JP2008112739A - Backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device that does not have rapid changes in the inclination of reflecting face and is capable of suppressing leakage of light. <P>SOLUTION: The backlight device 101 is equipped with a light guide plate 2, having an incident face 21 that has having an incident region 20 and a light-emitting face 22 opposite to this, and a light-emitting diode element row where a plurality of light-emitting diode elements 1 are arranged. The light guide plate 2 exists, extended on at least a first side 90 as seen from the incident region 20. The light guide plate 2 has a curved face part 23 so as to neighbor a second side 91. The curved face part 23 is used for receiving the light, made incident on the inside of the light guide plate 2 from the light-emitting diode elements 1 and reflecting the incident light toward the first side 90. C is a constant and a refractive index of the light guide plate 2 is n<SB>0</SB>; and a fixed angle α is assumed 0<α≤π/2-sin<SP>-1</SP>(1/n<SB>0</SB>) is satisfied, the cross-sectional shape of the curved face part 23 can be expressed as r=exp(-θ/tanα+C) in polar coordinate representation in which r and θ are used, with one point of the incident region 20 as the starting point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight device that irradiates a transmissive display panel with display light emitted from a plurality of light emitting diodes. The “transmissive display panel” is a transmissive liquid crystal panel that is used by being incorporated in, for example, a liquid crystal display (LCD). More specifically, the present invention relates to a backlight device for obtaining a uniform luminance distribution on a large screen such as a television receiver.

  Compared with a cathode ray tube (CRT) that has been widely used as a display device, the liquid crystal display device has a larger display screen, a lighter and thinner device, and reduced power consumption. Easy to plan. Therefore, for example, it is used for a television receiver and various display devices together with a self-luminous PDP (Plasma Display Panel).

  Here, “liquid crystal display device” means that liquid crystal is sealed between two transparent substrates of various sizes and the direction of liquid crystal molecules is changed by applying a voltage, thereby changing the light transmittance. Is a device for optically displaying a predetermined image or the like.

  Although the liquid crystal display device includes a liquid crystal panel, since the liquid crystal itself is not a light emitter, for example, a backlight device that functions as a light source is provided on the back surface of the liquid crystal panel. The backlight device includes, for example, a light source, a reflection plate, a diffusion plate, a lens sheet, and the like, and irradiates display light over the entire surface of the liquid crystal panel.

  Conventionally, many backlight devices use a cold cathode fluorescent lamp (CCFL) in which mercury or xenon is enclosed in a fluorescent tube as a light source. However, in recent years, backlight devices that employ light emitting diode (LED) elements are increasing in order to reduce the thickness. In addition, as a backlight device for a large-sized television receiver, an LED backlight device that uses LED elements that do not use mercury as a two-dimensional array and is used as an illuminating device is attracting attention due to the rise of environmental problems.

  However, since the LED element is a point light source, in order to use it as backlight illumination with a uniform luminance distribution, it is necessary to diffuse light so that the entire display region has a uniform luminance. Therefore, a method called “side light type” in which LED elements are arranged around the light guide plate is used. In the side light type, in addition to the type in which light is incident from the side of the light guide plate, an LED element is disposed at a position facing the light exit surface of the light guide plate, and reflected by the reflective surface, then the other part of the light guide plate There is a type to guide light. In this type, a reflection sheet and a reflection film are usually installed on the reflection surface, and there are problems such as an increase in cost due to an increase in members and absorption of light by the reflection sheet and reflection film.

As a technique conceived for solving these problems, there is a backlight device disclosed in Japanese Patent Laid-Open No. 2002-222605 (Patent Document 1). This backlight device includes a light guide plate having a special cross-sectional portion for changing the direction of light received from the light source at the end. As a technique for extending the light guide plate to a large LCD, there is a backlight device disclosed in Japanese Patent Application Laid-Open No. 2002-298629 (Patent Document 2). In this backlight device, a recess is provided in a region facing the LED element on the exit surface of the light guide plate, and the light emitted from the LED element is totally reflected by this recess and guided to the other part of the light guide plate. It has a structure. In this way, even if a large number of LEDs are arranged to obtain the luminance necessary for backlight illumination in a large display area, the LED elements can be dispersedly arranged, so that heat is generated locally and the temperature rise is large. The problem of becoming can be avoided.
JP 2002-222605 A JP 2002-298629 A

  However, in the backlight device disclosed in Patent Document 1, a portion for changing the direction of light is sawtooth when viewed in cross section, and there is a portion where the angle of the surface changes abruptly. Therefore, when processing an actual product, a certain degree of roundness occurs in a portion where the angle of the surface changes suddenly, and light actually leaks from that portion. In the backlight device disclosed in Patent Document 1, there are many such parts, and light leakage due to such a cause increases. Further, the portion for changing the direction of light is a complicated shape having a sawtooth cross-sectional shape, so that it is difficult to design and manufacture, which also causes an increase in cost.

