JP2009117304A - Surface light-emitting device, display device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light-emitting device which has as high brightness and superior in-plane brightness uniformity as in a point light source even in the case a linear light source is used as the light source. <P>SOLUTION: The surface light-emitting device 1A has a wedge-shape that becomes thinner in its plate thickness according as the distance from the linear light source 2 increases, and is equipped with a first prism pattern 31 on the light-emitting surface, while it is equipped with a second prism pattern 32 intersecting at right angles the first prism pattern 31 on the opposite side reflecting face. The first prism pattern 31 is equipped with a protrusion shaped part 33 extending from a light-incident end face 30 to an end face opposite to the end face 30 in a direction intersecting at right angles the linear light source 2, while the second prism pattern 32 is equipped with recessed shaped parts 34 having inclined faces 34a in which lengths are varied according to distances from the light incident end face 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface light-emitting device used for a liquid crystal display device and the like, and a display device and an electronic apparatus including the surface light-emitting device. Specifically, a light guide plate in which linear light sources are arranged on the sides improves the uniformity of luminance regardless of the distance from the light source and improves the luminance by using the prism patterns formed on the light emitting surface and the reflecting surface, respectively. It is to improve.

  With the recent increase in white light emitting diodes, sidelight type surface light emitting devices using point light sources have been proposed. In such a sidelight type surface light emitting device, it is possible to provide a surface light emitting device in which a concave / convex pattern such as a dot / prism pattern is formed on a light guide plate to improve the directivity (condensation) of light emitted from the light guide plate. (For example, refer to Patent Documents 1 and 2).

  On the other hand, in a sidelight type surface light emitting device using a linear light source, generally, the main surface (light emitting surface) is provided with fine blasting, and the surface opposite to the main surface (reflection surface) is linear. The light guide plate is formed with a configuration in which an arc extending in a vertical direction with respect to the light source or a triangular prism is formed. However, in this configuration, the light efficiency is dispersed, and the light use efficiency is lowered.

  Therefore, even in a sidelight type surface light emitting device using a linear light source, a surface light emitting device in which an uneven pattern is formed on the light emitting surface side of the light guide plate and the directivity of light emitted from the light guide is improved is provided. (For example, refer to Patent Document 3).

JP 2006-202039 A JP 2005-317435 A JP 2005-353406 A

  However, in a conventional surface light emitting device corresponding to a point light source, if the light source is replaced with a linear light source, sufficient luminance cannot be obtained when used for a medium-sized display having a screen size of 10 inches or more, In addition, variations in luminance occurred.

  Further, in the conventional surface light emitting device corresponding to the linear light source, a triangular prism is disposed on the light emitting surface side of the light guide plate, and the apex of the prism is easily damaged.

  The present invention has been made to solve such a problem, and even in a configuration using a linear light source as a light source, the surface has high brightness similar to a point light source and excellent uniformity of in-plane brightness. It is an object of the present invention to provide a light emitting device, and a display device and an electronic device including the surface light emitting device.

  In order to solve the above-described problems, the present invention provides a prism sheet on the light emitting surface side where light from the light guide plate is emitted and a linear light source is disposed facing the light incident end surface of the light guide plate through which light is propagated. And a diffusion sheet, and a reflection sheet is arranged on the reflection surface side opposite to the emission surface, and the light guide plate has a plate thickness on the opposite side from the light incident end surface side as the distance from the linear light source increases. The light emitting surface facing the prism sheet is provided with a first prism pattern in which irregularities are formed in a predetermined shape, and the first prism pattern is disposed on the reflecting surface facing the reflecting sheet. The first prism pattern of the light guide plate has a convex shape extending from the light incident end surface to the anti-light incident end surface in a direction perpendicular to the linear light source. A second light guide plate The prism pattern includes a plurality of concave-shaped portions extending in a direction orthogonal to the convex-shaped portion of the first prism pattern, and arranged at a predetermined interval along the extending direction of the convex-shaped portion. The concave portion has an inclined surface with an acute angle with respect to a virtual plane parallel to the light emitting surface of the light guide plate on the light incident end surface side, and the inclined surface of the inclined surface with a plurality of concave shapes has a constant inclination surface. And the prism sheet is orthogonal to the convex portion of the first prism pattern on the back surface of the light guide plate facing the first prism pattern, and The concave portion of the second prism pattern of the light guide plate and the linear light source are provided with a prism having irregularities formed in a predetermined shape.

  The display device of the present invention is a display device in which a surface light-emitting device is disposed on the back surface of a display panel that transmits light, and the display panel is irradiated with the surface light-emitting device, and includes the surface light-emitting device of the present invention described above. is there. The electronic device of the present invention is an electronic device including a display device in which a surface light-emitting device is disposed on the back surface of a display panel that transmits light, and the display panel is irradiated with the surface light-emitting device. A light emitting device is provided.

