JP2927619B2 - Optical print 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 light for converting an electric signal into an optical image by using an optical fiber array substrate for transmitting a one-dimensional optical image used in an electrophotographic printer or a digital copying machine. Regarding the print head.

[0002]

2. Description of the Related Art In recent years, an optical print head used as a writing light source of a non-impact printer has been developed and started to spread. An optical print head converts one-dimensional image information from an electrical signal into an optical image. One optical beam emitted from a gas laser or a semiconductor laser is modulated by a light modulation element, and this is electrophotographed by a rotating polygon mirror. A head that irradiates a photoreceptor, a long light-emitting diode array in which a plurality of light-emitting diode array chips are linearly mounted, and a head that uses a selfoc lens array are commercially available. The latter optical print head using a light-emitting diode array has features that it has a large amount of light, can perform parallel writing, and can be designed with a small optical system, and has been applied to high-speed printers and personal facsimile machines. I have.

A head using the light emitting diode array includes a head using a converging rod lens array as an equal-magnification optical lens or an optical fiber array substrate.
An optical print head that does not use an optical lens has been proposed (see JP-A-55-98879). An optical print head using an optical fiber array substrate does not require a converging rod lens array, and thus has an advantage that the device can be easily miniaturized and can be manufactured at low cost.

FIG. 6 is a diagram showing a conventional optical fiber array substrate and an optical fiber, (a) is a perspective view thereof,
(B) is an enlarged sectional view thereof, and (c) is a sectional view of an optical fiber. Conventionally, optical fiber arrays have been used as means for transmitting image information. Therefore, in order to prevent crosstalk of transmitted optical image information, the numerical aperture (N
As means for removing light having an angle larger than the incident angle corresponding to (A), as shown in (c), the core 64 of the optical fiber is used.
An optical fiber in which a clad 65 having a small refractive index is formed around the optical fiber, and a light absorber layer 66 is further formed around the optical fiber is conventionally used. In order to obtain an optical fiber array substrate in which a large number of optical fibers having such a structure are embedded in a glass substrate, a large number of optical fibers 63 are individually formed on the base glass 61.
Or a plurality of optical fibers 63 are once bundled and then integrated to form an integrated optical fiber bundle 62, which is then stacked in three rows as shown in FIG. An optical fiber array substrate as shown in (a) was formed by sandwiching the substrate, pressing, heating and melting.

Next, the structure and operation of a conventional optical print head will be described. FIG. 4 is a sectional view showing the structure of a conventional optical print head. In FIG. 4, reference numeral 41 denotes a base glass; 42, an optical fiber;
Are formed on the surface of the base glass 41 as shown in the figure. 44 is a light emitting diode array chip, 45 is a light emitting element, and 46 is an electrode.
Is disposed at a predetermined position of the circuit conductor layer 43 via the.

FIG. 5 is an explanatory diagram for explaining the operation of a conventional optical print head unit. Reference numeral 51 denotes a chassis in which a conventional optical print head is incorporated, and an electrophotographic photosensitive member 52 is arranged close to the optical print head. As the electrophotographic photosensitive member 52, an organic photoconductor (OPC), an amorphous silicon photosensitive member, or the like is used.

In the optical print head, the light emitting element 45 radiates light having a wavelength corresponding to the energy gap by the signal current flowing through the circuit conductor layer 43, and the light is incident on the optical fiber 42. Here, the optical fiber 4
The light 53 incident at an angle smaller than the incident angle i corresponding to the numerical aperture NA of 2 is transmitted through the optical fiber 42 by repeating perfect reflection, emitted from the other end face of the optical fiber array substrate, and electrophotographed. A predetermined position on the photoconductor 52 is irradiated to draw a latent image in the electrophotographic process.

