JP2006297814A - Optical printer head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical printer head which enhances the efficiency of utilization of light emitted from an organic EL. <P>SOLUTION: This optical printer head 101 comprises an organic EL panel 111, a rod lens array 112, and an optical sheet 113. In the organic EL panel 111, organic EL elements 115 are juxtaposed to each other. The rod lens array 112 makes incident light form an image in a predetermined position. The optical sheet 113, which is installed between the organic EL panel 111 and the rod lens array 112, has a prismatic surface 132 which is formed by arranging quadrangular pyramid-shaped prisms 133 on a surface facing the rod lens array. Thus, the light emitted from the organic EL panel 111 is deflected by the optical sheet 113 and made efficiently incident into the rod lens array 112. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical printer head using an organic EL element as a light source.

  Currently, a laser beam printer using a laser as a light source and an LED printer using an LED are put into practical use as printers.

  The laser beam printer scans the photosensitive drum (photoconductor) with a polygon mirror or the like while turning on / off the laser beam emitted from the laser diode according to the image pattern. However, in such a laser beam printer, in order to optically scan the laser beam from end to end of the photosensitive drum, a corresponding space is required between the polygon mirror and the photosensitive drum. Further, since the polygon mirror is rotated by a motor, it is difficult to reduce the size of the laser beam scanning system. Therefore, the laser beam printer is not suitable for downsizing. Further, in order to scan a laser beam on a larger photosensitive drum, a larger optical system and space are required. Furthermore, since the laser beam is incident on the photosensitive drum at a large angle near the end of the photosensitive drum, problems such as deformation of the laser beam are likely to occur.

  Second, LED printers can be made smaller than laser beam printers. However, since the LED printer has a large luminance variation for each LED chip, it is necessary to take measures against luminance unevenness such as selection of the LED chip and luminance adjustment by a drive circuit, which causes high cost.

  In recent years, development of display devices using organic thin film electroluminescence (hereinafter referred to as organic EL) elements has been actively conducted by research institutions and companies, and some manufacturers have been developing for commercialization. . Such an organic EL device can be manufactured on a glass substrate or a film in a lump, and when applied to a printer, it reduces luminance unevenness, downsizing the optical system, and reducing costs. Promising.

  On the other hand, since the organic EL element has a low light emission intensity per unit area, in order to obtain an output sufficient to sensitize the photosensitive drum, a higher voltage is applied to the organic EL element than when used as a display device. It is necessary to pass current. However, when the voltage applied to the organic EL element is increased and the current density of the flowing current is increased, the light emission efficiency of the organic EL element is lowered and the lifetime thereof is shortened. Therefore, the voltage applied to the organic EL element cannot be increased excessively.

  FIG. 1 is a schematic sectional view of an optical printer head 1 (Patent Document 1) of a conventional organic EL printer. The optical printer head 1 includes an organic EL panel 3 in which a plurality of organic EL elements 2 are arranged, and a rod lens array 5 for forming an image of light emitted from the organic EL elements 2 on a photosensitive drum 4. . The rod lens array 5 is installed between the organic EL element 2 and the photosensitive drum 4 and is configured by arranging a plurality of rod lenses 6. Each rod lens 6 constituting the rod lens array 5 has, for example, a central portion 6a having a high refractive index, a peripheral portion having a low refractive index cladding portion 6b, and an outer surface having a black coating 6c. Covered by.

  Thus, the light emitted from the organic EL element 2 and incident on the rod lens 6 with a relatively small angle of capture θ is confined in the core portion 6a of the rod lens 6 and guided, and is indicated by a solid arrow in FIG. In this way, the light is projected to a corresponding position on the surface of the photosensitive drum 4.

  However, the light emitted from the organic EL element 2 and incident on the rod lens 6 with a large capture angle θ enters the cladding portion 6b from the core portion 6a and is absorbed by the black coating 6c, as indicated by the broken line arrow in FIG. Will be.

  For this reason, the light that can be taken into the rod lens array 5 among the light emitted from the organic EL element 2 is limited. For example, in SLA-9A of Nippon Sheet Glass Co., Ltd., the light incident on the rod lens array 5 can be taken into the rod lens 6 if the take-in angle θ is within a range of ± 9 degrees or less. Light incident at the capture angle θ cannot be captured and used. Since the organic EL element 2 has a low directivity of light emitted forward and is almost Lambert-distributed, the light emitted within a range of ± 9 degrees or less is the total light emitted from the organic EL element 2. It is only about 20%. Thus, the conventional optical printer head 1 has a problem that the light emitted from the organic EL element 2 cannot be used effectively.

  Moreover, the invention disclosed in Patent Document 2 has been proposed as a solution to such a problem. Specifically, instead of the rod lens array, a hemispherical lens having the same size as each organic EL element is formed on the surface of the surface from which the light of the organic (inorganic) EL element emits, and the light emission direction is aligned. Has been proposed. However, with this method, light emitted from a position deviating from the central axis of the lens is deflected in a direction different from the direction parallel to the central axis and emitted from the lens. Therefore, since such light is not taken into the rod lens array, it is not used effectively. When the rod lens array is not used, the light is incident on a region to be irradiated with light from the adjacent organic EL element. There was a possibility of causing a decrease in resolution.

JP-A 63-103288 JP 2004-58448 A JP 2003-54030 A

  The present invention has been made in view of the technical problems as described above, and an object of the present invention is to provide an amount of light that can be effectively taken into each rod lens without increasing the voltage applied to the organic EL element. It is an object of the present invention to provide an optical printer head capable of increasing the number of times.

  The printer head according to the present invention applies light emitted from the light emitting surface of an organic EL panel formed by arranging a plurality of organic EL elements to a photoconductor via a rod lens array formed by arranging a plurality of cylindrical lenses. In the optical printer head for projecting, an optical sheet having a prism surface on one side of which conical prisms are arranged in an array is disposed with the surface opposite to the prism surface facing the light emitting surface, The light emitted from the light emitting surface is deflected by the optical sheet and is incident on the rod lens array.

  In the printer head of the present invention, the light emitted from the organic EL element can be collected in a direction parallel to the central axis of the rod lens by the prism of the optical sheet. Therefore, it is possible to increase the amount of light incident on the rod lens with an effective take-in angle among the light emitted from the organic EL element, and to increase the intensity of the light projected on the photoconductor. Therefore, the utilization efficiency of the light emitted from the organic EL panel can be increased, and power can be saved when the photosensitive member is exposed with the same light intensity as that of a printer head not provided with an optical sheet. At the same time, the deterioration of the organic EL element can be suppressed (substantial life is increased).

