JP2013103356A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide recorded matter which exhibits a high glossiness.SOLUTION: The inkjet recording method includes the following steps in the order: a pigment ink applying step in which pigment ink is applied to a recording medium; a first clear ink applying step in which a first clear ink is applied; and a second clear ink applying step in which a second clear ink is applied to at least a part of the region on the recording medium where the first clear ink is applied. The first clear ink includes an aqueous medium and a resin which has an acid value A. The second clear ink includes an aqueous medium and a resin which has an acid value B. The acid value A is 10 mgKOH/g or more to 120 mgKOH/g or less. The acid value B is 110 mgKOH/g or more to 250 mgKOH/g or less.

Description

  The present invention relates to an ink jet recording method.

  Conventional ink jet recording methods using pigment ink have a problem of low gloss. Here, “glossiness” includes both glossiness and image clarity in the entire image area, and “high glossiness” means that both glossiness and image clarity are high.

  As a technique for improving glossiness, Patent Document 1 describes a method of applying clear ink to the entire image area after recording.

JP 2002-200743 A

  However, as a result of studies by the present inventors, unevenness of the image is generated between the region to which the pigment ink is applied and the region to which the pigment ink is not applied, and sufficient glossiness cannot be obtained.

  Accordingly, an object of the present invention is to provide an ink jet recording method capable of giving an image having high glossiness, that is, excellent glossiness and image clarity.

The object of the present invention is achieved by the following configurations. That is, the present invention provides a pigment ink applying step for applying a pigment ink to a recording medium, and a first clear ink for applying a first clear ink so as to cover 80% or more of a desired area on the recording medium. An applying step, a drying step of drying the first clear ink applied to the recording medium, and a second clear ink in at least the region to which the first clear ink is applied among the regions on the recording medium. A second clear ink application step to be applied in this order, wherein the pigment ink includes an aqueous medium and a pigment, the first clear ink includes an aqueous medium and a resin having an acid value A, The clear ink includes an aqueous medium and a resin having an acid value B. The acid value A is 10 mgKOH / g or more and 120 mgKOH / g or less, and the acid value B is 110 mgKOH / g or more and 250. g KOH / g or less, and the acid value A and the acid value B is an ink jet recording method and satisfies the following formula (1).
Acid value A + 30 <acid value B Formula (1)

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording method which can give the image excellent in glossiness and image clarity can be provided.

It is a figure which shows the relationship between the coverage of clear ink, and image clarity. It is a figure which shows the relationship between drying of clear ink, and image clarity.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

<Ink set>
In the ink jet recording method of the present invention, pigment ink, first clear ink, and second clear ink are used. Hereinafter, each ink will be described in detail.

[Pigment ink]
The pigment ink of the present invention contains a pigment and an aqueous medium. The pigment used in the pigment ink is not particularly limited, and any known pigment can be suitably used. The pigment content in the pigment ink is preferably 0.01% by mass or more and 6.0% by mass or less, and preferably 0.1% by mass or more and 5.0% by mass or less with respect to the total mass of the ink. Is more preferable.

  Since the pigment does not dissolve in water, it is necessary to disperse the pigment in the ink. As a method for dispersing the pigment, known methods such as a method using a self-dispersing pigment, a method using a microcapsule pigment, and a method using a dispersant are known. Any of these methods can be suitably used. In the present invention, it is preferable to disperse the pigment using a dispersant.

(Dispersant)
As a dispersant for dispersing the pigment, an anionic resin is preferably used. Examples of the anionic resin include a hydrophobic monomer, a resin obtained from the anionic monomer, or a salt thereof. Examples of the hydrophobic monomer include methacrylic acid alkyl esters such as styrene, vinyl naphthalene and methyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate, p- Examples include acrylic acid alkyl esters such as tolyl methacrylate, sorbyl methacrylate, and methyl acrylate, phenyl acrylate, benzyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, and sorbyl acrylate.

  Examples of the anionic monomer include acrylic acid, methacrylic acid, maleic acid and the like. The resin obtained from the hydrophobic monomer and the anionic monomer may be any polymer such as a block copolymer, a random copolymer, and a graft copolymer. Examples of the anionic resin salt include alkali metal salts such as sodium salt, lithium salt, potassium salt, ammonium salt, alkylamine salt, alkanolamine salt, and the like.

