Resin composition for laser welding

Abstract

To provide a member for laser welding with excellent heat (moisture heat) discoloration resistance and strong laser welding despite a high degree of transparency.SOLUTION: Resin compositions for laser welding includes at least one kind of metal boride particle (B1) selected from the group consisting of La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr, and Ca to 100 parts by mass of transparent thermoplastic resin (A), or at least one kind of tungsten-based oxide particulate (B2) selected from potassium tungsten oxide, rubidium tungsten oxide, cesium tungsten oxide, and thallium tungsten oxide. 0.00035 to 0.5 parts by mass, and 0.00007 to 0.1 parts by mass of alkyl acid phosphate or its metal salt, or organic phosphonic acid (C).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin composition for laser welding, a member for laser welding, and a laser welded body.

Background Art

[0002] In laser welding, a member that transmits a laser and a member that absorbs the laser are brought into contact with each other at a portion where the two are to be adhered, and the laser absorbing member is irradiated from the side of the member that transmits the laser to weld and join the two members.

[0003] In general, carbon black is blended as a laser absorber in the laser absorbing member. In addition, various additives such as phthalocyanine compounds, polymethine compounds, and anthraquinone compounds have been proposed. However, carbon black is black, and the other additives are opaque or have some color. Therefore, it is inconvenient for obtaining a transparent laser welded body or for members where blackening or coloring of the joint is not preferable.

[0004] Patent Document 1 proposes a welding member containing fine particles of hexaboride as a polymer dispersant and a laser absorber, which is transparent and capable of laser welding. However, in applications that require a high degree of transparency such as medical devices and wearable devices, the transparency is not always sufficient, and there is a problem that it is easily restricted in use.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object (problem) of the present invention is to provide a resin composition for laser welding, a member for laser welding, and a laser welded body that have excellent heat (humid heat) discoloration resistance and enable strong laser welding despite having high transparency.

Means for Solving the Problem

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that a resin composition for laser welding containing metal boride fine particles (B1) or tungsten-based oxide fine particles (B2) and an alkyl acid phosphate or its metal salt or an organic phosphonic acid (C) in specific amounts can solve the above problems, and have reached the present invention. The present invention relates to the following resin composition for laser welding, member for laser welding, and laser welded body.

[0008] 1. A resin composition for laser welding, characterized in that it contains 0.00035 to 0.5 parts by mass of at least one kind of metal boride fine particles (B1) selected from the group consisting of La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr and Ca, or at least one kind of tungsten-based oxide fine particles (B2) selected from potassium tungstate, rubidium tungstate, cesium tungstate and thallium tungstate, and 0.00007 to 0.1 parts by mass of an alkyl acid phosphate or its metal salt or an organic phosphonic acid (C) with respect to 100 parts by mass of the transparent thermoplastic resin (A). 2. The resin composition for laser welding according to 1 above, further containing 0.005 to 0.5 parts by mass of a phosphite-based antioxidant with respect to 100 parts by mass of the transparent thermoplastic resin (A). 3. A member for laser welding comprising the resin composition for laser welding according to 1 above. 4. The member for laser welding according to 3 above, having a haze of 80% or less at a thickness of 2 mm. 5. A laser welded body obtained by laser welding the member for laser welding according to 3 or 4 above to another transparent resin member. 6. The laser welded body according to the above 5, wherein the haze of the other transparent resin member at a thickness of 2 mm is 8% or less.

Advantages of the Invention

[0009] The resin composition for laser welding of the present invention provides a laser welding member that has high transparency, excellent heat (humid heat) discoloration resistance, and enables strong laser welding. The laser welded body exhibits excellent transparency and excellent heat and humid heat discoloration resistance. The laser welded body can be particularly preferably used for medical devices and wearable devices that require high transparency.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail with reference to embodiments and examples, etc., but the present invention is not to be construed as being limited to the embodiments and examples shown below. In this specification, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0011] The resin composition for laser welding of the present invention is characterized by containing 0.00035 to 0.5 parts by mass of at least one metal boride fine particle (B1) selected from the group consisting of La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr, and Ca, or at least one tungsten-based oxide fine particle (B2) selected from potassium tungstate oxide, rubidium tungstate oxide, cesium tungstate oxide, and thallium tungstate oxide, and 0.00007 to 0.1 parts by mass of an alkyl acid phosphate or its metal salt, or an organic phosphonic acid (C) with respect to 100 parts by mass of the transparent thermoplastic resin (A).

[0012] [Transparent thermoplastic resin (A)] The transparent thermoplastic resin used in the resin composition for laser welding of the present invention is not particularly limited, and examples thereof include polycarbonate resins; acrylic resins such as polymethyl methacrylate resins; amorphous polyester resins such as polyethylene terephthalate (PET) resins; polystyrene-based resins; cyclic polyolefin-based resins; thermoplastic resins such as vinyl chloride resins, or polymer alloys composed of two or more of these thermoplastic resins. Among them, from the viewpoint of transparency, it is preferable to use polycarbonate resins and acrylic resins, and polycarbonate resins are particularly preferable.

[0013] <Polycarbonate resin> There is no limitation on the specific type of polycarbonate resin. For example, polycarbonate polymers obtained by reacting dihydroxy compounds with carbonate precursors can be mentioned. At this time, in addition to dihydroxy compounds and carbonate precursors, polyhydroxy compounds or the like may be reacted. Also, a method of reacting carbon dioxide as a carbonate precursor with a cyclic ether may be used. Further, the polycarbonate polymer may be linear or branched. Furthermore, the polycarbonate polymer may be a homopolymer composed of one type of repeating unit, or a copolymer having two or more types of repeating units. At this time, various copolymerization forms such as random copolymers and block copolymers can be selected for the copolymer. Usually, such polycarbonate polymers become thermoplastic resins.

[0014] In addition, polycarbonate resins can be classified into aromatic polycarbonate resins in which the carbons directly bonded to the carbonate bonds are aromatic carbons, and aliphatic polycarbonate resins in which they are aliphatic carbons, and either can be used. Among them, aromatic polycarbonate resins are preferable from the viewpoints of heat resistance, mechanical properties, electrical properties, etc.

