JP2008080552A - Apparatus for manufacturing optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing an optical film used for preparing a protective film for a polarizing sheet used for various displaying apparatuses such as a liquid crystal displaying apparatus (LCD) and an organic EL (electroluminescence) display, in more detail, the protective film for the polarizing sheet with a brightness improving function, the polarizing plate equipped with a film in which the brightness improving function and a polarizing sheet protective function are integrated on at least one face, and the liquid crystal displaying apparatus using it. <P>SOLUTION: The apparatus for manufacturing the optical film by a solution casting film manufacturing method casts a dope comprising a thermoplastic resin, an organic solvent and indefinite particles on a substrate through a manifold part and a slit part. In this apparatus, the cross-sectional area at an arbitrary place of the manifold part to the cross-sectional area of the inlet of the manifold of a casting die is 0.1-300% of the cross-sectional area of the inlet of the manifold part over the whole length of the manifold part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for producing an optical film used in various display devices such as a liquid crystal display device (LCD) or an organic EL (electroluminescence) display, and in particular, a protective film for a polarizing plate used in these display devices, And a polarizing plate using the same, and a liquid crystal display device, more specifically, a protective film for a polarizing plate with a brightness enhancement function, a polarizing plate provided with a film on which at least one brightness enhancement function and a polarizing plate protection function are integrated, The present invention also relates to an optical film manufacturing apparatus used for manufacturing a liquid crystal display device using the same.

  In general, natural light or light from an artificial light source is non-polarized light (random polarized light), but by using a polarizing plate, a polarized light (linearly polarized light, circularly polarized light, elliptically polarized light) component can be extracted. It can be said that the currently widely used liquid crystal display device is an apparatus that displays an image using the property of polarized light by incorporating the polarizing plate.

  Generally as a polarizing film used for a polarizing plate, the light absorption type polarizing film which consists of a polyvinyl-alcohol-type film is used. A polyvinyl alcohol polarizing film is produced by stretching a polyvinyl alcohol film and adsorbing iodine or a dichroic dye.

  The transmission axis (polarization axis) of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The light-absorbing polarizing film transmits only the polarization component parallel to the polarization axis and absorbs the polarization component in the direction orthogonal thereto. Therefore, the light utilization efficiency is theoretically 50% or less (actually lower value) or less.

As a technique for suppressing loss due to optical absorption of a polarizing plate, light utilization efficiency improving means of a light source using polarization scattering anisotropy in a transmissive liquid crystal display device is known and widely used as a brightness enhancement film. A polarizing film having polarization scattering anisotropy utilizes a property that a film obtained by stretching a composite of a polymer and a liquid crystal becomes an optically anisotropic scattering body (Liquid Crystals, 1993, 15 No. 3, described in pages 395 to 407), and transmits only the polarization component parallel to the polarization axis, similar to the light absorption polarizing film. On the other hand, a polarizing film having polarization scattering anisotropy scatters forward or backward without absorbing a polarization component orthogonal to the polarization axis, and improves the light use efficiency of the polarizing film.
JP-A-9-274108 Here, in Patent Documents 1 and 2, a method for producing an anisotropic scatterer by blending a positive intrinsic birefringent polymer and a negative intrinsic birefringent polymer and uniaxially stretching them is described in JP-A-11-174231. Has been proposed.

  However, in the production methods by stretching described in Patent Documents 1 and 2, in order to obtain a high orientation in order to obtain a sufficient brightness enhancement effect, a very large stretching ratio is required, and applicable polymer types are limited. In addition, there is a problem that the birefringence of the polymer itself which is unnecessary as a display member is generated due to excessive stretching.

  On the other hand, the polarizing plate is bonded to both sides of the polarizing film to protect the shape and prevent physical damage and durability based on environmental changes based on light, heat, oxygen, moisture, etc. Protection.

As a protective film for polarizing plate, a film composed of cellulose ester is generally used, but the film has birefringence, and a retardation value is generally present in the film plane or in the thickness direction of the film. To do.
JP, 2003-43261, A Here, as described in patent documents 3, the protective film which has the above-mentioned retardation value in the film plane or the thickness direction of a film is pasted on both sides of a dichroic polarizing film, and polarization is carried out. A configuration in which a plate is formed and a film (brightness enhancement film) having polarization scattering anisotropy is further bonded to one surface of the polarizing plate is common.

  When a film having polarization scattering anisotropy and a dichroic polarizing film are arranged as described above, and a film having birefringence exists between them, this acts as a function as a retardation film. Become.

  As a result, if a film having birefringence exists between the two, a change in transmittance and color will be given in the optical characteristics of the display, which will cause unnecessary image display. Therefore, it has been desired that no film exhibiting birefringence exists between the film having polarization scattering anisotropy and the dichroic polarizing film.

Further, Patent Document 3 discloses a method of providing a liquid crystal compound on a transparent support as a polarization scattering anisotropic layer by coating. However, this method has a problem that productivity is low.
In addition, as disclosed in Japanese Patent Application Laid-Open No. 11-509014, a film having polarization scattering anisotropy (also referred to as a brightness enhancement film) has an optically anisotropic refractive index and optical anisotropy. By forming a film that has substantially the same refractive index on the transmission axis side of the domain having the property, it selectively transmits predetermined polarized light, selectively scatters other polarized light, and reuses scattered light. By doing so, the luminance can be improved.

  However, in order to obtain a sufficient brightness enhancement effect, it is necessary that domains having optical anisotropy be oriented in the same direction. However, it is extremely difficult to produce a material having these requirements. was there.

  The object of the present invention is to solve the above-mentioned problems of the prior art and increase the degree of orientation of irregularly shaped particles (corresponding to the aforementioned domains having optical anisotropy) at the time of optical film production, An object of the present invention is to provide an apparatus for producing an optical film suitable for a polarizing plate protective film, which can enhance optical properties such as a brightness enhancement effect and increase the strength of the optical film.

  Another object of the present invention is to provide a polarizing plate protective film that can improve the optical characteristics of the display, particularly the brightness, and has excellent productivity and durability, because the polarizing plate protective film itself has polarization scattering anisotropy. An object of the present invention is to provide an apparatus for manufacturing an optical film.

  In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that a dope containing a thermoplastic resin, an organic solvent, and amorphous particles is placed on a support through a manifold part and a slit part of a casting die. An apparatus for producing an optical film by a solution casting film-forming method, wherein the cross-sectional area at an arbitrary position of the manifold portion is the total length of the manifold portion with respect to the cross-sectional area of the inlet portion of the casting die. The cross-sectional area of the manifold portion inlet is 0.1% to 300%.

  Here, the cross-sectional area at the inlet of the manifold part of the casting die means the cross-sectional area of the surface perpendicular to the flow direction of the dope at the inlet of the manifold part of the casting die.

  In addition, the cross-sectional area at an arbitrary position of the manifold portion means a cross-sectional area of a plane perpendicular to the dope flow direction at an arbitrary position of the manifold portion.

  The invention of claim 2 is the optical film manufacturing apparatus according to claim 1, wherein the cross-sectional area at an arbitrary position of the manifold part is the total length of the manifold part with respect to the cross-sectional area of the inlet of the manifold part of the casting die. It is characterized by being 1% to 200% of the cross-sectional area of the manifold portion inlet.

  The invention of claim 3 is the optical film manufacturing apparatus according to claim 1, wherein the cross-sectional area at an arbitrary position of the manifold portion is the total length of the manifold portion with respect to the cross-sectional area of the inlet of the manifold portion of the casting die. It is characterized by being 10% to 100% of the cross-sectional area of the manifold portion inlet.

  Invention of Claim 4 is a manufacturing apparatus of the optical film as described in any one of Claims 1-3, Comprising: The cross-sectional area in the arbitrary locations of the manifold part of a casting die is dope from this location. It is characterized by being 10% to 100% of the cross-sectional area of the manifold portion on the upstream side in the flow direction.

  Invention of Claim 5 is a manufacturing apparatus of the optical film as described in any one of Claims 1-4, Comprising: The width | variety of the slit gap of the slit part of a casting die is the downstream of the dope flow direction It is characterized by being made so narrow that it reaches.

  The invention of claim 6 is a method in which a melt obtained by melting and kneading a thermoplastic resin and amorphous particles is cast on a support through a manifold part and a slit part of a casting die and melted. An apparatus for producing an optical film by a casting film-forming method, wherein the cross-sectional area at an arbitrary position of the manifold portion is the same as the cross-sectional area at the manifold portion inlet of the casting die. It is characterized by being 0.1% to 300% of the area.

  Here, the cross-sectional area at the inlet of the manifold part of the casting die means the cross-sectional area of the surface perpendicular to the flow direction of the melt at the inlet of the manifold part of the casting die.

  Moreover, the cross-sectional area at an arbitrary position of the manifold portion means a cross-sectional area of a surface perpendicular to the flow direction of the melt at an arbitrary position of the manifold portion.

  The invention according to claim 7 is the optical film manufacturing apparatus according to claim 6, wherein the cross-sectional area at an arbitrary position of the manifold portion is the total length of the manifold portion with respect to the cross-sectional area of the inlet of the manifold portion of the casting die. It is characterized by being 1% to 200% of the cross-sectional area of the manifold portion inlet.

  The invention according to claim 8 is the optical film manufacturing apparatus according to claim 6, wherein the cross-sectional area at an arbitrary position of the manifold portion is the total length of the manifold portion with respect to the cross-sectional area of the inlet of the manifold portion of the casting die. It is characterized by being 10% to 100% of the cross-sectional area of the manifold portion inlet.

  Invention of Claim 9 is an optical film manufacturing apparatus as described in any one of Claims 5-7, Comprising: The cross-sectional area of the arbitrary locations of the manifold part of a casting die is a melt from this location. It is characterized by being 10% to 100% of the cross-sectional area of the manifold portion on the upstream side in the flow direction.

  Invention of Claim 10 is an optical film manufacturing apparatus as described in any one of Claims 6-9, Comprising: The width | variety of the slit gap of the slit part of a casting die is downstream of a melt flow direction. It is characterized by being made narrower toward the side.

  Invention of Claim 11 is an optical film manufacturing apparatus as described in any one of Claims 1-10, Comprising: The length of the slit part of a casting die is 1 mm-10000 mm, It is characterized by the above-mentioned. .

  Invention of Claim 12 is an optical film manufacturing apparatus as described in any one of Claims 1-10, Comprising: The length of the slit part of a casting die is 10 mm-1000 mm, It is characterized by the above-mentioned. .

  Invention of Claim 13 is an optical film manufacturing apparatus as described in any one of Claims 1-10, Comprising: The length of the slit part of a casting die is 100 mm-500 mm, It is characterized by the above-mentioned. .

