JP3537961B2 - Organic EL array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device which is suitably used for an optical printer head in an electrophotographic printer.
It relates to an L (electroluminescence) array.

[0002]

2. Description of the Related Art Conventionally, as a light source of an electrophotographic printer, for example, "Electrographic Society of Japan, Vol. 24, No. 2 (198
5) pp. 31-36; LED printers (Osamu Suzuki, Hiromi Takasu, Takeo Fukatsu) "are known. LED like this
An LED printer equipped with an array printer head has a high reliability because the LED array as a light source is solid-state as a head and has no mechanical driving unit such as a laser printer, and furthermore has a short optical path length. Therefore, miniaturization is possible. In addition, since the LED array is manufactured using semiconductor manufacturing technology with a proven track record of mass production, cost reduction can be expected by mass production.

[0003] In the LED printer disclosed in the above document, the printing process proceeds in the following order. First, a uniform charge is applied to the photosensitive drum using a charger. Next, the light from the LED array is focused on the photosensitive drum surface via the converging rod lens array to form a latent image. Next, the image is made visible by a developing machine, and then transferred and fixed on recording paper. Further, the residual toner is cleaned and the residual potential is removed, and the printing process is completed. Note that photosensitive drums having sensitivity characteristics suitable for the emission wavelength of the LED have been developed.

In this LED printer, an LED is used.
An LED array printer head equipped with an array has a substrate in which a thick film pattern is formed on an alumina ceramic substrate, an LED chip is arranged in a straight line at the center of the substrate, and an IC chip is placed on both sides of the substrate with conductive paste. In this case, die bonding is performed, and electrical connection is performed by wire bonding. Signals and power are supplied to the ceramic substrate via an FPC (flexible printed board) substrate. Whether the LED chips can be connected continuously depends on the cutting accuracy of the chips.

[0005] By the way, three characteristics are required for LED materials. a) the ability to isolate light, b) the use of a diffusion process capable of increasing the density, and c) the ability to obtain stable characteristics at an economical price. as,
At present, GaAsP grown in a vapor phase on a GaAs substrate is considered to be optimal.

In order to manufacture such an LED, an n-type G
An anti-diffusion film is formed on the aAsP wafer by a CVD method or the like, and a light emission window is opened on the anti-diffusion film by a photolithography method. Next, the wafer and P-type impurities are vacuum-sealed in a quartz ampoule and diffused at a temperature of about 700 ° C. for several hours to form a PN junction in the light emitting window. At this time, an appropriate diffusion depth is 5 to 7 μm.

Next, Al is deposited on the P side and Au alloy is deposited on the N side to form an ohmic electrode. The size of the light emitting part is generally determined by the density (resolution), and is 40 μm at 16 dots / mm (pitch: 62.5 μm). 1
The number of dots per chip is 6 depending on chip yield and size.
Four dots or 128 dots are practical. The emission wavelength is determined by the material, and is 660 nm in this example.

The variation in the amount of light in one chip is ± 1 at present.
A level from 0% to ± 40% is included in one wafer, and is selected by a prober inspection, and one having a level of ± 20% or less is used. The cutting accuracy of the LED chip affects the alignment accuracy, and a high-precision cutting technology within ± 5 μm is required. A scribing method using cleavage is used for cutting the connection portion.

[0009]

However, the above-mentioned LED array print head has the following disadvantages regarding the LED array. Variations in performance between elements due to defects inherent in the wafer and non-uniformity in the manufacturing process are inevitable. At present, a substrate such as GaAs serving as a substrate of the LED array is at most 3
It can only be made about an inch in size,
Moreover, it is expensive. Furthermore, if the number of dots is large in a monolithic type with many crystal defects, the yield will deteriorate.

In view of this, a large number of array chips having a small number of dots are produced and connected to cover the entire recording width. In this case, an arrangement error occurs in the chip connection portion, and as the density increases, the chip connection portion becomes more dense. Mounting on a board becomes very difficult, for example, due to an increase in the arrangement error.
Such difficulty in mounting is a major factor impairing cost reduction and high density. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic EL array capable of avoiding difficulty in mounting, reducing costs and increasing density. .

