Transparent resin components, resin molded objects, lamp covers, vehicle lamp covers, integrated lamp covers, and vehicle accessories.

Abstract

DEPCT64 Transparent resin components are those that consist of transparent resin. And light-diffusing materials with an average particle diameter of not less than 220 nanometers and not Larger than 300 nanometers and with an available ratio of such light scattering agents greater than 4.0. Parts per million by mass and less than 20 parts per million by mass of the components. Transparent Sin -----------------------------------------------------------

Description

Transparent resin composition, resin molded article, lamp cover, vehicle lamp cover, combination lamp cover and vehicle

[0001] The present invention relates to a transparent resin composition for providing a resin molded article with excellent transparency, brightness, low colorability, and a balance between transparency and brightness. The present invention also relates to a vehicle lamp cover, a combination lamp cover, and a vehicle, including the resin molded article. The present invention also relates to a lamp cover with excellent transparency, brightness, low colorability, and a balance between transparency and brightness, a combination lamp cover, and a vehicle, including the lamp cover. This application claims priority pursuant to Japanese Patent Application No. 2018-041052, filed in Japan on March 7, 2018, and Japanese Patent Application No. 2018-083828, filed in Japan on April 25, 2018, the contents of which are herein by reference.

[0002] Transparent resins such as methacrylic resins, polycarbonate resins, and polystyrene resins are lighter than glass and, among industrialized synthetic resins, offer an excellent balance of transparency, weather resistance, mechanical properties, and processability. Therefore, they are in demand for applications in vehicle interior and exterior components, lamp covers for lighting fixtures, and light guides for surface light source devices (hereinafter simply referred to as "vehicle interior and exterior components, etc."). In particular, recently, methacrylic resins have been adopted for vehicle interior and exterior components such as taillight covers and headlight covers (hereinafter also simply referred to as "lamp covers"), as well as visors, meter panels, display components, and pillars. In these applications for vehicle interior and exterior components, especially lamp covers, there is a growing demand for transparent resin compositions that emit high brightness when the light source is illuminated, in terms of visibility. Furthermore, in terms of design, there is a requirement for transparent and inconspicuous materials when the light source is off, resulting in a growing demand for transparent resin compositions with excellent transparency and suppressed coloration. Generally, the higher the transparency of a material, the less scattered the incident light becomes, and the lower the brightness tends to be. However, in lamp covers with curved shapes, compared to applications with light guide plates or planar light sources consisting only of flat shapes, the light incident on the lamp cover tends to exit at the curved portion, resulting in a shorter light guide distance. Combined with the recent increase in light guide distance due to the shift to LED light sources and the increasing size of vehicle components, there is a growing demand for materials that can maintain high brightness even with long light guide distances. In other words, there is a growing demand for transparent resin compositions that offer an excellent balance between transparency and brightness.

[0003] For example, as a technique to improve the brightness, light emission unevenness, and color unevenness of a light guide, an example in Patent Document 1 describes a light diffusing agent in which the 90% cumulative average particle size (D) is measured in the cumulative distribution curve of particle size. ９０ ) and 10% cumulative average particle size (D １０ ) ratio (D ９０ / D １０ A light guide plate is disclosed, which contains titanium dioxide with a coefficient of 2.8 to 10 in a methacrylic resin.

[0004] As a technique for improving the brightness of a light guide, Patent Document 2 discloses a light guide made of methacrylic resin in which the relationship between the titanium dioxide content and the optical path length is defined, and the examples disclose that titanium dioxide is contained in a range of 0.6 to 2.4 ppm as a light diffusing agent.

[0005] As a technology to improve transparency and brightness, Patent Document 3 discloses a light-emitting material containing light-diffusing agent particles in a methacrylic resin, and the examples disclose that the light-diffusing agent contains titanium dioxide with an average particle size of 1 μm.

[0006] Furthermore, as a technique for improving the brightness of a light guide, Patent Document 4 discloses a light guide containing a specific amount of inorganic fine particles having a specific average particle size in a methacrylic resin, and the examples disclose that titanium dioxide with an average particle size of 200 nm or 400 nm is included as a light diffusing agent.

[0007] Furthermore, as a technique for improving the brightness of a light guide, Patent Document 5 discloses a light guide containing 1.2 ppm of titanium dioxide particles with an average particle size of 200 nm as a light diffusing agent in a methacrylic resin.

[0008] Furthermore, as a technology to improve transparency and brightness, Patent Document 6 discloses a methacrylic resin light guide containing 10 ppm of titanium dioxide particles with an average particle size of 200 nm as a light diffusing agent in the methacrylic resin.

[0009] Japanese Patent Publication No. WO2007 / 058060, Japanese Patent Publication No. 2017-076460, Japanese Patent Publication No. WO2010 / 113422, Japanese Patent Publication No. 2004-351649, Japanese Patent Publication No. 2013-527968, Japanese Patent Publication No. 2006-342211

[0010] However, the light guide plate disclosed in Patent Document 1, which has a titanium dioxide content of 4 ppm by mass or less, had insufficient brightness. Furthermore, the light guide plate with a titanium dioxide content of 20 ppm by mass or more had an insufficient balance between transparency and brightness. In addition, the spread of the particle size distribution of titanium dioxide (D ９０ / D １０The large size of the titanium dioxide particles resulted in an insufficient balance between the transparency and brightness of the light guide plate. The light guide disclosed in the example of Patent Document 2 had insufficient brightness of the light guide plate due to its low titanium dioxide content. The light guide disclosed in the example of Patent Document 3 had an insufficient balance between transparency and brightness due to the large particle size of the titanium dioxide. Furthermore, when used as a light guide with a curved shape, the incident light would exit at the curved portion, posing a problem for use in lamp cover applications.

[0011] The light guide disclosed in the example of Patent Document 4 had a yellowish tint due to the small particle size of titanium dioxide (200 nm), resulting in a low haze value and insufficient brightness. Alternatively, the titanium dioxide particle size was large (400 nm), resulting in an insufficient balance between transparency and brightness. In other words, neither could be used as a lamp cover.

[0012] The light guides disclosed in the examples of Patent Documents 5 and 6 had small titanium dioxide particle sizes and low titanium dioxide content, resulting in low haze values ​​and insufficient brightness. In other words, they could not be used as lamp covers.

[0013] The present invention aims to solve these problems. Specifically, the objective of the present invention is to provide a transparent resin composition for providing a resin molded article that has excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. The transparent resin composition and resin molded article of the present invention have excellent visibility because they emit high brightness when the light source is lit, and excellent design because they are transparent and have a low presence when the light source is turned off, making them suitable for lamp covers, and in particular for vehicle lamp covers and combination lamp covers having a curved shape.

[0014] The present inventors have arrived at the present invention as a result of repeated studies to solve the above problems. [1] A transparent resin composition comprising a transparent resin and a light diffusing agent having an average particle diameter of 220 nm or more and 300 nm or less, wherein the content ratio of the light diffusing agent is greater than 4.0 ppm by mass and less than 20 ppm by mass with respect to the total mass of the transparent resin composition. [2] In the cumulative distribution curve of the particle diameter of the light diffusing agent, the 90% cumulative average particle size (D ９０), and the ratio of the 10% cumulative average particle size (D １０ ), to (D ９０ / D １０[1] The transparent resin composition according to [1], wherein the refractive index difference between the transparent resin and the light diffusing agent is 1.2 or more and 2.5 or less. [3] The transparent resin composition according to [1] or [2], wherein the refractive index difference between the transparent resin and the light diffusing agent is 0.3 or more and 3.0 or less. [4] The transparent resin composition according to any one of [1] to [3], wherein the transparent resin is at least one selected from methacrylic resin, polycarbonate resin and polystyrene resin. [5] The transparent resin composition according to any one of [1] to [4], wherein the light diffusing agent is titanium dioxide particles. [6] The transparent resin composition according to any one of [1] to [5], wherein the content ratio of the light diffusing agent is 6.5 ppm by mass or more and 18 ppm by mass or less with respect to the total mass of the transparent resin composition. [7] The transparent resin composition according to any one of [1] to [5], wherein the content ratio of the light diffusing agent is 7.2 ppm by mass or more and 16 ppm by mass or less with respect to the total mass of the transparent resin composition. [8] A resin molded article comprising the transparent resin composition described in any one of [1] to [7]. [9] A resin molded article comprising a transparent resin composition comprising a transparent resin and a light diffusing agent having an average particle diameter of 220 nm or more and 300 nm or less, wherein the total light transmittance (Tt) in the thickness direction, measured in accordance with ISO 13468, is 75% or more and less than 91%, the haze value (H) in the thickness direction, measured in accordance with ISO 14782, is 1.0% or more and 14.5% or less, and the yellowness (YI), total light transmittance (Tt), and haze value (H) in the thickness direction, measured in accordance with ISO 17223, satisfy the following formulas (1) and (2). 0.04 ≤ H / Tt ≤ 0.18 (1) 0.10 ≤ YI / H ≤ 0.28 (2)

[10] A resin molded article comprising a transparent resin composition containing a transparent resin and a light diffusing agent having an average particle diameter of 220 nm or more and 300 nm or less, wherein the total light transmittance (Tt) in the thickness direction, measured in accordance with ISO 13468, is 75% or more and less than 91%, the haze value (H) in the thickness direction, measured in accordance with ISO 14782, is 1.0% or more and 14.5% or less, and the luminance attenuation coefficient (m) when the resin molded article scatters light in the thickness direction of the resin molded article and guides light in the length direction of the resin molded article. －１) is 10 or more and 30 or less, and the brightness retention coefficient (m) obtained by dividing the brightness attenuation coefficient by the haze value (%) of the resin molded body. －１ A resin molded body having a % of 1.5 to 3.5.

[11] The resin molded body has a light incident end surface provided in at least a portion of the side end surface and a light emission surface provided on at least one main surface of the resin molded body, wherein the average in-plane luminance, which is the average value of the luminance of the light emission surface, is 500 cd / m². ２ The resin molded article according to [9] or

[10] , as described above.

[12] The particle size (D) at which the cumulative frequency in the cumulative frequency distribution curve of the particle size of the light diffusing agent is 90% ９０ ) and the particle size at which the cumulative frequency reaches 10% (D １０ ) ratio (D ９０ / D １０A resin molded article according to any one of [9] to

[11] , wherein the ratio of the light diffusing agent is 1.2 or more and 2.5 or less.

[13] A resin molded article according to any one of [9] to

[12] , wherein the content of the light diffusing agent is preferably more than 4.0 ppm by mass and less than 20 ppm by mass, more preferably 6.5 ppm by mass and 18 ppm by mass or less, and even more preferably 7.2 ppm by mass and 16 ppm by mass or less, with respect to the total mass of the transparent resin composition.

[14] A resin molded article according to any one of [9] to

[13] , wherein the transparent resin is at least one selected from methacrylic resin, polycarbonate resin and polystyrene resin.

[15] A resin molded article according to any one of [9] to

[14] , wherein the light diffusing agent is titanium dioxide particles.

[16] The resin molded body according to any one of the items [8] to

[15] , wherein the resin molded body is selected from the group consisting of vehicle interior and exterior members, lamp covers for lighting fixtures, and light guides for surface light source devices.

[17] The resin molded body according to

[16] , wherein the vehicle interior and exterior member is selected from the group consisting of vehicle lamp covers, visors, instrument panels, and pillars.

[18] A vehicle lamp cover comprising the resin molded body according to any one of the items [8] to

[15] .

[19] A combination lamp cover comprising a transparent or translucent headlamp cover or rear lamp cover substantially free of light diffusing agents and the vehicle lamp cover according to

[18] , wherein the vehicle lamp cover is disposed on the outer edge or at least a portion of the outer edge of the headlamp cover or rear lamp cover.

[20] A vehicle comprising the vehicle lamp cover according to

[18] or the combination lamp cover according to

[19] .

[21] A lamp cover having a total light transmittance (Tt) in the thickness direction of 75% or more and less than 91%, a haze value (H) in the thickness direction of 1.0% or more and 14.5% or less, measured in accordance with ISO 13468, and a yellowness (YI) in the thickness direction of 7.0 or less, measured in accordance with ISO 17223, wherein H / Tt and YI / H satisfy the following formulas (3) and (4).0.01 ≤ H / Tt ≤ 0.2 (3) -1.0 ≤ YI / H ≤ 1.0 (4)

[22] A lamp cover having a total light transmittance (Tt) in the thickness direction of 75% or more and less than 91%, measured in accordance with ISO 13468, a haze value (H) in the thickness direction of 1.0% or more and 14.5% or less, measured in accordance with ISO 14782, and a yellowness (YI) in the thickness direction of 7.0 or less, measured in accordance with ISO 17223, wherein the luminance attenuation coefficient (m) when the lamp cover scatters light in the thickness direction of the lamp cover and guides light in the length direction of the lamp cover. －１ The luminance retention coefficient (m) is obtained by dividing the above by the haze value (%) of the lamp cover. －１ A lamp cover wherein the % is 1.5 or more and 3.5 or less.

[23] The lamp cover according to

[21] or

[22] , wherein the lamp cover comprises a transparent resin and a light diffusing agent, wherein the content ratio of the light diffusing agent is 0.05 to 20 ppm by mass per 100 parts by mass of the transparent resin, and the average particle size of the light diffusing agent is 150 to 500 nm.

[24] The lamp cover according to

[21] or

[22] , wherein the lamp cover comprises a transparent resin and a light diffusing agent, wherein the content ratio of the light diffusing agent is 1.0 to 15 ppm by mass per 100 parts by mass of the transparent resin, and the average particle size of the light diffusing agent is 220 to 300 nm.