  According to the optical film manufacturing apparatus of the present invention, by increasing the degree of orientation of amorphous particles (corresponding to domains having optical anisotropy) at the time of manufacturing an optical film, There is an effect that an optical film having improved film strength can be produced.

  In addition, a polarizing plate having a protective film for a polarizing plate made of an optical film produced by the apparatus of the present invention on at least one surface can sufficiently play an important role in visualizing a change in liquid crystal orientation due to an electric field. There is an effect that can be done.

  Furthermore, the liquid crystal display device having this polarizing plate on at least one surface of the liquid crystal cell has an effect that the display quality is very excellent.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The optical film manufacturing apparatus of the present invention is applicable to both an optical film manufacturing apparatus by a solution casting film forming method and an optical film manufacturing apparatus by a melt casting film forming method, and in particular, dope or melting It has a feature in the shape of the casting die in the casting process of the object.

  In the present invention, when the cross-sectional area of the casting die with respect to the flow direction of the dope or melt is suddenly widened, the amorphous particles added to the dope or melt are easily oriented in the direction perpendicular to the flow direction. Became clear. From this, the casting die of the present invention is characterized in that the cross-sectional area with respect to the flow direction of the dope or the melt does not spread rapidly.

  In particular, the cross-sectional area with respect to the flow direction of the dope or the melt does not widen in the middle, and it becomes clear that the amorphous particles are more easily oriented in the flow direction of the dope or the melt by gradually narrowing.

  Further, it has been found that by increasing the shear time in the flow path portion in the casting die, the amorphous particles in the dope or the melt are easily oriented in the flow direction.

  In the present invention, it has been clarified that by extending the slit portion of the casting die, the degree of orientation of the amorphous particles in the flow direction of the dope or the melt becomes higher.

  In the present invention, amorphous particles are added to the dope or resin for the purpose of improving optical performance and film strength.

  1st invention of this invention is applied to the manufacturing apparatus of the optical film by a solution casting film forming method, dope containing a thermoplastic resin, an organic solvent, and an amorphous particle is used for a casting die. An optical film is manufactured by a solution casting method by casting on a support through a manifold part and a slit part. The feature of the first invention is that the cross-sectional area at an arbitrary position of the manifold part is 0.1% to 300% of the cross-sectional area of the manifold part over the entire length of the manifold part with respect to the cross-sectional area of the manifold part inlet of the casting die. It is. The cross-sectional area at an arbitrary location of the manifold portion is preferably 1% to 200%, more preferably 10% to 100%, of the cross-sectional area of the manifold portion inlet over the entire length of the manifold portion.

  Moreover, in this invention, it is preferable that the cross-sectional area in the arbitrary location of the manifold part of a casting die is 10%-100% of the cross-sectional area of the manifold part of the upstream of the dope flow direction from this location.

  Furthermore, in the present invention, it is preferable that the width of the slit gap of the slit portion of the casting die is made narrower toward the downstream side in the dope flow direction.

  That is, in the present invention, when the cross-sectional area of the casting die with respect to the flow direction of the dope spreads rapidly, it becomes clear that the amorphous particles added to the dope are easily oriented in the direction perpendicular to the flow direction. It was. From this, the casting die of the present invention is characterized in that the cross-sectional area with respect to the flow direction of the dope does not spread rapidly.

  In particular, the cross-sectional area with respect to the flow direction of the dope does not widen in the middle, and it becomes clear that the amorphous particles are more easily oriented in the flow direction of the dope by gradually narrowing.

  It has also been found that by increasing the shear time in the flow path section in the casting die, the amorphous particles in the dope are easily oriented in the flow direction.

  The second invention of the present invention is applied to an apparatus for producing an optical film by a melt casting film forming method. A melt obtained by melting and kneading a thermoplastic resin and amorphous particles is flown. The film is cast on a support through a manifold part and a slit part of a drawing die, and an optical film is manufactured by a melt casting film forming method.

  The feature of the second invention is that the cross-sectional area at an arbitrary position of the manifold portion is 0.1% to 300% of the cross-sectional area of the manifold portion over the entire length of the manifold portion with respect to the cross-sectional area of the manifold portion inlet of the casting die. It is. The cross-sectional area at an arbitrary position of the manifold portion is preferably 1% to 200%, more preferably 10% to 100%, of the cross-sectional area of the manifold portion inlet over the entire length of the manifold portion.

  Moreover, in this invention, it is preferable that the cross-sectional area of the arbitrary locations of the manifold part of a casting die is 10%-100% of the cross-sectional area of the manifold part of the upstream of a melt flow direction from this location.

  Furthermore, in this invention, it is preferable that the width | variety of the slit gap of the slit part of a casting die is made so narrow that it reaches the downstream of a melt flow direction.

  That is, in the present invention, when the cross-sectional area of the casting die with respect to the flow direction of the melt suddenly widens, it is clear that the amorphous particles added to the melt are easily oriented in the direction perpendicular to the flow direction. Became. From this, the casting die of the present invention is characterized in that the cross-sectional area with respect to the flow direction of the melt does not spread rapidly.

  In particular, the cross-sectional area with respect to the flow direction of the melt does not increase in the middle, and it becomes clear that the irregularly shaped particles are more easily oriented in the flow direction of the melt by gradually narrowing.

  Further, it has been found that by increasing the shear time in the flow path portion in the casting die, the amorphous particles in the melt are easily oriented in the flow direction.

  In the first and second inventions described above, the length of the slit portion of the casting die is 1 mm to 10000 mm. The length of the slit portion is preferably 10 mm to 1000 mm, and preferably 100 mm to 500 mm.

  In the present invention, “indefinite shape” refers to a particle in which X ≠ Y and the aspect ratio = Y / X is 2 or more, where Y is the absolute maximum length of the particle and X is the diagonal width. The amorphous particles used in the present invention may be anything other than spherical particles, and flat, rod, ellipsoid, needle, layer, thread, and the like are used. The aspect ratio (ratio of absolute maximum length to diagonal width) of the amorphous particles is preferably 2 or more and 10,000 or less, more preferably 3 or more and 1000 or less, and particularly preferably 5 or more and 100 or less. is there.

  Here, examples of the amorphous particles used in the present invention include inorganic compounds or organic compounds. Examples of the fine particles of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, Metal oxides such as kaolin, talc, clay, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate, hydroxide, silicate, phosphate, carbonate, silicic acid Examples include calcium, potassium titanate, aluminum borate, basic magnesium sulfate, and glass fiber. Examples of the organic compound fine particles include fine particles of silicone resin, fluororesin, acrylic resin, and the like.

  The particles used in the present invention are preferably subjected to various surface treatments for the purpose of improving the affinity with the resin.

  For fully dried particles, fatty acids, fats, surfactants, waxes, silane coupling agents, titanate coupling agents, carboxylic acid coupling agents, phosphoric acid coupling agents, polymer systems Various modifiers can be used.

  Methods for dispersing the surface-treated particles in the resin are roughly divided into a method using a disperser and a method using a kneader. When the melt casting film forming method is used, a kneader is used. When the solution casting film forming method is used, it can be used together with a disperser or a kneader.

  The former can be further divided into media distribution and medialess distribution. Examples of the media dispersion include those using a dispersing machine such as a ball mill, a sand mill, and a dyno mill. Examples of the medialess dispersion include an ultrasonic type, a centrifugal type, and a high-pressure type. Or dispersion using a kneader. As a kneading method, using one or two rotor extruders, resin is introduced from the hopper, and when the viscosity is reduced to some extent, particles are introduced from the side to minimize damage to the particles. And kneadability can be improved.

  Next, the optical film manufacturing apparatus of the first invention of the present invention using the solution casting film forming method will be described in detail.

  The apparatus for producing an optical film using the solution casting method of the present invention comprises a dope preparation step, a casting step, a drying step, and a winding step.

  That is, the apparatus for producing an optical film by the solution casting method of the present invention uses a dope (resin solution) obtained by dissolving a resin film raw material in a solvent from a casting die, for example, made of a rotationally driven metal having a width of 1.8 m or more. This is an apparatus for producing an optical film by rolling a web (film) cast on an endless belt (belt support) and drying the web (film) peeled off from the belt support.

[Dissolution process]
In the present invention, cellulose ester is preferably used as the resin film raw material. When cellulose ester is used as the resin film raw material, a mixed solvent of methylene chloride and alcohol is preferably used as the solvent.

  Other additives added to the dope include a plasticizer, an ultraviolet absorber, an antioxidant, a dye, and a matting agent. In the present invention, these additives may be added when preparing a cellulose ester solution, or may be added when preparing a dispersion such as a matting agent.

  Although the example in case resin of an optical film is a cellulose ester below is shown, this invention is not necessarily limited to this.

  First, for dissolution of cellulose ester, means such as a stirring dissolution method, a heating dissolution method, an ultrasonic dissolution method, etc. in a dissolution vessel are usually used. A method of heating at a temperature that does not boil and dissolving while stirring is more preferable in order to prevent the generation of massive undissolved material called gel or mamako. Further, a cooling dissolution method described in JP-A-9-95538 or a method of dissolving under high pressure described in JP-A-11-21379 may be used.

  A method in which the cellulose ester is mixed with a poor solvent and wetted or swollen, and then mixed with a good solvent and dissolved is also preferably used. At this time, an apparatus for mixing or dissolving cellulose ester with a poor solvent and an apparatus for mixing and dissolving with a good solvent may be separately provided.

  The type of the pressure vessel used for dissolving the cellulose ester is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition, instruments such as a pressure gauge and a thermometer are appropriately disposed in the pressurized container. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature after adding the solvent is higher than the boiling point of the solvent to be used. In the case of two or more mixed solvents, the heating temperature is higher than the boiling point of the lower boiling solvent and the solvent does not boil. Is preferred. If the heating temperature is too high, the required pressure increases and productivity decreases. The range of preferable heating temperature is 20-120 degreeC, 30-100 degreeC is more preferable, The range of 40-80 degreeC is further more preferable. The pressure is adjusted so that the solvent does not boil at the set temperature.

  After dissolving the cellulose ester, it is taken out from the container while cooling, or it is taken out from the container with a pump or the like and cooled with a heat exchanger or the like, and the resulting polymer dope is used for film formation. May be cooled to room temperature.

  The mixture of the raw material cellulose ester and the solvent is dissolved by a dissolving device having a stirrer, and at this time, the peripheral speed of the stirring blade is preferably at least 0.5 m / second and is dissolved by stirring for 30 minutes or more.

  In the present invention, the cellulose ester dope is filtered to remove foreign matter, particularly foreign matter that is mistakenly recognized as an image in a liquid crystal image display device.

