Light irradiation device and printing device

Abstract

A light irradiation device disclosed in the specification of the present application comprises a light-emitting element and a control unit for controlling the state of the light-emitting element. A state in which the temperature of the light-emitting element rises is defined as a first state, and a state in which the temperature rise of the light-emitting element is suppressed more than in the first state is defined as a second state. The control unit causes the light-emitting element to emit light in the second state after causing the light-emitting element to start emitting light in the first state.

Description

Light irradiation device and printing apparatus Cross-Reference to Related Applications

[0001] The present application claims priority from Japanese Patent Application No. 2025-030955 filed on February 28, 2025, and the entire disclosure of said Japanese application is incorporated herein by reference.

[0002] The technology disclosed in the present specification relates to a light irradiation device and a printing apparatus.

[0003] There is known a light irradiation device that irradiates an object with light, which includes a light-emitting element, a heat dissipation member thermally connected to the light-emitting element, an air blowing unit that blows air to the light-emitting element, and a housing that accommodates the light-emitting element, the heat dissipation member, and the air blowing unit (see, for example, Patent Document 1).

[0004] In a light irradiation device and a printing apparatus including the light irradiation device, there is room for improvement in terms of stabilizing the illuminance of an optical element.

[0005] Japanese Patent No. 7542429

[0006] A light irradiation device and a printing apparatus are disclosed.

[0007] One aspect of the light irradiation device includes a light-emitting element and a control unit for controlling the state of the light-emitting element, wherein a state in which the temperature of the light-emitting element rises is defined as a first state, a state in which the temperature rise of the light-emitting element is suppressed more than in the first state is defined as a second state, and the control unit causes the light-emitting element to start irradiation with light in the first state, and then causes the light-emitting element to irradiate light in the second state. One aspect of the printing apparatus includes the above light irradiation device.

[0008] Figure 1 is a side view showing an example of the configuration of a light irradiation device according to the first embodiment. Figure 2 is a front view showing an example of the configuration of a light irradiation device according to the first embodiment. Figure 3 is a bottom view showing an example of the configuration of a light irradiation device according to the first embodiment. Figure 4 is a schematic cross-sectional view showing an example of the configuration of a light irradiation device according to the first embodiment. Figure 5 is a schematic diagram showing an example of gas flow in a light irradiation device according to the first embodiment. Figure 6 is a schematic diagram showing an example of the configuration of a printing device according to the first embodiment. Figure 7 is a diagram showing an example of the time change in temperature of the heat dissipation member of the light irradiation device according to the first embodiment. Figure 8 is a diagram showing an example of the time change in illuminance of the light-emitting element of the light irradiation device according to the first embodiment. Figure 9 is a diagram showing an example of switching the illuminance of the light-emitting element of the light irradiation device according to the first embodiment. Figure 10 is a diagram showing an example of switching the illuminance of the light-emitting element of the light irradiation device according to the first embodiment. Figure 11 is a flowchart showing an example of operation when switching the illuminance of the light-emitting element. Figure 12 is a diagram showing an example of switching the operating intensity of the air blower section of the light irradiation device according to the first embodiment. Figure 13 is a flowchart showing an example of operation when switching the operating intensity of the air blower section.

[0009] A light irradiation device includes a light-emitting element, a heat dissipation member thermally connected to the light-emitting element, a blower unit that blows air onto the light-emitting element, and a housing that accommodates the light-emitting element, the heat dissipation member, and the blower unit, and is used to irradiate an object with light.

[0010] In the above-described light irradiation device, heat generated from the light-emitting element when it irradiates light is dissipated by a heat dissipation member, and the light-emitting element is cooled as needed by a blower.

[0011] Incidentally, since the illuminance of a light-emitting element fluctuates with temperature, if the temperature changes due to the heat generated by the light-emitting element, it may take some time for the illuminance to stabilize.

[0012] Therefore, there is room for improvement in stabilizing the illuminance of optical elements in light irradiation devices and printing apparatus equipped with light irradiation devices.

[0013] Therefore, the inventors of this disclosure have created a technology for stabilizing the illuminance of optical elements in a light irradiation device and a printing apparatus equipped with a light irradiation device.

[0014] The embodiments will be described below with reference to the attached drawings. In the following embodiments, detailed features will be shown for the purpose of explaining the technology, but these are illustrative, and not all of them are necessarily essential features for the embodiments to be implementable.

[0015] Please note that the drawings are for illustrative purposes only, and for the sake of clarity, some components may be omitted or simplified as appropriate. Furthermore, the relative sizes and positions of components shown in different drawings are not necessarily accurately represented and may be modified as appropriate. In addition, hatching may be used in drawings other than cross-sectional views, such as plan views, to facilitate understanding of the embodiment.

[0016] Furthermore, in the following explanations, identical components are denoted by the same reference numerals. Therefore, detailed explanations of these components may be omitted to avoid redundancy.

[0017] Furthermore, in the descriptions contained in this specification, when a certain component is described as "equipped with," "includes," or "has," unless otherwise specified, it is not an exclusive expression that excludes the existence of other components.

[0018] Furthermore, even if ordinal numbers such as "first" or "second" are used in the descriptions contained herein, these terms are used for convenience to facilitate understanding of the embodiments, and the contents of the embodiments are not limited to the order that may result from these ordinal numbers.

[0019] Furthermore, when the description in this specification states "A or B," such statement shall include both cases where only one of A or B is indicated, and cases where both A and B are indicated, as long as there is no contradiction.

[0020] Furthermore, even if terms such as "top," "bottom," "left," "right," "side," "bottom," "front," or "back" are used in the descriptions of this specification to indicate a specific position or direction, these terms are used for convenience to facilitate understanding of the embodiments and are not related to the actual position or direction in which the embodiments are carried out.

[0021] <First Embodiment> <Configuration> The configuration of the light irradiation device 1 according to the first embodiment will be described with reference to Figures 1 to 6. Figure 1 is a side view showing an example of the configuration of the light irradiation device 1 according to the first embodiment. Figure 2 is a front view showing an example of the configuration of the light irradiation device 1 according to the first embodiment. Figure 3 is a bottom view showing an example of the configuration of the light irradiation device 1 according to the first embodiment. Figure 4 is a schematic cross-sectional view showing an example of the configuration of the light irradiation device 1 according to the first embodiment. Figure 5 is a diagram schematically showing an example of gas flow in the light irradiation device 1 according to the first embodiment.

[0022] The light irradiation device 1 is a device that can irradiate an object (also called an object to be irradiated) with light. The light irradiated onto the object to be irradiated by the light irradiation device 1 may be light in a predetermined wavelength range, such as ultraviolet light. The light irradiation device 1 may be a type of light irradiation device (also called an air-cooled light irradiation device) that performs intake and exhaust between the internal space 3i and the external space 3o of the housing 3, for the purpose of enhancing the heat dissipation effect from the light-emitting element 2 located in the internal space 3i of the housing 3.

[0023] As shown in Figures 1 to 5, the light irradiation device 1 comprises a light-emitting element 2, a housing 3, a ventilation filter 4, and a drive substrate 8. In an example of the first embodiment, as shown in Figure 4, for example, the light irradiation device 1 further comprises a substrate 5, a heat dissipation member 6, a blower 7, and a connector 9.

