JP4498317B2 - Image forming method and image forming apparatus - Google Patents

Description

The present invention relates to an image forming method and an image forming equipment using an ink-jet recording system.

  The ink jet recording method is a method of forming an image pattern on a recording medium in a non-contact manner without using a plate, and is suitable for printing a small number of copies. In recent years, information has been digitized and image information can be easily operated. For this reason, the ink jet recording method is expected to be used in a wide range of printing fields, together with the fact that good prints can be obtained immediately without the need for high-level expertise or large-scale equipment. It is a recording method.

  However, although inkjet recording apparatuses are currently mainstream as image output apparatuses such as personal computers and digital cameras, their use in industrial fields has not progressed much. One of the reasons is that the image quality by the ink jet recording method greatly depends on the ink absorbability of the recording medium.

  The ink used in the ink jet recording system contains a large amount of moisture, and when printing on paper, many inks are fixed by penetrating into the printing paper. However, when printing is performed on an ink receptor such as a recording medium having poor ink absorbability (or at least a recording medium having a recording surface inferior in ink absorbability) such as plastic or film, the ink cannot be absorbed completely. May remain on the surface. Then, a phenomenon in which adjacent ink droplets are mixed (bleeding) and a phenomenon in which a plurality of adhered ink droplets are aggregated (beading) may occur, resulting in a reduction in image quality. In addition, it may cause poor drying that does not dry forever. Therefore, it is very difficult to form an image with high quality and fixability by an ink jet recording method on an ink receptor having poor ink absorbability.

  Therefore, various methods have been proposed for forming an image on an ink receiver having poor ink absorbability. Patent Document 1 proposes a method in which hot-melt ink is used, and the ink-jet head and the ink supply system are heated to discharge the hot-melt ink to an intermediate transfer member that is an ink receiver, thereby fixing the ink together with heat dissipation. ing. However, in order to generate ink phase change characteristics (solid-liquid phase change due to heat), it is necessary to use ink containing a very large amount of binder with respect to the colorant, and ink for obtaining a desired concentration. The amount given will increase. As a result, the ink thickness of the output image is increased, leading to a decrease in image quality such as sharpness. In addition, since solid ink is used at a steady temperature, it is necessary to heat and melt the ink in the ink flow path at the start of the image forming operation, and it takes time until image formation is possible. Moreover, since it is necessary to maintain a molten state at the time of apparatus operation, enormous energy is required.

  On the other hand, Patent Document 2 discloses a reaction liquid (ink containing color material) having an action of aggregating color material components in ink by contacting with ink (ink containing color material). A method of applying prior to image formation is disclosed. According to this, bleeding is suppressed and beading can be prevented unless the recording medium has extremely high water repellency.

JP-A-7-223312 JP 2002-370441 A

  As disclosed in Patent Document 2, even if bleeding is suppressed by forming an image on an ink receptor after applying an aggregation reaction liquid, the inventors of the present application are still insufficient for improving image quality. I found out. This has been confirmed to be particularly remarkable when two or more kinds of inks having different color tones are applied to substantially the same position or adjacent positions of the ink receiver.

  This will be described with reference to FIGS. 1 (a) and 1 (b) and FIGS. 2 (a) and 2 (b). These drawings illustrate the case where a reaction liquid, a cyan first ink droplet, a magenta second ink droplet, and a yellow third ink droplet are applied in this order to a recording medium that is an ink receptor. FIG. Here, FIG. 1A and FIG. 2A show sequential states from when the reaction liquid is applied to when the third ink droplet is applied to the recording medium 1 that is an ink receptor. It is a typical sectional side view. FIGS. 1B and 2B are schematic plan views showing sequential states from when the first ink droplet is applied to when the third ink droplet is applied.

  FIGS. 1A and 1B show a state in which the shape of the ink dot is stable and the colored area is as designed. In other words, the first ink droplet 2 that has landed first landed without causing the dot shape formed on the surface of the recording medium to be disturbed, and the second ink droplet 3 disturbed the dot shape formed on the surface of the recording medium. The third ink droplet 6 is landed without any problems. In such a state, the first ink droplet 2 and the second ink droplet 3 both satisfy the design coloring portions 4 and 5 and the overlapping portions become secondary colors, so that the image design is very easy. .

  However, when the first ink droplet 2, the second ink droplet 3, and the third ink droplet 6 are sequentially applied after the reaction liquid is applied, the present inventors, as shown in FIGS. It has been found that obtaining the state may be difficult. This is because an ink receptor having a poor ink absorbability (including a recording medium for obtaining a final recorded product) or an ink receptor having a surface having a poor ink absorbability (hereinafter referred to as an ink receptor such as these). This was remarkable when the recording surface was called “non-absorbing surface”.