  An embodiment of the printer head of the present invention is characterized in that a low refractive index layer having a refractive index lower than that of the air layer or the optical sheet is provided between the optical sheet and the light emitting surface. In this embodiment, since the low refractive index layer having a lower refractive index than the optical sheet is provided between the optical sheet and the light emitting surface of the organic EL panel, the light emitted from the light emitting surface is the prism surface of the optical sheet. The surface opposite to the surface is also collected in the direction perpendicular to the optical sheet. That is, the light emitted from the light emitting surface can be collected on both the prism surface of the optical sheet and the surface opposite to the prism surface, and the amount of light incident within the effective capture angle of the rod lens can be increased. it can.

  Another embodiment of the printer head of the present invention is characterized in that a low reflection layer is formed on the surface of the optical sheet opposite to the prism surface. According to such an embodiment, since loss due to Fresnel reflection between the optical sheet and the organic EL panel can be reduced, the utilization efficiency of the light emitted from the organic EL element can be improved and projected onto the photoreceptor. The intensity of the emitted light can be made higher.

  The low reflection layer can be formed of a multilayer thin film. If the reflective layer is formed of a multilayer thin film, a non-reflective coating is also possible, so that reflected light can be reduced with high efficiency. When a multilayer thin film is used for the low reflection layer, a multilayer film such as magnesium fluoride or silicon dioxide can be used.

  Further, the low reflection layer may be a concave or convex fine structure formed at an interval equal to or shorter than the wavelength of light emitted from the organic EL element. A microstructure having a concave or convex shape with an interval less than or equal to the wavelength of the emitted light has an average refractive index that is intermediate between the refractive index of air and the refractive index of the optical sheet. The reflectance on the opposite surface can be reduced. Further, in such a low reflection layer, the microstructure can be simultaneously formed when the prism surface is formed, and thus the manufacturing is simplified.

  Still another embodiment of the printer head of the present invention is characterized in that each of the prisms is contained in any region of the organic EL element when viewed from a direction perpendicular to the prism surface of the optical sheet. It is said. According to such an embodiment, since the prism is not disposed across the plurality of organic EL elements, the light emitted from the adjacent organic EL elements is mixed and hardly projected onto the photoconductor. Therefore, the resolution of the latent image on the photoconductor formed through the rod lens array is improved. In addition, if the length of the two sides of each prism is set to 1 / integer of the length of the two sides of the organic EL panel, the prism surface is formed so as not to leave a gap between the prisms. A prism can be arranged and the effect of an optical sheet can be heightened.

  Yet another embodiment of the printer head of the present invention is characterized in that the prism has a quadrangular pyramid shape, and the apex angle of the prism is in the range of 70 degrees to 110 degrees. In this embodiment, since the apex angle of the prism is formed within the range of 70 degrees or more and 110 degrees or less, the light emitted from the prism surface of the optical sheet is efficiently collected by the prism in the direction perpendicular to the optical sheet. Can do.

  Still another embodiment of the printer head according to the present invention is characterized in that a mark or notch for front / back discrimination is formed in a region other than the prism surface of the optical sheet. Since the prism provided on the optical sheet according to the present invention is very fine, it is difficult to discriminate between the front and the back by visual observation. According to such an embodiment, the front / back discrimination mark or the like is observed with a microscope or the like. By doing so, the front and back of the optical sheet can be easily distinguished.

  Still another embodiment of the printer head of the present invention is characterized in that a mark or a notch for alignment with the organic EL panel is formed in a region other than the prism surface of the optical sheet. Since the prism provided on the optical sheet according to the present invention is very fine, it is difficult to discriminate between the front and the back by visual observation. According to such an embodiment, the alignment mark or the like is observed with a microscope or the like. By doing so, the position of each prism can be easily adjusted to the organic EL element.

  The optical printer head according to the present invention can constitute a printer together with a photoconductor and a toner supply unit that supplies toner to the photoconductor. This printer can be used as a printing unit of various devices such as a printing machine, a fax machine, and a copying machine.

  In addition, the component demonstrated above of this invention can be combined arbitrarily as much as possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, it goes without saying that the present invention is not limited to the examples described below.

  FIG. 2 is a perspective view showing the optical printer head 101. FIG. 3 is a schematic diagram showing the optical printer head 101 and the photosensitive drum (photosensitive member) 114. The optical printer head 101 includes an organic EL panel 111, a rod lens array 112, and an optical sheet 113, and the optical sheet 113 is disposed between the organic EL panel 111 and the rod lens array 112. In addition, the organic EL panel 111 and the optical sheet 113 are separated from each other by a distance α1, and an air layer or a low refractive index layer 126 having a lower refractive index than the optical sheet 113 is provided between the organic EL panel 111 and the optical sheet 113. It has become. Further, the distance between the surface of the optical sheet 113 facing the organic EL panel 111 (light incident surface 130) and the surface of the rod lens array 112 facing the optical sheet 113 (light incident surface 141) is set to be a distance α2. ing. In addition, the photosensitive drum 114 is installed such that the distance from the surface (light emitting surface 142) opposite to the light incident surface 141 facing the optical sheet 113 of the rod lens array 112 to the surface of the photosensitive drum 114 is β. Yes.

  FIG. 4 shows a cross-sectional structure of the organic EL panel 111. On one surface of the organic EL panel 111, a plurality of organic EL elements 115 are arranged in a lattice pattern. The organic EL element 115 includes a sealing substrate 121, a transparent electrode 122, a light emitting layer 123, and a back electrode 124, and the light emitting layer 123 of each organic EL element 115 is turned on / off by turning on / off the voltage applied to the transparent electrode 122. Characters and images can be generated by emitting light. That is, the organic EL panel 111 includes a plurality of organic EL elements 115 arranged, and generates characters and images by controlling each organic EL element 115. In addition, the organic EL panel 111 includes an organic EL element 115 arranged in a grid as shown in FIG. 5A, a delta arrangement of the organic EL elements 115 as shown in FIG. 5B, and the like. There is.

  Further, as the material of the organic EL element 115, for example, non-alkali glass having good gas barrier properties, polyethylene terephthalate (PET), or the like can be used for the sealing substrate 121, and indium tin oxide (ITO) is used for the transparent electrode 122. ), Etc., tris (8-quinolinolato) aluminum complex (Alq3) can be used for the light emitting layer, and Al can be used for the back electrode.

  The optical sheet 113 is made of glass (refractive index 1.5), polymethyl methacrylate (PMMA, acrylic) (refractive index 1.49), polyolefin resin (refractive index 1.53, etc.), ultraviolet curable resin (refractive index 1). .37), polycarbonate (PC) (refractive index 1.58), PET (refractive index 1.6), and the like, are formed into a substantially rectangular flat plate shape, and the organic EL panel 111 and the rod lens array 112 are formed. It is arranged between.

