JP7552147B2 - Method for manufacturing optical film - Google Patents

Description

The present invention relates to a method for producing an optical film.

Polymers containing alicyclic structures generally do not have crystallinity, but some polymers containing alicyclic structures may have crystallinity. The applicant has previously proposed a technique for producing a film using a polymer containing alicyclic structures that has crystallinity (Patent Documents 1 and 2).

International Publication No. 2018/079627 International Publication No. 2019/003980

The physical properties of a resin containing a crystalline alicyclic structure-containing polymer can usually be improved by promoting the crystallization of the alicyclic structure-containing polymer. Therefore, when a film is produced using a resin containing a crystalline alicyclic structure-containing polymer, the production method may include a crystallization treatment to increase the crystallinity of the alicyclic structure-containing polymer contained in the film. Such a crystallization treatment has generally been carried out by heating.

When a film is produced using a resin containing a crystalline alicyclic structure-containing polymer, it may be desirable to form a resin layer using another resin on the layer of resin containing a crystalline alicyclic structure-containing polymer. In this case, in order to increase the adhesive strength between the layer of resin containing a crystalline alicyclic structure-containing polymer and the resin layer formed on the layer, it has been common to perform a crystallization process after forming a resin layer on the layer of resin containing a crystalline alicyclic structure-containing polymer. However, in this case, cracks may occur in the resin layer due to the heat applied during the crystallization process.

The present invention was devised in view of the above problems, and aims to provide a manufacturing method for an optical film comprising a resin layer (A) formed of a resin containing a crystalline alicyclic structure-containing polymer and a resin layer (B) formed on this resin layer (A), while suppressing cracks in the resin layer (B).

The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by a production method including, in this order, a step of preparing a resin layer (A) formed of a first resin containing a crystalline alicyclic structure-containing polymer, a step of subjecting the resin layer (A) to a crystallization treatment, and a step of forming a resin layer (B) on a surface of the resin layer (A) of a second resin, and have thus completed the present invention.
That is, the present invention includes the following.

[1] A step (I) of preparing a resin layer (A) formed of a first resin containing a crystalline alicyclic structure-containing polymer;
A step (II) of subjecting the resin layer (A) to a crystallization treatment;
and (III) forming a resin layer (B) on the surface of the resin layer (A) using a second resin.
[2] the surface free energy γ(A) of the surface of the resin layer (A) in the step (III);
the hydrogen bond component γ ^h (A) of the surface free energy γ(A);
The surface free energy γ(B) of the resin layer (B) formed in the step (III), and
The method for producing an optical film according to [1], wherein a hydrogen bond component γ ^h (B) of the surface free energy γ(B) satisfies the following formulas (1) and (2):
10mJ/m ² ≦ γ(A) - γ(B) ≦ 40mJ/m ² (1)
5mJ/m ² ≦ γ ^h (A) - γ ^h (B) ≦ 20mJ/m ² (2)
[3] The method for producing an optical film according to [1] or [2], further comprising a step (IV) of subjecting the surface of the resin layer (A) to a hydrophilization treatment between the steps (II) and (III).
[4] The method for producing an optical film according to any one of [1] to [3], wherein the step (III) includes a step (III-1) of applying a coating liquid containing the second resin to the surface of the resin layer (A).
[5] The method for producing an optical film according to any one of [1] to [4], wherein the alicyclic structure-containing polymer is a hydrogenated product of a ring-opening polymer of dicyclopentadiene.
[6] The method for producing an optical film according to any one of [1] to [5], wherein the alicyclic structure-containing polymer contained in the optical film has a crystallinity of 30% or more.

According to the present invention, a manufacturing method can be provided for manufacturing an optical film comprising a resin layer (A) formed of a resin containing a crystalline alicyclic structure-containing polymer and a resin layer (B) formed on the resin layer (A), while suppressing cracks in the resin layer (B).

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, and specifically refers to 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 following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effect of the present invention, for example, within a range of ±5°.

[1. Overview of the manufacturing method of optical film]
A method for producing an optical film according to one embodiment of the present invention includes the steps of:
A step (I) of preparing a resin layer (A) formed of a first resin containing an alicyclic structure-containing polymer having crystallinity;
A step (II) of subjecting the resin layer (A) to a crystallization treatment;
(III) forming a resin layer (B) on a surface of the resin layer (A) using a second resin;
In the following description, the alicyclic structure-containing polymer having crystallinity may be referred to as a "crystalline alicyclic polymer".

According to the above-mentioned manufacturing method, an optical film having a resin layer (A) and a resin layer (B) can be manufactured while suppressing cracks in the resin layer (B). In the manufactured optical film, the resin layer (A) and the resin layer (B) are usually in direct contact with each other. Unless otherwise specified, "directly" contacting two layers means that there is no other layer between the two layers.

[2. Step (I) of preparing resin layer (A)]
In step (I), a resin layer (A) formed of a first resin is prepared. The first resin is usually a thermoplastic resin, and contains a crystalline alicyclic polymer.

As described above, the crystalline alicyclic polymer refers to a polymer containing an alicyclic structure that has crystallinity. The alicyclic structure-containing polymer refers to a polymer containing an alicyclic structure in the molecule. The polymer containing an alicyclic structure may be, for example, a polymer obtained by a polymerization reaction using a cyclic olefin as a monomer, or a hydrogenated product thereof. In addition, the "polymer having crystallinity" refers to a polymer having a melting point Tm [i.e., the melting point can be observed by a differential scanning calorimeter (DSC)]. Thus, the crystalline alicyclic polymer may be a polymer containing an alicyclic structure in the molecule and having a melting point Tm. By using such a crystalline alicyclic polymer, the mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight of the optical film can be improved.

Examples of alicyclic structures include cycloalkane structures and cycloalkene structures. Among these, cycloalkane structures are preferred because they are more likely to produce optical films with excellent properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, and preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less. When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability are highly balanced.

In the crystalline alicyclic polymer, the ratio of the structural units containing an alicyclic structure to all structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 70% by weight or more. When the ratio of the structural units containing an alicyclic structure is high as described above, the heat resistance can be improved. The ratio of the structural units containing an alicyclic structure to all structural units can be 100% by weight or less. In the crystalline alicyclic polymer, the remainder other than the structural units containing an alicyclic structure is not particularly limited and can be appropriately selected depending on the purpose of use.

Examples of the crystalline alicyclic polymer include the following polymer (α) to polymer (δ). Among these, polymer (β) is preferred because it is easy to obtain an optical film having excellent heat resistance and flexibility.
Polymer (α): A ring-opening polymer of a cyclic olefin monomer, which has crystallinity.
Polymer (β): A hydrogenated product of polymer (α) and has crystallinity.
Polymer (γ): An addition polymer of a cyclic olefin monomer, which has crystallinity.
Polymer (δ): A hydrogenated polymer (γ) having crystallinity.

Specifically, the crystalline alicyclic polymer is preferably a ring-opening polymer of dicyclopentadiene that has crystallinity, or a hydrogenated ring-opening polymer of dicyclopentadiene that has crystallinity. Among them, a hydrogenated ring-opening polymer of dicyclopentadiene that has crystallinity is particularly preferred. Here, a ring-opening polymer of dicyclopentadiene refers to a polymer in which the ratio of structural units derived from dicyclopentadiene to all structural units is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight.

