JP4539104B2 - Image forming method using actinic ray curable ink and ink jet recording apparatus - Google Patents

Description

  The present invention relates to an image forming method and an ink jet recording apparatus using actinic ray curable ink capable of stably reproducing high-definition images on various recording materials.

  In recent years, the ink jet recording method can easily and inexpensively create an image, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as a color filter. In particular, inkjet recording devices that emit and control fine dots, inkjet inks with improved color reproduction range, durability, and emission suitability, and ink-jet ink absorbability, coloring material color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper that has been selected. The image quality improvement of today's ink jet recording system is mainly achieved only when all of the ink jet recording apparatus, ink jet ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by an ink jet method. Specifically, a phase change ink jet method using a wax ink solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, or actinic rays such as ultraviolet rays (UV light) after recording. And actinic ray curable ink jet method for crosslinking.

  In particular, the actinic ray curable inkjet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based inkjet method, and can record images on a recording medium that does not dry quickly or absorb ink. Many type inkjet inks are disclosed (for example, refer to Patent Documents 1 to 5).

  As the color material used in the inkjet recording method, an ink in which pigments are mainly dispersed is often used from the viewpoint of fastness of an image to be formed.

  In general, in order to achieve stable dispersion characteristics in pigment dispersion, how to adsorb the pigment and the dispersant is a major issue. If the solvent is polar, non-polar interaction, if non-polar, polar Interaction is used. For example, a nonpolar interaction is used in the case of an aqueous system, and a polar interaction is used in the case of a nonpolar solvent system.

  Ink-jet inks that are cured by actinic rays such as ultraviolet rays are solvent-based systems that have polar groups derived from polymerizable groups, and are therefore difficult to adsorb pigments and dispersants. Compared to conventional paints and the like, pigment dispersion is an important issue in inkjet inks. Since this is a recording method in which droplets are ejected at a higher speed than a fine nozzle, if the dispersion is unstable, the ejection becomes unstable, which is a fatal problem as an inkjet ink.

Even if ink can be ejected stably, curling or corrugation of the recording material may occur depending on the type of the recording material due to the ink curing shrinkage and heat generation during the curing reaction when irradiated with actinic rays. There was a problem that the value fell.
JP-A-6-200204 (Claims, Examples) JP 2000-504778 (Claims, Examples) JP 2002-188025 A (2nd to 7th pages, Examples) JP 2002-60463 A (Claims, Examples) JP 2003-252979 A (Claims, Examples)

  The present invention has been made in view of the above-mentioned problems, and its purpose is to achieve a highly stable image with excellent reproducibility without curling or undulation of a recording material with excellent character quality, no color mixing, and no curling or undulation of the recording material. An image forming method and an ink jet recording apparatus capable of recording are provided.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink has a maximum illuminance at 254 nm between 0.001 seconds and 1.0 seconds after landing on the recording material , and 1 An image forming method comprising curing after irradiation with an actinic ray by a light source having a power consumption per hour of less than 1 kW.

(Claim 2)
From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink is activated by a light source having a maximum illuminance at 254 nm between 0.001 second and 1.0 second after landing on the recording material. An image forming method comprising curing after irradiation with light .

(Claim 3)
From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink has a maximum illuminance at 254 nm between 0.001 second and 1.0 second after landing on the recording material , and ultraviolet rays An image forming method comprising : curing after irradiation with ultraviolet light from a light source in which a plurality of light emitting diodes generating light is arranged.

(Claim 4)
4. The total ink film thickness after the actinic ray curable ink has landed on the recording material and cured by irradiation with actinic rays is 2 to 25 [mu] m. The image forming method described in 1.

(Claim 5)
The image forming method according to claim 1, wherein the pigment contained in the actinic ray curable ink has an amine value larger than an acid value.

(Claim 6)
The at least one of the photoinitiators contained in the actinic radiation curable ink is a photoacid generator, and at least one of the photopolymerizable compounds is an epoxy compound. The image forming method according to any one of the above.

(Claim 7)
The image forming method according to claim 6, wherein the actinic ray curable ink further contains an oxetane compound as the photopolymerizable compound.

(Claim 8)
The image forming method according to claim 1, wherein the actinic ray is irradiated in a state where the actinic ray curable ink landed on the recording material is heated.

(Claim 9)
The actinic ray curable ink is ejected from the inkjet recording head in a state where the ink jet recording head and the actinic ray curable ink are heated to 35 to 80 ° C., respectively, and the actinic ray curable ink is applied onto the recording material. The image forming method according to claim 1, wherein the actinic ray is irradiated in a state where the temperature is maintained at 35 to 80 ° C. after landing.

(Claim 10)
It is an inkjet recording device used for the image forming method of any one of Claims 1-9, Comprising: After heating actinic-light curable ink and an inkjet recording head to 35 to 100 degreeC, from this inkjet recording head An inkjet recording apparatus, wherein the actinic ray curable ink is ejected.

(Claim 11)
An ink jet recording apparatus used in the image forming method according to claim 1, wherein an image is formed by ejecting an actinic ray curable ink from a line head type ink jet recording head, and the ink jet recording An inkjet recording apparatus, wherein an actinic ray irradiation light source is disposed at a rear portion of a head in a direction in which a recording medium is conveyed.

  According to the present invention, an image forming method and an ink jet recording apparatus that can record a high-definition image with excellent character quality, no color mixing, and very stably with high reproducibility without curling or waviness of a recording material Can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  In a conventional actinic ray curable ink, a method of dispersing a pigment as a coloring material using a basic dispersant is widely known. However, when the present inventor dispersed the pigment, it was stable over a long period of time. It was difficult to obtain a dispersion. Also, in the conventional actinic ray curable ink jet recording, a high pressure mercury lamp, a metal halide lamp, or an electrodeless lamp having a maximum illuminance near 365 nm and having illuminance peaks at a plurality of wavelengths such as 254 nm and 310 nm is used as a light source. However, these light sources give extra energy to the recording material, causing a problem that the recording material contracts due to heat from the light source, and there is a problem that the usable recording material is limited.

