JP3411858B2 - Light guide plate and flat lighting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight or the like used in a liquid crystal display device or the like, in which convex or concave dots are arranged in parallel or in parallel with the incident end face portion of a light guide plate. The present invention relates to a light guide plate and a flat lighting device that can be installed in parallel or in parallel at predetermined intervals to realize bright and uniform emitted light.

[0002]

2. Description of the Related Art As a conventional light guide plate, in order to uniformly emit the light incident from the incident end face portion, dots such as white ink are printed on the back surface so that the dot density is increased as the distance from the incident end face portion increases, and It is known that the dot area is increased as the distance from the end face is increased, and the entire light guide plate is made uniform by increasing the amount of light reflected from the dots.

Further, as a conventional light guide plate, convex portions or concave portions are randomly arranged on the front surface portion or the rear surface portion of the light guide plate, and the light is emitted to the front surface portion or the like by utilizing refraction or total reflection, and the incident end face portion is formed. It is also known that a larger amount of light is distributed as it is farther away from the light guide plate, and more refraction and total reflection are performed as the energy of light is reduced to obtain uniform emitted light over the entire light guide plate.

Further, as a conventional light guide plate, Japanese Patent Laid-Open No. 9-
The one shown in Japanese Patent No. 184920 is known. This light guide plate is of a type in which light sources are provided on both sides, but a plurality of V grooves having prism surfaces are juxtaposed on the back surface so that the distance between the V grooves becomes closer as the distance from the light source increases and the distance from the light source increases. It compensates for the darkness of the part. It is also known that the distance Vn from the fixed point on the end side of the n-th V-groove is such that the V-grooves are provided at V-groove intervals that satisfy the formula Xn = (a * n) ^{1 / c} + b.

[0005]

DISCLOSURE OF THE INVENTION As a conventional light guide plate,
In order to uniformly emit the light incident from the incident end face portion, the dots such as white ink are printed on the back surface so that the dot density is increased as the distance from the incident end face portion increases, or the dot area is increased as the distance from the incident end face portion increases. In the case where the entire light guide plate is made uniform by increasing the amount of light reflected from the dots, there is a problem in the conversion efficiency due to the energy loss of light due to the light absorbing action due to the scattering substances mixed in the white ink, and the dot area is large. There is a problem that there is a limit to the pod density.

Further, as a conventional light guide plate, convex portions or concave portions are randomly arranged on the front surface portion or the back surface portion of the light guide plate, and the light is emitted to the surface portion or the like by utilizing refraction or total reflection, and at the same time, the incident end face portion is formed. When the light is distributed farther away from the light source and more refracted or totally reflected as the energy of the light is reduced to obtain a uniform emitted light over the entire light guide plate, the light from the light source is guided as shown in FIG. When entering the incident end face portion 33 of the light plate 32,
Assuming that the refraction angle is γ, the light travels in the light guide plate 32 within a range that satisfies the expression of 0 ≦ | γ | ≦ sin ⁻¹ (1 / n). In addition, the light guide plate 32
And an air layer (refractive index n ₀ = 1) at the boundary surface (surface portion 35,
On the back surface portion 36), sinC = (n ₀ / n) = (1 /
The critical angle can be expressed by the equation of n). For example, since the refractive index of acrylic resin, which is a resin material used for the general light guide plate 32, is about n = 1.49, the maximum value of the refraction angle γ and the critical angle α are γ = 42 ° and α = 42. It will be about °.

Further, the surface portion 35 of the light guide plate 32 having the thickness d
The length S1 of the ray connecting the point A and the point B where the total reflection is repeated between the rear surface portion 36 and the back surface portion 36 at a critical angle α = 42 ° is S1 =
As represented by d / cos θ (where θ is the surface 3
Emission angle formed with the normal line of 5) It is more efficient to dispose a convex portion or a concave portion that breaks the critical angle at a point corresponding to a position such as point A or point B, and the shape of the light guide plate 32 is wedge-shaped. However, the same can be said, and when convex portions or concave portions are randomly arranged on the front surface portion 35 or the rear surface portion 36 of the light guide plate 32, there is a problem in efficiency.

