WO2006090541A1

WO2006090541A1 - Inkjet recorder, inkjet recording method and ultraviolet-curable ink

Info

Publication number: WO2006090541A1
Application number: PCT/JP2006/300927
Authority: WO
Inventors: Atsushi Nakajima
Original assignee: Konica Minolta Medical & Graphic, Inc.
Priority date: 2005-02-24
Filing date: 2006-01-23
Publication date: 2006-08-31
Also published as: JPWO2006090541A1

Abstract

Disclosed are an inkjet recorder and inkjet recording method wherein the problem of image quality degradation caused when an image formed of an ultraviolet-curable ink employing no aqueous solvent is cured using flash light is solved, and a high-gloss high-quality image can be attained quickly while eliminating deterioration in density and adhesion to a recording medium. With such an inkjet recorder and inkjet recording method, a high-quality image can be similarly attained even in case of a color image containing an ink of different infrared absorption such as a black ink. Also disclosed is an ultraviolet-curable ink used in such an inkjet recorder and inkjet recording method. The inkjet recorder comprises a flash light source, and is characterized by comprising a means for attenuating the quantity of light at least in a part of infrared wavelength region of flash light emitted from the flash light source.

Description

Specification

Inkjet recording apparatus, inkjet recording method, and ultraviolet curable ink

The present invention relates to a novel ink jet recording apparatus and ink jet recording method, and an ultraviolet curable ink used therefor.

Background art

[0002] A recording method in which an ink image curable by ultraviolet rays is formed by an ink jet method, and recording is fixed by irradiating ultraviolet rays has been developed in recent years and is being put to practical use. As ink techniques to be used, those described in W099 / 29787, W099 / 29788, WO97 / 31071, JP-A-5-214280, JP-A-2002-188025 and the like are known.

[0003] An ultraviolet curable ink undergoes a curing reaction by photopolymerization on a recording medium upon irradiation with an actinic ray such as ultraviolet light, and thus can be fixed and recorded on a recording medium that does not absorb ink, such as a plastic surface. Can form an image with good adhesion.

[0004] However, a relatively large ultraviolet ray source is required in the vicinity of the printing portion to irradiate ultraviolet rays sufficient for the curing reaction after ink has landed on the support (recording medium). A mercury lamp or the like is used. Moreover, since these ultraviolet ray sources emit not only ultraviolet rays but also visible light, infrared rays and the like simultaneously, a portion close to the light source is heated considerably. Therefore, overheating of the recording head and the recording medium occurs, and measures against overheating are required.

On the other hand, in the ink jet recording system, several attempts have been made to use flash light. For example, Patent Document 1 describes that flash light is used to speed up ink drying in an ink jet recording system.

[0006] In addition, Patent Document 2 describes a flash-curable inkjet ink having a high affinity for a plastic resin such as a water-based soft polyvinyl chloride vinyl resin. Thus, the ink is cured.

However, in Patent Document 1, the ink composition and characteristics suitable for this method are described in Patent Document 1. The above description is intended to speed up the drying and evaporation of the solvent using a flash light source for the ink mainly composed of a solvent such as ordinary water-based ink and solvent ink. In this case, a considerable amount of heat is required to dry and evaporate the ink (evaporation of water or solvent), and the flash light source requires a large number of irradiations.

[0008] With respect to Patent Document 2, an ultraviolet curable ink containing water is used, and an image is formed with good adhesion on a soft plastic film support such as bull chloride by irradiating a flash lamp a plurality of times. Proposals have been made. By using flash exposure, rather than using a normal high-pressure mercury lamp, the amount of heat generated on the support is suppressed, and a hydrophilic monomer capable of softening vinyl chloride is blended to obtain an ink with good fixability. Because it is a UV curable ink, it can fix the ink on the support without requiring the amount of heat required for evaporation of the solvent water, and it must be able to be exposed for a short time with a flash light source. In addition, since energy can be applied to the extreme surface of the support while suppressing thermal diffusion to the support, it is effective for evaporating the water in the ink even in plastic films that are susceptible to thermal deformation. Seem.

[0009] However, in the case of the ultraviolet curable ink containing water described above, since a very large amount of heat is required to remove the remaining water, only with flash exposure, the image has a sufficient amount of water remaining. It is difficult to get sex. Also, solvents such as moisture cannot be vaporized in time because of instantaneous curing, and remain in the cured film, reducing film properties. A large amount of heat is required to remove the solvent from the film once polymerized.

Patent Document 1: Japanese Patent Laid-Open No. 2000-272101

Patent Document 2: Special Table 2001-512777

Disclosure of the invention

Problems to be solved by the invention

[0010] When an ultraviolet curable ink that does not use a water solvent or the like is cured using flash light, it is not necessary to evaporate the solvent. However, in practice, the flash lamp's emission energy is large, and its emission wavelength extends beyond the visible region, which creates another problem and requires a solution. Has come to understand.

