JPH1158406A - Thin plate-shaped molding and its molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molding with birefringence controlled slightly such as a thin sheet-shaped injection-molded molding useful in optical applications requiring optical characteristics and in the field of display, and a decorated injection- molded molding such as a Fresnel lens, and its molding method. SOLUTION: A thin plate-shaped molding is a thin plate-shaped molding of a thermoplastic resin having a norbornane skeleton given by a formula, wherein A, B, C, and D represent a hydrogen atom and a monovalent organic group. The thermoplastic resin is packed into a mold in which the molding surface layer parts of a cavity mold and a core mold are a thin film metal layer, and on the inside of the layer is provided an insulating layer. A resin temperature is kept at the glass transition temperature (Tg) of the resin or above to alleviate shear strain at packing. The optical strain of the resin is 50 nm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin sheet-like injection molded article useful for optical applications requiring optical characteristics and a display field, and a decorative injection molded article such as a Fresnel lens. The present invention relates to an injection-molded article requiring a small control and a molding method thereof.

[0002]

2. Description of the Related Art Conventionally, thin injection molded products for optics are:
In order to facilitate cooling and solidification, a mold made of a metal material such as steel or stainless steel is used, and the mold temperature is set to be equal to or lower than the glass transition temperature (hereinafter referred to as Tg) of the resin. Was. However, in such a conventional method, the flow path is solidified and flows during molding, so that a large shear stress is applied, and since the molecular orientation in the flow direction is large, the optical anisotropy is increased, and the thin plate-shaped injection molded article is formed. The birefringence is usually as large as 100 nm or more, and the range in which the transparent resin is used for optical applications has been limited.

[0003]

Injection molding is an excellent molding method to obtain molded articles of various shapes, but the molecular orientation is not sufficiently relaxed and the shear stress is frozen as residual stress. It was not possible to mold a molded article having excellent optical properties with small birefringence. According to the present invention, when injection molding is performed in response to such a demand, a molten resin is filled in a cavity in a mold in which a surface layer portion is a thin film metal layer in both a cavity mold and a core mold, and a heat insulating layer is provided inside. By filling (injecting), it has been found that a molded article having a small birefringence can be obtained, and the present invention has been completed.

[0004]

That is, the present invention relates to a thin plate-like molded product made of a thermoplastic resin, wherein a molding surface layer portion of a cavity mold and a core mold is a thin film metal layer, and a heat insulating layer is provided inside the thin metal layer. Is filled with a thermoplastic resin, and the resin temperature is set to the glass transition temperature (T
g) The present invention provides a thin plate-like molded product characterized by having an optical distortion of 50 nm or less, which is held at or above, and alleviates shear distortion during filling, and a molding method thereof.

[0005] The thermoplastic resin in the present invention includes P
A transparent thermoplastic resin such as an MMA resin, a polycarbonate, and a thermoplastic norbornene resin can be used. The thermoplastic norbornene-based resin that can be used in the present invention has a norbornane skeleton in its repeating unit. For example, as this thermoplastic resin,
It contains a norbornane skeleton represented by the general formulas (1) to (4).

[0006]

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[0007]

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[0008]

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[0009]

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(In the formula, A, B, C and D represent a hydrogen atom or a monovalent organic group.) Examples of the thermoplastic resin having a norbornane skeleton which can be used in the present invention include those described in 60-1
68708, JP-A-62-252406,
JP-A-62-252407, JP-A-2-1334
No. 13, JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, and the like. .

As a specific example of the thermoplastic resin, at least one kind of a tetracyclododecene derivative represented by the following general formula (5) or an unsaturated cyclic compound copolymerizable with the tetracyclododecene is metathesized. Examples include a hydrogenated polymer obtained by hydrogenating a polymer obtained by polymerization.

