TW202138159A - Molded sheet, method for manufacturing molded sheet, and method for manufacturing optical element - Google Patents

Abstract

A method for manufacturing a molded sheet, the method including a hot-pressing step for obtaining a molded sheet by hot-press molding a sheet-form sheet material comprising a thermoplastic resin film at normal pressure using a pair of dies having a plurality of optical surface formation regions separated from each other.

Description

Molded sheet, manufacturing method of molded sheet, and manufacturing method of optical element

The present invention relates to a molded sheet, a method of manufacturing a molded sheet, and a method of manufacturing an optical element. Such a molded sheet, a manufacturing method of a molded sheet, and a manufacturing method of an optical element are really useful for the manufacture of a transmissive optical element.

In recent years, electronic and electrical equipment has gradually become lighter, smaller and thinner, and the demand for thinner and smaller diameters of the camera unit mounted on these electronic and electrical equipment is also increasing. In addition, there is a demand for higher image quality in such photographing units, and high performance is also required for transmissive optical elements such as lenses and ridges that these optical devices have.

Conventionally, transmissive optical elements such as lenses used in photographing units are generally manufactured by injection molding. However, in the case of forming a lens by an injection molding method, it is difficult to completely suppress the formation of weld lines in the obtained lens. In addition, birefringence is likely to occur in the lens obtained by the injection molding method. Therefore, in the obtained lens, it is difficult to sufficiently increase the ratio of the area that can exhibit sufficiently high optical performance. Even if a lens with a small diameter of less than 1 cm is formed according to the injection molding method, it is difficult to make it fully perform. The function of the lens.

Therefore, in recent years, methods for manufacturing transmissive optical elements such as small-diameter lenses by methods other than injection molding have been studied. For example, Patent Document 1 discloses a method of arranging a plurality of molds in the plane direction of a resin sheet, and simultaneously forming a plurality of lens portions with the molds. More specifically, Patent Document 1 discloses the following method: a resin sheet is placed in a fixed position on a plurality of female lower molds made of metal or the like, and a plurality of molds made of metal or the like are laminated. The upper mold is molded to plastically deform the resin sheet, and a plurality of lens portions are simultaneously formed by the mold.

『Patent Literature』 "Patent Document 1": International Patent Publication No. 2000/012291

However, in the above-mentioned conventional technology characterized by "arranging a plurality of molds in the plane direction of the resin sheet to simultaneously form a plurality of lens portions with the molds", in the manufacture of a plurality of optical surface shapes that can be used as, for example, lenses. In the case of forming a sheet in the part, it is impossible to efficiently manufacture a forming sheet having a plurality of optical surface-shaped parts with sufficiently high shape accuracy, small variations in thickness accuracy, and low birefringence.

Therefore, the object of the present invention is to provide a molded sheet having a plurality of optical surface-shaped portions with sufficiently high shape accuracy, small thickness accuracy and low birefringence.

In addition, an object of the present invention is to provide a method for producing a shaped sheet that can efficiently produce the above-mentioned shaped sheet.

Furthermore, the object of the present invention is to provide a method for manufacturing an optical element using the above-mentioned molded sheet.

The inventors of the present invention have devoted themselves to research in order to achieve the above-mentioned object. Then, the inventors found that by hot-press forming a cut sheet material made of a thermoplastic resin film under specified conditions, it is possible to provide a shape with high enough accuracy, small variations in thickness accuracy, and low birefringence. The forming sheet of the multiple optical surface parts, and then complete the present invention.

That is, this invention aims to solve the above-mentioned problems smoothly, and the method of manufacturing a molded sheet of the present invention is a method of thermoforming a thermoplastic resin film formed by using a thermoplastic resin to produce a molded sheet having a plurality of optical surface portions. A method of manufacturing a molded sheet is characterized by including a hot pressing step: using a pair of molds having a plurality of optical surface forming regions spaced apart from each other, the sheet material cut into sheets made of the aforementioned thermoplastic resin film is subjected to normal pressure Hot press forming to obtain a shaped sheet. If in this way, a pair of molds with a plurality of optical surface forming areas separated from each other are used to hot press the cut sheet material under normal pressure, it can be easily manufactured with high enough shape accuracy and small thickness accuracy. A molded sheet of multiple optical surface parts with low birefringence.

In addition, in this specification, the sheet material is "cut into sheets", which means that the sheet material is cut into a specified size and is not in a wound state.

In addition, in this specification, the so-called "normal pressure" refers to the air pressure at a certain place without pressurization and decompression, and is usually equal to the atmospheric pressure at this place. More specifically, the so-called "normal pressure" refers to the pressure range under the standard state specified in JIS Z8703:1983, which is within the range of atmospheric pressure 86 kPa or more and 106 kPa or less.

Here, the manufacturing method of the molded sheet of the present invention preferably includes a demolding step, which uses the glass transition temperature of the thermoplastic resin as Tg (°C), and the molded sheet obtained in the hot pressing step When demolding from the aforementioned pair of molds, demold the aforementioned pair of molds at a temperature of (Tg-80)°C or higher and (Tg-15)°C or lower. By implementing the demolding process in such a specified temperature range, the shape accuracy of the multiple optical surface-shaped parts included in the obtained molded sheet can be further improved, and the variation in thickness accuracy can be further reduced, and further reduced Birefringence.

In addition, in the present invention, the "glass transition temperature of thermoplastic resin" can be measured in accordance with JIS K7121:2012.

Furthermore, in the method of manufacturing a formed sheet of the present invention, in the hot pressing step, the cut sheet material will not be overfilled in the state where the cut sheet material is pressed through the pair of molds. The aforementioned pair of molds is preferred. By preventing the cut sheet material from filling up a pair of molds under pressure, the shape accuracy of the multiple optical surface parts included in the formed sheet can be further improved, and the variation in thickness accuracy can be reduced. , To further reduce the birefringence, and to further improve the production efficiency of the formed sheet.

Furthermore, in the manufacturing method of the molded sheet of the present invention, the aforementioned thermoplastic resin-based alicyclic structure-containing resin is preferably used. If the thermoplastic resin is a resin containing an alicyclic structure, the shape accuracy of the multiple optical surface parts included in the obtained molded sheet can be further improved, the variation in thickness accuracy can be further reduced, and the production efficiency of the molded sheet can be further improved.

