JP4659633B2 - Photocurable ink curing method and inkjet recording method - Google Patents

Description

  The present invention relates to a photocurable ink curing method in which an acid in ink generated by light irradiation is cured by heating and diffusion, and an ink jet recording method.

  Inkjet recording printers that use UV ink to cure and fix ink on recording media by light irradiation can print on various recording media. It is expected as an ink jet recording apparatus. (For example, refer to Patent Document 1).

  The ink used here contains a large amount of carcinogenic components such as radical generators, and volatile acrylic acid derivatives used as radical polymerizable monomers have large skin irritation and odor. That is, such ink requires care in handling. Furthermore, radical polymerization is significantly hindered by the presence of oxygen in the air, and the pigment contained in the ink absorbs exposure light, so that the exposure amount tends to be insufficient in the deep part of the ink layer. . Therefore, the conventional radically polymerizable ink has low sensitivity to light. Therefore, in order to obtain a high-quality printed material with this technique, a very large exposure system is necessary. In addition, since general UV ink has a large shrinkage at the time of curing, a recording medium on which printing can be performed is often limited.

  On the other hand, the photo-cationic polymerizable photosensitive ink has relatively low odor and high safety, and is not affected by oxygen. In addition, this type of UV ink is expected to be able to print on various types of recording media because it has less shrinkage than radically polymerizable UV inks.

  In order to accelerate the curing of the ink layer, an ink jet recording apparatus provided with a heating means has been proposed for a recording apparatus using a photocationic polymerizable photosensitive ink (see, for example, Patent Document 2 and Patent Document 3). ). What is used here is a photocurable inkjet UV ink containing a photoacid generator that generates an acid upon irradiation with light, a color component, and a solvent that polymerizes in the presence of the acid. By heating, the acid as a catalyst diffuses into the ink layer, and the polymerization and curing of the ink is promoted. Such a recording apparatus must be provided with a separate heating means, but has an effect of being able to cure ink that has penetrated into the absorbent paper surface.

  However, such a photocationic curable ink-jet ink has a problem that it is easily affected by moisture at the molecular level due to the nature of the polymerization reaction.

  In particular, it is easily affected by the environment at the time of curing, such as humidity and temperature at the time of curing, and in a low temperature or high humidity environment, the polymerization reaction is deteriorated and is difficult to cure.

  Therefore, a recording apparatus (for example, refer to Patent Document 4) provided with means for controlling the ink temperature inside the recording head and the temperature of the recording medium, and a recording apparatus (for example, patents) provided with means for heating ink on the recording medium. Document 5) and those provided with a mechanism for controlling light irradiation and ink temperature are known (for example, see Patent Document 6).

As such a photocationic curable ink jet ink, one containing a vinyl ether compound is known (for example, see Patent Document 7).
JP 2001-310454 A JP 2002-137375 A Japanese Patent Laid-Open No. 2004-2668 JP 2004-34543 A JP 2004-25480 A JP 2004-90303 A JP 2005-154734 A

  As described above, the photocation curable ink has a smaller shrinkage than the radical UV ink using the radical polymerizable monomer, and can be printed on various recording media such as resin, metal, and glass. However, each recording medium has a difference in the mechanical state and chemical state of the surface. In order to print on recording media of different materials such as resin, metal, and glass, it is necessary to adjust and use inks having different properties according to the recording media.

  Although the UV inkjet recording method has a possibility of printing on various recording media, its characteristics are not fully utilized. In addition, the current situation is hindering the reduction of ink cost and the expansion of the market.

  In addition, an inkjet recording method that can form an ink layer having excellent adhesion using a photocurable ink, on a recording medium that is made of an inorganic material such as metal or glass and has a relatively smooth surface, has not yet been developed. Not obtained.

  Accordingly, an object of the present invention is to provide a photocurable ink curing method that can be printed on various recording media, particularly recording media made of metal, glass, and the like, and that provides an ink layer with excellent adhesion. .

  Another object of the present invention is to provide an ink jet recording method in which a photocurable ink is ejected by an ink jet method to form a good image including an ink layer having excellent adhesion.

A photocurable ink curing method according to an aspect of the present invention includes a vinyl ether compound represented by the following chemical formula, a solvent that polymerizes in the presence of an acid, and a photoacid generator that generates an acid by light irradiation: And a step of adhering a photocurable ink containing a color component on a recording medium having at least a surface made of metal, glass or earthenware to form an ink layer;
The ink layer is irradiated with light having a wavelength absorbed by the photoacid generator at a light amount of 300 mJ / cm ² or less to generate an acid from the photoacid generator in the ink layer, and thereby the ink layer. A light irradiation process for curing a part;
Reduces the viscosity of the ink below the ink layer after the light irradiation, promotes the diffusion of the acid generated by the light irradiation into the ink layer, promotes the curing of the ink layer, and has no other substances at the interface And heating the recording medium on which the ink layer is formed so that the ink layer is in close contact with the recording medium,
In the light irradiation step, when another recording medium is stacked on the recording medium on which the ink layer is formed immediately after the light irradiation , light irradiation is performed in a range where the ink layer is not transferred to the other recording medium. ,
In the heating step, the ink layer is heated together with the recording medium with a heat amount of at least 50 J / cm ³ .

  An ink jet recording method according to an aspect of the present invention is a method of performing recording by ejecting a photocurable ink onto a recording medium by an ink jet method, and performing the recording. It is performed by

  According to one embodiment of the present invention, a method for curing a photocurable ink that provides an ink layer with excellent adhesion is provided. According to another aspect of the present invention, there is provided an ink jet recording method in which a photocurable ink is ejected by an ink jet method to form a good image including an ink layer having excellent adhesion.

  Embodiments of the present invention will be described below.

  In the method for curing a photocurable ink according to an embodiment of the present invention, a solvent containing at least one compound having a vinyl ether group, which is polymerized in the presence of an acid, and a photoacid generator that generates an acid by light irradiation. And a photocurable ink containing a color component. The image forming ability of such ink depends on the chemical amplification mechanism. First, an acid is generated from the photoacid generator by irradiation with light such as ultraviolet rays, and this acid diffuses by heating and functions as a catalyst for the crosslinking reaction.

  The ultraviolet rays irradiated here include wavelengths absorbed by the photoacid generator. When the acid diffuses, for example, the acid spreads to a portion where light does not reach due to the influence of a coloring material or the like and the acid is not generated, and curing is promoted in a wide range.

  Further, in the process of curing, the photocation curable ink tends to be affected by the atmospheric environment such as temperature and humidity during the curing process. Therefore, if the atmospheric environment in the vicinity of the ink is optimally controlled to reduce the influence on the curing characteristics, the curing can be promoted more stably.

  However, in order to optimally control the atmospheric environment in the vicinity of the ink when it is cured, there are problems such as a complicated process and an increase in size.

  In particular, in the ink jet recording method according to the embodiment of the present invention, it is desired that the ink is adjusted to a predetermined viscosity in order to stably eject the ink. For example, the viscosity at 25 ° C. is preferably 50 mPa · s or less, and more preferably 30 mPa · s or less.

