TW201625726A - Highly dispersible fine powder of alkaline earth metal compound, optical film, image display device and manufacturing method, method for evaluating dispersibility of fine powder, and device for evaluating dispersibility of fine powder - Google Patents

Abstract

A highly dispersible fine powder of an alkaline earth metal compound, which comprises the alkaline earth metal compound as a main component and in which a surfactant is attached to the surface of alkaline earth metal microparticles, said fine powder having a scattering peak in scattering intensity within a scattering angle (2[Theta]) range of 0.2-1.0 DEG , when measured by the small angle X-ray scattering method with X-ray irradiation of a wavelength of 0.154 nm. A method for evaluating the dispersibility of a fine powder, whereby the dispersibility of a fine powder of an alkaline earth metal compound in the state of being dispersed in a solvent is evaluated in the powdery state, said method comprising: an X-ray irradiation step for irradiating the fine powder of the alkaline earth metal compound with X-ray by the small angle X-ray scattering method to obtain a scattering intensity spectrum within a definite scattering angle range; a scattering intensity analysis step for analyzing, from the spectrum, whether or not a scattering peak in scattering intensity exists in a scattering angle (2[Theta]) range of 0.2-1.0 DEG ; and a dispersibility estimation step for estimating the dispersibility of the fine powder of the alkaline earth metal compound in the solvent on the basis of the scattering peak detection result thus obtained.

Description

High-dispersion alkaline earth metal compound fine powder, optical film, image display device, and high-dispersion alkaline earth metal compound fine powder manufacturing method, micro powder dispersibility evaluation method, and fine powder dispersibility evaluation device

The present invention relates to a highly dispersible alkaline earth metal compound micropowder, an optical film, an image display device, a method for producing a fine powder of a highly dispersible alkaline earth metal compound, a micro powder dispersibility evaluation method, and a micro powder dispersibility evaluation device, particularly A method for producing a highly dispersible alkaline earth metal compound fine powder, an optical film, an image display device, and a highly dispersible alkaline earth metal compound micropowder, and a micro powder dispersibility evaluation method and micro method for adhering a surfactant to a surface Powder dispersibility evaluation device.

The metal fine particles are used for various purposes, and are used by dispersing them in a solvent as needed. For example, the acicular strontium carbonate particles have a negative birefringence, and have an action of controlling the birefringence of the resin having positive birefringence as an optical resin filler. Therefore, it is necessary to make the cerium carbonate particles highly dispersed and blended in the resin. However, if the cerium carbonate particles are made fine in order to improve the transparency of the resin, the surface energy may increase and the fine particles may easily aggregate with each other, which may impair the transparency of the resin. The control effect of birefringence is reduced. Therefore, it is necessary to disperse and coat the surface of the cerium carbonate microparticles with a surfactant.

Patent Document 1 describes organic-inorganic composite particles which are dispersed as a primary particle in a solvent and/or a resin and have a plurality of organic groups different from each other on the surface of the inorganic particles. Further, it is described that the cerium carbonate particles have an average particle diameter of 200 μm or less, preferably 3 nm to 10 μm. Further, in the examples, in the state of the dispersion (the solvent is cyclohexane or the like), the dispersibility of the cerium carbonate particles is measured using a dynamic light scattering photometer, and the X-ray diffraction method is used ( XRD) confirmed that the particles were barium carbonate.

Patent Document 2 describes a surface treatment method of carbonate fine particles subjected to surface treatment by the following steps: surface modification step: wet treatment of carbonate fine particles by a surface modifier having a carboxylic acid group; and dispersion Step: Disperse the modified microparticles in the presence of a dispersing agent using a dispersing machine. Regarding the size of the carbonate fine particles, it is described that the average equivalent circle diameter (Heywood diameter) estimated from the projected area of the transmission electron microscope (TEM) image is 80 nm. Further, it is described that the dispersibility of the cerium carbonate microparticles is measured by a dynamic light scattering method using a dispersion liquid (solvent is ethanol).

Patent Document 3 describes a method for producing a cerium carbonate microparticle by mixing an aqueous solution of a cerium hydroxide compound with an alkali hydroxide and introducing a carbonic acid gas into the mixed liquid. Further, the long diameter of the cesium carbonate observed by a scanning electron microscope (SEM) is 15 to 2000 nm, and is 50 to 500 nm in the examples.

Patent Document 4 describes a method of treating the surface of the cerium carbonate microparticles with a surfactant containing a hydrophilic group and a hydrophobic group and further having an anion group in water. In the examples of this document, acicular strontium carbonate powder having an average aspect ratio of 2.70 and an average length of a long diameter of 110 nm as measured by an electron microscope image is described. Further, there is described a case where the acicular strontium carbonate powder is dispersed in methylene chloride to obtain a dispersion. The average particle diameter was 170 nm.

[Patent Document 1] Japanese Laid-Open Patent Publication No. 2011-236111 (Request Item 1, Paragraph 0118, Examples, etc.)

[Patent Document 2] Japanese Laid-Open Patent Publication No. 2008-101051 (Request Item 1, paragraphs 0071, 0098, etc.)

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2007-001796 (Request No. 1, 6, paragraphs 0029, 0030)

[Patent Document 4] International Publication No. 2012/111692 (Request Item 1, paragraphs 0036, 0037)

In order to evaluate the dispersibility of the cerium carbonate microparticles, it is necessary to measure the particle size distribution of the dispersion obtained by adding the dry powder obtained by adding cerium carbonate microparticles to an organic solvent, or to observe by an electron microscope (SEM) photograph. It takes a lot of work. Further, there is no method for determining whether or not the surfactant is completely coated around the primary particles, whether the dispersion treatment can be surely performed, and whether the amount of the surfactant to be added is optimal in the dry powder state.

Further, regarding the conventional cerium carbonate microparticles which have been subjected to surface treatment with a surfactant, there is still room for improvement in dispersibility when dispersed in a solvent, and higher dispersed cerium carbonate microparticles are required.

An object of the present invention is to provide a highly dispersible alkaline earth metal compound fine powder, an optical film, an image display device, and a highly dispersible alkali which have high dispersibility when dispersed in a solvent. A method for producing a fine metal powder of a soil metal compound.

Moreover, an object of the present invention is to provide an alkaline earth metal which can be used to evaluate the dispersibility of an alkaline earth metal compound fine powder in a solvent in a powder state without actually dispersing the alkaline earth metal compound fine powder in a solvent. A method for evaluating the dispersibility of a compound fine powder and an apparatus for evaluating the dispersibility of an alkaline earth metal compound fine powder.

The inventors of the present invention have diligently studied in order to achieve the above object, and as a result, it has been found that the fine powder is dispersed in a solvent based on the measurement of the alkaline earth metal compound fine powder by a small angle X-ray scattering method in a powder state. Dispersion of time. Further, as a result of evaluation by the small-angle X-ray scattering method, it was confirmed that fine powder which is more highly dispersed can be produced, and the present invention has been completed.

That is, the present invention is a highly dispersible alkaline earth metal compound fine powder in which an alkaline earth metal is used as a main component, and a surfactant is attached to an average long diameter of 10 to 100 nm and an average aspect ratio of 1.0 to 5.0. The surface of the alkaline earth metal compound fine particles is characterized in that the scattering intensity has a scattering peak in a range of 0.2 to 1.0° measured by a small angle X-ray scattering method to irradiate X-rays having a wavelength of 0.154 nm.

Further, it is preferable that the scattering angle 2 θ is in the range of 0.4 to 0.7°, and the calculated value of the interparticle distance d obtained by the Bragg formula based on the scattering angle 2 θ is in the range of 12.6 to 22.1 nm.

Further, in the above, the alkaline earth metal compound is preferably an alkaline earth metal carbonate. Further, in this case, the alkaline earth metal carbonate is preferably cesium carbonate.

Further, it is preferable that the surfactant contains a hydrophilic group and a hydrophobic group, and further has water. Forming an anion group.

In such a case, it is preferred that the surfactant is uniformly applied around the primary particles of the alkaline earth metal compound fine particles, and the alkaline earth metal compound fine particles are arranged at equal intervals.

Moreover, the present invention is an optical film characterized in that a highly dispersible alkaline earth metal compound fine powder according to any one of the above is dispersed in a resin.

In this case, the above resin is preferably selected from the group consisting of polycarbonate, polymethyl methacrylate, cellulose ester, polystyrene, styrene acrylonitrile copolymer, polyfumarate diester, polyarylate, poly Ether oxime, polyolefin, maleic amide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimine, polyamine, polyurethane One or more of the group.

Furthermore, the present invention provides an image display device comprising the optical film according to any one of the above.

