JP2007066952A - Light emitting device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve quick transition of the characteristics of a temperature dependent light emitting element to expected characteristics. <P>SOLUTION: The light emitting device 10 comprises a light emitting panel 20 including a plurality of light emitting elements E arranged on the surface of a substrate 21, a temperature sensor 32 for detecting the ambient temperature of each light emitting element E, an electric heater 34 for heating each light emitting element E, and a cooling body 36 for cooling each light emitting element E. When temperature T specified depending on a signal from the temperature sensor 32 is lower than a predetermined temperature T1, a controller 50 operates the electric heater 34 to heat each light emitting element E and operates the cooling body 36 to cool each light emitting element E when the temperature T exceeds a predetermined temperature T2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for causing a light emitting element formed of a light emitting material such as an organic EL (ElectroLuminescent) material to emit light.

Conventionally, light emitting devices having a structure in which a plurality of light emitting elements are arranged on a substrate have been proposed as display devices and exposure devices for various electronic devices. For example, Patent Document 1 discloses an image forming apparatus (printing apparatus) that exposes an image carrier such as a photosensitive drum by light emission of a light emitting element in which a light emitting layer made of an organic EL material is interposed between electrodes.
Japanese Patent Laying-Open No. 2005-149853 (FIG. 7)

  By the way, various luminescent materials represented by the organic EL material may change the light emission characteristics depending on the temperature. For example, the time from when the voltage is applied to the light emitting layer until the luminance of the light emission reaches a predetermined value increases as the temperature of the light emitting layer decreases. Therefore, for example, when an image forming apparatus using a light emitting element for exposure of an image carrier is used in a low-temperature environment, the exposure amount of the portion of the photosensitive drum that has been exposed first is the amount of subsequent exposure. The amount of exposure is insufficient as compared to the amount of light exposed at the stage where the temperature of the light emitting element has increased due to the progress. As a result, it is difficult to make the quality of the image uniform, such that the gradation of the image printed on the paper is different depending on the destination of printing, although it should be the same gradation. There was a problem that there was. In particular, since the organic EL material has a remarkable change in characteristics depending on the temperature as compared with other light emitting materials, the above problem is serious in an apparatus using a light emitting layer containing the organic EL material. The present invention has been made in view of such circumstances, and an object of the present invention is to solve the problem of quickly changing the characteristics of a light-emitting element depending on temperature to desired characteristics.

  In order to solve this problem, a light-emitting device according to the present invention includes a light-emitting panel in which a plurality of light-emitting elements are arranged on a surface of a substrate, and heating means for heating each light-emitting element (for example, in FIGS. 1 to 3). Electric heater 34). According to this configuration, since each light emitting element is heated by the heating means, for example, even when the light emitting device is used in a low temperature environment, each light emitting element can be quickly changed to an intended state. it can.

  Note that the light-emitting element in the present invention is an element that emits light, more specifically, an element that emits light by application of electric energy. Although the specific structure and material of the light emitting element in the present invention are arbitrary, for example, an element in which a light emitting layer made of an organic EL material or an inorganic EL material is interposed between electrodes can be adopted as the light emitting element of the present invention. Furthermore, various light emitting elements such as an LED (Light Emitting Diode) element and an element that emits light by plasma discharge can be used in the present invention.

  The position where the heating means is installed is arbitrary. For example, a heating unit is disposed in a housing of an electronic apparatus (for example, an image forming apparatus such as a printing apparatus) on which the light emitting device of the present invention is mounted. However, in order to realize efficient heating of each light emitting element, a configuration in which a heating unit is provided in the light emitting panel is preferable.

  The heating means of the present invention is, for example, an object that generates heat by application of electric energy, and is typically an electric heating body that radiates heat (Joule heat) by supplying electric current. According to this configuration, the light emitting element can be efficiently heated with an extremely simple structure. In a more preferred aspect, the electric heating element is disposed on the surface of the substrate on which the light emitting elements are arranged. According to this aspect, compared with the configuration in which the heating unit is disposed on the surface of the substrate opposite to the arrangement surface of the light emitting elements and the configuration in which the heating unit is disposed at a position separated from the substrate, The radiated heat can efficiently reach each light emitting element. The electric heating body in this embodiment is, for example, wiring such as a wiring obtained by patterning a conductive film formed on the surface of the substrate into a desired shape, or a nichrome wire fixed to a light emitting panel (particularly the surface of the substrate). However, the heating means of the present invention may be any means having the ability to increase the temperature of each light emitting element, and its specific structure and heating principle are not required. For example, you may employ | adopt as a heating means the heater which sends warm air with respect to a light emission panel.

  Each light emitting element of the present invention includes, for example, a first electrode and a second electrode facing each other, and a light emitting layer interposed between the first electrode and the second electrode. In the aspect in which the electrode is formed by patterning the conductive film formed on the surface of the substrate, the electric heating body of the present invention is preferably formed from the same layer as one of the first electrode and the second electrode. According to this aspect, since the electric heating body is formed in a process common to one of the first electrode and the second electrode, compared to a configuration in which the electric heating body is formed separately from the first electrode and the second electrode. In addition, the manufacturing process of the light emitting device can be simplified and the manufacturing cost can be reduced.

  In the present invention, the electric heating element and the electrode (one of the first electrode and the second electrode) are “formed from the same layer” means that the electric heating element and the electrode are formed from a single conductive film. This typically means that the electric heating element and the electrode are collectively formed in one process by selective removal (patterning) of a single conductive film formed on the surface of the substrate. . Therefore, the heating wire and one of the first electrode and the second electrode are formed with the same material and substantially the same film thickness.

