of parts, and the printed circuit board is folded by using a flexible FPC for connection wiring between the divided printed circuit boards, or It is done to slide.

In addition, recent portable information terminals (smartphones, tablets, and the like) consume more power than conventional mobile phones, and thus battery retention is poor. Therefore, it is necessary to increase the volume and capacity of the battery as much as possible, and there is a strong demand for miniaturization and thinning of members and parts other than the battery. For example, there is a demand for thinning the entire FPC bonded with a coverlay film. Yes.
Furthermore, in recent years, light shielding properties and design properties have become important, and coloring of cover lay films has been demanded.

Conventionally, as a coverlay film used for the purpose of thinning the entire FPC, a thin polyimide film coated with an adhesive is used (Patent Document 1). However, a thin polyimide film has poor processability in the manufacturing process, and has a problem that workability is poor when it is attached to an FPC.
In addition, since the conventional coverlay film lacks flexibility due to the difficulty in reducing the thickness, the followability to the step of the FPC is not sufficient, and a gap is formed. It was the cause of problems such as swelling. For this reason, it has been difficult to reduce the thickness of the entire FPC to which the coverlay film is bonded.

  In addition, for the purpose of improving the light-shielding property and design, a polyimide film containing a black pigment or a dye or a coverlay film containing a black pigment in one or both of an electrically insulating film and a thermosetting adhesive is proposed. However, no consideration is given to the above-described thinning.

Japanese Patent Laid-Open No. 9-135067

  In view of the above-described background art, an object of the present invention is to provide a coverlay film that is excellent in workability and workability at the time of manufacturing an FPC even if it is a thin film and excellent in followability to a step of the FPC.

  In order to improve the handleability, in the present invention, a base material made of a thin film of dielectric resin and an adhesive layer are sequentially laminated on one side of the support film. In addition, after the adhesive layer is superposed on the FPC and thermocompression bonded, the support film can be peeled off and transferred to the FPC.

  Moreover, in order to endure severe bending | flexion operation | movement and to make followability to FPC favorable, in this invention, the base material which consists of a thin film of dielectric resin with a large tensile elongation is used. The technical idea of the present invention is to produce a laminate in which an adhesive layer is laminated on a base material composed of at least a dielectric thin film resin layer.

  Further, in the present invention, in consideration of flexibility, a coated resin thin film resin layer is used as a base material made of a dielectric resin thin film, and a support layer and a release film are removed, and a cover layer is removed. The total thickness of the film can be reduced to 15 μm or less.

  In the present invention, the adhesive layer bonded to the FPC is a thermosetting resin layer, and the adhesion between the thermosetting resin layer and a base material made of a thin film resin layer such as polyimide is increased. An adhesive layer can also be provided between the thermosetting adhesive layer and the thermosetting adhesive layer.

  In the present invention, in order to solve the above-mentioned problems, a base material composed of a coated thin film resin layer and a thermosetting adhesive layer are sequentially laminated on one side of the support film. The cover lay film is characterized in that the substrate has a tensile elongation of 100% or more according to the method of JIS-K-7127.

  Further, in the present invention, in order to solve the above-mentioned problems, a base material composed of a dielectric thin film resin layer applied on one side of a support film, a thin film adhesive layer, and a thermosetting adhesive A cover lay film is provided in which layers are laminated in order, and the tensile elongation of the substrate according to the method of JIS-K-7127 is 100% or more.

  In the present invention, in order to solve the above-mentioned problems, a base material composed of a coated thin film resin layer and a thermosetting adhesive layer are sequentially laminated on one side of the support film. The cover lay film is characterized in that the tensile elongation of the laminate composed of the base material and the thermosetting adhesive layer excluding the support film is 100% or more.

  Further, in the present invention, in order to solve the above-mentioned problems, a base material composed of a dielectric thin film resin layer applied on one side of a support film, a thin film adhesive layer, and a thermosetting adhesive Layers, and a laminate comprising the base material, the thin film adhesive layer, and the thermosetting adhesive layer excluding the support film has a tensile elongation of 100% or more. A coverlay film characterized by the above is provided.

  It is preferable that at least one of the base material, the thin film adhesive layer, and the thermosetting adhesive layer contains a light absorber.

  It is preferable that the base material is composed of an insulating layer formed using a solvent-soluble polyimide and has a thickness of 1 to 9 μm.

  One or more black pigments 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, or colored pigment 1 It is preferable to include a light absorbing material composed of seeds or more.

  The thin film adhesive layer is one or more black pigments selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, manganese oxide, or colored It is preferable to include a light absorbing material composed of one or more pigments.

  The thermosetting adhesive layer is preferably a flame retardant thermosetting adhesive comprising a flame retardant phosphorus-containing polyurethane resin and an epoxy resin.

  The thermosetting adhesive layer is one or more black pigments selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, manganese oxide, or It is preferable to include a light absorbing material composed of one or more colored pigments.

  The present invention also provides a mobile phone in which the coverlay film is used as an FPC protection member.

