JPH09226171A - Organic el array printing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To collectively produce one org. EL array substrate by electrically connecting signal electrodes of which the number is same to the number of the light emitting dots on a glass substrate to hole injection electrodes and electrically connecting the hole injection electrodes to a hole transport layer by windows and forming the windows on an almost one line in an almost same area at an equal interval in the same number as the signal electrodes. SOLUTION: Signal electrodes 9 are formed on a glass substrate 8 in the same number as light emitting dots in a predetermined pattern and hole injection electrodes 10 are formed thereon in the predetermined pattern so as to contain the signal electrodes 9. Further, the signal electrodes 9 and the hole injection electrodes 10 are formed within the regions of the windows 12 of insulating films. The insulating films 11 are formed on the hole injection electrodes 10 within the region other than the windows 12 of the insulating films in a predetermined pattern. A hole transport layer 13 and a light emitting layer 14 are formed thereon and electron injection electrodes 15 are formed thereon in a predetermined pattern. The electron injection electrodes 15 are electrically connected to the common electrode 16 simultaneously with the signal electrodes 9 at positions sufficiently separated from the windows 12 of the insulating films.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical print head in an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, the name of the literature: "Electrophotographic Society, Vol. 24, No. 2 (1
985) pp. 31-36 "" LED printer "; Osamu Suzuki, Hiromi Takasu, Takeo Fukatsu.
As disclosed in the above-mentioned document, the LED array print head has high reliability as a light source of an electrophotographic printer.
It has features such as high speed, high image quality, and small size.

In the optical system, the LED array, which is a light source, is solid-stated as a head and does not have a mechanical drive unit such as a laser printer, so that high reliability is obtained. Moreover, since the optical path length is short, the size can be reduced. Furthermore, since the LED array is manufactured by a semiconductor manufacturing technology with a proven track record in mass production, cost reduction due to mass production is expected.

The printing process of the LED printer proceeds in the following order. First, a uniform charge is applied to the photosensitive drum using a charger. Next, LE on the photosensitive drum surface
Light from the D array is imaged through the converging rod lens array to form a latent image. Further, after being visualized by a developing machine, it is transferred and fixed on a recording paper. Further, the residual toner is cleaned and the residual potential is removed, and the printing process is completed.

As for the photosensitive drum, one having a sensitivity characteristic matching the emission wavelength of the LED has been developed. LED
As the portion of the LED array print head in the printer, the substrate is a ceramic substrate made of alumina and patterned with a thick film. LED chips are arranged in a straight line at the center of the substrate, IC chips are die-bonded on both sides with a conductive paste, and electrical connection is made by wire bonding. Signals and power are supplied to the ceramic substrate via an FPC (flexible printed board) substrate. LED
Whether the chips can be continuously connected depends on the cutting accuracy of the chips.

The LED material is required to have three characteristics. (A) The ability to isolate light, (b)
It is possible to use a diffusion process that enables high density, and (c) obtain stable characteristics at an economical price.
AsP is optimal. The LED manufacturing method is based on n-type GaA.
A diffusion prevention film is attached to the sP wafer by a method such as CVD, and a light emitting window is opened on the sP wafer by a photolithography method. Vacuum encapsulation of wafer and P-type impurities in a quartz ampoule
Diffusion is performed at a temperature of ° C for several hours to form a PN junction in the light emitting window. A suitable diffusion depth is 5 to 7 μm. Al on the P side,
Au alloy is vapor-deposited on the N side to form an ohmic electrode. The size of the light emitting part is determined by the density, and is approximately 16 dots / mm.
It becomes 40 μm at (pitch 62.5 μm). The number of dots per chip is practically 64 dots or 128 dots depending on the chip yield and size. The emission wavelength is determined by the material, but is 660 nm. As for the variation in the amount of light within one chip, the level of ± 10% to ± 40% is currently included in one wafer, and the one that is ± 20% or less is selected by the prober inspection. The cutting accuracy of the LED chip affects the alignment accuracy, and a high-precision cutting technology within ± 5 μm is required. In this case, the disconnection of the connecting portion is solved by using a scribing method utilizing cleavage.

