Coated alkaline earth metal carbonate fine particle, resin composition, and image display device

Abstract

To provide coated alkaline earth metal carbonate fine particles suitable as an inorganic filler, exhibiting superior resin dispersibility and thermal stability, and enabling formation of a molded article having superior transparency and durability when formulated into a resin composition.SOLUTION: The present invention provides a coated alkaline earth metal carbonate particle having a layer of an organic polymer on the surface of an alkaline earth metal carbonate fine particle. The layer of the organic polymer contains a material derived from polyoxyethylene styrenated phenyl ether phosphate and an acrylic resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to coated alkaline earth metal carbonate fine particles, a resin composition, and an image display device.

Background Art

[0002] Resins such as polycarbonate, polyethylene terephthalate, acrylate, and cycloolefin are excellent in transparency, weather resistance, chemical resistance, and optical properties. Moreover, since these resins are excellent in moldability and easy to process, they are used in optical members such as lenses and displays, automotive members, and medical supplies.

[0003] Optical members and the like are formed by an injection molding method or a melt extrusion method using a resin composition containing the above-described resin and an inorganic filler. In molding, since the resin composition is melted at a high temperature of 200°C or higher, coated alkaline earth metal compound fine particles have been proposed as an inorganic filler capable of maintaining high dispersibility during molding at a high temperature (see, for example, Patent Document 1). Further, acicular strontium carbonate fine powder excellent in dispersibility in a polymer resin solution has been disclosed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of molding by injection molding or melt extrusion, etc., it is required to avoid a decrease in thermal stability such as residence heat stability due to resin decomposition. In addition, for the molded member, it is required that there are no problems in appearance such as a decrease in mechanical properties or silver streaks. In particular, in the case of an optical member, high transparency is required.

[0006] Therefore, an object of the present invention is to provide coated alkaline earth metal carbonate fine particles which are excellent in dispersibility and thermal stability in a resin and are suitable as an inorganic filler capable of obtaining a molded article excellent in transparency and durability when blended in a resin composition.

Means for Solving the Problems

[0007] As a result of intensive studies to achieve the above object, the present inventors have found coated alkaline earth metal carbonate fine particles which are excellent in dispersibility and thermal stability in a resin and are suitable as an inorganic filler capable of obtaining a molded article excellent in transparency and durability when blended in a resin composition, and have thus completed the present invention.

[0008] That is, the present invention is coated alkaline earth metal carbonate particles having an organic polymer layer on the surface of alkaline earth metal carbonate fine particles, and the organic polymer layer contains a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin.

Effects of the Invention

[0009] According to the present invention, it is possible to provide coated alkaline earth metal carbonate fine particles which are excellent in dispersibility and thermal stability in a resin and are suitable as an inorganic filler capable of obtaining a molded article excellent in transparency and durability when blended in a resin composition.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] (Coated alkaline earth metal carbonate fine particles) The coated alkaline earth metal carbonate fine particles of the present invention are alkaline earth metal carbonate fine particles whose surfaces are coated with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin. The alkaline earth metal constituting the coated alkaline earth metal carbonate fine particles is preferably one selected from the group consisting of calcium, barium, and strontium. More specifically, examples of the alkaline earth metal carbonate fine particles include magnesium carbonate fine particles, calcium carbonate fine particles, strontium carbonate fine particles, and barium carbonate fine particles. Hereinafter, among the alkaline earth metal carbonate fine particles, strontium carbonate fine particles, which are a preferred embodiment of the present invention, will be described in detail.

[0012] The crystal form of the coated strontium carbonate is more preferably 95% by mass or more of the aragonite type. The content of the aragonite type strontium carbonate can be confirmed, for example, by XRD analysis. The BET specific surface area of strontium carbonate is preferably more than 30 m 2 / g, and more preferably 60 m 2 / g or more.

[0013] The coated strontium carbonate fine particles in the present invention preferably have a major axis diameter of 200 nm or less. Further, it is more preferably in the range of 30 to 100 nm, and most preferably in the range of 30 to 60 nm. When the major axis diameter is less than 30 nm, the particles are too small and tend to aggregate, and the dispersibility tends to deteriorate. On the other hand, when the major axis diameter exceeds 200 nm, the particles are too large and the transparency tends to deteriorate when mixed with the resin.

[0014] The particles having the major axis diameter and aspect ratio as described above preferably have a coefficient of variation of the major axis diameter of 0.5 or less. The coefficient of variation of the major axis diameter is represented by the ratio of the standard deviation of the major axis diameter to the average value of the major axis diameter, and can be obtained by the following mathematical formula (1).

[0015]

Number

[0016] In the above mathematical formula (1), r is the average value of the major axis diameter, n is the number of particles whose major axis diameter is measured, and r i represents the major axis diameter of the i-th measured particle. The value of n is defined as 100 or more, but the value of n is preferably large, and more preferably 200 or more. When the value of n is less than 100, the dispersion of the particles cannot be accurately reflected. When the coefficient of variation is expressed as a percentage, the value of the above mathematical formula (1) can be multiplied by 100 and expressed. For example, a coefficient of variation of 0.5 or less can be expressed as a coefficient of variation of 50% or less.

[0017] The coefficient of variation of the major axis diameter is preferably small. Specifically, it is preferably 0.5 or less, and more preferably 0.4 or less. When the coefficient of variation of the major axis diameter exceeds 0.5, the proportion of particles longer than the average value of the major axis diameter may increase and the light transmittance may decrease.

[0018] The coefficient of variation can be measured, for example, by the following method. First, well-dispersed carbonate fine particles are observed with a transmission electron microscope, and the taken particle photographs are captured by a scanner and saved as an image file. By measuring each particle using the image analysis type particle size distribution measurement software "Mac-View" Ver. 3 manufactured by Mountech Co., Ltd. and aggregating the results, the coefficient of variation can be obtained.

[0019] Here, the major axis can be measured by visually observing or automatically processing the image of the transmission electron microscope (TEM) photograph of the strontium carbonate fine particles. The major axis can be measured as the length in the longitudinal direction (the length of the long side) when the fine particle is regarded as a rectangle. Also, the minor axis can be measured as the length in the short transverse direction (the length of the short side) when the fine particle is regarded as a rectangle. Specifically, a rectangle with the minimum area that circumscribes the fine particle in the image is calculated, and the major axis and minor axis are obtained from the lengths of its long side and short side.

