JP2012243846A - Metal base circuit board and light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal base circuit board which is folded at normal temperature and prevents defects such as cracks during folding.SOLUTION: A metal base circuit board includes: a metal substrate 11; an insulation layer 12 laminated on the metal substrate 11; a conductive foil for circuit formation 13 locally laminated on the insulation layer 12; and a white film 14 laminated on parts of exposed surfaces of the conductive foil 13 and the insulation layer 12. The white film 14 includes a thermosetting silicon resin, and the tensile elongation percentage of the white film 14 is 10% or higher at normal temperature.

Description

  The present invention relates to a metal base circuit board and a light emitting device.

  A metal base circuit board with an insulating layer on a metal substrate, a conductive foil formed on it, and a white film on the exposed surface of the conductive foil and insulating layer is a heat-dissipating, electrically insulating, and light-reflective material. Therefore, it is used as a circuit board for mounting a heat-generating electronic component such as an LED (Patent Document 1).

  In recent years, a printed wiring board to which an LED is attached may be bent and used. However, an insulating layer in which an epoxy resin material is filled with a heat conductive inorganic filler, and a white film in which a white inorganic filler is filled in an acrylic resin or an epoxy resin are brittle. There is a problem that defects occur.

  In Patent Document 2, a printed wiring for attaching an electronic component to at least the insulating layer surface of the tip is provided integrally with a tip and a leg that intersects the tip by bending the metal substrate at a bent portion. A bending portion is provided by providing an insulating layer dividing portion that includes a plate portion and divides the insulating layer along the entire length of the bent portion. However, when such processing is performed, there is a problem that a step of processing the substrate in advance is required and the degree of freedom of the circuit pattern is limited.

International Publication WO2008 / 143076 JP 2010-129984 A

  An object of the present invention is to provide a metal base circuit board and a light-emitting element that can be bent at room temperature and do not cause defects such as cracks even when bent.

The metal base circuit board of the present invention includes a metal substrate, an insulating layer laminated on the metal substrate, a conductive foil for circuit formation locally laminated on the insulating layer, the conductive foil and the insulation. And a white film laminated on a part of the exposed surface of the layer, wherein the white film contains a thermosetting silicone resin, and the white film at room temperature Tensile elongation is 10% or more.
“Normal temperature” means a temperature range of 20 ° C. ± 15 ° C. (5-35 ° C.) defined in JIS Z 8703.
The conductive foil may be formed by rolling a conductive material.
The insulating layer may include liquid crystal polyester.
The light emitting device of the present invention includes the metal base circuit board of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the metal base circuit board and light emitting element which can be bent at normal temperature and do not generate | occur | produce defects, such as a crack, at the time of bending can be provided.

It is sectional drawing which shows one Embodiment of a light emitting element provided with the metal base circuit board.

FIG. 1 is a cross-sectional view showing an embodiment of a light emitting device including a metal base circuit board.
The light emitting element 1 includes a metal base circuit board 10 and a plurality of light sources 20 mounted on the metal base circuit board 10 via bonding members 15 such as solder.

  The metal base circuit board 10 includes a metal substrate 11, an insulating layer 12 stacked on the metal substrate 11, a conductive foil 13 for forming a circuit locally stacked on the insulating layer 12, and the conductive foil 13. A white film 14 laminated on a part of the surface exposed to the layer 12.

  The metal substrate 11 functions as a heat radiating member that radiates heat generated by the light source 20. The insulating layer 12 has a high thermal conductivity in the layer thickness direction in order to efficiently transmit the heat generated by the light source 20 to the metal substrate 11. The conductive foil 13 is patterned in the shape of a wiring part or an electrode part, and is configured to be locally disposed on a part of the insulating layer 12. The white film 13 covers substantially the entire surface of the conductive foil 13 except for a portion (electrode portion or the like) where the light source 20 of the conductive foil 13 is mounted. The light emitted from the light source 20 toward the metal substrate 11 is reflected by the white film 11 to the side opposite to the metal substrate 11. Thereby, almost all of the light emitted from the light source 20 can be supplied in one direction (the side opposite to the metal substrate 11).

