TECHNICAL FIELD

The present invention relates to a polycarbonate resin composition, and more specifically relates to a polycarbonate resin composition which exhibits excellent impact resistance, has a good hue and causes very little gas generation and mold contamination at the time of molding; and a molded article obtained by molding the composition.

BACKGROUND ART

Liquid crystal display devices used in personal computers, mobile telephones, and the like, include planar light source devices in order to meet demands for reduced thickness and weight, reduced energy consumption and higher resolution. In addition, such planar light source devices are devices in which one surface is provided with a light guide plate having a wedge-shaped cross section having a uniform slanted surface or a panel-shaped light guide plate in order to achieve the effect of uniformly and efficiently guiding incident light to the liquid crystal display side. In addition, a light-scattering function is imparted by forming a relief pattern on a surface of the light guide plate.

This type of light guide plate can be obtained by injection molding a thermoplastic resin, and a relief pattern is imparted through transfer of a relief part formed on a surface of an insert die. In the past, light guide plates were formed from resin materials such as polymethyl methacrylate (PMMA), but in recent years, there have been demands for display devices that project more vivid images, and because temperatures inside apparatuses tend to increase as a result of heat generated in the vicinity of a light source, conventional resin materials are being replaced by polycarbonate resin materials, which exhibit higher heat resistance.

Polycarbonate resins exhibit excellent mechanical properties, thermal properties, electrical properties and weather resistance, but exhibit lower light transmittance than PMMA and the like, and problems such as low brightness therefore occur in cases where a planar light source is constituted from a polycarbonate resin light guide plate and a light source. In addition, there have been demands in recent years for a reduction in differences in chromaticity between an incident part of a light guide plate and a position distant from the incident part, but polycarbonate resins are more likely to suffer from problems such as yellowing than PMMA.

PTL 1 proposes a method for improving light transmittance and brightness by adding an acrylic resin and an alicyclic epoxy compound, PTL 2 proposes a method for improving brightness by modifying a terminal of a polycarbonate resin and increasing the transferability of a relief part to a light guide plate, and PTL 3 proposes a method for improving brightness by introducing a copolyester carbonate having an aliphatic segment so as to improve transferability.

However, the method disclosed in PTL 1 achieves an improvement in hue by adding the acrylic resin, but cannot increase light transmittance and brightness due to white turbidness occurring, and adding the alicyclic epoxy compound can improve transmittance, but no improvement in hue has been confirmed. In the case of PTL 2 and PTL 3, advantageous effects can be expected in terms of improved fluidity and transferability, but the problem of reduced heat resistance occurs.

However, blending polyethylene glycol, poly(2-methyl)ethylene glycol, or the like, in a thermoplastic resin such as a polycarbonate resin is a known feature, and PTL 4 discloses a γ-radiation-resistant polycarbonate resin containing same, and PTL 5 discloses a thermoplastic resin composition which contains PMMA or the like and which exhibits excellent anti-static properties and surface appearance.

In addition, PTL 6 proposes improving transmittance and hue by blending a polyalkylene glycol constituted from a straight chain alkyl group. An improvement in transmittance and degree of yellowing (yellow index: YI) can be seen by blending polytetramethylene ether glycol.

Furthermore, PTL 7 discloses a method for producing a polycarbonate copolymer by using a diol obtained by diesterification of a polyalkylene glycol as a raw material (comonomer), but in this polycarbonate copolymer, the diol obtained by diesterification of a polyalkylene glycol is unstable, and the polycarbonate copolymer is inadequate in terms of impact resistance and is also poor in terms of hue and thermal discoloration resistance.

In recent years in particular, optical components such as light guide plates in hand-held terminals such as smart phones and tablets have become both thinner and larger at a remarkable rate, and there have been demands for higher barrel temperatures and higher injection speeds for molding light guide plates. As a result, the amount of gas generated at the time of molding has increased and problems have occurred, such as mold contamination readily occurring. Therefore, resin compositions used for molding such products require not only excellent optical characteristics, but also low mold contamination caused by gas generation during high temperature injection molding, and excellent impact resistance.

CITATION LIST

Patent Literature

[PTL 1] JP H11-158364 A

[PTL 2] JP 2001-208917 A

[PTL 3] JP 2001-215336 A

[PTL 4] JP H01-22959 A

[PTL 5] JP H09-227785 A

[PTL 6] JP 5699188 B2

[PTL 7] JP 2006-016497 A

SUMMARY OF INVENTION

Technical Problem

In view of the circumstances mentioned above, the purpose of the present invention is to provide a polycarbonate resin composition which has a good hue, exhibits excellent impact resistance, and causes very little gas generation and mold contamination at the time of molding.

Solution to Problem

As a result of repeated diligent research carried out in order to solve the problems mentioned above, the inventors of the present invention found that by blending a conventional polycarbonate resin with specific quantities of a phosphorus-containing stabilizer and a specific polycarbonate copolymer having carbonate bonding between bisphenol A and a polyalkylene glycol, it was possible to obtain a polycarbonate resin composition which exhibits excellent impact resistance, has a good hue and causes very little gas generation and mold contamination at the time of molding, and thereby completed the present invention.

The present invention relates to the following polycarbonate resin composition and molded article.

[1] A polycarbonate resin composition containing 0.1 to 10 parts by mass of a polycarbonate copolymer (B) having carbonate bonding between (B1) bisphenol A and a (B2) polyalkylene glycol and 0.005 to 0.5 parts by mass of a phosphorus-containing stabilizer (C) relative to 100 parts by mass of a polycarbonate resin (A).
[2] The polycarbonate resin composition according to [1] above, wherein the (B2) polyalkylene glycol that constitutes the polycarbonate copolymer (B) has a number average molecular weight (Mn) of 500 to 4,000.
[3] The polycarbonate resin composition according to [1] or [2] above, wherein the polycarbonate copolymer (B) has a weight average molecular weight (Mw) of 5,000 to 40,000.
[4] The polycarbonate resin composition according to any one of [1] to [3] above, wherein a mass ratio of the (B1) bisphenol A and the (B2) polyalkylene glycol that constitute the polycarbonate copolymer (B) is such that, relative to a total of 100 mass % of components (B1) and (B2), a proportion of component (B1) is not less than 5 mass % and less than 50 mass % and a proportion of component (B2) is more than 50 mass % and not more than 95 mass %.
[5] The polycarbonate resin composition according to any one of [1] to [4] above, wherein the (B2) polyalkylene glycol that constitutes the polycarbonate copolymer (B) is a polyalkylene glycol constituted of tetramethylene ether units.
[6] The polycarbonate resin composition according to any one of [1] to [5] above, which further contains an epoxy compound (D) and/or an oxetane compound (E) at an amount of 0.0005 to 0.2 parts by mass relative to 100 parts by mass of the polycarbonate resin (A).
[7] A molded article of the polycarbonate resin composition according to any one of [1] to [6] above.
[8] The molded article according to [7] above, which is an optical component.

Advantageous Effects of Invention

The polycarbonate resin composition of the present invention exhibits excellent impact resistance, has a good hue and causes very little gas generation and mold contamination at the time of molding, and a molded article comprising the polycarbonate resin composition exhibits excellent impact resistance and is particularly suitable for use as an optical component having a good hue.