Moreover, this invention aims to solve the above-mentioned problems smoothly. The manufacturing method of the optical element of the present invention is characterized in that the molded sheet obtained by following any of the above-mentioned manufacturing methods of the molded sheet is based on the aforementioned multiple optical surfaces. The shape parts are separated at corresponding positions to obtain optical elements. According to the manufacturing method of the present invention, it is possible to easily manufacture an optical element with sufficiently high shape accuracy, small thickness accuracy, and low birefringence.

In addition, this invention aims to solve the above-mentioned problems smoothly. The molded sheet of the present invention is a cut molded sheet having a plurality of optical surface portions formed by using a thermoplastic resin, and is characterized in that the aforementioned optical surface portions The arrangement density is 0.16 pcs/cm ² or more, and the minimum distance between adjacent optical surface parts is 1.0 mm or more. The diameter of the optical surface parts in a plan view is 1 mm or more and 15 mm or less. The phase difference of the shaped portion is 50 nm or less, and the variation in the thickness accuracy of the aforementioned optical surface-shaped portion is 0.2 μm or less. If the distribution density, minimum interval, diameter, phase difference, and thickness accuracy of the optical surface portion in the molded sheet are within the specified ranges, the shape accuracy of the optical surface portion of the molded sheet is excellent. Furthermore, by using such a molded sheet, an optical element with excellent optical performance can be efficiently manufactured.

In addition, the "phase difference" and the "variation in thickness accuracy" can be evaluated or measured using the methods described in the embodiments.

Here, in the molded sheet of the present invention, it is preferable that the cross-sectional shape of at least one surface of the optical surface portion in the thickness direction is an aspherical shape having an inflection point. The optical surface portion having such a shape can be advantageously used as a transmissive optical element such as a lens.

According to the present invention, it is possible to provide a molded sheet having a plurality of optical surface-shaped portions with sufficiently high shape accuracy, small variations in thickness accuracy, and low birefringence.

Furthermore, according to the present invention, it is possible to provide a method for producing a shaped sheet that can efficiently produce the above-mentioned shaped sheet.

Furthermore, according to the present invention, it is possible to provide a method of manufacturing an optical element using the above-mentioned molded sheet.

The following describes the implementation of the present invention in detail. The manufacturing method of the shaped sheet of the present invention, for example, can be used when manufacturing the shaped sheet of the present invention. In addition, the method of manufacturing an optical element of the present invention can be suitably used when manufacturing an optical element using a molded sheet obtained according to the method of manufacturing a molded sheet of the present invention. Moreover, the shaped sheet related to the present invention can be suitably used in the manufacture of optical elements having various shapes of optical surfaces without any particular limitation. Here, the so-called "optical surface" means an interface that can cause optical effects such as reflection, refraction, and penetration of light. Examples of its shape include plane, spherical, aspherical, free-form surface, cylindrical array, and Fresnel. Ear lens surface and so on. In addition, examples of "optical elements" that can be suitably manufactured using the molded sheet related to the present invention include transmissive optical elements such as optical lenses and ridges. Here, the so-called "optical lens" means a transparent body that shows the refraction of light. In addition, the so-called "稜鏡" means a transparent polyhedron that exhibits light scattering, refraction, total reflection, and/or birefringence, other than optical lenses. If the molded sheet related to the present invention is used, a transmissive optical element with high shape accuracy and low birefringence (ie, small phase difference) can be efficiently obtained. In particular, the molded sheet related to the present invention can be suitably used in the manufacture of aspheric lenses with inflection points on one side and/or on both sides among various shapes of optical elements. Furthermore, the aspheric lens can be suitably used as a lens of a photographing unit of, for example, small electronic and electrical equipment.

(Formed sheet)

The molded sheet of the present invention has a cross-sectional shape in the thickness direction, as shown in FIG. Moreover, in the molded sheet 10 of the present invention, the arrangement density of the optical surface portions 11 must be 0.16 pieces/cm ² or more, and the minimum distance P between the adjacent optical surface portions 11 must be 1.0 mm or more. The diameter D of the optical surface portion 11 must be 1 mm or more and 15 mm or less, the phase difference of the optical surface portion 11 must be 50 nm or less, and the thickness accuracy variation of the optical surface portion 11 must be 0.2 μm or less. If the distribution density, minimum interval, diameter, phase difference, and thickness accuracy of the optical surface portion are within the above-mentioned range, the shape accuracy can be improved. Furthermore, by using such a molded sheet, an optical element with excellent optical performance can be efficiently manufactured.

In addition, the shape of the optical surface portion of the molded sheet is not limited to the shape shown in FIG. Moreover, the optical surface portion of the molded sheet is not particularly limited, and for example, it can be cut from the molded sheet and suitably used as a lens. Here, from the viewpoint of advantageous use as a transmissive optical element such as a lens, it is preferable that at least one surface of the optical planar portion has a cross-sectional shape in the thickness direction having an inflection point.

<Thermoplastic resin>

Examples of thermoplastic resins include (meth)acrylic resins, alicyclic structure-containing resins, styrene resins, polycarbonate resins, polyester resins, polyether resins, urethane resins, and thiourethane resins. Resin etc. In addition, the so-called "(meth)acrylic acid" refers to acrylic acid and/or methacrylic acid. Moreover, the thermoplastic resin mentioned above may be used individually by 1 type, and 2 or more types may be mixed and used for it.

Among these, since it is possible to further improve the shape accuracy of the plurality of optical surface portions included in the obtained molded sheet, further reduce the variation in thickness accuracy, and further improve the production efficiency of the molded sheet, the thermoplastic resin contains Alicyclic structure resin is preferred. In addition, since the obtained molded sheet has excellent transparency, it is preferable that the thermoplastic resin contains an alicyclic structure-containing resin.

