JP2011124168A - Method of manufacturing light guiding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light guiding sheet inexpensively controlling the emitting direction of the emitting light with excellent productivity by a simple method. <P>SOLUTION: This manufacturing method of the light guiding sheet of a structure is provided by forming a recessed part reaching a core layer by penetrating through a clad layer, by laminating the clad layer lower in a refractive index than the core layer on both surfaces of the core layer mainly composed of a transparent resin, When forming the recessed part by irradiating a laser beam, an irradiation angle of the laser beam is set at a predetermined angle, and thereby, an inclination of a side wall surface of the recessed part is set at the predetermined angle within a range of 30-45 degrees. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a light guide sheet for a light source device used for a display device such as a backlight numeric keypad used in a mobile phone, a notebook computer, a liquid crystal television, a backlight keyboard of a personal computer, a display switch of an electric device, and the like. Is.

  Conventionally, as a light source device used for a mobile phone, a backlight keyboard, etc., a linear light source such as a fluorescent lamp or a light source such as a light emitting diode is disposed in a housing, on the side end face of a plate-like light guide plate A side light type in which a linear light source or a point light source is arranged is known.

  A sidelight-type back light source device usually uses a plate-like transparent material such as an acrylic resin plate as a light guide sheet, and guides light from a light source disposed facing the side end surface from the side end surface (light incident surface). The light is incident on the light sheet, and the incident light is emitted from the light emission surface by the light emission function formed on the front surface (light emission surface) or the back surface of the light guide sheet.

  In order to improve the light guiding performance and improve the light utilization efficiency, a laminated body provided with a core layer and a cladding layer having a refractive index lower than that of the core layer is used, and total reflection at the core-cladding interface is used. Patent Document 1 proposes a light guide sheet in which light is efficiently confined in a light guide sheet, and a discontinuous portion of a cladding layer is formed at a portion where light is desired to be emitted to emit light.

  In addition, since the direction of light emitted from the light exit surface is determined by the side wall shape of the interrupted portion, the shape of the interrupted portion should be optimized in order to improve the light utilization efficiency by controlling the light exit direction. That's fine. For example, by using a plate-like transparent material as a light guide sheet, providing a groove part that reflects the light being guided to the exit surface side, and designing the angle of the inclined surface on the light incident side of the groove part in an appropriate range, The light emission direction is controlled so that a viewing angle of a certain level or more is obtained, and the viewing angle is promoted to widen the angle, thereby further improving the image quality of the liquid crystal display device illuminated by the surface illumination device. A planar illumination device is proposed in Patent Document 2.

Published Patent Gazette Special Table 2008-508556 Japanese Patent Laid-Open No. 2003-100128

  In order to efficiently illuminate display devices of electric devices such as keyboards and portable switches, it is necessary to match the peak of the emitted light distribution with the normal direction of the emission surface. For this purpose, it is necessary to control the light emission direction by optimizing the inclination angle of the side wall surface of the interrupted portion. However, it is difficult to precisely control the shape of the interrupted portion, and even if precise control is possible, there is a problem that the processing method is complicated, productivity is low, and cost is high. . For example, when controlling the shape of the interrupted portion by cutting, the cutting must be performed using a cutting tool corresponding to a predetermined shape. That is, in order to provide various shapes in one light guide sheet, it was necessary to repeat the cutting operation many times while exchanging the cutting tool.

  An object of the present invention is to provide a method for manufacturing a light guide sheet capable of controlling the light emission direction and realizing further improvement in luminance at a low cost and with high reproducibility.

  In order to solve the above problems, in the present invention, a core layer mainly composed of a transparent resin, and a clad composed mainly of a resin having a refractive index lower than that of the transparent resin laminated on both surfaces of the core layer. A light guide sheet having a layer and a concave portion that penetrates the clad layer and reaches the core layer, wherein the optical axis of the laser is applied to the laminate including the core layer and the clad layer. A method of manufacturing a light guide sheet, wherein the concave portion is formed by irradiating the laminated body with the laser so that the predetermined angle is in a range of 60 degrees to 90 degrees with respect to the laminated body. Provided.

