JP2002156523A - Optical retardation plate and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical retardation plate capable of giving a uniform optical retardation to wavelengths in a wide wavelength band (the entire visible light region), having good lubricity and excellent in production stability. SOLUTION: The optical retardation plate has at least a layer containing a norbornene resin and an inorganic filler and a layer containing a styrene- maleic anhydride copolymer resin. Preferably the optical retardation plate has 0.1-0.5 μm average volume particle diameter of the inorganic filler and the optical retardation plate contains silicon oxide as the inorganic filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate and a method for producing the same, and more particularly, to a retardation plate having good slipperiness and excellent production stability when producing a film.

[0002]

2. Description of the Related Art As a retardation plate, a quarter-wave plate having a retardation (Re) of 1/4 of a wavelength and a half-wave plate of Re having a half of a wavelength are known. 1 /
The four-wavelength plate has various uses such as being used for a reflection type liquid crystal display device, an optical disk pickup, and an antiglare film. On the other hand, a half-wave plate also has various uses such as being used for a liquid crystal projector. It is desired that the １ ／ wavelength plate and the 望 ま wavelength plate fully exhibit their functions with respect to all incident light in the visible light region in various applications. As a broadband retarder that can fully demonstrate its function with respect to incident light in the entire visible light region,
For example, JP-A-5-27118, JP-A-5-10
JP-A No. 0114, JP-A-10-68816, JP-A-10-90521, and the like include those formed by laminating two polymer films having mutually different optical anisotropy.

[0003] However, in the conventional laminated retardation plate, two types of chips obtained by cutting a stretched birefringent film stretched in one direction at directions different from each other with respect to the stretching direction are used for the production. It is necessary to form, attach this chip with an adhesive, and laminate. In addition, when two chips are bonded, not only the cost of adhesive coating, chipping and bonding, but also the effect on performance, such as the decrease in performance due to the misalignment due to chip bonding, is affected. I can't ignore it.

[0004] If a retardation plate can be formed in a film form, wound up in a roll form, stored and transported, and then cut into desired dimensions, etc., the production becomes easy and the production cost can be reduced. For this purpose, the retardation plate is required to have optical characteristics according to the intended use, and to prevent slippage and wrinkles during running on the production line and during roll winding. It is required to be excellent.

[0005]

SUMMARY OF THE INVENTION The present invention provides a retardation plate which can provide a uniform phase difference with respect to a wide band (entire visible light) wavelength, has good slipperiness, and is excellent in manufacturing stability. The task is to Another object of the present invention is to provide a method of manufacturing a retardation plate capable of easily and stably producing a retardation plate capable of giving a uniform retardation with respect to a wide band (entire visible light wavelength). I do.

[0006]

Means for solving the above problems are as follows. <1> A retardation plate comprising at least a layer containing a norbornene-based resin and an inorganic filler, and a layer containing a styrene-maleic anhydride copolymer resin. <2> The inorganic filler has a number average particle size of 0.1 to 0.1.
The phase difference plate according to <1>, wherein the thickness is 5 μm. <3> The retardation plate according to <1> or <2>, wherein the inorganic filler is silicon oxide. <4> A molten norbornene-based resin containing an inorganic filler and a styrene-maleic anhydride copolymer resin in a molten state are co-extruded, and the layer containing the inorganic filler resin and the norbornene-based resin and the styrene- A method for producing a retardation plate, comprising: a co-extrusion step of forming a laminate with a layer containing a maleic anhydride copolymer resin, and a stretching step of stretching the laminate and adjusting retardation. is there.

The retardation plate of the present invention contains a layer containing a norbornene resin having a positive intrinsic birefringence value (NB layer) and a styrene-maleic anhydride copolymer resin having a negative intrinsic birefringence value. It is a laminate with a layer (ST layer). The NB
When the layer and the ST layer exhibit birefringence, the wavelength dispersion of retardation of each other is offset. as a result,
The retardation plate of the present invention has optical characteristics that can provide uniform retardation characteristics for a wide band of wavelengths. Further, in the retardation plate of the present invention, since the NB layer contains an inorganic filler,
The surface of the NB layer has an uneven shape, and the slipperiness is improved. As a result, during the manufacturing process, even when the NB layer is driven on the manufacturing line with the NB layer as the lowermost layer, no running failure or the like occurs. Also, wrinkles and the like can be prevented when winding a film-shaped retardation plate around a roll.

