JP2010097020A - Mother sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mother sheet for a thin film prism sheet, excellent in productivity and handling property of the mother sheet. <P>SOLUTION: The mother sheet has a three-layer structure composed of a first protective film, a plurality of optical films layered on one surface of the protective film and having a lens shape formed on one surface thereof, and a second protective film layered on the opposite face of the plurality of optical films to the first protective film, wherein the first protective film has a thickness of 60 to 150 μm, the second protective film has a thickness of 30 to 150 μm, and a 180° peeling strength between the protective film and the optical film is not more than 0.1 N/25 mm for both of the protective films. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mother sheet having excellent workability when each sheet is incorporated during the production of a backlight for a liquid crystal display device.

  Liquid crystal display devices are used in various applications such as notebook computers and mobile phone devices, televisions, monitors, car navigation systems, and the like. The liquid crystal display device incorporates a backlight unit serving as a light source, and is configured to display by controlling light beams from the backlight unit through a liquid crystal cell. The characteristic required for this backlight unit is not only as a light source that emits light, but also to make the entire screen shine brightly and uniformly.

  The configuration of the backlight unit can be roughly divided into two. One is a method called a direct type backlight. This is a system that is preferably used for television applications that require large size and high brightness, but the basic configuration is characterized by a structure in which fluorescent tubes are arranged directly behind the screen. By arranging a plurality of linear or partially linear fluorescent tubes in parallel at the back of the screen, it is possible to cope with a large screen and to secure sufficient brightness. Another method is called a sidelight type backlight. This is a method mainly used for mobile phones, notebook computers, etc., which are required to be thin and small, for example, but is characterized by using a light guide plate as a basic configuration. In the case of a sidelight-type backlight, a fluorescent tube is installed on the side surface of the light guide plate, light is incident on the light guide plate from the side surface, and light is propagated throughout the surface while totally reflecting inside the light guide plate. A part of the light is removed from the total reflection condition by diffusing dots or the like applied to the back surface of the light, and the light is collected from the front surface of the light guide plate, thereby functioning as a backlight, that is, a surface light source. In the case of a sidelight type backlight, in addition to these configurations, a reflection film that functions to reflect and reuse light leaking from the back surface of the light guide plate, and a diffusion sheet that equalizes the light emitted from the front surface of the light guide plate Many types of optical films are used, such as a light collecting sheet represented by a prism sheet that improves the front brightness and a brightness improving sheet that improves the brightness on the liquid crystal panel (Patent Documents 1 and 2).

  When producing a backlight, for example, in the case of a cellular phone, a light guide plate is fitted into a frame, a reflection plate is laminated on one side, a diffusion sheet and a prism sheet are laminated on the other, and fixed with a frame-like tape called a rim tape.

  In order to prevent scratches, the sheets have a protective film on one side or both sides, and a process for peeling the protective film is required when the sheet is incorporated into a backlight.

In the case of a small liquid crystal display device, since the sheets are also small, a multi-sided sheet (in the present invention, this is called a mother sheet) on which a plurality of cut optical films are mounted using at least one protective film as a mount In general, it is used for backlight production.
Japanese Patent No. 2670518 JP-A-9-21908

However, if the protective film is too thin, the mother sheet itself does not have rigidity, so the handleability is poor, and when the optical film is cut, it becomes easy to punch out the protective film that becomes the mount, and the yield decreases. To do. Furthermore, when peeling off the optical film from the protective film, if the adhesion between the films is too strong, it becomes difficult to peel off the optical film, resulting in poor productivity, or the optical film is broken or scratched. It becomes easy to stick and the yield decreases.
On the contrary, if the thickness of the optical film is too thin, the above-described problems will be further enhanced. In other words, handling and productivity are inferior and, of course, breakage and scratches easily occur.

  Therefore, in view of the background of such conventional technology, the present invention is intended to provide a mother sheet of a thin prism sheet that is excellent in the productivity and handling of the mother sheet.

  The present invention employs the following means in order to solve such problems. That is, the mother sheet of the present invention includes a first protective film, a plurality of optical films having a lens shape formed on one side of the first protective film, and a first of the plurality of optical films. A mother sheet having a three-layer laminated structure composed of a second protective film laminated on a surface opposite to the side facing the protective film, wherein the thickness of the first protective film is 60 to 150 μm, the thickness of the second protective film is 30 to 150 μm, and the 180 ° peel strength between the protective film and the optical film is 0.1 N / 25 mm or less. It is characterized by.

