JP3789207B2 - Method for manufacturing light guide member - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a light guide member used for illuminating an LCD (Liquid Crystal Display) having a predetermined area from the back side.
[0002]
[Prior art]
When illuminating an LCD or the like having a predetermined area from the back, the first consideration must be to make the light generated from the light source uniform over all parts of the predetermined area of the LCD.
[0003]
Therefore, conventionally, the light source is disposed on the side of the light guide member formed of a material having high light transmittance, and the light from the light source is guided in the surface direction of the light guide member, so that the light emitting surface of the light guide member When the light emitting member arranged in parallel is configured to scatter light emitted from the light emitting surface of the light guide member, a large number of protrusions are formed on the side surface opposite to the light emitting surface of the light guide member. Many of the surface light-emitting devices that reflect the light from the light source at these protrusions and make the brightness of the light-emitting surface uniform by forming more protrusions on the part far from the light source are put into practical use. Has been.
[0004]
According to the surface light emitting device configured as described above, the light guide member is mass-produced by injection molding using, for example, an acrylic resin material having high light transmittance. In this injection molding, a cavity for molding the light guide member is formed. The provided mold is mainly processed by chemical etching.
[0005]
FIG. 13 is an enlarged cross-sectional view (a) of a conventional light guide plate 10 and an enlarged cross-sectional view (b) of an injection mold 201 used for injection processing of the light guide plate 10.
[0006]
First, in FIG. 13B, when the mold recess 202 for molding the projection 16 of the light guide plate 10 is formed by chemical etching using the injection mold 201, the bottom surface portion of the cavity of the mold is predetermined. After covering with a resist film 203 provided with opening holes 203a having a pitch and a predetermined opening area, an etching solution is introduced to form a surface that contacts through the opening holes 203a by erosion, and then the resist film 203 Thus, the cavity of the injection mold 201 is formed.
[0007]
Using the injection mold 201 processed and formed in this way, as shown in FIG. 13A, the light guide plate 10 having a thickness H and formed with a large number of protrusions 16 is injection molded. As described above, light from the light source is reflected on the light emitting surface 10a of the light guide member 10, while more protrusions 16 are formed at a portion far from the light source so that the brightness on the light emitting surface becomes uniform. I have to.
[0008]
However, it is known that when the mold cavity is processed by the chemical etching process as described above, the opening hole portion 203a is hemispherical when it is a small-diameter dot, and is pan-shaped when it is a large-diameter dot.
[0009]
When so-called over-etching occurs during the chemical etching process, an over-etching portion 202a as shown in FIG. 13B is formed. Further, the communication portion 202b may be formed when the diameter d of the protrusion 16b is reduced to, for example, Φ0.3 mm or less and the arrangement pitch is reduced to 0.6 mm or less. Defects 16a and 16b as shown in the figure are formed on the protrusion 16 of the light guide plate 10 that is injection-molded.
[0010]
As a result, the light L from the light source is diffusely reflected by the defective portion 16a of the protrusion 16 or cannot be directed toward the light emitting surface 10a after being reflected by the protrusion 16, and the light is efficiently emitted from the light source. There is a problem in that it is impossible to select a shape that can be normally guided to a remote light guide plate part, and desired performance cannot be obtained.
[0011]
Furthermore, chemical etching processing is particularly difficult to manage the chemical concentration, temperature, etc., and it is very difficult to prevent the occurrence of variation due to the site when the density of the protrusions is set to be continuously variable. It was. For this reason, it is necessary to increase the spacing between the adjacent protrusions 16, and the arrangement density of the protrusions cannot be increased, which is naturally limited, and the amount of light emitted outside the light guide plate is increased. There was a limit to increasing the brightness.
[0012]
[Problems to be solved by the invention]
Therefore, by using an ultra-precision injection mold that is formed by processing other than the above-described etching, injection molding is performed with a light-transmitting resin material, so that a conical recess having an inclined surface is formed instead of the above-described protrusion. Thus, it is conceivable to increase the brightness by reflecting incident light incident at a critical angle β or more determined from the resin material on the inclined surface of the concave portion and directing it to the light emitting surface.
[0013]
According to the above-mentioned ultra-precision injection mold, the machining surface is cut with a special cutting drill so as to obtain a high density substantially proportional to the distance from the light source, so that the master recess is cut to a desired depth. It took a considerable amount of time to process. Also, if it is difficult to cut the concave part of the master mold until the desired depth is achieved with a single cutting process, it is necessary to perform the cutting process multiple times and to precisely control the depth of the cutting drill. Therefore, a special special jig was necessary for cutting.