  In the surface light emitting device of the present invention, the light emitted from the linear light source enters the light guide plate from the light incident end surface. Light incident on the light guide plate from the light incident end face is propagated from the light incident end face side to the opposite end face while being reflected by the first prism pattern and the second prism pattern of the light guide plate.

  The light propagated through the light guide plate and reflected by the convex portion of the first prism pattern is condensed from the light incident end surface toward the opposite end surface. The light guide plate is formed in a wedge shape in which the plate thickness decreases as the distance from the linear light source increases, thereby preventing a decrease in the amount of light on the side far from the linear light source.

  Further, the light propagated through the light guide plate and reflected by the inclined surface of the second prism pattern is incident on the first prism pattern at an incident angle that transmits the first prism pattern, and is refracted at a predetermined refraction angle. The light is emitted from the light guide plate.

  The light emitted from the first prism pattern of the light guide plate is refracted by entering the prism of the prism sheet, and is emitted from the prism sheet with a predetermined directivity.

  In the second prism pattern of the light guide plate, the length of the inclined surface is changed according to the distance from the incident end surface in the plurality of concave portions, and the distance from the light source, the thickness of the light guide plate, The surface uniformity of brightness is adjusted from the relationship of the length of the inclined surface of the prism pattern.

  In the display device and the electronic apparatus of the present invention, by providing such a surface light emitting device, the luminance of the screen is improved with a configuration in which a linear light source is provided on the side portion of the light guide plate, and the distance from the light source is increased. Regardless, the uneven brightness is eliminated.

  In the surface light emitting device of the present invention, the directivity of emitted light can be improved, the variation in luminance can be suppressed, the luminance can be increased, and the uniformity of in-plane luminance can be improved.

  In the display device and the electronic apparatus of the present invention, by providing such a surface light emitting device, the screen can be displayed with a luminance required according to the ambient brightness and the like, and the luminance is not uniform on the screen. Can be eliminated.

  In addition, by providing a high-luminance surface light-emitting device, it is possible to obtain a necessary luminance by suppressing the light emission amount of the light source, and to reduce power consumption.

  Hereinafter, embodiments of a surface light-emitting device, a display device, and an electronic apparatus according to the present invention will be described with reference to the drawings.

<Configuration Example of Surface Emitting Device of this Embodiment>
(1) Overall Configuration of Surface Light Emitting Device FIGS. 1 and 2 show an example of a surface light emitting device according to the present embodiment. FIG. 1A is a side view of a surface light emitting device 1A according to the present embodiment. 1 (b) is a perspective view of the surface light emitting device 1A. FIG. 2 is an exploded perspective view of the surface light emitting device 1A.

  The surface light emitting device 1A of the present embodiment is an object used as a backlight device such as a liquid crystal display panel, for example, and propagates light emitted from the linear light source 2 that emits light and the linear light source 2. The light guide plate 3 that emits light from the light emitting surface is provided. In addition, the surface light emitting device 1 </ b> A includes the prism sheet 4 and the diffusion sheet 5 that collect the light emitted from the light emitting surface of the light guide plate 3, and the light emitted from the reflective surface opposite to the light emitting surface of the light guide plate 3. A reflection sheet 6 is provided that reflects and re-enters the light guide plate 3.

  Here, in the surface light emitting device 1A, the direction along the linear light source 2 is defined as the Y axis, and the direction in which the light emitted from the linear light source 2 is propagated through the light guide plate 3 is defined as the X axis.

  The linear light source 2 is a rod-like, for example, cold cathode fluorescent lamp (CCFL) or hot cathode fluorescent lamp (HCFL), and includes a reflector 20 that collects light.

  The light guide plate 3 is formed in a predetermined shape with a transparent resin material that transmits light in a predetermined wavelength region, for example, an acrylic material. That is, in the light guide plate 3, one side surface facing the linear light source 2 becomes the light incident end surface 30, and the light incident end surface 30 is arranged in a direction along the Y axis parallel to the linear light source 2.

  In addition, the light guide plate 3 has a wedge-shaped shape in which the plate thickness decreases from the light incident end surface 30 side, which is a direction away from the linear light source 2 along the X axis, toward the counter light incident end surface side.

  Further, the light guide plate 3 has a surface (upper surface) facing the prism sheet 4 as a light emitting surface, and the first prism pattern 31 is formed with the light emitting surface as a predetermined uneven shape. Further, the light guide plate 3 has a surface (lower surface) facing the reflection sheet 6 as a reflection surface, and a second prism pattern 32 is formed in a direction perpendicular to the first prism pattern 31 with the reflection surface being a predetermined uneven shape. Is done.

  Here, in the light guide plate 3, the second prism pattern 32 on the reflecting surface side is arranged in the direction along the Y axis parallel to the linear light source 2, and the first prism pattern 31 on the light emitting surface side is arranged in a line. The direction is along the X axis perpendicular to the light source 2.

