JP3078063B2 - Backlight for panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a panel backlight for irradiating a transmissive or transflective panel from the back.

[0002]

2. Description of the Related Art Recently, a liquid crystal display device having a thin and easy-to-see backlight mechanism has been used as a display device such as a laptop or book type word processor or computer. As such a backlight, an edge light system in which a linear light source such as a fluorescent tube is provided at one end of a light-transmitting light guide plate as shown in FIG. 1 is often used. In the case of this edge light method, as shown in FIG. 2, one surface of the light guide plate is partially coated with a light diffusing substance having a higher refractive index than that of the light guide plate material, and almost the entire surface is mirror-reflected. Alternatively, many are arranged so as to be covered with a light diffusion reflector.

In recent years, in particular, in order to improve the performance of these word processors and personal computers, further reductions in size, improvement in visibility, and improvement in power consumption-luminance conversion efficiency have been demanded more and more. However, in a conventional backlight having a configuration in which a surface of a light guide plate partially covered with a light diffusion material is covered with a specular reflection plate or a light diffusion reflection plate (hereinafter, simply referred to as a reflection sheet), For example, when a certain force is applied to the reflection sheet or the light guide plate, a change in the distance between the light guide plate and the reflection sheet causes light interference, and a partial Newton's ring occurs. As a result, this is a cause of uneven brightness on the light exit surface. It may be.

[0004] In particular, as the size and thickness are reduced, the influence of the force on the pressure of the reflection sheet or the light guide plate is increased, and the above-mentioned problem is more likely to occur.

[0005]

Recently, as devices using a backlight have been miniaturized, a backlight having an efficient and flat luminance distribution characteristic has been demanded. An object of the present invention is to provide a backlight which can respond to miniaturization and has a uniform luminance distribution.

The present inventors have continued various studies on the configuration of the light-diffusing surface of the light guide plate of the backlight. As a result, the surface of the light guide plate and the specular reflection plate or the light diffusion reflection plate covering the light guide plate are described. during and 挾 lifting the transparent or light-diffusing film
When the configuration is urchin laminated, and completed the onsets present invention seen that uniform brightness distribution irrespective to the surface state of the surface state or specular reflector or a light diffuse reflector of the light guide plate is obtained.

[0007] The present invention is made of translucent material, a light scattering material partially coated with <br/> light diffusing imparted the light guide plate on a surface opposite to its light-emitting surface, this The light exit surface of the light guide plate
The light emitted from the light guide plate is stacked without passing through the film layer.
A light diffusing plate for scattering and passing the light, and the light guide plate
A plate or sheet of light diffusible reflective <br/> or specular reflection light diffusing stacked against imparted to surfaces of, the less of the light guide plate
A panel light source having a linear light source disposed close to an end of one side surface , wherein the coverage of the light diffusing substance is 1% to 50% in the vicinity of the linear light source, the furthest from the light source. to 20% to 100% in parts, and the light diffusibility of the light guide plate
Plate or sheet imparted with surface and a light diffuse reflection or specular reflection of
Relates transparent or light-diffusing film panel backlight interposed the between (but refers the via
The refractive index of the film is n1, and the refractive index of the light guide plate is n2.
When n1 <n2) .

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a perspective view of one embodiment of the present invention, and FIG.
Is a sectional view of the same. In the figure, reference numeral (1) denotes a light guide plate, which may be any substance that allows light to pass therethrough efficiently, such as a translucent natural or synthetic resin such as an acrylic resin. (2) is a light diffusion plate which scatters the light emitted from the light guide plate surface and passes it. In the present invention, one or more light diffusion plates are used.

A method for imparting light diffusing property to the light guide plate (1) is to partially cover a light scattering substance on one surface thereof as described later.
It can be carried out in Runa which way.

An example in which a light scattering substance is coated on one surface will be described below. The light scattering substance (6 in the figure) is a paint, a printing ink, or the like that has a higher refractive index than the material of the light guide plate and contains a pigment that diffuses light. These are printed in dot form on the light guide plate surface by a method such as screen printing.