[25] The lamp cover according to

[23] or

[24] , wherein the transparent resin is at least one selected from methacrylic resin, polycarbonate resin and polystyrene resin.

[26] The lamp cover according to any one of

[23] to

[25] , wherein the refractive index difference between the transparent resin and the light diffusing agent is 0.3 or more and 3.0 or less.

[27] The lamp cover according to any one of

[23] to

[26] , wherein the light diffusing agent is titanium dioxide particles.

[28] The lamp cover having a light incident end surface provided in at least a portion of the side end surface of the lamp cover and a light emission surface provided on at least one main surface of the lamp cover, wherein the in-plane average luminance, which is the average value of the luminance on the light emission surface, is 500 cd / m². ２The lamp cover described in any one of the paragraphs

[21] to

[27] above.

[29] A combination lamp cover having a transparent or translucent headlamp cover or rear lamp cover substantially free of light diffusing agents and a lamp cover described in any one of the paragraphs

[21] to

[28] , wherein the lamp cover is disposed in an area of ​​at least a part of the outer circumference or outer frame of the headlamp cover or the rear lamp cover.

[30] A vehicle equipped with a lamp cover described in any one of the paragraphs

[21] to

[28] or a combination lamp cover described in

[29] .

[0015] The present invention makes it possible to stably provide a transparent resin composition with excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. Resin molded articles manufactured from the transparent resin composition of the present invention have excellent design qualities because they are transparent and have little presence when the light source is off, and they have excellent visibility because they emit high brightness when the light source is on, that is, they have an excellent balance between transparency and brightness, making them suitable for vehicle interior and exterior components, lamp covers for lighting fixtures, and light guides for surface light source devices, and in particular for vehicle lamp covers for vehicle interior and exterior components. The present invention makes it possible to stably provide a lamp cover with excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. Such a lamp cover has excellent visibility because it emits high brightness when the light source is on, and excellent design qualities because it is transparent and has little presence when the light source is off, making it suitable for lamp covers, and in particular for tail lamp covers, head lamp covers, and combination lamp covers for vehicle components.

[0016] This is a schematic cross-sectional view showing an example of a lamp using the lamp cover of the present invention. This is a schematic cross-sectional view showing another example of a lamp using the lamp cover of the present invention. This is a schematic cross-sectional view seen from above showing an example of a combination lamp using the combination lamp cover of the present invention. This is a schematic front view seen from the side showing an example of a combination lamp using the combination lamp cover of the present invention. This is a schematic diagram for explaining the method of measuring the luminance attenuation coefficient, luminance retention coefficient, and in-plane average luminance. This is a cumulative frequency distribution curve of titanium dioxide (1) used as a light diffusing agent in the embodiment. This is a cumulative frequency distribution curve of titanium dioxide (2) used as a light diffusing agent in the embodiment. This is a schematic diagram showing a vehicle in which the resin molded body of the present invention is used as a vehicle exterior component, namely a vehicle lamp cover, visor, and pillar. This is a schematic diagram showing an example of a lighting fixture in which the resin molded body of the present invention is used as a lamp cover for a lighting fixture. This is a schematic diagram showing an example of using the resin molded body of the present invention in a surface light source device. This is a schematic diagram showing an example of using the resin molded body of the present invention in a vehicle interior component, namely a meter panel.

[0017] In this invention, "(meth)acrylic acid" means at least one selected from "acrylic acid" and "methacrylic acid." In this invention, "monomer" means an unpolymerized compound, and "repeating unit" means a unit derived from the monomer formed by polymerization of the monomer. The repeating unit may be a unit directly formed by a polymerization reaction, or it may be a unit in which a part of the unit is converted to a different structure by processing the polymer. In this invention, "mass%" indicates the content ratio of a specific component contained in 100% by mass of the total amount. Unless otherwise specified, numerical ranges expressed using "~" in this specification mean a range that includes the numbers written before and after "~" as the lower and upper limits, and "A~B" means A or more and B or less. In this invention, "transparent" means that the total light transmittance measured in accordance with JIS K7105 is 75% or more. In this invention, "translucent" means that the total light transmittance measured in accordance with JIS K7105 is 50% or more and less than 75%. In this invention, "lamp cover" means a cover that protects the light source and allows light from the light source to pass through and irradiate the outside. In this invention, "light source" means a light-emitting body that emits light using electricity. In this invention, "combination lamp cover" means a lamp cover that is provided on the front side of the light source of a combination lamp in a vehicle such as an automobile or motorcycle, so as to cover the front of the light source, and means a lamp cover that is composed of a lamp cover part that substantially does not contain a light diffusing agent and a lamp cover part that contains a light diffusing agent. In this invention, "vehicle" means a vehicle with wheels.

[0018] The present invention will be described in detail below, but the present invention is not limited to these embodiments.

[0019] The present invention relates to a transparent resin composition as a first embodiment, a resin molded article containing the transparent resin composition as a second embodiment, a vehicle lamp cover containing the resin molded article as a third embodiment, a combination lamp cover having the vehicle lamp cover as a fourth embodiment, and a vehicle including the vehicle lamp cover or the combination lamp cover as a fifth embodiment. Furthermore, the present invention relates to a lamp cover as a sixth embodiment, a combination lamp cover having the lamp cover as a seventh embodiment, and a vehicle equipped with the lamp cover or the combination lamp cover as an eighth embodiment.

[0020] <Transparent Resin Composition> The present invention describes a transparent resin composition, which is a first embodiment. The transparent resin composition of the present invention is a transparent resin composition comprising a transparent resin described later and a light diffusing agent described later. By including the transparent resin described later in the transparent resin composition of the present invention, the resulting resin molded article has excellent transparency. By including the light diffusing agent described later in the transparent resin composition of the present invention, the resulting resin molded article has excellent brightness, low coloration, and a good balance between transparency and brightness.

[0021] Furthermore, in the transparent resin composition of the present invention, the lower limit of the light diffusing agent content is preferably greater than 4.0 ppm by mass relative to the total mass of the transparent resin composition, from the viewpoint of the brightness of the resulting resin molded article and the balance between transparency and brightness. More preferably 6.5 ppm by mass or more, and even more preferably 7.2 ppm by mass or more. On the other hand, the upper limit of the light diffusing agent content is preferably less than 20 ppm by mass relative to the total mass of the transparent resin composition, from the viewpoint of the transparency of the resulting resin molded article and the balance between transparency and brightness. More preferably 18 ppm by mass or less, and even more preferably 16 ppm by mass or less. The above upper and lower limits can be arbitrarily combined. Alternatively, the light diffusing agent content of the transparent resin composition is preferably greater than 4.0 ppm by mass and less than 20 ppm by mass, more preferably 6.5 ppm by mass or more and 18 ppm by mass or less, and even more preferably 7.2 ppm by mass or more and 16 ppm by mass or less, relative to the total mass of the transparent resin composition.

[0022] In a more preferred embodiment of the transparent resin composition of the present invention, from the viewpoint of obtaining excellent transparency, brightness, low coloration, and balance between transparency and brightness of the resulting resin molded article, it is preferable to include a light diffusing agent having an average particle size of 220 to 300 nm in a content ratio of more than 4 ppm by mass and less than 20 ppm by mass relative to the total mass of the transparent resin composition. In an even more preferred embodiment of the transparent resin composition of the present invention, from the viewpoint of obtaining even better transparency, brightness, low coloration, and balance between transparency and brightness of the resulting curved resin molded article, it is more preferable to include a light diffusing agent having an average particle size of 220 to 300 nm in a content ratio of 6.5 ppm by mass or more and 18 ppm by mass or less relative to the total mass of the transparent resin composition, and even more preferable to include it in a content ratio of 7.2 ppm by mass or more and 16 ppm by mass or less.

[0023] In the transparent resin composition of the present invention, the lower limit of the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 or higher, and more preferably 0.8 or higher, from the viewpoint of maintaining good brightness of the resulting resin molded article. On the other hand, the upper limit of the refractive index difference is preferably 3.0 or lower, and more preferably 2.0 or lower, from the viewpoint of maintaining good transparency of the resulting resin molded article. The above upper and lower limits can be arbitrarily combined. Specifically, the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 or higher and 3.0 or lower, and more preferably 0.8 or higher and 2.0 or lower. In this specification, "refractive index" is a value measured by the Abbe method using sodium d-line (589 nm).

[0024] <Transparent Resin> The transparent resin is one of the components of the transparent resin composition of the present invention. The type of transparent resin is not particularly limited as long as it is a transparent thermoplastic resin with high light transmittance in the visible light region. For example, a transparent thermoplastic resin can be used which has a total light transmittance of 70% or more as measured in accordance with ISO 13468 and a haze value of 15% or less as measured in accordance with ISO 14782. Specifically, one type selected from transparent thermoplastic resins such as methacrylic resins, polycarbonate resins, polystyrene resins, and methyl methacrylate-styrene resins (MS resins) according to desired properties may be used alone, or two or more types may be used in mixture. Among these, polycarbonate resins are preferred in terms of heat resistance and impact resistance, and methacrylic resins are preferred in terms of transparency and weather resistance.

[0025] (Methacrylic resin) In the present invention, methacrylic resins that can be used as transparent resins include homopolymers of methyl methacrylate (hereinafter abbreviated as "MMA"), or MMA copolymers in which the content of repeating units derived from MMA (hereinafter abbreviated as "MMA units") is 70% by mass or more and less than 100% by mass of the total mass of the methacrylic resin, as these have good transparency. The MMA copolymer can be a polymer in which, with the total mass of the MMA copolymer being 100% by mass, 70% by mass or more and less than 100% by mass of MMA units and more than 0% by mass and 30% by mass or less of repeating units derived from other monomers (hereinafter abbreviated as "other monomer units") described later. A polymer containing 85 to 100% by mass of MMA units and 0 to 15% by mass of other monomer units is more preferred, and a polymer containing 90 to 100% by mass of MMA units and 0 to 10% by mass of other monomer units is even more preferred.

[0026] Other monomers are not particularly limited as long as they are monomers copolymerizable with MMA, and include, for example, the following a) to f): a) (meth)acrylic acid ester compounds other than MMA, such as methyl acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, lauryl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, 2-naphthyl (meth)acrylate, and phenoxymethyl (meth)acrylate. b) Aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p-methoxystyrene, p-acetoxystyrene, α-vinylnaphthalene, and 2-vinylfluorene. c) Unsaturated nitrile compounds such as acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, and vinylidene cyanide. d) Ethylene unsaturated ether compounds such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, and ethyl allyl ether. e) Halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, and 1,2-dibromoethylene. f) Aliphatic conjugated diene compounds such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadienes, and linear and side-chain conjugated hexadienes.

[0027] These other monomers may be used individually or in combination of two or more. Among these other monomers, alkyl acrylates with 1 to 8 carbon atoms in the alkyl group are preferred, from the viewpoint of not impairing the inherent performance of the methacrylic resin and having excellent thermal decomposition resistance of the resulting resin molded product, methyl acrylate, ethyl acrylate, and n-butyl acrylate are more preferred, and methyl acrylate and ethyl acrylate are even more preferred.

[0028] There are no particular restrictions on the polymerization method used when polymerizing monomer components. For example, known polymerization methods such as suspension polymerization, solution polymerization, and bulk polymerization can be employed, but bulk polymerization is preferred. Batch and continuous methods can be used for bulk polymerization. For example, polymers can be obtained with high productivity by continuously supplying monomer components and polymerization initiators into a reaction vessel and continuously withdrawing the resulting partial polymer after it has been retained in the reaction vessel for a predetermined time.

[0029] The polymerization initiator used when polymerizing monomer components is not particularly limited, and known radical polymerization initiators such as known azo compounds like azobisisobutyronitrile and known peroxides like 1,1-di(t-butylperoxy)cyclohexane can be used. The polymerization initiator may be used alone or in combination of two or more.

[0030] When polymerizing monomer components, a chain transfer agent can be used to adjust the molecular weight of the methacrylic resin. The type of chain transfer agent is not particularly limited, but preferred examples include mercaptans such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and 2-ethylhexyl thioglycolate. The chain transfer agent may be used alone or in combination of two or more types.

[0031] The weight-average molecular weight (Mw) of the methacrylic resin of the present invention is not particularly limited and can be appropriately set by those skilled in the art according to the shape and size of the resulting resin molded article, or the processing method of the resin molded article. The weight-average molecular weight (Mw) is generally set in the range of 20,000 to 1,000,000, and in the range of 50,000 to 200,000 for injection molding applications. In this specification, the number-average molecular weight is the value measured using gel permeation chromatography with standard polymethyl methacrylate as the standard sample.

[0032] Commercially available methacrylic resins include Acrypet VH, MD, and MF (product names, manufactured by Mitsubishi Chemical Corporation).

[0033] (Polycarbonate Resins) Examples of polycarbonate resins that can be used as transparent resins in the present invention include those obtained by reacting a known divalent phenol with a known carbonylating agent by interfacial polycondensation or molten transesterification; those obtained by polymerizing a known carbonate prepolymer by solid-phase transesterification; and those obtained by polymerizing a known cyclic carbonate compound by ring-opening polymerization.

[0034] Commercially available polycarbonate resins include the Panlite series (product name, manufactured by Teijin Chemicals), the Yupilon series (product name, manufactured by Mitsubishi Engineering Plastics), the SD Polycarbonate series (product name, manufactured by Sumitomo Dow), Caliber (product name, manufactured by Dow Chemical), the CZ series and PCZ series (product names, manufactured by Mitsubishi Gas Chemical Company), and the APEC series (product name, manufactured by Bayer).