[0024] The light-emitting element 2 can emit light. The light emitted by the light-emitting element 2 includes, for example, light in a predetermined wavelength range. The light in the predetermined wavelength range may be, for example, ultraviolet light. The light-emitting element 2 may have a configuration having, for example, a plurality of semiconductor layers and a pair of electrodes. The light-emitting element 2 may be, for example, a laser diode (LD) or a light-emitting diode (LED). When the light emitted by the light-emitting element 2 is ultraviolet light, the wavelength at which the peak is observed in the light spectrum (also called the peak wavelength) is set, for example, within the range of 280 nanometers (nm) to 440 nm.

[0025] The housing 3 has an internal space (internal space 3i). The light-emitting element 2 is located in the internal space 3i. The internal space 3i of the housing 3 may contain one light-emitting element 2, or it may contain multiple light-emitting elements 2. In one example of the first embodiment, as shown in Figure 4, in addition to the light-emitting element 2, the internal space 3i of the housing 3 contains a substrate 5, a heat dissipation member 6, a blower unit 7, and a drive substrate 8.

[0026] The housing 3 includes a light-passing opening 32, a ventilation section 34, and a ventilation section 36. The light-passing opening 32 is an opening through which light from the light-emitting element 2 can pass. Through this light-passing opening 32, light from the light-emitting element 2 located in the internal space 3i of the housing 3 can be emitted into the space located outside the housing 3 (external space 3o). The ventilation section 34 and the ventilation section 36 each connect the internal space 3i of the housing 3 to the external space 3o of the housing 3, and are parts through which gas (for example, air) can pass. In one example of the first embodiment, intake from the external space 3o to the internal space 3i occurs in the ventilation section 34, and exhaust from the internal space 3i to the external space 3o occurs in the ventilation section 36. This enhances the heat dissipation effect from, for example, the light-emitting element 2 located in the internal space 3i of the housing 3.

[0027] The housing 3 has, for example, a light-emitting surface 31 as a first outer surface. The light-emitting surface 31 has a light-passing opening 32. The light-emitting surface 31 is, for example, a planar surface or plane. In one example of the first embodiment, for example, as shown in Figures 1 to 4, the light-emitting surface 31 is a surface along a virtual horizontal plane parallel to the XY plane. In other words, the light-emitting surface 31 may be, for example, a planar surface or plane facing the -Z direction (also simply referred to as the -Z direction) as a third direction. In this case, the light-emitting surface 31 may be the bottom surface (also referred to as the base surface) of the housing 3. The light-emitting surface 31 has, for example, a rectangular shape. The rectangular shape may be a rectangular shape, or a shape based on a rectangle with one or more corners rounded, or a shape based on a rectangle with one or more corners having portions that form two or more obtuse angles.

[0028] The light-passing opening 32 may be located on the -Z direction side of the light-emitting element 2. The light-passing opening 32 may have a longitudinal direction along the light-emitting surface 31 and along the +Y direction (also simply referred to as the +Y direction), which is a fourth direction perpendicular to the third direction. The light-passing opening 32 is, for example, an opening with a rectangular outer shape. In an example of the first embodiment, for example, as shown in Figures 1, 3 and 4, the light-passing opening 32 is an opening with a rectangular outer shape having a longitudinal direction along the +Y direction and a short direction along the light-emitting surface 31 and along the +X direction (also simply referred to as the +X direction), which is a fifth direction perpendicular to the fourth direction. The light-passing opening 32 may be located, for example, from the end of the light-emitting surface 31 on the +Y direction side to the end on the -Y direction (also simply referred to as the -Y direction), which is a sixth direction opposite to the fourth direction.

[0029] A cover member made of a light-transmitting material may be placed along the light-passing opening 32. For example, glass may be used as the light-transmitting material that makes up the cover member. This light-transmitting material only needs to have the transmittance to allow light in a predetermined wavelength range to pass through at a certain amount or more. In other words, this light-transmitting material does not need to be transmittance to light of the entire range of wavelengths from ultraviolet to infrared. For example, a light-transmitting member such as a glass plate (also called a glass sheet) may be used as the cover member. For example, optical glass such as quartz glass or borosilicate crown glass (BK7) may be used as the material for the glass sheet. Here, for example, the cover member may be fitted along the light-passing opening 32 to the part of the housing 3 that constitutes the light-emitting surface 31 (also called the lower wall or bottom wall). In this case, the surface of the cover member on the light-emitting element 2 side may be considered to constitute the light-passing opening 32. Furthermore, the side of the cover member opposite to the light-emitting element 2 can be considered to constitute part of the light-emitting surface 31.

[0030] Furthermore, for example, the remaining portion of the housing 3, excluding the cover member, may be made of a light-shielding material. In this case, the light irradiation surface 31 has a light-passing opening 32 through which light from the light-emitting element 2 can pass, and a light-shielding portion (also referred to as a light-shielding part) that sandwiches the light-passing opening 32 in the +X direction. Depending on the specifications of the light irradiation device 1, the light-shielding part may surround the light-passing opening 32. The light-shielding part of the light irradiation surface 31 does not need to have light-shielding properties for all wavelengths of light in the wavelength range from ultraviolet to infrared.

[0031] The light-shielding material constituting the housing 3 may be, for example, aluminum (Al), stainless steel, or copper (Cu). The surfaces of the housing 3, excluding the light-passing opening 32, may be treated with a surface treatment or coating to reduce light reflection. For example, anodizing treatment on the surface of an aluminum alloy may be applied as a surface treatment. For example, black paint may be applied as a coating.

[0032] Here, for example, it is assumed that light from the light-emitting element 2 is emitted downward from the light-passing opening 32 of the light-emitting surface 31. In this case, the length (also referred to as height) of the housing 3 in the direction along the -Z direction (also referred to as the height direction) may be, for example, about 120 millimeters (mm) to 180 mm. The length (also referred to as width) of the housing 3 in the direction along the +Y direction (also referred to as the width direction) may be, for example, about 60 mm to 130 mm. The length (also referred to as depth) of the housing 3 in the direction along the +X direction (also referred to as the depth direction) may be, for example, about 80 mm to 120 mm.

[0033] A ventilation section 36 may be located on the side of the housing 3. The ventilation section 36 may be located, for example, along a region of the side of the housing 3 that is close to the light-emitting surface 31. The ventilation section 36 may have one or more vents 36A. Each of the one or more vents 36A connects, for example, an internal space 3i and an external space 3o, and through which a gas (for example, air) can pass. In other words, a gas (for example, air) can pass between the internal space 3i and the external space 3o through each of the one or more vents 36A. For example, each of the one or more vents 36A may penetrate the side of the housing 3.

[0034] In the example shown in Figure 2, the through-hole serving as the ventilation opening 36A penetrates the side of the housing 3 in the +X direction. The through-hole serving as the ventilation opening 36A may have a rectangular cross-section. The cross-section of the through-hole is the cross-section of the through-hole perpendicular to the direction in which it penetrates the housing 3. The cross-section of this through-hole serving as the ventilation opening 36A may have a longitudinal direction along the +Y direction and a short direction along the -Z direction.

[0035] The inclined surface 35 is, for example, a surface located at the +Z end of the housing 3. The inclined surface 35 is, for example, a surface that is inclined with respect to the side surface of the housing 3. In other words, the inclined surface 35 may be, for example, a surface located diagonally above the housing 3. The inclined surface 35 may be, for example, a planar surface or a flat surface. The portion of the housing 3 that constitutes the inclined surface 35 may be included in the ventilation portion 34.