The light diffusion or specular reflection plate (3) is disposed so as to cover almost the entire surface of the light guide plate coated with the light scattering substance. (4) is a linear light source. In a preferred embodiment, a reflector (lamp case) (5) having a gap (slit) for allowing light to enter the end of the light guide plate and covering the light source surface. . The light source is installed close to at least one end surface of the light guide plate so that its central axis is substantially parallel to the end surface of the light guide plate. The linear light source (4) includes a fluorescent tube, a tungsten incandescent tube, an optical rod, an LED array, and the like, but a fluorescent tube is preferable. From the viewpoint of uniformity of luminance distribution, a uniform light emitting portion excluding an electrode portion is used. Preferably, the length is equal to the length of the end of the adjacent light guide plate.

In the figure, (7) is a transparent or light-diffusing film which characterizes the present invention, which may be made of a transparent material and has transparency or light-diffusing properties.
Usually, polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate, cellulose acetate,
Films or sheets of polyolefins, polyvinyl chlorides and the like and their smoked products of 10 to 200
It has a thickness of μm.

According to the present invention, the transparent or light diffusing film is laminated and disposed over substantially the entire surface between the surface of the light guide plate on which the light scattering substance (6) is applied and the light diffusing or mirror reflecting plate (3). I do.

In the present invention, it is preferable to adopt the following configuration. That is, the light diffusing substance applied to the light guide plate of the present invention is formed in a dot shape, that is, a dot shape. However, the shape of the dot is not particularly limited, and may be formed in a circle, a square, or an intersection line. May be. These are applied on intersections (grids) of orthogonal lines having a certain interval imagined on the light guide plate, and the interval between the orthogonal lines is 0.5 to 3 m.
m is more preferably selected as appropriate between 0.8 and 2 mm according to the thickness of the light guide plate.

Further, it is preferable that the light diffusing material is coated on the light guide plate at a coverage of 1% to 50% in the vicinity of the linear light source portion and 20% to 100% in a portion farthest from the light source. ,
As the distance from the light source increases, it is preferable to cover the linear light source from the light source such that the coverage gradually increases starting from the coating point on one side end where the linear light source is brought closer. Here, the covering ratio means a ratio of a covering area of the light scattering substance applied per unit area of the light guide plate surface.

[0016]

According to the present invention, there is no occurrence of partial Newton's ring caused by light interference, the luminance distribution is constant, and the present invention can be effectively used for a small and thin display backlight.

[0017]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[0018]

EXAMPLES AND COMPARATIVE EXAMPLES A cold cathode fluorescent lamp having a thickness of 4.1 mm and a diameter of 7 mm longer than the length of the end of a rectangular light guide plate (225 mm × 127 mm) having a thickness of 2 mm as shown in FIG. A tube (Normal tube with a diameter of 4.1 mm manufactured by Harrison Electric Co., Ltd.) is arranged, and the outer periphery of the tube is provided with a gap of 2 mm and a slit of 2 mm in a portion in contact with the light guide plate.
It was covered with a polyester reflective case, and a silver-evaporated polyester sheet (thickness: 75 μm) was wrapped around the inner surface thereof, and was fixed to the end of the light guide plate using the tightening elastic force of the lip of the slit of the reflective case. The light emitted from the slit was arranged so as to enter the light guide plate from the end of the light guide plate.

On the other hand, the light diffusing substance to be coated on the light guide plate surface is a screen printed with a circular dot pattern, and the screen printing plate was prepared and used by CAD under the following conditions. . When the light diffusion material coverage is 6
%, 80% at the maximum, and exponentially increasing in the middle.

A light-guiding plate surface coated with a light-diffusing substance and a light-diffusing reflector ("Melinex" 329 manufactured by ICI, thickness 12
5 μm) and a transparent PET film (No. V516, thickness 100 μm, manufactured by Fuji Xerox Co., Ltd.) was used over the entire surface.