Further, the present invention is a method for producing a highly dispersible alkaline earth metal compound fine powder, which is a method for producing the above-mentioned highly dispersible alkaline earth metal compound fine powder, characterized by comprising: a dispersion step: presence of a surfactant The first dispersion liquid in which the alkaline earth metal compound fine particles having an average long diameter of 10 to 100 nm are dispersed in an aqueous solvent is subjected to shearing force, whereby the primary particles of the alkaline earth metal compound fine particles are dispersed in the water. In the solvent, the primary particles are brought into contact with the surfactant to obtain a second dispersion; and a drying step: heating the second dispersion at a temperature of 100 to 300 ° C to dry it to obtain a powder.

That is, the present invention is a method for evaluating the dispersibility of a fine powder, which is in a powder state. When the dispersibility of the alkaline earth metal compound fine powder in a solvent is dispersed, the X-ray irradiation step is performed by irradiating X-rays to the alkaline earth metal compound fine powder by a small-angle X-ray scattering method to obtain a specific Spectral of the scattering intensity of the scattering angle of the range; scattering intensity analysis step: whether the scattering angle of the scattering angle 2 θ is in the range of 0.2 to 1.0° according to the above spectral analysis; and the dispersion inference step: based on the detection of the above scattering peak As a result, the dispersibility of the above-mentioned alkaline earth metal compound fine powder in the above solvent was estimated.

Moreover, it is preferable that the dispersibility estimating step is that when the scattering peak is detected, the dispersibility of the alkaline earth metal compound fine powder in the solvent is relatively high.

Further, the scattering angle 2 θ is preferably in the range of 0.4 to 0.7°.

Moreover, the present invention is a micro-powder dispersibility evaluation apparatus which evaluates dispersibility when dispersing an alkaline earth metal compound fine powder in a solvent in a powder state, and has an X-ray irradiation means: using a small angle The X-ray scattering method irradiates the alkaline earth metal compound fine powder with X-rays to obtain a spectrum of the scattering intensity of the scattering angle of a specific range; and the scattering intensity analysis means: whether the scattering angle 2 θ is in the range of 0.2 to 1.0 ° according to the above spectral analysis A scattering peak having a scattering intensity; and a dispersibility estimating means: based on the detection result of the scattering peak, the dispersibility of the alkaline earth metal compound fine powder in the solvent is estimated.

Further, it is preferable that the dispersibility estimating means detects that the scattering peak is present, and it is estimated that the dispersibility of the alkaline earth metal compound fine powder in the solvent is relatively high.

Further, the scattering angle 2 θ is preferably in the range of 0.4 to 0.7°.

According to the present invention, it is possible to provide a highly dispersible alkaline earth metal compound fine powder having high dispersibility when dispersed in a solvent, and a method for producing the same.

Further, according to the present invention, it is possible to provide an alkaline earth metal which can be evaluated in a powder state by dispersing an alkaline earth metal compound fine powder in a solvent in a powder state without actually dispersing the alkaline earth metal compound fine powder in a solvent. A method for evaluating the dispersibility of a compound fine powder and an apparatus for evaluating the dispersibility of an alkaline earth metal compound fine powder.

Fig. 1 is a view showing the spectrum of a highly dispersible cerium carbonate micropowder measured by a small angle X-ray scattering method.

Fig. 2 is a schematic view showing the spectrum of a finely divided barium carbonate micropowder.

Fig. 3 is a flow chart showing the flow of the fine powder dispersibility evaluation method.

Fig. 4 is a schematic configuration diagram of a fine powder dispersibility evaluation device.

1. Highly dispersible alkaline earth metal compound fine powder

The highly dispersible alkaline earth metal compound fine powder of the present invention contains an alkaline earth metal compound as a main component, and an alkaline earth metal having an average long diameter of 10 to 50 nm and an average aspect ratio of 1.0 to 5.0 using a surfactant. Compound microparticles have been surface treated. In other words, it is a highly dispersible alkaline earth metal compound fine powder having a high dispersibility when the surfactant is attached to the surface of the alkaline earth metal compound fine particles and dispersed in a solvent.

(1) Alkaline earth metal compound particles (before surface treatment)

The average long diameter of the alkaline earth metal compound microparticles before the surface treatment by the surfactant is in the range of 10 to 100 nm, preferably in the range of 15 to 40 nm, more preferably 20 to 30 nm. Within the scope. When the average long diameter is less than 10 nm, the particles are too small to be easily aggregated, and the dispersibility is likely to deteriorate. On the other hand, when the average long diameter exceeds 50 nm, the particles are excessively large, and when mixed in a resin, transparency is likely to be deteriorated.

Here, the average long diameter can be measured by visually or automatically performing image processing on a scanning electron microscope (SEM) photograph of the alkaline earth metal compound fine particles. The long diameter of the alkaline earth metal compound fine particles can be measured as the length in the longitudinal direction (the length of the long side) when the alkaline earth metal compound particles such as cerium carbonate particles are regarded as a rectangle. In addition, the short diameter of the alkaline earth metal compound particles can be measured as the length in the short side direction (the length of the short side) when the alkaline earth metal compound particles are regarded as a rectangle. Specifically, a rectangle having the smallest area circumscribing the alkaline earth metal compound particles of the image is calculated, and the long diameter and the short diameter are obtained from the lengths of the long side and the short side. Further, the term "average" means an average value obtained by measuring the number of statistically reliable (N number) alkaline earth metal compounds, and as the number, it is usually 300 or more. It is 500 or more, more preferably 1,000 or more.

The average aspect ratio of the alkaline earth metal compound microparticles is in the range of 1.0 to 5.0, preferably in the range of 2.0 to 4.5, and particularly preferably in the range of 2.5 to 4.0. When the average aspect ratio exceeds 5.0, the fine particles become too long and are easily broken, which tends to cause deterioration of the particle size distribution and the like. Further, when the aspect ratio is too small, there is a case where the control of birefringence cannot be exerted.

Further, the term "aspect ratio" as used herein means "long diameter/short diameter" of particles. Further, the average aspect ratio means an average value of the aspect ratio, and the aspect ratio of one particle is measured to calculate an average value of the plurality of particles.

Examples of the alkaline earth metal compound fine particles include carbonates, sulfates, nitrates, oxides, chlorides, hydroxides, and the like of an alkaline earth metal. Also, as an alkaline earth Examples of the metal include calcium, barium, strontium, radium and the like. Therefore, examples of the alkaline earth metal compound fine particles include calcium carbonate fine particles, strontium carbonate fine particles, and cesium carbonate fine particles. In the above, from the viewpoint of controlling birefringence in the use of the optical resin filler or the like, cerium carbonate microparticles are preferred.

(2) Surfactant

The surfactant used in the present invention has a function of adhering to the surface of the alkaline earth metal compound fine particles to improve the dispersibility in the solvent. The type of the surfactant is not particularly limited, and an anionic surfactant is preferred. Among them, a compound containing a hydrophilic group and a hydrophobic group and having an anion group formed in water is particularly preferable. The hydrophilic group is preferably a polyoxyalkylene group containing an oxyalkylene having 1 to 8 carbon atoms. The hydrophobic group is preferably an alkyl group or an aryl group. The alkyl group and the aryl group may also have a substituent. The alkyl group generally has a carbon number of from 3 to 30, preferably from 10 to 18. The aryl group generally has a carbon number in the range of 6 to 30. The group forming an anion in water is preferably selected from the group consisting of a carboxylic acid group (-COOH), a sulfate group (-OSO ₃ H), a phosphate group (-OPO(OH) ₂ , -OPO(OH)O-). Acid base. The hydrogen atom of the acid group may be substituted with an alkali metal ion such as sodium or potassium or an ammonium ion.

In the above, the dispersibility of the alkaline earth metal compound fine particles in a solvent is preferably a polycarboxylic acid anionic surfactant, a polyphosphoric anionic surfactant, and a nonionic interfacial activity. Any one or more of the agents.

The anionic surfactant of the polycarboxylic acid type may, for example, be a compound represented by the following formula (I).

(herein, R ¹ means a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and E ¹ means an alkylene group having a carbon number in the range of 1 to 8. a means a number in the range of 1 to 20, preferably in the range of 2 to 6. Further, R ^{1 is} preferably an alkyl group having 10 or more carbon atoms, preferably 10 to 18 carbon atoms. ).

Examples of the polyphosphoric acid-based anionic surfactant include a compound (monomer) represented by the following formula (II), a compound (dimer) represented by the following formula (III), or a formula (II). a mixture of formula (III).

(herein, R ² means a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and E ² means an alkylene group having a carbon number of 1 to 8, and b means In the range of 1 to 20, preferably in the range of 2 to 6, further, R ^{2 is} preferably an alkyl group having 10 or more carbon atoms, preferably 10 to 18).

