JP2003177404A - Method of working metal mold for molding light transmission plate by resin, and metal mold and light transmission plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the permeability of light over the entire part of a light transmission plate having a prism surface. <P>SOLUTION: The transparent prism-molding surface 5 of the metal mold 1 for molding the light transmission plate is worked and finished to a mirror finished surface by elliptic vibration machining and the light transmission plate 10 is molded of a resin by the mold 1, by which the surface 5 (mirror finished surface) is transferred to the prism surface 9 of the plate 10 molded by the mold 1 and the surface 9 of the plate 10 is molded to the mirror finished surface to improve the permeability of the light over the entire part of the surface 9 (mirror finished surface), thereby improving the permeability of the light over the entire of the plate 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a metal mold for molding a light guide plate used in a liquid crystal display device, and an improvement of the mold and the light guide plate.

[0002]

2. Description of the Related Art First, a backlight unit (sidelight type) provided with a light guide plate in the above-mentioned liquid crystal display device.
Will be described. That is, conventionally, a prism sheet,
A multi-layer type backlight unit consisting of a diffusion sheet, a light guide plate, a reflection sheet, etc. was the mainstream, but due to cost reduction, reduction in the number of parts, shortening the manufacturing process, thinning the liquid crystal display device, etc. A backlight unit having a configuration as shown in 6 is under study. Further, as shown in FIG. 6, the above-mentioned backlight unit includes a cold cathode tube (fluorescent lamp) 51 serving as a light source and a prism surface 52 (light emitting surface).
And a lamp reflector 5 that reflects the light source 51 and guides light toward the light guide plate 53.
7, a diffusion sheet 54 provided on the light emitting surface side of the light guide plate 53 for reducing unevenness in brightness, and light leaking from the light guide plate 53 provided on the opposite side of the light guide plate 53 from the prism surface 52 side. And a reflection sheet 55 that reflects the light. Therefore, the light from the light source 51 (the lamp reflector 5
(Including light reflected at 7) is reflected from the light guide plate 53 to the reflection sheet 55 and emitted from the prism surface 52 of the light guide plate 53, and further passes through the diffusion sheet 54, and the liquid crystal panel of the liquid crystal display device. It will be irradiated in the direction (not shown). The arrow indicated by reference numeral 56 indicates the light that has passed through the diffusion sheet 54 and is emitted toward the liquid crystal panel.

Conventionally, a light guide plate (molded product) having a prism surface as shown in FIG. 6 is, for example, in a mold for molding a light guide plate, a resin is provided in a cavity of a mold for molding the light guide plate. Is molded by injection. Further, the above-mentioned mold is provided with a light guide plate prism molding surface of the mold corresponding to the prism surface of the light guide plate to be resin-molded, and the prism molding surface is usually processed by a cutting method. There is. That is, the fine grooves (concave portions) on the prism molding surface are processed by normally cutting the surface of the die material with a cutting tool such as a cutting tool. Therefore, the light guide plate having the prism surface is resin-molded by the mold having the prism molding surface.

[0004]

By the way, in recent years, it has been required to improve the brightness of the liquid crystal panel of the above-mentioned liquid crystal display device, and as in the backlight unit type shown in FIG. In the light guide plate that guides light to the panel side, it has been required to improve the light transmittance of the light guide plate. However,
In the above-mentioned normal cutting method, burrs are generated on the die groove side of the die prism molding surface on the die side, so that the die side burrs are transferred to the prism surface. Then, the light guide plate is resin-molded. That is, it is said that the mold side burr is transferred to the prism surface of the resin-molded light guide plate, and the transfer site becomes an obstacle to light, and the light transmittance of the light guide plate is lowered. There is an evil.

Therefore, an object of the present invention is to improve the light transmittance of a light guide plate which is resin-molded with a light guide plate molding die. Another object of the present invention is to provide a method for processing a mold and a mold for resin-molding a light guide plate having a prism surface, which can improve light transmittance in the light guide plate having a prism surface. To do. Another object of the present invention is to provide a light guide plate having a prism surface that can improve light transmittance.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] A method of processing a mold according to the present invention for solving the above technical problem is a method of processing a mold for resin-molding a light guide plate, wherein The light guide plate prism molding surface is processed by elliptical vibration cutting.

