JP2016081850A - Surface light source device, display device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin surface light source device capable of shortening a pitch of light sources mounted on the surface light source device, capable of improving luminance of illumination light, and having light reliability.SOLUTION: In a light guide plate of a surface light source device, provided is an inclination part that is arranged between a light incident surface and a light emission surface, and of which a thickness decreases from the light incident surface side toward the light emission surface side. On the inclination surface of the inclination part, formed is a cutout part having a surface vertical to the light incident surface, and on the surface vertical to the light incident surface in the cutout part, formed is an uneven structure increasing a contact area with an adhesive layer on a printed circuit board of a light source.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a surface light source device, a display device, and an electronic apparatus.

  In recent years, electronic devices are becoming smaller and thinner. The liquid crystal display device mounted on such an electronic device has a need for a narrower frame and a smaller thickness in order to obtain a larger display area with the same area. As a backlight of a liquid crystal display device, for example, an LED (Light Emitting Diode) that emits white light is used as a light source, and light is incident on a light guide plate (also referred to as a light guide) from a side surface (also referred to as an edge light method). ) Surface light source device is used.

  Further, in order to cope with further thinning of the portable information device, it is known to form an inclined portion whose thickness gradually decreases as the distance from the light incident end surface increases between the light incident end surface and the light emitting portion. Thus, by forming the inclined portion (inclined surface) near the light incident end face of the light guide plate, the thickness of the light emitting portion of the light guide plate can be reduced regardless of the thickness of the LED.

  Here, the LED is usually disposed so as to face the light incident end face of the light guide plate in a state of being mounted on a strip-shaped printed circuit board. Then, the LED is positioned and fixed with respect to the light guide plate by closely fixing the portion of the printed circuit board in front of the portion where the LED is mounted to the vicinity of the light incident end face of the light emitting portion of the light guide plate. Then, when the inclined portion is not formed near the light incident end surface of the light guide plate, the LED has a light emitting surface parallel to the light incident end surface of the light guide plate in a state where the printed circuit board is closely fixed to the light guide plate. Are arranged so as to face each other.

  However, when an inclined surface is formed in the vicinity of the light incident end surface of the light guide plate, in a state where the printed circuit board is closely fixed to the inclined surface of the light guide plate, the light emitting surface of the LED is the light incident end surface of the light guide plate. It is not possible to arrange them so as to be parallel to each other. That is, since the light incident end surface and the inclined surface of the light guide plate are not orthogonal, a part of the light emitted from the light emitting surface of the LED leaks outside without entering the light incident end surface of the light guide plate, In some cases, the light guide efficiency was lowered. In addition, even when the printed circuit board is fixed to either the vicinity of the light incident end face or the inclined surface of the emission plane, the printed circuit board is reflected when light incident near the light incident end face or the inclined surface of the emission plane is reflected. In some cases, the luminance of the illumination light may be reduced.

  On the other hand, the light guide plate is formed with an inclined portion whose thickness gradually decreases between the light incident end face and the emitting portion toward the emitting portion side, and a light source is provided on the inclined surface of the inclined portion. In the region excluding the front portion of the optical disk, a notch portion having a flat surface that can be attached while keeping the printed circuit board perpendicular to the light incident end face has been made. As a result, a horizontal region for attaching the printed circuit board is formed in a region excluding the front portion of the light source in the inclined surface of the inclined portion formed on the light guide plate. For this reason, the printed circuit board can be fixed horizontally to the light guide plate, and absorption of light by the printed circuit board can be suppressed. As a result, the luminance of the illumination light can be increased.

By the way, in the liquid crystal display device as described above, further improvement in the visibility of the display screen is required, and in the surface light source device used in such a liquid crystal display device, high brightness has been required. It was. Conventionally, since there has been a demand for low power consumption of the surface light source device, improvement has been mainly made in terms of how to improve luminance while reducing the number of light sources as much as possible. Due to the increase in battery capacity of electronic equipment itself and the improvement of charging environment, the demand for low power consumption is lower than before, and the pitch of the light source installed in the surface light source device is shortened, and more light sources are installed. However, it has become possible to select means for increasing the luminance by increasing the amount of light.

  And, when trying to shorten the pitch of the light source mounted on the surface light source device, the width of the above-mentioned notch portion in the printed circuit board is reduced, and the adhesion area between the printed circuit board and the notch portion is reduced, and as a result In some cases, the adhesive force or adhesive force of the printed circuit board to the light guide plate is reduced, leading to a decrease in reliability.

Japanese Patent No. 5278635 JP 2011-96523 A JP 2014-146535 A International Publication WO2008 / 153024 International Publication WO2010 / 070821 Pamphlet

  The present invention made in view of the above-mentioned problems of the prior art can shorten the pitch of the light source mounted on the surface light source device, can improve the luminance of the illumination light, and is more reliable and thin. An object of the present invention is to provide a surface light source device.

  The present invention for solving the above-mentioned problems is that the light guide plate of the surface light source device is disposed between the light incident surface and the light exit surface, and the thickness decreases as it goes from the light entrance surface side to the light exit surface side. A notch portion having a surface perpendicular to the light incident surface is formed on the inclined surface of the inclined portion, and a light source is provided on the surface perpendicular to the light incident surface in the notch portion. The most characteristic feature is that a concavo-convex structure that increases the contact area with the adhesive layer on the printed circuit board is formed.

More specifically, printed circuit boards and
A light source mounted on the printed circuit board;
A light source plate including light emitted from the light source introduced from a light incident surface, and guiding the introduced light to a light exit surface and emitting the light in a planar shape,
The light guide plate is provided with an inclined portion that is disposed between the light incident surface and the light emitting surface and has a thickness that decreases from the light incident surface side toward the light emitting surface side,
On the inclined surface which is the surface of the inclined portion, a notch portion having a surface intersecting with the light incident surface is formed,
The light source is disposed so as to face the light incident surface by attaching the printed circuit board to the notch of the inclined portion.
An uneven structure that increases a contact area with an adhesive layer provided on the printed circuit board is formed on a surface of the cutout portion that is perpendicular to the light incident surface.

  According to this, the adhesive force or adhesive force between a notch part and a printed circuit board can be strengthened by increasing a contact area with the adhesion layer provided on the printed circuit board. As a result, even when the pitch of the light source mounted on the surface light source device is shortened and the luminance of the illumination light is improved, the fixing strength of the light source can be improved and the reliability as the surface light source device can be maintained or improved. it can.

In the present invention, it is preferable that the height of the concavo-convex structure is smaller than the thickness of the adhesive layer. As a result, the adhesive layer of the printed circuit board can be more reliably brought into contact with the entire surface of the concavo-convex structure of the notch portion, and the adhesive force or adhesive force between the notch portion and the printed circuit board can be further increased. can do.

In the present invention, the height of the concavo-convex structure may be 30 μm or less. here,
Generally, the thickness of the double-sided tape for attaching the printed circuit board to the light guide plate is 100 μm or less, and the thickness of the adhesive layer is 40 μm or less. Therefore, by setting the height of the concavo-convex structure to 30 μm or less, the adhesive layer of the printed circuit board can be more reliably brought into contact with the entire surface of the concavo-convex structure of the notch. As a result, the adhesive force or adhesive force between the notch and the printed circuit board can be further increased.