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

  According to the above-described coverlay film of the present invention, by using a base material made of a thin film resin having a large tensile elongation and proper tensile strength, it follows without any gap when covering a wiring board or the like having a step, It is possible to manufacture a thin film coverlay film that can reduce the occurrence of problems due to swelling and penetration of a plating solution in processes such as a solder reflow process and a plating process.

  Further, by using a thin film resin film (thickness of 1 to 9 μm) of an insulating polyimide film as the base material, it is possible to have excellent bending characteristics that can withstand severe bending operations. As a result, the entire thickness of the coverlay film excluding the support film and the release film can be suppressed to 15 μm or less, which can contribute to reducing the overall thickness of the mobile phone and the electronic device.

  By mixing a light absorbing material composed of one or more kinds of black pigments or colored pigments into the base material or the adhesive layer, specific coloring can be performed on one side of the coverlay film.

  From the above, according to the present invention, in a heating process such as a solder reflow process after covering a wiring board or the like, there is no occurrence of problems due to swelling or penetration of a plating solution, which is flexible and thin. In addition, it is possible to provide a cover lay film excellent in bending characteristics that does not cause a decrease in FPC protection performance even when a severe bending operation is repeated.

It is a schematic sectional drawing which shows 1st Embodiment of the coverlay film concerning this invention. It is a schematic sectional drawing which shows 2nd Embodiment of the coverlay film concerning this invention.

  Hereinafter, preferred embodiments of the present invention will be described. The present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. The present embodiment includes the following first and second embodiments.

  When the coverlay film of this embodiment is bonded to an adherend FPC or the like, the outer surface is a dielectric, and the FPC wiring and circuit components can be electrically insulated. In addition, the coverlay film of the present embodiment has a reduced overall thickness in order to improve the bending characteristics with respect to the bending operation.

  In the coverlay film 10 of the first embodiment shown in FIG. 1, the substrate 12 has flexibility, a thickness of 1 to 9 μm, a tensile elongation of 100% or more, for example, a solvent-soluble polyimide. Examples thereof include thin film resin films such as polyimide films formed by use. Furthermore, the support film 11 is laminated on one surface of the substrate 12, and the adhesive layer 13 is laminated on the other surface of the substrate 12. The adhesive layer 13 is an electrically insulating adhesive layer bonded to the surface of the FPC, for example, a thermosetting adhesive layer. A release film 19 for protecting the adhesive layer 13 can be laminated on the surface of the adhesive layer 13. This cover lay film 10 can be used as a cover lay film (laminated body) 15 having a structure in which the adhesive layer 13 is laminated on one side of the substrate 12 by removing the support film 11 and the release film 19. . In the first embodiment, the adhesive layer 13 may be in contact with one surface of the substrate 12.

  In the coverlay film 20 of the second embodiment shown in FIG. 2, the base material 12 has flexibility, a thickness of 1 to 9 μm, a tensile elongation of 100% or more, for example, a solvent-soluble polyimide. Examples thereof include thin film resin films such as polyimide films formed by use. Furthermore, the support film 11 is laminated on one surface of the substrate 12, and the adhesive layer 14 and the adhesive layer 13 are laminated on the other surface of the substrate 12 in this order. The adhesive layer 14 is a thin adhesive layer that improves the adhesion between the adhesive layer 13 and the substrate 12. The adhesive layer 13 is an electrically insulating adhesive layer bonded to the surface of the FPC, for example, a thermosetting adhesive layer. A release film 19 for protecting the adhesive layer 13 can be laminated on the surface of the adhesive layer 13. The cover lay film 20 is used as a cover lay film (laminated body) 16 having a configuration in which the adhesive film 13 and 14 are laminated on one side of the base material 12 by removing the support film 11 and the release film 19. Can do. In the second embodiment, the adhesive layer 13 may be in contact with the adhesive layer 14, and the adhesive layer 14 may be in contact with one side of the substrate 12.

(Base material)
The base material 12 of the coverlay films 10, 15, 16, and 20 according to the present embodiment is an insulating layer made of a dielectric thin film resin layer. The thin film resin film of polyimide film formed using solvent-soluble polyimide has the high mechanical strength, heat resistance, insulation and solvent resistance that are characteristic of polyimide resin, and is chemically stable up to about 260 ° C. Therefore, it is suitable as the base material 12.

Examples of polyimide include thermosetting polyimide that is generated by a dehydration condensation reaction by heating polyamic acid, and solvent-soluble polyimide that is soluble in a non-dehydration condensation type solvent.
A generally known method for producing a polyimide film is to synthesize polyamic acid, which is an imide precursor, by reacting diamine and carboxylic dianhydride in a polar solvent, and heat the polyamic acid. Alternatively, a corresponding polyimide is formed by dehydration cyclization by using a catalyst. However, the temperature of the heat treatment in this imidization step is preferably a 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. If the heating temperature is higher than the above temperature, the compound may be thermally decomposed, which is not preferable.