The so-called alicyclic structure-containing resin is a polymer having an alicyclic structure such as a saturated cyclic hydrocarbon structure and an unsaturated cyclic hydrocarbon structure in the main chain and/or side chain. Among them, since it is easy to obtain a molded sheet having excellent mechanical strength and heat resistance, it is preferable to have a cycloalkane structure in the main chain. The proportion of repeating units having an alicyclic structure in the polymer constituting the alicyclic structure-containing resin (hereinafter also referred to as "alicyclic structure-containing polymer") is not particularly limited, but is relative to all the polymer contained The repeating unit is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 90% by mass or more. By using an alicyclic structure-containing polymer having an alicyclic structure with a repeating unit ratio of 50% by mass or more, the shape accuracy of the plurality of optical surface portions included in the obtained molded sheet can be further improved, and the thickness can be reduced. The accuracy is uneven, and the production efficiency of the formed sheet is further improved. In addition, by using an alicyclic structure-containing polymer in which the proportion of repeating units having an alicyclic structure is 50% by mass or more, it becomes easy to obtain a molded sheet excellent in transparency and heat resistance.

Specific examples of the alicyclic structure-containing polymer include nordenene-based polymers, monocyclic cycloolefin-based polymers, cyclic conjugated diene-based polymers, and vinyl alicyclic hydrocarbon-based polymers. Among these, from the viewpoint of improving the transparency, heat resistance, and mechanical strength of the obtained molded sheet, the shape accuracy of the plurality of optical surface portions included in the obtained molded sheet is further improved, and the thickness is further reduced. From the standpoint of uneven accuracy and further improvement of the production efficiency of the formed sheet, the lower ene-based polymer is better. In addition, since the shape accuracy of the multiple optical surface parts included in the obtained molded sheet can be further improved, the variation in thickness accuracy can be further reduced, and the production efficiency of the molded sheet can be further improved, so the lower ene-based polymer is used as good. In addition, in this specification, these polymers mean not only polymerization reaction products, but also hydrogenated products.

Norene-based polymers are polymers of norene-based monomers or their hydrogenated products. Examples of norene-based polymers include: ring-opening polymers of norene-based monomers, ring-opening polymers of norene-based monomers and other monomers capable of ring-opening copolymerization with them, norene Addition polymers of monomers, addition polymers of norene-based monomers and other monomers capable of addition copolymerization with them, and hydrogenated products of these polymers, etc. Among them, hydrogenated ring-opening polymers of norene-based monomers (ie hydrogenated ring-opening polymers of norene-based ring-opening polymers) are preferred. By using hydrogenated norene-based ring-opening polymer, the transparency, heat resistance and mechanical strength of the formed sheet can be further improved, and at the same time, the mold release and transferability of the formed sheet can be improved when using thermocompression molding. .

Examples of norene-based monomers include: bicyclo[2.2.1]hept-2-ene (common name: norene) and its derivatives, tricyclic [4.3.0 ^1,6 .1 ^2,5 ] decane -3,7-Diene (common name: dicyclopentadiene) and its derivatives, 7,8-benzotricyclo[4.3.0.1 ^2,5 ]dec-3-ene (common name: methyl bridged tetrahydropyridine; also known as 1,4-methylene bridge -1,4,4a, 9a- tetrahydro-fluorene) and derivatives thereof, tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] twelve-3-ene (common name : Tetracyclododecene) and its derivatives. Examples of the substituent contained in the derivative include an alkyl group, an alkylene group, a vinyl group, an alkoxycarbonyl group, an alkylene group, and the like. For example, a "drop 𦯉-based monomer as derivatives" include: 8-methoxycarbonyl tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] twelve-3-ene, 8 - methyl-8-methoxycarbonyl-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] twelve-3-ene, 8-ethylidene tetracyclo [4.4.0.1 ^2,5 .1 ^{7, 10} ] Dodec-3-ene and so on. These ene-based monomers can be used singly or in combination of two or more.

Examples of other monomers capable of ring-opening copolymerization with norene-based monomers include monocyclic cycloolefin-based monomers such as cyclohexene, cycloheptene, and cyclooctene. Examples of other monomers capable of addition copolymerization with norene-based monomers include: ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and other α-olefins with 2 to 20 carbon atoms, and These derivatives; cyclobutene, cyclopentene, cyclohexene, cyclooctene and cycloolefins such as 3a,5,6,7a-tetrahydro-4,7-methyl bridge-1H-indene and these Derivatives; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene and other non-conjugated dienes ;Wait.

Ring-opening polymers and addition polymers containing the above-mentioned norene-based monomers can be synthesized by polymerizing them in the presence of well-known catalysts. Moreover, these hydrides can be obtained by hydrogenation reaction using a well-known hydrogenation catalyst.

In addition, examples of monocyclic cycloolefin-based polymers, cyclic conjugated diene-based polymers, and ethylene alicyclic hydrocarbon-based polymers include those described in International Patent Publication No. 2017/126599.

In addition, as an alicyclic structure-containing polymer, a commercially available product may also be used. Commercial products include: Zeonex (registered trademark) manufactured by Zeon Corporation, APEL (registered trademark) manufactured by Mitsui Chemicals, ARTON (registered trademark) manufactured by JSR, and TOPAS manufactured by Polyplastics Co., Ltd. (Registered trademark) etc.

Furthermore, the glass transition temperature (Tg) of the thermoplastic resin is not particularly limited, but is preferably 100°C or higher, preferably 120°C or higher, and 200°C or lower, and 160°C or lower. If the glass transition temperature (Tg) of the thermoplastic resin is above the above lower limit, the shape accuracy of the optical surface portion of the molded sheet can be further improved, while the thickness accuracy of the optical surface portion can be reduced, and the thickness accuracy can be further improved. The manufacturing efficiency of the formed sheet. In addition, if the glass transition temperature (Tg) of the thermoplastic resin film is below the above upper limit value, the production efficiency of the molded sheet can be improved, and the shape accuracy of the optical surface portion can be further improved.

In addition, the molded sheet may contain components other than the resin components described above. Examples of components other than the resin component include additives such as light stabilizers, ultraviolet absorbers, infrared absorbers, antioxidants, mold release agents, antistatic agents, carbon materials, pigments, and dyes. The blending amount of these components is not particularly limited, and can be appropriately determined. For example, the total amount of these additives, with the resin component being 100% by mass, is, for example, 20% by mass or less, preferably 10% by mass or less.

