JP2009140743A - Light guide plate, and surface light-emitting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate capable of alleviating visual recognition of a bright line, and achieving sufficient homogenization of brightness in a surface even in a plan vision from a wide angle against a light-emitting face, and to provide a surface light-emitting device using the same. <P>SOLUTION: This is the light guide plate having a side face to which light from a point light source is made incident, a rear face in which a mirror surface flat region and a mirror surface reflecting region are arranged in this order from the side face side and the light from the point light source is reflected/diffused, and a front face from which the light from the point light source is emitted. This is the light guide plate in which the mirror surface flat region has a first light diffusion band while the mirror face reflection region has a second light diffusion zone, in which respective haze values are uniform in the first light diffusion zone and the second light diffusion zone, and in which the haze value of the first light diffusion zone is larger than that of the second light diffusion zone. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light guide plate and a surface light emitting device using the same.

2. Description of the Related Art Conventionally, surface light-emitting devices have been used for edge light type light guide plates used in small monitor applications such as digital still cameras, digital video cameras, mobile phones and portable terminals, notebook personal computers and liquid crystal televisions.
In such a surface light emitting device, the light emitted from the light source enters the light guide plate, and dot printing, embossing, and mirror finishing are performed on the back surface of the light guide plate in order to obtain uniform brightness in the surface by total reflection. Further, a process for imparting a light reflecting function such as a straight V-groove is applied.
However, when mirror reflection by a straight V-groove is used, problems such as the appearance of bright lines in the surface occur due to the shape and the like.
On the other hand, there has been proposed a method of providing orientation adjusting means between the light incident surface of the light guide plate and the display area (for example, Patent Document 1).

JP 2003-100132 A

By providing the alignment adjusting means as described above, the alignment distribution inside the light guide plate can be expanded while using the linear V-groove, and the in-plane luminance can be improved.
However, although the bright line in the observation from the normal direction of the light emitting surface is improved, the bright line in the oblique direction from the normal direction of the light emitting surface is still not improved, and further improvement is required at present. is there.

  The present invention has been made in view of the above problems, and a light guide plate capable of reducing the visibility of bright lines even in a plan view from a wide range of angles with respect to a light emitting surface and achieving uniform luminance in a plane. Another object is to provide a surface light emitting device using the same.

The light guide plate of the present invention has a side surface on which light from a point light source is incident,
A specular flat region and a specular reflection region are arranged in this order from the side surface side, and a back surface that reflects / diffuses light from the point light source,
A light guide plate having a surface for emitting light from the point light source,
The specular flat region has a first light diffusion band, the specular reflection region has a second light diffusion band,
Each of the first light diffusion band and the second light diffusion band has a uniform haze value,
The haze value of the first light diffusion band is larger than the haze value of the second diffusion band.
In such a light guide plate, the length ratio of the first light diffusion band to the second light diffusion band is preferably 1:12 or more and 1: 3 or less.
The first light diffusion band preferably occupies an area of 20% or more and 50% or less of the specular flat region.
Furthermore, it is preferable that the second light diffusion band occupies an area of 4% or more and 10% or less of the specular reflection region.
The surfaces of the first light diffusion band and the second light diffusion band are formed with a plurality of irregularities, and the deepest point of the recess in the second light diffusion band is from the center point of the recess. It is preferable that it is formed by being biased in the direction of the side surface opposite to the side surface.
Furthermore, the surface light-emitting device of the present invention includes the light guide plate described above and a point light source provided on an end surface of the light guide plate.

  According to the present invention, by performing the primary diffusion of the light incident from the point light source in the first light diffusion band, the primary diffusion with respect to the bright line in the normal plane view is performed, and at the same time, the oblique direction from the normal plane view. Can be mitigated with respect to the bright line. In addition, the second light diffusion band can further promote the relaxation of the bright line with respect to the bright line in the normal plane view, and the luminance can be sufficiently uniform even when viewed from a wide angle with respect to the light emitting surface. Can be achieved.