[0020] The "major axis / minor axis" of the particle is defined as the aspect ratio. The coated strontium carbonate fine particles in the present invention preferably have an aspect ratio of 2.0 or more. More preferably, it is in the range of 2.0 to 4.0, and most preferably, it is in the range of 2.0 to 3.0. When the aspect ratio is less than 2.0, it becomes difficult to exert an effect on the control of birefringence. On the other hand, when the aspect ratio exceeds 4.0, the particles become too elongated and are prone to breakage, which may lead to deterioration of the particle size distribution.

[0021] The content of the organic polymer is preferably 15 to 40 parts by mass with respect to 100 parts by mass of the strontium carbonate fine particles. More preferably, it is 15 to 35 parts by mass, and still more preferably, it is 15 to 25 parts by mass. The ratio of the organic polymer on the surface of the strontium carbonate fine particles can be determined from the weight change when burned at a temperature of 900 °C or higher. The coated alkaline earth metal carbonate fine particles are formed by coating a part or all of the surface of the alkaline earth metal carbonate fine particles with a layer of the organic polymer.

[0022] The organic polymer layer contains a material derived from polyoxyethylene styrenated phenyl ether phosphate and an acrylic resin. The organic polymer layer can be formed by a reaction product of polyoxyethylene styrenated phenyl ether phosphate and a polyacrylate. Alternatively, it may have a structure in which a first layer made of a material derived from polyoxyethylene styrenated phenyl ether phosphate and a second layer made of an acrylic resin are sequentially laminated. In any case, the dispersibility of the alkaline earth metal carbonate fine particles in a hydrophobic organic solvent is improved, and the environmental resistance and transparency of the resin composition described later are improved.

[0023] When the material derived from polyoxyethylene styrenated phenyl ether phosphate is formed by a reaction product of polyoxyethylene styrenated phenyl ether phosphate and a polyacrylate, it refers to the site derived from polyoxyethylene styrenated phenyl ether phosphate of the reaction product. When forming the first layer made of a material derived from polyoxyethylene styrenated phenyl ether phosphate, it refers to the material generated on the surface of the alkaline earth metal carbonate particles as a result of surface treatment with polyoxyethylene styrenated phenyl ether phosphate. Also, the acrylic resin refers to a polymer of an acrylate ester or a methacrylate ester. The material derived from polyoxyethylene styrenated phenyl ether phosphate improves the dispersibility, and the acrylic resin contributes to the environmental resistance.

[0024] In addition to having good dispersibility in the resin as described above, the coated alkaline earth metal carbonate fine particles of the present invention are also excellent in thermal stability. The thermal stability of the coated alkaline earth metal carbonate fine particles can be evaluated by the mass reduction rate when heated in an air atmosphere at room temperature to 300 °C. When performing thermogravimetry (TG) - differential thermal analysis (DTA) (TG - DTA) on the coated alkaline earth metal carbonate fine particles of the present invention in an air atmosphere, the mass reduction rate in the temperature range of room temperature to 300 °C is 10% by mass or less, preferably 8% by mass or less. Furthermore, the coated alkaline earth metal carbonate particles of the present invention have a mass reduction rate of 5% by mass or less in the temperature range from room temperature to 280°C, and a mass reduction rate of 4% by mass or less in the temperature range from room temperature to 260°C.

[0025] In addition, the surface-treated coated alkaline earth metal carbonate fine particles of the present invention exhibit excellent thermal stability not only in an air atmosphere but also in a nitrogen atmosphere. Specifically, when TG-DTA is performed in a nitrogen atmosphere, when the mass of the coated alkaline earth metal carbonate fine particles at the start of TG-DTA is taken as 100% by mass, the mass reduction rate in the temperature range from room temperature to 300°C is 5% by mass or less, preferably 4% by mass or less. Furthermore, the coated alkaline earth metal carbonate particles of the present invention have a mass reduction rate of 4% by mass or less in the temperature range from room temperature to 280°C.

[0026] The coated alkaline earth metal carbonate fine particles of the present invention can be used as fillers for paper materials, inks, paints, etc., as additives for plastics, adhesives, films, etc., or as carriers for foods, pharmaceuticals, etc.

[0027] (Method for producing coated alkaline earth metal carbonate fine particles) The coated alkaline earth metal carbonate fine particles of the present invention can be produced by a method comprising a step of obtaining an aqueous dispersion of alkaline earth metal carbonate fine particles, a step of aging the alkaline earth metal carbonate fine particles, a step of subjecting the aged alkaline earth metal carbonate fine particles to surface treatment and coating the surface with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin, and a step of drying the surface-treated alkaline earth metal carbonate fine particles. Each step will be described in detail below.

[0028] (Step of obtaining an aqueous dispersion of alkaline earth metal carbonate fine particles) As a raw material solution, an aqueous solution or an aqueous suspension of strontium hydroxide is prepared. There is no particular limitation on the concentration of strontium hydroxide in the raw material solution, but it is usually 1 to 20% by mass, preferably 2 to 15% by mass, and more preferably 3 to 8% by mass. While stirring the raw material solution, an organic acid is added and carbon dioxide gas is introduced to carbonize strontium hydroxide.

[0029] By carbonizing strontium hydroxide, spherical strontium carbonate is produced. The organic acid acts as a crystal growth inhibitor that suppresses the crystal growth of strontium carbonate. The organic acid also acts as an aggregation inhibitor that suppresses the aggregation of strontium carbonate fine particles generated by carbonization.

[0030] The organic acid contains at least one hydroxyl group and at least one carboxyl group, and a total of at least three. Preferably, the organic acid contains one or two carboxyl groups, and a total of 3 to 6 hydroxyl groups and carboxyl groups. Preferred organic acids include, for example, tartaric acid, malic acid, or gluconic acid. The addition amount of the organic acid is 0.1 to 20 parts by mass with respect to 100 parts by mass of strontium hydroxide, preferably 1 to 10 parts by mass.

[0031] The flow rate of carbon dioxide gas is 0.5 to 200 mL / min with respect to 1 g of strontium hydroxide, preferably 0.5 to 100 mL / min. The temperature of the raw material solution during carbonization is 0 to 40°C, preferably 0 to 30°C, and more preferably 5 to 15°C. The end point of carbonization is generally the point when the pH of the raw material solution becomes 7 or less.