[0014]
In addition, the shape and surface state of the cutting surface are determined by the shape of the rotating blade and the tip state of the blade portion of the special cutting drill that is driven to rotate, so that it has a conical shape and the cutting surface remains with a cutting mark. It was a thing. Further, according to the special cutting drill that is rotationally driven, the conical surface can be cut, but it has been impossible to cut into a triangular pyramid, a quadrangular pyramid, a polygonal pyramid, or a roof shape.
[0015]
Furthermore, while setting the apex angle of the special cutting drill to a desired range and forming the blade portion at the tip part, the tip part of the apex angle is very small, around 0.05 mm. Have difficulty. Moreover, it is practically impossible to form the blade portion by re-polishing after the cutting edge is worn out, and it is presumed to be disposable, resulting in an increase in cost.
[0016]
Therefore, the present invention has been made in view of the above-described problems, and the recesses processed on the processing surface of the molding die are processed in a very short time so as to obtain a high density substantially proportional to the distance from the light source. In addition, the concave portion can be processed into any shape other than the conical shape such as a triangular pyramid, a quadrangular pyramid, a polygonal pyramid, a roof shape, and the processing surface state is set to be glossy or rough at any time. An object of the present invention is to provide a method for manufacturing a light guide member.
[0017]
[Means for Solving the Problems]
  In order to solve the above-described problems and achieve the object, according to the light guide member manufacturing method of the present invention, the light source is disposed on at least one side of the light-transmitting plate-shaped light guide member, In order to guide the light from the light source to the inside of the light guide member from the side light incident surface and scatter the light in the diffusion member arranged in parallel with the light emitting surface of the light guide member to perform illumination A method of manufacturing a light guide member in which an infinite number of post-projections having a predetermined shape are formed on the back surface of the light emitting surface, wherein one processed surface is formed so as to have a high density substantially proportional to the distance from the light source. A forging process to obtain a molding die having a recess by sequentially forging with a plurality of punches, and using the molding die, injection molding is performed from a light-transmitting resin material to form innumerable projections after completion. A molding step of injection molding the light guide memberIn the forging step, forging is performed sequentially from a portion where the recesses are relatively dense to a portion where the recesses are low density.It is characterized by.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0019]
  First, FIG.Is, For example, is a cross-sectional view showing the main part of a surface light emitting device used for a backlight of a liquid crystal having no self-luminous capability.FIG. 2 is a sectional view taken along the line XX in FIG.
[0020]
1 and 2, the light source unit 4 is formed so that a high-intensity light emitting diode (LED) is bonded onto the substrate 5 and then sealed with silicon resin or epoxy resin. 5 can be turned on by connecting the electrode unit to a power source unit (not shown) so that the electrode unit 5 is exposed to the outside.
[0021]
On the other hand, the light guide plate 1 formed in a planar shape as shown in the figure has substantially the same shape and area as the planar display surface 15 of the liquid crystal, and the pair of light source sections on the light incident side surface 1f. 4 is formed, and a transparent acrylic resin, polycarbonate (PC) resin or the like is used as a material for injection molding. While the back surface 1b of the light guide plate 1 is formed of a mirror surface, the inclined surface of the convex portion 6 is made to be a mirror surface or a rough surface so that incident light having a critical angle β or more is totally reflected or irregularly reflected. .
[0022]
Further, the light emitting surface 1a, the left and right side surfaces 1d and 1e of the light guide plate 1, the opposite surface 1c and the back surface 1b are injection-molded so as to be mirror surfaces, and innumerable convex portions 6 are regularly formed on the back surface 1b. is doing. As shown in FIG. 2, the protrusions 6 are arranged so that the horizontal pitch Pw and the vertical pitch Pd are sparse in a portion close to the light source 4, while being separated from the light source 4. Accordingly, the horizontal pitch Pw and the vertical pitch Pd are gradually made dense.
[0023]
Further, as shown in the figure, by arranging the convex portions 6 so as to be staggered as much as possible, based on simulation analysis using a computer so that the light from the light source 4 can surely reach far away from the adjacent convex portions 6. The convex part 6 is arrange | positioned.
[0024]
On the other hand, the reflection frame 3 formed in a substantially box shape as shown in the figure is formed so as to have a box shape and a size that accommodates the light guide plate 1 without a substantial gap. In addition, the reflective frame 3 is formed by, for example, injection molding from white resin or electroless plating, so that the reflective inner surfaces 3a, 3b, 3c, and 3d are formed on the inner side. The light reflected by each reflection inner surface is directed toward the diffusion plate 2.