  The light source 20 is a light emitter that emits light by electric charges supplied from the conductive foil 13. For example, an LED package in which an LED chip is packaged is used as the light source 20, but the light source 20 is not limited to this. For example, a type (Chip On Board; COB) in which the LED chip is directly mounted on the metal base circuit board 10 may be used. Various forms such as a shell type and a surface mount type (SMD) can be adopted as the form of the LED package, and the form is not particularly limited. The configuration of the light source 20 and the method of mounting the light source 20 on the metal base circuit board 10 can also employ known ones and are not particularly limited.

  The light emitting element 1 described above is attached to another member by bending an end portion of the metal base circuit board 10. Therefore, the metal base circuit board 10 is required to have high durability against bending. In order to efficiently dissipate the heat from the light source 20 to the outside, the metal base circuit board 10 preferably has high heat dissipation. Hereinafter, a preferable configuration of the metal base circuit board 10 will be described in detail.

(Metal substrate)
As the metal substrate, a metal plate having a thermal conductivity of 60 W / mK or more is used. As a metal material constituting such a metal substrate, copper, aluminum, iron, stainless steel, or an alloy thereof is used. The thickness of the metal substrate is preferably 0.1 mm to 2 mm.

(Conductive foil)
As the conductive foil, copper, aluminum, nickel and alloys thereof are preferable, and the thickness is preferably 10 to 140 μm. When it exceeds 140 μm, not only the flexibility is lowered, but also the thickness is increased and it is difficult to reduce the size and the thickness. The conductive foil is preferably formed by rolling a conductive material such as a metal, that is, a thin film processed by rotating a plurality of rolls and passing the conductive material between them. Since the conductive foil formed by rolling is less prone to cracking when bent, it is suitable when the metal base circuit board is bent and used. For example, rolled copper foil can be used as the conductive foil.

(Insulating layer)
The thickness of the insulating layer is preferably 30 μm or more and 150 μm or less. When the thickness is less than 30 μm, the insulating property is low.

  As the insulating layer, it is preferable to use liquid crystal polyester which is a thermoplastic resin having high thermal conductivity. As the insulating layer, a thermosetting resin such as an epoxy resin, a phenol resin, a silicone resin, or an acrylic resin is usually used. However, the liquid crystal polyester particularly increases the thermal conductivity in the layer thickness direction as compared with these resins. Therefore, it is preferable in that heat dissipation to the metal substrate can be improved.

(Liquid crystal polyester)
The liquid crystalline polyester used in the present embodiment is a liquid crystalline polyester that exhibits liquid crystallinity in a molten state, and is preferably melted at a temperature of 450 ° C. or lower. The liquid crystal polyester may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide. The liquid crystal polyester is preferably a wholly aromatic liquid crystal polyester using only an aromatic compound as a raw material monomer.

  A typical example of the liquid crystal polyester is polymerization (polycondensation) of an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, and at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. At least one compound selected from the group consisting of aromatic dicarboxylic acids and aromatic diols, aromatic hydroxyamines and aromatic diamines, And those obtained by polymerizing a polyester such as polyethylene terephthalate and an aromatic hydroxycarboxylic acid. Here, the aromatic hydroxycarboxylic acid, the aromatic dicarboxylic acid, the aromatic diol, the aromatic hydroxyamine, and the aromatic diamine are each independently replaced with a part or all of the polymerizable derivative. Also good.