Further, a light guide plate molding die according to the present invention for solving the above-mentioned technical problem is a light guide plate molding die for resin-molding a light guide plate, and an ellipse is formed on the die. It is characterized in that it is provided with a light guide plate prism molding surface processed by vibration cutting.

The light guide plate according to the present invention for solving the above technical problem is a light guide plate which is resin-molded by using a light guide plate molding die, and is processed by elliptical vibration cutting. It is characterized in that resin molding is performed using a light guide plate molding die having a light guide plate prism molding surface.

Further, a light guide plate according to the present invention for solving the above technical problem is characterized in that a resin injection portion provided on the light guide plate is processed by elliptical vibration cutting.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the prism molding surface can be machined into a mirror surface by elliptical vibration cutting the light guide plate prism molding surface of the mold. That is, by resin-molding the light guide plate with a mold having the prism molding surface, the prism molding surface (mirror surface) can be transferred to the prism surface of the light guide plate resin-molded by the mold. The prism surface of the light guide plate described above can be formed into a mirror surface. That is, by forming the prism surface of the light guide plate as a mirror surface, it is possible to eliminate the factor of light obstruction due to the transfer of the mold side burr shown in the above-mentioned conventional example. It is possible to improve the light transmittance of the prism surface of the light plate. Therefore, it is possible to improve the light transmittance of the entire light guide plate having the prism surface.

[0011]

Embodiments will be described below with reference to the drawings. Figure 1
In (1), a configuration is shown in which the mold material is subjected to elliptical vibration cutting to process the prism molding surface of the light guide plate molding mold corresponding to the prism surface of the light guide plate. Further, FIG. 1 (2) shows a cutting tool used for the elliptical vibration cutting process shown in FIG. 1 (1). 2 (1) is a mold member having a prism molding surface machined by elliptical vibration cutting in FIG. 1 (1), and FIG. 2 (2) is the mold of FIG. 2 (1). It is the figure which expanded the prism formation surface of a member. 3 (1) and FIG.
(2) shows a step of resin-molding the light guide plate using the light guide plate molding die provided with the die member shown in FIG. 2 (1). Moreover, in FIG. 4, FIG. 3 (1) and FIG. 3 (2)
2 shows a light guide plate having a prism surface resin-molded. Further, FIG. 5 schematically shows a configuration (principle) in which a work material such as a mold material is cut by elliptical vibration with a cutting tool.

That is, the light guide plate 10 (molded product) having the prism surface 9 shown in FIG. 4 is, for example, as shown in FIGS.
It is molded using the light guide plate molding die 1 shown in (2). The mold 1 is composed of a fixed mold 2 and a movable mold 3, and the fixed mold 2 is provided with a resin molding cavity 4. In addition, the movable mold 3 described above
Is provided with a mold member 6 (prism molding portion) having a prism molding surface 5, and the mold member 6 is detachably mounted on the mold base portion 7 of the movable mold 3 described above. Is configured to be able to. Also, FIG.
As shown in (1), by clamping both the molds 1 (2, 3), the mold 1 is surrounded by the cavity 4 and the prism molding surface 5 of the mold member 6. The mold cavity space 8 for molding the light guide plate is formed. Although not shown in the drawing, a resin injection mold gate for injecting resin into the space 8 is formed in the mold cavity space 8 by resin molding in the mold cavity space 8, for example. The light guide plate 10 is provided at a position corresponding to the light source side (see the position of the resin injection part 23 shown in FIG. 4). Further, a sprue for resin transfer is provided in communication between the mold gate and a resin supply portion (not shown) provided in the mold 1. Therefore, the resin can be injected from the resin supply portion into the mold cavity space portion 8 through the gate (resin passage) including the sprue.

