JPH08136734A - Light control sheet and surface light emitting device having the same - Google Patents

Abstract

PURPOSE: To provide a light control sheet which is hard to be flawed and substantially prevented from the pickup of foreign matter by static electricity and a surface eight emitting device having the same. CONSTITUTION: A single layer sheet 11 of the light control sheet 10 is internally provided with many air layers 12 having an approximately triangular shape in the longitudinal cross-section and constant directivity. These air layers 12 have the approximately triangular shape in the longitudinal cross-section and are preferably formed so that the base of the triangular shapes exist on the upper side and the vertex angle on the lower side. The vertex angle αthereof is preferably in a range of 70 deg.<=α<=110 deg.. The length 1 of one side is preferably <=150μm. The respective vertex angles or circuit sides of the approximately triangular shape in the longitudinal cross-section may be provided with roundness. The spacings between the adjacent air layers 12 are preferably >=5μm. The surface light emitting device has the light control sheet 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control used for a surface light emitting device which constitutes a liquid crystal display such as a personal computer and a word processor, a liquid crystal color television, or a surface light emitting device which is used for an illuminated signboard, facility lighting and the like. The present invention relates to a sheet and a planar light emitting device including the sheet.

[0002]

2. Description of the Related Art In an edge light type planar light emitting device, a fluorescent tube 1 is arranged on an end face 3 side of a light guide plate 2 as shown in FIG. The back surface of the light guide plate 2 is provided with a dot pattern 4 formed by dot printing of a paint, and the back surface of the light guide plate 2 is further provided with a reflection plate 5.

In the above structure, the light beam emitted from the fluorescent tube 1 enters the inside of the light guide plate 2 from the end surface 3 of the light guide plate 2, is diffusely reflected by the dot pattern 4 on the back surface of the light guide plate 2, and is reflected from the surface of the light guide plate 2. Is released. FIG. 4 shows the intensity distribution of the light rays emitted from the surface of the light guide plate 2 with respect to the emission angle. Most of the light rays are emitted in a direction largely deviated from the direction normal to the light guide plate 2, and the distribution thereof is extremely steep (intensity distribution 6). For this reason, the screen is usually very dark for the user who observes from the normal direction of the light guide plate 2.

In order to overcome this drawback, a method of installing a light diffusion sheet on the surface of the light guide plate has been devised. The light diffusion sheet is a transparent plastic sheet surface coated with white pigment, titanium oxide, glass short fibers, etc., or contained therein, or the surface of the transparent plastic sheet is processed to have fine irregularities (matting, It is obtained by graining). FIG. 5 shows the intensity distribution with respect to the emission angle of light rays when the light diffusion sheet 7 is used. in this case,
It can be seen that the emission of light rays in the normal direction is increased as compared with FIG. 4 (intensity distribution 8).

However, in the intensity distribution when the light diffusing sheet 7 is used, a large number of light rays are emitted in a direction unnecessary for the user, and diffuse reflection at the interface between the light diffusing sheet 7 and the light guide plate 2 occurs. The loss of rays due to is not negligible. That is, the so-called light-collecting ability to direct light in the normal direction of the planar light emitting device is poor.

Therefore, as a method for improving these drawbacks, it has been attempted to use the prism sheet 9 having the structure shown in FIG.
-144102). The prism sheet 9 is formed by arranging small prisms having a substantially triangular cross section in a flat plate shape, and is an optical function sheet having a function of refracting or reflecting a light ray incident on the prism. When the prism sheet 9 is used, the intensity distribution with respect to the emission angle of the light beam is as shown in FIG. 7, and the emission of the light beam in the normal direction is significantly increased (intensity distribution 10).

[0007]

However, because of the shape of this prism sheet, the structure surface is easily scratched. Moreover,
Since the air layers having a triangular cross section are regularly arranged, the scratches are easily noticeable. Especially in mass production, appearance defects often occur on the light emitting surface, which makes mass production difficult.

Further, if foreign matter enters and adheres to the groove portion of the structural surface of the prism sheet due to static electricity, it is not easy to remove it, and this becomes a big problem when the prism sheet is incorporated into a planar light emitting device. .

In view of the above points, an object of the present invention is to provide a light control sheet in which scratches are less likely to occur and foreign matter is less likely to adhere due to static electricity, and a planar light emitting device including the light control sheet.

[0010]

SUMMARY OF THE INVENTION The present invention provides a light control sheet, characterized in that a plurality of air layers each having a substantially triangular longitudinal section and a constant direction are provided in a layer of a single layer sheet.

The present invention also provides a planar light emitting device including the above light control sheet.

Next, the present invention will be described in more detail.

FIG. 1 shows an example of the light control sheet of the present invention. The light control sheet 10 of the present invention is a single layer resin sheet 1.
In one layer, a large number of air layers 12 having a substantially triangular cross section and a constant directionality are provided.