  Even in the backlight device disclosed in Patent Document 2 that can be expanded to a large LCD, there is a portion where the angle of the surface changes abruptly at the center position of the recess, and in reality, the center of the recess is rounded. If such roundness is in a position overlapping with the LED element, the light emitted from the LED element cannot be totally reflected at the center of the recess, but passes through the recess and directly enters the transmissive display panel. Area becomes high, and it becomes difficult to obtain sufficient uniformity of luminance in the display area. Further, in the backlight device in which the depressions are linearly formed so as to face two or more LED elements disclosed in Patent Document 2, the light quantity distribution that guides the light from the depressions to the left and right due to the misalignment of the LED elements. It becomes difficult to obtain a uniform luminance distribution.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a backlight device that can suppress light leakage without causing a rapid change in the inclination of the reflecting surface.

In order to achieve the above object, a backlight device according to the present invention includes a light guide plate having an incident surface having a band-shaped incident region and an output surface facing the incident surface, and the light guide plate through the incident region. A light-emitting diode element array in which a plurality of light-emitting diode elements are arranged in a straight line facing the incident surface. The light guide plate extends at least on the first side when viewed from the incident region. The light guide plate has a curved surface portion extending in a strip shape parallel to the longitudinal direction of the incident region so as to be adjacent to the second side opposite to the first side of the emission surface. The curved surface portion is for receiving the light that has passed through the incident region from the light emitting diode element array and entered the light guide plate, and reflects the light toward the first side. The cross-sectional shape of the curved surface section cut by a plane perpendicular to the longitudinal direction is such that C is a constant, n ₀ is the refractive index of the light guide plate, and 0 <α ≦ π / 2−sin ⁻¹ (1 / n ₀ ). Assuming a constant angle α to be satisfied, it can be expressed by r = exp (−θ / tan α + C) in a polar coordinate display with a radius r and an angle θ with one point of the incident region as the origin.

  ADVANTAGE OF THE INVENTION According to this invention, there is no sudden change in the inclination of a reflective surface, and the backlight apparatus which can suppress the leakage of light is realizable.

(Embodiment 1)
(Constitution)
With reference to FIGS. 1-4, the backlight apparatus in Embodiment 1 based on this invention is demonstrated. A perspective view of the backlight device in this embodiment is shown in FIG. 1, and a cross-sectional view thereof is shown in FIG. FIG. 3 is a perspective view of only the light guide plate 2 taken out from the backlight device and viewed obliquely from below.

The backlight device 101 includes a light guide plate 2 having an incident surface 21 having a band-shaped incident region 20 and an output surface 22 opposite to the incident surface 21, and the incident surface 21 of the light guide plate 2 through the incident region 20. A plurality of light emitting diode elements (hereinafter referred to as “LED elements”) 1 facing each other is provided with a light emitting diode element array (hereinafter referred to as “LED element array”) 11 arranged linearly. The light guide plate 2 extends at least on the first side 90 when viewed from the incident region 20. The light guide plate 2 has a curved surface portion 23 extending in a strip shape parallel to the longitudinal direction 93 of the incident region 20 so as to be adjacent to the second side 91 opposite to the first side 90 of the emission surface 22. The curved surface portion 23 is for receiving light that has passed through the incident region 20 from the LED element array 11 and entered the light guide plate 2 and reflects the light toward the first side 90. The cross-sectional shape of the curved surface portion 23 cut by a plane perpendicular to the longitudinal direction 93 is such that C is a constant, n ₀ is the refractive index of the light guide plate 2, and 0 <α ≦ π / 2−sin ⁻¹ (1 / n ₀ ). Assuming a constant angle α that satisfies the above, it is possible to express r = exp (−θ / tan α + C) in polar coordinate display with a radius r and an angle θ with one point of the incident region 20 as the origin.

  In FIG. 1, the LED element 1 is mounted on the circuit board 3. In the example of FIG. 1, four LED elements 1 are arranged, but the number of LED elements 1 may be determined according to the required luminance and the output of the LED element 1.

