Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
  • G02B5/3083—Birefringent or phase retarding elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/911—Cooling
  • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
  • B29C48/914—Cooling of flat articles, e.g. using specially adapted supporting means cooling drums
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/918—Thermal treatment of the stream of extruded material, e.g. cooling characterized by differential heating or cooling
  • B29C48/9185—Thermal treatment of the stream of extruded material, e.g. cooling characterized by differential heating or cooling in the direction of the stream of the material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/001—Combinations of extrusion moulding with other shaping operations
  • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
  • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
  • B29C48/23—Articles comprising two or more components, e.g. co-extruded layers the components being layers with means for avoiding adhesion of the layers, e.g. for forming peelable layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
  • B29C48/918—Thermal treatment of the stream of extruded material, e.g. cooling characterized by differential heating or cooling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0037—Other properties
  • B29K2995/0072—Roughness, e.g. anti-slip
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K2323/00—Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
  • C09K2323/03—Viewing layer characterised by chemical composition
  • C09K2323/031—Polarizer or dye

Definitions

• the present invention relates to an optical film suitably used as a variety of films used in a flat panel display, etc. and a raw material film thereof, a production method of the optical film, a protective film of a polarizer composed of the optical film, a polarizing film having the protective film and a phase difference film obtained by performing stretch processing on the optical film.
• phase plate those obtained by stretching a raw material film, such as polycarbonate, giving a certain amount of retardation (also referred to as a phase difference) thereto, and putting two or more of them together are mainly used.
• polarizing plate those obtained by stacking a protective film on an upper surface and a lower surface of a polarizer made by polyvinyl alcohol are mainly used.
• protective film of a polarizer a film obtained by a solution casting method of triacetyl cellulose is mainly used.
• liquid crystal substrate film a film made by polyethylene terephthalate (PET) is mainly used.
• thermoplastic resin films have been required to have highly less optical distortion than those in the conventional ones. It is because when the optical distortion is large, optical defects, such as color unevenness and color absence, etc., allover the flat panel display are caused.
• an amount of retardation has been mainly used.
• an effort to diminish the optical distortion has been made.
• a polarizer protective film having a small and constant retardation amount allover the film has been its index.
• a film made by a solution casting method of triacetyl cellulose (TAC) has been mainly used.
• a solution casting method film of TAC has a relatively small retardation being relatively constant on a film surface.
• a solvent cannot be completely removed at the time of drying after the solution casting, and an emitted solvent gives an adverse effect on an electronic circuit and other parts of the flat panel display to cause an erroneous operation and display defective, etc.
• the Japanese Unexamined Patent Publication No. 2000-273204 discloses a technique of obtaining a sheet having a sheet thickness of 150 to 1000 ⁇ m, in-plane thickness tolerance (Rmax) on the sheet of 15 ⁇ m, roughness of the sheet surface of 0.06 ⁇ m, and a retardation amount (maximum value) on the sheet surface of 15 nm, wherein a retardation amount is relatively constant and relatively small by performing melt extrusion molding on a specific thermoplastic resin under a specific condition.
• An object of the present invention is to provide an optical film having no residual solvent problem, small optical distortion, and no problem of color unevenness and color absence of a liquid display to be obtained when used as a polarizer protective film, a process for producing the optical film, a polarizer protective film configured by the optical film, a polarizing film having the protective film, and a phase difference film with small optical distortion obtained by performing stretch processing on the optical film.
• the present inventors have been committed themselves to study for solving the above problems, consequently, found a technique of making a retardation amount (Re) of an optical film to be obtained to be 10 nm or less by optimizing a melt extrusion condition and an operation condition of cooling drums, and completed as another invention.
• the maximum value of Re becomes 0 nm, it means there is no in-plane optical distortion.
• the maximum value of Re is hardly made to be a certain level or less and there is a limit.
• the present inventors focused not only on the Re value but on the direction of a slow phase axis indicating directivity. At each point, the direction that birefringent becomes maximum is referred to as a slow phase axis, and the direction that the birefringent becomes minimum is referred to as a fast phase axis.
• the present invention was completed based on the knowledge.
• a value of said Re is 10 nm or less.
• thermoplastic resin is an alicyclic structure containing polymer.
• the optical film according to the present invention is preferably produced, for example, by a production method below.
• thermoplastic resin when assuming a resin contact time in said first cooling drum is t 1 (sec.), a temperature when said thermoplastic resin moves away from said first cooling drum is Tp 1 (° C.), and a glass transition temperature of said thermoplastic resin is Tg (° C.), t 1 ⁇ (Tp 1 ⁇ Tg) (unit: sec. ⁇ deg) is made to be ⁇ 50 or higher and 20 or lower to cool said thermoplastic resin.
• a ratio of the R 2 and R 1 is made to be 0.990 or more but less than 1.01 to cool said thermoplastic resin.
• thermoplastic resin moves away from said third cooling drum is Tp 3 (° C.) the Tp 3 is made to be a lower temperature than said Tg by 50 to 100° C. to cool said thermoplastic resin.
• thermoplastic resin moves away from said second cooling drum is Tp 2 (° C.)
• Tp 2 a temperature when said thermoplastic resin moves away from said second cooling drum
• the Tp 2 is made to be a lower temperature than said Tg by 0 to 60° C. to cool said thermoplastic resin.
• a temperature difference of said first cooling drum and said second cooling drum is made to be 20° C. or less to cool said thermoplastic resin.
• a protective film of a polarizer composed of any one of the above optical films.
• a polarizing film having a polarizer and the above protective film stacked on one surface or both surfaces of the polarizer via an adhesive layer.
• phase difference film obtained by performing stretch processing on any one of the above optical films.
• An optical film according to the present invention is configured by a thermoplastic resin film.
• thermoplastic resin film used in the present invention includes at least a thermoplastic resin.
• the thermoplastic resin is not particularly limited as far as it is a resin normally used in producing an optical film.
• polyethylene, polypropylene, an ethylene-propylene copolymer, polystyrene, polyacrylonitrile, an acrylonitrile-styrene copolymer, polyvinylchloride, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polycarbonate and an alicyclic structure containing polymer, etc. may be mentioned.
• polyethylene terephthalate, polybutylene terephthalate and an alicyclic structure containing polymer are preferable and, furthermore, an alicyclic structure containing polymer is particularly preferable because a phase difference is easily made small.
• An alicyclic structure containing polymer is a polymer having a cyclic structure made by carbon-carbon saturated bonds (referred to as “an alicyclic structure” in the present invention) in a repeat unit and, for example, a well-known polymer disclosed in the Japanese Unexamined Patent Publication No. 2002-321302 may be used.
• ring-opened polymers and the hydrogenated products of monomers having a norbornene ring (hereinafter, referred to as “norbornene”), addition polymers of norbornene and the hydrogenated products, addition copolymers of norbornene and a vinyl compound and the hydrogenated products; polymers obtained by hydrogenating aromatic ring of a polymer of polystyrene or other aromatic vinyl hydrocarbon compounds, addition polymers of monomers having an alicyclic structure and a vinyl group, addition polymers of monomers having one or more unsaturated bonds in a carbon-carbon cyclic structure and the hydrogenated products, etc. may be mentioned.
• the thermoplastic resin film used in the present invention may be blended with a variety of compounding agents in accordance with need other than the above thermoplastic resins.
• the compounding agents are not particularly limited. For example, antioxidants, heat stabilizers, light stabilizers, weather resistant stabilizers, ultraviolet ray absorbents, near infrared ray absorbents and other stabilizers; lubricants, plasticizers and other resin improvers; colorants, pigments and other coloring agents; antistatic agents, etc. may be mentioned.
• These compounding agents may be used alone or in combination of two or more kinds.
• a blending quantity of these compounding agents is suitably selected in a range of not hindering the objects of the present invention.
• antioxidants As antioxidants, phenol based antioxidants, phosphorus based antioxidants, and sulfur based antioxidants, etc. may be mentioned. Among these, phenol based antioxidants are preferable and alkyl-substituted phenol based antioxidants are particularly preferable.
• the antioxidants may be used alone or in combination of two or more kinds.
• a blending quantity of antioxidants is suitably selected in a range of not hindering the object of the present invention. Normally, it is 0.001 to 5 parts by weight or so and preferably 0.01 to 1 part by weight with respect to 100 parts by weight of a thermoplastic resin.
• the thermoplastic resin film used in the present invention is produced by performing melt extrusion molding on a molding material including at least a thermoplastic resin. Specifically, first, a molding material is obtained by, for example, mixing a thermoplastic resin and a variety of compounding agents. Next, the molding material is processed to be material pellets suitable for melt extrusion molding. Next, the material pellets are supplied to a melt extruding machine and processed to be a film shape by a melt extrusion method to obtain a thermoplastic resin film.
• the melt extrusion method is a method of heating and melting the material pellets in a cylinder, applying pressure by a screw, and extruding from a die, such as T-die, to be, for example, a film shape.
• thermoplastic resin in a molten state extruded from a die is successively transferred by being circumscribed with a plurality of cooling drums, cooled during that time, then, subjected to necessary steps to be a thermoplastic resin film.
• a width of the thermoplastic resin film after passing through the cooling drums becomes narrower by 2 to 10% due to neck-in comparing with a width of a molten thermoplastic resin immediately after being extruded from a die (same as a width of a lip of the die).
• An end of the thermoplastic resin film in the width direction (hereinafter., also simply referred to as “an end”) has a thicker thickness and larger optical distortion comparing with those on other parts of the film.
• thermoplastic resin film after cooling is for an optical use
• sides thereof are suitably cut off before winding with a wind drum.
• the cut off parts will be called “selvage” in the present invention.
• a part of the cooled thermoplastic resin film yet to be stretched after removing parts to be the selvage will be referred to as “an optical film” in the present invention.
• an optical film As in a protective film and a liquid crystal substrate, etc., when used in a state that a retardation amount is nearly zero, selvage is removed from the thermoplastic resin film yet to be stretched, the optical film is taken out and wound by a wind drum.
• thermoplastic resin film used in the present invention is made to be an optical film, wound to be a roll shape by a wind drum, then, it may be subjected to the next step: a stretch step and an adhesion step to other film, etc. to be value-added.
• An average thickness of the thermoplastic resin film used in the present invention is not particularly limited. To make an optical film taken out from the thermoplastic resin film used in the present invention suitable to a thin flat panel display, etc., it is preferable that an average thickness of the thermoplastic resin film is made to be normally 100 ⁇ m or less, preferably 80 ⁇ m or less, particularly preferably 60 ⁇ m or less. An average thickness of the thermoplastic resin film can be freely set by changing a feeding speed of the material pellets fed to the melt extrusion machine or a rotation speed of the cooling drum or the both, etc.
• thermoplastic resin film used in the present invention satisfies the relation of the formula below on the whole surface of the film when assuming that an angle made by the extruding direction from the melt extrusion machine and a slow phase axis at each point is ⁇ , and a retardation amount at each point is Re. [sin 2 2 ⁇ ] ⁇ [sin 2 ( ⁇ Re/ 550)] ⁇ 4.0 ⁇ 10 ⁇ 5
• the left side of the equation [sin 2 2 ⁇ ] ⁇ [sin 2 ( ⁇ Re/550)] is referred to as a Z value.
• the Z value is an amount corresponding to light leakage caused by retardation of the optical film.
• Linear polarization cannot transmit a polarizer having an absorption axis perpendicular to the light axis.
• the linear polarization transmits the optical film with optical distortion (retardation is not zero)
• a phase delays in the slow phase axis direction of the optical film and a part of the linear polarization can transmit the polarizer.
• color unevenness and color absence are caused in a liquid crystal display using the optical film.
• ⁇ is normally defined as an angle made by a slow phase axis of the film and a light axis of linear polarization.
• ⁇ cannot be defined. Therefore, the present inventors focused on an angle made by the extruding direction of the thermoplastic resin film to be an optical film from the melt extruding machine and a slow phase axis at each point, and used the same as a to define a Z value for an alternative characteristic.
• a maximum value of the Z value can be obtained by measuring over a suitable longitudinal length and measuring points including a part close to an end of the optical film in the width direction.
• the value can be applied as a substitute value.
• the maximum value of the Z value is normally required to be 4.0 ⁇ 10 ⁇ 5 , preferably 3.8 ⁇ 10 ⁇ 5 , and furthermore preferably 3.4 ⁇ 10 ⁇ 5 .
• the Z value is a predetermined value or less, a problem of color unevenness and color absence of a liquid crystal display to be obtained becomes furthermore smaller, and color unevenness and color absence are not visually sensed, so that the display quality is remarkably improved, which is preferable.
• the maximum value of Re is not particularly limited.
• Re over whole surface of the film is preferably 10 nm or less, more preferably 7 nm or less, and furthermore preferably 5 nm or less.
• the Re value is a predetermined value or less, a problem of color unevenness and color absence of a liquid crystal display to be obtained becomes furthermore smaller. Also, color unevenness and color absence after a durability test become furthermore smaller, which is preferable.
• the Re value can be measured by an optical method, such as an ellipsometer.
• an optical method such as an ellipsometer.
• a value obtained by measuring over a suitable longitudinal length and measuring points including a part close to an end of the optical film in the width direction can be applied as a substitute value.
• a method of producing an optical film according to the present invention which satisfies the above conditions is not particularly limited.
• a method of increasing a ratio of the selvage part to the whole film so as to satisfy the above conditions on the whole surface of the film may be mentioned.
• the ratio of the selvage part in this case is normally 3% or more on the right and the left, preferably 5% or more on the right and the left, particularly preferably 7% or more on the right and the left, preferably 40% or less on the right and the left, and particularly preferably 20% or less on the right and the left.
• an optical film of the present invention can be also produced by optimizing the conditions from melt extrusion to winding of the thermoplastic resin film.
• a production method of an optical film according to the present invention includes a step of cooling a molten thermoplastic resin extruded from an extruding machine by making it circumscribed with a first cooling drum, second cooling drum and third cooling drum successively. After that, more preferably, a step of cutting both end portions in the width direction of the cooled thermoplastic resin, and a step of winding the cut thermoplastic resin in a roll shape are included.
• thermoplastic resin is cooled to satisfy preferably at least any one of (1) to (6) below, more preferably at least (1) and (2) below, and particularly preferably all of (1) to (6) below.
• the ratio of the R 3 and R 2 (R 3 /R 2 ) is made to be preferably 0.990 or more but less than 0.999, and more preferably 0.995 or more but less than 0.998 to cool the thermoplastic resin.
• a sheet thermoplastic resin a molten thermoplastic resin extruded from the extruding machine
• the resin temperature is set to be appropriate for a contraction percentage of the resin caused by a temperature decline from around the second cooling drum temperature to around the third cooling drum temperature when transferring the sheet thermoplastic resin from the second cooling drum to the third cooling drum.
• t 1 ⁇ (Tp 1 ⁇ Tg) (unit: sec. ⁇ deg) is made to be preferably ⁇ 50 or higher and 20 or lower, and more preferably ⁇ 40 or higher and +15 or lower to cool the thermoplastic resin.
• the ratio of R 2 and R 1 is preferably set to 0.990 or more but less than 1.01, and more preferably 0.995 or more but less than 1.000 to cool the thermoplastic resin.
• R 2 /R 1 is in the ranges, unevenness of a retardation amount of an optical film to be obtained becomes particularly small, and wrinkles when winding is hard to arise.
• the Tp 3 is set to be lower than the above Tg preferably by 50 to 100° C., and more preferably by 60 to 80° C. to cool the thermoplastic resin.
• Tg a temperature when the thermoplastic resin moves away from the third cooling drum
• the value of the Tp 3 is in the ranges, unevenness of a retardation amount of an optical film to be obtained becomes particularly small, and wrinkles when winding is hard to arise.
• the Tp 2 is set to be lower than the above Tg preferably by 0 to 60° C., and more preferably by 20 to 40° C. to cool the thermoplastic resin.
• the value of the Tp 2 is in the ranges, unevenness of a retardation amount of an optical film to be obtained becomes particularly small, and wrinkles when winding is hard to arise.
• a temperature difference of the first cooling drum and the second cooling drum is made to be preferably 20° C. or less, and more preferably 10° C. or less to cool the thermoplastic resin.
• the optical film according to the present invention is suitable as a protective film of a polarizer of a liquid crystal display.
• the polarizer is obtained by performing stretch processing after doping with iodine on a film made by a vinyl alcohol based polymer, such as polyvinyl alcohol and partially formalization polyvinyl alcohol.
• the optical film of the present invention is staked as a protective film on one surface or both surfaces of the polarizer via a suitable adhesive layer, so that a polarizing film can be obtained.
• a suitable adhesive layer an adhesive agent, etc. wherein a suitable polymer is a base polymer, such as an acryl based polymer, a silicon based polymer, polyester, polyurethane, polyether, and synthetic rubber is used.
• the optical film of the present invention is suitable to a material for producing a polarizing film as a protective film by putting the longitudinal direction together with the longitudinal direction of a long polarizer (referred to as roll-to-roll), and adhering to stack.
• the optical film of the present invention may be furthermore subjected to stretch processing to obtain a phase difference film.
• a phase difference film is a film having a uniform retardation amount of a predetermined value over the whole surface of the phase difference film.
• a tenter is used for performing stretch processing on the optical film of the present invention.
• a film temperature during stretching is, for example, (Tg ⁇ 100)° C. or higher and (Tg +40)° C. or lower.
• Tg is a glass transition temperature of a thermoplastic resin to be a material.
• the stretching ratio depends on a retardation value to be obtained and a thickness of the phase difference film, it is normally 1.05 times or more and 3.0 times or less in the length direction (extruding direction of the thermoplastic resin film) and 0.2 times or less in the width direction, or may be uniaxially stretched in the length direction.
• film thickness was obtained by measuring at every 500 mm over 10 m in the film length direction (20 points) and at 5 points at regular intervals in the width direction (unit: ⁇ m).
• ⁇ and Re (unit:nm) were measured at every 500 mm over 10 m in the film length direction (20 points) and at 5 points at regular intervals in the width direction, a Z value was calculated from the results, and the maximum values of Re and Z value were obtained from the values.
• a measurement wavelength was set to be 550 nm and an incident angle was 0°.
• the whole light transmittance of the optical film was measured by the cross Nicole method based on JIS-K7105, and the average value was obtained (unit: %).
• the value is ideally 0, but preferable when 0.03% or less and defective when 0.04% or more.
• the measurement points in the present invention were at every 500 mm over 10 m in the film length direction and at 10 points at regular intervals in the width direction.
• a polarizing film was peeled from a liquid crystal cell very carefully on a display portion of a cellular phone on market (black and white two-graduation display, reflection type, a display area of 30 mm ⁇ 30 mm), and a polarizing film produced by using the optical film of the present invention was stacked as a protective film on both surfaces of the polarizer to produce a test liquid crystal display.
• a part close to the end of the optical film in the width direction was used as a sample piece, and 10 mass % of polyvinyl alcohol solution was used for stacking.
• the above test liquid crystal display was produced for each experiment example, a variety of characters and still images were displayed, and observed from viewable angles of 0° and 30° to visually observe existence of color unevenness and color absence (a part where a proper color is not displayed). Those at an approvable level were marked ⁇ , defectives were marked x, and those in the middle and not at an approvable level were marked ⁇ .
• a test piece of 1000 mm ⁇ 1000 mm was cut from the obtained optical film, and a high temperature high humidity durability promotion test at 80° C. and 90% RH for 100 hours was conducted thereon. After that, the same color unevenness test as that in (4) was conducted on the taken out test piece.
• cyclohexane and other volatile components were removed from the solution by using a cylinder shaped concentrating and drying device (made by Hitachi Ltd.), a molten hydrogenated polymer was extruded to be a strand shape from an extruding machine, cooled and pelletized to obtain a ring-opened polymer hydrogenate.
• the hydrogenate had a glass transition temperature,Tg of 140° C.
• the obtained pellets are subjected to melt extrusion by a single-screw extrusion molding machine (made by Japan Steel Works Ltd.) having a cylinder inner diameter of 50 mm and a screw L/D value of 28 at a barrel temperature of 260° C., and a sheet molten resin having a width of 650 mm was extruded from a coat hunger die at a die temperature of 260° C.
• the result was made close to a first cooling drum (diameter of 200 mm, temperature T 1 of 135° C., rotation speed R 1 of 14.50 m/min.), immediately transferred by a knife coater from the first cooling drum, then, to a second cooling drum (diameter of 350 mm, temperature T 2 of 125° C., rotation speed R 2 of 14.46 m/min.), then, to a third cooling drum (diameter of 350 mm, temperature T 3 of 80° C., rotation speed R 3 of 14.40 m/min.) successively, and cooling and smoothing of the front and back surfaces by transferring the cool drum surfaces were sequentially performed to obtain a thermoplastic resin film having a width of 550 mm (the neck-in was 50 mm on the right and the left). The thermoplastic resin film passed through an adjustment drum, then, 30 mm was removed as selvage from both ends by a cutter, the result was wound in a roll shape by a wind drum, and a rolled optical film was obtained.
• a contact time t 1 of the sheet thermoplastic resin with the first cooling drum was 3.1 (seconds)
• a resin temperature Tp 1 when moving away from the first cooling drum was 132 (° C.)
• a resin temperature Tp 2 when moving away from the second cooling drum was 119 (° C.)
• a resin temperature Tp 3 when moving away from the third cooling drum was 79 (° C.).
• (R 3 /R 2 ) 0.996
• (R 2 /R 1 ) 0.997
• (t 1 ⁇ (Tp 1 ⁇ Tg)) ⁇ 25 (unit: sec. ⁇ deg).
• the optical films of examples of the present invention have a small Z value comparing with those in the comparative examples, so that they are excellent in the whole light transmittance, polarization degree, color unevenness and color unevenness after a durability test.
• the maximum Re values are smaller than the result of the example 4, so that color unevenness and results of the simple liquid crystal display test are excellent.
• the Z values are smaller than those in the results of the examples 4 and 5, so that color unevenness after a durability test is excellent.
• the optical film obtained in the present invention can be made to be a phase difference film by performing stretch processing thereafter.
• a phase difference film is required to have a predetermined phase difference (retardation value), and the value has to be uniform.
• a test below was conducted.
• An obtained optical film obtained in the experiment was cut out to be a test piece (a width of 100 mm and a length of 150 mm), and the test piece was stretched at 140° C. by 1.1 to 2 times in the longitudinal direction at a speed of 100 mm/min. The stretching ratio was adjusted so that an average retardation becomes 275 ⁇ 10 nm.
• the retardation was measured by the same measurement method as that in the (2), and Re unevenness was obtained by dividing unevenness (difference between the maximum value and the minimum value) by an average value.
• the measurement points were at a center portion in the width direction and 10 points at every 10 mm near the center in the length direction.
• Table 3 shows results of measuring Re unevenness after stretching in respective examples. TABLE 3 Result of Re Unevenness Test after Stretching Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Re Unevenness Test 1.8 2.2 2.1 2.6 2.1 5.8 6.6 after Stretching (%)
• the optical films of the examples of the present invention have smaller Z values than those in the case of comparative examples, so that retardation unevenness after stretch processing is small, which is excellent.
• the optical film of the present invention is suitable as a raw material film of a phase difference film.
• the optical film of the present invention is useful as a variety of optical films of a flat panel display, such as a protective film of a polarizer and a liquid crystal cell substrate film. Also, the optical film of the present invention has small and uniform retardation, and it can be made to be a phase difference film having a predetermined uniform retardation by performing stretch processing after that. Therefore, the optical film of the present invention is useful as a raw material film of a phase difference film, etc.

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• 2003
  • 2003-03-24 WO PCT/JP2003/003506 patent/WO2003081299A1/ja active Application Filing
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  • 2003-03-24 JP JP2003578978A patent/JP4292993B2/ja not_active Expired - Lifetime
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• 2008
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