JPH0933705A - Optical control sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the optical control sheet which has high front luminance and has no dot seen and is low in cost by orienting and mixing fiber which has a lower refractive index than the refractive indexes of the components of a transparent resin sheet and is a polygonal pyramid or semicylinder, etc., in the transparent resin sheet. SOLUTION: The optical control sheet has many fibrous air layers, which have a lower refractive index than the refractive indexes of the components of the transparent resin sheet 1 and are in a columnar shape of 10μm in external diameter, arrayed in one direction in the transparent resin sheet 1. To manufacture the optical control sheet, hollow polyethylene terephthalate(PET) fibers 3 of 20μm in outer diameter and 10μm an inner diameter are uniformly arrayed in one direction in the transparent resin sheet 1, and also has nonhollow PET fibers are arrayed at right angles to the said fibers, thereby forming a 20μm mesh cloth. Then the cloth is embedded in the transparent resin sheet 1 consisting principally of PET by solution casting and the transparent resin sheet 1 is dried. This optical control diffuses light at right angles to the air layers 2 and does not diffuse it in the direction parallel to the air layers 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light control sheet used in a planar light emitting illuminating device using a plate-shaped light guide, and particularly to a light control sheet which is low in cost, excellent in brightness and image quality, and invisible to dots. The technology is effective when applied to the seat.

[0002]

2. Description of the Related Art Conventionally, a light control sheet of this type has a transparent resin sheet in which a transparent fine particle having a different refractive index from that of the transparent resin sheet is mixed as a light diffusing agent, or a transparent resin sheet is exposed to light. There is a resin coated with a diffusing agent (for example, disclosed in Japanese Utility Model Laid-Open No. 5-73601).

However, since such a light control sheet contains a spherical light diffusing agent, the light hitting the light diffusing agent is scattered at the interface between the light diffusing agent and the transparent resin sheet,
Refraction enters into the light diffusing agent and enters into the light diffusing agent to become completely diffused light, which is emitted in many directions other than the direction perpendicular to the light control sheet. Therefore, in order to emit light in a direction perpendicular to the light control sheet, one to three light condensing sheets and a light diffusing sheet are further used, the amount of the diffusing agent mixed is reduced, or the sheet thickness is reduced. Those with weakened diffusion have been proposed.

Further, such a light control sheet is provided with a concavo-convex shape on one side or both sides (see, for example, JP-A-6-591).
No. 08, JP-A-4-7505), a device that collects light in a direction perpendicular to the light control sheet is also proposed.

[0005]

However, the present inventors have found that the above-mentioned light control sheet has the following problems. That is, since the number of light diffusion sheets and light condensing sheets to be used increases, the cost increases. If the amount of diffusing agent mixed in is reduced or the sheet thickness is reduced to weaken the diffusing power, the dot concealment, which is the original function of the light control sheet, is impaired. In addition, a light control sheet with irregularities on one or both sides can emit prismatic light such as prisms and lenticular lenses because light with all angles hits the irregular slopes due to the fine particles and the emitted light is in all directions. The condensing principle of the various lens sheets will be completely impaired.

The object of the present invention is to solve the above-mentioned problems.
An object of the present invention is to provide a low-cost light control sheet with high front brightness and invisible dots. The above and other objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0007]

The outline of the invention disclosed in the present application will be briefly described as follows.
The light control sheet of the present invention has, in the transparent resin sheet, a fiber having a refractive index lower than that of the component of the transparent resin sheet and having a polygonal prismatic shape, a semi-cylindrical shape, a conical shape, a cylindrical shape or a polygonal pyramid shape. It has been mixed in.

[0008]

[Operation] According to the above-mentioned means, fibers in the transparent resin sheet having a refractive index lower than that of the components of the transparent resin sheet and having a shape of a polygonal prism, a semi-cylinder, a cone, a cylinder or a polygonal pyramid are used. Since the light is orientated and mixed, the light diffuses in the direction perpendicular to the fiber, but does not diffuse in the direction parallel to the fiber. Further, the light is condensed in one direction on the fiber slope of the polygonal prism or the polygonal pyramid.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detail with reference to the drawings. Also, components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. [Embodiment 1] FIG. 1 is a partial perspective view of a light control sheet according to a first embodiment of the present invention, and FIG. 2 shows light in a direction perpendicular to an air layer in the light control sheet according to the first embodiment of the present invention. FIG. 3 is a diagram showing a path of light in a direction parallel to an air layer in the light control sheet according to the first embodiment of the present invention.

In FIG. 1, the light control sheet has a large number of fibrous air in the transparent resin sheet 1, which has a refractive index lower than that of the components of the transparent resin sheet 1 and has a cylindrical shape with an outer diameter of 10 μm. The layers 2 are arranged in one direction. The method for manufacturing such a light control sheet is as follows. First, a hollow polyethylene terephthalate (PE) having an outer diameter of 20 μm and an inner diameter of 10 μm is used.
T) The fibers 3 are aligned in one direction and arranged, and PET fibers (not shown) which are not hollow are arranged in a direction perpendicular to the one direction to form a cloth having a mesh of 20 μm.

Then, the cloth is subjected to solution casting by PET.
Embedded in a transparent resin sheet 1 containing as a main component, and the transparent resin sheet 1 is dried. At that time, the air in the hollow PET fiber 3 expands, but the expanded air escapes from the hollow PET fiber 3 protruding from the transparent resin sheet 1, so that the transparent resin sheet 1 does not foam. Next, hollow P
The protruding portion of the ET fiber 3 was cut off to prepare a light control sheet.

