JP2000329910A - Optical material molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the molding method for optical material with high quality and high productivity which is adaptive to the size and thickness reduction of an optical material. SOLUTION: After a primary shape body 11 is molded, a 2nd mold 24 is opened and while the primary shape body 11 is placed in a 1st mold 21, a secondary molding mold 30 is connected to a 1st mold 32 to mold a secondary shape body 12. Consequently, a 2nd mold 24 and the secondary molding mold 30 are only replaced for the 1st mold 21 to mold the optical material 10 having the secondary shape body 12 stacked on the primary shape body 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding an optical material for illuminating an object such as a liquid crystal, and more particularly to a method of sequentially injecting and laminating transparent resins having different light scattering properties to form a flat plate. About.

[0002]

2. Description of the Related Art As an optical material for illumination of a liquid crystal display device or the like, a transparent resin portion (non-scattering region) having different light scattering performance and a portion (scattering region) in which fine particles are mixed in the transparent resin are formed into a flat plate shape. A molded light guide is used. This type of optical material receives light from a light source on at least one end surface of a flat plate, scatters the incident light with fine particles in a light guide, emits the light from a flat surface (light emission surface), and uniformly renders the back of the liquid crystal and the like. Surface illumination. This is when the light exit surface of the light guide is large (that is, when the object to be illuminated has a large area).
This is a method of controlling and uniformizing the light emission distribution from the light emission surface. In the light guide, the light emission distribution is obtained by partially changing the occupancy of the scattering region and the scattering region in the thickness direction. Is controlling.

As the above-mentioned optical material, for example, a material in which two thin triangular prisms (a non-scattering region and a scattering region) are superposed to form a flat plate and light is incident from one end surface is used. However, in recent years, there has been a strong demand for a thin liquid crystal display device and the like along with a demand for a large size. In response to a demand for a large size, simply entering light from one end surface results in insufficient brightness. For this reason, the primary shape having the inverted mountain-shaped concave portion is formed as a non-scattering region, the secondary shape having the mountain-shaped convex portion is formed as a scattering region, and the primary shape is laminated on the primary shape. By making the mountain shape a polygonal pyramid and entering light from each end face, high brightness can be obtained. The shape of the chevron is, for example, prismatic and quadrangular pyramid,
It becomes a very flat mountain shape corresponding to the reduction in thickness.

FIG. 4A shows a quadrangular pyramid (pyramid).
1 shows a perspective view of an optical material formed in a mountain shape of FIG. (B) is a sectional view taken along line IV-IV of (a). This optical material 10 has a first shape (non-scattering region) 11 having an inverted quadrangular pyramid (pyramid) concave portion and a second shape having a quadrangular pyramid convex portion.
And a next-shaped object (scattering region) 12. This optical material 10
As a method of forming the first shape, for example, a method is known in which the primary and secondary shapes are individually formed and bonded with an adhesive or the like. However, in this method, the workability is poor and the cost is high because the lamination is performed after molding. In addition, there is also a problem that it is difficult to secure planar accuracy because an adhesive or the like is used at the interface. In particular, it becomes more apparent when the optical material is made larger and thinner. In this case, from the viewpoint of productivity, the injection molding method is considered to be more advantageous than the conventional joining method.

[0005]

However, since the above-mentioned optical material has a flat mountain shape corresponding to the increase in size and reduction in thickness, there is the following problem when formed by a conventional injection molding method.

In the case of injection molding of an optical material, generally, FIG.
As shown in (b), the injection port 13 of the molding die is provided corresponding to the portion forming the outer portion of the display surface. This is because, when the injection port 14 of the molding die is provided in a portion facing the display surface, minute burrs (injection port marks) remain on the formed display surface, which are flawed and affect the display. For this reason, the resin is injected from the outer portion.
If the portion of the bottom apex 11a of the concave portion of the next shape 11 is thin (the gap is narrow in the molding die), it is difficult for the resin to pass through this portion. For this reason, it is necessary to increase the thickness of the bottom portion 11a to some extent, which makes it difficult to reduce the thickness.

Further, when the resin is injected from the outer portion, the flow distance of the resin from one outer portion to the other outer portion increases, so that the pressure and load for injection increase, and the distortion of the resin increases. In addition, there is a problem that unevenness occurs and the luminance becomes non-uniform.

[0008] Further, the first shaped article 1 is formed by an injection molding method.
In the case where the secondary shape 12 is molded after the molding of the first shape 1, since the bottom top 11a of the concave portion of the primary shape 11 is thin, pressure is applied to that portion by the injection pressure and heat is applied. When the resin of the next shape 12 flows, the bottom top 1
There is also a problem that unevenness is caused in the resin in the portion 1a and the luminance may be non-uniform.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a high-quality and high-productivity optical material forming method corresponding to an increase in the size and thickness of an optical material. .

