Drying apparatus, image forming apparatus and image forming method

Abstract

The present invention aims to provide a drying apparatus capable of drying an ink image formed on a recording medium in a short time, while minimizing degradation of the recording medium and the formed image. The drying apparatus that solves this problem dries an ink image containing undried ink formed on one side of a recording medium. This drying apparatus includes: an energy irradiation unit for irradiating one side of the recording medium with energy to heat and dry the ink image; and a temperature control unit configured to hold the recording medium between itself and the energy irradiation unit, and to contact the other side of the recording medium. The energy irradiation unit operates at 3 W / cm². 2 The above irradiance is applied to an infrared irradiation section irradiated with infrared light of wavelengths 0.8 μm or more and 3.0 μm or less, or to one surface of the above recording medium at an irradiance of 1 W / cm. 2 The above irradiance is applied to the ultraviolet irradiated part with an ultraviolet light wavelength of 200nm to 410nm.

Description

Technical Field

[0001] This invention relates to a drying apparatus, an image forming apparatus, and an image forming method. Background Technology

[0002] In recent years, methods for forming images by coating liquid ink onto low-absorbency or non-absorbent recording media have been widely used. According to this method, desired images can be formed even on recording media with low ink absorbency, enabling the manufacture of products with high aesthetic design.

[0003] In image forming apparatuses that perform such printing, after ink is coated onto a recording medium to form an ink image, solvents and other contaminants in the ink image are removed, and the colorant is fixed to the recording medium. One known method for removing solvents from the ink image is by blowing hot air. However, hot air drying requires a drying oven, which presents the problem of the apparatus becoming too large.

[0004] Therefore, it is also possible to remove solvents from ink images by heating them with infrared light (e.g., Patent Document 1).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-162870

[0006] In recent years, there has been a demand for high-speed printing and for ink images to dry in a short time. However, under long-wavelength infrared light irradiation as described in Patent Document 1, there are problems such as difficulty in raising the temperature of the ink image and the time-consuming removal of solvent (drying of the ink image).

[0007] To address this issue, a method was considered to increase the temperature of an ink image in a short time by irradiating it with high-output energy. However, when the ink image contains multiple colors of ink, the energy absorption rates differ among the inks. Furthermore, through in-depth research by the inventors, it was clarified that when irradiated with high-output energy, the degree of temperature rise differs significantly between areas with high and low energy absorption rates, leading to uneven ink temperature during heating. For example, if the irradiation energy is applied in conjunction with the drying conditions of inks with high energy absorption rates, the temperature of inks with low energy absorption rates will not rise sufficiently, resulting in inadequate drying. On the other hand, it was clarified that if the irradiation energy is applied in conjunction with the drying conditions of inks with low energy absorption rates, the temperature of the areas coated with inks with high energy absorption rates becomes excessively high, causing the resulting image and recording medium to deteriorate due to heat.

[0008] Furthermore, if markings, patterns, or other designs are pre-printed on the recording medium, and high-output irradiation energy is applied, the temperature of only the areas of the recording medium with high energy absorption rates is likely to rise, which can easily damage the recording medium. Summary of the Invention

[0009] The present invention was made in view of the following issues. Specifically, its object is to provide a drying apparatus that can dry an ink image formed on a recording medium in a short time, and that the recording medium and the formed image are not easily degraded. Furthermore, its object is to provide an image forming apparatus and an image forming method using the drying apparatus.

[0010] The present invention provides the following drying apparatus.

[0011] A drying apparatus is provided for drying an ink image containing undried ink formed on one side of a recording medium. The drying apparatus includes: an energy irradiation unit for irradiating one side of the recording medium with energy to heat and dry the ink image; and a temperature control unit configured to sandwich the recording medium, face the energy irradiation unit, and contact the other side of the recording medium. The energy irradiation unit includes either an infrared irradiation unit or an ultraviolet irradiation unit, wherein the infrared irradiation unit operates at 3 W / cm². 2 The above-mentioned irradiance is applied to infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less, and the ultraviolet light irradiation section applies 1 W / cm² to one surface of the recording medium. 2 The above irradiance is for ultraviolet light with wavelengths of 200nm to 410nm.

[0012] The present invention provides the following image forming apparatus.

[0013] An image forming apparatus includes: a conveying unit for conveying a recording medium; a primer ink discharge unit for discharging primer ink containing a coagulant; a color ink discharge unit for discharging color ink containing a colorant; and the drying device described above.

[0014] The present invention provides the following image formation method.

[0015] An image forming method includes: a step of coating an ink onto one side of a recording medium to form an ink image; and a step of irradiating one side of the recording medium with energy while a temperature control unit for controlling temperature is in contact with the other side of the recording medium, thereby drying the ink image, wherein in the step of drying the ink image, energy is applied at 3W / cm². 2 The above irradiance refers to infrared light with wavelengths above 0.8 μm and below 3.0 μm, or at a concentration of 1 W / cm². 2 The above irradiance refers to ultraviolet light with a wavelength of 200nm or higher and 410nm or lower.

[0016] According to the drying apparatus of the present invention, the ink image formed on the recording medium can be fully dried in a short time, and the recording medium and the formed image are not easily damaged. Attached Figure Description

[0017] Figure 1A This is a top view showing the structure of a drying apparatus according to one embodiment of the present invention. Figure 1B This is a side view showing the structure of the drying device.

[0018] Figure 2 This is a side view showing a modified example of a drying apparatus according to one embodiment of the present invention.

[0019] Figure 3A This is a top view showing the structure of an image forming apparatus according to one embodiment of the present invention. Figure 3B This is a side view of the print.

[0020] Figure 4 This is a side view illustrating a modified example of an image forming apparatus according to an embodiment of the present invention. Detailed Implementation

[0021] The following describes one embodiment of the present invention in detail. However, the present invention is not limited to this embodiment.

[0022] 1. Drying device

[0023] The drying apparatus of the present invention is an apparatus for drying an ink image formed on a recording medium containing undried ink. In this drying apparatus, the temperature of the ink image is raised by energy irradiation, causing solvents and the like to evaporate, thereby drying the ink image. The drying apparatus of the present invention is particularly useful for drying ink images formed on a recording medium containing inks of multiple colors, or for drying ink images formed on a recording medium having a portion of different colors.

[0024] As described above, when forming an ink image using multiple colors of ink or creating a printed material using a recording medium with different colored areas, irradiating the ink image or recording medium with high output energy can easily lead to temperature unevenness due to the difference in energy absorption rates between the ink and the recording medium. Specifically, in areas coated with color inks with high energy absorption rates or in areas of the recording medium with high energy absorption rates, the temperature rises rapidly. On the other hand, in areas coated with color inks with low energy absorption rates or in areas of the recording medium with low energy absorption rates, the temperature does not rise easily. Therefore, if the irradiation conditions are determined in conjunction with inks with high energy absorption rates, the drying of the ink image can easily become incomplete. On the other hand, if drying is performed in conjunction with inks with low energy absorption rates, areas coated with inks with high energy absorption rates or in areas of the recording medium with high energy absorption rates are prone to deterioration. Furthermore, such temperature unevenness is less likely to occur when irradiated with long-wavelength infrared light for extended periods.

[0025] exist Figure 1A The figure shows a top view of a drying apparatus 110 according to one embodiment of the present invention. Figure 1B The image shows a side view of the drying apparatus 110. Additionally, in... Figure 2 The image shows a side view of a modified example of the drying apparatus 110. (See image below.) Figure 1A , Figure 1B as well as Figure 2 As shown, the drying apparatus 110 of this embodiment includes: an energy irradiation unit 101 for irradiating energy onto an ink image 2 formed on one side (hereinafter also referred to as the "printing side") 1a of the recording medium 1; and a temperature control unit 102 configured to sandwich the recording medium 1, face the energy irradiation unit 101, and contact the other side (hereinafter also referred to as the "non-printing side") 1b of the recording medium 1. Figure 2 The drying device 110, except for the shape of the temperature control unit 102, is similar to... Figure 1A , Figure 1B The drying device 110 shown is the same.

