Light-emitting component and optical writing device and image forming system using the same

Abstract

This invention suppresses differences in temperature distribution in the direction of arrangement of multiple light-emitting elements in a light source means, thereby reducing variations in light intensity distribution for each lighting condition. [Solution] The light-emitting component 1 comprises a substrate 2, an array-shaped light source means 3 provided on the substrate 2 in which a plurality of light-emitting elements 4 are arranged along the main scanning direction, a control means 8 provided on the substrate 2 for controlling the current to turn each light-emitting element 4 of the light source means 3 on or off, a resistor means 5 provided on the side of the end of the substrate 2 of the light source means 3 in the main scanning direction and limiting the current supplied to each light-emitting element 4, and a heat-generating means 6 provided on the substrate 2 at a position parallel to the main scanning direction of the light source means 3 and away from the resistor means 5, and generating a heat amount that is less than the heat generated by the power supplied to the resistor means 5 and proportional to the heat generated. Optical writing devices including the light-emitting component 1 and image forming systems including the optical writing device are also covered.

Description

Technical Field

[0001] The present invention relates to a light-emitting component, an optical writing device using the same, and an image forming system.

Background Art

[0002] As conventional light-emitting components and optical writing devices using the same, those described in Patent Documents 1 to 3 are already known, for example. Patent Document 1 discloses an image reading device that forms a heating element row composed of a resistor or the like near a white LED element row, and controls the heat generation amount of the heating element so that the temperature distribution of each white LED junction is controlled flat regardless of the lighting / non-lighting of the white LED when controlling the orientation distribution in the main scanning direction by the white LED element row, or controls the heat generation amount of the heating element so that the temperature distribution when only the LED element row is driven is maintained even when the LED element row is not being driven. Patent Document 2 discloses a light-emitting unit in which a reference voltage generation circuit having a diode and two load resistors and outputting a reference voltage by dividing a power supply voltage with the diode and the load resistors, and a drive IC for driving an LED element based on the reference voltage are mounted on a substrate. Patent Document 3 discloses a thermal equivalent circuit that simulates the temporal change in heat generation when a current is supplied to a laser diode, a first current source that generates a drive current to be supplied to the laser diode, and a second current source that generates a monitor current corresponding to the drive power and supplies it to the thermal equivalent circuit, and a semiconductor light-emitting element drive circuit in which the first current source is controlled to generate a drive current such that a change in the light emission amount due to heat generation is compensated based on the simulated heat generation value of the laser diode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] The technical problem that this invention aims to solve is to provide a light-emitting component that suppresses differences in temperature distribution in the arrangement direction of light-emitting elements in a light source means having multiple light-emitting elements arranged in a sequence, thereby reducing fluctuations in light intensity distribution for each lighting condition, as well as a light writing device and an image forming system using the same. [Means for solving the problem]

[0005] A first technical feature of the present invention is a light-emitting component comprising: a substrate; an array-shaped light source means provided on the substrate, wherein a plurality of light-emitting elements are arranged along the main scanning direction; a control means provided on the substrate for controlling the current to turn each light-emitting element of the light source means on or off; a resistor means provided on the substrate to the side of the end of the light source means in the main scanning direction, which limits the current supplied to each light-emitting element; and a heat-generating means provided on the substrate at a position parallel to the main scanning direction of the light source means and away from the resistor means, which generates a heat amount that is less than the heat generated by the power supplied to the resistor means and is proportional to the heat generated.

[0006] A second technical feature of the present invention is a light-emitting component having the first technical feature, wherein one heating means is provided. A third technical feature of the present invention is a light-emitting component having the second technical feature, wherein one of the heating means is arranged to correspond to a position including the center of the main scanning direction of the light source means. A fourth technical feature of the present invention is a light-emitting component having the first technical feature, characterized in that a plurality of heating means are provided. A fifth technical feature of the present invention is a light-emitting component having the fourth technical feature, wherein the plurality of heating means are arranged symmetrically with respect to the center of the main scanning direction of the light source means. A sixth technical feature of the present invention is a light-emitting component having the fourth technical feature, wherein at least one of the plurality of heating means is arranged to correspond to a region closer to the center in the main scanning direction of the light source means. The seventh technical feature of the present invention is a light-emitting component having the first technical feature, wherein the heating means also serves as a part of the resistive means, and is arranged in a position parallel to the main scanning direction of the light source means, rather than being located on the side of the end in the main scanning direction of the light source means. The eighth technical feature of the present invention is a light-emitting component having the seventh technical feature, wherein the resistive means is provided in a divided manner for each of the multiple sets, in accordance with the division of the light-emitting element array of the light source means into multiple sets, and the heating means is configured to utilize the resistive means of any of the sets. The ninth technical feature of the present invention is a light-emitting component having the first technical feature, wherein the heat-generating means generates an amount of heat that reduces the difference in the fluctuation of the temperature distribution, taking into account the temperature distribution of the light source means in the main scanning direction caused by the heat generated by the resistive means. The tenth technical feature of the present invention is a light-emitting component having the ninth technical feature, wherein a plurality of heating means are provided, and the heating means located closer to the center in the main scanning direction of the light source means distributes a larger amount of heat than the other heating means. An eleventh technical feature of the present invention is a light-emitting component having the first technical feature, wherein the heating means generates heat when the power input to the resistive means is above a predetermined threshold, and does not generate heat when it is below the threshold.

[0007] The twelfth technical feature of the present invention is an optical writing device that comprises a light-emitting component having any of the first to eleventh technical features, and an imaging means for imaging light emitted from each light-emitting element of the light-emitting component at a predetermined position, and is characterized by writing an image using light. The thirteenth technical feature of the present invention is an image forming system comprising: an optical writing device having the twelfth technical feature; and an image holding means provided opposite the optical writing device for holding an image written by light from the optical writing device. [Effects of the Invention]

[0008] According to the first technical feature of the present invention, it is possible to suppress the difference in temperature distribution in the direction of the arrangement of the light-emitting elements in a light source means having multiple light-emitting elements arranged in a row, and to reduce the variation in light intensity distribution for each lighting condition. According to a second technical feature of the present invention, it is possible to suppress the difference in temperature distribution in the main scanning direction of the light source means with a simple configuration. According to a third technical feature of the present invention, it is possible to concentrate heating on areas in the main scanning direction of the light source means that are less susceptible to the effects of heat generation by the resistive means. According to the fourth technical feature of the present invention, the difference in temperature distribution in the main scanning direction of the light source means can be suppressed more effectively than when there is only one heating means. According to the fifth technical feature of the present invention, temperature distribution fluctuations in the main scanning direction of the light source means can be corrected symmetrically with respect to the center. According to the sixth technical feature of the present invention, the light source means can be appropriately heated, including in areas that are less susceptible to the effects of heat generation by the resistive means in the main scanning direction. According to the seventh technical feature of the present invention, a heat-generating means can be constructed that utilizes some of the existing resistive means, without increasing the number of components, and with reduced power input to the heat-generating means. According to the eighth technical feature of the present invention, a heating means can be easily constructed by utilizing a part of an existing resistive means. According to the ninth technical feature of the present invention, the amount of heat from the heat generating means can be easily selected. According to the tenth technical feature of the present invention, the amount of heat from multiple heat-generating means can be easily selected to suppress differences in temperature distribution in the main scanning direction of the light source means. According to the 11th technical feature of the present invention, when the difference in temperature distribution in the main scanning direction of the light source means affects the light intensity distribution fluctuations depending on the lighting conditions of the light source means, the temperature distribution fluctuations can be suppressed. According to the twelfth technical feature of the present invention, it is possible to construct an optical writing device equipped with a light-emitting component that can suppress differences in temperature distribution in the arrangement direction of the light-emitting elements of a light source means having multiple light-emitting elements arranged in a row, and reduce fluctuations in light intensity distribution for each lighting condition. According to the thirteenth technical feature of the present invention, an image forming system can be constructed that includes an optical writing device equipped with a light-emitting component capable of suppressing differences in temperature distribution in the arrangement direction of the light-emitting elements of a light source means having multiple light-emitting elements arranged in a sequence, thereby reducing fluctuations in light intensity distribution for each lighting condition. [Brief explanation of the drawing]

