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WO2024190432A1 - Ink composition containing plate-shaped alumina - Google Patents

Ink composition containing plate-shaped alumina Download PDF

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Publication number
WO2024190432A1
WO2024190432A1 PCT/JP2024/007464 JP2024007464W WO2024190432A1 WO 2024190432 A1 WO2024190432 A1 WO 2024190432A1 JP 2024007464 W JP2024007464 W JP 2024007464W WO 2024190432 A1 WO2024190432 A1 WO 2024190432A1
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WO
WIPO (PCT)
Prior art keywords
ink composition
alumina
alumina particles
mass
metal oxide
Prior art date
Application number
PCT/JP2024/007464
Other languages
French (fr)
Japanese (ja)
Inventor
一男 糸谷
正紀 飯田
正道 林
健一 濱田
Original Assignee
Dic株式会社
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Publication date
Application filed by Dic株式会社 filed Critical Dic株式会社
Publication of WO2024190432A1 publication Critical patent/WO2024190432A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/40—Compounds of aluminium
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/06—Treatment with inorganic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/16—Writing inks
    • C09D11/17—Writing inks characterised by colouring agents
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/16—Writing inks
    • C09D11/18—Writing inks specially adapted for ball-point writing instruments

Definitions

  • the present invention relates to an ink composition containing platelet alumina.
  • ink compositions containing, for example, a colorant and a solvent such as an organic solvent or water are known, and pigment inks containing a pigment as the colorant are widely used.
  • pigment inks containing a pigment as the colorant are widely used.
  • inks using titanium oxide as a white pigment, which has excellent hiding power and clarity, are widely used.
  • alumina may be added together with a colorant such as titanium oxide (Patent Documents 1 and 2).
  • a ballpoint pen tip has a ball and a ball holder, and by adding alumina, it is possible to reduce wear on the ball seat (referring to the contact point between the ball and the ball holder) caused by friction generated by the rotation of the ball during writing.
  • the frictional force between the ball and the ball seat is smaller than the frictional force between the paper surface and the ball, preventing skipping of the line.
  • alumina has low hiding power, and when added as an additive there is a risk that it will reduce the inherent hiding power of the ink composition.
  • Non-Patent Document 1 shows that plate-like NaNbO 3 of the submicron order has high hiding power, but even when alumina is similarly made to the submicron order, the improvement in hiding power is insufficient.
  • the objective of the present invention is to provide an ink composition containing alumina particles that can achieve high hiding power.
  • the present invention is as follows.
  • alumina particles of a specific particle size and thickness by surface treating alumina particles of a specific particle size and thickness, it is possible to provide an ink composition that achieves high hiding power.
  • the ink composition of the present invention is characterized in that it contains alumina particles having a specific particle size and aspect ratio, and the alumina particles have a metal oxide layer on the surface thereof.
  • the D50 of the alumina particles is 1 ⁇ m or more and 5 ⁇ m or less, and more preferably 1.1 ⁇ m or more and 4 ⁇ m or less.
  • the D50 is within the above range, the dry hide effect is easily exhibited when a metal oxide layer described later is provided, and the hiding power of the ink coating film can be improved.
  • D100 of the alumina particles there are no particular limitations on the D100 of the alumina particles, but it is preferable that D100 is 15 ⁇ m or less. If D100 is 15 ⁇ m or less, the proportion of coarse alumina particles is reduced, and a uniform and vivid color can be obtained when the ink is applied to the ink film.
  • D50 and D100 refer to values calculated from the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer.
  • the aspect ratio which is the ratio of the average particle diameter (D50) to the thickness of the alumina particles, is from 10 to 50, preferably from 12 to 45, and more preferably from 15 to 40.
  • D50 average particle diameter
  • the aspect ratio of the alumina particles is within the above range, good hiding performance can be obtained when the alumina particles are made into an ink coating.
  • the alumina particles are aluminum oxide and may be transition alumina of various crystal forms, such as gamma, delta, theta, and kappa, or may contain alumina hydrate in transition alumina, but the alpha crystal form (alpha type) is generally preferred because of its superior stability.
  • the alumina particles may further contain molybdenum, and may also contain impurities derived from the raw materials or shape control agents, as long as the effects of the present invention are not impaired.
  • the alumina particles used in the present invention may be produced by any method that satisfies the requirements for D50 and aspect ratio, and may be produced by known, commonly used production methods such as the hydrothermal method and the flux method.
  • a method for more simply obtaining the desired alumina particles includes the method described in JP 2016-222501 A, in which an aluminum compound is fired in the presence of a molybdenum compound and a shape control agent.
  • the metal oxide layer contained in the alumina particles is preferably one or more of zinc oxide, silicon dioxide, zirconium dioxide, and titanium oxide. Silicon dioxide is particularly preferable because it forms a porous structure and contains air on the surface of the alumina, thereby increasing the difference in refractive index between the binder and the metal oxide layer.
  • the metal oxide layer is preferably a single layer.
  • a single layer provides superior hiding power due to the difference in refractive index. Note that a single layer means that it is made of one type of component, and indicates that there are not two types of layers, for example, a zinc oxide layer and a silicon dioxide layer.
  • the metal oxide layer may be formed on at least a portion of the surface of the alumina particle, but is more preferably formed on the entire surface of the alumina particle.
  • the surface of the alumina particle means the outside of the surface of the alumina particle. Therefore, it is clearly distinguished from the surface layer containing mullite or germanium that is formed on the inside of the surface of the alumina particle.
  • the thickness of the metal oxide layer is not particularly limited, but from the standpoint of hiding power and cost, it is 0.1 nm or more, but is thin enough that it cannot be measured in an SEM image.
  • the amount of metal oxide in the metal oxide layer relative to the amount of alumina in the alumina particles is not particularly limited, but is preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably more than 0% by mass. Being within the above range is preferable because it provides excellent hiding power when made into an ink composition.
  • the method for forming the metal oxide layer is not particularly limited and may be a known method.
  • a porous silicon dioxide layer can be formed by adding a solution of sodium silicate, adjusting the pH with a strong acid, and then drying.
  • the content of the alumina particles having metal oxide may be set appropriately depending on the application, but is preferably 1 to 15% by mass, and more preferably 3 to 12% by mass, based on the total mass of the ink composition. Being within the above range is preferable because it provides both excellent hiding power and color development.
  • the ink composition of the present invention may further contain titanium oxide particles.
  • the titanium oxide particles are not particularly limited, and either rutile type or anatase type may be used, but it is preferable that the average particle size is 0.01 ⁇ m or more.
  • known titanium oxides such as Bayertitan R-FD-1, R-KB-3, and R-CK-20 (all manufactured by Bayer), TIPAQUE R-630, R-615, R-830, and LPT series (all manufactured by Ishihara Sangyo Kaisha, Ltd.), Unitane OR-342 (manufactured by ACC), Ti-pure R-900 and R-901 (manufactured by Chemours), and Luxelene Silk series (manufactured by Sumitomo Chemical Co., Ltd.) may be used.
  • the amount added is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less, and particularly preferably 0.02% by mass or more and 4% by mass or less, based on the total mass of the ink composition. If it is within the above range, the resulting coating film will have excellent hiding power and L value, and will also have excellent ink ejection performance, which is preferable.