(here, R ³ and R ⁴ may be the same or different, and mean a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and E ³ and E ⁴ may be the same or different, meaning The alkyl group having a carbon number in the range of 1 to 8, wherein c and d respectively mean a number in the range of 1 to 20, preferably 2 to 6; further, R ³ and R ^{4 are} preferred. All are alkyl groups having a carbon number of 10 or more, preferably 10 to 18).

The nonionic surfactant may, for example, be a compound represented by the following formula (IV).

(herein, R ⁵ means a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and E ⁵ and E ⁶ all mean an alkylene group having a carbon number in the range of 1 to 8. , e, f are both in the range of 1 to 20, preferably in the range of 2 to 6; further, R ⁵ is preferably in the range of 10 or more carbon atoms, preferably in the range of 10 to 18. Alkyl).

The surfactant may be used singly or in combination of two or more kinds of the alkaline earth metal compound fine powder. Further, the surfactant may be attached to only one layer of the surface of the alkaline earth metal compound fine powder, or two or more layers may be adhered thereto. When two or more layers are attached, the same surfactant may be used in each layer, or different surfactants may be used in each layer. Further, whether or not the surfactant adheres to the surface of the alkaline earth metal compound fine powder can be confirmed by measuring the infrared absorption spectrum of the particle surface by using a Fourier transform infrared spectrometer (FT-IR).

(3) Scattering peaks of small-angle X-ray scattering measurement

The highly dispersible alkaline earth metal compound fine powder of the present invention is characterized in that a peak search is performed on the scattering angle 2 θ when a small-angle X-ray scattering (SAXS) method is used to measure X-rays having a wavelength of 0.154 nm (Peak) Search), the result has a scattering peak in the range of 0.2~1.0°.

Here, the small-angle X-ray scattering method is a method of measuring a spectrum appearing in a low-angle region of 2 θ=10° or less in X-rays scattered by X-rays to a substance, and evaluating the structure of the substance. Small-angle X-ray scattering is commonly used to evaluate periodicity or alignment at molecular levels around 1 to 100 nm.

The measurement by the SAXS method can be performed using an X-ray structure evaluation device that can evaluate the molecular structure (large structure of 1 to 100 nm) to atomic structure (microstructure of 0.2 to 1 nm) of the substance (small angle X-ray scattering measurement) Device). By performing small-angle X-ray scattering measurement, the following items (1) to (3) can be analyzed and analyzed.

(1) Measurement of shape and size (particle size) "Diffuse scattering": shape, size, particle size, and void of a molecule; (2) Measurement of a crystalline periodic structure "Interference scattering, based on whether or not a scattering intensity has a peak": Layer Periodicity of the shape (slice) structure; (3) Measurement of the uneven structure of the material "interference scattering": phase change, solid solution-metal heterogeneous structure.

Fig. 1 is a view showing the spectrum of the highly dispersible cerium carbonate micropowder measured by the small angle X-ray scattering method, and Fig. 2 is a view showing the spectrum of the bismuth carbonate micropowder having low dispersibility. In either of the figures, the vertical axis represents the scattering intensity, and the horizontal axis represents the scattering angle 2 θ. As shown in FIG. 1 , in the fine powder of the highly dispersible alkaline earth metal compound of the present invention, the scattering angle 2 θ is The scattering intensity in the range of 0.2 to 1.0° has a scattering peak (maximum) (the portion surrounded by the dotted circle in the figure). On the other hand, as shown in Fig. 2, in the fine powder of cerium carbonate having low dispersibility, the scattering intensity does not have a scattering peak in the range of 0.2 to 1.0 in the scattering angle 2 θ.

The scattering peak of the small-angle X-ray scattering measurement method will be described in detail below in "3. Micro-powder dispersibility evaluation method and micro-powder dispersibility evaluation device".

(4) Distance between particles d

Preferably, the highly dispersible alkaline earth metal compound fine powder is in a range of 14 to 20 nm in accordance with the above-described scattering angle 2 θ by the Bragg equation.

Here, the Bragg type means the following formula (1).

2dsin θ=n λ (1)

(here, d means the distance between particles (also called "lattice spacing"), θ means the above-mentioned scattering angle, n means an integer, and λ means the wavelength of X-rays).

When the distance d between particles is less than 14 nm, it is considered that the cohesive force of the particles becomes high. Or the amount of the surfactant added is too small, the particles are too close to each other, and are not easily dispersed when dispersed in a solvent. On the other hand, when the distance d between the particles exceeds 21 nm, the amount of the surfactant added is too large, or the particles are excessively separated from each other, and the dispersibility is deteriorated when dispersed in a solvent.

Heretofore, in the case where the particle size distribution is measured by dynamic light scattering of an organic solvent dispersion, the smaller the particle, the more intense the Brownian motion, causing multiple scattering and it is difficult to measure the accurate particle size. However, in the present invention, since the scattering peak 2 θ has a scattering peak in the range of 0.2 to 1.0 °, the particles are arranged in a state of maintaining a certain fixed period in the state of the fine powder. That is, the primary particles are subjected to a complete coating treatment by a surfactant. Further, when the fine powder in this state is added to the solvent, since the primary particles are completely surface-treated, the particles are easily dispersed in the solvent. By evaluating the presence or absence of the above-mentioned scattering peak measured in the state of the fine powder, the dispersibility when dispersed in a solvent can be predicted. Therefore, the fine powder can be practically dispersed in a solvent and the particle size distribution can be measured in the state of the dispersion, and the dispersibility can be evaluated in the state of drying the fine powder, and the evaluation can be reduced.

The fine powder of the highly dispersible alkaline earth metal compound of the present invention has a scattering peak as described above, and in order to satisfy the above conditions, in addition to the kind or concentration of the surfactant, the production conditions of the highly dispersible alkaline earth metal compound fine powder may also be generated. influences. Hereinafter, a method for producing a highly dispersible alkaline earth metal compound fine powder will be described.

2. Method for producing highly dispersible alkaline earth metal compound fine powder

The method for producing a highly dispersible alkaline earth metal compound fine powder of the present invention is characterized by comprising the steps of: dispersing a step of obtaining an alkaline earth metal compound particle having an average long diameter in the range of 10 to 100 nm dispersed in an aqueous solvent; The dispersion (first dispersion) imparts shear force in the presence of the surfactant, thereby causing the primary particles to contact the surfactant while dispersing the primary particles of the alkaline earth metal compound particles in the aqueous solvent. Thereby, a dispersion liquid (second dispersion liquid) is obtained; and a drying step: the second dispersion liquid is heated at a temperature of 100 to 200 ° C to be dried to obtain a powder. The method for producing the alkaline earth metal compound fine powder before the surface treatment is not particularly limited, and a method in which an alkaline earth metal compound serving as a raw material is reacted to form an aqueous slurry and is matured can be mentioned.

Hereinafter, a step of producing a highly dispersible cerium carbonate micropowder will be described as an example of a highly dispersible alkaline earth metal compound fine powder.

(1) Reaction step

The reaction step is a step of introducing carbon dioxide gas in the presence of a crystal growth inhibitor in the presence of an aqueous solution or an aqueous suspension (hereinafter referred to as an aqueous slurry) which is a raw material to cause cesium hydroxide carbonate Thereby, spherical strontium carbonate fine particles having a low aspect ratio are produced. The concentration of barium hydroxide contained in the aqueous slurry is not particularly limited, and is usually in the range of 1 to 20% by mass, preferably 2 to 18% by mass, more preferably 3 to 15% by mass.

The crystal growth inhibitor is preferably an organic acid having two carboxyl groups and a total of 3 to 6 hydroxyl groups and the carboxyl groups. Preferred examples of the crystal growth inhibitor include tartaric acid, malic acid, and hydroxymalonic acid. As a crystal growth inhibitor, an organic acid having two carboxyl groups and a hydroxyl group and having a total of at least three can be used to adhere to the surface of the particles to be produced, to control grain growth, and to improve the dispersibility while maintaining fineness. In particular, it is more preferably a dicarboxylic acid having one or more hydroxyl groups or an anhydride thereof in the above molecule, and particularly preferably DL-tartaric acid. The amount of use of the crystal growth inhibitor 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 the cerium hydroxide.

The flow rate of the carbon dioxide gas is usually in the range of 0.5 to 200 mL/min, preferably in the range of 0.5 to 100 mL/min, relative to 1 g of barium hydroxide. By the reaction step, for example, fine spherical strontium carbonate fine particles having an average aspect ratio of less than 1.5 and approximately spherical shape can be obtained. Further, a method for producing spherical strontium carbonate fine particles is described in International Publication No. 2011/052680.