[0026] In the drying apparatus 110 of this embodiment, even when the ink image 2 and the recording medium 1 are irradiated with energy at a high output from the energy irradiation unit 101, the temperature of the recording medium 1 and the ink image 2 is homogenized by the temperature control unit 102 disposed on the non-printing surface 1b side of the recording medium 1. More specifically, by transferring heat from the recording medium 1 to the temperature control unit 102, the temperature of the recording medium 1 and the ink image 2 is less likely to rise excessively. On the other hand, the low-temperature areas in the recording medium 1 and the ink image 2 are heated by the temperature control unit 102. Therefore, according to this apparatus 110, the ink image 2 can be dried uniformly throughout in a short time. In addition, during the drying of the ink image 2, the temperature of the recording medium 1 and the ink image 2 does not rise excessively, so the degradation of the recording medium 1 and the obtained image is less likely to occur.

[0027] Furthermore, the drying apparatus 110 may include the aforementioned energy irradiation unit 101 and temperature control unit 102, but may also include a pressing unit (not shown) for pressing the recording medium 1 against the temperature control unit 102, a conveying unit (not shown) for conveying the recording medium 1, etc. Additionally, it may also include a housing (not shown) covering the energy irradiation unit 101, temperature control unit 102, etc. In the following description, Figure 1A , Figure 1B as well as Figure 2 The example shown is of using a strip-shaped recording medium 1, but the drying apparatus 110 can also be used to dry an ink image 2 formed on a sheet-shaped recording medium 1. The structure of the drying apparatus 110 will be described below.

[0028] (1) Energy Irradiation Section

[0029] The energy irradiation unit 101 is a structure for irradiating energy onto the ink image 2 formed on the printing surface 1a of the recording medium 1. By irradiating energy by the energy irradiation unit 101, the temperature of the ink image 2 formed on the recording medium 1 rises, the solvent and other substances in the ink image 2 evaporate, and the ink image 2 dries.

[0030] The energy irradiation unit 101 of this embodiment has an energy irradiation unit with a power of 3W / cm². 2 The above irradiance is applied to an infrared irradiated part with an infrared light wavelength of 0.8 μm or more and 3.0 μm or less, or at a concentration of 1 W / cm². 2 At least one of the above-mentioned ultraviolet irradiation sections irradiating with ultraviolet light of wavelengths from 200 nm to 410 nm is required, or both may be used. If infrared light is irradiated from the infrared irradiation section, the colorant and solvent in the ink image absorb the infrared light respectively. Furthermore, the temperature of the ink image increases, and the solvent evaporates. On the other hand, if ultraviolet light is irradiated from the ultraviolet irradiation section, the colorant in the ink image mainly absorbs ultraviolet light, and its temperature rises. Furthermore, heat is transferred to the solvent through thermal conduction, and the solvent evaporates. These will be explained separately below.

[0031] (Infrared light irradiation section)

[0032] If the infrared irradiation part can achieve 3W / cm 2 For output light with wavelengths between 0.8 μm and 3.0 μm, there are no particular restrictions on its structure. The infrared irradiation unit typically includes one or more heat sources, a control unit for controlling the output of infrared light from these heat sources, and a cooling unit for controlling the temperature. Other structures may also be included as needed.

[0033] In the infrared irradiation section, one or more heat sources are typically arranged to irradiate infrared light across the entire width of the recording medium 1. Furthermore, in this specification, "width direction" refers to the direction perpendicular to the transport direction of the recording medium 1 when viewed from above the drying apparatus 110. However, the heat sources may also be arranged so that infrared light is irradiated only a portion of the width of the recording medium 1, 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.

[0034] Furthermore, the length of the area irradiated by the infrared irradiation unit is appropriately selected based on the desired amount of infrared irradiation, irradiation time, etc. Multiple heat sources may also be arranged along the transport direction of the recording medium 1 within the infrared irradiation unit.

[0035] Furthermore, the heat source of the infrared irradiation unit is disposed with a gap between it and the recording medium 1. The distance between the heat source of the infrared irradiation unit and the recording medium 1 can be constant, continuous, or intermittent. However, the distance between the heat source of the infrared irradiation unit and the recording medium 1 is preferably 3 cm or more and 20 cm or less, more preferably 5 cm or more and 15 cm or less. If the distance between the heat source of the infrared irradiation unit and the recording medium is 5 cm or more, the recording medium and the heat source will not easily come into contact even if the recording medium 1 is bent. On the other hand, if the distance is 20 cm or less, infrared light can be efficiently irradiated from the heat source of the infrared irradiation unit onto the recording medium.

[0036] Here, the wavelength of the infrared light emitted by the heat source of the infrared irradiation section can 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. If the wavelength of the light emitted by the infrared irradiation section (heat source) is within this range, the temperature of the ink image 2 can be increased in a short time. In addition, for example, if the wavelength of the infrared light is set to 1.7 to 2.5 μm, not only can the ink temperature be increased in a short time, but the difference in the absorption of infrared light among various types of inks can also be minimized.

[0037] In addition, the output of infrared light from the infrared irradiation unit (heat source) is 3W / cm². 2 The above is sufficient, with 4W / cm being the preferred value. 2 Above and 35W / cm 2 The following is more preferably 6W / cm 2 Above and 15W / cm 2 The following applies. If the output from the infrared irradiation unit is within this range, the ink image can be dried in approximately 10 seconds, for example. Furthermore, the output of the infrared light can be determined based on the specifications of the heat source, etc.

[0038] Furthermore, the temperature of the heat source is preferably 900°C or higher, more preferably 900°C or higher and 2000°C or lower, and even more preferably 1400°C or higher and 2000°C or lower. If the temperature of the heat source is 900°C or higher, the temperature of the ink image will rise rapidly in a short time. However, if the temperature of the heat source is too high, deformation or deterioration of the recording medium may occur; therefore, it is preferable to be 2000°C or lower. The temperature of the heat source can be determined using a non-contact infrared sensor or the like.

[0039] There are no particular limitations on the heat source of the infrared irradiation section, provided it can emit infrared light at the aforementioned wavelength and output. Commonly known heat sources can be used. Furthermore, the heat source can be a point-like heat source or a linear heat source. Examples of such heat sources include halogen lamp heaters, quartz tube heaters, and carbon heaters. Additionally, there are no particular limitations on the number of heat sources in the infrared irradiation section; they can be appropriately selected to match the width and length of the area irradiating the infrared light.

[0040] On the other hand, the control unit of the infrared irradiation unit can, for example, monitor the temperature of the heat source or adjust the electrical power supplied to the heat source according to the temperature of the heat source, similar to the control unit of a known infrared irradiation device. Furthermore, the cooling unit is a structure that cools the heat source and its surroundings to prevent excessive temperature rise of the infrared irradiation unit; for example, it can be a blower or a water chiller.

[0041] (Ultraviolet light irradiation section)

[0042] If the ultraviolet irradiation section can achieve 1W / cm 2 For irradiance levels that emit light with wavelengths between 200 nm and 410 nm, there are no particular restrictions on their structure. The ultraviolet irradiation unit may include, for example, one or more light sources, a control unit for controlling the output of ultraviolet light from those light sources, and a cooling unit for adjusting the temperature.

[0043] In the ultraviolet light irradiation section, a light source is typically arranged so that ultraviolet light can be irradiated along the entire width of the recording medium 1. However, the light source may also be arranged so that ultraviolet light is irradiated only a portion of the width of the recording medium 1, 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.

[0044] Furthermore, the length of the area irradiated by the ultraviolet light irradiation unit is appropriately selected based on the desired ultraviolet light irradiation amount, irradiation time, etc. Multiple light sources may also be arranged along the transport direction of the recording medium 1 within the ultraviolet light irradiation unit.

[0045] Furthermore, the light source of the ultraviolet irradiation unit is arranged with a gap between it and the recording medium. The distance between the light source of the ultraviolet irradiation unit and the recording medium 1 can be constant, continuous, or intermittent. The distance between the light source of the ultraviolet irradiation unit and the recording medium 1 is generally more preferably 5 mm or less. If 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 onto the recording medium.

