Inkjet recording method and inkjet recording apparatus

Abstract

To provide a two-pack type inkjet recording method which improves color bleeding resistance, especially, blanked character quality, relating to an image formed on a recording medium, especially, a recording medium having low absorbency or non absorbency, and an inkjet recording device.SOLUTION: An inkjet recording method imparts a treatment liquid containing ink containing at least a color material and a treatment liquid containing at least a coagulant onto a recording medium surface by droplet discharge means and coalesce the treatment liquid with the recording medium surface, and thereby forms an image. The treatment liquid is imparted to an image formation region where the image is formed and a peripheral region of the image formation region, an imparting amount of the treatment liquid imparted to the peripheral region of the image formation region is controlled to be the same amount as the imparting amount of the treatment liquid at the end of the image formation region, and the surface tension of the treatment liquid is smaller than the surface tension of the ink at 25°C.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus, and more particularly to an inkjet recording method of a two-liquid system, and relates to an inkjet recording method and an inkjet recording apparatus in which the quality of an image formed on a recording medium, particularly a recording medium having low absorbency or non-absorbency, is improved.

Background Art

[0002] In an inkjet recording method, it is known that the image quality deteriorates due to a liquid pooling phenomenon in which droplets of ink coalesce on a recording medium, or color bleeding in which bleeding occurs between different colors. As solutions to these problems, a two-liquid system inkjet recording method is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-52867, in which a treatment liquid for aggregating coloring materials in the ink is discharged separately from the ink from an inkjet head (hereinafter also simply referred to as a "head") and combined with the ink on the recording medium, thereby fixing the ink well on the recording medium.

[0003] In this two-liquid system inkjet recording method, as a solution to color bleeding, a means is disclosed in which a relatively large amount of treatment liquid is applied to the image boundary portion between colors, and a small amount of treatment liquid is applied to the peripheral portion thereof.

[0004] For example, Patent Document 1 discloses an inkjet recording method in which a relatively large amount of treatment liquid is applied to the image boundary portion and the treatment liquid is applied to the peripheral portion thereof, whereby a good color image without bleeding or feathering phenomena can be obtained. Further, Patent Document 2 discloses a printing method in which the surface density of the treatment liquid in the boundary region of the printing region is set relatively higher than the surface density of the inner region of the printing region, thereby suppressing the occurrence of color bleeding and the like and improving the image quality.

[0005] Furthermore, Patent Document 3 discloses an inkjet recording method in which the ratio of aggregant to pigment is set high in printing areas and controlled within a predetermined range in boundary areas, in order to prevent a decrease in durability such as abrasion resistance of the recorded matter and bleeding at image boundary areas due to an excess of aggregant.

[0006] However, it was found that if the amount of treatment liquid is made different between a printing area and a boundary area where the same amount of ink is continuously applied, a difference in the cohesiveness of the ink occurs between the printing area and the boundary area, resulting in a deterioration of image quality such as the quality of cut-out characters. Furthermore, the problem of color bleeding has not been fully solved even in the two-liquid inkjet recording method.

[0007] In addition, the above-mentioned effects are more pronounced when a low-absorbency or non-absorbency recording medium such as a plastic substrate, a metal substrate, or a leather substrate is used as the recording medium, and the conventional two-liquid inkjet recording method is insufficient as a means for solving these problems. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 8-216393 [Patent Document 2] International Publication No. 2013 / 050080 [Patent Document 3] JP 2019-42997 A Summary of the Invention [Problem to be solved by the invention]

[0009] 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 which are capable of forming an image on a recording medium, particularly a low-absorbency or non-absorbency recording medium, in a two-liquid inkjet recording method, and which have improved color bleed resistance, particularly improved cut-out character quality.

Means for Solving the Problem

[0010] In order to solve the above problems, in the process of examining the causes of the above problems, the inventor used a treatment liquid containing ink and a flocculant, and when applying the treatment liquid to the image forming area and the peripheral area of the image forming area, the amount of the treatment liquid applied to the peripheral area of the image forming area was controlled to be the same as the amount of the treatment liquid applied at the end of the image forming area. It has been found that an inkjet image with improved color bleeding resistance, particularly the quality of knockout characters, can be obtained by the inkjet recording method.

[0011] That is, the above problems according to the present invention are solved by the following means.

[0012] 1. An inkjet recording method for forming an image by applying an ink containing at least a coloring material and a treatment liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means and combining them, applying the treatment liquid to an image forming area where the image is formed and a peripheral area of the image forming area, and controlling the amount of the treatment liquid applied to the peripheral area of the image forming area to be the same as the amount of the treatment liquid applied at the end of the image forming area, wherein the surface tension of the treatment liquid at 25°C is smaller than the surface tension of the ink く, The dynamic surface tension of the treatment liquid at 25°C and a lifetime of 50 ms, determined by the maximum bubble pressure method, is 25 to 36 mN / m, and the static surface tension of the treatment liquid is 22 to 26.7 mN / m characterized in that.

[0014] 2 . The inkjet recording method according to claim 1, wherein the peripheral area of the image forming area is an area within a range of 0.030 to 0.150 mm outside the outer periphery starting from the outer periphery of the image forming area. in the item described inkjet recording method.

[0015] 3. The processing liquid contains a polyvalent metal salt or a dissolved cationic polymer as the flocculant, and the processing liquid does not contain resin fine particles, according to claim 1. or Item in item 2 The inkjet recording method described.

[0017] 4 . An inkjet recording apparatus that forms an image by applying an ink containing at least a coloring material and a processing liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means and causing them to combine, The droplet ejection means having at least a discharge port for discharging the ink and a discharge port for discharging the processing liquid, The processing liquid is applied to the image forming region where the image is formed and the peripheral region of the image forming region, and means is provided for controlling the amount of the processing liquid applied to the peripheral region of the image forming region to be the same as the amount of the processing liquid applied at the end of the image forming region. and the surface tension of the treatment liquid at 25°C is less than the surface tension of the ink, The dynamic surface tension of the treatment liquid at 25°C and a lifetime of 50 ms, determined by the maximum bubble pressure method, is 25 to 36 mN / m, and the static surface tension of the treatment liquid is 22 to 26.7 mN / m . An inkjet recording apparatus characterized by the above.

Effects of the Invention

[0018] By the above means of the present invention, in a two-liquid type inkjet recording method, an inkjet recording method and an inkjet recording apparatus capable of obtaining an inkjet image with improved color bleeding resistance, particularly, knockout character quality (sharpness), can be provided for an image formed on a recording medium, particularly a low-absorbing or non-absorbing recording medium.

[0019] Regarding the mechanism or action mechanism for the manifestation of the effects of the present invention, the following speculation is made.

[0020] As described above, in the two - liquid type ink - jet recording method, if the amount of the treatment liquid is made different between the printed area and the boundary area with the same continuous ink - attached amount, a difference in the cohesiveness of the ink occurs between the printed area and the boundary area, and it has been found that this causes a deterioration in image quality. Further, in the two - liquid type ink - jet recording method, the problem of color bleeding has not been sufficiently solved. In particular, low - absorption and non - absorption substrates such as plastic substrates, metal substrates, and leather substrates show the above - mentioned influence significantly, and the conventional two - liquid type ink - jet recording method has been insufficient as a means to solve these problems. In the ink - jet recording method of the present invention, a treatment liquid is applied to an image formation area where an image is formed and a peripheral area of the image formation area, and by controlling the application amount of the treatment liquid applied to the peripheral area of the image formation area to be the same as the application amount of the treatment liquid at the end of the image formation area, it has been found that the above problems can be solved.

