JP4523530B2 - Surface light source device and display device - Google Patents

Description

  The present invention provides a mobile phone, a portable electronic terminal device, a car navigation device, a personal computer, a video camera, a digital camera, an electronic notebook, a liquid crystal television, etc., and a member to be illuminated such as a liquid crystal display panel and an advertisement plate from the back side. The present invention relates to a surface light source device used as a backlight for illuminating a surface, and a display device including the surface light source device.

  Conventionally, as shown in FIG. 7, the surface light source device 100 and the display device 101 including the surface light source device 100 have substantially the same shape as the emission surface 103 of the light guide plate 102 on the rectangular emission surface 103 of the light guide plate 102. The light diffusing member 104 and the light control members 105 to 106 are arranged so as to overlap each other, and a frame-shaped light shielding portion 107 is formed along the outer edge of the light diffusing member 104 facing the light exit surface 103 of the light guide plate 102. The light shielding portion 107 prevents light leakage from a gap between the light plate 102 and a frame (not shown) that accommodates the light guide plate 102, and emits light having a variation in emitted light brightness by the light shielding portion 107. The liquid crystal display panel (illuminated member) 108 is shielded and devised so that the liquid crystal display panel (illuminated member) 108 can be efficiently illuminated with light having substantially uniform luminance. A light reflecting member 109 is disposed on the back side of the light guide plate 102 (see Patent Document 1).

  However, in such a surface light source device 100, in particular, when a plurality of LEDs 110 are used as point light sources, as shown in FIG. 8, among the exit surfaces 103 near the entrance surface 111 of the light guide plate 102 (see FIG. 7). The vicinity of the light emitting part of the LED 110 shines brighter than the other part (becomes the bright part 112), and both corners between the adjacent LEDs 110 and 110 and the incident surface 111 side tend to be darker than the other part (the dark part 113 indicated by hatching). Prone). Such a difference in brightness produced on the exit surface 103 in the vicinity of the entrance surface 111 of the light guide plate 102 is observed from the exit surface 103 side of the light guide plate 102 as a so-called firefly phenomenon, and degrades the illumination quality.

  Therefore, the surface light source device 100 using the plurality of LEDs 110 as the light source effectively prevents the occurrence of the firefly phenomenon, as shown in FIG. 9, in the light shielding unit 107 located on the incident surface 111 side of the light guide plate 102. It is conceivable to make the emitted light luminance uniform by making the width larger than the other portions and narrowing the effective light emitting region.

  Further, as in the surface light source device 100 shown in FIG. 10, the light absorber 114 is partially disposed on the light diffusion member 104 disposed so as to face the emission surface of the light guide plate 102 so as to face the light emitting portion of the LED 110. It is also conceivable to arrange them in (Patent Document 2).

Japanese Patent Laying-Open No. 2005-24774 (see particularly FIG. 1). Japanese Patent Laid-Open No. 2004-213922 (see particularly FIG. 1).

  However, as shown in FIG. 9, when the width dimension of the light-shielding portion 107 located on the incident surface 111 side of the light guide plate 102 is increased, the amount of light absorption becomes too large, and the emitted light luminance is reduced overall ( Light utilization efficiency is reduced).

  In addition, as shown in FIG. 10, when a light shielding part (light absorber 114) is partially formed so as to face the light emitting part of the LED 110, a bright part tends to occur around the partial light shielding part, It was not easy to achieve uniform brightness.

  In view of this, the present invention provides a surface light source device that uses a point light source such as an LED as a light source so that the light use efficiency can be increased as much as possible, and the emitted light luminance can be made uniform easily and reliably. .

  According to the first aspect of the present invention, the light source has a shape in which the point light source is disposed along one side surface of the light guide plate, and the effective light emitting area of the light guide plate can be covered on the light emission surface side of the light guide plate. The present invention relates to a surface light source device in which members are arranged. In this surface light source device, the light diffusing member has a frame-shaped light shielding portion formed in a region along the outer edge of the light diffusing member on at least one main surface of the light diffusing member, and the point light source. And a light-absorbing projecting light-shielding part formed so as to project inward from the frame-shaped light-shielding part at a position corresponding to the above.