  This is formed first when the second ink droplet 3 lands on the dot formed by the first ink droplet 2 and when the third ink droplet 6 lands on the dot formed by the second ink droplet 3. This is because the shape of the ink dot is destroyed. As described above, in the configuration in which the reaction liquid is applied prior to the formation of the ink dots, the aggregation of the coloring material is advanced in the dots formed by the ink that has landed first, but as long as it contains moisture, the ink dots It has liquidity. For this reason, the previously formed ink dot is displaced as shown by the left-pointing arrow due to the impact force when the next ink lands.

  FIGS. 2A and 2B show this state. That is, the first ink droplet 2 initially forms an ink dot as designed on the non-absorbing surface, but the second ink droplet 3 then pushes away the fluidized first ink droplet 2 dot. , The dot shape of the first ink droplet 2 is disturbed. The ink dots formed by the first ink droplets 2 have agglomeration of the coloring material by the reaction liquid, and thus exhibit the color tone of the first ink while the dot shape is changed. That is, a change in dot shape leads to a change in the colored area of the ink. The same applies to the relationship between the second ink droplet 3 and the third ink droplet 6. On the other hand, when the reaction liquid is not used, the aggregation does not proceed, the dots due to the ink droplets that have landed first remain in a liquid state, and both inks even if the subsequent ink droplets land. Will be mixed and mixed, and the image will be severely degraded.

  In addition, the phenomenon shown in FIGS. 2A and 2B is affected by parameters such as the landing position of the ink droplets, the landing time difference, and the ink application density, and therefore varies depending on the situation. For example, the dot shape is not disturbed, or the amount of deviation from the design value of the colored area varies depending on where the subsequent ink droplets land on the ink dots of the preceding ink droplets. Also, if the ink dots are not isolated dots but are collective dots composed of a plurality of dots, and further include the case where the fourth ink droplet is present, the number of change patterns becomes enormous. Therefore, it is very difficult to predict various changes in the dot shape (colored area), and even if it can be predicted, a large amount of data is required to correct it properly. Design becomes difficult.

  Therefore, for example, it is also conceivable that the subsequent ink droplets are landed after a sufficient time has elapsed from the time when the preceding ink droplets land on the non-absorbing surface 1 until moisture evaporates and the fluidity is lost. However, such a sufficient time difference is not preferable from the viewpoint of recording speed. In addition, the ink used in the ink jet recording method generally contains a large amount of a moisturizing component in order to improve the discharge property and the like, and thus drying is slow. Therefore, it is not practical to set a sufficient time difference.

  The above problem becomes remarkable when an ink receptor having poor ink absorbability is used. However, even when an ink receptor having excellent ink absorbability is used, if the landing time difference between the ink droplets is short, the previously formed ink dots may remain with fluidity. So it can be a problem as well.

  The present invention has been made in view of the above problems. In the configuration in which the ink is applied after the reaction liquid is applied to the ink receiver, a good image can be obtained by stabilizing the ink dot shape. It aims to be able to form.

Therefore, the present invention provides an image forming method for forming an image using a plurality of types of ink on a recording medium having a non-absorbable recording surface .
A reaction liquid containing a component that reacts with the ink is applied to the recording surface of the recording medium, and after the reaction liquid is applied, the plurality of types of ink are applied in order from the one having the highest surface tension to perform the image formation. It is characterized by that.

The present invention also provides an image forming method for forming an image using a plurality of types of inks.
Applying a reaction liquid containing a component that reacts with the ink to an intermediate transfer member having a non-absorbing surface ;
A step of applying the plurality of types of inks in order from the one having the highest surface tension to the intermediate transfer member to which the reaction liquid has been applied, and forming an image on the intermediate transfer member;
Transferring the image formed on the intermediate transfer member to a recording medium;
It is characterized by having.

Furthermore, the present invention provides an image forming apparatus for forming an image using a plurality of types of ink on a recording medium having a non-absorbable recording surface .
Means for applying a reaction liquid containing a component that reacts with the ink to the recording surface of the recording medium ;
Means for forming the image by applying the plurality of types of inks in descending order of the surface tension to the recording medium to which the reaction liquid is applied;
It is characterized by comprising.

In addition, the present invention provides an image forming apparatus that forms an image using a plurality of types of ink.
Means for applying a reaction liquid containing a component that reacts with the ink to an intermediate transfer member having a non-absorbing surface;
Means for forming the image on the intermediate transfer body by applying the plurality of types of ink to the intermediate transfer body to which the reaction liquid has been applied in order from the one having the highest surface tension;
Means for transferring the image formed on the intermediate transfer member to a recording medium;
It is characterized by having .