[0011] UV curable ink that does not contain moisture has moisture with a large heat capacity and latent heat of vaporization. Therefore, when the infrared component contained in the flash light source is absorbed, the ink droplets are deformed by heating or the ink components are evaporated and the image quality deteriorates. In particular, black ink has a high light absorption efficiency, which causes convection of the ink and boiling of the monomer due to overheating before and after the ink liquid is cured, resulting in lower glossiness, lower density, lower adhesion, etc. The degree of image quality degradation is high.

That is, according to the inventor's study, the light emitted from the flash lamp extends from the visible part to the infrared part, and therefore, by applying a large amount of light energy to the flash light in a short time, the ink droplets are overheated. These thermal energy are preferably expended in accelerating photopolymerization, but if the energy of flash light is extremely high, the balance between the heating rate of the ink and the heat transfer (thermal convection) to the inside of the ink is balanced. It collapsed, and only the ink surface was locally overheated, causing boiling or excessive heat convection to cause wrinkling of the cured film and uneven color, resulting in a problem of lowering the image quality. In particular, when black ink that strongly absorbs infrared light and color ink with low absorption are mixed, it is very difficult to suppress deterioration in image quality due to infrared absorption while maintaining the same ultraviolet curing sensitivity for all colors. I understood.

[0013] The present invention has been made in order to solve the above-described problems, and an object of the present invention is to cure an image formed with an ultraviolet curable ink without using a water solvent or the like using flash light. For color images containing inks with different infrared absorption such as black, which can solve the problem of image quality degradation that occurs and can quickly obtain high-quality images without high glossiness or deterioration of adhesion to recording media. Similarly, the present invention provides an ink jet recording method and an ink jet recording apparatus capable of obtaining a high-quality image, and an ultraviolet curable ink used therefor.

Means for solving the problem

[0014] The above object of the present invention has been achieved by the following constitution.

[0015] 1. An inkjet recording apparatus including a flash light source, the inkjet recording apparatus having means for reducing at least a part of the amount of light in an infrared wavelength region of flash light emitted from the flash light source Recording device.

[0016] 2. Means for reducing the amount of light in the infrared wavelength range The amount of light in the wavelength range of 800 to 1100 nm 2. The ink jet recording apparatus as described in 1 above, wherein the ink jet recording apparatus is means for reducing to 1/2 or less.

[0017] 3. An ink jet recording method in which an ultraviolet curable ink is landed on a recording medium, and thereafter cured and fixed using flash light emitted from a flash light source, the flash light being infrared An ink-jet recording method characterized in that at least a part of the light wavelength range is reduced.

[0018] 4. The ink jet recording method according to 3 above, wherein the light intensity in the flash light intensity 800-: lOOnm wavelength region is reduced to 1/2 or less.

[0019] 5. The amount of light (B) in the wavelength range 800-: lOOnm of the flash light and the wavelength range 250

5. The ink jet recording method according to 3 or 4 above, wherein the ratio (BZA) force of light quantity (A) at ˜450 nm is smaller than 12.

[0020] 6. Any one of 3 to 5 above, wherein the total content of water and water-soluble solvent in the ultraviolet curable ink is 5% by mass or less of the total mass of the ultraviolet curable ink. The inkjet recording method according to item.

[0021] 7. The ink jet recording method according to any one of 3 to 6, wherein an image is formed using two or more kinds of ultraviolet curable inks having different infrared absorption capabilities.

[0022] 8. An ultraviolet curable ink characterized by being used in the ink jet recording method according to any one of 3 to 7.

[0023] 9. The ultraviolet curable ink as described in 8 above, wherein the total content of water and water-soluble solvent is 5% by mass or less of the total mass of the ultraviolet curable ink.

The invention's effect

[0024] According to the present invention, the problem of image quality degradation that occurs when ultraviolet curable ink is cured using flash light is solved, and the density with high gloss and adhesion to a recording medium is not degraded. Providing inkjet recording devices and inkjet recording methods that can produce high-quality images quickly and color images that contain black and other inks with different infrared absorption, as well as UV-curable inks used in them. Could be brief description of the drawings [0025] [FIG. 1] An emission spectrum of a flash light source.

FIG. 2 is a front view showing an example of a configuration of a main part of the ink jet recording apparatus according to the present invention.

FIG. 3 is a schematic view showing another example of the ink jet recording apparatus.

Explanation of symbols

[0026] 1 Recording device

2 Head carriage

3, 19 Recording head

4, 24 flash light ¾!

5 Platen section

6 Guide member

20 Recording media

41 Infrared filter

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the best mode for carrying out the present invention will be described, but the present invention is not limited thereto.

In the present invention, an ultraviolet curable ink is used, and after the ultraviolet curable ink is landed on a recording medium, it is cured by irradiation with ultraviolet rays to form an image. However, a flash light source is used as an ultraviolet light source for curing the ultraviolet curable ink, and the ultraviolet curable ink is cured in a short time and fixed on the recording medium.

[0029] As a result of intensive studies on the above problems, the present inventor has found that a flash with reduced infrared rays is used to prevent overheating of the ink droplets that have landed or the formed inkjet image on the recording medium. Fixing an image without causing color unevenness due to boiling, evaporation, or excessive convection inside the ink due to overheating of the ink or the ink surface, which is a drawback of fixing by flash light, by curing with a light source. It has been found that can be performed.