  Filter media used for filtration preferably have a low absolute filtration accuracy. However, if the absolute filtration accuracy is too low, the filter media is likely to be clogged, and the filter media must be frequently replaced, resulting in increased productivity. There is a problem of lowering.

  For this reason, in the present invention, the filter medium used for the cellulose ester dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and 0.003 to 0.006 mm. A range of filter media is more preferred.

  There are no particular restrictions on the material of the filter medium, and normal filter media can be used. However, plastic fiber filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel fibers are used to remove fibers. It is preferable because there is no

  In the present invention, filtration of the cellulose ester dope can be performed by a normal method, but the method of filtering while heating under pressure at a temperature not lower than the boiling point of the solvent at a normal pressure and the solvent does not boil is a filter material. The increase in differential pressure before and after (hereinafter sometimes referred to as filtration pressure) is small and preferable.

  A preferred temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and even more preferably 45 to 55 ° C.

  The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

[Casting process]
FIG. 1 illustrates an apparatus for producing an optical film by the solution casting method of the present invention.

  Referring to the figure, the dope adjusted in the melting pot is fed to the casting die (1) by a conduit and is transported infinitely, for example, on the support (11) made of a rotationally driven stainless steel endless belt. This is a step of casting the dope from the casting die (1) at the extending position.

  The casting die (1) of the present invention is preferably a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform.

  In the casting die (1), the angle formed by the inner slit wall surface and the surface of the support (11) is preferably 40 to 90 °, particularly preferably 60 to 75 °.

  The gap between the die lip of the casting die (1) and the surface of the support (11) is preferably set with a gap of 0.2 to 10 mm, more preferably a gap of 0.5 to 5 mm.

  The slit gap of the casting die (1) is preferably 0.05 to 1.5 mm, more preferably 0.15 to 1.0 mm.

  The ratio between the linear flow velocity U1 (m / second) of the dope discharged from the die slit and the traveling speed U2 (m / second) of the support (11), and the draft ratio β defined by U1 / U2 is 0.4 to 2.0 is preferable.

Casting die (1) solvent vapor concentration expressed by the following formula near the lower part of the side surface: α (%),
Solvent vapor concentration: α (%) =
(Volume of solvent vapor / volume of space containing solvent) × 100
Similarly, it is preferable that the ratio of α / V (second / m) to the wind speed V (m / second) near the lower part of the side surface of the casting die (1) is 10 or more. As a result, the solvent vapor concentration in the vicinity of the lower part of the side surface of the casting die (1) is always kept at an optimum value, and the edge of the web cast from the casting die (1) to the support (11) has a sawtooth shape ( It is possible to effectively prevent a film from being formed on the end portion of the die lip, which is caused by contacting the end portion of the web while vibrating, causing film breakage in a subsequent process after peeling.

  In the optical film manufacturing apparatus of the present invention, the vicinity of the lower end portion on the side surface of the casting die (1) is provided by providing an enclosure in the vicinity of the lower end portion on the side surface of the casting die (1) or spraying solvent vapor. Is preferably the desired solvent vapor concentration. Also by this, the quality of the film can be further improved.

For the same purpose, in the dope casting step, a dope-soluble solvent is allowed to flow from the lower end of the side surface of the casting die (1) onto the support (11), and the dope-soluble solvent is used. It is desirable that the flow rate of the solvent is 0.1 to 1.0 cm ³ / min, and the temperature of the dope-soluble solvent is not more than its boiling point.

  Next, the casting support (11) will be described.

  The surface roughness Ra of the support (11) is 0.0001 to 1 μm, more preferably 0.0003 to 0.1 μm, and further preferably 0.0005 to 0.05 μm.

  In the peeling process, the endless belt is provided with a roughened band having an average roughness Ra of 0.5 to 2 μm and cast so that a dope 5 to 30 mm wide overlaps the roughened band. Is preferable from the viewpoint of smoothly peeling.

  In the illustrated film forming apparatus having a rotationally driven endless belt as the support (11), the belt support (11) is disposed between the pair of drums (19) and the middle thereof, and the upper part of the endless belt support (11). It is comprised from the some roll (illustration omitted) which each supports the transition part and the lower transition part from the back side. The plurality of rolls are called support rolls, and the distance between adjacent support rolls is greater than 0 m and within a range of 5 m or less, preferably 1 to 5 m, and desirably 2 to 5 m. Further, among the support rolls supporting the upper transition portion (1a) of the endless belt support (11) from the back side, the distance between the adjacent support rolls is the lower transition of the endless belt support (11). Of the support rolls supporting the part from the back side, the distance is preferably narrower than the distance between the support rolls adjacent to each other.

  Further, one or both of the drums (19) at both ends of the rotary drive endless belt support (11) are provided with a driving device for applying tension to the belt support (11), whereby the belt support. (11) is used in a tensioned state.

  When an endless belt is used as the support (11), the belt temperature during film formation can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent, and further from 5 ° C. to the solvent. A range of boiling point of −5 ° C. is more preferable. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  Further, when the support (11) transport speed is 10 m / min or more, the cast film coming out from the lip of the casting die (12) is depressurized to mix air, or the horizontal streaks in the width direction of the film. In order to suppress fluttering of the casting ribbon, which is a cause of the production, it is preferable to provide a decompression chamber on the upstream side of the casting die (12) and decompress the pressure by 10 to 600 Pa, more preferably 10 to 200 Pa.

  The gap between the lower end surface of the decompression chamber and the surface of the support (11) is in the range of 0.5 to 5 mm so that the suction air volume does not become excessively large, so that the dope dry film on the lip end of the casting die (12) This is desirable because the occurrence of this is suppressed.

  Further, in order to increase the film forming speed, two or more pressure casting dies (12) may be provided on the casting support (11), and the dope amount may be divided to form a multilayer film.

  When casting the dope onto the support (11), it is preferable to control the temperature below the boiling point of the solvent used for dissolving the raw polymer and below the boiling point of the solvent having the lowest boiling point in the mixed solvent.

  In the system using an endless belt as the support (11), the web (10) is dried and solidified on the support (11) until the web (10) has a film strength that can be peeled from the support (11). It is preferable to dry the residual solvent amount to 150% by weight or less, and more preferably 80 to 120%. Moreover, as for web temperature when peeling a web (10) from a support body (11), 0-30 degreeC is preferable. Further, immediately after the web (10) is peeled off from the support (11), the temperature rapidly decreases once by evaporation of the solvent from the support (11) contact surface side, and volatile components such as water vapor and solvent vapor in the atmosphere. Is easy to condense, the web temperature during peeling is more preferably 5 to 30 ° C.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when the weight M is dried at 110 ° C. for 3 hours.

[Solvent evaporation step]
The dope film (web) formed by the dope cast on the endless belt support (11) is heated on the support (11), and the solvent is removed until the web can be peeled from the support (11). It is a process of evaporating.

  In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back surface of the support (11) by liquid, a method of transferring heat from the front and back by radiant heat, and the like.

[Peeling process]
In the system using an endless belt for the support (11), the release tension is usually 20 to 25 kg / m when peeling the support (11) and the web (10). In the cellulose ester film prepared according to the present invention, the web (10) is likely to wrinkle at the time of peeling. Therefore, it is preferable to peel at a minimum tension of 17 kg / m, more preferably at least It is peeling with a tension of ~ 14 kg / m.

[Drying process]
In the system using an endless belt for the support (11), the web (10) after peeling is introduced into the initial drying device (13). In the initial drying device (13), the web (10) is meandered by a plurality of conveying rolls (17) arranged in a staggered manner when viewed from the side, while the web (10) is in the bottom of the initial drying device (13). The hot air (23) is blown from the front part of the air and discharged from the rear part of the ceiling of the initial drying device (13).

  Further, while the amount of residual solvent in the web is 10 to 150% by weight, the web is very soft, so the diameter of the transport roll is thin (less than 85 mm), and the web is easily deformed by the force pressed against the roll. Not only that, but additives that deposit, evaporate or volatilize from the web will adhere to the roll, making it easier to soil the web or form a squeeze. In the case where the roll is thick (diameter exceeding 300 mm), if the tension applied to the web is weak, the friction between the web and the roll is not sufficient and slipping occurs, and the web is scratched. If a strong tension is applied to the web so that it does not slide, the soft web will expand and contract, and the desired optical properties will not be obtained. Also, the unevenness of the lines extending in the transport direction will be emphasized, and the web will be strongly pressed against the roll. Will be a problem. Therefore, the diameter of the roll used is preferably 85 to 300 mm, and more preferably 100 to 200 mm.

  FIG. 2 shows another example of an apparatus for producing an optical film by the solution casting film-forming method of the present invention, and a drum is used as the support (21).

  In the same figure, a dope was prepared in the same manner as described above, and the dope was cast from a casting die (1) onto a drum support (21) coated with hard chrome to obtain a web (10). When the web (10) moves approximately 3/4 rounds by the rotation of the drum support (21), the web (10) is peeled off by the peeling roll (16).

  The dope is fed to the casting die (1) through a pressurized metering gear pump, and the dope is cast from the casting die (1) onto the support (21) made of a drum at the casting position.

  Moreover, when using a drum as a support body (21), it is preferable that the temperature of the drum at the time of film forming cools to 10 degrees C or less, It is more preferable to cool to 0 degrees C or less, Cool to -10 degrees C or less More preferably. The dope cast on the drum surface increases the gel film strength (film strength) by cooling gelation, and the gel film strength (film strength) is also improved by promoting drying until stripping. To increase.

  Moreover, it is preferable to peel in the state whose supporting residual solvent amount of a web (10) is 10 to 250 weight%, and it is more preferable to peel in the state of 20 to 220 weight%. If the residual solvent amount exceeds 250% by weight, the cellulose acylate may not be peeled off on the support (21).

  Moreover, in the system using a drum for the support (21), the peeling is performed at a peeling tension of 0.1 to 6 kg / m when peeling the support (21) and the web (10).

  In the system using a drum for the support (21), after peeling, the drum is transported to a tenter drying device through a crossover. The crossing section is composed of zero or more transport rolls, preferably one or more transport rolls, and more preferably three or more transport rolls. It is preferable to adjust the temperature of the transfer roll (22) of the transfer section by attaching a temperature adjusting device in the same manner as the drum. For example, a method of attaching a jacket to each of the transport rolls (22) and circulating a cooling medium in the jacket can be used.

  Further, the temperature of each transport roll (22) is preferably 10 ° C. or less, more preferably 0 ° C. or less, and further preferably −10 ° C. or less, like the temperature of the drum. Further, the temperature in the transition room is preferably 10 ° C. or lower, more preferably 0 ° C. or lower, and further preferably −10 ° C. or lower, like the temperature of the drum. In addition, by cooling the web (10), the storage elastic modulus can be kept high, and the occurrence of defects during transportation can be prevented.