(2) ripening steps

The ripening step is a step of aging the aqueous slurry containing the spherical strontium carbonate fine particles obtained in the reaction step at a specific temperature and time, and the crystal grains are grown into needle-like strontium carbonate fine particles. The ripening step can be carried out in warm water. The ripening temperature is in the range of 75 to 115 ° C, preferably in the range of 80 to 110 ° C, and particularly preferably in the range of 85 to 105 ° C. If the ripening temperature is lower than 75 ° C, there is a spherical shape When the crystal growth of the strontium carbonate fine particles is not sufficient and the average aspect ratio is too low, when the temperature exceeds 115 ° C, the crystal growth of the short diameter of the spherical strontium carbonate fine particles is promoted, and the aspect ratio tends to be low. Further, the ripening time is not particularly limited, and is usually in the range of 1 to 100 hours, preferably in the range of 5 to 50 hours, and particularly preferably in the range of 10 to 30 hours.

In addition, the above-mentioned "(1) reaction step" and "(2) aging step" are steps of obtaining acicular strontium carbonate fine particles from cerium hydroxide as a raw material, and it is possible to obtain cerium carbonate microparticles as a commercial product. Commercial products can also be used.

(3) Surface treatment steps

The surface treatment step is a step of imparting shear force to a dispersion obtained by dispersing cerium carbonate microparticles having an average long diameter in the range of 10 to 100 nm in an aqueous solvent while dispersing the primary particles and a surfactant. Contact to obtain highly dispersible cesium carbonate. As the surfactant, those described above can be used.

When the dispersion liquid used in the surface treatment step is subjected to the aging step, the aqueous slurry after the aging step can be used, and when commercially available strontium carbonate fine particles are used, it can be used by dispersing it in an aqueous solution. The surface treatment step can be carried out by applying a shearing force to the dispersion liquid while applying a shearing force. The content of the cerium carbonate particles in the aqueous slurry is preferably in the range of 1 to 30% by mass. Regarding the amount of the surfactant to be added to the aqueous slurry, the total amount of the surfactant added is generally in the range of 1 to 60% by mass, preferably 10 to 50% by mass, more preferably 20 to 40% by mass. Within the range of %. The shearing force can be imparted by using a stirring device such as a stirring wing mixer, a homomixer, a magnetic stirrer, an air stirrer, an ultrasonic homogenizer, a Clair Mix, or a Mixix.

When using two or more surfactants for surface treatment, The amount of the surfactant to be added to the aqueous slurry is usually in the range of 1 to 40 parts by mass, preferably 3 to 30 parts by mass, per 100 parts by mass of the cerium carbonate particles in the aqueous slurry. The surfactant can be administered simultaneously or sequentially.

(4) Drying step

The drying step is a step of heating and drying the aqueous slurry obtained in the above (3) surface treatment step at a temperature in the range of 100 to 300 ° C to obtain a dried product of highly dispersible cerium carbonate micropowder. . When the drying temperature is lower than 100 ° C, drying tends to be insufficient, and when the drying temperature exceeds 200 ° C, breakage of the strontium carbonate fine powder is likely to occur. The drying temperature is preferably in the range of 110 to 180 ° C, more preferably in the range of 120 to 160 ° C. The drying step can be carried out by a known drying method using a spray dryer, a tumble dryer, a tray dryer or the like.

The highly dispersible alkaline earth metal compound fine powder of the present invention is excellent in dispersibility when dispersed in a solvent, and thus can be used in various applications. For example, highly dispersible strontium carbonate micropowders may be used for the purpose of inhibiting birefringence, or conversely for the purpose of birefringence. As such a use, an optical film of a liquid crystal display device can be mentioned. Examples of the optical film include a protective film, an antireflection film, a brightness enhancement film, a ruthenium film, a viewing angle improvement film, and a retardation film. Examples of the resin material of the film include triacetonitrile cellulose, polyethylene terephthalate, polycyclic olefin, polycarbonate, and polymethyl methacrylate. The optical film can be produced by mixing a fine powder of barium carbonate as a filler into a resin material, and forming a film by a known method such as solution casting film forming or melt extrusion. Extend as needed.

The solvent for dispersing the fine powder of the highly dispersible alkaline earth metal compound of the present invention is not particularly limited, and may be appropriately selected depending on the use and the like. The type of the solvent is not particularly limited, and can be appropriately selected depending on the nature of the resin or the like. As an example of a solvent, it is preferred Examples of the organic solvent include an alcohol (for example, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol), dichloromethane, and NMP (N-methyl-2). -pyrrolidone, N-methyl-2-pyrrolidone), tetrahydrofuran, MEK (Methyl Ethyl Ketone, methyl ethyl ketone), ethyl acetate, cyclohexane, toluene, and the like. Among these organic solvents, dichloromethane is particularly preferred. It is not limited to one of the above, and a plurality of combinations can be used.

3. Micro powder dispersibility evaluation method and micro powder dispersibility evaluation device

Hereinafter, the fine powder dispersibility evaluation method and the fine powder dispersibility evaluation apparatus of the present invention will be described with reference to Figs. 3 and 4 . Fig. 3 is a flow chart showing the flow of the method for evaluating the dispersibility of the fine powder of the present invention. As shown in the figure, the method for evaluating the dispersibility of the fine powder of the present invention is to evaluate the dispersibility when the fine powder of the alkaline earth metal compound is dispersed in a solvent in a powder state, and has the following steps: an X-ray irradiation step (S1): The X-ray of the alkaline earth metal compound fine powder is irradiated to the X-ray by a small-angle X-ray scattering method to obtain a spectrum of the scattering intensity of the scattering angle of a specific range; the scattering intensity analysis step (S2): the scattering angle 2 θ is analyzed according to the spectrum at 0.2~ Whether or not there is a scattering peak of scattering intensity in the range of 1.0°; and a dispersibility estimating step (S3): based on the detection result of the scattering peak, the dispersibility of the alkaline earth metal compound fine powder in the solvent is estimated.

Fig. 4 is a block diagram showing an embodiment of the fine powder dispersibility evaluation device of the present invention. As shown in the figure, the fine powder dispersibility evaluation device 1 mainly includes the light source control unit 11, the X-ray irradiation unit 12, the X-ray detecting unit 13, the spectrum generating unit 14, the scattering peak detecting unit 15, and the dispersion estimating unit 16. Components.

The light source control unit 11, the X-ray irradiation unit 12, the X-ray detection unit 13, and the spectrum generation unit 14 are means for performing the X-ray irradiation step (S1) of the present invention, and the scattering peak detection unit 15 performs the scattering intensity analysis step of the present invention. (S2) means, the dispersibility estimation unit 16 is implemented The means of the dispersibility inference step (S3) of the present invention. Hereinafter, each configuration will be described in detail.

The light source control unit 11 is a means for controlling the amount of X-ray irradiation or the like in the X-ray irradiation unit 12. The X-ray irradiation unit 12 is a means for irradiating the sample S with X-rays. The X-ray irradiation unit 12 has an X-ray tube (not shown) for irradiating X-rays. The X-ray tube is a tube that generates Kα rays such as Cu, receives a control signal from the light source control unit 11, and irradiates X-rays having a wavelength of 1 nm or less.

The sample S is placed on a mounting table (not shown), and is placed so as to be irradiated with X-rays from the X-ray irradiation unit 12. A portion of the X-rays that are irradiated to the sample S scatter. The X-ray detecting unit 13 is a means for detecting the intensity (scattering intensity) of X-rays (small-angle X-rays) of small angles in the X-rays scattered from the sample S. The small-angle X-ray detected by the X-ray detecting unit 13 is not particularly limited, and usually 2 θ is 10° or less. The mounting table on which the sample S is placed can change the tilt angle, and by irradiating X-rays while changing the tilt angle of the mounting table, the scattering angle 2 θ can be changed to measure the scattering intensity. The small-angle X-rays detected by the X-ray detecting unit 13 are recorded in the spectrum generating unit 14 as spectra of scattering intensity and 2θ.

The scattering peak detecting unit 15 is configured to analyze whether or not the scattering angle 2 θ has a scattering peak of the scattering intensity in the range of 0.2 to 1.0° based on the distribution of the spectrum generated by the spectrum generating unit 14. The dispersion estimating unit 16 is configured to determine that the dispersibility of the sample S is high when the scattering peak detecting unit 15 detects the scattering peak, and to determine that the dispersibility of the sample S is low when no peak is detected.

The spectrum generating unit 14, the scattering peak detecting unit 15, and the dispersion estimating unit 16 can be formed by using a known hardware such as a central processing unit (CPU) and a memory device (hard disk or memory), and a software stored in the memory device. .

