JP2006106360A - Light source of image forming apparatus and end face processing method of light guide plate used for this light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source that facilitates optical alignment for an image forming apparatus, and also to provide an end face processing method that can suppress generation of damage such as cracks and chipping of a light guide plate when it is manufactured for the use of the light source. <P>SOLUTION: In the structure of the light source, there are mounted on a base material 11, a light guide plate 2 that converges light D emitted from a light emitting element 3 and that has a plurality of waveguide lines emitting the converged light D individually, and a lens array 12 that forms an image on a photoreceptor drum 40 with the light exited from the emitting face of the light guide plate 2. The base material 11 is equipped with a means for positioning the light emitting face 24 of the light guide plate 2, at a position corresponding to each focus on the base material 11 of the mounted lens array. In addition, the end face processing of the light guide plate 2 employs a method in which the light guide plate 2 is polished together with a substrate 25 for forming a light guide plate and a substrate 4 for holding the upper part in a state clamped between the substrate 25 for forming a light guide plate and the substrate 4 for holding the upper part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light source of an image forming apparatus and a method of processing an end face of a light guide plate used for the light source. The present invention relates to a light source of a forming apparatus and an end face processing method of a light guide plate used for the light source.

  In recent years, image forming apparatuses such as copiers, printers, facsimile machines, and multi-function machines have been required to have a function of printing high-resolution images in a short time.

  In order to print a high-resolution image, it is necessary that a light source for forming a latent image of the printed image on the photoconductor can be exposed at a narrow pitch in the main scanning direction. In order to perform printing in a short time, it is necessary to form a latent image on the photoconductor in a short time, that is, to sufficiently increase the amount of light applied to the photoconductor to shorten the exposure time. .

  As a typical light emitting element used for the light source, there is an LED (Light Emitting Diode). For example, when a light source of 2400 dpi is to be formed, the LEDs need to be formed at a pitch of about 10 μm, and at this time, the size of one element needs to be about 5 μm. In the formation of an LED having such a size, it is difficult to form a diffusion layer (pn junction) to be a light emitting portion, and even if it can be formed, the area of the light emitting portion is the same as the element area. Therefore, it was difficult to achieve both the arrangement of the light emitting elements at a narrow pitch and the shortening of the exposure time.

  Therefore, the applicant of the present application has proposed a light source 100 shown in a perspective view of FIG. 6 and a side view of FIG. As shown in FIGS. 6 and 7, the light source 100 has a core (light guide path) extending on a light guide plate forming substrate 205 in a direction perpendicular to the surface of the photoreceptor 400 (hereinafter referred to as a light transmission direction). 201 includes a plurality of light guide plates 200 arranged in a direction parallel to the surface of the photoreceptor 400 (hereinafter referred to as a main scanning direction), and has a light emitting surface that is long in the light transmission direction on the upper surface of each core 201. A light emitting element 300 is formed.

  The light D emitted from the light emitting element 300 repeats total reflection in the core 201 and is emitted from the emission surface 203 which is one end surface of the core 201 in the light transmission direction. In addition, the reflective material 204 is laminated | stacked on the other end surface of the optical transmission direction of the core 201, and the leakage of the light D is reduced.

  As described above, the light emitted from the core 201 forms an image on the surface of the photoreceptor 400 via the lens array 102 such as a GI (Graded Index) fiber lens or a rod lens. Therefore, the exit surfaces 203 of the plurality of cores 201 are made to have the same area as that required for one pixel of the latent image formed on the photoconductor 400 and arranged at the same pitch as the pitch between pixels. The light source 100 that is arranged at a narrow pitch in the main scanning direction and can emit a large amount of light can be realized. As shown in FIGS. 6 and 7, the light guide plate 200 and the lens array 102 are arranged such that the emission surface 203 of the core 201 is positioned at one focal point of the lens array 102 on the base material 101 made of, for example, aluminum. And is aligned so that the other focal point of the lens array 102 is the surface of the photoreceptor 400.

