Inkjet recording method and inkjet recording apparatus

Abstract

The present invention addresses the problem of providing an inkjet recording method and an inkjet recording device which can form an image with good glossiness and little ink bleeding.　This inkjet recording method forms an image by applying an ink that includes a coloring material and a processing liquid that includes a coagulant, onto a recording medium surface with a liquid droplet ejection means, the method being characterized in that, in a region where the application amount of the ink is equal to or greater than a reference value, the application amount of the processing liquid is controlled so that the application amount of the processing liquid decreases in a region as the application amount of the ink is high, and, in an image contour peripheral region, the application amount of the processing liquid is controlled so as to increase the application amount of the processing liquid.

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus. More specifically, the present invention relates to an inkjet recording method capable of forming an image having good gloss and little ink bleeding. [Background technology]

[0002] It is known that in inkjet recording methods, image quality is reduced due to a phenomenon in which ink droplets landing on a recording medium merge together, or color bleeding, which occurs when different colors bleed. As a means for solving these problems, a two-liquid inkjet recording method has been disclosed in which a treatment liquid that aggregates the coloring material in the ink is applied from an inkjet head (hereinafter also simply referred to as a "head") in addition to the ink, thereby fixing the ink well to the recording medium (see, for example, Patent Document 1).

[0003] However, while two-liquid inkjet recording methods can prevent problems such as ink bleeding, if the amount of treatment liquid applied is not properly controlled, the ink can aggregate excessively, resulting in a poor glossiness of the image.

[0004] As a method for controlling the amount of treatment liquid applied, means have been disclosed for varying the amount of treatment liquid ejected from the head depending on the amount of ink applied (see, for example, Patent Documents 2 and 3). However, these technologies are primarily intended to suppress curling and cockling of the paper, which is the recording medium, and are insufficient as a means for preventing ink bleeding while maintaining the gloss of the image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-52867 [Patent Document 2] JP 2002-321349 A [Patent Document 3] Patent No. 4742637 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide an inkjet recording method and an inkjet recording apparatus that are capable of forming images with good gloss and little ink bleeding. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors investigated the causes of the above problems and found that it is possible to provide an inkjet recording method and the like that can form images with good gloss and little ink bleeding by controlling the amount of treatment liquid applied in high-density regions so that the amount of treatment liquid applied is less in unit regions to which a greater amount of ink is applied, and by controlling the amount of treatment liquid applied so that additional treatment liquid is applied in regions around the image contour, thus arriving at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. An inkjet recording method for forming an image by applying an ink containing a coloring material and a treatment liquid containing a coagulant to a surface of a recording medium by a droplet ejection means, comprising: controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied to a unit region where the amount of ink applied is greater is smaller; controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or less than the reference value among the regions to which the ink is applied, the amount of treatment liquid applied is increased in a unit region where a larger amount of ink is applied; and, 1. An ink jet recording method comprising: controlling an amount of the treatment liquid to be applied so as to add an amount of the treatment liquid to a peripheral region of an image contour.

[0009] 2. The ink jet recording method described in item 1, wherein the reference value is a value that is 50% of the maximum amount of the ink applied.

[0011] 3 .1. Item 1 is characterized by a multi-path system. or No. In item 2 The inkjet recording method according to claim 1,

[0012] 4 The recording medium is an absorbent recording medium, and The method according to any one of claims 1 to 5, characterized in that, when the reference value is A and the amount of the treatment liquid applied in the region where the amount of the ink applied is the reference value is B, the amount of the treatment liquid applied is controlled so that the ratio B / A falls within a range of 0.14 to 0.50. 3 Item 1. The ink jet recording method according to any one of items 1 to 9.

[0013] 5 The recording medium is a non-absorbent recording medium, and The method according to any one of claims 1 to 5, characterized in that the amount of the treatment liquid applied is controlled so that the ratio B / A falls within a range of 0.14 to 0.30, where A is the reference value and B is the amount of the treatment liquid applied in the region where the amount of the ink applied is the reference value. 3 Item 1. The ink jet recording method according to any one of items 1 to 9.

[0014] 6 The method according to any one of claims 1 to 5, characterized in that the amount of the treatment liquid applied is controlled so that the ratio D / C falls within a range of 0.01 to 0.1, where C is the maximum value of the amount of the ink applied and D is the amount of the treatment liquid applied in the region where the amount of the ink applied is the maximum value. 5 Item 1. The ink jet recording method according to any one of items 1 to 9.

[0015] 7 When applying a plurality of types of ink, the amount of the treatment liquid applied to each unit area is determined for each type of ink. 6 Item 1. The ink jet recording method according to any one of items 1 to 9.

[0016] 8An inkjet recording apparatus for forming an image by applying ink containing a coloring material and a treatment liquid containing a coagulant to a surface of a recording medium by a droplet ejection means, controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied to a unit region where the amount of ink applied is greater is smaller; controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or less than the reference value among the regions to which the ink is applied, the amount of treatment liquid applied is increased in a unit region where a larger amount of ink is applied; and, 1. An ink jet recording apparatus comprising: an ink jet head; a recording medium for recording a recording medium on which the ink is applied; Effect of the Invention

[0017] According to the above-mentioned means of the present invention, it is possible to provide an inkjet recording method and an inkjet recording apparatus which are capable of forming an image having good gloss and little ink bleeding.

[0018] Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows.

[0019] The present invention is characterized in that in an area where the amount of ink applied is equal to or greater than a reference value (high density area), the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied is smaller in a unit area where the amount of ink applied is greater, thereby preventing the ink from coagulating too much and maintaining the glossiness of the image. However, simply reducing the amount of treatment liquid applied to areas where a large amount of ink is applied reduces the effectiveness of preventing bleeding. In the present invention, the amount of treatment liquid applied is not simply reduced in areas where a large amount of ink is applied, but is controlled so that, in addition to the changed amount of application, an additional amount of treatment liquid is applied in areas surrounding boundaries (also called "image contours") where there is a large difference in the shading of the image, thereby making it possible to efficiently prevent ink bleeding. This makes it possible to prevent the ink from coagulating too much while also compensating for the bleeding prevention effect.

[0020] It is believed that these mechanisms of expression or action make it possible to provide an inkjet recording method capable of forming images with good gloss and little ink bleeding. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an example of a main part of a two-liquid inkjet recording device to which the present invention can be applied; [Diagram 2] FIG. 2 is a schematic diagram showing how ink and treatment liquid are applied from a droplet ejection means onto a recording medium surface by the device shown in FIG. [Diagram 3] Graph showing an example of the relationship between the amount of ink applied and the amount of treatment liquid applied in a high density region [Figure 4] Graph 1 showing an example of the relationship between the amount of ink applied and the amount of treatment liquid applied in a low density region [Diagram 5] Graph 2 showing an example of the relationship between the amount of ink applied and the amount of treatment liquid applied in a low density region [Figure 6] Graph 3 showing an example of the relationship between the amount of ink applied and the amount of treatment liquid applied in a low density region [Figure 7] FIG. 2 is a diagram showing a schematic view of an image contour peripheral region; [Figure 8] 11 is a graph showing the relationship between the amount of ink deposited and the amount of treatment liquid deposited when the treatment liquid deposition amount control type is Type 1 in the embodiment. [Figure 9] 11 is a graph showing the relationship between the amount of ink deposited and the amount of treatment liquid deposited when the treatment liquid deposition amount control type is Type 2 in the embodiment; [Figure 10] 11 is a graph showing the relationship between the amount of ink deposited and the amount of treatment liquid deposited when the treatment liquid deposition amount control type is Type 3 in the embodiment. [Figure 11] 11 is a graph showing the relationship between the amount of ink deposited and the amount of treatment liquid deposited when the treatment liquid deposition amount control type is Type 4 in the embodiment. [Figure 12] Document image data 1 in the embodiment [Figure 13] Original image data 2 in the embodiment [Figure 14]Original image data 3 in the embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The inkjet recording method of the present invention (hereinafter also simply referred to as the "recording method") is an inkjet recording method for forming an image by applying an ink containing a colorant and a treatment liquid containing a coagulant to the surface of a recording medium by a droplet ejection means, and is characterized in that in areas where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied is less in unit areas where the amount of ink applied is greater, and the amount of treatment liquid applied is controlled so that additional treatment liquid is applied in areas around the image contour. This feature is a technical feature common to or corresponding to the following embodiments.