[0021] That is, by applying the treatment liquid to the image formation area where the image is formed and the peripheral area of the image formation area, and controlling the application amount of the treatment liquid applied to the peripheral area of the image formation area to be the same as the application amount of the treatment liquid at the end of the image formation area, by further promoting the unification with the ink in the boundary area of the image formation area, by suppressing feathering etc. at the edge part of the ink - jet image, the quality of missing characters etc., for example, the sharpness of the ink image can be dramatically improved.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0023] The inkjet recording method of the present invention is an inkjet recording method in which an ink containing at least a coloring material and a processing liquid containing at least a flocculant are applied to the surface of a recording medium by droplet ejection means and combined to form an image, wherein the processing liquid is applied to an image formation area where the image is formed and a peripheral area of the image formation area, and the application amount of the processing liquid applied to the peripheral area of the image formation area is controlled to be the same as the application amount of the processing liquid at the end of the image formation area. This feature is a technical feature common to or corresponding to the following embodiments.

[0024] As an embodiment of the present invention, from the viewpoint of the manifestation of the effects of the present invention, the application amount of the ink at the end of the image formation area is 15 g / m 2 When the following conditions are met, it is preferable in that the object effect of the present invention can be more manifested by controlling so that the processing liquid is not applied to the peripheral area of the end portion.

[0025] Further, it is preferable that the peripheral area of the image formation area is an area within a range of 0.030 to 0.150 mm outside the outer periphery starting from the outer periphery of the image formation area, because it can more promote the combination of the processing liquid and the ink and form a sharp ink image with more suppressed color bleeding.

[0026] Also, it is preferable that the processing liquid contains a polyvalent metal salt or a dissolved cationic polymer as the flocculant.

[0027] Generally, when using an organic acid, the pH generally becomes acidic. Therefore, resins such as adhesives used in an inkjet head may be deteriorated, and the inkjet head resistance may become inferior. A polyvalent metal salt has a pH in the neutral range to weak alkaline range, and by appropriately selecting the product number and the like for the dissolved cationic polymer, the pH can be adjusted to the neutral range. Therefore, since the above problems can be solved, it is more preferable that the flocculant is a dissolved cationic polymer or a polyvalent metal salt.

[0028] Also, it is preferable that the treatment liquid does not contain resin fine particles in terms of being able to exhibit more effective coalescence with respect to the ink. Since the treatment liquid does not contain resin fine particles, it is preferable in terms of exhibiting the effect that the treatment liquid hardly dries and thickens on the nozzle surface of the head, and the ejection property of the inkjet becomes good.

[0029] It is preferable that the dynamic surface tension of the treatment liquid at 25 °C and a lifetime of 50 ms, determined by the maximum bubble pressure method, is 35 mN / m or less in terms of being able to more effectively exhibit the object and effect of the present invention.

[0030] Further, as the inkjet recording apparatus of the present invention, an inkjet recording apparatus that forms an image by applying and coalescing at least an ink containing a coloring material and a treatment liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means, respectively, and that includes at least droplet ejection means having a discharge port for discharging the ink and a discharge port for discharging the treatment liquid, is characterized by having means for applying the treatment liquid to an image formation region where the image is formed and a peripheral region of the image formation region, and controlling so that the application amount of the treatment liquid applied to the peripheral region of the image formation region is the same as the application amount of the treatment liquid at the end of the image formation region.

[0031] Hereinafter, the present invention, its components, and the forms and modes for implementing the present invention will be described in detail. In this application, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value.

[0032] 《Inkjet Recording Method》 The inkjet recording method of the present invention (hereinafter, also referred to as the inkjet method or simply the "recording method") is an inkjet recording method for forming an image by applying an ink containing at least a coloring material and a treatment liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means and combining them. The treatment liquid is applied to the image formation region where the image is formed and the peripheral region of the image formation region, and the application amount of the treatment liquid applied to the peripheral region of the image formation region is controlled to be the same as the application amount of the treatment liquid at the end of the image formation region.

[0033] First, the basic configuration of an inkjet recording apparatus applicable to the recording method of the present invention will be described.

[0034] The recording method of the present invention is a so-called two-liquid type recording method for forming an image by applying an ink containing at least a coloring material and a treatment liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means and combining them.

[0035] 《Inkjet Recording Apparatus》 FIG. 1 schematically shows an example of the main part of a two-liquid type inkjet recording apparatus (scanning type, hereinafter, also simply referred to as the "recording apparatus") applicable to the recording method of the present invention. Further, FIG. 2 schematically shows a state in which ink and a treatment liquid are applied from droplet ejection means to the surface of a recording medium by the apparatus shown in FIG. 1. Hereinafter, with reference to FIGS. 1 and 2, the recording method of the present invention will be described by taking image formation by the scanning method as an example, but the recording method of the present invention is not limited thereto. It is also applicable to the line type inkjet recording apparatus described later.

[0036] In the recording method using the recording apparatus shown in FIG. 1, as shown in FIG. 2, while the droplet discharging means 20 discharges inks Y, M, C, K (yellow, magenta, cyan, black) of each color and the processing liquid Pr onto the recording medium M, it moves in the scanning direction X (hereinafter, also referred to as the "X direction"), thereby forming an image. In the recording apparatus shown in FIG. 1, the recording medium M is sequentially conveyed in the direction Y (hereinafter, also referred to as the "conveying direction Y" or "Y direction") orthogonal to the scanning direction X by a conveying means (not shown), so that an image can be formed on substantially the entire surface (image forming surface) of the recording medium M.

[0037] The droplet discharging means 20 includes a head 1Pr for the processing liquid and heads 1Y, 1M, 1C, 1K corresponding to inks of each color (hereinafter, these are also collectively referred to as the "head unit 1"), and a carriage 22 for arranging and holding these heads along the scanning direction X.

[0038] On the surface (nozzle surface) of each head facing the surface of the recording medium M, a plurality of nozzles are arranged along the direction Y orthogonal to the scanning direction X, and by appropriately applying pressure to the ink and the processing liquid, minute droplets are discharged from these nozzles. The droplet discharging means 20 is supported in a state where the nozzle surface in the head unit 1 is separated from the surface by a predetermined distance in the direction (height direction) orthogonal to the surface of the recording medium M.

[0039] The droplet discharging means 20 is scanned in the scanning direction X by the scanning unit 30. The scanning unit 30 includes, for example, a rail that supports the carriage 22 in a state where the nozzle surface is separated from the surface of the recording medium M by the above-mentioned predetermined distance in the height direction, and enables the carriage 22 to move along the rail extending along the scanning direction X.

[0040] FIG. 1 shows the entire printing area P as the range in which an image can be formed on the recording medium M by the scanning of the droplet discharging means 20 in the X direction and the conveyance of the recording medium M in the Y direction. Let the length of the entire printing area P in the X direction be the printing area width PW, and the length in the Y direction be the printing area length PL.

[0041] When the droplet ejection means 20 moves once in the scanning direction X, for the print area width PW of the entire print area P, in the area of width W in the direction Y orthogonal to the scanning direction X of the head unit 1, ink Y, M, C, K (hereinafter also collectively referred to as "In") and the processing liquid Pr are applied. In the scanning method recording method as shown in FIG. 1, the operation of applying the ink In and the processing liquid Pr to the recording medium M by one movement of the droplet ejection means 20 in the scanning direction X is taken as one print pass, and a plurality of print passes are performed in the same area, and finally a desired image is formed on the recording medium M.

[0042] Here, in the recording apparatus, according to the image data of the document, in the control unit, the presence or absence and the amount of application of the ink are determined for each pixel area, and the droplet ejection means forms an image by applying the ink to the surface of the recording medium M based on this determination. There are cases where image formation on the recording medium M is completed in one print pass, but when forming an image with a high resolution (dpi), the image is decomposed and a plurality of print passes are performed to form an image on the recording medium M.

[0043] In FIG. 1, the area where the ink and the processing liquid are applied by one movement of the droplet ejection means 20 is an area of the product of the print area width PW in the scanning direction X and the width W in the direction Y orthogonal to the scanning direction X of the head unit 1 (hereinafter also referred to as "the width W of the head unit 1").

