JPH08209110A - Infrared absorbing material and its production - Google Patents

Abstract

PURPOSE: To obtain an ultraviolet absorbing material made of YbPO4 which material absorbs light only in the infrared range with excellent absorption properties in the near infrared range in particular and does not absorb light in the visible light range while having a good affinity for an ink. CONSTITUTION: This ultraviolet absorbing material is high-crystallinity YbPO4 particles having a particle size of at most 0.5μm. The YbPO4 particles may be surface-treated with a coupling agent. The treatment of surface can prevent aggregation of the particles, and can improve the chemical stability of the particle surfaces against solvents, acids, bases, etc., and the physical strength of the particles. For preparation of the YbPO4 particles, an ytterbium alkoxide and a phosphoric alkoxide are hydrolyzed. The hydrolysis is pref. effected in the presence of ultrasonic waves because the hydrolysis reaction is promoted. Tributoxytterbium and phosphoric tributoxide are pref. used as the alkoxides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is substantially invisible to the naked eye, but is a material for forming optically identifiable code patterns and marks such as detection marks by absorbing infrared rays. It is a material with excellent infrared absorption used as, consisting of fine particles,
The present invention relates to an infrared absorbing material excellent in inking property and a method for producing the same. In particular, the present invention relates to an infrared absorbing material having excellent absorption characteristics in the near infrared region around 975 nm.
Further, the present invention relates to an ink and an invisible pattern using the infrared absorbing material.

[0002]

2. Description of the Related Art In recent years, bar codes as code patterns using optical reading have been widely used mainly for physical distribution management systems. For example, barcodes are widely used as optical data carriers such as JAN codes for POS (point of sale) systems, delivery slips, packing slips, and barcode tags for delivery.

Light source light for optical reading of these conventional bar codes is 650 nm, 800 nm or 950 nm.
A semiconductor laser or a light emitting diode having an emission wavelength in the vicinity is mainly used. Therefore, since the wavelength range of the light source is restricted, the bar code has an absorption characteristic in the ink using carbon black having an absorption band in the visible light range or in the red / infrared wavelength range of the cyan / green system. Printed or printed with ink.

The bar code printing method is letterpress, offset, flexo, gravure or silk printing, and is mainly applied to mass printing called source marking. Bar code printing methods are dot impact, thermal transfer, direct thermal, electrophotography, inkjet printing, etc., and are mainly applied to individual printing called in-store marking or manufacturing of small lot information code labels. .

However, there is a strong demand for eliminating such visible information codes because they impose design restrictions on printed matter. Therefore, an attempt has been made to make the information code transparent by printing or printing an ink having no absorption band in the visible light region to make visual judgment difficult.

As one of the attempts to make transparent, it is known to form an infrared pattern by using an ink which mainly absorbs infrared rays outside the visible light region [see, for example, Japanese Patent Laid-Open No. 60-260674). Kaisho 61-86752,
JP-A-63-116286, JP-A-3-154187
Japanese Patent Application Laid-Open No. 3-227378, Japanese Patent Application Laid-Open No. 3-27538.
9, JP-A-4-70349, and JP-A-5-93160.
No. 6-2997889].

[0007]

Dyes having an absorption region in the infrared region which have been conventionally used include cyanine dyes, phthalocyanine dyes, naphthoquinone dyes, anthraquinone dyes, zirol dyes, triphenylmethane dyes and the like. is there. However, these are cyan colors because they have an absorption band in the wavelength region of 600 nm or more, or have a slightly reddish cream color because they have 30-40% absorption in the visible region (380 nm-700 nm). There is. Therefore, it was not possible to form a completely transparent barcode. Further, since these dyes are dyes, there is a drawback that light resistance as an ID carrier cannot be expected. In addition, there is also one that uses a cyan filter glass as an infrared absorbing pigment, but in this case, the glass contains Cu ²⁺ ions, and since the absorption starts from 550 nm, a cyan color is exhibited. Under these circumstances, in order to provide a transparent invisible barcode, it is desired to provide a material that absorbs infrared rays but does not absorb visible rays.

By the way, there is a field in which an infrared absorbing material can be used in a field other than the infrared absorbing code pattern. For example, when an image is formed on a transparent sheet for an over head projector (OHP) by a copying machine using an optical detection method, the transparent sheet for the transparent sheet is set in order to set the paper feed timing of the transparent sheet. A detection mark is provided at the edge. Optical detection is, for example, L
It is considered that an ED and a phototransistor are combined and an infrared absorbing material can be used as a detection mark.

However, conventionally, for example, Japanese Patent Laid-Open No. 3-99
As described in Japanese Patent No. 878, the detection mark was formed of an opaque material. However, the opaque detection mark is displayed on the OHP together with the target image, which makes it difficult to view the displayed image. Therefore, if a detection mark that is transparent but can be optically detected is provided, such a defect is eliminated.

Therefore, the present inventor previously found YbPO ₄ (ytterbium phosphate) as a new material having absorption only in the infrared region and not absorbing in the visible light region, and applied for a patent. 7-53946]. However, Y
When bPO ₄ is used as the ink pigment, fine particles are required. This is because the pigment is better adapted to the ink and the thickness of the printing layer of the ink is thinner. However, the particle size of YbPO ₄ obtained by the method described in the above application is several tens of μm, and even if it is pulverized, the average particle size is about 1 μm. Further, it was practically difficult to grind so that the particle diameter would be larger than that. Furthermore, YbPO ₄
Although the cause is not clear by crushing, there was also a problem that the absorption characteristics in the near-infrared region were significantly reduced.