Further, the conventional light guide plate disclosed in Japanese Patent Application Laid-Open No. 9-184920 is a type in which light sources are provided on both sides. The distance between the V-grooves becomes closer as the distance increases and the darkness of the portion farther from the light source is compensated for. Further, the distance Xn from the fixed point on the end side of the n-th V-groove is Xn = (a * n)
^{When the} V-grooves are formed at the V-groove intervals that meet the formula of ^{1 / c} + b, as described in FIG. 2, the V-grooves parallel to the incident end face portion 33 are formed at the points corresponding to the positions such as the points A and B. In this arrangement, there is a problem that an abnormally high brightness is emitted and a bright line is generated in the vicinity of the incident end face portion 33 because the V groove is parallel to the incident end face portion 33.

The present invention has been made to solve such a problem, and its purpose is to connect convex or concave dot portions on the front surface or the back surface of the light guide plate in parallel with the incident end surface portion in parallel. Installed or arranged in parallel, and the distance between these arranged or arranged in series is set to be 1.5 to 10 mm from the incident end face portion.
By dividing by the square root of 1.8 and by sequentially dividing the next distance in the direction of the reflecting end surface portion by the previous distance by the square root of 1.5 to 1.8, the incident end surface portion close to the light source is obtained. An object of the present invention is to provide a light guide plate and a flat illumination device that can obtain uniform and bright light without generation of bright lines in the vicinity.

[0010]

In order to solve the above-mentioned problems, a light guide plate according to a first aspect of the present invention has a convex or / and concave dot portion on a front surface portion and / or a rear surface portion in parallel with an incident end surface portion in parallel. The distance between the continuous or parallel installation and the distance between the continuous or parallel installation from the incident end face portion is 1.
The distance is divided by the square root of 5 to 1.8, and the next distance in the direction of the reflection end face is sequentially divided by the square root of 1.5 to 1.8. It is characterized in that it is randomly dispersed with a distribution amount of 0.2 to 1 ppm.

The light guide plate according to claim 1 has a surface portion or /
And the convex or / and concave dot portions are arranged in parallel or in parallel in parallel with the incident end surface portion on the back surface portion, and the distance between the continuous arrangement or the parallel arrangement is determined by the distance from the incident end surface portion. Is divided by a square root of 1.5 to 1.8, and the next interval is sequentially set to 1.
The value is divided by the square root of 5 to 1.8, and the dot portions are randomly dispersed with a distribution amount of 0.2 to 1 ppm between the intervals, so that reflection and refraction can be efficiently performed, and the dots are closely connected. Even if installed or in parallel, the continuous or parallel installation is partially broken to prevent the occurrence of moire, and the distribution amount is 0.2
Since it is about 1 ppm, it does not obstruct the light emitted from the dot portions 9 arranged inconspicuously or side by side, and the convex or concave shape applied to the front surface portion 5 or the rear surface portion 6 is like a groove or prism. It is possible to prevent the generation of bright lines because the dot portions 9 are not formed in a linear shape.

Further, in the flat illumination device according to the second aspect of the present invention, convex or / and concave dot portions are arranged in parallel or in parallel with the incident end face portion on the front surface portion and / or the rear surface portion of the light guide plate. , The distance between consecutively arranged or juxtaposed with each other is divided by the square root of 1.5 to 1.8 from the distance from which the incident end face is first consecutively arranged or juxtaposed with each other, and the next gap in the direction of the reflecting end face is calculated as follows. The distance is set to a value obtained by dividing the distance by the square root of 1.5 to 1.8, and the dot portion is 0.2 to 1 between the distances.
It is characterized in that it is randomly dispersed with a distribution amount of ppm.