  The light guide plate of the present invention is usually formed of a material excellent in light transmittance. For example, the basic planar shape is the type and number of light emitting devices used, the shape and performance of the intended surface light emitting device and the monitor used, etc. For example, a circular shape, a quadrangular shape, a polygonal shape, and a shape approximating these are suitable. Examples of the material excellent in light transmittance include acrylate, polycarbonate (PC), polymethyl methacrylate (PMMA), acrylic and cycloolefin resin materials, and materials having light transmittance equivalent to or higher than these materials.

  The light guide plate is usually plate-shaped, a side surface on which light from a point light source described later is incident, a back surface that reflects / diffuses light from the point light source, and a surface that emits light from the point light source (hereinafter referred to as “light source”). It may be referred to as “light emitting surface”). The thickness of the light guide plate may be uniform over the whole when not considering the processing state of the front and back surfaces, which will be described later, and is partially different, for example, the thickness gradually decreases with increasing distance from the point light source. Also good.

  The side surface of the light guide plate faces the point light source in order to make light incident efficiently. For example, when the basic planar shape is a substantially square shape, the side surface may be a side surface on one side, a long side, or a short side, or may be a shape with chamfered corners and a side surface of the corner portion. In addition, the side surface may be linear when viewed from the light emitting surface side, or may have irregularities such as a circle and a polygon so as to surround a point light source to be described later. The side surface is preferably smooth.

  On the back surface of the light guide plate, a specular flat region and a specular reflection region are arranged in this order from the side surface side (that is, the side closer to the point light source).

  The specular flat region includes a first light diffusion band in the region. Usually, the surface is generally flatter than the specular reflection region described later, and the specular flat region that is not the first light diffusion band has a flatness of λ / 8 (less than 0.1 μm) as measured by a laser interferometer. It is preferable.

The first light diffusion band has a roughened surface, that is, a plurality of irregularities are formed on the surface, and has a function of irregularly reflecting light in an unspecified direction. This unevenness can be represented by, for example, a haze value. It is suitable that the haze value of the first light diffusion band is uniform within the band, for example, a haze value Th (JIS K 7105, the same applies hereinafter) in a range of about 10% or less and about 60% or more. It is suitable to be. For example, the light diffusing band is irregularly or regularly processed by using a known method such as blasting or laser dot texture processing, or by using a mold subjected to such roughing. It can be realized by transferring the shape.
In addition, it is suitable that the number density of the unevenness | corrugation which the 1st light diffusion zone has on the surface is larger than the 2nd light diffusion zone mentioned later, and the diameter of an unevenness | corrugation is small from another viewpoint. From another viewpoint, it is suitable that the height difference is set to be large.

  The length of the specular flat region and the first light diffusion band can be appropriately adjusted in consideration of, for example, the size of the light guide plate, the type and number of point light sources used, the performance of the light guide plate to be obtained, and the like. . For example, when the total length of the light guide plate (for example, the length in the direction of arrow u in FIG. 1A) is about 40 to 80 mm, about 1 to 5 mm and about 0.4 to 2.0 mm, respectively, and 1.5 to 4 mm, respectively. And about 0.5 to 1.0 mm. From another viewpoint, lengths of about 1 to 10% and about 0.1 to 5% of the total length of the light guide plate, and about 0.5 to 3% and about 2 to 6% are mentioned. The light diffusion effect can be adjusted by adjusting the degree and length of the rough surface of the first light diffusion band. From yet another point of view, the first light diffusion band may occupy an area of about 20 to 50% of the specular flat region. Accordingly, it is possible to prevent strong light emission in the first diffusion band, to secure the light incident efficiency, and to prevent a decrease in luminance. In addition, it is preferable that the first light diffusion band is disposed outside a display region (two-dot chain line in FIG. 1A) in a monitor on which a surface light emitting device including the light guide plate is mounted.