  In the present invention, the concavo-convex structure may be a groove structure including a plurality of grooves formed to extend in a direction perpendicular to the light incident surface. The groove in the groove structure may be a V-shaped groove having a V-shaped cross section in a direction parallel to the light incident surface. According to this, when processing the shaping | molding die for shaping | molding a light-guide plate, an uneven structure can be more easily formed in a notch part.

  In the present invention, the groove may be formed such that a cross section in a direction parallel to the light incident surface is asymmetric with respect to the groove center. According to this, when processing the mold for forming the light guide plate, the uneven structure of the notch is processed with the same bite as the structure for forming other groove structures having various functions in the light guide plate. It is possible to improve the productivity of the light guide plate.

Further, in the present invention, on the inclined surface that is the surface of the inclined portion, the directivity spread in the thickness direction of the light guide plate of the light incident from the light incident surface is a direction parallel to the surface direction of the light guide plate. A first directivity conversion pattern for converting into a directivity characteristic inclined toward the
The first directivity conversion pattern may be configured to alternately repeat ridge lines and valley lines along the width direction of the light guide plate. According to this, when processing a forming die for forming the light guide plate, the first directivity conversion pattern and the concavo-convex structure can be continuously processed with the same cutting tool. It is possible to further improve the productivity. In the present invention, when the concavo-convex structure and the ridge line in the first directivity conversion pattern are matched, the first directivity conversion pattern is formed when a forming die for forming the light guide plate is processed. And the uneven structure can be processed more reliably and continuously, and the productivity of the light guide plate can be further improved.

In the present invention, between the inclined portion and the light exit surface of the light guide plate,
A terminal portion having a second inclined surface with a gentler inclination angle than the inclined surface which is the surface of the inclined portion is provided,
A second directivity that equalizes the amount of light emitted from the light emitting surface by dispersing light guided by the inclined portion in the width direction of the light guide plate on the second inclined surface of the terminal portion. A conversion pattern is provided,
The second directivity conversion pattern may be configured to alternately repeat ridge lines and valley lines along the width direction of the light guide plate.
According to this, when processing the mold for forming the light guide plate, the first directivity conversion pattern, the second directivity conversion pattern, and the concavo-convex structure are continuously processed with the same tool. It is possible to improve the productivity of the light guide plate more remarkably. Further, in the present invention, when ridge lines in the concavo-convex structure, the first directivity conversion pattern, and the second directivity conversion pattern are made to coincide, when processing a forming die for forming a light guide plate The first directivity conversion pattern and the concavo-convex structure can be processed more reliably and continuously, and the productivity of the light guide plate can be further improved.

  The present invention may also be a liquid crystal display device comprising the above surface light source device and a liquid crystal panel that receives light emitted from the surface light source device. In such a display device, since the surface light source device according to the present invention is provided, a display device having high luminance, excellent display quality, and high reliability can be provided.

  Further, the present invention may be an electronic device including the above liquid crystal display device. In such an electronic device, since the display device using the surface light source device according to the present invention is provided, an electronic device having high luminance, excellent display quality, and high reliability can be provided.

  In the present invention, the above means can be used in combination as much as possible.

  According to the present invention, the pitch of the light sources mounted on the surface light source device can be shortened, the luminance of the illumination light can be improved, and the reliability can be further increased.

It is the disassembled perspective view which showed the surface light source device and liquid crystal panel in the Example of this invention. It is a disassembled perspective view of the surface light source device in the Example of this invention. It is A-A 'sectional drawing of the surface light source device in the Example of this invention. It is a perspective view which shows the inclination part vicinity of the light-guide plate which concerns on a prior art. It is a figure for demonstrating the influence by shortening the pitch of a light source in the Example of this invention. It is a perspective view which shows the inclination part vicinity of the light-guide plate in the Example of this invention. It is a graph which shows the relationship between the contact area ratio of the fixing member contact surface in the Example of this invention, a fixing member, and adhesive force. It is a figure which shows the variation of the cross-sectional shape of the uneven | corrugated groove | channel of the uneven | corrugated contact surface in the Example of this invention. It is a perspective view which shows the inclination part vicinity of the light-guide plate in Example 2 of this invention. It is a figure for demonstrating the effect | action of the 1st directivity conversion pattern of the inclination part in Example 2 of this invention. It is a figure which shows the variation of the cross-sectional shape of the 1st directivity conversion pattern of the inclination part in Example 2 of this invention. It is a graph which shows the relationship between the opening angle of the pattern groove | channel of the 1st directivity conversion pattern in Example 2 of this invention, and light guide efficiency. It is a figure which shows the variation regarding the planar view of the 1st directivity conversion pattern of the inclination part in Example 2 of this invention. It is a figure which shows the other variation regarding the planar view of the 1st directivity conversion pattern of the inclination part in Example 2 of this invention. It is a perspective view which shows the inclination part vicinity of the light-guide plate in Example 3 of this invention. It is a figure which shows the top view and side view of a light-guide plate in Example 3 of this invention. It is a figure for demonstrating the relationship between the inclination angle of the terminal part of the light-guide plate in Example 3 of this invention, and an inclination angle, and HotSpot amount. It is a figure for demonstrating the HotSpot amount of the light-guide plate in Example 3 of this invention. It is a figure for demonstrating the cross-sectional shape of the 2nd directivity conversion pattern of the light-guide plate in Example 3 of this invention. It is a figure for demonstrating the cross-sectional shape of the 2nd directivity conversion pattern of the light-guide plate in Example 3 of this invention. It is a graph which shows the relationship between the opening angle of the pattern groove | channel of the 2nd directivity conversion pattern in Example 3 of this invention, and the amount of HotSpots. It is a top view which shows the inclination part vicinity of the light-guide plate in Example 3 of this invention. It is a figure which shows the variation of the cross-sectional shape of the 2nd directivity conversion pattern in Example 3 of this invention. It is a figure shown about the light source and light guide plate at the time of arrange | positioning a several light source facing the light-incidence surface of the light guide plate in Example 3 of this invention. It is a figure shown about the relationship between the 1st directivity conversion pattern of the inclination part in Example 3 of this invention, and the 2nd directivity conversion pattern of a termination | terminus part. It is a figure shown about the variation of the shape of the light-projection surface of the light-guide plate in Example 3 of this invention. It is a figure shown about the variation of the inclination aspect of the structure of the upper end of the light-incidence surface in Example 3 of this invention, an inclination part, and a termination | terminus part, and a 1st directivity conversion pattern and a 2nd directivity conversion pattern. It is a figure shown about the electronic device in the Example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below shows an example for carrying out the present invention, and the present invention is not limited to a specific configuration described below.

<Example 1>
(Configuration of liquid crystal display device)
FIG. 1 is a perspective view illustrating the configuration of a liquid crystal display device as an example of a display device according to this embodiment. As shown in FIG. 1, the liquid crystal display device according to this embodiment includes a surface light source device 1 disposed as a backlight and a liquid crystal panel 2 that receives light emitted from the surface light source device 1. The liquid crystal panel 2 is a display panel that displays an image by applying a voltage to a liquid crystal sandwiched between glass plates to increase or decrease the light transmittance. In the following embodiments, the liquid crystal display device is similarly configured. In the following description, the embodiment may be described with the liquid crystal panel 2 side as the upper side and the opposite side as the lower side in the surface light source device 1 of FIG.

