JP4511262B2 - Light emitting device and image recording device - Google Patents

Description

  The present invention relates to a self-scanning light-emitting device having a light-emitting thyristor and integrated transfer switch elements by optical excitation, and further relates to an image recording apparatus using the light-emitting device.

  A light-emitting thyristor, which is a negative resistance element having a pnpn structure, is used as a light-emitting device as a light-emitting device used as an optical printer head that is one of the exposure devices of an electrophotographic printer among image recording devices. Proposals have been made for light emitting devices that can be arranged as element rows and realize light emission state transfer. By using this for an optical printer head, it is easy to mount and a light emitting element array can be made compact. (For example, refer to Patent Documents 1 and 2).

FIG. 4 shows an equivalent circuit diagram showing a schematic circuit configuration of a basic structure of a conventional first light emitting device having such a light emission state transfer function, and a diagram showing waveforms of each clock pulse and light emission intensity. The light emitting thyristors T0 to Tn are arranged in a substantially linear shape, and are configured such that the light emission of each light emitting thyristor sequentially enters the adjacent light emitting thyristor. Since each of the light emitting thyristors T0 to Tn has a characteristic that a threshold voltage or a threshold current is reduced by receiving light irradiation, the threshold voltage of the light emitting thyristor adjacent to the light emitting thyristor is decreased. Become. In addition, three transfer clock lines φ1, φ2, and φ3 are repeatedly connected to the anode terminal of each light-emitting thyristor every three light-emitting thyristors, and each of the transfer clock lines φ1, φ2, and φ3 has a current source. I ₁ , I ₂ , and I ₃ are connected, and the light emission signal φI is configured to control the amount of current (see, for example, Patent Document 2 and Patent Document 3).

  FIG. 5 is a cross-sectional view of the light-emitting thyristor array portion of the light-emitting device shown in the equivalent circuit diagram of FIG. In FIG. 5, 21 is an n-type semiconductor substrate such as GaAs, 22 is an n-type semiconductor layer, 23 is a p-type semiconductor layer, 24 is an n-type semiconductor layer, 25 is a p-type semiconductor layer, 26 is an ohmic contact layer, 27 is An insulating layer, 28 is an anode terminal, 30 is a translucent protective film, and 32 is a light emitting thyristor. In the example shown in FIG. 5, when the right light-emitting thyristor 32 is in the light-emitting state, the light is emitted not only from the surface of the light-emitting thyristor 32 but also from the side surface of the semiconductor layer as indicated by the arrows in the figure. The light emitted from the side surface is irradiated onto the adjacent light emitting thyristor 32, so that the adjacent light emitting thyristor 32 is in a photoexcited state.

  The operation of the light emitting state transfer function in the conventional first light emitting device will be described with reference to FIG. First, the start pulse line φS changes from the low level to the high level, whereby the first light emitting thyristor T0 changes from the off state to the on state and emits light. The light emitted from the light emitting thyristor T0 enters the adjacent light emitting thyristor T1, and the threshold voltage of the light emission is lowered by light excitation. At this time, since the light-emitting thyristor T2 and the subsequent light-emitting thyristors T0 are further away from the light-emitting thyristor T0, the incident light is weaker and the threshold voltage for light emission is less lowered. That is, the greater the distance from the light emitting thyristor T0, the weaker the incident light, and the smaller the change in threshold voltage in the light emitting thyristor. In this state, when the transfer clock line φ1 next changes from the low level to the high level, the light emission threshold voltage of the light-emitting thyristor T1 decreases due to the light irradiation from the light-emitting thyristor T0. By setting the level according to the threshold voltage, the light emitting thyristor T1 changes from the off state to the on state and emits light. At this time, since the light emitting thyristor T4 to which the same transfer clock line φ1 is connected is sufficiently separated from the light emitting thyristor T0, there is almost no decrease in the threshold voltage of the light emission, so that the clock line at a level for causing the light emitting thyristor T1 to emit light. At the high level of φ1, no light is emitted, and only the light emitting thyristor T1 is turned on to emit light. Next, by setting the start pulse line φS to the low level, the light emitting thyristor T0 changes from the on state to the off state, and the light emission ends. As a result, the ON state is transferred from the light emitting thyristor T0 to the adjacent light emitting thyristor T1.

  Similarly, by changing the waveform of the clock pulse of each transfer clock line φ1 to φ3 as shown in the diagram of FIG. 4, the light emission thyristor T1 then emits light from the light emission thyristor T2, and then the light emission thyristor T2 emits light. The on state (light emission state) is transferred to the thyristor T3 with time.