  The prism sheet 4 is disposed to face the light emitting surface on which the first prism pattern 31 of the light guide plate 3 is formed, and the diffusion sheet 5 is disposed on the surface of the prism sheet 4. Further, the reflection sheet 6 is disposed so as to face the reflection surface on which the second prism pattern 32 of the light guide plate 3 is formed.

  The prism sheet 4 is configured such that a prism surface 40 is formed with the back surface of the light guide plate 3 facing the first prism pattern 31 having a predetermined concavo-convex shape, and a so-called reverse prism sheet having a prism surface on the lower surface is used as the lens sheet. Good.

  In the prism sheet 4, the convex portion of the prism surface 40 is perpendicular to the first prism pattern 31 of the light guide plate 3, and is parallel to the second prism pattern 32 of the light guide plate 3 and the linear light source 2. It is arranged in the direction along.

(2) Configuration Example of First Prism Pattern of Light Guide Plate FIG. 3 is a cross-sectional view of the main part of the light guide plate 3 showing details of the first prism pattern 31.

  The first prism pattern 31 of the light guide plate 3 has a substantially semi-cylindrical convex portion 33 formed in an orientation along the X axis perpendicular to the linear light source 2 and parallel to the light incident end face 30 on which light is incident. The radius of curvature of the arc R in the cross section along the Y-axis is a substantially constant shape. The distance Dr between the center line L (1) of the arc R (1) having the first prism pattern 31 and the center line L (2) of the adjacent arc R (2) is arranged at a constant pitch. ing.

  Further, the central angle θR of the arc R of the convex portion 33 of the first prism pattern 31 is set in a range of about 60 ° to 120 °.

  More preferably, the center line L (1) of the arc R (1) having the first prism pattern 31, the center point O (1) of the arc R (1), and the arcs R (1), R (2). The angle θr at which the line LC connecting the intersection point C intersects is preferably in the range of about 45 ° to about 60 °, and the center angle θR of the arc R has a shape that is about 90 ° to about 120 °. preferable.

  And the convex-shaped part 33 of the 1st prism pattern 31 is longer than the length of the X-axis direction of the effective light emission range E shown in FIG.1 (b), and each is formed in parallel, and within the effective light emission range E, X The cross section along the Y axis is formed in the same shape at any position on the axis.

  FIG. 4 is an operation explanatory view showing the light condensing effect of the first prism pattern 31 in the light guide plate 3 of the surface light emitting device 1A of the present embodiment, and FIG. FIG. 4B is a schematic diagram showing the propagation of light rays to be emitted, and FIG. 4B is a graph showing the intensity distribution of the condensed light.

  In addition, FIG. 5 is an operation explanatory view of a light guide plate in which a prism pattern having a predetermined shape is not formed on the light emitting surface as a comparative example, and FIG. 5A is a schematic diagram illustrating propagation of light that is not condensed, FIG. 5B is a graph showing the intensity distribution of light that is not condensed.

  In a conventional light guide plate in which a prism pattern of a predetermined shape is not formed on the light emitting surface, the traveling direction of light incident from the linear light source 2 does not change when reflected by the light emitting surface. Like the light ray G2 shown in FIG. 5 (a), it propagates in the Y-axis direction. Thereby, the light emitted from the light emitting surface of the light guide plate (Z-axis direction) becomes light having a spread with respect to the normal direction (0 °) as shown in FIG. It is bad and causes a decrease in luminance.

  In contrast, in the present embodiment, the first prism pattern 31 in which the arc-shaped convex portion 33 is formed on the light emitting surface of the light guide plate 3 along the light propagation direction is provided. The incident light from the light source 2 is reflected by the first prism pattern 31 to change its traveling direction, and is condensed and propagated in the X-axis direction as a light beam G1 shown in FIG. . As a result, the light emitted from the first prism pattern 31 which is the light emitting surface of the light guide plate 3 (Z-axis direction) rises with respect to the normal direction (0 °) as shown in FIG. By becoming (condensed) light and effectively contributing to the second prism pattern 32 on the reflecting surface side, it becomes possible to increase directivity and improve luminance.

  FIG. 6 is an explanatory view showing a simulation example in the case where the center angle of the arc of the first prism pattern 31 is changed in the light guide plate 3 of the surface light emitting device 1A of the present embodiment, and FIG. FIG. 6B shows the state of light propagation when the angle is 60 °, and FIG. 6B shows the state of light propagation when the center angle is 120 °.

  FIG. 6C is a graph showing the light intensity distribution, where the vertical axis indicates the luminance and the horizontal axis indicates the distance from the light source.

  When the spread of light is simulated when the central angle of the arc R of the first prism pattern 31 shown in FIG. 3 is set to 60 ° and 120 °, as shown in FIG. It can be seen that the directivity in the X-axis direction is stronger when the central angle of the arc of the prism pattern 31 is 120 °. Further, as shown in FIG. 6C, it can be seen that the brightness is generally higher when the central angle of the arc of the first prism pattern 31 is 120 ° than when it is 60 °.