[0036] The ventilation filter 4 can capture foreign matter such as dust and dirt in the gas (e.g., air) passing through it. The ventilation filter 4 can be made of an object that has a large number of fine holes and / or gaps through which gas (e.g., air) can pass. More specifically, the ventilation filter 4 can be made of a soft object such as a sponge or nonwoven fabric. In the ventilation section 34, the presence of ventilation openings and the ventilation filter 4 through which gas (e.g., air) can pass can reduce the intrusion of foreign matter such as dust and dirt from the external space 3o to the internal space 3i of the housing 3. In other words, the ventilation filter 4 has the role of reducing the intrusion of foreign matter such as dust and dirt from the external space 3o to the internal space 3i of the housing 3.

[0037] The ventilation filter 4 is fixed and held to the inclined surface 35 by screws or the like using a dedicated filter cover 4A.

[0038] The substrate 5 is a substrate on which the light-emitting element 2 is mounted. In other words, the substrate 5 may support the light-emitting element 2. One or more light-emitting elements 2 may be mounted on the substrate 5. In one example of the first embodiment, one or more light-emitting elements 2 is multiple light-emitting elements 2. For example, on the substrate 5, multiple light-emitting elements 2 may be arranged in a single row, or multiple light-emitting elements 2 may be arranged in a matrix-like arrangement having multiple rows. The light irradiation device 1 may comprise one or more substrates 5, or it may comprise multiple substrates 5.

[0039] The substrate 5 is a substrate on which one or more light-emitting elements 2 are arranged (also referred to as a substrate for arranging light-emitting elements). For example, the substrate 5 may be a ceramic plate-shaped substrate (also referred to as a ceramic wiring substrate). For example, there may be wiring conductors (also referred to as wiring conductors) on the surface and inside the substrate 5 that electrically conduct electricity between the inside and outside of the substrate 5. For example, conductive materials such as tungsten (W), molybdenum (Mo), manganese (Mn), copper (Cu), or gold (Au) may be used as the material for the wiring conductors. If the substrate 5 is a ceramic wiring substrate, the base material of the ceramic wiring substrate is an insulating ceramic. For this reason, the ceramic wiring substrate may have heat resistance against the heat generated by the light emission of one or more light-emitting elements 2.

[0040] The heat dissipation member 6 is a component (also called a heat sink) intended for heat dissipation and heat absorption. The heat dissipation member 6 can dissipate the heat generated in the light-emitting element 2 and the substrate 5 when the light-emitting element 2 emits light. The substrate 5 and the light-emitting element 2 are thermally connected to the heat dissipation member 6. Here, the state in which the first part is thermally connected to the second part means that heat can be transferred between the first part and the second part. More specifically, the state in which the first part is thermally connected to the second part may mean that heat can be directly transferred between the first part and the second part, or that heat can be transferred through one or more objects located between the first part and the second part. Each of these one or more objects may be an object with excellent thermal conductivity. The form in which the substrate 5 is thermally connected to the heat dissipation member 6 may be a form in which the substrate 5 is directly connected to the heat dissipation member 6, or it may be a form in which the substrate 5 is indirectly connected to the heat dissipation member 6 via one or more objects with excellent thermal conductivity. In other words, the configuration in which the substrate 5 is thermally connected to the heat dissipation member 6 may be such that heat is transferred between the substrate 5 and the heat dissipation member 6 by the substrate 5 being in contact with the heat dissipation member 6, or it may be such that heat is transferred between the substrate 5 and the heat dissipation member 6 through one or more objects. Each of the one or more objects may have excellent thermal conductivity.

[0041] The material used for the heat dissipation member 6 may be, for example, a metal with excellent thermal conductivity such as aluminum (Al) or copper (Cu).

[0042] The heat dissipation member 6 may include, for example, a portion (base portion 61) to which the substrate 5 is thermally connected, and a plurality of protruding portions 62 that protrude from the base portion 61. The base portion 61 may have, for example, a plate-like or block-like shape. For the purpose of indirectly measuring the temperature of the light-emitting element 2, a thermistor 42 for measuring the temperature of the base portion 61 may be attached to the base portion 61. However, the location where the thermistor 42 is provided is not limited to the case shown in Figure 4, as long as the temperature of the light-emitting element 2 can be measured indirectly. For example, a plate-like fin may be applied to each of the plurality of protruding portions 62. For example, the heat dissipation member 6 is configured such that the base portion 61 is located on the side of the light-passing opening 32, and the plurality of protruding portions 62 are located on the side opposite to the light-passing opening 32 with respect to the base portion 61. For example, the substrate 5 may be thermally connected to the surface of the base portion 61 on the side of the light-passing opening 32. The plurality of protruding portions 62 may be located close to the ventilation portion 36.

[0043] The air blower 7 can, for example, generate a flow of gas (e.g., air) to increase heat dissipation from the light-emitting element 2 (in other words, to cool the light-emitting element 2). In one example of the first embodiment, the air blower 7 can generate a flow of gas (e.g., air) (also called an airflow) that flows along the heat-dissipating member 6. More specifically, the air blower 7 can generate an airflow to release the gas (e.g., air) in the internal space 3i of the housing 3, which has been heated by the heat dissipated from the heat-dissipating member 6, into the external space 3o of the housing 3. For example, a cooling fan can be applied to the air blower 7. For example, if an axial flow fan is applied to the air blower 7, the air blower 7 can generate a larger airflow while remaining compact. For example, other types of fans other than axial flow fans may be applied to the air blower 7. The air blower 7 has the function of increasing heat dissipation from the light-emitting element 2, but the means to realize the function of increasing heat dissipation from the light-emitting element 2 is not limited to air blowing, but may also include, for example, a liquid refrigerant.

[0044] As shown in Fig. 4, the blower unit 7 is located between the heat dissipation member 6 and the ventilation portion 34, for example. For example, the blower unit 7 is fixed to the inner surface side of the housing 3. For example, as shown in Fig. 6, the blower unit 7 may blow air toward the heat dissipation member 6. Accordingly, a flow of gas (e.g., air) that can efficiently cool the heat dissipation member 6 between the ventilation portion 34 and the ventilation portion 36 can be generated by the blower unit 7. Therefore, the cooling efficiency of the heat dissipation member 6 can be improved by the air blowing from the blower unit 7.

[0045] In Fig. 5, an example of the flow of gas (e.g., air) introduced from the external space 3o of the housing 3 to the internal space 3i of the housing 3 via the ventilation portion 34 is schematically shown by an arrow drawn with a thin two-dot chain line. An example of the flow of gas (e.g., air) from the blower unit 7 to the heat dissipation member 6 is schematically shown by an arrow drawn with a thin two-dot chain line. An example of the flow of gas (e.g., air) directed from the region along the heat dissipation member 6 to the external space 3o outside the housing 3 via the ventilation portion 36 is schematically shown by an arrow drawn with a thin two-dot chain line. As shown in Fig. 5, for example, when the blower unit 7 blows air toward the heat dissipation member 6, a flow of gas (e.g., air) can be generated, in which the gas (e.g., air) introduced from the external space 3o of the housing 3 to the internal space 3i of the housing 3 via the ventilation portion 34 passes through the region along the heat dissipation member 6 and is discharged to the external space 3o of the housing 3 via the ventilation portion 36.