[0011]

In the organic EL array according to the present invention, an insulating substrate and a part of each of the reflecting electrodes which are substantially the same in number as the number of light emitting dots formed on the insulating substrate are covered. A light guide made of a light-transmitting insulator formed on the insulating substrate, and partially covering the upper surface of each of the reflective electrodes; A plurality of transparent electrodes formed on each of the reflective electrodes so as to cover the portion; and a plurality of transparent electrodes formed on the insulative substrate so as to cover a part of each of the transparent electrodes, and formed directly on each of the transparent electrodes. A positive electrode formed in contact with each of an insulating film having a window opening at an upper portion including a position immediately above the rear surface of the light guide, and a transparent electrode covering the window and facing out of the window. A hole transport layer, formed on the hole transport layer covering a position immediately above the window portion; A light emitting layer, and an electron injection electrode formed on the insulating substrate in contact with the light emitting layer, covering the light emitting layer and the hole transport layer, and did.

According to this organic EL array, since it is manufactured collectively on an insulative substrate such as glass which can be made slender, a large number of LED chips are arranged in a straight line as in a conventional LED array. The above difficulties are avoided. In addition, since the light generated on the rear surface of the light guide is mainly used, and the light is extracted from the front surface of the light guide, the size of the organic EL array itself can be reduced unlike the case where the light is extracted from the upper surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an organic EL array of the present invention will be described in detail with reference to embodiments. FIG. 1 (a),
(B) is a diagram showing a first embodiment of the present invention. In these figures, reference numeral 1 denotes an organic EL array serving as a light source of a print head. This organic EL array 1 has a large number of light emitting dots, and a plurality of reflective electrodes 3...
, A plurality of transparent electrodes 5, an insulating film 6, and a hole transport layer 7
And a light emitting layer 8 and an electron injection electrode 9.

As shown in FIG. 1A, the reflective electrodes 3 are rectangular in plan view and formed on the substrate 2 by a number corresponding to the number of light-emitting dots. In this case, they are arranged side by side in a state facing the short side direction of the substrate 2. The material of the reflective electrodes 3 is not particularly limited as long as the reflectivity is high. In this example, the reflective electrodes 3 are made of aluminum (Al) and have a thickness of 200 nm.
Is formed.

On these reflective electrodes 3...
As shown in (a) and (b), a rectangular parallelepiped light guide 4 is formed on the insulating substrate 2 so as to cover a part of each of the reflective electrodes 3. The light guide 4 has a light-transmitting property, that is, a light-transmitting property with respect to the emission wavelength. In this example, the light guide 4 is formed of SiN _x or SiO _x to a thickness of 2.5 μm. The light guide 4 is arranged to be biased toward one long side of the substrate 2, and the long side is a front surface 4a serving as an emission side as described later, and the opposite surface is a rear surface. 4b.

Immediately above each of the reflective electrodes 3,
The light guide 4 covers a part of the upper surface thereof and is in contact therewith.
A plurality of transparent electrodes 5 are formed to cover a part of the rear surface 4b and a part of the upper surface. Under such a configuration, the transparent electrodes 5 are electrically connected to the reflective electrodes 3. These transparent electrodes 5 are made of a material having a light-transmitting property, that is, a light-transmitting property with respect to the emission wavelength, similarly to the light guide 4, and a hole transport layer 7 which is an organic film as described later. In order to facilitate the injection of holes into the conductor, the conductor is made of a conductor having a large work function. In this example, the conductor is formed of indium-tin oxide (ITO) to a thickness of 150 nm.

The transparent electrode 5 is provided on the substrate 2.
The insulating film 6 is formed so as to cover a part (substantially most part in this example) of each of the... In the insulating film 6, windows 6a are formed just above the transparent electrodes 5 and open to include the position right above the rear surface 4b of the light guide 4. The window 6a serves as a light emitting dot, and by forming the window 6a for each transparent electrode 5, the organic EL array 1 has a plurality of light emitting dots. The reason why the insulating film 6 is necessary is as follows.