As a result of intensive studies in view of the above problems, the present inventor can obtain a very stable pigment dispersion by using a dispersant having an acid value larger than an amine value for dispersing pigment particles, As a result, stable ejection properties can be realized, and 1) after the actinic ray curable ink has landed on the recording material, the maximum illuminance reaches 254 nm between 0.001 second and 1.0 second. And a curing is performed after irradiation with an actinic ray by a light source having an hourly power consumption of less than 1 kW. 2) 0.001 second after the actinic ray curable ink has landed on the recording material As described above, the composition is cured after being irradiated with an actinic ray by a light source having the maximum illuminance at 254 nm for 1.0 second or less, and 3) after the actinic ray curable ink has landed on the recording material, 0. 25 seconds between 001 seconds and 1.0 seconds nm to have a maximum illumination intensity, and after the ultraviolet is irradiated by a light source a light emitting diode and a plurality sequences to generate ultraviolet rays, than curing, that can solve the problems of the above was having conventional active ray curable ink I found.

In particular, by using a photocationic polymerization-type actinic ray curable ink using a photoacid generator as a photoinitiator, an epoxy compound as a photopolymerizable compound, and an oxetane compound in addition thereto, the above-described ejection stability and curing can be achieved. As soon as the present inventors have found that the problem of alteration of the recording material accompanying shrinkage can be dramatically solved, the present invention will be described in detail.

  The actinic ray curable ink according to the present invention (hereinafter also simply referred to as ink) is characterized by containing a dispersant having an acid value larger than the amine value, and the pigment has an amine value higher than the acid value. It is preferable to use a pigment having a large diameter.

  The acid value and amine value as referred to in the present invention can be determined by potentiometric titration. For example, it can be determined by measurement according to the method described in Color Material Association Journal 61, [12] 692-698 (1988). In addition, when using multiple types of pigments and dispersing agents, it can obtain | require as each mass average.

  The acid value of the dispersant contained in the ink according to the present invention is larger than the amine value, and the difference is preferably 1 mg / g KOH or more and less than 30 mg / g KOH. If the difference is less than 1 mg / g KOH, it is difficult to obtain the object effect of the present invention, and if it is 30 mg / g KOH or more, there is a concern that it is cured by a thermal reaction.

  As the dispersant according to the present invention, either a low molecular dispersant or a high molecular dispersant can be used, and among them, a high molecular dispersant is preferable. Preferable specific examples of the dispersant include, for example, Ajimoto PB822 manufactured by Ajinomoto Fine-Techno Co., and Ajisper PB821 manufactured by Ajinomoto Fine-Techno Co., but the present invention is not limited thereto.

  The amine value of the pigment contained in the ink according to the present invention is preferably larger than the acid value, and the difference is more preferably 1 mg / g KOH or more and less than 10 mg / g. If the difference is less than 1 mg / g KOH, it is difficult to obtain the object effect of the present invention, and if it is 10 mg / g or more, it is necessary to excessively perform basic treatment, which is not preferable because of cost increase.

  As the pigment that can be used in the present invention, a pigment having an amine value larger than an acid value can be selected from the pigments listed below, but the present invention is not limited thereto.

<C. I. Pigment Yellow>
1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 151, 154,
<C. I. Pigment Red>
5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202,
<C. I. Pigment Violet>
19, 23,
<C. I. Pigment Blue>
1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60,
<C. I. Pigment Green>
7, 36,
<C. I. Pigment White>
6, 18, 21
<C. I. Pigment Black>
7,
The pigment according to the present invention may be subjected to various known surface treatments as necessary.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid if necessary. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. However, the actinic ray curable ink according to the present invention is preferably solventless because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle size of the pigment particles is 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained. The pigment concentration is preferably 1% by mass to 10% by mass of the entire composition.

  In the image forming method of the present invention, a method is preferred in which the ink according to the present invention is ejected and drawn on a recording material by an ink jet recording method, and then the ink is cured by irradiation with actinic rays such as ultraviolet rays.

  The image forming method of the present invention is characterized in that the ink is cured by a light source whose power consumption per hour is less than 1 kW in order to form an image on various recording materials without curling or undulation. Examples of light sources that consume less than 1 kW per hour include, but are not limited to, fluorescent tubes, cold cathode tubes, hot cathode tubes, and light emitting diodes (LEDs).

The image forming method of the present invention is characterized in that a light source having a maximum illuminance at 254 nm is used in order to form images on various recording materials in an energy efficient manner. Examples of the light source having the highest illuminance at 254 nm include, but are not limited to, a cold cathode tube, a hot cathode tube, and an LED using a diamond thin film.

  The image forming method of the present invention is characterized by curing with a light source in which a plurality of light emitting diodes (LEDs) generating ultraviolet rays are arranged in order to form an image on various recording materials with high energy efficiency. Light emitting diodes (LEDs) that generate ultraviolet rays are preferable because they have dramatically improved output while reducing power consumption in recent years.

  By using each of the image recording methods of the present invention, a high-definition image can be formed, and the curling and undulation of the recording material can be kept within a practically acceptable level.