  • the ink composition of the present invention may contain an organic solvent, for example, aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, etc., aliphatic hydrocarbon solvents such as n-hexane, n-heptane, isoheptane, n-octane, isooctane, etc., cycloparaffin solvents such as methylcyclohexane, ethylcyclohexane, etc., ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, etc., glycol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerin, etc., glycol ether solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, etc., which may be used alone or in combination of two or more.
  • the amount of organic solvent contained is not particularly limited, but from the viewpoint of the drying speed of the ink coating, it is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass, based on the total mass of the ink composition.
  • the ink composition of the present invention may contain a resin, and examples thereof include polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, polyvinylpyrrolidone resin, ethylene oxide polymer, acrylic resin, styrene-acrylic resin, styrene-maleic acid resin, and the like. These may be used alone or in combination of two or more kinds.
  • the resin content is preferably 0.05 to 30% by mass, and particularly preferably 0.1 to 25% by mass, based on the total mass of the ink composition.
  • the ink composition of the present invention may contain a dispersant, and examples thereof include nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene methyl ether, polyoxyethylene lanolin alcohol, polyoxyethylene alkylamines, and polyoxyethylene fatty acid amides; anionic surfactants such as alkyl sulfates, N-acylamino acid salts, polyoxyethylene alkyl ether acetates, and alkyl phosphates; cationic surfactants such as alkylamine salts and quaternary ammonium salts; amphoteric surfactants such as alkyl betaines, alkyl amine oxides, and phosphatidylcholines; and polymeric surfactants such as acrylics.
  • nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene methyl ether, polyoxyethylene lanolin alcohol, polyoxyethylene alkylamines, and polyoxyethylene fatty acid amides
  • the amount of dispersant contained is determined appropriately depending on the solvent and other components used, but from the standpoint of dispersion stability and ink viscosity, it is preferably 0.1 to 30 mass% of the total mass of the ink composition, and particularly preferably 0.5 to 20 mass%.
  • additives such as colorants such as organic pigments, inorganic pigments, acid dyes, basic dyes, and direct dyes; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, metal salt compounds, and phosphate compounds; preservatives such as carbolic acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; silicone-based, mineral oil-based, polyether-based, and fluorine-based defoamers; antioxidants; stabilizers; inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate, and organic basic compounds such as water-soluble amine compounds, and the like, may also benzotriazole, tolyltri
  • the ink composition of the present invention can be produced by a known method without any particular limitation.
  • the ink composition can be produced by mixing the above-mentioned components in appropriate amounts and mixing them with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or various dispersers such as a bead mill.
  • various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or various dispersers such as a bead mill.
  • a disperser such as a bead mill or a paint conditioner.
  • the viscosity of the ink composition is not particularly limited, but the ink viscosity at 20°C and a shear rate of 5 sec -1 (at rest) is preferably 30,000 mPa ⁇ s or less, and more preferably 25,000 mPa ⁇ s or less. When it is equal to or less than the upper limit, it is preferable in terms of excellent ink dischargeability and writing comfort. From the viewpoint of suppressing ink leakage, it is preferably 500 mPa ⁇ s or more, and more preferably 1,000 mPa ⁇ s or more.
  • the structure of the writing implement to which the ink composition of the present invention is applied is not particularly limited.
  • the ink composition of the present invention is not only highly opaque, but is also expected to exhibit low abrasion effects due to the use of alumina, and is therefore suitable for use as an ink for a ballpoint pen having a ball and a ball seat.
  • By using the writing implement of the present invention it is possible to stably draw lines while maintaining opaqueness.
  • the obtained light blue powder was dispersed in 150 mL of 0.5% ammonia water, and the dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, after which the ammonia water was removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 47 g of light blue powder.
  • the obtained powder was confirmed to have a plate-like shape by SEM observation. Furthermore, when X-ray diffraction (XRD) measurement was performed, sharp peak scattering due to ⁇ -alumina was observed, and no alumina crystal system peaks other than the ⁇ crystal structure were observed, confirming that the particles were plate-like alumina particles with a dense crystal structure.
  • the ⁇ conversion rate was 99% or more (almost 100%).
  • the obtained light blue powder was dispersed in 150 mL of 0.5% ammonia water, and the dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, after which the ammonia water was removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 47 g of light blue powder.
  • the obtained powder was confirmed to have a polygonal plate shape by SEM observation. Furthermore, when X-ray diffraction (XRD) measurement was performed, sharp peak scattering due to ⁇ -alumina was observed, and no alumina crystal system peaks other than the ⁇ crystal structure were observed, confirming that the particles were plate-shaped alumina particles with a dense crystal structure.
  • the ⁇ conversion rate was 99% or more (almost 100%).
  • the resulting light blue powder was then dispersed in 150 mL of 0.5% aqueous ammonia, and the dispersion was stirred at room temperature (25-30°C) for 0.5 hours.
  • the aqueous ammonia was then removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 33.5 g of light blue powder.
  • SEM observation of the resulting powder confirmed that it was plate-like in shape, with very few aggregates.
  • XRD measurement revealed sharp peak scattering due to ⁇ -alumina, and no alumina crystal peaks other than the ⁇ crystal structure were observed, confirming that the particles were plate-like alumina particles with a dense crystal structure.
  • the ⁇ conversion rate was 99% or more (almost 100%).
  • titanium oxide particles (Typaque R-830, manufactured by Ishihara Sangyo Kaisha, Ltd.) were prepared (T-1).
  • Aspect ratio D50/D particle diameter D50 of plate-like alumina particles / average thickness D of plate-like alumina particles
  • the plate-like alumina particles were placed on a measurement sample holder with a depth of 0.5 mm, packed flat under a constant load, and then set in a wide-angle X-ray diffraction apparatus (Rigaku Corporation, Rint-Ultma) and measured under conditions of Cu/K ⁇ radiation, 40 kV/30 mA, a scan speed of 2 degrees/min, and a scan range of 10 to 70 degrees.
  • the ⁇ conversion rate was calculated from the ratio of the strongest peak heights of ⁇ -alumina and transition alumina.
  • the fillers used in the examples and comparative examples are as shown in Table 1.
  • the obtained white ink composition was applied to a colored drawing paper (Koikura, manufactured by PLUS Corporation) to form a coating film using a bar coater RDS20.
  • the coating film was dried at room temperature for one day and night, and the hiding power of the coating surface was evaluated by the L value.
  • the L value was measured using a spectro-guide 45/0 gloss (manufactured by BYK-Gardner GmbH).
  • An L value of 89 or more was evaluated as ⁇ , indicating that the coating sufficiently concealed the coating surface and was good, and an L value below that was evaluated as ⁇ , indicating that the hiding power was insufficient.
  • Examples 1 and 2 and Comparative Example 1 confirmed that forming a metal oxide layer on alumina particles of a specific particle size provides good hiding power.
  • Examples 1 and 2 and Comparative Example 2 confirmed that forming a metal oxide layer improves hiding properties.
  • Examples 1 and 2 and Comparative Example 3 confirmed that alumina particles with a metal oxide layer formed thereon have better hiding power than titanium oxide particles alone.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)

Abstract

The objective of the present invention is to provide an ink composition containing alumina particles, the ink composition being capable of achieving high hiding power. Specifically, the ink composition is characterized by containing plate-shaped alumina particles having a volume-based median diameter D50 of 1 μm to 5 μm, and an aspect ratio of 10 to 50 in a laser diffraction-type particle size distribution measurement, and also having a metal oxide layer on the surface layer thereof.

