JP7619261B2 - Optical Film - Google Patents

Description

The present invention relates to an optical film.

Conventionally, films formed from thermoplastic resins have been known. For example, Patent Document 1 describes a technology for forming an optical film from a cycloolefin resin.

JP 2017-102310 A

In recent years, optical films using cycloolefin resins are often used in deformable articles. For this reason, optical films are required to have high resistance to deformation. Specifically, they are required to have high tensile elongation at break and excellent bending resistance.

The present invention has been devised in consideration of the above-mentioned problems, and aims to provide an optical film that has high tensile elongation at break and excellent bending resistance.

The present inventors have conducted extensive research to solve the above problems, and as a result, have found that an optical film having a first resin layer formed of a first thermoplastic resin containing a norbornene-based polymer selected from the group consisting of polymers of specific norbornene-based monomer compositions and hydrogenated products thereof and having a specific weight-average molecular weight, and a light absorbent in a predetermined amount, has a large tensile elongation at break and excellent bending resistance, thereby completing the present invention.
That is, the present invention includes the following.

（式（Ｔ）において、
ｎｔ１及びｎｔ２は、それぞれ独立に、１又は２を表し、
ｎｔ１が１である場合、Ｒ^ｔ１は、２価の炭化水素基を表し、
ｎｔ１が２である場合、Ｒ^ｔ１は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｔ２が１である場合、Ｒ^ｔ２は、２価の炭化水素基を表し、
ｎｔ２が２である場合、Ｒ^ｔ２は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し；
式（Ｄ）において、
ｎｄ１、ｎｄ２及びｎｄ３は、それぞれ独立に、１又は２を表し、
ｎｄ１が１である場合、Ｒ^ｄ１は、水素原子、アルキル基、アルキルオキシカルボニル基、又は、２価の炭化水素基を表し、
ｎｄ１が２である場合、Ｒ^ｄ１は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｄ２が１である場合、Ｒ^ｄ２は、水素原子、アルキル基、アルキルオキシカルボニル基、又は、２価の炭化水素基を表し、
ｎｄ２が２である場合、Ｒ^ｄ２は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｄ３が１である場合、Ｒ^ｄ３は、２価の炭化水素基を表し、
ｎｄ３が２である場合、Ｒ^ｄ３は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表す。）
〔２〕 前記ノルボルネン系単量体組成物が、下記式（Ｎ）で表される単量体を１重量％～１５重量％含む、〔１〕に記載の光学フィルム。

（式（Ｎ）において、
ｎｎ１及びｎｎ２は、それぞれ独立に、１又は２を表し、
ｎｎ１が１である場合、Ｒ^ｎ１は、２価の炭化水素基を表し、
ｎｎ１が２である場合、Ｒ^ｎ１は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｎ２が１である場合、Ｒ^ｎ２は、２価の炭化水素基を表し、
ｎｎ２が２である場合、Ｒ^ｎ２は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表す。）
〔３〕 前記光吸収剤が、紫外線吸収剤及び赤外線吸収剤からなる群より選ばれる少なくとも１種類を含む、〔１〕又は〔２〕に記載の光学フィルム。
〔４〕 前記光吸収剤の分子量が、８００以下である、〔１〕～〔３〕のいずれか一項に記載の光学フィルム。
〔５〕 前記光吸収剤が、トリアジン系紫外線吸収剤及びベンゾトリアゾール系紫外線吸収剤からなる群より選ばれる少なくとも１種を含む、〔１〕～〔４〕のいずれか一項に記載の光学フィルム。
〔６〕 前記光吸収剤が、ペンタエリスリトール系赤外線吸収剤を含む、〔１〕～〔５〕のいずれか一項に記載の光学フィルム。
〔７〕 第二熱可塑性樹脂で形成された第二樹脂層と、前記第一樹脂層と、第三熱可塑性樹脂で形成された第三樹脂層とを、この順に備える、〔１〕～〔６〕のいずれか一項に記載の光学フィルム。 [1] A light-absorbing film having a first resin layer formed of a first thermoplastic resin containing a norbornene-based polymer and a light-absorbing agent,
the norbornene-based polymer is selected from the group consisting of polymers of norbornene-based monomer compositions and hydrogenated products thereof,
The norbornene-based monomer composition contains 50% by weight or more of one or more monomers selected from the group consisting of a monomer represented by the following formula (T) and a monomer represented by the following formula (D),
The norbornene-based polymer has a weight average molecular weight of 38,000 or more and 100,000 or less,
The amount of the light absorber in the first thermoplastic resin is 2% by weight to 30% by weight.

(In formula (T),
Each of nt1 and nt2 independently represents 1 or 2;
When nt1 is 1, R ^t1 represents a divalent hydrocarbon group;
When nt1 is 2, each R ^t1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nt2 is 1, R ^t2 represents a divalent hydrocarbon group;
When nt2 is 2, each R ^t2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
In formula (D),
nd1, nd2 and nd3 each independently represent 1 or 2;
When nd1 is 1, R ^d1 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd1 is 2, each R ^d1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd2 is 1, R ^d2 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd2 is 2, each R ^d2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd3 is 1, R ^d3 represents a divalent hydrocarbon group;
When nd3 is 2, each R ^d3 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group.
[2] The optical film according to [1], wherein the norbornene-based monomer composition contains 1% by weight to 15% by weight of a monomer represented by the following formula (N):

(In formula (N),
nn1 and nn2 each independently represent 1 or 2;
When nn1 is 1, R ⁿ¹ represents a divalent hydrocarbon group;
When nn1 is 2, each R ⁿ¹ independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nn2 is 1, R ⁿ² represents a divalent hydrocarbon group;
When nn2 is 2, each R ⁿ² independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group.
[3] The optical film according to [1] or [2], wherein the light absorbent includes at least one selected from the group consisting of an ultraviolet absorbent and an infrared absorbent.
[4] The optical film according to any one of [1] to [3], wherein the molecular weight of the light absorbent is 800 or less.
[5] The optical film according to any one of [1] to [4], wherein the light absorber includes at least one selected from the group consisting of a triazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber.
[6] The optical film according to any one of [1] to [5], wherein the light absorbent comprises a pentaerythritol-based infrared absorbent.
[7] The optical film according to any one of [1] to [6], comprising, in this order, a second resin layer formed of a second thermoplastic resin, the first resin layer, and a third resin layer formed of a third thermoplastic resin.

According to the present invention, an optical film having high tensile elongation at break and excellent bending resistance can be provided.

FIG. 1 is a cross-sectional view that illustrates an example of an optical film according to an embodiment of the present invention. FIG. 2 is a cross-sectional view that illustrates another example of an optical film according to an embodiment of the present invention.

The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents.

In the following description, a "long" film refers to a film that is 5 times or more longer than its width, preferably 10 times or more longer, specifically a film that is long enough to be wound into a roll for storage or transportation. There is no particular upper limit to the ratio of the length to the width of the film, but it can be, for example, 100,000 times or less.

In the structural formulas shown in the following explanation, the following line segments represented by a combination of parallel solid and dashed lines represent either single bonds or double bonds, unless otherwise specified.

[1. Overview of Optical Films]
An optical film according to an embodiment of the present invention includes a first resin layer formed of a first thermoplastic resin. The first thermoplastic resin contained in the first resin layer includes one or more norbornene polymers selected from the group consisting of polymers of norbornene monomer compositions and hydrogenated products thereof, and a light absorber. The term "norbornene monomer composition" refers to a general term for monomers used as raw materials for norbornene polymers. The norbornene monomer composition includes not only materials containing two or more types of monomers, but also materials consisting of a single monomer. Thus, a norbornene polymer may generally have a structure formed by polymerization of a norbornene monomer composition, or a structure in which the carbon-carbon unsaturated bond of the structure is hydrogenated.

The norbornene-based monomer composition contains one or more monomers selected from the group consisting of a monomer represented by formula (T) and a monomer represented by the following formula (D) in a specific ratio.

（式（Ｔ）において、
ｎｔ１及びｎｔ２は、それぞれ独立に、１又は２を表し、
ｎｔ１が１である場合、Ｒ^ｔ１は、２価の炭化水素基を表し、
ｎｔ１が２である場合、Ｒ^ｔ１は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｔ２が１である場合、Ｒ^ｔ２は、２価の炭化水素基を表し、
ｎｔ２が２である場合、Ｒ^ｔ２は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し；
式（Ｄ）において、
ｎｄ１、ｎｄ２及びｎｄ３は、それぞれ独立に、１又は２を表し、
ｎｄ１が１である場合、Ｒ^ｄ１は、水素原子、アルキル基、アルキルオキシカルボニル基、又は、２価の炭化水素基を表し、
ｎｄ１が２である場合、Ｒ^ｄ１は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｄ２が１である場合、Ｒ^ｄ２は、水素原子、アルキル基、アルキルオキシカルボニル基、又は、２価の炭化水素基を表し、
ｎｄ２が２である場合、Ｒ^ｄ２は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表し、
ｎｄ３が１である場合、Ｒ^ｄ３は、２価の炭化水素基を表し、
ｎｄ３が２である場合、Ｒ^ｄ３は、それぞれ独立に、水素原子、アルキル基又はアルキルオキシカルボニル基を表す。）

(In formula (T),
Each of nt1 and nt2 independently represents 1 or 2;
When nt1 is 1, R ^t1 represents a divalent hydrocarbon group;
When nt1 is 2, each R ^t1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nt2 is 1, R ^t2 represents a divalent hydrocarbon group;
When nt2 is 2, each R ^t2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
In formula (D),
nd1, nd2 and nd3 each independently represent 1 or 2;
When nd1 is 1, R ^d1 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd1 is 2, each R ^d1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd2 is 1, R ^d2 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd2 is 2, each R ^d2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd3 is 1, R ^d3 represents a divalent hydrocarbon group;
When nd3 is 2, each R ^d3 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group.

In addition, the norbornene-based polymer has a weight average molecular weight Mw in a specific range. Furthermore, the amount of the light absorber in the first thermoplastic resin is in a specific range.

Figure 1 is a cross-sectional view showing an example of an optical film according to one embodiment of the present invention. Figure 2 is a cross-sectional view showing another example of an optical film according to one embodiment of the present invention. For example, as shown in Figure 1, the optical film 100 may be a single-layer film having only a first resin layer 110. For example, as shown in Figure 2, the optical film 200 may be a multi-layer film having optional layers such as a second resin layer 220 and a third resin layer 230 in combination with the first resin layer 110.

