JPH10253806A - Optical control sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical control sheet capable of ensuring a high handling function even in the case of a large size, the high accuracy of surface irregular shapes, and low mat density on the reverse surface. SOLUTION: An optical control sheet 1 is made of an irregular layer 2 of polycarbonate resin having a mean molecular weight of 17,000 and a mat layer 3 of polycarbonate resin having a mean molecular weight of 25,000. Also, the irregular layer 2 has 50μm thickness, and is formed to have an irregular surface 4. The mat layer 3 has 130μm thickness and is formed to have a mat surface 5. The irregular surface 4 of the irregular layer 2 is formed to have a corrugated cross section having a crest, angle of 100 degrees and a corrugation pitch of 100μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light control sheet for forming a planar light emitting device. The planar light emitting device
LCDs such as personal computers and word processors, LCD color TVs, and even electric signs,
Widely used for facility lighting.

[0002] Throughout this specification, the term "sheet" does not mean a strict definition based on thickness, but also includes a relatively thin film usually called a film.

[0003]

2. Description of the Related Art Since liquid crystal display screens such as personal computers and word processors do not have a self-luminous property, a light source device called a backlight unit that shines light on the liquid crystal display screen from the back is usually used. The backlight unit needs to be thin and irradiate the entire display screen almost uniformly. In general, the backlight unit is a planar light emitting device, and the most frequently used planar light emitting device is an edge light single-light type in which a light source is provided on one end surface of a light guide plate, that is, a light introducing surface. In this scheme,
The light emitted from the light source can be emitted almost uniformly from the entire surface of the light control sheet such as the surface of the light guide plate or the light diffusion plate provided on the front surface of the light guide plate.

In recent years, there has been an increasing demand for a large display screen, and in order to cope with this, a backlight unit and a light control sheet having a large size of 12 inches or more are required.

However, when the size of the light control sheet is increased as described above, the stiffness of the light control sheet is reduced. This causes problems such as breakage. For example, a conventional light control sheet obtained by laminating a high-flow polycarbonate resin and a low-flow polycarbonate resin in two layers and embossing the surface of the former resin layer (see Japanese Patent Application Laid-Open No. Hei 4-327937). ) Has the disadvantage that the stiffness decreases as the size increases, and the handleability in assembling work into a backlight unit and the like deteriorates. If the material resin of the conventional light control sheet has a large molecular weight, the shapeability of the unevenness on the surface of the high-flowability polycarbonate resin layer is poor, and the accuracy of the unevenness shape is reduced. When the thickness is small, the moldability of the irregularities on the surface of the high-flowability polycarbonate resin layer is improved, but the mat transferability of the opposite surface is too high, and the obtained light control sheet has a high mat density. And dislike light collection.

[0006]

In view of the above, the present invention has excellent handling properties even in a large size of 12 inches or more, and has excellent surface irregularity accuracy.
It is another object of the present invention to provide a light control sheet having a low mat density on the opposite surface.

[0007]

The light control sheet according to the present invention has been devised to achieve the above object, and is a sheet in which two or more different types of polycarbonate resins are laminated in a multilayer form. One outermost layer of the laminated sheet is made of a polycarbonate resin having a molecular weight of less than 20,000,
And the surface has an uneven shape, and the other outermost layer has a molecular weight of 20.
It is characterized by having a matte surface or a mirror surface having a center line surface roughness (Ra) of 0.5 μm or less on the surface, made of a polycarbonate resin of 000 or more.

The material resin of the multilayer sheet constituting the light control sheet according to the present invention is polycarbonate. Polycarbonate is suitable for obtaining a sheet having a high refractive index and good transparency, and such properties provide a high light control function. Further, since the material resin of the multilayer sheet is polycarbonate as described above, the adhesive strength of each layer in the molten state is high, and the obtained laminated sheet does not cause delamination. A sheet made of a polycarbonate resin becomes a light control sheet having a desired stiffness when these are laminated in a multilayer.

