JP3507982B2 - Mold and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used for manufacturing a transparent substrate of a planar lighting device used for lighting means such as signboards and various reflection type display devices, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Liquid crystal display devices that operate with low power consumption are
Because of its features such as thinness and lightness, the demand as a display device mainly for computer applications is increasing. Since the liquid crystal which is a constituent member of the liquid crystal display device does not emit light by itself, unlike a light emitting element such as a cathode ray tube, an illuminating means for observing an image is required. In particular, in response to the recent demand for thinning, a flat plate sidelight type (light guide plate type) planar illumination device is often used as the illumination means for illuminating the liquid crystal display device.

As an example of such a sidelight type planar illumination device, a transparent substrate 102 made of a translucent material, for example, as shown in FIG. 4, is arranged so as to cover the screen (observation surface) of the liquid crystal display device, One end surface 103a of the transparent substrate 102
(Linear light source arranged close to (left end face in FIG. 4))
(Not shown in the drawings).

A light reflection pattern 112 is formed on one surface of the transparent substrate 102. The light reflection pattern 112 is
The one side end face 103a extends parallel to the one side end face 103a.
A large number of groove portions 113 having a substantially triangular cross-section, which are arranged from a toward the opposite end surface 103b (right end surface in FIG. 4).
And a flat portion 114 adjacent to each groove 113. The depth of the groove 113 is constant and the light source is
The flat portion 11 is formed so that a large number of groove portions 113 are formed as the distance from the (not shown, left side in FIG. 4) increases (the right side in FIG. 4).
4 is gradually narrowed (the width of the mold flat portion 133 is gradually narrowed in the mold 130 described later). By providing the light reflection pattern 112, the brightness is made substantially uniform at any position of the transparent substrate 102 without being influenced by the distance from the light source.

The transparent substrate 102 (light reflection pattern 11
2) is manufactured by injection molding, thermal processing molding, extrusion molding, cast molding, or the like, using a mold 130 having a surface portion 131 having a shape opposite to the light reflection pattern 112 including the groove portion 113. Surface part 131 of mold 130
Includes a plurality of projections 132 corresponding to the groove 113 of the light reflection pattern 112 and the flat portion 1 of the light reflection pattern 112.
14, a flat portion (hereinafter referred to as a mold flat portion) 133 formed between the convex portions 132 is formed, and the surface portion 131 has the shape of the transparent substrate 1 as described above.
The pattern is opposite to the light reflection pattern 112 of No. 02.

As shown in FIGS. 5 and 6, the mold 130 is manufactured by cutting using a cutting tool 140. In this case, the bite 140 has a width dimension W of its tip.
Of the flat portion 114 of the transparent substrate 102 having a minimum width (hereinafter, referred to as a minimum width flat portion 114a; the right side of FIG. 4) is set to be equal (slightly shorter).

Then, the mold 1 using the cutting tool 140
The cutting process of 30 is performed as follows. That is,
As shown in FIG. 4, the cutting process of the mold 130 is performed on the transparent substrate 1
The part 135 of the mold 130 corresponding to the flat part 114 of No. 02 (hereinafter referred to as the cutting target part) 135 is performed.
Then, as shown in FIGS. 4 and 6A, the transparent substrate 1
For the portion of the mold 130 (hereinafter referred to as the first cutting target portion) 135a corresponding to the minimum width flat portion 114a of No. 02, the first cutting target portion 135a is cut by the cutting tool 140 to have a predetermined width (width). One die flat portion 133 having a dimension corresponding to the dimension W) is formed.

The minimum width flat portion 11 of the transparent substrate 102
For the portion (hereinafter referred to as the second cutting target portion) 135b of the die 130 corresponding to the flat portion (indicated by reference numeral 114b) adjacent to 4a, the second cutting is performed as shown in FIG. 6 (b). The target part 135b is once cut with the cutting tool 140. After that, the bite 140 is moved to the left in FIG.
As shown in (c), the second cutting target portion 135b is cut again, and as shown in FIG. 6D, the second cutting target portion 135b is formed into the first cutting target portion 135a. In comparison, one die flat portion 133 having a wider width is formed. Hereinafter, similarly, a plurality of cutting processes are performed in order to obtain one die flat portion 133, and the die 130 having the plurality of die flat portions 133 formed is manufactured.

