JP2006276673A - Retardation film made of cyclic olefin polymer - Google Patents

Abstract

【Task】
A retardation film having a small thickness and capable of expressing a desired retardation is provided.
[Solution]
A retardation film comprising a cyclic olefin polymer, wherein the cyclic olefin polymer is sheared at 10 ° C. at a temperature 120 ° C. higher than the glass transition temperature of the cyclic olefin polymer using a capillary rheometer. A retardation film which is a cyclic olefin polymer having a swell ratio (SR) of 1.5 or more and 4 or less measured under the condition of s ⁻¹ ).
[Selection figure] None

Description

  The present invention relates to a retardation film composed of a cyclic olefin polymer.

Thinning of the liquid crystal panel used for a display of a cellular phone or the like is demanded, and a study on thinning of a retardation film which is one of members constituting the liquid crystal panel is actively performed. As the retardation film, a film made of polycarbonate or a film made of a cyclic olefin polymer is known (see Patent Document 1 and Patent Document 2).
Japanese Patent Application Laid-Open No. 07-256749 Japanese Patent Laid-Open No. 05-2108

  However, when the conventional retardation film is further thinned, there is a problem that a desired retardation cannot be expressed. The present invention finds that a retardation film that has a small thickness and expresses a desired retardation is obtained by using a retardation film having a swell ratio measured in a specific range within a specific range. It is to provide.

That is, the present invention is a retardation film comprising a cyclic olefin polymer, wherein the cyclic olefin polymer is 120 ° C. higher than the glass transition temperature of the cyclic olefin polymer using a capillary rheometer. The retardation film is a cyclic olefin polymer having a swell ratio (SR) of 1.5 or more and 4 or less measured under conditions of a shear rate of 10 (s ⁻¹ ).

The retardation film of the present invention can develop a desired retardation even if the thickness is small.

（式中、Ｒ⁷〜Ｒ¹⁸はそれぞれ独立に、水素原子、水酸基、アミノ基、ホスフィノ基、または炭素原子数１〜２０の有機基であり、Ｒ¹⁶とＲ¹⁷は環を形成してもよい。ｍは０以上の整数を示す。） The polymer constituting the retardation film of the present invention is preferably a cyclic olefin polymer. The cyclic olefin polymer in the present invention is a polymer containing 30 mol% or more of a structural unit derived from a cyclic olefin monomer in the polymer, specifically, ethylene and a carbon atom number 3 to 12 Addition polymer (polymer [A]) of a monomer selected from the group consisting of α-olefin and a cyclic olefin monomer described later (polymer [A]), ring-opening homopolymer of cyclic olefin monomer or two or more kinds of copolymers (polymer) Polymer [B]), or hydrogenated product of polymer [B] (polymer [C]).
The cyclic olefin monomer in the present invention is a compound represented by the following formula [I].

Wherein R ^{7 to} R ¹⁸ are each independently a hydrogen atom, a hydroxyl group, an amino group, a phosphino group, or an organic group having 1 to 20 carbon atoms, and R ¹⁶ and R ¹⁷ may form a ring. M is an integer of 0 or more.

Specific examples of the organic group having 1 to 20 carbon atoms include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group and dodecyl group; aryl such as phenyl group, tolyl group and naphthyl group An aralkyl group such as a benzyl group or a phenethyl group; an alkoxy group such as a methoxy group or an ethoxy group; an aryloxy group such as a phenoxy group; an acyl group such as an acetyl group; an alkoxycarbonyl group such as a methoxycarbonyl group or an ethoxycarbonyl group; Aryloxycarbonyl group or aralkyloxycarbonyl group; acyloxy group such as acetyloxy group; alkoxysulfonyl group such as methoxysulfonyl group and ethoxysulfonyl group; aryloxysulfonyl group or aralkyloxysulfonyl group; substituted silyl group such as trimethylsilyl group; A dialkylamino group such as a ruamino group and a diethylamino group; a carboxyl group; a cyano group; and a part of the hydrogen atoms of the alkyl group, aryl group and aralkyl group are a hydroxyl group, amino group, acyl group, carboxyl group, alkoxy group, alkoxycarbonyl group And a group substituted with a group, an acyloxy group, a substituted silyl group, an alkylamino group or a cyano group.

