JP2014173023A - Aqueous liquid for recording, recording method and recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous liquid for recording which is used for protection of an image and securing of fastness of prints in recording using an aqueous recording ink containing a color material, contains a slightly water-soluble near-infrared absorber but no color material and is fixed by near-infrared irradiation.SOLUTION: (1) An aqueous liquid for recording contains at least water and an aqueous organic solvent but no color material and additionally contains a near-infrared absorber having a maximum absorption wavelength in the range of 800-1,200 nm, and the near-infrared absorber is included in and/or adsorbed on fine resin particles and dispersed. (2) With the maximum absorbance of the near-infrared absorber in the range of 800-1,200 nm as Abs1 and the maximum absorbance in the range of 400-700 nm as Abs2, the ratio Abs2/Abs1 is 0.5 or lower.

Description

  The present invention relates to an aqueous recording liquid, and a recording method and a recording apparatus using the aqueous recording liquid.

Ink-jet printing for the purpose of recording on plain paper is mainly water-based ink from the viewpoint of safety and environmental considerations. Conventionally, most of the water-based inkjet recording inks used in offices and homes can be sufficiently dried by natural drying without using any drying means. However, in recent years, there has been a demand for higher printing speeds and compatibility with various recording media. Drying cannot catch up with natural drying, and there is a risk that paper conveyance will be hindered. In addition, in the coated paper for printing in which water-based ink is difficult to permeate, the ink tends to stay on the surface and tends to be weak against rubbing.
In order to solve these problems, a method of providing a protective layer has been proposed. For example, in Patent Document 1, a thermal transfer ribbon is brought into contact with a printing unit to provide a protective layer. However, when forming an image with an aqueous recording liquid, the recording liquid needs to be sufficiently dried before the protective layer is overlaid. There is a problem that the heating mechanism is required and the apparatus becomes complicated.

As a method for forming the protective layer in a non-contact manner, a method in which a transparent liquid containing a polymer is ejected to an image forming unit by inkjet and dried. Examples of the drying means include hot air drying, infrared irradiation, ultraviolet irradiation, microwave irradiation, and the like, and are proposed as drying means for ink containing a color material.
Patent Document 2 proposes a solvent-based ink for printing to which a compound having an infrared absorbing ability is added in order to promote thermal drying. However, solvent-based inks have a disadvantage that a large amount of organic solvent evaporates during drying, which has a great adverse effect on the environment and the human body.

  The present invention is used for recording an aqueous recording ink containing a coloring material, for protecting images, ensuring the fastness of printed matter, and the like. It is an object of the present invention to provide an aqueous recording liquid that does not contain and is fixed by near infrared irradiation.

The above problem is solved by the following invention 1).
1) An aqueous recording liquid which contains at least water and a water-soluble organic solvent and does not contain a coloring material, and further includes a near-infrared absorber having a maximum absorption wavelength at 800 to 1200 nm, and the near-infrared absorber is encapsulated in resin fine particles. An aqueous recording liquid which is adsorbed and / or dispersed.

  According to the present invention, in recording using a water-based recording ink containing a coloring material, it is used for protecting images, ensuring the fastness of printed matter, and the like, including a near-infrared absorber hardly soluble in water, An aqueous recording liquid which does not contain a material and can be fixed by irradiation with near infrared rays can be provided. This aqueous recording liquid has high safety without generating a large amount of harmful organic solvent by drying.

The schematic diagram which shows an example of a near-infrared unit. The figure which shows the spectral absorption spectrum of FF IRSORB201, FFIRSORB202, FFIRSORB203. The figure which shows the spectral absorption spectrum of IR-T and IR-13F.

Hereinafter, the present invention 1) will be described in detail. Further, since the following 2) to 5) are also included in the embodiment of the present invention, these will be described together.
2) Abs2 / Abs1 is 0.5 or less, where Abs1 is the maximum absorbance at 800 to 1200 nm and Abs2 is the maximum absorbance at 400 to 700 nm of the near infrared absorber. Aqueous recording liquid.
3) A method of recording on a recording medium provided with a coating layer on at least one surface of a support using an aqueous recording ink containing a coloring material and the aqueous recording liquid described in 1) or 2). The recording method is characterized in that the transfer amount of pure water at a contact time of 100 ms as measured with a dynamic scanning absorption meter is 3 to 15 mL / m ² .
4) A means for recording an aqueous recording ink containing a coloring material on a recording medium by ejecting it from the head, and using the aqueous recording liquid described in 1) or 2) on the portion recorded by the recording means. An ink jet recording apparatus comprising: means for overlapping recording; and means for irradiating near infrared rays to the overlapping recorded portion.
5) The inkjet recording apparatus according to 4), wherein the means for irradiating near infrared rays is a light source unit that irradiates near infrared rays having a wavelength of 800 to 1200 nm.

The present invention relates to an aqueous recording liquid containing at least water and a water-soluble organic solvent and not containing a coloring material, and further comprising a near-infrared absorber having a maximum absorption wavelength in the near-infrared region of 800 to 1200 nm. An aqueous recording liquid characterized in that an absorbent is encapsulated and / or adsorbed in resin fine particles and dispersed in the form of near-infrared absorbent-containing resin fine particles.
Aqueous recording liquids are preferred from the standpoint of safety and environmental impact, but generally known compounds that absorb in the near infrared region are hardly soluble in water and can be used as materials for aqueous recording liquids. It was difficult to do. The present invention uses water-dispersible resin fine particles that do not fix at room temperature but soften and instantaneously absorb and absorb heat of 50 ° C. or higher, and absorb near infrared rays in the resin fine particles. By encapsulating and / or adsorbing the agent and dispersing it in the aqueous recording liquid, it is possible to disperse the near-infrared absorbent, which is hardly soluble in water, in water, and to dry and fix it by near-infrared irradiation. Is. The inclusion and adsorption may be any, but in a normal preparation method, the inclusion and adsorption coexist.