[0030] Details of the present invention will be described below.

[0031] [Flash light source] The flash light source according to the present invention is not particularly limited, but for example, a xenon flash or the like is representative. In order to efficiently use ultraviolet rays, it is preferable to use ultraviolet ray transmissive tubes and filters for the light source lamp. As described above, flash light sources generally emit light for a short time of lmsec or less, and flash light has a very large amount of energy per unit time, that is, illuminance. In addition to the ultraviolet component that mainly contributes to the polymerization reaction (curing reaction) of the ultraviolet curable ink, these flash lights include light in the visible to infrared region. As a result, the ink is absorbed by the recording medium, and as a result, overheating of the ink causes the ink to boil (bounce) or cause the monomer component to evaporate and scatter.

[0032] When high-intensity infrared light is applied to ink droplets in a short time with excessive energy, the infrared light is mainly absorbed by the surface area of the ink and converted into heat, and the inside of the heat energy. The diffusion to the surface is a process that is relatively slower than the irradiation time of the flash light, so that thermal diffusion in the direction of the ink thickness (which is in the range of several μm to several tens of μm) does not occur sufficiently, resulting in The ink surface is excessively heated, causing problems such as boiling at the ink surface layer and monomer evaporation. In addition, excessive convection occurs due to the temperature difference between the ink surface and the interior, thereby causing unevenness in the ink density of the formed image, curing spots, and the like.

[0033] The spectral emission spectrum of the flash light source according to the present invention has, for example, a large amount of emitted light in the infrared region as well as in the ultraviolet region as shown in FIG. The flash light with reduced infrared rays according to the present invention refers to light obtained by reducing light in the wavelength range of 800 to 1100 ηm to ½ or less of the light emitted from the flash light source. Furthermore, the ratio (B / A) of the light quantity (B) in the wavelength range of 800 to 1100 nm and the light quantity (A) in the wavelength range of 250 to 450 nm is preferably flash light smaller than 1/2. preferable.

[0034] In the present invention, for measuring the spectral energy of the flash light as described above, for example, an L 1 745 ultraviolet one visible one near infrared radiance measuring device (manufactured by Asahitsu Trading Co., Ltd.) is used. Measuring power S. Specifically, spectral spectra measured with OL-745-PMT and ○ L-745-Si are synthesized.

[0035] The inkjet recording apparatus of the present invention is characterized by having means for reducing the amount of light in at least a part of the infrared wavelength range, but there are no particular restrictions on the specific means. Although it is preferable to apply a filter that cuts light in the visible light region and infrared light region, examples of filters that cut light in the visible light region and infrared light region include color glass filters, Various optical filters such as a dielectric film filter and an interference filter can be used as appropriate. In particular, a cold filter with a heat-absorbing glass coated with a dielectric film filter is preferred. As these cold filters, for example, those commercially available from Sigma Koki Co., Ltd. can be used. An ND filter can be used to control the total amount of light.

In the present invention, the emission energy of flash light with reduced infrared rays is in the range of 0.1 to 10 j / cm ² (per 1 flash), and the emission time of flash light is 0.5 to 5 ms. Is preferable.

[0037] As the flash lamp used in the present invention, a xenon flash lamp is generally used, and a xenon rectangular pulse light source or the like may be used. Various strobe light sources can also be used. For example, a xenon flash lamp is a discharge lamp in which Xe gas or the like is sealed in a glass tube, a main electrode is provided at both ends of the glass tube, and a trigger electrode is provided on the tube wall. When a trigger voltage is applied to one electrode, the insulation in the tube is broken and main discharge between the main electrodes starts at once, and a flash is emitted in the ultraviolet to infrared region for a predetermined period. Yes, light emission with high illuminance can be obtained in a short time.

[0038] In general, the emission intensity of flash light increases as the lamp input power per flash increases, and the emission time increases and decreases as the lamp input power decreases, but to a certain extent so that sufficient ink curing occurs. In order to have a high intensity and a relatively long light emission time, it is necessary to select an optimal flash light source. Further, as described in Japanese Patent Laid-Open No. 2001-142347, the flash light source and its drive circuit can be set to have a relatively long flash light emission time while ensuring input power, for example, a flash lamp, A method of controlling the light emission time by devising the circuit such as the capacitance of the capacitor and the charging voltage may be used.

[0039] As these flash lamps, the power of which the xenon flash is representative is, for example, a xenon lamp manufactured by Hamamatsu Photovitas Co., Ltd., a xenon lamp SXC-150L manufactured by Nisshin Denki Kogyo Co., Ltd., etc. Hard glass xenon for copy machines and printers manufactured by Miyata Elevum Co., Ltd. Flash lamps and XZ series manufactured by Nowright Corporation can be used.

