JP2006100438A - Light emitting device and image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable light emitting device in which transfer switch elements of optical excitation are integrated with simplified entire structure. <P>SOLUTION: The light emitting device comprises multiple three-terminal light emitting switch elements 15 capable of controlling a threshold voltage or current from outside by radiating light, and controls a three-terminal light emitting element 14 corresponding to the three-terminal light emitting switch element 15 by electrically connecting gate terminals. Relating to the three-terminal light emitting switch element 15, one of adjoining elements protrudes to the other side while the other one runs along the protruded part when viewed from above. Since one side of the three-terminal light emitting switch element 15 protrudes to the other side while the other side runs along the protruded part, the areas of a light receiver and light emitter are larger, resulting in improving light transmission efficiency between adjoining elements. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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. 5 is 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 (self-scanning function), and lines showing waveforms of clock pulses and light emission intensity. The figure is shown. 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. The light-emitting thyristors T0 to Tn have a rectangular shape when viewed from above. Such light emitting thyristors T0 to Tn each have a characteristic that their threshold voltage or threshold current is reduced by receiving light irradiation. Therefore, the threshold voltage of the light emitting thyristor adjacent to the light emitting thyristor or The threshold current will drop. In addition, three clock lines φ1, φ2, φ3 are repeatedly connected to every two light emitting thyristors to the anode terminal of each light emitting thyristor, and each clock line φ1, φ2, φ3 has a current source I _1. , I ₂ , I ₃ are connected, and the light emission signal φI controls the amount of current (see, for example, Patent Documents 2 and 3).

  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. Next, when the clock line φ1 changes from the low level to the high level in this state, the light emission threshold voltage of the light emitting thyristor T1 is reduced by 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 clock line φ1 is connected is sufficiently away from the light emitting thyristor T0, there is almost no decrease in the threshold voltage of the light emission, so that the clock line φ1 at a level for causing the light emitting thyristor T1 to emit light. No light is emitted at the high level, and only the light emitting thyristor T1 is turned on to emit light. Next, by setting the start pulse φS to a low level, the light-emitting thyristor T0 changes from the on state to the off state, and light emission ends. As a result, the ON state is transferred from T0 to T1.

  Similarly, by changing the waveforms of the clock pulses φ1 to φ3 as shown in the diagram of FIG. 5, the light emitting thyristor T1 is then changed to the light emitting thyristor T2, and then the light emitting thyristor T2 is changed to the light emitting thyristor T3. The on state (light emission state) is transferred with time.

For example, when only the 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 most strongly incident on the adjacent light-emitting thyristors T2 and T4, and the threshold voltage of these light emission is set. 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 so much. In this state, when the clock line φ1 changes from the low level to the high level, the threshold voltage V _TH (T4) of the light emitting thyristor T4 is lower than the threshold voltage V _TH (T1) of the light emitting thyristor T1. , a high-level voltage _{V H} of the clock pulse φ1 only _{V TH (T4) <V H} <V TH (T1) and the light-emitting thyristor by setting T4 emits light in the oN state, the light-emitting thyristor T1 is in an off state Will remain. Then, when the clock line φ3 is changed 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 on the clock lines φ1, φ2, and φ3 so as to slightly overlap each other, the on states (light emitting states) of the light emitting thyristors T0 to Tn are sequentially transferred.

  Further, as shown in the diagram of FIG. 5, 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.

  However, in this conventional first light-emitting device, as can be seen from the diagrams of the light emission intensities L (T0) to L (T5) shown in FIG. Even when light to be emitted is not emitted, a certain amount of light emission (bias light) is generated from each light emitting thyristor in an on state (light emission state) for transferring a 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 conventional second light emitting device having such a 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 switch thyristors (T1 to Tn) and the light emitting thyristors (L1 to Ln) have a rectangular shape when viewed from above. Such switch thyristors and light-emitting thyristors are electrically connected at their corresponding gate terminals (for example, the gate terminals of the n-th switch thyristor Tn and the n-th light-emitting thyristor Ln). 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 between the light emission threshold voltage of the second switch thyristor T2 and the light emission threshold voltage of the second switch thyristor T4. Thus, 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 2001-077421