  The weight molecular weight of the dispersant is preferably 5000 or more and 20000 or less, and more preferably 7000 or more and 15000 or less. The ratio of the amount of pigment to the amount of dispersant in the pigment ink (P / B ratio) is preferably in the range of 1/50 to 2/1, and preferably in the range of 1/10 to 1/1. More preferred.

(Aqueous medium)
The pigment ink of the present invention contains an aqueous medium. Although only water may be used as the aqueous medium, it is preferable to use a mixed solvent of water and a water-soluble organic solvent as the aqueous medium. Examples of the water-soluble organic solvent include those having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and n-pentanol. Alkyl alcohols; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tri Oxyethylene or oxypropylene polymers such as propylene glycol, polyethylene glycol, polypropylene glycol; ethylene glycol, propylene glycol Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as benzene, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,2-hexanediol; -Triols such as hexanetriol, glycerin, trimethylolpropane; lower alkyl ethers of glycols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl, butyl) ether Lower polyalkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether; monoethanolamine, diethanolamine Alkanolamines such as triethanolamine; sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, urea, ethylene urea, bishydroxyethyl sulfone, diglycerin, tri Although glycerol etc. are mentioned, it is not limited to this. Particularly preferable examples include ethylene glycol, 1,2-hexanediol, glycerin, diglycerin, polyethylene glycol, ethylene urea, and trimethylolpropane. The content of the water-soluble organic solvent is preferably 3.0% by mass or more and 30% by mass or less, and preferably 5.0% by mass or more and 20% by mass or less with respect to the total mass of the ink. More preferred. The water content is preferably 50% by mass or more and 95% by mass or less based on the total mass of the ink.

(Surfactant)
The pigment ink of the present invention may contain a surfactant. The surfactant is not particularly limited, and any known surfactant can be suitably used. However, it is preferable to use an acetylene glycol surfactant as the surfactant. The acetylene glycol surfactant can increase the wettability of the recording surface such as a recording medium to increase the ink permeability. Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, 5-dimethyl-1-hexyn-3-ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. Moreover, a commercial item can also be utilized for acetylene glycol type-surfactant, for example, Orphine E1010, STG, Y (above, Nissin Chemical Co., Ltd.), Surfinol 104, 82, 465, 485, TG (above , Air Products and Chemicals Inc.). The surfactant content is preferably 0.1% by mass or more and 2.0% by mass or less, more preferably 0.3% by mass or more and 1.0% by mass or less, based on the total mass of the ink. preferable.

[First clear ink]
The first clear ink of the present invention includes an aqueous medium and a resin having an acid value. In the present invention, it is preferable that the first clear ink does not substantially affect the hue of an image formed by the above-described pigment ink. Therefore, the amount of the color material in the first clear ink is preferably 0.001% by mass or less with respect to the total mass of the ink, and more preferably the first clear ink does not contain the color material.

(resin)
The resin contained in the first clear ink has an acid value. Moreover, the acid value of the resin is 10 mgKOH / g or more and 120 mgKOH / g or less. The acid value of the resin in the first clear ink is preferably 50 mgKOH / g or more and 100 mgKOH / g or less, more preferably 60 mgKOH / g or more and 80 mgKOH / g or less. In the present invention, the resin used for the first clear ink only needs to satisfy the above-described range (10 mgKOH / g or more and 120 mgKOH / g or less). Any known monomer such as a hydrophobic monomer or an anionic monomer that can be suitably used as a dispersant for the pigment ink thus obtained can be preferably used.

  The weight molecular weight of the resin in the first clear ink is preferably 5000 or more and 20000 or less, and more preferably 7000 or more and 15000 or less. The content of the resin in the first clear ink is preferably 3.0% by mass to 10.0% by mass with respect to the total mass of the first clear ink, and is preferably 4.0% by mass or more and 7. It is more preferably 0% by mass or less.

(Aqueous medium)
The first clear ink contains an aqueous medium. As the aqueous medium, any of the aqueous media that can be suitably used for the pigment ink described above can be preferably used.