  Next, the image forming method of the present invention will be described in more detail.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, as the irradiation conditions of the active light, characterized in that active light is irradiated between 0.001 seconds to 1.0 seconds after ink landing, more preferably 0.001 second to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, irradiation with actinic rays is divided into two stages. First, actinic rays are irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further, actinic rays are irradiated after all printing is completed. The method is also a preferred embodiment. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording material and cured by irradiation with actinic rays is preferably 2 to 25 μm. In the actinic ray curable ink jet recording in the screen printing field, the total ink film thickness currently exceeds 25 μm, but in the flexible packaging printing field where the recording material is often a thin plastic material, the recording material described above is used. In addition to the problem of curling and wrinkles, there is a problem in that the entire printed material is changed in its strain and texture.

  Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink heating and ejection conditions)
In the image recording method of the present invention, it is preferable to irradiate actinic rays with the actinic ray curable ink heated.

  As one of the methods, it is preferable from the viewpoint of ejection stability that the ink jet recording head and the ink are heated to 35 to 100 ° C. and the ink is ejected onto the recording material in the heated state.

  Further, as a method of the present invention, the ink jet recording head and the ink are respectively heated to 35 to 80 ° C., and after the ink is ejected from the ink jet recording head and the ink has landed on the recording material, the temperature is 35 to 80 ° C. It is preferable from the viewpoint of ejection stability to irradiate with actinic rays in a state maintained in the above.

  In the present invention, the method for heating and keeping the ink jet recording head and ink at a predetermined temperature is not particularly limited. For example, ink supply such as an ink tank constituting a head carriage, a supply pipe, a front chamber ink tank immediately before the head, etc. There is a method in which a system, a pipe with a filter, a piezo head, and the like are insulated and heated to a predetermined temperature by a panel heater, a ribbon heater, warm water or the like.

  In addition, as a method of maintaining a predetermined temperature after the ink has landed on the recording material, for example, a method of incorporating a panel heater in the recording material holding unit, or surrounding the recording material conveying unit and heating with warm air or the like A method can be mentioned.

  Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when ejection is performed with a small droplet amount such as 2 to 15 pl, the ejection stability is improved and a high-definition image can be stably formed.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) of the present invention will be described.

  The recording apparatus of the present invention will be described below with reference to the drawings as appropriate. Note that the recording apparatus of the drawings is merely one aspect of the recording apparatus of the present invention, and the recording apparatus of the present invention is not limited to this drawing.

  FIG. 1 is a front view showing the configuration of the main part of the recording apparatus of the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the recording material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording material P is guided by the guide member 6 and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). A head scanning unit (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the recording material P, and stores a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the recording material P, with the discharge ports arranged on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 is white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan (Lc). Although the drawing is carried out assuming that the recording heads 3 of light black (Lk) and white (W) are accommodated, the number of colors of the recording heads 3 accommodated in the head carriage 2 is determined as appropriate. Is.

  The recording head 3 has a discharge port by operating a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). To the recording material P. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.

  During the scanning in which the recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording material P On the other hand, UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode) and the like can be applied. A cathode tube, a hot cathode tube, a mercury lamp or black light is preferred. In particular, a low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet light having a wavelength of 254 nm are preferable because they can prevent bleeding and control the dot diameter efficiently. By using black light as the radiation source of the irradiation means 4, the irradiation means 4 for curing the UV ink can be produced at low cost.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording material P.

  As described above, as a means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, the ink discharge of the recording head 3 is determined from the distance h1 between the irradiation means 4 and the recording material P. It is effective to increase the distance h2 between the portion 31 and the recording material P (h1 <h2), or to increase the distance d between the recording head 3 and the irradiation means 4 (d is increased). Further, it is more preferable to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be changed as appropriate by replacing the ultraviolet lamp or filter provided in the irradiation means 4.

  The ink of the present invention has excellent ejection stability and is particularly effective when an image is formed using a line head type recording apparatus.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording material P. ing.

  On the other hand, on the downstream side of the head carriage 2, that is, the rear part of the head carriage 2 in the direction in which the recording material P is conveyed, the entire width of the recording material P is also covered so as to cover the entire area of the ink printing surface. Arranged irradiation means 4 are provided. As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In this line head system, the head carriage 2 and the irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

  Next, components other than those described above of the ink used for image formation of the present invention will be described.

  In particular, the ink according to the present invention includes a “photocuring system (Chapter 4)” described in “Photocuring Technology—Selection of Resin / Initiator and Blending Conditions and Measurement / Evaluation of Curing Level—Technical Association Information”. ) "" Curing system using photoacid / base generator (Section 1) "," light-induced alternating copolymerization (Section 2) ", and the like.

  The ink according to the present invention is composed of a pigment, a photopolymerizable compound, a dispersant, a photoinitiator, and the like, and is photopolymerizable when the photoinitiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by crosslinking or polymerization reaction of the compound. However, as the ink according to the present invention, the photoinitiator may be excluded when an ink that conforms to the “photo-induced alternating copolymerization (section 2)” of the above-mentioned reference is used.

  In the actinic ray curable ink of the present invention, the photopolymerizable compound is roughly classified into a radical polymerization ink containing a radical polymerizable compound and a cation polymerization ink containing a cationic polymerizable compound. Ink can be applied as the ink according to the present invention, respectively, and in the present invention, a hybrid ink in which radical polymerization ink and cationic polymerization ink are combined may be applied.

  When the ink according to the present invention is a radical polymerization type ink, the radical polymerizable compound is 1) high in water, 2) low in viscosity, 3) has photopolymerization, and 4) has excellent cured film properties. Therefore, radically polymerizable acrylic monomers can be preferably used.