[0023] In an embodiment of the recording method of the present invention, it is preferable that the reference value be a value that is 50% of the maximum amount of the ink applied, from the viewpoint of the balance between the range in which the amount of treatment liquid applied is controlled as a high-concentration region and the range in which the amount of treatment liquid applied is controlled as a low-concentration region.

[0024] In an embodiment of the recording method of the present invention, it is preferable from the viewpoint of preventing ink bleeding in low-concentration regions to control the amount of treatment liquid applied in an area where the amount of ink applied is equal to or less than the reference value, such that the amount of treatment liquid applied is greater in a unit area where a greater amount of ink is applied.

[0025] A preferred embodiment of the recording method of the present invention is a multi-pass method, which, when combined with the method of controlling the amount of treatment liquid applied according to the present invention, makes it possible to form a high-definition image with good gloss and little ink bleeding.

[0026] In an embodiment of the recording method of the present invention, when the recording medium is an absorbent recording medium, it is preferable in terms of improving image quality in primary color solid areas to control the amount of treatment liquid applied so that the ratio B / A falls within a range of 0.14 to 0.50, where A is the reference value and B is the amount of treatment liquid applied in an area where the amount of ink applied is the reference value.

[0027] In an embodiment of the recording method of the present invention, when the recording medium is a non-absorbent recording medium, it is preferable in terms of improving image quality in primary color solid areas to control the amount of treatment liquid applied so that the ratio B / A falls within a range of 0.14 to 0.30, where A is the reference value and B is the amount of treatment liquid applied in an area where the amount of ink applied is the reference value.

[0028] In one embodiment of the recording method of the present invention, when the maximum amount of the ink applied is C and the amount of the treatment liquid applied in the region where the amount of the ink applied is at the maximum is D, it is preferable from the viewpoint of realizing the effects of the present invention to control the amount of the treatment liquid applied so that the value of the ratio D / C is within a range of 0.01 to 0.1. When the value of the ratio D / C is 0.01 or more, it is possible to minimize the aggregation of the ink, and when the value of the ratio D / C is 0.1 or less, it is possible to prevent a decrease in gloss due to excessive aggregation.

[0029] In an embodiment of the recording method of the present invention, when multiple types of ink are applied, it is preferable to determine the amount of treatment liquid applied for each unit area, which is changed according to the amount of ink applied, for each type of ink, in order to be able to adjust the amount of treatment liquid applied according to the ease with which each type of ink aggregates.

[0030] The inkjet recording apparatus (hereinafter also simply referred to as the "recording apparatus") of the present invention is an inkjet recording apparatus that forms an image by applying an ink containing a colorant and a treatment liquid containing a coagulant to the surface of a recording medium by a droplet ejection means, and is characterized in that in areas where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied is less in unit areas where the amount of ink applied is greater, and the amount of treatment liquid applied is controlled so that additional treatment liquid is applied in areas surrounding the image contour.

[0031] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as the lower limit and upper limit.

[0032] (1) Outline of the inkjet recording method of the present invention The inkjet recording method of the present invention is an inkjet recording method for forming an image by applying an ink containing a coloring material and a treatment liquid containing a coagulant to the surface of a recording medium by a droplet ejection means, and is characterized in that in areas where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied is less in unit areas where a greater amount of ink is applied, and the amount of treatment liquid applied is controlled so that additional treatment liquid is applied in areas around the image contour.

[0033] In the recording method of the present invention, first, the amount of ink to be applied is determined for each unit area. The amount of treatment liquid to be applied is determined so that the amount of treatment liquid to be applied for each unit area is changed according to the amount of ink to be applied. In addition, the amount of treatment liquid to be applied to the peripheral area of ​​the image contour is determined.

[0034] "In areas where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied is smaller in unit areas where the amount of ink applied is greater" specifies how the amount of treatment liquid applied is changed according to the amount of ink applied in high concentration areas.

[0035] "Amount applied" refers to the amount applied to a certain unit area, and is the total amount dispensed for each dot in that unit area. The unit of amount applied is g / m 2 It can be expressed as:

[0036] The "reference value" refers to the reference amount of ink applied for dividing an area where ink is applied into a high-density area and a low-density area. In the present invention, an area where the amount of ink applied is equal to or greater than the reference value is referred to as a "high-density area," and an area where ink is applied where the amount of ink applied is equal to or less than the reference value is referred to as a "low-density area." An area where the amount of ink applied is the reference value is referred to as a "reference value area," and for convenience, the reference value area is included as part of both the high-density area and the low-density area.

[0037] The reference value can be set arbitrarily depending on the image to be formed. In the present invention, the amount of treatment liquid applied is controlled in the high-density region and the low-density region separated by the arbitrarily set reference value.

[0038] The "image contour peripheral region" refers to a region that has a certain width on both sides of the image contour as its starting point. The distance from the image contour as the starting point to both ends of the image contour peripheral region in the width direction is approximately the same.

[0039] "Image contour" refers to the boundary where there is a large difference in the shading of the image. Image contours can be detected using commercially available image processing software or various methods (Sobel method, Laplacian of Gaussian method, Canny method, etc.). Note that the periphery of the area to which ink is applied does not necessarily match the image contour.

[0040] (2) Examples of recording methods and devices The inkjet recording method of the present invention is a so-called two-liquid recording method in which an image is formed by applying an ink and a treatment liquid to the surface of a recording medium by droplet ejection means.

[0041] An example of the main components of a two-liquid inkjet recording device to which the present invention can be applied is shown typically in Fig. 1. Also, Fig. 2 shows a schematic diagram of an example of how ink and treatment liquid are applied from a droplet ejection means to a recording medium surface by the device shown in Fig. 1.

[0042] Hereinafter, the recording method and recording device of the present invention will be described using the multi-pass method (also called the "scan method") as an example, with reference to Figures 1 and 2. Note that the recording method and recording device of the present invention are not limited to this. They can also be applied to the single-pass method (also called the "line method") described later.

[0043] In a recording method using the recording apparatus shown in Fig. 1, an image is formed by moving a droplet ejection means 20 in a scanning direction X (hereinafter also referred to as "X direction") while ejecting inks In of each color (yellow ink Y, magenta ink M, cyan ink C, black ink K) and a treatment liquid Pr onto a recording medium Me as shown in Fig. 2. In the recording apparatus shown in Fig. 1, the recording medium Me is sequentially transported by a transport means (not shown) in a direction Y (hereinafter also referred to as "transport direction Y" or "Y direction") perpendicular to the scanning direction X, so that an image can be formed on substantially the entire surface (image forming surface) of the recording medium Me.

[0044] The droplet ejection means 20 has a head 1Pr for treatment liquid, a head 1Y for yellow ink, a head 1M for magenta ink, a head 1C for cyan ink, and a head 1K for black ink (hereinafter, these are collectively referred to as "head unit 1"), and a carriage 22 for positioning and holding this head unit 1 along the scanning direction X.

[0045] On the surface (nozzle surface) of each head facing the surface of the recording medium Me, multiple nozzles 21 are arranged along a transport direction Y perpendicular to the scanning direction X, and minute droplets are ejected from these nozzles 21 by applying an appropriate pressure to the ink In and treatment liquid Pr. The droplet ejection means 20 is supported in a state where the nozzle surface in the head unit 1 is spaced a predetermined distance from the surface of the recording medium Me in a direction (height direction) perpendicular to the surface of the recording medium Me.

[0046] The droplet ejection means 20 is scanned in the scanning direction X by the scanning unit 30. The scanning unit 30 includes, for example, rails that support the carriage 22 with the nozzle surface spaced apart from the surface of the recording medium Me by the above-mentioned predetermined distance in the height direction, and allows the carriage 22 to move along the rails that extend along the scanning direction X.

[0047] 1 is the range in which an image can be formed on the recording medium Me by scanning the droplet ejection means 20 in the X direction and transporting the recording medium Me in the Y direction. The length of the entire printing area P in the X direction is the printing area width PW, and the length in the Y direction is the printing area length PL.

[0048] When the droplet ejection means 20 moves once in the scanning direction X, the ink In and the treatment liquid Pr are applied to an area of ​​width W in the direction Y perpendicular to the scanning direction X of the head unit 1, for a printing area width PW of the entire printing area P. In a multi-pass recording method as shown in Fig. 1, an operation of applying the ink In and the treatment liquid Pr to the recording medium Me by a single movement of the droplet ejection means 20 in the scanning direction X is considered to be one printing pass, and multiple printing passes are performed on the same area to finally form a desired image on the recording medium Me.