(Surfactant)
The first clear ink may contain a surfactant. The surfactant is not particularly limited, and any known surfactant can be suitably used. However, it is preferable to use an acetylene glycol surfactant or a polysiloxane surfactant as the surfactant. . As the acetylene glycol-based surfactant, any acetylene glycol-based surfactant that can be suitably used for the above-described pigment ink can be used. Examples of the polysiloxane surfactant include BYK-333, BYK-347, BYK-348 (all manufactured by Big Chemie Japan). BYK-333 and BYK-348 contain polyether-modified polydimethylsiloxane as a main component, and BYK-347 contains polyether-modified siloxane. The surfactant is preferably 0.5% by mass or more and 10% by mass or less with respect to the total mass of the first clear ink.

[Second clear ink]
The second clear ink of the present invention contains an aqueous medium and a resin having an acid value. In the present invention, it is preferable that the second clear ink does not substantially affect the hue of the image formed by the above-described pigment ink. Therefore, the amount of the color material in the second clear ink is preferably 0.001% by mass or less with respect to the total mass of the ink, and more preferably the second clear ink does not contain the color material.

  The acid value of the resin contained in the second clear ink of the present invention is 110 mgKOH / g or more and 250 mgKOH / g or less. The acid value of the resin contained in the second clear ink is preferably 130 mgKOH / g or more and 200 mgKOH / g or less, and more preferably 150 mgKOH / g or more and 180 mgKOH / g or less.

  The second clear ink only needs to contain a resin that satisfies the above-mentioned acid value range (110 mgKOH / g or more and 250 mgKOH / g or less), and other materials in the clear ink such as a monomer or an aqueous medium constituting the resin. The same as those shown in the first clear ink can be preferably used.

The acid value A of the resin contained in the first clear ink of the present invention and the acid value B of the resin contained in the second clear ink satisfy the relationship represented by the following formula (1).
Acid value A + 30 <acid value B Formula (1)

That is, in the present invention, the acid value B is larger than the value obtained by adding 30 to the acid value A (mgKOH / g). In the present invention, the acid value B is preferably larger than the value obtained by adding 50 to the acid value A.
Next, the ink jet recording method of the present invention will be described in more detail.

<Inkjet recording method>
The inkjet recording method of the present invention includes a pigment ink applying step for applying a pigment ink, a first clear ink applying step for applying a first clear ink, a drying step for drying the first clear ink, and a second clear ink. The second clear ink application step for applying the ink is in this order.

  In the present invention, first, an image is formed on a recording medium using pigment ink. Thereafter, the first clear ink is applied so as to cover 80% or more of a desired area on the recording medium on which the image is formed (so that the coverage is 80% or more). The desired area refers to an area where gloss is desired to be improved. For example, when it is desired to increase the glossiness of the entire area of the recording medium on the surface to which the pigment ink has been applied, the first clear ink is applied so as to cover an area of 80% or more of the entire area of the recording medium. When it is desired to increase the glossiness only in the region to which the pigment ink has been applied, the first clear ink is applied so as to cover 80% or more of the region to which the pigment ink has been applied.

  FIG. 1 is a diagram showing the relationship between coverage and image clarity in the present invention. The figure is obtained when the first clear ink and the second clear ink described in Example 2 described later are used. In addition, as the pigment ink, PFC-103Bk manufactured by Canon Inc. is used, and an image is formed by applying the pigment ink at a 75% duty. In the present invention, the duty is a value obtained by multiplying the number of ink dots applied to a unit area divided by the product of the number of vertical pixels per unit area and the number of horizontal pixels per unit area by 100. is there. Also, in the figure, the image clarity on the vertical axis is determined by measuring the sharpness value by the same method as the image clarity measurement method described in the examples described later, and the obtained sharpness value is used as the image clarity value. . As is apparent from FIG. 1, in the present invention, the coverage is preferably 85% or more, more preferably 90% or more, and particularly preferably 100%.

