JP4717627B2 - Inkjet recording method and inkjet recording apparatus - Google Patents

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus. Specifically, an ink jet recording method and method for recording a secondary color image using a reaction liquid that insolubilizes or agglomerates ink colorants such as dyes and pigments, and two types of inks having different colorants. The present invention relates to an inkjet recording apparatus to be executed.

  The ink jet recording method performs recording by ejecting small droplets of recording liquid (ink) and attaching them to a recording medium such as paper. As a method for ejecting ink, for example, a method in which droplets are ejected by generating bubbles by applying thermal energy generated by an electrothermal converter to the ink is well known. This method has an advantage that a high-density multi-orifice of a recording head can be easily realized and a high-resolution and high-quality image can be recorded at high speed (see Patent Documents 1 to 3).

  However, in the ink jet recording method, when a color image is to be recorded, the next ink is superimposed before fixing each of a plurality of color inks, so that the problem caused by an increase in the amount of ink applied is a problem. It is known that it can occur. In other words, due to the large amount of applied ink, there is a problem in that the image quality deteriorates due to color blurring or non-uniform mixing at the boundary between different colors of the recorded image (hereinafter also referred to as bleeding). is there.

  In particular, when a secondary color image is recorded using two different color inks, bleeding and color reduction occur more remarkably for the reasons described below. When an image of a secondary color is recorded using two different colors of ink, the permeability of the ink to the recording medium may be reduced in order to prevent the colorant in the ink from sinking into the recording medium. However, in this case, before the ink first applied to the recording medium is fixed, the next ejected ink is applied in an overlapping manner (on the first applied ink). As a result, the amount of ink per unit area that does not penetrate and is present on the recording medium is greater than when a primary color image is recorded. In this case, the occurrence of bleeding may become more conspicuous at a boundary portion with another image area adjacent to the secondary color image forming area.

  In order to suppress this bleeding, it is known to use an ink in which a compound that enhances permeability such as a surfactant is added to the ink (see Patent Document 4). However, the penetrability of the recording medium to the ink is increased by the surfactant or the like of the ink applied first. As a result, when the next ink is applied in an overlapping manner, a highly permeable ink is applied to a highly permeable recording medium. Then, the ink colorant penetrates deeply into the recording paper, resulting in inconveniences such as a decrease in image density, a decrease in image clarity, and an image appearing through the back of the recording medium.

  On the other hand, a method is known in which a liquid that makes a good image adhere to a recording sheet prior to ink application. For example, a recording method has been proposed in which a solution of a polymer such as carboxymethyl cellulose, polyvinyl alcohol, or polyvinyl acetate is jetted onto a recording medium in advance (see Patent Document 5). According to this method, although bleeding is improved, there is a concern that the solution itself is poorly dried and the fixability is lowered.

  In order to improve this, there is known a method of applying an ink containing an anionic dye after applying a liquid containing an organic compound having two or more cationic groups per molecule (see Patent Document 6). Yes. Similarly, a method of applying an ink after applying an acidic liquid containing succinic acid or the like (see Patent Document 7) or a method of applying a liquid that insolubilizes a dye before recording (see Patent Document 8) is also known. ing.

  However, both methods apply ink after the reaction liquid penetrates into the recording medium and exists in the recording medium and disappears from the surface of the recording medium. For this reason, although bleeding can be suppressed to some extent, when a secondary color image is recorded by applying another color ink after that, there is a problem caused by the fact that it cannot sufficiently react with the reaction liquid. May occur. That is, since most reactions occur in the recording medium, there is a problem that the color developability is not improved, and there is a problem that the colorant is visually recognized on the back surface of the recording medium.

  On the other hand, after applying the reaction liquid to the recording medium, a proposal has been made to apply ink at least once on the area to which the reaction liquid has been applied, and further to apply the reaction liquid to the area to which the ink has been applied. (See Patent Document 9).

Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914 JP 55-65269 A JP-A-56-89595 JP 63-29971 A Japanese Unexamined Patent Publication No. 64-9279 JP-A-64-63185 JP 2002-337332 A

  As described above, the conventional technique for improving bleeding using a reaction liquid sufficiently records the recording quality such as the density or color developability of the recorded image by sufficiently reacting the ink and the reaction liquid when recording a secondary color image. There is a difficulty in raising it. This is because, in the above-described prior art, the reaction liquid and ink application interval is not appropriately set in accordance with the permeability of the reaction liquid and ink or a mixture thereof to the recording medium. This is because the reaction between the liquid and the ink may be insufficient. As a result, sufficient color development may not be obtained, and further bleeding may not be completely prevented.

