JP4631662B2 - Surface light source device, optical member, original reading device using the optical member, and surface light source device - Google Patents

Description

  The present invention relates to a surface light source device. The present invention also relates to an optical member, a document reading device using the optical member, and a surface light source device.

  2. Description of the Related Art Conventionally, there has been proposed a lighting device including an electroluminescence element (hereinafter, the electroluminescence element may be referred to as an EL element) as a backlight of a liquid crystal display device. The light emitted from the EL element is emitted in all directions. Accordingly, in an illuminating device in which an EL element is formed on a transparent substrate, the angle of light incident on the transparent substrate from the EL element varies, and a part of the light incident on the transparent substrate is an emission surface of the transparent substrate. And cannot be emitted from the transparent substrate. That is, there is a problem in that the efficiency of extracting light incident on the transparent substrate from the EL element from the transparent substrate is low.

  As a technique for improving this problem, an EL element in which a microlens array element is provided on a light emitting surface of a transparent substrate has been proposed (for example, see Patent Document 1). As shown in FIG. 7, the EL element 50 includes a transparent substrate 51, a transparent electrode 52 formed on the lower surface of the transparent substrate 51, an EL light emitting layer 53 formed on the lower surface of the transparent electrode 52, and an EL light emitting layer. The rear surface electrode 54 is formed on the lower surface of 53, and the minute lens array element 55 is provided on the emission surface of the transparent substrate 51. The micro lens array element 55 is composed of a large number of conical or quadrangular pyramidal lens elements 55a formed adjacent to each other.

  In addition, the liquid crystal device includes a liquid crystal panel and an illuminating device, and the illuminating device includes a light emitting unit using an EL element as a light source, and a prism sheet disposed on the light emitting unit, and configures the light emitting unit. There has been proposed a liquid crystal device in which scattering means for scattering light is provided on the light emitting surface side of an EL element (see, for example, Patent Document 2). At least one surface side of the prism sheet is a prism surface having a prism shape for condensing the light emitted from the light emitting section, and the apex angle of the prism is 95 ° or more and 125 ° or less.

  A facsimile, a copy, a scanner, and the like have a document reading device that reads information described in a document. In the document reading apparatus, light from a light source is irradiated onto a document, and light reflected by the document is received by a sensor. Then, information written on the original is read based on the intensity of the received light.

  In recent years, there has been an increasing demand for miniaturization of devices such as facsimiles, and accordingly, it has become necessary to reduce the size of document reading devices used for facsimiles and the like. At the same time, there is a strong demand for shortening the time for reading a document and improving the read image quality, and it is also necessary to increase the light from the light source used in the document reading apparatus.

In order to satisfy these requirements at the same time, for example, in the document reading apparatus described in Patent Document 1, a long EL (electroluminescence) element is used as an illumination light source in the document reading apparatus, and light from the EL element is used as the illumination light source. As a light guide for obliquely guiding in the width direction and condensing on the reading part, a prism array formed by arranging a number of long micro prisms in parallel with the EL elements and collecting them in a flat plate shape is used. The prism array is placed in parallel to the glass plate directly under the glass plate. As a result, the size of the apparatus is reduced and the read image quality is improved.
JP 2003-59641 A (paragraph [0008] of the specification, FIGS. 1 and 3) JP 2003-75834 A (paragraph [0009] of the specification, FIG. 1) Japanese Patent Laid-Open No. 6-217083

  In the configuration of Patent Document 1, only the light having a specific incident angle is emitted from the transparent substrate 51 in the front direction (upward in FIG. 7) by the microlens array elements 55 regularly arranged. The light repeats total reflection on the light emitting surface and reflection on the back electrode 54 (metal electrode) or emits light in directions other than the front direction. Therefore, since there is a lot of light emitted in the direction other than the front direction, it is difficult to increase the luminance.

  Further, in the illumination device having the configuration of Patent Document 2, the scattering means is provided on the light emitting surface side of the EL element, and after the light extraction efficiency is improved by the scattering means, the extracted light is collected by the prism sheet. Is shining. For this reason, it is easy to increase the brightness as compared with the configuration of Patent Document 1. However, Patent Document 2 uses only one prism sheet.

  As a method of further increasing the front luminance of the lighting device using a prism sheet in which periodic irregularities in the shape of side triangular waves are formed as described in Patent Document 2, the light emission surface of the light emitting unit is A configuration in which two prism sheets are arranged so that the extending directions of the prisms are orthogonal to each other is conceivable. When this configuration is used, the front luminance is highest when the apex angle of the prism of each prism sheet is 90 °. On the other hand, in the illuminating device having this configuration, out of the light emitted from the light emitting surface of the light emitting unit, the light emitted in the polar angle near 50 ° is condensed by the prism sheet and emitted in the front direction. ing. Therefore, in order to further increase the brightness, it is necessary to increase the amount of light emitted from the light emitting unit in the direction near 50 ° at the polar angle. However, in the scattering means provided on the light extraction surface described in Patent Document 2, since the light emitting unit emits light in various directions, a large amount of light is emitted in a polar angle near 50 °. I can't do it. Therefore, it is difficult to further increase the brightness.

  The present invention has been made in view of the above-mentioned conventional problems, and the purpose thereof is to increase the proportion of light emitted from the prism sheet in the front direction out of the light incident on the two prism sheets, An object of the present invention is to provide a surface light source device capable of increasing the luminance in the front direction as compared with the conventional device.

  In addition, when an optical member such as a prism array for condensing light from an EL element as described in Patent Document 3 is used, the luminance in the condensing direction can surely be improved. On the contrary, the illuminance at the reading portion of the target document may decrease. This is because the light from the EL element is attenuated while passing through the optical member.

In addition, when an optical member such as a diffusion sheet for extracting light from the EL element is used, light can be extracted efficiently and light utilization efficiency can be improved, but the light is extracted in a specific direction. I can't. This is because light from the EL element is diffused by the diffusion sheet, and a large amount of light cannot be extracted only in a specific direction (in the original reading apparatus, the original reading portion).
The present invention has been made in view of the above-described problems, and an object thereof is to provide an optical member that can extract light in a specific direction, and such an optical member is used. An original reading apparatus is provided.

