Resin composition and optical member

Abstract

Provided is a resin composition that has a low in-plane birefringence (ΔNxy) within a certain range and can be used to form optical components with excellent transparency. [Solution] A resin composition containing a cycloolefin-based resin and particles of a composite carbonate represented by the following chemical formula (1), blended in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the cycloolefin-based resin. Ca z Sr 1-z CO3(0.1≦z<0.5) (1)

Description

[Technical Field]

[0001] The present invention relates to a resin composition and an optical member. [Background technology]

[0002] Cycloolefin resins are amorphous transparent resins with an excellent balance of optical properties and excellent heat resistance, making them suitable for producing optical components (see, for example, Non-Patent Document 1). It has been disclosed that optical components are molded using optical resins containing alkaline earth metal carbonate powder in order to suppress the occurrence of birefringence distribution when the optical components are used in a bent state (see, for example, Patent Document 1).

[0003] In order to improve the viewing angle characteristics of an optical element, it is necessary to reduce the out-of-plane retardation (Rth) and in-plane retardation (Re). Furthermore, the lower the haze, calculated as the ratio of diffusely transmitted light to the total light transmission, the lower the turbidity and therefore the more transparent the optical element. In other words, the lower the values ​​of the out-of-plane retardation (Rth), in-plane retardation (Re), and haze, the better the optical element.

[0004] As resins suitable for optical resin lenses, products using cyclic olefin-based cycloolefin polymers (COP) and cycloolefin copolymers (COC) dominate the market for small lenses for smartphones and other devices. COC has superior moldability and impact resistance compared to COP, and its resin composition, a polymer of norbornene and ethylene, has low polarizability. Furthermore, it can achieve birefringence in addition to a high Abbe number (an index for evaluating the chromatic dispersion of transparent bodies) (see, for example, Non-Patent Document 2). For this reason, COC holds the top share in the resin lens market.

[0005] On the other hand, COP and COC have positive birefringence, although it is smaller than that of polycarbonate (PC), etc. It is desirable to offset the birefringence caused by stress due to the shape and conditions during molding by combining it with a material that has negative birefringence, etc. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-47402 [Patent Document 2] International Publication No. 2022 / 059650 [Patent Document 3] International Publication No. 2022 / 255150 [Non-patent literature]

[0007] [Non-Patent Document 1] Journal of the Imaging Society of Japan, Vol. 55, No. 2, 236-242 (2016) [Non-patent document 2] Polymers Vol. 55, September 739 (2006) Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a resin composition that has a low in-plane birefringence (ΔNxy) within a certain range and can be used to form an optical element with excellent transparency, and an optical element made of a molded article of the resin composition. [Means for solving the problem]

[0009] As a result of investigations conducted by the present inventors to solve the above problems, they found that a resin composition containing a composite carbonate of a predetermined composition in a predetermined ratio relative to a cycloolefin-based resin can form an optical component having a low in-plane birefringence (ΔNxy) within a certain range and excellent transparency with a haze of 1% or less.

[0010] That is, the present invention provides a resin composition containing a cycloolefin-based resin and particles of a composite carbonate represented by the following chemical formula (1), which are blended in an amount of 0.1 part by mass or more and 1.0 part by mass or less per 100 parts by mass of the cycloolefin-based resin. Ca z Sr1-z CO3(0.1≦z<0.5) (1)

[0011] The present invention also provides an optical member made from a molded article of the above-mentioned resin composition. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a resin composition that has a low in-plane birefringence (ΔNxy) within a certain range and that can be used to form an optical member with excellent transparency, and an optical member obtained by molding the resin composition. [Brief explanation of the drawings]

[0013] [Figure 1] X-ray diffraction pattern of complex carbonate (CazSr1-zCO3). [Figure 2] Transmission electron micrograph of composite carbonate particles. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] The resin composition of the present invention contains a cycloolefin resin and particles of a composite carbonate of a predetermined composition blended in a predetermined ratio. The composite carbonate is represented by the following chemical formula (1). Ca z Sr 1-z CO3(0.1≦z<0.5) (1) By adding such composite carbonate particles, the positive intrinsic birefringence of the cycloolefin resin is offset, making it possible to produce a molded article with a birefringence close to zero.

[0016] (cycloolefin resin) Cycloolefin resins are polymers having an alicyclic structure in their structural units. Cycloolefin resins include polymers having an alicyclic structure in the main chain, polymers having an alicyclic structure in the side chain, polymers having alicyclic structures in the main chain and the side chain, and mixtures of two or more of these in any ratio. Among these, polymers having an alicyclic structure in the main chain are preferred from the viewpoints of mechanical strength and heat resistance.

[0017] Examples of the alicyclic structure include saturated alicyclic hydrocarbon (cycloalkane) structures and unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures. Among these, from the viewpoint of mechanical strength and heat resistance, cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are more preferred. In the present invention, a cycloolefin copolymer, which is a cyclic olefin copolymer having an alicyclic structure and an aliphatic structure, is suitable. The cycloolefin copolymer is represented, for example, by the following general formula:

[0018] [ka]

[0019] In the above general formula, x and y each represent a positive integer.

