JP2007207956A - Light-emitting element array, optical printing head and device for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element array capable of equalizing the amount of a receiving light emitted from a light-emitting element and received by a lens array, even when lenses having the same size cannot be formed by the occupied region of the light-emitting element. <P>SOLUTION: Irradiation-region reducers 6a to 6d are formed so as to coat light emitters 4a to 4d for the light-emitting elements 5a to 5d fitted to a substrate 3 so as to be arranged at equal pitches L1. The irradiation-region reducing characteristics of the end-section irradiation-region reducer 6a fitted to the light emitter 4a arranged at an end are made higher than those of the intermediate-section irradiation-region reducers 6b to 6d fitted to the light emitters 4b to 4d disposed at an intermediate section excepting the end. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting element array, an optical print head, and an image forming apparatus.

  Light emitting element array formed by arranging a plurality of light emitting elements at equal intervals as a light emitting apparatus used as an optical print head which is one of exposure apparatuses in image forming apparatuses such as electrophotographic printers, facsimiles, and copiers Is used as a light source. The optical print head includes a light emitting element array and a lens array that irradiates the electrophotographic photosensitive member with light emitted from the light emitting element array, and electrostatically irradiates the charged electrophotographic photosensitive member with light. A latent image is formed.

  As a light emitting element array, for example, a light emitting element including a compound semiconductor layer made of gallium arsenide (GaAs) including a light emitting layer formed by epitaxial growth on a single crystal substrate is known. In an optical print head having such a light emitting element array, light emitted from the light emitting elements is divergent light, so that only a part of the emitted light can enter the rod lens. If the amount of light incident on the rod lens is small, the amount of light emitted from the optical print head cannot be made necessary, and the electrostatic latent image formed on the electrophotographic photosensitive member becomes unclear.

  Increasing the amount of light emitted from the optical print head can be achieved by increasing the current value flowing through the light emitting element and increasing the amount of light emitted from the light emitting element, but by increasing the current value flowing through the light emitting element, There arises a problem that an IC driver for driving the light emitting element and a drive circuit board on which the IC driver is mounted are increased in size. Further, increasing the value of the current flowing through the light emitting element causes a problem of shortening the lifetime of the light emitting element.

  In order to solve such a problem, there has been proposed a light emitting element array capable of increasing the amount of light emitted from the optical print head without increasing the value of a current flowing through the light emitting element (see, for example, Patent Documents 1 to 3). ). The light emitting element arrays disclosed in Patent Documents 1 to 3 include lenses provided in each light emitting part so as to cover each light emitting part of a plurality of light emitting elements arranged. According to such a light emitting element array, the amount of light incident on the lens array can be increased by condensing the light emitted from the light emitting elements with the lenses provided in the respective light emitting units. This makes it possible to obtain a sufficient amount of light for forming a clear electrostatic latent image on the electrophotographic photosensitive member.

JP 2005-159773 A JP 2005-175417 A JP-A-2005-212157

  For example, 64, 128, or 256 light emitting elements are formed in one light emitting element array. When the optical print head is constituted by a 600 dpi (dot per inch) specification light emitting element array having 128 light emitting elements in one light emitting element array, 40 light emitting element arrays in A4 size, and 60 light emitting elements in A3 size. A light emitting element array is required.

  The light emitting element array is formed by cutting a single crystal wafer on which a plurality of light emitting elements are formed in a process called dicing. FIG. 3 is a diagram for explaining the present invention. However, referring to FIG. 3, the light emitting elements 5 a to 5 d are arranged at an equal pitch L <b> 1 and arranged at the end of the light emitting element array 1. The distance L2 between the light emitting element 5a and the cut surface 18 is smaller than L1 / 2. This is to prevent the pitch between the light emitting elements 5a and 17a arranged at the ends of the adjacent light emitting element arrays 1 and 17 from becoming larger than L1 due to an error caused by cutting.

  When the distance L2 between the light emitting element 5a arranged at the end of the light emitting element array 1 and the cut surface 18 becomes smaller than L1 / 2, the light emitting part 4a of the light emitting element 5a arranged at the end is changed. In some cases, a covering lens cannot be formed. In such a case, the amount of light received from the light emitting element 5a disposed at the end and received by the lens array is emitted from the light emitting elements 5b to 5d disposed at the intermediate portion excluding the end, There is a problem that the amount of light received by the lens array is smaller than the amount of light received. Patent Documents 1 to 3 do not disclose how to form a lens that collects light from the light emitting element 5a at the end.

  An object of the present invention is to emit light that can equalize the amount of light received from a light emitting element and received by a lens array even when a lens of the same size cannot be formed due to the area occupied by the light emitting element. An element array and an optical printhead including the element array are provided.

The light emitting element array of the present invention includes a substrate,
A plurality of light emitting elements provided on the substrate so that each of the light emitting parts is arranged between two points spaced apart from each other;
Among the light emitting elements, the light emitting part of the light emitting element disposed at the end is provided so as to cover, and the irradiation area on a predetermined virtual plane of light emitted from the light emitting element disposed at the end is reduced. A light emitting element disposed to cover the light emitting part of the light emitting element disposed in the intermediate part excluding the end part, and disposed in the intermediate part excluding the end part. An irradiation area reduction means including an intermediate irradiation area reduction unit for reducing the irradiation area on the predetermined virtual plane of light emitted from the edge irradiation area reduction unit, The area is smaller than the area of the area occupied by the intermediate irradiation area reduction part with respect to the substrate, and the irradiation area reduction characteristic of the edge irradiation area reduction part is more than the irradiation area reduction characteristic of the intermediate irradiation area reduction part. High, characterized in that it comprises a configured irradiation region reduction means.

Further, in the light emitting element array of the present invention, the irradiation region reducing means is
By using materials having different refractive indexes for the edge irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the edge irradiation region reduction unit is obtained by using the intermediate part irradiation region reduction unit. It is characterized by higher than the irradiation area reduction characteristics of

Further, in the light emitting element array of the present invention, the irradiation region reducing means is
By varying the height of protrusion from the substrate between the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the end irradiation region reduction unit is set to the intermediate part irradiation. It is characterized by higher than the irradiation area reduction characteristic of the area reduction part.

Further, in the light emitting element array of the present invention, the irradiation region reducing means is
By changing the shape of the exit surface between the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the end irradiation region reduction unit is changed to the intermediate irradiation region reduction unit. It is characterized by higher than the irradiation area reduction characteristics of

The optical print head of the present invention comprises a plurality of the light emitting element arrays of the present invention,
Including a lens array for irradiating the electrophotographic photosensitive member with light emitted from the light emitting element array,
The plurality of light emitting element arrays are arranged along an arrangement direction of the light emitting elements.

The image forming apparatus of the present invention includes the optical print head of the present invention,
Transfer means for transferring an image formed by a developer on the electrophotographic photoreceptor to a recording sheet;
And fixing means for fixing the developer transferred to the recording sheet.

  According to the present invention, the light emitting element array includes a substrate and a light emitting part, and the light emitting elements provided on the substrate so that the light emitting parts are arranged side by side between two points spaced from each other. And an irradiation area reduction means including an edge irradiation area reduction part and an intermediate irradiation area reduction part provided in each light emission part so as to cover the light emission part of the light emitting element, and provided in the light emission part arranged at the edge part The irradiation area reduction characteristic of the edge irradiation area reduction part is enhanced as compared with the intermediate irradiation area reduction part provided in the light emitting part arranged in the intermediate part excluding the edge part. The irradiation area reduction characteristic is a characteristic that can reduce the area of the irradiation surface irradiated with the emitted light when the light incident on the irradiation area reduction part is emitted from the irradiation area reduction part. When the irradiation region reduction characteristic of the irradiation region reduction unit is increased, when the light incident on the irradiation region reduction unit is emitted from the irradiation region reduction unit, the area of the irradiation surface irradiated with the emitted light can be reduced. .

  The distance between the light emitting element disposed at the end of the light emitting element array and the cut surface of the substrate of the light emitting element array is shorter than half the distance between the light emitting elements, and the distance between the light emitting element array and the substrate at the reduced area of the end irradiation region is reduced. The area of the occupied region is smaller than the area of the occupied region with respect to the substrate of the intermediate irradiation region reduced portion. In such a case, if an irradiation area reduction section having the same irradiation area reduction characteristics is used as the edge irradiation area reduction section and the intermediate irradiation area reduction section, the intermediate irradiation area reduction of the end irradiation area reduction section is achieved. The irradiation area of the light incident on the portion of the occupied area smaller than the area cannot be reduced, and the received light quantity of the light emitted from the light emitting element at the end and received by the lens array is the light emission of the intermediate section. The amount of light received from the element and received by the lens array is smaller than the amount of light received.

  Therefore, by providing an irradiation area reduction means for improving the irradiation area reduction characteristic of the edge irradiation area reduction part in advance as compared with the irradiation area reduction characteristic of the intermediate irradiation area reduction part, the edge irradiation area reduction part with respect to the substrate is provided. Even when the area of the occupied region is smaller than the area of the occupied region with respect to the substrate of the intermediate irradiation region reduction unit, the amount of light received from the light emitting element and received by the lens array Uniformity can be achieved between the light emitting element and the intermediate light emitting element.

  Further, according to the present invention, by using materials having different refractive indexes in the end irradiation region reduction portion and the intermediate portion irradiation region reduction portion, the irradiation region reduction characteristics of the end irradiation region reduction portion are: This is higher than the irradiation area reduction characteristic of the intermediate irradiation area reduction part. By changing the refractive index of the material used for the edge irradiation area reduction part and the intermediate part irradiation area reduction part, the emission position of the emitted light at the interface between the edge irradiation area reduction part and air, and the intermediate part irradiation The emission position at the interface between the area reduction part and the air can be made different, and the irradiation area reduction characteristics of the end part irradiation area reduction part and the intermediate part irradiation area reduction part can be made different.

For example, by selecting a material higher than the refractive index of the material used for the intermediate irradiation region reduction unit as the material used for the edge irradiation region reduction unit, the emission light at the interface between the edge irradiation region reduction unit and air is selected. The emission position can be closer to the optical axis of the emitted light from the light emitting element than the emission position at the interface between the intermediate irradiation area reduction part and the air. Further, it is possible to improve the irradiation area reduction characteristic in the intermediate area irradiation area reduction part. Thus, the lens array having a surface for receiving light from the light emitting element, and the amount of light received by the lens array having the light receiving surface having a constant area is more reduced than the light emitted from the intermediate light emitting element. It is possible to increase the light emitted from the light emitting elements. In this way, it is possible to improve the irradiation area reduction characteristic of the edge irradiation area reduction part where the area of the occupied area with respect to the substrate is small, and the received light quantity of the light received by the lens array is intermediate between the light emitting element at the edge and It is possible to make uniform between the light emitting elements.