  Examples of polymerizable derivatives of a compound having a carboxyl group such as aromatic hydroxycarboxylic acid and aromatic dicarboxylic acid include those obtained by converting a carboxyl group into an alkoxycarbonyl group or an aryloxycarbonyl group (ester), carboxyl Examples include those obtained by converting a group into a haloformyl group (acid halide), and those obtained by converting a carboxyl group into an acyloxycarbonyl group (acid anhydride). Examples of polymerizable derivatives of hydroxyl group-containing compounds such as aromatic hydroxycarboxylic acids, aromatic diols and aromatic hydroxyamines include those obtained by acylating hydroxyl groups and converting them to acyloxyl groups (acylated products) ). Examples of polymerizable derivatives of amino group-containing compounds such as aromatic hydroxyamines and aromatic diamines include those obtained by acylating an amino group and converting it to an acylamino group (acylated product).

The liquid crystalline polyester preferably has a repeating unit represented by the following formula (1) (hereinafter sometimes referred to as “repeating unit (1)”), and the repeating unit (1) and the following formula (2) A repeating unit represented (hereinafter sometimes referred to as “repeating unit (2)”) and a repeating unit represented by the following formula (3) (hereinafter sometimes referred to as “repeating unit (3)”). And more preferably.
(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
(3) ^-X-Ar 3 -Y-
(Ar ¹ represents a phenylene group, a naphthylene group, or a biphenylylene group. Ar ² and Ar ³ each independently represent a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4). X And Y each independently represents an oxygen atom or an imino group (—NH—), and each hydrogen atom in the group represented by Ar ¹ , Ar ² or Ar ³ is independently a halogen atom or an alkyl group. Alternatively, it may be substituted with an aryl group.)
(4) -Ar ⁴ -Z-Ar ^5-
(Ar ⁴ and Ar ⁵ each independently represent a phenylene group or a naphthylene group. Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.)

As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group, An n-octyl group and an n-decyl group are mentioned, The carbon number becomes like this. Preferably it is 1-10. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the carbon number thereof is preferably 6-20. is there. When the hydrogen atom is substituted with these groups, the number is independently preferably 2 or less for each group represented by Ar ¹ , Ar ² or Ar ³ , more preferably 1 or less.

  Examples of the alkylidene group include a methylene group, an ethylidene group, an isopropylidene group, an n-butylidene group, and a 2-ethylhexylidene group, and the carbon number thereof is preferably 1-10.

The repeating unit (1) is a repeating unit derived from a predetermined aromatic hydroxycarboxylic acid. As the repeating unit (1), Ar ¹ is a p-phenylene group (repeating unit derived from p-hydroxybenzoic acid), and Ar ¹ is a 2,6-naphthylene group (6-hydroxy-2). -Repeating units derived from naphthoic acid) are preferred.

The repeating unit (2) is a repeating unit derived from a predetermined aromatic dicarboxylic acid. As the repeating unit (2), Ar ² is a p-phenylene group (a repeating unit derived from terephthalic acid), Ar ² is an m-phenylene group (a repeating unit derived from isophthalic acid), Ar ² Is a 2,6-naphthylene group (a repeating unit derived from 2,6-naphthalenedicarboxylic acid), and Ar ² is a diphenyl ether-4,4′-diyl group (diphenyl ether- 4,4′-dicarboxylic acid-derived repeating units) are preferred.

The repeating unit (3) is a repeating unit derived from a predetermined aromatic diol, aromatic hydroxylamine or aromatic diamine. As the repeating unit (3), Ar ³ is a p-phenylene group (a repeating unit derived from hydroquinone, p-aminophenol or p-phenylenediamine), and Ar ³ is a 4,4′-biphenylylene group. Those (4,4′-dihydroxybiphenyl, 4-amino-4′-hydroxybiphenyl or repeating units derived from 4,4′-diaminobiphenyl) are preferred.

  The content of the repeating unit (1) is the total amount of all repeating units (the mass equivalent amount of each repeating unit (moles by dividing the mass of each repeating unit constituting the liquid crystal polyester by the formula amount of each repeating unit). ), And the total value thereof) is preferably 30 mol% or more, more preferably 30 mol% or more and 80 mol% or less, still more preferably 30 mol% or more and 60 mol% or less, and even more preferably 30 mol%. It is mol% or more and 40 mol% or less.

