JPH10104432A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device which has a uniform and a sufficient luminance. SOLUTION: The surface light source device has a thin plate type light transmitting substrate 2 and a primary light source 1 which irradiates the light transmitting substrate 2 with illumination light from its peripheral edge side and is composed of incident light scattering structure so that one of the front and rear surfaces of the light transmitting substrate 2 is varied in the radio of an uneven part composed of recessed and projections and an optical plate part with the distance from the primary light source while the other surface is uniformly roughened; and the uniform rough surface 7 has a 1.0 to 6.5 ratio (Ra/Sm) of mathematical means roughness Ra(μm) prescribed by JIS B0601 and a mean interval Sm(mm) of unevenness.

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 surface light source devices such as a lighting signboard and a lighting body.

[0002]

2. Description of the Related Art A conventional surface light source device used for various surface light sources is basically provided on a light-transmitting substrate, a primary light source and a light-transmitting substrate provided in parallel with an incident end face of the light-transmitting substrate. And an incident light scattering / reflecting structure. The surface light source device requires sufficient luminance and luminance uniformity in terms of performance. In order to improve these performances, in an incident light scattering / reflecting structure, a dot pattern which is an aggregate having a shape in which the area of a single shape portion is changed has been made.

[0003] For example, as disclosed in Japanese Patent Publication No. 7-9515, a dot pattern is formed by screen printing on a light-transmitting substrate according to the separation distance from the primary light source and the luminance of emitted light. In addition, instead of an incident light scattering / reflecting structure or screen printing having a V-shaped groove in the traveling direction of incident light or in a direction orthogonal to the incident light,
Incident light scattering / reflecting structures composed of circular or polygonal uneven surfaces (hereinafter, rough surfaces) have also been used. (JP-A-7-2
No. 8061) In any case, by adjusting the area ratio of the optical plane portion and the rough surface portion in an arbitrary region, the amount of light emitted from the region is adjusted, and the surface luminance is made uniform. It is.

However, in a surface light source device which attempts to equalize the luminance of the rear surface of the light transmitting substrate by adjusting the area ratio between the rough surface portion and the smooth surface of the dot pattern to adjust the amount of scattering and reflection of light. However, since the scattered and reflected light is emitted only at an angle equal to or less than the critical angle with respect to the exit plane, which is an optical plane, the problem that the incident light from the illumination device is not sufficiently utilized. There was a point.

[0005]

Therefore, in the present invention,
It is an object of the present invention to provide a surface light source device having sufficient luminance and high luminance uniformity.

[0006]

Means for Solving the Problems The present invention has the following arrangement to solve the above-mentioned problems. The surface light source device according to claim 1, wherein the light transmitting substrate is a thin plate, and the primary light source irradiates illumination light from a peripheral side of the light transmitting substrate.
Wherein one of the front and rear surfaces of the light-transmitting substrate (2) is formed from a rough surface portion and an optical flat surface portion having irregularities, and a ratio between the rough surface portion and the optical flat surface portion. Is changed as the distance from the primary light source (1) increases, and the other surface of the light-transmitting substrate (2) is formed as a uniform rough surface (7) having uniform unevenness. (7) is the arithmetic average roughness Ra (μm) specified in JIS B0601 and the average spacing Sm (m)
m) (Ra / Sm) is set to 1.0 or more and 6.5 or less.

According to a second aspect of the present invention, there is provided a surface light source device, wherein a rectangular light transmitting substrate (2) and a primary light source for illuminating light incident on the light transmitting substrate (1) from at least one peripheral side of four circumferences of the light transmitting substrate (2). A surface light source device comprising a light source (1) and a reflective film (3) covering the other periphery and the rear surface of the light-transmitting substrate (2), wherein one of the front and rear surfaces of the light-transmitting substrate (2) is The light-transmitting substrate (2) is formed from a rough surface portion and an optical flat surface portion having irregularities, and the ratio between the rough surface portion and the optical flat portion is changed as the distance from the primary light source (1) increases. A surface light source device in which the other surface has a uniform rough surface (7) having uniform unevenness, wherein the uniform rough surface (7) is JIS B
The ratio (Ra / Sm) of the arithmetic average roughness Ra (μm) and the average interval Sm (mm) of the concavities and convexities specified in 0601 is not less than 1.0 and not more than 6.5. With this configuration, the dot pattern composed of the rough surface portion and the optical flat portion ensures the uniformity of luminance in the surface required for practical use, and the light is scattered by the uniform rough surface, so that it is sufficient. A surface light source device having high luminance can be provided.

Preferably, in the surface light source device according to any one of the first and second aspects, as in the surface light source device according to the third aspect, the uniform rough surface (7) is JIS B060.
The ratio (Ra / Sm) of the arithmetic average roughness Ra (μm) and the average interval Sm (mm) of the irregularities specified in Section 1 is 2.0 (Ra / Sm).
It is characterized by being not less than 5.0 and not more than 5.0.

