JP2011014255A - Light emitting device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated body having a structure capable of measuring emitted light quantity of a light emitting layer effectively, a light emitting device and an image forming device.SOLUTION: The laminated body is provided with a light emitting element and a light detecting element for detecting light emitted by the light emitting element, and the light detecting element has two gate electrodes, with one of the gate electrodes being an electrode equipped with the light emitting element.

Description

  The present invention relates to a light emitting device and an image forming apparatus.

  As this type of technology, for example, Patent Document 1 discloses a buffer memory in which correction data for correcting the amount of light emitted from the LED light emitting element is stored, the correction data is read from the buffer memory, and the LED light emitting element is turned on. Drive having output control means for outputting to the driver circuit together with the image data to be turned off, and LED drive means for driving more LED elements than the number of outputs of the driver circuit according to the correction data and image data inputted to the driver circuit A control device is disclosed.

JP-A-11-138890

  However, Patent Document 1 does not disclose a structure that can efficiently measure the amount of light emitted from a light emitting element (in particular, a light emitting layer). When measuring the amount of light emitted from the light emitting layer, it is desirable to be able to efficiently measure the amount of light emitted from the light emitting layer.

  In view of the above points, an object of the present invention is to provide a light emitting device and an image forming apparatus having a structure capable of efficiently measuring the amount of light emitted from a light emitting layer.

A light emitting device according to a first aspect of the present invention provides:
A light emitting element;
A light detecting element for detecting the light emitted by the light emitting element,
The photodetecting element comprises two gate electrodes,
One of the two gate electrodes is an electrode included in the light emitting element.

  The light emitting element and the light detection element may be formed in a stacked body.

  The other of the two gate electrodes may shield part of the light emitted from the light emitting element.

  The light detection region included in the light detection element may overlap the light emitting surface of the light emitting layer when viewed from the thickness direction of the light emitting layer of the light emitting element.

The light emitting device
A plurality of the light detection elements are provided,
Each gate electrode, each source electrode, and each drain electrode included in each of the light detection elements may be electrically connected.

  An image forming apparatus according to a second aspect of the present invention includes the light emitting device described above.

  The light emitting device and the image forming apparatus according to the present invention have a structure capable of efficiently measuring the amount of light emitted from the light emitting element.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic configuration diagram of a light emitting device according to a first embodiment of the present invention. It is an equivalent circuit diagram of the principal part of the light emitting device according to the first embodiment of the present invention. It is a timing chart which shows operation | movement of the optical detection of the light-emitting device which concerns on 1st embodiment of this invention. It is a principal part schematic diagram for demonstrating the structure of the laminated body which concerns on 1st embodiment of this invention. It is a principal part schematic sectional drawing for demonstrating the structure of the laminated body which concerns on 1st embodiment of this invention. It is a schematic block diagram of the light-emitting device which concerns on 2nd embodiment of this invention. It is a principal part schematic diagram for demonstrating the structure of the laminated body which concerns on 2nd embodiment of this invention. It is a principal part schematic sectional drawing for demonstrating the structure of the laminated body which concerns on 2nd embodiment of this invention. It is an equivalent circuit schematic of the principal part of the light-emitting device which concerns on 2nd embodiment of this invention. It is a schematic block diagram of the light-emitting device which concerns on 3rd embodiment of this invention. It is the equivalent circuit schematic of the principal part of the light-emitting device which concerns on 3rd embodiment of this invention. It is a timing chart which shows operation | movement of the optical detection of the light-emitting device which concerns on 3rd embodiment of this invention. It is a schematic block diagram of the light-emitting device which concerns on 4th embodiment of this invention. It is the equivalent circuit schematic of the principal part of the light-emitting device which concerns on 4th embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment and drawing. It goes without saying that the following embodiments and drawings can be modified without changing the gist of the present invention.

  In the following, an embodiment in which the light emitting element is an organic EL (Organic Electro-Luminescence) element will be described. However, the light emitting element may be another light emitting element (for example, an LED (Light Emitting Diode)). The organic EL element is sometimes called an organic light-emitting diode (OLED) or a light emitting polymer (LEP). Moreover, the laminated body which concerns on each following embodiment is used for a light-emitting device. The light emitting device is an exposure device (exposure head) or the like. The light emitting device is used in an image forming apparatus (for example, a printing apparatus or an electrophotographic apparatus). In addition, the use of the laminated body and light-emitting device which concern on this invention is not restricted to said use. In order to facilitate understanding of the present invention, the following embodiment will be described assuming that the image forming apparatus forms a monochrome image, but the image forming apparatus may form a color image. . Examples of the image forming apparatus that forms a color image include a tandem image forming apparatus. In this case, the image forming apparatus includes a plurality of (black, cyan, magenta, and yellow) light emitting devices, a photosensitive drum, and the like. Each light emitting device, photosensitive drum, and the like have substantially the same configurations as those in the following embodiments. Further, the lighting circuit described later may be a lighting circuit of an arbitrary method regardless of an active method / passive method, constant voltage writing / constant current writing, or the like.

(First embodiment)
As illustrated in FIG. 1, the image forming apparatus 500 includes an image forming unit 510 and a control unit 550.

  The control unit 550 controls the image forming unit 510. Then, the image forming unit 510 forms characters or images on the paper 600 under the control of the control unit 550. The control unit 550 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown).

  The image forming unit 510 includes a light emitting device (exposure head) 511, a photosensitive drum 513, a charging roller 515, a developing device 517, a developing roller 519, a conveying belt 521, a transfer roller 523, a fixing roller 524a, and the like. 524b, a cleaning device 526, and an eraser light source 528.

  The photosensitive drum 513 is charged to form an electrostatic latent image, is driven by a drive unit (not shown), and rotates about an axis in the direction of the arrow. The photosensitive drum 513 is composed of a negatively charged OPC (Organic Photo Conductor) photosensitive member.