Examples of radical polymerizable acrylic monomers include N, N-dimethylaminoethyl methacrylate, CH ₂ ═C (CH ₃ ) —COO—CH ₂ CH ₂ N (CH ₃ ) ₂ : N, N-dimethylaminoethyl acrylate, _{CH 2 = CH-COO-CH} 2 CH 2 N (CH 3) 2: N, N- dimethylaminopropyl _{methacrylate, CH 2 = C (CH 3} ) -COO-CH 2 CH 2 CH 2 N (CH 3) 2 : N, N-dimethylaminopropyl _{acrylate, CH 2 = CH-COO-} CH 2 CH 2 CH 2 N (CH 3) 2: N, N- dimethylamino _{acrylamide, CH 2 = CH-CON (} CH 3) 2: N, N-dimethylamino _{methacrylamide, CH 2 = C (CH 3} ) -CON (CH 3) 2: N, N- dimethylaminoethyl acrylamide, CH ₂ = CH-CO _{HC 2 H 4 N (CH 3} ) 2: N, N- dimethylaminoethyl _{methacrylamide, CH 2 = C (CH 3} ) -CONHC 2 H 4 N (CH 3) 2: N, N- dimethylaminopropyl acrylamide, _{CH 2 = CH-CONH-C} 3 H 6 N (CH 3) 2: N, N- dimethylaminopropyl _{methacrylamide, CH 2 = C (CH 3} ) -CONH-C 3 H 6 N (CH 3) 2: In addition, these quaternized substances are particularly preferred because they are excellent in colorant dyeing properties. In addition, (meth) acrylic acid ester of polyhydric alcohol, (meth) acrylic acid ester of glycidyl ether of polyhydric alcohol, (meth) acrylic acid ester of polyethylene glycol, (meth) acrylic acid ester of polyhydric alcohol ethylene oxide addition compound Known ultraviolet curable monomers and oligomers such as a reaction product of a polybasic acid anhydride and a hydroxyl group-containing (meth) acrylic acid ester are used. Among these substances, substances having high compatibility with ink and high hydrophilicity are appropriately selected and used. The amount of these water-soluble monomers used is preferably in the range of 1 to 40% by mass with respect to the total mass of the ink.

  As a method of using the photopolymerization initiator in the radical ink, one type of photoinitiator may be used, two or more types may be used, and a photoinitiator and a sensitizer may be used. The selection, combination and blending ratio of main photoinitiators and sensitizers may be appropriately selected depending on the monomers used and the equipment used.

  The main radical photoinitiators and sensitizers include, for example, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, p-dimethylaminopropiophenone, benzophenone. 2-chlorobenzophenone, pp'-dichlorobenzophene, pp'-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n -Butyl ether, benzyl dimethyl ketal, tetramethyl thiuram monosulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, azobisisobut Ronitrile, benzoin peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropan-1-one and methylbenzoyl formate. The amount used is preferably 0.1 to 10% by mass with respect to the total amount of the water-soluble monomer that is solidified by energy application.

  When radical ink is used using a normal metal halide lamp, a high pressure mercury lamp, or the like, the lamp becomes hot and the odor generated at the time of curing is serious, which is a problem. With the configuration of the present invention, the above problem is remarkably reduced even if radical ink is used.

  In the present invention, a cationic polymerization ink with little or no shrinkage at the time of curing is preferable because of its excellent functionality and versatility.

  When the ink according to the present invention is a cationic polymerization type ink, the photopolymerizable compound used preferably contains an epoxy compound having at least one oxirane group.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  In the present invention, from the viewpoint of safety such as AMES and sensitization, it is preferable to contain at least one of an epoxidized fatty acid ester and an epoxidized fatty acid glyceride as an epoxy compound having an oxirane group.

The epoxidized fatty acid ester and the epoxidized fatty acid glyceride are not particularly limited as long as an epoxy group is introduced into the fatty acid ester or fatty acid glyceride.
The epoxidized fatty acid ester is produced by epoxidizing an oleic acid ester, and examples thereof include methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate and the like. Similarly, the epoxidized fatty acid glyceride is produced by epoxidizing soybean oil, linseed oil, castor oil and the like, and epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil and the like are used. Examples of commercially available epoxidized vegetable oils include Sansizer E-4030 manufactured by Shin Nippon Chemical Co., Ltd., Vf7170, Vf7190, Vf5075, Vf4050, Vf7010, Vf9010, Vf9040, and Vf7040 manufactured by ATOFINA Chemical.

  In addition, the cationic polymerization ink according to the present invention preferably includes a compound containing an oxetane ring for further improving curability and ejection stability.

  As the oxetane compound that can be used in the present invention, any known oxetane compound as introduced in JP-A Nos. 2001-220526 and 2001-310937 can be used. Further, the combined use of a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings improves the film strength after curing and the adhesion to a recording medium. preferable.

  Furthermore, any known vinyl ether compound may be used in the cationic polymerization ink of the present invention.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylol. Di- or trivinyl ether compounds such as propane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  In the ink according to the present invention, it is preferable that at least one of the photoinitiators is a photoacid generator.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  Further, in the cationic polymerization ink according to the present invention, the amount of the photopolymerizable monomer added is 30 to 95% by mass of a compound having at least one oxetane ring and an epoxy compound having at least one oxirane group. 5 to 70% by mass, and preferably at least one vinyl ether compound is 0 to 40% by mass.

Further, it is preferable that the ink has a viscosity of 7 to 50 mPa · s at 25 ° C. in order to stably discharge and obtain good curability regardless of the environment such as ambient temperature and humidity.

  Various additives other than those described above can be used in the actinic ray curable ink according to the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving the storage stability of the cationic polymerization ink, any known basic compound can be used. Typical examples include basic alkali metal compounds, basic alkaline earth metal compounds, amines. And basic organic compounds such as

  By containing the basic compound, not only the ejection stability becomes good, but also the generation of wrinkles due to curing shrinkage is suppressed even under low humidity. As the basic compound, any known compounds can be used, and typical examples include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines.