[Stretching process]
As a film for an image display member, a tenter method is known in which both side edges of a web (or film) are fixed with a clip or the like and stretched, which is preferable for improving flatness and dimensional stability.

  1 and 2, as a method using this tenter (14), for example, Japanese Patent Application Laid-Open No. 59-211006 discloses a technique for manufacturing a substrate of a liquid crystal display panel from a film of phenoxy resin or the like. It is suggested that cellulose acetate film can also be used for this film. Japanese Patent Application Laid-Open Nos. 4-284221 and 62-115535 disclose methods for producing a cellulose triacetate film using a tenter dryer.

  In particular, in the drying step after peeling from the support (11), the web (or film) tends to shrink in the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film.

  From this point, as a method of using the tenter (14), for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed with a clip in the width direction. The method of drying while maintaining the width / tenter method is preferred.

  When the residual solvent amount is 10 to 100% by weight, and / or when the residual solvent amount is 5 to 10% by weight and when the residual solvent amount is 90 to 150 ° C., the tenter (14) maintains the width or the film. It is particularly preferable to perform stretching by about 1 to 20% with respect to the width because the effect of improving the planarity of the cellulose ester film is large.

Moreover, it is preferable that the difference of the tension | tensile_strength which acts on a web (10) along a conveyance direction before and behind a tenter (14) is 8 N / mm < ² > or less.

  A preheating step for preheating the web (10), a stretching step for stretching the web (10) using the tenter dryer (14) after the preheating step, and a web (10) after the stretching step. And a relaxation step of relaxing the amount by a smaller amount than the stretching amount in the stretching step, and the temperature T1 in the preheating step and the stretching step is equal to or higher than the glass transition temperature Tg-60 ° C of the film, and the relaxation step It is preferable to set the temperature T2 at (T1 ° C.-10 ° C.) or less.

  In particular, the stretch rate of the web (10) in the stretching step is 0 to 30% in terms of the ratio of the web width immediately before entering the stretching step, while the stretch rate of the web (10) in the relaxation step is − It is desirable to set it as 10 to 10%.

  In the stretching step by the tenter device (14), for example, the stretching ratio when producing the cellulose ester film is 1.01 to 3 times, preferably 1.5 to the film forming direction or the width direction. 3 times. When stretching in the biaxial direction, the side to be stretched at a high magnification is 1.01 to 3 times, preferably 1.5 to 3 times, and the stretching ratio in the other direction is 0.8 to 1.5. The film can be stretched by a factor of preferably 0.9 to 1.2.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter device (14), and may be a pin tenter or a clip tenter.

  In the stretching process by the tenter device (14), the web is blown from the front portion of the bottom of the tenter device (14) and discharged from the rear portion of the ceiling of the tenter device (14) by the hot air (24). (10) is dried with stretching.

  It is preferable to provide a post-drying device (15) after the stretching step by the tenter device (14). In the post-drying device (15), the web (10) is meandered by a plurality of transport rolls (17) arranged in a staggered manner as viewed from the side, and the web (10) is dried during that time. The film transport tension in the post-drying device (15) is affected by the physical properties of the dope, the amount of residual solvent at the time of peeling and in the film transport process, the temperature in the post-drying device (15), etc. / M is preferable, and 60 to 150 N / m is more preferable. 80 to 120 N / m is most preferable.

  The means for drying the web (or film) (10) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity, for example, warm air (25 which is blown from the front portion of the bottom of the post-drying device (15) and discharged from the rear portion of the ceiling of the post-drying device (15). ). The drying temperature is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  The web conveyance tension at the time of drying is 30 to 300 N / width m, and 40 to 270 N / width m is more preferable.

  It is preferred that a device for cleaning the surface of the web (or film) (10) is arranged before and / or after the drying step and / or the thermal straightening device.

  The cleaning device applies ultrasonic vibration to the web (or film) (10) in the middle of conveyance, blows high-pressure air onto the surface, blows off the adhering matter, and sucks it, and removes adhering dust and the like. Is. In addition, known means and methods such as a method for performing flame treatment (corona treatment, plasma treatment) and a method for installing an adhesive roll can be used without any particular limitation.

  In addition, the cleaning means to arrange | position may be single and may be two or more.

  Since the adhesion of dust or the like to the web (10) is often due to the effect of static electricity, it is possible to remove static electricity from the web (10) by disposing a static elimination means, for example, a static elimination bar, in front of the above-described cleaning device. preferable. As the charge removal bar, a known bar can be used without any particular limitation.

  In the drying process, as a measure to suppress the phenomenon that the plasticizer contained in the web (or film) (10) evaporates and condenses on the roll or wall surface, a fresh gas of a specific amount or more with respect to the supplied air volume per unit time Is preferably introduced. And it is preferable to set the quantity of the fresh gas supplied to 5 to 50% of the total supply air volume.

  The reason why the supply amount of fresh gas is 5 to 50% is that if the amount is less than 5%, the amount of fresh gas is too small to suppress the plasticizer condensation. If the amount exceeds 50%, the amount of fresh gas is too large. This is because the running cost increases waste.

  In addition to the above measures, for example, the following configuration can be adopted. First, a configuration in which a part of the air in the drying / correction process chamber is circulated and the plasticizer is forcibly removed by passing it through a cooler coil or the like and then raised to a specified temperature with a heater. A configuration in which the temperature of the portion in contact with the metal surface is increased, for example, a configuration in which the temperature of the portion in contact with the metal surface is increased by a steam / surface heater or the like. Third, fresh air is supplied to lower the vapor pressure of the plasticizer on the roll surface. As a means for supplying fresh air, a configuration in which a slit is provided in the width direction in the vicinity of the roll and air is supplied from the punch plate box to suppress the air velocity distribution of the supplied air is used. It is not something.

  In addition, it is preferable that the film temperature at the time of taking out a film from a drying process or a heat correction process chamber or the cooling process of the film which came out of them shall be 60 degrees C or less.

  Here, it is because it is in the conditions which are easy to generate | occur | produce the condensation of a plasticizer when it carries out from the correction | amendment and cooling process box at the temperature exceeding 60 degreeC.

  In order to prevent the film from stretching in the transport direction in the post-drying device (15), it is preferable to provide a tension cut roll. After drying, it is preferable to provide a slitter and cut off the end portion before winding to obtain a good winding shape.

[Embossing process]
Next, embossing provided on both side edges of the polymer film will be described. The polymer film that has finished the transport drying process is subjected to processing for forming an emboss on the film by an embossing apparatus prior to introduction into the winding process. As an embossing apparatus, an apparatus described in JP-A-63-74850 can be used.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . For example, when the film thickness is 40 μm and the film width is 100 cm, the thickness of the emboss 31 is set to 2 to 12 μm and the emboss width is set to 5 to 30 mm.

  Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. For example, when the film thickness is 40 μm, the emboss height h 1 + h 2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The lower limit of the embossed height is from the height necessary to prevent partial uneven adhesion between the films. On the other hand, the upper limit is too high, and the embossed shape is too high. This is because it deforms to induce a failure.

  Regarding the width of the emboss, the embossed part will eventually become a loss part, but it is desirable to reduce it. For example, when the film thickness is reduced from 80 μm to 40 μm, the frictional force between the film and the roll becomes 50 μm as a boundary. It was found that the grip force was extremely reduced, and when the film-forming speed was increased to 30 m / min or more, it was found that the friction force between the film and the roll was extremely reduced especially at 50 m / min or more. did. For this reason, the emboss width is the minimum necessary for suppressing slipping of the film, particularly when a high-speed film formation of 50 m / min or more is performed with a thin film of 50 μm or less. However, it is also linked to the height of the above-mentioned embossing, and the embossing height × embossing width for clearing all of the pyramid shape, horse back, polygonal shape, and winding failure are determined. In addition, embossing can be arrange | positioned not only at the both ends of a film but at the center part.

[Static elimination process]
In the present invention, it is preferable that a static eliminator is installed before winding and immediately after the winding unit to neutralize the film.

  The static eliminator can be configured in such a way that a reverse potential is applied by a static eliminator or a forced charging device at the time of winding so that the charging potential when the original winding is re-drawn is ± 2 KV or less. It can also be set as the structure which static-eliminates with the static elimination device converted into positive / negative alternately at 1-150Hz.

  Moreover, it can replace with said static elimination device and can utilize the ionizer and static elimination bar which generate | occur | produce ion wind. Here, the ionizer static elimination is performed by blowing an ion wind toward the film wound up from the embossing device through the transport roll. The ion wind is generated by a static eliminator. Any known static eliminator can be used without limitation.

  The static elimination at the time of film formation winding is to induce coating unevenness when the charged potential is ± 2KV or more when the original film is redrawn and the functional film is applied. Especially when pursuing thin film and high speed Since film peeling electrification at the time of re-feeding becomes high, static elimination during film formation is essential.

[Winding process]
In this step, the web (10) after drying is wound up as a film by a winder (18) to obtain the original roll of the optical film. When the residual solvent amount of the film 14 that has finished drying is 0.5% by weight or less, preferably 0.1% by weight or less, a film having good dimensional stability can be obtained.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  At the start of the initial winding, it is preferable that the winding tension is 280 N / m width or less and only the embossed portion is wound so that the pressing force of the touch roll winding + the initial winding tension is 60 N / m width or more.

  With respect to the winding condition range of 280 N / m or more, the radial tension applied to the embossed part due to the tension during winding and the pressing force of the touch roll is too large, and the film peeling charge amount during the aforementioned re-feeding is too large. On the other hand, at 60 N / m or less, the take-up tension is too weak, especially during long take-up of 2000 m or more, and when the finished product roll is transported or unwound due to the feed tension at the time of re-feeding This is because

  The pressure of the touch roll (not shown) is preferably monitored by installing a pressing pressure detector and set to 3 to 100 N / m width.

  As the pressing means of the touch roll, for example, a double-acting low friction cylinder or a servomotor is used to apply tension feedback, and the pressing is performed so that each side can be controlled independently. It is preferable to measure the pressure on both sides with a pressure detector.

  The material of the touch roll is metal or hard synthetic resin. The position to be touched is preferably the position immediately after the tangent line where the film contacts the product roll.

  The direction in which the touch roll moves as it rolls up is more preferably the normal direction from the winding core.

  It is preferable to perform winding by setting the control of the edge point control (EPC) of the winding unit to be fixed automatically from 0 to 5 seconds before winding is completed and from 0 to 5 seconds after winding is started. .

The winding hardness of the wound product original is
[Winding hardness of embossed portion−winding hardness of intermediate position from film end to center] <170
Is preferable.