  Since the calorific value of the electric heating element is proportional to its electric resistance, it is desirable that the electric heating element is formed of a conductive material having a high resistivity (specific resistance) from the viewpoint of sufficiently ensuring the calorific value of the electric heating element. Therefore, in a desirable mode of the present invention, the electric heating element is formed from the same layer as the electrode made of a material having a high resistivity among the first electrode and the second electrode. However, when a heat amount sufficient for heating each light-emitting element can be obtained by a heating wire formed of a material having a low resistivity among the first electrode and the second electrode (or a heating wire is formed by a material having a high resistivity). In this case, the heating element may be formed of the low-resistance material.

  In a desirable mode of the present invention, the electric heating element is formed in a shape surrounding a set of a plurality of light emitting elements. According to this aspect, the plurality of light-emitting elements are uniformly and efficiently heated as compared with the configuration in which the electric heating body is provided close to only the specific light-emitting element. Therefore, according to this aspect, the variation in the characteristic of each light emitting element depending on temperature can be suppressed effectively.

  In a desirable aspect of the present invention, the light-emitting panel includes a sealing body that is bonded to the substrate and covers each light-emitting element, and the electric heating body is a surface of the substrate on which the light-emitting elements are arranged, and the sealing body It is formed in an uncovered area (for example, area 201 in FIG. 3). According to this aspect, each light emitting element can be efficiently heated as compared with a configuration in which the electric heating body is installed in another location. However, in the present invention, the position where the electric heating element is installed and its form are arbitrary. For example, an electric heating element may be disposed on the surface of the substrate opposite to the arrangement surface of each light emitting element, or an electric heating element may be disposed on the upper surface (surface opposite to the substrate) or side end surface of the sealing body. May be.

  A light-emitting device according to a preferred embodiment of the present invention includes a temperature detection unit (for example, the temperature sensor 32 in FIG. 2) that detects the temperature of each light-emitting element or its surroundings, and the temperature detected by the temperature detection unit is a predetermined threshold (for example, FIG. And a control means (for example, the control device 50 in FIG. 1) for operating the heating means when the temperature is lower than 4 (T1). According to this aspect, since the heating unit operates when the temperature detected by the temperature detection unit is lower than the predetermined threshold value, each light emitting element is maintained at a temperature substantially equal to or higher than the predetermined temperature. Therefore, a situation in which the characteristics of each light emitting element are different from the desired characteristics due to the low temperature is effectively avoided.

  In addition, a light emitting device according to another aspect of the present invention includes a temperature detection unit (for example, temperature sensor 32 in FIG. 2) that detects the temperature of each light emitting element or its surroundings, and a cooling unit (for example, FIG. 2) that cools each light emitting element. 1 to 3) and control means for operating the cooling means when the temperature detected by the temperature detecting means exceeds a predetermined threshold (eg, temperature T2 in FIG. 4) (eg, the control device 50 in FIG. 1). It comprises. Each light emitting element can become high temperature due to overheating by the heating means or lighting for a long time. However, according to this aspect, the cooling means operates when the temperature detected by the temperature detecting means exceeds a predetermined threshold value. The element is maintained at a temperature substantially equal to or below a predetermined temperature. Therefore, a situation in which the characteristics of each light emitting element are different from the desired characteristics due to the high temperature is effectively avoided.

A light-emitting device according to a further desirable aspect of the present invention includes a temperature detection unit (for example, the temperature sensor 32 in FIG. 2) for detecting the temperature of each light-emitting element or its surroundings, and a cooling unit (for example, FIG. 1 to FIG. 1). When the temperature detected by the cooling body 36) in FIG. 3 and the temperature detection means falls below a predetermined threshold (for example, temperature T1 in FIG. 4), the heating means is operated, while the temperature detected by the temperature detection means is the predetermined threshold. Control means (for example, the control device 50 in FIG. 1) that operates the cooling means when the temperature exceeds (eg, temperature T2 (T2 ≧ T1) in FIG. 4) is provided. According to this aspect, since the temperature of each light emitting element is controlled to a temperature within a predetermined range (ideally a specific temperature), the characteristics of each light emitting element are the desired characteristics due to the high and low temperatures. Therefore, it is possible to effectively prevent a situation different from the above.
Note that the temperature detection means in this aspect includes, for example, a sensor that detects a temperature that serves as an index for distinguishing between operation and non-operation of the cooling means and a temperature that serves as an index for distinguishing between operation and non-operation of the heating means. The sensor to detect may be included separately. However, from the viewpoint of simplification of configuration and reduction of manufacturing cost, a configuration in which a sensor is also used for controlling both the heating means and the cooling means (that is, the control means based on the temperature detected by a single sensor). Is preferable to control both the heating means and the cooling means.

  The specific mechanism of the cooling means in the present invention includes an air-cooled mechanism (fan) that blows or sucks air to and from the light-emitting panel and light-emitting elements, and water-cooling that circulates a fluid serving as a refrigerant in a pipe line close to each light-emitting element. A thermoelectric conversion mechanism that generates heat transfer by a thermoelectric conversion element typified by a Peltier element or the like is preferably employed. However, the cooling means of the present invention may be any means provided with the ability to lower the temperature of each light emitting element, and its specific structure and cooling principle are arbitrary. Further, the position where the cooling means is disposed is arbitrary. For example, in a configuration in which a sealing body that covers each light emitting element is bonded to the substrate, the surface of the sealing body on the side opposite to the substrate is disposed. A configuration provided with a cooling means is particularly suitable. According to this configuration, each light emitting element can be efficiently cooled.

