JP2004327077A - Light guide member, surface light source device equipped with it, liquid crystal display device equipped with light guide member as surface light source, and machining method of light guide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide uniform luminance by restraining luminance irregularity throughout the entire area of an emission surface of a light guide member. <P>SOLUTION: An irregular uneven shape 4f having an average surface roughness Ra of 0.01-0.5 μm in the X-direction along an incident surface 4a through an end 4d facing the the incident surface 4a and an average surface roughness Ra of 0.01-1.0 μm in the Y-direction along the incident surface 4a is formed on the emission surface 4c to roughen it. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides, for example, a transmissive or semi-transmissive liquid crystal display panel and a light guide member mounted on an electronic device including the same as a display screen, a surface light source device including the light guide member, and a light guide member including 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]
Further, the present invention provides, for example, a backlight type or front light type display device, a light guide member mounted on an electronic device 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 method of processing 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]
As a conventional light guide member, a prism is formed on a reflection surface facing an emission surface (for example, see Patent Document 2), and a prism processing is performed on a reflection surface facing the emission surface to prevent sticking to the emission surface. (For example, see Patent Literature 3), in which a hairline processing is performed instead of a prism on a reflection surface facing an emission surface (for example, Patent Literature 4) Or a configuration in which a prism is formed on an emission surface and a reflection surface facing the emission surface (for example, see 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]
JP-A-51-88042 [Patent Document 5]
JP-A-10-282342.
[0006]
[Problems to be solved by the invention]
A conventional display device 31 shown in FIG. 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. A light-transmitting sheet member 3 such as a prism sheet, a light-transmitting light guiding member 34 provided on the back surface of the sheet member 3, a reflecting member 5 disposed on the back surface of the light guiding member 34, A reflective frame 6 covering each surface other than the incident surface 4a of the light member 34, and a linear shape (such as a cold cathode tube) or a plurality of dot shapes (such as a white LED) for receiving light from the incident surface 4a of the light guide member 34; Light source 7.
[0007]
The light emitted from the light source 7 enters through the incident surface 4 a of the light guide member 34, is reflected by the reflection surface 4 b and the reflection 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-described configuration, in Patent Documents 1 and 2, a triangular prism groove 4e is formed on the reflection surface 34a facing the emission surface 34b of the light guide member 34, thereby increasing the light emission efficiency from the emission surface 34b. However, when the prism groove 4e is formed on the reflection surface 4a and the light exit surface 34b is flat and is not processed, especially in the case of a point light source, the luminance distribution near the light source becomes brighter at a position straight from the light source, Luminance unevenness such as darkening occurs in an area between the point light sources.
[0009]
Further, since the prism groove 4e formed on the reflection surface 4a is formed in a linear shape over the entire width and parallel to the incident surface 4a, a linear streak is obtained when the emission surface 34b is viewed from above when the light source is turned on. Can be done.
[0010]
Further, when hairline processing is performed instead of a prism on the reflection surface facing the emission surface as in Patent Literature 4, the processing surface becomes rough, and the amount of light output near the light source increases.
[0011]
Further, as described in Patent Documents 3 and 5, when processing is performed on both the exit surface and the reflection surface facing the exit surface, the exit surface is not roughened and the exit direction of light is always constant. Therefore, the diffusion effect is reduced. Further, regular grooves in the width direction cause a moiré phenomenon with the liquid crystal pixels, which eventually requires a diffusion sheet or the like, so that there are problems such as a decrease in light amount and an increase in cost.
[0012]
The present invention has been made in view of the above-described problems, and has as its object to suppress a luminance unevenness over the entire area of an emission surface and provide a light guide member capable of achieving uniform brightness, a surface light source device including the light guide member, and the light guide. An object of the present invention 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 on which light from a light source is incident, a reflecting surface for reflecting light incident from the incident surface, and a reflecting surface opposed to the reflecting surface. The light guide member includes a light exit surface that emits light reflected by the reflection surface. The light guide member has regular irregularities formed on the reflection surface in a direction along the light entrance surface. The average surface roughness in the direction along the end facing the incident surface is from 0.01 to 0.5 μm, and the average surface roughness in the direction along the incident surface is from 0.01 to 1.0 μm. Irregularities are formed.
[0014]
Further, a surface light source device according to the present invention includes the above light guide member.
