JP6884534B2 - Printhead and image forming device - Google Patents

Description

Embodiments of the present invention relate to printheads, image forming devices, and light emitting devices.

Printers, copiers, and multi-function peripherals (MFPs) that use electrophotographic processes are known. As the exposure means (exposure unit) of these devices, two methods called a laser optical system (LSU: laser scan unit) and a print head (solid-state head) are known. In the laser optical system, the photoconductor drum is exposed by a laser beam scanned by a polygon mirror. In the print head, the photoconductor drum is exposed by the light output from a plurality of light emitting elements such as LEDs (Light Emitting Diodes).

Since the laser optical system needs to rotate the polygon mirror at high speed, it consumes a lot of energy when forming an image and an operating sound can be heard. Further, since a mechanism for scanning the laser beam is required, the unit shape tends to be large.

One printhead can be configured with a small exposure unit. A small exposure unit is realized by using a lens called a rod lens array that forms an erect image with the light emitted from the light emitting element. Moreover, since there are no moving parts, it is a quiet exposure unit.

In addition to those using LEDs, print heads using organic EL (Electroluminescence) have also been developed. In the organic EL, the organic EL can be collectively formed on the substrate by using a mask, and the light emitting elements can be arranged more accurately than the LEDs are arranged. Therefore, when an organic EL is used as the light emitting element, there is an advantage that a highly accurate image can be formed.

For example, there is known an example in which a plurality of light emitting elements made of an organic EL are formed on a glass substrate. When a current sufficient to secure the amount of emitted light required for image formation is passed through the above structure, deterioration progresses and the amount of emitted light decreases with the cumulative emission time. If the amount of emitted light decreases, an appropriate image density cannot be obtained.

JP-A-2007-283599

An object of the present invention is to provide a print head, an image forming device, and a light emitting device capable of suppressing deterioration of the light emitting element while securing the amount of emitted light required for forming an image from the light emitting element.

The printhead of the embodiment includes a transparent substrate, a drive circuit, a first light emitting element, a second light emitting element, and a lens. The drive circuit supplies current. The first light emitting element is an element on the transparent substrate, and outputs the first light having a predetermined wavelength by supplying the current. The second light emitting element is an element on the transparent substrate, and outputs the second light having the predetermined wavelength by supplying the current. The lens collects a third light in which the first light and the second light are superimposed.

It is a figure which shows an example of the positional relationship between a photoconductor drum and a print head. It is a figure which shows an example of the transparent substrate which constitutes a print head. It is a figure which shows the 1st example of 1 set of light emitting elements (light emitting element group). It is a figure which shows the 2nd example of 1 set of light emitting elements (light emitting element group). It is a figure which shows an example of the DRV circuit for driving a light emitting element. It is a figure which shows the 1st example of the printhead circuit block which includes the 1st and 2nd light emitting elements connected in series. A head circuit block B2 that includes a first light emitting element and a second light emitting element connected in parallel, and associates one DRV circuit with one light emitting element group including the first light emitting element and the second light emitting element. It is a figure which shows an example. It is a figure which shows an example of the head circuit block which includes the 1st light emitting element and the 2nd light emitting element connected in parallel, and each of the 1st light emitting element and the 2nd light emitting element is associated with the DRV circuit. It is a figure which shows an example of the image forming apparatus to which the print head of this embodiment is applied.

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

FIG. 1 is a diagram showing an example of the positional relationship between the photoconductor drum and the print head used in the electrophotographic process. For example, an image forming apparatus such as a printer, a copying machine, or a multifunction device includes a photoconductor drum 111 shown in FIG. 1, and a print head 1 is arranged so as to face the photoconductor drum 111.

As shown in FIG. 1, the print head 1 includes a transparent substrate 11 and a rod lens array 12. For example, the transparent substrate 11 is a glass substrate. Light from the plurality of light emitting elements forming the light emitting element rows 13 on the transparent substrate 11 passes through the rod lens array 12 and is focused on the photoconductor drum 111. The light emitting element row 13 is composed of a plurality of light emitting element groups 130, and the light emitting element group 130 is composed of a plurality of light emitting elements. For example, the light emitting element group 130 is composed of multiplexed light emitting elements, for example, a first light emitting element 131 and a second light emitting element 132. The multiplexing structure of the light emitting element will be described in detail later.