Therefore, first, as shown in FIG.
The inside of the mold cavity space portion 8 is obtained by clamping both molds 1 (2, 3) described above, injecting and filling the cavity space portion 8 with the heated and melted resin from the mold gate, and cooling the resin. Then, the light guide plate 10 having the prism surface 9 is resin-molded. Further, as shown in FIG. 3B, the two molds 1 (2, 3) are opened to provide a resin-molded prism surface 9 in the cavity space 8. The light guide plate 10 can be taken out.

Further, as shown in FIG. 2A, a predetermined range 1 corresponding to the cavity 4 in the mold member 6 is provided.
1 has a prism molding surface 5 formed thereon, and as shown in FIG. 2B, the prism molding surface 5 has a required number of fine grooves 11 (recesses) arranged in parallel in a predetermined same direction. It is formed in the state. Also, each of the fine grooves 1 described above
Each of the 2 is formed with a predetermined same depth 13, a predetermined same groove pitch width 14, and a predetermined same angle 15, for example. The fine grooves 12 (recesses) correspond to the protrusions 20 (peaks) on the prism surface 9 of the resin-molded light guide plate 10 shown in FIG. 4, and the protrusions 16 on the prism molding surface 5 are This corresponds to the recess 21 (valley) on the prism surface 9 of the light guide plate 10 shown in FIG.

Further, as shown in FIG. 1 (1), a predetermined range 11 of the die material 17 (workpiece) to be the die member 6 is elliptically vibrated using a cutting tool 18 such as a cutting tool. The required number of fine grooves 1 in the predetermined range 11
2 can be processed to form the prism molding surface 5 on the mold member 6 described above. Further, the tip angle 19 of the cutting tool 18 shown in FIG. 1B is configured corresponding to the angle 15 of the fine groove 12, and the cutting tool 18
For example, a diamond tool or the like is used. In FIG. 1A, A is a cutting direction, B is a main component force direction, D is a back force component direction, 34 is a locus of elliptical vibration drawn by the tip of the cutting tool 18, and 22 is It is the direction of the groove pitch width 14 shown in FIG.

Next, the elliptical vibration cutting process will be described with reference to the example shown in FIG. That is, in the example of the elliptical vibration cutting process shown in FIG. 5, the cutting tool 31 described above is used for the work material 3 such as steel.
2 (the die material 17) a predetermined cutting thickness 33
An elliptical vibration cutting device is used to perform the elliptical vibration cutting of the work material 32 described above. Further, the elliptical vibration cutting device is provided with, for example, a piezoelectric element (not shown) that applies vibration to the cutting edge of the cutting tool 31 in the X direction or in the X direction, respectively,
A sinusoidal voltage is separately input to the piezoelectric element for generating vibrations in the XY two-directions with a predetermined voltage, a predetermined frequency (for example, an ultrasonic range), and a predetermined phase difference (for example, 90 degrees). It is configured to be able to. Therefore, in the above elliptical vibration cutting device, by inputting a predetermined sinusoidal voltage to each of the piezoelectric elements, the vibrations generated in the two directions of XY are mechanically resonantly combined to perform the cutting. The cutting edge of the tool 31 is configured to generate an elliptical vibration trajectory 34 having a predetermined cycle. In FIG. 5, the X direction is
It corresponds to the cutting direction A and the main component force direction B, and the Y direction described above corresponds to the back component force direction D.