In the method for manufacturing a retardation plate according to the present invention,
A laminate of the NB layer and the ST layer is formed by co-extrusion, and thereafter, the retardation is adjusted by uniaxially stretching to produce a retardation plate. No complicated steps such as sticking are required, and the production is simple. Furthermore, N
Since the B layer contains an inorganic filler, it has excellent slipperiness. As a result, when the stretched film is run after the stretching process, and when the stretched film is wound into a roll after the stretching process, poor running and generation of wrinkles do not occur, and a retardation plate can be stably manufactured. Can be.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The retardation plate of the present invention comprises at least one layer (NB layer) containing a norbornene resin and a layer (S layer) containing a styrene-maleic anhydride copolymer resin.
T layer). The norbornene-based resin is a resin having a characteristic exhibiting optically positive uniaxiality and having a positive intrinsic birefringence value. That is, when light enters the layer formed by the molecules of the norbornene-based resin having a uniaxial orientation, the refractive index of the light in the orientation direction is larger than the refractive index of the light in the direction orthogonal to the orientation direction. growing. on the other hand,
The styrene-maleic anhydride copolymer resin is a resin having a characteristic of exhibiting optically negative uniaxiality and having a negative intrinsic birefringence value. That is, when light is incident on a layer formed by the molecules of the styrene-maleic anhydride copolymer resin having a uniaxial orientation, the refractive index of the light in the orientation direction is the light in the direction orthogonal to the orientation direction. Becomes smaller than the refractive index.

[0010] The retardation plate of the present invention comprises the NB layer and the NB layer.
By stretching the laminate of ST layers, the NB
The birefringence is developed in the layer and the ST layer, respectively, and is manufactured.
be able to. The NB layer and the ST layer are in the same direction.
The slow axes are orthogonal to each other
The wavelength dispersion of the retardation of each layer is
Offset by Stretch fill of the stretched laminate
The wavelength dispersion of the retardation of the
Wavelength of the retardation of each of the layer and the ST layer
The dispersibility is offset. As a result, the broadband (wave
Letter on the short wavelength side for light with a length of 400-700 nm)
The retardation is small and the retardation on the long wavelength side
Can be increased (ie, Re (λ₁) <Re
(Λ_Two) (Λ ₁<Λ_Two)) And the above range
It is necessary to provide a uniform phase difference characteristic for light of a broadband wavelength.
Can be.

Further, since the NB layer contains an inorganic filler, when formed into a film by a stretching treatment or the like, an uneven shape is formed on the film surface by the inorganic filler. As a result, when the NB layer is used as the lowermost layer, the slipperiness of the surface is improved, and running defects are less likely to occur when running the film on a production line. Further, when the film is wound up on a roll, there is no wrinkle or the like, and the film is excellent in production stability.

The norbornene-based resin has a norbornene skeleton as a repeating unit. Specific examples thereof include JP-A-62-252406 and JP-A-62-252406.
JP-A-252407, JP-A-2-133413,
JP-A-63-145324, JP-A-63-264
626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403,
JP-A-5-43663, JP-A-5-43834, JP-A-5-70655, JP-A-5-279
554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, JP-A-9-241484, and the like can be suitably used. It is not limited. These may be used singly or may be used alone.
More than one species may be used in combination.

Further, as the norbornene-based resin,
Commercial products can also be used. For example, "ARTON" made by Japan Synthetic Rubber, "ZEONEX" and "ZEONOR" made by Zeon Corporation, "APO" made by Mitsui Petrochemical, and the like are preferable.

As the styrene-maleic anhydride copolymer resin, resins produced by various processes can be used. A commercial product may be used as the styrene-maleic anhydride copolymer resin. For example, “DAIRAK D332” manufactured by Nova Chemical Co., Ltd. is preferable.