  Among the above-mentioned conventional techniques, the method of applying the ink after applying the reaction liquid, and further applying the reaction liquid thereon, always applies the reaction liquid before applying the ink. The reaction between the reaction liquid and the ink is relatively good. However, in order to be able to record an image of a secondary color by one scan by this method, it is necessary to provide a reaction liquid discharge nozzle for each color ink discharge nozzle. As a result, in the case where the reaction liquid and the asserting nozzle are provided for each ink nozzle as described above to increase the recording speed, the cost of the recording head increases, which is not preferable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus, which improve bleeding when recording an image of a secondary color, improve color developability, and solve the problem of ink see-through in a recording medium. It is to provide.

  Therefore, in the present invention, the first ink, the second ink having a color different from that of the first ink, and the reaction liquid for aggregating or insolubilizing the components in the first and second inks are used as a recording medium. An ink jet recording method for applying and recording, wherein a first applying step for applying the reaction liquid to the recording medium, and at least a part of a region to which the reaction liquid is applied in the first applying step A second applying step for applying the first ink, and a third applying step for applying the second ink to at least a part of the region to which the first ink has been applied in the second applying step. An application step, wherein a wetting time Tw1 of the reaction liquid with respect to the recording medium and a time Td1 from application of the reaction liquid to application of the first ink satisfy a relationship of Td1 <Tw1. And before The relationship between the wetting time Tw2 of the mixture of the first ink and the reaction liquid with respect to the recording medium and the time Td2 from when the first ink is applied to when the second ink is applied satisfies the relationship Td2 <Tw2. It is characterized by satisfying.

  And applying means for applying a first ink, a second ink having a color different from that of the first ink, and a reaction liquid for aggregating or insolubilizing the coloring material of the first and second inks. An inkjet recording apparatus that performs recording on a recording medium using the first ink after applying the first ink to at least a part of a region on the recording medium to which the reaction liquid has been applied. Control means for controlling the application means so as to apply the second ink to at least a part of the applied area, and the control means is a wetting time Tw1 of the reaction liquid with respect to the recording medium. And a time Td1 from application of the reaction liquid to application of the first ink satisfies a relationship of Td1 <Tw1, and a mixture of the first ink and the reaction liquid with respect to the recording medium. The application unit is controlled such that the time Td2 and the time Td2 from application of the first ink to application of the second ink satisfy a relationship of Td2 <Tw2. .

  According to the above configuration, the time Tw1 from when the reaction liquid is applied to the start of permeation into the recording medium and the time from when the mixture of the reaction liquid and the first ink is generated to start permeation into the recording medium. Tw2 becomes longer than the time until ink is applied next. Thereby, the reaction between the reaction liquid and the ink or the mixture thereof and the ink is sufficiently performed on the recording medium.

  As a result, bleeding when recording an image of a secondary color is improved, color developability is improved, and it is possible to perform recording in which the problem of ink breakthrough in the recording medium is solved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In an inkjet recording method according to an embodiment of the present invention, a reaction liquid containing polyvalent metal ions is applied on a recording medium, and then a plurality of pigment inks having a surface tension lower than the surface tension of the reaction liquid is applied. This is an ink jet recording method for performing recording. Specifically, it has a first application step of applying a reaction liquid for aggregating a pigment as an ink colorant onto the recording medium. In addition, there is a second application step of applying the first pigment ink to at least a part of the region to which the reaction liquid is applied on the recording medium by the first application step. Further, a second pigment ink different from the first pigment ink is applied to at least a part of the region where the first pigment ink is applied on the recording medium by the second application step. And three granting steps.

The wetting time Tw1 of the reaction liquid with respect to the recording medium and the time Td1 from application of the reaction liquid to application of the first pigment ink are as follows:
Td1 <Tw1 Formula 1
It is in the relationship shown by. Furthermore, the wetting time Tw2 of the mixture of the first ink and the reaction liquid with respect to the recording medium, and the time Td2 from when the first pigment ink is applied to when the second pigment ink is applied,
Td2 <Tw2 Formula 2
It is in the relationship shown by.

  In the above recording method, the method for applying the reaction liquid to the recording medium in the first applying step (hereinafter referred to as the applying method) is not particularly limited, but application by an inkjet method which is a well-known technique can be preferably used. In addition, as an application method by the ink jet method, for example, a method of ejecting ink using thermal energy, or a piezoelectric element that deforms according to an applied voltage is provided. The method of discharging is mentioned. Further, the method for applying the pigment ink to the recording medium in the second and third application steps is not particularly limited, and the same method as the method for applying the reaction liquid can be used.