  FIG. 6 is a front view of the optical sheet 113. The optical sheet 113 has a flat light incident surface 130 formed on one surface and a light emitting surface 131 formed on the other surface. As shown in FIGS. 7 and 8, the light exit surface 131 is formed with a prism surface 132 on which a plurality of prisms 133 each having a quadrangular pyramid shape are arranged. Then, as shown in FIG. 3, the light incident surface 130 is disposed so as to face the light emitting surface 125 of the organic EL panel 111, and the light emitted from the organic EL panel 111 is deflected by the optical sheet 113. The traveling direction of the light can be collected in a direction perpendicular to the optical sheet 113 relative to the light incident on the optical sheet 113 and emitted to the rod lens array 112 side.

  Further, since the prism 133 formed on the prism surface 132 of the optical sheet 113 is fine, it is difficult to visually distinguish the front and back of the optical sheet 113, that is, the light incident surface 130 and the light emitting surface 131. Therefore, as shown in FIG. 6, a notch 135 is provided in a region other than the prism surface 132 of the optical sheet 113, and the position of the notch 135 differs depending on whether the optical sheet 113 is faced up or down. The light incident surface 130 and the light emitting surface 131 of the sheet 113 can be distinguished visually.

  The prism 133 formed on the prism surface 132 corresponds to each organic EL element 115 in a one-to-one correspondence with each organic EL element 115 when the optical sheet 113 is properly disposed facing the front surface of the organic EL panel 111. Of the prism 133 coincides with the boundary of the prism 133. The sizes of the prisms 133 are equal to each other, and are the same as or smaller than the organic EL element 115. However, in the case where the size of the prism 133 is smaller than the size of the organic EL element 115, the vertical and horizontal dimensions of the prism 133 are respectively the organic EL element in order for the boundary of the organic EL element 115 to coincide with the boundary of the prism 133. It must be an integer fraction of 115 vertical and horizontal dimensions.

  FIG. 9A shows a state in which one prism 133 is arranged so as to overlap each organic EL element 115 arranged in a lattice shape, and FIG. 9B shows the arrangement in a lattice shape. In addition, a plurality of prisms 133 are arranged so as to overlap each organic EL element 115. FIG. 10A shows a state in which one prism 133 is arranged so as to overlap each organic EL element 115 arranged in a delta shape, and FIG. 10B shows a delta shape. A state is shown in which a plurality of prisms 133 are arranged so as to overlap each organic EL element 115 arranged. In particular, when a plurality of prisms 133 are made to correspond to the delta-arranged organic EL elements 115 as shown in FIG. 10B, a plurality of prisms 133 arranged corresponding to one organic EL element 115. Are arranged in a lattice pattern. 9A, 9B and 10A, 10B, the thick line represents the outline of the organic EL element 115.

  For example, in the case of a printer with a resolution of 600 dpi, since one dot (one organic EL element 115) has a side of about 42 μm, one side of the prism 133 is also 42 μm, or 42 μm such as 21 μm and 14 μm. / An integer. Further, it is necessary to align the organic EL panel 111 and the optical sheet 113 so that one prism 133 does not face the two or more organic EL elements 115. As shown in FIG. 7, when the angle formed by the inclined surfaces facing each other of the prism 133 is defined as the apex angle ω, the apex angles ω of the prisms 133 are equal to each other, and the apex angle ω is about 70 to 110 degrees as will be described later. It is set in the range of degrees, more preferably in the range of 80 degrees to 110 degrees. In particular, the prism 133 has the highest light utilization efficiency when its apex angle ω is 90 degrees.

  When the organic EL element 115 has a rectangular shape, the bottom surface of the prism 133 must be rectangular if one or more prisms 133 are arranged without a gap. Therefore, the prism 133 to be used is preferably a pyramid shape as shown in FIG. 11A, but even in the case of the conical prism 133, a part thereof is cut as shown in FIG. If the bottom surface is rectangular, it can be used.

  In the rod lens array 112, a plurality of rod lenses 140 having a columnar shape as shown in FIG. 12 are arranged in accordance with the arrangement of the organic EL elements 115 and prisms 133, and face the prism surface 133 of the optical sheet 113. The light incident surface 141 and the light emitting surface 142 are provided on the opposite side. Further, the light incident surface 141 is composed of an aggregate of one circular surface of each rod lens 140, and the light emitting surface 142 is composed of an assembly of the other circular surface of each rod lens 140. Furthermore, the light incident surface 141 of the rod lens array 112 is installed at a position that is separated from the light incident surface 141 of the optical sheet 113 by a distance α2.

  The rod lens 140 may be one having a gradient distribution so that the refractive index gradually decreases from the center toward the outer periphery in an arbitrary cross section (refractive index distribution type rod lens), and around the core portion having a relatively large refractive index. May be covered with a clad portion having a refractive index smaller than that of the core portion (step type rod lens). The rod lens array 112 functions as a lens that forms an image generated by the organic EL panel 111 at a position separated from the light emitting surface 142 of the rod lens array 112 by a distance β. Accordingly, the distance α2 from the optical sheet 113 to the rod lens array 112 and the distance β from the rod lens array 112 to the surface of the photosensitive drum 114 are both equal to the focal length of the lot lens 140 or the rod lens 140 The distance is about the same as the focal length.

  The photosensitive drum 114 changes the charging polarity at the position where light is irradiated (exposed). Although not particularly illustrated, an image, a character, or the like is printed on paper by adhering toner or the like to the portion where the charging polarity is changed and transferring the toner onto the paper.

  FIG. 13 is a diagram for explaining the behavior of the light emitted from the organic EL panel 111 until it reaches the photosensitive drum 114. When a driving voltage is applied to the organic EL panel 111, the organic EL element 115 where the voltage is applied emits light. The light 185 emitted from the light emitting surface 125 of the organic EL panel 111 has a substantially Lambertian directional characteristic having a spread of about 180 degrees with respect to the light emitting surface 125. Light 185 emitted from the light emitting surface 125 of the organic EL panel 111 and reaching the light incident surface 130 of the optical sheet 113 enters the optical sheet 113. At that time, the light 185 is refracted at the interface between the low refractive index layer 126 and the light incident surface 130, so that the light traveling direction is deflected so that the light 185 is close to the direction perpendicular to the light incident surface 130 of the optical sheet 113. The Further, the light 185 is refracted by the inclined surface of the prism 133 when exiting from the prism surface 132 of the optical sheet 113, and further deflected so as to gather in a direction perpendicular to the light incident surface 130 of the optical sheet 113. Therefore, the light 185 emitted from the light emitting surface 131 of the optical sheet 113 is incident on the rod lens array 112 at a small capture angle θ (incident angle to the rod lens 140) with respect to the central axis of the rod lens 140.