  The invention according to claim 2 is a light diffusion method in which a point light source is disposed along one side surface of the light guide plate, and the effective light emitting region of the light guide plate can be entirely covered on the light emission surface side of the light guide plate. The present invention relates to a surface light source device in which members are arranged. This surface light source device is a surface light source device in which a light shielding frame formed so as to surround the outside of the effective light emitting region is arranged on at least one main surface side of the front and back surfaces of the light diffusing member. And the said light-shielding frame is connected to the said frame-shaped light-shielding part in the position corresponding to the said point light source, and the frame-shaped light-shielding part formed in the area | region along the outer edge of the said light-diffusion member, and it protrudes in the inner direction And a light-absorbing protruding light-shielding portion formed on the substrate.

According to a third aspect of the present invention, in the surface light source device according to the first or second aspect, the light emission center position of the point light source is matched with the center position in the width direction of the protruding light-shielding portion, and the effective light is transmitted from the one side surface of the light guide plate. L is the shortest distance from the one side surface of the light guide plate to the inner periphery of the frame-shaped light-shielding portion, and L ₁ is the shortest distance from the light source plate to the outer edge on the point light source side. the shortest distance from the periphery to the tip of the protruding shielding portion and L _2, the incident width of the one side opposite to the light emitting portion of the point light source and W _L, of the frame-like light shielding portion and the protruding shielding portion When the width of the connecting portion and W _B, the critical angle determined by the material of the light guide plate and theta,
L ≧ L ₁ + L ₂
and

W _B ≧ W _L + 2L ₁ tan θ
It is characterized by becoming.

  A fourth aspect of the invention includes the surface light source device according to any one of the first to third aspects of the invention, and a member to be illuminated that is illuminated by the planar illumination light emitted from the surface light source device. This is a display device.

  According to the first and second aspects of the present invention, light leaking from the outer edge side of the light guide plate is absorbed by the frame-shaped light-shielding portion, and light that cannot be used as illumination light is prevented from leaking through the light control member. In addition, the so-called firefly phenomenon corresponding to the light emitting part of the point light source can be prevented by the protruding light shielding part, and uniform illumination light can be emitted efficiently.

  According to the invention of claim 3, the size of the protruding light-shielding portion is determined according to the material (refractive index) of the light guide plate and the width and position of the desired effective light emitting area (emitted light area usable as illumination light). Therefore, the light-shielding area (frame-like light-shielding part and protruding light-shielding part) can be formed to the minimum necessary size, light loss in the light-shielding area can be minimized, and the light-emitting area can be uniform in the effective light-emitting area. Efficient illumination light can be emitted efficiently.

  According to the fourth aspect of the present invention, the illuminated member is illuminated by the homogeneous illumination light emitted from the surface light source device, and the display quality is improved.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings.

(Configuration of surface light source device and display device including the same)
1 to 3 show a display device 1 according to the present embodiment. Among these, FIG. 1 shows an exploded perspective view of the display device 1. 2 is a cross-sectional view of the display device 1 cut along the line AA in FIG. FIG. 3 is a plan view of the display device 1 with the liquid crystal display panel (illuminated member) 3 and the first and second light control members 12 and 13 removed.

  The display device 1 shown in these drawings illuminates a liquid crystal display panel (illuminated member) 3 in a planar shape by a surface light source device 2. The surface light source device 2 includes a light guide plate 4, a plurality of LEDs (light emitting diodes) 6 as point light sources arranged to face the incident surface (side surface) 5 of the light guide plate 4, and the back surface 7 side of the light guide plate 4. The light reflecting member 8 is disposed on the light guide plate 4, the light diffusing member 11 is disposed on the light exit surface 10 side of the light guide plate 4, and the two light control members 12 to 13 are disposed. The light diffusing member 11 disposed at a position closest to the light guide plate 4 is a diffusion sheet that diffuses and emits light emitted from the light guide plate 4. Further, the first and second light control members 12 and 13 arranged on the light diffusing member 11 collect light from the light diffusing member 11 closer to the normal direction of the exit surface 10 of the light guide plate 4. It is a prism sheet that functions to emit light.