6 conceptually shows the light source 100 using the light guide plate 200 in which the cores 201 are simply arranged at a predetermined interval on the light guide plate forming substrate 205, but in reality, In order to facilitate the formation of the light emitting element 300 on the upper surface of each core 201, a cladding 202 (shown by a two-dot chain line in FIG. 6) having a lower refractive index than the core 201 is interposed between the cores 201. The optical plate 200 has a flat upper surface.
International Publication No. 2004/039595 Pamphlet

  As described above, the distance between the exit surface 203 of the light guide plate 200 and the entrance surface of the lens array 102 and the distance between the exit surface of the lens array 102 and the photoreceptor 400 form a good latent image. In order to achieve this, it is necessary to match the focal length F of the lens array 102. Further, as indicated by a one-dot chain line in FIG. 7, the optical axis L of the light D transmitted through the light guide plate 200 and the lens array 102 must also be incident on the surface of the photosensitive member 400 at a substantially vertical angle. The optical plate 200 and the lens array must be mounted on the substrate 101 in such an optically aligned state.

  The optical alignment needs to be performed with very high accuracy (for example, alignment accuracy of several μm) with a light source having a miniaturized structure in order to meet the demand for higher resolution of the image forming apparatus. Therefore, assembling the light source 100 is a very difficult task.

  On the other hand, the exit surface 203 of the light guide plate 200 is desirably a smooth surface in order to increase the incident efficiency of the light D to the light transmission means 102. In order to obtain such a smooth exit surface 203, FIG. End face processing (end face polishing) is performed as shown in a). That is, a polishing tool P such as a polishing plate or a polishing pad is disposed so as to be orthogonal to the light transmission direction with respect to the end surface on the emission surface 203 side of the light guide plate forming substrate 205 on which the light guide plate 200 is formed. The end face is polished and processed into a smooth surface by repeatedly moving in the vertical direction (or left and right direction, circular shape) while the tool P is in contact with the light guide plate forming substrate.

  However, since the light guide plate 200 is a thin film having a thickness of about 150 μm formed on the upper surface of the light guide plate forming substrate 205, the vibration or impact applied to the light guide plate 200 during polishing causes, for example, FIG. As shown by the arrow X in the plan view showing the light guide plate 200 after the end face processing, peeling occurs on the joint surface between the core 201 and the clad 202 or the joint surface between the light guide plate forming substrate 205 and the clad 202, As shown by an arrow Y in the plan view shown in FIG. 8B and the front view showing the light guide plate 200 after end face processing in FIG. 8C, there is a problem that cracks, chipping, etc. occur on the polished surface. there were. In FIGS. 8B and 8C, the chipping portion is shown in white.

  The light guide plate 200 may be manufactured by forming a large size on the light guide plate forming substrate 205 and then dividing it into a desired size using a technique such as scribing or dicing (cutting). However, even in this division, there is a problem that the same problem as polishing occurs due to impact and vibration.

  The present invention has been proposed based on the above-described conventional circumstances, and an object thereof is to provide a light source of an image forming apparatus capable of easily performing optical alignment. Another object of the present invention is to provide an end face processing method capable of suppressing the occurrence of damage such as cracking and chipping of the light guide plate when manufacturing the light guide plate used for the light source of the image forming apparatus.

  The present invention employs the following means in order to achieve the above object. That is, the light source of the image forming apparatus according to the present invention condenses the light emitted from the light emitting element provided on the upper surface, and includes a light guide plate having a plurality of light guide paths for individually emitting the collected light. And a lens array that forms an image of light emitted from the exit surface of the light guide on the photosensitive member. And the said base material is provided with the positioning means which positions the output surface of the said light-guide plate in the focus on the base material of the mounted lens array.

