Birefringence reducing agent and thermoplastic resin composition

Abstract

Provided is a birefringence reducer that is an additive for reducing birefringence of resin, and comprises an organosiloxane compound having an aromatic group.

Description

Technical Field

[0001] The present invention relates to a birefringence reducing agent and a thermoplastic resin composition, and more particularly to a birefringence reducing agent for reducing the birefringence of a resin and a thermoplastic resin composition containing the same and having reduced birefringence.

Background Art

[0002] Optical lenses made of optically transparent resins have the advantages of being mass-produced by injection molding and being easy to manufacture aspherical lenses, and are used as lenses for cameras, telescopes, and projectors. Examples of optically transparent resins include thermoplastic resins such as polycarbonate resins made from 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), polymethyl methacrylate, or amorphous polyolefins.

[0003] One of the important optical properties that must be considered when using an optically transparent resin as an optical member is birefringence. That is, it is not preferable for an optically transparent resin to have a large birefringence. In particular, in high-end cameras, liquid crystal display devices, projectors, etc., if a lens or the like having a large birefringence is present in the optical path, it will have an adverse effect on image quality and signal reading performance, so an optically transparent resin with birefringence suppressed as small as possible is strongly required.

[0004] However, for example, polycarbonate resins made from bisphenol A as a raw material have the advantages of high refractive index and high heat resistance, but have the disadvantage of large birefringence.

[0005] In response to the requirement for reducing birefringence, it is known to use a polycarbonate resin made from a bisphenol having a specific structure of the resin itself as a raw material. For example, in Patent Document 1, it is disclosed that a special polycarbonate copolymer obtained by copolymerizing spirobisindane bisphenol with bisphenol A has a small birefringence. However, because these special resins are not general-purpose resins, their properties (mechanical properties) and molding conditions are unique, and their use is also limited by their cost. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 06-313035 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above circumstances, and its object (problem) is to provide a birefringence reducing agent that can reduce birefringence simply by being incorporated into an optical transparent resin, and a thermoplastic resin composition containing the same. [Means for solving the problem]

[0008] As a result of diligent research to solve the above-mentioned objectives (problems), the inventors have found that certain organosiloxane compounds can reduce the birefringence of resins. The present invention relates to the following birefringence reducing agents, thermoplastic resin compositions, and molded articles.

[0009] 1. An additive for reducing the birefringence of a resin, comprising an organosiloxane compound having an aromatic group, which is a birefringence reducing agent. 2. The birefringence reducing agent according to claim 1 above, wherein the organosiloxane compound having an aromatic group is a cyclic organosiloxane compound represented by the following general formula (1). [ka] [In formula (1), R represents an aryl group having 6 to 14 carbon atoms, which may have substituents, and n is an integer from 1 to 5.] 3. The birefringence reducing agent according to 2 above, wherein R in formula (1) comprises a phenyl group or a naphthyl group.

[0010] 4. A thermoplastic resin composition comprising a thermoplastic resin and a birefringence reducing agent as described in any of the above 2 to 3. 5. The thermoplastic resin composition according to item 4, wherein the thermoplastic resin has aromatic rings in the main chain and has positive intrinsic birefringence. 6. The thermoplastic resin composition according to 4 or 5 above, wherein the thermoplastic resin is an aromatic polycarbonate resin or an aromatic polyester resin having a glass transition temperature of 160°C or higher. 7. The thermoplastic resin composition according to 6, wherein the aromatic polycarbonate resin is a resin containing 70 mol% or more of the constituent unit represented by the following formula (2) in all constituent units excluding the terminal groups. [ka] 8. The thermoplastic resin composition according to any one of 4 to 7 above, wherein the content of the birefringence reducing agent is more than 2 parts by mass and 15 parts by mass or less per 100 parts by mass of the thermoplastic resin. 9. A thermoplastic resin composition according to any one of the above 4 to 8, wherein birefringence is reduced. 10. A molded article made from any of the thermoplastic resin compositions described in 4 to 9 above. 11. The molded article described in item 10 above, which is an optical molded article. 12. A molded body according to item 10 or 11 above, which is an optical lens. [Effects of the Invention]