[0049] Here, in the recording device, the control unit determines whether or not to apply ink In for each unit area and the amount of ink to be applied in accordance with the image data of the original, and further determines whether or not to apply the amount of treatment liquid Pr for each unit area and the amount of treatment liquid Pr to be applied in accordance with this determination, and an image is formed by the droplet ejection means applying ink In and treatment liquid Pr to the surface of the recording medium Me based on this determination.

[0050] The decision as to whether or not to apply the ink In for each unit area and the amount of ink to be applied is made by a known method according to the image data of the document. For example, in the case of an image of a document on a personal computer, the arrangement of pixels to which the ink In is applied in the entire printing area P, the amount of ink to be applied, etc. are decided based on the image data that has been halftone processed.

[0051] The determination of whether or not to apply the treatment liquid Pr for each unit area and the amount of the treatment liquid Pr to be applied is performed, for example, according to the control method of the present invention by a program installed in the control unit.

[0052] In some cases, image formation on the recording medium Me is completed in a single printing pass, but when forming an image with high resolution (dpi), the image is decomposed and multiple printing passes are performed to form the image on the recording medium Me.

[0053] The number of printing passes is determined by a program preset in the control unit in accordance with the document image. The number of printing passes is generally set to about 2 to 4, depending on the document image.

[0054] The size of the unit area (hereinafter also referred to as "unit area U") in which the image is formed is appropriately selected within a range in which the effects of the present invention can be realized. Specifically, one pixel may be the unit area U. Since this makes it easier to realize the effects of the present invention, it is preferable that the unit area U be four pixels or more per unit. Furthermore, it is more preferable that the unit area U be four pixels consisting of two pixels vertically and two pixels horizontally, 16 pixels consisting of four pixels vertically and four pixels horizontally, or 36 pixels consisting of six pixels vertically and six pixels horizontally.

[0055] In FIG. 1, the area to which the ink In and the treatment liquid Pr are applied in one movement of the droplet ejection means 20 is an area (hereinafter also referred to as the "printing area A") having an area obtained by multiplying the printing area width PW in the scanning direction X by the width W of the head unit 1 in the direction Y perpendicular to the scanning direction X (hereinafter also referred to as the "width W of the head unit 1").

[0056] The total printing area P is a collection of these printing areas A. The number of printing areas A that make up the total printing area P is indicated by the value obtained by dividing the printing area length PL by the width W of the head unit 1. For example, in the case of the recording medium Me shown in FIG. 1, the number of printing areas A that make up the total printing area P is six, and the total printing area P is made up of printing areas A1, A2, A3, A4, A5, and A6 arranged in sequence from the front to the back of the recording medium Me.

[0057] In Fig. 1, in the entire printing area P, images have already been formed in the printing areas A1, A2, and A3. In the printing area A4, an image is being formed by the droplet ejection means 20, and in the printing areas A5 and A6, images will be formed sequentially after the image formation in the printing area A4 is completed. In Fig. 1, Im indicates the ink application area.

[0058] The recording method of the present invention is a recording method in which, for example, using the recording apparatus shown in Fig. 1, the ink In and the treatment liquid Pr are applied to the surface of the recording medium Me by the droplet ejection means 20 and then united as described above to form an image. Although Figs. 1 and 2 show a form in which the treatment liquid Pr is applied to the surface of the recording medium Me before the ink In, in the recording method of the present invention, the treatment liquid Pr may be applied after the ink In. For example, a configuration in which the treatment liquid head 1Pr is disposed behind the ink heads 1Y, 1M, 1C, and 1K, and the treatment liquid Pr is applied after the ink In is applied may also be used.

[0059] The type of each head is not particularly limited, and may be either an on-demand type or a continuous type. Examples of on-demand type heads include electro-mechanical conversion types including single cavity type, double cavity type, bender type, piston type, shear mode type, and shared wall type, and electro-thermal conversion types including thermal inkjet type and bubble jet type ("Bubble Jet" is a registered trademark of Canon Inc.).

[0060] Of the above heads, a head using a piezoelectric element as the electro-mechanical conversion element used in the electro-mechanical conversion method (also called a "piezo type inkjet head") is preferable.

[0061] The application amounts of the ink In and the treatment liquid Pr can be appropriately adjusted by adjusting the amount of liquid per droplet ejected from the nozzle 21 in each head, and it is also easy to make the amounts of both different. The ejection mechanism for the ink In or the treatment liquid Pr in the head will be explained in the recording apparatus described later, but the amount of liquid per droplet of the ink In and the treatment liquid Pr ejected from the nozzle 21 (drop amount per dot) can be adjusted within the range of approximately 2 to 40 pL.

[0062] In addition, the landing time of the ink In discharged from the nozzle 21 in the head is preferably 1.0 second or less, more preferably 0.6 second or less. Similarly, the landing time of the treatment liquid Pr discharged from the nozzle 21 is preferably 1.0 second or less, more preferably 0.6 second or less. The landing time of the ink In and the treatment liquid Pr corresponds to the time from when the ink In and the treatment liquid Pr are discharged from the nozzle 21 to when they are united on the recording medium Me. That is, the time from when the ink In and the treatment liquid Pr are discharged to when they are united is preferably 1.0 second or less, more preferably 0.6 second or less. In addition, the moving speed of the droplet discharge means 20 having the head unit 1 is preferably 300 to 800 mm / sec.

[0063] Up to this point, the recording method and recording apparatus of the present invention have been explained using Figures 1 and 2 taking the multi-pass system as an example, but as mentioned above, the recording method and recording apparatus of the present invention are also applicable to the single-pass system.

[0064] In the case of the single pass method, the droplet ejection means 20 has a length equal to or greater than the printing area width PW of the entire printing area P relative to the recording medium Me, and the treatment liquid head 1Pr and the ink heads 1Y, 1M, 1C, and 1K are sequentially arranged along the transport direction Y so as to be parallel to the printing area width PW. The treatment liquid head 1Pr may be arranged before or after the ink heads 1Y, 1M, 1C, and 1K.

[0065] In the single-pass type droplet ejection means, one head unit 1 having a width equal to or greater than the print area width PW may be used, or a plurality of head units 1 may be combined to provide a width equal to or greater than the print area width PW.

[0066] In addition, a plurality of head units 1 may be arranged side by side with their nozzles 21 staggered to increase the resolution of the droplet ejection means of these heads as a whole. In addition, a plurality of such droplet ejection means may be arranged side by side along the transport direction Y of the recording medium.

[0067] (3) Controlling the amount of processing solution applied in the high concentration region In the present invention, the term "high-density region" refers to a region where the amount of ink applied is equal to or greater than a reference value. As described above, the "reference value region" refers to a region where the amount of ink applied is equal to a reference value, and is included as part of both the high-density region and the low-density region for the sake of convenience.

[0068] The recording method of the present invention is characterized in that the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied to a unit area having a larger amount of ink applied in a high-density area is reduced, thereby preventing the ink from coagulating excessively and maintaining the glossiness of the image.

[0069] Furthermore, when the amounts of ink and treatment liquid applied are both large, the coffee ring phenomenon causes unevenness in which the concentration of colorant is partially higher at the edge of the coffee ring; however, as in the present invention, by controlling the amount of treatment liquid applied in high concentration regions so that the amount of treatment liquid applied is smaller in unit regions where a greater amount of ink is applied, the coffee ring phenomenon is less likely to occur and the occurrence of unevenness can be suppressed.

[0070] For example, when the maximum amount of ink applied is taken as 100%, and the reference value is set to a value that is 50% of the maximum amount of ink applied, an area that is within the range of 50 to 100% of the maximum amount of ink applied is regarded as a high-density area, and the amount of treatment liquid applied is controlled so that the amount of treatment liquid applied to a unit area having a greater amount of ink applied in that high-density area is reduced.

[0071] Here, the "maximum amount of ink applied" refers to the amount of ink applied to a unit area in the image to be formed that has the largest amount of ink applied. For example, when using the subtractive color mixing method in which two types of ink from yellow ink, magenta ink, and cyan ink are dropped onto the same location to form red, green, and blue secondary color dots, the amount of ink applied in the area with the greatest density gradation among areas containing only secondary colors (also called "secondary color solid area") is the "maximum amount of ink applied."