The optical film described above has the advantages of high tensile elongation at break and excellent bending resistance.

In the following description, the monomer represented by formula (T) may be referred to as a "TCD-based monomer." The monomer represented by formula (D) may be referred to as a "DCP-based monomer."

[2. Norbornene-based polymer]
The norbornene polymer is selected from the group consisting of polymers of norbornene monomer compositions and hydrogenated products thereof. The norbornene monomer composition contains one or more monomers selected from the group consisting of TCD monomers and DCP monomers. If necessary, the norbornene monomer composition may contain any monomer other than the TCD monomer and the DCP monomer.

The TCD monomer is represented by formula (T). Under appropriate conditions, this TCD monomer can undergo polymerization reactions such as ring-opening polymerization and addition polymerization. Furthermore, the polymer obtained by the polymerization reaction can be hydrogenated to convert the carbon-carbon unsaturated bonds into carbon-carbon single bonds. For example, when a TCD monomer represented by formula (T-1) described below undergoes ring-opening polymerization and hydrogenation, a polymer containing a repeating unit represented by formula (T-A) can be obtained.

In formula (T), nt1 and nt2 each independently represent 1 or 2. When nt1 is 1, the bond of R ^t1 may represent a double bond. When nt1 is 2, the bond of R ^t1 may represent a single bond. When nt2 is 1, the bond of R ^t2 may represent a double bond. When nt2 is 2, the bond of R ^t2 may represent a single bond. Thus, formula (T) encompasses structures represented by the following formulae (T-1) to (T-4). In particular, structures in which nt1 is 1 may be represented by formulae (T-2) and (T-4), and structures in which nt1 is 2 may be represented by formulae (T-1) and (T-3). Furthermore, the structure in which nt2 is 1 can be represented by formula (T-2) and formula (T-3), and the structure in which nt2 is 2 can be represented by formula (T-1) and formula (T-4).

When nt1 is 1, R ^t1 represents a divalent hydrocarbon group. As the divalent hydrocarbon group, from the viewpoint of obtaining an optical film particularly excellent in tensile elongation at break and bending resistance, an aliphatic hydrocarbon group is preferable, and a saturated aliphatic hydrocarbon group is more preferable. The number of carbon atoms of this divalent hydrocarbon group is usually 1 or more, and usually 6 or less, preferably 4 or less, more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film particularly excellent in tensile elongation at break and bending resistance can be obtained. Examples of the divalent hydrocarbon group include a methylidene group and an ethylidene group.

When nt1 is 2, R ^t1 each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The number of carbon atoms of the alkyl group as R ^t1 is usually 1 or more, usually 6 or less, preferably 4 or less, more preferably 2 or less. The number of carbon atoms of the alkyl group contained in the alkyloxycarbonyl group is usually 1 or more, usually 6 or less, preferably 4 or less, more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained. Examples of the alkyl group include a methyl group and an ethyl group. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ^t1 is preferably a hydrogen atom. When nt1 is 2, the TCD-based monomer may contain multiple R ^t1 in the molecule, and these R ^t1 may be the same or different.

When nt2 is 1, R ^t2 represents a divalent hydrocarbon group. As the divalent hydrocarbon group represented by R ^t2 , those in the same range as the divalent hydrocarbon group represented by R ^t1 can be used, and the same advantages as those described for R ^t1 can be obtained.

When nt2 is 2, R ^t2 each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The alkyl group and alkyloxycarbonyl group represented by R ^t2 can be the same as the alkyl group and alkyloxycarbonyl group represented by R ^t1 , and the same advantages as those described for R ^t1 can be obtained. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ^t2 is preferably a hydrogen atom. When nt2 is 2, the TCD monomer may contain multiple R ^t2 in the molecule, and these R ^t2 may be the same or different.

Examples of TCD-based monomers include the following monomers:

TCD-based monomers may be used alone or in combination of two or more types in any ratio.

The amount of the TCD-based monomer is usually set so that the amount of one or more monomers selected from the group consisting of TCD-based monomers and DCP-based monomers relative to 100% by weight of the total amount of the norbornene-based monomer composition falls within a specific range. Specifically, the amount of one or more monomers selected from the group consisting of TCD-based monomers and DCP-based monomers is usually 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, relative to 100% by weight of the total amount of the norbornene-based monomer composition, and is usually 100% by weight or less, preferably 99% by weight or less. When the amount of one or more monomers selected from the group consisting of TCD-based monomers and DCP-based monomers is within the above range, an optical film having excellent tensile elongation at break and bending resistance can be obtained.

The amount of the TCD-based monomer is preferably 20% by weight or more, more preferably 22% by weight or more, and particularly preferably 25% by weight or more, relative to 100% by weight of the total amount of the norbornene-based monomer composition, and is preferably 99% by weight or less, more preferably 97% by weight or less, and particularly preferably 95% by weight or less. When the amount of the TCD-based monomer is within the above range, an optical film having particularly excellent tensile elongation at break while improving heat resistance can be obtained.

The DCP monomer is represented by formula (D). Under appropriate conditions, this DCP monomer can undergo polymerization reactions such as ring-opening polymerization and addition polymerization. Furthermore, the polymer obtained by the polymerization reaction can be hydrogenated to convert the carbon-carbon unsaturated bonds into carbon-carbon single bonds. For example, when a DCP monomer represented by formula (D-1) described below undergoes ring-opening polymerization and hydrogenation, a polymer containing a repeating unit represented by formula (D-A) can be obtained.

In formula (D), nd1, nd2 and nd3 each independently represent 1 or 2. When nd1 is 1, the bond of R ^d1 may represent a single bond or a double bond. When nd1 is 2, the bond of R ^d1 may represent a single bond. Furthermore, when nd2 is 1, the bond of R ^d2 may represent a single bond or a double bond. When nd2 is 2, the bond of R ^d2 may represent a single bond. When the bond between the carbon atom to which R ^d1 is bonded and the carbon atom to which R ^d2 is bonded (i.e., the bond represented by a combination of a solid line and a dashed line included in a 5-membered ring) is a double bond, nd1 may be 1, the bond of R ^d1 may be a single bond, and nd2 may be 1, the bond of R ^d2 may be a single bond. On the other hand, when the bond between the carbon atom to which R ^d1 is bonded and the carbon atom to which R ^d2 is bonded is a single bond, nd1 may be 1 or 2, the bond of R ^d1 may be a single bond or a double bond, nd2 may be 1 or 2, and the bond of R ^d2 may be a single bond or a double bond. Furthermore, when nd3 is 1, the bond of R ^d3 may be a double bond. Furthermore, when nd3 is 2, the bond of R ^d3 may be a single bond. Thus, formula (D) encompasses structures represented by the following formulae (D-1) to (D-10). In particular, structures in which nd1 is 1 can be represented by formulae (D-1), (D-2), (D-4), (D-7), (D-8) and (D-10), and structures in which nd1 is 2 can be represented by formulae (D-3), (D-5), (D-6) and (D-9). In addition, the structure in which nd2 is 1 can be represented by formula (D-1), formula (D-2), formula (D-5), formula (D-7), formula (D-9) and formula (D-10), and the structure in which nd2 is 2 can be represented by formula (D-3), formula (D-4), formula (D-6) and formula (D-8). Furthermore, the structure in which nd3 is 1 can be represented by formula (D-2), formula (D-6), formula (D-8), formula (D-9) and formula (D-10), and the structure in which nd3 is 2 can be represented by formula (D-1), formula (D-3), formula (D-4), formula (D-5) and formula (D-7).

When nd1 is 1, R ^d1 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group. When nd1 is 2, R ^d1 each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The number of carbon atoms of the alkyl group as R ^d1 is usually 1 or more, and usually 6 or less, preferably 4 or less, and more preferably 2 or less. The number of carbon atoms of the alkyl group contained in the alkyloxycarbonyl group is usually 1 or more, and usually 6 or less, preferably 4 or less, and more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained. Examples of the alkyl group include a methyl group and an ethyl group. In addition, as the divalent hydrocarbon group, from the viewpoint of obtaining an optical film having particularly excellent tensile elongation at break and bending resistance, an aliphatic hydrocarbon group is preferable, and a saturated aliphatic hydrocarbon group is more preferable. The number of carbon atoms of this divalent hydrocarbon group is usually 1 or more, and usually 6 or less, preferably 4 or less, and more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained. Examples of the divalent hydrocarbon group include a methylidene group and an ethylidene group. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ^d1 is preferably a hydrogen atom. When nd1 is 2, the DCP monomer may contain multiple R ^d1 in the molecule, and these R ^d1 may be the same or different.

When nd2 is 1, R ^d2 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group. When nd2 is 2, R ^d2 each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. As the alkyl group, alkyloxycarbonyl group, and divalent hydrocarbon group represented by R ^d2 , those in the same range as the alkyl group, alkyloxycarbonyl group, and divalent hydrocarbon group represented by R ^d1 can be used, and the same advantages as those described for R ^d1 can be obtained. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ^d2 is preferably a hydrogen atom. When nd2 is 2, the DCP-based monomer may contain multiple R ^d2 in the molecule, and these R ^d2 may be the same or different.

When nd3 is 1, R ^d3 represents a divalent hydrocarbon group. As the divalent hydrocarbon group represented by R ^d3 , those in the same range as the divalent hydrocarbon group represented by R ^d1 can be used, and the same advantages as those described for R ^d1 can be obtained.

When nd3 is 2, R ^d3 each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The alkyl group and alkyloxycarbonyl group represented by R ^d3 can be the same as the alkyl group and alkyloxycarbonyl group represented by R ^d1 , and the same advantages as those described for R ^d1 can be obtained. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ^d3 is preferably a hydrogen atom. When nd3 is 2, the DCP monomer may contain multiple R ^d3 in the molecule, and these R ^d3 may be the same or different.

Examples of DCP-based monomers include the following monomers:

DCP-based monomers may be used alone or in combination of two or more types in any ratio.

The amount of DCP-based monomer is preferably 65% by weight or more, more preferably 66% by weight or more, and particularly preferably 67% by weight or more, relative to 100% by weight of the total amount of the norbornene-based monomer composition, and is preferably 80% by weight or less, more preferably 77% by weight or less, and particularly preferably 75% by weight or less. When the amount of DCP-based monomer is within the above range, an optical film having particularly excellent tensile elongation at break can be obtained.

