JP3359207B2 - Recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head used as a print head in a printer, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art FIG. 8 is a side view showing the appearance of a conventional recording head. In FIG. 8, reference numeral 200 denotes a substrate;
A light emitting element array chip 201 and a driving IC chip 202 for driving the same are mounted. The light emitting element array chip 201 and the driving IC chip 202 are connected by wire bonding. Further, a heat radiating plate 203 is attached to the substrate 200, and is configured to radiate heat generated in the light emitting element array chip 201 and the driving IC chip 202. As the substrate 200 to be used, a ceramic substrate or a glass resin having a small thermal expansion coefficient is used in order to minimize the influence of expansion and contraction due to thermal expansion.

FIG. 9A is a plan view of the substrate 200 of FIG. 8 as viewed from above. A plurality of light emitting element array chips 201 and drive IC chips 202 are arranged on the substrate 200 in rows. Further, a connector 204 for connecting the recording head to the outside is provided at a corner of the substrate 200. FIG. 9B is an enlarged view of a portion circled in FIG. 9A. The light emitting element array chip 201 includes a large number of light emitting portions 205 arranged in a row, and a wiring pad 206 is provided corresponding to each light emitting portion 205. The driving IC chip 202 is also provided with a wiring pad 206 corresponding to each light emitting unit 205,
Wire bonding 2 between both wiring pads 206
07, the light emitting element array chip 201 and the driving IC chip 202 are connected. The drive IC chip 202 includes a drive circuit corresponding to each light emitting unit 205, and performs recording by controlling each light emitting unit 205.

As a conventional recording head, as proposed in Japanese Patent Application Laid-Open No. Hei 7-186442, a surface-emitting type light emitting element array and a driving unit are used in order to reduce the distance between the recording head and the photosensitive drum. It is also known that the light emitting element array is divided and mounted on the same substrate, and the light emitting element array and the driving unit are connected by wire bonding, and the light emitting output of the surface emitting light emitting element array is emitted in a direction parallel to the substrate surface. .

[0005]

In the conventional recording head, when the recording density of the recording head is increased, the density of the light emitting portion is increased as shown in FIG. 9B. A method of connecting directly by wire bonding is employed. However, when the light emitting element array chip and the driving IC chip are connected by wire bonding as described above, the distance between the light emitting element array chip and the driving IC chip is short, and heat generated in the driving IC chip is easily transmitted to the light emitting element array chip. Therefore, there is a problem that the amount of light emitted from the light emitting element array chip is adversely affected.

It is generally said that the light intensity of an AlGaAs light emitting element decreases by about 0.6% to 1.0% when the temperature rises by 1 ° C., and the light intensity change of the light emitting element array chip is a negligible light intensity change. Did not. In addition, when the temperature of the light emitting element array chip rises in this way, the substrate on which it is mounted is also heated, so that a substrate made of a material having a small coefficient of thermal expansion must be used, resulting in an increase in cost. Was. Furthermore, in order to achieve high-density recording of 400 DPI or more, when the light emitting element array chip and the driving IC chip are made to correspond one-to-one as shown in FIG. Is difficult to implement.

In such a case, a method of arranging driving IC chips on both sides of the light emitting element array chip and alternately bonding the light emitting portion of the light emitting element array chip and the driving IC chips on both sides can be considered. In this case, not only the bonding is very difficult, but also the driving IC chip that generates heat cannot be kept away from the driving IC chip, and the higher the density, the greater the influence of the heat of the light emitting element.

In view of the above-mentioned conventional problems, the present invention divides the printing element array and the substrate of the driving unit for driving the printing element array, thereby thermally isolating the printing element array and the driving unit which is a heat source, and It is an object of the present invention to provide a recording head capable of eliminating the influence of heat generated by the recording head.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting element array arranged in a row and a drive unit for driving the light emitting elements, and drive control of the light emitting elements according to signals. A first substrate having the light emitting element array, a second substrate having the driving section, and a heat dissipating member provided with the substrates and dissipating the heat of the substrate. Has a surface portion on which the first substrate is arranged, and a side surface portion provided on the other side of the light irradiation side on which the first substrate is arranged, and on which the second substrate is arranged, The first substrate and the second substrate are connected by a flexible wiring so that the light emitting element array faces downward.
This is achieved by a recording head characterized by being arranged .