[0009] [Figure 1] (a) is an explanatory diagram showing an overview of an embodiment of an image forming system to which the present invention is applied, (b) is an explanatory diagram showing an example of the configuration of each light-emitting element chip used in (a), and (c) is an explanatory diagram showing the operation of the light-emitting element chip. [Figure 2] This is an explanatory diagram showing the overall configuration of the image forming system according to Embodiment 1. [Figure 3] This is an explanatory diagram showing an example of an optical writing device used in the image forming system according to Embodiment 1. [Figure 4] (a) is a perspective view illustrating an example configuration of the optical writing device shown in Figure 3, and (b) is an explanatory diagram showing the light-emitting element chip array used in the optical writing device. [Figure 5] (a) is an explanatory diagram showing an example of the configuration of a light-emitting element chip used in the light-emitting element chip array according to Embodiment 1, and (b) is an explanatory diagram showing the temperature characteristics of the light-emitting element chip shown in (a). [Figure 6]It is an explanatory diagram showing a circuit configuration example of a light-emitting element chip according to Embodiment 1. [Figure 7] It is an explanatory diagram showing operation signals of each part of a light-emitting element chip according to Embodiment 1. [Figure 8] (a) is an explanatory diagram showing a configuration example of a light-emitting element chip according to Comparative Form 1, and (b) is an explanatory diagram showing the temperature characteristics of the light-emitting element chip shown in (a). [Figure 9] (a) is an explanatory diagram showing a configuration example of a light-emitting element chip according to Embodiment 2, and (b) is an explanatory diagram showing the temperature characteristics of the light-emitting element chip shown in (a). [Figure 10] It is an explanatory diagram showing a circuit configuration example of a light-emitting element chip according to Embodiment 2. [Figure 11] It is an explanatory diagram showing a configuration example of a light-emitting element chip according to Embodiment 3. [Figure 12] It is an explanatory diagram showing a circuit configuration example of a light-emitting element chip according to Embodiment 3. [Figure 13] It is an explanatory diagram in which a part of FIG. 12 is enlarged. [Figure 14] (a) is an explanatory diagram showing a configuration example of a light-emitting element chip according to Embodiment 4, and (b) is an explanatory diagram showing the temperature characteristics of the light-emitting element chip shown in (a). [Figure 15] It is an explanatory diagram showing a circuit configuration example of a light-emitting element chip according to Embodiment 4. [Figure 16] It is an explanatory diagram showing a specific example of a circuit configuration example of a light-emitting element chip according to Embodiment 4. [Figure 17] (a) is an explanatory diagram showing a configuration example of a light-emitting element chip according to Embodiment 5, and (b) is an explanatory diagram showing the temperature characteristics of the light-emitting element chip shown in (a). [Figure 18] (a) is a graph showing the change in light amount for each lighting rate of a light-emitting element chip according to Comparative Example 1, and (b) is a graph showing the change in temperature for each lighting rate of the light-emitting element chip according to Comparative Example 1. <00001​​​​​​​​Figure 1(a) shows an overview of an embodiment of an image forming system to which the present invention is applied. In the figure, the image forming system 10 comprises an optical writing device 11 and an image holding means 12 provided opposite the optical writing device 11 and holding the image written by the optical writing device 11. Here, the optical writing device 11 comprises a light-emitting component 1 and an imaging means 9 that focuses the light emitted from each light-emitting element chip U of the light-emitting component 1 onto an image holding means 12 capable of holding an image using light, and writes an image using light to the image holding means 12. The image holding means 12 referred to here is not limited to a photoreceptor, but also includes dielectrics, and its form can be appropriately selected, such as a drum shape or a belt shape. Furthermore, an image formed by light can be, for example, an electrostatic latent image formed by a potential difference created when the material is charged to a predetermined level and then discharged with light corresponding to the image pattern. Furthermore, the imaging means 9 can be any lens that refracts light on its surface (e.g., a cylindrical lens) or any lens that refracts light internally (e.g., a refractive index distribution lens), as long as it is used to image the light emitted from each light-emitting element chip U of the light-emitting component 1 onto the image holding means 12.

[0011] Furthermore, as shown in Figure 1(b), the light-emitting element chip U comprises a substrate 2, an array-shaped light source means 3 provided on the substrate 2 in which a plurality of light-emitting elements 4 are arranged along the main scanning direction, a control means 8 provided on the substrate 2 for controlling the current to turn each light-emitting element 4 of the light source means 3 on or off, a resistor means 5 provided on the side of the end of the substrate 2 of the light source means 3 in the main scanning direction and limiting the current supplied to each light-emitting element 4, and a heat-generating means 6 provided on the substrate 2 at a position parallel to the main scanning direction of the light source means 3 and away from the resistor means 5, and generating a heat amount that is less than the heat generated by the power supplied to the resistor means 5 and proportional to the heat generated. In Figure 1(b), m indicates the main scanning direction. Reference numeral 7 denotes an electrode pad that supplies predetermined power to the control means 8 and the resistor means 5, etc., by connecting to a power supply means (not shown) provided by the light-emitting component 1.

[0012] In such technical means, the array-like light source means 3 can be appropriately selected as long as it consists of multiple light-emitting elements 4 arranged along the main scanning direction. Here, the light-emitting elements 4 are preferably light-emitting thyristors whose light intensity can be changed, but are not limited to these, and include light-emitting diodes and the like. Furthermore, the control means 8 may be configured to include, for example, a circuit for turning on the light-emitting element 4 and a circuit for turning it off. Furthermore, the resistor 5 is often located to the side of the end of the array-shaped light source 3 in the main scanning direction. This is because it reduces the amount of wiring required and makes it easier to secure space for installing the resistor 5. Furthermore, in the example shown in Figure 1(b), resistors 5 (specifically 5a and 5b) are provided on both sides of the main scanning direction of the array-shaped light source means 3. This is intended to reduce the voltage drop due to the resistance of the wiring to each light-emitting element 4 compared to supplying power from both sides of the main scanning direction of the light source means 3, thereby making the light intensity of each light-emitting element 4 uniform.

[0013] Furthermore, the heating element 6 is not limited to one; multiple elements may be provided. Furthermore, the heat generating means 6 only needs to generate an amount of heat that is less than the amount of heat generated by the power supplied to the resistor means 5 and is proportional to the amount of heat generated by the resistor means 5. The reason for setting an upper limit on the amount of heat generated by the heat generating means 6 is to eliminate concerns about increasing the difference in temperature distribution in the direction of the arrangement of the light-emitting elements 4 of the light source means 3. Also, the amount of heat generated by the heat generating means 6 should be selected from among the amounts of heat that are proportional to the amount of heat generated by the resistor means 5. Specifically, it is preferable to select the amount of heat generated by the heat generating means 6 from the viewpoint of suppressing the difference in temperature distribution in the direction of the arrangement of the rows of light-emitting elements 4 of the light source means 3. In particular, in an embodiment equipped with multiple heating means 6, it is preferable that the heating means 6 located closer to the center Oc in the main scanning direction of the light source means 3 be allocated a larger amount of heat than the other heating means. Furthermore, it is preferable to exclude the end region of the light source 3 in the main scanning direction from the installation location of the heating means 6. This is because if the heating means 6 is installed in a location corresponding to the end region of the light source 3 in the main scanning direction, the following problems will occur. In other words, there is a concern that the end region of the light source 3 will be increasingly heated and its temperature will rise, further widening the temperature difference in the temperature distribution of the light source 3.

[0014] A light-emitting element chip U having the above-described configuration requirements operates as follows: In other words, as shown in Figure 1(c), the heat generated by the resistors 5 (5a, 5b) causes a temperature change along the main scanning direction of the light source 3 within the light-emitting element chip U. The light intensity of the light-emitting element 4 decreases as the temperature increases. Also, the amount of heat generated by the resistors 5 changes depending on the ignition rate, so the temperature distribution and light intensity distribution change. If the heat-generating means 6 is not provided, the temperature distribution of the 4 rows of light-emitting elements in the light source 3 changes as shown by the dotted line in Figure 1(c). The temperature distribution shown by the dotted line in Figure 1(c) is lowest in the center of the main scanning direction and higher on both sides of the main scanning direction, forming a quadratic curve with a temperature difference ΔT'. However, in this embodiment, a heating means 6 is provided parallel to the main scanning direction of the light source means 3. The amount of heat generated from the heating means 6 heats the areas of the light-emitting element 4 rows of the light source means 3, excluding the ends.

[0015] For example, let's assume that one heating means 6 is provided and is positioned corresponding to a location including the center Oc in the main scanning direction of the light source means 3. In this case, the temperature distribution of the four light-emitting elements of the light source means 3 will show a temperature increase near the center Oc in the main scanning direction of the light source means 3, as shown by the solid line in Figure 1(c). Therefore, the temperature distribution shown by the solid line in Figure 1(c) will change to a state in which the temperature difference ΔT1 (ΔT1 < ΔT') is reduced compared to the case where the heating means 6 is not provided. Furthermore, let's assume that multiple heating means 6 (for example, 6a, 6b) are provided and are arranged symmetrically with respect to the center Oc in the main scanning direction of the light source means 3. In this case, the temperature distribution of the four light-emitting elements of the light source means 3 will show a temperature increase near the locations where the heating means 6 (6a, 6b) are located, as shown by the dashed line in Figure 1(c). Therefore, the temperature distribution shown by the dashed line in Figure 1(c) will change to a state in which the temperature difference ΔT2 (ΔT2 < ΔT') is reduced compared to the case where the heating means 6 are not provided. Thus, the temperature distribution of the four light-emitting elements of the light source means 3 undergoes a shape change in which the temperature difference is mitigated as the temperature rises in areas other than the edges. For this reason, the shape change of the temperature distribution of the light source means 3 is corrected to have a smaller temperature difference for each lighting condition (lighting rate, brightness) of the light source means 3.

[0016] Furthermore, in this embodiment, the resistive means 5 and the heating means 6 are provided separately, but this is not the only possible configuration. For example, the heating means 6 may also serve as part of the resistive means 5, and may be positioned differently from the position on the side of the end of the light source means 3 in the main scanning direction to a position parallel to the main scanning direction of the light source means 3. Furthermore, the resistive means 5 may be divided and provided in groups corresponding to the division of the rows of light-emitting elements 4 of the light source means 3 into multiple groups. In this case, the heating means 6 may be configured using any of the resistive means 5 in any of the groups.

[0017] Furthermore, in this example, the heating means 6 is configured to always generate heat in accordance with the power supplied to the resistive means 5. However, when the power supplied to the resistive means 5 is low, the difference in temperature distribution fluctuations in the direction of the arrangement of the light-emitting elements 4 of the light source means 3 is smaller compared to when the power supplied to the resistive means 5 is high. Here, the power supplied to the resistive means 5 increases or decreases depending, for example, on the illumination rate of each light-emitting element 4 in the light source means 3. Therefore, when the illumination rate of each light-emitting element 4 is low, the power supplied to the resistive means 5 decreases. Conversely, when the illumination rate of each light-emitting element 4 is high, the power supplied to the resistive means 5 increases. Therefore, the heat-generating means 6 can be configured to generate heat when the power supplied to the resistive means 5 exceeds a predetermined threshold, and not generate heat when it falls below the threshold.