  In the present invention, the ink is applied after the reaction liquid is applied. By applying the ink in the descending order of the surface tension, the dots formed by the previously applied ink droplets are pushed away by the ink droplets landed later. The phenomenon is alleviated and the irregular shape of the previous ink dot is suppressed. Thereby, it is in the structure which provides ink after giving a reaction liquid with respect to an ink receptor with inferior ink absorbency, and it can form a favorable image by suppressing the shift | offset | difference from the design value of a coloring area become.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(Basic concept of the present invention)
As described above, the phenomenon that the shape of the ink dot formed by the preceding ink droplet is disturbed is due to the fact that the ink dot has fluidity and is pushed away by the landing of the subsequent ink droplet. Therefore, the present inventors use a plurality of types of inks with different (or different) surface tensions and regulate the application order to alleviate such displacement and suppress dot shape disturbance. I came up with the idea. This utilizes the property that when a liquid having a low surface tension comes into contact with a liquid having a high surface tension, the low surface tension liquid spreads at the interface.

  This will be described with reference to FIGS. 1 (a) and 1 (b) and FIGS. 2 (a) and 2 (b).

  If the surface tension of the ink applied after the previously applied ink is lower, that is, if the force to form a sphere is weaker, the subsequently applied ink droplet will displace the previously formed ink dot. Will not spread and will spread over the ink dots. For example, in the relationship between the first, second and third ink droplets, the surface tension of the ink forming them is low in that order, and is applied in that order. In this case, the dots formed by the first ink droplets 2 are not pushed away by the second ink droplets 3, and the second ink droplets 3 spread on the dots formed by the first ink droplets 2. The same phenomenon occurs in the relationship between the second ink droplet 3 and the third ink droplet 6. That is, this is the state shown in FIGS. 1A and 1B, and both the first ink droplet 2 and the second ink droplet 3 satisfy the design coloring portions 4 and 5, respectively.

  On the other hand, if the surface tension of the ink applied later than the ink applied earlier is higher, that is, if the force to become a sphere is stronger, the ink droplet applied later becomes the ink formed earlier. The dots are pushed out and spread on the recording medium. For example, in the relationship between the first, second and third ink droplets, the surface tension of the ink forming them is high in that order, and is applied in that order. In this case, the dots formed by the first ink droplet 2 are pushed away by the second ink droplet 3. The same phenomenon occurs in the relationship between the second ink droplet 3 and the third ink droplet 6. In other words, this is the state shown in FIGS. 2A and 2B, and a colored area as expected, that is, as designed, cannot be obtained.

  As described above, in the present invention, by performing image formation so that dots of ink with low surface tension overlap with dots formed with ink with high surface tension, disturbance of the ink dots formed earlier is suppressed. Is.

(First embodiment)
FIG. 3 shows an example of an image forming apparatus for carrying out the present invention. The apparatus of this example is for recording directly on the non-absorbing surface of the recording medium 11 as the recording surface 12. That is, in this example, the ink receiver is a recording medium for obtaining a final recorded matter.

  The recording medium 11 has a non-absorbing surface 12 facing upward, and a surface treatment device 13, a reaction solution applying device 14, a water removal promotion device 15 for the reaction solution, an ink jet recording device 17, The ink is removed under the moisture removal promoting device 18. A heating roller 16 for contacting the back surface of the recording medium 11 and promoting drying / fixing is provided downstream of the recording position by the ink jet recording apparatus 17 in the transport direction.

  These parts are described in detail below.

Surface treatment device 13
When the non-recording surface of the recording medium 11 strongly repels ink, it is desirable to make the surface hydrophilic in advance, and for this purpose, a surface treatment device 13 is provided. By making it hydrophilic, it is possible to form a thin layer uniformly on the recording surface without causing the reaction liquid or ink to bounce.

  Any known hydrophilic means can be used without limitation. For example, ultraviolet irradiation, plasma treatment, corona discharge treatment, flame treatment method and the like can be used as a method for irradiating energy on the recording surface 12 in a non-contact state. Moreover, what gives a surface active agent etc. may be sufficient and these may be used together.

Reaction liquid application device 14
Further, when an image with a large amount of ink applied is formed or when high speed is required, the reaction material applying device 14 aggregates or insolubilizes the color material components in the ink in order to suppress image deterioration such as bleeding. For this purpose, a reaction liquid is applied to the recording surface 12 in advance. As the form of the reaction liquid applying device 14, a reaction liquid is applied using a roller, a blade, a spray, or the like, or a recording head equivalent to a recording head for ejecting ink is used, and selective to a recording dot formation position. And the like that discharge the reaction liquid.