Therefore, an object of the present invention is to use a material Y which absorbs only in the infrared region and does not absorb in the visible light region.
YbPO, which is bPO ₄ (ytterbium phosphate), is a fine particle that has excellent absorption characteristics in the near infrared region, has good compatibility with ink, and is compatible with thin printing layers.
An object is to provide an infrared absorbing material composed of ₄ and a manufacturing method thereof.

Further, the object of the present invention is invisible to the naked eye using the above infrared absorbing material composed of YbPO ₄ , and also has infrared absorbing characteristics, weather resistance, light resistance, inking characteristics, printability, printability and It is to provide an ink having excellent weather resistance.

Another object of the present invention is to provide a material which absorbs infrared rays but not visible rays in order to provide a transparent detection mark that can be attached to a transparent OHP sheet. That is, it is an object of the present invention to provide a material that can be optically detected by absorbing infrared rays and can provide a transparent detection mark by not absorbing visible rays, and an ink using the material.

[0014]

The present invention relates to an infrared absorbing material characterized by comprising YbPO ₄ particles having a high crystallinity and a particle diameter of 0.5 μm or less. Further, the present invention relates to an infrared absorbing material having high crystallinity, a particle diameter of 0.5 μm or less, and composed of YbPO ₄ particles surface-treated with a coupling agent.

Furthermore, the present invention hydrolyzes ytterbium alkoxide and phosphoric acid alkoxide to produce YbPO ₄
The present invention relates to a method for producing an infrared absorbing material composed of YbPO ₄ particles having a high crystallinity and a particle diameter of 0.5 μm or less, which is characterized by producing particles. In addition, the present invention is characterized by reacting the YbPO ₄ particles obtained by the above method with a coupling agent, which has high crystallinity and a particle diameter of 0.5 μm or less, and a surface treatment with the coupling agent. For producing an infrared absorbing material composed of the above YbPO ₄ particles. The present invention will be described below.

The infrared absorbing material of the present invention is YbPO ₄ particles having a high crystallinity and a particle diameter of 0.5 μm or less. In the present invention, the high crystallinity of YbPO ₄ particles means that the diffraction X-ray spectrum measured using an X-ray diffractometer has a crystallinity such that the diffraction peak does not become broad like amorphous and the spectrum can be read. Is the meaning of. More specifically, the case where the peak at which the main peak 2θ of the diffraction X-ray spectrum of YbPO ₄ is about 26 is 10 times or more the noise width of the background is “high crystallinity” in the present invention. For example, as shown in FIG. 3, the YbPO ₄ infrared absorbing material of the present invention obtained in Example 1 has a ratio of the noise width between the main peak and the background of 100 times or more, and is extremely “highly crystalline” YbPO ₄ Is.

Further, the infrared absorbing material of the present invention is YbPO ₄ particles having a particle size (secondary particle size) of 0.5 μm or less. The particles include primary particles and secondary particles, and ordinary particles exist as secondary particles which are aggregates of primary particles. When the pigment is made into an ink, the particle size of the secondary particles becomes a problem. Therefore, the infrared absorbing material of the present invention has a particle size (secondary particle size) of 1 μm or less, and is excellent in ink formation characteristics and the like. The particle size of the YbPO ₄ particles is preferably in the range of 5 to 500 nm, more preferably 10
Is in the range of up to 200 nm. Particles having a particle diameter of 200 nm or less do not absorb visible light, and an infrared absorbing material made of such particles is preferable from the viewpoint of high transparency to visible light.

The infrared absorbing material according to another embodiment of the present invention has high crystallinity, a particle diameter of 0.5 μm or less, and is composed of YbPO ₄ particles surface-treated with a coupling agent. The coupling agent is not particularly limited as long as it can bond with the YbPO ₄ particles and the resin that serves as the ink vehicle. For example,
Examples thereof include silane compounds, titanium compounds, zirconium compounds, aluminum compounds and metal chelate compounds. In particular, the chemical properties are stable (strong resistance to solvents), the physical strength is strong, and various functional groups with good adhesiveness to the ink vehicle are added, so that the degree of selection is great. From the above, a silane coupling agent is preferable.

The following can be exemplified as the silane coupling agent. However, it goes without saying that the present invention is not limited to these. Tetramethoxysilane (TMOS), γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, aminosilane, γ
-Methacryloxypropyltrimethoxysilane, N-β
-(N-Vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane ・ hydrochloride, γ-glycidoxypropyltrimethoxysilane, aminosilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane , Vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane,
Hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane.

Further, in addition to the silane coupling agent, a zirconium coupling agent, an aluminum coupling agent, and a titanium coupling agent can be used. Yb
The amount of the coupling agent with respect to the PO ₄ particles is YbPO ₄
Although it can be appropriately determined depending on the particle size of the particles and the type of the coupling agent, for example, the range of 0.1 to 10 parts by weight of the coupling agent is generally suitable for 100 parts by weight of the YbPO ₄ particles.

The infrared absorbing material of the present invention is 975n
It has a very strong absorption peak in the near infrared region near m.
For example, FIG. 1 shows the reflectance spectrum of the infrared absorbing material of the present invention obtained in Example 1. This infrared absorbing material does not substantially absorb in the visible light region of 400 to 700 nm, and has a very strong absorption peak in the near infrared region near 975 nm.

