JP2744548B2 - Line 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 line head in which edge emitting EL elements are connected in an array.

[0002]

2. Description of the Related Art In recent years, an EL (Electro Luminescence) element is one of the light emitting elements that have been put into practical use, and there is a demand for an improvement in emission luminance, which tends to be insufficient. Therefore, an edge-emitting EL element which emits light at a luminance about 100 times that of a conventional EL element whose surface emits light has been developed. The edge-emitting EL element is formed by surrounding a thin-film active layer made of zinc sulfide or the like containing an active element with a dielectric layer to form an optical waveguide, and forming an opposing electrode layer on the outer surface of the dielectric layer. When a high voltage pulse is applied between these electrode layers, an extremely flat light beam is emitted from the end face of the active layer.

A conventional example of a line head in which such edge emitting EL elements are provided in series will be described with reference to FIGS. First, as illustrated in FIG. 8, the edge emitting EL element 2 of the line head 1 includes an active layer 3 made of zinc sulfide or the like containing an active element such as manganese and a dielectric layer 4 made of yttrium trioxide or the like. 5 and the electrode layers 6 and 7 are formed on the upper and lower surfaces. And as illustrated in FIG. 7, this line head 1
A large number of the edge emitting EL elements 2 are separately formed on a transparent substrate 8 made of low alkali glass or the like by a thin film technique, and for example, as illustrated in FIG.
The L element 2 in the m-number of the common electrodes 9 ₁ ~9m and n blocks electrodes 10 ₁ to 10n has a like matrix wiring structure.

More specifically, as shown in FIGS. 10 and 11, in this line head 1, at least the front surface is transparent, and a cover member 11 having a shape surrounding the edge emitting EL element 2 is provided on the transparent substrate. 8 and a moisture-proofing agent 1 such as resin in the inner space of the cover member 11.
2 are enclosed. A rod lens array 13 as a light condensing element is disposed at a position facing the edge emitting EL element 2 via the moisture proof agent 12 and the cover member 11 via a spacer (not shown). ing.

Therefore, the line head 1 having such a structure is described.
As shown in FIG. 12, a line printer 14 using at least a charging charger (not shown) is provided at a position facing the outer peripheral surface of a photosensitive drum 15 rotatably supported.
A liner 1, a developing device (not shown), and a transfer charger (not shown) are sequentially arranged, and a transfer path for printing paper is formed between the transfer charger and the photosensitive drum 15. Has become. Note that this line printer 1
In 4, the end surface emitting EL element 2 of the line head 1 is opposed to the photosensitive drum 15 via a rod lens array 13, and a driving circuit 16 is mounted at the rear of the line head 1.

In such a configuration, the line head 1 can drive the edge emission type EL element 2 at a predetermined position to emit light by selectively applying a drive pulse to each of the electrodes 9 and 10 from the drive circuit 16. Therefore, an electrostatic latent image can be formed on the charged outer peripheral surface of the rotating photosensitive drum 15 of the line printer 14. Therefore, the electrostatic latent image on the photosensitive drum 15 is developed with the charged toner supplied from the developing device, and is transferred to the printing paper by the discharge potential of the transfer charger, so that the printed image of the dot matrix is printed on the printing paper. Will be formed.

In this line head 1, the rod lens array 13 converges the light emitted from the edge emitting EL element 2 to improve its optical characteristics and contribute to higher density of a printed image. Has become. Further, in the line head 1, the edge emitting EL element 2 is sealed with the cover member 11 and the moisture proofing agent 12, thereby preventing destruction due to short-circuit of a high-voltage driving pulse and erosion due to contact with high humidity outside air. It has become.

[0008]

In the line head 1 described above, the light-emitting end face of the end face light-emitting type EL element 2 is shielded from the outside air by a cover member 11 or a moisture proofing agent 12 to prevent deterioration. Here, in the line head 1, since the light emitted from the edge emitting EL element 2 reaches the outside through the moistureproofing agent 12 and the cover member 11, it tends to be refracted and scattered in this process.