[0012]

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(Wherein A to D are the same as above.) In the tetracyclododecene derivative represented by the general formula (5), a polar group may be contained in A, B, C and D. Heat resistance and good affinity with the mold surface are preferable in that high surface accuracy can be obtained. Further, the polar group ^{_{- (CH 2) n COOR 1}} ( wherein, R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, n represents an integer of 0) is a group represented by It is preferable because the resulting hydrogenated polymer has a high glass transition temperature. Especially,
It is preferable that one group represented by — (CH ₂ ) _n COOR ¹ is contained per molecule of the tetracyclododecene derivative of the general formula (5). In the general formula,
R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, and it is preferable in terms of decreasing the hygroscopicity of the obtained hydrogenated polymer as the number of carbon atoms increases. From the viewpoint of balance, a chain alkyl group having 1 to 4 carbon atoms or a (poly) cyclic alkyl group having 5 or more carbon atoms is preferable, and a methyl group, an ethyl group, and a cyclohexyl group are particularly preferable. Further,-(CH ₂ ) _n C
The carbon atom to which the group represented by OOR ¹ is bonded has 1 carbon atom
The tetracyclododecene derivative of the general formula (5), in which 10 to 10 hydrocarbon groups are bonded as a substituent, is preferable because it reduces the hygroscopicity. In particular, the tetracyclododecene derivative of the general formula (5) in which the substituent is a methyl group or an ethyl group is preferable in that the synthesis is easy. Specifically, 8-methyl-8-methoxycarbonyltetracyclo [4.4.0.1 ^2,5 . [ ^1,7,10 ] dodec-8-ene is preferred.

These tetracyclododecene derivatives or a mixture of an unsaturated cyclic compound copolymerizable therewith can be used, for example, in JP-A-4-77520, page 4, upper right column, line 12 to page 6, lower right column. The thermoplastic resin used in the present invention can be obtained by metathesis polymerization and hydrogenation by the method described in line 6. In the present invention,
The hydrogenated polymer desirably has an intrinsic viscosity ([η] inh) measured at 30 ° C. in chloroform of 0.3 to 1.5 dl / g. When [η] inh is in the above range, the resulting resin has a good balance of moldability, heat resistance, and mechanical properties. Further, the glass transition temperature (Tg) of the hydrogenated polymer is preferably in the range of 100 ° C to 250 ° C, particularly preferably in the range of 120 to 200 ° C. If the temperature is lower than 100 ° C., the heat resistance of a molded article made of the resin is inferior. On the other hand, when the Tg exceeds 250 ° C., the molding temperature becomes high, and it becomes difficult to obtain a high-quality molded product such that the resin is burnt and colored. The hydrogenation rate of the hydrogenated polymer is at least 50%, preferably at least 90%, more preferably at least 98%, as measured by 60 MHz, ¹ H-NMR. The higher the hydrogenation rate, the better the stability to heat and light. In the present invention,
The hydrogenated polymer used as the thermoplastic resin having a norbornane skeleton preferably has a gel content of 5% by weight or less, more preferably 1% by weight, in the hydrogenated polymer.
It is preferred that

As the polycarbonate resin used in the present invention, those containing an aromatic bisphenol such as bisphenol A as a main component, for example, Panlite (manufactured by Teijin Chemicals Ltd.), Lexan (manufactured by General Electric), Iupilon (Mitsubishi) Gas Chemical Co., Ltd.) and Toughlon (Idemitsu Petrochemical Co., Ltd.). The acrylic resin used in the present invention preferably has a heat deformation temperature of 100 ° C. or higher.
Kuraray) and Chemax (manufactured by Sumika Haas Co., Ltd.). These acrylic resins may be modified with a cyclohexyl group or a norbornene-based resin, or may be imidized.

The thermoplastic resin used in the present invention may contain, if necessary, a known antioxidant such as 2,6-di-t-butyl-4-methylphenol, 2,2'-dioxy-3,
3'-di-t-butyl-5,5'-dimethylphenylmethane, tetrakis [methylene-3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate] methane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl-benzene, stearyl-
β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2′-dioxy-3,3′-
Di-t-butyl-5,5′-diethylphenylmethane,
3,9-bis [1,1-dimethyl-2- [β- (3-t
-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl], 2,4,8,10-tetraoxyspiro [5,5] undecane, tris (2,4-di-t-butylphenyl) phospho Phyte, cyclic neopentanetetraylbis (2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methylphenyl) phosphite, 2,2-methylenebis (4,6-
Di-t-butylphenyl) octyl phosphite can be added.