[0032] (Step of aging alkaline earth metal carbonate fine particles) By holding the obtained aqueous dispersion of strontium carbonate fine particles at a predetermined temperature for a predetermined time for aging, the spherical strontium carbonate fine particles grow in the major axis direction. The temperature of the aging step is 60 °C or higher, preferably 60 to 100 °C, more preferably 70 to 100 °C. The aging time is not particularly limited as long as needle-like particles of a predetermined shape are obtained and can be set as appropriate.

[0033] In the aqueous dispersion of needle-like strontium carbonate fine particles obtained by the aging step, although a part of the primary particles may aggregate to form secondary particles, it is considered that most of the primary particles maintain a dispersed state.

[0034] (Step of subjecting alkaline earth metal carbonate fine particles to surface treatment) A predetermined surface treatment agent is added to the aqueous dispersion of needle-like grown strontium carbonate fine particles, and a strong shearing force is applied to the aqueous dispersion, whereby the strontium carbonate fine particles are subjected to surface treatment. As a result of the surface treatment, a part or all of the surface of the strontium carbonate fine particles is coated with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin.

[0035] For the formation of the organic polymer layer, two types of surface treatment agents, namely polyoxyethylene styrenated phenyl ether phosphate ester as the first surface treatment agent and polyacrylate as the second surface treatment agent, are used. Examples of the polyacrylate include water-soluble ammonium polyacrylate and water-soluble sodium polyacrylate.

[0036] The total amount of the first surface treatment agent and the second surface treatment agent added is 5 to 40 parts by mass, preferably 5 to 35 parts by mass, and more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the acicular strontium carbonate fine particles. The amount of the first surface treatment agent added is preferably 10 to 30 parts by mass, more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the acicular strontium carbonate fine particles. Further, the amount of the second surface treatment agent added is preferably 5 to 30 parts by mass, more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the acicular strontium carbonate fine particles.

[0037] The two types of surface treatment agents can be simultaneously added to the aqueous dispersion of strontium carbonate fine particles for dispersion treatment to perform surface treatment on the strontium carbonate fine particles. In this case, an organic polymer layer containing a reaction product of polyoxyethylene styrenated phenyl ether phosphate as the first surface treatment agent and polyacrylate as the second surface treatment agent is formed. Examples of the reaction product include a compound resinified with polyacrylate via the -OH group of polyoxyethylene styrenated phenyl ether phosphate.

[0038] Alternatively, the first surface treatment agent and the second surface treatment agent can be used separately. After adding the first surface treatment agent for dispersion treatment, the second surface treatment agent can be added for dispersion treatment. In this case, two layers formed by the respective surface treatment agents are formed as an organic polymer layer. That is, an organic polymer layer in which a first layer made of a material derived from polyethylene polyoxyethylene styrenated phenyl ether phosphate and a second layer made of an acrylic resin are sequentially formed is obtained.

[0039] When the dispersion treatment is performed with the first surface treatment agent after the dispersion treatment with the second surface treatment agent, a layer made of a material derived from polyethylene polyoxyethylene styrenated phenyl ether phosphate ester as the first surface treatment agent becomes the surface layer of the organic polymer layer. When the strontium carbonate fine particles having such a coating layer are blended with a polycarbonate resin as an inorganic filler to produce a resin composition, thermal phosphoric acid is generated by partial thermal decomposition during melt-kneading, and the thermal phosphoric acid reduces the molecular weight of the polycarbonate resin. In order to avoid deterioration of the strength of the molded body, it is desirable to perform the dispersion treatment with the second surface treatment agent after the dispersion treatment with the first surface treatment agent.

[0040] When performing the surface treatment, in order to apply a strong shearing force to the aqueous dispersion of acicular strontium carbonate fine particles, a rotating body that rotates at a peripheral speed of 10 to 60 m / sec is used. The peripheral speed of the rotating body is more preferably 20 to 50 m / sec, and even more preferably 30 to 40 m / sec. The apparatus for applying the shearing force is not particularly limited as long as it can apply the necessary shearing force.

[0041] The aggregation of the acicular strontium carbonate fine particles is resolved by the strong shearing force, and the dispersibility is improved. In some cases, there may be acicular strontium carbonate fine particles whose aggregation is not resolved to primary particles. Since the applied shearing force is very strong, it is considered that at least near the primary particles is resolved. While this effect persists, the surface of the primary particles of the acicular strontium carbonate fine particles and the secondary particles resolved near the primary particles is treated.

[0042] Part or all of the surface of the primary particles and the secondary particles resolved near the primary particles is coated with a layer of an organic polymer. The layer of the organic polymer only needs to coat part of the surface of the primary particles or the like, but it is preferably coated on the entire surface. Coating part of the surface means that the layer of the organic polymer only needs to adhere to the surface of the particles. By coating at least part of the surface with a layer of an organic polymer, the dispersed state of the primary particles and the secondary particles resolved near the primary particles of the strontium carbonate fine particles after the surface treatment is maintained.

[0043] (Step of drying the alkaline earth metal carbonate fine particles after surface treatment) The aqueous dispersion of the surface-treated coated strontium carbonate fine particles can be dried by any method to remove water. For drying, for example, a spray dryer, a drum dryer, or the like can be used.

[0044] (Resin composition and optical film) The coated alkaline earth metal carbonate fine particles of the present invention are suitably used as an inorganic filler to be blended in a resin composition used for manufacturing an optical member or the like. Since the coated alkaline earth metal carbonate of the present invention is excellent in thermal stability, a resin composition containing such a coated alkaline earth metal carbonate is also excellent in thermal stability.

[0045] The thermal stability of the resin composition containing the coated alkaline earth metal carbonate of the present invention can be evaluated, for example, by examining the reduction rate of the weight average molecular weight before and after melt extrusion of the resin composition melt-extruded under melt kneading conditions of a melting temperature of 230 to 250 ° C and a screw rotation speed of 150 to 300 rpm. The reduction rate of the weight average molecular weight in the present invention is preferably 15% or less, more preferably 12% or less, and even more preferably 10% or less. Since the reduction rate of the weight average molecular weight is small, it can be handled without significantly changing the melt kneading conditions of the resin.