R ^{7 to} R ¹⁸ are preferably each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or 1 to 1 carbon atom. They are 20 acyl groups, C2-C20 alkoxycarbonyl groups, C1-C20 acyloxy groups, or C1-C20 disubstituted silyl groups. m is an integer of 0 or more, preferably an integer in the range of 0 ≦ m ≦ 3.

Preferred examples of the cyclic olefin monomer represented by the general formula [I] include norbornene, 5-methylnorbornene, 5-ethylnorbornene, 5-butylnorbornene, 5-phenylnorbornene, 5-benzylnorbornene, tetracyclododecene, Tricyclodecene, tricycloundecene, pentacyclopentadecene, pentacyclohexadecene, 8-methyltetracyclododecene, 8-ethyltetracyclododecene, 5-acetylnorbornene, 5-acetyloxynorbornene, 5-methoxycarbonylnorbornene 5-ethoxycarbonylnorbornene, 5-methyl-5-methoxycarbonylnorbornene, 5-cyanonorbornene, 8-methoxycarbonyltetracyclododecene, 8-methyl-8-tetracyclododecene, You can list preliminary 8-cyano tetracyclododecene. When polymerizing the polymer used in the present invention, only one type of cyclic olefin monomer represented by the formula [I] may be used, or two or more types may be used.

Among the cyclic olefin polymers preferably used in the present invention, the polymer [A] is one or more monomers selected from the group consisting of ethylene and an α-olefin having 3 to 12 carbon atoms, and the formula [I]. It is an addition type copolymer with the 1 or more types of cyclic olefin monomer represented.

Examples of the α-olefin having 3 to 12 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene. From the viewpoint of the heat resistance of the obtained film, the α-olefin is preferably ethylene, propylene or 1-butene.

The glass transition temperature of the polymer [A] can be controlled by changing the copolymerization ratio of ethylene or an α-olefin having 3 to 12 carbon atoms and a cyclic olefin. The content of the structural unit derived from each monomer in the polymer can be measured by a ¹ H-NMR spectrum or a ¹³ C-NMR spectrum.

In the polymer [A], ethylene or an α-olefin having 3 to 12 carbon atoms and a vinyl monomer other than the cyclic olefin monomer may be introduced by copolymerization. Examples of the vinyl monomer include an alicyclic vinyl monomer having cyclopentane, cyclohexane or the like as a substituent, or an aromatic vinyl monomer having a benzene ring or naphthalene ring as a substituent. Among these, a ternary system obtained by copolymerizing a monomer selected from vinylcyclohexane, styrene, vinylnaphthalene, and derivatives thereof with ethylene or an α-olefin having 3 to 12 carbon atoms and a cyclic olefin monomer. This cyclic olefin polymer is preferably used because it has a smaller photoelastic coefficient than binary cyclic olefin polymers such as the polymer [A]. From the viewpoint of the photoelastic coefficient, the copolymerization ratio of the vinyl monomer in the polymer [A] is preferably 2 mol% or more. Moreover, when the organic solvent resistance is calculated | required by the molded object which consists of this polymer [A], it is preferable that the copolymerization ratio of the vinyl monomer in polymer [A] shall be 30 mol% or less.

Among the cyclic olefin polymers preferably used in the present invention, the polymer [B] is a polymer obtained by ring-opening polymerization using one or more cyclic olefin monomers represented by the formula [I]. It is. Among the cyclic olefin polymers in the present invention, the polymer [C] is a polymer obtained by hydrogenating the polymer [B].

