Light-emitting device

Abstract

To provide a light-emitting device in which a light-emitting element and a pixel driving circuit are arranged in an appropriate positional relationship in accordance with a demand for each of them.SOLUTION: According to a first aspect of the present invention, there is provided a light-emitting device comprising: a plurality of light emitting elements disposed on a main surface of a substrate and arranged in M columns and N rows; and a plurality of pixel driving circuits (M and N are integers of 1 or more) disposed in M columns and N rows for driving corresponding light emitting elements among the plurality of light emitting elements. The N rows extend in a first direction and the M columns extend in a second direction. A first arrangement pitch of a first light emitting element and a second light emitting element which are adjacent to each other in the first direction parallel to the N rows among the plurality of light emitting elements is different from a second arrangement pitch of a first pixel driving circuit and a second pixel driving circuit which are adjacent to each other in the first direction among the plurality of pixel driving circuits.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a light emitting device, for example, a light emitting device having a light emitting element. [Background technology]

[0002] An optical writing device (OLED-PH: OLED Print Head) for use in image forming devices has been proposed, which uses organic light-emitting diodes (OLEDs) as the light source. OLED-PH has the advantage of being compact and low-cost, since the OLEDs and the transistors that drive them can be formed on the same substrate. In particular, when a silicon wafer is used as the substrate, it is possible to form the driving circuits finely, which results in a higher density of the OLEDs that serve as the light source. This makes it possible to form higher-resolution images.

[0003] Patent Document 1 discloses an OLED-PH in which a plurality of rectangular light-emitting devices, each equipped with a plurality of OLEDs, are arranged in a line. The light output of a single light-emitting element using an OLED as a light source for an image forming device may not be sufficient. Therefore, Patent Document 1 describes a configuration in which light is irradiated from a plurality of light-emitting elements onto the same portion of the surface of a photoconductor to supplement the light output required to form an electrostatic latent image on the surface of the photoconductor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-96966 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 does not provide any detailed information about the positional relationship between the light-emitting elements and the pixel drive circuits that drive the light-emitting elements. In a light-emitting device, by arranging the light-emitting elements and pixel drive circuits in an appropriate positional relationship depending on what is required of each, it is possible to achieve miniaturization or improved performance. [Means for solving the problem]

[0006] One aspect of the present disclosure relates to a light-emitting device having a plurality of light-emitting elements arranged on a main surface of a substrate and arranged in M ​​columns and N rows, and a plurality of pixel driving circuits arranged in M ​​columns and N rows and driving corresponding light-emitting elements of the plurality of light-emitting elements, wherein M and N are integers greater than or equal to 1, the N rows extend in a first direction, and the M columns extend in a second direction, and a first arrangement pitch of first light-emitting elements and second light-emitting elements adjacent to each other in the first direction parallel to the N rows among the plurality of light-emitting elements is different from a second arrangement pitch of first pixel driving circuits and second pixel driving circuits adjacent to each other in the first direction among the plurality of pixel driving circuits.

[0007] Another aspect of the present disclosure relates to a light-emitting device that includes: a plurality of light-emitting elements arranged in a matrix on a main surface of a substrate; a plurality of pixel driving circuits arranged in a matrix, each having a transistor that drives a corresponding light-emitting element among the plurality of light-emitting elements; and a current control circuit that, in a planar view relative to the main surface, is adjacent to some of the plurality of pixel driving circuits in a first direction, and in the planar view, at least some of the plurality of light-emitting elements overlap with the current control circuit. [Effects of the Invention]

[0008] It is possible to provide a light-emitting device in which the light-emitting elements and pixel driving circuits are arranged in a suitable positional relationship. [Brief explanation of the drawings]

[0009] [Figure 1] (a) is a perspective view of an example of a photosensitive drum and an exposure head, and (b) is a cross-sectional view of an example of the photosensitive drum and exposure head in (a). [Figure 2]FIG. 1 is a diagram showing an example of a printed circuit board provided in an exposure head; [Figure 3] 1 is a cross-sectional view of an example of a light-emitting device according to Embodiment 1. [Figure 4] 1 is a block diagram of an example of a light emitting device according to embodiment 1. [Figure 5] FIG. 1 is a diagram showing an example of a pixel driving circuit according to the first embodiment; [Figure 6] FIG. 1 is a diagram showing an example of a circuit layout of a light emitting device according to a first embodiment. [Figure 7] 1 is a plan view of an example of a light emitting device according to a first embodiment; [Figure 8] 1 is a cross-sectional view of an example of a light-emitting device according to Embodiment 1. [Figure 9] 1 is a plan view of an example of a light emitting device according to a second embodiment. [Figure 10] 1 is a cross-sectional view of an example of a light-emitting device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) Examples of light emitting devices according to the present embodiment will be described with reference to Figures 1 to 8. Note that the following embodiments all show examples of the present embodiment, and the numerical values, shapes, materials, components, arrangement and connection of the components, etc. do not limit the present embodiment.

[0011] In the following, an OLED will be described as an example of a light-emitting element, but the present disclosure is not limited to OLEDs and can be applied to current-driven light-emitting devices in general, such as LEDs (Light Emitting Diodes).

[0012] 1(a) is a perspective view of an example of a photosensitive drum 001 and an OLED-PH006 (exposure head), and FIG. 1(b) is a cross-sectional view of an example of the photosensitive drum 001 and an OLED-PH006.