  If the winding hardness exceeds 170, the adhesive strength of the embossed part is too large, and the problem of the film peeling charge amount at the time of re-feeding is too large at the time of re-feeding the product roll. This is because the winding state in the middle becomes a loose winding state, and the product original winding is distorted into a polygonal shape and causes a failure.

  The winding hardness can be measured according to a JIS standard viscous hardness meter, or PROCEQ S., Switzerland. A. An electronic film hardness tester, an echo chip, or a Paro tester 2 manufactured by the company can be used. The impact device uses the D type.

  Hardness value: L is measured by the rebound speed V / the striking speed V0. The rebound speed V is the rebound speed from the impact body specimen, and the impact speed V0 is the impact speed from the impact body specimen, and the average value of 10-point measurement was calculated. In addition, since the hardness of the central portion has a large variation in the hardness measurement point in the original winding, it is set as an intermediate portion between the upper surface of the embossed portion, the embossed portion, and the central portion.

  The process average atmosphere (US Federal Standard Federal Standard 209D) until the web (10) is peeled from the support (11) is set to class 10 or higher and class 10,000 or lower, and the web (10) is peeled from the support (11). By setting the process average atmosphere (Federal Standard 209D) after class to a class of 100 or more and class 10000 or less, the number of foreign matters that are a major problem with display defects and appearance deterioration when processed into a display device Can be obtained.

  Next, the optical film manufacturing apparatus of the present invention using the melt casting film forming method will be described.

  FIG. 3 is a flow sheet schematically showing an apparatus for producing an optical film by the melt casting film forming method of the present invention.

  Referring to the figure, for example, cellulose ester pellets, a plasticizer, and an antioxidant are introduced into the hopper (31), and the raw materials are conveyed from the hopper (31) to the Henschel mixer (32) at a predetermined supply rate. , Mixed. The raw materials mixed by the Henschel mixer (32) are conveyed to an extruder (33) and heated and melted at, for example, 250 ° C., and the melt is extruded from the casting die (1) according to the present invention. The melt extruded from the casting die (1) is cooled and surface-corrected by the cooling roll (35). In this case, it is preferable that the web (film) (40) and the cooling roll (35) are in close contact with each other. For example, a touch roll (36) is used as a method for bringing the web (film) (40) into close contact with the cooling roll (35). Press.

  Next, the web (film) (40) is guided to a stretching machine (not shown), and stretched in the longitudinal direction in the stretching machine, and then the web (film) (40) is stretched in the width direction using a tenter (37). The film is relaxed after stretching, and after being transported by the transport roll (38), it is wound up by a winder (39) to obtain a roll-shaped cellulose ester film.

  In the present invention, the thermoplastic resin used is not particularly limited as long as it can be formed by a melt casting film forming method. For example, cellulose ester, polycarbonate, alicyclic structure-containing polymer, polyvinyl alcohol, polyamide, polyimide, polyester and the like can be mentioned. Among them, cellulose esters and alicyclic structure-containing polymers are preferable because of their small photoelastic coefficient, and alicyclic structure-containing polymers are particularly preferable because of their low water absorption.

  In the present invention, the optical film includes an ester plasticizer having a structure in which an organic acid and a trihydric or higher alcohol are condensed as an additive, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, At least one plasticizer selected from ester plasticizers composed of monovalent carboxylic acids and monohydric alcohols, phenolic antioxidants, hindered amine light stabilizers, phosphorus stabilizers, and sulfur stabilizers. It is preferable to contain a stabilizer, and in addition, a peroxide decomposing agent, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, a pigment, and other plasticizers and hinders. Antioxidants other than dephenol antioxidants can be included.

  When the film composition is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by deterioration of the strength of the constituent material due to coloring or molecular weight reduction. Moreover, generation | occurrence | production of an unfavorable volatile component may be accompanied by the decomposition reaction of a film composition.

  When the film composition is heated and melted, the presence of the above-mentioned additives is excellent in terms of suppressing the deterioration of the strength based on the deterioration and decomposition of the material, or maintaining the inherent strength of the material. In the presence of the aforementioned additives.

  It is preferable to dry the resin pellets and the powder material as raw materials in advance. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

When the raw material is introduced from the supply hopper (31) shown in FIG. 3 into the extruder (33), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere. When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder (33). In order to add uniformly, it is preferable to use a mixing device such as a static mixer. In the present invention, pellets made of thermoplastic resin and powder are melt-kneaded with an extruder (not shown) to produce pellets. The pellets are melt-kneaded by another extruder (33) and cast from a casting die (1) onto a cooling roll (metal support) (35) to form a film; Both the method in which pellets and powder are melt-kneaded by an extruder (33) and cast from a casting die (1) onto a cooling roll (metal support) (35) to form a film. Can be used for film formation.

  The particle size of the powder is preferably a sieve mesh opening of 250 μm or less (JIS Z 8801-1). If the particle size of the powder is too large, sufficient mixing and dispersion cannot be obtained even by kneading in the extruder (33), and in some cases, the powder adheres to the inner wall of the barrel of the extruder (33). The heat-degraded product of the resin accumulates in the part, and it occasionally flows out, and the trouble of the foreign matter due to the heat-degraded product is likely to occur in the film. Further, when the particle size is too small, it may cause a problem in handling. The pellets preferably have a diameter and a particle size of 1 to 5 mm in length.

  In a system in which a plurality of materials having different melting points are mixed, a semi-molten product is once produced at a temperature at which only a material having a low melting point is melted, and the semi-molten product is put into an extruder (33). It is also possible to form a film. When using resins and additives that are susceptible to thermal decomposition, in order to reduce the number of times the resin is melted, a method of directly forming a film without producing pellets, A method of forming a film from is preferred.

  In the present invention, the extruder (33) used for film formation may be a single screw extruder (33) or a twin screw extruder (33). When forming a film directly without forming pellets from the material, it is preferable to use a twin screw extruder (33) because an appropriate degree of kneading is required, but even with a single screw extruder (33), the shape of the screw By changing to a kneading type screw such as a Maddock type, Unimelt type, or Dalmage, moderate kneading can be obtained and film formation becomes possible. In both the single-screw extruder and the twin-screw extruder, it is desirable to provide a vent port and remove the gas from the vent port using a vacuum pump or the like. In the case of producing a pellet or braided semi-melt, it may be a single screw extruder (33) or a twin screw extruder (33).

  In the cooling step in the extruder (33) and after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

The melting temperature of the resin in the extruder (33) varies depending on the viscosity of the resin, the discharge amount, the thickness of the sheet to be produced, etc., but in general, the Tg relative to the glass transition temperature (Tg) of the molding material. As mentioned above, it is preferable that it is the range of Tg + 100 degrees C or less. More preferably, the melting temperature is Tg + 10 ° C. or higher and Tg + 90 ° C. or lower. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. The residence time of the resin in the extruder (33) is preferably shorter, and is within 5 minutes, more preferably within 3 minutes, and most preferably within 2 minutes. The residence time depends on the type of the extruder (33) and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, etc. Is possible.

  The shape, rotation speed, and the like of the screw of the extruder (33) are appropriately selected depending on the viscosity and discharge amount of the resin. In the present invention, the shear rate in the extruder (33) is preferably 1 / second to 10000 / second, more preferably 5 / second to 1000 / second, and most preferably 10 / second to 100 / second. In order to prevent biting of the gear pump and to reduce the main filter load, it is preferable to provide a prefilter on the outlet side of the extruder (33).

  For example, a 50/80/100 mesh screen or a metal fiber sintered filter is preferably provided as necessary. It is preferable to use a type that can be changed online.

  If the thickness of the resin immediately after adhering to the first cooling roll (35) is h, t / h is 10 or less when the film thickness is 70 μm or more and less than 100 μm, and t / h when 50 μm or more and 70 μm or less. When h is 15 or less, and t is less than 50 μm, t / h is preferably 20 or less. By setting t / h to the above value, the elongation of the ribbon can be suppressed and the retardation in the flow direction can be kept small. By making R at the lip tip preferably 100 μm or less, more preferably 50 μm or less, the flatness of the film can be kept good.

  Thickness adjustment mechanisms include a heater type that adjusts the temperature by dividing in the width direction, a manual bolt type that adjusts the lip opening mechanically, or a lip opening adjustment that uses expansion and contraction of the bolts with a heater. It is preferable to use a heat bolt system or the like.

The die material is sprayed or plated with nickel, hard chromium, chromium carbide, chromium nitride, titanium carbide , titanium carbonitride, titanium nitride, carbide , ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. Stuff.

  A preferable material of the die slip portion is the same as that of the die. In order to prevent shark skin, it is important to reduce friction between the lip and the resin, and Dual Spiral Systems Inc. It is preferable to use K05MFC manufactured by the company. Further, the surface roughness of the lip portion is preferably 0.5 S or less, and more preferably 0.2 S or less.

  In the present invention, the material extruded from the casting die (1) is cooled and surface-corrected by the cooling roll (35). When the first cooling roll (35) is the cooling roll (35) with which the material extruded from the casting die (1) first contacts, the material contacts the first cooling roll (35) from the casting die (1). A shorter time is preferable, and it is within 10 seconds, preferably within 5 seconds, and most preferably within 2 seconds. The distance from the casting die (1) to the first cooling roll (35) is preferably 10 mm or more and 100 mm or less.

  The temperature of the resin immediately before closely contacting the first cooling roll (35) is preferably Tg or higher, more preferably Tg + 50 ° C. or higher. By keeping the temperature of the resin high, retardation in the flow direction generated by the elongation of the ribbon can be reduced. It is preferable to keep the temperature of the resin in the air gap immediately before the resin comes into close contact with the first cooling roll (35) from the outlet of the casting die (1). As the heat-retaining method, induction heating using a microwave, radiant heat heating using an infrared heater, or the like can be preferably used. As the infrared heater, an electric, gas, oil or steam far infrared ceramic heater can be used.

  In the present invention, when the polymer flows out from the casting die (1), in order to prevent contamination of the casting die (1) and the cooling roll (35) with sublimates, a suction device is provided in the vicinity of the casting die (34). It is preferable to attach. The suction device needs to be treated such as heating with a heater so that the device itself does not become a place where the sublimate is attached. Further, if the suction pressure is too large, the film quality such as unevenness is affected. If the suction pressure is too small, the sublimate cannot be sucked effectively.

  In the present invention, the film and the cooling roll (35) are preferably in close contact. As a method for bringing the film and the cooling roll (35) into close contact, pressing using a touch roll (36), an electrostatic contact method, an air knife, a decompression chamber, or the like can be used.