(Cross-section shape of curved surface)
The cross-sectional shape of the curved surface portion 23 will be described in more detail with reference to FIG. 4 which is an enlarged view. As shown in FIG. 4, the cross-sectional shape of the curved surface portion 23 is such that light is incident on the light guide plate 2 and one point in the incident area is the origin O, and r = exp (−θ / tan α + C) in polar coordinate display (r, θ). (1)
The shape is represented by Here, C is a constant, and α is the refractive index of the light guide plate 2 n _0.
As
α ₀ = π / 2−sin ⁻¹ (1 / n ₀ ) (2)
0 <α ≦ α ₀ ……………………………………………………………………………………………………………… (3)
Is an arbitrary value. As shown in FIG. 4, r = exp (−θ / tan α) is such that the angle formed by the straight line connecting the origin O and an arbitrary point A on the curved portion 23 and the tangent line at the point A of the curved portion 23 is always α. When the total reflection angle of the light guide plate 2 is φ, φ = sin ⁻¹ (1 / n ₀ ) …………………………………………………………………………………… (4)
Therefore, the expression (3) is 0 <α ≦ π / 2−φ (5)
Thus, it can be seen that the light emitted from the origin O is incident on the curved surface portion 23 at an incident angle equal to or greater than the total reflection angle, that is, all the light emitted from the origin O is totally reflected. In FIG. 4, the curved surface portion 23 has a shape according to the formula (1) in the range of α ≦ θ ≦ π / 2 + α, and is connected to the emission surface 22 at the point of θ = α, and θ = π / 2 + α. The point is connected to a vertical plane 30 which is a plane perpendicular to the incident plane 21.

Some preferred items are summarized as follows.
The curved surface portion 23 is preferably present only in a range where θ in the polar coordinate display of the cross-sectional shape satisfies α ≦ θ ≦ π / 2 + α.

  The light guide plate 2 has a vertical surface 30 that is a surface perpendicular to the incident surface 21, and the curved surface portion 23 continues to the vertical surface 30 at a position where θ in the polar coordinate display of the cross-sectional shape is θ = π / 2 + α. Preferably it is.

The curved surface portion 23 has an exit surface 22 at a position where θ is θ = α in the polar coordinate display of the cross-sectional shape.
It is preferable that it is connected to.

  Although light may leak from the vertical surface 30, if the region where light is incident on the light guide plate in PMMA (polymethyl methacrylate) generally used for the light guide plate is parallel to the output surface, the following The light does not leak for the reason.

This will be described with reference to FIG. Although the incident angle σ from the air on the incident surface 21 to the light guide plate 2 can be 90 ° at the maximum, since the refractive index of PMMA is 1.49, the light 81 incident at the maximum incident angle σ = 90 ° is As the light 82 in the light guide plate 2,
sin ⁻¹ (1 / 1.49) = 42.1 ° (6)
It proceeds at an emission angle τ = 42.1 ° as calculated. This is the maximum value of τ. In this case, the incident angle υ (upsilon) from the light guide plate 2 to the air on the vertical surface 30 is
90-42.1 = 47.9 ° ………………………………………………………… (7)
It becomes. This is the minimum value of υ. The total reflection angle when entering from the PMMA into the air is 42.1 ° according to the equation (6), that is, the total reflection occurs when the incident angle is larger than 42.1 °. On the other hand, since the minimum value 47.9 ° of υ is larger than 42.1 °, the light 82 is always totally reflected on the vertical plane 30 regardless of the incident angle σ of the light 81. Therefore, no leakage of light to the outside of the light guide plate 2 at the vertical surface 30 occurs.

  Here, the vertical surface 30 is a surface perpendicular to the incident surface 21, but is positioned between the curved surface portion 23 and the incident surface 21 like the side surfaces 31 and 32 shown in FIGS. 6 and 7. Even when the side surface is not exactly perpendicular to the incident surface 21, the angle θ may be adjusted as appropriate so that the curved surface portion 23 is smoothly connected to the side surface. In FIG. 6 and FIG. 7, the components other than the light guide plate are not shown.

Next, the constant C will be described. The constant C may be set as appropriate, but as shown in FIG.
C = α / tan α + ln (d / sin α) (8)
It is preferable that This is because the curved surface portion 23 and the light exit surface 22 of the light guide plate are smoothly connected. If there is a corner at the boundary between the curved surface portion 23 and the exit surface 22, luminance unevenness is caused. Therefore, it is preferable to suppress luminance unevenness by setting C to the value of the equation (8).