(Configuration of the surface light source device 1)
FIG. 2 is a perspective view illustrating the configuration of the surface light source device 1 according to this embodiment. The surface light source device 1 in this embodiment includes a light guide plate 10, a plurality of light sources 11, a flexible printed circuit board (hereinafter also referred to as “FPC”) 12, a frame 13, and a fixing member 14. Further, the surface light source device 1 includes a reflection sheet 15 disposed on the lower surface side of the light guide plate 10. The surface light source device 1 includes a diffusion sheet 16, prism sheets 17 a and 17 b, and a light shielding sheet 18 that are sequentially stacked on the upper surface side of the light guide plate 10.

  The light guide plate 10 has a substantially plate shape and is formed of a translucent material such as polycarbonate resin or polymethyl methacrylate resin. The upper surface of the light guide plate 10 is a light emitting surface from which light is emitted. The light guide plate 10 guides the light introduced from the light source 11 into the light guide plate 10 to the light exit surface using total reflection so that the entire light exit surface shines uniformly. In the light guide plate 10, a light incident surface on which light from the light source 11 is incident is provided on the side surface where the light emitting surface of the light source 11 faces.

The light source 11 is an LED light source that emits white light from a fluorescent part (an example of a “light emitting part”), but an LED light source other than white or a light source other than an LED light source may be used. The lead frame (not shown) is joined to the land of the FPC 12 and driven by receiving power from the FPC 12. The FPC 12 is a wiring board configured by providing a wiring with a conductive foil on a base material that is a flexible insulating film and bonding a cover lay that is a protective insulating film on the surface. On the FPC 12, a plurality of light sources 11 are mounted in a line at regular intervals.

  The frame 13 is a frame-shaped member having an opening and having four sides. The frame 13 is molded from a polycarbonate resin containing titanium oxide or the like. The light guide plate 10 is fitted into the frame 13, and the inner peripheral surface of the frame 13 surrounds the side surface forming the outer peripheral surface of the light guide plate 10. The frame 13 has a high reflectance, and reflects light so that light in the light guide plate 10 does not leak from the outer peripheral surface of the light guide plate 10. A housing part that houses the light source 11 is provided on one side of the frame 13, and a reflecting wall that reflects light from the light source 11 is provided in the housing part.

  The fixing member 14 is disposed on the lower surface of the FPC 12 and fixes the FPC 12, the frame 13, and the light guide plate 10. The fixing member 14 is, for example, a double-sided adhesive tape whose upper and lower surfaces are adhesive surfaces, but is not limited to a double-sided adhesive tape. An adhesive tape other than the double-sided adhesive tape, an adhesive, or an adhesive may be used. The reflection sheet 15 is a smooth sheet made of a highly reflective white resin sheet, metal foil, or the like, and reflects light so that light in the light guide plate 10 does not leak from the lower surface of the light guide plate 10. The diffusion sheet 16 is a translucent resin film, and diffuses the light emitted from the light exit surface of the light guide plate 10 to widen the light directivity. The prism sheets 17a and 17b are transparent resin films having a triangular prism-like fine pattern formed on the upper surface, condensing the light diffused by the diffusion sheet 16, and viewing the surface light source device 1 from the upper surface side. Increase the brightness. The light shielding sheet 18 is a black pressure-sensitive adhesive sheet whose upper and lower surfaces are adhesive surfaces. The light shielding sheet 18 has a frame shape and suppresses light from leaking out.

  FIG. 3 is a cross-sectional view of the surface light source device 1 according to this embodiment. FIG. 3 shows an A-A ′ cross section (see FIG. 2) of the surface light source device 1. In FIG. 3, the diffusion sheet 16 and the prism sheets 17 a and 17 b are stacked on the upper surface side of the light guide plate 10. The FPC 12 on which the light source 11 is mounted is disposed on the upper side of the light guide plate 10. The light shielding sheet 18 covers the light source 11 and the FPC 12 from above. The reflection sheet 15 overlaps the lower surface of the light guide plate 10. In the following description, the right side toward the paper surface of FIG. 3, that is, the direction in which the light emitted from the light source 11 travels is the front side, the opposite side is the rear side, the back side of the paper surface is the left side, and the front side of the paper surface is the right side. An explanation may be given.

  In FIG. 3, the light guide plate 10 is provided with a wedge-shaped light introducing portion 10b having a thickness larger than that of the light guide plate main body portion 10a at the end of the plate-shaped light guide plate main body portion 10a having a uniform thickness. . A large number of minute optical patterns 10c are formed on the lower surface of the light guide plate main body 10a, and the upper surface of the light guide plate main body 10a is a light emitting surface 10d. The light introducing portion 10b has an inclined portion 10f that is an inclined surface connecting the end portion 10g of the light incident surface 10e for taking in light from the light source 11 and the light emitting surface 10d. The inclined portion 10f is inclined so that the height decreases from the end portion 10g of the light incident surface 10e toward the light emitting surface 10d.

  Next, the light introduction part 10b of the conventional light guide plate 10 will be described with reference to FIG. As shown in FIG. 4, the light introduction part 10 b of the conventional light guide plate 10 is formed at a position between the plurality of light sources 11 so as to cut out the inclined part 10 f horizontally in the middle of the inclined surface. A fixing member contact surface 10h that is a horizontal surface is provided. The height of the step between the fixing member contact surface 10h and the end portion 10g of the light incident surface 10e is set to be slightly smaller than the thickness of the fixing member 14, and the FPC 12 is set to the light emitting surface 10d of the light guide plate 10. The fixing member 14 can be fixed horizontally while absorbing the thickness thereof. As a result, the light source 11 can be fixed so as to face the light-emitting surface 10e of the light guide plate 11 in parallel with the light-emitting surface 10e. In addition, the dimension of the fixing member contact surface 10h in the left-right direction is formed so as not to prevent the light emitted from the light source 11 from proceeding to the light guide plate body 10a.

Here, as described above, in recent years, there has been an increasing demand for shortening the pitch of the light sources 11 mounted on the surface light source device 1 and mounting more light sources 11 to increase the luminance. When this request is answered, as shown in FIG. 5, the pitch between the light source 11 and the adjacent light source 11 is shortened, and the width in the left-right direction of the fixing member contact surface 10h is narrowed. As a result, the contact area between the fixing member 14 and the fixing member contact surface 10h is reduced, and sufficient adhesive force or adhesive force for fixing the FPC 12 may not be obtained.

  Therefore, in the present embodiment, as shown in FIG. 6, an uneven surface is added to the fixing member contact surface 10 h to form the uneven contact surface 10 j, thereby increasing the bonding area with the fixing member 14. As described above, when the uneven contact surface 10j is added to the fixing member contact surface 10h to form the uneven contact surface 10j, and the adhesion area of the fixing member 14 to the light guide plate 10 is increased, as shown in FIG. It becomes possible to increase the adhesive force of the fixing member 14 substantially in proportion to the contact area.

Here, when the height of the concavo-convex shape is higher than the thickness of the adhesive layer of the fixing member 14, the adhesive area is reduced and the adhesive force may be reduced. Therefore, the height of the concavo-convex shape needs to be lower than the thickness of the adhesive layer of the fixing member 14. Therefore, when it is assumed that a general fixing member 14 having a thickness of about 100 μm is used, the contact area can be favorably increased if the height of the concavo-convex shape is set to, for example, 30 μm or less.