[0011] The birefringence reducing agent of the present invention can reduce birefringence simply by being incorporated into a resin. A thermoplastic resin composition in which this agent is incorporated into a thermoplastic resin exhibits reduced birefringence without reducing the transparency (transmittance) of the thermoplastic resin itself, and also has excellent heat aging resistance, no mold contamination problems during molding, and excellent fluidity (moldability). For these reasons, the resulting molded articles are suitable for optical applications, particularly as optical lenses for single-lens reflex cameras, digital still cameras, video cameras, camera phones, film cameras with lenses, telescopes, binoculars, microscopes, or projectors. The organosiloxane compound having an aromatic ring used in the present invention can cancel the birefringence by canceling the polarization anisotropy it has with the polarization anisotropy of the resin. In particular, the cyclic organosiloxane compound represented by the general formula (1) has a structure in which the aromatic ring of the aryl group R stands perpendicular to the cyclic plane of the cyclic organosiloxane. On the other hand, it is considered that the birefringence is effectively canceled by canceling the polarization anisotropies of both the aromatic rings that are planar-oriented in the molecular chain direction, which are particularly possessed by thermoplastic resins.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, each component and the like used in the resin composition constituting the birefringence reducing agent and the thermoplastic resin composition of the present invention will be described in detail. In this specification, when a range is expressed using "~" with numerical values or physical property values sandwiching the front and back thereof, it means a range including the values before and after.

[0013] [Birefringence Reducing Agent] The birefringence reducing agent of the present invention is composed of an organosiloxane compound having an aromatic group. The organosiloxane compound having an aromatic group may have an aromatic group such as a phenyl group or a naphthyl group, and may be either a cyclic or linear organosiloxane compound, but preferably a cyclic organosiloxane compound.

[0014] The linear organosiloxane compound having an aromatic group is a linear organosiloxane in which a siloxane substituted with an aryl group is bonded, and is preferably an organosiloxane composed of a phenyl group-substituted siloxane unit or a siloxane unit substituted with an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group and a phenyl group, and may contain a siloxane unit disubstituted with an alkyl group, such as a dimethylsiloxane unit, a diethylsiloxane unit, or an ethylmethylsiloxane unit.

[0015] As a cyclic organosiloxane compound that is preferable as an organosiloxane compound having an aromatic group, a cyclic organosiloxane compound represented by the following general formula (1) is particularly preferably mentioned. [Chemical formula] [In formula (1), R represents an aryl group having 6 to 14 carbon atoms which may have a substituent, and n is an integer of 1 to 5.]

[0016] R is an aryl group having 6 to 14 carbon atoms, which may have a substituent. Here, examples of the substituent include an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, etc., or a phenyl group, a phenyl group having an alkyl group (such as the above-mentioned alkyl group), etc. Examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, etc., and among them, a phenyl group is preferable. Specific examples of R preferably include a phenyl group, a toluyl group, a dimethylphenyl group, a naphthyl group, a biphenyl group.

[0017] The cyclic organosiloxane compound represented by the general formula (1) may have only one kind of aryl group, or may have two or more different kinds of aryl groups. n is an integer of 1 to 5, preferably an integer of 2 to 4, more preferably 2 or 3, and particularly preferably n is 3.

[0018] Specific examples of the cyclic organosiloxane compound represented by the general formula (1) include octaphenylcyclotetrasiloxane, octanaphthylcyclotetrasiloxane, octatoluylcyclotetrasiloxane, octabiphenylcyclotetrasiloxane, hexaphenylcyclotrisiloxane, decaphenylcyclopentasiloxane, etc., and octaphenylcyclotetrasiloxane is particularly preferable. The cyclic organosiloxane compound may be used alone as only one kind, or may be used in combination of two or more different kinds.