[0008]

However, in the above-mentioned optical fiber array substrate, the numerical aperture of the optical fiber is N.
The light 54 incident at an angle greater than the incident angle i corresponding to A does not propagate through the single optical fiber 42, but instead passes from the core 64 to the clad 65 shown in FIG. The layer 66 is reached. Here, since the light absorber layer 66 has an absorption wavelength region in a short wavelength region, it can effectively transmit image information to light having a short wavelength, but has an emission wavelength of a light emitting diode array. 660
Since the absorptance in the near infrared region such as nm or 720 nm is low, the light is not sufficiently absorbed by the light absorber layer 66 and leaks from the single optical fiber 42. Further, the leaked light traverses the other optical fibers 42 one after another, and eventually penetrates the fiber array substrate and is irradiated on the photoconductor 52. For this reason, photocharges are generated on the photoreceptor 52 to draw a pseudo-latent image on a portion other than the exposed surface, which causes a problem that the printing quality is significantly deteriorated by affecting the resolution and brightness.

Therefore, in order to prevent such deterioration in print quality, it is necessary to remarkably increase the thickness of the light absorber layer 66 coated on the optical fiber 42 or use a fiber array substrate having a large thickness. In addition, the material of the light absorber layer 66 cannot easily cope with an arbitrary emission wavelength in fiber production due to the adhesion to glass. For this reason, there is a problem that light sources of various wavelengths cannot be easily handled. Therefore, it must be said that it is extremely difficult to provide a low-cost optical print head by such means.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is intended to prevent light from penetrating an optical fiber array substrate and reaching a photoreceptor even in the near infrared region, which is the emission wavelength of a light emitting diode array chip. Accordingly, an object of the present invention is to provide an optical print head that enables high-quality writing on a photoconductor.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a plurality of optical fibers are buried in a part of a base glass having a plurality of circuit conductor layers formed on a surface thereof in a thickness direction thereof. Along with a position where the end face of the optical fiber of the base glass is exposed, an optical print head in which a plurality of light emitting elements are arranged, wherein the optical fiber and
Forming a light absorbing layer at the interface where the base glass contacts
It is characterized by that. Further, the aperture of the optical fiber
Number (NA), optical fiber bundle width (W), and optical fiber
Refractive index (n1) of the core and the thickness of the base glass
(D) is W / d <[(n1 / NA) ² -1)] ^-0.5
It is characterized by the following relationship.

[0012]

[0013]

According to the above construction, the optical print head has a plurality of optical fibers embedded in a part of the base glass having a plurality of circuit conductor layers formed on the surface thereof in a thickness direction thereof. A plurality of light emitting elements are arranged and formed on the glass surface at an upper position where the end face of the optical fiber is exposed. In addition, several embedded in the base glass
Light absorbing layer at the boundary where the optical fiber and the base glass are in contact
Is formed.

Here, of the light emitted from the light emitting element, light incident at an angle smaller than the incident angle corresponding to the numerical aperture (NA) of the optical fiber is completely reflected in the optical fiber embedded in the base glass. And the light is efficiently emitted from the end face of the optical fiber opposite to the incident side to the electrophotographic photosensitive member. Light incident at an angle equal to or larger than the incident angle is transmitted through the base glass while being attenuated in a form crossing the optical fiber without being transmitted through the optical fiber, and is absorbed by the light absorbing layer.

[0015]

[0016]

Here, the relationship among the numerical aperture (NA) of the optical fiber, the width (W) of the optical fiber bundle, the thickness (d) of the base glass, and the refractive index (n1) of the core of the optical fiber is expressed as W / d <.
^{[(N1 / NA) 2 -1} )] - if ^0.5, the light incident on the optical fiber at least an incident angle corresponding to NA are all absorbed by the light absorbing layer. Therefore, the light emitted from the light emitting element is efficiently and accurately irradiated through the optical fiber without leaking to the electrophotographic photosensitive member to which the optical print head is brought close.