  The temperature detection means in this invention is arrange | positioned in the location where temperature changes according to the temperature of each light emitting element. For example, in the configuration in which the light emitting element is sealed on the surface of the substrate by the sealing body bonded to the substrate, the portion covered by the sealing body (that is, the space sealed by the sealing body together with each light emitting element). ) Is provided with temperature detecting means. According to this aspect, the temperature of each light emitting element can be detected with high accuracy. But the position where a temperature detection means is installed is not limited to this illustration. For example, a configuration in which the temperature detection unit is installed apart from the light-emitting panel (for example, a configuration in which the temperature detection unit is installed in a housing to which the light-emitting panel is fixed) may be employed. The “periphery of each light emitting element” that is a target of temperature detection by the temperature detecting means of the present invention means a range in which the temperature changes in conjunction with the temperature of the light emitting element. It does not matter whether the temperature detection means in the present invention includes only one temperature sensor or includes a plurality of temperature sensors.

  The light emitting device according to the present invention is used in various electronic devices. A typical example of this electronic apparatus is an image forming apparatus using the light emitting device of the present invention as an exposure device (exposure head). This image forming apparatus includes an image carrier on which a latent image is formed on an image forming surface by exposure, a light emitting device of the present invention that exposes the image forming surface, and a developer image (eg, toner) attached to the latent image. And a developing device for forming the. According to the light-emitting device of the present invention, for example, even when the light-emitting device is used in a low-temperature environment, the state of each light-emitting element can be quickly changed to an intended state. Regardless of the temperature of the environment used, it is possible to uniformly expose the image forming surface to form a high-quality and homogeneous image on a recording material (such as paper). In a preferred embodiment of this type of image forming apparatus, the plurality of light emitting elements are arranged in a line. According to this aspect, there is an advantage that each light emitting element can be easily heated compared to the configuration in which a plurality of light emitting elements are arranged in a planar shape.

  However, the use of the light emitting device according to the present invention is not limited to exposure. For example, the light-emitting device of the present invention can be used as a display device for various electronic devices. Examples of this type of electronic device include a personal computer and a mobile phone. The light emitting device of the present invention can also be used as various lighting devices such as a device (backlight) that is arranged on the back side of a liquid crystal device and illuminates the device, and a device that is mounted on an image reading device such as a scanner and irradiates light on a document. The device is preferred.

  The present invention is also specified as a method for controlling a light emitting device. That is, one aspect of the control method according to the present invention includes a light-emitting panel in which a plurality of light-emitting elements are arranged on the surface of a substrate, temperature detecting means for detecting the temperature of each light-emitting element or its surroundings, and each light-emitting element. A method for controlling a light emitting device comprising a heating means for heating an element and a cooling means for cooling each light emitting element, wherein the heating means is activated when the temperature detected by the temperature detection means falls below a predetermined threshold value. On the other hand, the cooling means is operated when the temperature detected by the temperature detection means exceeds a predetermined threshold value.

  Embodiments of the present invention will be described with reference to the drawings. In the following drawings, the ratio of the dimensions of each part is made different from the actual one for convenience.

<A: Configuration>
FIG. 1 is a perspective view showing a partial configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus includes a cylindrical photosensitive drum 110 that is supported so as to be rotatable in the sub-scanning direction, and an outer peripheral surface (hereinafter referred to as an “image forming surface”) of the photosensitive drum 110. And a light emitting device 10 that exposes 110A.

  The light emitting device 10 includes a light emitting panel (optical head) 20 that emits light toward the photosensitive drum 110, a converging lens array 40 installed in the gap between the light emitting panel 20 and the photosensitive drum 110, and the light emitting panel 20. And a control device 50 for controlling the operation of Light emitted from the light emitting panel 20 passes through the converging lens array 40 and then reaches the image forming surface 110 </ b> A of the photosensitive drum 110. The converging lens array 40 is means for condensing the light emitted from the light emitting panel 20. As the converging lens array 40, for example, SLA (Selfoc lens array) provided by Nippon Sheet Glass Co., Ltd. is suitably employed (“SELFOC / SELFOC” is a registered trademark of Nippon Sheet Glass Co., Ltd.).

  The light emitting panel 20 has a structure in which a large number of light emitting elements (not shown in FIG. 1) are sealed in the gap between the substrate 21 and the sealing body 29. As shown in FIG. 1, the light emitting panel 20 is fixed in a posture in which the substrate 21 is opposed to the image forming surface 110 </ b> A of the photosensitive drum 110. The substrate 21 is a substantially rectangular plate material made of a light transmissive insulating material such as glass or plastic.

  2 is a plan view of the light emitting panel 20 as viewed from the side opposite to the photosensitive drum 110 (upper side of FIG. 1), and FIG. 3 is a cross-sectional view taken along the line III-III in FIG. As shown in FIGS. 2 and 3, a plurality of light emitting elements E each emitting light under the control of the control device 50 are disposed on the surface of the substrate 21 opposite to the photosensitive drum 110. . These light emitting elements E are arranged in two rows and zigzag along the direction of the rotation axis of the photosensitive drum 110 (longitudinal direction of the substrate 21). The control device 50 selectively causes each of the plurality of light emitting elements E to emit light according to the form of an image to be printed on a recording material such as paper. As indicated by arrows in FIG. 3, the light emitted from each light emitting element E passes through the substrate 21 and then reaches the image forming surface 110A of the photosensitive drum 110 from the converging lens array 40 (bottom emission type). By this exposure, a latent image (electrostatic latent image) corresponding to a desired image is formed on the image forming surface 110A. In addition, the pattern of the arrangement | sequence of the light emitting element E is arbitrary, For example, a single row or 3 or more rows may be sufficient, and another suitable pattern may be sufficient.