[0035] (Polystyrene Resin) In the present invention, polystyrene resins that can be used as transparent resins include homopolymers of styrene (hereinafter abbreviated as "St"), or styrene copolymers in which the content of repeating units derived from St (hereinafter abbreviated as "St units") is 70% by mass or more and less than 100% by mass of the total mass of the polystyrene resin. Specifically, polystyrene resins include polystyrene, styrene-acrylonitrile resin, acrylonitrile-butadiene-styrene resin, and methyl methacrylate-styrene resin (MS resin). Preferably, it is methyl methacrylate-styrene resin. Commercially available polystyrene products include PSJ polystyrene and the ET series (trade names, manufactured by PS Japan Co., Ltd.). Commercially available MS resins include the Estyrene MS series (trade name, manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), the Sebian MAS series, and the MAS series (trade names, manufactured by Daicel Polymer Co., Ltd.).

[0036] <Light Diffuser> The light diffuser is one of the components of the transparent resin composition of the present invention. By including the light diffuser of the present invention in the transparent resin composition of the present invention, the resulting resin molded articles and lamp covers will have excellent transparency, brightness, low coloration, and a good balance between transparency and brightness.

[0037] When a resin molded article containing the transparent resin composition of the present invention is used in an edge-lit vehicle interior and exterior component or a light guide for a surface light source device, if the particle size of the light diffuser is too small, the proportion of forward scattering tends to increase, and the proportion of orthogonal scattering and backscatter tends to decrease. Conversely, if the particle size of the light diffuser is too large, the proportion of backscatter increases, and the proportion of forward scattering and orthogonal scattering decreases. In other words, if the particle size of the light diffuser is too small or too large, the brightness of orthogonal scattering required for an edge-lit vehicle interior and exterior component or a light guide for a surface light source device tends to be insufficient. This effect is particularly pronounced in lamp covers with curved shapes. Furthermore, the smaller the particle size of the light diffuser, the more the relatively short-wavelength blue light in the wavelength range of the incident visible light is scattered by the fine particles, resulting in a tendency for the light to take on a yellowish tint. Therefore, increasing the particle size of the light diffuser may reduce the light diffusivity, and it is necessary to increase the amount of light diffuser added to obtain sufficient brightness. Increasing the amount of light-diffusing agent increases brightness, but tends to decrease transparency, disrupting the balance between transparency and brightness. Furthermore, it is known that the smaller the refractive index difference between the light-diffusing agent and the transparent resin, the more likely it is that a change will occur in the hue of the light observed near the light source incident end face of the light guide and the light observed at positions further away from that incident end face. However, in the transparent resin composition of the present invention, by optimizing the combination of the particle size of the light-diffusing agent and the content ratio of the light-diffusing agent, it is possible to improve not only the brightness of orthogonal scattering but also the brightness across all angles measured with respect to the surface normal of the resulting resin molded body. In particular, the above effects are especially pronounced in lamp covers with curved shapes, so by optimizing the combination of the particle size of the light-diffusing agent, the refractive index difference between the light-diffusing agent and the transparent resin, and the content of the light-diffusing agent, it is possible to improve not only the brightness of orthogonal scattering but also the brightness across all angles measured with respect to the surface normal of the lamp cover.

[0038] The lower limit of the average particle size of the light diffusing agent of the present invention is preferably 220 nm or higher, from the viewpoint of excellent brightness and low coloration of the resulting resin molded article. The upper limit of the average particle size is preferably 300 nm or lower, and more preferably 280 nm or lower, from the viewpoint of excellent transparency of the resulting resin molded article. The method for measuring the average particle size of the light diffusing agent will be described later.

[0039] In the lamp cover of the present invention, the lower limit of the average particle size of the light diffusing agent is preferably 150 nm or more, and more preferably 220 nm or more, from the viewpoint of excellent brightness and low coloration of the lamp cover. The upper limit of the average particle size is preferably 500 nm or less, and more preferably 300 nm or less, from the viewpoint of maintaining good transparency of the lamp cover. The above upper and lower limits can be arbitrarily combined. Specifically, the average particle size of the light diffusing agent is preferably 150 to 500 nm, and more preferably 220 to 300 nm.

[0040] Furthermore, the lower limit of the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 or higher, and more preferably 0.8 or higher, from the viewpoint of maintaining good brightness of the lamp cover. The upper limit of the refractive index difference is preferably 3.0 or lower, and more preferably 2.0 or lower, from the viewpoint of maintaining good transparency of the lamp cover. The above upper and lower limits can be combined arbitrarily. Specifically, the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 to 3.0, and more preferably 0.8 to 2.0.

[0041] In a more preferred embodiment, the mixture containing the transparent resin and the light diffusing agent preferably contains a light diffusing agent having an average particle size of 150 to 500 nm in a content ratio of 0.05 to 20 ppm by mass relative to the total mass of the mixture, from the viewpoint of achieving excellent transparency, brightness, low coloration, and balance between transparency and brightness of the lamp cover. In an even more preferred embodiment, from the viewpoint of achieving even better transparency, brightness, low coloration, and balance between transparency and brightness of the curved lamp cover, it is more preferable that the mixture contains a light diffusing agent having an average particle size of 220 to 300 nm in a content ratio of 1.0 to 15 ppm by mass relative to the total mass of the mixture. Known fine particles such as titanium dioxide, aluminum oxide, zinc oxide, zinc sulfide, and barium sulfate can be used as the light diffusing agent. When the transparent resin is a methacrylic resin, titanium dioxide, aluminum oxide, zinc oxide, and zinc sulfide are preferred, and titanium dioxide is more preferred. In particular, for applications such as lamp covers with a curved shape, titanium dioxide particles having an average particle size of 150 to 500 nm are preferred, and titanium dioxide particles having an average particle size of 220 to 300 nm are more preferred. Even with a curved lamp cover, the incident light does not significantly escape from the curved portion, thus enabling good transparency, brightness, low coloration, and a good balance between transparency and brightness.

[0042] The particle size distribution of the light diffusing agent of the present invention is such that the cumulative frequency in the cumulative frequency distribution curve of the particle size of the light diffusing agent reaches 90%, from the viewpoint of achieving a better balance between the transparency and brightness of the resin molded article, the particle size (D ９０ ) and the particle size at which the cumulative frequency reaches 10% (D １０ ) ratio (D ９０ / D １０ ) is preferably 1.2 to 2.5, more preferably 1.5 to 2.3, and even more preferably 1.7 to 2.1. A method for obtaining the cumulative frequency distribution curve of the particle size of the light diffusing agent will be described later. D ９０ / D １０ As the value approaches 1, the particle size distribution of the light diffusing agent becomes sharper, which tends to increase the light diffusion efficiency of the resin molded body. Conversely, this tends to decrease the balance between the transparency and brightness of the resin molded body. From this perspective, D ９０ / D１０ The lower limit is preferably 1.2 or higher, more preferably 1.5 or higher, and even more preferably 1.7 or higher.

[0043] D ９０ / D １０ The upper limit is D １０ It gets smaller and D ９０ / D １０ As D increases, the balance between transparency and brightness of the resulting resin molded product tends to decrease, while D ９０ It grew bigger D ９０ / D １０ As the value increases, the light diffusion efficiency tends to worsen, and the brightness of the resulting resin molded product tends to decrease. From this viewpoint, a value of 2.5 or less is preferable. A value of 2.3 or less is more preferable, and a value of 2.1 or less is even preferable.

[0044] Note D ９０ / D １０ A resin molded article containing a transparent resin composition that includes a light diffusing agent having a value of 2.5 or less, more preferably 2.3 or less, and an average particle diameter within the range of 220 nm to 300 nm, in an amount greater than 4.0 ppm by mass and less than 20 ppm by mass, more preferably 6.5 ppm to 18 ppm by mass, and even more preferably 7.2 ppm to 16 ppm by mass, relative to the total mass of the transparent resin composition, exhibits particularly excellent transparency, brightness, low coloration, and a balance between transparency and brightness.

[0045] The light diffusing agent can be any known fine particles such as titanium dioxide, aluminum oxide, zinc oxide, zinc sulfide, or barium sulfate. When the transparent resin is a methacrylic resin, titanium dioxide, aluminum oxide, zinc oxide, or zinc sulfide are preferred from the viewpoint of excellent transparency and brightness, with titanium dioxide being more preferred.

[0046] <Method for Producing the Transparent Resin Composition> The transparent resin composition of the present invention is produced by mixing the transparent resin and a mixture containing the light diffusing agent. The mixing method is not particularly limited, and methods such as melt kneading, solvent kneading, and dry blending can be used, with melt kneading and dry blending being preferred in terms of productivity. As equipment used for mixing, ordinary mixers and kneaders can be used, and specifically, examples include single-screw extruders, twin-screw extruders, ribbon blenders, Henschel mixers, Banbury mixers, and drum tumblers. In the transparent resin composition of the present invention, by using a twin-screw extruder, the light diffusing agent can be uniformly dispersed in the transparent resin composition without aggregation, resulting in a resin molded article with excellent transparency, brightness, low coloration, and balance between transparency and brightness. Specifically, the mixture containing the transparent resin and the light diffusing agent can be melted and mixed using a twin-screw extruder at a temperature range above the melting point of the transparent resin and below the melting point + 100°C to obtain a pelletized transparent resin composition. By using a twin-screw compounding extruder to melt and mix the mixture containing the transparent resin and the light-diffusing agent, and setting the temperature within a range of above the melting point of the transparent resin and below the melting point + 100°C, the deterioration and discoloration of the mixture due to heating can be suppressed, resulting in a resin molded article with excellent low-coloration properties.

[0047] The transparent resin composition used in the present invention may optionally contain various additives, such as antioxidants, stabilizers, ultraviolet absorbers, lubricants, processing aids, antistatic agents, colorants, impact-absorbing aids, foaming agents, fillers, matting agents, and other known additives, to the extent that they do not impair the effects of the present invention.

[0048] <Resin Molded Article> A resin molded article containing the transparent resin composition, which is a second embodiment of the present invention, will now be described. One embodiment of the resin molded article, which is a second embodiment of the present invention, is a resin molded article obtained by molding a resin composition containing the transparent resin composition of the present invention. That is, the resin molded article of the present invention is a resin molded article containing the transparent resin composition of the present invention. The shape of the resin molded article may be a flat plate, a plate with a concave curved surface, or a plate with a convex curved surface.

[0049] Furthermore, another embodiment of the resin molded article, which is a second embodiment of the present invention, is a resin molded article comprising a transparent resin composition containing the transparent resin and a light diffusing agent having an average particle diameter of 220 nm or more and 300 nm or less, wherein when the transparent resin composition is evaluated as a plate-shaped molded article having a flat, concave, or convex surface, the total light transmittance (Tt) in the thickness direction when the optical path length of the transmitted light is 4 mm, as measured in accordance with ISO 13468 (hereinafter abbreviated as "total light transmittance") The resin molded body has a light transmittance of 75% or more and less than 91%, a haze value (H) in the thickness direction (hereinafter abbreviated as "haze value") measured in accordance with ISO 14782 when the optical path length of transmitted light is 4 mm, which is 1.0% or more and 14.5% or less, and a yellowness (YI) in the thickness direction (hereinafter abbreviated as "yellowness"), total light transmittance (Tt), and haze value (H) measured in accordance with ISO 17223 when the optical path length of transmitted light is 4 mm, which satisfy the following equations (1) and (2): 0.04 ≤ H / Tt ≤ 0.18 (1) 0.10 ≤ YI / H ≤ 0.28 (2)

[0050] Alternatively, another embodiment of the resin molded article, which is a second embodiment of the present invention, is a resin molded article comprising a transparent resin composition containing a transparent resin and a light diffusing agent having an average particle diameter of 220 nm or more and 300 nm or less, wherein the total light transmittance (Tt) in the thickness direction, measured in accordance with ISO 13468, is 75% or more and less than 91%, the haze value (H) in the thickness direction, measured in accordance with ISO 14782, is 1.0% or more and 14.5% or less, and the luminance attenuation coefficient (m) when the resin molded article scatters light in the thickness direction of the resin molded article while guiding light in the length direction of the resin molded article is －１ ) is 10 or more and 30 or less, and the brightness retention coefficient (m) obtained by dividing the brightness attenuation coefficient by the haze value (%) of the resin molded body. －１ The resin molded article has a ratio of 1.5 to 3.5.

[0051] In this specification, the thickness direction of a resin molded article refers to the direction approximately perpendicular to the surface of the resin molded article. The total light transmittance (Tt) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the resin molded article to 4 mm, but rather specifies the value obtained when the total light transmittance is measured with the optical path length of transmitted light being 4 mm. The haze value (H) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the resin molded article to 4 mm, but rather specifies the value obtained when the haze value (H) is measured with the optical path length of transmitted light being 4 mm. The yellowness (YI) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the resin molded article to 4 mm, but rather specifies the yellowness (YI) obtained when the yellowness (YI) is measured with the optical path length of transmitted light being 4 mm. If the thickness of the resin molded article is not 4 mm, the total light transmittance per 4 mm thickness is determined based on the measured total light transmittance (Tt). The same applies to haze value (H) and yellowness (YI).