[0025]
The above is the schematic configuration of the surface light-emitting device, and its dimensions are appropriately determined according to the liquid crystal size. When the liquid crystal size is large, a fluorescent lamp serving as a line light source is appropriately used as the light source 4. When the backlight is horizontally long, the apparatus shown in FIGS. 1 and 2 is symmetrically provided so as to be opposed to each other so that the convex portions 6 are densely arranged at the central portion. Will be.
[0026]
Next, FIG. 3A is a schematic diagram showing a state of reflection of the light L entering the light guide plate 1, and FIG. 3B shows a state of reflection of the light L at the convex portion 6. FIG.
[0027]
First, in FIG. 3A, the light L emitted from the light source 4 and indicated by a broken line in the figure has a critical angle β of 42.16 because the refractive index n of the acrylic resin is n = 1.49. When the incident angle is 42.16 ° or more, each surface is totally reflected. That is, light incident on the light guide plate 1 at an angle α formed with the perpendicular from the light guide plate 1 is refracted at a critical angle β, but α is 90 ° in the relational expression n = sin α / sin β. Then, 42.16 ° of the critical angle β is obtained from sin β = sin (90 °) / n.
[0028]
Similarly, in the case of PC resin, since n = 1.59, the critical angle is 38.97 °, and total reflection occurs when incident on each surface at an incident angle of 38.97 ° or more.
[0029]
  Therefore, the light L incident from the light incident side surface 1f of the light guide plate 1 formed from acrylic resin is incident on the left and right side surfaces 1d, 1e, the light emitting surface 1a, and the back surface 1b at an angle of 47.84 ° or more which is greater than the critical angle.ConvexThe light enters the part other than the part 6 and is totally reflected. Similarly, in the case of PC resin, all the light incident from the light incident side surface 1f is totally reflected.
[0030]
The light reaching the opposite surface 1c while repeating the total reflection as described above is emitted from the light guide plate 1 to the outside, then reflected by the reflection inner surface 3b of the reflection frame 3, and then enters the light guide plate 1 again. It will be.
[0031]
Next, the most characteristic convex portion 6 of the present invention is formed on the back surface 1b as shown in FIG. 3B, and the incident angle of the convex portion 6 with respect to the reflecting surface 6a is not less than the critical angle β. If there is, it is formed so as to be totally reflected as shown by a broken line. Further, when the reflecting surfaces 6a and 6b are roughened, they are directed as shown by broken lines while partially diffusing on the reflecting surface 6a.
[0032]
When the incident angle is less than or equal to the critical angle β on the light emitting surface 1a, the light is not reflected by the light emitting surface 1a but is refracted and emitted from the light guide plate 1 to reach the diffusion plate 2 where it is diffused. In addition, incident light having an incident angle greater than or equal to the critical angle β on the light emitting surface 1a is totally reflected and guided to the back side in the light guide plate.
[0033]
On the other hand, although not shown in the figure, the light incident at the critical angle β or less with respect to the back surface 1b is emitted from the back surface 1b, directed to the reflecting surface 3a of the reflecting frame 3, and reflected by the reflecting surface 3a. Again, the light is incident on the light guide plate 1 and directed toward the light emitting surface 1a.
[0034]
The light diffused in the diffusion plate 2 as described above forms a surface light source, and in the case of a liquid crystal backlight, passes through the LCD transmission pattern 15 shown in FIG. become.
[0035]
Further, as shown in the figure, the convex portion 6 is formed so as to protrude in a conical shape from the back surface 1b of the light guide plate 1 toward the light emitting side surface 1a. Is 110 ° to 150 °, preferably 120 °. By forming the convex portion 6 in this way, the light that has entered the back surface 1b at a critical angle β or more and that should be totally reflected and guided on the back surface 1b surface is reflected by the convex portion 6. It is configured to be able to emit light from the light emitting surface 1a so as to be totally reflected on the surface 6a and to be directed to the light emitting surface 1a.
[0036]
The protrusions 6 formed as described above are arranged so that the lateral pitch Pw and the vertical pitch Pd gradually become denser as they are separated from the light source 4 as described above, and are further staggered as much as possible. Thus, the light from the light source 4 can surely reach the opposite surface 1c.
[0037]
As a result of various experiments on the apex angle θ of the protrusion, it was confirmed that the efficiency was the best around 120 ° as described above, and the height h of the convex portion 6 was 0.05 mm and the diameter d was 0.25 mm. There is a portion where the convex portions 6 are provided at the highest density, and the horizontal pitch Pw and the vertical pitch Pd in the portion close to the opposite surface 1c shown in FIG. I was able to get it.
[0038]
Next, FIG. 4 is a schematic diagram showing a configuration example of a forging device used in the forging process of the mold material for the light guide plate 1 that is injection-molded as described above.