  The first pigment ink applied in the second application process has at least a part of the reaction liquid applied in the first application process, preferably a reaction liquid application area and a pigment ink application area as much as possible. It is given to match in many areas. However, if the respective areas do not completely match, it does not mean that the image quality improvement effect due to the reaction between the reaction liquid and the pigment ink cannot be obtained. Further, in the present embodiment, from the viewpoint of bringing the reaction liquid and the first pigment ink into contact with each other in liquid form, and from the viewpoint of promptly fixing the aggregate generated by the reaction between the first pigment ink and the reaction liquid. The permeability of the pigment ink is made higher than the permeability of the reaction liquid. Specifically, the surface tension of the first pigment ink is set lower than the surface tension of the reaction liquid. The relationship between the surface surface forces can be adjusted, for example, by changing the content ratio of the surfactant in the reaction liquid and the first pigment ink.

  Further, the reaction liquid starts to penetrate into the recording medium when the wetting time Tw for the recording medium has elapsed. Therefore, in the present embodiment, the recording is performed such that the wetting time Tw and the time Td1 from application of the reaction liquid to application of the first pigment ink satisfy the relationship defined by the above formula 1 (Td1 <Tw1). I do. That is, the pigment ink is applied and brought into contact with the reaction liquid before the permeation of the reaction liquid starts. Thereby, the pigment ink can be brought into contact with the interface of the reaction liquid existing in a liquid state on the recording medium.

  As described above, the wetting time Tw is a delay time from when the reaction liquid contacts the surface of the recording medium until absorption starts. This wetting time Tw can be obtained by the Bristow method. The Bristow method is JAPANTAPPI paper pulp test method no. 51, “Method for testing liquid absorbency of paper and paperboard”. According to this, the wetting time Tw can be obtained by an absorption curve defined by the absorption coefficient Ka (mL / m 2 · ms 1/2) and the roughness index Vr (mL / m 2). An example of this absorption curve is shown in FIG.

  As shown in FIG. 1, the wetting time Tw in this embodiment is represented by an approximate straight line A by the least square method for calculating the absorption coefficient Ka, a liquid transfer amount V, and a roughness index Vr, V = Vr. The time until the intersection AB with the straight line B of FIG. In general, the liquid absorbability of a recording medium such as plain paper can be controlled with the surface tension of the liquid as a main factor. In a general ink jet recording method, since the application time difference (landing time difference) Td is several milliseconds or more, the surface tension of the reaction solution is desirably 35 mN / m to 60 mN / m.

  Here, strictly speaking, the landing time difference Td1 between the reaction liquid and the first pigment ink in this embodiment is recorded after the first pigment ink is discharged after the reaction liquid is discharged and landed on the recording medium. This is the time until landing on the medium. However, in general, the time from when the reaction liquid or ink is ejected from the recording head to when the ink lands on the recording medium is not necessarily the same time each time, and varies depending on the type of reaction liquid or ink. Because there is, it is difficult to grasp accurately. Even if there is some variation in the time from when a certain ink is ejected to landing, the difference is so small as to be negligible compared to the landing time difference. From these points, the landing time difference Td in this embodiment is defined as the time from when the reaction liquid is discharged until when the first pigment ink is discharged.

The time Td1 from when the reaction liquid is discharged to when the first pigment ink is discharged is the distance between the nozzles for discharging the reaction liquid and the ink, the drive frequency of each nozzle, and the recording resolution. Can be controlled through. Specifically, the distance in the main scanning direction between the nozzle for discharging the reaction liquid and the nozzle for discharging the second pigment ink is Amm, the driving frequency of each nozzle is BHz, and the recording resolution is Cdpi. Then, the landing time difference Td1 is obtained by the following equation.
Td1 = C × A / 25.4 × (1 / B)
For example, if the distance between the discharge ports is 2 mm, the drive frequency is 20 kHz, and the resolution is 1200 dpi, the landing time difference Td is about 5 msec.

  Further, a third application process for applying the second pigment ink having a color different from that of the first pigment ink to the first pigment ink applied in the second application process is as follows. The second pigment ink is different from the first pigment ink because, in the present embodiment, the purpose is to improve the image quality of the secondary color. Specifically, when creating a blue image with a cyan pigment and a magenta pigment for the first pigment and the second pigment, respectively, when creating a green image with a cyan pigment and a yellow pigment, the magenta pigment and the yellow pigment, respectively. In this case, a red image is created. However, the order in which the secondary colors are created does not matter.

  In the third application step, as described above, the wetting time Tw2 of the aggregate (hereinafter also referred to as a mixture) of the first ink and the reaction liquid with respect to the recording medium and the first pigment ink are applied. The time difference Td2 until the pigment ink is applied satisfies the relationship of the above formula 2. This defines the timing for applying the second pigment ink in the third application step. Specifically, after the first pigment ink is applied in the second application step, before the wetting time Tw of the mixture of the reaction liquid and the first pigment ink existing on the recording medium elapses, Two pigment inks are applied.