[0007]

However, variations in performance among devices due to defects inherent in the wafer, non-uniformity of the manufacturing process, and the like are inevitable. Further, the substrate such as GaAs, which is the substrate of the LED array, can be only about 3 inches in size at most, and is expensive. Moreover,
There are many crystal defects, and if the number of dots in the monolithic type is increased, the yield becomes poor. Therefore, it is necessary to fabricate a large number of array chips with a small number of dots and connect them so as to cover the entire recording width. In addition, an array error occurs in the chip connection portion, and as the density becomes higher, mounting becomes more difficult. These problems bring limits to cost reduction and high density.

According to the present invention, an organic EL array print head which eliminates the above-mentioned problems and is capable of achieving high density, high speed and low cost by manufacturing one organic EL array substrate at a time. The purpose is to provide.

[0009]

In order to achieve the above-mentioned object, the present invention provides: (1) The same number of signal electrodes as the number of light emitting dots on a glass substrate, and the signal electrodes partially on the signal electrodes. The hole injection electrodes are formed in the same number as the signal electrodes overlapped with each other, an insulating film having a window serving as a light emitting portion is formed on the hole injection electrodes, and the windows are included on the insulating film. The formed hole transport layer, the light emitting layer formed on the hole transport layer including the window, and the electron injection electrode formed on the light emitting layer including the hole transport layer and the light emitting layer. And a common electrode electrically connected to the electron injecting electrode outside the region where the windows are arranged, the signal electrode is electrically connected to the hole injecting electrode, respectively. The hole injection electrode is electrically connected to the hole transport layer at the window. The windows are formed in substantially the same area on a substantially straight line and at substantially equal intervals as many as the signal electrodes.

As described above, since the organic EL is used as the light source, one organic EL array substrate can be manufactured at one time, and in the conventional LED, many LED chips are arranged in a straight line. Such mounting difficulties can be avoided and cost reduction can be achieved. Also,
Regarding the densification, in the LED, there is an upper limit due to an alignment error between chips, but in the organic EL, since this problem does not exist, the densification is easy.

Further, since the edge-emitting type can increase the amount of light emission per unit area,
Higher speed can be achieved. (2) In the organic EL array printhead according to (1) above, at the rear surface side end portion of the insulating film, each of the signal electrodes is formed electrically close to the electron injection electrode. About the same number of reflective electrodes as the signal electrodes, which are connected to each of them and are separated from the electron injecting electrodes, are provided.

As described above, since the end face reflection film is formed on the rear surface side, the emitted light can be effectively used. Therefore, a larger amount of light emission per unit area can be obtained for the same input power, and the light emission efficiency can be improved. As a result, low power consumption can be achieved without sacrificing speeding up.

(3) In the organic EL array printhead according to the above (1), the hole transport layer and the light emitting layer exposed from the electron injection electrode are provided on the insulating film near the front end of the insulating film. And an insulating film that is substantially transparent to the emission wavelength of the organic EL. As described above, since the end face emission film is formed on the front surface side, it is possible to further effectively use the light emission, and it is possible to reduce the power consumption without sacrificing the speedup.

(4) In the organic EL array printhead according to (1), the window is formed wider than the hole injection electrode in the window, and the hole injection electrode is wider than the signal electrode. It is designed to be widely formed. In this way, the window is formed wider than the hole injecting electrode, so that the light to the side surface side can be effectively used. Therefore, it is possible to further reduce the power consumption without impairing the speedup.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an organic EL array printhead showing a first embodiment of the present invention. Chip-on-board (hereinafter referred to as COB) substrate 1
Organic EL array substrate 3 having organic EL array 2 on top
1 and a plurality of driver ICs 4 are arranged.