〈Optical surface section〉

The arrangement density of the optical surface part (11 in Figure 1) must be 0.16 pieces/cm ² or more. The arrangement density of the optical surface part is ^{preferably 0.30 pieces/cm 2} or more, and 0.40 pieces/cm ² or more. Preferably, it is preferably 3.0 pieces/cm ² or less, preferably 2.0 pieces/cm ² or less, more preferably 1.0 pieces/cm ² or less, and particularly preferably 0.60 pieces/cm ² or less. If the arrangement density of the optical surface-shaped portion is 0.16 pieces/cm ² or more, the variation in the thickness accuracy of the optical surface-shaped portion can be reduced, and the shape accuracy can be improved at the same time. In addition, if the arrangement density of the optical surface portion is below the above upper limit value, the shape accuracy can be improved, the birefringence can be reduced, and the variation in thickness accuracy can be further reduced.

In addition, the minimum distance between adjacent optical surfaces (P in Figure 1) must be 1.0 mm or more, preferably 3.0 mm or more, preferably 5.0 mm or more, and more preferably 7.0 mm or more. If the minimum distance between the optical surface parts is 1.0 mm or more, the variation in the thickness accuracy of the optical surface parts can be reduced, the shape accuracy can be improved, and the birefringence can be further reduced. In addition, if the minimum distance between the optical surface portions is 1.0 mm or more, even in the case of using a molding method such as press molding, the generation of bubbles and trapped air in the molded sheet can be suppressed. In addition, the minimum interval between the optical surface parts is usually 20 mm or less.

Furthermore, the diameter of the optical surface in a plan view (D in Figure 1) must be 1 mm or more and 15 mm or less, and the diameter of the optical surface is preferably 3 mm or more, and preferably 9 mm or less . If the diameter of the optical surface-shaped portion is within the above range, the variation in thickness accuracy of the optical surface-shaped portion can be reduced, and the shape accuracy can be improved.

In addition, the thickness of the center of the optical surface portion (H _{mid in} FIG. 1) is preferably 50 μm or more, more preferably 100 μm or more, preferably 1500 μm or less, and more preferably 1000 μm or less. If the thickness of the center of the optical surface portion is within the above range, it can be advantageously used as a transmissive optical element such as a lens.

Furthermore, the unevenness of the thickness accuracy of the optical surface portion must be 0.2 μm or less, preferably 0.1 μm or less. If the variation in thickness accuracy is less than the above upper limit, the birefringence in the optical surface portion can be reduced.

In addition, the retardation of the optical surface portion must be 50 nm or less, preferably 20 nm or less. If the phase difference is less than or equal to the above upper limit, the birefringence in the optical surface portion will be sufficiently small. Furthermore, when the phase difference is not more than the above upper limit value, the variation in the thickness accuracy of the optical surface-shaped portion can be reduced, and the shape accuracy can be improved.

Here, the thickness of the thinnest part of the formed sheet (H _{min in} Fig. 1) is preferably 50 μm or more, preferably 100 μm or more, preferably 500 μm or less, and preferably 300 μm or less, It is more preferably less than 200 μm. If the thickness of the thinnest part is less than the above upper limit, the variation in the thickness accuracy of the optical surface-shaped portion can be reduced, and the shape accuracy can be improved. In addition, if the thickness of the thinnest portion is more than the above lower limit, the strength of the formed sheet can be sufficiently increased.

(Method of manufacturing formed sheet)

The method of manufacturing a molded sheet of the present invention is a method of hot-press molding a thermoplastic resin film formed using a thermoplastic resin to produce a molded sheet having a plurality of optical surface portions. It can be used when forming a sheet without particular limitation. Moreover, the method of manufacturing a molded sheet of the present invention is characterized by comprising: using a pair of molds having a plurality of optical surface forming regions spaced apart from each other, and cutting a sheet material made of a thermoplastic resin film under normal pressure The "hot pressing process" to obtain a formed sheet by hot pressing. Furthermore, the manufacturing method of the shaped sheet of the present invention preferably includes a "demolding step" of releasing the shaped sheet obtained in the hot pressing step from a pair of molds. In the manufacturing method of the formed sheet of the present invention, since a pair of molds having a plurality of optical surface forming regions spaced apart from each other are used in the "hot pressing process", the cut sheet material is hot pressed under normal pressure Since it is formed, it is possible to easily manufacture a formed sheet with multiple optical surface-shaped portions with sufficiently high shape accuracy, small thickness accuracy, and small birefringence.

<Forming sheet>

The molded sheet manufactured by the method of manufacturing the molded sheet of the present invention is not particularly limited as long as it is a cut sheet having a plurality of optical surface-shaped portions separated from each other by a certain distance. Among them, the shaped sheet preferably has the same properties as the shaped sheet of the present invention described above.

<Thermoplastic resin film>

The thermoplastic resin used for the thermoplastic resin film is not particularly limited, and examples thereof include the same thermoplastic resins as those of the above-mentioned molded sheet of the present invention. In addition, the so-called "thin film" means an object having a shape in which the outer surface and the inner surface (that is, the main surface) face each other at a distance of the thickness component.

In addition, there is no particular limitation on the method for producing the thermoplastic resin film, and a conventionally well-known suitable method can be used. For example, after mixing the specified components to obtain a molding material for manufacturing a thermoplastic resin film, it can be used and the thermoplastic resin can be obtained by melt extrusion molding, melt casting, injection molding, etc. film.

The thickness of the thermoplastic resin film can be appropriately selected in accordance with the diameter of the optical surface portion of the molded sheet to be manufactured. For example, the thickness of the thermoplastic resin film is usually 50 μm or more, preferably 70 μm or more, and usually 500 μm or less, preferably 400 μm or less. In addition, in the case where the thickness of the thermoplastic resin film is uneven, the thickness of the thermoplastic resin film is equivalent to the simple arithmetic average value of the thickness at a plurality of measurement points selected at random.

Moreover, the thermoplastic resin film, for example, can be cut into a desired size such as A4 size to 50 cm×50 cm size, and made into a sheet material that is cut into sheets.