  The origin O is preferably a point at the end of the first side 90 in the incident region 20. In FIG. 4, the origin O is set to meet this condition. This is because the angle of incidence on the curved surface portion 23 becomes the smallest in the light incident region 20 on the incident surface 21 at the end of the first side 90, and this position is the origin O and the curved surface portion 23. In this case, all the light incident from the light incident area 20 enters the curved surface portion 23 at an angle satisfying the total reflection condition. As a result, light leakage to the outside of the light guide plate 2 at the curved surface portion 23 is prevented. This is to eliminate it.

(Action / Effect)
In the backlight device according to the present embodiment, light that has entered the light guide plate from the LED element array via the incident surface can be redirected toward the first side at the curved surface portion without leaking, and is transmitted through the light guide plate. The light is emitted from the emission surface at any location and used as display light. Therefore, there is no abrupt change in the inclination of the reflecting surface, and the backlight device can suppress light leakage.

  In the backlight device 101, the end portion of the first side 90 of the light guide plate 2 is simply a vertical surface and no light source is disposed, but the second end portion of the first side 90 is also second. Alternatively, the curved surface portion 23, the LED element array 11, and the circuit board 3 may be arranged symmetrically with the end portion of the side 91.

(Embodiment 2)
(Constitution)
With reference to FIG. 8, the backlight apparatus in Embodiment 2 based on this invention is demonstrated. The backlight device 102 in the present embodiment includes a plurality of unit backlight units using the backlight device 101 described in the first embodiment as a unit backlight unit, and the plurality of unit backlight units are adjacent to each other and are planar. Are arranged. That is, as shown in FIG. 8, a plurality of backlight devices 101 are arranged in a plane as unit backlight portions 40a and 40b. In FIG. 8, the unit backlight units 40a and 40b are arranged in the same direction. That is, each of the plurality of unit backlight portions 40a and 40b is arranged so that the curved surface portions 23a and 23b are located on the same side (left side in FIG. 8) with respect to the emission surface 22.

  In the backlight device 102 shown in FIG. 8, the plurality of unit backlight units include a first unit backlight unit 40a and a second unit backlight unit 40b adjacent to the first unit backlight unit 40a. The light guide plate 2a of the 1-unit backlight unit 40a has a vertical drop surface 35 that is a plane that vertically falls continuously from the emission surface 22 at the end on the second unit backlight unit 40b side. The curved surface portion 23b of the unit backlight portion 40b is adjacent to the vertical drop surface 35 of the first unit backlight portion 40a.

(Action / Effect)
With such a configuration, it is possible to apply to a display device with a large screen that cannot be handled by only one of the backlight devices described in Embodiment Mode 1. As a method of arrangement, in addition to arranging in the same direction as shown in FIG. 8, the following may be used.

  A modification of the backlight device in this embodiment is shown in FIG. In the backlight device 103 shown in FIG. 9, the plurality of unit backlight units include a first unit backlight unit 41a and a second unit backlight unit 41b adjacent to the first unit backlight unit. At the boundary between the first unit backlight portion 41a and the second unit backlight portion 41b, the curved surface portion 23h of the first unit backlight portion 41a and the curved surface portion 23i of the second unit backlight portion 41b face each other. Yes. With such a configuration, two rows of LED element rows 11 can be mounted together on a single circuit board 3e disposed at the boundary between the light guide plates, so that the number of boards can be reduced. Cost can be reduced. Further, in the backlight device 103 shown in FIG. 9, LED elements are also provided on each curved surface portion of the backlight device 103 shown in FIG. Because it is arranged, it can be solved. However, since a large number of LED elements 1 as heat sources are concentrated in a narrow area of the circuit board 3e, care must be taken to properly dissipate heat.

  In the backlight devices described in the first and second embodiments, when the LED element 1 and the incident surface 21 are connected via a resin, when the incident surface 21 is provided with a diffraction grating, When a material having a rate of 1.4 or less is used for the light guide plate, light is not totally reflected on the side surface between the curved surface portion 23 and the incident surface 21 of the light guide plate, and part of the light is outside the light guide plate. The light emitted from the side faces enters the adjacent light guide plate and travels through the adjacent light guide plate as it is, so that it is possible to suppress light loss.

(Embodiment 3)
(Constitution)
With reference to FIG. 10, the backlight apparatus in Embodiment 3 based on this invention is demonstrated. In the backlight device 104 according to the present embodiment, the plurality of unit backlight portions 43a and 43b are formed by integrating light guide plates. The backlight device 104 corresponds to a structure in which the light guide plates are connected and integrated in the backlight device 102 shown in FIG.

(Action / Effect)
Also in the present embodiment, the same effect as in the second embodiment can be obtained. Since the light guide plate is integrated, the number of parts of the light guide plate can be reduced. Although the light guide plate has an area that can be formed as a single body, the backlight device according to the present embodiment is effective for use on a large screen where the amount of light is insufficient with only one LED element row.