  As shown in FIG. 3, each light emitting element E has a structure in which a first electrode 22, a light emitting layer 25, and a second electrode 27 are laminated in this order from the substrate 21 side. Among these, the 1st electrode 22 is an electrode formed mutually spaced apart for every light emitting element E, and functions as an anode of the light emitting element E. FIG. The first electrode 22 in the present embodiment is formed of a light transmissive conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).

  A bank layer 23 is formed of an insulating material on the surface of the substrate 21 on which the first electrode 22 is formed. The bank layer 23 is a partition wall formed in a lattice shape so as to partition the space on the surface of the substrate 21 for each light emitting element E. The light emitting layer 25 is formed in a space (concave portion) surrounded by the inner wall of the bank layer 23 and having the first electrode 22 as a bottom surface.

  The second electrode 27 is a conductive film body that is continuously distributed over the plurality of light emitting elements E so as to cover the bank layer 23 and each light emitting layer 25, and functions as a cathode of the light emitting element E. The second electrode 27 is formed of a light-reflective material such as a single metal such as aluminum or silver or an alloy mainly containing these metals. The light emitted from the light emitting layer 25 to the side opposite to the substrate 21 is reflected by the surface of the second electrode 27 and used for exposure of the image forming surface 110A.

  The light emitting layer 25 is a film body made of an organic EL material, and emits light with luminance according to a potential difference between the first electrode 22 and the second electrode 27 (in other words, a current flowing between the first electrode 22 and the second electrode 27). To do. A structure in which a hole injection layer or a hole transport layer is interposed between the light emitting layer 25 and the first electrode 22, or an electron injection layer or an electron transport layer between the light emitting layer 25 and the second electrode 27. It is good also as a structure in which is inserted. That is, it is sufficient if the light emitting layer 25 is interposed between the first electrode 22 and the second electrode 27 facing each other.

  As illustrated in FIGS. 2 and 3, the sealing body 29 is bonded to the surface of the substrate 21 with, for example, an adhesive so as to cover (seal) the plurality of light emitting elements E. The sealing body 29 is a substantially rectangular plate having an outer dimension smaller than that of the substrate 21, and cooperates with the substrate 21 to isolate the plurality of light emitting elements E from the outside air (particularly moisture and oxygen).

  By the way, the characteristic of the light emitting layer 25 in this embodiment changes according to the temperature. For example, the time from when the voltage is applied to the light emitting layer 25 until the luminance of the light emission reaches a predetermined value is longer as the temperature of the light emitting layer 25 is lower (in other words, the light is emitted more quickly as the temperature is higher). Accordingly, the amount of light emitted from the light emitting panel 20 to the photosensitive drum 110 depends on the temperature of the light emitting layer 25 of each light emitting element E. The light emitting device 10 according to the present embodiment is as shown in FIGS. 1 to 3 in order to maintain the light emitting layer 25 at a temperature within a predetermined range and maintain the amount of light irradiated to the photosensitive drum 110 at a predetermined value. Are provided with a temperature sensor 32, an electric heating element 34, and a cooling element 36. Although FIG. 2 is a plan view, hatching in the same manner as the cross-sectional view of FIG. 3 is applied to the electric heating body 34 and the cooling body 36 for convenience.

  As shown in FIG. 2, the temperature sensor 32 is disposed adjacent to the light emitting element E in a region of the substrate 21 covered with the sealing body 29. The temperature sensor 32 is a means for detecting the temperature of each light emitting element E or its surroundings (that is, the temperature in the space surrounded by the substrate 21 and the sealing body 29), and depends on the ambient temperature of itself. A sensor (for example, a thermistor) that outputs a signal. In addition, the temperature sensor 32 should just be installed in the location where temperature changes according to the temperature of the light emitting element E, and the position is not limited to the illustration of FIG. For example, the temperature sensor 32 may be disposed on a region 201 (see FIG. 3) protruding from the outer peripheral edge of the sealing body 29 in the substrate 21, a side end surface of the substrate 21, or a surface facing the photosensitive drum 110. However, it may be fixed to any part of the sealing body 29.

  As shown in FIGS. 2 and 3, the electric heating body 34 is disposed in a region 201 of the substrate 21 that protrudes from the outer peripheral edge of the sealing body 29. The electric heating element 34 is means for heating each light emitting element E under the control of the control device 50. As shown in FIG. 2, the electric heating body 34 in the present embodiment is a wiring formed in a shape surrounding a set of a plurality of light emitting elements E along the periphery of the substrate 21 (in other words, a shape surrounding the sealing body 29). (Heating wire), and generates heat (Joule heat) according to the current supplied from the control device 50 to each end 341. Depending on whether or not current is supplied from the control device 50, the electric heating element 34 is alternatively selected from an operating state in which each light emitting element E is heated and a non-operating state in which each light emitting element E is not heated. Controlled.

  The electric heating elements 34 are formed at positions separated from the respective light emitting elements E. The light emitting elements E are heated by conduction of radiant heat from the electric heating elements 34 to the light emitting elements E through the substrate 21. As described above, according to the configuration in which the electric heating body 34 indirectly heats each light emitting element E, each electric heating body 34 in contact with each light emitting element E heats each light emitting element E directly. It is possible to effectively prevent overheating of the light emitting element E and deterioration of characteristics due to this.

  The electric heating element 34 of the present embodiment is formed of the same layer as the first electrode 22 having a higher resistivity than the second electrode 27. That is, in the manufacturing process of the light emitting panel 20, first, a single conductive film that covers the substrate 21 is formed of, for example, ITO (Indium Tin Oxide), and secondly, the first electrode 22 of the conductive film. The first electrode 22 and the electric heater 34 are collectively formed in one process by selectively removing the portion excluding the electric heater 34 and the electric heater 34. According to this structure, compared with the case where the 1st electrode 22 and the electrothermal body 34 are formed in a separate process, the simplification of a manufacturing process and the reduction of the manufacturing cost by this can be implement | achieved.