[0020] Cyclic olefin copolymers are copolymers of cyclic olefins and α-olefins, and are synthesized by addition copolymerization of cyclic olefins and α-olefins. The reason they are copolymers of cyclic olefins and α-olefins rather than homopolymers of cyclic olefins is because homopolymers of cyclic olefins are crystalline resins, and transparency is impaired by diffuse reflection between the crystalline and amorphous parts. Copolymers of cyclic olefins and α-olefins are amorphous resins and exhibit transparency. Cycloolefin copolymers belong to the cyclic olefin copolymer family and are copolymers of norbornene-based cyclic olefins and ethylene.

[0021] The number of carbon atoms constituting the alicyclic structure is preferably 4 to 30 per alicyclic structure. When the number of carbon atoms constituting the alicyclic structure is within this range, the molded product has a good balance of mechanical strength, heat resistance, and moldability. The number of carbon atoms constituting the alicyclic structure is more preferably 5 or more, particularly preferably 6 or more, and more preferably 20 or less, particularly preferably 15 or less per alicyclic structure.

[0022] In the cycloolefin resin, the proportion of structural units having an alicyclic structure is preferably 50% by weight or more. When the proportion of structural units having an alicyclic structure in the cycloolefin resin is within this range, the transparency and heat resistance of the molded product are improved. The proportion of structural units having an alicyclic structure is more preferably 70% by weight or more, and particularly preferably 90% by weight or more.

[0023] Specific examples of the cycloolefin resin include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, norbornene polymers and hydrogenated products thereof are more preferred from the viewpoints of transparency and moldability.

[0024] Examples of norbornene polymers include ring-opening polymers of monomers having a norbornene structure and their hydrogenated products, and addition polymers of monomers having a norbornene structure and their hydrogenated products. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith.

[0025] Furthermore, examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of these polymers include the polymers disclosed in JP-A-2002-321302. Among these, hydrogenated products of ring-opening polymers of monomers having a norbornene structure are particularly suitable from the viewpoints of transparency, moldability, heat resistance, low moisture absorption, dimensional stability, and light weight. Specific examples of cycloolefin resins include "ARTON" (registered trademark) manufactured by JSR Corporation; "APEL" (registered trademark) manufactured by Mitsui Chemicals, Inc.; "TOPAS" manufactured by TOPAS ADVANCED POLYMERS; and "ZEONEX" (registered trademark) manufactured by ZEON Corporation.

[0026] Among these, cycloolefin copolymers having both alicyclic and aliphatic structures are synthesized by direct addition polymerization of norbornene-based monomers and ethylene. These resins have excellent transparency and heat resistance that can withstand the usage environment and processing conditions. In particular, they exhibit high refractive index and low birefringence, making them superior as optical materials compared to other resins of the same type. In the present invention, cycloolefin copolymer (COC) is used as the cycloolefin-based resin.

[0027] The number average molecular weight of the cycloolefin resin (cycloolefin copolymer), as a polystyrene-equivalent value measured by GPC (gel permeation chromatography) using a toluene solvent, is 10,000 to 200,000, preferably 15,000 to 100,000, and more preferably 20,000 to 50,000. The cycloolefin resin also has a glass transition temperature of preferably 80°C or higher, more preferably 100 to 250°C.

[0028] (composite carbonate particles) The composite carbonate particles are composed mainly of composite carbonate. The term "main component" means that the particles may contain auxiliary components such as a surface treatment agent in addition to the composite carbonate, and that the composite carbonate is contained in an amount of, for example, 80% by mass or more. The composite carbonate particles have an average major axis in the range of 10 to 100 nm, preferably in the range of 15 to 75 nm. If the average major axis is less than 10 nm, the particles are too small and tend to aggregate, resulting in poor dispersibility. On the other hand, if the average major axis is more than 100 nm, the particles are too large and tend to result in poor transparency when mixed with a resin.

[0029] The composite carbonate particles preferably have an aspect ratio (ratio of average major axis / average minor axis) of 1.1 or more, more preferably in the range of 1.2 to 5.0, and particularly preferably in the range of 1.3 to 4.0.

[0030] The average major and minor diameters of composite carbonate particles can be measured by visual inspection or automatic image processing of SEM (scanning electron microscope) photographs of the particles. The major diameter of a particle can be measured as the longitudinal length (length of the long side) when the particle is considered to be a rectangle.

[0031] The minor axis of a particle can be measured as the length in the short direction (the length of the short side) when the particle is considered as a rectangle. Specifically, a rectangle that circumscribes the particle in the image and has the smallest area is calculated, and the major axis and minor axis are determined from the lengths of the long and short sides. "Average" refers to the average value obtained by measuring the major axis and minor axis of a statistically reliable number of particles (N number), and the number is usually 100 or more, preferably 300 or more, and more preferably 500 or more.