[0072] The smaller the reference value is set, the wider the range in which the amount of applied treatment liquid is controlled as a high concentration region, and the larger the reference value is set, the wider the range in which the amount of applied treatment liquid is controlled as a low concentration region. In the present invention, the reference value can be set arbitrarily within the range of the amount of ink applied, but from the viewpoint of the balance between the range in which the amount of treatment liquid applied is controlled as a high-concentration region and the range in which the amount of treatment liquid applied is controlled as a low-concentration region, the reference value is preferably a value within a range of 30 to 70% of the maximum amount of ink applied, more preferably a value within a range of 50 to 70%, and even more preferably a value of 50%.

[0073] When applying multiple types of ink, in order to adjust the amount of treatment liquid applied depending on the tendency of each type of ink to aggregate, it is preferable to determine the amount of treatment liquid applied for each unit area, which is changed depending on the amount of ink applied, for each type of ink. When applying a plurality of types of ink, the amount of treatment liquid applied is the sum of the amounts of treatment liquid applied determined for each type of ink.

[0074] The amount of treatment liquid applied in the reference value region can be adjusted as appropriate. When the amount of ink applied as a reference value is A and the amount of treatment liquid applied in the reference value region is B, it is preferable that the ratio B / A is within a range of 0.14 to 0.50 when the recording medium is an absorbent recording medium, and within a range of 0.14 to 0.30 when the recording medium is a non-absorbent recording medium. The difference between absorbent recording media and non-absorbent recording media is described below. This improves image quality in areas where only one type of ink is applied (also called "primary color solid area").

[0075] Furthermore, the amount of treatment liquid applied in the region where the amount of ink applied is at its maximum (hereinafter also referred to as the "maximum value region") can also be adjusted as appropriate. When the maximum amount of ink applied is C and the amount of treatment liquid applied in the maximum value region is D, it is preferable that the ratio D / C is within the range of 0.01 to 0.1. When the ratio D / C is 0.01 or more, the ink can be aggregated to a minimum extent, and when the ratio D / C is 0.1 or less, a decrease in gloss due to excessive aggregation can be prevented.

[0076] The graph in FIG. 3 shows an example of the relationship between the amount of ink applied of the present invention and the amount of treatment liquid applied in a high density region, taking as an example a case where the reference value is set to a value that is 50% of the maximum amount of ink applied.

[0077] In the graph in Figure 3, the standard value A is 6.5 g / m 2 , the amount of processing liquid applied in the reference value region B is 1.3 g / m 2 , the maximum amount of ink applied C is 13 g / m 2 , the amount of processing liquid applied in the maximum region D is 0.39 g / m 2 This shows the relationship between the amount of ink applied and the amount of treatment liquid applied when controlling the amount of treatment liquid applied so that the amount of treatment liquid applied to a unit area having a larger amount of ink applied in a high density area is smaller. In this case, the ratio B / A is 0.2 and the ratio D / C is 0.03. It should be noted that the amounts of treatment liquid applied shown in this graph do not include the amount added in edge treatment, which will be described later.

[0078] (4) Controlling the amount of processing solution applied in the low concentration region In the present invention, the term "low-density region" refers to a region where the amount of ink applied is equal to or less than a reference value among regions where ink is applied. As described above, the "reference value region" which refers to the region where the amount of ink applied is the reference value is conveniently included as part of both the high-density region and the low-density region.

[0079] In the recording method of the present invention, the method for controlling the amount of treatment liquid applied in low-concentration regions is not particularly limited. However, from the viewpoint of preventing ink bleeding in low-concentration regions, it is preferable to control the amount of treatment liquid applied so that the amount of treatment liquid applied is greater in unit regions where a greater amount of ink is applied in the low-concentration regions, as shown in FIG. 4 . In particular, in the case of the multi-pass method, by controlling the amount of treatment liquid applied in low-density regions using the control method shown in FIG. 4, it is possible to effectively prevent ink bleeding in low-density regions.

[0080] Alternatively, the amount of treatment liquid applied can be controlled so that it is constant in low-density regions, as shown in Fig. 5. For example, in the case of the single-pass method, ink for the entire image is applied at one time, so the control method shown in Fig. 5 can also effectively prevent ink bleeding in low-density regions.

[0081] In addition, depending on the printing method and other conditions, as shown in Figure 6, in low-density regions, as in high-density regions, the amount of treatment liquid applied can be controlled so that the amount of treatment liquid applied increases in unit regions where a greater amount of ink is applied.

[0082] As with the control in high-density regions, when multiple types of ink are applied in low-density regions, it is preferable to determine the amount of treatment liquid to be applied for each unit region, which is changed according to the amount of ink applied, for each type of ink.

[0083] (5) Control of the amount of processing liquid applied to the peripheral area of ​​the image contour (edge ​​processing) The recording method of the present invention is characterized in that the amount of treatment liquid applied is controlled so as to add to the peripheral area of ​​the image contour. The amount of treatment liquid added is in addition to the amount of treatment liquid applied that has been changed in the high-density area and the low-density area described above. This makes it possible to efficiently prevent ink bleeding. In the present invention, adding the amount of treatment liquid applied to the peripheral area of ​​the image contour is hereinafter also referred to as "edge processing".

[0084] In the present invention, the "image contour peripheral region" refers to a region that has a certain width on both sides of the image contour as its starting point, as described above. The distances from the image contour as the starting point to both ends of the image contour peripheral region in the width direction are approximately the same.

[0085] As described above, the "image contour" refers to a boundary where there is a large difference in the shading of an image. The image contour can be detected using commercially available image processing software or various methods (such as the Sobel method, the Laplacian of Gaussian method, and the Canny method). For example, when using Photoshop (registered trademark), the image contour can be detected by applying the "contour tracing" of the "expression method" with an appropriate threshold level setting. It should be noted that the outer periphery of the area to which ink is applied does not necessarily coincide with the contour of the image.

[0086] 7 is a diagram showing a schematic diagram of the image contour peripheral region. Starting from the image contour G shown by the dashed line, the region existing on both sides of the image contour G with a certain width is the image contour peripheral region S. The distance from the image contour G as the starting point to both ends in the width direction of the image contour peripheral region S is approximately the same. The width Sw of the image contour peripheral region S can be set arbitrarily, but from the viewpoint of preventing bleeding, it is preferably within the range of 60 to 300 μm, and more preferably within the range of 100 to 250 μm.

[0087] Ink bleeding is likely to occur in the peripheral regions of the image contour, but by controlling the amount of treatment liquid applied so as to add more treatment liquid to these regions, ink bleeding can be effectively prevented.

[0088] Furthermore, the edge treatment accelerates ink coagulation and fixation, making the coffee ring phenomenon less likely to occur. This, combined with the effect of suppressing the coffee ring phenomenon in high-density areas, makes it possible to form images with less unevenness with the recording method of the present invention.

[0089] The treatment liquid added to the peripheral region of the image contour is applied in droplets at the same positions as the positions where the ink is applied in the peripheral region of the image contour to form the same dots. The amount of treatment liquid applied is preferably within a range of 10 to 50% of the amount of ink applied per dot.

[0090] The amount of treatment liquid added to the image contour peripheral region is the sum of the amounts of treatment liquid applied to each unit region in the image contour peripheral region. The amount of treatment liquid applied to each unit region is the sum of the amounts of treatment liquid dropped to each dot in the unit region. Therefore, it is preferable that the amount of treatment liquid added to the image contour peripheral region is within a range of 10 to 50% of the amount of ink applied to the image contour peripheral region.

[0091] (6) Ink The ink according to the present invention contains at least a coloring material. In addition, the ink according to the present invention preferably contains a resin, a water-soluble solvent, and water in addition to the coloring material.

[0092] <Coloring material> The coloring material contained in the ink according to the present invention is preferably a pigment. As the pigment, an anionic dispersed pigment, for example, an anionic self-dispersing pigment or a pigment dispersed with an anionic polymer dispersant can be used, and in particular, a pigment dispersed with an anionic polymer dispersant is preferred.

[0093] As the pigment, any conventionally known pigment can be used without any particular limitation. For example, organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as titanium oxide can be preferably used.