[0019] [Thermoplastic resin composition] When the above-mentioned birefringence-reducing agent is incorporated into a resin, a resin composition is obtained in which the birefringence is reduced compared to the composition before incorporation. As the resin, a thermoplastic resin is preferred, and a thermoplastic resin having an aromatic ring in the main chain is particularly preferred because it tends to have a large birefringence. Furthermore, a thermoplastic resin having a positive intrinsic birefringence is preferred because the birefringence reducing agent of the present invention has a negative intrinsic birefringence, resulting in a greater effect in reducing birefringence. A thermoplastic resin having an aromatic ring in the main chain and having a positive intrinsic birefringence is particularly preferred.

[0020] Preferred thermoplastic resins include polycarbonate resins and polyester resins.

[0021] [Polycarbonate resin] There are no restrictions on the type of polycarbonate resin, and birefringence-reducing agents can be added to any of them. However, aromatic polycarbonate resins, which have aromatic rings in the main chain, are preferred because they have a greater effect in reducing birefringence.

[0022] Aromatic polycarbonate resin is an aromatic polycarbonate polymer obtained by reacting an aromatic hydroxy compound with a phosgene or carbonic acid diester. The aromatic polycarbonate polymer may be branched. The method for producing aromatic polycarbonate resin is not particularly limited and can be conventional methods such as the phosgene method (interfacial polymerization method) or the melting method (transesterification method).

[0023] Representative aromatic dihydroxy compounds include, for example, 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 4,4-bis(4-hydroxyphenyl)heptane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4'-dihydroxybiphenyl, 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl, bis(4-hydroxyphenyl)sulfone, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)ether, and bis(4-hydroxyphenyl)ketone.

[0024] The above aromatic dihydroxy compounds may be used individually or as a mixture of two or more. Among the aromatic dihydroxy compounds mentioned above, 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A) and 2,2-bis(4-hydroxy-3-methylphenyl)propane (i.e., bisphenol C), which result in polycarbonate resins with high birefringence, are preferred. However, 1,1-bis(4-hydroxyphenyl)-1-phenylethane (i.e., bisphenol AP), which exhibits lower birefringence in comparison, or any of the above, are also preferable as they exhibit a birefringence-reducing effect.

[0025] Polycarbonate resins having the following formula (2) constituent units derived from 1,1-bis(4-hydroxyphenyl)-1-phenylethane, i.e., bisphenol AP, are preferred because they exhibit high heat resistance. [ka]

[0026] In polymerization by transesterification, diester carbonates are used as monomers instead of phosgene. Diester carbonates of the above-mentioned aromatic dihydroxy compounds are used, such as substituted diaryl carbonates represented by diphenyl carbonate and dityl carbonate. These diester carbonates can be used individually or in mixtures of two or more.

[0027] The viscosity-average molecular weight (Mv) of polycarbonate resin is preferably in the range of 10,000 to 50,000, more preferably 45,000 or less, even more preferably 40,000 or less, and particularly preferably 38,000 or less. In the case of optical molded articles, it is preferably 10,000 to 30,000. Having a viscosity-average molecular weight in this range results in excellent fluidity (moldability), hue, and mechanical strength, making it suitable for optical molded articles. Furthermore, two or more aromatic polycarbonate resins with different viscosity-average molecular weights may be mixed and used. In this case, polycarbonate resins whose viscosity-average molecular weight is outside the preferred range described above may also be mixed.

[0028] The viscosity-average molecular weight Mv of polycarbonate resin was determined using a Ubbelohde viscometer at 25°C with methylene chloride as the solvent, and the intrinsic viscosity [η] (unit: dl / g) was calculated using Schnell's viscosity formula: η = 1.23 × 10⁻⁶ -4 Mv 0.83 It refers to the value calculated from [the formula]. In addition, intrinsic viscosity [η] is the specific viscosity [η] at each solution concentration [C] (g / dl). sp This value was calculated by measuring [the value] and using the following formula.