[0046] Here, the wavelength of the ultraviolet light emitted by the light source of the ultraviolet irradiation section can be 200nm or more and 410nm or less. When using an LED, it is preferable to have a wavelength of 350nm or more and 410nm or less. If the wavelength of the ultraviolet light is 200nm or more and 410nm or less, the ultraviolet light is easily absorbed by the colorant contained in the ink image 2, thereby increasing the temperature of the ink image 2 in a short time.

[0047] In addition, the irradiance of ultraviolet light from the ultraviolet irradiation unit (light source) is 1 W / cm². 2 The above is acceptable, but 2W / cm is preferred. 2 Above and 4W / cm 2The following applies if the output from the ultraviolet irradiation unit is 1 W / cm². 2 In this way, the ink images can be dried quickly, for example, by setting the illumination time of each ink image to within 10 seconds. The irradiance of the ultraviolet light is measured by an illuminance meter (such as the UIT-201 illuminance system manufactured by USHIO Electric Corporation).

[0048] There are no particular limitations on the light source of the ultraviolet irradiation unit if it can emit ultraviolet light at the aforementioned wavelength and irradiance; any known light source can be used. This light source can be a point light source or a line light source. Examples of such light sources include halogen lamps and UV-LED lamps. Specific examples of UV-LED lamps include 300nm LEDs, 375nm LEDs, 395nm LEDs, and 410nm LEDs, appropriately selected in conjunction with the type of colorant contained in the ink image (colored ink). When drying an ink image 2 containing multiple colored inks, multiple types of LED lamps can also be combined. Furthermore, there are no particular limitations on the number of light sources in the ultraviolet irradiation unit; they can be appropriately selected in conjunction with the width and length of the area irradiated with ultraviolet light.

[0049] On the other hand, the control unit of the ultraviolet irradiation unit can, for example, monitor the amount of light from the light source or adjust the electrical power supplied to the light source according to the amount of light from the light source, and is the same as the control unit of a known ultraviolet irradiation device. Furthermore, the cooling unit is a structure that can cool the light source and its surroundings to prevent the temperature of the ultraviolet irradiation unit from rising excessively, and can be, for example, a blower or a water chiller.

[0050] (2) Temperature control unit

[0051] The temperature control unit 102 is a component for making the temperature of the recording medium 1 uniform. For example, it has a heat conduction part 102a with high thermal conductivity 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.

[0052] The heat conduction section 102a is composed of components with high thermal conductivity and is used to release heat from high-temperature areas of the recording medium 1 and the ink image 2 or to heat low-temperature areas when energy is irradiated from the energy irradiation section 101, thereby making the temperature of the recording medium 1 and the ink image 2 uniform. The heat conduction section 102a is usually appropriately heated or cooled by the temperature adjustment mechanism 102b, which will be described later, so that its surface temperature reaches a set temperature.

[0053] The thermal conductivity of the heat-conducting section 102a is preferably 150 kcal / (m·h·℃) or higher. If the thermal conductivity of the heat-conducting section is 150 kcal / (m·h·℃) or higher, the temperature of the recording medium 1 can be easily homogenized in a short time. Furthermore, thermal conductivity is a material-specific value, and the conductivity of the heat-conducting section 102a can be determined based on the type of material it is composed of. However, when the heat-conducting section 102a is composed of multiple materials, it can be calculated by multiplying the content ratio of each material by the thermal conductivity of that material and then adding them together.

[0054] The material constituting the heat conduction part 102a is preferably a metal, preferably copper, aluminum, or a composite thereof. Among these, copper is particularly preferred due to its high thermal conductivity, low cost, and good processability.

[0055] Here, the shape of the heat conduction section 102a is not particularly limited if it is a shape that can contact the non-printing surface 1b of the recording medium 1 during the irradiation of the recording medium 1 and the ink image 2 by the energy irradiation section 101. For example, the heat conduction section 102a can be as follows: Figure 1B It can be flat as shown, or it can be like... Figure 2 As shown, it is roller-shaped.

[0056] like Figure 2 As shown, the heat conduction section 102a is roller-shaped. If the heat conduction section 102a is supported by a shaft and can rotate, it rotates in conjunction with the movement of the recording medium 1. Therefore, excessive friction is less likely to occur between the recording medium 1 and the heat conduction section 102a, and the non-printing surface of the recording medium 1 is less prone to wear. Furthermore, if the heat conduction section 102a rotates, it is less likely to irradiate a specific area of ​​the heat conduction section 102a with prolonged energy, and the temperature of the heat conduction section 102a is less likely to rise excessively. Therefore, it also has the advantage of easy temperature adjustment based on the temperature adjustment mechanism 102b.

[0057] The width of the area where the heat conduction portion 102a contacts the recording medium 1 is not particularly limited, but it may be at least the width of the area irradiated by the energy irradiation portion 101. However, it is more preferable that the width of the area where the heat conduction portion 102a contacts the recording medium 1 is at least the width of the recording medium 1. If the width of the area where the heat conduction portion 102a contacts the recording medium 1 is at least the width of the recording medium 1, then the overall temperature of the recording medium 1 is adjusted to be constant.

[0058] Furthermore, the length of the area where the heat conduction section 102a contacts the recording medium 1 (the distance in the direction parallel to the transport direction of the recording medium) is preferably at least the length of the area irradiated by the energy irradiation section 101.

[0059] In addition, it is preferable that the non-printing surface 1b of the recording medium 1 contacts the heat conduction section 102a in approximately the entire area irradiated by the energy irradiation section 101.

[0060] On the other hand, the temperature adjustment mechanism 102b of the temperature control unit 102 can be a structure capable of controlling the surface temperature of the heat conduction section 102a. For example, a structure having the following units can be adopted: a heating unit for raising the temperature of the heat conduction section 102a, a cooling unit for lowering the temperature of the heat conduction section 102a, a temperature measuring unit for directly or indirectly measuring the surface temperature of the heat conduction section 102a, and a control unit for controlling the heating unit and the cooling unit based on a set temperature and the temperature measured by the temperature measuring unit.

[0061] Examples of heating units include known heaters, and examples of cooling units include blowers and water chillers. The heating and cooling units can be located inside the heat conduction section 102a or on the outside.

[0062] (3) Other structures

[0063] The drying apparatus 110 may also include a pressing unit (not shown) for bringing the recording medium 1 into closer contact with the temperature control unit 102. This pressing unit may be configured to press the printing surface 1a of the recording medium 1 towards the temperature control unit 102, or to press the temperature control unit 102 towards the recording medium 1, or to press the recording medium 1 and the temperature control unit 102 against each other. During the period when energy is irradiated by the energy irradiation unit 101, a constant tension may be applied to the recording medium 1 by measuring and adjusting the tension using a pressure gauge or the like.

[0064] The drying apparatus 110 may also include a transport unit (not shown) for transporting the recording medium 1. The transport unit can move the recording medium 1 and the energy irradiation unit 101 relative to each other; for example, it can be a unit that moves the recording medium 1, a unit that moves the energy irradiation unit 101, or a unit that moves both. Furthermore, the transport unit can coordinate with the position of the energy irradiation unit 101 to move the temperature control unit 102. This transport unit can move the recording medium 1, the energy irradiation unit 101, etc., continuously or intermittently.

[0065] Furthermore, the drying device 110 may also have a housing for protecting the energy irradiation unit 101, temperature control unit 102, recording medium 1, etc. from dust, dirt, etc., or for preventing energy from the energy irradiation unit from leaking to the outside.

[0066] (4) Drying method using a drying device

[0067] The drying method for the ink image 2 using the drying apparatus 110 described above will now be explained. As described above, in the drying apparatus 110, the ink image 2 containing undried ink formed on the recording medium 1 is heated and dried. Here, the ink image 2 can be dried while the recording medium 1 is moving relative to the energy irradiation unit 101, or the ink image 2 can be dried while the recording medium 1 and the energy irradiation unit 101 are fixed. Furthermore, when drying while the recording medium 1 is moving relative to the energy irradiation unit 101, the moving speed can be constant, or it can be varied continuously or intermittently in conjunction with the position, pattern, and type of recording medium of the ink image 2.