The spectrum generating unit 14 can be realized, for example, by a software that stores a signal of the X-ray intensity transmitted by the X-ray detecting unit 13 as a distribution of the scattering intensity and 2θ in the memory device, and a central computing device that executes the software. . Thereby, the data of the scattering intensity sequentially transmitted by the X-ray detecting unit 13 can be stored in the memory device as spectral data together with the information of the scattering angle 2 θ calculated from the angle of the mounting table, and displayed on the display device (not shown). In the device, etc.

The scattering peak detecting unit 15 can be realized by a software that discriminates whether or not there is a maximum value of the scattering intensity in the range of 0.2 to 1.0° according to the spectrum generated in the spectrum generating unit 14; and the central processing unit: executes The software. As the software, a well-known algorithm for calculating the maximum value by the differential method or the like can be used. Thereby, it is possible to automatically detect whether or not the scattering angle 2 θ has a scattering peak of the scattering intensity in the range of 0.2 to 1.0°.

The dispersibility estimating unit 16 can be realized by a software that reports at least one of high dispersibility when a scattering peak is detected and low dispersibility when no scattering peak is detected; and a central computing device: Execute the software. For example, when a scattering peak is detected, a content with high dispersibility can be displayed on the screen, and when the scattering peak is not detected, a content with low scattering can be displayed on the screen.

Hereinafter, the relationship between the scattering peak of the spectrum and the dispersibility will be described. As shown in Fig. 1 above, in the fine powder of barium carbonate having high dispersibility, the scattering intensity 2 θ has a scattering peak (maximum) in the range of 0.2 to 1.0° (the portion surrounded by the dotted circle in the figure). On the other hand, as shown in Fig. 2, in the fine powder of barium carbonate having low dispersibility, the scattering intensity does not have a scattering peak in the range of 0.2 to 1.0 in the scattering angle 2 θ.

That is, the result of the peak search of the scattering angle 2 θ is detected in the range of 0.2 to 1.0°. To the scattering peak, it means that the microparticles are regularly arranged at a certain fixed distance according to a certain period.

Heretofore, in the case where the particle size distribution is measured by dynamic light scattering of an organic solvent dispersion, the smaller the particle, the more intense the Brownian motion, causing multiple scattering and it is difficult to measure the accurate particle size. However, in the present invention, by discriminating whether or not there is a scattering peak in the range of 0.2 to 1.0° in the scattering angle 2 θ, the particles are arranged in a state of maintaining a certain fixed period in the state of the fine powder. Further, when a fine powder in this state is added to the solvent, the particles are easily dispersed in the solvent. By evaluating the presence or absence of the above-described scattering peak measured in the state of the fine powder, the dispersibility when dispersed in a solvent can be predicted. Therefore, the fine powder can be practically dispersed in a solvent and the particle size distribution can be measured in the state of the dispersion, and the dispersibility can be evaluated in the state of drying the fine powder, which can reduce the evaluation time.

Further, the higher the height of the scattering peak, the higher the dispersibility is evaluated. Here, the height of the scattering peak may be a value (absolute value) of the dispersion intensity, or may be a ratio (relative value) of the scattering intensity of the scattering peak to the scattering intensity of the specific 2θ (for example, θ=0°). Therefore, it is possible to estimate not only the dispersibility, but also the degree of dispersion when the dispersibility is good.

Further, the fine powder of the alkaline earth metal compound and the index of dispersibility (for example, wettability of the powder) and the scattering intensity of the scattering peak measured by various fine particles of the alkaline earth metal compound can be measured in advance, and These results (the type of the alkaline earth metal compound fine powder, the type of the solvent, the index of the dispersibility, and the scattering intensity) are registered in the database. Further, the alkaline earth metal compound fine powder and the solvent to be measured may be selected from the database, and the value of the dispersibility index may be automatically extracted based on the value of the dispersion intensity of the dispersion peak of the spectrum obtained in the measurement. Thereby, the dispersibility can be more accurately evaluated based on the kind of the alkaline earth metal compound fine powder and the kind of the solvent as a specific index.

The micro powder dispersibility evaluation method of the present invention can also automatically perform the X-ray irradiation step (S1) and the scattering intensity analysis step (S2) by using one apparatus as in the case of using the fine powder dispersibility evaluation apparatus shown in FIG. The dispersibility inference step (S3), but a part of the steps may be performed manually, or a part of the steps may be performed by other means.

As a case of performing a part of the steps manually, for example, the X-ray irradiation step (S1) and the scattering intensity analysis step (S2) can be used to automatically detect the scattering peaks using a commercially available small-angle X-ray scattering device, and for the dispersion. The inference step (S3) is manually determined based on the result of the presence or absence of the scattering peak.

Further, as a case where a part of the steps are performed by another device, for example, spectral data may be acquired for the X-ray irradiation step (S1) using a commercially available small-angle X-ray scattering device, and the scattering intensity analysis step (S2) and dispersion may be performed. The sex inference step (S3) performs the detection of the scattering peak and the estimation of the dispersion property using a general personal computer or the like based on the spectral data obtained in the small-angle X-ray scattering device.

Further, in the present invention, it is preferable to calculate the interparticle distance d by the Bragg formula from the scattering angle 2 θ. Here, the Bragg type means the following formula (1).

2dsin θ=n λ (1)

(here, d means the distance between particles (also called "lattice spacing"), θ means the scattering angle mentioned above, n means an integer, λ means the wavelength of X-rays)

When the distance d between the particles is small, it is considered that the cohesive force of the particles becomes high. That is, the particles are too close to each other, or the amount of the surfactant attached to the surface of the particles is too small, and it is difficult to disperse when dispersed in a solvent. On the other hand, if the distance d between the particles is large, the particles are excessively separated from each other, the regularity is lowered, or the amount of the surfactant on the surface of the particles is excessively dispersed, and dispersed in the solvent. Sex is easy to get worse. Thus, by measuring the distance d between the particles, it is possible to evaluate the dispersion. Although it depends on the type of the alkaline earth metal compound fine particles, in the nano particles having a long diameter of 50 nm or less, the preferred interparticle distance d is usually in the range of 10 nm to 30 nm. Further, when the surface-treated nanoparticles were not subjected to the measurement in the present invention, no scattering peak was observed, and the d value could not be obtained.

4. Optical film

The highly dispersible alkaline earth metal compound fine powder of the present invention can be formed into an optical film by mixing a resin to form a resin composition and forming a film. Hereinafter, the optical film will be described.

The resin to be used in the resin composition is not particularly limited as long as it is a resin used in a general optical film, and various resins can be selected depending on the purpose. Examples of such a resin include cellulose esters such as polycarbonate, polymethyl methacrylate, and triethyl fluorene cellulose, polystyrene, styrene acrylonitrile copolymer, polyfumaric acid diester, and polyarylene. Polyolefins, polyether oximes, polyolefins such as polycyclic olefins, maleimide copolymers, polyethylene terephthalate, polyethylene naphthalate, polyimine, polyamine One or more of the group consisting of polyurethanes.

The content of the alkaline earth metal compound fine powder with respect to the entire resin composition is preferably in the range of 0.1 to 50% by mass. When the content of the alkaline earth metal compound fine powder is less than 0.1% by mass, the birefringence control effect by the alkaline earth metal compound fine powder becomes too small. On the other hand, when the content of the alkaline earth metal compound fine powder exceeds 50% by mass, the ratio of the alkaline earth metal compound fine powder to the resin is relatively large, and the transparency of the formed film is deteriorated. The content of the alkaline earth metal compound fine powder relative to the entire resin composition is preferably in the range of 0.5 to 40% by mass, particularly preferably in the range of 1 to 35% by mass.

It can be prepared by mixing the above resin with an alkaline earth metal compound fine powder. Resin composition. The mixing of the alkaline earth metal compound fine powder and the resin can be carried out by a known method such as a method using an ultrasonic homogenizer or a stirring blade or a liquid jet mill.

Further, a film optical film may be prepared by adjusting a dope solution obtained by mixing a resin composition and a suitable solvent. The type of the solvent is not particularly limited, and can be appropriately selected depending on the nature of the resin or the like. Examples of the solvent are preferably organic solvents, and examples of the organic solvent include alcohols (for example, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol), dichloromethane, and NMP, tetrahydrofuran, MEK, ethyl acetate, cyclohexane, toluene, and the like. Among these organic solvents, dichloromethane is particularly preferred. It is not limited to one of the above, and a plurality of combinations may be used.

The ratio of the resin to the solvent is preferably in the range of from 1:10 to 10:1 by mass. The doping solution may be prepared by mixing a resin and a solvent to prepare a resin mixed solution, adding an alkaline earth metal compound fine powder thereto, or mixing the alkaline earth metal compound fine powder with a solvent to prepare a powder mixed solution. , a resin is added thereto and mixed. Further, the resin mixed solution and the powder mixed solution described above may be separately prepared and mixed to form a doping solution. The alkaline earth metal compound fine powder and the resin and the solvent can be mixed by a known method such as a method using an ultrasonic homogenizer or a stirring blade or a liquid jet mill.