[0015] Among the monomers that are raw materials for aromatic polycarbonate resins, examples of aromatic dihydroxy compounds include Dihydroxybenzenes such as 1,2-dihydroxybenzene, 1,3-dihydroxybenzene (i.e., resorcinol), 1,4-dihydroxybenzene; Dihydroxybiphenyls such as 2,5-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl; Dihydronaphthalenes such as 2,2'-dihydroxy-1,1'-binaphthyl, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene; Dihydroxydiaryl ethers such as 2,2'-dihydroxydiphenyl ether, 3,3'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, 1,4-bis(3-hydroxyphenoxy)benzene, 1,3-bis(4-hydroxyphenoxy)benzene;

[0016] 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), 1,1-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane (i.e., bisphenol C), 2,2-bis(3-methoxy-4-hydroxyphenyl)propane, 2-(4-hydroxyphenyl)-2-(3-methoxy-4-hydroxyphenyl)propane, 1,1-bis(3-tert-butyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 2-(4-hydroxyphenyl)-2-(3-cyclohexyl-4-hydroxyphenyl)propane, α,α'-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)cyclohexylmethane, bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)(4-propenylphenyl)methane, bis(4-hydroxyphenyl)diphenylmethane, bis(4-hydroxyphenyl)naphthylmethane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane (i.e., bisphenol AP), 1,1-bis(4-hydroxyphenyl)-1-naphthylethane, 1,1-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)hexane, 2,2-bis(4-hydroxyphenyl)hexane, 1,1-bis(4-hydroxyphenyl)octane, 2,2-bis(4-hydroxyphenyl)octane, 4,4-bis(4-hydroxyphenyl)heptane, 2,2-bis(4-hydroxyphenyl)nonane, 1,1-bis(4-hydroxyphenyl)decane, 1,1-bis(4-hydroxyphenyl)dodecane, and bis(hydroxyaryl)alkanes such as;

[0017] 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,4-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,5-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxy-3,5-dimethylphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3-propyl-5-methylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3-tert-butyl-cyclohexane, 1,1-bis(4-hydroxyphenyl)-3-phenylcyclohexane, 1,1-bis(4-hydroxyphenyl)-4-phenylcyclohexane, bis(hydroxyaryl)cycloalkanes such as these;

[0018] 9,9-bis(4-hydroxyphenyl)fluorene, bisphenols containing a cardo structure such as 9,9-bis(4-hydroxy-3-methylphenyl)fluorene; 4,4'-dihydroxydiphenyl sulfide, dihydroxydiaryl sulfides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide; 4,4'-dihydroxydiphenyl sulfoxide, dihydroxydiaryl sulfoxides such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; 4,4'-dihydroxydiphenyl sulfone, dihydroxydiaryl sulfones such as 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone; and the like.

[0019] Among these, bis(hydroxyaryl)alkanes are preferred, and among them, bis(4-hydroxyphenyl)alkanes are preferred. Particularly, from the viewpoints of impact resistance, heat resistance, and transparency, 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), 2,2-bis(3-methyl-4-hydroxyphenyl)propane (i.e., bisphenol C), and 1,1-bis(4-hydroxyphenyl)-1-phenylethane (i.e., bisphenol AP) are preferred. In addition, as the aromatic dihydroxy compound, one kind may be used, or two or more kinds may be used in combination at an arbitrary combination and ratio.

[0020] Among the monomers used as raw materials for the aromatic polycarbonate resin, examples of the carbonate precursor include carbonyl halide, carbonate ester, etc. In addition, as the carbonate precursor, one kind may be used, or two or more kinds may be used in combination at an arbitrary combination and ratio.

[0021] Specific examples of the carbonyl halide include, for example, phosgene; halocarbonates such as bischloroformate of dihydroxy compound and monochloroformate of dihydroxy compound.

[0022] Specific examples of the carbonate ester include, for example, diaryl carbonates such as diphenyl carbonate and ditolyl carbonate; dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; carbonate bodies of dihydroxy compounds such as biscarbonate of dihydroxy compound, monocarbonate of dihydroxy compound, and cyclic carbonate.

[0023] The production method of the polycarbonate resin is not particularly limited, and any method can be adopted. Examples thereof include the interfacial polymerization method, the melt transesterification method, the pyridine method, the ring-opening polymerization method of cyclic carbonate compounds, and the solid-phase transesterification method of prepolymers.

[0024] The molecular weight of the polycarbonate resin is arbitrary and may be appropriately selected and determined. The viscosity average molecular weight [Mv] is usually 10,000 or more, preferably 14,000 or more, more preferably 16,000 or more, and is usually 40,000 or less, preferably 30,000 or less. By setting the viscosity average molecular weight to be equal to or higher than the lower limit value of the above range, the mechanical strength of the resin composition can be further improved, which is more preferable when used in applications with high requirements for mechanical strength. On the other hand, by setting the viscosity average molecular weight to be equal to or lower than the upper limit value of the above range, the decrease in the fluidity of the resin composition can be suppressed and improved, and the moldability can be enhanced to facilitate the molding process. In addition, two or more types of polycarbonate resins having different viscosity average molecular weights may be mixed and used. In this case, a polycarbonate resin having a viscosity average molecular weight outside the above preferred range may be mixed.

[0025] The polycarbonate resin preferably contains a high molecular weight polycarbonate resin, for example, preferably a polycarbonate resin having a viscosity average molecular weight [Mv] of 50,000 to 95,000. The viscosity average molecular weight of the high molecular weight polycarbonate resin is more preferably 55,000 or more, further preferably 60,000 or more, particularly preferably 61,000 or more, especially 62,000 or more, and is more preferably 90,000 or less, further preferably 85,000 or less, particularly preferably 80,000 or less, especially 75,000 or less, particularly 70,000 or less.