More specifically, in the line head 1 having the above-described structure, the refraction process is different if the number of boundary surfaces that pass through to the outside is different, and as shown in FIG. A top region that sequentially passes through the desiccant 12 and the upper portion of the cover member 11, a middle region that passes through the front of the desiccant 12 and the cover member 11, a moisture barrier 12 and the transparent substrate 8.
The degree of scattering of the outgoing light is greatly different between the low region and the low region which sequentially passes through the desiccant 12 and the front part of the cover member 11. That is, the refractive index of the desiccant 12 is ns, and the cover member 1
Nb a refractive index of 1 and the transparent substrate 8, and the refractive index of the active layer of the edge emission type EL devices 2 and n _1, as illustrated in FIG. 14 (a), edge-emitting surface direction of the thin-film layer as a reference The angle of inclination of the emitted light in the mold EL element 2 is θ ₁ , the angle of inclination of the emitted light when entering the desiccant 12 is θ ₂ , and the transmitted light of the desiccant 12 is the upper surface of the internal space of the cover member 11. inclination angle theta ₃ at the time of entering, when the inclination angle when emitted to the outside from the front surface of the cover member 11 and theta _4, the inclination angle theta ₄ of the light emitted at this top region, theta ₄ = sin ~ ¹ [nb × sin {cos ~ ¹ (1 / nb√ (ns ² −n ₁ ² × sin
² θ ₁ )))]. Then, as exemplified in FIG. 2B, the inclination angle of the emitted light in the edge emitting EL element 2 is θ ₁ , and the inclination angle when the emitted light is incident on the desiccant 12 is θ ₂ . Assuming that the inclination angle when the transmitted light of the desiccant 12 is incident on the rear surface of the internal space of the cover member 11 is θ ₃ ′, and the inclination angle when the transmitted light is emitted from the front surface of the cover member 11 to the outside is θ ₄ ′, The inclination angle θ ₄ ′ of the emitted light in the middle area is θ ₄ ′ = sin ~ ¹ (n ₁ × sin ² θ ₁ ). Further, as illustrated in FIG. 3C, the inclination angle of the emitted light in the edge emitting EL element 2 is θ ₁ , and the inclination angle when the emitted light is incident on the desiccant 12 is θ ₂ . The angle of inclination when the transmitted light of the desiccant 12 is incident on the transparent substrate 8 is θ ₃ ″, and the angle of inclination when the transmitted light of the transparent substrate 8 is incident on the desiccant 12 again is θ ₄ ″. Assuming that the inclination angle when the transmitted light of the incident light enters the rear surface of the internal space of the cover member 11 is θ ₅ and the inclination angle when the transmitted light is emitted from the front surface of the cover member 11 to the outside is θ ₆ , inclination angle theta ₆ of the emitted ^{_{light, θ 6 = sin ~ 1 [}} nb × sin {cos ~ 1 (1 / nb√ (ns 2 -n 1 2 × sin
² θ ₁ ))}] In this line head 1, since the front edge of the transparent substrate 8 protrudes forward from the front edge of the edge emitting EL element 2, the edge of the edge emitting EL element 2 The emitted light passes through the transparent substrate 8. Therefore, here, the transparent substrate 8 actually made of the same material is assumed to be a part of the cover member 11 and the refractive index is shared by nb, so that the inclination angles θ ₄ and θ ₆ between the top region and the low region Are the same.

In the actual line head 1, the refractive index NB of the transparent substrate 8 made of low alkali glass and the cover member 11 is 1.53, the refractive index ns of the moisture proofing agent 12 made of resin is 1.42, and the edge emitting type EL element. 2, the refractive index n ₁ of the active layer 3 = 2.4, and the scattering angle θ of the light emitted from the edge emitting EL element 2
_{If 1} = ± 10 °, θ ₄ ≒ 39 °, θ ₄ ′ = 10 °, θ ₆ ≒ 39
°, which indicates that the inclination angle of the emitted light is extremely large between the top region and the low region. In this case, in the line head 1, as shown in FIG. 15, only the light emitted from the middle region enters the rod lens array 13, and the light emitted from the top region and the low region is not used for image scanning. Since the light intensity of the line head 1 with respect to the photosensitive drum 15 is reduced,
The print quality of No. 4 is impaired.