The reaction liquid to be used is determined depending on the type of ink. As an example, an aqueous solution containing a polymer flocculant or metal ions is preferably used. Examples of the polymer flocculant include a cationic polymer flocculant, an anionic polymer flocculant, a nonionic polymer flocculant, and an amphoteric polymer flocculant. Examples of the metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ^2+, and Zn ^2+, and trivalent metal ions such as Fe ³⁺ and Al ³⁺ . And when using and providing these ions, it is desirable to provide them as an aqueous metal salt solution. Examples of the anion of the metal salt include Cl ⁻ , NO ₃ ⁻ , SO ₄ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , RCOO ⁻ (R is an alkyl group), and the like.

  In addition, a material having a reversal to the ink used can be used as an image fixing component. For example, if the ink is anionic or alkaline, a cationic or acidic material that is the opposite of the ink can be an image fixing component.

Reaction solution water removal promoting device 15
The reaction solution moisture removal accelerating device 15 is provided as necessary to dry the reaction solution applied to the recording surface 12 by the reaction solution applying device 14.

The ink jet recording device 17 and the ink ink jet recording device 17 apply ink for image formation. As an ink jet recording apparatus, there are a number of systems which are not particularly limited. It may be based on a continuous method or a drop-on-demand method. In the latter case, the energy used for ejecting the ink may be one using a heating element that generates thermal energy that causes film boiling in the ink according to the drive signal (thermal method), An element that generates mechanical energy, such as a piezoelectric element, may be used.

  Further, in this embodiment, the inkjet head 17A that performs ink application has nozzles for ejecting ink in a direction different from the recording medium conveyance direction (for example, a direction perpendicular to the paper surface of FIG. 3) and the entire width of the recording medium. A line type array is used that is arranged over the corresponding range. The ink jet head 17A is provided corresponding to the color tone of the ink to be used. In this embodiment, black (K) is included in addition to the so-called three primary colors of printing of cyan (C), magenta (M) and yellow (Y). Four inks are used corresponding to the four color inks. The ink-jet heads for the respective color inks are arranged so as to eject ink having a higher surface tension toward the upstream side in the recording medium conveyance direction in accordance with the provisions of the present invention.

  A system that uses a line-type inkjet head and forms an image in one pass of the recording medium is preferable because it can perform recording at high speed. In addition, a head that discharges ink having a high surface tension is preferable because it can satisfy the requirements of the present invention simply by disposing it on the upstream side. In this case, when considering a preferable application order according to the color, an ink that satisfies the surface tension requirement of the present invention is selected according to the arrangement position of the head according to the order, or each color ink Should be designed.

  However, the present invention does not exclude a configuration using a so-called serial scan type inkjet head having a plurality of nozzles and scanning in a direction perpendicular to the paper surface of FIG. Any arrangement may be used as long as the arrangement of each color head, ink selection or design, drive order control, and the like are performed in accordance with the provisions of the present invention.

  In general, an ink set having a combined surface tension is used in an ink jet recording apparatus. However, in the present invention, it is premised that a plurality of types of inks whose surface tensions are appropriately different (or different) from the reaction liquid are used. As described above, this is to alleviate the phenomenon in which the dots formed by the previously applied ink droplets are pushed away by the ink droplets that have landed later, and suppress the disorder of the dot shape.

  This property is more pronounced in systems containing surfactants. It is assumed that the surfactant spreads immediately at the interface where the two liquids are in contact. Although the surface tension difference of each ink varies depending on the ink formulation and ejection conditions, it is preferably about 2 dyn / cm or more, more preferably 4 dyn / cm or more under general conditions. By utilizing this characteristic, an ink dot having a low surface tension is formed on an ink dot having a high surface tension, and a change in the coloring area of each color ink can be suppressed.

  The ink to be used is not limited other than the permutation of the surface tension listed above, and any ink using a conventionally known dye or pigment as a coloring material can be used. Among these, a pigment ink containing a fine particle dispersion such as a pigment is preferably used in combination with a reaction liquid using metal ions.

  Specifically, examples of the dye include C.I. I Direct Blue 6, 8, 22, 34, 70, 71, 76, 78, 86, 142, 199, C.I. I Acid Blue 9, 22, 40, 59, 93, 102, 104, 117, 120, 167, 229, C.I. I Direct Red 1, 4, 17, 28, 83, 227, C.I. I Acid Red 1, 4, 8, 13, 14, 15, 18, 21, 26, 35, 37, 249, 257, 289, C.I. I Direct Yellow 12, 24, 26, 86, 98, 132, 142, C.I. I Acid Yellow 1, 3, 4, 7, 11, 12, 13, 14, 19, 23, 25, 34, 44, 71, C.I. I Food Black 1, 2, C.I. I acid black 2, 7, 24, 26, 31, 52, 112, 118 and the like.