  Of the light 185 incident on the rod lens array 112, light incident at an incident angle narrower than a certain capture angle θ is transmitted through the rod lens array 112 and at a position facing the light emitting position of the organic EL panel 111. 114 is incident. Here, since the light 185 incident on the light incident surface 141 of the rod lens array 112 is collected in a direction parallel to the central axis of the rod lens 140 by the optical sheet 113, the light 185 is more than in the case where the optical sheet 113 is not installed. The light 185 passes through the rod lens array 112 and reaches the photosensitive drum 114. Therefore, the characters and images generated by the organic EL panel 111 are imaged on the surface of the photosensitive drum 114 with a large light intensity, and the latent image is generated on the photosensitive drum 114. Therefore, since it is not necessary to increase the applied voltage of the organic EL panel 111 in order to project strong light on the photosensitive drum 114, the life of the organic EL panel 111 can be extended.

  Next, an example of a method for manufacturing the optical sheet 113 will be described with reference to FIGS. The optical sheet 113 is molded using the upper mold 150 and the lower mold 151. The surface of the lower mold 151 is a flat surface 152 for molding the light incident surface 130 of the optical sheet 113. The upper mold 150 is a pattern molding surface 153 on which a plurality of concave patterns (or convex patterns) 154 for molding the prism surface 132 of the optical sheet 113 is formed.

  Therefore, when the optical sheet 113 is molded, an upper mold 150 and a lower mold 151 are prepared as shown in FIG. Next, as shown in FIG. 14B, the upper mold 150 and the lower mold 151 are opposed to each other, and a thermoplastic resin sheet 158 is sandwiched between the upper mold 150 and the lower mold 151 to apply heat. Then, the concave pattern 154 formed on the upper mold 150 is transferred to one surface of the thermoplastic resin sheet 158, and the flat surface 152 formed on the lower mold 151 is transferred to the other surface of the thermoplastic resin sheet 158. . Thereafter, when the upper mold 150 and the lower mold 151 are opened, the optical sheet 113 is formed by the thermoplastic resin sheet 158 as shown in FIG. Then, a light emitting surface 131 having a prism surface is formed on one surface of the optical sheet 113, and a flat light incident surface 130 is formed on the other surface.

  Here, as a manufacturing method of the upper mold 150 and the lower mold 151, for example, the upper mold 150 and the lower mold 151 are formed by processing a material such as oxygen-free copper. Specifically, the lower mold 151 has a flat surface corresponding to the light incident surface of a rectangular flat plate material by polishing or the like. As shown in FIG. 15 (a), the upper die 150 uses a cutting tool 156 made of diamond at the tip, and moves the cutting tool 156 in the X direction along one surface of a base plate 157 made of oxygen-free copper and having a rectangular flat plate shape. And the groove 154a is cut and the cutting tool 156 is sequentially scanned at a constant pitch in the Y direction to repeat the cutting process. Next, as shown in FIG. 15B, the cutting tool 156 is moved in the Y direction along one surface of the base material 157 to cut the groove 154b, and the cutting tool 156 is sequentially scanned at a constant pitch in the X direction. And repeat the cutting process. As a result, a large number of pyramid-shaped concave patterns 154 corresponding to the prisms 133 of the optical sheet 113 are formed on one surface of the base material 157 by the grooves in the X direction and the grooves in the Y direction, and the upper mold 150 is completed.

  According to this method, the apex angle ω of the prism 133 formed on the optical sheet 113 can be formed in an arbitrary shape by changing the cutting edge angle of the cutting tool 156. Further, by cutting with the cutting depth and pitch of the concave pattern 154 matched to the cutting edge angle of the cutting tool 156, the prism 133 can be formed without a gap.

  For example, if the material of the lower mold 151 is not oxygen-free copper but glass or the like that transmits ultraviolet rays, an ultraviolet curable resin can be used instead of the thermoplastic resin 158. Then, an ultraviolet curable resin is sandwiched between the upper mold 150 and the lower mold 151, and ultraviolet rays are irradiated from the lower mold 151 side, whereby the concave pattern 154 of the upper mold 150 and the flat surface 152 of the lower mold 151 are transferred. The sheet 113 can be manufactured. Further, in this case, since the ultraviolet curable resin is cured by irradiation with ultraviolet rays, it is not necessary to apply heat, and deformation due to the influence of thermal expansion or the like can be suppressed to a small level. Further, the material of the upper mold 150 is not particularly required to be oxygen-free copper as long as it can be cut, and resin, glass, silicon, other metals, and the like may be used.

  Next, the characteristic evaluation result by simulation of the optical printer head in which the optical sheet 113 shown in Example 1 is combined with the rod lens array 112 will be described. First, in order to verify the reliability when evaluating the optical printer head by simulation, the dependence of the light emitted from the optical sheet 113 on the emission angle was compared between the actual measurement and the simulation results. In the actual measurement and simulation, an optical sheet 113 having a refractive index of 1.58 in which prisms 133 each having a square bottom with a side of 20 μm and a quadrangular pyramid shape having an apex angle ω of 70 degrees are arranged in a lattice form vertically and horizontally is used. . This optical sheet 113 was placed in front of the organic EL panel 111 through an air layer, and the dependency of the light emitted from the organic EL panel 111 on the emission angle after passing through the optical sheet 113 was examined.

  FIG. 16 is a diagram showing a comparison of the emission angle dependency by actual measurement and simulation. In FIG. 16, the horizontal axis represents the emission direction of light emitted from the optical sheet, that is, the capture angle θ, and the vertical axis represents the light intensity (arbitrary unit) in each direction. Also, a solid line curve L1 shown in FIG. 16 represents an actual measurement value, and a broken line curve L2 represents a calculation result by simulation. As can be seen from FIG. 16, the calculation result by the simulation reflects the actual measurement value, and hence the evaluation result by the simulation is shown hereinafter.

  First, the emission angle dependency of the light emitted from the light emission surface 131 of the optical sheet 113 was evaluated. The result is shown by a curve L3 in FIG. For this evaluation, the same model as the optical sheet was used. That is, an optical sheet 113 in which square bases having a square bottom with a side of 20 μm, an apex angle ω of 70 degrees, and a refractive index of 1.58 are arranged in a grid pattern vertically and horizontally is used. The optical sheet 113 is installed in front of the organic EL panel 111 through an air layer, and the angle at which the light emitted from the organic EL panel 111 enters the rod lens array 112 after passing through the optical sheet 113. θ was examined.