The photoconductor drum 111 is uniformly charged by the charger and exposed by the light from the light emitting element group 130, so that its potential is lowered. That is, by controlling the light emission and non-light emission of the light emitting element group 130, an electrostatic latent image can be formed on the photoconductor drum 111.

FIG. 2 is a diagram showing an example of a transparent substrate constituting the print head.

As shown in FIG. 2, a light emitting element row 13 is formed in the central portion on the transparent substrate 11 along the longitudinal direction of the transparent substrate 11. In the vicinity of the light emitting element row 13, a DRV circuit row 14 for driving (lighting) each light emitting element (multiplexed first light emitting element 131 and second light emitting element 132) is formed.

Although FIG. 2 shows an example in which the DRV circuit rows 14 are arranged on both sides of the light emitting element row 13, the DRV circuit rows 14 may be arranged on one side.

Further, the transparent substrate 11 includes an IC (Integrated Circuit) 15. The IC 15 includes a D / A (digital to analog) conversion circuit 150, a selector 153, an address counter 154, and the like. The D / A conversion circuit 150, the selector 153, and the address counter 154 supply a signal for controlling the light emission intensity and on / off of each light emitting element to the DRV circuit 140. Further, the transparent substrate 11 includes a connector 16. The connector 16 electrically connects the print head 1 to a printer, a copying machine, or a multifunction device.

For example, the transparent substrate 11 is provided with a substrate for sealing each light emitting element, the DRV circuit 140, and the like so as not to come into contact with the outside air.

FIG. 3 is a diagram showing a first example of a set of light emitting elements (light emitting element group).

The light emitting element group 130 includes a laminated first light emitting element 131 and a second light emitting element 132. Further, the first light emitting element 131 and the second light emitting element 132 are connected in series. In FIG. 3, the substrate for sealing is omitted.

A plurality of light emitting element groups 130 are formed on the transparent substrate 11. For example, one light emitting element group 130 includes a first light emitting element 131 and a second light emitting element 132. The first light emitting element 131 and the second light emitting element 132 are sandwiched between the electrode (+) 133a and the electrode (−) 133c insulated by the insulating layer 133b. Further, the electrode 133d is sandwiched between the first light emitting element 131 and the second light emitting element 132.

The first light emitting element 131 has a configuration in which the electrode (+) 133a and the electrode 133d on the transparent substrate 11 are in contact with each other and sandwiched. The first light emitting element 131 includes a first hole transport layer 131a, a first light emitting layer 131b, and a first electron transport layer 131c. For example, the first light emitting layer 131b is an organic EL.

The second light emitting element 132 has a configuration in which the electrode 133d and the electrode (−) 133c are in contact with each other and sandwiched. The second light emitting element 132 includes a second hole transport layer 132a, a second light emitting layer 132b, and a second electron transport layer 132c. For example, the second light emitting layer 132b is an organic EL.

The wavelength of the first light output by the first light emitting element 131 (predetermined wavelength) and the wavelength of the second light output by the second light emitting element 132 (predetermined wavelength) are substantially the same (with the first light). The peak intensity of the second light is substantially the same). Those included in the range of wavelength error due to individual differences between the first light emitting element 131 and the second light emitting element 132 are substantially the same. In other words, the first light and the second light have substantially the same color (for example, red), and the print head 1 superimposes the same color to secure the amount of light required for image formation. The first light emitting element 131 and the second light emitting element 132 are made of the same material in order to output light having substantially the same wavelength.

The side of the second light emitting layer 132b opposite to the transparent substrate 11 has a structure that reflects the second light emitted by the second light emitting layer 132b. For example, the second electron transport layer 132c has a structure (reflection characteristic) for reflecting the second light from the second light emitting layer 132b. Alternatively, the electrode (−) 133c has a structure (reflection characteristic) for reflecting the second light from the second light emitting layer 132b.

The second hole transport layer 132a, the electrode 133d, the first electron transport layer 131c, and the first hole transport layer 131a are the first light emitted by the first light emitting layer 131b and the second light emitting layer. It is transparent to the second light emitted by 132b. With such a structure, the first light and the second light are output toward the transparent substrate 11. In other words, the second light is output toward the first light, and the third light in which the first light and the second light are superimposed is output toward the transparent substrate 11.