For example, as described above, even if the line head 1 has a reduced light emission intensity because only a part of the light emitted from the edge emitting EL element 2 can be used, it is necessary to increase the drive power supplied to the line head 1. Although it is conceivable to secure a high light emission intensity, this is not practical because the power consumption of the line printer 14 increases and the drive circuit 16 and the power supply circuit (not shown) need to be enlarged.

An object of the present invention is to provide a line head having a high emission intensity and capable of reducing power consumption.

[0013]

SUMMARY OF THE INVENTION An edge emitting type E in which opposing electrode layers are located on the outer surface of a dielectric layer surrounding an active layer.
L elements are continuously arranged in an array on a substrate, and at least a position facing the light-emitting end face in a shape surrounding the light-emitting end face of the edge-emitting EL element located on the substrate is transparent on the substrate. In a line head in which the light-emitting end face of the edge emitting EL element is sealed by enclosing a moisture-proofing agent in the internal space of the cover member, the refractive index ns of the moisture-proofing agent and the refractive index nb of the cover member are: The relationship of ns> nb is satisfied.

[0014]

The light emitted from the edge-emitting EL element having a small scattering angle can be totally reflected at the boundary between the desiccant and the cover member, so that the scattering of the emitted light from the edge-emitting EL element can be effectively reduced. It is possible to obtain a line head that can increase the amount of light that can be used and that has high emission intensity and can reduce power consumption.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, as shown in FIG. 6, the line head 17 is formed as a part of an electrophotographic line printer 18. Here, this line printer 1
Reference numeral 8 designates a toner cleaner 20, a charging charger 21, the line head 17, a developing device 22, a transfer charger 23, and the like, sequentially disposed on the outer peripheral surface of a photosensitive drum 19 rotatably supported on a shaft. A paper conveyance path is formed between the photosensitive drum 19 and the photosensitive drum 19.

The line head 17 of this embodiment, which is a part of the line printer 18, has a large number of edge emitting EL elements 2 connected in an array as shown in FIGS. An upper cover 25 having a concave groove 24 formed on the bottom surface and a flat lower cover 26 are attached to each of the upper and lower surfaces of the formed transparent substrate 8, and a flat transparent front plate is provided on the front surfaces of these covers 25 and 26. It has a structure to which the unit cover 27 is attached. Here, the upper and lower covers 25, 26
Protrudes forward from the front edge of the transparent substrate 8, and spacers 28 are attached to opposing sides. Therefore, in the line head 17, the covers 25, 26
The front cover 27 and the spacer 28 form a cover member 29 that surrounds the edge emitting EL element 2, and a moisture proof agent 30 is sealed in the internal space of such a cover member 29. Here, in the line head 17, an inlet 32 for the desiccant 30 is formed at one end of the upper cover 25 of the cover member 29, and an air outlet 3 for air is formed at the other end.
3 are formed, and the exhaust port 33 and the injection port 32 are formed.
Is sealed by bonding the sealing plate 34.

In the line head 17, the refractive index ns of the desiccant 30, the refractive index nb of the cover member 29, and the refractive index ng of the transparent substrate 8 satisfy the relationship of ns> nb ns> ng. Are to be satisfied together. More specifically, in the line head 17 exemplified in this embodiment, the refractive index ng of the transparent substrate 8 made of low alkali glass is 1.53, and the refractive index nb of the cover member 29 made of the same low alkali glass is 1.53. , A moisture barrier made of silicone oil 30
By setting the refractive index ns to 1.54, the above conditional expression is satisfied. In this line head 17, the refractive index ng of the transparent substrate 8 made of low alkali glass and the refractive index nb of the cover member 29 are the same as in the line head 1 described above as a conventional example. The explanation will be made instead.