  When the first pigment ink is applied to the reaction liquid that exists in a liquid state on the recording medium so as to satisfy the relationship of the above formula 1, a mixture of the reaction liquid and the first pigment ink is generated. Here, the mixture exists in a liquid state immediately after the first pigment ink is applied, and starts to penetrate into the recording medium when the wetting time Tw2 has elapsed. Accordingly, the pigment ink can be brought into contact with the interface of the mixture existing on the recording medium by applying the second pigment ink before the permeation is completely completed.

  According to the above-described recording method of the present embodiment, the reaction liquid, the first pigment ink, and the second pigment ink can be sufficiently reacted on the recording medium. On the other hand, when any one of the conditions shown in the above formulas 1 and 2 is not satisfied, the reaction liquid and the pigment ink cannot sufficiently react.

  Moreover, in order to satisfy the relationship of the said Formula 1 and Formula 2 simultaneously, it is desirable to provide a reaction liquid, the 1st pigment ink, and the 2nd pigment ink by the same scanning. On the other hand, in a general recording head, when a secondary color image is to be recorded by a plurality of scans, for example, the reaction liquid is applied in the first scan and the first pigment is applied in the second scan. It is conceivable to apply an ink and a second pigment ink. In this case, there is a high possibility that the reaction liquid application time Tw1 elapses between the application of the reaction liquid in the first scan and the application of the pigment ink in the second scan. By sinking in, both inks may not sufficiently react with the reaction liquid. In addition, when the reaction liquid and the first pigment ink are applied during the first scanning and the second pigment ink is applied during the second scanning, similarly, until the second pigment ink is applied, There is a high possibility that the wetting time Tw2 of the mixture of the reaction liquid and the first pigment ink will elapse.

  Next, the reaction solution used in this embodiment will be described. The most suitable reactant that reacts with the pigment ink contained in the reaction liquid of this embodiment is a polyvalent metal salt. The polyvalent metal salt is composed of a divalent or higher polyvalent metal ion and an anion that binds to the polyvalent metal ion. In the reaction solution, at least a part of the polyvalent metal salt is dissociated.

  Specific examples of the polyvalent metal ions include divalent metal ions such as Ca 2+, Cu 2+, Ni 2+, Mg 2+ and Zn 2+, and trivalent metal ions such as Fe 3+ and Al 3+. Examples of the anion include Cl-, NO3-, SO42-, and the like. In order to form an aggregated film by reacting instantaneously, it is desirable that the total charge concentration of the polyvalent metal ions in the reaction solution is twice or more the total charge concentration of the reverse polarity ions in the pigment ink.

  Examples of the water-soluble organic solvent that can be used in the reaction solution of the present embodiment include amides such as dimethylformamide and dimethylacetamide, ketones such as acetone, and ethers such as tetrahydrofuran and dioxane. Examples of the water-soluble organic solvent include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, and 1,2,6-hexanetriol. Furthermore, examples of the water-soluble organic solvent include alkylene glycols such as thiodiglycol, hexylene glycol, and diethylene glycol, ethylene glycol methyl ether, and diethylene glycol monomethyl ether. Furthermore, examples of the water-soluble organic solvent include lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether, and monohydric alcohols such as ethanol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol. In addition to these, examples of water-soluble organic solvents include glycerin, N-methyl-2-pyrrolidone, 1,3-dimethyl-imidazolidinone, triethanolamine, sulfolane, dimethylsulfoxide, and the like. Although there is no restriction | limiting in particular about content of the said water-soluble organic solvent in the reaction liquid of this embodiment, It is 5-60 mass% of the reaction liquid total mass, Preferably it is the range of 5-40 mass%.

  Moreover, you may mix | blend suitably additives, such as a viscosity modifier, a pH adjuster, antiseptic | preservative, and antioxidant, with the reaction liquid of this embodiment as needed. However, the selection and addition amount of the surfactant that functions as a penetration accelerator must be considered in order to suppress the permeability of the reaction liquid to the recording medium. In addition, the reaction liquid of the present embodiment is more preferably colorless, but it may be light in a range that does not change the color tone of each color ink when mixed with ink on a recording medium. Furthermore, as a preferable range of various physical properties of the reaction solution as described above, the viscosity at around 25 ° C. is 1 to 30 cps. What was adjusted so that it might become the range of this is preferable. Further, as described above, the landing time difference Td is several milliseconds or more, and the surface tension of the reaction liquid is 35 mN / m to 60 mN / m from the viewpoint of sufficiently reacting the pigment ink and the reaction liquid on the paper surface. It is desirable that