[0010]

According to a first aspect of the present invention, there is provided a method of molding an optical material, comprising: sequentially injecting and laminating a first resin and a second resin having different light scattering performance; The first mold and the second mold are formed in a plate shape.
Injecting the first resin into the primary molding die
After molding the second shape, the second mold is opened, and the second shape is connected to the first mold in a state where the first shape is placed in the first mold. By injecting the second resin into the molding die to mold the secondary shape, the secondary shape is laminated on the primary shape.

According to the above-described method for molding an optical material, after the first shaped article is molded, the second mold is opened, and the first shaped article is placed in the first mold. Since the secondary mold is connected to the mold and the secondary molded article is molded, the first molded article can be obtained simply by exchanging the second mold and the secondary mold for the first mold. Can be laminated with a secondary shape.
Therefore, unlike the related art, it is not necessary to separately mold and bond the primary shape and the secondary shape, so that the optical material can be molded at one time, so that the productivity is high and the adhesive at the interface is high. Since flatness is not used, planar accuracy can be ensured. Moreover, since the primary and secondary shapes are sequentially formed, the thickness of each shape does not increase, and the cooling time of the resin can be shortened, so that the production cycle time can be shortened.

Further, the first resin and the second resin have different light scattering performances by varying the degree of mixing (degree of polymerization) of the fine particles, and the materials of the first resin and the second resin themselves are different. Are preferably of the same composition. The use of materials having the same composition facilitates adhesion at the interface during lamination. Further, if the materials are the same, the refractive index becomes the same, which is the same as the case where there is no interface, so that the reflection does not occur at the interface and the brightness does not become uneven due to the reflection at the interface. Even if the first resin and the second resin are materials having different compositions, it is preferable that the two resins have substantially the same material such that the difference in refractive index between them is within 0.1. Similarly, almost no reflection occurs at the interface, and thus unevenness in luminance does not occur.

The method for molding an optical material according to the second aspect is the first aspect.
In the first aspect, the optical material has an inverted mountain-shaped concave portion.
And a secondary shape having a mountain-shaped convex portion, wherein the primary shape is a primary mold provided corresponding to a portion forming the vicinity of the bottom and top of the concave portion. The mold is formed by injecting the first resin from the injection port.

According to the optical material molding method, since the injection port of the primary molding die is provided corresponding to the portion forming the vicinity of the bottom and top of the concave portion of the primary shape, (1) By directly injecting the first resin from the narrow space, the first resin flows from the narrow space to the wide space, so compared to flowing the resin from the wide space to the narrow space by providing an injection port on the outside, Injection is easy even if the gap is small. (2) The flow distance of the resin to each outer part is shortened. Therefore, according to (1), the injection can be performed even if the gap is small, so that the bottom top can be made thinner, and as a result, the thickness of the optical material can be made thinner. In addition, it can cope with large size.
From (2), the pressure and load for injection are reduced, and the distortion of the resin can be reduced, so that no unevenness occurs and the luminance can be made uniform. Further, even if a resin having low fluidity, that is, a resin having a higher viscosity (high molecular weight, high melting point, high heat resistance) is used as the first resin, the resin can be sent to the outer portion with a small injection pressure because the flow distance is short. In addition, the optical material can be formed thin, and the optical material can be reduced in thickness. Although fine burrs (injection mark) remain as scratches on the surface of the bottom of the primary shape, the secondary shape is formed after forming the primary shape, that is, two-stage molding is performed. Therefore, when the second resin of the secondary shape flows along the primary shape, the burrs left on the primary shape can be melted and eliminated.

According to a third aspect of the present invention, there is provided a method of molding an optical material.
In the above, the secondary shape is molded by injecting a second resin from an injection port of a secondary molding die provided corresponding to a portion forming an outer portion thereof. Therefore, since the injection port is provided on the outer side of the secondary mold,
No flaws remain on the display surface and the display is not affected.

According to a fourth aspect of the present invention, there is provided a method for molding an optical material.
In any one of (1) to (3), the second shape
The melt index of the resin is 10 g / 10 min or more greater than the melt index of the first resin of the primary shape. Here, the melt index (hereinafter, M
The term “I”) refers to a measure of the outflow rate of a thermoplastic resin extruded from an orifice having a specified diameter and length at a constant temperature and pressure, that is, the ease with which the resin can flow.

