JP2007144684A - Inkjet recording method and inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method with no strike through without depending on a paper type, without carelessly decreasing print density, and with high speed printing characteristics, and an inkjet printer. <P>SOLUTION: The inkjet recording method performs printing on both faces on a regular paper by using an ink comprising 10-45% water and 50-90% solvent with a surface tension at 25°C of ≥25 mN/m and ≤40 mN/m, with a viscosity at 25°C of ≥1 mPa s and ≤50 mPa s, and a vapor pressure at 25°C of ≤133 Pa. In the inkjet recording method, a light source 5, a light detector 2 for detecting a reflective light from the paper based on the light source, and a color patch 3 are provided. The reflective light of the regular paper on the back surface of which the color patch is set is measured by the light detector, and a transmission density of the regular paper is obtained, and the maximum amount of feeding of the ink is determined in accordance with the transmission density. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method and an ink jet printer, and more particularly to an ink jet recording method and an ink jet printer capable of high-quality double-sided printing.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, ink jet recording devices that emit and control fine dots, ink with improved color reproduction gamut, durability, and emission suitability, ink absorbency, coloring material color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper.

  However, in an inkjet image recording system that requires special paper, there is a problem of an increase in the cost of the recording medium due to restrictions on the recording media that can be used.

  On the other hand, in the office, there is an increasing need for a system capable of performing full color printing at high speed without being restricted by a recording medium (for example, plain paper, coated paper, art paper, plain paper double-sided printing, etc.).

  As for the composition of the ink-jet ink, it can be printed at high speed, has good character reproducibility on plain paper, and shows through when printing (the phenomenon that the printed ink passes through the recording medium and the image appears on the back), feathering Various studies have been made from the viewpoints of no occurrence of image bleeding, rapid penetration into paper, and quick drying.

  In particular, for inkjet recording devices intended for double-sided printing, when performing double-sided printing on plain paper, if the back-through on printing is large, the back-through image overlaps with the printed content on the back, making it very difficult to see. End up.

  On the other hand, in the case of a printing form with high-speed printing in mind, the printed matter is superimposed immediately after printing, and the ink of the lower paper is reflected on the back surface of the upper paper, so that the surface drying property of the ink is required.

  If an ink that uses a liquid with a high vapor pressure as a solvent is selected as the ink with a high surface drying property, the ink transfer due to the overlap of printed matter can be suppressed, but the head maintenance and output stability will be impaired. It is not suitable for high-speed printing applications such as heads that require emission stability.

  As a method for achieving both the emission stability and the surface drying property, a method for improving the surface drying property by increasing the permeability of the ink into the paper and realizing high-speed printing is employed. However, when ink with high penetrability is used, the ink color material easily penetrates into the inside of the paper, the back-through becomes large, and when double-sided printing is created, the printing quality is deteriorated.

  Therefore, it is necessary to have a technique for controlling the show-through caused by the penetration of the ink coloring material when a highly penetrating ink is used.

  The main causes of the show-through are 1) When the information on the front surface can be seen through due to the transparency of the paper itself, 2) When the color material penetrates near the back surface, and 3) The solvent of the ink is paper There are three cases in which the transparency of the paper is increased while remaining inside.

  With regard to 1), in Patent Document 1, density selection means is provided, and when double-sided printing is performed, the density is lowered to prevent back-through.

  Furthermore, taking into consideration the versatility of the recording medium, the thickness of the recording paper is measured, and based on the value, the amount of ink shot that does not cause back-through is read from a table measured in advance, and the back of various papers is read. Patent Document 2 discloses a recording method capable of easily creating a printed material that does not cause omission.

  However, even with paper of the same thickness, the degree of strike-through varies due to the influence of the additive and the paper making density. It was insufficient to detect the difference in plain paper used in the office and to control the show-through without reducing the surface density more than necessary.

  On the other hand, with respect to 2), as an ink that is suitable for plain paper double-sided printing and does not cause cockling, Patent Document 3 proposes an ink characterized by using a solvent that satisfies a specific condition and water as solvents. As a result, penetrating performance close to that of water-based ink having low penetrability is achieved while having high penetrability.