[0039]
In this figure, the forging apparatus 20 is partly based on the operating principle of a Vickers hardness tester that measures the hardness of the object to be measured from the size of the indentation remaining when a known load is applied to the surface to be measured. Although based, the forging device 20 is completely different from the hardness meter as shown in the figure.
[0040]
First, the forging device 20 is provided with a turning table 22 that is arbitrarily turned in the direction of an arrow by a drive motor 22b on a base 21 serving as a base. A left / right moving table 23 that is arbitrarily translated in the direction of the left / right arrow shown in the figure by a drive motor 23b is fixed on the turning table 22. Further, on the left / right moving table 23, a front / rear moving table 24 that is arbitrarily translated in the front and back direction of the drawing by a drive motor 24b is fixed.
[0041]
On this back-and-forth moving table 24, a work clamp 25 equipped with a mechanical fixture shown in the figure is fixed, or connected to a vacuum pressure supply source in order to fix the molding die M in a stationary state by vacuum pressure. Yes. On the other hand, the drive motors 22b, 23b, and 24b are respectively connected to a control device 45 having a built-in motor driver. With the above configuration, the indentation forming the recess 102 can be processed at an arbitrary position by moving the molding die M to a desired relative position with respect to the punch 30. Next, the punch 30 is fixed to a chuck 26 that can be easily replaced, such as a three-claw chuck, and is fixed at the tip of a shaft body 27 that supports the chuck 26 so as to be movable up and down. A position detection sensor 44 is provided in the vicinity of the shaft body 27 to detect the amount of movement of the shaft body 27 in units of microns, and the measurement value is sent to the control device 45.
[0042]
The shaft body 27 is provided so as to be movable up and down by a precision thrust bearing 28 fixed to the overhang portion 21b of the base 21, and the chuck 26 can be moved in the illustrated vertical arrow direction with zero radial play. ing. The connecting lever 29 is connected to the upper end portion of the shaft body 27 via a rotating portion 29b that is rotatably supported. Further, the upper end of the connecting lever 29 is rotatably connected at a rotating portion 33 b of the main lever 33.
[0043]
The right end portion of the main lever 33 is swingably supported by a bearing 32 serving as a swing fulcrum fixed to the overhang portion 21b. Further, a rubber bush 37 for buffering an impact load is fixed to the left end portion of the main lever 33, and the upper end portion of the rod 38 is located through the rubber bush 37 as shown in the drawing, and the main lever 33 is in a position shown in a broken line. It is supported so that it can always move in the vertical direction as it moves. A plate 39 for mounting a weight 40 for weighing is fixed to the lower end of the rod 38.
[0044]
Further, the distance L2 from the bearing 32 to the rubber bush 37 is set to a distance that is exactly 10 times the distance L1 from the bearing 32 to the rotating portion 33b, and a load that is simply 10 times the weight of the weight 40 is punched. I am trying to join 30. A spring hook 34 is fixed to the upper end of the main lever 33, and a lower end portion of a spring 35 whose upper end is supported by an adjustable spring support portion 36 fixed on the base 21 is supported by the spring hook 34. Thus, the zero point adjustment before setting the weight 40 on the plate 39 is performed.
[0045]
On the other hand, the sliding surface 33c of the main lever 33 or the bearing fixed to the main lever always abuts against the cam surface 43b of the cam plate 43 to maintain the position shown in the figure, and after the weight 40 is set. As the cam plate 43 rotates in the direction of the arrow d2, the main lever 33 is driven to swing between the positions indicated by the solid line and the broken line. For this purpose, the cam plate 43 is pivotally supported by a shaft body 42 fixed to the base 21 and obtains power from a cam motor 41 fixed to the base 21. This cam motor 41 is connected to a control device 45.
[0046]
In the forging device 20 configured as described above, the cam surface 43b of the cam plate 43 is set so that the punch 30 moves up and down as shown in the timing chart of FIG. That is, the punch 30 descends toward the machining surface of the molding die M at time t1, and the forging of a predetermined depth is performed in the latter half of the time t2 with a gentle descending speed just before contacting the machining surface. Later, the punch 30 is rapidly raised within time t3. Following this, at the time t4, the parallel movement tables 23 and 24 are moved to perform the next forging process. By repeating the above operation, a molding die M for injection-molding the convex portion 6 as shown in FIG. 2 is obtained.
[0047]
  In this forging process, when the light source 4 is disposed on one side of the light guide member 1 as shown in FIG. 2, the forging process is sequentially performed in order from the part far from the light source.Do. Further, when the light source 4 is disposed on the opposite sides of the light guide member 1 using a single light guide member 1, forging is performed sequentially from the central portion toward the side..