In addition, the uneven | corrugated shape in the uneven | corrugated contact surface 10j is good also as an uneven | corrugated groove | channel provided along the front-back direction of the light-guide plate 10, as shown in FIG. Further, the cross-sectional shape of the concave and convex grooves may be V-shaped or mountain-shaped, curved or corrugated, polygonal, rectangular or trapezoidal in which the side surface of the V-groove is bent halfway as shown in FIG. Further, the cross section of the concave and convex grooves may not be bilaterally symmetric with respect to the groove center, and may be, for example, a left-right asymmetric V-groove. Although not shown, the uneven shape on the uneven contact surface 10 j may be an uneven groove provided along the left-right direction or another direction of the light guide plate 10. Furthermore, it may not be an uneven groove, and may be a shape in which discrete protrusions or depressions are dispersed, or a rough surface shape.

<Example 2>
Next, a second embodiment of the present invention will be described. In this embodiment, the inclined portion of the light guide plate is provided with a pattern for controlling the directivity of light from the light source incident from the light incident surface, and the similar pattern is also provided on the uneven contact surface as the uneven groove. An example will be described.

  In FIG. 9, the perspective view of inclination part 10f vicinity of the light-guide plate 10 which concerns on a present Example is shown. In the present embodiment, for example, a first directivity conversion pattern 20 that widens the directivity of light incident from the light source to the left and right is formed in at least the region surrounded by the broken line of the inclined portion 10f. The first directivity conversion pattern 20 suppresses the amount of light that enters the light guide plate 10 from the light incident surface 10e and is not reflected by the inclined portion 10f but leaks outside through the inclined portion 10f. Is to do. The first directivity conversion pattern 20 is formed so that each pattern is parallel to the front-rear direction of the light guide plate 10 when viewed from above the light guide plate 10.

  In the present embodiment, the concavo-convex groove on the concavo-convex contact surface 10 j has the same cross-sectional shape as the first directivity conversion pattern 20. Therefore, at the time of processing the forming mold for forming the light guide plate 10, the concave and convex grooves on the concave and convex contact surface 10j and the first directivity conversion pattern 20 can be continuously processed with the same tool. Productivity can be improved. Further, the light guide efficiency of the light guide plate 10 can be improved by the effect of the first directivity conversion pattern 20. In the above description, it is desirable that the concavo-convex groove on the concavo-convex contact surface 10j matches the ridge line with the pattern in the first directivity conversion pattern 20 of the inclined portion 10f. This makes it possible to more reliably and continuously process the concave and convex grooves on the concave and convex contact surface 10j and the first directivity conversion pattern 20 when processing a molding die for molding the light guide plate 10. The productivity of the optical plate 10 can be further improved.

(Cross-sectional shape of the first directivity conversion pattern of the inclined portion)
Here, the cross-sectional shape of the first directivity conversion pattern in the inclined portion 10f will be described in detail. FIG. 10 is a view of the light guide plate 10 as viewed from the rear side (behind the light source 11). As shown in FIG. 10, the cross-sectional shape of the first directivity conversion pattern 20 of the inclined portion 10 f in the present embodiment is a V-groove along the front-rear direction of the light guide plate 10. The V-groove pattern does not have a symmetrical shape, but has at least a part of a region having an asymmetric cross-sectional shape. Here, an alternate long and short dash line indicates a plane that passes through the light emission center of the light source 11 and is perpendicular to the light incident surface 10e and the light emitting surface 10d of the light guide plate 10.

  Most or all of the pattern grooves constituting the directivity conversion pattern 20 have an asymmetric shape with respect to the groove center when the cross section parallel to the light incident surface 10e is viewed as described above. That is, the pattern slope 20a that connects a certain ridge line (maximum point of the cross section) in the pattern and one valley line (minimum point of the cross section) adjacent to the ridge line, and the other valley line (cross section adjacent to the ridge line and the ridge line). The pattern slope 20b (these pattern slopes constitute the side surfaces of adjacent V-grooves) that are connected to the minimum point) are asymmetrical with respect to a straight line passing through the ridge line and perpendicular to the light exit surface 10d.

  In the left region from the center of the light source 11, when a normal line N (not shown) is set on each of the pattern inclined surfaces 20 a and 20 b from the inside of the light guide plate 10 to the outside, the normal line N is the light source center. The width of the pattern slope 20b inclined to the side is larger than the width of the pattern slope 20a where the normal N is inclined to the side opposite to the light source center. Similarly, also in the region on the right side from the light source center, the horizontal width of the pattern slope 20b in which the normal line N is inclined toward the light source center side is equal to the pattern slope 20a in which the normal line N is inclined to the opposite side to the light source center. It is larger than the width.

  As a result, the area of the pattern inclined surface 20a on which light emitted in an oblique direction from the center of the light source 11 is incident at an angle close to the vertical is narrower than in the case where the pattern groove is the first directivity conversion pattern that is symmetric. The light is less likely to leak from the pattern slope 20a. Furthermore, the inclination angle of the pattern inclined surface 20a in which the normal line N is inclined to the side opposite to the light source center is increased, and the pattern groove of the first directivity conversion pattern is incident on the pattern inclined surface 20a as compared with the case where the pattern groove is symmetrical. Since the incident angle of light is increased, it is difficult for light to leak from the pattern slope 20a. As a result, light leakage from the inclined portion 10f can be suppressed, and the light guide efficiency of the light guide plate 10 is improved.

  In the first directivity conversion pattern 20, the cross-sectional shape of the pattern groove may be changed according to the distance from the light source center. There are a variety of such embodiments. For example, in the inclined portion 10f shown in FIG. 11A, the pattern groove opening angle W gradually decreases as the distance from the light source center increases. In the inclined portion 10f shown in FIG. 11B, the pattern groove opening angle W gradually increases as the distance from the light source center increases. FIG. 11C shows the first directivity conversion pattern 20 in which pattern grooves having curved surfaces are arranged instead of complete V-grooves, and the degree of curve of the pattern grooves gradually changes as the distance from the light source center increases.

(Vertical angle range)
FIG. 12 is a graph showing the relationship between the apex angle W (angle formed by the side surfaces of adjacent V grooves) and the light guide efficiency in the first directivity conversion pattern 20 including a plurality of V grooves. The vertical axis in FIG. 12 represents the light guide efficiency of the light guide plate as 100% when the same symmetrical pattern elements are arranged. According to FIG. 12, the light guide efficiency is highest when the opening angle W is about 120 °, and the light guide efficiency is improved as compared with the conventional case when the opening angle W is in the range of 57 ° ≦ W ≦ 145 °. I understand that Therefore, the vertex opening angle W in the first directivity conversion pattern 20 is 1
A value close to 20 ° is desirable.

(Various forms of the first directivity conversion pattern)
Next, variations of the form of the first directivity conversion pattern 20 in plan view will be described. FIGS. 13A to 13C and FIGS. 14A to 14C are schematic plan views showing various aspects of the first directivity conversion pattern 20 and the uneven contact surface 10j. The first directivity conversion pattern 20 can be formed in various modes as shown in the figure when viewed from above the light guide plate 10. In the embodiment shown in FIG. 13A, the first directivity conversion pattern 20 is formed from the middle of the inclined surface of the inclined portion 10f to the lower end of the inclined portion 10f, that is, the boundary portion between the inclined portion 10f and the light emitting surface 10d. Yes. And the uneven | corrugated contact surface 10j is mainly formed in the right-and-left both ends of the area | region in which the 1st directivity conversion pattern 20 is not formed among the inclination parts 10f.