  Furthermore, as a modification of the backlight device in the present embodiment, the backlight device 105 shown in FIG. 11 may be used. The backlight device 105 corresponds to a structure in which the light guide plates are connected and integrated in the backlight device 103 shown in FIG. The backlight device 105 includes a plurality of unit backlight units 45a and 45b.

  In the present embodiment, the valley portion of the light guide plate occurs in the portion where the unit backlight portions are connected to each other, and for this reason, the deepest portion of the valley portion is unavoidably rounded due to processing, but the deepest portion as in the conventional example Since the LED element is not arranged directly below the part, the light component incident on the deepest part is only the one that travels obliquely from the LED element, and these light components are totally reflected at the deepest part, or Even if it radiates | emits from these roundness, it will inject into the light guide plate of an adjacent unit backlight part again. Therefore, it is difficult to form a locally high-brightness region that has been a problem in the conventional example.

However, when a plurality of unit backlight portions are arranged as in the second and third embodiments, the curved surface portion is located inside the display area. Since there is no light emission at the curved surface portion, it becomes dark locally. Therefore, it is preferable to intentionally leak the necessary light quantity from the curved surface portion. for that purpose,
(A) α ≧ π / 2−φ,
(B) The design origin is shifted to the left from the point O in FIG.
There are several possible countermeasures. However, if the above countermeasure is applied to the backlight device 102 shown in FIG. 8, since the light from the LED element is directly emitted to the outside, the brightness in the vicinity of the LED element may be increased. is there. Desirably, as in the backlight device 103 shown in FIG. 9, a method of emitting light guided through the light guide plate from two LED element arrays facing each other on one light guide plate from the curved surface portion is a luminance. This is because it becomes easy to suppress unevenness.

(Embodiment 4)
(Constitution)
Embodiment 4 based on this invention is demonstrated. In FIG. 9 referred to in the second embodiment, a plurality of unit backlight units are used. However, in this embodiment, only one unit backlight unit is added to the configuration shown in FIG. Will be described.

  A backlight device 107 in this embodiment is shown in FIG. The backlight device 107 includes one light guide plate 2h. A cross-sectional view of the backlight device 107 is shown in FIG. The backlight device 107 has, in addition to the curved surface portion 23 adjacent to the second side 91 of the emission surface, another curved surface portion 23j adjacent to the first side of the emission surface. , Another band-shaped incident region 20j is provided at a position corresponding to the other curved surface portion 23j.

  Even in this configuration, if it is normal, as described above after the third embodiment, it becomes a problem that the curved surface portions 23 and 23j are locally darkened, but they are arranged on two opposite sides, respectively. By emitting the light guided from the LED element rows 11 and 11j through a certain path from the curved surface portions 23 and 23j, the luminance on the curved surface portions 23 and 23j is uniform as described after the third embodiment. Is possible.

  Here, for example, in order to adjust the amount of light emitted from the left curved surface portion 23 in FIG. 12, the degree of scattering near the curved surface portion 23 may be increased, but from the LED element array 11 close to the target curved surface portion 23. It is required to mainly scatter light from the LED element array 11j on the opposite side, not light. This is because if the light from the LED element array 11 adjacent to the target curved surface portion 23 is scattered in the vicinity of the curved surface portion 23, the luminance near the LED element array is increased more than necessary.

  Similarly, in order to adjust the amount of light emitted from the right curved surface portion 23j in FIG. 12, it is required to mainly scatter light from the LED element array 11 on the opposite side in the vicinity of the curved surface portion 23j.

  Next, a configuration will be described in which light from the LED element rows on the opposite sides is mainly scattered on the incident surface 21 in the vicinity of each curved surface portion without much scattering of light from adjacent LED element rows. The backlight device 107 in this embodiment has this configuration. FIG. 14 shows a perspective view of the light guide plate 2h alone taken out from the backlight device 107 and viewed obliquely from below.

  In describing this configuration, the previous “curved surface portion” is replaced with “second curved surface portion”, “another curved surface portion” is replaced with “first curved surface portion”, and “band-shaped incident region” is replaced with “Second band-shaped incident area” and “another band-shaped incident area” are read as “first band-shaped incident area”. Therefore, when a reference numeral is given, the first curved surface portion 23j, the second curved surface portion 23, the first strip-shaped incident region 20j, and the second strip-shaped incident region 20 are obtained. For both the “curved surface portion” and the “band-like incident area”, the suffix “j” is attached to the symbol of “first”, and the suffix “j” is not attached to the symbol of “second”. Be careful.