For example, when only the transfer clock line φ3 is at a high level and the light-emitting thyristor T3 is in the on state, the light emission from the light-emitting thyristor T3 is the strongest incident on the adjacent light-emitting thyristors T2 and T4, and the threshold voltage of these light emission. Reduce. At this time, since the light-emitting thyristors T1 and T5 are located farther from the light-emitting thyristor T3 than the light-emitting thyristors T2 and T4, the light incident from the light-emitting thyristor T3 is weak, and the threshold voltage of the light emission does not decrease much. In this state, when the transfer clock line φ1 changes from the low level to the high level, the threshold voltage V _TH (T4) of the light emitting thyristor T4 becomes lower than the threshold voltage V _TH (T1) of the light emitting thyristor T1. Therefore, by setting the high level voltage V _H of the clock pulse of the transfer clock line φ1 as V _TH (T4) <V _H <V _TH (T1), only the light emitting thyristor T4 is turned on to emit light, and the light emitting thyristor T1 remains off. Then, by changing the transfer clock line φ3 from the high level to the low level, the light emitting thyristor T3 is turned off, and the on state (light emitting state) is transferred from the light emitting thyristor T3 to the light emitting thyristor T4.

  In this way, by setting the high levels of the clock pulses of the transfer clock lines φ1, φ2, and φ3 so as to slightly overlap each other, the on states (light emission states) of the light emitting thyristors T0 to Tn are sequentially transferred.

  Further, as shown in the diagram of FIG. 4, when only the light emitting thyristor T3 emits light strongly, the light emission signal φI is set to the high level in accordance with the timing at which the light emitting thyristor T3 emits light. As a result, the amount of current applied only to the light-emitting thyristor T3 which is the light-emitting element at that time is increased, and the light emission intensity L (T3) is also increased.

  The conventional first light-emitting device uses light emitted from the light-emitting thyristor T3 as light for irradiating the outside.

  The reason why three transfer clock lines φ1 to φ3 are necessary is that the light emitting thyristors on both sides of the light emitting thyristor in the light emitting state are both in the photoexcited state, and the transfer direction cannot be specified with two clock lines. .

  However, as can be seen from the diagram of the light emission intensity L (T3) shown in FIG. 4, this conventional first light emitting device emits light to be irradiated to the outside when applied to an optical printer head or the like. Even at times other than that, a certain amount of light emission (bias light) is generated from each light emitting thyristor in the on state (light emission state) for transferring the switching signal. This is because weak light emission is generated from each light-emitting thyristor due to the current for maintaining the on-state. However, when this conventional first light-emitting device is applied to an optical printer head or the like of an image recording apparatus, this bias light is used. However, since the photosensitive member is irradiated with light and acts as noise with respect to the irradiation light for original image recording, there is a problem that the image quality is deteriorated.

  In order to solve such problems, a structure in which elements for transferring a switching signal are separated and these elements are electrically controlled has been proposed (see, for example, Patent Document 4). ).

FIG. 6 is an equivalent circuit diagram showing a schematic circuit configuration of a basic structure of a second conventional light emitting device having such a light emitting state transfer function (self-scanning function). The light-emitting thyristor array in the conventional second light-emitting device has a portion in which switch thyristors (T1 to Tn) for switching signals are arranged substantially linearly, and a light-emitting device for emitting light to be irradiated to the outside. The light emitting thyristors (L1 to Ln) have portions arranged in a substantially straight line. The corresponding gate terminals of the switch thyristor and the light emitting thyristor are electrically connected to each other (for example, the gate terminals of the nth switch thyristor Tn and the nth light emitting thyristor Ln are connected to each other). .) The gate terminal of the first switch thyristor T1 is connected to the start pulse line φS. The gate terminals of the switch thyristors T1 to Tn are connected to the control power supply V _GK via the load resistor _RL, and the clock terminals φ1 and φ2 are connected to every other one of the anode terminals. The

  The gate terminal of the first switch thyristor T1 is electrically connected to the gate terminal of the second switch thyristor T2 via the transfer direction designating diode D. Thereafter, each gate terminal is repeatedly connected in the same manner. Are electrically connected.

  A description will be given of the light emission state transfer and light emission using a switch element by conventional electrical control in such a conventional second light emitting device.