The infrared absorbing material of the present invention can be produced by hydrolyzing the ytterbium alkoxide and the phosphoric acid alkoxide to produce YbPO ₄ particles. The ytterbium alkoxide and the alkoxide of phosphoric acid alkoxide are preferably alkoxides having a low solubility in water and having 4 or more carbon atoms, from the viewpoints of preventing particle association of ultrafine particles and facilitating surface treatment with a coupling agent. . For example, as an alkoxide,
Butoxide can be mentioned. Therefore, for example, tributoxy ytterbium can be used as the ytterbium alkoxide. As the phosphoric acid alkoxide, for example, tributoxide phosphoric acid can be used. Tributoxide phosphoric acid [PO ₄ (C ₄ H ₉ O) ₃ ]
Is commercially available (for example, manufactured by Kojundo Chemical Laboratory Co., Ltd.) and is easily available.

Further, the reaction product of orthophosphoric acid (H ₃ PO ₄ ) and alcohol can be used as the phosphoric acid alkoxide. Orthophosphoric acid usually contains about 15% water,
Such an orthophosphoric acid is dissolved in alcohol to form a phosphoric acid alkoxide, and the obtained product is directly used as Y
It can be used for bPO ₄ particle formation reaction. By using the above-mentioned reaction product of orthophosphoric acid and alcohol as the phosphoric acid alkoxide, YbPO ₄ particle generation reaction by hydrolysis, which is a subsequent reaction, can be achieved.
₄ has the advantage of increasing the crystallization rate and increasing the yield of YbPO ₄ particles. As the alcohol, those having low solubility in water are preferable, for example, having 3 carbon atoms.
The above alcohols are suitable. The use of an alcohol having 3 or more carbon atoms also has the advantage of preventing the association of the YbPO ₄ particles in the YbPO ₄ particle formation reaction and facilitating the surface treatment with the coupling agent. Further, a linear alcohol is preferable from the viewpoint of easy elimination in the hydrolysis reaction which is a subsequent reaction. From this point of view, as the alcohol, for example, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol and the like can be used.

Further, tributoxy ytterbium [Yb
(C ₄ H ₉ O) ₃ ] is, for example, 1 mol of ytterbium oxide [Yb ₂ O ₃ ] fine powder (commercial product, for example, manufactured by Shin-Etsu Chemical Co., Ltd.) and 6 mol of acetic acid are vacuum dehydrated to yield ytterbium acetate. the resulting [Yb (CH ₃ COO) _3] as a precipitate, but still there this acetate ytterbium and tributoxyethyl barium _{[Ba (C 4 H 9 O)} 2 ] (also commercially available, n-
It can also be obtained by dissolving metal barium in butanol) and refluxed in a solvent (for example, n-butanol).

The above reaction and hydrolysis reaction are represented by chemical formulas as follows. Yb ₂ O ₃ + 6CH ₃ COOH → 2Yb (CH ₃ CO
O) ₃ (precipitation) + 3H ₂ O 2Yb (CH ₃ COO) ₃ + 3Ba (C ₄ H ₉ O) ₂ →
2Yb (C ₄ H ₉ O) ₃ + 3Ba (CH ₃ COO) ₂ Yb (C ₄ H ₉ O) ₃ + PO ₄ (C ₄ H ₉ O) ₃ → Yb
PO ₄ (crystal) + 6C ₄ H ₉ OH

From the viewpoint of accelerating the hydrolysis reaction, it is preferable to carry out the lower hydrolysis in the presence of ultrasonic waves. The frequency of the ultrasonic wave is, for example, 1 to 20 from the viewpoint that energy is sufficient and it is easy to secure the ultrasonic wave generation source.
A suitable range is 00 kHz. It is preferably in the range of 5 to 100 kHz. Further, it is preferable that an alkali catalyst is present in the above hydrolysis from the viewpoint of promoting crystallization. Examples of the alkaline catalyst include ammonia. The amount of the alkali catalyst can be appropriately determined in consideration of the type of the catalyst and the like, but in the case of ammonia, for example, it is suitable to be in the range of 10 ⁻⁶ to 10 ⁻² molar equivalent. Preferably 10
It is in the range of ^-5 to 10 ^-3 molar equivalent.

Further, the above-mentioned hydrolysis is suitably carried out in the presence of a solvent, and examples of such a solvent include benzene, toluene, butanol, propanol, hexanol, octanol, nonanol, decanol or a mixed solvent thereof. be able to. In addition, a small amount of water is added for hydrolysis. In addition, it is appropriate that the hydrolysis temperature is in the range of 0 ° C to 50 ° C from the viewpoint of efficient transmission of ultrasonic waves. Further, the reaction time can be appropriately determined in consideration of the reaction temperature, the amount of catalyst, ultrasonic waves, the carbon number of the alcohol of the alkoxide, etc.
A range of 0 minutes to 10 hours is suitable.

By the above hydrolysis, 0.5 μm of the present invention is obtained.
YbPO ₄ particles having the following particle size can be obtained. The particles are further surface-treated with a coupling agent for the purpose of preventing agglomeration and maintaining a desired particle size and for improving the chemical stability and physical strength of the particle surface against solvents, acids, bases and the like. . The surface treatment is preferably carried out in the same reaction vessel after completion of the above hydrolysis. The surface treatment is carried out by adding and mixing in a solvent in which the YbPO ₄ particles are dispersed, thereby selectively hydrolyzing on the particle surface with a small amount of water adsorbed on the surface of the YbPO ₄ particles, preferably water equivalent to the alcohol of the alkoxide. It can be decomposed and surface treated. The YbPO ₄ particles obtained by the surface treatment can be easily recovered as a wet cake from the solvent by centrifugation or the like. The obtained wet cake can be used as it is for ink production. However, it can be dried if necessary.