[0026] When a high molecular weight polycarbonate resin is included, it is preferably contained in the polycarbonate resin at 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit is preferably 40% by mass or less, more preferably 30% by mass or less.

[0027] In the present invention, the viscosity average molecular weight [Mv] of the polycarbonate resin is determined by using methylene chloride as a solvent and an Ubbelohde viscometer to obtain the intrinsic viscosity [η] (unit: dl / g) at a temperature of 25°C, and using the Schnell viscosity formula, that is, η = 1.23×10-4 Mv 0.83 means the value calculated from The intrinsic viscosity [η] is the specific viscosity [η sp measured at each solution concentration [C] (g / dl) and calculated by the following formula.

[0028]

Equation

[0029] The terminal hydroxyl group concentration of the polycarbonate resin is arbitrary and can be appropriately selected and determined. Usually, it is 2000 ppm or less, preferably 1500 ppm or less, more preferably 1000 ppm or less. Thereby, the retention thermal stability and color tone of the resin composition of the present invention can be further improved. Also, the lower limit is usually 10 ppm or more, preferably 30 ppm or more, more preferably 40 ppm or more, particularly for polycarbonate resins produced by the melt transesterification method. Thereby, a decrease in molecular weight can be suppressed, and the mechanical properties of the resin composition of the present invention can be further improved.

[0030] The unit of the terminal hydroxyl group concentration is the mass of the terminal hydroxyl group expressed in ppm with respect to the mass of the polycarbonate resin. The measurement method is colorimetric determination by the titanium tetrachloride / acetic acid method (the method described in Macromol.Chem. 88 215 (1965)). Also, in order to improve the appearance and fluidity of the molded product, the polycarbonate resin may contain a polycarbonate oligomer. The viscosity average molecular weight [Mv] of this polycarbonate oligomer is usually 1500 or more, preferably 2000 or more, and usually 9500 or less, preferably 9000 or less. Further, the polycarbonate oligomer to be contained is preferably 30% by mass or less of the polycarbonate resin (including the polycarbonate oligomer).

[0031] The polycarbonate resin may be not only virgin resin, but also polycarbonate resin recycled from used products (so-called materially recycled polycarbonate resin), or polycarbonate resin produced from polycarbonate resin chemically decomposed back to raw materials (so-called chemically recycled polycarbonate resin). It is also preferable to contain both virgin resin and recycled resin, and it may also consist of recycled polycarbonate resin. When recycled polycarbonate resin is included, the proportion of recycled polycarbonate resin in the polycarbonate resin is preferably 40% or more, 50% or more, 60% or more, 80% or more, and it is also preferable that the recycled polycarbonate resin is 100%.

[0032] <Acrylic resin> The acrylic resin is preferably a methyl methacrylate-based resin, and the monomer amount of the constituent unit of methyl methacrylate is preferably 80 mol% or more, preferably 90 mol% or more, based on the total monomer amount of all constituent units. The acrylic resin is also preferably a copolymer of methyl methacrylate and other methyl acrylates, ethyl acrylate, butyl acrylate, etc.

[0033] Also, the acrylic resin preferably has a mass average molecular weight of 20,000 to 200,000, and preferably 50,000 to 150,000. The mass average molecular weight of the acrylic resin is a value measured using gel permeation chromatography with standard polystyrene as a standard sample.

[0034] The production method of the acrylic resin is generally classified into an emulsion polymerization method, a suspension polymerization method, and a continuous polymerization method. The acrylic resin used in the present invention is preferably an acrylic resin produced by the continuous polymerization method. Furthermore, the continuous production method can be divided into a continuous bulk polymerization method and a continuous solution polymerization method, but in the present invention, acrylic resins obtained by any production method can be used. One type of acrylic resin may be used alone, or two or more types may be used in combination.

[0035] As described above, as the transparent thermoplastic resin (A), a polycarbonate resin or an acrylic resin is preferable. However, when containing other thermoplastic resins other than the polycarbonate resin or the acrylic resin, the content thereof is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less with respect to 100 parts by mass of the polycarbonate resin or the acrylic resin.

[0036] [Metal boride fine particles (B1), tungsten-based oxide fine particles (B2)] The resin composition for laser welding of the present invention contains at least one kind of metal boride fine particles (B1) selected from the group consisting of La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr and Ca, or at least one kind of tungsten-based oxide fine particles (B2) selected from potassium tungstate, rubidium tungstate, cesium tungstate and thallium tungstate in an amount of 0.00035 to 0.5 part by mass with respect to 100 parts by mass of the transparent thermoplastic resin (A).

[0037] The metal boride fine particles (B1) are inorganic fine particles having a function of absorbing light in the laser light wavelength range, and are fine particles having a large amount of free electrons and generating plasma resonance vibration. When laser light is incident on the metal boride fine particles (B1), free electrons are excited according to the vibration frequency of the light, and collective vibration of electrons occurs, and energy is absorbed and radiated. The absorption wavelength at this time depends on the free electron density and the energy structure of the fine particles, and has a plasma absorption wavelength in the vicinity of the wavelength range of 800 to 1200 nm of Nd:YAG laser or semiconductor laser light.

[0038] The metal boride fine particles (B1) are represented by the general formula XB6 (where X is one or more metal elements selected from La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr and Ca).), and may contain a small amount of other borides represented by XB4, XB 12 etc.

[0039] As X, among the above, La and Ce are preferable, and LaB6 and CeB6 are preferable because of their remarkable absorbability and transparency, and LaB6 is particularly preferable.

[0040] The average dispersed particle diameter of the metal boride fine particles (B1) is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 85 nm or less. The lower limit is not particularly limited, but for example, 1 nm or more is preferable because industrial production is easy. The average dispersed particle diameter can be measured by a particle size measuring device based on the dynamic light scattering method, and is the median value (D 50 ) measured by the laser diffraction scattering method.