The resin composition or the doping solution can be formed into a film by a known method. As the film formation method, a known film formation method such as the above-described melt extrusion film formation method or solution casting film formation method can be mentioned. The melt extrusion film formation method is a method in which a resin composition is heated and melted to obtain a melt, which is cast into a film on a support and cooled and solidified. Further, the solution casting film forming method is a method in which a doping solution is cast on a support to evaporate a solvent to form a film.

Depending on the type of resin, convection occurs in the resin solution during film formation. The case of the Benadite flow structure. When the Benadite flow structure is formed, the alkaline earth metal compound fine powder aggregates, and the transparency of the optical film is deteriorated. Further, this coagulation reduces the birefringence adjustment action by the alkaline earth metal compound-based fine powder. Therefore, it is preferred to add a surface modifier to the resin composition or the doping solution for the purpose of improving the wettability with the support and suppressing the formation of the Benadite flow. When polycarbonate is used as the resin, the Benadite flow is easily formed, and the effect of improving the transparency obtained by adding the surface modifier is remarkable. Examples of the surface modifier include a vinyl-based surfactant, a fluorine-based surfactant, and a polyoxygenated oil.

The film after film formation can be suitably extended according to the use, etc. Examples of the stretching method include uniaxial stretching, biaxial stretching, and the like. The biaxial extension can be extended sequentially or simultaneously. The extension can be carried out using a known stretching device such as a tenter.

The optical film thus obtained is excellent in transparency because it contains fine and highly dispersed alkaline earth metal compound fine powder, and the birefringence of the optical film itself can be adjusted by adjusting the content of the alkaline earth metal compound fine powder relative to the entire optical film. . Since the alkaline earth metal compound fine powder exhibits negative birefringence itself, the birefringence of the optical film can be adjusted according to the use of the target optical film or the like.

For example, by adding an alkaline earth metal compound fine powder to a resin exhibiting positive intrinsic birefringence such as polycarbonate or polycyclic olefin, the intrinsic birefringence of the resin can be offset to form an optical film having a birefringence close to zero. As such an optical film, a protective film is mentioned, for example. The protective film includes a protective film of a polarizing element that directly coats the surface of the polarizing element and protects the polarizing element, in addition to a general protective film laminated on the surface of the polarizing plate.

Alternatively, an optical having positive birefringence can also be produced by adding a small amount of an alkaline earth metal compound fine powder to a resin exhibiting positive birefringence such as polycarbonate or polycyclic olefin. membrane. Further, an optical film having negative birefringence can also be produced by adding a large amount of the alkaline earth metal compound fine powder to the resins exhibiting positive birefringence. The term "birefringence" as used herein means the value of the in-plane birefringence (?Nxy) described above. As such an optical film which exhibits a positive or negative in-plane birefringence, a retardation film can be mentioned. Examples of the retardation film include a quarter wave plate, a 1/2 wavelength plate, and the like.

On the contrary, an optical film exhibiting negative birefringence can also be produced by using a resin exhibiting negative birefringence or a resin having a small birefringence such as polymethyl methacrylate or polystyrene. As such an optical film, a retardation film is mentioned. Examples of the retardation film include a quarter wave plate, a 1/2 wavelength plate, and the like.

Examples of the optical film of the present invention include an antireflection film, an antiglare film, a brightness enhancement film, a ruthenium film, and a viewing angle improvement film, in addition to the retardation film or the protective film.

The haze of the optical film can be 10% or less, preferably 5% or less, and more preferably 1% or less. Further, the haze can be deliberately deteriorated depending on the use of the optical film. For example, an anti-glare film can be produced by adding light-scattering fine particles such as glass beads to the resin composition to deteriorate the haze. Further, the light transmittance of the optical film can be set to 85% or more, preferably 88% or more, and more preferably 90% or more.

The optical film of the present invention can also be laminated with other optical films to form an optical laminate. Examples of the other optical film include a polarizing film (also referred to as a polarizing element), a base film, and the like. The optical layered body may be a polarizing plate obtained by laminating a protective film of the optical film of the present invention and a polarizing film, or an elliptically polarizing plate obtained by laminating a retardation film of the optical film of the present invention and a polarizing film. A phase difference plate or the like obtained by laminating a retardation film of the optical film of the present invention and a base film.

5. Image display device

The image display device of the present invention is characterized by comprising the optical film of the present invention. Examples of the type of the image display device include a liquid crystal display device (LCD), an organic electroluminescence display device, and the like. Further, examples of the use of the video display device include a mobile information display terminal such as a television, a computer display, a mobile phone, a smart phone, and a PDA.

[Examples]

Hereinafter, the present invention will be specifically described based on examples, but these do not limit the object of the present invention.

(1) SEM observation

(1-1) Surface untreated product

Regarding the surface-untreated cerium carbonate microparticles, cerium carbonate microparticles were added to pure water and dispersed by an ultrasonic homogenizer. The dispersion was dropped on a sample mounting table and allowed to dry naturally, and then cerium carbonate microparticles were coated with cerium to prepare a sample. The prepared samples were photographed by an electro-radiation scanning electron microscope (FE-SEM). From the obtained FE-SEM photograph, the length (maximum length) and the length in the short side direction (minimum length) of each particle were measured, and the average value of the length in the longitudinal direction was defined as the average long diameter of the particles. Further, the aspect ratio is calculated from the values of the obtained long diameter and short diameter.

(1-2) Surface treatment products

The surface-treated cerium carbonate microparticles were dissolved in 0.01 g of methylene chloride, and dispersed in an ultrasonic bath for 1 minute, and the obtained dispersion was vacuum dried. Thereafter, ruthenium was applied to prepare a sample. The prepared samples were photographed by an electro-radiation scanning electron microscope (FE-SEM). Measure each particle based on the obtained FE-SEM photograph The length in the longitudinal direction (long diameter) and the length in the short side direction (short diameter), and the average of the length in the longitudinal direction is defined as the average long diameter of the particles. Further, the aspect ratio is calculated from the values of the obtained long diameter and short diameter.

(2) Small angle X-ray scattering measurement

The surface-treated cerium carbonate microparticles and the untreated microparticles were each filled in a capillary tube, and measured by a small-angle scattering measuring device NANO-Viewer (manufactured by Rigaku Corporation). The exposure time was divided into upper, middle and lower portions and exposed for 5 minutes each. The details of the device are as follows.

Tube: CuKα

Output: 40kV-30mA

Slit:

First slit = 0.40mm

Second slit = 0.20mm

Third slit = 0.45mm

Measurement method: transmission method

Counter: Pilatus 100K

Camera length: 570mm

(3) Particle size distribution measurement

The measurement was carried out using a laser diffraction type particle size distribution measuring device (Microtrac 9320HRA, manufactured by Nikkiso Co., Ltd.) or a dynamic light scattering type particle size distribution measuring device (Nanotrac UPA-150, manufactured by Nikkiso Co., Ltd.). The sample for the measurement of the average particle diameter was obtained by adding a highly dispersible cerium carbonate micropowder to an organic solvent (dichloromethane: WAKO grade) to prepare a dispersion having a concentration of 1%, and filtering it with a 1 μm glass filter. . Measurement system will be continuously measured The average value of the amount of 5 times is set as the measured value.

(4) Surfactant

The surfactants used in the following examples are as follows.

‧ Surfactant A: Polycarboxylate anionic surfactant (polymaleic anhydride-polyoxyethylene ester copolymer)

‧ Surfactant B: polycarboxylate anionic surfactant (in the above formula (I), R ¹ is an alkyl group having 13 carbon atoms, E ¹ is C ₂ H ₄ , and a polymer having an average of 9.3)

‧ Surfactant C: polycarboxylic acid anionic surfactant (in the above formula (I), R ¹ is an alkyl group having 12 carbon atoms, E ¹ is C ₂ H ₄ , and a polymer having an average of 2.3)

‧ Surfactant D: polycarboxylate anionic surfactant (in the above formula (I), R ¹ is an alkyl group having 18 carbon atoms, E ¹ is C ₂ H ₄ , and a polymer having an average of 2)

‧ Surfactant E: polyphosphate anionic surfactant (which is a mixture of the above formula (II) and formula (III), R ² , R ³ , and R ⁴ are each a C 13 alkyl group, E ² , E ³ And E ⁴ is a polymer of C ₂ H ₄ , b, c, and d which is a total of 6.0)

‧ Surfactant F: Polyethylene glycol amine type nonionic surfactant (in the above formula (IV), R ⁵ is an alkyl group having 18 carbon atoms, E ⁵ and E ⁶ are both C ₂ H ₄ , e and f total of 4.0 polymers)

1. Embodiment 1

(1) Manufacture of strontium carbonate microparticles

(a) Reaction step

DL-tartaric acid (special grade reagent, purity: 99% or more) was added to 3 L of pure water having a water temperature of 10 ° C, and the mixture was stirred and dissolved in an aqueous suspension. 366 g of barium hydroxide octahydrate (special grade reagent, purity: 96% or more) was charged and mixed to prepare a hydrogen peroxide having a concentration of 5.6% by mass. Hydrophobic suspension. While maintaining the aqueous cesium hydroxide suspension at 10 ° C while stirring, the carbon dioxide was blown into the aqueous suspension at a flow rate of 0.5 L/min (a flow rate of 22 mL/min with respect to 1 g of cesium hydroxide). The gas was allowed to form cerium carbonate particles until the pH of the aqueous suspension became 7. Thereafter, stirring was further continued for 30 minutes to obtain an aqueous suspension of cerium carbonate particles.