[0068] The drying apparatus 110 does not impose any particular limitation on the drying time of the ink image. Generally, the shorter the drying time, the better. However, it is preferable that the drying apparatus 110 has a wide range of drying times that can simultaneously achieve suppression of damage to the recording medium and sufficient drying of the ink image, which facilitates the design of image forming apparatuses using the drying apparatus and enables stable printing. For example, the range of drying times that do not damage the recording medium and can sufficiently dry the color ink is preferably 3 seconds or more, more preferably 5 seconds or more.

[0069] In this specification, the drying time of the ink image refers to the time from the start of energy irradiation to the end of irradiation. More specifically, when the energy irradiation unit 101 is an infrared irradiation unit, and drying is performed while the recording medium 1 is being transported, the moment when a predetermined position of the recording medium 1 is directly below the upstream end of the heat source of the infrared irradiation unit is defined as the start of irradiation, and the moment when the predetermined position of the recording medium 1 is directly below the downstream end of the heat source is defined as the end of irradiation. On the other hand, when the energy irradiation unit 101 is an ultraviolet irradiation unit, and drying is performed while the recording medium 1 is being transported, the moment when a predetermined position of the recording medium 1 is directly below the upstream end of the light source of the ultraviolet irradiation unit is defined as the start of irradiation, and the moment when the predetermined position of the recording medium 1 is directly below the downstream end of the light source is defined as the end of irradiation.

[0070] Furthermore, during the period when energy is irradiated from the energy irradiation unit 101 onto the recording medium 1 and the ink image 2, it is preferable to keep the surface temperature of the heat conduction section 102a of the temperature control unit 102 constant. For example, if energy is irradiated continuously or intermittently from the energy irradiation unit 101, the temperature of the heat conduction section 102a itself may rise. In such cases, the heat conduction section 102a is cooled by the temperature adjustment mechanism 102b within the temperature control unit 102. On the other hand, if it is desired to raise the temperature of the recording medium 1 from the non-printing surface 1b side, the heat conduction section 102a is heated by the temperature adjustment mechanism 102b.

[0071] When the energy irradiation unit 101 irradiates the recording medium 1, the surface temperature of the heat conduction section 102a is preferably a temperature that does not affect the recording medium 1. For example, if the recording medium 1 is made of resin, it is preferably set to a temperature at least 5°C lower than the glass transition temperature (Tg) of the recording medium 1 (resin). Furthermore, regardless of the type of recording medium 1, the surface temperature of the heat conduction section 102a is preferably less than 80°C, more preferably less than 70°C. On the other hand, the lower limit is preferably 50°C, more preferably 60°C. If the surface temperature of the heat conduction section 102a is less than 80°C, the recording medium 1 and the obtained image are less likely to degrade.

[0072] (Recording medium)

[0073] Here, the recording medium 1 used in the aforementioned drying apparatus 110 is preferably made of a material that is not easily degraded by heating caused by irradiation with infrared or ultraviolet light. The recording medium 1 can be a single layer or a structure obtained by stacking multiple layers. Furthermore, it can be a material with printed surfaces, embossed surfaces, or perforated surfaces. The printed surface 1a of the recording medium 1 can be entirely of the same color, or it can have a portion where the color differs from other areas (areas with different energy absorption rates). For example, as... Figure 1A As shown, the recording medium 1 may also have pre-printed markings on the recording medium 1 for aligning positions during the formation of the ink image, markings indicating the cutting position for cutting the printed material, and patterns for improving the appearance of the printed material (hereinafter, these are also referred to as "printed portions 4"). Since the printed portions 4 are formed on the recording medium 1, if the color of the printed portions 4 is too concentrated, the temperature of the printed portions 4 may easily rise during the drying of the ink image 2, or the recording medium 1 may easily deform. However, according to the drying apparatus 110 described above, the heat conduction section 102a of the temperature control section 102 ensures a uniform temperature for the recording medium 1, thus preventing such deformation.

[0074] There are no particular limitations on the method of forming the printed part 4. The printed part 4 can also be printed using known printing methods, such as inkjet printing, gravure printing, screen printing, etc.

[0075] Furthermore, as described above, the recording medium 1 can be in the form of a strip or a sheet. Here, the recording medium 1 may also have areas with different thicknesses, but from the perspective of easy temperature adjustment by the temperature control unit 102 of the drying device 110, a constant thickness is preferred.

[0076] Examples of recording medium 1 include known plastic films, including polyester films such as polyethylene terephthalate, polyolefin films such as polyethylene film and polypropylene film, polyamide films such as nylon, polystyrene film, polyvinyl chloride film, polycarbonate film, polyacrylonitrile film, polylactic acid film, and other biodegradable films. Alternatively, recording medium 1 can also be an inorganic film such as a metal plate, metal film, glass, or leather. Furthermore, recording medium 1 can also be a laminate of these materials.

[0077] The thickness of the recording medium 1 is appropriately selected based on the intended use of the printed material and the type of the recording medium 1. However, if the thickness of the recording medium 1 is excessively thick, it can be difficult to adjust the temperature using the temperature control unit 102 during the drying of the ink image 2. 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, the more easily it is affected during the drying of the ink image 2.

[0078] (Ink image)

[0079] There are no particular limitations on the pattern, area, etc., of the ink image 2 that can be dried by the aforementioned drying apparatus 110. For example, the ink image 2 may be formed on the entire printing surface 1a of the recording medium 1, or it may be formed only in a portion of the printing surface 1a. Furthermore, the ink image 2 may contain only one type of ink, or it may contain multiple types of ink.

[0080] Furthermore, in particular, when the energy absorptivity at wavelength 1.2 μm of the recording medium 1 is set to 1, it is preferable that the ink image 2 includes a region with an energy absorptivity at wavelength 1.2 μm of 1.3 or higher. Thus, in a conventional drying apparatus, uneven heating occurs when the energy absorptivity of the recording medium 1 differs significantly from that of the ink region 2. In contrast, according to the drying apparatus 110, even if the energy absorptivity of the recording medium 1 differs significantly from that of the ink image 2, the temperatures of both the recording medium 1 and the ink image 2 tend to become uniform. Moreover, the energy absorptivity at wavelength 1.2 μm of the recording medium 1 and the energy absorptivity at wavelength 1.2 μm of the ink image 2 are measured using a Fourier transform infrared spectrophotometer.

[0081] Here, the composition of the ink constituting the ink image 2 is not particularly limited if it can be dried by heating, and it can consist only of colored ink containing colorants and solvents. However, it is particularly preferable that the ink image 2 includes primer ink and colored ink. If the ink image 2 includes primer ink and colored ink, even if the time from the formation of the ink image 2 to its drying is extended, the ink image 2 is less prone to bleeding, and a desired high-quality image can be obtained. In addition, when the ink image 2 includes primer ink and colored ink, as described in the section on image forming apparatus, the ink image forming section and the drying section can be arranged separately. Therefore, the heat generated in the drying section can suppress nozzle clogging or ink deterioration during ink coating.

[0082] Preferably, the ink image 2 contains 5-35% by mass of a water-soluble solvent in its undried state. More preferably, the amount of water-soluble solvent in the ink image 2 is 5-20% by mass.

[0083] The following describes the colored inks and primer inks that constitute ink image 2.

[0084] Colored inks

[0085] Colored inks can contain at least a colorant, such as inks containing a colorant, a dispersant for dispersing the colorant, resin particles, and a solvent.

[0086] Examples of colorants include known pigments. Colorants can be either organic or inorganic pigments. When used with a primer ink (described later) in conjunction with colored inks, the colorant is preferably anionic. If the colorant is anionic, it is easily fixed by the primer ink (described later). Furthermore, the average particle size of the pigment in the colored ink is preferably 50 nm or more and less than 200 nm. The average particle size of the pigment is a value determined by dynamic light scattering.

[0087] There is no particular limitation on the amount of colorant in colored inks, but when the colorant is an inorganic pigment, it is preferably 7 to 18% by mass, and when the colorant is an organic pigment, it is preferably 0.5 to 7% by mass.

[0088] Furthermore, examples of dispersants used to disperse colorants include polymeric dispersants having anionic groups. The molecular weight of the polymeric dispersant is preferably between 5,000 and 200,000.

