JPH04173139A - Light pervious colored co-extrusion sheet - Google Patents

Abstract

PURPOSE:To obtain a highly accurate colored sheet capable of being made large-sized and a light guide plate using the same by forming a multilayer structure wherein a colored acrylic resin layer is strongly bonded to at least one surface of a transparent acrylic resin base material layer by co-extrusion using a plurality of extruders. CONSTITUTION:A light pervious colored acrylic resin laminated sheet wherein a surface layer part is formed so that the thickness of a colored acrylic resin layer is 0.01mm or more and becomes 40% or less the whole thickness of a multilayer sheet 1 is obtained by a co-extrusion method wherein a transparent acrylic resin and a colored acrylic resin are respectively extruded from separate extruders to be formed into a laminated structure in a die part. This sheet 1 can be used as a light guide plate 1 propagating the light incident from the side surface of an edge light type surface light emitting system. In this case, as the transparent acrylic resin, one wherein 20wt.% or less of alkyl acrylate having a 1-4C alkyl group is copolymerized is pref. The colored acrylic resin layer can be obtained by compounding one kind or several kinds of an org. dye of a phthalocyanine type, a perinone type, an azo type or an anthraquinone type or inorg. pigment such as titanium yellow with the acrylic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a colored acrylic resin sheet with excellent light transmittance and a method for producing the same.

[Conventional technology and problems]

Acrylic resin sheets not only have a beautiful appearance such as high transparency and elegant surface gloss, but also have excellent mechanical and thermal properties and good weather resistance. Widely used for lights, showcases, lighting covers, etc.

Lighting panels, advertising lights, especially combined with electric lighting equipment,
It is widely used in fields such as emergency guide lights, as it is easy to color and print.

Furthermore, in recent years, surface emitting systems with uniform brightness over the entire surface have been adopted for illumination displays and backside illumination of liquid crystal display screens, and acrylic resin sheets are also used for these.

In the past, this surface-emitting system used a backlight method in which light was emitted from a large number of lamps from behind, but in recent years the edge-light method was developed to make the system thinner. It began to be used to illuminate the back side of liquid crystal display screens in word processors and other devices.

The Edgelight method is a system that uses a light guide plate made of processed acrylic sheet, a straight tube light source is placed on the side of the light guide plate, and the light guided inside the light guide plate is emitted uniformly in the surface direction.
The acrylic sheet used here is particularly required to have a high degree of transparency in order to prevent light attenuation inside the light guide plate.

In addition, colored acrylic resin sheets can be used for applications such as lighting advertising lights and surface lighting systems that are uniformly colored over the entire surface.・It is common to use

As a method for manufacturing colored acrylic resin sheets, continuous extrusion processing of raw materials mixed with colorants in advance to form sheets has been adopted as an industrially advantageous method.
In order to obtain the same transmitted color, it was necessary to adjust the amount of colorant blended depending on the thickness of the board being manufactured.

Furthermore, in the edge-light type light guide plate described above, when a colored sheet manufactured using the conventional manufacturing method is used, the attenuation of light incident from the edge portion is large, and the brightness of the light-emitting surface decreases as the distance from the light source increases. Therefore, it was difficult to increase the size.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problems in the production of colored acrylic resin, eliminate the complexity of changing the colorant formulation for each board thickness, and High brightness and/or
Another object of the present invention is to obtain a colored sheet that can be made large, especially a light guide plate using the same.

[Means to solve the problem]

As a result of intensive research to solve the above problems, the present inventors have found that a colored acrylic resin layer is added to at least one surface of a transparent acrylic resin base layer by coextrusion using multiple extruders. By extrusion molding the multi-layered structure with strong adhesion to the material, we have finally succeeded in solving the problems, leading to the present invention.

That is, the present invention uses a coextrusion method in which a transparent acrylic resin and a colored acrylic resin are extruded using separate extruders, and a laminated structure is formed in a die part, so that the thickness of the colored acrylic resin layer is 0.01 mm or more, and the multilayer Total sheet thickness 40
The present invention provides a light-transmissive colored acrylic resin laminated sheet characterized by having a structure formed on the surface layer so that the amount of

Note that the present invention also includes an invention in which the sheet is used as a light guide plate that propagates light incident from the side surface of an edge-light type surface emitting system.

In the present invention, the transparent acrylic resin is an acrylic resin having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms (hereinafter abbreviated as C) that can be extruded, and has stability during extrusion and geothermal processing. From the point of C1 to C
It is preferable to copolymerize an alkyl acrylate having an alkyl group of 4 within 20% by weight.

Examples of the alkyl methacrylate having an alkyl group of 01 to C4 include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and among these, methyl and ethyl methacrylate are most preferred in terms of physical properties.

Examples of the alkyl acrylate having an alkyl group of 01 to C4 include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate), and the like.

The colored acrylic resin layer is made by adding general-purpose dyes and pigments such as phthalocyanine-based organic pigments, perinone-based, azo-based, anthraquinone-based organic dyes, and inorganic pigments such as titanium yellow alone or in combination with the transparent acrylic resin. It can be easily obtained by adding and blending.

It is also possible to use inorganic light diffusing agents such as barium sulfate and calcium carbonate, and organic light diffusing agents such as styrene resin.

In this way, by using the same type of acrylic resin for both the transparent and colored layers, it is possible to obtain a multilayer sheet that is strongly adhered and integrated.