  The first light diffusion band formed in the specular flat region can be arranged in various shapes and desired positions. Usually, it is suitable that the first light diffusion band is arranged so as to be biased toward the side closer to the specular reflection region. When the planar shape of the specular flat region is substantially square, it is longer than the specular flat region. It is suitable that the length is a substantially square. Moreover, it may be an irregular shape such that a part of the outer shape of the first light diffusion band is defined by a curve depending on the position of the point light source.

The specular reflection region has a function of totally reflecting light and emitting light to the light emitting surface side. For this purpose, the specular reflection region usually has regular prism protrusions on the surface thereof. The specular reflection region includes a second light diffusion band in the region. Suitably, the specular reflection region is arranged adjacent to the specular flat region.
Plural prism protrusions are linearly formed in the width direction of the light guide plate (direction orthogonal to the length direction, hereinafter the same), and a plurality of prism protrusions are formed in the length direction. The prism protrusions may be formed continuously in the length direction in the specular reflection region (continuous: refer to the shape in FIG. 1F) or at a predetermined interval (discontinuous: refer to FIG. 1D). ) May be formed. The cross-sectional shape is not particularly limited, and for example, the apex angle is about 50 to 160 degrees, further about 60 to 120 degrees, and the height (t in FIG. 1D) is, for example, 0.1 About 50 μm. The pitch (s in FIG. 1D) is, for example, about 10 to 300 μm, and further about 40 to 80 μm.

  The second light diffusion band has a roughened surface, that is, a plurality of irregularities are formed on the surface, and has a function of irregularly reflecting light in an unspecified direction. This unevenness can be represented by, for example, a haze value. Therefore, the second light diffusion band has both the prism protrusion and the rough surface at the same time. The rough surface (unevenness) may be formed on an inclined surface constituting the prism protrusion, or the prism protrusions are formed at predetermined intervals in the length direction as shown in FIG. 1D. In addition, it is preferably formed on the inclined surfaces constituting the prism protrusions and also on the surfaces between the prism protrusions. By having such a rough surface, it is possible to sufficiently draw out the light diffusion effect, to secure or improve the luminance on the light emitting surface, and to improve the uniformity of the luminance.

  The light diffusion band can be formed by the same method as described above. Here, the haze value of the second light diffusion band is suitably uniform within the band, and it is suitable that the haze value is smaller than that of the first light diffusion band. For example, the range is about 85% or less and about 60% or more. From another viewpoint, it is suitable that the haze value of the second light diffusion band is larger than the haze value of the first light diffusion band. In other words, it is suitable that the second light diffusion band has a smaller number density of unevenness on the surface than the first light diffusion band, and the diameter of the unevenness is larger from another viewpoint. From another point of view, it is suitable that the height difference is set small. Specifically, the haze value of the first light diffusion band is suitably 2 times or more of the haze value of the second diffusion band, and is preferably set to 4 times or less. In the present invention, as the light guide plate is moved away from the point light source, the surface roughness does not gradually change, and the region having a small surface roughness and the region having a large surface roughness are arranged with a clear boundary. Thereby, the bright line in the visual recognition from the normal direction of the light guide plate can be further relaxed, and unbalance of the entire light emitting surface due to strong light emission can be further prevented.

  The lengths of the specular reflection region and the second light diffusion band can be appropriately adjusted in consideration of, for example, the size of the light guide plate, the type and number of point light sources used, the performance of the light guide plate to be obtained, and the like. However, when the total length of the light guide plate (for example, the length in the direction of the arrow u in FIG. 1A) is about 40 to 80 mm, about 35 to 79 mm and about 2 to 10 mm, and further about 78.5 to 36 mm and 2. About 5-5.0 mm is mentioned. From another viewpoint, lengths of about 90 to 99% and about 0.5 to 25% of the total length of the light guide plate, and about 97 to 99.5% and about 10 to 30% are mentioned. From another viewpoint, the second light diffusion band may occupy an area of about 4 to 10% of the specular reflection region. Further, the second light diffusion band may be set so that the length ratio between the first light diffusion band and the second light diffusion band is about 1:12 to 1: 3. Thereby, it is possible to reduce the bright line in the visual recognition from the normal direction of the light guide plate and to prevent unbalance of the entire light emitting surface due to strong light emission.