  Examples of basic alkali metal compounds include alkali metal hydroxides (eg, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), alkali metal carbonates (eg, lithium carbonate, sodium carbonate, potassium carbonate, etc.), Examples include alkali metal alcoholates (for example, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, and the like).

  As the basic alkaline earth metal compound, similarly, an alkaline earth metal hydroxide (eg, magnesium hydroxide, calcium hydroxide, etc.), an alkali metal carbonate (eg, magnesium carbonate, calcium carbonate, etc.), Examples include alkali metal alcoholates (eg, magnesium methoxide).

  Examples of the basic organic compound include amines and nitrogen-containing heterocyclic compounds such as quinoline and quinolidine. Among these, amines are preferable from the viewpoint of compatibility with the photopolymerization monomer, for example, octylamine, naphthylamine, Xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylenetetramine and triethanolamine, etc. Is mentioned.

  The concentration when the basic compound is present is preferably in the range of 10 to 1000 ppm by mass, particularly 20 to 500 ppm by mass relative to the total amount of the photopolymerizable monomer. In addition, a basic compound may be used individually or may be used in combination of multiple.

  As the recording material that can be used in the image forming method of the present invention, various types of non-absorbable plastics and films used for so-called soft packaging can be used in addition to ordinary uncoated paper and coated paper. Examples of plastic films include polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, An acetyl cellulose (TAC) film can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Moreover, it is applicable also to metals and glass. Among these recording materials, the structure of the present invention is effective particularly when an image is formed on a PET film, an OPS film, an OPP film, an ONy film, or a PVC film that can be shrunk by heat. These substrates are not only susceptible to curling and deformation of the film due to ink curing shrinkage and heat generation during the curing reaction, but also the ink film is difficult to follow the substrate shrinkage.

  The surface energy of these various plastic films varies greatly depending on the characteristics of the material, and it has been a problem that the dot diameter after ink landing changes depending on the recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording material in terms of the cost of the recording material such as packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  The ink according to the present invention preferably constitutes an inkjet ink set having at least a yellow inkjet ink, a magenta inkjet ink, a cyan inkjet ink, and a black inkjet ink, and is generally used for so-called color inkjet printing. It refers to an ink set in which a plurality of inks are set. In the image forming method of the present invention, it is preferable that the ink-jet ink set is composed entirely of the ink according to the present invention. When an ink-jet image is formed using this ink set, an image in which color mixing is solved is formed. Can do.

  Furthermore, in order to form a photographic image by inkjet, so-called dark and light inks having different pigment contents can be prepared and used. It is also preferable for color reproduction to use special color inks such as red, green, blue, and white as necessary.

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

<< Preparation of pigment dispersion >>
[Preparation of Pigment Dispersion Group A]
(Preparation of pigment dispersion 1)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

PB822 (manufactured by Ajinomoto Fine Techno Co., Ltd., polymer dispersant, acid value 18.5 mg / g KOH, amine value 15.9 mg / g KOH) 8 parts tetraethylene glycol diacrylate (bifunctional) 72 parts Next, the above solution was cooled to room temperature Then, the following pigment was added to this, put in a glass bottle with 200 g of zirconia beads having a diameter of 1 mm, sealed, and dispersed for 4 hours with a paint shaker, and then the zirconia beads were removed to prepare pigment dispersion 1. .

Pigment Black 7 20 parts adjusted to an amine value of 7.0 mg / g KOH and an acid value of 6.3 mg / g KOH The above-described dispersants and pigments and the amine values and acid values of the dispersants and pigments described below Was determined according to the following method.

<Measurement of amine value of dispersant>
The dispersant was dissolved in methyl isobutyl ketone, potentiometric titration was performed with a 0.01 mol / L methyl isobutyl ketone perchlorate solution, and the value converted to KOH mg / g was used as the amine value of the dispersant. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of acid value of dispersant>
Dispersing the dispersant in methyl isobutyl ketone, performing potentiometric titration with 0.01 mol / L potassium methoxide-methyl isobutyl ketone / methanol (4: 1) solution, and converting to KOH mg / g, the acid value of the dispersant It was. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of amine value of pigment>
To the pigment was added 0.01 mol / L methyl butyl ketone perchlorate solution, and ultrasonic dispersion was performed. Thereafter, the supernatant was subjected to potentiometric titration with a 0.01 mol / L potassium methoxide-methylisobutyl ketone / methanol (4: 1) solution by centrifugation, and the amount of perchloric acid reduced by the pigment was converted to KOH mg / g. Was the amine value of the pigment. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of acid value of pigment>
A 0.01 mol / L tetrabutylammonium hydroxide-methylbutylketone solution was added to the pigment, and ultrasonic dispersion was performed. Thereafter, the supernatant was subjected to potentiometric titration with a 0.01 mol / L methyl isobutyl ketone perchlorate solution by centrifugation, and the 0.01 mol / L tetrabutylammonium hydroxide reduction amount by the pigment was converted to KOH mg / g. This was the acid value of the pigment. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

(Preparation of pigment dispersion 2)
Pigment dispersion 2 was prepared in the same manner as in the preparation of pigment dispersion 1, except that the following pigment was used instead of Pigment Black 7.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of Pigment Dispersion 3)
Pigment dispersion 3 was prepared in the same manner as in the preparation of pigment dispersion 1, except that the following pigment was used instead of Pigment Black 7.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 4)
In the preparation of Pigment Dispersion 1, Pigment Dispersion 4 was prepared in the same manner except that the following pigment was used instead of Pigment Black 7.