  The horizontal axis of FIG. 17 represents the capture angle θ of light incident on the rod lens array 112, and the vertical axis represents the efficiency η at the capture angle θ. Here, the efficiency η at the capture angle θ is a value obtained by dividing the light intensity at the capture angle θ when the optical sheet 113 is provided by the light intensity at the capture angle θ when the optical sheet 113 is not provided. It represents.

  As can be seen from FIG. 17, when the optical sheet 113 according to Example 1 is disposed in front of the organic EL panel 111, the efficiency η increases in the region where the angle of incorporation θ into the rod lens array 112 is 50 degrees or less. It can be seen that the efficiency η decreases conversely when the insertion angle θ is 50 degrees or more. In particular, when the capture angle θ is around 9 degrees (this is almost the maximum value of the effective capture angle θ in the rod lens array 112), the efficiency η is greatly increased to about 1.6 to 1.8 times. I understand that

  FIG. 18 shows the efficiency η at the take-in angle θ when the apex angle ω of the prism 133 is changed as a parameter. Curves L4, L5, L6, L7, and L8 shown in FIG. 18 represent the efficiency η when the apex angle ω of the prism 133 is 70 degrees, 80 degrees, 90 degrees, 100 degrees, and 110 degrees, respectively. According to FIG. 18, in the prism 133 having the apex angle ω of 70 degrees to 110 degrees, the capture angle θ is at least 0 degrees to 50 degrees, and the efficiency η is greater than 1, and the prism lens array 112 captures them. It can be seen that the amount of light that can be increased. In particular, it can be seen that the best results can be obtained when the optical sheet 113 having the prism 133 with an apex angle ω of approximately 90 degrees is used.

  A curve L9 shown in FIG. 18 represents a simulation result when the optical sheet 113 is disposed in the reverse direction, that is, when the prism surface 132 is opposed to the organic EL panel 111. The apex angle ω of the prism 133 used for the simulation of the curve L9 is 90 degrees. As can be seen from FIG. 18, when the prism surface 132 of the optical sheet 113 is disposed in the reverse direction toward the organic EL panel 111, the efficiency η is worse than when the optical sheet 113 is not disposed. .

  FIG. 19 is a diagram illustrating the relationship between the efficiency η of the optical sheet 113 and the apex angle ω of the prism 133. Here, an optical sheet 113 is used in which prisms 133 each having a square bottom surface with a side of 20 μm and a square pyramid shape with a refractive index of 1.58 are arranged in a grid pattern vertically and horizontally. Then, when the apex angle ω of the prism 133 was changed from 70 degrees to 110 degrees and the efficiency η at the capture angle θ = 10 degrees was obtained, a curve L10 in FIG. 19 was obtained. From this curve L10, it can be seen that when the take-in angle θ is 10 degrees (near 9 degrees), the apex angle ω is approximately 90 degrees and the efficiency η is the best.

  Next, FIG. 20 shows the result of examining the change in efficiency η when the optical sheet 113 is used while changing the refractive index of the prism 133. Here, an optical sheet 113 is used in which prisms 133 each having a square bottom with a side of 20 μm and an apex angle ω of 70 degrees are arranged in a lattice form vertically and horizontally. Then, the efficiency η was examined using the optical sheet 113 in which the refractive index of the prism 133 was made different from 1.33, 1.49, and 1.58.

  Curves L11, L12, and L13 shown in FIG. 20 represent the efficiency η when using the optical sheet 113 having a refractive index of 1.37, 1.49, and 1.58, respectively. As can be seen from FIG. 20, when the apex angle ω of the prism 133 is the same, the higher the refractive index of the prism 133, the higher the efficiency η can be obtained. Accordingly, the various materials described above can be used as the material of the optical sheet 113, but a higher effect can be expected by using a resin such as PC or PET having a high refractive index.

  Next, ray diagrams of the light 185 transmitted through the optical sheet 113 are shown in FIGS. 21 and 22. FIGS. 21 and 22 are diagrams schematically showing one of the prisms 133 provided on the optical sheet 113 according to the first embodiment as a prism 170, which is formed on the light emitting surface 131 of the optical sheet 113. The prism 133 is represented by both oblique sides 172 of the prism 170, and the light incident surface 130 of the optical sheet 113 is represented by the bottom 171 of the prism 170. FIG. 21 shows the behavior of light emitted from the point light source 180 arranged on the perpendicular bisector 173 of the bottom 171 of the prism 170 (corresponding to the light incident surface 130 of the optical sheet 113 in FIGS. 21 and 22). It is a figure which shows the calculated result. FIG. 22 is a diagram showing the result of calculating the behavior of the light emitted from the point light source 181 arranged at a position shifted from the vertical bisector 173. 23 and 24 show a comparative example in which the behavior of the light 185 is calculated on a two-dimensional plane when a hemispherical lens 174 is used instead of the quadrangular pyramid prism 170 used in the first embodiment. FIG. 23 is a diagram showing a calculation result of the behavior of light emitted from the point light source 182 arranged on the vertical bisector 176 of the base 175 in the cross section of the lens 174, and FIG. It is a figure which shows the result of having calculated the behavior of the light radiate | emitted from the point light source 183 arrange | positioned in the position shifted | deviated from the dividing line 176. FIG.

  As can be seen from FIG. 21, the light emitted from the point light source 180 on the perpendicular bisector 173 of the base 171 of the prism 170 having a quadrangular pyramid shape passes through the prism 170, and thereby the vertical two of the base 171. It is deflected in a direction parallel to the equipartition line 173. Similarly, as can be seen from FIG. 23, the light emitted from the point light source 182 on the vertical bisector 176 of the base 175 of the hemispherical lens 174 passes through the lens 174, thereby It is deflected in a direction parallel to the vertical bisector 176.

  On the other hand, in the case of the prism 170 having a quadrangular pyramid shape as shown in FIG. 22, even if the point light source 181 is displaced from the vertical bisector 173 of the prism 170, the light emitted from the hypotenuse 172 of the prism 170 is It is emitted in a direction parallel to the vertical bisector 173 to some extent. On the other hand, in the case of a hemispherical lens 174 as shown in FIG. 24, when the point light source 183 is displaced from the vertical bisector 176 of the lens 174, the light emitted from the lens 174 is almost perpendicular. It can be seen that the light is not emitted in a direction parallel to the equisegmentation line 176.