  In the aspect shown in FIG. 13B, the first directivity conversion pattern 20 is formed on the entire inclined portion 10f. The uneven contact surface 10j is formed by setting the inclination angle of a part of the inclined portion 10f to 0 degree (horizontal). In the mode shown in FIG. 13C, the first directivity conversion pattern 20 is formed only in the central portion of the inclined portion 10f located in front of the light source 11, and the uneven contact surface 10j is on the left and right sides of the inclined portion 10f. The first directivity conversion pattern 20 is formed at the end of the region where the pattern is not formed.

  In the embodiment shown in FIG. 14A, the first directivity conversion pattern 20 is formed, and the lower edge of the inclined portion 10f is bent or curved in a convex shape when viewed from above. The uneven contact surface 10j is formed by setting the inclination angle of a part of the inclined portion 10f to 0 degree (horizontal). Further, in the conventional mode, the first directivity conversion pattern 20 is formed so that each pattern is parallel to the front-rear direction of the light guide plate 10 when viewed from the upper side of the light guide plate 10. In the embodiment shown in FIG. 14B, the pattern grooves of the first directivity conversion pattern 20 are not parallel but are arranged in a radial pattern. The uneven contact surface 10j is formed by setting the inclination angle of a part of the inclined portion 10f to 0 degree (horizontal), and the uneven grooves are also arranged radially.

  Furthermore, the first directivity conversion pattern 20 shown in FIG. 14C is configured by a pattern groove bent in a zigzag manner. The uneven contact surface 10j is formed by setting the inclination angle of a part of the inclined portion 10f to 0 degree (horizontal), and the uneven groove is also constituted by a pattern groove bent in a zigzag manner.

<Example 3>
Next, Embodiment 3 of the present invention will be described. In the present embodiment, the first directivity conversion pattern is provided on the inclined portion as in the second embodiment, and the same uneven groove of the first directivity conversion pattern is provided on the uneven contact surface. And between the inclination part in which the 1st directivity conversion pattern was provided, and the light-projection surface, the termination | terminus part from which the inclination angle differs from the inclination part and the 2nd directivity conversion pattern was formed is further provided.

  In FIG. 15, the perspective view of inclination part 10f vicinity of the light-guide plate 10 which concerns on a present Example is shown. In the present embodiment, the first directivity conversion pattern 20 that widens the directivity of the light incident from the light source left and right is formed in the inclined portion 10f. The first directivity conversion pattern 20 is the same as that described in the second embodiment. And the 2nd directivity conversion pattern 22 is formed between the inclination part 10f and the light-projection surface 10d, and the termination | terminus part 10k which made the inclination angle smaller than the inclination part 10f is provided. As with the first directivity conversion pattern 20, the second directivity conversion pattern 22 is formed so that each pattern is parallel to the front-rear direction of the light guide plate 10 when viewed from the upper side of the light guide plate 10. Has been. Here, the inclined surface at the terminal portion 10k corresponds to the second inclined surface.

  The termination portion 10k is formed in the region indicated by the broken line in the drawing after increasing the light guide efficiency of the light incident from the light incident surface 10e by the first directivity conversion pattern 20 in the inclined portion 10f. The second directivity conversion pattern 22 serves to equalize the distribution of light guided through the light guide plate 10 to the light exit surface 10d.

  FIG. 16 shows a specific plan view of the light guide plate 10 having the uneven contact surface 10j, the inclined portion 10f, the first directivity conversion pattern 20, the terminal portion 10k, and the second directivity conversion pattern 22 in this embodiment. A side view is shown. The plan view shown in FIG. 16 illustrates only a portion corresponding to one light source 11 in the light guide plate 10. That is, the light guide plate 10 in the present embodiment has a plurality of light sources 11 arranged at intervals of 4.7 mm, and FIG. 16 shows a range with a width of 4.7 mm centered on one light source 11.

  In the plan view of FIG. 16, the LED that is the light source 11 has an opening of 2 mm. And the uneven | corrugated contact part 10j is provided in the left-right both ends of the inclination part 10f of the area | region of 4.7 mm in width. In addition, in the front-rear direction of the light guide plate 10, a range from the light incident surface 10e to 1 mm on the front side is an inclined portion 10f. The inclination angle θf of the inclined portion 10f with respect to the horizontal plane is 9 ° to 10 °. As described above, the first directivity conversion pattern 20 is formed on the inclined portion 10f (a range indicated by a solid square).

  Further, the end portion 10k is a range from 1 mm to 1.5 mm from the light incident surface 10e. A second directivity conversion pattern 22 is formed in the terminal portion 10k (a range indicated by a dashed square). Further, the inclination angle θk of the terminal portion 10k is 1.5 ° with respect to the horizontal line.

  Further, in the present embodiment, the light emission surface 10d (display region) is a range in front of 2.5 mm from the light incident surface 10e. In this embodiment, the height of the light incident surface 10e is 0.4 mm, and the height of the light emitting surface 10d (display area) is 0.23 mm. A lenticular pattern is formed on the light exit surface 10d along the front-rear direction of the light guide plate 10. The light guide plate 10 in this embodiment is made of polycarbonate and has a refractive index of 1.59.

(Optimum value of the inclination angle of the end part)
In the above, the inclination angle θk of the terminal portion 10k is 1.5 °, but the inclination angle θk of the terminal portion 10k is not necessarily 1.5 °. Hereinafter, the condition of the inclination angle θk of the terminal portion 10k will be described. FIG. 17A shows the inclination angle θf of the inclined portion 10f and the inclination angle θk of the end portion 10k, and FIG. 17B shows the relationship between the inclination angle θk of the end portion 10k and the HotSpot amount. The graph to represent is shown. In FIG. 17B, the horizontal axis represents θk, and the vertical axis represents the amount of HotSpot.

  Here, the HotSpot amount will be described first with reference to FIG. FIG. 18 is a plan view of the light guide plate 10 and how light incident from the light source 11 is distributed on the light exit surface 10d, that is, how light incident from the light source 11 is visually recognized in the display area. FIG. 18A shows an example where the amount of HotSpot is large (bad), and FIG. 18B shows an example where the amount of HotSpot is small (good).

As can be seen from FIG. 18A, in particular, in an example where the amount of HotSpot is large (bad), the bright part and the dark part clearly appear at the end of the light guide plate 10 on the light source 11 side. . The amount of HotSpot is obtained by dividing the light amount of the bright portion at the end of the display area on the light source 11 side by the light amount of the dark portion, as shown in Equation (1).

HotSpot amount = light amount of light portion at light source side end of display area ÷ light amount of dark portion (1)

As shown in FIG. 18B, the measurement range of the amount of light when detecting the HotSpot amount is D0 in the front-rear direction of the light guide plate 10 and W0 in the left-right direction at the end of the display area on the light source 11 side. It is an area. Here, in this embodiment, D0 = 1 mm. W0 is

W0 = (distance to display area × tan (arcsin (1 ÷ refractive index n of light guide plate)) + light source emission width / 2) (2)

Determined by. However, when the pitch of the light sources 11 is smaller, the pitch of the light sources 11 is set. When the distance to the display area is 2.5 mm, the width of the light source 11 is 2 mm, and the refractive index n of the light guide plate is 1.59 (polycarbonate), the evaluation width W0 ≦ ± 3 mm.