<Pigment>
20 parts of Pigment Red 122 adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH [Preparation of Pigment Dispersion Group B]
(Preparation of pigment dispersion 5)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

PB821 (manufactured by Ajinomoto Fine-Techno Co., Ltd., polymer dispersant, acid value 30.4 mg / g KOH, amine value 10.2 mg / g KOH) 9 parts OXT211 (manufactured by Toagosei Co., Ltd., oxetane compound) 71 parts After cooling, add the following pigment to this, and put it in a glass bottle together with 200 g of zirconia beads having a diameter of 1 mm, disperse with a paint shaker for 4 hours, and then remove the zirconia beads to prepare pigment dispersion 5 did.

20 parts of Pigment Black 7 prepared by adjusting the amine value to 7.0 mg / g KOH and the acid value to 6.3 mg / g KOH (Preparation of Pigment Dispersion 6)
In the preparation of the pigment dispersion 5, a pigment dispersion 6 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of pigment dispersion 7)
In the preparation of Pigment Dispersion 5, Pigment Dispersion 7 was prepared in the same manner except that the following pigment was used instead of Pigment Black 7.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 8)
Pigment dispersion 8 was prepared in the same manner as in the preparation of pigment dispersion 5 except that the following pigment was used instead of Pigment Black 7 for the pigment.

<Pigment>
20 parts of Pigment Red 122 adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH [Preparation of Pigment Dispersion Group C]
(Preparation of pigment dispersion 9)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

Disparon ED-251 (manufactured by Enomoto Kasei Co., Ltd., polymer dispersant, acid value 19 mg / g KOH, amine value 13.4 mg / g KOH) 10 parts tetraethylene glycol diacrylate (bifunctional) 70 parts After cooling, add the following pigment to this, put it in a glass bottle together with 200 g of zirconia beads having a diameter of 1 mm, seal it with a paint shaker for 4 hours, remove the zirconia beads, and prepare pigment dispersion 9 did.

20 parts of Pigment Black 7 prepared by adjusting the amine value to 5.2 mg / g KOH and the acid value to 3.6 mg / g KOH (Preparation of Pigment Dispersion 10)
A pigment dispersion 10 was prepared in the same manner as in the preparation of the pigment dispersion 9 except that the following pigment was used instead of the pigment black 7 in the pigment.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of Pigment Dispersion 11)
In the preparation of the pigment dispersion 9, a pigment dispersion 11 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 12)
In the preparation of the pigment dispersion 9, a pigment dispersion 12 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Pigment Red 122 20 parts adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH [Preparation of Pigment Dispersion Group D]
(Preparation of pigment dispersion 13)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

PB822 (manufactured by Ajinomoto Fine Techno Co., Ltd., polymer dispersant, acid value 18.5 mg / g KOH, amine value 15.9 mg / g KOH) 8 parts OXT221 (manufactured by Toa Gosei Co., Ltd., oxetane compound) 72 parts After cooling, add the following pigment to this, and put it in a glass bottle together with 200 g of zirconia beads having a diameter of 1 mm, disperse in a paint shaker for 4 hours, and then remove the zirconia beads to prepare a pigment dispersion 13 did.

20 parts of Pigment Black 7 prepared by adjusting the amine value to 5.2 mg / g KOH and the acid value to 3.6 mg / g KOH (Preparation of Pigment Dispersion 14)
In the preparation of the pigment dispersion 13, a pigment dispersion 14 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of pigment dispersion 15)
In the preparation of the pigment dispersion 13, a pigment dispersion 15 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 16)
In the preparation of the pigment dispersion 13, a pigment dispersion 16 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
20 parts of Pigment Red 122 adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH [Preparation of Pigment Dispersion Group E]
(Preparation of pigment dispersion 17)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

Disperbyk 161 (manufactured by Big Chemie, polymer dispersant, acid value 4.4 mg / g KOH, amine value 10.9 mg / g KOH) 8 parts OXT221 (manufactured by Toa Gosei Co., Ltd., oxetane compound) 72 parts The above solution was then cooled to room temperature. Thereafter, the following pigment was added thereto, sealed in a glass bottle with 200 g of zirconia beads having a diameter of 1 mm, sealed with a paint shaker for 4 hours, and then the zirconia beads were removed to prepare a pigment dispersion 17.

20 parts of Pigment Black 7 prepared by adjusting the amine value to 5.2 mg / g KOH and the acid value to 3.6 mg / g KOH (Preparation of Pigment Dispersion 18)
In the preparation of the pigment dispersion 17, a pigment dispersion 18 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of pigment dispersion 19)
In the preparation of the pigment dispersion 17, a pigment dispersion 19 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 20)
A pigment dispersion 20 was prepared in the same manner as in the preparation of the pigment dispersion 17 except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
20 parts of Pigment Red 122 adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH [Preparation of Pigment Dispersion Group F]
(Preparation of pigment dispersion 21)
The following compounds were put in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C.

Solspers 32000 (manufactured by Avicia, polymer dispersant, acid value 24.8 mg / g KOH, amine value 27.1 mg / g KOH) 8 parts OXT221 (manufactured by Toa Gosei Co., Ltd., oxetane compound) 72 parts Next, the above solution was cooled to room temperature Then, the following pigment was added thereto, and the mixture was sealed in a glass bottle together with 200 g of zirconia beads having a diameter of 1 mm, and dispersed with a paint shaker for 4 hours, and then the zirconia beads were removed to prepare a pigment dispersion 21. .

20 parts of Pigment Black 7 prepared by adjusting the amine value to 5.2 mg / g KOH and the acid value to 3.6 mg / g KOH (Preparation of Pigment Dispersion 22)
In the preparation of the pigment dispersion 21, a pigment dispersion 22 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Cyanine 4044 (manufactured by Sanyo Dye Co., Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts (Preparation of pigment dispersion 23)
A pigment dispersion 23 was prepared in the same manner as in the preparation of the pigment dispersion 21 except that the following pigment was used instead of the pigment black 7 in the pigment.