The polycarbonate resin constituting one outermost layer of the laminated sheet may be one generally used as a material resin of the light control sheet. As the outermost layer has higher transparency, the function as a light control sheet is improved. Therefore, a resin is appropriately selected according to required quality and intended use.
The molecular weight of the polycarbonate resin is less than 20,000 (weight average molecular weight). If the molecular weight exceeds 20,000, the outermost layer surface may lack the uneven shaping properties. The concavo-convex shape provided on one outermost layer controls the optical function. The concavo-convex shape is, for example, a prism shape, a cross-sectional wave shape, a cross-sectional sine wave shape, a cross-sectional sawtooth shape, or the like, and is appropriately selected from these depending on the purpose of use. The method of forming the uneven shape on the surface of one outermost layer is not particularly limited. For example, a method of transferring this shape to the surface of the outermost layer using a metal uneven plate, a method of cutting the surface of the outermost layer, and the like can be used.

[0010] The thickness of the outermost layer is not particularly limited, and may be any thickness that can be processed so that the uneven shape can be formed without hindrance. The preferred layer thickness is about 10 to 300 μm.

The polycarbonate resin constituting the other outermost layer of the laminated sheet has a molecular weight (weight average molecular weight) of 20.
000 or more. If the molecular weight is less than 20,000, a sheet having excellent stiffness cannot be obtained. As a result, when the sheet is adapted to a large-sized display device of 12 inches or more, the sheet loses its independence due to a decrease in the stiffness of the sheet. In such a case, there may be a problem that the sheet is broken or the like, and when the sheet is formed, the mat transferability to the sheet is excessively increased, and the light condensing property of the finished sheet is deteriorated to a high mat density.

The surface of the other outermost layer has a center line surface roughness (R
a) It has a thickness of 0.5 μm or less. If this value exceeds 0.5 μm, the light-collecting properties of the sheet will be impaired.

[0013] The method of matting the surface of the other outermost layer is not particularly limited. For example, a method of performing sandblasting on the surface of a plate-like material of a polycarbonate resin, pressing a rubber-like pressing member whose surface is polished to an arbitrary roughness onto a polycarbonate resin melted in a film form, thereby obtaining a surface of the member. A method of transferring the roughness to the surface of the resin melt is exemplified.

The method of mirror-finishing the surface of the other outermost layer is not particularly limited. For example, a method using a mirror roll or a mirror plate is exemplified.

The thickness of the other outermost layer is not particularly limited, and excessive matting can be suppressed.
In addition, the sheet may have a thickness of 12 inches or more as long as the sheet can maintain the stiffness. The preferred layer thickness is about 5 to 300 μm.

Examples of a method of forming a laminated sheet by laminating two or more different polycarbonate resins in multiple layers include a co-extrusion method, forming each sheet constituting the laminated sheet in advance, and then laminating these sheets. And the like. As a method of joining the respective sheets, there is a method of using a colorless and transparent adhesive, a method of bonding the respective sheets to each other in a molten state, and the like. The latter method is suitable for obtaining high adhesive strength.

When three or more sheets are laminated, that is, when one or more intermediate sheets are further sandwiched between one outermost layer and the other outermost layer, the polycarbonate resin constituting the intermediate sheet has a molecular weight of 15,000. The thickness is preferably 300 μm or more.

The method for forming the light control sheet according to the present invention is not particularly limited, and examples thereof include the following methods. a) The multilayer resin material melted in the form of a film is provided between an embossing roll and a rubber roll such that a sheet to be one outermost layer is on the former side and a sheet to be the other outermost layer is on the latter side, respectively ( In the case of three or more layers, a method of arranging such that the intermediate sheet is located between these layers) and sandwiching with a roll to form. This method is advantageous because it can be easily implemented by using a known multi-manifold die or feed block. b)
Between a template having an uneven surface and a template having a matte surface,
The outermost sheet on the former side and the outermost sheet on the other side should be on the latter side. (When three or more sheets are laminated, one or more intermediate sheets are placed between them.) How to arrange and press each sheet as if to come.

[0019]

In the light control sheet according to the present invention, one of the outermost layers of the laminated sheet is made of a polycarbonate resin having a molecular weight of less than 20,000, so that it has excellent irregularity shaping properties, and the other outermost layer is made of a polycarbonate resin having a molecular weight of 20,000 or more. And the other outermost layer has a matte surface or a mirror surface having a center line surface roughness (Ra) of 0.5 μm or less on the surface, and thus has excellent light condensing properties. Therefore, the light control sheet according to the present invention has autonomy even when the size is large, so that it has excellent handling properties even in a large size of 12 inches or more, and has excellent uneven shaping properties on one surface. With excellent light gathering on the other side,
It has both functions.