[0032] As described above, the composite carbonate of the present invention is a strontium carbonate (SrCO3) in which part of the strontium is replaced with calcium. z Sr 1-z CO3 (0.1≦z<0.5).

[0033] Ca z Sr 1-zIn aragonite-type complex carbonates with a composition expressed as CO3 (0.1≦z<0.5), when z is less than 0.1, the amount of particles with an aspect ratio of less than 2.0 increases, while when z is 0.5 or greater, the amount of heterophase CaCO3 (calcite) increases. The preferred range for z is 0.15≦z≦0.4, and the more preferred range is 0.2≦z≦0.335. The presence of Ca in complex carbonates can be confirmed by energy dispersive X-ray spectroscopy (EDS).

[0034] Ca z Sr 1-z The X-ray diffraction results of the complex carbonates represented by CO3 (x = 0.1, 0.2, 0.335, 0.5) are shown in Figure 1. Figure 1(a) shows the Ca z Sr 1-z CO3 is shown to be a single aragonite phase. Also, Figure 1(b) shows a peak shift due to solid solution. The presence of Ca was confirmed by EDS. On the other hand, Ca at z=0.5 z Sr 1-z In addition to the aragonite phase, CO3 also contains calcite as a secondary phase.

[0035] The composite carbonate particles may have a surfactant on their surfaces. That is, they may be surface-treated with a surfactant. Particles surface-treated with a surfactant have improved dispersibility. When producing a resin composition, if the particles themselves do not require dispersibility, such as when the composite carbonate particles are mechanically dispersed, the particles do not need to be surface-treated with a surfactant.

[0036] The surfactant may be a compound having at least one of a hydrophilic group and a hydrophobic group, and a group that forms an anion in water. When the hydrophilic group is a polyoxyalkylene group, a compound having a hydrophobic group attached to one end of the polyoxyalkylene group and a group that forms an anion in water attached to the other end may be used. The hydrophobic group may be an aryl group such as a phenyl group, or an alkyl group. The group that forms an anion in water may be selected from a carboxylic acid group, a sulfate group, and a phosphate group.

[0037] Examples of surfactants include phosphate esters, in which the group that forms an anion in water is a phosphate group. Phosphate esters have higher heat resistance than carboxylic acid esters and sulfate esters, so polymer compositions containing alkaline earth metal carbonate particles that have been surface-treated with phosphate esters are less likely to be discolored by thermal decomposition of the surfactant. Examples of phosphate esters include polyoxyethylene styrenated phenyl ether phosphate esters and polyoxyethylene alkyl ether phosphate esters.

[0038] The amount of surfactant on the surface of the composite carbonate particles is generally in the range of 1 to 40 parts by mass, preferably 3 to 30 parts by mass, per 100 parts by mass of the composite carbonate particles. If the amount of surfactant is too small, it may be difficult to obtain the effect of improving dispersibility. On the other hand, if the amount of surfactant is too large, the surfactant may become a foreign matter during the production of the resin composition, which may reduce the visible light transmittance of the resulting resin composition or increase the haze. An increase in haze indicates a decrease in transparency. The content of surfactant in the composite carbonate particles can be measured, for example, by TG-DTA (thermogravimetric differential thermal analyzer).

[0039] (Method for producing composite carbonate particles) The method for producing the composite carbonate particles of the present invention is described below. The composite carbonate particles can be produced, for example, by a method including a reaction step of reacting a hydroxide of an alkaline earth metal (specifically, strontium and calcium) with carbon dioxide in the presence of a crystal growth inhibitor to produce a composite carbonate, an aging step of growing the composite carbonate into acicular particles, a surface treatment step of treating the composite carbonate particles with a surfactant, and a drying step of drying the composite carbonate particles.

[0040] (Reaction step) In the reaction step, carbon dioxide gas is preferably introduced into a raw material solution containing a crystal growth inhibitor and an alkaline earth metal hydroxide while stirring the raw material solution, thereby carbonating the alkaline earth metal hydroxide and producing a composite carbonate. The raw material solution may be either an aqueous solution in which an alkaline earth metal hydroxide is dissolved, or an aqueous suspension in which an alkaline earth metal hydrate is dispersed. The concentration of the alkaline earth metal hydroxide in the raw material solution is not particularly limited, but is usually in the range of 1% to 20% by mass, preferably 2% to 18% by mass, and more preferably 3% to 15% by mass.

[0041] Strontium hydroxide octahydrate is used as the strontium source, and calcium hydroxide is used as the calcium source. By adjusting the mixing ratio of these, the value of z in the above chemical formula (1) can be adjusted. For example, when the molar ratio of strontium hydroxide octahydrate to calcium hydroxide is 9 / 1, z = 0.1. The higher the proportion of calcium hydroxide, the larger the value of z.

