JP2013073729A - Light guide, lighting device having the same, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide hardly damaged and having high performance with easy assembling works.SOLUTION: The light guide 7 that is translucent has a first primary surface 7a, a second primary surface 7b opposite to the first primary surface 7a, and four side end faces 7L, 7S, 7L, and 7S connecting the first primary surface 7a and the second primary surface 7b. A plurality of light sources 6 facing to at least one side end face 7L, 7S, 7L, or 7S among the four side end faces 7L, 7S, 7L, and 7S are arranged by lining up in an extended direction each of the side end faces 7L, 7S, 7L, and 7S, and a light deflection element 18 for deflecting light guided in the light guide 7 to a second primary surface 7b side is formed on the first primary surface 7a. The light guide 7 has bezels which are arranged at most on two sides or less.

Description

  The present invention relates to a light guide used mainly for illumination light path control, an illumination device, and a display device.

  In recent large-sized liquid crystal televisions, flat display panels and the like, a direct type illumination device and an edge light illumination device are mainly used. In the direct type illumination device, a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are regularly arranged as light sources on the back surface of the panel. A light diffusing plate is used between the image display element such as a liquid crystal panel and the light source so that a cold cathode tube or LED as a light source is not visually recognized.

  On the other hand, in an edge light type lighting device, a plurality of cold-cathode tubes and LEDs are arranged on an end face of a translucent plate called a light guide plate. In general, light that efficiently enters incident light that is incident from an end surface of the light guide plate onto a surface (light deflection surface) opposite to the light emission surface (surface that faces the image display element) of the light guide plate. A deflection element is formed. At present, the light deflection element formed on the light deflection surface is generally one in which white ink is printed in the form of dots (for example, Patent Document 1). However, since the light incident on the white dots is diffusely reflected almost omnidirectionally, the light extraction efficiency to the exit surface side of the light guide plate is low. Light absorption by white ink cannot be ignored.

  Therefore, recently, a method of forming a microlens on the light deflection surface of a light guide plate by an ink jet method, a method of forming a light deflection element by a laser ablation method, and the like have been proposed. Unlike white ink, light absorption hardly occurs because it uses reflection, refraction, and transmission due to the difference in refractive index between the resin of the light guide plate and air. Therefore, a light guide plate having a higher light extraction efficiency than that of white ink can be obtained.

  However, the formation of the light deflection element by the ink jet method or the laser ablation method is formed in a separate process after the light guide plate is formed into a flat plate, as in the case of printing with white ink, so the number of manufacturing steps is not reduced. Rather, there is a problem that the tact time is longer than the white ink printing process and the initial cost of the equipment is high, resulting in high costs.

  Therefore, a method has been proposed in which the light guide plate is formed by an injection molding method or an extrusion molding method, and the light deflection element is directly shaped at the time of extrusion (for example, Patent Document 2). Since the light deflection element is formed simultaneously with the formation of the light guide plate, the number of processes is reduced, and the cost can be reduced.

  However, when a light guide plate is manufactured by an injection molding method, the higher the size, the higher the pressure required for the injection molding machine. Therefore, for manufacturing a light guide plate for a relatively small display device such as a mobile phone or a laptop computer. Although suitable, it is difficult to apply to large display devices such as televisions. On the other hand, the extrusion molding method is a production method suitable for producing a large light guide plate, but it is necessary to produce a cylindrical roll mold having a high degree of difficulty.

JP-A-1-241590 JP 2000-89033 A

Since it is the dots that are responsible for the light launching performance of the light guide plate, it is important how to deliver the dots to the end user without any scratches. However, it is hard to say that the current state of technology development has been made as shown below.
The light guide plate is transported while being protected from foreign objects and scratches by a protective film, and the protective film is peeled off during assembly. In particular, since a foreign substance is generated in the polishing process, the current protective film is essential. On the other hand, the light guide plate has a dot-free bezel at the edge. Since the bezel is a mirror surface, it is in close contact with the protective film and prevents the protective film from being peeled off during transportation. However, the work of peeling off the protective film is performed in a clean room and is in a gloved state, and the protective film is difficult to peel off, reducing productivity.
Moreover, since the convex lens used normally is easily damaged when the protective film is peeled off, the adhesion of the protective film must be increased. Further, after the protective film is peeled off, it is rubbed and damaged in the television casing, and the light launch performance is deteriorated.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light guide that is not easily damaged, has high performance, and is easy to assemble, and an illumination device and a display device including the light guide. is there.