In such a configuration, when an image is printed by the line printer 18 illustrated in this embodiment, the outer peripheral surface of the rotating photosensitive drum 19 is cleaned by the toner cleaner 20 and then the corona discharge of the charging charger 21 is performed. The latent image is charged, and an electrostatic latent image is formed by selective light irradiation of the line head 17 that operates according to the image signal. And
The electrostatic latent image on the outer peripheral surface of the photosensitive drum 19 is
The image is printed on the printing paper 35 by developing it with the charged toner supplied from the printer and transferring it to the printing paper 35 with the discharge potential of the transfer charger 23.

In the line head 17, the transparent substrate 8 and the cover member 29, both made of low alkali glass, are used.
And the moisture-proofing agent 30 made of silicone oil
Satisfying the relationship of ns> nb, the total reflection at the interface between these members is increased, the scattering of the light emitted from the edge emitting EL element 2 is reduced, and the emission intensity is reduced. To improve it. That is, similarly to the line head 1 described above as a conventional example, the line head 17 emits light having a large scattering angle from the edge emitting EL element 2 to the moisture proofing agent 30 and the cover member 29.
Are emitted to the top region which sequentially passes through the upper cover 25 and the front cover 27 of the above, and the low region which sequentially passes through the desiccant 30, the transparent substrate 8, the desiccant 30, and the front cover 27 of the cover member 29. However, when the refractive indices of the transparent substrate 8, the cover member 29, and the desiccant 30 are specified as described above, the light emitted from the edge-emitting EL element 2 having a small scattering angle is not covered by the upper cover of the desiccant 30 and the cover member 29. At the interface with 25,
Since the light is totally reflected at the interface between the moisture proofing agent 30 and the transparent substrate 8 or the like, as shown in FIG. 1, the light is emitted to a middle area or the like and enters the rod lens array 13. More specifically, the refractive index nb of the transparent substrate 8 made of low alkali glass and the cover member 29 is 1.53, the refractive index ns of the moisture barrier 30 made of silicon oil is 1.54, and the active layer 3 of the edge emitting EL element 2 is formed. If the refractive index of n ₁ = 2.4,
The present applicant has confirmed by optical simulation that the above-described total reflection occurs at the boundary surface if the scattering angle θ ₁ ≦ ± 8 ° of the edge emitting EL element 2.

By doing so, the line head 17 can reduce the scattering of the light emitted from the edge emitting EL element 2 and improve the amount of light reaching the photosensitive drum 19 and the like, so that the driving power is increased. It is possible to increase the emission intensity of the emitted light without performing the above-mentioned steps, thereby contributing to the improvement of the print quality of the line printer 18. If the emission intensity is the same, the power consumption can be reduced. Can also contribute.

In this line head 17 as well, outgoing light having an excessively large scattering angle of the edge emitting EL element 2 is emitted to the top region and the low region.
As described on the basis of 4, the inclination angle theta ₄ of the emitted light between the top region and the low region in this case, the _{θ 6, θ 4 = θ 6} = sin ~ 1 [nb × sin {cos ~ 1 (1 / Nb√ (ns ² −n ₁ ²
× sin ² θ ₁ ))}], the scattering angle θ of the edge-emitting EL element 2
_{If 1} = ± 10 °, then θ ₄ = θ ₆ ≒ 12. In other words, in the line head 17, since the inclination angles of the light emitted from the top region and the low region are extremely small, it is possible to improve the light emission intensity by making these light incident on the rod lens array 13. .

In the line head 17 of this embodiment,
As described above, the transparent substrate 8 through which the light emitted from the edge emitting EL element 2 is transmitted is assumed to be a part of the cover member 29, and the refractive index is shared by nb. When the material of the member 29 is different from that of the member 29, as described above, the refractive index ns of the desiccant 30 and the refractive index nb of the cover member 29 are used.
The material is selected so that the refractive index ng of the transparent substrate 8 satisfies the relationship of ns> nb ns> ng. The relationship between the refractive indices of the various members with respect to the moisture proofing agent 30 is similarly applied to the case where the materials of the upper cover 25 and the front cover 27 of the cover member 29 are different.