[0089] Examples of polymeric dispersants include block copolymers and random copolymers of two or more monomers selected from styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, and fumaric acid derivatives, as well as their salts, polyoxyethylene, and polyoxyethylene alkyl ethers. Commercially available polymeric dispersants can be used; examples of commercially available polymeric dispersants include BASF's 819, etc.

[0090] The amount of dispersant relative to the amount of colorant is preferably 10 to 100% by mass, more preferably 10 to 40% by mass.

[0091] The aforementioned colorants and dispersants are preferably contained in colored inks in a state where the colorant is covered by the dispersant, a state known as encapsulated pigment. There are no particular limitations on the method of covering the colorant with a dispersant; for example, phase inversion emulsification or acid precipitation can also be used. Alternatively, the colorant can be dispersed in a dispersion medium using a polymeric surfactant, and monomers that form a polymeric dispersant can be supplied to the dispersion medium to polymerize it, thereby covering the colorant with a polymeric dispersant.

[0092] The resin particles contained in the colored ink are preferably water-insoluble resin particles (hereinafter also referred to as "water-insoluble resin particles"). Examples of water-insoluble resin particles include polyester resins, polyurethane resins, polyacrylic resins, or composite resins of polyurethane resins and polyacrylic resins. These water-insoluble resin particles are preferably anionic.

[0093] From the viewpoint of enabling emulsification in solvents described later without the use of surfactants, it is preferable that water-insoluble resin particles have an acid structure. Examples of acid structures include carboxyl groups (-COOH), sulfonic acid groups (-SO3H), etc. The acid structure may also be present in the side chain or at the end of the resin.

[0094] Furthermore, if the water-insoluble resin particles have an acidic structure, part or all of that acidic structure can be neutralized. If the acidic structure is neutralized, the water dispersibility of the water-insoluble resin particles is improved. Examples of neutralizing agents include organic amines, specifically trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine.

[0095] Resin microparticles can be commercially available products, including, in this case, PESRESIN A-110F, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX manufactured by Takamatsu Oils & Fats Co., Ltd., and Elitel 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 manufactured by UNITICA Co., Ltd.

[0096] Examples of commercially available urethane-based resin microparticles include NeoRez R-967, R-600, and R-9671 manufactured by Kusunoki Chemical Co., Ltd., and W-6061, W-5661, and WS-4000 manufactured by Mitsui Chemicals Co., Ltd.

[0097] Examples of commercially available acrylic resin microparticles include NeoCryl A-1127 and Ja, manufactured by Kusumoto Chemical Co., Ltd. p an c o Mowinyl 6899D, 6969D, 6800D, 6810 manufactured by Atresin, and TOCRYL W-7146, W-7150, W-7152 manufactured by Toyo-chem, etc.

[0098] The amount of resin particles in the colored ink is not particularly limited, but is preferably 2 to 10% by mass, more preferably 2 to 5% by mass.

[0099] The solvents contained in colored inks are preferably water and / or water-soluble solvents. A water-soluble solvent is defined as a solvent that, when mixed with 100 parts by weight of water at 20°C and stirred, maintains a uniform appearance even after flow. Examples of water-soluble solvents include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols with four or more carbon atoms. Inks may contain only one solvent, or they may contain two or more solvents.

[0100] 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-nonanol, tridecanol, n-undecanol, stearyl alcohol, oleyl alcohol, benzyl alcohol, etc.

[0101] Examples of polyvalent alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol with 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol with 4 or more propylene oxide groups, butanediol, hexanediol, pentanediol, glycerol, hexanediol, thiodiglycol, etc.

[0102] Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.

[0103] Examples of amides include formamide, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0104] 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, and tripropylene glycol monomethyl ether.

[0105] Examples of 1,2-alkanediols with 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol.

[0106] In the above, from the viewpoint of suppressing ink bleeding in the image, polyvalent alcohols are preferred, particularly 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol. From the viewpoint of easily improving wettability to non-absorbent recording media, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol are especially preferred.

[0107] Furthermore, it is preferable that the colored ink contains both water and a water-soluble solvent as solvents. The amount of water in the colored ink is not particularly limited, but is preferably 45-80% by mass. On the other hand, the amount of water-soluble solvent in the colored ink is preferably 5-35% by mass, more preferably 5-25% by mass, and even more preferably 5-20 parts by mass.

[0108] In addition, depending on the requirements, colored inks may also contain known surfactants, preservation stabilizers, etc.

[0109] Here, the viscosity of the colored ink before it is coated onto the recording medium, measured by an Antonpaar viscometer (MCR-102) at a temperature of 25°C and a shear rate of 1000 (1 / s), is preferably 1–40 mPa·s at 25°C, more preferably 2–10 mPa·s. If the viscosity of the colored ink is within this range, it will not flow easily after being coated onto the recording medium, making it easier to obtain high-quality images.

[0110] Furthermore, it is preferable that the static surface tension of the ink applied before the recording medium is greater than that of the primer ink described later. From the viewpoint of being able to form images with high quality on a non-absorbent recording medium, the static surface tension of the color ink is preferably 22–33 mN / m at 25°C, more preferably 22–26 mN / m. The static surface tension of the color ink can be measured by a surface tension meter.

[0111] Primer ink

[0112] The primer ink only needs to contain a coagulant; for example, it can be an ink containing both a coagulant and a solvent. With such a primer ink, even if colored ink is applied without allowing it to dry, bleeding or other defects are less likely to occur. Therefore, a drying and curing process is unnecessary before applying colored ink, allowing for the formation of an ink image in a simple process. Furthermore, if a primer ink with this composition is used, even if the drying time after the ink image is formed is relatively long, bleeding is less likely. Therefore, a high-quality image is obtained. In addition, the primer ink may also contain surfactants, crosslinking agents, mildew inhibitors, bactericides, etc., as needed, but it is preferable that the primer ink does not contain the aforementioned resin particles. Because the primer ink does not contain resin particles, it is less likely to cause thickening.

[0113] A coagulant is sufficient to form agglomerates when combined with the aforementioned color inks. This coagulant functions to fix the ink image onto the recording medium. The coagulant is appropriately selected based on the type of colorant in the color ink.

[0114] Examples of coagulants include thermally decomposable cationic polymers, polyvalent metal salts, or organic acids, with cationic polymers or polyvalent metal salts being more preferred from the perspective of having a neutral or weakly alkaline pH.

[0115] Dissolving cationic polymers and polyvalent metal salts cause the anionic components (colorants, etc.) in the aforementioned colored inks to coagulate through salting out. On the other hand, organic acids cause the anionic components in the aforementioned colored inks to coagulate through pH changes.

[0116] Examples of cationic polymers that are solvents include polyallylamine, polyethyleneamine, polyethyleneimine, and polydiallyldimethylammonium chloride. Other commercially available examples include KHE100L and FPA100L manufactured by Senka, and PAS-92A, PAS-M-1A, and PAS-21CL manufactured by Nitobomedical.

[0117] Examples of polyvalent metal salts include water-soluble salts such as calcium, magnesium, aluminum, and zinc salts. Compounds that form salts with polyvalent metals include hydrochloric acid, bromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, thiocyanate, as well as organic carboxylic acids and organic sulfonic acids such as acetic acid, oxalic acid, lactic acid, fumaric acid, citric acid, salicylic acid, and benzoic acid.

[0118] Examples of organic acids include 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, etc.

[0119] Furthermore, the organic acid is preferably an acid with a first dissociation constant of 3.5 or less, and more preferably a first dissociation constant of 1.5 to 3.5. If the first dissociation constant is within this range, it is easier to fix the color ink to the recording medium.

[0120] The primer ink preferably contains 5% by mass or less of a coagulant, more preferably 1% to 4% by mass of a coagulant. If the primer ink contains a coagulant within this range, the anionic components in the color ink are effectively coagulated, resulting in good image quality. Furthermore, the amount of coagulant in the primer ink can be determined using known methods. For example, when the coagulant is a polyvalent metal salt, it can be determined by ICP-luminescence analysis, and when the coagulant is an organic acid, it can be determined by high-performance liquid chromatography (HPLC).