  Further, according to the present invention, the end irradiation region reduction unit and the intermediate irradiation region reduction unit have different projection heights from the substrate, thereby reducing the irradiation region of the end irradiation region reduction unit. The characteristic is enhanced more than the irradiation area reduction characteristic of the intermediate irradiation area reduction part. By making the protrusion height from the substrate different between the edge irradiation area reduction part and the intermediate part irradiation area reduction part, the distance between the interface between each irradiation area reduction part and air and the lens array can be made different. And a lens array provided corresponding to each light emitting element and each light emitting element with respect to the air that increases the divergence angle of the light emitted from the light emitting element. It is possible to make the direction of the arrangement different.

  For example, by making the protrusion height from the substrate of the edge irradiation region reduction portion larger than the protrusion height from the substrate of the intermediate irradiation region reduction portion, the position of the interface between the edge irradiation region reduction portion and the air, The position can be closer to the lens array than the position of the interface between the intermediate irradiation region reduced portion and air. As a result, the irradiation area reduction characteristic of the edge irradiation area reduction part with a small area occupied by the substrate can be improved, and the amount of light received by the lens array can be changed between the light emitting element at the edge and the intermediate part. It can be made uniform between the light emitting elements.

  Further, according to the present invention, by changing the shape of the exit surface in the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristics of the end irradiation region reduction unit, This is higher than the irradiation area reduction characteristic of the intermediate irradiation area reduction part. By making the shape of the exit surface different between the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the incident angle of light incident on the air from the end irradiation region reduction unit and the intermediate irradiation region reduction unit The incident angle of the light incident on the air can be made different, and the exit angle from the end irradiation region reduction unit can be made different from the emission angle from the intermediate irradiation region reduction unit. it can.

  Here, when the emission surface of the irradiation region reduction portion is formed to be convex toward the lens array side, the light emitted from the light emitting element and transmitted through the irradiation region reduction portion can be collected. For example, the area of the occupying area with respect to the substrate is reduced by changing the shape of the exit surface of each irradiation area reduction section so that the end irradiation area reduction section has higher light collection characteristics than the intermediate irradiation area reduction section. The irradiation area reduction characteristic of the edge irradiation area reduction part can be improved, and the amount of light received by the lens array can be made uniform between the light emitting element at the end and the light emitting element at the intermediate part. it can. The condensing characteristic is a characteristic capable of condensing the light incident on the irradiation region reduced portion. When having the condensing characteristic, the divergence angle of the light beam emitted from the irradiation region reduction unit can be made smaller than the divergence angle of the light beam incident on the irradiation region reduction unit. The divergence angle of the light beam emitted from the reduction unit can be made smaller than the divergence angle of the light beam incident on the irradiation region reduction unit.

  According to the invention, the optical print head includes a plurality of light emitting element arrays that achieve the above effect, and a lens array that irradiates the electrophotographic photosensitive member with light emitted from the light emitting element array. Such an optical print head includes a light emitting element array in which the amount of received light emitted from the light emitting element and received by the lens array is made uniform regardless of where the light emitting element is disposed. It is possible to prevent unevenness in the amount of light irradiated to the electrophotographic photosensitive member.

  According to the invention, the image forming apparatus includes an optical print head that achieves the effect, a developer supply unit that supplies a developer to the electrophotographic photosensitive member irradiated with light from the optical print head, and an electronic The image forming apparatus includes a transfer unit that transfers an image formed on the photographic photosensitive member with a developer onto a recording sheet, and a fixing unit that fixes the developer transferred onto the recording sheet. In such an image forming apparatus, since unevenness in the amount of light irradiated to the electrophotographic photosensitive member is prevented, the amount of light irradiated to the electrophotographic photosensitive member is small compared to other portions. It is possible to prevent the occurrence of white streaks that occur in parts and black streaks that occur in parts where the amount of light irradiated to the electrophotographic photosensitive member is larger than other parts, and a good image without image defects can be obtained. Can be formed.

  FIG. 1 is a partial cross-sectional view showing a configuration of an optical print head 2 including a light emitting element array 1 according to a first embodiment of the present invention. The light-emitting element array 1 of the present embodiment includes a substrate 3 and a plurality of light-emitting elements 5a, 5b, 5c, 5d,... (Hereinafter referred to as light-emitting elements 5 except when specific light-emitting elements are shown), And an irradiation area reduction means 6.

  The light-emitting element 5 includes light-emitting portions 4a, 4b, 4c, 4d,... (Hereinafter referred to as the light-emitting portion 4 except when a specific light-emitting portion is shown), and the light-emitting portions 4 are spaced from each other. It is provided on the substrate 3 so as to be arranged side by side between the two opened points. Of the light emitting elements 5, the light emitting element 5 a disposed at the end of the substrate 3 is hereinafter referred to as an end light emitting element 5 a. In addition, among the light emitting elements 5, the light emitting elements 5b, 5c, 5d,... Disposed in the intermediate portion excluding the end portion of the substrate 3 may be hereinafter referred to as the intermediate light emitting element 5b. The light emitting part 4a of the end light emitting element 5a is hereinafter referred to as an end light emitting part 4a, and the light emitting parts 4b, 4c, 4d,... Of the intermediate light emitting elements 5b, 5c, 5d,. It may be described as 4b.

The irradiation area reduction means 6 is provided so as to cover the light emitting part 4a of the light emitting element 5a disposed at the end, and irradiation on a predetermined virtual plane of light emitted from the light emitting element 5a disposed at the end. Are provided so as to cover the edge irradiation area reduction part 6a for reducing the area and the light emitting parts 4b, 4c, 4d,... Of the light emitting elements 5b, 5c, 5d,. Intermediate portion irradiation region reduction units 6b, 6c, 6d,... That reduce the irradiation region on the predetermined virtual plane of light emitted from the light emitting elements 5b, 5c, 5d,. Including. The predetermined virtual plane is a substrate 3 to be described later.
This surface is parallel to the element array surface 3a. In the present embodiment, the predetermined virtual plane is an end face facing the light emitting element 5 of the lens array 7 to be described later.

Further, the irradiation region reducing means 6 has an area occupied by the edge irradiation region reduction unit 6a with respect to the substrate 3 smaller than an area of the region occupied by the intermediate irradiation region reduction units 6b, 6c, 6d. The irradiation region reduction characteristics of the end irradiation region reduction unit 6a are configured to be higher than the irradiation region reduction characteristics of the intermediate irradiation region reduction units 6b, 6c, 6d.

  Hereinafter, the intermediate portion irradiation region reduction portions 6b, 6c, 6d,... Are referred to as an intermediate portion irradiation region reduction portion 6b except when a specific intermediate portion irradiation region reduction portion is indicated.

  Further, in the present embodiment, the irradiation area reduction means 6 is the light transmission layer 6, and the end light transmission part 6a that is the end irradiation area reduction part 6a and the end light that is the intermediate part irradiation area reduction part 6b. By making the protrusion height from the substrate 3 different from that of the transmission part 6b, the irradiation area reduction characteristic of the end light transmission part 6a can be enhanced more than the irradiation area reduction characteristic of the intermediate light transmission part 6b. And

  Although only one optical print head 2 of the present embodiment is shown in FIG. 1, the optical print head 2 includes a plurality of light emitting element arrays 1 and a plurality of lens arrays 7. The optical print head 2 is used, for example, as means for exposing an electrophotographic photosensitive member provided in an image forming apparatus such as a printer, a facsimile, and a copier using an electrophotographic system.

  FIG. 2 is a perspective view of the optical print head 2 used as exposure means. The optical print head 2 has a plurality of light emitting element arrays 1 arranged at equal intervals along the direction in which the light emitting elements 5 are arranged in the light emitting element array 1 (hereinafter referred to as the light emitting element arrangement direction). Is provided on one surface 8a. The light emitting element array 1 is provided so that one surface 8a of the drive circuit board 8 faces the electrophotographic photosensitive member 9, and the light emitting element array 1 is interposed between the plurality of light emitting element arrays 1 and the electrophotographic photosensitive member 9. A lens array 7 is provided to irradiate the electrophotographic photosensitive member 9 with light emitted from the lens. The drive circuit board 8 and the lens array 7 on which the plurality of light emitting element arrays 1 are provided are fixedly supported by the housing.

  The substrate 3 on which the plurality of light emitting elements 5 are arranged is a semiconductor substrate such as gallium arsenide (GaAs) or silicon (Si). When a semiconductor substrate made of Si is used as the substrate 3, for example, an ingot of single crystal Si is formed by a CZ method (Czochralski method) for pulling up a single crystal from a melt of a molten semiconductor material, and this is formed into 250 to 350 μm. After slicing to the thickness dimension, a single crystal wafer is obtained by polishing the sliced surface.

  On the substrate 3, a plurality of light emitting elements 5 are arranged in a straight line at regular intervals in the main scanning direction of the optical print head 2. The optical print head 2 of the present embodiment has a resolution of 600 dpi (dot per inch), and is a distance between the center of the light emitting element 5 in the light emitting element arrangement direction and the center of the light emitting element 5 adjacent to the light emitting element 5. A plurality of light-emitting elements 5 are arranged on the element array surface 3a, which is one surface of the substrate 3, with a distance from each other so that the pitch L1 is 42.3 μm.

  As described above, a plurality of light emitting elements 5 are formed on one surface of a single crystal wafer obtained by, for example, the CZ method and polished after slicing. The light emitting element array 1 is formed by cutting a single crystal wafer on which a plurality of light emitting elements 5 are formed in a process called dicing.

The light-emitting element 5 is formed on one surface of a single crystal wafer by metal organic vapor phase epitaxy (Metal Organic).
A compound semiconductor layer such as GaAs formed by epitaxial growth using a method such as Chemical Vapor Deposition (abbreviation: MOCVD method) and an electrode layer ohmic-bonded to the compound semiconductor layer are provided. In addition, a protective film made of an inorganic material or an organic material is formed on the compound semiconductor layer constituting the light emitting element 5. In the present embodiment, the light-emitting element 5 is formed of GaAs so that the shape when viewed from the thickness direction of the substrate 3 is formed in a rectangular shape, and the width W in the light-emitting element arrangement direction is 0.57 × L1 or less. The light emitting element 5 including the compound semiconductor layer is formed.