A preferred embodiment of the mother sheet of the present invention is:
(1) The thickness of the optical film is 60 μm or less,
(2) The lens surface of the optical film has a prism shape,
It is.

  According to the present invention, the mother sheet is excellent in productivity, the thin prism sheet can be easily peeled off from the protective film, and a mother sheet excellent in handleability can be provided. There is an advantage that the yield is improved without fear of breaking or scratching.

  The present invention is not only excellent in the above-mentioned problems, that is, productivity and handleability, but also intensively studied on a process that is not easily broken or scratched in the peeling operation, and the thickness of the first protective film and the thickness of the second protective film Surprisingly, when the thickness was specified and the peeling force between the protective film and the optical film was set to a specific condition of 0.1 N / 25 mm or less, the above problems were unexpectedly solved. As a result, the present invention has been achieved.

  The protective film will be described. Examples of the material for the protective film include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, cyclohexanedimethanol copolymer polyester resin, isophthalic acid copolymer polyester resin, spiroglycol copolymer polyester resin, and fluorene. Polyester resins such as copolyester resins, polyolefin resins such as polyethylene, polypropylene, polymethylpentene and alicyclic olefin copolymer resins, acrylic resins such as polymethyl methacrylate, polycarbonate, polystyrene, polyamide, polyether, polyesteramide , Polyetheresters, polyvinyl chloride, copolymers containing these as components, or mixtures of these resins Sex resins. Among these, in terms of mechanical strength and workability, polyethylene, polypropylene, polyethylene terephthalate, copolymers with other components based on these, or polyester resins such as a mixture are more preferably used.

  About the thickness of a protective film, in the 1st protective film, Preferably it is 60-150 micrometers, More preferably, it is 70-130 micrometers. If the thickness is less than 60 μm, the first protective film may be punched out when half-cutting the optical sheet. Moreover, in a 2nd protective film, Preferably it is 30-150 micrometers, More preferably, it is 30-100 micrometers, More preferably, it is 30-60 micrometers. When the thickness is 30 μm or less, workability at the time of peeling is deteriorated, and when the thickness is more than 100 μm, it is difficult to half-cut the optical sheet.

  The peel strength of the protective film with respect to the optical film is preferably 0.1 N / 25 mm or less when tested at a test angle of 180 ° and a test speed of 300 mm / min, but is 0.005 N / 25 mm. If it is smaller, the adhesion with the optical film may be deteriorated.

  In the case where the mother sheet of the present invention is a mother sheet in which the first protective film is larger than the optical film product and the second protective film is cut to the same size as the optical film product, the mother sheet More preferably, the optical film product is peeled off from the first protective film prior to the second protective film when the second protective film is bent outward.

  The protective film is preferably transparent so that the appearance inspection of the optical sheet can be easily performed. Furthermore, it is preferable that the second protective film is colored so that it can be recognized when it is forgotten to peel off.

Next, a method for manufacturing a mother sheet will be described with reference to FIGS. The punching blade die 4 is attached to the press machine 5, the blade die is pressed from the second protective film 3 side, and the second protective film 3 and the optical film 2 are cut. There are pinnacle blades, Thomson blades, NC blades, and the like, but it is preferable to use pinnacle blades in terms of accuracy.
Next, the configuration of the mother sheet will be described. For example, when the optical sheet is a prism, as shown in FIG. 2, the direction of the prism surface may be either up or down, but it is preferable that the prism surface is directed upward in order to prevent mistakes when incorporated in the backlight. . Further, as shown in FIG. 3, (a) only half-cutting may be performed, (b) unnecessary portions may be removed after half-cutting, and a first protective film and an optical film are attached as shown in (c). The two protective films may be bonded after half-cutting and removing unnecessary portions after combining.

  Below, the measuring method and evaluation method of each Example and a comparative example are demonstrated. In each of the following measurements, each sample was evaluated with an average value of values obtained by performing the measurement three times. The following measurements were all performed under conditions of room temperature of 23 ° C. and humidity of 65%.

