JP4307137B2 - Light guide member, surface light source device including the light guide member, liquid crystal display device including the light guide member as a surface light source, and method for processing the light guide member - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides, for example, a light guide member mounted on a transmissive or transflective liquid crystal display panel or an electronic device including the same as a display screen, a surface light source device including the light guide member, and a surface of the light guide member. The present invention relates to a liquid crystal display device provided as a light source and a method for processing the light guide member.
[0002]
In addition, the present invention provides, for example, a backlight type or front light type display device or a light guide member mounted on an electronic apparatus including the display device as a display screen, a surface light source device including the light guide member, and the light guide member. And a processing method of the light guide member.
[0003]
[Prior art]
2. Description of the Related Art Conventionally, a light guide member is mounted on a backlight unit such as a liquid crystal display device for the purpose of reducing luminance unevenness (for example, see Patent Document 1).
[0004]
And as a conventional light guide member, the structure which formed the prism in the reflective surface facing the output surface (for example, refer patent document 2), prism processing is given to the reflective surface facing the output surface, and sticking to an output surface is prevented. For this reason, a configuration in which convex stripes (which do not affect the optical characteristics) are formed (see, for example, Patent Document 3), and a reflective surface facing the exit surface is subjected to hairline processing instead of a prism (for example, Patent Document 4) Or a configuration in which a prism is formed on the exit surface and a reflective surface facing the exit surface (see, for example, Patent Document 5).
[0005]
[Patent Document 1]
JP-A-9-184920 [Patent Document 2]
JP-A-11-219609 [Patent Document 3]
JP 2000-56137 A [Patent Document 4]
Japanese Patent Laid-Open No. 51-88042 [Patent Document 5]
Japanese Patent Laid-Open No. 10-282342.
[0006]
[Problems to be solved by the invention]
9 includes a transmissive or transflective electro-optical (liquid crystal, LCD) panel 2 in which a plurality of pixels are formed in a matrix, and a diffusion sheet provided on the back surface of the panel 2. Alternatively, a translucent sheet member 3 such as a prism sheet, a translucent light guide member 34 provided on the back surface of the sheet member 3, a reflection member 5 disposed on the back surface of the light guide member 34, and a light guide The reflective frame 6 that covers each surface other than the incident surface 4a of the light member 34, and a linear shape (such as a cold-cathode tube) that receives light from the incident surface 4a of the light guide member 34 or a plurality of dot shapes (such as a white LED). The light source 7 is provided.
[0007]
The light emitted from the light source 7 enters from the incident surface 4 a of the light guide member 34, is reflected by the reflective surface 4 b and the reflective member 5 of the light guide member 34, passes through the light guide member 34, and is transmitted by the sheet member 3. The panel 2 is illuminated after being corrected in the normal direction.
[0008]
In the above configuration, in Patent Documents 1 and 2, the light emission efficiency from the emission surface 34b is increased by forming the triangular prism groove 4e on the reflection surface 34a facing the emission surface 34b of the light guide member 34. However, when the prism groove 4e is formed on the reflecting surface 4a and the exit surface 34b is not processed while being flat, particularly in the case of a point light source, the luminance distribution in the vicinity of the light source becomes bright at a position straight from the light source, In the region between the point light sources, luminance unevenness that is dark occurs.
[0009]
The prism groove 4e formed on the reflecting surface 4a is formed in a linear shape parallel to the incident surface 4a and over the entire width. Therefore, when the emission surface 34b is viewed from above when the light source is turned on, the linear stripes are formed. Can be done.
[0010]
In addition, as in Patent Document 4, when the hairline processing is performed on the reflection surface facing the emission surface instead of the prism, the processing surface becomes rough and the amount of light emitted in the vicinity of the light source increases.
[0011]
Furthermore, as in Patent Documents 3 and 5, when processing is performed on both the exit surface and the reflective surface facing the exit surface, the exit surface is not roughened and the light exit direction is always constant. So the diffusion effect is low. Further, the regular widthwise grooves cause a moire phenomenon with the liquid crystal pixels, and eventually a diffusion sheet or the like is required, which causes problems such as a reduction in light amount and an increase in cost.