[0121] The solvent in the primer ink is preferably water and / or a water-soluble solvent, preferably both. The type of water-soluble solvent is the same as that contained in the aforementioned color inks. Furthermore, the amount of water in the primer ink is preferably 45-80% by mass. On the other hand, the amount of water-soluble solvent in the primer ink is preferably 5-35% by mass, more preferably 5-20% by mass.

[0122] Furthermore, the viscosity of the primer ink, measured using an Antonpaar viscometer (MCR-102) at 25°C and a shear rate of 1000 l / s, is preferably 1–40 mPa·s, more preferably 1–10 mPa·s, and even more preferably 4–7 mPa·s. If the viscosity of the primer ink is within this range, it will not flow easily after being applied to the recording medium, resulting in high-quality images.

[0123] As mentioned above, the static surface tension of the primer ink at 25°C is preferably lower than that of the colored ink. The static surface tension of the primer ink is preferably 22–30 mN / m at 25°C, and more preferably 22–26 mN / m.

[0124] 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 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 tension meter. Unless otherwise specified, the dynamic surface tension in this specification refers to the dynamic surface tension at 25°C and 50 ms.

[0125] 2. Image forming apparatus

[0126] The aforementioned drying device can be used alone, or it can be combined with an ink image forming unit, etc., for use in an image forming apparatus. Figure 3A The image forming apparatus 100 according to one embodiment of the present invention is shown in the figure. Figure 3B The image forming apparatus 100 is shown in the side view. The image forming apparatus 100 includes: a transport section (not shown) for transporting the recording medium 1; an ink image forming section 120 (primer ink discharge section 12P and color ink discharge section 12Q) for forming an ink image; and a drying section (the aforementioned drying device) 110 for forming the ink image.

[0127] Furthermore, depending on the requirements, the image forming apparatus may also include a fixing section (not shown) for further fixing the image dried by the drying section 110 onto the recording medium 1, a winding section (not shown) for winding out the recording medium 1, and a winding section (not shown) for winding the recording medium 1. Since the drying section 110 is the same as the drying apparatus 110 described above, its description is omitted. Hereinafter, the ink image forming section 120 will be described.

[0128] (Ink Image Forming Section)

[0129] The ink image forming unit 120 may also have only a color ink discharge unit 12Q for discharging color ink, but... Figure 3A as well as Figure 3B The image system device shown includes a primer ink discharge section 12P and a color ink discharge section 12Q.

[0130] Furthermore, if the ink image forming section only has a colored ink discharge section 12Q, and the drying time after applying the colored ink is long, ink bleeding may occur. Therefore, it is preferable to position the ink image forming section 120 (colored ink discharge section Q) close to the drying section 110. However, if the distance between the ink image forming section 120 and the drying section 110 is too close, the heat from the drying section 110 can easily be transferred to the ink image forming section 120, which may cause the ink to thicken within the ink image forming section 120 or cause nozzle clogging.

[0131] Therefore, the ink image forming unit 120 preferably has a primer ink discharge unit 12P and a color ink discharge unit 12Q. If color ink is discharged onto the undried primer ink after the primer ink has been applied to the recording medium 1, the ink image 2 is easily retained on the recording medium 1. Therefore, for example... Figure 3A , Figure 3B As shown, the ink image forming section 120 and the drying section 110 are configured to be fully separated.

[0132] Here, the primer ink discharge section 12P should be able to discharge the desired primer ink. The primer ink described above is cited as an example of a primer ink. If the primer ink described above is used, colored ink can be applied after the primer ink has been applied without allowing it to dry. However, colored ink can also be applied after the primer ink has dried.

[0133] On the other hand, the colored ink discharge section 12Q can also discharge the desired colored ink; as an example of colored ink, the aforementioned colored ink is listed. Furthermore, there are no particular limitations on the type of colored ink discharged by the colored ink discharge section Q. Figure 3A , Figure 3B In the process, the color ink ejection section Q includes a black ink ejection section 12K, a cyan ink ejection section 12C, a magenta ink ejection section 12M, and a yellow ink ejection section 12Y, but is not limited to these. Furthermore, the arrangement order of the various color ink ejection sections is appropriately selected to match the desired printed material, and is not limited to... Figure 3A , Figure 3B As shown in the diagram.

[0134] Here, when the energy irradiation section 101 of the drying section 110 has an infrared irradiation section, if two or more colored inks containing pigments with different absorption rates of infrared light at specific wavelengths selected from 0.8 μm to 3.0 μm are coated as the aforementioned colored inks, the temperature rise of each colored ink will be different. Therefore, the drying speed will easily differ between them. Therefore, the composition of the colored inks can be adjusted as needed so that the drying speeds of these two or more colors at different temperatures, for example, the drying rates when drying in an oven at 100°C for 30 seconds, are different. The infrared absorption rate of the pigments contained in each colored ink can be determined by a UV-Vis-NIR spectrophotometer (e.g., Hitachi High-Tech Co., Ltd., UH4150, etc.). Furthermore, when measuring the infrared absorption rate of multiple pigments separately, the measurement wavelength is the same.

[0135] On the other hand, regarding the aforementioned drying rate, the same amount (e.g., 10g each) of each ink was dropped into a petri dish, and its mass A was measured. Furthermore, a hot air oven was set to 100°C, left to stand for 30 seconds, and then its mass B was measured. The drying rate was then defined as the weight reduction in the hot air oven (AB) divided by the amount of ink ((AB) / 10) × 100.

[0136] Here, as a method for adjusting the drying rate of multiple color inks, a solvent with a high boiling point is used for the color ink for which a lower drying rate is desired, or its amount is adjusted. On the other hand, a solvent with a low boiling point is used for the color ink for which a higher drying rate is desired, or its amount is reduced.

[0137] Furthermore, it is preferable to adjust the drying rate of color inks that are not easily heated, i.e., color inks containing pigments with high infrared light absorption rates, to be lower than that of color inks containing pigments with low infrared light absorption rates.

[0138] Furthermore, if the energy irradiation section 101 of the drying section 110 has an ultraviolet light irradiation section, and if two or more colored inks containing pigments with different absorption rates of ultraviolet light at specific wavelengths selected from 200 nm to 410 nm are coated as the aforementioned colored inks, the temperature rise of each colored ink will differ. Therefore, the drying speed may differ between them. Therefore, in this case, the composition of the ink can be adjusted as needed to make the drying speed of these two or more colors, for example, the drying rate when drying in an oven at 100°C for 30 seconds, different. The ultraviolet light absorption rate of the pigments contained in each colored ink can be determined using an ultraviolet-visible-near-infrared spectrophotometer (e.g., Hitachi High-Tech Co., Ltd., UH4150, etc.). Furthermore, when measuring the ultraviolet light absorption rate of multiple pigments separately, the measurement wavelength is the same. Furthermore, the method for measuring the drying rate and the method for adjusting the drying rate are the same as described above.

[0139] In addition, at this time, it is preferable to adjust the drying rate of the colored ink that is not easily heated, that is, the colored ink containing the above-mentioned colorant with a high absorption rate of ultraviolet light, to be lower than the drying rate of the colored ink containing the colorant with a low absorption rate of ultraviolet light.

[0140] Here, as Figure 3A , Figure 3B As shown, the primer ink discharge section 12P and the color ink discharge section 12Q (hereinafter, they are also collectively referred to as "ink discharge section 12") can be either linear discharge sections or serial discharge sections. However, from the viewpoint of being able to form an ink image in a short time, a linear discharge section is more preferred. When the ink discharge section 12 is a linear discharge section, the primer ink discharge section 12P is usually disposed on the upstream side, and the color ink discharge section 12Q is disposed on the downstream side. However, the primer ink discharge section 12P may also be disposed at a position downstream of the color ink discharge section 12Q. In addition, it may be necessary to have a structure for temporarily curing the primer ink discharged by the primer ink discharge section 12P or the color ink discharged by the color ink discharge section 12Q.

