JP2007304559A - Polarizing plate protective film having polarized light scattering anisotropy, polarizing plate using the same and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective film of a polarizing plate which can improve optical characteristics of a display, particularly luminance because the polarizing plate protective film itself has polarized light scattering anisotropy, and which is excellent in productivity and durability. <P>SOLUTION: The polarizing plate protective film having the polarized light scattering anisotropy comprises at least a cellulose ester-based optical continuous phase and domains having optical anisotropy and an aspect ratio of ≥2, wherein an average angle of directions of the domains having the optical anisotropy is in a direction perpendicular or parallel to the film forming direction of the polarizing plate protective film, and an average H of the absolute values of the angles between the average angle of the directions and the respective domains is within 20°, and wherein at least one surface of the polarizing plate protective film having the polarized light scattering anisotropy has a contact angle to water of 60-80° before saponification treatment and a contact angle to water of 15-40° after saponification treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate protective film having polarization scattering anisotropy, a polarizing plate using the polarizing plate protective film, and a liquid crystal display device, and more particularly, providing a polarizing plate protective film with a luminance improving function, a luminance improving function and a polarizing plate protective function. The present invention relates to a polarizing plate provided with a film in which at least one surface is integrated, and a liquid crystal display device using the polarizing plate.

  Natural light and light from an artificial light source are non-polarized light (random polarized light), but by using a polarizing plate, 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 a device 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. However, the polarizing film having polarization scattering anisotropy scatters forward or backward without absorbing the polarization component orthogonal to the polarization axis, and improves the light use efficiency of the polarizing film. Patent Documents 1 and 2 propose a method for producing an anisotropic scatterer by blending a positive intrinsic birefringent polymer and a negative intrinsic birefringent polymer and uniaxially 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 the polarizing plate protective film, a film composed of cellulose ester is generally used, but the film has birefringence, and the retardation value is generally present in the film plane or in the thickness direction of the film. To do.

  Conventionally, a polarizing plate is formed by pasting a protective film having the above retardation value in the film plane or in the thickness direction of the film on both sides of the dichroic polarizing film, and further polarizing scattering on one side of the polarizing plate. The structure by which the film (brightness improvement film) which has anisotropy was bonded was common (for example, refer patent document 3).

  When a film having polarization scattering anisotropy and a dichroic polarizing film are arranged as described above, if a film having birefringence exists between them, this will function as a retardation film. . As a result, if a film having birefringence exists between the two, the optical characteristics of the display are changed in transmittance and color, which causes 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.
JP-A-9-274108 JP-A-11-174231 JP 2003-43261 A

  Therefore, an 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. And providing a polarizing plate using the polarizing plate protective film and providing a liquid crystal display device using the polarizing plate.

  The above object of the present invention is achieved by the following configurations.

1. A polarizing plate protective film having polarization scattering anisotropy comprising at least an optical continuous phase mainly composed of cellulose ester and a domain having an optical anisotropy having an aspect ratio of 2 or more defined by the following formula:
The average azimuth angle of the domain having optical anisotropy is perpendicular or parallel to the film forming direction of the polarizing plate protective film, and the absolute value of the angle formed by the average azimuth angle and each domain The average value H is within 20 °, and at least one surface of the polarizing plate protective film having polarization scattering anisotropy has a contact angle with water before saponification treatment of 60 ° or more and 80 ° or less, and saponification treatment. A polarizing plate protective film having polarization scattering anisotropy, characterized in that the subsequent contact angle with water is 15 ° or more and 40 ° or less.

Expression Aspect ratio = absolute maximum length / diagonal width (here, the diagonal width is the shortest distance between two straight lines when sandwiching the image of the domain projected by two straight lines parallel to the absolute maximum length) .)
2. A polarizing plate integrated in the order of a polarizing plate protective film having polarization scattering anisotropy as described in 1 above / a dichroic polarizing film / polarizing plate protective film B utilizing a light absorption action by a dichroic substance. A polarizing plate, wherein the absorption axis of the dichroic polarizing film is in the longitudinal direction of the film.

  3. 3. A liquid crystal display device comprising the polarizing plate according to 2 and a polarizing plate protective film having polarization scattering anisotropy disposed on a light source side.

  According to the present invention, since the polarizing plate protective film itself has polarization scattering anisotropy, it is possible to improve the optical characteristics of the display, particularly the luminance, and to provide a polarizing plate protective film excellent in productivity and durability, and A polarizing plate using a polarizing plate protective film and a liquid crystal display device using the polarizing plate can be provided.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The present invention relates to a polarizing plate protective film having polarization scattering anisotropy comprising at least an optical continuous phase mainly composed of cellulose ester and a domain having optical anisotropy having an aspect ratio of 2 or more defined by the following formula: The average azimuth angle of the domain having optical anisotropy is perpendicular or parallel to the film forming direction of the polarizing plate protective film, and the angle formed by the average azimuth angle and each domain The average value H of the absolute values of the polarizing plate protective film is within 20 °, and at least one surface of the polarizing plate protective film has a contact angle with water before saponification treatment of 60 ° or more and 80 ° or less, and water after saponification treatment. A polarizing plate protective film having polarization scattering anisotropy characterized in that the contact angle with respect to the polarizing plate is 15 ° or more and 40 ° or less, whereby the luminance can be improved and the polarizing plate protective film excellent in productivity and durability And providing a polarizing plate using the polarizing plate protective film, and providing a liquid crystal display device using the polarizing plate.