As described above, the first light emitting element 131 and the second light emitting element 132 emit the first light and the second light having substantially the same wavelength. The second electron transport layer 132c or the electrode (-) 133c on the opposite side of the transparent substrate 11 reflects the first light and the second light emitted by the first light emitting element 131 and the second light emitting element 132. Has a structure. As a result, the first light and the second light can be superposed in one direction and output as the third light. Compared with the case where the light from one light emitting element is output, a large amount of light can be obtained by using this third light.

The first light emitting element 131 and the second light emitting element 132 shown in FIG. 3 have a structure in which they are connected in series. In such a structure, the first light emitting element 131 and the second light emitting element 132 can be made to emit light by passing an electric current through the electrode (+) 133a and the electrode (−) 133c in the forward direction. Substantially the same current flows through the first light emitting element 131 and the second light emitting element 132.

FIG. 4 is a diagram showing a second example of a set of light emitting elements (light emitting element group). The light emitting element group 130 includes a laminated first light emitting element 131 and a second light emitting element 132. Further, the first light emitting element 131 and the second light emitting element 132 are connected in parallel. That is, the electrodes are independently pulled out from the first light emitting element 131 and the second light emitting element 132, respectively. In FIG. 4, the substrate for sealing is omitted.

As shown in FIG. 4, the light emitting element group 130 is formed on the transparent substrate 11. For example, the light emitting element group 130 includes a first light emitting element 131 and a second light emitting element 132. The first light emitting element 131 and the second light emitting element 132 are laminated via the insulating layer 134d. The first light emitting element 131 is sandwiched between the electrode (+) 134a and the electrode (−) 134c insulated by the insulating layer 134b. Further, the second light emitting element 132 is sandwiched between the electrode (+) 134e insulated by the insulating layer 134f and the electrode (−) 134g in contact with each other.

By providing the insulating layer 134d between the first light emitting element 131 and the second light emitting element 132, the structure is such that the independent first light emitting element 131 and the second light emitting element 132 are stacked.

In order to output the first light from the first light emitting element 131 and the second light from the second light emitting element 132 to the transparent substrate 11 side, the insulating layer 134d with respect to the first and second lights. Has transparency.

The side of the second light emitting layer 132b opposite to the transparent substrate 11 has a structure that reflects the second light emitted by the second light emitting layer 132b. For example, the second electron transport layer 132c has a structure (reflection characteristic) for reflecting the second light from the second light emitting layer 132b. Alternatively, the electrode 134g has a structure (reflection characteristic) for reflecting the second light from the second light emitting layer 132b.

The second hole transport layer 132a, the electrode (+) 134e, the insulating layer 134d, the electrode (-) 134c, the first electron transport layer 131c, and the first hole transport layer 131a have a first light emitting layer 131b. It is transparent to the first light that emits light and the second light that the second light emitting layer 132b emits. With such a structure, the first light and the second light are output toward the transparent substrate 11. In other words, the third light, in which the first light and the second light are superimposed, is output toward the transparent substrate 11.

As described above, the first light emitting element 131 and the second light emitting element 132 emit the first light and the second light having substantially the same wavelength. The second electron transport layer 132c or the electrode (-) 134 g on the opposite side of the transparent substrate 11 reflects the first light and the second light emitted by the first light emitting element 131 and the second light emitting element 132. Has a structure. As a result, the first light and the second light can be superposed in one direction and output as the third light. Compared with the case where the light from one light emitting element is output, a large amount of light can be obtained by using this third light.

By having the first light emitting element 131 and the second light emitting element 132 having an independent structure, the first light emitting element 131 and the second light emitting element 132 can be driven independently.

FIG. 5 is a diagram showing an example of a DRV circuit for driving a light emitting element.

The selection signal S1 is supplied to the gate of the switching thin film transistor 141 and becomes an “L” level when the emission intensity of the first light emitting element 131 and the second light emitting element 132 connected to the DRV circuit 140 is changed. .. When the selection signal S1 reaches the “L” level, the voltage of the capacitor 142 changes according to the voltage of the emission level signal S2 supplied to the gate of the driving thin film transistor 143.

