Drying device, image forming device, and image forming method

Abstract

The present invention addresses the problem of providing a drying device that makes it possible to dry an ink image formed on a recording medium in a short period of time and is not liable to degrade a recording medium or a formed image.　The drying device that solves the problem dries an ink image including undried ink formed on one surface of a recording medium. The drying device has an energy irradiation unit that irradiates the one surface of the recording medium with energy and is used to heat and dry the ink image, and a temperature control unit that is arranged to contact the other surface of the recording medium so as to face the energy irradiation unit across the recording medium. The energy irradiation unit is an infrared light irradiation unit that performs irradiation of infrared light having a wavelength of 0.8-3.0 μm inclusive with an output of 30 kW / m 2 or more, or is an ultraviolet light irradiation unit that irradiates the one surface of the recording medium with ultraviolet light having a wavelength of 200-410 nm with an illumination of 1 W / cm 2 or more.

Description

Technical Field

[0001] The present invention relates to a drying device, an image forming device, and an image forming method.

Background Art

[0002] In recent years, a method of forming an image by applying liquid ink onto a low-absorbing or non-absorbing recording medium has been widely used. According to this method, a desired image can be formed even on a recording medium with low ink absorbency, and it is possible to manufacture a highly designed product.

[0003] In an image forming device that performs such printing, after applying ink onto a recording medium to form an ink image, a solvent or the like in the ink image is removed, and a colorant is fixed to the recording medium. As a method of removing the solvent in the ink image, a method of blowing hot air is known. However, in hot air drying, there is a problem that a drying furnace is required and the device tends to be large.

[0004] Therefore, heating an ink image with infrared light to remove a solvent in the ink image has also been performed (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, speeding up of various types of printing has been demanded, and it has been required to dry an ink image in a shorter time. However, in the irradiation with long-wavelength infrared light as described in Patent Document 1, there is a problem that the temperature of the ink image hardly increases and it takes time to remove the solvent (dry the ink image).

[0007] In view of such problems, a method of irradiating an ink image with high-power energy to increase the temperature of the ink image in a short time can be considered. However, when the ink image contains a plurality of colors of ink, the energy absorption rates differ between the inks. And, as a result of the inventors' intensive studies this time, it has become clear that when irradiating with high-power energy, the degree of temperature rise differs greatly between the region with a high energy absorption rate and the region with a low energy absorption rate, and it has been found that unevenness is likely to occur in the temperature of the ink when heated. For example, when irradiating energy in accordance with the drying of the ink with a high energy absorption rate, the temperature of the ink with a low energy absorption rate does not increase sufficiently, resulting in insufficient drying. On the other hand, when irradiating energy in accordance with the drying conditions of the ink with a low energy absorption rate, it has become clear that the temperature of the region coated with the ink with a high energy absorption rate rises too much, and the formed image and the recording medium deteriorate due to heat.

[0008] Also, when a mark, pattern, or the like is printed in advance on the recording medium, when irradiating with high-power energy, the temperature of only the region with a high energy absorption rate of the recording medium is likely to rise, and the recording medium is likely to be damaged.

[0009] The present invention has been made in view of such problems. Specifically, an object of the present invention is to provide a drying device capable of drying an ink image formed on a recording medium in a short time and further making it difficult for the recording medium and the formed image to deteriorate. Another object is to provide an image forming apparatus using the drying device and an image forming method.

Means for Solving the Problems

[0010] The present invention provides the following drying device. A drying device for drying an ink image containing undried ink formed on one surface of a recording medium, the drying device including: an energy irradiation unit configured to irradiate energy onto one surface of the recording medium to heat and dry the ink image; and a temperature control unit disposed to face the energy irradiation unit with the recording medium interposed therebetween and to contact the other surface of the recording medium. The energy irradiation unit includes an infrared light irradiation unit configured to irradiate infrared light having a wavelength of 0.8 μm or more and 3.0 μm or less at an output of 30 kW / m 2 or more, or an ultraviolet light irradiation unit configured to irradiate ultraviolet light having a wavelength of 200 nm to 410 nm on one surface of the recording medium at an illuminance of 1 W / cm 2 or more. The drying device includes either one of the above units.

[0011] The present invention provides an image forming apparatus as follows. An image forming apparatus including: a conveyance unit configured to convey a recording medium; a primer ink ejection unit configured to eject a primer ink containing a flocculant; a color ink ejection unit configured to eject a color ink containing a colorant; and the drying device described above.

[0012] The present invention provides an image forming method as follows. An image forming method including: a step of applying ink to one surface of a recording medium to form an ink image; and a step of irradiating energy onto one surface of the recording medium while bringing a temperature control unit for controlling temperature into contact with the other surface of the recording medium to dry the ink image. In the step of drying the ink image, infrared light having a wavelength of 0.8 μm or more and 3.0 μm or less is irradiated at an output of 30 kW / m 2 or more, or ultraviolet light having a wavelength of 200 nm or more and 410 nm or less is irradiated at an illuminance of 1 W / m 2 or more.

Advantages of the Invention

[0013] According to the drying device of the present invention, it is possible to sufficiently dry an ink image formed on a recording medium in a short time, and it is difficult to cause damage to the recording medium or the formed image.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

[0015] Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment.

[0016] 1. Drying apparatus The drying apparatus of the present invention is an apparatus for drying an ink image containing undried ink formed on a recording medium. In the drying apparatus, the temperature of the ink image is raised by energy irradiation, and a solvent or the like is volatilized to dry the ink image. The drying apparatus of the present invention is very useful when drying an ink image containing a plurality of colors of ink formed on a recording medium, or when drying an ink image formed on a recording medium having regions of different colors in part.

[0017] As described above, when forming a printed matter by forming an ink image with inks of a plurality of colors or using a recording medium having regions of different colors in part, when irradiating the ink image or the recording medium with energy at a high output, temperature unevenness was likely to occur due to the difference in the energy absorption rate of the ink or the recording medium. Specifically, in a region coated with a color ink having a high energy absorption rate or in a region of the recording medium having a high energy absorption rate, the temperature rises in a short time. On the other hand, in a region coated with a color ink having a low energy absorption rate or in a region of the recording medium having a low energy absorption rate, the temperature hardly rises. Therefore, when determining the energy irradiation conditions according to the ink having a high energy absorption rate, the drying of the ink image is likely to be insufficient. On the other hand, when drying according to the ink having a low energy absorption rate, the regions coated with the ink having a high energy absorption rate or the regions of the recording medium having a high energy absorption rate are likely to deteriorate. Note that when irradiating with infrared light having a long wavelength for a long time, such temperature unevenness is less likely to occur.

[0018] FIG. 1A shows a plan view of a drying device 110 according to an embodiment of the present invention, and FIG. 1B shows a side view of the drying device 110. Further, FIG. 2 shows a side view of a modified example of the drying device 110. As shown in FIGS. 1A, 1B, and 2, the drying device 110 of this embodiment includes an energy irradiation unit 101 for irradiating energy to an ink image 2 formed on one surface (hereinafter, also referred to as "printing surface") 1a of a recording medium 1, and a temperature control unit 102 disposed so as to face the energy irradiation unit 101 with the recording medium 1 interposed therebetween and in contact with the other surface (hereinafter, also referred to as "non-printing surface") 1b of the recording medium 1. The drying device 110 in FIG. 2 is the same as the drying device 110 shown in FIGS. 1A and 1B except for the shape of the temperature control unit 102.

[0019] In the drying device 110 of the present embodiment, even if energy is irradiated from the energy irradiation unit 101 to the ink image 2 and the recording medium 1 at high power, the temperature of the recording medium 1 and the ink image 2 is equalized by the temperature control unit 102 disposed on the non-printing surface 1b side of the recording medium 1. More specifically, heat is transferred from the recording medium 1 to the temperature control unit 102, making it difficult for the temperature of the recording medium 1 and the ink image 2 to rise excessively. On the other hand, the temperature control unit 102 warms the regions with a low temperature in the recording medium 1 and the ink image 2. Therefore, according to the device 110, it is possible to uniformly dry the entire ink image 2 in a short time. Also, during the drying of the ink image 2, since the temperature of the recording medium 1 and the ink image 2 does not rise excessively, deterioration of the recording medium 1 and the resulting image is less likely to occur.