Description

板状アルミナ含有インキ組成物Plate-like alumina-containing ink composition
　本発明は、板状アルミナ含有インキ組成物に関する。 The present invention relates to an ink composition containing platelet alumina.
　従来、インキ組成物としては、例えば着色剤と、有機溶剤や水等の溶媒とを含有するものが知られており、前記着色剤として顔料を含有する顔料インキが広く使用されている。なかでも、白色顔料としては、隠蔽力や鮮明さに優れる酸化チタンを用いたものが多く使われている。 Conventionally, ink compositions containing, for example, a colorant and a solvent such as an organic solvent or water are known, and pigment inks containing a pigment as the colorant are widely used. Among these, inks using titanium oxide as a white pigment, which has excellent hiding power and clarity, are widely used.
　筆記具用インキ組成物においては、アルミナを酸化チタン等の着色剤と併せて添加することがある（特許文献１、２）。アルミナを添加することで、例えば、ボールペンチップは、ボールとボールホルダーとを有しているが、筆記時にボールが回転することで発生する摩擦によるボール受け座（ボールとボールホルダーの接触部を示す）の摩耗を低減することができる。また、長距離筆記の際、ボールとボール受け座の摩擦力が、紙面とボールとの摩擦力よりも小さい為、線飛びを防ぐことができる。 In ink compositions for writing instruments, alumina may be added together with a colorant such as titanium oxide (Patent Documents 1 and 2). For example, a ballpoint pen tip has a ball and a ball holder, and by adding alumina, it is possible to reduce wear on the ball seat (referring to the contact point between the ball and the ball holder) caused by friction generated by the rotation of the ball during writing. In addition, when writing long distances, the frictional force between the ball and the ball seat is smaller than the frictional force between the paper surface and the ball, preventing skipping of the line.
特開２０１５－０９１９４４号公報JP 2015-091944 A 特開２０２０－２０３９６９号公報JP 2020-203969 A
　しかしながら、アルミナは隠蔽力が低く、添加剤として加えた場合にインキ組成物本来の隠蔽力を低下させる恐れがあった。 However, alumina has low hiding power, and when added as an additive there is a risk that it will reduce the inherent hiding power of the ink composition.
　非特許文献１では、サブミクロンオーダーの板状ＮａＮｂＯ３が隠蔽力に高いことが示されているが、アルミナを同様にサブミクロンオーダーとするも隠蔽力の改善が不十分であった。 Non-Patent Document 1 shows that plate-like NaNbO 3 of the submicron order has high hiding power, but even when alumina is similarly made to the submicron order, the improvement in hiding power is insufficient.
　本発明の課題は、高い隠蔽力を達成できるアルミナ粒子を含有するインキ組成物を提供することにある。 The objective of the present invention is to provide an ink composition containing alumina particles that can achieve high hiding power.
　本発明者らは、鋭意検討した結果、特定粒子径及び厚みのアルミナ粒子を表面処理することで、隠蔽力に優れたインキ塗膜とすることを見出し、本発明を完成させるに至った。すなわち本発明は以下の通りである。 After extensive research, the inventors discovered that by surface-treating alumina particles of a specific particle size and thickness, an ink coating with excellent hiding power can be produced, leading to the completion of the present invention. That is, the present invention is as follows.
（１）　レーザー回折式粒度分布測定における体積基準のメディアン径Ｄ５０が１μｍ以上５μｍ以下、アスペクト比が１０以上５０以下であり、かつ金属酸化物層を表層に有する板状アルミナ粒子を含有するインキ組成物。 (1) An ink composition containing plate-like alumina particles having a volume-based median diameter D50 of 1 μm or more and 5 μm or less, an aspect ratio of 10 or more and 50 or less, and a metal oxide layer on the surface.
（２）　前記板状アルミナ粒子のレーザー回折式粒度分布測定における体積基準の累積粒子径Ｄ１００が１５μｍ以下である上記（１）に記載の組成物。 (2) The composition described in (1) above, in which the volume-based cumulative particle diameter D100 of the plate-like alumina particles is 15 μm or less in a laser diffraction particle size distribution measurement.
（３）　前記金属酸化物が二酸化珪素である上記（１）または（２）に記載のインキ組成物。 (3) The ink composition according to (1) or (2) above, in which the metal oxide is silicon dioxide.
（４）　さらに酸化チタン粒子を含む上記（１）～（３）のいずれか１つに記載のインキ組成物。 (4) An ink composition according to any one of (1) to (3) above, further comprising titanium oxide particles.
（５）　インキ組成物において前記板状アルミナ粒子を含有し、その含有量がインキ組成物全量に対して１質量％以上１５質量％以下である上記（１）～（４）のいずれか１つに記載のインキ組成物。 (5) The ink composition according to any one of (1) to (4) above, which contains the platelet alumina particles in an amount of 1% by mass or more and 15% by mass or less based on the total amount of the ink composition.
　本発明によれば、特定粒子径及び厚みのアルミナ粒子を表面処理することで、高い隠蔽力を達成するインキ組成物を提供することができる。 According to the present invention, by surface treating alumina particles of a specific particle size and thickness, it is possible to provide an ink composition that achieves high hiding power.
　以下、本発明の実施形態を詳細に説明する。 The following describes an embodiment of the present invention in detail.
　〔インキ組成物〕
　本発明のインキ組成物は、特定の粒子径、アスペクト比を有するアルミナ粒子を含み、前記アルミナ粒子は表層に金属酸化物層を有することを特徴とする。 [Ink composition]
The ink composition of the present invention is characterized in that it contains alumina particles having a specific particle size and aspect ratio, and the alumina particles have a metal oxide layer on the surface thereof.
　（アルミナ粒子）
　アルミナ粒子のＤ５０は、１μｍ以上５μｍ以下であり、１．１μｍ以上４μｍ以下であるとより好ましい。Ｄ５０が前記範囲内にあることで、後述する金属酸化物層を設けた際にドライハイド効果が発現しやすくなり、インキ塗膜の隠蔽性を向上することができる。 (Alumina particles)
The D50 of the alumina particles is 1 μm or more and 5 μm or less, and more preferably 1.1 μm or more and 4 μm or less. When the D50 is within the above range, the dry hide effect is easily exhibited when a metal oxide layer described later is provided, and the hiding power of the ink coating film can be improved.
　アルミナ粒子のＤ１００は特に制限されるものではないが、Ｄ１００は１５μｍ以下であると好ましい。Ｄ１００が１５μｍ以下であると、粗大なアルミナ粒子の割合が低減され、インキ塗膜とした際に均一で鮮やかな発色を得ることができる。 There are no particular limitations on the D100 of the alumina particles, but it is preferable that D100 is 15 μm or less. If D100 is 15 μm or less, the proportion of coarse alumina particles is reduced, and a uniform and vivid color can be obtained when the ink is applied to the ink film.
　本明細書において、Ｄ５０、Ｄ１００とは、レーザー回折式粒度分布測定装置により測定された体積基準の累積粒度分布から算出された値を意味する。 In this specification, D50 and D100 refer to values calculated from the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution analyzer.