As a near-infrared absorber, a compound having a maximum absorption wavelength in the range of 800 to 1200 nm is used. There is no clear definition regarding the wavelength range of near infrared rays, and it usually seems to refer to a range of about 800 to 2500 nm. However, in the present invention, by using a compound in the wavelength range, near infrared rays are efficiently absorbed, Can be evaporated.
The aqueous recording liquid of the present invention is used for the purpose of fixing a coloring material in a recording portion using an aqueous recording ink containing a coloring material (hereinafter also referred to as ink), and the color of a recorded image. It is preferable that the absorption in the visible region is small so as not to impair the taste, and it is more preferable that the transparency is high. Specifically, when the maximum absorbance at 400 to 700 nm is Abs1, and the maximum absorbance at 800 to 1200 nm is Abs2, Abs2 / Abs1 is preferably 0.5 or less. Within this range, a good image can be formed without deteriorating the quality of the recorded image.

Although the near-infrared irradiation device depends on the specification, the temperature can be raised to about 800 ° C., and the solvent in the aqueous recording liquid can be evaporated. Since dripping called “cockling” may occur on the recording medium due to rapid evaporation, it is necessary to select a drying method according to the method for placing the aqueous recording liquid.
Further, a protective layer can be formed in a non-contact manner by recording on the image recorded with the ink in a non-contact manner using the aqueous recording liquid of the present invention and irradiating with near-infrared rays for drying. In addition, it is possible to ensure the robustness of the printed matter even in the coated paper for printing in which the aqueous recording liquid hardly permeates.

Since the near-infrared absorber (organic dye) is hardly soluble in water, it must be dispersed in an aqueous medium using a dispersant. As a means for dispersing a water-insoluble near-infrared absorber in water, a method of kneading by applying a shear stress using a disperser such as a bead mill or a roll mill together with a surfactant or a polymer dispersant is known. . However, in the present invention, in order to provide excellent long-term storage stability and excellent fixability, the near-infrared absorber is encapsulated and / or adsorbed on the resin fine particles.
The near-infrared absorber can be encapsulated in and / or adsorbed in resin fine particles and dispersed in water by copolymerizing a monomer mixture by a known polymerization method such as a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Resin fine particles are used. As the polymerization method, solution polymerization using a polar organic solvent is preferable. Examples of the polar organic solvent include ester solvents, aliphatic alcohols, and ketone solvents.

As a preferred example, resin polymerization is first performed by solution polymerization using a polar organic solvent. Next, a neutralizing agent and water are added to and mixed with the solution containing the resin fine particles, and then a near infrared absorber is added and kneaded. Further, there is a method in which water is added and dispersed, and the polar organic solvent is removed from the obtained dispersion to obtain an aqueous dispersion.
Examples of the polymer to be synthesized include thermoplastic polymers such as polyester, polyurethane, and vinyl polymer. In the present invention, these polymers are preferable in that when the printed matter is dried by irradiating near infrared rays, the resin is softened and the color material in the ink can be quickly fixed.

Such an aqueous recording liquid is used for the purpose of protecting an image by recording on an image-formed portion using ink and ensuring the fastness of a printed matter.
Since the protective layer can be formed in a non-contact manner after the image is formed with ink, it is preferably ejected by inkjet.
In order to be ejected by inkjet, the viscosity of the aqueous recording liquid is 25 ° C., preferably 5 to 20 mPa · s, and more preferably 6 to 12 mPa · s. If the viscosity is in the range of 5 to 20 mPa · s, sufficient ejection stability can be ensured.
The surface tension of the aqueous recording liquid is preferably 20 to 40 mN / m at 20 ° C. If the surface tension is 23 mN / m or more, bleeding on the recording medium will not be noticeable, and stable jetting will not be obtained. Further, if it is 40 mN / m or less, the aqueous recording liquid will sufficiently penetrate into the recording medium, and when it is recorded on the portion where the image is formed using ink, it is sufficiently wet spread on the image. There will be no increase in the drying time of the recording liquid.
The pH of the aqueous recording liquid is preferably 7-10.
The physical properties change when the aqueous recording liquid is stored for a long time. Particularly when heated and stored, the viscosity and pH of the aqueous recording liquid are increased, but the change is preferably as small as possible. For example, the rate of thickening after storage at 60 ° C. for 2 weeks is preferably within 5%, and the rate of decrease in pH is preferably within −5%.

<Water-based recording ink containing ink (ink)>
The ink includes at least water, a water-soluble organic solvent, and a coloring material, but may further include a near infrared absorber. When the near-infrared absorber is included, it is preferable that the near-infrared absorber is encapsulated and / or adsorbed in the resin fine particles and dispersed in the ink, as in the case of the aqueous recording liquid. As the near-infrared absorber and resin fine particles, the same ones as in the case of the aqueous recording liquid can be used.
The color of the ink is not particularly limited, and may be various colors such as cyan, magenta, yellow, and black. However, in the case of black, since the color material itself absorbs near infrared rays, it is not necessary to add a near infrared absorber.

Examples of the coloring material include phthalocyanine blue, phthalocyanine green, quinacridone, anthraquinone, perylene, (thio) indigoid, heterocyclic yellow, pyranthrone, and carbon black. These color materials have a maximum absorption wavelength in the visible light region of less than about 800 nm.
Representative examples of phthalocyanine blue include copper phthalocyanine blue and its derivative (Pigment Blue 15).
Representative examples of quinacridone include Pigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Violet 19 and Pigment Violet 42. Can be mentioned.
Representative examples of anthraquinone include pigment red 43, pigment red 194 (perinone red), pigment red 216 (brominated pyrantron red) and pigment red 226 (pyrantron red).