[0020] Note that the drying device 110 only needs to have the above-described energy irradiation unit 101 and temperature control unit 102. In addition to these, it may also have a pressing means (not shown) for bringing the recording medium 1 into close contact with the temperature control unit 102, a conveying means (not shown) for conveying the recording medium 1 and the like, and the like. Further, it may further have a housing (not shown) that covers the energy irradiation unit 101, the temperature control unit 102, and the like. In the following description, FIGS. 1A, 1B, and 2 show an example using a long recording medium 1, but the drying device 110 may also be used when drying an ink image 2 formed on a sheet-like recording medium 1. Hereinafter, each configuration of the drying device 110 will be described.

[0021] (1) Energy irradiation unit The energy irradiation unit 101 is a configuration for irradiating energy to the ink image 2 formed on the printing surface 1a of the recording medium 1. By irradiating energy with the energy irradiation unit 101, the temperature of the ink image 2 formed on the recording medium 1 rises, the solvent and the like in the ink image 2 volatilize, and the ink image 2 dries.

[0022] The energy irradiation unit 101 of the present embodiment irradiates infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less at 30 kW / m 2An infrared light irradiation unit that irradiates with the above output, or an ultraviolet light irradiation unit that irradiates ultraviolet light with a wavelength of 200 nm to 410 nm at an illuminance of 1 W / cm 2 It suffices to have at least one of them, and it may have both. When infrared light is irradiated from the infrared light irradiation unit, the colorant and solvent in the ink image absorb the infrared light respectively. Then, the temperature of the ink image rises and the solvent volatilizes. On the other hand, when ultraviolet light is irradiated from the ultraviolet light irradiation unit, the colorant in the ink image mainly absorbs the ultraviolet light and its temperature rises. Then, heat is transferred to the solvent by heat conduction and the solvent volatilizes. Each will be described below.

[0023] (Infrared light irradiation unit) The infrared light irradiation unit is not particularly limited in its configuration as long as it can emit light with a wavelength of 0.8 μm or more and 3.0 μm or less at an output of 30 kW / cm 2 or more. The infrared light irradiation unit usually has one or more heat sources, a control unit for controlling the output of infrared light from the heat source, a cooling unit for controlling the temperature, etc. It may have other configurations as needed.

[0024] In the infrared light irradiation unit, usually one or more heat sources are arranged so that infrared light can be irradiated over the entire width direction of the recording medium 1. Note that the "width direction" in this specification is the direction perpendicular to the conveyance direction of the recording medium 1 when the drying device 110 is viewed in plan. However, depending on the formation position of the ink image 2, the shape of the recording medium 1, the type of the recording medium 1, etc., the heat source may be arranged so as to irradiate infrared light only on a part of the width direction of the recording medium 1.

[0025] Also, the length of the region irradiated with infrared light by the infrared light irradiation unit is appropriately selected according to the desired infrared light irradiation amount, irradiation time, etc. A plurality of heat sources may be arranged along the conveyance direction of the recording medium 1 in the infrared light irradiation unit.

[0026] In addition, the heat source of the infrared light irradiation unit is arranged with a gap from the recording medium 1. The distance between the heat source of the infrared light irradiation unit and the recording medium 1 may be constant, or may change continuously or intermittently. However, the distance between the heat source of the infrared light irradiation unit and the recording medium 1 is preferably 3 cm or more and 20 cm or less, and more preferably 5 cm or more and 15 cm or less. When the distance between the heat source of the infrared light irradiation unit and the recording medium is more than 5 cm, even if the recording medium 1 is bent, it is difficult for the recording medium and the heat source to come into contact. On the other hand, when it is 20 cm or less, infrared light can be efficiently irradiated from the heat source of the infrared light irradiation unit to the recording medium.

[0027] Here, the wavelength of the infrared light emitted by the heat source of the infrared light irradiation unit may be 0.8 μm or more and 3.0 μm or less, preferably 0.8 to 2.5 μm, and more preferably 1.7 to 2.5 μm. When the wavelength of the light emitted by the infrared light irradiation unit (heat source) is within this range, the temperature of the ink image 2 can be increased in a short time. Further, for example, when the wavelength of the infrared light is 1.7 to 2.5 μm, not only can the ink temperature be increased in a short time, but also the difference in the infrared light absorbability of a plurality of types of inks can be suppressed to be small.

[0028] In addition, the output of the infrared light from the infrared light irradiation unit (heat source) is 30 kW / m 2 or more, and 40 kW / m 2 or more and 350 kW / m 2 or less is preferable, and 60 kW / cm 2 or more and 150 kW / m 2 or less is more preferable. When the output from the infrared light irradiation unit is within this range, for example, it becomes possible to dry the ink image in about 10 seconds. The output of the infrared light can be specified from the specifications of the heat source and the like.

[0029] In addition, the temperature of the heat source is preferably 900 °C or more, more preferably 900 °C or more and 2000 °C or less, and even more preferably 1400 °C or more and 2000 °C or less. When the temperature of the heat source is 900 °C or more, the temperature of the ink image increases in a short time. However, since there is a possibility that deformation or deterioration of the recording medium may occur if the temperature of the heat source is excessively high, 2000 °C or less is preferable. The temperature of the heat source can be specified by a non-contact type infrared sensor or the like.

[0030] The heat source of the infrared light irradiation unit is not particularly limited as long as it can emit infrared light with the above wavelength and output, and a known heat source can be used. Further, the heat source may be a point heat source or a linear heat source. Examples of such heat sources include halogen lamp heaters, quartz tube heaters, carbon heaters, etc. Further, the number of heat sources included in the infrared light irradiation unit is not particularly limited, and is appropriately selected according to the width and length of the region irradiated with infrared light.

[0031] On the other hand, the control unit of the infrared light irradiation unit may, for example, monitor the temperature of the heat source or adjust the amount of electric power supplied to the heat source according to the temperature of the heat source, as long as it is possible, and is the same as the control unit of a known infrared light irradiation device. Further, the cooling unit may have a configuration capable of cooling the heat source and its surroundings, etc. in order to suppress the excessive rise in the temperature of the infrared light irradiation unit, and may be, for example, a blower or a water-cooled chiller.

[0032] (Ultraviolet light irradiation unit) The configuration of the ultraviolet light irradiation unit is not particularly limited as long as it can emit light with a wavelength of 200 nm or more and 410 nm or less at an illuminance of 1 W / cm 2 or more. The ultraviolet light irradiation unit has, for example, one or more light sources, a control unit for controlling the output of ultraviolet light from the light source, a cooling unit for adjusting the temperature, etc.

[0033] In the ultraviolet light irradiation unit, usually, the light sources are arranged so that ultraviolet light can be irradiated over the entire width direction of the recording medium 1. However, depending on the formation position of the ink image 2, the shape of the recording medium 1, the type of the recording medium 1, etc., the light sources may be arranged so as to irradiate ultraviolet light only on a part of the width direction of the recording medium 1.

[0034] Further, the length of the region irradiated with ultraviolet light by the ultraviolet light irradiation unit is appropriately selected according to the desired ultraviolet light irradiation amount, irradiation time, etc. A plurality of light sources may be arranged in the ultraviolet light irradiation unit along the conveyance direction of the recording medium 1.

[0035] Furthermore, the light source of the ultraviolet light irradiation unit is arranged with a gap from the recording medium. The distance between the light source of the ultraviolet light irradiation unit and the recording medium 1 may be constant, or may change continuously or intermittently. The distance between the light source of the ultraviolet light irradiation unit and the recording medium 1 is preferably usually 5 mm or less. When the distance between the light source and the recording medium is 5 mm or less, ultraviolet light can be efficiently irradiated from the light source to the recording medium.

[0036] Here, the wavelength of the ultraviolet light emitted by the light source of the ultraviolet light irradiation unit may be 200 nm or more and 410 nm or less. When using an LED, 350 nm or more and 410 nm or less is preferable. When the wavelength of the ultraviolet light is 200 nm or more and 410 nm or less, the ultraviolet light is easily absorbed by the colorant contained in the ink image 2, and thus the temperature of the ink image 2 can be increased in a short time.

