JPH08304610A - Multilayered embossed sheet of transparent thermoplastic resin for optical application and its production - Google Patents

Abstract

PURPOSE: To allow the meticulous transfer of the rugged shapes of a metallic embossing roll by setting the melt viscosity of the resin of a transparent thermoplastic resin layer having an embossed structural surface lower than the melt viscosity of the resin of the transparent thermoplastic resin layer at the same temp. CONSTITUTION: A resin having a low viscosity, i.e., a high flow property at the time of melting is used for the thermoplastic resin (A) on the side of the surface to which the surface rugged shapes of the metallic embossing roll are transferred. The melt viscosity at the time of discharge from metal molds is set at preferably <=4000 poises and the spacing between the front end of the metal molds and clamping parts is set at <=150mm. The transferability is maintained by maintaining the resin temp. and melt viscosity at the time of discharge from the metal molds. The thermoplastic resin (B) having a high viscosity, i.e., the low flow property at the time of melting is used for another surface side. The resin discharged from a Tee die is clamped and cooled by the embossing roll and a rubber roll in such a manner that the surface rugged shapes of the metallic embossing rolls are transferred on the surface of the thermoplastic resin (A), by which the uniform multilayered embossed sheet is molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent thermoplastic resin multi-layer embossed sheet for optical use in which at least one surface is provided with an uneven shape and a method for producing the same.

More specifically, the present invention relates to a light control sheet used in a planar light emitting device and a method for manufacturing the same.

[0003]

2. Description of the Related Art Conventionally, in an embossed sheet made of a transparent thermoplastic resin, a molten resin is supplied by a T-die between a metal embossing roll having a predetermined shape engraved on its surface and a rubber roll, and a pressing force is applied. By cooling, a predetermined uneven shape was transferred to one surface to obtain an embossed sheet.

[0004]

However, in the conventional method, in order to improve the transferability of the embossing roll, there is a limit to the moldable resin viscosity in consideration of the flow characteristics of the thermoplastic resin in the molten state. there were. On the other hand, a method of improving the transferability by increasing the surface hardness of the rubber roll of the molding machine can be considered, but the resin viscosity is also required to be low in order to precisely transfer the uneven shape of the metal embossing roll surface. However, for the above reason, a resin having a sufficiently low melt viscosity cannot be used, and therefore, it is insufficient to precisely transfer the uneven shape of the metal embossing roll surface.

In view of the above problems, the inventors of the present invention have earnestly studied, and as a result, by using at least two kinds of transparent thermoplastic resins having specific resin melt viscosities, the uneven shape of the surface of the metal embossing roll can be made precise. The inventors have found that a transferred transparent thermoplastic resin multilayer embossed sheet for optical use can be produced, and completed the present invention.

An object of the present invention is to provide a transparent thermoplastic resin multilayer embossed sheet for optical use in which the uneven shape of the metal embossing roll surface is precisely transferred, and a method for producing the same.

[0007]

That is, the present invention provides a multi-layer embossed sheet in which at least two kinds of transparent thermoplastic resins (A) and (B) having an embossed structure surface on one surface are laminated. Provided is a transparent thermoplastic resin (A) layer resin melt viscosity which is lower than the transparent thermoplastic resin (B) layer resin melt viscosity at the same temperature. Is.

The present invention also provides a transparent thermoplastic resin (B).
And a transparent thermoplastic resin (A) having a lower melt viscosity than the transparent thermoplastic resin (B) at the same temperature are discharged from the T die in a laminated and molten state, and the discharged molten resin is a transparent thermoplastic resin. (A) Transparent thermoplastic resin multilayer for optical use, characterized in that the embossing roll shape is precisely transferred to the sheet surface by pinching and cooling with an embossing roll and a rubber roll so that the layer contacts the embossing roll. A method for manufacturing an embossed sheet is provided.

The sheet of the transparent thermoplastic resin multi-layer embossed sheet for optical use in the present invention includes not only a sheet in a strict sense limited by thickness but also a thin sheet usually called a film. The average thickness is preferably 50 μm or more, more preferably 100 μm to 350 μm.
Is.

The optical-use transparent thermoplastic resin multilayer embossed sheet of the present invention is a sheet obtained by laminating at least two kinds of transparent thermoplastic resins (A) and (B), and has a low melt viscosity. It is a multilayer embossed sheet in which the embossing roll shape is precisely transferred to the surface of the resin layer consisting of A).