Yb ^{3+ in} YbPO ₄ particles has an absorption band based on the transition of ² F _7/2 → ³ F _5/2 of Yb ³⁺ in the infrared region in the ionic state. Further, this absorption is not colored because it does not become broad and does not have absorption in the visible region, unlike coloring due to a transition metal ion.

The infrared absorbing material of the present invention having the above characteristics remarkably absorbs the irradiation light in the infrared region having a peak at about 975 nm as shown in FIG.
It has no absorption in the visible region of 00 nm. Therefore, when a bar code is formed with ink or the like using the infrared absorbing material of the present invention, a bar portion (printing portion) that absorbs,
Between the reflection space and the non-printed area, the density of reflected light of absorption / reflection of irradiation infrared light is formed, and the barcode signal can be read, but it cannot be visually recognized with the naked eye. . Furthermore, when a detection mark is formed with ink or the like using the infrared absorbing material of the present invention, absorption / reflection of irradiation infrared light is prevented between the detection mark (printed portion) for absorption and the non-printed portion for reflection. The shade of reflected light is formed, and the detection mark is recognized, but it is not visible to the naked eye.

The infrared absorbing material of the present invention is used as an offset ink for offset printing, thermal transfer printing, inject printing, electrophotographic printing, which is a printing method suitable for printing a code pattern among marks.
When used as a pigment of a thermal transfer ribbon ink, an inkjet ink, or a toner ink, the infrared absorbing material of the present invention has an average particle diameter of 0.01 μm to 0.1 μm and a maximum particle diameter of 0.5 μm or less. It is preferably a powder. The printed film thickness or the printed film thickness obtained by the above method is usually about 1 to 2 μm, and at most 3
Since it is about μm, by setting the average particle diameter of the infrared absorbing material to the submicron order within the above range,
This is because uneven printing can be suppressed. The same applies to the gravure ink for gravure printing the detection mark.

Further, in consideration of the ink characteristics, for offset inks, thermal transfer ribbon inks, and toner inks whose binder component is non-polar, a lipophilic coating is applied to the surface of the powder of the infrared absorbing material to form an ink binder. It is preferable to improve the dispersibility of the infrared absorbing material particles. By improving the dispersibility, the formed mark can be read well.

That is, in the offset printing, it is possible to prevent the infrared absorbing material powder from being deposited from the ink during printing, and the occurrence of a missing state where the infrared absorbing portion is not printed. Further, in the case of the thermal transfer ribbon, it is possible to obtain a uniform ribbon coating of the coating layer, and it is possible to prevent transfer failure during printing. Furthermore, even for toner for electrophotographic prints,
The infrared ray absorbing material powder content of the toner ink can be kept uniform, and a mark having a stable absorption level can be obtained.

The refractive index of YbPO ₄ was measured and found to be 1.505. From this, it is suitable that the ink vehicle used when the YbPO ₄ which is the infrared absorbing material of the present invention is made into an ink does not have a large difference in refractive index from YbPO ₄ . From such a viewpoint, as the above-mentioned ink vehicle, one having a refractive index in the range of 1.3 to 1.7 is suitable.

In the offset and letterpress inks of the present invention, the resin constituting the vehicle is generally a natural resin such as protein, rubber, celluloses, shellac, copal, starch, rosin, vinyl resin, acrylic resin. Thermoplastic resin such as resin, styrene resin, polyolefin resin, novolac type phenol resin, etc., thermosetting resin such as resole type phenol resin, urea resin, melamine resin, polyurethane resin, epoxy, unsaturated polyester, etc. . Further, in the vehicle, if necessary, a plasticizer for stabilizing the flexibility and strength of the printed film, a solvent for adjusting viscosity and drying property, and an auxiliary agent for drying, viscosity, dispersibility, various reaction agents, etc. Can be added as appropriate.

However, since it is not desirable that the formed mark adsorb contaminants by the oil and fat component, it is preferable to use a photopolymerization curable or electron beam curable ink that does not use the oil and fat component that is liquid at room temperature. To form. The main component of the cured product of these inks is an acrylic resin. Therefore, the ink contains an alkyl monomer, and specific examples thereof include the following acrylic monomers that are commercially available.

As the monofunctional acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl EO adduct acrylate, ethoxydiethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, caprolactone adduct of 2-hydroxyethyl acrylate, 2- Phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, nonylphenol EO adduct acrylate,
Acrylate obtained by adding caprolactone to nonylphenol EO adduct, 2-hydroxy-3-phenoxypropyl acrylate, tetrahydrofurfuryl acrylate, furofuryl alcohol caprolactone adduct acrylate, acryloylmorpholine, dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentyl acrylate Pentenyloxyethyl acrylate, isobornyl acrylate, acrylate of caprolactone adduct of 4,4-dimethyl-1,3-dioxolane, acrylate of caprolactone adduct of 3-methyl-5,5-dimethyl-1,3-dioxolane, etc. Can be used.