[0013] 1, the OLED-PH006 is fixed by a fixing member (not shown) in a position facing the surface of the photosensitive drum 001. The OLED-PH006 has a light-emitting device 040 that emits light and a printed circuit board 022 on which the light-emitting device 040 is mounted. The OLED-PH006 also has a rod lens array 023 that focuses (focuses) the light emitted from the light-emitting device 040 on the photosensitive drum 001, and a housing 024 to which the rod lens array 023 and printed circuit board 022 are fixed.

[0014] 2(a) and 2(b) are diagrams showing the mounting surfaces on one side and the other side of the printed circuit board 022 included in the OLED-PH006. FIG. 2(c) is an enlarged view of region V shown in FIG. 2(b). FIG. 2(a) shows the surface of the printed circuit board 022 opposite to the side on which the light-emitting devices are arranged, on which a connector 021 is arranged. The connector 021 may be connected to a control signal cable from the image controller and a power cable from the power supply. The control signal cable may include, for example, at least one of a chip select signal line, a clock signal line, an image data signal line, a line synchronization signal line, and a communication signal line.

[0015] 2(b) shows the surface of the printed circuit board 022 opposite to the surface on which the light emitting devices are arranged. As shown in FIG. 2(b), 17 light emitting devices 040 are mounted on the printed circuit board 022 in a staggered arrangement in two rows. Furthermore, within each light emitting device 040, 872 light emitting elements 050 are arranged at a predetermined resolution pitch in its longitudinal direction (first direction). Furthermore, within each light emitting device 040, four light emitting elements 050 are arranged at a predetermined pitch in its lateral direction (second direction). That is, within each light emitting device 040, the light emitting elements 050 are arranged two-dimensionally. The four light emitting elements 050 arranged in the lateral direction form the same pixel by multiple exposure.

[0016] In this embodiment, the resolution pitch of the light emitting device 040 can be, for example, 1200 dpi (approximately 21.16 μm). The distance from one end to the other end in the longitudinal direction of the light emitting elements 050 of each light emitting device 040 (arrangement pitch) is, for example, approximately 18.451 mm. Here, the longitudinal arrangement pitch of the light emitting elements refers to, for example, the distance in the longitudinal direction from the end of the first electrode of a light emitting element to the end of the first electrode of a light emitting element adjacent to that light emitting element.

[0017] That is, for example, the LED-PH006 has a total of 14,824 light-emitting elements 050 in the longitudinal direction, which allows exposure processing corresponding to a longitudinal image width of approximately 315 mm (≒ approximately 18.5 mm x 17 chips). Furthermore, in the transverse direction of the light-emitting device 040, the arrangement pitch L1 between the light-emitting elements 050 of adjacent light-emitting devices 040 is approximately 350 μm. By reducing the arrangement pitch L1, the light-emitting elements can be positioned at the center of the lens, improving the light utilization efficiency of the light-emitting device 040. This arrangement pitch L1 is set taking into account various variations, such as variations in the mounting equipment (die bonder) and variations in the light-emitting element manufacturing process.

[0018] Furthermore, adjacent light-emitting devices 040 in the second direction may be arranged so that their light-emitting elements 050 overlap in the first direction. During the mounting process of the light-emitting devices 040, misalignment can occur, resulting in misalignment of the light irradiated on the photosensitive drum 001 at the boundary between the light-emitting devices 040, resulting in shading and image streaks. However, by arranging the light-emitting elements 050 of adjacent light-emitting devices 040 in the second direction so that they overlap in the first direction, the boundaries between the light-emitting element rows become unclear, thereby preventing shading and image streaks due to misalignment of the irradiated light. The overlap amount is calculated from the maximum amount of mounting variation in the mounting device (die bonder) and is set to an amount that prevents gaps from forming between the light-emitting elements 050 of adjacent light-emitting devices 040 in the short direction. This more effectively prevents shading and image streaks due to misalignment of the irradiated light.

[0019] FIG. 3 is a cross-sectional view showing an example of a light-emitting element and a transistor connected to the light-emitting element. A transistor is an example of an active element. FIG. 3 shows a light-emitting element 050 and a transistor 114. A pixel drive circuit that drives the light-emitting element 050 has, for example, a transistor 114 connected to the light-emitting element 050, as shown in FIG. 3. The transistor 114 disposed on a silicon substrate 110 is composed of a transistor gate 113, a transistor drain 112, and a transistor source 111. Here, an example of a MOSFET transistor having an active layer in a single-crystal silicon substrate is shown.

[0020] There are a plurality of contact plugs 115_1 to 115_4 that electrically connect the drain 112 of the transistor and the light emitting element 050, and wiring 117 made up of a plurality of metal layers 116_1 to 116_4, and an insulating layer 119 is provided between each wiring. Although the insulating layer 119 is illustrated as a single layer in Fig. 3, it may have a laminated structure made up of multiple layers.

[0021] The light-emitting element 050 is composed of a first electrode 116-4, an organic compound layer 121 having a light-emitting layer, and a second electrode 122, with two adjacent first electrodes 116-4 separated by an insulating layer. While FIG. 3 illustrates the organic compound layer as a single layer, the organic compound layer 121 may be composed of multiple layers. In the light-emitting element 050, the second electrode 122 is a transparent electrode, allowing light from the organic compound layer 121 to be extracted to the outside. A protective layer 125 is provided on the second electrode 122 to reduce deterioration of the light-emitting element. The second electrode 122 of the light-emitting element 050 is shared by multiple light-emitting elements 050 and serves as a common electrode.

[0022] Between each light-emitting element 050, a structure 127 having a large step directly below the organic compound layer 121 also thins the organic compound layer 121, electrically isolating the two light-emitting elements 050. The second electrodes 122 are electrically connected and serve as a common electrode for the plurality of light-emitting elements 050. In the light-emitting device 040, combinations of the light-emitting elements 050 and pixel drive circuits having transistors 114 are repeatedly arranged in the row and column directions.