The light control sheet of the present invention has an effect of condensing light by refracting the light at the boundary between the air layer 12 and the resin sheet 11. Therefore, the shape of the air layer 12 greatly contributes to the light collecting performance. The shape of the air layer 12 is generally triangular in vertical section, and it is desirable that the air layer 12 is provided so that the base of the triangle is on the upper side and the apex angle is on the lower side. The apex angle α is preferably in the range of 70 ° ≦ α ≦ 110 °, and particularly 90 °
° is optimal. Furthermore, the length of one side l is 15
It is preferably 0 μm or less. If it exceeds 150 μm, the light-collecting ability and the image quality may be deteriorated. It should be noted that roundness may be provided at each apex angle or each side of the substantially vertical cross section. Thereby, the absolute value of the viewing angle can be adjusted.

The distance between adjacent air layers 12 is 5 μm.
It is desirable that this is the case. If it is less than 5 μm, a problem may occur in strength.

The air layer 12 may be provided in two stages as shown in FIG. 2, instead of being provided in one horizontal row as shown in FIG. Thereby, the light collecting performance is further improved.

The material of the light control sheet is not particularly limited as long as it is a transparent resin, but a resin having good light transmittance such as polymethylmethacrylate or polycarbonate is suitable. Then, a predetermined sheet is obtained by shaping these resins by a method such as heat melting or photocuring, but the manufacturing method is not particularly limited.

The total thickness of the light control sheet is 0.10 to 0.
50 mm is preferable. If the thickness is 0.10 mm or less, the light control sheet is not stiff and is difficult to handle. If it is 0.50 mm or more, there is a problem in that it is difficult to miniaturize a planar light emitting device using the same and the like.

The surface of the light control sheet may be a smooth surface, or may be matted for the purpose of imparting diffusibility.

[0020]

Next, an embodiment of the present invention will be described. The present invention is not limited to the examples described below, and various configurations are possible without departing from the spirit of the present invention.

The light control sheet of each Example or Comparative Example was attached to the surface light emitting device shown below, and the front luminance, the adhesion of foreign matter, and the easiness of scratching were examined.

(Surface emitting device used) System: Edge light system on one side (1 lamp on short side) Light source: Cold cathode tube with thickness 3.5 mm, length 135 mm Light guide plate: Thickness 3 mm, width 205 mm, length 135 mm Of P
MMA plate Light diffusion sheet: A commercially available light diffusion sheet made of polycarbonate with a thickness of 0.20 mm (embossed with fine irregularities on the surface) is used to prevent the visibility of the dot pattern for imparting diffusivity to the back surface of the light guide plate. did. Applied pressure: 12V

(Evaluation Method of Frontal Luminance) Luminance from the frontal direction (normal direction) at 9 points where the backlight is determined is JI.
It measured based on S-C761 and calculated | required the average value.

[Example 1] Material: Polycarbonate Air layer cross-sectional shape: triangle with apex angle α = 90 °, side length l (l) = 100 μm Distance between adjacent air layers: 10 μm Sheet thickness: 250 μm Air Number of layers: One (corresponding to Figure 1)

[Example 2] Material: Polycarbonate Air layer cross-sectional shape: triangle with apex angle α = 100 °, side length l (L) = 80 μm Distance between adjacent air layers: 20 μm Sheet thickness: 400 μm Air Number of layers: Two (corresponding to Fig. 2)

Comparative Example 1 Material: Polycarbonate Structure surface: A prism shape having an apex angle α = 90 ° and a pitch = 80 μm is applied. Sheet thickness: 250 μm

[Comparative Example 2] Material: Polycarbonate Structure surface: Arbitrary unevenness is applied ( _Ra = 100 to 120 μm)
m) Sheet thickness: 250 μm

[Comparative Example 3] Material: Polycarbonate Air layer cross-sectional shape: triangle with apex angle α = 130 °, side length l (L) = 120 μm Distance between adjacent air layers: 80 μm Sheet thickness: 250 μm

The evaluation results are shown in Table 1. In Table 1, the evaluation of the effect of cleaning for removing the adhered substances and the easiness of getting scratches are shown by ⊚ when extremely good, ◯ when good, and × when bad.

[0030]

[Table 1]

[0031]

As described above, according to the light control sheet of the present invention, the light condensing ability is maintained by the prism effect of the air layer having a triangular cross section provided in the single layer sheet, and the structural surface is provided on the surface. By not providing it, the handling suitability improves, scratches do not occur, and adhesion of foreign matter can be prevented. Therefore, the planar light emitting device provided with this light control sheet has high front luminance and high mass productivity.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a light control sheet according to the present invention.

FIG. 2 is a side view showing another embodiment of the light control sheet according to the present invention.

FIG. 3 is a perspective view showing an example of a planar light emitting device.

FIG. 4 is an explanatory diagram showing an emitted light distribution of a conventional planar light emitting device that does not use a light control sheet.

FIG. 5 is an explanatory diagram showing an outgoing light distribution of a conventional planar light emitting device using a light diffusion sheet.

FIG. 6 is a perspective view showing an example of a prism sheet.

FIG. 7 is an explanatory diagram showing outgoing light distribution of a conventional planar light emitting device using a prism sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent tube 2 Light guide plate 3 End surface of light guide plate 4 Dot pattern 5 Reflective plate 10 Light control sheet 11 Resin image 12 Air layer

Claims (2)

[Claims] 1. A light control sheet comprising a plurality of air layers each having a substantially triangular vertical cross section and a constant directionality in a layer of the single layer sheet. 2. A planar light emitting device comprising the light control sheet according to claim 1.