[0044] The entire print area P is an aggregate of these print areas A. The number of print areas A constituting the entire print area P is indicated by the value obtained by dividing the print area length PL by the width W of the head unit 1. For example, in the case of the recording medium M shown in FIG. 1, the number of print areas A constituting the entire print area P is 6, and the print areas A1, A2, A3, A4, A5, and A6 are arranged in parallel in order from the front to the back of the recording medium M to form the entire print area P.

[0045] 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 discharging means 20, and in the printing areas A5 and A6, images are sequentially formed after the image formation in the printing area A4 is completed. In FIG. 1, Im indicates the image formation area.

[0046] In the recording method of the present invention, for example, using the recording apparatus shown in FIG. 1, an ink In and a processing liquid Pr are applied to the surface of the recording medium M by the droplet discharging means 20 as described above and combined to form an image. In FIGS. 1 and 2, the form in which the processing liquid Pr is applied to the surface of the recording medium M before the ink In is shown, but in the recording method of the present invention, the application of the processing liquid Pr may be performed after the ink In. For example, by disposing the head 1Pr for the processing liquid Pr behind the head for the ink, a configuration in which the processing liquid Pr is applied after the application of the ink In may be employed.

[0047] In the recording method of the present invention, it is preferable that the ink In and the processing liquid Pr are applied to the image formation area where an image is formed, for example, the area indicated by Im in FIG. 1, so as to meet the following control conditions (1) and (2).

[0048] (1) The application amount of the processing liquid is changed according to the application amount of the ink for each unit area where the image is formed, and the application amount of the processing liquid is 5 g / m 2 or less in all of the unit areas. Control is performed as follows.

[0049] (2) When the image is formed by a plurality of printing passes, in the unit area where the application amount of the processing liquid is 0.8 g / m 2 or more, control is performed so that the deviation when comparing the average of the application amounts of the processing liquid in the unit area in each printing pass among the printing passes is within ±30%.

[0050] Further, when the droplet discharging means is of the line type, the droplet discharging means has a length equal to or greater than the printing area width PW of the entire printing area P with respect to the recording medium M, and the head 1Pr for the processing liquid and the heads 1Y, 1M, 1C, 1K corresponding to the inks of the respective colors are arranged in order along the conveyance direction Y so as to be parallel to the printing area width PW. The head 1Pr for the processing liquid may be arranged before or after the heads for the inks of the respective colors.

[0051] In the line type droplet discharging means, one head unit 1 (a set of the head 1Pr and the heads 1Y, 1M, 1C, 1K) having a length equal to or greater than the printing area width PW may be used, or a plurality of head units 1 may be combined so as to have a length equal to or greater than the printing area width PW.

[0052] Further, a plurality of head units 1 may be arranged side by side such that their nozzles are staggered, so as to increase the resolution of the droplet discharging means as a whole. Also, such droplet discharging means may be arranged in a plurality side by side along the conveyance direction Y of the recording medium. In that case, the number of printing passes according to the control condition in (2) above corresponds to the number of head units 1 arranged side by side along the conveyance direction Y.

[0053] The type of each head is not particularly limited, and any of an on-demand type head and a continuous type head may be used. Examples of on-demand type heads include electro-mechanical conversion types including single cavity type, double cavity type, vender type, piston type, shear mode type, and shared wall type, and electro-thermal conversion types including thermal inkjet type and bubble jet (where “bubble jet” is a registered trademark of Canon Inc.) type.

[0054] Among the above heads, it is preferable that a head using a piezoelectric element as an electro-mechanical conversion element used in the electro-mechanical conversion method (also referred to as a “piezo type inkjet head”) is used.

[0055] 《Edge Processing》 In the recording method of the present invention, the treatment liquid is applied to the image forming area where the recording image is formed and the peripheral area of the image forming area, and the application amount of the treatment liquid applied to the peripheral area of the image forming area is controlled to be the same as the application amount of the treatment liquid at the end of the image forming area, and image formation is performed. The specific method of edge processing will be described later.

[0056] As an embodiment of the recording apparatus of the present invention, from the viewpoint of expressing the effects of the present invention, the treatment liquid is applied to the image forming area where the image is formed and the peripheral area of the image forming area, and the application amount of the treatment liquid applied to the peripheral area of the image forming area is controlled to be the same as the application amount of the treatment liquid at the end of the image forming area.

[0057] Furthermore, as described above, when the application amount of the ink at the end of the image forming area is 15 g / m 2 Under the following medium - to - low concentration conditions, it is preferable not to apply the treatment liquid to the peripheral area of the end.

[0058] FIG. 3 shows an example of a recording medium on which an image is formed by the recording method of the present invention using the recording apparatus of FIG. 1. The image forming area Im shown in FIG. 3 corresponds to the original image. Note that, for the recording medium M in which the image is being formed in FIG. 1, FIG. 3 shows the state where the image formation is completed. When forming an image on the entire printing area P on the surface of the recording medium M by a two - liquid type inkjet recording method, for example, if it is an image of a document on a personal computer, based on the halftone - processed image data, the arrangement, application amount, etc. of the pixels to which the ink In is applied in the entire printing area P are determined, and correspondingly, the arrangement, application amount, etc. of the pixels to which the treatment liquid Pr is applied are determined.

[0059] In the example shown in FIG. 3, the ink In is applied to the image forming area Im on the recording medium M according to the application position and application amount determined based on the image data of the original manuscript. Also, for the processing liquid Pr, the application amount of the processing liquid is changed in the image forming area Im according to the application amount of the ink, and the application amount of the processing liquid is 5 g / m in all of the unit areas. 2 Control is performed as follows.

[0060] In the present invention, for the formed image described in FIG. 3, the processing liquid Pr is applied not only to the image forming area but also to the peripheral area of the image forming area. And it is characterized in that the application amount of the processing liquid Pr applied to the peripheral area is the same as the application amount of the processing liquid Pr at the end of the image forming area adjacent to the peripheral area.

[0061] FIG. 4 is a diagram showing another example of a recording medium on which an image is formed by the recording method of the present invention using the recording apparatus of FIG. 1. The image forming area Im shown in FIG. 4 is formed using the same original manuscript image as the image forming area Im shown in FIG. 3 and corresponds to the original manuscript image. In the example shown in FIG. 4, the ink In is applied only to the image forming area Im on the recording medium M, and the processing liquid Pr is applied to both the image forming area Im and the peripheral area S of the image forming area Im.

[0062] In the example of FIG. 4, in the image forming area Im, the ink In and the processing liquid Pr are applied by the recording method of the present invention in the same manner as in the example of FIG. 3. And the processing liquid Pr is also applied to the peripheral area S. The application amount of the processing liquid Pr applied to the peripheral area S is the same as the application amount of the processing liquid Pr applied to the end of the image forming area Im adjacent to the peripheral area S. Thereby, an effect of suppressing the occurrence of bleeding of the ink in the vicinity of the boundary between the image forming area Im and its peripheral area S can be obtained.

[0063] For example, at the end of the image forming area Im adjacent to the peripheral area S, if the processing liquid Pr applied to the unit area is 2 g / m 2 then, in the peripheral area S, the application amount is 2 g / m 2The processing liquid Pr is applied. If the amount of the processing liquid Pr applied in the peripheral region S is larger than the amount of the processing liquid Pr applied to the end portion of the image forming region Im adjacent to the peripheral region S, cracks may occur in the ink coating film. If it is smaller, bleeding of the ink near the boundary between the image forming region Im and its peripheral region S may not be sufficiently suppressed. In the present invention, the "same amount" is treated as the "same amount" as long as it is within the error range of the applied amount caused by the performance of the recording apparatus such as the discharge performance of the processing liquid Pr in the head.