  In the photocurable ink used in the method according to the embodiment of the present invention, the solvent that polymerizes in the presence of an acid (acid-polymerizable solvent) specifically includes an alicyclic in addition to a compound having a vinyl ether group. At least one selected from the group consisting of an epoxy compound containing a formula skeleton and / or an aliphatic skeleton, an oxirane group-containing compound, and an oxetane ring-containing compound can be used. In particular, an acid-polymerizable compound having an alicyclic skeleton and / or an aliphatic skeleton having a viscosity of 50 mPa · s or less at normal temperature and normal pressure and a boiling point of 100 ° C. or higher is preferable as the acid-polymerizable solvent.

In particular, any compound represented by the following chemical formula is preferred as the acid polymerizable solvent. Such a compound has extremely low mutagenicity by the AMES test, high safety, excellent adhesion to various recording media, particularly metal-based recording media, and excellent properties in that it has high curing hardness. Has been found by the present inventors.

  Examples of photoacid generators that generate acid upon irradiation with light include onium salts, diazonium salts, quinonediazide compounds, organic halides, aromatic sulfonate compounds, bisulfone compounds, sulfonyl compounds, sulfonate compounds, sulfonium compounds, sulfamide compounds, An iodonium compound, a sulfonyldiazomethane compound, a mixture thereof, or the like can be used.

  The photoacid generator is usually used at a ratio of about 0.5 to 10 parts by weight with respect to 100 parts by weight of the acid-polymerizable solvent. In the case of a 1: 1 mixture with polycarbonate or the like, it is used at a ratio of about 1 to 20 parts by weight with respect to 100 parts by weight of the acid-polymerizable solvent. The blending amount of the photoacid generator is more preferably about 1 part by weight or more and 12 parts by weight or less with respect to 100 parts by weight of the acid polymerizable solvent.

  In addition to the components described above, the photocurable ink used in the embodiment of the present invention contains a color component. As the color component, a pigment can be used, and either organic or inorganic may be used. The blending amount of the color component is usually about 0 to 20 parts by weight with respect to 100 parts by weight of the acid polymerizable solvent. A more preferable amount of the color component is about 3 parts by weight or more and 6 parts by weight or less with respect to 100 parts by weight of the acid polymerizable compound. In particular, when ultraviolet rays having a peak near 250 nm or 365 nm are used for light irradiation, the photocurable ink has a pigment content of 3 to 20 parts by weight with respect to 100 parts by weight of the solvent polymerized in the presence of an acid. It is preferable to contain as.

  A photocurable ink used in the method according to the embodiment of the present invention is obtained by uniformly mixing predetermined components and filtering the mixture using a PTFE filter or the like.

  Next, a method according to an embodiment of the present invention will be described with reference to the drawings, taking as an example a photocuring ink curing method using an ink jet recording apparatus.

  FIG. 1 is a diagram schematically showing an ink jet recording apparatus according to an embodiment of the present invention. The ink jet recording apparatus 1 includes a transport unit 3 that transports a recording medium 2. At least the recording medium temperature adjusting means 7, the ink jet recording head 4, the light irradiation means 5, and the heating means 6 are sequentially arranged from the upstream side to the downstream side along the moving direction of the conveying means 3. In the illustrated inkjet recording apparatus 1, the recording medium preheating stocker 16 that accommodates the recording medium 2 is provided in the front stage of the transport unit 3, but the configuration is not necessarily limited thereto. In some cases, the recording medium preheating stocker 16 can be omitted together with the recording medium temperature adjusting means 7 for preheating the recording medium 2 as shown in FIG.

  The recording medium 2 is not particularly limited as long as it is a base material (recording medium) that can be printed with photocurable ink. For example, paper, wood, OHP sheet, resin film, non-woven fabric, porous film, plastic board, circuit board, metal board, metal board, glass board, ceramic board, and ceramics such as tile are used as the recording medium 2 can do. The recording medium 2 may be configured by a combination of these materials. For example, a structure in which a resin is laminated on a metal plate, an enamel coated with glass on an iron plate, and the like can be given.

  Further, the recording medium 2 is not limited to a flat plate as illustrated, and may be a three-dimensional shape.

  The conveying unit 3 conveys the recording medium 2 so that the recording medium 2 sequentially passes through the front of the recording medium temperature adjusting unit 7, the inkjet recording head 4, the light irradiation unit 5, and the heating unit 6. In the inkjet recording apparatus 1 shown in the figure, the conveying means 3 conveys the recording medium 2 from the right side to the left side in the drawing. The transport unit 3 can be configured by, for example, a belt and / or roller that moves the recording medium 2 and a drive mechanism (not shown) that drives the belt. Further, the conveying means 3 may further be provided with a guide member for assisting the movement of the recording medium 2. Alternatively, the transport means 3 may have a stage structure that slides on a linear base that transports the single-sheet recording medium 2.

  The ink jet recording head 4 ejects photocurable ink onto the recording medium 2 in response to the image signal to form an ink layer. As the inkjet recording head 4, for example, a serial scanning inkjet head mounted on a carriage or a line scanning inkjet head having a width equal to or larger than the width of the recording medium 2 can be used. From the viewpoint of high-speed printing, the latter is usually more advantageous than the former. Further, the inkjet recording head 4 may be provided with a plurality of monochrome or multicolored units. The method for discharging the photocurable ink from the inkjet recording head 4 is not particularly limited. For example, it is possible to employ a technique in which ink droplets are ejected using the pressure of vapor generated by the heat of the heating element. Alternatively, ink droplets may be ejected using mechanical pressure pulses generated by a piezoelectric element.

  The ink layer is desirably formed on the recording medium 2 with a film thickness of 20 μm or less. If the thickness of the ink layer exceeds 20 μm, the generation of acid by the light of the light irradiation means and the diffusion of the acid by the heating means become insufficient, which may cause a problem that uncured portions are generated inside the ink layer.

  The light irradiation means 5 irradiates the ink layer on the recording medium 2 with light to generate an acid in the ink layer. The acid thus generated initiates polymerization of the acid polymerizable solvent, and a part of the ink layer is cured. Examples of the light irradiation means 5 include mercury lamps such as low, medium and high pressure mercury lamps, tungsten lamps, xenon lamps, arc lamps, excimer lamps, excimer lasers, semiconductor lasers, YAG lasers, lasers and nonlinear optical crystals. A combined laser system, a high frequency induced ultraviolet ray generator, an electron beam irradiation device, an X-ray irradiation device, an ultraviolet LED lamp, or the like can be used. Among them, it is desirable to use a high-frequency induced ultraviolet ray generator, a high / low pressure mercury lamp, a semiconductor laser, or the like because it has high output and high efficiency and can simplify the system. The wavelength when ultraviolet rays are used is preferably about 100 nm to 600 nm. The light output from the light irradiation means 5 is not limited to ultraviolet rays. It can be suitably selected according to the sensitivity wavelength of the photoacid generator contained in the photocurable ink. In particular, it is more preferable to have a peak in the vicinity of 250 nm or 365 nm. Further, the light irradiating means 5 may be provided with a condensing mirror or a running optical system.