The hydrogenated dicyclopentadiene ring-opening polymer preferably has a high ratio of racemo dyads. Specifically, the ratio of racemo dyads in the repeating units in the hydrogenated dicyclopentadiene ring-opening polymer is preferably 51% or more, more preferably 70% or more, and particularly preferably 85% or more. A high ratio of racemo dyads indicates high syndiotactic stereoregularity. Therefore, the higher the ratio of racemo dyads, the higher the melting point of the hydrogenated dicyclopentadiene ring-opening polymer tends to be.
The ratio of the racemo dyads can be determined based on the ¹³ C-NMR spectrum analysis described in the Examples below.

As the above polymer (α) to polymer (δ), polymers obtained by the production methods disclosed in WO 2018/062067 and WO 2018/079627 can be used.

The melting point Tm of the crystalline alicyclic polymer is preferably 200°C or higher, more preferably 230°C or higher, and preferably 290°C or lower. When a crystalline alicyclic polymer having such a melting point Tm is used, an optical film with an even better balance between moldability and heat resistance can be obtained.

Typically, a crystalline alicyclic polymer has a glass transition temperature Tg. The specific glass transition temperature Tg of a crystalline alicyclic polymer is not particularly limited, but is typically 85°C or higher and typically 170°C or lower.

Since crystalline alicyclic polymers have crystallinity, crystallization proceeds at a specific temperature. In this case, the temperature at which the crystallization rate is the fastest is sometimes called the "crystallization temperature." The crystallization temperature Tpc of crystalline alicyclic polymers is preferably 100°C or higher, more preferably 130°C or higher, and particularly preferably 160°C or higher, and is preferably 230°C or lower, more preferably 210°C or lower, and particularly preferably 190°C or lower.

The melting point Tm, glass transition temperature Tg, and crystallization temperature Tpc of a polymer can be measured by the following method. First, the polymer is melted by heating, and the molten polymer is quenched with liquid nitrogen. Next, using this polymer as a test specimen, the melting point Tm, glass transition temperature Tg, and crystallization temperature Tpc of the polymer can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C/min (heating mode).

The weight average molecular weight (Mw) of the crystalline alicyclic polymer is preferably 1,000 or more, more preferably 2,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less. A crystalline alicyclic polymer having such a weight average molecular weight has an excellent balance between moldability and heat resistance.

The molecular weight distribution (Mw/Mn) of the crystalline alicyclic polymer is preferably 1.0 or more, more preferably 1.5 or more, and preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. A crystalline alicyclic polymer having such a molecular weight distribution has excellent moldability.

The weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer can be measured in polystyrene equivalent values by gel permeation chromatography (GPC) using tetrahydrofuran as the developing solvent.

The degree of crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) prepared in step (I) is not particularly limited. Since the degree of crystallinity of the crystalline alicyclic polymer can be increased by the crystallization treatment performed in step (II), even if the degree of crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) prepared in step (I) is low, an optical film containing a crystalline alicyclic polymer having a preferred degree of crystallinity can be obtained according to the manufacturing method of this embodiment. The specific range of the degree of crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) prepared in step (I) is preferably 10% or less, more preferably 5% or less, and particularly preferably 3% or less, from the viewpoint of simplifying the manufacturing method of the optical film by omitting steps for increasing the degree of crystallinity other than step (II).

The degree of crystallization is an index showing the proportion of crystallized crystalline alicyclic polymers contained in the first resin. The degree of crystallization can be measured by X-ray diffraction. Specifically, in accordance with JIS K0131, the diffracted X-ray intensity from the crystalline portion is measured using a wide-angle X-ray diffractometer (e.g., Rigaku Corporation's "RINT 2000"), and the crystallization degree can be calculated from the ratio to the total diffracted X-ray intensity according to the following formula (I).
Xc=K・Ic/It (I)
In the above formula (I), Xc represents the crystallinity of the test sample, Ic represents the diffracted X-ray intensity from the crystalline portion, It represents the total diffracted X-ray intensity, and K represents a correction term.

The crystalline alicyclic polymer may be used alone or in combination of two or more types in any ratio.

The proportion of the crystalline alicyclic polymer in the first resin is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the proportion of the crystalline alicyclic polymer is equal to or more than the lower limit of the above range, the birefringence expression and heat resistance of the optical film can be improved. The upper limit of the proportion of the crystalline alicyclic polymer can be 100% by weight or less.

The first resin may contain optional components in addition to the crystalline alicyclic polymer. Optional components include, for example, antioxidants such as phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants; light stabilizers such as hindered amine-based light stabilizers; waxes such as petroleum wax, Fischer-Tropsch wax, and polyalkylene wax; nucleating agents such as sorbitol-based compounds, metal salts of organic phosphoric acids, metal salts of organic carboxylic acids, kaolin, and talc; diaminostilbene derivatives, coumarin derivatives, and azole-based derivatives (e.g., benzoxazole derivatives, benzotriazole derivatives, benzimidazolate derivatives, and benzotriazole derivatives). Examples of the optional components include fluorescent brighteners such as benzothiazole derivatives, carbazole derivatives, pyridine derivatives, naphthalic acid derivatives, and imidazolone derivatives; ultraviolet absorbers such as benzophenone-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers; inorganic fillers such as talc, silica, calcium carbonate, and glass fiber; colorants; flame retardants; flame retardant assistants; antistatic agents; plasticizers; near-infrared absorbers; lubricants; fillers; and any polymer other than crystalline alicyclic polymers, such as soft polymers. One type of optional component may be used alone, or two or more types may be used in any ratio.

The resin layer (A) is usually prepared as a film formed from the first resin. The resin layer (A) may be prepared by purchasing from the market, or may be prepared by manufacturing from the first resin. Examples of methods for manufacturing the resin layer (A) from the first resin include a resin molding method in which the first resin is molded into a film. Examples of resin molding methods include injection molding, extrusion molding, press molding, inflation molding, blow molding, calendar molding, cast molding, and compression molding, and among these, extrusion molding is preferred because it is easy to control the thickness.

The manufacturing conditions in the extrusion molding method are preferably as follows. The cylinder temperature (molten resin temperature) is preferably Tm or higher, more preferably "Tm + 20 ° C" or higher, and preferably "Tm + 100 ° C" or lower, more preferably "Tm + 50 ° C" or lower. In addition, the cooling body that the molten resin extruded into a film first comes into contact with is not particularly limited, but a cast roll is usually used. The cast roll temperature is preferably "Tg - 50 ° C" or higher, more preferably "Tg - 30 ° C" or higher, preferably "Tg + 70 ° C" or lower, more preferably "Tg + 40 ° C" or lower, even more preferably Tg or lower, and particularly preferably "Tg - 15 ° C" or lower. Furthermore, the cooling roll temperature is preferably "Tg - 70 ° C" or higher, more preferably "Tg - 50 ° C" or higher, and preferably "Tg + 60 ° C" or lower, more preferably "Tg + 30 ° C" or lower. When the resin layer (A) is manufactured under such conditions, a resin layer (A) having a thickness of 1 μm to 1 mm can be easily manufactured. Here, "Tm" represents the melting point of the crystalline alicyclic polymer, and "Tg" represents the glass transition temperature of the crystalline alicyclic polymer.