On the other hand, as the polyfunctional acrylate, hexanediol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, hydroxypivalic acid neopentyl glycol ester diacrylate, hydroxypivalic acid neopentyl glycol ester. Diacrylate of caprolactone adduct of
Acrylic acid adduct of diglycidyl ether of 1,6-hexanediol, diacrylate of acetal compound of hydroxypivalaldehyde and trimethylolpropane, 2,2-bis [4- (acryloyloxydiethoxy) phenyl] propane, 2,2-bis [4- (acryloyloxydiethoxy, phenyl] methane, hydrogenated bisphenol A ethylene oxide adduct diacrylate, tricyclodecane dimethanol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, Trimethylol propane propylene oxide adduct triacrylate, glycerin propylene oxide adduct triacrylate, dipentaerythritol hexaacrylate / pentaacrylate mixture, dipentaery Lower fatty acids and esters of acrylic acid Lithol, dipentaerythritol caprolactone adduct acrylate, tris (acryloyloxyethyl) isocyanurate, and 2-acryloyloxyethyl phosphate may be used.

Inks made of these resins or monomers are solvent-free, and undergo a chain polymerization reaction upon irradiation with electromagnetic waves or electron beams to cure. Among these, for the ultraviolet irradiation type, a photopolymerization initiator and, if necessary, a polymerization inhibitor, a chain transfer agent and the like as a sensitizer and an auxiliary agent are added.

As the photopolymerization initiator, 1) direct photolysis type arylalkylketone, oxime ketone, acylphosphine oxide, etc. 2) radical polymerization type benzophenone derivative, thioxanthone derivative, etc.
3) There are aryl diazonium salts, aryl iodonium salts, aryl sulfonium salts, aryl acetophenones, etc. as the cationic polymerization reaction type, and in addition, 4) energy transfer type, 5) photoredox type, and 6) electron transfer type are used. obtain.

For the electron beam curing type, the same resins or monomers as those used in the ultraviolet irradiation type described above are used, and a photopolymerization initiator is not required, and various auxiliaries can be added if necessary.

The ink jet ink may contain water and an aqueous organic solvent in addition to the infrared absorbing material powder of the present invention and the vehicle. The water may have a purity of ion-exchanged water or higher.

The water-soluble organic solvent is used for the purpose of preventing the ink from drying and imparting penetrability, for example, ethylene glycol,
Polyhydric alcohols such as diethylene glycol, polyethylene glycol and glycerin: N-alkylpyrrolidones: Esters such as ethyl acetate and amyl acetate: Lower alcohols such as methanol, ethanol, propanol and butanol: ethylene oxide of methanol, butanol and phenol Alternatively, glycol ethers such as propylene oxide adducts can be used. These water-soluble organic solvents are not limited to the above-mentioned solvent examples, and may be used alone or in a plurality in consideration of hygroscopicity, moisture retention, dye solubility and penetrability of the solvent, ink viscosity and freezing point. Used in. The amount of the water-soluble organic solvent used is preferably in the range of 0.1 to 70% by weight of the ink.

In order to satisfy various conditions required for the system of the ink jet recording apparatus, it is possible to add additives conventionally known as ink components, if necessary. Examples of these additives include alcohol amines as pH adjusters, ammonium salts, metal hydroxides: organic salts as resistivity adjusters, inorganic salts: antioxidants: antiseptics: fungicides: sequestering agents. Examples of the chelating agent and the like.

In addition to the above composition, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, styrene acrylic acid resin, styrene maleic acid resin, etc. are added to the extent that clogging of the jetting nozzle portion and change in the ink discharge direction do not occur. A water-soluble resin can also be added.

In addition to the infrared absorbing material powder of the present invention, the thermal transfer ribbon ink and the gravure ink and the screen ink for printing the detection mark are blended with a synthetic resin as a vehicle, a wax, and if necessary, a solvent and a colorant. And prepare. As the synthetic resin, an appropriate one is used alone or as a mixture in consideration of the voltage and melting point of the thermal head. Specific examples include polyethylene, polystyrene, polypropylene, polybutyne, petroleum resin,
Vinyl chloride resin, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose plastic, nitrocellulose, polyacetal, and the like. The wax can be appropriately selected and used from beeswax, touch wax, ivowa wax, wool wax, shellac wax, carnauba wax, montan wax, paraffin wax, candelilla wax, betorolactam, microcrystalline wax and the like.

The solvent is used when the thermal transfer ribbon ink composition is made into an ink which can be applied by a usual printing method. Benzene, xylene, toluene, trichlene, white spirit, ethyl acetate, n-butyl acetate, methanol,
Examples are ethanol, isopropanol, n-butanol, ethylcyclohexane, methyl ethyl ketone, ethyl cellosolve, butyl cellosolve, cyclohexanone. In particular, methyl ethyl ketone, ethyl acetate, methanol, ethanol, xylene and toluene are preferably used.

The thermal transfer ribbon ink may be a thermal transfer sheet provided on a base film. As a material for the base film, a commonly used material may be used. Specifically, polyester, polypropylene, cellophane,
Films of plastics such as acetate and polycarbonate, and papers such as condenser paper and paraffin paper can be used.

In the case of the electrophotographic system, the constituent components of the toner ink are the infrared absorbing material powder of the present invention, a vehicle, and if necessary, a charge control agent, an offset preventing agent, and an external additive (fluidizing agent). Examples of the vehicle include thermoplastic resins such as polystyrene resins, styrene-acrylic copolymers, styrene-butadiene copolymers, polyester resins, epoxy resins and polyolefin resins. Regarding the contact charging property, a compound containing an electron-donating substituent such as an amino group is likely to be positively charged, and a compound having an electron-accepting substituent such as fluorine or a carboxyl group is likely to be negatively charged.