Further, in addition to the above-mentioned antioxidant, if necessary, an ultraviolet absorber such as pt-butylphenyl salicylate, 2, 2
2'-dihydroxy-4-methoxybenzophenone,
2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2- (2′-dihydroxy-4′-m-octoxyphenyl) benzotriazole; stabilizer, antistatic agent, flame retardant, for improving impact resistance An elastomer or the like can be added. Further, additives such as a plasticizer and a softener can be added for the purpose of improving moldability and workability.

In the thin plate-shaped molded article of the present invention, the above thermoplastic resin is injected into a mold having a thin film metal layer on the surface layer in both the cavity mold and the core mold and having a heat insulating layer inside thereof. , The temperature of the mold surface is raised to Tg or higher by the heat of the molten resin itself, the shear strain at the time of filling is sufficiently relaxed, and then cooled and taken out.

As a result of our intensive studies, the reason why birefringence is greatly developed in injection molded products is that the molecules near the surface of the mold during injection molding are oriented by the shear stress in the flow direction.
It has been found that, due to the mold temperature set lower than the Tg of the thermoplastic resin, the solidified resin is cooled and solidified from the mold surface and is frozen as it is. Further, since the generated shear stress is cooled and solidified before being alleviated, the stress is frozen, which causes an increase in residual strain. The present invention uses a mold having a heat-insulating structure so that the heat of the molten resin raises the surface temperature of the mold to a temperature equal to or higher than the Tg of the thermoplastic resin without losing the heat of the molten resin. By maintaining the temperature at or above Tg, it is possible to prevent cooling and solidification during filling of the molten resin. In this case, as in the case where a mold having no heat insulating structure is used, the molecules are once oriented in the flow direction during the flow, but after the mold surface temperature rises to Tg or higher, even after the mold is filled. However, the molecular chain is still in a state capable of movement such as rotation and expansion and contraction, and the molecules that have been gradually oriented by being maintained at a temperature equal to or higher than Tg are gradually relaxed, and the anisotropy is gradually reduced. Small molded products can be obtained.

Various materials can be used as the material of the heat insulating layer of the mold. Preferred specific examples of the material of the heat insulating layer include:
Examples include a porous body of a metal or a synthetic resin, a thermoplastic resin composition in which a curing agent is blended with a thermoplastic resin, a thermosetting resin, a thermosetting resin composition, and the like. Among them, the most effective material is a thermosetting resin composition in which a filler is combined with a thermoplastic resin and a curing agent. Examples of the thermosetting resin include epoxy resin, polyester resin, and phenol resin, and examples of the filler include glass powder, silica powder, and talc powder. The thickness of the heat insulating layer is usually 0.1 to 10 mm, preferably 0.2 to 5 m.
m, more preferably 0.3 to 3 mm, particularly preferably 0.5 to 1.5 mm.

As the material for the thin film metal layer of the mold, zinc, zinc alloy, nickel, nickel alloy, chromium metal, beryllium copper and the like can be used. The thickness of the metal layer is 0.001 to 3 mm, preferably 0.005 to 1 mm.
mm, more preferably 0.01 to 0.5 mm.

Further, the resin temperature of the thermoplastic resin when injected into the mold is (Tg + 50 ° C.) to (Tg + 2
(Tg + 70 ° C.) to (Tg + 180 ° C.), and particularly preferably (Tg + 90 ° C.) to (Tg + 150).
° C). When the resin temperature is lower than Tg + 50 ° C., distortion occurs in the molded optical molded product, the birefringence is increased, the optical characteristics are deteriorated, and the transfer accuracy of the mold surface is deteriorated. On the other hand, when the resin temperature is higher than Tg + 200 ° C., the resin may be colored yellow, or may be decomposed or burnt, and in any case, it is difficult to obtain a thin plate-shaped molded product aimed at by the present invention. .