[0018]

FIG . 1A shows a first comparison of an optical print head.
FIG. 2B is a perspective view showing an example, and FIG. 2B is a sectional view taken along line AA ′ in FIG. In FIG. 1A, reference numeral 11 denotes a base glass in which an optical fiber 12 is embedded so as to penetrate in a thickness direction. 13 is a circuit conductor layer. Also,
In (b), 14 is a light emitting diode array chip, 15 is a light emitting element, 16 is an electrode, 17 is a translucent insulating resin, and 18 is a light absorbing layer.

The operation of the optical print head constructed as described above is as follows. First, an on-off electric signal is transmitted to each of the light emitting diodes 15 on the light emitting diode array chip 14 through the circuit conductor layer 13 formed on the base glass 11. Accordingly, each light emitting diode 15 is turned on and off. In the case of lighting, the emitted light is incident on the opposing optical fiber 12. Here, the light emission intensity of the light emitting diode 15 has an angle dependency, and the light is incident on the optical fiber 12 at any angle.

On the other hand, an incident angle i corresponding to a numerical aperture NA defined by NA = n0 × sin (i) (where n0 is a refractive index of a medium on which light is incident and i is an incident angle, respectively).
Light incident at a smaller angle is transmitted through the optical fiber 12 and is efficiently emitted from the end face of the optical fiber 12 opposite to the incident side. On the other hand, light incident at an angle equal to or greater than the incident angle i is transmitted through the optical fiber 12 without transmitting through the fiber 12 and finally reaches the second back surface of the optical fiber array substrate. . The leaked light is sufficiently absorbed by the light absorbing layer 18 formed thereon, and does not pass through the optical fiber array substrate.

Accordingly, with respect to the light emitted from the light emitting diode array chip 14 mounted face-down on the front side of the optical fiber array substrate, the light having an angle of incidence i or less passes through the single optical fiber 12 completely. The light is efficiently transmitted while repeating reflection, and is emitted from the back surface of the optical fiber array substrate. Light having an incident angle i or more traverses the plurality of optical fibers 12 while being attenuated, and is formed on the back surface of the optical fiber array substrate. Since the light reaches the light absorbing layer 18 and is absorbed there, the leaked light does not reach the electrophotographic photosensitive member.

Next, a method for manufacturing the optical print head configured as described above will be specifically described. First, a single crystal III-V semiconductor substrate (wafer) provided with a light emitting diode 15 and an electrode 16 such as a bump is formed on a single crystal III-V semiconductor substrate (wafer) using a semiconductor manufacturing process. In this comparative example , a light emitting element having a light emission wavelength of 660 to 740 nm formed at 12 dots / mm is used. Further, the electrode 16 is formed by a plating method so as to protrude from the wafer surface by about several μm to 20 μm. Thereafter, the wafer is cut by a high-precision dicing technique, and the light emitting diode array chips 14 are formed.

Further, regarding the optical fiber array substrate,
First, a substrate equivalent to a conventional one is made. That is, FIG.
In the optical fiber array substrate shown in (a), (b) and (c), the optical fiber 63 has a core diameter of 10 to 25 μm (here, 20 μm), and the numerical aperture is NA = 0.
57. Each core 64 is covered with a clad 65 having a thickness of about 2 μm and a light absorber layer 66 having a thickness of about 2 μm. Then, the optical fiber bundle 62 is formed by collecting a plurality of such optical fibers 63. Subsequently, the optical fiber bundle 6 is placed between the base glass 61 having substantially the same characteristics as the thermal expansion coefficient of the optical fiber 63.
After 2 are stacked in three rows and arranged so as to be sandwiched between them, they are melted by being pressurized while being heated and integrated. As a result, the optical fiber bundle which was initially circular is deformed to assume a pentagonal or hexagonal shape.