  The surface light source device 2 allows light from the LED 6 to enter the inside of the light guide plate 4 from the incident surface 5 of the light guide plate 4, and then out of the light propagating inside the light guide plate 4. After the light whose incident angle with respect to the light is equal to or smaller than the critical angle is emitted from the emission surface 10 of the light guide plate 4 and the emitted light is diffused by the light diffusion member 11, the first to second light control members 12 to 13. Therefore, the light is condensed toward the normal direction of the exit surface 10 of the light guide plate 4.

(Light guide plate)
The light guide plate 4 is formed using a material having excellent light transmittance such as polymethyl methacrylate (PMMA), polycarbonate (PC), and cycloolefin resin material. As shown in FIGS. 1 to 3, the light guide plate 4 is a plate-like body having a substantially quadrangular planar shape, and has the largest thickness on the incident surface 5 side where the LEDs 6 are arranged. The plate thickness is gradually reduced (for example, the plate thickness is gradually reduced at the inclination angle α) as it moves away from (from the Y direction).

  In addition, on the back surface 7 of the light guide plate 4, a texture (not shown) that promotes the emission of light from the emission surface 10 is formed. The texture formed on the back surface 7 of the light guide plate 4 is determined in its shape, distribution state (pattern shape, etc.) and distribution density in accordance with required outgoing light characteristics.

(Light diffusion member)
The light diffusing member 11 is formed in a film shape with a resin material (for example, polyethylene terephthalate (PET), PMMA, PC) having excellent light transmittance, and has a planar shape as shown in FIGS. It is formed in a rectangular shape that is substantially the same as the exit surface 10 of the optical plate 4 and slightly larger than the exit surface 10 of the light guide plate. The light diffusing member 11 has a rough surface at least one of the incident surface (the lower surface facing the light guide plate 4) and the emitting surface (the upper surface facing the first light control member 12). The light emitted from the light plate 4 is emitted to the first light control member 12 side in a diffused state. A light-shielding member (light-shielding ink having a light-absorbing property such as black or gray) is applied to the lower surface side of the outer edges (four sides) 14 to 17 of the light diffusing member 11 by a predetermined width. The light shielding region (frame-shaped light shielding portion) 20 is formed. The first light shielding region 20 absorbs light leaking upward from the four side surfaces 5 and 21 to 23 of the light guide plate 4 (for example, upward from a gap with a frame not shown), and cannot be used as illumination light. Is prevented from leaking to the liquid crystal display panel 3 side.

In addition, as shown in FIGS. 1 to 4, the light diffusion member 11 is a first light shielding region 20 on the LED 6 side, and a light shielding member is applied in a rectangular shape at a position facing the LED 6. Second light-shielding regions (projecting light-shielding portions) 24 and 24 projecting from the light-shielding region 20 are formed. The second light-shielding region 24 matches the center position C1 in the width direction with the light emission center position C2 of the LED 6, and extends from the incident surface 5 of the light guide plate 4 to the outer edge 30 of the effective light emission region on the LED 6 side (point light source side). , And the shortest distance from the incident surface 5 of the light guide plate 4 to the inner periphery of the first light shielding region 20 of the light diffusing member 11 disposed on the light guide plate 4 is L _1. the shortest distance to the tip of the second shaded area 24 and L ₂ from the W _L of the light emitting portion width of the LED 6, a second light shielding region 24 the width at the connecting portion between the first light-blocking region 20 When W is _B and the critical angle determined by the material of the light guide plate 4 is θ, it is formed so as to satisfy the following formula. Note that L1 may be a minimum width necessary to block light leaking to the liquid crystal display panel 3 side from a gap between the incident surface 5 and a frame (not shown).

(Equation 1)
L ≧ L ₁ + L ₂

(Equation 2)
W _B ≧ W _L + 2 · L ₁ tan θ

(First light control member)
The first light control member 12 is formed into a film shape with a resin material (for example, polyethylene terephthalate (PET), PMMA, PC) having excellent light transmittance, and is flat as shown in FIGS. The shape of the light guide plate 4 is formed so as to be substantially the same as that of the light exit surface 10. And this 1st light control member 12 is extended along the longitudinal direction (width direction of FIG. 1) of the entrance plane 5 of the light-guide plate 4 in the upper surface (surface on the opposite side to the light-diffusion member 11) side. A large number of prismatic protrusions 25 are formed in parallel and continuously. The prismatic protrusions 25 of the first light control member 12 are formed in a substantially triangular cross section, and in a virtual plane orthogonal to the incident surface 5 of the light guide plate 4 and orthogonal to the emission surface 10, the light diffusing member. It functions to deflect the light emitted from 11 toward the normal direction of the exit surface 10 of the light guide plate 4.