number

[0029] Aromatic polycarbonate resins with a glass transition temperature of 160°C or higher are preferred. A glass transition temperature of 160°C or higher allows for higher heat resistance. A glass transition temperature of 165°C or higher is more preferable, and 170°C or higher is particularly preferable. The glass transition temperature of polycarbonate resin is measured using a differential scanning calorimeter (DSC) in accordance with JIS K7122, under the following conditions. Measurement start temperature: 25℃ Heating rate: 10°C / min Achieved temperature: 300℃ Cooling rate: 10℃ / min

[0030] The polycarbonate resin may be virgin resin, as well as polycarbonate resin recycled from used products (so-called material-recycled polycarbonate resin), or polycarbonate resin manufactured from polycarbonate resin that has been chemically decomposed and returned to its raw materials (so-called chemical-recycled polycarbonate resin). It is also preferable to contain both virgin resin and recycled resin, or to consist solely of recycled polycarbonate resin. The proportion of recycled polycarbonate resin in the polycarbonate resin is preferably 40% or more, 50% or more, 60% or more, or 80% or more, and it is also preferable for the recycled polycarbonate resin to be 100%.

[0031] [Polyester resin] There are no restrictions on the type of polyester resin, and the birefringence reducing agent of the present invention can be incorporated into any of them. However, aromatic polyester resins having aromatic rings in the main chain are preferred because they often exhibit positive birefringence and have a greater effect in reducing birefringence. Aromatic polyester resins having aromatic rings in the main chain include polycondensates formed from aromatic dicarboxylic acids and diols.

[0032] As the dicarboxylic acid, aromatic dicarboxylic acids are preferred, such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and the like.

[0033] Examples of diols include aliphatic diols such as ethylene glycol, 1,3-propanediol, diethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,6-cyclohexanedimethanol, tricyclohexanedimethanol, polyethylene oxide glycol, and polypropylene oxide glycol, or aromatic diols such as 1,2-diphenylethane-1,2-diol, 1,1,2,2-tetraphenylethane-1,2-diol, and benzene-1,2-,-1,3-, and-1,4-dimethanol. Bisphenols such as bisphenol A, bisphenol F, bisphenol S, bisphenol AP, tetramethylbisphenol A, and 4,4'-dihydroxydiphenyl-2,2-butane can also be mentioned. These can be used individually or in pairs or more simultaneously.

[0034] From the viewpoint of transparency for optical molded articles, amorphous polyester resin is preferred as the polyester resin. Amorphous polyester resin is defined as a resin in which no clear melting point is observed when heated at a rate of 10°C / min using a differential thermal analyzer.

[0035] The intrinsic viscosity IV of the polyester resin is preferably 0.3 to 1.5 dl / g, more preferably 0.4 to 1.2 dl / g. The intrinsic viscosity IV of polyester resin is measured at 30°C in a 1:1 (mass ratio) mixed solvent of tetrachloroethane and phenol.

[0036] When the birefringence-reducing agent of the present invention is blended with a thermoplastic resin, the content is preferably more than 2 parts by mass and 15 parts by mass or less, and more preferably 2.3 parts by mass or more and 13 parts by mass or less, per 100 parts by mass of the thermoplastic resin. With such a content, the effect of reducing birefringence is sufficiently exhibited, the fluidity (moldability) of the resin composition is sufficient, the heat aging resistance is excellent, and mold contamination is not a problem.

[0037] [Additives, etc.] The resin composition may contain additives such as stabilizers, release agents, flame retardants, flame retardant aids (anti-dripping agents), ultraviolet absorbers, fluorescent whitening agents, antistatic agents, plasticizers, and compatibilizers. These additives or other resins may be blended one or more types.

[0038] [Stabilizer] The resin composition preferably contains a stabilizer, and phosphorus-based stabilizers or phenol-based stabilizers are preferred.

[0039] Any known phosphorus-based stabilizer can be used. Specific examples include phosphoric acid, phosphonic acid, phosphorous acid, phosphinic acid, polyphosphate, and other phosphorus oxoacids; acidic pyrophosphate metal salts such as sodium acidic pyrophosphate, potassium acidic pyrophosphate, and calcium acidic pyrophosphate; phosphates of Group 1 or Group 2B metals such as potassium phosphate, sodium phosphate, cesium phosphate, and zinc phosphate; and organic phosphate compounds, organic phosphite compounds, and organic phosphonite compounds, with organic phosphite compounds and organic phosphate compounds being particularly preferred.