  Such a light emitting element 5 is a light emitting diode (LED) or a light emitting thyristor in which a compound semiconductor layer is formed by sequentially laminating an n type semiconductor layer and a p type semiconductor layer, for example. When power is applied to the light emitting element 5 through an electrode pattern formed on the substrate 3, holes are injected into the n-type semiconductor layer and electrons are injected into the p-type semiconductor layer. The light-emitting element 5 recombines holes in the n-type semiconductor layer and electrons in the p-type semiconductor layer near the pn junction between the n-type semiconductor layer and the p-type semiconductor layer, and converts the energy generated by the coupling into light. For example, the light is emitted at a wavelength of 850 nm.

  The light-emitting element 5 is a surface-emitting light-emitting element that emits light in a direction perpendicular to the element array surface 3 a that is a surface on which the light-emitting elements 5 of the substrate 3 are arrayed, and light is emitted from the light-emitting element 5. It has the light emission part 4 which is a part. In the present embodiment, the area of the surface of the light emitting unit 4 parallel to the substrate array surface 3a of the substrate 3 is the same as the area of the surface of the light emitting element 5 parallel to the substrate array surface 3a. The width of the light emitting unit 4 in the light emitting element arrangement direction is equal to the width of the light emitting element 5.

  The substrate 3 on which the light emitting elements 5 are arranged is mounted on a driving circuit substrate 8 such as a glass substrate on which an IC driver 10 that controls driving of the light emitting elements 5 is mounted. The light emitting element 5 is electrically connected to the IC driver 10 through an electrode pattern formed on the substrate 3. The electrode pattern is connected to the circuit pattern of the IC driver 10 by a bonding wire. For example, the drive circuit board 8 of the optical print head 2 corresponding to the A3 size has the light emitting element array 1 of the present embodiment configured according to the specification of 600 dpi having 128 light emitting elements in one light emitting element array. Are arranged.

  The lens array 7 is an optical system in which a large number of rod lenses, which are rod-shaped or cylindrical lenses, are arranged in parallel, and an erecting equal-magnification image by each lens is superimposed to form one continuous image as a whole. As the rod lens, for example, a refractive index distribution lens such as a SELFOC lens (trade name) having a cylindrical shape and a refractive index distribution in which the refractive index continuously decreases from the central axis of the cylinder toward the outer periphery. (Grin lens; GRIN; Gradient Index) can be used. The lens array 7 is not limited to an array in which rod-shaped or cylindrical rod lenses are used, and may be an array in which, for example, a roof-shaped roof mirror lens is used.

  The lens array 7 includes a rod lens group in which light emitted from one light emitting element 5 includes one rod lens 11 or a plurality of rod lenses 11 corresponding to each light emitting element 5 (hereinafter, the rod lens group is also referred to as the rod lens 11). It is arrange | positioned so that it may irradiate. The rod lens 11 receives light from the corresponding light emitting element 5, emits light from the surface opposite to the light receiving side, and forms an image of the light from the light emitting element 5 on the electrophotographic photosensitive member 9. Thereafter, the rod lens that receives light from the specific light emitting elements 5a, 5b, 5c, 5d,... And irradiates the electrophotographic photosensitive member 9 with the light received from the specific light emitting elements 5a, 5b, 5c, 5d,. 11 are referred to as corresponding rod lenses 11a, 11b, 11c, 11d,. The distance H0 between the rod lens 11 and the light emitting element 5 is determined by the viewing angle (or opening angle), the aperture, and the like of the rod lens 11.

  Since the rod lens 11 cannot be used for light emitted from the light emitting element 5 and incident at an incident angle larger than the half angle of the viewing angle of the rod lens 11, other than the corresponding light emitting element 5. Even if the light emitted from the light emitting element 5 is irradiated, the light is not used for irradiation to the electrophotographic photosensitive member 9. Of the light emitted from the light emitting element 5, light that does not enter the corresponding rod lens 11 is flare light. The gap between the rod lenses 11 is filled with an opaque material to prevent flare light from leaking from the gap between the rod lenses 11 and irradiating the electrophotographic photosensitive member 9.

  However, such flare light is likely to be incident on a rod lens 11 different from the corresponding rod lens 11 at an incident angle smaller than a half angle of the viewing angle of the rod lens 11 due to reflection of the flare light. It is preferable that generation is suppressed. In the present embodiment, among the light emitted from the light emitting element 5, the light emitted from each light emitting unit 4 so that more light can enter the rod lens 11 corresponding to the light emitting element 5. Are formed. The light transmissive layer 6 is formed to include the end irradiation region reduction unit 6a and the intermediate irradiation region reduction units 6b, 6c, 6d,.

  The light transmission layer 6 of the present embodiment is provided so as to cover the end light emitting portion 4a of the end light emitting element 5a, and the end light transmitting portion that reduces the irradiation area of the light emitted from the end light emitting element 5a. 6a and an intermediate light transmitting portion 6b that is provided so as to cover the intermediate light emitting portion 4b of the intermediate light emitting element 5b and that reduces the irradiation area of the light emitted from the intermediate light emitting device 5b. The end light transmission part 6a is configured to have a higher irradiation area reduction characteristic than the intermediate light transmission parts 6b, 6c, 6d. Hereinafter, the end light transmissive part 6a and the intermediate light transmissive parts 6b, 6c, 6d,... May be collectively referred to as irradiation region reduced parts 6a, 6b, 6c, 6d,.

  The irradiation area reduction units 6a, 6b, 6c, 6d,... Are divided according to the area occupied by the light emitting unit 4 with respect to the substrate 3, and light that reduces the irradiation area of the light from the light emitting unit 4 existing in the occupied area. Transmission parts 6a, 6b, 6c, 6d,. In the present embodiment, a plurality of light transmitting portions 6a, 6b, 6c, 6d,... Provided in the light emitting portions 4a, 4b, 4c, 4d,.

  The occupied area of the light emitting unit 4 is determined as follows. First, the virtual plane 12 perpendicular to the light emitting element array direction and the plurality of virtual planes 12 having the same distance from the center in the light emitting element array direction of the light emitting portions 4 of the two adjacent light emitting elements 5 are arranged on the substrate 3. The surface 3a is cut to define a plurality of divided surfaces 13a, 13b, 13c, 13d,... (Hereinafter referred to as a divided surface 13 unless a specific divided surface is shown). . Here, by describing the alphabetical suffix added to the reference numerals of the light emitting units 4 arranged on the dividing surface 13, which light emitting unit 4 occupies the divided surface 13. Indicates. A region including the dividing surface 13 to which the same subscript as that of the light emitting unit 4 is added and divided by two adjacent virtual planes 12 is referred to as an occupied region of the light emitting unit 4. The occupied area of the light emitting unit 4 may be described as the occupied area of the light emitting element 5. In addition, an alphabetic suffix added to the reference symbol of the light emitting unit 4 may be described together, and may be described as an occupied area of the light transmitting unit 6 with respect to the substrate 3.

  In the light transmissive layer 6 of the present embodiment, the first light transmissive layer 14 and the second light transmissive layer 15 having different refractive indexes are laminated on the element arrangement surface 3a of the substrate 3 on which the light emitting element 5 is formed in this order. Further, the third light transmission layer 16 is formed in the end light transmission part 6a which is the end irradiation region reduction part 6a provided in the end light emitting part 4a disposed at the end. The light transmission layer 6 of the present embodiment is formed in a rectangular shape when viewed from the thickness direction of the substrate 3. Further, in the present embodiment, the first to third lights are set so that the thickness of the first light transmission layer 14 is t1, the thickness of the second light transmission layer 15 is t2, and the thickness of the third light transmission layer 16 is t3. Transmission layers 14, 15, and 16 are formed.

  The light transmissive layer 6 of the present embodiment has the first to third light beams so that the refractive index of the layer on the side away from the light emitting element 5 is higher than the refractive index of the layer on the side close to the light emitting element 5. The transmissive layers 14, 15, and 16 are laminated. In the present embodiment, when the refractive index of the first light transmission layer 14 is n1, the refractive index of the second light transmission layer 15 is n2, and the refractive index of the third light transmission layer 16 is n3, n1 <n2 <n3. It becomes.

  The first to third light transmission layers 14, 15, 16 constituting the light transmission layer 6 have a refractive index lower than the refractive index of the light emitting element 5, and have a refractive index higher than the refractive index of air, It consists of the material which has translucency. Examples of the material used for the first to third light transmission layers 14, 15, and 16 include a resin having translucency.

  The resin having translucency is not particularly limited as long as it has translucency in a wavelength region of light emitted from the light emitting element 5, for example, 400 nm to 1000 nm, and in this embodiment, 850 nm. Examples of the light-transmitting resin include tetrafluoroethylene resin (PTFE; polytetrafluoroethylene), methyl methacrylate resin (PMMA), benzocyclobutene resin (BCB), polystyrene (PS), and polycarbonate (PC). , And polyimide (PI). The refractive indexes of these resins are as follows: PTFE is 1.36, PMMA is 1.49, BCB is 1.50, and PS is PS when light having a wavelength of 770 nm is incident at room temperature (24 ° C.). 1.59, PC is 1.59, and PI is 1.78. The refractive index of the light emitting element 5 measured under the same conditions is, for example, about 3.60 to 3.70 when the compound semiconductor layer of the light emitting element 5 is made of GaAs. The refractive index of air measured under the same conditions is 1.00.

  The light transmissive layer 6 is selected from, for example, three kinds of materials as the first to third light transmissive layers 14, 15, and 16, and sequentially laminated on the light emitting portion 4 of the light emitting element 5 from a material having a low refractive index. To be formed. The light transmissive layer 6 is formed, for example, by sequentially laminating the first to third light transmissive layers 14, 15, and 16 by a light transmissive layer forming method including the following coating process and solvent removing process.