  Similarly, the content of the repeating unit (2) is preferably 35 mol% or less, more preferably 10 mol% or more and 35 mol% or less, further preferably 20 mol% or more 35 with respect to the total amount of all repeating units. The mol% or less, more preferably 30 mol% or more and 35 mol% or less.

  Similarly, the content of the repeating unit (3) is preferably 35 mol% or less, more preferably 10 mol% or more and 35 mol% or less, further preferably 20 mol% or more 35 with respect to the total amount of all repeating units. The mol% or less, more preferably 30 mol% or more and 35 mol% or less.

  As the content of the repeating unit (1) increases, the heat resistance, the strength and the rigidity are easily improved. However, when the content is too large, the solubility in a solvent tends to be low.

  The ratio between the content of the repeating unit (2) and the content of the repeating unit (3) is expressed as [content of repeating unit (2)] / [content of repeating unit (3)] (mol / mol). The ratio is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and still more preferably 0.98 / 1 to 1 / 0.98.

  In addition, liquid crystalline polyester may have 2 or more types of repeating units (1)-(3) each independently. The liquid crystalline polyester may have a repeating unit other than the repeating units (1) to (3), but the content thereof is preferably 10 mol% or less, based on the total amount of all repeating units. Preferably it is 5 mol% or less.

  The liquid crystalline polyester has, as the repeating unit (3), one or both of X and Y are imino groups, that is, a repeating unit derived from a predetermined aromatic hydroxylamine and an aromatic diamine. It is preferable to have one or both of the repeating unit derived from it, since the solubility in a solvent is excellent, and as the repeating unit (3), one or both of X and Y are imino groups It is more preferable to have only.

  The liquid crystal polyester is preferably produced by melt polymerization of raw material monomers corresponding to the repeating units constituting the liquid crystal polyester, and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, high molecular weight liquid crystal polyester having high heat resistance, strength and rigidity can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, And nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine and 1-methylimidazole, and nitrogen-containing heterocyclic compounds are preferably used.

  The liquid crystal polyester has a flow initiation temperature of preferably 250 ° C. or higher, more preferably 250 ° C. or higher and 350 ° C. or lower, and further preferably 260 ° C. or higher and 330 ° C. or lower. As the flow start temperature is higher, the heat resistance, strength, and rigidity are more likely to be improved. However, if the flow start temperature is too high, the solubility in a solvent tends to be low, and the viscosity of the liquid composition tends to be high.

The flow start temperature is also called flow temperature or flow temperature, and the temperature is raised at a rate of 4 ° C./min under a load of 9.8 MPa (100 kg / cm ² ) using a capillary rheometer while liquid crystal polyester is used. Is a temperature showing a viscosity of 4800 Pa · s (48000 poise) when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm, and is a measure of the molecular weight of the liquid crystalline polyester (Naide Koide, “ “Liquid Crystal Polymer—Synthesis / Molding / Application—”, CMC Co., Ltd., June 5, 1987, p. 95).

(Inorganic filler)
As the inorganic filler contained in the insulating layer, it is preferable to select a filler having a thermal conductivity of 30 W / mK or more and an excellent insulating property. Particles such as alumina, magnesium oxide, beryllium oxide, aluminum hydroxide, zinc oxide, aluminum nitride, boron nitride are preferred.

  The shape of the particles is preferably spherical because the particles of the inorganic filler are easily packed in the liquid crystal polyester resin. When it is not spherical, it is preferable that the inorganic filler is made into a fine powder and then molded into a substantially spherical shape by a powder spray method.

  In order to improve the adhesion and dispersibility of the inorganic filler with the resin, it is desirable to treat the surface of the inorganic filler particles with a surface treatment agent. Surface treatment agents include silane coupling agents, titanium coupling agents, aluminum and zirconium coupling agents, long chain fatty acids, isocyanate compounds, epoxy groups, methoxysilyl groups, amino groups, hydroxyl groups and other highly polar materials. Molecules and reactive polymers are preferred.