  Next, the pigment ink used in this embodiment will be described. The pigment used in the pigment ink of the present embodiment is used in a mass ratio of 1 to 20 mass%, preferably 2 to 12 mass%, based on the total mass of the pigment ink. The following are mentioned as a pigment of this embodiment. Examples of yellow pigments include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow2. Furthermore, C.I. I. Pigment Yellow 3, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 16, C.I. I. Pigment Yellow 83 or the like. Examples of magenta pigments include C.I. I. PigmentRed5, C.I. I. PigmentRed7, C.I. I. PigmentRed 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn). Furthermore, C.I. I. Pigment Red 57 (Ca), C.I. I. PigmentRed 112, C.I. I. PigmentRed122 etc. are mentioned. Examples of cyan pigments include C.I. I. PigmentBlue1, C.I. I. PigmentBlue 2, C.I. I. PigmentBlue 3, C.I. I. PigmentBlue 15: 3, C.I. I. PigmentBlue16. Furthermore, C.I. I. PigmentBlue 22, C.I. I. VatBlue4, C.I. I. VatBlue6 etc. are mentioned. Of course, it is not restricted to these. In addition to the above, newly produced pigments such as self-dispersing pigments can also be used.

  The pigment dispersant may be any water-soluble resin, but preferably has a weight average molecular weight in the range of 1,000 to 30,000. More preferably, the one in the range of 3,000 to 15,000 is used. Examples of such dispersants include styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid, and the like. There are derivatives. Examples of the dispersant include itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, vinyl pyrrolidone, and acrylamide. Furthermore, a block copolymer comprising at least two monomers (of which at least one is a hydrophilic polymerizable monomer) selected from the above derivatives or the like as a dispersant, or a random copolymer. Examples thereof include polymers, graft copolymers, and salts thereof. Furthermore, natural resins such as rosin, shellac and starch can also be preferably used as the dispersant. These resins are soluble in an aqueous solution in which a base is dissolved, and are alkali-soluble resins. In addition, it is preferable to contain the water-soluble resin used as these pigment dispersants in the range of 0.1 to 5% by mass with respect to the total mass of the pigment ink.

  In particular, in the case of a pigment ink containing a pigment as described above, the entire pigment ink is preferably adjusted to be neutral or alkaline. By setting it as such, the solubility of the water-soluble resin used as a pigment dispersant can be improved, and a pigment ink having further excellent long-term storage stability can be obtained. However, in this case, since it may cause corrosion of various members used in the ink jet recording apparatus, it is desirable that the pH range is 7-10.

  Examples of the pH adjuster used in this case include various organic amines such as diethanolamine and triethanolamine, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide, Examples include organic acids and mineral acids. The above-described pigment and dispersant water-soluble resin are dispersed or dissolved in an aqueous liquid medium.

  A suitable aqueous liquid medium in the pigment ink containing the pigment used in the present embodiment is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  The water-soluble organic solvent used by mixing with water is, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, or sec-butyl alcohol. Moreover, C1-C4 alkyl alcohols, such as tert- butyl alcohol; Amides, such as a dimethylformamide and a dimethylacetamide, can be used. Furthermore, ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol can be used. Furthermore, alkylene glycols can also be used. These alkylene glycols include ethylene glycol, propylene glycol, butylene glycol, and triethylene glycol. In some cases, alkylene groups such as 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol contain 2 to 6 carbon atoms. The water-soluble organic solvent further includes glycerin. Furthermore, the water-soluble organic solvents include lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether. Furthermore, water-soluble organic solvents include N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

  The content of the water-soluble organic solvent as described above in the pigment ink is generally in the range of 3 to 50% by mass of the total mass of the pigment ink. Preferably, it is used in the range of 3 to 40% by mass. The water content used is in the range of 10 to 90 mass%, preferably 30 to 80 mass% of the total mass of the pigment ink.

  In addition to the above-described components, a surfactant, an antifoaming agent, a preservative, and the like are appropriately added to the pigment ink of the present embodiment, in addition to the above components, in order to obtain a pigment ink having a desired physical property value as necessary be able to. In particular, the surfactant functioning as a penetration accelerator needs to be added in an appropriate amount to play a role of promptly penetrating the liquid component of the reaction liquid and the pigment ink into the recording medium. As an example of the addition amount, 0.05 to 10% by mass, preferably 0.5 to 5% by mass is suitable.

  As examples of the anionic surfactant, any commonly used ones such as a carboxylate type, a sulfate type, a sulfonate type, and a phosphate type can be preferably used.

  The method for preparing the pigment ink containing the pigment as described above is as follows. First, the pigment is added to an aqueous medium containing at least a water-soluble resin as a dispersant and water, mixed and stirred, and then dispersed as described below. Dispersion is performed using means. In addition, a desired dispersion is obtained by performing a centrifugal separation process as necessary. Next, a sizing agent and appropriately selected additive components such as those mentioned above are added to the dispersion and stirred to obtain a pigment ink used in the present invention.