  The number of the cooling rolls (35) may be one or more, but it is preferable that two or more cooling rolls (35) are brought into contact with the cooling roll (35) in order to improve the smoothness on both sides of the film. The cooling roll (35) can be provided with cleaning equipment such as a cleaning roll. The temperature unevenness of the cooling roll (35) is preferably 0.5 ° C. or less. Speed unevenness is O. 5% or less is preferable. The surface of the cooling roll (35) can use hard chrome plating, but is not limited thereto. The surface roughness is preferably 0.1 s or less. As the material of the touch roll (36), a metal or a material obtained by winding a resin, rubber or the like around a metal roll can be used.

  Further, a crown roll having a diameter changed as it goes from the width central portion to the side can also be used.

  Further, the temperature immediately before contacting the touch roll (36) is preferably Tg or more, more preferably Tg + 50 ° C. or more.

  The temperature of the cooling roll (35) is preferably adjusted by flowing a heat medium such as water or oil through the cooling roll (35).

  The cooled and solidified film is stretched in the width direction. The molecules are oriented by stretching. As a stretching method, a known tenter (37) or the like can be preferably used.

  The stretching is preferably performed under a controlled uniform temperature distribution. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  For the purpose of reducing the dimensional change rate of the thermoplastic resin film produced by the above method, the film may be stretched or shrunk in the longitudinal direction or the width direction. In order to shrink in the longitudinal direction, for example, there is a method in which the film is contracted by temporarily stretching out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine. The latter method can be performed by using a general simultaneous biaxial stretching machine and by using a pantograph method or a linear drive method to drive the clip portion in a smooth and gradually narrowing interval between adjacent clips in the longitudinal direction. it can. You may combine with extending | stretching of arbitrary directions (diagonal direction) as needed. The dimensional change rate of the optical film can be reduced by shrinking 0.5% to 10% in both the longitudinal direction and the width direction.

  The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purpose of reducing the film thickness variation, a method of stretching in the biaxial directions orthogonal to each other is effective, and the stretching ratios in the biaxial directions orthogonal to each other are finally 1.0-2. It is preferable that the range is 1.01 to 2.5 times in the width direction, 0 times, 1.01 to 1.5 times in the casting direction, and 1.05 to 2.0 times in the width direction. Is preferable.

  The method for stretching the film is not particularly limited. For example, a method in which a difference in peripheral speed is provided between a plurality of rolls and the film is stretched in the longitudinal direction using the difference in peripheral speed between the rolls, both ends of the web (10) are clipped. There are a method of fixing with a pin and extending the interval between clips and pins in the moving direction and extending in the vertical direction, a method of extending in the horizontal direction and extending in the horizontal direction, or a method of extending both in the vertical and horizontal directions and extending in both the vertical and horizontal directions. Can be mentioned. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  Before winding with a winder (39), the end may be slit and trimmed to the width of the product, and knurled (embossing) may be applied to both ends to prevent sticking or scratching during winding. Good. The method of knurling can process a metal ring having an uneven putter on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding part of the clip of both ends of a film is cut out, and is reused as a raw material.

  The thermoplastic resin film stretched in the width direction obtained as described above has a fixed retardation with molecules oriented by stretching. The retardation variation is preferably as small as possible, and is usually within 15 nm, preferably 10 nm or less, more preferably 4 nm or less.

  The film thickness of the optical film produced by the production apparatus of the present invention varies depending on the purpose of use, but from the viewpoint of thinning the liquid crystal display device and film strength, it is preferable to adjust the finished film to a range of 10 to 150 μm, Furthermore, it is more preferable to adjust to the range of 20-100 micrometers, and it is especially preferable to adjust to the range of 25-80 micrometers.

  When the cellulose ester film produced by the production apparatus of the present invention is used as an LCD member, high flatness is required to reduce the light leakage of the film, but the center line average roughness of the optical film is required. (Ra) is defined in JIS B 0601, and examples of the measuring method include a stylus method or an optical method.

  In the present invention, the protective film for a polarizing plate is a protective film for a polarizing plate made of an optical film produced by the production apparatus of the present invention and having a polarization scattering anisotropy containing amorphous particles, at the time of film production The average value of the angles (orientation angles) formed by the long-axis direction of each irregularly shaped particle is 0 to 40 °, preferably 0 to 0, when the transport direction is 0 ° and the width direction of the film is 90 °. 20 °, more preferably 0 to 10 °.

  In this invention, a polarizing plate has the protective film for polarizing plates which consists of an optical film manufactured by said this invention on an at least one surface.

  And in this invention, a liquid crystal display device has said polarizing plate in the at least one surface of a liquid crystal cell.

  Next, these polarizing plates and a liquid crystal display device using the polarizing plates will be described.

  The polarizing plate can be produced by a general method. The cellulose ester film according to the present invention subjected to alkali saponification treatment is bonded to at least one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Is preferred. The cellulose ester film according to the present invention may be used on the other surface, or another protective film for polarizing plate may be used. With respect to the cellulose ester film according to the present invention, a commercially available cellulose ester film can be used as the protective film for polarizing plate used on the other surface. For example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA, KC8UX-RHA-N (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used. Or you may use films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate, as a protective film for polarizing plates of the other surface. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

  The polarizing plate is obtained by using the cellulose ester film according to the present invention as a protective film for a polarizing plate on at least one side of a polarizer. At that time, the cellulose ester film is preferably disposed so that the slow axis of the cellulose ester film is substantially parallel or perpendicular to the absorption axis of the polarizer.

  It is preferable that the cellulose ester film by this invention is arrange | positioned at the liquid crystal display cell side as one polarizing plate arrange | positioned on both sides of the liquid crystal cell which is a horizontal electric field switching mode type | mold.

  Examples of the polarizer preferably used for the polarizing plate include a polyvinyl alcohol polarizing film, which includes a polyvinyl alcohol film dyed with iodine and a dichroic dye dyed. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound.

  The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm. On the surface of the polarizer, one side of the cellulose ester film according to the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like. Moreover, in the case of resin films other than a cellulose ester film, it can be bonded to the polarizing plate via an appropriate adhesive layer.

  Since the polarizer is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction orthogonal to the stretching ( Usually stretches in the width direction). As the film thickness of the protective film for polarizing plate decreases, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizer increases. Usually, the stretching direction of the polarizer is bonded to the casting direction (MD direction) of the protective film for polarizing plate. Therefore, when thinning the protective film for polarizing plate, it is important to suppress the stretch rate in the casting direction. It is. Since the cellulose ester film according to the present invention is excellent in dimensional stability, it is suitably used as such a protective film for a polarizing plate.

  The polarizing plate can be constituted by further bonding a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

  A liquid crystal display device using an optical film produced according to the present invention has excellent quality with no unevenness on the screen.

  Since the polarizer is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction orthogonal to the stretching (usually normal) Extends in the width direction. As the film thickness of the protective film for polarizing plate decreases, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizer increases. Usually, the stretching direction of the polarizer is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when the protective film for the polarizing plate is thinned, it is particularly important to suppress the stretching rate in the casting direction. is there. Since the cellulose ester film produced by the present invention is excellent in dimensional stability, it is suitably used as such a protective film for a polarizing plate.

  The polarizing plate can be constituted by further bonding a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

(Liquid crystal display device)
By incorporating a polarizing plate using an optical film produced according to the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced.

  Here, the liquid crystal display device generally absorbs light by a polarizing plate protective film / dichroic material having polarizing scattering anisotropy adjacent to a light reflection plate, a backlight, a light guide plate, and a light diffusion plate. It is preferable that the structure of the dichroic polarizing film / polarizing plate protective film using the action, and the liquid crystal display panel and the viewing side polarizing plate are stacked in this order.

  The optical film produced by the present invention can be used in various drive systems such as reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA, MVA) and IPS. It is preferably used in LCDs. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot in the periphery of the screen, and the effect is maintained for a long time, and a remarkable effect is obtained in the MVA liquid crystal display device. Is recognized. In particular, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even during long viewing.

  As described above, a liquid crystal display device having a polarizing plate using an optical film produced according to the present invention on at least one surface of a liquid crystal cell has very excellent display quality.

  Hereinafter, the present invention will be described in detail by way of examples of solution film formation of cellulose ester, but the present invention is not limited thereto.

Example 1
First, the Example using the optical film manufacturing apparatus by the solution casting film forming method of this invention is described.

[Production of cellulose ester film]
(Preparation of dope)
A dope of cellulose triacetate was prepared as follows.

Cellulose triacetate 100 parts by weight (acetyl substitution degree 2.88, number average molecular weight 150,000)
Triphenyl phosphate 10 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 1 part by weight AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.1 part by weight Needle-like TiO ₂ (Ishihara Sangyo Co., Ltd.) Product name FTL-100) 5 parts by weight Methylene chloride 660 parts by weight Ethanol 40 parts by weight The above materials are put into a sealed container in order, and the temperature in the kettle is raised from 20 ° C to 80 ° C. While maintaining at 80 ° C., stirring was performed for 3 hours to completely dissolve the cellulose triacetate. After that, the stirring was stopped, the liquid temperature was lowered to 43 ° C., and then immediately sent through a connected pipe to the filtration process. Using a filter paper with an absolute filtration accuracy of 0.005 mm, a filtration flow rate of 300 L / m ² · hour Filtration was performed at a filtration pressure of 1.0 × 10 ⁶ Pa.

  The dope prepared as described above was formed using the solution casting film forming apparatus shown in FIG. That is, the dope is flowed on a support (11) made of a stainless steel endless belt through a casting die (1) (casting die A shown in FIG. 4) kept at 30 ° C. by circulating hot water. Extended. The dope viscosity at the time of casting was 50 poise.

Here, as shown in FIGS. 4a and 4b, the casting die A has a manifold portion with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die A: 3850 mm ² (100%). The maximum cross-sectional area of (3) is 11500 mm ² (299%), the minimum cross-sectional area is 1500 mm ² (39%), and the cross-sectional area of the inlet part (2) of the manifold part (3) over the entire length of the manifold part (3) 39% to 299%. The length (L) of the slit portion (4) is 5 mm.

  And finally after drying on a support body (11) until the amount of residual solvent in a web (10) becomes 100 weight%, a web (10) is peeled from a support body (11) with a peeling roll (16). It peeled.

  Next, the web (10) is dried with a drying air (23) of 120 ° C. in an initial drying device (13) equipped with transport rolls (17) arranged in a staggered manner, and then introduced into a tenter (14). Then, both ends of the web (10) are clipped, dried with a drying air (24) of 105 ° C. while maintaining the width, and further provided with a transport roll (17) arranged in a staggered manner after drying device (15 ) With a drying air (25) at 100 ° C., and the cellulose triacetate film was wound up by a winder (18) to finally produce a cellulose triacetate film (20) having a thickness of 80 μm. In addition, through all the above steps, the conveyance speed of the support (11) made of an endless belt and the winding of the winder (18) so that the conveyance tension of the web (10) and the film is 180 N / width m. The speed was adjusted accordingly.