Step (I) may include a step of performing a preheating treatment to heat the resin layer (A) to a stretching temperature after preparing the resin layer (A) and before stretching the resin layer (A). Usually, the preheating temperature and the stretching temperature are the same, but they may be different. The preheating temperature is preferably T1-10°C or more, more preferably T1-5°C or more, and is preferably T1+5°C or less, more preferably T1+2°C or less, relative to the stretching temperature T1. The preheating time is optional, and is preferably 1 second or more, more preferably 5 seconds or more, and is preferably 60 seconds or less, more preferably 30 seconds or less.

Step (I) may include a step of preparing a resin layer (A), optionally preheating the resin layer (A), and then stretching the resin layer (A). Usually, the molecules of the crystalline alicyclic polymer contained in the resin layer (A) can be oriented in a direction corresponding to the stretching direction by stretching. In the following description, the film-like resin layer (A) before stretching may be called the "film before stretching" and the film after stretching may be called the "stretched film".

There is no restriction on the stretching direction, and examples of the stretching direction include the longitudinal direction, the width direction, and the diagonal direction. Here, the diagonal direction refers to a direction perpendicular to the thickness direction, and is neither parallel nor perpendicular to the width direction. The stretching direction may be one direction or two or more directions. Thus, examples of the stretching method include uniaxial stretching methods such as a method of uniaxially stretching the pre-stretched film in the longitudinal direction (longitudinal uniaxial stretching method) and a method of uniaxially stretching the pre-stretched film in the width direction (transverse uniaxial stretching method); biaxial stretching methods such as a simultaneous biaxial stretching method in which the pre-stretched film is stretched in the longitudinal direction and at the same time in the width direction, and a sequential biaxial stretching method in which the pre-stretched film is stretched in one of the longitudinal direction and the width direction and then stretched in the other direction; and a method of stretching the pre-stretched film in a diagonal direction (diagonal stretching method).

The stretching ratio is preferably 1.1 times or more, more preferably 1.2 times or more, and preferably 20.0 times or less, more preferably 10.0 times or less, even more preferably 5.0 times or less, and particularly preferably 2.0 times or less. For example, when stretching is performed in multiple different directions such as a biaxial stretching method, the stretching ratio refers to the total stretching ratio expressed as the product of the stretching ratios in each stretching direction. It is desirable to appropriately set the specific stretching ratio according to factors such as the optical properties, thickness, and strength of the optical film to be manufactured. When the stretching ratio is equal to or greater than the lower limit of the above range, the birefringence can be significantly changed by stretching. Also, when the stretching ratio is equal to or less than the upper limit of the above range, the direction of the slow axis can be easily controlled and film breakage can be effectively suppressed.

The stretching temperature is preferably "Tg-30°C" or higher, more preferably "Tg-10°C" or higher, even more preferably "Tg+5°C" or higher, and particularly preferably "Tg+10°C" or higher, and is preferably "Tg+100°C" or lower, more preferably "Tg+90°C" or lower, even more preferably "Tg+60°C" or lower, and particularly preferably "Tg+50°C" or lower. Here, "Tg" represents the glass transition temperature of the crystalline alicyclic polymer. When the stretching temperature is equal to or higher than the lower limit of the above range, the first resin can be sufficiently softened to perform uniform stretching. When the stretching temperature is equal to or lower than the upper limit of the above range, the hardening of the first resin due to the progress of crystallization of the crystalline alicyclic polymer can be suppressed, so that the stretching can be performed smoothly, and large birefringence can be expressed by stretching.

[3. Step (II) of subjecting resin layer (A) to crystallization treatment]
After preparing the resin layer (A) in step (I), step (II) is performed. In step (II), the resin layer (A) is subjected to a crystallization treatment. The crystallization treatment can increase the crystallinity of the crystalline alicyclic polymer contained in the resin layer (A).

As the crystallization treatment, any method capable of increasing the crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) can be used. Among them, as the crystallization treatment, a heat treatment in which the temperature of the resin layer (A) is adjusted to a predetermined heating temperature is preferable.

The heating temperature in the heat treatment can be set in a temperature range of the glass transition temperature Tg or more and the melting point Tm or less of the crystalline alicyclic polymer. The specific heating temperature range is preferably Tg+20°C or more, more preferably Tg+30°C or more, and preferably Tm or less, more preferably Tm-20°C or less, and even more preferably Tm-40°C or less. The heating temperature is preferably close to the crystallization temperature Tpc of the crystalline alicyclic polymer, and is particularly preferably in the range of Tpc-10°C to Tpc+10°C. In step (II), the heating temperature may vary within the above range, but is preferably constant. When the heating temperature is equal to or higher than the lower limit of the above range, the crystallization of the crystalline alicyclic polymer can be effectively promoted, and the heat resistance of the film can be improved. When the heating temperature is equal to or lower than the upper limit of the above range, the haze of the resin layer (A) can be reduced, and an optical film with low haze can be obtained.

As the heating device used in the heat treatment, a heating device capable of increasing the atmospheric temperature of the resin layer (A) is preferred since no contact between the heating device and the resin layer (A) is required. Specific examples of suitable heating devices include an oven and a heating furnace.

In step (II), the crystallization time for maintaining the resin layer (A) within the above heating temperature range is preferably 1 second or more, more preferably 5 seconds or more, even more preferably 10 seconds or more, particularly preferably 20 seconds or more, and preferably 30 minutes or less, more preferably 10 minutes or less, even more preferably 50 seconds or less, particularly preferably 30 seconds or less. When the crystallization time is equal to or greater than the lower limit of the above range, the crystallization of the crystalline alicyclic polymer can be sufficiently advanced, and the heat resistance of the optical film can be improved. When the crystallization time is equal to or less than the upper limit of the above range, the haze of the resin layer (A) can be reduced, and an optical film with low haze can be obtained.

It is preferable to carry out the crystallization treatment while holding at least two sides of the resin layer (A). "A state in which at least two sides of the resin layer (A) are held" refers to a state in which the resin layer (A) is held by a holder to such an extent that no bending is observed in the resin layer (A). However, this state does not include a holding state in which the resin layer (A) is substantially stretched. In addition, "substantially stretched" refers to a stretching ratio in either direction of the resin layer (A) being usually 1.1 times or more. When the crystallization treatment is carried out while holding at least two sides of the resin layer (A), the resin layer (A) is in a tensed state under tension, so that shrinkage and bending are suppressed. Therefore, the resin layer (A) is maintained flat, so that deformation such as rippling and wrinkles can be suppressed, and a resin layer (A) having a flat shape can be obtained. The crystallization treatment mode in which at least two sides of the resin layer (A) are held may be the same as that described in, for example, WO 2018/061841 and WO 2018/079627.

[4. Step (IV) of subjecting the resin layer (A) to hydrophilic treatment]
The method for producing an optical film according to an embodiment of the present invention preferably includes a step (IV) of subjecting the surface of the resin layer (A) to a hydrophilic treatment between the steps (II) and (III). The hydrophilic treatment usually enhances the adhesive strength between the resin layer (A) and the resin layer (B).

Examples of hydrophilic treatments include corona treatment, plasma treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, and chemical treatment. By subjecting the surface of the resin layer (A) to these hydrophilic treatments, hydrophilic groups such as hydroxyl groups, carboxyl groups, and carbonyl groups are usually generated on the surface. Thus, the hydrophilicity of the surface of the resin layer (A) can be improved. Furthermore, the hydrophilic treatments usually allow the surface free energy of the surface of the resin layer (A) to be adjusted. Among the hydrophilic treatments, corona treatment and plasma treatment are preferred from the viewpoint of treatment efficiency, and corona treatment is particularly preferred.