  For the positioning means, for example, a step formed at a position corresponding to the focal point on the base material of the lens array so that the mounting surface of the light guide plate is lower than the mounting surface of the lens array can be employed. At this time, the optical alignment between the lens array and the light guide plate is performed automatically by bringing the end surface on the light emitting plate forming substrate on which the light guide plate is formed into contact with the step, for example. Can be performed automatically. At this time, if the exit surface of the light guide plate and the end surface on the exit surface side of the light guide plate forming substrate are flush with each other, the step is formed at a position away from the entrance surface of the lens array by the focal length. In this case, the accuracy of the optical alignment depends on the position accuracy and shape accuracy of the step and the smoothness of the end surface of the light guide plate forming substrate. By performing the conversion with high accuracy, alignment can be performed easily and with high accuracy.

  On the other hand, for end surface processing in which the exit surface of the light guide plate and the end surface on the exit surface side of the light guide plate forming substrate are flush with each other, a support substrate (hereinafter referred to as an upper support substrate) that supports the light guide plate on the upper surface of the light guide plate. Is attached, and at least one light guide path end surface is polished together with the light guide plate forming substrate and the upper support substrate in a state where the light guide plate is sandwiched between the light guide plate forming substrate and the upper support substrate, A method of separating the upper support substrate from the light guide plate after polishing may be employed.

  According to this, in end face processing, it can control that a crack, chipping, etc. occur in a light guide plate, and can improve a yield rate. In addition, if the light guide plate is sandwiched between the light guide plate forming substrate and the upper support substrate, the light guide plate is divided by dicing, scribe (cutting), etc., and then the end face is polished. In this case, the occurrence of cracks and chipping in the light guide plate can also be suppressed.

  According to the present invention, when the light source is assembled, the exit surface of the light guide plate can be automatically aligned with the focal point on the substrate of the lens array, so that optical alignment becomes very easy.

  In addition, when the end face processing (end face polishing) of the light guide plate is performed, the light guide plate is sandwiched between the light guide plate forming substrate and the upper support substrate. The occurrence of damage such as cracks and chipping can be suppressed, and the yield rate can be significantly improved. Also, when the light guide plate is divided, the occurrence of damage such as cracking and chipping can be suppressed by sandwiching the light guide plate between the light guide plate forming substrate and the upper support substrate. The rate can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a light source 1 of the image forming apparatus of the present invention. FIG. 2 is a schematic cross-sectional view of the SS portion of FIG.

  As shown in FIG. 1, the light source 1 has a configuration in which a light guide plate 2 and a lens array 12 such as a GI fiber lens or a rod lens are mounted on a base material 11 in the same manner as the conventional light source 100 described above. .

  Further, as shown in FIG. 2, the light guide plate 2 has a structure in which a plurality of cores 21 are embedded in a plate-like clad 22 provided on a light guide plate forming substrate 25 at a predetermined pitch. A light emitting element 3 (electroluminescence element) using an organic or inorganic light emitting material is formed on the upper surface of 21.

  The light emitting element 3 includes a lower layer electrode 31 (individual transparent electrode), a light emitting layer 32, and an upper layer electrode 33 (common metal electrode). The light emitting layer 32 in a region sandwiched between the lower layer electrode 31 and the upper layer electrode 33 includes both electrodes. Light is emitted at a light emission intensity corresponding to the voltage (or current) applied between them.

  The light guide plate 2 only needs to be formed on the light guide plate forming substrate 25, and the formation method does not directly relate to the present invention, and any method can be used. For example, the light guide plate 2 can be formed by the following method.

  First, a liquid clad material made of thermosetting or UV (Ultra Violet) curable resin is applied on a light guide plate forming substrate 25 made of silicon, quartz or the like having a thickness of about 1 mm by spin coating or screen printing. After that, a plate-like clad 22 is formed by performing a curing process such as heating or UV light irradiation.

  Next, a liquid translucent core material made of UV curable resin is applied onto the clad 22. The core material is irradiated with UV light from above via a mask (a mask having an opening corresponding to the pattern of the core 21). At this time, since only the core material located in the opening of the mask is cured, the rectangular pattern of the core 21 shown in FIG. 2 is formed by washing and removing the uncured core material using an organic solvent or the like. .

  Subsequently, a liquid clad material is filled between the patterns of the core 21, and the core 21 is covered with the clad 22 by curing the clad material. Then, the light guide plate 2 including a plurality of cores 21 (light guide paths) shown in FIG. 2 is obtained by polishing the clad 22 from the upper surface and exposing the surface of the core 21.