(Second light control member)
Similarly to the first light control member 12, the second light control member 13 is formed in a film shape with a resin material excellent in light transmittance (for example, polyethylene terephthalate (PET), PMMA, PC), As shown in FIGS. 1 and 2, the planar shape is formed so as to be substantially the same square shape as the light exit surface 10 of the light guide plate 4. The second light control member 13 extends on the upper surface (surface opposite to the first light control member 12) side in a direction perpendicular to the prismatic protrusions 25 of the first light control member 12. A large number of prismatic protrusions 26 are formed in parallel and continuously. The prism-shaped protrusions 26 of the second light control member 13 are formed in a substantially triangular shape in cross section, and in the virtual plane that is parallel to the incident surface 5 of the light guide plate 4 and orthogonal to the emission surface 10, It functions to deflect the light emitted from the light control member 12 toward the normal direction of the emission surface 10 of the light guide plate 4.

(Light reflecting member)
The light reflecting member 8 is made by mixing a white pigment with a sheet of PET sheet having excellent light reflectivity and a metal having excellent light reflectivity such as aluminum on the surface of the sheet-like resin member (for example, PET sheet). It is a vapor-deposited film-like member, and its planar shape is substantially the same as the back surface 7 of the light guide plate 4 as shown in FIGS. 1 and 2. The light reflecting member 8 functions to reflect the light emitted from the back surface 7 side of the light guide plate 4 and return it to the inside of the light guide plate 4. The light reflecting member 8 has a frame (not shown) in which the light guide plate 4 is housed as a surface having excellent light reflectivity (a whitened surface), and the frame itself having the light reflecting function is light-transmitted. It may be a reflective member. The light reflecting member 8 may be a mirror reflecting member made of silver or aluminum.

(Other embodiments)
The first and second light shielding regions 20 and 24 are formed in the light diffusing member 11 disposed in opposition to the light exit surface 10 of the light guide plate 4 (arranged immediately above the light exit surface 10) shown in the best mode. Another embodiment is shown in FIGS.

  In the display device 1 ′ (surface light source device 2 ′) shown in FIG. 5, a member other than a member for adjusting the emission direction of illumination light arranged between the light guide plate 4 and the liquid crystal display panel (illuminated member) 3. The configuration is the same as the configuration shown in the above-described best mode. Here, only the structure of the member different from the best mode is shown. First, the light diffusing member 18 that does not form the first and second light shielding regions 20 and 24 is disposed on the light exit surface 10 of the light guide plate 4, and the first and second light similar to the best mode is disposed thereon. The control members 12 and 13 are arranged so as to overlap each other, and the light diffusion member 11 is further arranged thereon. The light diffusing member 11 is formed with first and second light shielding regions 20 and 24 similar to the best mode described above.

  A display device 1 ″ (surface light source device 2 ″) shown in FIG. 6 has a light shielding frame 41 arranged instead of the light diffusing member 11 of the display device 1 ′ (surface light source device 2 ′) of FIG. The same components as those of the display device 1 ′ of FIG. 5 are denoted by the same reference numerals, and the description that overlaps with the display device 1 ′ of FIG. 5 is omitted. In the display device 1 ″ shown in FIG. 6, the light shielding frame 41 is a frame-like film member constituted by the first and second light shielding regions 20 and 24 of the light diffusing member 11 shown in FIG. 6 shows a mode in which the light shielding frame 41 is disposed between the liquid crystal display panel 3 and the second light control member 13, but the present invention is not limited to this, and the liquid crystal display panel 3 The light shielding frame 41 may be disposed not on the second light control member 13 but on the main surface side of either the front or back of the light diffusion member 18.