  The light emission state transfer starts when the start pulse line φS changes from the high level to the low level. As a result, the threshold voltage for light emission of the first switch thyristor T1 is lowered. At this time, the clock line φ2 is changed from the low level to the high level, so that the first switch thyristor T1 is turned on to emit light. After the second switch thyristor T2, the transfer direction designation diode D causes the switch thyristors T2, T3,... According to the forward voltage drop of the transfer direction designation diode D as the distance from the first switch thyristor T1 increases. The voltage applied to the gate terminal rises. Therefore, in the third switch thyristor T3 to which the same clock line φ2 is connected, the light emission threshold voltage is increased by the forward voltage drop corresponding to the two transfer direction designating diodes D, so that the clock pulse φ2 By using a start pulse whose high level is equal to or lower than the threshold voltage for light emission of the third switch thyristor T3, only the first switch thyristor T1 is turned on to emit light.

  In this state, when the power supply line φI for the light emitting thyristors L1 to Ln is changed from the low level to the high level, in the first light emitting thyristor L1, the light emission on condition is the first in which the gate terminals are electrically connected to each other. Therefore, the first light emitting thyristor L1 is turned on and emits light, and the first light emitting unit emits light and is lit. Next, by returning the power supply line φI to the low level, the first light-emitting thyristor L1 is turned off and light emission ends.

  Next, the light emission state transfer (transfer of the ON condition) from the first switch thyristor T1 to the second switch thyristor T2 will be described. Even when the first light-emitting thyristor L1 is turned off, the clock line φ2 remains at the high level, so the first switch thyristor T1 is kept in the on-state (light-emitting state). At this time, the voltage applied to the gate terminal of the second switch thyristor T2 is higher than the first switch thyristor T1 by the forward voltage drop of one transfer direction designation diode D, and the same clock line φ1 is connected. In the fourth switching thyristor T4, the voltage applied to the gate terminal is further increased by the forward voltage drop of two transfer direction designating diodes D. When the clock line φ1 is changed from the low level to the high level in this state, the voltage is set to a voltage between the light emission threshold voltage of the second switch thyristor T2 and the light emission voltage of the fourth switch thyristor T4. If the high level of the clock pulse φ1 is selected, only the second switch thyristor T2 is turned on to emit light.

After the second switch thyristor T2 is turned on (light emission state) in this way, the first switch thyristor T1 becomes the first light emission thyristor L1 by changing the clock line φ2 from the high level to the low level. In the same manner as when the light is turned off, the light is turned off and light emission ends. At this time, since the start pulse line φS changes from the low level to the high level, the voltage applied to the gate terminal of the first switch thyristor T1 by the transfer direction designation diode D is substantially equal to the voltage of the control power supply V _GK. Thus, the switch thyristor having the lowest emission threshold voltage is the second switch thyristor T2. Thus, the ON state (light emission state) of the switch thyristor is transferred from the first switch thyristor T1 to the second switch thyristor T2. At this time, when the power supply line φI is changed from the low level to the high level, only the second light emitting thyristor L2 is turned on to emit light.

By sequentially repeating the above operations, the light emission states of the switch thyristors T0 to Tn are sequentially transferred, and the light emission states of the light emission thyristors L1 to Ln can be controlled accordingly.
JP-A-49-124992 Japanese Patent No. 2757334 Japanese Patent No. 3020177 Japanese Patent No. 2577089 JP 2003-243696 A Japanese Patent No.2683781

  In the conventional first light emitting device, the light emitting thyristor is required to have high light receiving efficiency because the light emitting thyristor receives light emitted from the light emitting thyristor and the adjacent light emitting thyristor is optically excited. However, as indicated by broken arrows in FIG. 5, light emitted from the light emitting thyristor 32 is not irradiated to the adjacent light emitting thyristor 32 but is absorbed by the n-type semiconductor substrate 21 or emitted to the outside. Therefore, there is a problem that the amount of light that can be received by the adjacent light emitting thyristor 32 is reduced. In addition, there is a problem that the image quality deteriorates when applied to an optical printer head or the like because bias light is generated at the same time as there is light emitted to the outside.

In the second conventional light emitting device, the light receiving efficiency between the switch thyristors is not important because the light excitation of the light emitting thyristor is not used for signal transfer in the switch thyristor. However, a switch thyristor is used as a switch element that is electrically driven for signal transfer, and the light emission state of the light-emitting thyristor as a light-emitting element is transferred by its electrical control. A transfer direction designating diode D, a load resistor _RL for controlling the gate voltage of the switching thyristor, and the like are required, and these are formed by using a part of the thyristor (pnpn) structure. For this reason, the structure of the switch thyristor is complicated, and the number of processes is increased in manufacturing, resulting in poor productivity.

  The present invention has been made in view of the problems in the conventional techniques as described above, and an object of the present invention is to provide a transfer switch element by optical excitation that can simplify the entire structure and is excellent in reliability. It is an object of the present invention to provide a light emitting device that can improve the light receiving efficiency of adjacent light emitting thyristors in a switch thyristor. Another object of the present invention is to provide an image recording apparatus using the light emitting device of the present invention, which can obtain a recorded image with good image quality.