[0018] The present invention will be described in more detail below based on the embodiments shown in the attached drawings. ◎Embodiment 1 -Overall configuration of the image forming system- Figure 2 shows the overall configuration of the image forming system according to Embodiment 1. In the figure, the image forming system 20 is a tandem-type image forming system. This image forming system 20 comprises an image forming process unit 21, an image output control unit 40, and an image processing unit 50. Here, the image forming process unit 21 is a functional unit that performs image forming corresponding to image data of each color. The image output control unit 40 is a functional unit that controls the image forming process unit 21. Furthermore, the image processing unit 50 is connected to, for example, a personal computer (PC) 61 or an image reading device 62, and performs predetermined image processing on the image data received from these devices.

[0019] The image forming process unit 21 includes image forming units 22 arranged in parallel at regular intervals. These image forming units 22 consist of four image forming engines 23 (23a to 23d), which are an example of toner image forming means. The toner image forming means here refers to a functional unit that forms toner images of four colors (in this example, yellow (Y), magenta (M), cyan (C), and black (K)). Each image forming engine 23 (23a to 23d) is equipped with an image holding means that forms an electrostatic latent image and holds the toner image. In this example, a drum-shaped photoreceptor 24 is used as an example of the image holding means. A charger 25, an optical writing device 26, and a developer 27 are provided around the photoreceptor 24. The charger 25 uniformly charges the surface of the photoreceptor 24 at a predetermined potential. The optical writing device 26 exposes the photoreceptor 24 charged by the charger 25 to form an electrostatic latent image. The developing unit 27 develops the electrostatic latent image formed by the optical writing device 26.

[0020] Then, the image-forming engines 23 (23a to 23d) each form toner images of yellow (Y), magenta (M), cyan (C), and black (K). Furthermore, the image forming process unit 21 transfers the toner images of each color formed on the photoreceptor 24 of each image forming engine 23 (23a to 23d) onto recording paper 29, which is an example of a recording medium, and fixes them. In this example, the image forming process unit 21 is equipped with a paper transport belt 30, a transfer unit 31, and a fuser unit 32. Here, the paper transport belt 30 transports the recording paper 29. The transfer unit 31 transfers the toner image of the photoreceptor 24 onto the recording paper 29, and in this example, a transfer roll is used. The fuser unit 32 fixes the toner image transferred onto the recording paper 29.

[0021] In this image forming system 20, the image forming process unit 21 performs image forming operations based on various control signals supplied from the image output control unit 40. When image data is received from the personal computer (PC) 61 or image reading device 62, it is processed as follows: The image data is processed by the image processing unit 50 under the control of the image output control unit 40 and then supplied to the image forming engine 23. Then, for example, in the black (K) image engine 23d, the photoreceptor 24 rotates in the direction of the arrow and is charged to a predetermined potential by the charger 25. After that, the photoreceptor 24 is exposed by the light writing device 26, which emits light based on the image data supplied from the image processing unit 50. As a result, an electrostatic latent image relating to the black (K) image is formed on the photoreceptor 24. The electrostatic latent image formed on the photoreceptor 24 is then developed by the developer 27, and a black (K) toner image is formed on the photoreceptor 24. Similarly, in each image engine 23 (23a to 23c), yellow (Y), magenta (M), and cyan (C) toner images are formed, respectively.

[0022] The toner images of each color formed on the photoreceptor 24 by each image engine 23 (23a to 23d) are transferred in multiple layers onto the recording paper 29. In this example, the recording paper 29 is supplied as the paper transport belt 30 moves in the direction of the arrow. The toner images of each color are then sequentially transferred to the recording paper 29 by electrostatic transfer using a transfer electric field applied to the transfer unit 31 (transfer roll). As a result, a composite toner image is formed on the recording paper 29 in which the toners of each color are superimposed. Subsequently, the recording paper 29 on which the composite toner image has been electrostatically transferred is transported to the fuser 32. There, the composite toner image on the recording paper 29 is fixed by heat and pressure treatment in the fuser 32 and then discharged from the image forming system 20.

[0023] -Example configuration of an optical writing device- Figure 3 shows an example configuration of an optical writing device 26 to which this embodiment is applied, and Figure 4(a) shows a perspective view thereof. In the figure, the optical writing device 26 comprises a device housing 71, a light-emitting element chip array 72, and an imaging lens 73 as an example of an imaging means. Here, the light-emitting element chip array 72 is held in the device housing 71 and is equipped with multiple LEDs as light-emitting elements. The imaging lens 73 is also held in the device housing 71 and forms an image of the light output emitted from the light-emitting elements of the light-emitting element chip array 72, exposing the photoreceptor 24 to form an electrostatic latent image. In this example, the device housing 71 is made of, for example, metal, and holds the light-emitting element chip array 72 and the imaging lens 73. The device housing 71 is configured to align the light-emitting point of the light-emitting element 86 (see Figure 6) of the light-emitting element chip array 72 with the focal plane of the imaging lens 73. The imaging lens 73 is also positioned along the axial direction of the photoreceptor 24 (corresponding to the main scanning direction). Furthermore, the light-emitting element chip array 72 is connected to a control board 75, which is equipped with a signal generation circuit (not shown), via a flexible substrate 74.

[0024] -Example configuration of a light-emitting element chip array- Figure 4(b) shows an example of the configuration of the light-emitting element chip array 72. In the figure, the light-emitting element chip array 72 consists of multiple light-emitting element chips U (U1 to Un) arranged in a staggered pattern on the circuit board 90, facing each other in two rows in the main scanning direction. Within each light-emitting element chip U (U1 to Un), light-emitting elements are arranged in a line in the main scanning direction. Furthermore, various control signals from the signal generation circuit 110 (see Figure 6) mounted on the control board 75 are used to control the lighting and extinguishing of each light-emitting element 86 of the multiple light-emitting element chips U. In this way, the light emission of each light-emitting element 86 is individually controlled by the signal generation circuit 110. In this example, the light-emitting element chips U are arranged in a staggered pattern for the following reason: If multiple light-emitting element chips U were arranged in one direction, it would be impossible to maintain a consistent spacing between the light-emitting elements at the ends of the chips U.

[0025] -Example configuration of a light-emitting element chip- In this example, the light-emitting element chip U has a rectangular substrate 2 with a long surface shape, as shown in Figure 5(a). On the surface of this substrate 2, there is an array of light-emitting points 81, which serves as an array-type light source means, in which multiple light-emitting elements are arranged in a row along one of the long sides. In this example, the light-emitting point array 81 is configured so that the LEDs, as light-emitting elements, are light-emitting points (regions that emit light in a point-like manner). In this example, the direction in which the light-emitting elements are arranged is treated as the main scanning direction, and the direction perpendicular to and intersecting this main scanning direction is treated as the sub-scanning direction. Furthermore, a light-emitting point control unit 82 is provided on the surface of the substrate 2 as a control means for sequentially controlling the lighting and extinguishing of each light-emitting element of the light-emitting point array 81. Furthermore, electrode pads 7 (specifically 7a and 7b) are provided at both ends of the long side of the surface of the substrate 2 as means of power supply. These electrode pads 7 receive various control signals from the signal generation circuit 110 mounted on the control board 75. In this example, the electrode pads 7 are connected to supply power to each light-emitting element of the light-emitting element array 81 from both sides of the pair of pads, and control signals are input to the light-emitting element control unit 82.

[0026] In this example, current limiting resistors 84 are provided on both sides of the main scanning direction end of the light-emitting point array 81 on the surface of the substrate 2. More specifically, the current limiting resistors 84 (specifically 84a and 84b) are installed in the region between the light-emitting point array 81 and the electrode pads 7. The installation space for these current limiting resistors 84 was selected considering that the region between the light-emitting point array 81 and the electrode pads 7 is an area with minimal wiring. In this example, the current limiting resistors 84 limit the current supplied to each light-emitting element of the light-emitting point array 81.

[0027] Furthermore, in this example, a heat source 85 is provided on the surface of the substrate 2 at a position parallel to the main scanning direction of the light-emitting point array 81. A resistive element is used as the heat source 85 and is installed at a position away from the current limiting resistors 84 (84a, 84b). In this example, the heat source 85 is positioned corresponding to a position including the center Oc in the main scanning direction of the light-emitting point array 81. Furthermore, the heat source 85 is selected to generate an amount of heat that is less than the amount of heat generated by the power supplied to the current limiting resistor 84, but proportional to the amount of heat generated by the current limiting resistor 84. The amount of heat generated by the heat source 85 is appropriately selected within a range of, for example, 0.3 to 0.9 times (for example, 0.8 times) the amount of heat generated by the power supplied to the current limiting resistor 84.

[0028] -Each element of the light-emitting element chip- <Electrode Pads> In this example, as shown in Figure 6, the electrode pad 7 is equipped with terminals corresponding to the Clk terminal, IN terminal, WR terminal, and VL terminal of the signal generation circuit 110. Here, the Clk terminal is a terminal that inputs a clock signal, which is the reference operating timing, to the light emission point control unit 82. The IN terminal is a terminal that inputs a start signal of the image signal sequence associated with the switching of the sub-scanning direction to the light emission point control unit 82. The WR terminal is a terminal that inputs an image signal (H or L) indicating whether or not the light is lit to the light emission point control unit 82. The VL terminal is a terminal that supplies a reference potential to the light emission point array 81.