In corona treatment, a corona is usually generated by applying a high voltage at high frequency between a dielectric and an insulated electrode, and the surface of the resin layer (A) is treated by passing the resin layer (A) between the dielectric and the electrode. In general, the surface free energy of the corona-treated surface is adjusted according to the type of electrode, electrode spacing, voltage, humidity, and type of resin layer (A) being treated.

The treatment conditions of the corona treatment are preferably set so as to increase the adhesive strength between the resin layer (A) and the resin layer (B). In one embodiment, the distance between the electrode and the resin layer (A) is preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm, and particularly preferably 1 mm to 3 mm. The conveying speed of the resin layer (A) to be subjected to the corona treatment is preferably 0.01 m/min to 20 m/min, more preferably 0.05 m/min to 10 m/min. The electrode length is preferably 0.1 m to 2 m. The corona output is preferably 20 W or more, more preferably 40 W or more, and particularly preferably 100 W or more, and from the viewpoint of suppressing damage to the resin layer (A), it is preferably 5 kW or less, more preferably 3 kW or less, and particularly preferably 1.5 kW or less. In the corona treatment performed while conveying the resin layer (A), the treatment strength is calculated by "treatment strength = (output) / (conveying speed x electrode length)". This treatment intensity is preferably 1 W·min/m2 or ^more , more preferably 10 W·min/m2 ^or more, particularly preferably 100 W·min/m2 or ^more , and is preferably 2000 W·min/m2 ^or less, more preferably 1000 W·min/m2 or ^less , particularly preferably 800 W·min/m2 ^or less.

In particular, from the viewpoint of effectively increasing the adhesive strength between the resin layer (A) and the resin layer (B), it is preferable to set the treatment conditions of the above-mentioned hydrophilization treatment so that the surface of the resin layer (A) has a surface free energy that satisfies the formulas (1) and (2) described below. Therefore, it is preferable to set the specific treatment conditions of the hydrophilization treatment according to the composition of the second resin that forms the resin layer (B).

[5. Step (III) of forming resin layer (B) on the surface of resin layer (A)]
In the method for producing an optical film according to one embodiment of the present invention, step (III) is carried out after step (II). In step (III), a resin layer (B) is formed on the surface of the resin layer (A) using a second resin. In addition, when the method for producing an optical film includes step (IV), step (III) is carried out after step (IV). In this case, the resin layer (B) is usually formed on the hydrophilized surface of the resin layer (A).

The second resin may be a resin having a different composition from the first resin. Among them, the second resin is preferably a resin that satisfies specific requirements regarding surface free energy. Specifically, the second resin is preferably one that satisfies the requirements represented by the following formulas (1) and (2).
10mJ/m ² ≦ γ(A) - γ(B) ≦ 40mJ/m ² (1)
5mJ/m ² ≦ γ ^h (A) - γ ^h (B) ≦ 20mJ/m ² (2)
(γ(A) represents the surface free energy of the surface of the resin layer (A) from which the resin layer (B) is formed in the step (III),
γ ^h (A) represents the hydrogen bond component of the surface free energy γ(A);
γ(B) represents the surface free energy of the resin layer (B) formed in step (III);
γ ^h (B) represents the hydrogen bond component of the surface free energy γ(B).

The significance of the requirements expressed by formulas (1) and (2) will be explained below.
In accordance with the theory of Kitazaki and Hata, the surface free energy γ _SV of a solid is expressed by the following formula (3), the surface free energy γ _LV of a liquid is expressed by the following formula (4), and the adhesion work W _SL between a solid and a liquid is expressed by formula (5). When the relationship in formula (5) is applied to the Young-Dupre equation expressed by formula (6), formula (7) is derived. Here, γ _SV ^d , γ _SV ^p , and γ _SV ^h represent the dispersion component, polar component, and hydrogen bond component of the surface free energy γ _SV of a solid. γ _LV ^d , γ _LV ^p , and γ _LV ^h represent the dispersion component, polar component, and hydrogen bond component of the surface free energy γ _LV of a liquid. θ represents the contact angle of the liquid with respect to the solid.

According to the Kitazaki-Hata theory, the surface free energy γ(A) of the surface of the resin layer (A) from which the resin layer (B) is formed in step (III) is expressed by the following formula (8) with its dispersion component ^γd (A), polar component ^γp (A) and hydrogen bond component ^γh (A): Also, the surface free energy γ(B) of the resin layer (B) formed in step (III) is expressed by the following formula (9) with its dispersion component ^γd (B), polar component ^γp (B) and hydrogen bond component ^γh (B):
γ (A) = γ ^d (A) + γ ^p (A) + γ ^h (A) (8)
γ (B) = γ ^d (B) + γ ^p (B) + γ ^h (B) (9)

Therefore, "γ(A)-γ(B)" in the above formula (1) represents the difference between the surface free energy of the surface of resin layer (A) and the surface free energy of resin layer (B) in contact with that surface. Also, "γ ^h (A)-γ ^h (B)" in the above formula (2) represents the difference between the hydrogen bond component of the surface free energy of the surface of resin layer (A) and the hydrogen bond component of the surface free energy of resin layer (B) in contact with that surface.

Therefore, formula (1) indicates that the difference Δγ (= γ (A) - γ (B)) in the surface free energy between the surfaces in contact at the interface between resin layer (A) and resin layer (B) is within a specific range. Furthermore, formula (2) indicates that the difference Δγ ^h (= γ ^h (A) - γ ^h (B)) in the hydrogen bond component of the surface free energy between the surfaces in contact at the interface between resin layer (A) and resin layer (B) is within a specific range. According to the findings of the inventors through repeated experiments, when the requirements represented by formulas (1) and (2) are satisfied, the adhesion strength between resin layer (A) and resin layer (B) can be significantly increased. According to the inventors' experiments, no correlation was found between the dispersion component and polar component of the surface free energy and the adhesion strength, so it is presumed that the surface free energy and its hydrogen bond component have a specific effect that affects the adhesion strength.

Formula (1) will be described in more detail. From the viewpoint of significantly increasing the adhesive strength between the resin layer (A) and the resin layer (B), the surface free energy difference Δγ (=γ(A)-γ(B)) represented by formula (1) is preferably 10 mJ/m2 or ^more , more preferably 12 mJ/m2 ^or more, particularly preferably 14 mJ/m2 or ^more , and is preferably 40 mJ/m2 or ^less , more preferably 38 mJ/m2 or ^less , particularly preferably 35 mJ/m2 ^or less.

Formula (2) will be explained in more detail. From the viewpoint of significantly increasing the adhesion strength between resin layer (A) and resin layer (B), the difference Δγ ^h (=γ ^h (A)-γ ^h (B)) in the hydrogen bond component of the surface free energy expressed by formula (2) is preferably 5 mJ/ ^m2 or more, more preferably 6 mJ/m2 or ^more , particularly preferably 7 mJ/m2 or ^more , and is preferably 20 mJ/m2 ^or less, more preferably 18 mJ/m2 or ^less , particularly preferably 16 mJ/m2 or ^less .