[0094] In the case of titanium oxide, for which it is generally difficult to ensure ink ejection stability and adhesion (adhesion between the ink and a recording medium), the present invention is particularly advantageous in that it makes bleeding less likely to occur and also improves adhesion.

[0095] Titanium oxide has three crystal forms: anatase, rutile, and brookite, but the most commonly used are roughly classified into anatase and rutile. Although not particularly limited, rutile is preferred because it has a high refractive index and high hiding power. Specific examples include the TR series from Fuji Titanium Industry Co., Ltd., the JR series from Teika Corporation, and Typeque from Ishihara Sangyo Co., Ltd.

[0096] The insoluble pigment is not particularly limited, but examples thereof include azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0097] Specific examples of organic pigments that can be preferably used include the following pigments.

[0098] Examples of pigments for magenta or red include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 202, CI Pigment Red 222, and CI Pigment Violet 19.

[0099] Examples of pigments for orange or yellow include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 15:3, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 128, CI Pigment Yellow 94, CI Pigment Yellow 138, and CI Pigment Yellow 155. In particular, CI Pigment Yellow 155 is preferred in terms of the balance between color tone and lightfastness.

[0100] Examples of pigments for green or cyan include CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, CI Pigment Blue 60, CI Pigment Green 7, and the like.

[0101] Examples of black pigments include CI Pigment Black 1, CI Pigment Black 6, and CI Pigment Black 7.

[0102] <Resin> The resin used in the ink according to the present invention is preferably resin fine particles, particularly preferably water-insoluble resin fine particles. The water-insoluble resin fine particles used in the present invention are fine particles of a water-insoluble resin that can receive ink and exhibits solubility or affinity for the ink.

[0103] Water-insoluble resin microparticles are essentially water-insoluble, but have a form in which the resin disperses in an aqueous medium as microscopic microparticles, and are water-insoluble resins that are forcibly emulsified and dispersed in water using an emulsifier or the like, or water-insoluble resins that are self-emulsifiable to form a stable aqueous dispersion by themselves without using an emulsifier or dispersion stabilizer by introducing a hydrophilic functional group into the molecule. These resins are usually used in a state of being emulsified and dispersed in water or a water / alcohol mixed solvent.

[0104] The resin particles used in the ink are preferably polyester-based resin particles, polyurethane-based resin particles, polyacrylic-based resin particles, or composite resin particles of a polyurethane-based resin and a polyacrylic-based resin. The resin particles used in the ink are preferably anionic.

[0105] The resin particles used in the ink preferably contain an acid structure, which allows them to be dispersed in water even with a small amount of surfactant added, improving the water resistance of the ink layer. This is called a self-emulsifying type, and means that the urethane resin can be dispersed and stabilized in water using only molecular ionicity without the use of a surfactant. Examples of acid structures include carboxyl groups (-COOH), sulfonic acid groups (-SO 3 The acid structure may be present in a side chain or at the end of the resin.

[0106] It is preferable that the acid structure is partially or entirely neutralized. By neutralizing the acid structure, the water dispersibility of the resin can be improved. As an example of a neutralizing agent for neutralizing the acid structure, organic amines are preferable, and it is preferable to use organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine.

[0107] The resin particles used in the ink may be commercially available products. Examples of commercially available resin particles are listed below by type of resin.

[0108] Commercially available polyester resin microparticles include PESRESIN A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, and A-647GEX manufactured by Takamatsu Oil Co., Ltd., and Eliteru KA-5034, KA-5071S, KA-1449, KA-0134, KA-3556, KA-6137, KZA-6034, KT-8803, KT-8701, KT-9204, KT-8904, KT-0507, and KT-9511 manufactured by Unitika Ltd.

[0109] Examples of commercially available urethane resin fine particles include NeoRez R-967, R-600, and R-9671 manufactured by Kusumoto Chemicals, Inc., and W-6061, W-5661, and WS-4000 manufactured by Mitsui Chemicals, Inc.

[0110] Commercially available acrylic resin particles include NeoCryl A-1127 manufactured by Kusumoto Chemical Industries, Ltd.; Mowinyl 6899D, 6969D, 6800, and 6810 manufactured by Japan Coating Resins Co., Ltd.; and TOCRYL W-7146, W-7150, and W-7152 manufactured by Toyochem Co., Ltd.

[0111] The content of the resin particles in the ink is not particularly limited, but is preferably within the range of 2 to 10% by mass, and more preferably within the range of 2 to 5% by mass.

[0112] <Water-soluble solvent> Examples of the water-soluble solvent contained in the ink include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

[0113] Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol, and benzyl alcohol.

[0114] Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols having 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycols having 4 or more propylene oxide groups, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, and thiodiglycol.

[0115] Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, and tetramethylpropylenediamine.

[0116] Examples of amides include formamide, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0117] Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether.

[0118] Examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol.

[0119] Particularly preferred water-soluble solvents are polyhydric alcohols, which can effectively suppress bleeding during high-speed printing. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferred.

[0120] The ink may contain one or a combination of two or more selected from these water-soluble solvents.

[0121] The content of the water-soluble solvent in the ink is not particularly limited, but is preferably within the range of 10 to 60% by mass.

[0122] <Water> The water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water. The water content in the ink is not particularly limited, but is preferably within the range of 45 to 80% by mass.

[0123] <Polymer dispersant> The polymer dispersant used to disperse the pigment is not particularly limited, but is preferably a polymer dispersant having an anionic group, and one having a molecular weight in the range of 5,000 to 200,000 can be suitably used.

[0124] Examples of polymer dispersants include block copolymers and random copolymers having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, as well as salts thereof, polyoxyalkylenes, and polyoxyalkylene alkyl ethers.

[0125] The polymer dispersant preferably has an acryloyl group, and is preferably neutralized with a neutralizing agent (neutralizing base) before addition. The neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, morpholine, etc. In particular, when the pigment is titanium oxide, the titanium oxide is preferably dispersed with a polymer dispersant having an acryloyl group.

[0126] As the polymer dispersant, a commercially available product may be used. Examples of commercially available polymer dispersants include Joncryl 819 manufactured by BASF.

[0127] The amount of the polymer dispersant added is preferably within a range of 10 to 100% by mass, and more preferably within a range of 10 to 40% by mass, relative to the pigment.

[0128] It is particularly preferred that the pigment has a form of a so-called capsule pigment in which the pigment is coated with the polymer dispersant. As a method for coating the pigment with the polymer dispersant, various known methods can be used, and preferred examples thereof include a phase inversion emulsification method, an acid precipitation method, and a method in which the pigment is dispersed in a polymerizable surfactant, a monomer is supplied thereto, and the monomer is coated while being polymerized.

[0129] A particularly preferred method is to dissolve a water-insoluble resin in an organic solvent such as methyl ethyl ketone, partially or completely neutralize the acidic groups in the resin with a base, add a pigment and ion-exchanged water, disperse the pigment, remove the organic solvent, and add water as necessary to prepare the dispersion.

[0130] The average particle size of the pigment in the dispersed state in the ink is preferably 50 nm or more and less than 200 nm. This can improve the dispersion stability of the pigment and the storage stability of the ink. The particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, or the like, but the measurement by the dynamic light scattering method is simple and can measure the particle size range with high accuracy.

[0131] The pigment can be dispersed in a dispersing machine together with a dispersant and other additives required for various desired purposes.

[0132] As the dispersing machine, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, etc. can be used. Among them, dispersing the pigment with a sand mill is preferable because it results in a sharp particle size distribution. The material of the beads used for the sand mill dispersion is not particularly limited, but is preferably zirconia or zircon from the viewpoint of preventing the generation of bead fragments and contamination of ion components. Furthermore, the diameter of the beads is preferably within the range of 0.3 to 3 mm.

[0133] The content of the pigment in the ink is not particularly limited, but for titanium oxide, it is preferably within the range of 7 to 18 mass %, and for organic pigments, it is preferably within the range of 0.5 to 7 mass %.

[0134] <Surfactant> The ink preferably contains a surfactant, which can improve the ink ejection stability and control the spread (dot diameter) of droplets that land on a recording medium.

[0135] The surfactant that can be used in the ink according to the present invention is not particularly limited. However, when the other constituent components of the ink contain an anionic compound, the ionicity of the surfactant is preferably anionic, nonionic or betaine type.