[0064] Regarding the bleeding of the ink near the boundary between the image forming region Im and its peripheral region S, it is likely to occur when the amount of the ink In applied to the end portion of the image forming region Im is large, and the effect of applying the processing liquid Pr to the peripheral region S is great. On the other hand, when the amount of the ink In applied to the end portion of the image forming region Im is small, applying the processing liquid Pr to the peripheral region S may conversely cause bleeding of the ink near the boundary.

[0065] From such a viewpoint, in the recording method of the present invention, when the amount of the ink In applied to the end portion of the image forming region Im is 15 g / m 2 Hereinafter, more specifically, when the amount of the ink In applied to the unit region U at the end portion of the image forming region Im is 15 g / m 2 Hereinafter, it is preferable to control so that the processing liquid Pr is not applied to the peripheral region S of the end portion.

[0066] The peripheral region S is preferably a region from the end portion G of the image forming region Im to the outside of the end portion G up to 0.030 to 0.150 mm. That is, the width Sw of the peripheral region S is preferably 0.030 to 0.150 mm.

[0067] Note that the edge G of the image forming area Im indicates the contour of the image forming area Im. When there is a white area Wh where no image is formed inside, like the image forming area Im shown in Fig. 4, the boundary line between the white area Wh and the image forming area Im is also within the scope of the edge G. Here, when determining the arrangement of pixels to which the ink In is applied by performing halftone processing on the image of the original document, the edge G of the image forming area Im can be detected as a boundary with a large difference in image shading by various methods (Sobel method, Laplacian of Gaussian method, Canny method, etc.) with respect to the image of the original document before halftone processing.

[0068] In the recording method of the present invention, after applying and unifying the ink In and the processing liquid Pr on the surface of the recording medium as described above, usually, the unified liquid component is dried to obtain an ink coating film to form an image. Drying can be performed by a known method according to the composition and application amount of the ink In and the processing liquid Pr described below.

[0069] Fig. 5 shows the inkjet image formed at the cutting plane A - A and the application area of the processing liquid alone formed in the peripheral area in the configuration described in Fig. 4.

[0070] Fig. 5(a) is a cross-sectional view of the inkjet image according to the present invention, and Fig. 5(b) shows an example of the image configuration by the ink In and the processing liquid Pr.

[0071] As shown in Figs. 5(a) and (b), the image forming area Im of the inkjet image is configured as an aggregate of droplets of the ink In and the processing liquid Pr, and in the peripheral area S of the image forming area Im, the same amount of the processing liquid Pr as the application amount of the processing liquid Pr at the edge G of the image forming area Im is applied.

[0072] Next, the processing method in the edge processing will be further described.

[0073] Fig. 6 is a flowchart showing an example of the edge processing in the recording method of the present invention. 1) For example, an image represented in RGB is displayed on a personal computer screen. This RGB image is converted into a CMYK image using commercially available image processing software, such as Photoshop or the like.

[0074] 2) Perform halftone processing on the produced CMYK image. Halftone processing is a technique for expressing image density as area gradation such as the size and surface density of dots formed by ink, and can be performed by applying known error diffusion methods, dither methods, or the like.

[0075] 3) Detection of the edge part of the CMYK image. For the CMYK image before halftone processing, the edge part (the part with a large difference in shading) of the image can be detected by various methods (Sobel method, Laplacian of Gaussian method, Canny method, etc.).

[0076] 4) Processing liquid amount adjustment means Next, adjust the amount of the processing liquid by the following method. (1) Vary the amount of the processing liquid applied according to the amount of the ink applied for each unit area where the image is formed, and control so that the amount of the processing liquid applied in all of the unit areas is 5 g / m 2 is as follows.

[0077] (2) When the image is formed in a plurality of printing passes, control so that the deviation when comparing the average of the amount of the processing liquid applied to the unit area in each printing pass among the printing passes is within ±30% in the unit area where the amount of the processing liquid applied is 0.8 g / m 2 or more.

[0078] 5) Expansion of the edge region For the edge processing of the image, record the pixel addresses detected as the edge part in the image before halftone processing, and add pixels to which the processing liquid is applied so as to expand the pixels within a specified range from the pixels corresponding to the recorded pixel addresses in the image of the processing liquid whose amount has been adjusted. At this time, control so that the amount of the processing liquid applied in the expanding range becomes the same as the amount of the processing liquid applied in the printing area.

[0079] 6) Application of the processing liquid to the peripheral area. By arranging new processing liquid pixels at the periphery of the pixels of the processing liquid image corresponding to the edge detection part of the CMYK image, ink bleeding at the edge part can be prevented.

[0080] Here, when the amount of the processing liquid protruding from the ink printing area is larger than that of the ink printing area adjacent to the edge detection part, cracks occur in the ink coating film, and when it is smaller, ink bleeding cannot be sufficiently suppressed, leading to a deterioration in image quality.

[0081] 《Method for Forming Inkjet Image》 In the inkjet recording method of the present invention (hereinafter, also simply referred to as the "recording method"), an image is formed by applying an ink containing at least a coloring material and a processing liquid containing at least a flocculant to the surface of a recording medium by droplet ejection means and causing them to combine. At this time, it is preferable to control the relationship between the application amount of the ink and the application amount of the processing liquid to form an image.

[0082] (1) Vary the application amount of the processing liquid according to the application amount of the ink for each unit area where the image is formed, and the application amount of the processing liquid is 5 g / m in all of the unit areas. 2 Control as follows.

[0083] (2) When the image is formed by a plurality of printing passes, in the unit area where the application amount of the processing liquid is 0.8 g / m or more, control such that the deviation when comparing the average of the application amounts of the processing liquid in the unit area in each printing pass among the printing passes is within ±30%. 2

[0084] In the recording method of the present invention, the amount of ink In applied to each pixel region is determined by a known method according to the image data of the original document. In the recording method of the present invention, as described above, the relationship between the amount of ink In applied to the surface of the recording medium M thus determined and the amount of the treatment liquid Pr applied is controlled as in the above (1) and (2).

[0085] In the above (1), the control of the amount of the treatment liquid Pr applied is performed so as to change according to the amount of ink In applied for each unit region where an image is formed. However, the amount of the treatment liquid Pr applied is 5 g / m 2 The control of the amount of the treatment liquid Pr applied is performed as follows.

[0086] The size of the unit region (hereinafter, also referred to as "unit region U") where an image is formed is appropriately selected within a range where the effects of the present invention can be exhibited. Specifically, one pixel may be used as the unit region U. Since it is easy to exhibit the effects of the present invention, it is preferable that the unit region U is composed of 4 or more pixels as one unit. Further, it is more preferable to use 4 pixels composed of 2 pixels in the vertical direction × 2 pixels in the horizontal direction, 16 pixels composed of 4 pixels in the vertical direction × 4 pixels in the horizontal direction, and 36 pixels composed of 6 pixels in the vertical direction × 6 pixels in the horizontal direction as the unit region U.

[0087] 《Materials for Forming Inkjet Images》 Next, the ink In containing at least a coloring material and the treatment liquid Pr containing at least a flocculant used in the recording method of the present invention will be described.

[0088] 〔Ink〕 The ink In according to the present invention contains at least a coloring material. The coloring material is preferably a pigment. The ink In preferably contains, for example, a pigment as a coloring material, a polymer dispersant and resin fine particles for dispersing the pigment, and water and an organic solvent as a medium.

[0089] (Coloring Material) As the coloring material contained in the ink according to the present invention, it is preferably a pigment. As the pigment applicable to the present invention, an anionic dispersed pigment, for example, an anionic self-dispersing pigment or a pigment dispersed by an anionic polymer dispersant can be used. In particular, it is preferable to apply a pigment dispersion liquid in which a pigment is dispersed by an anionic polymer dispersant.

[0090] As the pigment, conventionally known ones can be used without particular limitation. For example, organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as titanium oxide can be preferably used.

