JPH08248210A - Light condensing sheet - Google Patents

Abstract

PURPOSE: To make it possible to surely and easily build a light condensing sheet consisting of plural prisms having different half vertexes into the normal position of a back light by providing the light condensing sheet with means for identifying asymmetrical shapes when viewed from the exit surface of rays. CONSTITUTION: This light condensing sheet 21 consists of the plural prisms having the different half vertexes and controls the emission characteristics of the rays in the back light. Such light condensing sheet 21 is provided with the visual sensation identifying means capable of identifying the shapes asymmetrical in vertical and lateral directions when viewed from the exit surface of the rays by visual sensation or the tactile sense identifying means capable of identifying these shapes by tactile sense. For example, the light condensing sheet 21 is provided with the visual sensation identifying means 21a arranged with plural characters and numerals. The visual sensation identifying means 21a may be symbols and patterns as well and are more preferably disposed in the part of the back light where the visual sensation is less affected, for example, in the peripheral part where the pixels of liquid crystal do not exist in the upper part. As a result, the light condensing sheet 21 is correctly built into the back light even if the differences, etc., the slopes of the fine prisms is not checked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light collecting sheet used for a liquid crystal backlight, and more particularly to a light collecting sheet having a plurality of prisms having different half apex angles.

[0002]

2. Description of the Related Art A conventional backlight for illuminating liquid crystal on a uniform surface is provided with a light source and a light guide plate for emitting light rays from the light source. The light source is arranged on the side surface of the light guide plate. Therefore, even if the diffused reflection layer is provided on the light guide plate, the emitted light has a strength distribution in which the light is emitted not in the direction perpendicular to the light guide plate but in the direction away from the light source.

To solve this problem, Japanese Unexamined Patent Publication (Kokai) No. 5-2
Japanese Patent No. 32466 discloses an invention in which a light-condensing sheet having prisms having different cross-sections and having half-vertical angles is arranged on a light guide plate. It should be noted that although it is called a transparent sheet in the publication, it is called a light-condensing sheet in the present invention.

A diagram of this prior art backlight is shown in FIG. In the figure, light is incident on a side surface of a light guide plate 1 made of acrylic resin from a cold cathode tube 2 which is a light source, and is reflected by a diffuse reflection layer 1a provided with a print pattern or a concavo-convex pattern in a dot shape or a linear shape, and condensed. The light is emitted through the sheet 3. The light collecting sheet 3 is provided with a prism 3a, and the prism 3a
Is a normal 3 connecting the flat surface portion 3b and the apex 3c of the prism 3a.
The angle formed with d, that is, the half apex angles a and b are different, and are formed asymmetrically. Therefore, the light rays emitted from the light guide plate 1 are emitted in the direction of the normal line 3d by the prism 3a of the light-condensing sheet 3, and when used as a backlight of a liquid crystal (not shown), they are uniform in the normal viewing direction. A light intensity distribution is obtained.

[0005]

However, the above-mentioned light collecting sheet has the following problems. That is, one of the performances required for the backlight is thinning, and as a result, the light collecting sheet is also required to be thinning. The thickness of a current light-condensing sheet is about 0.2 mm, and the pitch of prisms is about 0.05 mm. The half apex angle a of the prism is 2
Assuming that the condensing sheet is 0 ° and the half apex angle b is 35 °, the width of the inclined surface of the prism is 1 when viewed from the emission surface through which the light rays are emitted.
It becomes 8 microns and 32 microns. Since the width of the inclined surface is so small, the difference cannot be easily recognized with the naked eye even when observing the light-condensing sheet, and when the backlight is assembled, the inclined surface having a half-vertical angle of 20 ° is used. Where the light source side should be arranged, there is a risk that the inclined surface having a half-vertical angle of 35 ° may be mistakenly arranged on the light source side for assembly. in this way,
If assembled incorrectly, the light beam from the light guide plate will not be refracted in the desired direction, and the function of the backlight as a surface light source will be lost.

In view of the above problems, the present invention allows a light collecting sheet having a plurality of prisms having different half-vertical angles to be incorporated into a backlight securely and easily at a proper position to prevent misalignment. It proposes a light-condensing sheet that has been prevented.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a light-condensing sheet having a plurality of prisms having different half-vertical angles and controlling the emission characteristics of light rays in a backlight. This is achieved by providing a visually discriminating means or a tactile discriminating means which is asymmetrical in the vertical and horizontal directions as seen from the emission surface of the light ray and which can be discriminated by touch.