  In the above conventional first light emitting device, the light emitted from the light emitting thyristor is received and the adjacent light emitting thyristor is optically excited. Therefore, it is required that the light transmission thyristors have high light transmission efficiency. However, among the light emitted from the light-emitting thyristor to transfer the switching signal, there is light that is not irradiated to the adjacent light-emitting thyristor but is absorbed by the substrate holding the light-emitting thyristor or is irradiated to the outside. There is a problem that the amount of light that can be received by the adjacent light emitting thyristors is reduced. Further, there is a problem that image quality deteriorates when applied to an optical printer head or the like due to generation of bias light for transferring a switching signal.

Further, in the above-described conventional second light emitting device, since light excitation of the light emitting thyristor is not used for signal transfer in the switch thyristor, it is not important that the light transmission efficiency between the switch thyristors is high. However, since a switching thyristor is used as a switch element that is electrically driven to transfer a switching signal, and the light emission state of the light-emitting thyristor as a light-emitting element is transferred by its electrical control, the transfer direction is designated. And a load resistance _RL for controlling the voltage applied to the gate terminal of the switching thyristor are required, and these are formed by using a part of the thyristor (pnpn) structure. Yes. 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 technology as described above, and an object of the present invention is to provide a transfer switch element by optical excitation that can simplify the overall structure and is excellent in reliability. It is an object of the present invention to provide a light emitting device that can enhance the transmission efficiency of light emission between switch thyristors. Another object of the present invention is to provide an image recording apparatus using the light emitting device of the present invention to obtain a recorded image with good image quality.

The light-emitting device according to 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 that can control the light emission threshold voltage or threshold current by irradiating light from the outside. The light emitted from the three terminal light emitting switch elements is linearly arranged on the substrate so as to enter the adjacent three terminal light emitting switch elements, and the anode terminal or the cathode terminal of each of the three terminal light emitting switch elements. A three-terminal light emitting switch element array having a clock line connected to
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 in which the terminal or the cathode terminal 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 each formed on a first conductive semiconductor substrate, a first one conductive semiconductor layer, a first other conductive semiconductor layer, and a second one conductive semiconductor layer. And the second other conductivity type semiconductor layer are sequentially laminated, and the anode terminal or the cathode terminal is connected to the second other conductivity type semiconductor layer, and the one conductivity type semiconductor substrate or the first one conductivity type. A light emitting thyristor in which the cathode terminal or the anode terminal is electrically connected to the type semiconductor layer, and the gate terminal is electrically connected to the second one-conductivity type semiconductor layer,
The three-terminal light-emitting switch element is characterized in that the shape in a top view is such that one of the adjacent elements projects to the other side and the other extends along the projecting portion.

  In the light emitting device of the present invention, the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate in the above configuration, A light-shielding layer is provided on the surface of the substrate to block light emitted in the vertical direction, light emitted in the direction of the three-terminal light-emitting element, and light emitted in the opposite direction of the three-terminal light-emitting element. is there.