Further, in the line head 17 of the present embodiment, the emitted light is transmitted through the front edge of the transparent substrate 8 which is structurally protruded forward from the front edge of the edge emitting type EL element 2, so that this transparent Although the description has been made in consideration of the refractive index of the substrate 8, the present invention is not limited to the above structure. For example, the light emitting end face of the edge emitting EL element 2 and the front edge of the transparent substrate 8 are flush with each other. A line head that is positioned above so that light emitted from the edge emitting EL element 2 does not pass through the transparent substrate 8
(Not shown) can also be implemented.

When the line head 17 of this embodiment is implemented, the moisture proofing agent 30 is inserted into the inlet 32 of the cover member 29.
And the air is evacuated from the exhaust port 33,
After filling the interior space of the cover member 29 with the desiccant 30, the sealing plate 34 is bonded to the inlet 32 and the outlet 33. By doing so, in the line head 17, the moisture proofing agent 30 can be easily and quickly injected into the minute internal space of the cover member 29. Further, in the line head 17, by forming the concave groove 24 on the lower surface of the upper cover 25, the end surface emitting EL element 2 can be continuously filled with the moisture proof agent 30 even in a portion having a complicated shape. Has become.

Here, in the line head 17 having the above-described structure, the bonding connection or the chip is formed on the electrodes 9 and 10 formed on the rear edge of the upper surface of the transparent substrate 8 by being connected to the edge emitting EL element 2. Since components are to be mounted, it is desirable that the reference surface be located on the lower surface side of the transparent substrate 8. In the line head 17, the sealing plate 34
Is mounted on the upper surface of the cover member 29 and the bottom surface is flat, so that the positioning and mounting of the line head 17 can be favorably performed using this as a reference surface.

[0026]

According to the present invention, as described above, edge emitting EL elements in which opposing electrode layers are located on the outer surface of a dielectric layer surrounding an active layer are continuously provided in an array on a substrate. A cover member, which surrounds the light emitting end face of the edge emitting EL element located on the substrate and is transparent at least at a position facing the light emitting end face, is fixed to the substrate, and a moisture-proofing agent is sealed in the internal space of the cover member. Then, in the line head in which the light emitting end face of the edge emitting type EL element is sealed, the refractive index ns of the moisture proofing agent and the refractive index nb of the cover member satisfy the relationship of ns> nb. Since the emitted light having a small scattering angle of the EL element can be totally reflected at the boundary surface between the desiccant and the cover member, the scattering of the emitted light from the edge emitting EL element is reduced, and the amount of light that can be effectively used is increased. Can be , Those having the effect of such may be the emission intensity to obtain a line head capable of reducing the high power consumption.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of the present invention.

FIG. 2 is a perspective view.

FIG. 3 is an exploded perspective view.

FIG. 4 is a perspective view showing an enlarged main part.

FIG. 5 is a vertical sectional front view.

FIG. 6 is a vertical sectional side view showing the line printer.

FIG. 7 is a perspective view showing a conventional example.

FIG. 8 is a perspective view showing an enlarged main part.

FIG. 9 is a circuit diagram.

FIG. 10 is a vertical sectional side view showing a specific structure.

FIG. 11 is a perspective view.

FIG. 12 is a vertical sectional side view showing a main part of the line printer.

FIG. 13 is a characteristic diagram showing optical characteristics of a line head prototyped by the present applicant.

FIG. 14 is a characteristic diagram showing optical characteristics in various optical paths.

FIG. 15 is a vertical sectional side view showing a scattering state of emitted light.

[Explanation of symbols]

 2 Edge emitting EL element 3 Active layer 4, 5 Dielectric layer 6, 7 Electrode layer 8 Substrate 8, 29 Cover member 17 Line head 30 Moisture proof

Claims (1)

(57) [Claims] 1. An edge emitting type EL device in which opposing electrode layers are located on an outer surface of a dielectric layer surrounding an active layer, and are arranged in an array on a substrate, and the edge emitting EL devices located on the substrate are arranged. At least a position facing the light-emitting end face and surrounding the light-emitting end face of the type EL element is fixed to the substrate, and a moisture-proofing agent is sealed in an inner space of the cover member. 3. The line head according to claim 1, wherein the refractive index ns of the desiccant and the refractive index nb of the cover member satisfy a relationship of ns> nb.