[0136] In the present invention, fluorine-based or silicone-based surfactants having high static surface tension reducing ability, anionic surfactants such as dioctyl sulfosuccinate having high dynamic surface tension reducing ability, and nonionic surfactants such as relatively low molecular weight polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, Pluronic surfactants (Pluronic is a registered trademark), and sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having high dynamic surface tension reducing ability.

[0137] By adding a silicone-based or fluorine-based surfactant as the surfactant, it is possible to suppress ink mixing (beading) on ​​non-water-absorbent recording media, thereby obtaining high-quality images.

[0138] The silicone surfactant is preferably a polyether-modified polysiloxane compound, such as KF-351A and KF-642 manufactured by Shin-Etsu Chemical Co., Ltd., BYK345, BYK347, and BYK348 manufactured by BYK-Chemie, and Tegowet 260 manufactured by Evonik.

[0139] The fluorine-based surfactant means a surfactant in which a part or all of the hydrogen atoms bonded to the carbon of the hydrophobic group of a normal surfactant are replaced with fluorine. Among these, those having a perfluoroalkyl group in the molecule are preferred.

[0140] Some of the above fluorinated surfactants are commercially available from Dainippon Ink and Chemicals under the trade name Megafac F, from Asahi Glass Co., Ltd. under the trade name Surflon, from Minnesota Mining and Manufacturing Company under the trade name Fluorad FC, from Imperial Chemical Industries, Inc. under the trade name Monflor, from E.I. duPont Nemelas & Co. under the trade name Zonyls, and from Farbewerke-Hoechst under the trade name Licowet VPF.

[0141] The content of the surfactant in the ink is not particularly limited, but is preferably within the range of 0.1 to 5.0% by mass.

[0142] <Other additives> The ink according to the present invention may contain various known additives as necessary for the purpose of improving ejection stability, compatibility with print heads and ink cartridges, storage stability, image storage stability, and other performance properties.

[0143] In addition to the above, the ink used in the present invention may contain various known additives, such as polysaccharides, viscosity modifiers, resistivity modifiers, film-forming agents, ultraviolet absorbers, antioxidants, color-fading inhibitors, antifungal agents, and rust inhibitors, which may be appropriately selected and used according to the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other performances. For example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, and other oil droplet fine particles, 193, 57-87988, 62-261476, etc.; anti-fading agents described in JP-A-57-74192, 57-87989, 60-72785, 61-146591, 1-95091, 3-13376, etc.; fluorescent brightening agents described in JP-A-59-42993, 59-52689, 62-280069, 61-242871, 4-219266, etc.

[0144] <Ink properties> The viscosity of the ink according to the present invention at a temperature of 25°C is preferably within a range of 1 to 40 mPa·s, and more preferably 2 to 10 mPa·s. The viscosity of the ink can be measured by a rotational viscometer. Unless otherwise specified, the viscosity in this specification is the viscosity at a temperature of 25°C.

[0145] The static surface tension of the ink according to the present invention is preferably greater than the static surface tension of the treatment liquid at a temperature of 25° C. Furthermore, the static surface tension of the ink at a temperature of 25° C. is preferably within a range of 25 to 33 mN / m, and more preferably within a range of 25 to 29 mN / m. The static surface tension of the ink can be measured by a surface tensiometer that applies the platinum plate method (Wilhelmy method), etc. Unless otherwise specified, the static surface tension in this specification is the static surface tension at a temperature of 25°C.

[0146] (7) Processing solution The treatment liquid according to the present invention contains at least a flocculant. In addition, the treatment liquid according to the present invention preferably contains a water-soluble solvent and water in addition to the flocculant.

[0147] It is preferable that the treatment liquid does not contain resin fine particles. By not containing resin fine particles, the treatment liquid hardly dries and thickens on the nozzle surface of the head, which has the effect of improving the inkjet ejection properties.

[0148] <Flocculant> The treatment liquid according to the present invention contains a material that generates an aggregate when it is combined with an ink containing a coloring material, i.e., an aggregating agent, which enhances the interaction with the ink and acts to fix the ink dots. The aggregating agent can be selected according to the type of coloring material contained in the ink.

[0149] The flocculant is preferably any one of a thermally decomposable soluble cationic polymer, an organic acid, or a polyvalent metal salt, and more preferably a soluble cationic polymer or a polyvalent metal salt.

[0150] The dissolved cationic polymer and the polyvalent metal salt can aggregate the anionic components in the ink (usually coloring materials, pigments, etc.) by salting out, and the organic acid can aggregate the anionic components in the ink by changing the pH.

[0151] When an organic acid is used, the pH generally becomes acidic. This can cause deterioration of resins such as adhesives used in inkjet heads, resulting in poor inkjet head resistance. Polyvalent metal salts have a pH in the neutral to weakly alkaline range, and the pH of the soluble cationic polymer can be adjusted to the neutral range by appropriately selecting the product number, etc. Therefore, it is more preferable that the flocculant is a soluble cationic polymer or a polyvalent metal salt, since this can solve the above problems.

[0152] Examples of the dissolved cationic polymer contained in the treatment liquid as a flocculant include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride. Examples of commercially available dissolving cationic polymers include KHE100L and FPA100L manufactured by Senka Corporation, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nittobo Medical Co., Ltd.

[0153] The organic acid contained in the treatment liquid as an aggregating agent is capable of aggregating the coloring material contained in the ink, and preferably has a first dissociation constant of 3.5 or less, preferably within the range of 1.5 to 3.5. Within this range, liquid shifting in low concentration areas is further prevented, and ink mixing (beading) in high concentration areas is improved.

[0154] In addition, by using an organic acid, the storage stability of the treatment liquid is easily maintained, and blocking is less likely to occur after the treatment liquid is applied and dried. From the above viewpoints, formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and its derivatives, methacrylic acid and its derivatives, acrylamide and its derivatives, and other compounds having a carboxy group, sulfonic acid derivatives, or phosphoric acid and its derivatives are preferred as the organic acid contained in the flocculant.

[0155] Examples of the polyvalent metal salt contained in the treatment liquid as a flocculant include water-soluble salts such as calcium salts, magnesium salts, aluminum salts and zinc salts. Examples of compounds that form salts with polyvalent metals include hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanic acid, organic carboxylic acids, and organic sulfonic acids. Examples of the organic carboxylic acids include acetic acid, oxalic acid, lactic acid, fumaric acid, citric acid, salicylic acid, and benzoic acid.

[0156] The coagulant is preferably contained in the treatment liquid in an amount of 5% by mass or less, and preferably in an amount of 1 to 4% by mass, from the viewpoints of effectively coagulating the anionic components in the ink and achieving a balance between image quality and hot water resistance.

[0157] Furthermore, when the flocculant is an organic acid, the content of the organic acid may be an amount that adjusts the pH of the treatment liquid to less than the first dissociation constant of the organic acid. By adding an organic acid to the treatment liquid in an amount that adjusts the pH of the treatment liquid to less than the first dissociation constant of the organic acid, bleeding during high-speed printing can be effectively suppressed.

[0158] The content of the flocculant in the treatment liquid can be measured by a known method. For example, when the flocculant is a polyvalent metal salt, the content can be measured by ICP emission spectrometry, and when the flocculant is an acid, the content can be measured by high performance liquid chromatography (HPLC).

[0159] <Water-soluble solvent> The treatment liquid according to the present invention may contain a water-soluble solvent in addition to water. The water-soluble solvent may be the same as those exemplified for the ink. The content of the water-soluble solvent in the treatment liquid is not particularly limited, but is preferably within the range of 10 to 50% by mass.

[0160] <Water> The water contained in the treatment liquid according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water. The water content in the treatment liquid is not particularly limited, but is preferably within the range of 45 to 80 mass %.

[0161] <Surfactant> The treatment liquid according to the present invention may contain a surfactant. The surfactant may be the same as those exemplified for the ink. The content of the surfactant in the treatment liquid is not particularly limited, but is preferably within the range of 0.05 to 3% by mass.

[0162] <Other additives> The treatment liquid may contain other components, such as a crosslinking agent, an antifungal agent, a bactericide, etc., as appropriate, within the scope of not impairing the effects of the present invention.

[0163] Further, for example, ultraviolet absorbents described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, discoloration inhibitors described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091 and JP-A-3-13376, anions, It is also possible to contain various known additives such as various cationic or nonionic surfactants, fluorescent brightening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-219266, antifoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, etc.