<Pigment>
20 parts of Pigment Yellow 138 adjusted to an amine value of 5.8 mg / g KOH and an acid value of 2.6 mg / g KOH (Preparation of Pigment Dispersion 24)
In the preparation of the pigment dispersion 21, a pigment dispersion 24 was prepared in the same manner except that the pigment was replaced with Pigment Black 7 and the following pigment was used.

<Pigment>
Pigment Red 122 20 parts adjusted to an amine value of 6.1 mg / g KOH and an acid value of 4.1 mg / g KOH << Preparation of ink >>
Using each of the prepared pigment dispersions, the additives shown in Tables 1 to 6 were sequentially mixed to prepare ink composition sets 1 to 6. In addition, the numerical value of Table 1-Table 6 represents the mass%.

  Details of each additive described in abbreviations in Tables 1 to 6 are as follows.

[Photopolymerizable compound]
(* E1: Alicyclic epoxy compound)
LDO: LDO (manufactured by ATOFINA)
UVR6110: UVR-6110 (manufactured by Dow Chemical Company)
S2021P: Celoxide 2021P (manufactured by Daicel Chemical Industries)
(* E2: Epoxidized linseed oil)
Vf9040: Vikoflex 9040 (manufactured by ATOFINA)
(* E3: epoxidized fatty acid butyl)
E4030: Sansosizer E-4030 (manufactured by Shin Nippon Rika Co., Ltd.)
(* O: Oxetane compound)
OXT101: OXT-101 (manufactured by Toa Gosei Co., Ltd.)
OXT211: OXT-211 (manufactured by Toa Gosei Co., Ltd.)
OXT212: OXT-212 (manufactured by Toa Gosei Co., Ltd.)
OXT221: OXT-221 (manufactured by Toa Gosei Co., Ltd.)
E-1: Compound E-1 as described above
(* R: radical polymerizable compound)
* A: Lauryl acrylate (monocyclic)
* B: Tetraethylene glycol diacrylate (bifunctional)
* C: ε-caprolactam-modified dipentaerythritol hexaacrylate (hexafunctional)
(Other)
A400: NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.)
[Photoacid generator]
DTS102: DTS-102 (Midori Chemical Co., Ltd.)
UVI6992: UVI6992 (Dow Chemical Co.)
I-250: Irgacure 250 (Ciba Specialty Chemicals)
SP152: Triphenylsulfonium salt (“Adekaoptomer SP152” manufactured by Asahi Denka Co., Ltd.)
[Photo radical initiator]
I-184: Irgacure 184 (Ciba Specialty Chemicals)
I-369: Irgacure 369 (Ciba Specialty Chemicals)
I-651: Irgacure 651 (Ciba Specialty Chemicals)
I-2959: Irgacure 2959 (Ciba Specialty Chemicals)
[Basic compounds]
* 1: N-ethyldiethanolamine * 2: Tributylamine [* Sol: Water-soluble organic solvent]
* 3: Diethylene glycol (reagent)
* 4: Isopropyl alcohol (reagent)
[Surfactant]
F178k: Megafax F178k Perfluoroalkyl group-containing acrylic oligomer (Dainippon Ink Chemical Co., Ltd.)
F475: Megafax F475 Perfluoroalkyl group-containing acrylic oligomer (Dainippon Ink & Chemicals, Inc.)
F1405: Megafax F1405 Perfluoroalkyl group-containing ethylene oxide adduct (manufactured by Dainippon Ink & Chemicals, Inc.)
[Compatibilizer]
BDB: High Solve BDB (Toho Chemical Co., glycol ether)
H-MB: Himic MB (manufactured by Toho Chemical Co., Anisole)
[Others]
GP600: Sannix GP-600 (manufactured by Sanyo Chemical Industries, polyether polyol)
<< Inkjet image formation >>
[Image Forming Method A]
Each of the ink sets 1 to 3 prepared above is loaded into an ink jet recording apparatus having the structure shown in FIG. 1 having a piezo type ink jet nozzle, and each of the lengths of 600 mm in width and 500 m in length shown in Table 7 is provided. Images 1 to 12 were obtained by continuously performing the following image recording on the recording material. The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank just before the head, a pipe with a filter, and a piezo head. The ink was insulated from the front chamber tank to the head portion and heated at 50 ° C. The piezo head was driven so that 2 to 25 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi, and each ink was ejected continuously. At this time, the conveyance guide plate (platen part) was heated to 50 ° C., so that the ink was maintained at about 50 ° C. even after landing on the recording material. After landing on the recording material, it was cured instantaneously (less than 1.0 second after landing) by the lamp units on both sides of the carriage. After recording, the total ink film thickness was measured and found to be in the range of 2.3-18 μm. In the present invention, dpi represents the number of dots per 2.54 cm. Inkjet images were formed in an environment of 27 ° C. and 80% RH according to the above method.

[Image Forming Method B]
In the formation method A, the line 13 recording type ink jet recording apparatus shown in FIG. 2 was used as the ink jet recording apparatus, and each of the ink 13 and ink sets 4 to 6 was loaded to form an image. ~ 22 were obtained.

  The details of the abbreviations of the recording materials listed in Table 7 are as follows.

OPP (Yupo): oriented polypropylene
PET: Polyethylene terephthalate
PVC: polyvinyl chloride
Moreover, the detail of each irradiation light source of Table 7 is as follows.