[0091] In the case of titanium oxide, where it is generally difficult to ensure ink ejection stability and adhesion, the present invention can particularly preferably make it less likely to cause bleeding and enhance the adhesion.

[0092] Titanium oxide has three crystal forms: anatase type, rutile type, and brookite type. As general-purpose types, they can be roughly classified into anatase type and rutile type. Although not particularly limited, the rutile type with a large refractive index and high hiding power is preferable. Specifically, examples include the TR series of Fuji Titanium Industry Co., Ltd., the JR series of Tayca Corporation, and Taypek of Ishihara Sangyo Co., Ltd.

[0093] As the insoluble pigment, although not particularly limited, for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole, etc. are preferable.

[0094] Specific organic pigments that can be preferably used include the following pigments.

[0095] Examples of pigments for magenta or red include, for example, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, C.I. Pigment Violet 19, and the like.

[0096] Examples of pigments for orange or yellow include, for example, C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, C.I. Pigment Yellow 155, and the like. Particularly in terms of the balance between color tone and lightfastness, C.I. Pigment Yellow 155 is preferred.

[0097] Examples of pigments for green or cyan include, for example, C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, C.I. Pigment Green 7, and the like.

[0098] Examples of pigments for black include, for example, C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, and the like.

[0099] (Polymeric dispersant) The polymeric dispersant used for dispersing pigments is not particularly limited, but a polymeric dispersant having an anionic group is preferred, and those having a molecular weight in the range of 5000 to 200000 can be preferably used.

[0100] Examples of the polymeric dispersant include block copolymers, random copolymers and their salts having a structure derived from two or more monomers selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, polyoxyalkylene, polyoxyalkylene alkyl ether, and the like.

[0101] The polymeric dispersant preferably has an acryloyl group and is preferably added after being neutralized with a neutralizing agent (neutralizing base). Here, the neutralizing base is not particularly limited, but organic bases such as ammonia, monoethanolamine, diethanolamine, N-methylethanolamine, N-methyldiethanolamine, triethanolamine, morpholine are preferred. In particular, when the pigment is titanium oxide, it is preferred that the titanium oxide is dispersed with a polymeric dispersant having an acryloyl group.

[0102] Commercially available products may be used as the polymeric dispersant. Examples of commercially available products of the polymeric dispersant include Joncryl 819 manufactured by BASF.

[0103] Also, the addition amount of the polymeric dispersant is preferably in the range of 10 to 100% by mass, more preferably in the range of 10 to 40% by mass, based on the pigment.

[0104] As the pigment, it is also preferable to have a form of so-called capsule pigment in which the surface of the pigment particles is coated with the above polymer dispersant. As a method for coating the pigment with the polymer dispersant, various known methods can be used. For example, the phase inversion emulsification method, the acid precipitation method, or a method in which the pigment is dispersed with a polymerizable surfactant, a monomer is supplied thereto, and the coating is carried out while polymerizing can be preferably exemplified.

[0105] As a particularly preferred method, an insoluble resin in water is dissolved in an organic solvent such as methyl ethyl ketone, and after the acidic groups in the resin are partially or completely neutralized with a base, a pigment and ion-exchanged water are added, dispersed, and then the organic solvent is removed, and water is added as necessary for preparation.

[0106] The average particle diameter of the dispersion state of the pigment in the ink is preferably 50 nm or more and less than 200 nm. Thereby, the dispersion stability of the pigment can be improved, and the storage stability of the ink can be improved. The particle diameter measurement of the pigment can be determined by a commercially available particle diameter measuring device using the dynamic light scattering method, the electrophoresis method, etc. The measurement by the dynamic light scattering method is simple and can accurately measure the particle diameter region.

[0107] The pigment can be dispersed and used by a dispersing machine together with a dispersant and additives necessary according to other desired purposes.

[0108] As the dispersing machine, conventionally known dispersing devices such as a ball mill, a sand mill, a line mill, a high-pressure homogenizer, etc. can be used. Among them, it is preferable to disperse the pigment with a sand mill because the particle size distribution becomes sharp. Also, the material of the beads used for sand mill dispersion is not particularly limited, but from the viewpoint of preventing the generation of bead fragments and the contamination of ion components, it is preferably zirconia or zircon. Further, the bead diameter is preferably in the range of 0.3 to 3.0 mm.

[0109] The content of the pigment in the ink is not particularly limited. However, for titanium oxide, the range of 7 to 18% by mass is preferable, and for organic pigments, the range of 0.5 to 7% by mass is a preferable range.

[0110] (Resin fine particles) The resin fine particles used in the ink according to the present invention are preferably water-insoluble resin fine particles. The water-insoluble resin fine particles used in the present invention are fine particle dispersions of a water-insoluble resin that can accept the ink and has solubility or affinity for the ink.

[0111] As described above, the water-insoluble resin fine particles are those that are originally water-insoluble but have a form in which the resin is dispersed in an aqueous medium as microscopic fine particles. They are non-water-soluble resins that are forcibly emulsified using an emulsifier or the like and dispersed in water, or non-water-soluble resins that can self-emulsify to form a stable aqueous dispersion by introducing a hydrophilic functional group into the molecule without using an emulsifier or a dispersion stabilizer. These resins are usually used in a state of being emulsified and dispersed in water or a water / alcohol mixed solvent.

[0112] As the resin to be used, at least polyester-based resin, polyurethane-based resin, polyacrylic-based resin, or composite resin fine particles of polyurethane-based resin and polyacrylic-based resin are preferably used.

[0113] Regarding the above polyester-based resin, polyurethane-based resin, polyacrylic-based resin, or composite resin fine particles of polyurethane-based resin and polyacrylic-based resin, those described in detail in the section of the treatment liquid described later are preferably used as appropriate. However, the resin fine particles used in the treatment liquid are preferably cationic or nonionic in terms of ionic property, while the resin fine particles used in the ink are preferably anionic.

[0114] Among them, the resin fine particles used in the ink preferably contain an acid structure. Even when the addition amount of the surfactant is small, they can be dispersed in water, and the water resistance of the formed ink image is improved. This is called self-emulsifying type, which means that the urethane resin can be dispersed and stabilized in water only by molecular ionic properties without using a surfactant. Examples of the acid structure include acid groups such as carboxy group (-COOH) and sulfonic acid group (-SO 3 H), etc. The acid structure may be present in the side chain or at the terminal of the resin.

[0115] Preferably, some or all of the above acid structures are neutralized. By neutralizing the acid structure, the water dispersibility of the resin can be improved. As examples of the neutralizing agent for neutralizing the acid structure, organic amines are preferred. For example, it is preferable to use organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine.

[0116] Commercially available products may be used as the resin fine particles used in the ink. Examples of commercially available products of resin fine particles are listed below according to the type of resin.

[0117] 〈Polyester type〉 Manufactured by Takamatsu Yushi Co., Ltd.; Pes Resin A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX, manufactured by Unitika Ltd.; Elite KA-5034, KA-5071S, KA-1449, KA-0134, KA-3556, KA-6137, KZA-6034, KT-8803, KT-8701, KT-9204, KT-8904, KT-0507, KT-9511, etc. 〈Urethane type〉 Manufactured by Kusumoto Chemical Co., Ltd.; NeoRez R-967, R-600, R-9671, manufactured by Mitsui Chemicals, Inc.; W-6061, W-5661, WS-4000, etc. 〈Acrylic type〉 Manufactured by Enomoto Kasei Co., Ltd.; NeoCryl A-1127, manufactured by Japan Coating Resin Co., Ltd.; Mobinyl 6899D, 6969D, 6800, 6810, manufactured by Toyochem Co., Ltd.; TOCRYL W-7146, W-7150, W-7152, etc. The content of the resin fine particles in the ink is not particularly limited, but is preferably in the range of 2 to 10% by mass, and more preferably in the range of 2 to 5% by mass.