The cyclic olefin polymer can be polymerized by a known method. The polymer [A] is produced by a homogeneous catalyst composed of a vanadium compound and an organic aluminum compound part as disclosed in, for example, Japanese Patent No. 2693596. The polymer [B] is, for example, a combination of a tungsten compound as disclosed in, for example, Japanese Patent No. 294014 and a compound such as a group IA, IIA, or IIB in the Deming periodic table and having the element-carbon bond It can be produced using a metathesis polymerization catalyst. The polymer “C” is usually obtained by reacting the polymer [B] with hydrogen gas at a reaction temperature of 20 to 150 ° C. under 3 to 150 atm.

  Since the cyclic olefin-based polymer having an unsaturated bond is likely to deteriorate during film forming and foreign matter is likely to be generated in the resulting film, the polymer [A] or the polymer [C] may be used in the present invention. preferable.

  The cyclic olefin polymer constituting the retardation film of the present invention is preferably a polymer having a glass transition temperature (Tg) of 100 ° C. or higher, and more preferably a polymer having a Tg of 120 ° C. or higher. When the glass transition temperature is less than 100 ° C., there is a possibility that use in applications requiring heat resistance such as a liquid crystal display used for a monitor of a car navigation system may be limited. The upper limit of the glass transition temperature is preferably 200 ° C. or less from the viewpoint of moldability. The glass transition temperature (Tg) is a value measured under a nitrogen gas atmosphere using a differential thermal scanning calorimeter (DSC) according to JIS K7121.

The retardation film is produced by producing a raw film for a retardation film and stretching the raw film so that a desired retardation is developed. As the raw film for retardation film, an optically homogeneous non-oriented film or a film close to non-oriented film is preferable. Examples of the method for producing a raw film for retardation film include a solvent casting method and an extrusion molding method. In the former method, a solution in which a polymer is dissolved in an organic solvent is cast on a substrate such as a biaxially stretched polyester film having releasability by a die coater, and then dried to remove the organic solvent. This is a method of forming an original film for retardation film on top. The raw film is used after being peeled off from the substrate. The latter method is a method in which a polymer is melt-kneaded in an extruder, extruded from a T-die, and brought into contact with a roll and taken out while being cooled and solidified to obtain a raw film.

Next, a retardation film can be obtained by stretching the raw film obtained by the above method by a known method. Examples of the stretching method include a method of stretching an original film by a difference in rotational speed between two or more rolls, and a tenter method of stretching an original film having both ends fixed with a chuck or the like with an increased chuck interval in an oven. It is done. Usually, the stretching temperature is not less than the glass transition temperature (Tg) of the polymer and not more than (Tg + 30) ° C., and the stretching ratio is 1.2 to 4 times. By stretching under such conditions, a retardation film with little variation in birefringence in the film width direction can be obtained.

The retardation required for the retardation film is around 290 nm in the case of the (1/2) λ retardation film, and around 140 nm in the case of the (¼) λ retardation film. That is, it is required to express a phase difference of 100 to 300 nm with a small thickness. The retardation film made of a cyclic olefin polymer having a swell ratio of 1.5 or more and 4 or less according to the present invention can exhibit a retardation of 100 to 300 nm with a thickness of 100 μm or less. The thickness of the retardation film of the present invention is preferably 80 μm or less, more preferably 60 μm or less, and more preferably 50 μm or less. The lower limit of thickness should just be a grade which can maintain the required intensity, and is usually 10 μm or more.

The swell ratio (SR) of the cyclic olefin polymer in the present invention is a shear rate of 10 s ^{−1 at a} temperature 120 ° C. (Tg + 120 ° C.) higher than the glass transition temperature of the cyclic olefin polymer using a capillary rheometer. It is a value calculated | required by the following formula from the strand diameter measured on condition of this.
SR (-) = A / B
Here, A is the diameter of the strand made of a cyclic olefin polymer extruded from the discharge port of the capillary rheometer. The strand diameter is a diameter of a portion 30 mm from the discharge port when the length of the strand from the discharge port of the capillary rheometer becomes 70 mm. B is the diameter of the orifice of the capillary rheometer used for the measurement.