[0042] The crystal growth inhibitor is a carboxylic acid having a hydroxyl group that adheres to the generated composite carbonate and inhibits the crystal growth of the composite carbonate particles. The crystal growth inhibitor is preferably an organic acid having two carboxyl groups and a total of 3 to 6 hydroxyl groups. A dicarboxylic acid or anhydride thereof containing one or more hydroxyl groups in the molecule is more preferred. A monomer that is a raw material for the resin to which the composite carbonate particles are added can also be used as the crystal growth inhibitor. The content of the crystal growth inhibitor in the raw material solution is generally in the range of 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of alkaline earth metal hydroxide.

[0043] The temperature of the raw material liquid is preferably within a range of 5° C. to 60° C. The flow rate of carbon dioxide gas introduced into the raw material liquid is generally within a range of 0.5 mL / min to 200 mL / min, preferably 0.5 mL / min to 100 mL / min, per 1 g of alkaline earth metal hydroxide.

[0044] The particle shape of the composite carbonate produced in the reaction step is not particularly limited and may be either granular or needle-like. The shape and size of the composite carbonate particles can be adjusted by conditions such as the liquid temperature of the raw material liquid, the concentrations of the alkaline earth metal hydroxide and monomer in the raw material liquid, and the flow rate of carbon dioxide gas introduced into the raw material liquid. Note that if the composite carbonate particles produced in the reaction step are needle-like, the subsequent aging step may be omitted.

[0045] (ripening process) In the aging step, the aqueous suspension of composite carbonate particles obtained in the reaction step is heated and aged at a temperature in the range of 75°C to 115°C, thereby growing the composite carbonate particles into needle-like particles. If the heating temperature is less than 75°C, crystal growth of the major axis of the composite carbonate particles tends to be insufficient, resulting in a low average aspect ratio. On the other hand, if the heating temperature exceeds 115°C, crystal growth of the minor axis of the particles tends to be promoted, resulting in a low aspect ratio.

[0046] The heating temperature is preferably in the range of 80°C to 110°C, particularly preferably in the range of 85°C to 105°C. Heat aging is preferably carried out with stirring. The heating time is not particularly limited, but is usually in the range of 1 hour to 100 hours, preferably in the range of 5 hours to 50 hours, particularly preferably in the range of 10 hours to 30 hours.

[0047] (Surface treatment process) In the surface treatment step, a surfactant is preferably added to the slurry of acicular composite carbonate particles obtained in the aging step to treat the surfaces of the composite carbonate particles with the surfactant, thereby obtaining an aqueous slurry of highly dispersible acicular composite carbonate particles. After adding the surfactant to the slurry, the slurry is preferably stirred to make the surfactant concentration uniform, and then shear force is applied to the slurry. By applying shear force to break down agglomerates of the composite carbonate particles, the surfaces of the composite carbonate particles (primary particles) can be uniformly treated with the surfactant. The amount of surfactant added to the slurry is generally in the range of 1 to 40 parts by mass, preferably 3 to 30 parts by mass, per 100 parts by mass of composite carbonate particles in the slurry.

[0048] (drying process) In the drying step, the aqueous slurry of highly dispersible acicular composite carbonate particles obtained in the surface treatment step is dried to obtain composite carbonate particles. The drying step can be carried out by a known drying method using a dryer such as a spray dryer or a drum dryer.

[0049] The resin composition of the present invention can be prepared by mixing the above-mentioned cycloolefin-based resin (COC) with particles of the composite carbonate represented by the chemical formula (1). The content of the composite carbonate particles is specified to be 0.1 to 1.0 parts by mass relative to 100 parts by mass of the cycloolefin-based resin. By injection molding such a resin composition, an injection-molded article having a low in-plane birefringence (ΔNxy) within a certain range and excellent transparency can be produced. Moreover, the obtained molded article also has a reduced in-plane retardation (Re) while maintaining a low out-of-plane retardation (Rth) within a certain range. The content of the composite carbonate particles is preferably 0.1 to 0.5 parts by mass, more preferably 0.1 to 0.2 parts by mass, relative to 100 parts by mass of the cycloolefin-based resin.

[0050] A molded article having a diameter of 30 mm and a thickness of 1.5 mm, injection-molded using the resin composition of the present invention, has an in-plane birefringence ΔNxy at the center portion of -0.000080 or more and less than 0.000003, preferably -0.000050 or more and 0.000002 or less, and more preferably -0.000030 or more and 0.000001 or less. The in-plane birefringence ΔNxy can be calculated from the relationship (Re = ΔNxy × d) between the in-plane retardation Re and the sample thickness d. Re can be measured, for example, using a retardation measurement device manufactured by Oji Scientific Instruments.

[0051] The haze of the injection-molded article is preferably 1% or less, and more preferably 0.6% or less. Haze can be calculated from the relational expression HAZE = (Dif / TT) x 100 (HAZE: haze, Dif: diffuse transmittance, TT: total light transmittance). Each value can be measured, for example, with a haze meter manufactured by Nippon Denshoku Industries Co., Ltd.