(White film)
The white film preferably has a reflectance of 70% or more, more preferably 80% or more, in the visible light region of 420 nm to 800 nm. In the present specification, the “white film” refers to a film in which the reflectance of light of each wavelength of 460 nm, 525 nm, and 620 nm is 80% or more. As such a white film, a white solder resist can be preferably used.

  The white solder resist preferably contains a thermosetting silicone resin and has a tensile elongation of 4% or more at room temperature, and more preferably has a tensile elongation of 10% or more at room temperature. . By using a white solder resist having a high tensile elongation, it is possible to prevent the occurrence of defects such as cracks even during bending. Further, if necessary, it can be used in combination with a thermosetting epoxy resin, an ultraviolet curable acrylic resin, or the like.

  The white pigment contained in the white solder resist is preferably anatase type or rutile type titanium oxide particles. Titanium dioxide can be used alone or in combination with other white pigments typified by zinc oxide, barium sulfate, aluminum hydroxide and the like.

  The content of titanium oxide is preferably 30 to 60% by mass in the white film from the viewpoint of the reflectance, durability, and tensile elongation of the white film itself. When the amount is less than this, the reflectance is low, and when the amount is large, the durability is deteriorated and cracks are generated during bending due to a decrease in the tensile elongation.

<Manufacture of liquid crystal polyester>
In a reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer and reflux condenser, 1976 g (10.5 mol) of 2-hydroxy-6-naphthoic acid and 1474 g (9.75 mol) of 4-hydroxyacetanilide, 1620 g (9.75 mol) of isophthalic acid, and 2374 g (23.25 mol) of acetic anhydride were charged. After sufficiently replacing the atmosphere in the reactor with nitrogen gas, the temperature was raised to 150 ° C. over 15 minutes under a nitrogen gas stream, and the mixture was refluxed at this temperature for 3 hours.

  Thereafter, while distilling off the distilled by-product acetic acid and unreacted acetic anhydride, the temperature was raised to 300 ° C. over 170 minutes, and when the increase in torque was observed, the reaction was considered to be complete. Was taken out. The taken-out contents were cooled to room temperature and pulverized with a pulverizer to obtain a liquid crystal polyester powder having a relatively low molecular weight.

  It was 235 degreeC when the flow start temperature of the obtained powder was measured by Shimadzu Corporation flow tester CFT-500. Moreover, this liquid crystalline polyester powder was heat-treated at 223 ° C. for 3 hours in a nitrogen atmosphere to cause solid phase polymerization. The flow starting temperature of the liquid crystal polyester after solid phase polymerization was 270 ° C.

<Preparation of liquid crystal polyester solution>
2200 g of liquid crystal polyester obtained by the above-mentioned method was added to 7800 g of N-methyl-2-pyrrolidone (NMP) and heated at 100 ° C. for 2 hours to obtain a liquid crystal polyester solution. The viscosity of this solution was 400 cP. This viscosity is a value measured at 23 ° C. using a B-type viscometer (manufactured by Toki Sangyo, “TVL-20 type”, rotor No. 21 (rotation speed: 5 rpm)).

<Manufacture of copper foil with liquid crystal polyester>
The obtained liquid crystal polyester solution was applied onto a copper foil having a thickness of 70 μm so as to have a thickness of 300 μm. Subsequently, this was dried at 100 ° C. for 20 minutes and then heat-treated at 300 ° C. for 3 hours. As a result, a liquid crystal polyester film having a copper foil formed on the surface was obtained.

<Manufacture of metal base circuit board>
Thereafter, the above-mentioned liquid crystal polyester film was laminated on an aluminum alloy plate having a thermal conductivity of 140 W / (m · K) and a thickness of 1.0 mm. At this time, the surface of the liquid crystal polyester film (the surface on which the copper foil was not formed) was in contact with the surface of the aluminum alloy plate. Then, the aluminum alloy plate and the liquid crystal polyester film were thermally bonded by performing a heat treatment at a pressure of 200 kg / cm ² and a temperature of 340 ° C. for 20 minutes. About the obtained laminated board, after masking a predetermined position with an etching resist and etching copper foil, the etching resist was removed and the circuit copper foil was formed, and it was set as the metal base circuit board.