  In one aspect of the present invention, the side wall surface constituting the concave portion includes a slope having a predetermined angle in the range of 30 degrees to 45 degrees.

  According to the production method of the present invention, a light guide sheet in which the emission direction of emitted light is controlled can be produced by a simple method with good productivity and at low cost.

It is a schematic diagram of the light guide sheet based on this invention. It is a schematic diagram of the laser apparatus based on this invention. It is a schematic diagram of the light guide sheet manufactured with the manufacturing method based on this invention. It is a schematic diagram of the laser apparatus at the time of using the manufacturing method based on this invention. It is a schematic diagram of the measurement system used in the Example of this invention. It is a graph of the emitted light distribution of the light guide sheet produced based on the Example of this invention. It is a cross-sectional photograph of the light guide sheet produced based on the Example of this invention.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated, referring an accompanying drawing.

  FIG. 1 is a configuration diagram of a multilayer light guide sheet used in the present invention. The light guide sheet 10 includes a core layer 11 having a thickness a and a clad layer 12 having a thickness b having a refractive index lower than that of the core layer 11, and faces the output surface 13 and the output surface of the light guide sheet 10. 14 is a laminate in which a clad layer 12 is formed on a light guide sheet.

  FIG. 3 shows a light guide sheet having a substantially triangular cross section as a light emitting means for emitting light, and a concave portion 15 that penetrates the cladding layer 12 and reaches the core layer 11. 10 is shown. The light guide sheet 10 includes a light incident surface 16 on which light from a light source is incident and a light emitting surface 13 on which incident light is emitted. The laminated body in which the clad layer 12 is laminated on the core layer 11 before the concave portion 15 as the light emitting means is formed is not strictly a light guide sheet for use in a light source device or the like. Since there is no great change in the laminated structure, such a laminated body is also referred to as a light guide sheet for convenience in the description of the present invention.

  Next, a method of actually forming a concave portion using a laser and controlling the inclination angle of the side wall surface will be described.

  FIG. 2 is a schematic diagram when the light guide sheet 10 is fixed using the laser device 20 and the laser is irradiated from directly above. The angle of the optical axis of the laser with respect to the horizontal plane of the light guide sheet 10 (the light exit surface 13 of the light guide sheet 10) is defined as an incident angle α. When the light guide sheet 10 is fixed in a horizontal state and the laser is irradiated vertically, the incident angle α of the laser is 90 °.

  FIG. 3 is a schematic diagram of the light guide sheet 10 and the concave portion 15 formed when the light guide sheet 10 is irradiated with laser at a laser incident angle α of 90 °. As shown in FIG. 3, a concave portion 15 having a height c having a substantially triangular shape and a symmetrical cross section is formed. Of the side wall surfaces constituting the concave portion 15, the inclination angle between the side wall surface 17 located on the light source side (that is, the light incident end surface 16 side) and the horizontal plane of the light guide sheet 10 is β. The shape of the concave portion 15 may be a U-shaped, rectangular or polygonal cross section depending on the processing conditions. A concave portion 15 having a height c and having a light reflecting function is formed so as to penetrate the cladding layer 12 and reach the inside of the core layer 11, and a, b, and c satisfy the following formula (1). It is a light sheet.

b <c <a + 2b (1)
At this time, the laser processing conditions (light intensity, scanning speed) for forming the concave portion 15 satisfying the expression (1) vary depending on the types of the core layer 11 and the cladding layer 12 or the type of processing laser. The optimum conditions are appropriately selected during processing.

  By changing the incident angle α of the laser with respect to the light guide sheet 10, the triangular cross-sectional shape of the concave portion 15 to be formed can be changed, and the inclination angle β of the side wall surface 17 can be changed. Adjustment of the incident angle α of the laser is performed by adjusting a fixed angle of the light guide sheet 10 that is an irradiated portion.