[0052] The lower limit of the total light transmittance of the resin molded article of the present invention is 75% or more, more preferably 78% or more, and even more preferably 80% or more, from the viewpoint that high transparency of the resin molded article when the light source is turned off reduces the presence of the resin molded article, resulting in superior design for lamps, vehicles, etc. The upper limit of the total light transmittance of the resin molded article is not particularly limited, but from the viewpoint that the resin molded article has excellent light diffusion properties and high brightness, it is less than 91%, more preferably 87% or less, and even more preferably 85% or less. The above upper and lower limits can be arbitrarily combined. Specifically, the total light transmittance of the resin molded article is preferably 75% or more and less than 91%, more preferably 78-87%, and even more preferably 80-85%. The total light transmittance of the resin molded article of the present invention can be controlled by adjusting the type of transparent resin, the type, shape and content ratio of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0053] The lower limit of the haze value of the resin molded article of the present invention is 1.0% or more, and more preferably 6.0% or more, from the viewpoint of the resin molded article having excellent light diffusion properties and high brightness. The upper limit of the haze value of the resin molded article is 14.5% or less, and more preferably 13.0% or less, from the viewpoint of having good brightness when the light source is on, and when the light source is off the resin molded article has transparency and the presence of the resin molded article can be reduced, thus resulting in excellent design. The above upper and lower limits can be arbitrarily combined. Specifically, the haze value of the resin molded article is preferably 1.0 to 14.5%, and more preferably 6.0 to 13.0%. The haze value of the resin molded article of the present invention can be controlled by adjusting the type of transparent resin, the type, shape and content ratio of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0054] In one embodiment of a resin molded article, which is a second embodiment of the present invention, the value obtained by dividing the haze value (H) by the total light transmittance (Tt) (H / Tt value) is an indicator of the transparency and brightness of the resin molded article, and satisfies the following formula (1). Furthermore, the value obtained by dividing the yellowness (YI) by the haze value (H) (YI / H value) is an indicator of the uniformity of brightness and hue of the resin molded article, and satisfies the following formula (2). 0.04 ≤ H / Tt ≤ 0.18 (1) 0.10 ≤ YI / H ≤ 0.28 (2)

[0055] The lower limit of the H / Tt value is 0.04 or higher, more preferably 0.06 or higher, and even more preferably 0.08 or higher, from the viewpoint of high light diffusion and good brightness of the resin molded article when the light source is lit. On the other hand, the upper limit of the H / Tt value is 0.18 or lower, more preferably 0.14 or lower, from the viewpoint of good transparency of the resin molded article. The above upper and lower limits can be arbitrarily combined. Specifically, the H / Tt value is preferably 0.04 to 0.18, more preferably 0.06 to 0.14, and even more preferably 0.08 to 0.14. The H / Tt value of the resin molded article of the present invention can be controlled by adjusting the type of transparent resin, the type, shape and content ratio of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0056] The lower limit of the YI / H value is 0.10 or higher, and more preferably 0.12 or higher, from the viewpoint of suppressing the bluish tint of the resin molded body when the light source is turned on, and ensuring good low coloration and transparency. On the other hand, the upper limit of the YI / H value is 0.28 or lower, and more preferably 0.24 or lower, from the viewpoint of maintaining light diffusion and ensuring good brightness. The above upper and lower limits can be combined arbitrarily. Specifically, the YI / H value is preferably 0.10 to 0.28, and more preferably 0.12 to 0.24. The YI / H value of the resin molded body of the present invention can be controlled by adjusting the type of transparent resin, the type, shape and content ratio of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0057] In another embodiment of a resin molded body, which is a second embodiment of the present invention, the luminance attenuation coefficient (unit: m) when the resin molded body scatters light in the thickness direction of the resin molded body while guiding light in the length direction of the resin molded body is －１ ) is 10 or more and 30 or less, AND the luminance retention coefficient (unit: m －１ The percentage ( / %) is between 1.5 and 3.5.

[0058] The luminance attenuation coefficient is an indicator of the luminance of a resin molded body. It is the slope obtained when plotting the logarithm of the luminance value (in cd) of light emitted in a direction perpendicular to the main plane tangent to one end face of a sheet-shaped resin molded body, and the distance from the end face (in m), when light is emitted from a light source placed on one end face of the resin molded body through the end face. A larger luminance attenuation coefficient indicates that more light can be extracted per unit length in the light guide direction. A smaller luminance attenuation coefficient means a longer light guide distance for the resin molded body, but the luminance becomes insufficient. Therefore, the lower limit of the luminance retention coefficient is 10 or more, and 15 or more is more preferable. On the other hand, a larger luminance attenuation coefficient improves the luminance of the resin molded body, but the light guide distance becomes shorter. Therefore, the upper limit of the luminance retention coefficient is 30 or less, and 25 or less is more preferable. The above upper and lower limits can be combined arbitrarily. Alternatively, the luminance attenuation coefficient is preferably 10 or more and 30 or less, and 15 or more and 25 or less.

[0059] The luminance retention coefficient is an indicator related to the balance between transparency and luminance of a resin molded article. It defines that the article achieves high luminance when the light source is on, while maintaining excellent transparency when the light source is off. The luminance retention coefficient is the value obtained by dividing the luminance attenuation coefficient by the haze value (%) of the resin molded article, measured with a light path length of 4 mm. By keeping the value of the luminance retention coefficient within an optimal range, the balance between transparency and luminance of the resin molded article of the present invention can be improved. A smaller value of the luminance retention coefficient improves the transparency of the resin molded article and increases the light guide distance, but the luminance becomes insufficient. Therefore, the lower limit of the luminance retention coefficient is 1.5 or higher, and 2.0 or higher is more preferable. On the other hand, a larger value of the luminance retention coefficient improves the luminance of the resin molded article, but the transparency becomes insufficient and the light guide distance becomes shorter. Therefore, the upper limit of the luminance retention coefficient is 3.5 or lower, and 2.5 or lower is more preferable. The above upper and lower limits can be combined arbitrarily. Alternatively, the luminance retention coefficient is preferably 1.5 or higher and 3.5 or lower, and 2.0 or higher and 2.5 or lower is more preferable.

[0060] Furthermore, the following points should be noted when measuring the luminance attenuation coefficient: 1. Place a material that does not reflect light easily and has light-shielding properties, such as black paper or cloth, on the back of the resin molded test piece. This is to remove light emitted from the back side and eliminate the influence of disturbances such as stray light, thereby improving the accuracy of the analysis. 2. Near the end face facing the incident surface, the measured luminance may be affected by the reflection of light from the end face; therefore, apply an absorption treatment to the end face facing the incident surface. Specific methods of absorption treatment include applying black ink to the end face facing the incident surface or closely attaching black paper. 3. Near the incident end face, the relationship between the logarithm of the luminance value of the emitted light (unit: cd) and the distance from the end face (unit: m) may not be linearly approximated; therefore, this portion should be excluded when deriving the luminance attenuation coefficient.

[0061] Furthermore, in the resin molded article which is a second embodiment of the present invention, the lower limit of the content ratio of the light diffusing agent in the transparent resin composition is preferably 4.0 ppm by mass or more, more preferably 6.5 ppm by mass or more, and even more preferably 7.2 ppm by mass or more, relative to the total mass of the transparent resin composition, from the viewpoint of excellent transparency, brightness, and balance between transparency and brightness of the resin molded article. The upper limit of the amount of light diffusing agent added is preferably 20 ppm by mass or less, more preferably 18 ppm by mass or less, and even more preferably 16 ppm by mass or less, relative to the total mass of the transparent resin composition, from the viewpoint of excellent transparency, brightness, and balance between transparency and brightness of the resin molded article. The above upper and lower limits can be arbitrarily combined. Alternatively, in the resin molded article of the present invention, the content ratio of the light diffusing agent in the transparent resin composition is preferably more than 4.0 ppm by mass and less than 20 ppm by mass, more preferably 6.5 ppm by mass or more and 18 ppm by mass or less, and even more preferably 7.2 ppm by mass or more and 16 ppm by mass or less, relative to the total mass of the transparent resin composition.

[0062] In a more preferred embodiment of the resin molded article, which is a second embodiment of the present invention, it is preferable to include a light diffusing agent having an average particle size of 220 to 300 nm in a content ratio of more than 4 ppm by mass and less than 20 ppm by mass, from the viewpoint of achieving excellent transparency, brightness, low coloration, and balance between transparency and brightness of the resin molded article. In an even more preferred embodiment of the resin molded article, which is a second embodiment of the present invention, it is more preferable to include a light diffusing agent having an average particle size of 220 to 300 nm in a content ratio of 6.5 ppm by mass or more and 18 ppm by mass or less, and even more preferable to include it in a content ratio of 7.2 ppm by mass or more and 16 ppm by mass or less, from the viewpoint of achieving even better transparency, brightness, low coloration, and balance between transparency and brightness of the resin molded article having a curved shape.

[0063] These resin molded articles, which are a second embodiment of the present invention, are plate-shaped molded articles having a flat, concave, or convex surface, wherein at least a portion of the side end surface of the resin molded article is the light incident end surface, and at least one main surface of the resin molded article is the light emission surface, and the maximum brightness of the light emitted from the light emission surface is 2200 cd / m². ２When the output of the LED light source is adjusted as follows, the average in-plane luminance, which is the average luminance on the light-emitting surface, is 500 cd / m². ２ A value of 1000 cd / m² is preferable as it suppresses the occurrence of brightness variations. ２ The above is more preferable. The average in-plane brightness is 500 cd / m². ２ To achieve the above, adjustments can be made by controlling the type of light diffusing agent, the average particle size of the light diffusing agent, the content ratio of the light diffusing agent, the type of transparent resin, and the refractive index difference between the transparent resin and the light diffusing agent, as described above. The method for measuring the average in-plane brightness will be described later.

[0064] In the resin molded article of the present invention, the light diffusing agent can be one of the light diffusing agents described in the section on transparent resin compositions above.

[0065] In the resin molded article of the present invention, the transparent resin can be one of the transparent resins described in the section on transparent resin compositions above. From the viewpoint of excellent heat resistance and impact resistance, polycarbonate resins are preferred, and from the viewpoint of excellent transparency, brightness, low coloration, and balance between transparency and brightness when titanium dioxide is used, methacrylic resins are preferred.

[0066] The lower limit of the thickness of the resin molded article according to the present invention is not particularly limited, but from the viewpoint of having good mechanical properties in addition to the brightness of the resin molded article, it is preferably 1 mm or more. More preferably 3 mm or more, and even more preferably 5 mm or more. On the other hand, the upper limit of the thickness of the resin molded article is not particularly limited, but from the viewpoint of having good transparency of the resin molded article, it is preferably 20 mm or less. More preferably 15 mm or less, and even more preferably 10 mm or less. Specifically, the thickness of the resin molded article is preferably 1 to 20 mm, more preferably 3 to 15 mm, and even more preferably 5 to 10 mm.

[0067] <Method for Manufacturing Resin Molded Articles> Methods for obtaining the resin molded articles of the present invention include, for example, known molding methods such as injection molding, extrusion molding, and pressure molding. Alternatively, the obtained molded articles may be further subjected to secondary molding using known molding methods such as pressure molding and vacuum molding. Molding conditions such as molding temperature and molding pressure can be set as appropriate. Specifically, the pelletized transparent resin composition obtained by the above-described method for manufacturing the transparent resin composition can be dried at 70 to 100°C for 4 to 24 hours, and the moisture content of the dried transparent resin composition can be reduced to 0.1% or less of the total mass of the transparent resin composition. The resin molded articles of the present invention can then be molded using known molding methods such as injection molding, extrusion molding, and pressure molding. By drying at 70 to 100°C for 4 to 24 hours, deterioration and discoloration of the transparent resin composition due to heating can be suppressed, resulting in resin molded articles with excellent transparency and low discoloration. By performing injection molding with a moisture content of 0.1% or less relative to the total mass of the transparent resin composition, the resulting resin molded article is less prone to surface defects such as silver streaks, and a resin molded article with excellent transparency and a good appearance can be obtained.

[0068] <Vehicle interior and exterior components, lamp covers for lighting fixtures, light guides for surface light source devices, and vehicles> The resin molded articles of the present invention are excellent in transparency, brightness, low coloration, and balance between transparency and brightness. Therefore, by using the resin molded articles of the present invention with a light source placed in at least a portion of the side end surface of the resin molded articles, they emit high brightness when the light source is lit, resulting in excellent visibility, and when the light source is turned off, they are transparent and have a low presence, resulting in excellent design. Therefore, they can be suitably used as vehicle interior and exterior components, lamp covers for lighting fixtures, and light guides for surface light source devices. The resin molded articles of the present invention can obtain uniform emitted light even in large applications with curved shapes, so they can be suitably used as vehicle exterior components, for example, the vehicle lamp cover 22, visor 23, and pillar 24 (hereinafter simply referred to as "vehicle exterior components") shown in Figure 7. In the vehicle 21 of Figure 7, light from an LED light source (not shown in Figure 7) is incident from the side end of the vehicle exterior component, causing the vehicle exterior component to function as a surface light source, thereby providing the vehicle 21 with a novel design.

[0069] The resin molded body of the present invention can be suitably used as a vehicle interior component, for example, in the meter panel shown in Figure 10. In the meter panel of Figure 10, a light-shielding member (black cutting sheet) 25 with light-transmitting portions 26 such as numbers and symbols formed thereon is installed on the surface (light-emitting surface 15b) of the resin molded body 18. By shining light from an LED light source 4 connected to a power supply unit 19 and a power cord 20 into the light-incident end surface 15a of the resin molded body 18, the numbers and symbols on the light-transmitting portions 26 are made to stand out, thereby providing a novel design to the vehicle interior component.

[0070] The resin molded article of the present invention can be suitably used as a vehicle exterior component, for example, in a combination lamp cover as shown in Figure 3, as described later. It is particularly suitable for vehicle lamp covers.