Electrical connection between the COB substrate 1 and the driver IC 4, and the driver IC 4 and the organic EL array substrate 3
The bonding wires 5 are used to electrically connect the COB substrate 1 and the organic EL array substrate 3 to each other. Light emitted from the organic EL array 2 is emitted to the end surface side of the glass substrate and is focused on the photosensitive drum 7 via the converging rod lens array 6.

The number of driver ICs 4 required is the total number of dots per head divided by the total number of dots arranged per chip of the driver IC. For example, A4
As for the size, if 600 dots is used and 128 dots per chip, approximately 5120 dots are required, so 5120 /
128 requires 40 chips. However, unlike the case where the gap between the adjacent LED chips has to be set to 1 dot pitch or less as in the case of the LED array print head, the organic EL array 2 and the wire bond 5 can be arranged with a sufficient distance. On the organic EL array substrate 3, wire bonding does not become difficult,
Rather, it becomes possible to freely arrange the bonding points.

Further, in the organic EL array 2, since all dots can be manufactured at once by forming a thin film and a photolithography method, it is possible to save the labor of arranging a plurality of LED chips and to reduce the cost. . Furthermore, LED
In the case of chips, the displacement of the layout between adjacent chips becomes a problem as the densification progresses, but the organic EL array does not have the mounting difficulty associated with such densification.

On the other hand, the photosensitive drum has to be selected in accordance with the emission wavelength of the organic EL, but there is a wide range of selection of materials for both the organic EL and the photosensitive drum, and there are few difficulties in realization. In this embodiment, OPC (Organic photo)
An oxidative conductor was used. FIG. 2 is a plan view of the organic EL array substrate showing the first embodiment of the present invention.

As shown in this figure, on the glass substrate 8,
The signal electrodes 9 are arranged in the same number as the number of dots of the organic EL. Each signal electrode 9 partially overlaps with each hole injection electrode 10. The hole injecting electrode 10 has an insulating film 11
In a region shown as a window 12 of the insulating film which is spatially a hole inside, it faces the electron injection electrode 15 with the hole transport layer 13 and the light emitting layer 14 interposed therebetween. This sectional structure will be described later.

Light emission occurs in the region of the window 12 of the insulating film. The electron injection electrode 15 is electrically connected to the common electrode 16 outside the region where the windows 12 of the insulating film are lined up. This sectional structure will also be described later. Hole injection electrode 10
Is preferably an electrode having a large work function in order to facilitate injection of holes into the hole transport layer 13 which is an organic film. Indium-tin oxide, so-called ITO or the like is suitable. However, it is not necessarily limited to a transparent electrode such as ITO. This is because even if the hole injection electrode 10 is not a transparent electrode such as ITO, the insulating film 11, the hole transport layer 13, and the light emitting layer 14 guide light to the end face.

On the other hand, the signal electrode 9 is intended to facilitate bump formation so as to facilitate wire bonding and to lower the resistance of the electrode, but many metals satisfy both conditions. Of these, Al and the like are preferable. However, the hole injection electrode 10 is I
The signal electrode 9 must not be transparent if it is a transparent electrode such as TO. This is because light is directly emitted from the light emitting layer 14 to the back surface of the glass substrate 8, and the light that can be extracted to the end face is significantly reduced.

However, the following description will be made assuming that the signal electrode 9 is an opaque electrode and the hole injection electrode 10 is a transparent electrode unless otherwise specified. The formation order of the insulating film 11 is after the hole injection electrode 10. This sectional structure will be described later. Insulating film 11
The reason why is necessary is that the hole transport layer 13 and the light emitting layer 14, which are organic films, cannot withstand the steps required for patterning using the photolithography method.