[0048]
Further, in the forging process, an optimum molding die M can be obtained by using a punch 30 having a glossy surface or a rough surface and performing forging by combining any of the following conditions: it can.
(A) A constant load is applied at a constant speed to the processing surface of the molding die M made of a metal material including iron, aluminum, gold, brass, copper, and beryllium copper.
(B) move at a constant depth
(C) Repeat the same process shown in FIG. 5 to change the constant depth in multiple stages to the final depth.
(D) using a plurality of punches 30 having the same shape or different shapes, and moving the depth by a plurality of times.
(E) Forging is performed simultaneously or individually using a plurality of punches 30 having the same shape or different shapes.
[0049]
Next, FIG. 6 is a diagram showing experimental data of forging by the forging device 20, and the vertical axis indicates the depth F (unit: microns) formed by the tip 30t of the punch 30 reaching the vertical axis. The indentation radius (unit: micron) is shown on the horizontal axis. In addition, it is a diagram showing the raised height of the peripheral portion of the indentation after forging by H so that the horizontal axis coincides with the surface of the processing surface of the molding die M.
[0050]
In this figure, M1, M2, M3, and M4 are extracted as metal materials of the molding die M, the weight 40 is set to 450, 1000, and 2000 g, and the actual load is set to 0.45, 1, and 2 kg, and the results shown in the figure are obtained. It was.
[0051]
As shown in the drawing, a metal having a low raised height H in the peripheral portion like M1 is preferable, and a value obtained by dividing the height H by the depth F is 10% or less. It can be used. That is, it is not necessary to perform secondary processing by grinding or the like on the height H of the peripheral portion. Examples of the metal material having such a low raised height H include metals having high forgeability such as copper, brass, and gold.
[0052]
  The processed surface of the molding die M obtained by the forging process as described above is smoothed, and the indentations that serve as the mold recesses 102 for forming the projections 6 of the light guide plate 1 are high density portions (lateral The part where the pitch Pw and the vertical pitch Pd are, for example, 0.3 mm or less)ProcessedSince the shape of the mold recess 102 is affected and may be deformed, forging is performed by sequentially forging from the mold recess 102 at a location far from the light source 4.InEven if the shape distortion occurs, it is possible to make the processing distortion only on the reflective surface 6b (FIG. 3B) side of the light source in the convex portion 6.
[0053]
That is, as described with reference to FIG. 3, the reflecting surface 6 a of the convex portion 6 that contributes to reflection is forged by the punch 30 so as to be an accurate inclined surface, so that light is reflected in the convex portion 6. Can minimize the impact of the process.
[0054]
Next, the molding die M having the indented mold recess 102 forged as described above is removed from the work clamp 25 of the forging apparatus 20 and then set in the injection molding machine.
[0055]
Although this injection molding is well known, in simple terms, in the schematic diagram of FIG. 7, a molding die M having a cavity C is obtained, and an acrylic resin material is used for injection molding under predetermined conditions. The light plate 1 is obtained. At this time, the smooth portion 106 for forming the back surface of the light guide plate is processed to be a mirror surface. In addition, when the light source 4 is arrange | positioned in the both sides of the light-guide plate 1 and the light-incidence surface 1f is provided in both sides | surfaces, in order to avoid the influence of a process distortion as mentioned above, it is an outer side in order from the center part of the cavity C. It will be forged toward the end.
[0056]
In the forging device 20 shown in FIG. 4, the tip portion has a conical shape, and the apex angle of the punch 30 is set in the range of around 110 ° to 150 °, and good results can be obtained. It was. Further, since the punch 30 is used for forging, the surface shape and the finished surface state of the punch 30 are transferred as they are to the processing surface side of the molding die M. Scratch-like cutting marks are not left. That is, according to the punch 30, it should be noted that no cutting trace remains.
[0057]
Further, according to the cutting drill driven to rotate, cutting into a triangular pyramid, a quadrangular pyramid, a polygonal pyramid, or a roof shape other than the conical surface is impossible at all. Can be processed.
[0058]
8 and 9 are lists showing that the punch 30 can be forged into an arbitrary shape. In both figures (a) to (o), a front view showing the shape of the front end of the punch, a plan view of the front end of the punch, a shape that is injection-molded as a convex portion 6 on the light guide plate, and a critical angle or more The external perspective view which showed a mode that the light which light-entered in (5) is reflected is each shown.
[0059]
First, in FIG. 8A, the punch is ground and polished into a conical shape having an apex angle of 110 ° to 150 °, and is injection-molded as a conical convex portion as shown in the drawing on the light guide plate. As a result, as described with reference to FIG. 3, light incident at a critical angle β or more is reflected in the direction of the arrow.
