JP2015150813A - Protective film for distributing board, coverlay and printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film for a distributing board, which has a high optical reflectance, and the optical reflectance of which hardly lowers.SOLUTION: The protective film for a distributing board includes: a transparent fluororesin layer containing a fluororesin as a main component; and a reflective layer laminated on the rear surface of the fluororesin layer directly or through a transparent adhesive layer. The fluororesin layer has on the rear surface, a modified layer containing a siloxane bond and a hydrophilic organic functional group. A light transmittance to light having a wavelength of 600 nm of the fluororesin layer is preferably 60% or more. The reflective layer may contain a metal film or a white pigment and a binder thereof. A contact angle with pure water of the rear surface of the fluororesin layer is preferably 90° or less. An average thickness of the modified layer is preferably 400 nm or less. The hydrophilic organic functional group is preferably a hydroxyl group, a carboxyl group, a carbonyl group, an amino group, an amido group, a sulfide group, a sulfonyl group, a sulfo group, a sulfonyl dioxin group, an epoxy group, a methacrylic group or a mercapto group.

Description

  The present invention relates to a protective film for a wiring board, a coverlay, and a printed wiring board.

  In recent years, the use efficiency of light generated by light-emitting diodes has been further improved due to the expansion of the range of use of light-emitting diodes (LEDs) such as lighting devices. Since light emitting diodes are often used in a state where they are mounted on a printed wiring board, the light utilization rate can be improved by reflecting light emitted from the light emitting diodes toward the printed wiring board. Therefore, a technique is known in which light emitted from a light emitting diode mounted on a printed wiring board is diffusely reflected by laminating a white film containing a white pigment and a resin binder on the surface of the printed wiring board.

  However, when such a white film is used, the resin binder may be discolored due to oxidation and moisture absorption of the resin binder, and the light reflectance may be reduced. On the other hand, it has also been proposed to use a fluororesin or the like as the resin binder of the white film to reduce the light reflectivity associated with the discoloration of the white film by lowering the oxidizability and water absorption (special feature). (See JP 2013-38384).

JP 2013-38384 A

  However, when a hydrophobic resin binder is used as disclosed in the above publication, it is not easy to uniformly disperse the pigment in the binder, so it is easy to increase the light reflectance of the white film to 90% or more. is not.

  The present invention has been made based on the above-described circumstances, and has a high light reflectivity and a low light reflectivity, and a protective film for a wiring board, and a coverlay using the protective film for a wiring board. It is another object of the present invention to provide a printed wiring board.

  The invention made in order to solve the above problems comprises a transparent fluororesin layer mainly composed of a fluororesin, and a reflective layer laminated on the back surface of the fluororesin layer directly or via a transparent adhesive layer. And a protective film for a wiring board, wherein the fluororesin layer has a modified layer containing a siloxane bond and a hydrophilic organic functional group on the back surface.

  The protective film for a wiring board of the present invention has a high light reflectivity, and the light reflectivity is hardly lowered.

It is typical sectional drawing which shows the protective film for wiring boards of one Embodiment of this invention. It is typical sectional drawing which shows the protective film for wiring boards of embodiment different from FIG. It is typical sectional drawing which shows the protective film for wiring boards of embodiment different from FIG.1 and FIG.2. It is typical sectional drawing which shows the protective film for wiring boards of embodiment different from FIG.1, FIG.2 and FIG.3. It is typical sectional drawing which shows a printed wiring board provided with the protective film for wiring boards of FIG.

  The present invention comprises a transparent fluororesin layer mainly composed of a fluororesin and a reflective layer laminated directly or via a transparent adhesive layer on the backside of the fluororesin layer, the fluororesin layer being on the backside And a protective film for a wiring board having a modified layer containing a siloxane bond and a hydrophilic organic functional group.

  Since the protective film for a wiring board is provided with the hydrophobic fluororesin layer on the surface as described above, moisture absorption of the reflective layer can be prevented, and thus a decrease in light reflectance of the light reflective layer is suppressed. For this reason, a structure with higher light reflectance can be adopted as the light reflecting layer. Moreover, since the fluororesin layer has high transparency, a high light reflectance can be obtained as the whole protective film for wiring boards. In addition, since the fluororesin layer itself is less likely to be discolored due to oxidation, ultraviolet absorption, moisture absorption, or the like, the protective film for a wiring board is unlikely to have low light reflectance. In addition, since the protective film for a wiring board has a modified layer containing a hydrophilic organic functional group, the fluororesin layer has excellent adhesion between the fluororesin layer and the reflective layer or the adhesive layer. Since dirt hardly adheres to the surface of the resin layer, it is possible to suppress a decrease in light reflectance due to the dirt. Furthermore, since the protective film for a wiring board has a two-layer structure of a fluororesin layer and a reflective layer, reflection at the interface between the fluororesin layer and the reflective layer can also be obtained. As a result, the protective film for wiring boards has a high light reflectivity, and the light reflectivity is unlikely to decrease.

  The light transmittance of the fluororesin layer with respect to light having a wavelength of 600 nm is preferably 60% or more. Thus, by setting the light transmittance of the fluororesin layer to light having a wavelength of 600 nm to be equal to or higher than the lower limit, light absorption in the fluororesin layer is reduced, and thus the light reflectance can be further increased.

  The reflective layer may be a metal film. As described above, when the reflective layer is a metal film, a mirror surface with high light reflectance can be formed. Moreover, since this mirror surface is protected by the fluororesin layer, high light reflectance can be maintained.

  The reflective layer may include a white pigment and a binder thereof. By forming the reflective layer as a light diffusing layer containing a white pigment and a binder in this way, a high light reflectance can be obtained, and a high light reflectance can be maintained by protecting the reflective layer with a fluororesin layer. it can.

  The contact angle with the pure water on the back surface of the fluororesin layer is preferably 90 ° or less. Thus, when the contact angle with the pure water on the back surface of the fluororesin layer is less than or equal to the above upper limit, the adhesiveness between the fluororesin layer and the reflective layer is high, and it is possible to prevent a decrease in light reflectivity due to delamination of these layers. Therefore, the light reflectance can be increased, and the decrease in the light reflectance can also be prevented.

  The average thickness of the modified layer is preferably 400 nm or less. Thus, by setting the average thickness of the modified layer to be equal to or less than the above upper limit, the light reflectance can be increased by thinning the modified layer that may lower the light transmittance.

  The average surface roughness Ra of the back surface of the fluororesin layer is preferably 4 μm or less. Thus, by making average surface roughness Ra of a modification layer below the said upper limit, the adhesiveness of a fluororesin layer and a reflection layer can be improved more and a reflectance can be made high. In addition, since the average surface roughness Ra is small in this way, a thin modified layer can be formed on the entire back surface of the fluororesin layer, and the light reflectance can be increased by suppressing irregular reflection at the interface. Furthermore, the back surface of the modified layer having high adhesion can be reduced in surface roughness in this way, and it is not necessary to roughen the surface for laminating the reflective layer.