  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. The three-terminal light-emitting switch elements are arranged in a straight line on the substrate so that light emitted from one three-terminal light-emitting switch element is incident on an adjacent three-terminal light-emitting switch element, and a clock line is connected to each anode terminal or cathode terminal of the three-terminal light-emitting switch element. A three-terminal light-emitting switch element array, and a three-terminal light-emitting element having an anode terminal, a cathode terminal, and a gate terminal that can electrically control a threshold voltage or a threshold current of light emission from the outside via a gate terminal Are arranged on the substrate in correspondence with the three-terminal light-emitting switch element, and the gate terminal of the three-terminal light-emitting element is A three-terminal light-emitting element array electrically connected to a gate terminal of the corresponding three-terminal light-emitting switch element, and an anode terminal or a cathode terminal of the three-terminal light-emitting element connected to a line for supplying voltage or current for light emission; Each of the three-terminal light-emitting switch element and the three-terminal light-emitting element has a first one-conductivity-type semiconductor layer, a first other-conductivity-type semiconductor layer, and a second one-conductor-conductivity on a one-conductivity-type semiconductor substrate, respectively. A semiconductor layer and a second other conductive semiconductor layer are sequentially stacked, and an anode terminal or a cathode terminal is provided on the second other conductive semiconductor layer, and one conductive semiconductor substrate or the first one conductive semiconductor is provided. A light emitting thyristor in which a cathode terminal or an anode terminal is electrically connected to a layer, and a gate terminal is electrically connected to a second one-conductivity type semiconductor layer. Since the child has a shape in a top view in which one of the adjacent elements protrudes to the other side and the other extends along the protruding part, the signal transfer by the three-terminal light emitting switch element is performed by the light emitting thyristor. By adopting a configuration that uses light excitation, the three-terminal light-emitting switch element array section does not require a transfer direction designating diode or a load resistance for gate voltage control, and has a simplified array structure compared to conventional light-emitting devices. A terminal light emitting switch element array section can be formed, and the number of processes can be reduced in manufacturing. In addition, since the three-terminal light-emitting switch element and the three-terminal light-emitting element are individually provided, there is no problem of bias light due to the combined use of the light-emitting switch element and the light-emitting element as in the conventional first light-emitting device. When the light emitting device of the present invention is used in an electrophotographic image recording apparatus, a recorded image with excellent image quality can be obtained. Furthermore, since the shape of the top view of the three-terminal light-emitting switch element is such that one of the adjacent elements protrudes to the other side and the other extends along the protruding portion, the light emission of the three-terminal light-emitting switch element The area of the light receiving portion and the light receiving portion is increased, and the light extraction efficiency and light receiving sensitivity of the three-terminal light emitting switch element can be increased, so that the light transmission efficiency is high. In this light emitting thyristor, the light emitting portion includes a first other conductive semiconductor layer and a second one conductive semiconductor layer, and the light receiving portion includes the first one conductive semiconductor layer and the first other conductive semiconductor. And a second one-conductivity-type semiconductor layer.

  According to the light-emitting device of the present invention, in the above configuration, the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate, and light emitted from the three-terminal light-emitting switch element is emitted. Among these, when a light-shielding layer is provided on the surface of the substrate to block light emitted in the vertical direction, light emitted in the direction of the three-terminal light-emitting element, and light emitted in the direction opposite to the three-terminal light-emitting element, light leaked from the three-terminal light-emitting switch element array The light emission in the direction perpendicular to the surface of the substrate, the light emission in the direction of the three-terminal light-emitting element, and the light emission in the direction opposite to the three-terminal light-emitting element are sufficiently shielded by this light-shielding layer. Light can be efficiently used only in the direction of the adjacent three-terminal light-emitting switch element to which the light is transferred, the influence of leakage light can be suppressed, and It becomes that can be efficiently extracted only the output light from the array 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 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 shown in FIGS. 1 and 2, the light-emitting device of the present invention has 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. A number of three-terminal light-emitting switch elements 15 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 an adjacent three-terminal light-emitting switch element 15, and a three-terminal light-emitting switch A three-terminal light-emitting switch element array in which clock lines (φ1, φ2, φ3) 11 are connected to the anode terminal or cathode terminal of each element 15, and a threshold voltage or threshold current for light emission from the outside via a gate terminal A plurality of three-terminal light-emitting elements 14 having anode terminals, cathode terminals, and gate terminals, which can be controlled in a controlled manner, in correspondence with the three-terminal light-emitting switch elements 15. And the gate terminals of the three-terminal light-emitting elements 14 are electrically connected to the corresponding gate terminals of the three-terminal light-emitting switch elements 15 by the inter-gate wirings 10, and the anode terminals or the cathode terminals of the three-terminal light-emitting elements 14 are connected to each other. A three-terminal light-emitting element array connected to a line (φI) 9 for supplying a voltage or current for light emission, and each of the three-terminal light-emitting switch element 15 and the three-terminal light-emitting element 14 has one conductive type semiconductor substrate The first one-conductivity-type semiconductor layer 2, the first other-conductivity-type semiconductor layer 3, the second one-conductivity-type semiconductor layer 4, and the second other-conductivity-type semiconductor layer 5 are sequentially stacked on the substrate 1. In addition, an anode terminal or a cathode terminal is provided on the second other conductive type semiconductor layer 5, and one conductive type semiconductor substrate 1 or the first one conductive type semiconductor layer 2 (in this example, a cathode terminal or a cathode terminal). A light emitting thyristor in which an anode terminal is electrically connected to one conductive type semiconductor substrate 1 and a gate terminal is electrically connected to a second one conductive type semiconductor layer 4, and the three-terminal light emitting switch element 15 has a top view shape, One of the adjacent elements projects to the other side and the other extends along the projecting portion.