[0141] In addition, each ink ejection section 12 includes a head for ejecting primer ink and color ink, and an ink reservoir for storing primer ink and color ink. The type of head for each ink ejection section 12 is not particularly limited; it can be either on-demand or continuous. Examples of on-demand heads include electromechanical conversion types such as single-chamber, dual-chamber, supplier, piston, Shear mode, and shared-wall types, as well as electrothermal conversion types such as thermal inkjet and bubble jet (“bubble jet” is a registered trademark of Canon Corporation). Among these, electromechanical conversion heads are preferred, and heads using piezoelectric elements (also called “piezoelectric inkjet heads”) are particularly preferred.

[0142] (Conveying Department)

[0143] The type of transport unit is not particularly limited if it can transport the recording medium 1 from the ink image forming unit 120 side to the drying unit 110 side, and it can adopt the same structure as the transport unit of a known image forming apparatus. In addition, the transport unit may also be configured to support the recording medium 1 from the non-printing side, but in the drying unit 110 described above, it is preferable to support the recording medium 1 so that the non-printing surface of the recording medium 1 is in close contact with the heat conduction part 102a of the temperature control unit 102.

[0144] (Image forming method using the above-described image forming apparatus)

[0145] In the image forming method using the image forming apparatus 100 described above, 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 to the recording medium 1 by the primer ink discharge unit 12P, and color ink is applied to the undried primer ink by the color ink discharge unit 12Q.

[0146] After the desired ink image 2 is formed, the recording medium 1 is moved towards the drying section 110 via the transport section. Then, while the heat conduction section 102a of the temperature control section 102 is brought into contact with the non-printing surface 1b of the recording medium 1, energy is irradiated onto the printing surface 1a of the recording medium 1 from the energy irradiation section 101. At this time, the energy irradiation section 101 operates at 3 W / cm². 2 The above irradiance refers to infrared light with wavelengths above 0.8 μm and below 3.0 μm, or at a concentration of 1 W / cm². 2 The above irradiance is applied to ultraviolet light with a wavelength of 200 nm or more and 410 nm or less. On the other hand, in the temperature control unit 102, the temperature of the heat conduction unit 102a is adjusted by the temperature adjustment mechanism 102b to keep the temperature of the recording medium 1 and the ink image 2 constant.

[0147] Furthermore, the energy irradiation time of the energy irradiation unit 101 and the surface temperature of the heat conduction unit 102a controlled by the temperature control unit 102 are the same as those in the drying method described above.

[0148] (other)

[0149] As described above, the image forming apparatus 100 may also include structures 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 below. Figure 4 Furthermore, regarding... Figure 3A , Figure 3B The image forming apparatus shown has the same structure and is labeled with the same reference numerals; detailed descriptions are omitted.

[0150] This modified image forming apparatus 200 is an image forming apparatus for roll-to-roll printing. In addition to the ink image forming unit 120 and drying unit 110 described above, it also has a roll-out unit 131 for rolling 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 the printed material. Furthermore, this image forming apparatus 200 has: a first ink image forming unit 120A having a primer ink discharge unit 12P and a color ink discharge unit 12Q (white ink discharge unit 12W), and a second ink image forming unit 120B having a primer ink discharge unit 12P and a color ink discharge unit 12Q (yellow ink discharge unit 12Y, magenta ink discharge unit 12M, cyan ink discharge unit 12C, black ink discharge unit 12K). The first drying unit 110A and the second drying unit 110B are respectively disposed downstream of the first ink image forming unit 120A and the second ink image forming unit 120B.

[0151] In this image forming apparatus 200, a primer ink and a white ink are coated onto the recording medium 1 wound from the winding section 131 by the first ink image forming unit 120A. Then, the ink image is dried by the first drying unit 110A.

[0152] Next, a primer ink and various color inks are further coated onto 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.

[0153] Then, hot air is blown onto the recording medium 1 through the fixing unit 132 to further fix the image onto the recording medium 1. Then, the printed material is wound onto the roller through the winding unit 133. Furthermore, the structures of the take-up unit 131, the winding unit 133, and the fixing unit 132 are the same as those of existing image forming apparatuses.

[0154] Example

[0155] Hereinafter, specific embodiments and comparative examples of the present invention will be described together, but the present invention is not limited thereto. In addition, in the embodiments, unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass".

[0156] (1) Preparation of primer ink

[0157] A primer ink was prepared by mixing 3 parts by weight of calcium acetate, 20 parts by weight of propylene glycol, 0.5 parts by weight of surfactant (KF-351A, manufactured by Shin-Etsu Chemical Co., Ltd.), and 66.5 parts by weight of water. The viscosity of this primer ink, measured using an Antonpaar viscometer (MCR-102) at 25°C and a shear rate of 1000 rpm, was 4.89 mPa·s. The static surface tension, measured by a surface tension meter at 25°C, was 28.8 mN / m, and the dynamic surface tension, measured at 25°C and 50 ms, was 38.3 mN / m.

[0158] (2) Preparation of colored inks

[0159] According to the compositions shown in Table 1 and Table 2, the components shown in Table 1 are mixed to prepare yellow ink (Y), magenta ink (M), cyan ink (C), black ink (K) and white ink (W) to form each color ink group.

[0160] (3) Determination of the ultraviolet and infrared light absorption rates of the colorants (pigments) contained in colored inks

[0161] The ultraviolet (UV) and infrared (IR) absorbance of the pigments contained in the aforementioned colored inks were determined using a UV-Vis-NIR spectrophotometer (Hitachi High-Tech Co., Ltd., UH4150). For the UV absorbance measurement, the absorbance of light at a wavelength of 365 nm was measured. For the IR absorbance measurement, the absorbance of light at a wavelength of 1.2 μm was measured.

[0162] (4) Drying rate when heated at 100℃ for 30 seconds

[0163] Add equal amounts (e.g., 10g each) of inks from ink groups 5 to 7 to petri dishes and measure their mass A. Then, set a hot air oven to 100°C and leave the petri dishes in the oven for 30 seconds. Then, measure the mass B after heating.

[0164] Based on the obtained value, determine the drying rate (=((AB) / 10)×100).

[0165] [Table 1]

[0166]

[0167] (3) Examples and Comparative Examples

[0168] Example 1

[0169] The ink image forming section, which includes a primer ink ejection section and a color ink ejection section, is filled with primer ink and various color inks from color ink group 1. The primer ink ejection section and the color ink ejection section utilize a structure equipped with an independently driven inkjet head (360 dpi, ejection volume: 7 pL for small droplets, 15 pL for medium droplets, and 23 pL for large droplets) manufactured by Konica Minolta. Furthermore, the inkjet head is mounted on a roll-to-roll assembly and connected to a head control device IJCS-1 manufactured by Konica Minolta. Moreover, primer ink is applied to a strip-shaped polyethylene terephthalate film (recording medium) with a recording medium thickness of 20 μm, covering 20% ​​of the area, and color inks are applied to cover 100% of the area according to various colors, forming an ink image.

[0170] Next, the recording medium with the ink image formed is moved to the drying section, which has a temperature control unit. The infrared irradiation unit uses a mid-wavelength carbon IR heater manufactured by Hereus (wavelength 1.2 μm, heat source temperature: 1200°C). Furthermore, the temperature control unit of the drying section includes a metal roller (heat conduction section) and a temperature adjustment mechanism disposed within the metal roller. The temperature adjustment mechanism is used to adjust the surface temperature of the metal roller to maintain a constant surface temperature of 60°C, while the metal roller remains in contact with the recording medium during drying.

[0171] Furthermore, the output value of the infrared irradiation unit is set to 3W / cm. 2 6W / cm 2 10W / cm 2 and 15W / cm 2 The drying properties of the colored inks were confirmed by changing the infrared light irradiation time. The evaluation was conducted as follows. The results are shown in Table 2.

[0172] OK: The ink is completely dry, and there is no change even after wiping or peeling off the tape.

[0173] Undried: The ink is in an undried state and can be removed by wiping or peeling off with tape.

[0174] Substrate deformation: Deformation or burning of the substrate (recording medium)

[0175] Example 2

[0176] Except that the surface temperature of the metal roller in the temperature control unit was always adjusted to 50°C, the ink image was dried in the same manner as in Example 1. The results are shown in Table 2.

[0177] Comparative Example 1

[0178] Except for the absence of a metal roller with a temperature control unit, the ink image was dried in the same manner as in Example 1. The results are shown in Table 2.

