JP3208303B2 - Manufacturing method of light guide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-light emitting display device,
For example, the present invention relates to a method for manufacturing a light guide for a surface light source, which is suitable for use in a backlight that irradiates a liquid crystal display device with light from the back.

[0002]

2. Description of the Related Art Information devices such as personal computers, word processors, portable information terminal devices, and liquid crystal televisions or consumer devices have been put into practical use as devices using a non-light emitting display device represented by a liquid crystal display device as a display. In these devices, as shown in FIG. 4, a light guide 11 and fluorescent tubes 1 arranged on both sides thereof are provided on the back of a liquid crystal panel 10.
2, a backlight 14 comprising a lens film 13 disposed on the light exit surface side of the light guide 11 is provided;
A structure in which the liquid crystal panel 10 is irradiated with uniform light from the back side thereof is known (Nikkei Micro Device 1).
(See page 79, October 995).

[0003]

The price requirements of devices incorporating such a backlight 14 in the market are severe, and further reduction in manufacturing costs is desired in order to have price competitiveness.

The present invention has been made for the purpose of reducing the manufacturing cost.

[0005]

According to a first aspect of the present invention, there is provided a method of manufacturing a light guide in which a light emitting surface is arranged on one surface side. An exchangeable pattern mold having a pattern corresponding to the shape of the light emitting surface of the light guide is held by a common mold of one mold by a holding member exchangeable with the common mold. A step of combining the first mold and the second mold, a step of filling the cavity surrounded by the first mold and the second mold with a resin, and a step of curing the resin. At least, the holding member defines a part of the cavity,
The outer shape of the light guide is defined, and light guides having a plurality of outer shapes are manufactured by replacing the holding member.

[0006] The manufacturing method of the invention according to claim 2 is characterized in that:
The pattern mold is formed with a fine pattern that gives a lens effect to light emitted from the light emitting surface.

Further, the manufacturing method according to the third aspect of the present invention is characterized in that:
A rough surface pattern for blocking light transmission is formed on a surface of the mold facing the light emitting surface.

[0008]

[0009]

1 and 2 are schematic views showing the resin molding process for explaining the manufacturing method of the present invention in each state, and FIG. 3 is a cross-sectional view of a light guide manufactured by the resin molding process. is there.

In the resin molding process shown in FIGS. 1 and 2, the first and second molding dies 1, which can be divided as shown in FIG.
2 is prepared, the second mold 2 is moved to the first mold 1 side, and the two are joined. Thereafter, a molten thermoplastic resin (for example, acrylic resin) held at about 200 degrees Celsius from an injection port (not shown) in a cavity 3 formed at the center by surrounding the first and second molds 1 and 2. 200 kg / cm ²
Liquid-filled at a pressure of As such a thermoplastic resin, polycarbonate or a material rich in optical properties can be used. When the filling is completed, the light guide 4 is cooled and held for a predetermined time based on a temperature program determined by the curing condition of the resin material, and the light guide 4 having a predetermined shape is formed.

As shown in FIG. 3, the light guide 4 formed in this embodiment has a light exit surface 4a for emitting light incident from the side to the liquid crystal display side with uniform directionality. The shape shows a fine pattern protruding in a mountain shape (prism shape) or a quadrangular pyramid shape. This fine pattern has, for example, a vertex angle (prism angle) of 90 degrees, a pitch of 31 μm, and a height of 31 μm, and is uniformly formed on the entire light emitting surface 4a. (A direction perpendicular to the light exit surface 4a).

Therefore, in order to form such a fine pattern on the light guide 4, an inverted fine pattern (an inverted pattern in an uneven state) is formed on the mold side. The fine pattern on the mold side is formed so as to correspond to the entire surface of the light emitting surface 4a of the light guide 4, and the pattern is miniaturized, the area of the light guide 4 is increased, and further, a different pattern is formed. Considering the response of
A plate-shaped pattern mold 1b is added to the common mold 1a of the first mold 1.
Are exchangeably held by the holding member 1c over the entire periphery thereof. In other words, when a fine pattern is formed, the use of a flat plate is excellent in workability even for a large area.

In the pattern mold 1b according to this embodiment, an original plate is formed by photolithography and physical vapor deposition (PVD).
After being formed by the method, it is formed into a thin plate having a thickness of about several mm by electroforming plating so as to cover the pattern.
That is, after forming an original plate having the same fine pattern as the light emitting surface 4a of the light guide 4 by photolithography and sputtering or vacuum evaporation, the fine pattern surface is durable with nickel or the like by electroforming plating. A metal rich in iron is deposited in a thickness of 0.2 to 3 mm to form a thin plate. Thereafter, the back surface (the surface facing the fine pattern) of the thin metal plate is polished to make the back surface a mirror surface. When the mirror polishing is completed, the metal sheet is separated from the original plate. The mirror polishing of the back surface of the pattern mold 1b is combined with the mirror polishing of the common mold 1a with which the back surface is in contact, to enhance the positional accuracy of the fine pattern.

Regarding the formation of the pattern mold 1b, a metal flat plate is prepared in addition to the electroforming plating method, and a fine pattern is formed directly on the surface by a laser beam method or a photolithography method. good.