[0023] In a thin plate-like molded product formed by the method of the present invention, a mold having no heat insulating layer and having a mold temperature of Tg
If it is lower than that, cooling proceeds rapidly. The molecular orientation of the flow is greatest near the mold surface where the shear stress is maximum, and is the part that receives cooling first, so within a few seconds from the start of filling, this orientation layer becomes Tg or less, The molecular orientation is frozen without being relaxed, and causes optical distortion to remain. In contrast, when a mold having a heat insulating layer is used, the orientation layer near the mold surface is also maintained at Tg or higher, so that the molecular orientation is relaxed with time,
After that, if the molded product is taken out after cooling to Tg or less, no optical distortion remains. Even if the thickness distribution is in the molded product, the effect is exhibited.

The relaxation of the shear strain at the time of filling is preferably 50 nm or less, more preferably 10 nm or less, particularly preferably 5 nm or less, as represented by the retardation of the molded article. The relaxation time of the shear strain at the time of filling varies depending on the resin temperature and the molecular weight of the resin, but when the mold temperature is Tm (° C.) and the holding time (relaxation time) is t (second), logt + (Tm− Tg) /
The value of 20 is preferably 3.5 or more, more preferably 4 to 6, and particularly preferably 4.5 to 5.5. That is, the difference (° C.) between the mold temperatures Tm and Tg is 50 ° C.
In this case, the holding time t is preferably at least 10 seconds, particularly preferably at least 100 seconds.

In the present invention, after the resin is filled into the mold, the surface temperature of the mold is raised to Tg of the thermoplastic resin without losing the heat of the molten resin by the heat insulating effect of the heat insulating layer of the mold. Heating, and keeping the thermoplastic resin at a temperature of Tg or more,
The molded article is taken out after the mold is cooled after alleviating the shear strain during filling. The cooling rate is not particularly limited.
C./min or more, more preferably 1 ° C./min.
0 ° C./min, particularly preferably 0.3 to 10 ° C./sec. As a method of cooling, a method of leaving naturally or a method using a cooling device is used, but a method of leaving naturally may greatly change a cooling rate depending on environmental conditions,
A method of cooling with a cooling device is more desirable.

The birefringence of the sheet-like molded article of the present invention obtained by the above method is 50 nm or less, preferably 30 n.
m, more preferably 10 nm or less, particularly preferably 5 nm
It is as follows. The thickness of the molded product is preferably 10 mm or less, more preferably 0.1 to 7 mm, more preferably 0.2 to 5 mm, particularly preferably 0.3 to 5 mm.
3 mm.

In the present invention, the shape of the thin plate-shaped molded product surface may be various shapes such as a flat plate, one having a taper or a step, one having an uneven surface, a flat surface, a curved surface, a free curved surface, a rectangle, and a disk. . The same effects as described above can be obtained with these thin plate-shaped molded products having various shapes, and the surface properties are also improved because the transfer of the mold surface is improved. In addition, the formation of a Fresnel lens shape having fine irregularities on the surface thereof, and a disk having fine irregularities formed by a stamper are particularly effective in improving the shape transfer. The thin plate-shaped molded product of the present invention can be used for a wide range of applications such as thin lenses such as Fresnel lenses, optical disks, and optical thin plates.

[0029]

EXAMPLES The present invention will be described more specifically with reference to examples, reference examples and comparative examples, but the present invention is not limited to the examples.