  FIG. 4 is a schematic view of a method of changing the incident angle α of the laser by changing the fixing angle of the light guide sheet 10. The fixed angle of the light guide sheet 10 is γ. The end surface on the light incident side of the light guide sheet 10 is fixed, and the light incident end surface 16 of the light guide sheet 10 is fixed with a rectangular parallelepiped block as shown in FIG. By irradiating the laser in this state, the incident angle α of the laser with respect to the light guide sheet 10 changes. At this time, if the block which fixes the light guide sheet 10 is a block with the height equivalent to the length of the light guide sheet 10, a kind will not be limited.

  Alternatively, the light guide sheet 10 may be fixed and the angle may be adjusted by irradiating the laser at an angle.

  At this time, the inclination angle β of the side wall surface 17 can be controlled by controlling the incident angle α of the laser. In particular, in the present invention, by setting the incident angle α of the laser to a predetermined angle in the range of 45 degrees or more and 60 degrees or less, the inclination angle β of the side wall surface 17 constituting the recessed portion 15 is 30 degrees or more and 45 degrees or less. It was found that the angle can be controlled to a predetermined angle. When the incident angle α of the laser is 75 degrees, the inclination angle β of the side wall surface 17 can be controlled to about 50 degrees. However, from the viewpoint of increasing the luminance of the emitted light, the inclination angle β of the side wall surface 17 is increased. Is preferably 30 degrees or more and 45 degrees or less, and therefore the incident angle α of the laser is preferably 45 degrees or more and 60 degrees or less.

  As for the arrangement pattern of the recessed part 15 which has a light reflection function, it is desirable that it is line shape. The line direction is preferably perpendicular to the light guide direction. If it is that direction, the length of the line is not particularly limited.

As the processing laser, a resin processing laser can be used and is not particularly limited. Among these, it is preferable to use a CO ₂ laser generally used for resin processing.

  As the core layer 11, a known material can be used, and for example, a methyl methacrylate homopolymer (PMMA) or copolymer can be used as a main component.

  Among them, it is preferable that PMMA is used as a main component because it is excellent in permeability durability and is inexpensive. In addition, when using the copolymer of methyl methacrylate, it is preferable that content of methyl methacrylate shall be 50 mass% or more. Moreover, you may comprise the core layer 11 using the material which has a polycarbonate-type resin as a main component. Since the polycarbonate resin has a higher refractive index than PMMA, the numerical aperture is increased, the amount of received light can be increased, and light leakage when the sheet is bent can be suppressed to a low level. Furthermore, when the heat resistance is well supplied, the above-mentioned polycarbonate resin or alicyclic polyolefin resin can be used. The thickness of the core layer is appropriately selected depending on the size of the light source, but is generally set to about 0.1 mm to 6 mm.

  As the clad layer 12, a known material can be used, and for example, it can be composed of a resin composition containing a fluorine-containing olefin resin as a main component.

  Examples of the fluorinated olefin resin include a vinylidene fluoride copolymer, and specifically, a binary copolymer of vinylidene fluoride and tetrafluoroethylene, vinylidene fluoride and hexafluoroacetone, and the like. And a binary copolymer of vinylidene fluoride and trifluoroethylene, a terpolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoroethylene, and the like. The light guide sheet with a clad layer preferably has flexibility due to its handleability. The thickness of the cladding layer is preferably in the range of 3 μm to 500 μm.

  As a method of laminating the core layer 11 and the clad layer 12, a method in which the core layer clad layer is integrally formed by multilayer melt extrusion, or a method in which a resin sheet (or film) corresponding to the core layer is coated with a resin corresponding to the clad layer. and so on.

Example 1
The light guide sheet 10 was molded in a three-layer structure of clad / core / clad using a coextrusion sheet manufacturing machine having a T-die having a width of 1200 mm. The core layer 11 is made of acrylic resin (Mitsubishi Rayon, Acrypet VH000, refractive index 1.49), and the clad layer 12 is made of vinylidene fluoride copolymer (Arkema, KYNAR720, refractive index 1.42). A light guide sheet 10 having a thickness of 980 mm and a thickness of 0.3 mm was manufactured. When the thickness of the clad layer 12 of the light guide sheet 10 was measured with a film thickness meter, the upper surface side and the lower surface side were about 5 μm, and the total thickness of the light guide sheet 10 was about 300 μm. Width The light guide sheet 10 100 mm, cut into a rectangular length 280 mm, set using the Keyence Corp. CO ₂ laser marker ML-Z9520T from the light incident face 16 to the site of 50 mm, the incident angle α of the laser 60 And laser processing. The pattern was a line shape perpendicular to the light guide direction, and one pattern having a length of 10 mm was provided. In order to evaluate the shape of the obtained concave portion 15, the cross section of the groove portion was evaluated with an optical microscope. The cross-sectional shape is shown as (3) in FIG.