[Ultraviolet curable ink]

In the ultraviolet curable ink according to the present invention, the total content of water and water-soluble solvent in the ink is preferably 5.0% by mass or less. If the ink contains a large amount of water or water-soluble solvent, these solvents remain after the ink is cured, and the durability of the image deteriorates. In addition, since the monomer is polymerized after the ink is cured, the diffusibility of the solvent is reduced, and a large amount of heat is required to volatilize, so the amount of water and water-soluble solvent in the ink is low. I prefer it.

[0041] When water and a water-soluble solvent are added to the ink, it should be 5.0% by mass or less, and the ink should be subjected to a solvent removal treatment in advance before exposure to flash light. And are preferred.

In the present invention, the water-soluble solvent is a non-polymerizable solvent that is freely mixed with water or has a solubility of 10% by mass or more at 25 ° C. with respect to water. , Alcohols, acetones, ethylene glycols and the like.

[0043] There are two types of ultraviolet curable ink, radical polymerizable and cationic polymerizable, depending on the reaction mechanism, and both types can be used in the present invention. However, UV curable inks using radically polymerizable compounds with a high polymerization rate are preferred from the viewpoint of reactivity in short-time irradiation such as flash light.

[0044] The radically polymerizable ink has the ability to inhibit curing due to oxygen S, and the sensitivity can be drastically improved when high-illuminance exposure is performed for a short time with flash light as in the present invention. Preferably, the average value of the incident light energy per emission time (half width) is 250 W / cm ² or more, more preferably 500 W / cm ² . Increasing the illuminance can reduce oxygen inhibition and increase the cure rate. However, if the illuminance is simply increased, the intensity of the infrared light increases, and particularly in the formation of a black image, an overheating phenomenon occurs and the image quality deteriorates.

[0045] The ultraviolet curable ink according to the present invention is prepared by blending and dispersing a dispersing agent, a coloring material, and other additives as appropriate in a photopolymerizable composition such as a photopolymerizable compound and a photopolymerization initiator. Be done [0046] Among the polymerizable compounds, examples of the radical polymerizable compound include, for example, JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863. Can be mentioned.

[0047] Specific examples of the compound having radical polymerizability include aliphatic (meth) acrylate, alicyclic (meth) acrylate, aromatic (meth) acrylate, ether (meth). Examples include acrylate, bull monomers, and (meth) acrylamides. In addition, (meth) atalylate means one containing at least one of attalylate and metaatherate.

[0048] Examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include, for example, unsaturated rubonic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof. , Esters, urethanes, amide anhydrides, acrylonitrile, styrene, and various radically polymerizable compounds such as unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

Specifically, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxychetil acrylate, canolebitono acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate Bis (4-Atalyloxypolyethoxyphenyl) propane, neopentyl glycol ditalylate, 1,6-hexanediol ditalylate, ethylene glycol ditalylate, diethylene glycol ditalylate, triethylene glycol ditalylate, tetraethylene Glycol diatalylate, polyethylene glycol diatalylate, polypropylene glycol diatalylate, pentaerythritol retinoretria talylate, pentaerythritol tetratalylate, dipen Acrylic acid derivatives such as erythritol tetratalylate, trimethylolpropane tritalylate, tetramethylolmethanetetratalylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide and epoxy acrylate; methyl metatalylate, n-butanol Metatalylate, 2_ethylhexylmetatalylate, Laurinolemetatalylate, Arylmethacrylate, Glycidylmetatalylate, Benzylmetatalylate, Dimethylaminomethylmetatalylate, 1,6-Hexanediono Resin methacrylate, ethylene glycoloresimethacrylate, triethylene glycol dimetatalate, polyethylene glycol dimetatalate poly Methacrylic acid derivatives such as propylene glycol dimethacrylate, trimethylol ethane trimethacrylate, trimethylol propane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) bread; other, allylglycidyl Derivatives of allylic compounds such as ether, diallyl phthalate, triallyl trimellitate and the like can be mentioned. More specifically, Junzo Yamashita “Cross-linking agent handbook”, (1981 Taiseisha); Curing Handbook (Raw Materials), (1985, Polymer Publications); Radtech Research Group, “Application and Application of UV'EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “ Polyester Resin Handbook ”, (1988, Nikkan Kogyo Shimbun Co., Ltd.), etc., or a radically polymerizable or crosslinkable module known in the industry. Normalers, oligomers and polymers can be used.

[0049] The amount of the radical polymerizable compound added to the ultraviolet curable ink is preferably 1 to 97 mass%, more preferably 30 to 95 mass%, based on the total mass of the ink.

[0050] In the present invention, as the color material, a color material that can be dissolved or dispersed in the photopolymerizable compound can be used. A pigment is preferable from the viewpoint of weather resistance.

[0051] Pigments that can be preferably used in the present invention are listed in paragraph No. (0086) of JP-A-2004-131588.

[0052] For the dispersion of the pigment, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. In addition, a dispersant can be added when dispersing the pigment. As the dispersant, it is preferable to use a polymer dispersant S. Specific examples of these dispersants include the dispersants described in paragraphs (0088) to (0093) of JP-A-2004-131588, Examples include a dispersion aid.