　アルミナ粒子の厚みに対する平均粒子径（Ｄ５０）の比率であるアスペクト比は、１０以上５０以下であり、１２以上４５以下であることが好ましく、１５以上４０以下であることがより好ましい。アルミナ粒子のアスペクト比が前記範囲内であると、インキ塗膜とした際に良好な隠蔽性能を得ることができる。 The aspect ratio, which is the ratio of the average particle diameter (D50) to the thickness of the alumina particles, is from 10 to 50, preferably from 12 to 45, and more preferably from 15 to 40. When the aspect ratio of the alumina particles is within the above range, good hiding performance can be obtained when the alumina particles are made into an ink coating.
　アルミナ粒子は酸化アルミニウムであり、例えば、γ、δ、θ、κ等の各種の結晶形の遷移アルミナであっても、又は遷移アルミナ中にアルミナ水和物を含んでいてもよいが、より安定性に優れる点で、基本的にはα結晶形（α型）であることが好ましい。 The alumina particles are aluminum oxide and may be transition alumina of various crystal forms, such as gamma, delta, theta, and kappa, or may contain alumina hydrate in transition alumina, but the alpha crystal form (alpha type) is generally preferred because of its superior stability.
　アルミナ粒子はさらにモリブデンを含んでいてもよく、また、本発明の効果を損なわない限り、原料又は形状制御剤由来の不純物を含んでもよい。 The alumina particles may further contain molybdenum, and may also contain impurities derived from the raw materials or shape control agents, as long as the effects of the present invention are not impaired.
　本発明に用いられるアルミナ粒子は、Ｄ５０及びアスペクト比の性能を満たすことができればどのような製造方法を用いてもよく、水熱法、フラックス法等の公知慣用の製造方法で製造することができる。より簡便に所望のアルミナ粒子を得る製造方法としては、モリブデン化合物及び形状制御剤の存在下、アルミニウム化合物を焼成する特開２０１６－２２２５０１号公報に記載の方法が挙げられる。 The alumina particles used in the present invention may be produced by any method that satisfies the requirements for D50 and aspect ratio, and may be produced by known, commonly used production methods such as the hydrothermal method and the flux method. A method for more simply obtaining the desired alumina particles includes the method described in JP 2016-222501 A, in which an aluminum compound is fired in the presence of a molybdenum compound and a shape control agent.
　（金属酸化物層）
　アルミナ粒子に含まれる金属酸化物層は、酸化亜鉛、二酸化珪素、二酸化ジルコニウム、酸化チタンのいずれか１種以上であることが好ましい。多孔質構造を形成しアルミナ表面に空気を含有することでバインダーとの屈折率差がより大きくなる二酸化珪素であると特に好ましい。 (Metal Oxide Layer)
The metal oxide layer contained in the alumina particles is preferably one or more of zinc oxide, silicon dioxide, zirconium dioxide, and titanium oxide. Silicon dioxide is particularly preferable because it forms a porous structure and contains air on the surface of the alumina, thereby increasing the difference in refractive index between the binder and the metal oxide layer.
　金属酸化物層は、単層であることが好ましい。単層であると、屈折率差による隠蔽力の向上により優れる。なお、単層とは１種類の成分からなることを意味し、例えば、酸化亜鉛の層と二酸化珪素の層と２種類の層が存在しないことを示す。 The metal oxide layer is preferably a single layer. A single layer provides superior hiding power due to the difference in refractive index. Note that a single layer means that it is made of one type of component, and indicates that there are not two types of layers, for example, a zinc oxide layer and a silicon dioxide layer.
　金属酸化物層は、アルミナ粒子の表面の少なくとも一部に形成されていれば良いが、より好ましくは、アルミナ粒子の表面の全体に形成されていることが好ましい。なお、「アルミナ粒子の表面」とは、アルミナ粒子の表面の外側を意味する。よって、アルミナ粒子の表面の内側に形成される、ムライトやゲルマニウムを含む表層とは明確に区別される。 The metal oxide layer may be formed on at least a portion of the surface of the alumina particle, but is more preferably formed on the entire surface of the alumina particle. Note that "the surface of the alumina particle" means the outside of the surface of the alumina particle. Therefore, it is clearly distinguished from the surface layer containing mullite or germanium that is formed on the inside of the surface of the alumina particle.
　金属酸化物層の厚みは、特に限定されるものではないが、隠蔽性とコストの観点から、０．１ｎｍ以上であるが、ＳＥＭ画像では測定されない程度に薄いものである。 The thickness of the metal oxide layer is not particularly limited, but from the standpoint of hiding power and cost, it is 0.1 nm or more, but is thin enough that it cannot be measured in an SEM image.
　アルミナ粒子のアルミナの量に対する金属酸化物層の金属酸化物の量は、特に限定されるものではないが、例えば５質量％以下であると好ましく、３質量％以下であるとさらに好ましく、０質量％より上であると好ましい。前記範囲内にあることで、インキ組成物とした際に隠蔽性に優れるため好ましい。 The amount of metal oxide in the metal oxide layer relative to the amount of alumina in the alumina particles is not particularly limited, but is preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably more than 0% by mass. Being within the above range is preferable because it provides excellent hiding power when made into an ink composition.
〔金属酸化物層の形成方法〕
　金属酸化物層の形成方法は、特に制限されず公知の方法により形成することができる。例えば、二酸化珪素の場合、ケイ酸ソーダの溶液を添加し強酸によりｐＨ調整後、乾燥させることで多孔質の二酸化珪素層を形成することができる。 [Method of forming metal oxide layer]
The method for forming the metal oxide layer is not particularly limited and may be a known method. For example, in the case of silicon dioxide, a porous silicon dioxide layer can be formed by adding a solution of sodium silicate, adjusting the pH with a strong acid, and then drying.
　金属酸化物を有するアルミナ粒子の含有量は、用途に応じて適宜設定すればよいが、インキ組成物中の全質量に対して１～１５質量％であると好ましく、３～１２質量％であるとより好ましい。前記範囲内にあることで、優れた隠蔽力、発色性を兼備できるため好ましい。 The content of the alumina particles having metal oxide may be set appropriately depending on the application, but is preferably 1 to 15% by mass, and more preferably 3 to 12% by mass, based on the total mass of the ink composition. Being within the above range is preferable because it provides both excellent hiding power and color development.