[0009]

By the way, in the above-mentioned conventional technique, the cutting tool 140 is moved to perform one or more cutting operations in order to obtain one die flat portion 133.
Therefore, as shown in FIG. 7, a step 151 may occur at the mating portion of the cutting tool 140 in the mold flat portion 133.

Then, the transparent substrate 1 is formed by the mold 130.
In the case of producing (molding) 02, the produced transparent substrate 10
A step (hereinafter, referred to as a substrate-side step, not shown) corresponding to the step 151 is formed on the second flat portion 114. In the transparent substrate 102 having the substrate-side step on the flat portion 114 as described above, light is scattered due to the substrate-side step, resulting in not only loss of light but also stray light, which leads to deterioration of display contrast. .

As another example of the mold used for manufacturing the transparent substrate, the interval between the adjacent convex portions (corresponding to the interval between the groove portions in the transparent substrate corresponding to the mold) is made constant and convex. There is one in which the width and height (corresponding to the width and the depth in the transparent substrate corresponding to the mold) of the parts are set to be sequentially changed (for example, increased) along the arrangement direction. Also in this mold, the width dimension of the mold flat portion changes along the arrangement direction similarly to the mold flat portion 133 of the mold 130. Therefore, if this mold is manufactured by cutting as described above, a step may occur in the flat part of the mold as in the case shown in FIG. 7. Then, in the transparent substrate manufactured by using this mold, a substrate-side step is formed in the flat portion, which causes the loss of light and the deterioration of the display contrast as in the conventional example.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a mold and a method for manufacturing the same, which makes it possible to manufacture a transparent substrate having good optical characteristics.

[0013]

According to a first aspect of the present invention, there is provided a light reflection having a plurality of groove portions on a surface portion and a plurality of flat portions having an equal width formed between the groove portions. A method for manufacturing a die for a transparent substrate provided with a pattern, wherein a width dimension of the flat portion is formed on a surface portion of the die so as to leave a plurality of convex portions forming a reverse pattern with the groove portions of the plurality of rows. Is used to cut a portion of the surface portion between the plurality of protrusions.

According to a second aspect of the present invention, the transparent substrate is provided with a light reflection pattern having a plurality of groove portions and a plurality of flat portions of equal width formed between the groove portions on the surface portion. A plurality of mold flats having the same width dimension between the protrusions of the plurality of protrusions, the protrusions of the plurality of protrusions forming an inverse pattern to the groove of the plurality of protrusions are left on the surface portion. It is characterized in that a part is formed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. The same parts and members as those in FIGS. 4 to 6 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. The present invention is mainly shown in FIGS. 2 and 3, but prior to the description thereof, a planar lighting device 1 using a transparent substrate 2 produced by a mold 30 shown in FIGS. 2 and 3 will be described. It will be described based on.

In FIG. 1, a planar lighting device 1 is generally constructed by arranging a light source 4 close to one end face 3a of a substantially rectangular transparent substrate 2 made of a translucent material. It is arranged so as to cover the observation surface of a liquid crystal element (not shown) and is used as auxiliary illumination.

The light source 4 is a light guide body 5 made of a linear transparent material, which is arranged close to the one end surface 3a of the transparent substrate 2.
And a point light source 6 arranged facing the one end 5a of the light guide 5. The other end 5b of the light guide 5
The reflection plate 7 is disposed so as to face.

The transparent substrate 2 is made of a material that allows light rays to pass through efficiently. Acrylic resin is most suitable for this material because of its transparency and processability.
Instead of this, it is also possible to use various thermoplastic transparent resins such as vinyl chloride resin, polycarbonate resin, olefin resin, and styrene resin. In addition, thermosetting transparent resins such as epoxy resin and allyl diglycol carbonate resin, and inorganic transparent materials such as various glass materials can be applied depending on the case.

The transparent substrate 2 is manufactured using a mold 30. As a method for producing the transparent substrate 2, direct machining such as cutting and grinding, or various molding methods such as a casting method, a hot press molding method, an extrusion molding method, and an injection molding method can be applied. From the viewpoint of productivity, the injection molding method using a resin material is most suitable.

The transparent substrate 2 has the same plate thickness as a whole between the one end face 3a and the other end face 3b opposed thereto. One (the upper side in FIG. 1) of the surface portions of the transparent substrate 2 having a large area (observation surface; hereinafter referred to as the surface).
The light reflection pattern 12 having a shape corresponding to the surface of the mold 30 is formed on the surface 11a. In addition, the surface portion (the lower surface portion in FIG. 1) facing the surface 11a of the transparent substrate 2 is
Hereinafter, it is referred to as the back surface 11b.