[0040] Examples of organic phosphite compounds include triphenyl phosphite, tris(mononylphenyl) phosphite, tris(mononyl / dinonylphenyl) phosphite, tris(2,4-di-tert-butylphenyl) phosphite, monooctyldiphenyl phosphite, dioctylmonophenyl phosphite, monodecyldiphenyl phosphite, didecylmonophenyl phosphite, tridecyl phosphite, trilauryl phosphite, tristearyl phosphite, and 2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite. Examples of such organic phosphite compounds include, for example, "ADEKA Stab 1178," "ADEKA Stab 2112," and "ADEKA Stab HP-10" from ADEKA Corporation, "JP-351," "JP-360," and "JP-3CP" from Johoku Chemical Industry Co., Ltd., and "Irgaphos 168" from BASF.

[0041] Suitable organic phosphate compounds include metal salts of organic phosphates. Specifically, examples include mixtures of zinc salts of distearyl acid phosphate and zinc salts of monostearyl acid phosphate, monostearyl acid phosphates, and distearyl acid phosphates. Examples of such organic phosphate metal salts include "JP-518Zn" manufactured by Johoku Chemical Industry Co., Ltd. and "AX-71" manufactured by ADEKA Corporation.

[0042] Furthermore, the phosphorus-based stabilizer may be present in any combination and ratio, or in any combination of two or more types.

[0043] The phosphorus-based stabilizer content is typically 0.001 parts by mass or more, preferably 0.01 parts by mass or more, and more preferably 0.03 parts by mass or more, per 100 parts by mass of thermoplastic resin, and typically 1 part by mass or less, preferably 0.7 parts by mass or less, and more preferably 0.5 parts by mass or less. If the phosphorus-based stabilizer content is below the lower limit of the above range, the thermal stabilization effect may be insufficient, and if the phosphorus-based stabilizer content exceeds the upper limit of the above range, the effect may plateau and become uneconomical.

[0044] Examples of phenolic stabilizers include hindered phenolic antioxidants. Specific examples include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphoate, 3,3',3”,5,5',5”-hexa-tert-butyl-a,a',a”-(mesitylene-2,4,6- Examples include triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-ylamino)phenol, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

[0045] Among these, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate are preferred. Examples of such phenolic antioxidants include BASF's "Irganox 1010" and "Irganox 1076," and ADEKA's "ADEKA Stab AO-50" and "ADEKA Stab AO-60." Furthermore, the product may contain one type of phenolic stabilizer, or two or more types in any combination and ratio.

[0046] The content of the phenolic stabilizer is usually 0.001 parts by mass or more, preferably 0.01 parts by mass or more, and usually 1 part by mass or less, preferably 0.5 parts by mass or less, per 100 parts by mass of thermoplastic resin. If the content of the phenolic stabilizer is below the lower limit of the above range, the effect of the phenolic stabilizer may be insufficient, and if the content of the phenolic stabilizer exceeds the upper limit of the above range, the effect may plateau and become uneconomical.

[0047] [Release agent] The resin composition preferably contains a release agent. While known release agents commonly used with resins can be used, polyolefin compounds and fatty acid ester compounds are preferred.

[0048] Examples of polyolefin compounds include those selected from paraffin wax and polyethylene wax, with a preferred weight-average molecular weight of 700 to 10,000, and more preferably 900 to 8,000.

[0049] Examples of fatty acid ester compounds include saturated or unsaturated monovalent or divalent aliphatic carboxylic acid esters, glycerol fatty acid esters, sorbitan fatty acid esters, and other fatty acid esters and their partially saponified products. Among these, mono or di fatty acid esters composed of a fatty acid having 11 to 28 carbon atoms, preferably 17 to 21 carbon atoms, and an alcohol are preferred.