[0041] The tungsten-based oxide fine particles (B2) are selected from potassium tungstate, rubidium tungstate, cesium tungstate, and thallium tungstate. By adding an element M of potassium, rubidium, cesium, or thallium to tungsten oxide WO3 to form a composite tungsten oxide, free electrons are generated in WO3, and particularly strong absorption characteristics derived from free electrons are exhibited in the near-infrared region, making it effective as laser light absorbing fine particles near a wavelength of 1000 nm. As the composite tungsten oxide, when represented as MxWyOz (where M is potassium, rubidium, cesium, or thallium, W is tungsten, and O is oxygen), a composite tungsten oxide satisfying the relationship of 0.01 ≦ x / y ≦ 1 and 2.0 ≦ z / y ≦ 3 is more preferable.

[0042] The average dispersed particle diameter of the tungsten-based oxide fine particles (B2) is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 85 nm or less. The lower limit is not particularly limited, but for example, 1 nm or more is preferable because industrial production is easy. The average dispersed particle diameter can be measured by a particle size measuring device based on the dynamic light scattering method, and is the median value (D50 ) is as follows.

[0043] The content of the metal boride fine particles (B1) or the tungsten-based oxide fine particles (B2) is 0.00035 to 0.5 parts by mass with respect to 100 parts by mass of the transparent thermoplastic resin (A). By setting the content to such a value, good transparency and laser weldability can be achieved. The content is preferably 0.0005 parts by mass or more, more preferably 0.001 parts by mass or more, and particularly preferably 0.0015 parts by mass or more, especially 0.002 parts by mass or more. Preferably, it is 0.4 parts by mass or less, more preferably 0.3 parts by mass or less, and particularly preferably 0.2 parts by mass or less, 0.1 parts by mass or less, 0.05 parts by mass or less, 0.03 parts by mass or less, especially 0.02 parts by mass or less. The preferable amount in the case of containing (B1) and (B2) together is also this amount.

[0044] [Alkyl acid phosphate, its metal salt, organic phosphonic acid (C)] The resin composition for laser welding of the present invention contains an alkyl acid phosphate or its metal salt, or an organic phosphonic acid (C).

[0045] The alkyl acid phosphate is preferably represented by the following formula (1). O=P(OH) n (OR) 3-n …(1) [In formula (1), R is an alkyl group having 9 to 30 carbon atoms, and n represents an integer of 1 or 2. When n is 1, the two Rs may be the same or different. ) The alkyl acid phosphate is represented by the above formula (1), and the metal salt of the alkyl acid phosphate is preferably a metal salt such as a zinc salt or an aluminum salt of the alkyl acid phosphate represented by the above formula (1).

[0046] The alkyl group represented by R in the above formula (1) may be a linear alkyl group or may have a branch. Specific examples of the alkyl group of R include nonyl, isononyl, decyl, isodecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, o Examples include cetadecyl (i.e., stearyl), eicosyl, tetracosyl groups, etc. The number of carbon atoms in the alkyl group is more preferably any of 13, 18, and 24. As the alkyl acid phosphate, in particular, a mixture of distearyl acid phosphate with n = 1 and monostearyl acid phosphate with n = 2 is preferred.

[0047] As the metal salt of the alkyl acid phosphate, a mixture of zinc salt of distearyl acid phosphate with n = 1 and zinc salt of monostearyl acid phosphate with n = 1 is particularly preferred.

[0048] As the organic phosphonic acid, those represented by the following formula (2) are preferred. R-P(=O)(OH)2…(2) [In formula (2), R is a group selected from the group consisting of an aryl group, an aralkyl group, and an alkyl group.] Examples of the aryl group in the above formula (2) include phenol, hydroxyphenyl, naphthyl, etc. Examples of the aralkyl group include benzyl, p-hydroxybenzyl, 4-hydroxy-2,5-di-t-butylbenzyl, etc. Examples of the alkyl group include ethyl, propyl, butyl, hexyl, octyl, etc.

[0049] Preferred specific examples of the organic phosphonic acid include phenylphosphonic acid, tolylphosphonic acid, benzylphosphonic acid, p-hydroxybenzylphosphonic acid, 4-hydroxy-3,5-di-t-butylbenzylphosphonic acid, ethylphosphonic acid, etc. Among these, arylphosphonic acids such as phenylphosphonic acid are preferred.

[0050] The content of the alkyl acid phosphate, its metal salt, and the organic phosphonic acid (C) is 0.00007 to 0.1 part by mass with respect to 100 parts by mass of the transparent thermoplastic resin (A). By containing such an amount, the resin composition, the welding member, and the welded body of the present invention can provide a laser welding member having high transparency, excellent heat (humid heat) discoloration resistance, and capable of strong laser welding. The welded body obtained by laser welding exhibits excellent transparency and can be excellent in heat discoloration resistance and humid heat discoloration resistance. The content is preferably 0.0001 part by mass or more, more preferably 0.0005 part by mass or more, particularly preferably 0.001 part by mass or more, preferably 0.08 part by mass or less, and even more preferably 0.07 part by mass or less.

[0051] [Phosphite-based antioxidant] It is also preferable that the resin composition for laser welding of the present invention further contains a phosphite-based antioxidant. The phosphite compound is a trivalent phosphorus compound represented by the general formula: P(OR)3, and R represents a monovalent or divalent organic group.

[0052] Examples of such phosphite compounds include triphenyl phosphite, tris(monononylphenyl)phosphite, tris(monononyl / dinonylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, monooctyldiphenylphosphite, dioctylmonophenylphosphite, monodecyldiphenylphosphite, didecylmonophenylphosphite, tridecyl phosphite, trilauryl phosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, bis(2,4-di-tert-butyl-4-methylphenyl)pentaerythritol phosphite, bis(2,6-di-tert-butylphenyl)octyl phosphite, 2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene-diphosphite, 6-[3-(3-tert-butyl-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]-dioxaphosphepine, and the like.

[0053] Among such phosphite compounds, aromatic phosphite compounds represented by the following formula (3) or the following formula (4) having a spiro ring skeleton are more preferable.

[0054] [Chemical formula] [In formula (3), R 1 , R 2 and R 3 may be the same or different from each other and each represents an aryl group having 6 to 30 carbon atoms.]