When the selection signal S1 becomes “H”, the voltage of the capacitor 142 is held. Even if the voltage of the light emission level signal S2 changes, the voltage level of the capacitor 142 does not change.

A drive current I corresponding to the voltage held in the capacitor 142 flows through the first light emitting element 131 and the second light emitting element 132 connected to the DRV circuit 140.

A predetermined light emitting element group 130 can be selected from a plurality of light emitting element groups 130 included in the light emitting element row 13 by the selection signal S1, the light emitting intensity can be determined by the light emitting level signal S2, and the light emitting intensity can be maintained. ..

Next, an example in which the first light emitting element 131 and the second light emitting element 132 are connected to one DRV circuit 140 will be described.

FIG. 6 is a diagram showing a first example of a printhead circuit block including first and second light emitting elements connected in series. As shown in FIG. 6, one DRV circuit 140 is connected to the first light emitting element 131 and the second light emitting element 132 connected in series. This is because the wavelength (wavelength band) of the first light from the first light emitting element 131 and the wavelength (wavelength band) of the second light from the second light emitting element 132 are substantially the same. Circuit configuration is possible.

The output of the D / A conversion circuit 150 is connected to the emission level signal S2 of the DRV circuit 140 described above. The input of the D / A conversion circuit 150 is the image data D input to the print head.

The output of the selector 153 is connected to the selection signal S1 of the DRV circuit 140. The input of the selector 153 is the output of the address counter 154. The DRV circuit 140 is selected according to the output value of the address counter 154.

The address counter 154 counts the clock C input to the print head 1. The count of the address counter 154 is reset by the horizontal synchronization signal S input to the print head 1.

By inputting the horizontal synchronization signal S to the print head 1 and inputting the image data D in synchronization with the clock C, the light emitting element group 130 can be made to emit light in order with the emission intensity according to the image data.

FIG. 7 includes a first light emitting element and a second light emitting element connected in parallel, and one DRV circuit 140 is associated with one light emitting element group including the first light emitting element and the second light emitting element. It is a figure which shows an example of the head circuit block B2. As shown in FIG. 7, one DRV circuit 140 is connected to the first light emitting element 131 and the second light emitting element 132 connected in parallel. This is because the wavelength (wavelength band) of the first light from the first light emitting element 131 and the wavelength (wavelength band) of the second light from the second light emitting element 132 are substantially the same. Circuit configuration is possible.

The difference between the circuit configuration of the head circuit block B2 shown in FIG. 7 and the circuit configuration of the head circuit block B1 shown in FIG. 6 is the connection of the first light emitting element 131 and the second light emitting element 132 to the DRV circuit 140. The operation of the head circuit block B2 is basically the same as the operation of the head circuit block B1, and the details will be omitted.

FIG. 8 shows an example of a head circuit block including a first light emitting element and a second light emitting element connected in parallel, and a DRV circuit is associated with each of the first light emitting element and the second light emitting element. It is a figure.

The difference between the circuit configuration of the head circuit block B3 shown in FIG. 8 and the circuit configuration of the head circuit block B2 shown in FIG. 7 is that the DRV circuit 141 is connected to each of the first light emitting elements 131 in the head circuit block B3, and the second The point is that the DRV circuit 142 is connected to each of the light emitting elements 132 of the above. Further, a predetermined level of current is supplied from the DRV circuit 141 to the first light emitting element 131, and similarly, a predetermined level of current is supplied from the DRV circuit 142 to the second light emitting element 132. Further, the D / A conversion circuit 151 is connected to one system of the DRV circuit 141, and the D / A conversion circuit 152 is connected to one system of the DRV circuit 142. The operation of the head circuit block B3 is basically the same as the operation of the head circuit block B1 or B2, and details thereof will be omitted.

By simultaneously inputting two image data D systems in synchronization with the horizontal synchronization signal S and the clock C to the print head 1, the emission intensity of the first light emitting element 131 and the second light emitting element 132 stacked is controlled separately. Can be done.