The light-emitting device of the present invention includes a large number of three-terminal light-emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, which can control a light emission threshold voltage or threshold current by irradiating light from the outside. The light from the three terminal light emitting switch elements is linearly arranged on the substrate so that light emitted from the adjacent three terminal light emitting switch elements is incident on the substrate, and a clock line is connected to the anode terminal of each of the three terminal light emitting switch elements. A three-terminal light emitting switch element array, and a three-terminal light emitting element having an anode terminal, a cathode terminal, and the gate terminal, capable of electrically controlling a threshold voltage or a threshold current of light emission from the outside via the gate terminal. A plurality of gate terminals arranged on the substrate in correspondence with the three-terminal light-emitting switch elements, and the gate terminals of the three-terminal light-emitting elements; Is electrically connected to the gate terminal of the corresponding three-terminal light-emitting switch element, and the anode terminal of the three-terminal light-emitting element is connected to a line for supplying voltage or current for light emission. The three-terminal light-emitting switching element and the three-terminal light-emitting element are respectively formed on a n-type semiconductor substrate, on a first n-type semiconductor layer, a first p-type semiconductor layer, and a second n-type. A light-receiving unit in which a type semiconductor layer is sequentially stacked; and a light-emitting unit in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked on the light-receiving unit. The anode terminal is electrically connected to the n-type semiconductor layer, the cathode terminal is electrically connected to the n-type semiconductor substrate or the first n-type semiconductor layer, and the gate terminal is electrically connected to the second or third n-type semiconductor layer. Luminous Silice , And the said 3-terminal light emitting switch element array is a between the 3-terminal light emitting switch element adjacent the major surface of the substrate on the side where the 3-terminal light emitting switch element array is provided one main surface of the substrate provided in the upper, by reflecting the light-emitting, reflective layer to be incident on the light receiving portion of the adjacent said 3-terminal light emitting switch element that is provided.

The light emitting device according to the present invention has the above-described configuration, wherein the light emitting device is provided on the three terminal light emitting switch element array so as to cover the three terminal light emitting switch element array, and is emitted on the three terminal light emitting switch element array. The light emitting device further includes a second reflective layer that reflects light emitted from the terminal light emitting switch element and enters the adjacent three terminal light emitting switch element .

  An image recording apparatus of the present invention is characterized in that the light emitting device of the present invention having any one of the above-described structures is used in an exposure device for a photoreceptor.

  According to the light emitting device of the present invention, a large number of three-terminal light emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, which can control the light emission threshold voltage or threshold current by irradiating light from the outside. 3 arranged linearly on the substrate so that light emitted from one three-terminal light-emitting switch element is incident on an adjacent three-terminal switch element, and a clock line is connected to each anode terminal of the three-terminal light-emitting switch element. A terminal light-emitting switch element array, and a number of three-terminal light-emitting elements having an anode terminal, a cathode terminal, and a gate terminal capable of electrically controlling a threshold voltage or threshold current of light emission from the outside via a gate terminal; The three terminal light emitting switch elements are arranged on the substrate in correspondence with the three terminal light emitting switch elements, and the three terminal light emitting elements respectively correspond to the three terminal light emitting elements. A three-terminal light emitting switch comprising: a three-terminal light-emitting element array electrically connected to a gate terminal of the switch element; and an anode terminal of the three-terminal light-emitting element connected to a line for supplying voltage or current for light emission A light receiving section in which a first n-type semiconductor layer, a first p-type semiconductor layer, and a second n-type semiconductor layer are sequentially stacked on an n-type semiconductor substrate; A light emitting portion in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked is provided on the light-receiving portion, and an anode terminal is provided on the second p-type semiconductor layer. Since this is a light emitting thyristor in which a cathode terminal is electrically connected to one n-type semiconductor layer and a gate terminal is electrically connected to a second or third n-type semiconductor layer, signal transfer by a switch thyristor is used for optical excitation of the light emitting thyristor. Yo With this configuration, the switch thyristor portion does not require a transfer direction designation diode or a load resistance for gate voltage control, and the switch thyristor portion is configured with a simpler array structure than conventional light emitting devices. In addition, the number of processes can be reduced during manufacturing. Further, since the three-terminal light emitting switch element array is provided with a reflective layer that reflects light emission on the substrate between the adjacent three terminal light emitting switch elements, the light emitted toward the substrate by the reflective layer is adjacent. Can be incident on the light receiving portion of the three-terminal light-emitting switch element, and the light-receiving efficiency between the adjacent three-terminal light-emitting switch elements can be increased, so that the light-emission output of the three-terminal light-emitting switch element can be suppressed. The power consumption in the light emitting switch element array can be reduced, and the three terminal light emitting switch element can be prevented from deteriorating and stably operated over a long period of time. Even if the light emission output of the three-terminal light-emitting switch element is suppressed, the light emission state can be transferred to the adjacent three-terminal light-emitting switch element by light excitation.