The swell ratio (SR) of the cyclic olefin polymer constituting the retardation film of the present invention is 1.5 or more and 4 or less. The reason for such a retardation film is not clear, but can exhibit a large retardation with a small thickness. The SR of the cyclic olefin polymer in the present invention is preferably 1.8 or more, and more preferably 2 or more.

  The retardation film of the present invention comprises a cyclic olefin polymer having a swell ratio (SR) of 1.5 or more and 4 or less measured under the above conditions. As a method for controlling the SR of the cyclic olefin polymer within the range of the present invention, (i) a method using a crosslinking agent that causes a crosslinking reaction by heat, (ii) a crosslinking agent that causes a crosslinking reaction by a factor other than heat is used. (Iii) A method of irradiating high-energy radiation such as β-rays or γ-rays, (iv) A bifunctional or higher functional vinyl monomer is blended when polymerizing, and a three-dimensional gel is overlapped at the time of polymerization. The method of producing | generating in coalescence is mentioned. Hereinafter, each method will be described in detail.

Examples of the crosslinking agent that causes a crosslinking reaction by heat used in the method (i) include various peroxides. For example, a polymer used for film molding impregnated with a peroxide, or a mixture of a peroxide and a polymer is introduced into an extruder, and at a temperature higher than the decomposition half-life temperature of the peroxide. After forming the original film for retardation film by melt kneading and extrusion molding, the retardation film of the present invention can be obtained by stretching the original film. Also, after forming a raw film for retardation film by a solvent casting method using a mixture of a crosslinking agent and a polymer that causes a crosslinking reaction by heat, the crosslinking agent is allowed to act by heat during drying, and then stretched. Thus, the retardation film of the present invention can be obtained.

  Examples of the crosslinking reaction caused by factors other than heat used in the method (ii) include those that cause a crosslinking reaction with water, such as silicon compounds. For example, a mixture of a silicon compound and a polymer is produced by manufacturing a raw film sheet for retardation film by a method that does not use water, such as an extrusion molding method, and then the raw film is treated with water or warm water, and then stretched By performing the step, the retardation film of the present invention can be obtained. In the method (iii), the retardation film of the present invention can be obtained by irradiating a raw film for retardation film formed by a known method with high-energy radiation such as β-rays or γ-rays and then stretching. Can do. As the method of (iv), for example, when ethylene and norbornene are copolymerized, a bifunctional or higher vinyl monomer such as a diene compound or divinylbenzene is added and copolymerized, and then the solvent is cast or extrusion is performed. The retardation film of this invention can be obtained by shape | molding the original film for retardation films, and extending | stretching after that.

As the method for producing the retardation film of the present invention, the radiation irradiation method (iii) is preferable because it can be produced at low cost and the control of SR of the cyclic olefin polymer constituting the retardation film is easy. . When performing radiation irradiation, it is preferable to provide a radiation irradiation process continuously between manufacture of an original film for retardation films, and a extending process. In order to obtain a retardation film composed of a cyclic olefin polymer having an SR of 1.5 or more and 4 or less, an irradiation dose of radiation applied to the raw film is 10 to 600 kGy. By increasing the irradiation dose, a raw film made of a cyclic olefin polymer having a large SR can be obtained, and by reducing the irradiation dose, a raw film made of a cyclic olefin polymer having a small SR can be obtained. it can. The acceleration voltage of radiation is usually 50 kV or more. When irradiating a raw film with radiation, it is preferable to irradiate under a nitrogen atmosphere from which oxygen is removed as much as possible. When the oxygen concentration is high, the cyclic olefin polymer activated by radiation irradiation and oxygen may react to cause a deterioration reaction of the polymer. When the deterioration progresses, the retardation film may be colored yellow. The oxygen concentration in the irradiation atmosphere is preferably 10,000 ppm or less.

The retardation film of the present invention can be used for a liquid crystal panel such as a mobile phone, a personal computer, and a large TV. Since the retardation film of the present invention expresses a desired retardation with a very thin thickness, the use of the retardation film of the present invention can reduce the thickness and weight of the liquid crystal panel.