[0015]
Further, a liquid crystal display device according to the present invention includes the light guide member as a surface light source.
[0016]
In addition, according to the present invention, an incident surface on which light from a light source is incident, a reflecting surface for reflecting light incident from the incident surface, and a light that is disposed to face the reflecting surface and emits light reflected by the reflecting surface. The processing method of the light guide member including the light exit surface is such that the rotator and the light guide member are in a state where the rotator having the surface to which the polycrystalline particles are bonded is in contact with the light exit surface of the light guide member. Is relatively moved from the incident surface in a direction along an end portion opposed to the incident surface, the output surface is ground along the thickness direction, and the output surface is subjected to grinding from the incident surface to the incident surface. An irregular surface having an average surface roughness of 0.01 to 0.5 μm in a direction toward the end portion facing the surface and an average surface roughness of 0.01 to 1.0 μm in a direction along the incident surface is formed. I do.
[0017]
BEST MODE FOR CARRYING OUT 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 a means for realizing the present invention, and the present invention can be applied to a modification or modification of the following embodiment without departing from the gist thereof.
[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) and a plan view of a light guide member according to an 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 has 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 reflecting member 5 disposed on the back surface of the light guiding member 4, a reflecting frame 6 covering each surface of the light guiding member 4 other than the incident surface 4a, and a line for entering light from the incident surface 4a of the light guiding member 4. (Eg, a cold cathode tube) or a plurality of point-like (eg, white LEDs) light sources 7.
[0021]
The light guide member 4 includes an incident surface 4a on which the light from the light source is incident, a reflecting surface 4b for diffusing and scattering the light incident from the incident surface 4a, and a reflecting surface 4b which is disposed to face the reflecting surface 4b and has a corresponding reflection. It is composed of a rectangular plate material having an emission surface 4c for emitting the light reflected by the surface 4b, and an end surface 4d parallel to the incidence surface 4a and facing the incidence surface 4a, and having a substantially uniform thickness. ing. The thickness of the light guide member 4 is not limited to a uniform configuration, but 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, for example, a transparent material such as transparent acrylic, polycarbonate (including highly transparent), urethane, and zeonor.
[0023]
The reflecting surface 4b of the light guide member 4 has a regular (periodic) periodic triangular cross section along the X direction formed of a linear prism groove or a hemispherical dot pattern in the direction (Y direction) along the incident surface 4b. The projection / recess shape 4e is formed, and a vertical stripe pattern is formed in the Y direction when the emission surface 4c is viewed from a plane. It is desirable that the uneven shape 4e is formed by grinding.
[0024]
The concave-convex shape 4e formed on the reflection surface 4b has an effect of diffusing light incident from the incident surface 4a and a function of bending the light to the exit surface 4c. However, since the function of the surface light source is required to have uniform luminance over the entire surface, it is not preferable to emit strong light in the vicinity of the incident surface 4b. Care is taken to avoid distractions.
[0025]
The output surface 4c has an arithmetic mean surface roughness Ra of 0.01 to 0.5 μm in a direction (X direction) from the incident surface 4a to the end 4d facing the incident surface 4a by a grinding process described later. Thus, a fine irregular irregular shape 4f having an arithmetic average surface roughness Ra of 0.01 to 1.0 μm in the direction (Y direction) along the incident surface 4a is formed and roughened.
[0026]
[Processing method of light exit surface of light guide member]
Next, a method of processing the exit surface of the light guide member of the present embodiment will be described.
[0027]
FIG. 4 is a diagram for explaining a method of processing the emission surface of the light guide member.
[0028]
As shown in FIG. 4, the emission surface 4c of the light guide member 4 is ground by a disk-shaped grinding blade (grinding stone) 11 as a rotating body. A polycrystalline granular material such as diamond is adhered to the outer surface of the grinding blade 11 including the radial outer peripheral portion (grinding surface 11a) 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 the present 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 to a table (not shown) that can reciprocate in the X direction and the Y direction, and the grinding blade 11 is moved at a high rotation speed of 10,000 to 30,000 rpm with the relative movement direction of the light guide member 4. The grinding blade 11 is fixed in a state where the grinding blade 11 is rotated in the same direction (right rotation in FIG. 3) and adjusted to a height at which the grinding surface 11a of the grinding blade 11 contacts the emission surface 4c of the light guide member 4 with a predetermined pressing force. The table is moved in the direction of arrow S1 while keeping the light guide member 4 moving relative to the grinding blade 11 from the incident surface 4a toward the end 4d in the X direction relative to the feed speed of about 0.5 to 10 mm / sec. Then, the emission surface 4c is ground in the thickness direction with a predetermined grinding allowance 12 (forward grinding).