[0118] (Organic solvent) As the organic solvent contained in the ink, a water-soluble organic solvent can be preferably used. Examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.

[0119] 〈Alcohols〉 Examples of the 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, benzyl alcohol, and the like.

[0120] 〈Polyhydric alcohols〉 Examples of the polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having 4 or more propylene oxide groups, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, and the like.

[0121] 〈Amines〉 Examples of the amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, and the like.

[0122] 〈Amides〉 Examples of the amides include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, and the like.

[0123] 〈Glycol ethers〉 Examples of the 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, tripropylene glycol monomethyl ether, and the like.

[0124] 〈1,2-Alkanediols having 4 or more carbon atoms〉 Examples of the 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

[0125] Particularly preferred organic solvents are polyhydric alcohols, which can preferably suppress bleeding during high-speed printing. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferred.

[0126] The ink can contain one or a combination of two or more selected from these organic solvents.

[0127] The content of the organic solvent in the ink is not particularly limited, but is preferably in the range of 10 to 60% by mass.

[0128] (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 content of water in the ink is not particularly limited, but is preferably in the range of 45 to 85% by mass.

[0129] (Other additives) The ink according to the present invention can contain various known additives as needed for the purpose of improving surfactant, ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances.

[0130] 〈Surfactant〉 In the ink according to the present invention, it is preferable to contain a surfactant, which can improve the ejection stability of the ink from the nozzle and control the spread (expansion of the dot diameter) of the ink droplets landing on the recording medium.

[0131] The surfactant that can be used in the ink according to the present invention can be used without particular limitation. However, when the other components of the ink contain an anionic compound, the ionic property of the surfactant is preferably anionic, nonionic, or betaine type.

[0132] In the present invention, preferably, a fluorine-based or silicone-based surfactant having a high ability to reduce static surface tension, an anionic surfactant such as dioctyl sulfosuccinate having a high ability to reduce dynamic surface tension, a relatively low molecular weight polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, acetylene glycols, a Pluronic type surfactant (Pluronic is a registered trademark), and a nonionic surfactant such as a sorbitan derivative are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high ability to reduce dynamic surface tension.

[0133] As a surfactant, by adding a silicone-based or fluorine-based surfactant, it is possible to further suppress ink bleeding (beading) with respect to recording media made of various hydrophobic resins such as vinyl chloride sheets and recording media with low ink absorption ability such as printed paper, and it is preferable in that a high-quality printed image can be obtained.

[0134] As the above silicone-based surfactant, preferably there is a polyether-modified polysiloxane compound. For example, KF-351A, KF-642 manufactured by Shin-Etsu Chemical Co., Ltd., BYK345, BYK347, BYK348 manufactured by Big Chemie, Tegowet260 manufactured by Evonik Corporation, etc. can be mentioned.

[0135] The above fluorine-based surfactant means one in which part or all of the hydrogen bonded to the carbon of the hydrophobic group of a normal surfactant is replaced with fluorine. Among these, those having a perfluoroalkyl group in the molecule are preferable.

[0136] Among the above fluorine-based surfactants, certain ones are commercially available under the trade name Megafac F from Dainippon Ink and Chemicals, Inc., under the trade name Surflon from Asahi Glass Co., Ltd., under the trade name Fluorad FC from Minnesota Mining and Manufacturing Company, under the trade name Monflor from Imperial Chemical Industries, under the trade name Zonyls from E.I. du Pont de Nemours and Company, and under the trade name Licowet VPF from Farbenfabriken Bayer AG, respectively.

[0137] The content of the surfactant in the ink is not particularly limited, but it is preferably in the range of 0.1 to 5.0% by mass of the total mass of the ink.

[0138] In the ink used in the present invention, in addition to those described above, if necessary, various known additives can be appropriately selected and used according to the purpose of improving emission stability, print head and ink cartridge compatibility, storage stability, image storage property, and other various performances. For example, polysaccharides, viscosity modifiers, specific resistance modifiers, film-forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, fungicides, rust inhibitors, etc. can be used. For example, oil droplet microparticles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, JP-A-62-261476, etc., anti-fading agents described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc., and fluorescent brightening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, JP-A-4-219266, etc. can be mentioned.

[0139] For the ink In used in the present invention, the viscosity of the ink In is preferably 1 to 40 mPa·s at 25°C, more preferably 2 to 10 mPa·s. The viscosity of the ink In can be measured by a rotational viscometer. Unless otherwise specified, the viscosity in this specification is the viscosity at 25°C.

[0140] Also, the static surface tension of the ink In at 25°C is preferably greater than the static surface tension of the treatment liquid Pr. The static surface tension of the ink In is preferably in the range of 25 to 33 mN / m at 25°C, more preferably in the range of 25 to 29 mN / m. The static surface tension of the ink In can be measured by a surface tensiometer applying the platinum plate method (Wilhelmy method) or the like. Unless otherwise specified, the static surface tension in this specification is the static surface tension at 25°C.

[0141] 〔Treatment liquid〕 The treatment liquid Pr applied to the inkjet recording method of the present invention contains at least a flocculant. The viscosity of the treatment liquid Pr is adjusted by adding a solvent or the like so that it can be ejected from the nozzles of the head 1Pr by the inkjet method. The treatment liquid Pr contains a flocculant as an essential component, and further contains water, an organic solvent, and a surfactant as basic components. Also, it is preferable that the treatment liquid Pr does not contain resin fine particles.

[0142] The viscosity of the treatment liquid Pr is preferably in the range of 1 to 40 mPa·s at 25°C, and more preferably in the range of 1 to 10 mPa·s.

[0143] Also, the static surface tension of the treatment liquid Pr at 25°C is preferably smaller than the static surface tension of the ink In. The static surface tension of the treatment liquid Pr is preferably in the range of 22 to 30 mN / m at 25°C, and more preferably in the range of 22 to 26 mN / m.

[0144] Also, the dynamic surface tension of the treatment liquid Pr at 25°C and 50 ms is preferably 40 mN / m or less, more preferably 36 mN / m or less, and still more preferably in the range of 25 to 35 mN / m. The dynamic surface tension of the treatment liquid Pr was determined as the value at a lifetime of 50 ms when continuously generating bubbles using a Dynamic Surface Tension Meter BP-D4 type manufactured by Kyowa Interface Science Co., Ltd. at 25°C. Unless otherwise specified, the dynamic surface tension in this specification is the dynamic surface tension measured at 25°C and 50 ms using the maximum bubble pressure method.

[0145] (Flocculant) The treatment liquid according to the present invention has a material that has a function of generating aggregates when combined with an ink containing a coloring material, that is, by containing a flocculant, the interaction when combined with the ink becomes large, and it has the effect of fixing the dots of the ink and suppressing the expansion of the dot diameter. The flocculant can be selected according to the type of coloring material contained in the ink.

[0146] The flocculant preferably contains any of a dissolved cationic polymer, an organic acid, or a polyvalent metal salt, and more preferably a dissolved cationic polymer or a polyvalent metal salt.

[0147] The above-mentioned dissolved cationic polymer and polyvalent metal salt can aggregate anionic components (usually colorants, pigments, etc.) in the ink by salting out. The above-mentioned organic acid has a function of aggregating anionic components in the ink by pH fluctuation.

[0148] Examples of the above-mentioned dissolved cationic polymer include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride. Commercially available products of dissolved cationic polymers include, for example, those manufactured by Senka Corporation; KHE100L, FPA100L, and those manufactured by Nitto Boehringer Medical Co., Ltd.; PAS-92A, PAS-M-1A, PAS-21CL, etc.

[0149] The above-mentioned organic acid can aggregate pigments that may be contained in the ink, and preferably has a first dissociation constant of 3.5 or less, and preferably within the range of 1.5 to 3.5. When within this range, liquid pooling in the low-concentration part with a low printing rate is further prevented, and beading in the high-concentration part with a high printing rate is further improved.