　（酸化チタン粒子）
　本発明のインキ組成物はさらに酸化チタン粒子を含むことができる。前記酸化チタン粒子は、特に制限されるものではなく、ルチル型、アナターゼ型のいずれも使用することができるが、平均粒子径は０．０１μｍ以上であると良い。例えば、Ｂａｙｅｒｔｉｔａｎ Ｒ－ＦＤ－１・Ｒ－ＫＢ－３・Ｒ－ＣＫ－２０（以上、バイエル社製）、ＴＩＰＡＱＵＥ Ｒ－６３０・Ｒ－６１５・Ｒ－８３０、ＬＰＴシリーズ（以上、石原産業株式会社製）、Ｕｎｉｔａｎｅ ＯＲ－３４２（Ａ．Ｃ．Ｃ．社製）、Ｔｉ－ｐｕｒｅ Ｒ－９００・Ｒ－９０１（Ｃｈｅｍｏｕｒｓ社製）、ルクセレンシルクシリーズ（住友化学株式会社製）等、公知の酸化チタンを用いることができる。 (Titanium oxide particles)
The ink composition of the present invention may further contain titanium oxide particles. The titanium oxide particles are not particularly limited, and either rutile type or anatase type may be used, but it is preferable that the average particle size is 0.01 μm or more. For example, known titanium oxides such as Bayertitan R-FD-1, R-KB-3, and R-CK-20 (all manufactured by Bayer), TIPAQUE R-630, R-615, R-830, and LPT series (all manufactured by Ishihara Sangyo Kaisha, Ltd.), Unitane OR-342 (manufactured by ACC), Ti-pure R-900 and R-901 (manufactured by Chemours), and Luxelene Silk series (manufactured by Sumitomo Chemical Co., Ltd.) may be used.
　添加量は、インキ組成物中の全質量に対して０．００１質量％以上１０質量％以下であると好ましく、０．００５質量％以上５質量％以下であるとさらに好まし、０．０２質量％以上４質量％以下であると特に好ましい。前記範囲内にあると得られる塗膜の隠蔽性とＬ値が優れ、インキ吐出性能にも優れ好ましい。 The amount added is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 5% by mass or less, and particularly preferably 0.02% by mass or more and 4% by mass or less, based on the total mass of the ink composition. If it is within the above range, the resulting coating film will have excellent hiding power and L value, and will also have excellent ink ejection performance, which is preferable.
　（有機溶剤）
　本発明のインキ組成物は有機溶剤を含むことができ、例えば、トルエン、キシレン、エチルベンゼンなどの芳香族炭化水素系溶剤、ｎ－ヘキサン、ｎ－ヘプタン、イソヘプタン、ｎ－オクタン、イソオクタンなどの脂肪族炭化水素系溶剤、メチルシクロヘキサン、エチルシクロヘキサンなどのシクロパラフィン系溶剤、メチルイソブチルケトン、メチルエチルケトンなどのケトン系溶剤、エチレングリコール、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、ポリエチレングリコール、グリセリンなどのグリコール系溶剤、エチレングリコールモノメチルエーテル、ジエチレングルコールモノメチルエーテルなどのグリコールエーテル系溶剤等が挙げられ、これらは１種または２種以上併用して用いても良い。水溶性であり、かつ、筆記性と安全性に優れるという観点において、グリコールエーテル系溶剤が好ましい。 (Organic Solvent)
The ink composition of the present invention may contain an organic solvent, for example, aromatic hydrocarbon solvents such as toluene, xylene, ethylbenzene, etc., aliphatic hydrocarbon solvents such as n-hexane, n-heptane, isoheptane, n-octane, isooctane, etc., cycloparaffin solvents such as methylcyclohexane, ethylcyclohexane, etc., ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, etc., glycol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, glycerin, etc., glycol ether solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, etc., which may be used alone or in combination of two or more. Glycol ether solvents are preferred from the viewpoints of water solubility and excellent writing properties and safety.
　有機溶剤の含有量は特に制限されるものではないが、インキ塗膜の乾燥速度という観点から、インキ組成物中の全質量に対して１０～９０質量％であると好ましく、２０～８０質量％であるとより好ましい。 The amount of organic solvent contained is not particularly limited, but from the viewpoint of the drying speed of the ink coating, it is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass, based on the total mass of the ink composition.
　（樹脂）
　本発明のインキ組成物は樹脂を含んでいてもよく、例えば、ポリビニルブチラール樹脂、ケトン樹脂、ポリアセタール樹脂、ポリビニルアルコール樹脂、セルロース樹脂、テルペン樹脂、アルキッド樹脂、フェノキシ樹脂、ポリ酢酸ビニル樹脂、ポリビニルピロリドン樹脂、エチレンオキサイド重合体、アクリル樹脂、スチレン－アクリル樹脂、スチレン－マレイン酸樹脂などが挙げられ、これらは１種または２種以上併用して用いても良い。 (resin)
The ink composition of the present invention may contain a resin, and examples thereof include polyvinyl butyral resin, ketone resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, polyvinylpyrrolidone resin, ethylene oxide polymer, acrylic resin, styrene-acrylic resin, styrene-maleic acid resin, and the like. These may be used alone or in combination of two or more kinds.
　樹脂の含有量は、インキ粘度やインキ漏れの観点から、インキ組成物中の全質量に対して、０．０５～３０質量％であると好ましく、０．１～２５質量％であると特に好ましい。 From the viewpoint of ink viscosity and ink leakage, the resin content is preferably 0.05 to 30% by mass, and particularly preferably 0.1 to 25% by mass, based on the total mass of the ink composition.
　（分散剤）
　本発明のインキ組成物は分散剤を含んでいてもよく、例えば、グリセリン脂肪酸エステル、ポリオキシエチレンメチルエーテル、ポリオキシエチレンラノリンアルコール、ポリオキシエチレンアルキルアミン、ポリオキシエチレン脂肪酸アミド等のノニオン系界面活性剤；アルキル硫酸塩、Ｎ－アシルアミノ酸塩、ポリオキシエチレンアルキルエーテル酢酸塩、アルキル燐酸塩等のアニオン系界面活性剤；アルキルアミン塩、第４級アンモニウム塩等のカチオン系界面活性剤；アルキルベタイン、アルキルアミンオキサイド、ホスファジルコリン等の両性系界面活性剤；アクリル系等の高分子型界面活性剤などが挙げられる。 (Dispersant)
The ink composition of the present invention may contain a dispersant, and examples thereof include nonionic surfactants such as glycerin fatty acid esters, polyoxyethylene methyl ether, polyoxyethylene lanolin alcohol, polyoxyethylene alkylamines, and polyoxyethylene fatty acid amides; anionic surfactants such as alkyl sulfates, N-acylamino acid salts, polyoxyethylene alkyl ether acetates, and alkyl phosphates; cationic surfactants such as alkylamine salts and quaternary ammonium salts; amphoteric surfactants such as alkyl betaines, alkyl amine oxides, and phosphatidylcholines; and polymeric surfactants such as acrylics.
　分散剤の含有量は、用いられる溶媒等のその他成分によって適宜決定されるが、分散安定性やインキ粘度の点から、インキ組成物中の全質量に対して、０．１～３０質量％であると好ましく、０．５～２０質量％であると特に好ましい。 The amount of dispersant contained is determined appropriately depending on the solvent and other components used, but from the standpoint of dispersion stability and ink viscosity, it is preferably 0.1 to 30 mass% of the total mass of the ink composition, and particularly preferably 0.5 to 20 mass%.