Expression Aspect ratio = absolute maximum length / diagonal width (here, the diagonal width is the shortest distance between two straight lines when sandwiching the image of the domain projected by two straight lines parallel to the absolute maximum length) .)
A film having polarization scattering anisotropy (also referred to as a brightness enhancement film) is composed of a domain having a refractive index of an optical continuous phase and an optical anisotropy, as disclosed in JP-A-11-509014. By forming a film with substantially the same refractive index on the transmission axis side, it selectively transmits predetermined polarized light, selectively scatters other polarized light, and reuses scattered light to reduce brightness. Can be improved. However, in order to sufficiently improve the light utilization rate of the film having polarization scattering anisotropy, the optical continuous phase must be colorless and transparent and easily stretched. Although it is necessary that the difference in refractive index between the transmission axis side and the slow axis side of the domain having a directivity is large, selection of a material satisfying these requirements has been extremely difficult.

  As a result of intensive studies on the above problems, the present inventors have found that a polarizing plate protective film having polarizing scattering anisotropy / dichroic polarizing film / polarizing plate protective film utilizing light absorption by a dichroic substance. B has a monolithic structure and mainly uses cellulose ester as an optical continuous phase, and the domain having optical anisotropy has an average azimuth with respect to the film forming direction of the polarizing plate protective film, A polarizing plate protective film that is orthogonal or parallel and is arranged such that an average value H of absolute values of angles formed by the average azimuth angle and each domain is within 20 °, and further has the polarization scattering anisotropy It was found that by adjusting the suitability of saponification treatment on at least one side, it is possible to improve the luminance, and to obtain a polarizing plate excellent in productivity and productivity by reducing the number of members and simplifying the manufacturing process. A. Hereinafter, the polarizing plate protective film having polarization scattering anisotropy according to the present invention may be simply referred to as a polarizing plate protective film, and will be handled separately from the polarizing plate protective film B.

  In the present invention, the optical continuous phase refers to an optical phase in which the refractive index of each portion of the polymer film is substantially constant and continuous, and the variation in each portion of the refractive index is less than 0.01. The variation in refractive index is preferably 0.005 or less, particularly preferably 0.001 or less. The domain having optical anisotropy refers to a minute region having a difference in refractive index between the major axis direction of the domain and the minor axis direction perpendicular to the domain, and the difference in refractive index is preferably 0.01 or more.

  FIG. 1 is a schematic view of a polarizing plate protective film having polarization scattering anisotropy including an optical continuous phase mainly composed of cellulose ester and domains according to the present invention.

  FIG. 1a shows a state in which an optically anisotropic domain is oriented in a substantially constant direction in the width direction (TD direction) of the polarizing plate protective film in the optical continuous phase 1 mainly composed of cellulose ester. ing. When the refractive index of the optical continuous phase (resin) is n1, the refractive index in the major axis direction of the domain is n2, and the refractive index in the minor axis direction of the domain is n3, when n1 = n2 and n2 <n3, the domain The polarized light parallel to the major axis direction is transmitted through the polarizing plate protective film, and the polarized light parallel to the minor axis direction is scattered. If the transmitted polarized light is parallel to the transmission axis of the light absorbing polarizer, the polarized light is transmitted through the polarizer.

  FIG. 1 b shows a state in which optically anisotropic domains are arranged in a substantially constant direction in the longitudinal direction (MD direction) of the polarizing plate protective film in the optical continuous phase 1 mainly composed of cellulose ester. . Also in this case, when the refractive index of the optical continuous phase (resin) is n1, the refractive index in the major axis direction of the domain is n2, and the refractive index in the minor axis direction of the domain is n3, n1 = n3 and n2 <n3. At some point, polarized light parallel to the short axis direction of the domain is transmitted and polarized light parallel to the long axis direction is scattered. If the transmitted polarized light is parallel to the transmission axis of the light absorbing polarizer, the polarized light is transmitted through the polarizer.

  The domain having optical anisotropy according to the present invention is a domain having an aspect ratio defined by the above formula of 2 or more. The aspect ratio is preferably in the range of 2 to 100, more preferably in the range of 2 to 25.

  Evaluation of the orientation state and dispersion state of the domains in the film can be obtained using image data obtained by observing the domains in the film with an electron microscope.

  From the image data, an azimuth angle and an aspect ratio are obtained for each domain. The aspect ratio can be obtained by the above formula. The absolute maximum length corresponds to the length (major axis) of the major axis of the domain.

  A domain having an aspect ratio of less than 2 such as a foreign substance or a broken domain becomes noise, and is excluded from the calculation of the average azimuth angle and the average inter-domain distance, and is obtained for each domain having an aspect ratio of 2 or more.