  In order to achieve the above object, an invention according to claim 1 is a surface light source device including a light emitting unit and two prism sheets in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch. The light emitting unit includes an electroluminescent element and a plurality of three-dimensional optical elements provided on the light emitting surface side of the light emitting unit, and the electroluminescent element includes an anode, a light emitting layer, and a cathode. Yes. The two prism sheets are arranged on the light extraction side of the surface light source device so that the extending directions of the prisms are orthogonal to each other, and the light emitting unit has an azimuth angle with respect to the extending direction of the prisms of the prism sheet. The polar angle has a peak at 30 ° to 70 ° with respect to the average luminous intensity in four directions forming 45 °. Here, the “polar angle” means an angle formed with a direction perpendicular to the light emitting surface of the light emitting unit. For example, light emitted perpendicularly from the light emitting surface has a polar angle of 0 °.

  In the present invention, in the light emitted from the light emitting part, the light emitted in the direction near the polar angle of 50 ° can be increased, and the luminance in the front direction of the surface light source device when two prism sheets are used can be increased. It can be higher than the conventional device.

  According to a second aspect of the present invention, there is provided a surface light source device including a light emitting unit and two prism sheets each having a prism having an apex angle of 90 ° formed in parallel at a predetermined pitch. The light emitting unit includes an electroluminescence element and a plurality of three-dimensional optical elements each having a rectangular virtual bottom surface provided on the light emitting surface side of the light emitting unit. The electroluminescence element includes an anode, a light emitting layer, And a cathode. The two prism sheets are arranged on the light extraction side of the surface light source device so that the extending directions of the prisms are orthogonal to each other, and the light emitting unit is a direction in which one side of the virtual bottom surface of the optical element extends. The polar angle has a peak at 30 ° to 70 ° with respect to the average luminous intensity in four directions that form an azimuth angle of 45 °.

  Also in this invention, in the light emitted from the light emitting part, the light emitted in the direction near the polar angle of 50 ° can be increased, and the luminance in the front direction of the surface light source device when two prism sheets are used can be increased. It can be higher than the conventional device.

According to a third aspect of the present invention, in the first or second aspect of the present invention, at least a part of the plurality of optical elements has a rectangular virtual bottom surface and faces two opposing triangular side surfaces. It consists of a pentahedron with two asymmetric trapezoidal sides .

According to the present invention, light can be extracted from the four triangular side surfaces and the four trapezoidal side surfaces, so that light can be extracted in a specific direction.

The invention according to claim 4 is the invention according to claim 3, wherein at least a part of the plurality of optical elements is perpendicular to the bonding line of the trapezoidal side surface and is one bottom of a triangle in a cross section perpendicular to the virtual bottom surface. When the angle is the angle θ3 and the other base angle is the angle θ4, the angles θ3 and θ4 satisfy the following relationship.
Angle θ3 <angle θ4.

Also in the present invention, light can be extracted in a specific direction by configuring the optical element with a pentahedron having a rectangular virtual bottom surface and satisfying a specific condition.

According to a fifth aspect of the invention, in the invention of the third or fourth aspect, all the optical elements have the same shape.

The invention according to claim 6 is the invention according to any one of claims 3 to 5, wherein the virtual bottom surface of the optical element is a square.

The invention described in claim 7 is the invention described in any one of claims 3 to 6, wherein the plurality of optical elements are arranged in a matrix.

The invention according to claim 8 is the invention according to claims 3 to 7, in which the optical element includes one of the base angles of the trapezoid in the cross section perpendicular to the virtual bottom surface including the joining line of the two trapezoidal side surfaces. When the other base angle is angle θ2, orthogonal to the joining line of the trapezoidal side surface, and one base angle of the triangle in the cross section perpendicular to the virtual bottom surface is angle θ3 and the other base angle is angle θ4, the angle θ1, θ2, θ3, and θ4 satisfy the following relationship.
10 ° ≦ angle θ3 ≦ 25 °
45 ° ≦ angle θ4 ≦ 85 °
60 ° ≦ angle θ1 + angle θ2 ≦ 130 °

In the present invention, by forming the optical element by a pentahedron having a rectangular virtual bottom surface and satisfying a specific condition, in the light emitted from the light emitting unit, the light emitted in the direction near the polar angle of 50 ° may be increased. In addition, the luminance in the front direction of the surface light source device when two prism sheets are used can be increased as compared with the conventional device.

The invention according to claim 9, which is another invention of the present application, is a document reading device having the surface light source device according to any one of claims 4 to 8, wherein a transparent plate on which a document is placed; A sensor that reads light reflected from a portion to be read of the document, and the surface light source device is scanned along the transparent plate, the electroluminescence element is formed in a linear shape, and the plurality of optical elements The element is arranged so that the joining line on the trapezoidal side surface is parallel to the longitudinal direction of the electroluminescence element, and the reading target portion of the base angle of the triangle in the cross section perpendicular to the virtual bottom surface The base angle closer to is an angle θ4, and the other base angle is an angle θ3.

According to a tenth aspect of the invention, in the ninth aspect of the invention, the angle θ3 increases as the plurality of optical elements are arranged from the side closer to the reading target portion to the side farther from the reading target portion.

According to an eleventh aspect of the present invention, in the invention according to the ninth or tenth aspect, two illumination devices are provided symmetrically with respect to the sensor. By providing two illumination devices symmetrically with respect to the sensor, the illuminance on the document can be further increased.

  According to the present invention, it is possible to increase the proportion of light emitted from the prism sheet in the front direction out of the light incident on the two prism sheets, and to increase the luminance in the front direction as compared with the conventional device.

  Furthermore, according to the present invention, it is possible to provide an optical member that can extract light in a specific direction, and a document reading device and a surface light source device using such an optical member.

(First embodiment)
Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. 1A is a schematic diagram of a surface light source device, FIG. 1B is a partial schematic perspective view of FIG. 2A, FIG. 2A is a plan view of an optical element, and FIG. 1B is a BB line of FIG. Sectional drawing and (c) are CC sectional view taken on the line of (a). FIG. 1A schematically shows the configuration of the surface light source device. For convenience of illustration, some dimensions are exaggerated for easy understanding. The ratio of dimensions such as length and thickness is different from the actual ratio. Further, hatching is omitted in FIGS. 2 (b) and 2 (c).

As shown in FIG. 1A, the surface light source device 10 includes a light emitting unit 23 and two prism sheets 22.
The light emitting unit 23 includes a substrate 11 and an organic EL element 12 as an electroluminescence element provided on the surface of the substrate 11 opposite to the light emitting side. In this embodiment, a transparent glass substrate is used as the substrate 11.

  The organic EL element 12 is formed by sequentially laminating a first electrode 13, an organic EL layer 14 including a light emitting layer, a second electrode 15, and a protection unit 16 from the substrate 11 side. The organic EL element 12 constitutes a so-called bottom emission type organic EL element in which light from the organic EL layer 14 is extracted (emitted) from the substrate 11 side. The first electrode 13 and the second electrode 15 are constituted by, for example, solid electrodes. In this embodiment, the first electrode 13 constitutes an anode and the second electrode 15 constitutes a cathode.