The amount of DCP-based monomer is preferably equal to or greater than the amount of TCD-based monomer. More specifically, the amount of DCP-based monomer per 100 parts by weight of TCD-based monomer is preferably equal to or greater than 100 parts by weight, more preferably equal to or greater than 150 parts by weight, particularly preferably equal to or greater than 200 parts by weight, and is preferably equal to or less than 500 parts by weight, more preferably equal to or less than 450 parts by weight, particularly preferably equal to or less than 400 parts by weight. When the amount of DCP-based monomer is within the above range, an optical film having particularly excellent tensile elongation at break can be obtained.

The norbornene-based monomer composition may contain, in addition to the TCD-based monomer and the DCP-based monomer, any monomer polymerizable with the TCD-based monomer or the DCP-based monomer, as long as the effect of the present invention is not significantly impaired. The any monomer may be used alone or in combination of two or more types in any ratio.

A preferred optional monomer is, for example, a monomer represented by the following formula (N). In the following description, the monomer represented by formula (N) may be referred to as an "NB-based monomer". Under appropriate conditions, the NB-based monomer can undergo polymerization reactions such as ring-opening polymerization and addition polymerization. In addition, the polymer obtained by the polymerization reaction can be hydrogenated to convert the carbon-carbon unsaturated bond into a carbon-carbon single bond. For example, when the NB-based monomer represented by formula (N-1) described later undergoes ring-opening polymerization and hydrogenation, a polymer containing a repeating unit represented by formula (N-A) can be obtained. When the norbornene-based monomer composition contains an NB-based monomer, an optical film having particularly excellent tensile elongation at break can be obtained.

In formula (N), nn1 and nn2 each independently represent 1 or 2. When nn1 is 1, the bond of R ⁿ¹ may represent a double bond. When nn1 is 2, the bond of R ⁿ¹ may represent a single bond. When nn2 is 1, the bond of R ⁿ² may represent a double bond. When nn2 is 2, the bond of R ⁿ² may represent a single bond. Thus, formula (N) encompasses structures represented by the following formulae (N-1) to (N-4). In particular, structures in which nn1 is 1 are represented by formulae (N-2) and (N-4), and structures in which nn1 is 2 are represented by formulae (N-1) and (N-3). Furthermore, the structure in which nn2 is 1 can be represented by formula (N-2) and formula (N-3), and the structure in which nn2 is 2 can be represented by formula (N-1) and formula (N-4).

When nn1 is 1, R ⁿ¹ represents a divalent hydrocarbon group. As the divalent hydrocarbon group, from the viewpoint of obtaining an optical film particularly excellent in tensile elongation at break and bending resistance, an aliphatic hydrocarbon group is preferable, and a saturated aliphatic hydrocarbon group is more preferable. The number of carbon atoms of this divalent hydrocarbon group is usually 1 or more, and usually 6 or less, preferably 4 or less, more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film particularly excellent in tensile elongation at break and bending resistance can be obtained. Examples of the divalent hydrocarbon group include a methylidene group and an ethylidene group.

When nn1 is 2, R ⁿ¹ each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The number of carbon atoms of the alkyl group as R ⁿ¹ is usually 1 or more, usually 6 or less, preferably 4 or less, more preferably 2 or less. The number of carbon atoms of the alkyl group contained in the alkyloxycarbonyl group is usually 1 or more, usually 6 or less, preferably 4 or less, more preferably 2 or less. When the number of carbon atoms is within the above range, an optical film having particularly excellent tensile elongation at break can be obtained. Examples of the alkyl group include a methyl group and an ethyl group. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ⁿ¹ is preferably a hydrogen atom. When nn1 is 2, the NB-based monomer may contain multiple R ⁿ¹ in the molecule, and these R ⁿ¹ may be the same or different.

When nn2 is 1, R ⁿ² represents a divalent hydrocarbon group. As the divalent hydrocarbon group represented by R ⁿ² , those in the same range as the divalent hydrocarbon group represented by R ⁿ¹ can be used, and the same advantages as those described for R ⁿ¹ can be obtained.

When nn2 is 2, R ⁿ² each independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The alkyl group and alkyloxycarbonyl group represented by R ⁿ² can be the same as the alkyl group and alkyloxycarbonyl group represented by R ⁿ¹ , and the same advantages as those described for R ⁿ¹ can be obtained. Among them, from the viewpoint of effectively improving the tensile elongation at break, R ⁿ² is preferably a hydrogen atom. When nn2 is 2, the NB monomer may contain multiple R ⁿ² in the molecule, and these R ⁿ² may be the same or different.

Examples of NB-based monomers include the following monomers:

NB-based monomers may be used alone or in combination of two or more types in any ratio.

The amount of NB-based monomer is usually 0% by weight or more, preferably 1% by weight or more, and usually 15% by weight or less, preferably 10% by weight or less, more preferably 8% by weight or less, based on 100% by weight of the total amount of the norbornene-based monomer composition. When the amount of NB-based monomer is within the above range, an optical film having particularly excellent tensile elongation at break can be obtained.

The amount of NB-based monomer is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more, particularly preferably 1.0 part by weight or more, and is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, particularly preferably 10 parts by weight or less, relative to 100 parts by weight of the amount of one or more monomers selected from the group consisting of TCD-based monomers and DCP-based monomers. When the amount of NB-based monomer is within the above range, an optical film having particularly excellent tensile elongation at break can be obtained.

The norbornene-based monomer composition may contain monomers other than TCD-based monomers, DCP-based monomers, and NB-based monomers, as long as the effects of the present invention are not significantly impaired. The amount of monomers other than TCD-based monomers, DCP-based monomers, and NB-based monomers is preferably 0% by weight to 5.0% by weight, more preferably 0% by weight to 3.0% by weight, and particularly preferably 0% by weight to 1.0% by weight, relative to 100% by weight of the total amount of the norbornene-based monomer composition. In particular, it is preferable that the norbornene-based monomer composition does not contain monomers other than TCD-based monomers, DCP-based monomers, and NB-based monomers.

The norbornene-based polymer is selected from the group consisting of the polymer of the norbornene-based monomer composition and its hydrogenated product. Examples of the polymer of the norbornene-based monomer composition include a ring-opening polymer of the norbornene-based monomer composition and an addition polymer of the norbornene-based monomer composition. The hydrogenated product may be a polymer in which the non-aromatic carbon-carbon unsaturated bond in the polymer is hydrogenated, a polymer in which the aromatic carbon-carbon unsaturated bond in the polymer is hydrogenated, or a polymer in which both the non-aromatic carbon-carbon unsaturated bond and the aromatic carbon-carbon unsaturated bond in the polymer are hydrogenated. In particular, a hydrogenated product of a ring-opening polymer of a norbornene-based monomer composition is preferred, and a hydrogenated product in which both the non-aromatic carbon-carbon unsaturated bond and the aromatic carbon-carbon unsaturated bond in the ring-opening polymer of a norbornene-based monomer composition are hydrogenated is even more preferred. By using such a norbornene-based polymer, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained. Furthermore, it is usually possible to improve the mechanical strength, moisture resistance, heat resistance, and other properties of the optical film.

The hydrogenation rate of the hydrogenated product may be any value within a range that does not significantly impair the effects of the present invention. From the viewpoint of improving the transparency and heat resistance of the optical film, the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds is preferably 90% to 100%, more preferably 97% to 100%, and particularly preferably 99% to 100%. From the viewpoint of improving the transparency and heat resistance of the optical film, the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds is preferably 90% to 100%, more preferably 93% to 100%, and particularly preferably 95% to 100%. The hydrogenation rate can be measured by ¹ H-NMR.

The weight average molecular weight Mw of the norbornene-based polymer is usually 3.8 × 10 ⁴ or more, preferably 3.9 × 10 ⁴ or more, more preferably 4.0 × 10 ⁴ or more, and usually 10.0 × 10 ⁴ or less, preferably 8.0 × 10 ⁴ or less, more preferably 6.0 × 10 ⁴ or less. By using a norbornene-based polymer having a weight average molecular weight Mw in the above range, an optical film excellent in tensile elongation at break and bending resistance can be obtained.

In addition, the molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the norbornene-based polymer is preferably 3.0 or less, more preferably 2.8 or less, and preferably 1.0 or more, more preferably 1.2 or more. By using a norbornene-based polymer having a molecular weight distribution Mw/Mn in the above range, an optical film with excellent heat resistance can be obtained.

The weight average molecular weight Mw and number average molecular weight Mn of the polymer can be measured in terms of polyisoprene by gel permeation chromatography using cyclohexane as the eluent. If the polymer is not soluble in cyclohexane, gel permeation chromatography can be performed using tetrahydrofuran (THF) as the eluent. When the eluent is THF, the weight average molecular weight Mw and number average molecular weight Mn of the polymer can be measured in terms of polystyrene.

The norbornene-based polymers may be used alone or in any combination of two or more types in any ratio.

Norbornene-based polymers can be produced, for example, by a production method including polymerizing a norbornene-based monomer composition in the presence of a suitable catalyst. In addition, when producing a hydrogenated product as a norbornene-based polymer, the production method of a norbornene-based polymer may include, after the polymerization, contacting the resulting polymer with hydrogen in the presence of a hydrogenation catalyst containing a transition metal such as nickel, palladium, or ruthenium to hydrogenate the carbon-carbon unsaturated bonds.

3. Light absorber
The light absorbent refers to a compound capable of absorbing light. The light that can be absorbed by the light absorbent includes not only visible light, but also ultraviolet light and infrared light. The ultraviolet light refers to light having a wavelength of 1 nm or more and less than 400 nm. Moreover, the visible light refers to light having a wavelength of 400 nm or more and 800 nm or less. Furthermore, the infrared light refers to light having a wavelength of more than 800 nm. The light absorbent may be an inorganic compound or an organic compound, but from the viewpoint of increasing the transparency of the optical film, an organic compound is preferable.

From the viewpoint of suppressing coloration of the optical film, it is preferable to use one or more compounds selected from the group consisting of ultraviolet absorbers and infrared absorbers as the light absorber. Ultraviolet absorbers and infrared absorbers usually have little ability to absorb visible light or no ability to absorb visible light. Therefore, by using one or more compounds selected from the group consisting of ultraviolet absorbers and infrared absorbers as the light absorber, an optical film with little absorption of visible light can be obtained, and coloration of the optical film can be suppressed and transparency can be increased.

