JP2007050595A - Light quantity controller and method for controlling light quantity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light quantity controller capable of maintaining the light quantity of an organic EL device at a constant level without directly monitoring the lowering of the light quantity by using a sensor or the like, and a method for controlling the light quantity. <P>SOLUTION: This light quantity controller comprises an organic EL device 12, a memory 13 storing a setting value for allowing the organic EL device 12 to emit a light in a level corresponding to the accumulated light emission time period of the organic EL device 12, and a CPU 11 that determines the setting value to be applied to the organic EL device 12 by referencing the memory 13 based on the accumulated light emission time period and applies the determined setting value to the organic EL device 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light amount control device and a light amount control method for controlling an exposure amount to an organic EL element in an exposure apparatus that is used for a printer, a digital copying machine, a facsimile, and the like and performs exposure using an organic EL element. .

  When an organic EL element is used as an exposure apparatus for a print head (for example, Patent Document 1), the amount of light emitted from the organic EL element is significantly reduced according to the accumulated light emission time, and the light quantity deterioration of the organic EL element is a big problem. .

  For this reason, it is necessary to keep the light emission amount constant by changing the current or voltage applied to the organic EL element, the duty ratio of the current, or the value of the voltage duty ratio in accordance with the decrease in the light emission amount of the organic EL element.

At this time, if the light emission amount itself can be monitored, a decrease in the light emission amount can be detected from the output value, and the light emission amount can be kept constant. However, it has been difficult to implement monitoring with a printing apparatus based on high efficiency and low cost.
JP 2003-94729 A

  There is no means to detect the decrease in the amount of light emission due to deterioration of the organic EL element other than by directly monitoring the light emission amount using a sensor or the like, and it is difficult to maintain the light emission amount in a printing apparatus premised on cost reduction. there were. As a result, in a print head using an organic EL element as an exposure apparatus, it has been difficult to maintain a uniform print image quality.

  An object of the present invention is to provide a light amount control device and a light amount control method that maintain a constant light emission amount without directly monitoring a decrease in the light emission amount of an organic EL element using a sensor or the like.

  The present invention provides an organic EL element, a storage means for storing a set value for causing the organic EL element to emit light according to the accumulated light emission time of the organic EL element, and a storage means based on the accumulated light emission time of the organic EL element. The control unit is configured to determine a set value to be given to the organic EL element with reference, and to give the decided set value to the organic EL element.

  Thereby, the setting value for making an organic EL element light-emit can be changed according to the accumulation light emission time of an organic EL element.

  According to the present invention, the amount of light emitted from the organic EL element can be easily controlled without directly monitoring it with a sensor or the like, and a uniform amount of light emitted from the organic EL element can be obtained over time. . In particular, by using the light quantity control device of the present invention as an exposure device of an image forming apparatus, it is possible to provide a stable image forming apparatus at low cost.

  The invention according to claim 1 of the present application relates to an organic EL element, storage means for storing a set value for causing the organic EL element to emit light according to the accumulated light emission time of the organic EL element, and the accumulated light emission time of the organic EL element. Based on this, a setting value to be given to the organic EL element is determined with reference to the storage means, and a control means for giving the determined setting value to the organic EL element is provided.

  Thereby, the setting value for making an organic EL element light-emit can be changed according to the accumulation light emission time of an organic EL element.

  The invention according to claim 2 of the present application is configured such that, in the invention according to claim 1, the set value includes at least one of a current value, a voltage value, a current duty ratio, and a voltage duty ratio.

  Thereby, the setting value for making an organic EL element light-emit can be changed according to the accumulation light emission time of an organic EL element.

  The invention according to claim 3 of the present application is the invention according to claim 1, wherein the organic EL light-emitting element constitutes an exposure apparatus for forming an electrostatic latent image on the image carrier in the image forming apparatus. did.

  Accordingly, the set value for causing the organic EL element to emit light can be changed according to the accumulated light emission time of the organic EL element, and stable quality printing can be performed in the image forming apparatus using the exposure apparatus. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
In the organic EL element, the light emission luminance is lowered according to the accumulated light emission time, and the light emission luminance is suddenly lowered after a certain time to reach its lifetime. The miracle of the light emission luminance with respect to the cumulative light emission time until the end of the lifetime is not significantly different in any element, and follows a very similar locus.

  In the present embodiment, paying attention to the above points, the accumulated light emission time and the maximum luminance value of the organic EL element at that time are set as a set, and information is stored in some memories in the case of different accumulated light emission times. Thus, the deterioration information of the organic EL element can be detected, and the current, voltage, current duty ratio, or voltage duty ratio value applied to the organic EL element is changed according to the accumulated light emission time. Thus, the light emission amount is kept constant, and the print image quality is kept constant.

  This will be described in detail below.

  FIG. 1 is a block diagram showing a configuration of a light amount control apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, the CPU 11 gives a drive signal Sig <b> 1 to the organic EL element 12. The luminance value of the organic EL element 12 is configured to vary according to the drive signal Sig1.

  In FIG. 1, one organic EL element 12 and one drive signal Sig1 to be given to the organic EL element 12 are described. However, the organic EL element 12 and the drive signal Sig1 only need to exist in the same number of sets, It is not limited to one.

  A memory 13 stores necessary information when the CPU 11 executes the program. Although FIG. 1 shows the form of the internal memory of the CPU 11, the form is not limited to this form and may be outside the CPU 11.

  Note that the light amount control device shown in FIG. 1 is practically effective when used in an image forming apparatus such as an exposure device that forms an electrostatic latent image on an image carrier.

  FIG. 2 is a flowchart for explaining the flow of light amount correction in the first embodiment of the present invention.