[0055] [Chemical formula] [In formula (4), R 4 and R 5 may be the same or different from each other and each represents an aryl group having 6 to 30 carbon atoms.]

[0056] As the phosphite antioxidant represented by the above formula (3), triphenyl phosphite, tris(monononylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite and the like are particularly preferable, and tris(2,4-di-tert-butylphenyl) phosphite is more preferable. Specific examples of such phosphite antioxidants include "ADEKA STAB 1178" manufactured by ADEKA Corporation, "Sumilizer TNP" manufactured by Sumitomo Chemical Co., Ltd., "JP-351" manufactured by Johoku Chemical Industry Co., Ltd., "ADEKA STAB 2112" manufactured by ADEKA Corporation, "Irgafos 168" manufactured by BASF Corporation, "JP-650" manufactured by Johoku Chemical Industry Co., Ltd., and the like.

[0057] As the phosphite antioxidant represented by the above formula (4), those having a pentaerythritol diphosphite structure such as bis(2,4-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphite are particularly preferable. Specific examples of such phosphite antioxidants include "ADEKA STAB PEP-36" manufactured by ADEKA Corporation, "Doverphos S-9228" manufactured by Doverchemical Corporation, and the like.

[0058] In addition, the phosphite antioxidant may contain one kind, or may contain two or more kinds in any combination and ratio.

[0059] The content of the phosphite antioxidant is preferably 0.005 to 0.5 parts by mass, preferably 0.01 part by mass or more, more preferably 0.02 part by mass or more, and preferably 0.4 part by mass or less, more preferably 0.3 part by mass or less, particularly preferably 0.2 part by mass or less, 0.1 part by mass or less, especially preferably 0.05 part by mass or less, based on 100 parts by mass of the transparent thermoplastic resin (A). In such an amount, when combined with an alkyl acid phosphate or its metal salt, or an organic phosphonic acid (C), excellent color tone (haze), heat discoloration resistance, and wet heat discoloration resistance can be further improved, and the generation of voids after the wet heat test can be suppressed.

[0060] [Release agent] Moreover, the resin composition for laser welding of the present invention preferably contains a release agent (lubricant). Examples of the release agent include aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds having a number average molecular weight of 200 to 15,000, polysiloxane-based silicone oils, and the like.

[0061] Examples of the aliphatic carboxylic acid include saturated or unsaturated aliphatic monovalent, divalent, or trivalent carboxylic acids. Here, the aliphatic carboxylic acid also includes alicyclic carboxylic acids. Among these, preferred aliphatic carboxylic acids are monovalent or divalent carboxylic acids having 6 to 36 carbon atoms, and aliphatic saturated monovalent carboxylic acids having 6 to 36 carbon atoms are more preferred. Specific examples of such aliphatic carboxylic acids include palmitic acid, stearic acid, caproic acid, capric acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, melissic acid, tetratriacontanoic acid, montanic acid, adipic acid, azelaic acid, and the like.

[0062] As the aliphatic carboxylic acid in the ester of an aliphatic carboxylic acid and an alcohol, for example, the same ones as the above aliphatic carboxylic acids can be used. On the other hand, examples of the alcohol include saturated or unsaturated monohydric or polyhydric alcohols. These alcohols may have substituents such as fluorine atoms and aryl groups. Among these, monohydric or polyhydric saturated alcohols having 30 or fewer carbon atoms are preferred, and aliphatic saturated monohydric alcohols or aliphatic saturated polyhydric alcohols having 30 or fewer carbon atoms are more preferred. Here, aliphatic is used as a term that also includes alicyclic compounds.

[0063] Specific examples of such alcohols include octanol, decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol, diethylene glycol, glycerin, pentaerythritol, 2,2-dihydroxyperfluoropropanol, neopentylene glycol, ditrimethylolpropane, dipentaerythritol, and the like.

[0064] Note that the above ester may contain an aliphatic carboxylic acid and / or an alcohol as impurities. Also, the above ester may be a pure substance or a mixture of a plurality of compounds. Further, for the aliphatic carboxylic acid and the alcohol that combine to form one ester, each may use one kind, or two or more kinds may be used in combination at an arbitrary combination and ratio.

[0065] Specific examples of the ester of an aliphatic carboxylic acid and an alcohol include beeswax (a mixture mainly composed of myricyl palmitate), stearyl stearate, behenyl behenate, behenyl stearate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, and the like.

[0066] Examples of the aliphatic hydrocarbon having a number average molecular weight of 200 to 15,000 include, for example, liquid paraffin, paraffin wax, micro wax, polyethylene wax, Fischer-Tropsch wax, α-olefin oligomers having 3 to 12 carbon atoms, and the like. Here, the aliphatic hydrocarbon includes alicyclic hydrocarbons. Further, these hydrocarbons may be partially oxidized. Among these, paraffin wax, polyethylene wax or a partially oxidized product of polyethylene wax is preferable, and paraffin wax and polyethylene wax are more preferable. Further, the number average molecular weight of the aliphatic hydrocarbon is preferably 5,000 or less. The aliphatic hydrocarbon may be a single substance, or may be a mixture of various components and molecular weights, as long as the main component is within the above range, it can be used.

[0067] Examples of the polysiloxane-based silicone oil include dimethyl silicone oil, methylphenyl silicone oil, diphenyl silicone oil, fluorinated alkyl silicone, and the like.

[0068] In addition, the above-described release agent may contain one kind, or may contain two or more kinds in any combination and ratio.

[0069] The content of the release agent is usually 0.001 part by mass or more, preferably 0.01 part by mass or more, and usually 2 parts by mass or less, preferably 1 part by mass or less, based on 100 parts by mass of the transparent thermoplastic resin (A). When the content of the release agent is less than the lower limit value of the above range, the effect of mold release may not be sufficient. When the content of the release agent exceeds the upper limit value of the above range, a decrease in hydrolysis resistance, mold contamination during injection molding, etc. may occur.