  The first electrode 13 is formed of a known transparent conductive material. For example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), SnO2 (tin oxide), or the like is used. Can be used.

The organic EL layer 14 is formed in a single layer or a multilayer using a known organic EL material, and is configured according to a target emission color of the organic EL element 12.
For the second electrode 15, a conventionally known cathode material, a material similar to the first electrode 13, or the like can be used. For example, a metal such as aluminum, gold, silver, copper, or chromium, or an alloy thereof is used. . In this embodiment, aluminum having light reflectivity is used.

  The organic EL element 12 is provided with a protection unit 16 for protecting the organic EL layer 14 from oxygen and moisture. In this embodiment, the protection unit 16 is formed of a known passivation film, for example, a silicon nitride film. Has been.

  Moreover, as shown to Fig.1 (a), the light emission part 23 is equipped with the optical element sheet | seat 17 as an optical member in the surface at the side of the light emission of the board | substrate 11. As shown in FIG. As shown in FIG. 1B, the optical element sheet 17 is provided with a plurality of optical elements 18 in a matrix.

  The optical element sheet 17 is formed of a transparent material and is bonded to the substrate 11 via an adhesive (not shown) on the surface opposite to the surface on which the optical element 18 is formed. In this embodiment, the optical element sheet 17 is formed of a transparent resin, for example, acrylic, polyethylene, polycarbonate, or the like, and each optical element 18 is manufactured by a mold. As the adhesive, an ultraviolet curable adhesive or a polymer adhesive having a refractive index that is the same as or close to the refractive index of the optical element sheet 17 is used. “Near refractive index” means that the difference in refractive index is within several percent.

  As shown in FIGS. 2A, 2B, and 2C, each optical element 18 has a rectangular virtual bottom surface, two opposing triangular side surfaces 19a and 19b, and two opposing trapezoidal side surfaces. It is comprised by the pentahedron provided with 20a, 20b. In this embodiment, the virtual bottom surface is formed in a square shape.

  The optical element 18 is formed so that the two trapezoidal side surfaces 20a and 20b are asymmetric. One base angle of the trapezoid in the cross section including the joining line 21 of the trapezoidal side surfaces 20a and 20b and perpendicular to the virtual bottom surface is perpendicular to the joining line 21 of the trapezoidal side surfaces 20a and 20b. When one base angle of the triangle in the cross section perpendicular to the virtual bottom surface is the angle θ3 and the other base angle is the angle θ4, the angles θ1, θ2, θ3, and θ4 satisfy the following relationship.

10 ° ≦ angle θ3 ≦ 25 °
45 ° ≦ angle θ4 ≦ 85 °
60 ° ≦ angle θ1 + angle θ2 ≦ 130 °
The size of the optical element 18 is preferably in the range of several times (for example, five times) or more of the wavelength of light to be used and 200 μm or less. If it is less than several times the wavelength of light, it is not preferable due to the influence of light interference, and if it is greater than 200 μm, the light and darkness of each optical element 18 may be visually recognized.

  As shown in FIG. 1A, the two prism sheets constituting the surface light source device 10 are arranged so that the light from the surface light source device 10 faces the optical element sheet 17 forming the light emitting surface of the light emitting unit 23. Arranged on the take-out side. The two prism sheets 22 include prisms having an apex angle of 90 °, and are arranged so that the extending directions of the prisms are orthogonal to each other. Of the two prism sheets 22, the prism sheet 22 disposed so as to face the optical element sheet 17 (on the lower side in FIG. 1A) is such that the direction in which the prism extends is the bonding line 21 of the optical element 18. Are arranged in parallel with each other.

Next, the operation of the surface light source device 10 configured as described above will be described.
The surface light source device 10 is used as a backlight of a liquid crystal display device, for example.
When a DC drive voltage is applied between the first electrode 13 and the second electrode 15 of the organic EL element 12, the organic EL layer 14 emits light. Light emitted from the organic EL layer 14 enters the substrate 11 through the first electrode 13. Of the light incident on the substrate 11, most of the light traveling toward the optical element sheet 17 is emitted from the optical element sheet 17.

  When a diffusion sheet is provided instead of the optical element sheet 17 on the light emitting surface of the light emitting unit 23, the light emitted from the light emitting unit 23 is most emitted in the direction where the polar angle is near 0 °. Therefore, there is little light emitted in the direction where the polar angle is around 50 °. On the other hand, in this embodiment, since the optical element sheet 17 in which the optical elements 18 having a specific pentahedral structure are arranged in a matrix is provided on the light emitting surface of the light emitting unit 23, the polar angle is around 50 °. The ratio of the light emitted in the direction increases. Here, the “polar angle” means an angle formed with a line perpendicular to the emission surface P1, as shown in FIG. Further, the azimuth angle means an angle formed with the reference line in the emission surface P1. In this embodiment, the output surface P1 is described as a virtual surface parallel to the substrate 11 instead of the side surfaces 19a, 19b, 20a, and 20b.

  Further, the ratio of the light emitted in the direction in which the polar angle is in the vicinity of 50 ° is not the same in each of the side surfaces 19a, 19b, 20a, and 20b of the optical element 18, but is the largest in the trapezoidal side surface 20a. The light emitted from the triangular side surfaces 19a and 19b in the direction where the polar angle is around 50 ° is less than the light emitted from the trapezoidal side surfaces 20a and 20b. The triangular side surfaces 19a and 19b serve to increase the light emitted from the entire optical element sheet 17.

  Front luminance of the surface light source device 10 including the optical element sheet 17 having a size of 20 mm × 30 mm and the two prism sheets 22 in which a plurality of optical elements 18 having a square virtual bottom surface with a side length of 50 μm are formed. Were analyzed by simulation with various angles θ1, θ2, θ3, and θ4 of the optical element 18 changed. Among them, the optical element sheet 17 was produced for the best angle condition. And about the surface light source device 10 provided with the produced optical element sheet | seat 17 and the prism sheet 22, the taking-out light quantity (A) from the light emission part 23, the taking-out light quantity (B) from the prism sheet 22, the front light from the prism sheet 22 (Light within a polar angle of 15 °) Measurement was performed on the extracted light quantity (C), the leaked light quantity (D) from the side surface of the substrate 11, and the like. Moreover, it replaced with the optical element sheet | seat 17, and the same measurement was performed also about the surface light source device provided with the commercially available diffusion sheet. The light amounts A, B, C, and D correspond to the arrows in FIG.