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram that best illustrates the features of the present invention. In FIG. 1, reference numeral 101 denotes a light emitting element array chip in which a plurality of light emitting elements are formed in a row on the same wafer. The light emitting element array chip 101
It has a self-scanning circuit inside, and is configured so that one light emitting element array chip can emit light sequentially with one light emitting signal and three scanning signals. A plurality of light emitting element array chips 101 are mounted on a substrate 102 in a row.

Reference numeral 104 denotes a driving IC for driving the light emitting element array chip 101. In the present embodiment, one driving IC 104 drives five light emitting element array chips 101. These drive ICs 104
Is a substrate 10 on which the light emitting element array chip 101 is mounted.
2 is mounted on a different substrate 106. A current limiting resistor R for limiting a drive current is mounted on the substrate 106 in addition to the drive IC 104. The current limiting resistor R is 1
One light emitting element array chip 101 is required, and one light emitting element array chip 101 is provided for each light emitting element array chip 101. A connector capacitor (not shown) for connecting to the outside is provided on the substrate 106.
Is provided. The board 102 and the board 106 are connected by wiring.
3 are connected.

The self-scanning function of the light emitting element array chip 101 is described in JP-A-1-238962, JP-A-2-2008067, JP-A-2-212170, JP-A-3-20457 and JP-A-3-20457. -1949
No. 78, JP-A-4-5872, JP-A-4-2
No. 3367, Japanese Unexamined Patent Publication No. Hei 4-296579, Japanese Unexamined Patent Publication No. Hei 5-84771, etc., and a detailed description is omitted here. The substrate 102 on which the light emitting element array chip 101 is mounted is
The number of wires between the boards 106 on which the C104 is mounted is
It can be reduced to 1/0. Therefore, a normal bundled wire or a flexible cable can be used as the wiring between the two substrates 102 and 106, which means that the substrate 102 of the light emitting element array chip 101 is moved away from the substrate 106 such as the other driving IC 104. It is possible to do that.

FIG. 2 is a diagram showing an example of a case where the above-mentioned substrate 102 and substrate 106 are used as a recording head. In FIG. 2, reference numeral 107 denotes a holding member formed in an L-shape in cross section.
08 is attached. On the side of the heat sink 108,
The substrate 106 on which the drive IC 104 and the current limiting resistor R described in FIG. 1 are mounted is mounted, and the substrate 102 on which the light emitting element array chip 101 is mounted is mounted below. Therefore, in the example of FIG. 2, the substrate 102 and the substrate 106 are disposed on two adjacent surfaces of the heat sink 108 at an angle of 90 degrees, and the two substrates 102 and 106 are connected to the flexible cable at the position of the angle of 90 degrees. 103
Connected by At the lower end of the L-shaped holding member 107, a lens fiber array 109 is arranged in a row facing the light emitting element array chip 101. The light emitted from each light emitting element of the light emitting element array chip 101 is configured to irradiate a photosensitive drum (not shown) via the lens fiber array 109.

Here, as the flexible cable 103, in the case of a 600 DIP recording head (length of about 300 mm), the number of lines is about 200, and a flexible cable having a density of 2 / mm and a width of about 20 mm is used. The two substrates 102 and 106 can be easily connected by soldering and thermocompression bonding each flexible cable. Further, in FIG. 2, as described above, the substrate 102
Since the current limiting resistor R, which generates the most heat, is disposed above the substrate 106, the current limiting resistor R on the substrate 106 and the heat of the driving IC 104 are not easily transmitted to the substrate 102, Current limiting resistor R
Or drive IC chip 104 with light emitting element array chip 101
From the light emitting element array chip 101.
Can be significantly reduced as compared with the related art. Therefore, in the light emitting element array chip 101,
Thermally stable emission output can be obtained, and as the substrate 102 on which the light emission output is mounted, it is not necessary to use a substrate having a particularly small thermal expansion coefficient, so that the cost can be reduced.

FIG. 3 is a diagram showing an electric circuit configuration of the recording head described with reference to FIGS. In this embodiment, one light emitting element array chip 101 is composed of 128 light emitting elements, and one driving IC 104 drives five light emitting element array chips 101. The driving ICs 104 are connected in cascade. Here, various signals for driving and controlling the recording head, which are input from a main control circuit (not shown) such as a printer or a copying machine when the recording head is driven, will be described.
First, print data (here, 8 bits are used)
Is supplied to the first drive IC 104 connected in cascade. Only the print data is supplied to the first drive IC 104, and the other signals are supplied to each drive IC 104.