  Therefore, it can be seen that the use efficiency of light is improved by using the prism 170 having a quadrangular pyramid shape rather than using the lens 174 having a hemispherical shape.

  Thus, in the optical printer head 101 according to the first embodiment, the light emitted from the organic EL element 115 is deflected by the optical sheet 113 and collected within a narrow range of the capture angle, and the rod lens array 112 is efficiently collected. Since it can be taken in, the light usage efficiency is excellent. Further, the luminance in the direction perpendicular to the rod lens array 112 can be improved without changing the applied voltage. In addition, when the brightness of the same level as that of the conventional optical printer head is sufficient, the applied voltage can be lowered, so that power saving and long life of the organic EL can be achieved.

  In addition, since light emitted from the optical sheet 113 in an unnecessary direction does not pass through the rod lens array 112, the light emitted in an unnecessary direction enters the region of the photosensitive drum 114 to be irradiated by the adjacent organic EL element 115. The incident light is exposed and the resolution is not lowered.

  Note that, if the distance α1 between the organic EL panel 111 and the optical sheet 113 becomes too large, light beam interference occurs in front of the optical sheet 113. Therefore, it is preferable that the distance α1 be as close as possible while sandwiching an air layer. . Further, since the refractive index differs between the air layer and the light incident surface 130 of the optical sheet 113 by sandwiching the air layer, the light can be deflected by the light incident surface 130 of the optical sheet 113 (FIG. 13). reference).

  In the second embodiment, the manufacturing method of the upper mold and the lower mold used when manufacturing the optical sheet 113 is different from the manufacturing method of the upper mold 150 shown in the first embodiment. A method for manufacturing the upper mold 190 will be described with reference to FIGS. The upper mold 190 according to the second example is a replica mold produced by using the upper mold 150 produced in the first example and using a technique such as photolithography.

  First, in the same manner as the upper mold 150 of Example 1 (see FIGS. 15A and 15B), a concave pattern 192 is formed using a cutting tool 156 having a diamond tip, and the mold master 191 of the upper mold 190 is formed. It is produced (FIG. 25 (a)). However, the wedge-shaped concave pattern 192 is formed so as to be shifted from the upper mold 150 shown in the first embodiment by ½ pitch. Next, as shown in FIG. 25B, nickel or the like is formed on the concave pattern 192 formed on the mold original plate 191 by electroforming, and the mold original plate 191 is peeled off. The upper mold 190 having the pattern 154 is obtained (FIG. 25C).

  Since the upper mold 190 manufactured in this way is made of a material such as hard nickel, it is less likely to be consumed during the production of the optical sheet 113 than the upper mold 150 made of oxygen-free copper shown in the first embodiment. Therefore, the cost at the time of mass production can be reduced. Further, since the optical sheet 113 is not manufactured by using the mold master 191, even when the upper mold 190 is consumed, the upper mold 190 can be easily copied from the stored mold master 191 again by electroforming. it can.

  Although the upper mold 190 is described in the second embodiment, the lower mold is manufactured by preparing a rectangular flat plate made of the same material as that of the upper mold 190 and by polishing in the same manner as in the first embodiment. Alternatively, it may be manufactured by an electroforming method in the same manner as the manufacturing method of the upper mold 190 shown in the second embodiment.

  The third embodiment is different from the first embodiment in the manufacturing method of the upper mold used when the optical sheet 113 is manufactured. A method of manufacturing the upper mold 193 according to the example 3 will be described with reference to FIGS. The upper mold 193 according to Example 3 is produced by producing a mask for dry etching using the upper mold 150 produced in Example 1 and dry etching the base material 194.

  First, a concave pattern 195 is formed using a cutting tool 156 made of diamond at the tip in the same manner as the upper mold 150 of Example 1 (see FIGS. 15A and 15B), and a mold master 196 of the upper mold 193 is produced. (FIG. 26A). However, the wedge-shaped concave pattern 195 is formed so as to be shifted from the upper mold 150 shown in the first embodiment by ½ pitch. At the same time, as shown in FIG. 26 (b), a material in which an ultraviolet curable resin 197 is applied on a base material 194 capable of dry etching such as glass is prepared. For the base material 194 and the cured UV curable resin 197 (etching mask 198), materials that can make the etching rate of dry etching equal are selected. As shown in FIG. 26C, the ultraviolet curable resin 197 is cured by pressing the concave pattern 195 of the mold master 196 against the ultraviolet curable resin 197 and irradiating it with ultraviolet rays. If the mold master 196 is peeled off when the UV curable resin 197 is sufficiently cured, a substrate in which an etching mask 198 having a pyramidal convex pattern 199 is formed on the base material 194 as shown in FIG. . Next, etching is performed from the surface of the base material 194 where the etching mask 198 is formed until the etching mask 198 is completely removed by dry etching (FIG. 26E). Since the base material 194 and the etching mask 198 have the same etching rate, a pyramidal concave pattern in which the pyramidal convex pattern 199 of the etching mask 198 is transferred to the base material 194 as shown in FIG. An upper mold 193 having 200 is obtained.

  Note that the etching mask 198 may be made of a thermoplastic resin or a thermosetting resin that can be dry-etched. In this case, the base material 194 can be an opaque material that can be dry etched.

  Since the upper mold 193 produced in this way is produced by duplicating the mold original plate 194, each upper mold 193 is compared with one produced by cutting a single upper mold 193 by a cutting tool or the like. The variation of can be reduced. Therefore, when a large amount of the upper mold 193 having the same concave pattern 199 is used for mass production or the like, it is possible to reduce the variation among lots and the variation among manufacturing lines.

  The fourth embodiment is different in the method of forming the upper mold 150 for forming the optical sheet 133 shown in the first embodiment. The manufacturing method of the upper mold 201 according to the example 4 is that the upper mold 201 is manufactured by anisotropic etching of silicon crystal. A method for manufacturing the upper mold 201 will be described with reference to FIGS.

  First, as shown in FIGS. 27A and 27B, a resist pattern 203 is formed on the silicon substrate 202 by photolithography so that an appropriate concave pattern is formed. Next, as shown in FIG. 27C, anisotropic etching of the silicon substrate 202 is performed to form a concave pattern 204. If the resist pattern 203 is removed, an upper mold 201 made of silicon can be obtained (see FIG. 27D).

  The lower mold may be manufactured by polishing silicon in the same manner as in the first embodiment, or when forming a pattern on the lower mold, the upper mold 201 shown in the fourth embodiment is used. Similar to this manufacturing method, it may be manufactured by anisotropic etching of silicon.