As described above, the thin plate-shaped pattern mold 1b is advantageous in terms of workability of the pattern as compared with the case where the pattern is directly formed on the mold without using the pattern mold 1b. Furthermore, in the case of supporting various patterns, if a mold dedicated to the pattern is prepared, the cost of the mold is added to the manufacturing cost of the light guide 4, which is one barrier to cost reduction.

On the other hand, in this embodiment, the light exit surface 4
The portion of the first mold 1 that determines the pattern (shape) a is a thin plate with respect to the common mold 1a and is freely replaceable, so that the total cost including pattern processing costs, pattern repair costs, and replacement costs is obtained. The aim is to reduce production costs.

As shown in FIG. 4, the conventional backlight 14 requires a separate part of the lens film 13 on the light exit surface side of the light guide 11, but the fine pattern gives a lens effect. Therefore, by using the light guide 4 shown in FIG. 3, such a film lens 13 becomes unnecessary.

As a result, not only can the cost of the lens film as a backlight be reduced, but also the light guide 11 can be reduced.
At the same time, it is possible to avoid a decrease in light transmission efficiency due to a difference in refractive index between the two at the interface between the lens film 13 and the air layer. Therefore, it is possible to provide a high-brightness backlight having improved light transmission efficiency as compared with the conventional product shown in FIG. 4, and if this high-brightness backlight is used at the same brightness as the conventional product, power consumption is reduced. Reduction can be achieved. That is, when the backlight is driven by a battery, the power consumption reduction effect is particularly beneficial.

On the other hand, the protruding portion 2a of the second mold 2, which fits with the first mold 1 and forms a cavity, has a rough surface pattern whose surface is roughened by sandblasting or the like. As a result, the surface of the light guide 4 opposite to the light exit surface 4a, that is, the back surface 4b has a rough surface, and the transmission of light from the back surface 4b is prevented.

Further, in this mold, in order to reduce the manufacturing cost, the holding member 1c for holding the pattern mold 1b of the first mold 1 on the outer periphery thereof and defining the outer shape of the light guide 4 is various. In order to correspond to the outer shape (including different sizes) of the light guide 4 described above, the light guide 4 can be exchanged for the common mold 1a.
That is, when the fine pattern is common and only the outer shape differs,
By simply setting a desired holding member 1c in place of the holding member 1c used previously in the common mold 1a and exchanging the second mold 2 with one corresponding to the shape, a different light guide 4 can be used. Manufacturing becomes possible.

In the embodiment shown in FIGS. 1 and 2, the projecting portion 2a of the second mold 2 is configured to be fitted into the first mold 1 to form the cavity 3. 2a is made flat without protruding, and by forming a rough surface pattern on the flat surface corresponding to the light guide 4 of the largest size that can be manufactured by the replaceable holding member 1c, the above-mentioned different shape is obtained. The second mold 2 does not need to be replaced when the light guide 4 is manufactured, and the sharing of the mold is further promoted, and the manufacturing cost can be reduced.

Also, in this embodiment, one set of molds
Although the manufacture of the light guides 4 has been described, the present invention is not limited to this, and it is possible to cope with the manufacture of a plurality of light guides 4 by devising the shape of the holding member 1c. It is also possible to manufacture the light guide 4 of (size), and in that case, if the combination is determined in consideration of the size of the mold, the use efficiency of the mold can be improved,
Further reduction in manufacturing cost can be achieved.

[0023]

As described above, according to the manufacturing method of the present invention, the manufacturing cost of the light guide can be reduced, and an inexpensive light guide can be provided.

Further, by forming a fine pattern that gives a lens effect on a surface that defines the shape of the light emitting surface, a high-luminance backlight with improved light transmission efficiency can be provided. When the backlight is used with the same brightness as the conventional product, reduction in power consumption can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one state of a resin molding step of the production method of the present invention.

FIG. 2 is a schematic view showing another state of the resin molding step of the production method of the present invention.

FIG. 3 is a sectional view showing a light guide manufactured by the manufacturing method of the present invention.

FIG. 4 is a side view showing a conventional liquid crystal display device including a backlight.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first mold 1a common mold 1b pattern mold 1c holding member 2 second mold 3 cavity 4 light guide 4a light emitting surface 4b back surface

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-134821 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 33/02-33/54 G02B 6 / 00

Claims (3)

(57) [Claims] 1. A method for producing a light guide to place the light emitting surface on one side, of a pair of molds, a common mold of the first mold, the light emission of the light guide member Holding a replaceable pattern mold having a pattern corresponding to the shape of a surface by a replaceable holding member on the common mold ; and coupling the first mold and the second mold . And a step of filling the cavity surrounded by the first mold and the second mold with a resin, and a step of curing the resin, wherein the holding member partially covers the cavity. A method of manufacturing a light guide in which a plurality of light guides having a plurality of outer shapes are manufactured by exchanging the holding member, by defining the outer shape of the light guide by partitioning. 2. A method according to claim 1, wherein the pattern mold is provided on the light emitting surface.
Form a fine pattern that gives a lens effect to the emitted light
The method for producing a light guide according to claim 1, wherein: 3. A surface of the mold facing the light exit surface.
3. The method for manufacturing a light guide according to claim 1, wherein a rough surface pattern for preventing light transmission is formed.