  FIG. 7 is an explanatory diagram showing a stacked state of the light guide plate 3 and the prism sheet 4. In the surface light emitting device 1A, the prism sheet 4 is laminated on the light guide plate 3, and the convex portion 33 of the first prism pattern 31 of the light guide plate 3 and the prism surface of the prism sheet 4 are arranged depending on vibration, environmental conditions, and the like. The structure which reduces the frictional scratches which occur when 40 convex-shaped parts collide is provided.

  That is, as shown in FIG. 3, the light guide plate 3 does not have the convex portion 33 of the first prism pattern 31 with respect to the virtual plane H1 passing through the apex of each convex portion of the prism surface 40 of the prism sheet 4. Uniform height.

  As a result, as shown in FIG. 7, there is a non-contact range S between the convex portions of the first prism pattern 31 of the light guide plate 3 and the prism surface 40 of the prism sheet 4 that face each other, and the light guide plate 3 and the prism sheet 4. And the occurrence of frictional scratches can be prevented.

  However, in the light guide plate 3, when the height difference of the convex portion 33 of the first prism pattern 31 becomes large, a striped pattern becomes visible when light is emitted, and therefore, as shown in FIG. It is preferable that the height difference Dh of the convex portion 33 of the prism pattern 31 varies in the range of about 0 to 20 μm.

  FIG. 8 is an operation explanatory view showing an outline of a manufacturing process of a mold for forming the first prism pattern 31 of the light guide plate 3. Since the light guide plate 3 is manufactured by integral molding using a mold, the mold 101 for molding the first prism pattern 31 has an arc shape in accordance with the arc-shaped convex portion 33 of the first prism pattern 31. The concave portion 102 is formed.

  In the mold 101, the arc-shaped concave shape portion 102 is formed by cutting with the cutting tool B1, but in order to form a plurality of concave shape portions 102 at a constant interval, the feed amount PB1 of the cutting tool B1 is made constant. It ’s fine. Further, in order to change the depth of the concave shaped portion 102, the driving depth amount Dp may be changed.

  Thereby, in the light guide plate 3, it is easy to process the mold 102 for forming the convex portions 33 of the first prism pattern 31 at a constant pitch and at a nonuniform height. Therefore, it is possible to suppress an increase in manufacturing cost and reduce product cost.

(3) Configuration Example of Second Prism Pattern of Light Guide Plate FIG. 9 is a cross-sectional view of the main part of the light guide plate 3 showing details of the second prism pattern 32. The second prism pattern 32 of the light guide plate 3 includes a triangular prism-shaped concave portion 34 having an inclined surface 34a that rises at a predetermined angle with respect to the traveling direction of the light incident from the light incident end surface 30. The concave portions 34 and the flat portions 35 are alternately arranged along the X axis orthogonal to the linear light source 2.

  The light guide plate 3 is inclined on the reflection surface side on which the second prism pattern 32 is formed so that the light guide plate 3 has a wedge shape with a thickness decreasing from the light incident end surface 30 side toward the counter light incident end surface side. . In the second prism pattern 32, an angle θ1 at which the inclined surface 34a intersects a predetermined acute angle with respect to a virtual plane H2 parallel to the light emitting surface formed by the first prism pattern 31 of the light guide plate 3. Thus, the angle θ2 at which the inclined surface 34a and the flat portion 35 intersect is set to an obtuse angle.

  That is, the light guide plate 3 reflects the light G3 incident and propagated from the light incident end surface 30 by the inclined surface 34a of the second prism pattern 32, and makes the light G3 enter the first prism pattern 31 that is the light emitting surface. . At this time, the incident angle of light with respect to the first prism pattern 31 is such that the angle θ1 of the inclined surface 34a of the second prism pattern 32 is such that the incident light is refracted at a predetermined angle and enters the prism sheet 4. Is set.

  Further, in the second prism pattern 32, the angle θ3 at which the other inclined surface of the concave portion 34 intersects the flat portion 35 is set to an obtuse angle narrower than the angle θ2 at which the inclined surface 34a intersects the flat portion 35, and The shape portions 34 are configured to be arranged at a predetermined pitch.

  Here, the concave shaped portion 34 of the second prism pattern 32 is longer than the length of the effective light emission range E shown in FIG. 1B in the Y-axis direction, and is formed in parallel, and within the effective light emission range E, The cross section along the X axis is formed in the same shape at any position on the Y axis.

  FIG. 10 is a ray diagram showing the relationship between the incident angle and the refraction angle of light in the light guide plate 3 and the prism sheet 4. Next, a specific shape of the second prism pattern 32 in the light guide plate 3 will be described.

Here, when light is incident on a material having a refractive index n _{1 from} a material having a refractive index n ₂ (n ₁ > n ₂ ) at an incident angle θa, the reflection angle θb is equal to the incident angle, and the refractive angle θc is Snell's According to the law, n ₁ sin θa = n ₂ sin θc.