[0053] These dispersants and dispersion aids are preferably added in an amount of:! To 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion of the pigment is performed using a solvent or a polymerizable compound. However, in consideration of the deterioration of solvent resistance and the adverse effects of volatilization of the remaining solvent, the ultraviolet curable ink according to the present invention can be used for a short time immediately after ink landing. Therefore, the content of water or a water-soluble solvent as a dispersion medium is preferably 5% by mass or less, and more preferably no solvent. Therefore, the dispersion medium is not a solvent but a polymerizable compound, most of them Low viscosity, preferred for dispersion suitability, to select monomer.

[0054] For the dispersion of the pigment, it is preferable that the average particle diameter of the pigment particles is 0 · 08-0.5 _β m. The maximum particle size is 0.3 to 10 μ 10η, preferably 0.3. The selection of the pigment, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set so as to be ˜3 μΐη. This particle size control can suppress clogging of the ink jet recording head and maintain ink storage stability, ink transparency, and curing sensitivity.

[0055] In the ultraviolet curable ink according to the present invention, the amount of the color material is preferably 1% by mass to 10% by mass of the entire ink.

[0056] In the present invention, in order to perform the curing reaction more efficiently, a photopolymerization initiator is added and cured. Photopolymerization initiators are radical generators, and radical generators can be broadly classified into two types: intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

Examples of these radical generators include compounds described in paragraph numbers (0 073) to (0074) of JP-A No. 2004-131588.

[0058] The addition amount is usually preferably in the range of 0.01 to 10:00 mass% in the ink composition.

However, in the present invention, since high-illuminance exposure using flash light is performed, the reaction start point increases with the amount of addition of a normal photopolymerization initiator, and as a result, the degree of polymerization is prevented from decreasing. It is more preferable that the amount of addition of (radical generator) is in the range of 0.01 to 3.0% by mass in the ink composition.

[0059] Although the ultraviolet curable ink according to the present invention is cured by irradiation with ultraviolet rays, a photosensitizer can be used in combination in order to perform the curing reaction more efficiently. Examples of such a photosensitizer include compounds described in paragraph No. (0085) of JP-A-2004-131588. The amount of the photosensitizer used is in the range of 0.01 to 10.0% by mass, more preferably 0.01 to 3.0% by mass in the ink composition.

[0060] In addition to these components, the ultraviolet curable ink according to the present invention includes a surfactant, a leveling additive, a matting agent, a polyester resin for adjusting film properties, if necessary, Can contain polyurethane resin, vinyl resin, acrylic resin, rubber resin, and wax.

[0061] Further, a polymerization inhibitor that suppresses polymerization by heat or actinic rays is added to the ink. Both are preferable. As the polymerization inhibitor, it is preferable to add various antioxidants (AO agents), nitrosamine compounds, and hydroquinone compounds. Specifically, for example, MEH Q (P-methoxyphenol) can be used.

[0062] Since excessive addition of these polymerization inhibitors causes a decrease in ink sensitivity, an amount capable of preventing polymerization at the time of pigment dispersion is appropriately set while maintaining storage stability as an ink. It is desirable to blend them. The amount of the polymerization inhibitor in the ink is preferably 200-20, OOOppm.

[0063] It is also effective to add a trace amount of an organic solvent in order to improve adhesion to a recording medium (also referred to as a base material or a support) after ink curing with ultraviolet rays. In this case, force that can be applied within the range that does not cause problems with solvent resistance and VC, use it as much as possible. If necessary, the addition amount is 0.:!~5. / ₀ more preferably preferably fixture is 1-3% 0.1.

[0064] Further, as a means for preventing a decrease in sensitivity due to the light-shielding effect due to the colorant in the ink, a cationic polymerizable compound having a long initiator lifetime and the initiator are combined to form a radical cation hybrid type curable ink. Is also possible.

In the ink jet recording method of the present invention, it is preferable to form an image using two or more kinds of ultraviolet curable inks having different infrared absorption capabilities from the viewpoint of being able to fully exhibit the object effects of the present invention. In this way, when two or more types of ultraviolet curable inks with different infrared absorption capabilities are used, for example, when a secondary color or black image is formed, the infrared absorption capability differs depending on the color of the ink. In order to obtain the above, it was difficult to obtain high-quality images due to uneven heat generation of the ink, but a flash light source having means for reducing at least part of the amount of light in the infrared wavelength range defined in the present invention was used. By applying this, high-quality images can be obtained.

[0066] In the present invention, as the two or more kinds of ultraviolet curable inks having different infrared absorption capabilities, for example, yellow dark ink, magenta dark ink, cyan dark ink, black ink, white ink, yellow Examples include light ink, magenta light ink, cyan light ink, orange ink, green ink, and transparent ink.

[Production method and characteristics of ultraviolet curable ink] In the method for producing an ultraviolet curable ink according to the present invention, a method for mixing a coloring material such as a dye or a pigment is not particularly limited. For example, the pigment is mixed with a pigment as a coloring material and polymerization as a medium. This is carried out by using a reactive compound, a solvent, a polymer dispersing agent or the like, further mixing necessary additives, and mixing and dispersing them. Examples of the mixing / dispersing apparatus include various mills such as the above-described ball mill and sand mill, and dispersing machines such as a homogenizer.