  In addition, when using alkali-soluble resin as mentioned above as a dispersing agent, it is necessary to add a base in order to dissolve resin. As the bases at this time, organic amines such as monoethanolamine, diethanolamine, triethanolamine, aminemethylpropanol and ammonia, or inorganic bases such as potassium hydroxide and sodium hydroxide are preferably used.

  In addition, in the method for producing the pigment ink, it is effective to perform premixing for 30 minutes or more before stirring and dispersing the aqueous medium containing the pigment. That is, such a premixing operation is preferable because it can improve the wettability of the pigment surface and promote the adsorption of the dispersant to the pigment surface.

  Any disperser may be used as long as it is a commonly used disperser. For example, a ball mill, a roll mill, a sand mill, etc. are mentioned. Among these, a high speed type sand mill is preferably used. Examples of such include a super mill, a sand grinder, a bead mill, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  In addition, in an inkjet recording method using a pigment ink, a pigment having an optimum particle size distribution is used because of demands such as clogging resistance. As a method of obtaining a pigment having a desired particle size distribution, there are a method of reducing the size of the pulverizing media of the disperser and an increase in the filling rate of the pulverizing media. Other methods include increasing the processing time, decreasing the discharge speed, classifying with a filter or centrifuge after pulverization, and a combination of these methods.

(Example)
Hereinafter, specific examples and comparative examples of the present invention will be described. In the following description, “part” or “%” is based on mass unless otherwise specified. First, cyan (C), magenta (M), and yellow (Y) pigment inks C1, M1, and Y1, each containing a pigment and an anionic compound, were obtained as described below.

(Pigment ink)
<Preparation of pigment dispersion>
・ Styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight = 5,000) 1.5 parts monoethanolamine 1.0 part diethylene glycol 5.0 parts ion-exchanged water 81.5 parts

The above components are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component. To this solution, 10 parts of newly prepared Pigment Blue 15 and 1 part of isopropyl alcohol were added, premixed for 30 minutes, and then dispersed under the following conditions.
・ Disperser: Sand grinder (Igarashi Machine)
・ Crushing media: Zirconium beads, 1 mm diameter ・ Filling rate of grinding media: 50% (volume ratio)
-Grinding time: 3 hours Further, centrifugal separation (12,000 rpm, 20 minutes) was performed to remove coarse particles to obtain a pigment dispersion.

<Preparation of Pigment Ink C1>
Using the above dispersion, components having the following composition ratios were mixed to prepare an ink containing a pigment to obtain a pigment ink. The surface tension at this time was 34 mN / m.
-30.0 parts of the above pigment dispersion-10.0 parts of glycerin-5.0 parts of ethylene glycol-5.0 parts of N-methylpyrrolidone-2.0 parts of ethyl alcohol-Acetylenol EH
(Manufactured by Kawaken Fine Chemical Co., Ltd.) 1.0 part ・ Ion-exchanged water 47.0 parts

(Pigment ink M1, Y1)
Pigment inks M1 and Y1 containing pigments were prepared in the same manner as the pigment ink C1 except that 10 parts of Pigment Blue 15 used in the preparation of the pigment ink C1 were replaced with the pigments shown in Table 1 below. The surface tension at this time was 31 mN / m and 33 mN / m, respectively.

(Reaction liquids S1 to S3)
Next, the following components were mixed and dissolved, and then pressure filtered through a membrane filter (trade name: Fluororepore filter, manufactured by Sumitomo Electric) having a pore size of 0.22 μm, and the pH was adjusted to 3.8. Reaction liquid S1 was obtained. Similarly, reaction liquids S2 to S3 having the compositions shown in Table 2 below were prepared.

  Next, the wetting time Tw1 (msec) of the reaction liquids S1 to S3 with respect to a predetermined recording medium was measured by the Bristow method. For the measurement, the absorption coefficient Ka was measured together with the roughness index using a dynamic permeability test apparatus (manufactured by Toyo Seiki Seisakusho). Table 3 shows the results of the measured application time Tw1 (msec). Here, as shown in FIG. 1, the calculation method of the wetting time Tw is an approximate straight line A by the least square method for calculating the absorption coefficient Ka, a liquid transfer amount V, and V = represented by a roughness index Vr. It was set as the time to the intersection AB with the straight line B of Vr.

  Next, after the pigment ink C1 and the reaction liquid S1 were mixed and stirred at a ratio of 1: 1, the supernatant liquid excluding the aggregate of the pigment ink was taken out, and the wetting time Tw2 (msec) was measured by the Bristow method. With respect to the reaction solutions S2 to S3, the coating time Tw2 (msec) was measured by the same method. The measurement method used was the same method as described above. The results are shown in Table 4.