The surface free energy γ(A) and its hydrogen bond component γ ^h (A) of the resin layer (A) are measured on one of both surfaces of the resin layer (A) on which the resin layer (B) is to be formed. The surface free energy γ(A) and its hydrogen bond component γ ^h (A) are preferably measured immediately before forming the resin layer (B). Thus, when the method for producing an optical film includes step (IV), the surface free energy γ(A) and its hydrogen bond component γ ^h (A) can be measured after step (IV).

Usually, the surface free energy of both sides of the resin layer (B) is equal. Therefore, the surface free energy γ(B) of the resin layer (B) and its hydrogen bond component γ ^h (B) can be measured on the surface opposite to the resin layer (A). The surface free energy γ(B) and its hydrogen bond component γ ^h (B) of the resin layer (B) measured on the surface opposite to the resin layer (A) in this way can usually be equal to the surface free energy γ(B) and its hydrogen bond component γ ^h (B) of the surface of the resin layer (B) that contacts the resin layer (A) (i.e., the surface of the resin layer (B) on the resin layer (A) side). In formula (1) and formula (2), this is used to define the relationship between the surfaces that contact at the interface between the resin layer (A) and the resin layer (B).

The surface free energy and hydrogen bond components of a solid sample (such as resin layer (A) and resin layer (B)) can be measured by measuring the contact angle θ with respect to the solid sample using three types of liquids with known surface free energies, and then applying the measured value to equation (7) to solve the three-variable simultaneous equation. Specific measurement conditions may be those described in the examples below.

The surface free energy γ(A) of the surface of the resin layer (A) is preferably in a range that satisfies the above-mentioned formula (1). From the viewpoint of obtaining the effects of the present invention remarkably, the specific range of the surface free energy γ(A) is preferably 40 mJ/ ^m2 or more, more preferably 50 mJ/ ^m2 or more, particularly preferably 55 mJ/ ^m2 or more, and preferably 90 mJ/ ^m2 or less, more preferably 85 mJ/ ^m2 or less, particularly preferably 80 mJ/m2 ^or less.

The hydrogen bond component γ ^h (A) of the surface free energy γ (A) of the surface of the resin layer (A) is preferably in a range satisfying the above formula (2). From the viewpoint of obtaining the effects of the present invention remarkably, the specific range of the hydrogen bond component γ ^h (A) is preferably 5 mJ/ ^m2 or more, more preferably 8 mJ/ ^m2 or more, particularly preferably 10 mJ/ ^m2 or more, and is preferably 30 mJ/m2 or ^less , more preferably 25 mJ/m2 or ^less , particularly preferably 20 mJ/m2 ^or less.

The surface free energy γ(A) of the resin layer (A) and its hydrogen bond component γ ^h (A) can be adjusted, for example, by the type and amount of functional groups contained in the crystalline alicyclic polymer, the composition of the first resin, and the conditions of the hydrophilization treatment performed in step (IV).

The surface free energy γ(B) of the resin layer (B) is preferably in a range satisfying the above-mentioned formula (1). From the viewpoint of obtaining the effects of the present invention remarkably, the specific range of the surface free energy γ(B) is preferably 30 mJ/ ^m2 or more, more preferably 35 mJ/ ^m2 or more, particularly preferably 40 mJ/m2 or ^more , and preferably 70 mJ/m2 or ^less , more preferably 60 mJ/m2 or ^less , particularly preferably 55 mJ/m2 ^or less.

The hydrogen bond component γ ^h (B) of the surface free energy γ (B) of the resin layer (B) is preferably in a range satisfying the above-mentioned formula (2). From the viewpoint of obtaining the effects of the present invention remarkably, the specific range of the hydrogen bond component γ ^h (B) is preferably 1 mJ/m2 or ^more , more preferably 2 mJ/m2 or ^more , and preferably 20 mJ/m2 or ^less , more preferably 15 mJ/ ^m2 or less.

The surface free energy γ(B) of the surface of the resin layer (B) and its hydrogen bond component γ ^h (B) can be adjusted, for example, by the structure and functional groups of the polymer contained in the second resin, the types and amounts of optional components that the second resin may contain, and the like.

Examples of the second resin include urethane resin, olefin resin, polyester resin, epoxy resin, carbonate resin, and acrylic resin. In particular, the type of second resin is preferably selected so that the resin layer (B) formed by the second resin satisfies the above-mentioned requirements related to surface free energy. For example, when a commercially available resin is used as the second resin, it is preferable to select a resin that forms a resin layer and whose surface free energy and hydrogen bond components satisfy the above-mentioned requirements.

The second resin may contain a polymer. However, the polymer contained in the second resin is usually a polymer other than a crystalline alicyclic polymer. One type of polymer may be used alone, or two or more types may be used in combination in any ratio. The proportion of the polymer in the second resin is preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more.

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

As the second resin, a curable resin such as a thermosetting resin or a photocurable resin may be used. When a curable resin is used as the second resin, typically, in step (III), a layer of the uncured second resin is formed on the surface of the resin layer (A), and the second resin is then cured to obtain a resin layer (B) containing the cured second resin.

There is no limitation on the method for forming the resin layer (B) in step (III). Usually, step (III) includes step (III-1) of applying a coating liquid containing a second resin to the surface of the resin layer (A).

The coating liquid may contain a solvent in combination with the second resin, if necessary. The solvent that the coating liquid may contain may be either a liquid that dissolves the second resin or a liquid that disperses the second resin, or a combination of both. The type of solvent may be selected appropriately depending on the types of the first resin and the second resin. Examples of the solvent include water; alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, and N-methylpyrrolidone; ether solvents such as tetrahydrofuran, ethylene glycol monomethyl ether, and ethylene glycol monobutyl ether; dimethyl sulfoxide; and triethylamine. One type of solvent may be used alone, or two or more types may be used in combination.

Examples of coating methods include wire bar coating, dip coating, spraying, spin coating, roll coating, gravure coating, air knife coating, curtain coating, slide coating, and extrusion coating.

When the coating liquid contains a solvent, step (III) usually includes step (III-2) of drying the coating liquid after step (III-1). Any drying method may be used, and examples of such drying methods include drying under reduced pressure and drying by heating. By drying, the solvent is removed from the layer of the coating liquid formed on the surface of the resin layer (A), and thus a resin layer (B) containing the second resin is obtained.

For example, when the second resin is a curable resin, the above-mentioned step (III) may include a step (III-3) of curing the second resin applied to the surface of the resin layer (A). By carrying out the step (III-3), the second resin can be cured, and a resin layer (B) having excellent mechanical strength can be obtained. The curing method may be a method according to the type of the second resin. For example, when the second resin is a thermosetting resin, the second resin can be cured by heating. Also, for example, when the second resin is a photocurable resin, the second resin can be cured by irradiating it with light such as ultraviolet light. However, when the second resin is a thermosetting resin, if the second resin is dried by heating in the step (III-2), the effect of the second resin can progress simultaneously with the drying, so the step (III-3) may be omitted.

6. Optional steps
The above-mentioned method for producing an optical film may further include any step as necessary. For example, the method for producing an optical film may include a step of thermally shrinking the resin layer (A) after the step (II) and before the step (III) to remove residual stress contained in the resin layer (A).

According to the above-described method for producing an optical film, a long optical film can be produced. Therefore, the method for producing an optical film may include a step of winding up the obtained optical film to obtain a roll.
The method for producing the optical film may also include a step of trimming the optical film into a desired shape.