[0068] The ultraviolet curable ink according to the present invention has a viscosity at 25 ° C of 15 to 500 mPa's so that the dots are appropriately leveled on the recording medium after landing and to obtain adhesion. The surface tension is preferably in the range of 22 to 38 mNZm, more preferably in the range of 24 to 35 mNZm.

[0069] Further, it is preferable from the viewpoints of the power S for controlling the temperature by heating and ink jet recording so that the ink viscosity at the time of ink ejection is 6 to 20 mPa's.

[0070] The discharge conditions of the ultraviolet curable ink according to the present invention from the ink jet recording head include that the recording head and the ink are heated to 35 to 100 ° C, and the ink heated to that temperature range is discharged. It is preferable in terms of stability. For UV curable inks, the viscosity fluctuation range due to temperature fluctuations greatly affects the droplet size and droplet ejection speed, causing deterioration in image quality. Therefore, keep the temperature constant while raising the ink temperature. It is necessary. The control range of the ink temperature is set temperature ± 5 ° C, preferably set temperature ± 2 ° C, more preferably set temperature ± 1 ° C.

Further, in the present invention, it is preferable that the droplet volume force of the ink discharged from each nozzle of the ink jet recording head is from about 40 pl to 40 pl. In order to form a high-definition image, the ink droplet amount needs to be within this range.

[Recording medium]

As a recording medium that can be used in the ink jet recording method of the present invention, for example, a non-absorbent support can be used in addition to printing paper such as high-quality paper and coated paper. It is preferable to use a body.

[0073] In the present invention, various non-absorbable plastics and films thereof can be used as the non-absorbent support, and polyethylene plastic films can be used as the various plastic films. Taleate (PET), stretched polystyrene (OPS), stretched nylon (O Ny), stretched polypropylene (OPP), polyvinyl chloride (PVC), various polyolefin films, PE film, TAC finalem can be cited. Other plastics include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubber. It can also be applied to metals and glass. Among these recording materials, the configuration of the present invention is effective particularly when an image is formed on a PET film, a PS film, a PP PP film, a Ny film, or a PVC film that can be shrunk by heat. These recording media are not only susceptible to curling and deformation of the film due to the curing shrinkage of the ink and the heat generated during the curing reaction, but the ink film is difficult to follow the shrinkage of the recording medium.

[0074] In the ink jet recording method of the present invention, as the irradiation condition of the flash light in which the light amount in the infrared wavelength region according to the present invention is reduced, the flash light is irradiated between 0.001 and 2.0 seconds after ink landing. More preferably, it is 0.001 to 1.0 seconds. In order to prevent ink beading and bleeding on the recording medium and form a high-definition image, it is particularly important that the irradiation timing is as fast as possible. The flash light is preferably irradiated a plurality of times and sufficiently cured.

[0075] According to this, unnecessary heating is not performed on a member around the head, such as a recording medium or a platen, in a short time compared to a case where a light source such as a high-pressure mercury lamp is provided in the vicinity of the recording head unit. Efficient ink fixing can be performed in a short time. In addition, the flash light source according to the present invention has the advantage of being inexpensive and low in mass as compared with a high-pressure mercury lamp.

[Inkjet recording apparatus]

Next, an ink jet recording apparatus of the present invention (hereinafter simply referred to as a recording apparatus) will be described with reference to the drawings as appropriate. Note that the recording apparatus in the drawings is only one aspect of the recording apparatus that can be preferably used in the present invention, and the present invention is not limited to the drawing of the recording apparatus exemplified here.

FIG. 2 is a front view showing an example of a configuration of a main part used in the serial printing method in the ink jet recording apparatus that can be used in the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, a flash light source 4 as an irradiation means, a platen unit 5, and the like. In this recording apparatus 1, a platen unit 5 is installed under a recording medium 20. Flash light An infrared light cut filter 41 for reducing the amount of light in the infrared region, for example, a cold filter that reflects near infrared light and transmits light having a wavelength less than or equal to visible light, is installed on the front surface of the light emitting unit of source 4. Yes.

The platen unit 5 has a function of absorbing ultraviolet rays and absorbs excess ultraviolet rays that have passed through the recording medium 20. As a result, a high-definition image can be reproduced very stably.

The recording medium 20 is guided by the guide member 6 and moves from the near side to the far side in FIG. 2 by the operation of the conveying means (not shown). The head stroking means (not shown) performs stroking of the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

[0080] The head carriage 2 is installed on the upper side of the recording medium 20, and a plurality of recording heads 3 to be described later are arranged according to the number of colors used for image printing on the recording medium 20, and the discharge ports are arranged on the lower side. Pay. The head carriage 2 is installed with respect to a single recording apparatus so as to reciprocate in the Y direction in FIG. 2, and moves back and forth in the Y direction in FIG. 2 by driving the head scanning means.