[0071] The resin molded body of the present invention can be suitably used, for example, as a lamp cover for a lighting fixture as shown in Figure 8. Figure 8 is a schematic diagram showing an example of a lighting fixture using the resin molded body of the present invention. In Figure 8, an LED light source is used as the light source. The lamp cover 1 in Figure 8 has a structure in which it is positioned in front of the LED light source 4, which is fixed on a support substrate (not shown), as a lamp cover for a lighting fixture to protect the LED light source 4.

[0072] The resin molded body of the present invention can be suitably used, for example, in the surface light source device shown in Figure 9. Figure 9 is a schematic diagram showing an example of a surface light source device using the resin molded body of the present invention. In Figure 9, an LED light source is used as the light source. The surface light source device of Figure 9 has the function of a surface light source because the light from the LED light source 4, which is connected to the light source unit 19 by a power cord 20, is incident on the resin molded body 18 from the light incident end face 15a and extracted from the light emission surface 15b.

[0073] <Vehicle Lamp Cover, Combination Lamp Cover, and Vehicle> The third embodiment of the present invention, a vehicle lamp cover, the fourth embodiment, a combination lamp cover, and the fifth embodiment, a vehicle, will be described. The third embodiment of the present invention, a vehicle lamp cover, is a vehicle lamp cover that includes a resin molded body, which is the second embodiment. Because the vehicle lamp cover includes the resin molded body, it has excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. One specific embodiment of the fourth embodiment of the present invention, a combination lamp cover, is a combination lamp cover having a transparent or translucent headlamp cover or rear lamp cover that is substantially free of light diffusing agents and the vehicle lamp cover of the present invention, wherein the vehicle lamp cover is disposed on the outer edge or at least a part of the outer edge of the headlamp cover or rear lamp cover. Substantially free means that the content ratio of the light diffusing agent is less than 0.05 ppm by mass with respect to the total mass of the transparent or translucent headlamp cover or rear lamp cover.

[0074] The aforementioned combination lamp is manufactured by injection molding of multiple components, preferably two components, in which only one component constituting the vehicle lamp cover contains a light diffuser, and the other component constituting the transparent or translucent headlamp cover or rear lamp cover substantially does not contain a light diffuser. Specifically, as the other component, a component other than the light diffuser from the components described in the <Transparent Resin Composition> above can be used. In this way, it is possible to manufacture a lamp cover in which the component containing the light diffuser exhibits a specific shape or pattern. By using a light source placed in at least a portion of the side end surface of the vehicle lamp cover of the combination lamp cover, when the light source is turned off, that is, when there is no light incidence, the vehicle lamp cover appears as a homogeneous and transparent molded body, and because it is transparent and has a low presence, it has excellent design. However, when the light source is turned on, it emits high brightness, so only the part of the lamp cover containing the light diffuser emits light, resulting in excellent visibility. A vehicle equipped with the vehicle lamp cover or combination lamp cover of the present invention has excellent design and visibility of the vehicle lamp cover. A vehicle equipped with the lamp cover or combination lamp cover of the present invention offers excellent design and visibility of the lamp cover.

[0075] <Lamp Cover> A lamp cover, which is a sixth embodiment of the present invention, will now be described. The lamp cover of the present invention is used for vehicle component applications and lighting applications, and has a curved shape in at least a part of the lamp cover. The lamp (hereinafter also referred to as "light source") is not particularly limited, and examples include light-emitting diodes such as LED light sources, incandescent bulbs, halogen bulbs, fluorescent lamps, semiconductor lasers, etc. Figure 1 is a schematic cross-sectional view showing an example of a lamp using the lamp cover of the present invention. Figure 1 is an example of a headlamp cover using an LED light source as the light source, and the lamp cover 1 protects the headlight of the vehicle and diffuses and emits light from the LED light source with high brightness. In the lamp cover 1 of Figure 1, the lamp cover 1 is positioned in front of the projection lens 3 so as to protect the projection lens 3 which is positioned in front of the LED light source 4 fixed on the support substrate 5, and the lamp cover 1 and the housing 2 have a structure in which a lamp chamber is formed. Figure 2 is a schematic cross-sectional view showing another example of a lamp using the lamp cover of the present invention. Figure 2 shows an example of a headlamp cover using a halogen lamp 6 as the light source. The lamp cover 1 protects the vehicle's headlight and diffuses the light from the halogen lamp with high brightness. In the rear lamp cover 2 of Figure 2, the lamp cover 1 is positioned in front of the halogen lamp 6 to protect the halogen lamp 6, and the lamp cover 1 and housing 2 form a lamp chamber. As shown in Figure 2, it is preferable that the lamp cover 1 of the present invention is curved so as to protrude on the side opposite to the light source.

[0076] The lamp cover of the present invention can be made from a transparent resin composition containing a transparent resin and a light diffusing agent, as described later.

[0077] One embodiment of the lamp cover, which is the sixth embodiment of the present invention, is a lamp cover in which the total light transmittance (Tt) in the thickness direction (hereinafter abbreviated as "total light transmittance") measured in accordance with ISO 13468 when the optical path length of transmitted light is 4 mm is 75% or more, the haze value (H) in the thickness direction (hereinafter abbreviated as "haze value") measured in accordance with ISO 14782 when the optical path length of transmitted light is 4 mm is 1.0% or more and 14.5% or less, and the yellowness (YI) in the thickness direction (hereinafter abbreviated as "yellowness") measured in accordance with ISO 17223 when the optical path length of transmitted light is 4 mm is 2.1 or less, and H / Tt and YI / H satisfy the following equations (1) and (2): 0.01 ≤ H / Tt ≤ 0.2 (1) -1.0 ≤ YI / H ≤ 1.0 (2)

[0078] Alternatively, another embodiment of the lamp cover, which is a sixth embodiment of the present invention, has a total light transmittance (Tt) in the thickness direction of 75% or more and less than 91%, a haze value (H) in the thickness direction of 1.0% or more and 14.5% or less, as measured in accordance with ISO 13468, a yellowness (YI) in the thickness direction of 7.0 or less, as measured in accordance with ISO 17223, and the luminance attenuation coefficient (m) when the lamp cover scatters light in the thickness direction of the lamp cover while guiding light in the length direction of the lamp cover. －１ The luminance retention coefficient (m) is obtained by dividing the ) by the haze value (%) of the lamp cover. －１ This is a lamp cover where the / %) is between 1.5 and 3.5.

[0079] In this specification, the thickness direction of the lamp cover refers to the direction approximately perpendicular to the surface of the lamp cover. The total light transmittance (Tt) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the lamp cover to 4 mm, but rather specifies the value obtained when the total light transmittance is measured with the optical path length of transmitted light being 4 mm. The haze value (H) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the lamp cover to 4 mm, but rather specifies the value obtained when the haze value (H) is measured with the optical path length of transmitted light being 4 mm. The yellowness (YI) in the thickness direction when the optical path length of transmitted light is 4 mm does not limit the thickness of the lamp cover to 4 mm, but rather specifies the yellowness (YI) obtained when the yellowness (YI) is measured with the optical path length of transmitted light being 4 mm.

[0080] The lower limit of the total light transmittance of the lamp cover of the present invention is 75% or more, preferably 80% or more, and more preferably 85% or more, from the viewpoint that high transparency of the lamp cover when the light source is turned off reduces the presence of the lamp cover, resulting in superior design for lamps and vehicles. The upper limit of the total light transmittance of the lamp cover is less than 91%, and more preferably 87% or less, from the viewpoint that the lamp cover has excellent light diffusion properties and high brightness. The above upper and lower limits can be combined arbitrarily. Specifically, the total light transmittance of the lamp cover is preferably 75% or more and less than 91%, more preferably 80-87%, and even more preferably 85-87%. The total light transmittance (Tt) of the lamp cover of the present invention can be achieved by optimizing the type of transparent resin, the type, shape and content of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0081] The lower limit of the haze value (H) of the lamp cover of the present invention is 1.0% or more, and more preferably 6.0% or more, from the viewpoint of the lamp cover having excellent light diffusion properties and high brightness. The upper limit of the haze value of the lamp cover is 14.5% or less, and more preferably 13.0% or less, from the viewpoint of having good brightness when the light source is lit and having a transparent appearance when the light source is turned off, thus reducing the presence of the lamp cover, and thus having excellent design qualities for lamps and vehicles. The above upper and lower limits can be arbitrarily combined. Specifically, the haze value of the lamp cover is preferably 1.0 to 14.5%, and more preferably 6.0 to 13.0%. The haze value of the lamp cover of the present invention can be achieved by optimizing the type of transparent resin, the type, shape and content of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0082] The upper limit of the yellowness (YI) of the lamp cover of the present invention is 7.0 or less, preferably 1.5 or less, and more preferably 1.0 or less, from the viewpoint of suppressing the bluish tint of the lamp cover when the light source is lit, thus achieving good low-coloration properties, and from the viewpoint of the lamp cover having transparency when the light source is turned off, thus reducing the presence of the lamp cover and resulting in excellent design for the lamp and vehicle. The lower limit of the yellowness of the lamp cover is not particularly limited, but a small value is preferred. The yellowness of the lamp cover of the present invention can be achieved by optimizing the type of transparent resin, the type, shape and content of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0083] In one embodiment of the lamp cover, which is the sixth embodiment of the present invention, the value obtained by dividing the haze value (H) by the total light transmittance (Tt) (H / Tt value) is an indicator of the transparency and brightness of the lamp cover, and satisfies the following formula (3). Also, the value obtained by dividing the yellowness (YI) by the haze value (H) (YI / H value) is an indicator of the brightness and hue of the lamp cover, and satisfies the following formula (4). 0.01 ≤ H / Tt ≤ 0.2 (3) -1.0 ≤ YI / H ≤ 1.0 (4)

[0084] The lower limit of the H / Tt value is 0.01 or higher, more preferably 0.02 or higher, and even more preferably 0.04 or higher, from the viewpoint of high light diffusion and good brightness of the lamp cover when the light source is lit. On the other hand, the upper limit of the H / Tt value is 0.2 or lower, more preferably 0.18 or lower, from the viewpoint of good transparency of the lamp cover. The above upper and lower limits can be arbitrarily combined. Specifically, the H / Tt value is preferably 0.01 to 0.2, and more preferably 0.02 to 0.18. The H / Tt value of the lamp cover of the present invention can be achieved by optimizing the type of transparent resin, the type, shape and content of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0085] The lower limit of the YI / H value is -1.0 or higher, and more preferably 0.1 or higher, from the viewpoint of suppressing the bluish tint of the lamp cover when the light source is lit and achieving good low coloration and transparency. On the other hand, the upper limit of the YI / H value is 1.0 or lower, and more preferably 0.6 or lower, from the viewpoint of maintaining light diffusion and achieving good brightness. The above upper and lower limits can be arbitrarily combined. Specifically, the YI / H value is preferably -1.0 to 1.0, and more preferably 0.1 to 0.6. The YI / H value of the lamp cover of the present invention can be achieved by optimizing the type of transparent resin, the type, shape and content of the light diffusing agent, and the conditions of the manufacturing method in the transparent resin composition.

[0086] In another embodiment of the lamp cover, which is a sixth embodiment of the present invention, the luminance attenuation coefficient (unit: m) when the lamp cover scatters light in the thickness direction of the resin molded body while guiding light in the length direction of the lamp cover is －１ ) is 10 or more and 30 or less, AND the luminance retention coefficient (unit: m －１ The percentage ( / %) is between 1.5 and 3.5.

[0087] The lower the luminance attenuation coefficient, the longer the light guide distance of the lamp cover becomes, but the luminance becomes insufficient. Therefore, the lower limit of the luminance retention coefficient is 10 or more, and 15 or more is more preferable. On the other hand, the higher the luminance attenuation coefficient, the brighter the lamp cover becomes, but the light guide distance becomes shorter. Therefore, the upper limit of the luminance retention coefficient is 30 or less, and 25 or less is more preferable. The above upper and lower limits can be combined arbitrarily. Alternatively, the luminance attenuation coefficient is preferably 10 or more and 30 or less, and 15 or more and 25 or less.

[0088] The lower limit of the luminance retention coefficient is 1.5 or higher, and more preferably 2.0 or higher, because a smaller value of the luminance retention coefficient improves the transparency of the lamp cover and increases the light guide distance, but the luminance becomes insufficient. On the other hand, the higher the value of the luminance retention coefficient, the higher the luminance of the lamp cover, but the transparency becomes insufficient and the light guide distance becomes shorter. Therefore, the upper limit of the luminance retention coefficient is 3.5 or lower, and more preferably 2.5 or lower. The above upper and lower limits can be combined arbitrarily. Alternatively, the luminance retention coefficient is preferably between 1.5 and 3.5, and more preferably between 2.0 and 2.5.

[0089] The lower limit of the length in the thickness direction of the lamp cover according to the present invention (thickness of the lamp cover) is not particularly limited, but from the viewpoint of good mechanical properties in addition to the brightness of the lamp cover, it is preferably 1 mm or more. More preferably 3 mm or more, and even more preferably 5 mm or more. On the other hand, the upper limit of the thickness of the lamp cover is not particularly limited, but from the viewpoint of good transparency of the lamp cover, it is preferably 20 mm or less. More preferably 15 mm or less, and even more preferably 10 mm or less. The above upper and lower limits can be arbitrarily combined. Specifically, the thickness of the lamp cover is preferably 1 to 20 mm, more preferably 3 to 15 mm, and even more preferably 5 to 10 mm. The length of the lamp cover according to the present invention is not particularly limited, but in applications as a vehicle component such as an automobile, it is usually 50 mm to 1000 mm.