In the curing method according to the embodiment of the present invention, the recording medium on which the ink layer is formed is irradiated with light having a light quantity of at least 50 mJ / cm ² . The light quantity here is a value measured by a illuminometer UVR-T1 (sensor unit: UD-T36) manufactured by Topcon Corporation. Since the generation of the acid necessary for curing the ink layer becomes insufficient, the lower limit of the light amount is defined as 50 mJ / cm ² . When the amount of exposure light is too large, acid is rapidly generated near the surface of the ink layer, and the vicinity of the surface is initially completely cured. In this case, even if it is subsequently heated, the diffusion of the acid is insufficient, and as a result, there is a risk of poor curing. In order to avoid this, it is desirable that the amount of light applied to the ink layer is limited to about 300 mJ / cm ² at the maximum.

  In addition, the recording medium on which the ink layer is formed is also supplied with heat together with the amount of light as described above, whereby the recording medium is heated together with the ink layer. As a result, the temperature of the ink layer is raised higher than the initial temperature (the temperature immediately before light irradiation).

  The heating means 6 heats the ink layer on the recording medium 2 and promotes a crosslinking reaction using an acid generated in the ink layer by light irradiation as a catalyst. For example, an infrared lamp, a (far-infrared) halogen heater, a far-infrared ceramic heater, a roller (heat roller) incorporating a heating element, an IH heater, a blower that blows hot air or hot air, and the like can be used. Examples of the far infrared ceramic heater include a far infrared ceramic heater PLC-32 series manufactured by Noritake Company Limited. In particular, in a high-speed printing apparatus with a printing speed of several tens of m / min, when a metal recording medium such as stainless steel, aluminum, or copper is used, the surface temperature of the recording medium may be increased instantaneously. desired. This can be achieved by using a non-contact type condensing halogen heater, for example, a halogen line heater condensing type NIL-2 manufactured by Infridge Industries Co., Ltd.

In particular, in the method according to the embodiment of the present invention, the ink layer is heated with a heat amount of at least 50 J / cm ³ before the temperature of the ink layer returns to the initial temperature. When the temperature of the ink layer returns to the initial temperature, it is necessary to increase the heating amount by the heating means. Further, it is disadvantageous in that the diffusion of the acid proceeding inside the ink layer is not performed smoothly, resulting in poor curing. The amount of heat for heating can be set to 50 J / cm ³ or more by changing conditions such as temperature, time, and output of the heating means.

  It is desirable to perform heating under optimum conditions by selecting temperature and time according to the material of the recording medium. For example, in the case of a recording medium made of resin such as PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), and acrylic, the heating may be performed at a temperature of at least 60 ° C. for at least 1 minute. In the case of a recording medium made of metal such as stainless steel, aluminum, copper, or brass, heating at a temperature of at least 80 ° C. for at least 5 minutes is preferable. Alternatively, the heating may be performed at a temperature of at least 120 ° C. for at least 1 minute. Furthermore, in the case of glass / ceramic recording media such as tiles, ceramics, and stones, heating can be performed at a temperature of at least 100 ° C. for at least 5 minutes, or at least at a temperature of 120 ° C. for at least 1 minute.

In the case of a recording medium made of any material, heating is performed with a heat quantity of at least 50 J / cm ³ . Needless to say, when the amount of heat of heating is less than 50 J / cm ³ , the diffusion of the acid generated by the light of the light irradiating means becomes insufficient, and the adhesion state of the interface between the recording medium surface and the ink layer is insufficient. It becomes. As a result, the present inventors have found that the adhesiveness with the recording medium after curing is affected. Therefore, in the embodiment of the present invention, the amount of heat after exposure is specified to be 50 J / cm ³ or more.

For example, in the case of a recording medium having a laminated structure of two or more materials, the temperature and time are appropriately set so that heating is performed with a heat quantity of at least 50 J / cm ³ in consideration of the thickness and specific heat of each material. Just choose.

  FIG. 3 shows a cross-sectional view of an example of a halogen heater that can be used. As shown in the drawing, the halogen heater 22 is housed in a housing 21 with the periphery covered by a reflecting plate 23. A focal point 24 exists at a predetermined position below the halogen heater 22 and is focused here. Therefore, it is desirable to set the distance at which the halogen heater is disposed so that the recording medium 2 passes through the focal point 24.

  As shown in FIG. 1, the recording medium temperature adjusting means 7 can be arranged on either the lower or upper side of the conveying means 3 or on both the upper and lower sides. Further, either a fixed type or a movable type may be used, and further, either a contact type or a non-contact type may be used. For example, an infrared lamp, a (far-infrared) halogen heater, a far-infrared ceramic heater, a roller (heat roller) with a built-in heating element, an IH heater, and a blower that blows hot air or hot air are used as the recording medium temperature adjusting means 7. can do.

  In preheating the recording medium 2, it is not always necessary to provide the recording medium temperature adjusting means 7 in the ink jet recording apparatus 1. For example, as shown in FIG. 1, the recording medium preheating stocker 16 can be provided in the front stage of the conveying means 3 of the inkjet recording apparatus 1. The recording medium 2 accommodated in the recording medium preheating stocker 16 is preheated at a predetermined temperature (batch type preliminarily) by a heating means (not shown) equipped in the recording medium preheating stocker 16. After being heated, it is transported by the transport means 3. Such a technique is particularly effective when recording on the recording medium 2 having a large heat capacity and in which the surface temperature is unlikely to decrease instantaneously. Examples of such a recording medium include a metal having a high density or specific gravity or a material having a large volume such as a thickness.

  In any case, the recording medium temperature adjusting means 7 preheats the recording medium 2 conveyed by the conveying means 3 and raises the recording medium 2 to a predetermined temperature before reaching the inkjet recording head 4. Let me. Furthermore, the effect that the heating of the ink layer on the recording medium 2 by the heating means 6 is promoted by preheating the recording medium 2 is also obtained.

  A method for printing (image formation) on the recording medium 2 using the inkjet recording apparatus 1 shown in FIG. 1 will be described in detail below.

  First, the recording medium 2 is conveyed from the right side to the left side in the drawing by the conveying unit 3. The conveyance speed of the recording medium 2 is appropriately selected according to the purpose of use and is controlled within a range of, for example, about several tens of m / min. When the recording medium 2 is conveyed, the recording medium 2 is preheated by the recording medium temperature adjusting means 7 disposed above or below the conveying means 3 according to the material, thickness, and the like. The range of preliminary heating by the recording medium temperature adjusting means 7 can be up to the vicinity of the position where an image is formed by the inkjet recording head 4. Alternatively, as shown in FIG. 1, preliminary heating may be performed by the recording medium temperature adjusting unit 7 up to a position near the heating unit 6 irradiated with light such as ultraviolet rays by the light irradiation unit 5. However, depending on the type of the recording medium 2 or the conditions for curing, there is no need for preheating.

  When the recording medium 2 is preheated, the specific range includes the curing sensitivity of the photocurable ink, the conveyance speed of the recording medium 2 (moving speed of the printing surface), and the type (material, thickness) of the recording medium 2. Etc.) can be set as appropriate. However, it is desirable that the temperature of the recording medium 2 when reaching the inkjet recording head 4 is higher than the temperature of the ink ejected from the inkjet recording head 4. The temperature of the ink ejected from the inkjet recording head 4 is usually about 20 to 60 ° C. When the temperature of the recording medium 2 is the same as or lower than the temperature of the ink, the temperature of the ink ejected to the recording medium is lowered. Also, the heat of the ink tends to escape. In either case, it is difficult to cure the ink layer efficiently. For this reason, the optimum irradiation conditions necessary for curing the ink by light irradiation are limited to a narrow range.