[0012]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a light guide member capable of suppressing luminance unevenness over the entire area of the emission surface and achieving uniform brightness, a surface light source device including the light guide member, and the light guide. It is to provide a liquid crystal display device including a member as a surface light source and a method for processing the light guide member.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, according to the present invention, an incident surface for incident light from a point light source, a reflecting surface for reflecting light incident from the incident surface, and the reflecting surface light guide member disposed opposite and a emission surface for emitting the light reflected by the reflecting surface, the reflecting surface, regular unevenness in a direction along the said incident surface is formed, on the emission surface The average surface roughness in the direction along the end surface facing the incident surface from the incident surface is 0.01 to 0.5 μm, and the average surface roughness in the direction along the incident surface is 0.01 to 1.0 μm. Irregular surface irregularities are formed, and the surface accuracy of the irregularities in the direction along the end surface facing the incident surface from the incident surface of the exit surface is set to a value smaller than the surface accuracy of the irregularities in the direction along the incident surface. .
[0014]
The surface light source device according to the present invention includes the light guide member.
[0015]
The liquid crystal display device according to the present invention includes the light guide member as a surface light source.
[0016]
Further, according to the present invention, an incident surface on which light from a point light source is incident, a reflecting surface that reflects light incident from the incident surface, and light that is disposed opposite to the reflecting surface and reflected by the reflecting surface working method of the light guide member having an exit surface for emitting, in a state where polycrystalline granules have contacted with the exit surface of the light guide member rotating member having an adhesive surface, said guide and said rotary member The light member is relatively moved from the incident surface in a direction along the end surface facing the incident surface, the exit surface is ground along the thickness direction, and the exit surface is moved from the entrance surface to the exit surface. An irregular surface having an average surface roughness in the direction toward the end surface facing the incident surface of 0.01 to 0.5 μm and an average surface roughness in the direction along the incident surface of 0.01 to 1.0 μm. An unevenness is formed, in a direction along the end surface facing the incident surface from the incident surface of the emission surface. The surface accuracy of the unevenness was set to a value smaller than the surface accuracy of the unevenness in the direction along the incident surface .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0018]
The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.
[0019]
[Configuration of display device]
FIG. 1 is an exploded perspective view (a) and a side sectional view (b) showing a display device according to an embodiment of the present invention, and FIG. 2 is a plan view (a) of a light guide member according to the embodiment of the present invention. It is a front view (b). In the following description, members having the same functions as those of the conventional configuration shown in FIG. 9 are denoted by the same reference numerals.
[0020]
As shown in FIGS. 1 and 2, a backlight type display device 1 exemplified as an embodiment according to the present invention includes a transmissive or semi-transmissive electro-optical (liquid crystal) in which a plurality of pixels are formed in a matrix. LCD) panel 2, a translucent sheet member 3 such as a diffusion sheet or a prism sheet provided on the back surface of the panel 2, a translucent light guide member 4 provided on the back surface of the sheet member 3, A reflection member 5 disposed on the back surface of the light guide member 4, a reflection frame 6 covering each surface other than the incident surface 4 a of the light guide member 4, and a line for entering light from the incident surface 4 a of the light guide member 4. And a plurality of point-like (white LED etc.) light sources 7.
[0021]
The light guide member 4 has an incident surface 4a on which light from a light source is incident, a reflective surface 4b that diffuses and scatters light incident from the incident surface 4a, and is disposed so as to face the reflective surface 4b. The output surface 4c that emits the light reflected by the surface 4b and the end surface 4d that is parallel to the incident surface 4a and that faces the incident surface 4a are configured by a rectangular plate having a substantially uniform thickness. ing. The thickness of the light guide member 4 is not limited to a uniform configuration, and may be a configuration in which the thickness changes linearly or discontinuously (non-linearly) from the incident surface 4a toward the end surface 4d.
[0022]
The light guide member 4 is made of a translucent material such as transparent acrylic, polycarbonate (including highly transparent), urethane, zeonore, and the like.