  In this example, an element array using a light emitting thyristor as a light emitting element is a three terminal light emitting switch element array in which three terminal light emitting switch elements 15 which are light emitting thyristors for switching signals are arranged linearly. A start switch thyristor 16 comprising the same light emitting thyristors, and a three terminal light emitting switch element array in which three terminal light emitting elements 14 which are light emitting thyristors are arranged in a straight line, The gate terminal of the three-terminal light-emitting switch element 15 corresponding to each element array and the gate terminal of the three-terminal light-emitting element 14 are electrically connected by an inter-gate wiring 10 that is a wiring in which the gate terminals are shared. Yes. The gate terminal of the start switch thyristor 16 is connected to the start pulse line φS, and three clock lines (φ1, φ1) are connected to the anode terminal of each three-terminal light-emitting switch element 15 of the three-terminal light-emitting switch element array. .phi.2, .phi.3) 11 are connected one by one every two in turn.

  Then, the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate 1, so that a light-emitting device as a line head such as an optical printer head for an electrophotographic image recording apparatus can be obtained. Used.

  In addition, the energy gap and carrier density of each semiconductor layer constituting the light emitting thyristor used in the present invention are preferably designed so as to increase the light receiving sensitivity, the light extraction efficiency to the outside, and the light emitting efficiency of the light emitting thyristor. Specifically, the first one-conductivity-type semiconductor layer 2 and the second one-conductivity-type semiconductor layer 5 are compared with the energy gap between the first other-conductivity-type semiconductor layer 3 and the second one-conductivity-type semiconductor layer 4. What is necessary is just to enlarge an energy gap.

  By setting such an energy gap, the light generated in the light emitting portion composed of the first other-conductivity-type semiconductor layer 3 and the second one-conductivity-type semiconductor layer 4 is converted into the first one-conductivity-type semiconductor layer 2 and Since the adjacent light emitting thyristor is irradiated without being absorbed by the second other conductive type semiconductor layer 5, it becomes a light emitting thyristor with high light extraction efficiency. In such a light emitting thyristor, the light receiving section is composed of a first one-conductivity-type semiconductor layer 2, a first other-conductivity-type semiconductor layer 3, and a second one-conductivity-type semiconductor layer 4.

  In such a light emitting thyristor, a light emitting thyristor having one conductivity type as n type and the other conductivity type as p type has clock lines 10 (φ1), 11 (φ2), 12 (φ3) and line 8 (φI) as anodes. It is preferable that the cathode voltage be 0 V because a positive power source can be used as a power source for applying voltage or current to the light emitting thyristor. Also, even if one conductivity type is p-type and the other conductivity type is n-type, the same operation as a light-emitting thyristor having one conductivity type n-type and the other conductivity type p-type can be achieved by reversing the polarity of the bias voltage. Obtainable. For this reason, the combination of the semiconductor layers constituting the light-emitting thyristor is selected so that the light extraction efficiency and the light-emitting efficiency of the light-emitting part and the light-receiving sensitivity of the light-receiving part are optimized, and the manufacturing process for manufacturing these semiconductor layers is selected. From the point of view, the conductivity type may be determined.