ΦS, Φ1, Φ2, and ΦI are timing signals for driving each light emitting element of the light emitting element array chip 101, and SCK, LOADX, RS, and RCK are controls for controlling a recording operation by the light emitting element array chip 101. Signal. These signals are supplied to the respective drive ICs 104, and print data is recorded on the photosensitive drum line by line based on these signals as described later in detail. Further, φS, φ1, φ2, and φI are signals generated based on the previous φS, φ1, φ2, and φI in the driving IC 104, among which φS is five light emission from the driving IC 104 via the resistor R _S. The light is supplied to the element array chip 101 and is commonly used by the five light emitting element array chips 101. Further, φI is supplied to five light emitting element array chips 101 via respective current limiting resistors R, and φ1,
φ2 is also supplied to each of the five light emitting element array chips 101, and one driving IC 104 drives the five light emitting element array chips 101. In addition,
The operation using the above signals will be described later in detail.

FIG. 4 is an equivalent circuit diagram showing the light emitting element array chip 101 in detail. Although FIG. 4 shows only five light emitting elements, one light emitting element array chip 101 has 128 light emitting elements as described above. In FIG. 4, R _{1 to} R ₅ are resistors of 50 to 100 KΩ, and D _{1 to} D ₆ are diodes. Diode D _1-
D ₅ are connected in series, the connection point of the diode comrade a
The other end of each resistor whose one end is connected to VGA (ground) is connected to .about.e. SR1 'to SR5' are transfer thyristors, and SR1 to SR5 are light-emitting thyristors, which are light-emitting elements. The gate terminals of these transfer thyristors and light-emitting thyristors are connected to the respective connection points.

[0018] That is, resistor, transfer thyristors, the light-emitting thyristor is a respective pair is connected from the top of the resistor R ₁ to the gate terminal of the transfer thyristor SR1 'and the light emitting thyristor SR1 via a connection point a ing. Also,
Transfer thyristor S from the following resistor R ₂ via the node b
R2 'and the gate terminal of the light emitting thyristor SR2. Hereinafter, the configuration is the same.

Next, the operation of the light emitting element array chip 101 will be described with reference to FIG. FIG. 5A shows a start pulse φS, and when the level changes from a low level to a high level, the operation of the light emitting element array chip 101 starts. FIG.
5B shows the drive timing signal φ1, and FIG. 5C shows the drive timing signal φ2. φ1 is an odd-numbered thyristor SR1, SR3 among transfer thyristors as shown in FIG.
Are supplied to the cathode terminals of SR5,... And φ2 are supplied to the cathode terminals of even-numbered thyristors SR2 ′, SR4 ′,.
Here, when the start pulse φS goes to a high level, and in this state, φ1 goes from a high level to a low level as shown in FIG. 5B, the first transfer thyristor SR1 ′ is turned on.

When the transfer thyristor SR1 'is turned on,
Since the gate voltage becomes the anode potential (about 5 V),
When the recording signal φI changes from the low level to the high level at the next timing as shown in FIG. 5D, the first light-emitting thyristor SR1 is turned on and emits light for recording for a time period T. The light from the light-emitting thyristor SR1 is applied to a photosensitive drum (not shown) via the lens fiber array 109 as described with reference to FIG. In this case, the other light-emitting thyristors do not emit light because the gate voltage is not 5 V.

Next, as shown in FIG. 5D, the recording signal φI
Returns to the high level, the first light-emitting thyristor SR1
Is turned off, and as shown in FIG. 5C, when φ2 changes from the high level to the low level at the next timing, the transfer thyristor SR2 'in the next stage is turned on. That is, the gate voltage (about 5V) is the transfer thyristor SR via a diode D ₁ connected to the gate of the transfer thyristor SR1 '
Since it is connected to the gate of 2 ', the gate voltage of the transfer thyristor SR2' is about 3.6V. Therefore, when φ2 goes low in this state, the transfer thyristor SR2 'is turned on.

Subsequently, when φ1 changes from low level to high level as shown in FIG. 5B, the transfer thyristor SR
1 'is turned off, but the transfer thyristor SR2' holds the on state, and in this state, the recording signal φ as shown in FIG.
When I goes high, the next light emitting thyristor SR2
Is turned on for a time T, and the emitted light is applied to the photosensitive drum. By repeating this operation 64 times, 128 light-emitting thyristors are scanned. In practice,
Since the plurality of light emitting element array chips 101 are provided in a plurality of rows, scanning is performed by the same operation in other light emitting element array chips.