[0023]
The reflecting surface 4b of the light guide member 4, the incidence surface 4 along the a (Y direction) cross section of the triangular regularly along the X direction and the like linear prism grooves or hemispherical dot pattern ( A periodic uneven shape 4e is formed, and a vertical stripe pattern is formed in the Y direction when the emission surface 4c is viewed from the plane. The uneven shape 4e is preferably formed by grinding.
[0024]
The uneven shape 4e formed on the reflection surface 4b has the effect of diffusing the light incident from the incident surface 4a and the function of bending the output surface 4c. However, as a function of the surface light source, the luminance of the over the entire surface is required to be uniform, strong light emission is undesirable in the vicinity of the incidence surface 4 a, electrically bending of light becomes extremely light Rukoto are allowance to avoid such in the hinder.
[0025]
The output surface 4c has an arithmetic average surface roughness Ra of 0.01 to 0.5 μm in a direction (X direction) along the end surface 4d facing the incident surface 4a from the incident surface 4a by grinding processing described later. Thus, a fine and irregular concavo-convex shape 4f having an arithmetic average surface roughness Ra in a direction along the incident surface 4a (Y direction) of 0.01 to 1.0 μm is formed and roughened.
[0026]
[Processing method of exit surface of light guide member]
Next, the processing method of the output surface of the light guide member of this embodiment will be described.
[0027]
FIG. 4 is a diagram illustrating a method for processing the exit surface of the light guide member.
[0028]
As shown in FIG. 4, the exit surface 4 c of the light guide member 4 is ground by a disk-shaped grinding blade (grinding stone) 11 as a rotating body. On the outer surface including the outer peripheral edge (grinding surface 11a) in the radial direction of the grinding blade 11, a polycrystalline granular material such as diamond is adhered as a grain with a binder. The grinding blade 11 has a diameter of φ50 to 60 mm, a thickness (width of the grinding surface) L1 of 0.1 to 0.5 mm (0.2 mm in this embodiment), and a high R shape (roundness) of the grinding surface 11a. The length L2 has a substantially flat shape of about 0.09 mm in the radial direction.
[0029]
At the time of processing, the light guide member 4 is chucked on a table (not shown) that can reciprocate in the X direction and the Y direction, and the grinding blade 11 is moved in the relative movement direction of the light guide member 4 at a high speed of 10,000 to 30,000 rpm. Rotate in the same direction (right rotation in FIG. 3), and fix the grinding blade 11 in a state where the grinding surface 11a of the grinding blade 11 is adjusted to a height at which it is in contact with the light exit surface 4c of the light guide member 4 with a predetermined pressing force. By moving the table in the direction of arrow S1 while moving the light guide member 4 relative to the grinding blade 11 from the incident surface 4a toward the end surface 4d, a feed speed of about 0.5 to 10 mm / second in the X direction. And the exit surface 4c is ground in the thickness direction at a predetermined grinding allowance 12 (forward grinding).
[0030]
Thereafter, the light guide member 4 is moved in the direction (Y direction) along the incident surface 4a with a feed amount (pitch) of about 10 to 100 μm (Y direction feed) by moving the table in the arrow S3 direction.
[0031]
Next, the grinding blade 11 is rotated in the opposite direction to the forward grinding so as to be in the same direction as the relative movement direction of the light guide member 4 (left rotation in FIG. 3), and the table is moved in the direction of the arrow S2 opposite to the arrow S1. By moving, the light guide member 4 is moved from the end face 4d toward the incident surface 4a at a relatively similar feed speed in the X direction to perform grinding in the X direction (return grinding).
[0032]
By performing the entire surface grinding for the exit surface 4c of the light guide member 4 by the above method, the direction (X direction) toward the end face 4d facing the incidence surface 4 a to the incidence surface 4 a on the exit surface 4c the average surface roughness Ra 0.5μm 0.01, irregular uneven shape 4f of the average surface roughness Ra 1.0μm 0.01 to direction (Y-direction) along the incidence surface 4 a is formed .
[0033]
In the above embodiment, the light guide member 4 is moved while the grinding blade 11 is fixed, but the light guide member 4 may be fixed and the grinding blade 11 may be moved relatively. Further, when the table is moved in the direction of arrow S3, the table is fed in the Y direction so that the machined surface just ground and the machined surface to be ground next overlap each other. In addition, even in the cutting process or the same grinding process, the processed surface becomes a mirror surface, so that the effect of increasing the brightness and uniformity as in the present embodiment cannot be obtained.