[0029] <Light source array> In this example, the light-emitting point array 81 is formed by arranging light-emitting elements 86, which are LEDs, in a row along the main scanning direction, as shown in Figure 6. In Figure 6, each light-emitting element 86 is labeled L1, L2, L3, and so on. In this example, the anode (positive electrode) of each light-emitting element 86 is connected to a reference potential line (VL=6V) from the VL terminal. In the light-emitting point array 81, "row-like" typically refers to a configuration in which multiple light-emitting elements 86 are arranged in a straight line, as shown in Figure 6. However, in this example, "row-like" is not limited to a straight line arrangement and includes configurations that approximate it. For example, each of the multiple light-emitting elements 86 may be arranged with different amounts of offset from each other in a direction perpendicular to the row direction. Alternatively, for example, if the light-emitting surface of the light-emitting element 86 is considered a pixel, each light-emitting element 86 may be arranged with an amount of offset of several pixels or tens of pixels in a direction perpendicular to the row direction. Furthermore, they may be arranged alternately between adjacent light-emitting elements 86, or in a zigzag pattern between every group of light-emitting elements 86.

[0030] <Light source control unit> In this example, the light emission control unit 82 includes a plurality of flip-flops 87, a plurality of AND gates 88, and a plurality of buffer circuits 89, as shown in Figure 6. In this example, the flip-flops 87 are arranged in multiple stages corresponding to the number of light-emitting elements 86 in the light-emitting element array 81. The flip-flops 87 have a clock input terminal (clk), an input terminal (in), and an output terminal (out). The buffer circuit 89 is made up of, for example, a transistor. In this example, the flip-flops 87, AND gate 88, and buffer circuit 89 constitute a so-called shift register circuit. In this example, the clock signal from the Clk terminal of the electrode pad 7 is input to the clock input terminal (clk) of each flip-flop 87. Additionally, the start signal for the sub-scanning image signal sequence from the IN terminal of the electrode pad 7 is input to the input terminal (in) of the first flip-flop 87. Furthermore, the output terminal (out) of the preceding flip-flop 87 is connected to the input terminal (in) of the subsequent flip-flop 87.

[0031] Furthermore, a serial image signal (H=3.3V or L=0) from the WR terminal of electrode pad 7 is input to one input terminal of ANDGATE 88. In addition, the output signals G (G1, G2, G3...) from the output terminals (out) of each flip-flop 87 are input to the other input terminal of ANDGATE 88. Then, the output from the AND gate 88 is input to the buffer circuit 89, and the output terminal of the buffer circuit 89 is connected to the cathode of each light-emitting element 86.

[0032] <Current Limiting Resistor> In this example, the current limiting resistor 84 is connected in series with the cathode of each light-emitting element 86 via the reference potential line 101 from the VL terminal of the electrode pad 7. Note that in Figure 6, the current limiting resistors 84 (84a, 84b) are denoted as RL. <Heat source> The heat source 85 is connected to the center of the second reference potential line 102, which is arranged in parallel with the reference potential line 101 from the VL terminal of the electrode pad 7. In this example, current is supplied to the reference potential line 101 and the second reference potential line 102 at the timing when each light-emitting element 86 emits light. In Figure 6, the heat source 85 is represented by its resistance Rha.

[0033] - Operation of the light-emitting element chip - Figure 7 shows the operating signals of each part of the light-emitting element chip according to Embodiment 1. In the figure, each flip-flop 87 of the light-emitting point control unit 82 receives a clock signal from the electrode pad 7. Furthermore, the input terminal (in) of the first-stage flip-flop 87 of the light-emitting point control unit 82 receives the start signal of the image signal sequence associated with the switching of the sub-scan direction. As a result, the output signals G1, G2, G3... of each flip-flop 87 are shifted and output according to the clock signal. Meanwhile, an image signal is input serially from the WR terminal of the electrode pad 7 to the light emission control unit 82.

[0034] When an H-level input signal (G+WR) is input to both input terminals of each AND gate 88, each light-emitting element 86 operates as follows: That is, each light-emitting element 86 lights up sequentially from the first stage according to the image signal, as shown in L1, L2, L3... in Figure 7. In other words, each light-emitting element 86 lights up according to the illumination rate of a predetermined image signal sequence. If the image signal sequence has an illumination rate of, for example, 100%, the light-emitting point array 81 lights up all the light-emitting elements 86 sequentially. If the image signal sequence has an illumination rate of 25%, the light-emitting point array 81 lights up a portion of all the light-emitting elements 86 according to the illumination rate. In this state, current flows through the reference potential line from the VL terminal each time one of the light-emitting elements 86 in the light-emitting point array 81 lights up. As a result, the current-limiting resistor 84 (labeled RL in Figures 6 and 7) is energized according to the illumination rate of each light-emitting element 86, and the current-limiting resistor 84 generates heat accordingly. On the other hand, the heat source 85 (labeled as resistance Rha in Figures 6 and 7) is connected to a second reference potential line 102, which is arranged in parallel with the reference potential line 101 from the VL terminal. Therefore, the heat source 85 always generates heat equal to the power inversely proportional to the resistance value of the heat source.

[0035] In this example, one heat source 85 is provided and positioned to correspond to a location including the center Oc in the main scanning direction of the light-emitting point array 81. In this case, the temperature distribution of the light-emitting elements 86 in the arrangement direction of the light-emitting point array 81 changes as shown in Figure 5(b). In the temperature distribution shown in Figure 5(b), the temperature rises near the center of the light-emitting point array 81 in the main scanning direction due to the heat generated from the heat source 85. In this state, the ends of the light-emitting point array 81 in the main scanning direction are also heated by the heat generated from the current limiting resistor 84. Therefore, the light-emitting point array 81 experiences a temperature rise not only at the ends but also near the center in the main scanning direction. As a result, it is presumed that the temperature distribution along the main scanning direction of the light-emitting point array 81 will have a reduced temperature difference compared to when the heat source 85 is not provided.

[0036] Here, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting point array 81 is 100%. The temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting point array 81 changes as shown by the solid line in Figure 5(b). The temperature distribution shown by the solid line in Figure 5(b) changes to a state where the temperature difference is reduced by ΔT100. Furthermore, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting point array 81 is 25%. The temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting point array 81 changes as shown by the dotted line in Figure 5(b). The temperature distribution shown by the dotted line in Figure 5(b) changes to a state where the temperature difference is reduced by ΔT25. In this example, the relationship ΔT100 > ΔT25 is satisfied.

[0037] ◎Comparison Form 1 Next, in order to evaluate the performance of the light-emitting element chip U according to Embodiment 1, we will explain using the light-emitting element chip U' according to Comparative Embodiment 1 as an example. As shown in Figure 8(a), the light-emitting element chip U' in comparative embodiment 1 comprises a substrate 2, a light-emitting point array 81, a light-emitting point control unit 82, electrode pads 7, and a current-limiting resistor 84. However, unlike embodiment 1, the light-emitting element chip U' does not include a heat source 85. Therefore, according to the light-emitting element chip U' of comparative form 1, the temperature distribution in the array direction of the light-emitting element 86 of the light-emitting point array 81 changes as shown in Figure 8(b). The temperature distribution shown in Figure 8(b) is a quadratic curve, with the lowest temperature in the center of the main scanning direction and higher temperatures on both sides of the main scanning direction.

[0038] Here, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting point array 81 is 100%. The temperature distribution of the light-emitting element 86 of the light-emitting point array 81 changes as shown by the solid line in Figure 8(b). The temperature distribution shown by the solid line in Figure 8(b) has a larger temperature difference ΔT100 between the center and both ends in the main scanning direction than in Embodiment 1. Furthermore, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting point array 81 is 25%. The temperature distribution of the light-emitting elements 86 of the light-emitting point array 81 changes as shown by the dotted line in Figure 8(b). The temperature distribution shown by the dotted line in Figure 8(b) has a larger temperature difference ΔT25 between the center and both ends in the main scanning direction than in Embodiment 1. In this example, the relationship ΔT100 > ΔT25 is satisfied. Thus, the light-emitting element chip U according to Embodiment 1 can be said to have superior performance compared to the light-emitting element chip U' according to Comparative Embodiment 1. In other words, the light-emitting element chip U according to Embodiment 1 can make the temperature distribution in the arrangement direction of the light-emitting elements 86 of the light-emitting point array 81 closer to uniform.

[0039] ◎Transformation form 1 In Embodiment 1, the heat source 85 is configured to always generate heat in accordance with the power supplied to the current limiting resistor 84. However, when the power supplied to the current limiting resistor 84 is low, the temperature difference in the temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting point array 81 is smaller compared to when the power supplied to the current limiting resistor 84 is high. Here, the power supplied to the current limiting resistor 84 increases or decreases depending on, for example, the illumination rate of each light-emitting element 86 in the light-emitting point array 81. Therefore, when the illumination rate of each light-emitting element 86 is low, the power supplied to the current limiting resistor 84 decreases. Conversely, when the illumination rate of each light-emitting element 86 is high, the power supplied to the current limiting resistor 84 increases. Therefore, if there is a requirement to minimize the heat generation of the heat source 85, the heat generation of the heat source 85 may be controlled according to the power supplied to the current limiting resistor 84. In this case, a switching element can be connected in series with the heat source 85, and the power supply to the heat source 85 can be controlled by switching the switching element. The heat source 85 should be configured to generate heat when the power supplied to the current limiting resistor 84 is above a predetermined threshold, and not generate heat when it is below the threshold. It goes without saying that this modified form 1 may also be similarly modified in the embodiments 2 to 5 shown below.

[0040] ◎Embodiment 2 Figure 9(a) shows an example of the configuration of a light-emitting element chip according to Embodiment 2. In this figure, the basic configuration of the light-emitting element chip U is substantially the same as in Embodiment 1, but the installation state of the heat source 85 differs from that of Embodiment 1. Components similar to those in Embodiment 1 are denoted by the same reference numerals as in Embodiment 1, and their detailed descriptions are omitted here. In this example, the heat source 85 is provided on the substrate 2 at a position parallel to the main scanning direction of the light-emitting point array 81, similar to the first embodiment. However, in this example, the heat source 85 is composed of multiple (three in this example) resistive elements. The first heat source 85a(85) is positioned within the central Oc of the main scanning direction of the light-emitting point array 81. The second heat source 85b and the third heat source 85c are positioned symmetrically with respect to the central Oc of the main scanning direction of the light-emitting point array 81. In this example, the second heat source 85b and the third heat source 85c are positioned near the ends of the main scanning direction of the light-emitting point array 81. For example, they can be appropriately selected within the range of 2 / 3 to 3 / 4 of the region from the center to the ends of the light-emitting point array 81 when viewed from the center.