  The charging roller 515 charges the photosensitive drum 513 uniformly. The charging roller 515 is a negative charger, and a negative voltage is applied from a charging power source (not shown), and the peripheral surface of the photosensitive drum 513 is uniformly negatively charged and initialized.

  The light emitting device 511 performs optical writing (exposure) on the charged photosensitive drum 513, and forms an electrostatic latent image on the photosensitive drum 513 by performing optical writing.

  The light emitting device 511 includes a light emitting element (organic EL element) and a light detecting element. The light detection element outputs the amount of light emitted from the light emitting element as an electrical signal. The control unit 550 controls the light emission intensity of the light emitting element by correcting the supply current to the light emitting element based on the electrical signal output from the light detection element. Such control is performed by a known method. With this control, it is possible to make up for the deterioration over time of the light emission amount of the light emitting element and to keep the light emission amount of the light emitting element constant.

  The developing unit 517 stores toner. The developing roller 519 rotates and conveys the toner stored in the developing device 517 to a portion facing the photosensitive drum 513. A developing bias is applied to the developing roller 519 from a developing bias power source (not shown). The developing roller 519 attaches toner accommodated in the developing device 517, and rotates and conveys the attached toner to the photosensitive drum 513.

  When the developing roller 519 rotates and conveys the toner to a portion facing the photosensitive drum 513, the toner is transferred to the charged photosensitive drum 513 and a toner image 540 is formed. The toner adhesion amount (developed image density) of the toner image 540 is determined by the potential corresponding to the exposure amount on the photosensitive drum 513.

  The transport belt 521 is for transporting the paper 600 placed thereon. The transfer roller 523 is for transferring the toner image 540 formed on the photosensitive drum 513 to the paper 600 and is disposed below the photosensitive drum 513.

  Fixing rollers 524 a and 524 b heat-fix the toner image 540 on the paper 600 and discharge the heat-fixed paper 600 out of the image forming apparatus 500. The cleaner 526 removes transfer leakage toner remaining on the photosensitive drum 513. The eraser light source 528 uniformly removes the surface of the photosensitive drum 513.

  The photosensitive drum 513 rotates and is charged by the charging roller 515. The light emitting device 511 performs optical writing on the charged photosensitive drum 513 to form an electrostatic latent image on the photosensitive drum 513. The developing roller 519 attaches toner accommodated in the developing device 517, and rotates and conveys the attached toner to the photosensitive drum 513. As a result, the toner is transferred to the charged photosensitive drum 513 and a toner image 540 is formed. On the other hand, the paper 600 is transported by the transport belt 521. The toner image 540 formed on the photosensitive drum 513 is transferred onto the paper 600 by the transfer roller 523. Fixing rollers 524a and 524b heat-fix the toner image 540 on the paper 600, and discharge the heat-fixed paper 600 to the outside of the image forming apparatus 500. The cleaning device 526 removes transfer leakage toner remaining on the photosensitive drum 513. The eraser light source 528 removes the surface of the photosensitive drum 513 uniformly.

  In the printing process described above, the control unit 550 temporarily stores image data D_image supplied from the outside using a raster image processor unit (not shown) included in the control unit 550. The controller 550 is also supplied with data such as paper size from the outside. The controller 550 generates a horizontal control signal / HSYNC, a vertical control signal / VSYNC, and a control signal S_print in accordance with the supplied data and a preset transport speed. The horizontal control signal / HSYNC is a synchronization signal in the main scanning direction of the image forming apparatus 500. The control unit 550 supplies the image data D_image to the image forming unit 510 and supplies the generated control signals to the image forming unit 510. The control unit 550 controls the image forming unit 510.

  As shown in FIG. 2, the light emitting device 511 includes a head controller 40, an organic EL panel 41, a select driver 42, an anode driver 43, a data driver 44, and a sensor driver 45. The light emitting device 511 also includes a lens array (not shown). The lens array forms an image of the light flux from the organic EL panel. The head controller 40 includes a CPU, a ROM, a RAM, and the like.

  The organic EL panel 41 includes a plurality (n) of cells 41 (1, 2, 3,... N). n is a natural number. Each cell 41 (1, 2, 3,... N) includes a plurality of sets of light emitting units 150 and optical sensor units 170 as shown in FIG. Here, each of the cells 41 (1, 2, 3,... N) includes six sets of light emitting units 150 and optical sensor units 170. The number of sets of the light emitting unit 150 and the optical sensor unit 170 included in one cell 41 (i) can be determined as appropriate. i is any one of 1 to n. 3 shows a part of the light emitting units 150 and the optical sensor units 170 of a certain cell 41 (i), the structures of the respective light emitting units 150 and the respective optical sensor units 170 are the same.

  Here, the light emitting unit 150 is a lighting circuit. The light emitting unit 150 includes an organic EL element 151, a selection TFT 153, a driving TFT 155, and a holding capacitor 157.

  The organic EL element 151 is a light emitting element having a structure in which an anode electrode, an organic EL layer, and a cathode electrode are stacked, and the cathode electrode is grounded. The anode electrode is connected to the source of the driving TFT 155.

  The selection TFT 153 is a transistor that functions as a switch for selecting the organic EL element 151 that emits light. The drain of the selection TFT 153 is connected to the data line Ld, the source is connected to the gate of the driving TFT 155 and the holding capacitor 157, and the gate is connected to the selection line Ls.

  The driving TFT 155 is a driving transistor for the organic EL element 151, and has a drain connected to the anode line La and a source connected to the anode electrode of the organic EL element 151.

  The holding capacitors 157 are for holding the gate-source voltage of the driving TFT 155 and are connected between the gate and source of the driving TFT 155.

  Note that light emitted from one light emitting unit 150 corresponds to one pixel of an image. The light emitting unit 150 may include a resetting transistor (not shown). This transistor is a transistor for resetting the level of the data line Ld, its drain is connected to the data line Ld, and its source is grounded. Then, a high level reset signal Reset is supplied to the gate from, for example, the data driver 44 to turn on, and the voltage level of the data line Ld is reset.