[0052] Furthermore, the injection-molded article has an out-of-plane birefringence ΔP of -0.000080 to 0.000007, preferably -0.000050 to 0.000002, and more preferably -0.000030 to 0.000001. The out-of-plane birefringence ΔP can be calculated from the relationship between the out-of-plane retardation Rth and the sample thickness d (Rth = ΔP × d). Rth can be measured, for example, using a retardation measurement device manufactured by Oji Scientific Instruments.

[0053] To produce an injection-molded product, first, composite carbonate particles and a cycloolefin resin are blended and premixed in a predetermined ratio, and then strands are produced using a twin-screw extruder. The kneading temperature can be, for example, 180 to 210°C, and the diameter of the strands can be 1 to 2 mm. Then, pellets 2 to 4 mm long are produced from the strands using a pelletizer.

[0054] The resulting pellets are placed in an injection molding machine and injection molded at a predetermined mold temperature to obtain a molded product. In the present invention, the temperature of the mold surface into which the resin flows in the injection molding machine is referred to as the mold temperature. The mold temperature can generally be controlled to a predetermined temperature by adjusting the temperature setting of the injection molding machine itself.

[0055] For example, the mold temperature can be within a range of 50 to 130°C, and preferably 50 to 100°C. The temperature of the resin before being introduced into the mold during injection molding is not particularly limited and can be appropriately selected within a range of, for example, 250 to 300°C, and preferably 255 to 265°C. For example, when the resin temperature is 260°C, the mold temperature can be 130°C.

[0056] The molded product may be, for example, a disk-shaped resin plate having a thickness of about 1 to 2 mm and a diameter of about 5 to 30 mm. The disk-shaped resin plate may have a convex upper surface. For example, a resin plate simulating an optical lens having a diameter of 30 mm, an edge thickness of 1.0 mm, and a center thickness of 1.5 mm may be used.

[0057] The resin composition of the present invention exhibits particularly excellent effects when composite carbonate particles are contained together with a cycloolefin copolymer, as described below. The composite carbonate particles are needle-shaped and have negative birefringence in the major axis direction. When added to a resin, these composite carbonate particles align parallel to the orientation direction of the resin, thereby offsetting the positive birefringence of the resin.

[0058] Injection-molded resins have a large expansion component perpendicular to the resin flow direction from the gate. Furthermore, when the molded shape is circular (lens-shaped), this range becomes even larger. This suggests that the composite carbonate particles in the resin composition have a larger component oriented perpendicular to the MD direction (direction of resin flow) of injection. Meanwhile, because resin birefringence is manifested by stress generated in the surface layer, where temperature change is greater, the composite carbonate particles are less likely to suppress birefringence.

[0059] COP has a higher melt flow rate (MFR value) than COC. The MFR value is a measure of melt fluidity, with a higher value indicating better fluidity. This means that the fluidity after injection is good, the proportion of expansion flow is large, and there is a high probability that the orientation will become random before the fluidity decreases due to cooling. For this reason, it is thought that COC is more likely to exhibit the birefringence suppression effect of adding composite carbonate particles in injection-molded products such as lens shapes.

[0060] The resin composition of the present invention preferably has a melt volume flow rate (hereinafter sometimes abbreviated as "MVR") measured in accordance with JIS K6719 at 260 and a load of 21.18 N of 40 g / 10 min or more, preferably 45 g / 10 min or more, more preferably 50 g / 10 min or more, and is preferably 80 g / 10 min or less, and more preferably 60 g / 10 min.

[0061] If the resin composition has an MVR equal to or greater than the lower limit, the birefringence of the resulting optical component can be reduced, and molding defects such as weld lines and stringiness can be suppressed. On the other hand, if the MVR is equal to or less than the upper limit, the moldability of the resin composition can be improved. The MVR of the resin composition can be adjusted by the MVR of the alicyclic structure-containing polymer, the content of the alicyclic structure-containing polymer, etc.

[0062] An injection-molded article produced by injection molding the resin composition of the present invention containing a cycloolefin copolymer as a cycloolefin-based resin together with composite carbonate particles can be effectively used as an optical component such as an optical resin lens, a camera module for a smartphone, or a cover sheet for an in-vehicle display.

[0063] The following additional notes are further disclosed regarding the above-described embodiments of the present invention.

[0064] <1> A resin composition comprising a cycloolefin resin and particles of a composite carbonate represented by the following chemical formula (1), blended in an amount of 0.1 part by mass or more and 1.0 part by mass or less per 100 parts by mass of the cycloolefin resin: Ca z Sr 1-z CO3(0.1≦z<0.5) (1) <2> The particles have a surfactant on the surface thereof. <1> The resin composition according to claim 1. <3> The particles have an aspect ratio of 1.1 or more. <2> The resin composition according to claim 1. <4> The particles have an average major axis of 10 nm or more and 100 nm or less. <2> or <3> The resin composition according to claim 1. <5> The aforementioned <1> ~ <4> 2. An optical member comprising an injection-molded article of the resin composition according to any one of claims 1 to 11. [Example]

[0065] Next, the present invention will be specifically explained by way of examples, but the present invention is not limited to the following examples.