[0046] Specifically, prepare pellets of the resin composition as a sample and dry them at 100 to 120 ° C for about 6 to 12 hours. Then, after dissolving the pellets in chloroform heated to 40 ° C at 0.1 wt%, measure the weight average molecular weight (Mw) using an HLC-8320GPC device manufactured by Tosoh Corporation. The reduction rate of the weight average molecular weight is calculated by the formula (100 × ((Mw(0)) - (Mw(1))) / (Mw(0))) using the weight average molecular weight (Mw(0)) before melt kneading and the weight average molecular weight (Mw(1)) after melt kneading.

[0047] The resin composition of the present invention, in accordance with JIS K7210, has a melt volume rate (hereinafter sometimes abbreviated as "MVR") measured at a temperature of 280°C and a load of 1.2 kgf of 40 cm 3 / 10 min or more, preferably 45 cm 3 / 10 min or more, more preferably 50 cm 3 / 10 min or more. The MVR is preferably 80 cm 3 / 10 min or less, more preferably 60 cm 3 / 10 min or less.

[0048] For a resin composition with an MVR of 40 cm 3 / 10 min or more, the occurrence of molding defects such as weld lines and insufficient filling into the mold can be suppressed, and an optical element with further reduced birefringence can be obtained. On the other hand, if the MVR is 80 cm 3 / 10 min or less, the moldability of the resin composition can be improved. However, if it exceeds the upper limit, the fluidity becomes too high and stringing occurs during molding, which is not preferable. The MVR of the resin composition can be adjusted by the addition amount of the inorganic filler, the composition of the surface treatment agent, the resin additive amount, etc.

[0049] By forming a film of the resin composition containing the coated alkaline earth metal carbonate of the present invention, an optical film having desired characteristics can be produced. Hereinafter, the optical film will be described.

[0050] The resin is not particularly limited as long as it is a resin used in a normal optical film, and various resins can be selected according to the purpose. However, the resin is a different organic polymer (second organic polymer) from the organic polymer (first organic polymer) in the coated alkaline earth metal carbonate. Examples of such resins include polycarbonate resins, cycloolefin resins (including cyclic olefin copolymers), polymethyl methacrylate resins, and polyester resins.

[0051] Furthermore, one or more selected from the group consisting of cellulose esters such as triacetyl cellulose, polystyrene, styrene acrylonitrile copolymer, poly(diethyl fumarate), polyarylate, polyethersulfone, polyolefins such as polycyclic olefin, maleimide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, and polyurethane can also be used. However, when a polycarbonate resin is used as the resin, the effect of the coated alkaline earth metal carbonate fine particles as an inorganic filler of the present invention is sufficiently exhibited.

[0052] The content of the alkaline earth metal carbonate is preferably in the range of 1 to 10% by mass based on the total resin composition. When the content of the alkaline earth metal carbonate is less than 1% by mass, the birefringence control effect by the alkaline earth metal carbonate becomes too small. On the contrary, when the content of the alkaline earth metal carbonate exceeds 10% by mass, the ratio of the alkaline earth metal carbonate to the resin becomes relatively too large, so that the transparency of the formed film deteriorates and the mechanical strength also deteriorates. The content of the alkaline earth metal carbonate based on the total resin composition is more preferably in the range of 1 to 5% by mass.

[0053] By mixing the resin and the inorganic filler as described above, a resin composition can be obtained. As a method for dispersing the inorganic filler in the resin, a method of dissolving the resin in a dispersion containing the inorganic filler (solution casting method), a method of uniformly dissolving a polymer in a dispersion containing the inorganic filler, then removing the solvent, and pelletizing or powdering, a method of melt-kneading a dry mixture of the inorganic filler and the polymer with an extruder or the like (melt-kneading method), etc. can be mentioned. Also, a masterbatch may be prepared in advance and kneaded with a kneader. The masterbatch can be prepared by the above solution casting method, melt-kneading method, etc.

[0054] Alternatively, a dope solution may be prepared by mixing a resin composition with a suitable solvent, and an optical film may be formed therefrom. The solvent is not particularly limited and can be appropriately selected and used according to the properties of the resin and the like. As an example of the solvent, an organic solvent is preferable. For example, alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol), methylene chloride, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), methyl ethyl ketone (MEK), ethyl acetate, cyclohexane, toluene, etc. can be mentioned. Among the above-mentioned organic solvents, methylene chloride is particularly preferable.

[0055] The ratio of the resin to the solvent is preferably in the range of 100:10 to 100:30 in terms of mass ratio (solvent: resin). The dope solution can be prepared by mixing the resin and the solvent to form a resin mixed solution, and adding an inorganic filler thereto. Alternatively, an inorganic filler may be dispersed in the solvent to form an inorganic filler dispersion, and the resin may be added thereto and mixed. Further, the above-mentioned resin mixed solution and inorganic filler dispersion may be prepared respectively, and both may be mixed to form a dope solution. Known methods can be adopted for mixing the inorganic filler, the resin, and the solvent. For example, methods using an ultrasonic homogenizer, a stirring blade, a liquid jet mill, etc. can be mentioned.

[0056] On the other hand, examples of the apparatus used for dry mixing include a Henschel mixer, a V-type mixer, a tumbler mixer, etc. The mixing time is not particularly limited as long as a predetermined dispersion is obtained. Thereafter, foreign matters may be removed by sieving with a sieve.

[0057] The resin composition and the dope solution can be formed into an optical film by a known method. Examples of the film-forming method include known film-forming methods such as a melt extrusion film-forming method and a solution casting film-forming method. The melt extrusion film-forming method is a method of heating and melting a resin composition to form a melt, and casting this in a film shape on a support and then cooling and solidifying it. The solution casting film-forming method is a method of casting a dope solution on a support and evaporating the solvent to form a film.

[0058] Depending on the type of resin, convection may occur in the resin solution during film formation, and a Benard cell structure may be formed. When the Benard cell structure is formed, the inorganic filler aggregates, deteriorating the transparency of the optical film. Also, this aggregation reduces the birefringence adjustment effect of the inorganic filler. Therefore, it is preferable to add a surface modifier to the resin composition or dope solution for the purpose of improving the wettability with the support and suppressing the formation of Benard cells. When using polycarbonate as the resin, since Benard cells are likely to be formed, the effect of improving transparency by adding a surface modifier is significant. Examples of the surface modifier include vinyl-based surfactants, fluorine-based surfactants, and silicone oils.