  Further, the amount of heat radiated from the electric heater 34 is proportional to the resistance of the electric heater 34. In this embodiment, since the electric heating body 34 can be made to have a high resistance by forming the electric heating body 34 from the same layer as the first electrode 22 having a higher resistivity than the second electrode 27, Compared with the case where the electric heating element 34 is formed from the same layer, a sufficient amount of heat generated by the electric heating element 34 can be secured.

  As shown in FIGS. 2 and 3, the cooling body 36 is installed on the surface of the sealing body 29 opposite to the substrate 21. The cooling body 36 is a means for cooling each light emitting element E under the control of the control device 50. The cooling body 36 in the present embodiment is a Peltier module in which a plurality of Peltier elements having a structure in which a P-type thermoelectric semiconductor and an N-type thermoelectric semiconductor are connected in series are arranged in a planar shape. The cooling body 36 of this structure is selected between an operating state in which each light emitting element E is cooled and a non-operating state in which each light emitting element E is not cooled depending on whether or not current is supplied from the control device 50. It is controlled uniformly.

<B: Operation>
As described above, the control device 50 according to the present embodiment controls the light emission of each light emitting element E according to a desired image, and also maintains the temperature of each light emitting element E within a predetermined range as shown in FIG. The timer interrupt process is repeatedly executed. The process shown in FIG. 5 is executed in response to a timer interrupt that occurs at a predetermined interval.

  When the timer interruption process is started, the control device 50 first detects the temperature T around the temperature sensor 32 based on the signal output from the temperature sensor 32 (step S1). Next, the control device 50 determines whether or not the detected temperature (hereinafter referred to as “detected temperature”) T is lower than a predetermined temperature T1 (step S2). The temperature T1 is a lower limit value of a target range of the temperature T. When the result in step S2 is affirmative (T <T1), the control device 50 operates the electric heating element 34 for a predetermined time by supplying power to the electric heating element 34 (step S3). Each light emitting element E is heated by the operation of the electric heating element 34. On the other hand, when the result of the determination in step S2 is negative (T ≧ T1), the control device 50 shifts the process to step S4 without passing through step S3. At this time, each light emitting element E is not heated.

  In step S4, the control device 50 determines whether or not the detected temperature T in step S1 exceeds a predetermined temperature T2. This temperature T2 is the upper limit (T2> T1) of the target range of the detected temperature T. If the result of the determination in step S4 is affirmative (T> T2), the control device 50 operates the cooling body 36 for a predetermined time by supplying power to the cooling body 36 (step S5), and then the current timer End the interrupt process. Each light emitting element E is cooled by the operation of the cooling body 36. On the other hand, when the result of the determination in step S4 is negative (T ≦ T2), the control device 50 ends the timer interrupt process without passing through step S5. At this time, each light emitting element E is not cooled.

  By repeating the above-described timer interrupt processing, the temperature T of each light emitting element E (more precisely, the temperature T detected by the temperature sensor 32) converges in the range of the temperature T1 or more and the temperature T2 or less ( T1 ≦ T ≦ T2). As described above, according to the present embodiment, each light emitting element E is quickly and surely adjusted to a desired temperature as compared with the conventional configuration in which the electric heating body 34 and the cooling body 36 are not disposed. The characteristics of the element E (particularly the time from application of voltage to actual light emission) can be maintained at the desired characteristics regardless of the temperature of the environment in which the light emitting device 10 is used. Therefore, according to the present embodiment, it is possible to form a uniform latent image by controlling the exposure amount of the image forming surface 110A of the photosensitive drum 110 to a predetermined value with high accuracy, and furthermore, a recording material such as paper It is possible to maintain the image formed in the desired quality.

<C: Modification>
Various modifications can be made to the above embodiment. An example of a specific modification is as follows. In addition, you may combine each following aspect suitably.

(1) Modification 1
In the above embodiment, the configuration in which one temperature sensor 32 is installed in the light emitting device 10 is illustrated, but a configuration in which a plurality of temperature sensors 32 is installed may be employed. Each of these temperature sensors 32 is distributed and installed at different positions. In this configuration, the control device 50 controls the electric heating body 34 and the cooling body 36 based on the temperature T detected by each of the temperature sensors 32. For example, the control device 50 operates the electric heating element 34 when the temperature T detected by at least one temperature sensor 32 of the plurality of temperature sensors 32 is lower than the temperature T1, and the temperature T detected by at least one temperature sensor 32 is When the temperature T2 is exceeded, the cooling body 36 is operated.

  Moreover, in the aspect in which the several temperature sensor 32 was installed, it is good also as a structure provided with several electric heating body 34 corresponding to the separate temperature sensor 32, respectively. Each electric heating element 34 is installed in the vicinity of the temperature sensor 32 corresponding to this. In this configuration, the control device 50 identifies the temperature sensor 32 whose detected temperature T is lower than the temperature T1, and selectively activates only the electric body 34 corresponding to the identified temperature sensor 32 among the plurality of electric bodies 34. . Similarly, it is good also as a structure provided with the some cooling body 36 which is located in the vicinity of the separate temperature sensor 32, respectively. In this configuration, the control device 50 selectively activates only the cooling body 36 located in the vicinity of the temperature sensor 32 in which the detected temperature T exceeds the temperature T2. According to the above configuration, the temperature of each light emitting element E can be set to high accuracy even in a configuration in which a plurality of light emitting elements E are distributed over a wide range (that is, a configuration in which the temperature of each light emitting element E is likely to vary). It is possible to control the temperature within a predetermined range.