As the charge control agent, a nigrosine dye, a quaternary ammonium compound or the like is used for positive charging, and a metal complex of alkylsalicylic acid or an azo metal-containing complex is used for the negatively charged toner. As other additives, low molecular weight polyethylene, low molecular weight polypropylene, etc. are used as offset preventing agents for heat roll fixing.

Further, the ink of the present invention may contain an irreversible decolorizable colorant in the composition. The decolorizable colorant in this case is a colorant that maintains a visible state in the visible light range and irreversibly changes to an invisible state by an operation for decoloring, for example, an operation such as irradiation of near infrared rays. When a code pattern is formed with an ink composition containing such a color erasable colorant, the printed image can be visually identified and the printing accuracy can be improved. After that, the code pattern can be changed to the invisible state by performing the erasing operation.

As a specific example, the coexistence of an erasable colorant IR820B (manufactured by Showa Denko) represented by the following structural formula, a cyanine dye, and an organic boron ammonium salt such as tetrabutylammonium / butyltriphenylborate. There are some that absorb near-infrared light and couple with each other to become irreversibly transparent.

[0053]

Embedded image

The infrared absorbing material of the present invention exhibits a sharp absorption at about 975 nm as shown in FIG. Therefore, a code pattern or a detection mark formed using this infrared absorbing material is used as an irradiation light source, for example, for pulsed infrared light of a semiconductor laser or infrared light emission of a light emitting diode.
When a lens coated with a bandpass filter that absorbs light of 00 nm or less and light of 1000 nm or more is attached to the light receiving sensor side and infrared rays are irradiated, it can be identified as a sharp absorption signal.

The present invention includes an invisible pattern and an invisible information pattern using the infrared absorbing material. Here, the pattern includes a non-information pattern and an information pattern. The non-information pattern may be a detection mark or the like. The information pattern may be a code pattern. As a code pattern,
A barcode can be exemplified, and the barcode may be a two-dimensional code or the like other than the one-dimensional barcode. In particular, the present invention is effective for a two-dimensional code because a high resolution can be obtained.

The detection mark is a mark provided for setting the paper feed timing of a transparent sheet which is not optically detected when an image is formed by a copying machine using an optical detection method. . The shape of the detection mark and the position of the detection mark on the transparent sheet are not particularly limited. For example, JP-A-58-106550 and JP-A-58-1
No. 05157, 59-7367 and JP-A-3-99.
A detection mark as described in Japanese Patent No. 878 can be used.

[0057]

EXAMPLES The present invention will be further described below based on examples.

Example 1 Ytterbium oxide [Yb ₂ O ₃ ] fine powder (manufactured by Shin-Etsu Chemical Co., Ltd.) was reacted with 7.9 parts by weight and 7.2 parts by weight of acetic acid for 30 minutes under reflux at 140 ° C. for 30 minutes to yield ytterbium acetate [Yb ( C
H ₃ COO) ₃ ] .nH ₂ O was obtained as a precipitate, and 90
Vacuum drying was performed at 12 ° C for 12 hours to obtain anhydrous powder. Next, the obtained ytterbium acetate anhydrous powder and 17.9 parts by weight of tri-n-
Butoxybarium [Ba (C ₄ H ₉ O) ₂ ] (prepared by dissolving metallic barium (manufactured by Junsei Kagaku) in n-butanol)
And 1 in 1000 parts by weight of n-butanol at 160 ° C.
The mixture was refluxed for a period of time to obtain a tri-n-butoxy ytterbium [Yb (C ₄ H ₉ O) ₃ ] solution, which was separated by barium acetate precipitation and centrifugation (3500 rpm, 30 minutes). 1000 parts by weight and 1000 parts by weight of a solution prepared by dissolving 1000 parts by weight of the above-obtained tri-n-butoxy ytterbium solution and 4.2 parts by weight of tri-n-butoxide phosphate in 100 parts by weight of n-butanol, respectively. Toluene is added to make 50% butanol solvent and then mixed,
Water with addition of 1 × 10 ⁻⁴ parts by weight of ammonia 1.6
2 parts by weight was added, and the hydrolysis reaction was performed while applying ultrasonic waves of 20 kHz. As a result, after 30 minutes, ytterbium phosphate was produced as transparent fine crystals.

Then, in a solvent containing ytterbium phosphate, Si (CH ₃ O) ₃ (C which is a silane coupling agent is used.
_{H 2 = C (CH 3)} -COOCH the surface treatment was performed by adding 1 part by weight relative to the ₂ CH ₂ CH ₂₎ 100 parts by weight of phosphoric acid ytterbium. The surface-treated ytterbium phosphate was recovered as a wet cake (solid content 18%) by centrifugation (3500 rpm, 30 minutes) (yield: 74%).

FIG. 1 shows the results of measuring the spectral reflectance of the YbPO ₄ wet cake obtained above. The measurement was carried out using a self-recording spectrophotometer UV3101PC manufactured by Shimadzu Corporation, with the reflectance of barium sulfate being 100%. Further, the particle size of the crystals in the YbPO ₄ wet cake obtained above was measured by a particle size distribution meter (Photal particle size distribution analyzer PAR-III). The result is shown in FIG. As a result, the wet cake is about 70-48.
It can be seen that YbPO ₄ crystals having a particle size of 0 nm are included. Further, the X-ray diffraction pattern of the crystal in the wet cake of YbPO ₄ obtained above was measured (measuring device: Rigaku, RINT-1500) and shown in FIG. As a result, it is found that this crystal has extremely high crystallinity.