[0060]
In FIG. 8B, the punch is ground and polished into a conical shape with an apex angle of 110 ° to 150 °, while the apex portion is rounded into a spherical shape. In the molding die obtained from this punch, the light guide plate is injection-molded as a conical convex portion as shown in the figure, and can be configured so that the spherical portion does not stand out. As a result, as shown in FIG. The light incident above can be reflected in the direction of the arrow and the spherical portion can be made inconspicuous.
[0061]
In FIG. 8C, the punch is ground and polished into the above-mentioned conical shape, while the apex portion is processed flat. In the molding die obtained from this punch, the light guide plate is injection-molded as a conical convex portion as shown in the figure, and by setting the area of the flat portion appropriately, as described in FIG. It becomes possible to control the amount of light when the light incident on is reflected in the direction of the arrow.
[0062]
In FIG. 8D, the punch is composed of a regular triangular body, and a triangular pyramid is formed at the tip as shown. The molding die obtained from this punch is injection-molded as a triangular pyramid convex portion as shown in the figure on the light guide plate. For example, it enters at an angle of 180 ° or more from the three sides with a critical angle β or more from the three sides. The emitted light can be reflected in the direction of the arrow.
[0063]
Further, in FIG. 8 (e), the punch has a square body, and a quadrangular pyramid is formed at the tip as shown. The molding die obtained from this punch is injection-molded as a convex portion of a quadrangular pyramid as shown in the figure on the light guide plate, and is incident at a critical angle β or more with respect to the inclined surface from four directions at intervals of 90 degrees. The reflected light can be reflected in the direction of the arrow. Therefore, for example, the light source can be arranged on all four side surfaces so that the luminance can be significantly increased. In addition, it is possible to obtain various colors by arranging light sources of different colors on the four side surfaces so that additive colors are mixed at the convex portions.
[0064]
In FIG. 8 (f), the punch is formed of a square body, and a quadrangular pyramid is formed at the tip as shown in the drawing, and the apex is spherical. The molding die obtained from this punch can be configured so that the spherical portion is not conspicuous in the same manner as in FIG. 8B. As a result, as shown in FIG. While reflecting in a direction, it can comprise so that a spherical part may not be conspicuous.
[0065]
In FIG. 8 (g), the punch is formed of a square body, and a flat portion is formed by forming a square pyramid at the tip as shown. In the molding die obtained from this punch, the amount of light can be controlled in substantially the same manner as in FIG.
[0066]
In FIG. 9 (h), the punch is formed of a square body, and a roof-like shape portion is formed at the tip as shown. In the molding die obtained from this punch, as shown in the external perspective view, the light incident at a critical angle β or more can be reflected in the arrow direction from the left and right directions as described in FIG.
[0067]
In FIG. 9 (i), the roof-like apex portion of FIG. 9 (h) is rounded, and the portion is configured so as not to stand out.
[0068]
Further, in FIG. 9 (j), the punch is formed of a body portion having a rectangular cross section, and a roof-like shape portion of the approaching ridge is formed at the tip as shown in the drawing. In the molding die obtained from this punch, as shown in the external perspective view, light incident at a critical angle β or more from the left and right front-rear direction can be reflected in the arrow direction.
[0069]
Further, in FIG. 9 (k), the punch is composed of a body portion having an oval cross section, and a roof-like shape portion of the deformation ridge is formed at the tip as shown in the drawing. In the molding die obtained from this punch, as shown in the external perspective view, light incident at a critical angle β or more from the front and rear, right and left directions can be reflected in the arrow direction.
[0070]
In FIG. 9 (l), the punch is composed of a body portion having an oval cross section, and forms a roof-like shape portion of a deformed ridge consisting of an arc surface and a flat surface at the distal end portion as shown. In the molding die obtained from this punch, as shown in the external perspective view, light incident at a critical angle β or more from the front and rear, right and left directions can be reflected in the arrow direction.
[0071]
In FIG. 9 (m), the punch is composed of a body portion having an oval cross section, and a trapezoidal conical shape portion is formed at the tip as shown. In the molding die obtained from this punch, as shown in the external perspective view, light incident at a critical angle β or more from the front and rear, right and left directions can be reflected in the arrow direction.
[0072]
In FIG. 9 (o), the punch has a rectangular body having a rectangular cross section, and a deformed gable roof-shaped portion is formed at the tip as shown. In the molding die obtained from this punch, as shown in the external perspective view, only light incident at a critical angle β or more from the left direction can be reflected in the arrow direction.
[0073]
According to the luminance characteristics obtained by observing the light guide plate injection-molded from the molding die obtained using the punch described above from an oblique direction, for example, the angle characteristics can be improved more than ensuring the luminance, or from the vertical direction. It can be arbitrarily set, such as greatly improving the brightness of the screen.