[0046] Here, in an example of the first embodiment, for example, as shown in FIGS. 4 and 5, the blower unit 7 is fixed to a pedestal (also referred to as a separating portion or a separating plate) 71 that is located in the internal space 3i of the housing 3 and has a plate-like shape fixed to the housing 3. The separating portion 71 separates, for example, the internal space 3i of the housing 3 into a region connected to the ventilation portion 34 (also referred to as an upper region) and a region where the heat radiating member 6 is located and connected to the ventilation portion 36 (also referred to as a lower region). In an example of the first embodiment, for example, as shown in FIGS. 4 and 5, the separating portion 71 may be located along a virtual horizontal plane parallel to the XY plane, for example. The separating portion 71 has a vent (not shown herein) connected to the blower unit 7. Due to the presence of this separating portion 71, for example, the flow of gas (e.g., air) reaching the space between the ventilation portion 34 and the blower unit 7 by a part of the gas (e.g., air) warmed by heat dissipated from the heat radiating member 6 can be reduced. Thereby, the dissipation of heat from the heat radiating member 6 can be enhanced by the air blown by the blower unit 7. As a result, the light emitting element 2 can be efficiently cooled via the heat radiating member 6.

[0047] The drive substrate includes, for example, an electric circuit (also referred to as a drive circuit) for driving the light emitting element 2. The drive substrate may include, for example, an electric circuit (drive circuit) for driving the blower unit 7. The drive substrate may be electrically connected to the substrate 5 via, for example, a cable or a flexible printed circuits (FPC) or the like. The drive substrate may be electrically connected to the blower unit 7 via, for example, a cable or a flexible printed circuit (FPC) or the like. The drive substrate may include, for example, a wiring substrate and one or more drive circuits.

[0048] The wiring board may be, for example, a printed circuit board. The wiring board is fixed to the inner surface of the housing 3, for example. For example, the wiring board may be fixed to the inner surface of the housing 3 by screws or the like via a base, support, or spacer placed on the inner surface of the housing 3. Alternatively, for example, the wiring board may be fixed to the inner surface of the housing 3 by fitting it into grooves or protrusions placed on the inner surface of the housing 3. The wiring board may be positioned along a virtual plane parallel to the YZ plane, for example.

[0049] One or more drive circuits may include, for example, one or more electronic components. One or more electronic components may be mounted on a wiring board, for example. One or more drive circuits may, for example, supply power to the light-emitting element 2 and control the light emission of the light-emitting element 2. Also, one or more drive circuits may, for example, supply power to the air blower 7 and control the operation of the air blower 7. For example, one or more drive circuits may control the rotation speed of the fan of the air blower 7 according to the heat generation state of the light-emitting element 2. One or more drive circuits may, for example, recognize the heat generation state of the light-emitting element 2 in response to an electrical signal transmitted via a cable from a thermistor 42 attached to a heat dissipation member 6, etc.

[0050] The connector 9 is a part for connecting a plurality of wires connected to the drive board 8 (also referred to as first wires) and a plurality of wires located outside the housing 3 (also referred to as second wires). Each of the plurality of first wires may be, for example, a cable or a harness. Each of the plurality of second wires may be, for example, a cable or a harness. The connector 9 may be located, for example, in a form that penetrates the housing 3, or it may be located along the outer surface of the housing 3. The connector 9 may be located, for example, on the upper surface of the light irradiation device 1. The light irradiation device 1 may have one connector 9, or it may have two or more connectors 9.

[0051] Through the connector 9, power can be supplied from outside the light irradiation device 1 to the drive board 8, and signals (such as control signals) can be exchanged between the outside of the light irradiation device 1 and the drive board 8.

[0052] Figure 6 is a schematic diagram showing an example of the configuration of a printing apparatus 900 according to the first embodiment. As shown in Figure 6, in the example of the first embodiment, the printing apparatus 900 comprises a light irradiation device 1, a transport unit 920, a printing unit 930, and a control unit 940.

[0053] The transport unit 920 can transport the printing medium 911 in the order described above, passing it through the region facing the printing unit 930 and the region facing the light irradiation device 1. Here, for example, the transport unit 920 can transport the printing medium 911 in a predetermined direction (transport direction) while facing the light irradiation surface 31 of the light irradiation device 1. Here, the light irradiation surface 31 of the light irradiation device 1 and the surface of the printing medium 911 passing through are arranged, for example, parallel or substantially parallel.

[0054] In the example shown in Figure 6, the transport unit 920 transports the printing medium 911, which is located along a virtual plane parallel to the horizontal plane, in the +X direction. In this case, the width direction of the printing medium 911 may be perpendicular to the transport direction of the printing medium 911, or it may be in the +Y direction. The thickness direction of the printing medium 911 may be in the +Z direction.

[0055] As shown in Figure 6, the transport unit 920 includes, for example, a pair of transport rollers 921 located upstream of the printing device 900 and a pair of transport rollers 922 located downstream of the printing device 900. Each of the transport rollers 921 and the transport rollers 922 can hold the medium to be printed 911 by sandwiching it from above and below. The medium to be printed 911 can be transported in the transport direction by the rotation of the downstream transport rollers 922 and the rotation of the upstream transport rollers 921. The rotation of each of the transport rollers 921 can be achieved by a drive such as an electric motor. The rotation of each of the transport rollers 922 can be achieved by a drive such as an electric motor.

[0056] The transport unit 920 may have a support section that supports the printing medium 911 from below, for example, between a pair of upstream transport rollers 921 and a pair of downstream transport rollers 922. For example, a plurality of cylindrical or columnar rollers (also referred to as support rollers) may be applied to this support section. The plurality of support rollers may be arranged in the transport direction, and each of the plurality of support rollers may have an axial direction along a direction perpendicular to the transport direction. For example, a platform on which the printing medium 911 is placed (also referred to as a placement platform) may be applied to the support section. In this case, the printing medium 911 can be moved by sliding against the placement platform while it is placed on the placement platform.

[0057] The printing unit 930 can deposit ink 912 onto the printing medium 911 being transported by the transport unit 920. For example, an inkjet (IJ) head that ejects ink 912 is applied to the printing unit 930. For example, a photocurable ink (also called a photocurable ink) as a photosensitive material is applied to the ink 912. A photocurable ink is an ink that hardens (also called photocuring) in response to irradiation with light in a predetermined wavelength range. For example, a UV-curable ink (also called a UV ink) that hardens (photocures) in response to irradiation with ultraviolet light as light in a predetermined wavelength range is applied to the photocurable ink.

[0058] The printing unit 930 can, for example, adhere ink 912 to the upper surface of the printing medium 911 being transported by the transport unit 920. Here, the IJ head of the printing unit 930 can adhere droplets of ink 912 to the upper surface of the printing medium 911 being transported by the transport unit 920. Here, the printing unit 930 can, for example, adhere ink 912 to the upper surface of the printing medium 911 in a desired pattern. The printing unit 930 may, for example, adhere ink 912 to substantially the entire upper surface of the printing medium 911, or it may adhere ink 912 to a part of the upper surface of the printing medium 911.

[0059] Here, for example, a line-type IJ head is applied to the IJ head of the printing unit 930. The line-type IJ head has a plurality of ink ejection holes arranged in a line (linear) shape. The line-type IJ head can eject ink 912 from each of the plurality of ink ejection holes. The direction in which the plurality of ink ejection holes are arranged (also referred to as the arrangement direction) is, for example, a direction that is perpendicular to the direction in which the medium to be printed 911 is transported by the transport unit 920 and is also parallel to the upper surface of the medium to be printed 911 being transported by the transport unit 920. In other words, the arrangement direction of the plurality of ink ejection holes is, for example, a direction that is perpendicular to the width direction of the medium to be printed 911 being transported by the transport unit 920. In the example of Figure 6, the arrangement direction of the plurality of ink ejection holes is a direction that is parallel to the +Y direction. With this configuration, ink 912 is ejected from multiple ink ejection holes of the line-type IJ head onto the printing medium 911 being transported in the transport direction by the transport unit 920, thereby allowing the ink 912 to adhere to the upper surface of the printing medium 911. As a result, the printing unit 930 can adhere the ink 912 to the upper surface of the printing medium 911 in a desired pattern.