  The backlight device 107 is incident on the light guide plate 2h from the first band-shaped incident region 20j, and is reflected on the first curved surface portion 23j and incident on the light guide plate 2 from the second band-shaped incident region 20. The first light scattering region 26a, which is the region on the incident surface 21 where the light reflected by the second curved surface portion 23 can first reach, and the first band-shaped incident region 20 on the incident surface 21. The second light scattering region 26b is a portion sandwiched between the second band-shaped incident regions 20j and not corresponding to the first light scattering region 26a. The degree of scattering is larger than that of the first light scattering region 26a. The second light scattering region 26b is divided into two portions so as to sandwich the first light scattering region 26a.

  The distinction between the first light scattering region 26a and the second light scattering region 26b on the incident surface 21 will be described in more detail. As shown in FIG. 15, the light incident from the second band-shaped incident region 20 that is the incident region on the second side 91 is totally reflected by the curved surface portion 23 and then reaches the incident surface 21. Since this light travels in the light guide plate 2 toward the first side 90 before reaching the incident surface 21, the second band-shaped incident is located at a position near the second band-shaped incident region 20 on the second side 91. A region where light incident from the region 20 hardly reaches is generated. This region is a second light scattering region 26b. On the other hand, both the light incident from the first band-shaped incident area 20 and the light incident from the first band-shaped incident area 20j on the opposite side can reach the first place away from the second band-shaped incident area 20 to some extent. New areas arise. This is the first light scattering region 26a. Here, “first reachable” refers to the first outer surface of the light guide plate that directly reaches the light incident from each band-shaped incident area after being reflected once by the corresponding curved surface portion and not reflected by the other surface. It means you can.

  As shown in FIG. 14, the incident surface 21 has a second band-shaped incident area 20, a second light scattering area 26b, a first light scattering area 26a, a second light scattering area 26b, and a first band incident. Each region is arranged in the order of the region 20j.

(Action / Effect)
In the backlight device 107 according to the present embodiment, since the scattering degree of the second light scattering region 26b is larger than the scattering degree of the first light scattering region 26a, the second light scattering region near the curved surface portion 23 is used. In 26b, the light from the LED element row 11j which opposes can be mainly scattered, without scattering the light from the LED element row | line | column 11 which adjoins very much. As a result, luminance unevenness near the curved surface portion 23 can be suppressed. Here, the description has been made by paying attention to the left end side in FIG. 12, but the same applies to the vicinity of the right end side in FIG. That is, in the second light scattering region 26b in the vicinity of the curved surface portion 23j, light from the LED element rows 11 facing each other can be mainly scattered without scattering much light from the adjacent LED element rows 11j. As a result, it is possible to suppress luminance unevenness near the curved surface portion 23j.

  The “scattering degree” used in the above description represents the average deviation from regular reflection on the incident surface, and the larger this deviation, the higher the probability that the total reflection condition cannot be satisfied on the exit surface. Therefore, the amount of light emitted from the exit surface increases.

  The first and second light scattering regions include a plurality of light scattering elements disposed in the region, and the density or individual size of the plurality of light scattering elements in the second light scattering region is the first light scattering region. It is preferable that it is larger than that in the light scattering region. This is because the degree of scattering can be easily increased in this way.

  Here, the “light scattering element” is preferably any one of a dot pattern, a texture pattern, a microprism, and a microlens. This is because these can be easily realized.

  In this embodiment, the backlight device 107 having only one unit backlight unit has been described. However, the invention described in this embodiment is not limited to a single unit backlight unit. The present invention can also be applied to a configuration including a unit backlight unit.

(Embodiment 5)
(Constitution)
With reference to FIGS. 16 and 17, a backlight device according to Embodiment 5 of the present invention will be described. As shown in FIG. 16, the backlight device 106 in the present embodiment includes a plurality of unit backlight units using the backlight device 101 described in the first embodiment as a unit backlight unit, and includes a plurality of unit backlight units. Are similar to those arranged in a plane adjacent to each other. The plurality of unit backlight units include a first unit backlight unit 47a and a second unit backlight unit 47b adjacent to the first unit backlight unit 47a. The first unit backlight unit 47a includes a light guide plate 2f having an emission surface 22f. The second unit backlight unit 47 b includes the light guide plate 2 having the emission surface 22. FIG. 17 shows an enlarged cross section near the boundary between the first unit backlight portion 47a and the second unit backlight portion 47b. The end of the second unit backlight unit 47b on the first unit backlight unit 47a side is a curved surface part 23b, and the end of the first unit backlight unit 47a on the second unit backlight unit 47b side is The concave portion 25 is recessed along the shape of the curved surface portion 23b of the second unit backlight portion 47b. The curved surface portion 23b of the second unit backlight portion 47b and the concave surface portion 25 of the first unit backlight portion 47a face each other with a gap 24 through which outside air can enter. That is, the gap 24 is an air layer.