[0037] Also, the illuminance of the ultraviolet light from the ultraviolet light irradiation unit (light source) may be 1 W / cm 2 or more, but preferably 2 W / cm 2 or more and 4 W / cm 2 or less. When the output from the ultraviolet light irradiation unit is 1 W / cm 2 or more, the ink image is likely to dry in a short time. For example, the time for irradiating each ink image with the light source can be within 10 seconds. The illuminance of the ultraviolet light is measured with an illuminance meter (for example, the illuminance system UIT-201 manufactured by Ushio Electric Co., Ltd., etc.).

[0038] The light source of the ultraviolet light irradiation unit is not particularly limited as long as it can emit ultraviolet light with the above wavelength and the above illuminance, and a known light source can be used. The light source may be a point light source or a linear light source. Examples of such light sources include halogen lamps and UV-LED lamps. Specific examples of UV-LED lamps include 300 nm LED, 375 nm LED, 395 nm LED, 410 nm LED, etc., and are appropriately selected according to the type of colorant contained in the ink image (color ink). When drying an ink image 2 containing a plurality of color inks, a plurality of types of LED lamps may be combined. Also, the number of light sources included in the ultraviolet light irradiation unit is not particularly limited, and is appropriately selected according to the width and length of the region irradiated with ultraviolet light.

[0039] On the other hand, the control unit of the ultraviolet light irradiation unit may, for example, monitor the amount of light from the light source or adjust the amount of power supplied to the light source according to the amount of light of the light source, as long as it is possible, and is the same as the control unit of a known ultraviolet light irradiation device. Further, the cooling unit may have a configuration capable of cooling the light source and its surroundings, etc. in order to suppress the excessive rise in the temperature of the ultraviolet light irradiation unit, and can be, for example, a blower or a water-cooled chiller.

[0040] (2) Temperature control unit The temperature control unit 102 is a member for making the temperature of the recording medium 1 uniform, and includes, for example, a highly thermally conductive heat conduction part 102a that contacts the non-printing surface 1b of the recording medium 1, and a temperature adjustment mechanism 102b for adjusting the temperature of the heat conduction part 102a.

[0041] The heat conduction part 102a is composed of a member with high thermal conductivity, etc., and when irradiating energy from the energy irradiation part 101, it releases the heat in the high-temperature region of the temperature of the recording medium 1 or the ink image 2, or warms the low-temperature region, etc., to make the temperature of the recording medium 1 and the ink image 2 uniform. The heat conduction part 102a is usually appropriately heated or cooled by a temperature adjustment mechanism 102b described later so that its surface temperature becomes the set temperature.

[0042] The thermal conductivity of the heat conduction part 102a is preferably 150 kcal / m·h·°C or more. When the thermal conductivity of the heat conduction part is 150 kcal / m·h·°C or more, it is easy to make the temperature of the recording medium 1 uniform in a short time. Note that the thermal conductivity is a value specific to the material, and the conductivity of the heat conduction part 102a can be specified from the type of the constituent material. However, when the heat conduction part 102a is composed of a plurality of materials, it can be calculated by multiplying the content ratio of each material by the thermal conductivity of the material and adding them together.

[0043] The material constituting the heat conduction part 102a is preferably a metal, and copper, aluminum, or a composite thereof, etc. are preferable. Among these, copper is particularly preferable in terms of high thermal conductivity, low cost, good workability, etc.

[0044] Here, the shape of the heat conduction part 102a is not particularly limited as long as it can contact the non-printing surface 1b of the recording medium 1 while the energy irradiation part 101 irradiates energy on the recording medium 1 or the ink image 2. For example, as shown in FIG. 1B, the heat conduction part 102a may be flat plate-shaped, or may be roll-shaped as shown in FIG. 2.

[0045] As shown in FIG. 2, when the heat conduction part 102a is roll-shaped and the heat conduction part 102a is rotatably supported, the heat conduction part 102a rotates in accordance with the movement of the recording medium 1. Therefore, excessive friction hardly occurs between the recording medium 1 and the heat conduction part 102a, and the non-printing surface of the recording medium 1 is hardly worn. Further, when the heat conduction part 102a rotates, energy is hardly irradiated on a specific area of the heat conduction part 102a for a long time, and the temperature of the heat conduction part 102a hardly rises excessively. Therefore, there is also an advantage that the temperature adjustment by the temperature adjustment mechanism 102b is easy.

[0046] The width of the area where the heat conduction part 102a contacts the recording medium 1 is not particularly limited, and it may be at least the width of the area irradiated with energy by the energy irradiation part 101 or more. However, it is more preferable that the width of the area where the heat conduction part 102a contacts the recording medium 1 is the width of the recording medium 1 or more. When the width of the area where the heat conduction part 102a contacts the recording medium 1 is the width of the recording medium 1 or more, the temperature of the entire recording medium 1 is adjusted uniformly.

[0047] Also, the length of the area where the heat conduction part 102a contacts the recording medium 1 (the distance in the direction parallel to the conveyance direction of the recording medium) is preferably at least the length of the area irradiated with energy by the energy irradiation part 101 or more.

[0048] Also, it is preferable that the non-printing surface 1b of the recording medium 1 and the heat conduction part 102a are in contact with each other in substantially all of the area irradiated with energy by the energy irradiation part 101.

[0049] On the other hand, the temperature adjustment mechanism 102b of the temperature control unit 102 only needs to be configured to be able to control the surface temperature of the heat conduction unit 102a. For example, heating means for raising the temperature of the heat conduction unit 102a, cooling means for lowering the temperature of the heat conduction unit 102a, temperature measurement means for directly or indirectly measuring the temperature of the surface of the heat conduction unit 102a, a set temperature, and control means for controlling the heating means and the cooling means based on the temperature measured by the temperature measurement means, etc. can be configured.

[0050] Examples of the above heating means include known heaters, etc., and examples of the cooling means include blowers, water-cooled chillers, etc. The heating means and the cooling means may be arranged inside the heat conduction unit 102a or outside.

[0051] (3) Other configurations The drying device 110 may further include pressing means (not shown) or the like for bringing the recording medium 1 and the temperature control unit 102 into closer contact. The pressing means may have a structure that presses the printing surface 1a of the recording medium 1 against the temperature control unit 102 side, a structure that presses the temperature control unit 102 against the recording medium 1, or a structure that presses the recording medium 1 and the temperature control unit 102 against each other. While the energy irradiation unit 101 irradiates energy, the tension may be measured and adjusted by a pressure gauge or the like so that a certain tension is applied to the recording medium 1.

[0052] The drying device 110 may further include conveying means (not shown) for conveying the recording medium 1. The conveying means only needs to be able to relatively move the recording medium 1 and the energy irradiation unit 101. For example, it may be means for moving the recording medium 1, means for moving the energy irradiation unit 101, or means for moving both of them. Also, the conveying means may move the temperature control unit 102 in accordance with the position of the energy irradiation unit 101. The conveying means may continuously move the recording medium 1, the energy irradiation unit 101, etc., or intermittently move them.

[0053] Furthermore, the drying device 110 may have a housing for protecting the energy irradiation unit 101, the temperature control unit 102, the recording medium 1, etc. from dust, dirt, etc., and preventing the energy from the energy irradiation unit from leaking to the outside.

[0054] (4) Drying method using a drying device The drying method of the ink image 2 using the drying device 110 will be described below. As described above, in the drying device 110, the ink image 2 including the undried ink formed on the recording medium 1 is heated and dried. Here, the drying of the ink image 2 may be performed while relatively moving the recording medium 1 with respect to the energy irradiation unit 101, or may be performed with the recording medium 1 and the energy irradiation unit 101 fixed. When drying is performed while relatively moving the recording medium 1 with respect to the energy irradiation unit 101, the moving speed may be constant, or may continuously or intermittently change according to the position and pattern of the ink image 2, the type of the recording medium, etc.

[0055] The drying time of the ink image by the drying device 110 is not particularly limited. Generally, the shorter the drying time, the better. However, in the drying device 110, it is more preferable that the selection range of the drying time that can balance the suppression of damage to the recording medium and the sufficient drying of the ink image is wider, because it is easier to design an image forming device using the drying device and it is possible to stably form printed matter. For example, it is preferable that the selection range of the drying time that can sufficiently dry the color ink without causing damage to the recording medium is 3 seconds or more, and more preferably 5 seconds or more.