Irradiation light source A: High pressure mercury lamp VZero085 (manufactured by INTEGRATION TECHNOLOGY)
Irradiation light source B: LED (manufactured by Nichia Corporation, special order product, less than 1 kW)
Irradiation light source C: hot cathode tube (manufactured by Nippon, special order, 200 W power supply)
Irradiation light source D: 120 W / cm metal halide lamp (manufactured by Nippon Battery Co., Ltd. MAL 400NL 3kW power source)
Irradiation light source E: Low-pressure mercury lamp (manufactured by Iwasaki Electric Co., Ltd., special order product, 200W power supply)
Moreover, the illumination intensity of each irradiation light source of Table 9 measured and displayed the integrated illumination intensity of 254 nm using UVPF-A1 by Iwasaki Electric Co., Ltd. and displayed.

  Moreover, the detail of each irradiation method (area) of Table 8 is as follows.

Irradiation position A: The apparatus shown in FIG. 1 is used and linear light sources are arranged at both ends of the recording head. Irradiation position B: A plurality of LED chips are arranged at both ends of the recording head using the apparatus shown in FIG. C: A linear light source is arranged on the downstream side in the recording material conveyance direction using the apparatus shown in FIG. 2. Irradiation position D: A plurality of LED chips are arranged on the downstream side in the conveyance direction of the recording material using the apparatus shown in FIG.

<Evaluation of inkjet recording image>
Each image recorded by the above image forming method was subjected to the following evaluations. Each evaluation was performed on a 1 m sample, a 10 m sample, and a 100 m sample after printing of continuously ejected image records.

(Evaluation of printed wrinkles and curls)
Immediately after printing 10 m, 100 m, and 500 m, each printed matter was visually observed for wrinkles and curls due to irradiation and curing, and evaluated according to the following evaluation criteria.

○: Wrinkles and curls are not generated and good △: Slight wrinkles and curls are observed, but within a practically acceptable range ×: Strong wrinkles and curls are recognized in the printed matter, which is a practical problem. (Evaluation of character quality)
For each color of Y, M, C, and K, a 6-point MS Mincho character was printed at a target density, and the character roughness was enlarged and observed with a loupe, and character quality was evaluated according to the following criteria.

◎: No rusting ○: Slight rustling is observed △: Gashesiness is admitted, but it can be recognized as text ×: The level is harsh and the text is faint and unusable (uses color mixing) Evaluation)
At 720 dpi, printing was performed so that 1 dot of each color of Y, M, C, and K was adjacent to each other, each adjacent color dot was enlarged with a loupe, the degree of bleeding was visually observed, and color mixing was evaluated according to the following criteria.

◎: Adjacent dot shape maintains a perfect circle and no blurring ○: Adjacent dot shape maintains a perfect circle and almost no blur Δ: Adjacent dot is slightly blurred and the dot shape is slightly displaced , Practical quality x: Quality in which adjacent dots are blurred and mixed and are problematic in practice Table 8 shows the evaluation results obtained as described above.

  As is apparent from the results shown in Table 8, the image of the present invention was obtained using an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value. Compared with the comparative example, the image formed by the forming method is superior in character quality to any recording material, can produce a high-definition color image without color mixing, and can be used for wrinkles and curls in printed matter. It turns out that there is no outbreak.

It is a front view which shows an example of a structure of the principal part of the inkjet recording device of this invention. It is a top view which shows another example of a structure of the principal part of the inkjet recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

Claims (11)

From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink has a maximum illuminance at 254 nm between 0.001 seconds and 1.0 seconds after landing on the recording material , and 1 An image forming method comprising curing after irradiation with an actinic ray by a light source having a power consumption per hour of less than 1 kW. From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink is activated by a light source having a maximum illuminance at 254 nm between 0.001 second and 1.0 second after landing on the recording material. An image forming method comprising curing after irradiation with light . From the ink jet recording head, an actinic ray curable ink containing a photoinitiator, a photopolymerizable compound and a pigment, and a dispersant having an acid value larger than the amine value is jetted onto the recording material, and printing is performed on the recording material. An image forming method to be performed , wherein the actinic ray curable ink has a maximum illuminance at 254 nm between 0.001 second and 1.0 second after landing on the recording material , and ultraviolet rays An image forming method comprising : curing after irradiation with ultraviolet light from a light source in which a plurality of light emitting diodes generating light is arranged. 4. The total ink film thickness after the actinic ray curable ink has landed on the recording material and cured by irradiation with actinic rays is 2 to 25 [mu] m. The image forming method described in 1. The image forming method according to claim 1, wherein the pigment contained in the actinic ray curable ink has an amine value larger than an acid value. The at least one of the photoinitiators contained in the actinic radiation curable ink is a photoacid generator, and at least one of the photopolymerizable compounds is an epoxy compound. The image forming method according to any one of the above. The image forming method according to claim 6, wherein the actinic ray curable ink further contains an oxetane compound as the photopolymerizable compound. The image forming method according to claim 1, wherein the actinic ray is irradiated in a state where the actinic ray curable ink landed on the recording material is heated. The actinic ray curable ink is ejected from the inkjet recording head in a state where the ink jet recording head and the actinic ray curable ink are heated to 35 to 80 ° C., respectively, and the actinic ray curable ink is applied onto the recording material. The image forming method according to claim 1, wherein the actinic ray is irradiated in a state where the temperature is maintained at 35 to 80 ° C. after landing. It is an inkjet recording device used for the image forming method of any one of Claims 1-9, Comprising: After heating actinic-light curable ink and an inkjet recording head to 35 to 100 degreeC, from this inkjet recording head An inkjet recording apparatus, wherein the actinic ray curable ink is ejected. An ink jet recording apparatus used in the image forming method according to claim 1, wherein an image is formed by ejecting an actinic ray curable ink from a line head type ink jet recording head, and the ink jet recording An inkjet recording apparatus, wherein an actinic ray irradiation light source is disposed at a rear portion of a head in a direction in which a recording medium is conveyed.

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