[0060] The IJ head used as the printing unit 930 may be of a different type, such as a serial IJ head, which is different from a line-type IJ head. The serial IJ head can move along the width direction of the printing medium 911. In this case, for example, the ejection of ink 912 onto the upper surface of the printing medium 911 by the serial IJ head while it is moving along the width direction of the printing medium 911 alternates with the movement of the printing medium 911 in the transport direction by the transport unit 920. This allows the printing unit 930 to adhere the ink 912 to the upper surface of the printing medium 911 in a desired pattern.

[0061] The light irradiation device 1 can irradiate the printing medium 911 being transported in the transport direction by the transport unit 920 with light from the light passage opening 32. The light irradiation device 1 is located downstream of the printing unit 930 in the transport direction in which the printing medium 911 is transported by the transport unit 920. The light irradiation surface 31 of the light irradiation device 1 is positioned downwards. Therefore, the light irradiation device 1 can irradiate the ink 912 adhering to the upper surface of the printing medium 911 with light from the light passage opening 32. In Figure 6, the outer edge of the light path irradiated from the light passage opening 32 to the printing medium 911 is schematically shown by a thin dashed line.

[0062] Here, for example, it is assumed that the ink 912 is a photocurable ink. In this case, if the light irradiated onto the upper surface of the printing medium 911 by the light irradiation device 1 is light in a predetermined wavelength range for causing curing (photocuring) of the photocurable ink, the ink 912 attached to the upper surface of the printing medium 911 can be cured by the light from the light irradiation device 1. For example, if the ink 912 is an ultraviolet-curable ink (UV ink), if the light irradiated onto the upper surface of the printing medium 911 by the light irradiation device 1 is ultraviolet light in a predetermined wavelength range, the UV ink as the ink 912 attached to the upper surface of the printing medium 911 can be cured.

[0063] Here, for example, as shown in Figure 6, the inclined surface 35 of the light irradiation device 1 may face the downstream side in the transport direction. From another point of view, for example, in the light irradiation device 1, the ventilation section 34 and ventilation section 36 may be located on the downstream side in the transport direction. In other words, in the light irradiation device 1, the ventilation section 34 and ventilation section 36 may be located on the opposite side from the area where the printing section 930 is located. With this configuration, the influence of airflow turbulence due to supply and exhaust in the ventilation section 34 and ventilation section 36 of the light irradiation device 1 on the printing section 930 can be reduced. More specifically, for example, the problem of the trajectory of ink droplets 912 ejected from the printing section 930 toward the printing medium 911 being altered by airflow turbulence due to supply and exhaust can be reduced. As a result, the decrease in the accuracy of the position where the ink 912 is deposited on the upper surface of the printing medium 911 can be reduced.

[0064] Here, for example, it is assumed that the printing device 900 has the form of a line printer in which the width of the IJ head, which is the printing unit 930, is approximately the same as the width of the printing medium 911. In this case, for example, a plurality of light irradiation devices 1 may be arranged in the +Y direction, which is the width direction of the printing medium 911, so that the width of the printing medium 911 and the total width of the plurality of light irradiation devices 1 are set to be approximately the same. Alternatively, the width of the light irradiation device 1 and the width of the printing medium 911 may be set to be approximately the same. In this case, for example, the shape of the light irradiation device 1 may be such that the width direction is the longitudinal direction.

[0065] The control unit 940 can control the operation of each part of the printing apparatus 900. The control unit 940 has various electrical circuits, such as a processor and memory. The control unit 940 is electrically connected to each part of the printing apparatus 900, for example, using cables. For example, the control unit 940 may be electrically connected to the connector 9 of the light irradiation device 1 via cables. The control unit 940 may be electrically connected to the transport unit 920 and the printing unit 930, for example, via cables.

[0066] The control unit 940 can, for example, control the transport of the printing medium 911 by the transport unit 920. The control unit 940 can, for example, control the ejection of ink 912 by the IJ head of the printing unit 930. The control unit 940 can, for example, control the operation of the air blower 7 in the light irradiation device 1 via the drive substrate 8. For example, the light emission of one or more light-emitting elements 2 in the light irradiation device 1 can be controlled via the drive substrate 8 and the substrate 5. The control unit 940 has, for example, an internal memory. For example, if the ink 912 is a photocurable ink, this memory may store information indicating the characteristics of light that can relatively well photocur the ink 912 ejected from the IJ head of the printing unit 930. Specific examples of this information include the characteristics of the wavelength distribution of light suitable for causing photocuring of droplets of ink 912 ejected from the IJ head, and numerical values ​​representing the light intensity (emission intensity in each wavelength range). In the printing apparatus 900, for example, the control unit 940 may adjust the magnitude of the drive current input to one or more light-emitting elements 2 in the light irradiation device 1 based on information in memory. This allows, for example, one or more light-emitting elements 2 in the light irradiation device 1 to emit light with an appropriate amount of light according to the characteristics of the ink 912 being used, and the ink 912 to be cured with relatively low-energy light.

[0067] Furthermore, an illuminance meter 44 can be provided in the area of ​​the transport unit 920 facing the light irradiation device 1, at a position that does not overlap with the printing medium 911 in a plan view. The illuminance meter 44 is, for example, a photodiode. The illuminance meter 44 is positioned at, for example, one end of the transport unit 920 in the Y direction, while maintaining its positional relationship with the light irradiation surface 31 of the light irradiation device 1 (i.e., not transported in the transport direction). Light from the light-emitting element 2 of the light irradiation device 1 is irradiated onto the illuminance meter 44, and the illuminance of the light is measured. The measured illuminance is transmitted as an electrical signal to the control unit 940 or the drive board 8. Here, illuminance is an index that indicates how much light irradiated from the light source hits the target surface. Note that the location where the illuminance meter 44 is provided is not limited to the case shown in Figure 6, and for example, it may be provided at the edge of the light passage opening 32 in the area where light from the light-emitting element 2 is irradiated.

[0068] <Operation> Next, the operation of the light irradiation device 1 according to the first embodiment will be explained with reference to Figures 7 to 13. Figure 7 is a diagram showing an example of the time change in temperature of the heat dissipation member 6 of the light irradiation device 1 according to the first embodiment. Figure 8 is a diagram showing an example of the time change in illuminance of the light-emitting element 2 of the light irradiation device 1 according to the first embodiment. Figure 9 is a diagram showing an example of switching the illuminance of the light-emitting element 2 of the light irradiation device 1 according to the first embodiment. Figure 10 is a diagram showing an example of switching the illuminance of the light-emitting element 2 of the light irradiation device 1 according to the first embodiment. Figure 11 is a flowchart showing an example of operation when switching the illuminance of the light-emitting element 2. Figure 12 is a diagram showing an example of switching the operating intensity (fan rotation speed, etc.) of the air blower 7 of the light irradiation device 1 according to the first embodiment. Figure 13 is a flowchart showing an example of operation when switching the operating intensity (fan rotation speed, etc.) of the air blower 7.