　（その他添加剤）
　必要に応じて、有機顔料、無機顔料、酸性染料、塩基性染料、直接染料等の着色剤；ベンゾトリアゾール、トリルトリアゾール、ジシクロヘキシルアンモニウムナイトライト、ジイソプロピルアンモニウムナイトライト、サポニン、金属塩系化合物、リン酸エステル系化合物等の防錆剤；石炭酸、１，２－ベンズチアゾリン３－オンのナトリウム塩、安息香酸ナトリウム、デヒドロ酢酸ナトリウム、ソルビン酸カリウム、パラオキシ安息香酸プロピル、２，３，５，６－テトラクロロ－４－（メチルスルフォニル）ピリジン等の防腐剤；シリコーン系、鉱物油系、ポリエーテル系、フッ素系等の消泡剤；酸化防止剤；安定剤；炭酸ナトリウム、リン酸ナトリウム、酢酸ソーダ等の無機塩類、水溶性のアミン化合物等の有機塩基性化合物等等のｐＨ調製剤などの添加剤を添加することもできる。 (Other additives)
If necessary, additives such as colorants such as organic pigments, inorganic pigments, acid dyes, basic dyes, and direct dyes; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, saponin, metal salt compounds, and phosphate compounds; preservatives such as carbolic acid, sodium salt of 1,2-benzthiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; silicone-based, mineral oil-based, polyether-based, and fluorine-based defoamers; antioxidants; stabilizers; inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate, and organic basic compounds such as water-soluble amine compounds, and the like, may also be added.
〔インキ組成物の製法〕
　本発明のインキ組成物は、特に制限されず公知の方法により製造することができる。前述の成分を適量配合し、プロペラ攪拌、ホモディスパー、またはホモミキサーなどの各種攪拌機やビーズミルなどの各種分散機などにて混合し、製造することができる。なお、着色剤として顔料を添加する場合は、ビーズミルやペイントコンディショナーなどの分散機を用いることが好ましい。 [Method of producing ink composition]
The ink composition of the present invention can be produced by a known method without any particular limitation. The ink composition can be produced by mixing the above-mentioned components in appropriate amounts and mixing them with various stirrers such as a propeller stirrer, a homodisper, or a homomixer, or various dispersers such as a bead mill. When a pigment is added as a colorant, it is preferable to use a disperser such as a bead mill or a paint conditioner.
　（粘度）
　インキ組成物の粘度は、特に制限されるものではないが、２０℃、剪断速度５ｓｅｃ－１（静止時）におけるインキ粘度は、３０，０００ｍＰａ・ｓ以下であると好ましく、２５，０００ｍＰａ・ｓ以下であるとより好ましい。前記上限値以下であると、インキ吐出性や書き心地に優れ好ましい。また、インキ漏れ抑制の観点から５００ｍＰａ・ｓ以上であると好ましく、１，０００ｍＰａ・ｓ以上であるとより好ましい。 (viscosity)
The viscosity of the ink composition is not particularly limited, but the ink viscosity at 20°C and a shear rate of 5 sec -1 (at rest) is preferably 30,000 mPa·s or less, and more preferably 25,000 mPa·s or less. When it is equal to or less than the upper limit, it is preferable in terms of excellent ink dischargeability and writing comfort. From the viewpoint of suppressing ink leakage, it is preferably 500 mPa·s or more, and more preferably 1,000 mPa·s or more.
　〔用途〕
　本発発明のインキ組成物を充填する筆記具の構造は特に制限されるものではない。本発明のインキ組成物は、隠蔽性が高いだけでなく、アルミナを用いることにより低摩耗性の効果も発現されると期待されることから、ボールとボール受け座を有するボールペン用インキとして好適に用いられる。本発明の筆記具を用いれば、隠蔽性を保持しつつ、安定して描線を実現することができる。 [Application]
The structure of the writing implement to which the ink composition of the present invention is applied is not particularly limited. The ink composition of the present invention is not only highly opaque, but is also expected to exhibit low abrasion effects due to the use of alumina, and is therefore suitable for use as an ink for a ballpoint pen having a ball and a ball seat. By using the writing implement of the present invention, it is possible to stably draw lines while maintaining opaqueness.
　次に実施例を示して本発明をさらに詳細に説明するが、本発明は以下の実施例に限定されるものではない。 The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples.
　（アルミナの合成）
〔製造例１〕
　水酸化アルミニウム（日本軽金属株式会社製、平均粒子径1μｍ）１４２．３ｇと、二酸化珪素（関東化学株式会社製、特級）３．７ｇと、三酸化モリブデン（太陽鉱工株式会社製）４．７ｇと、を乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１２００℃まで昇温し、１２００℃で１０時間保持し焼成を行なった。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、９５ｇの薄青色の粉末を得た。 (Synthesis of Alumina)
[Production Example 1]
A mixture was obtained by mixing 142.3 g of aluminum hydroxide (manufactured by Nippon Light Metals Co., Ltd., average particle size 1 μm), 3.7 g of silicon dioxide (manufactured by Kanto Chemical Co., Ltd., special grade), and 4.7 g of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.) in a mortar. The resulting mixture was placed in a crucible and heated to 1200°C at 5°C/min in a ceramic electric furnace, and then fired by holding at 1200°C for 10 hours. The temperature was then lowered to room temperature at 5°C/min, and the crucible was removed to obtain 95 g of a light blue powder.
　続いて、得られた前記薄青色粉末の５０ｇを０．５％アンモニア水の１５０ｍＬに分散し、分散溶液を室温（２５～３０℃）で０．５時間攪拌後、ろ過によりアンモニア水を除き、水洗浄と乾燥を行う事で、粒子表面に残存するモリブデンを除去し、４７ｇの薄青色の粉末を得た。得られた粉末はＳＥＭ観察により形状が板状であることが確認された。さらに、Ｘ線回折（ＸＲＤ）測定を行ったところ、α－アルミナに由来する鋭いピーク散乱が現れ、α結晶構造以外のアルミナ結晶系ピークは観察されなく、緻密な結晶構造を有する板状アルミナ粒子であることを確認した。また、α化率は９９％以上（ほぼ１００％）であった。 Next, 50 g of the obtained light blue powder was dispersed in 150 mL of 0.5% ammonia water, and the dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, after which the ammonia water was removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 47 g of light blue powder. The obtained powder was confirmed to have a plate-like shape by SEM observation. Furthermore, when X-ray diffraction (XRD) measurement was performed, sharp peak scattering due to α-alumina was observed, and no alumina crystal system peaks other than the α crystal structure were observed, confirming that the particles were plate-like alumina particles with a dense crystal structure. The α conversion rate was 99% or more (almost 100%).
〔製造例２〕
水酸化アルミニウム（日本軽金属株式会社製、平均粒子径２μｍ）１４２．３ｇと、二酸化珪素（関東化学株式会社製、特級）２．８ｇと、三酸化モリブデン（太陽鉱工株式会社製）４．７ｇと、を乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１２００℃まで昇温し、１２００℃で１０時間保持し焼成を行なった。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、９５ｇの薄青色の粉末を得た。 [Production Example 2]
A mixture was obtained by mixing 142.3 g of aluminum hydroxide (manufactured by Nippon Light Metals Co., Ltd., average particle size 2 μm), 2.8 g of silicon dioxide (manufactured by Kanto Chemical Co., Ltd., special grade), and 4.7 g of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.) in a mortar. The mixture was placed in a crucible and heated to 1200° C. at 5° C./min in a ceramic electric furnace, and then fired at 1200° C. for 10 hours. The temperature was then lowered to room temperature at 5° C./min, and the crucible was removed to obtain 95 g of a light blue powder.