  As the hydrophilic organic functional group, a hydroxyl group, carboxy group, carbonyl group, amino group, amide group, sulfide group, sulfonyl group, sulfo group, sulfonyldioxy group, epoxy group, methacryl group or mercapto group is preferable. Thus, by making a hydrophilic organic functional group into the above thing, the adhesiveness with respect to the reflection layer of the back surface of a fluororesin layer can further be improved.

  Moreover, this invention includes a coverlay provided with the said protective film for wiring boards, and the adhesive bond layer laminated | stacked on the back surface of this protective film for wiring boards. The cover lay has a high light reflectance by providing the protective film for the wiring board on the front surface, and can be easily attached to the wiring board by providing the adhesive layer on the back surface. For this reason, the coverlay can be used to increase the light reflectivity of the wiring board and increase the light utilization rate.

  The present invention also includes a resin base film, a wiring board laminated on the surface side of the base film and having a conductive layer including a conductive pattern, a light emitting diode mounted on the wiring board, and the wiring board. A printed wiring board provided with the said protective film for wiring boards laminated | stacked other than the said light emitting diode mounting area | region among surface side is included. In the printed wiring board, the wiring board protective film emits light emitted from the light emitting diode by laminating the wiring board protective film having a high light reflectivity in a region other than the light emitting diode mounting region of the wiring board. The light utilization efficiency is high.

  Here, the “main component” is a component having the highest content, for example, a component having a content of 50% by mass or more. “Hydrophilic organic functional group” refers to a functional group composed of only a nonmetallic element such as a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom and having a hydrophilic property. The “light transmittance with respect to light having a wavelength of 600 nm” is a value obtained by measuring the transmittance of light having a wavelength of 600 nm in accordance with the total light transmittance measuring method of JIS-K-7375 (2008). The “contact angle with pure water” is a value of a contact angle measured by a JIS-R-3257 (1999) sessile drop method. “Average surface roughness Ra” means arithmetic average roughness measured according to JIS-B-0601 (2013). In addition, “front” and “back” mean the direction in which the side laminated on the wiring board is the front side and the opposite side is the back side in the thickness direction of the protective film for the wiring board. It does not mean the front and back of the protective film, the coverlay or the printed wiring board in use. Furthermore, “chemical bond” as used herein is a concept including hydrogen bonds.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First embodiment]
The protective film 1 for a wiring board shown in FIG. 1 includes a transparent fluororesin layer 2 and a reflective layer 3 laminated on the back surface of the fluororesin layer 2.

<Fluorine resin layer>
The fluororesin layer 2 has a modified layer 4 containing a fluororesin as a main component and including a siloxane bond and a hydrophilic organic functional group on the back surface.

  Here, the fluororesin is an organic group in which at least one hydrogen atom bonded to the carbon atom constituting the repeating unit of the polymer chain has a fluorine atom or a fluorine atom (hereinafter also referred to as “fluorine atom-containing group”). Refers to the substituted one. The fluorine atom-containing group is a group in which at least one hydrogen atom in a linear or branched organic group is substituted with a fluorine atom, and examples thereof include a fluoroalkyl group, a fluoroalkoxy group, and a fluoropolyether group. .

  The “fluoroalkyl group” means an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkyl group”. Specifically, a “fluoroalkyl group” is a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkyl group are substituted with fluorine atoms. Group.

  The “fluoroalkoxy group” means an alkoxy group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkoxy group”. Specifically, a “fluoroalkoxy group” is a group in which all hydrogen atoms of an alkoxy group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkoxy group are substituted with fluorine atoms. Group.

  The “fluoropolyether group” is a monovalent group having an oxyalkylene unit as a repeating unit and having an alkyl group or a hydrogen atom at the terminal, and at least one hydrogen of the alkylene oxide chain or the terminal alkyl group A monovalent group in which an atom is substituted with a fluorine atom. The “fluoropolyether group” includes a “perfluoropolyether group” having a plurality of perfluoroalkylene oxide chains as repeating units.

  Examples of the fluororesin constituting the fluororesin layer 2 include polytetrafluoroethylene (PTFE), polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). , Tetrafluoroethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinyl fluoride (PVF), In addition, a thermoplastic fluororesin (THV) composed of three types of monomers such as tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and fluoroelastomer may be mentioned. Further, a mixture or copolymer containing these compounds can also be used as a material constituting the fluororesin layer 2.

  Among these, as the fluororesin constituting the fluororesin layer 2, tetrafluoroethylene / hexaoropropylene copolymer (FEP), polytetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), or polytetrafluoroethylene ( PTFE) is preferred. By using these fluororesins, the fluororesin layer 2 has flexibility, light transmittance, heat resistance, and flame retardancy.

  Moreover, the fluororesin layer 2 can contain, for example, engineering plastics, flame retardants, flame retardant aids, antioxidants, lubricants, processing stabilizers, plasticizers, reinforcing materials and the like as optional components. Further, by irradiating the fluororesin with electromagnetic radiation such as radiation, the transparency, heat resistance, creep resistance, adhesion to the reflective layer 3, fluidity during molding, and the like of the fluororesin layer 2 can be improved.

  As said engineering plastic, it can select and use from a well-known thing according to the characteristic calculated | required by the fluororesin layer 2, Typically, aromatic polyether ketone can be used.

  This aromatic polyetherketone has a structure in which the benzene rings are bonded to the para position and the benzene rings are connected to each other by a rigid ketone bond (—C (═O) —) or a flexible ether bond (—O—). It is a thermoplastic resin. As the aromatic polyether ketone, for example, ether ether ketone (PEEK) having a structural unit in which an ether bond, a benzene ring, an ether bond, a benzene ring, a ketone bond and a benzene ring are arranged in this order, an ether bond, a benzene ring, Examples include polyether ketone (PEK) having a structural unit in which a ketone bond and a benzene ring are arranged in this order. Among them, PEEK is preferable as the aromatic polyether ketone. Such an aromatic polyether ketone is excellent in wear resistance, heat resistance, insulation, workability and the like.

  A commercially available product can be used as the aromatic polyether ketone such as PEEK. As aromatic polyether ketones, those of various grades are commercially available, and a single grade of aromatic polyether ketone that is commercially available may be used alone, or multiple grades of aromatic polyether ketone. A ketone may be used in combination, or a modified aromatic polyether ketone may be used.