  In the surface light emitting device 1 </ b> A, in order to improve the luminance, the light emitted from the first prism pattern 31 that is the light emitting surface of the light guide plate 3 is normal (0 °) to the light emitting surface of the prism sheet 4. It is necessary to collect light in the direction.

  When the refractive indexes of the light guide plate 3 and the prism sheet 4 are n = 1.49, in order to condense the light in the normal direction by the prism sheet 4, the light refraction angle in the prism sheet 4 is the Snell's When calculated according to the law, the optimum angle of the exit angle (refraction angle) θd from the first prism pattern 31 of the light guide plate 3 is calculated to be approximately 20 ° to 30 °.

  When the incident angle for converging the light incident on the first prism pattern 31 of the light guide plate 3 in the direction of the emission angle θd is calculated, the second light that reflects the light incident on the first prism pattern 31 is reflected. The inclination angle θ1 of the inclined surface 34a of the prism pattern 32 is preferably about 5 ° to 10 °.

  FIG. 11 is an explanatory view showing a method for calculating the lengths of the inclined surface 34 a of the concave portion 34 and the flat portion 35 in the second prism pattern 32 of the light guide plate 3, and FIG. FIG. 11B is a plan view of the main part of the light guide plate 3.

Here, in the second prism pattern 32 of the light guide plate 3, the length of the inclined surface 34a of the concave portion 34 is ph (h = ₁ to m ₁ ), and the length of the flat portion 35 is di (i = 1). To m ₂ ).

  The light guide plate 3 has a plurality of concave portions 34 formed between the length L from the light incident end surface 30 to the anti-light incident end surface along the X axis, and the inclination angle θ1 of the inclined surface 34a of the concave portion 34. Are all configured at the same angle.

  Further, the light guide plate 3 is configured such that the length di of the flat portion 35 is the same length as di = d, and the interval between the plurality of concave-shaped portions 34 is constant (d = d1 = d2 = d3 =...). It is.

  On the other hand, the light guide plate 3 adjusts the surface uniformity of the luminance within the effective light emission range by changing the length Ph of the inclined surface 34 a according to the distance from the light incident end surface 30.

  In the light guide plate 3, when light is incident from the light incident end face 30, the ratio between the section that becomes the flat portion 35 and the section that becomes the inclined surface 34 a in the second prism pattern 32 and the luminance on the light emitting surface. There is a correlation.

  For this reason, as a method of calculating the lengths of the inclined surface 34a and the flat portion 35 in the second prism pattern 32, the light guide plate 3 is divided by a certain number of divisions in the length L direction, and in each divided section. The ratio of the section that becomes the inclined surface 34a of the second prism pattern 32 and the section that becomes the flat portion 35 is determined by the correlation with the luminance.

That is, in the light guide plate 3, when the length of each divided section is aj (j = 1 to m ₃ ), the length L of the light guide plate 3 is L = Σaj. In addition, among the lengths aj of the divided sections, the sum of the lengths di of the sections to be the flat portions 35 is Σdi = d1 + d2 + d3 +... And the sum of the lengths ph of the sections to be the inclined surfaces 34a. Is Σpi = p1 + p2 + p3 +.

  Thereby, the length aj of each divided section is aj = Σdi + Σpi. In each divided section, the ratio of the sum Σdi of the length di of the section that becomes the flat portion 35 to the length aj and the sum Σpi of the length pi of the section that becomes the inclined surface 34a is expressed as luminance. Determine by correlation.

  Then, the length di of the flat portion 35 is determined from the ratio of the section to be the flat portion 35 and the section to be the inclined surface 34a, and the number of the concave shape portions 34 in the divided sections and the height of the concave shape portion 34 are determined. The length of the inclined surface 34a that defines the thickness is calculated.

  FIG. 12 shows the height of the second prism pattern 32 obtained by calculating the ratio of the section serving as the inclined surface 34a and the section serving as the flat portion 35 from the correlation with the luminance in the second prism pattern 32 of the light guide plate 3. It is a graph which shows an example of thickness distribution. In FIG. 12, the horizontal axis indicates the distance from the light incident end face 30, and the vertical axis indicates the height of the concave portion 34.

  13 shows the second prism pattern 32 of the second prism pattern 32 of the light guide plate 3 obtained by calculating the ratio of the section that becomes the inclined surface 34a and the section that becomes the flat portion 35 from the correlation with the luminance. It is a graph which shows an example of pitch distribution of. In FIG. 14, the horizontal axis indicates the distance from the light incident end face 30, and the vertical axis indicates the apex pitch of the concave portion 34.

  When light from the linear light source 2 is incident on the light guide plate 3 from the light incident end surface 30, the light emitting surface of the light guide plate 3 has a light guide plate 3 having a wedge shape so that the plate thickness is increased. On the near side, light is guided through the light guide plate 3, so the brightness is low, and on the side of the light incident end face far from the light source, the plate thickness is thin, so that light is easily emitted and the brightness is increased. There is a nature.