[0081] In FIG. 2, the head carriage 2 draws the drawing as assuming that the recording head 3 of yellow (Y), magenta (M), cyan (C), and black (K) is housed. In this case, the number of colors of the recording head 3 housed in the head carriage 2 can be determined as appropriate.

[0082] The recording head 3 has a discharge port formed by an operation of a discharge means (not shown) provided with a plurality of ultraviolet curable inks according to the present invention supplied by an ink supply means (not shown). To the recording medium 20. The ultraviolet curable ink discharged from the recording head 3 contains a colorant and a photopolymerizable composition, and has a property of being cured by a polymerization reaction when irradiated with ultraviolet rays.

[0083] The recording head 3 moves from one end of the recording medium 20 to the other end of the recording medium 20 in the Y direction in FIG. The actinic ray curable ink is ejected as ink droplets to a certain region (landing possible region), and ink droplets are landed on the landing possible region.

[0084] After the above-described stroking is repeated as many times as necessary, actinic ray curable ink is ejected toward one landable area, and then the recording medium 20 is conveyed from the front to the back in FIG. While moving the head appropriately, the head scanning means scans again, and the recording head 3 discharges the actinic ray curable ink to the next landable area adjacent to the rearward direction in FIG. I do.

The above operation is repeated, and actinic ray curable ink is collected on the recording medium 20 by ejecting actinic ray curable ink from the recording head 3 in conjunction with the head running means and the conveying means. A body image is formed.

In the present invention, the flash light source 4 is preferably a flash lamp such as a xenon flash.

The flash light source 4 is fixedly installed on both sides of the head carriage 2 so as to be substantially parallel to the recording medium P. When ink is ejected from the recording head as the head carriage 2 travels in the Y direction (main travel), the ink droplets ejected onto the recording medium are on the opposite side of the carriage movement direction. It is cured by receiving flash light intermittently with the flash light source 4 of the above. The flash light intensity of the ink discharge portion can be adjusted by the distance between the flash light source 4 and the recording medium 20. Also, the timing of flash light irradiation can be adjusted by the distance between the recording head 3 and the flash light source 4.

[0088] Since the flash light source irradiates intermittently, the flash exposure width X flash cycle force or more (ie, the scanning distance (ink landing area) with respect to the distance that the recording head travels on the recording medium per unit time. ) At least once (can be covered with multiple flashes). Preferably 2 or more. This condition applies to serial, line, and drum recording methods.

[0089] In order to suppress the illuminance of the ink discharge section so that the ink is irradiated with flash light before landing on the recording medium and does not cure at that time, the entire recording head 3 is shielded from light, or further, In addition, the distance h2 between the ink ejection part 3 1 of the recording head 3 and the recording medium 20 is made larger than the distance hi between the flash light source and the recording medium 20 (hl <h2). It is effective to adjust by increasing the distance d (by increasing d). Further, a bellows structure 7 may be provided between the recording head 3 and the flash light source 4.

As described above, in the serial printing method, the ink ejected from the recording head is transferred from the flash light source 4 attached to the carriage by the carriage in the Y direction. The flash light is irradiated for 0 · 001 -2. 0 seconds, more preferably 0 · 001-1. 0 seconds. In order to form a high-definition image, it is important that the irradiation timing is as early as possible. In the case of high-speed printing (printing), sufficient irradiation energy that allows the carriage to move quickly is obtained. If not, adjust the flash timing, cycle, and flash exposure width (irradiation range in the main scanning width direction) to achieve multiple flashes.

As described above, in FIG. 2, in addition to the force described using the serial printing method as an example, it is possible to use the ink jet recording apparatus of each ink jet recording method as shown in FIG.

In FIG. 3, a) in FIG. 3 is a method in which the recording head 19 is arranged in the width direction of the recording medium 20 and the recording and the flash light source 24 irradiates flash light while transporting the recording medium. B) in FIG. 3 is a method in which the recording head 19 performs printing while moving in the secondary running direction, and further irradiates flash light from the flash light source 24 (flat head method). C) is a method in which the recording head 19 described above performs printing while scanning in the width direction on the recording medium, and the flash light source 24 provided at both ends irradiates flash light intermittently (serial printing method). V and displacement methods can also be used.

Example

[0093] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Unless otherwise specified in the text, “part” means “part by mass”.

[0094] Example 1

An inkjet ink was prepared according to the following.