Comparative Example 1 Ytterbium oxide [Yb ₂ O ₃ ] powder (commercially available) 10
0 part by weight and 100 parts by weight of phosphorus pentoxide (P ₂ O ₅ ) powder were mixed, and the mixture was put into a platinum crucible and heated and melted in an electric furnace heated to 1300 ° C. for 2 hours. Then 200
It was annealed at a rate of ° C / hr to obtain a solid. When this solid was pulverized with an alumina ball mill, the average particle size was about 20.
μm. Further, this solid was pulverized to obtain a powder having an average particle diameter of about 1 μm. The spectral reflectance and X-ray diffraction pattern of the solid having an average particle diameter of about 20 μm and the powder having an average particle diameter of about 1 μm are shown in FIGS. 4 and 5, respectively. As a result, it is found that the pulverization reduces the absorption in the near infrared region. Further, it can be seen that the X-ray diffraction pattern has large background noise and almost no crystallinity in any case.

Example 2 Tri-n-butoxyytterbium solution (toluene-butanol 1: 1 solution) 1000 was prepared in the same manner as in Example 1.
Parts by weight were obtained. Apart from this, orthophosphoric acid (water content 1
12 parts by weight (5%) was dissolved in 200 parts by weight of 200 parts by weight of a toluene-butanol 1: 1 solution to synthesize tributoxide phosphate. The obtained reaction solution and the above-mentioned tri-n-butoxyytterbium solution were mixed, and further 1 × 10
-1.62 parts by weight of water containing ⁴ parts by weight of ammonia was added, and the hydrolysis reaction was carried out while applying an ultrasonic wave of 20 kHz. As a result, after 30 minutes, ytterbium phosphate was produced as transparent fine crystals.

Then, in a solvent containing ytterbium phosphate, Si (CH ₃ O) ₃ (C which is a silane coupling agent is used.
_{H 2 = C (CH 3)} -COOCH the surface treatment was performed by adding 1 part by weight relative to the ₂ CH ₂ CH ₂₎ 100 parts by weight of phosphoric acid ytterbium. The surface-treated ytterbium phosphate was recovered as a wet cake (solid content 20%) by centrifugation (3500 rpm, 30 minutes) (yield: 85%).

The spectral reflectance of the YbPO ₄ wet cake obtained above was measured in the same manner as in Example 1. FIG. 6 shows the results. Further, as a result of measuring the particle size and X-ray diffraction pattern of the crystals in the obtained YbPO ₄ wet cake, almost the same results as the results of Example 1 were obtained.

Example 3 60 parts by weight of the wet cake (solid content: 18%) obtained in Example 1 was added with 2 parts by weight of an acrylate monomer, 4 parts by weight of an acrylate oligomer, 3 parts by weight of a wax and 0.
Add to and mix with 5 parts by weight of offset vehicle,
Flushing was performed in a vacuum blender to remove the solvent component, and an offset ink was prepared. This ink was offset-printed on a coated paper with a bar code by a conventional method.

The bar code obtained was not visible to the naked eye. An infrared light emitting diode (SHARP, GL480) was used as a light source for this bar code, and a CCD linear sensor (SONY, ILX503) was used as a light receiving unit to perform a reading test. As a result, the barcode information could be read. Furthermore, the obtained bar code was subjected to a UV irradiation deterioration test using an arc lamp for 100 hours,
Further, the bar code information could be read even after the chemical deterioration test with weak acid and weak alkali, and the weather resistance was excellent.

Example 4 30 parts by weight of the wet cake (solid content: 18%) obtained in Example 1 and 5 parts by weight of wax were mill-stirred to obtain an ink ribbon ink, which was coated on a PET film having a thickness of 4 μm. It was pier-coated to obtain an ink ribbon. A bar code was printed on a coated paper by a conventional method using this ink ribbon.

The obtained bar code could not be recognized with the naked eye, as in Example 2. Furthermore, infrared light emitting diodes (SHARP, GL
480) and a CCD linear sensor (S
A read test was performed using ONY, ILX503). As a result, the barcode information could be read.

Example 5 50 parts by weight of the wet cake (solid content 18%) obtained in Example 1 was used in an amount of 2.4 parts by weight of acrylic resin, 6.4 parts by weight of nitrified cotton, 13.0 parts by weight of isopropyl alcohol, and modified. The mixture was stirred with 15.9 parts by weight of ethanol, 31.9 parts by weight of ethyl acetate and 5.4 parts by weight of propylene glycol monopropyl ether to obtain a gravure ink. The obtained ink was gravure printed on the edge of a PET sheet having a thickness of 100 μm to obtain a transparent OHP sheet having an optical detection mark. The gravure printed detection mark portion of this OHP sheet was also transparent.

The obtained transparent OHP sheet was subjected to a print test with a copying machine equipped with a light-sensitive sheet detection device. As a result, both the sheet detection property and the paper feeding property were good. Further, since the detection mark portion of the image-formed sheet is transparent, the image when used in OHP was easy to see.

Example 6 Except that 60 parts by weight of the wet cake (solid content 18%) obtained in Example 1 was replaced with 60 parts by weight of the wet cake obtained in Example 2 (solid content 20%). An offset ink was prepared in the same manner as in Example 3. A barcode using this ink was offset printed on a white PET film (thickness 188 μm). The measurement result of the spectral reflectance of the obtained printed layer is shown in FIG.