  In the present invention, after the first clear ink is applied, the first clear ink is dried. The method for drying the first clear ink is not particularly limited, and may be naturally dried by leaving it in the air for a certain period of time, or may be dried using an aggressive drying means such as hot air drying. Also good. FIG. 2 is a diagram showing the relationship between the drying time of the first clear ink and the image clarity. FIG. 2 is a plot obtained by using the ink set of Example 2 of the present invention, which will be described later, and variously changing the time from application of the first clear ink to application of the second clear ink. In addition, it was left to stand in the environment of normal temperature (25 degreeC) and humidity 50% after giving a 1st clear ink and providing a 2nd clear ink.

  In this way, excellent image clarity can be obtained by sufficiently drying the first clear ink. As apparent from FIG. 2, when the first clear ink is naturally dried, it is preferably left for 6 seconds or more, and more preferably for 8 seconds or more.

  In the present invention, after the first clear ink is dried, the second clear ink is applied to at least the region to which the first clear ink has been applied. The area where the second clear ink is applied is preferably the entire surface of the recording medium.

  Furthermore, in the present invention, as described above, the acid value A of the resin contained in the first clear ink is 10 mgKOH / g or more and 120 mgKOH / g or less, and the acid value B of the resin contained in the second clear ink is It is 110 mgKOH / g or more and 250 mgKOH / g or less, and acid value A and B satisfy | fill the relationship represented by following formula (1).

Acid value A + 30 <acid value B Formula (1)
When the first clear ink and the second clear ink satisfy the relationship of the acid values, an image having excellent glossiness and image clarity can be obtained. The estimation mechanism is shown below.

  The first clear ink that satisfies the above relationship with the acid value of the resin is less likely to penetrate inside the recording medium and inside the pigment, and is likely to remain on the area where the pigment is applied or on the recording medium. The resin can form a film so as to cover the pigment and the recording medium. Since the film formed by the first clear ink has the property of preventing liquid from penetrating, if the second clear ink is applied on the film, the second clear ink is difficult to penetrate inside the film and is retained on the film. Is done. The second clear ink in which the acid value of the resin satisfies the relationship described above can smooth the unevenness formed by the pigment ink or the first clear ink. Thereby, the outstanding glossiness can be obtained.

  That is, in the present invention, a film is formed on the surface of the recorded material by the first clear ink so that the second clear ink does not penetrate into the pigment or the recording medium, and the second clear ink is formed on the formed film. Excellent glossiness is obtained by applying a clear ink to smooth the surface of the recorded matter.

  On the other hand, when the acid value of the resin in the first clear ink does not satisfy the above relationship, particularly when a resin having an acid value greater than 120 mgKOH / g is used, the clear ink is in the pigment or the recording medium. And the film cannot be formed on the pigment and the recording medium. As a result, the second clear ink applied after the first clear ink also penetrates into the pigment or the recording medium as in the first clear ink, and sufficient glossiness cannot be obtained.

  Further, when the acid value of the resin in the second clear ink does not satisfy the above relationship, particularly when a resin having an acid value smaller than 110 mgKOH / g is used, the resin in the second clear ink A film is formed along the unevenness formed by the pigment ink or the first clear ink, and the unevenness cannot be sufficiently smoothed, and sufficient glossiness cannot be obtained.

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

[Preparation of clear ink]
Mix and stir the resin, organic solvent, surfactant, and ion-exchanged water in the blending amounts shown in Table 1 below, adjust the pH to 9.5 with an aqueous KOH solution, and pass it through a glass filter AP20 (Millipore). Thus, clear inks C1 to C6 were obtained. The unit of the numerical values described in Table 1 is% by weight, and adjustment was performed using ion-exchanged water so that the total weight of the clear ink was 100% by weight. V1 to V5 are all styrene acrylic acid random copolymers. Moreover, the weight average molecular weight of V1-V5 is as showing below.
V1: 14000, V2: 14000, V3: 14000, V4: 12000, V5: 13000

[Measurement of acid value]
The acid values of the resins V1 to V5 described above were measured. Specifically, 2 g of V1 to V5 resins were added to a mixture of 200 mL of THF and 100 mL of ethanol, respectively, and neutralization titration (based on JIS0070) was performed using an ethanol KOH solution with a known normality, and the acid value was measured. .