[0066] As composite carbonate particles, Ca z Sr 1-z CO3 (0.1≦z<0.5) particles were prepared. (Production of composite carbonate particles) (a) Reaction step A mixed aqueous suspension containing strontium hydroxide and calcium hydroxide was prepared by adding 2196 g of strontium hydroxide octahydrate (special grade reagent, purity: 96% or higher) and 67.92 g of calcium hydroxide (special grade reagent, purity: 96% or higher) to 20 L of purified water at 10°C and mixing them. The concentration of strontium hydroxide in the mixed aqueous suspension was 5.0 mass% and the concentration of calcium hydroxide was 0.3 mass%. DL-tartaric acid (special grade reagent, purity: 99% or higher) was added to this mixed aqueous suspension and stirred to dissolve in the aqueous suspension.

[0067] Next, while maintaining the temperature of the mixed aqueous suspension at 10°C and continuing stirring, carbon dioxide gas was blown in at a flow rate of 3.3 L / min (a flow rate of 3 mL / min per 1 g of strontium hydroxide) until the pH of the aqueous suspension reached 7, producing composite carbonate particles containing Ca and Sr. Stirring was then continued for a further 30 minutes to obtain an aqueous suspension of composite carbonate particles.

[0068] (b) Aging process The resulting aqueous suspension of composite carbonate particles was placed in a stainless steel tank and heated at 80°C for 24 hours to separate the Ca 0.1 Sr 0.9 The CO3 was allowed to grow into needle-like particles, which were then allowed to cool to room temperature to produce an aqueous slurry of composite carbonate particles.

[0069] (c) Surface treatment and drying process 3000 g of an aqueous slurry of composite carbonate particles (concentration: 5.3% by mass) was placed in a homomixer (TK Homomixer Mark II, manufactured by Primix Corporation), and while stirring by rotating the homomixer's stirring blades at a peripheral speed of 7.85 m / s, 44.5 g of polyoxyethylene styrenated phenyl ether phosphate was added and dissolved. The amount of polyoxyethylene styrenated phenyl ether phosphate was equivalent to 28 parts by mass per 100 parts by mass of the composite carbonate particles.

[0070] After that, stirring and mixing was continued for 1 hour. The aqueous slurry after stirring and mixing was dried to obtain particles of surface-treated composite carbonate (A-1). The obtained composite carbonate particles were observed using a JEOL JEM-2100F field emission transmission electron microscope (hereinafter referred to as TEM) at an acceleration voltage of 120 kV. The results are shown in Figure 2. From the photograph in Figure 2, it was confirmed that the particles were acicular particles with an average major axis of 60 nm. The composition of composite carbonate (A-1) was Ca 0.1 Sr 0.9 It is CO3.

[0071] As the cycloolefin-based resin, a cycloolefin copolymer resin (Mitsui Chemicals' cycloolefin copolymer APL5014CL) was prepared. The glass transition temperature Tg of the cycloolefin-based resin used here was 135°C.

[0072] Example 1 Ca as complex carbonate 0.1 Sr 0.9 A resin composition containing 0.1 parts by mass of CO3 particles and 100 parts by mass of a cycloolefin copolymer resin was prepared, and a molded article was manufactured using this composition by injection molding. Specifically, first, Ca 0.1 Sr 0.9 10 g of CO3 particles and 10,000 g of cycloolefin copolymer resin were premixed and extruded into strands with a diameter of 2 mm at a mixing temperature of 195 °C using a twin-screw extruder (manufactured by Berstorff). Then, pellets with a length of 3 mm were obtained from the strands using a pelletizer.

[0073] The resulting pellets were placed in an injection molding machine manufactured by Meiho Co., Ltd. and injection molded under conditions of a resin temperature of 260°C and a mold temperature of 130°C to produce an injection-molded product of Example 1 (a disc-shaped resin plate with a diameter of 30 mm, an edge thickness of 1.0 mm, and a center thickness of 1.5 mm, resembling a convex optical lens). The mold temperature was the temperature of the mold surface into which the resin flowed in the injection molding machine, and was controlled to a predetermined temperature by the temperature setting of the injection molding machine itself.

[0074] Example 2 Ca 0.1 Sr 0.9 An injection-molded product of Example 2 was obtained in the same manner as in Example 1, except that the amount of CO3 particles was changed to 1.0 part by mass.

[0075] Example 3 Composite carbonate particles Ca 0.2 Sr 0.8 An injection-molded product of Example 3 was obtained in the same manner as in Example 1, except that CO3 particles were used instead. 0.2 Sr 0.8CO3 particles were prepared in the same manner as above, except that the ratio of strontium hydroxide octahydrate to calcium hydroxide was changed.

[0076] Example 4 Ca 0.2 Sr 0.8 An injection-molded product of Example 4 was obtained in the same manner as in Example 3, except that the amount of CO3 particles added was changed to 0.5 parts by mass.