  The lower limit of the ratio of the total engineering plastic content in the fluororesin layer 2 to the fluororesin is not particularly limited, but is preferably 10% by mass, more preferably 20% by mass, and even more preferably 35% by mass. When the total content of the engineering plastic is less than the above lower limit, the characteristics of the fluororesin layer 2 may not be sufficiently improved. On the other hand, the upper limit of the ratio of the total content of engineering plastics to the fluororesin is not particularly limited, but is preferably 50% by mass and more preferably 45% by mass. When the content of the engineering plastic exceeds the above upper limit, the advantageous characteristics of the fluororesin may not be sufficiently exhibited.

  Various known flame retardants can be used, and examples thereof include halogen flame retardants such as bromine flame retardants and chlorine flame retardants.

  Various known flame retardant aids can be used, and examples include antimony trioxide.

  Various known antioxidants can be used as the antioxidant, and examples thereof include phenolic antioxidants.

  Examples of the reinforcing material include carbon fibers, glass fibers, aramid fibers, alumina fibers, and the like, and twisted yarns and cloths formed from these, such as glass cloths, may be used.

  The lower limit of the average thickness of the fluororesin layer 2 is preferably 0.1 μm, and more preferably 6 μm. When the average thickness of the fluororesin layer 2 is less than the above lower limit, the strength of the protective film 1 for wiring boards may be insufficient. On the other hand, the upper limit of the average thickness of the fluororesin layer 2 is preferably 5000 μm, and more preferably 55 μm. When the average thickness of the fluororesin layer 2 exceeds the above upper limit, the light transmittance of the fluororesin layer 2 and thus the light reflectivity of the wiring board protective film 1 may be insufficient, or the wiring board protective film. The flexibility of 1 may be insufficient.

  Moreover, as a minimum of the light transmittance with respect to the light of wavelength 600nm of the fluororesin layer 2, 60% is preferable and 90% is more preferable. When the light transmittance with respect to the said wavelength is less than the said minimum, there exists a possibility that the light reflectance of the said protective film 1 for wiring boards may become inadequate because the fluororesin layer 2 absorbs light. In addition, although it does not specifically limit as an upper limit of the light transmittance with respect to the said wavelength of the fluororesin layer 2, A theoretical limit value is 100%. The light transmittance can be measured using a spectrophotometer, for example, “U-4100” manufactured by Hitachi High-Technologies Corporation.

The upper limit of the water vapor permeability of the fluororesin layer 2 is preferably 0.1 g / m ² · 24h. When the water vapor permeability of the fluororesin layer 2 exceeds the above upper limit, there is a possibility that a decrease in light reflectance due to moisture absorption of the reflective layer 3 cannot be sufficiently suppressed. The water vapor permeability is a value measured under conditions of a temperature of 25 ° C. and a relative humidity difference of 90% in accordance with JIS-K-7129 (2008) Appendix A.

  Moreover, as an upper limit of the water absorption rate of the fluororesin layer 2, 0.01 mass% is preferable. When the water absorption rate of the fluororesin layer 2 exceeds the above upper limit, there is a possibility that a decrease in light reflectance due to moisture absorption of the reflective layer 3 cannot be sufficiently suppressed. In addition, a water absorption is a value measured based on JIS-K-7209 (2000).

  The modifying layer 4 is formed by bonding a modifying agent having a hydrophilic organic functional group and forming a siloxane bond (Si—O—Si) to the fluororesin constituting the fluororesin layer 2. That is, in the modified layer 4, the hydrophilic organic functional group is bonded to Si atoms constituting the siloxane bond. This hydrophilic organic functional group imparts wettability to the back surface of the fluororesin layer 2. The chemical bond between the fluororesin and the modifier may be composed of only a covalent bond or may include a covalent bond and a hydrogen bond. The modified layer 4 is a region that is considered to have a different microstructure, molecular structure, and ratio of elements to other regions of the fluororesin layer 2 excluding the modified layer 4.

The Si atom constituting the siloxane bond (hereinafter, this atom is referred to as “Si atom of siloxane bond”) is bonded to the fluororesin layer via at least one of N atom, C atom, O atom, and S atom. It is covalently bonded to two C atoms. For example, Si atoms of the siloxane _{bond, -O -, - S -,} - S-S -, - (CH 2) n -, - NH -, - (CH 2) n-NH -, - (CH 2) _{n-O- (CH 2) m-} (n, m is 1 or more is an integer.) binds to the C atom of fluorine resin through an atomic group, and the like.

  The hydrophilic organic functional group is preferably a hydroxyl group, carboxy group, carbonyl group, amino group, amide group, sulfide group, sulfonyl group, sulfo group, sulfonyldioxy group, epoxy group, methacryl group, or mercapto group. Among these, those containing N atoms or S atoms are more preferable. These hydrophilic organic functional groups improve the adhesion of the back surface of the fluororesin layer 2. The modified layer 4 may contain two or more of these hydrophilic organic functional groups. Thus, by imparting hydrophilic organic functional groups having different properties to the modified layer 4, the reactivity of the back surface of the fluororesin layer 2 can be varied. These hydrophilic organic functional groups are bonded to Si atoms, which are constituents of siloxane bonds, directly or via one or more C atoms (for example, a methylene group or a phenylene group).

  As the modifier for forming the modified layer 4 having the above characteristics, a silane coupling agent having a hydrophilic organic functional group in the molecule is preferable, and a hydrolyzable functional group containing Si atoms. A silane coupling agent having a group is more preferable. Such a silane coupling agent is chemically bonded to the fluororesin constituting the fluororesin layer 2.

  The hydrolyzable functional group containing the Si atom is specifically a group in which an alkoxy group is bonded to the Si atom. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, and a pentyloxy group.

  Examples of the hydrophilic organic functional group containing an N atom include an amino group and a ureido group.

  Examples of the silane coupling agent having a hydrophilic organic functional group containing an N atom include aminoalkoxysilane, ureidoalkoxysilane, and the like, and derivatives thereof.

  Examples of the aminoalkoxysilane include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and N- (2-aminoethyl) -3. -Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane and the like.

  Examples of aminoalkoxysilane derivatives include ketimines such as 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, and N-vinylbenzyl-2-aminoethyl-3-aminopropyltrimethoxysilane acetic acid. Examples thereof include salts of silane coupling agents such as salts.

  Examples of the ureidoalkoxysilane include 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, N- (2-ureidoethyl) -3-aminopropyltrimethoxysilane, and the like.

  Examples of the hydrophilic organic functional group containing an S atom include a mercapto group and a sulfide group.

  Examples of the silane coupling agent having a hydrophilic organic functional group containing an S atom include mercaptoalkoxysilane, sulfide alkoxysilane, and derivatives thereof.

  Examples of mercaptoalkoxysilanes include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyl (dimethoxy) methylsilane.

  Examples of the sulfide alkoxysilane include bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide.

  The silane coupling agent may be one having a modified group introduced. As the modifying group, a phenyl group is preferable.

  Examples of the silane coupling agent include 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and bis. (3-Triethoxysilylpropyl) tetrasulfide is preferred.