That is, it means that it is difficult to process these organic films into a predetermined pattern after forming a thin film. Therefore, there is no choice but to form a substantially predetermined pattern by a method such as mask vapor deposition. After all, the light emitting area must be accurately controlled not by the organic film but by the other inorganic film. As described above, the insulating film window 12
The light emitting area can be defined by the area. This light emitting area is approximately proportional to the amount of light emitted to the end face side. That is, if the light emitting area is determined, the amount of light emitted from the end face is uniquely determined. This will be described in detail later.

Since the amount of light emitted from this end face must be the same for all dots, these light emitting areas must be made to be exactly the same area over all dots. Also, if the distance to the end face is different, the degree of attenuation will also be different, and the amount of light emitted from the end face will be different.Therefore, it is clear that the light emitting region with these light emitting areas must be on a substantially straight line over all dots. Is. It is obvious that the amount of light emission increases as the distance to the end face side increases.

Furthermore, since the intervals of the print dots also need to be substantially equal intervals as a matter of course, similarly,
It is necessary to arrange these light emitting regions at substantially equal intervals. In other words, it means that the windows 12 of the insulating film may be formed on all the dots in a substantially straight line, in substantially the same area, and at substantially equal intervals. Of course, this insulating film window 12
Since the same number of signal electrodes 9 as signals are required, it is necessary to form at least the number of signal electrodes 9.

On the other hand, the accuracy of the light emitting area can be obtained by forming the insulating film 11 having the window 12 of the insulating film by the photolithography method before forming the organic film. Of course, the insulating film 11 must be transparent to the emission wavelength. Therefore, the insulating film 11 is a SiNx film,
A SiOx film or the like is sufficient. The hole transport layer 13 and the light emitting layer 14 are made of an organic film. In this embodiment, the light emitting layer 1
For 8 was used 8 quinolinol aluminum complex (Alq ₃ ). Diamine derivative (TPD) is used for the hole transport layer 13.
Was used. Each was formed by vacuum evaporation by resistance heating.
This is mask vapor deposition in which only the region to be formed is vapor deposited. The thickness was 500 Å each.

The hole transport layer 13 must have an electron-donating molecule having a low ionization potential or a substituent. It must also be transparent to the emission wavelength. Triphenylamine derivatives, such as benzidine type, styrylamine type and diamine type. The light emitting layer 14
A fluorescent dye is used. The ionization potential is preferably 6 eV or less for facilitating the injection of holes, and the electron affinity is preferably 2.5 eV or more for facilitating the injection of electrons. Examples include metal chelate compounds, polycyclic condensed or conjugated aromatic hydrocarbons, benzoxazole or benzothiazole derivatives, perylene compounds, and coumarin compounds.

Further, as a method for controlling the wavelength of light emission and increasing the light emission efficiency, doping with a fluorescent dye is effective. Examples include pyran derivatives, coumarin derivatives, cyanine derivatives, and quinacridone derivatives. The ionization potential of the light emitting layer 14 must be lower than that of the hole transporting layer 13 so that holes can be easily injected from the hole transporting layer 13 into the light emitting layer 14.

The electron injection electrode 15 preferably has a low work function so that electrons can be easily injected into the light emitting layer 14. In this example, a MgAg alloy was used. In addition, In, Mg
There are In alloy, MgCu alloy, MgLi alloy and the like. The common electrode 16 has a low resistance in order to pass a large current,
Further, although it should be selected for the reason that wire bonding is easy, etc., Al is sufficient because it is the same condition as the signal electrode 9 described above. In that case, they can be formed simultaneously.

FIG. 3 shows a sectional view taken along the line AA of FIG.
As shown in this figure, the signal electrode 9 is formed on the glass substrate 8.
Are formed in a predetermined pattern. The hole injection electrode 10 is formed on the signal electrode 9 in a predetermined pattern. An insulating film 11 is formed thereon in a predetermined pattern in a region other than the window 12 of the insulating film. It is important that the length of the window 12 of the insulating film can be set relatively freely. This is an advantage peculiar to the edge emitting type.