Examples 1-7
After the reaction liquid S1 is applied to PB paper (Canon), which is plain paper, the pigment ink C1 is applied, and further the pigment ink M1 is applied, so that a blue square image having a side of 1 cm is so-called 100% duty. It was recorded as a solid image. At this time, the time difference Td1 from application of the reaction liquid to application of the pigment ink C1 and the time difference Td2 from application of the pigment ink C1 to application of the pigment ink M1 are the time differences shown in Table 5. The drive of the recording head was controlled.

  The ink and the reaction liquid were applied by a recording operation using an ink jet recording apparatus using a recording head. The recording head used was an array of nozzles at a density of 1200 dpi, and this recording head was driven at a driving frequency of 20 kHz. Further, the volume of each ejected ink droplet and reaction droplet is 4 pl. The environmental conditions for the above recording are 25 ° C. and 55% RH. It should be noted that the amount of the pigment ink and the reaction liquid applied when creating the solid image is the same.

  FIG. 2 is a perspective view for explaining a schematic configuration of the recording apparatus used in this embodiment. The recording apparatus 50 of this example is a serial scanning type recording apparatus, and a carriage 53 is guided by guide shafts 51 and 52 so as to be movable in the main scanning direction of an arrow A. The carriage 53 is reciprocated in the main scanning direction by a driving force transmission mechanism such as a carriage motor and a belt for transmitting the driving force.

  On the carriage 53, a recording head 10 (not shown in FIG. 2) and an ink tank 54 for supplying ink to the recording head 10 are mounted. The recording head 10 and the ink tank 54 may constitute an ink jet cartridge. The recording head 10 has a plurality of nozzles arranged at a density of 1200 dpi as described above for each of cyan, magenta, yellow, black, and reaction solution. The ink tank 54 is composed of ink tanks for storing cyan, magenta, yellow, black, and reaction liquid.

  The above-described paper P as a recording medium is inserted from the insertion port 55 provided at the front end of the apparatus, and then the transport direction is reversed, and then the transport roller 56 transports the paper P in the sub-scanning direction indicated by the arrow B. . The recording apparatus 50 performs a recording operation of ejecting ink toward the print area of the paper P on the platen 57 while moving the recording head 10 in the main scanning direction. Further, during this scanning, a transport operation for transporting the paper P in the sub-scanning direction by a distance corresponding to the recording width of the recording head is performed. By repeating these, images are sequentially recorded on the paper P.

  A recovery system unit (recovery processing means) 58 is provided at the left end in FIG. 2 in the movement region of the carriage 53 so as to face the surface on which the ejection port 15 of the recording head 10 mounted on the carriage 53 is formed. The recovery system unit 58 includes a cap capable of capping the discharge port 15 of the recording head 10 and a suction pump capable of introducing a negative pressure into the cap. Thereby, by introducing a negative pressure into the cap covering the ejection port 15, the ink is sucked and discharged from the ejection port 15, and a recovery process (“suction recovery” is performed to maintain a good ink ejection state of the recording head 10. Process "). Further, a recovery process (also referred to as “ejection recovery process”) is performed in order to maintain a good ink ejection state of the recording head 10 by ejecting ink not contributing to an image from the ejection port 15 toward the inside of the cap. You can also.

  FIG. 3 is a schematic block diagram of the control system of the recording apparatus to which the present invention is applicable. In FIG. 3, the CPU 100 executes control processing of the operation of the recording apparatus, data processing, and the like. The ROM 101 stores programs such as those processing procedures, and the RAM 102 is used as a work area for executing these processes. Ink is ejected from the recording head 10 when the CPU 100 supplies drive data (image data) and drive control signals (heat pulse signals) of the heating elements 19 to the head driver 10A. The CPU 100 controls the carriage motor 103 for driving the carriage 53 in the main scanning direction via the motor driver 103A, and the P.P. The F motor 104 is controlled via the motor driver 104A.

  The processing executed by the CPU 100 includes processing for driving the corresponding nozzles in the recording head at the discharge intervals Td1 and Td2 based on the recording data input starting from the recording of the 1 cm square image described above. Of course.

Comparative Examples 1-4
Recorded matter was created in the same manner as in Examples 1-7. Here, the time difference Td1 from application of the reaction liquid to application of the pigment ink C1 and the time difference Td2 from application of the pigment ink C1 to application of the pigment ink M1 are the time differences shown in Table 5, respectively. Thus, the drive of the recording head was controlled.

  Next, the recorded materials created in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated by the following evaluation methods and evaluation criteria.