Representative examples of perylene include Pigment Red 123 (Bell Million), Pigment Red 149 (Scarlet), Pigment Red 179 (Maroon), Pigment Red 190 (Red), Pigment Violet, Pigment Red 189 (Yellow Shade Red) and And CI Pigment Red 224.
Representative examples of thioindigoid include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181, Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.
Representative examples of the heterocyclic yellow include pigment yellow 117 and pigment yellow 138.
Examples of coloring pigments other than those described above include those described in The Color Index, Third Edition (The Society of Dyers and Colorists, 1982).

As the carbon black, known ones can be used. In particular, the primary particle size is 10 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, and the DBP oil absorption is 40 to 150 mL / 100 g. Those having the following are preferred.
Specific examples of these include, for example, # 2700, # 2650, # 2600, # 2450B, # 2400B, # 2350, # 230, # 1000, # 990, # 980, # 970, # 960, # 950, # 900. , # 850, # 750B, MCF88, # 650B, MA600, MA77, MA7, MA8, MA11, MA100, MA100R, MA100S, MA220, MA230, MA200RB, MA14, # 52, # 50, # 47, # 45, # 45L # 44, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 95, # 85, CF9, # 260 (Mitsubishi Chemical Corporation), Raven700, 5750, 5250, 5000, 3500, 1255 (above Colombia), Regal 400R, 30R, 660R, MoguL, Monarch700, 800, 880, 900, 1000, 1100, 1300, Monarch1400 (above, manufactured by Cabot), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S160, Printex 35, U, V, 140U, 140V, Special Black 6, 5, 4A, 4 (above Degussa), Talker Black # # 8500, # 8300, # 7550, # 7400, # 7360, # 7350, # 7350, # 7270, # 7100 (above, manufactured by Tokai Carbon Co., Ltd.), Shiyo Black N110, N220, N234, N339 N330, N326, N330T, MAF, N550 Although Cabot Japan Co., Ltd.), but is not limited thereto.

There is no restriction | limiting in particular in the water-soluble organic solvent used for ink, According to the objective, it can select suitably.
Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,3-butanediol, 2,3- Butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, Polyhydric alcohols such as 1,6-hexanediol, glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,6-hexanetriol, petriol; ethylene glycol monoethyl ether , Ethylene glycol monob Polyhydric alcohol alkyl ethers such as ether ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether; polyvalent alcohols such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether Alcohol aryl ethers; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, and ε-caprolactam; formamide, N- Amides such as methylformamide and N, N-dimethylformamide; monoethanolamine, diethanolamine, triethanolamine Amines such as ethylene, monoethylamine, diethylamine and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol; propylene carbonate and ethylene carbonate. These may be used alone or in combination of two or more.

Among these, from the point that an excellent effect is obtained for prevention of poor jetting properties due to solubility and water evaporation, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, Tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5 -Pentanediol, 2-methyl-2,4-pentanediol, 1,6-hexanediol, glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol, 2-pyrrolidone, N-methyl- 2-pyrrolidone, N-hydroxyethyl-2-pyrrole Down it is preferred.
The content of the water-soluble organic solvent in the ink is preferably 15 to 40% by weight, and more preferably 20 to 35% by weight. If the content is too small, the nozzle is likely to be dried and defective ejection of droplets may occur. If the content is too large, the ink viscosity will be high and the proper viscosity range may be exceeded.

It is preferable to add a surfactant to the ink to improve dispersibility. As the surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, or a fluorosurfactant may be used alone or in combination of two or more. be able to.
Anionic surfactants include alkyl allyl sulfonate, alkyl naphthalene sulfonate, alkyl phosphate, alkyl sulfate, alkyl sulfonate, alkyl ether sulfate, alkyl sulfosuccinate, alkyl ester sulfate, alkyl benzene Sulfonate, alkyl diphenyl ether disulfonate, alkyl aryl ether phosphate, alkyl aryl ether sulfate, alkyl aryl ether ester sulfate, olefin sulfonate, alkane olefin sulfonate, polyoxyethylene alkyl ether phosphate, Polyoxyethylene alkyl ether sulfate ester salt, ether carboxylate, sulfosuccinate, α-sulfo fatty acid ester, fatty acid salt, condensate of higher fatty acid and amino acid, naphthene Salts and the like.
Examples of the cationic surfactant include alkylamine salts, dialkylamine salts, aliphatic amine salts, benzalkonium salts, quaternary ammonium salts, alkylpyridinium salts, imidazolinium salts, sulfonium salts, phosphonium salts, and the like. Can be mentioned.

Nonionic surfactants include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, and the like.
Examples of amphoteric surfactants include imidazoline derivatives such as imidazolinium betaine, dimethylalkyllauryl betaine, alkylglycine, and alkyldi (aminoethyl) glycine.
As fluorosurfactants, Surflon S-111, S-112, S-113, S121, S131, S132, S-141, S-145 (Asahi Glass Co., Ltd.), Fullrad FC-93, FC are commercially available. -95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431, FC-4430 (manufactured by Sumitomo 3M); Megafac F-470, F-1405, F474 (large Nippon Ink Chemical Co., Ltd.); Zonyl FS-300, FSN, FSN-100, FSO (DuPont); Ftop EF-351, 352, 801, 802 (Gemco); Softanol EP-7025 (Nippon Catalyst) Etc.).

The ink may contain known additives such as a penetrating agent, a pH adjusting agent, and a rust preventive as necessary.
Examples of the penetrant include diol compounds having 7 to 11 carbon atoms. The content is preferably 1 to 5% by weight. If it is less than 1% by weight, sufficient permeability cannot be obtained, and if it exceeds 5% by weight, the storage stability may be lowered.
As the diol compound, for example, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol and the like are suitable.
By adding a penetrating agent, the penetrability of the recording paper is improved and the paper is rubbed and smeared during paper conveyance, or the ink is attached to the conveyance belt when the recording surface of the recording medium is reversed for double-sided printing. Therefore, a good image can be formed without causing stains.