As one aspect of the structure surface of the transparent thermoplastic resin (A) layer which is one surface of the multilayer embossed sheet, one surface has a large number of peaks having a convex or convex arc-shaped cross section and a concave or concave arc-shaped cross section. There are structural surfaces in which a large number of valleys are alternately and substantially parallel to each other. In this case, there is only one slope, peak and valley bottom formed by the convex or convex arc-shaped cross section and the concave or concave arc-shaped cross section that are alternately formed substantially parallel to one surface. Alternatively, it may be composed of a plurality of flat surfaces, may be formed of curved surfaces, or may be formed of both flat and curved surfaces. The inclination of the plane and the slope of the curved surface is very important for the performance of collecting light on the front surface, but may be designed according to the desired performance. Further, the narrower the intervals between the peaks and the peaks and the valleys that are formed substantially in parallel, the more excellent the surface uniformity is, and preferably 150 μm or less.

Further, the transparent thermoplastic resin used in the present invention is a material for a sheet light emitting sheet light control sheet used for optical applications, particularly for liquid crystal displays, and therefore it must be transparent and emits light. A resin having a refractive index of 1.4 or more is preferable in terms of the function of controlling the direction. Examples thereof include a polycarbonate resin, an acrylic resin typified by polymethylmethacrylate resin, a polyester resin typified by polyethylene terephthalate, an amorphous copolyester resin, a polystyrene resin, and a polyvinyl chloride resin.

In order to produce an embossed sheet, the thermoplastic resin is heated and melted in an extruder, adjusted to a uniform thickness by a T die, discharged, and engraved into a desired shape in a molten state. It is supplied between the metal embossing roll and the rubber roll.

The surface temperature of the metal embossing roll is preferably 5 to 10 ° C. lower than the freezing point temperature of the thermoplastic resin used, and when the surface temperature of the metal embossing roll is 10 ° C. or more lower than the freezing point temperature of the thermoplastic resin. If the resin hardens by the time the surface irregularities of the roll are transferred to the sheet surface, and the surface temperature of the metal embossing roll is within 5 ° C below the freezing point temperature of the thermoplastic resin or higher than the freezing point temperature of the thermoplastic resin, the metal When the embossing roll made of embossing roll is transferred onto the surface of the sheet having an uneven surface, the shape cannot be maintained because the curing is insufficient. In order to precisely transfer the uneven surface shape of the metal embossing roll onto the sheet surface, it is preferable that the melt viscosity of the thermoplastic resin during pressing is lower, preferably 4000 poise or less, more preferably 3500 po.
It is less than or equal to ise.

However, the melt viscosity is 4000 pois.
When a resin of e or less is molded, the melt tension is too low for a single layer, and it is extremely difficult to uniformly mold the resin discharged from the T die into a sheet. In the present invention, this problem can be solved by multilayering at least two transparent thermoplastic resins having different melt viscosities.

That is, in the method for producing a transparent thermoplastic resin multilayer embossed sheet for optical use of the present invention, the thermoplastic resin (A) on the side for transferring the surface irregularities of the metal embossing roll to the surface has a low viscosity, that is, when melted. The resin having a high fluidity is used, and the melt viscosity at the time of discharging the mold is preferably 4000 poise or less, more preferably 3500 po.
and the distance between the tip of the mold and the pressing portion is preferably 150 mm or less, more preferably 100 mm or less to maintain the resin temperature and melt viscosity at the time of discharging the mold to maintain transferability, and the other surface On the side, a thermoplastic resin (B) having a high viscosity, that is, a fluidity when melted is small is used. Then, the resin discharged from the T-die in a laminated and molten state is sandwiched and cooled by an embossing roll and a rubber roll so that the surface unevenness of the metal embossing roll is transferred to the surface of the thermoplastic resin (A). By doing so, a uniform multilayer embossed sheet is formed.

The melt viscosity of the thermoplastic resin (B) having a high viscosity, that is, having a low fluidity when melted, when sandwiched is preferably 4500 p under the same temperature condition as that of the resin (A) for transferring the uneven shape.
Oise or more, more preferably 5000 poise or more.

The at least two transparent thermoplastic resins used in the present invention may be of any kind as long as they have different melt viscosities, but may be resins of the same kind but different in fluidity when melted. If so, the adhesive force between the resin layers is sufficient, which is preferable. In the case of different kinds of resins, it is necessary to consider the interlayer adhesive force, and depending on the combination, it is necessary to provide an interlayer adhesive resin layer to form three layers. The layer thickness of each resin is not so important, and the layer thickness on the uneven transfer surface side may be equal to or larger than the embossing depth of the metal embossing roll to be transferred.