That is, as shown in FIG. 5, first, the work material 32 is moved by the cutting tool 31 in the main component force direction B (leftward in the illustrated example) according to the locus 34 of the elliptical vibration.
And the cutting tool 31 is cut into
To the back force direction D (upward in the illustrated example). At this time, the chips 35 cut from the work material 32 are pulled up in the back force direction D (upward in the illustrated example) by the cutting tool 31 to remove the chips 35.
Since 5 flows out in the chip outflow direction E, the frictional resistance to the above elliptical vibration cutting is reduced or reversed (negative frictional resistance) as compared with the normal cutting method. That is, the work material 3 for the cutting tool 31 is described above.
The cutting resistance of No. 1 is reduced, and the cutting force of the cutting tool 31 can be reduced to improve the machinability. Further, next, the cutting tool 31 is separated from the chip 35 in the main component force direction B (right direction in the example), and the cutting tool 31 is moved in the back component force direction D (down direction in the example). That is, it is moved to the work material 31 side. Therefore, by vibrating the cutting tool 31 periodically according to the locus 34 of the elliptical vibration, the workpiece 31 can be machined by elliptical vibration cutting. Further, in the cutting by the elliptical vibration described above, as compared with the normal cutting method, the thickness of the chips 35 is reduced, the cutting resistance is reduced, and mirror finishing can be performed. There are advantages such as prolonging the service life, improving the precision of the processed shape, suppressing burrs, preventing chatter vibration, and reducing cutting heat. Examples of the material of the work material 31 to be mirror-finished include hardened steel, plastic, resin, and the like. Further, in the conventional normal cutting method, since the work material is cut in a state of being compressed by the cutting tool, the cutting resistance is high, and the chips are in the form of compressed powder, and Burrs will be generated on the cutting surface. However, in the cutting method by elliptical vibration cutting, the above-mentioned chips 3
5 is configured to be able to be pulled upward by the cutting tool 31 described above, cutting resistance is reduced, and the chips 35 can be formed into a continuous shape (for example, an elongated shape) and discharged (continuous). It is possible to suppress the occurrence of burrs, which is called a ductile mode), and to machine the cutting surface of the work material 31 into a mirror surface. In addition, 36 shows a shear angle, and if the shear angle 36 is increased, the machinability of the work material 32 is improved.

That is, as shown in FIG. 1 (1), the predetermined range 11 of the die material 17 is elliptically vibrated by the cutting tool 31 to be machined.
As shown in (2), the mold member 6 having the prism molding surface 5 can be formed. Further, by performing the elliptical vibration cutting process described above, it is possible to efficiently prevent the occurrence of mold side burrs on the prism molding surface 5 as compared with the normal cutting method, and due to the advantages of the elliptical vibration cutting process described above. , The prism molding surface 5
Can be efficiently processed into a mirror surface. That is, by forming a prism molding surface 5 having fine grooves 12 by cutting a predetermined range 11 of the die material 17 with an elliptical vibration, a prism surface 9 capable of improving light transmittance is provided. A mold (the mold member 6) capable of resin-molding the light guide plate 10 can be processed. Therefore, as shown in FIGS. 3 (1) and 3 (2), the mold member 6 having the prism molding surface 5 is detachably mounted on the mold 1 (the movable mold 3), The light guide plate 10 having the prism surface 9 can be resin-molded in the mold 1 (the cavity space 8).

That is, since the prism molding surface 5 (mirror surface) can be transferred onto the prism surface 9 of the light guide plate 10, the prism surface 9 serving as the transfer surface can be formed into a mirror surface. Further, by forming the prism surface 9 of the light guide plate 10 as a mirror surface, it is possible to eliminate the factor of light obstruction due to the transfer of the mold side burr shown in the above-mentioned conventional example. It is possible to eliminate the factor that hinders the light that is generated and to improve the light transmittance of the prism surface 9 described above. Therefore,
It is possible to improve the light transmittance of the entire light guide plate 10 having the prism surface 9 as compared with the light guide plate using a mold processed by the conventional normal cutting method.

Further, in the above-mentioned embodiment, the fixed mold 2
The mold 1 including the movable mold 3 and the movable mold 3 has been described as an example.
The light guide plate 10 described above using the prism molding surface 5 described above.
Any mold configuration may be used as long as the prism surface 9 can be resin-molded.

Further, in the above-mentioned embodiment, the above-mentioned prism molding surface 5 is formed by elliptical vibration cutting the above-mentioned mold material 17.
Although the configuration for processing is exemplified, a configuration for processing the inner surface of the cavity 4 of the mold by elliptical vibration cutting may be adopted. In this case, as in the above-described embodiment,
Since the entire surface of the light guide plate including the prism molding surface can be formed into a mirror surface, it is possible to improve the light transmittance of the entire light guide plate (including the light reflected by the reflection sheet in the backlight unit). . In addition,
This configuration is not limited to the light guide plate having the prism surface, and can be adopted for various light guide plates resin-molded by the light guide plate molding die.

