JPH10133022A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a surface light source device capable of effectively utilizing light from a light source and having high and uniform luminance by setting up the roughened face part of incident light scattering/reflecting structure to specific roughness. SOLUTION: A roughened surface 7 is constituted so that its average interval Sm is 0.02 to 0.6mm and the ratio Ra/Sm of arithmetic average roughness Ra to the rugged average interval Sm is 0.5 to 20. When a factor Ra/Sm for regulating the shape of the roughened surface 7 is <0.5, light to be scattered on the roughened surface part 7 is not scattered and the quantity of light projected from a projection face is reduced less than the luminance of a surface light source. When the Ra/Sm of the roughened surface part 7 is >20, scattering on the surface part 7 is increased, but the quantity of projected light in the vicinity of a primary light source 1 is increased too much and the uniformity of luminance on the surface is made difficult, so that it is necessary to set up the Ra/Sm to a range of 0.5<=Ra/Sm<=20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal backlight,
The present invention relates to a surface light source device used for various light sources such as a lighting signboard and a lighting body.

[0002]

2. Description of the Related Art As surface light source devices, there are a so-called direct type having a light source below a light emitting surface and an edge light type having a light source on a side surface of a light emitting surface. The mold is mainly used. The edge light type surface light source is usually provided on at least one of the light transmitting substrate, the primary light source disposed on one end surface of the light transmitting substrate, the light emitting surface (front surface) of the light transmitting substrate, and the opposite surface (rear surface). And a reflection surface (reflection layer) covering the rear surface and the end surface of the incident light scattering / reflection structure. What is incident light scattering / reflection structure?
The purpose is to obtain a sufficient amount of light even in a portion far from the primary light source by scattering the light of the secondary light source, and a structure is adopted in which the surface of the light transmitting substrate is roughened to scatter and reflect the incident light. . A roughened surface is partially provided on the surface of the light-transmitting substrate, and an incident light scattering / reflecting structure is provided such that the roughened surface is less near the primary light source and the area increases as the distance from the primary light source increases. It is also considered that by providing the light source, the amount of light emitted from the front surface of the light-transmitting substrate is adjusted to make the in-plane luminance of the edge light type surface light source uniform.

[0003]

In the surface light source device, it is required for the performance of the light source to increase the luminance and to make the luminance uniform, but sufficient luminance and uniformity have not yet been obtained.

[0004]

Means for Solving the Problems As a result of repeated studies on this problem, the inventors have found that the roughened surface portion of the incident light scattering / reflecting structure has a specific roughness, thereby increasing the amount of emitted light and facilitating uniform control. And completed the present invention. The gist of the present invention is to provide a light-transmitting substrate, a primary light source disposed on at least one end surface of the light-transmitting substrate, a reflecting surface disposed on a rear surface of the light-transmitting substrate and an end surface on which the primary light source is not provided. And a surface light source device having a front surface or a rear surface of a light-transmitting substrate having a roughened surface for incident light scattering whose area increases as the distance from the primary light source increases, wherein the roughened surface portion has an average distance (Sm) of 0.1 mm. 02 to 0.6 mm, arithmetic average roughness (R
a) and a surface light source device having a rough surface portion having a ratio (Ra / Sm) of an average interval (Sm) of irregularities of 0.5 to 20.
Hereinafter, an example of the apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view of an example of the apparatus of the present invention, and FIG.
FIG. 3 is a longitudinal sectional view of the device shown in FIG. 1, and FIG. 3 is an explanatory view showing an example of a pattern of the incident light scattering / reflecting structure in a plan view.
In the figure, 1 is a primary light source, 2 is a light transmitting substrate, 3 is a reflective layer, 4 is an emission surface (front surface), 5 is an incident surface, 6 is a reflective cylinder, 7 is a rough surface portion,
Numeral 8 indicates a smooth portion. In the surface light source device of the present invention, as shown in FIG. 1, at least one end face of a light-transmitting substrate (transparent substrate) 2 has an incident light surface 5, which is orthogonal to the incident light surface 5.
One surface is defined as an outgoing light surface (front surface) 4, and one surface such as a fluorescent lamp or a cold cathode tube installed substantially parallel to the incident light surface 5 of the light transmitting substrate 2.
A secondary light source 1, a reflecting surface 3 made of a metal layer of silver, aluminum, or the like provided on an end surface and a rear surface other than the incident light surface 4 and the outgoing light surface 5, and an outgoing light surface 4 of the light transmitting substrate 2, or A rough surface portion 7 is formed on at least one of the opposite surface (rear surface).

In this surface light source device, the incident light incident from the incident light surface 5 travels inside the transparent substrate 2, is scattered by the rough surface portion 7 shown in FIG. You. Although the example in which the light source 1 is provided on one end face of the light transmitting substrate 2 is shown, a light source can be further provided on another end face. 1
The secondary light source 1 is driven to emit light by power supply from a power supply 10 or the like, and the emitted light is incident on the transparent substrate 2 through the incident light surface 5. A reflection tube 6 is provided around the light source 1 other than the incident light surface 5, and reflects light emitted from the light source 1 to the incident light surface 5 side, thereby improving the irradiation efficiency of the light source 1. Is increasing.