As will be described later, since the hole transport layer 7 and the light emitting layer 8 are organic films, they cannot withstand a patterning step using a photolithography method, so that this patterning cannot be performed. Therefore, the area where the transparent electrode 5 and the hole transport layer 7 formed on the insulating film 6 are in contact with each other must be accurately formed in order to define the area where light emission occurs. Therefore, after the transparent electrode 5 is formed, an insulating film 6 that can be accurately patterned is formed between the transparent electrode 5 and the hole transport layer 7, and the insulating film 6 is interposed between the transparent electrode 5 and the hole transport layer 7. 7 and insulating film 6
By bonding through the window 6a formed in the insulating film 6, the window 6a of the insulating film 6 is accurately patterned, so that the region where the transparent electrode 5 and the hole transport layer 7 are in contact with each other, that is, the region where light emission occurs. The area can be accurately defined. For this reason, it is preferable that the insulating film 6 is formed from a material that can be formed into a fine pattern by photolithography.
Such as N _x film and SiO _x film is formed to a thickness of 300 nm.

The window 6 is formed on the insulating film 6.
The hole transport layer 7 is formed so as to cover “a”. The hole transport layer 7 is formed in contact with each of the transparent electrodes 5 facing out of the window 6a of the insulator 6 as described above, and is made of an organic film. As the hole transport layer 7, an electron-donating molecule having a low ionization potential,
Or a compound having a substituent, which must be transparent to the emission wavelength. Specifically, a triphenylamine derivative, such as a benzidine type, a styrylamine type, or a diamine type, is preferable. In this example, a diamine derivative ( TPD) is used and has a thickness of 50 nm by vacuum evaporation by resistance heating.
Is formed. In addition, as this vacuum evaporation, mask evaporation in which only an area to be formed is evaporated is employed.

A light emitting layer 8 is formed on the hole transport layer 7 so as to cover a position immediately above the window 6a of the insulating film 6. The light emitting layer 8 preferably has an electron affinity of 2.5 eV or more so that electrons can be easily injected. Specifically, the light emitting layer 8 includes a metal chelate compound, a polycyclic fused or conjugated aromatic hydrocarbon, benzoxazole or benzoxazole. Thiazole derivatives, perylene-based compounds, coumarin-based compounds, and the like are preferable, and doping with a fluorescent dye, such as a pyran derivative, a coumarin derivative, a cyanine derivative, or a quinacridone derivative, for controlling the emission wavelength or increasing the efficiency is also preferable. It is valid. The light emitting layer 8 must have an ionization potential lower than that of the hole transport layer 7 so that holes can be easily injected from the hole transport layer 7 into the light emitting layer 8. In view of such conditions, in this example, an 8-quinolinol aluminum complex (Alq ₃ ) is used as the light emitting layer 8, and the thickness of the light emitting layer 8 is reduced to 50 nm by vacuum deposition by resistance heating similarly to the hole transport layer 7. Has formed.

An electron injection electrode 9 is formed on the substrate 2 so as to cover the light emitting layer 8 and the hole transport layer 7 and to be in contact with the light emitting layer 8. The electron injection electrode 9 preferably has a low work function so that electrons can be easily injected into the light emitting layer 8. Specifically, the electron injection electrode 9 is made of a MgAg alloy, In, MgIn.
Alloys, MgCu alloys, MgLi alloys and the like are suitable,
In this example, a MgAg alloy is used and has a thickness of 200 n.
m. The electron injection electrode 9 is formed so as to cover the hole transport layer 7 and the light emitting layer 8 because the hole transport layer 7 and the light emitting layer 8 are organic films. This is to prevent it.

As shown in FIG. 1A, the electron injection electrode 9 is electrically connected to a common electrode 10 formed simultaneously with the reflection electrode 3 on both sides of the substrate. Under such a configuration, the organic EL array 1 includes the hole transport layer 7 and the light emitting layer 8 between each transparent electrode 5 and the electron injection electrode 9 at the window 6 a of the insulating film 6. And sandwiched between.

Next, the organic EL array 1 having such a configuration will be described.
An example in which is applied to a print head will be described with reference to FIG. In FIG. 2, reference numeral 1 denotes FIG.
The organic EL array shown in (b) is shown, and the substrate 2 of the organic EL array 1 is mounted on a drive circuit board 11 together with a driver IC 12. The drive circuit board 11 and the driver IC 12 are electrically connected by bonding wires 13. Similarly, driver IC1
2 and the substrate 2 of the organic EL array 1, and the substrate 2 of the organic EL array 1 and the drive circuit substrate 11 are also electrically connected by bonding wires 13.