　続いて、得られた前記薄青色粉末の５０ｇを０．５％アンモニア水の１５０ｍＬに分散し、分散溶液を室温（２５～３０℃）で０．５時間攪拌後、ろ過によりアンモニア水を除き、水洗浄と乾燥を行う事で、粒子表面に残存するモリブデンを除去し、４７ｇの薄青色の粉末を得た。得られた粉末はＳＥＭ観察により形状が多角板状であることが確認された。さらに、Ｘ線回折（ＸＲＤ）測定を行ったところ、α－アルミナに由来する鋭いピーク散乱が現れ、α結晶構造以外のアルミナ結晶系ピークは観察されなく、緻密な結晶構造を有する板状アルミナ粒子であることを確認した。また、α化率は９９％以上（ほぼ１００％）であった。 Next, 50 g of the obtained light blue powder was dispersed in 150 mL of 0.5% ammonia water, and the dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, after which the ammonia water was removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 47 g of light blue powder. The obtained powder was confirmed to have a polygonal plate shape by SEM observation. Furthermore, when X-ray diffraction (XRD) measurement was performed, sharp peak scattering due to α-alumina was observed, and no alumina crystal system peaks other than the α crystal structure were observed, confirming that the particles were plate-shaped alumina particles with a dense crystal structure. The α conversion rate was 99% or more (almost 100%).
〔製造例３〕
　水酸化アルミニウム（日本軽金属株式会社製、平均粒子径１２μｍ）５０ｇと、二酸化珪素（関東化学株式会社製、特級）０．６５ｇと、三酸化モリブデン（太陽鉱工株式会社
製）１．７２ｇと、を乳鉢で混合し、混合物を得た。得られた混合物を坩堝に入れ、セラミック電気炉にて５℃／分の条件で１２００℃まで昇温し、１２００℃で１０時間保持し焼成を行った。その後５℃／分の条件で室温まで降温後、坩堝を取り出し、３４．２ｇの薄青色の粉末を得た。得られた粉末を乳鉢で、１０６μｍ篩を通るまで解砕した。 [Production Example 3]
50 g of aluminum hydroxide (manufactured by Nippon Light Metals Co., Ltd., average particle size 12 μm), 0.65 g of silicon dioxide (manufactured by Kanto Chemical Co., Ltd., special grade), and 1.72 g of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.) were mixed in a mortar to obtain a mixture. The obtained mixture was placed in a crucible, heated to 1200° C. at 5° C./min in a ceramic electric furnace, and held at 1200° C. for 10 hours for firing. After that, the temperature was lowered to room temperature at 5° C./min, and the crucible was removed to obtain 34.2 g of a light blue powder. The obtained powder was crushed in a mortar until it passed through a 106 μm sieve.
　続いて、得られた前記薄青色粉末を０．５％アンモニア水の１５０ｍＬに分散し、分散溶液を室温（２５～３０℃）で０．５時間攪拌後、ろ過によりアンモニア水を除き、水洗浄と乾燥を行う事で、粒子表面に残存するモリブデンを除去し、３３．５ｇの薄青色の粉末を得た。得られた粉末はＳＥＭ観察により形状が板状であり、凝集体が極めて少ないことが確認された。さらに、ＸＲＤ測定を行ったところ、α－アルミナに由来する鋭いピーク散乱が現れ、α結晶構造以外のアルミナ結晶系ピークは観察されなく、緻密な結晶構造を有する板状アルミナ粒子であることを確認した。また、α化率は９９％以上（ほぼ１００％）であった。 The resulting light blue powder was then dispersed in 150 mL of 0.5% aqueous ammonia, and the dispersion was stirred at room temperature (25-30°C) for 0.5 hours. The aqueous ammonia was then removed by filtration, and the molybdenum remaining on the particle surface was removed by washing with water and drying, yielding 33.5 g of light blue powder. SEM observation of the resulting powder confirmed that it was plate-like in shape, with very few aggregates. Furthermore, XRD measurement revealed sharp peak scattering due to α-alumina, and no alumina crystal peaks other than the α crystal structure were observed, confirming that the particles were plate-like alumina particles with a dense crystal structure. The α conversion rate was 99% or more (almost 100%).
　比較用として酸化チタン粒子（タイペークＲ－８３０、石原産業株式会社製）を準備した（Ｔ－１）。 For comparison, titanium oxide particles (Typaque R-830, manufactured by Ishihara Sangyo Kaisha, Ltd.) were prepared (T-1).
（粒度分布の計測）
　板状アルミナ粒子０．０５ｇを０．２％ヘキサメタリン酸水溶液５０ｇに混合し、超音波ホモジナイザーを用いて５分間分散し、レーザー光散乱回折法粒度測定機（マイクロトラックベル社製、ＭＴ３３００ＥＸＩＩ）を用いて粒度分布の測定を行い、５０％、１００％体積平均径Ｄ５０、Ｄ１００（μｍ）を求めた。 (Measurement of particle size distribution)
0.05 g of the plate-like alumina particles was mixed with 50 g of a 0.2% aqueous hexametaphosphoric acid solution and dispersed for 5 minutes using an ultrasonic homogenizer. The particle size distribution was measured using a laser light scattering diffraction particle size measuring device (MT3300EXII, manufactured by Microtrackbell Co., Ltd.) to determine the 50% and 100% volume average diameters D50 and D100 (μm).
（平均厚さＤの計測）
　板状アルミナ粒子について、走査型電子顕微鏡（ＳＥＭ）を用いて、５０個の厚さを測定した平均値を採用し、平均厚さＤ（μｍ）とし、アスペクト比Ｄ５０／Ｄを下記の式を用いて求めた。 (Measurement of average thickness D)
For the plate-like alumina particles, the thickness of 50 particles was measured using a scanning electron microscope (SEM), and the average value was adopted as the average thickness D (μm). The aspect ratio D50/D was calculated using the following formula.
（アスペクト比Ｄ５０／Ｄ）
　アスペクト比＝板状アルミナ粒子の粒子径Ｄ５０／板状アルミナ粒子の平均厚さＤ　　 (Aspect ratio D50/D)
Aspect ratio = particle diameter D50 of plate-like alumina particles / average thickness D of plate-like alumina particles
（板状アルミナ粒子のα化率の分析）
　板状アルミナ粒子を０．５ｍｍ深さの測定試料用ホルダーにのせ、一定荷重で平らになるよう充填し、それを広角Ｘ線回析装置（株式会社リガク製Ｒｉｎｔ－Ｕｌｔｍａ）にセットし、Ｃｕ／Ｋα線、４０ｋＶ／３０ｍＡ、スキャンスピード２度／分、走査範囲１０～７０度の条件で測定を行った。α－アルミナと遷移アルミナの最強ピーク高さの比よりα化率を求めた。 (Analysis of Alpha-conversion Rate of Plate-shaped Alumina Particles)
The plate-like alumina particles were placed on a measurement sample holder with a depth of 0.5 mm, packed flat under a constant load, and then set in a wide-angle X-ray diffraction apparatus (Rigaku Corporation, Rint-Ultma) and measured under conditions of Cu/Kα radiation, 40 kV/30 mA, a scan speed of 2 degrees/min, and a scan range of 10 to 70 degrees. The α conversion rate was calculated from the ratio of the strongest peak heights of α-alumina and transition alumina.