According to another aspect of the flat illumination device of the present invention, convex or / and concave dot portions are arranged in parallel on the front surface portion and / or the back surface portion of the light guide plate in parallel with the incident end surface portion or in parallel. The distance from the incident end face portion to the first or next distance is divided by the square root of 1.5 to 1.8, and the next distance in the direction of the reflecting end face portion is the previous distance. Is divided by the square root of 1.5 to 1.8, and the dot portion is further 0.2 to 1 ppm between the intervals.
Since it is dispersed randomly with the distribution amount of, even if densely arranged or arranged in parallel, the continuous or parallel arrangement is partially broken to prevent the generation of moire, and the distribution amount is about 0.2 to 1 ppm,
It does not obstruct the light emitted from the dot portions 9 arranged inconspicuously or in parallel, and the convex or concave shape on the front surface portion 5 or the rear surface portion 6 is not a linear shape like a groove or prism and is a dot. Part 9
As a result, the generation of bright lines can be prevented.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

In the present invention, convex or concave dot portions are continuously or parallelly provided on the front surface portion or the rear surface portion of the light guide plate in parallel with the incident end surface portion, and the intervals of these continuous or parallel arrangement are set at the incident end surface portion. The first distance from the first or the next is divided by the square root of 1.5 to 1.8, and the next distance in the direction of the reflection end face is sequentially decreased by the square root of 1.5 to 1.8. And the dot portion is 0.2 between the intervals.
An object of the present invention is to provide a light guide plate and a planar illuminating device which can be uniformly distributed with a distribution amount of ˜1 ppm and which can obtain uniform and bright light without generation of bright lines in the vicinity of the incident end face portion near the light source.

FIG. 1 is a schematic perspective view of a flat lighting device according to the present invention.

The flat lighting device 1 shown in FIG. 1 comprises a light guide plate 2, a light source 10, a reflector 11 and a reflector 12.

The light guide plate 2 is formed of a transparent acrylic resin (PMMA), polycarbonate (PC) or the like having a refractive index of about 1.4 to 1.7, and an incident end face portion 3 for guiding light from the light source 10, The reflecting end surface portion 4 located on the opposite side of the incident end surface portion 3, side surface portions 7 and 8 connected to the incident end surface portion 3 and the reflecting end surface portion 4, a surface portion 5 for emitting light, and this surface portion. 5 and a back surface portion 6 located on the opposite side.

Further, the light guide plate 2 has dot portions 9 having a convex shape or a concave shape on the front surface portion 5, the rear surface portion 6 and the like. As a result, the light from the light source 10 becomes 0 after entering from the incident end face portion 3.
The light travels into the light guide plate 2 with a refraction angle γ (γ = ± 42 °) within a range that satisfies the expression ≦ | γ | ≦ sin ⁻¹ (1 / n). Then, the boundary surface between the front surface portion 5 and the back surface portion 6 (air layer (refractive index n
₀ = 1)), sin C = (n ₀ / n) = (1 / n)
The light in the vicinity of the critical angle α (α = about 42 °) is refracted or totally reflected to be emitted to the outside, but as in the case shown in FIG. The length S1 of the light beam that repeats total reflection between is equal to S1 at the thickness d of the light guide plate 2.
= D / cos θ, and these convex or concave dot portions 9 are arranged on the surface portion 5 of the light guide plate 2 so that convex portions or concave portions are arranged at points corresponding to positions where total reflection is repeated. The back surface portion 6 and the like are provided continuously or in parallel.

Further, the interval between the dot portions 9 arranged or arranged in parallel is the distance obtained by dividing the distance from the incident end face portion 3 which is arranged or arranged in the first direction by the square root of 1.5 to 1.8. The dot portion 9 is provided as a value obtained by dividing the following distance by the square root of 1.5 to 1.8 in the direction of the reflection end face portion 4 sequentially.

Table 1 shows the ratio when the arrangement of the dot portions 9 according to the present invention is divided by the square root of 1.65. Note that, hereinafter, Tables 1 and 2 show the tendency of the distribution amount of dots when the horizontal axis 0 is set as the light incident portion (incident end surface portion 3) toward the reflective end surface portion 4 direction.

[0022]

[Table 1]

Further, regarding the conventional light guide plate disclosed in Japanese Unexamined Patent Publication No. 9-184920, n with respect to the distance between the V grooves.
The distance Xn from the fixed point on the end side of the th V groove is Xn =
As an example applied to the formula of (a * n) ^{1 / c} + b,
Table 2 shows the ratios when a = 60, b = 130, and c = 3.