  As another forming method, a groove corresponding to the core 21 is formed in the plate-like clad 22 formed as described above by a known fine processing technique such as photolithography and etching, and a liquid core material is formed in the groove. And a method of forming a clad 22 having a groove corresponding to the core 21 by a known molding technique using a mold or the like, filling the groove with a liquid core material, and curing the same. is there.

  As shown in FIG. 4, the light guide plate 2 formed as described above is divided by scribing, dicing (cutting) or the like so that the light transmission direction and / or the main scanning direction have a desired size. Thereafter, the light emitting element 3 is formed on the upper surface of each core 21.

  Such division may be performed after the light emitting element 3 is formed on the light guide plate 2 and further a protective film made of a polyimide film or the like is formed on the uppermost surface. In this embodiment, the light emitting element 3 is formed. The division is done before.

  In the step of forming the light emitting element 3, the lower layer electrode 31 and the light emitting layer 32 are formed in order of submicron thickness by vapor deposition, spin coating, or the like, and the upper layer electrode 33 is formed on the light emitting layer 32. As shown in FIG. 6, each layer may be formed individually on each core 21. However, in the example of FIG. 2, in order to facilitate the manufacturing process, each layer 21 is individually provided as a lower layer electrode 31. A transparent electrode is formed, and the light emitting layer 32 and the upper layer electrode 33 form a common layer (a single layer covering all the lower layer electrodes 31). Further, in the drawing, the light emitting layer 32 is shown as a single layer structure, but a multilayer structure including an electron transport layer, a hole transport layer, and the like may be used.

  The light guide plate 2 including the light emitting element 3 formed as described above can collect the light emitted from each light emitting element 3 by the corresponding core 21 and emit the light from one end surface of the core 21 in the light transmission direction. it can. A reflective material 24 is applied or vapor-deposited on the surface opposite to the light exit surface of each core 21 of the light guide plate 2.

  In the light source 1 of the present invention, the light guide plate 2 including the light emitting element 3 and the lens array 12 are mounted on the base material 11 using a known die bond material or the like. Although not described in detail because it is not directly related to the present invention, an arbitrary location on the substrate 11 includes a polysilicon TFT (Thin Film Transistor) for controlling the light emission of each light emitting element 3 or the like. A power supply control circuit is formed as necessary and connected to each light emitting element 3 by wire bonding or the like.

  As shown in FIG. 1, the base 11 used in the light source 1 of the present invention is mounted on the light guide plate 2 in order to position the exit surface 23 of the light guide plate 2 at the focal position on the base 11 of the lens array 12. The surface 11 a is provided with a step 13 (positioning means) dug down from the mounting surface 11 b of the lens array 12. The size of the step 13 may be such that the end face of the light guide plate forming substrate 25 can be positioned (for example, several hundred μm). However, the size of the step 13 and the focal point of the lens array 12 with respect to the mounting surface 11b are not limited. The height h2 (hereinafter referred to as the optical axis height h2) and the height h3 (hereinafter referred to as the optical axis height h3) of the core 21 with respect to the mounting surface 11a of the light guide plate 2 are h1 = h3−h2. The relational expression is satisfied. For example, when the thickness of the light guide plate forming substrate 25 is 1 mm, the thickness of the clad 22 is 150 μm, the thickness of the core 21 is 103 μm (corresponding to a resolution of 200 dpi), and the optical axis height h3 of the lens array 12 is 500 μm, The size of the step 13 is about 600 μm.

  In the example of FIG. 1, the step 13 is such that the distance from the end surface 14 of the substrate 11 on the photoconductor 400 side (hereinafter referred to as the emission-side end surface 14) is the length L of the lens array 12 in the light transmission direction. The lens array 12 is formed at a position that is a total distance (L + F) with the focal length F of the lens array 12, and is mounted in a state where the end face 26 of the light guide plate forming substrate 25 on the emission surface 23 side is in contact with the step 13. . Then, the lens array 12 is mounted by being aligned with respect to the emission side end face 14 of the base material 11, so that the emission surface 23 can be automatically arranged at the focal position of the lens array.