(2) Modification 2
In the above embodiment, the configuration in which the temperature T1 that is the threshold value for operating the electric heating body 34 and the temperature T2 that is the threshold value for operating the cooling body 36 is different is illustrated, but compared with the detected temperature T in step S2. The temperature T1 and the temperature T2 compared with the detected temperature T in step S4 may be equal. According to this configuration, the temperature of each light emitting element E can be converged to a specific temperature (T1 = T2) with high accuracy.

(3) Modification 3
In the above embodiment, the configuration in which both the electric heating body 34 and the cooling body 36 are controlled based on the detected temperature T is exemplified. However, both the electric heating body 34 and the cooling body 36 are controlled based on the detected temperature T. It does not necessarily have to be done. For example, the electric heating body 34 may be operated at any time (for example, at a predetermined interval) regardless of the detected temperature T, and the cooling body 36 may be controlled based on the detected temperature T. The body 36 may be operated regardless of the detected temperature T and the electric heater 34 may be controlled based on the detected temperature T.

(4) Modification 4
In the above embodiment, the configuration in which the control device 50 that controls the light emission of each light emitting element E also executes the control of the electric heater 34 and the cooling body 36 is exemplified. And may be controlled by separate devices. Further, the electric heating body 34 and the cooling body 36 may be controlled by separate devices.

(5) Modification 5
In the above embodiments, the first electrode 22 functions as an anode and the second electrode 27 functions as a cathode. On the contrary, the first electrode 22 functions as a cathode and the second electrode. 27 may function as an anode. Further, in the embodiment, the bottom emission type light emitting panel 20 is exemplified, but the present invention is also applied to a top emission type light emitting panel. In the top emission type light emitting panel, a cooling body 36 is installed on the surface of the substrate 21 opposite to the sealing body 29.

<D: Electronic equipment>
<D-1: Image forming apparatus>
Next, with reference to FIG. 5, an image forming apparatus which is one aspect of the electronic apparatus according to the invention will be described. This image forming apparatus is a tandem type full-color image forming apparatus using a belt intermediate transfer body system.

  In this image forming apparatus, four light emitting devices (exposure devices) 10K, 10C, 10M, and 10Y each having the same configuration are provided with four photosensitive drums (image carriers) 110K having the same configuration. , 110C, 110M, and 110Y are disposed at positions facing the image forming surface 110A. The light emitting devices 10K, 10C, 10M, and 10Y are the light emitting devices 10 according to the embodiments exemplified above.

  As shown in FIG. 5, the image forming apparatus is provided with a driving roller 121 and a driven roller 122. An endless intermediate transfer belt 120 is wound around these rollers 121 and 122, and an arrow indicates. As shown, the periphery of the rollers 121 and 122 is rotated. Although not shown, tension applying means such as a tension roller that applies tension to the intermediate transfer belt 120 may be provided.

  Around the intermediate transfer belt 120, four photosensitive drums 110K, 110C, 110M, and 110Y each having a photosensitive layer on the outer peripheral surface are arranged at a predetermined interval. The subscripts “K”, “C”, “M”, and “Y” mean that they are used to form black, cyan, magenta, and yellow visible images, respectively. The same applies to other members. The photosensitive drums 110K, 110C, 110M, and 110Y are rotationally driven in synchronization with the driving of the intermediate transfer belt 120.

  Around each photosensitive drum 110 (K, C, M, Y), there is a corona charger 111 (K, C, M, Y), a light emitting device 10 (K, C, M, Y), and a developing unit. 114 (K, C, M, Y) are arranged. The corona charger 111 (K, C, M, Y) uniformly charges the image forming surface 110A (outer peripheral surface) of the corresponding photosensitive drum 110 (K, C, M, Y). The light emitting device 10 (K, C, M, Y) writes an electrostatic latent image on the charged image forming surface 110A of each photosensitive drum. In each light emitting device 10 (K, C, M, Y), as shown in FIG. 2, a plurality of light emission is performed along the bus (main scanning direction) of the photosensitive drum 110 (K, C, M, Y). Elements E are arranged. The electrostatic latent image is written by irradiating the photosensitive drum 110 (K, C, M, Y) with light by a plurality of light emitting elements E. The developing device 114 (K, C, M, Y) attaches toner as a developer to the electrostatic latent image to thereby develop a visible image (that is, a visible image) on the photosensitive drum 110 (K, C, M, Y). ).

  The black, cyan, magenta, and yellow developed images formed by the four-color single-color image forming station are superimposed on the intermediate transfer belt 120 by sequentially being sequentially transferred onto the intermediate transfer belt 120. As a result, a full-color visible image is formed. Four primary transfer corotrons (transfer devices) 112 (K, C, M, Y) are arranged inside the intermediate transfer belt 120. The primary transfer corotron 112 (K, C, M, Y) is disposed in the vicinity of the photosensitive drum 110 (K, C, M, Y), and the photosensitive drum 110 (K, C, M, Y). The electrostatic image is electrostatically attracted from the toner image to transfer the visible image to the intermediate transfer belt 120 passing between the photosensitive drum and the primary transfer corotron.

  A sheet 102 as an object (recording material) on which an image is to be finally formed is fed one by one from the sheet feeding cassette 101 by the pickup roller 103 and is subjected to secondary transfer with the intermediate transfer belt 120 in contact with the driving roller 121. Sent to the nip between the rollers 126. The full-color visible image on the intermediate transfer belt 120 is secondarily transferred to one side of the sheet 102 by the secondary transfer roller 126 and fixed on the sheet 102 through the fixing roller pair 127 as a fixing unit. . Thereafter, the sheet 102 is discharged onto a paper discharge cassette formed in the upper part of the apparatus by a paper discharge roller pair 128.