[Create recorded material]
The clear ink combinations of Examples 1 to 5 and Comparative Examples 1 to 5 shown in Table 2 were filled in the red ink and green ink chambers of an ink jet printer (“iPF5100” manufactured by Canon Inc.), respectively. Ink cartridges other than clear were each loaded with the following color inks.
Yellow: PFI-101M (manufactured by Canon Inc.)
Magenta: PFI-101Y (Canon)
Cyan: PFI-101C (manufactured by Canon Inc.)

  Using the inkjet printer described above, yellow glossy paper (manufactured by Canon Inc.), yellow ink, magenta ink, and cyan ink are used to produce yellow, magenta, cyan, red, green, and blue images, high-duty images, and low-duty images. Two types of duty images were formed. Specifically, low-duty images were formed for yellow, magenta, cyan, red, green, and blue so that the print duty was 10%. For secondary color images such as red, green, and blue, adjust the duty of yellow, magenta, and cyan inks so that yellow ink is applied at 5% duty and cyan ink is applied at 5% duty. And produced. In the same way, high duty images were formed for yellow, magenta, cyan, red, green, and blue so that the print duty was 160%. The volume of one ink drop was 4.8 pL. The image pattern was printed in an area of 50 mm × 50 mm, and the “clean” mode was used in the printer driver.

  After forming each image by the method described above, the recording medium was discharged from the ink jet printer. Subsequently, the recording medium on which the image was formed was fed again, and the first clear ink was applied to the entire image at 100% duty in one pass. After applying the first clear ink, the recording medium was discarded and fed again, and the second clear ink was applied to the entire image at 100% duty in one pass. At this time, the time from application of the first clear ink to application of the second clear ink was 8 seconds. During this 8 seconds, the recording medium was stored in an environment of room temperature and 50% humidity.

[Evaluation of recorded material]
(20 degree gloss)
The 20-degree gloss of each duty of each color was measured with GMX-203 (Murakami Color Research Laboratory Co., Ltd.), and the glossiness (lowest glossiness) of the image with the lowest glossiness in the high-duty image and the low-duty image The glossiness of the image having the lowest glossiness was evaluated according to the following criteria. The results are shown in Table 2. In Table 2, “duty high” and “low” represent an evaluation result in a high duty image and an evaluation result in a low duty image, respectively.
5: Minimum glossiness of 80 or more 4: Minimum glossiness of 75 or more and less than 80 3: Minimum glossiness of 70 or more and less than 75 2: Minimum glossiness of 60 or more and less than 70 1: Minimum glossiness of less than 60 (Transparency)
The image clarity (sharpness value) of each duty of each color is measured with DIAS (QEA), and the image clarity (minimum sharpness value) of the image with the lowest image clarity in the high duty image and the image clarity of the low duty image. The image clarity of images with low image quality was evaluated according to the following criteria. The results are shown in Table 2.
5: Minimum sharpness value of 5.0 or more 4: Minimum sharpness value of 4.5 or more and less than 5.0 3: Minimum sharpness value of 4.0 or more and less than 4.5 2: Minimum sharpness value of 3.0 or more Less than 0 1: Minimum sharpness value is less than 3.0

Claims (2)

A pigment ink application step for applying a pigment ink to a recording medium;
A first clear ink application step of applying a first clear ink so as to cover 80% or more of a desired area on the recording medium;
A drying step of drying the first clear ink applied to the recording medium;
A second clear ink application step of applying a second clear ink to at least an area of the recording medium on which the first clear ink has been applied, in this order,
The pigment ink includes an aqueous medium and a pigment, the first clear ink includes an aqueous medium and a resin having an acid value A, and the second clear ink includes an aqueous medium and a resin having an acid value B,
The acid value A is 10 mgKOH / g or more and 120 mgKOH / g or less, the acid value B is 110 mgKOH / g or more and 250 mgKOH / g or less,
The acid value A and the acid value B satisfy the following formula (1).
Acid value A + 30 <acid value B Formula (1)   The inkjet recording method according to claim 1, wherein the resin is a resin obtained from a hydrophobic monomer and an anionic monomer.