[0074]
As described above, by directly forging a mold for injection molding the light guide plate 1 with a punch, it is possible to freely set the shape, size, and the like of the convex portion 6 of the light guide plate after injection molding. it can. In addition, according to the forging device 20 described above, since the weight of the weight is used as a load, the cutting edge does not escape as in the case of cutting even when the processing surface is inclined, so that forging is surely performed. Can do. In addition, since the interval between the protrusions 6 can be made extremely narrow and the amount of light emitted from the light guide plate can be increased, the brightness is increased by about 1.5 times or more than that of conventional chemical etching. I confirmed that.
[0075]
Note that the light guide plate 1 is used for a liquid crystal backlight for a mobile phone, a notebook personal computer or a car navigation device having a larger display screen, and suppresses the power consumption of a fluorescent lamp as a light source as much as possible. Excellent performance for liquid crystal backlights used when desired. Further, the light guide plate can be applied in various other ways, and a light source and a reflection frame are appropriately designed according to the purpose of use of the surface light emitting device using the light guide plate. Further, as a rough surface processing method of the punch, various types of processing can be performed in addition to the sand blasting method, for example, an etching method for forming a texture performed after die processing.
[0076]
FIG. 10 is a schematic diagram showing another configuration example of the forging device used in the forging process of the mold material for the light guide plate 1 injection-molded as described above.
[0077]
In this figure, the forging device is based in part on the operating principle of a Vickers hardness tester that measures the hardness of the object to be measured from the size of the indentation remaining when a known load is applied to the surface to be measured. However, the forging device is completely different from the hardness meter as shown in the figure.
[0078]
First, the forging apparatus is provided with a front / rear / left / right moving table 324 on a base 321 serving as a base, and is connected to a vacuum pressure supply source for fixing the molding die M to a stationary state by a vacuum pressure. Or a work clamp with the illustrated mechanical fixture is secured. On the other hand, an air cylinder 337 connected to the control device is provided on the upper portion of the base 321.
[0079]
A shaft body 4 having a weight 340 fixed thereto is connected to the air cylinder 337, and the compression spring 333 at the lower end of the shaft body 341 is moved by a predetermined stroke S as the air reeler 337 is driven so that the spring guide 334. In this state, the punch 30 at the lower end of the moving shaft 327 is formed by moving the moving shaft 327 movably provided by the sliding bearing 328 at the lower end of the compression spring 333 in the vertical direction. The recesses are processed so as to bite into the upper part of the mold M.
[0080]
In addition, a chain 335 is provided between the lower end of the shaft body 341 and the upper end of the moving shaft 327 so as to be stretched and slackened, and a tensile force is applied when the moving shaft 327 moves upward.
[0081]
With the above configuration, the indentation that becomes the concave portion 102 can be processed at an arbitrary position by moving the molding die M to a desired relative position with respect to the punch 30.
[0082]
Next, FIG. 11 is a relationship diagram of the stroke S and the depth of the impression by the movement of the air cylinder 337, and FIG. 12 is a flowchart for explaining the operation of this apparatus.
[0083]
11 and 12, in step S <b> 1, the air cylinder is driven up, and the punch 30 is separated from the processing surface of the mold M. Next, in step S2, the shaft body 341 is lowered downward, the punch 30 comes into contact with the machining surface, the shaft body 341 is further lowered, the compression spring 333 is compressed by the action of the weight 340, and machining starts. Further lowered in S4, the weight of the weight 340 and the compression force of the compression spring 333 are balanced. Before and after this, the chain 335 is loosened.
[0084]
Next, in step S5, the shaft body 341 is further lowered, the limit switch 399 is turned on, and a temporary standby is performed in the lowered state. Next, in step S6, the air cylinder 337 is operated to raise the shaft body 341, and the punch 30 is separated from the processing surface. In step S6, the table 324 is driven to move to the next machining site. Next, in step S8, the process returns to step S2 and is repeatedly executed.
[0085]
In this forging process, when the light source 4 is arranged on one side of the light guide member 1 as shown in FIG. 2, the forging process is sequentially performed from the part far from the light source, and the influence of the distortion after processing is affected. Do not extend to subsequent processing. Further, when the light source 4 is disposed on the opposite sides of the light guide member 1 using a single light guide member 1, the forging process is performed sequentially from the center to the side. This prevents the subsequent distortion from affecting the subsequent processing.