[0164] <Properties of processing solution> The viscosity of the treatment liquid according to the present invention is preferably within a range of 1 to 40 mPa·s, and more preferably within a range of 1 to 10 mPa·s, at a temperature of 25° C. The viscosity of the treatment liquid can be measured using a rotational viscometer. Unless otherwise specified, the viscosity in this specification is the viscosity at a temperature of 25° C.

[0165] The static surface tension of the treatment liquid according to the present invention is preferably smaller than the static surface tension of the ink at a temperature of 25° C. Furthermore, the static surface tension of the treatment liquid is preferably within a range of 22 to 30 mN / m, and more preferably within a range of 22 to 26 mN / m, at a temperature of 25° C. This makes it possible to aggregate the ink while increasing the dot diameter. The static surface tension of the treatment liquid can be measured by a surface tensiometer that applies the platinum plate method (Wilhelmy method), etc. Unless otherwise specified, the static surface tension in this specification is the static surface tension at a temperature of 25°C.

[0166] The dynamic surface tension of the treatment liquid according to the present invention is preferably 40 mN / m or less, more preferably 36 mN / m or less, and even more preferably within the range of 25 to 35 mN / m, at a temperature of 25° C. and a life time of 50 ms. The dynamic surface tension of the treatment liquid can be measured by a dynamic surface tensiometer using a maximum bubble pressure method. For example, a Dynamic Surface Tension Meter BP-D4 type manufactured by Kyowa Interface Science Co., Ltd. can be used as the dynamic surface tensiometer. Unless otherwise specified, the dynamic surface tension in this specification is the dynamic surface tension at a temperature of 25°C and a lifetime of 50 ms.

[0167] (8) Recording medium The recording medium that can be used in the present invention is not particularly limited, and may be either a non-absorbent recording medium or an absorbent recording medium.

[0168] In the present invention, when measured by the Bristow method described in J. TAPPI Paper Pulp Test Method No. 51 "Liquid Absorbency Test Method for Paper or Paperboard", the liquid absorbency is measured within 30 msec from the start of contact. 1 / 2 The water absorption of recording media up to 0.3 g / m 2 Recording media with a solubility of 0.3 g / m or less are called non-absorbent recording media. 2 Recording media that are more porous are referred to as absorbent recording media.

[0169] <Non-absorbent recording media> Examples of non-water-absorbent recording media that can be used include known plastic films. Specific examples include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, polylactic acid films, and other biodegradable films. In addition, in order to impart gas barrier properties, moisture resistance, and aroma retention properties, films coated with polyvinylidene chloride on one or both sides, and films vapor-deposited with metal oxides can also be preferably used. As the non-water-absorbent film, both unstretched and stretched films can be preferably used.

[0170] In addition to these, examples of non-water-absorbent recording media include recording media made of inorganic compounds such as metals and glass.

[0171] It can also be suitably used as a packaging material for retort foods, in which a thermosetting resin is provided as a coating layer on a metal recording medium. The packaging material for retort foods is made of a film in which a thermoplastic resin layer and an aluminum foil layer are laminated (laminated) to block air, moisture, and light and seal the food inside, for example, polypropylene on the food side and polyester on the outside.

[0172] Further examples of non-absorbent recording media include leather substrates. Leather used for printing purposes is generally cowhide. Cowhide is usually tanned using a chromium compound to add durability. The tanned leather is generally coated with an acrylic or urethane white pigment paint to make a recording medium.

[0173] <Absorbent recording medium> Examples of absorbent recording media include plain paper (for example, copy paper, plain paper for printing), coated paper, art paper, paper specifically for inkjet printing, glossy inkjet paper, cardboard, wallpaper, and wood.

[0174] <Thickness of recording medium> In the present invention, the thickness of the recording medium is appropriately selected depending on the type of recording medium. When the recording medium is a plastic film, the thickness of the recording medium is preferably within the range of 10 to 120 μm, more preferably 12 to 60 μm. When the recording medium is a metal recording medium, the thickness of the recording medium is preferably within the range of 0.05 to 0.5 mm, more preferably 0.1 to 0.3 mm. When the recording medium is a leather substrate, the thickness of the recording medium is preferably within the range of 1 to 5 mm, more preferably 1 to 3 mm. When the recording medium is an absorbent recording medium, the thickness of the recording medium is preferably within the range of 50 to 500 μm. EXAMPLES

[0175] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified.

[0176] <Ink Preparation> Cyan ink was prepared by mixing the materials in the amounts shown in Table I. Yellow ink, magenta ink and black ink were also prepared using the same materials and amounts as those shown in Table I, except that the pigments were changed to Pigment Yellow 155, a 1:1 (mass ratio) mixture of Pigment Red 202 and Pigment Violet 19, and Pigment Black 7, respectively.

[0177] The physical properties of the prepared cyan ink are also shown in Table I. The physical properties of the yellow ink, magenta ink and black ink were the same as those of the cyan ink shown in Table I.

[0178] The viscosity was measured at 25°C using a rotational viscometer. The static surface tension was measured at a temperature of 25° C. using a surface tensiometer employing the platinum plate method (Wilhelmy method). [Table 1]

[0179] <Preparation of processing solution> A processing solution was prepared by mixing the materials in the amounts shown in Table II. The physical properties of the processing solution prepared are also shown in Table II.

[0180] The viscosity was measured at 25°C using a rotational viscometer. The static surface tension was measured at a temperature of 25° C. using a surface tensiometer employing the platinum plate method (Wilhelmy method). The dynamic surface tension was measured by the maximum bubble pressure method using a dynamic surface tensiometer at a temperature of 25° C. and a life time of 50 ms.

[0181] [Table 2]

[0182] <Image formation> Using the ink and processing liquid prepared above, images based on the original image data 1 to 3 shown in Figures 8 to 10 were formed on the surface of a recording medium by recording methods No. 1 to 35 shown in Tables III and IV.

[0183] Each of the original image data 1 to 3 is mainly composed of a yellow solid area y, a magenta solid area m, a cyan solid area c, a black solid area k, a red solid area r, a green solid area g, and a blue solid area b.

[0184] The primary color solid areas, namely, yellow solid area y, magenta solid area m, cyan solid area c, and black solid area k, were formed by applying only yellow ink, magenta ink, cyan ink, and black ink, respectively.

[0185] The secondary color solid areas - red solid area r, green solid area g, and blue solid area b - were each formed by applying two types of ink in layers. The red solid area r was formed by applying yellow ink and magenta ink in layers. The green solid area g was formed by applying yellow ink and cyan ink in layers. The blue solid area b was formed by applying magenta ink and cyan ink in layers.

[0186] The document image data 1 is image data of a density gradation chart composed of solid areas of each color. In either recording method, the maximum amount of ink applied in an image based on the document image data 1 is 13.0 g / m 2 The amount of ink applied was set to the maximum value of 13.0 g / m 2 The area where this occurs is the area where the density gradation is maximum among the secondary color solid areas r, g, and b.

[0187] The original image data 2 is composed of the solid areas of each color mentioned above, and is image data in which the solid areas of each color are adjacent to each other and cut-out characters (4pt, 6pt, 8pt) are drawn. In either recording method, the amount of ink applied in an image based on the original image data 2 is 6.5 g / m for the primary color solid areas y, m, c, and k. 2 , 13.0 g / m for secondary color solid areas r, g, b 2 It was decided.

[0188] The document image data 3 is image data in which each of the solid color areas is individually drawn. In either recording method, the amount of ink applied in an image based on the document image data 3 is 6.5 g / m for the primary color solid areas y, m, c, and k. 2 , 13.0 g / m for secondary color solid areas r, g, b 2 It was decided.

[0189] The recording media used were polyester film (Futamura Chemical Co., Ltd., FE2001, thickness 50 μm, indicated as "PET" in the table) as a non-absorbent recording medium, and coated paper (Oji Paper Co., Ltd. OK Topcoat, thickness 100 μm) as an absorbent recording medium.

[0190] The printing method was either single-pass or multi-pass. In the case of the single-pass method, it is indicated as "single" in the table. In the case of the multi-pass method, it is indicated as "multi" in the table.

[0191] In the case of the single-pass method, the recording device used was an independently driven inkjet head module (resolution: 1200 dpi, ejection volume: small droplets 3 pL) manufactured by Konica Minolta, Inc. The head movement speed was 500 mm / sec.