The light reflection pattern 12 extends in parallel with the one end face 3a and is arranged from the one end face 3a to the other end face 3b, and has a multiplicity of grooves 13 having a substantially triangular cross-section.
It is composed of a flat portion 14 adjacent to each groove portion 13. The flat portion 14 [corresponding to the die flat portion 33 in the die 30 corresponding to the transparent substrate 2]. ] Has a constant width t2
[Corresponding to width dimension W1 (dimension t1) described later],
The width and depth of the groove 13 [corresponding to the width and height of the protrusion 32 in the mold 30. ] Is formed so as to increase as the distance from the light source 4 increases.

By providing the light reflection pattern 12 as described above, the brightness is made substantially uniform at any position of the transparent substrate 2 without being influenced by the distance from the light source 4. Since the groove 13 of the light reflection pattern 12 formed on the transparent substrate 2 is extremely fine, it is difficult to visually confirm it when observing the screen.

In FIG. 1, reference numeral 15 denotes a frame made of a metal such as aluminum or stainless steel having a substantially U-shape, which covers the light guide 5 and is on the side of the one end face 3a of the transparent substrate 2 (hereinafter, the transparent substrate base). It holds up to eight.

The optical path changing means 1 is provided on one surface 5c of the light guide 5.
6 is provided. The optical path changing means 16 is composed of a groove portion 16a having a substantially triangular cross section and a flat portion 16b formed between the groove portions 16a.
It is uniformly radiated on the other surface portion 5d facing to.

The light guide 5 is made of a material that allows light rays to pass through efficiently. Acrylic resin is most suitable because of its transparency and processability. Instead of this, it is also possible to use various thermoplastic transparent resins such as vinyl chloride resin, polycarbonate resin, olefin resin, and styrene resin. In addition, thermosetting transparent resins such as epoxy resin and allyl diglycol carbonate resin, and inorganic transparent materials such as various glass materials can be applied depending on the case.

As the method for producing the light guide 5, direct machining such as cutting and grinding, or various molding methods such as casting method, thermocompression molding method, extrusion molding method and injection molding method can be applied. However, from the viewpoint of productivity, the injection molding method using a resin material is most suitable.

Here, a method of manufacturing the mold 30 and a method of manufacturing the transparent substrate 2 using the mold 30 will be described with reference to FIG.
And FIG. 3 will be described. The transparent substrate 2 (light reflection pattern 12) has a mold 30 having a surface portion 31 having a shape opposite to the light reflection pattern 12 including the groove portion 13.
Is produced by injection molding, thermal processing molding, extrusion molding, cast molding or the like as described above.

On the surface portion 31 of the die 30, a plurality of projections 32 corresponding to the grooves 13 of the light reflection pattern 12 and the flat portions 14 of the light reflection pattern 12 are formed between the projections 32. A flat portion 33 (hereinafter referred to as a mold flat portion) is formed, and the shape of the surface portion 31 is a pattern opposite to the light reflection pattern 12 of the transparent substrate 2 as described above. That is, the mold 30 has the mold flat portion 33.
The width t1 (corresponding to the width W1 of the tip portion of the cutting tool 40 described later) is made constant, and the width and height of the convex portion 32 are formed so as to increase as the distance from the light source 4 increases. Since the width dimension t1 of the die flat portion 33 and the width and height of the convex portion 32 are formed in this manner, the interval dimension t3 of the adjacent convex portions 32 is the arrangement direction of the convex portions 32 (the transparent substrate 2). Then, the interval dimension t4 of the adjacent groove portions 13 differs depending on the arrangement direction of the groove portions 13).

The mold 30 is manufactured by cutting using a cutting tool 40. In this case, in the cutting tool 40, the width dimension W1 of the tip end portion thereof is the width dimension t2 of the flat portion 14 of the transparent substrate 2 (each width dimension of the plurality of flat portions 14 is equal as described above). (T2 corresponds to approximately t1) is used (slightly shorter).

Then, the die 30 using the cutting tool 40
The cutting process of is performed as follows. That is, FIG.
As shown in FIG. 5, a part of the die 30 corresponding to one flat part 14 of the transparent substrate 2 (referred to as a cutting target part) 35 is subjected to one cutting process by a cutting tool 40 (that is, a cutting tool). One die flat portion 33 having a predetermined width dimension t1 is formed without laterally feeding 40.