[0086]
【The invention's effect】
  As described above, according to the present invention, it is possible to reliably process the recesses processed on the processing surface of the molding die within a very short time so as to obtain a high density substantially proportional to the distance from the light source. In addition, the concave portion can be processed into any other shape such as a triangular pyramid, a quadrangular pyramid, a polygonal pyramid, a roof shape other than the conical shape, and can be set as needed so that the processed surface state is glossy or rough. Therefore, according to this molding die, a method for manufacturing a light guide member having unprecedented excellent optical characteristics can be provided.In addition, by forging in order from the part where the recesses have a relatively high density to the part where the recesses are made to have a low density, the effect of processing distortion during forging is minimized when light is reflected in the convex part after completion. Can be limited.
[0087]
[Brief description of the drawings]
[Figure 1]surfaceCross section of light emitting deviceIt is.
FIG. 2 is a cross-sectional view taken along the line XX in FIG.
FIG. 3A is a schematic diagram showing a state of reflection of light L entering the light guide plate 1; FIG. 5B is a cross-sectional view of a main part showing a state of reflection of the light L at the convex portion 6.
FIG. 4 is a schematic configuration diagram of a forging device.
FIG. 5 is a timing diagram for driving the punch up and down.
FIG. 6 is a diagram showing experimental data for forging.
FIG. 7 is a process diagram of injection molding.
FIG. 8 is a list showing that the punch 30 can be forged into an arbitrary shape.
FIG. 9 is a list showing that the punch 30 can be forged into an arbitrary shape.
FIG. 10 is a schematic configuration diagram of a forging device.
FIG. 11 is a timing diagram for driving the punch up and down.
12 is an operation flowchart of the apparatus shown in FIG.
13A is an enlarged cross-sectional view of a conventional light guide plate 10, and FIG. 13B is an enlarged cross-sectional view of an injection mold 201 used for injection processing the light guide plate 10. FIG.
[Explanation of symbols]
1 light guide plate,
2 diffusion plate,
3 Reflective frame,
4 Light source,
5 Substrate
6 Convex,
20 forging machine,
30 punches,
M mold,
β critical angle

Claims (6)

A light source is disposed on at least one side of a light-transmissive plate-shaped light guide member, and light from the light source is guided from the side light incident surface to the inside of the light guide member. In order to illuminate by diffusing light in a diffusing member arranged side by side on the light emitting surface of the light member, there is a method for manufacturing a light guide member in which an infinite number of post-projections having a predetermined shape are formed on the back surface of the light emitting surface. And
A forging step of obtaining a molding die having a recess by sequentially forging a processed surface with one or a plurality of punches so as to have a high density substantially proportional to the distance from the light source;
Using the molding die, and injection molding the light guide member formed by injection molding from a light-transmitting resin material and forming innumerable convex portions after completion, and a molding step ,
In the forging step, forging is performed in order from a portion having a relatively high density of the concave portion to a portion having a low density .   The predetermined shape is set so that incident light incident at a critical angle β or more determined from the resin material is reflected toward the light emitting surface on the inclined surface of the convex portion after completion, and the back surface is made a mirror surface The manufacturing method of the light guide member of Claim 1 characterized by the above-mentioned. The shape of the tip portion of the punch used to form the inclined surface of the finished rear protrusions, conical or polygonal cone shape apex angle is Ru contained in the range of 150 degrees to 110 degrees, gable roof shape, submitted building roof shape, or, the top portion is spherical or flat conical or pyramid shape, or according to claim 2, wherein the top portion thereof is either roof spherical shape Manufacturing method of light guide member. In the forging step, the recess is
When the light source is disposed on one side of the light guide member, the light source is formed at a relatively high density in a portion far from the light source and closer to the opposite side of the light guide member. when each disposed laterally of claims 1 to 3, characterized in that it is relatively densely formed than portions closer to each of the light source at the center of the site between the light source The manufacturing method of the light guide member of any one of Claims 1. In the forging step, using the punch whose surface has a glossy surface or a rough surface ,
(A) a forging process in which a constant external energy is applied to the processing surface of the molding die made of a predetermined metal material;
(B) Forging process for moving a certain depth,
(C) a forging process in which the predetermined depth is changed in a plurality of stages to a final depth;
(D) Forging process in which a plurality of punches having the same shape or different shapes are used, and the depth is moved by a plurality of times.
(E) using a plurality of punches or having different shapes have the same shape, either simultaneously or separately carried out forging,
The method for manufacturing a light guide member according to claim 1, wherein the molding die is obtained by combining any of the above . As the metal material constituting the molding die, a metal material having a raised height in the periphery after forging a certain depth of the concave portion of the molding die is 10% or less of the certain depth is used. The manufacturing method of the light guide member of any one of Claim 1 thru | or 5 characterized by the above-mentioned.

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