  3) is a problem that can be solved over time by drying the ink. Depending on the purpose of the printed matter, it may be a problem, but it is not included in the scope of study in this study.

  Further, in Patent Document 4 as an apparatus having a configuration close to the present invention, a light source that generates light having a wavelength corresponding to substantially the center of the visible light region, and a photodetector that detects reflected light from a sheet based on the light source, The whiteness W of the paper is detected by comparing the irradiation light intensity Ti of the light source and the reflected light intensity Io of the photodetector, and information on the ink discharge amount stored in advance corresponding to the whiteness W There is a disclosure of an ink jet printer comprising a data processing unit that outputs a data processing unit and a control unit that drives an ink cartridge so that ink is ejected in accordance with information on the ink ejection amount.

However, Patent Document 4 is a technique for controlling the print quality of the surface of a white background, and there is no description of ink nor a description of providing a color patch at a light reflecting portion. Furthermore, the configuration having the color patch of the present invention on the back side of plain paper is in the direction of hindering the effects of the invention in Patent Document 4.
JP-A-7-314734 JP 2002-137382 A JP 2005-220296 A JP-A-8-11310

  Therefore, in view of the above problems, an object of the present invention is to provide an inkjet recording method and an inkjet printer that do not show through regardless of the paper type, do not inadvertently drop the print density, and have high-speed printing characteristics. .

  The above object of the present invention is achieved by the following configurations.

  1. 10 to 45% of water, the surface tension at 25 ° C. is 25 mN / m or more and 40 mN / m or less, the viscosity at 25 ° C. is 1 mPa · s or more and 50 mPa · s or less, and the vapor pressure at 25 ° C. is 133 Pa or less. In an ink jet recording method for performing double-sided printing on plain paper with an ink containing 50 to 90% of a solvent, a light source, a photodetector for detecting reflected light from the paper based on the light source, and a color patch, An ink jet recording method comprising: measuring reflected light of plain paper with a color patch on the back surface by a photodetector to determine a transmission density of the plain paper, and determining a maximum ink ejection amount according to the transmission density.

  2. 2. The inkjet according to 1 above, wherein the color patch is black, the visual density in status A is 0.6 or more, and the wavelength measured by the photodetector is a wavelength selected from a range of 500 nm to 600 nm. Recording method.

  3. 10 to 45% of water, the surface tension at 25 ° C. is 25 mN / m or more and 40 mN / m or less, the viscosity at 25 ° C. is 1 mPa · s or more and 50 mPa · s or less, and the vapor pressure at 25 ° C. is 133 Pa or less. An ink containing 50 to 90% of a certain solvent, a light source, a photodetector for detecting reflected light from the paper based on the light source, and a color patch, and the color patch on the back surface by the photodetector An ink jet printer characterized in that the reflected light of a plain paper set is measured to determine the transmission density of the plain paper, and the maximum ink ejection amount is determined according to the transmission density.

  4). 4. The inkjet according to item 3, wherein the color patch is black, the visual density in status A is 0.6 or more, and the wavelength measured by the photodetector is a wavelength selected from a range of 500 nm to 600 nm. Printer.

  According to the present invention, it is possible to provide an ink jet recording method and an ink jet printer that do not show through regardless of the paper type, do not inadvertently drop the print density, and have high-speed printing characteristics.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  As a result of intensive studies in view of the above problems, the present inventors have found that the water has a surface tension of 10 to 45% and a surface tension at 25 ° C. of 25 mN / m to 40 mN / m and a viscosity at 25 ° C. of 1 mPa · s. By using an inkjet ink containing 50 to 90% of a solvent having a vapor pressure of 25 Pa or less and a vapor pressure of 133 Pa or less at 25 ° C., by controlling the maximum driving amount according to the transmission density of plain paper, It has been found that a printed matter with no show-through can be produced without inadvertently reducing the print density of various plain papers.

  The transmission density of plain paper in the present invention refers to the color density of the color patch that appears to be transmitted from the front side when the color patch is installed on the back side of the plain paper.