  In the coating step, for example, a coating solution prepared by dissolving a resin constituting each layer in a solvent such as an organic solvent that can be dissolved is applied by a method such as spin coating to form a coating solution layer. In the solvent removal step, for example, the formed coating solution layer is heated in a curing furnace or the like to evaporate and remove the solvent in the coating solution layer, thereby forming a light transmission layer. Here, the third light transmission layer 16 is formed only in a necessary portion by masking other than the portion to be formed. After the third light transmission layer 16 is formed on the entire surface of the second light transmission layer 15 on the side opposite to the substrate 3, the third light transmission layer 16 formed in an unnecessary portion is removed by photoetching or the like. Also good. The third light transmission layer 16 may be formed by a method such as potting in which a coating liquid used in the spin coating method is ejected by an ink jet ejection means or the like.

  The first to third light transmission layers 14, 15, and 16 are formed by using a film forming technique such as sputtering, CVD (Chemical Vapor Deposition), or vacuum deposition, using a thin film made of oxide or nitride. Also good.

  In the present embodiment, each of the first light transmission layer 14 and the second light transmission layer 15 is formed so as to overlap with each other and has a simple shape having a rectangular shape as described above. Positioning of the first light transmission layer 14 and the second light transmission layer 15 with respect to the light emitting portion 4 is not necessary, and fine processing such as photolithography is not required, and the film can be formed by a simple method only of film formation. Since it can do, manufacture of the light emitting element array 1 becomes easy. Further, since the first light transmission layer 14 and the second light transmission layer 15 have a simple shape like a laminated film, the irradiation region reduction portions 6b, 6c, 6d provided in the intermediate light emitting portions 4b, 4c, 4d,. ,..., Uniform optical characteristics can be obtained.

  FIG. 3 is a partial cross-sectional view of the optical print head 2 showing the arrangement of the light emitting elements 5 and the light emitting element array 1. An end light emitting element 5 a disposed at the end of the light emitting element array 1, and a light emitting element 17 a disposed at an end on the light emitting element array 1 side of another light emitting element array 17 adjacent to the light emitting element array 1, The plurality of light emitting element arrays 1 and 17 are arranged on one surface of the drive circuit board 8 so that the distance between them is equal to the pitch L1.

  As described above, the light emitting element array 1 includes the substrate 3 obtained by cutting a single crystal wafer on which the plurality of light emitting elements 5 are formed in a process called dicing. Here, in the dicing process, the pitch between the end light emitting elements 5a and 17a arranged at the end portions of the adjacent light emitting element arrays 1 and 17 is prevented from being larger than the pitch L1 due to an error caused by cutting. Therefore, the single crystal wafer is cut so that the distance L2 between the end light emitting element 5a and the cut surface 18 is smaller than L1 / 2. Thereby, the area of the area occupied by the substrate 3 of the end light emitting section 4a is smaller than the area of the area occupied by the substrate 3 of the light emitting section 4b arranged at the intermediate portion excluding the end.

  Here, a case where the third light transmission layer 16 formed in this embodiment is not provided will be described. If the area of the area occupied by the substrate of the end light emitting section is smaller than the area of the area occupied by the substrate of the intermediate light emitting section, the area of the area occupied by the substrate 3 of the end light transmitting section provided in the end light emitting section is reduced. The light amount of the light that is smaller than the area of the area occupied by the intermediate light transmitting portion provided in the intermediate light emitting portion with respect to the substrate 3 and is incident on the corresponding rod lens through the end light transmitting portion is intermediate light. It becomes smaller than the light quantity of the light which permeate | transmits a permeation | transmission part and injects into a corresponding rod lens.

  When the light amount of the light passing through the end light transmitting portion and entering the corresponding rod lens is smaller than the light amount passing through the intermediate light transmitting portion and entering the corresponding rod lens, the end light transmitting portion The amount of light irradiated to the electrophotographic photosensitive member from the rod lens corresponding to is smaller than the amount of light irradiated to the electrophotographic photosensitive member from the rod lens corresponding to the intermediate light transmitting portion. Causes unevenness. When an optical print head that generates unevenness in the amount of irradiation light is used as a means for exposing an electrophotographic photosensitive member used in an image forming apparatus, image defects such as white streaks occur in the formed image.

  In the present embodiment, the end light transmitting portion 6a provided in the end light emitting portion 4a whose area occupied by the substrate 3 is smaller than that of the intermediate light emitting portion 4b which is the other light emitting portion 4 is the third light transmitting portion. It is configured including the layer 16. By forming the third light transmitting layer 16 in the end light transmitting portion 6a, the protruding height H1 of the end light transmitting portion 6a from the substrate 3 is set to the protruding height of the intermediate light transmitting portion 6b from the substrate 3. It can be larger than the height H2. In this way, by changing the protruding height from the substrate 3 between the end light transmitting portion 6a and the intermediate light transmitting portion 6b, the irradiation area reduction characteristic of the end light transmitting portion 6a is changed to the intermediate light transmitting portion. This can be higher than the irradiation area reduction characteristic of 6b. Hereinafter, with reference to the drawings, the projection height H1 of the end light transmission portion 6a is formed to be larger than the projection height H2 of the intermediate light transmission portion 6b, thereby reducing the irradiation region reduction characteristic of the end light transmission portion 6a. The reason why can be improved more than the irradiation region reduction characteristic of the intermediate light transmitting portion 6b will be described.

  FIG. 4 is a diagram illustrating an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. The light emitted from the light emitting element 5 becomes divergent light because the refractive index of GaAs is higher than the refractive index of air and the refractive index of a material such as a resin constituting the light transmission layer 6. In FIG. 4, the light paths of some components of the divergent light are indicated by arrows. In the drawing showing the optical path of the light incident on the lens array 7, the drawing becomes complicated, and therefore some hatching descriptions are omitted.

  Light from the intermediate light emitting element 5 b passes through the first light transmission layer 14 and the second light transmission layer 15 and is emitted into the air, and travels toward the lens array 7. Of the light emitted from the intermediate light emitting element 5b, the light emitted at an emission angle equal to or less than a threshold value that makes the incident angle when entering the rod lens 11b equal to or less than a half angle of the viewing angle of the rod lens 11b is the optical path 19a, As indicated by 19b and 19c, the light passes through the first light transmission layer 14 and the second light transmission layer 15 and enters the corresponding rod lens 11b. Further, paying attention to the optical path 19b, when the first light transmission layer 14 and the second light transmission layer 15 are not provided, the optical path can be incident on the corresponding rod lens 11b as indicated by the two-dot chain line arrow 20b. The light which has not been refracted by the first light transmissive layer 14 and the second light transmissive layer 15, and the emission position of the light emitted from the second light transmissive layer 15 to the air is moved closer to the emission optical axis 19a. It can guide so that it may inject into the rod lens 11b to do. Light emitted at an emission angle larger than the threshold is not sufficiently bent even if the first light transmission layer 14 and the second light transmission layer 15 are provided, as shown by an optical path 19d, and the corresponding rod lens. 11b cannot enter.

  The light from the end light emitting element 5 a passes through the first light transmission layer 14, the second light transmission layer 15, and the third light transmission layer 16, is emitted into the air, and travels toward the lens array 7. The light emitted from the end light emitting element 5a whose optical path is indicated by arrows 21a, 21b, 21c and 21d in FIG. 4 is emitted from the intermediate light emitting element 5b whose optical path is indicated by arrows 19a, 19b, 19c and 19d. It is the light emitted at the same emission angle as the incident light.

  Pay attention to the optical path 21c. Although the light having the same emission angle emitted from the intermediate light emitting element 5b can be incident on the corresponding rod lens 11b as shown by the optical path 19c, the light from the end light emitting element 5a indicating the optical path by the arrow 21c is shown. The emitted light is scattered at the end 22 of the light transmission layer 6 from the end 22 of the light transmission layer 6 and enters the air having optically different properties from the light transmission layer 6, and the corresponding rod lens. 11a cannot be made incident. As described above, since the region where the end light transmitting portion 6a is formed is smaller than the intermediate light transmitting portion 6b, the light emitted from the end light emitting element 5a is emitted from the intermediate light emitting device 5b. There is a problem that the amount of light incident on the corresponding rod lens 11 is reduced as compared with light.

  In the present embodiment, the third light transmission layer 16 is formed only in the end light transmission portion 6a, so that the amount of light that has been reduced is compensated, and the rod lens 11a corresponding to the end light emitting element 5a is compensated. The amount of incident light can be made closer to the amount of incident light on the rod lens 11b corresponding to the intermediate light emitting element 6b.

  Note the optical path 21b. Light having the same emission angle emitted from the intermediate light emitting element 6b can be incident on the corresponding rod lens 11b as shown in the optical path 19b. An alternate long and two short dashes line 19b is an optical path described by superposing the optical path 19b emitted from the intermediate light emitting element 6b on the optical path 21b of the light having the same emission angle emitted from the end light emitting element 5a. In this way, the optical path indicated by the two-dot chain line is an optical path described by superimposing the optical path indicated by the solid line of the same reference number on the light emitted from the different light emitting elements. The description of the optical path is omitted.

  The light emitted from the end light emitting element 5a, which indicates the optical path by the arrow 21b, passes through the first light transmissive layer 14, the second light transmissive layer 15, and the third light transmissive layer 16, and is emitted into the air. It enters the rod lens 11a. The light path 21b of the light emitted from the end light emitting element 5a includes the third light transmitting layer 16 in addition to the first light transmitting layer 14 and the second light transmitting layer 15 through which the light emitted from the intermediate light emitting element 5b passes. Since the light is transmitted, it moves closer to the outgoing optical axis 21a than the optical path 19b of the outgoing light from the intermediate light emitting element 5b.

  Note the optical path 21d. For the light having the same emission angle emitted from the intermediate light emitting element 5b, the first light transmission layer 14 and the second light transmission layer 15 can be provided because the emission angle is larger than the threshold, as shown in the optical path 19d. The bending of the optical path is inadequate and cannot be incident on the corresponding rod lens 11b. On the other hand, the light emitted from the end light emitting element 5a indicated by the arrow 21d passes through the first light transmission layer 14, the second light transmission layer 15, and the third light transmission layer 16, and enters the air. Since the emission position of the emitted light from the end light transmission portion 6a to the air is moved closer to the emission optical axis 21a than the emission position of the emission light from the intermediate light transmission portion 6b to the air, the optical path The light indicated by 21d can be incident on the corresponding rod lens 11a. Thus, by providing the third light transmission layer 16, and making the protruding height H1 at the end light transmitting portion 6a larger than the protruding height H2 of the intermediate light transmitting portion 6b, the end light emitting element 5a. Of the light emitted from the light and transmitted through the light transmission layer 6 on the side opposite to the cut surface 18 of the substrate 3, the threshold value of the light emission angle that can be incident on the corresponding rod lens 11a can be increased.