  Note that the second light diffusion band formed in the specular reflection region can be arranged in various shapes and desired positions. Usually, the second light diffusion band is suitable to be biased to the side closer to the specular flat region, and when the planar shape of the specular reflection region is substantially square, it is longer than the specular reflection region. It is suitable that the length is a substantially square. Also, the shape and position of the first light diffusion band may be an irregular shape such that a part of the outer shape of the second light diffusion band is defined by a curve.

In both of the first and second light diffusion bands, the light diffusion effect from the point light source increases as the band increases in width or area, while the light guide amount in the intended direction due to irregular reflection. It is preferable to occupy only a part of these areas rather than occupying the entire area of the specular flat area or the specular reflection area.
The first and second light diffusion bands are preferably adjacent to each other. However, depending on the design and characteristics of the light guide plate, the type and number of point light sources used, the specular flat region and / or the specular reflection region is sandwiched. It may be arranged.

In addition, the individual concave portions and / or convex portions of the concave and convex portions that define the surface roughness in the first light diffusion band and the second light diffusion band do not necessarily have a bilaterally or point-symmetric shape, For example, the shape may be biased. In other words, the shape may not be a shape such as a hemisphere or a triangular pyramid (for example, refer to the shape as shown in FIG. 1F), and a shape in which the deepest or highest point is shifted from the center of each concave or convex portion (for example, (See shape as shown in 1D 12aa). In particular, it is preferable that the deepest point of the concave portion in the second light diffusion band has a shape that is deviated from the central point of the concave portion toward the side surface opposite to the light source. Thereby, according to the specification of a light-guide plate, it becomes possible to adjust suitably the relaxation of a bright line, the balance of light diffusion, the improvement of a brightness | luminance, etc. Moreover, it is preferable that the depth and / or height of the concave portion and / or the convex portion in the second light diffusion band is formed so as to increase from one side surface to the side surface opposite to the side surface. .
Such a left-right asymmetrical or point-asymmetrical concavo-convex shape allows the object to be blown in the blasting process described above to be in an arbitrary direction, preferably from the light source side, instead of from the normal direction of the light guide plate surface. It can form by inclining from and spraying. For example, the inclination angle at this time is suitably about 30 ° or less from the normal direction of the surface of the light guide plate.

  The surface of the light guide plate is a surface that emits light from a point light source, and is preferably flat, for example, but may have irregularities, prism protrusions, etc. regularly or irregularly. . For example, a plurality of prism protrusions are linearly formed in the length direction of the light guide plate (for example, the length in the direction of arrow u in FIG. 1A) and in the width direction, and are continuous in the width direction in the region corresponding to the specular reflection region. Or you may arrange | position discontinuously. The cross-sectional shape is not particularly limited, and examples thereof include an apex angle of about 50 to 160 degrees, and further about 60 to 120 degrees. The height is, for example, about 0.1 to 50 μm, and the pitch is preferably smaller than that in the mirror reflection region on the back side, for example, about 1 to 50 μm, and further about 10 to 40 μm.

Moreover, the surface light-emitting device of this invention is comprised including the light guide plate mentioned above and the point light source provided in the end surface of this light guide plate.
As the point light source, a light source used for a monitor or a display, for example, an LED or the like can be used. The point light source is disposed so as to face the side surface of the light guide plate.
A prism sheet, a protective sheet, a reflection sheet, etc. having various functions such as light control and light diffusion are arranged on the light emitting surface of the light guide plate or the opposite surface, so as to face the light guide plate, and an appropriate stacking order. May be arranged.
As a prism sheet, what has arbitrary surface shapes, such as a predetermined prism pitch and height, formed of the material excellent in light transmittance, such as PET (polyethylene terephthalate), PC, PMMA, is mentioned, for example.
As the protective sheet, a sheet formed of a material excellent in light transmittance as described above is preferably used.
Examples of the reflective sheet include a silver deposited sheet having a high reflectance or a white PET material.