The MI of the second resin is 10 times greater than the MI of the first resin.
When the size is less than g / 10 min, unevenness occurs in the optical material. In the case of a size of 10 g / 10 min or more,
Since the resin of the secondary shape is easy to flow, the injection pressure can be reduced, and unevenness does not occur, so that the luminance becomes uniform. Further, since the MI of the first and second resins can be set by changing the degree of mixing (degree of polymerization) of the fine particles, the first and second resins having substantially the same material as described above are used. Since the MI can be controlled only by changing the degree of polymerization of each resin, optical materials having the above characteristics can be easily produced, and the yield can be improved by using the same material.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus used in a method for molding an optical material according to an embodiment of the present invention. The optical material 10 molded according to the present invention includes, for example, a primary shape 11 having an inverted quadrangular pyramid (pyramid) concave portion shown in FIG. 4A and a second shape having a quadrangular pyramid convex portion. Next shape object 12
Consists of In the apparatus shown in FIG. 1, a primary molding die 20 and a secondary molding die 30 are arranged with a die rotating mechanism 17 including a vertical rotation axis interposed therebetween. , An injection device 18 for injecting the second resin 3
9 are arranged.

A primary molding die 20 for molding the primary shape 11 comprises a first die 21 and a second die 24, and the second die 24 is a mold 22, which can be separated from each other. 23. The cavity 25 (FIG. 2A) formed between the first mold 21 and the second mold 24 has a shape that matches the primary shape 11. The injection port 20a of the primary mold 20 is
It is provided corresponding to a portion forming the vicinity of the bottom top 11a of the concave portion of the primary shape object 11. In this example, the inlet 2
0 a is oriented in a direction orthogonal to the bottom surface of the primary shape object 11.

The secondary molding die 30 for molding the secondary shaped object 12 comprises dies 32 and 33 which can be separated from each other. A cavity 35 (FIG. 2 g) formed between the primary shape 11 and the secondary mold 30 has a shape that matches the secondary shape 12. The injection port 30a of the secondary mold 30 is
It is provided corresponding to a portion forming the outer portion of the next shape object 12. In this example, the inlet 30a is the second shaped object 1
2 is directed to the direction in which the resin is injected from the outside to the outside. The mold 23 of the primary mold 20 and the secondary mold 3
The 0 type 33 can be commonly used. The die rotation mechanism 17 rotates the first die 21 of the primary molding die 20 in the R direction.

FIG. 2 is a schematic view showing a method for molding an optical material according to one embodiment of the present invention. Hereinafter, a method of forming the optical material 10 will be described. First, in a state where the primary molding die 20 is set (FIG. 2A), the first resin 2 of the primary shape 11 is injected into the cavity 25 from the injection port 20a of the primary molding die 20 (FIG. 2B). ). The temperature of the first resin 2 to be injected is 240 to 270 ° C., and the MI is 2 to 10 g / 10 m.
In, the injection pressure is preferably in the range of 600 to 1200 kg / cm ² . After the first resin 2 is filled into the cavity 25 and is almost cured, and the primary shape 11 is formed (FIG. 2C), the second mold 24 is opened (FIG. 2D). At this time, a minute burr (injection port mark) 28 remains on the surface of the concave portion 11a of the primary shape object 11.

Next, the first die 21 is rotated in the R direction in a horizontal plane by the die rotating mechanism 17 with the primary shape object 11 placed in the first die 21 (FIG. 2E). , Second
It is set at a position facing the next mold 30 (FIG. 2f). Subsequently, the secondary mold 30 is advanced to the first mold 21 and connected thereto (FIG. 2g). The second resin 3 of the secondary shape 12 is injected into the cavity 35 from the injection port 30a of the secondary mold 30 (FIG. 2h). Injected second resin 3
Is 240 to 270 ° C., MI is 12 to 30 g /
10 min, injection pressure 600-1200 kg / cm ²
Is preferable. After the second resin 3 is filled in the cavity 35 and almost hardened to form the secondary shape 12 (FIG. 2I), the secondary mold 30 is opened (FIG. 2J). When the resin 3 of the secondary shape 12 is filled along the primary shape 11, the burr 28 previously left on the primary shape 11 is melted and eliminated. Thereby, the secondary shape object 12 is laminated on the primary shape object 11. Finally, the protruding resin portion 12a formed at the injection port 30a is cut off, and the flattened optical material 10 (FIG. 4) is formed.

In this embodiment, an optical material having a quadrangular pyramid (pyramid) mountain shape is formed. However, a prism shape or a triangular pyramid mountain shape may be used. May be molded.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the molding method of the present invention, when the optical material is thin and large, for example, the flatness (aspect ratio defined by thickness / length) of the optical material is 10 or more and the size is 120 mm.
It is particularly suitable when the size is 90 mm or more. The first resin and the second resin are made of polymethyl methacrylate or the like as a base material, and transparent fine particles (1 μm to 100 μm in diameter) such as silicone and glass having different refractive indices from the base material are dispersed and mixed therein.
What adjusted light scattering ability is used. The examples of the optical materials shown below are all molded by the molding method of FIG. 2, and the compositions of the first resin and the second resin are different from each other.