  Furthermore, in order to form a white film having a high reflectance on the metal base circuit board, various white solder resist layers were applied and cured with heat and ultraviolet rays. At this time, no white film is formed on the portion where the light source is mounted (the portion patterned as the electrode portion of the copper foil).

[Example 1]
As a white solder resist, “SWR-PK-01” manufactured by Asahi Rubber Co., Ltd. was used. SWR-PK-01 is a polyalkylalkenylsiloxane or polyalkylhydrogensiloxane with a platinum compound added as a curing catalyst, titanium dioxide or aluminum hydroxide added as a white inorganic filler, and a coating film is formed to a thickness of 40 μm. Then, a white film was obtained by thermosetting at 150 ° C. for 1 hour.

[Example 2]
As a white solder resist, 5 g each of silicone resins EG-6301A and B (manufactured by Dow Corning Toray), 20 g of titanium oxide CR-58 (manufactured by Ishihara Sangyo Co., Ltd.), and 10 g of methyl ethyl ketone (manufactured by Aldrich) are mixed by a stirring defoaming machine. Using the dispersion, a coating film was formed so that the film thickness after solvent drying was 40 μm, and then a white film was obtained by thermosetting at 150 ° C. for 1 hour.

[Comparative Example 1]
As the white solder resist, “PSR-9000FLX05W” manufactured by Taiyo Ink Co., Ltd. was used. PSR-9000FLX05W is a product obtained by adding a photopolymerization initiator to an acrylate resin and titanium oxide and aluminum hydroxide as a white inorganic filler. After forming the coating film, the PSR-9000FLX05W was photocured by ultraviolet irradiation to obtain a white film.

[Comparative Example 2]
“PSR-4000LEW3” manufactured by Taiyo Ink Co., Ltd. was used as the white solder resist. PSR-4000LEW3 is obtained by adding a photopolymerization initiator and titanium oxide and aluminum hydroxide as a white inorganic filler to an acrylate resin. After forming a coating film, it was photocured by ultraviolet irradiation to obtain a white film.

[Comparative Example 3]
As a white solder resist, 5 g each of silicone resins SCR-1011A and B (manufactured by Shin-Etsu Chemical Co., Ltd.), 20 g of titanium oxide CR-58 (manufactured by Ishihara Sangyo Co., Ltd.), and 15 g of methyl ethyl ketone (manufactured by Aldrich) are mixed and dispersed by a stirring defoamer. After forming the coating film so that the film thickness after solvent drying was 40 μm, a white film was obtained by thermosetting at 150 ° C. for 1 hour.

-Reflectivity The compositions of the above examples and comparative examples were applied to the surface of a 50 mm × 50 mm × 1 mmt aluminum plate that had been degreased in advance so as to have a thickness of 50 μm, and then heated at 80 ° C. in a hot air circulating drying oven. Dry for 30 minutes. Thereafter, the silicone resin was thermally cured at 150 ° C. for 1 hour, and the acrylic resin was photocured by irradiating with ultraviolet rays under a condition of an integrated exposure amount of 500 mJ / cm ^{2 with} a mercury short arc lamp. Thereafter, the copper foil was removed by etching with an aqueous ferric chloride solution and washed with water to obtain an evaluation sample.

  Using the above evaluation sample, in accordance with JIS K7105-1981 total light reflectance measurement method A (standard white plate: barium sulfate), a self-recording spectrophotometer ("U-3500" manufactured by Hitachi, Ltd.) The diffuse reflectance with respect to light beams having wavelengths of 460 nm, 525 nm, and 620 nm was measured. The diffuse reflectance is a relative value when the diffuse reflectance of a standard white plate of barium sulfate is 100%.