  In the following description, one conductivity type is n-type and the other conductivity type is p-type. Thus, in the light emitting device of the present invention, the anode terminal is connected to the second other conductive type semiconductor layer 5, and three clock lines (φ1, φ2, φ3) 11 are sequentially connected to the anode terminal. A cathode terminal is connected to the conductive semiconductor substrate 1, and a line 9 (φI) for supplying voltage or current for light emission is connected to the anode terminal of the three-terminal light-emitting element 14.

  On the other hand, the conductive type (n-type) semiconductor substrate 1 is one on which a III / V group semiconductor layer or a II / VI group semiconductor layer can be grown, and is made of, for example, GaAs, InP, GaP, Si, Ge, or the like.

The first one-conductivity type (n-type) semiconductor layer 2 preferably has a carrier density of about 1 × 10 ¹⁸ cm ⁻³ and is made of, for example, GaAs, AlGaAs, InGaP, or the like.

The first other conductivity type (p-type) semiconductor layer 3 preferably has an energy gap smaller than that of the first one conductivity type (n-type) semiconductor layer 2 and a carrier density of about 1 × 10 ¹⁸ cm ⁻³ . For example, it is made of AlGaAs, GaAs or the like. In particular, when the thickness of this layer is 50 to 1000 mm, the current amplification factor of the portion functioning as a phototransistor (npn portion) of the light receiving portion increases, so that light from the outside can be efficiently received.

The second one-conductivity-type (n-type) semiconductor layer 4 has an energy gap smaller than that of the first one-conductivity-type (n-type) semiconductor layer 2, and the carrier density is the smallest among all layers, 1 × 10 ¹⁶ cm ^−. It is desirable that it is about ³ to 1 × 10 ¹⁷ cm ⁻³ , and it is made of, for example, GaAs, AlGaAs or the like.

  The second other conductivity type (p-type) semiconductor layer 5 has an energy gap larger than that of the first other conductivity type (p-type) semiconductor layer 3 and the second one conductivity type (n-type) semiconductor layer 4. Desirably, for example, when it is made of AlGaAs, InAlGaP or the like, high internal quantum efficiency can be obtained.

  In FIG. 2, a one-conductivity (n-type) buffer layer may be interposed between the one-conductivity-type (n-type) semiconductor substrate 1 and the first one-conductivity-type (n-type) semiconductor layer 2. Good. Further, the other conductivity type (p-type) ohmic contact layer 6 may be interposed between the second other conductivity type (p-type) semiconductor layer 5 and the anode terminal.

  Reference numeral 7 denotes a metal layer that is provided in ohmic contact with the ohmic contact layer 6 and functions as an anode terminal, and is made of, for example, Au, AuGe, AuZn, or the like. Here, as shown in FIG. 2, by forming the metal layer 7 so as to cover almost the entire surface of the ohmic contact layer 6, the electric field to each semiconductor layer of the light-emitting thyristor can be made uniform and radiated thereby. The light emission intensity can be increased.

  Reference numeral 8 denotes an insulating layer for ensuring electrical insulation between the clock line (φ1, φ2, φ3) 11 or a line (φI) 9 for supplying voltage or current for light emission and each semiconductor layer of the light emitting thyristor. An insulating film having translucency and flatness such as polyimide is used.

  A line (φI) 9 is connected to the ohmic contact layer 7 of each light emitting thyristor of the three-terminal light emitting element array, and a part thereof has a function as a gate terminal of the start switch thyristor 16. It consists of Au, AuGe, Ni, Al or the like. A metal layer 7 that functions as an anode terminal together with the line (φI) may be interposed between the line (φI) 9 and the ohmic contact layer 6.

  The inter-gate wiring 10 functions as a gate terminal in the light-emitting thyristor by forming an ohmic junction with the second one-conductivity type (n-type) semiconductor layer 4 and is made of, for example, Au, AuGe, Ni, or the like.

  The clock line (φ1, φ2, φ3) 11 is made of, for example, Au, AuGe, Ni, Al or the like.

  Reference numeral 13 denotes a back electrode which is in ohmic contact with the one-conductivity type (n-type) semiconductor substrate 1 and functions as a cathode terminal, and is made of, for example, Au, AuGe, Ni or the like.

