Polycarbonate resin compositions with consistent color and stable blue-cut performance

Abstract

Embodiments of the disclosure relate to a series of PC resin additives for maintaining the color stability and blue-cut performance during injection molding. The additives may be used to adapt a PC resin customarily used for sun protection lenses for clear lens applications.

Claims

1. A high blue-cut performance polycarbonate resin composition for use in clear lenses comprising: a polycarbonate polymer base resin; 0.05 to 1% by weight of a UV absorber, based on the weight of the base resin; 0.05 to 1% by weight of an antioxidant, based on the weight of the base resin; at least one selective blue blocking filter that at least partially blocks blue light in a wavelength range chosen within the 400-460 nm range; a colorant additive; and 0.05 to 1% by weight of a hindered amine light stabilizer, based on the weight of the base resin; wherein: the resin composition blocks>99% of light with a wavelength less than 400 nm at each wavelength in the wavelength range of 315-400 nm; and the color stability and blue-cut performance of the resin composition are maintained during an injection molding process.

2. The polycarbonate resin composition of claim 1, wherein a weight average molecular weight of the polycarbonate polymer base resin ranges from about 20,000 to about 40,000 g/mol.

3. The polycarbonate resin composition of claim 1, wherein the UV absorber is a benzotriazole absorber.

4. The polycarbonate resin composition of claim 3, wherein the UV absorber is 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1,1-dimethylethyl)-4-methyl phenol.

5. The polycarbonate resin composition of claim 1, wherein the colorant additive is a blue dye, a violet dye, a red dye, or any combination thereof.

6. The polycarbonate resin composition of claim 1, wherein the colorant additive is 1,4-di(2,6-dibromo-4-methylphenylamino) anthracene-9,10-dione.

7. The polycarbonate resin composition of claim 1, wherein the antioxidant is a benzenepropanoic acid ester.

8. The polycarbonate resin composition of claim 7, wherein the antioxidant is benzenepropanoic acid, 3(1,1-dimethylethyl)-4-hydroxy-5-methyl-1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)] ester.

9. The polycarbonate resin composition of claim 1, wherein the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate.

10. A clear lens comprising a high blue-cut performance polycarbonate resin composition, comprising: a polycarbonate polymer base resin; 0.05 to 1% by weight of a UV absorber, based on the weight of the base resin; 0.05 to 1% by weight of an antioxidant, based on the weight of the base resin; at least one selective blue blocking filter that at least partially blocks blue light in a wavelength range chosen within the 400-460 nm range; a colorant additive; and 0.05 to 1% by weight of a hindered amine light stabilizer, based on the weight of the base resin; wherein: the resin composition blocks>99% of light with a wavelength less than 400 nm at each wavelength in the wavelength range of 315-400 nm; the color stability and blue-cut performance of the resin composition are maintained during an injection molding process; and a D65 transmittance of a 1.1 mm thick clear lens is greater than 85%.

11. The clear lens of claim 10, wherein the clear lens comprises a BVC(B′) value of ≥20%.

12. The clear lens of claim 11, wherein the clear lens further comprises a wafer overmold for increasing at least one of blue-cut performance, color balance, and lens clarity.

13. A method for maintaining the color stability and blue-cut performance of a resin composition during an injection molding process, comprising: obtaining a base resin comprising a polycarbonate polymer base resin and adding to said base resin 0.05 to 1% by weight of a UV absorber, based on the weight of the base resin, 0.05 to 1% by weight of an antioxidant, based on the weight of the base resin, at least one selective blue blocking filter that at least partially blocks blue light in a wavelength range chosen within the 400-460 nm range, a colorant additive and 0.05 to 1% by weight of a hindered amine light stabilizer, based on the weight of the base resin, injection molding the resin composition to produce a high blue-cut performance polycarbonate clear lens, wherein the lens blocks>99% of light with a wavelength less than 400 nm at each wavelength in the wavelength range of 315-400 nm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a graph depicting yellowness index (YI) and BVC(B′) of a series of lenses formed by injection molding of a commercially available polycarbonate resin. The upward drifting of YI and evolution of BVC(B′) demonstrate the insufficiency of commercial PC resins of 400 nm UV cut-off in maintaining the color stability and blue-cut performance during injection molding.

(2) FIG. 2 is a graph depicting the transmission spectrum of one embodiment of a blue-cut polycarbonate resin lens.

DETAILED DESCRIPTION

(3) Various features and advantageous details are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and/or rearrangements will be apparent to those of ordinary skill in the art from this disclosure.

(4) In the following description, numerous specific details are provided to provide a thorough understanding of the disclosed embodiments. One of ordinary skill in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

(5) Disclosed herein is a method for improving the color stability of existing polycarbonate resins during processing and that of the lenses made therefrom. More specifically, a combination of various additives including UV blockers, antioxidants, light stabilizers, for example, hindered amine light stabilizers, and colorants may be added to a polycarbonate base resin before being formed into optical lenses. The resulting lenses exhibit consistent color and notable blue-cut performance. The modified resin formulations may be used to produce clear lenses help protect prescription eyeglass wearers from phototoxic blue light.