  FIG. 4 shows the light intensity at each polar angle from the light emitting unit 23 when the optical element sheet 17 of the embodiment is provided on the light emitting surface of the light emitting unit 23 and when the best available diffusion sheet is provided. . Here, the vertical axis represents a relative value when the luminous intensity in the polar angle 0 ° direction of the light emitting unit 23 including the best diffusion sheet is 1. In addition, the same measurement was performed using several available diffusion sheets, and the average value of all the measured values was also illustrated. The angle conditions of the optical element sheet 17 of the embodiment are when the angle θ1 = 50 °, the angle θ2 = 40 °, the angle θ3 = 25 °, and the angle θ4 = 75 °.

In FIG. 4, lines connecting the measurement points are drawn to group measurement points under the same conditions, and do not indicate values between the measurement points.
Table 1 shows values of the respective light quantities and the like for the surface light source device 10 of the embodiment shown in FIG. 4 and the surface light source device 10 using the best diffusion sheet. The value of each light amount is a relative value when the light amount value of the light source is 100. (Here, “light source” indicates a portion that emits light. For example, in this embodiment, the organic EL element 12 is indicated.)

表１から、発光部２３の光出射面に実施形態の光学素子シート１７を設けた場合は、最良の拡散シートを設けた場合よりも、面光源装置１０のプリズムシート２２からの正面光の取り出し光量は約１割増加することが確認できる。

From Table 1, when the optical element sheet 17 of the embodiment is provided on the light emitting surface of the light emitting unit 23, the front light is extracted from the prism sheet 22 of the surface light source device 10 more than when the best diffusion sheet is provided. It can be confirmed that the amount of light increases by about 10%.

  Further, from FIG. 4, in the light emitting unit 23 provided with the optical element sheet 17 of the embodiment, the light intensity at each polar angle in the polar angle range of 23 ° to 70 ° is that of the light emitting unit 23 provided with the best diffusion sheet. It is confirmed that it is larger than the luminous intensity. And the luminous intensity of the light emitting part 23 provided with the optical element sheet 17 of the embodiment in the polar angle range of 25 ° to 50 ° is larger than the luminous intensity at the polar angle 0 ° of the light emitting part 23 provided with the best diffusion sheet. It is confirmed that Therefore, it is confirmed that the amount of front light extracted from the prism sheet 22 is increased when the optical element sheet 17 is used as compared with the conventional configuration using a diffusion sheet.

  Next, FIG. 5 and Table 2 show the results of analysis by simulation of the degree of increase in luminance when the angles θ1 and θ2 are 37.5 ° and the angles θ3 and θ4 are changed. In addition, the angle θ1 and θ2 are set to the same value, the total value of the angles θ1 and θ2 is changed, the angle θ3 is kept constant at 25 °, and the analysis result by simulation of the brightness increase degree when the angle θ4 is changed Is shown in FIG. Here, the “brightness increase degree” refers to optical instead of a diffusion sheet when the front luminance of the surface light source device 10 including the light emitting unit 23 provided with the best diffusion sheet and the two prism sheets 22 is 1. It means the relative value of the front luminance of the surface light source device 10 on which the element sheet 17 is arranged.

  5 and 6, lines connecting the analysis points are drawn for grouping analysis points under the same conditions, and do not indicate values between the analysis points.

図５及び表２から、１０°≦角度θ３≦２５°のときに、光学素子シート１７を備えた面光源装置１０が、最良の拡散シートを備えたものより正面輝度が大きくなることが確認される。また、図６及び表３から、４５°≦角度θ４≦８５°かつ６０°≦角度θ１＋角度θ２≦１３０°のときに、光学素子シート１７を備えた面光源装置１０が、最良の拡散シートを備えたものより正面輝度が大きくなることが確認される。

5 and Table 2, when 10 ° ≦ angle θ3 ≦ 25 °, it is confirmed that the surface light source device 10 provided with the optical element sheet 17 has a higher front luminance than that provided with the best diffusion sheet. The Also, from FIG. 6 and Table 3, when 45 ° ≦ angle θ4 ≦ 85 ° and 60 ° ≦ angle θ1 + angle θ2 ≦ 130 °, the surface light source device 10 including the optical element sheet 17 is the best diffusion sheet. It is confirmed that the front brightness is higher than that provided.

  In each of the above examples, the angle θ1 and the angle θ2 are the same angle, but the angle θ1 and the angle θ2 are not limited to the same, and even when they are different, by arranging the optical element sheet 17 instead of the best diffusion sheet, It was confirmed by simulation analysis that the front luminance of the surface light source device 10 is larger than that provided with the best diffusion sheet. The analysis results are shown in Tables 4 and 5. Table 4 shows an example in which the angle θ1 and the angle θ2 are changed under the conditions of the angle θ3 = 15 ° and the angle θ4 = 65 °, and Table 5 shows the angle θ3 = 15 ° and the angle θ4 = 75 °. An example in the case where the angle θ1 and the angle θ2 are changed under conditions is shown.

この実施形態では以下の効果を有する。

This embodiment has the following effects.

  (1) The surface light source device 10 includes a light emitting unit 23 and two prism sheets 22 in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch. The light emitting unit 23 includes the organic EL element 12 and a plurality of three-dimensional optical elements 18 each having a rectangular virtual bottom surface provided on the light emitting surface side of the light emitting unit 23. The organic EL element 12 includes: A first electrode 13 as an anode, an organic EL layer 14 including a light emitting layer, and a second electrode 15 as a cathode are provided. The two prism sheets 22 are arranged on the light extraction side of the surface light source device 10 so that the extending directions of the prisms are orthogonal to each other, and the light emitting unit 23 extends the prisms of the prism sheet 22. The polar angle has a peak at 30 ° to 70 ° with respect to the average luminous intensity in four directions that form an azimuth angle of 45 ° relative to the direction. Therefore, among the light emitted from the light emitting unit 23, the light emitted in the direction near the polar angle of 50 ° can be increased, and in the front direction of the surface light source device 10 when the two prism sheets 22 are used. The luminance can be increased as compared with the conventional device.