The thickness of the colored acrylic resin layer is preferably 1.1 mm or more and 40% or less of the total thickness of the multilayer sheet; if it is less than 0.01 mm, a sufficient coloring effect cannot be obtained, and the layer For layer configurations exceeding 40% of the total thickness,
Convenience in producing colored sheets is lost, and it is also unfavorable in terms of light transmission.

Next, in the present invention, a laminated sheet is formed by coextrusion, which is usually carried out using two or more extruders.

The transparent acrylic resin layer (base 1 layer) has a thickness of 40. Go, 9
With an extruder such as 0°120+nmφ, on the other hand, the colored acrylic resin on the surface layer is smaller than the extruder described above.
This is carried out using an extruder with a diameter of 40 mm or 60 mm.

Either a foot block or multi-manifold method can be used as a lamination guide, and the overall thickness of the laminated sheet can be adjusted by the extrusion amount, the interval between polishing rolls, the sheet take-up speed, etc., and the thickness of each laminated layer can be adjusted. The desired configuration can be achieved by adjusting the output ratio of each extruder.

〔Example〕

The present invention will be described in detail below with reference to Examples.

Example 1 As a transparent acrylic resin, Dell 6,71 manufactured by Asahi Kasei Kogyo ■
, ■LP-1- (copolymer of %f/□A7.Wu1, and 7-kel acrylate) was used in an extruder with a diameter of 80 mm, and a colored acrylic resin (red) was used on the surface layer. Then, coextrusion was performed using a foot block method using an extruder with a diameter of 30 mm.

The lip opening of the die is 6 mm, and the overall thickness of the laminated sheet is adjusted by the extrusion rate of the two extruders, the interval between the polishing rolls, and the sheet take-up speed, and the thickness of the transparent layer and colored layer is adjusted by the thickness of each extruder. By adjusting the extrusion ratio, the width can be increased to 600 mm.
A two-layer adhesive layer sheet with a total sheet thickness of 2 and 4n++n and a surface layer thickness of 0.5 mm was prepared.

Table 1 summarizes the evaluation results of the in-plane transmitted chromaticity of the colored laminated sheet thus obtained.

For evaluation of transmitted chromaticity, use a spectrophotometer UV manufactured by Shimadzu Corporation.
-210A model with A light source.

Table-1 Comparative Example 1 Delpet ■8ON #331.40 (manufactured by Asahi Kasei Corporation)
0.5 and 2 n
A sheet of ++n was obtained, and the transmitted chromaticity in the plane direction was evaluated, and the results are shown in Table 2.

Table 2 From the above results, it can be seen that the transmitted chromaticity of the colored sheet according to the present invention does not change regardless of the thickness of the entire sheet.

In addition, in order to move on to the production of the next transparent sheet following Example], the 30mm extruder was stopped, and the resin was replaced only at the die part, so that normal transparent sheet production could be started immediately. On the other hand, in order to produce a transparent sheet after Comparative Example 1, it is necessary to replace the resin in a part of the raw material supply hopper, the extrusion section, and the die section, compared to when producing a transparent sheet following Example 1. , required more time and amount of purging resin.

Example 2 Coextrusion was carried out in the same manner as in Example 1 to obtain a laminated colored sheet with a total sheet thickness of 4 mm and a surface layer thickness of 0.2 mm.
The sheet was processed into a light guide plate, and an edge-light square surface light emitting system having a length of 22 am on each side having the configuration shown in FIG. 1 was assembled, and the light emitting state was visually evaluated.

Comparative Example 2 Example, 7th Angel J1'l L? ,-detly<,y,■
Using a raw material obtained by diluting 8ON #33140 20 times with LP-1, extrude it in a single layer in the same manner as Comparative Example 1, and make a 4 m
m sheets were obtained.

This material had a transparent color in the plane direction that was almost as solid as that of the laminated color-containing sheet of Example 2.

It was processed into a light guide plate in the same manner as in Example 2, and further assembled as a surface emitting system, and the light emitting state was visually evaluated.

Also, cut each sheet into a 2 cm x 22 cm rectangle, stack the three sheets together and bind tightly with transparent cellophane tape, and then tape the end faces of both short sides on a flat surface with #120° and #320.
．． Polish with #400 sandpaper and further #
Gently sand with #1000 and #1500 water-resistant sandpaper, then cover with another cloth to create a parallel and smooth surface. Long optical path transmission color difference meter MODEL manufactured by Tokyo Juishiki
-The light transmittance in the long side direction using the C light source was measured using TC-11600LP.

The above results are summarized in Table 3.

Table 3 From the above results, the colored sheet of the present invention is Etsujirai!・
It can be seen that the light guide plate is excellent as a light guide plate for a surface emitting system.

〔Effect of the invention〕

The present invention has the effect that the attenuation of incident light is extremely small and that a colored sheet having a high degree of light transmittance can be provided in large quantities with good productivity. On the other hand, the present invention is applicable to wall-mounted illuminated displays, personal computers,
It is particularly useful for edge-light colored light guide plates used in display screens of word processors and other devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an edge-light type surface emitting system assembled in Example 2. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. An acrylic resin sheet with a multilayer structure comprising a transparent acrylic resin sheet and a colored acrylic resin layer on at least one side, where the thickness of the colored acrylic resin layer is 0.01 mm or more, and the entire multilayer sheet thickness of 40
% or less by a coextrusion method using a plurality of extruders.