FIG. 6 is a block diagram showing the driving IC 104 in detail, and FIG. 7 is a time chart showing signals of various parts of the driving IC 104. In FIG. 6, reference numeral 120 denotes a shift register for taking in print data line by line. In the present embodiment, as described above, the print data is 8 bits, and one driving IC 104 drives five light emitting element array chips 101 each having 128 light emitting elements. Sixteen shift registers 120 are provided for each 101, and one drive IC 104 as a whole has 80 shift registers 120.
Is provided. The print data is taken into the shift register 120 in synchronization with the shift clock SCK shown in FIG.

Reference numeral 121 denotes a latch for holding the data set in the shift register 120. Latch 12
1 is provided corresponding to each shift register 120 (latch capacity is 128 × 5 bits), and the data of each shift register 120 is transferred to each latch 121 at the low level timing of the latch clock LOADX in FIG. Latched. Therefore, the data shift operation and the printing operation can be performed in parallel. In this way, one line of print data is held.

Reference numeral 122 denotes a counter for counting the read clock RCK, and reference numeral 123 denotes a selector for switching reading of data from the latch 123 in accordance with the output of the counter 122. Five selectors 123 are provided corresponding to the five light emitting element array chips 101. More specifically, first, the counter 122 is set to an initial value by the read start signal RS in FIG. 7C, and counts the read clock RCK in FIG. 7C. Each selector 12
In step 3, 128-bit latch data is sequentially output according to the output of the counter 122. FIG. 7E shows the output of the selector 123. When the counter 122 counts up to 128, the selector 123 finishes outputting the 128-bit data.
Is set to the initial value again, and the same operation is repeated thereafter. In this way, recording is performed for each line.

The output signal of each selector 123 is ΦI which determines the light emission timing of the light emitting element at the NAND gate 124.
The signal and the NAND are taken and output via the buffer 125. This output signal corresponds to φI described with reference to FIGS.
This is a recording signal for turning on or off the light emitting element. This signal is output from each selector 123 to 5
For each of the light emitting element array chips 101, φI−1,
are output as φI-2... φI-5. The ΦS signal described with reference to FIG. 3 is output via the buffer 126. This signal φS is used as a start signal of the light emitting element array chip 101 as described above.

The Φ1 signal is output via the buffer 127 and the resistor 128, and is output as the Φ1 signal described with reference to FIGS. φ1 signal is 5 light emitting element array chips 1
01 are supplied as φ1-1, φ1-2,... Φ1-5. The φ2 signal is also output via the buffer 127 and the resistor 128, which is also used for the five light emitting element array chips 10.
1 are supplied as φ2-1, φ2-2,... Φ2-5. The ICONT signal is a control signal for adjusting the current values of the φ1 signal and the φ2 signal. As described above, the driving IC 104 generates a signal for driving the light emitting element array chip 101 based on the input various signals, and generates the signal for driving the light emitting element array chip 101 as described with reference to FIGS.
Controls the operation of the individual light emitting elements within. As a result, the light emitting elements arranged in a row emit or emit light in response to the recording signal, and perform recording on the photosensitive drum.

In the above embodiment, the recording head using the light emitting element array chip having the self-scanning function has been described as an example. However, the present invention is not limited to this, and the scanning is performed in the same process as the light emitting element. , A shift register on silicon, and a GaAs-based light-emitting element on it, or vice versa, and m elements in n-dimensional matrix. And the number of drive wirings is (n × m) ^{1 / n}
It is also possible to apply to a case where the number is reduced.
Further, the present invention is also effective for a device using an element such as a liquid crystal which controls light transmission and reflection.

Further, in the above embodiment, the two substrates are connected using the flexible cable.
When the substrate 106 is connected to the board 106, a so-called flat cable bundle may be used instead of the flexible cable because the number of wires is small. In addition, since the connection density is low as the connection method of the wiring, a normal connector can be used without being limited to the thermocompression bonding with solder.

In the embodiment, the heat radiating plate 108 is
However, the substrate 102 may be formed in, for example, an L-shaped cross section, and the substrate 102 may be attached to the bottom surface and the substrate 106 may be attached to the side surface. By doing so, the substrate 1
Since the protrusion of No. 06 is eliminated, the size of the recording head can be further reduced. Further, in the embodiment, the two substrates 1
02 and 106 are connected by the flexible cable 103. However, since the substrate 106 on which the drive IC 104 is mounted does not need to be flat, the drive IC 104 may be mounted on a flexible substrate. Accordingly, in this case, since the connection on the driving IC 104 side is eliminated, the labor for the operation can be saved by that much, and the cost required for manufacturing can be reduced.