Examples 2-13
Although it carries out similarly to the case of Example 1, the casting die A shown in FIG. 4 is changed into the casting die B-casting die M shown in FIGS. Film formation was performed in the same manner to produce a cellulose triacetate film.

Here, as shown in FIGS. 5 a and 5 b, the casting die B has a manifold portion with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die B: 3850 mm ² (100%). The maximum cross-sectional area of (3) is 7000 mm ² (182%), the minimum cross-sectional area is 1500 mm ² (39%), and the cross-sectional area of the inlet part (2) of the manifold part (3) over the entire length of the manifold part (3) 39% to 182%. The length (L) of the slit portion (4) is 5 mm.

Further, as shown in FIGS. 6 a and 6 b, the casting die C has a manifold section (3%) with respect to the cross-sectional area: 3850 mm ² (100%) of the inlet section (2) of the manifold section (3) of the casting die C. 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 1500 mm ² (39%), and 39 of the cross-sectional area of the inlet part (2) of the manifold part (3) over the entire length of the manifold part (3). % To 100%. The length (L) of the slit portion (4) is 5 mm.

Further, as shown in FIGS. 7a and 7b, the casting die D has a manifold portion (3%) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die D: 3850 mm ² (100%). 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 5 mm ² (0.13%), and the cross-sectional area of the inlet section (2) of the manifold section (3) over the entire length of the manifold section (3). Of 0.13% to 100%. The length (L) of the slit portion (4) is 5 mm.

Further, as shown in FIGS. 8a and 8b, the casting die E has a manifold portion (3) with respect to a cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die E: 3850 mm ² (100%). 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 50 mm ² (1.5%), and the cross-sectional area of the inlet section (2) of the manifold section (3) over the entire length of the manifold section (3). Of 1.5% to 100%. The length (L) of the slit portion (4) is 5 mm.

Further, as shown in FIGS. 9a and 9b, the casting die F has a manifold portion (3%) with respect to the cross-sectional area: 3850 mm ² (100%) of the inlet portion (2) of the manifold portion (3) of the casting die F. 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 500 mm ² (15%), and the cross-sectional area of the inlet part (2) of the manifold part (3) is 15 over the entire length of the manifold part (3). % To 100%. The length (L) of the slit portion (4) is 5 mm.

Also, as shown in FIGS. 10a and 10b, the casting die G has a manifold portion (3) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die G: 3850 mm ² (100%). 3) The cross-sectional area in the middle is 800 mm ² (21%), and there is a widened portion after this, the wide cross-sectional area is 3800 mm ² (99%), the minimum cross-sectional area is 1500 mm ² (39%), and the manifold It is 21% to 100% of the cross-sectional area of the inlet part (2) of the manifold part (3) over the entire length of the part (3). The length (L) of the slit portion (4) is 5 mm.

Further, as shown in FIGS. 11a and 11b, the casting die H has a manifold portion (3%) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die H: 3850 mm ² (100%). 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 1500 mm ² (39%), and 39 of the cross-sectional area of the inlet part (2) of the manifold part (3) over the entire length of the manifold part (3). % To 100%. Further, the length (L) of the land portion (4) is 1 mm.

  The casting dies I to M have substantially the same configuration as the casting die H shown in FIGS. 11 a and 11 b, but the length (L) of the slit portion (4) is different as shown in Table 1. .

  That is, the length (L) of the slit portion (4) of the casting die I is 10 mm. The length (L) of the slit part (4) of the casting die J is 100 mm. The length (L) of the slit part (4) of the casting die K is 500 mm. The length (L) of the slit part (4) of the casting die L is 1000 mm. The length (L) of the slit part (4) of the casting die M is 10,000 mm.

  The structure of the casting dies A to M is as described above. However, in claim 1 of the present invention, the manifold portion corresponds to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die. Since the cross-sectional area at an arbitrary location of (3) is 0.1% to 300% of the cross-sectional area of the inlet portion (2) of the manifold portion (3) over the entire length of the manifold portion (3), the casting die A to M correspond to claim 1 of the present invention.

  Further, in claim 2 of the present invention, the cross-sectional area at an arbitrary position of the manifold portion (3) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die is the manifold portion (3). Therefore, the casting dies B to C and the casting dies E to M are defined in claim 2 of the present invention, since the sectional area of the inlet portion (2) of the manifold portion (3) is 1% to 200%. Corresponding.

  According to claim 3 of the present invention, the cross-sectional area of the manifold portion (3) at an arbitrary position is the total length of the manifold portion (3) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die. Since the cross-sectional area of the inlet portion (2) of the manifold portion (3) is 10% to 300%, the casting die C and the casting dies F to M correspond to claim 3 of the present invention. is there.

  According to claim 4 of the present invention, the cross-sectional area at an arbitrary position of the manifold portion (3) is the total length of the manifold portion (3) with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3) of the casting die. The casting die C, the casting die F, and the casting dies H to M are claimed in claim 4 of the present invention because they are 10% to 100% of the cross-sectional area of the inlet portion (2) of the manifold portion (3). It corresponds to.

Comparative Examples 1 and 2
For comparison, the same procedure as in Example 1 is performed, except that the casting die A is changed to the casting die N and the casting die O shown in FIGS. 12 and 13. Film formation was performed in the same manner as described above to prepare a cellulose triacetate film.

Here, the casting die N corresponds to the casting used in the conventional optical film manufacturing apparatus. As shown in FIGS. 12a and 12b, the casting die N has a manifold portion (3). The cross-sectional area of the inlet part (2): 3850 mm ² (100%), whereas the maximum cross-sectional area of the manifold part (3) is 16000 mm ² (4160%) and the minimum cross-sectional area is 1500 mm ² (39%). It is 39% to 4160% of the cross-sectional area of the inlet portion (2) of the manifold portion (3) over the entire length of 3).

Further, as shown in FIGS. 13a and 13b, the casting die O has a manifold portion (3%) with respect to the cross-sectional area: 3850 mm ² (100%) of the inlet portion (2) of the manifold portion (3) of the casting die O. 3) has a maximum cross-sectional area of 3850 mm ² (100%) and a minimum cross-sectional area of 1 mm ² (0.03%), and the cross-sectional area of the inlet section (2) of the manifold section (3) over the entire length of the manifold section (3). Of 0.03% to 100%.

  In the case of Comparative Example 2 using the casting die O shown in FIG. 13, the dope could not be cast.

<Measurement of orientation degree of amorphous particles>
Using a microtome, a thin section having a thickness of about several hundreds of nanometers was taken out from the cellulose triacetate films prepared in Examples 1 to 13 and Comparative Examples 1 and 2 and photographed at a magnification of 20,000 with a transmission electron microscope. The image is read with a monochrome 256 gradation of 300 dpi using a flatbed scanner, and the read image is taken into image processing software WinROOF (manufactured by Mitani Corporation) installed in a personal computer. Perform domain image extraction on the captured image, confirm that there are more than 300 irregular shaped particles on the screen after extracting irregular shaped particles, and if the extraction is not enough, manually adjust the detection level, Adjustment is performed so that 300 or more irregular particles are detected and extracted. The major axis diameter / minor axis diameter (length in the major axis direction / length in the minor axis direction) is measured for each of the irregular shaped particles of the image data extracted in this manner, and the aspect ratio of the average number of irregular shaped particles is measured. Was calculated. In addition, when the angle formed by the film-forming direction of the protective film for polarizing plate and the major axis direction of the amorphous particles is taken as the orientation angle, the average value of the absolute value of the orientation angle is determined using a transmission electron microscope. After positioning in the film forming direction, each angle between this axis and about 300 irregular shaped particles was measured, and the total number of these was obtained by averaging. The obtained results are shown in Table 1 below.

<Appearance evaluation of display screen and image>
Using the produced cellulose triacetate film, a polarizing plate was produced by the following method, and the appearance was evaluated by attaching it to a panel.

(Preparation of polarizing plate)
A polyvinyl alcohol film having a thickness of 50 μm was uniaxially stretched in the film forming direction (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 6 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of a ratio of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a polarizer. This polarizer had an absorption axis in the film forming direction.

  Subsequently, a polarizing plate was produced according to the following first to fifth steps.

  First step: As the protective film for polarizing plate, the prepared cellulose triacetate film prepared in Examples and Comparative Examples was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried. The side to be bonded to the polarizer was saponified.

  Similarly, saponification of a commercially available cellulose triacetate film KC8UCR-5 (manufactured by Konica Minolta Opto Co., Ltd .: retardation film) was also performed as a protective film for the polarizing plate on the opposite side.

  Second step: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

  Third step: Lightly wipe off excess adhesive adhering to the polarizer in the second step, and use the polarizer as a protective film for polarizing plate treated in the first step on the saponified surface of the brightness enhancing cellulose triacetate film. In addition, as a polarizing plate protective film on the opposite side, the saponified surface of the commercially available cellulose triacetate (TAC) film KC8UCR-5 processed in the first step was laminated so as to be in contact with the polarizer to obtain a polarizing plate. .

Fourth Step: A polarizing plate obtained by laminating a cellulose triacetate film and a cellulose triacetate (TAC) film and a polarizer in the third step was bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Process 5: The polarizing plate produced at the 4th process was dried for 2 minutes in the 80 degreeC drying machine.

<Evaluation of polarizing plate>
The following evaluation was implemented using the polarizing plate produced as mentioned above.

(Production of liquid crystal display device)
A liquid crystal panel for evaluating visibility was produced as follows.

  The polarizer on the backlight side of the 15-inch liquid crystal display VL-1530S manufactured by Fujitsu was peeled off, and the prepared polarizing plates were each bonded to the glass surface of the liquid crystal cell.

  At that time, the direction of bonding of the polarizing plate is such that the surface of the cellulose triacetate film of the polarizing plate is on the backlight side, and the absorption axis is in the same direction as the polarizing plate previously bonded. A liquid crystal display device was produced.

(Evaluation of brightness improvement effect)
The front luminance of the manufactured liquid crystal display device was visually evaluated. Evaluation was performed in the following four stages of x to ◎.

◎: Very high brightness improvement effect ○: Brightness improvement effect △: Slight brightness improvement effect ×: No brightness improvement effect

  As can be seen from the comparison between Examples 1 to 13 and Comparative Example 1, the maximum cross-sectional area of the manifold portion (3) is 300% or less with respect to the cross-sectional area of the inlet portion (2) of the manifold portion (3). Thus, the needle-shaped amorphous particles can be easily oriented in the dope casting direction, and can be more easily oriented when the amount is 200% or less, and can be particularly easily oriented when the amount is 100% or less. Recognize.