Further, according to the light emitting device of the present invention, when the second reflective layer is provided, light emitted from the three-terminal light-emitting switch element array is emitted in the direction perpendicular to the surface of the substrate and in the direction of the three-terminal light-emitting element. Since the light emission and the light emission in the opposite direction of the three-terminal light-emitting element are sufficiently shielded from light by the second reflection layer, the light-emitting state is transferred to the adjacent three-terminal light-emitting switch element direction in the three-terminal light-emitting switch element array. Only light emission can be used efficiently, the influence of leakage light can be suppressed, and only output light from the three-terminal light emitting element array can be efficiently extracted to the outside.

  According to the image recording apparatus of the present invention, since the electrophotographic image recording apparatus uses the light emitting device of the present invention for the exposure device for the photosensitive member, in the light emitting device as the exposure device. Since the light emitting element for performing image exposure on the photosensitive member and the switch element for signal transfer can be integrated, a circuit board that mounts the light emitting device and constitutes the exposure apparatus is provided. The size can be reduced, and the number of wire bondings to the circuit board and the number of drive ICs to be mounted on the circuit board can be reduced, so that it is possible to reduce the size and provide a low-cost exposure apparatus. An image recording apparatus can be provided. Further, since there is no problem of bias light as in the conventional light emitting device, an image with excellent image quality can be obtained by electrophotographic image recording.

  Hereinafter, an example of an embodiment of a light emitting device of the present invention will be described with reference to the drawings.

  FIG. 1 is a main part plan view showing an example of an embodiment of a light emitting device of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A ′ in FIG. 1.

  As in the example shown in FIGS. 1 and 2, the light-emitting device of the present invention includes an anode terminal, a cathode terminal, and a gate terminal, which can control the threshold voltage or threshold current of light emission by irradiating light from the outside. Are arranged in a straight line on the substrate 1 so that light emitted from one three-terminal light-emitting switch element 15 is incident on the adjacent three-terminal switch element 15 and three-terminal light-emitting elements A three-terminal light-emitting switch element array in which the clock line (φ1, φ2, φ3) 8 is connected to each anode terminal of the switch element 15, and a threshold voltage or threshold current for light emission is electrically supplied from the outside via the gate terminal. Many controllable three-terminal light-emitting elements 14 having an anode terminal, a cathode terminal, and a gate terminal are arranged on the substrate 1 so as to correspond to the three-terminal light-emitting switch element 15. The gate terminal of the three-terminal light-emitting element 15 is electrically connected to the corresponding gate terminal of the three-terminal light-emitting switch element 14 by the inter-gate wiring 13, and the anode terminal of the three-terminal light-emitting element 14 is a voltage or current for light emission. A three-terminal light-emitting element array connected to a line (φI) 12 for supplying the three-terminal light-emitting switch element 15 and the three-terminal light-emitting element 14 on the n-type semiconductor substrate 1, respectively. A light receiving portion in which an n-type semiconductor layer 2, a first p-type semiconductor layer 3, and a second n-type semiconductor layer 4 are sequentially laminated, and a third n-type semiconductor layer 5 and a second n-type semiconductor layer 5 on the light receiving portion. a light-emitting portion on which the p-type semiconductor layer 6 is stacked, and an anode terminal for the second p-type semiconductor layer 6, the n-type semiconductor substrate 1 or the first n-type semiconductor layer 2, in this example, n-type A cathode terminal is provided on the semiconductor substrate 1, and the second or third n The light emitting thyristor has a gate terminal electrically connected to each of the semiconductor layers 4 and 5, and the three terminal light emitting switch element array has a reflective layer 10 that reflects light emission on the substrate 1 between adjacent three terminal light emitting switch elements 15. It is provided.

  In this example, an element array using a light emitting thyristor as a light emitting element has a three-terminal light emitting switch element 15 which is a light emitting thyristor for a signal transfer switch arranged in a straight line, and a start composed of the same light emitting thyristor. The switch thyristor 16 is connected, and the light emitting thyristor 3 terminal light emitting element 14 is linearly arranged, and the gate of the corresponding 3 terminal light emitting switch element 15 of each element array. The terminal and the gate terminal of the three-terminal light emitting element 14 are electrically connected by the inter-gate wiring 13. The gate terminal of the start switch thyristor 16 is connected to a start pulse line φS which is a signal input portion, and three clock lines (φ1, φ2, φ3) 8 are connected to the anode terminal of the three-terminal light emitting switch element 15. Are connected one by one every third.