The pH adjuster is not particularly limited as long as the pH can be adjusted to 7 or more without adversely affecting the prepared ink, and any substance can be used according to the purpose.
Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide, quaternary ammonium hydroxide, quaternary Examples thereof include phosphonium hydroxides, carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate.
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and benzotriazole.

The physical properties of the ink are the same as in the case of the aqueous recording liquid, and the viscosity is 25 ° C., preferably 5 to 20 mPa · s, more preferably 6 to 12 mPa · s. If the viscosity is in the range of 5 to 20 mPa · s, sufficient ejection stability can be ensured.
The surface tension is preferably 20 to 40 mN / m at 20 ° C. When the surface tension is 23 mN / m or more, bleeding on the recording medium is not noticeable, and stable jetting cannot be obtained. Further, if it is 40 mN / m or less, the aqueous recording liquid will sufficiently penetrate into the recording medium, and when it is recorded on the portion where the image is formed using ink, it is sufficiently wet spread on the image. There will be no increase in the drying time of the recording liquid.
The pH is preferably 7-10.
The physical properties change when ink is stored for a long time. Particularly when heated and stored, an increase in viscosity and a decrease in pH are observed, but it is preferable that the change be as small as possible. For example, the rate of thickening after storage at 60 ° C. for 2 weeks is preferably within 5%, and the rate of decrease in pH is preferably within −5%.

(recoding media)
When the aqueous recording liquid of the present invention is used, an excellent image can be formed even on a recording medium such as coated paper having poor water absorbability. Here, coated paper with poor water absorbability means that a coated layer is provided on at least one surface of a support, and the transfer of pure water to a recording medium at a contact time of 100 ms measured with a dynamic scanning absorptiometer. It refers to coated paper for printing whose amount is 3 to 15 mL / m ² .
The liquid absorption characteristics can be measured using a dynamic scanning liquid absorption meter (DSA) manufactured by Kyowa Seiko Co., Ltd. The dynamic scanning absorptiometer (DSA, PAPER PAPER TECHNOLOGY, Vol. 48, May 1994, pp. 88-92, Kuju Shigenori) accurately measures the amount of absorbed liquid in an extremely short time. A) The liquid absorption speed is directly read from the movement of the meniscus in the capillary. B) The sample is formed into a disk shape, and the liquid absorption head is scanned in a spiral shape. C) The liquid is scanned according to a preset pattern. The measurement is automated by a method in which the speed is automatically changed and the measurement is performed as many times as necessary with one sample.
A liquid supply head for a paper sample is connected to a capillary via a Teflon (registered trademark) tube, and the position of the meniscus in the capillary is automatically read by an optical sensor.

There is no restriction | limiting in particular as said support body, According to the objective, it can select suitably, For example, sheet-like substances, such as a nonwoven fabric mainly composed of wood fiber and wood fiber, and synthetic fiber, etc. are mentioned.
There is no restriction | limiting in particular as said paper, According to the objective, it can select suitably according to the objective, For example, wood pulp, waste paper pulp, etc. are used. Examples of the wood pulp include NBKP, LBKP, NBSP, LBSP, GP, TMP, and the like.
Examples of the internal filler used for the support include conventionally known white pigments.
Examples of the white pigment include light calcium carbonate, heavy calcium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, White inorganic pigments such as calcium silicate, magnesium silicate, synthetic silica, aluminum hydroxide, alumina, lithopone, zeolite, magnesium carbonate, magnesium hydroxide; styrene plastic pigment, acrylic plastic pigment, polyethylene, microcapsule, urea resin And organic pigments such as melamine resin. These may be used individually by 1 type and may use 2 or more types together.

Examples of the internally added sizing agent used for making the support include, for example, neutral rosin sizing agents used for neutral papermaking, alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), and petroleum resin. System sizing agents and the like. Among these, a neutral rosin sizing agent or alkenyl succinic anhydride is particularly preferable.
The alkyl ketene dimer can be added in a small amount because of its high size effect, but it may be unsatisfactory from the viewpoint of transportability during ink jet recording because the friction coefficient on the surface of the recording medium is lowered and it becomes slippery.

The coating layer contains a pigment and a binder (binder), and if necessary, contains a surfactant and other components. As the pigment, an inorganic pigment is used, or an inorganic pigment and an organic pigment are used in combination.
Examples of inorganic pigments include kaolin, talc, heavy calcium carbonate, light calcium carbonate, calcium sulfite, amorphous silica, titanium white, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and water. Examples of the pigment include zinc oxide and chlorite.
Of these, kaolin is preferable because it has excellent glossiness and can have a texture close to that of paper for offset printing. Kaolin includes delaminated kaolin, calcined kaolin, engineered kaolin by surface modification, etc., but considering gloss development, the proportion of particle size of 2 μm or less has a particle size distribution of 80% by weight or more. It is desirable that kaolin accounts for 50% by weight or more of the entire kaolin.
The blending amount of kaolin is preferably 50 parts by weight or more. If it is less than 50 parts by weight, it is difficult to expect a sufficient effect on glossiness. Although there is no particular upper limit, considering the fluidity of kaolin, particularly thickening under high shear force, less than 90 parts by weight is more preferable from the viewpoint of coating suitability.

On the other hand, examples of the organic pigment include water-soluble dispersions such as styrene / acrylic copolymer particles, styrene / butadiene copolymer particles, polystyrene particles, and polyethylene particles. These organic pigments may be used in combination of two or more.
Since the organic pigment is excellent in gloss expression and its specific gravity is smaller than that of the inorganic pigment, a coating layer having high bulkiness and high gloss and good surface coverage can be obtained.
The compounding quantity of an organic pigment is 2-20 weight part. If the amount is less than 2 parts by weight, the above effect is not obtained. If the amount exceeds 20 parts by weight, the fluidity of the coating liquid deteriorates, leading to a decrease in coating operability, and it is not economical from the viewpoint of cost.
The organic pigment has a solid type, a hollow type, a donut type, and the like in its form, but the average particle size is 0.2 to 3 in view of the balance of gloss development, surface coverage, and fluidity of the coating liquid. It is desirable to be in the range of 0.0 μm, more preferably a hollow mold having a porosity of 40% or more is employed.