  However, due to the anisotropic etching process of silicon, the silicon pattern cannot be completely etched at the portion where the resist pattern 203 is formed. Therefore, in the optical sheet 206 formed using the upper mold 201, a gap portion 208 having a constant interval δ is formed between adjacent prisms 207 as shown in FIGS. 28 (a) and 28 (b). For example, when a gap portion 208 having a spacing δ of 1.2 μm is formed for a prism 207 having a square pyramid shape with a base of 20 μm square, about 6% of the total becomes the gap portion 208. Furthermore, the smaller the size of the prism 207 of the quadrangular pyramid, the larger the proportion of the area of the gap portion 208 becomes, and the proportion of the prism 207 in the entire prism surface 209 decreases, and the organic EL panel 111. The effect of refracting the light 185 emitted from the light beam becomes small. Further, although the area of the gap 208 can be reduced, it is difficult to control and causes a decrease in yield. Therefore, it is not suitable for production of the optical sheet 113 that requires high resolution. Further, when the upper mold 201 is manufactured by using anisotropic etching of silicon, the shape of the quadrangular pyramid is determined by the crystal orientation of the silicon, so that the upper mold 201 having the apex angle ω of 70.5 degrees is manufactured. However, there is a limitation that it cannot be produced at any other apex angle ω and the efficiency η cannot be optimized. However, it is effective when manufacturing the optical sheet 113 that does not require relatively high accuracy.

  The optical sheet 220 according to the fifth embodiment is different from the front / back discriminating means of the optical sheet 113 according to the first embodiment. FIG. 29 is a plan view of the optical sheet 220 according to the fifth embodiment. As with the optical sheet 113, the optical sheet 220 has a light incident surface (not shown) formed on one surface and a light output surface 225 formed on the other surface. Further, a prism surface 226 in which a plurality of prisms 227 are formed is formed on the light emitting surface 225. On the other hand, the notch 135 is not formed on the outer periphery of the optical sheet 220. Instead, an alignment mark 228 is provided in a region where the prism surface 226 of the light emitting surface 225 of the optical sheet 220 is not formed. Further, when a plurality of alignment marks 228 are provided, they are arranged so as not to be point symmetric or line symmetric.

  If the alignment mark 228 is formed with a pattern corresponding to the alignment mark 228 on the mold in the same manner as the prism 227 and is formed simultaneously with the formation process of the prism 227, the manufacturing process can be reduced. . Furthermore, if the cross-sectional shape of the alignment mark 228 is a quadrangular pyramid shape and a hemispherical convex shape or concave shape similar to the cross section of the prism 227, the optical sheet 220 is visually observed due to the difference in the brightness of transmitted light due to light refraction. You can check the front and back. Further, the alignment mark 228 can be used as a reference for alignment between the optical sheet 220 and the organic EL panel 111.

  As a modification, a through hole 229 may be provided in the outer peripheral portion of the light emitting surface 225 other than the region of the prism surface 226 like the optical sheet 221 shown in FIG. Further, a notch 230 (notch) 230 may be provided as in the optical sheet 222 shown in FIG.

  In the optical sheet 113 according to the first example, the light incident surface 130 is formed to be a flat surface, so that light emitted from the light emitting surface 125 of the organic EL panel 111 is reflected by the light incident surface 130 of the optical sheet 113 by Fresnel reflection. And is not incident on the optical sheet 113, and therefore, a light loss is caused accordingly. Therefore, there is a possibility that the light utilization efficiency is deteriorated. The optical sheet 240 according to the sixth example prevents reflection at the light incident surface 241 of the optical sheet 240 and further increases the light use efficiency. FIG. 31 is a cross-sectional view of the optical sheet 240 according to the sixth embodiment.

  The optical sheet 240 according to the sixth example is obtained by providing a fine convex or concave antireflection pattern 242 on the light incident surface 130 of the optical sheet 113 shown in the first example. The convex or concave antireflection patterns 242 are arranged at intervals shorter than the wavelength of the light emitted from the organic EL element 115. When the fine convex or concave antireflection pattern 242 is formed at an interval shorter than the wavelength of light, the refractive index of the layer is the region where the refractive index is 1 (air in the concave portion) and the refractive index of the optical sheet 240 is refracted. Since a region equal to the refractive index (the convex portion of the optical sheet 240) is mixed, the refractive index of the layer provided with the antireflection pattern 242 is an intermediate refractive index between the refractive index of the optical sheet 240 and the refractive index of air. Can be considered. Therefore, it functions in the same manner as when the low refractive index layer is provided on the light incident surface 130 of the optical sheet 240, and the incident light is not easily reflected by the light incident surface 130 of the optical sheet 240. In addition, since the antireflection pattern 242 can be formed at the same time when the prism surface 132 of the prism 133 is formed on the optical sheet 240, the optical sheet 240 can be easily manufactured.

  As a modification, a low reflection layer 246 in which a multilayer film such as magnesium fluoride or silicon dioxide is formed by vapor deposition or sputtering is provided on the light incident surface 130 of the optical sheet 113 as in the optical sheet 245 shown in FIG. The same effect as the optical sheet 240 can be obtained. In such a multilayer film, a non-reflective coating can be used, and thus a high antireflection effect can be obtained.

  Although not shown, a so-called airgel layer may be attached to the back surface of the optical sheet, or airgel may be filled between the optical sheet and the organic EL panel. An airgel is a transparent porous body in which minute bubbles are dispersed in a matrix. Regarding the airgel, for example, Japanese Patent Application Laid-Open No. 2005-37927, Japanese Patent Application Laid-Open No. 2004-195567, Japanese Patent Application Laid-Open No. 2003-119052, Sakuo Sakuo, “Application of Sol-Gel Method” (Agne Jofusha, 1997) Pp. 42-47).

  A printer 250 according to the seventh embodiment incorporates the optical printer head described above. FIG. 33 shows a configuration diagram of the printer 250. The operation of the printer 250 will be described with reference to FIG. The paper 251 to be printed flows in the direction of arrow A, and the photosensitive drum 252 rotates in the direction of arrow B. Initially, the surface of the photosensitive drum 252 includes a positively charged portion and a negatively charged portion. When the surface is in contact with the charging roller 253, the entire surface is electrically negatively charged.

  Next, a character or image to be printed is written as a latent image on the photosensitive drum 252 by the optical printer head 254. That is, the portion where the organic EL element emits light corresponding to the character or image data to be printed and the light of the photosensitive drum 252 is irradiated is positively charged, and the other portions remain negatively charged.

  Next, the toner 256 is attached to the surface of the photosensitive drum 252 by the developing device 255, but the toner 256 is negatively charged and is attached only to the positively charged portion of the photosensitive drum 252.