[0090] <Transparent Resin Composition> The transparent resin composition is a raw material constituting a lamp cover, which is the sixth embodiment of the present invention. The transparent resin composition is a resin composition comprising the transparent resin described above and the light diffusing agent described above. The inclusion of the transparent resin described above in the transparent resin composition results in excellent transparency of the lamp cover. The inclusion of the light diffusing agent described above in the transparent resin composition results in excellent transparency, brightness, low coloration, and a good balance between transparency and brightness of the lamp cover.

[0091] Furthermore, from the viewpoint of excellent transparency, brightness, and balance between transparency and brightness of the lamp cover, the lower limit of the light diffusing agent content in the transparent resin composition is preferably 0.05 ppm by mass or more, and more preferably 1.0 ppm by mass or more, relative to the total mass of the transparent resin composition. From the viewpoint of excellent transparency, brightness, and balance between transparency and brightness of the lamp cover, the upper limit of the light diffusing agent content is preferably 20 ppm by mass or less, and more preferably 15 ppm by mass or less, relative to the total mass of the transparent resin composition. The above upper and lower limits can be combined arbitrarily. Specifically, the light diffusing agent content is preferably 0.05 to 20 ppm by mass, and more preferably 1.0 to 15 ppm by mass, relative to the total mass of the transparent resin composition.

[0092] In the transparent resin composition of the present invention, the lower limit of the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 or more, and more preferably 0.8 or more, from the viewpoint of having superior brightness of the lamp cover. The upper limit of the refractive index difference is preferably 3.0 or less, and more preferably 2.0 or less, from the viewpoint of having superior transparency of the lamp cover. The above upper and lower limits can be arbitrarily combined. Specifically, the refractive index difference between the transparent resin and the light diffusing agent is preferably 0.3 to 3.0, and more preferably 0.8 to 2.0.

[0093] <Manufacturing Method for Lamp Covers> The lamp cover of the present invention can be obtained by forming the transparent resin composition into pellet-shaped molding material, filling (injecting) it into a mold in a molten state, and then, after cooling, peeling the molded body from the mold. Specifically, the pellet-shaped transparent resin composition obtained by the above manufacturing method for transparent resin compositions is dried at 70 to 100°C for 4 to 24 hours, and the moisture content of the dried transparent resin composition is 0.1% or less of the total mass of the transparent resin composition, and then injection molding is performed to obtain the lamp cover of the present invention. By drying at 70 to 100°C for 4 to 24 hours, deterioration and discoloration of the transparent resin composition due to heating can be suppressed, resulting in a lamp cover with excellent transparency and low discoloration. By injection molding with a moisture content of 0.1% or less of the total mass of the transparent resin composition, appearance defects such as silver streaks are less likely to occur in the lamp cover after injection molding, and a lamp cover with excellent transparency and a good appearance can be obtained.

[0094] Specifically, as an injection molding method, for example, a transparent resin composition with a moisture content of 0.1% or less relative to the total mass of the transparent resin composition is introduced from the hopper of an injection molding machine, the resin composition is metered into the cylinder by rotating and retracting the screw, the resin composition is melted, the molten resin composition is filled into the mold under pressure, the pressure is held for a certain period of time until the mold has cooled sufficiently, and then the mold is opened and the molded body is removed, thereby producing the lamp cover of the present invention. The various conditions for producing the lamp cover of the present invention (for example, the melting temperature of the molding material, the mold temperature when injecting the molding material into the mold, the pressure when holding the resin composition after filling the mold, etc.) can be set as appropriate and are not particularly limited.

[0095] Furthermore, from the viewpoint of achieving excellent transparency, brightness, and balance between transparency and brightness of the lamp cover, the lower limit of the amount of light diffusing agent added to the transparent resin composition is preferably 0.05 ppm by mass or more, and more preferably 1.0 ppm by mass or more, relative to the total mass of the transparent resin composition. From the viewpoint of achieving excellent transparency, brightness, and balance between transparency and brightness of the lamp cover, the upper limit of the amount of light diffusing agent added is preferably 20 ppm by mass or less, and more preferably 15 ppm by mass or less, relative to the total mass of the transparent resin composition. The above upper and lower limits can be combined arbitrarily. Specifically, the amount of light diffusing agent added is preferably 0.05 to 20 ppm by mass, and more preferably 1.0 to 15 ppm by mass, relative to the total mass of the transparent resin composition. In a more preferred embodiment, the mixture containing the transparent resin and the light diffusing agent is preferably a mixture containing a light diffusing agent having an average particle size of 150 to 500 nm in a content ratio of 0.05 to 20 ppm by mass, from the viewpoint of achieving excellent transparency, brightness, low coloration, and balance between transparency and brightness of the lamp cover. In a more preferred embodiment, from the viewpoint of achieving better transparency, brightness, low coloration, and balance between transparency and brightness of the curved lamp cover, the mixture is more preferably a mixture containing a light diffusing agent having an average particle size of 220 to 300 nm in a content of 1.0 to 15 ppm by mass.

[0096] The light diffusing agent is preferably titanium dioxide particles. The specific form of the titanium dioxide particles is as described in the lamp cover section above.

[0097] The transparent resin can be at least one selected from methacrylic resin, polycarbonate resin, and polystyrene resin, in addition to having excellent transparency for the lamp cover, as well as excellent mechanical properties, weather resistance, and processability. Specific embodiments of the methacrylic resin, polycarbonate resin, and polystyrene resin are as described in the lamp cover section above.

[0098] <Combination Lamp Cover and Vehicle> A combination lamp cover, which is the seventh embodiment of the present invention, and a vehicle, which is the eighth embodiment, will be described. The form of the lamp cover of the present invention is not particularly limited, but it can have a light incident end surface provided in at least a part of the side end surface of the lamp cover and a light emission surface provided on at least one main surface of the lamp cover. In the lamp cover, the in-plane average luminance, which is the average value of the luminance on the light emission surface, is 500 cd / m². ２ A value of 1000 cd / m² is preferable as it suppresses the occurrence of brightness variations. ２ The above is more preferable. The average in-plane brightness is 500 cd / m². ２ To achieve the above, the values ​​can be adjusted by the type of light diffusing agent, the average particle size of the light diffusing agent, the content ratio of the light diffusing agent, the type of transparent resin, and the refractive index difference between the transparent resin and the light diffusing agent, as mentioned above.

[0099] The lamp cover of the present invention offers excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. Therefore, when the lamp cover of the present invention is used with a light source placed in at least a portion of the side end surface, it emits high brightness when the light source is lit, resulting in excellent visibility, and when the light source is off, it is transparent and unobtrusive, resulting in excellent design. Furthermore, it can obtain uniform emitted light even in large applications with curved shapes, making it suitable for lamp covers and combination lamp covers of vehicle components with curved shapes. One specific embodiment of the combination lamp cover is an automobile combination lamp cover having a transparent or translucent headlamp cover or rear lamp cover that is substantially free of light diffusing agents and the lamp cover of the present invention, wherein the lamp cover of the present invention is disposed in at least a portion of the outer circumference or outer frame of the headlamp cover or rear lamp cover. "Substantially free" means that the content ratio of the light diffusing agent is less than 0.05 ppm by mass relative to the total mass of the transparent or translucent headlamp cover or rear lamp cover.

[0100] Figures 3A and 3B are schematic cross-sectional views showing an example of a combination lamp using the combination lamp cover of the present invention. In the combination lamp cover 11 of Figures 3A and 3B, the lamp cover 1 of the present invention is arranged in at least a portion of the outer circumference or outer frame of a transparent or translucent headlamp cover or rear lamp cover 10 that substantially does not contain a light diffusing agent. The combination lamp cover 11 of Figures 3A and 3B is formed as an integrated luminaire by attaching a single inner lens 9 to the opening of an integrated housing 2. In this case, in the rear combination lamp of Figures 3A and 3B, for example, a turn signal section 8a that is required to emit yellow light, a brake light section 8b that is required to emit red light, and a reverse indicator section 8c that is required to emit white light are required. Therefore, as shown in Figures 3A and 3B, the housing 2 is divided into lamp compartments 8a to 8c by partitions, and a light source 7 is arranged in each of these compartments. The inner lens 9 also has a structure in which, for example, a yellow inner lens 9a, a red inner lens 9b, and a white inner lens 9c are formed, corresponding to the lamp chambers 8a to 8c.

[0101] The aforementioned combination lamp cover is manufactured by injection molding of multiple components, preferably two components, in which only one component constituting the lamp cover contains a light-diffusing agent, and the other component constituting the transparent or translucent headlamp cover or rear lamp cover substantially does not contain a light-diffusing agent. In this way, it is possible to manufacture a lamp cover in which the component containing the light-diffusing agent exhibits a specific shape or pattern. By using a combination lamp cover with a light source placed in at least a portion of the side end surface of the lamp cover, when the light source is turned off, i.e., in a state without light incidence, the lamp cover appears as a homogeneous and transparent molded body, and because it is transparent and has a low presence, it has excellent design qualities. However, when the light source is turned on, it emits high brightness, so only the portion of the lamp cover containing the light-diffusing agent emits light, resulting in excellent visibility. A vehicle equipped with the lamp cover or combination lamp cover of the present invention has excellent design qualities and visibility of the lamp cover.

[0102] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. <Measurement Method> The evaluations in the examples and comparative examples were carried out by the following method.

[0103] <Preparation of Test Specimens> The pellets of the transparent resin composition obtained in the examples and comparative examples were supplied to an injection molding machine (model name "N70A", manufactured by Japan Steel Works Ltd.), and the molding temperature was set to 260°C to obtain test specimens (flat plates with a thickness of 4 mm, a width of 50 mm, and a length of 200 mm).

[0104] (1) Total Light Transmittance (Tt) As an indicator of the transparency of the resin molded product, a haze meter (model name: HM-100, manufactured by Murakami Color Technology Research Institute Co., Ltd.) was used, and the total light transmittance (%) of a test piece (thickness: 4 mm) was measured using a D65 light source in accordance with ISO 13468. Three test pieces were used, and one measurement was taken for each test piece, and the average value was taken as the total light transmittance (Tt). Furthermore, the following criteria were used for judgment: AA: Total light transmittance of 78% or more and 87% or less A: Total light transmittance of 75% or more and less than 78% or more than 87% and less than 91% B: Total light transmittance of less than 75% or 91% or more

[0105] (2) Haze Value (H) As an indicator of the transparency of the resin molded product, a haze meter (model name: HM-100, manufactured by Murakami Color Technology Laboratory Co., Ltd.) was used, and the haze value (%) of the test piece (thickness: 4 mm) was measured using a D65 light source in accordance with ISO 14782. Three test pieces were used, and one measurement was taken for each test piece, and the average value was taken as the haze value (H). Furthermore, the following criteria were used for judgment: AA: Haze value of 6.0% or more and 13.0% or less A: Haze value of 1.0% or more and less than 7.0% or greater than 13.0% and 14.5% or less B: Haze value of less than 1.0% or greater than 14.5% or greater than 15%

[0106] (3) Yellowness (YI) As an indicator of the transparency of the test specimen, a spectrophotometer (model name: U4100, manufactured by Hitachi High-Technologies Corporation) was used to measure the yellowness of the test specimen (thickness: 4 mm) using a C light source in accordance with ISO 17223. Three test specimens were used, and one measurement was taken for each specimen, with the average value being taken as the yellowness (YI). Furthermore, the following criteria were used for evaluation: AA: YI is 1.5 or less A: YI is greater than 1.5 and 7.0 or less B: YI is greater than 7.0

[0107] (4) H / Tt value, YI / H value The H / Tt value and YI / H value were calculated from the total light transmittance (Tt), haze value (H), and yellowness (YI). For the transparent resin composition, which is the first embodiment of the present invention, and the resin molded article, which is the second embodiment, the H / Tt value was determined using the following criteria. The determination results are shown in Table 2. AA: H / Tt is 0.06 or more and 0.14 or less A: H / Tt is 0.04 or more and less than 0.06 or greater than 0.14 and less than or equal to 0.18 B: H / T is less than 0.04 or greater than 0.18

[0108] For the transparent resin composition, which is the first embodiment of the present invention, and the resin molded article, which is the second embodiment, the YI / H value was determined using the following criteria. The determination results are shown in Table 2. AA: YI / H is 0.15 or more and 0.24 or less A: YI / H is 0.10 or more and less than 0.15 or greater than 0.24 and 0.28 or less B: YI / H is less than 0.10 or greater than 0.28

[0109] For the transparent resin composition for lamp covers, which is the sixth embodiment of the present invention, the H / Tt ratio was determined using the following criteria. The results are shown in Table 4. AA: H / Tt is 0.02 or more and 0.18 or less A: H / Tt is 0.01 or more and less than 0.02 or greater than 0.18 and 0.20 or less B: H / T is less than 0.01 or greater than 0.20

[0110] For the transparent resin composition for lamp covers, which is the sixth embodiment of the present invention, the YI / H value was determined using the following criteria. The determination results are shown in Table 4. AA: YI / H is 0.1 or more and 0.6 or less A: YI / H is -1.0 or more and less than 0.1 or greater than 0.6 and 1.0 or less B: YI / H is less than -1.0 or greater than 1.0

[0111] (4) As an indicator of the brightness of the luminance of the luminance resin molded product, a luminance meter (model name: RISA-COLOR / CD7, manufactured by Highland Co., Ltd.) was used to measure the brightness of the test piece (cd / cm²). ２ The following measurements were taken: Three test specimens were used, and one measurement was taken for each specimen. The average value was defined as the luminance.