This will be described. First, light emission occurs in the region of the window 12 of the insulating film. Speaking in the layer direction, fluorescence is generated at the interface side of the light emitting layer 14 with the hole transport layer 13. At this time, the light travels in all directions. However, since the space between the signal electrode 9 and the electron injection electrode 15 is transparent, the exit is obtained while reflecting between the two electrodes. In this figure, the SiNx film is an insulating film 11 made of a SiOx film or a hole injection electrode 10 made of ITO on the front surface side (the side having the focusing rod lens array) and the rear surface side (the side opposite to the front surface side). You can see that it goes out from.

Although not shown in this figure, there is of course light leakage to the side surface. After all, the light emitted to the front end surface can be the light that contributes to printing. In other words,
That is, the longer the length of the window 12 of the insulating film, the greater the amount of light emitted to the front end face. This means that the amount of light emitted from the front end face per unit area can be controlled by this length.

The hole transport layer 13 and the light emitting layer 14 are formed so as to include the window 12 of the insulating film. Hole transport layer 1
3 and the light emitting layer 14 have approximately the same area, but they do not necessarily have to have the same area. Since the formation area of both is formed by a method such as mask vapor deposition that is not accurate in terms of dimensional accuracy, there is no problem even if it is slightly displaced as long as the window 12 of the insulating film is included. It is only necessary that both layers be formed in the window 12 region of the insulating film.

Next, an electron injection electrode 15 is formed so as to include the hole transport layer 13 and the light emitting layer 14. By forming the electron injection electrode 15 so as to include the entire formation region of the hole transport layer 13 and the light emitting layer 14, these organic films are not exposed in the final form. If exposed, since it is an organic film, it deteriorates from the exposed portion due to moisture or oxygen in the air, and the deterioration eventually progresses into the light emitting region, that is, the window 12 of the insulating film. This is because things cannot be avoided.

On the other hand, the electron injecting electrode 15 reflects light, so that it is preferable that the front surface side does not have a structure that blocks light. As can be seen in this figure, the hole transport layer 1
It can be seen that the electron injection electrode 15 plays a role like an eaves on the front surface side as well as on the rear surface side because of the configuration including 3 and the light emitting layer 14. This eaves has the effect of reducing the amount of light emitted from the end face. But this is
It is unavoidable because of the above-mentioned problem of deterioration. However, since it is clear that covering the insulating film 11 also results in reducing the light emitted to the front end face, the end portion of the electron injection electrode 15 is located inside the end portion of the insulating film 11.

FIG. 4 is a sectional view taken along line BB of FIG.
As shown in this figure, signal electrodes 9 are formed on a glass substrate 8 in a predetermined pattern. The hole injection electrode 10 is formed thereon in a predetermined pattern so as to include the signal electrode 9. However, this does not mean that the hole injection electrode 10 needs to be formed wider than the signal electrode 9. It is sufficient that the signal electrode 9 and the hole injection electrode 10 are formed in the region of the window 12 of the insulating film. It goes without saying that there is no change in operation even if the width is reversed outside the window 12 of the insulating film.

An insulating film 11 is formed on the hole injection electrode 10.
Are formed in a predetermined pattern in a region other than the window 12 of the insulating film. A hole transport layer 13 and a light emitting layer 14 are formed thereon, and an electron injection electrode 15 is formed thereon in a predetermined pattern. The electron injection electrode 15 is electrically connected to the common electrode 16 formed at the same time as the signal electrode 9 at a position sufficiently separated from the window 12 of the insulating film.

Next, an organic EL showing the first embodiment of the present invention
The operation of the array head will be described. In FIG.
The data of the content to be printed is sent to the driver IC 4 on the COB board 1. The dots for which the data is “ON” are connected from the driver IC 4 through the bonding wire 5 to the organic E
A current is supplied to the signal electrode 9 on the L array substrate 3. No current is supplied to the signal electrode 9 from the driver IC 4 through the bonding wire 5 to the dot whose data is “OFF”.