As described above, the print head 1 has a structure in which the first light emitting element 131 and the second light emitting element 132 are stacked. The first light from the stacked first light emitting element 131 and the second light from the second light emitting element 132 are output in the same direction and superposed to obtain the third light from one light emitting element. It is possible to extract light stronger than that of.

When light having substantially the same wavelength is output from the first light emitting element 131 and the second light emitting element 132, the current flowing through each light emitting element is reduced, and the life of the light emitting element can be extended.

In the present embodiment, an example in which two light emitting elements are stacked has been described, but the present invention is not limited to two, and three or more light emitting elements may be stacked.

Further, in the present embodiment, the electrode (+) and the hole transport layer are arranged on the transparent substrate 11 side, and the electron transport layer and the electrode (-) are arranged on the opposite side of the light emitting layer. The arrangement is not limited to this, and the electrode (-) and the electron transport layer are arranged on the transparent substrate 11 side, and the hole transport layer and the electrode (+) are arranged on the opposite side of the light emitting layer. You may.

FIG. 9 is a diagram showing an example of an image forming apparatus to which the printhead 1 of the present embodiment is applied. Although FIG. 9 shows an example of a monochrome image forming apparatus, the print head 1 of the present embodiment can also be applied to a color image forming apparatus.

The image forming apparatus 100 includes an image forming unit 102 and a scanner unit 105. The mechanism of the image forming unit 102 will be described. The image forming unit 102 includes a charged charger 112, a developing device 113, a transfer charger 114, a peeling charger 115, and a cleaner 116 around the photoconductor drum 111. The charging charger 112 uniformly charges the photoconductor drum 111. The developer 113 develops a latent image created based on the image data from the scanner unit 105 on the charged photoconductor drum 111. The transfer charger 114 transfers the image developed on the photoconductor drum 111 to the paper P. The cleaner 116 cleans the current agent remaining on the photoconductor drum 111.

The charged charger 112, the developing device 113, the transfer charger 114, the peeling charger 115, and the cleaner 116 are sequentially arranged according to the rotation direction of the arrow A of the photoconductor drum 111. Further, the image forming unit 102 includes a print head 1 arranged to face the photoconductor drum 111.

The image forming unit 102 includes a transport belt 120 and a paper discharge transport guide 121. The transport belt 120 and the paper discharge transport guide 121 transport the paper P on which the toner image is transferred in order from the release charger 115 downstream in the paper transport direction. Further, the image forming unit 102 includes a fixing device 122 and a paper ejection roller 123. The fixing device 122 fixes the paper P in order from the paper discharge transport guide 121 to the downstream side in the paper transport direction, and the paper discharge roller 123 discharges the paper P.

Next, the process operation of image formation will be described.

The electrostatic latent image formed on the photoconductor drum 111 by the light (third light) from the print head 1 (first light emitting element 131 and second light emitting element 132) is supplied from the developing device 113. Developed with toner (developer). The photoconductor drum 111 on which the toner image is formed transfers the electrostatic latent image onto the paper P by the transfer charger 114.

After the transfer to the paper is completed, the residual toner on the surface of the photoconductor drum 111 is removed by the cleaner 116 to return to the initial state, and the photoconductor drum 111 is in a standby state for the next image formation.

By repeating the above process operation, the image forming operation is continuously performed.

The printhead 1 of the present embodiment is not limited to the printhead in the electrophotographic process, and can also be used as an exposure means for a film or the like.