Examples are shown below, but the present invention is not limited thereto.
(1) Measuring method of swell ratio (SR) SR was measured using a capillary rheometer “Capillograph” manufactured by Toyo Seiki Co., Ltd. An orifice having a diameter (B) of 2.095 mm and a length of 8.0 mm is set, and a retardation film is pulverized into a powder in a cylinder adjusted to a measurement temperature: (glass transition temperature of polymer +120) ° C. 8 g was added and left for 5 minutes while lightly held by a piston. Thereafter, the piston was lowered at a speed at which the shear rate became 1.0S- ¹ . After confirming that the state of the strand extruded from the discharge port at the tip of the orifice is stable, once the strand is cut at the discharge port and the strand is extruded to a length of 70 mm, the strand 30 mm from the discharge port The diameter was measured with a laser attached to the device. The value was A (mm), and SR was obtained from the following equation.
SR (-) = A / B
(2) Measurement of retardation The retardation R (nm) of the stretched film (retardation film) was measured using an automatic birefringence measurement apparatus (KOBRA 31PR manufactured by Oji Scientific Instruments Service Co., Ltd.).
(3) Measurement of film thickness The film thickness (d (μm)) was measured using a film thickness meter.

[Example 1]
An ethylene-tetracyclododecene polymer (ED copolymer) (APEL5014DP (Tg = 136 ° C., trade name, manufactured by Mitsui Chemicals, Inc.)) dried at 110 ° C. for 5 hours and a cylinder temperature of 280 ° C. is a 50 mmφ extruder. The mixture was melt-kneaded and extruded from a 450 mm wide T-die attached to the extruder. The extruded film-like molten cyclic olefin polymer was taken up by a polishing roll having a 250 mmφ casting roll whose temperature was adjusted to 120 ° C. to obtain a 160 μm-thick cyclic olefin polymer film. A4 size test pieces were prepared from the film and irradiated with radiation (β rays). For irradiation, a nitrogen atmosphere with an oxygen concentration of 0.03 vol.% Was used while moving a test piece attached to a PET substrate at a line speed of 3.1 m / min using a radiation irradiation apparatus manufactured by Iwasaki Electric Co., Ltd. The test piece was irradiated with radiation (β rays) having an acceleration voltage of 150 kV and a radiation dose of 300 kGy to obtain a raw film for retardation film. Next, the said raw film was extended | stretched using the tensile tester (Shimadzu Corporation AGS-500D) which has arrange | positioned the thermostat. A test piece of 75 mm (MD direction) × 40 mm (TD direction) was prepared from the raw film, and the test piece was attached to a chuck in a thermostatic chamber adjusted to 151 ° C. (distance between chucks: 30 mm). It was left for about 5 minutes until the temperature stabilized at 151 ° C. Thereafter, the film was stretched at a speed of 100 mm / min until the distance between the chucks became 60 mm (stretching ratio: 2) to obtain a retardation film. The retardation and thickness of the obtained retardation film were measured. Moreover, SR was measured using the obtained retardation film. These results are shown in Table 1.

[Comparative Example 1]
It carried out similarly to Example 1 except not irradiating, and measured the phase difference and thickness of the obtained film. In addition, SR was measured using the obtained retardation film. These results are shown in Table 1.
[Comparative Example 2]
It carried out similarly to Example 1 except having set the irradiation dose of the radiation to 200 kGy, and measured the phase difference and thickness of the obtained film. In addition, SR was measured using the obtained retardation film. These results are shown in Table 1.

Claims (2)

A retardation film comprising a cyclic olefin polymer, wherein the cyclic olefin polymer is sheared at 10 ° C. at a temperature 120 ° C. higher than the glass transition temperature of the cyclic olefin polymer using a capillary rheometer. A retardation film which is a cyclic olefin polymer having a swell ratio (SR) of 1.5 or more and 4 or less measured under the condition of s ⁻¹ ). The retardation film according to claim 1, wherein the thickness is 100 μm or less and the retardation is 100 to 300 nm.