(Measurement and evaluation method)
A. Peeling force A sample having a two-layer structure in which a protective film and an optical sheet are laminated is cut to a width of 25 mm and a length of 180 mm. This sample was subjected to a peel test using an autograph (AGS-J, manufactured by Shimadzu Corporation) at a test speed of 300 mm / min and a test angle of 180 °, and the peel force was measured. The value is determined as the peel force by calculating the average value up to 150 mm after rejecting the data up to 20 mm from the beginning. However, if the length of 150 mm cannot be measured because the sample is small, a plurality of samples are measured so that the total exceeds 150 mm, and the average value is similarly calculated.

Example 1
(Lamination of protective film)
Toraytec 7721 (made by Toray Film Processing Co., Ltd.) having a thickness of 100 μm for the first protective film, L-7325 (made by Hitachi Chemical Co., Ltd.) for the second protective film, and ThinBEF (made by 3M) for the optical film having a thickness of 60 μm Was used. A laminated sheet 1 was obtained by simultaneously laminating L-7325 on the prism surface of ThinBEF and Tretec 7721 on the non-prism surface at a linear pressure of 5 kg / cm. When the peeling force was measured, L-7325 was 0.02 N / 25 mm, and Tretec 7721 was 0.02 N / 25 mm.
(Mother sheet production)
A 3 × 4 cm rectangular pinnacle blade mold was pressed from the L-7325 side of the laminated sheet 1 to cut L-7325 and ThinBEF to obtain a mother sheet 1.
The mother sheet 1 could be easily peeled off by bending the first protective film a little and the optical film product could be easily taken out. At this time, the optical film product was not broken or damaged.

(Example 2)
A 3 × 4 cm rectangular pinnacle blade mold was pressed from the L-7325 side of the laminated sheet 1, L-7325 and ThinBEF were cut, unnecessary portions were removed, and a mother sheet 2 was obtained.
The mother sheet 2 could be easily peeled off by bending the first protective film a little, and the optical film product could be easily taken out. At this time, the optical film product was not broken or damaged.

(Example 3)
The laminated sheet 2 was obtained by laminating Tretec 7721 on the non-prism surface of ThinBEF at a linear pressure of 5 kg / cm. A 3 × 4 cm rectangular pinnacle blade mold was pressed from the prism surface of the laminated sheet 2 to cut the ThinBEF, and after removing unnecessary parts, the mother surface was laminated with Tretec 7721 having a thickness of 60 μm at a linear pressure of 5 kg / cm. Sheet 3 was obtained.
When the peeling force was measured, L-7325 was 0.02 N / 25 mm (Examples 1 and 2), and Tretec 7721 was 0.02 N / 25 mm (Example 3).
The mother sheet 3 was easily bent with the first protective film down, and the second protective film could be easily peeled off, and the optical film product could be easily taken out. At this time, the optical film product was not broken or damaged.

(Comparative Example 1)
L-7235 / ThinBEF / DP-1010
When this mother sheet tried to peel off the protective film 2, the protective film 2 and the optical film product could not be separated at a rate of 2 out of 10 times, and the mother sheet could come off from the mount. After that, even if the protective film 2 and the optical film were forcibly separated, the optical film product was broken or damaged, and was no longer usable for the backlight.

  The mother sheet of the present invention can be applied to various fields such as a liquid crystal display member.

It is the schematic of the manufacturing apparatus of a mother sheet. (A) And (b) illustrates typically the structure of the mother sheet | seat of this invention. (A)-(c) illustrates typically the structure of the mother sheet | seat of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st protective film 2 Optical film 3 2nd protective film 4 Punching blade type | mold 5 Press machine

Claims (3)

A first protective film; a plurality of optical films having a lens shape formed on one side thereof laminated on one side of the first protective film; and a side of the plurality of optical films facing the first protective film A mother sheet having a three-layer laminated structure composed of a second protective film laminated on the opposite surface to
The thickness of the first protective film is 60 to 150 μm, the thickness of the second protective film is 30 to 150 μm, and the 180 ° peel strength between the protective film and the optical film is any A mother sheet that is 0.1 N / 25 mm or less.   The mother sheet according to claim 1, wherein the optical film has a thickness of 60 μm or less.   The mother sheet according to claim 1, wherein a lens surface of the optical film has a prism shape.

Images