[0112] (6) In-plane average brightness As an indicator of the brightness of light emitted from the resin molded body, the in-plane average brightness of the test piece was measured using the following method. Figure 4 is a schematic diagram illustrating the method for measuring the in-plane average brightness. One side of the flat test piece 15 (thickness 4 mm × width 50 mm × length 200 mm) with a thickness of 4 mm × width 50 mm was designated as the light incident end face 15a, and the other side with a width of 50 mm × length 200 mm was designated as the light emission end face 15b. Forty LED light sources 17 (4 mm surface mount type) arranged at 5 mm intervals were arranged to form an LED edge light adjacent to the light incident end face. The output of the LED light source was set so that the maximum brightness of the light emitted from the test piece was 2200 cd / m ２ The following adjustments were made:

[0113] A line connecting the center of the light incident end face and the center of the end face opposite the light incident end face (200 mm from the light incident end face) was divided into 10 equal parts at 20 mm intervals from the light incident end face, creating 11 points. When measuring luminance and chromaticity coordinates (x, y), the light incident end face (0 mm from the light incident end face) and the end face opposite the light incident end face (200 mm from the light incident end face) are susceptible to the influence of reflected light. Therefore, six points were used as luminance measurement points, excluding three points at 0 mm, 20 mm, and 40 mm from the incident end face side, and two points at 0 mm and 20 mm from the end face opposite the light incident end face. The luminance was measured using a luminance meter 17 according to the method described in "(4) Luminance".

[0114] To avoid the influence of incident light from the surface opposite the light-emitting surface when measuring luminance and chromaticity coordinates, a black cloth was placed on the surface opposite the light-emitting surface.

[0115] The average in-plane luminance was calculated as the average of the luminance measurements taken at the six locations mentioned above. Furthermore, the following criteria were used for evaluation: AA: Average in-plane luminance of 1000 cd / m² ２ A: In-plane average brightness is 500 cd / m². ２ More than 1000cd / m ２ Less than B: In-plane average brightness is 500 cd / m² ２ less than

[0116] (Brightness attenuation coefficient, brightness retention coefficient) The brightness attenuation coefficient was measured as an indicator of the brightness of light emitted from the resin molded body, and the brightness retention coefficient was measured as an indicator of the balance between transparency and brightness, using the method described below.

[0117] 1) A flat test specimen (4 mm thick x 50 mm wide x 200 mm long) was placed on a test stand set up in a darkroom. One of the 4 mm x 50 mm surfaces was designated as the light incidence end face, and the other of the 50 mm x 200 mm surface was designated as the light emission surface. A black cloth was placed on the surface (back side) corresponding to the light emission surface of the test specimen to absorb the light emitted from the back side. 2) An LED edge light, consisting of 40 LED light sources (4 mm surface mount type) arranged at 5 mm intervals, was placed adjacent to the light incidence end face of the test specimen. 3) A luminance meter (model name: RISA-COLOR / CD7, manufactured by Highland Co., Ltd.) was set up so that the distance between the detection surface of the luminance meter and the light emission surface of the test specimen was 2000 mm. 4) Light from the LED light source was incident from the light incidence end face. At this time, the output of the LED light source was set so that the maximum luminance of the light emitted from the test specimen was 2200 cd / m². ２ The following adjustments were made: 5) With the incident end face at position 0m, the luminance (unit: cd / cm²) was measured at three points on the main plane tangent to the incident end face at 0.06m, 0.08m, and 0.10m from the incident end face. ２ ) was measured. 6) Brightness value (unit: cd / cm²) ２ The relationship between the logarithm of ) and the distance from the end face (unit: m) is plotted, and the slope of the line obtained by linear approximation is the luminance attenuation coefficient (unit: m) －１) was used. 7) The obtained luminance attenuation coefficient was divided by the haze value (H) measured by the method described above to obtain the luminance retention coefficient (m －１ It was set to / %).

[0118] The obtained luminance attenuation coefficients were evaluated using the following criteria: AA: Luminance attenuation coefficient of 15m －１ More than 20m －１ Below, A: Brightness attenuation coefficient is 10m －１ 15m or more －１ Less than or 20m －１ Over 30m －１ Less than B: Brightness attenuation coefficient is 10 m －１ Less than 30m －１ Beyond

[0119] The obtained luminance retention coefficient was evaluated using the following criteria: AA: Luminance retention coefficient is 2.0 m －１ / % or more 2.5m －１ / % or less A: Brightness retention coefficient is 1.5m －１ / % or more 2.0m －１ / % or less than 2.5m －１ / % exceeds 3.5m －１ / % or less B: Brightness retention coefficient is 1.5m －１ / % or less than 3.5m －１ / exceeding %

[0120] (7) Average particle size and particle size distribution of the light diffusing agent (D ９０ / D １０ ) Light diffusing agent (e.g., TiO ２The average particle size and particle size distribution of the particles were measured by the following method. A glass slide was immersed in a formvar solution, quickly removed, and dried at room temperature. Next, a sample paste was prepared by mixing collodion and isoamyl acetate with light-diffusing agent particles, applied to the glass slide, and dried at room temperature. After drying, cuts were made in the dried sample on the glass slide using tweezers, and the glass slide was tilted and gradually immersed in water in a petri dish. The sample that detached from the glass slide and floated on the water surface was scooped up with tweezers onto a microgrid (150 mesh, copper with round holes), placed on filter paper, dried, and used as the sample for TEM observation. Transmission electron microscope images (TEM images) of the sample for TEM observation were taken using a transmission electron microscope (model name: H-7000, manufactured by Hitachi, Ltd.) according to a known method. The average particle size of the light diffusing agent was determined by using an image analysis device (Luzex AP, manufactured by Nireco Corporation). 50 light diffusing agent particles were arbitrarily selected from the obtained TEM image, and the maximum particle diameter of each light diffusing agent particle was measured. The average of these measured values ​​was then used as the average particle size of the light diffusing agent.

[0121] The particle size distribution of the light-diffusing agent was determined by using an image analysis device (Luzex AP, manufactured by Nireco Corporation). 200 light-diffusing agent particles were arbitrarily selected from the resulting TEM images, and the maximum particle diameter of each light-diffusing agent particle was measured. This was defined as the particle size of the light-diffusing agent. Next, the particle sizes of the 200 light-diffusing agents were divided into the following categories: greater than 0.0 μm and less than or equal to 0.10 μm, greater than 0.10 μm and less than 0.15 μm, greater than 0.15 μm and less than 0.20 μm, greater than 0.20 μm and less than 0.25 μm, greater than 0.25 μm and less than 0.30 μm, greater than 0.30 μm and less than 0.35 μm, greater than 0.35 μm and less than 0.40 μm, greater than 0.40 μm and less than 0.45 μm, greater than 0.45 μm and less than 0.50 μm, and greater than 0.50 μm and less than 0.55 μm. The frequency percentage (in %) of each category was calculated, and a particle size frequency distribution curve was created by approximating it with a normal distribution curve. Next, a cumulative frequency distribution curve was created from the above frequency distribution curve, and the particle size at which the cumulative frequency reaches 90% was D ９０ The particle size at which the cumulative frequency reaches 10% is defined as D. １０ D９０ and D １０ ratio of (D ９０ / D １０ ) was calculated.

[0122] (8) Content ratio test of light diffusing agent The ratio of the light diffusing agent (e.g., TiO ２ etc.) in the test piece was measured by the following method. The test piece was heated and ashed at 600 °C, and the mass of the remaining ash was regarded as equivalent to the content of the light diffusing agent (e.g., TiO ２ etc.) in the test piece. The value obtained by dividing the mass of the ash by the mass of the test piece was taken as the content (ppm by mass) of the light diffusing agent.

[0123] <Raw materials> Methacrylic resin (1) Methyl methacrylate (MMA)-methyl acrylate (MA) copolymer, refractive index 1.492 (trade name: Acrypet VH, manufactured by Mitsubishi Chemical Corporation) Titanium dioxide (1) Average particle diameter 260 nm, refractive index 2.70, D ９０ / D １０ = 2.13 titanium dioxide particles (trade name: R-820, manufactured by Ishihara Sangyo Co., Ltd.) Titanium dioxide (2) Average particle diameter 210 nm, refractive index 2.70, D ９０ / D １０ = 2.17 titanium dioxide particles (trade name: CR-60, manufactured by Ishihara Sangyo Co., Ltd.) Titanium dioxide (3) Acicular crystal particles of titanium dioxide with a short diameter of 270 nm × a long diameter of 5150 nm and a refractive index of 2.70 (trade name: FTL-300, manufactured by Ishihara Sangyo Co., Ltd.) Titanium dioxide (4) Titanium dioxide particles with an average particle diameter of 100 nm and a refractive index of 2.70 (trade name: PT-401L, manufactured by Ishihara Sangyo Co., Ltd.) Titanium dioxide (5) Non-spherical particles of titanium dioxide with a short diameter of 10 nm × a long diameter of 30 nm and a refractive index of 2.70 (trade name: TTO-51, manufactured by Ishihara Sangyo Co., Ltd.) Titanium dioxide (6): Titanium dioxide (2) and titanium dioxide (7) were mixed at a mass ratio of 20:80, with an average particle diameter of 298 nm, a refractive index of 2.70, D ９０ / D １０= 2.59 Titanium dioxide particles (mixture) Titanium dioxide (7) Titanium dioxide particles with an average particle size of 320 nm and a refractive index of 2.70 (product name: R-820N, manufactured by Ishihara Sangyo Co., Ltd.) Barium sulfate (1) Barium sulfate particles with an average particle size of 2000 nm and a refractive index of 1.650 (product name: AD Barium Sulfate, manufactured by Nippon Chemical Industrial Co., Ltd.) Barium sulfate (2) Barium sulfate particles with an average particle size of 30 nm and a refractive index of 1.640 (product name: BF-20, manufactured by Sakai Chemical Industry Co., Ltd.) Silicone beads (1) Silicone beads with an average particle size of 2000 nm and a refractive index of 1.420 (product name: TSR9000, manufactured by Momentive Performance Materials Japan LLC)

[0124] Examples 1 to 3 and Comparative Examples 1 to 11 relate to a transparent resin composition which is a first embodiment of the present invention, and a resin molded article which is a second embodiment containing the transparent resin composition.

[0125] Examples 4 to 7 and Comparative Examples 12 to 25 relate to a combination lamp cover having a lamp cover that is the sixth embodiment of the present invention and the lamp cover that is the seventh embodiment.

[0126] [Example 1] 100 parts by mass of methacrylic resin (1) as a transparent resin and 0.00134 parts by mass of titanium dioxide (1) as a light diffusing agent were supplied to a twin-screw extruder (model name "PCM45", manufactured by Ikegai Co., Ltd.) and kneaded at 250°C to obtain a pellet-shaped transparent resin composition (light diffusing agent content of 13.4 ppm). Following the method described above, plate-shaped test pieces (thickness 4 mm × width 50 mm × length 200 mm) were prepared from the pellets of the obtained transparent resin composition. The obtained test pieces were evaluated according to the evaluation method described above. The evaluation results are shown in Table 2.

[0127] [Example 2, Comparative Examples 1-7] Test specimens were prepared in the same manner as in Example 1, except that the type of light diffusing agent and the amount of light diffusing agent added (content ratio) were as described in Table 1. The evaluation results of the obtained test specimens are shown in Table 2. [Example 3, Comparative Examples 8-11] Test specimens were prepared in the same manner as in Example 1, except that the type of light diffusing agent and the amount of light diffusing agent added (content ratio) were as described in Table 1. The evaluation results of the obtained test specimens are shown in Table 2.

[0128] [Example 4] 100 parts by mass of methacrylic resin (1) as a transparent resin and 0.0001 parts by mass of titanium dioxide (1) as a light diffusing agent were supplied to a twin-screw extruder (model name "PCM45", manufactured by Ikegai Co., Ltd.) and kneaded at 250°C to obtain a pellet-shaped transparent resin composition for lamp covers (light diffusing agent content of 0.1 ppm by mass). Following the method described above, plate-shaped test pieces (thickness 4 mm × width 50 mm × length 200 mm) were prepared from the pellets of the obtained transparent resin composition. The obtained test pieces were evaluated according to the evaluation method described above. The evaluation results are shown in Table 4.

[0129] [Examples 5-7, Comparative Examples 12-24] Test specimens were prepared in the same manner as in Example 1, except that the type of light diffusing agent and the amount (content) of light diffusing agent added were as described in Table 3. The evaluation results of the obtained test specimens are shown in Table 4.

[0130] [Example 25] Example of a combination lamp cover: A combination lamp cover in which the contour of the automobile headlamp cover is illuminated by light from an LED light source was manufactured by the following method: A combination lamp cover was manufactured by integrally molding a headlamp cover molded from a polycarbonate resin (product name: Yupiron HL-3503, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) using a two-component injection molding method, and a lamp cover molded from the transparent resin composition of Example 1 being positioned on the outer edge of the lamp cover.

[0131] The combination lamp cover was then placed on the headlamp cover of an automobile, and the LED light source was positioned so that light from the LED light source could enter the lamp cover from the side. When the LED light source is not lit, the outline of the headlamp cover is not recognized. However, when the LED light source is lit, as the light from the LED light source passes through the inside of the lamp cover, the effect of the light diffusing agent causes it to emit light, and the outline of the headlamp cover becomes visible and illuminated. On the other hand, when the light from the LED light source passes through the inside of the headlamp cover, which is molded from a polycarbonate resin, it does not light up. In other words, only the outline of the headlamp cover of the combination lamp cover was visible, illuminated by the light from the LED light source.