Next, the operation when the data is "ON" will be described. The current from the signal electrode 9 flows into the hole injection electrode 10 as it is, and causes the hole injection into the hole transport layer 13 in the region of the window 12 of the insulating film. On the other hand, electrons are similarly injected from the electron injection electrode 15 into the light emitting layer 14. The electrons move in the light emitting layer 14 toward the hole transport layer 13, and when the electrons reach the boundary surface with the hole transport layer 13, the movement is blocked. This is because there is a difference in electron affinity.

However, the holes move in the hole transport layer 13 toward the light emitting layer 14, and the light emitting layer 1
When it reaches the boundary surface with 4, it is easily injected into the light emitting layer 14. At that time, it recombines with the electron that was waiting there.
This recombination energy causes the excitation of Alq ₃ .
Then, it emits fluorescence when returning to the ground state. 540n
m is the emission wavelength.

The light generated at this time reaches the end face while repeating reflection in the space surrounded by the signal electrode 9 and the electron injecting electrode 15, and goes out. Of these, the light emitted to the front end surface passes through the converging rod lens array 6 and is condensed on the photosensitive drum 7. Then, irradiation is performed for the time required for printing.
From this point onward, it is the same as a normal electrophotographic printer. Through these light emitting operations, the current flowing to the electron injection electrode 15 flows to the common electrode 16 and is returned to the COB substrate 1 via the bonding wire 5.

Next, a second embodiment of the present invention will be described. FIG. 5 is a plan view of an organic EL array substrate showing a second embodiment of the present invention, which aims to reduce power consumption by increasing luminous efficiency. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 5, the end face reflection film 17 is electrically separated from the electron injection electrode 15 after the electron injection electrode 15 in the vicinity of the end face portion on the rear surface side of the insulating film 11. Form individually. With such a configuration, the light to the rear surface side is also reflected to the front surface side and the emitted light can be effectively used.

FIG. 6 shows a sectional view taken along the line CC of FIG.
As shown in this figure, the light-emitting layer 14 is still the electron injection electrode 1.
Since it is not covered with 5, the end face reflection film 17 is formed after the electron injection electrode 15 and cannot be formed before it. The reason why the electron injection electrode 15 must be electrically separated is that in order to prevent the light traveling toward the rear surface side from leaking to the outside from the rear surface side end surface, it is connected to the opaque signal electrode 9 and the end portion is connected. Is effective because there are no transparent parts. However, regarding this, the hole injection electrode 1
If 0 is not transparent, the end surface reflection film 17 is the hole injection electrode 1
It goes without saying that it is enough to contact 0.

Next, an organic EL showing a second embodiment of the present invention
The operation of the array head will be described. With such a configuration, the light to the rear surface side can be effectively reflected by being reflected to the front surface side without waste. The light generated in the light emitting layer 14 easily enters the transparent hole transport layer 13 and the insulating film 11, but is reflected by the signal electrode 9 and the electron injection electrode 15 which are non-transparent electrodes. The light emitted from the light emitting layer 14 toward the front surface side exits to the front end surface at a considerable ratio.

However, unless the light emitted toward the rear surface side is reflected somewhere, it is emitted to the end surface on the rear surface side and becomes light that does not contribute to printing. However, a considerable amount of light returns to the front surface side by the end face reflection film 17. Electron injection electrode 15 protruding on the insulating film 11
Of course, the light leaks to the gap between the end face reflection film 17 and the end face reflection film 17. However, since the light totally reflected does not leak out, it can be directed to the front side. Overall, light leakage from this part is negligible.

Next, a third embodiment of the present invention will be described. FIG. 7 is a plan view of an organic EL array substrate showing a third embodiment of the present invention, which aims at further reduction of power consumption by further increasing luminous efficiency. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 7, the electron injection electrode 15 is formed so as to expose the hole transport layer 13 and the light emitting layer 14 on the front surface side. As shown in this figure, the end face emission film 18 is formed after the formation of the electron injection electrode 15 so as to include all the exposed portions of the hole transport layer 13 and the light emitting layer 14 from the electron injection electrode 15. The reason it must be included has already been mentioned.