  Further, as can be seen from Examples 4 to 6 and Comparative Example 2, if there is a very narrow part in the manifold (3) with respect to the cross-sectional area of the inlet part (2) of the manifold part (3), it takes a die. Since the pressure increases and casting stops, and the film thickness distribution of the manufactured film deteriorates, the manifold part (3) has a cross-sectional area of the inlet part (2) of the manifold part (3). It can be seen that the minimum cross-sectional area is preferably 0.1% or more, more preferably 1% or more, and particularly preferably 10% or more.

  In Example 7, the maximum cross-sectional area of the manifold part (3) is the same as that of Example 3, but the cross-sectional area of the manifold part (3) has been widened after being narrowed once. Comparison of Example 3 and Example 7 It can be seen that the cross-sectional areas of all the manifold parts (3) are preferably equal to or smaller than the cross-sectional areas of all the manifold parts (3) upstream in the casting direction. In order to make the film thickness distribution uniform, the cross-sectional area is preferably 10% or more.

  Examples 8 to 13 are casting dies in which the length (L) of the slit portion (4) is changed from the die C of Example 3. From these comparisons, it can be seen that the longer the length (L) of the slit portion (4), the higher the average orientation degree. Moreover, since the pressure concerning a casting die (1) and piping will become high too much when the length (L) of a slit part (4) is too long, it is preferable that it is 10000 mm or less.

  Moreover, it can be seen from the comparison between Example 7 and Example 3 that the average degree of orientation is increased by gradually narrowing the slit portion (4).

  Further, from the results of Table 1, it can be seen that the brightness enhancement effect and the average degree of orientation of the particles are correlated, and it is found that the average degree of orientation of the particles needs to be improved in order to enhance the brightness enhancement effect.

Example 14
Next, examples using the optical film manufacturing apparatus according to the melt casting method of the present invention will be described.

[Production of cellulose ester film]
(Thermoplastic resin)
100 parts by weight of cellulose acetate propionate (acetyl substitution degree: 2.0, propionyl substitution degree: 0.7,
Number average molecular weight: 75000)
(Plasticizer)
Trimethylolpropane tribenzoate 10 parts by weight Sumilizer GP 0.5 part by weight (antioxidant)
IRGANOX1010 1 part by weight (Ciba Specialty Chemicals)
Needle-like TiO ₂ (trade name FTL-100, manufactured by Ishihara Sangyo Co., Ltd.) 5 parts by weight First, cellulose acetate propionate was dried in air at 120 ° C. for 1 hour and allowed to cool to room temperature. Next, the dried cellulose acetate propionate was heated using an extruder to produce pellets and allowed to cool.

  Referring to FIG. 1, cellulose pellets, plasticizer, antioxidant and needle-like particles are mixed and introduced into a raw material supply hopper (31), and raw materials are fed to a Henschel mixer (32) at a supply rate of 2.0 Kg / hr. Carried and mixed. The mixed raw material is conveyed to an extruder (33), heated and melted at 250 ° C., and the melt is extruded from a casting die (1) according to the present invention (casting die A shown in FIG. 4). As the casting die A, the one shown in FIGS. 4a and 4b of Example 1 was used.

  The melt extruded from the casting die (1) is cooled and surface-corrected by the cooling roll (35). In this case, it is preferable that the web (film) (40) and the cooling roll (35) are in close contact with each other. For example, a touch roll (36) is used as a method for bringing the web (film) (40) into close contact with the cooling roll (35). Press.

  Next, the web (film) (40) is guided to a stretching machine (not shown), and stretched in the longitudinal direction at a temperature of 150 ° C. in the stretching machine, and subsequently obtained using a tenter (37) in the width direction. After the film is stretched at a temperature of 160 ° C., it is relaxed, and after being conveyed by the conveying roll (38), it is wound up at 30 ° C. in a winder (39) to obtain a roll-like cellulose acetate propionate film. .

Examples 15-26
Although it carries out similarly to the case of Example 14, it changes like the case of Example 14 except having changed casting die A into casting die B-casting die M shown in the above-mentioned FIGS. Thus, a cellulose acetate propionate film was produced.

Comparative Examples 3 and 4
For comparison, the same procedure as in Example 14 is performed except that the casting die A is changed to the casting die N and the casting die O shown in FIGS. 12 and 13 described above. Film formation was performed in the same manner as in No. 1 to produce a cellulose acetate propionate film. In the case of Comparative Example 4 using the casting die O shown in FIG. 13, casting of the melt was impossible.

Next, for the cellulose acetate propionate films prepared in Examples 14 to 26 and Comparative Examples 3 and 4, the average orientation angle of the acicular irregularly shaped particles is measured in the same manner as in Examples 1 to 13 above. At the same time, a polarizing plate was prepared using these cellulose acetate propionate films, and the appearance was evaluated by attaching the polarizing plate to a panel. Further, the luminance of liquid crystal display devices was evaluated in Examples 1 to 13. The results obtained are shown in Table 2 below.

  As is clear from the results in Table 2 above, the same results as in Examples 1 to 13 were obtained for Examples 14 to 26 using the optical film manufacturing apparatus according to the melt casting film forming method of the present invention. Thus, it was found that in the melt film formation, in the cellulose acetate propionate film produced using the production apparatus of the present invention, the amorphous particles are easily oriented in the casting direction of the melt.

It is a schematic longitudinal cross-sectional view which shows the example of the apparatus which manufactures an optical film with the solution casting film forming method of this invention. It is a schematic longitudinal cross-sectional view which shows another example of the apparatus which manufactures an optical film with the solution casting film forming method of this invention. It is a flow sheet which shows typically the manufacture device of the optical film by the melt casting film forming method of the present invention. The casting die A used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 4a is an enlarged front view, FIG. 4b is an enlarged side view. The casting die B used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 5a is an enlarged front view, FIG. 5b is an enlarged side view. The casting die C used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 6a is an enlarged front view, FIG. 6b is an enlarged side view. The casting die D used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 7a is an enlarged front view, FIG. 7b is an enlarged side view. The casting die E used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 8a is an enlarged front view, FIG. 8b is an enlarged side view. The casting die F used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 9a is an enlarged front view, FIG. 9b is an enlarged side view. The casting die G used for the manufacturing apparatus of the optical film of this invention is shown, FIG. 10a is an enlarged front view, FIG. 10b is an enlarged side view. FIG. 11A is an enlarged front view, and FIG. 11B is an enlarged side view, showing casting dies H to M used in the optical film manufacturing apparatus of the present invention. The casting die N used for the manufacturing apparatus of the optical film of a comparative example is shown, FIG. 12a is an enlarged front view, and FIG. 12b is an enlarged side view. The casting die O used for the manufacturing apparatus of the optical film of a comparative example is shown, FIG. 13a is an enlarged front view, FIG. 13b is an enlarged side view.

Explanation of symbols

1: Casting die 2: Inlet part 3: Manifold part 4: Slit part 10: Web 11: Endless belt support 12: Casting die 13: Roll conveying initial drying device 14: Tenter drying device 15: Drying device after roll conveyance 16: peeling roll 17: guide roll (conveyance roll)
18: Winding machine 20: Film 31: Supply hopper 32: Henschel mixer 33: Extruder 35: Cooling roll 36: Touch roll 37: Tenter 38: Conveying roll 39: Winding machine 40: Web (film)

Claims (13)

  A dope containing a thermoplastic resin, an organic solvent, and amorphous particles is cast on a support through a manifold part and a slit part of a casting die, and an optical film is produced by a solution casting film forming method. The cross-sectional area of the manifold part at the arbitrary position of the manifold part is 0.1% to 300% of the cross-sectional area of the manifold part over the entire length of the manifold part. An apparatus for producing an optical film, comprising:   The cross-sectional area at an arbitrary position of the manifold part is 1% to 200% of the cross-sectional area of the inlet of the manifold part over the entire length of the manifold part with respect to the cross-sectional area of the inlet of the manifold part of the casting die. Item 2. An optical film manufacturing apparatus according to Item 1.   The cross-sectional area at an arbitrary position of the manifold part is 10% to 100% of the cross-sectional area of the manifold part inlet over the entire length of the manifold part with respect to the cross-sectional area of the inlet of the manifold part of the casting die, The apparatus for producing an optical film according to claim 1.   The cross-sectional area at an arbitrary location of the manifold portion of the casting die is 10% to 100% of the cross-sectional area of the manifold portion on the upstream side in the dope flow direction from the location. The manufacturing apparatus of the optical film as described in any one of them.   The width of the slit gap of the slit part of the casting die is narrowed so as to reach the downstream side in the dope flow direction, The optical film according to any one of claims 1 to 4, Manufacturing equipment.   A melt obtained by melting and kneading thermoplastic resin and amorphous particles is cast on a support through the manifold part and slit part of a casting die, and optically obtained by a melt casting film forming method. An apparatus for producing a film, wherein a cross-sectional area at an arbitrary position of the manifold part is 0.1% to a cross-sectional area of the manifold part inlet over the entire length of the manifold part with respect to a cross-sectional area of the manifold part inlet of the casting die An apparatus for producing an optical film, characterized by being 300%.   The cross-sectional area at an arbitrary position of the manifold part is 1% to 200% of the cross-sectional area of the inlet of the manifold part over the entire length of the manifold part with respect to the cross-sectional area of the inlet of the manifold part of the casting die. Item 7. The optical film manufacturing apparatus according to Item 6.   The cross-sectional area at an arbitrary position of the manifold part is 10% to 100% of the cross-sectional area of the manifold part inlet over the entire length of the manifold part with respect to the cross-sectional area of the inlet of the manifold part of the casting die, The manufacturing apparatus of the optical film of Claim 6.   The cross-sectional area of an arbitrary portion of the manifold portion of the casting die is 10% to 100% of the cross-sectional area of the manifold portion on the upstream side in the melt flow direction from the portion. The manufacturing apparatus of the optical film as described in any one of them.   The optical film according to any one of claims 6 to 9, wherein the width of the slit gap of the slit portion of the casting die is made narrower toward the downstream side in the melt flow direction. Manufacturing equipment.   The length of the slit part of a casting die is 1 mm-10000 mm, The optical film manufacturing apparatus as described in any one of Claims 1-10 characterized by the above-mentioned.   The length of the slit part of a casting die is 10 mm-1000 mm, The optical film manufacturing apparatus as described in any one of Claims 1-10 characterized by the above-mentioned.   The length of the slit part of a casting die is 100 mm-500 mm, The optical film manufacturing apparatus as described in any one of Claims 1-10 characterized by the above-mentioned.

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