  The angle with the reference axis when taking the absolute maximum length of the domain is taken as the azimuth angle. The reference axis can be set arbitrarily, but can be set, for example, in the width direction of the film. The azimuth angle of each domain was determined, and the average value was taken as the average azimuth angle.

  Next, the direction of the obtained average azimuth angle was set as a new reference axis, the angle difference between the azimuth angle and the average azimuth angle direction was obtained for each domain, and the average of the absolute values of the angle differences was obtained. This is [the average value H of the absolute value of the angle formed by the direction of the average azimuth and the azimuth of each domain]. In the present invention, the average azimuth angle of the domain having optical anisotropy is perpendicular or parallel to the film forming direction of the polarizing plate protective film, and the H is within 20 °.

  A specific evaluation method will be described. The produced film was photographed at a magnification of 20,000 with a transmission electron microscope, and the image was read with a scanner Canon Scan FB 636U by Canon Inc. in 300 dpi monochrome 256 gradation.

  The read image was taken into the image processing software WinROOF Ver3.60 (manufactured by Mitani Corp.) installed in the Endeavor Pro720L (CPU: Athlon-1 GHz, memory: 512 MB) which is a personal computer manufactured by Epson Direct.

  As an image pre-processing for the captured image, a field range of 2 × 2 μm was extracted (automatic binarization of the image) to extract a domain image. Confirm that 90% or more of the domain has been extracted on the screen after extracting the domain image. If the extraction is not sufficient, manually adjust the detection level so that 90% or more of the domain is detected and extracted. Make adjustments.

  When the number of domains in the observation range was less than 1000, the same operation was performed for another 2 × 2 μm field of view until the total number of domains reached 1000 or more.

  The azimuth angle was measured for each domain of the image data extracted in this way. The azimuth angle of the domain will be described with reference to FIG.

  FIG. 2 shows an example of an image obtained by photographing a film containing a domain at a magnification of 20,000 with a microscope and reading it with a scanner. For each domain, the azimuth of the absolute maximum length (major axis direction) of the domain with respect to the reference axis is calculated. a1, a2 ... an. The average value A = ave (a1 to an) of these azimuths is calculated and set as the average azimuth. As the number of domains (n), 1000 or more are measured, and an average value is calculated.

  When this average azimuth is within ± 5 ° with respect to the film forming direction of the film, it is said to be parallel to the film forming direction (longitudinal direction). Similarly, when it is within ± 5 ° with respect to the direction (width direction) perpendicular to the film forming direction of the film, it is said to be in the direction orthogonal to the film forming direction of the film. Preferably, the average azimuth angle is preferably in the direction of ± 3 °, more preferably in the direction of ± 1 °, particularly preferably ± 0, with respect to the film forming direction or the width direction of the film. It is in the direction of 5 °.

  Further, [the average value H of the absolute value of the angle formed by the direction of the average azimuth angle and the azimuth angle of each domain] is within 20 °.

FIG. 3 illustrates H. In the figure, b1, b2, b3,..., Bn are angles formed by the average maximum azimuth direction of the absolute maximum length direction (major axis direction) of each domain,
H = ave (| b1 | ˜ | bn |)
Thus, an average value H of the absolute values is obtained. This is also measured for 1000 or more domains, as in the calculation of A above.

  H is within 20 °, preferably 2 to 19 °, and most preferably 2 to 11 °.

  As a method of dispersing and orienting domains, there are a method of stretching a film to TD or MD at the time of film production (casting), or a method of orienting domains in a form along this flow by creating a dope flow at the time of casting. It is possible to take. Furthermore, domain orientation can be promoted by an electric field or a magnetic field.

  As a method for producing a polarizing plate protective film containing these domains, a dispersion containing at least a domain and a resin for dispersing the domain is prepared in advance, and then the dispersion and the cellulose ester are mixed with a solvent. It can obtain by the manufacturing method of the polarizing plate protective film which casts a solution using dope prepared by. Similarly, a polarizing plate protective film can be obtained by a melt casting method.

  Hereinafter, the domain according to the present invention will be further described.

  The material forming the domain of the present invention is not particularly limited, but is a polymer or polymer nanoparticle exhibiting negative birefringence in the stretching direction and the flow direction, positive in the stretching direction and the flow direction. It is preferable to use a liquid crystal polymer exhibiting birefringence as appropriate.

  In any case, birefringence can be exhibited by deforming the film by an external force in a state of being phase-separated in the film.

  The polymer or polymer nanoparticles exhibiting negative birefringence with respect to the stretching direction or the flow direction means a material exhibiting negative birefringence with respect to the stretching direction or the flow direction in the cellulose ester film.

  The mass fraction of the cellulose ester and the polymer, polymer nanoparticles, or liquid crystal polymer constituting the polarizing plate protective film of the present invention is 0 <[(polymer, polymer nanoparticles or liquid crystal polymer) / (cellulose ester)] <1. 0.0 relationship is preferable. Furthermore, a relationship of 0.001 <[(polymer, polymer nanoparticle or liquid crystal polymer) / (cellulose ester)] <0.5 is preferable.