The cover lay films 10, 15, 16, and 20 of the present embodiment use extremely thin polyimide films having a thickness of less than 10 μm in order to further improve the flexibility of the substrate 12.
In this embodiment, it consists of a base material formed by laminating a thin polyimide film on one side of a support film 11 used as a reinforcing material for strength, or only a thin polyimide film without using the support film 11. Any of the substrates can be used.
When the thickness of the polyimide film to be used is thinner than about 7 μm, it is preferable to form a thin polyimide film on one side of the support film 11 used as a reinforcing material for strength. For example, a coating liquid containing polyamic acid can be cast on one surface of the support film 11 and heated to form a polyimide film.

However, the polyimide film itself has heat resistance against heat treatment at a heating temperature of 200 ° C. to 250 ° C. However, as the support film 11, a general-purpose heat resistant resin is used because of the balance between price and heat resistant temperature performance. When using a film such as a polyethylene terephthalate (PET) resin film that does not have high heat resistance, a method of forming polyimide from a polyamic acid that is a conventional imide precursor cannot be employed.
The solvent-soluble polyimide is complete in imidization of the polyimide and is soluble in the solvent. After applying the coating solution dissolved in the solvent, the solvent is volatilized at a low temperature of less than 200 ° C. A film can be formed. For this reason, the base material 12 used for the cover lay film of this embodiment applies the coating liquid of the solvent-soluble polyimide which is a non-dehydration condensation type | mold on the single side | surface of the support body film 11, Then, temperature is 200 degreeC. It is preferable to dry at a heating temperature lower than that to form a thin film resin film of a polyimide film formed using a solvent-soluble polyimide. By carrying out like this, the very thin polyimide film whose thickness is 1-9 micrometers can be laminated | stacked on the single side | surface of the support body film 11 which consists of a general purpose heat resistant resin film. Similarly to the adhesive layers 13 and 14, the base material 12 is formed by coating (coating), whereby the support film 11 is conveyed along its longitudinal direction, and the base material 12 and the adhesive layer 13 are formed thereon. , 14 and the like can be continuously formed, so that roll-to-roll production is possible, and processability and productivity are excellent.

  The solvent-soluble polyimide that is a non-dehydrating condensation type that can be used for the substrate 12 of the present embodiment is not particularly limited, but a commercially available solvent-soluble polyimide coating solution can be used. Specific examples of commercially available solvent-soluble polyimide coating solutions include Solpy 6,6-PI (Solpy Industry), Q-IP-0895D (PI Engineering), PIQ (Hitachi Chemical Industry), SPI-200N (Nippon Steel Chemical). ), Rika Coat SN-20, Rika Coat PN-20 (New Nippon Rika) and the like. The method for applying the solvent-soluble polyimide coating solution on the support film 11 is not particularly limited, and can be applied by a coater such as a die coater, a knife coater, or a lip coater.

The thickness of the substrate 12 of the present embodiment (for example, the thickness of the polyimide film) is preferably 1 to 9 μm. Forming a polyimide film with a thickness of less than 0.8 μm is technically difficult because the mechanical strength of the formed film is weak. Moreover, when the thickness of the base material 12 such as a polyimide film exceeds 10 μm, it is difficult to obtain coverlay films (laminates) 15 and 16 that are thin and have excellent bending performance.
Further, when the thickness of the polyimide film to be used is thinner than about 7 μm, it is difficult to adjust the tension at the time of winding on a roll. Therefore, a thin polyimide film is formed on one side of the support film 11 used as a reinforcing material for strength. It is preferably formed by laminating films.
The thickness in the case of using the substrate 12 made of only a thin polyimide film without using the support film 11 is preferably about 1 to 9 μm.

Moreover, since the base material 12 of this embodiment improves the followable | trackability with respect to the level | step difference of FPC, it is preferable that tensile elongation is large. The tensile elongation of the substrate 12 is preferably 100% or more, and preferably 250% or less. Here, the tensile elongation is a percentage of the elongation at the time when the film is cut by constant-speed tension. The larger the tensile elongation, the more flexible the tensile strength. For this reason, in order that the said laminated bodies 15 and 16 have sufficient softness | flexibility and express the outstanding followable | trackability to the unevenness | corrugation and level | step difference of FPC, it is preferable that the said tensile elongation is 100% or more. .
Moreover, it is preferable that the elasticity modulus of the base material 12 is 1.0 GPa or more and 2.5 GPa or less. When the base material 12 having a large tensile elongation is composed of a polyimide film, for example, it is preferable to use a polyimide material having an aliphatic unit having 3 or more carbon atoms between aromatic units. Further, the aliphatic unit preferably contains a polyalkyleneoxy group having an alkylene group having about 1 to 10 carbon atoms.
The tensile elongation of the substrate is measured as the tensile strain of the plastic based on the description of JIS-K-7127. The elastic modulus of the substrate is measured as the tensile elastic modulus of the plastic based on the description of JIS-K-7161.