  Therefore, in order to increase the luminance on the light incident end surface 30 side in the light guide plate 3, in the second prism pattern 32, the length of the inclined surface 34a in the vicinity of the light incident end surface 30 is increased, and the height of the concave portion 34 is increased. It is high.

  After a certain distance from the light incident end surface 30, the length of the inclined surface 34a is shorter than the inclined surface 34a near the light incident end surface 30 in the vicinity of the center OL along the X axis, and the height of the concave portion 34 is increased. The height is lowered. Here, there is little difference in height between the plurality of concave portions 34 located near the center of the light guide plate 3.

  Furthermore, in order to contribute to the second prism pattern 32 without wasting light that escapes to the side opposite to the light incident end surface, the length of the inclined surface 34a on the side opposite to the light incident end surface is increased, and The height is increased again on the non-input end face side.

  On the other hand, the pitch of the apex of the concave portion 34 near the center OL along the X-axis of the light guide plate 3 is made shorter than the pitch of the apex of the concave portion 34 on the light incident end face 30 side and the counter light incident end face side. By increasing the pitch of the apex of the concave portion 34 on the light end face 30 side and the counter-incident light end face side, the length of the flat portion 35 between the concave shape portions 34 becomes the same.

  Thereby, in the light guide plate 3, when light enters the light incident end surface 30 from the linear light source 2, the prism sheet 4 facing the light emitting surface side of the light guide plate 3 is caused by the second prism pattern 32 having the shape described above. The light is collected in an optimal direction so that a predetermined directivity can be obtained by the prism sheet 4. Therefore, when assembled as the surface light emitting device 1A, a high luminance and surface uniform state can be obtained.

  FIG. 14 is an operation explanatory diagram of a simulation example showing the uniformity of luminance. It can be seen that when the light from the linear light source 2 is incident on the light guide plate 3 having the second prism pattern 32 having the shape obtained by the calculation method described above, the entire light emitting surface emits light substantially uniformly.

  FIG. 15 is an operation explanatory view showing an outline of a manufacturing process of a mold for forming the second prism pattern 32 of the light guide plate 3. In the mold 103 for molding the second prism pattern 32, an inclined surface forming portion 104a and a flat portion forming portion 104b having a predetermined length are formed in accordance with the concave shape portion 34 of the second prism pattern 32.

  In the mold 103, the inclined surface forming portion 104a and the flat portion forming portion 104b are formed by cutting with the cutting tool B2. For this reason, the cutting tool B2 has an inclined surface cutting part B21 and a flat part cutting part B22.

  Here, as described with reference to FIG. 11 and the like, when the length of the flat portion 35 of the second prism pattern 32 in the light guide plate 3 is made constant, the flat portion forming portion 104b of the mold 103 that forms the flat portion 35 is formed. The length can be defined by the length DL of the flat part cutting part B22 of the cutting tool B2.

  On the other hand, in order to change the length of the inclined surface forming portion 104a of the mold 103 in order to change the length of the inclined surface 34a of the second prism pattern 32, the feed amount of the cutting tool B2 may be changed. When the feed amount is reduced from PBL to PBS, the length of the inclined surface forming portion 104a can be shortened.

  Thereby, in the light guide plate 3, it is easy to process the mold 103 for forming the concave portions 34 of the second prism pattern 32 at a constant pitch and the inclined surface 34a with a non-uniform length. Therefore, it is possible to suppress an increase in manufacturing cost and reduce product cost.

<Configuration Example of Display Device and Electronic Device of Embodiment>
FIG. 16 is a cross-sectional view illustrating an example of the display device of this embodiment. A display device 10 according to the present embodiment is a liquid crystal display device used for a television receiver, a monitor, a computer, and the like, and includes a transmissive liquid crystal display panel 11 and the surface light emitting device 1A described above.

  The liquid crystal display panel 11 includes a liquid crystal layer between electrodes, and can be switched between a state where light is transmitted and a state where light is shielded by changing the alignment of the liquid crystal by applying a voltage.

  The surface light emitting device 1 </ b> A is disposed on the back surface of the liquid crystal display panel 11 and functions as a backlight, and images such as images and characters are displayed depending on whether light is transmitted through the liquid crystal display panel 11.

  FIG. 17 is a perspective view illustrating an example of an electronic device of this embodiment. The electronic device 12 of the present embodiment is, for example, a notebook personal computer, and includes a liquid crystal display 13 and a surface light emitting device 1A shown in FIG.

  Other examples of electronic devices to which the present invention can be applied include monitors for desktop personal computers, television receivers, and the like, for example, display devices having a screen size of 10 inches or more, preferably more than 20 inches. It is applied to the configuration that comprises.