  Examples of the pigment include C.I. Pigment Blue 1, 2, 3, 15: 3, 16, 22, C.I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 112, 122, C.I. I pigment yellow 1, 2, 3, 13, 16, 83, carbon black No 2300, 900, 33, 40, 52, MA7, 8, MCF88 (manufactured by Mitsubishi Kasei), RAVEN 1255 (manufactured by Colombia), REGAL 330R, 660R, MOGUL ( Cabot), Color Black FW1, FW18, S170, S150, Printex35 (Degussa), and the like.

  These pigments are not limited in form, and for example, any of self-dispersion type (type without dispersant), resin dispersion type, microcapsule type and the like can be used. As the pigment dispersant used in this case, a water-soluble dispersion resin having a weight average molecular weight of about 1,000 to 15,000 can be preferably used. Specifically, for example, vinyl water-soluble resins, styrene and derivatives thereof, vinyl naphthalene and derivatives thereof, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and derivatives thereof, maleic acid and derivatives thereof Derivatives, itaconic acid and its derivatives, block copolymers or random copolymers composed of fumaric acid and its derivatives, salts thereof, and the like can be mentioned.

  An organic solvent can be contained in the aqueous liquid medium constituting the ink together with the above-described color material. As the organic solvent to be used, the following water-soluble solvents are preferably used. Examples include polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol, hexylene glycol, diethylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, glycerin, and the like. Two or more kinds selected from among them can be mixed and used. Also, alcohols such as ethyl alcohol and isopropyl alcohol and surfactants can be added to the ink as components for adjusting viscosity, surface tension, and the like.

  Above all, the surfactant is an important material for controlling the surface tension of the ink, and can be adjusted by the amount and type of the surfactant. The surfactant that can be used is not limited. For example, select from general cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, fluorosurfactants, silicone surfactants, etc. be able to. The blending ratio of the components constituting the ink is not limited, and can be appropriately prepared within a dischargeable range from the selected inkjet recording method, the discharge force of the head, the nozzle diameter, and the like. Generally, on a mass basis, the colorant is 0.1 to 10%, the resin component is 0.1 to 20%, the solvent is 5 to 40%, the surfactant is 0.001 to 5% or less, and the rest is pure water. The adjusted ink can be used.

  In addition, in order to improve the fastness of the finally formed image, a water-soluble resin or a water-soluble crosslinking agent can be added to the ink or the reaction liquid. Materials used by adding to the reaction solution are limited to those that can coexist with the image fixing component. As the water-soluble resin, PVA, PVP or the like is preferably used particularly when a highly reactive metal salt is used as the ink viscosity increasing component. As the water-soluble crosslinking agent, oxazoline or carbodiimide that reacts with a carboxylic acid preferably used for dispersing a colorant in the ink is preferably used. Among them, aziridine is a material that can achieve both relatively high ink viscosity and image fastness.

Ink moisture removal promoting device 19 and heating roller 16
The ink moisture removal accelerating device 19 and the heating roller 16 are provided as necessary to promote drying and fixing of the ink applied to the recording surface 12 by the ink jet recording device 17. As its form, it can be configured using known appropriate means.

(Second Embodiment)
FIG. 4 is a schematic diagram showing a schematic configuration of an image forming apparatus according to a second embodiment to which the present invention is applicable. The apparatus of this example is of a form in which an ink image is formed on an intermediate transfer member using an ink jet recording method, and the ink image is transferred to a recording medium for recording. That is, in this example, the ink receiver is an intermediate transfer member.

  In FIG. 4, reference numeral 21 denotes a drum-shaped intermediate transfer member that is rotationally driven in the direction of arrow F around a shaft 21 </ b> A, and has a non-absorbing surface 22. A surface treatment device 13, a reaction liquid applying device 14, an ink jet recording device 17, and a water removal promoting device 18 are arranged along the circumferential direction of the intermediate transfer member 21. These have the same configuration as in the first embodiment and can perform the same operation.

  The intermediate transfer body 21 is preferably an elastic body in consideration of the followability to the recording medium, and the rubber hardness (value measured by a rubber hardness meter type A (conforming to JIS K6253)) is 40 to 80 °. If so, most of the recording paper can be handled. Specifically, NBR, urethane rubber, chloroprene rubber and its surface treatment, fluorine rubber, silicone rubber, or fluorosilicone rubber can be suitably used. It is also possible to perform surface treatment according to the state (characteristic) of the surface. Further, the intermediate transfer member 21 may be formed by laminating a surface layer such as silicone rubber around a support member such as aluminum.