The luminance at 40 different points on the light emitting surface was measured by a luminance meter (Topcon BM-8) when the cold cathode tube was driven at a constant current by applying an alternating voltage of 30 KHz from the inverter. Are shown in Table 1. Note that the maximum value of the luminance is 391.2, the minimum value is 336.1, the average value is 363.7, and the luminance unevenness is ((maximum-minimum) / (maximum +
(Minimum) x 100): 7.6%.

Furthermore, although the center of the light exit surface was lightly pressed with a fingertip, the luminance portion state of the light exit surface did not change and a constant luminance was maintained.

On the other hand, Table 2 shows the results of measuring the luminance at 40 different points on the light emitting surface of the backlight which did not use the PET film used in the examples.
Further, substantially the center of the light emitting surface was similarly pressed, but Newton rings appeared around the pressed portion, causing uneven brightness. Maximum luminance: 427.4, minimum: 244.8, average: 336.1, luminance unevenness ((max−min) / (max +
(Minimum) x 100): 31.1%.

Table 1 No. Brightness No. Brightness No. Brightness No. Brightness 1 391.2 11 343.2 21 378.4 31 363.1 2 342.7 12 342.7 22 375.4 32 362.1 3 336.1 13 371.3 23 362.6 33 377.4 4 342.2 14 370.3 24 370.8 34 356.0 5 363.1 15 363.1 25 359.6 35 348.3 6 365.1 16 364.1 26 353.4 36 358.0 7 360. 1 17 360.1 27 352.9 37 368.7 8 370.8 18 356.0 28 370.3 38 365.3 9 368.2 19 357.0 29 377.4 39 356.5 10 345.8 20 362.6 30 371.8 40 366.2 Table 2 No. Brightness No. Brightness No. Brightness No. Luminance 1 316.2 11 343.2 21 343.7 31 285.1 2 310.6 12 347.8 22 318.2 32 252.5 3 320.8 13 338.6 23 284.6 33 410.04 334.1 14 312.6 24 246.3 34 359.0 5 333.5 15 279.0 25 427.4 35 362.16 317.2 16 244.8 26 366.7 36 360.1 7 284. 1 17 420.2 27 372.3 37 348.8 8 284.9 18 365.7 28 366.7 38 318.8 9 386.6 19 366.2 29 346.8 39 292.2 10 345.8 20 363.1 30 316.7 40 258.6

[Brief description of the drawings]

FIG. 1 is a perspective view of a backlight according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a backlight according to an embodiment of the present invention.

[Explanation of symbols]

 1: Light guide plate 2: Light diffusion plate 3: Specular reflection plate or light diffusion reflection plate 4: Linear light source 5: Reflector (lamp case) 6: Light scattering material 7: Transparent or light diffusion film

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-81683 (JP, A) JP-A-3-204683 (JP, A) JP-A-5-27236 (JP, A) JP-A-5-27236 66404 (JP, A) JP-A-3-265889 (JP, A) JP-A-4-199001 (JP, A) JP-A-4-269702 (JP, A) JP-A-4-280224 (JP, A) JP-A-4-280225 (JP, A) JP-A-5-61046 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13357

Claims (1)

(57) [Claims] 1. A made of a light-film light-emitting surface of the the light exit surface and the opposite surface to the light scattering material partially coated with light guide plate imparted with light diffusibility, the light guide plate Through layers
Scatters light emitted from the light guide plate when stacked
And a light diffusion plate for passing by, a light diffusing property of the light guide plate
Light diffuse reflection or specular reflection stacked on the given surface
A plate or sheet of at least one side end of the light guide plate
And a linear light source disposed in close proximity to the light source. The light-diffusing material has a coverage of 1% to 50% in the vicinity of the linear light source, and 20% in the farthest part from the light source. 1
And 00% and transparent between the plate or sheet imparted with surface <br/> a light diffuse reflection or specular reflection light diffusibility of the light guide plate
Or a panel backlight having a light diffusing film interposed (provided that the interposed film has a refractive index of n1 and a light guide
When the refractive index of the plate is n2, except that n1 <n2
H) .