  The back-through prevention method of the present invention utilizes the fact that the correlation between the transmission density of the recording paper and the maximum ink ejection amount that does not cause back-through occurs in the inkjet recording method of the present invention. In the ink jet recording method of the present invention, although the ink used in the present invention has a high solvent permeability, the coloring material tends to remain near the surface (printing surface) of the paper. It is considered that the correlation between the maximum ink ejection amount that does not cause omission increases.

  Details of the present invention will be described below.

  The plain paper in the present invention will be described. Examples of the plain paper in the present invention include what are generally called high-quality paper, neutral paper, and copy paper. In the text, the term “recording paper” or “paper” means plain paper.

  The transmission density of plain paper in the present invention refers to the color density of the color patch that appears to be transmitted from the front side when the color patch is installed on the back side of the plain paper.

  The transmission density in the present invention can be obtained from Equation 1 by irradiating plain paper with a color patch on the back side from the light source from the light source and measuring the reflected light from the plain paper with a photodetector.

Formula 1 D. = Log (I0 / I)
Where T.W. D. : Transmission density, I0: Light intensity of light source, I: Reflected light intensity from paper with color patches on the back.

  The light source used in the present invention needs to have an intensity in the visible light range. The wavelength of the light source is preferably 400 nm to 650 nm, more preferably 500 nm to 600 nm.

  The type of the light detector used in the present invention is not particularly specified as long as the intensity in the wavelength region of the light source can be measured. The detection range is preferably in the range of 400 nm to 650 nm, and more preferably in the range of 500 to 600 nm.

  It is also possible to use the transmission density of the wavelength according to the color of the ink to be used, measure the intensity of the transmission density for each color, and make the density control mechanism independent for each color.

  The color patch used in the present invention refers to a portion or a portion where coloring having absorption in the visible light region is made. There is no particular limitation on the size, but it is necessary to cover the reflection portion of the reflected light measured by the photodetector. The color patch can be attached to a part of the part, or a part of the part can be painted as a color patch.

  The color patch preferably has a density at the measurement wavelength of 0.6 or more, and more preferably 0.8 or more. As the density of the color patch is higher, the measured value becomes larger with respect to the variation in the density of the white background depending on the type of plain paper. In particular, the visual density in the status A of the color patch is 0.6 or more, and measuring the transmission density of the wavelength in the range of 500 to 600 nm is consistent with the visual evaluation of the print-through and the measurement sensitivity. Is also preferable.

  The color patch is provided so as to face the light source and the photodetector. Since the paper needs to be positioned between the light source and the photodetector and the color patch, the gap between the light source and the photodetector and the color patch is 1 mm or more, or the gap is variably operated to sandwich the paper. It is preferable that In addition, it is preferable that the paper is in contact with the color patch during transmission density measurement.

  As an example of a transmission density measuring mechanism having the light source, photodetector, and color patch, the configuration of the apparatus is shown in FIG. In FIG. 1, the color patch 3 is provided on the back surface of the recording paper 1, and the light density from the light source 5 can be measured by the photodetector 2 via the integrating sphere 4.

  A reflection densitometer can be cited as an apparatus having a light source and a photodetector that can measure the transmission density.

  The light source, the light detector, and the color patch are installed on a paper transport mechanism inside the printer, and are configured to perform measurement immediately before printing and control the amount of ink applied according to the transmission density obtained thereby. Is preferable from the viewpoint of convenience.

  Moreover, you may attach the light-shielding plate for reducing the influence of the integrating sphere for condensing reflected light and the external light source as needed.

  Next, control of the ink ejection amount will be described.

  For controlling the ink ejection amount, the relationship between the transmission density of the paper and the ejection amount that does not cause back-through is measured in advance, and the ejection amount obtained from the light transmittance of the recording paper measured by the above method from this relationship. Print with.

  The method for controlling the ink ejection amount is not particularly specified, but it is easy to perform the ejection amount control.

  Specific examples of the discharge amount control method include a method of changing the droplet amount of one dot, a method of controlling the temperature of the head, a method of thinning out the number of ejection times, and a method of reducing the total ink ejection amount by color management. Although it is mentioned, it is not limited to these.