  In the above description, the case where the end face in the light transmission direction of the light guide plate forming substrate 25 and the light exit surface 23 of the light guide plate 2 are flush with each other is explained. However, the light exit surface 23 of the light guide plate 2 is used for light guide plate formation. When formed so as to be offset inward with respect to the end face of the substrate 25 in the light transmission direction, the step 13 has a distance from the emission side end face 14 of the base material 11 in the light transmission direction of the lens array 12. What is necessary is just to form in the position used as the distance which added the said offset distance to the total distance of length L and the focal distance F of the lens array 12. FIG.

  In the above description, the configuration in which the lens array 12 is aligned with the emission-side end surface 14 of the base material 11 has been described. However, as shown in FIG. In addition, the base 11 may be configured to include the second step 15 obtained by deepening the mounting surface 11b of the lens array 12. At this time, the height difference h4 between the mounting surface 11a of the light guide plate 2 and the mounting surface 11b of the lens array 12 is set to a size satisfying the relational expression h4 = h3-h2.

  Further, the positioning means is preferably formed integrally with the base material 11, but as shown in FIG. 3B, a separate plate material 16 may be arranged. In this case, in order to match the optical axis heights of the light guide plate 2 and the lens array 12, the thickness of the light guide plate forming substrate 25 of the light guide plate 2 may be adjusted. Further, as shown in FIG. 3C, the positioning means is not limited to a level difference (protrusion) continuous in the main scanning direction, and may be a protrusion 17 divided into a plurality in the main scanning direction.

  If it is set as the said structure, the optical alignment of the light source 1 can be performed automatically and an assembly will become very easy. In order to obtain higher alignment accuracy, the end face 26 of the light guide plate forming substrate 25 that is in contact with the step 13 is preferably extremely smooth, and the end face 26 and the exit face 23 are flush with each other. preferable.

  Therefore, an end face processing method suitable for forming such an end face 26 will be described below. FIG. 5 is a schematic diagram showing an end face processing method according to the present invention.

  As shown in FIG. 5A, in the end face processing method according to the present invention, first, a thickness of about 0.5 to 1 mm made of quartz, silicon or the like is formed on the upper surface of the light guide plate 2 formed as described above. The upper support substrate 4 is pasted by using an adhesive that can separate the upper support substrate 4 in a later process, such as a known high heat-resistant wax. At this time, if necessary, a lower support substrate made of the same material as that of the upper support substrate 4 may be attached to the lower surface of the light guide plate forming substrate 25. In the present embodiment, since the thickness of the light guide plate forming substrate 25 is about 1 mm, the lower support substrate is not attached, and the light guide plate forming substrate 25 is used as the lower support substrate.

  Next, in the state where the light guide plate 2 is sandwiched between the light guide plate forming substrate 25 and the upper support substrate 4 as described above, a surface perpendicular to the light transmission direction is formed with respect to the emission surface 23 of the light guide plate 2. Polishing is performed. That is, the polishing tool P such as a polishing plate and a polishing pad arranged so as to be a surface perpendicular to the light transmission direction is in contact with the light guide plate 2, the light guide plate forming substrate 25, and the upper support substrate 4. It is repeatedly moved up and down (or left and right, circular), and the light exit surface 23 of the light guide plate 2 is polished together with the light guide plate forming substrate 25 and the upper support substrate 4.

  At this time, if the polishing surface 10 to be polished is a surface cut by scribing or dicing (cutting) shown in FIG. 4 before polishing, the polishing amount should be an amount that eliminates the unevenness formed by the division. Therefore, the polishing time can be shortened (FIG. 5B). The division by scribing or dicing (cutting) is preferably performed in a state where the light guide plate 2 is sandwiched between the upper support substrate 4 and the light guide plate forming substrate 25 (lower support substrate). In FIG. 4, only the outline of the upper support substrate 4 is indicated by a broken line, and the upper support substrate is transmitted. Further, if necessary, the surface (surface on which the reflecting material 24 is laminated) facing the emission surface 23 of the light guide plate 2 is also polished (FIG. 5C).