[0030]
Thereafter, the table is moved in the direction of arrow S3 to move the light guide member 4 in a direction (Y direction) along the incident surface 4a at a feed amount (pitch) of about 10 to 100 μm (Y direction feed).
[0031]
Next, the grinding blade 11 is rotated in the direction opposite 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 arrow S2 opposite to arrow S1. By moving, the light guide member 4 is relatively moved in the X direction from the end surface 4d toward the incident surface 4a at the same feed speed to perform grinding in the X direction (return grinding).
[0032]
The entire surface of the light exit surface 4c of the light guide member 4 is ground by the above-described method, so that the light exit surface 4c has an average surface in the direction (X direction) from the incident surface 4b to the end 4d facing the incident surface 4b. Irregular irregularities 4f having a roughness Ra of 0.01 to 0.5 μm and an average surface roughness Ra of 0.01 to 1.0 μm in the direction (Y direction) along the incident surface 4b are 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 relatively moved. When the table is moved in the direction of arrow S3, the table is sent in the Y direction so that the processing surface ground immediately before and the processing surface to be ground next overlap each other. In addition, in the case of cutting and polishing, even in the case of polishing, the processed surface becomes a mirror surface, so that the effects of high brightness and uniformity as in the present embodiment cannot be obtained.
[0034]
[Grinding result]
FIGS. 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 emission surface when the feed amount in the Y direction is 100 μm, 50 μm, and 10 μm, respectively. FIG.
[0035]
As shown in FIGS. 5 to 7, the average surface roughness Ra of the emission surface 4c along the Y direction is 0.5 μm or less, and the emission surface 4c has a substantially regular (periodic) uneven shape in the Y direction. I have. In addition, the surface accuracy of the emitting surface 4c along the Y direction 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]
In addition, as shown in FIGS. 5 to 7, the average surface roughness Ra of the emission surface 4c along the X direction is 0.3 μm or less, and the emission surface 4c has an irregular uneven shape in the X direction. Further, the surface accuracy of the emission surface 4c along the X direction is 3 μmp-p or less. The surface accuracy in the X direction is irregular depending on the particle size of the polycrystalline granular material of the grinding blade 11.
[0037]
Here, when viewed in the X direction of the emission surface 4c, the irregularities 4f are formed as grooves substantially parallel to the light traveling direction (substantially perpendicular to the incidence surface 4a) from the incidence surface 4a along the end surface 4d. Both the average surface roughness Ra and the surface accuracy are smaller than those in the Y direction. The reason for this is that in order to achieve uniform in-plane luminance, extreme obstruction of light guide must be avoided. Irregularities 4e (linear prism grooves or hemispherical dot patterns) provided on the reflection surface 4b are subjected to gradation such that the amount of emitted light in the X direction becomes uniform to some extent at any position. When the surface 4c is extremely roughened, light (R2 in FIG. 3) that should be guided in a region near the incident surface 4a emits a large amount of light (R1 in FIG. 3) near the incident surface 4a. As a result, the brightness near the end face 4d far from the incident surface decreases. Ideally, the light R1 emitted from the emission surface 4c is emitted in the normal direction to the emission surface 4c. However, when the emission surface 4c is extremely roughened, the emitted light and the normal line Angle becomes large, and the luminance decreases. Therefore, as shown in FIG. 5 to FIG. 7, the emission surface 4 c has an irregular uneven shape, but it is better that the variation in the surface accuracy is small, and it is desirable to be 3 μmp-p or less experimentally.