  The preheating temperature of the recording medium 2 to be conveyed may be set to a temperature that does not hinder the effect of heating by the heating means 6 to be described later or cause image deterioration. This temperature is desirably high as long as it does not cause deformation of the recording medium 2. It is required that the heat radiated from the light irradiation means 5 is efficiently given to the ink without being taken away by the transport means 3 of the recording medium 2 or the like. It is preferable that the acid generated by the exposure is sufficiently diffused to the deep part of the ink layer and heated to a temperature at which uniform curing is possible before the light irradiation is performed. Accordingly, the recording medium 2 is preheated to the extent that heating after light irradiation is not required. The preheating of the recording medium 2 is also required to be performed within a range in which an acid necessary for curing can be sufficiently diffused to the deep part of the ink layer to achieve an effect that enables uniform curing. Actually, it is desirable to test the ink curing characteristics by conducting experiments in advance and to set the preheating conditions. Specifically, although it depends on the composition of the ink, the ink temperature, the material of the recording medium, and the like, it can be within a range of 35 to 120 ° C., more preferably about 50 to 70 ° C.

  With such a configuration, when the recording medium 2 is conveyed to the front of the recording head 4, the inkjet recording head 4 ejects photocurable ink corresponding to the image signal. As a result, an ink layer is formed on the recording medium 2.

The recording medium 2 on which the ink layer is formed is conveyed to the front of the light irradiation means 5. When the recording medium 2 passes through the front of the light irradiation means 5, the light irradiation means 5 emits light toward the ink layer to generate an acid in the ink layer. The irradiation light intensity at the position of the ink layer surface varies depending on the wavelength of the light source used, but is usually in the range of several mW / cm ^{2 to} 10 W / cm ² . The irradiation light intensity is preferably in the range of about several tens of mW / cm ^{2 to 5} W / cm ² . The exposure amount to the ink layer can be appropriately set according to the sensitivity of the ink, the conveyance speed of the recording medium 2 (moving speed of the printing surface), and the like.

  Subsequently, the recording medium 2 is conveyed into or near the heating means 6. When the recording medium 2 passes through or in the vicinity of the heating unit 6, the heating unit 6 heats the ink layer formed on the recording medium 2 and promotes a crosslinking reaction in the ink layer. In the ink jet recording apparatus 1 shown in FIG. 1, the heating time by the heating means 6 is usually 0. It is relatively short, from several seconds to several tens of seconds. Therefore, when the ink layer is cured almost completely by the heating means 6, the heating is performed so that the maximum temperature reaches a relatively high temperature of, for example, about 200 ° C. or less, particularly about 80 ° C. to 200 ° C. Is desired. Or it is good also as a temperature range of about 60 degreeC-180 degreeC depending on the kind of ink.

  When the printing speed or the conveyance speed of the recording medium 2 is slow, the heating means 6 may have a heating tunnel-like configuration such as a furnace for the purpose of increasing the heating time.

  As described above, when heating is performed by the heating unit 6, sufficient acid necessary for curing the ink is generated from the photoacid generator in the ink layer. Heating can promote efficient and uniform diffusion of the acid thus generated in the ink layer and promote curing. Furthermore, the viscosity of the lower part of the ink layer is reduced by heating, so that the ink layer is in close contact with the recording medium without the intervention of other substances. That is, since there is no other substance such as air between the ink layer and the recording medium, they are completely in contact with each other, leading to improved adhesion.

  Thereafter, the recording medium 2 is conveyed into a stocker (or container) (not shown). This completes printing.

  The heating means 6 for heating the ink layer is not limited to the heating means 6 disposed downstream of the light irradiation means 5 as shown in FIGS. In the ink jet recording apparatus 1 shown in FIGS. 1 and 2, since the heating means 6 is disposed in the middle of the conveyance path of the recording medium 2, it is difficult to heat each recording medium 2 for a long time. In order to heat the recording medium 2 for a long time, the recording medium after exposure may be accommodated and heated together. In this case, for example, a stocker 15 provided with a heater (not shown) as shown in FIG. 4 can be used. In the apparatus 1 shown in FIG. 4, since the stocker 15 has a built-in heater, the recording medium 2 after exposure can be accommodated and batch-type heating can be performed collectively. In addition, since a plurality of recording media 2 can be heated together in the stocker 15, it is advantageous from the viewpoint of power consumption. Furthermore, when the individual recording media 2 can be heated for a long time, the following points are also advantageous.

  That is, depending on the combination of the recording medium 2 and the inkjet ink to be used, reflowing may proceed and the image quality may be degraded by the method of heating at a high temperature for a short time. Such a decrease in image quality is caused by reflowing at a high temperature, and can be prevented by heating the ink layer at a relatively low temperature for a long time. For example, by holding the exposed recording medium 2 in the stocker 15 at about 50 ° C. to 80 ° C. for several minutes or more, the ink layer can be almost completely cured without causing deterioration in image quality.

  The stocker 15 is preferably provided with a discharge mechanism for sequentially discharging the recording medium 2 held in a heated state for a predetermined time. The heating and holding time can be set according to the photocurable ink to be used, the heating temperature, and the like. For example, when the heating temperature is about 80 ° C. to 180 ° C., 0.5 to 20 minutes. It is sufficient to hold the degree. Depending on the type of ink and the type of the recording medium 2, the heating temperature can be set to about 60 ° C. to 160 ° C. even with the same holding time. When the recording medium accommodated in the stocker 15 is held for several hours, heating with a heater can be omitted.

  Alternatively, when the ink layer is exposed, the light irradiation means 5 may be used as a heat source by bringing the light irradiation means 5 close to the recording medium 2 without damaging the printing surface. The light source may be used as a heat source by not providing the light source with a heat removal mechanism such as a cold mirror. In the case of a high-power bulb (lamp) of several hundred watts, it has a cooling mechanism at the same time. Therefore, a mechanism for intentionally reducing the heat to the recording medium 2 by changing a part of the exhaust heat mechanism is provided. Provided (not shown). Thereby, the ink layer can be heated by the heat generated from the light irradiation means 5.

  More specifically, the light irradiation means 5 having an output of 100 watts or more having a mechanism used for heating by re-introducing the airflow having cooled the light irradiation means 5 into the recording medium 2 or the transport / holding mechanism corresponds to this. . The temperature reached by the recording medium 2 due to the reduction of the heat of the light irradiation means 5 may be a temperature at which the same effect as the heating by the heating means 6 described above is obtained. The preferred temperature varies depending on the heating time, but is usually at least 60 ° C or higher, more preferably 80 ° C to 150 ° C. Further, when the exposure speed is as high as several meters / second, since it is heated instantaneously, the temperature may be as high as about 180 ° C.

  As described above, when a plurality of exposed recording media are accommodated in the stocker 15 and batch-type heating is performed, the recording media on which the ink layer is formed are stacked. The layer will be in contact with the back side of the recording medium above it. At this time, it is desirable that the ink does not transfer (transfer) to the back surface of the recording medium. For this reason, in the light irradiation step, light is irradiated until the ink layer becomes tack-free and temporarily cured.