  Here, the shape of the three-terminal light-emitting switch element 15 in a top view is such that one of the adjacent terminals projects to the other side and the other extends along the projecting portion. In the example shown in FIG. 1, the shape of the top view of the three-terminal light-emitting switch element 15 is the same as that of the other three-terminal light-emitting switch element 15 adjacent to the end of the one-terminal three-terminal light-emitting switch element 15 on the three-terminal light-emitting element 14 side. A first convex portion extending toward the three-terminal light-emitting switch element 15 is provided at the end opposite to the three-terminal light-emitting element 14 of the other three-terminal light-emitting switch element 15. As the provided shape, the first convex portion of one three-terminal light emitting switch element 15 and the second convex portion of the other three-terminal light emitting switch element 15 face each other between adjacent three-terminal light emitting switch elements 15. By arranging, one of the three-terminal light-emitting switch elements 15 protrudes to the other three-terminal light-emitting switch element 15 side by the first convex part, and the other three-terminal light-emitting switch element 15 extends from the second convex part. Overhanging part of one 3-terminal light emitting switch element 15 It is assumed to be along the (first convex portion). FIGS. 3A to 3C are schematic plan views of main parts of examples of the shape of the top view of the three-terminal light emitting switch element 15 in the light emitting device of the present invention. In FIG. 3, a protruding portion where one of the adjacent three-terminal light-emitting switch elements 15 extends to the other side is denoted by 15a, and a portion along the protruding portion 15a is denoted by 15b. The shape of the top view of the three-terminal light-emitting switch element 15 may be a parallelogram shape as shown in FIG. 3A, or a convex portion (on one of adjacent elements as shown in FIG. 3B). A projecting portion 15a) may be provided and the other projecting portion (the projecting portion 15a) may be enclosed on the other side, that is, a recess 15b may be provided along the projecting portion 15a, as shown in FIG. In addition, as a shape having a large number of projections and depressions, by arranging the projections and depressions between adjacent three-terminal light emitting switch elements 15 so as to mesh with each other, one of the adjacent elements projects to the other side and the other is It is good also as a shape which has the site | part 15b which follows the overhang | projection part 15a. Moreover, it is good also as a shape where the convex part of FIG. 1, FIG.3 (b), (c) and the corner | angular part of a recessed part were rounded. 3A to 3C, 15c indicated by a broken line indicates a portion to which the clock line (φ1, φ2, φ3) 11 is connected.

  The three-terminal light-emitting switch element 15 having such a shape has a larger light-receiving area and light-emitting area on the side surface on the adjacent element side than the conventional three-terminal light-emitting switch element 15 having a rectangular shape when viewed from above. Therefore, the light receiving sensitivity and the light extraction efficiency are improved, and when used in a light emitting device, the light transmission efficiency between elements can be made high. Also, since the shape of the top view of the three-terminal light-emitting switch element 15 is such that one of the adjacent elements projects to the other side and the other extends along the projecting portion, The distance between the light receiving part of the element and the light emitting part of the other element can be made substantially constant without variation in each part of the element, and adjacent elements can be arranged densely. The light transmission efficiency can be increased without increasing the size of the light source. Furthermore, since it is only necessary to change the patterning shape of each semiconductor layer of the light-emitting thyristor constituting the three-terminal light-emitting switch element 15 in manufacturing, the manufacturing can be performed without increasing the number of processes.

  In addition, the light quantity distribution in the light receiving part of the light emitting thyristor is received by the ray tracing simulation that calculates the light quantity in the light receiving part when the light (light ray) irradiated from the light emitting part of the light emitting thyristor reaches the light receiving part of the adjacent light emitting thyristor. If the shape of the light-receiving thyristor is calculated by changing the shape of the light-emitting thyristor, it is found that the amount of light received by the light-receiving thyristor is convex. Accordingly, the three-terminal light-emitting switch element 15 has a shape in a top view between adjacent three-terminal light-emitting switch elements 15 by providing one or more convex portions or concave portions as shown in FIGS. 1 and 3. By making one project to the other side and the other along the projecting portion, the light transmission efficiency between the elements can be improved as compared with the conventional rectangular shape.