One side of the organic EL array 1, that is,
Although not shown in FIG. 2, a converging rod lens array 14 and a photosensitive drum 15 are arranged in this order on the front surface 4a side of the light guide 4 on the substrate 2. Under such a configuration, the light emitted from the organic EL array 1
The light is emitted toward the front surface 4 a (not shown) of the upper light guide 4, and is focused on the photosensitive drum 15 through the converging rod lens array 14.

Next, the operation of the organic EL array 1 shown in FIGS. 1A and 1B will be described based on the configuration of the print head shown in FIG. First, in FIG. 2, the data of the content to be printed is stored in the driver IC 1 on the drive circuit board 11.
Send to 2. Then, the organic E shown in FIGS. 1A and 1B is obtained.
In the L array 1, the dot whose data is “ON” (window portion 6)
In a), a predetermined voltage is applied between the reflective electrode 3 and the electron injection electrode 9, and a current flows through the reflective electrode 3. here,
Whether it is “ON” or “OFF” is determined by the presence or absence of a current supplied to the reflective electrode 3.

In the case of "ON", the operation is as follows. First, a supply current from the driver IC 12 is supplied to the reflection electrode 3 through the bonding wire 13 and further flows to the transparent electrode 5. As a result, holes are injected into the hole transport layer 7. On the other hand, electron injection from the electron injection electrode 9 to the light emitting layer 8 occurs in the same manner. The electrons injected into the light emitting layer 8 move toward the hole transport layer 7 in the light emitting layer 8 and reach the interface with the hole transport layer 7. Its movement is blocked by the difference in electron affinity with layer 7.

However, the holes injected into the hole transport layer 7 move toward the light emitting layer 8 in the hole transport layer 7 and reach the interface with the light emitting layer 8. The electrons are easily injected into the light emitting layer 8 and recombine there with the electrons waiting. Then, the recombination energy causes the excitation of the 8-quinolinol aluminum complex (Alq ₃ ) forming the light emitting layer 8, and further, when returning from the excited state to the ground state, emits fluorescence having an emission wavelength of 540 nm.

The light generated by such a mechanism undergoes the following action in the organic EL array 1 and is extracted to the outside as emitted light. First,
Inside the window 6a of the insulating film 6 which is a light emitting region, the light emitting region is divided into the following three places. (1) a region where the transparent electrode 5 is in contact with the reflective electrode 3 (2) a rear surface 4b region of the light guide 4 (3) an upper surface region of the light guide 4

Light generated in the region (1) out of these three regions hardly enters the light guide 4. Therefore, it hardly contributes as emitted light. (2)
Most of the light generated in the region is extracted outside. This is because the intensity of the light from the organic EL is greatest in the direction normal to the light emitting surface, but the light generated in the area (2) is a light-extraction place in the normal direction. This is because the front surface 4a of the light body 4 is provided.

Since the light generated in the region (3) has a normal direction perpendicular to the lower surface of the light guide 4, the total amount of light that can be extracted to the outside is substantially equal to the total amount of light emitted from the light emitting surface. Becomes about 1/10. this is,
Light that deviates from the normal direction and travels in an oblique direction also
This is because the light is reflected by the electron injection electrode 9 on the upper side and the reflective electrode 3 on the lower side, and after some reflections, a part thereof is extracted to the outside. However, the light reflected by the reflective electrode 3 tends to be taken out toward the front surface 4a of the light guide 4, but is conversely returned to the front surface 4a again toward the rear surface 4b. It is absorbed without being. Therefore, as described above, the total amount of light that can be extracted to the outside is about 1/10 of the total amount of light emitted from the light emitting surface.

As described above, most of the light from the rear surface 4b and about 1/10 of the light from the upper surface can be extracted to the outside. The light extracted to the outside is converged on the converging rod lens array 1 as shown in FIG.
After passing through 4, the light is focused on the photosensitive drum 15 and irradiated for a required time. From here on, the operation is similar to that of a normal electrophotographic printer. In the case of a dot whose data is “OFF”, no voltage is applied between the reflective electrode 3 and the electron injection electrode 9, and therefore no current flows through the reflective electrode 3, so that the dot (window 6 a) emits light. Does not occur.