[0070] [Ultraviolet Absorber] The resin composition for laser welding of the present invention preferably further contains an ultraviolet absorber. Examples of the ultraviolet absorber include inorganic ultraviolet absorbers such as cerium oxide and zinc oxide; organic ultraviolet absorbers such as benzotriazole compounds, benzophenone compounds, salicylate compounds, cyanoacrylate compounds, triazine compounds, oxanilide compounds, malonic ester compounds, and hindered amine compounds. Among these, organic ultraviolet absorbers are preferred, and benzotriazole compounds are more preferred. By selecting an organic ultraviolet absorber, the transparency and mechanical properties of the resin composition of the present invention become good.

[0071] Specific examples of the benzotriazole compound include, for example, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]-benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butyl-phenyl)-benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butyl-phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amyl)-benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], etc. Among them, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole and 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol] are preferred, and particularly 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole is preferred. Specific examples of such benzotriazole compounds include, for example, "Seesorb 701", "Seesorb 705", "Seesorb 703", "Seesorb 702", "Seesorb 704", "Seesorb 709" manufactured by Cipro Kasei Co., Ltd., "Biosorb 520", "Biosorb 582", "Biosorb 580", "Biosorb 583" manufactured by Kyodo Yakuhin Co., Ltd., "Chemisorb 71", "Chemisorb 72" manufactured by Chemipro Kasei Co., Ltd., "SiaSorb UV5411" manufactured by Cytec Industries Inc., "LA-32", "LA-38", "LA-36", "LA-34", "LA-31" manufactured by ADEKA Corporation, "Tinuvin P", "Tinuvin 234", "Tinuvin 326", "Tinuvin 327", "Tinuvin 328" manufactured by BASF Corporation, etc.

[0072] Specific examples of the benzophenone compounds include, for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-n-dodecyloxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, etc. Specific examples of such benzophenone compounds include, for example, "Seesorb 100", "Seesorb 101", "Seesorb 101S", "Seesorb 102", "Seesorb 103" manufactured by Cipro Kasei Co., Ltd., "Biosorb 100", "Biosorb 110", "Biosorb 130" manufactured by Kyodo Yakuhin Co., Ltd., "Chemisorb 10", "Chemisorb 11", "Chemisorb 11S", "Chemisorb 12", "Chemisorb 13", "Chemisorb 111" manufactured by Chemipro Kasei Co., Ltd., "Uvinul 400" manufactured by BASF, "Uvinul M-40" manufactured by BASF, "Uvinul MS-40" manufactured by BASF, "Ciasorb UV9", "Ciasorb UV284", "Ciasorb UV531", "Ciasorb UV24" manufactured by Cytec Industries, "Adekastab 1413", "Adekastab LA-51" manufactured by ADEKA, etc.

[0073] Specific examples of the salicylate compounds include, for example, phenyl salicylate, 4-tert-butylphenyl salicylate, etc. Specific examples of such salicylate compounds include, for example, "Seesorb 201", "Seesorb 202" manufactured by Cipro Kasei Co., Ltd., "Chemisorb 21", "Chemisorb 22" manufactured by Chemipro Kasei Co., Ltd., etc.

[0074] Specific examples of the cyanoacrylate compound include, for example, ethyl-2-cyano-3,3-diphenyl acrylate, 2-ethylhexyl-2-cyano-3,3-diphenyl acrylate, etc. Specific examples of such cyanoacrylate compounds include, for example, "Seesorb 501" manufactured by Shipro Kasei Co., Ltd., "Biosorb 910" manufactured by Kyodo Yakuhin Co., Ltd., "Uvisolator 300" manufactured by Daiichi Kasei Co., Ltd., "Uvinul N-35", "Uvinul N-539" manufactured by BASF Co., Ltd., etc.

[0075] Specific examples of the oxanilide compound include, for example, 2-ethoxy-2'-ethyloxalyni c acid bisanilide, etc. Specific examples of such oxanilide compounds include, for example, "Sanduvor VSU" manufactured by Clariant Co., Ltd., etc.

[0076] As the malonic ester compound, 2-(alkylidene) malonic esters are preferable, and 2-(1-arylalkylidene) malonic esters are more preferable. Specific examples of such malonic ester compounds include, for example, "PR-25" manufactured by Clariant Japan Co., Ltd., "B-CAP" manufactured by BASF Co., Ltd., etc.

[0077] When the resin composition for laser welding of the present invention contains an ultraviolet absorber, its content is usually 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and usually 1 part by mass or less, preferably 0.5 parts by mass or less, based on 100 parts by mass of the transparent thermoplastic resin (A). When the content of the ultraviolet absorber is less than the lower limit value of the above range, the effect of improving weather resistance may be insufficient. When the content of the ultraviolet absorber exceeds the upper limit value of the above range, mold deposits and the like may occur, which may cause mold contamination. Note that one kind of ultraviolet absorber may be contained, or two or more kinds may be contained in any combination and ratio.

[0078] [Other components] The laser welding resin composition of the present invention may contain other components in addition to those described above, as necessary, as long as the desired physical properties are not significantly impaired. Examples of other components include various resin additives and other resins. The other components may be contained alone or in any combination and ratio of two or more.

[0079] <Resin additives> Examples of resin additives include flame retardants, flame retardant auxiliaries, fillers, fluorescent whitening agents, impact resistance improvers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, compatibilizers, antibacterial agents, etc. Note that one type of resin additive may be contained, or two or more types may be contained in any combination and ratio. In addition to the above-mentioned components, other resins, additives, etc. may be contained as needed, so long as the desired physical properties are not significantly impaired.

[0080] <Other resins> Other resins include, for example, thermoplastic polyester resins such as polyethylene terephthalate resin, polytrimethylene terephthalate resin, and polybutylene terephthalate resin; styrene-based resins such as polystyrene resin, high impact polystyrene resin (HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), and acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin); polyolefin resins such as polyethylene resin and polypropylene resin; polyamide resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene ether resin; polyphenylene sulfide resin; and polysulfone resin. The other resins may be contained either alone or in any combination and ratio of two or more. However, when other resins are contained, the content thereof is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, per 100 parts by mass of the polycarbonate resin (A).