That is, according to the first embodiment, the cylindrical air layer 2 having a refractive index lower than that of the components of the transparent resin sheet 1 and being oriented in the transparent resin sheet 1 is mixed. Then, as shown in FIG. 2, light diffuses in the direction perpendicular to the air layer 2 and does not diffuse in the direction parallel to the air layer 2 as shown in FIG. [Embodiment 2] FIG. 4 is a partial perspective view of a light control sheet according to a second embodiment of the present invention, and FIG. 5 is a view showing paths of light in a light control sheet according to the second embodiment of the present invention. .

In FIG. 3, the light control sheet has a plurality of fibrous fibers having a refractive index lower than that of the components of the transparent resin sheet 1 and having a regular triangular prism shape with a side of 8 μm in the transparent resin sheet 1. The air layers 4 are arranged in one direction. The manufacturing method of such a light control sheet is as follows.
A plurality of hollow PET fibers 5 each having a hollow of a regular triangular prism of which one side is 8 μm are aligned in one direction, and the adjacent PET fibers 5 are arranged so as to be closely adjacent to each other.
ET fibers (not shown) are arranged to form a cloth having a mesh of 20 μm. In this case, the interval between the hollow PET fibers 5 is preferably 1/2 or less of the outer diameter of the hollow PET fibers 5,
Optimally 1/5 or less.

As shown in FIG. 5, when the cross section of the air layer 4 is an inverted triangle (the lower half surface of the air layer 4 has an inclination), the light entering the air layer 4 is unidirectional on the slope of the air layer 4. Is focused on
The light reflected by the air layer 4 is diffused. Then, the cloth is solution cast to form a transparent resin sheet 1 containing PET as a main component.
It is embedded inside and the transparent resin sheet 1 is dried. that time,
The air in the hollow PET fiber 5 expands, but the expanded air escapes from the hollow PET fiber 5 protruding from the transparent resin sheet 1, so the transparent resin sheet 1 does not foam. Next, cut off the protruding portion of the hollow PET fiber 5,
A light control sheet was produced.

Therefore, according to the second embodiment, the transparent resin sheet 1 has a lower refractive index than that of the components of the transparent resin sheet 1 and the air layer 4 having a triangular prism shape is orientated and mixed. , The light diffuses in the direction perpendicular to the air layer 4,
It does not diffuse in the direction parallel to the air layer 4. Comparative Example 1 10 parts by weight of PVDF powder having a particle diameter of 20 μm was dispersed and blended in 100 parts by weight of a polycarbonate resin sheet, and then uniaxially stretched to prepare a light control sheet.

[Comparative Example 2] On a PET sheet having a thickness of 120 μm, 10 parts by weight of polystyrene beads having a particle size of 5 μm and a layer using 100 parts by weight of an acrylic polymer as a binder were laminated to prepare a light control sheet. did. Next, when the light control sheets of Examples 1 and 2 and Comparative Examples 1 and 2 described above are individually arranged in the backlight module, the brightness in the screen normal direction, the dot appearance, and the respective light control sheets The cost required for the component and the yield at the time of production of each light control sheet were compared and evaluated. Table 1 shows the evaluation results.

[0017]

[Table 1]

Thus, according to this embodiment, as is clear from Table 1, the cost is low and the production yield is good. Further, since the light can be diffused only in the necessary direction, the front brightness is improved and the dot appearance can be prevented. As described above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist thereof. It goes without saying that.

In the present embodiment, the transparent resin sheet 1 uses the cylindrical or triangular air layers 2 and 4 having a refractive index lower than that of the components of the transparent resin sheet 1, but the components of the transparent resin sheet 1 are used. A polygonal prism having a refractive index lower than that of
Similar effects can be expected by orienting and mixing a fibrous air layer or a light diffusing agent layer having a semi-cylindrical, conical or polygonal pyramid shape.

Furthermore, one or both sides of the transparent resin sheet 1 in which the air layers 2 and 4 are mixed may be embossed. The air layers 2 and 4 are, of course, arranged in one direction from one end to the other end of the transparent resin sheet 1.
The intermittent air layers 2 and 4 may be oriented in one direction and distributed.

[0021]

The effects obtained by the invention disclosed in the present application will be briefly described as follows.
According to the present invention, the light control sheet, in the transparent resin sheet, of the refractive index lower than the refractive index of the components of the transparent resin sheet,
Since the fibers having the shape of a polygonal column, a semi-cylinder, a cone, a cylinder, or a polygonal pyramid are oriented, it becomes possible to manufacture with an inexpensive material and the yield at the time of production is improved. Further, the front brightness is increased and a bright screen can be obtained. Further, the dot concealing property can be improved and the cost can be reduced.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a path of light in a direction perpendicular to an air layer in the light control sheet according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a path of light in a direction parallel to an air layer in the light control sheet according to the first embodiment of the present invention.

FIG. 4 is a partial perspective view of a light control sheet according to a second embodiment of the present invention.

FIG. 5 is a diagram showing paths of light in a light control sheet that is a second embodiment of the present invention.

[Explanation of symbols]

 1 Transparent resin sheet 2,4 Air layer 3,5 Hollow PET fiber

Claims (1)

[Claims] 1. A transparent resin sheet having fibers having a refractive index lower than that of the components of the transparent resin sheet and having a polygonal prism shape, a semi-cylinder shape, a conical shape, a circular cylinder shape, or a polygonal pyramid orientation is mixed. The light control sheet characterized in that