In such an organic EL array 1,
Since it can be manufactured collectively on one substrate 2,
It is possible to avoid the difficulty in mounting such as arranging a large number of LED chips on a straight line as in a conventional LED array, and to reduce the cost. In addition, the light guide 4
Mainly using the light generated on the rear surface 4b,
Since the structure is taken out from the upper side, the organic EL array 1 itself is reduced in size differently from the case where the organic EL array is taken out from the upper surface, so that the entire print head using the organic EL array 1 can be downsized.

FIGS. 3A and 3B are diagrams showing a second embodiment of the present invention.
Is an organic EL array. The difference between the organic EL array 20 and the organic EL array 1 shown in FIGS. 1A and 1B is that the organic EL array 20 is different from the organic EL array 1 shown in FIGS.
As shown in (b), the same number of the reflection electrodes 3 are formed, and these light guides 21 are formed only directly above the reflection electrodes 3, respectively. Therefore, each light guide 21 is independent for each dot. It is the point that has become.

That is, the organic EL in this embodiment is
The light guides 21 of the array 20 are arranged one by one on each reflective electrode 3, that is, one by one for each dot, and are formed so as to fit within the reflective electrodes 3. It has become something. The left and right width of the light guide 21 is formed to be slightly smaller than the width of the reflective electrode 3 so as to fit on the reflective electrode 3.
Is formed slightly before the edge of the reflective electrode 3 so as not to protrude from the edge of the reflective electrode 3.
As in the first embodiment, the electron injection electrode 9 is arranged so that it does not come into direct contact with the transparent electrode 5 so that the front surface 21 a
The edge of the insulating film 6 is formed so as to be closer to the edge of the insulating film 6 on the front surface 21a side.

Even in such an organic EL array 20, like the above-mentioned organic EL array 1, it is used by being applied to the print head having the configuration shown in FIG. At this time, as can be seen from FIG. 3A, since the light emitting region itself is not different from that of the first embodiment, (1), (2), ( The total amount of light entering the light guide 21 from the three light emitting regions of 3) is the same.
In this organic EL array 20, unlike the case of the first embodiment, the light guides 21...
As shown in (b), each of the light guides 21 is covered with the electron injection electrode 9 on both left and right side surfaces thereof.

Therefore, of the light entering the light guide 21, the light traveling toward the left and right side surfaces of the light guide 21 is reflected by the electron injection electrode 9 and returns to the inside of the light guide 21 again.
Therefore, the organic EL array 20 of the present embodiment can extract more of the generated light to the outside without changing the light emitting area as compared with the organic EL array 1 of the first embodiment. This allows the organic EL array 20 to increase the total amount of light that can be irradiated onto the photosensitive drum 15 per unit time, thereby shortening the light emission time. Further, since the total amount of light that can be extracted to the outside for the same supply current can be increased, the power consumption itself can be reduced.

As described above, in the organic EL array 20 of the present embodiment, the cost can be reduced and the size can be reduced by avoiding the difficulty in mounting, as in the first embodiment. As a matter of course, the structure is such that the light directed to the left and right side surfaces in the light guide 21 can be effectively guided to the front surface 21a side, so that the amount of light that can be extracted to the outside can be increased, thereby shortening the light emission time. The printing speed of the printer can be increased, and the power consumption can be reduced.

FIGS. 4A and 4B are diagrams showing a third embodiment of the present invention.
Is an organic EL array. The difference between the organic EL array 30 and the organic EL array 1 shown in FIGS. 1A and 1B is that the rear surface 31 b of the light guide 31 located in the window 6 a of the insulating film 6 is different from the substrate 2. The point is that it is a slope facing the opposite side. That is, the organic E in the present embodiment example
The rear surface 31b of the light guide 31 of the L array 30
As shown in (b), the light guide 31 is formed to be inclined so as to gradually separate from the front surface 31a as going from the upper surface side to the lower surface side. Therefore, as the light guide 31 goes from the rear end to the front surface 31a side,
It is formed so that its thickness gradually increases.