[0031]

As described above, the present invention has the following effects. (1) A first substrate having a light emitting element array, a second substrate having a driving unit, and a heat radiating member for radiating heat from the first and second substrates are included. It is provided on the other side with respect to the light irradiation side surface where the substrate is arranged,
A side portion on which the second substrate is disposed, wherein the first substrate and the second
The substrates are connected by flexible wiring, and the light emitting element array
The heat generated by the drive unit is transmitted to the light emitting element array without increasing the size of the heat dissipating member.
Can be made very small, and the exposure
The drop can be prevented . (2) Since the substrate of the light emitting element array can be thermally isolated,
The use of expensive substrates with small coefficients of thermal expansion can be minimized,
It can be manufactured inexpensively. (3) Since the light emitting element array and the substrate of the drive section are divided into two, each substrate can be attached to two surfaces of the heat radiating plate, and the occupied area of the recording head can be reduced.
Accordingly, it is possible to use a photosensitive drum having a smaller diameter, and the size of the apparatus can be reduced. (4) Since the area of the substrate of the light emitting element array is reduced,
It is possible to reduce the number of steps required to secure the high-precision flatness particularly required for the substrate, for example, the processing cost of polishing a heat sink to which the substrate is attached, and thereby reduce the cost. (5) Since the substrate for the light emitting element array and the driving element is divided into two, the yield when the substrate is completed is improved and the cost is reduced as compared with the case where the light emitting element and the driving section are mounted on one substrate. Can be planned.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration example of a main part of a recording head of the present invention.

FIG. 2 is a front view showing the appearance of the recording head of the present invention.

FIG. 3 is a block diagram showing an example of an electrical circuit configuration of the printhead of the present invention.

FIG. 4 is a circuit diagram showing an example of a light emitting element array chip used for the recording head of the present invention.

FIG. 5 is a time chart for explaining the operation of the light emitting element array chip of FIG. 4;

FIG. 6 is a block diagram illustrating an example of a driving IC used for the recording head of the present invention.

FIG. 7 is a time chart for explaining an operation of the driving IC of FIG. 6;

FIG. 8 is a side view showing the appearance of a conventional recording head.

FIG. 9 is a plan view of the recording head of FIG.

[Explanation of symbols]

Reference Signs List 101 light emitting element array chip 102 substrate 103 flexible cable 104 drive IC 106 substrate 107 holding member 108 heat sink 109 lens fiber cable 110 connector 120 shift register 121 latch 122 counter 123 selector 124 NAND gate 125 to 126 buffer R current limiting resistance D _{1 to} D ₅ Diode SR1 'to SR5' Transfer thyristor SR1 to SR5 Light emitting thyristor

──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takahiro Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Naohisa Nagata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Hiroshi Tanioka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuo Komaki 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hideyuki Tanaami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigemi Kumagai 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (72) Invention Person Shigeo Hatake 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-59-184681 (JP, A) JP-A-63-265662 JP, A) JP-A-63-260465 (JP, A) JP-A-5-84971 (JP, A) JP-A-3-15150 (JP, U) JP-A-1-70549 (JP, U) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 H01L 33/00

Claims (4)

(57) [Claims] 1. A recording head that has a light emitting element array arranged in a row and a driving unit that drives the light emitting element, and performs recording by controlling driving of the light emitting element according to a signal. A first substrate having the light emitting element array, a second substrate having the driving unit, and a heat dissipating member provided with the substrates and dissipating the heat of the substrate, wherein the heat dissipating member is provided with the first substrate A surface portion, and a side surface portion provided on the other side of the light irradiation side on which the first substrate is disposed and on which the second substrate is disposed, wherein the first substrate and the second substrate are movable. Connected by flexible wiring ,
A recording head, wherein the light-emitting element array is arranged downward . 2. The current limit that generates the most heat on the second substrate.
2. The recording head according to claim 1, wherein a resistance element is further away from the first substrate than a driving element . 3. The recording head according to claim 1, wherein said light emitting element array includes a self-scanning circuit therein so as to sequentially select a recording operation of a recording element. 4. The driving section has a driving element, the driving element comprising: means for holding data to be recorded; and means for sequentially outputting the data of the holding means to the plurality of light emitting elements in a serial manner. The recording head according to claim 1, wherein: