JP4171168B2 - Production method of retardation plate - Google Patents

Description

【００３２】
次に、これらの延伸フィルムについて、４５０ｎｍ、４８１ｎｍ、５４７ｎｍ、６２９ｎｍ及び６５０ｎｍにおいて、レターデーションを測定し、その波長分散性を調べた。測定には、王子計測社製、「ＫＯＢＲＡ２１ＡＤＨ」を用いた。その結果をグラフ１〜３にまとめた。
【００３３】
グラフ１に示す結果から、延伸温度１２０℃であり、且つＮＢ層とＳＴ層との厚み比が３：１〜１：１の範囲内にある延伸フィルム１〜４のレターデーションは、いずれも理想値に近似した波長分散性を示し、広帯域１／４波長板として実用上充分な光学特性を示すことがわかった。
【００３４】
グラフ２に示す結果から、延伸温度１１５℃であり、且つＮＢ層とＳＴ層との厚み比が３：１〜１：１の範囲内にある延伸フィルム５〜７のレターデーションは、いずれも理想値に近似した波長分散性を示し、広帯域１／４波長板として実用上充分な光学特性を示すことがわかった。一方、厚み比が３：１〜１：１を超えた延伸フィルム８のレターデーションは、理想値からはずれた波長分散性を示していた。
【００３５】
グラフ３に示す結果から、ＮＢ層とＳＴ層との厚み比が１．９３：１であり、且つ「ダイラーク Ｄ３３２」のガラス転移点Ｔｇ（Ｌ）℃（即ち１３１℃）と（Ｔｇ（Ｌ）−２０）≦Ｔ≦（Ｔｇ（Ｌ）＋１０）の関係を満たすＴ℃で延伸した延伸フィルム９〜１１のレターデーションは、いずれも理想値に近似した波長分散性を示し、広帯域１／４波長板として実用上充分な光学特性を示すことがわかった。
【００３６】
【発明の効果】
以上説明した様に、本発明によると、可視光全域の入射光に対して均一な位相差特性を与え得る広帯域位相差板を簡易に且つ安定的に製造可能な位相差板の製造方法を提供することができる。
【図面の簡単な説明】
【図１】 本発明の位相差板の製造方法に利用可能な製造装置の一例を概略的に示した斜視図である。
【図２】 実施例で作製した延伸フィルムのレターデーションの波長分散性を示すグラフである。
【図３】 実施例で作製した延伸フィルムのレターデーションの波長分散性を示すグラフである。
【図４】 実施例で作製した延伸フィルムのレターデーションの波長分散性を示すグラフである。
【符号の説明】
１０ 製造装置
１２、１４ 押出し機
１６ 押出しダイ
１８ 積層フィルム
１８’ 延伸フィルム
２０、２２、２４ ロール
２６、２８ 延伸ロール
３０ コントローラ
３２ 光学測定器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel method for producing a retardation plate comprising a stretched film.
[0002]
[Prior art]
As a retardation plate, a quarter wavelength plate having a retardation (Re) of ¼ of a wavelength and a ½ wavelength plate having a Re of ½ of a wavelength are known. The quarter-wave plate has various uses such as a reflection type liquid crystal display device, an optical disk pickup and an antiglare film. On the other hand, the half-wave plate has various uses such as being used in a liquid crystal projector. The quarter-wave plate and the half-wave plate are desired to exhibit their functions sufficiently for all incident light in the visible light region in various applications. As a broadband retardation plate capable of sufficiently exhibiting the function with respect to incident light in the entire visible light region, for example, JP-A-5-27118, JP-A-5-100114, JP-A-10-68816 And those obtained by laminating two polymer films having different optical anisotropies, such as JP-A-10-90521.