Hereinafter, embodiments of the light guide plate and the surface light emitting device of the present invention will be described in detail with reference to the drawings.
Example 1
As shown in FIGS. 1A to F, the light guide plate 10 of this embodiment has a basic plane shape formed by a thin plate made of polycarbonate so as to have a substantially square shape (about 65 mm × about 48 mm). An uneven surface 13 corresponding to the shape of the point light source 1 is formed on one side surface thereof so that light from the point light source 1 can be efficiently introduced.

On the back surface of the light guide plate 10, a specular flat region (length: about 2.3 mm) 11 and a specular reflection region (length: about 62 mm) 12 are formed in order from the side where the light source is arranged.
In the specular flat region 11, a first light diffusion band (length: about 0.3 mm) 11a is formed in a strip shape at a predetermined distance from the point light source (see FIG. 1C).
The first light diffusion zone 11a is roughened so that the haze value is uniform within the zone. For example, it has a haze value of about 80%.
In the specular reflection region 12, a second light diffusion band (length of about 4 mm) 12a is formed in a band shape so as to be adjacent to the first light diffusion band 11a.
The second light diffusion band 12a regularly has prism protrusions 12aa (see FIG. 1D) on the surface thereof. A plurality of prism protrusions 12aa are formed linearly in the width direction of the light guide plate 10 and in the length direction. The prism protrusion 12aa has a cross-sectional shape of, for example, an apex angle of about 110 to 115 ° and a height (t in FIG. 1D) that increases with distance from the light source, and is about 0.45 to 18.45 μm and a pitch ((FIG. 1D S) is about 140 to 230 μm.
The second light diffusion band 12a is roughened so that the haze is uniform in the band and the haze value is smaller than that of the first light diffusion band 11a. For example, it has a haze value of about 50%. In the roughened surface, the prism protrusions 12aa are formed at predetermined intervals in the length direction, and are not formed on the inclined surfaces constituting the prism protrusions 12aa, but on the surfaces between the prism protrusions 12aa. Is formed.

  On the surface of the light guide plate 10, prism protrusions 14 are regularly provided in a region corresponding to the specular reflection region. The prism protrusions 14 are formed in a straight line in the length direction of the light guide plate 10 and a plurality of the prism protrusions 14 in the width direction. The cross-sectional shape is, for example, an apex angle of about 128 °, the height is about 8.15 μm, and the pitch is about 35 μm.

Using such a light guide plate, luminance unevenness on the light emitting surface was measured. In the measurement, the light guide plate 10 in which four LEDs are arranged as the point light source 15 as shown in FIG. 1A is mounted on the support base 40 as the 3.0-type light guide plate panel 41 as shown in FIG. 2A. The measuring instrument 42 was opposed to the support base 40 in the vertical direction, and the light intensity along the line AA ′ in FIG. 1A was measured. The measurement was performed at 0 ° (viewing from the vertical direction), 3 °, and 8 ° with respect to the surface of the support base 40 for the light guide plate panel 41.
For comparison, a light guide plate substantially similar to the above example was prepared except that the first light diffusion band was not provided, and the measurement was performed in the same manner.
The results are shown in FIG. 2B.
In Example 1, substantially uniform light intensity is obtained at any viewing angle of 0 to 8 ° over the entire display or monitor display area of the light guide plate from the light source side, and uneven brightness in the surface is obtained. It was confirmed to be good. On the other hand, in the comparative example, it was confirmed that in any viewing angle, unevenness that can be visually recognized was observed with non-uniform light intensity.

As described above, the light guide plate of the present embodiment prevents strong light emission in the first light diffusion band, ensures the light incident efficiency, prevents the luminance from decreasing, and reduces the first light. The light diffusion effect can be adjusted by adjusting the degree and length of the rough surface of the diffusion band.
Further, by combining the first and second light diffusion bands, the light diffusion effect can be sufficiently extracted, the luminance on the light emitting surface can be ensured or improved, and the uniformity of the luminance can be improved. It is possible to further relax the bright line in visual recognition from the normal direction and the inclined angle, and to further prevent unbalance of the entire light emitting surface due to strong light emission.