[0020]

Next, examples of the present invention and some comparative examples for comparison with the present invention will be described.

<Embodiment 1> Referring to FIG.
Reference numeral 1 denotes an uneven layer 2 made of a polycarbonate resin having an average molecular weight of 17000, and a mat layer 3 made of a polycarbonate resin having an average molecular weight of 25,000. The uneven layer 2 has a layer thickness of 50 μm and the surface is formed as an uneven surface 4. The mat layer 3 has a layer thickness of 130 μm and the surface is formed as a mat surface 5. The uneven surface 4 of the uneven layer 2 is formed in a wavy cross section having a peak angle of 100 ° and a pitch between peaks of 100 μm.

The manufacture of the light control sheet was performed as follows. First, a resin laminate is prepared by melting into a film composed of a sheet serving as the uneven layer 2 and a sheet serving as the mat layer 3, and then the laminate is sandwiched between an embossing roll and a rubber roll. Layer 2 and mat layer 3 were arranged on the latter side, respectively, and were formed by being sandwiched between rolls.

<Comparative Example 1> This light control sheet is used in Example 1.
Has the same shape as the light control sheet 1 but has an average molecular weight of 1
It is composed of a single layer of 7000 polycarbonate resin. The layer thickness is 180 μm. Other configurations are
This is the same as that of the first embodiment.

<Comparative Example 2> This light control sheet was also used in Example 1.
Has the same shape as the light control sheet 1 but has an average molecular weight of 2
It is composed of a single layer of 5000 polycarbonate resin. The layer thickness is 180 μm. Other configurations are
This is the same as that of the first embodiment.

Comparative Example 3 The light control sheet 1 is composed of an uneven layer 2 made of a polycarbonate resin having an average molecular weight of 25,000 and a mat layer 3 made of a polycarbonate resin having an average molecular weight of 17000. Uneven layer 2 is 5
The mat layer 3 has a layer thickness of 130 μm with a layer thickness of 0 μm. Other configurations are the same as those of the first embodiment.

Evaluation Tests The light control sheets of Examples and Comparative Examples were subjected to the following evaluation tests. The test method is as follows.

A) Depth of the valley of the concave and convex shape: After addition-reaction silicone is applied to the concave and convex surface of the sheet and solidified by reaction, the sheet is cut, and the cut surface is scaled by an optical microscope to form a valley. Asked for the depth.

B) Stiffness: Sheet is 50 mm ×
The sheet was cut into a strip of 150 mm, a strip piece was placed on a flat table by only 50 mm on one end side, a weight was placed thereon, and the distance between the other end of the hanging sheet and the height of the table was measured with a caliper.

C) Matt surface roughness: The center line surface roughness (Ra) on the mat side or the mirror side of the sheet is defined by JIS-B0.
601 was measured.

Table 1 shows the test results.

[0031]

[Table 1]

As can be seen from Table 1, the light control sheets of the examples showed good results in any of the items.

[0033]

In the light control sheet according to the present invention, one outermost layer has excellent irregularity shaping properties, and the other outermost layer has excellent stiffness and excellent light collecting properties. Therefore,
According to the present invention, even if the size increases, it has autonomy,
For this reason, a light control sheet that has excellent handling properties even in a large size of 12 inches or more, and has excellent concavo-convex shaping properties on one side and excellent condensing properties on the other side, and has both functions. can do.

[Brief description of the drawings]

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

[Explanation of symbols]

 1: light control sheet 2: uneven layer 3: mat layer 4: uneven surface 5: mat surface

Claims (1)

[Claims] 1. A sheet in which two or more different polycarbonate resins are laminated in a multilayer form, wherein one outermost layer of the laminated sheet is made of a polycarbonate resin having a molecular weight of less than 20,000 and has an uneven surface. The other outermost layer is made of a polycarbonate resin having a molecular weight of 20,000 or more, and has a center line surface roughness (Ra) of 0.5 on the surface.
A light control sheet having a matte surface or a mirror surface of μm or less.