The ink used in the present invention will be described.
A solvent having a surface tension at 25 ° C. of 25 mN / m or more and 40 mN / m or less, a viscosity at 25 ° C. of 1 mPa · s or more and 50 mPa · s or less, and a vapor pressure at 25 ° C. of 133 Pa or less will be described. .

  As described above, in the solvent (aqueous solvent) according to the present invention, as one requirement, the surface tension at 25 ° C. is 25 mN / m or more and 40 mN / m or less, preferably 25 mN / m or more. 32 mN / m or less. In addition, the viscosity at 25 ° C. is one of the characteristics that it is 1 mPa · s or more and 50 mPa · s or less, and preferably 1 mPa · s or more and 30 mPa · s or less. Moreover, although it is one of the characteristics that the vapor pressure in 25 degreeC is 133 Pa or less, Preferably it is 1-67 Pa.

  The solvent (aqueous solvent) that can be used in the present invention is not particularly limited as long as it satisfies all the three liquid properties defined above. For example, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, Propylene glycol monobutyl ether, dipropylene glycol monomethyl ether , Dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, diethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether , Diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dibutyl ether, 3-methyl-2,4-pentanediol, diethylene glycol monoethyl ether Or the like can be mentioned acetate.

  The ink used in the present invention contains various functional additives in addition to the above-described solvents.

  The ink used in the present invention contains a colorant in the above-mentioned solvent, and further contains each additive as described below, as the hue of the colorant used in the present invention, for example, Yellow, magenta, cyan, black, blue, green, and red are preferably used, and yellow, magenta, cyan, and black colorants are particularly preferable.

  The ink used in the present invention is a dye ink in which the colorant is a dye, or a pigment ink or a colorant that forms a dispersion containing fine pigment particles, in which the colorant is insoluble in the solvent constituting the inkjet ink. The present invention can be applied to various ink-jet inks such as a dispersion ink composed of a dispersion of a colored polymer.

  Examples of the dye that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the specific compounds include: For example, the dye illustrated in Unexamined-Japanese-Patent No. 2002-264490 can be mentioned.

  In addition, for oil-soluble dyes that form colored fine particles together with the polymer or the like and serve as a colorant, they are usually soluble in organic solvents that do not have a water-soluble group such as carboxylic acid and sulfonic acid and are insoluble in water, such as dispersed A dye or the like is selected. Also included are dyes that exhibit oil solubility by salting a water-soluble dye with a long-chain base. For example, acid dyes, direct dyes, salt-forming dyes of reactive dyes and long-chain amines are known. .

  However, in the ink used in the present invention, it is preferable to use a pigment as the colorant, and a pigment having no solubility in the solvent system is preferable from the viewpoint of exerting the intended effect of the present invention.

  As the pigment that can be used in the present invention, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments, and the like can be used, for example, organic pigments such as insoluble pigments and lake pigments, An inorganic pigment such as carbon black can be preferably used.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

In addition to the above, when red, green, blue and intermediate colors are required, the following pigments are preferably used alone or in combination. I. Pigment Red; 209, 224, 177, 194,
C. I. Pigment Orange; 43,
C. I. Vat Violet; 3,
C. I. Pigment Violet; 19, 23, 37,
C. I. Pigment Green; 36, 7,
C. I. Pigment Blue; 15: 6,
Etc. are used.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The pigment used in the present invention is preferably used after being dispersed by a disperser together with a dispersant and other necessary additives according to desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used.

  The average particle size of the pigment dispersion used in the ink used in the present invention is preferably 10 nm to 200 nm, more preferably 10 nm to 100 nm, and still more preferably 10 nm to 50 nm. If the average particle size of the pigment dispersion exceeds 100 nm, the dispersion becomes unstable. In addition, even when the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  By using such an ink, it is possible to perform printing with high surface dryness and good suitability for high-speed printing. Furthermore, although it is highly penetrable, only the solvent penetrates into the paper and the coloring material remains on the surface, so it is considered that the correlation between the transmission density of the paper and the back-through is high. Further, as described in Japanese Patent Application No. 2005-220296, the print density itself is as high as that of water-based ink.

  In the ink-jet ink used in the present invention, a surfactant can be used as an additive during dispersion. As the surfactant used in the present invention, any of cationic, anionic, amphoteric and nonionic can be used.

  Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

  Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, acylated peptide, alkyl sulfonate, Alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate, secondary higher alcohol Sulfate ester, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphate ester, alkyl phosphate ester Examples include tellurium salts.

  Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic activators include polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, Oxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, polyoxyethylene Fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetyl Glycol, acetylene alcohol, and the like.

  Further, it is preferable to use a surfactant in order to accelerate the penetration of ink droplets after ink ejection into plain paper, and such a surfactant has an adverse effect on the ink, such as storage stability. The surfactant is not limited as long as it does not affect the surface, and the same surfactants as those used as an additive at the time of dispersion can be used.

  Further, in the ink used in the present invention, the total content of calcium ions, magnesium ions and iron ions, which are polyvalent metal ions of the ink, is preferably 10 ppm or less, more preferably 0.1 to 0.1 ppm. 5 ppm, particularly preferably 0.1 to 1 ppm.

  By setting the content of polyvalent metal ions in the inkjet ink to the amount specified above, an ink having high dispersion stability can be obtained. The polyvalent metal ion according to the present invention is contained in sulfates, chlorides, nitrates, acetates, organic ammonium salts, EDTA salts and the like.

  In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust preventives, etc. may be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicon oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988, and 62-261476, As described in Kaisho 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A Nos. 59-42993, 59-52689, 62-280069, 61-242871, and JP-A-4-219266 Can be mentioned.

  In the ink jet recording method of the present invention, for example, an ink jet print is obtained by ejecting ink as droplets from an ink jet head based on a digital signal and adhering it to plain paper by a printer loaded with ink jet ink.

  In the ink jet recording method of the present invention, the ink jet head to be used may be an on-demand system or a continuous system. Also, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, thermal ink jet) Any ejection method such as a mold, a bubble jet (registered trademark) mold, or the like may be used.

  Among them, in the ink jet recording method of the present invention, the ink of the present invention is ejected from a piezo ink jet recording head having a nozzle diameter of 30 μm or less, recording is performed on plain paper, and the nozzle diameter is 30 μm or less. It is preferable to perform recording on plain paper by discharging from a piezo-type inkjet recording head of the line head type. The printing characteristics of the ink of the present invention can be sufficiently extracted by printing on the shuttle head type recording head using a line head type recording head.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Preparation of pigment dispersion A]
15 parts by mass of MA100 (Mitsubishi Carbon Black MA100, manufactured by Mitsubishi Chemical Corporation) as a pigment, 15 parts by mass of Jonkrill 501 (polymer dispersant: Jonkrill 501, manufactured by Johnson Polymer Co., Ltd.) as a dispersion resin, tripropylene glycol monomethyl After mixing 5 parts by mass of ether and 65 parts by mass of water, 200 g of zirconia beads having a diameter of 0.5 mm were placed in a polypropylene plastic bottle and sealed, and dispersed in a paint shaker for 5 hours. A pigment dispersion A was obtained.

[Preparation of ink]
A solvent and water were added to the plastic bottle containing the dispersion so as to have the following combination, and the mixture was stirred for about 30 minutes with a paint shaker. The numerical value of the addition amount in the table represents parts by mass. Thereafter, the beads were removed, and filtration and membrane deaeration treatment using a hollow fiber membrane were performed to prepare an ink.

Solvent: Tripropylene glycol monomethyl ether 230 parts by weight Water 45 parts by weight Pigment dispersion A 100 parts by weight The above solvent has a surface tension at 25 ° C. of 25 mN / m to 40 mN / m and a viscosity at 25 ° C. of 1 mPa · It is a solvent having a vapor pressure at 25 ° C. of not less than 50 mPa · s and not more than 133 Pa.

[Measurement of transmission density of paper]
Table 1 shows the prepared paper and the transmission density of each paper.

  The transmission density was measured using Xrite 938 (Japanese lithographic equipment). A thick paper having a visual density of 1.46 in status A was prepared as a color patch, and a recording paper was placed thereon, and a transmission density was measured by Xrite 938 from above. The measurement wavelength was set in the range of 500 nm to 600 nm.

〔Print〕
The ink prepared above was used in a Hewlett-Packard printer HP-PSC1610.