Moreover, it is preferable that the water vapor permeability of the polyimide film used with the base material 12 of this embodiment is 500 g / m ² · day or more. When the water vapor permeability is lower than 500 g / m ² · day, in the heating process such as solder reflow after coating the FPC, the outgas from the residual solvent and adhesive of each layer and the moisture in the film are abrupt. Each layer may be peeled off by water vapor generated by being heated. There is no particular upper limit to the water vapor transmission rate, but as long as the same material is used, the water vapor transmission rate is inversely proportional to the thickness. Therefore, when the water vapor transmission rate is increased by reducing the thickness, the water vapor transmission rate falls within the above range. It is preferable.

(Support film)
Examples of the substrate of the support film 11 used in this embodiment include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene.
When the base material of the support film 11 has a certain degree of peelability on the base material itself, such as polyethylene terephthalate, for example, it is directly applied to the support film 11 without performing a peeling treatment. The base material 12 made of a coated thin film resin film of dielectric material may be laminated, or the surface of the support film 11 may be subjected to a peeling treatment for making the base material 12 easier to peel off.

  In addition, when the base film used as the support film 11 does not have releasability, a release treatment such as amino alkyd resin or silicone resin is applied and then dried by heating. Applied. Since the coverlay films 10, 15, 16, and 20 of this embodiment are bonded to the FPC, it is desirable not to use a silicone resin for this release agent. This is because when a silicone resin is used as a release agent, a part of the silicone resin is transferred to the surface of the base material 12 in contact with the surface of the support film 11, and further through the inside of the coverlay films 10, 15, 16, 20. There is a risk of migration from the material 12 to the surface of the adhesive layer 13. This is because the silicone resin transferred to the surface of the adhesive layer 13 may weaken the adhesive force of the adhesive layer 13.

  The thickness of the support film 11 used in the present embodiment is not particularly limited because it is excluded from the total thickness of the coverlay films (laminates) 15 and 16 when used while being coated on an FPC. Usually, it is about 12 to 150 μm. By using the support film 11, the workability when forming the base material 12 and the adhesive layers 13 and 14 and the workability at the time of bonding to the FPC can be improved.

  The color of the support film 11 may be colorless (uncolored) or colored. When the support film 11 is colored, it is preferably a color having a large contrast with respect to the colors of the coverlay films (laminates) 15 and 16 excluding the support film 11 and the release film 19. For example, when the coverlay films (laminates) 15 and 16 are dark colors such as black, the support film 11 is preferably light colors such as white and yellow. Thereby, the handleability of peeling the coverlay films (laminates) 15 and 16 from the support film 11 and the confirmation of whether or not the support film 11 is peeled can be improved. The support film 11 can be colored using a known pigment, dye or the like. Examples of the support film 11 include a white PET film having a thickness of 30 μm to 60 μm.

(Thermosetting adhesive layer)
The coverlay films 10, 15, 16, and 20 according to the present embodiment are preferably thermosetting adhesive layers as the adhesive layer 13 bonded to the FPC. As the thermosetting adhesive used for the adhesive layer 13, generally used are acrylic adhesive, polyurethane adhesive, epoxy adhesive, rubber adhesive, silicone adhesive, and the like. A thermosetting adhesive is mentioned. Furthermore, a flame retardant material such as a phosphorus-based or bromine-based flame retardant is preferably used, but is not particularly limited. A polyurethane resin containing phosphorus in the molecular structure of the resin can be used as a thermosetting adhesive by using a phosphorus-containing compound as a polyol compound or polyisocyanate compound as a raw material of polyurethane. It is preferable that the thermosetting adhesive layer 13 includes a phosphorus-containing polyurethane resin composition and an epoxy resin.

  As for the thickness of the thermosetting adhesive bond layer 13, 1-8 micrometers is preferable, for example. The thermosetting adhesive layer 13 can be formed by application, for example. When the thermosetting adhesive layer 13 contains a flame retardant, the cover lay films (laminates) 15 and 16 excluding the support film 11 and the release film 19 without adding the flame retardant to the substrate 12. It is possible to impart flame retardancy.

  The adhesive strength of the thermosetting adhesive is not particularly limited, but the measuring method is JIS-C-6471 “Testing method for copper-clad laminates for flexible printed wiring boards” in 8.1.1, Method A (90 The range of 5 to 30 N / inch is preferable. When the adhesive force is less than 5 N / inch, for example, the coverlay films (laminates) 15 and 16 bonded to the FPC may peel off or float due to heat or bending.

The thermosetting adhesive is preferably not an adhesive that exhibits pressure-sensitive adhesiveness at room temperature but an adhesive by heating and pressurization because the adhesive force is unlikely to be reduced with respect to repeated bending. The conditions for heat and pressure adhesion to the FPC are not particularly limited, and examples include conditions of heat pressing for 60 minutes at a temperature of 160 ° C. and a pressure of 4.5 MPa.
When the cover lay films (laminates) 15 and 16 excluding the support film 11 and the release film 19 are heated and pressed against the FPC, the support film 11 is removed from the cover lay films (laminates) 15 and 16 in advance. May be. In addition, it is possible to heat and press the FPC including the support film 11. In this case, the support film 11 may be peeled off from the laminates 15 and 16 after the heat and pressure bonding process for the FPC.