<Hot Pressing Process>

In the hot pressing process, a pair of molds having a plurality of optical surface forming regions spaced apart from each other are used to heat-press a cut sheet material made of a thermoplastic resin film under normal pressure. In addition, when the hot pressing process is started, it is necessary to implement the arrangement operation of installing the cut sheet material in the hot pressing device. FIG. 2 is a schematic diagram for explaining the hot pressing process in the manufacturing method of the formed sheet according to an example of the present invention. As shown in FIG. 2, in the hot pressing process related to this example, a pair of molds 1 consisting of an upper mold 1A and a lower mold 1B is used to heat press and cut the sheet material 10' into a sheet. Moreover, it is good that as shown in the bottom diagram of Fig. 2, in a state where the cut sheet material 10' is pressed through a pair of molds 1, the cut sheet material 10' will not fill a pair of molds 1. By preventing the cut sheet material 10' from filling a pair of molds 1 under pressure, the shape accuracy of the multiple optical surface parts included in the obtained molded sheet can be improved, and the thickness can be reduced. The accuracy is uneven, and the birefringence is further reduced, and the production efficiency of the formed sheet can be further improved. In addition, in the manufacturing method of the molded sheet of the present invention, the thermoplastic resin film is supplied to the hot pressing using the mold without the injection molding method, thereby suppressing the birefringence in the optical surface portion of the obtained molded sheet. produce.

[Mould]

The pair of molds 1 is not particularly limited as long as at least one of them has a plurality of female mold portions that are regions for forming optical surface portions, and a mold of any shape such as a flat mold can be used.

In addition, as the material used for the mold, a well-known material can be used. Examples include carbon steel, stainless steel, and alloys based on these, among which, from the viewpoint of workability and hardness, stainless steel such as STAVAX (registered trademark) material (manufactured by Uddeholm) is preferred. In addition, from the viewpoint of mold release properties, it is better to use a mold that is electroplated with metals such as chromium, titanium, and nickel on the mold surface. Among them, electroless nickel-phosphorus plating is used on the mold surface. A mold made of Ni-P plating is preferable.

Furthermore, at least one of the molds used in the manufacturing method of the present invention is formed by arranging a plurality of female mold portions discretely in the plane direction of the mold. The plurality of female mold parts are preferably arranged at equal intervals in the plane direction of the mold.

Here, a pair of molds may each have a plurality of female mold parts. This is because by using a pair of molds each having a female mold part for molding, it is possible to efficiently manufacture a double-sided shaped molded sheet. In addition, the shape of each of the pair of molds depends on the shape of the formed sheet to be manufactured, and of course they can be the same or different.

The placement density of the female mold part is ^{preferably 0.16 pieces/cm 2} or more, preferably 0.30 pieces/cm ² or more, more preferably 0.40 pieces/cm ² or more, and preferably 3.0 pieces/cm ² or less, It is preferably 2.0 pieces/cm ² or less, more preferably 1.0 pieces/cm ² or less, and particularly preferably 0.60 pieces/cm ² or less. If the disposition density of the female mold part is 0.16 pieces/cm ² or more, the variation in the thickness accuracy of the optical surface part of the obtained molded sheet can be reduced, and the shape accuracy can be improved at the same time. In addition, if the placement density of the female mold portion is below the above upper limit value, the shape accuracy of the obtained molded sheet can be improved, the birefringence can be reduced, and the variation in thickness accuracy can be further reduced.

In addition, the minimum distance between adjacent female mold parts (equivalent to P in Figure 1) is preferably 1.0 mm or more, preferably 3.0 mm or more, more preferably 5.0 mm or more, and 7.0 mm or more Especially good. If the minimum interval (P) between the female mold parts is 1.0 mm or more, the variation in the thickness accuracy of the optical surface part of the obtained molded sheet can be reduced, the shape accuracy can be improved, and the birefringence can be further reduced. In addition, if the minimum interval between the female mold parts is 1.0 mm or more, the generation of bubbles and trapped air in the formed sheet can be suppressed. In addition, the minimum interval between the female mold parts is usually 20 mm or less.

Furthermore, the diameter of the female mold portion (equivalent to D in Fig. 1) in a plan view is preferably 1 mm or more and 15 mm or less, preferably 3 mm or more, and preferably 9 mm or less. If the diameter of the female mold part is within the above-mentioned range, the variation in thickness accuracy of the optical surface-shaped part of the obtained molded sheet can be reduced, and the shape accuracy can be improved.

In addition, the depth of the center of the female mold portion (the distance in the direction corresponding to the thickness direction of the center of the formed optical surface portion; H _mid ) in the state where the mold is closed (mold closed state) is 50 μm or more Preferably, it is more than 100 μm, more preferably 1500 μm or less, and more preferably 1000 μm or less. If the depth of the center of the female mold portion is within the above range, the optical surface portion of the obtained molded sheet can be advantageously used as a transmissive optical element such as a lens.

_{Furthermore, the minimum distance (H min} ) between the forming surfaces of the molded sheet in the closed state of the mold is preferably 50 μm or more, preferably 100 μm or more, and preferably 500 μm or less, and 300 μm or less It is more preferable, and 200 μm or less is more preferable. If the minimum interval is less than the above upper limit, the variation in the thickness accuracy of the optical surface portion of the obtained molded sheet can be reduced, and the shape accuracy can be improved. In addition, if the minimum interval is more than the above lower limit value, the strength of the obtained molded sheet can be sufficiently ensured.

[Pressure temperature]

In the hot pressing process, the pressing temperature (mold temperature) when the thermoplastic resin film is hot pressed with a pair of molds is 40°C higher than the glass transition temperature (Tg) of the thermoplastic resin (Tg+40°C) or higher. Preferably, the pressing temperature is preferably 50°C higher than the glass transition temperature (Tg+50°C), and more preferably 55°C higher than the glass transition temperature (Tg+55°C). If the pressing temperature is higher than the above-mentioned lower limit value, the variation in the thickness accuracy of the optical surface portion of the obtained molded sheet can be reduced, and the shape accuracy can be improved. In addition, from the viewpoint of efficient production of formed sheets, the pressing temperature is preferably set at a temperature (Tg+80°C) or lower that is 80°C higher than the glass transition temperature.

In addition, the pressing temperature is not particularly limited, and can be appropriately adjusted by controlling the temperature of the mold according to a known general method (for example, using a known temperature control method such as a heater and a cooler).