The invention of claim 1 is a translucent light guide,
The light guide has a first main surface, a second main surface facing the first main surface, and four side end surfaces connecting the first main surface and the second main surface,
A plurality of light sources facing at least one side end face of the four side end faces are arranged side by side in the extending direction of the side end face,
The first main surface is formed with a light deflecting element that deflects light guided through the light guide body toward the second main surface,
Of the four peripheral edges along the four side end faces of the first main surface, one or two peripheral edges have a belt-like bezel on which the light deflection element is not formed.
It is the light guide characterized by this.

The invention of claim 2 is the light guide according to claim 1,
The light deflection element is a concave dot;
Depending on the distance from the side end face where the light source faces, any one of dot size, shape, and arrangement interval is different.
It is the light guide characterized by this.

The invention of claim 3 is the light guide according to claim 1 or 2,
The portion where the area occupation density of the light deflection elements in the first main surface is 50 to 95% is a bezelless portion that does not have the bezel among the peripheral portions of the four sides of the first main surface. ,
It is the light guide characterized by this.

The invention of claim 4 is the light guide according to claim 3,
The total length of the portion where the area occupation density of the light deflection element is 50 to 95% along the peripheral edge of the first main surface is 0.1 to 30% with respect to the total length of the bezelless portion.
It is the light guide characterized by this.

Invention of Claim 5 is the light guide in any one of Claims 1 thru | or 4, Comprising:
The light deflection element has a shape having a height difference with respect to the first main surface, and a height difference of the light deflection element with respect to the first main surface is not less than 5 μm and not more than 70 μm.
It is the light guide characterized by this.

The invention of claim 6 is the light guide according to any one of claims 1 to 5,
The second main surface has an uneven optical element that deflects light emitted from the second main surface to the outside of the light guide,
It is the light guide characterized by this.

The invention of claim 7 is the light guide according to any one of claims 1 to 6,
Antistatic treatment on the surface,
It is the light guide characterized by this.

The invention of claim 8 is an illuminating device disposed behind a transmissive illumination type image display element that defines a display image,
A light source;
The light guide plate according to any one of claims 1 to 7, which guides light from the light source;
At least one optical sheet through which diffused light emitted from the light guide plate is transmitted;
It is an illuminating device provided with.

The invention of claim 9
A transmission illumination type image display element that defines a display image according to transmission / light-shielding in pixel units;
The illumination device according to claim 8 disposed on a back surface of the image display element;
It is provided with the following.

If this invention is used, even if it does not depend on the adhesive force of a protective film, the high performance light-guide plate which prevents the damage | wound of a dot and maintains light launching performance can be produced. Improvements in workability and productivity can also be realized.
First, since there is a chance to peel off the protective film, workability for removing the protective film is improved. Moreover, since the trigger portion is limited, it is possible to prevent the protective film from being unintentionally peeled off during transportation. Even if it is peeled off, the dots are not damaged because of the concave shape. Even after the protective film is peeled off, the dots are not damaged in the television casing.

It is explanatory drawing of the display apparatus provided with the illuminating device of the edge light system which concerns on one Embodiment of this invention. (A)-(c) is a perspective view which shows the structural example of the light guide of FIG. (A), (b) is explanatory drawing which shows the light guide which concerns on one Embodiment of this invention, (c) is explanatory drawing which shows the conventional light guide.