  The optical sensor unit 170 is an optical sensor circuit that measures the amount of light emitted from the organic EL element 151 to be measured. The amount of emitted light is the product of the light emission intensity per unit area of the organic EL element 151 and the light emission time.

  The optical sensor unit 170 outputs a signal Vout corresponding to the light emission amount of the organic EL element 151 to be measured. The optical sensor unit 170 includes an optical sensor TFT 171, a charge readout TFT 173, and a capacitor 175.

  The photo sensor TFT 171 is a transistor for detecting light, and its drain is connected to the source of the charge readout TFT 173. The source of the photosensor TFT 171 is grounded. The photosensor TFT 171 is supplied with a refresh signal RFSH at its gate. The photosensor TFT 171 is turned on when a high level refresh signal RFSH higher than the threshold voltage is supplied.

  The optical sensor TFT 171 is turned off when the refresh signal RFSH becomes a low level. Further, when light is irradiated to the photosensor TFT 171, a channel is formed between the drain and the source, and a drain current having a current amount corresponding to the light emission amount of the organic EL element 151 flows.

  The charge readout TFT 173 is a charging TFT, and its source is connected to the drain of the photosensor TFT 171 and its drain is connected to Vdd / Vout. The gate is connected to CHG / READ.

  The capacitor 175 is a dark current holding capacitor, and both ends thereof are connected to the drain and source of the photosensor TFT 171, respectively. The capacitor 175 is charged when the charge reading TFT 173 is turned on, and discharged when the drain current flows through the photosensor TFT 171.

  Each TFT described above is a thin film transistor (TFT) constituted by an n-channel FET (Field Effect Transistor).

  The select driver 42 is a driver for selecting the cell 41 (i). The select driver 42 is supplied with a timing signal from the head controller 40, and generates a high-level cell selection signal Select (1) to (n) for selecting the cell 41 (i) based on the timing signal.

  The select driver 42 sequentially outputs the generated high-level cell selection signals Select (1) to (n) to the corresponding select lines Ls in the order of 1 to n, and the cells 41 (1) to (n). Are selected sequentially.

  The anode driver 43 sequentially applies, to the cells 41 (1) to 41 (n), for example, anode signals Anode (1) to Anode (n) of a voltage VH set to + 15V to the anode line La. It is a driver for causing an EL element to emit light.

  The anode driver 43 is supplied with a timing signal from the head controller 46 and generates anode signals Anode (1) to Anode (n).

  The anode driver 43 sequentially outputs the anode signal Anode (i) of the voltage VH to the anode line La, thereby causing the organic EL elements in the cells 41 (i) selected by the select driver 42 to emit light sequentially. Note that which organic EL element in one cell 41 (i) emits light depends on the gradation signals Vdata (1) to (6) supplied by the data driver 44.

  The data driver 44 writes the gradation signals Vdata (1) to (6) supplied from the head controller 46 to the holding capacitor 157 selected by the select driver 42.

  For example, when the select driver 42 outputs a high level select signal Select (1) and the anode driver 43 outputs an anode signal Anode (1) having a voltage VH, the cell 41 (1) is selected. The data driver 44 outputs the gradation signals Vdata (1) to (6) to the data line Ld, respectively. In this way, the data driver 44 writes the gradation signals Vdata (1) to (6) to the holding capacitors 157 of the cells 41 (1) selected by the selector driver 42, respectively.

  Specifically, when the select driver 42 outputs a High level signal Select (1) to the select line Ls, the selection TFT 153 is turned on. When the gradation signal Vdata (1) is supplied to the light emitting unit 150, the gradation current Idata (1) flows from the data driver 44 to the gate of the driving TFT 155 and the holding capacitor 157, and the gradation signal is supplied to the holding capacitor 157. A signal charge corresponding to Vdata (1) is written. In this way, signal charges corresponding to the gradation signals Vdata (1) to (6) are written in the holding capacitors 157.

  When the anode driver 43 outputs the anode signal Anode (1) having the voltage VH to the anode line La, the driving TFT 155 supplies the current Ie corresponding to the signal charge written in each holding capacitor 157 of the cell 41 (1) to each of the currents Ie. The organic EL element 151 is supplied. Each organic EL element 151 emits light with a luminance corresponding to the supplied current Ie. When the select driver 42 causes the signal Select (1) to fall to the low level, the selection TFT 153 is turned off. Since the holding capacitor 157 holds the gate voltage of the driving TFT 155 even when the selection TFT 153 is turned off, the driving TFT 155 supplies the current Ie corresponding to the signal charge written in the holding capacitor 157 to the organic EL element 151. The organic EL element 151 continuously emits light with a luminance corresponding to the supplied current Ie.

  Note that the period during which the anode signal Anode (i) of the voltage VH is supplied is the light emission period of the organic EL element and is the anode time.

  The select driver 42, the anode driver 43, and the data driver 44 cause the organic EL elements to emit light one by one when measuring the amount of light emitted from the organic EL elements.

  The sensor driver 45 drives and controls each light detection element of the organic EL panel 41. The sensor driver 45 is supplied with a timing signal from the head controller 40, generates a control signal CHG / READ (i), a refresh signal RFSH (i), and a charge signal Vdd (i), and outputs these generated signals. By supplying the organic EL panel 41, the optical sensor unit is driven. The control signal CHG / READ (i), the refresh signal RFSH (i), and the charge signal Vdd (i) here correspond to the six optical sensor units 170 provided in the cell 41 (i), respectively. These are six signals, and each signal is supplied to each optical sensor unit 170. That is, in FIG. 2, there is one line connecting the sensor driver 45 and each cell 41 (i), but there are actually six lines.

  The sensor driver 45 detects Vout (i) output from the optical sensor unit 170. The detected Vout (i) is amplified by a predetermined circuit provided in the sensor driver 45, and the amplified Vout (i) is output to the head controller 40. Here, Vout (i) is six signals corresponding to the six optical sensor units 170 included in the cell 41 (i), and each signal is supplied to each sensor driver 45. That is, in FIG. 2, there is one line connecting the sensor driver 45 and each cell 41 (i), but there are actually six lines.