Further, the edge emitting film 18 must be a film transparent to the emission wavelength. This film is also SiNx
An insulating film such as a film or a SiOx film is suitable. Here, the end face emitting film 18 may not be a conductor as long as it is transparent. This is because in the case of a conductor, it is necessary to electrically separate each dot, and the light emitting layer 14 cannot be completely covered.

FIG. 8 shows a sectional view taken along the line DD of FIG.
As shown in FIG. 8, by forming the end face emission film 18, a structure that prevents reduction in the amount of light emitted from the end face due to the eaves of the electron injection electrode 15 on the front face side end face is formed. Next, the operation of the organic EL array head showing the third embodiment of the present invention will be described.

With this structure, since the electron injection electrode 15 includes the end portions of the hole injection layer 13 and the light emitting layer 14 in the light to the front surface side, the end surface on the front surface side is formed. It becomes possible to more effectively extract the light that could not be extracted from the inside. Next, a fourth embodiment of the present invention will be described. FIG. 9 is a plan view of an organic EL array substrate showing a fourth embodiment of the present invention, which aims at further reduction of power consumption by further increasing luminous efficiency. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 9, the width of the window 12 of the insulating film is formed wider than the width of the hole injection electrode 10. FIG. 10 is a sectional view taken along line EE of FIG. As can be seen from these figures, by forming the window 12 of the insulating film wider than the hole injection electrode 10, on the side surface end portion of the signal electrode 9,
Light in the hole transport layer 13 and the light emitting layer 14 is optically blocked by a bent portion such as an eaves of the electron injection electrode 15. However, in the case of adopting this structure, the hole injection electrode 10 has to be formed wider than the signal electrode 9 also from the description so far. That is, the signal electrode 9 should not be directly connected to the hole transport layer 13. This is because the hole injection electrode 10 has a property of easily injecting holes.

On the other hand, the definition of the light emitting area by the area of the window 12 of the insulating film as described in the first embodiment is defined by the window 1 of the insulating film.
2 is different from the definition of the light emitting area by the area of the hole injection electrode 10 in 2, and the light emitting area can be accurately defined. Next, the operation of the organic EL array head showing the fourth embodiment of the present invention will be described.

With such a structure, a part of the reflected light from the inside of the bent portion of the electron injecting electrode 15, which is shaped like this eave, out of the emitted light directed to the side surface is converted into the front surface. Can be taken out as light to the side. In addition, the end face reflection film 17 as shown in the second embodiment, and the third
If the edge emitting film 18 as shown in the embodiment is provided,
The amount of light emitted from the front end face can be further increased.

In the first embodiment of the present invention, the application to the light source of the electrophotographic printer has been described. This allows
A low-cost, high-density electrophotographic printer can be realized. Further, since the end face light emitting type is used and the amount of light emission per unit area can be freely increased, the speed can be increased. Further, in the second and third embodiments, it has been shown that by providing the end face reflection film and the end face emission film on the rear surface side and the front surface side, respectively, it is possible to reduce the power consumption by increasing the luminous efficiency.

Further, in the fourth embodiment, the light to the side surface is also reflected and returned to be used, so that the luminous efficiency is further increased.
It was shown that low power consumption can be further improved. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0056]

As described above, according to the present invention, the following effects can be obtained. (1) According to the invention as set forth in claim 1, since the organic EL is used as the light source, one organic EL array substrate can be manufactured at one time. It is possible to avoid the difficulty in mounting such that the individual pieces are arranged in a straight line, and it is possible to reduce the cost.