  Among them, in the shape shown in FIG. 3B, the side of the three-terminal light-emitting switch element 15 provided with the convex portion is the switching signal receiving side, that is, the side on which light emitted from the adjacent three-terminal light-emitting switch element 15 is incident. The side where the concave portion is provided so as to surround the convex portion of the adjacent three-terminal light emitting switch element 15 is the switching signal transmission side, that is, the side that emits light to the adjacent three-terminal light emitting switch element 15. Since the light emitted from the terminal light emitting switch element 15 can be concentrated and received by the convex portion of the three terminal light emitting switch element 15, the light transmission efficiency between adjacent elements can be further increased.

  Here, it is preferable that the convex portion of one element and the concave portion of the other element are close to each other between the adjacent three-terminal light emitting switch elements 15. Further, in order to increase the light receiving efficiency, it is preferable that the convex portion is large. However, when a certain number of three-terminal light emitting switch elements 15 are arranged on the substrate 1 having a certain size, if the shape of the convex portion is too large, During manufacture, patterning of the three-terminal light emitting switch element 15 becomes difficult and productivity is lowered. Therefore, the size of the convex portion may be determined in consideration of light receiving efficiency and productivity.

  For example, in a three-terminal light-emitting switch element array in which three-terminal light-emitting switch elements 15 are arranged at a density of 600 dpi, the rectangular three terminals are 30 μm in the horizontal direction (arrangement direction) and 40 μm in the vertical direction. Compared with the case where the light emitting switch element 15 is used, the three-terminal light emitting switch element 15 shown in FIG. 1 having the same length in the vertical direction of 40 μm and the first and second protrusions of 10 μm in the horizontal direction is used. If this occurs, the amount of light received is improved by about 40%.

  Reference numeral 12 denotes a light shielding layer. In particular, when the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate 1, the substrate out of the light emitted from the three-terminal light-emitting switch element 15. 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 such a light shielding layer 12, light emitted from the three-terminal light-emitting switch element array is emitted in the direction perpendicular to the surface of the substrate 1, emitted in the direction of the three-terminal light-emitting element 14, and opposite to the three-terminal light-emitting element 14. This light emission is sufficiently shielded by the light shielding layer 12, so that when the light emitting device of the present invention is used as an exposure device in an electrophotographic image recording apparatus, image deterioration due to such leaked light occurs. Therefore, excellent image quality can be obtained. Various materials can be used for the light shielding layer 12 as long as the light from the three-terminal light emitting switch element 15 is absorbed almost completely with a thickness of about 2 to 3 μm. For example, polyimide or the like can be used. The film may be formed by spin coating and processing into a predetermined pattern by photoetching. Further, in order to reflect light emitted from the three-terminal light-emitting switch element 15 by the light-shielding layer 12 and efficiently enter the light-receiving portion of the adjacent three-terminal light-emitting switch element 15, the light-shielding layer 12 includes the three-terminal light-emitting switch element 15 It is preferable to use a material made of an insulating material such as polyimide that absorbs the light emission wavelength (600 to 800 nm) almost completely, or has a high reflectance with respect to the light emission wavelength and a refractive index lower than that of the insulating layer 8. In this way, the light shielding layer 12 has a function of reflecting the light emitted from the three-terminal light emitting switch element 15 in addition to the function of shielding the leaked light, and is incident on the light receiving portion of the three-terminal light emitting switch element 15. Since the amount of light increases, a light emitting device with extremely high light receiving efficiency can be obtained.

  In the light emitting device of the present invention having the above configuration, one conductivity type may be p-type and the other conductivity type may be n-type, so that the light emitting device of the present invention has a cathode on the second other conductivity type semiconductor layer 5. Terminals are connected, and clock lines (φ1, φ2, φ3) 11 are sequentially connected to the cathode terminals, while an anode terminal is connected to the conductive semiconductor substrate 1, and light is emitted to the cathode terminals of the three-terminal light-emitting element 14. Therefore, the line 9 (φI) for supplying the voltage or current is connected. In this case, for example, GaAs, InP, GaP, Si, Ge or the like may be used as the one-conductivity type (p-type) semiconductor substrate 1.