In the method for producing a transparent thermoplastic resin multi-layer embossed sheet for optical use of the present invention, a multi-manifold method and a feed block method are known as a method of multi-layer coextrusion, but any method is not particularly limited.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[Embodiment 1] As a metal embossing roll, its surface is a right angle 2 whose cross-sectional shape is 90 ° in vertical angle.
An equilateral triangle in which peaks and peaks and valleys and valleys were engraved regularly and continuously at 50 μm intervals was used. As thermoplastic resin, polycarbonate resin MF
R15 and MFR30 have a thickness of 10
It was adjusted to 0 μm and 50 μm and discharged from a T die at 300 ° C. by a feed block method. 30 of MFR15 resin
Melt viscosity at 0 ° C is 4700 poise, MFR3
No. 0 resin has a melt viscosity at 300 ° C. of 3300 poi
It is se. The surface of the metal embossing roll is controlled to 135 ° C., and the resin of MFR30 is sandwiched between the rubber embossing roll and the rubber roll through which cooling water is passed,
The transparent thermoplastic resin multilayer embossed sheet for optical use of the present invention was molded. In forming, the sheet can be formed uniformly in all width without any problem, and the uneven shape of the sheet is exactly the same as that of the plate of the metal embossing roll. For example, the depth of the sheet unevenness is 17.7 μm for the plate depth. Sa 17.
A 6 μm sheet was obtained.

[Comparative Example 1] As a metal embossing roll, the surface thereof is an isosceles right triangle having a vertical cross section of 90 ° and an isosceles right triangle alternately and in parallel.
Those engraved regularly and at intervals of 0 μm were used. As thermoplastic resin, polycarbonate resin MF
R30 was adjusted to a thickness of 150 μm and discharged from a T die. The surface of the metal embossing roll was controlled at 135 ° C., and the sheet was molded by sandwiching it with a rubber roll that passed cooling water. In the molding, the distribution of the resin from the T die discharge part was not stable, and it was not possible to mold the sheet thickness uniformly over the entire width.

[Comparative Example 2] As a metal embossing roll, the surface thereof is an isosceles right triangle having a vertical cross section of 90 ° and an isosceles right triangle alternately and parallel to each other.
Those engraved regularly and at intervals of 0 μm were used. As thermoplastic resin, polycarbonate resin MF
R15 was adjusted to a thickness of 200 μm and discharged from a T die. The surface of the metal embossing roll was controlled at 135 ° C., and the sheet was molded by sandwiching it with a rubber roll that passed cooling water. In forming, there was no particular problem and the sheet could be formed uniformly over the entire width, but the shape of the embossing roll could not be precisely transferred to the sheet. For example, the plate depth of the metal embossing roll was 17. The depth of the unevenness of the sheet was 14.2 μm with respect to 7 μm.

[Comparative Example 3] As a metal embossing roll, the surface thereof is an isosceles right triangle having a vertical cross section of 90 ° and an isosceles right triangle alternately and in parallel.
Those engraved regularly and at intervals of 0 μm were used. As thermoplastic resin, polycarbonate resin MF
Thickness of R30 and MFR15 is 100 respectively
It was adjusted to μm and 50 μm and discharged from a T die at 300 ° C. by a feed block method. 300 of MFR15 resin
Melt viscosity at ℃ 4700poise, MFR30
Resin has a melt viscosity at 300 ° C of 3300 pois.
It is e. The metal embossing roll is controlled at 135 ℃,
A sheet was formed by sandwiching the resin of MFR15 with a rubber roll that passed cooling water so that the resin was in contact with the metal embossing roll. In the molding, the embossing roll shape could be formed uniformly in the entire width without any particular problem, but it was not possible to precisely transfer the embossing roll shape to the sheet. For example, when the plate depth of the metal embossing roll was 17.7 μm, the sheet unevenness was uneven. The depth was 14.2 μm.

[0025]

According to the present invention, the transparent thermoplastic resin (B) and the transparent thermoplastic resin (A) having a lower melt viscosity than the transparent thermoplastic resin (B) at the same temperature are laminated on the T-die. A sheet having an embossed roll shape is formed by discharging the molten resin in a molten state and pressing and cooling the discharged molten resin with an embossing roll and a rubber roll so that the transparent thermoplastic resin (A) layer contacts the embossing roll. It can be transferred to the surface extremely precisely.

Claims (2)

[Claims] 1. A multilayer embossed sheet in which at least two kinds of transparent thermoplastic resins (A) and (B) each having an embossed structure surface on one side are laminated, and a transparent thermoplastic resin (A) which is an embossed structure surface. A transparent thermoplastic resin multilayer embossed sheet for optical use, wherein the layer resin melt viscosity is lower than the transparent thermoplastic resin (B) layer resin melt viscosity at the same temperature. 2. A transparent thermoplastic resin (B) and a transparent thermoplastic resin (A) whose melt viscosity is lower than that of the transparent thermoplastic resin (B) at the same temperature are discharged from a T die in a laminated and molten state. By pressing and cooling the discharged molten resin with an embossing roll and a rubber roll so that the transparent thermoplastic resin (A) layer contacts the embossing roll,
A method for producing a transparent thermoplastic resin multi-layer embossed sheet for optical use, which comprises precisely transferring an embossed roll shape onto a sheet surface.