[0024]

[Table 2]

As described above, the distribution table 1 according to the present invention and the conventional distribution table 2 have different rises in the vicinity of the incident end face portion 3, and the light guide plate 2 of the present invention is reflected in the vicinity of the incident end face portion 3. As the distance from the incident end face portion 3 becomes farther without performing treatment such as refraction, it is not a perfect linear shape, and the distance in which the dot portions 9 are continuously arranged or juxtaposed is divided by the square root of 1.5 to 1.8.
The light is uniformly emitted from the incident end face 3 to the reflection end face 4 and no bright line is generated in the vicinity of the incident end face 3.

Further, the light guide plate 2 has a front surface portion 5 and a rear surface portion 6.
Further, since the dot portions 9 are formed so as to be randomly dispersed with a distribution amount of 0.2 to 1 ppm between the intervals of the convex or concave dot portions 9 and the like, even if they are densely connected or arranged in parallel. Prevents the occurrence of moire by partially breaking the continuous or parallel arrangement,
In addition, since the amount of distribution is about 0.2 to 1 ppm, it does not obstruct the light emitted from the dot portions 9 arranged inconspicuously or arranged in parallel, and the convex or concave shape applied to the front surface portion 5 or the rear surface portion 6 Since the dots and the like are not linear like grooves and prisms, and do not form bright lines.

The light source 10 has a linear shape such as a CFL (cold shadow tube), and direct light enters the light guide plate 2 through the incident end face portion 3 of the light guide plate 2, while other light is reflected by the reflector 11. The light enters the light guide plate 2 through the space between the light source 10 and the reflector 11.

The reflector 11 is made of a white insulating material, a sheet-shaped metal or the like in which a metal such as aluminum is vapor-deposited, or the like, and surrounds the incident end face portion 3 of the light guide plate 2 and the light source 10 so that the light from the light source 10 is emitted. Is reflected and the reflected light is re-incident on the incident end face portion 3 of the light guide plate 2.

The reflector 12 is a sheet in which a white material such as titanium oxide is mixed in a thermoplastic resin, a sheet of a thermoplastic resin on which metal such as aluminum is vapor-deposited, a metal foil is laminated, or a sheet metal. Etc. The reflector 12 covers portions other than the incident end face portion 3 and the surface portion 5,
Light from the light source 10 is reflected or irregularly reflected by the light guide plate 2 except for being emitted to the surface portion 5, and is again incident on the light guide plate 2 so that all the light from the light source 10 is emitted from the surface portion 5. .

As described above, in the light guide plate and the flat lighting device of the present invention, convex or concave dot portions are arranged in parallel or in parallel with the incident end face portion on the front surface portion or the back surface portion of the light guide plate, The distance from the incident end face portion to the first or next from the incident end face is divided by the square root of 1.5 to 1.8. The distance is divided by the square root of 1.5 to 1.8, and the dots are randomly distributed with a distribution amount of 0.2 to 1 ppm between the intervals, so that dots with convex or concave shapes are misleading. Instead of arranging randomly, the light guide plate emits a strong bright line at the position of the front surface and the back surface that coincides with light rays that undergo total reflection at a critical angle. Is provided to enable efficient emission and obtain bright and uniform brightness. It is possible to prevent the occurrence of bright lines while preventing occurrence of moire.

[0031]

As described above, in the light guide plate according to the first aspect, the convex or / and concave dot portions on the front surface portion and / or the back surface portion are arranged in parallel or in parallel with the incident end surface portion. Then, the distance between the continuous or parallel installations is divided by the square root of 1.5 to 1.8 from the distance from the incident end face to which the first serial connection or parallel is arranged, and the next interval is moved forward by one in the direction of the reflective end face. And the dot portion is 0.2-1p between the intervals.
Since it is randomly dispersed in the distribution amount of pm, it can be efficiently reflected and refracted, and bright and uniform brightness can be obtained. Moreover, even when densely arranged or arranged in parallel, the continuous or parallel arrangement is partially collapsed to prevent the generation of moire, and since the distribution amount is about 0.2 to 1 ppm, the dots are arranged inconspicuously or arranged in parallel. It does not interfere with the light emitted from the portion 9, and the convex portions or the concave portions formed on the front surface portion 5, the rear surface portion 6 and the like are not the linear shapes such as grooves and prisms but the dot portions 9, so that a bright line is generated. And a stable and uniform light source can be obtained.