  As a printing pattern, an image pattern A for printing 10 cm × 10 cm solid black only on the front surface, an image pattern B for printing a 10 cm × 10 cm black solid image on the front surface, and a 5-point Mincho font on the back surface were prepared.

  The recording paper (size A4) shown in Table 1 was used as the recording paper.

  During printing, printing was performed by controlling the maximum ink ejection amount based on the value of the transmission density of the paper. As a method for controlling the driving amount, a method for controlling the driving amount by converting the density of the input file based on a relational expression obtained in advance and outputting it is used. The actually used relational expression is shown in Equation 2.

Formula 2 (Concentration after conversion) = (Density of input file) × (1.52−TD × 7.48)
Where T.W. D. Represents the transmission density.

(Missing evaluation)
For each solid image of Pattern A, the surface density and the back surface density were measured 3 days after printing. Since the density of the back surface is greatly affected by the color of the paper itself, the value calibrated based on the density of the non-printed area of the paper was used in order to match the actual sense of see-through. . That is, the surface concentration and the back surface concentration were defined as follows.

Surface density: (Measurement value of density on the printed surface)
Back surface density: (Measurement value of density on the back side of the printed part)-(Measurement value of density on the non-printed part)
For the measurement of the print density, Xrite 938 (Japanese lithographic equipment) was used, and the visual density in status A was used as a value.

  Table 1 shows the results.

  In any of the plain papers, the back surface density was 0.06 to 0.08, which could be suppressed to a level with no problem. Furthermore, even with CFPaver having the same thickness as J paper, it was possible to suppress the showthrough without inadvertently reducing the print density.

  Furthermore, although visual evaluation was performed about the pattern B, there were no problems, such as becoming difficult to read a character by a back-through.

(High-speed printing suitability evaluation)
About each paper of Table 1, immediately after pattern A was printed, the unprinted paper was pressed from the top and it was confirmed whether ink adhesion would occur.

  There was no ink adhesion on any of the papers.

  From the above, it has been found that ink jet recording can be performed without any show-through regardless of the paper type, high print density, and high-speed printing characteristics. Furthermore, an ink jet printer capable of the ink jet recording could be provided.

It is a structural example of the apparatus of the transmission density measuring mechanism which has a light source, a photodetector, and a color patch.

Explanation of symbols

1 Recording Paper 2 Photodetector 3 Color Patch 4 Integrating Sphere 5 Light Source

Claims (4)

10 to 45% of water, the surface tension at 25 ° C. is 25 mN / m or more and 40 mN / m or less, the viscosity at 25 ° C. is 1 mPa · s or more and 50 mPa · s or less, and the vapor pressure at 25 ° C. is 133 Pa or less. In an ink jet recording method for performing double-sided printing on plain paper with an ink containing 50 to 90% of a solvent, a light source, a photodetector for detecting reflected light from the paper based on the light source, and a color patch, An ink jet recording method comprising: measuring reflected light of plain paper with a color patch on the back surface by a photodetector to determine a transmission density of the plain paper, and determining a maximum ink ejection amount according to the transmission density. 2. The color patch according to claim 1, wherein the color patch is black, the visual density in status A is 0.6 or more, and the wavelength measured by the photodetector is a wavelength selected from a range of 500 nm to 600 nm. Inkjet recording method. 10 to 45% of water, the surface tension at 25 ° C. is 25 mN / m or more and 40 mN / m or less, the viscosity at 25 ° C. is 1 mPa · s or more and 50 mPa · s or less, and the vapor pressure at 25 ° C. is 133 Pa or less. An ink containing 50 to 90% of a certain solvent, a light source, a photodetector for detecting reflected light from the paper based on the light source, and a color patch, and the color patch on the back surface by the photodetector An ink jet printer characterized by measuring the reflected light of the installed plain paper to determine the transmission density of the plain paper and determining the maximum amount of ink to be ejected according to the transmission density. 4. The color patch according to claim 3, wherein the color patch is black and the visual density in status A is 0.6 or more, and the wavelength measured by the photodetector is a wavelength selected from a range of 500 nm to 600 nm. Inkjet printer.

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