[0095] << Preparation of inkjet ink >>

C. I. pigment Blue 15: 3 5 parts

43 parts of tetraethylene glycol ditalylate

ε-force prolatatam modified dipentaerythritol hexaatalylate 20 parts Phenoxetyl metaatalylate 30 parts

Polymerization initiator (Irgacure 907: manufactured by Ciba Gaigi Co., Ltd.) 2 parts

<Preparation of ink 2 (magenta)> CI pigment Red 57: 1 5 parts

43 parts of tetraethylene glycol ditalylate

ε-force prolatatam-modified dipentaerythritol hexaatalylate-20 parts Phenoxetyl metaatalylate-30 parts

C. I. pigment Yellow— 13 5 parts

43 parts of tetraethylene glycol ditalylate

Carbon black 5 parts

43 parts of tetraethylene glycol ditalylate

Polymerization initiator (Irgacure 907: manufactured by Ciba Gaigi Co., Ltd.) 2 parts Each of the produced inks 1 to 4 was mounted on the apparatus shown in FIG. 2 and a printing test was performed as follows. In the print test, using the inkjet recording head shown in Fig. 2 above, 4 drops of 4 pl droplets per cycle at a drive cycle of 4 kHz were set to express five gradations with a positive expression. A four-pass recording was performed at 720 dpi x 720 dpi (dpi is the number of dots per 2.54 cm). The ink flow path, ink chamber, and nozzle were heated by a heater and the ink liquid temperature was controlled at 55 ° C.

[0096] The recording medium used was Oupo SGG # 110 manufactured by Oji Oil Chemical Co., Ltd., and a thickness of 110 μm.

[0097] Further, after printing, the ink ejected from the recording head onto the recording medium in accordance with the movement of the carriage in the main running direction by the printing is sequentially and intermittently performed by the flash light source 4 (xenon flash lamp). Was irradiated. Carriage speed 500mm / s (main runner) The energy on the recording medium (per flash) is 3. Oj / cm ² , and the flash light source is driven with a flash emission time (half width) of 0.8 msec, frequency of 10 Hz, and flash exposure. The width (light source width) of 100 mm was used, and at the carriage main scanning speed, the flash exposure width X flash cycle was set to 2 with respect to the running distance per unit time of the recording head. (In short, the main run for the flash exposure width is performed in two flash cycles.)

At this time, a cold filter that cuts light of 700 nm or more is installed in front of the flash light source, and the ratio of the light quantity (A) with a wavelength of 250 to 450 nm and the light quantity (B) with a wavelength of 800 to lOOm (A / B) was set to 0.6, and compared with the image characteristics when the filter was not installed.

The following points were evaluated using the obtained print sump nore.

[0099] 《Ink bumping》

Observe the solid image part of the recording medium after printing with the naked eye, and mark X if the monomer volatile component is attached around the solid image part. Δ.

[0100] 《Curing sheet》

The solid image portion was visually observed. The solid image portion where the gloss did not deteriorate due to the curing stain was marked with ◯, the slightly visible portion was marked with Δ, and the clearly observed portion was marked with X.

[0101] 《Adhesion》

After attaching a 25 mm wide cello tape (registered trademark) on the surface of the solid image area and pressing it firmly, it was peeled off quickly at a peeling angle of 90 ° and observed for peeling.

◯: No image peeling

Δ: Slight peeling of image was observed

X: Image peeling was observed

Table 1 shows the evaluation results.

[0102] [Table 1]

[0103] Example 2

In addition, using inks 1 to 4 used in Example 1 and an ink jet recording apparatus, adjusting the transmittance of a cold filter that cuts light of 700 nm or more, the light quantity (A) with a wavelength of 250 to 450 nm and the wavelength The ratio (A / B) of light quantity (B) from 800 to 1 lOOnm was set to 0.4.

[0104] The results of the same evaluation as in Example 1 are shown.

[0105] [Table 2]

As is clear from Table 1 and Table 2 above, it can be seen that the light cut in the infrared region under the conditions specified in the present invention has good characteristics.

Claims

The scope of the claims

[1] An ink jet recording apparatus comprising a flash light source, comprising: means for reducing at least a part of light in an infrared wavelength region out of flash light emitted from the flash light source.

[2] The means for reducing the amount of light in the infrared wavelength range is a means for reducing the amount of light in the wavelength range of 800 to l lOOnm to 1/2 or less. Inkjet recording device.

[3] An inkjet recording method in which an ultraviolet curable ink is landed on a recording medium, and then cured and fixed using flash light generated by a flash light source, and the flash light has an infrared wavelength range. An ink jet recording method characterized in that at least a part of the amount of light is reduced.

[4] The inkjet recording method according to claim 3, wherein the amount of light in the flash light intensity of 800 to: lOOnm is reduced to 1/2 or less.

[5] The light intensity (B) of the flash light in the wavelength range from 800 to l lOOnm and the wavelength range from 250 to 4

5. The ink jet recording method according to claim 3, wherein the ratio (B / A) of light quantity (A) at 50 nm is smaller than 1/2.

6. The total content of water and water-soluble solvent in the ultraviolet curable ink is 5% by mass or less of the total mass of the ultraviolet curable ink. The inkjet recording method according to any one of the above.

7. The ink jet recording method according to any one of claims 3 to 6, wherein an image is formed using two or more kinds of ultraviolet curable inks having different infrared absorption capabilities.

[8] An ultraviolet curable ink, which is used in the ink jet recording method according to any one of claims 3 to 7, wherein

[9] The ultraviolet curable ink according to item 8, wherein the total content of water and water-soluble solvent is 5% by mass or less of the total mass of the ultraviolet curable ink.