[0034]
[Grinding result]
5 to 7 show the measurement results of the surface accuracy (a) in the Y direction and the surface accuracy (b) in the X direction of the exit surface when the feed amount in the Y direction is ground at 100 μm, 50 μm, and 10 μm. FIG.
[0035]
As shown in FIG. 5 to FIG. 7, the average surface roughness Ra along the Y direction of the emission surface 4 c is 0.5 μm or less, and the emission surface 4 c has a substantially regular uneven shape in the Y direction. Yes. Further, the surface accuracy along the Y direction of the emission surface 4c is 10 μmp-p (peak to peak) or less. The surface accuracy in the Y direction depends on the thickness L1 of the grinding blade 11 and the feed speed.
[0036]
As shown in FIGS. 5 to 7, the average surface roughness Ra along the X direction of the emission surface 4c is 0.3 μm or less, and the emission surface 4c has irregular irregular shapes in the X direction. Further, the surface accuracy along the X direction of the emission surface 4c is 3 μmp-p or less. The surface accuracy in the X direction is irregular depending on the grain size of the polycrystalline particles of the grinding blade 11.
[0037]
Here, when the X direction of the exit surface 4c is viewed, the uneven shape 4f is a groove substantially parallel to the light traveling direction from the entrance surface 4a to the end surface 4d (substantially perpendicular to the entrance surface 4a). The average surface roughness Ra and the surface accuracy are both smaller than those in the Y direction. The reason is that, in order to aim for uniform in-plane brightness, extreme obstruction of the light guide must be avoided. The concavo-convex shape 4e (linear prism groove or hemispherical dot pattern) provided on the reflecting surface 4b is provided with a gradation so that the amount of emitted light in the X direction is uniform to some extent at any position. When the surface 4c is extremely roughened, a large amount of light (R2 in FIG. 3) that should originally be guided in a region near the incident surface 4a is emitted in the vicinity of the incident surface 4a (R1 in FIG. 3). As a result, the luminance in the vicinity of the end surface 4d far from the incident surface is lowered. The light R1 emitted from the exit surface 4c is ideally emitted in the normal direction with respect to the exit surface 4c, but the emitted light and the normal line when the exit surface 4c is extremely roughened. As a result, the angle is increased and the luminance is lowered. Therefore, as shown in FIGS. 5 to 7, the emission surface 4 c has an irregular concavo-convex shape, but it is better that the variation of the surface accuracy is small, and it is desirably 3 μmp-p or less experimentally.
[0038]
By roughening the exit surface 4c, as shown in FIG. 3, in the conventional configuration in which the exit surface is not roughened, the light R incident on the entrance surface 4a from the light source 7 is constant with respect to the exit surface 4c. When the angle θ1 is equal to or larger than the angle θ1, the light is emitted as the light R1 from the light emitting surface 4c, and uneven brightness is generated in the vicinity of the light source 7. The light can be guided to a position farther from the light source 7 toward the end face 4d while being reflected in all directions in the −Y plane. In addition, since refraction of light is suppressed in the X direction and refraction is promoted in the Y direction, luminance unevenness in the vicinity of the light source is suppressed, and the luminance is increased and made uniform over the entire emission surface 4c. A light source can be realized.
[0039]
FIG. 8 shows a comparison of each surface emission state of a conventional light guide member (a) having a non-roughened exit surface and a light guide member (b) of this embodiment having a rough exit surface. In the conventional structure (a), the luminance unevenness in the vicinity of the incident surface 4a is conspicuous, whereas in the structure (b) of the present embodiment, the luminance unevenness is greatly improved. In addition, it can be seen that the light emission efficiency is high without lowering the average luminance value of the emission surface 4c as compared with the conventional case, and that the luminance can be increased and made uniform over the entire emission surface 4c.
[0040]
FIG. 8 illustrates the case where the feed amount in the Y direction is 50 μm. However, when the feed amount is 100 μm, the amount of emitted light in the region close to the light source increases, and when the feed amount is 10 μm, from the light source as shown in FIG. Since bright lines can be seen, the optimum feed amount in the Y direction is about 50 μm.