The difference between the glass transition point of the norbornene-based resin and the glass transition point of the styrene-maleic anhydride copolymer resin is preferably small, preferably 10 ° C. or less, and more preferably 5 ° C. or less. More preferably, 0
° C, ie, identical. As a preferable combination in which the difference between the glass transition points is within the above range, “Zeonor 142” is used as the norbornene-based resin.
0 "(manufactured by Zeon Corporation) and" DAIRAK D332 "(Tg) as the styrene-maleic anhydride copolymer resin.
= 131 ° C).

Examples of the inorganic filler include particles of silicon oxide, calcium carbonate, alumina, titanium dioxide and the like. Among them, oxide particles are preferable, and silicon oxide particles are particularly preferable. It is preferable to use silicon oxide as the inorganic filler because it is possible to prevent generation of voids around the particles in the NB layer. Further, silicon oxide particles are preferable because they can be contained in a monodispersed state in the NB layer. That is, the silicon oxide is NB
Hardly aggregates in the layer, and the whitening (increase in haze) of the NB layer caused by the aggregation of particles does not occur.
This is preferable since it does not affect the optical characteristics.

The number average particle size of the inorganic filler is from 0.1 to
It is preferably 0.5 μm, more preferably 0.1 to 0.4 μm, and even more preferably 0.1 to 0.3 μm. When the number average particle diameter is in the above range, it is possible to suppress the generation of voids around the particles in the NB layer while maintaining the slipperiness improving effect, and it is preferable since the optical characteristics are not affected. In particular, as the inorganic filler,
It is preferable to use silicon oxide particles having a number average particle size of 0.1 to 0.5 μm.

It is preferable that the inorganic filler has a sharp particle diameter distribution. It is also preferable not to contain extremely small particles and extremely large particles,
Preferably, it does not contain particles having a particle size of less than 0.01 μm and particles having a particle size of more than 1.0 μm.

The inorganic filler preferably has a shape close to a sphere, particularly a shape close to a true sphere. The particle size ratio (major axis / minor axis) is preferably 1.0 to 1.2, more preferably 1.0 to 1.1, and 1.0 to 1.1.
More preferably, it is 1.05. When the particle size ratio is in the above range, voids are less likely to be generated around the particles in the NB layer, and as a result, an increase in haze due to the generated voids can be prevented.

The inorganic filler is preferably contained in an amount of 300 ppm or less (by mass) with respect to the norbornene-based resin, more preferably 10 to 150 ppm (by mass). When the content of the inorganic filler is within the above range, it is preferable because the haze can be prevented from increasing and the optical characteristics can be prevented from being affected, while maintaining good slidability.

The retardation plate of the present invention may have two or more NB layers and two or more ST layers. In particular, the N
Since the B layer has higher strength than the ST layer, the NB
It is preferable that the layer, the ST layer, and the NB layer are sequentially laminated because handling properties and durability as a retardation plate are improved. When each of the NB layer and the ST layer has two or more layers, the material contained in the NB layer and the material contained in the ST layer are preferably the same. In the aspect having two or more NB layers, the inorganic filler need not be contained in all NB layers, but may be contained in one NB layer. It is preferable to include it in the NB layer serving as the lowermost surface layer.

Further, in order to improve the adhesiveness between the NB layer and the ST layer and improve the handleability, the NB layer is used.
An adhesive layer can also be arranged between the layer and the ST layer. As the retardation plate having the adhesive layer, a form of NB layer / adhesive layer / ST layer / adhesive layer / NB layer is preferably exemplified. For the adhesive layer, a resin having an affinity for both the norbornene-based resin and the styrene-maleic anhydride copolymer resin can be used. The glass transition point of the resin used for the adhesive layer is a resin lower by 5 ° C. or lower (more preferably 10 ° C. or lower) than the respective glass transition points of the norbornene-based resin and the styrene-maleic anhydride resin. Is preferred. However, it is not limited to this. The product of the birefringence and the thickness of the adhesive layer is preferably small.