〔製造例４～６〕
　（金属酸化物層の形成）
　上記製造例で得られた板状アルミナ粒子をイオン交換水中に分散し、撹拌しながら３号珪酸ソーダ（富士化学株式会社）を滴下した。アルミナ１００質量部に対し、酸化ケイ素３質量部となるように添加した。
　滴下後１０分撹拌し、１Ｍ硫酸を滴下し、ｐＨを６．０に調整した。その後、ろ過、イオン交換水にて洗浄し、１５０℃、５時間乾燥し、薄青色の粉末を得た。 [Production Examples 4 to 6]
(Formation of Metal Oxide Layer)
The plate-like alumina particles obtained in the above Production Example were dispersed in ion-exchanged water, and No. 3 sodium silicate (Fuji Chemical Industry Co., Ltd.) was added dropwise with stirring to give 3 parts by mass of silicon oxide per 100 parts by mass of alumina.
After the dropwise addition, the mixture was stirred for 10 minutes, and 1M sulfuric acid was added dropwise to adjust the pH to 6.0.The mixture was then filtered, washed with ion-exchanged water, and dried at 150° C. for 5 hours to obtain a light blue powder.
　実施例、比較例に用いられるフィラーは表１の通りである。 The fillers used in the examples and comparative examples are as shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

　（インキ組成物の製造）
　タイペークＲ－８３０（石原産業株式会社製）５．５質量部、プライマルＡＳＥ－６０（ダウケミカル社製）１．０質量部、精製グリセリン（新日本理化株式会社）６．５質量部、Ｊｏｎｃｒｙｌ７０Ｊ（ＢＡＳＦ社製）１１．７質量部、イオン交換水１２．９質量部を混合した。得られた混合液に表１に示すフィラーを４質量部添加し、さらに混合し、白色インキ組成物を得た。 (Production of Ink Composition)
5.5 parts by mass of Typeque R-830 (manufactured by Ishihara Sangyo Kaisha), 1.0 part by mass of Primal ASE-60 (manufactured by The Dow Chemical Company), 6.5 parts by mass of purified glycerin (manufactured by New Japan Chemical Co., Ltd.), 11.7 parts by mass of Joncryl 70J (manufactured by BASF Corporation), and 12.9 parts by mass of ion-exchanged water were mixed together. 4 parts by mass of a filler shown in Table 1 was added to the resulting mixture and further mixed to obtain a white ink composition.
　［隠蔽性の評価］
　得られた白色インキ組成物を、色画用紙（こいくろ、プラス株式会社製）にバーコータＲＤＳ２０を用いて塗膜を形成した。塗膜を一昼夜室温で乾燥させ、被塗膜面に対する隠蔽性をＬ値により判定した。Ｌ値はｓｐｅｃｔｒｏ－ｇｕｉｄｅ　４５／０　ｇｌｏｓｓ（ＢＹＫ－Ｇａｒｄｎｅｒ　ＧｍｂＨ製）にて測定した。Ｌ値８９以上を被塗膜面を十分に隠蔽しており、良好な塗膜として〇、それ未満を隠蔽性が不十分として×とした。 [Evaluation of Concealment]
The obtained white ink composition was applied to a colored drawing paper (Koikura, manufactured by PLUS Corporation) to form a coating film using a bar coater RDS20. The coating film was dried at room temperature for one day and night, and the hiding power of the coating surface was evaluated by the L value. The L value was measured using a spectro-guide 45/0 gloss (manufactured by BYK-Gardner GmbH). An L value of 89 or more was evaluated as ◯, indicating that the coating sufficiently concealed the coating surface and was good, and an L value below that was evaluated as ×, indicating that the hiding power was insufficient.
　上記評価結果を表２に示した。 The above evaluation results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

　実施例１、２および比較例１より、特定粒子径のアルミナ粒子に金属酸化物層を形成すると隠蔽性が良好となることが確認された。 Examples 1 and 2 and Comparative Example 1 confirmed that forming a metal oxide layer on alumina particles of a specific particle size provides good hiding power.
　実施例１、２および比較例２より、金属酸化物層を形成することにより隠蔽性が良好となることが確認された。 Examples 1 and 2 and Comparative Example 2 confirmed that forming a metal oxide layer improves hiding properties.
　実施例１、２および比較例３より、金属酸化物層を形成したアルミナ粒子は酸化チタン粒子単独よりも隠蔽性が良好となることが確認された。 Examples 1 and 2 and Comparative Example 3 confirmed that alumina particles with a metal oxide layer formed thereon have better hiding power than titanium oxide particles alone.

Claims (5)

  1. 　レーザー回折式粒度分布測定における体積基準のメディアン径Ｄ５０が１μｍ以上５μｍ以下、アスペクト比が１０以上５０以下であり、かつ金属酸化物層を表層に有する板状アルミナ粒子を含有するインキ組成物。 An ink composition containing plate-like alumina particles having a volume-based median diameter D50 of 1 μm or more and 5 μm or less, an aspect ratio of 10 or more and 50 or less, and a metal oxide layer on the surface, as measured by laser diffraction particle size distribution measurement.
  2. 　前記板状アルミナ粒子のレーザー回折式粒度分布測定における体積基準の累積粒子径Ｄ１００が１５μｍ以下である請求項１に記載のインキ組成物。 The ink composition according to claim 1, wherein the plate-like alumina particles have a volume-based cumulative particle diameter D100 of 15 μm or less as measured by laser diffraction particle size distribution measurement.
  3. 　前記金属酸化物が二酸化珪素である請求項１に記載のインキ組成物。 The ink composition according to claim 1, wherein the metal oxide is silicon dioxide.
  4. 　さらに酸化チタン粒子を含む請求項１に記載のインキ組成物。 The ink composition according to claim 1, further comprising titanium oxide particles.
  5. 　インキ組成物における板状アルミナ粒子の含有量がインキ組成物全量に対して１質量％以上１５質量％以下である請求項１に記載のインキ組成物。 The ink composition according to claim 1, wherein the content of the platelet alumina particles in the ink composition is 1% by mass or more and 15% by mass or less based on the total amount of the ink composition.
PCT/JP2024/007464 2023-03-14 2024-02-29 Ink composition containing plate-shaped alumina WO2024190432A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007040206A1 (en) * 2005-10-03 2007-04-12 Dainichiseika Color & Chemicals Mfg. Co., Ltd. Pearlescent pigment, process for producing the same, coating material composition and coating film composition
JP2010507009A (en) * 2006-10-18 2010-03-04 ビー・エイ・エス・エフ、コーポレーション Multi-layer pigment showing color transfer
JP2013108089A (en) * 2000-12-07 2013-06-06 Merck Patent Gmbh Silver luster pigment
JP2021024928A (en) * 2019-08-02 2021-02-22 株式会社サクラクレパス Aqueous ink composition

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013108089A (en) * 2000-12-07 2013-06-06 Merck Patent Gmbh Silver luster pigment
WO2007040206A1 (en) * 2005-10-03 2007-04-12 Dainichiseika Color & Chemicals Mfg. Co., Ltd. Pearlescent pigment, process for producing the same, coating material composition and coating film composition
JP2010507009A (en) * 2006-10-18 2010-03-04 ビー・エイ・エス・エフ、コーポレーション Multi-layer pigment showing color transfer
JP2021024928A (en) * 2019-08-02 2021-02-22 株式会社サクラクレパス Aqueous ink composition

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