With such a configuration, the uniformity of luminance is further improved while maintaining sufficient luminance.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Here, FIG. 1 is a schematic perspective view of the surface light source device according to the first embodiment of the present invention, and FIG. 2 is a partial cross-sectional view of the surface light source device along AA. As shown in FIG. 1, the surface light source device is basically connected to a DC power source, and irradiates the light from the primary light source 1, which is a cold-cathode tube, and the primary light source 1 from one circumferential side of four sides of a square. A light-transmitting substrate 2 arranged so as to allow direct incidence, a reflective film 3 coated on one surface of the light-transmitting substrate 2,
And a reflector 6 disposed around the secondary light source 1. Here, the surface of the light-transmitting substrate 2 opposite to the surface coated with the reflective film 3 is the emission surface 4, and the surface facing the primary light source is the incidence surface 5.
And In the present embodiment, the primary light source 1
Is designed to make incident light incident only from one peripheral side of the four circumferences, but one or more may be disposed on other peripheral sides depending on the size and use of the light transmitting substrate 2.

The light-transmitting substrate 2 is made of, for example, a transparent resin such as polymethyl methacrylate (PMMA) or polycarbonate (PC), has a refractive index of about 1.4 to 1.6, and has a light-emitting surface. On the other hand, light incident at an angle of incidence larger than the critical angle is reflected between the light transmitting substrate and the air interface, and
Does not exit from For this reason, in the light transmitting substrate 2, in order to further emit light from the emission surface 4, the emission surface 4
At least one of the opposite surfaces is formed as a uniform rough surface 7 having uniform unevenness. By making the surface rough, the incident light is scattered at the corners of the rough surface and becomes light having a certain angular distribution width. Light rays incident on the exit surface 4 at an incident angle smaller than the critical angle of the surface increase. Therefore, compared with the case where the light is simply emitted out of the light-transmitting substrate 2 from the light-emitting surface 4 of the optical plane, the ratio of light emission is higher, and the light-emitting surface 4 is further illuminated, and sufficient luminance is obtained. .

On the rear surface of the light-transmitting substrate 2, a dot pattern is formed by combining an optical plane portion composed of a rough surface portion and a smooth surface in order to make the luminance uniform. Here, the dot pattern refers to an aggregate in which single-shaped portions such as a circular shape having a perfect circular shape or an elliptical planar shape, a square shape having a square or rectangular shape, and the like are arranged in parallel according to a certain rule. Due to the property of reflecting light at the flat portion of the dot pattern and scattering light at the rough surface portion, the area ratio of the flat portion / rough surface portion in an arbitrary region is determined by the position of the light transmitting substrate 2 or the distance from the primary light source 1. , The uniformity of in-plane luminance is achieved. More specifically, since the irradiation light amount from the primary light source 1 decreases as the distance from the primary light source 1 increases, the arrangement is made such that the area of the single shape portion increases.

Generally, the shape of the rough surface formed by the dot pattern on the light transmitting substrate 2 needs to have a surface roughness sufficient to scatter incident light. For this purpose, the surface roughness of the rough surface portion is determined according to JIS B
10 point average roughness R which is a parameter defined by 0601
It is preferable that z is 1 μm or more. In the present invention, as shown in FIG. 2, one of the light-emitting surface 4 and the opposite surface of the light-transmitting substrate 2 is a uniform rough surface 7. Here, the uniform rough surface 7 has an arithmetic average roughness Ra (μ) which is a parameter indicating the surface roughness specified in JIS B0601.
m), and the ratio Ra / S of the average interval Sm (mm) between the irregularities.
m. The range of Ra / Sm is preferably in the range of 1.0 to 6.5, and more preferably in the range of 2.0 to 5.0. Here, Ra is JIS B0
One of the parameters indicating the surface roughness defined by the reference numeral 601, the surface is extracted from the roughness curve by a reference length in the direction of the average line, the X axis is set in the direction of the average line of the extracted portion, and the X axis is set in the direction of the vertical magnification. When the Y axis is taken and the roughness curve is represented by y = f (x), the value obtained by the following equation is expressed in μm (μm).

[0014]

(Equation 1)

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 direction of the average line, and corresponds to one valley adjacent to one peak in the extracted portion. The sum of the lengths of the average lines (hereinafter referred to as the interval between the irregularities) is obtained, and the arithmetic mean value of the intervals between the many irregularities is expressed in millimeters (mm).

[0016]

(Equation 2)

If the value of Ra / Sm is greater than 6.5, a sufficient emission rate can be obtained, but the amount of light emitted near the primary light source 1 becomes too large, and it is difficult to make the in-plane luminance uniform. It is. If it is less than 1.0, high brightness cannot be obtained.
Note that the emission ratio here means that the amount of light or brightness of light incident on a minute region at an arbitrary position of the light transmitting substrate 2 is scattered and reflected by the incident light scattering / reflection structure from the emission surface of the minute region. It is defined as the ratio of the amount of light or the luminance of the light emitted from the emission surface. A high emission ratio means that a large amount of light is emitted from the region and a small amount of light is incident on a region adjacent to the region.