[0069] Figure 7 shows the temperature measurement results of the heat dissipation member 6, which is thermally connected to the light-emitting element 2 and the substrate 5. The temperature of the heat dissipation member 6 is measured, for example, by a thermistor 42 attached to the base portion 61. In Figure 7, the vertical axis represents the temperature of the heat dissipation member 6, and the horizontal axis represents the light emission time of the light-emitting element 2.

[0070] As shown in Figure 7, the temperature of the heat dissipation member 6 rises in accordance with the light emission time of the light-emitting element 2, and after a predetermined time has elapsed, the temperature rise becomes sufficiently small and the temperature becomes constant (referred to as the saturation temperature). It is assumed that the saturation temperature of the heat dissipation member 6 is the same as the saturation temperature of the light-emitting element 2 which is thermally connected to the heat dissipation member 6.

[0071] In Figure 7, a thin line indicates that the output of the light-emitting element 2 is 100%, a thick line indicates that the output is 90%, a dashed-dotted line indicates that the output is 80%, and a double-dashed-dotted line indicates that the output is 70%. The output of the light-emitting element 2 is adjusted by the current control of the light-emitting element 2 by the driving substrate 8. Here, "100% output" means that a certain reference value of the current flowing from the driving substrate 8 to the light-emitting element 2 is 100%. In other words, the value of the current at which the output is 100% is arbitrary.

[0072] As illustrated in Figure 7, the saturation temperature of the light-emitting element 2 increases with increasing output power. On the other hand, the time required to reach the saturation temperature at each output level is constant and determined by the heat capacity of the light-emitting element 2, regardless of the output level of the light-emitting element 2. In other words, the higher the output power of the light-emitting element 2, the higher the rate of temperature rise per unit time.

[0073] Figure 8 shows the rate of change in illuminance of light emitted from the light-emitting element 2. In Figure 8, the vertical axis represents the rate of change in illuminance relative to the initial illuminance, and the horizontal axis represents the emission time of the light-emitting element 2. In Figure 8, the time change of light emitted from the light-emitting element 2, as measured by the illuminance meter 44, is shown as a rate of change (decrease rate) relative to the stable illuminance (initial illuminance) at the start of irradiation.

[0074] The illuminance of the light-emitting element 2 decreases with increasing temperature. Referring to Figure 8, the rate of change in illuminance increases with the emission time of the light-emitting element 2, that is, the illuminance decreases. This is because, as shown in Figure 7, the temperature of the light-emitting element 2 increases with increasing emission time. According to Figure 8, the illuminance of the light-emitting element 2 reaches a constant rate of change after a predetermined time has elapsed, that is, the decrease in illuminance becomes sufficiently small. The rate of change in illuminance of the light-emitting element 2 at this time is also called the saturation rate of change, and the illuminance is also called the saturation illuminance.

[0075] In Figure 8, a square indicates that the output of the light-emitting element 2 is 100%, a thick triangle indicates that the output is 90%, an X indicates that the output is 80%, and a circle indicates that the output is 70%. The output of the light-emitting element 2 is adjusted by the current control of the light-emitting element 2 by the driving substrate 8.

[0076] As shown in Figure 8, the saturation rate of the light-emitting element 2 increases as the output of the light-emitting element 2 increases (the change becomes larger), and the saturation illuminance of the light-emitting element 2 decreases as the output of the light-emitting element 2 increases. This is because the temperature of the light-emitting element 2 (including the saturation temperature) increases as the output of the light-emitting element 2 increases. On the other hand, the saturation rate of change and the time to reach saturation illuminance at each output are determined and constant according to the heat capacity of the light-emitting element 2, regardless of the output level of the light-emitting element 2. In other words, according to Figures 7 and 8, the higher the output of the light-emitting element 2, the faster the temperature rise and the faster the illuminance change.

[0077] Here, it is desirable for the illuminance of the light-emitting element 2 to stabilize early, but since the illuminance changes until the temperature of the light-emitting element 2 reaches its saturation temperature, it is necessary for the light-emitting element 2 to reach its saturation temperature early.

[0078] In contrast, as shown in Figures 7 and 8, the higher the output of the light-emitting element 2, the faster the temperature rise and the faster the illuminance change. Therefore, the time required to raise the temperature of the light-emitting element 2 to the target temperature (saturation temperature), and the time required to reduce the illuminance of the light-emitting element 2 to the target illuminance change rate (saturation change rate), both become shorter as the output of the light-emitting element 2 increases.

[0079] Therefore, the time it takes for the light-emitting element 2 to reach its saturation temperature at the first output (low output) is shorter when the light-emitting element 2 is powered at a second output (high output) which is higher than the first output, than when the light-emitting element 2 is powered at the first output (low output) to raise its temperature.

[0080] Furthermore, the time it takes for the light-emitting element 2 to reach its saturation rate of change at the first output (low output) is shorter when the light-emitting element 2 is output at a second output (high output), which is higher than the first output, to reduce its illuminance, compared to when the light-emitting element 2 is output at the first output (low output) to reduce its illuminance.

[0081] According to the method described above, the illuminance of the light-emitting element 2 can be stabilized quickly.

[0082] Figures 9 and 10 show an example in which the output of the light-emitting element 2 is switched midway through to shorten the time it takes to stabilize the illuminance of the light-emitting element 2. Figure 11 shows a flowchart of this switching operation. In Figure 9, the vertical axis shows the illuminance change rate relative to the initial illuminance, and the horizontal axis shows the light emission time of the light-emitting element 2. Also in Figure 9, a square indicates that the output is 100%, a thick triangle indicates that the output is 90%, and a circle indicates that the output of the light-emitting element 2 is switched.

[0083] To shorten the time it takes to reach the saturation rate when the output is 90%, light is first irradiated with the output of the light-emitting element 2 set to 100% (step ST01). The stable illuminance at the start of irradiation with the light-emitting element 2 set to 100% output is defined as the initial illuminance.

[0084] Next, the illuminance of the light irradiating at 100% output is measured (step ST02). This measurement is performed, for example, using an illuminance meter 44. The illuminance of the light is measured continuously from the start of light irradiation by the light-emitting element 2, or sequentially at regular intervals.

[0085] Next, the rate of change of the measured illuminance relative to the initial illuminance is calculated as the illuminance change rate (step ST03). This calculation is performed, for example, by the control unit 940 or the drive board 8.

[0086] Next, it is determined whether the illuminance change rate calculated in step ST03 corresponds to the saturation change rate (illuminance change rate corresponding to saturation illuminance) when the output is 90% (step ST04). This determination is performed, for example, by the control unit 940 or the drive board 8. When the illuminance change rate calculated in step ST03 corresponds to the saturation change rate when the output is 90%, it is not limited to cases where the two are exactly the same, but also includes cases where they are sufficiently close values. If the illuminance change rate calculated in step ST03 corresponds to the saturation change rate when the output is 90%, the process proceeds to step ST05. On the other hand, if the illuminance change rate calculated in step ST03 does not correspond to the saturation change rate when the output is 90%, the process returns to step ST02.

[0087] In step ST05, the output of the light-emitting element 2 is switched to 90% at that timing.

[0088] Since the saturation rate of change when the output of the light-emitting element 2 is 90% is about 17%, in Figure 9, the output of the light-emitting element 2 is maintained at 100% until the illuminance change rate reaches about 17%, and at the moment the illuminance change rate reaches about 17%, the output of the light-emitting element 2 is switched to 90%. The light-emitting element 2, whose output has been switched to 90%, has already reached the saturation temperature when the output is 90%, and the illuminance change rate is also at the saturation rate, so the subsequent illuminance change becomes sufficiently small.