[0050] Examples of fatty acids include palmitic acid, stearic acid, caproic acid, capric acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, melissic acid, tetrariacontanoic acid, montanic acid, adipic acid, and azelaic acid. Furthermore, fatty acids may also be alicyclic. Examples of alcohols include saturated or unsaturated monohydric or polyhydric alcohols. These alcohols may have substituents such as fluorine atoms or aryl groups. Among these, monohydric or polyhydric saturated alcohols with 30 or fewer carbon atoms are preferred, and aliphatic saturated monohydric or polyhydric alcohols with 30 or fewer carbon atoms are more preferred. Here, "aliphatic" includes alicyclic compounds. 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, and dipentaerythritol. The above-mentioned ester compounds may contain aliphatic carboxylic acids and / or alcohols as impurities, and may also be mixtures of multiple compounds.

[0051] Specific examples of fatty acid ester compounds include glycerin monostearate, glycerin monobehenate, glycerin dibehenate, glycerin-12-hydroxymonostearate, sorbitan monobehenate, pentaerythritol monostearate, pentaerythritol distearate, stearyl stearate, and ethylene glycol montanate.

[0052] The release agent content is preferably 0.1 to 3 parts by mass, more preferably 0.2 to 2.5 parts by mass, and even more preferably 0.25 to 2 parts by mass, per 100 parts by mass of thermoplastic resin. If the content is less than 0.1 parts by mass, surface quality tends to deteriorate due to poor release during melt molding. On the other hand, if it exceeds 3 parts by mass, the kneading workability of the resin composition tends to deteriorate, and clouding tends to occur on the surface of the molded article.

[0053] [Flame retardant] The resin composition of the present invention may also contain a flame retardant. Examples of flame retardants include organometallic salt-based flame retardants, phosphorus-based flame retardants, boron-based flame retardants, nitrogen-based flame retardants, halogen-based flame retardants, and antimony compounds.

[0054] However, when pursuing a resin composition with high transparency and low birefringence for optical molded articles, it is preferable to have a low flame retardant content. Even when an organometallic salt-based flame retardant, which is a transparent flame retardant, is included, its content is preferably less than 0.01 parts by mass, and more preferably less than 0.005 parts by mass, per 100 parts by mass of thermoplastic resin.

[0055] [Manufacturing of resin compositions] There are no restrictions on the method of producing the resin composition, and a wide range of known methods for producing thermoplastic resin compositions can be employed. For example, one method involves pre-mixing the resin, organosiloxane compound, and other components as needed using various mixers such as a tumbler or Henschel mixer, and then melt-kneading them using a mixer such as a Banbury mixer, roll, braver, single-screw extruder, twin-screw extruder, or kneader.

[0056] The resin composition can be used to produce various molded articles by molding pellets obtained by pelletizing the above-mentioned resin composition using various molding methods. Alternatively, the resin can be melted and kneaded in an extruder and then directly molded to produce a molded article without going through the pellet stage.

[0057] The resin composition of the present invention exhibits extremely reduced birefringence without impairing the transparency of the resin itself, has excellent heat aging resistance, and is free from problems of fluidity and mold contamination during molding. Therefore, its applications include optical molded articles, specifically various lenses such as those for cameras (SLR cameras, digital still cameras, video cameras, disposable cameras, etc.), telescopes, microscopes, projectors, optical measuring devices, mobile phone cameras, smartphone cameras, tablet cameras, in-car cameras, action cameras, notebook PC cameras, drive recorders, surveillance cameras, small cameras mounted on drones, various optical discs, home televisions, PC displays, in-car monitors, smartphones, head-mounted displays, barcode readers, scanners, and panel members and films used in these applications. [Examples]

[0058] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

[0059] The raw materials used in the following examples and comparative examples are shown in Table 1 below. [Table 1]