<Effects of Surface Emitting Device, Display Device, and Electronic Device of Embodiment>
In the surface light emitting device 1A of the present embodiment, the directivity (condensation) of light emitted from the light guide 3 can be improved as compared with the conventional structure. As a result, a surface light emitting device having high luminance and excellent in-plane luminance uniformity can be realized. Further, the scratch resistance of the light guide plate 3 can be improved, and the display quality can be improved.

  Further, when the prism shape is processed into a mold for forming the prism pattern of the light guide plate 3, a desired shape can be obtained simply by changing the feeding pitch of the cutting tool, and the mold can be easily processed. .

  Further, the density distribution of the second prism pattern for adjusting the luminance uniformity can be easily determined, the number of trial productions can be reduced, and the cost can be reduced.

  In addition, by providing a surface light emitting device with high brightness in this way, it is possible to reduce power consumption of display devices and electronic devices.

  The present invention is applied to a backlight of a liquid crystal display.

It is a block diagram which shows an example of the surface emitting device of this Embodiment. It is a block diagram which shows an example of the surface emitting device of this Embodiment. It is principal part sectional drawing of the light-guide plate which shows the detail of a 1st prism pattern. It is operation | movement explanatory drawing which shows the condensing effect of the 1st prism pattern in the light-guide plate of the surface emitting device of this Embodiment. It is operation | movement explanatory drawing of the light-guide plate in which the prism pattern of a predetermined shape is not formed in the light emission surface. It is explanatory drawing which shows the example of a simulation at the time of changing the center angle of the circular arc of a 1st prism pattern in the light-guide plate of the surface emitting device of this Embodiment. It is explanatory drawing which shows the lamination | stacking state of a light-guide plate and a prism sheet. It is operation | movement explanatory drawing which shows the outline | summary of the manufacturing process of the metal mold | die which shape | molds the 1st prism pattern of a light-guide plate. It is principal part sectional drawing of the light-guide plate which shows the detail of a 2nd prism pattern. It is a light ray diagram which shows the relationship between the incident angle of light and a refraction angle in a light guide plate and a prism sheet. It is explanatory drawing which shows the calculation method of the length of the inclined surface of the concave shape part in a 2nd prism pattern of a light-guide plate, and a flat part. It is a graph which shows an example of the height distribution of the 2nd prism pattern in a light-guide plate. It is a graph which shows an example of the pitch distribution of the 2nd prism pattern in a light-guide plate. It is operation | movement explanatory drawing of the example of simulation which shows the uniformity of a brightness | luminance. It is operation | movement explanatory drawing which shows the outline | summary of the manufacturing process of the metal mold | die which shape | molds the 2nd prism pattern of a light-guide plate. It is sectional drawing which shows an example of the display apparatus of this Embodiment. It is a perspective view which shows an example of the electronic device of this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A ... Surface light-emitting device, 10 ... Display apparatus, 12 ... Electronic device, 2 ... Linear light source, 3 ... Light guide plate, 30 ... Light-incidence end surface, 31 ... 1st 1 prism pattern, 32... Second prism pattern, 33. Convex portion, 34. Concave shape portion, 34 a. Inclined surface, 35. Flat portion, 4. Prism Sheet, 40 ... prism surface, 5 ... diffusion sheet, 6 ... reflection sheet

Claims (10)