Examples of ultraviolet absorbers include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, acrylonitrile-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, azomethine-based ultraviolet absorbers, indole-based ultraviolet absorbers, naphthalimide-based ultraviolet absorbers, and phthalocyanine-based ultraviolet absorbers.

As the triazine-based UV absorber, for example, a compound having a 1,3,5-triazine ring is preferable. Specific examples of triazine-based UV absorbers include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, etc. Commercially available products of such triazine-based UV absorbers include, for example, "Tinuvin 1577ED" manufactured by BASF, and "LA-F70" and "LA-46" manufactured by ADEKA.

Benzotriazole-based ultraviolet absorbers include, for example, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl 3-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol, reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300, 2-(2H-benzotriazol-2-yl)-6-(straight-chain and side-chain dodecyl)-4-methylphenol, and the like. Examples of commercially available triazole-based ultraviolet absorbers include "ADEKA STAB LA-31" manufactured by ADEKA Corporation and "TINUVIN 328" manufactured by Ciba Specialty Chemicals Corporation.

Examples of azomethine-based ultraviolet absorbers include the materials described in Japanese Patent No. 3366697, and commercially available products include "BONASORB UA-3701" manufactured by Orient Chemical Co., Ltd.

Examples of indole-based UV absorbers include the materials described in Japanese Patent No. 2846091, and commercially available products include "BONASORB UA-3911" and "BONASORB UA-3912" manufactured by Orient Chemical Co., Ltd.

Examples of phthalocyanine-based ultraviolet absorbers include the materials described in Japanese Patent No. 4,403,257 and Japanese Patent No. 3,286,905, and commercially available products include "FDB001" and "FDB002" manufactured by Yamada Chemical Industry Co., Ltd.

Among the above-mentioned ultraviolet absorbents, from the viewpoint of obtaining an optical film having particularly excellent tensile elongation at break and bending resistance, ultraviolet absorbents selected from the group consisting of triazine-based ultraviolet absorbents and benzotriazole-based ultraviolet absorbents are preferred.

Examples of infrared absorbers include pentaerythritol-based infrared absorbers, phthalocyanine-based infrared absorbers, etc.

Examples of pentaerythritol-based infrared absorbers include tetra(2-ethylhexanoate)pentaerythritol, dipentaerythritol, etc.

Examples of phthalocyanine infrared absorbers include "FDN001" and "FDN008" manufactured by Yamada Chemical Industry Co., Ltd.

Among the infrared absorbents mentioned above, pentaerythritol-based infrared absorbents are preferred from the viewpoint of obtaining an optical film that is particularly excellent in tensile elongation at break and bending resistance.

The molecular weight of the light absorbent is preferably 800 or less, more preferably 750 or less, and particularly preferably 700 or less. By using a light absorbent having a molecular weight in this range, an optical film that is particularly excellent in tensile elongation at break and bending resistance can be obtained. The lower limit of the molecular weight of the light absorbent is preferably 350 or more, more preferably 380 or more, and particularly preferably 400 or more, from the viewpoint of suppressing bleed-out of the light absorbent.

A single type of light absorbent may be used, or two or more types may be used in any combination in any ratio.

[4. First resin layer]
The first resin layer is made of a first thermoplastic resin containing a norbornene-based polymer and a light absorbing agent. By including the first resin layer made of the first thermoplastic resin, the optical film according to the present embodiment has excellent tensile elongation at break and bending resistance.

The amount of norbornene-based polymer contained in the first thermoplastic resin is arbitrary within a range that allows an optical film having excellent tensile elongation at break and bending resistance to be obtained. Specifically, the amount of norbornene-based polymer contained in the first thermoplastic resin is preferably 70% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and preferably 98% by weight or less, relative to 100% by weight of the first thermoplastic resin.

The amount of light absorbent contained in the first thermoplastic resin is preferably 2% by weight or more, more preferably 3% by weight or more, particularly preferably 4% by weight or more, and preferably 30% by weight or less, more preferably 20% by weight or less, particularly preferably 15% by weight or less, relative to 100% by weight of the first thermoplastic resin. By using a first thermoplastic resin containing such an amount of light absorbent, an optical film having excellent tensile elongation at break and bending resistance can be obtained.

The amount of the light absorber contained in the first thermoplastic resin is preferably 1.5% by weight or more, more preferably 2% by weight or more, even more preferably 3% by weight or more, and preferably 40% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less, and particularly preferably 15% by weight or less, relative to 100 parts by weight of the norbornene-based polymer contained in the first thermoplastic resin. When the amount of the light absorber is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained.

The first thermoplastic resin may contain optional components in addition to the norbornene polymer and the light absorber. Examples of optional components include antioxidants, heat stabilizers, light stabilizers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystallization nucleating agents, reinforcing agents, antiblocking agents, antifogging agents, release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposers, metal deactivators, antifouling agents, and antibacterial agents. One type of optional component may be used alone, or two or more types may be used in combination in any ratio.

The glass transition temperature Tg of the first thermoplastic resin is preferably 100°C or higher, more preferably 101°C or higher, particularly preferably 102°C or higher, and is preferably less than 135°C, more preferably less than 130°C, particularly preferably less than 125°C. When the glass transition temperature Tg of the first thermoplastic resin is equal to or higher than the lower limit of the above range, relaxation of the orientation of the norbornene-based polymer in a high-temperature environment can be suppressed. Thus, changes in the retardation of the optical film in a high-temperature environment can be suppressed. On the other hand, when the glass transition temperature Tg of the first thermoplastic resin is less than the upper limit of the above range, it is easy to increase the retardation of the optical film.

The glass transition temperature Tg of a thermoplastic resin can be measured using a differential scanning calorimeter at a heating rate of 10°C/min in accordance with JIS K 6911.

The glass transition temperature Tg of the first thermoplastic resin can be adjusted, for example, by the types and quantitative ratios of monomers contained in the norbornene-based monomer composition used as the raw material for the norbornene-based polymer; the content of the norbornene-based polymer in the first thermoplastic resin; and the type and content of the light absorber.

The thickness of the first resin layer is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, particularly preferably 9 μm or more, and is preferably 35 μm or less, more preferably 30 μm or less, particularly preferably 25 μm or less. When the thickness of the first resin layer is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained.

When the optical film includes any layer in combination with the first resin layer, the ratio "t1/T" of the thickness t1 of the first resin layer to the total thickness T of the optical film is preferably 0.2 or more, more preferably 0.25 or more, particularly preferably 0.3 or more, and preferably 0.9 or less, more preferably 0.87 or less, particularly preferably 0.85 or less. When the thickness ratio "t1/T" is within the above range, an optical film that is particularly excellent in tensile elongation at break and bending resistance can be obtained.

5. Optional Layers
The optical film may include any layer in combination with the first resin layer described above. For example, the optical film preferably includes a second resin layer formed of a second thermoplastic resin and a third resin layer formed of a third thermoplastic resin in combination with the first resin layer. In this case, the optical film preferably includes the second resin layer, the first resin layer, and the third resin layer in this order in the thickness direction. In such an optical film, the second resin layer and the third resin layer suppress the movement of the light absorbent contained in the first resin layer. Therefore, it is possible to suppress the bleeding out of the light absorbent.

There is no limitation on the second thermoplastic resin contained in the second resin layer, and any thermoplastic resin containing a polymer can be used. The polymer may be used alone or in combination of two or more types in any ratio. In particular, it is preferable that the second thermoplastic resin contains the above-mentioned norbornene-based polymer. By making the second resin layer from a second thermoplastic resin containing a norbornene-based polymer, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained. The norbornene-based polymer contained in the second thermoplastic resin may be different from the norbornene-based polymer contained in the first thermoplastic resin, but from the viewpoint of obtaining an optical film having particularly excellent tensile elongation at break and bending resistance, it is preferable that it is the same as the norbornene-based polymer contained in the first thermoplastic resin.

The amount of norbornene-based polymer contained in the second thermoplastic resin is arbitrary within a range that allows an optical film having excellent tensile elongation at break and bending resistance to be obtained. Specifically, the amount of norbornene-based polymer contained in the second thermoplastic resin is preferably 85% by weight to 100% by weight, more preferably 90% by weight to 100% by weight, and particularly preferably 95% by weight to 100% by weight, relative to 100% by weight of the second thermoplastic resin.

The second thermoplastic resin may contain a light absorbing agent. However, from the viewpoint of effectively suppressing bleed-out of the light absorbing agent, it is preferable that the second thermoplastic resin contains a small amount of light absorbing agent, and it is more preferable that the second thermoplastic resin does not contain a light absorbing agent. In terms of a specific range, the amount of light absorbing agent contained in the second thermoplastic resin is preferably 0% by weight to 5% by weight, more preferably 0% by weight to 3% by weight, and particularly preferably 0% by weight to 1% by weight, relative to 100% by weight of the second thermoplastic resin.

The second thermoplastic resin may contain an optional component in combination with the polymer. Examples of the optional component include the same optional components as those that the first thermoplastic resin may contain. In addition, the optional component may be used alone or in combination of two or more types in any ratio.

There are no particular limitations on the glass transition temperature Tg of the second thermoplastic resin. The glass transition temperature of the second thermoplastic resin can be any temperature selected from the range described as the range of the glass transition temperature Tg of the first thermoplastic resin. When the glass transition temperature Tg of the second thermoplastic resin is within the range described as the range of the glass transition temperature Tg of the first thermoplastic resin, the same advantages as those described in the section on the first resin layer can be obtained.

The thickness of the second resin layer is preferably 1.5 μm or more, more preferably 2 μm or more, particularly preferably 2.5 μm or more, and is preferably 10 μm or less, more preferably 9.5 μm or less, particularly preferably 9 μm or less. When the thickness of the second resin layer is within the above range, an optical film having particularly excellent tensile elongation at break and bending resistance can be obtained.

There is no limitation on the third thermoplastic resin contained in the third resin layer, and any thermoplastic resin including a polymer can be used. The polymer may be used alone or in combination of two or more types in any ratio. In particular, it is preferable to use a thermoplastic resin selected from the range described as the second thermoplastic resin contained in the second resin layer as the third thermoplastic resin. Therefore, the type and amount of components contained in the third thermoplastic resin and the physical properties of the third thermoplastic resin can be selected and applied from the range described as the type and amount of components contained in the second thermoplastic resin and the physical properties of the second thermoplastic resin. This allows the same advantages as those described for the second resin layer to be obtained.