  In this way, by making the protruding height H1 of the end light transmitting portion 6a provided in the end light emitting portion 4a larger than the protruding height H2 of the intermediate light transmitting portion 6b provided in the intermediate light emitting portion 4b. The irradiation area reduction characteristics of the end light transmission part 6a can be improved more than the irradiation area reduction characteristics of the intermediate light transmission part 6b. In the end light transmitting portion 6a, the threshold of the emission angle can be increased on the side opposite to the cut surface 18 of the substrate 3, and the amount of incident light to the corresponding rod lens 11a can be increased. As a result, it is possible to compensate for the amount of light that is emitted from the end portion 22 of the light transmission layer 6 on the cut surface 18 side of the substrate 3 and scattered and cannot be incident on the corresponding rod lens 11a. In this way, the amount of light received by the rod lens 11a corresponding to the end light emitting portion 4a is increased, and the distance between the rod lens 11a corresponding to the end light emitting portion 4a and the rod lens 11b corresponding to the intermediate light emitting portion 4b. Thus, the amount of received light can be made uniform.

  Here, the light transmission layer 6 is preferably formed such that the end 22 in the light emitting element arrangement direction is closer to the end light emitting element 5 a than the cut surface 18. The light transmission layer 6 is usually formed after the plurality of light emitting elements 5 are formed on the single crystal wafer and before the dicing process.

  When the end 22 in the light emitting element arrangement direction of the light transmitting layer 6 is not closer to the end light emitting element 5a than the cut surface 18, for example, the light transmitting layer 6 formed in the light emitting element array 1, the light emitting element array 1, When the light transmissive layer 17b formed in another adjacent light emitting element array 17 is integrally formed, the light transmissive layers 6 and 17b are cut together with the single crystal wafer in the dicing process. , 17b, microcracks are generated at the cut portions. If microcracks occur in the light transmissive layers 6 and 17b, the light transmittance in the light transmissive layers 6 and 17b is reduced and the light amount is lost. Therefore, the amount of light that cannot be compensated for by increasing the protrusion height is reduced. .

  Even when the light transmission layer 6 formed in the light emitting element array 1 and the light transmission layer 17b formed in another light emitting element array 17 adjacent to the light emitting element array 1 are formed separately, If the distance between the light transmission layers 6 and 17b is short, microcracks may occur due to vibrations of a cutting means such as a blade in the dicing process.

  Therefore, in the light transmission layer 6, the distance L3 between the end 22 of the light transmission layer 6 and the cut surface 18 of the substrate 3 is 0.15 × (L2−W / 2) or more and (L2−W / 2) or less. Thus, it is preferably formed. By forming the light transmission layer 6 so that the distance L3 falls within the above range, generation of microcracks in the dicing process can be prevented. If the distance L3 from the cut surface 18 of the substrate 3 is less than 0.15 × (L2−W / 2), microcracks may occur due to vibrations of cutting means such as blades in the dicing process. When the distance L3 from the cut surface 18 of the substrate 3 exceeds (L2-W / 2), the amount of light that decreases due to the emission light from the light emitting element 5 being emitted from the end 22 of the light transmission layer 6 increases. Thus, even if the protruding height H1 of the end light transmitting portion 6a is increased, there is a possibility that the reduced amount of light cannot be compensated.

  The protruding height H1 of the end light transmitting portion 6a from the substrate 3 and the protruding height H2 of the intermediate light transmitting portion 6b from the substrate 3 are determined as follows. First, the protrusion height H2 of the intermediate light transmitting portion 6b with respect to the substrate 3 is determined. The preferable protruding height H1 of the end light transmitting portion 6a with respect to the protruding height H2 of the intermediate light transmitting portion 6b is the refractive index of the material constituting the first to third light transmitting layers 14, 15, 16 and the like. It is decided according to. Therefore, after forming the first light transmission layer 14 and the second light transmission layer 15 constituting the intermediate light transmission portion 6b having the protrusion height H2, for example, the amount of light actually received by the rod lens 11 is measured. For example, the thickness of the third light transmission layer 16 is determined so that the amount of received light is uniform between the rod lens 11a corresponding to the end light emitting element 5a and the rod lens 11b corresponding to the intermediate light emitting element 5b. . As described above, the protruding height H1 of the end light transmitting portion 6a with respect to the substrate 3 determined by the thicknesses t1, t2, and t3 of the first to third light transmitting layers 14, 15, and 16 is determined.

  For example, when the first light transmission layer 14 and the second light transmission layer 15 are formed by a spin coating method, the protrusion height H2 of the intermediate light transmission unit 6b with respect to the substrate 3 is the viscosity of the coating solution and the rotation speed of the spin coater. (Rotational speed) etc. When the thickness t1 of the first light transmission layer 14 and the thickness t2 of the second light transmission layer 15 determined by the spin coating method are, for example, 2.5 μm or more and 7.5 μm or less, the protrusion height H2 is 5 μm or more and 15 μm. It becomes as follows.

  When the protruding height H2 of the intermediate light transmitting portion 6b with respect to the substrate 3 is 5 μm or more and 15 μm or less, the protruding height H1 of the end light transmitting portion 6a with respect to the substrate 3 is the protruding height of the intermediate light transmitting portion 6b with respect to the substrate 3. The third light transmission layer 16 is formed so as to be larger than the height H2. The protrusion height H1 of the end light transmitting portion 6a with respect to the substrate 3 is preferably 15 μm or more and 215 μm or less. However, when the protruding height H2 of the intermediate light transmitting portion 6b is 15 μm, the protruding height H2 of the end light transmitting portion 6a is set to be larger than 15 μm. When the protruding height H1 of the end light transmitting portion 6a is in the above range, the thickness t3 of the third light transmitting layer 16 is not less than 10 μm and not more than 200 μm.

  In the above case, when the thickness t3 of the third light transmission layer 16 is less than 10 μm, the emission position of the emitted light from the end light transmission part 6a to the air is changed from the intermediate light transmission part 6b to the air. Although it can be moved closer to the optical axis with respect to the emission position of the emitted light, the amount of movement is small, the amount of light incident on the rod lens 11a from the end light emitting element 5a, and the rod light from the intermediate light emitting element 5b. There is a possibility that the irradiation area reduction characteristic cannot be improved so that the amount of incident light 11b can be made uniform. In the above case, if the thickness t3 of the third light transmission layer 16 exceeds 200 μm, light loss may occur due to transmission through the third light transmission layer 16. Therefore, in the above case, in order to make the light quantity of light incident on the rod lens 11a from the end light emitting element 5a and the light quantity of light incident on the rod lens 11b from the intermediate light emitting element 5b uniform, The thickness t3 of the light transmission layer 16 is preferably 10 μm or more and 200 μm or less.

  Such a third light transmission layer 16 can also be formed by spin coating as described above. When the third light transmission layer 16 is formed by the spin coating method, the viscosity of the coating liquid to be used is higher than the viscosity of the coating liquid used when forming the first light transmission layer 14 and the second light transmission layer 15. preferable. Further, it is preferable that the rotation speed of the spin coater when forming the third light transmission layer 16 is smaller than the rotation speed of the spin coater when forming the first light transmission layer 14 and the second light transmission layer 15.

  In such a third light transmission layer 16, it is preferable that the end 23 opposite to the end 22 of the light transmission layer 6 is formed near the center of the occupied region of the end light emitting section 4a. When the end portion 23 of the third light transmission layer 16 opposite to the end portion 22 of the light transmission layer 6 is formed near the center of the area occupied by the end light emitting portion 4a, the intermediate portion adjacent to the end light emitting element 5a is provided. The light emitted from the partial light emitting element 5b can be prevented from passing through the third light transmission layer 16 and entering the rod lens 11a corresponding to the end light emitting element 5a, and the light emitted from the intermediate light emitting element 5b can be prevented. It is possible to prevent the light from being reflected by the end portion 23 of the third light transmission layer 16 and becoming scattered light.

  The distance L4 between the virtual plane 12 having the same distance in the light emitting element arrangement direction from the end light emitting section 4a and the intermediate light emitting section 4b and the end 23 of the third light transmission layer 16 is 0.15 × (L1− W) / 2 or more and (L1-W) / 2 or less is preferable. When the third light transmission layer 16 is formed inside the area occupied by the end light emitting portion 4a so as to be in the above range, the emitted light from the intermediate light emitting element 5b is transmitted through the third light transmission layer 16 or It is possible to prevent reflection at the end portion 23 of the third light transmission layer 16. When the distance L4 is less than 0.15 × (L1-W) / 2, the emitted light from the intermediate light emitting element 5b is transmitted through the third light transmission layer 16 or at the end 23 of the third light transmission layer 16. There is a risk of reflection. When the distance L4 exceeds (L1-W) / 2, the area where the third light transmission layer 16 is formed becomes small, and there is a possibility that the irradiation area reduction characteristic is deteriorated.

  The light transmission layer 6 as described above is not limited to the above-described configuration, and various modifications can be made. For example, in the present embodiment, when the refractive index of the first light transmission layer 14 is n1, the refractive index of the second light transmission layer 15 is n2, and the refractive index of the third light transmission layer 16 is n3, n1 <n2 Although the light transmissive layer 6 is composed of the first to third light transmissive layers 14, 15, and 16 having different refractive indexes, the refractive index n1 of the first light transmissive layer 14, the first The magnitude relationship between the refractive index n2 of the two light transmitting layer 15 and the refractive index n3 of the third light transmitting layer 16 may be appropriately changed. Further, if the protruding height H1 of the end light transmitting portion 6a and the protruding height H2 of the intermediate light transmitting portion 6b are different, the same material is used for the first to third light transmitting layers in one layer. The number of layers forming the light transmission layer may be appropriately reduced or increased, for example, by forming the transmission layer 6.

  The light-emitting element array 1 including the light transmission layer 6 as described above is configured such that the end light transmission portion 6a and the intermediate light transmission portion 6b have different protrusion heights from the substrate 3 to thereby transmit the end light transmission. The irradiation area reduction characteristic of the part 6a is enhanced more than the irradiation area reduction characteristic of the intermediate light transmission part 6b. In the present embodiment, the protrusion height H1 of the end light transmission part 6a from the substrate 3 is set to be larger than the protrusion height H2 of the intermediate light transmission part 6b from the substrate 3 to thereby increase the edge in the substrate thickness direction. The position of the interface between the partial light transmitting portion 6a and the air can be closer to the lens array 7 than the position of the interface between the intermediate light transmitting portion 6b and the air. As a result, the irradiation area reduction characteristic of the end light transmitting portion 6a having a small area of the occupied area with respect to the substrate 3 can be improved, and the received light quantity of the light received by the lens array 7 is intermediate to that of the end light emitting element 5a. It is possible to make uniform between the partial light emitting elements 5b.