In the retardation plate of the present invention, the ratio of the thickness of the NB layer to the thickness of the ST layer is preferably 3: 1 to 1: 1. The thickness of the entire retardation plate is preferably, for example, 50 μm or more and 120 μm or less when a quarter wavelength plate is used. When the NB layer and the ST layer each have two or more layers, the ratio of the total thickness of all NB layers included in the retardation plate to the total thickness of all ST layers is 3: 1 to 1: 1.
Preferably it is 1: 1.

The retardation plate of the present invention coextrudes a norbornene-based resin in a molten state containing an inorganic filler and a styrene-maleic anhydride copolymer resin in a molten state, and the inorganic filler resin and the norbornene-based resin are co-extruded. It can be produced from a co-extrusion step of forming a laminate of a layer containing the styrene-maleic anhydride copolymer resin and a layer containing the styrene-maleic anhydride copolymer resin, and a stretching step of stretching the laminate to adjust retardation.

In the co-extrusion step, the norbornene-based resin containing the inorganic filler and plasticized, the styrene-maleic anhydride copolymer resin and, if desired, the resin for the adhesive layer are guided into the extrusion die, and the inside of the die or It can be carried out by bringing each resin into contact with the opening of the die and extruding it into an integrated laminate.
As the die, a T die can be used, and an internal shape thereof is not particularly limited, and dies having various shapes can be used. The extruded laminate in the molten state is
The thickness of the stacked body can be adjusted by stretching the roll and moving the roll so as to follow the rotation of the roll. Thereafter, the laminate may be subjected to a stretching step, or once the laminate is wound into a roll,
It can be subjected to a stretching step. When the laminate has the adhesive layer, the adhesive layer is preferably formed by co-extrusion.

The inorganic filler can be contained in the norbornene-based resin in a monodispersed state by mixing and stirring with the norbornene-based resin under heating. The mixing and stirring of the inorganic filler and the norbornene-based resin can be performed using a twin-screw kneading extruder, a Banbury mixer, or the like.

The stretching step can be performed using various stretching machines. For example, longitudinal uniaxial stretching that extends in the mechanical flow direction, tenter stretching that extends in the direction perpendicular to the mechanical flow direction, and the like can be preferably used.In addition, it is possible to impart biaxiality for controlling the thickness direction. is there. The stretching ratio in the stretching step is a retardation (Re).
, The thickness of the laminate before stretching, the stretching temperature, and the stretching speed may be appropriately determined, and are generally from 1.1 to 3.0. In the case where longitudinal uniaxial stretching is performed in the stretching step, a stretching process can be performed by using at least one set of nip rolls and making a difference in peripheral speed between the rolls.

In the stretching step, the stretching apparatus is preferably provided with a heating means in order to carry out the stretching at a predetermined stretching temperature. As a configuration of the stretching apparatus provided with the heating means, for example, a configuration in which a heater is provided at a core portion of a stretching roll can be given. In addition, there is a configuration in which a heating device (for example, an infrared heating device) is disposed near the stretching roll, and the laminate is heated during stretching. Further, there is a configuration in which the entire stretching apparatus is housed inside the heating apparatus to perform stretching.

In order for the retardation plate of the present invention to have characteristics as a broadband retardation plate, Re (450) <Re (55).
0) <Re (650) must be satisfied. The retardation of each wavelength can be adjusted to a value satisfying the above relational expression by the following operation. The melt softening temperatures of the styrene-maleic anhydride copolymer resin and the norbornene resin are Ts and Tn, respectively. Ts <
In the case of Tn, when the laminate of the NB layer and the ST layer is stretched at a temperature close to Tn, the molecules in the ST layer are easily relaxed in orientation, the molecules in the ST layer are hardly oriented, and the ST layer has birefringence. do not do. As a result, the stretched film of the laminate in which the NB layer and the ST layer are laminated has substantially the same wavelength dispersion as that of the NB layer alone. As the stretching temperature is lowered, the molecules in the ST layer become oriented, and the ST layer becomes birefringent. Since the retardation of the ST layer is negative, the positive retardation of the layer made of the norbornene resin decreases. The reduction rate of the retardation is that the retardation is greatly reduced on the short wavelength side due to the wavelength dispersion of the ST layer, and as a result, Re (450) <Re
(550) <Re (650) is obtained. By controlling the stretching temperature, Re over the entire visible light wavelength range is obtained.
(Λ) / λ is constant, and a retardation plate exhibiting uniform retardation characteristics over a wide band can be obtained. Further, by adjusting the stretching ratio, it is possible to obtain characteristics of a wide band of １ ／ wavelength and 波長 wavelength.