(b) ripening step

The obtained aqueous suspension of cerium carbonate particles was placed in a stainless steel tank, and heated at a temperature of 95 ° C for 12 hours to grow cerium carbonate particles in a needle shape. Thereafter, it was left to cool to room temperature to produce an aqueous slurry of cerium carbonate microparticles. The slurry was dried in a tumble dryer to obtain cerium carbonate microparticles. The cerium carbonate microparticles were observed by the method described in "(1) SEM observation" ("1-1) Surface untreated product", and the average long diameter was 35 nm. The results are shown in Table 1.

(2) Manufacture of highly dispersible strontium carbonate micropowder

(a) Surface treatment steps

To the aqueous slurry (solid content: 6 mass%) of the cerium carbonate microparticles prepared above, the surfactant A was added and dissolved, and stirred by a stirrer for 5 minutes. Then, the surfactant B was added to the aqueous slurry to be dissolved in a mass ratio of 28% by mass, and the mixture was stirred for 5 minutes by a stirrer, and then subjected to a dispersing treatment by applying a shear force by a Crea kneading machine. Thereby, a water slurry of highly dispersible cerium carbonate particles is obtained. The two kinds of surfactants are laminated on the surface in such a manner as to form two layers.

(b) drying step (drum dryer)

Mixing and mixing the aqueous slurry into a rotary drum dryer heated to 110~120 °C Blowing to obtain a highly dispersible cerium carbonate micropowder. The highly dispersible cerium carbonate fine powder obtained by observation with an electron microscope was confirmed to be a fine powder of acicular particles. The highly dispersible cerium carbonate micropowder was observed by the method described in "(1) SEM observation" "(1-2) Surface-treated article", and the average long diameter was 35 nm. The conditions such as the kind of the surfactant are shown in Table 1.

(3) Small-angle X-ray scattering measurement of highly dispersed barium carbonate micropowder

The highly dispersible cerium carbonate micropowder obtained in the above was measured by the method described in "(2) Small-angle X-ray scattering measurement" and "(3) Particle size distribution measurement". As a result of the peak search, a scattering peak was observed at 2 θ = 0.46°, and the d value was 19.2 nm. Moreover, when measuring the particle size distribution in the organic solvent dispersion liquid of this powder, D50 is 50 nm or less. The results are shown in Table 2.

2. Example 2

In the "(a) surface treatment step" of the first embodiment, the surfactant C was added and dissolved in an amount of 30% by mass, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. In the same manner as in the first embodiment, the small-angle X-ray measurement and the measurement of the average length and the like of the particle size distribution were performed. The results are shown in Tables 1 and 2.

3. Example 3

In the "(a) surface treatment step" of the first embodiment, the surfactant E was added and dissolved in an amount of 30% by mass, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. The average major axis and the like were measured in the same manner as in the first embodiment. The results are shown in Tables 1 and 2.

4. Example 4

In the "(a) surface treatment step" of the first embodiment, the surfactant D was added and dissolved in an amount of 30% by mass, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. The average major axis and the like were measured in the same manner as in the first embodiment. The results are shown in Tables 1 and 2.

5. Example 5

In the "(1) Manufacture of strontium carbonate microparticles" of the first embodiment, strontium carbonate microparticles having an average long diameter of 20 nm were used, and in the "(a) surface treatment step", a surfactant was added in an amount of 47% by mass. D was dissolved and one surfactant was applied to the surface layer of the cerium carbonate particles. The average major axis and the like were measured in the same manner as in the first embodiment. The results are shown in Tables 1 and 2.

6. Example 6

In the "(1) Manufacture of strontium carbonate microparticles" of the first embodiment, strontium carbonate microparticles having an average long diameter of 20 nm were used, and in the "(a) surface treatment step", a surfactant was added in an amount of 47% by mass. C was dissolved and one surfactant was applied to one surface layer of the cerium carbonate particles. The average major axis and the like were measured in the same manner as in the first embodiment. The results are shown in Tables 1 and 2.

7. Comparative Example 1

In the "(a) surface treatment step" of the first embodiment, the surfactant A was added and dissolved in an amount of 8 mass%, and stirred by a stirrer for 5 minutes. Then, the surfactant F was added to and dissolved in the aqueous slurry so as to be 23% by mass, and stirred by a stirrer for 5 minutes. The average major axis and the like were measured in the same manner as in the first embodiment.

8. Comparative Example 2

In the "(a) surface treatment step" of the first embodiment, the surfactant C is added to and dissolved in the aqueous slurry so as to be 10% by mass, and one type of surfactant is applied to the surface layer of the cerium carbonate particles. 1 story. The average long diameter and the like were measured in the same manner as in Example 1, and the distribution was calculated in the same manner as in Comparative Example 1. The results are shown in Tables 1 and 2.

9. Comparative Example 3

In the "(a) surface treatment step" of the first embodiment, the water is made to be 20% by mass. Surfactant C was added to the slurry and dissolved, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. The average long diameter and the like were measured in the same manner as in Example 1, and the distribution was calculated in the same manner as in Comparative Example 1. The results are shown in Tables 1 and 2.

10. Comparative Example 4

In the "(2) Production of highly dispersible cerium carbonate micropowder" of the first embodiment, the surface treatment was not performed in the "(a) surface treatment step", and the average long diameter and the like were measured in the same manner as in the first embodiment. In small angle X-ray scattering, no scattering peaks can be observed. The results are shown in Tables 1 and 2.

11. Comparative Example 5

In the "(a) surface treatment step" of the first embodiment, the surfactant C was added and dissolved in an amount of 30% by mass, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. In the small-angle X-ray scattering, the dry powder was not measured, but the powder was dispersed in cyclohexane so as to have a solid content concentration of 1% by mass. As a result, scattering peaks could not be observed. The results are shown in Tables 1 and 2.

12. Comparative Example 6

In the "(a) surface treatment step" of the first embodiment, the surfactant C was added and dissolved in an amount of 30% by mass, and one type of surfactant was applied to the surface layer of the cerium carbonate particles. In the small-angle X-ray scattering, the dry powder was not measured, but the powder was dispersed in water and measured in such a manner that the solid content concentration was 1% by mass. As a result, scattering peaks could not be observed. The results are shown in Tables 1 and 2.

From the above results, in each of Examples 1 to 6, the scattering intensity has a scattering peak in the range of 0.2 to 1.0 in 2θ in the state of the fine powder of the highly dispersible alkaline earth metal compound. Further, from the results of measurement of the particle size distribution, it was found that the dispersibility was good. It can be seen that these implementations In the example, an optimum amount of the surfactant is added, and the coating treatment and the dispersion treatment are completely applied to the primary particles.

<Polycarbonate (PC) film>

Hereinafter, an example in which a polycarbonate film is produced by using the highly dispersible cerium carbonate micropowder produced in the above-described Example 4 and Comparative Example 4 will be described.

13. Example 7

(1) Method for preparing doping liquid by adding SrCO ₃

6 g of polycarbonate (hereinafter referred to as "PC") was added to 25 g of dichloromethane, and the mixture was stirred for 6 hours to prepare a PC-dichloromethane solution. Next, 0.48 g of the surface-treated powder 1 of Example 4 was added to 10 g of dichloromethane, and the mixture was placed in an ultrasonic bath for 30 seconds, and directly filtered with a membrane filter having a pore size of 1 μm without being pressurized to prepare a dispersion 1 . The PC-dichloromethane dispersion was mixed with the dispersion 1, and 0.026 g of a vinyl-based surface modifier was added, and dispersion treatment was carried out by an ultrasonic homogenizer to obtain a doping liquid A-1 to which SrCO ₃ was added.