  In order to control the birefringence of the polarizing plate protective film of the present invention, it is preferable to add at least one kind of the polymer, polymer nanoparticles or liquid crystal polymer, but two or more kinds may be used.

  Examples of the polymer oriented by stretching or flow and exhibiting negative birefringence include polystyrene and polymethyl methacrylate described in JP-A No. 2004-109355.

  In the present invention, it is preferable to use the following polymers or polymer nanoparticles that exhibit negative birefringence in the stretching direction and the flow direction.

  Whether or not the polymer or polymer nanoparticle exhibits negative birefringence by stretching can be determined by the following test method.

<Birefringence test of polymer or polymer nanoparticles>
Polymer or polymer nanoparticles were added to cellulose ester, dissolved in a solvent, cast into a film, stretched in one direction, dried by heating, and evaluated for birefringence of a film having a transmittance of 80% or more. Refractive index measurement was performed using a multiwavelength light source for the Abbe refractometer 1T. The refractive index in the in-plane direction orthogonal to ny in the stretching direction was defined as nx. When the (ny-nx) difference for each refractive index at 550 nm shows a lower value or a negative value than the same refractive index difference of the film of the same draw ratio without the polymer or polymer nanoparticles, the polymer or polymer nano It is judged that the particles have negative birefringence in the stretching direction.

<polymer>
Although it is not particularly limited as a polymer showing negative birefringence with respect to the stretching direction and the flow direction used in the present invention, for example, a weight average molecular weight obtained by polymerizing an ethylenically unsaturated monomer is 500 or more. It is preferable to contain a polymer that is 10,000 or less.

  Furthermore, the polarizing plate protective film of the present invention preferably contains an acrylic polymer having a weight average molecular weight of 500 or more and 100,000 or less that exhibits negative birefringence in the stretching direction, and the acrylic polymer has an aromatic ring. An acrylic polymer having a side chain or an acrylic polymer having a cyclohexyl group in the side chain is preferred.

  By controlling the composition of the polymer having a weight average molecular weight of 700 to 50,000, the compatibility between the cellulose ester and the polymer can be improved, and neither evaporation nor volatilization occurs during film formation. . In particular, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or an acrylic polymer having a cyclohexyl group in the side chain preferably has a weight average molecular weight of 500 to 5,000, in addition to the above. The latter cellulose ester film has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 700 or more and 50000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like. The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring. The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl) acrylate (2-ethoxyethyl), etc., or the acrylic acid ester can be exemplified those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. Is preferred. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Examples include benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, and acrylic acid (2-naphthyl), but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  In the acrylic polymer having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. It is preferable to have. The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

  In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and preferably 50 to 80% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  Polymers obtained by polymerizing the above ethylenically unsaturated monomers, acrylic polymers, acrylic polymers having an aromatic ring in the side chain, and acrylic polymers having a cyclohexyl group in the side chain are all compatible with the cellulose resin. Excellent.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in an acrylic polymer in an amount of 2 to 20% by mass.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is acrylic acid-2-hydroxyethyl and methacrylic acid-2-hydroxyethyl. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, low moisture permeability, and polarized light. It is particularly excellent in adhesiveness with a polarizer as a protective film for plates, and has the effect of improving the durability of the polarizing plate.

  Moreover, in this invention, when blending a polymer or a polymer nanoparticle with a cellulose ester, in order to give compatibility, it is preferable to have a hydroxyl group at the terminal of at least one of the principal chain of an acrylic polymer. The method of having a hydroxyl group at the end of the main chain is not particularly limited as long as it has a hydroxyl group at the end of the main chain, but a radical having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method using a polymerization initiator, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and a method of having a hydroxyl group at the terminal by living ion polymerization Bulk polymerization using a compound having one thiol group and a secondary hydroxyl group as described in JP-A No. 2000-128911 or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination The method described in the publication is particularly preferable. The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  Furthermore, when polymer or polymer nanoparticles are blended into cellulose ester, negative refraction is a polymer using styrene as an ethylenically unsaturated monomer that exhibits negative birefringence in the stretching direction and flow direction. It is preferable for expressing the sex. Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, and vinyl benzoic acid methyl ester. Although it is mentioned, it is not a thing limited to these. It may be copolymerized with the exemplified monomers listed as the unsaturated ethylenic monomer, or may be used by being dissolved in a cellulose ester using two or more of the above polymers for the purpose of controlling birefringence.

  The polymer nanoparticles referred to in the present invention refer to nano-level polymer ultrafine particles having a particle size of several nanometers to several hundred nanometers, and exhibit various surface effects because of their high specific surface area.