[0059] The film after film formation can be appropriately stretched according to the intended use and the like. Examples of the stretching method include uniaxial stretching and biaxial stretching. Biaxial stretching can be sequential or simultaneous stretching. Stretching can be performed using a known stretching device such as a tenter.

[0060] The optical film thus obtained contains an inorganic filler with excellent thermal stability, and therefore has excellent optical properties. Since the alkaline earth metal carbonate fine particles in the coated alkaline earth metal carbonate fine particles as the inorganic filler exhibit negative birefringence by themselves, the birefringence of the optical film can be adjusted according to the intended use and the like of the target optical film.

[0061] For example, by adding the coated alkaline earth metal carbonate of the present invention as an inorganic filler to a resin exhibiting positive intrinsic birefringence such as polycarbonate or polycyclic olefin, the intrinsic birefringence of the resin can be offset to obtain an optical film with birefringence close to zero. Examples of such an optical film include a protective film. The protective film includes not only a normal protective film laminated on the surface of a polarizing plate or the like, but also a polarizer protective film laminated directly on the surface of a polarizer to protect the polarizer.

[0062] Alternatively, by adding a small amount of the coated alkaline earth metal carbonate of the present invention to a resin that exhibits positive birefringence, such as polycarbonate or polycyclic olefin, it may be used as an optical film having positive birefringence. Furthermore, by adding a large amount of the coated alkaline earth metal carbonate agent of the present invention to these resins that exhibit positive birefringence, it may be used as an optical film having negative birefringence. The "birefringence" mentioned here means the value of the in-plane birefringence rate (ΔNxy) described above. Examples of such optical films that exhibit positive or negative in-plane birefringence rates include retardation films. Examples of retardation films include quarter-wave plates, half-wave plates, and the like.

[0063] Conversely, by using it in a resin that exhibits negative birefringence, such as polymethyl methacrylate or polystyrene, or a resin with low birefringence, it is also possible to obtain an optical film that exhibits negative birefringence. Examples of such optical films include retardation films. Examples of retardation films include quarter-wave plates, half-wave plates, and the like.

[0064] Examples of optical films include, in addition to retardation films and protective films, antireflection films, antiglare films, brightness enhancement films, prism films, viewing angle improvement films, and the like.

[0065] The haze of the optical film can be 10% or less, preferably 5% or less, and more preferably 1% or less. It should be noted that depending on the application of the optical film, it is also possible to intentionally deteriorate the haze. For example, by adding light-scattering fine particles such as glass beads to the resin composition, the haze can be deteriorated to obtain an antiglare film. Also, the total light transmittance of the optical film can be 85% or more, preferably 88% or more, and more preferably 90% or more. In this way, an optical film with excellent optical properties can be obtained.

[0066] The optical film as described above can also be laminated with other optical films to form an optical laminate. Examples of other optical films include a polarizing film (also referred to as a polarizer), a base film, and the like. Examples of the optical laminate include a polarizing plate in which the protective film as the optical film of the present invention and the polarizing film are laminated, an elliptical polarizing plate in which the retardation film as the optical film of the present invention and the polarizing film are laminated, and a retardation plate in which the retardation film as the optical film of the present invention and the base film are laminated.

[0067] (Image display device) The optical film of the present invention can be used in an image display device. Examples of the type of the image display device include a liquid crystal display device (LCD), an organic electroluminescence display device, and the like. Examples of the use of the image display device include a television, a computer monitor, a mobile phone, a smartphone, a portable information terminal (PDA), and other portable information terminals.

[0068] (Injection molded product) The injection molded product manufactured by injection molding the resin composition of the present invention can be effectively used as an optical member such as an optical resin lens, a camera module for a smartphone, a cover sheet for an in-vehicle display, and the like. The haze of the optical lens can be 10% or less, preferably 5% or less. Further, the light transmittance of the optical lens can be 80% or more, preferably 85% or more, and more preferably 90% or more.

[0069] Here, a part of the embodiments of the present invention is organized. <1> Coated alkaline earth metal carbonate particles having an organic polymer layer on a part or all of the surface of the alkaline earth metal carbonate fine particles, The organic polymer layer contains a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin, The mass reduction rate when heated in an air atmosphere at room temperature to 300 ° C is 10% by mass or less, Coated alkaline earth metal carbonate fine particles with a mass reduction rate of 5% by mass or less when heated in a nitrogen atmosphere at room temperature to 300 °C. <2> The coated alkaline earth metal carbonate fine particles according to <1> above, wherein the content of the organic polymer is 15 to 40 parts by mass with respect to 100 parts by mass of the alkaline earth metal carbonate fine particles. <3> The coated alkaline earth metal carbonate fine particles according to <1> or <2> above, wherein the alkaline earth metal is at least one selected from the group consisting of calcium, barium, and strontium. <4> A resin composition comprising a resin and the coated alkaline earth metal carbonate fine particles according to any one of <1> to <3> above. <5> The resin composition according to <4> above, wherein the resin is an organic polymer different from the organic polymer. <6> The resin composition according to <4> or <5> above, wherein the content of the coated alkaline earth metal carbonate fine particles is 1 to 10% by mass of the entire resin composition. <7> The resin composition according to any one of <4> to <6> above, wherein the resin is at least one selected from the group consisting of a polycarbonate resin and a cycloolefin resin. <8> The resin composition according to any one of <4> to <7> above, wherein the rate of decrease in the weight average molecular weight when treated under melt kneading conditions of a melt temperature of 230 to 250 °C and a screw rotation speed of 150 to 300 rpm is 15% or less. <9> An optical film comprising the resin composition according to any one of <4> to <8> above. <10> An image forming apparatus comprising the optical film according to <9> above. <11> A step of obtaining an aqueous dispersion of alkaline earth metal carbonate fine particles, A step of aging the alkaline earth metal carbonate fine particles, A step of subjecting the aged alkaline earth metal carbonate fine particles to a surface treatment and coating the surface with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin, and A method for producing coated alkaline earth metal carbonate fine particles, comprising a step of drying the alkaline earth metal carbonate fine particles after the surface treatment. <12> Coated alkaline earth metal carbonate particles produced by the method of <11>. <13> A resin composition containing a resin and an inorganic filler, having a melt temperature of 230 to 250 °C and a weight average molecular weight reduction rate of 15% or less when treated under melt kneading conditions of a screw rotation speed of 150 to 300 rpm, The inorganic filler is a coated alkaline earth metal carbonate particle having an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin on the surface of the alkaline earth metal carbonate fine particles. <14> A resin composition containing an inorganic filler, In accordance with JIS K7210, the melt volume rate measured under the conditions of a temperature of 280 °C and a load of 1.2 kgf is 40 cm 3 / 10 min or more.