[0041] Furthermore, in this example, the amount of heat generated from the first heat source 85a to the third heat source 85c is selected as follows. The amount of heat generated by the first heat source 85a is appropriately selected within a range of, for example, 0.4 to 0.6 times (0.5 times in this example) the amount of heat generated, which depends on the power supplied to the current limiting resistor 84. The amount of heat generated by the second heat source 85b is appropriately selected within a range of, for example, 0.3 to 0.5 times (0.4 times in this example) the amount of heat generated, which depends on the power supplied to the current limiting resistor 84. The heat output of the third heat source 85c is selected in the same way as that of the second heat source 85b. In particular, in this example, the amount of heat generated from the first heat source 85a is allocated more than that from the second heat source 85b and the third heat source 85c. Such a distribution of heat is effective in suppressing differences in temperature distribution fluctuations in the main scanning direction of the light-emitting point array 81. It is also possible to distribute the heat from all heat sources 85a to 85c to approximately equal amounts, or to allocate more heat from the second heat source 85b and the third heat source 85c than from the first heat source 85a. However, in these cases, it is necessary to note that the temperature distribution at the ends of the light-emitting point array 81 in the main scanning direction tends to rise excessively.

[0042] Figure 10 also shows an example of the circuit configuration of the light-emitting element chip used in Embodiment 2. In the figure, the circuit configuration of the light-emitting element chip U is substantially the same as that of Embodiment 1, except for the heat source 85 (85a to 85c). In this example, the heat sources 85 (85a to 85c) are connected to a second reference potential line 102, which is arranged in parallel with the reference potential line 101 from the VL terminal of the electrode pad 7. The first heat source 85a is connected near the center of the second reference potential line 102. The second heat source 82b and the third heat source 85c are connected at symmetrical positions with respect to the center of the second reference potential line 102. In this example as well, current is supplied to the reference potential line 101 and the second reference potential line 102 at the timing when each light-emitting element 86 emits light.

[0043] - Operation of the light-emitting element chip - The basic operation of the light-emitting element chip U is substantially the same as in Embodiment 1. Then, current flows through the reference potential line 101 from the VL terminal each time one of the light-emitting elements 86 in the light-emitting point array 81 lights up. As a result, the current-limiting resistor 84 (labeled RL in Figure 10) is energized according to the illumination rate of each light-emitting element 86, and the current-limiting resistor 84 generates heat accordingly. On the other hand, the heat sources 85 (85a to 85c: indicated as resistances Rha to Rhc in Figure 10) are connected to a second reference potential line 102, which is arranged in parallel with the reference potential line 101 from the VL terminal. Therefore, the heat sources 85 (85a to 85c) generate heat in proportion to the power of each heat source.

[0044] In this example, multiple (specifically three) heat sources 85 are provided and are arranged to correspond to positions near the center Oc in the main scanning direction of the light-emitting point array 81 and symmetrically with respect to the center. Here, the amount of heat generated from the first heat source 85a (Rha) is selected to be slightly more than the amount of heat generated from the second heat source 85b (Rhb) and the third heat source 85c (Rhc). If the amount of heat generated by the current limiting resistor 84 is 1, then the amount of heat from the first heat source 85a is, for example, 0.5, and from the second heat source 85b and the third heat source 85c is, for example, 0.4. In this case, the temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting element array 81 changes as shown in Figure 9(b). The temperature distribution shown in Figure 9(b) shows that the temperature rises near the center Oc and near the edges of the light-emitting element array 81 in the main scanning direction due to the heat generated from the three heat sources 85. In particular, in this example, the heat output of the second heat source 85b and the third heat source 85c is selected to be less than that of the first heat source 85a. Therefore, there is no concern that the temperature near the edges of the light-emitting element array 81 in the main scanning direction will rise excessively.

[0045] Here, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting element array 81 is 100%. The temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting element array 81 changes as shown by the solid line in Figure 9(b). The temperature distribution shown by the solid line in Figure 9(b) changes to a state where the temperature difference is reduced by ΔT100. Furthermore, we assume that the illumination rate of the light-emitting element 86 rows of the light-emitting point array 81 is 25%. The temperature distribution in the direction of the arrangement of the light-emitting elements 86 of the light-emitting point array 81 changes as shown by the dotted line in Figure 9(b). The temperature distribution shown by the dotted line in Figure 9(b) changes to a state where the temperature difference is reduced by ΔT25. In this example, the relationship ΔT100 > ΔT25 is satisfied. Here, when comparing the temperature differences ΔT100 and ΔT25 between Embodiment 2 and Embodiment 1, both were found to be significantly smaller in Embodiment 2.

[0046] ◎Embodiment 3 Figure 11 is an explanatory diagram showing an example of the configuration of a light-emitting element chip according to Embodiment 3. In the figure, the basic configuration of the light-emitting element chip U is substantially the same as that of Embodiment 1. Specifically, it comprises a substrate 2, a light-emitting point array 81, a light-emitting point control unit 82, an electrode pad 7, a current-limiting resistor 84, and a heat source 85. In this example, the light-emitting point array 81 is formed by arranging light-emitting elements 96 in a row along the long side of the substrate 2, different from those in Embodiments 1 and 2. In this example as well, the direction in which the light-emitting elements 96 are arranged is treated as the main scanning direction. Furthermore, the light-emitting point control unit 82 includes an on / off circuit 97 that controls the on / off of each light-emitting element 96. In this example, the light-emitting point control unit 82 controls the lighting and extinguishing of odd-numbered rows of light-emitting elements 96 and even-numbered rows of light-emitting elements 96 in parallel.

[0047] Furthermore, the electrode pad 7 inputs various control signals to the light-emitting point array 81 and the light-emitting point control unit 82. In this example as well, a pair of electrode pads 7 are provided at both ends of the substrate 2 in the main scanning direction. Here, the pair of electrode pads 7, as in Embodiment 1, divide the on / off circuits 97 of each light-emitting element 96 of the light-emitting element array 81 and the light-emitting element control unit 82, and input control signals to them. In other words, in this example, the light-emitting element chip U is configured as two chip divisions CL and CR (see Figure 12) that are divided left and right with the center of the main scanning direction of the substrate 2 in between. Furthermore, a pair of current limiting resistors 84 are provided on both sides of the main scanning direction of the light-emitting point array 81. In this example, each light-emitting element 96 is configured so that odd-numbered and even-numbered rows are processed in parallel. For this reason, two current limiting resistors 84a are provided, corresponding to the odd-numbered row groups of each light-emitting element 96. Two current limiting resistors 84b are provided, corresponding to the even-numbered row groups of each light-emitting element 96.

[0048] Furthermore, similar to Embodiment 2, multiple heat sources 85 are provided on the substrate 2 at positions parallel to the main scanning direction of the light-emitting point array 81. In this example, the heat source 85 is composed of multiple (four in this example) resistive elements. Here, the multiple heat sources 85 (specifically 85a to 85d) are arranged symmetrically in pairs with respect to the center Oc of the main scanning direction of the light-emitting point array 81. In this example, the first heat source 85a and the second heat source 85b are positioned to divide the region to the left of the center Oc of the main scanning direction of the light-emitting point array 81 into approximately three equal parts. The third heat source 85c and the fourth heat source 85d are positioned to divide the region to the right of the center Oc of the main scanning direction of the light-emitting point array 81 into approximately three equal parts. In this example, the first heat source 85a and the third heat source 85c are located near the edge of the main scanning direction of the light-emitting point array 81.

[0049] -Each element of the light-emitting element chip- Figure 12 shows an example of the circuit configuration of a light-emitting element chip according to Embodiment 3, and Figure 13 is an enlarged explanatory diagram of a part of Figure 12. <Electrode Pads> In this example, the electrode pad 7 is equipped with terminals corresponding to the φ1 terminal, φ2 terminal, φW terminal, VGA terminal, and φI terminal of the signal generation circuit 110, as shown in Figure 12.

[0050] <Light source array> In Figures 12 and 13, the light-emitting point array 81 is formed by arranging light-emitting elements 96, which are made up of light-emitting thyristors, along the main scanning direction. In other words, the light-emitting point array 81 comprises a series of light-emitting thyristors L (L1, L2, L3...) arranged sequentially as light-emitting elements 96. In this example, unlike LEDs, the light-emitting thyristor L is preferable because both the light-emitting point array 81 and the light-emitting point control unit 82 can be formed from thyristors, making it simpler. In this example, the light-emitting thyristor L is a semiconductor device having a first gate, a second gate, an anode, and a cathode. In this example, the cathodes of odd-numbered light-emitting thyristors L1, L3, L5, etc. are connected to the illumination signal line 90-1. The illumination signal line 90-1 is then connected to the φI terminal via a current-limiting resistor 84 (84a). Note that in Figures 12 and 13, the current-limiting resistor 84 (84a) is denoted as RL1. On the other hand, the cathodes of the even-numbered light-emitting thyristors L2, L4, L6, etc., are connected to the illumination signal line 90-2. In this example, illumination signal line 90-2 is connected in parallel to illumination signal line 90-1. Furthermore, illumination signal line 90-2 is connected to the φI terminal via the current limiting resistor 84 (84b). The illumination signal φI is transmitted to the φI terminal. Note that in Figures 12 and 13, the current limiting resistor 84 (84b) is denoted as RL2.