Hereinafter, a display device according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the light guide and the light guide plate indicate the same thing.
First, a display device including an edge light type illumination device according to an embodiment of the present invention will be described with reference to FIG. The display device 1 according to the present embodiment includes an illumination device 3 and a liquid crystal panel 2.
The illuminating device 3 plays a role of entering the light emitted from the light source 6 and deflecting it to the emitted light K toward the liquid crystal panel 2. The light guide 7 is housed in the housing 5 of the lighting device 3.
As shown in FIGS. 2A to 2C, the light guide 7 includes a first main surface 7a, a second main surface 7b facing the first main surface 7a, and the first main surfaces 7a. And four side end faces 7L, 7S, 7L, 7S connecting the second main surface 7b. The first main surface 7a and the second main surface 7b are rectangular, and the side end surfaces 7L and 7L are connected to both long sides thereof, and the side end surfaces 7S and 7S are connected to both short sides thereof.
A plurality of light deflection elements 18 are formed on the first main surface 7a to deflect the light guided through the light guide 7 toward the second main surface 7b. The structure of each light deflection element 18 will be described in detail later. In addition, a reflection sheet 5 a is provided on the bottom surface of the housing 5 facing the first main surface 7 a of the light guide 7.
The light from the light source 6 is incident on the side end surface 7L of the light guide 7. The light is deflected by the light deflection element 18 on the first main surface 7a and is emitted from the second main surface 7b. When the second main surface 7b has the optical element 19 as shown in FIG. The optical element 19 will also be described in detail later. Thereafter, the light passes through the diffusion sheet 8, the prism sheet 20, and the deflection separation sheet 28 shown in FIG. 1 and is emitted as the emitted light K from the illumination device 3.
In FIG. 1, the observer of the display device 1 is in the direction of arrow F.

As shown in FIGS. 2A to 2C, the light deflection elements 18 are dots arranged on the mirror surface of the first main surface 7a. The optical element 19 is a lens arranged without gaps.
The light guide 7 is made of a transparent resin such as acrylic, polycarbonate, polystyrene, AS resin, or MS resin.
The light guide 7 is formed into a square resin plate by injection molding, extrusion molding, or casting.

The light deflection element 18 can be composed of various materials and shapes.
For example, the light deflection element 18 is a printed white circular dot. Examples of white ink include a mixture of a pigment such as titanium oxide in a base resin. The resin is UV curable and may be cured after printing.
For example, the light deflection element 18 is a translucent three-dimensional dot printed by inkjet. The three-dimensional shape is adjusted by the ink viscosity, drying conditions, and printing method.
For example, the light deflection element 18 is the surface of the first major surface 7a ablated with a laser. The shape of ablation depends on conditions such as laser intensity and scanning, but all are expressed as dots. Under certain conditions, the surface is roughened and the dots appear white, and under certain conditions, the dots are dug into a concave shape. Each of the light deflection elements 18 configured as described above has an appearance as shown in FIG.
Further, for example, as shown in FIG. 2B, the light deflection element 18 is a concave dot on the surface of the first major surface 7a created by machining.
Furthermore, for example, as shown in FIGS. 2B and 2C, the light deflection element 18 is a concave or convex dot on the first main surface 7a created by a mold. The dots may be created by putting them in a mold when the light guide 7 is formed, or may be created by pressing a heated mold after the formation.
Examples of the dot shape include hemispherical dots, pyramidal dots, cubes, and the like, in addition to those described above according to processing conditions. From the viewpoint of being hard to be damaged, the dots constituting the light deflection element 18 are preferably concave, and more preferably concave dots having a height difference from the first main surface 7a of 5 μm to 70 μm. If it is less than 5 μm, it is too shallow to prevent scratches, and if it is deeper than 70 μm, it is very difficult to remove if foreign matter has entered.
The light deflection element 18 differs in dot size, shape, or arrangement interval depending on the distance from the light source.

The optical element 19 can be composed of various materials and shapes.
For example, the optical element 19 is a lens formed of a UV curable resin on the second main surface 7b.
For example, the optical element 19 is a concave lens of the second main surface 7b created by machining.
For example, the optical element 19 is a concave or convex lens of the second main surface 7b created by a mold. The lens may be formed in a mold when the light guide 7 is formed, or may be formed in a heated mold after formation.
Examples of the shape of the lens include a prism lens, a lenticular lens, and a trapezoid lens well known in the art.
The optical element 19 is not essential when considering the function of the light guide 7. In that case, the second main surface 7b is merely a flat surface, and the optical element 19 can be omitted.
Unlike the light deflection element 18, the optical element 19 is arranged side by side on the second main surface 7 b without a gap. Therefore, if there is the optical element 19, a protective film (damage of the light guide 7 or foreign matter is present on the second main surface 7 b side). There is no problem in peeling off a film (not shown) that is stuck during transportation to prevent adhesion. That is, from the viewpoint of easy removal of the protective film, it is more preferable that the optical element 19 is on the second main surface 7b.