[0008]

Embodiments of the present invention will be described in detail with reference to FIGS.

FIG. 2 is a perspective view of a light collecting sheet used in the present invention, and FIG. 3 is a sectional view thereof. The light collecting sheet 11 has a plurality of prisms 11a formed of polycarbonate and having different half apex angles. In this embodiment, unlike the prior art, the prism 11a is provided on the upper part,
Either the upper part or the lower part may be used. With reference to the flat surface portion 11b which is a surface facing the prism 11a, the prism 1
The normal 11d connecting the apex 11c of 1a to the inclined surface 11
When the angle A formed with e is a half-vertical angle A and the angle B formed with the inclined surface 11f is a half-vertical angle B, the half-vertical angle A is larger than the half-vertical angle B in the present embodiment. As a result, the light emitted from the light incident on the flat surface portion 11b has a strong intensity distribution on the left side of the drawing. Therefore, when light having a strong intensity distribution to the right enters the flat surface portion 11b, light having a uniform intensity distribution is emitted to the left and right.

However, if the top, bottom, left and right positions and the front and back of the light collecting sheet 11 are erroneously arranged, the light will be emitted in a completely inappropriate direction, so it is necessary to surely arrange the light collecting sheet 11 at a proper position. For this reason, the condensing sheet of the present invention is shown in FIG.
As shown in FIGS. 12 to 12, a visual identification means capable of visual identification or a tactile identification means capable of tactile identification with a hand is provided.

FIG. 4 is a view of a light-collecting sheet provided with a plurality of characters and numbers as an example of the visual identification means, as seen from the emission surface of the light beam. Identification means 21a is provided. Visual identification means 21
The symbol a is not limited to letters and numbers, but may be a symbol or a pattern, but a portion that has little effect on the visual sense of the backlight is desirable, and for example, a peripheral portion where liquid crystal pixels do not exist in the upper portion is desirable. The letters, numbers, symbols or patterns may be provided by printing, or may be directly stamped on the mold of the light collecting sheet.

The point is that any structure may be used as long as the operator assembling the backlight can correctly determine the top, bottom, left, and right and the front and back of the light-condensing sheet and arrange them in the proper positions.

FIG. 5 is a view in which the top and bottom of the light-condensing sheet 21 are erroneously arranged, and FIG. 6 is a view in which the light-condensing sheet 21 is flipped left and right and the front and back are erroneous. In both cases, light is emitted in an abnormal direction.

FIG. 7 is a view of a light-collecting sheet, in which one character is cut out, as seen from the light emitting surface, as an example of the visual identification means. The light-condensing sheet 31 has a character 31a P as the visual identification means. It is cut out with a mold. The letter is not limited to P, and any letter, number, symbol or pattern can be used. For example, A, C, D, E,
H, I, K, M, N, O, S, T, U, V, W, X,
Characters such as Y, Z or 1,3,6,8,9,0 having line symmetry and point symmetry and characters confusing depending on the posture are apt to be erroneous, and thus should not be used. Also, if the width to be cut out is too large, optical effects may occur, so
It is preferable to have a minimum width that can be identified and processed.

FIG. 8 is a view of a light-condensing sheet using a pattern as an example of the visual identification means as seen from the light emitting surface, and the light-condensing sheet 41 is provided with a pattern 41a by embossing or the like. If this pattern is provided in one of the four corners defined in advance, the regular position can be easily identified.

FIG. 9 is a view of a light-condensing sheet having an asymmetrical outer shape as seen from the light emitting surface as an example of the visual identification means. Since the light-condensing sheet 51 is provided with convex portions 51a and concave portions 51b. As long as the assembler recognizes the proper state in advance, there will be no mistake in the assembly. It should be noted that the outer shape may be any shape, but it is necessary that the outer shape be capable of discriminating between upper, lower, left, right and front. Further, this embodiment can also be used as a tactile identification means.