[0051] <Light source control unit> In this example, the light-emitting point control unit 82 includes the aforementioned on / off circuit 97. The on / off circuit 97 includes a transfer thyristor array 98 and a write thyristor array 99. Here, the transfer thyristor array 98 consists of transfer thyristors T(T1, T2, T3...) arranged in a row, similar to the light-emitting thyristor array 100. In this example, the transfer thyristor array 98 consists of two transfer thyristors T1, T2, T3... paired in numerical order. The transfer thyristor array 98 is also equipped with pnp bipolar transistors, which are coupled transistors Qt1, Qt2, Qt3..., between each pair. On the other hand, the write thyristor array 99 consists of write thyristors S1, S2, S3... arranged in a row, similar to the light-emitting thyristor array 100. The write thyristor array 99 is equipped with write transistors Qs1, Qs2, Qs3... corresponding to each of the write thyristors S1, S2, S3...

[0052] Furthermore, a first transfer signal line 91 for transmitting the first transfer signal φ1 and a second transfer signal line 92 for transmitting the second transfer signal φ2 are formed on the surface of the substrate 2. Current limiting resistors R1 and R2 are connected in series to the first transfer signal line 91 and the second transfer signal line 92, respectively, to prevent excessive current from flowing. Furthermore, a first write signal line 93 for transmitting a first write signal φW1 and a second write signal line 94 for transmitting a second write signal φW2 are formed on the surface of the substrate 2. Current limiting resistors RW1 and RW2 are connected in series to the first write signal line 93 and the second write signal line 94, respectively, to prevent excessive current from flowing.

[0053] Here, the transfer thyristor T and the write thyristor S are semiconductor elements having a first gate, a second gate, an anode, and a cathode, similar to the light-emitting thyristor L. The coupling transistor Qt and the write transistor Qs are also semiconductor elements having a collector, a base, and an emitter, but odd-numbered coupling transistors Qt have two collectors (multi-connectors). Furthermore, in Figures 12 and 13, the first gate of the transfer thyristor T is denoted as Gtf and the second gate as Gts, the first gate of the write thyristor S is denoted as Gsf and the second gate as Gss, and the first gate of the light-emitting thyristor L is denoted as Glf. Similarly, the first collector Cf and second collector Cs are denoted for odd-numbered multi-collector coupled transistors Qt, and the collector C is denoted for even-numbered coupled transistors Qt. In addition, the collector C is denoted for the write transistor Qs.

[0054] Next, the electrical connections of each element in the transfer thyristor array 98 and the write thyristor array 99 will be described (see Figures 12 and 13). <Transfer thyristor sequence> The anodes of the transfer thyristor T, the write thyristor S, and the light-emitting thyristor L are connected to board 2. In addition, the emitters of the coupling transistor Qt and the write transistor Qs are also connected to board 2. These anodes and emitters are connected to a power line (not shown) via a back electrode, which is a Vsub terminal, located on the back surface of the substrate 2. This power line is supplied with a reference potential Vsub from a reference potential supply unit (not shown). Along the transfer thyristor array 98, the cathodes of odd-numbered transfer thyristors T1, T3, T5, etc., are connected to the first transfer signal line 91. The first transfer signal line 91 is connected to the φ1 terminal via a current-limiting resistor R1. A first transfer signal line (not shown) is connected to this φ1 terminal, and the first transfer signal φ1 is transmitted. Meanwhile, along the transfer thyristor array 98, the cathodes of even-numbered transfer thyristors T2, T4, T6, etc., are connected to the second transfer signal line 92. The second transfer signal line 92 is connected to the φ2 terminal via a current-limiting resistor R2. A second transfer signal line (not shown) is connected to this φ2 terminal, and the second transfer signal φ2 is transmitted.

[0055] Furthermore, along the transfer thyristor array 98, the first gate Gtf of the odd-numbered transfer thyristors T is connected to the power line 95 via a resistor Rt. The second gate Gts is connected to the base of the odd-numbered coupling transistor Qt. The power line 95 is connected to the VGA terminal. The first collector Cf of the odd-numbered coupling transistor Qt is connected to power line 95 via resistor Rs. Furthermore, the first collector Cf of the odd-numbered transistor is connected to the first gate Gsf of the odd-numbered write thyristor S and the even-numbered write thyristor S which is one number higher. The second collector Cs is connected to the first gate Gtf of the even-numbered (later stage) transfer thyristor T which is one number higher. The first gate Gtf of the even-numbered transfer thyristor T is connected to power line 95 via resistor Rt. The second gate Gts is connected to the base of the even-numbered coupled transistor Qt. The collector C of the even-numbered coupled transistor Qt is connected to the first gate Gtf of the odd-numbered (next stage) transfer thyristor T, which is one number higher.

[0056] <Write thyristor sequence> Furthermore, along the write thyristor array 99, the cathodes of odd-numbered write thyristors S are connected to the first write signal line 93. The first write signal line 93 is connected to the φW1 terminal via a current limiting resistor Rw1. A write signal line (not shown) is connected to this φW1 terminal, and the first write signal φW1 is transmitted. Meanwhile, along the write thyristor array 99, the cathodes of even-numbered write thyristors S are connected to the second write signal line 94. The second write signal line 94 is connected to the φW2 terminal via a current limiting resistor Rw2. A write signal line (not shown) is connected to this φW2 terminal, and the second write signal φW2 is transmitted.

[0057] Furthermore, the second gate Gss of the writing thyristor S is connected to the base of the correspondingly provided writing transistor Qs. The collector C of the writing transistor Qs is connected to the power line 95 via resistor R1 and is also connected to the first gate Glf of the light-emitting thyristor L of the same number. As described above, in the light-emitting element chip U according to Embodiment 3, an odd-numbered transfer thyristor T is connected to a write thyristor S with the same number and one number higher, and a light-emitting thyristor L is connected to each write thyristor S. In other words, the odd-numbered transfer thyristor T controls the two light-emitting thyristors L. Although odd-numbered coupling transistors Qt are shown as multi-connectors, they may have only one collector, and the first gate Gsf of the write thyristor S and the first gate Gtf of the transfer thyristor T may be connected in common.

[0058] <Heat source> In this example, four heat sources 85 are provided. In Figure 12, the first heat source 85a to the fourth heat source 85d are denoted as Rha, Rhb, Rhc, and Rhd. In this example, the first heat source 85a and the third heat source 85c are positioned near the edges of the light-emitting point array 81 in the main scanning direction. The second heat source 85b and the fourth heat source 85d are positioned near the center of the light-emitting point array 81 in the main scanning direction. The first heat source 85a and the third heat source 85c are connected to the first write signal line 93. The second heat source 85b and the fourth heat source 85d are connected to the second write signal line 94. Here, the heat values ​​of the first heat source 85a to the fourth heat source 85d can be selected as appropriate. In this example, when the heat value of the current limiting resistor 84 (RL1 or RL2) is set to 1, the heat values ​​of the first heat source 85a and the third heat source 85c were selected to be 0.4, and the heat values ​​of the second heat source 85b and the fourth heat source 85d were selected to be 0.5.

[0059] - Operation of the light-emitting element chip - In this example, each light-emitting element 96 of the light-emitting element array 81 is controlled to turn on and off by the on / off circuit 97 of the light-emitting element control unit 82. Therefore, in this example, each light-emitting element 96 of the light-emitting element array 81 repeatedly turns on and off in parallel, with the odd-numbered rows and even-numbered rows alternating between each other. In this state, when an odd-numbered row of light-emitting elements 96 lights up, current is supplied to the lighting signal line 90-1 and the first write signal line 93. As a result, current flows through the current-limiting resistor 84a (RL1) connected to the lighting signal line 90-1, causing it to heat up. In addition, current flows through the first heat source 85a (Rha) and the third heat source 85c (Rhc) connected to the first write signal line 93, causing them to heat up. Furthermore, when the even-numbered light-emitting elements 96 are lit, current is supplied to the lit signal line 90-2 and the second write signal line 94. As a result, current flows through the current-limiting resistor 84b(RL2) connected to the lit signal line 90-2, causing it to heat up. Also, current flows through the second heat source 85b(Rhb) and the fourth heat source 85d(Rhd) connected to the second write signal line 94, causing them to heat up as well.

[0060] In this example, the temperature distribution of the light-emitting elements 96 of the light-emitting element array 81 in the direction of arrangement is such that the temperature rises near the center and near the edges of the light-emitting element array 81 in the main scanning direction due to the heat generated from the four heat sources 85 (85a to 85d). In particular, in this example, the amount of heat generated by the heat sources 85 (85a, 85c) located near the edges of the light-emitting element array 81 in the main scanning direction is selected to be less than the amount of heat generated by the heat sources 85 (85b, 85d) located near the center. Therefore, there is no concern that the temperature near the edges of the light-emitting element array 81 in the main scanning direction will rise excessively. Here, the temperature distribution in the direction of the arrangement of the light-emitting elements 96 of the light-emitting point array 81 changes to a state in which the temperature difference ΔT is reduced compared to when the heat source 85 is not provided. This situation is more pronounced the higher the illumination rate of the 96 light-emitting elements in the light-emitting point array 81.

[0061] ◎Embodiment 4 Figure 14(a) shows the main part of the light-emitting element chip according to Embodiment 4. In the figure, the basic configuration of the light-emitting element chip U is substantially the same as that of Embodiment 3. Specifically, it comprises a substrate 2, a light-emitting point array 81, a light-emitting point control unit 82, an electrode pad 7, and a current-limiting resistor 84. However, the light-emitting element chip U in this example is equipped with a heat source 85 that is different from any of the embodiments 1 to 3. In this example, as shown in Figures 14 to 16, two sets of current limiting resistors 84 are provided to limit the power supplied to the light-emitting elements 96 in the odd and even rows of the light-emitting element array 81. The first set of current limiting resistors 84 (84a) is positioned to correspond to the light-emitting elements 96 in the odd rows of the light-emitting element array 81. The second set of current limiting resistors 84 (84b) is positioned to correspond to the light-emitting elements 96 in the even rows of the light-emitting element array 81. In Figure 16, current limiting resistor 84a is denoted as RL1 and current limiting resistor 84b is denoted as RL2.