[0023] For example, in FIG. 3, the arrangement pitch Pp of light-emitting elements in the direction X refers to the distance from one end (here, the left end) of the first electrode of a light-emitting element shown in FIG. 3 to the end of the first electrode of an adjacent light-emitting element on the same side (here, the left side). Furthermore, the arrangement pitch Pd of pixel driving circuits in the direction X may be the distance from one end to the other end of a repeating unit defined so that a corresponding pixel driving circuit is included in a repeating unit arranged in the direction X, with each pixel driving circuit being a repeating unit. For example, it may be the distance between the centers of two circuit separators arranged on either side of a pixel driving circuit in the direction X. Furthermore, for example, it may be the distance from the end (here, the left end) of the gate electrode of a transistor 114 shown in FIG. 3 to the end of the gate electrode of a transistor 114 of an adjacent pixel driving circuit on the same side (here, the left side).

[0024] The method of electrical connection with the electrodes (source electrode, drain electrode) included in the transistor is not limited to the mode shown in Fig. 3. Either the source electrode or the drain electrode of the transistor may be electrically connected in accordance with the polarity of the first electrode 116_4 or the polarity of the transistor.

[0025] Furthermore, the transistor is not limited to a transistor using a single-crystal silicon wafer, but may be a thin-film transistor (TFT) having an active layer on an insulating surface of a substrate. Examples of the active layer include single-crystal silicon, amorphous silicon, non-single-crystal silicon such as microcrystalline silicon, and non-single-crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide. Using a transistor using a single-crystal silicon wafer as the transistor allows for miniaturization of pixel driving circuits and speed-up of circuits having transistors.

[0026] 4 is an example of a circuit block diagram of a light emitting device 040 according to this embodiment. The light emitting device 040 has an input interface circuit 300, a register 301, a reference current generating unit 310, a programmable current source 311, a bias current source group 312, a current control circuit 313, a pixel driving circuit group 314, and a horizontal scanning circuit 317. The horizontal scanning circuit 317 has a data holding circuit 315 and a shift register 316. The input interface circuit 300 receives mode information for accessing the power supply and registers and information related to image data from an external interface, and outputs data signals to the register 301 and the horizontal scanning circuit 317.

[0027] Programmable current source 311 uses the output current of reference current generation unit 310 as a reference and outputs a current corresponding to the digital value supplied from register 301 to a group of bias current sources. The drive current of group of pixel drive circuits 314 is controlled by the setting value of register 301. Group of bias current sources 312 supplies an output current corresponding to the setting value set in register 301 to current control circuit 313. Current control circuit 313 generates a bias voltage for group of pixel drive circuits 314.

[0028] The shift register 316 controls the timing of emitting or not emitting light of the light emitting elements based on the data signal from the input interface circuit 300. The data holding circuit 315 holds information corresponding to each light emitting element and determines whether the light emitting element emits light or not.

[0029] The pixel drive circuit group 314 is connected to the light emitting elements, and the drive current is determined by the bias voltage supplied from the current control circuit 313, and the light emitting elements are controlled to emit or not emit light by a signal supplied from the data holding circuit 315. The pixel drive circuit group 314 has a plurality of pixel drive circuits, and each of the plurality of pixel drive circuits drives a corresponding light emitting element among the plurality of light emitting elements.

[0030] An example of a driving section for a light emitting element is shown in Figure 5. A method for adjusting the light emitting current of the light emitting element and light emission control will be described.

[0031] As shown in Figure 5, the pixel driving circuit 332 of the light-emitting element has a first transistor 330 and a second transistor 331 connected in series. For the sake of explanation, it is assumed that all the transistors have substantially the same size. The bias current source group 312 is made up of transistors M0 to Mi. The current control circuit is made up of transistors M1a to Mia and buffers B1 to Bi connected between the gate and drain terminals of the transistors M1a to Mia.

[0032] The pixel driving circuit group 314 has a first transistor group M11 to Mik and a second transistor group M111 to Mi1k, and each transistor M111 to Mi1k of the second transistor group is connected in series with a corresponding light emitting element O11 to Oik. The multiple current control circuits 313 are divided into multiple blocks 320 to 32i.

[0033] The output current I of the programmable current source 311 out is connected to the drain terminal of the transistor M0 of the bias current source group 312. The transistor M0 is diode-connected, and a voltage Vbn determined by the current Iout is commonly applied to the gates of the transistors M0 to Mi. i I out The same current flows.

[0034] In block 320, the drain terminal of transistor M1a, which constitutes current control circuit 313, is connected in series with the drain terminal of transistor M1. The gate terminal of transistor M1a is connected to the drain terminal via buffer B1. Buffer B1 is a voltage buffer with a gain of 1, and serves to absorb fluctuations in the gate potential of the first group of transistors M11 to M1k caused by the light emission control operation of the pixel drive circuit.

[0035] The transistor M1a is diode-connected via the buffer B1, and the gate potential is the voltage V determined by the current I1. bp1 is applied in common to the gates of the first transistors M11 to M1k. The gate-source voltages of the first transistors M11 to M1k are equal, and the same driving current I 11 ~I 1k The first transistor functions as a constant current source.

[0036] Whether or not a current is supplied to the light-emitting elements is controlled by applying a drive voltage to the gates of the second transistors M111 to M11k from the data holding circuit 315. The second transistors function as switches.