(Adhesive layer)
The adhesive layer 14 used for the coverlay films 16 and 20 of the second embodiment is improved in adhesion between a thin film such as a polyimide film as the substrate 12 and the adhesive layer 13 as a thermosetting adhesive layer. Therefore, it is provided as an anchor layer. As shown in the first embodiment, the adhesive layer 14 can be omitted.
The adhesive layer 14 is preferably made of an adhesive having excellent heat resistance because the adhesive temperature of the thermosetting adhesive layer 13 laminated thereon is 150 to 250 ° C. by heating and pressing. Moreover, it is preferable that the adhesive force with respect to insulating resin, such as a polyimide film used as the base material 12, and the thermosetting adhesive bond layer 13, is excellent.

As the adhesive resin composition used for the adhesive layer 14, a thermoplastic resin such as a polyester resin, a polyurethane resin, a (meth) acrylic resin, a polyethylene resin, a polystyrene resin, or a polyamide resin is preferably used. Moreover, thermosetting types, such as an epoxy resin, an amino resin, a polyimide resin, (meth) acrylic resin, may be sufficient.
Particularly preferred as the adhesive resin composition for the adhesive layer 14 is an adhesive resin composition for crosslinking a polyester resin composition having an epoxy group, or an adhesive resin in which an epoxy resin is mixed as a curing agent with a polyurethane resin. It is a composition. For this reason, the adhesive layer 14 has harder physical properties than the base material 12 made of a thin film such as a polyimide film. The polyester-based resin composition having an epoxy group is not particularly limited. For example, an epoxy resin having two or more epoxy groups per molecule (its uncured resin) and two or more carboxyls per molecule. It can be obtained by reaction with a polyvalent carboxylic acid having a group. For crosslinking of the polyester-based resin composition having an epoxy group, a crosslinking agent for epoxy resin that reacts with the epoxy group can be used.

  It is preferable that the thickness of the adhesive layer 14 is about 0.05 to 1 μm. If the thickness is about this level, sufficient adhesion with the thermosetting adhesive layer 13 can be obtained. When the thickness of the adhesive layer 14 is 0.05 μm or less, the adhesive force between the substrate 12 and the thermosetting adhesive layer 13 may be reduced. Further, even if the thickness of the adhesive layer 14 exceeds 1 μm, there is no effect in increasing the adhesive force to the base material 12 made of a polyimide film or the like or the thermosetting adhesive layer 13. It is not preferable to exceed 1 μm because the cost increases. The adhesive layer 14 can be formed by application, for example.

(Light absorber)
Coverlay film (laminated body) excluding support film 11 and release film 19 in order to impart light-shielding properties to coverlay films (laminates) 15 and 16 or improve design properties in a state of being bonded to FPC. ) A light absorbing material may be included in any of the layers 15 and 16. The layer that can contain a light absorbing material for this purpose is the substrate 12, the thermosetting adhesive layer 13, or any layer that can be provided between the substrate 12 and the thermosetting adhesive layer 13. Yes, for example, one layer or two or more layers of at least one of the substrate 12, the thermosetting adhesive layer 13, and the adhesive layer 14 may be mentioned. Examples of the light absorber include one or more black pigments or colored pigments 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 done. The type and blending amount of the light absorber are preferably selected so that the layer containing the light absorber maintains electrical insulation.

  In 1st Embodiment shown in FIG. 1, a light absorber can be mix | blended with either the base material 12 or the thermosetting adhesive bond layer 13, or both. A light absorber may be blended only in the substrate 12, a light absorber may be blended only in the thermosetting adhesive layer 13, and a light absorber is mixed in the substrate 12 and the thermosetting adhesive layer 13. You may mix | blend. When the layer containing the light absorber (light absorption layer) also serves as at least one of the base material 12 and the thermosetting adhesive layer 13, the layered body 15 has a higher structure than the case where the light absorption layer is separately laminated. This is preferable because an increase in thickness can be suppressed.

  In the second embodiment shown in FIG. 2, a light absorber can be blended in one or more of the base material 12, the adhesive layer 14, and the thermosetting adhesive layer 13. For example, a light absorber may be blended in the thermosetting adhesive layer 13 and the adhesive layer 14, or a light absorber may be blended in the base material 12 and the adhesive layer 14, and only the adhesive layer 14. You may mix | blend a light absorber, you may mix | blend a light absorber with all the layers of the base material 12, the adhesive bond layer 14, and the thermosetting adhesive bond layer 13, and mix | blend a light absorber only with the base material 12. Alternatively, the light absorber may be blended only in the thermosetting adhesive layer 13, or the light absorber may be blended in the substrate 12 and the thermosetting adhesive layer 13. When the layer containing the light absorber (light absorption layer) also serves as at least one of the base material 12, the adhesive layer 14, and the thermosetting adhesive layer 13, compared to the case where a light absorption layer is separately laminated. It is preferable because an increase in the thickness of the laminate 16 can be suppressed.