  When a high level refresh signal RFSH is supplied to the photosensor unit 170, the photosensor TFT 171 is turned on, the charge remaining in the capacitor 175 is discharged, and the capacitor 175 is refreshed. Next, the refresh signal RFSH is set to Low level, and the photosensor TFT 171 is turned off.

  After that, as shown in FIG. 4, the high level charge signal Vdd and the control signal CHG / READ are supplied to the optical sensor unit 170. Along with this, the charge readout TFT 173 is turned on, and the capacitor 175 is charged with a voltage corresponding to Vdd. Then, the potential Vc increases. Further, the charge readout TFT 173 is turned off thereafter. On the other hand, a current is also supplied to the organic EL element 151 and the organic EL element 151 emits light. At this time, when the light is applied to the light sensor TFT 171, a channel is formed between the drain and the source, a drain current having a current amount corresponding to the light emission amount of the organic EL element 151 flows, and the potential Vc gradually decreases. Go. Then, after a predetermined time has elapsed, a high level control signal CHG / READ is supplied to the charge readout TFT 173, the charge readout TFT 173 is turned on again, and Vout is output. From this Vout, the amount of light emitted from the light emitting unit 150 is known. When Vout is small or zero, the amount of emitted light is large, and when Vout is large, the amount of emitted light is small. Thus, the optical sensor unit 170 can detect light from the organic EL element 151, and more specifically, can measure the amount of light emitted from the organic EL element 151.

  The light emitting device 511 includes the stacked body 100 illustrated in FIGS. 5 and 6. FIG. 6 is a cross-sectional view taken along the line AA. The stacked body 100 is formed on the transparent substrate 101. The organic EL panel 41 includes a laminate 100 and a transparent substrate 101. The stacked body 100 includes a gate electrode layer 103, a transmissive portion 104, a first insulating layer 102, a second insulating layer 108, a source electrode layer 109, a semiconductor layer 111, a drain electrode layer 113, and an anode electrode 121. A contact portion 123, a source extension electrode 125, a contact portion 127, an organic EL layer 131, a bank 133, and a cathode electrode 135.

  The gate electrode layer 103, the first insulating layer 102, the source electrode layer 109, the semiconductor layer 111, and the drain electrode layer 113 constitute an optical sensor TFT 171. The anode electrode 121, the organic EL layer 131, and the cathode electrode 135 constitute an organic EL element. The stacked body 100 also includes a gate electrode layer 105, a source electrode layer 115, a semiconductor layer 117, a drain electrode layer 119, and the like. The first insulating layer 102, the gate electrode layer 105, the source electrode layer 115, the semiconductor layer 117, and the drain electrode layer 119 constitute a driving TFT 155. The stacked body 100 also includes a selection TFT 153, a charge / read TFT 173, a holding capacitor 157, a capacitor 175, and a part of each line (Ls, Ld, La, etc.). The electrode layer, the semiconductor layer, etc. constituting these are also formed in the same manner as the electrode layer, the semiconductor layer, etc. constituting the photosensor TFT 171. In addition, the electrode layers are electrically connected as appropriate by contact portions or the like. Thus, the laminated body 100 is formed in the structure which implement | achieves the circuit shown in FIG. Note that the semiconductor layer, gate electrode layer, and source electrode layer of each TFT included in the stacked body 100, the electrode layer of each capacitor, and the electrode layer (conductive layer) constituting each line are the gate electrode layer 103. Since the source electrode layer 109 and the semiconductor layer 111 are formed in the same process, the gate electrode layer 103, the source electrode layer 109, and the semiconductor layer 111 will be described below. Description of the TFT semiconductor layer, gate electrode layer, source electrode layer, and the like is omitted.

  The transparent substrate 101 is an insulating transparent substrate (colorless transparent or colored transparent, the same applies hereinafter). The transparent substrate 101 is a glass substrate, for example.

  The gate electrode layer 103 is formed of a conductive material, such as a Mo film, a Cr film, an Al film, a Cr / Al laminated film, an AlTi alloy film, an AlNdTi alloy film, or a MoNb alloy film, and is formed on the transparent substrate 101. Formed.

  The first insulating layer 102 (gate insulating film) is formed of an insulating material, for example, SiN, and is formed so as to cover the transparent substrate 101, the gate electrode layer 103, and the like. The first insulating layer 102 (gate insulating film) is transparent.

  The semiconductor layer 111 includes a microcrystalline silicon film (semiconductor film). The semiconductor layer 111 is formed on the first insulating layer 102. Further, the semiconductor layer 111 appropriately includes a stopper film (transparent) formed on the upper surface (surface opposite to the transparent substrate 101). The stopper film is formed on the upper surface of the semiconductor film. The stopper film is made of an insulating material, for example, SiN. The stopper film is preferably transparent.

  Further, the semiconductor layer 111 may include not only one layer formed of microcrystalline silicon but also a stacked layer of two layers of a microcrystalline silicon film and an amorphous silicon film. The thickness of the amorphous silicon film is preferably about 10 to 50 nm in order to reduce unevenness on the surface of the microcrystalline silicon film and obtain a good bonding surface.

  The source electrode layer 109 and the drain electrode layer 113 are formed so as to cover part of the semiconductor layer 111. The source electrode layer 109 and the drain electrode layer 113 are formed of a conductive layer such as aluminum-titanium (AlTi) / Cr, AlNdTi / Cr, or Cr.

  The source electrode layer 109 may include a source region formed between the conductive layer and the semiconductor layer 111, that is, below the conductive layer. The drain electrode layer 113 may include a drain region formed between the conductive layer and the semiconductor layer 111, that is, below the conductive layer. The source region and the drain region are formed from doped amorphous silicon.