  (2) The surface light source device 10 includes a light emitting unit 23 and two prism sheets 22 in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch. The light emitting unit 23 includes the organic EL element 12 and a plurality of three-dimensional optical elements 18 having a rectangular virtual bottom surface provided on the light emitting surface side of the light emitting unit 23. The organic EL element 12 includes a first electrode 13 as an anode, an organic EL layer 14 including a light emitting layer, and a second electrode 15 as a cathode. The two prism sheets 22 are arranged on the light extraction side of the surface light source device 10 so that the extending directions of the prisms are orthogonal to each other, and the light emitting unit 23 is provided on the virtual bottom surface of the optical element 18. The polar angle has a peak at 30 ° to 70 ° with respect to the average luminous intensity in four directions that form an azimuth angle of 45 ° with respect to the direction in which one side extends. Therefore, among the light emitted from the light emitting unit 23, the light emitted in the direction near the polar angle of 50 ° can be increased, and in the front direction of the surface light source device 10 when the two prism sheets 22 are used. The luminance can be increased as compared with the conventional device.

  (3) The optical element 18 is a pentahedron having a rectangular virtual bottom surface and two opposing triangular side surfaces 19a, 19b and two opposing trapezoidal side surfaces 20a, 20b. In a cross section including two trapezoidal side joining lines 21 and perpendicular to the virtual bottom surface, one base angle of the trapezoid is defined as angle θ1, and the other base angle is defined as angle θ2, perpendicular to the joint line 21 on the trapezoidal side surface and on the virtual bottom surface. When one base angle of the triangle in the vertical cross section is the angle θ3 and the other base angle is the angle θ4, the angles θ1, θ2, θ3, and θ4 satisfy the following relationship. 10 ° ≦ angle θ3 ≦ 25 °, 45 ° ≦ angle θ4 ≦ 85 °, 60 ° ≦ angle θ1 + angle θ2 ≦ 130 °. Therefore, among the light emitted from the light emitting unit 23, the light emitted in the direction near the polar angle of 50 ° can be increased, and in the front direction of the surface light source device 10 when the two prism sheets 22 are used. The luminance can be increased as compared with the conventional device.

  (4) The optical element 18 is provided in the organic EL element 12 by sticking an optical element sheet 17 including a plurality of optical elements 18 to the substrate 11. Therefore, the optical element 18 can be easily formed (processed) as compared with the case where the optical element 18 is directly formed on the substrate 11.

(5) The light emitting unit of the surface light source device 10 is composed of the organic EL element 12. Therefore, it can be driven at a lower voltage than when an inorganic EL element is used.
The embodiment is not limited to the above, and may be configured as follows, for example.

  The shape of the optical element 18 provided on the light emitting surface of the light emitting unit 23 is such that two prism sheets in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch are perpendicular to each other. In the state where it is arranged on the light emitting side of the light emitting part, the polar angle has a peak at 30 ° to 70 ° with respect to the average luminous intensity of the four light emitting parts in the azimuth angle of 45 ° with respect to the direction in which the prism extends. Any shape is acceptable. For example, it is good also as a solid shape comprised from a rectangular virtual bottom face, two opposing triangles, and two opposing quadrangles.

  The virtual bottom surface of the optical element 18 may be a rectangle, and is not limited to a square but may be a rectangle.

  The surface light source device 10 is not limited to the configuration in which the optical element 18 is provided on the light emitting surface side of the light emitting unit 23, and the optical element sheet 17 including the optical element 18 is not limited to a configuration attached via an adhesive. It is good also as a structure fixed to the light emission side of the light emission part 23 with the other fixing means.

  The optical element 18 may be directly formed on the light emitting side surface of the substrate 11.

  The substrate 11 is not limited to glass but may be made of resin. In the case of resin, when the optical element 18 is directly formed on the substrate 11, the processing becomes easier than the glass substrate.

  The organic EL element 12 is not limited to the bottom emission type, and may be formed in a top emission type. For example, in the organic EL element 12, the first electrode 13, the organic EL layer 14, and the second electrode 15 are sequentially formed on the substrate, and light from the organic EL layer 14 is extracted from the second electrode 15. In this case, the substrate and the first electrode 13 may or may not be transparent to light. However, the second electrode 15 needs to be transparent. When the second electrode 15 is formed of a non-metallic transparent electrode such as ITO, it is preferable that the second electrode 15 is an anode and the first electrode 13 is a cathode. However, when the second electrode 15 is formed of a very thin (50 nm or less) metal layer and transparent, the second electrode 15 may be a cathode.

  An inorganic EL element may be used instead of the organic EL element 12 as the EL element.

(Second Embodiment)
A second embodiment in which the present invention is embodied in an original reading apparatus of a scanner will be described below with reference to FIGS. 8 is a schematic cross-sectional view of the scanner, FIG. 9 is a schematic plan view of the illuminating device and sensor, FIG. 10 is a schematic cross-sectional view of the illuminating device along line AA in FIG. 9, and FIG. (B) is the BB sectional drawing of (a), (c) is CC sectional view taken on the line (a). For convenience of illustration, some dimensions are exaggerated for easy understanding, and the ratio of dimensions such as the width, length, and thickness of each part is different from the actual ratio. Also, hatching is omitted in FIGS. 11 (b) and 11 (c).

  As shown in FIG. 8, a scanner device 101 serving as a document reading device irradiates light onto a glass plate 102 that is a transparent plate and a document plate 103 that is disposed below the glass plate 102 and placed on the glass plate 102. And a sensor 105 that receives the light reflected by the original 103. Then, a part (reading target portion R) of the original 103 is illuminated with light emitted from the illumination device 104, light reflected from the reading target portion R of the original 103 is received by the sensor 105, and reflected light. The information described in the reading target portion R of the original 103 is read according to the strength of. The whole of the original 103 is read by scanning the illumination device 104 and the sensor 105 integrally along the glass plate 102 (in the direction of arrow D in FIG. 8).

  The illumination device 104 includes an organic electroluminescence element (organic EL element) 106 that is a light source and an optical member 108 in which a plurality of optical elements 107 (see FIG. 10) are arranged in a matrix. In this embodiment, as shown in FIGS. 8 and 9, two illumination devices 104 are provided symmetrically with respect to the sensor 105, and both illumination devices 104 are arranged in parallel with the glass plate 102.

  As shown in FIG. 9, the organic EL element 106 has a rectangular shape and a linear shape whose long side is significantly longer than the short side, and the light emitting unit extends along the long side located on the sensor 105 side of the two long sides. 109 is provided. The optical member 108 is provided over the entire length of the light emitting unit 109 over the entire light emitting side of the organic EL element 106. Further, the organic EL element 106 has two electrode terminals 110 and 111 for supplying power to the organic EL element 106 on the side opposite to the sensor 105 with respect to the light emitting unit 109.

  As shown in FIG. 10, the organic EL element 106 has a structure in which a first electrode 121, an organic layer 122 including a light emitting layer, a second electrode 123, and a protective film 124 are stacked in this order on a substrate 120.