  Returning to the description of FIG. As shown in FIG. 17B, the amount of HotSpot becomes the minimum value when the inclination angle θk of the terminal portion 10k is 1.5 °, and then increases as the inclination angle θk increases. Further, in the conventional light guide plate, the Hot Spot amount often shows a value of 2 or more, and if the Hot Spot amount is 1.5 or less, it is considered that the brightness non-uniformity is sufficiently improved. Therefore, it can be said that the inclination angle θk of the terminal portion 10k is preferably 3.5 ° or less, and more preferably 1.5 °.

Furthermore, as a result of investigations by the inventors,
(1) Average inclination angle of terminal portion <maximum inclination angle of inclined portion (2) Average inclination angle of terminal portion <3.5 °
(3) End portion height Hk <(total height Hfk of inclined portion and end portion) / 3
It was found that the amount of HotSpot can be suppressed to a sufficiently small value by satisfying this condition. It is desirable that the dimensional relationship between the inclined portion 10f and the terminal portion 10k is determined so as to satisfy the conditions (1) to (3).

(Cross-sectional shape of the second directivity conversion pattern of the terminal portion)
Next, the cross-sectional shape of the second directivity conversion pattern 22 in the terminal portion 10k will be described. As shown in FIG. 19, the second directivity conversion pattern 22 in the terminal portion 10 k of the present embodiment is a V-groove along the front-rear direction of the light guide plate 10. The cross-sectional shape of the V-groove does not have a symmetrical shape with respect to the groove center, but at least a region having a cross-sectional shape that is asymmetric with respect to the groove center exists. In FIG. 19, a one-dot chain line indicates a plane that passes through the light emission center of the light source 11 and is perpendicular to the light incident surface 10 e and the light emitting surface 10 d of the light guide plate 10.

  In the light guide plate 10 of the present embodiment, most or all of the pattern grooves (V grooves) constituting the second directivity conversion pattern 22 have an asymmetric shape with respect to the groove center as described above. Yes. That is, the pattern slope 22a connecting a certain ridge line (maximum point of the cross section) and one valley line (minimum point of the cross section) adjacent to the ridge line, and the other valley line (minimum of the cross section) adjacent to the ridge line and the ridge line. The pattern slope 22b connecting the point) is asymmetric with respect to a straight line passing through the ridge line and perpendicular to the light exit surface 10d. However, some of the pattern grooves (for example, the pattern groove at the center of the light source) may be bilaterally symmetric.

  Further, in the region on the left side in the drawing from the center of the light source 11, when the normal line N is set on each of the pattern inclined surfaces 22a and 22b from the inside of the light guide plate 10 to the outside, the normal line N moves toward the light source center side. The average value of the width D2 of the inclined pattern slope 22b (the average value of the width D2 of each pattern slope 22b in the region on the left side of the light source center) of the pattern slope 46a in which the normal N is inclined to the opposite side of the light source center. It is larger than the average value of the horizontal width D1 (the average value of the horizontal width D1 of each pattern slope 22a in the left region of the light source center).

  Similarly, also in the region on the right side from the light source center, when the normal line N is set on each of the pattern inclined surfaces 22a and 22b from the inside of the light guide plate 10 to the outside, the normal line N is inclined toward the light source center side. The average value of the width D2 of the pattern slope 22b is larger than the average value of the width D1 of the pattern slope 22a in which the normal N is inclined to the side opposite to the light source center.

  In order to realize such a configuration, the width D2 of the pattern slope 22b in which the normal line N is inclined toward the light source center side in all of the two adjacent pattern slopes 22a and 22b, and the normal line N is the light source center. It may be larger than the width D1 of the pattern inclined surface 22a inclined to the opposite side, or may be the same in part. That is, in the second directivity conversion pattern 22, at least a part of the pattern grooves has a width D2 of the pattern slope 22b in which the normal line N is inclined toward the light source center side, and the normal line N is inclined toward the opposite side of the light source center. It is only necessary to satisfy the condition that the pattern slope 22a is larger than the lateral width D1.

  As a result, the area of the pattern groove 22b that reflects the light passing through the terminal end 10k to the side opposite to the center of the light source 11 is equal to the pattern slope 22a that reflects the light passing through the terminal end 10k toward the center of the light source 11. Widened compared to the area. Therefore, the light passing through the terminal portion 10k can be more widely dispersed in the left-right direction, and the light quantity distribution on the light exit surface 10d can be made more uniform.

(Specification by the inclination angle of the normal of the pattern slope)
Here, in the above, as shown in FIG. 20A, the horizontal width D2 of the pattern slope 22b in which the normal line N is inclined toward the light source center side is inclined to the side opposite to the light source center. By making it larger than the width D1 of the pattern slope 22a, the second directivity conversion pattern is asymmetrical with respect to the groove center. Thus, it has been explained that the light passing through the terminal end portion 10k can be more efficiently dispersed in the left-right direction, and the light amount distribution on the light exit surface 10d can be made uniform.

  In addition to the conditions regarding the horizontal width of the pattern slopes 22a and 22b as described above, as shown in FIG. 20B, the angle θ1 of the normal N of the pattern slope 22a with respect to the vertical line in the second directivity conversion pattern 22 The condition of the left-right asymmetry of the second directivity conversion pattern may be specified based on the condition that the average value is larger than the average value of the angle θ2 of the normal line N of the pattern slope 22b.

  In order to satisfy the above condition, in all two adjacent pattern slopes 22a and 22b, the outward normal angle θ1 of the pattern slope 22a is larger than the inward normal angle θ2 of the pattern slope 22b, Or what is necessary is just to be the same in a part of pattern slope. Even if this condition is satisfied, the area of the pattern groove 22 b that reflects the light passing through the terminal end 10 k to the side opposite to the center of the light source 11 is compared with the area of the pattern slope 22 a that reflects to the center side of the light source 11. And can be widened. As a result, the light passing through the terminal portion 10k can be more widely dispersed in the left-right direction, and the light quantity distribution on the light exit surface 10d can be made more uniform.

  Next, the condition of the opening angle (vertical angle) of the pattern slopes 22a and 22b as shown in FIG. 20C will be described.

FIG. 21 is a graph showing the relationship between the opening angle W between the pattern slopes 22a and 22b in the second directivity conversion pattern 22 and the amount of HotSpot described above. As can be seen from FIG. 21, if the opening angle W is in the range of 90 ° to 170 °, the amount of HotSpot can be suppressed to 1.5 or less. It can also be seen that when the opening angle W is 135 °, the HotSpot amount shows a minimum value.

  Here, as described above, the light guide efficiency in the light guide plate 11 was the highest when the opening angle of the pattern slope in the first directivity conversion pattern 20 of the inclined portion 10f was 120 °. Considering these conditions, by making the opening angle of the pattern slope in the second directivity conversion pattern 22 of the terminal portion 10k smaller than the opening angle of the pattern slope in the first directivity conversion pattern 20 in the inclined portion 10f, It can be said that it is possible to optimize both the light guide efficiency of the light guide plate 10 and the uniformity of the amount of light on the light exit surface 10d.