[0003]
However, in the conventional laminated phase difference plate, for production thereof, two kinds of chips are formed by cutting a stretched birefringent film stretched in one direction in directions that make different angles with respect to the stretch direction, This chip needs to be bonded and laminated with an adhesive material. In addition, when bonding two chips, not only the cost increase due to adhesive material coating, chip formation, and bonding, but also the effect on performance, such as the performance degradation due to the angle shift accompanying chip bonding It cannot be ignored. Moreover, in the multilayered phase difference plate formed by chip bonding, performance degradation due to an increase in thickness may be a problem.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems, and the retardation (Re) at an arbitrary wavelength λ ₁ and λ ₂ (λ ₁ <λ ₂ ) of wavelengths from 400 nm to 700 nm is Re (λ ₁ ) <Re Manufacturing that can easily and stably produce a broadband retardation plate that satisfies (λ ₂ ), provides uniform retardation characteristics to incident light in the wavelength range, and has uniform Re in the width direction and longitudinal direction It is an object to provide a method.
[0005]
[Means for Solving the Problems]
Means for solving the above problems are as follows. That is,
<1> Stretching step of stretching a laminate having at least one layer containing a norbornene-based resin (NB layer) and at least one layer containing a styrene-maleic anhydride copolymer resin (ST layer) to obtain a stretched film The glass transition point at which the stretching temperature T ° C. in the stretching step is lower than the glass transition point of the norbornene-based resin and the styrene-maleic anhydride copolymer resin is expressed as Tg (L ) ° C., (Tg (L) −20) ≦ T ≦ (Tg (L) +10), and the ratio of the thickness of the NB layer and ST layer of the stretched film is 3: 1 to 1: 1 is a method of manufacturing a retardation plate, wherein
[0006]
<2> The method for producing a retardation plate according to <1>, further comprising a coextrusion step in which at least a norbornene-based resin and a styrene-maleic anhydride copolymer resin are coextruded to form the laminate.
<3> The method for producing a retardation plate according to <1> or <2>, wherein a difference between a glass transition point of the norbornene-based resin and a glass transition point of the styrene-maleic anhydride copolymer resin is 10 ° C. or less. It is.
<4> The method for producing a retardation plate according to any one of <1> to <3>, wherein the laminate is a laminate in which the NB layer, the ST layer, and the NB layer are sequentially arranged.
[0007]
<5> The method for producing a retardation plate according to any one of <1> to <4>, wherein the laminate is a laminate in which an adhesive layer is disposed between the NB layer and the ST layer. is there.
<6> The retardation according to any one of <2> to <5>, wherein in the coextrusion step, the material contained in the adhesive layer is coextruded with a norbornene-based resin and a styrene-maleic anhydride copolymer resin. It is a manufacturing method of a board.
<7> In the stretching step, the retardation of the stretched film at two or more wavelengths selected from the visible light wavelength range is measured, and the stretching temperature is controlled based on the measured retardation value. 6> The method for producing a retardation plate according to any one of the above items.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The method for producing a retardation plate of the present invention comprises stretching a laminate having at least one layer containing a norbornene resin (NB layer) and at least one layer containing a styrene-maleic anhydride copolymer resin (ST layer). And a stretching process for obtaining a stretched film. The norbornene-based resin is a resin having a characteristic of exhibiting optically positive uniaxiality and a positive intrinsic birefringence value. That is, when light is incident on a layer in which the molecules of the norbornene-based resin have a uniaxial orientation, the refractive index of light in the orientation direction is greater than the refractive index of light in the direction perpendicular to the orientation direction. growing. On the other hand, the styrene-maleic anhydride copolymer resin is a resin having a characteristic of negative optically uniaxial property and a negative intrinsic birefringence value. That is, when light is incident on a layer formed by uniaxial orientation of molecules of the styrene-maleic anhydride copolymer resin, the refractive index of light in the orientation direction is light in a direction perpendicular to the orientation direction. Less than the refractive index.
[0009]
In the production method of the present invention, the laminate of the NB layer and the ST layer is stretched in a predetermined temperature range, and birefringence is expressed in the NB layer and the ST layer, respectively. Since the NB layer and the ST layer are stretched in the same direction, their slow axes are orthogonal to each other, and the wavelength dispersion of the retardation of each layer cancels each other. The retardation wavelength dispersion of the stretched film obtained by the stretching treatment is such that the retardation wavelength dispersion of each of the NB layer and the ST layer is offset. Furthermore, in the manufacturing method of the present invention, by adjusting the thickness ratio of the NB layer and the ST layer within a predetermined range, the degree to which the NB layer and the ST layer contribute to the retardation of the stretched film is adjusted. Yes. As a result, the retardation on the short wavelength side is small and the retardation on the long wavelength side can be increased with respect to light in a wide band (wavelength 400 to 700 nm) (that is, Re (λ ₁ ) <Re (λ ₂ ) (λ ₁ <λ ₂ ), and a retardation plate can be produced that gives uniform retardation characteristics to light having a broadband wavelength in the above range.
[0010]
As the norbornene-based resin, “Arton” made by Nippon Synthetic Rubber, “Zeonex” and “Zeonor” made by Nippon Zeon, “APO” made by Mitsui Petrochemical, etc. are preferable. Further, as the styrene-maleic anhydride copolymer resin, “DAILARK D332” manufactured by Nova Chemical Co., etc. is preferable.
[0011]
The stretching step causes the NB layer and the ST layer to exhibit birefringence, but if the stretching temperature in the stretching step is too high, the birefringence of the NB layer and the ST layer tends to be difficult to develop. . On the other hand, when the stretching temperature is too low, uneven expression of birefringence tends to occur. Moreover, the ratio of the thickness of the NB layer and the ST layer in the stretched film obtained by the stretching treatment also affects the degree of contribution to the retardation of the stretched film. As a result of intensive studies by the inventor, when the stretching temperature T ° C is Tg (L) ° C, the glass transition point of the norbornene-based resin and the styrene-maleic anhydride copolymer resin is a low glass transition point. When (Tg (L) -20) ≦ T ≦ (Tg (L) +10) and the ratio of the thickness of the NB layer and the ST layer in the stretched film is 3: 1 to 1: 1, It is preferable because the NB layer and the ST layer can exhibit a sufficient and uniform birefringence and can provide a broadband retardation plate capable of giving a uniform retardation characteristic to light having a broadband wavelength. Further, when the stretching step is carried out at a ratio of the stretching temperature in the above range and the thickness in the above range, the stretching temperature and / or the thickness ratio may be reduced even when the wavelength dispersion of retardation of the obtained stretched film deviates from the ideal value. By fine adjustment, it can be brought close to the ideal value, and the manufacturing stability is also excellent.
[0012]
In particular, the difference between the glass transition point of the norbornene resin and the glass transition point of the styrene-maleic anhydride copolymer resin is preferably small, preferably 10 ° C. or less, and preferably 5 ° C. or less. Is more preferred and is ideally 0 ° C., ie identical. As a preferable combination in which the difference between the glass transition points is within the above range, “Zeonor 1420” (manufactured by Nippon Zeon Co., Ltd.) as the norbornene-based resin and “Dilark D332” (Tg = 131 ° C.).
[0013]
The ratio of the thickness of the NB layer and the ST layer after the stretching treatment is 3: 1 to 1: 1, more preferably 2: 1 to 1.5: 1. The thickness ratio of each layer in the stretched film is before stretching. It is substantially determined by the thickness ratio of each layer in the laminate.
[0014]
The laminate may include two or more layers of the NB layer and the ST layer. In particular, since the NB layer has a higher strength than the ST layer, when the stacked body is configured by sequentially arranging the NB layer, the ST layer, and the NB layer, the handleability and durability as a retardation plate are achieved. This is preferable because the property is improved. When the laminate includes two or more NB layers and ST layers, it is preferable that the materials contained in the NB layer and the materials contained in the ST layer are the same.
In the laminate, when there are two or more NB layers and ST layers, the ratio between the total thickness of all NB layers included in the laminate and the total thickness of all ST layers. Is preferably 3: 1 to 1: 1.
[0015]
Further, in order to improve the adhesion between the NB layer and the ST layer and improve the handleability, an adhesive layer can be disposed between the NB layer and the ST layer. As a preferable form of the laminate having the adhesive layer, a form of NB layer / adhesive layer / ST layer / adhesive layer / NB layer may be mentioned. For the adhesive layer, a resin having affinity with 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 having a lower temperature of 5 ° C. or less (more preferably 10 ° C. or less) compared to the glass transition points of the norbornene resin and the styrene-maleic anhydride resin. Is preferred. However, it is not limited to this. The product of birefringence and thickness of the adhesive layer is preferably small.
[0016]
The stretching step can be performed using various stretching machines. For example, longitudinal uniaxial stretching that stretches in the mechanical flow direction and tenter stretching that stretches in the direction perpendicular to the mechanical flow direction can be suitably used, and biaxiality can also be imparted for thickness direction control. is there. The stretching ratio in the stretching step may be appropriately determined according to the Re target, the thickness of the laminate before stretching, the stretching temperature, and the stretching speed, and is generally 1.1 or more and 3.0 or less. In the stretching step, when the longitudinal uniaxial stretching is performed, the stretching process can be performed by using at least one pair of nip rolls and making a difference in peripheral speed between the rolls.
[0017]
In the stretching step, in order to perform stretching at a predetermined stretching temperature, the stretching apparatus preferably includes a heating unit. As a structure of the extending | stretching apparatus provided with the said heating means, the structure provided with the heater at the core part of the extending | stretching roll is mentioned, for example. Moreover, the structure which arrange | positions a heating apparatus (for example, infrared heating apparatus) in the vicinity of an extending | stretching roll, and heats a laminated body at the time of extending | stretching is mentioned. Furthermore, the structure which implements extending | stretching by storing the whole extending | stretching apparatus inside a heating apparatus is mentioned.
[0018]
When the stretching temperature in the stretching process varies, the wavelength dispersion of retardation exhibited by the produced retardation plate also varies. Therefore, from the viewpoint of production stability, it is preferable to keep the fluctuation of the stretching temperature low, and it is preferable to control the fluctuation of the stretching temperature to be within a range of ± 1 ° C. In addition, even if the stretching temperature and the thickness ratio of each layer are optimized before production, the retardation wavelength dispersion from the ideal value due to unexpected disturbances such as changes in the environment during production and changes in the composition of raw materials. There will also be situations where it will deviate significantly. Such a situation can be prevented by feedback control of the stretching temperature. For example, for a stretched film after stretching, the retardation is measured with at least two wavelengths, the wavelength dispersion of the retardation is tracked, and the temperature of the heating means such as a hot roll is fed back according to the deviation from the target value. It is preferable to control.
[0019]
The stretched film obtained by the stretching step has different optical characteristics depending on its thickness. For example, when a quarter wave plate is used, the thickness of the stretched film is preferably 50 μm or more and 120 μm or less.
[0020]
The said laminated body provided to the said extending process can be produced by various methods. . Among these, it is preferable to form by coextrusion of at least a norbornene resin and a styrene-maleic anhydride copolymer resin. It is preferable to produce the laminate by a co-extrusion process because the production of the laminate is facilitated, the transition from the co-extrusion process to the stretching process can be automated, and the production process can be further simplified. That is, it is preferable that the method for producing a retardation plate of the present invention includes at least a coextrusion step in which a norbornene resin and a styrene-maleic anhydride copolymer resin are coextruded and the stretching step.
In addition, when the said laminated body has the said contact bonding layer, it is preferable to form the said contact bonding layer also by coextrusion.
[0021]
In the coextrusion step, the plasticized norbornene-based resin, the styrene-maleic anhydride copolymer resin, and, if necessary, the adhesive layer resin are introduced into the extrusion die, and each resin is brought into contact with the inside of the die or the opening of the die. Then, it can be carried out by extruding as an integrated laminate. As the die, a T-die can be used, and the internal shape is not particularly limited, and dies having various shapes can be used. The thickness of the laminated body can be adjusted by stretching the extruded laminated body on a plurality of rolls and moving the laminated body following the rotation of the rolls. Thereafter, the laminate may be subjected to a stretching step, or the laminate may be once wound into a roll and then subjected to a stretching step.
[0022]
When the laminate is produced by a co-extrusion step, the thickness ratio of each layer in the stretched film can be optimized by controlling the extrusion amount of each resin per unit time.
[0023]
FIG. 1 shows a schematic perspective view of an example of a manufacturing apparatus capable of performing the retardation plate manufacturing method according to the present invention.