  The substrate 120 is a plate-like member for supporting the organic EL element 106, and a transparent substrate showing a high transmittance for the extracted light is used. For example, glass showing high transmittance in the visible light region, transparent acrylic resin, or the like can be used.

  A known transparent electrode material is used for the first electrode 121, and for example, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), or the like can be used.

  For the second electrode 123, an electrode material having reflectivity with respect to the light emitted from the organic layer 122 is used. As the electrode material, a known metal electrode or alloy electrode can be used. For example, Ag or Al is used.

  The organic layer 122 provided between the first electrode 121 and the second electrode 123 is composed of an organic layer including a light emitting layer. For example, the organic layer 122 includes a single light emitting layer, a hole injection layer, In some cases, the light-emitting layer includes a combination of one or more of a hole transport layer, an electron injection layer, an electron transport layer, a hole block layer, a buffer layer, and the like. In the present embodiment, the organic layer 122 is configured to emit white light.

  The protective film 124 is for protecting the first electrode 121, the organic layer 122, and the second electrode 123 from external moisture, oxygen, and the like, and is formed of a known passivation film. As the protective film, an inorganic compound film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, an organic compound film such as a resin film, or the like can be employed.

  The transparent electrode 121 extends to the outside of the protective film 124, and the outer part of the protective film 124 constitutes one electrode terminal 110. Further, in this organic EL element 106, the portion where the organic layer 122 and the second electrode 123 overlap constitutes the light emitting unit 109.

  An optical member 108 is provided on the light emission side of the organic EL element 106. The optical member 108 is provided with a plurality of optical elements 107 in a matrix. The optical member 108 is formed of a transparent material, and is bonded to the glass substrate 120 via an adhesive (not shown) on the surface opposite to the surface on which the optical element 107 is formed. In this embodiment, the optical member 108 is formed of a transparent resin, for example, acrylic, polyethylene, polycarbonate, and the like, and each optical element 107 is manufactured by a mold. As the adhesive, an ultraviolet curable adhesive or a polymer adhesive having a refractive index that is the same as or close to the refractive index of the optical member 108 is used. “Near refractive index” means that the difference in refractive index is within several percent.

  As shown in FIGS. 11A, 11B, and 11C, each optical element 107 has a rectangular virtual bottom surface, two opposing triangular side surfaces 125a and 125b, and two opposing trapezoidal side surfaces. It is composed of a pentahedron including a virtual bottom surface provided with 126a and 126b. In this embodiment, the optical elements 107 are formed in the same shape, and the virtual bottom surface is formed in a square shape.

  The optical element 107 is formed so that two triangular side surfaces 125a and 125b are symmetric, and at least a part of the two trapezoidal side surfaces 126a and 126b is formed asymmetric. The trapezoidal side surfaces 126a and 126b include the joining line 127, and one base angle of the trapezoid in the cross section perpendicular to the virtual bottom surface is perpendicular to the joining line 127 of the trapezoidal side surfaces 126a and 126b. When the base angle closer to the reading target portion R is the angle θ4 and the other base angle is the angle θ3 among the triangular base angles in the cross section perpendicular to the virtual bottom surface, the angles θ3 and θ4 have the following relationship: Satisfied.

Angle θ3 <angle θ4
The size of the optical element 107 is preferably in the range of several times (for example, five times) or more and 200 μm or less of the wavelength of light to be used. If it is less than several times the wavelength of light, it is not preferred due to the influence of light interference, and if it is larger than 200 μm, the brightness of each optical element 107 may affect image information.

  The sensor 105 is for detecting the intensity of light reflected from the document 103, and a known image sensor can be used. If necessary, a lens or the like for collecting the reflected light may be provided between the document 103 and the sensor 105.

  Operations of the illumination device 104 and the scanner device 101 configured as described above will be described.

  When a voltage is applied between both electrode terminals 110 and 111 of the organic EL element 106, the light emitting layer in the organic layer 122 emits light. Part of this light passes directly through the glass substrate 120, and the remaining part is reflected by the second electrode 123 and then enters the optical member 108 through the glass substrate 120. Then, most of the light incident on the optical member 108 is emitted from the optical member 108.

  Here, when a diffusion sheet is provided on the light emission surface of the organic EL element 106 instead of the optical member 108, a part of the light emitted from the diffusion sheet reaches the reading target portion R of the original 103 directly. To do. However, since the light emission characteristic of the organic EL element 106 is isotropic and is diffused by the diffusion sheet, most of the other light does not go directly to the read target portion R of the original 103.

  On the other hand, in this embodiment, an optical member 108 in which optical elements 107 having a pentagonal structure with a specific shape are arranged in a matrix is provided on the light emitting surface of the organic EL element 106. Since the optical member 108 can extract light in a specific direction, most of the light emitted from the optical member 108 directly reaches the reading target portion R of the original 103, and the illuminance of the reading target portion R is improved. To do.

  The light reaching the reading target portion R of the original 103 is reflected by this portion and travels toward the sensor 105. At this time, the reflected light changes depending on the state of the reading target portion R, that is, what color. Since the organic EL element 106 emits white light, the state of the light reflected by the reading target portion R is close to the state of the color recognized by the human eye under natural light. The light reflected in this way is received by the sensor 105, and the state of the received light is converted into an electrical signal and read as an image.

  After reading the information described in the reading target portion R of the document 103 in this way, the sensor 105 and the illumination device 107 are moved integrally along the glass plate 102 to read the reading target portion on the document 103. Change R. Then, as described above, the information described in the new reading target portion R is read. By performing (scanning) such a reading operation over the entire document 103, all information described in the document 103 is read.