(When the pattern groove changes according to the distance from the light source center)
In the second directivity conversion pattern 22, the cross-sectional shape of each pattern groove may be changed according to the distance from the light source center in the left region and the right region of the light source center. FIG. 22 shows the second directivity conversion pattern 22 in which the cross-sectional shape of the pattern groove changes depending on the distance from the light source center.

  In FIG. 22, the characteristics of the pattern are changed in two steps, the second directivity conversion pattern 22 on the light source center side and the second directivity conversion pattern on the inter-light source side. Specifically, in the left region and the right region of the light source 11, the pattern in which the normal N is inclined to the opposite side of the light source center, with the width D2 of the pattern slope 22 b in which the normal N is inclined toward the light source center. The ratio of the slope 22a to the lateral width D1 is larger in the second directivity conversion pattern 22 in the inter-light source side region than in the second directivity conversion pattern 22 in the light source center side region.

  According to this, compared with the area | region of the light source center side, in the area | region between light sources, the light which passes the termination | terminus part 10k can be disperse | distributed more notably to right and left. Thereby, the light which passes the light-guide plate 10 can be equalized more reliably, and distribution of the light quantity in the light-projection surface 10d can be equalized more reliably.

  In addition, the inward normal angle θ2 of the pattern inclined surface 22b and the outward normal angle θ1 of the pattern inclined surface 22a between the second directivity conversion pattern 22 on the light source center side and the second directivity conversion pattern on the inter-light source side. The ratio may be larger in the second directivity conversion pattern 22 in the region between the light sources than in the second directivity conversion pattern 22 in the region on the light source center side.

  Further, the ratio of the area seen from the upper side of the pattern slope 22b where the normal N is inclined to the light source center side to the area seen from the upper side of the pattern slope 22a where the normal N is inclined to the opposite side to the light source center is Compared with the second directivity conversion pattern 22 in the region on the side, the second directivity conversion pattern 22 in the region on the light source side may be larger.

(Variation of pattern groove at end)
FIG. 23 shows various variations of the cross section of the pattern groove of the second directivity conversion pattern 22. As a cross section of the pattern groove, in addition to the V shape, for example, a curved line having a tip R or a corrugated shape, or a polygon obtained by further bending the slope of the V groove in the middle may be used. Further, with the opening angle W between the pattern slope 22a and the pattern slope 22b constant with respect to the light source center, the pattern slope 22a and the pattern slope 22b tilt in the opposite direction to the light source center as the distance from the light source center increases. It does not matter if it has a shape that goes on.

(Surface light source device with multiple light sources)
Next, the conditions of the region where the terminal portion 10k is formed when a plurality of light sources 11 are provided will be described. FIG. 24 is a diagram illustrating the light source 11 and the light guide plate 10 when a plurality of light sources 11 are arranged facing the light incident surface 10 e of the light guide plate 10. In this case, the first directivity conversion pattern 2 has the same period as the pitch P of the light sources 11 with the middle between the light sources 11 and 11 as a boundary.
Zero and second directivity conversion patterns 22 are formed periodically. For example, when the pitch of the light sources 32 is 4.7 mm as described above, the period of the first directivity conversion pattern 20 and the second directivity conversion pattern 22 is also 4.7 mm.

  When a plurality of light sources 11 are arranged in this way, light from the light sources 11 on both sides reaches the intermediate portion of the adjacent light sources 11 in the first directivity conversion pattern 20 and the second directivity conversion pattern 22. There is. Here, when light from the light sources 11 on both sides is simultaneously incident on a place where the first directivity conversion pattern 20 and the second directivity conversion pattern 22 are present, light leakage is less likely to occur for both lights. Alternatively, it is difficult to optimally design so that the light quantity distribution on the light exit surface 10d is uniform for both lights. Therefore, when light from the light sources 11 on both sides is simultaneously incident on a place where the first directivity conversion pattern 20 and the second directivity conversion pattern 22 are present, the light guide efficiency of the light guide plate 10 is reduced or the light exit surface There is a possibility that the uniformity of the light amount distribution at 10d may be lowered.

Therefore, basically, it is desirable to prevent light from the plurality of light sources 11 from entering the first directivity conversion pattern 20 and the second directivity conversion pattern 22. Here, the incident angle Y of the light emitted from the light source 11 and entering the light introducing portion 10b from the light incident surface 10e is determined by Fresnel's law.
Y = arcsine (1 / n) (3)

It is expressed. Here, n is the refractive index of the light guide plate 10. Therefore, the spread of light in the light introducing portion 10b is in the Y range from side to side with the light source center as the center.

The spread g in the horizontal direction of the light in the first directivity conversion pattern 20 and the second directivity conversion pattern 22 is expressed by Equation 10 above.

g = S · tanY≈S · Y = S · arcsine (1 / n) (4)

It becomes. In order that the light guided in the Y direction from the center of the light source does not enter the adjacent region, the lateral spread g only needs to be smaller than ½ of the pitch P of the light source 11,
g ≦ P / 2 (5)
It becomes.

However, S is the distance from the end surface of the light source 11 (that is, the light incident surface 10e) to the tip of the second directivity conversion pattern 22 measured. Therefore, the condition for preventing the light from the two directions from reaching the first directivity conversion pattern 20 and the second directivity conversion pattern 22 is as follows.

S ≦ P / [2 · arccine (1 / n)] (6)

It becomes.

Therefore, in the case where a plurality of light sources 11 are used, the distance S from the end face of the light source 11 (that is, the light incident face 10e) to the tip of the second directivity conversion pattern 22 satisfies the condition of formula (6). If determined in this way, the first directivity conversion pattern 20 and the second directivity conversion pattern 22 can be optimally designed. That is, in this case, light leakage at the inclined portion 10f of the light guide plate 10 can be reduced to increase the light guide efficiency, and the light quantity on the light exit surface 10d can be made uniform. For example, when the pitch of the light sources 11 is P = 4.7 mm and the refractive index of the light guide plate 10 is n = 1.59 (polycarbonate resin), S is about 3.5 m.
If m or less, it will suffice.

(Relationship between directivity conversion patterns at the inclined part and terminal part)
FIG. 25 shows the relationship between the first directivity conversion pattern 20 of the inclined portion 10f and the second directivity conversion pattern 22 of the terminal portion 10k in the present embodiment. As can be seen from FIG. 25, in the present embodiment, the pattern grooves of the first directivity conversion pattern 20 and the ridge lines of the pattern grooves of the second directivity conversion pattern 22 coincide. In addition, the ridge lines of the concavo-convex grooves on the concavo-convex contact surface 10 j also coincide with the ridge lines of the pattern grooves of the first directivity conversion pattern 20 and the second directivity conversion pattern 22. In this way, when processing a mold for forming the light guide plate 10, the concave and convex grooves on the concave and convex contact surface 10j, the pattern grooves of the first directivity conversion pattern 20, and the second directivity conversion pattern 22 are formed. Pattern grooves can be processed continuously at a time. As a result, the productivity of the light guide plate 10 can be improved.

(Variation of the surface shape of the light exit surface 10d)
FIG. 26 shows variations in the surface shape of the light exit surface 10 d of the light guide plate 10. As the surface shape of the light emitting surface 10d, for example, a lenticular shape as shown in FIG. 26 (A), a mirror shape as shown in FIG. 26 (B), or a polished eye shape as shown in FIG. 26 (C) is adopted. It doesn't matter. Here, the lenticular shape is formed by arranging a plurality of bowl-shaped lenses formed along the front-rear direction of the light guide plate 10. A mirror surface is one in which irregularities are eliminated as much as possible. Further, the polishing eye is a surface state in which fine processing traces due to surface grinding are formed along the front-rear direction of the light guide plate 10.