(Action / Effect)
In the present embodiment, a part of the light emitted from the light guide plate 2 to the air layer in the gap 24 is again taken into the adjacent light guide plate 2f and can be used as display light. However, if the gap 24 is very narrow, water may enter the gap 24 due to condensation or the like, and the gap 24 may not necessarily be an air layer. When the gap 24 is not an air layer, the light incident on the curved surface portion 23b from the light guide plate 2 is not totally reflected, passes through the curved surface portion 23b into the gap 24, enters the light guide plate 2f as it is, and further passes through the light guide plate 2f. The light exits from the exit surface 22f. For this reason, the luminance is increased only in the band-like region in the vicinity of the LED element array 11, and the luminance distribution is not uniform in the entire display region. In order to suppress the influence of dew condensation or the like, the interval of the gap 24 may be made larger than a certain distance. For this purpose, for example, as shown in FIG. 17, a spacer member 4 for maintaining the gap 24 may be disposed in the gap 24. The backlight device 106 according to the present embodiment preferably maintains the gap 24 between the curved surface portion 23b of the second unit backlight portion 47b and the concave surface portion 25 of the first unit backlight portion 47a. A spacer member 4 is disposed.

  In Embodiments 2 to 5, an example in which only two unit backlight units are arranged in one backlight device has been described, but the number of unit backlight units is not limited to two. A configuration in which three or more unit backlight units are arranged in accordance with the size and shape of the display area may be employed. The arrangement of the unit backlight units is not limited to one column, and may be two-dimensionally arranged as two or more columns.

  In each of the above embodiments, the material of the light guide plate is PMMA. However, the material may be other than PMMA.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

It is a perspective view of the backlight apparatus in Embodiment 1 based on this invention. It is sectional drawing of the backlight apparatus in Embodiment 1 based on this invention. It is a perspective view of the light-guide plate contained in the backlight apparatus in Embodiment 1 based on this invention. It is an expanded sectional view of the curved surface part vicinity of the backlight apparatus in Embodiment 1 based on this invention. It is explanatory drawing of the course of the light in the vertical surface vicinity of the backlight apparatus in Embodiment 1 based on this invention. It is a partial side view of the 1st modification of the light-guide plate of the backlight apparatus in Embodiment 1 based on this invention. It is a partial side view of the 2nd modification of the light-guide plate of the backlight apparatus in Embodiment 1 based on this invention. It is a perspective view of the backlight apparatus in Embodiment 2 based on this invention. It is a perspective view of the modification of the backlight apparatus in Embodiment 2 based on this invention. It is a perspective view of the backlight apparatus in Embodiment 3 based on this invention. It is a perspective view of the modification of the backlight apparatus in Embodiment 3 based on this invention. It is a perspective view of the backlight apparatus in Embodiment 4 based on this invention. It is sectional drawing of the backlight apparatus in Embodiment 4 based on this invention. It is a perspective view of the light-guide plate contained in the backlight apparatus in Embodiment 4 based on this invention. It is explanatory drawing of the course of the light inside the backlight apparatus in Embodiment 4 based on this invention. It is a perspective view of the backlight apparatus in Embodiment 5 based on this invention. It is an expanded sectional view of the vicinity of the boundary of the unit backlight parts of the backlight apparatus in Embodiment 5 based on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 LED element, 2, 2f, 2h Light guide plate, 3, 3e Circuit board, 4 Spacer member, 11 LED element row | line | column, 20 Incident area (2nd strip | belt-shaped incident area), 20j Another strip | belt-shaped incident area | region (1st , 21 incident surface, 22, 22f exit surface, 23 curved surface portion (second curved surface portion), 23a, 23b, 23h, 23i curved surface portion, 23j another curved surface portion (first curved surface portion) , 24 gap, 25 concave portion, 26a first light scattering region, 26b second light scattering region, 30 vertical surface, 31, 32 side surface, 35 vertical drop surface, 40a, 41a, 47a first unit backlight portion 40b, 41b, 47b Second unit backlight unit, 43a, 43b, 45a, 45b Unit backlight unit, 81, 82 light, 90 first side, 91 second side, 93 (incident area Longitudinal direction (101, 102, 103, 104, 105, 106, 107) of the area and the curved surface part.