[0037] When the pixel drive circuit 332 is affected by power supply fluctuations, the current driving the light-emitting elements changes, resulting in unevenness in the output image of the image forming apparatus. By arranging the transistor M0 and the transistors M1 to Mi close to each other to form a current mirror circuit configuration, the configuration is less susceptible to fluctuations in the power supply line, so adopting the circuit configuration of this embodiment is advantageous in reducing unevenness. Similarly, by arranging the transistor M1a and the first transistors M11 to M1k close to each other to form a current mirror circuit configuration, the configuration is advantageous in reducing unevenness.

[0038] Similarly, the light emitting elements O21 to O2k are driven to emit light by the first transistors M21 to M2k and the second transistors M211 to M21k, and the light emitting elements Oi1 to Oik are driven to emit light by the first transistors Mi1 to Mik and the second transistors Mi11 to Mi1k.

[0039] In this embodiment, the transistor sizes are substantially the same, but the transistor sizes may be adjustable by register 301. If the transistor sizes of transistors M1 to Mi in bias current source group 312 are adjusted by register settings, the mirror ratio to transistor M0 changes, allowing for coarse adjustment of the current in the pixel drive circuit. Similarly, if the transistor sizes of transistors M1a to Mia in current control circuit 313 can be adjusted by register settings, the current in the pixel drive circuit can be coarsely adjusted.

[0040] Fig. 6 is an example of a planar layout diagram of the circuit blocks and light-emitting elements of the light-emitting device of Fig. 4. In Fig. 5, the substrate is shown as an example of a rectangle having long sides extending in a first direction and short sides extending in a second direction, but it may be another polygon such as a parallelogram.

[0041] The input unit interface circuits 300-1 to 300-2 have terminals 340 to 343 for inputting power, control signals, etc. for the light emitting device, and an interface circuit 334 arranged along the first direction. The light emitting elements 050 are 872 light emitting elements arranged at a predetermined resolution pitch in the longitudinal direction. Each row consists of 872 light emitting elements, and four rows of light emitting elements are arranged in the lateral direction. The pixel drive circuits 332 for each light emitting element 050 are arranged below the light emitting elements (on the substrate side). The register 301, shift register 316, and data retention circuit 315 are controlled by the input unit interface circuit 300, and are therefore arranged in plan view near the input unit interface circuit 300.

[0042] Since the data retention circuit 315 controls the light emission of the light-emitting elements and the current control circuit 313 controls the amount of light emitted by the light-emitting elements, it is necessary to wire control signals from each circuit block to the pixel drive circuit group 314. The current control circuit 313, pixel drive circuit group 314, and data retention circuit 315 are arranged in this order in the short side direction. This allows the control wiring for the data retention circuit to be wired from the side of the pixel drive circuit group 314 that extends in the long side direction in the short side direction. Furthermore, the control wiring for the current control circuit 313 can be wired from the other side of the pixel drive circuit group 314 that extends in the long side direction in the short side direction. This makes it easy to connect the control wiring for the data retention circuit and the control wiring for the current control circuit 313.

[0043] 7 shows an example of the arrangement of light-emitting elements and pixel driving circuits in region 350 shown in FIG. 6. In FIG. 7, the light-emitting device includes a plurality of light-emitting elements arranged on a main surface of a substrate in M ​​columns and N rows, and a plurality of pixel driving circuits arranged in M ​​columns and N rows, each driving corresponding one of the plurality of light-emitting elements. Here, M and N are integers greater than or equal to 1, the N rows extend in a first direction, and the M columns extend in a second direction intersecting the first direction. A first arrangement pitch of first and second light-emitting elements adjacent to each other in the first direction parallel to the N rows among the plurality of light-emitting elements is different from a second arrangement pitch of first and second pixel driving circuits adjacent to each other in the first direction among the plurality of pixel driving circuits.

[0044] The light emitting device will be described in more detail with reference to Fig. 7. Fig. 7(a) shows an example of the arrangement of first electrodes of light emitting elements arranged in a matrix of 4 rows and 8 columns in region 350 of Fig. 6.

[0045] The first electrodes of the light-emitting elements in the Nth row are arranged at a pitch of L1h in the longitudinal direction. The first electrodes of the light-emitting elements in the Nth and N+1th rows are arranged at an arrangement pitch of L1v in the lateral direction, and the first electrodes of the light-emitting elements in the Nth row and the first electrodes of the light-emitting elements in the N+1th row are arranged with a longitudinal offset of ΔL (L1h / 4) (N is 1 or greater but less than 3). By arranging the first electrodes with an offset of ΔL in the longitudinal direction, an exposure image with a higher resolution than the first electrode arrangement pitch L1h can be formed on the photosensitive drum. The design value of ΔL is not limited to L1h / 4, but can be selected from 0 to L1h depending on the balance between resolution and required light intensity. Here, an example is shown in which four light-emitting elements are arranged in one column, but this embodiment is not limited to this configuration. For example, if I (I is an integer greater than or equal to 2) light-emitting elements are arranged in one column, the longitudinal offset ΔL between the first electrodes of adjacent light-emitting elements in the row direction may be L1h / I.

[0046] Fig. 7(b) shows an example of the arrangement of pixel driving circuits connected to the first electrodes of the light-emitting elements in Fig. 7(a). The pixel driving circuits 332 arranged in a matrix of 4 rows and 8 columns are aligned at an arrangement pitch of L2h in the longitudinal direction and at an arrangement pitch of L2v in the lateral direction.