  The light transmittance of the coverlay films (laminates) 15 and 16 excluding the support film 11 and the release film 19 is preferably 5% or less. Examples of the light transmittance include visible light transmittance and total light transmittance. When the base material 12 is comprised from a solvent soluble polyimide, the base material 12 containing a light absorber can be provided.

Among the light absorbing materials, black pigments such as carbon black are preferable in order to effectively reduce the light transmittance and improve the light shielding property. The light absorbing material composed of a black pigment or a colored pigment is preferably contained at 0.1 to 30% by weight in any layer. The black pigment or the colored pigment preferably has an average primary particle size of about 0.02 to 0.1 μm by SEM observation. The thickness of the layer containing the light absorber is preferably larger than the particle size of the light absorber so that the fine particles of the light absorber are not exposed.
Moreover, as a black pigment, a silica particle etc. may be immersed in a black color material, and only a surface layer part may be made black, and it may be formed from a black colored resin etc. and may become black over the whole. Further, the black pigment includes particles exhibiting a color similar to black, such as gray, dark brown, or dark green, in addition to true black, and can be used as long as it is a dark color that hardly reflects light.

(Peeling film)
As described above, the coverlay films 10 and 20 can have the release film 19 in order to protect the thermosetting adhesive layer 13. Examples of the base material of the release film 19 include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. After applying a release agent such as amino alkyd resin or silicone resin to these base films, the release treatment is performed by drying by heating. Since the coverlay films 10, 15, 16, and 20 of this embodiment are bonded to the FPC with the release film 19 removed, it is desirable not to use a silicone resin for the release agent. This is because when a silicone resin is used as a release agent, a part of the silicone resin is transferred to the surface of the thermosetting adhesive layer 13 in contact with the surface of the release film 19 to weaken the adhesive force of the thermosetting adhesive layer 13. Because there is a fear. The thickness of the release film 19 used in the present embodiment is not particularly limited because it is excluded from the total thickness of the coverlay films (laminates) 15 and 16 when used while being coated on an FPC. It is about 12 to 150 μm.

(Coverlay film)
The coverlay films 10, 15, 16, and 20 of the present embodiment can be suitably used as a coverlay film having excellent bending characteristics that can be used by being bonded to an FPC that is repeatedly bent. . Moreover, the coverlay film of this embodiment can be used as a member for FPC protection. The FPC on which the coverlay film of this embodiment is bonded can be used for various electronic devices such as a mobile phone, a notebook personal computer, and a mobile terminal. As a manufacturing method of the coverlay films 10, 15, 16, and 20 of this embodiment, the base material 12 and the adhesive layers 13 and 14 are sequentially formed on the support film 11 from the side close to the support film 11. The method of laminating by application | coating of is mentioned. Furthermore, as described above, the release film 19 may be bonded onto the thermosetting adhesive layer 14.

The coverlay films 10, 15, 16, and 20 of the present embodiment are preferably used by being bonded to the FPC in the state of the laminates 15 and 16 when the FPC performs a bending operation. Here, the laminates 15 and 16 are laminates obtained by removing the support film 11 and the release film 19 from the coverlay films 10 and 20 when the coverlay films 10 and 20 have the release film 19. When the coverlay films 10 and 20 do not have the release film 19, the coverlay films 10 and 20 are laminated bodies excluding the support film 11. The laminates 15 and 16 may include the above-described anchor layer, light absorption layer, and the like.
The total thickness of the coverlay films (laminates) 15 and 16 excluding the support film 11 and the release film 19 is preferably 15 μm or less, for example, 5 to 15 μm or 12 μm or less. The thickness of the coverlay films (laminates) 15 and 16 is the sum of the thicknesses of the substrate 12 and the thermosetting adhesive layer 13 in the case of the first embodiment, and the substrate in the case of the second embodiment. 12 is the total thickness of the adhesive layer 14 and the thermosetting adhesive layer 13.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
A polyethylene terephthalate (PET) film having a thickness of 50 μm and subjected to a peeling treatment on one side was used as the support film 11. On one side of the support film 11, a solvent-soluble polyimide coating solution having a tensile elongation of 170% after drying is cast-coated and dried so that the thickness after drying becomes 4 μm. A substrate 12 made of a thin film resin film was laminated. In order to form an adhesive layer 14 on the formed base material 12, in which non-conductive carbon black is mixed as a black pigment of a light absorbing material and a polyester resin composition having a heat resistant temperature of 260 to 280 ° C. The coating layer was applied so that the thickness after drying was 1 μm, and the adhesive layer 14 was laminated. On the adhesive layer 14, 100 parts of a phosphorus-containing polyurethane resin solution (Toyobo: UR3575), 2.4 parts of polyfunctional epoxy resin (Toyobo: HY-30), 4.7 parts of fumed silica (manufactured by Nippon Aerosil) : R972) were sequentially added and agitated, and the thermosetting adhesive was applied and dried so that the thickness after drying was 6 μm, and the thermosetting adhesive layer 13 was formed. Example 1 A coverlay film was obtained.