In the manufacturing apparatus 10 of FIG. 1, two extruders 12 and 14 are integrally combined with an extrusion die 16. The resin hopper extruded into the extrusion die 16 from the extruders 12 and 14 becomes a laminated film 18 and is extruded from the lower part of the extrusion die 16. In the case of forming a laminate of three or more layers, an extruder leading to the extrusion die 16 may be further added in addition to the extruders 12 and 14. Further, for example, when forming a laminate having a three-layer structure of NB layer / ST layer / NB layer, the extrusion flow path from the extruder for extruding the norbornene resin is branched, and the inside of the extrusion die 16 You may comprise so that a three-layer laminated body may be formed.
[0024]
The extruded laminated film 18 sequentially moves following the rotation of the rolls 20, 22, and 24. Since the rolls 20, 22 and 24 rotate at mutually different peripheral speeds, the laminated film 18 is cooled and adjusted to a desired thickness while moving. Subsequently, the laminated film 18 is stretched by the nip portion of the heat rolls 26 and 28 to become a stretched film 18 ′ exhibiting birefringence. The drawing rolls 26 and 28 have a heater (not shown) built in the core. The temperature of each heater is controlled by the controller 30, and the stretching temperature of the laminated film 18 is kept constant.
[0025]
The optical measuring instrument 32 measures the retardation (preferably retardation at least two wavelengths) of the stretched film 18 ′ immediately after stretching. The detection data of the measurement wavelength and retardation are input from the optical measuring device 32 to the controller 30. The controller 30 is preliminarily inputted with ideal wavelength-retardation correlation standard data, and a program is inputted so as to raise and lower the stretching temperature based on the deviation of the input data from the standard data. In this way, when retardation at two or more wavelengths of the stretched film is measured and the stretching temperature is controlled based on this data, a wave plate with uniform wavelength dispersion can be stably produced.
[0026]
Since the thickness ratio of each layer also affects the wavelength dispersion of retardation, the extrusion amount of each resin per unit time from the extruder is controlled based on the measured value of the retardation of the stretched film on the line. May be.
[0027]
Thereafter, the stretched film 18 ′ is cut into a desired size by a cutting machine (not shown) disposed further downstream, and used for various applications as a retardation plate. Further, for example, the stretched film 18 ′ can be temporarily wound into a roll shape, and temporarily stored and transported.
[0028]
The retardation plate manufactured by the manufacturing method of the present invention can be used for various applications as a half-wave plate, a quarter-wave plate, and the like, depending on its optical characteristics.
[0029]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
NB layer using “Zeonor 1420” (manufactured by ZEON Corporation, Tg = 136 ° C.) as the norbornene-based resin, and “DILARK D332” (manufactured by Nova Chemical Co., Tg = 131 ° C.) as the styrene-maleic anhydride copolymer resin. A quarter-wave plate composed of / ST layer / NB layer was produced. An apparatus having the same configuration as that shown in FIG. 1 was used for the production. However, the extrusion flow path of the extruder 14 is branched into two, and the resin extruded from the branched flow path sandwiches the resin extruded from the extruder 12 and is laminated in a three-layer configuration inside the extrusion die 16. A device configured to form a body was used.
[0030]
“Dylark D332” was stored in the extruder 12 and “Zeonor 1420” was stored in the extruder 14, and the extrusion temperatures were 240 ° C. and 245 ° C., respectively. From the lower part of the extrusion die 16, a laminate having a three-layer structure of NB layer / ST layer / NB layer was extruded, and the laminate was continuously stretched in the longitudinal direction. The draw ratio was 1.6 times. Throughout the stretching process, the temperature of the stretching rolls 26 and 28 was maintained at a constant temperature. Stretched films 1 to 11 shown in Table 1 below were produced by changing the stretching temperature and / or the extrusion amount of each resin per unit time. In addition, the thickness of NB layer in following Table 1 is the sum total of the thickness of two layers. The same applies to the thickness ratio.
[0031]
[Table 1]

[0032]
Next, with respect to these stretched films, retardation was measured at 450 nm, 481 nm, 547 nm, 629 nm, and 650 nm, and the wavelength dispersibility thereof was examined. For the measurement, “KOBRA21ADH” manufactured by Oji Scientific Instruments was used. The results are summarized in graphs 1 to 3.