  Further, the optical print head 2 of the present embodiment irradiates the electrophotographic photoreceptor 9 with a plurality of light emitting element arrays 1 on which the light transmitting layer 6 as described above is formed and light emitted from the light emitting element array 1. And a lens array 7. Such an optical print head 2 includes the light emitting element array 1 in which the amount of received light emitted from the light emitting element 5 and received by the lens array 7 is made uniform regardless of the place where the light emitting element 5 is disposed. Therefore, it is possible to prevent unevenness in the amount of light irradiated from the lens array 7 to the electrophotographic photosensitive member 9. Further, by preventing the generation of unevenness in the amount of light irradiated to the electrophotographic photosensitive member 9, compared to other portions, the white streaks generated in the portions where the amount of irradiated light is small compared to other portions and other portions. Generation of black streaks or the like generated in a portion where the amount of irradiation light is large can be prevented, and a good image without image defects can be formed.

  The light emitting element array 1 and the optical print head 2 are not limited to the above configuration, and various modifications can be made. For example, the optical print head 2 of the present embodiment has a resolution of 600 dpi and the light emitting elements 5 are arranged at an equal pitch L1 = 42.3 μm. However, the present invention is not limited to this, and the resolution is, for example, 1200 dpi. The light emitting element array 1 and the optical print head 2 in which the light emitting elements 5 are arranged at an equal pitch L1 = 21.1 μm may be used.

  The problem of a decrease in the amount of light due to the small area of the area occupied by the edge light emitting element 5a with respect to the substrate 3 tends to increase as the resolution increases. Therefore, in the light emitting element array 1 having a narrow pitch L1 of 21.1 μm, it is more difficult to form a light transmission layer on the end light emitting portion 4a than the light emitting element array 1 having a pitch L1 of 42.3 μm, for example. There is a possibility that the area of the occupied region of the light transmission part 6a may be reduced. In such a case, the amount of light emitted from the end light emitting portion 4a and incident on the lens array 7 is likely to be smaller than the amount of light emitted from the intermediate light emitting portion 4b and incident on the lens array 7. Therefore, as in the present embodiment, by making the protruding height H1 of the end light transmitting portion 6a larger than the protruding height H2 of the intermediate light transmitting portion 6b, the light received by the lens array 7 is received. The configuration in which the amount of light is made uniform between the end light emitting element 5a and the intermediate light emitting element 5b is preferably used in the light emitting element array 1 with high resolution.

  FIG. 5 is a partial cross-sectional view showing a configuration of an optical print head 32 including a light emitting element array 31 according to the second embodiment of the present invention. The optical print head 32 according to the present embodiment is similar to the optical print head 2 according to the first embodiment described above, and portions having the same configuration are denoted by the same reference numerals and description thereof is omitted.

  The light emitting element array 31 according to the present embodiment includes a substrate 3, a light emitting element 5 having a light emitting unit 4, and a light transmission layer 33 provided so as to cover the light emitting unit 4 of each light emitting element 5. The optical print head 32 according to the present embodiment includes a plurality of light emitting element arrays 31 and a lens array 7.

  The light emitting element array 31 according to the present embodiment includes an end light transmitting portion 33a of the light transmitting layer 33 and intermediate light transmitting portions 33b, 33c, 33d,... (Hereinafter, a specific intermediate light transmitting portion is shown). (Excluding the intermediate light transmission part 33b), the irradiation area reduction characteristic of the end light transmission part 33a is made to be different from the irradiation area reduction characteristic of the intermediate light transmission part 33b. It is characterized by increasing.

  In the present embodiment, the exit surface shape of the intermediate light transmitting portion 33b is a planar shape, and the exit surface shape of the end light transmitting portion 33a is a curved shape that is convex toward the lens array 7 side. The light transmissive layer 33 of the present embodiment is composed of two light transmissive layers 14 and 34 made of a material such as a resin having a light transmitting property, like the light transmissive layer 6 of the first embodiment described above. .

  A convex portion 35 is formed in the second light transmission layer 34 in a region occupied by the substrate 3 of the end light emitting element 5a. The convex portion 35 is formed in a curved surface shape known as a hemispherical or aspherical lens. As a result, the exit surface of the end light transmitting portion 33a is formed in a curved shape. In the present embodiment, the center of the convex portion 35 in the plane parallel to the element array surface 3a of the substrate 3 is shifted from the center of the light emitting portion 4a, and the surface of the convex portion 35 on the substrate 3 side is a circle having a radius r. A convex portion 35 is formed.

  As a method of forming the convex portion 35 of the second light transmission layer 34, for example, after forming the second light transmission layer having a flat emission surface shape, a mask such as a metal layer is formed on a portion where the convex portion 35 is to be formed. And the exit surface of the second light transmission layer on which the mask is formed is etched by reactive ion etching (RIE) or chemical dry etching (CDE). When such an etching method is used, the end portion of the mask gradually recedes inward, so that the convex portion 35 having a curved surface shape can be easily formed. As a material for the metal layer forming the mask, titanium (Ti), aluminum (Al), chromium (Cr), or the like is preferably used. The material for forming the mask may not be a metal material as long as the etching rate is lower than that of the material constituting the second light transmission layer 34.

  In addition, as another method of forming the convex portion 35 of the second light transmission layer 34, for example, after forming the second light transmission layer 34 having a flat emission surface shape, After discharging a resin solution prepared by dissolving a translucent resin in a solvent such as an organic solvent capable of dissolving a translucent resin by an inkjet method or the like, and forming a convex resin solution part by the surface tension of the resin solution, the solvent The method of removing and hardening | curing is mentioned.

  FIG. 6 is a diagram showing an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. FIG. 7 shows incident light when the light emitted from the light emitting element 5 enters the air from the light transmission layer 33. It is a figure which shows a corner | angular. The optical paths 19a, 19b, 19c, 19d of the light emitted from the intermediate light emitting element 5b are the same as those shown in FIG.

  As shown by optical paths 36a, 36b, and 36d, part of the light from the end light emitting element 5a is transmitted through the first light transmitting layer 14 and the second light transmitting layer 15 and emitted into the air, and the corresponding rod. The light enters the lens 11a. Further, the light emitted from the end light emitting element 5a indicating the optical path by the arrow 36c is scattered at the end 37 of the light transmission layer 33 and cannot enter the corresponding rod lens 11a.

  Note the optical path 36b. The light emitted from the end light emitting element 5a indicated by the arrow 36b is transmitted through the first light transmitting layer 14 and the second light transmitting layer 15 and emitted into the air, and enters the corresponding rod lens 11a. When the exit surface shape of the end light transmitting portion 33 a is a curved surface shape having the convex portion 35 on the lens array 7 side, the normal line 38 of the curved surface at the light incident position is in a direction perpendicular to the element array surface 3 a of the substrate 3. By inclining the light, the light incident on the air from the second light transmission layer 34 at the incident angle θ is refracted toward the center side of the rod lens 11a. Thus, the end light transmission part 33a can condense incident light by making the output surface of the end light transmission part 33a into a curved surface shape.

  Similarly, when the light is emitted from the intermediate light emitting element 5b, the end light transmitting portion 33a emits light emitted at the same emission angle as the light emitted by the optical path 19d that cannot be incident on the corresponding rod lens 11b. Then, the light can be refracted to the center side of the corresponding rod lens 11a at the interface between the second light transmission layer 15 and air and can be incident on the corresponding rod lens 11a.

  As described above, the shape of the exit surface of the light transmission layer 33 is occupied by each light emitting element 5 so that the light collection characteristic of the end light transmission part 33a is higher than the light collection characteristic of the intermediate light transmission part 33b. Therefore, the irradiation area reduction characteristic of the end light transmission part 33a with a small area of the occupied area with respect to the substrate 3 can be improved, and the amount of light received by the lens array 7 can be changed. It is possible to make uniform between the end light emitting element 5a and the intermediate light emitting element 5b.

  The exit surface shape of the end light transmitting portion 33a is determined as follows when the exit surface shape of the intermediate light transmitting portion 33b is a planar shape. When the radius of curvature in the vicinity of the apex of the convex portion 35 of the end light transmitting portion 33a is R and the protruding height of the convex portion 35 is h, the ratio of the radius of curvature R to the protruding height h (R / h) is appropriately set. By doing this, the shape of the exit surface of the end light transmission part 33a is set. For example, when the protrusion height h is 5 μm or more and 100 μm or less, the ratio (R / h) of the curvature radius R to the protrusion height h is set to be greater than 0.7 and less than 5.0.

  When the convex portion 35 of the end light transmitting portion 33a is formed so that the ratio of the radius of curvature R to the protrusion height h is in the above range, the light collecting characteristics in the end light transmitting portion 33a are improved, and the end light emission is performed. The amount of light incident on the rod lens 11a from the element 5a and the amount of light incident on the rod lens 11b from the intermediate light emitting element 5b can be made uniform. If the ratio of the curvature radius R to the protrusion height h is 0.7 or less, the radius r of the convex portion 35 becomes small, and the light irradiation region reduction characteristics as the entire end light transmitting portion 33a may not be improved. There is. When the ratio of the curvature radius R to the protrusion height h is 5.0 or more, the amount of light incident on the rod lens 11a from the end light emitting element 5a and the amount of light incident on the rod lens 11b from the intermediate light emitting element 5b. There is a possibility that the light condensing characteristics cannot be improved to such an extent that can be made uniform.

  In the present embodiment, the exit surface shape of the intermediate light transmitting portion 33b is a planar shape, and the shape of the end light transmitting portion 33a is a curved surface shape having a convex portion 35 on the lens array 7 side. Various modifications are possible without being limited to the above. For example, the exit surface shape of the intermediate light transmitting portion is also a curved surface shape, and the curvature of the curved surface shape of the end light transmitting portion is larger than the curvature of the curved shape of the intermediate light transmitting portion. Even with such a light transmissive layer, the light collection characteristic of the end light transmission part is higher than the light collection characteristic of the intermediate light transmission part, so that the irradiation of the end light transmission part with a small area of the occupied area with respect to the substrate is performed. The area reduction characteristic can be improved, and the amount of received light can be made uniform between the end light emitting element and the intermediate light emitting element.