Examples

[0070] Hereinafter, the present invention will be specifically described based on examples, but these do not limit the present invention.

[0071] <Production of Strontium Carbonate Fine Particles> (a) Reaction step 3 L of pure water at a water temperature of 10 °C was added with 7.08 g of DL-tartaric acid as a crystal growth inhibitor and stirred to prepare a solution. To the obtained aqueous solution, 366 g of strontium hydroxide octahydrate was added and mixed to prepare an aqueous suspension of 5.0 mass% strontium hydroxide. While maintaining the obtained aqueous suspension at 10 °C and continuing stirring, 8.5 parts by mass (14.2 g) of tartaric acid was added as an organic acid with respect to 100 parts by mass of strontium hydroxide. Thereafter, carbon dioxide was introduced at a flow rate of 0.5 L / min (3.0 mL / min with respect to 1 g of strontium hydroxide), and strontium hydroxide was carbonated while checking the pH. After the pH reached 7, stirring was continued for another 30 minutes to obtain an aqueous dispersion of strontium carbonate fine particles.

[0072] (b) Aging process The aqueous dispersion of strontium carbonate fine particles obtained in the above (a) was treated at 85 °C for 12 hours while stirring to grow the strontium carbonate fine particles into needles. For stirring the aqueous dispersion, a stirring blade rotating at a peripheral speed of 2.5 m / sec was used. Thereafter, it was allowed to cool to room temperature to produce an aqueous slurry of strontium carbonate fine particles.

[0073] The obtained strontium carbonate fine particles were observed at an acceleration voltage of 120 kV using a JEM-2100F field emission transmission electron microscope (hereinafter referred to as TEM) manufactured by JEOL Ltd. The results are shown in FIG. 1. The morphology of the particles analyzed from the photograph in FIG. 1 was needle-shaped particles with a major axis of 68.0 nm, a minor axis of 29.8 nm, an aspect ratio of 2.28, and a coefficient of variation of 0.15. The crystal structure of the obtained particles was determined by the XRD analysis method. It can be seen from the X-ray diffraction pattern in FIG. 2 that the prepared strontium carbonate is a single-phase aragonite.

[0074] (c) Surface treatment process To an aqueous slurry of strontium carbonate fine particles obtained in the above (b) (solid concentration: 6% by mass), polyoxyethylene styrenated phenyl ether phosphate ester (5 parts by mass with respect to 100 parts by mass of strontium carbonate) and water-soluble ammonium polyacrylate (15 parts by mass with respect to 100 parts by mass of strontium carbonate) were added as surface treatment agents and dissolved. After stirring with a stirrer for 5 minutes, dispersion treatment was performed by applying a shearing force using a Clearmix (manufactured by M. Technique Co., Ltd.). The polyoxyethylene styrenated phenyl ether phosphate ester used here is Pliserf AL manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and the water-soluble ammonium polyacrylate is Sharol AH103P manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0075] (d) Drying step (spray dryer) The aqueous slurry of highly dispersible acicular strontium carbonate fine particles obtained in the above (c) was dried using a spray dryer set at an inlet temperature of 200°C and an outlet temperature of 100°C to obtain the coated strontium carbonate fine particles of Example (I-1). The coated strontium carbonate fine particles of Example (I-1) are strontium carbonate fine particles whose part or all of the surface is coated with a mixed resin of a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin.

[0076] Also, except for changing the addition amount of polyoxyethylene styrenated phenyl ether phosphate ester with respect to 100 parts by mass of strontium carbonate fine particles as follows, the coated strontium carbonate fine particles of Examples (I-2) to (I-5) were produced by the same method as in Example (I-1).

[0077] Example (I-2): Changed to 10 parts by mass Example (I-3): Changed to 15 parts by mass Example (I-4): Changed to 19 parts by mass Example (I-5): Changed to 23 parts by mass

[0078] Furthermore, coated strontium carbonate fine particles of Comparative Examples (I-1) to (I-5) were produced in the same manner as in Example (I-1), except that the surface treatment agent was changed as follows.

[0079] Comparative Example (I-1): Changed to only polyoxyethylene styrenated phenyl ether phosphate (30 parts by mass with respect to 100 parts by mass of strontium carbonate fine particles) Comparative Example (I-2): Changed to only polyoxyethylene tridecyl ether phosphate (30 parts by mass with respect to 100 parts by mass of strontium carbonate fine particles) Comparative Example (I-3): Changed to only poly-N-vinylacetamide (30 parts by mass with respect to 100 parts by mass of strontium carbonate fine particles) Comparative Example (I-4): Changed to only polyvinylpyrrolidone (25 parts by mass with respect to 100 parts by mass of strontium carbonate fine particles) Comparative Example (I-5): Changed to only ammonium polyacrylate (25 parts by mass with respect to 100 parts by mass of strontium carbonate)

[0080] Regarding the coated strontium carbonate fine particles of the examples and comparative examples, the thermal changes in the air atmosphere and nitrogen atmosphere were determined by TG-DTA analysis method. Specifically, thermogravimetric measurement and differential thermal analysis were performed using Smart loader Thermo plus Evo2 TG8121 manufactured by Rigaku Corporation, and the mass reduction rate (%) when heated at 100 to 300 °C was determined. The results are shown in Tables 1 and 2 below together with the composition of the surface treatment agent.