[0056] In this specification, the drying time of the ink image refers to the time from the start to the end of energy irradiation. More specifically, when the energy irradiation unit 101 is an infrared light irradiation unit and drying is performed while transporting the recording medium 1, the irradiation start is defined as the time when a predetermined position on the recording medium 1 is located directly below the most upstream end of the heat source of the infrared light irradiation unit, and the irradiation end is defined as the time when the predetermined position on the recording medium 1 is located directly below the most downstream end of the heat source. On the other hand, when the energy irradiation unit 101 is an ultraviolet light irradiation unit and drying is performed while transporting the recording medium 1, the irradiation start is defined as the time when a predetermined position on the recording medium 1 is located directly below the most upstream end of the light source of the ultraviolet light irradiation unit, and the irradiation end is defined as the time when the predetermined position on the recording medium 1 is located directly below the most downstream end of the light source.

[0057] Also, while energy is being irradiated from the energy irradiation unit 101 to the recording medium 1 and the ink image 2, it is preferable that the surface temperature of the heat conduction part 102a of the temperature control unit 102 is constant. For example, when energy is being continuously or intermittently irradiated by the energy irradiation unit 101, the temperature of the heat conduction part 102a itself may increase. In such a case, the heat conduction part 102a is cooled by the temperature adjustment mechanism 102b inside the temperature control unit 102. On the other hand, when it is desired to increase the temperature of the non-printing surface 1b side of the recording medium 1, the heat conduction part 102a is heated by the temperature adjustment mechanism 102b.

[0058] The surface temperature of the heat conduction part 102a when energy irradiation is performed by the energy irradiation unit 101 is preferably a temperature that does not affect the recording medium 1. For example, when the recording medium 1 is made of resin, it is preferably set to a temperature 5°C or more lower than the glass transition temperature (Tg) of the recording medium 1 (resin). Also, regardless of the type of the recording medium 1, the surface temperature of the heat conduction part 102a is preferably less than 80°C, more preferably less than 70°C. On the other hand, the lower limit is preferably 50°C, and preferably 60°C. When the surface temperature of the heat conduction part 102a is less than 80°C, it is difficult for the recording medium 1 and the resulting image to deteriorate.

[0059] (Recording medium) Here, the recording medium 1 that can be used in the drying device 110 is preferably made of a material that is less likely to deteriorate by heating by irradiation with infrared light or ultraviolet light. The recording medium 1 may be composed of a single layer or may be a laminate of a plurality of layers. Further, it may be one with printing on the surface, or one with embossing, punching, or the like. The printed surface 1a of the recording medium 1 may have the same color throughout, or may have a region (region with different energy absorption rate) with a color different from other regions in part. For example, as shown in FIG. 1A, marks for alignment when forming an ink image printed on the recording medium 1 in advance, marks indicating a cutting position for cutting the printed matter, and patterns for enhancing the design of the printed matter (hereinafter, these are also collectively referred to as "pre-printed portions 4") may be provided on the recording medium 1. When the pre-printed portion 4 is formed on the recording medium 1 and the color of the pre-printed portion 4 is dark, for example, when the ink image 2 is dried, the temperature of the pre-printed portion 4 may rise, and the recording medium 1 may be easily deformed. However, according to the drying device 110 described above, since the heat conduction portion 102a of the temperature control portion 102 makes the temperature of the recording medium 1 uniform, such deformation is less likely to occur.

[0060] The method for forming the pre-printed portion 4 is not particularly limited. The pre-printed portion 4 may be printed by a known printing method, such as an inkjet method, gravure printing, screen printing, or the like.

[0061] Also, as described above, the recording medium 1 may be in a long strip shape or a single-sheet shape. Here, the recording medium 1 may have regions with different thicknesses in part, but it is preferable that the thickness is constant because it is easier to adjust the temperature by the temperature control portion 102 of the drying device 110 described above.

[0062] Examples of the recording medium 1 include known plastic films. Examples of plastic films include polyester films such as polyethylene terephthalate; polyolefin films such as polyethylene films and polypropylene films; polyamide-based films such as nylon; polystyrene films; polyvinyl chloride films; polycarbonate films; polyacrylonitrile films; biodegradable films such as polylactic acid films; etc. Further, the recording medium 1 may be a metal plate, a metal film, an inorganic film such as glass, leather, etc. Furthermore, the recording medium 1 may be a laminate of these.

[0063] The thickness of the recording medium 1 is appropriately selected according to the use of the printed matter, the type of the recording medium 1, etc. However, if the thickness of the recording medium 1 is excessively thick, it may be difficult to adjust the temperature by the above-described temperature control unit 102 when the ink image 2 dries. Therefore, when the recording medium 1 is a plastic film, its thickness is preferably 5 to 150 μm, more preferably 10 to 120 μm, and even more preferably 12 to 60 μm. When the recording medium 1 is a metal plate, its thickness is preferably 0.05 to 0.5 mm, more preferably 0.1 to 0.3 mm. When the recording medium 1 is leather, its thickness is preferably 1 to 5 mm, more preferably 1 to 3 mm. The thinner the recording medium 1 is, the more easily the recording medium 1 itself is affected when the ink image 2 dries.

[0064] (Ink image) The pattern, area, etc. of the ink image 2 that can be dried by the above-described drying device 110 are not particularly limited. For example, the ink image 2 may be formed on the entire printing surface 1a of the recording medium 1, or may be formed only on a partial region of the printing surface 1a. Further, the ink image 2 may contain only one type of ink, or may contain a plurality of types of inks.

[0065] In particular, when the absorption rate of the energy with a wavelength of 1.2 μm of the recording medium 1 is set to 1, the ink image 2 preferably includes a region where the absorption rate of the energy with a wavelength of 1.2 μm is 1.3 or more. In this way, when the absorption rate of the energy of the recording medium 1 and the absorption rate of the energy of the ink region 2 are significantly different, uneven heating occurs in a general drying device. On the other hand, according to the drying device 110, even if the energy absorption rate of the recording medium 1 and the energy absorption rate of the ink image 2 are significantly different, the temperatures of the recording medium 1 and the ink image 2 are likely to be uniform. The absorption rate of the energy with a wavelength of 1.×μm of the recording medium 1 and the absorption rate of the energy with a wavelength of 1.2 μm of the ink image 2 are measured by a Fourier transform infrared spectrophotometer.

[0066] Here, the composition of the ink constituting the ink image 2 is not particularly limited as long as it can be dried by heating, and it may be composed only of a color ink containing a colorant and a solvent. However, an embodiment in which the ink image 2 includes a primer ink and a color ink is particularly preferable. When the ink image 2 includes a primer ink and a color ink, even if the time from the formation to the drying of the ink image 2 is prolonged, the ink image 2 is less likely to bleed, and a desired high-quality image can be obtained. Further, when the ink image 2 includes a primer ink and a color ink, as described in the section on the image forming apparatus, it is possible to arrange the ink image forming section and the drying section separately. Therefore, it is possible to suppress clogging of the nozzles for ink application and deterioration of the ink due to the heat generated in the drying section.

[0067] The ink image 2 preferably contains 5 to 35% by mass of a water-soluble solvent in the undried state. The amount of the water-soluble solvent in the ink image 2 is more preferably 5 to 20% by mass.

[0068] Hereinafter, the color ink and the primer ink constituting the ink image 2 will be described.

[0069] · Color Ink The color ink only needs to contain at least a colorant, and for example, it can be an ink containing a colorant, a dispersant for dispersing the colorant, resin fine particles, and a solvent.

[0070] Examples of colorants include known pigments. The colorant can be either an organic pigment or an inorganic pigment. When using the primer ink described later together with the color ink, an anionic pigment is preferably used as the colorant. When the colorant is an anionic pigment, it is more easily fixed by the primer ink described later. Also, the average particle diameter of the pigment in the color ink is preferably 50 nm or more and less than 200 nm. The average particle diameter of the pigment is a value measured by the dynamic light scattering method.

[0071] The amount of the colorant in the color ink is not particularly limited, but when the colorant is an inorganic pigment, 7 to 18% by mass is preferable, and when the colorant is an organic pigment, 0.5 to 7% by mass is preferable.