  As the modifier, other coupling agents can be used in addition to the silane coupling agent. Any other coupling agent may be used as long as it has reactivity with the fluororesin of the fluororesin layer 2 or its radical, and for example, a titanium coupling agent can be used.

  Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tristearoyl titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri ( Dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phos) Fight) Titanate, Tetra (2 2-diallyloxymethyl-1-butyl) bis (ditridecylphosphite) titanate, dicumylphenyloxyacetate titanate, bis (dioctylpyrophosphate) oxyacetate titanate, diisostearoylethylene titanate, bis (dioctylpyrophosphate) ethylene titanate Bis (dioctylpyrophosphate) diisopropyl titanate, tetramethyl orthotitanate, tetraethyl orthotitanate, tetrapropyl orthotitanate, tetraisopropyl tetraethyl orthotitanate, tetrabutyl orthotitanate, butyl polytitanate, tetraisobutyl orthotitanate, 2-ethylhexyl titanate, stearyl Titanate, cresyl titanate monomer, cresyl tita Polymers, diisopropoxy-bis (2,4-pentadionate) titanium (IV), diisopropyl-bis (triethanolamino) titanate, octylene glycol titanate, titanium lactate, acetoacetic estiltitanate, diisopropoxybis (Acetylacetonato) titanium, di-n-butoxybis (triethanolaminato) titanium, dihydroxybis (lactato) titanium, titanium-isopropoxyoctylene glycolate, tetra-n-butoxytitanium polymer, tri-n-butoxytitanium Monostearate polymer, butyl titanate dimer, titanium acetylacetonate, poly (titanium acetylacetonate), titanium octylene glycolate, titanium lactate ammonium salt, titanium Examples include lactate ethyl ester, titanium triethanolamate, and polyhydroxytitanium stearate.

  The upper limit of the contact angle with respect to pure water on the back surface of the modified layer 4 is preferably 90 °, and more preferably 80 °. When the contact angle with respect to the pure water on the back surface of the modified layer 4 exceeds the above upper limit, the adhesive strength with the reflective layer 3 becomes insufficient, and delamination occurs, thereby reducing the light reflectivity of the protective film 1 for wiring boards. There is a risk. On the other hand, the lower limit of the contact angle with respect to pure water on the back surface of the modified layer 4 is not particularly limited. The contact angle with respect to pure water can be measured using a contact angle measuring instrument “GI-1000” manufactured by ERMA.

  The lower limit of the wetting tension on the back surface of the fluororesin layer 2 is preferably 50 mN / m, more preferably 60 mN / m. If the wetting tension is less than the above lower limit, the adhesion is insufficient and the reflective layer 3 may be peeled off. The lower limit of the wetting tension is larger than the wetting tension of pure polytetrafluoroethylene (PTFE). That is, by forming the modified layer 4 on the back surface of the fluororesin layer 2, the adhesion of the back surface becomes higher than that of a normal fluororesin. The “wetting tension” is a value measured according to JIS-K-6768 (1999).

The modified layer 4 preferably has the following etching resistance. That includes iron chloride, density 1.31 g / cm ³ or more 1.33 g / cm ³ or less, free hydrochloric acid concentration of 0.1 mol / L or more 0.2 mol / L or less, the etching solution temperature of 45 ° C. or less It is preferable that the modified layer 4 is not removed with respect to the etching treatment in which the immersion is performed for 1 minute or more and 2 minutes or less. Here, that the modified layer 4 is not removed means that the hydrophilicity of the back surface of the fluororesin layer 2 is not lost. For example, the contact angle of the back surface of the fluororesin layer 2 with pure water does not exceed 90 °. Show. In some cases, the etching process may cause a small portion of hydrophobicity to appear in the region where the modified layer 4 is formed. However, if the entire region has hydrophilicity, such a state may be hydrophilic. It is assumed that sex is maintained.

  Although it does not specifically limit as a minimum of the average thickness of the modification layer 4, 1 nm is preferable and 10 nm is more preferable. When the average thickness of the modified layer 4 is less than the above lower limit, the entire surface of the fluororesin layer 2 cannot be sufficiently modified, and peeling of the reflective layer 3 may not be prevented. On the other hand, the upper limit of the average thickness of the modified layer 4 is preferably 400 nm, and more preferably 100 nm. When the average thickness of the modified layer 4 exceeds the above upper limit, the light transmittance can be lower than that of the region where the modified layer 4 of the fluororesin layer 2 is not modified. There is a possibility that the light reflectivity of the liquid crystal becomes insufficient. The average thickness of the modified layer can be measured using an optical interference type film thickness measuring instrument, an X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy) analyzer, an electron microscope, or the like.

  The upper limit of the average surface roughness Ra on the back surface of the modified layer 4 is preferably 4 μm and more preferably 1 μm. When the average surface roughness Ra of the back surface of the modified layer 4 exceeds the above upper limit, it may be difficult to adhere the reflective layer 3 in close contact with the fluororesin layer 2 or the entire back surface of the fluororesin layer 2 may be cut off. If the modified layer 4 is not formed, the thickness of the modified layer 4 that may lower the light transmittance may be increased. Therefore, the light reflectance of the protective film 1 for a wiring board may be insufficient. Further, when the back surface of the modified layer 4 is roughened so that the average surface roughness Ra exceeds the upper limit, the production cost may be excessive. On the other hand, the lower limit of the average surface roughness Ra on the back surface of the modified layer 4 is not particularly limited.

<Reflective layer>
The reflective layer 3 is composed of a metal film laminated on the back surface of the fluororesin layer 2, that is, the modified layer 4. The reflective layer 3 is a layer that specularly reflects light incident through the fluororesin layer 2. The reflective layer 3 can be composed of a metal foil.

  Examples of the metal constituting the reflective layer 3 include silver, aluminum, aluminum alloy, gold, palladium, rhodium, and SUS. The material of the reflective layer 3 is preferably selected from a metal having a high light reflectivity according to the wavelength emitted by the light source disposed on the wiring board using the wiring board protective film 1.

  The lower limit of the average thickness of the reflective layer 3 is preferably 0.01 μm, and more preferably 0.1 μm. When the average thickness of the reflective layer 3 is less than the lower limit, uniform film formation is not easy, and thus the entire surface of the fluororesin layer 2 may not be covered. On the other hand, the upper limit of the average thickness of the reflective layer 3 is preferably 100 μm and more preferably 2 μm. When the average thickness of the reflective layer 3 exceeds the above upper limit, the flexibility of the wiring board protective film 1 may be insufficient.

  The lower limit of the total light reflectance on the surface of the reflective layer 3 (the surface on the fluororesin layer 2 side) is preferably 70%, more preferably 90%. When the surface total light reflectivity of the reflective layer 3 is less than the lower limit, the light reflectivity of the wiring board protective film 1 may be insufficient. The total light reflectance is a value measured in accordance with JIS-K-7375 (2008).