  FIG. 4 is an equivalent circuit diagram showing a schematic circuit configuration of the basic structure in the example of the embodiment of the light emitting device of the present invention. The light emitting thyristors T0 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 Ti of the light-emitting switch element array is connected to the gate terminal of the i-th light-emitting thyristor Li 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 to φ3) are connected to the anode terminal of the light emitting thyristor of the three-terminal light emitting switch element array, every two in turn. 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 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 anode 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 anode terminal is sufficiently away from the start switch thyristor T0, the threshold voltage of light emission due to 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 the elements 15 and the three-terminal light-emitting elements 14 are integrated is arranged on a circuit board in a straight line to form a light-emitting device having a three-terminal light-emitting switch element array and a three-terminal light-emitting element array, respectively. A driver IC is mounted on the board.

  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 for the exposure device for the photosensitive member, the three-terminal light emitting switch element 15 and the three terminals by the light emitting thyristor of the present invention are used. An exposure apparatus can be manufactured at low cost using an array in which the light-emitting elements 14 are integrated, and since the exposure apparatus does not generate bias light or leakage light, it has an exposure apparatus that can form high-quality images at low cost. An image forming apparatus can be provided.

  In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention.

It is a principal part top view which shows an 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. (A)-(c) is a typical top view which shows the example of the shape of the top view of the 3 terminal light emission switch element 15 in the light-emitting device of this invention, respectively. It is an equivalent circuit diagram which shows the schematic circuit structure of the basic structure in an 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. 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 ... Substrate 2 ... 1st one conductivity type semiconductor layer 3 ... 1st other conductivity type semiconductor layer 4 ... 2nd one conductivity type semiconductor layer 5 ... 2nd other conductivity type Type semiconductor layer 6 ... ohmic contact layer 7 ... metal layer 8 ... insulating layer 9 ... line (φI)
10 ... Wiring between gates
11 ・ ・ ・ Clock line (φ1, φ2, φ3)
12 ... Light shielding layer
13 ... Back electrode
14 ... 3 terminal light emitting device
15 ... 3 terminal light emitting switch element T0, T1, T2, T3 to Tn ... light emitting thyristor (3 terminal light emitting switch element 15)
L1, L2, L3 to Ln ... Light-emitting thyristor (3-terminal light-emitting element 14)

Claims (3)

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. Are arranged in a straight line on the substrate so that light emitted from the three-terminal light-emitting switch elements is incident on the adjacent three-terminal light-emitting switch elements, and a clock line is connected to the anode terminal or the cathode terminal of each of the three-terminal light-emitting switch elements. A terminal light emitting switch element array;
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 in which the terminal or the cathode terminal 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 each formed on a first conductive semiconductor substrate, a first one conductive semiconductor layer, a first other conductive semiconductor layer, and a second one conductive semiconductor layer. And the second other conductivity type semiconductor layer are sequentially laminated, and the anode terminal or the cathode terminal is connected to the second other conductivity type semiconductor layer, and the one conductivity type semiconductor substrate or the first one conductivity type. A light emitting thyristor in which the cathode terminal or the anode terminal is electrically connected to the type semiconductor layer, and the gate terminal is electrically connected to the second one-conductivity type semiconductor layer,
The three-terminal light emitting switch element is characterized in that the shape of the top view is such that one of the adjacent terminals projects to the other side and the other extends along the projecting portion. The three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate, and light emitted from the three-terminal light-emitting switch element is emitted in a direction perpendicular to the surface of the substrate. The light-emitting device according to claim 1, further comprising a light-shielding layer that shields light emitted in the direction of the three-terminal light-emitting element and light emitted in a direction opposite to the three-terminal light-emitting element. An image recording apparatus, wherein the light emitting device according to claim 1 or 2 is used in an exposure device for a photosensitive member.

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