(Relationship between horizontal part, inclined part and terminal part)
In FIG. 27, the configuration of the upper end 10g, the inclined portion 10f, and the end portion 10k of the light incident surface of the light guide plate 10 in the present embodiment, and the inclined aspects of the first directivity conversion pattern 20 and the second directivity conversion pattern 22 are shown. It shows about the variation. In FIG. 27, a portion indicated by a thick solid line is a region having a mirror surface, a portion indicated by a thick dotted line is a region where the first directivity conversion pattern 20 is formed, and a portion indicated by a thick broken line is a second directivity conversion pattern 22. This is a region where is formed. Moreover, the place where the arrow is given is a part in which the bending point was formed.

  In the light guide plate 10 of FIG. 27A, the upper end 10g of the light incident surface is a horizontal surface having a mirror surface. The inclined portion 10f is formed of an inclined plane, and the first directivity conversion pattern 20 is formed on the surface. Further, a second directivity conversion pattern is formed on the terminal portion 10k, which is an inclined plane having a smaller inclination angle than the inclined portion 10f.

  Next, in the light guide plate 10 of FIG. 27B, the upper end 10g of the light incident surface is configured with a horizontal plane, and the inclined portion 10f is configured with an inclined plane. A first directivity conversion pattern 20 is formed in the portion 10f. Further, a second directivity conversion pattern is formed on the terminal portion 10k, which is an inclined plane having a smaller inclination angle than the inclined portion 10f.

  In the light guide plate 10 of FIG. 27C, the upper end 10g of the light incident surface is configured with a horizontal plane, and the inclined portion 10f is configured with an inclined plane, and the upper end 10g of the light incident surface and the inclined portion 10f are The first directivity conversion pattern 20 is formed. In addition, the terminal portion 10k having a smaller inclination angle than the inclined portion 10f is a two-step plane that changes so that the inclination angle becomes smaller on the way, and a second directivity conversion pattern is formed.

In the light guide plate 10 of FIG. 27D, the upper end 10g of the light incident surface is configured as a horizontal plane, and the inclined portion 10f is configured as a two-step inclined plane that changes so that the inclination angle increases in the middle. A first directivity conversion pattern 20 is formed on the upper end 10g of the light incident surface and the inclined portion 10f. Further, the end portion 10k is an inclined plane having an inclination angle smaller than that of the inclined portion 10f.
A second directivity conversion pattern is formed.

  In the light guide plate 10 of FIG. 27 (E), the upper end 10g of the light incident surface is constituted by a horizontal plane, and the inclined portion 10f is constituted by a two-stage inclined plane that changes so that the inclination angle increases in the middle. Yes. The upper end 10g of the light incident surface and the upper plane of the inclined portion 10f are mirror surfaces, and the first directivity conversion pattern 20 is formed on the lower plane of the inclined portion 10f. Further, a second directivity conversion pattern is formed on the terminal portion 10k, which is an inclined plane having a smaller inclination angle than the inclined portion 10f.

(application)
If the surface light source device 1 described in the above embodiment is applied to the liquid crystal display device shown in FIG. 1 as a backlight, the light guide efficiency is high, the luminance is uniform, the light quantity distribution is uniform, and the visibility is good. A highly reliable liquid crystal display device can be provided.

  Furthermore, such a liquid crystal display device can be mounted on various electronic devices. As an electronic device provided with such a liquid crystal display device, a digital camera, a tablet terminal, an electronic book, a wearable device, a car navigation device, an electronic dictionary, an electronic advertising board, etc. can be exemplified in addition to the smartphone as shown in FIG. . Then, it is possible to provide an electronic device with high luminance, good visibility, and high reliability.

DESCRIPTION OF SYMBOLS 1 ... Surface light source device 10 ... Light guide plate 10a ... Main-body part 10b ... Light introducing | transducing part 10d ... Light-emitting surface 10e ... Light incident surface 10f ... Inclined part 10g ... Upper end of light incident surface 10h: Fixing member contact surface 10j: Concavity and convexity contact surface 10k ... Termination part 11 ... Light source 12 ... Flexible printed circuit board 13 ... Frame 13a ... Projection part 16 ... Diffusion sheets 17a, 17b ... Prism sheet 18 ... Light shielding sheet 20 ... First directivity conversion pattern 22 ... Second directivity conversion pattern

Claims (12)

A printed circuit board;
A light source mounted on the printed circuit board;
A light source plate including light emitted from the light source introduced from a light incident surface, and guiding the introduced light to a light exit surface and emitting the light in a planar shape,
The light guide plate is provided with an inclined portion that is disposed between the light incident surface and the light emitting surface and has a thickness that decreases from the light incident surface side toward the light emitting surface side,
On the inclined surface which is the surface of the inclined portion, a notch portion having a surface intersecting with the light incident surface is formed,
The light source is disposed so as to face the light incident surface by attaching the printed circuit board to the notch of the inclined portion.
The surface light source device according to claim 1, wherein an uneven structure for increasing a contact area with an adhesive layer provided on the printed circuit board is formed on a surface perpendicular to the light incident surface of the notch.   The surface light source device according to claim 1, wherein a height of the uneven structure is smaller than a thickness of the adhesive layer. The surface light source device according to claim 2, wherein a height of the uneven structure is 30 μm or less.   4. The surface light source device according to claim 1, wherein the concavo-convex structure is a groove structure including a plurality of grooves formed to extend in a direction perpendicular to the light incident surface. 5. .   5. The surface light source device according to claim 4, wherein the groove in the groove structure is a V-shaped cross section in a direction parallel to the light incident surface.   6. The surface light source device according to claim 4, wherein the groove is formed such that a cross section in a direction parallel to the light incident surface is asymmetrical with respect to the groove center. The inclined surface which is the surface of the inclined portion has a directivity characteristic in which the directivity spread in the thickness direction of the light guide plate of light incident from the light incident surface is inclined in a direction parallel to the surface direction of the light guide plate. A first directivity conversion pattern to be converted into
The said 1st directivity conversion pattern is comprised so that a ridgeline and a valley line may be repeated alternately along the width direction of the said light-guide plate, It is characterized by the above-mentioned. Surface light source device.   The surface light source device according to claim 7, wherein the concavo-convex structure and a ridge line in the first directivity conversion pattern coincide with each other. Between the inclined portion and the light exit surface of the light guide plate,
A terminal portion having a second inclined surface with a gentler inclination angle than the inclined surface which is the surface of the inclined portion is provided,
A second directivity that equalizes the amount of light emitted from the light emitting surface by dispersing light guided by the inclined portion in the width direction of the light guide plate on the second inclined surface of the terminal portion. A conversion pattern is provided,
The surface light source device according to claim 7, wherein the second directivity conversion pattern is configured to alternately repeat a ridge line and a valley line along a width direction of the light guide plate. The surface light source device according to claim 9, wherein ridge lines in the concavo-convex structure, the first directivity conversion pattern, and the second directivity conversion pattern coincide with each other. A surface light source device according to any one of claims 1 to 10,
A liquid crystal panel for receiving light emitted from the surface light source device;
A display device comprising:   An electronic apparatus comprising the display device according to claim 11.