Next, the circuit conductor layer 13 is formed on the surface of the optical fiber array substrate on which the light emitting diode array chips 14 are to be arranged, using a thick film printing technique or vapor deposition and photo etching techniques. Further, the light absorbing layer 18 is formed in the same manner on the opposite surface where the circuit conductor layer 13 is formed, except for the end face of the optical fiber 12 from which the light incident at an angle smaller than the incident angle i corresponding to the numerical aperture NA is emitted. It is formed to form an optical fiber array substrate. Here, the light absorption layer 18
A phthalocyanine pigment having a high absorption efficiency from 0 nm to 800 nm is dispersed in an epoxy resin and printed by screen printing to a film thickness of about 5 μm.

Subsequently, a predetermined amount of an acrylate-based light-transmitting insulating resin 17 is applied to the optical fiber array substrate by a stamping method, a screen printing method, or the like. 13 are arranged face-down so as to come into contact with predetermined positions. Thereafter, while applying pressure from above the light-emitting diode array chip 14, the light-transmitting insulating resin 17 is irradiated with ultraviolet rays through the base glass 11 to be cured, thereby completing the mounting.

In the optical print head obtained in this way, when the same light emitting element as the conventional optical print head using the SELFOC lens array is used to illuminate the electrophotographic photosensitive system recording medium, it is about 1.4. A double optical signal output was obtained. Figure 2 shows a second comparison of optical printheads
It is sectional drawing which shows an example . In the figure, 11 is a base glass, 12 is an optical fiber, 13 is a circuit conductor layer, 14 is a light emitting diode array chip, 15 is a light emitting diode,
6 is an electrode and 17 is a translucent insulating resin.
This is the same as the configuration shown by. The difference from FIG. 1B is that the numerical aperture NA on the opposite surface on which the circuit conductor layer 13 is formed is different.
The metal film 21 is formed at a position other than the end face of the optical fiber 12 from which the light incident at an angle smaller than the incident angle i corresponding to the light exits, and a light-transmissive insulating film 22 is formed on the metal film 21. It is. In the present embodiment, the metal film 21 is formed from aluminum having a thickness of 0.5 μm to 1 μm by a vacuum deposition method using aluminum.
m.

In the optical print head configured as described above, of the light emitted from the light-emitting diode array chip 14, light having an angle of incidence i or more traverses the plurality of optical fibers 12 while being attenuated. It reaches the back of the array substrate. Then, the reaching light is specularly reflected at the interface between the metal film 21 and the base glass 11 according to the law of reflection and returns to the base glass 11 again. Therefore, the leaked light does not reach the electrophotographic photosensitive member.

Further, since the optical print head is used in proximity to the electrophotographic photosensitive member, the metal film 21 does not abnormally bend the lines of electric force in the vicinity of the photosensitive member to prevent the generated carriers from moving. The metal film 21 is covered with a translucent insulating film 22. In this case, the sheet resistance of the insulating film is 10
It is desirable to be ¹⁵ Ω or more. Further, since the insulating film is transparent, it can be formed not only on the metal film 21 but also on the optical fiber 12, which facilitates the manufacturing. In this embodiment, as the light-transmitting insulating film 22, silicon dioxide is formed by an evaporation method.

The material of the metal film 21 may be silver, gold, rhodium, copper, titanium, or the like, in addition to aluminum. When silver is used, it may be formed using a silver mirror reaction. Alternatively, a thick film paste such as gold or silver-platinum or silver-palladium may be printed at a desired position using a thick film printing technique and then fired. FIG. 3 is a sectional view showing an embodiment of the optical print head according to the present invention. In FIG. 3, reference numeral 11 denotes a base glass in which an optical fiber 12 is embedded so as to penetrate in a thickness direction.
13 is a circuit conductor layer. 14 is a light emitting diode array chip, 15 is a light emitting diode, 16 is an electrode, and 17 is a translucent insulating resin. Reference numeral 23 denotes a light absorption layer formed at the interface between the optical fiber 12 and the base glass 11.