[Pressure pressure]

In the hot pressing process, it is better to increase the pressing pressure when the thermoplastic resin film is hot-pressed with the mold to the final pressing pressure at a specified pressure increasing rate, and then arbitrarily maintain the final pressing pressure for a specified time.

―Boost speed―

Here, the average pressure increase rate of the applied pressure is preferably 0.1 MPa/sec or less, preferably 0.07 MPa/sec or less, and more preferably 0.05 MPa/sec or less. If the average pressure increase speed is below the above upper limit, the birefringence of the optical surface portion of the obtained molded sheet can be reduced, and the shape accuracy can be improved. In addition, from the viewpoint of efficient production of formed sheets, the average pressure increase rate is preferably set to 0.04 MPa/sec or more.

―Finally put pressure on the pressure―

The final applied pressure is not particularly limited, and can be set to, for example, 1 MPa or more and 10 MPa or less. If the final pressing pressure is within the above range, the shape accuracy of the optical surface portion of the obtained molded sheet can be further improved, and at the same time, the variation in thickness accuracy and birefringence can be further reduced.

[Other pressure conditions]

In addition, the pressing time in the hot pressing process is not particularly limited, and can be appropriately determined according to the type and size of the thermoplastic resin film used, and the shape and size of the intended molded sheet. For example, the time to increase the applied pressure to the final applied pressure can be set to 20 seconds or more and 300 seconds or less, and the time to maintain the applied pressure at the final applied pressure can be set to be 0 second or more and 180 seconds or less .

〈Demoulding process〉

In the demolding process, when the formed sheet obtained in the hot pressing process is demolded from a pair of molds, the pair of molds are set at a temperature above (Tg－80)℃ and below (Tg－15)℃ (there are below: It is also called "release temperature".) Demolding. By implementing such a process, the shape accuracy of the plurality of optical surface-shaped parts included in the obtained molded sheet can be further improved, the variation in thickness accuracy can be further reduced, and the birefringence can be further reduced. In addition, the starting point of the demolding process may be, for example, "after a specified time has elapsed from the start of the hot pressing process, the temperature control for cooling the mold is started" or "the specified time has passed since the start of the hot pressing process" After the time, the time point when the heat input to the mold is stopped".

[Release temperature]

The demolding temperature must be below the glass transition temperature (Tg) of the thermoplastic resin, preferably 15℃ lower than the glass transition temperature (Tg-15℃), and 20℃ lower than the glass transition temperature (Tg-20°C) or lower is preferable, and a temperature (Tg-30°C) or lower 30°C lower than the glass transition temperature is more preferable. In addition, the demolding temperature is preferably 80°C lower than the glass transition temperature (Tg-80°C) or higher, and preferably 75°C lower than the glass transition temperature (Tg-75°C) or higher. If the demolding temperature is below the above upper limit, demolding is easy, and the shape accuracy of the optical surface portion of the obtained molded sheet can be effectively improved. Furthermore, if the mold release temperature is below the above upper limit, the variation in the thickness accuracy of the optical surface portion of the obtained molded sheet can be reduced, and the birefringence can be reduced. Moreover, if the demolding temperature is below the above upper limit, the occurrence of failures during demolding can be suppressed, and the manufacturing efficiency of the formed sheet can be further improved. In addition, if the demolding temperature is higher than the above lower limit, the temperature adjustment time required for cooling a pair of molds and heating in the subsequent hot pressing process can be shortened, and the manufacturing efficiency of the formed sheet can be further improved.

[Other demolding conditions]

The time required to cool the mold to the demolding temperature (mold cooling time) and mold cooling rate are not particularly limited. It can be adapted to the type and size of the sheet material to be cut, and the optical surface of the intended molded sheet The shape and size of the shaped portion are appropriately determined. For example, the mold cooling time can be set to 10 seconds or more and 100 seconds or less, and the mold cooling rate can be set to 50°C/min or more and 300°C/min or less.

Furthermore, in the demolding step, after the mold is cooled to a demolding temperature, the hot-pressed film is demolded from the mold to obtain a molded sheet.

(Method of manufacturing optical element)

The manufacturing method of the optical element of the present invention is characterized by including an optical element separation step: the molded sheet obtained according to the manufacturing method of the present invention is separated according to the positions corresponding to the multiple optical surface portions, respectively, to obtain multiple optical elements. According to the manufacturing method of the present invention, it is possible to easily manufacture an optical element with sufficiently high shape accuracy, small thickness accuracy, and low birefringence.

<Optical element separation process>

In the optical element separation process, a plurality of optical elements are separated from the molded sheet obtained according to the manufacturing method of the present invention. The separation method is not particularly limited, and the optical elements can be separated from the formed sheet by any known methods such as punching with a cutting die or laser cutting.

"Example"

Examples and comparative examples are listed below to further illustrate the present invention in detail. In addition, the present invention is not limited by these examples. In the Examples and Comparative Examples, the glass transition temperature of the thermoplastic resin was measured in the following manner. In addition, in the Examples and Comparative Examples, the shape accuracy, thickness accuracy, and phase difference of the optical surface portion of the molded sheet, and the productivity of the molded sheet were evaluated as follows. The various operations from configuration to demolding in the examples and comparative examples are all carried out under normal pressure, that is, under conditions that do not make the inside of the mold a pressurized or reduced gas atmosphere.

<Glass transition temperature of thermoplastic resin>

The glass transition temperature (Tg) of the thermoplastic resin is measured using a differential scanning calorimeter (manufactured by Hitachi High-Tech Science, "DSC6220"), based on JIS K7121:2012, at a temperature increase rate of 10°C/min.

〈Shape accuracy〉

The optical surface part of the formed sheet is punched out to obtain an optical lens, which is used as a quantity test sample. In addition, the optical lens obtained according to the embodiment and the comparative example is an aspheric lens in which the outer surface and the inner surface respectively have an "aspherical shape with an inflection point in the cross-sectional shape along the thickness direction of the optical lens".