  For example, when a light irradiation means 5 that can generate infrared light in addition to visible light is used, heating can be performed simultaneously with the light irradiation. In this case, since hardening can be accelerated | stimulated, it is preferable.

  In the method for curing a photocurable ink according to an embodiment of the present invention, a photoacid generation that includes at least one compound having a vinyl ether group, polymerizes in the presence of an acid, and generates an acid by light irradiation. A photocurable ink containing an agent and a color component is attached onto a recording medium to form an ink layer. The ink layer thus formed is irradiated with light containing a wavelength that is absorbed by the photoacid generator, and an acid is generated from the photoacid generator in the ink layer to cure a part of the ink layer. After the light irradiation, the ink viscosity of the ink layer is decreased, the acid generated by the light irradiation is promoted to diffuse into the ink layer to promote the curing of the ink layer, and the ink layer is formed without any other substances. The recording medium on which the ink layer is formed is heated so as to be in close contact with the recording medium.

In the light irradiation step, heat is applied to the recording medium together with a light amount of at least 50 mJ / cm ² , whereby the ink layer is heated together with the recording medium, and the temperature of the ink layer is raised from the initial temperature. In the heating step, the recording medium on which the ink layer is formed is heated with a heat amount of at least 50 J / cm ³ before the temperature of the ink layer thus increased returns to the initial temperature. In the light irradiation step, light irradiation is performed until the ink layer formed on the recording medium is tack-free. In the heating step, the heat amount of the ink layer together with the recording medium is at least 50 J / cm ³ . Is heated.

After the light irradiation satisfying the predetermined condition, the ink layer is heated together with the recording medium with a heat amount of at least 50 J / cm ³ , so that the mechanical state of the surface is changed by the method according to the embodiment of the present invention. It has become possible to form printed images made of a cured product having excellent curability and adhesion on various recording media having different chemical states.

  Further, since high-quality printing can be performed on various recording media of different materials, according to the curing method according to the embodiment of the present invention, a single ink can be used for various purposes. Furthermore, since the amount used can be increased, there is an effect that cost reduction and market expansion can be expected.

  As described above, the method according to the embodiment of the present invention can be applied to inkjet printing expected in the future such as various printing apparatuses, particularly on-demand and variable printing apparatuses, and forms high-quality printed images. Can offer to do.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to specific examples.

A photocurable ink was prepared and its curing characteristics were examined. In preparing the ink, an epoxy compound, an oxetane compound, and a vinyl ether compound as shown below were mixed at a blending ratio (weight ratio) described in Table 1 below to obtain acid-polymerizable compositions a to m.

The epoxy compound (C3000, SR-NPG) used is shown in the following chemical formula.

  Celoxide 3000 is (manufactured by Daicel Chemical Industries), and SR-NPG is (manufactured by Sakamoto Pharmaceutical).

The oxetane compounds (OXT-221 and OXT-211) used are shown in the following chemical formula.

  Both OXT-221 and OXT-211 are (manufactured by Toagosei Co., Ltd.).

The vinyl ether compounds (DVE3, ISB-DVE, ONB-DVE) used are shown in the following chemical formula.

  DVE-3 is (manufactured by ISP), and ISB-DVE and ONB-DVE are (manufactured by Daicel Chemical Industries).

  Carbon black coloring matter (black pigment) as a color component was kneaded with an acrylic resin in an amount corresponding to 5% by weight to form a mill base. Along with this mill base, 200 ppm of a nonionic surfactant (manufactured by Sumitomo 3M) and a commercially available dispersant (manufactured by Ajinomoto Fine-Techno, product name Ajisper) were added to the acid-polymerizable composition a.

Further, 8% by weight of UVACURE1591 (manufactured by Daicel UCB) as a photoacid generator was added. This photoacid generator is a propylene carbonate solution containing a sulfonium salt at a concentration of 50% by weight, and is obtained by dissolving two types of compounds (PAG1 and PAG2) represented by the following chemical formula in an equal amount of propylene carbonate. It is a solution.

Next, for the purpose of increasing the photosensitivity of the photoacid generator, a sensitizer was added at a ratio of 35% by weight to 100% by weight of the photoacid generator. As a sensitizer, ANTHRACURE UVS-1331 manufactured by Kawasaki Chemical Industry Co., Ltd. was used. Its structure is shown in the chemical formula below.

  Thereafter, these mixtures were dispersed with a paint shaker all day and night, and the mixture after dispersion treatment was filtered with a 5 μm PTFE filter. 1 was obtained. Further, the photocurable ink No. 1 was used in the same manner as described above except that each of the acid polymerizable compositions b to m was used. 2-13 were obtained.

  Using the inkjet recording apparatus 1 shown in FIG. 1 to 13 were printed, and their curing characteristics (pencil hardness of the ink cured film, adhesion to the recording medium by cross-cutting, solvent resistance by ethanol) were examined.

  Each member of the inkjet recording apparatus 1 was prepared as follows. As the conveying means 3, a metal endless belt having high heat resistance and low heat capacity was used, and was arranged in a state where tension was applied between a driving roller and a driven roller. The recording head 4 is a CB1 inkjet recording head manufactured by Toshiba Tec Corporation, and the light irradiation means 5 is a UV irradiation system LH-6 (D bulb: peak wavelength 350 nm, manufactured by Fusion UV Systems Japan Co., Ltd.). ~ 390nm) was used. As the heating means 6, a far infrared ceramic heater PLC-32 series manufactured by Noritake Company Limited was used.

  Moreover, the batch-type heating means 6 provided with the heater in the stocker 15 was produced with the following configuration. Inside, a hot plate EC-1200 (manufactured by ASONE) was provided. The wall of the box-shaped heating stocker was covered with a resin wall with urethane foam attached inside. By using a highly heat-insulating material such as urethane foam, it is possible to reduce heat released to the surroundings as much as possible. The heater temperature was set by a controller built in the hot plate. For the temperature measurement, DIGITAL SURFACE THERMOMETER HL-20 manufactured by Anritsu Keiki Co., Ltd. was used. The recording medium temperature adjusting means 7 is a means for carrying a silicon rubber heater manufactured by OM Heater Co., Ltd. on a heat-resistant resin plate-like member having a low thermal conductivity, such as a POM board, from the paper feeding position to the light irradiation means 5 position. 3 was placed close to the bottom.

  The printing conditions for all samples were as follows.

The resolution of the inkjet recording head 4 was 300 dpi, and the ink discharge volume per nozzle was 42 pl. At this time, the thickness of the ink layer on the recording medium 2 is about 5 μm. The ink film thickness was changed depending on the number of inkjet recording heads 4. For example, when there are two inkjet recording heads 4, the ink film thickness is about 10 μm, when three are about 15 μm, and when four are four, it is about 20 μm.
The printing speed (conveying speed of the belt that is the recording medium conveying means 3) was 25 m / min.

The change of the output of the light irradiation means 5 was adjusted by an output adjustment knob (volume) attached to the UV irradiation system LH-6 manufactured by Fusion UV Systems Japan. The amount of irradiation light was adjusted in the range of approximately 5 mJ / cm ^{2 to} 250 mJ / cm ² .