The third thermoplastic resin may be a resin different from the second thermoplastic resin, or may be the same resin. In particular, it is preferable to use the same resin as the second thermoplastic resin and the third thermoplastic resin. By using the same resin as the second thermoplastic resin and the third thermoplastic resin, it is possible to reduce the manufacturing cost of the optical film and to suppress curling of the optical film.

It is preferable that the thickness of the third resin layer is within the range described as the range of thickness of the second resin layer. When the thickness of the third resin layer is within the range described as the range of thickness of the second resin layer, the same advantages as those described in the section on the second resin layer can be obtained. In particular, from the viewpoint of suppressing curling of the optical film, it is preferable that the second resin layer and the third resin layer have the same thickness.

The optical film may have layers other than the first resin layer, the second resin layer, and the third resin layer. Examples of such layers include an easy-adhesion layer, a pressure-sensitive adhesive layer, an adhesive layer, a hard coat layer, an index matching layer, an anti-reflection layer, a masking layer, an optically anisotropic layer, and a protective layer. However, from the viewpoint of obtaining an optical film that is particularly excellent in tensile elongation at break and bending resistance, it is preferable that the first resin layer and the second resin layer are directly in contact with each other without any other layer therebetween, and it is also preferable that the first resin layer and the third resin layer are directly in contact with each other without any other layer therebetween.

6. Characteristics of Optical Films
The optical film described above is unlikely to break when pulled. Therefore, the optical film can have a large tensile breaking elongation E. The specific tensile breaking elongation E of the optical film is preferably 90% or more, more preferably 95% or more, and particularly preferably 100% or more. There is no particular limit to the upper limit of the tensile breaking elongation E of the optical film, and it can be, for example, 150% or less.

The tensile elongation at break E of the optical film can be measured by the following method in accordance with JIS K7127.
Ten dumbbell-shaped test pieces of type 1B are punched out from the optical film to be measured. When punching out the test pieces, the longitudinal direction of five test pieces and the longitudinal direction of the other five test pieces are set perpendicular to each other. For example, in a long optical film, the longitudinal direction of five test pieces can be set parallel to the longitudinal direction of the optical film, and the longitudinal direction of the other five test pieces can be set parallel to the width direction of the optical film. Then, the tensile elongation at break is measured for these test pieces. The tensile elongation at break is measured using a tensile tester with a thermo-hygrostat (for example, "5564" manufactured by Instron) at a pulling speed of 20 mm/min in an environment of normal temperature and normal pressure. The average value of the measured tensile elongation at break of the test pieces can be the tensile elongation at break E of the optical film.

When an optical film is folded, cracks are unlikely to occur. Therefore, the optical film can have high bending resistance. Specifically, when the optical film is folded in one or more folding directions, the formation of cracks can be suppressed. The folding direction is usually an in-plane direction perpendicular to the thickness direction of the optical film, and represents the direction in which the part of the optical film that moves due to folding moves. When folding in a manner that forms a crease, this folding direction is usually a direction perpendicular to the crease.

For example, four bending directions are set at 45° intervals, and a bending resistance test is performed in which the optical film is folded 100,000 times in each of these bending directions. When these bending resistance tests are performed, the optical film can suppress cracks in bending resistance tests in usually one or more, preferably two or more, more preferably three or more, and particularly preferably four, bending directions. The bending resistance test can be performed under conditions of a stretch width of 50 mm, a bending radius of 1 mm, and a stretch speed of 80 times/min. The bending can also be performed using a tabletop durability tester (Yuasa System Co., Ltd.'s "DLDMLH-FS") using a method for a planar body no-load U-shaped stretch test.

The optical film may have retardation. For example, when the optical film is a stretched film, the molecules of the norbornene-based polymer may be oriented by stretching, and the optical film may be an optically anisotropic film having birefringence according to the orientation of the molecules. In this case, the optical film may have retardation. The specific range of retardation may be appropriately set depending on the application of the optical film.

The in-plane retardation Re of the optical film is preferably 5 nm or less, more preferably 3 nm or less. The absolute value |Rth| of the thickness direction retardation Rth of the optical film is preferably 15 nm or less, more preferably 10 nm or less. The lower limits of Re and |Rth| are not particularly limited, but are both ideally 0. When the retardation of the optical film is within the above range, an optical film having particularly excellent bending resistance can be obtained.

The in-plane retardation Re of an optical film is a value expressed by Re = (nx - ny) x d, unless otherwise specified. The retardation Rth in the thickness direction of the film is a value expressed by Rth = [{(nx + ny) / 2} - nz] x d, unless otherwise specified. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the film (in-plane direction) that gives the maximum refractive index. ny represents the refractive index in the in-plane direction that is perpendicular to the direction of nx. nz represents the refractive index in the thickness direction. d represents the thickness of the film. Re and Rth can be values for light with a wavelength of 590 nm.

It is preferable that the optical film has a high total light transmittance. The specific total light transmittance of the optical film is preferably 85% to 100%, more preferably 87% to 100%, and particularly preferably 90% to 100%. The total light transmittance can be measured in the wavelength range of 400 nm or more and 700 nm or less using a commercially available spectrophotometer.

From the viewpoint of improving the image clarity of an image display device to which the optical film is applied, it is preferable that the optical film has a small haze. The haze of the optical film is preferably 1% or less, more preferably 0.8% or less, and particularly preferably 0.5% or less. The haze can be measured using a turbidity meter in accordance with JIS K7361-1997.

The thickness of the optical film is not particularly limited, but is preferably 10 μm or more, more preferably 15 μm or more, particularly preferably 20 μm or more, and is preferably 35 μm or less, more preferably 27 μm or less, particularly preferably 25 μm or less. When the thickness of the optical film is within the above range, an optical film that is particularly excellent in tensile elongation at break and bending resistance can be obtained.

[7. Manufacturing method of optical film]
The optical film described above can be manufactured, for example, by a manufacturing method including molding a first thermoplastic resin to form a first resin layer. There is no limitation on the molding method. Examples of the molding method include extrusion molding, solution casting, and inflation molding. Among them, extrusion molding and solution casting are preferred, and extrusion molding is particularly preferred.

For example, an optical film having a first resin layer, a second resin layer, and a third resin layer can be manufactured by a manufacturing method including molding a first thermoplastic resin to form the first resin layer, molding a second thermoplastic resin to form the second resin layer, and molding a third thermoplastic resin to form the third resin layer. Examples of such molding methods include a co-extrusion method and a co-casting method. Among these molding methods, the co-extrusion method is preferred because it has excellent manufacturing efficiency and is less likely to leave volatile components remaining in the film.

The co-extrusion method involves co-extruding a first thermoplastic resin, a second thermoplastic resin, and a third thermoplastic resin. In this case, examples of the method for extruding each resin include the co-extrusion T-die method, the co-extrusion inflation method, and the co-extrusion lamination method. Among these, the co-extrusion T-die method is preferred. The co-extrusion T-die method includes the feed block method and the multi-manifold method, and the feed block method is particularly preferred because it is easy to disassemble and clean.

The manufacturing method of the optical film may further include any step, if necessary. For example, the manufacturing method may include a step of stretching the optical film. This stretching orients the molecules of the norbornene-based polymer in the film, so that the optical film can exhibit the desired optical properties. In the following description, in order to distinguish between the optical film before stretching and the optical film after stretching, the optical film before stretching may be referred to as an "unstretched film" and the optical film after stretching as a "stretched film". The stretching conditions may be set arbitrarily within a range in which the desired optical properties are obtained.

The stretching mode may be, for example, uniaxial stretching, in which stretching is performed in one direction, or biaxial stretching, in which stretching is performed in two non-parallel directions. Furthermore, the biaxial stretching may be simultaneous biaxial stretching, in which stretching is performed in two directions at the same time, or sequential biaxial stretching, in which stretching is performed in one direction and then in the other direction.

The areal stretching ratio of the stretching is preferably 1.3 or more, more preferably 1.35 or more, particularly preferably 1.4 or more, and is preferably 1.65 or less, more preferably 1.6 or less, particularly preferably 1.55 or less. The areal stretching ratio represents the product of the stretching ratios in each stretching direction. Thus, for example, in uniaxial stretching, the stretching ratio of the uniaxial stretching represents the areal stretching ratio. Also, for example, in biaxial stretching, the product of the stretching ratios in the two directions represents the areal stretching ratio. When the areal stretching ratio is within the above range, a stretched film that is particularly excellent in breaking elongation and handleability can be obtained.

The stretching temperature is preferably Tg°C or higher, more preferably Tg+5°C or higher, and preferably Tg+40°C or lower, more preferably Tg+30°C or lower. Here, Tg represents the glass transition temperature of the first thermoplastic resin. When the stretching temperature is within the above range, it is easy to make the thickness of the stretched film uniform.

Further optional steps include, for example, a step of trimming the optical film, a step of laminating the optical film with another film, a step of forming further optional layers on the optical film, etc.

According to the above manufacturing method, a long optical film can be obtained. Such a long optical film can be manufactured continuously, and has excellent productivity. Furthermore, lamination with other films can be performed by roll-to-roll, and in this respect too, it has excellent productivity. Usually, a long optical film is wound up and stored and transported in a roll state.

[8. Uses of Stretched Film]
The optical film described above can be provided in an image display device such as a liquid crystal display device. In this case, the optical film may be provided alone in the image display device, or may be attached to any film and provided in the image display device. As a specific example, the optical film may be attached to a polarizing film to obtain a multilayer film, and the multilayer film may be provided in the image display device.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples, and can be modified and carried out as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto.
In the following description, the units "%" and "parts" expressing amounts are by weight unless otherwise specified. The following operations were carried out in air at room temperature and normal pressure unless otherwise specified.