  Note that the optical sensor TFT 171 includes an amorphous silicon layer serving as a source region and a drain region, a source electrode layer 109, and a drain electrode layer 113 after a stopper film is formed over the semiconductor film (after the semiconductor layer 111 is formed). A conductive layer is formed and etched. For this reason, the shape of the conductive layer and the source region of the source electrode layer 109 (the shape seen from the thickness direction of the organic EL element) is formed in substantially the same shape. In addition, the shape of the conductive layer and the drain region of the drain electrode layer 113 (the shape seen from the thickness direction of the organic EL element) is formed in substantially the same shape. However, the present invention is not limited to this, a stopper film is formed over the semiconductor film, an amorphous silicon layer is formed, etched, a metal film is formed, and the source electrode layer 109 and the drain electrode layer 113 are electrically conductive. Etching may be applied to the shape of the layer.

  The second insulating layer 108 (gate insulating film) is formed of an insulating material, for example, SiN, and the second insulating layer 108 covers the source electrode layer 109, the drain electrode layer 113, the semiconductor layer 111, and the like. Formed. The second insulating layer 108 is transparent.

  The anode electrode 121 is made of a light-transmitting conductive material such as ITO (Indium Tin Oxide), ZnO, or the like. The anode electrode 121 is electrically connected to the source electrode layer 115 through the contact portion 123. The contact portion 123 is formed by burying an electrode formed integrally with the anode electrode 121 so as to be connected to the anode electrode 121 in the through hole formed in the second insulating layer 108.

  The source extension electrode 125 is made of a light-transmitting conductive material, for example, ITO (Indium Tin Oxide), ZnO, or the like. Further, the source extension electrode 125 is electrically connected to the source electrode layer 109 through the contact portion 127. The source extension electrode 125 is connected to the outside. The contact portion 127 is formed by burying an electrode that is connected to the source extension electrode 125 and is formed integrally with the source extension electrode 125 in a through hole formed in the second insulating layer 108.

  A bank 133 is formed on the second insulating layer 108 so as to cover part of the anode electrode 121 and the source extension electrode 125. The bank 133 is formed by curing an insulating material, for example, a photosensitive resin such as polyimide. The banks 133 are formed in two rows along the main scanning direction. An organic EL layer 131 is formed between the banks 133 along the main scanning direction.

  The organic EL layer 131 is a light emitting layer, and is a layer in which a hole injection layer, an interlayer, and a light emitting film are stacked in this order from the substrate side. The light emitting layer may be at least provided with a light emitting film. The hole injection layer, the interlayer, and the light emitting film serve as a carrier transport layer in which electrons and holes are transported as carriers.

  The hole injection layer is formed on the second insulating layer 108 and the anode electrode 121 and has a function of supplying holes to the light emitting layer. The hole injection layer is made of an organic polymer material capable of injecting and transporting holes. As an organic compound-containing liquid containing an organic polymer hole injection / transport material, for example, polyethylenedioxythiophene (PEDOT) as a conductive polymer and polystyrene sulfonic acid (PSS) as a dopant are dispersed in an aqueous solvent. There is a PEDOT / PSS aqueous solution that is a dispersion.

  The interlayer is formed on the hole injection layer. The interlayer has a function of suppressing the hole injection property of the hole injection layer to facilitate recombination of electrons and holes in the light emitting layer, and is provided to increase the light emission efficiency of the light emitting layer. .

  The light emitting layer is formed on the interlayer. The light emitting layer has a function of generating light by applying a voltage between the anode electrode and the cathode electrode. The light emitting layer is composed of a known polymer light emitting material capable of emitting fluorescence or phosphorescence, for example, a light emitting material containing a conjugated double bond polymer such as polyparaphenylene vinylene or polyfluorene. In addition, these luminescent materials are appropriately coated with a solution (dispersion) dissolved (or dispersed) in an aqueous solvent or an organic solvent such as tetralin, tetramethylbenzene, mesitylene, and xylene by a nozzle coating method, an inkjet method, or the like. It is formed by volatilizing.

  The cathode electrode is provided on the light emitting layer side, and includes a conductive material, for example, an electron injecting lower layer made of a material having a low work function such as Li, Mg, Ca, Ba, and an upper layer made of a light reflective conductive metal such as Al. It is formed with the laminated structure which has.

  Next, the formation method of the laminated body 100 is demonstrated here.

  First, for example, a gate electrode layer is formed on the transparent substrate 101 by a sputtering method, a vacuum deposition method, or the like, and is patterned into a shape of the gate electrode layer 103 or the like. Subsequently, the first insulating layer 102 is formed so as to cover the gate electrode layer 103 and the like by a CVD (Chemical Vapor Deposition) method or the like.

  Next, a semiconductor film (microcrystalline silicon film) is formed over the first insulating layer 102 by a CVD method or the like. At this time, the microcrystalline silicon film may be so-called as depo μc-Si that is polycrystallized at the time of film formation, or may be formed by performing an annealing process after the amorphous silicon is formed to be polycrystallized. Note that in the case of using a two-layer structure of microcrystalline silicon and amorphous silicon, the microcrystalline silicon is as depo μc-Si so that unnecessary levels are not formed at the interface, and the amorphous silicon is the same as the microcrystalline silicon. It is preferable to perform continuous film formation using the apparatus.

  Next, a silicon nitride layer is formed over the microcrystalline silicon film by a CVD method or the like. Subsequently, after forming a resist on the silicon nitride layer, exposing the resist through a mask having a pattern corresponding to the shape of the stopper film, and developing the resist, a resist corresponding to the shape of the stopper film is obtained. Remains. After processing by dry etching or wet etching through this resist, the resist is peeled off to form a stopper film. In this way, the semiconductor layer 111 including the semiconductor film and the stopper film is formed.

  Next, after depositing an amorphous silicon layer containing an n-type impurity, the drain region, the source region, the semiconductor layer 111, and the like are formed by etching together with the lower microcrystalline silicon film by photolithography. Next, the conductive layer is coated by a sputtering method, a vacuum evaporation method, or the like, and patterned by photolithography to form a source electrode layer 109 including a source region, a drain electrode layer 113 including a drain region, and the like.