1. Image Density For the solid images created in Examples 1 to 8 and Comparative Examples 1 to 11, the reflection density was measured using a reflection densitometer. The results are shown in Table 5.

The evaluation criteria are as follows.
A: Reflection density is 1.0 or more.
A: The reflection density is 0.85 or more and less than 1.0.
X: Reflection density is less than 0.85.

2. The through- through was evaluated in the same manner as the back-through image density. That is, the reflection density on the back side of the recording part of the recording medium was measured. The results are shown in Table 5.

The evaluation criteria are as follows.
A: Reflection density is less than 0.2.
○: Reflection density is 0.2 or more and less than 0.4.
Δ: The reflection density is 0.4 or more and less than 0.6.
X: Reflection density is 0.6 or more.

Example 8
After applying the reaction liquid S1 to PB paper (Canon), which is plain paper, the pigment ink C1 was applied so that the time difference Td1 from application of the reaction liquid to application of the pigment ink was 5 mmsec. Then, the pigment inks M1 and Y1 are applied so that the time difference Td2 from the application of the pigment ink C1 to the application of the pigment inks M1 and Y1 is 5 mmsec and 10 mmsec, respectively. It was recorded as a so-called solid image.

  The recording head used had a nozzle arrangement density of 1200 dpi, and its driving condition was a driving frequency of 15 kHz. The volume of each ejected droplet of ink and reaction solution is 4 pl. Further, the environmental conditions during recording are 25 ° C. and 55% RH.

  The recorded material had no bleeding and no intercolor bleeding was observed. When the recording portion was rubbed with an edge portion of another paper after about 5 seconds had elapsed after recording, the recorded image did not remain.

As described above, the time from application of the reaction liquid to application of the first pigment ink is Td1, the application time of the reaction liquid is Tw1, and the first pigment ink is applied to the reaction liquid. To Td2 as the time until the second pigment ink is applied, and Tw2 as the wetting time of the mixture of the reaction liquid and the first pigment ink.
Td1 <Tw1
Td2 <Tw2
Depending on the recording conditions, it is possible to prevent bleeding and improve fixability and color developability, particularly when an image of a secondary color is created.

(Other embodiments)
In the above-described embodiments and examples, the relationship between the wetting time and the discharge time difference when the pigment ink and the reaction liquid that agglomerates the pigment is used has been described. However, the application of the present invention is not limited to this example. For example, in the case where an ink using a dye as a colorant and a reaction liquid that insolubilizes the dye are used, by satisfying the above-described relationship between the wetting time and the discharge time difference, bleeding can be prevented and color development can be prevented. Can be improved, and recording can be performed without show-through.

It is a figure explaining the absorption curve in the Bristow method. 1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a control configuration of the recording apparatus illustrated in FIG. 2.

Explanation of symbols

10 Recording head 100 CPU

Claims (3)

Recording is performed by applying to the recording medium a first ink, a second ink having a different color from the first ink, and a reaction liquid that aggregates or insolubilizes the components in the first and second inks. An ink jet recording method comprising:
A first application step of applying the reaction liquid to the recording medium;
A second application step of applying the first ink to at least a part of the region to which the reaction liquid is applied in the first application step;
A third application step of applying the second ink to at least a part of the region to which the first ink is applied in the second application step;
A wetting time Tw1 of the reaction liquid with respect to the recording medium and a time Td1 from application of the reaction liquid to application of the first ink are as follows:
Td1 <Tw1
And satisfy the relationship
A wetting time Tw2 of the mixture of the first ink and the reaction liquid with respect to the recording medium, and a time Td2 from when the first ink is applied to when the second ink is applied,
Td2 <Tw2
An inkjet recording method characterized by satisfying the relationship: The first and second inks contain pigments of different colors;
2. The ink jet recording method according to claim 1, wherein the reaction solution contains a polyvalent metal salt for aggregating the pigment. Using a first ink, a second ink having a color different from that of the first ink, and an applying means for applying a reaction liquid for aggregating or insolubilizing the coloring material of the first and second inks An inkjet recording apparatus for recording on a recording medium,
After applying the first ink to at least a part of the region on the recording medium to which the reaction liquid is applied, the second ink is applied to at least a part of the region to which the first ink is applied. Control means for controlling the application means so as to apply ink;
The control means includes a wetting time Tw1 of the reaction liquid with respect to the recording medium and a time Td1 from application of the reaction liquid to application of the first ink.
Td1 <Tw1
And satisfy the relationship
A wetting time Tw2 of the mixture of the first ink and the reaction liquid with respect to the recording medium, and a time Td2 from when the first ink is applied to when the second ink is applied,
Td2 <Tw2
An inkjet recording apparatus, wherein the applying unit is controlled so as to satisfy the relationship.

Images