  Moreover, in order to improve the light reflectance of the protective film 1 for wiring boards, the metal foil constituting the reflective layer 3 is preferably laminated after the surface irregularities are reduced by electrolytic polishing or the like.

[Method for producing protective film for wiring board]
Next, a method for manufacturing the wiring board protective film 1 will be described.

  The wiring board protective film 1 can be manufactured by a manufacturing method including a modifier attaching step and a fluororesin laminating step.

<Modifier adhesion process>
The modifier adhering step includes a primer containing alcohol, water, and a modifier for modifying the fluororesin layer 2 to form the modified layer 4 on the surface of the metal foil forming the reflective layer 3. It is the process of attaching. The method for attaching the primer to the metal foil is not particularly limited, but for example, an immersion method, a spray method, a coating method, or the like can be adopted. Then, the primer alcohol is removed by drying. The alcohol can be removed by natural drying, drying by heating, drying by reduced pressure, or the like. In addition, you may perform this drying continuously in the press machine which performs the thermocompression bonding of the following lamination process. After drying, heating (for example, 120 ° C. for 15 minutes) is performed to form a Si—O—Si bond.

  As a minimum of content in the whole primer of a modifier, 0.1 mass% is preferred and 0.5 mass% is more preferred. When content of a modifier is less than the said minimum, there exists a possibility that the back surface of the fluororesin layer 2 cannot fully be modified. On the other hand, the upper limit of the content of the modifier is preferably 5% by mass, and more preferably 3% by mass. When the content of the modifier exceeds the above upper limit, the modifier is aggregated, and there is a possibility that a primer film having a uniform thickness cannot be formed on the surface of the metal foil.

  Although the amount of water in the primer is sufficient, it is an essential substance for the condensation of the modifier. As content in the whole primer of water, it can be 0.01 mass% or more and 0.1 mass% or less, for example.

<Fluorine resin lamination process>
The fluororesin laminating step is a step of laminating a fluororesin sheet constituting the fluororesin layer 2 on the surface of the reflective layer 3, that is, on the primer adhered in the modifier adhering step. The laminated body of the fluororesin layer 2 and the reflective layer 3 is thermocompression bonded by a press machine. In order to prevent bubbles or voids from being formed between the fluororesin layer 2 and the reflective layer 3, this thermocompression bonding is preferably performed under reduced pressure. By this thermocompression bonding, a chemical bond is formed through another atom between the C atom of the fluororesin and the Si—O—Si bond formed from the modifier. Moreover, in order to suppress the oxidation of the metal foil which comprises the reflection layer 3, it is preferable to perform thermocompression bonding under low oxygen conditions, such as in nitrogen atmosphere.

  As the lower limit of the thermocompression bonding temperature, the melting point of the fluororesin constituting the fluororesin layer 2 is preferable, and the decomposition start temperature of the fluororesin is more preferable. Further, the lower limit of the difference between the thermocompression bonding temperature and the melting point of the fluororesin is preferably 30 ° C, more preferably 50 ° C. When the thermocompression bonding temperature is lower than the above lower limit, the fluororesin is not activated and the reaction with the modifier may be insufficient. Further, by setting the thermocompression bonding temperature to be equal to or higher than the decomposition start temperature of the fluororesin, it is considered that a part of the fluororesin is more likely to be a radical and is further bonded to the modifier via other atoms. On the other hand, the upper limit of the thermocompression bonding temperature is preferably the decomposition temperature of the fluororesin. Here, the decomposition start temperature refers to the temperature at which the fluororesin begins to thermally decompose, and the decomposition temperature refers to the temperature at which the mass of the fluororesin decreases by 10% due to thermal decomposition. When the thermocompression bonding temperature exceeds the above upper limit, the fluororesin may be decomposed and the fluororesin layer 2 may be damaged.

  As an example, when the fluororesin constituting the fluororesin layer 2 is a tetrafluoroethylene / hexafluoropropylene copolymer (FEP), the melting point of the fluororesin is about 270 ° C. 300 degreeC is preferable and 320 degreeC is more preferable. On the other hand, the upper limit of the thermocompression bonding temperature at this time is preferably 600 ° C, and more preferably 500 ° C.

  The pressure during thermocompression bonding is preferably 0.01 MPa or more and 100 MPa or less. The pressurization time for thermocompression bonding is preferably 0.01 minutes or more and 1000 minutes or less. However, the thermocompression bonding pressure and the pressurizing time are not limited to these, and may be set in consideration of the reactivity of the modifier.

  By such thermocompression bonding, a Si—O—Si bond is formed from the modifier, and a part thereof is bonded to the fluororesin via another atom. These bonds are presumed to include covalent bonds because the modified layer 4 has the above-mentioned etching resistance. In addition, the modified layer 4 is composed of a polymer spread in a film shape, and a large number of hydrogen bonds are formed between the polymer and the fluorine tree, so there is a possibility that both are strongly bonded. The bond is presumed to include a hydrogen bond. On the other hand, since the Si—O—Si bond and the hydrophilic organic functional group exist in the vicinity of the surface of the metal foil, the metal foil is fixed to the surface of the fluororesin.

  Moreover, in this fluororesin lamination process, in addition to the above-mentioned pressure heating, other known radical generation methods such as electron beam irradiation may be used in combination. Examples of electron beam irradiation include γ-ray irradiation treatment. Since the radicals of the fluororesin can be generated more effectively by using electron beam irradiation or the like together, the reliability of adhesion between the fluororesin layer 2 and the metal foil forming the reflective layer 3 is further enhanced. be able to. Moreover, the electron beam irradiation is not necessarily performed in the bonding step, and may be performed at the same time when the fluororesin layer 2 is formed, for example, or may be performed after the bonding step.

[advantage]
Since the protective film 1 for a wiring board has a two-layer structure composed of a transparent fluororesin layer 2 and a reflective layer 3, the fluororesin layer 2 suppresses dirt on the surface and moisture absorption of the reflective layer 3, thereby reducing the light reflectance. Prevent decline. Specifically, since the fluororesin layer 2 is hydrophobic, it is difficult for dirt to adhere to the surface, and since the weather resistance is high, transparency can be maintained for a long time even in a high temperature and high humidity environment. Further, the hydrophobic fluororesin layer 2 has a high barrier property against moisture, so that the oxidation of the metal forming the reflective layer 3 is suppressed and the light reflectance of the reflective layer 3 is prevented from being lowered. Moreover, since the said protective film 1 for wiring boards forms the mirror surface which reflects light in the interface of the fluororesin layer 2 and the reflection layer 3, its light reflectance is high. Furthermore, the protective film 1 for wiring boards has a high bonding strength between the fluororesin layer 2 and the reflective layer 3 due to the hydrophilic modified layer 4 formed on the back surface of the fluororesin layer 2, and is due to delamination. A decrease in light reflectance can be prevented.