  The irradiation output (ultraviolet illuminance) was measured using a UV intensity meter (industrial UV checker UVR-T1: (sensor unit: UD-T36)) manufactured by Topcon Corporation. In the following, the same ultraviolet intensity meter is used for measuring the light quantity.

  When the recording medium 2 was preheated using the recording medium preliminary temperature adjusting means 7, the heating temperature was 60 ° C. This was also performed when no preheating was performed. The heating temperature (recording medium temperature) by the heating means 5 was adjusted in the range of 60 ° C to 160 ° C.

  Under the conditions described above, the photocurable ink was printed on various recording media and cured to form a printed image made of a cured product. The printed image was a solid image having an area of 2 cm × 10 cm. About the obtained hardened | cured material, sclerosis | hardenability (hardness), adhesiveness, solvent resistance, etc. were investigated and the hardening characteristic was evaluated.

  As the recording medium 2, PET, PP, PE, acrylic, stainless steel plate, aluminum plate, copper plate, and glass plate having a thickness of 100 μm (= 0.01 cm) were prepared.

  In addition, tiles having a thickness of 3 mm, ceramic plates, and stone materials were also prepared.

  The curability (hardness) of the printed image was measured according to Japanese Industrial Standard JIS K5600-5-4 scratch hardness (pencil method) (using pencils 2B to 3H manufactured by MITSU-BISHI) and was as follows. Judgment was made in five stages of A, B, C, D, and E.

A: 2H or more B: H and F
C: HB
D: B
E: 2B or less If curability is B or more, it is a pass range.

  The adhesion of the printed image was measured according to the Japanese Industrial Standard JIS K5600-5-6 adhesion (cross-cut method) and evaluated with reference to an adhesion test which is a mechanical property of the cured film. Specifically, the cured product formed on the recording medium 2 is scratched in a grid pattern at intervals of about 1 mm using a cutter knife so that only the cured product is damaged. At this time, care is taken so that scratches do not reach the recording medium 2. Then, the adhesive tape is attached so as to be in close contact with the object, and thereafter, the attached adhesive tape is peeled off while being pulled in a direction of about 45 ° with respect to the object surface, and both the adhesive tape side and the recording medium 2 side are removed. The state of was evaluated. At this time, 3M Scotch clear tape CP-18 was used as the adhesive tape.

  The result of the test was determined in 6 stages of classification 0-5 according to JIS K5600-5-6.

  In the cross-cut tape peeling test, the adhesion was examined by the ratio of the area where the cured film was peeled off, and evaluated according to the following criteria.

A: Very good (classification 0 to 1; peeled area is less than 5% of the whole)
B: Good (Class 2; Peeled area is less than 15% of the total)
C: Slightly poor (Category 3; peeled area is less than 35% of the total)
D: Defect (classification 4-5)
If adhesion is B or more, it is a pass range.

  Regarding the solvent resistance of the printed image, the ink layer surface cured on the recording medium 2 is rubbed 100 times with a cotton swab soaked in ethanol 100 times, and the state of the ink cured film surface after rubbing is evaluated. The determination was made in the following five stages.

A: Extremely good (no change)
B: Good (slightly changed)
C: Slightly defective (slight peeling was seen)
D: Pretty bad (peeled off)
E: Defect (all peeled off)
If solvent resistance is B or more, it is an acceptable range.

  Here, the tack-free property will be described. Tack-free refers to a state in which, even if another recording medium is overlaid immediately after light irradiation, the photocurable ink is not transferred to the back of the stacked recording medium.

  The degree of tack-free property was determined according to the following criteria.

      A: Tack free: No change in the ink layer even when rubbed lightly with Kimwipe 5 times.

B: Slightly tack-free: the ink layer becomes thin when rubbed lightly 5 times with Kimwipe C: Not tack-free ... When rubbed once with Kimwipe, the ink layer peels off (hardening failure).

  The tack-free property is required to be A.

First, the photocurable ink No. A cured product was formed by curing under standard conditions as shown below using 1 to 13. As the recording medium 2, a PET film having a thickness of 100 μm (= 0.01 cm) was used, and the film thickness of the ink layer formed thereon was about 5 μm (300 dpi, per 42 pl / 1 nozzle: equivalent). The amount of light applied to the ink layer from the light irradiation means 4 was about 140 mJ / cm ² .

  The ink layer after light irradiation was heated by the stocker 15 provided with a heating means under the following heating standard conditions.

Heating temperature (recording medium temperature): 100 ° C
Heating time: 1 minute In the examples, after light irradiation, heating was performed immediately by the stocker 15 equipped with heating means. Note that “immediate heating” means that the recording medium temperature rises compared to the ambient temperature due to heat applied from the light irradiation means 4 at the same time as the light irradiation, and then the temperature of the recording medium before the light irradiation (ambient temperature). It means that it is heated by the stocker 15 provided with a heating means before returning to the equivalent).

  In the comparative example, the recording medium after light irradiation was left at room temperature. After the temperature of the recording medium sufficiently returned to the ambient temperature, heating was performed by the heating means 5.

The curability (pencil hardness) of the obtained cured product is examined by the method described above, and the results are summarized in Table 2 below.

  As shown in Table 2, the cured product formed by the method of the example tends to have a higher pencil hardness than that of the comparative example. From this result, it was confirmed that the hardness of the obtained cured product is improved by immediately heating the ink layer after light irradiation without lowering the temperature of the ink layer.

Next, photocurable ink No. 2, 7 and 10 were used to change the amount of light irradiated from the light irradiation means 4 to form a cured product. The amount of irradiation light was changed in the range of 5 mJ / cm ^{2 to} 250 mJ / cm ² . About the obtained hardened | cured material, the sclerosis | hardenability after light irradiation, the tack free property after light irradiation, the sclerosis | hardenability after heating after light irradiation, and adhesiveness were investigated. Photocurable ink No. The results for 2, 7, and 10 are summarized in Tables 3, 4, and 5, respectively.

  As shown in the above table, when any ink is used, curability is enhanced by heating after light irradiation. In addition, it can be seen that there is an appropriate range in the amount of light to be irradiated in order to impart a desired tack-free property to the ink layer after light irradiation. In order to make the adhesion of the cured product obtained after heating an acceptable range, there is an appropriate range in the amount of light to be irradiated. It was also confirmed that there was a difference in curing characteristics depending on the type of ink, that is, the type of solvent polymerized in the presence of the acid constituting the ink.

  This is explained as follows. By irradiating the ink layer formed on the recording medium with a predetermined amount of light, heat is applied to the ink layer in addition to the light. In this case, the temperature of the ink layer rises and is raised from the initial temperature. By heating the ink layer before the temperature of the ink layer returns to the initial temperature, the following effects can be obtained. First, in the ink layer, sufficient acid necessary for curing the ink is generated from the photoacid generator. Heating can promote efficient and uniform diffusion of the acid thus generated in the ink layer and promote curing. Furthermore, the viscosity of the lower portion of the ink layer is reduced by heating, so that the ink layer is in close contact with the recording medium without the intervention of other substances. As a result, by adopting the method according to the embodiment of the present invention, printing made of a cured product having excellent curability and adhesion to various recording media having different surface mechanical and chemical states. An image can be formed.