Example 2
As shown in FIG. 3, the light guide plate 20 of this embodiment is not formed with irregularities for point light sources, chamfers both corners of one side surface of the light guide plate 20, and arranges LEDs as the point light sources 15 in that portion. Except for the above, the specular flat region 21, the first light diffusion band 21a, the specular reflection region 22, and the second light diffusion band 22a have substantially the same configuration as in the first embodiment.
Also in the obtained light guide plate, the same effect as in Example 1 is obtained.

Example 3
As shown in FIG. 4, the light guide plate 30 of this embodiment is not formed with irregularities for point light sources, chamfers both corners of one side of the light guide plate 30, and arranges LEDs as point light sources 15 in that portion. The third embodiment is substantially the same as the third embodiment except that the specular flat region 31, the first light diffusion band 31a, the specular reflection region 32, and the second light diffusion band 32 are arranged in parallel to the surface of the LED facing the light guide plate 30. It has the same composition as.
Incidentally, in this embodiment, the mirror flat region 31, the first light diffusion zone 31a, specular reflection area 32, the area of the second light diffusion zone 32, respectively, about 10.5 mm ^2, about 14.5 mm ² About 3100 mm ² and about 132.5 mm ² .
Also in the obtained light guide plate, the same effect as in Example 1 is obtained.

  The present invention can be widely applied to various surface light emitting devices such as small monitors such as digital still cameras, digital video cameras, mobile phones, and mobile terminals, particularly as edge light type light guide plates.

Schematic plan view (A) for explaining the light guide plate of the present invention, AA ′ cross-sectional view (B) in FIG. 1A, enlarged view (C) of X portion in FIG. 1B, enlarged view of Y portion in FIG. 1C (D), BB 'sectional drawing (E) of FIG. 1A, and the enlarged view (F) of Z part in FIG. 1E. It is the schematic of the principal part for demonstrating the method to measure the surface nonuniformity of the light in the light-guide plate of FIG. 1A. It is a table | surface which shows the result of having measured the surface nonuniformity of the light in the light-guide plate of FIG. 1A. It is a schematic plan view for demonstrating another light-guide plate of this invention. It is a schematic plan view for demonstrating another light-guide plate of this invention.

Explanation of symbols

10, 20, 30 Light guide plate 11, 21, 31 Specular flat area 11a, 21a, 31a First light diffusion band 12, 22, 32 Specular reflection area 12a, 22a, 32a Second light diffusion band 12aa, 14 Prism projection 13 Concavity and convexity 15 Point light source 40 Support base 41 Light guide plate panel 42 Measuring instrument

Claims (6)

A side surface on which light from a point light source is incident;
A specular flat region and a specular reflection region are arranged in this order from the side surface side, and a back surface that reflects / diffuses light from the point light source,
A light guide plate having a surface for emitting light from the point light source,
The specular flat region has a first light diffusion band, the specular reflection region has a second light diffusion band,
Each of the first light diffusion band and the second light diffusion band has a uniform haze value,
The light guide plate, wherein a haze value of the first light diffusion band is larger than a haze value of the second diffusion band.   The light guide plate according to claim 1, wherein a length ratio of the first light diffusion band to the second light diffusion band is 1:12 or more and 1: 3 or less.   The light guide plate according to claim 1, wherein the first light diffusion band occupies an area of 20% or more and 50% or less of the specular flat region.   The light guide plate according to claim 1, wherein the second light diffusion band occupies an area of 4% or more and 10% or less of the specular reflection region.   A plurality of irregularities are formed on the surfaces of the first light diffusion band and the second light diffusion band, and the deepest point of the concave portion in the second light diffusion band is the side surface from the central point of the concave portion. The light guide plate according to any one of claims 1 to 4, wherein the light guide plate is formed by being biased in a direction of a side surface on the opposite side.   A surface light emitting device comprising: the light guide plate according to claim 1; and a point light source provided on an end surface of the light guide plate.

Images