  Further, the apparatus shown in FIG. 4 has an apparatus configuration peculiar to the intermediate transfer system, a pressure roller 23 for bringing the intermediate transfer body 21 into contact with a recording medium 111 for obtaining a final recorded product, and an intermediate transfer. In order to repeatedly use the body surface, a cleaning unit 25 and the like for cleaning the body surface are provided. Furthermore, by adding fixing means such as the fixing roller 24 to the recording medium 111 on which the transfer has been performed, the recorded matter can be instantly made robust.

  The outline of the operation of the apparatus according to this example will be described. In forming an image, first, a reaction liquid is applied by the reaction liquid applying apparatus 14 disposed in contact with the non-absorbing surface 22 of the intermediate transfer member 21. Thereafter, ink is ejected from the inkjet recording device 17, and an image (mirror image) is formed on the surface of the intermediate transfer body 1. Note that the configuration of each of these units, the ejection method and form of the inkjet head in the inkjet recording apparatus 17, the arrangement of each color, and the like can be selected in the same manner as in the first embodiment.

  Then, the recording surface of the recording medium 111 is brought into contact with the image formed on the intermediate transfer member 21, and the image is transferred and formed on the recording medium 111 by applying pressure from the back surface side by the pressure roller 23. Further, the intermediate transfer member 21 after the ink image is transferred to the recording medium 111 is cleaned by the next-stage cleaning unit 25 in preparation for receiving the next image.

  The intermediate transfer member is not limited to the drum-shaped member as described above. Any form may be used as long as the surface can be at least in line contact with the recording medium. For example, in the form of a roller, belt, or sheet according to the form of the image forming apparatus to be applied or the transfer to the recording medium. Etc. can also be used. Further, not only those that are in line contact, but also a material having a large elastic deformation such as a pad used in pad printing can be used as the intermediate transfer member.

(Specific examples)
Next, some examples and comparative examples will be given to describe the present invention more specifically. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Example 1>
This is an example in which a non-absorbable surface of a recording medium is used as a recording surface and recording is directly performed thereon, and corresponds to the first embodiment.

  First, a commercially available white PET film (thickness 0.1 mm) is used as the recording medium 11, and a reaction liquid (a 10% by mass aqueous solution of aluminum chloride hexahydrate) is applied to the recording apparatus 11 on a recording apparatus 11 in the form of a roll coater. Granted.

  Next, as the ink jet recording device 17, an ink jet head 17A having a nozzle arrangement density of 1200 dpi (dot / inch; reference value) and an ejection amount of 4 pl is disposed, and two types of inks having the following prescription are continuously used at a driving frequency of 8 kHz. And granted. The ink application area was adjusted to 50% when each ink was ejected independently at an equal pitch.

First ink formulation (surface tension 34.9 dyn / cm)
Cyan pigment: Pigment Blue 15 5 parts Dispersion resin: Styrene-acrylic acid-ethyl acrylate copolymer 1 part
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 0.5 part acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
100 copies in total
Second ink formulation (surface tension 29.6 dyn / cm)
-Magenta pigment: 5 parts of pigment red 7-Dispersing resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: manufactured by Seimi Chemical Co., Surflon S-141 0.005 part ・ Ion-exchanged water balance
A total of 100 parts The colored areas of each of the formed patterns were analyzed with an image processing analyzer (Dot Analyzer, manufactured by Oji Scientific Instruments). Deviations from the design values (50%) of the respective colored areas were -2.4% for the first ink and + 1.9% for the second ink.

<Comparative Example 1>
Under the same conditions as in Example 1, each colored area was analyzed by changing the second ink to the following formulation.

Second ink formulation (surface tension 34.6 dyn / cm)
-Magenta pigment: 5 parts of pigment red 7-Dispersing resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 0.5 part acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
Total 100 parts The deviation from the design value (50%) of each colored area was -17.5% for the first ink and -7.8% for the second ink.

  As apparent from the above, the first and second surface tensions in the comparative example 1 are substantially equal in the configuration in which the two types of ink are applied after the reaction liquid is applied to the non-absorbing surface of the recording medium. Ink is used. On the other hand, in Example 1, the first ink and the second ink having a surface tension smaller than this by 5 dyn / cm or more are applied in this order. As a result, in Example 1, the deviation of the colored area of each ink from the design value is much smaller than that in Comparative Example 1, and a good image can be formed by suppressing the phenomenon shown in FIG. Was confirmed.

<Example 2>
This is an example in which an ink image is formed on an intermediate transfer member, the ink image is transferred to a recording medium, and recording is performed, and corresponds to the second embodiment.