Claims (15)

A light guide plate having an incident surface having a band-shaped incident region and an output surface facing the incident surface;
A plurality of light emitting diode elements arranged in a straight line facing the incident surface of the light guide plate through the incident region;
The light guide plate extends at least on the first side when viewed from the incident region;
The light guide plate has a curved surface portion extending in a strip shape parallel to the longitudinal direction of the incident region so as to be adjacent to the second side opposite to the first side of the emission surface,
The curved surface part is for receiving the light that has passed through the incident region from the light emitting diode element array and entered the light guide plate and reflects the light toward the first side,
The cross-sectional shape of the curved surface section cut by a plane perpendicular to the longitudinal direction is such that C is a constant, n ₀ is the refractive index of the light guide plate, and 0 <α ≦ π / 2−sin ⁻¹ (1 / n ₀ ). By assuming a constant angle α to be satisfied, the backlight device can be expressed by r = exp (−θ / tan α + C) in polar coordinate display using a radius r and an angle θ with one point of the incident region as an origin.   2. The backlight device according to claim 1, wherein the origin is a point at an end of the first side in the incident region.   3. The backlight device according to claim 1, wherein the curved surface portion exists only in a range where θ in the polar coordinate display of the cross-sectional shape satisfies α ≦ θ ≦ π / 2 + α. The light guide plate has a vertical surface which is a surface perpendicular to the incident surface,
4. The backlight device according to claim 1, wherein the curved surface portion is connected to the vertical surface at a position where θ in the polar coordinate display of the cross-sectional shape is θ = π / 2 + α.   4. The backlight device according to claim 1, wherein the curved surface portion is connected to the emission surface at a position where θ in the polar coordinate display of the cross-sectional shape is θ = α.   6. The constant C is any one of claims 1 to 5, wherein C = [alpha] / tan [alpha] + ln (d / sin [alpha]), where d is the distance in the thickness direction of the light guide plate from the origin to the exit surface. Backlight device.   In addition to the curved surface portion adjacent to the second side of the emission surface, the curved surface portion has another curved surface portion adjacent to the first side of the emission surface, and the incident surface is the other curved surface. The backlight device according to claim 1, further comprising another band-shaped incident region at a position corresponding to the portion.   The backlight device according to claim 1, wherein the backlight device includes a plurality of the unit backlight units, and the plurality of unit backlight units are arranged adjacent to each other in a planar manner. Light equipment.   9. The backlight device according to claim 8, wherein each of the plurality of unit backlight portions is arranged so that the curved surface portions are all located on the same side with respect to the emission surface.   The backlight device according to any one of claims 1 to 6, wherein the backlight device includes a plurality of unit backlight units, and the plurality of unit backlight units are arranged adjacent to each other in a planar manner. In the apparatus, the plurality of unit backlight units include a first unit backlight unit and a second unit backlight unit adjacent to the first unit backlight unit, and the first unit backlight unit includes: The light guide plate has a vertical drop surface that is a flat surface that vertically falls continuously from the emission surface at an end of the second unit backlight portion, and the curved surface of the second unit backlight portion. The unit is adjacent to the vertical drop surface of the first unit backlight unit.   11. The backlight device according to claim 10, wherein each of the plurality of unit backlight portions is arranged so that the curved surface portions are all located on the same side with respect to the emission surface.   The plurality of unit backlight units include a first unit backlight unit and a second unit backlight unit adjacent to the first unit backlight unit, and the first unit backlight unit and the second unit backlight unit. The backlight device according to claim 8, wherein the curved surface portion of the first unit backlight portion and the curved surface portion of the second unit backlight portion face each other at a boundary with the light portion.   The backlight device according to any one of claims 8 to 12, wherein the plurality of unit backlight portions are formed such that the light guide plates are integrated.   The plurality of unit backlight units include a first unit backlight unit and a second unit backlight unit adjacent to the first unit backlight unit, and the first unit backlight of the second unit backlight unit. The end portion on the light unit side is the curved surface portion, and the end portion on the second unit backlight portion side of the first unit backlight portion is in the shape of the curved surface portion of the second unit backlight portion. The curved surface portion of the second unit backlight portion and the concave surface portion of the first unit backlight portion are opposed to each other through a gap through which outside air can enter. Item 9. The backlight device according to Item 8.   The backlight according to claim 14, wherein a spacer member for maintaining the gap is disposed between the curved surface portion of the second unit backlight portion and the concave surface portion of the first unit backlight portion. Light equipment.

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