In the present embodiment, a plurality of the cutting target parts 35 are provided at equal intervals, but the cutting tool 40 is also similarly provided for each of the plurality of cutting target parts 35.
Thus, one die flat portion 33 having a predetermined width t1 is formed by performing one cutting process (that is, without laterally feeding the cutting tool 40). Then, by performing this cutting process on all the cutting target portions 35, an equal width (t1)
A mold 30 having a plurality of mold flat portions 33 is manufactured.

As described above, one die flat portion 33 is formed by one cutting process, and a plurality of cutting tools are used to obtain one die flat portion as described in the prior art.
There is no step difference that may occur due to laterally moving and cutting.

Then, using the mold 30 having no steps on the mold flat portion 33, the transparent substrate 2 is
It is produced by injection molding, heat processing molding, extrusion molding, cast molding, or the like. When the transparent substrate 2 is manufactured (molded) as described above, since the mold 30 does not have a step in the mold flat portion 33, the flat portion 14 of the manufactured transparent substrate 2 has the above-mentioned conventional structure. A step (step on the substrate side) that can occur in the technology is not formed, and the surface accuracy becomes excellent. Therefore, the light reflection pattern 12 of the transparent substrate 2 exhibits good light characteristics, does not cause light scattering or loss, and further does not cause display contrast reduction.

In the above embodiment, the transparent substrate 2 has the same plate thickness as a whole between the one end face 3a and the other end face 3b, but instead of this, the one end face 3a to the other side. The plate thickness becomes gradually thinner as it becomes the end face 3b,
The transparent substrate 2 may be formed in a so-called wedge shape.

In the above-mentioned embodiment, the transparent substrate 2 is taken as an example of the transparent substrate of the present invention, but instead of this, the light guide 5 is targeted, and the same method as the die 30 is applied to the light guide 5. You may make it produce using.

[0036]

According to the present invention, the width of the flat portion of the transparent substrate is substantially the same as the width of the flat portion of the transparent substrate so that a plurality of convex portions forming a reverse pattern to the plurality of groove portions of the transparent substrate are left on the surface portion of the mold. By using a bite having the same width, the portion between the plurality of convex portions on the surface portion of the die is cut, and each one die flat portion can be produced by one cutting operation. No step is formed on the flat part of the mold. Therefore, no step is formed in the flat portion of the light reflection pattern of the transparent substrate manufactured by using the mold, which does not lead to light scattering or loss, and further lowers the display contrast. There is nothing.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a planar lighting device using a transparent substrate according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the transparent substrate of FIG. 1 and a mold used for manufacturing the transparent substrate.

FIG. 3 is a diagram schematically showing a method of manufacturing the mold shown in FIG.

FIG. 4 is a diagram showing an example of a transparent substrate of a conventional planar lighting device and a mold used for manufacturing the transparent substrate.

FIG. 5 is a diagram schematically showing a method of manufacturing the mold shown in FIG.

6A to 6C are process diagrams showing a method for manufacturing the mold of FIG.

FIG. 7 is a diagram showing a problem in the method of manufacturing the mold of FIG.

[Explanation of symbols]

2 transparent substrate 12 light reflection patterns 14 Flat part 30 molds 33 Flat part of mold 40 bytes

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-8-229955 (JP, A) JP-A-9-115189 (JP, A) JP-A-2000-305073 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 33/00-33/76 G02B 6/00 331

Claims (2)

(57) [Claims] 1. A method of manufacturing a mold for a transparent substrate, the surface of which is provided with a light reflection pattern including a plurality of groove portions and a plurality of flat portions having an equal width formed between the plurality of groove portions. The surface part of the mold is formed by using a cutting tool having a width substantially equal to the width of the flat part so as to leave a plurality of convex parts forming an inverse pattern with the groove parts of the mold part. 2. A method for manufacturing a die, comprising cutting a portion between the plurality of convex portions in the above. 2. A mold for a transparent substrate, wherein a light reflection pattern comprising a plurality of groove portions and a plurality of flat portions having an equal width formed between the plurality of groove portions is provided on a surface portion. A plurality of flat mold portions having the same width dimension are formed between the convex portions of the plurality of ridges, leaving a plurality of convex portions of the plurality of ridges forming a reverse pattern on the surface portion. And the mold.