  The three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate 1, for example, the n-type semiconductor substrate 1, so that an optical printer head for an electrophotographic image recording apparatus or the like It is used for a light emitting device as a line head.

  In FIG. 2, an n-type buffer layer may be interposed between the n-type semiconductor substrate 1 made of Si, GaAs, or the like and the first n-type semiconductor layer 2. Further, a p-type ohmic contact layer may be interposed between the second p-type semiconductor layer 6 and the clock line 8 serving as an anode terminal.

  The insulating layer 7 is for securing electrical insulation between the clock line 8 or the line 12 for supplying a voltage or current for light emission and each semiconductor layer, and has translucency such as polyimide, and A flat insulating film is used.

  11 is a back electrode functioning as a cathode terminal.

The light generated from the second p-type semiconductor layer 6 which is the light-emitting layer of the light emitting part is directly incident on the light receiving part of the adjacent three-terminal light emitting switch element 15 as indicated by an arrow in FIG. According to the light emitting device of the present invention, the light receiving part in which the light emitted toward the substrate 1 is reflected by the reflective layer 10 provided on the substrate 1 between the adjacent three-terminal light emitting switch elements 15. It will enter into. Further, as in this example, by providing the second reflective layer 9 for shielding the light emission in the vertical direction on the surface of the substrate 1 so as to cover the three-terminal light emitting switch element array, the light emitted to the outside is also this first. It can be reflected by the two reflective layers 9 and incident on the light receiving portion of the adjacent three-terminal light emitting switch element 15. Since the amount of light incident on the adjacent three-terminal light-emitting switch element 15 is increased by these reflections, the light-receiving efficiency of the adjacent three-terminal light-emitting switch element 15 is extremely high according to the light-emitting device of the present invention.

  Such a reflective layer 10 may be formed by forming a layer made of Ti, Cr, Al, Au or the like between the three-terminal light emitting switch elements 15 with a thickness of 0.1 μm to 2 μm by a vacuum deposition method or a sputtering method.

In addition, the second reflective layer 9 is formed on the substrate out of the light emitted from the three-terminal light-emitting switch element 15, particularly when the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate. The light emission in the vertical direction and the light emission in the direction of the three-terminal light-emitting element 14 are shielded on the surface of 1. By providing the second reflective layer 9 as described above, out of the leakage light from the three-terminal light-emitting switch element array, light emission in the direction perpendicular to the surface of the substrate 1, light emission in the direction of the three-terminal light-emitting element 14, and three-terminal light-emitting element 14 Since the light emission in the opposite direction is sufficiently shielded by the second reflective layer 9, when the light-emitting device of the present invention is used as an exposure device in an electrophotographic image recording apparatus, it is caused by such leakage light. It is possible to obtain excellent image quality without image deterioration. The second reflective layer 9, if example embodiment, the polyimide is spin-coated, may be formed by processing into a predetermined pattern by photo-etching. In addition, in order to reflect the light emitted from the three-terminal light emitting switch element 15 by the second reflective layer 9 and efficiently enter the light receiving portion of the adjacent three-terminal light emitting switch element 15, the second reflective layer 9 includes : high reflectivity for light emission wavelength, it is preferred to use one made of an insulating material such as polyimide having a lower refractive index than the insulating layer 7.

  FIG. 3 is an equivalent circuit diagram showing a schematic circuit configuration in the example of the embodiment of the light emitting device of the present invention. The light emitting thyristors T1 to Tn as the three terminal light emitting switch elements 15 constituting the three terminal light emitting switch element array and the light emitting thyristors L1 to Ln as the three terminal light emitting elements 14 constituting the three terminal light emitting element array are respectively linear. The gate terminals of the corresponding light emitting thyristors T1 to Tn and the gate terminals of the light emitting thyristors L1 to Ln of each element array are electrically connected (for example, three terminals). The gate terminal of the i-th (i <n) light-emitting thyristor Tn of the light-emitting switch element array is connected to the gate terminal of the i-th light-emitting thyristor Ln of the 3-terminal light-emitting element array.), The start switch thyristor T0 A start pulse line φS is connected to the gate terminal of the gate terminal to serve as a signal input section. Including the start switch thyristor T0, three clock lines (φ1, φ2, φ3) are sequentially connected to the anode terminals of the light-emitting thyristors of the three-terminal light-emitting switch element array. ing.