  Next, the optical characteristics of the light guide sheet 10 obtained by the present invention were confirmed.

  FIG. 5 shows an outline of the measurement system. In the measurement, the laser-treated surface of the light guide sheet for measurement was directed downward, and the non-processed surface was the exit surface. In order to effectively use the light emitted from the processed surface, a reflection sheet (Lumilor E20 manufactured by Toray Industries, Inc.) was disposed on the surface opposite to the emission surface via an air layer.

  A light source 30 driven by a constant current power supply 40 at 20 mA (using five LEDs NSSW020BT manufactured by Nichia Corporation) is disposed on one end face of the light guide sheet 10 to be measured, and a luminance meter 50 (luminance manufactured by TOPCOM) A surface perpendicular to the light guide sheet surface in parallel with the luminance and light guide direction of light emitted from the exit surface of the area with a viewing angle of 2 ° centered on each part provided with the output mechanism. The luminance distribution at an outgoing light angle from −90 ° to 90 ° was measured. The measurement results are shown in FIG. The luminance in the normal direction is shown in Table 1.

(Example 2)
A light guide sheet 10 was prepared in the same manner as in Example 1 except that laser processing was performed with the laser incident angle α set to 45 degrees. The cross-sectional shape is shown in FIG. 7 (4), and the luminance measurement results are shown in Table 1.

(Comparative Example 1)
A light guide sheet 10 was prepared in the same manner as in Example 1 except that laser processing was performed with the laser incident angle α set to 90 degrees. The cross-sectional shape is shown in FIG. 7 (1), and the luminance measurement results are shown in Table 1.

(Comparative Example 2)
A light guide sheet 10 was prepared in the same manner as in Example 1 except that laser processing was performed with the laser incident angle α set to 75 degrees. The cross-sectional shape is shown in FIG. 7 (2), and the luminance measurement results are shown in Table 1.

  As shown in FIG. 7, it can be seen that the inclination angle β of the side wall surface 17 formed by changing the incident angle α of the laser is controlled.

Further, as shown in FIG. 6 and Table 1, in (1) and (2) manufactured based on Comparative Examples 1 and 2, the peak luminance was 300 cd / m ² or less, whereas in Examples 1 and 2, In the manufactured (3) and (4), the peak luminance of the emitted light was 3000 cd / m ² or more, and the luminance was greatly improved.

DESCRIPTION OF SYMBOLS 10 Light guide sheet 11 Core layer 12 Clad layer 13 Light emission surface 14 Processing surface 15 Concave part 16 Light incident surface 17 Side wall surface 20 Laser apparatus 30 Light source 40 Constant current power supply 50 Luminance meter α Laser incident angle β Side wall angle of inclined surface γ Fixed angle of light guide sheet

Claims (2)

A core layer mainly composed of a transparent resin;
A laminated body having a clad layer composed mainly of a resin having a refractive index lower than that of the transparent resin and laminated on both surfaces of the core layer, the concave portion penetrating the clad layer and reaching the core layer. A method of manufacturing a light guide sheet having:
The concave portion is formed by irradiating the laminated body with the laser so that the optical axis of the laser is at a predetermined angle in the range of 45 degrees to 60 degrees with respect to the laminated body. The manufacturing method of a light guide sheet. It is a manufacturing method of the light guide sheet according to claim 1,
The method for producing a light guide sheet, wherein the side wall surface constituting the concave portion includes a slope having a predetermined angle in a range of 30 degrees to 45 degrees.