[0089] In Figure 10, the vertical axis represents the illuminance of the light-emitting element 2, and the horizontal axis represents the light-emitting time of the light-emitting element 2. In Figure 10, a square indicates that the output is 100%, a triangle indicates that the output is 90%, and a circle indicates that the output of the light-emitting element 2 is switched. The illuminance of the light-emitting element 2 in Figure 10 is measured, for example, using an illuminance meter 44. The switching operation shown in Figure 10 is the same as the switching operation shown in Figure 9.

[0090] In Figure 10, light is first emitted with the output of the light-emitting element 2 set to 100%. Then, at a timing where the rate of change in illuminance when the output is 100% corresponds to the rate of change in saturation when the output is 90% (the rate of change in illuminance corresponding to the saturation illuminance), the output of the light-emitting element 2 is switched to 90%.

[0091] As shown in Figure 10, when the output of the light-emitting element 2 is switched from 100% to 90%, the illuminance of the light-emitting element 2 decreases from approximately 83% to approximately 74%. The light-emitting element 2, with its output switched to 90%, has already reached the saturation temperature and saturation rate of change at 90% output, and any subsequent illuminance changes become sufficiently small.

[0092] By referring to the change in illuminance rate when the output is 90% as shown in Figure 9, or the change in illuminance when the output is 90% as shown in Figure 10, it can be seen that the above switching operation shortens the time it takes to stabilize the illuminance of the light-emitting element 2.

[0093] In the above example, the switching of the output of the light-emitting element 2 was performed based on the illuminance change rate when the output is 100%, but it may also be performed based on the temperature of the light-emitting element 2, for example.

[0094] In other words, the temperature of the light-emitting element 2, which is irradiated with light at 100% output, is measured, and it is determined whether the measured temperature corresponds to the saturation temperature when the output is 90%. If the measured temperature corresponds to the saturation temperature when the output is 90%, it is not limited to cases where the two are exactly the same, but also includes cases where they are sufficiently close values. Then, at the timing when the measured temperature corresponds to the saturation temperature when the output is 90%, the output of the light-emitting element 2 is switched to 90%. Here, the temperature of the light-emitting element 2 is measured indirectly, for example, by measuring the temperature of the heat dissipation member 6 with a thermistor 42.

[0095] Furthermore, in the above description, the switching of the output of the light-emitting element 2 was performed based on the illuminance change rate when the output is 100%, but it may also be performed based on, for example, the light emission time of the light-emitting element 2.

[0096] Specifically, the time it takes for the illuminance change rate of the light-emitting element 2, which is emitting light at 100% output, to reach the saturation rate when the output is 90% (also called the saturation time) is measured in advance, and it is determined whether the light emission time of the light-emitting element 2 at 100% output corresponds to the saturation time when the output is 90%. If this time corresponds to the saturation time, it is not limited to cases where the two values ​​are exactly the same, but also includes cases where they are sufficiently close values. Then, at the timing when this time corresponds to the saturation time, the output of the light-emitting element 2 is switched to 90%.

[0097] The method of switching the output of the light-emitting element 2 can also be described as a method of changing the state in which the temperature of the light-emitting element 2 rises (the degree to which it rises) to a state in which the temperature rise is suppressed. In addition to switching the output of the light-emitting element 2, another method of switching the state in which the temperature of the light-emitting element 2 rises (the degree to which it rises) is, for example, switching the operating intensity (fan speed) of the air blower 7, which acts as a cooling unit to cool the light-emitting element 2.

[0098] Figure 12 shows an example in which the operating intensity (fan speed) of the air blower 7 that blows air onto the light-emitting element 2 is switched midway through the process to shorten the time it takes to stabilize the illuminance of the light-emitting element 2. Figure 13 shows a flowchart of this switching operation. In Figure 12, the vertical axis represents the illuminance of the light-emitting element 2, and the horizontal axis represents the light emission time of the light-emitting element 2. The illuminance of the light-emitting element 2 in Figure 12 is measured, for example, using an illuminance meter 44.

[0099] In Figure 12, a thin circle indicates a high operating intensity of the air blower 7, a thick circle indicates a low operating intensity of the air blower 7, and a square indicates when the operating intensity of the air blower 7 is switched. The operating intensity of the air blower 7 is adjusted by voltage control of the air blower 7 by the drive board 8.

[0100] In order to shorten the time it takes to reach the saturation rate of change when the operating intensity of the blower unit 7 is high (high intensity), first, the operating intensity of the blower unit 7 is set low and light is emitted from the light-emitting element 2 (step ST11). The stable illuminance at the start of irradiation of light emitted from the light-emitting element 2 when the operating intensity of the blower unit 7 is set low is defined as the initial illuminance.

[0101] Next, the illuminance of the light is measured when the operating intensity of the blower unit 7 is low (step ST12). This measurement is performed, for example, using an illuminance meter 44. The illuminance of the light is measured continuously from the start of light irradiation by the light-emitting element 2, or sequentially at regular intervals.

[0102] Next, it is determined whether the illuminance measured in step ST12 corresponds to the saturation illuminance when the operating intensity of the air blower 7 is high (step ST13). This determination is made, for example, by the control unit 940 or the drive board 8. When the illuminance measured in step ST12 corresponds to the saturation illuminance when the operating intensity of the air blower 7 is high, it is not limited to cases where the two values ​​are exactly the same, but also includes cases where they are sufficiently close values. If the illuminance measured in step ST12 corresponds to the saturation illuminance when the operating intensity of the air blower 7 is high, the process proceeds to step ST14. On the other hand, if the illuminance measured in step ST12 does not correspond to the saturation illuminance when the operating intensity of the air blower 7 is high, the process returns to step ST12.

[0103] In step ST14, the operating intensity of the blower unit 7 is switched to a higher setting at that timing.

[0104] When the operating intensity of the air blower 7 is low, the saturation illuminance is reached at approximately 0.82, assuming an initial illuminance of 1. Therefore, in Figure 12, the operating intensity of the air blower 7 is maintained at a low level until the illuminance reaches approximately 0.82, at which point the operating intensity of the air blower 7 is switched to a higher level. The light-emitting element 2, when the operating intensity of the air blower 7 is switched to a higher level, has already reached the saturation temperature for when the operating intensity of the air blower 7 is high, and the subsequent change in illuminance becomes sufficiently small.

[0105] The switching operation only needs to result in a switch that increases the operating intensity of the air blower 7. For example, even if the operating intensity of the air blower 7 before switching is relatively high, it is sufficient if the operating intensity of the air blower 7 after switching is even higher, and even if the operating intensity of the air blower 7 after switching is relatively low, it is sufficient if the operating intensity of the air blower 7 before switching is even lower. Furthermore, the state in which the operating intensity of the air blower 7 is low includes the state in which the air blowing is stopped. In addition to using a cooling unit, another method for switching the state (degree of increase) in which the temperature of the light-emitting element 2 rises is to switch the operating intensity (heating temperature) of the heating element that heats the light-emitting element 2. By lowering the operating intensity (heating temperature) of the heating element 2 midway through, or by stopping the heating of the heating element 2, the time required to stabilize the illuminance of the light-emitting element 2 can be shortened. In the method of switching the operating intensity of the cooling unit or the operating intensity of the heating element 2, the output of the light-emitting element 2 may be set to 0 (no irradiation) before switching the operation, and output (start of irradiation) may be set to the light-emitting element 2 after switching the operation.