[0060] The above-mentioned bisphenol C type aromatic polycarbonate (A5) was produced in the following production example 1. <Manufacturing Example 1: Manufacturing of Bisphenol C-type Polycarbonate Resin (A5)> 26.14 moles (6.75 kg) of 2,2-bis(3-methyl-4-hydroxyphenyl)propane (hereinafter referred to as "BPC") and 26.79 moles (5.74 kg) of diphenyl carbonate were placed in a SUS reactor (internal volume 10 liters) equipped with a stirrer and a distillation condenser. After replacing the reactor with nitrogen gas, the temperature was raised to 220°C over 30 minutes under a nitrogen gas atmosphere. Next, the reaction mixture in the reactor is stirred, and cesium carbonate (Cs2CO3) is added to the molten reaction mixture as a transesterification catalyst at a rate of 1.5 × 10⁻¹⁶ per mole of BPC. -6 The reaction mixture was added to form moles and stirred and matured at 220°C for 30 minutes under a nitrogen gas atmosphere. Next, the pressure in the reactor was reduced to 100 Torr over 40 minutes at the same temperature, and the reaction was continued for another 100 minutes to distill off the phenol. Next, the temperature in the reactor was raised to 284°C over 60 minutes and the pressure was reduced to 3 Torr, and phenol equivalent to almost the entire theoretical distillation amount was distilled off. Next, the pressure in the reactor was maintained at less than 1 Torr at the same temperature, and the reaction was continued for another 60 minutes to complete the polycondensation reaction. At this time, the stirring speed of the stirrer was 38 revolutions per minute, the reaction solution temperature just before the end of the reaction was 289°C, and the stirring power was 0.75 kW. Next, the molten reaction solution was fed into a twin-screw extruder, and 4 times the molar amount of p-toluenesulfonate butyl relative to cesium carbonate was supplied from the first feed port of the twin-screw extruder and mixed with the reaction solution. Then, the reaction solution was extruded in a strand shape through the die of the twin-screw extruder and cut with a cutter to obtain pellets of bisphenol C type polycarbonate resin (A5).

[0061] (Examples) 8~12, 15~16, and refer to Examples 1~7. 13-14, 17, Comparative Examples 1-6) [Manufacturing of resin composition pellets] The polycarbonate resin and various additives listed in Table 1 were blended in the proportions (parts by mass) shown in Table 2 and below. After mixing in a tumbler for 20 minutes, the mixture was kneaded using a vented single-screw extruder with a screw diameter of 50 mm (Tanabe Plastics Co., Ltd. "VS50-34V") at a cylinder temperature of 250°C to 280°C and a screw rotation speed of 80 rpm. The extruded strands were then cut to produce pellets.

[0062] The pellets obtained as described above were dried at 120°C for 5 hours, and then 3 mm thick test specimens were produced by injection molding using an injection molding machine (Sumitomo Heavy Industries, Ltd. "SE50DUZ"). The injection molding conditions were as follows: when bisphenol A type aromatic polycarbonate resin (A1, A2) and bisphenol C type aromatic polycarbonate resin (A5) were included, the cylinder temperature was 280°C and the mold temperature was 80°C; when bisphenol AP type aromatic polycarbonate resin (A3, A4) was included, the cylinder temperature was 300°C and the mold temperature was 100°C. The obtained pellets or test specimens were evaluated as follows.

[0063] [Glass transition temperature (Tg)] The glass transition temperature (Tg) of the resin composition pellets obtained above was measured using a differential thermal scanning calorimeter (DSC, Hitachi High-Tech Science Corporation "DSC7000X") in accordance with JIS K7211 under the following conditions. The measurement conditions are as follows: Sample volume: 5 mg, Atmosphere: Nitrogen gas atmosphere, Noise reduction conditions: 10 degrees / min

[0064] [Evaluation of birefringence] Birefringence was evaluated using a wide-range two-dimensional birefringence evaluation system (Photonic Lattice "WPA-200", measurement wavelength: 523 nm). The values ​​of the 3 mm thick test specimens obtained above were measured before and after annealing. Annealing was performed for 3 hours at a temperature 20°C lower than the Tg of each composition. Birefringence was evaluated using the pre-annealing value of the 3 mm thick test specimen obtained in Comparative Example 1 as 100% (reference value).