Furthermore, the method for producing an optical film may further include a step of providing an optional layer. Examples of the optional layer include a conductive layer, an anti-reflection layer, a hard coat layer, an antistatic layer, an anti-glare layer, an anti-fouling layer, a separator film, etc.

[7. Manufactured Optical Film]
According to the above-mentioned method for producing an optical film, an optical film can be obtained that includes a resin layer (A) formed of a first resin and a resin layer (B) formed on the resin layer (A) of a second resin. The above-mentioned production method does not include a step of applying a large amount of heat to the resin layer (B), so that the occurrence of cracks in the resin layer (B) can be suppressed. Therefore, the resin layer (B) of the obtained optical film can have a small number of cracks or no cracks. In one embodiment, the number of cracks having a length of 100 μm or more per 2 mm×2 mm area of the resin layer (B) can be less than 3.

The adhesive strength between the resin layer (A) and the resin layer (B) of the optical film is preferably high. Such high adhesive strength can be achieved when the requirements regarding the surface free energy expressed by the formulas (1) and (2) are satisfied. In one embodiment, as described in the examples below, a cellophane tape checkerboard peeling test is performed on the optical film in accordance with JIS K5600-5-6. In this case, for every 100 compartments formed in the resin layer (B), the number of compartments that remain on the optical film without peeling even when the cellophane tape is peeled off can be 90 or more.

The resin layer (A) of the optical film contains a first resin. Because this first resin contains a crystalline alicyclic polymer, the optical film can exhibit the excellent properties exhibited by the crystalline alicyclic polymer. Therefore, the optical film usually has excellent properties such as mechanical strength, transparency, dimensional stability, light weight, flexibility, heat resistance, folding resistance, and low water absorption.

The degree of crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) of the optical film may be higher than that of step (I). The range of the degree of crystallinity of the crystalline alicyclic polymer contained in the resin layer (A) of the optical film is preferably 30% or more, more preferably 35% or more, and particularly preferably 40% or more. The upper limit of the degree of crystallinity is usually 100%, and may be 90% or less, 80% or less, 70% or less, 60% or less, etc. When the crystalline alicyclic polymer has such a high degree of crystallinity, the optical film can have particularly good properties such as flexibility, heat resistance, folding resistance, and low water absorption.

There are no particular limitations on the thickness of the resin layer (A). The specific thickness of the resin layer (A) in the optical film is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 15 μm or more, and is preferably 100 μm or less, more preferably 75 μm or less, particularly preferably 50 μm or less.

As described above, the optical film has a resin layer (B) on the surface of the resin layer (A). The resin layer (B) may be formed on only one surface of the resin layer (A), or on both surfaces. In an optical film having a resin layer (B) on both surfaces of the resin layer (A), both resin layers (B) may be formed simultaneously.

By providing the resin layer (B), the optical film can exhibit excellent properties based on the resin layer (B). For example, when the resin layer (B) contains a resin with excellent adhesive properties such as a urethane resin or an acrylic resin as the second resin, the optical film can exhibit excellent adhesive properties on the surface of the resin layer (B).

There is no particular limitation on the thickness of the resin layer (B). The specific thickness of the resin layer (B) in the optical film is preferably 10 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more, and is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less.

It is preferable that the optical film has a high total light transmittance. Specifically, the total light transmittance of the optical film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. The total light transmittance can be measured in the wavelength range of 400 nm to 700 nm using an ultraviolet-visible spectrometer.

It is preferable that the optical film has a small haze. Specifically, the haze of the optical film is preferably less than 3.0%, more preferably less than 2%, particularly preferably less than 1%, and ideally 0%. The haze can be measured using a haze meter (e.g., "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd.).

The optical film can be applied to any optical application, and can be used as a component of a display device such as a liquid crystal display device or an organic electroluminescence display device. In particular, the optical film is preferably used as a component of a touch sensor of a display device, taking advantage of its excellent heat resistance and mechanical strength (particularly flexibility). In particular, an optical film having a resin layer (A) containing a crystalline alicyclic polymer has excellent folding resistance, and is therefore applicable to flexible display devices, and is therefore preferable.

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

In the following explanation, the amounts in "%" and "parts" are by weight unless otherwise specified. In addition, the operations described below were carried out at room temperature (25°C), normal pressure (1 atm), and in the atmosphere unless otherwise specified.

[Evaluation method]
(Method of measuring weight average molecular weight Mw and number average molecular weight Mn of polymer)
The weight average molecular weight Mw and number average molecular weight Mn of the polymer were measured as polystyrene equivalent values using a gel permeation chromatography (GPC) system ("HLC-8320" manufactured by Tosoh Corporation). In the measurement, an H-type column (manufactured by Tosoh Corporation) was used as the column, and tetrahydrofuran was used as the solvent. The temperature during the measurement was 40° C.

(Method of measuring hydrogenation rate of polymer)
The hydrogenation rate of the polymer was measured by ¹ H-NMR measurement at 145° C. using orthodichlorobenzene- ^d4 as a solvent.

(Methods for measuring glass transition temperature Tg, crystallization temperature Tpc, and melting point Tm)
The sample was heated to 320°C in a nitrogen atmosphere and melted, and then quenched with liquid nitrogen. The sample was heated at 10°C/min using a differential scanning calorimeter (DSC) to measure the glass transition temperature Tg, crystallization temperature Tpc, and melting point Tm of the sample. The glass transition temperature Tg is the minimum value of the endothermic peak, the crystallization temperature Tpc is the maximum value of the exothermic peak, and the melting point Tm is the minimum value of the endothermic peak.

(Method for measuring the ratio of racemo-dyads in polymers)
The ratio of the racemo-dyad in the polymer was measured as follows. The polymer was subjected to ¹³ C-NMR measurement by applying the inverse-gated decoupling method at 200°C using orthodichlorobenzene- ^d4 as a solvent. In the results of this ¹³ C-NMR measurement, a signal at 43.35 ppm derived from the meso-dyad and a signal at 43.43 ppm derived from the racemo-dyad were identified, with the peak at 127.5 ppm of orthodichlorobenzene- ^d4 as the reference shift. The ratio of the racemo-dyad in the polymer was calculated based on the intensity ratio of these signals.

(Method of measuring the crystallinity of a polymer)
The crystallinity was confirmed by X-ray diffraction in accordance with JIS K 0131. Specifically, the diffracted X-ray intensity from the crystallized portion was determined using a wide-angle X-ray diffractometer (Rigaku Corporation, "RINT 2000"), and the crystallinity was calculated from the ratio to the total diffracted X-ray intensity according to the following formula (I).
Xc=K・Ic/It (I)
In the above formula (I), Xc represents the crystallinity of the test sample, Ic represents the diffracted X-ray intensity from the crystallized portion, It represents the total diffracted X-ray intensity, and K represents a correction term.

(Method of measuring surface free energy)
The contact angles of water, diiodomethane and diethylene glycol were measured at 10 points on the surface of the sample using an automatic contact angle meter ("AutoDispenser AD-31" manufactured by Kyowa Interface Science Co., Ltd.). The measurement was performed using a sessile drop method, and the contact angle was measured from the shape of the droplet 3000 ms after it landed. From the average value of the obtained contact angles, the surface free energy was calculated according to the Kitazaki-Hata method (Journal of the Japan Adhesion Association, Vol. 8, No. 3, 1972, pp. 131-141).