A water-based resin is preferably used as the binder, and a water-soluble resin and a water-dispersible resin are suitably used as the water-based resin.
There is no restriction | limiting in particular in the said water-soluble resin, According to the objective, it can select suitably, For example, modified products of polyvinyl alcohol, such as polyvinyl alcohol, anion modified polyvinyl alcohol, cation modified polyvinyl alcohol, acetal modified polyvinyl alcohol; Polyurethane Polyvinylpyrrolidone and polyvinylpyrrolidone and vinyl acetate copolymer, vinylpyrrolidone and dimethylaminoethyl / methacrylic acid copolymer, quaternized vinylpyrrolidone / dimethylaminoethyl / methacrylic acid copolymer, vinylpyrrolidone and methacrylic acid Modified products of polyvinylpyrrolidone such as a copolymer of amidopropyltrimethylammonium chloride; cellulose such as carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose Modified products of cellulose such as cationized hydroxyethyl cellulose; polyesters, polyacrylic acid (esters), melamine resins, or synthetic resins such as these modified products, copolymers of polyester and polyurethane; poly (meth) acrylic acid, poly ( Examples thereof include (meth) acrylamide, oxidized starch, phosphate esterified starch, self-modified starch, cationized starch, or various modified starches, polyethylene oxide, sodium polyacrylate, and sodium alginate.
These may be used individually by 1 type and may use 2 or more types together.
Among these, from the viewpoint of ink absorbability, polyvinyl alcohol, cation-modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, polyester, polyurethane, a copolymer of polyester and polyurethane, and the like are particularly preferable.

There is no restriction | limiting in particular in the formation method of the said coating layer, According to the objective, it can select suitably, For example, it can form by the method of impregnating or adhering a coating layer liquid to a support body.
The impregnation or adhesion method of the coating layer liquid is not particularly limited and can be appropriately selected depending on the purpose. For example, conventional size press, gate roll size press, film transfer size press, blade coater, rod coater, air It is possible to apply with various coaters such as knife coaters and curtain coaters, but from the viewpoint of cost, impregnation or conventional size press, gate roll size press, film transfer size press etc. installed in paper machine It can be attached and finished on-machine.

  Commercially available products include OK Top Coat, OK Astro Gloss, OK Non Wrinkle, SA Kanto +, OK Kanto +, OK Non Wrinkle, (F) MCOP, OK Astro Dull, OK Astro Matt, OK Ultra Aqua Satin, OK embossed silk, OK embossed satin, OK embossed fabric, OK embossed home span, OK opto gloss, OK bullion, OK Casablanca, OK Casablanca-V, OK Casablanca-X, OK Kanto one side, OK coat L, OK coat L Green 100, OK Coat N Green 100, OK Coat V, OK Medium Coat (for Offset), OK Top Coat S, OK Top Coat Dull, OK Top Coat Mat N, OK Trinity, OK Trinity NaVi, OK Trinity NaVi-V , OK Neo Top Coat, OK Neo Top coat mat, OK non-wrinkle AL, OK non-wrinkle DL, OK non-wrinkle BL, OK white L, OK mat coat L green 100, OK mat coat green 100, OK royal coat, OK white L, Z coat, Z coat green 100, Ultra Satin Kinto N, Golden Matte, Satin Kinto N, New Age, New Age Green 100, Mirror Coat Gold, Mirror Coat Platinum, Royal Coat L, Roston Color, POD Super Gloss, POD Gloss Coat, POD Matt Coat , Made by Oji Paper Co., Ltd.), Broad mat A, Broad gloss A, White pearl coat N, New V mat, Pearl coat, Dignity, Vistaros, N pearl coat L, Utrillo, EP-D gloss, EP L gloss, EP-L mat, EP-D premium white, EP-super fine quality (above, manufactured by Mitsubishi Paper Industries), Hi-a, α mat, Kinmari Hi-L, mu coat, mu mat, mu white (above , Manufactured by Hokuetsu Paper Co., Ltd.).

(Cartridge containing water-based recording liquid and / or ink)
The aqueous recording liquid and / or ink can be accommodated in a container and used as a cartridge. The same cartridge as the ink cartridge can be used.
In general, the ink cartridge has other members appropriately selected as needed in addition to the container. The container is not particularly limited, and its shape, structure, size, material and the like can be appropriately selected according to the purpose. For example, a container having an ink bag formed of an aluminum laminate film, a resin film, or the like. Can be mentioned. Moreover, the form which inserts a tube in the container with a plastic lid | cover can also be selected. This container with a lid can be preferably used in a large-sized ink jet recording apparatus because it can be easily filled with ink and can cope with a large capacity.

(Recording method and recording apparatus)
The recording method of the present invention includes at least an ink and aqueous recording liquid flying step and a near-infrared irradiation step, and further includes other steps appropriately selected as necessary, for example, a stimulus generation step, a control step, and the like.
The recording apparatus of the present invention has at least ink and aqueous recording liquid flying means and near infrared irradiation means, and further has other means appropriately selected as necessary, for example, stimulus generation means, control means and the like.
The recording method of the present invention can be preferably carried out by the recording apparatus of the present invention, and the ink and aqueous recording liquid flying step can be suitably carried out by the ink and aqueous recording liquid flying means. Moreover, the said near infrared irradiation process can be suitably performed by the said near infrared irradiation process means. Moreover, the said other process can be suitably performed by the said other means.
In addition, the aqueous recording liquid of the present invention can be ejected from a head or can be applied by a roller or the like. The aqueous recording liquid of the present invention imparts image rub resistance, and is applied over the image recording portion or a part of the image recording portion without being applied over the entire surface of the recording medium. By this, it is possible to ensure scratching.