The resin used for resin molding of the light guide plate 10 having the prism surface 9 is an acrylic resin,
A methacrylic resin, a polycarbonate, or a resin (clear resin) that forms an optical system molded article such as a lens can be used.

Further, as the material of the mold material 17,
Materials that are usually used as mold materials, for example, hardened steel, iron-based materials such as stainless steel, aluminum materials, etc., as well as surface-treated mold materials, such as copper plating, nickel plating, nickel An example of the die material is a surface treatment of phosphorous plating. That is, elliptical vibration cutting can be performed on the above-mentioned plated surface-treated layer to process fine grooves (prism molding surface) having a depth shallower than the thickness of the above-mentioned plated surface-treated layer. Therefore, the surface material of the prism molding surface is the material of the plating surface treatment layer.

Further, resin is injected from the mold gate into the mold cavity space portion 8 of the mold 1 to mold the light guide plate 10 having the prism surface 9 to mold the sprue resin. After the removal, the resin residue remains in the resin injection part 23 of the light guide plate 10 shown in FIG. Therefore, conventionally, the above-mentioned resin residue (the above-mentioned resin injection part)
Was usually removed by a cutting method. However, in the above-mentioned normal cutting method, a resin burr is generated in the above-mentioned resin injecting portion, and the resin burr blocks light from the light source, resulting in low light transmittance in the light guide plate. Further, in the above-described normal cutting method, powdery chips are generated, the powdery chips are fitted into the valleys 21 of the prism surface 9 of the light guide plate 10, and a cleaning step is performed to remove the powdery chips. It cannot be removed even if repeated. Therefore, in order to solve the above-mentioned light transmission and powdery chips, the resin residue (the resin injecting portion 23) of the light guide plate 10 is removed by elliptical vibration cutting to remove the resin injecting portion 23 from a mirror surface. It is processed into. That is, by processing the resin injection part 23 into a mirror surface, the light transmittance of the resin injection part 23 can be improved, and thus the light transmittance of the entire light guide plate 10 can be improved. . Further, since the chips produced by the elliptical vibration cutting are continuous, the continuous chips do not fit into the valleys 21 of the prism surface 9, and the cleaning process as described above is unnecessary. In the above-described embodiment, the mold gate is provided at a position corresponding to the light source side of the light guide plate 10, but the mold gate is provided at an arbitrary position in the mold cavity space 8. be able to.

After the light guide plate 10 is molded in the mold cavity space 8 described above, the resin of the resin passage (the mold gate resin including the sprue resin) is connected to the light guide plate 10. The position of (the resin injection portion) may be cut (gate cut) by a normal cutting method. However, similar to the removal of the resin residue, the light transmittance is lowered, and the powdery chips are fitted into the valleys 21 of the prism surface 9 described above. Therefore,
Connection part with the above-mentioned light guide plate 10 (the resin injection part 23)
Is cut by elliptical vibration to cut the resin injection portion 23 into a mirror surface. That is, as with the removal of the resin residue, the light transmissivity in the resin injection part 23 can be improved, so that the light transmissivity in the entire light guide plate 10 can be improved and the continuous shape can be achieved. The chips do not fit into the troughs 21 of the prism surface 9, and the cleaning process as described above is unnecessary.

Incidentally, the structure for cutting the resin injection portion of the light guide plate into an elliptical vibration and processing it into a mirror surface is not limited to the light guide plate having the prism surface, and various kinds of resin molded by a light guide plate molding die. It can be applied to the light guide plate. In addition,
In recent years, the liquid crystal display device (liquid crystal panel) described above has become larger, and the area of the resin injection portion 23 tends to increase.
The cutting of the gate by the above-mentioned elliptical vibration cutting process can greatly contribute to the improvement of light transmittance.