(Method for evaluating crack suppression ability (method for evaluating film appearance))
Nine samples of 2 mm x 2 mm were cut out from the optical film. The surface of the resin layer (B) of each sample was observed using an optical microscope (Olympus BX51) to determine the average number of cracks with a length of 100 μm or more. An average number of cracks less than 3 was judged as "good", and an average number of cracks 3 or more was judged as "bad".

(Method for evaluating adhesion strength (peel test))
Nine samples were cut out from the optical film. Each sample was subjected to a cellophane tape checkerboard peeling test in accordance with JIS K5600-5-6. Specifically, the resin layer (B) was scored to form 100 sections of 2 mm x 2 mm in a checkerboard pattern. Cellophane tape (manufactured by Nichiban Co., Ltd., width 24 mm) was attached onto the 100 sections and peeled off within 1 second. The number of sections that remained on the optical film without peeling off even after peeling off the cellophane tape was counted. Of the 100 sections, those with an average of 90 or more remaining were judged to be "good", and those with less than 90 remaining were judged to be "poor".

[Production Example 1. Production of crystalline alicyclic structure-containing polymer]
A metallic pressure-resistant reactor was thoroughly dried and then purged with nitrogen. 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution of dicyclopentadiene (endo isomer content of 99% or more) (30 parts as the amount of dicyclopentadiene), and 1.9 parts of 1-hexene were added to the metallic pressure-resistant reactor, and the reactor was heated to 53°C.

A catalyst solution was prepared by adding 0.061 parts of a 19% diethylaluminum ethoxide/n-hexane solution to a solution prepared by dissolving 0.014 parts of tetrachlorotungsten phenylimide (tetrahydrofuran) complex in 0.70 parts of toluene and stirring for 10 minutes. This catalyst solution was added to a pressure-resistant reactor to initiate a ring-opening polymerization reaction. The reaction was then continued for 4 hours while maintaining the temperature at 53°C, to obtain a solution of a ring-opening polymer of dicyclopentadiene.
The number average molecular weight (Mn) and weight average molecular weight (Mw) of the resulting ring-opened polymer of dicyclopentadiene were 8750 and 28,100, respectively, and the molecular weight distribution (Mw/Mn) calculated from these was 3.21.

0.037 parts of 1,2-ethanediol was added as a terminator to 200 parts of the resulting solution of ring-opened dicyclopentadiene polymer, and the mixture was heated to 60°C and stirred for 1 hour to terminate the polymerization reaction. 1 part of a hydrotalcite-like compound (Kyowa Chemical Industry Co., Ltd.'s "Kyoward (registered trademark) 2000") was added to the solution, which was then heated to 60°C and stirred for 1 hour. 0.4 parts of a filter aid (Showa Chemical Industry Co., Ltd.'s "Radiolight (registered trademark) #1500") was then added, and the adsorbent and the solution were filtered using a PP pleated cartridge filter (Advantec Toyo Co., Ltd.'s "TCP-HX").

100 parts of cyclohexane were added to 200 parts of the filtered ring-opening polymer solution (polymer amount 30 parts), and 0.0043 parts of chlorohydridocarbonyltris(triphenylphosphine)ruthenium was added, and a hydrogenation reaction was carried out at 6 MPa hydrogen pressure and 180°C for 4 hours. This produced a reaction liquid containing a hydride of the ring-opening polymer of dicyclopentadiene. The hydride precipitated from this reaction liquid, forming a slurry solution.

The hydride and the solution contained in the reaction liquid were separated using a centrifuge and dried under reduced pressure at 60°C for 24 hours to obtain 28.5 parts of a crystalline ring-opening polymer of dicyclopentadiene. The hydrogenation rate of this hydride was 99% or more, the glass transition temperature Tg was 94°C, the melting point (Tm) was 262°C, the crystallization temperature Tpc was 170°C, and the racemo-dyad ratio was 89%.

100 parts of the hydrogenated product of the ring-opening polymer of dicyclopentadiene was mixed with 0.5 parts of an antioxidant (tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane; "Irganox (registered trademark) 1010" manufactured by BASF Japan Ltd.) to obtain crystalline resin A as the first resin.

[Example 1]
(1-1. Production of pre-stretched film)
Crystalline resin A was charged into a twin-screw extruder ("TEM-37B" manufactured by Toshiba Machine Co., Ltd.) equipped with four die holes with an inner diameter of 3 mm. Crystalline resin A was molded into a strand-shaped molded body by hot melt extrusion molding using the twin-screw extruder. This molded body was chopped with a strand cutter to obtain pellets of crystalline resin A.

The pellets were then fed to a hot melt extrusion film molding machine equipped with a T-die. A long pre-stretched film (width 120 mm, thickness 20 μm) was produced from the crystalline resin A using this film molding machine, and wound up on a roll at a speed of 27 m/min. The operating conditions of the film molding machine are shown below.
・Barrel temperature setting: 280℃～290℃
Die temperature: 270°C
Screw rotation speed: 30 rpm
Cast roll temperature: 70°C

(1-2. Stretching of Pre-Stretched Film)
A small-sized stretching machine equipped with an oven was prepared, and the oven temperature was set to 130° C. Using this small-sized stretching machine, the long unstretched film was stretched in the longitudinal direction at a stretching temperature of 130° C., a stretching speed of 4.0 mm/min, and a stretching ratio of 1.2 times to obtain a long stretched film.

(1-3. Crystallization Treatment)
A square stretched film measuring 350 mm x 350 mm was cut out from the long stretched film. This cutting was performed so that each edge of the square of the obtained stretched film was parallel to the longitudinal direction or width direction of the long stretched film. The square stretched film was then placed in a small stretching machine ("EX10-B type" manufactured by Toyo Seiki Seisakusho Co., Ltd.). This small stretching machine had a structure that included multiple clips capable of gripping the four edges of the film and could stretch the film by moving the clips.

The stretched film placed in the small stretching machine was subjected to a heat treatment as a crystallization treatment. This heat treatment was performed by holding the four edges of the film and bringing the secondary heating plates attached to the small stretching machine close to the upper and lower surfaces of the stretched film and holding them there for 30 seconds. The temperature of the secondary heating plates was 170°C, and the distance from the film was 8 mm both above and below. The crystallinity of the hydrogenated ring-opening polymer of dicyclopentadiene contained in the stretched film after the treatment was 45%.

(1-4. Surface treatment)
The surface of the stretched film was subjected to a discharge treatment as a hydrophilization treatment using a corona treatment device (manufactured by Kasuga Electric Co., Ltd.) under conditions of an output of 300 W, an electrode length of 340 mm, and a conveying speed of 6 m/min. The surface free energy γ(A) and its hydrogen bond component ^γh (A) of the surface of the stretched film after the discharge treatment were measured.

(1-5. Formation of resin layer (B))
A coating liquid containing a chlorinated polypropylene modified acrylic resin (DIC Corporation "WML-350") and methyl ethyl ketone was prepared. This coating liquid was applied to the discharge-treated surface of the stretched film using a bar coater. The coating thickness of the coating liquid was adjusted so that the thickness of the resulting resin layer (B) was 0.5 μm. The applied coating liquid was then dried under drying conditions of a drying temperature of 90° C. and a drying time of 120 seconds to form a resin layer (B) on the surface of the stretched film. By the above method, an optical film including a stretched film as the resin layer (A) and a resin layer (B) was obtained.