[0106] In this case, the method for switching the operating intensity of the air blower 7 described above may be set based on the saturation rate, as shown in Figure 9.

[0107] Furthermore, in the above description, the switching of the operating intensity of the air blower 7 was performed based on the illuminance when the operating intensity of the air blower 7 was low, but it may also be performed based on, for example, the temperature of the light-emitting element 2.

[0108] In other words, the temperature of the light-emitting element 2, which is irradiated with light when the operating intensity of the air blower 7 is low, is measured, and it is determined whether the measured temperature corresponds to the saturation temperature when the operating intensity of the air blower 7 is high. If the measured temperature corresponds to the saturation temperature when the operating intensity of the air blower 7 is high, it is not limited to cases where the two are exactly the same, but also includes cases where they are sufficiently close values. Then, at the timing when the measured temperature corresponds to the saturation temperature when the operating intensity of the air blower 7 is high, the operating intensity of the air blower 7 is switched to high. Here, the temperature of the light-emitting element 2 is measured indirectly, for example, by measuring the temperature of the heat dissipation member 6 with a thermistor 42.

[0109] Furthermore, in the above description, the switching of the operating intensity of the air blower 7 was performed based on the illuminance when the operating intensity of the air blower 7 is low, but it may also be performed based on, for example, the light emission time of the light-emitting element 2.

[0110] In other words, the time it takes for the rate of change in illuminance of the light-emitting element 2, which is irradiated with light when the operating intensity of the blower unit 7 is low, to reach the saturation rate of change when the operating intensity of the blower unit 7 is high (also called the saturation time) is measured in advance, and it is determined whether the light emission time of the light-emitting element 2 when the operating intensity of the blower unit 7 is low corresponds to the saturation time when the operating intensity of the blower unit 7 is high. If this time corresponds to the saturation time, it is not limited to cases where the two are exactly the same, but also includes cases where they are sufficiently close values. Then, at the timing when this time corresponds to the saturation time, the operating intensity of the blower unit 7 is switched to a high setting.

[0111] Furthermore, a method for switching the operating intensity of the air blower 7 and a method for switching the output of the light-emitting element 2 may be combined.

[0112] This disclosure includes the following:

[0113] (1) In one embodiment, the light irradiation device comprises a light-emitting element and a control unit for controlling the state of the light-emitting element, wherein a state in which the temperature of the light-emitting element rises is defined as a first state, and a state in which the temperature rise of the light-emitting element is suppressed more than that of the first state is defined as a second state, and the control unit starts irradiating light from the light-emitting element in the first state, and then irradiates light from the light-emitting element in the second state.

[0114] (2) In the light irradiation device described in (1), the output when the light-emitting element irradiates light includes a first output and a second output which is lower than the first output, and the first state is a state in which the light-emitting element irradiates light with the first output under the control of the control unit, and the second state is a state in which the light-emitting element irradiates light with the second output under the control of the control unit.

[0115] (3) The light irradiation apparatus according to (1) or (2) further comprises a cooling unit for cooling the light-emitting element, wherein the control unit controls the intensity at which the cooling unit cools the light-emitting element, and the intensity at which the cooling unit cools the light-emitting element includes a first intensity and a second intensity which is lower than the first intensity, wherein the first state is a state in which the cooling unit cools the light-emitting element at the second intensity under the control of the control unit, and the second state is a state in which the cooling unit cools the light-emitting element at the first intensity under the control of the control unit.

[0116] (4) The light irradiation device according to any one of (1) to (3) further comprises an illuminance measuring unit for measuring the illuminance of light irradiated from the light-emitting element, wherein in the second state, the rate of change of the illuminance of the light irradiated from the light-emitting element at the saturation temperature is defined as the saturation rate of change, and the control unit may irradiate light from the light-emitting element in the second state at a timing corresponding to the rate of change of the illuminance of the light measured by the illuminance measuring unit in the first state.

[0117] (5) In the light irradiation device described in any one of (1) to (3), the device further comprises a temperature measuring unit for measuring the temperature of the light-emitting element that is irradiated with light, and the control unit may irradiate the light-emitting element with light in the second state at a timing in which the temperature of the light-emitting element measured by the temperature measuring unit in the first state corresponds to the saturation temperature of the light-emitting element that is irradiated with light in the second state.

[0118] (6) In the light irradiation device described in any one of (1) to (3), the time it takes for the temperature of the light-emitting element in the first state to reach the saturation temperature of the light-emitting element irradiated with light in the second state is defined as the saturation time, and the control unit may cause the light-emitting element to irradiate light in the second state at a timing corresponding to the saturation time for the time the light-emitting element has been irradiated with light in the first state.

[0119] (7) In one embodiment, the printing apparatus comprises a light irradiation device according to any one of (1) to (6).

[0120] 1 Light irradiation device 2 Light-emitting element 42 Thermistor 44 Illuminance meter 900 Printing device 940 Control unit

Claims

1. A light irradiation device comprising a light-emitting element and a control unit for controlling the state of the light-emitting element, wherein a state in which the temperature of the light-emitting element rises is defined as a first state, and a state in which the temperature rise of the light-emitting element is suppressed more than that of the first state is defined as a second state, and the control unit starts irradiating light from the light-emitting element in the first state, and then irradiates light from the light-emitting element in the second state.

2. A light irradiation device according to claim 1, wherein the output when the light-emitting element irradiates light includes a first output and a second output which is lower than the first output, the first state is a state in which the light-emitting element irradiates light with the first output under the control of the control unit, and the second state is a state in which the light-emitting element irradiates light with the second output under the control of the control unit.

3. A light irradiation device according to claim 1 or 2, further comprising a cooling unit for cooling the light-emitting element, wherein the control unit controls the intensity in which the cooling unit cools the light-emitting element, and the intensity in which the cooling unit cools the light-emitting element includes a first intensity and a second intensity which is lower than the first intensity, the first state is a state in which the cooling unit cools the light-emitting element at the second intensity under the control of the control unit, and the second state is a state in which the cooling unit cools the light-emitting element at the first intensity under the control of the control unit.

4. A light irradiation device according to any one of claims 1 to 3, further comprising an illuminance measuring unit for measuring the illuminance of light emitted from the light-emitting element, wherein the rate of change of the illuminance of the light emitted from the light-emitting element in the second state at the saturation temperature is defined as the saturation rate of change, and the control unit causes the light-emitting element to emit light in the second state at a timing corresponding to the rate of change of the illuminance of the light measured by the illuminance measuring unit in the first state.

5. A light irradiation device according to any one of claims 1 to 3, further comprising a temperature measuring unit for measuring the temperature of the light-emitting element that is irradiated with light, wherein the control unit causes the light-emitting element to irradiate light in the second state at a timing in which the temperature of the light-emitting element measured by the temperature measuring unit in the first state corresponds to the saturation temperature of the light-emitting element that is irradiated with light in the second state.

6. A light irradiation device according to any one of claims 1 to 3, wherein the time it takes for the temperature of the light-emitting element in the first state to reach the saturation temperature of the light-emitting element irradiated with light in the second state is defined as the saturation time, and the control unit causes the light-emitting element to irradiate light in the second state at a timing corresponding to the saturation time, during which the time the light-emitting element has been irradiated with light in the first state.

7. A printing apparatus comprising a light irradiation device according to any one of claims 1 to 6.

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