The light-transmitting substrate 2 of the present invention is made of a transparent resin such as poly (methyl methacrylate) (PMMA) or polycarbonate (PC), and has a refractive index of light of about 1.4 to about air. It is about 1.6. Therefore,
Light that has entered the outgoing light surface 4 at an incident angle larger than the critical angle is reflected at the light-transmitting substrate-air interface and does not exit from the front surface (outgoing light surface).

In order to emit light from the front surface 4, a rough surface portion 7 is provided on the front surface 4 of the transparent substrate 2 or on the opposite surface thereof, that is, on at least one of the rear surfaces. As a result, the incident light is scattered and reflected, and light is emitted from the front surface 4. Rough surface 7
FIG. 3 shows an example of the formation pattern of the above. In this example, the rough surface portion 7 is set to be elliptical, and the size of the ellipse is increased as the distance from the light source 1 is increased, the ratio of the smooth portion 8 is reduced, and the amount of scattered reflection is increased. Face part 7
Is not limited to such an elliptical shape, and may be any shape such as a circle or a square.
In this case, the pattern may be rough, and may be provided densely as the distance from the light source 1 increases.

When the factor Ra / Sm defining the shape of the rough surface portion 7 is less than 0.5, the light scattered by the rough surface portion 7 is close to the light reflected by the smooth portion 8 (optical plane). However, the incident light is not scattered, the amount of light emitted from the exit surface is reduced, and the luminance of the surface light source is also reduced. Also, the rough surface portion 7
When Ra / Sm is larger than 20, scattering by the rough surface portion 7 increases, but the amount of light emitted near the primary light source 1 becomes too large, and it becomes difficult to make the in-plane luminance uniform.
Needs to be in the range of 0.5 to 20.

The range of Ra / Sm is more preferably in the range of 1 to 15, and particularly preferably in the range of 5 to 12, and it is desirable to ensure uniformity of in-plane luminance while effectively using incident light. It becomes even easier. Arithmetic average roughness Ra
(Μm) is one of the parameters indicating the surface roughness defined by JIS B0601, and is extracted from the roughness curve by a reference length in the direction of the average line, and the X axis is set in the direction of the average line of the extracted portion. Take the Y axis in the direction of the vertical magnification,
When the roughness curve is represented by y = f (x), the value obtained by the following equation is represented by micrometer (μm).

[0011]

(Equation 1)

The average distance Sm (mm) between the irregularities is 0.02 to
It is 0.6 mm, preferably 0.03-0.3 mm. Sm is a parameter indicating the surface condition defined by JIS B0601, and is extracted from the roughness curve by a reference length in the average line direction, and an average line corresponding to one peak and one valley adjacent to one peak in the extracted portion. (Hereinafter referred to as the distance between the irregularities), and the arithmetic mean value of the distance between the many irregularities is expressed in millimeters (mm).

[0013]

(Equation 2)

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface light source device of the present invention will be specifically described with reference to the following embodiments. (Preparation of rough surface with different Ra / Sm) A dot pattern in which ellipses with a minor axis / major axis = 0.5 are arranged on a polished metal plate by changing etching conditions, and a mold having a different Ra / Sm. It was created. (Preparation of Light Guide) A light-transmitting plate (120 × 90 mm, PMMA) having a dot pattern consisting of a rough surface / optical surface and a uniform rough surface on its reflection surface using the above metal plate by injection molding.
And a component used for an edge light type surface light source device, such as a cold cathode tube, a reflector, a reflection sheet, and the like, were installed therein, thereby forming a surface light source device according to the present invention. The luminance of the light source device was measured using a luminance meter at a plurality of points of the surface light source device, and the results shown in Table 1 were obtained using the arithmetic average value as the average luminance.

[0015]

[Table 1]

[0016]

The present invention has been described above. According to the present invention, a surface light source device having high luminance and uniform luminance can be produced by effectively utilizing light from a light source.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of a surface light source device according to the present invention.

FIG. 2 is a cross-sectional view of an example of the surface light source device of the present invention.

FIG. 3 is an explanatory diagram of an example of a pattern of a rough surface portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary light source 2 Translucent board 3 Reflecting surface 4 Outgoing surface 5 Incident surface 6 Reflecting cylinder 7 Rough surface part 8 Smooth part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigekuni Dewa 4-5-1 Nihonbashi Muromachi, Chuo-ku, Tokyo Yuka Denshi Co., Ltd. (72) Kunikawa Kurokawa 4-1-1 Nihonbashi Muromachi, Chuo-ku, Tokyo No. 5 Yuka Electronics Co., Ltd.

Claims (3)

[Claims] 1. A light-transmitting substrate, a primary light source disposed on at least one end surface of the light-transmitting substrate, and a reflecting surface disposed on a rear surface of the light-transmitting substrate and an end surface on which the primary light source is not provided. A surface light source device comprising a front surface or a rear surface of a light-transmitting substrate, and a roughened surface for incident light scattering that increases in area as the distance from the primary light source increases, wherein the roughened surface has an average distance (Sm) of 0.1 mm.
A surface light source device having a rough surface part having a ratio (Ra / Sm) of 0.5 to 20 of arithmetic mean roughness (Ra) and average interval (Sm) of irregularities of 0.5 to 20 mm. 2. An average interval (Sm) of the rough surface portion is 0.03 to 0.03.
The surface light source device according to claim 1, wherein the surface light source device is 0.3 mm. 3. The surface light source device according to claim 1, wherein Ra / Sm of the rough surface portion is 5 to 12.