  The transfer machine 257 is charged positively more strongly than the surface of the photosensitive drum 252, and the negatively charged toner 256 adheres to the paper 251 as it moves toward the transfer machine 257. The paper 251 to which the toner 256 is attached is sent in the direction of arrow A, and heat and pressure are applied by the fixing device 258, whereby the toner 256 is fixed on the paper 251 and printed. The toner 256 remaining in the cleaner 259 is dropped on the photosensitive drum 252, and is contacted with the charging roller 253 again to be charged. Characters and images are printed on the paper 251 by repeating this cycle.

It is sectional drawing which showed the optical system of the conventional organic EL printer. 1 is a perspective view of an optical printer head according to Embodiment 1. FIG. 1 is a cross-sectional view of an optical system of a printer according to Example 1. FIG. It is sectional drawing to which some organic EL panels used for the optical system of the printer same as the above were expanded. (A), (b) is the figure which showed arrangement | positioning of the organic EL element currently formed in the organic EL panel same as the above. 3 is a top view of an optical sheet used in the optical printer head according to Example 1. FIG. It is sectional drawing of an optical sheet same as the above. It is a perspective view of the optical sheet of FIG. (A), (b) is a front view which shows the prism arrange | positioned with respect to the organic EL element arrange | positioned at a grid | lattice form. (A), (b) is a front view which shows the prism arrange | positioned with respect to the organic EL element arrange | positioned in delta form. (A) is a perspective view of a prism having a pyramid shape, and (b) is a perspective view showing a cylindrical prism partially cut away. 1 is a perspective view of a rod lens array used in an optical printer head according to Example 1. FIG. FIG. 4 is a cross-sectional view for explaining the behavior of light in the optical system of the printer of FIG. 3. (A)-(c) is a figure for demonstrating the manufacturing process of the optical sheet used for the optical system of the printer of Example 1. FIG. (A), (b) is a figure for demonstrating the manufacturing process of the type | mold used in order to manufacture the optical sheet same as the above. It is the figure which compared the output angle dependence of the light radiate | emitted from the organic electroluminescent panel by the result of measurement and simulation. It is the figure which showed the calculation result which evaluated the output angle dependence of the light radiate | emitted from the light-projection surface of an optical sheet. It is the figure which showed the relationship between the taking angle (theta) to the rod lens array and efficiency (eta) when changing the vertex angle (omega) of the prism formed in the optical sheet. It is the figure which showed the relationship of efficiency (eta) when changing the apex angle (omega) of a prism in case the taking-in angle (theta) to a rod lens array is 10 degree | times. It is the figure which showed the relationship between the taking angle (theta) to the rod lens array and efficiency (eta) when changing the refractive index of the material of an optical sheet. It is a figure which shows the result of having calculated the behavior with the light radiate | emitted from the perpendicular | vertical which passes along the center of the bottom face of a quadrangular pyramid in the prism of a quadrangular pyramid shape. It is a figure which shows the result of having calculated the behavior with the light radiate | emitted from the position which remove | deviated from the perpendicular | vertical line which passes along the center of the bottom face of a square pyramid in a square pyramid shaped prism. It is a figure which shows the result of having calculated the behavior of the light radiate | emitted from the perpendicular line which passes along the center of the bottom face of a hemispherical lens in a hemispherical lens. It is a figure which shows the result of having calculated the behavior of the light radiate | emitted from the position which remove | deviated from the perpendicular | vertical line which passes along the center of a hemispherical lens bottom surface in a hemispherical lens. (A)-(c) is a figure explaining the manufacturing method of the type | mold for optical sheet manufacture concerning Example 2. FIG. (A)-(e) is a figure explaining the manufacturing method of the type | mold for optical sheet manufacture concerning Example 3. FIG. (A)-(d) is a figure explaining the manufacturing method of the type | mold for optical sheet manufacture concerning Example 4. FIG. (A) is sectional drawing of the optical sheet manufactured using the type | mold same as the above. (B) is a top view of the optical sheet manufactured using the same mold. 10 is a top view of an optical sheet according to Example 5. FIG. (A), (b) is a top view which shows the modification of the optical sheet concerning Example 5. FIG. 10 is a cross-sectional view of an optical sheet according to Example 6. FIG. FIG. 10 is a cross-sectional view showing a modification of the optical sheet according to Example 6. FIG. 10 is a schematic cross-sectional view illustrating the configuration of a printer according to Example 7;

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical printer head 102 Optical system 112 Rod lens array 113 Optical sheet 114 Photosensitive drum 125 Light emission surface 130 Light incident surface 131 Light output surface 132 Prism surface 133 Prism 135 Notch part 140 Lot lens 141 Light incident surface 142 Light output surface 250 Printer 251 Paper 252 Photosensitive drum 253 Charging roller 254 Optical printer head 255 Developer 256 Toner 257 Transfer machine 258 Fixing machine 259 Cleaner

Claims (10)

In an optical printer head for projecting light emitted from a light emitting surface of an organic EL panel formed by arranging a plurality of organic EL elements onto a photoconductor via a rod lens array formed by arranging a plurality of cylindrical lenses,
An optical sheet having a prism surface on one side of which prismatic prisms are arranged in an array, is disposed with the surface opposite to the prism surface facing the light emitting surface,
An optical printer head characterized in that light emitted from the light emitting surface is deflected by the optical sheet and is incident on the rod lens array.   The optical printer head according to claim 1, wherein an air layer or a low refractive index layer having a lower refractive index than that of the optical sheet is provided between the optical sheet and the light emitting surface.   The optical printer head according to claim 1, wherein a low reflection layer is formed on a surface of the optical sheet opposite to the prism surface.   The optical printer head according to claim 3, wherein the low reflection layer is a multilayer thin film.   4. The optical printer head according to claim 3, wherein the low reflection layer is a concave or convex fine structure formed at intervals equal to or less than a wavelength of light emitted from the organic EL element.   2. The optical printer head according to claim 1, wherein each of the prisms is accommodated in any region of the organic EL element when viewed from a direction perpendicular to the prism surface of the optical sheet.   2. The optical printer head according to claim 1, wherein the prism has a quadrangular pyramid shape, and an apex angle of the prism is in a range of 70 degrees to 110 degrees.   2. The optical printer head according to claim 1, wherein a mark or notch for front / back discrimination is formed in a region other than the prism surface of the optical sheet.   The optical printer head according to claim 1, wherein a mark or a notch for alignment with the organic EL panel is formed in a region other than the prism surface of the optical sheet.   A printer comprising the optical printer head according to claim 1, a photoconductor, and a toner supply unit that supplies toner to the photoconductor.

Images