(6) Blue-cut of a lens is typically defined by:
Blue light cut (%)=100−T.sub.sb

(7) $T_{\mathrm{sb}}=\frac{{\int }_{380\mathrm{nm}}^{500\mathrm{nm}}T\left(\lambda \right).Math.E_{s\lambda }\left(\lambda \right).Math.B\left(\lambda \right).Math.d\lambda }{{\int }_{380\mathrm{nm}}^{500\mathrm{nm}}{E}_{s\lambda }\left(\lambda \right).Math.B\left(\lambda \right).Math.d\lambda }$ where T(λ): Transmittance (%) with 5 nm pitch E.sub.sλ(λ): Solar spectral irradiation (ISO 8980-3: Annex B)

(8) B(λ): Blue light hazard function (ISO 8980-3: Annex B)

(9) The experiments and observations disclosed herein espouse a blue-cut performance measure characterized by:

(10) $\mathrm{BVC}\left(B^{\prime }\right)=100\%-\frac{{\int }_{400\mathrm{nm}}^{455\mathrm{nm}}{B}^{\prime }\left(\lambda \right).Math.T\left(\lambda \right).Math.d\lambda }{{\int }_{400\mathrm{nm}}^{455\mathrm{nm}}{B}^{\prime }\left(\lambda \right).Math.d\lambda }$$\mathrm{or}$$\mathrm{BVC}\left(B\right)=100\%-\frac{{\int }_{400\mathrm{nm}}^{455\mathrm{nm}}B\left(\lambda \right).Math.T\left(\lambda \right).Math.d\lambda }{{\int }_{400\mathrm{nm}}^{455\mathrm{nm}}B\left(\lambda \right).Math.d\lambda }$

(11) where T(λ): Transmittance (%) with 10 nm pitch B′(λ): Blue light hazard function (Arnault et al., PlosOne, 2013)

(12) B(λ): Blue light hazard function (ISO 8980-3: Annex B)

(13) The blue-cut performance of a lens is a function of the transmittance T(λ), which is directly linked to its color appearance corresponding to a specific transmission spectrum. Hence, it is important for a lens to have consistent and stable color to achieve constant blue-cut performance. During lens injection molding processes, insufficient protection from heat and oxidation may cause a lens color to vary. A typical indicator of lens color variation is the continuous evolution of the yellowness index (YI) from lens to lens (FIG. 1). Lens color could also change due to photo-degradation of the base PC resin and the constituent additives and colorants. The increase of YI during the production of successive lenses indicates that heat and/or oxidation are adversely affecting lens quality.

(14) In order to enhance protection of commercial PC resins of 400 nm UV cut-off from degradation/oxidation due to high heat, an antioxidant or heat stabilizer such as a benzenepropanoic acid may be added to a base PC resin. 3(1,1-dimethylethyl)-4-hydroxy-5-methyl-1,1′-[1,2-ethanediylbis(oxy-2,1-e-thanediyl)] ester is a commercially available benzenepropanoic acid sold under the name Irganox® 245 sold by Ciba part of BASF. In some embodiments, 0.05 to 1% by weight of a benzenepropanioc acid is added. In order to reduce or prevent photo-degradation of the resulting lenses, a light stabilizer may be added to a base PC resin. In some embodiments, the light stabilizer bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate may be added to a base PC resin. This compound is commercially available as Tinuvin® 144, and is sold by Ciba part of BASF. In some aspects, 0.05 to 1% by weight of a light stabilizer is added to the resin

(15) Experimental Section

(16) Injection Molding of a commercial PC resin

(17) Injection molding of 1.50B SFSV lenses with Teijin Panlite L-1250VX PC resin having 400 nm UV-cut was carried out using a Nissei FN4000 injection molding machine with the following process parameters:

(18) Melt temperature: 515 F

(19) Mold temperature: 270 F

(20) Screw speed: 15 rpm

(21) Injection speed: 6%

(22) Packing pressure: 1220 psi

(23) Packing time: 10 s

(24) Cooling time: 250 s

(25) The graph depicted in FIG. 1 illustrates the YI and BVC(B′) data of the resulting comparative lenses. As seen in FIG. 1, the upward drift of YI and the evolution of BVC(B′) are apparent, which demonstrate clearly the insufficiency of commercial PC resins of 400 nm UV cut-off in maintaining the color stability and blue-cut performance during injection molding.

(26) According to the invention, a combination of various additives including UV blockers, antioxidants, light stabilizers, for example, hindered amine light stabilizers, and colorants may be added to the above polycarbonate base resin before being formed into optical lenses to maintaining the color stability and blue-cut performance during injection molding and produce clear blue-cut performance lenses with stable color.

(27) The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.