(Ink and aqueous recording liquid flying process and flying means)
The ink and aqueous recording liquid flying step is a step of recording an image by applying a stimulus to the ink and the aqueous recording liquid to fly. The ink and the aqueous recording liquid flying means are means for recording an image by applying a stimulus to the ink and the aqueous recording liquid to fly.
The ink and the aqueous recording liquid flying means are not particularly limited, and examples thereof include various nozzles for discharging ink. The nozzle diameter of the inkjet nozzle is preferably 30 μm or less, and preferably 1 to 20 μm.

(Near infrared irradiation process)
The near-infrared irradiation step is a step of irradiating the formed image with near-infrared rays including a wavelength of at least 800 to 1200 nm to dry the formed image.
As the near-infrared irradiation device, a known one may be used as appropriate, but a general near-infrared irradiation unit includes a near-infrared irradiation lamp and a reflection mirror, for example, as shown in a schematic diagram in FIG. As a specific example, an apparatus including a halogen lamp and a reflection mirror is known. A halogen heater is incorporated in the reflection mirror and a heating unit is realized to achieve efficient heating. For example, UH-USC-CL300, UH-USC-CL700, UH-USC-CL1000, UH-USD-CL300, UH-USD-CL700, UH-USD-CL1000, UH-MA1-CL300, UH-MA1-CL700, UH-MA1-CL1000 (all manufactured by USHIO INC.) And the like.

The aqueous recording liquid of the present invention can be applied not only to a serial type (shuttle type) ink jet recording apparatus that is scanned by a carriage but also to a line type ink jet recording apparatus having a line type head.
The recording method and recording apparatus of the present invention can be applied to various types of recording by the ink jet recording method, and are particularly suitable for, for example, an ink jet recording printer, a facsimile apparatus, a copying apparatus, and a printer / fax / copier multifunction machine. Can be applied to.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples. In the examples, “parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified.

  Resin fine particle dispersions (1) to (5) in which a near-infrared absorber was encapsulated were prepared by the methods shown in Preparation Examples 1 to 5 below. Of the used near-infrared absorber, the maximum absorbance (Abs1) at the maximum absorption wavelength (λmax) in the range of 800 to 1200 nm, the maximum absorbance (Abs2) at the maximum absorption wavelength (λ2nd) in the range of 400 to 700 nm, and the ratio ( Abs2 / Abs1) is shown in Table 1.

Preparation Example 1 [Preparation of resin fine particle dispersion (1) encapsulating near-infrared absorber]
[Synthesis of polymer (A)]
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.2 part of 2-mercaptoethanol, 16 parts of methacrylic acid, 15 parts of styrene macromer (AS-6S / manufactured by Toagosei Co., Ltd.), 10 parts of n-butyl methacrylate, 34 parts of styrene monomer, hydroxyl group 10% of each of 25 parts of terminal monomethacrylate (Blemmer 50PEP-300 / manufactured by NOF Corporation) was added and mixed to obtain a monomer solution.
In the dropping funnel, the remaining 90% of each of the above monomers was charged, and 0.27 part of 2-mercaptoethanol, 60 parts of methyl ethyl ketone and 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) were added. And mixed with nitrogen gas to obtain a dropped monomer solution. Under a nitrogen atmosphere, the initially charged monomer solution in the reaction solution was heated to 75 ° C. while stirring, and the monomer in the dropping funnel was dropped into the reaction vessel little by little over 3 hours.
After completion of the dropwise addition, the temperature of the reaction solution was maintained at 75 ° C. for 2 hours, and then a solution in which 0.3 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in 5 parts of methyl ethyl ketone was reacted. The solution was further aged at 75 ° C. for 2 hours and then at 85 ° C. for 2 hours to complete the reaction, whereby a polymer solution was obtained.
The obtained polymer solution was dried at 105 ° C. under reduced pressure for 2 hours, and the polymer (A) was isolated by removing methyl ethyl ketone.

[Preparation of Resin Fine Particle Dispersion (1) Encapsulating Near-Infrared Absorber]
A solution obtained by dissolving 20.0 parts of polymer (A) in 20.0 parts of methyl ethyl ketone in Ultra Disper (manufactured by Asada Tekko Co., Ltd.), which is a high-speed stirring and mixing device, 5N sodium hydroxide aqueous solution (sodium hydroxide concentration 16.8%) ) 4.4 parts (neutralization degree of polymer carboxy group 50 mol%) and ion-exchanged water 26.6 parts (weight ratio of water to organic solvent = 1.5) Rotated 2000 and processed for 30 minutes.
After the obtained mixture was charged in an atmospheric pressure kneader (manufactured by Moriyama Co., Ltd.), a near-infrared absorber (FF IRSORB 201 / manufactured by Fuji Film / λmax 1094 nm) was added, and the kneader was covered and sealed. Cooling water at 1 ° C. was passed through the jacket and kneaded at 25 ° C. for 2 hours to obtain a dispersion (1-1). To the obtained dispersion (1-1), 222.1 parts of ion-exchanged water was added, and the disper blade was rotated 8000 per minute and treated at 15 ° C. for 1 hour.
Further, 1.0 part of 5N sodium hydroxide aqueous solution and 46.3 parts of ion-exchanged water were added, and the mixture was charged into TK Robotics (Homo Disper) manufactured by Primics, and the disper blade was rotated 8000 per minute at 1 Time treatment was performed to obtain Dispersion (1-2).
Dispersion (1-2) was treated with a microfluidizer (manufactured by Micro fluidics) at a pressure of 200 MPa for 20 passes to obtain dispersion (1-3).
After adding 250 parts of ion-exchanged water to the dispersion (1-3) and stirring, methyl ethyl ketone and a part of water were removed under reduced pressure at 60 ° C., and 20 weights of resin fine particles containing a near-infrared absorber were added. % Resin fine particle dispersion (1) was obtained. Part of the near-infrared absorber is dispersed while adsorbed on the resin fine particles. This also applies to Preparation Examples 2 to 5.
A spectral absorption spectrum of FF IRSORB 201 is shown in FIG.