(Operations and effects of the best mode and other embodiments)
The best mode for carrying out the above-described invention and other embodiments are the side surfaces 21 and 23 orthogonal to the incident surface 5 of the light guide plate 4, the side surface 22 facing the incident surface 5, and a frame (not shown). The light leaking from the space can be absorbed by the light diffusing member 11 and the first light shielding region 20 of the light shielding frame 41, and light that cannot be used as illumination light can be prevented from leaking to the liquid crystal display panel 3 side. A so-called firefly phenomenon corresponding to the light emitting portion of the LED 6 can be prevented by the first light shielding region 20 and the second light shielding regions 24 and 24 on the incident surface 5 side, and uniform illumination light can be emitted.

  Further, the light diffusing member 11 and the light shielding frame 41 of the above-described embodiment form the first light shielding region 20 with a substantially uniform width along the outer edge thereof, and are observed brightly locally from the vicinity of the LED 6. By forming the second light-shielding regions 24 and 24 for shielding the part of the emitted light with the minimum necessary size, a problem such as the conventional example shown in FIG. 9 (the light absorption rate becomes too large). In this case, it is possible to increase the light use efficiency and emit uniform and bright illumination light.

  In addition, since the light diffusing member 11 and the light shielding frame 41 of the above-described embodiment can effectively prevent the so-called firefly phenomenon by the first light shielding region 20 and the second light shielding region 24, the effective light emitting region (FIG. 4 can be widened.

  Further, as in the above-described embodiment, the light shielding frame 41 that is separated from the light diffusion member 11 and only the first and second light shielding regions 20 and 24 are formed is a base material having a light shielding property (black sheet). Etc.) Since it can be formed by punching itself, compared with the case where the first and second light shielding regions 20 and 24 are formed on the light diffusion member 11 by printing, The printing process itself can be omitted, and the manufacturing process can be simplified and the cost can be reduced.

  Note that a prism-shaped protrusion (not shown) having a substantially triangular cross section extending in a direction substantially perpendicular to the incident surface 5 (Y direction in FIG. 1) is formed on the light exit surface 10 of the light guide plate 4 or the surface facing the light exit surface 10. You may form many in parallel along the longitudinal direction (width direction of FIG. 1) of the entrance plane 5, and continuously. Since the prism-like projections provide the same effect as the second light control member 13, the second light control member 13 may be omitted. Further, the first light control member 12 is arranged so that the prism surface thereof faces the light exit surface 10 of the light guide plate 4, and the first and second light shielding regions 20 and 24 are arranged on the first light control member 12. It is also possible to increase the brightness by forming the light diffusing member 11 disposed on the surface.

  Further, the present invention is limited to a mode in which a plurality of (two or more) LEDs 6 are arranged and the second light shielding regions 24 and 24 are formed corresponding to the LEDs 6 as in the above-described embodiment. Alternatively, only a single LED 6 may be used, and the second light shielding region 24 may be formed corresponding to only the single LED 6.

  In addition, the present invention is not limited to the above-described embodiment in which the light diffusing member 11 and the second light shielding region 24 of the light shielding frame 41 are formed in a rectangular shape, and may be a square, a half moon shape, a trapezoidal shape, other polygonal shapes, or the like. It may be formed.

  Moreover, this invention is not limited to the aspect which reduces gradually as the plate | board thickness of the light-guide plate 4 distances from the entrance plane 5 like the above-mentioned embodiment, You may form in flat form.

  Further, the light diffusing member 11 and the light shielding frame 41 shown in FIG. 4 extend the incident surface 5 side to a position covering the LED 6 (for example, extend in the −Y direction by ΔL), and accordingly, the first on the incident surface 5 side. The light shielding region 20 may be expanded in the −Y direction. In this case, the width of the first light shielding region 20 on the LED 6 side is L1 + ΔL.

  Further, in the light diffusion member 11 or the light shielding frame body 41 shown in FIG. 4, the first light shielding region 20 is formed with substantially the same width along the outer edges 14 to 17 of the light diffusion member 11 or the light shielding frame body 41. However, the present invention is not limited to this. For example, the width of the first light-shielding region 20 on the outer edge 14 side and the width of the first light-shielding region 20 on the other outer edges 15 to 17 may be different dimensions. Good. It should be noted that the second light shielding regions 24 and 24 act more effectively as L / P ≦ 0.65 (P: the arrangement pitch of the LEDs 6), and more effective as L / P ≦ 1 / In the case of (2 · tan θ), the so-called firefly phenomenon occurrence portion is outside the effective light emitting region without forming the second light shielding regions 24, 24 outside this range. It becomes unnecessary.