Secondly, for 300 test samples in the punched optical surface, a shape measuring device (manufactured by Panasonic, "UA-3P") was used to measure the PV value based on the design value of the optical surface (The maximum error of the surface of the measurement sample relative to the shape of the reference surface, that is, the difference between the highest point (Peak) and the lowest point (Valley) in the measurement range). Then, take the simple average of the measured PV value as the shape accuracy, and evaluate it using the following criteria. A: The simple average value of PV value is 0.5 μm or less B: The simple average value of the PV value exceeds 0.5 μm and is 1.0 μm or less C: The simple average of the PV value exceeds 1.0 μm and is 2.0 μm or less D: The simple average value of PV value exceeds 2.0 μm

<Variations in thickness accuracy>

The optical surface part of the formed sheet is punched out, and an optical lens is obtained as a quantity test sample.

Secondly, for 300 test samples of the obtained optical lens, the thickness of the center was measured using a shape measuring device (manufactured by Panasonic, "UA-3P"). Then, take the standard deviation of the measured thickness as the variation in thickness accuracy, and evaluate it using the following criteria. A: The standard deviation is 0.1 μm or less B: The standard deviation exceeds 0.1 μm and is less than 0.2 μm C: The standard deviation exceeds 0.2 μm

<Phase Difference>

The optical surface part of the formed sheet is punched out, and an optical lens is obtained as a quantity test sample.

Secondly, with respect to 300 test samples of the obtained optical lens, the phase difference was measured using a resin molded lens inspection system (manufactured by Photonic Lattice, "WPA-100").

Use the simple average value of the phase difference obtained in the form of the normalized value of the measured wavelength (543 nm), and evaluate it according to the following criteria. The smaller the value of the phase difference, the smaller the birefringence. A: The simple average value of the phase difference is 20 nm or less B: The simple average value of the retardation exceeds 20 nm and is less than 50 nm C: The simple average value of the phase difference exceeds 50 nm

〈Continuous productivity〉

According to the following criteria, the sum of the stopping time of the device caused by the failure when processing 100 sheets of cut sheet material into a formed sheet was evaluated. A: The stop time is less than 30 minutes B: Stop time is more than 30 minutes and less than 120 minutes C: Stop time is more than 120 minutes

(Example 1)

The thermoplastic resin (ZEONEX E48R (manufactured by Zeon Corporation), glass transition temperature: 139°C) containing the hydride of the norene-based ring-opening polymer is put into the film extrusion machine (uniaxial extruder, ⌀=20) mm, made by GSI Creos), melted at 260°C, extruded the molten resin from the T-die and cooled it to obtain a thermoplastic resin film with a thickness of 500 μm and a width of 295 mm with a length of 100 m or more. The thermoplastic resin film obtained in this way is cut into 250 mm squares and used as a sheet material for cutting into sheets.

The sheet material cut into pieces obtained by following the above is installed in a thermoforming machine equipped with a temperature adjusting device and equipped with a pair of 300 mm square molds (configuration operation). In addition, as a pair of molds, those having the properties shown in Table 1 were used.

Then, after raising the temperature of the mold to the pressure temperature shown in Table 1, under the conditions shown in Table 1, the cut sheet material was increased to 9.5 MPa at a pressure increase rate of 0.045 MPa/sec. The hot pressing (hot pressing process).

Then, while maintaining the pressure on the cut sheet material, the pair of molds are cooled to 100° C., and the formed sheet sandwiched between the molds is cooled. After that, the pair of molds were opened, and the molded sheet having the properties shown in Table 1 was peeled from the pair of molds (release step). In addition, the diameter of the optical surface portion in the forming sheet corresponds to the diameter D of the female mold portion in the mold, the minimum interval between the optical surface portions corresponds to the minimum interval P between the female mold portions in the mold, and the configuration of the optical surface portion The setting density corresponds to the distribution density of the female part of the mold, the thickness of the center of the optical surface part corresponds to the depth H _mid of the center of the female part in the closed state, and the thickness of the thinnest part of the formed sheet corresponds to the closed state _{The minimum interval H min} between the forming surfaces of the next formed sheet.

The results of the various evaluations performed on the obtained shaped sheets according to the above are shown in Table 1 together with the time (cycle time) from the arrangement of the sheet materials to the demolding of the shaped sheets.

(Examples 2 to 4)

Except that the pair of molds were changed to molds with the properties shown in Table 1, molded sheets were produced in accordance with Example 1, and various evaluations were performed. The results are shown in Table 1.

(Examples 5-7)

Except that the mold release temperature in the mold release process was changed to the temperature shown in Table 1, a molded sheet was produced in accordance with Example 1, and various evaluations were performed. The results are shown in Table 1.

(Example 8)

Except for using a sheet material cut into a 400 mm square, a shaped sheet was produced in accordance with Example 1, and various evaluations were performed. The results are shown in Table 1. In the hot pressing process according to this embodiment, a pair of molds are formed at the edges of the cut sheet material.

(Example 9)

In addition to the use of thermoplastic resins (TOPAS 6013 (manufactured by Polyplastics Co., Ltd.), glass Transition temperature: 138°C) was used to prepare a thermoplastic resin film, and the pressing temperature was changed to a temperature other than the temperature shown in Table 1. A molded sheet was produced in accordance with Example 1, and various evaluations were performed. The results are shown in Table 1.

(Example 10)

Except that polycarbonate resin (WONDERLITE PC-115 (manufactured by Asahi Kasei Co., Ltd.), glass transition temperature: 145°C) was used to make a thermoplastic resin film, and the pressing temperature was changed to the temperature shown in Table 1, the comparison was carried out in Example 1. The formed sheet was manufactured and various evaluations were performed. The results are shown in Table 1.

(Example 11)

Except that polymethyl methacrylate resin (DELPET 80NH (manufactured by Asahi Kasei Chemicals), glass transition temperature: 100°C) is used to make a thermoplastic resin film, and the pressing temperature is changed to the temperature shown in Table 1, cf. Example 1 A formed sheet was produced, and various evaluations were performed. The results are shown in Table 1.

(Example 12)

Except that polyester resin (OKP-1 (manufactured by Osaka Gas Chemicals), glass transition temperature: 132°C) was used to make a thermoplastic resin film, and the pressing temperature was changed to the temperature shown in Table 1, the comparison was carried out in Example 1. The formed sheet was manufactured and various evaluations were performed. The results are shown in Table 1.