This embodiment has the following effects.
(6) An optical member 108 provided with a plurality of pentahedral optical elements 107 is attached to the light emitting side of the organic EL element 106. For this reason, the illuminating device 104 can take out the light emitted inside the organic EL element 106 in a specific direction. Therefore, the scanner light source 101 can efficiently extract the light from the organic EL element 106 in the direction of the reading target portion R. In the scanner device 101, the illuminance of the reading target portion R can be improved, and the organic EL element 106 necessary for obtaining the same illuminance can be reduced in size. Moreover, the electric power supplied to the organic EL element 106 required to obtain the same illuminance can be reduced.
(7) The optical member 108 is provided over the entire length of the light emitting unit 109 over the entire light emitting side of the organic EL element 106. For this reason, the illuminating device 104 can extract the light from the organic EL element 106 to the outside efficiently. In the scanner device 101, the light from the organic EL element 106 can be efficiently extracted in the direction of the reading symmetrical portion R.
(8) The optical elements 107 of the optical member 108 are formed in the same shape. For this reason, much light emitted inside the organic EL element 106 is extracted in a specific direction. The scanner light source 101 can efficiently extract the light from the organic EL element 106 in the direction of the reading target portion R.
(9) The sensor 105 and the illumination device 104 are scanned along the glass plate 102 integrally. For this reason, even if the small sensor 105 and the illuminating device 104 are used, it is possible to read information written on a large document.
(10) Two illumination devices 104 are provided symmetrically with respect to the sensor 105. For this reason, the illuminance on the reading target portion R of the original 103 can be further increased.
(11) The organic layer 122 is configured so that the organic EL element 106 emits white light. Therefore, it is possible to illuminate the reading target portion R of the original 103 in substantially the same state as natural light, and the state of the light reflected by the reading target portion R is close to the color state recognized by the naked eye under natural light. can do.
(12) A linear organic EL element 106 is used as a light source. For this reason, the light source can be made small (thin), and the scanner device 101 can also be made small (thin) as a whole.

  Hereinafter, the result of confirming the effect of the present embodiment by simulation will be shown.

  In a scanner apparatus in which organic EL elements having a light emitting portion width of 8 mm are provided on both sides of a sensor having a width of 4.5 mm as shown in FIG. 12, the illuminance of the reading target portion R located 14 mm above the center of the sensor. Was calculated by optical simulation.

<Example 2>
An optical member having the same length and width as the glass substrate of the organic EL element was provided on the light emitting side of the organic EL element. The plurality of pentahedral optical elements had a virtual virtual bottom surface with a side length of 50 μm, and each was formed in the same shape. The angles θ1 to θ2 of the optical element were set to angle θ1 = angle θ2 = 65 °, angle θ3 = 20 °, and angle θ4 = 60 °.

<Comparative Example 1>
For comparison, the illuminance of the reading target portion R when a commercially available diffusion sheet was provided instead of the optical member on the light emitting side of the organic EL element was calculated by simulation. The case where a diffusion sheet having the highest illuminance (best diffusion sheet) was provided by simulation was referred to as Comparative Example 1.

As a result of simulation in the above case, when the relative illuminance of Comparative Example 1 is 1, the relative illuminance of Example 2 is 1.2. That is, it can be seen that by providing the optical member of the present embodiment, the illuminance of the reading target portion R is about 1.2 times. From this, it was confirmed that the amount of light emitted from the organic EL element was extracted in the direction of the reading target portion R by the optical member.
Note that the optimum values of the angles θ1 to θ4 depend on the emission characteristics of the light source and the relative positional relationship between the light source and the reading target portion R, and in each case, it is necessary to obtain the optimum values by trial manufacture and simulation. There is.

(Third embodiment)
The third embodiment is different from the second embodiment in that the optical member is divided into several regions and the shape of the optical element is changed for each region. Other parts are the same as those in the second embodiment.

  In the present embodiment, the angle θ3 and the angle θ4 of the optical element are changed to arbitrary angles for each region, and the angle at which the light emitted inside the organic EL element 106 is extracted changes for each region. That is, by changing the angle θ3 and the angle θ4 to arbitrary angles for each region, light can be condensed (extracted) on a specific portion to be irradiated (read target portion R).

The second embodiment has the following effects in addition to the same effects as the effects (6), (7), (9) to (12) of the second embodiment.
(13) The optical member was divided into several regions, and the shape of the optical element was changed for each region. For this reason, the light emitted inside the organic EL element 106 is extracted at a different angle for each region, and the light can be condensed on a specific portion to be irradiated. Therefore, the scanner light source 101 can efficiently extract the light from the organic EL element 106 in the direction of the reading target portion R, and can collect the light on the reading target portion R.

  Hereinafter, the results of the third embodiment also confirmed by simulation. Similar to the second embodiment, the scanner device has the configuration shown in FIG.

<Example 3>
The optical member shown in Example 2 is divided into eight regions having the same width with respect to the width direction of the organic EL element, and Table 6 shows the angles θ3 and θ4 of the pentahedral optical element for each region. It was changed as follows. The angles θ1 and θ2 were 65 °. In Table 6, the region 1, the region 2, the region 3,...

以上のような場合でシミュレーションを行った結果、比較例１の相対照度を１とすると、実施例３の相対照度は１．４４となった。すなわち、本実施例の光学部材を設けることにより、読取対象部分Ｒの照度が約１．４４倍になることがわかる。このことから、有機ＥＬ素子から発せられた光が、光学部材によって読取対象部分Ｒの方向に取り出される光量が多くなったことが確認できた。
なお、角度θ１〜角度θ４の最適値は、光源の出射特性や、光源と読取対象部分Ｒとの相対的な位置関係に依存するので、それぞれの場合において、試作やシミュレーションによって最適値を求める必要がある。

As a result of simulation in the above case, when the relative illuminance of Comparative Example 1 is 1, the relative illuminance of Example 3 is 1.44. That is, it can be seen that by providing the optical member of the present embodiment, the illuminance of the reading target portion R is about 1.44 times. From this, it was confirmed that the amount of light emitted from the organic EL element was extracted in the direction of the reading target portion R by the optical member.
Note that the optimum values of the angles θ1 to θ4 depend on the emission characteristics of the light source and the relative positional relationship between the light source and the reading target portion R, and in each case, it is necessary to obtain the optimum values by trial manufacture and simulation. There is.

  The embodiment is not limited to the above, and may be configured as follows, for example.

  Although the organic EL element 106 is used as the light source, other light emitting devices such as LEDs, cold cathode tubes, and inorganic EL elements can be used as the light source. Even when an LED, a cold cathode tube, an inorganic EL element, or the like is used, light can be extracted in a specific direction by the optical member.

  In the above embodiment, the organic EL element 106 is a so-called bottom emission type in which light is emitted from the substrate side, but may be a top emission type in which light is emitted from the side opposite to the substrate. When a top emission type organic EL element is employed as the light source, the second electrode 123 and the protective film 124 need to be transparent, and the substrate 120 and the first electrode 121 do not need to be transparent. The optical member 108 is provided on the protective film 124.

  Although the scanner apparatus 101 is used as the document reading apparatus, it can be used for a facsimile apparatus and a copying apparatus in addition to the scanner apparatus.

  In the scanner device 101, it is not necessary to use two illumination devices 104 at the same time, and only one illumination device 104 may be used.