Further, the flat illumination device according to claim 2 is
Convex or / and concave dot portions are arranged in parallel or in parallel on the front surface portion and / or the back surface portion of the light guide plate in parallel with the incident end surface portion, and the intervals of the continuous arrangement or the parallel arrangement are first from the incident end surface portion. The distances arranged in series or juxtaposed were divided by the square root of 1.5 to 1.8, and the next distance in the direction of the reflection end face was sequentially divided by the square root of 1.5 to 1.8. The value is 0.2-
Since it is randomly dispersed with a distribution amount of 1 ppm, even if it is densely connected or arranged in parallel, the continuous or parallel arrangement is partially broken to prevent the generation of moire, and since the distribution amount is about 0.2 to 1 ppm, It does not obstruct the light emitted from the dot portions 9 arranged inconspicuously or in parallel, and the convex or concave shape on the front surface portion 5 or the rear surface portion 6 is not a linear shape like a groove or prism and is a dot. Since it comprises the portion 9, it is possible to prevent the generation of bright lines and obtain a flat light source which is easy to see.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a flat lighting device according to the present invention.

FIG. 2 Conventional light guide plate

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Planar illuminating device, 2, 32 ... Light guide plate, 3, 33 ... Incident end surface part, 4 ... Reflection end surface part, 5, 35 ... Surface part, 6, 36
... back surface part, 7, 8 ... side surface part, 9 ... dot part, 10 ... light source, 11 ... reflector, 12 ... reflector, A, B ... dot, d
... Thickness, γ ... Refractive angle, n ₀ , n ... Refractive index, α ... Critical angle,
θ: outgoing angle, S1: length of light beam.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI // F21Y 103: 00 F21Y 103: 00 (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/00 331 F21V 8/00 601 G02F 1/13357 G09F 9/00 336

Claims (2)

(57) [Claims] 1. An incident end face portion on which light is incident, a reflection end face portion located on the opposite side of the incident end face portion, a surface portion on which light is emitted from the incident end face portion, and an opposite side of the surface portion. A light guide plate comprising a rear surface portion located on the front surface portion and / or the rear surface portion of the light guide plate, wherein convex or / and concave dot portions are arranged in parallel or in parallel with the incident end surface portion. , The distance between the consecutively arranged or arranged in parallel from the incident end face portion is divided by the square root of 1.5 to 1.8, and the following distances are sequentially arranged in the direction of the reflecting end face portion. with the previous interval distance and the square root value division in the 1.5 to 1.8
In addition, the dot portion of 0.2 ~ 1ppm between the intervals
A light guide plate characterized by being dispersed randomly according to a distribution amount . 2. A light source, an incident end face portion that guides light from the light source, a reflecting end face portion located on the opposite side of the incident end face portion, and a side surface that connects the incident end face portion and the reflecting end face portion. Portion, a light guide plate having a front surface portion that emits light guided from the incident end surface portion, and a back surface portion that is located on the opposite side of the front surface portion, and reflects the light of the light source to enter the incident end surface portion again. In the flat lighting device including a reflector for causing the light guide plate, convex or / and concave dot portions are provided in parallel or in parallel with the incident end face portion on the front surface portion and / or the back surface portion of the light guide plate. The distance between the incident end face portion and the distance between the incident end face portion and the incident end face portion is divided by the square root of 1.5 to 1.8, and the following distances are sequentially applied to the reflecting end face portion. The previous distance is 1. A flat illumination device characterized in that the value is divided by a square root of 5 to 1.8 and the dot portions are randomly dispersed in a distribution amount of 0.2 to 1 ppm between the intervals.