  Next, another embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This image forming apparatus is a rotary developing type full-color image forming apparatus using a belt intermediate transfer body system. As shown in FIG. 6, a corona charger 168, a rotary developing unit 161, the light emitting device 10 according to the above embodiment, and an intermediate transfer belt 169 are provided around the photosensitive drum 110. Yes.

  The corona charger 168 uniformly charges the outer peripheral surface of the photosensitive drum 110. The light emitting device 10 writes an electrostatic latent image on the charged image forming surface 110 </ b> A (outer peripheral surface) of the photosensitive drum 110. In the light emitting device 10, as shown in FIG. 2, a plurality of light emitting elements E are arranged along the bus (main scanning direction) of the photosensitive drum 110. The electrostatic latent image is written by irradiating the photosensitive drum 110 with light from the light emitting elements E.

  The developing unit 161 is a drum in which four developing units 163Y, 163C, 163M, and 163K are arranged at an angular interval of 90 °, and can rotate counterclockwise about the shaft 161a. The developing units 163Y, 163C, 163M, and 163K supply yellow, cyan, magenta, and black toner to the photosensitive drum 110, respectively, and attach the toner as a developer to the electrostatic latent image, thereby causing the photosensitive drum 110 to adhere. A visible image (ie, a visible image) is formed.

  The endless intermediate transfer belt 169 is wound around a driving roller 170a, a driven roller 170b, a primary transfer roller 166, and a tension roller, and is rotated around these rollers in a direction indicated by an arrow. The primary transfer roller 166 transfers the visible image to the intermediate transfer belt 169 that passes between the photosensitive drum 110 and the primary transfer roller 166 by electrostatically attracting the visible image from the photosensitive drum 110.

  Specifically, in the first rotation of the photosensitive drum 110, an electrostatic latent image for a yellow (Y) image is written by the light emitting device 10, and a developed image of the same color is formed by the developing device 163Y. The image is transferred to the transfer belt 169. Further, in the next rotation, an electrostatic latent image for a cyan (C) image is written by the light emitting device 10 and a developed image of the same color is formed by the developing device 163C, and an intermediate transfer is performed so as to overlap the yellow developed image. Transferred to the belt 169. Then, during the four rotations of the photosensitive drum 110 in this manner, the yellow, cyan, magenta, and black visible images are sequentially superimposed on the intermediate transfer belt 169, and as a result, a full-color visible image is formed on the transfer belt 169. Formed on top. When images are finally formed on both sides of a sheet as an object on which an image is to be formed, the same color images of the front and back surfaces are transferred to the intermediate transfer belt 169, and then the front and back surfaces are transferred to the intermediate transfer belt 169. A full-color visible image is formed on the intermediate transfer belt 169 in such a manner that the visible image of the next color is transferred.

  The image forming apparatus is provided with a sheet conveyance path 174 through which a sheet passes. The sheets are picked up one by one from the paper feed cassette 178 by the pick-up roller 179, advanced through the sheet transport path 174 by the transport roller, and between the intermediate transfer belt 169 and the secondary transfer roller 171 in contact with the drive roller 170a. Pass through the nip. The secondary transfer roller 171 transfers the developed image to one side of the sheet by electrostatically attracting a full-color developed image from the intermediate transfer belt 169 collectively. The secondary transfer roller 171 can be moved closer to and away from the intermediate transfer belt 169 by a clutch (not shown). The secondary transfer roller 171 is brought into contact with the intermediate transfer belt 169 when a full-color visible image is transferred onto the sheet, and is separated from the secondary transfer roller 171 while the visible image is superimposed on the intermediate transfer belt 169.

  The sheet on which the image has been transferred as described above is conveyed to the fixing device 172 and is passed between the heating roller 172a and the pressure roller 172b of the fixing device 172, whereby the visible image on the sheet is fixed. The sheet after the fixing process is drawn into the discharge roller pair 176 and proceeds in the direction of arrow F. In the case of double-sided printing, after most of the sheet passes through the paper discharge roller pair 176, the paper discharge roller pair 176 is rotated in the reverse direction and introduced into the double-sided printing conveyance path 175 as indicated by an arrow G. The Then, the visible image is transferred to the other surface of the sheet by the secondary transfer roller 171, the fixing process is performed again by the fixing device 172, and then the sheet is discharged by the discharge roller pair 176.

  The image forming apparatus illustrated in FIGS. 5 and 6 uses the light emitting element E including the light emitting layer 25 made of an organic EL material as a light source (exposure means), so that the apparatus is more than the case where a laser scanning optical system is used. Is miniaturized. Note that the light-emitting device of the present invention can also be adopted in an electrophotographic image forming apparatus other than those exemplified above. For example, the light emitting device according to the present invention is also applied to an image forming apparatus that directly transfers a visible image from a photosensitive drum to a sheet without using an intermediate transfer belt, and an image forming apparatus that forms a monochrome image. Can be applied.

<D-2: Image Reading Device>
The light emitting device 10 according to the above embodiment is used in an image reading apparatus as a line type optical head for irradiating light to a reading target. As such an image reading apparatus, there is a scanner, a copying unit of a copying machine or a facsimile, a barcode reader, or a two-dimensional image code reader for reading a two-dimensional image code such as a QR code (registered trademark).

  FIG. 7 is a cross-sectional view illustrating a configuration of an image reading apparatus using the light emitting device 10 as a line type optical head. A flat platen glass 602 is provided on the upper part of the cabinet 601 of the image reading apparatus, and a document 603 to be read is placed on the platen glass 602 with its image surface facing downward. A platen cover (not shown) presses the document 603 toward the platen glass 602.