[0038]
By roughening the emission surface 4c, as shown in FIG. 3, in the conventional configuration in which the emission surface is not roughened, the light R incident on the incidence surface 4a from the light source 7 is constant with respect to the emission surface 4c. Is emitted from the emission surface 4c as light R1 at an angle θ1 or more and luminance unevenness is generated in the vicinity of the light source 7, whereas even at an angle θ1 or more, the light R2 is emitted as light R2 without being emitted from the emission surface 4c. The light can be guided toward the end face 4d to a position farther from the light source 7 while being reflected in all directions in the −Y plane. Further, since refraction of light is suppressed in the X direction and refraction is promoted in the Y direction, unevenness in brightness near the light source is suppressed, and a surface with high brightness and uniformity over the entire emission surface 4c is provided. A light source can be realized.
[0039]
FIG. 8 shows a comparison between the surface light emission states of the conventional light guide member (a) having a roughened emission surface and the light guide member (b) of the present embodiment having a roughened emission surface. It is a diagram. In the conventional structure (a), luminance unevenness near the incident surface 4a is conspicuous, whereas in the structure (b) of the present embodiment, the luminance unevenness is greatly improved. In addition, the light emission efficiency is increased without lowering the average luminance value of the emission surface 4c as compared with the related art, and it can be seen that the luminance can be increased and uniformized over the entire surface of the emission surface 4c.
[0040]
FIG. 8 illustrates a case where the feed amount in the Y direction is 50 μm. When the feed amount is 100 μm, the amount of light output in an area close to the light source increases, and when the feed amount is 10 μm, the light amount from the light source as shown in FIG. Since the bright line becomes visible, 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 (a configuration including the elements denoted by reference numerals 3, 4, 5, 6, and 7) or the light guide member as a surface light source It is used for a liquid crystal display of a small portable terminal, a mobile phone, or the like, for example, in a liquid crystal display device (a configuration including the components denoted by reference numerals 2, 3, 4, 5, 6, 7).
[0042]
【The invention's effect】
As described above, according to the present invention, brightness unevenness can be suppressed and uniform brightness can be achieved without impairing the light output efficiency over the entire area of the emission 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 view showing a part of a side cross section for explaining an operation of the light guide member of the embodiment.
FIG. 4 is a diagram illustrating a method of processing the light exit surface of the 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 emission surface when grinding is performed with the feed amount in the Y direction being 100 μm.
FIG. 6 is a diagram showing measurement results of the surface accuracy (a) in the Y direction and the surface accuracy (b) in the X direction of the emission surface when grinding is performed with the feed amount in the Y direction set to 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 emission surface when grinding is performed with the feed amount in the Y direction being 10 μm.
FIG. 8 shows a comparison between respective light emitting states of a conventional light guide member (a) having an unroughened emission surface and a light guide member (b) of the present embodiment having a roughened emission surface. FIG.
FIG. 9 is a front view (a), a plan view (b), and a view (c) showing a part of a side cross section for explaining an operation of the light guide member of the conventional light guide member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Electro-optical panel 3 Sheet member 4 Light guide member 4a Incident surface 4b Reflective surface 4c Outgoing surface 4d End surface 4e Regular uneven shape 4f Irregular uneven shape 5 Reflective member 6 Reflective frame 7 Light source 11 Grinding blade 12 Grinding allowance

Claims (4)

A light guide including an incident surface for receiving light from a light source, a reflecting surface for reflecting light incident from the incident surface, and an emitting surface disposed opposite to the reflecting surface and emitting light reflected by the reflecting surface. A member,
On the reflecting surface, regular irregularities are formed in a direction along the incident surface,
The output surface has an average surface roughness of 0.01 to 0.5 μm in a direction from the incident surface to an end portion facing the incident surface, and an average surface roughness in a direction along the incident surface of 0.1 to 0.5 μm. A light guide member having irregular irregularities of 01 to 1.0 μm. 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. A light guide comprising: an incident surface on which light from a light source is incident; a reflecting surface for reflecting light incident from the incident surface; and an emission surface disposed to face the reflecting surface and emitting light reflected by the reflecting surface. A method of processing a member,
In a state in which the rotating body having the surface to which the polycrystalline particles are adhered is in contact with the light emitting surface of the light guide member, the rotating body and the light guide member are separated from the light incident surface by the end facing the light incident surface. Relative to the direction along, grinding the emission surface along the thickness direction,
The output surface has an average surface roughness of 0.01 to 0.5 μm in a direction from the incident surface to an end facing the incident surface, and an average surface roughness of 0. 0 in the direction along the incident surface. A method characterized by forming irregular irregularities of 01 to 1.0 μm.

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