Here, the first main surface 7a of the light guide 7 will be described in detail. FIG.3 (c) is explanatory drawing which shows the conventional light guide. In FIG.3 (c), the light guide 7 and the light source 6 are seen from the upper surface. Conventionally, the bezel 30 is provided on the four sides of the peripheral edge along the side end faces 7L, 7S, 7L, and 7S of the light guide 7. The bezel 30 refers to a region of the first major surface 7a where the light deflection element 18 is not present. And there is a light guide region 31 with the light deflection element 18 surrounded by the bezel 30. In the figure, for the sake of simplicity, a square is shown, but in reality, it is often a square. One of the reasons why the bezel 30 is provided is that when the light deflection element 18 is added to the light guide body 7, it is troublesome to add the light deflection element 18 to the end. Further, the technical verification of the presence of the bezel 30 was insufficient.
Note that the bezel 30 has a width of 1 mm or more, and if the width is less than 1 mm, it is a part of the arrangement pattern of the light deflection elements 18. A region where there is no light deflection element 18 having a width of less than 1 mm does not contribute to the adhesion of the protective film.

  Since the optical path of the light guide 7 is changed due to scratches or foreign matter, the light guide 7 is handled after being manufactured with a protective film until it is assembled. Since the surface of the bezel 30 is a mirror surface, the protective film adheres well, but there is a problem that it is difficult to peel off.

  3A and 3B are explanatory views showing a light guide according to an embodiment of the present invention. In this embodiment, the bezel 30 is not on all four sides of the first main surface 7a, but only on one side or two sides. The peripheral portion of the side without the bezel 30 is hereinafter referred to as a bezel-less portion 32, and the range of the bezel-less portion 32 is 5 mm inside from the side of the first major surface 7a. The bezelless portion 32 has the light deflecting element 18 as far as the end, so that the protective film is peeled off. In addition, when the bezel-less part 32 exists more than 5 mm beyond the edge | side of the 1st main surface 7a, the part does not contribute to the ease of peeling of a protective film.

The bezelless portion 32 has a more preferred occupancy density of the light deflection elements 18. The occupation density of the light deflection elements 18 is the ratio of the area occupied by the dots of the light deflection elements 18 in the area in plan view. The occupation density that is easy to peel off was 50% or more and 95%. If it is less than 50%, the protective film is difficult to peel off and does not trigger. Since the dot cannot be created at an occupation density of 95% or more, it has not been confirmed.
The preferred occupied area of the bezelless portion 32 is as described above. However, if all the bezelless portions 32 have the occupied area, the protective film is peeled off during transportation. Hereinafter, the portion where the occupation density of the optical element 18 is 50% or more and 95% or less is referred to as “trigger”. In order to prevent peeling of the protective film during transportation, there is a preferable size (length) as a trigger.

  The total length of the bezelless portion 32 is obtained by adding the length of the bezelless portion 32 along the side of the light guide 7. In the present invention, the bezel 30 has one to two sides of the first main surface 7a, and the bezelless portion 32 has two to three sides of the first main surface 7a. Therefore, the total length of the bezelless portion 32 is the four sides of the light guide 7. More than half of the total length. It is preferable that the length of the trigger portion is 0.1 to 30% with respect to the total length of the bezelless portion 32. If it is less than 0.1%, it is difficult to peel off as a trigger, and if it exceeds 30%, the protective film may be peeled off during transportation.

In the present embodiment, a preferable trigger size is derived as a ratio of the length of the side of the light guide 7 as a result of trial and error. If the light guide 7 becomes smaller, the chance becomes smaller and it will be difficult to peel off. That is, it is considered that the present invention cannot be applied to the light guide body 7 having the first main surface 7a having a small size. When the size of the first main surface 7a of the light guide 7 is increased, the trigger is also increased, and unexpected peeling is likely to occur. The light guide 7 to which the present invention can be applied is set to 23 inches or more and 108 inches or less where the effect is actually recognized.
In addition, as in the case of the conventional light guide 7 shown in FIG. 3C, even when all four sides of the first main surface 7 a are the bezel 30 and a trigger is created on a part of the bezel 30, it seems to be effective. However, in reality, the bezel 30 has a strong adhesion, and the trigger effect was not obtained.