Preparation Example 2 [Preparation of Resin Fine Particle Dispersion (2) Encapsulating Near Infrared Absorber]
Near-infrared absorption in the same manner as in Preparation Example 1 except that the near-infrared absorber was changed to FF IRSORB 202 (Fuji Film / λmax 898 nm) in the production process of the dispersion (1-2) of Preparation Example 1. A resin fine particle dispersion (2) containing the agent was obtained.
A spectral absorption spectrum of FF IRSORB 202 is shown in FIG.

Preparation Example 3 [Preparation of Resin Fine Particle Dispersion (3) Encapsulating Near Infrared Absorber]
Near-infrared absorption in the same manner as in Preparation Example 1 except that the near-infrared absorber was changed to FF IRSORB 203 (Fuji Film / λmax 842 nm) in the production process of the dispersion (1-2) of Preparation Example 1. A resin fine particle dispersion (3) containing the agent was obtained.
A spectral absorption spectrum of FF IRSORB 203 is shown in FIG.

Preparation Example 4 [Preparation of Resin Fine Particle Dispersion (4) Encapsulating Near Infrared Absorber]
Near-infrared rays in the same manner as in Preparation Example 1 except that the near-infrared absorber was changed to Karenz IR-T (manufactured by Showa Denko KK / λmax 817 nm) in the production process of the dispersion (1-2) of Preparation Example 1. A resin fine particle dispersion (4) containing an absorbent was obtained.
In addition, the spectral absorption spectrum of IR-T is shown in FIG.

Preparation Example 5 [Preparation of Resin Fine Particle Dispersion (5) Encapsulating Near Infrared Absorber]
Near-infrared rays in the same manner as in Preparation Example 1, except that the near-infrared absorber was changed to Karenz IR-13F (manufactured by Showa Denko KK / λmax 819 nm) in the production process of the dispersion (1-2) of Preparation Example 1. A resin fine particle dispersion (5) containing an absorbent was obtained.
In addition, the spectral absorption spectrum of IR-13F is shown in FIG.

Preparation Example 6 (Preparation of aqueous dispersion of near-infrared absorber with surfactant)
20 types of near infrared absorbers (FF IRSORB 201 / Fuji Film / λmax 1094 nm), 7 parts of Neugen EA-177 (nonionic surfactant / Daiichi Kogyo Seiyaku), 73 parts of ion-exchanged water Was circulated and dispersed with a bead mill (manufactured by Shinmaru Enterprises Co., Ltd .: KDL type, media: 0.3 mmφ zirconia ball used) to prepare an aqueous dispersion of a near infrared absorber.

Examples 1-7, Comparative Examples 1-2 (Preparation of aqueous recording liquid)
The material of the composition shown in each column of the Example of Table 2 and a comparative example was prepared, and it adjusted with sodium hydroxide so that pH might be set to 9. Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and prepared each aqueous recording liquid which does not contain the coloring material of an Example and a comparative example.
In the table, “Sanmor EW102” is an acrylic-silicone polymer dispersion containing no near-infrared absorber manufactured by Sanyo Chemical Industries, Ltd., and “Softanol EP-7005” is a fluorine-based product manufactured by Nippon Shokubai Co., Ltd. It is a surfactant.
The various characteristics of the obtained aqueous recording liquids were measured and evaluated as follows. The results are shown in Table 3.

<Viscosity>
It measured at 25 degreeC using RL-500 (made by Toki Sangyo Co., Ltd.).
<Surface tension>
Measurement was performed at 23 ° C. ± 2 ° C. using a static surface tension meter (BVP-Z, manufactured by Kyowa Interface Chemical Co., Ltd.).
<PH>
Measurement was performed at 23 ° C. ± 2 ° C. using a pH meter (HM-A, manufactured by Toa Denpa Kogyo Co., Ltd.).
<Storage stability>
The ink or aqueous recording liquid was placed in a polypropylene jar (50 mL) and stored at 50 ° C. for one month, then taken out of the jar and left for one day. And the viscosity after a preservation | save was measured and the preservation | save stability was determined on the following reference | standard by the change rate of the viscosity after an preservation | save with respect to the initial viscosity measured before the preservation | save.
〔Evaluation criteria〕
○: Viscosity change rate after storage with respect to initial viscosity is less than ± 3% △: Viscosity change rate after storage with respect to initial viscosity is ± 3% or more and less than ± 6% ×: Viscosity change rate after storage with respect to initial viscosity is ± 6% or more

(Preparation of pigment dispersion)
Each pigment dispersion was prepared as follows.

Preparation Example A (Preparation of phthalocyanine pigment dispersion)
C. I. After premixing 150 g of Pigment Blue 15: 3 and 120 g of the compound represented by the following [Chemical Formula 1] (polyoxyethylene-β-naphthyl ether), a disk type bead mill (manufactured by Shinmaru Enterprises, Inc .: KDL type, The mixture was circulated and dispersed with a medium (using zirconia balls having a diameter of 0.3 mm) to obtain a pigment dispersion.

Preparation Example B (Preparation of dimethylquinacridone pigment dispersion)
C. I. 150 g of Pigment Red 122 and 100 g of the compound represented by the above [Chemical Formula 1] (polyoxyethylene-β-naphthyl ether) were premixed, and then a disk-type bead mill (manufactured by Shinmaru Enterprises Co., Ltd .: KDL type, media) : Using a zirconia ball having a diameter of 0.3 mm) to obtain a pigment dispersion.