[0150] In addition, by using an organic acid, it is easy to maintain the storage stability of the treatment liquid, and blocking is less likely to occur after the treatment liquid is applied and dried. Preferred organic acids from the above viewpoints include compounds having a carboxy group such as 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, or acrylamide and its derivatives, sulfonic acid derivatives, or phosphoric acid and its derivatives.

[0151] The content of the organic acid in the treatment liquid Pr may be an amount that adjusts the pH of the treatment liquid to less than the first dissociation constant of the organic acid. By including in the treatment liquid an amount of the organic acid such that the pH of the treatment liquid becomes less than the first dissociation constant of the organic acid, bleeding during high-speed printing can be effectively suppressed.

[0152] Examples of the above polyvalent metal salts include water-soluble salts such as calcium salts, magnesium salts, aluminum salts, and zinc salts. Compounds that form salts with polyvalent metals include hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanic acid, and organic carboxylic acids such as acetic acid, oxalic acid, lactic acid, fumaric acid, maleic acid, citric acid, salicylic acid, benzoic acid, and organic sulfonic acids.

[0153] The flocculant is preferably contained in the treatment liquid in a range of 5% by mass or less, and containing it within a range of 1 to 4% by mass is preferable from the viewpoint of effectively aggregating anionic components in the ink and balancing image quality and hot water resistance.

[0154] The content of the flocculant in the treatment liquid Pr 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 analysis, and when the flocculant is an acid, the content can be measured by high-performance liquid chromatography (HPLC).

[0155] (Water, organic solvent, and surfactant) The water contained in the treatment liquid Pr according to the present invention is not particularly limited and can be ion-exchanged water, distilled water, or pure water. The content of water in the treatment liquid Pr is not particularly limited, but is preferably within a range of 45 to 80% by mass.

[0156] In addition, as a solvent for the treatment liquid Pr according to the present invention, an organic solvent can be contained in addition to water. As the organic solvent, the same organic solvents as those exemplified in the above ink In can be used. The content of the organic solvent in the treatment liquid Pr is not particularly limited, but is preferably within a range of 10 to 50% by mass.

[0157] The processing liquid Pr according to the present invention can contain a surfactant. As the surfactant, the same surfactants as those exemplified in the above ink In can be used. The content of the surfactant in the processing liquid Pr is not particularly limited, but is preferably in the range of 0.08 to 3% by mass.

[0158] In addition, other components such as crosslinking agents, antifungal agents, and bactericides can be appropriately blended in the processing liquid as long as the effects of the present invention are not impaired.

[0159] Furthermore, for example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, anti-fading agents 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, various anionic, 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, defoaming agents, lubricants such as diethylene glycol, preservatives, thickeners, antistatic agents, and other known various additives can also be contained.

[0160] 〔Recording Medium〕 The recording medium applicable to the recording method of the present invention is not particularly limited, but is preferably a recording medium made of a non-absorbent material (hereinafter also referred to as a "non-absorbent recording medium"). By using a non-absorbent recording medium, the effects of the recording method of the present invention are more remarkable. The non-absorbency referred to in the present invention means non-absorbency to water.

[0161] As an example of a non-absorbent recording medium, a known plastic film can be used. Specific examples include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide-based films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, biodegradable films such as polylactic acid films, and the like. In addition, in order to impart gas barrier properties, moisture resistance, fragrance retention properties, etc., a film coated with polyvinylidene chloride on one or both sides of the film, or a film vapor-deposited with a metal oxide can also be preferably used. The non-absorbent film can be preferably used whether it is an unstretched film or a stretched film.

[0162] In addition to these, as a non-absorbent recording medium, a recording medium made of inorganic compounds such as metals and glass can be mentioned.

[0163] Also, leather can be used. As the leather used for printing purposes, cowhide is generally used. However, since cowhide does not have durability as it is, it is preferably subjected to chrome tanning. It is common to apply an acrylic or urethane-based white pigment paint to the tanned leather to make a recording medium.

[0164] In addition, it can also be suitably used for packaging materials for retort foods, etc., in which a thermosetting resin is provided as a coating layer on a metal recording medium. The packaging material for retort foods blocks air, moisture, and light and seals the internal food. For example, it is composed of a film obtained by laminating (laminating) a thermoplastic resin layer or an aluminum foil layer such as polypropylene on the food side and polyester on the outside to block air, moisture, and light and seal the internal food.

[0165] In the present invention, the thickness of the recording medium is in the range of 10 to 120 μm, more preferably 12 to 60 μm if it is a film substrate. Further, if it is a metal substrate, it is in the range of 0.05 to 0.5 mm, more preferably 0.1 to 0.3 mm. Further, if it is a leather substrate, it is preferably in the range of 1 to 5 mm, more preferably 1 to 3 mm.

Example

[0166] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "% by mass".

[0167] 〔Preparation of Ink Set A〕 (Preparation of Cyan Ink) Each constituent material described in Table I was mixed to prepare a cyan ink. The cyan pigment used was Pigment Blue 15:3. As the pigment dispersant, an acrylic dispersant having a neutralized carboxy group ("Joncryl 819" manufactured by BASF, acid value 75 mgKOH / g, solid content 20% by mass), propylene glycol as the ink solvent, and a predetermined amount of ion-exchanged water were premixed, and then dispersed using a sand grinder filled with 0.5 mm zirconia beads at a volume ratio of 50% to prepare a cyan pigment dispersion having a cyan pigment content of 18% by mass. The average particle size of the pigment particles contained in this pigment dispersion was 110 nm. When preparing the ink, the cyan pigment dispersion was used so that the cyan pigment became 5.0% by mass as a solid content. The cyan pigment dispersion was used such that the cyan pigment was 5.0% by mass as a solid content when forming the ink.

[0168] As a result of measuring the viscosity of the cyan ink at 25 °C with a rotational viscometer, it was 5.12 mPa / s. Further, as a result of measuring the static surface tension of the cyan ink at 25 °C by the platinum plate method (Wilhelmy method), it was 28.7 mN / m.

Table 1

[0169] (Preparation of Yellow Ink, Magenta Ink, and Black Ink) In the preparation of the above cyan ink, except that C.I. Pigment Yellow 155 was used as the yellow pigment, C.I. Pigment Red 202 / Pigment Violet 19 was used as the magenta pigment, and Pigment Black 7 was used as the black pigment instead of Pigment Blue 15:3 which is a cyan pigment, yellow ink, magenta ink, and black ink were prepared in the same manner.

[0170] (Preparation of Ink Set A) An ink set A composed of the above-prepared cyan ink, yellow ink, magenta ink, and black ink was prepared.

[0171] [Preparation of Treatment Liquids A to C] The polyvalent metal salt (calcium acetate), ink solvent (propylene glycol), surfactant, and ion-exchanged water described in Table II were sequentially added while stirring, and then filtered through a 5.0 μm filter to obtain treatment liquids A, B, and C. There was no substantial compositional change before and after filtration.

[0172] The static surface tension and dynamic surface tension of each of the above-prepared treatment liquids are as follows.

[0173] Treatment Liquid A: Viscosity = 4.89 mPa·s, Static Surface Tension = 28.8 mN / m, Dynamic Surface Tension = 38.3 mN / m Treatment Liquid B: Viscosity = 5.02 mPa·s, Static Surface Tension = 26.7 mN / m, Dynamic Surface Tension = 35.6 mN / m Treatment Liquid C: Viscosity = 5.09 mPa·s, Static Surface Tension = 25.5 mN / m, Dynamic Surface Tension = 32.1 mN / m Note that the viscosity and static surface tension were measured by the above method, and the dynamic surface tension was determined as the value at a lifetime of 50 ms when continuously generating bubbles at 25°C using a Dynamic Surface Tension Meter BP-D4 type manufactured by Kyowa Interface Science Co., Ltd. by the maximum method pressure method. [Table 2]

[0174] "Formation of Inkjet Images" Using the following scanning method, with the combination of ink set A and the treatment liquid described in Table III, solid images of each color with varying ink amounts from high concentration to low concentration as shown in Fig. 7 were produced. Note that the vertical axis in Fig. 7 indicates the ink amount (%).