[0077] Example 5 Composite carbonate particles Ca 0.335 Sr 0.665 An injection-molded product of Example 5 was obtained in the same manner as in Example 1, except that CO3 particles were used instead. 0.335 Sr 0.665 CO3 particles were prepared in the same manner as above, except that the ratio of strontium hydroxide octahydrate to calcium hydroxide was changed.

[0078] Example 6 Ca 0.335 Sr 0.665 An injection-molded product of Example 6 was obtained in the same manner as in Example 5, except that the amount of CO3 particles added was changed to 0.5 parts by mass.

[0079] Example 7 Ca 0.335 Sr 0.665 An injection-molded product of Example 7 was obtained in the same manner as in Example 5, except that the amount of CO3 particles was changed to 1.0 part by mass.

[0080] Example 8 Ca 0.1 Sr 0.9 10 g of CO3 particles and 10,000 g of cycloolefin copolymer resin were premixed to form Ca 0.1 Sr 0.9 The raw material was prepared by compounding 0.1 parts by mass of CO3 particles. This premixed raw material was placed in an injection molding machine manufactured by Meiho Co., Ltd. and injection molded at a resin temperature of 260°C and a mold temperature of 130°C to obtain an injection-molded product of Example 8.

[0081] Example 9 Ca 0.1 Sr 0.9 An injection-molded product of Example 9 was obtained in the same manner as in Example 8, except that the amount of CO3 particles was changed to 0.5 parts by mass.

[0082] (Comparative Example 1) An injection-molded article of Comparative Example 1 was obtained in the same manner as in Example 1, except that no composite carbonate particles were mixed.

[0083] (Comparative Example 2) An injection-molded product of Comparative Example 2 was obtained in the same manner as in Example 1, except that the composite carbonate particles were changed to 1.0 part by mass of strontium carbonate (SrCO3) particles. SrCO3 was prepared in the same manner as above, except that calcium hydroxide was not used.

[0084] (Comparative Example 3) An injection-molded article of Comparative Example 3 was obtained in the same manner as in Comparative Example 1, except that the blending amount of SrCO3 particles was changed to 3.0 parts by mass.

[0085] Comparative Example 4 An injection-molded article of Comparative Example 4 was obtained in the same manner as in Comparative Example 1, except that the amount of SrCO3 particles was changed to 4.0 parts by mass.

[0086] (Comparative Example 5) The composite carbonate particles were mixed with 0.5 parts by mass of Ca 0.5 Sr 0.5 An injection-molded product of Comparative Example 5 was obtained in the same manner as in Example 1, except that CO3 particles were used instead.

[0087] (Comparative Example 6) Ca 0.5 Sr 0.5 An injection-molded product of Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the amount of CO3 particles was changed to 1.0 part by mass.

[0088] (Comparative Example 7) Ca 0.2 Sr 0.8An injection-molded product of Comparative Example 7 was obtained in the same manner as in Example 3, except that the amount of CO3 particles added was changed to 2.0 parts by mass.

[0089] (Comparative Example 8) Ca 0.335 Sr 0.335 An injection-molded product of Comparative Example 8 was obtained in the same manner as in Example 5, except that the amount of CO3 particles was changed to 2.0 parts by mass.

[0090] Comparative Example 9 Composite carbonate particles Ca 0.005 Sr 0.95 An injection-molded product of Comparative Example 9 was obtained in the same manner as in Example 1, except that CO3 particles were used instead.

[0091] (Comparative Example 10) Ca 0.005 Sr 0.95 An injection-molded product of Comparative Example 10 was obtained in the same manner as in Comparative Example 9, except that the amount of CO3 particles added was changed to 1.0 part by mass.

[0092] (Comparative Example 11) Ca 0.1 Sr 0.9 An injection-molded product of Comparative Example 11 was obtained in the same manner as in Example 1, except that the amount of CO3 particles added was changed to 0.05 parts by mass.

[0093] (Comparative Example 12) Ca 0.335 Sr 0.665 An injection-molded product of Comparative Example 12 was obtained in the same manner as in Example 5, except that the amount of CO3 particles was changed to 0.05 parts by mass.

[0094] The physical properties of the injection molded articles of the Examples and Comparative Examples were examined as follows. Haze: Measured using a spectrophotometer (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.). Birefringence (ΔNxy, ΔP): Using a phase measurement device (KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd.), the in-plane retardation (retardation) Re and the out-of-plane retardation (retardation in the thickness direction / retardation in the thickness direction) Rth were measured.

[0095] Here, the physical properties of the optical member will be described. Ideally, optical components (lenses, sheets, etc.) should have no birefringence, meaning that both the in-plane retardation (Re) and out-of-plane retardation (Rth) are zero. Lenses with small incident light angles, in particular, require Re to be close to zero. Optical lenses used in typical image sensors combine multiple elements (usually 5 to 6), so a configuration that can cancel out birefringence as a whole is desirable. Even if the birefringence of each lens is small, it will increase if it is in the same direction, so combining lenses with partially negative values ​​can be effective.