  Next, the second insulating layer 108 is formed so as to cover the semiconductor layer 111, the source electrode layer 109, the drain electrode layer 113, the first insulating layer 102, and the like by a CVD (Chemical Vapor Deposition) method or the like. Next, a contact hole which is a through hole is formed in the second insulating layer 108, and then a transparent conductive film such as ITO is coated on the insulating film by a sputtering method or a vacuum evaporation method, and then patterned by photolithography. An anode electrode 121, a contact portion 123, a source extension electrode 125, a contact portion 127, and the like are formed.

  Next, photosensitive polyimide is applied so as to cover the anode electrode 121, the contact portion 123, the source extension electrode 125, the contact portion 127, the second insulating layer 108, and the like, and through a mask corresponding to the shape of the bank 133. A bank 133 having openings is formed by patterning by exposure and development.

  Next, an organic compound-containing liquid containing a hole injection material is applied to the opening by a nozzle printing apparatus or the like that continuously flows. Subsequently, the transparent substrate 101 after the application of the organic compound-containing liquid is heated in an air atmosphere to volatilize the solvent of the organic compound-containing liquid, thereby forming a hole injection layer. The organic compound-containing liquid may be applied in a heated atmosphere.

  Next, the organic compound containing liquid containing the material used as an interlayer is apply | coated on a positive hole injection layer using a nozzle printing apparatus etc. FIG. Thereafter, the transparent substrate 101 after the application of the organic compound-containing liquid is heat-dried in a nitrogen atmosphere or heat-dried in a vacuum, and the residual solvent is removed to form an interlayer. The organic compound-containing liquid may be applied in a heated atmosphere.

  Next, the organic compound-containing liquid is similarly applied by a nozzle printing apparatus or the like and heated in a nitrogen atmosphere to remove the residual solvent, thereby forming a light emitting layer. The organic compound-containing liquid may be applied in a heated atmosphere.

  Next, the cathode electrode 135 having a two-layer structure is formed on the transparent substrate 101 formed with the light emitting layer by vacuum deposition or sputtering. In this way, the laminate 100 is formed.

  Note that the upper surface of the laminate 100 is bonded to the sealing substrate with a sealing resin made of an ultraviolet curable resin or a thermosetting resin, and then the sealing resin is cured by ultraviolet rays or heat to seal the laminate 100 with the sealing body. It is preferable to join the substrate.

  The width of the organic EL layer 131 (light emitting layer) in the main scanning direction (the vertical direction in FIG. 5) is defined by the width of the anode electrode 131 in the main operation direction. Further, the width of the organic EL layer 131 in the sub-scanning direction (left-right direction in FIG. 5) is defined by the distance between the two banks 133. The plurality of organic EL layers 131 are arranged in a line in an array along the main scanning direction.

  The organic EL layer 131 emits light in a planar shape. Part of the light emitted from the organic EL layer 131 is transmitted through the transmission unit 104 and is emitted from the transparent substrate 101 to the outside. The size of the transmissive portion 104 is one pixel. The transmission part 104 is formed by a through hole formed in the light shielding part (however, the first insulating layer 102 may enter the through hole). The light shielding portion shields part of the light emitted from the light emitting layer. Here, the gate electrode 103 is part of the light shielding portion. Note that only part of the gate electrode 103 functions as a gate electrode, and this is called the gate electrode 103 as a whole. Thus, in the present invention, if only a part of a certain component exhibits a function derived from the name of the component, the entire component is integrally formed of the same material. The whole component that can be seen as is represented by the name of the component as one component. In addition, you may provide a light-shielding part elsewhere. Note that the semiconductor layer 111 corresponds to a light detection region that detects light emitted from the light emitting layer.

  As described above, the stacked body 100 according to the present embodiment includes the organic EL layer 131 (the same applies to other light-emitting layers) and a light detection element that detects light emitted from the organic EL layer 131 ( The photodetection area of the photosensor TFT 171 overlaps the light emitting surface of the organic EL layer 131 when viewed from the thickness direction of the organic EL layer 131. As a result, the light detection region is located immediately below the light emitting surface, and thus the laminate 100 has a structure capable of efficiently measuring the light emission amount of the light emitting layer. In addition, although it is desirable for both to overlap so that the light emission surface of the organic EL layer 131 may completely (all) cover the light detection region, in the present invention, the term “overlap” is an expression including a case where they partially overlap.

  In addition, as described above, the stacked body 100 according to the present embodiment includes the transmission unit 104 that transmits part of the light emitted from the organic EL layer 131 and the part of the light emitted from the organic EL layer 131. A light shielding portion (in this embodiment, the gate electrode 103, the source electrode 109, and the drain electrode 113 of the photosensor TFT 171). The light emitting surface has a shape in which the dimension in the first direction (sub-scanning direction) in the surface of the light emitting surface is longer than the dimension in the second direction (main scanning direction) perpendicular to the first direction, The light detection region and the transmission part 104 are arranged in the first direction when viewed from the thickness direction of the organic EL layer 131. With such a configuration, the channel width dimension can be increased without changing the TFT channel length depending on the photoelectric efficiency of the semiconductor layer used and the amount of emitted light to be measured. Is possible. In addition, the photodetection area can be increased without changing the pitch between the organic EL layers 131 (the pitch between pixels). Further, when the light shielding portion is the gate electrode 103, the source electrode 109, and the drain electrode 11 of the photosensor TFT 171, it is not necessary to newly provide the light shielding portion.

  The light detection region overlaps with the light shielding part and does not overlap with the transmission part 104 when viewed from the thickness direction of the organic EL layer 131. As a result, it is possible to prevent or reduce a decrease in light transmittance, light emission unevenness, or an obstacle to the optical profile caused by the light detection element, which occurs when the emitted light for exposing the photosensitive drum 513 passes through the optical sensor TFT 171. .