  The surface light source device of the present invention can be widely used not only as an image display device using a liquid crystal display panel as a member to be illuminated, but also as a surface light source for indoor lighting devices and advertising plates.

1 is an exploded perspective view of a display device and a surface light source device according to the best mode of the present invention. It is sectional drawing of the display apparatus and surface light source device which are cut | disconnected and shown along the AA line of FIG. It is a top view of the display apparatus which removes a liquid crystal display panel (illuminated member) and the 1st and 2nd light control member. It is a top view which shows the relationship between LED, a light-guide plate, and the light-diffusion member or the light-shielding area | region formed in the light-shielding frame. It is a disassembled perspective view of the display apparatus and surface light source device which concern on other embodiment (1st example) of this invention. It is a disassembled perspective view of the display apparatus and surface light source device which concern on other embodiment (2nd example) of this invention. It is a disassembled perspective view of the display apparatus and surface light source device which concern on a 1st prior art example. It is a figure which shows the relationship between LED of a display apparatus and a surface light source device in the prior art example of FIG. 5, a light-guide plate, and a light-diffusion member. It is a figure which shows the relationship between LED in a 2nd prior art example, a light-guide plate, and a light-diffusion member. It is a figure which shows the relationship between LED in the 3rd prior art example, a light-guide plate, and a light-diffusion member.

Explanation of symbols

  1, 1 ', 1 "... display device, 2, 2', 2" ... surface light source device, 3 ... liquid crystal display panel (illuminated member), 4 ... light guide plate, 5 ... incident surface (one Side surface), 6 ... LED (point light source), 10 ... emission surface, 11 ... light diffusing member, 14, 15, 16, 17 ... outer edge, 20 ... first light shielding region (frame-shaped light shielding portion) ), 24... 2nd light shielding area (protruding light shielding part), 41.

Claims (4)

Place the point light source along one side of the light guide plate,
In the surface light source device in which a light diffusing member having a shape capable of covering the entire effective light emitting region of the light guide plate is disposed on the light exit surface side of the light guide plate,
The light diffusing member is
On at least one main surface of the front and back of the light diffusing member,
A frame-shaped light shielding part formed in a region along the outer edge of the light diffusing member;
A light-absorbing protruding light-shielding portion formed so as to be connected to the frame-shaped light-shielding portion at a position corresponding to the point light source and project inward.
A surface light source device. Place the point light source along one side of the light guide plate,
In the surface light source device in which a light diffusing member having a shape capable of covering the entire effective light emitting region of the light guide plate is disposed on the light exit surface side of the light guide plate,
On at least one main surface side of the front and back of the light diffusing member, a light shielding frame formed so as to surround the outside of the effective light emitting region is disposed,
The light shielding frame is formed so as to protrude from the frame-shaped light-shielding portion formed in a region along the outer edge of the light diffusing member to the frame-shaped light-shielding portion at a position corresponding to the point light source. A light-absorbing protruding light-shielding portion,
A surface light source device. Match the light emission center position of the point light source with the center position in the width direction of the protruding light shielding part,
L is the shortest distance from the one side surface of the light guide plate to the outer edge of the effective light emitting region on the point light source side,
L ₁ is the shortest distance from the one side surface of the light guide plate to the inner periphery of the frame-shaped light shielding portion,
L ₂ is the shortest distance from the inner peripheral edge of the frame-shaped light shielding portion to the tip of the protruding light shielding portion,
The incident width dimension on the one side surface facing the light emitting portion of the point light source is W _L ,
The width of the connection portion between the frame-shaped light shielding portion and the protruding shielding portion and W _B,
When the critical angle determined by the material of the light guide plate is θ,
L ≧ L ₁ + L ₂
and

W _B ≧ W _L + 2L ₁ tan θ
The surface light source device according to claim 1, wherein:   4. A display device comprising: the surface light source device according to claim 1; and a member to be illuminated that is illuminated by planar illumination light emitted from the surface light source device.

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