  In the scanner device 101, it is not necessary to scan the sensor 105 and the illumination device 104 integrally. For example, the sensor 105 may be fixed to the glass plate 102 and only the illumination device 104 may be scanned. In this case, the reflected light from the original 103 may be guided to the sensor 105 using a separate optical system.

  ○ As the optical member 108, the optical elements 107 are arranged in a matrix, but the optical elements may be arranged randomly instead of being arranged in a matrix.

  As the optical member 108, the shape of the optical element 107 may be gradually changed for each region. For example, the scanner device 101 may be formed such that the angle θ3 of the optical element 107 gradually increases as it is arranged in a region farther from the side closer to the reading target portion R. Further, only the optical element 107 in a specific area may be changed.

  O Although the illuminating device 104 was arrange | positioned in parallel with the glass plate 102, you may incline and arrange | position with respect to the glass plate 102. FIG.

  In the illuminating device 104, a reflecting plate may be provided on the optical member 108 on the light emission surface side.

  The following technical idea (invention) can be understood from the embodiment.

  (1) In the invention according to any one of claims 1 to 4, the EL element is an organic EL element.

(A) is a schematic diagram of a surface light source device, (b) is a schematic perspective view of an optical element sheet | seat. (A) is a top view of an optical element, (b) is the BB sectional view taken on the line of (a), (c) is the CC sectional view taken on the line (a). The schematic diagram which shows a polar angle and an azimuth. The graph which shows the relationship between the polar angle and luminous intensity in a light emission part. The graph which shows the relationship between the shape of an optical element, and the front luminance of a surface light source device. The graph which shows the relationship between the shape of an optical element, and the front luminance of a surface light source device. The schematic diagram of a prior art. 1 is a schematic cross-sectional view of a scanner device. The schematic plan view of the sensor of FIG. 1, and an illuminating device. The schematic cross section in the AA of the organic EL element in FIG. (A) is a top view of an optical element, (b) is the BB sectional view taken on the line of (a), (c) is the CC sectional view taken on the line (a). The schematic diagram which shows the conditions of simulation.

Explanation of symbols

.theta.1, .theta.2, .theta.3, .theta.4 ... angle, 10 .... surface light source device, 11 .... substrate, 12 .... organic EL element as electroluminescent element, 13 .... first electrode as anode, 14 .... organic EL layer, 15 .... as cathode 17 ... Optical element sheet as an optical member, 18 ... Optical element, 19a, 19b ... Triangular side face, 20a, 20b ... Trapezoid side face, 21 ... Joining line, 22 ... Prism sheet, 23 ... Light emitting part DESCRIPTION OF SYMBOLS 101 ... Scanner apparatus as document reading apparatus 102 ... Glass plate as transparent plate 104 ... Illumination device 105 ... Sensor 106: Organic EL element as light source 107 ... Optical element 108 ... Optical member R ... The part to be read.

Claims (13)

A surface light source device including a light emitting unit and two prism sheets in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch,
The light emitting unit includes an electroluminescence element and a plurality of three-dimensional optical elements provided on the light emitting surface side of the light emitting unit,
The electroluminescence element includes an anode, a light emitting layer, and a cathode,
The two prism sheets are arranged on the light extraction side of the surface light source device so that the extending directions of the prisms are orthogonal to each other.
The surface light source device characterized in that the light emitting section has a peak at a polar angle of 30 ° to 70 ° with respect to an average luminous intensity in four directions having an azimuth angle of 45 ° with respect to the extending direction of the prism of the prism sheet. . A surface light source device including a light emitting unit and two prism sheets in which prisms having an apex angle of 90 ° are formed in parallel at a predetermined pitch,
The light emitting unit includes an electroluminescence element and a plurality of three-dimensional optical elements whose virtual bottom surface provided on the light emitting surface side of the light emitting unit is rectangular,
The electroluminescence element includes an anode, a light emitting layer, and a cathode,
The two prism sheets are arranged on the light extraction side of the surface light source device so that the extending directions of the prisms are orthogonal to each other.
The light emitting part has a peak at a polar angle of 30 ° to 70 ° with respect to an average luminous intensity in four directions that make an azimuth angle of 45 ° with respect to a direction in which one side of the virtual bottom surface of the optical element extends. A surface light source device. Wherein at least a portion of the plurality of optical elements, a virtual bottom rectangular, 請 Motomeko 1 which consists of pentahedron having a two triangular side surfaces facing, and two asymmetrical trapezoidal opposing sides Or the surface light source device of Claim 2. When at least a part of the plurality of optical elements is orthogonal to the joining line of the trapezoidal side surface and one base angle of a triangle in a cross section perpendicular to the virtual bottom surface is an angle θ3 and the other base angle is an angle θ4 The surface light source device according to claim 3, wherein the angles θ3 and θ4 satisfy the following relationship.
Angle θ3 <angle θ4 The surface light source device according to claim 3, wherein all of the plurality of optical elements have the same shape. The surface light source device according to claim 3, wherein virtual bottom surfaces of the plurality of optical elements are square. The surface light source device according to any one of claims 3 to 6, wherein the plurality of optical elements are arranged in a matrix. The optical element includes a joining line of the two trapezoidal side surfaces, and one base angle of the trapezoid in a cross section perpendicular to the virtual bottom surface is an angle θ1, the other base angle is an angle θ2, and the joining line of the trapezoidal side surface The angle θ1, θ2, θ3, θ4 satisfies the following relationship when one base angle of a triangle in a cross section perpendicular to the virtual bottom surface is an angle θ3 and the other base angle is an angle θ4: The surface light source device of 3-7.
10 ° ≦ angle θ3 ≦ 25 °
45 ° ≦ angle θ4 ≦ 85 °
60 ° ≦ angle θ1 + angle θ2 ≦ 130 ° A document reading device comprising the surface light source device according to any one of claims 4 to 8,
A transparent plate on which the document is placed;
A sensor that reads the light reflected by the reading target portion of the document,
The surface light source device is scanned along the transparent plate and the electroluminescent element is formed in a linear shape, and the plurality of optical elements have a bonding line on the trapezoidal side surface in the longitudinal direction of the electroluminescent element. Of the triangles in the cross section perpendicular to the virtual bottom surface, the base angle closer to the portion to be read is the angle θ4, and the other base angle is the angle θ3. An original reading apparatus characterized by the above. The document reading apparatus according to claim 9, wherein the angle θ3 increases as the plurality of optical elements are arranged from a side closer to the reading target portion to a side farther from the reading target portion. 11. The document reading device according to claim 9, wherein two illumination devices are provided symmetrically with respect to the sensor.   Delete   Delete

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