Further, with respect to the densification, in the LED, there is an upper limit due to the problem of arrangement error between chips, but in the organic EL, since this problem does not exist, the densification is easy. Furthermore, since the edge-emitting type can increase the amount of light emission per unit area, the speed can be increased. (2) According to the invention described in claim 2, since the end face reflection film is formed on the rear surface side, the emitted light can be effectively used.

Therefore, a larger amount of light emission per unit area can be obtained for the same input power, and the light emission efficiency can be improved. As a result, low power consumption can be achieved without sacrificing speeding up. (3) According to the invention described in claim 3, since the end face emission film is formed on the front surface side, it is possible to further effectively use the light emission, and to reduce the power consumption without sacrificing the speedup. Will be possible.

(4) According to the invention described in claim 4, since the window is formed wider than the hole injecting electrode, the light to the end face side can be effectively used. Therefore, it is possible to further reduce the power consumption without impairing the speedup.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an organic EL array printhead showing a first embodiment of the present invention.

FIG. 2 is a plan view of an organic EL array substrate showing a first embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is a plan view of an organic EL array substrate showing a second embodiment of the present invention.

FIG. 6 is a sectional view taken along the line CC of FIG. 5;

FIG. 7 is a plan view of an organic EL array substrate showing a third embodiment of the present invention.

8 is a sectional view taken along the line DD of FIG. 7;

FIG. 9 is a plan view of an organic EL array substrate showing a fourth embodiment of the present invention.

FIG. 10 is a sectional view taken along line EE of FIG. 9;

[Explanation of symbols]

 1 Chip On Board Substrate (COB Substrate) 2 Organic EL Array 3 Organic EL Array Substrate 4 Driver IC 5 Bonding Wire 6 Focusing Rod Lens Array 7 Photosensitive Drum 8 Glass Substrate 9 Signal Electrode 10 Hole Injection Electrode 11 Insulating Film 12 Insulating Film Window 13 Hole transport layer 14 Light emitting layer 15 Electron injection electrode 16 Common electrode 17 Edge reflection film 18 Edge emission film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04N 1/036 H05B 33/00 (72) Inventor ▲ Takahashi Wataru Toranomon 1-chome, Minato-ku, Tokyo 7-12 Oki Electric Industry Co., Ltd.

Claims (4)

[Claims] 1. An organic EL array printhead comprising an organic EL array substrate having an organic EL array on a glass substrate and a substrate on which a driver IC for driving the organic EL array is mounted, wherein light-emitting dots are provided on the glass substrate. The same number as the number of signal electrodes, substantially the same number as the signal electrodes as the signal electrodes formed on the signal electrodes so as to partially overlap with the signal electrodes, and the light emitting portion on the hole injection electrodes. An insulating film having a window, a hole transport layer formed on the insulating film to include the window, a light emitting layer formed on the hole transport layer to include the window, and on the light emitting layer. An electron injection electrode formed to include the hole transport layer and a light emitting layer; and a common electrode formed to be electrically connected to the electron injection electrode, wherein the signal electrode is the hole injection electrode. And the hole injection The electrode is electrically connected to the hole transport layer in the window, and the windows are formed in substantially the same area on substantially the same line and at substantially the same number as the signal electrodes. Characteristic organic EL array print head. 2. The organic EL array printhead according to claim 1, wherein at the rear end portion of the insulating film, the signal electrodes are formed electrically from each of the signal electrodes to near the electron injection electrode. An organic EL array printhead, wherein substantially the same number of reflective electrodes as the signal electrodes which are connected to each of the above and are separated from the electron injecting electrodes are provided. 3. The organic EL array printhead according to claim 1, further comprising the hole transport layer and the light emitting layer exposed from the electron injecting electrode, on the insulating film near the front end of the insulating film. An organic EL array printhead, which is provided with an insulating film which is substantially transparent to the emission wavelength of the organic EL. 4. The organic EL array printhead according to claim 1, wherein in the window, the window is formed wider than the hole injection electrode, and the hole injection electrode is formed wider than the signal electrode. An organic EL array print head characterized in that