[0065] [Total light transmittance (%)] For the 3 mm thick test specimens obtained as described above, the total light transmittance (unit: %) was measured using a spectroscopic haze meter (SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7375.

[0066] [Mold contamination evaluation] The resin composition pellets obtained above were molded 500 times using an injection molding machine (Sumitomo Heavy Industries, Ltd. "SE7MII") under the following conditions: cylinder temperature: 270°C, mold shape: teardrop, mold temperature: 80°C. The adhesion to the mold after this was visually evaluated according to the following criteria. A: Almost no deposits are observed. B; Adhering substances are observed. C: Many deposits are observed. [Liquidity Q value (unit: cm)] 3 / s)] The resin composition pellets obtained above were dried at 120°C for 4 hours, and then the Q value (unit: cm) was measured using a flow tester (Shimadzu Corporation "CFT-500D") in accordance with JIS K7210 under the following conditions. 3 The measurement was taken ( / s). Sample quantity: 1-2g, Temperature: 280℃, Load: 160kgf

[0067] <Evaluation of heat aging resistance (ΔYI)> The YI (initial YI) of the 3 mm thick test specimens obtained by the method described above was measured using the SH7000 manufactured by Nippon Denshoku Industries Co., Ltd. Furthermore, the aforementioned test specimens were subjected to 1000 hours of treatment at 125°C using an accelerated life testing apparatus (EHS-221MD manufactured by ESPEC Corporation), and the YI (YI after 1000 hours of treatment) was measured in the same manner. The heat aging resistance was evaluated using ΔYI in the following formula. [YI after 1000 hours of processing] - [YI after molding]

[0068] The evaluation results are shown in Table 2 and below. In the table, "Actual n" represents "Example n," and "Ratio n" represents "Comparative Example n."

[0069] [Table 2]

[0070] In Comparative Example 3 and Example 7, since they used bisphenol C type aromatic polycarbonate (A5) with a low Tg, it was not possible to perform aging at 125°C for 1000 hours, and therefore ΔYI could not be measured.

[0071] [Table 3] [Industrial applicability]

[0072] The birefringence-reducing agent of the present invention has a significant effect in reducing birefringence. Resin compositions containing it exhibit extremely reduced birefringence without impairing the transparency of the resin itself, have excellent heat aging resistance, and do not have problems with fluidity or mold contamination during molding. Therefore, they can be suitably used as high-performance optical molded articles.

Claims

1. A thermoplastic resin composition characterized by containing, per 100 parts by mass of an aromatic polycarbonate resin, more than 2 parts by mass and 15 parts by mass or less of a birefringence reducing agent consisting of a cyclic organosiloxane compound represented by the following general formula (1), and the aromatic polycarbonate resin containing 70% by mass or more and 100% by mass or less of a polycarbonate resin having the constituent unit of the following formula (2) derived from 1,1-bis(4-hydroxyphenyl)-1-phenylethane. 【Chemistry 1】 [In formula (1), R represents an aryl group having 6 to 14 carbon atoms, which may have substituents, and n is an integer from 1 to 5.] 【Chemistry 2】

2. The thermoplastic resin composition according to claim 1, wherein R in formula (1) comprises a phenyl group or a naphthyl group.

3. The thermoplastic resin composition according to claim 1 or 2, wherein the aromatic polycarbonate resin is an aromatic polycarbonate resin having a glass transition temperature of 160°C or higher.

4. The thermoplastic resin composition according to any one of claims 1 to 3, wherein the aromatic polycarbonate resin is a resin containing 70 mol% or more of the constituent unit represented by formula (2) in all constituent units excluding the terminal groups.

5. A thermoplastic resin composition according to any one of claims 1 to 4, wherein birefringence is reduced.

6. A molded article comprising the thermoplastic resin composition according to any one of claims 1 to 5.

7. The molded article according to claim 6, which is an optical molded article.

8. The molded article according to claim 6 or 7, which is an optical lens.

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