[0072] Examples of the dispersant for dispersing the colorant include polymer dispersants having an anionic group. The molecular weight of the polymer dispersant is preferably 5000 to 200000.

[0073] Examples of the polymer dispersant include block copolymers, random copolymers, and salts thereof of two or more monomers selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives; polyoxyalkylene; polyoxyalkylene alkyl ether; and the like. Commercially available products can be used as the polymer dispersant, and examples of commercially available products of the polymer dispersant include 819 manufactured by BASF.

[0074] The amount of the dispersant is preferably 10 to 100% by mass, more preferably 10 to 40% by mass, based on the amount of the colorant.

[0075] The above coloring agent and dispersant are preferably contained in the color ink in a state where the coloring agent is coated with the dispersant, i.e., in the state of so-called capsule pigment. The method of coating the coloring agent with the dispersant is not particularly limited, and for example, a phase inversion emulsification method or an acid precipitation method may be used. Further, the coloring agent may be dispersed in a dispersion medium by a polymerizable surfactant, a monomer serving as a raw material of a polymer dispersant may be supplied to the dispersion medium, and the coloring agent may be coated with the polymer dispersant by polymerization.

[0076] The resin fine particles contained in the color ink are preferably resin fine particles insoluble in water (hereinafter, also referred to as "water-insoluble resin fine particles"). Examples of the water-insoluble resin fine particles include polyester resins, polyurethane resins, polyacrylic resins, or composite resins of polyurethane resins and polyacrylic resins. These water-insoluble resin fine particles are preferably anionic.

[0077] From the viewpoint that the water-insoluble resin fine particles can be emulsified in a solvent described later without using a surfactant or the like, the water-insoluble resin fine particles preferably have an acid structure. Examples of the acid structure include a carboxy group (-COOH), a sulfonic acid group (-SO3H), and the like. The acid structure may be present in the side chain of the resin or at the terminal.

[0078] Further, when the water-insoluble resin fine particles have an acid structure, part or all of the acid structure may be neutralized. When the acid structure is neutralized, the water dispersibility of the water-insoluble resin fine particles is improved. Examples of the neutralizing agent include organic amines, and specific examples thereof include trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, triethanolamine, and the like.

[0079] The resin fine particles may be commercially available products. Examples thereof include Pes resin A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX manufactured by Takamatsu Oil & Fat Co., Ltd.; Elite KA-5034, KA-5071S, KA-1449, KA-0134, KA-3556, KA-6137, KZA-6034, KT-8803, KT-8701, KT-9204, KT-8904, KT-0507, KT-9511, etc. manufactured by Unitika Ltd.

[0080] Examples of commercially available products of urethane resin fine particles include NeoRez R-967, R-600, R-9671 manufactured by Enomoto Kasei Co., Ltd.; W-6061, W-5661, WS-4000, etc. manufactured by Mitsui Chemicals, Inc.

[0081] Examples of commercially available products of acrylic resin fine particles include NeoCryl A-1127 manufactured by Enomoto Kasei Co., Ltd.; Mobinyl 6899D, 6969D, 6800D, 6810 manufactured by Japan Coating Resin Co., Ltd.; TOCRYL W-7146, W-7150, W-7152, etc. manufactured by Toyochem Co., Ltd.

[0082] The amount of the resin fine particles in the color ink is not particularly limited, preferably 2 to 10% by mass, more preferably 2 to 5% by mass.

[0083] The solvent contained in the color ink is preferably water and / or a water-soluble solvent. A water-soluble solvent means a solvent that, at 20°C, when 100 parts by mass of the solvent is mixed with 100 parts by mass of water and stirred, maintains a uniform appearance even after the flow has subsided. Examples of water-soluble solvents include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, etc. The ink may contain only one kind or two or more kinds of solvents.

[0084] Specific examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol, benzyl alcohol, and the like.

[0085] Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having 4 or more propylene oxide groups, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, and the like.

[0086] Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, and the like.

[0087] Examples of amides include formamide, N,N-dimethylformamide, N,N-dimethylacetamide, and the like.

[0088] Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, and the like.

[0089] Examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

[0090] Among these, polyhydric alcohols are preferred from the viewpoint of suppressing bleeding of the ink image, and 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferred. From the viewpoint of being likely to have good wettability to a non-absorbent recording medium, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol are particularly preferred.

[0091] The color ink preferably contains both water and a water-soluble solvent as the solvent. The amount of water in the color ink is not particularly limited, but is preferably 45 to 80% by mass. On the other hand, the amount of the water-soluble solvent in the color ink is preferably 5 to 35% by mass, more preferably 5 to 25% by mass, and still more preferably 5 to 20% by mass.

[0092] The color ink may further contain a known surfactant, a storage stabilizer, etc. as necessary.

[0093] Here, the viscosity of the color ink before being applied to the recording medium, measured by a viscometer (MCR-102) manufactured by Anton Paar at a temperature of 25°C and a shear rate of 1000 (1 / sec), is preferably 1 to 40 mPa·s at 25°C, and more preferably 2 to 10 mPa·s. When the viscosity of the color ink is within this range, after being applied to the recording medium, the color ink is less likely to flow, and a high-quality image is easily obtained.

[0094] Also, the static surface tension of the ink before being applied to the recording medium is preferably greater than the static surface tension of the primer ink described later. From the viewpoint of being able to form an image with high quality on a non-absorbent recording medium, the static surface tension of the color ink is preferably 22 to 33 mN / m at 25°C, more preferably 22 to 26 mN / m. The static surface tension of the color ink can be measured with a surface tension meter.

[0095] · Primer Ink The primer ink only needs to contain at least a flocculant, and for example, it can be an ink containing a flocculant and a solvent. According to such a primer ink, bleeding or the like is less likely to occur even when the color ink is applied without drying after the application of the primer ink. Therefore, before applying the color ink, there is no need for a drying or curing process, and an ink image can be formed in a simple process. Also, when using a primer ink having such a composition, even if the time until drying is long after the formation of the ink image, the ink image is less likely to bleed. Therefore, a high-quality image can be obtained. Note that the primer ink may further contain a surfactant, a crosslinking agent, a fungicide, a bactericide, etc. as needed, but the primer ink preferably does not contain the above-mentioned resin fine particles. Since the primer ink does not contain resin fine particles, thickening of the primer ink is less likely to occur.

[0096] The flocculant only needs to be able to cause aggregates when combined with the above color ink. The flocculant functions to fix the ink image on the recording medium. The flocculant is appropriately selected according to the type of colorant in the color ink.

[0097] Examples of the flocculant include a dissolution-type cationic polymer having thermal decomposability, a polyvalent metal salt, or an organic acid, and in terms of its pH being neutral or weakly alkaline, a dissolution-type cationic polymer or a polyvalent metal salt is more preferable.

[0098] The dissolution-based cationic polymer and the polyvalent metal salt aggregate the anionic components (such as colorants) in the color ink by salting out. On the other hand, the organic acid aggregates the anionic components in the color ink by pH fluctuation.

[0099] Examples of the dissolution-based cationic polymer include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride. Examples of commercially available products include KHE100L and FPA100L manufactured by Senka Corporation; PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nittobo Medical Co., Ltd.

[0100] Examples of the polyvalent metal salt include water-soluble salts such as calcium salts, magnesium salts, aluminum salts, and zinc salts. Compounds that form salts with polyvalent metals include hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanic acid, and organic carboxylic acids such as acetic acid, oxalic acid, lactic acid, fumaric acid, citric acid, salicylic acid, and benzoic acid, and organic sulfonic acids.

[0101] Examples of the organic acid include compounds having a carboxy group such as formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, lactic acid, acrylic acid and its derivatives, methacrylic acid and its derivatives, acrylamide and its derivatives; sulfonic acid derivatives; phosphoric acid and its derivatives; and the like.

[0102] Note that the organic acid is preferably an acid having a first dissociation constant of 3.5 or less, and more preferably 1.5 to 3.5. When the first dissociation constant is within this range, it is easy to fix the color ink on the recording medium.