The method of forming a rough surface defining Ra / Sm is as follows.
Although not particularly limited in the present invention, a rough surface can be formed by chemical processing such as etching, or mechanical processing such as sand blasting or machining. By changing these processing conditions, rough surfaces having different Ra / Sm can be formed. Can be formed. Thus, in the surface light source device of the present invention, Ra /
Since the uniform rough surface 7 defined by Sm is formed on one surface, and the incident light scattering / reflecting structure composed of the dot pattern is arranged on the other surface, the in-plane luminance is sufficiently high and the luminance is low. Become uniform.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface light source device of the present invention will be described in the following embodiments.
This will be specifically described. First, a rough surface is formed as follows by changing the arithmetic average roughness Ra (μm) specified in JIS B0601 and the ratio (Ra / Sm) to the average interval Sm (mm) of unevenness.

Particles such as glass beads and alumina particles were sprayed on one surface of a SUS304 plate having a polished surface of a metal plate to uniformly roughen the surface. Separately, a dot pattern was formed on a mirror plate of SUS304 having a metal plate surface polished to # 800 by an etching method. Next, the light transmitting substrate 2 is formed. The light transmitting substrate 2 is a polymethyl methacrylate (PMMA) plate having a thickness of 3 mm and a size of 255 mm × 205 m.
m was sandwiched between two types of metal plates, and a replica was created by hot pressing. Ra and Sm of the prepared translucent substrate 2 were measured using a surface roughness meter (Surfcom manufactured by Toyo Seimitsu Co., Ltd.).

The created replica is processed and the light transmitting substrate 2
Then, the surface light source device was prepared by disposing the primary light source 1 as a cold cathode tube, the reflector 6 wound around the cold cathode tube, and the reflection film 3. The luminance of the surface light source device was measured using a luminance meter (BM-7, manufactured by Topcom).
The luminance was measured at a plurality of points of the surface light source device, and the arithmetic average value was measured as the average luminance, and the results shown in the following table were obtained. It should be noted that one surface has a dot pattern, and the other surface is smoothed. The average luminance ratio with respect to the reference value of Comparative Example 1 was set to 1.0.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, a surface light source device having a thin plate-shaped light transmitting substrate (2) and a primary light source (1) for irradiating illumination light from the peripheral side of the light transmitting substrate (2). One of the front and rear surfaces of the light-transmitting substrate (2) is formed of a rough surface portion and an optical flat surface portion having irregularities, and the ratio between the rough surface portion and the optical flat surface portion is separated from the primary light source. A surface light source device wherein the other surface of the light-transmitting substrate (2) has a uniform rough surface (7) made of uniform irregularities, wherein the uniform rough surface has an arithmetic average defined by JIS B0601. Roughness Ra (μm) and average spacing S of unevenness
With a configuration in which the ratio (Ra / Sm) to m (mm) is 1.0 or more and 6.5 or less, the dot pattern allows
The uniformity of the in-plane luminance required for practical use is ensured, and light is scattered by the uniform rough surface, so that there is an effect that a surface light source device having sufficient luminance can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary light source 2 Translucent board 3 Reflective film 4 Outgoing surface 5 Incident surface 6 Reflector 7 Uniform rough surface

 ──────────────────────────────────────────────────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 surface light source device comprising: a thin plate-shaped light transmitting substrate (2); and a primary light source (1) for irradiating illumination light from a peripheral side of the light transmitting substrate (2). Either of the front and rear surfaces of (2) is formed of a rough surface portion and an optical flat surface portion having irregularities, and the ratio between the rough surface portion and the optical flat surface portion changes as the distance from the primary light source (1) increases. A surface light source device in which the other surface of the light-transmitting substrate (2) has a uniform rough surface (7) made of uniform unevenness, wherein the surface roughness of the uniform rough surface (7) is defined by JIS B0601. A surface light source device characterized in that the arithmetic average roughness Ra (μm) and the ratio (Ra / Sm) to the average interval Sm (mm) of the concavities and convexities are 1.0 or more and 6.5 or less. 2. A light-transmitting substrate (2) having a rectangular shape, and a light-transmitting substrate (2) from at least one peripheral side of four circumferences of the light-transmitting substrate (2).
Primary light source (1) for irradiating illumination light to a light-transmitting substrate (2)
And a reflection film (3) covering the periphery and the rear surface of the light-transmitting substrate (2), wherein one of the front and rear surfaces of the light-transmitting substrate (2) is formed of a rough surface portion made of irregularities and an optical flat surface portion. And the ratio between the rough surface portion and the optical flat portion is changed as the distance from the primary light source (1) increases, and the other surface of the light-transmitting substrate (2) is formed as a uniform rough surface having uniform unevenness ( 7), wherein the surface roughness of the uniform rough surface (7) is calculated by calculating the ratio (Ra) of the arithmetic average roughness Ra (μm) specified in JIS B0601 and the average interval Sm (mm) of the unevenness. / Sm) 1.0 or more and 6.
A surface light source device characterized by having 5 or less. 3. The surface light source device according to claim 1, wherein the surface roughness of the uniform rough surface (7) is determined by arithmetic mean roughness Ra (μm) defined by JIS B0601 2.0 or more at a ratio (Ra / Sm) of the average interval Sm (mm).
A surface light source device characterized by being 0 or less.