  As the intermediate transfer member 21, a silicone rubber (KE30 manufactured by Shin-Etsu Chemical Co., Ltd.) having a rubber hardness of 60 ° is coated around an aluminum drum with a thickness of 0.5 mm, and the surface is subjected to plasma treatment under the following conditions. The primary recording surface was hydrophilic.

Plasma treatment conditions , treatment pressure: atmospheric pressure, treatment distance: 2 mm
・ Input voltage: 240V
・ Frequency: 10 kHz
Introducing gas: N ₂ / O ₂ = 97: 3
・ Processing speed: 30 sec / sec
Next, a reaction liquid having the following formulation was applied to the surface of the intermediate transfer member (primary recording surface) with a roll coater.

Reaction liquid formulation · Calcium chloride dihydrate 10 parts · Crosslinking agent 1 part (Nisshinbo Carbodilite V-02)
・ Ion exchange water balance
100 parts in total Next, as the ink jet recording apparatus 17, an ink jet head 17A having a nozzle arrangement density of 1200 dpi (dots / inch; reference value) and an ejection amount of 4 pl was disposed, and at a driving frequency of 8 kHz, two types of the following prescriptions were used. Ink was applied continuously. The ink application area was adjusted to 20% when each ink was ejected independently at equal intervals.

First ink formulation (surface tension 38.6 dyn / cm)
Black pigment: Carbon black (MCF88 manufactured by Mitsubishi Chemical) 5 parts Dispersion resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer (acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 0.17 parts acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
100 copies in total
Second ink formulation (surface tension 35.7 dyn / cm)
Cyan pigment: Pigment Blue 15 5 partsDispersion resin: Styrene-acrylic acid-ethyl acrylate copolymer 1 part
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: Acetyleneol EH 0.4 parts manufactured by Kawaken Fine Chemicals ・ Ion-exchanged water balance
100 copies in total
Third ink formulation (surface tension 33.3 dyn / cm)
-Magenta pigment: 5 parts of pigment red 7-Dispersing resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 1 part acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
100 copies in total
Fourth ink formulation (surface tension 30.5 dyn / cm)
-Yellow pigment: Pigment Yellow 74 5 parts-Dispersing resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 1.7 parts acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
Total 100 parts Next, warm air is applied to the ink image on the intermediate transfer member to promote moisture removal. Thereafter, the intermediate transfer member was contacted with a surface-coated printing paper having a low ink absorbability (Npi coat, 40.5, manufactured by Nippon Paper Industries Co., Ltd.) with a pressure roller to transfer an ink image.

  About this transferred pattern, each coloring area was analyzed with the image processing analysis apparatus (Oji Scientific Instruments dot analyzer). Deviations from the design values (20%) of the respective colored areas are as follows: -3.6% for the first ink, -2.4% for the second ink, -1.8% for the third ink, The ink of 4 was + 0.7%.

<Comparative Example 2>
Under the same conditions as in Example 2, each colored area was analyzed by changing the first, second, and fourth inks to the following recipes.

First ink formulation (surface tension 32.9 dyn / cm)
Black pigment: Carbon black (MCF88 manufactured by Mitsubishi Chemical) 5 parts Dispersion resin: Styrene-acrylic acid-ethyl acrylate copolymer 1 part
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 1.1 parts acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
100 copies in total
Second ink formulation (surface tension 33.1 dyn / cm)
Cyan pigment: Pigment Blue 15 5 parts Dispersion resin: Styrene-acrylic acid-ethyl acrylate copolymer 1 part
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 1 part acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
100 copies in total
Fourth ink formulation (surface tension 32.5 dyn / cm)
-Yellow pigment: Pigment Yellow 74 5 parts-Dispersing resin: 1 part of styrene-acrylic acid-ethyl acrylate copolymer
(Acid value 240, weight average molecular weight 5000)
・ Glycerin 10 parts ・ Ethylene glycol 5 parts ・ Surfactant: 0.9 part acetylenol EH manufactured by Kawaken Fine Chemicals ・ Balance of ion-exchanged water
Total 100 parts Deviations from the design values (20%) of the respective colored areas are -13.7% for the first ink, -18.3% for the second ink, and -12.4 for the third ink. %, The fourth ink was -0.8%.

  As is apparent from the above, the first to fourth in the comparative example 2 have the structure in which the four types of ink are applied after the reaction liquid is applied to the non-absorbing surface of the intermediate transfer member. Ink is used. On the other hand, in the second embodiment, the first to fourth inks having a surface tension of 2 dyn / cm or more are applied in this order. As a result, in Example 2, the deviation from the design value of the coloring area of each ink was remarkably reduced as compared with Comparative Example 1, and it was confirmed that a good image could be formed.