[Second Embodiment]
A protective film 11 for a wiring board in FIG. 2 includes a transparent fluororesin layer 2 mainly composed of a fluororesin, and a reflective layer 13 laminated on the back surface of the fluororesin layer 2. In the protective film 11 for wiring boards of FIG. 2, since the fluororesin layer 2 is the same as the fluororesin layer 2 of the protective film 1 for wiring boards of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

<Reflective layer>
The reflective layer 13 is composed of a metal thin film laminated on the back surface on which the modified layer 4 of the fluororesin layer 2 is formed. This reflective layer 13 is a layer that mirror-reflects the light incident through the fluororesin layer 2 in the same manner as the reflective layer 3 in FIG. 1, but vapor deposition, sputtering, plating, printing, coating, etc. on the back surface of the fluororesin layer 2 1 is different from the reflective layer 3 in FIG. As the metal constituting the reflective layer 13, the same as the reflective layer 3 in FIG. 1 or a composition comprising metal particles and a binder can be used.

  The lower limit of the average thickness of the reflective layer 13 is preferably 0.01 μm, and more preferably 0.1 μm. When the average thickness of the reflective layer 13 is less than the above lower limit, uniform film formation is not easy, and the entire back surface of the fluororesin layer 2 may not be covered. On the other hand, the upper limit of the average thickness of the reflective layer 13 is preferably 1 μm, and more preferably 0.5 μm. When the average thickness of the reflective layer 13 exceeds the upper limit, the wiring board protective film 11 may be unnecessarily expensive.

[Method for producing protective film for wiring board]
Next, a method for producing the wiring board protective film 11 will be described.

  The protective film 11 for a wiring board in FIG. 2 can be manufactured by a manufacturing method including a fluororesin modification step and a reflective layer lamination step.

<Fluorine resin modification process>
The fluororesin reforming step is a step of forming the reforming layer 4 by applying a reforming agent to the back surface of the resin film mainly composed of the fluororesin constituting the fluororesin layer 2 and performing heat treatment as necessary. is there. Na etching treatment, plasma treatment, sputtering treatment, plasma discharge treatment, corona discharge treatment, far-ultraviolet irradiation, excimer laser on the back side of the resin film in order to improve the modifier coating property and omit the heat treatment (radicalization) process Pretreatment such as irradiation may be performed.

  For example, in the Na etching treatment, a solution containing sodium is applied to the surface of the fluororesin, and F radicals on the surface of the fluororesin are extracted using the reducing power of Na to generate carbon radicals. It reacts with oxygen, hydrogen, water or the like to form functional groups such as hydroxyl group (—OH), carboxyl group (—COOH), carbonyl group (—C (═O) —). Thereby, the hydrolyzable functional group of the silane coupling agent can be easily bonded to the fluororesin.

<Reflective layer lamination process>
The reflective layer laminating step is a step of forming the reflective layer 13 by laminating a metal thin film on the back surface of the modified layer 4 formed on the fluororesin layer 2. Lamination of the metal thin film can be performed using a known film forming technique such as vapor deposition, sputtering, plating, printing, coating, and the like. In addition, when laminating the reflective layer 13 by printing or coating, a paste containing metal particles and a binder is used. By adding the modifier to the paste, the fluororesin modification step and the paste are added. The reflective layer stacking step can also be performed simultaneously.

[advantage]
In the protective film 11 for a wiring board, a reflective layer 13 that forms a mirror surface with high light reflectance can be laminated by using a known film forming technique. Since the surface of the reflective layer 13 is protected by the fluororesin layer 2, the light reflectance is not easily lowered.

[Third embodiment]
The protective film 21 for a wiring board in FIG. 3 includes a transparent fluororesin layer 2 mainly composed of a fluororesin and a reflective layer 23 laminated on the back surface of the fluororesin layer 2. 2, the fluororesin layer 2 is the same as the fluororesin layer 2 of the wiring board protective film 1 shown in FIG.

<Reflective layer>
The reflective layer 23 is a layer laminated on the back surface on which the modified layer 4 of the fluororesin layer 2 is formed, and includes a white pigment 25 and a binder 26 thereof. The reflective layer 23 is a layer that diffusely reflects light incident through the fluororesin layer 2.

(White pigment)
The white pigment 25 randomly refracts and diffuses light incident on the reflection layer 23 and finally emits the light from the reflection layer 23 toward the fluororesin layer 2 side. The material of the white pigment 25 is preferably a material having a high whiteness and a low light absorption rate. Specific examples include titanium oxide, barium sulfate, aluminum oxide, calcium carbonate, zinc oxide, and silicon oxide.

  The lower limit of the average particle size of the white pigment 25 is preferably 0.01 μm and more preferably 0.1 μm. When the average particle diameter of the white pigment 25 is less than the above lower limit, the white pigment 25 tends to aggregate and it may be difficult to uniformly disperse it in the binder 26. On the other hand, the upper limit of the average particle diameter of the white pigment 25 is preferably 50 μm and more preferably 10 μm. When the average particle diameter of the white pigment 25 exceeds the above upper limit, light cannot be sufficiently diffused, and there is a possibility that the white pigment 25 cannot be sufficiently emitted to the fluororesin layer 2 side.

  The lower limit of the light reflectance of the white pigment 25 at a wavelength of 600 nm and an incident angle of 82 ° is preferably 70%, and more preferably 90%. When the light reflectance of the white pigment 25 is less than the lower limit, the reflective layer 23 having sufficient light reflectance may not be formed. The “light reflectance” is measured using a spectrophotometer, for example, “U-4100” manufactured by Hitachi High-Technologies Corporation, with a barium sulfate standard white plate as a reference.

  As a minimum of content of white pigment 25 in reflective layer 23, 0.1 mass% is preferred and 1 mass% is more preferred. When the content of the white pigment 25 is less than the above lower limit, the light reflectance of the reflective layer 23 may be insufficient. On the other hand, as an upper limit of content of the white pigment 25 in the reflective layer 23, 90 mass% is preferable and 50 mass% is more preferable. When the content of the white pigment 25 exceeds the above upper limit, the strength of the reflective layer 23 may be insufficient due to a decrease in the content of the binder 26 described later.

(binder)
The binder 26 disperses and holds the white pigment 25. The binder 26 may be made of a material having a high light transmittance, and examples thereof include epoxy resins, phenol resins, polyesters, polyurethanes, acrylic resins, melamine resins, polyimides, polyamideimides, etc., one of these. Or 2 or more types can be used. Among these, a thermosetting resin that can improve the heat resistance of the reflective layer 23 is preferable, and an epoxy resin is particularly preferable.