  In the present embodiment, the convex portion 35 is formed by shifting the center of the convex portion 35 in the plane parallel to the element array surface 3a of the substrate 3 and the center of the light emitting portion 4a. The convex portion 35 may be formed by aligning the center of the convex portion 35 in the plane parallel to the element array surface 3a of the substrate 3 and the center of the light emitting portion 4a. By matching the center of 4a, the size of the projection 35 may be smaller than when the center of the projection 35 and the center of the light emitting unit 4a are not matched. When the size of the convex portion 35 is reduced, the light condensing characteristic is deteriorated. Therefore, by shifting the center of the convex portion 35 in the plane parallel to the element arrangement surface 3a of the substrate 3 and the center of the light emitting portion 4a, It is preferable to form the portion 35 as large as possible within the range of the area occupied by the substrate 3 of the light emitting portion 4a.

  Also in the present embodiment, the number of layers constituting the light transmission layer 33 can be appropriately reduced or increased.

  FIG. 8 is a partial cross-sectional view showing a configuration of an optical print head 42 including a light emitting element array 41 according to the third embodiment of the present invention. The optical print head 42 according to the present embodiment is similar to the optical print head 32 according to the second embodiment described above, and portions having the same configuration are denoted by the same reference numerals and description thereof is omitted.

  The light emitting element array 41 of the present embodiment includes a substrate 3, a light emitting element 5 having a light emitting part 4, a first light transmission layer 14 provided to cover the light emitting part 4 of each light emitting element 5, and lenses 43a, 43b, 43c, 43d,... (Hereinafter referred to as the lens 43 except when a specific lens is shown). The optical print head 42 according to the present embodiment includes a plurality of light emitting element arrays 41 and a lens array 7.

  In the light emitting element array 41 according to the present embodiment, a lens 43 that is an irradiation region reduction unit is formed instead of the second light transmission layer. The lens 43a formed on the end light emitting portion 4a is called an end lens 43a, and the lenses 43b, 43c, 43d,... Formed on the intermediate light emitting portions 4b, 4c, 4d,. , 43d,..., And among these intermediate lenses, it is described as an intermediate lens 43b except when a specific intermediate lens is shown. The lens 43 is formed on the side of the first light transmission layer 14 opposite to the light emitting element 5, the surface of the lens 43 on the first light transmission layer 14 side is planar, and the surface of the lens array 7 side is convex outward. This is a curved surface shape.

  The intermediate lens 43b has a hemispherical surface having a radius Rb1 and a height Rb2 on the lens array 7 side. Therefore, the radius of curvature Rb near the apex of the intermediate lens 43b in the present embodiment is equal to the radius Rb1. Since the end lens 43a has a height of Ra2 and the area of the area occupied by the end light emitting element 5a is smaller than the area of the area occupied by the intermediate light emitting element 5b, the end lens 43a in the light emitting element arrangement direction. The length is twice that of Ra1, which is smaller than twice that of Rb1. The radius of curvature near the apex of the end lens 43a is Ra.

  In the present embodiment, the end lens 43 a and the intermediate lens 43 b have the same protruding height, which is the height in the thickness direction of the substrate 3. Accordingly, the end lens 43a and the intermediate lens 43b have a height of Ra2 (= Rb2). Here, when the value obtained by dividing the height of the lens by the half length of the lens is defined as the flatness, the flatness (Ra2 / Ra1) of the end lens 43a is greater than one. Further, the flatness ratio (Rb2 / Rb1) of the intermediate lens 43b is 1.

  Similar to the light transmissive layer of the above-described embodiment, such a lens 43 is formed by forming a light transmissive layer whose surface on the lens array 7 side is a flat surface by a light transmissive layer forming method including a coating process and a solvent removing process, for example. It is formed by removing unnecessary portions by etching or the like. The lens 43 may be formed by an inkjet method or the like. When forming the lens 43 by the inkjet method, for example, different solvents are used as the solvent of the resin solution to be ejected, and the surface tension of the resin solution is made different so that the end lens 43a and the intermediate lens 43b have different shapes. be able to.

  FIG. 9 is a diagram illustrating an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. The optical paths 44a, 44b, 44c, 44d of the light emitted from the intermediate light emitting element 5b are optical paths 19a, 19b shown in FIG. 4 except that they pass through the intermediate lens 43b instead of transmitting through the second light transmission layer 15. Since it is the same as 19b, 19c, and 19d, the description is omitted.

  Here, when the hemispherical lens 45 having the same shape as the intermediate lens 43b provided in the intermediate light emitting part 4b is provided in the end light emitting part 4a having a smaller area than the intermediate light emitting part 4b. The optical path of the incident light is indicated by two-dot chain lines 45b and 45d. The intermediate lens 43b has a bottom surface radius Ra and a protrusion height Ra. Also, 46a, 46b, 46c and 46d indicate the optical paths of the emitted light when the end lens 43a of the present embodiment is provided.

  As shown by optical paths 46a, 46b, and 46d, part of the light from the end light emitting element 5a is transmitted through the first light transmission layer 14 and the end lens 43a and emitted into the air, and the corresponding rod lens 11a. Is incident on. In addition, the light emitted from the end light emitting element 5a indicated by the arrow 46c is scattered at the end 47 of the first light transmission layer 14, and cannot be incident on the corresponding rod lens 11a.

  Note the optical paths 46b and 46d. Comparing the optical path of light incident on the hemispherical lens 45 having a flatness ratio of 1 with the optical path of light incident on the end lens 43a having a flatness ratio greater than 1, the hemispherical lens 45 and the end lens 43a Thus, the condensing characteristic of the end lens 43a having a flatness greater than 1 is improved over the condensing characteristic of the hemispherical lens 45 by the difference in the incident angle of light when entering the air from the lens. The

  FIG. 10 is a diagram showing an incident angle when the light emitted from the light emitting element 5 enters the air from the lens 43. Note the optical path 46b. The light emitted from the end light emitting element 5a indicated by the arrow 46b passes through the first light transmission layer 14 and the end lens 43a, is emitted into the air, and enters the corresponding rod lens 11a. Since the exit surface shape of the end lens 43a is a curved surface convex toward the lens array 7 and the flatness is larger than 1, the normal 48 of the curved surface at the light exit position is the exit of the hemispherical intermediate lens 43b. The inclination angle of the substrate 3 with respect to the element array surface 3a is larger than the normal line 49 of the emission position of the surface shape.

  As a result, the incident angle θa of the light incident on the air from the end lens 43a becomes larger than the incident angle θb of the light incident on the air from the intermediate lens 43b, so that the condensing characteristic of the end lens 43a is the intermediate portion. It becomes higher than the condensing characteristic of the lens 43b.

  As described above, by changing the shape of the exit surface of the lens 43 so that the condensing characteristics of the end lens 43a are higher than those of the intermediate lens 43b, the end of the area occupied by the substrate 3 is small. The irradiation area reduction characteristic of the lens 43a can be improved, and the amount of light received by the lens array 7 can be made uniform between the end light emitting element 5a and the intermediate light emitting element 5b.

The shape and size of such a lens are determined as follows. As described above, when the radius of curvature near the apex of the end lens 43a is Ra, the projection height is Ra2, the radius of curvature near the apex of the intermediate lens 43b is Rb, and the projection height is Rb2, the following formula (1 ) Holds.
k · Ra / Ra2 = Rb / Rb2 (1)

  However, k is a number greater than 1 and less than or equal to 5. By forming the end lens 43a and the intermediate lens 43b so as to satisfy the above formula, the amount of light incident on the rod lens 11a from the end light emitting element 5a and the incident on the rod lens 11b from the intermediate light emitting element 5b The amount of light to be emitted can be made uniform. When k in Formula (1) is 1 or less, the amount of light incident on the rod lens 11a from the end light emitting element 5a and the amount of light incident on the rod lens 11b from the intermediate light emitting element 5b are made uniform. Therefore, there is a possibility that the condensing characteristic of the end lens 43a cannot be improved as compared with the condensing characteristic of the intermediate lens 43b. When k in the formula (1) exceeds 5, the radius Ra1 of the end lens 43a becomes small, and there is a possibility that the light irradiation area reduction characteristic as the entire end lens 43a cannot be improved.

  The light emitting element array 41 and the optical print head 42 according to the present embodiment are not limited to the above configuration, and various modifications can be made. For example, in the present embodiment, one light transmission layer 13 is formed between the light emitting element 5 and the lens 43, but the present invention is not limited to this. For example, the light transmission layer 13 may be configured by a plurality of layers, or the lens 43 may be formed directly on the light emitting element 5 and the light transmission layer 13 may not be provided.

  The formation of the light transmission layer 13 can improve the wettability between the resin solution for forming the lens 43 and the light transmission layer 13 by appropriately selecting the material of the light transmission layer 13. It is preferable at the point which can enlarge the adhesive strength of 43 and the light transmissive layer 13. FIG.

  FIG. 11 is a partial cross-sectional view showing a configuration of an optical print head 52 including a light emitting element array 51 according to a fourth embodiment of the present invention. FIG. 11 shows an optical path of light emitted from the light emitting element 5 and transmitted through the lenses 53 and 43b having different refractive indexes. The optical print head 52 according to the present embodiment is similar to the optical print head 42 according to the third embodiment described above, and portions having the same configuration are denoted by the same reference numerals and description thereof is omitted.

  The light emitting element array 51 of the present embodiment includes a substrate 3, a light emitting element 5 having a light emitting part 4, a first light transmission layer 14 provided to cover the light emitting part 4 of each light emitting element 5, an end lens 53, and Intermediate lenses 43b, 43c, 43d,... The optical print head 52 of this embodiment includes a plurality of light emitting element arrays 51 and a lens array 7.

  In the present embodiment, by using materials having different refractive indexes for the end lens 53 and the intermediate lens 43b, the irradiation region reduction characteristic of the end lens 53 is made to be greater than the irradiation region reduction characteristic of the intermediate lens 43b. It is characterized by increasing.

  The end lens 53 of the present embodiment is formed in the same shape and size as the end lens 43a of the third embodiment described above, and the refractive index of the material constituting the end lens 53 is the intermediate lens 43b. It is formed so as to be higher than the refractive index of the material constituting the.