A linear light source is disposed opposite the light incident end face of the light guide plate through which light is propagated,
A surface light emitting device in which a prism sheet and a diffusion sheet are disposed on a light emitting surface side where light of the light guide plate is emitted, and a reflective sheet is disposed on a reflective surface side opposite to the light emitting surface,
The light guide plate has a wedge shape in which the plate thickness on the opposite side from the light incident end surface side becomes thinner as the distance from the linear light source is increased, and irregularities are formed in a predetermined shape on the light emitting surface facing the prism sheet. And a second prism pattern in which irregularities are formed in a predetermined shape orthogonal to the first prism pattern on a reflective surface facing the reflective sheet.
The first prism pattern of the light guide plate includes a convex portion extending from the light incident end surface to the counter light incident end surface in a direction orthogonal to the linear light source,
The second prism pattern of the light guide plate extends in a direction orthogonal to the convex portion of the first prism pattern, and a plurality of concave portions arranged at predetermined intervals along the direction in which the convex portion extends. With a shape part,
The concave portion of the second prism pattern has an inclined surface at an acute angle with respect to a virtual plane parallel to the light emitting surface of the light guide plate on the light incident end surface side. The inclination angle of the inclined surface is constant, and the length of the inclined surface is changed according to the distance from the light incident end surface,
The prism sheet is orthogonal to the convex portion of the first prism pattern on the back surface of the light guide plate facing the first prism pattern, and is formed on the second prism pattern of the light guide plate. A surface light emitting device comprising: a prism having irregularities formed in a predetermined shape parallel to the concave portion and the linear light source. The second prism pattern of the light guide plate has a length of the inclined surface shorter near the center than the inclined surface on the light incident end surface side and the counter light incident end surface side, and from the concave shape portion near the center. The surface light emitting device according to claim 1, wherein a height of the concave portion on the light incident end face side and the counter light incident end face side is increased. In the second prism pattern of the light guide plate, the interval between the vertices of the concave shape portions is shortened near the center from the light incident end surface side and the anti-light incident end surface side, so that each flat portion between the concave shape portions is flat. The surface light-emitting device according to claim 2, wherein the length of the portion is configured to be constant. The first prism pattern of the light guide plate is configured such that a cross-sectional shape of the convex portion is an arc having a substantially constant radius of curvature, and the plurality of convex portions are the centers of adjacent arcs from the center point of the arc. The surface emitting device according to claim 2, wherein the distances to the points are arranged at regular intervals. The surface light-emitting device according to claim 4, wherein the first prism pattern of the light guide plate is configured such that a center angle of an arc of the convex portion is in a range of 1 ° to 60 °. The surface light-emitting device according to claim 4, wherein the first prism pattern of the light guide plate is configured such that heights of the plurality of convex portions are uneven. The surface light-emitting device according to claim 6, wherein the first prism pattern of the light guide plate is configured such that a difference in height between the plurality of convex portions is 20 μm. The first prism pattern of the light guide plate is formed such that a plurality of the convex portions are longer than the effective light emission range, and the convex portions are arranged in parallel.
The second prism pattern of the light guide plate is characterized in that a plurality of the concave-shaped portions are formed in a range longer than an effective light emission range, and each of the concave-shaped portions is arranged in parallel. Item 3. A surface emitting device according to Item 2. In a display device in which a surface light emitting device is disposed on the back surface of a display panel that transmits light, and the display panel is irradiated with the surface light emitting device,
In the surface light emitting device, a linear light source is disposed opposite to a light incident end surface of a light guide plate through which light is propagated,
A prism sheet and a diffusion sheet are disposed on the light emitting surface side where light of the light guide plate is emitted, and a reflection sheet is disposed on the reflective surface side opposite to the light emitting surface,
The light guide plate has a wedge shape in which the plate thickness on the opposite side from the light incident end surface side becomes thinner as the distance from the linear light source is increased, and irregularities are formed in a predetermined shape on the light emitting surface facing the prism sheet. And a second prism pattern in which irregularities are formed in a predetermined shape orthogonal to the first prism pattern on a reflective surface facing the reflective sheet.
The first prism pattern of the light guide plate includes a convex portion extending from the light incident end surface to the counter light incident end surface in a direction orthogonal to the linear light source,
The second prism pattern of the light guide plate extends in a direction orthogonal to the convex portion of the first prism pattern, and a plurality of concave portions arranged at predetermined intervals along the direction in which the convex portion extends. With a shape part,
The concave portion of the second prism pattern has an inclined surface at an acute angle with respect to a virtual plane parallel to the light emitting surface of the light guide plate on the light incident end surface side. The inclination angle of the inclined surface is constant, and the length of the inclined surface is changed according to the distance from the light incident end surface,
The prism sheet is orthogonal to the convex portion of the first prism pattern on the back surface of the light guide plate facing the first prism pattern, and is formed on the second prism pattern of the light guide plate. A display device, comprising: a prism having irregularities formed in a predetermined shape parallel to the concave portion and the linear light source. In an electronic apparatus provided with a display device in which a surface light emitting device is disposed on the back surface of a display panel that transmits light, and the display panel is irradiated with the surface light emitting device.
In the surface light emitting device, a linear light source is disposed opposite to a light incident end surface of a light guide plate through which light is propagated,
A prism sheet and a diffusion sheet are disposed on the light emitting surface side where light of the light guide plate is emitted, and a reflection sheet is disposed on the reflective surface side opposite to the light emitting surface,
The light guide plate has a wedge shape in which the plate thickness on the opposite side from the light incident end surface side becomes thinner as the distance from the linear light source is increased, and irregularities are formed in a predetermined shape on the light emitting surface facing the prism sheet. And a second prism pattern in which irregularities are formed in a predetermined shape orthogonal to the first prism pattern on a reflective surface facing the reflective sheet.
The first prism pattern of the light guide plate includes a convex portion extending from the light incident end surface to the counter light incident end surface in a direction orthogonal to the linear light source,
The second prism pattern of the light guide plate extends in a direction orthogonal to the convex portion of the first prism pattern, and a plurality of concave portions arranged at predetermined intervals along the direction in which the convex portion extends. With a shape part,
The concave portion of the second prism pattern has an inclined surface at an acute angle with respect to a virtual plane parallel to the light emitting surface of the light guide plate on the light incident end surface side. The inclination angle of the inclined surface is constant, and the length of the inclined surface is changed according to the distance from the light incident end surface,
The prism sheet is orthogonal to the convex portion of the first prism pattern on the back surface of the light guide plate facing the first prism pattern, and is formed on the second prism pattern of the light guide plate. An electronic apparatus comprising: a prism in which irregularities are formed in a predetermined shape parallel to the concave portion and the linear light source.