[0047] FIG. 7(c) shows the planar relationship when the elements are stacked by superimposing the plan views of FIG. 7(a) and FIG. 7(b). In plan view, the pixel driving circuit and the light-emitting element have at least a partial overlapping area. By having an overlapping area, the wiring connecting the pixel driving circuit and the light-emitting element can be shortened and the layout can be simplified. Generally, the light-emitting elements and the pixel driving circuits for the light-emitting elements are arranged at the same pitch. However, in this embodiment, the arrangement pitch L1h of the first electrodes of the light-emitting elements in the longitudinal direction is different from the arrangement pitch L2h of the pixel driving circuits.

[0048] When priority is given to resolution, the arrangement pitch of the light-emitting elements can be set narrower than the arrangement pitch of the pixel drive circuits, and when priority is given to light intensity, the arrangement pitch of the light-emitting elements can be set wider than the arrangement pitch of the pixel drive circuits. Because the design requirements for the light-emitting elements and the pixel drive circuits are different, designing them to appropriate sizes according to each requirement can achieve the characteristics of the light-emitting device and reduce costs.

[0049] As a light source for an image forming device, the light output of a single OLED-based light-emitting element may be insufficient. Increasing the light output of a light-emitting device requires a design that creates large light-emitting elements within a range that satisfies the specified resolution pitch. However, OLEDs are sensitive to heat, and the current that can flow per unit area is small compared to the current supply capacity per unit area of ​​the pixel drive circuit. Enlarging the pixel drive circuit to the same extent as the light-emitting element increases the chip size, reducing the yield of light-emitting devices per substrate and hindering cost reduction.

[0050] In this embodiment, the arrangement pitch L1h (first arrangement pitch) of the first electrodes in the longitudinal direction is larger than the arrangement pitch L2h (second arrangement pitch) of the pixel driving circuits. That is, the size of the pixel driving circuits can be made smaller in the longitudinal direction relative to the light-emitting elements. Alternatively, the size of the light-emitting elements can be made larger in the longitudinal direction relative to the pixel driving circuits. For example, the difference between the arrangement pitch L1h and the arrangement pitch L2h in the longitudinal direction is equal to or smaller than the value obtained by dividing the distance in the longitudinal direction from one end to the other end of the area in which the light-emitting elements are arranged by the number of pixel columns.

[0051] In this way, by reducing the longitudinal size of the pixel drive circuit, other circuits can be placed in the space freed up, thereby making the light-emitting device smaller and achieving cost reduction effects. Therefore, the advantages of using a silicon substrate can be further realized. Furthermore, compared to when the light-emitting elements are arranged in line with the pixel drive circuit, the area of ​​the light-emitting elements can be made larger, thereby increasing the amount of light emitted for exposure.

[0052] Similarly, in the short-side direction (second direction), the arrangement pitch L1v (first arrangement pitch) of the first electrodes is larger than the arrangement pitch L2v (second arrangement pitch) of the pixel driving circuits. Specifically, the fifth arrangement pitch of the first and third light-emitting elements adjacent to each other in two directions among the plurality of light-emitting elements is different from the sixth arrangement pitch of the first and third pixel driving circuits adjacent to each other in the second direction among the plurality of pixel driving circuits. More specifically, the fifth wiring pitch is larger than the sixth wiring pitch.

[0053] In this way, by reducing the size of the pixel drive circuit in the short direction, the light emitting device can be made smaller, resulting in cost reduction. Also, by increasing the size of the light emitting element, the amount of light emitted can be increased.

[0054] One side extending in the longitudinal direction of the first electrode 116-4 of the light-emitting element may or may not overlap with one side extending in the longitudinal direction of the pixel drive circuit 332. The arrangement and size of the light-emitting element are determined according to the amount of light required for the photosensitive drum, so they may be set appropriately according to each requirement.

[0055] 8(a) is a schematic cross-sectional view taken along line A-A' in FIG. 7(c). The first transistors 330 of the pixel driving circuit 332 are arranged at an arrangement pitch of L2h in the longitudinal direction. The first electrodes 116-4 of the light-emitting elements are arranged at an arrangement pitch of L1h. Metal wiring 350-352 electrically connected to the second transistors 331 of the pixel driving circuit 332 passes above the first transistors 330 and is connected to the first electrodes 116-4 of the light-emitting elements via contact holes.

[0056] Figure 8(b) is a schematic cross-sectional view taken along line BB' in Figure 7(c). The second transistors 331 of the pixel driving circuit 332 are arranged at the same arrangement pitch L2h as the first transistors 330. The drain terminals of the second transistors 331 are electrically connected to the metal wiring 350 via contact holes.

[0057] By adopting the configuration described in this embodiment, the size of the light emitting device can be reduced and the yield of light emitting devices per substrate can be increased, thereby achieving the effect of manufacturing light emitting devices at low cost.

[0058] (Embodiment 2) The light emitting device according to this embodiment will be described with reference to Figures 9 and 10. Only the outline and parts that differ from the first embodiment will be described, and the same or similar parts will be given the same reference numerals and descriptions thereof will be omitted.

[0059] FIG. 9(a) shows an example of the arrangement of the first electrodes of the light-emitting elements arranged in a matrix in the region 350 of FIG.

[0060] 9(b) shows an example of the arrangement of pixel drive circuits connected to the first electrodes of the light-emitting elements, in which a plurality of current control circuits 313 are added compared to FIG.

[0061] The pixel drive circuits are divided into pixel drive circuit blocks 363-366 in the first direction by circuit isolation sections 360-362 and arranged at an array pitch L3h. In other words, the circuit isolation sections 360-362 are arranged at a wiring pitch L3h (third array pitch) in the first direction. The third array pitch may be, for example, the distance from one end (e.g., the left end) of one circuit isolation section in the first direction to the end (here, the left end) of the circuit isolation section adjacent to that circuit isolation section, with one pixel drive circuit block sandwiched between them.