(Second embodiment)
The second embodiment is different from the first embodiment in that the gate electrode 103, the source electrode 109, and the drain electrode 113 of each photosensor TFT 171 in the first embodiment are shared by common electrodes, and the charge readout TFT 173 is used. The capacitor 175 is shared. The common charge readout TFT 273, capacitor 275, and optical sensor TFTs 171 constitute an optical sensor unit 270 as a whole (see FIG. 10). This sharing is performed for all the optical sensor TFTs 171 here, but may be performed for each group (for example, the cell 41 (i)) including a plurality of optical sensor TFTs 171. Below, the second embodiment will be described with respect to differences from the first embodiment, and redundant description will be omitted. 7 to 10, the same or corresponding members as those of the first embodiment will be described with appropriate reference numerals.

  As shown in FIG. 7, in the case of the present embodiment, only one signal line is required for the sensor driver 45 to supply or receive a signal. As shown in FIGS. 8 and 9, each gate electrode 203 (corresponding to the gate electrode 103 of the first embodiment) is connected to the gate common electrode 291 and shared. Each gate electrode 203 (corresponding to the gate electrode 103 of the first embodiment) is connected to the gate common electrode 291 and shared. Each source electrode 109 is connected to the source common electrode 292 via the contact portions 226 and 227 and is shared. Each drain electrode 213 (corresponding to the drain electrode 113 of the first embodiment) is connected to the drain common electrode 293 and shared. 9 is a cross-sectional view taken along the line BB in FIG.

  The gate common electrode 291 is formed integrally with the gate electrode 203 using the same material as the gate electrode 203. The source common electrode 292 is formed of the same material as the gate electrode 203 and separately from the gate electrode 203. The contact portions 226 and 227 are made of the same material as that of the anode electrode 121, and separately from the anode electrode 121, through holes formed in the first insulating layer, and through holes formed in the first insulating layer and the second insulating layer Formed. The contact portions 226 and 227 electrically connect the source electrode 109 and the source common electrode 292. The drain common electrode 293 is formed integrally with the drain electrode 213 using the same material as the drain electrode 213.

  FIG. 10 shows a circuit diagram of the present embodiment. Since the light emission of the light emitting unit 150 of the present embodiment is the same principle as that of the first embodiment, the description thereof is omitted. Moreover, the light detection of the optical sensor unit 270 is also performed by detecting the light emission of each light emitting unit 150, and the principle is the same as that of the first embodiment, and thus the description thereof is omitted. The charge read TFT 273 corresponds to the charge read TFT 173, and the capacitor 275 corresponds to the capacitor 175.

  The laminate 200 according to the present embodiment includes a plurality of light emitting layers (organic EL layers 131) and a plurality of light detection elements (light sensor TFTs 171) corresponding to the light emission layers, and includes at least one light detection element. The drain electrode, the source electrode, or the gate electrode is electrically connected to the drain electrode, the source electrode, or the gate electrode of another photodetecting element. Thereby, the circuit wiring with which a light-emitting device is provided can be reduced significantly. Further, in the case of measuring the light emission amount of the light emitting element, the light emitting elements emit light one by one, so that only the light detection of the emitted light emitting elements can be detected, and thus the laminate 200 employs such a configuration. But there is no particular inconvenience.

(Third embodiment)
The third embodiment is different from the first embodiment in that each photosensor TFT 371 is a double gate transistor (see FIG. 12). In this case, the structure of the laminated body can employ substantially the same structure as that of the laminated body 100 of the first embodiment. Each photosensor TFT 371 has a double gate structure depending on how the voltage is applied. Note that the photosensor TFT 371 includes the gate electrode layer 103, the first insulating layer 102, the source electrode layer 109, the semiconductor layer 111, the drain electrode layer 113, and the anode electrode 121 in FIGS. Configured. Further, the gate electrode layer 103 and the anode electrode 121 become the first and second gates. In the following, the difference between the third embodiment and the first embodiment will be described, and overlapping description will be omitted. 11 to 12, the same or corresponding members as those of the first embodiment will be described with appropriate reference numerals.

  As shown in FIG. 11, in the present embodiment, when the sensor driver 45 supplies a signal, GATE2 is also newly supplied. As shown in FIG. 12, one gate of the photosensor TFT 371 is connected to the anode of the organic EL element 151. That is, one gate is the anode of the organic EL element 151.

  The operations until the light emission and the refresh of the capacitor 175 in the circuit of FIG. 12 are the same as those in the first embodiment, and thus the description thereof is omitted.

  As shown in FIG. 13, the high level charge signal Vdd and the control signal CHG / READ are supplied to the optical sensor unit 370. Along with this, the charge readout TFT 173 is turned on, and the capacitor 175 is charged with a voltage corresponding to Vdd. Then, the potential Vc increases. Further, the charge readout TFT 173 is turned off thereafter. On the other hand, a current is also supplied to the organic EL element 151 and the organic EL element 151 emits light. Further, a voltage signal GATE1 (for example, + 10V) applied to the organic EL element 151 and an anode minus voltage signal GATE2 (for example, −20V) are applied to the two gates of the photosensor TFT 371, respectively. Further, a potential Vc (for example, 5 V) is applied to the drain of the photosensor TFT 371. In this state, when light is applied to the photosensor TFT 371, a channel is formed between the drain and the source, a drain current having a current amount corresponding to the light emission amount of the organic EL element 151 flows, and the potential Vc gradually decreases. Go. Then, after a predetermined time has elapsed, a high level control signal CHG / READ is supplied to the charge readout TFT 173, the charge readout TFT 173 is turned on again, and Vout is output. From this Vout, the amount of light emitted from the light emitting unit 150 is known. When Vout is small or zero, the amount of emitted light is large, and when Vout is large, the amount of emitted light is small. As described above, the optical sensor unit 370 can detect light from the organic EL element 151, and more specifically, can measure the light emission amount of the organic EL element 151.