  Examples of the epoxy resin used as the binder 26 include bisphenol A type, F type, S type, AD type, copolymerized type of bisphenol A type and bisphenol F type, naphthalene type, novolac type, biphenyl type, dicyclopentadiene type, and the like. And a phenoxy resin which is a polymer epoxy resin.

  The binder 26 can be used after being dissolved in a solvent. Examples of the solvent include ester-based, ether-based, ketone-based, ether-ester-based, alcohol-based, hydrocarbon-based, and amine-based organic solvents, and one or more of them can be used.

  Further, a curing agent can be added to the binder 26. Examples of the curing agent include amine curing agents, polyaminoamide curing agents, isocyanate curing agents, acid and acid anhydride curing agents, basic active hydrogen compounds, tertiary aminos, and imidazoles.

  In addition to the components described above, auxiliary agents such as thickeners and leveling agents can be added to the binder 26.

  The white pigment 25 can be evenly dispersed in the binder 26 by mixing the white pigment 25 and the binder 26 with, for example, a three-roller or a rotary stirring deaerator.

[Method for producing protective film for wiring board]
Next, a method for producing the wiring board protective film 21 will be described.

  The wiring board protective film 21 can be manufactured by a manufacturing method including a reflective layer forming step, a modifier attaching step, and a fluororesin laminating step. In this manufacturing method, the modifier adhering step and the fluororesin laminating step are the same as the modifier adhering step and the fluororesin laminating step in the method of manufacturing the wiring board protective film 1 in FIG. .

<Reflective layer forming step>
The reflective layer forming step is a step of forming the reflective layer 23 by forming a composition containing the white pigment 25 and the binder 26 into a sheet shape. Examples of the method for forming the composition into a sheet include a method of applying a paint containing the white pigment 25 and the binder 26 on the release sheet, a method of extruding a composition containing the white pigment 25 and the binder 26, and the like. There is.

[advantage]
The protective film 21 for a wiring board can achieve high light reflectivity because reflection at the interface between the fluororesin layer 2 and the reflective layer 3 is obtained in addition to diffuse reflection by the white pigment dispersed in the reflective layer 23. . Moreover, since the fluororesin layer 2 prevents discoloration due to moisture absorption of the reflective layer 23, the light reflectivity of the protective film 21 for wiring boards is unlikely to decrease.

[Fourth embodiment]
The protective film 31 for a wiring board in FIG. 4 includes a transparent fluororesin layer 2 mainly composed of a fluororesin, and a reflective layer 3 laminated on the back surface of the fluororesin layer 2 via a transparent adhesive layer 37. With. In the protective film 31 for wiring boards of FIG. 4, since the fluororesin layer 2 is the same as the fluororesin layer 2 of the protective film 1 for wiring boards of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The material of the adhesive layer 37 is not particularly limited, but is preferably excellent in flexibility and heat resistance. Examples of the adhesive include epoxy resin, polyimide, polyester, phenol resin, polyurethane, Various resin-based adhesives such as acrylic resin, melamine resin, polyamideimide, and high fluid fluororesin can be used.

  Moreover, as a minimum of the average thickness of the adhesive bond layer 37, 5 micrometers is preferable and 10 micrometers is more preferable. When the average thickness of the adhesive layer 37 is less than the above lower limit, the adhesive strength between the fluororesin layer 2 and the reflective layer 3 may be insufficient. On the other hand, the upper limit of the average thickness of the adhesive layer 37 is preferably 50 μm, and more preferably 40 μm. When the average thickness of the adhesive layer 37 exceeds the upper limit, the wiring board protective film 31 may be unnecessarily thick.

[Method for producing protective film for wiring board]
Next, a method for producing the wiring board protective film 31 will be described.

  The protective film 31 for a wiring board in FIG. 5 can be manufactured by a manufacturing method including a fluororesin reforming step, an adhesive layer laminating step, and a reflective layer pressing step. In this manufacturing method, the fluororesin laminating step is the same as the fluororesin laminating step in the method for manufacturing the wiring board protective film 11 in FIG.

<Adhesive layer lamination process>
In the adhesive layer laminating step, an adhesive having fluidity is applied to the back surface of the modified layer 4 formed on the fluororesin layer 2 or is placed on the back surface of the fluororesin layer 2 by placing a sheet-like adhesive on top of each other. The adhesive layer 37 is laminated.

<Adhesive layer lamination process>
In the reflective layer press-bonding step, a metal foil constituting the reflective layer 3 is disposed on the back surface of the adhesive layer 37 and bonded by thermocompression bonding. Thereby, the fluororesin layer 2, the adhesive layer 37, and the reflective layer 3 are integrated.

[advantage]
In the protective film 31 for the wiring board, the reflective layer 3 is laminated on the fluororesin layer 2 via the transparent adhesive layer 37. However, the modified layer 4 formed on the fluororesin layer 2 is composed of the fluororesin layer 2. The adhesive strength to the adhesive layer 37 is improved. Therefore, the protective film 31 for the fluororesin layer wiring board in FIG. 4 also covers the reflective layer 3 with the fluororesin layer 2 and suppresses the moisture absorption of the reflective layer 3, similarly to the protective film 1 for the wiring board in FIG. 1. Accordingly, it is possible to prevent the reflectance of the reflective layer 3 from being lowered.

[Printed wiring board]
The printed wiring board of FIG. 5 is a flexible printed wiring board having flexibility. The printed wiring board includes a wiring board 8, a light emitting diode 9 mounted on the wiring board 8, and a coverlay 10 stacked on the surface side of the wiring board 8 other than the mounting region of the light emitting diode 9.

<Wiring board>
The wiring board 8 includes a resin base film 41 and a conductive layer 42 that is laminated on the surface side of the base film 41 and includes a conductive pattern.

(Base film)
The base film 41 is made of a resin sheet-like member having flexibility and electrical insulation. As a material of the base film 41, for example, polyimide, polyethylene terephthalate or the like is preferably used.

  As a minimum of average thickness of base film 41, 5 micrometers is preferred and 10 micrometers is more preferred. When the average thickness of the base film 41 is less than the above lower limit, the strength of the base film 41 may be insufficient. On the other hand, the upper limit of the average thickness of the base film 41 is preferably 100 μm, and more preferably 50 μm. If the average thickness of the base film 41 exceeds the above upper limit, the printed wiring board may become unnecessarily thick or the flexibility of the printed wiring board may be insufficient.

(Conductive layer)
The conductive layer 42 is a layer formed of a conductor such as metal, and has a planar shape including a conductive pattern constituting an electric flow path of an electric circuit. This planar shape is formed, for example, by etching a conductor laminated on the base film 41. The conductive layer 42 may be made of any material as long as it has conductivity, but is preferably formed of a metal, typically copper.