[0081] [Production of resin composition] There is no limitation on the method for producing the laser weldable resin composition of the present invention, and a wide range of known methods for producing resin compositions can be used. A specific example is a method in which the above-mentioned essential components (A) to (C) and other components that are added as needed are premixed using various mixers such as a tumbler or a Henschel mixer, and then melt-kneaded using a mixer such as a Banbury mixer, a roll, a Brabender, a single-screw kneading extruder, a twin-screw kneading extruder, a kneader, etc. In this case, it is also preferable to side-feed each component as needed.

[0082] Alternatively, for example, the laser weldable resin composition can be produced by not mixing the components in advance, or by mixing only some of the components in advance, feeding the mixture into an extruder using a feeder, and melt-kneading the mixture. In addition, for example, a resin composition obtained by pre-mixing some of the components, feeding the mixture to an extruder, and melt-kneading the mixture can be used as a masterbatch, and the masterbatch can be mixed again with the remaining components and melt-kneaded to produce a laser welding resin composition. Alternatively, the masterbatch may be mixed with resin pellets as a base material and then directly charged into a molding machine to produce a molded product. Furthermore, when mixing a component that is difficult to disperse, the component may be dissolved or dispersed in advance in a solvent such as water or an organic solvent, and then the resulting solution or dispersion may be kneaded to enhance dispersibility.

[0083] [Molded body] The laser weldable resin composition of the present invention is molded into a laser weldable member. The forming method can arbitrarily adopt the forming methods generally used for thermoplastic resin compositions. Examples thereof include injection molding methods, ultra-high-speed injection molding methods, injection compression molding methods, two-color molding methods, hollow molding methods such as gas assist, molding methods using heat-insulating molds, molding methods using rapidly heated molds, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating molding) molding methods, extrusion molding methods, sheet molding methods, thermoforming methods, rotational molding methods, lamination molding methods, press molding methods, blow molding methods, etc. Also, a molding method using a hot runner system can be used. Among these, injection molding methods such as injection molding methods, ultra-high-speed injection molding methods, and injection compression molding methods, sheet extrusion molding methods, profile extrusion molding methods, etc. are preferable.

[0084] The molded body formed from the resin composition of the present invention is used for laser welding as a member for laser welding (laser light absorber). The haze of the laser welding member molded using the laser welding resin composition of the present invention is preferably 80% or less, more preferably 70% or less, 60% or less, 55% or less, particularly preferably 50% or less, and preferably 20% or more, more preferably 30% or more, particularly preferably 40% or more, as measured at a thickness of 2 mm and a wavelength of 1070 nm in accordance with ISO13468-#.

[0085] The shape of the molded body formed and used from the laser welding resin composition of the present invention is not limited, and it may be a flat plate or a non-planar shape such as a curved surface shape. For example, it may be dome-shaped, hemispherical, cylindrical, pyramid-shaped, corrugated, etc., or a complex shape combining a plane and a non-plane.

[0086] The method of laser welding is not particularly limited and can be performed by a normal method. Preferably, the laser welding member obtained from the laser welding resin composition of the present invention is used as the absorption side (laser absorption side member), and it is brought into surface contact or butting contact with another transparent resin member (transmission side member) of the mating material, and the two members are welded and integrated into a laser welded body by irradiating laser light from the transmission side member side.

[0087] As other transparent resin components for the counterpart material, transparent thermoplastic resins are preferred, and examples thereof include thermoplastic resins such as polycarbonate resins; acrylic resins such as polymethyl methacrylate resins; amorphous polyester resins such as polyethylene terephthalate (PET) resins; polystyrene-based resins; cyclic polyolefin-based resins; and vinyl chloride resins, or polymer alloys consisting of two or more of these thermoplastic resins. Among these, from the viewpoint of transparency, it is preferable to use polycarbonate resin or acrylic resin, and polycarbonate resin is particularly preferable. From the viewpoint of compatibility, it is preferable to use a material containing the same type of transparent thermoplastic resin as the laser welding member (laser light absorbing material) as the main component.

[0088] The type of laser light irradiated in laser welding can be any near-infrared laser light, and preferred examples include YAG (yttrium aluminum garnet crystal) lasers (wavelength 1064 nm) and LD (laser diode) lasers (wavelengths 808 nm, 840 nm, 940 nm).

[0089] The welded body integrated by laser welding may have any shape, size, thickness, etc., and is suitable as a component for products that require a high degree of transparency, such as wearable devices, medical device parts, optical components, lighting equipment, lenses, lens covers, various displays, electrical and electronic devices, laptop computers, pachinko, pachislot, amusement equipment such as games, office automation equipment, information terminal equipment, home appliances, vehicle parts (lights, interior parts, panels), transparent partitions, panel components such as product displays, partition boards for vending machines, ticket vending machines, signs, watches, accessories, etc. EXAMPLES

[0090] The present invention will be explained in more detail below by showing examples, but the present invention should not be construed as being limited to the following examples. The components used in the examples and comparative examples are as shown in Table 1 below.

[0091]

Table 1

[0092] (Examples 1 to 4、9~ 11, Reference Examples 5 to 8 , Comparative Examples 1 to 9) [Manufacture of Resin Pellets] Each component described in Table 1 was blended at the ratios (parts by mass) described in Table 2 below, mixed in a tumbler mixer for 20 minutes, and then supplied to a twin-screw extruder "TEX25αIII" manufactured by Japan Steel Works, Ltd. The mixture was kneaded under the conditions of a screw rotation speed of 200 rpm, a discharge rate of 25 kg / hr, and a cylinder temperature of 280°C, and extruded in a strand form from the tip of the extrusion nozzle. The extrudate was rapidly cooled in a water tank and cut using a pelletizer to obtain pellets of the polycarbonate resin composition.