  Based on the example configured as described above, switching signal transfer and light emission operation in the light emitting device of the present invention will be described.

  The transfer of the switching signal is started by changing the clock line φ3 connected to the anode terminal of the start switch thyristor T0 to the high level and changing the start pulse line φS from the high level to the low level (the gate satisfying the emission condition of the light emitting thyristor T0). It starts by changing to a voltage below the voltage. As a result, the start switch thyristor T0 is turned on to emit light. The light emitted from the start switch thyristor T0 is configured so that a part thereof is most strongly incident on the next light emitting thyristor T1, and the light emission threshold voltage of the light emitting thyristor T1 is reduced by this light irradiation. .

Next, transfer of the ON condition from the light emitting thyristor T0 to the light emitting thyristor T1 will be described. The light emission by the light emission from the light emitting thyristor T0 reduces the light emission threshold voltage of the light emitting thyristor T1, and in this state, the clock line φ1 connected to the gate terminal of the light emitting thyristor T1 is changed from the low level to the high level. . At this time, since the light emitting thyristor T4 having the same clock line φ1 connected to the gate terminal is sufficiently away from the start switch thyristor T0, the threshold voltage of light emission due to the light emission of the light emission of the start switch thyristor T0. There is almost no decline. Therefore, the high level V _H (φ1) of the clock line φ1 is set to a voltage between the light emission threshold voltage V _TH (T4) of the light emitting thyristor T4 and the light emission threshold voltage V _TH (T1) of the light emitting thyristor T1. If this is set (that is, if V _H (φ1) is set as V _TH (T1) <V _H (φ1) <V _TH (T4)), only the light-emitting thyristor T1 is turned on and emits light.

After the light emitting thyristor T1 is turned on and emits light, the light emitting thyristor T0 is turned off and the light emission ends by changing the clock line φ3 from the high level to the low level. Thus, the ON state of the light-emitting thyristor constituting the three-terminal light-emitting switch element array is transferred from the start switch thyristor T0 to the next light-emitting thyristor T1. At this time, by changing the start pulse line φS from the low level to the high level, the start switch thyristor T0 is kept off even if the clock line φ3 is changed to the high level again. Here, the line φI for supplying the voltage or current for light emission is changed from the low level to the high level. In the first light-emitting thyristor L1 of the three-terminal light-emitting element array, since the light-emitting thyristor T1 of the corresponding three-terminal light-emitting switch element array is in the on state, the voltage applied to its gate terminal is approximately 0V. In the second light-emitting thyristor L2, the corresponding light-emitting thyristor T2 of the three-terminal light-emitting switch element array is in an off (light-excited) state, and the threshold voltage of light emission of the first and second light-emitting thyristors L1 and L2 of the three-terminal light-emitting element array _Are V _TH (L1) and V _TH (L2), respectively, the high level V _H (φI) of the clock line φ1 is expressed as V _TH (L1) <V _H (φI) <V _TH (L2) as described above. If so, only the light-emitting thyristor L1 is turned on and emits light. When the line φI for supplying the voltage or current for light emission is changed from the high level to the low level, the first light-emitting thyristor L1 of the three-terminal light-emitting element array is turned off and the light emission ends.

  By sequentially repeating the switching signal transfer by the three-terminal light-emitting switch element array and the light-emission operation by the corresponding three-terminal light-emitting element array as described above, the start switch thyristor T0 is turned on (light-emitting state). Are sequentially transferred to the light emitting thyristors T1, T2, T3... As a switching signal, and the light emitting operation of the light emitting thyristors L1, L2, L3.

  The reason why three clock lines φ1, φ2 and φ3 are required as clock lines for supplying clock pulses for the operation of the three-terminal light-emitting switch element array is that the switching signal is transferred in the three-terminal light-emitting switch element array to emit light. For example, for the light emitting thyristor T2, the light emitting thyristor T1 and T3 adjacent to each other is irradiated with light emitted from the light emitting thyristor T2, and both of them are in a state where the threshold voltage or threshold current of the light emission is lowered. This is because both T1 and T3 are in a light emitting state next to the light emitting thyristor T2, and cannot be sequentially transferred from T1 to T2 and from T2 to T3.

  The image forming apparatus of the present invention is an electrophotographic image forming apparatus in which the light emitting device of the present invention is used as an exposure device for a photoreceptor. The configuration example includes, for example, a photoconductor, a charging device, an exposure device, a developing device, a transfer device, and a fixing device, and the exposure device for the photoconductor is a three-terminal light emitting switch using the light emitting thyristor of the present invention. An array in which elements and three-terminal light-emitting elements are integrated is linearly arranged on a circuit board to form a light-emitting device having a three-terminal light-emitting switch element array and a three-terminal light-emitting element array, respectively. It is configured with a driver IC for driving.