Preparation Example C (Preparation of monoazo yellow pigment dispersion)
C. I. 150 g of Pigment Yellow 74 and 100 g of the compound represented by the above [Chemical Formula 1] (polyoxyethylene-β-naphthyl ether) were premixed, and then a disk type bead mill (manufactured by Shinmaru Enterprises, Inc .: KDL type, media) : Using a zirconia ball having a diameter of 0.3 mm) to obtain a pigment dispersion.

(Preparation of water-based recording ink)
A material having the composition shown in each column of Preparation Examples 7 to 10 in Table 4 containing the pigment dispersion was prepared, and adjusted with sodium hydroxide so that the pH was 9 to obtain an aqueous recording ink.
“Surflon S-111” in the table is a fluorosurfactant manufactured by Asahi Glass Co., Ltd.
Various characteristics of the obtained water-based recording inks were measured and evaluated in the same manner as in the case of the water-based recording liquid. The results are shown in Table 5.
The volume average particle diameter (D50) was measured by diluting each aqueous recording liquid with pure water and using a particle size distribution measuring device (Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

  The above water-based recording ink and water-based recording liquid were combined as shown in the respective columns of Table 6, and recording was performed on plain paper and coated paper as follows, and the respective recording characteristics were evaluated. The results are shown in Table 6.

★ Image quality on plain paper <Image density>
Inkjet printer IPSiO GX5000 (manufactured by Ricoh) was filled with yellow, magenta and cyan aqueous recording inks, and the washed black head was filled with aqueous recording liquid. First, printing was performed on Type 6200 paper (manufactured by Ricoh) at a resolution of 600 dpi using an aqueous recording ink. Next, the output image was quickly put in a manual feed tray, an aqueous recording liquid was printed on the print image portion, and immediately after printing, the printed material was passed through the near infrared irradiation unit shown in FIG. 1 at a speed of 60 m / min and dried. About the printed matter after drying, the image density was measured using a reflection type color spectrocolorimetric densitometer (manufactured by X-Rite).
UH-MA1-CL1000 / USHIO Co., Ltd. was used for the near-infrared irradiation unit with a reflecting mirror in FIG.

<Abrasion>
For the printed matter printed and dried in the same manner as in the case of <Image Density>, after drying, the printed portion was rubbed 10 times with a cotton cloth, and the pigment transfer condition to the cotton cloth was visually observed and evaluated according to the following criteria.
〔Evaluation criteria〕
○: Pigment transfer to cotton fabric is hardly seen Δ: Some pigment transfer is seen ×: Pigment is clearly transferred

<Drying>
For the printed matter that was printed and dried in the same manner as in the case of <Image Density>, after drying, the filter paper was pressed against the print portion, the transfer condition to the filter paper was visually observed, and the following criteria were evaluated.
〔Evaluation criteria〕
○: Pigment transfer to cotton fabric is hardly seen Δ: Some pigment transfer is seen ×: Pigment is clearly transferred

<Coloring of recording medium>
The black head of an inkjet printer IPSiO GX5000 (manufactured by Ricoh) was washed and filled with an aqueous recording liquid. A solid print was made at a resolution of 600 dpi and a printing rate of 30% on the recording medium, and the color difference from the background was measured using a reflective color spectrocolorimetric densitometer (manufactured by X-Rite), and evaluated according to the following criteria.
〔Evaluation criteria〕
A: Both Δa * and Δb * are −0.5 or more and +0.5 or less ○: Both Δa * and Δb * are −1.0 or more and less than −0.5, or
+0.5 and +1.0 or less Δ: Both Δa * and Δb * are less than −1.0 or more than +1.0

★ Image quality in coated paper Type 6200 paper (manufactured by NBS Ricoh Co., Ltd.) was changed to OK top-coated paper (manufactured by Oji Paper Co., Ltd., pure water transfer amount: 6 mL / m ² ) and LumiArtGloss paper (manufactured by Stora Enso). Except for the above, the image density, scratchability, drying property, and coloring of the recording medium were evaluated in the same manner as in the case of “★ Image quality on plain paper”.

As can be seen from the results in Table 6 above, good results were obtained in all the examples. On the other hand, in the case of the aqueous recording liquid of Comparative Example 1, the image was not output by the printer because of poor stability. Further, in the case of the aqueous recording liquid of Comparative Example 2, since the near-infrared absorber was not included, the scratching property and the drying property were poor.
In the combination of Preparation Example 7 / Example 2, Abs2 / Abs1 exceeded 0.5, and coloring was observed on the recording medium. Further, in the combination of Preparation Example 7 / Example 5, since the amount of the near-infrared absorber contained in Example 5 was large, the recording medium was colored.

JP 2002-154276 A Japanese Patent Publication No. 60-44336

Claims (5)

  The aqueous recording liquid which contains at least water and a water-soluble organic solvent and does not contain a coloring material further includes a near infrared absorber having a maximum absorption wavelength at 800 to 1200 nm, and the near infrared absorber is encapsulated in the resin fine particles. Alternatively, an aqueous recording liquid characterized by being adsorbed and dispersed.   The Abs2 / Abs1 is 0.5 or less, where Abs1 is the maximum absorbance at 800 to 1200 nm and Abs2 is the maximum absorbance at 400 to 700 nm of the near-infrared absorber. Aqueous recording liquid. A method for recording on a recording medium provided with a coating layer on at least one surface of a support, using an aqueous recording ink containing a coloring material and the aqueous recording liquid according to claim 1, A recording method, wherein the recording medium has a transfer amount of pure water of 3 to 15 mL / m ² at a contact time of 100 ms as measured by a dynamic scanning absorption meter.   A means for discharging a water-based recording ink containing a coloring material from a head and recording it on a recording medium, and a portion recorded by the recording means are overlaid using the water-based recording liquid according to claim 1 or 2. An ink jet recording apparatus comprising: means for recording; and means for irradiating near-infrared rays to the overlappingly recorded portion.   The inkjet recording apparatus according to claim 4, wherein the means for irradiating near infrared rays is a light source unit that irradiates near infrared rays having a wavelength of 800 to 1200 nm.

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