The present invention is not limited to the above-mentioned embodiments, and within the scope of the present invention,
It can be arbitrarily and appropriately changed / selected and adopted as needed.

[0028]

According to the present invention, in a light guide plate resin-molded with a light guide plate molding die, the excellent effect that the light transmittance can be improved is exhibited.

Further, according to the present invention, there is provided a mold processing method and a mold for resin-molding a light guide plate having a prism surface, which can improve the light transmittance of the light guide plate having the prism surface. It has an excellent effect that can be achieved.

Further, according to the present invention, there is an excellent effect that a light guide plate having a prism surface capable of improving the light transmittance can be provided.

[Brief description of drawings]

1 (1) is a schematic perspective view for schematically explaining a method of processing a mold for resin-molding a light guide plate according to the present invention, and FIG. 1 (2) is FIG. 1 (1). It is an expansion schematic perspective view which expands and shows the cutting tool shown in FIG.

FIG. 2 (1) is a vertical cross-sectional view showing a prism molding surface of the mold processed in FIG. 1 (1), and FIG. 2 (2) is a cross-sectional view of the mold shown in FIG. 2 (1). It is an expanded longitudinal cross-sectional view which expanded and showed the principal part of the prism molding surface.

3 (1) is a vertical cross-sectional view showing a mold for resin-molding a light guide plate according to the present invention, showing a mold clamping state, and FIG. 3 (2) shows FIG. It is a longitudinal cross-sectional view of the mold corresponding to (1), showing the mold open state.

FIG. 4 is a schematic perspective view schematically showing a light guide plate having a prism surface resin-molded with the mold shown in FIGS. 3 (1) and 3 (2).

FIG. 4 is a schematic front view for schematically explaining the method of processing a mold of the present invention.

FIG. 6 is a schematic front view schematically illustrating and explaining a backlight unit using a light guide plate having a prism surface.

[Explanation of symbols]

1 mold 2 fixed type 3 movable 4 cavities 5 Prism molding surface 6 Mold member (prism molding part) 7 Mold base 8 Mold cavity space 9 Prism surface 10 Light guide plate 11 predetermined range 12 Fine groove 13 depth (fine groove) 14 groove pitch width 15 angles (fine groove) 16 convex 17 Mold material 18 cutting tools 19 Tip angle (cutting tool) 20 Convex part (mountain part) 21 recess (valley) 22 Groove pitch width direction 23 Resin injection part 31 cutting tools 32 Work material 33 Cut thickness 34 Elliptical vibration locus 35 chips 36 Shear angle 51 light source 52 Prism surface 53 Light guide plate 54 Diffusion sheet 55 Reflective sheet 56 light 57 Lamp reflector A cutting direction B Main force direction D Back force direction E Chip outflow direction

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masako Namiko             5 Toamigamicho, Minami-ku, Kyoto-shi, Kyoto Prefecture             Towa Co., Ltd. (72) Inventor Kazuhiro Harada             5 Toamigamicho, Minami-ku, Kyoto-shi, Kyoto Prefecture             Towa Co., Ltd. F-term (reference) 2H038 AA55 BA06                 2H091 FA14Z FA16X FA21X FA23Z                       FA42Z LA11 LA12 LA13                       LA16 LA30                 4F202 CA01 CA11 CB01 CD18 CK11                       CK43

Claims (4)

[Claims] 1. A method of processing a mold for resin-molding a light guide plate, characterized in that the light guide plate prism molding surface of the mold is processed by elliptical vibration cutting. 2. A light guide plate molding die for resin-molding a light guide plate, comprising: a light guide plate prism molding surface machined by elliptical vibration cutting in the mold. Type. 3. A light guide plate formed by resin molding using a light guide plate molding die, wherein the light guide plate molding die having a light guide plate prism molding surface processed by elliptical vibration cutting is used for resin molding. A light guide plate characterized by being. 4. The light guide plate according to claim 3, wherein the resin injection portion provided on the light guide plate is processed by elliptical vibration cutting.