  In FIG. 2, the relationship between the accumulated light emission time and the luminance value of the organic EL element 12 is measured (step 21), and the current value applied to the organic EL element 12 is determined (step 22).

  Next, the current value determined in step 22 is stored in the memory 13 of the CPU 11 (step 23). When causing the organic EL element 12 to emit light, the CPU 11 refers to the memory 13 based on the accumulated light emission time so far, determines a current value to be given to the organic EL element 12, and sets it to the drive signal Sig1.

  FIG. 3 is a diagram showing the relationship between the cumulative light emission time and the luminance value of the organic EL element according to Embodiment 1 of the present invention, and is a visualization of the result of step 21 in FIG.

  As shown in FIG. 3, the maximum luminance value of the organic EL element 12 decreases greatly at the beginning with the increase of the cumulative light emission time, but thereafter, the stable maximum luminance value is maintained, and the maximum luminance value is reached as the lifetime approaches. Fell greatly.

  FIG. 4 is a diagram showing the relationship between the accumulated light emission time and the current value of the organic EL element in the first embodiment of the present invention, and visualizes the result of step 22 in FIG.

  As shown in FIG. 4, the luminance is made constant according to the cumulative light emission time of the organic EL element 12 based on the data indicating the relationship between the cumulative light emission time and the luminance value of the organic EL element 12 shown in FIG. 3. The relationship with the current value necessary for maintaining is determined in advance.

  FIG. 5 is an operation flowchart of the light quantity control device according to the first embodiment of the present invention, and shows the operation of the CPU 11 when driving the organic EL element 12.

  In FIG. 5, the CPU 11 refers to the memory 13 in the CPU 11 and grasps the accumulated light emission time of all the organic EL elements 12 at that time, and determines the drive signal Sig1 as follows.

  When the drive signal Sig1 is given to the organic EL element 12, it is determined whether or not the accumulated light emission time at that time is within 10 hours (step 41). If the determination result shows that the accumulated light emission time is less than 10 hours, 50 [μA] is set in the drive signal Sig1 (step 42).

  If the result of determination in step 41 is that the accumulated light emission time is 10 hours or longer, it is subsequently determined whether or not the accumulated light emission time is less than 60 hours (step 43). If the determination result shows that the accumulated light emission time is less than 60 hours, 55 [μA] is set in the drive signal Sig1 (step 44).

  If the result of determination in step 43 is that the accumulated light emission time is 60 hours or longer, it is subsequently determined whether or not the accumulated light emission time is less than 110 hours (step 45). If the determination result shows that the accumulated light emission time is less than 110 hours, 65 [μA] is set in the drive signal Sig1 (step 46).

  If the result of determination in step 45 is that the accumulated light emission time is 110 hours or longer, it is subsequently determined whether or not the accumulated light emission time is less than 160 hours (step 47). If the determination result shows that the accumulated light emission time is less than 160 hours, 85 [μA] is set in the drive signal Sig1 (step 48).

  If the result of determination in step 47 is that the accumulated light emission time is 160 hours or longer, 100 [μA] is set in the drive signal Sig1 (step 49). Subsequently, it is determined whether or not the accumulated light emission time is less than 190 hours (step 50), and if it is 190 hours or more, it is notified that the life of the organic EL element 12 is near (step 51).

  As described above, by creating a relationship between the cumulative light emission time of the organic EL element 12 and the current value applied to the organic EL element 12 in advance, a reduction in the amount of light due to deterioration of the organic EL element 12 is prevented, and the element lifetime is increased. The amount of light can be kept constant until approaching. As a result, the print quality of the print head can be maintained.

  In the present embodiment, the current value is set to Sig1 in order to drive the organic EL element 12. However, the current value is not limited to this, and the voltage value or the PWM signal with the voltage duty ratio changed, Further, a PWM signal or the like in which the duty ratio of the current is changed may be set.

  Since the light quantity control device according to the present invention can change the set value for causing the organic EL element to emit light according to the accumulated light emission time of the organic EL element, it can obtain a stable print quality when used as an exposure device. It is useful for an image forming apparatus.

The block diagram which shows the structure of the light quantity control apparatus in Embodiment 1 of this invention. Flowchart for explaining the flow of light amount correction in Embodiment 1 of the present invention The figure which shows the relationship between the cumulative light emission time of the organic EL element in Embodiment 1 of this invention, and a luminance value. The figure which shows the relationship between the accumulation light emission time of the organic EL element in Embodiment 1 of this invention, and an electric current value. Operation flow chart of light quantity control device in Embodiment 1 of the present invention

Explanation of symbols

11 CPU
12 Organic EL elements 13 Memory

Claims (5)

An organic EL light emitting element;
Storage means for storing a set value for causing the organic EL element to emit light according to a cumulative light emission time of the organic EL element;
Control means for determining a set value to be given to the organic EL element with reference to the storage means based on a cumulative light emission time of the organic EL element, and for giving the determined set value to the organic EL element. A light quantity control device characterized.   The light quantity control device according to claim 1, wherein the set value includes at least one of a current value, a voltage value, a current duty ratio, and a voltage duty ratio.   2. The light quantity control device according to claim 1, wherein the organic EL light-emitting element constitutes an exposure device for forming an electrostatic latent image on an image carrier in the image forming apparatus. Measuring a relationship between a cumulative light emission time of the organic EL element and a luminance value, and storing a setting value for causing the organic EL element to emit light according to the cumulative light emission time of the organic EL element;
Determining a set value to be given to the organic EL element with reference to the storage means based on the accumulated light emission time of the organic EL element;
Providing the determined set value to the organic EL element.   5. The light quantity control method according to claim 4, wherein the set value includes at least one of a current value, a voltage value, a current duty ratio, and a voltage duty ratio.

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