(2) PC film forming method

The doping liquid A-1 to which SrCO _{3 was} added was coated with a wet film thickness of 11 mil on a polyethylene terephthalate (hereinafter, "PET") film using a Baker applicator. It was dried at 40 ° C for 2 minutes, dried at 80 ° C for 4 minutes, and dried at 120 ° C for 30 minutes. The PC film was peeled off from the PET film to obtain PC film A-1. The PC film A-1 was subjected to a free end uniaxial stretching to 2.0 times at 160 ° C using a film stretching apparatus (manufactured by Imoto Seisakusho Co., Ltd.) to obtain a PC stretching film A-1.

(3) Transmittance and haze measurement

The visible light transmittance and haze measurement of the PC stretched film A-1 were carried out using a spectrophotometer (manufactured by JASCO Corporation).

(4) Evaluation of phase difference of film

The film thickness of the PC stretched film A-1 was measured by a micrometer. Thereafter, the phase difference (ΔNxy) of the stretched film was measured using a phase measuring device (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA-WR). The results are shown in Table 3.

14. Comparative Example 7

The same procedure as in Example 7 was carried out except that the powder of Comparative Example 4 (SrCO ₃ not subjected to surface treatment) was used instead of the powder of Example 4. Thereby, the PC stretching film H-1 was obtained. The characteristics of the obtained film were evaluated in the same manner as in Example 7. The results are shown in Table 3.

When Example 7 was compared with Comparative Example 7, it was found that the haze of Example 7 subjected to the surface treatment was lower than that of Comparative Example 7 which was not subjected to the surface treatment, and the value of the birefringence (ΔNxy × 10 ^-3 ) was low. . Therefore, it is understood that the surface-treated cerium carbonate microparticles are preferred from the viewpoint of transparency and birefringence.

<Polymethyl methacrylate (PMMA) film>

Hereinafter, an example in which a polymethyl methacrylate film is produced by using the highly dispersible cerium carbonate fine powder produced in the above-described Example 4 and Comparative Example 4 will be described.

15. Example 8

(1) Method for preparing doping liquid by adding SrCO ₃

6 g of polymethyl methacrylate (hereinafter referred to as "PMMA") was added to 25 g of dichloromethane, and the mixture was stirred for 3 hours to prepare a PMMA-dichloromethane solution. Next, 0.48 g of the surface-treated powder 1 of Example 4 was added to 10 g of dichloromethane, and the mixture was placed in an ultrasonic bath for 30 seconds, and directly filtered with a membrane filter having a pore size of 1 μm without being pressurized to prepare a dispersion 1 . The PMMA-dichloromethane dispersion was mixed with the dispersion 1 and subjected to dispersion treatment by an ultrasonic homogenizer to obtain a doping liquid I-1 to which SrCO ₃ was added.

(2) PMMA film forming method

The doping solution I-1 to which SrCO _{3 was} added was coated on the PET film with a wet film thickness of 11 mil using a Baker-type applicator. It was dried at 40 ° C for 2 minutes, dried at 80 ° C for 15 minutes, and dried at 85 ° C for 30 minutes. The PMMA film was peeled off from the PET film to obtain a PMMA film I-1. The PMMA film I-1 was subjected to a free end uniaxial stretching to 2.0 times at 90 ° C using a film stretching device (manufactured by Imoto Seisakusho Co., Ltd., IMC-1A8D type) to obtain a PMMA stretching film I-1. The characteristics of the obtained film were evaluated in the same manner as in Example 7. The results are shown in Table 4.

16. Comparative Example 8

The same procedure as in Example 8 was carried out except that the powder of Comparative Example 4 (SrCO ₃ not subjected to surface treatment) was used instead of the powder of Example 4. Thereby, the PMMA stretched film N-1 was obtained. The characteristics of the obtained film were evaluated in the same manner as in Example 7. The results are shown in Table 4.

When Example 8 was compared with Comparative Example 8, it was found that the haze of Example 8 subjected to the surface treatment was lower than that of Comparative Example 8 in which no surface treatment was performed, and the value of birefringence (ΔNxy × 10 ^-3 ) was obtained. low. Therefore, it is understood that the surface-treated cerium carbonate microparticles are preferred from the viewpoint of transparency and birefringence. From the above, it is understood that the alkaline earth metal compound fine powder of the present invention is particularly suitable for an optical film having high transparency and high birefringence, such as a retardation film of a polarizing plate.

Claims (15)

A highly dispersible alkaline earth metal compound fine powder comprising an alkaline earth metal compound as a main component and an activator attached to an alkaline earth metal compound having an average major diameter of 10 to 100 nm and an average aspect ratio of 1.0 to 5.0. The surface of the microparticles is characterized in that the scattering intensity has a scattering peak in a range of 0.2 to 1.0° measured by a small angle X-ray scattering method of irradiating X-rays having a wavelength of 0.154 nm. The highly dispersible alkaline earth metal compound fine powder according to claim 1, wherein the scattering angle 2 θ is in the range of 0.4 to 0.7°, and the interparticle distance d obtained by the Bragg formula according to the scattering angle 2 θ The calculated value is in the range of 12.6 to 22.1 nm. A highly dispersible alkaline earth metal compound fine powder according to claim 1 or 2, wherein the alkaline earth metal compound is an alkaline earth metal carbonate. A highly dispersible alkaline earth metal compound fine powder according to claim 3, wherein the alkaline earth metal carbonate is barium carbonate. The highly dispersible alkaline earth metal compound fine powder according to claim 1, wherein the surfactant contains a hydrophilic group and a hydrophobic group, and further has an anion group formed in water. An optical film in which a highly dispersible alkaline earth metal compound fine powder of any one of claims 1 to 5 is dispersed in a resin. The optical film of claim 6, wherein the resin is selected from the group consisting of polycarbonate, polymethyl methacrylate, cellulose ester, polystyrene, styrene acrylonitrile copolymer, polyfumarate diester, Polyarylate, polyether oxime, polyolefin, maleic amide copolymer, polyethylene terephthalate, polyethylene naphthalate, polyimine, One or more of the group consisting of polyamine and polyurethane. An image display device comprising the optical film of claim 6 or 7. A method for producing a highly dispersible alkaline earth metal compound fine powder, which is a method for producing a highly dispersible alkaline earth metal compound fine powder according to any one of claims 1 to 5, characterized in that it comprises: a dispersion step: In the presence of a surfactant, a shearing force is imparted to the first dispersion obtained by dispersing the fine particles of the alkaline earth metal compound having an average long diameter in the range of 10 to 100 nm in an aqueous solvent, thereby causing the alkaline earth metal compound microparticles Dispersing the primary particles in the aqueous solvent, contacting the primary particles with the surfactant to obtain a second dispersion; and drying step: heating the second dispersion at a temperature of 100 to 300 ° C to dry the particles It is made into a powder. A method for evaluating a dispersibility of a fine powder, which is characterized in that, in a powder state, a dispersibility in dispersing an alkaline earth metal compound fine powder in a solvent is characterized in that it has an X-ray irradiation step: using a small-angle X-ray scattering method, Irradiating X-rays of alkaline earth metal compound fine powder to obtain a spectrum of scattering intensity of a specific range of scattering angle; scattering intensity analysis step: analyzing whether scattering angle 2 θ has scattering intensity scattering in the range of 0.2 to 1.0° according to the spectrum Peak; and dispersion inference step: based on the detection result of the scattering peak, the dispersibility of the alkaline earth metal compound fine powder in the solvent is estimated. The micro powder dispersibility evaluation method according to claim 10, wherein the dispersibility estimating step is inferred to be the alkaline earth metallization in the solvent when the scattering peak is detected. The dispersibility of the fine powder is relatively high. The micro powder dispersion evaluation method according to claim 10, wherein the scattering angle 2 θ is in the range of 0.4 to 0.7°. A fine powder dispersibility evaluation device for evaluating dispersibility when a fine powder of an alkaline earth metal compound is dispersed in a solvent in a powder state, characterized by having an X-ray irradiation means: using a small-angle X-ray scattering method The alkaline earth metal compound fine powder irradiates X-rays to obtain a spectrum of the scattering intensity of the scattering angle of a specific range; and the scattering intensity analysis means: according to the spectrum, whether the scattering angle 2 θ has a scattering intensity scattering in the range of 0.2 to 1.0° Peak; and dispersibility estimating means: based on the detection result of the scattering peak, the dispersibility of the alkaline earth metal compound fine powder in the solvent is estimated. The fine powder dispersibility evaluation device according to claim 13, wherein the dispersibility estimating means determines that the dispersibility of the alkaline earth metal compound fine powder in the solvent is relatively high when the scattering peak is detected. The fine powder dispersibility evaluation device according to claim 13, wherein the scattering angle 2 θ is in a range of 0.4 to 0.7°.