  The polymer nanoparticles used in the present invention are preferably particles having a particle diameter of 1 nm to 500 nm, more preferably 10 nm to 350 nm, still more preferably 10 nm to 150 nm, and particularly preferably 10 nm to 100 nm. If it is less than 1 nm, the effect of controlling birefringence is insufficient, and if it exceeds 500 nm, an increase in haze is observed. The particle diameter in the present invention is defined as a value obtained on average as a volume particle diameter in terms of a sphere. The measurement method can be determined using techniques such as, but not limited to, standard dynamic light scattering, small angle neutron scattering NMR diffusion, X-ray scattering, and gel phase chromatography. For example, an average particle size index is obtained by gel permeation chromatography (GPC) elution time obtained for polymer nanoparticles. The particle size of the polymer nanoparticles can be determined by comparing the polymer nanoparticles to a polystyrene standard with known molecular weight and hydrodynamic radius. The gel permeation chromatography technique used uses a column containing a 10 μm PL gel to determine the elution time of the crosslinked polymer nanoparticles and the elution time of a polystyrene standard with known molecular weight and hydrodynamic radius. This is done by comparing.

  The material of the polymer nanoparticles is not particularly limited, but examples include (meth) acrylic, styrene, (meth) acryl-styrene, fluorine-substituted (meth) acrylic and fluorine-substituted (meth) acrylic. It is preferable to use polymer nanoparticles which are at least one (co) polymer selected from styrene.

  The polymer nanoparticles as a (meth) acrylic (co) polymer are used as a (co) polymer of a (meth) acrylic acid ester monomer or a copolymer with another monomer. Examples of the (meth) acrylate monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylic acid Butyl, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Acid nonyl, decyl (meth) acrylate, dodecyl (meth) acrylate, phenyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, (meth ) Acrylic acid such as butoxyethyl acrylate and ethoxypropyl (meth) acrylate Acid alkyl esters; dialkylaminoalkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate; (meth) acrylamides; (meth) acrylamides such as N-methylol (meth) acrylamide and diacetone acrylamide and glycidyl (meth) acrylates; (Poly) alkylene such as ethylene glycol diacrylate, diethyl glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate Diacrylate of glycols; Dimethacrylate of ethylene glycol, Dimethacrylate of diethylene glycol (Poly) such as dicarboxylic acid ester of triethylene glycol, dimethacrylic acid ester of polyethylene glycol, dimethacrylic acid ester of propylene glycol, dimethacrylic acid ester of dipropylene glycol, dimethacrylic acid ester of tripropylene glycol, etc. Examples thereof include dimethacrylic acid esters of alkylene glycol.

  Other monomers other than the (meth) acrylic monomer described above include, for example, styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl. Alkyl styrenes such as styrene and octyl styrene; Halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and chloromethylstyrene; Styrenes such as nitrostyrene, acetylstyrene, methoxystyrene, α-methylstyrene, vinyltoluene Mention may be made of monomers.

  Furthermore, as monomers other than styrene monomers, for example, silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate , Vinyl esters such as vinyl caproate, vinyl persuccinate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pt-butylbenzoate, vinyl salicylate; vinylidene chloride, vinyl chlorohexanecarboxylate, acrylic acid -2-chloroethyl, methacrylic acid-2-chloroethyl and the like.

  Furthermore, if necessary, as other monomers having a functional group, for example, acrylic acid, methacrylic acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, bicyclo [ 2,2,1] hept-2-ene-5,6-dicarboxylic acid and the like, and as derivatives thereof, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride Acid, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid anhydride, and for example, a polymerization reactive monomer having a hydroxyl group (OH; hydroxyl group) includes 2-hydridoacrylic acid. Xylethyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 1,1, -Trihydroxymethylethane triacrylate, 1,1,1-trishydroxymethylmethylethane triacrylate, 1,1,1-trishydroxymethylpropane triacrylate; hydroxyalkyl vinyl ethers such as hydroxy vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether And hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl acrylate, and diethylene glycol mono (meth) acrylate, and the like. These single or two or more kinds of monomer composites are suitably used as appropriate. Can be used.

  The polymer nanoparticles formed from the above-described resin can be appropriately prepared by soap-free emulsion polymerization, suspension polymerization, emulsion polymerization or the like. When preparing a polymer nanoparticle suspension by soap-free emulsion polymerization, it is generally sufficient that persulfates such as potassium persulfate and ammonium persulfate are soluble in an aqueous medium during polymerization as a polymerization initiator. Moreover, what is necessary is just to add a polymerization initiator in 0.1-10 mass parts with respect to 100 mass parts of polymerization monomers normally, Preferably it is 0.2-2 mass parts. In the case of an emulsion polymerization method, a suspension thereof is prepared. As a polymerization initiator, a persulfate such as potassium persulfate or ammonium persulfate is used. An alkylbenzene sulfone such as sodium dodecylbenzenesulfonate is used with the above monomer as an emulsifier. An emulsifier such as an acid salt and polyethylene glycol alkyl ether such as polyethylene glycol nonylphenyl ether is usually 0.01 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the polymerization monomer. It is mixed with a medium to make an emulsified state. Similarly, usually, the polymerization initiator may be added in an amount of 0.1 to 10 parts by mass, preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the polymerization monomer. In addition, a method for producing fine particles of an organic compound by laser light irradiation described in JP-A-2001-113159 can also be applied.