Example 1 The first resin was Acrypet®
Grade VH (Mitsubishi Rayon Co., Ltd., MI = 2.0
g / 10 min, according to ASTM-D1238), and the second resin was Delpet grade 70FR (manufactured by Asahi Kasei Corporation, MI = 12 g / 10 min) and Tospearl grade 145 (manufactured by Toshiba Silicone Co., Ltd.). 0.3 wt% mixed and pelletized material (M
I = 12 g / 10 min). First resin and second
The difference in MI between the resins was 10 g / 10 min, and almost no unevenness of the optical material occurred.

Example 2 The same resin as in Example 1 was used as the first resin, and the second resin was Parapet grade H-.
S (Made by Kuraray Co., Ltd., MI = 22g / 10min)
Then, 0.3 wt% of Tospearl Grade 145 (manufactured by Toshiba Silicone Co., Ltd.) is mixed, and a pelletized material (MI = 22 g / 10 min) is used. The difference in MI between the first resin and the second resin was 20 g / 10 min, and no unevenness of the optical material occurred.

[Comparative Example] The first resin was the same as that used in Example 1, and the second resin was Acrypet grade TF.
8 (Mitsubishi Rayon Co., Ltd., MI = 10g / 10mi
To n), 0.3 wt% of Tospearl Grade 145 (manufactured by Toshiba Silicone Co., Ltd.) is mixed, and a pelletized material (MI = 10 g / 10 min) is used. The difference in MI between the first resin and the second resin was 8 g / 10 min, and unevenness of the optical material occurred.

FIG. 3 shows a luminance distribution near the injection port of the secondary molding die. The horizontal axis indicates the distance (mm) from the injection port, and the vertical axis indicates the luminance (cd / m ² ). Example 2 is shown by a solid line and a comparative example is shown by a broken line. Although the optical material of the comparative example has unevenness, the optical material of Example 2 has no unevenness and high uniformity of luminance.

[0029]

As described above, according to the present invention, after the primary shape is molded, the second mold is opened, and the primary shape is placed in the first mold. Since the secondary mold is connected to the first mold and the secondary shape is molded, only the second mold and the secondary mold are exchanged for the first mold.
The secondary shape article can be laminated on the primary shape article. Therefore, unlike the related art, there is no need to separately mold and bond the primary shape and the secondary shape,
Since the optical material can be molded at one time, the productivity is high, and the planar accuracy can be ensured because no adhesive or the like is used. In addition, since the primary and secondary shapes are sequentially formed, the thickness of each shape does not increase, and the cooling time can be shortened, so that the production cycle time can be shortened.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing an apparatus used for a method for molding an optical material according to an embodiment of the present invention.

FIG. 2 is a schematic view illustrating a method for molding an optical material according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a luminance distribution near a secondary injection port.

FIG. 4A is a perspective view of an example of an optical material, and FIG. 4B is a cross-sectional view taken along line IV-IV of FIG.

[Explanation of symbols]

2 ... first resin, 3 ... second resin, 10 ... optical material, 11 ... primary shape, 12 ... secondary shape, 17 ... die rotation mechanism, 20 ... primary molding die, 20a ... Injection port of primary mold, 21 ... first mold, 24 ... second mold, 30 ... secondary mold, 30a ... inlet of secondary mold.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masaya Morino 1-4-5 Kamimaezu, Naka-ku, Nagoya City, Aichi Prefecture Inside Hayashi Telemp Co., Ltd. (72) Inventor Hiroshi Nakayama 1-4-4 Kamimaezu, Naka-ku, Nagoya City, Aichi Prefecture No.5 Hayashi Telemp Co., Ltd. F-term (reference) 2H042 BA02 BA12 BA15 BA20 4F206 AA21 AH75 JB22 JC06 JN12 JQ81

Claims (4)

[Claims] 1. A method for molding an optical material in which a first resin and a second resin having different light scattering performances are sequentially injected and laminated to form a flat plate, comprising: a first mold and a second mold. After injecting the first resin into the primary molding die made of and molding the primary molded article, the second mold is opened, and the primary molded article is placed in the first mold. A secondary mold is connected to the first mold, and a second resin is injected into the secondary mold to mold the secondary molded article, thereby forming a secondary molded article on the primary molded article. A method for molding an optical material for laminating shaped objects. 2. The optical member according to claim 1, wherein the optical member includes a primary shape having an inverted mountain-shaped concave portion and a secondary shape having a mountain-shaped convex portion. A molding method of an optical material to be molded by injecting a first resin from an injection port of a primary molding die provided corresponding to a portion forming the vicinity of the bottom top of the concave portion. 3. The method according to claim 2, wherein the secondary resin is formed by injecting a second resin from an injection port of a secondary molding die provided corresponding to a portion forming an outer portion thereof. A molding method of an optical material to be molded. 4. The method according to claim 1, wherein a melt index of the second resin of the secondary shape is:
10 from the melt index of the first resin of the primary shape
g / 10 min or more.