[0132]

[0133]

[0134]

[0135]

[0136] The test specimens of Examples 1 to 3 exhibited excellent transparency, brightness, low coloration, and a good balance between transparency and brightness. Note that the test specimen of Example 3 was D ９０ / D １０Because the ratio was large, the balance between transparency and brightness, as shown by the brightness retention coefficient, was slightly lower compared to Example 1. The test piece of Comparative Example 1 had a low content of light diffusing agent, resulting in insufficient brightness and a poor balance between transparency and brightness, as shown by the brightness retention coefficient. The test piece of Comparative Example 2 had a low content of light diffusing agent, resulting in insufficient brightness, as shown by the brightness attenuation coefficient. The test piece of Comparative Example 3 had a small average particle size of 200 nm for the light diffusing agent and a low content of the light diffusing agent, resulting in insufficient brightness, as shown by the brightness attenuation coefficient. The test piece of Comparative Example 4 had a small average particle size of 200 nm for the light diffusing agent and a low content of the light diffusing agent, resulting in excessively high transparency and an insufficient balance between transparency and brightness, as shown by the brightness attenuation coefficient and the brightness retention coefficient. The test piece of Comparative Example 5 had a large average particle size of 5150 nm for the light diffusing agent, resulting in an insufficient balance between brightness, as shown by the brightness attenuation coefficient and the brightness retention coefficient. The test specimen of Comparative Example 6 showed discoloration because the average particle size of the light diffuser was small (100 nm). Furthermore, the brightness indicated by the brightness attenuation coefficient was insufficient. The test specimen of Comparative Example 7 showed discoloration because the average particle size of the light diffuser was small (30 nm). Furthermore, the transparency was too high, resulting in insufficient brightness indicated by the brightness attenuation coefficient. The test specimens of Comparative Examples 8 and 9 had a high proportion of light diffuser, resulting in low transparency and an insufficient balance between transparency and brightness as indicated by the brightness retention coefficient. The test specimen of Comparative Example 10 showed discoloration because the average particle size of the light diffuser was small (210 nm). Furthermore, the brightness indicated by the brightness attenuation coefficient was insufficient. The test specimen of Comparative Example 11 had insufficient transparency because the average particle size of the light diffuser was large (320 nm).

[0137] The test specimens of Examples 4 to 7 exhibited excellent transparency, brightness, low coloration, and a good balance between transparency and brightness, making them suitable for lamp covers.

[0138] The test specimen of Comparative Example 12 had poor brightness because it did not contain a light diffusing agent. The test specimen of Comparative Example 13 had a large average particle size of light diffusing agent and a content of 1.0 ppm, resulting in excessive transparency and insufficient brightness. The test specimen of Comparative Example 14 had a large average particle size of light diffusing agent and a content of 10 ppm, resulting in an insufficient balance between transparency and brightness. The test specimen of Comparative Example 15 had a small average particle size of light diffusing agent (100 nm) and a content of 1.0 ppm, resulting in excessive transparency and a low YI / H value. The test specimen of Comparative Example 16 showed discoloration because the average particle size of light diffusing agent was small (100 nm) and the content was 10 ppm. The test specimens of Comparative Examples 17 and 18 had a small average particle size of light diffusing agent, resulting in excessive transparency and insufficient brightness. The test specimens of Comparative Examples 19 and 20 had a large average particle size of the light diffuser (2 μm) and a small difference in refractive index between the transparent resin and the light diffuser, resulting in excessive transparency and insufficient brightness. The test specimens of Comparative Examples 21 and 22 had a small difference in refractive index between the transparent resin and the light diffuser and a small average particle size of the light diffuser (30 nm), resulting in excessive transparency and insufficient brightness. The test specimens of Comparative Examples 23 and 24 had a small difference in refractive index between the transparent resin and the light diffuser and a large average particle size of the light diffuser, resulting in excessive transparency and insufficient brightness.

[0139] The resin molded article of the present invention, for example, can have a light source such as an LED placed in at least a portion of the side end surface of the resin molded article, and the light that enters from the end surface can be guided into the resin molded article and emitted in the direction of the surface. Discoloration is suppressed, and when the light source is off it is transparent and has a low presence, so it has excellent design qualities, and when the light source is on it it emits high brightness, so it has excellent visibility. Furthermore, it has an excellent balance between transparency and brightness. Such a transparent resin composition and a resin molded article containing the transparent resin composition can be used in applications such as vehicle interior and exterior components, lamp covers for lighting fixtures and light guides for surface light source devices, and in particular, in applications such as vehicle lamp covers, visors, meter panels, pillars, and combination lamp covers for vehicle interior and exterior components.

[0140] The lamp cover of the present invention can be used as a lamp cover or combination lamp cover for vehicles such as automobiles, such as a headlamp cover or a rear lamp cover. The lamp cover of the present invention can be used as a light guide plate or surface light source by, for example, arranging a light source such as an LED in at least a portion of the side end surface of the lamp cover, guiding the light that enters from the end surface into the lamp cover, and emitting it in the surface direction. When the light source is lit, it emits high brightness, so it has excellent visibility, and when the light source is turned off, it is transparent and has a low presence, so it has excellent design. Such a lamp cover or combination lamp cover can be suitably used in vehicles.

[0141] 1 Lamp cover 2 Housing 3 Projection lens 4 LED light source 5 Support substrate 6 Halogen lamp 7 Light source 8a Turn signal section 8b Brake light section 8c Reverse indicator section 9a Yellow inner lens 9b Red inner lens 9c White inner lens 10 Transparent or translucent lamp cover substantially free of light diffusing agent 11 Combination lamp cover 15 Resin molded body (test piece) 15a Light incident end face 15b Light emission surface 16 LED light source 17 Luminance meter 18 Resin molded body 19 Power supply unit 20 Power cord 21 Vehicle 22 Vehicle lamp cover 23 Visor 24 Pillar 25 Light shielding member (black cutting sheet) 26 Light transmitting section

Claims

DEPCT641. A transparent resin composition consisting of a transparent resin and a light-diffusing agent with an average particle diameter of not less than 220 nm and not more than 300 nm, where the available ratio of such light-diffusing agent is greater than 4.0 parts per million by mass and less than 20 parts per million by mass to the total mass of the transparent resin composition.

2. A transparent resin composition specified in Relief 1 where the ratio between the cumulative average particle diameter of 90% (D90) and the cumulative average particle diameter of 10% (D10) (D90 / D10) in the cumulative distribution curve of the particle diameters of such light-diffusing agent is not less than 1.2 and not more than 2.

5.

3. A transparent resin composition specified in Relief 1 or 2 where the refractive index difference between such transparent resin and such light-diffusing agent is not less than 0.3 and not more than 3.

0.

4. A transparent resin composition specified in any one of Reliefs 1 to 3 where such transparent resin is at least one type selected from methacrylic resins, polycarbonate resins, and polystyrene resins. 5.

6. A transparent resin composition specified in any of Reputations 1 to 4 in which the light-diffusing agent is titanium dioxide particles.

7. A transparent resin composition specified in any of Reputations 1 to 5 in which the contained ratio of such light-diffusing agent is not less than 6.5 parts per million by mass and not more than 18 parts per million by mass to the total mass of the transparent resin composition.

8. A transparent resin composition specified in any of Reputations 1 to 5 in which the contained ratio of such light-diffusing agent is not less than 7.2 parts per million by mass and not more than 16 parts per million by mass to the total mass of the transparent resin composition.

9. Resin molded objects containing a transparent resin composition specified in any of Reputations 1 to 7.Resin molding material consisting of a transparent resin composition and a light-diffusing agent with an average particle diameter of not less than 220 nm and not more than 300 nm, and a resin molding material in which the total light penetration ratio (Tt) of the thickness direction, measured according to ISO13468, is not less than 75% and not more than 91%, and the turbidity value (H) of the thickness direction, measured according to ISO14782, is not less than 1.0% and not more than 14.5%, and the yellowness value (YI) of the thickness direction, measured according to ISO17223, the total light penetration ratio (Tt) and turbidity value (H) fulfill the following equations (1) and (2): 0.04 less than or equal to H / Tt less than or equal to 0.18(1), 0.10 less than or equal to YI / H less than or equal to 0.28(2), 10.Resin-molded objects are those composed of a transparent resin material containing a light-diffusing agent, with an average particle diameter of not less than 220 nm and not more than 300 nm. The total light transmission ratio (Tt) in the thickness direction, measured according to ISO 13468, is not less than 75% and not more than 91%. The turbidity (H) in the thickness direction, measured according to ISO 14782, is not less than 1.0% and not more than 14.5%. When the resin-molded object scatters light in the thickness direction and the light is directed in the length direction, the brightness reduction coefficient (per meter) is not less than 10% and not more than 30%. The brightness retention coefficient (per meter / %), calculated by dividing the brightness reduction coefficient by the turbidity (percentage) of the resin-molded object, is not less than 1.5% and not more than 3.5%.

11. Resin molded objects specified in Requisition 9 or 11, which consist of an incident end plane provided at least part of the area of ​​the lateral end plane of such resin molded object and an emitted light plane provided at least one side of the main surface of such resin molded object, and have an average brightness in the plane which is the average of the brightness of such emitted light planes of not less than 500 candela / m².

12. Resin molded objects specified in any of Requisitions 9 through 11, in which the ratio between the particle diameter at cumulative frequency of 90 percent (D90) and the particle diameter at cumulative frequency of 10 percent (D10) (D90 / D10) in the cumulative frequency distribution curve of particle diameters of such light diffuser is not less than 1.2 and not more than 2.

5.

13. Resin molded objects specified in any of Requisitions 9 through 12, in which the available ratio of such light diffuser is greater than 4.0 parts per million by mass and less than 20 parts per million by mass to the total mass of the transparent resin components. 14.

15. Resin molded objects specified in any of Reputations 9 through 13 where at least one of the transparent resins is selected from the methacrylic resins, polycarbonate resins, and polystyrene resins.

16. Resin molded objects specified in any of Reputations 9 through 14 where the light diffuser is titanium dioxide particles.

17. Resin molded objects specified in any of Reputations 8 through 15 where at least one of the resin molded objects is selected from the group comprising vehicle interior and exterior trim parts, lamp covers for lighting fixtures, and light conductors for planar light source units.

18. Resin molded objects specified in Reputation 16 where at least one of the vehicle interior and exterior trim parts is selected from the group comprising vehicle lamp covers, sun visors, windshields, instrument panels, and pillars.

19. Vehicle lamp covers comprising resin molded objects specified in any of Reputations 8 through 15.A combined lamp cover is a lamp cover consisting of a transparent or semi-transparent headlight or taillight cover that does not contain any actual light-diffusing material and a lamp cover for the vehicle specified in Reputation 18, and on the outer edge of such headlight or taillight cover, or at least a portion of the area of ​​such outer edge, a lamp cover for such vehicle is placed.

20. A vehicle consisting of a lamp cover for the vehicle specified in Reputation 18 or a combined lamp cover. As specified in claim 1921. The lamp cover shall have a total light transmission ratio (Tt) of the thickness direction as measured in accordance with ISO13468 of not less than 75% and not less than 91%, and a turbidity (H) of the thickness direction as measured in accordance with ISO14782 of not less than 1.0% and not more than 14.5%, and a yellowness (YI) of the thickness direction as measured in accordance with ISO17223 of not more than 7.0, and H / Tt and YI / H fulfill the following equations (3) and (4) 0.01 less than or equal to H / Tt less than or equal to 0.2(3)-1.0 less than or equal to YI / H less than or equal to 1.0(4)22. Lamp covers which are lamp covers which have a total light radiation transmission ratio (Tt) of the thickness direction as measured in accordance with ISO13468 of not less than 75% and less than 91% and a turbidity value (H) of the thickness direction as measured in accordance with ISO14782 of not less than 1.0% and not more than 14.5% and a yellowness value (YI) of the thickness direction as measured in accordance with ISO17223 of not more than 7.0 and have a luminance retention coefficient (per meter / %) divided by the luminance reduction coefficient (per meter) when such lamp cover scatters light in the thickness direction of such lamp cover and light is directed in the length direction of such lamp cover with a turbidity value (%) of such lamp cover of not less than 1.5 and not more than 3.

523. Lamp covers specified in claims 21 or 22 which are lamp covers composed of transparent resin and light diffusers and the ratio of such light diffusers is 0.

23. The lamp cover specified in Reputation 21 or 22, where the transparent resin and the light diffuser have an available ratio of 1.0 to 15 parts per million by mass per 100 parts by mass of such transparent resin and an average particle diameter of such light diffuser of 220 to 300 nanometers.

24. The lamp cover specified in Reputation 21 or 22, where the transparent resin is at least one of the selected types from methacrylic resins, polycarbonate resins, and polystyrene resins.

26. The lamp cover specified in either Reputation 23 to 25, where the refractive index difference between such transparent resin and such light diffuser is not less than 0.3 and not more than 3.

0.

27. The lamp cover specified in either Reputation 23 to 26, where the light diffuser is titanium dioxide particles. 28.

29. A lamp cover that is a combined lamp cover consisting of an incident end plane provided at least part of the area of ​​the lateral end plane of such lamp cover and an emitted plane provided at least one side of the main surface of such lamp cover and having an average illuminance in the plane that is an average of the illuminances on the emitted plane of not less than 500 candela / m².

29. A combined lamp cover that is a combined lamp cover consisting of a transparent or semi-transparent headlight or taillight cover that does not contain any actual light-diffusing material and a lamp cover that is specified in any of the claims 21 to 28 and on the perimeter or at least part of the area of ​​the outer frame of such headlight or taillight cover, such lamp cover is placed.

30. A vehicle that is equipped with a lamp cover that is specified in any of the claims 21 to 28 or a combined lamp cover that is specified in claim 29.