  Then, after the polishing is completed (FIG. 5D), the upper support substrate 4 is separated from the upper surface of the light guide plate 2 by a heating process or a peeling process using a release agent (FIG. 5E). The light emitting element 3 is formed on the upper surface of the core 21 as described above.

  The light guide plate 2 subjected to the end face processing as described above can be divided together with both substrates with the upper surface attached to the upper support substrate 4 and the lower surface attached to the light guide plate forming substrate 25 (lower support substrate). Since polishing is performed, the occurrence of peeling of the core 21 and the clad 22, damage such as cracking and chipping is suppressed. For this reason, by adopting the end face processing method according to the present invention, the defect rate in the end face processing step of the light guide plate 2 can be significantly reduced.

  The light source of the image forming apparatus according to the present invention has an effect that optical alignment can be easily performed, and is useful as a light source that enables high-resolution printing. In addition, the end face processing method according to the present invention has the effect that the occurrence of defects in the end face processing step of the light guide plate used for the light source of the image forming apparatus can be remarkably reduced, and the light source to which this method is applied has a high resolution. It is useful as a light source that enables printing.

Sectional drawing of the light source of this invention. FIG. 2 is a cross-sectional view of a main part of an SS part in FIG. Sectional drawing of the modification of the light source of this invention. Explanatory drawing explaining division | segmentation of a light-guide plate. The schematic diagram which shows the end surface processing method of this invention. The perspective view which shows the conventional light source applied to the image forming apparatus. The schematic diagram which shows the manufacturing method of the conventional light source. The figure which shows the defect by the conventional end surface processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light guide plate 3 Light emitting element 4 Upper support substrate 11 Base material 12 Lens array 13 Level difference (positioning means)
21 Core 22 Cladding 23 Output surface 24 Reflector 25 Light guide plate forming substrate (lower support substrate)
DESCRIPTION OF SYMBOLS 31 Lower layer electrode 32 Light emitting layer 33 Upper layer electrode 100 Light source 101 Base material 102 Lens array 200 Light guide plate 201 Core 202 Clad 203 Output surface 205 Light guide plate formation substrate 300 Light emitting element 400 Photoconductor

Claims (6)

In a light source of an image forming apparatus including a light emitting element and a lens array that forms an image of light emitted from the light emitting element on a photoconductor,
The light-emitting element is provided on the upper surface, condenses the light emitted from the light-emitting element, and a light guide plate including a plurality of light guide paths for individually emitting the collected light to the lens array;
A substrate on which the light guide plate and the lens array are mounted;
Positioning means for positioning the exit surface of the light guide plate provided at a focal position on the substrate of the mounted lens array;
A light source for an image forming apparatus.   The light source of the image forming apparatus according to claim 1, wherein the positioning unit is a step where positioning is performed by bringing a surface corresponding to the emission surface into contact.   The light guide plate is formed on the light guide plate forming substrate so that one end surface of the light guide plate forming substrate and the light exit surface are flush with each other, and positioning is performed by bringing the one end surface into contact with the step. The light source of the image forming apparatus according to claim 2, which is performed. In the end face processing method of the light guide plate comprising a light guide path arranged in a plurality of horizontal directions,
Affixing a support substrate for supporting the light guide plate on the upper and lower surfaces of the light guide plate;
Polishing at least one end surface of the light guide path in the light transmission direction together with both support substrates in a state where the light guide plate is sandwiched between the support substrates;
An end face processing method for a light guide plate, comprising:   5. The method of processing an end face of a light guide plate according to claim 4, further comprising the step of dividing the light guide plate in a state where the light guide plate is sandwiched between the support substrates, and performing the polishing after the division. The end face processing of the light guide plate according to claim 4 or 5, wherein one of the support substrates is a light guide plate forming substrate on which the light guide plate is formed, and only the other support substrate is attached to the light guide plate. Method.

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