  In the present embodiment, the laminate further includes an electrode layer (anode electrode 121) for causing the light emitting layer (organic EL layer 131) to emit light between the light emitting layer and the light detection element (photosensor TFT 371). The electrode layer functions as a second gate electrode of the photodetecting element. By doing so, the light detection element becomes a double gate structure element, and the sensitivity of light detection is improved. Further, in the TFT structure of the light detection element, the second insulating layer 108 is affected by the electric field from the anode electrode 121 of the light emitting element (organic EL element 151) according to the dielectric constant and thickness of the second insulating layer 108 and the voltage applied to the anode electrode 121. . When the light emitting element emits light, a voltage of plus several volts to several tens of volts is applied to the anode electrode 121 to generate an electric field. When a large electric field exceeding Vth is generated, a channel is formed in the TFT and a current flows. However, a negative gate voltage is applied to the gate electrode below the photodetecting element to form a double gate structure sensor structure. As a result, the sensitivity is improved. For this reason, this light emitting device has a structure capable of efficiently measuring the amount of light emitted from the light emitting layer.

  The light emitting device according to this embodiment includes a light emitting element (organic EL element 151) and a light detecting element (photosensor TFT 371) for detecting light emitted from the light emitting element, and a light detecting element (anode). The electrode 121) includes two gate electrodes, and one of the two gate electrodes may be an electrode included in the light emitting element. Even with such a light emitting device, the above-described effects can be obtained. For this reason, the light emitting element and the light detection region do not have to overlap each other when viewed from the film thickness direction of the light emitting element. Further, the light emitting element and the light detecting element are formed in the stacked body.

  In this embodiment, the other one of the two gate electrodes shields part of the light emitted from the light emitting element. With such a configuration, the gate electrode can be used effectively.

  Further, in the present embodiment, the light detection region provided in the light emitting detection element overlaps the light emitting surface of the light emitting layer when viewed from the thickness direction of the light emitting layer of the light emitting element. Thereby, it has a structure which can measure the emitted light quantity of a light emitting layer efficiently.

(Fourth embodiment)
The difference between the fourth embodiment and the third embodiment is that the gate electrode 103, the source electrode 109, and the drain electrode 113 of each photosensor TFT 371 in the third embodiment are shared by a common electrode and charged. This is because the readout TFT 173 and the capacitor 175 are shared (see FIG. 12). That is, the fourth embodiment is a modification of the third embodiment, just as the first embodiment is changed to the second embodiment. In the following, the differences between the fourth embodiment and the first to fourth embodiments will be described, and overlapping descriptions will be omitted. Moreover, in FIG. 14 thru | or 15, the same code | symbol is suitably attached | subjected and demonstrated about the member which is the same as the member of 1st embodiment, or respond | corresponds. Moreover, the structure similar to 2nd embodiment is employable as structures, such as a laminated body which concerns on 4th embodiment. As shown in FIG. 14, in the case of this embodiment, only one signal line is required for the sensor driver to supply or receive a signal.

  FIG. 15 shows a circuit diagram of this embodiment. Since the light emission of the light emitting unit 150 of the present embodiment is the same principle as that of the first embodiment, the description thereof is omitted. Further, the light detection of the light sensor unit 470 is also performed by detecting the light emission of each light emitting unit 150, and the principle is the same as that of the third embodiment, and the description thereof is omitted. The charge readout TFT 473 corresponds to the charge readout TFT 173, and the capacitor 475 corresponds to the capacitor 175.

  In the present embodiment, a plurality of light detection elements are provided, and each gate electrode, each source electrode, and each drain electrode included in each light detection element are electrically connected. In this way, the light emitting device according to this embodiment has the advantages of the second embodiment and the third embodiment.

40 ... head controller, 41 ... organic EL panel, 41 (1,2, ... n) ... cell, 42 ... select driver, 43 ... anode driver, 44 ... data Driver, 45 ... Sensor driver, 100 ... Laminated body, 101 ... Transparent substrate, 102 ... First insulating layer, 103 ... Gate electrode layer, 104 ... Transmission part, 108 ... Second insulating layer 109 ... source electrode layer 111 ... semiconductor layer 113 ... drain electrode layer 121 ... anode electrode 123 ... contact part 125 ... source extension electrode DESCRIPTION OF SYMBOLS 127 ... Contact part, 131 ... Organic EL layer, 133 ... Bank, 135 ... Cathode electrode, 150 ... Light emission part, 151 ... Organic EL element, 153 ... Selection TFT 155 Drive TFT, 157... Holding capacitor, 170... Photosensor unit, 171... Photosensor TFT, 173... Charge readout TFT, 175. .. Gate electrode, 213... Drain electrode, 226... Contact portion, 227... Contact portion, 270... Optical sensor portion, 273. ..Gate common electrode, 292 ... Source common electrode, 293 ... Drain common electrode, 371 ... Photosensor TFT, 370 ... Photosensor part, 470 ... Photosensor part, 471 ... Light sensor TFT, 473 ... Charge readout TFT, 475 ... Capacitor, 500 ... Image forming device, 510 ... Image forming unit, 550 ... Control unit, 511. Light emitting device, 513 ... photosensitive drum, 515 ... charging roller, 517 ... developer, 519 ... developing roller, 521 ... conveying belt, 523 ... transfer roller, 524a ... Fixing roller, 524b, fixing roller, 526, cleaning device, 528, eraser light source, 540, toner image, 600, paper

Claims (6)

A light emitting element;
A light detecting element for detecting the light emitted by the light emitting element,
The photodetecting element comprises two gate electrodes,
One of said two gate electrodes is an electrode with which the said light emitting element is provided, The light-emitting device characterized by the above-mentioned.   The light emitting device according to claim 1, wherein the light emitting element and the light detecting element are formed in a stacked body.   3. The light emitting device according to claim 1, wherein the other one of the two gate electrodes shields part of light emitted from the light emitting element. 4.   The light detection region provided in the light detection element overlaps with the light emitting surface of the light emitting layer as viewed from the thickness direction of the light emitting layer of the light emitting element. The light-emitting device of description. A plurality of the light detection elements are provided,
5. The light emitting device according to claim 1, wherein each gate electrode, each source electrode, and each drain electrode included in each of the light detection elements is electrically connected. 6. .   An image forming apparatus comprising the light emitting device according to claim 1.

Images