Further, in the present embodiment, the case where the transparent substrate 11 or the like is applied to the print head 1 and the case where the print head 1 is applied to the image forming apparatus have been described, but the present embodiment is not limited to this. For example, the transparent substrate 11 can be applied to various displays (display devices) to form a display composed of the transparent substrate 11. Such a display makes it possible to secure the amount of emitted light and suppress deterioration of the light emitting element at the same time.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.
Hereinafter, the inventions described in the claims at the time of filing will be added.
[C1]
With a transparent board
The drive circuit that supplies the current and
A first light emitting element which is an element on the transparent substrate and outputs a first light having a predetermined wavelength by supplying the current, and a first light emitting element.
A second light emitting element which is an element on the transparent substrate and outputs a second light having the predetermined wavelength by supplying the current, and a second light emitting element.
A lens that collects a third light in which the first light and the second light are superimposed,
Print head with.
[C2]
The second light emitting element is formed on the first light emitting element, and the second light emitting element is formed.
The first light emitting element outputs the first light in a predetermined direction.
The second light emitting element is a print head of [C1] that outputs the second light in the predetermined direction.
[C3]
The printhead according to [C1], wherein the first light emitting element and the second light emitting element are connected in series to the drive circuit.
[C4]
The printhead according to [C1], wherein the first light emitting element and the second light emitting element are connected in parallel to the drive circuit.
[C5]
With a transparent board
A first drive circuit that supplies a first predetermined level of current,
A second drive circuit that supplies a second predetermined level of current,
A first light emitting element which is an element on the transparent substrate and outputs a first light having a predetermined wavelength by supplying the current from the first drive circuit.
A second light emitting element which is an element on the transparent substrate and outputs a second light having the predetermined wavelength by supplying the current from the second drive circuit.
A lens that collects a third light in which the first light and the second light are superimposed,
Print head with.
[C6]
The first and second light emitting elements are any one printhead of [C1] to [C5] which is an organic EL.
[C7]
The print head according to any one of [C1] to [C6] and
Photoreceptor and
A charger that charges the photoconductor and
A developer that develops a latent image on the photoconductor, and
With
The print head is an image forming apparatus that irradiates the photoconductor with the third light, exposes the photoconductor charged by the charger, and forms the latent image on the photoconductor.
[C8]
With a transparent board
The drive circuit that supplies the current and
A first light emitting element which is an element on the transparent substrate and outputs a first light having a predetermined wavelength by supplying the current, and a first light emitting element.
A second light emitting element which is an element on the transparent substrate and outputs a second light having a predetermined wavelength by supplying the current toward the first light.
A light emitting device equipped with.

1 Printhead 11 Transparent substrate 12 Rod lens array 13 Light emitting element row 14 Circuit row 16 Connector 100 Image forming device 102 Image forming unit 105 Scanner part 111 Photoreceptor 111 Photoreceptor drum 112 Charged charger 113 Developer 113 Developer 114 Transfer charger 115 Peeling Charger 116 Cleaner 120 Conveyance Belt 121 Paper Discharge Transport Guide 122 Fixing Device 123 Paper Discharge Roller 130 Light Emitting Element Group 131 First Light Emitting Element 131 First Optical Element 131a First Hole Transporting Layer 131b First Light Emitting Layer 131c First electron transport layer 132 Second optical element 132 First light emitting element 132 Second light emitting element 132a Second hole transport layer 132b Second light emitting layer 132c Second electron transport layer 133a Electrode (+)
133b Insulation layer 133c Electrode 133c Electrode (-)
133d electrode 134a electrode (+)
134b Insulation layer 134c Electrode (-)
134c Electrode 134d Insulation layer 134e Electrode (+)
134e Electrode 134f Insulation layer 134g Electrode (-)
134g Electrode 140 Circuit 141 Circuit 142 Circuit 150 Conversion Circuit 151 Conversion Circuit 152 Conversion Circuit 153 Selector 154 Address Counter

Claims (3)

With a transparent board
A first drive circuit that supplies a first predetermined level of current,
A second drive circuit that supplies a second predetermined level of current,
A first light emitting element which is an element on the transparent substrate and outputs a first light having a predetermined wavelength by supplying the current from the first drive circuit.
The wiring on the transparent substrate, the first wiring connecting the first drive circuit and the first light emitting element, and the wiring.
A second light emitting element which is an element on the transparent substrate and outputs a second light having the predetermined wavelength by supplying the current from the second drive circuit.
A second wiring that is on the same surface as the first wiring of the transparent substrate and connects the second drive circuit and the second light emitting element.
A lens that collects a third light in which the first light and the second light are superimposed,
Print head with. The print head according to claim 1 , wherein the first and second light emitting elements are organic EL. The print head according to any one of claims 1 or 2.
Photoreceptor and
A charger that charges the photoconductor and
A developer that develops a latent image on the photoconductor, and
With
The print head is an image forming apparatus that irradiates the photoconductor with the third light, exposes the photoconductor charged by the charger, and forms the latent image on the photoconductor.

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