[I. Methods for measuring and calculating physical properties of polymers and resins]
(Method for measuring weight average molecular weight Mw of polymer)
The weight average molecular weight Mw of the polymer was measured by gel permeation chromatography (GPC) using cyclohexane as an eluent, and was calculated as a standard polyisoprene equivalent value. When the polymer was not soluble in cyclohexane, THF was used as the eluent. When THF was used as the eluent, the weight average molecular weight Mw was measured in terms of polystyrene.
As the standard polyisoprene, standard polyisoprene manufactured by Tosoh Corporation (Mw=602, 1390, 3920, 8050, 13800, 22700, 58800, 71300, 109000, 280000) was used.
The measurement was performed using three columns (TSKgel G5000HXL, TSKgel G4000HXL, and TSKgel G2000HXL) manufactured by Tosoh Corporation connected in series under conditions of a flow rate of 1.0 mL/min, a sample injection amount of 100 μL, and a column temperature of 40°C.

(Method of measuring glass transition temperature Tg)
The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC6220SII manufactured by Nano Technology Corporation) in accordance with JIS K 6911 at a temperature rise rate of 10° C./min.

II. Film Evaluation Method
(Method of measuring film thickness)
The total thickness of the film was measured with a snap gauge ("ID-C112BS" manufactured by Mitutoyo Corporation). The thicknesses of the first resin layer, the second resin layer, and the third resin layer of the film were measured with an infrared film thickness meter (manufactured by Kurabo Industries, Ltd.) that calculates the film thickness from the absorbance of each layer.

(Method of measuring film retardation)
The in-plane retardation Re and the retardation Rth in the thickness direction of the film were measured using a phase difference meter ("AXOScan" manufactured by Axometrics).

(Method of measuring tensile elongation at break E)
In accordance with JIS K7127, the tensile elongation at break of the film to be measured was measured by the following method.
Ten dumbbell-shaped test pieces of type 1B were punched out from the film to be measured. Five of the test pieces were punched out so that the MD direction (flow direction, corresponding to the longitudinal direction) of the film was parallel to the longitudinal direction of the dumbbell shape of the test piece. The remaining five test pieces were punched out so that the TD direction (direction perpendicular to the flow direction, corresponding to the width direction) of the film was parallel to the longitudinal direction of the dumbbell shape of the test piece. The tensile elongation at break of the test pieces thus obtained was measured using a tensile tester (Instron "5564 type") equipped with a thermo-hygrostat. The tensile speed was 20 mm/min. The average value of the measured values of five test pieces having a longitudinal direction parallel to the MD direction of the film and the measured values of five test pieces having a longitudinal direction parallel to the TD direction of the film was calculated, and this average value was taken as the tensile elongation at break E of the film.

(Method of evaluating flex resistance by flex resistance test)
The optical films obtained in each of the Examples and Comparative Examples were subjected to a bending resistance test using a tabletop durability tester (Yuasa System Co., Ltd.'s "DLDMLH-FS") by a method of a planar body no-load U-shape stretching test. The bending was performed up to 100,000 times under the conditions of a stretching width of 50 mm, a bending radius of 1 mm, and a stretching speed of 80 times/min. The bending was performed in four bending directions, namely, the MD direction, the TD direction, a 45° oblique direction that forms an angle of 45° to the MD direction, and a 135° oblique direction that forms an angle of 135° to the MD direction. Thereafter, the optical film was removed from the machine and visually observed to evaluate the bending resistance according to the following criteria.
A+: No cracks in the film even after bending in any bending direction.
A: The film cracks only after bending in a specific bending direction.
B: After bending in any bending direction, cracks extending from the edge of the film are generated at the edge of the film.
C: Cracks occur at the film edge and center after bending in any bending direction.

[Example 1]
(1-1) Preparation of norbornene ring-opening polymer:
In a glass reactor with the inside substituted with nitrogen, 200 parts of dehydrated cyclohexane, 0.7 mol% of 1-hexene, 0.15 mol% of diisopropyl ether, and 0.44 mol% of triisobutylaluminum were placed at room temperature relative to a total of 100 parts by weight of the monomers described below, and mixed. Thereafter, while maintaining the polymerization temperature at 45°C, 70 parts by weight of dicyclopentadiene (abbreviated as "DCPD") and 30 parts by weight of tetracyclododecene (abbreviated as "TCD") as monomers, and 0.02 mol% of tungsten hexachloride (0.65 wt% toluene solution) were continuously added in parallel to the reactor over a period of 2 hours, and polymerization was carried out. Next, 0.2 mol% of isopropyl alcohol was added to the polymerization solution to inactivate the polymerization catalyst, and the polymerization reaction was stopped. In the above explanation, the amount indicated by the unit "mol%" is a value in which the total amount of the monomers is 100 mol%. As a result, a reaction solution containing a norbornene-based ring-opening polymer as a polymer of the monomer was obtained. The weight average molecular weight Mw of the obtained norbornene-based ring-opening polymer was 3.1×10 ^4. The conversion rate of the monomer to the polymer was 100%.

(1-2) Production of norbornene-based hydrides by hydrogenation:
Next, 67 parts by weight of cyclohexane was added to 183 parts by weight of the reaction solution containing the norbornene-based ring-opening polymer obtained in the above step (1-1), and 0.8% by weight of a diatomaceous earth-supported nickel catalyst ("T8400RL" manufactured by JGC Chemical Industries, Ltd., nickel loading rate 57%) was further added as a hydrogenation catalyst. The amount of hydrogenation catalyst represents a value relative to 100% by weight of the norbornene-based ring-opening polymer contained in the reaction solution. Thereafter, the reaction solution was pressurized to 4.5 MPa with hydrogen and heated to a temperature of 190° C. while stirring, and a hydrogenation reaction was carried out for 8 hours. As a result, a reaction solution containing a norbornene-based hydrogenated product as a hydrogenated product of the norbornene-based ring-opening polymer was obtained. When the hydrogenation rate of this norbornene-based hydrogenated product was measured by ¹ H-NMR, the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bond was 99.9%.

The obtained reaction solution was filtered under pressure at a pressure of 0.25 MPa using Radiolite #500 as a filter bed ("Fundaback Filter" manufactured by Ishikawajima-Harima Heavy Industries Co., Ltd.) to remove the hydrogenation catalyst, and a colorless and transparent solution was obtained. The obtained solution was poured into a large amount of isopropanol to precipitate a norbornene-based hydrogenated product. The precipitated norbornene-based hydrogenated product was filtered off. Then, 2.0 parts of a xylene solution in which 0.1 parts of an antioxidant [pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] ("Irganox (registered trademark) 1010" manufactured by Ciba Specialty Chemicals Co., Ltd.)] was dissolved was added to 100 parts of the norbornene-based hydrogenated product. Next, the mixture was dried in a vacuum dryer (200°C, 1 Torr) for 6 hours to obtain a thermoplastic norbornene-based resin that does not contain a light absorber. The weight average molecular weight of the norbornene hydride was 4.4 × 10 ^4. In the following description, this thermoplastic norbornene resin not containing a light absorbent may be referred to as "resin F".

The glass transition temperature Tg of the resin F was measured by the method described above. The glass transition temperature Tg of the resin F was 116°C.

(1-3) Preparation of thermoplastic resin containing light absorber:
A twin-screw extruder (manufactured by Toshiba Corporation, ratio L/D = 42 of screw length L to screw diameter D) with a screw having a total length of 1848 mm and a diameter of 44 mm was prepared. This screw had a total of three kneading zones at positions 685 mm, 920 mm, and 1190 mm away from the upstream end of the screw. Here, the distance from the upstream end of the screw to the position of the kneading zone refers to the distance from the upstream end of the screw to the upstream end of the kneading zone. In addition, upstream refers to the upstream in the resin flow direction. Furthermore, the ratio Lnx/D of the length Lnx of each kneading zone to the screw diameter D was Lnx/D = 4, Lnx/D = 2, and Lnx/D = 2, in that order from the upstream kneading zone.

100 parts of resin F produced in the above step (1-2), 6 parts of a benzotriazole-based ultraviolet absorber ("LA-31" manufactured by ADEKA, molecular weight 659) as a light absorber, and 3 parts of a pentaerythritol-based infrared absorber ("Tetra(2-ethylhexanoate)pentaerythritol" molecular weight 641 manufactured by Fuji Film Wako Chemicals) were added to this twin-screw extruder and kneaded to obtain a thermoplastic resin containing a light absorber. In the following explanation, this thermoplastic norbornene-based resin containing a light absorber may be referred to as "resin FA". The content of the light absorber in this resin FA was 8.3% by weight, and the glass transition temperature of resin FA was 106°C.

(1-4. Production of Unstretched Film)
A double-flight type single-screw extruder (screw diameter D = 50 mm, ratio of screw length L to screw diameter D = 28) equipped with a leaf disk-shaped polymer filter with a mesh size of 3 μm was prepared. The resin FA produced in the above step (1-3) was introduced into this single-screw extruder, melted, and fed to the single-layer die through a feed block. The resin FA was introduced into the single-screw extruder through a hopper loaded in the single-screw extruder. The surface roughness (arithmetic mean roughness Ra) of the die lip of the single-layer die was 0.1 μm. Furthermore, the temperature of the resin FA at the extruder outlet was 260 ° C.

On the other hand, a single screw extruder (screw diameter D = 50 mm, ratio of screw length L to screw diameter D L/D = 30) equipped with a leaf disk-shaped polymer filter with a mesh size of 3 μm was prepared. Resin F produced in the above step (1-2) was introduced into this single screw extruder, melted, and supplied to the above single layer die via a feed block. The temperature of resin F at the extruder outlet was 260°C.

The resins FA and F were then extruded from a single-layer die in a molten state at 260°C so as to be extruded into a film containing three layers: a layer of resin F, a layer of resin FA, and a layer of resin F (co-extrusion molding process). The extruded resin was then cast onto a cooling roll whose temperature was adjusted to 100°C, and passed through a cooling roll whose temperature was adjusted to 50°C to obtain an unstretched film as a long optical film. When the resin was extruded from the single-layer die and cast onto the cooling roll, the air gap amount was set to 50 mm. Edge pinning was used as a method for casting the molten film-like resin onto the cooling roll.

The obtained unstretched film was a two-type, three-layer film having a second resin layer formed from resin F, a first resin layer formed from resin FA, and a third resin layer formed from resin F, in that order in the thickness direction. "Two types, three layers" means that the film contains three layers, and these layers are made of two types of resin. The total thickness of this unstretched film was 25 μm. The total thickness of the two layers formed from resin F (i.e., the second resin layer and the third resin layer) was 5 μm, and the thickness of the first resin layer formed from resin FA was 20 μm.

The obtained optical film was evaluated by the method described above. As a result, the tensile breaking elongation E was 110%, and the result of the bending test was A+.