[0081]

Table 1

[0082] The coated strontium carbonate fine particles of the examples are strontium carbonate fine particles coated with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate and an acrylic resin on part or all of the surface. The coated strontium carbonate fine particles of the examples had a mass reduction rate of less than 10% from room temperature to 300 °C and less than 5% from room temperature to 280 °C in an air atmosphere. Also, the mass reduction rate from room temperature to 300 °C was less than 5%, and the mass reduction rate from room temperature to 280 °C was less than 4% in a nitrogen atmosphere. Thus, since it has a layer of a predetermined organic polymer on the surface, it was confirmed that the coated strontium carbonate fine particles have excellent thermal stability.

[0083]

Table 2

[0084] The organic polymer layer in the coated strontium carbonate fine particles of the comparative examples does not contain at least one of a material derived from polyoxyethylene styrenated phenyl ether phosphate and an acrylic resin. The coated strontium carbonate fine particles of Comparative Example (I-1) that do not contain an acrylic resin had a mass reduction rate of more than 10% from room temperature to 300 °C in an air atmosphere and also more than 5% from room temperature to 300 °C in a nitrogen atmosphere.

[0085] The coated strontium carbonate fine particles of Comparative Example (I-5) that do not have a material derived from polyoxyethylene styrenated phenyl ether phosphate had a mass reduction rate of more than 5% from room temperature to 300 °C in a nitrogen atmosphere. The coated alkaline earth metal carbonate particles of Comparative Examples (I-2) and (I-3) that do not have any of the materials had a mass reduction rate of more than 10% from room temperature to 300 °C in an air atmosphere. In particular, the coated alkaline earth metal carbonate particles of Comparative Example (I-2) had a large mass reduction rate of 20% from room temperature to 300 °C in a nitrogen atmosphere.

[0086] In addition, although the coated alkaline earth metal carbonate particles of Comparative Example (I-4) had a small mass reduction rate when heated at room temperature to 300 °C in an air atmosphere or a nitrogen atmosphere, as described below, the reduction rate of the weight average molecular weight of the resin composition was large.

[0087] <Example II: Production of a Resin Composition Containing Coated Strontium Carbonate Fine Particles> Using the coated strontium carbonate fine particles of Examples (I-1) to (I-5) and Comparative Examples (I-1) to (I-5) as inorganic fillers respectively, resin compositions are prepared. Each resin composition is formed into a film to produce the optical films of Examples (II-1) to (II-5) and Comparative Examples (II-1) to (II-5), and their physical properties are examined. Furthermore, a resin composition without an inorganic filler is prepared and used as Comparative Example (II-6).

[0088] In the production, first, 100 parts by mass of polycarbonate resin pellets (L-1225Y manufactured by Teijin Limited), 0.2 parts by mass of a phosphite-based antioxidant (trimethyl phosphate, TMP), and a predetermined amount of an inorganic filler are uniformly mixed using a Henschel mixer. Next, using a twin-screw extruder (KZW15TW-30MG manufactured by Techno Bel, L / D = 30, number of barrels 2), the mixture is supplied from the barrel to the extruder at a barrel temperature of 250 °C, a screw rotation speed of 120 rpm, and a discharge rate of 1 kg / hr, and melted and kneaded to produce pellets of the resin composition.

[0089] Using the pellets of the resin composition obtained by the above method, a vacuum-heated press film is produced using a vacuum-heated press machine (SA-303 type manufactured by Tester Sangyo Co., Ltd.). In the vacuum-heated press, it is held for 15 min under the conditions of 250 °C and a degree of vacuum of -0.1 MPa or less, and then pressurized at 20 MPa for 4 min.

[0090] Regarding the pellets of the resin composition, the weight-average molecular weight before and after melt-kneading was measured, and the decrease in the weight-average molecular weight due to melt-kneading was examined. Specifically, after drying the pellets of each resin composition at 120 °C for 6 hours or more, the weight-average molecular weight (Mw) was evaluated using a HLC-8320GPC device manufactured by Tosoh Corporation, columns (Shodex K-G + K-805L × 2 pieces + K-800D), and CHCl3 as the eluent. Using the weight-average molecular weight before melt-kneading (Mw(0)) and the weight-average molecular weight after melt-kneading (Mw(1)), the reduction rate was calculated by the formula (100×((Mw(0))-(Mw(1))) / (Mw(0))). The reduction rate of the weight-average molecular weight is preferably 12% or less, more preferably 10% or less, and even more preferably 9% or less.

[0091] Regarding the vacuum-heated press film of the resin composition, the total light transmittance (T.T) and haze (HAZE) were determined using a Haze meter NDH4000 manufactured by Nippon Denshoku Industries Co., Ltd., and the optical properties were evaluated. The total light transmittance (T.T) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The haze (HAZE) is preferably 10% or less, more preferably 5% or less, and even more preferably 2% or less.

[0092] In addition, for each vacuum-heated press film, a high-temperature and high-humidity test was conducted to examine the durability. Specifically, using an SH241 manufactured by Espec Corporation, the test was carried out at 80 °C, 95% RH, and 504 hours, and the presence or absence of whitening was confirmed visually and with a Haze meter, and evaluated according to the following criteria. 〇: Transparent (※HAZE < 10%) ×: Whitened and opaque (※HAZE ≧ 10%)

[0093] Regarding the pellets of each resin composition, a melt volume rate (MVR) was evaluated at a temperature of 260 °C and a load of 1.2 kgf in accordance with JIS K7210 using a melt flow index tester 120-FWP-W type manufactured by Yasuda Seiki Seisakusho Co., Ltd.

[0094] The evaluation results for the pellets of the resin composition and the vacuum pressure press film, together with the types and amounts of inorganic fillers used in each resin composition, are summarized in Tables 3 and 4 below.

[0095]

Table 3

[0096] The resin compositions of Examples (II-1) to (II-5) contain coated strontium carbonate fine particles of the example composed of strontium carbonate fine particles having an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin on part or all of the surface as an inorganic filler. Therefore, the decrease in the weight average molecular weight of the resin composition by melt kneading is limited to a maximum of 11.6%. Also, the total light transmittance and HAZE are good, excellent in transparency, and there is no problem with durability. Moreover, the MVR is 55 to 76 cm 3 / 10 min. Thus, a polycarbonate resin composition with all excellent properties could be obtained.