(Comparative example 1)

Except that the pair of molds were changed to molds with the properties shown in Table 1, molded sheets were produced in accordance with Example 1, and various evaluations were performed. The results are shown in Table 1.

(Comparative example 2)

Changed "Hot press forming machine with a pair of 300 mm square molds" to "Hot press forming machine with four pairs of 100 mm square molds in a 2×2 configuration with the interval between the molds set to 20 mm" . In addition to using this hot press forming machine to simultaneously shape the cut sheet material with four pairs of dies, the manufacturing of the formed sheet was attempted according to Example 1. However, the sheet material was broken in the gap between the molds during the forming, and the shape could not be manufactured. Thin slices.

"Table 1" Comparative example 2 250 mm square 500 139 without 4 100 mm square 205 66 9.5 60 100 39 360 5 0 4 600 150 - - - - Comparative example 1 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 0 4 600 150 D C C C Example 12 250 mm square 500 132 without 1 300 mm square 190 55 9.5 60 100 32 337 5 9 0.5 600 150 B B A B Example 11 250 mm square 500 100 without 1 300 mm square 155 55 9.5 60 80 20 265 5 9 0.5 600 150 B B A B Example 10 250 mm square 500 145 without 1 300 mm square 200 55 9.5 60 100 40 353 5 9 0.5 600 150 B B A B Example 9 250 mm square 500 138 without 1 300 mm square 195 57 9.5 60 100 38 345 5 9 0.5 600 150 A A A A Example 8 400 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 9 0.5 600 150 C B B B Example 7 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 130 9 330 5 9 0.5 600 150 C B B B Example 6 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 120 19 340 5 9 0.5 600 150 B B B A Example 5 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 110 29 350 5 9 0.5 600 150 B B A A Example 4 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 1 2.8 600 150 B B B A Example 3 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 3 1.6 600 150 B A B A Example 2 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 5 1 600 150 B A A A Example 1 250 mm square 500 139 without 1 300 mm square 205 66 9.5 60 100 39 360 5 9 0.5 600 150 A A A A shape Thickness (μm) Glass transition temperature (℃) Vacuum attraction Number of molds (pair) Mold size Pressure temperature (℃) Pressure temperature-Tg(℃) Final pressure (MPa) Final pressure holding time (seconds) Demoulding temperature (℃) Tg－ demolding temperature (℃) Cycle time (seconds) Diameter D (mm) Minimum interval P(mm) Distribution density (pcs/cm ² ) Center depth H _mid (μm) The minimum interval between the forming surfaces of the formed sheet H _min (μm) Shape accuracy Thickness accuracy Phase difference Continuous productivity Hot pressing process Demoulding process Optical surface Cut into sheets of material Hot pressing conditions Mold properties (corresponding to the properties of the formed sheet) Evaluation

It can be seen from Table 1 that the molded sheets of Examples 1 to 12 have a plurality of optical surface portions with sufficiently high shape accuracy, small variations in thickness accuracy, and sufficiently small birefringence. Furthermore, it can be seen that the formed sheets of Examples 1 to 12 are excellent in continuous productivity. In addition, it can be seen that the shape accuracy of the optical surface portion of the molded sheet of Comparative Example 1 is low, the thickness accuracy is large, and the birefringence is large. In addition, it can be seen that the formed sheet of Comparative Example 1 lacks continuous productivity.

According to the present invention, it is possible to provide a molded sheet having a plurality of optical surface-shaped portions with sufficiently high shape accuracy, small variations in thickness accuracy, and low birefringence.

Furthermore, according to the present invention, it is possible to provide a method for producing a shaped sheet that can efficiently produce the above-mentioned shaped sheet.

Furthermore, according to the present invention, it is possible to provide a method of manufacturing an optical element using the above-mentioned molded sheet.

1: a pair of molds 1A: Upper mold 1B: Lower mold 10: forming sheet 10′: Cut into sheets of material 11: Optical surface

<Figure 1> is a schematic cross-sectional view showing a cross-section in the thickness direction of a formed sheet related to an example of the present invention.

<Figure 2> is a schematic diagram for explaining the hot pressing process in the manufacturing method of the formed sheet according to an example of the present invention.

10: forming sheet

11: Optical surface

D: diameter

H _mid : the thickness of the center

H _min : the thickness of the thinnest part

P: minimum interval

Claims (7)

A method of manufacturing a molded sheet, which is a method of hot press molding a thermoplastic resin film formed using a thermoplastic resin to produce a molded sheet with a plurality of optical surface portions, including: a hot pressing process, using A pair of molds with a plurality of optical surface forming regions separated by a distance from each other heat and press the cut sheet material made of the aforementioned thermoplastic resin film under normal pressure to obtain a shaped sheet. The method for manufacturing a formed sheet according to claim 1, which comprises: a demolding step, setting the glass transition temperature of the thermoplastic resin as Tg (°C), and the formed sheet obtained in the hot pressing step is obtained from the aforementioned When demolding a pair of molds, demold the aforementioned pair of molds at a temperature above (Tg-80)°C and below (Tg-15)°C. The method for manufacturing a shaped sheet according to claim 1 or 2, wherein in the hot pressing step, the cut sheet material is pressed through the pair of molds, and the cut sheet material The aforementioned pair of molds will not fill up. The method for producing a molded sheet according to claim 1 or 2, wherein the thermoplastic resin is a resin containing an alicyclic structure. A method for manufacturing an optical element, comprising: an optical element separation step, wherein the molded sheet obtained according to the method for manufacturing a molded sheet according to any one of claims 1 to 4 is separated into the plurality of optical surface portions Separate the corresponding positions to obtain multiple optical elements. A molded sheet, which is a cut molded sheet having a plurality of optical surface portions formed by using a thermoplastic resin, wherein the arrangement density of the optical surface portions is 0.16 pcs/cm ² or more, and the optical surfaces adjacent to each other The minimum distance between the surface portions is 1.0 mm or more, the diameter of the optical surface portion in a plan view is 1 mm or more and 15 mm or less, the phase difference of the optical surface portion is 50 nm or less, the optical surface portion The variation of thickness accuracy is less than 0.2 μm. The molded sheet according to claim 6, wherein the cross-sectional shape of at least one surface of the optical surface portion in the thickness direction is an aspherical shape having an inflection point.

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