[0103] The primer ink preferably contains 5% by mass or less of a flocculant, more preferably 1 to 4% by mass. When the primer ink contains a flocculant within this range, the anionic components in the color ink are effectively flocculated, resulting in good image quality. The amount of the flocculant in the primer ink can be measured by known methods. For example, when the flocculant is a polyvalent metal salt, it can be measured by ICP emission spectrometry, and when the flocculant is an organic acid, it can be measured by high performance liquid chromatography (HPLC).

[0104] The solvent in the primer ink is preferably water and / or a water-soluble solvent, and it is preferable to contain both of them. The types of water-soluble solvents are the same as those in the color ink described above. Also, the amount of water in the primer ink is preferably 45 to 80% by mass. On the other hand, the amount of the water-soluble solvent in the primer ink is preferably 5 to 35% by mass, more preferably 5 to 20% by mass.

[0105] Moreover, the viscosity of the primer ink measured by an Anton Paar viscometer (MCR-102) at a temperature of 25°C and a shear rate of 1000 (1 / sec) is preferably 1 to 40 mPa·s, more preferably 1 to 10 mPa·s, and even more preferably 4 to 7 mPa·s. When the viscosity of the primer ink is within this range, after being applied to the recording medium, the primer ink is less likely to flow, and high-quality images can be easily obtained.

[0106] Also, as described above, the static surface tension of the primer ink at 25°C is preferably smaller than the static surface tension of the color ink. The static surface tension of the primer ink is preferably 22 to 30 mN / m at 25°C, more preferably 22 to 26 mN / m.

[0107] The dynamic surface tension of the primer ink at 25°C and 50 ms is preferably 40 mN / m or less, more preferably 36 mN / m or less, and even more preferably 35 mN / m or less. The lower limit value of the dynamic surface tension is preferably 25 mN / m. The dynamic surface tension of the primer ink can be measured by a dynamic surface tensiometer. Unless otherwise specified, the dynamic surface tension in this specification is the dynamic surface tension at 25°C and 50 ms.

[0108] 2. Image forming apparatus The above drying device may be used alone or in combination with an ink image forming unit or the like for use in an image forming apparatus. A plan view of an image forming apparatus 100 according to an embodiment of the present invention is shown in FIG. 3A, and a side view of the image forming apparatus 100 is shown in FIG. 3B. The image forming apparatus 100 includes a conveyance unit (not shown) for conveying a recording medium 1, an ink image forming unit 120 (a primer ink ejection unit 12P and a color ink ejection unit 12Q) for forming an ink image, and a drying unit (the above drying device) 110 for forming the ink image.

[0109] In addition, the image forming apparatus may, if necessary, include a fixing unit (not shown) for further fixing the image after drying in the drying unit 110 to the recording medium 1, a feeding unit (not shown) for feeding out the recording medium 1, a winding unit (not shown) for winding up the recording medium 1, and the like. Since the drying unit 110 is the same as the above-described drying device 110, the description thereof is omitted, and hereinafter, the ink image forming unit 120 will be described.

[0110] (Ink image forming unit) The ink image forming unit 120 may have only the color ink ejection unit 12Q for ejecting color ink, but in the image system apparatus shown in FIGS. 3A and 3B, it has a primer ink ejection unit 12P and a color ink ejection unit 12Q.

[0111] In addition, when the ink image forming unit has only the color ink ejection unit 12Q, if the time from applying the color ink to drying is long, the ink image may bleed. Therefore, it is preferable to arrange the ink image forming unit 120 (color ink ejection unit Q) at a position close to the drying unit 110. However, if the distance between the ink image forming unit 120 and the drying unit 110 is short, the heat from the drying unit 110 is likely to be transmitted to the ink image forming unit 120, and the ink may thicken or the nozzles may become clogged within the ink image forming unit 120.

[0112] Therefore, it is preferable that the ink image forming unit 120 includes a primer ink ejection unit 12P and a color ink ejection unit 12Q. When the primer ink is applied onto the recording medium 1 and then the color ink is ejected onto the undried primer ink, the ink image 2 is likely to be retained on the recording medium 1. Thus, for example, as shown in FIGS. 3A and 3B, the ink image forming unit 120 and the drying unit 110 can be arranged at a sufficient distance from each other.

[0113] Here, the primer ink ejection unit 12P only needs to be able to eject a desired primer ink. Examples of the primer ink include those described above. When the above-described primer ink is used, after the application of the primer ink, the color ink can be applied without drying the primer ink. However, the color ink may also be applied after drying the primer ink.

[0114] On the other hand, the color ink ejection unit 12Q only needs to be able to eject a desired color ink. Examples of the color ink include those described above. The type of the color ink ejected by the color ink ejection unit Q is not particularly limited. In FIGS. 3A and 3B, the color ink ejection unit Q includes a black ink ejection unit 12K, a cyan ink ejection unit 12C, a magenta ink ejection unit 12M, and a yellow ink ejection unit 12Y, but is not limited thereto. Also, the arrangement order of the respective color ink ejection units is appropriately selected according to a desired printed matter and is not limited to the mode shown in FIGS. 3A and 3B.

[0115] Here, when the energy irradiation unit 101 of the drying unit 110 has an infrared light irradiation unit, when applying two or more color inks each containing colorants with different absorption rates of infrared light having a specific wavelength selected from 0.8 μm or more and 3.0 μm or less as the color ink, the degree of temperature rise of the temperature of each color ink is different. Therefore, the drying speeds are likely to be different among them. Thus, if necessary, the composition of the color ink may be adjusted so that the drying speeds of these two or more colors, for example, the drying rates when dried in an oven at 100 °C for 30 seconds, are different. The absorption rate of infrared light of the colorant contained in each color ink can be specified by an ultraviolet-visible-near-infrared spectrophotometer (for example, UH4150 manufactured by Hitachi High-Technologies Corporation, etc.). When measuring the absorption rate of infrared light for a plurality of colorants, the measurement wavelength shall be the same wavelength.

[0116] On the other hand, for the drying rate, the same amount (for example, 10 g each) of each ink is dropped into a petri dish, and its mass A is measured. Then, the hot air oven is set to 100 °C, left standing for 30 seconds, and then the mass B is measured. And the value obtained by dividing the weight reduction amount (A - B) in the hot air oven by the ink amount ((A - B) / 10)×100) is defined as the drying rate.

[0117] Here, as a method for adjusting the drying rates of a plurality of color inks, for the color ink for which the drying rate is desired to be decreased, a solvent with a high boiling point is used or its amount is adjusted. On the other hand, for the color ink for which the drying rate is desired to be increased, a solvent with a low boiling point is used or its amount is reduced.

[0118] Note that it is preferable to adjust so that the drying rate of the color ink with a low temperature rise, that is, the color ink containing the colorant with a high absorption rate of the infrared light, is lower than the drying rate of the color ink containing the colorant with a low absorption rate of the infrared light.

[0119] Also, when the energy irradiation unit 101 of the drying unit 110 has an ultraviolet light irradiation unit, when applying two or more color inks each containing a colorant with different absorption rates of ultraviolet light having a specific wavelength selected from 200 nm to 410 nm as the color ink, the degree of temperature rise of the temperature of each color ink is different. Therefore, the drying speeds are likely to be different among them. Thus, also in this case, if necessary, the composition of the ink may be adjusted so that the drying speeds of these two or more colors, for example, the drying rates when dried in an oven at 100°C for 30 seconds, are different. The absorption rate of ultraviolet light of the colorant contained in each color ink can be specified by an ultraviolet-visible near-infrared spectrophotometer (for example, UH4150 manufactured by Hitachi High-Technologies Corporation, etc.). Also, when measuring the absorption rate of ultraviolet light for a plurality of colorants, the measurement wavelength shall be the same wavelength. Also, the method for measuring the drying rate and the method for adjusting the drying rate are the same as above.

[0120] Also at this time, it is preferable to adjust so that the drying rate of the color ink with a difficult temperature rise, that is, the color ink containing the colorant with a high absorption rate of the ultraviolet light, becomes lower than the drying rate of the color ink containing the colorant with a low absorption rate of the ultraviolet light.