  The method of laminating the conductor on the base film 41 is not particularly limited. For example, an adhesion method in which a metal foil is bonded with an adhesive, or a casting method in which a resin composition that is a material of the base film 41 is applied on the metal foil. A sputtering / plating method in which a metal layer is formed by electrolytic plating on a thin conductive layer having a thickness of several nanometers formed on the base film 41 by sputtering or vapor deposition, a laminating method in which a metal foil is attached by hot press, or the like is used. be able to.

  The lower limit of the average thickness of the conductive layer 42 is preferably 2 μm and more preferably 5 μm. When the average thickness of the conductive layer 42 is less than the above lower limit, the conductivity may be insufficient. On the other hand, the upper limit of the average thickness of the conductive layer 42 is preferably 30 μm and more preferably 20 μm. When the average thickness of the conductive layer 42 exceeds the upper limit, the printed wiring board may be unnecessarily thick.

<Light emitting diode>
The light emitting diode 9 is mounted on the surface side of the wiring board 8, preferably on a conductive pattern region formed by the conductive layer 42. The light emitting diode 9 may be a bare chip type or a package type. As a method for mounting the light emitting diode 9 on the wiring board 8, solder reflow, die bonding using a conductive paste, wire bonding using a metal wire, or the like can be used.

<Coverlay>
The coverlay 10 includes a wiring board protective film 1 and a protective film adhesive layer 43 laminated on the back surface of the wiring board protective film 1. In the printed wiring board of FIG. 4, since the protective film 1 for wiring boards is the same as the protective film 1 for wiring boards of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  This cover lay 10 is laminated by a protective film adhesive layer 43 on the surface side of the wiring board 8 other than the light emitting diode mounting region. The cover lay 10 is formed with an opening and a notch so as to open a mounting region of the light emitting diode 9.

(Protective film adhesive layer)
Although it does not specifically limit as an adhesive agent which comprises the protective film adhesive bond layer 43, The thing excellent in the softness | flexibility and heat resistance is preferable, As such an adhesive agent, for example, nylon type, an epoxy type, a butyral type And an acrylic resin adhesive.

  The lower limit of the average thickness of the protective film adhesive layer 43 is preferably 5 μm and more preferably 10 μm. When the average thickness of the protective film adhesive layer 43 is less than the lower limit, the adhesion of the protective film 1 for the wiring board to the wiring board 8 is insufficient, or the wiring board 8 (particularly the conductive layer 42) is a reflective layer. There is a possibility that the reflective layer 3 may be damaged by coming into contact with 3. On the other hand, the upper limit of the average thickness of the protective film adhesive layer 43 is preferably 50 μm, and more preferably 25 μm. When the average thickness of the protective film adhesive layer 43 exceeds the above upper limit, the coverlay 10 and thus the flexibility of the printed wiring board may be insufficient.

[advantage]
In the printed wiring board, the coverlay 10 provided with the protective film for wiring board in FIG. 1 is laminated on the surface side, so that the light incident on the protective film 1 for wiring board out of the light emitted from the light-emitting diode 9 can be obtained. Since most of the light can be reflected, light utilization efficiency, that is, energy efficiency is high.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  The wiring board protective film is preferably provided as a cover lay having an adhesive layer, but the wiring board protective film on which the adhesive layer is not laminated is laminated on the wiring board coated with the adhesive. May be.

  The reflective layer containing a white pigment and a binder may be formed by applying a paint containing a white pigment and a binder to the back surface of the fluororesin layer on which the modified layer is formed. The film may be formed into a shape, and this film may be laminated by hot pressing on the back surface of the fluororesin layer on which the modified layer is formed.

  The coverlay and the printed wiring board may include the wiring board protective film of FIG. 2 or 3.

  Moreover, the said protective film for wiring boards, the said coverlay, and the said printed wiring board may be equipped with another layer in addition to each layer demonstrated in the above-mentioned embodiment. Adhesiveness to the back surface of the protective film for wiring boards, for example, a base material layer for forming a reflective layer made of a metal thin film independently of the fluororesin layer, a protective layer for protecting the reflective layer, and an adhesive layer It may have an adhesion promoting layer or the like for enhancing the resistance. Moreover, you may adhere the said protective film for wiring boards to the wiring board by which the conventional coverlay was laminated | stacked on the surface.

  The printed wiring board may be obtained by laminating the protective film for a wiring board on the surface side of an inflexible wiring board.

  As described above, since the protective film for a wiring board and the cover lay of the present invention have high light reflectivity and the light reflectivity is unlikely to decrease, the protective film and cover lay can be widely used for suppressing light absorption of various wiring boards. Moreover, since the printed wiring board of this invention has high light reflectivity and the light reflectivity does not fall easily, it can be utilized suitably as circuit boards, such as a LED lighting apparatus.

DESCRIPTION OF SYMBOLS 1, 11, 21, 31 Protective film 2 for wiring boards 2 Fluororesin layer 3, 13, 23 Reflective layer 4 Modification layer 8 Wiring board 9 Light emitting diode 10 Coverlay 25 White pigment 26 Binder 37 Adhesive layer 41 Base film 42 Conductivity Layer 43 Protective film adhesive layer

Claims (10)

A transparent fluororesin layer mainly composed of a fluororesin, and a reflective layer laminated directly or via a transparent adhesive layer on the back surface of the fluororesin layer,
A protective film for a wiring board, wherein the fluororesin layer has a modified layer containing a siloxane bond and a hydrophilic organic functional group on the back surface.   The protective film for wiring boards according to claim 1, wherein the fluororesin layer has a light transmittance of 60% or more with respect to light having a wavelength of 600 nm.   The protective film for a wiring board according to claim 1, wherein the reflective layer is a metal film.   The protective film for a wiring board according to claim 1 or 2, wherein the reflective layer contains a white pigment and a binder thereof.   The protective film for a wiring board according to any one of claims 1 to 4, wherein a contact angle between the back surface of the fluororesin layer and pure water is 90 ° or less.   The protective film for a wiring board according to any one of claims 1 to 5, wherein an average thickness of the modified layer is 400 nm or less.   The protective film for a wiring board according to any one of claims 1 to 6, wherein an average surface roughness Ra of the back surface of the fluororesin layer is 4 µm or less.   The hydrophilic organic functional group is a hydroxyl group, carboxy group, carbonyl group, amino group, amide group, sulfide group, sulfonyl group, sulfo group, sulfonyldioxy group, epoxy group, methacryl group or mercapto group. The protective film for wiring boards of any one of Claim 7.   A coverlay comprising the protective film for a wiring board according to claim 1 and an adhesive layer laminated on the back surface of the protective film for a wiring board. A resin base film, and a wiring board laminated on the surface side of the base film and having a conductive layer including a conductive pattern;
A light emitting diode mounted on the wiring board;
A printed wiring board provided with the protective film for wiring boards of Claim 1 laminated | stacked other than the said light emitting diode mounting area | region among the surface sides of the said wiring board.

Images