[Example 2]
In the above step (1-3), the light absorber used was changed to 5 parts of a triazine-based ultraviolet absorber (BASF's "Tinuvin 1577ED" molecular weight 425). The glass transition temperature of the obtained resin FA was 112°C.
In addition, in the above-mentioned process (1-4), by adjusting the extrusion speed of resin F and resin FA, the total thickness of the two layers formed with resin F (i.e., the second resin layer and the third resin layer) was changed to 16 μm, and the thickness of the first resin layer formed with resin FA was changed to 9 μm.
Except for the above, the same method as in Example 1 was used to produce and evaluate an unstretched film as an optical film.

[Example 3]
In the above step (1-1), the combination of monomers used was changed to 29 parts by weight of tetracyclododecene (TCD), 70 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB). The weight average molecular weight Mw of the obtained norbornene-based hydride was 4.2×10 ⁴ , and the glass transition temperature of resin F was 111° C.
In addition, in the above step (1-3), a pentaerythritol-based infrared absorbing agent was not used as a light absorbing agent. The glass transition temperature of the obtained resin FA was 104°C.
Except for the above, the same method as in Example 1 was used to produce and evaluate an unstretched film as an optical film.

[Example 4]
In the above step (1-1), the combination of monomers used was changed to 29 parts by weight of tetracyclododecene (TCD), 70 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB). The weight average molecular weight Mw of the obtained norbornene-based hydride was 4.2×10 ⁴ , the glass transition temperature of resin F was 111° C., and the glass transition temperature of resin FA was 101° C.
Except for the above, the same method as in Example 1 was used to produce and evaluate an unstretched film as an optical film.

[Example 5]
In the above step (1-1), the combination of monomers used was changed to 29 parts by weight of tetracyclododecene (TCD), 70 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB). The weight average molecular weight Mw of the obtained norbornene-based hydride was 4.2×10 ⁴ , and the glass transition temperature of resin F was 111° C.
In the step (1-3), the light absorber used was changed to 5 parts of a triazine-based ultraviolet absorber ("Tinuvin 1577ED" manufactured by BASF). The glass transition temperature of the obtained resin FA was 107°C.
Furthermore, in the above-mentioned process (1-4), by adjusting the extrusion speed of resin F and resin FA, the total thickness of the two layers formed with resin F (i.e., the second resin layer and the third resin layer) was changed to 16 μm, and the thickness of the first resin layer formed with resin FA was changed to 9 μm.
Except for the above, the same method as in Example 1 was used to produce and evaluate an unstretched film as an optical film.

[Example 6]
In the above step (1-1), the combination of monomers used was changed to 29 parts by weight of tetracyclododecene (TCD), 70 parts by weight of dicyclopentadiene (DCPD), and 1 part by weight of norbornene (NB). The weight average molecular weight Mw of the obtained norbornene-based hydride was 4.2×10 ⁴ , and the glass transition temperature of resin F was 111° C.
In the above step (1-3), the amount of the benzotriazole-based ultraviolet absorber was changed to 8 parts, and no pentaerythritol-based infrared absorber was used. The glass transition temperature of the obtained resin FA was 102°C.
Furthermore, in the above-mentioned step (1-4), by adjusting the extrusion speed of resin F and resin FA, the total thickness of the two layers formed with resin F (i.e., the second resin layer and the third resin layer) was changed to 17 μm, the thickness of the first resin layer formed with resin FA was changed to 15 μm, and the total thickness of the unstretched film was changed to 32 μm.
Except for the above, an unstretched film was produced in the same manner as in Example 1.

The unstretched film was fed to an oblique stretching machine using a tenter method. Using this oblique stretching machine, the unstretched film was stretched in an oblique direction by 1.5 times while adjusting the take-up tension and the tenter chain tension, to obtain an obliquely stretched film as an optical film having a thickness of 21 μm. The oblique direction as the stretching direction in this example was a direction forming an angle of 45° with respect to the longitudinal direction of the unstretched film. The stretching temperature of the oblique stretching machine was 109° C.
The optical film thus obtained was evaluated by the above-mentioned method.

[Example 7]
In the above step (1-1), the combination of monomers used was changed to 28 parts by weight of tetracyclododecene (TCD), 70 parts by weight of dicyclopentadiene (DCPD), and 2 parts by weight of norbornene (NB). The weight average molecular weight Mw of the obtained norbornene-based hydride was 3.9×10 ⁴ , and the glass transition temperature of resin F was 108° C.
In the above step (1-3), the amount of the benzotriazole-based ultraviolet absorber was changed to 8 parts, and no pentaerythritol-based infrared absorber was used. The glass transition temperature of the obtained resin FA was 99° C.
Furthermore, in the above-mentioned step (1-4), by adjusting the extrusion speed of resin F and resin FA, the total thickness of the two layers formed with resin F (i.e., the second resin layer and the third resin layer) was changed to 18 μm, the thickness of the first resin layer formed with resin FA was changed to 15 μm, and the total thickness of the unstretched film was changed to 33 μm.
Except for the above, an unstretched film was produced in the same manner as in Example 1.

The unstretched film was fed to an oblique stretching machine using a tenter method. Using this oblique stretching machine, the unstretched film was stretched in an oblique direction by 1.45 times while adjusting the take-up tension, the tenter chain tension, and the tenter chain speed, to obtain an obliquely stretched film as an optical film having a thickness of 23 μm. The oblique direction as the stretching direction in this example was a direction forming an angle of 45° with respect to the longitudinal direction of the unstretched film. The stretching temperature of the oblique stretching machine was 110° C.
The optical film thus obtained was evaluated by the above-mentioned method.

[Example 8]
(8-1) Preparation of 8-methyl-8- ^{methoxycarbonyltetracyclo} [ ^{4.4.0.12,5.17,10} ]-3-dodecene (abbreviation "DNM"):
Methyl 2-methylbicyclo[2,2,1]-5-heptene-2-carboxylate (Cas. 7398-76-7; manufactured by Angene International Limited) and dicyclopentadiene (DCPD) were charged in a high pressure vessel at a molar ratio of 88:12. Thereafter, the air in the high pressure vessel was replaced with nitrogen, and the temperature was raised to 165°C at a stirring speed of 600 rpm and held for 1 minute. Thereafter, the temperature was raised to 200°C and reacted for 3 hours to obtain 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]-3-dodecene (DNM).

(8-2) Preparation of norbornene ring-opening polymer:
In a glass reactor with the inside replaced with nitrogen, 200 parts of dehydrated toluene and 13 parts of 1-hexene were put at room temperature relative to a total of 100 parts by weight of the monomers described below, and mixed. Then, while maintaining the temperature at 100°C, 92 parts of 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]-3-dodecene (DNM) as a monomer were put into the reactor, and then 0.005 parts of triethylaluminum and 0.005 parts of methanol-modified tungsten hexachloride were added, and further 8 parts of norbornene (NB) as a monomer were added over 20 minutes. Then, the reaction was continued for another 45 minutes. Next, 0.2 mol% of isopropyl alcohol was added to the polymerization solution to inactivate the polymerization catalyst, and the polymerization reaction was stopped. In the above explanation, the amount indicated by the unit "mol%" is a value in which the total amount of the monomers is 100 mol%. As a result, a reaction solution containing a norbornene-based ring-opening polymer as a polymer of the monomer was obtained. The conversion rate of the monomer to the polymer was 100%.

(8-3) Production of norbornene-based hydrides by hydrogenation:
Next, 67 parts of toluene was added to 183 parts of the reaction solution containing the norbornene-based ring-opening polymer obtained in the above step (8-2), and 0.0043 parts of chlorohydridocarbonyltris(triphenylphosphine)ruthenium (hereinafter, may be appropriately abbreviated as "ruthenium catalyst") was further added as a hydrogenation catalyst. Thereafter, a hydrogenation reaction was carried out at a hydrogen pressure of 4.5 MPa and 160°C for 4 hours. As a result, a reaction solution containing a norbornene-based hydride as a hydrogenated product of the norbornene-based ring-opening polymer was obtained.

The obtained solution was poured into a large amount of isopropanol to precipitate a norbornene-based hydride. The precipitated norbornene-based hydride was collected by filtration. Then, 2.0 parts of a xylene solution in which 0.1 parts of an antioxidant [pentaerythritol-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by Ciba Specialty Chemicals, Inc., "Irganox (registered trademark) 1010") was dissolved] was added to 100 parts of the norbornene-based hydride. Next, the mixture was dried for 6 hours in a vacuum dryer (200°C, 1 Torr) to obtain a thermoplastic norbornene-based resin containing no light absorbent as resin F. The weight-average molecular weight of the norbornene-based hydride was 5.0 x ¹⁰⁴ .

The glass transition temperature Tg of the resin F was measured by the method described above. The glass transition temperature Tg of the resin F was 136°C.

(8-4) Production of thermoplastic resin containing ultraviolet absorber:
Instead of the resin F produced in Example 1, the resin F produced in the above step (8-3) was used. In addition, the amount of the benzotriazole-based ultraviolet absorber was changed to 13 parts, and no pentaerythritol-based infrared absorber was used. Except for the above, a thermoplastic resin containing a light absorber was obtained as resin FA by the same method as step (1-3) of Example 1. The glass transition temperature of the obtained resin FA was 122°C.

(8-5) Production of unstretched film:
Instead of the resin F and resin FA produced in Example 1, the resin F and resin FA produced in the above steps (8-3) and (8-4) were used. In addition, by adjusting the discharge speed of the resin F and resin FA, the total thickness of the two layers (i.e., the second resin layer and the third resin layer) formed with the resin F was changed to 5 μm, the thickness of the first resin layer formed with the resin FA was changed to 15 μm, and the total thickness of the unstretched film was changed to 20 μm. Except for the above, an unstretched film was obtained as a long optical film by the same method as in step (1-4) of Example 1. The obtained optical film was evaluated by the above-mentioned method.

[Comparative Example 1]
(C1-1) Production of thermoplastic resin containing norbornene-based hydride:
The combination of monomers used was changed to 60 parts by weight of methanotetrahydrofluorene (MTF) and 40 parts by weight of tetracyclododecene (TCD). The amount of 1-hexene was changed to 0.8 mol%. The polymerization temperature of the monomers was changed to 55°C. Except for the above, a thermoplastic norbornene-based resin was obtained as resin F containing a norbornene-based hydride and an antioxidant but not a light absorbent, by the same method as in step (1-1) and step (1-2) of Example 1. The weight average molecular weight Mw of the obtained norbornene-based hydride was 3.1 x 10 ⁴ , and the glass transition temperature of resin F was 161°C.