If the inclination angle θ of the rear surface 31b is too large, the area of the rear surface 31b itself is a vertical surface (that is, θ = 90 °), that is, the area of the light guide 4 in the first embodiment. As it is close to the area of the rear surface 4b, it is hard to expect that the degree of light entering increases as described later,
On the other hand, if it is too small, the area increases, but the number of reflections in the light guide 31 also increases, and the degree of loss of light until it reaches the front surface 31a increases, and the light extracted from the front surface 31a increases. The increase in the amount cannot be expected much. For such a reason, the inclination angle θ of the rear surface 31b is preferably about 40 ° to 50 °. In this example, the inclination angle θ was set to 45 ° (see FIG. 4).
In (b), θ is increased for convenience.) Therefore, the depth width of the rear surface 31a is the same as the thickness of the light guide 31, that is, 2.5 μm.

Even in such an organic EL array 30, as in the case of the organic EL array 1, it is used by being applied to the print head having the configuration shown in FIG. At this time, as can be seen from FIG. 4A, the light emitting region itself is not different from that of the first embodiment. In the organic EL array 20, unlike the case of the first embodiment, the rear surface 31b of the light guide 31 is an inclined surface facing the side opposite to the substrate 2, so that the rear surface 31b is The area is larger (about 1.4 times in this example) than in the case of a vertical plane (that is, in the case of the rear face 4b of the light guide 4 in the first embodiment). The light emission amount in the indicated area can be increased.

In this example, as described above, the area of the rear surface 31b is approximately 1.4 times that of the vertical surface, so that the amount of light that can be extracted to the outside is also approximately 1.4 times. As expected, in fact, the increase was only about 1.3 times due to light attenuation due to reflection. However, the increase in the amount of light emission achieved in this manner does not require an increase in the supply current, and thus does not cause an increase in current consumption.

In the organic EL array 20 of this embodiment, as in the case of the first embodiment, it is possible to reduce the cost and to reduce the size while avoiding difficulty in mounting. Of course, since the rear surface 31b of the light guide 31 is formed as an inclined surface, the area thereof is increased, and the light emitting area in this region is increased. Therefore, the amount of light that can be extracted to the outside can be increased. Since the printing speed of the printer can be increased by shortening the time, and the amount of light that can be extracted to the outside without increasing the current consumption can be increased, the power consumption can be reduced. You can also plan.

FIGS. 5A and 5B show a fourth embodiment of the present invention.
Is an organic EL array. This organic EL array 40 is the organic EL of the second embodiment shown in FIGS. 3A and 3B.
The difference from the array 20 is that the transparent electrodes 42 are formed at positions directly below the window 6a of the insulating film 6 so as to cover the left and right side surfaces of the light guide 41, respectively.

That is, the organic EL array 40 has a light guide 4 similar to the organic EL array 20 of the second embodiment.
1 is arranged one by one on each reflective electrode 3, that is, one by one for each dot, and each is formed so as to fit within the reflective electrode 3. I have. The light guide 41 is formed such that its left and right widths are smaller than the width of the reflective electrode 3 so as to fit on the reflective electrode 3, and the front surface 41 a does not protrude from the edge of the reflective electrode 3. Thus, it is formed so as to be slightly before the edge of the reflective electrode 3.

The transparent electrode 42 is formed on the window 6 of the insulating film 6.
The light guide 41 is formed so as to directly cover the left and right sides of the light guide 41 in the area a. Therefore, the width of the light guide 41 is wider than the width of the light guide 4. The window 6a of the insulating film 6
Are formed wider than the left and right widths of the transparent electrode 42. The electron injection electrode 9 has an edge on the front surface 41a side of the light guide 41 that is closer than the edge on the front surface 41a side of the insulating film 6 so that the electron injection electrode 9 does not come into direct contact with the transparent electrode 42 as in the second embodiment. It is formed to be in the foreground.

Even in such an organic EL array 40, as in the organic EL array 20 of the second embodiment,
This is applied to the print head having the configuration shown in FIG. At this time, in the organic EL array 40, unlike the case of the second embodiment, light emission also occurs at positions on the left and right sides of the light guide 41. Therefore, the three light emitting regions as shown in the second embodiment are added to each of the left and right side surface regions to become five, and the light emitting surface which can contribute to obtaining the emitted light is the rear surface 41b region. And the area of the upper surface and the area of each of the left and right sides, so that the light emission amount itself can be naturally increased. Also,
Since the left and right side surfaces of the light guide 41 are structured to be covered with the electron injection electrodes 9, the total amount of light that can be extracted from the front surface 41a of the light guide 41 to the outside is also the same as in the second embodiment. Can be increased. However, as the light emitting area increases, the supply current also increases.