  The light emitted from the end light emitting element 5a that passes through the end lens 53 is emitted when the end lens is formed of a material having the same refractive index as that of the material constituting the intermediate lens 43b. The optical paths can be condensed closer to the center of the corresponding rod lens 11a as indicated by arrows 54b and 54d than the optical paths 46b and 46d.

  As described above, according to the present embodiment, by selecting a material having a refractive index higher than that of the material used for the intermediate lens 43b as the material used for the end lens 53, the end lens is obtained. The light collecting amount of the corresponding rod lens 11 that further improves the light condensing characteristics of 53 and receives the light from the light emitting element 5 within the light receiving surface having a certain area is obtained from the light emitted from the intermediate light emitting element 5b. Also, the light emitted from the end light emitting element 5a can be increased. As a result, the amount of light received by the lens array 7 can be made uniform between the end light emitting element 5a and the intermediate light emitting element 5b. The shape and size of such a lens are determined in the same manner as in the third embodiment described above.

  FIG. 12 is a side view showing the basic configuration of the image forming apparatus 87 according to the embodiment of the present invention. The image forming apparatus 87 is an electrophotographic image forming apparatus, and includes the light emitting device 60 that is the light emitting element array described above. The light emitting device 60 is used as an exposure device for the photosensitive drum 90 that is an electrophotographic photosensitive member. I am using it. In the present embodiment, the light-emitting device 60 includes the light-emitting element array 1 shown in FIG. 1 and the IC driver 10 that is the driving means shown in FIG. Further, the lens array 7 shown in FIG. The light emitting device 60 and the light condensing means 88 constitute the optical print head 2 shown in FIG.

  The image forming apparatus 87 is an apparatus that employs a tandem system that forms four color images of Y (yellow), M (magenta), C (cyan), and K (black), and is roughly divided into four light emitting elements. The devices 60Y, 60M, 60C, and 60K, the condensing means 88Y, 88M, 88C, and 88K, the circuit board on which the four light emitting devices 60Y, 60M, 60C, and 60K corresponding to the respective colors are mounted and the condensing means 88 are held. First holders 89Y, 89M, 89C, 89K, four photosensitive drums 90Y, 90M, 90C, 90K, four developer supply means 91Y, 91M, 91C, 91K, a transfer belt 92 as transfer means, and four cleaners 93Y. , 93M, 93C, 93K, four chargers 94Y, 94M, 94C, 94K, a fixing unit 95 and a control unit 96.

  Each light emitting device 60 operates by giving color image information of each color to the IC driver 10. For example, the length in the arrangement direction X of the four light emitting devices 60 is selected from 200 mm to 400 mm, for example.

  Light from the light emitting element T of each light emitting device 60 is condensed and applied to each of the photosensitive drums 90Y, 90M, 90C, and 90K through the light condensing means 88. The condensing means 88 includes, for example, a plurality of lenses disposed on the optical axis of the light emitting element, and is configured by integrally forming these lenses.

  The drive circuit board on which the light emitting device 60 is mounted and the light condensing means 88 are held by the first holder 89. By the holder 89, the light irradiation direction of the light emitting element T and the optical axis direction of the lens of the condensing means 88 are aligned so as to substantially coincide.

  Each of the photoconductive drums 90Y, 90M, 90C, and 90K is formed, for example, by adhering a photoconductive layer on the surface of a cylindrical base, and the outer peripheral surface receives light from the light emitting devices 60Y, 10M, 10C, and 10K. Then, an electrostatic latent image forming position where the electrostatic latent image is formed is set.

  The exposed photosensitive drums 90Y, 90M, 90C, and 90K are sequentially exposed at the periphery of the photosensitive drums 90Y, 90M, 90C, and 90K toward the downstream side in the rotational direction with respect to the electrostatic latent image forming positions. Developer supplying means 91Y, 91M, 91C, 91K for supplying developer to the transfer belt 92, cleaners 93Y, 93M, 93C, 93K, and chargers 94Y, 94M, 94C, 94K are arranged, respectively. A transfer belt 92 that transfers an image formed on the photosensitive drum 90 with a developer onto a recording sheet is provided in common to the four photosensitive drums 90Y, 90M, 90C, and 90K.

  The photosensitive drums 90Y, 90M, 90C, and 90K are held by a second holder, and the second holder and the first holder 89 are relatively fixed. The photoconductor drums 90Y, 90M, 90C, and 90K are aligned so that the rotation axis directions of the respective light-emitting devices 60 and the arrangement direction X of the light emitting devices 60 substantially coincide with each other.

  The recording sheet is conveyed by the transfer belt 92, and the recording sheet on which an image is formed by the developer is conveyed to the fixing unit 95. The fixing unit 95 fixes the developer transferred to the recording sheet. The photosensitive drums 90Y, 90M, 90C, and 90K are rotated by a rotation driving unit.

  The control means 96 gives image information to the first and second drive ICs 61 and 62 and the selection drive IC 63 described above, and also provides rotational drive means and developer supply for rotationally driving the photosensitive drums 90Y, 90M, 90C and 90K. The units 91Y, 91M, 91C, and 91K, the transfer unit 92, the charging units 94Y, 94M, 94C, and 94K, and the fixing unit 95 are controlled.

  In the image forming apparatus 87 having such a configuration, since the optical print head including the light emitting element array described above is used as an exposure apparatus, unevenness in the amount of light irradiated onto the electrophotographic photosensitive member is prevented. . As a result, white streaks appear in areas where the amount of light irradiated to the electrophotographic photosensitive member is small compared to other parts, and occur in areas where the amount of light irradiated to the electrophotographic photosensitive member is large compared to other parts. It is possible to stably form a good image free from image defects such as black streaks.

It is a fragmentary sectional view which shows the structure of the optical print head 2 provided with the light emitting element array 1 which is 1st Embodiment of this invention. It is a perspective view of the optical print head 2 used as an exposure means. 3 is a partial cross-sectional view of the optical print head 2 showing the arrangement of the light emitting elements 5 and the light emitting element array 1. FIG. 4 is a diagram illustrating an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. It is a fragmentary sectional view which shows the structure of the optical print head 32 provided with the light emitting element array 31 which is the 2nd Embodiment of this invention. FIG. 4 is a diagram illustrating an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. 4 is a diagram illustrating an incident angle when light emitted from the light emitting element 5 enters the air from the light transmission layer 33. FIG. It is a fragmentary sectional view which shows the structure of the optical print head provided with the light emitting element array 41 which is the 3rd Embodiment of this invention. FIG. 4 is a diagram illustrating an optical path of light emitted from the light emitting element 5 and incident on the lens array 7. It is a figure which shows an incident angle when the light radiate | emitted from the light emitting element 5 injects into the air from the lens 43. FIG. It is a fragmentary sectional view which shows the structure of the optical print head 52 provided with the light emitting element array 51 which is the 4th Embodiment of this invention. 1 is a side view showing a basic configuration of an image forming apparatus 87 according to an embodiment of the present invention.

Explanation of symbols

1, 17, 31, 41, 51 Light emitting element array 2, 32, 42, 52 Optical print head 3 Substrate 4, 4a, 4b, 4c, 4d Light emitting part 5, 5a, 5b, 5c, 5d, 17a Light emitting element 6, 17b, 33 Irradiation area reduction means (light transmission layer)
6a, 33a Edge irradiation area reduction means (edge light transmission part)
6b, 6c, 6d, 33b, 33c, 33d Intermediate part irradiation area reduction part (intermediate part light transmission part)
7 Lens array 8 Drive circuit board 9 Electrophotographic photosensitive member 10 IC driver 11, 11a, 11b, 11c, 11d Rod lens 12 Virtual plane 13a, 13b, 13c, 13d Dividing surface 14 First light transmitting layer 15, 34 Second light Transmission layer 16 Third light transmission layer 18 Cut surface 22, 37, 47 Light transmission layer one end 23 Light transmission layer other end 35 Convex 43a, 53 End lens 43b, 43c, 43d Intermediate lens 45 Semispherical lens

Claims (6)

A substrate,
A plurality of light emitting elements provided on the substrate so that each of the light emitting parts is arranged between two points spaced apart from each other;
Among the light emitting elements, the light emitting part of the light emitting element disposed at the end is provided so as to cover, and the irradiation area on a predetermined virtual plane of light emitted from the light emitting element disposed at the end is reduced. A light emitting element disposed to cover the light emitting part of the light emitting element disposed in the intermediate part excluding the end part, and disposed in the intermediate part excluding the end part. An irradiation area reduction means including an intermediate irradiation area reduction unit for reducing the irradiation area on the predetermined virtual plane of light emitted from the edge irradiation area reduction unit, The area is smaller than the area of the area occupied by the intermediate irradiation area reduction part with respect to the substrate, and the irradiation area reduction characteristic of the edge irradiation area reduction part is more than the irradiation area reduction characteristic of the intermediate irradiation area reduction part. Emitting element array which comprises a higher composed irradiation region reduction means. The irradiation area reduction means includes:
By using materials having different refractive indexes for the edge irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the edge irradiation region reduction unit is obtained by using the intermediate part irradiation region reduction unit. The light emitting element array according to claim 1, wherein the light emitting element array has a higher irradiation area reduction characteristic. The irradiation area reduction means includes:
By varying the height of protrusion from the substrate between the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the end irradiation region reduction unit is set to the intermediate part irradiation. 3. The light emitting element array according to claim 1, wherein the light emitting element array has a higher irradiation area reduction characteristic than that of the area reduction portion. The irradiation area reduction means includes:
By changing the shape of the exit surface between the end irradiation region reduction unit and the intermediate irradiation region reduction unit, the irradiation region reduction characteristic of the end irradiation region reduction unit is changed to the intermediate irradiation region reduction unit. The light emitting element array according to claim 1, wherein the light emitting element array has a higher irradiation region reduction characteristic. A plurality of the light emitting element arrays according to any one of claims 1 to 4,
Including a lens array for irradiating the electrophotographic photosensitive member with light emitted from the light emitting element array,
The plurality of light emitting element arrays are arranged along an arrangement direction of the light emitting elements. An optical print head according to claim 5;
Developer supplying means for supplying a developer to the electrophotographic photosensitive member irradiated with light from the optical print head;
Transfer means for transferring an image formed by a developer on the electrophotographic photosensitive member to a recording sheet;
An image forming apparatus comprising: fixing means for fixing the developer transferred to the recording sheet.

Images