The surface free energy γ(B) and its hydrogen bond component γ ^h (B) of the resin layer (B) of the obtained optical film on the surface opposite to the stretched film were measured. Furthermore, the appearance of the optical film was observed by the above-mentioned method to evaluate the crack suppression ability. Furthermore, a peel test was performed by the above-mentioned method to evaluate the adhesion strength between the stretched film and the resin layer (B).

[Example 2]
The coating liquid was changed to a coating liquid containing a urethane acrylate resin ("FA-3291" manufactured by Nippon Kako Toryo Co., Ltd.) and methyl ethyl ketone. In addition, after the coating liquid applied to the discharge-treated surface of the stretched film was dried, ultraviolet light was irradiated to cure the urethane acrylate resin on the discharge-treated surface. This ultraviolet light irradiation was performed using a high-pressure mercury lamp under conditions of an illuminance of 350 mW/cm ² and an integrated light quantity of 1000 mJ/cm ^2. Except for the above, the optical film was produced and evaluated in the same manner as in Example 1.

[Example 3]
An optical film was produced and evaluated in the same manner as in Example 1, except that the conveying speed during the discharge treatment of the stretched film was changed to 1.2 m/min.

[Example 4]
During the discharge treatment of the stretched film, the conveying speed was changed to 1.2 m/min. The coating liquid was changed to a coating liquid containing a urethane acrylate resin ("FA-3291" manufactured by Nippon Kako Toryo Co., Ltd.) and methyl ethyl ketone. After drying the coating liquid applied to the discharge-treated surface of the crystallized film, ultraviolet light was irradiated to harden the urethane acrylate resin on the discharge-treated surface. This ultraviolet light irradiation was performed using a high-pressure mercury lamp under conditions of an illuminance of 350 mW/cm ² and an integrated light quantity of 1000 mJ/cm ^2. Except for the above, the optical film was produced and evaluated in the same manner as in Example 1.

[Example 5]
An optical film was produced and evaluated in the same manner as in Example 1, except that the coating liquid was changed to a coating liquid containing an isocyanate carbonate resin ("Superflex 420" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and water.

[Example 6]
The conveying speed was changed to 1.2 m/min during the discharge treatment of the stretched film. The coating liquid was changed to a coating liquid containing an acrylic resin (Hitachi Chemical's "Hitaloid 7975D") and methyl ethyl ketone. After drying the coating liquid applied to the discharge-treated surface of the stretched film, ultraviolet light was irradiated to harden the urethane acrylate resin on the discharge-treated surface. This ultraviolet light irradiation was performed using a high-pressure mercury lamp under conditions of an illuminance of 350 mW/ ^cm2 and an integrated light quantity of 1000 mJ/ ^cm2 . Except for the above, the optical film was manufactured and evaluated in the same manner as in Example 1.

[Example 7]
An optical film was produced and evaluated in the same manner as in Example 1, except that the coating liquid was changed to a coating liquid containing an aromatic isocyanate ether resin ("Superflex 870" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and water.

[Comparative Example 1]
(C1-1. Surface treatment)
A long unstretched film was produced in the same manner as in Example 1, and stretched to obtain a long stretched film. The surface of this stretched film was subjected to a discharge treatment as a hydrophilization treatment using a corona treatment device (manufactured by Kasuga Electric Co., Ltd.) under the conditions of an output of 300 W, an electrode length of 340 mm, and a conveying speed of 6 m/min. The surface free energy γ(A) and its hydrogen bond component γ ^h (A) of the surface of the stretched film after the discharge treatment were measured. In addition, the crystallinity of the hydrogenated product of the ring-opening polymer of dicyclopentadiene contained in this stretched film was 3%.

(C1-2. Formation of resin layer (B))
A coating liquid containing a chlorinated polypropylene modified acrylic resin (DIC Corporation, "WML-350") and methyl ethyl ketone was prepared. This coating liquid was applied to the discharge-treated surface of the stretched film using a bar coater. The coating thickness of the coating liquid was adjusted so that the thickness of the resulting resin layer (B) was 0.5 μm. The applied coating liquid was then dried under drying conditions of a drying temperature of 90° C. and a drying time of 120 seconds to form a resin layer (B) on the surface of the stretched film, thereby obtaining an intermediate film.

(C1-3. Crystallization Treatment)
A square intermediate film measuring 350 mm x 350 mm was cut out from the long intermediate film, and was subjected to a heat treatment as a crystallization treatment. The cutting out and crystallization treatment of the intermediate film were performed under the same conditions as those of the cutting out and crystallization treatment of the stretched film in Example 1. The crystallization treatment promoted crystallization of the hydrogenated product of the ring-opening polymer of dicyclopentadiene in the stretched film, and an optical film was obtained. This optical film was evaluated in the same manner as in Example 1.

[result]
The results of the Examples and Comparative Examples are shown in the following table. In the table, the abbreviations have the following meanings.
Crystallized DCPD: A hydrogenated product (crystallized) of a crystalline ring-opening polymer of dicyclopentadiene.
DCPD: A crystalline hydrogenated ring-opening polymer of dicyclopentadiene.
WML-350: Chlorinated polypropylene modified acrylic resin "WML-350" manufactured by DIC Corporation.
FA-3291: Urethane acrylate resin "FA-3291" manufactured by Nippon Kako Paint Co., Ltd.
SF420: "Superflex 420", an isocyanate carbonate resin manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
7975D: Hitachi Chemical's acrylic resin "Hitaroid 7975D".
SF870: Aromatic isocyanate ether resin "Superflex 870" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
MEK: methyl ethyl ketone.
In the step order column, "Sequential" means that the resin layer (B) was formed after the crystallization treatment.
In the column of the process order, "reverse" means that the crystallization treatment was carried out after the resin layer (B) was formed.

Claims (5)

A step (I) of preparing a resin layer (A) formed of a first resin containing an alicyclic structure-containing polymer having crystallinity;
A step (II) of subjecting the resin layer (A) to a crystallization treatment;
and (III) forming a resin layer (B) on the surface of the resin layer (A) using a second resin,
the surface free energy γ(A) of the surface of the resin layer (A) in the step (III);
the hydrogen bond component γ ^h (A ) of the surface free energy γ(A );
The surface free energy γ(B) of the resin layer (B) formed in the step (III), and
The method for producing an optical film, wherein a hydrogen bond component γ ^h (B) of the surface free energy γ(B) satisfies the following formulas (1) and (2) :
10mJ/m ² ≦ γ(A) - γ(B) ≦ 40mJ/m ² (1)
5mJ/m ² ≦ γ ^h (A) - γ ^h (B) ≦ 20mJ/m ² (2) The method for producing an optical film according to claim 1 , further comprising a step (IV) between the step (II) and the step (III) of subjecting the surface of the resin layer (A) to a hydrophilic treatment. The method for producing an optical film according to claim 1 or 2 , wherein the step (III) comprises a step (III-1) of applying a coating liquid containing the second resin to the surface of the resin layer (A). 4. The method for producing an optical film according to claim 1, wherein the alicyclic structure-containing polymer is a hydrogenated product of a ring-opening polymer of dicyclopentadiene. 5. The method for producing an optical film according to claim 1, wherein the alicyclic structure-containing polymer contained in the optical film has a crystallinity of 30% or more.