In the stretching step, in order to facilitate the adjustment of the retardation, the lower glass transition point of the norbornene resin and the styrene-maleic anhydride copolymer resin is set to Tg (L) ° C. When (T
g (L) −20) ≦ T ≦ (Tg (L) +10).

When the stretching temperature varies in the stretching step, the wavelength dispersion of Re of the retardation plate produced also varies. Therefore, from the viewpoint of production stability, it is preferable to suppress the fluctuation of the stretching temperature, and it is preferable to control the fluctuation of the stretching temperature to be within a range of ± 1 ° C. Further, even if the stretching temperature and the thickness ratio of each layer are optimized before manufacturing, the wavelength dispersion of the retardation is remarkable from an ideal value due to unexpected disturbances such as a change in the environment during manufacturing and a change in the blending of raw materials. There is also a situation where it deviates. Such a situation can be prevented by feedback control of the stretching temperature. For example, for a stretched film after stretching, its retardation is measured at least at two wavelengths, the wavelength dispersion of the retardation is tracked, and the temperature of a heating means such as a hot roll is fed back according to the deviation from a target value. It is preferable to control.

After the stretching step, the stretched film travels in a production line, is wound into a roll, and is stored and transported. Since the NB layer contains an inorganic filler, it is excellent in slipperiness. Therefore, by running and winding the stretched film with the NB layer as the lowermost layer, it is possible to prevent troubles such as running failure and wrinkles from occurring, and to form the retardation plate with high stability. Can be manufactured.

[0033]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. “Zeonor 1420” (manufactured by Zeon Corporation, Tg = 136 ° C.) as a norbornene-based resin, “Dailac D332” (manufactured by Nova Chemical Co., Tg = 131 ° C.) as a styrene-maleic anhydride copolymer resin, and oxidation as an inorganic filler Using silicon particles, a quarter-wave plate consisting of an NB layer / ST layer / NB layer was produced. The device shown in FIG. 1 was used for fabrication.

The production apparatus 10 shown in FIG. 1 has two extruders 1
2 and 14 are integrally combined with the extrusion die 16. The resin hopper extruded from the extruders 12 and 14 into the extrusion die 16 becomes a laminated film 18 and is extruded from the lower part of the extrusion die 16. The extrusion flow path of the extruder 14 branches into two, and the resin extruded from the branched flow path sandwiches the resin extruded from the extruder 12,
It is configured such that a three-layered laminate can be formed inside the extrusion die 16. The extruded laminated film 18 moves sequentially following the rotation of the rolls 20, 22 and 24.
Since the rolls 20, 22, and 24 are rotating at different peripheral speeds, while moving, the laminated film 18 is cooled and adjusted to a desired thickness. Subsequently, the laminated film 18 is stretched by the nip portions of the heat rolls 26 and 28, and becomes a stretched film 18 'having birefringence. The stretching rolls 26 and 28 have built-in heaters (not shown) at their cores. The temperature of each heater is controlled by the controller 30, and the stretching temperature of the laminated film 18 is kept constant. The controller 30 is configured to control the temperature of the heater based on the retardation (preferably, the retardation at at least two wavelengths) of the stretched film 18 ′ immediately after stretching measured by the optical measuring device 32. I have.

In the extruder 12, “Dilark D332” was stored as a styrene-maleic anhydride copolymer resin, and in the extruder 14, a norbornene-based resin “Zeonor 1420” containing silicon oxide particles dispersed therein was stored. The extruding temperature was 240 ° C. and 245 ° C., respectively. From the lower part of the extrusion die 16, the NB layer / ST
Layer / NB layer is extruded into a three-layer laminate, and the laminate is
Subsequently, it was longitudinally and uniaxially stretched to produce a retardation plate. The stretching ratio was 1.6 times. Throughout the stretching process, the temperature of the stretching rolls 26 and 28 was maintained at a constant temperature.