  According to the image forming apparatus of the present invention having such a configuration, since the light emitting device of the present invention is used in the exposure device for the photosensitive member, the three-terminal light emitting switch element and the three terminal light emitting by the light emitting thyristor of the present invention are used. An exposure apparatus can be manufactured at low cost by using an array in which elements are integrated, and since no bias light or leakage light is generated from the exposure apparatus, an image provided with an exposure apparatus capable of forming an inexpensive and high-quality image. A forming apparatus can be provided.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

It is a principal part top view which shows the example of embodiment of the light-emitting device of this invention. FIG. 2 is a cross-sectional view taken along line A-A ′ in FIG. 1. It is an equivalent circuit diagram which shows the schematic circuit structure in the example of embodiment of the light-emitting device of this invention. It is the equivalent circuit diagram which shows the schematic circuit structure of the basic structure of the conventional 1st light-emitting device, and the diagram which shows the waveform of each clock pulse and light emission intensity. FIG. 5 is a cross-sectional view of a light emitting thyristor array portion of the light emitting device shown in an equivalent circuit diagram in FIG. 4. It is an equivalent circuit diagram which shows the schematic circuit structure of the basic structure of the conventional 2nd light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... n-type semiconductor substrate 2 ... 1st n-type semiconductor layer 3 ... 1st p-type semiconductor layer 4 ... 2nd n-type semiconductor layer 5 ... 3rd n-type Semiconductor layer (light emitting layer)
6 ... 2nd p-type semiconductor layer 7 ... Insulating layer 8 ... Clock line 9 ... 2nd reflective layer
10 ... Reflective layer
11 ... Back electrode
12 ... Line for supplying voltage or current for light emission
13 ... Wiring between gates
14 ... 3 terminal light emitting device
15 ... 3 terminal light emitting switch element
16 ... Start switch thyristor

Claims (5)

A large number of three-terminal light-emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, each of which can control a light-emission threshold voltage or a threshold current by irradiating light from the outside. A three-terminal light-emitting switch element array in which light emission from the light is incident on the adjacent three-terminal switch elements in a straight line on the substrate and a clock line is connected to each anode terminal of the three-terminal light-emitting switch elements When,
A number of three-terminal light-emitting elements having an anode terminal, a cathode terminal, and the gate terminal, the threshold voltage or threshold current of light emission being electrically controllable from the outside via the gate terminal, the three-terminal light-emitting switch element The gate terminals of the three-terminal light-emitting elements are electrically connected to the gate terminals of the corresponding three-terminal light-emitting switch elements, and the anodes of the three-terminal light-emitting elements are arranged on the substrate. A three-terminal light-emitting element array having terminals connected to a line for supplying voltage or current for light emission;
The three-terminal light-emitting switch element and the three-terminal light-emitting element are each formed by sequentially stacking a first n-type semiconductor layer, a first p-type semiconductor layer, and a second n-type semiconductor layer on an n-type semiconductor substrate. And a light emitting portion in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked on the light-receiving portion, and the anode terminal is connected to the second p-type semiconductor layer. A light emitting thyristor in which the cathode terminal is electrically connected to the n-type semiconductor substrate or the first n-type semiconductor layer, and the gate terminal is electrically connected to the second or third n-type semiconductor layer.
The 3-terminal light emitting switch element array is a between the 3-terminal light emitting switch element adjacent, provided on the main surface of the substrate on which the 3-terminal light emitting switch element array is provided one main surface of the substrate is, by reflecting the light emission, light emitting reflective layer to be incident on the light receiving portion of the adjacent said 3-terminal light emitting switch element is provided apparatus. It is provided on the three-terminal light-emitting switch element array so as to cover the three-terminal light-emitting switch element array, and the light emitted from the three-terminal light-emitting switch element emitted on the three-terminal light-emitting switch element array is reflected and adjacent. The light emitting device according to claim 1, further comprising a second reflective layer incident on the three-terminal light emitting switch element. The light emitting device according to claim 2, further comprising a light-transmitting insulating layer provided between the second reflective layer and the three-terminal light emitting switch element array . The light-emitting device according to claim 1, further comprising a back electrode provided on a back surface side of the main surface of the substrate . Image recording apparatus, wherein a light-emitting device of any serial mounting of claims 1 to 4 is used in the exposure apparatus to the photoreceptor.

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