[0093] [Transmittance at 1070 nm (2 mmt, unit: %)] After drying the pellets obtained above at 120°C for 5 hours, using an injection molding machine ("EC-50" manufactured by Nissei Plastic Industrial Co., Ltd.), plates in three stages of 90 mm × 60 mm (1 mmt, 2 mmt, 3 mmt thick) were manufactured at a cylinder temperature of 280°C and a mold temperature of 80°C. Using an ultraviolet-visible near-infrared spectrophotometer ("UV-3600" manufactured by Shimadzu Corporation), in accordance with ISO 13468-2, the transmittance (unit: %) at a wavelength of 1070 nm was determined.

[0094] [Haze (2 mmt, unit: %)] The flat plate (2 mm thick) obtained by the above method was measured for haze (unit: %) at a D65 light source and a 10° field of view using a turbidity meter ("NDH-4000" manufactured by Nippon Denshoku Industries Co., Ltd.) based on JIS K7136 and JIS K7361.

[0095] [Difference in haze before and after hydrothermal treatment (ΔHaze, unit: %)] The flat plate (2 mm thick) obtained by the above method was subjected to damp heat treatment at 85 °C and 95% RH for 264 hours using a pressure cooker tester, and then the haze was measured. The difference between the haze values before and after the damp heat treatment was calculated as Δhaze (unit: %), and used as an index of damp heat resistance.

[0096] [Total light transmittance (2mmt, unit: %)] The total light transmittance (unit: %) of the flat plate (2 mm thick) obtained by the above method was measured using a turbidimeter ("NDH-4000" manufactured by Nippon Denshoku Industries Co., Ltd.).

[0097] [Evaluation of laser weldability] After drying the pellets obtained above at 120 °C for 5 hours, using an injection molding machine ("J55" manufactured by Japan Steel Works, Ltd.), under the conditions of a cylinder temperature of 280 °C and a mold temperature of 80 °C, an ASTM No. 4 dumbbell piece #1 (laser welding member, = laser light absorber) with a thickness of 1.5 mm was manufactured. Also, as the mating material, a polycarbonate resin ("Iupilon S-3000" manufactured by Mitsubishi Engineering Plastics Corporation, Mv = 21000) was used, and in the same manner as above, an ASTM No. 4 dumbbell piece #2 (= laser light transmitting material) with a thickness of 1.5 mm was manufactured. The obtained ASTM No. 4 dumbbell pieces #1 and #2 were used, and the two were overlapped, and the overlapped portion was irradiated with laser light for laser welding.

[0098] Laser welding was performed using a "Galvano scanning type laser processing machine FIBER ELEPHANT(3D)" manufactured by ARGES under the conditions of a laser wavelength of 1070 nm, a laser output of 100 W, a laser scan speed of 150 mm / second, a pressure of 0.4 MPa, and a welded portion size of 2 × 6 mm.

[0099] Using a tensile testing machine ("5544" manufactured by Instron Corporation), grasping the opposite sides of the welded portions of the welded dumbbell piece #1 and dumbbell piece #2 respectively, applying a load at a tensile speed of 5 mm / min in the tensile direction, observing the state of shear fracture, and evaluating according to the following criteria. 〇: Base material fracture occurs, and the welding strength is extremely high. ×: Fracture occurs at the welded surface or there is no welding at all.

[0100] [Transmittance of the laser welded body after welding (unit: %)] The total transmittance (3 mmt, unit: %) of the dumbbell piece #1 (1.5 mm t) and the dumbbell piece #2 (1.5 mm t) after laser welding was measured in the same manner as above, and the transparency of the welded body after welding was evaluated.

[0101] The above evaluation results are shown in Table 2 below.

[0102]

Table 2

[0103]

Table 3

Industrial Applicability

[0104] The welded body obtained by laser welding the resin composition for laser welding of the present invention exhibits excellent transparency and excellent heat discoloration resistance and moisture and heat discoloration resistance, and thus can be suitably used as parts for applications where transparency is required.

Claims

Claim 1: Based on 100 parts by mass of the polycarbonate resin (A), 0.00035 to 0.02 parts by mass of at least one metal boride fine particle (B1) selected from the group consisting of La, Ce, Pr, Nd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr, and Ca, or at least one tungsten-based oxide fine particle (B2) selected from potassium tungstate, rubidium tungstate, cesium tungstate, and thallium tungstate, 0.00007 to 0.08 parts by mass of an alkyl acid phosphate represented by the following formula (1) or an organic phosphonic acid represented by the following formula (2), and 0.01 to 0.1 parts by mass of bis(2,4-dicumylphenyl)pentaerythritol diphosphite which is a phosphite-based antioxidant, and the content of resins other than the polycarbonate resin (A) is 3 parts by mass or less. A resin composition for laser welding characterized by the above. O = P(OH)n(OR)3−n …(1) [In formula (1), R is an alkyl group having 9 to 30 carbon atoms, and n represents an integer of 1 or 2. When n is 1, the two Rs may be the same or different. ] R−P(=O)(OH)2 …(2) [In formula (2), R is a group selected from the group consisting of an aryl group, an aralkyl group, and an alkyl group. ] Claim 2: The resin composition for laser welding according to Claim 1, wherein Δ haze, which is the difference between the haze values before and after the hydrothermal treatment, is 0.47 or less after hydrothermally treating a 2-mm thick flat test piece of the resin composition at 85 °C and 95% RH for 264 hours. Claim 3 A laser welding member comprising the resin composition for laser welding according to Claim 1 or 2. Claim 4 The laser welding member according to Claim 3, having a haze of 80% or less at a thickness of 2 mm. Claim 5: The laser welding member according to Claim 3 or 4, having a transmittance of 80% or less at a wavelength of 1070 nm measured at a thickness of 2 mm. Claim 6 A laser welded body obtained by laser welding the laser welding member according to any one of Claims 3 to 5 to another polycarbonate resin member. Claim 7 The laser welded body according to Claim 6, wherein the haze of the other polycarbonate resin member at a thickness of 2 mm is 8% or less. Claim 8: The laser welded body according to Claim 6 or 7, having a transmittance of 73.3% or more after welding.

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