[0062] The control circuits 313 are divided into blocks in the first direction by block separators 371 and arranged at an arrangement pitch L4h (fourth arrangement pitch). The fourth arrangement pitch may be, for example, the distance from one end (e.g., the left side) of one block separator in the first direction to the end (here, the left end) of the circuit separator adjacent to that block separator across one block.

[0063] The third arrangement pitch is smaller than the fourth arrangement pitch, and multiple pixel driving circuit blocks are arranged in an area corresponding to one block of the control circuit 313 in the second direction. The block isolation section 371 and the circuit isolation section 361 are aligned in the second direction (short side direction). Therefore, for example, a first circuit isolation section included in the multiple circuit isolation sections is arranged in a position overlapping with a first block isolation section included in the multiple block isolation sections in the second direction. The length of the first circuit isolation section in the first direction is smaller than the length of the first block isolation section in the first direction.

[0064] If the misalignment between the light-emitting elements and the pixel drive circuits electrically connecting them becomes large, the resistance of the wiring connecting the two elements increases, degrading the current accuracy of the pixel drive circuits. By making the arrangement pitch L3h of the pixel drive circuit blocks an integer multiple of the arrangement pitch L1h of the light-emitting elements, the misalignment between the light-emitting elements and the pixel drive circuits can be kept within a certain range.

[0065] Dividing the pixel drive circuit into blocks and arranging a current control circuit near the pixel drive circuit for each block makes it possible to reduce the effects of power supply shading. By setting the arrangement pitch L2h of the pixel drive circuit shorter than the arrangement pitch L1h of the light-emitting elements, it is possible to free up space for arrangement of isolation parts such as the circuit isolation part 361 and the block isolation part 371. By arranging the block isolation parts between the blocks 320 and 321, it is possible to bias the back gates of the transistors at an appropriate potential for each block, which is advantageous in terms of current accuracy of the pixel drive circuit compared to a case where the blocks are not separated.

[0066] Reducing the number of current control circuits is advantageous for reducing the power consumption of the light-emitting device, so in this embodiment, two pixel drive circuit blocks are driven by a single current control circuit. Furthermore, when a large current is required to drive the light-emitting elements belonging to a pixel drive circuit block, it is desirable to drive one pixel drive circuit block with a single current control circuit in order to reduce the effects of power supply shading. The arrangement pitch L3h of the pixel drive circuit blocks need only be equal to or less than the arrangement pitch L4h of the current control circuits, and the arrangement pitch of both circuits can be set taking into consideration the power consumption of the light-emitting device, the drive current of the light-emitting elements, and the current accuracy of the pixel drive circuits.

[0067] FIG. 9(c) shows the planar relationship when the elements are stacked by superimposing the plan views of FIG. 9(a) and FIG. 9(b). As shown in FIG. 9(c), in a plan view of the substrate (main surface), at least a portion of the light-emitting element overlaps with the current control circuit. In the short direction (second direction), the arrangement pitch of the pixel drive circuits is smaller than the arrangement pitch of the light-emitting elements, so a space is created below the light-emitting elements. By arranging at least a portion of the current control circuit in this area, the light-emitting device can be made smaller by the amount of overlap compared to when the current control circuit and the light-emitting element are arranged so that they do not overlap. Furthermore, in the planar view, the light-emitting element may overlap with at least one of the circuit isolation sections.

[0068] Since the OLED-PH has multiple light-emitting devices 040 arranged in a staggered pattern, the light-emitting element 050 is arranged at a position away from the center of the rod lens array 023 in the short-side direction in a planar view. By placing the light-emitting element 050 closer to the long-side edge of the light-emitting device 040, the light-emitting element 050 is brought closer to the center of the rod lens array 023, which is advantageous for increasing the amount of exposure light on the photosensitive drum. In this embodiment, by having an area where some of the light-emitting elements (or the first electrode 116-4) and the current control circuit 313 overlap in a planar view, the light-emitting element can be brought closer to the long-side edge, which is advantageous for increasing the amount of exposure light. It is desirable that the width of the overlapping area in the short-side direction be equal to or less than the overlapping width L1v.

[0069] Figure 10(a) is a schematic cross-sectional view taken along line A-A' in Figure 9(c). The first transistors 330 of the pixel driving circuits 332 are arranged at an arrangement pitch of L2h in the longitudinal direction, and pixel driving circuit blocks made up of multiple pixel driving circuits are arranged at an arrangement pitch of L3h.

[0070] In this embodiment, the circuit isolation sections 360 and 362 have an element isolation structure, and the circuit isolation section 361 has a structure in which a well of a different polarity from the well in which the first transistor is disposed is disposed.

[0071] Figure 10(b) is a schematic cross-sectional view taken along line BB' in Figure 9(c). The second transistors 331 of the pixel driving circuits 332 are arranged at an arrangement pitch of L2h in the longitudinal direction, and pixel driving circuit blocks each consisting of a plurality of pixel driving circuits are arranged at an arrangement pitch of L3h. In this embodiment, the longitudinal length of the element isolation structure of the circuit isolation sections 360, 362 is longer than the longitudinal length of the element isolation structure between the second transistors 331.

[0072] Figure 10(c) is a schematic cross-sectional view taken along line CC' in Figure 9(c). Current control circuits 313 are arranged in the longitudinal direction at an arrangement pitch of L4h. In the circuit isolation portion 371 of the current control circuit, a well of a different polarity from the well in which the first transistor is arranged is arranged.