In this way, retardation plates 1 to 5 were produced using various silicon oxide particles having different number average particle sizes shown in Table 1 below. Further, a retardation plate 6 was produced in the same manner as the retardation plates 1 to 5 except that silicon oxide was not contained in the NB layer.

With respect to the produced retardation plates 1 to 6, 450
In the range of nm to 650 nm, the retardation was measured, and the wavelength dispersion was examined. “KOBRA21ADH” manufactured by Oji Scientific Instruments was used for the measurement. Phase difference plate 1
6 shows a small retardation on the short wavelength side,
Further, it was found that the retardation plate was a broadband retardation plate having a large retardation on a long wavelength side.

Further, with respect to the produced retardation plates 1 to 6, the following items were evaluated for the production stability. Evaluation of Wrinkle Generation For each of the produced retardation films, a film-like retardation film was wound around a roll, and the occurrence of wrinkles was visually evaluated. In the corresponding columns of Table 1 below, “〇” indicates that no wrinkles were generated by roll winding, and “x” indicates that wrinkles were generated by roll winding.

Evaluation of Slip Stick Occurrence For each of the produced retardation plates, two sheet-like retardation plates were superimposed, and the upper sheet was pulled under a load of 10 g / cm ² to check for the occurrence of slip stick. It was visually observed. In the corresponding columns of Table 1 below, “〇” indicates that no slip stick has occurred, and “x” indicates that a slip stick has occurred.

The presence or absence of haze was evaluated for each of the produced retardation plates by visual inspection for the occurrence of haze (cloudiness). In the corresponding column of Table 1 below,
"〇" indicates that no haze had occurred,
"△" indicates that haze occurred slightly, and "x"
Indicates that the generation of haze was significant.

Retardation uniformity For each of the produced retardation plates, a wavelength of 450 nm
Retardation at 70 nm and 650 nm
The measurement was performed at 5 points per 10 cm × 10 cm, and the uniformity of the retardation was evaluated. In the corresponding column of Table 1 below,
"〇" indicates that the retardation was uniform,
“Δ” indicates that the sample was slightly uneven, and “X” indicates that the sample was uneven.

[0042]

[Table 1]

[0043]

As described above, according to the present invention, a uniform phase difference can be provided for a wide band (entire visible light) wavelength, and a phase difference excellent in slipperiness and excellent in manufacturing stability can be obtained. Boards can be provided. Further, according to the present invention, it is possible to provide a method of manufacturing a retardation plate capable of easily and stably producing a retardation plate capable of giving a uniform retardation with respect to a wide band (entire visible light wavelength). it can.

[Brief description of the drawings]

FIG. 1 is a manufacturing apparatus capable of performing a manufacturing method of the present invention used in an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 12, 14 Extruder 16 Extrusion die 18 Laminated film 18 'Stretched film 20, 22, 24 Roll 26, 28 Stretch roll 30 Controller 32 Optical measuring instrument

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 B29L 7:00 9:00 9:00 11:00 11:00 F term (Reference) 2H049 BA06 BA42 BB00 BB03 BB42 BB50 BC03 BC09 BC22 4F210 AA12 AA13E AA20E AB11 AB16 QA03 QG01 QG15 QG18

Claims (4)

[Claims] 1. A retardation plate comprising at least a layer containing a norbornene resin and an inorganic filler, and a layer containing a styrene-maleic anhydride copolymer resin. 2. The inorganic filler has a number average particle size of 0.1.
The retardation plate according to claim 1, wherein the thickness is from 0.5 m to 0.5 m. 3. The retardation plate according to claim 1, wherein the inorganic filler is silicon oxide. 4. A molten norbornene-based resin containing an inorganic filler and a styrene-maleic anhydride copolymer resin in a molten state are co-extruded to form a layer containing the inorganic filler resin and the norbornene-based resin. Production of a retardation plate, comprising: a co-extrusion step of forming a laminate with a layer containing a styrene-maleic anhydride copolymer resin; and a stretching step of stretching the laminate and adjusting retardation. Method.