[0175] 〔Formation of Image 1〕 (Scanning Method) An independently driven inkjet head (360 dpi, ejection volume: small droplet 7 pL, medium droplet 15 pL, large droplet 23 pL) manufactured by Konica Minolta was installed as shown in Image Diagram 1. By moving the head and the stage, a polyester film (manufactured by Futamura Chemical Co., Ltd., FE2001, thickness: 50 μm) was used as the recording medium. CMYK, which is ink set A, and treatment liquid A were ejected onto the recording medium, and solid ink images with high, medium-high, medium, medium-low, and low concentrations were formed with the ink application amounts and treatment liquid application amounts described in Table III.

[0176] At this time, for high, medium-high, medium, medium-low, and low concentrations, for C, M, Y, and K, they correspond to the concentrations (100%, 80%, 60%, 40%, 20%) corresponding to the maximum concentration among the concentrations obtained by dividing 100 - 0% into five equal parts. For R, G, and B, they correspond to the concentrations (200%, 160%, 120%, 80%, 40%) corresponding to the maximum concentration among the concentrations obtained by dividing 200 - 0% (which is twice that) into five equal parts.

[0177] Also, for the application order of Pr and CMYK, Pr can be applied either before or after CMYK, or both are acceptable.

[0178] Also, when forming solid images of each color, a 6-point knockout character image with the configuration shown in Fig. 3 was formed.

[0179] The moving speed of the IJ head was set at 500 mm / sec. An image of 720 dpi×720 dpi was divided into four images (180 dpi×180 dpi) by splitting it in two in each of the head moving direction and the stage moving direction, and the image was formed by printing one printing area four times.

[0180] After printing by the inkjet method, the recording medium was put into a dryer and dried at each set temperature for 10 minutes to obtain an image recording.

[0181] In the formation of Image 1, edge processing and application of the processing liquid to the peripheral area were not performed.

[0182] [Formation of Image 2] In the production of the above Image 1, Image 2 was formed in the same manner except that edge processing was performed according to the following method.

[0183] Edge processing was performed according to the following method.

[0184] [Halftone processing] This is a method of expressing the image density as area gradation such as the size and surface density of dots formed by ink, and halftone processing was performed by applying a known error diffusion method.

[0185] [Edge detection] For the CMYK image before halftone processing, the edge part (the part with a large difference in shading) of the image was detected by the Canny method.

[0186] Next, when the application amount at the end of the image area was 100%, the application amount in the peripheral area was set to 125% and applied to the area 0.176 mm from the end (edge part) inside the 6-point knockout character image.

[0187] [Formation of Image 3] In the production of the above Image 2, Image 3 was formed in the same manner except that when the application amount at the end of the image area was 100%, the application amount in the peripheral area was set to 75% and applied to the area 0.176 mm from the end (edge part) inside the 6-point knockout character image.

[0188] [Formation of Image 4] In the production of the above Image 2, except that in the region 0.176 mm from the edge (edge part) inside the 6-point knockout character image, when the application amount at the end of the image region was set to 100%, the application amount in the peripheral region was made 100%, that is, the same application amount as the application amount of the treatment liquid at the end of the image region, Image 4 was formed in the same manner.

[0189] [Formation of Image 5] In the production of the above Image 4, except that the application of the treatment liquid to the region adjacent to the edge detection part was not performed in the following region, Image 5 was produced in the same manner. 2 except that the application of the treatment liquid to the region adjacent to the edge detection part was not performed in the following region, Image 5 was produced in the same manner.

[0190] [Formation of Image 6] In the production of the above Image 4, except that the region from the end of the edge detection part to which the treatment liquid is applied was changed to 0.141 mm, Image 6 was produced in the same manner.

[0191] [Formation of Image 7] In the production of the above Image 4, except that the region from the end of the edge detection part to which the treatment liquid is applied was changed to 0.035 mm, Image 7 was produced in the same manner.

[0192] [Formation of Image 8] In the production of the above Image 4, except that the treatment liquid was changed from treatment liquid A to treatment liquid B, Image 8 was produced in the same manner.

[0193] [Formation of Image 9] In the production of the above Image 4, except that the treatment liquid was changed from treatment liquid A to treatment liquid C, Image 9 was produced in the same manner.

[0194] [Evaluation of Knockout Character Quality] In the above image formation, regarding the image quality in which 6-pt knockout characters were drawn on the solid images of each set ink application amount of each color, the bleeding situation as an image was visually observed and evaluated according to the following ranks.

[0195] 1: No bleeding or unevenness is observed. 2: Slight bleeding and unevenness are visible, but the quality is practically acceptable. 3: Obvious bleeding and unevenness are observed, and the quality lacks sharpness. The results obtained as above are shown in Table III.

Table 3

[0196] Regarding the above-formed image, as a result of evaluating the color bleeding resistance according to a conventional method, the present invention exhibited excellent effects. In addition, in the "Remarks" column of "Table 3", read "Reference Example" instead of "The present invention" for image numbers 4, 5, 6, and 7.

Explanation of Signs

[0197] 1 Head unit 1C, 1M, 1Y, 1K, 1Pr heads 20 Droplet ejection means 22 Carriage 30 Scanning unit A1 - A6 Printing areas C, M, Y, K, In inks G End Im Image forming area M Recording medium P Total printing area PL Printing area length PW Printing area width Pr Processing liquid S Peripheral area Sw Width of peripheral area S W Width Wh White non-printing area

Claims

1. An inkjet recording method for forming an image by applying an ink containing at least a coloring material and a treatment liquid containing at least an aggregating agent to a surface of a recording medium by a droplet ejection means and allowing the ink to coalesce, comprising: applying the treatment liquid to an image forming area where the image is to be formed and to a peripheral area of ​​the image forming area, and controlling an amount of the treatment liquid applied to the peripheral area of ​​the image forming area to be the same as an amount of the treatment liquid applied to an end of the image forming area; the surface tension of the treatment liquid at 25° C. is smaller than the surface tension of the ink; The dynamic surface tension of the treatment liquid at 25° C. and with a life time of 50 ms, as determined by a maximum bubble pressure method, is 25 to 36 mN / m; The ink-jet recording method according to the present invention, wherein the static surface tension of the treatment liquid is from 22 to 26.7 mN / m.

2. 2. The inkjet recording method according to claim 1, wherein the peripheral region of the image forming region is a region within a range of 0.030 to 0.150 mm from the outer periphery of the image forming region as a starting point.

3. 3. The ink jet recording method according to claim 1, wherein the treatment liquid contains a polyvalent metal salt or a dissolved cationic polymer as the flocculant, and does not contain resin fine particles.

4. An inkjet recording apparatus for forming an image by applying ink containing at least a coloring material and a treatment liquid containing at least an aggregating agent to a surface of a recording medium by a droplet ejection means and combining the ink and the treatment liquid, a droplet ejection means having an ejection port for ejecting the ink and an ejection port for ejecting the treatment liquid; a control unit for controlling an amount of the treatment liquid applied to the peripheral area of ​​the image forming area so as to be equal to an amount of the treatment liquid applied to an end portion of the image forming area, the surface tension of the treatment liquid at 25° C. is smaller than the surface tension of the ink; The dynamic surface tension of the treatment liquid at 25° C. and with a life time of 50 ms, as determined by a maximum bubble pressure method, is 25 to 36 mN / m; The inkjet recording apparatus is characterized in that the static surface tension of the treatment liquid is 22 to 26.7 mN / m.

Images