[0073] By adopting the configuration described in this embodiment, the light emitting elements and pixel driving circuits can be arranged in an optimal positional relationship, thereby improving the amount of light incident on the photosensitive drum. Furthermore, the accuracy of the driving current of the pixel driving circuit that drives each light emitting element can be improved. Therefore, this configuration is advantageous in terms of light intensity and uniformity as a light source device for an image forming apparatus.

[0074] The present disclosure includes, for example, the following configurations.

[0075] (Configuration 1) A plurality of light emitting elements arranged on a main surface of a substrate in M ​​columns and N rows; a plurality of pixel driving circuits arranged in M ​​columns and N rows, each driving a corresponding one of the plurality of light emitting elements; and M and N are integers of 1 or more, the N rows extend in a first direction and the M columns extend in a second direction; A light-emitting device in which a first arrangement pitch of a first light-emitting element and a second light-emitting element that are adjacent to each other in a first direction parallel to the N rows among the plurality of light-emitting elements is different from a second arrangement pitch of a first pixel driving circuit and a second pixel driving circuit that are adjacent to each other in the first direction among the plurality of pixel driving circuits.

[0076] (Configuration 2) 2. The light emitting device according to claim 1, wherein at least a portion of the first light emitting element overlaps with the first pixel driving circuit in a plan view relative to the main surface.

[0077] (Configuration 3) The light emitting device of Configuration 1 or 2, wherein the first arrangement pitch is larger than the second arrangement pitch.

[0078] (Configuration 4) 4. The light emitting device according to any one of configurations 1 to 3, wherein the substrate has a long side along the first direction and a short side along a second direction that intersects with the first direction.

[0079] (Configuration 5) 5. The light emitting device according to any one of configurations 1 to 4, wherein each of the plurality of pixel driving circuits includes a transistor that drives the corresponding light emitting element.

[0080] (Configuration 6) 6. The light emitting device of any one of configurations 1 to 5, wherein, in a plan view with respect to the main surface, the plurality of pixel drive circuits are divided into a plurality of pixel drive circuit blocks in the first direction by a plurality of circuit separation portions.

[0081] (Configuration 7) a current control circuit adjacent to the pixel drive circuit in the second direction; The light emitting device of any one of Configurations 1 to 6, wherein, in a plan view relative to the main surface, the current control circuit is divided into a plurality of blocks in the first direction by a plurality of block separation portions.

[0082] (Configuration 8) a current control circuit adjacent to the pixel drive circuit in the second direction; In a plan view with respect to the main surface, the plurality of pixel driving circuits are divided into a plurality of pixel driving circuit blocks in the first direction by a plurality of circuit isolation portions; the plurality of circuit isolation portions are arranged at a third arrangement pitch in the first direction, and the plurality of block isolation portions are arranged at a fourth arrangement pitch in the first direction; The light emitting device of any one of configurations 1 to 5, wherein the third arrangement pitch is smaller than the fourth arrangement pitch.

[0083] (Configuration 9) The light emitting device of Configuration 8, wherein a first circuit separation portion of the plurality of circuit separation portions is disposed at a position overlapping a first block separation portion of the plurality of block separation portions in the second direction.

[0084] (Configuration 10) 10. The light emitting device of configuration 8 or 9, wherein the length of the first circuit isolation portion in the first direction is shorter than the length of the first block isolation portion in the first direction.

[0085] (Configuration 11) 10. The light emitting device according to any one of Configurations 6, 8, and 9, wherein the light emitting element overlaps one of the circuit isolation portions in a plan view relative to the main surface.

[0086] (Configuration 12) A light-emitting device according to any one of configurations 1 to 11, wherein a fifth arrangement pitch of a first light-emitting element and a third light-emitting element adjacent to each other in the second direction among the plurality of light-emitting elements is different from a sixth arrangement pitch of a first pixel driving circuit and a third pixel driving circuit adjacent to each other in the second direction among the plurality of pixel driving circuits.

[0087] (Configuration 13) 13. The light emitting device of configuration 12, wherein the fifth arrangement pitch is larger than the sixth arrangement pitch.

[0088] (Configuration 14) 14. The light emitting device of any one of Configurations 1 to 3 and 5 to 13, wherein the substrate has a short side along the first direction and a long side along a second direction that intersects with the first direction.

[0089] (Configuration 15) a plurality of light emitting elements arranged in a matrix on a main surface of a substrate; a plurality of pixel drive circuits arranged in a matrix, each having a transistor for driving a corresponding one of the plurality of light emitting elements; a current control circuit adjacent to some of the plurality of pixel drive circuits in a first direction in a plan view with respect to the main surface; and In the plan view, at least a portion of the plurality of light-emitting elements overlaps with the current control circuit.

[0090] (Configuration 16) 16. The light emitting device of claim 15, wherein the substrate has a short side extending in the first direction and a long side extending in a second direction intersecting the first direction.

[0091] (Configuration 17) In the plan view, the plurality of pixel driving circuits are divided into a plurality of pixel driving circuit blocks in a second direction intersecting the first direction by a plurality of circuit isolation portions; In a plan view with respect to the main surface, the current control circuit is divided into a plurality of blocks in the second direction by a plurality of block separation portions, the plurality of circuit isolation portions are arranged at a third arrangement pitch in the second direction, and the plurality of block isolation portions are arranged at a fourth arrangement pitch in the second direction; 16. The light emitting device of claim 15, wherein the third arrangement pitch is smaller than the fourth arrangement pitch.

[0092] (Configuration 18) A light emitting device of structure 15 or 16, wherein the first circuit separation portion of the plurality of circuit separation portions is arranged in a position that overlaps with the first block separation portion of the plurality of block separation portions in the first direction.