Next, a cured product was formed by curing using the photocurable ink Nos. 2, 5, 7, 10, and 13 under the following conditions. As the recording medium 2, a PET film having a thickness of 100 μm (= 0.01 cm) was used. Since the PET film used here is made of a resin, the amount of heat required to obtain the same temperature can be reduced from the relationship between specific heat and density. The film thickness of the ink layer formed thereon was about 5 μm (300 dpi, per 42 pl / 1 nozzle: equivalent). The amount of light applied to the ink layer from the light irradiation means 4 was about 140 mJ / cm ² .

The ink layer after light irradiation was heated by the heating means 5. As the heating means 5, a far infrared ceramic heater PLC-32 series manufactured by Noritake Company Limited was used. The heating amount was changed within a range of about 8 to 211 J / cm ³ (recording medium, per unit volume). This amount of heat is applied to a resin-based recording medium (for example, a recording medium having physical properties of specific heat: 1.3 J / g · ° C. and density: 1.3 g / cm ³ ) from 25 ° C. (room temperature) to 30 ° C., 45 ° C. , 60 ° C., 90 ° C., 120 ° C., or 150 ° C.

  Heating by the heating means 5 was performed immediately after light irradiation. Note that “immediate heating” means that the recording medium temperature rises compared to the ambient temperature due to heat applied from the light irradiation means 4 at the same time as the light irradiation, and then the temperature of the recording medium before the light irradiation (ambient temperature). It means that heating is performed by the heating means 5 before returning to the equivalent).

The curability (pencil hardness) of the obtained cured product was examined by the method described above. The results are summarized in Table 6 below together with the amount of heat given to the recording medium in the heating step. The amount of heat is determined from the temperature of the recording medium. Specifically, the temperature of the recording medium 2 when the recording medium 2 passed through the heating means 6 was measured in advance, and this was converted into an amount of heat.

  As shown in Table 6 above, it can be seen that there is a lower limit to the amount of heat applied to the recording medium in the heating step in order to form a cured product having a desired hardness.

  Next, the ink was cured under the same conditions as described above except that the recording medium was preheated at 60 ° C. to form a cured product. The ink and recording medium used were the same as described above. That is, the photocurable ink No. 2, 5, 7, 10 and 13 were used to form a cured product on a 100 μm thick PET film.

The curability (pencil hardness) of the obtained cured product was examined by the method described above. The results are summarized in Table 7 below together with the amount of heat given to the recording medium in the heating step.

  It can be seen from the comparison between Table 7 and Table 6 that the curability of the obtained cured product is improved by preheating the recording medium. That is, by preheating the surface temperature of the recording medium to at least the temperature of the photocurable ink attached on the recording medium, acid can be efficiently generated from the photoacid generator in the ink layer. At the same time, acid diffusion by heating is efficiently promoted. As a result, it has become possible to form a printed image made of a high-quality cured product with even better curability and adhesion.

  The photocurable ink used here contains a pigment (carbon black) as a color component at a concentration in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the acid polymerizable solvent. When a photocurable ink having such a composition is used, an equivalent result can be obtained if the thickness of the formed ink layer is about 20 μm or less.

  When the content of the pigment in the photocurable ink is in the range of 3 to 10 parts by weight with respect to 100 parts by weight of the acid-polymerizable solvent, or when the film thickness of the ink layer is about 20 μm or less, the effect is further increased. Enhanced.

From the above results, it can be seen that, among the 13 types of photocurable inks, No. 13 has the most excellent curing characteristics, that is, hardness, adhesion, and solvent resistance. Therefore, no. Using 13 photocurable inks, cured products were formed on various recording media. As the recording medium 2, a PET film, a PE film, a PP sheet, an acrylic plate, a stainless plate, an aluminum plate, a glass plate, and a ceramic plate were prepared. The thickness of each recording medium is 100 μm (= 0.01 cm). The film thickness of the ink layer formed thereon was about 5 μm (300 dpi, per 42 pl / 1 nozzle: equivalent). The amount of light applied to the ink layer from the light irradiation means 4 was changed between about 5 to 250 mJ / cm ² .

  The ink layer after light irradiation was immediately heated by a batch type stocker 15 equipped with a heater. Note that “immediate heating” means that the recording medium temperature rises compared to the ambient temperature due to heat applied from the light irradiation means 4 at the same time as the light irradiation, and then the temperature of the recording medium before the light irradiation (ambient temperature). It means heating before returning to the equivalent). The heating temperature is 45 ° C, 60 ° C, 80 ° C, 90 ° C, 100 ° C, 120 ° C, 140 ° C, (160 ° C), and the heating time is 1 minute, 5 minutes, 10 minutes, 15 minutes, (20 minutes).

  A cured product was formed on various recording media by combining conditions such as the amount of irradiated light, heating temperature, and heating time, and the curability, adhesion and solvent resistance were examined.

Tables 8 to 10 below show the results for PET films. .

As shown in these tables, when the amount of light applied to the ink layer is less than 50 mJ / cm ² , a cured product having desired curing characteristics cannot be obtained. Even when light is irradiated with a light amount of 50 mJ / cm ² or more, a cured product satisfying curability, adhesion and solvent resistance cannot be obtained if the heating temperature is less than 60 ° C.

When a PET film is used as a recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 60 ° C. for at least 1 minute before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion, and solvent resistance are increased. It is possible to form a printed image made of a cured product having excellent properties.

  Next, an ink cured product was formed under the same conditions as described above except that the recording medium was changed to a PE film, a PP sheet, and an acrylic plate. About the obtained hardened | cured material, sclerosis | hardenability, adhesiveness, and solvent resistance were investigated, and it considered as follows from the result.

When a PE film is used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 60 ° C. for at least a few dozen seconds before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability and adhesion are improved. It is possible to form a printed image made of a cured product having excellent properties and solvent resistance.

When a PP film is used as a recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 60 ° C. for at least several seconds before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion, and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above.

When an acrylic plate is used as the recording medium, heat is applied at the same time when the light is irradiated with a light amount of at least 50 mJ / cm ² to raise the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 60 ° C. for at least several tens of seconds before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion, and resistance are improved. It is possible to form a printed image made of a cured product having excellent solvent properties.

Tables 11 to 13 below show the results for the stainless steel plate.

As shown in these tables, when the amount of light applied to the ink layer is less than 50 mJ / cm ² , a cured product having desired curing characteristics cannot be obtained. Even when light is irradiated with a light amount of 50 mJ / cm ² or more, a cured product satisfying curability, adhesion and solvent resistance cannot be obtained if the heating temperature is less than 80 ° C.

When a stainless steel plate is used as a recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 80 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. If the heating temperature is high, a cured product having equivalent curing characteristics can be formed in a shorter heating time. Heating may be performed at a temperature of at least 100 ° C. or 120 ° C. for at least 1 minute.

  Next, an ink cured product was formed under the same conditions as described above except that the recording medium was changed to an aluminum plate and a copper plate. About the obtained hardened | cured material, sclerosis | hardenability, adhesiveness, and solvent resistance were investigated, and it considered as follows from the result.

When an aluminum plate is used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 90 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. Similarly, when heating is performed at a temperature of at least 100 ° C. or 120 ° C. for at least 10 minutes, a printed image made of a cured product having excellent curability, adhesion, and solvent resistance can be obtained.