・ Tensile elongation (tensile elongation at break)
The compositions of the above Examples and Comparative Examples were applied on a copper foil having a thickness of 18 μm that had been previously degreased, and dried at 80 ° C. for 30 minutes in a hot-air circulating drying furnace. Thereafter, the silicone resin was heat-cured at 150 ° C. for 1 hour, and the acrylic resin was photocured by irradiating with ultraviolet rays under the condition of an integrated exposure amount of 500 mJ / cm 2 with a mercury short arc lamp. Thereafter, the copper foil was removed by etching with an aqueous ferric chloride solution and washed with water to obtain an evaluation sample.

  The tensile elongation rate (tensile elongation at break) of the evaluation sample was measured based on the tensile elongation test method described in JIS C2151 (1990). The tensile elongation was measured at room temperature (25 ° C.), a constant speed tension type tensile tester was used as a test apparatus, and the tensile speed was 5 mm / min. The thickness of the evaluation sample (the thickness of the white film) is 40 μm.

-Adhesion strength of the insulating layer As a test of the adhesion strength of the insulating layer, a pattern having a width of 10 mm was formed by etching the copper foil on the insulating layer, and this copper foil pattern was formed at a rate of 50 mm / min in the vertical direction. The strength at the time of peeling (T peel strength between insulating layer / copper foil) was measured.

・ Presence or absence of cracks when bent 90 ° at room temperature (25 ° C) The presence or absence of cracks when bent 90 ° at room temperature is determined by the insulation layer after conducting 90 ° bending with a radius of curvature of 1 mm. The foil and white film were magnified 10 times with an optical microscope and observed visually.

・ Dielectric breakdown voltage when bent 90 ° under normal temperature (25 ° C) Measurement of dielectric breakdown voltage when bent 90 ° under normal temperature is based on a metal base circuit board formed with a circular pattern of φ20mm as copper foil. In order to include the circular pattern of φ20 mm, the metal base circuit board is bent by 90 ° along a bending line passing through the center of the circular pattern with a radius of curvature of 1 mm, and the circular pressure is increased by the step-up method defined in JIS C 2110. The breakdown voltage between the pattern and the metal substrate was measured.

  Table 1 shows the evaluation results of Examples 1 and 2 and Comparative Examples 1, 2, and 3.

  As shown in Table 1, in Examples 1 and 2, the tensile elongation of the white film is 10% or more, which is much larger than that of Comparative Examples 1, 2 and 3 of less than 4%. It has become. In Comparative Examples 1, 2, and 3, cracks occurred when bent at 90 ° at room temperature, whereas in Examples 1 and 2, no cracks occurred even when bent at 90 ° at room temperature. It has high durability. Moreover, in Examples 1 and 2, it has a high characteristic in any of the reflectance, the adhesion strength of the insulating layer, and the dielectric breakdown voltage in a state of being bent at 90 ° at room temperature, and is suitable for the use in which it is bent. It becomes the composition.

  The present invention can be used for a metal base circuit board and a light emitting device.

DESCRIPTION OF SYMBOLS 1 ... Light emitting element, 10 ... Metal base circuit board, 11 ... Metal substrate, 12 ... Insulating layer, 13 ... Conductive foil, 14 ... White film, 20 ... Light source

Claims (4)

A metal substrate, an insulating layer stacked on the metal substrate, a conductive foil for forming a circuit locally stacked on the insulating layer, and a part of an exposed surface of the conductive foil and the insulating layer A metal-based circuit board comprising a laminated white film,
The metal base circuit board, wherein the white film includes a thermosetting silicone resin, and the tensile elongation at normal temperature of the white film is 10% or more.   The metal base circuit board according to claim 1, wherein the conductive foil is formed by rolling a conductive material.   The metal base circuit board according to claim 1, wherein the insulating layer includes liquid crystal polyester.   The light emitting element provided with the metal base circuit board of any one of Claim 1 thru | or 3.

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