(Example 2)
A coverlay film of Example 2 was obtained in the same manner as in Example 1 except that non-conductive carbon black was mixed with the thermosetting adhesive to form the thermosetting adhesive layer 13.

(Example 3)
The adhesive layer 14 is formed without adding non-conductive carbon black to the coating liquid for forming the adhesive layer 14, and the non-conductive carbon black is added to the solvent-soluble polyimide coating liquid to form the substrate 12. A coverlay film of Example 3 was obtained in the same manner as Example 1 except that was formed.

Example 4
A non-conductive carbon black is added to a solvent-soluble polyimide coating solution having a tensile elongation of 120% after drying to form the base material 12, the adhesive layer 14 is omitted, and heat is directly applied on the base material 12. A coverlay film of Example 4 was obtained in the same manner as Example 1 except that the curable adhesive layer 13 was formed.

(Comparative Example 1)
The support film 11 is not used, and a polyimide film made of a thermosetting polyimide (no Tg) having a thickness of 10 μm is used as the base material 12, and a thermosetting adhesive is mixed with non-conductive carbon black in a thermosetting adhesive. A coverlay film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the layer 13 was formed.

(Comparative Example 2)
Without using the support film 11, a polyimide film made of thermosetting polyimide (without Tg) having a thickness of 12.5 μm is used as the base material 12, and non-conductive carbon black is mixed with the thermosetting adhesive and thermosetting. A coverlay film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the adhesive layer 13 was formed.

(Example 5)
Except that the base material 12 was formed using a solvent-soluble polyimide coating solution having an elastic modulus of 3.2 GPa and the thermosetting adhesive layer 13 was formed using a polyurethane resin not containing phosphorus, the same as in Example 1. Thus, a coverlay film of Example 5 was obtained.

(Example 6)
The base material 12 is formed using a solvent-soluble polyimide coating solution having a tensile elongation of 120% and an elastic modulus of 9.1 GPa after drying, and non-conductive carbon is used as a coating solution for forming the adhesive layer 14. A coverlay film of Example 6 was obtained in the same manner as in Example 1 except that the adhesive layer 14 was formed without adding black.

(Followability evaluation method)
The thermosetting adhesive surface of the coverlay film is overlaid on a test pattern in which a copper wiring pattern having a thickness of 75 μm and L / S = 75 μm / 75 μm is formed on a polyimide film having a thickness of 12.5 μm, temperature 140 ° C., speed 1 m Lamination was performed by thermal lamination at a rate of / min. After peeling off the support film 11, it was hot-pressed under the conditions of 160 ° C., 4.5 MPa, 65 minutes to obtain a follow-up evaluation sample. A cross section of the obtained sample was observed, and “◯” was given when the wiring pattern was followed, and “X” was given when the sample was floating from the wiring pattern without following it.

(Evaluation method of concealment)
The obtained coverlay film is hot-pressed on the test pattern (see the followability evaluation method) on which the above copper wiring pattern is formed by the above method (see the followability evaluation method), and a concealment evaluation sample is obtained. Obtained. If the difference in concealment between the polyimide part and the copper wiring part (especially the end part) of the obtained sample is not observed, “○”, a part of the copper wiring end part is seen through and the difference is seen “Δ” when the phenomenon occurred, “×” when the difference was seen through most of the copper wiring end. Further, Example 6 in which no layer contains a light absorbing material was not evaluated.

(Flame retardancy evaluation method)
The obtained cover lay film was hot-pressed on a polyimide film having a thickness of 12.5 μm by the above-described method (see the follow-up evaluation method) to obtain a sample for evaluation of flame retardancy. The flame retardancy was evaluated according to the method of UL-94 Thin Material Vertical Combustion Test (ASTM D4804). When the flame retardancy was equivalent to VTM-0, “◯”, when not flame retardancy (VTM-2) Non-conformity) was set to “x”.

(Handling evaluation method)
When the obtained coverlay film is sampled to 50cm square and superimposed on a flexible printed wiring board, the case where it can be quickly aligned and handled well is marked as "O" and twisted or wrinkled. The case where it took time for alignment and was inferior in handleability was defined as “x”.