  More preferably, the surface of the light guide 7 has an antistatic treatment. The antistatic treatment prevents foreign matter from adhering to static electricity after the protective film is peeled off. In the antistatic treatment, an antistatic agent may be kneaded into the resin of the light guide 7 or applied to the surface after the light guide 7 is formed.

A light guide was made by extrusion. The light deflection element and the optical element were made by stamping during extrusion. On the second main surface of the light guide, trapezoidal lenses with optical elements 19 having a pitch of 150 μm and a height of 50 μm are arranged without gaps. The light deflection element 18 has a concave shape of a hemisphere with a depth of 20 μm, and the occupation density is changed depending on the arrangement interval.
Table 1 shows the size of the prototype light guide, the number of bezels, and the ratio of the trigger length to the total length of the bezel-less part (indicated in the table as the trigger length). The four sides of the bezel are conventional light guides.
The extruded light guide was cut into an approximate size, a commercially available protective film was attached, and the side end face 7L was polished and used as a sample. Ten samples of the same type were made.

The prepared sample is stored for one day, wrapped in a plastic bag, placed in a plastic box, transported in accordance with JIS Z 0232, transported to a clean room, and checked for peeling of the protective film by hand. The protective film was peeled off. Two workers were peeled off by 5 sheets. The results are shown in Table 1. For ease of peeling, the average peeling time per sheet was 30 seconds or more, x within 10 seconds was Δ, and within 5 seconds was ○.
From Table 1, in the tested sample size, as compared with the comparative example having four sides of the bezel, the light guides of the present invention having the bezel only on one or two sides were easy to peel off the protective film. That is, the superiority of the present invention was shown about the peelability of a protective film. The reason that the four sides of the bezel were difficult to remove was that the protective film was firmly attached to the bezel. On the other hand, when the bezel was one or two sides, a clear tendency appeared with the length of the trigger regardless of the size of the light guide. When the trigger length was 0.05%, the protective film was slightly difficult to peel off. In 40%, a sample in which the protective film peeled off during transportation was observed. All samples from 0.1% to 30% were good. From the above, it was found that the trigger length is preferably from 0.1% to 30%.
With the light guide with one side of the bezel and the light guide with two sides, the protective film was peeled off faster when the bezel was less. However, since the bezel is indispensable on the side close to the light source of the light guide, whether one side or two sides is determined by the illumination device or the display device.

  From the results of the protective film peeling test, it became clear about the appropriate trigger for the protective film operation. While the protective film is on, dot scratches and foreign matter can be eliminated. In addition, in order to obtain a higher performance light guide, a countermeasure against foreign matter caused by static electricity when the protective film was peeled off, and a concave shape of dots that could deal with scratches and foreign matters after peeling were verified.

  Since the sample of Table 1 did not take any countermeasure against static electricity, foreign matter was adsorbed on the sample surface after the peel test by static electricity. Therefore, the samples with the marks (*) in Table 1 were subjected to the same test after applying an antistatic agent before applying the protective film, and no foreign matter was attracted by static electricity.

About the sample which attached | subjected the mark (*) of Table 1, the thing of dot concave shape depth was 2, 5, 10, 20, 50, 70, 80 micrometers. After making the light guide according to the above procedure → transport test → peeling the protective film, it was incorporated into a commercially available display device, and the display device was packed in a cardboard box and transported according to JIS Z 0232.
As a result, the depth of 2 μm was too shallow, so the dots were scratched. The others were not scratched. However, it was determined that it was difficult to remove the foreign matter that had entered the dots for those having a thickness of 80 μm, and it was difficult to maintain the optical performance of the dots.

  A test was conducted to confirm how the difference of the samples verified so far brings about the performance as an actual light guide. Three types of light guides (one type of comparative example and two types of examples) shown in Table 2 were prepared for the samples marked with a mark (*) in Table 1. Without the protective film of the comparative example, the protective film is not pasted after the light guide is formed. In the same procedure as described above, light guide preparation → transport test → protection film was peeled off, and then integration → display device transport was tested. Thereafter, the display device was taken out of the package, and the performance of the display device was evaluated. The results are shown in Table 2. The highest luminance ratio in the table was 1.0.