[0192] In the case of the multi-pass method, a recording device was used in which an independently driven inkjet head manufactured by Konica Minolta (resolution: 360 dpi, ejection volume: small droplets 7 pL, medium droplets 15 pL, large droplets 23 pL) was installed as shown in Fig. 1. The independently driven inkjet head corresponds to the droplet ejection means 20 in Fig. 1. The head movement speed was 500 mm / sec, and the printing pass was four times.

[0193] The "treatment liquid deposition amount control type" in the table refers to the control type of the relationship between the amount of ink deposited and the amount of treatment liquid deposited, and is any one of Types 1 to 4 shown in Figures 11 to 14. Types 1 and 2 are according to the present invention, and Types 3 and 4 are comparative examples.

[0194] In the case of Type 1, the amount of treatment liquid applied was controlled so that in high-density regions, the amount of treatment liquid applied was smaller in unit areas to which more ink was applied, and in low-density regions, the amount of treatment liquid applied was controlled so that the amount of treatment liquid applied was larger in unit areas to which more ink was applied.

[0195] In the case of Type 2, in high-density regions, the amount of treatment liquid applied was controlled so that the amount of treatment liquid applied was smaller in unit regions where a larger amount of ink was applied, and in low-density regions, the amount of treatment liquid applied was controlled so that the amount of treatment liquid applied was constant.

[0196] In the case of Type 3, the amount of treatment liquid applied was controlled so that the more ink was applied to the unit area, the greater the amount of treatment liquid applied to that area. The reference value was set to 50% of the maximum value, but this was for convenience, and there was no difference in the control of the amount of treatment liquid applied between high-concentration areas and low-concentration areas.

[0197] In the case of Type 4, the amount of treatment liquid applied was controlled so that it was constant in all areas where ink was applied. The reference value was set to 50% of the maximum value, but this was for convenience, and there was no difference in the control of the amount of treatment liquid applied in high-concentration areas and low-concentration areas.

[0198] The reference values ​​shown in Tables III and IV are values ​​when the maximum amount of ink applied is taken as 100%. The maximum amount of ink applied for all the formed images was 13.0 g / m 2 Therefore, for example, the standard value is 6.5 g / m 2 In this case, the value in the table will be 50%.

[0199] In the table, "A" indicates the reference value, "B" indicates the amount of treatment liquid applied in the area where the amount of ink applied is the reference value, "C" indicates the maximum amount of ink applied, and "D" indicates the amount of treatment liquid applied in the area where the amount of ink applied is the maximum.

[0200] For edge treatment, the treatment liquid was applied dropwise to the same positions as those where the ink was applied dropwise in the peripheral region of the image contour, in an amount that was 30% of the ink amount (maximum ink application amount being 100%). The image contour peripheral region was defined as a region having a width Sw of 200 μm as shown in FIG. 7, starting from the image contour detected from the document image data using Photoshop (registered trademark). The distance from the image contour as the starting point to both ends of the image contour peripheral region in the width direction was 100 μm. The image contour was detected in Photoshop (registered trademark) by applying "contour tracing" under "expression method" with the threshold level set to 35.

[0201] <Evaluation method> The images formed by each recording method were evaluated by the following methods.

[0202] (Bleeding) For the images formed based on the original image data 1 and 2, the state of bleeding in the areas where solid areas of each color were adjacent to each other and in the cut-out characters was visually checked and evaluated according to the following criteria. ○: No bleeding △: Slight bleeding ×: Bleeding

[0203] (Glossy) For an image formed based on original image data 3, the glossiness was measured for the solid areas of the primary color yellow and the secondary color red, and evaluated according to the following criteria: The glossiness was measured at an angle of 60° using a glossmeter (PG-IIM manufactured by Nippon Denshoku Industries Co., Ltd.). ◎: Glossiness is 35 or more ○: Glossiness is 25 or more and less than 35 ×: Glossiness is less than 25

[0204] (Gloss Difference) The difference in gloss level between the solid area of ​​the yellow primary color and the solid area of ​​the red secondary color measured above was calculated and evaluated according to the following criteria. ○: Gloss difference is 6 or less ×: Gloss difference is greater than 6

[0205] (reflection density) For an image formed based on document image data 3, the reflection density of a solid area of ​​the primary color yellow was measured and evaluated according to the following criteria. The reflection density was measured under a D50 light source using a fluorescent spectrodensitometer (FD-7 manufactured by Konica Minolta, Inc.). ◎: Reflection density is 1.5 or more ○: Reflection density is 1.3 or more and less than 1.5 ×: Reflection density is less than 1.3

[0206] (dryness) An image formed based on document image data 1 was dried in an oven at 80° C. for 1 minute, and then rubbed with a finger to check the drying property, and evaluated according to the following criteria. ◎: No peeling when rubbed with fingers ○: Part of the surface peeled off when rubbed with fingers ×: Large peeling off when rubbed with fingers

[0207] The evaluation results for the images formed by each recording method are shown in Tables III and IV. In addition, in Tables III and IV, "the present invention" in the Remarks column for Recording Methods No. 2, 7 and 18 should be read as "Reference Example."

[0208] [Table 3]

[0209] [Table 4]

[0210] From the evaluation results shown in Tables III and IV, it is apparent that the recording method of the present invention can form images having good gloss and little ink bleeding. [Industrial Applicability]

[0211] The present invention can be used in an inkjet recording method and an inkjet recording apparatus that can form images with good gloss and little ink bleeding. [Explanation of symbols]

[0212] 1 Head Unit 1C, 1M, 1Y, 1K, 1Pr head 20 Droplet discharge means 21 Nozzle 22 Carriage 30 Scanning unit W Head unit width A1~A6 print area P Full print area PL print area length PW Print area width Me Recording Media Im Ink application area G Image Contour S Image contour surrounding area Sw Width of the area around the image edge C, M, Y, K, Ink Pr processing solution

Claims

1. An inkjet recording method for forming an image by applying an ink containing a coloring material and a treatment liquid containing a flocculant to a surface of a recording medium by a droplet ejection means, comprising: controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied to a unit region where the amount of ink applied is greater is smaller; controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or less than the reference value among the regions to which the ink is applied, the amount of treatment liquid applied is increased in a unit region where a larger amount of ink is applied; and 1. An ink jet recording method comprising: controlling an amount of the treatment liquid to be applied so as to add an amount of the treatment liquid to a peripheral region of an image contour.

2. 2. The ink jet recording method according to claim 1, wherein the reference value is a value that is 50% of the maximum amount of the ink applied.

3. 3. The ink-jet recording method according to claim 1, which is a multi-pass method.

4. the recording medium is an absorbent recording medium, and The inkjet recording method according to any one of claims 1 to 3, characterized in that, when the reference value is A and the amount of the treatment liquid applied in a region where the amount of the ink applied is the reference value is B, the amount of the treatment liquid applied is controlled so that a value of a ratio B / A falls within a range of 0.14 to 0.

50.

5. the recording medium is a non-absorbent recording medium, and The inkjet recording method according to any one of claims 1 to 3, characterized in that, when the reference value is A and the amount of the treatment liquid applied in a region where the amount of the ink applied is the reference value is B, the amount of the treatment liquid applied is controlled so that a value of a ratio B / A falls within a range of 0.14 to 0.

30.

6. The inkjet recording method according to any one of claims 1 to 5, wherein the amount of the treatment liquid applied is controlled so that a ratio D / C falls within a range of 0.01 to 0.1, where C is a maximum value of the amount of the ink applied and D is an amount of the treatment liquid applied in a region where the amount of the ink applied is at the maximum value.

7. 7. The inkjet recording method according to claim 1, wherein, when a plurality of types of ink are applied, the amount of the treatment liquid applied, which is changed according to the amount of the ink applied for each unit area, is determined for each type of ink.

8. An inkjet recording apparatus for forming an image by applying ink containing a coloring material and a treatment liquid containing a flocculant to a surface of a recording medium by a droplet ejection means, comprising: controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or greater than a reference value, the amount of treatment liquid applied to a unit region where the amount of ink applied is greater is smaller; controlling the amount of treatment liquid applied such that, in a region where the amount of ink applied is equal to or less than the reference value among the regions to which the ink is applied, the amount of treatment liquid applied is increased in a unit region where a larger amount of ink is applied; and 1. An ink jet recording apparatus comprising: an ink jet head; a recording medium for recording a recording medium on which the ink is applied;

Images