  Among these, in order to exhibit negative birefringence with respect to stretching and flow, the composition of the polymer nanoparticles can be appropriately selected. In addition, the polymer constituting the polymer nanoparticles is not limited by the molecular weight of the polymer that affects the compatibility, and the particle size for preventing light from scattering in the visible light region may be in the above range.

  The method for adding the polymer nanoparticles is not particularly limited, but it is preferable to add the polymer nanoparticles in-line together with a matting agent and the like which will be described later in view of being uniformly dispersed in the film.

  On the other hand, examples of liquid crystal polymers exhibiting positive birefringence in the stretching direction include room temperature such as cyanobiphenyl, cyanophenylcyclohexane, cyanophenyl ester, benzoic acid phenyl ester, phenylpyrimidine, and mixtures thereof. Alternatively, a low molecular liquid crystal or a crosslinkable liquid crystal monomer exhibiting a nematic phase or a smectic phase at a high temperature, or a liquid crystal polymer exhibiting a nematic phase or a smectic phase at a room temperature or a high temperature. The crosslinkable liquid crystal monomer is usually subjected to an alignment treatment, and then subjected to a crosslinking treatment by an appropriate method using heat, light, or the like to obtain a polymer.

  The liquid crystal polymer that can be preferably used in view of the formability of a micro region having excellent uniformity of particle size distribution, thermal stability, moldability to a film, ease of alignment treatment, and the like, has a polymerization degree of 8 or more, especially 10 or more. In particular 15-5000.

  When a liquid crystal polymer is used, cellulose ester and one or more liquid crystal polymers for forming a microregion are mixed to form a cellulose ester film containing the liquid crystal polymer dispersed in a microregion state. It can be performed by a method of forming a region having different birefringence by orientation treatment by a method. In view of controlling the refractive index difference by the alignment treatment, those exhibiting a nematic liquid crystal phase in a temperature range having a glass transition temperature of 50 ° C. or higher and lower than the glass transition temperature of the cellulose ester can be preferably used. Incidentally, specific examples thereof include a side chain type liquid crystal polymer having a monomer unit represented by the following general formula.

  In the above general formula, X is a skeleton group that forms the main chain of the liquid crystal polymer, and may be formed of an appropriate connecting chain such as linear, branched, or cyclic. Examples include polyacrylates and polymethacrylates, poly-α-haloacrylates and poly-α-cyanoacrylates, polyacrylamides and polyacrylonitriles, polymethacrylonitriles and polyamides, polyesters and polyurethanes. , Polyethers, polyimides, polysiloxanes and the like.

  Y is a spacer group branched from the main chain, and preferable spacer group Y is, for example, ethylene, propylene, butylene, pentylene, hexylene, octylene, decylene, etc. Undecylene, dodecylene, octadecylene, ethoxyethylene, methoxybutylene, and the like.

  On the other hand, Z is a mesogenic group that imparts liquid crystal alignment, and examples thereof include the following compounds.

  The terminal substituent A in the compound is, for example, a cyano group, an alkyl group, an alkenyl group, an alkoxy group, an oxaalkyl group, a haloalkyl group, a haloalkoxy group, or a haloalkenyl group in which one or more of hydrogen is substituted with fluorine or chlorine. It may be appropriate.

  In the above, the spacer group Y and the mesogenic group Z may be bonded via an ether bond, that is, —O—. Further, the phenyl group in the mesogenic group Z may have one or two hydrogens substituted with halogen, in which case chlorine or fluorine is preferred as the halogen.

  The nematic alignment side chain type liquid crystal polymer described above may be an appropriate thermoplastic polymer such as a homopolymer or copolymer having the monomer unit represented by the above general formula, and among them, those having excellent monodomain alignment properties. preferable.

  A polarizing plate protective film using a liquid crystal polymer with nematic orientation is formed by forming a cellulose ester film containing the liquid crystal polymer dispersed in a minute region, and then heat-treating the liquid crystal polymer forming the domain to form a nematic liquid crystal. It can be performed by a method of aligning the phases and cooling and fixing the alignment state.

  Formation of the cellulose ester film containing the above-mentioned domain dispersedly, that is, the film to be oriented is obtained by an appropriate method such as a casting method, an extrusion molding method, an injection molding method, a roll molding method, or a casting method. It can also be carried out by a method in which it is developed in a monomer state and polymerized by heat treatment or radiation treatment such as ultraviolet rays to form a film.

  From the viewpoint of obtaining a polarizing plate protective film having excellent domain uniform distribution, a method of forming a film of a mixture of a forming material through a solvent by a casting method, a casting method, or the like is preferable. In that case, the size and distribution of the microscopic region can be controlled by the type of solvent, the viscosity of the liquid mixture, the drying speed of the liquid mixture spreading layer, and the like. Incidentally, in order to reduce the area of the domain, it is advantageous to reduce the viscosity of the mixed liquid or to accelerate the drying speed of the mixed liquid spreading layer.