In the optical print head thus configured, of the light emitted from the light emitting diode array chip 14, the light having an incident angle i or more corresponding to the numerical aperture NA is attenuated by a plurality of optical fibers 12. , But is absorbed by the light absorbing layer 23 formed at the interface between the optical fiber 12 and the base glass 11.
It does not enter inside. Here, the numerical aperture (NA) of the optical fiber 12, the width (W) of the optical fiber bundle, and the thickness (d) of the base glass are W / d <[(n1 / NA) ² −1] −
^When the relationship of ^0.5 (where n1 indicates the refractive index of the core of the optical fiber) is satisfied, all the light incident on the optical fiber 12 at an incident angle i or more corresponding to the numerical aperture NA reaches the light absorbing layer 23. Therefore, a high-performance optical print head can be obtained.

In order to manufacture an optical print head as described above, first, a plurality of optical fibers 12 equivalent to a conventional one are put together to form an optical fiber bundle 62. Next, the light absorbing layer 23 is formed on one surface of the base glass 11 having substantially the same characteristic as the thermal expansion coefficient of the optical fiber 12, and the optical fiber bundles 62 are stacked and arranged thereon in three rows. Next, after the light absorbing layer 23 is formed on another base glass 11, the light absorbing layer 23 is arranged on the side of the optical fiber bundle 62, and is melted by applying pressure while heating. Integrate. After that, the thickness d that satisfies the above-mentioned conditions is appropriate.
Is cut out on a plane perpendicular to the optical fiber 12 and polished.

In this embodiment, the light absorbing layer 23 is formed of the same material as the glass of the absorber layer of the optical fiber 12. The light absorbing layer 23 has a thickness of 660 nm to 740 nm and a transmittance of 1 to 1% so that the transmittance is 5% or less. 0.5 mm. In the optical print head thus obtained, light leakage to the photoreceptor was reduced, and an optical print head having good print quality could be obtained.

[0033]

According to the present invention, in an optical print head using a light-emitting diode array, image information of an arbitrary wavelength incident on an optical fiber at a large angle can be transmitted to an electrophotographic photosensitive member. And high quality image transmission. As a result, the printing quality can be significantly improved.

The optical print head according to the present invention has a relatively large depth of focus and has excellent resolution characteristics.
Further, it is possible to avoid image deterioration due to static electricity due to friction and flaws due to wear. Moreover, the manufacturing process is simple, and an inexpensive optical print head can be provided.

[Brief description of the drawings]

FIG. 1A is a perspective view illustrating a first comparative example of an optical print head, and FIG. 1B is a cross-sectional view taken along line AA ′ in FIG.

FIG. 2 is a cross-sectional view illustrating a second comparative example of the optical print head.

FIG. 3 is a sectional view showing an embodiment of the optical print head according to the present invention.

FIG. 4 is a cross-sectional view showing a structure of a conventional optical print head.

FIG. 5 is an explanatory diagram for explaining an operation of a conventional optical print head unit.

6A and 6B are views showing a conventional optical fiber array substrate and an optical fiber, wherein FIG. 6A is a perspective view thereof, FIG. 6B is an enlarged sectional view thereof, and FIG. 6C is a sectional view of the optical fiber.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-316019 (JP, A) JP-A-1-122462 (JP, A) JP-A-3-95243 (JP, U) JP-A-2- 82541 (JP, U) Japanese Utility Model 4-124647 (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B41J 2/44 B41J 2/45 B41J 2/455 G03B 27/32 H04N 1/036

Claims (2)

(57) [Claims] A plurality of optical fibers penetrating a part of a base glass having a plurality of circuit conductor layers formed on a surface thereof in a thickness direction thereof, and a portion of the base glass at a position where the end face of the optical fiber is exposed. An optical print head in which a plurality of light emitting elements are arranged above, wherein a light absorbing layer is formed at an interface where the optical fiber and the base glass are in contact with each other. 2. The numerical aperture (NA) of the optical fiber, the width (W) of the optical fiber bundle, the refractive index (n1) of the core of the optical fiber, and the thickness (d) of the base glass are W /
^2. The optical print head according to claim 1, wherein d <[(n1 / NA) 2-1)]- ^0.5 .