(C1-2) Preparation of thermoplastic resin containing light absorber:
Resin F produced in the above step (C1-1) was used instead of Resin F produced in Example 1. Except for the above, a thermoplastic resin containing a light absorbent was obtained as Resin FA by the same method as in Step (1-3) of Example 1. The glass transition temperature of the obtained Resin FA was 151°C.

(C1-3) Production of unstretched film:
Resin F and Resin FA produced in the above steps (C1-1) and (C1-2) were used instead of Resin F and Resin FA produced in Example 1. Except for the above, a long unstretched film was obtained in the same manner as in step (1-4) of Example 1. The obtained unstretched film was evaluated by the method described above.

[Comparative Example 2]
(C2-1) Production of thermoplastic resin containing norbornene-based hydride:
The combination of monomers used was changed to 10 parts by weight of methanotetrahydrofluorene (MTF), 40 parts by weight of tetracyclododecene (TCD), and 50 parts by weight of dicyclopentadiene (DCPD). The amount of 1-hexene was changed to 0.76 mol%. Furthermore, the polymerization temperature of the monomers was changed to 55°C. Except for the above, a thermoplastic norbornene-based resin was obtained as resin F containing a norbornene-based hydride and an antioxidant but not containing a light absorber by the same method as in step (1-1) and step (1-2) of Example 1. The weight average molecular weight Mw of the obtained norbornene-based hydride was 3.6 x 10 ⁴ , and the glass transition temperature of resin F was 128°C.

(C2-2) Preparation of thermoplastic resin containing light absorber:
Instead of the resin F produced in Example 1, the resin F produced in the above step (C2-1) was used. In addition, the amount of the benzotriazole-based ultraviolet absorber was changed to 8 parts, and no pentaerythritol-based infrared absorber was used. Except for the above, a thermoplastic resin containing a light absorber was obtained as resin FA by the same method as step (1-3) of Example 1. The glass transition temperature of the obtained resin FA was 119°C.

(C2-3) Production of unstretched film:
Resin F and resin FA produced in the above steps (C2-1) and (C2-2) were used instead of resin F and resin FA produced in Example 1. In addition, by adjusting the discharge speed of resin F and resin FA, the total thickness of the two layers (i.e., the second resin layer and the third resin layer) formed with resin F was changed to 20 μm, the thickness of the first resin layer formed with resin FA was changed to 15 μm, and the total thickness of the unstretched film was changed to 35 μm. A long unstretched film was obtained by the same method as step (1-4) of Example 1 except for the above.

(C2-4) Production of stretched film:
The unstretched film was fed to an oblique stretching machine using a tenter method. Using this oblique stretching machine, the unstretched film was stretched in an oblique direction by 1.45 times while adjusting the take-up tension, the tenter chain tension, and the tenter chain speed, to obtain an obliquely stretched film having a thickness of 24 μm. The oblique direction as the stretching direction in this example was a direction forming an angle of 45° with respect to the longitudinal direction of the unstretched film. The stretching temperature of the oblique stretching machine was 110° C.
The obliquely stretched film thus obtained was evaluated by the method described above.

[Comparative Example 3]
(C3-1) Production of thermoplastic norbornene-based resin containing norbornene-based hydride:
The amount of 8-methyl-8-methoxycarbonyltetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]-3-dodecene (DNM) was changed to 100 parts. The amount of 1-hexene was changed to 10 parts. Furthermore, norbornene (NB) was not used. Except for the above, a thermoplastic norbornene resin was obtained as resin F containing a norbornene-based hydride and an antioxidant but not a light absorber by the same method as in step (8-2) and step (8-3) of Example 8. The weight average molecular weight Mw of the obtained norbornene-based hydride was 13.0×10 ⁴ , and the glass transition temperature of resin F was 165° C.

(C3-2) Preparation of thermoplastic resin containing light absorber:
Resin F produced in the above step (C3-1) was used instead of Resin F produced in Example 1. In addition, no pentaerythritol-based infrared absorbent was used. Except for the above, a thermoplastic resin containing a light absorbent was obtained as Resin FA by the same method as in Step (1-3) of Example 1. The glass transition temperature of the obtained Resin FA was 158°C.

(C3-3) Production of unstretched film:
Resin F and Resin FA produced in the above steps (C3-1) and (C3-2) were used instead of Resin F and Resin FA produced in Example 1. A long unstretched film was obtained in the same manner as in step (1-4) of Example 1, except for the above.
The unstretched film thus obtained was evaluated by the method described above.

[Comparative Example 4]
Resin F produced in Example 1 was introduced into a single-screw extruder, melted, and fed to a single-layer die via a feed block. The same single-layer die as that used in Example 1 was used. Resin F was extruded from the single-layer die in a molten state at 260°C (extrusion molding process). The extruded resin was cast onto a cooling roll as in Example 1, and passed through the cooling roll to obtain a long unstretched film with a thickness of 40 μm.
The resulting unstretched film was evaluated by the methods described above.

[result]
The results of the above-mentioned Examples and Comparative Examples are shown in the following table. In the following table, the meanings of the abbreviations are as follows.
TCD: tetracyclododecene.
DNM: 8-methyl-8- ^{methoxycarbonyltetracyclo} [ ^{4.4.0.12,5.17,10} ]-3-dodecene.
DCPD: dicyclopentadiene.
NB: Norbornene.
MTF: methanotetrahydrofluorene.
Light absorber A: Triazine-based ultraviolet absorber ("Tinuvin 1577ED" manufactured by BASF, molecular weight 425).
Light absorber B: Benzotriazole-based ultraviolet absorber ("LA-31" manufactured by ADEKA Corporation, molecular weight 659).
Light absorber C: Pentaerythritol-based infrared absorber ("Tetra(2-ethylhexanoate)pentaerythritol" molecular weight 641, manufactured by Fuji Film Wako Chemicals).
Re: in-plane retardation of the film.
Rth: Retardation in the thickness direction of the film.

100, 200 Optical film 110 First resin layer 220 Second resin layer 230 Third resin layer

Claims (8)

A first resin layer is formed of a first thermoplastic resin containing a norbornene-based polymer and a light absorbing agent,
the norbornene-based polymer is selected from the group consisting of polymers of norbornene-based monomer compositions and hydrogenated products thereof,
The norbornene-based monomer composition contains one or more monomers selected from the group consisting of a monomer represented by the following formula (T) and a monomer represented by the following formula (D),
The amount of the monomer represented by the following formula (D) is 65% by weight or more and 80% by weight or less with respect to 100% by weight of the total amount of the norbornene-based monomer composition,
The norbornene-based polymer has a weight average molecular weight of 38,000 or more and 100,000 or less,
The amount of the light absorber in the first thermoplastic resin is 2% by weight to 30% by weight.

(In formula (T),
Each of nt1 and nt2 independently represents 1 or 2;
When nt1 is 1, R ^t1 represents a divalent hydrocarbon group;
When nt1 is 2, each R ^t1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nt2 is 1, R ^t2 represents a divalent hydrocarbon group;
When nt2 is 2, each R ^t2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
In formula (D),
nd1, nd2 and nd3 each independently represent 1 or 2;
When nd1 is 1, R ^d1 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd1 is 2, each R ^d1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd2 is 1, R ^d2 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd2 is 2, each R ^d2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd3 is 1, R ^d3 represents a divalent hydrocarbon group;
When nd3 is 2, each R ^d3 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The optical film of claim 1 , wherein the light absorber comprises a pentaerythritol-based infrared absorber. A first resin layer is formed of a first thermoplastic resin containing a norbornene-based polymer and a light absorbing agent,
the norbornene-based polymer is selected from the group consisting of polymers of norbornene-based monomer compositions and hydrogenated products thereof,
The norbornene-based monomer composition contains 50% by weight or more of one or more monomers selected from the group consisting of a monomer represented by the following formula (T) and a monomer represented by the following formula (D),
The norbornene-based polymer has a weight average molecular weight of 38,000 or more and 100,000 or less,
the amount of the light absorber in the first thermoplastic resin is 2% by weight to 30% by weight;
The optical film , wherein the light absorber comprises a pentaerythritol-based infrared absorber .

(In formula (T),
Each of nt1 and nt2 independently represents 1 or 2;
When nt1 is 1, R ^t1 represents a divalent hydrocarbon group;
When nt1 is 2, each R ^t1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nt2 is 1, R ^t2 represents a divalent hydrocarbon group;
When nt2 is 2, each R ^t2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
In formula (D),
nd1, nd2 and nd3 each independently represent 1 or 2;
When nd1 is 1, R ^d1 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd1 is 2, each R ^d1 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd2 is 1, R ^d2 represents a hydrogen atom, an alkyl group, an alkyloxycarbonyl group, or a divalent hydrocarbon group;
When nd2 is 2, each R ^d2 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nd3 is 1, R ^d3 represents a divalent hydrocarbon group;
When nd3 is 2, each R ^d3 independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The optical film according to any one of claims 1 to 3 , wherein the norbornene-based monomer composition contains 1 wt % to 15 wt % of a monomer represented by the following formula (N):

(In formula (N),
nn1 and nn2 each independently represent 1 or 2;
When nn1 is 1, R ⁿ¹ represents a divalent hydrocarbon group;
When nn1 is 2, each R ⁿ¹ independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group;
When nn2 is 1, R ⁿ² represents a divalent hydrocarbon group;
When nn2 is 2, each R ⁿ² independently represents a hydrogen atom, an alkyl group, or an alkyloxycarbonyl group. The optical film according to any one of claims 1 to 4 , wherein the light absorbing agent comprises at least one selected from the group consisting of an ultraviolet absorbing agent and an infrared absorbing agent. The optical film according to any one of claims 1 to 5 , wherein the molecular weight of the light absorbing agent is 800 or less. The optical film according to any one of claims 1 to 6 , wherein the light absorber comprises at least one selected from the group consisting of triazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers. The optical film according to any one of claims 1 to 7, comprising: a second resin layer formed of a second thermoplastic resin, the first resin layer, and a third resin layer formed of a third thermoplastic resin, in this order.

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