(Method for evaluating heat resistance)
The obtained coverlay film was hot-pressed on a polyimide film having a thickness of 25 μm by the above-described method (see the follow-up evaluation method) to obtain a sample for heat resistance evaluation. A test piece was cut to a size of 2.5 cm × 3 cm, dipped in a solder bath at 290 ° C. for 10 seconds, and then pulled up. Observe the appearance of the coverlay film after immersion in the solder bath visually for abnormalities such as floating, deformation, and shrinkage. "

(Measurement method of tensile elongation)
The tensile elongation of the laminate was measured based on IPC-TM-650 2.4.19, with a sample size of 15 mm wide, a chuck-to-chuck distance of 100 mm, and a measurement speed of 50 mm / min (measured with the number of samples N = 5). And took the average value). The tensile elongation of the coverlay film (laminate) excluding the support film was measured using the laminate excluding the support film as a sample.
The tensile elongation of the base material is a sample of the base material obtained by applying a solvent-soluble polyimide coating solution on one side of a release film similar to the support film, and peeling and removing the release film after drying. It measured by the method of JIS-K-7127.

(Test results)
About Examples 1-6 and Comparative Examples 1-2, a cover-lay film was evaluated by said evaluation method, and the obtained evaluation result was shown to Tables 1-2. In the column of the material of the heat-adhesive adhesive layer, “PU1” means the heat-adhesive adhesive containing the flame-retardant polyurethane used in Example 1, and “PU2” is the polyurethane used in Example 5. Means a heat-adhesive adhesive containing “None” written in the thickness column means that the layer is not provided.

According to the evaluation results shown in Tables 1 and 2, it can be seen that when the tensile elongation of the substrate 12 is 100% or more, the followability and heat resistance are improved. That is, when the tensile elongation of the base material 12 is low, the followability with respect to the step is deteriorated, and an abnormality occurs when the heat resistance is evaluated.
Moreover, when the tensile elongation of a coverlay film (laminated body) except a support body film is 100% or more, it turns out that followable | trackability becomes favorable. That is, when the tensile elongation of the laminate was low, the followability to the step was deteriorated.
Furthermore, according to Examples 1-4 and 6, by blending a flame retardant with the thermosetting adhesive layer 13, good flame retardancy is ensured without blending a flame retardant with the substrate 12. I was able to.
In addition, according to Examples 1 to 6, the support film increases the thickness, improves the handleability when being bonded to the flexible wiring board, and can remove the support film 11 before or after hot pressing. It has become possible to improve work efficiency and make it thinner.
Moreover, according to Examples 1-5, light-shielding property and design property are improved effectively by including a light-absorbing material in at least any one of a base material, an adhesive layer of a thin film, and a thermosetting adhesive layer. I was able to.

  The cover lay film of the present invention can be used as a protective member for FPC in various electronic devices such as mobile phones, notebook computers, and mobile terminals.

DESCRIPTION OF SYMBOLS 10,15,16,20 ... Cover-lay film, 11 ... Support film, 12 ... Base material, 13, 14 ... Adhesive layer, 19 ... Release film.

Claims (12)

  A base material composed of a coated dielectric thin film resin layer and a thermosetting adhesive layer are sequentially laminated on one side of the support film, and the base material is pulled by the method of JIS-K-7127. A coverlay film having an elongation of 100% or more.   On one side of the support film, a base material composed of a coated dielectric thin film resin layer, a thin film adhesive layer, and a thermosetting adhesive layer are sequentially laminated. A coverlay film having a tensile elongation of 100% or more according to the method of -7127.   On the one side of the support film, a base material composed of a coated dielectric thin film resin layer, a thermosetting adhesive layer, are sequentially laminated, and the base material excluding the support film, A coverlay film, wherein the laminate comprising a thermosetting adhesive layer has a tensile elongation of 100% or more.   On one side of the support film, a base material composed of a coated dielectric thin film resin layer, a thin film adhesive layer, and a thermosetting adhesive layer were sequentially laminated, and the support film was removed. A cover lay film, wherein the laminate comprising the substrate, the thin film adhesive layer, and the thermosetting adhesive layer has a tensile elongation of 100% or more.   5. The coverlay film according to claim 1, wherein a light absorber is contained in at least one of the base material, the thin film adhesive layer, and the thermosetting adhesive layer.   The coverlay film according to any one of claims 1 to 5, wherein the substrate is made of an insulating layer formed using a solvent-soluble polyimide and has a thickness of 1 to 9 µm.   One or more black pigments 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, or colored pigment 1 The coverlay film according to any one of claims 1 to 6, further comprising a light absorbing material composed of seeds or more.   The thin film adhesive layer is one or more black pigments selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, manganese oxide, or colored The coverlay film according to claim 2 or 4, further comprising a light absorbing material composed of one or more pigments.   9. The flame retardant thermosetting adhesive according to claim 1, wherein the thermosetting adhesive layer comprises a flame retardant phosphorus-containing polyurethane resin and an epoxy resin. The coverlay film as described.   The thermosetting adhesive layer is one or more black pigments selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, manganese oxide, or The coverlay film according to any one of claims 1 to 9, further comprising a light absorbing material composed of one or more colored pigments.   A mobile phone in which the coverlay film according to any one of claims 1 to 10 is used as an FPC protection member.   An electronic device in which the coverlay film according to any one of claims 1 to 10 is used as a member for FPC protection.

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