The bar code obtained was not visible to the naked eye. Infrared light emitting diode (SHARP, GL480, peak emission wavelength 950
nm) and a CCD linear sensor (SO
A reading test was performed using NY, ILX503, and a peak emission wavelength of 960 nm). As a result, the barcode information could be read.

Example 7 Wet cake obtained in Example 2 (solid content 20%) 200
10 parts by weight of MMA (methyl methacrylate), 30 parts by weight of cyclohexanone and 10 parts by weight of SWAZOL
00 mixed with a vehicle made by adding 20 parts by weight,
A silk screen ink was obtained. This ink is white PET
Silk-printed on a film (thickness 188 μm) using a 250 mesh barcode screen plate. The measurement result of the spectral reflectance of the obtained printed layer is shown in FIG.

The obtained bar code could not be recognized with the naked eye, as in Example 6. Further, a reading test was conducted on this bar code by using the same light source and light receiving unit as in Example 6. As a result, the barcode information could be read.

Example 8 Wet cake (solid content 20%) 210 obtained in Example 2 210
By weight, 14 parts by weight of an acrylic resin, 27 parts by weight of toluene and 3 parts by weight of an anti-settling agent were stirred to obtain a gravure ink. The resulting ink was applied to a PET sheet (thickness 100 μ
Gravure printing was performed on the edge of m) to obtain a transparent OHP sheet having an optical detection mark. The gravure printed detection mark portion of this OHP sheet was also transparent. The results of measuring the spectral reflectance of this detection mark are shown in FIG.

The obtained transparent OHP sheet was subjected to a print test with a copying machine equipped with a light-sensitive sheet detecting device. As a result, both the sheet detection property and the paper feeding property were good. Further, since the detection mark portion of the image-formed sheet is transparent, the image when used in OHP was easy to see.

[0077]

According to the present invention, there is no absorption in the visible light region, a sharp absorption peak in the near infrared region near 975 nm, and an infrared absorption mark such as an infrared absorption code pattern or an infrared absorption detection mark. It is possible to provide an excellent material and ink material for forming the ink. Particularly, when the infrared light emitting diode or gallium arsenide semiconductor laser is used as the light source, the infrared absorbing material of the present invention has a wavelength near the absorption peak very close to the peak wavelength of the light from the light source, and further the spectrum of the photodiode which is the light receiving element. Since the sensitivity characteristic is almost the same as the absorption characteristic, there is also an advantage that the near infrared absorption characteristic can be easily used as a signal.

[Brief description of drawings]

1 shows a spectrum of spectral reflectance of YbPO ₄ powder obtained in Example 1. FIG.

FIG. 2 shows the particle size distribution of the YbPO ₄ crystals obtained in Example 1.

FIG. 3 shows an X-ray diffraction pattern of the YbPO ₄ crystal obtained in Example 1.

FIG. 4 shows a spectrum of spectral reflectance of YbPO ₄ powder (average particle size 20 μm and 1 μm) obtained in Comparative Example 1.

FIG. 5 shows an X-ray diffraction pattern of the YbPO ₄ powder (average particle size 20 μm and 1 μm) obtained in Comparative Example 1.

FIG. 6 shows a spectrum of spectral reflectance of YbPO ₄ powder obtained in Example 2.

FIG. 7 shows a spectrum of spectral reflectance of the printed layer obtained in Example 6.

FIG. 8 shows a spectrum of spectral reflectance of the printed layer obtained in Example 7.

9 shows a spectrum of spectral reflectance of a detection mark obtained in Example 8. FIG.

Claims (14)

[Claims] 1. An infrared absorbing material comprising YbPO ₄ particles having a high crystallinity and a particle diameter of 0.5 μm or less. 2. The infrared absorbing material according to claim 1, which has a particle size in the range of 5 to 500 nm. 3. An infrared absorbing material having high crystallinity, a particle diameter of 0.5 μm or less, and composed of YbPO ₄ particles surface-treated with a coupling agent. 4. The infrared absorbing material according to claim 1, which has an absorption peak in the vicinity of 975 nm. 5. The method for producing an infrared absorbing material according to claim 1, wherein the ytterbium alkoxide and the phosphoric acid alkoxide are hydrolyzed to produce YbPO ₄ particles. 6. The production method according to claim 5, wherein the ytterbium alkoxide is tributoxy ytterbium, and the phosphoric acid alkoxide is tributoxide phosphoric acid. 7. The production method according to claim 5, wherein a reaction product of orthophosphoric acid and an alcohol is used as the phosphoric acid alkoxide. 8. The method according to claim 7, wherein the alcohol is selected from the group consisting of propanol, butanol, pentanol, hexanol, heptanol, octanol and nonanol. 9. The production method according to claim 5, wherein the hydrolysis is performed in the presence of ultrasonic waves. 10. The method for producing an infrared absorbing material according to claim 3, wherein the YbPO ₄ particles obtained by the method according to any one of claims 5 to 9 are reacted with a coupling agent. . 11. An ink containing the infrared absorbing material according to any one of claims 1 to 4 and a vehicle. 12. The ink according to claim 11, wherein the vehicle has a refractive index in the range of 1.3 to 1.7. 13. An invisible pattern containing the infrared absorbing material according to claim 1. 14. An invisible information pattern containing the infrared absorbing material according to any one of claims 1 to 4.