[0179] [Table 2]

[0180]

[0181] Example 3

[0182] Except for replacing the infrared irradiation unit of the drying apparatus with an ultraviolet irradiation unit (light source: LED lamp, wavelength: 385nm), the drying of the ink image coated with primer ink and the colored ink of ink group 1 was performed in the same manner as in Example 1. Furthermore, the irradiance from the ultraviolet irradiation unit was set to 4W / cm². 2 2W / cm 2 and 1W / cm 2 The drying properties of the colored inks were confirmed under varying UV irradiation times. The results are shown in Table 3.

[0183] Example 4

[0184] Except that the surface temperature of the metal roller in the temperature control unit was always adjusted to 50°C, the ink image was dried in the same manner as in Example 3. The results are shown in Table 3.

[0185] Comparative Example 2

[0186] Except for the absence of a metal roller with a temperature control unit, the ink image was dried in the same manner as in Example 3. The results are shown in Table 3.

[0187] [Table 3]

[0188]

[0189] As shown in Tables 2 and 3 above, when the ink image is dried while the temperature is controlled by the temperature control unit, the deviation in the drying properties of each color ink is small, and even when infrared or ultraviolet light is irradiated at a high output, deformation of the recording medium is not easily caused (Examples 1-4). On the other hand, when the temperature is not adjusted by the temperature control unit, the recording medium is prone to deterioration or insufficient curing (Comparative Examples 1 and 2).

[0190] Example 5

[0191] Using the primer ink described above, as well as the Y ink and K ink from ink groups 1 to 6, an ink image was formed in the same manner as in Example 1, and then dried. At this time, the output of the infrared irradiation unit was set to 10 W / cm². 2The temperature of the temperature control unit was set to 60°C. Furthermore, by varying the drying time, a range of irradiation times was determined for both Y-ink and K-ink to ensure proper drying without deformation of the recording medium. This range is shown in Table 4.

[0192] [Table 4]

[0193] Ink group types Irradiation time range Ink Group 1 1-2 seconds Ink Group 2 0.5 to 2 seconds Ink Group 3 0.5 to 2 seconds Ink Group 4 0.5 to 2 seconds Ink Group 5 0.5 to 6 seconds Ink Group 6 0.5 to 6 seconds

[0194] As shown in Table 4 above, it can be seen that when two colors of ink (Y ink and K ink) containing colorants with different infrared light absorption rates are coated and dried, by using ink groups 5 and 6 with different drying rates according to each color, the drying time of each color ink can be extended without deforming the recording medium.

[0195] Example 6

[0196] Using the primer ink described above, as well as the Y ink and M ink of ink groups 1 and 7, an ink image was formed in the same manner as in Example 3, and then dried. At this time, the irradiance from the ultraviolet light irradiation section was set to 4 W / cm². 2 The temperature of the temperature control unit was set to 60°C. Furthermore, by varying the drying time, a range of irradiation times was determined for both Y ink and M ink to allow for drying without deformation of the recording medium. This range is shown in Table 5.

[0197] [Table 5]

[0198] Ink group types Irradiation time range Ink Group 1 1-2 seconds Ink Group 7 1 to 6 seconds

[0199] As shown in Table 5 above, it can be seen that when two colors of ink (Y ink and M ink) containing colorants with different ultraviolet light absorption rates are coated and dried, by using ink group 7 with different drying rates according to each color, the drying time of each color ink can be further extended without deforming the recording medium.

[0200] Industrial availability

[0201] The drying apparatus according to the present invention enables the ink image formed on the recording medium to dry sufficiently in a short time, and the recording medium and the formed image are less prone to damage. Therefore, it is useful in various printing fields.

[0202] Explanation of reference numerals: 1...Recording medium; 1a...One side (printing side) of the recording medium; 1b...The other side (non-printing side) of the recording medium; 2...Ink image; 4...Printed section; 12C...Cyan ink discharge section; 12K...Black ink discharge section; 12M...Magenta ink discharge section; 12P...Primer ink discharge section; 12Q...Color ink discharge section; 12Y...Yellow ink discharge section; 100, 200...Image forming apparatus; 101...Energy irradiation section; 102...Temperature control section; 102a...Heat conduction section; 102b...Temperature adjustment mechanism; 110...Drying apparatus (drying section); 120...Ink image forming section; 131...Roll-out section; 132...Fixing section; 133...Wrapping section.

Claims

1. A drying apparatus for drying an ink image formed on one side of a recording medium, containing undried ink, wherein, The drying device has: An energy irradiation unit is used to irradiate energy onto one side of the recording medium to heat the ink image and dry the ink image. as well as The temperature control unit is configured to sandwich the recording medium, face the energy irradiation unit, and contact the other side of the recording medium. The energy irradiation unit includes either an infrared irradiation unit or an ultraviolet irradiation unit, wherein the infrared irradiation unit operates at 3 W / cm². 2 The above irradiance is provided by irradiating infrared light with a wavelength of 0.8 μm or more and 3.0 μm or less, and the ultraviolet light irradiation section directs 1 W / cm onto one surface of the recording medium. 2 The above irradiance is for ultraviolet light with wavelengths of 200nm to 410nm. The temperature control unit adjusts its surface temperature by heating and cooling, thereby making the temperature of the recording medium uniform.

2. The drying apparatus according to claim 1, wherein, When energy is irradiated through the energy irradiation unit, the temperature control unit adjusts the surface temperature of the temperature control unit to be less than 80°C.

3. The drying apparatus according to claim 1 or 2, wherein, The temperature control unit has a metal roller that contacts the other side of the recording medium.

4. The drying apparatus according to claim 3, wherein, The thermal conductivity of the metal roller is above 150 kcal / (m·h·℃).

5. The drying apparatus according to any one of claims 1, 2, and 4, wherein, The energy irradiation unit includes the infrared light irradiation unit. The temperature of the heat source of the infrared irradiation section is above 900°C.

6. An image forming apparatus comprising: The conveyor section transports the recording media. Primer ink discharge section, used to discharge primer ink containing coagulant; A colored ink discharge section for discharging colored ink containing colorant; and The drying apparatus according to any one of claims 1 to 5.

7. An image forming method, comprising: The process of coating one side of a recording medium with ink to form an ink image; as well as A process in which a temperature control unit, used for temperature control, is in contact with one side of the recording medium, while energy is irradiated onto one side of the recording medium to dry the ink image. In the process of drying the ink image, at 3W / cm 2 The above irradiance refers to infrared light with wavelengths above 0.8 μm and below 3.0 μm, or at a concentration of 1 W / cm². 2 The above irradiance refers to ultraviolet light with wavelengths above 200 nm and below 410 nm. In the process of drying the ink image, the temperature control unit adjusts the surface temperature of the temperature control unit by heating and cooling, thereby making the temperature of the recording medium uniform.

8. The image forming method according to claim 7, wherein, When the absorption rate of energy at wavelength 1.2 μm of the recording medium is set to 1, the ink image contains a region with an absorption rate of energy at wavelength 1.2 μm of 1.3 or higher.

9. The image forming method according to claim 7 or 8, wherein, One side of the recording medium has a region with different energy absorption rates.

10. The image forming method according to claim 7 or 8, wherein, The ink contains 5-20% by mass of a water-soluble solvent.

11. The image forming method according to claim 7 or 8, wherein, In the process of forming the ink image, Apply a primer ink containing at least a coagulant and a colored ink containing at least a colorant.

12. The image forming method according to claim 7 or 8, wherein, In the process of forming the ink image, The coating consists of two or more colored inks containing colorants with different absorption rates of infrared light of specific wavelengths selected from 0.8 μm to 3.0 μm, or colorants with different absorption rates of ultraviolet light of specific wavelengths selected from 200 nm to 410 nm.

13. The image forming method according to claim 12, wherein, The drying rates of the two or more colored inks when dried in an oven at 100°C for 30 seconds are different.

14. The image forming method according to claim 13, wherein, The ink containing pigments with high absorption rates of infrared or ultraviolet light among the two or more colored inks has a low drying rate when dried in an oven at 100°C for 30 seconds.

Images