  For example, the orientation treatment of the domain is a uniaxial or biaxial, a sequential biaxial or Z-axial stretching treatment method, a rolling method, an electric field or a magnetic field applied at a temperature equal to or higher than the glass transition temperature or liquid crystal transition temperature, and is rapidly cooled for orientation. One or two types of appropriate methods capable of controlling the refractive index by orientation, such as a method of fixing, a method of fluid orientation during film formation, and a method of self-aligning liquid crystals based on a slight orientation of an isotropic polymer The above can be used.

(Cellulose ester)
Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester which concerns on this invention, Cotton linter, wood pulp, kenaf etc. can be mentioned. Moreover, the cellulose ester obtained from them can be used individually or in mixture in arbitrary ratios, respectively.

In the cellulose ester according to the present invention, when the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), an organic solvent such as acetic acid or an organic solvent such as methylene chloride is used. The reaction is carried out using a protic catalyst such as sulfuric acid. When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804. In the cellulose ester, the acyl group reacts with the hydroxyl group of the cellulose molecule. Cellulose molecules are composed of many glucose units linked, and there are three hydroxyl groups per glucose unit. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cellulose triacetate has an acetyl group bonded to all three hydroxyl groups of the glucose unit.

  The cellulose ester that can be used for the polarizing plate protective film preferably has a total acyl group substitution degree of 2.4 to 2.8.

  The molecular weight of the cellulose ester used in the present invention is 50,000 to 350,000 in terms of weight average molecular weight (Mw). More preferable is 60000-300000, and 80000-250,000 is particularly preferable.

  In the cellulose ester used in the present invention, the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), Mw / Mn is preferably 1.4 to 3.9 as described above, and more preferably. It is in the range of 1.6 to 3.5.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples were used. The 13 samples are preferably used at approximately equal intervals.

  The cellulose ester used in the present invention is a carboxylic acid ester having about 2 to 22 carbon atoms, and is particularly preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate phthalate, etc. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate as described in U.S. Pat. No. 8,231,761, U.S. Pat. No. 2,319,052 can be used. Alternatively, esters of aromatic carboxylic acids and cellulose and cellulose acylate described in JP-A Nos. 2002-179701, 2002-265639, and 2002-265638 are also preferably used. Among the above descriptions, the lower fatty acid esters of cellulose particularly preferably used are cellulose triacetate and cellulose acetate propionate. These cellulose esters can be used as a mixture.

  A preferred cellulose ester other than cellulose triacetate has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of acetyl group is X, and the substitution degree of propionyl group or butyryl group is Y, It is a cellulose ester that simultaneously satisfies (a) and (b).

Formula (a) 2.4 ≦ (X + Y) ≦ 2.8
Formula (b) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used, among which 1.5 ≦ X ≦ 2.5, preferably 0.1 ≦ Y ≦ 2.0, and more preferably 0.3 ≦ Y ≦ 1. 5 is preferred.

  The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods. These acyl group substitution degrees can be measured according to the method prescribed in ASTM-D817-96.

  In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds simultaneously, and the polymer chain is broken and the acetyl group is decomposed. Therefore, it is necessary to set the reaction time within a certain range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions vary and greatly vary depending on the reaction equipment, equipment and other conditions. As the decomposition of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. That is, in the process of acetylation of cellulose triacetate, the weight average molecular weight (Mw) is used as one index of the degree of reaction for allowing the acetylation reaction to take place for a sufficient time for acetylation without being excessively decomposed. ) / Number average molecular weight (Mn).

  An example of a method for producing a cellulose ester is shown below: 100 parts by mass of a flocculent linter was crushed as a cellulose raw material, 40 parts by mass of acetic acid was added, and pretreatment activation was performed at 36 ° C. for 20 minutes. Thereafter, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride and 350 parts by mass of acetic acid were added, and esterification was performed at 36 ° C. for 120 minutes. After neutralizing with 11 parts by mass of a 24% by mass magnesium acetate aqueous solution, saponification aging was performed at 63 ° C. for 35 minutes to obtain acetylcellulose. This was stirred for 160 minutes at room temperature using a 10-fold acetic acid aqueous solution (acetic acid: water = 1: 1 (mass ratio)), then filtered and dried to obtain purified acetylcellulose having an acetyl substitution degree of 2.75. . This acetylcellulose had Mn of 92000, Mw of 156000, and Mw / Mn of 1.7. Similarly, cellulose esters having different degrees of substitution and Mw / Mn ratios can be synthesized by adjusting the esterification conditions (temperature, time, stirring) and hydrolysis conditions of the cellulose ester.

  The synthesized cellulose ester is preferably purified to remove low molecular weight components or to remove unacetylated components by filtration.

  In the case of a mixed acid cellulose ester, it can be obtained by the method described in JP-A-10-45804. The measuring method of the substitution degree of an acyl group can be measured according to the provisions of ASTM-D817-96.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. It easily forms a coordination compound, that is, a complex with a ligand, and forms scum (insoluble starch, turbidity) derived from many insoluble calcium.

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma emission spectroscopy analyzer).