[0097] Also, for the resin composition of Example (II-1), the in-plane retardation (Re) was evaluated using KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd. The Re of the film uniaxially stretched under the conditions of Tg + 25°C, 1.5 times, and 2.5 mm / min was 60 nm compared to 90 nm for the blank of the reference example, confirming the effect of reducing the retardation.

[0098]

Table 4

[0099] The coated strontium carbonate fine particles (Comparative Examples (I-1) to (I-5)) contained as inorganic fillers in the resin compositions of Comparative Examples (II-1) to (II-5) do not have at least one of a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin on the surface.

[0100] The resin composition of Comparative Example (II-1) has a decrease in weight average molecular weight exceeding 32% after melt-kneading, and the MVR also reaches 305 cm 3 / 10 min. The resin compositions of Comparative Examples (II-2) to (II-4) cannot be applied to optical films. Moreover, the resin composition of Comparative Example (II-2) has a decrease rate of weight average molecular weight exceeding 32% after melt-kneading. The resin composition of Comparative Example (II-5) containing the coated strontium carbonate fine particles of Comparative Example (I-5) has an MVR of 10 cm 3 / 10 min or less, so the occurrence of molding defects cannot be avoided.

[0101] Regarding the vacuum-heated press films of the resin compositions of Example (II-1) and Comparative Example (II-5), the dispersion state of the inorganic filler was observed. Specifically, after each sample was embedded with a photocurable acrylic resin, trimming and surface exposure were performed. Further, ultra-thin sections were prepared with ULTRACUTS manufactured by LEICA, and the cross-sections were observed. Fig. 3 shows a TEM photograph of Example (II-1), and Fig. 4 shows a TEM photograph of Comparative Example (II-5).

[0102] As shown in the TEM photograph of Fig. 3, in the film made of the resin composition of Example (II-1), although there are also aggregated particles of 100 nm size, many particles crushed to primary particles of less than 100 nm size are confirmed. The presence of a large number of primary particles achieves high transparency.

[0103] On the other hand, as shown in the TEM photograph of Fig. 4, the particles dispersed in the film made of the resin composition of Comparative Example (II-5) are almost all aggregated particles of more than about 100 nm size. The strontium carbonate fine particles of Comparative Example (I-5) have only an acrylic resin on the surface and are likely to solidify when spray-dried. High crushing energy is required to disperse the particles during melt-kneading, and the filler dispersion in the resin composition is likely to vary. As a result, the transparency is likely to deteriorate.

[0104] Furthermore, although the resin composition of Comparative Example (II-5) has relatively high retention thermal stability, as shown in Table 4, its MVR is quite low at 10 cm 3 / 10 min. In order to improve the moldability during injection molding, the molding temperature needs to be increased, but the matrix polycarbonate will be adversely affected by high heat such as deterioration. In this case, a molded article with excellent durability cannot be obtained.

Claims

1. Coated alkaline earth metal carbonate particles having an organic polymer layer on the surface of alkaline earth metal carbonate fine particles, wherein the organic polymer layer contains a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin, and the coated alkaline earth metal carbonate fine particles.

2. The coated alkaline earth metal carbonate fine particles according to claim 1, wherein the organic polymer is a reaction product of polyoxyethylene styrenated phenyl ether phosphate ester and polyacrylate.

3. The coated alkaline earth metal carbonate fine particles according to claim 1, wherein the organic polymer layer includes a first layer and a second layer laminated in sequence, the first layer is made of a material derived from polyoxyethylene styrenated phenyl ether phosphate ester, and the second layer is made of an acrylic resin.

4. The coated alkaline earth metal carbonate fine particles according to claim 1, wherein the content of the organic polymer is 15 to 40 parts by mass with respect to 100 parts by mass of the alkaline earth metal carbonate fine particles.

5. The coated alkaline earth metal carbonate fine particles according to claim 1, wherein the alkaline earth metal is at least one selected from the group consisting of calcium, barium, and strontium.

6. The weight loss rate when heated from room temperature to 300 °C in an air atmosphere is 10% by weight or less, The coated alkaline earth metal carbonate fine particles according to claim 1, wherein the weight loss rate when heated from room temperature to 280 °C in an air atmosphere is 5% by weight or less.

7. A process for obtaining an aqueous dispersion of alkaline earth metal carbonate fine particles, A process for aging the alkaline earth metal carbonate fine particles, A process for surface-treating the aged alkaline earth metal carbonate fine particles to coat the surface with an organic polymer layer containing a material derived from polyoxyethylene styrenated phenyl ether phosphate ester and an acrylic resin, and A method for producing coated alkaline earth metal carbonate fine particles, comprising a step of drying the surface-treated alkaline earth metal carbonate fine particles.

8. The method for producing coated alkaline earth metal carbonate particles according to claim 7, wherein the surface treatment is performed using a surface treatment agent containing polyoxyethylene styrenated phenyl ether phosphate ester and polyacrylate.

9. The surface treatment is A first surface treatment for forming a first layer using polyoxyethylene styrenated phenyl ether phosphate ester, A second surface treatment for forming a second layer using polyacrylate on top of the first layer and The method for producing coated alkaline earth metal carbonate particles according to claim 7, comprising.

10. Coated alkaline earth metal carbonate particles produced by the method according to any one of claims 7 to 9.

11. A resin composition comprising a resin and the coated alkaline earth metal carbonate fine particles according to any one of claims 1 to 6.

12. The resin composition according to claim 11, wherein the resin is an organic polymer different from the organic polymer.

13. The resin composition according to claim 11, wherein the content of the coated alkaline earth metal carbonate fine particles is 1 to 10% by mass of the entire resin composition.

14. The resin composition according to claim 11, wherein the resin is at least one selected from the group consisting of a polycarbonate resin and a cycloolefin resin.

15. The resin composition according to claim 11, wherein the rate of decrease in the weight average molecular weight when kneaded and melted under the conditions of a temperature of 230 to 300 ° C and a screw rotation speed of 150 to 300 rpm is 15% or less.

16. Based on JIS K7210, the melt volume rate measured under the conditions of a temperature of 280 °C and a load of 1.2 kgf is 40 cm ３ / 10 min or more, and the resin composition according to claim 11.

17. An optical film comprising the resin composition according to claim 11.

18. An image forming apparatus including the optical film according to claim 17.

19. An optical element comprising a molded body of the resin composition according to claim 11.

Images