(Other)
In each of the above-described embodiments and examples, the recording medium or the intermediate transfer member has been described as an ink receiver having a non-absorbing surface. In these ink receivers, the ink dots formed by the preceding ink droplets are applied with the subsequent ink droplets while having fluidity, so that the effect of applying the present invention is high. However, the present invention does not require the quality or degree of ink absorbability of the ink receiver, and of course can be applied to any of them. For example, even when an ink receptor having excellent ink absorbency is used, if the difference in landing time of each ink droplet is short, the subsequent ink droplet is applied while the previously formed ink dot remains fluid. Therefore, the application of the present invention is effective. In other words, it is possible to contribute to shortening the landing time difference between the ink droplets, that is, to increase the recording speed, regardless of whether the ink absorption of the ink receiver is good or not.

  In the present invention, the type and number of color tones are not limited to the above as long as image formation is performed by applying a plurality of inks after applying the reaction liquid. For example, in the above example, four inks including black in addition to the so-called three primary colors of cyan, magenta and yellow are used, but only cyan, magenta and yellow inks may be used. Instead of or in combination with these, red, green, blue or other colors may be used. In addition, inks of similar colors or different densities may be used, and the color tone referred to in this specification is a concept including density. However, in any case, it is a matter of course to use an ink set that satisfies the preferable surface tension requirements, apply the liquid, and then apply the ink in descending order of surface tension.

(A) and (b) show a state in which three types of ink droplets having different color tones are sequentially applied to a recording medium as an ink receptor by an ink jet recording apparatus, and ink dots formed by preceding ink droplets are shown. It is explanatory drawing when the change of a coloring area has not arisen. (A) and (b) show a state in which three types of ink droplets having different color tones are sequentially applied to a recording medium as an ink receptor by an ink jet recording apparatus, and ink dots formed by preceding ink droplets are shown. It is explanatory drawing when the change of the coloring area has arisen. 1 is a schematic side view illustrating an embodiment of an image forming apparatus to which the present invention is applicable. FIG. 6 is a schematic side view showing another embodiment of an image forming apparatus to which the present invention is applicable.

Explanation of symbols

1000 Host device (computer)
DESCRIPTION OF SYMBOLS 1 Recording medium 2 1st ink drop 3 2nd ink drop 4 1st ink drop design coloring part 5 2nd ink drop design coloring part 11 Recording medium 12 Recording surface (non-absorbing surface)
DESCRIPTION OF SYMBOLS 13 Surface treatment apparatus 14 Reaction liquid application apparatus 15 Reaction liquid water removal promotion apparatus 16 Heating roller 17 Inkjet recording apparatus 17A Inkjet head 18 Ink dot 19 Ink water removal promotion apparatus 21 Intermediate transfer body 22 Intermediate transfer body surface 23 Pressure roller 24 Fixing Roller 25 Cleaning unit

Claims (6)

In an image forming method for forming an image using a plurality of types of ink on a recording medium having a non-absorbable recording surface ,
A reaction liquid containing a component that reacts with the ink is applied to the recording surface of the recording medium, and after the reaction liquid is applied, the plurality of types of ink are applied in order from the one having the highest surface tension to perform the image formation. An image forming method.   The image forming method according to claim 1, wherein the plurality of types of ink include at least cyan, magenta, and yellow ink.   The image forming method according to claim 1, wherein the plurality of types of ink includes a fine particle dispersion, and the reaction liquid includes a metal salt. In an image forming method for forming an image using a plurality of types of ink,
Applying a reaction liquid containing a component that reacts with the ink to an intermediate transfer member having a non-absorbing surface ;
A step of applying the plurality of types of inks in order from the one having the highest surface tension to the intermediate transfer member to which the reaction liquid has been applied, and forming an image on the intermediate transfer member;
Transferring the image formed on the intermediate transfer member to a recording medium;
An image forming method comprising: In an image forming apparatus that forms an image using a plurality of types of ink on a recording medium having a non-absorbable recording surface ,
Means for applying a reaction liquid containing a component that reacts with the ink to the recording surface of the recording medium ;
Means for forming the image by applying the plurality of types of inks in descending order of the surface tension to the recording medium to which the reaction liquid is applied;
An image forming apparatus comprising: In an image forming apparatus that forms an image using a plurality of types of ink,
Means for applying a reaction liquid containing a component that reacts with the ink to an intermediate transfer member having a non-absorbing surface;
Means for forming the image on the intermediate transfer body by applying the plurality of types of ink to the intermediate transfer body to which the reaction liquid has been applied in order from the one having the highest surface tension;
Means for transferring the image formed on the intermediate transfer member to a recording medium;
An image forming apparatus comprising:

Images