[0121] Here, the primer ink ejection unit 12P and the color ink ejection unit 12Q (hereinafter, these are also collectively referred to as "ink ejection unit 12") may be a line-type ejection unit or a serial head-type ejection unit as shown in FIGS. 3A and 3B. However, from the viewpoint of being able to form an ink image in a short time, a line-type ejection unit is more preferable. When the ink ejection unit 12 is a line-type ejection unit, usually, the primer ink ejection unit 12P is arranged on the upstream side and the color ink ejection unit 12Q is arranged on the downstream side. However, the primer ink ejection unit 12P may be arranged on the downstream side of the color ink ejection unit 12Q. Also, it may have a configuration for temporarily curing the primer ink ejected by the primer ink ejection unit 12P or the color ink ejected by the color ink ejection unit 12Q, if necessary.

[0122] Each ink ejection unit 12 includes a head for ejecting primer ink and color ink, and an ink tank for storing the primer ink and color ink. The type of the head of each ink ejection unit 12 is not particularly limited, and may be either an on-demand type or a continuous type. Examples of the on-demand type head include electro-mechanical conversion types such as single cavity type, double cavity type, vender type, piston type, share mode type, and shared wall type; electro-thermal conversion types such as thermal inkjet type and bubble jet (the “bubble jet” is a registered trademark of Canon Inc.) type. Among these, the electro-mechanical conversion type head is preferable, and particularly, a head using a piezoelectric element (also referred to as a “piezo type inkjet head”) is preferable.

[0123] (Conveying unit) The type of the conveying unit is not particularly limited as long as it can convey the recording medium 1 from the ink image forming unit 120 side to the drying unit 110 side, and it can have the same structure as the conveying unit of a known image forming apparatus. The conveying unit may be structured to support the recording medium 1 from the non-printing surface side, but in the drying unit 110 described above, it is preferable to support the recording medium 1 such that the non-printing surface of the recording medium 1 is in close contact with the heat conducting portion 102a of the temperature control unit 102.

[0124] (Image forming method using the above image forming apparatus) In the image forming method using the above-described image forming apparatus 100, ink is applied to the printing surface 1a of the recording medium 1 by the ink image forming unit 120 to form an ink image 2. At this time, in the ink image forming unit 120, primer ink is applied onto the recording medium 1 by the primer ink ejection unit 12P, and color ink is applied onto the undried primer ink by the color ink ejection unit 12Q.

[0125] After forming the desired ink image 2, the transport unit moves the recording medium 1 toward the drying unit 110. Then, while bringing the heat conduction part 102a of the temperature control unit 102 into contact with the non-printing surface 1b of the recording medium 1, energy is irradiated from the energy irradiation unit 101 onto the printing surface 1a of the recording medium 1. At this time, the energy irradiation unit 101 irradiates infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less at an output of 30 kW / m 2 or more, or irradiates ultraviolet light with a wavelength of 200 nm or more and 410 nm or less at an illuminance of 1 W / m 2 or more. On the other hand, in the temperature control unit 102, the temperature of the heat conduction part 102a is adjusted by the temperature adjustment mechanism 102b so that the temperature of the recording medium 1 and the ink image 2 becomes constant.

[0126] Note that the energy irradiation time by the energy irradiation unit 101, the surface temperature of the heat conduction part 102a controlled by the temperature control unit 102, etc. are the same as in the above drying method.

[0127] (Others) As described above, the image forming apparatus 100 may include components other than the ink image forming unit 120 and the drying unit 110. A side view showing a modified example of the image forming apparatus 100 is shown in FIG. 4. Note that the same components as those of the image forming apparatus shown in FIGS. 3A and 3B are denoted by the same reference numerals, and detailed description thereof is omitted.

[0128] The image forming apparatus 200 according to this modification example is an image forming apparatus that performs printing in a roll-to-roll method. In addition to the above-described ink image forming unit 120 and drying unit 110, it further includes a feeding unit 131 for feeding out the recording medium 1, a fixing unit 132 for further fixing the image dried by the drying unit 110 onto the recording medium 1, and a winding unit 133 for winding up the printed matter. Further, the image forming apparatus 200 includes a first ink image forming unit 120A having a primer ink ejection unit 12P and a color ink ejection unit 12Q (white ink ejection unit 12W), and a second ink image forming unit 120B having a primer ink ejection unit 12P and color ink ejection units 12Q (yellow ink ejection unit 12Y, magenta ink ejection unit 12M, cyan ink ejection unit 12C, black ink ejection unit 12K). A first drying unit 110A and a second drying unit 110B are respectively arranged downstream of the first ink image forming unit 120A and the second ink image forming unit 120B.

[0129] In the image forming apparatus 200, primer ink and white ink are applied to the recording medium 1 fed out from the feeding unit 131 by the first ink image forming unit 120A. Then, the ink image is dried by the first drying unit 110A.

[0130] Subsequently, primer ink and each color ink are further applied to the recording medium 1 by the second ink image forming unit 120B. Then, the ink image formed by the second ink image forming unit 120B is dried by the second drying unit 110B.

[0131] Thereafter, the fixing unit 132 blows hot air onto the recording medium 1 to further fix the image onto the recording medium 1. Then, the winding unit 133 winds up the printed matter into a roll. Note that the configurations of the feeding unit 131, the winding unit 133, and the fixing unit 132 are the same as those of the respective components of a conventional image forming apparatus.

Example

[0132] Hereinafter, specific examples of the present invention will be described together with comparative examples, but the present invention is not limited thereto. In the examples, "parts" and "%" mean "parts by mass" and "mass %" unless otherwise specified.

[0133] (1) Preparation of primer ink 3 parts by mass of calcium acetate, 20 parts by mass of propylene glycol, 0.5 parts by mass of a surfactant (KF-351A, manufactured by Shin-Etsu Chemical Co., Ltd.), and 66.5 parts by mass of water were mixed to obtain primer ink. The viscosity of the primer ink measured by a viscometer (MCR-102) manufactured by Anton Paar at a temperature of 25°C and a shear rate of 1000 (1 / sec) was 4.89 mPa·s. At 25°C, the static surface tension measured by a surface tension meter was 28.8 mN / m, and the dynamic surface tension at 25°C and 50 ms was 38.3 mN / m.

[0134] (2) Preparation of color ink Each component shown in Table 1 was mixed in the compositions shown in Table 1 and Table 2 to prepare yellow ink (Y), magenta ink (M), cyan ink (C), black ink (K), and white ink (W), respectively, and each was made into a color ink set.

[0135] (3) Measurement of ultraviolet light absorption rate and infrared light absorption rate of colorants (pigments) contained in color ink The ultraviolet light absorption rate and infrared light absorption rate of the colorants contained in the above color ink were specified by an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Technologies Corporation). When measuring the ultraviolet light absorption rate, the absorption rate of light with a wavelength of 365 nm was measured. When measuring the infrared light absorption rate, the absorption rate of light with a wavelength of 1.2 μm was measured.

[0136] (4) Drying rate when heated at 100°C for 30 seconds The inks of ink sets 5 to 7 were each dropped in the same amount (for example, 10 g each) into a petri dish, and their mass A was measured. Then, a hot air oven was set to 100°C, and the petri dish was left in the oven for 30 seconds. Then, the mass B after heating was measured. From the obtained values, the drying rate (= ((A - B) / 10) × 100) was specified.

[0137]

Table 1

[0138] (3) Examples and Comparative Examples · Example 1 An ink image forming unit including a primer ink ejection unit and a color ink ejection unit was filled with primer ink and each color ink of Color Ink Set 1. The primer ink ejection unit and the color ink ejection unit used those equipped with an independently driven inkjet head (360 dpi, ejection volume: small droplet 7 pL, medium droplet 15 pL, large droplet 23 pL) manufactured by Konica Minolta. Further, the inkjet head was disposed on a roll-to-roll apparatus, and the inkjet head was connected to a head control device IJCS-1 manufactured by Konica Minolta. Then, on a long polyethylene terephthalate film (recording medium) with a recording medium thickness of 20 μm, the primer ink was applied in a solid 20% pattern, and the color ink was applied in a solid 100% pattern for each color to form an ink image.

[0139] Subsequently, the recording medium with the ink image formed thereon was moved to a drying unit having a temperature control unit. A medium wavelength carbon IR heater (wavelength 1.2 μm, heat source temperature: 1200 °C) manufactured by Heraeus was used for the infrared light irradiation unit. Also, the temperature control unit of the drying unit was assumed to have a metal roll (heat conduction unit) and a temperature adjustment mechanism disposed within the metal roll. Then, the temperature of the surface of the metal roll was adjusted by the temperature adjustment mechanism so that the surface temperature of the metal roll was always 60 °C, and drying was performed while bringing the metal roll into contact with the recording medium.