[0093] (Configuration 19) 19. The light emitting device of configuration 18, wherein the length of the first circuit isolation portion in the second direction is shorter than the length of the first block isolation portion in the second direction intersecting with the first direction.

[0094] (Configuration 20) A photosensitive drum; an exposure head disposed opposite the photosensitive drum, the exposure head comprises a light-emitting device according to any one of configurations 1 to 19; an image forming apparatus having a lens array that focuses light emitted from the light emitting device onto the photosensitive drum; [Explanation of symbols]

[0095] 040 Light-emitting device 050 Light-emitting element 313 Current Control Circuit 332 Pixel driving circuit

Claims

1. a plurality of light-emitting elements arranged on a main surface of a substrate in M ​​columns and N rows; a plurality of pixel drive circuits arranged in M ​​columns and N rows, each of which drives a corresponding one of the plurality of light-emitting elements; and M and N are integers of 1 or more, The N rows extend in a first direction and the M columns extend in a second direction; A light-emitting device in which a first arrangement pitch of a first light-emitting element and a second light-emitting element that are adjacent to each other in a first direction parallel to the N rows among the plurality of light-emitting elements is different from a second arrangement pitch of a first pixel driving circuit and a second pixel driving circuit that are adjacent to each other in the first direction among the plurality of pixel driving circuits.

2. The light emitting device according to claim 1 , wherein at least a portion of the first light emitting element overlaps with the first pixel driving circuit in a plan view with respect to the main surface.

3. The light emitting device according to claim 1 , wherein the first arrangement pitch is larger than the second arrangement pitch.

4. The light emitting device according to claim 1 , wherein the substrate has a long side along the first direction and a short side along a second direction intersecting the first direction.

5. The light emitting device according to claim 1 , wherein each of the plurality of pixel driving circuits includes a transistor that drives the corresponding light emitting element.

6. The light emitting device according to claim 1 , wherein, in a plan view relative to the main surface, the plurality of pixel driving circuits are divided into a plurality of pixel driving circuit blocks in the first direction by a plurality of circuit isolation portions.

7. a current control circuit adjacent to the pixel drive circuit in the second direction; The light emitting device according to claim 1 , wherein, in a plan view relative to the main surface, the current control circuit is divided into a plurality of blocks in the first direction by a plurality of block separation portions.

8. a current control circuit adjacent to the pixel drive circuit in the second direction; In a plan view with respect to the main surface, the plurality of pixel drive circuits are divided into a plurality of pixel drive circuit blocks in the first direction by a plurality of circuit isolation portions, the plurality of circuit isolation portions are arranged at a third arrangement pitch in the first direction, and the plurality of block isolation portions are arranged at a fourth arrangement pitch in the first direction; The light emitting device according to claim 1 , wherein the third arrangement pitch is smaller than the fourth arrangement pitch.

9. The light emitting device according to claim 1 , wherein the first circuit isolation portions of the plurality of circuit isolation portions are arranged at positions overlapping with the first block isolation portions of the plurality of block isolation portions in the second direction.

10. The light emitting device according to claim 9 , wherein the length of the first circuit isolation portion in the first direction is smaller than the length of the first block isolation portion in the first direction.

11. The light emitting device according to claim 6 , wherein the light emitting element overlaps one of the circuit isolation portions in a plan view relative to the main surface.

12. 2. The light-emitting device according to claim 1, wherein a fifth arrangement pitch of a first light-emitting element and a third light-emitting element adjacent to each other in the second direction among the plurality of light-emitting elements is different from a sixth arrangement pitch of a first pixel driving circuit and a third pixel driving circuit adjacent to each other in the second direction among the plurality of pixel driving circuits.

13. The light emitting device according to claim 12 , wherein the fifth arrangement pitch is larger than the sixth arrangement pitch.

14. The light emitting device according to claim 1 , wherein the substrate has a short side along the first direction and a long side along a second direction intersecting the first direction.

15. a plurality of light emitting elements arranged in a matrix on a main surface of a substrate; a plurality of pixel drive circuits arranged in a matrix, each having a transistor for driving a corresponding one of the plurality of light emitting elements; a current control circuit adjacent to some of the plurality of pixel drive circuits in a first direction in a plan view with respect to the main surface; and In the plan view, at least a portion of the plurality of light-emitting elements overlaps with the current control circuit.

16. The light emitting device according to claim 15 , wherein the substrate has a short side extending in the first direction and a long side extending in a second direction intersecting the first direction.

17. In the plan view, the plurality of pixel drive circuits are divided into a plurality of pixel drive circuit blocks in a second direction intersecting the first direction by a plurality of circuit isolation portions, In a plan view with respect to the main surface, the current control circuit is divided into a plurality of blocks in the second direction by a plurality of block separation portions, the plurality of circuit isolation portions are arranged at a third arrangement pitch in the second direction, and the plurality of block isolation portions are arranged at a fourth arrangement pitch in the second direction; The light emitting device according to claim 15 , wherein the third arrangement pitch is smaller than the fourth arrangement pitch.

18. The light emitting device according to claim 15 , wherein the first circuit isolation portions of the plurality of circuit isolation portions are arranged at positions overlapping with the first block isolation portions of the plurality of block isolation portions in the first direction.

19. The light emitting device according to claim 18 , wherein a length of the first circuit isolation portion in a second direction intersecting the first direction is smaller than a length of the first block isolation portion in the second direction.

20. A photosensitive drum; an exposure head disposed opposite the photosensitive drum, The exposure head comprises: a light emitting device according to any one of claims 1 to 19; an image forming apparatus having a lens array that focuses light emitted from the light emitting device onto the photosensitive drum;

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