When a copper plate is used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to raise the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 90 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. Similarly, when heating is performed at a temperature of at least 100 ° C. or 120 ° C. for at least 10 minutes, a printed image made of a cured product having excellent curability, adhesion, and solvent resistance can be obtained.

Tables 14 to 16 below show the results for glass plates.

As shown in these tables, when the amount of light applied to the ink layer is less than 50 mJ / cm ² , a cured product having desired curing characteristics cannot be obtained. Even when light is irradiated with a light amount of 50 mJ / cm ² or more, a cured product satisfying curability, adhesion, and solvent resistance is not necessarily obtained when the heating temperature is less than 120 ° C.

When a glass plate is used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to raise the temperature of the ink layer. By heating and heating the recording medium together with the ink layer at a temperature of at least 100 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product having excellent properties. If the heating temperature is high, a cured product having equivalent curing characteristics can be formed in a shorter heating time. Heating may be performed at a temperature of at least 120 ° C. for at least 1 minute.

  Next, an ink cured product was formed under the same conditions as described above except that the recording medium was changed to tile, ceramic, and stone. About the obtained hardened | cured material, sclerosis | hardenability, adhesiveness, and solvent resistance were investigated, and it considered as follows from the result.

When tiles are used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 100 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. Even when heating is performed at a temperature of at least 120 ° C. for at least 1 minute, a printed image made of a cured product having excellent curability, adhesion, and solvent resistance can be obtained.

When ceramic is used as the recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to increase the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 100 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. Even when heating is performed at a temperature of at least 120 ° C. for at least 1 minute, a printed image made of a cured product having excellent curability, adhesion, and solvent resistance can be obtained.

When a stone is used as a recording medium, when light is irradiated with a light amount of at least 50 mJ / cm ² , heat is simultaneously applied to raise the temperature of the ink layer. By heating the recording medium together with the ink layer at a temperature of at least 100 ° C. for at least 5 minutes before the temperature of the ink layer returns to the initial temperature (the temperature immediately before light irradiation), the curability, adhesion and solvent resistance are increased. It is possible to form a printed image made of a cured product excellent in the above. Even when heating is performed at a temperature of at least 120 ° C. for at least 1 minute, a printed image made of a cured product having excellent curability, adhesion, and solvent resistance can be obtained.

  In the method for curing a photocurable ink according to an embodiment of the present invention, a photoacid generation that includes at least one compound having a vinyl ether group, polymerizes in the presence of an acid, and generates an acid by light irradiation. A photocurable ink containing an agent and a color component is attached onto a recording medium to form an ink layer. The ink layer thus formed is irradiated with light containing a wavelength that is absorbed by the photoacid generator, and an acid is generated from the photoacid generator in the ink layer to cure a part of the ink layer. After the light irradiation, the ink viscosity of the ink layer is decreased, the acid generated by the light irradiation is promoted to diffuse into the ink layer to promote the curing of the ink layer, and the ink layer is formed without any other substances. The recording medium on which the ink layer is formed is heated so as to be in close contact with the recording medium.

In the light irradiation step, heat is applied to the recording medium together with a light amount of at least 50 mJ / cm ² , whereby the ink layer is heated together with the recording medium, and the temperature of the ink layer is raised from the initial temperature. In the heating step, the recording medium on which the ink layer is formed is heated with a heat amount of at least 50 J / cm ³ before the temperature of the ink layer thus increased returns to the initial temperature. In the light irradiation step, light irradiation is performed until the ink layer formed on the recording medium is tack-free. In the heating step, the heat amount of the ink layer together with the recording medium is at least 50 J / cm ³ . Is heated.

After the light irradiation satisfying the predetermined condition, the ink layer is heated together with the recording medium with a heat amount of at least 50 J / cm ³ , so that the mechanical state of the surface is changed by the method according to the embodiment of the present invention. It has become possible to form printed images made of a cured product having excellent curability and adhesion on various recording media having different chemical states.

  Further, since high-quality printing can be performed on various recording media of different materials, according to the curing method according to the embodiment of the present invention, a single ink can be used for various purposes. Furthermore, since the amount used can be increased, there is an effect that cost reduction and market expansion can be expected.

1 is a schematic view of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 6 is a schematic view of an ink jet recording apparatus according to another embodiment of the present invention. Sectional drawing of an example of the halogen heater which can be used as a heating means. FIG. 6 is a schematic view of an ink jet recording apparatus according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus; 2 ... Recording medium, 3 ... Conveyance means; 4 ... Recording head 5 ... Light irradiation means; 6 ... Heating means; 7 ... Recording medium temperature adjustment means 15 ... Stocker provided with heating means; Medium preheating stocker 21 ... housing; 22 ... halogen heater; 23 ... reflector; 24 ... focus.

Claims (7)

At least a surface of a photocurable ink containing any vinyl ether compound represented by the following chemical formula, containing a solvent that polymerizes in the presence of an acid, a photoacid generator that generates an acid by light irradiation, and a color component Forming an ink layer on a recording medium made of metal, glass or earthenware ,

The ink layer is irradiated with light having a wavelength absorbed by the photoacid generator at a light amount of 300 mJ / cm ² or less to generate an acid from the photoacid generator in the ink layer, and thereby the ink layer. A light irradiation process for curing a part;
Reduces the viscosity of the ink below the ink layer after the light irradiation, promotes the diffusion of the acid generated by the light irradiation into the ink layer, promotes the curing of the ink layer, and has no other substances at the interface And heating the recording medium on which the ink layer is formed so that the ink layer is in close contact with the recording medium,
In the light irradiation step, when another recording medium is stacked on the recording medium on which the ink layer is formed immediately after the light irradiation , light irradiation is performed in a range where the ink layer is not transferred to the other recording medium. ,
In the heating step, the ink layer is heated with a heat quantity of at least 50 J / cm ³ together with the recording medium . The photocurable ink contains 3 to 20 parts by weight of a pigment as the colorant with respect to 100 weights of the solvent that is polymerized in the presence of the acid, and the light irradiated in the light irradiation step is ultraviolet light. The method of curing a photocurable ink according to claim 1 . The ink layer, method for curing light-curable ink according to claim 1 or 2, characterized in Rukoto formed on the recording medium under the following film thickness 20 [mu] m. Pre-heating the recording medium before forming the ink layer on the recording medium, and increasing the surface temperature of the recording medium to at least the temperature of the photocurable ink deposited on the recording medium. further comprising to curing method photocurable ink according to any one of claims 1 to 3, wherein Rukoto. Wherein in the heating step, the curing method of the photocurable ink according to any one of claims 1 to 4 wherein the recording medium is characterized Rukoto heated more at the same time. The photocurable ink comprises an acid-polymerizable compound having an alicyclic skeleton and / or an aliphatic skeleton having a viscosity of 50 mPa · s or less at normal temperature and pressure and a boiling point of 100 ° C. or higher in the presence of the acid. method for curing light-curable ink according to any one of claims 1 to 4, wherein that you containing as a solvent for polymerization. 7. A method of discharging a photocurable ink onto a recording medium by an ink jet method and curing the recording medium, wherein the photosensitive ink is cured by the method according to any one of claims 1 to 6. An inkjet recording method characterized by the above .

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