[0062] In this example, the heat source 85 is configured to also serve as a part of the current limiting resistor 84. Specifically, the heat source 85 also serves as the first set of current limiting resistors RL1 (84a), but its position has been changed from the end side of the main scanning direction of the light-emitting point array 81 to a different location. In this example, the heat source 85 can be configured by changing the position of the first set of current limiting resistors 84a (RL1) to a position parallel to the main scanning direction of the light-emitting point array 81. In this example, the first set of current limiting resistors RL1, which serves as the heat source 85, can be arranged symmetrically with respect to the center Oc of the main scanning direction of the light-emitting point array 81. For example, one current limiting resistor 84a (RL1) is positioned to roughly bisect the area located to the left of the center Oc of the main scanning direction of the light-emitting point array 81. The other current limiting resistor 84a (RL1) is positioned to roughly bisect the area located to the right of the center Oc of the main scanning direction of the light-emitting point array 81.

[0063] Furthermore, in this example, the placement of the current limiting resistor RL1(84a) will be changed from its original position. However, the current limiting resistor RL1(84a) must be connected in series with the lighting signal line 90-1. In Figure 16, the current limiting resistor RL1, which also serves as the heat source 85, is represented as two heat sources 85a and 85b (Rha, Rhb). In this example, the heat source 85 also serves as the first set of current limiting resistors RL1, but this is not the only option; it may also serve as the second set of current limiting resistors RL2.

[0064] - Operation of the light-emitting element chip - In this example, the heat source 85 also serves as the current limiting resistor 84a (RL1). In this example, the end of the light-emitting point array 81 in the main scanning direction is heated by the heat generated by the current limiting resistor RL2. On the other hand, the area around the installation location of the heat source 85, which straddles the center Oc in the main scanning direction of the light-emitting point array 81, is heated by the heat generated by the heat source 85, which also serves as the current limiting resistor RL1. In this case, the current limiting resistor RL1, which also serves as a heat source 85, is installed away from the end of the light-emitting point array 81 in the main scanning direction. Therefore, the end of the light-emitting point array 81 in the main scanning direction is not overheated by the heat generated by the current limiting resistor RL1. Here, we assume that the illumination rate of the 96 light-emitting elements in the light-emitting point array 81 is 100%. The temperature distribution in the direction of the arrangement of the 96 light-emitting elements in the light-emitting point array 81 changes as shown by the solid line in Figure 14(b). The temperature distribution shown by the solid line in Figure 14(b) changes to a state where the temperature difference is reduced by ΔT100.

[0065] Furthermore, we assume that the illumination rate of the 96 light-emitting elements in the light-emitting point array 81 is 25%. The temperature distribution in the direction of the arrangement of the light-emitting elements 96 in the light-emitting point array 81 changes as shown by the dotted line in Figure 14(b). The temperature distribution shown by the dotted line in Figure 14(b) changes to a state where the temperature difference is reduced by ΔT25. In this example, the relationship ΔT100 > ΔT25 is satisfied. Furthermore, in this example, the current limiting resistor RL1, which also serves as a heat source 85, hardly heats the area near the end of the light-emitting point array 81 in the main scanning direction. Therefore, in this example, it is presumed that the temperature rise near the ends of the light-emitting point array 81 in the main scanning direction will be reduced by the amount that does not affect the heat generated by the current limiting resistor RL1.

[0066] ◎Embodiment 5 Figure 17(a) shows the main part of the light-emitting element chip according to Embodiment 5. In the figure, the basic configuration of the light-emitting element chip U is substantially the same as that of Embodiment 4. Specifically, it comprises a substrate 2, a light-emitting point array 81, a light-emitting point control unit 82, an electrode pad 7, and a current-limiting resistor 84. However, unlike in Embodiment 4, the light-emitting element chip U in this example uses all of the current-limiting resistors 84 as the heat source 85. In other words, in this example, the current limiting resistor 84 is not located on the end side of the light-emitting point array 81 in the main scanning direction.

[0067] In this example, the heat source 85 serves as both the current limiting resistor 84 (84a, 84b) and is positioned parallel to the main scanning direction of the light-emitting point array 81. In this example, four heat sources 85 are provided. In this example, the four heat sources 85 (85a to 85d) are arranged symmetrically with respect to the center Oc of the main scanning direction of the light-emitting point array 81. More specifically, the first heat source 85a and the third heat source 85c are provided in a region outside the end of the main scanning direction of the light-emitting point array 81, and at a location away from the end in the sub-scanning direction. In contrast, the second heat source 85b and the fourth heat source 85d are provided at locations that roughly bisect the center and end of the main scanning direction of the light-emitting point array 81.

[0068] In this example, the end of the light-emitting point array 81 in the main scanning direction is not directly heated by the heat generated by the current-limiting resistor 84(RL). The current-limiting resistors RL1(84a) and RL2(84b), which also serve as heat sources 85, are heated almost uniformly from a point parallel to the main scanning direction of the light-emitting point array 81. Here, we assume that the illumination rate of the 96 light-emitting elements in the light-emitting point array 81 is 100%. The temperature distribution in the direction of the arrangement of the 96 light-emitting elements in the light-emitting point array 81 changes as shown by the solid line in Figure 17(b). The temperature distribution shown by the solid line in Figure 17(b) changes to a state where the temperature difference is reduced by ΔT100. Furthermore, we assume that the illumination rate of the 96 light-emitting elements in the light-emitting point array 81 is 25%. The temperature distribution in the direction of the arrangement of the light-emitting elements 96 in the light-emitting point array 81 changes as shown by the dotted line in Figure 17(b). The temperature distribution shown by the dotted line in Figure 17(b) changes to a state where the temperature difference is reduced by ΔT25. In this example, the relationship ΔT100 > ΔT25 is satisfied. [Examples]

[0069] ◎Example 1 Example 1 is an embodiment of the light-emitting element chip according to Embodiment 1 (using one heat source). In this example, the size of the light-emitting element chip is approximately 14 mm in the x-direction and approximately 0.4 mm in the y-direction. ◎Example 2 Example 2 is an embodiment of the light-emitting element chip according to Embodiment 2 (using three heat sources). In this example, the size of the light-emitting element chip is the same as in Example 1. ◎Example 3 Example 3 is an embodiment of the light-emitting element chip according to Embodiment 4 (with two heat sources and a combined current-limiting resistor). In this example, the size of the light-emitting element chip is the same as in Example 1. ◎Example 4 Example 4 is an embodiment of the light-emitting element chip according to Embodiment 5 (with four heat sources also serving as current-limiting resistors). In this example, the size of the light-emitting element chip is the same as in Example 1. ◎Comparative Example 1 Comparative Example 1 is an embodiment of the light-emitting element chip according to Comparative Example 1 (without using a heat source). In this example, the size of the light-emitting element chip is approximately 14 mm in the x-direction and approximately 0.39 mm in the y-direction.

[0070] -Verification of characteristics of the light-emitting element chip related to Comparative Example 1- When the light intensity fluctuation characteristics and temperature distribution characteristics in the main scanning direction of the light-emitting element chip according to Comparative Example 1 were measured, the results shown in Figures 18(a) and 18(b) were obtained. Figure 18(a) shows the light intensity fluctuation characteristics of the light-emitting element chip according to Comparative Example 1 in the main scanning direction. In the figure, the illumination rate (Cin) of each light-emitting element in the light-emitting element chip was varied, and the variation in light intensity of the light-emitting element chip for each illumination rate was measured. Here, illumination rates (Cin) of 100%, 75%, 50%, 25%, and 12.5% ​​are shown as examples. In Figure 18(a), the horizontal axis indicates the position of the light-emitting element chip in the main scanning direction, and the vertical axis indicates the relative light intensity with the reference light intensity set to 1.

[0071] Figure 18(b) shows the temperature fluctuation characteristics of the light-emitting element chip according to Comparative Example 1 in the main scanning direction. In the figure, the illumination rate (Cin) of each light-emitting element in the light-emitting element chip was varied, and the temperature fluctuation of the light-emitting element chip was measured for each illumination rate. Here, illumination rates (Cin) of 100%, 50%, and 25% are shown as examples. In Figure 18(b), the horizontal axis indicates the position of the light-emitting element chip in the main scanning direction, and the vertical axis indicates the temperature fluctuation value with the lowest temperature point of the light-emitting element chip as the reference (0).

[0072] First, as shown in Figure 18(b), the temperature distribution of the light-emitting element chip in the main scanning direction changes quadratically, with a minimum near the center. It can be seen that the higher the illumination rate, the greater the temperature fluctuation of the light-emitting element chip. Furthermore, it can be seen that the temperature difference of the light-emitting element chip changes by approximately 4°C depending on the illumination rate. Furthermore, as shown in Figure 18(a), it can be seen that the greater the illumination rate, the greater the variation in light intensity of the light-emitting element chip. For example, at an illumination rate of 100%, the light intensity difference ΔW100 is 4.5%, and at an illumination rate of 25%, the light intensity difference ΔW25 is 3.5%. Thus, it is understood that there is a dependent relationship between temperature and light intensity in a light-emitting chip. In this example, the light intensity decreases at higher temperatures on the light-emitting chip, so the difference in light intensity on the chip changes by about 1% with changes in illumination rate (e.g., 100% and 25%). Generally, it is known that in a light-emitting chip, the internal quantum efficiency of the light-emitting points made up of light-emitting elements decreases with increasing temperature. The temperature coefficient of light intensity for this type is, for example, about -0.2% / °C.