[0096] The same is true for Rth; the more negative the value, the better. In applications with a wide angle of incidence (such as cover sheets), laminating a combination of resins with negative values ​​can reduce the overall Rth and prevent degradation of display quality due to viewing angle. In other words, to obtain optical lenses for use in general image sensors, a resin composition with Rth close to zero in both positive and negative values ​​is required.

[0097] The above-mentioned phase measurement device measures the in-plane retardation R0 using light incident perpendicularly to the measurement object (plate), and the retardation R using light incident at an incident angle of 40° to the measurement object. θ Measure the in-plane retardation R0 and retardation R θ The out-of-plane retardation Rth is calculated from the thickness d (input value) of the object to be measured and the average refractive index Navr (input value) of the object to be measured. Here, in the examples and comparative examples described in this specification, the out-of-plane retardation Rth is defined as a value for light having a wavelength of 587.3 nm. A smaller value indicates lower birefringence.

[0098] The results obtained are summarized in the table below, along with the formulation of the resin composition. In both the Examples and Comparative Examples, injection molding was carried out under the same conditions: a resin temperature of 260°C and a mold temperature of 130°C. In order to equalize the influence of lens thickness, the in-plane retardation (Re) and out-of-plane retardation (Rth) were each normalized to 100 μm.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] [Table 4]

[0103] As shown in the table above, when 0.1 to 1.0 parts by mass of composite carbonate particles are contained per 100 parts by mass of cycloolefin copolymer, molded articles having a low in-plane birefringence (ΔNxy) within a certain range and excellent transparency are obtained. Moreover, the molded articles of the examples maintain a low out-of-plane retardation (Rth) within a certain range, while also having a low in-plane retardation (Re).

[0104] In contrast, if either the composition or the blending amount of the composite carbonate is not satisfied, the desired molded article cannot be obtained. Specifically, if the composition of chemical formula (1) is not satisfied (Comparative Examples 1 to 6, 9, and 10), a molded article having a low in-plane birefringence (ΔNxy) within a certain range and excellent transparency cannot be obtained. Even with the specified blending amount, in Comparative Example 9, the in-plane birefringence ΔNxy is outside the range, and in Comparative Example 10, both the in-plane birefringence ΔNxy and the haze are outside the range.

[0105] The composite carbonate used in Comparative Examples 7, 8, 11, and 12 has the composition of chemical formula (1), but the blending amount is outside the range. When the blending amount of the composite carbonate particles is less than 0.1 part by mass relative to 100 parts by mass of the cycloolefin copolymer (Comparative Examples 11 and 12), or exceeds 1.0 part by mass (Comparative Examples 7 and 8), the in-plane birefringence ΔNxy is shown to be outside the range.

[0106] Optical lenses used in general image sensors are configured so that multiple lenses can be combined to cancel out birefringence as a whole. To this end, the molded article of Comparative Example 1 was combined with the molded article of any of Examples 4, 5, and Comparative Example 5 to form a two-layer laminate, and the in-plane retardation (Re) and out-of-plane retardation (Rth) were evaluated.

[0107] The results are summarized in the table below. In order to equalize the influence of lens thickness, the in-plane retardation (Re) and out-of-plane retardation (Rth) are each normalized to 100 μm.

[0108] [Table 5]

[0109] As shown in the above table, by combining an injection-molded article exhibiting a positive in-plane retardation (Re) (Comparative Example 1) with an injection-molded article exhibiting a negative retardation (Re) (Example 4, Example 5, Comparative Example 5), an injection-molded article was obtained which not only had an in-plane birefringence ΔNxy within a predetermined range and excellent transparency, but also had a low in-plane retardation (Re) while maintaining a low out-of-plane retardation (Rth) within a certain range.

Claims

1. A resin composition comprising a cycloolefin resin and particles of a composite carbonate represented by the following chemical formula (1), blended in an amount of 0.1 parts by mass or more and 1.0 parts by mass or less per 100 parts by mass of the cycloolefin resin: Ca ｚ Sr １－ｚ CO ３ (0.1≦z<0.5) (�

2. The resin composition according to claim 1 , wherein the particles have a surfactant on the surface thereof.

3. The resin composition according to claim 1 or 2, wherein the particles have an aspect ratio of 1.1 or more.

4. 3. The resin composition according to claim 1, wherein the particles have an average major axis of 10 nm or more and 100 nm or less.

5. 3. The resin composition according to claim 1, wherein the melt volume flow rate measured in accordance with JIS K6719 at 260°C under a load of 21.18 N is 40 g / 10 min or more.

6. An optical member comprising a molded article made of the resin composition according to claim 1 or 2.

7. 7. The optical member according to claim 6, wherein the molded article has an in-plane birefringence ΔNxy of −0.000080 or more and less than 0.000003, and a haze of 1% or less.

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