Examples 1 to 5 and Comparative Examples 1 and 2 As thermoplastic resins, intrinsic viscosity was 0.55 and Tg was 17
1 ° C. norbornene resin (ARTON manufactured by Japan Synthetic Rubber) was used. This resin was subjected to injection molding using a mold having a heat insulating structure in the form of a flat plate of 200 × 150 × 1.0 mm. Thereafter, the molded product was taken out when the mold was cooled and the mold temperature became constant. In order to prevent sink marks on the surface of the molded product, the molten resin was kept for a fixed time after filling. The thickness of the heat-insulating layer in the mold is mm, the material is epoxy resin, and the material of the thin-film metal layer on the molding surface is mm.
Thick nickel was used. For cooling, the temperature-controlled oil was circulated inside the mold on both the fixed side and the moving side. After the molded article was taken out, the retardation at the center of the molded article was measured using an ellipsometer (manufactured by Mizojiri Optical). The cooling rate of the resin temperature after molding was 15 ° C./min. Further, as a comparative example, molding was performed in the same manner as in Example 1 using a normal mold having no heat insulating structure.
Table 1 shows the evaluation results.

[0031]

[Table 1]

[0032]

As can be seen from Table 1, when a mold having a thin-film metal layer formed on a heat insulating layer was used (Examples 1 to 5).
In any case, a molded article having small retardation and excellent optical properties can be obtained. On the other hand, Comparative Example 1 is a mold having no heat insulating layer, and when the mold temperature is 150 ° C., good retardation cannot be obtained. Comparative Example 2 is a case where the mold temperature is set to 165 ° C. in the same mold, but the reduction of the retardation is still insufficient.

Examples 6 to 8 and Comparative Examples 3 and 4 As a thermoplastic resin, a polycarbonate resin having a Tg of 148 ° C. (PANLIGHT AD5503 manufactured by Teijin Chemicals Ltd.) was used.
This resin was prepared in the same manner as in Example 1 by 200 × 150 ×
Injection molding was performed using a 1.0 mm flat plate mold. Thereafter, the molded product was taken out when the mold was cooled and the mold temperature became constant. In order to prevent sink marks on the surface of the molded product, the molten resin was kept for a fixed time after filling. As a comparative example, molding was performed in the same manner as in Example 6, using a normal mold having no heat insulating structure. Table 2 shows the evaluation results.

[0035]

[Table 2]

Examples 9 to 11 and Comparative Examples 5 to 6 As the thermoplastic resin, an acrylic resin having a Tg of 120 ° C. was used. This resin was prepared in the same manner as in Example 1 by 200 × 150
Injection molding was performed using a flat mold of × 1.0 mm. Thereafter, the molded product was cooled and when the mold temperature reached 95 ° C., the molded product was taken out. Thereafter, the molded product was taken out when the mold was cooled and the mold temperature became constant. In order to prevent sink marks on the surface of the molded product, the molten resin was kept for a fixed time after filling.
As a comparative example, molding was performed in the same manner as in Example 9 using a normal mold having no heat insulating structure. Table 3 shows the evaluation results.

[0037]

[Table 3]

[0038]

According to the present invention, the birefringence of the obtained molded product can be reduced by using a mold in which a heat insulating layer is formed inside during injection molding of a resin and a metal layer is formed on a surface layer. Can not be used, but can also be used for applications requiring high optical characteristics.

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Claims (4)

[Claims] 1. A thin plate-like molded product made of a thermoplastic resin, wherein a molding surface layer portion of a cavity mold and a core mold is a thin film metal layer, and a thermoplastic resin is provided in a mold provided with a heat insulating layer inside thereof. Wherein the resin temperature is maintained at or above the glass transition temperature (Tg) of the thermoplastic resin, and the shear distortion at the time of filling is reduced, and the optical distortion is 50 nm or less. . 2. A thermoplastic resin is filled into a mold having a cavity surface layer and a core mold in which a molding surface layer portion is a thin film metal layer, and a heat insulating layer is provided inside the mold, and the resin temperature is maintained at Tg or more. The method for forming a thin plate-shaped molded product according to claim 1, wherein a shear strain at the time of filling is reduced. 3. The thin plate-shaped molded article according to claim 1, wherein the thermoplastic resin is a thermoplastic norbornene-based resin. 4. The thin plate-like molded product according to claim 1, wherein the thermoplastic resin is at least one selected from an acrylic resin and a polycarbonate resin.