In the organic EL array 40 according to the present embodiment, the cost can be reduced and the size can be reduced by avoiding the difficulty in mounting, as in the first embodiment.
Further, similarly to the second embodiment, the amount of light that can be extracted to the outside can be increased by guiding light toward the left and right side surfaces to the front surface 41a in the light guide 41. In addition, the light guide 4
Since light was generated from both left and right sides of 1,
The light emission amount itself is increased, and the amount of light that can be extracted to the outside can be further increased. As a result, the light emission time can be shortened, and the printing speed of the printer can be further increased.

[0048]

As described above, since the organic EL array of the present invention can be manufactured collectively on an insulating substrate, a large number of LED chips are arranged in a straight line like a conventional LED array. It is possible to avoid difficulties in mounting, and thereby reduce costs. Further, since the light generated on the rear surface of the light guide is mainly used and is extracted from the front surface of the light guide, the organic EL array itself is reduced in size differently from the case where the light is extracted from the upper surface. A device such as a print head using an EL array can be reduced in size.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a schematic configuration of an organic EL array according to a first embodiment of the present invention;
(A) is a plan view, and (b) is a cross-sectional view taken along line BB of (a).

FIG. 2 is a schematic configuration diagram of a print head using the organic EL array shown in FIG.

FIGS. 3A and 3B are diagrams showing a schematic configuration of an organic EL array according to a second embodiment of the present invention;
(A) is a plan view, and (b) is a cross-sectional view taken along line BB of (a).

FIGS. 4A and 4B are diagrams showing a schematic configuration of an organic EL array according to a third embodiment of the present invention;
(A) is a plan view, and (b) is a cross-sectional view taken along line BB of (a).

FIGS. 5A and 5B are diagrams showing a schematic configuration of an organic EL array according to a fourth embodiment of the present invention;
(A) is a plan view, and (b) is a cross-sectional view taken along line BB of (a).

[Explanation of symbols]

1,20,30,40 Organic EL array 2 Substrate 3 reflective electrode 4, 21, 31, 41 Light guide 4b Rear 5, 42 transparent electrode 6 Insulating film 6a Window 7 hole transport layer 8 Emitting layer 9 Electron injection electrode

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yukio Nakamura 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A 8-248276 (JP, A) JP JP-A-8-108568 (JP, A) JP-A-8-16774 (JP, A) JP-A-61-195586 (JP, A) JP-A-62-43096 (JP, A) JP-A-39-3739 (JP, A) , Y1) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 33/00-33/28 B41J 2/44-2/455

Claims (4)

(57) [Claims] 1. An organic EL array having a plurality of light emitting dots, comprising: an insulating substrate; approximately the same number of reflecting electrodes as the number of the light emitting dots formed on the insulating substrate; A light guide made of a translucent insulator formed on the insulating substrate to cover a part thereof; and a part of a rear surface of the light guide, covering a part of an upper surface of each of the reflective electrodes. And a plurality of transparent electrodes formed on each of the reflective electrodes so as to cover a part of the upper surface, and the transparent electrode formed on the insulating substrate so as to cover a part of each of the transparent electrodes. An insulating film having a window portion that is opened immediately above the light guide including the position immediately above the rear surface of the light guide; and a transparent electrode that covers the window portion and faces the outside from inside the window portion. The formed hole transport layer, and covering the position immediately above the window portion, A light emitting layer formed on the hole transport layer; and an electron injection electrode formed on the insulating substrate in contact with the light emitting layer and covering the light emitting layer and the hole transport layer. An organic EL array comprising: 2. The organic EL array according to claim 1, wherein said light guides are formed in substantially the same number as said reflection electrodes, and said light guides are respectively formed only immediately above said reflection electrodes. Organic EL array. 3. The organic EL array according to claim 1, wherein a rear surface of the light guide located in a window of the insulating film is an inclined surface facing a side opposite to the insulating substrate. Organic EL array. 4. The organic EL array according to claim 2, wherein each of the transparent electrodes is formed so as to cover left and right side surfaces of the light guide at a position directly below a window of the insulating film. Organic EL array.