[0073] Next, the temperature difference in the temperature distribution of the light-emitting point array was measured for the light-emitting chips of Examples 1 to 4 and Comparative Example 1, and the results shown in Table 1 were obtained. In Table 1, ΔT100 represents the temperature difference when the illumination rate is 100%, ΔT25 represents the temperature difference when the illumination rate is 25%, and ΔT100-25 represents the difference between ΔT100 and ΔT25. According to Table 1, it can be seen that in Examples 1 to 4, ΔT100, ΔT25, and ΔT100-25 are all kept lower compared to Comparative Example 1. Furthermore, comparing Examples 1 and 2, it can be seen that in Example 2, ΔT100 and ΔT100-25 are suppressed to a lower level compared to Example 1. Furthermore, comparing Examples 3 and 4 with Examples 1 and 2, it can be seen that in Examples 3 and 4, ΔT100, ΔT25, and ΔT100-25 are all kept lower compared to Examples 1 and 2.

[0074] [Table 1]

[0075] (Note) (((1))) circuit board and The substrate is provided with an array-shaped light source means in which a plurality of light-emitting elements are arranged along the main scanning direction, A control means provided on the substrate for controlling the current to turn each light-emitting element of the light source means on or off, A resistor is provided on the side of the end of the substrate in the main scanning direction of the light source means, which limits the current supplied to each of the light-emitting elements. The substrate includes a heating means provided at a position parallel to the main scanning direction of the light source means and away from the resistor means, which generates a heat amount that is less than the heat generated by the power supplied to the resistor means and is proportional to the heat generated; A light-emitting component characterized by comprising the following features. (((2))) In the light-emitting component described in (((1))), A light-emitting component characterized by having one of the aforementioned heating means. (((3))) In the light-emitting component described in (((2))), A light-emitting component characterized in that one of the heating means is arranged corresponding to a position including the center in the main scanning direction of the light source means. (((4))) In the light-emitting component described in (((1))), The light-emitting component is characterized by having multiple heat-generating means. (((5))) In the light-emitting component described in (((4))), The light-emitting component is characterized in that the plurality of heating means are arranged symmetrically with respect to the center of the main scanning direction of the light source means. (((6))) In the light-emitting component described in (((4))) or (((5))), A light-emitting component characterized in that at least one of the multiple heating means is arranged to correspond to a region closer to the center of the main scanning direction of the light source means. (((7))) In any of the light-emitting components described in (((1))) to (((6))), The light-emitting component is characterized in that the heating means also serves as a part of the resistive means, and is positioned from a position on the side of the end in the main scanning direction of the light source means to a position parallel to the main scanning direction of the light source means. (((8))) In the light-emitting component described in (((7))), The resistive means is provided in a manner that divides the light-emitting element array of the light source means into multiple sets, and is provided in a manner that divides it into multiple sets. The light-emitting component is characterized in that the heat-generating means is configured using any set of the resistive means. (((9))) In the light-emitting component described in any of (((1))) to (((8))), The heat-generating means is characterized by generating an amount of heat that reduces the difference in the temperature distribution, taking into account the temperature distribution of the light source means in the main scanning direction caused by the heat generated by the resistive means. (((10))) In the light-emitting component described in (((9))), A light-emitting component characterized in that a plurality of the aforementioned heating means are provided, and the heating means located closer to the center in the main scanning direction of the light source means distributes a larger amount of heat than the other heating means. (((11))) In any of the light-emitting components described in (((1))) to (((10))), The heat-generating means is characterized in that it generates heat when the power input to the resistive means is above a predetermined threshold, and does not generate heat when it is below the threshold. (((12))) A light-emitting component as described in any of (((1))) to (((11))), An optical writing device comprising an imaging means for imaging light emitted from each light-emitting element of the aforementioned light-emitting component at a predetermined position, and characterized in that it writes an image using light. (((13))) The optical writing device described in (((12))) and An image forming system characterized by comprising: an image holding means provided opposite to the optical writing device, which holds an image written by the optical writing device using light.

[0076] According to the light-emitting component of (((1))), it is possible to suppress the difference in temperature distribution in the direction of arrangement of the light-emitting elements of a light source means in which multiple light-emitting elements are arranged, and to reduce the variation in light intensity distribution for each lighting condition. According to the light-emitting component in (((2))), it is possible to suppress the difference in temperature distribution in the main scanning direction of the light source means with a simple configuration. According to the light-emitting component in (((3))), it is possible to concentrate heating on areas that are less affected by heat generation from the resistive means in the main scanning direction of the light source means. According to the light-emitting component in (((4))), the difference in temperature distribution in the main scanning direction of the light source can be suppressed more appropriately compared to the case where there is only one heat-generating means. According to the light-emitting component in (((5))), temperature distribution fluctuations in the main scanning direction of the light source means can be corrected symmetrically with respect to the center. According to the light-emitting component in (((6))), the light source means can be appropriately heated, including in areas that are less affected by heat generation from the resistive means in the main scanning direction of the light source means. According to the light-emitting component in (((7))), a heat-generating means can be constructed that utilizes some of the existing resistive means, without increasing the number of components, and with reduced power input to the heat-generating means. According to the light-emitting component related to (((8))), a heat-generating means can be easily constructed by utilizing a part of the existing resistive means. According to the light-emitting component related to (((9))), the amount of heat from the heat-generating means can be easily selected. According to the light-emitting component related to (((10))), the amount of heat from multiple heat-generating means can be easily selected in order to suppress the difference in temperature distribution in the main scanning direction of the light source means. According to the light-emitting component of (((11))), when the difference in temperature distribution in the main scanning direction of the light source means affects the light intensity distribution fluctuations depending on the lighting conditions of the light source means, it is possible to suppress such temperature distribution fluctuations. According to the optical writing device described in (((12))), it is possible to construct an optical writing device equipped with a light-emitting component that can suppress the difference in temperature distribution in the arrangement direction of the light-emitting elements of a light source means in which a plurality of light-emitting elements are arranged, and reduce the variation in light intensity distribution for each lighting condition. According to the image forming system described in (((13))), an image forming system can be constructed that includes an optical writing device equipped with a light-emitting component capable of suppressing differences in temperature distribution in the arrangement direction of the light-emitting elements of a light source means having multiple light-emitting elements arranged in a row, and reducing fluctuations in light intensity distribution for each lighting condition. [Explanation of Symbols]

[0077] 1…Light-emitting component, 2…Substrate, 3…Light source means, 4…Light-emitting element, 5(5a,5b)…Resistor means, 6(6a,6b)…Heating means, 7…Electrode pad, 8…Control means, 9…Imaging means, 10…Image forming system, 11…Optical writing device, 12…Image holding means, m…Main scanning direction, Oc…Center, U…Light-emitting element chip

Claims

1. circuit board and The substrate is provided with an array-shaped light source means in which a plurality of light-emitting elements are arranged along the main scanning direction, A control means provided on the substrate for controlling the current to turn each light-emitting element of the light source means on or off, A resistor is provided on the side of the end of the substrate in the main scanning direction of the light source means, which limits the current supplied to each of the light-emitting elements. The substrate includes a heating means provided at a position parallel to the main scanning direction of the light source means and away from the resistor means, which generates a heat amount that is less than the heat generated by the power supplied to the resistor means and is proportional to the heat generated; A light-emitting component characterized by comprising the following features.

2. In the light-emitting component according to claim 1, A light-emitting component characterized by having one of the aforementioned heating means.

3. In the light-emitting component according to claim 2, A light-emitting component characterized in that one of the heating means is arranged corresponding to a position including the center in the main scanning direction of the light source means.

4. In the light-emitting component according to claim 1, The light-emitting component is characterized by having multiple heat-generating means.

5. In the light-emitting component according to claim 4, The light-emitting component is characterized in that the plurality of heating means are arranged symmetrically with respect to the center of the main scanning direction of the light source means.

6. In the light-emitting component according to claim 4, A light-emitting component characterized in that at least one of the multiple heating means is arranged to correspond to a region closer to the center of the main scanning direction of the light source means.

7. In the light-emitting component according to claim 1, The light-emitting component is characterized in that the heating means also serves as a part of the resistive means, and is positioned from a position on the side of the end in the main scanning direction of the light source means to a position parallel to the main scanning direction of the light source means.

8. In the light-emitting component according to claim 7, The resistive means is provided in a manner that divides the light-emitting element array of the light source means into multiple sets, and is provided in a manner that divides it into multiple sets. The light-emitting component is characterized in that the heat-generating means is configured using any set of the resistive means.

9. In the light-emitting component according to claim 1, The heat-generating means is characterized by generating an amount of heat that reduces the difference in the temperature distribution, taking into account the temperature distribution in the main scanning direction of the light source means caused by the heat generated by the resistive means.

10. In the light-emitting component according to claim 9, A light-emitting component characterized in that a plurality of the aforementioned heating means are provided, and the heating means located closer to the center in the main scanning direction of the light source means distributes a larger amount of heat than the other heating means.

11. In the light-emitting component according to claim 1, The heat-generating means is characterized in that it generates heat when the power input to the resistive means is above a predetermined threshold, and does not generate heat when it is below the threshold.

12. A light-emitting component according to any one of claims 1 to 11, An optical writing device comprising imaging means for imaging light emitted from each light-emitting element of the aforementioned light-emitting component at a predetermined position, and characterized in that it writes an image using light.

13. The optical writing device according to claim 12, An image forming system characterized by comprising: an image holding means provided opposite to the optical writing device, which holds an image written by the optical writing device using light.

Images