FIG. 10 is a view of a light-condensing sheet provided with a plurality of protrusions as an example which can be used for both the visual discriminating means and the tactile discriminating means, as seen from the light emitting surface. Is provided with a protrusion 61a. Therefore, the light-condensing sheet can be arranged at a proper position by visual recognition or by touch with a hand. It should be noted that the protrusion is not limited to the one shown in the drawing, but it is necessary to provide it at a position where it is possible to discriminate between the upper, lower, left, right, and front and back.

FIG. 11 is a view of a light-condensing sheet provided with a plurality of projections as an example which can be mainly used as a tactile-sense identifying means, as seen from the light-emission surface.
A plurality of protrusions 71a are provided on the side surface of the. Therefore, the light-condensing sheet can be arranged at a proper position by a tactile sensation with a hand without visually recognizing it. Similar to the above, it is necessary to provide it at a position where it is possible to discriminate between the top, bottom, left, right and front and back.
Note that a recess may be used instead of the protrusion.

FIG. 12 is a perspective view in which a visual identification means is provided on a protective film provided to prevent scratches or dust from adhering to the flat surface portion or prism surface of the light collecting sheet. That is, the protective film 82 attached to the light condensing sheet 81 has a visual identification means 82 composed of symbols and characters.
Since a is provided, if it is assembled as it is, it can be assembled in a proper position without error, and after the assembly, the protective film 8
If 2 is peeled off, there is no optical influence as shown in FIG.

If the visual identification means or the tactile identification means are arranged in vertically and horizontally asymmetrical positions when the light-condensing sheet is viewed from the emission surface of the light rays as in each of the embodiments described above, the vertical and horizontal directions will be erroneous. There is no need to place it, and there is no mistake on the front and back.

[0021]

According to the light-condensing sheet according to the first to fifth aspects of the present invention, when assembling the light-condensing sheet into a backlight, a fine prism inclined surface difference and a prism half-vertical angle difference are assembled. Even if the person does not confirm it, the light condensing sheet can be easily identified by the visual identification means or the tactile identification means provided on the light condensing sheet or the protective film, so that the light condensing sheet is erroneously placed. And the time required for the placement work is shortened.

[Brief description of drawings]

FIG. 1 is a diagram of a prior art backlight.

FIG. 2 is a perspective view of a light collecting sheet used in the present invention.

FIG. 3 is a cross-sectional view of a light collecting sheet used in the present invention.

FIG. 4 is a view of a light-condensing sheet provided with a plurality of letters and numbers as seen from a light emitting surface.

5 is a diagram in which the top and bottom of the light collecting sheet in FIG. 4 are erroneously arranged.

FIG. 6 is a diagram in which the light condensing sheet of FIG.

FIG. 7 is a view of a light-condensing sheet in which one character is cut out as seen from a light emitting surface.

FIG. 8 is a view of a light-collecting sheet having a pattern as seen from a light emitting surface.

FIG. 9 is a view of a light-condensing sheet having an asymmetric outer shape as seen from a light ray emission surface.

FIG. 10 is a view of a light-condensing sheet provided with a plurality of protrusions as seen from a light ray emission surface.

FIG. 11 is a diagram of a light-condensing sheet provided with a plurality of protrusions as seen from a light ray emission surface.

FIG. 12 is a perspective view of a protective film provided with visual identification means.

[Explanation of reference numerals] 1 light guide plate 2 cold cathode tube 3, 11, 21, 31, 41, 51, 61, 71, 81
Light condensing sheet 3a, 11a Prism 21a, 82a Visual identification means 31a Character 41a Pattern 51a Convex part 61a, 71a Protruding part 82 Protective film

Claims (5)

[Claims] 1. A light-condensing sheet that has a plurality of prisms having different half-vertical angles and controls the emission characteristics of light rays in a backlight. A light-condensing sheet, characterized in that an asymmetrically-shaped visual identification means or a tactile identification means capable of tactile identification is provided. 2. The light collecting sheet according to claim 1, wherein the visual identification means is a character, a number, a symbol, or a pattern. 3. The light condensing sheet according to claim 1, wherein the visual identification means is an outer shape portion of the light condensing sheet. 4. The light condensing sheet according to claim 1, wherein the tactile identification means is a convex portion or a concave portion. 5. The light collecting sheet according to claim 1, wherein the visual identification means or the tactile identification means is provided on a protective film attached to the light collecting sheet.