[0140] And the output value of the infrared light irradiation unit was 30 kW / m 2 , 60 kW / m 2 , 100 kW / m 2 , and 150 kW / m 2and the drying property of the color ink when the irradiation time of the infrared light was changed was confirmed. The evaluation was conducted as follows. The results are shown in Table 2. OK: The ink is completely dried and there is no change even when wiping or tape peeling is performed. Not dried: The ink is in an undried state and is removed by wiping or tape peeling. Substrate deformation: The substrate (recording medium) is deformed or burned.

[0141] · Example 2 The ink image was dried in the same manner as in Example 1, except that the surface temperature of the metal roll of the temperature control unit was always adjusted to 50°C. The results are shown in Table 2.

[0142] · Comparative Example 1 The ink image was dried in the same manner as in Example 1, except that the metal roll of the temperature control unit was not used. The results are shown in Table 2.

[0143]

Table 2

[0144] · Example 3 The drying of the ink image coated with the primer ink and the color ink of Ink Set 1 was performed in the same manner as in Example 1, except that the infrared light irradiation unit of the drying device was changed to an ultraviolet light irradiation unit (light source: LED lamp, wavelength: 385 nm). The illuminance from the ultraviolet light irradiation unit was set to 4 kW / cm 2 , 2 kW / cm 2 , and 1 kW / cm 2 , and the drying property of the color ink when the irradiation time of the ultraviolet light was changed was confirmed. The results are shown in Table 3.

[0145] · Example 4 The ink image was dried in the same manner as in Example 3, except that the surface temperature of the metal roll of the temperature control unit was always adjusted to 50°C. The results are shown in Table 3.

[0146] · Comparative Example 2 The ink image was dried in the same manner as in Example 3, except that the metal roll of the temperature control unit was not used. The results are shown in Table 3.

[0147]

Table 3

[0148] As shown in Tables 2 and 3 above, when the ink image was dried while controlling the temperature in the temperature control unit, there was little variation in the drying properties of each color ink, and even when irradiating with infrared light or ultraviolet light at a higher output, deformation of the recording medium was unlikely to occur (Examples 1 to 4). On the other hand, when the temperature was not adjusted in the temperature control unit, the recording medium was likely to deteriorate or the curing was likely to be insufficient (Comparative Examples 1 and 2).

[0149] · Example 5 Using the above-described primer ink and the Y ink and K ink of Ink Sets 1 to 6, an ink image was formed and dried in the same manner as in Example 1. At this time, the output of the infrared light irradiation unit was 100 kW / m 2 and the temperature of the temperature control unit was 60°C. Also, by changing the drying time, the range of irradiation time in which there was no deformation of the recording medium and both inks could be dried was specified for the Y ink and K ink. The said range is shown in Table 4.

[0150]

Table 4

[0151] As shown in Table 4 above, when applying and drying two-color inks (Y ink and K ink) containing colorants with different infrared light absorption rates, by using Ink Sets 5 and 6 with different drying rates for each color, it became clear that the time during which each color ink could be sufficiently dried without deforming the recording medium was extended.

[0152] · Example 6 Using the above primer ink, Ink Sets 1 and 7, and the Y and M inks, an ink image was formed and dried in the same manner as in Example 3. At this time, the illuminance from the ultraviolet light irradiation unit was 4 kW / cm 2 and the temperature of the temperature control unit was set to 60°C. Also, by changing the drying time, the range of irradiation time in which there was no deformation of the recording medium and both inks could be dried was specified for the Y and M inks. Table 5 shows this range.

[0153]

Table 5

[0154] As shown in Table 5 above, when applying and drying two colors of ink (Y ink and M ink) containing colorants with different ultraviolet light absorption rates, by using Ink Set 7 with different drying rates for each color, it became clear that the time during which each color ink could be sufficiently dried was extended without deforming the recording medium.

Industrial Applicability

[0155] According to the drying device of the present invention, it is possible to sufficiently dry the ink image formed on the recording medium in a short time, and it is difficult to damage the recording medium and the formed image. Therefore, it is useful in various printing fields.

Explanation of Reference Numerals

[0156] 1 Recording medium 1a One surface (printing surface) of the recording medium 1b The other surface (non-printing surface) of the recording medium 2 Ink image 4 Printed area 12C Cyan ink ejection unit 12K Black ink ejection unit 12M Magenta ink ejection unit 12P Primer ink ejection unit 12Q Color ink ejection unit 12Y Yellow ink ejection unit 100, 200 Image forming apparatus 101 Energy irradiation unit 102 Temperature control unit 102a Heat conduction part 102b Temperature adjustment mechanism 110 Drying device (drying part) 120 Ink image forming part 131 Unwinding part 132 Fixing part 133 Rewinding part

Claims

1. A drying device for drying an ink image containing undried ink formed on one surface of a recording medium, comprising: an energy irradiation unit that irradiates energy onto one surface of the recording medium to heat and dry the ink image; a temperature control unit that is disposed so as to face the energy irradiation unit with the recording medium interposed therebetween and that contacts the other surface of the recording medium; and having the temperature control unit includes a metal roll that contacts the other surface of the recording medium. The energy irradiation unit irradiates infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less at an output of 30 kW / m ２ or more, or an infrared light irradiation unit that irradiates ultraviolet light with a wavelength of 200 nm to 410 nm on one surface of the recording medium at an illuminance of 1 W / cm ２ or more, and includes any one of ultraviolet light irradiation units. A drying device.

2. When irradiating energy by the energy irradiation unit, the temperature control unit adjusts the surface temperature of the temperature control unit to less than 80°C. The drying device according to claim 1.

3. The drying device according to claim 1, wherein the thermal conductivity of the metal roll is 150 kcal / m·h·°C or more. The drying device according to claim 1.

4. The energy irradiation unit includes an infrared light irradiation unit, and the temperature of the heat source of the infrared light irradiation unit is 900°C or more. The drying device according to any one of claims 1 to 3.

5. a conveyance unit that conveys a recording medium; a primer ink ejection unit that ejects primer ink containing a flocculant; a color ink ejection unit that ejects color ink containing a colorant; and the drying device according to any one of claims 1 to 4. An image forming apparatus having

6. A step of applying ink to one surface of a recording medium to form an ink image; A step of irradiating energy onto one surface of the recording medium while bringing a temperature control unit for controlling temperature into contact with the other surface of the recording medium to dry the ink image, including the temperature control unit includes a metal roll that contacts the other surface of the recording medium. In the step of drying the ink image, infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less is irradiated with an output of 30 kW / m ２ or more, or ultraviolet light with a wavelength of 200 nm or more and 410 nm or less is irradiated with an illuminance of 1 W / m ２ or more, an image forming method.

7. When the absorption rate of the energy having a wavelength of 1.2 μm of the recording medium is set to 1, the ink image includes a region having an absorption rate of the energy having a wavelength of 1.2 μm of 1.3 or more. The image forming method according to claim 6.

8. One surface of the recording medium has regions with different energy absorption rates in part. The image forming method according to claim 6 or 7.

9. The ink contains 5 to 20% by mass of a water-soluble solvent. The image forming method according to any one of claims 6 to 8.

10. In the step of forming the ink image, applying at least primer ink containing a flocculant, and applying at least color ink containing a colorant. The image forming method according to any one of claims 6 to 9.

11. In the step of forming the ink image, applying two or more color inks each containing a colorant having different absorption rates of infrared light with a specific wavelength selected from 0.8 μm or more and 3.0 μm or less in wavelength, or a colorant having different absorption rates of ultraviolet light with a specific wavelength selected from 200 nm to 410 nm in wavelength; The image forming method according to any one of claims 6 to 10.

12. The two or more color inks have different drying rates when dried in an oven at 100° C. for 30 seconds. The image forming method according to claim 11.

13. Among the two or more color inks, the ink containing a colorant having a high absorption rate of infrared light or ultraviolet light has a lower drying rate when dried in an oven at 100° C. for 30 seconds. The image forming method according to claim 12.

Images