[0041]
As an application example of the light guide member of the present embodiment, a surface light source device including the light guide member 4 (configuration including each element of reference numerals 3, 4, 5, 6, and 7) or the light guide member as a surface light source. It is used for liquid crystal screens such as small portable terminals and mobile phones in liquid crystal display devices (configurations having elements 2, 3, 4, 5, 6, and 7).
[0042]
【The invention's effect】
As described above, according to the present invention, luminance unevenness can be suppressed and uniform luminance can be achieved without impairing light output efficiency over the entire exit surface of the light guide member.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view (a) and a side sectional view (b) showing a display device according to an embodiment of the present invention.
FIG. 2 is a plan view (a) and a front view (b) of a light guide member according to an embodiment of the present invention.
FIG. 3 is a diagram showing a part of a side cross section for explaining the operation of the light guide member of the present embodiment.
FIG. 4 is a diagram for explaining a method of processing an exit surface of a light guide member.
FIG. 5 is a diagram showing the measurement results of the surface accuracy (a) in the Y direction and the surface accuracy (b) in the X direction of the exit surface when grinding is performed with the feed amount in the Y direction being 100 μm.
FIG. 6 is a diagram showing the measurement results of the surface accuracy (a) in the Y direction and the surface accuracy (b) in the X direction of the exit surface when grinding is performed with the feed amount in the Y direction being 50 μm.
FIG. 7 is a diagram showing the measurement results of the surface accuracy (a) in the Y direction and the surface accuracy (b) in the X direction of the exit surface when grinding is performed with the feed amount in the Y direction being 10 μm.
FIG. 8 shows a comparison of each surface emission state of a conventional light guide member (a) having a non-roughened output surface and a light guide member (b) of the present embodiment having a rough output surface. FIG.
FIG. 9A is a front view of a conventional light guide member, FIG. 9B is a plan view of the conventional light guide member, and FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Electro-optical panel 3 Sheet | seat member 4 Light guide member 4a Incident surface 4b Reflective surface 4c Output surface 4d End surface 4e Regular uneven | corrugated shape 4f Irregular uneven | corrugated shape 5 Reflective member 6 Reflective frame 7 Light source 11 Grinding blade 12 Grinding allowance

Claims (4)

An incident surface on which light from a point light source is incident, a reflective surface that reflects light incident from the incident surface, and an output surface that is disposed opposite to the reflective surface and emits light reflected on the reflective surface A light guide member,
Regular irregularities are formed on the reflecting surface in a direction along the incident surface,
The exit surface has an average surface roughness of 0.01 to 0.5 μm along the end surface facing the entrance surface from the entrance surface, and an average surface roughness along the entrance surface of 0.1 μm. Irregular irregularities of 01 to 1.0 μm are formed ,
The light guide member , wherein the surface accuracy of the unevenness in the direction along the end surface facing the incident surface from the incident surface of the exit surface is set to a value smaller than the surface accuracy of the unevenness in the direction along the incident surface .   A surface light source device comprising the light guide member according to claim 1.   A liquid crystal display device comprising the light guide member according to claim 1 as a surface light source. An incident surface on which light from a point light source is incident, a reflective surface that reflects light incident from the incident surface, and an output surface that is disposed opposite to the reflective surface and emits light reflected on the reflective surface A method of processing a light guide member,
In a state where the polycrystalline granules have contacted with the exit surface of the light guide member rotating member having an adhesive surface, opposite ends to the incident surface and the light guide member and the rotating member from the incident surface Relatively moving in the direction along the surface , grinding the emission surface along the thickness direction,
The average surface roughness in the direction from the incident surface to the end surface facing the incident surface is 0.01 to 0.5 μm, and the average surface roughness in the direction along the incident surface is 0. Forming irregular irregularities of 01 to 1.0 μm ,
The surface accuracy of the irregularities in the direction along the end surface facing the incident surface from the incident surface of the exit surface is set to a value smaller than the surface accuracy of the irregularities in the direction along the incident surface .

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