  Inside the cabinet 601, a high-speed carriage 604 and a low-speed carriage 605 are arranged so as to be movable in the horizontal direction. The light-emitting device 10 that irradiates the original 603 and the reflecting mirror 607 are mounted on the high-speed carriage 604, and two reflecting mirrors 608 and 609 are mounted on the low-speed carriage 605. The light emitting device 10 and the three reflecting mirrors (607, 608, 609) extend in a direction (main scanning direction) perpendicular to the paper surface of FIG. In addition, the light emitting device 10 is installed such that the arrangement direction of the plurality of light emitting elements E is along the main scanning direction.

  A document reader 610 is fixed inside the cabinet 601. The document reader 610 includes an imaging lens 612 that forms an image of light emitted from the low-speed carriage 605, and a line sensor (light receiving device) 613 in which a large number of light receiving elements are arranged. The line sensor 613 extends in a direction (main scanning direction) perpendicular to the paper surface of FIG. 7, and is installed so that the direction of arrangement of the plurality of light receiving elements is along the main scanning direction.

  Light emitted from the light emitting device 10 passes through the platen glass 602 and is reflected by the lower surface of the document 603. Reflected light from the original 603 passes through the platen glass 602, is sequentially reflected by the three reflecting mirrors (607, 608, 609), passes through the imaging lens 612, and is imaged by the line sensor 613. To do. The high-speed carriage 604 moves in the horizontal direction to irradiate the entire surface of the original 603 with the light emitting device 10, and the low-speed carriage 605 moves at half the speed of the high-speed carriage 604, and the optical path length from the original 603 to the line sensor 613 Is maintained substantially constant.

  The configuration of the image reading apparatus in which the light emitting device of the present invention is adopted is not limited to that shown in FIG. For example, the light receiving device may move together with the light emitting device 10 as the illumination device, or the reading target may be moved and read after both the light receiving device and the light emitting device 10 are fixed.

<D-3: Others>
Note that the use of the light-emitting device according to the present invention is not limited to exposure. For example, the light-emitting device of the present invention can be used as display devices for various electronic devices. Examples of electronic devices in which the light emitting device of the present invention is used as a display device include a portable personal computer, a mobile phone, a personal digital assistant (PDA), a digital still camera, a television, a video camera, and a car navigation system. Examples include a device, a pager, an electronic notebook, electronic paper, a calculator, a word processor, a workstation, a videophone, a POS terminal, a printer, a scanner, a copying machine, a video player, and a device equipped with a touch panel.

It is a perspective view which shows the structure of the light-emitting device and photoreceptor drum in embodiment of this invention. It is a top view which shows the structure of the light emission panel when it sees from the opposite side to a photoconductive drum. It is sectional drawing seen from the III-III line in FIG. It is a flowchart which shows operation | movement of a control apparatus. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus that is an example of an electronic apparatus according to the invention. It is sectional drawing which shows the structure of the image forming apparatus which concerns on another form. 1 is a cross-sectional view illustrating a configuration of an image reading apparatus that is an example of an electronic apparatus according to the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light emitting device, 20 ... Light emitting panel, E ... Light emitting element, 21 ... Substrate, 22 ... First electrode, 23 ... Bank layer, 25 ... Light emitting layer, 27 ... Second electrode, 29 ... Sealed body, 32 ... Temperature sensor, 34 ... Electric heating body (heating means), 36 ... Cooling body (cooling means), 40 ... Converging lens array, 50 ... Control device, 110 ... Photosensitive Body drum.

Claims (12)

A light-emitting panel in which a plurality of light-emitting elements are arranged on the surface of the substrate;
A light emitting device comprising: heating means for heating each light emitting element. The light emitting device according to claim 1, wherein the heating unit is an electric heating body installed on the light emitting panel. The light emitting device according to claim 2, wherein the electric heating body is disposed on a surface of the substrate on which the light emitting elements are arranged. Each of the light emitting elements includes a first electrode and a second electrode facing each other, and a light emitting layer interposed between the first electrode and the second electrode,
The light emitting device according to claim 3, wherein the electric heating body is formed from the same layer as one of the first electrode and the second electrode. The light emitting device according to claim 4, wherein the electric heating body is formed of the same layer as an electrode made of a material having a high resistivity among the first electrode and the second electrode. The light emitting device according to any one of claims 2 to 5, wherein the electric heating body is formed in a shape surrounding a set of the plurality of light emitting elements. The light-emitting panel includes a sealing body that is bonded to the substrate and covers the light-emitting elements,
The light emitting device according to any one of claims 2 to 5, wherein the electric heating body is formed in a region of the substrate on which the light emitting elements are arranged and not covered with the sealing body. . Temperature detecting means for detecting the temperature of each light emitting element or its surroundings;
The light-emitting device according to any one of claims 1 to 7, further comprising: a control unit that operates the heating unit when the temperature detected by the temperature detection unit is lower than a predetermined threshold value. Temperature detecting means for detecting the temperature of each light emitting element or its surroundings;
Cooling means for cooling each light emitting element;
The light-emitting device according to claim 1, further comprising a control unit that activates the cooling unit when the temperature detected by the temperature detection unit exceeds a predetermined threshold value. Temperature detecting means for detecting the temperature of each light emitting element or its surroundings;
Cooling means for cooling each light emitting element;
Control means for operating the heating means when the temperature detected by the temperature detection means falls below a predetermined threshold, and for operating the cooling means when the temperature detected by the temperature detection means exceeds a predetermined threshold; The light emitting device according to any one of claims 1 to 7, further comprising: The light emitting device according to claim 9 or 10, wherein the cooling unit is installed on a surface opposite to the substrate in a sealing body that is bonded to the substrate and covers the light emitting elements. The electronic device which comprises the light-emitting device in any one of Claims 1-11.

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