  First, all of the comparative examples had a low luminance ratio. This was because the performance was greatly reduced due to scratches during transportation because there was no protective film. It was found that a protective film was essential. From this, it was found that the ease of peeling of the protective film of the present invention is a very useful performance for the light guide plate. All examples with a protective film had a high luminance ratio. Among them, a difference was seen in the depth of the concave dot shape. As described above, since the depth of 2 μm is shallow, there were some scratches that reached the dots after the protective film was peeled off. In addition, once the foreign matter is attached to 80 μm, it is difficult to blow off the foreign matter with air or the like, and this is considered to be a factor of lowering the luminance ratio. In any case, since the luminance ratio is better than that of the comparative example, it is desirable that the dot concave shape depth is 5 μm or more and 70 μm or less.

  As mentioned above, if this invention is used, the light-guide plate (light guide) which has the problem of a damage | wound and a foreign material and has a high-performance light starting-up performance can be provided. Furthermore, since the protective film can be easily peeled off, workability and productivity are improved, leading to cost reduction of the lighting device and the display device. Moreover, if the light guide plate of the present invention is prepared, a high-performance lighting device and display device can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Display apparatus 2 ... Liquid crystal panel 3 ... Illumination device 5 ... Housing | casing (reflection sheet)
6 ... Light source 7 ... Light guide 7a ... 1st main surface 7b ... 2nd main surface 7L ... Side end surface (light incident surface)
7S ... side end face 8 ... diffusion sheet 9, 10 ... deflection plate 11 ... liquid crystal panel 18 ... light deflecting element 19 ... optical element 20 ... prism sheet 23 ... substrate 23a ... light exit surface 23b ... light incident surface 24 ... prism lens 28 ... Deflection separation sheet 30 ... Bezel 31 ... Light guide region K ... Emission light F from illumination device ... Direction of observer

Claims (9)

A translucent light guide,
The light guide has a first main surface, a second main surface facing the first main surface, and four side end surfaces connecting the first main surface and the second main surface,
A plurality of light sources facing at least one side end face of the four side end faces are arranged side by side in the extending direction of the side end face,
The first main surface is formed with a light deflecting element that deflects light guided through the light guide body toward the second main surface,
Of the four peripheral edges along the four side end faces of the first main surface, one or two peripheral edges have a belt-like bezel on which the light deflection element is not formed.
A light guide characterized by that. The light guide according to claim 1,
Depending on the distance from the side end face where the light source faces, any one of dot size, shape, and arrangement interval is different.
A light guide characterized by that. The light guide according to claim 1 or 2,
The portion where the area occupation density of the light deflection elements in the first main surface is 50 to 95% is a bezelless portion that does not have the bezel among the peripheral portions of the four sides of the first main surface. ,
A light guide characterized by that. The light guide according to claim 3,
The total length of the portion where the area occupation density of the light deflection element is 50 to 95% along the peripheral edge of the first main surface is 0.1 to 30% with respect to the total length of the bezelless portion.
A light guide characterized by that. The light guide according to any one of claims 1 to 4,
The light deflection element has a shape having a height difference with respect to the first main surface, and a height difference of the light deflection element with respect to the first main surface is not less than 5 μm and not more than 70 μm.
A light guide characterized by that. The light guide according to any one of claims 1 to 5,
The second main surface has an uneven optical element that deflects light emitted from the second main surface to the outside of the light guide,
A light guide characterized by that. The light guide according to any one of claims 1 to 6,
Antistatic treatment on the surface,
A light guide characterized by that. An illumination device disposed behind a translucent image display element that defines a display image,
A light source;
The light guide plate according to any one of claims 1 to 7, which guides light from the light source;
At least one optical sheet through which diffused light emitted from the light guide plate is transmitted;
A lighting device comprising: A transmission illumination type image display element that defines a display image according to transmission / light-shielding in pixel units;
The illumination device according to claim 8 disposed on a back surface of the image display element;
A display device comprising:

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