[0033]
From the results shown in graph 1, the retardation of stretched films 1 to 4 having a stretching temperature of 120 ° C. and a thickness ratio of the NB layer to the ST layer in the range of 3: 1 to 1: 1 is ideal for all. It was found that the wavelength dispersibility approximated to the value was exhibited, and the optical characteristics sufficient for practical use as a broadband quarter-wave plate were exhibited.
[0034]
From the results shown in Graph 2, the retardation of stretched films 5-7 having a stretching temperature of 115 ° C. and a thickness ratio of the NB layer to the ST layer in the range of 3: 1 to 1: 1 is ideal. It was found that the wavelength dispersibility approximated to the value was exhibited, and the optical characteristics sufficient for practical use as a broadband quarter-wave plate were exhibited. On the other hand, the retardation of the stretched film 8 having a thickness ratio exceeding 3: 1 to 1: 1 showed wavelength dispersibility deviating from the ideal value.
[0035]
From the results shown in Graph 3, the thickness ratio of the NB layer to the ST layer is 1.93: 1, and the glass transition point Tg (L) ° C. (that is, 131 ° C.) and (Tg (L) of “Dilark D332”. The retardation of the stretched films 9 to 11 stretched at T ° C. satisfying the relationship of −20) ≦ T ≦ (Tg (L) +10) shows wavelength dispersion close to the ideal value, and has a broadband quarter wavelength. It was found that the optical properties sufficient for practical use as a plate were exhibited.
[0036]
【The invention's effect】
As described above, according to the present invention, there is provided a method of manufacturing a retardation plate that can easily and stably manufacture a broadband retardation plate capable of giving uniform retardation characteristics to incident light in the entire visible light region. can do.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing an example of a manufacturing apparatus that can be used in a method of manufacturing a retardation plate according to the present invention.
FIG. 2 is a graph showing the wavelength dispersion of retardation of a stretched film produced in an example.
FIG. 3 is a graph showing the wavelength dispersion of retardation of a stretched film prepared in an example.
FIG. 4 is a graph showing the wavelength dispersion of retardation of a stretched film produced in an example.
[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 device

Claims (7)

It has a stretching step of stretching a laminate having at least one layer containing a norbornene resin (NB layer) and at least one layer containing a styrene-maleic anhydride copolymer resin (ST layer) to obtain a stretched film. It is a manufacturing method of a phase difference plate, Comprising: The glass transition point in which the extending | stretching temperature T degreeC in the said extending | stretching process is low among the glass transition points of the said norbornene-type resin and the said styrene-maleic anhydride copolymer resin is Tg (L) degreeC. (Tg (L) -20) ≦ T ≦ (Tg (L) +10), and the ratio of the thickness of the NB layer and the ST layer of the stretched film is 3: 1 to 1: 1. A method for producing a retardation film, comprising: The method for producing a retardation plate according to claim 1, further comprising a co-extrusion step in which at least a norbornene-based resin and a styrene-maleic anhydride copolymer resin are co-extruded to form the laminate. The method for producing a retardation plate according to claim 1 or 2, wherein a difference between a glass transition point of the norbornene resin and a glass transition point of the styrene-maleic anhydride copolymer resin is 10 ° C or less. The method for producing a retardation plate according to any one of claims 1 to 3, wherein the laminate is a laminate in which the NB layer, the ST layer, and the NB layer are sequentially arranged. The method for manufacturing a retardation plate according to any one of claims 1 to 4, wherein the laminate is a laminate in which an adhesive layer is disposed between the NB layer and the ST layer. 6. The production of a retardation plate according to claim 2, wherein in the co-extrusion step, a material contained in the adhesive layer is co-extruded together with a norbornene resin and a styrene-maleic anhydride copolymer resin. Method. 7. The stretching process according to claim 1, wherein in the stretching step, the retardation of the stretched film at two or more wavelengths selected from the visible light wavelength region is measured, and the stretching temperature is controlled based on the measured retardation value. A method for producing the retardation plate according to claim 1.

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