(Organic solvent)
Organic solvents that dissolve cellulose esters and are useful for forming cellulose ester solutions or dopes include chlorinated organic solvents and non-chlorinated organic solvents. Methylene chloride (methylene chloride) can be mentioned as a chlorinated organic solvent, and it is suitable for dissolving cellulose esters, particularly cellulose triacetate. Due to recent environmental problems, the use of non-chlorine organic solvents has been studied. Examples of the non-chlorine organic solvent include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1, Examples include 1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, and the like. When these organic solvents are used for cellulose triacetate, a dissolution method at room temperature can be used, but an insoluble material can be obtained by using a dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method. Can be reduced, which is preferable. Although methylene chloride can be used for cellulose esters other than cellulose triacetate, methyl acetate, ethyl acetate, and acetone are preferably used. Particularly preferred is methyl acetate. In the present invention, an organic solvent having good solubility with respect to the cellulose ester is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is a main (organic) solvent or a main ( Organic) solvent.

  The dope according to the present invention preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. These are gelling solvents that make dope film (web) gel when the dope is cast on a metal support and the solvent starts to evaporate and the ratio of alcohol increases, making the web strong and easy to peel off from the metal support. When these ratios are small, there is also a role of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, and has good drying properties. These organic solvents are called poor solvents because they are not soluble in cellulose esters alone.

  It is preferable that the concentration of the cellulose ester in the dope is adjusted to 15 to 30% by mass and the dope viscosity is adjusted to a range of 100 to 500 Pa · s in order to obtain good film surface quality.

  Additives added to the dope include plasticizers, ultraviolet absorbers, antioxidants, dyes, and fine particles. In the present invention, additives other than fine particles may be added during the preparation of the cellulose ester solution, or may be added during the preparation of the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to the polarizing plate used in the liquid crystal image display device. The additive will be described below.

(Plasticizer)
In the cellulose ester solution or dope used in the present invention, a compound known as a so-called plasticizer is added for the purpose of improving mechanical properties, imparting flexibility, imparting water absorption resistance, reducing water vapor transmission rate, adjusting retardation, etc. For example, phosphoric acid esters and carboxylic acid esters are preferably used.

  Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like.

  Examples of carboxylic acid esters include phthalic acid esters and citric acid esters; phthalic acid esters such as dimethyl phthalate, diethyl phosphate, dioctyl phthalate and diethyl hexyl phthalate; and citrate esters such as acetyl triethyl citrate and acetyl citrate. Tributyl can be mentioned. Other examples include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and triacetin. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Collate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferably used. These alkyl phthalyl alkyl glycolates may be used in combination of two or more.

  Polyhydric alcohol esters are also preferably used.

  The polyhydric alcohol used in the present invention is represented by the following general formula (1).

Formula (1) R _1- (OH) n
However, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  It is preferable that these compounds are contained so that it may become 1-30 mass% with respect to a cellulose ester, Preferably it is 1-20 mass%. In order to suppress bleeding out during stretching and drying, a compound having a vapor pressure at 200 ° C. of 1400 Pa or less is preferable.

  These compounds may be added together with the cellulose ester or the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

  As other additives, polyesters and polyester ethers described in JP-A No. 2002-22956, urethane resins described in JP-A No. 2003-171499, rosins and rosin derivatives described in JP-A No. 2002-146044, epoxy resins, and ketone resins , Toluenesulfonamide resin, ester of polyhydric alcohol and carboxylic acid described in JP-A-2003-96236, compound described in general formula (1) of JP-A-2003-165868, polyester weight described in JP-A-2004-292696 Examples thereof include a coalescence or a polyurethane polymer. These additives can be contained in the dope or fine particle dispersion.

(UV absorber)
The polarizing plate protective film of the present invention can contain an ultraviolet absorber. Examples of ultraviolet absorbers that can be used include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. A benzotriazole-based compound with little coloring is preferable. Further, ultraviolet absorbers described in JP-A-10-182621, JP-A-8-337574, JP-A-2001-72782, JP-A-6-148430, JP-A-2002-31715, JP-A-2002-169020, 2002-2002. Polymer ultraviolet absorbers described in 47357, 2002-363420, and 2003-113317 are also preferably used. As an ultraviolet absorber, from the viewpoint of preventing the deterioration of polarizers and liquid crystals, it is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Is preferred.

  Specific examples of UV absorbers useful in the present invention include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) Benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis ( 4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'- ert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5 -Chloro-2H-benzotriazol-2-yl) phenyl] propionate and the like can be mentioned, but not limited thereto. As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used. An example of the polymeric ultraviolet absorber is a reactive ultraviolet absorber RUVA-93 manufactured by Otsuka Chemical Co., Ltd.

  Specific examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but is not limited thereto.

  The ultraviolet absorber described above preferably used in the present invention is preferably a benzotriazole-based ultraviolet absorber or a benzophenone-based ultraviolet absorber, which has high transparency and is excellent in the effect of preventing the deterioration of the polarizing plate and the liquid crystal element, and unnecessary coloring. A benzotriazole-based ultraviolet absorber with a lower content is particularly preferably used.

  The ultraviolet absorber can be added to the dope without limitation as long as it dissolves the ultraviolet absorber in the dope, but in the present invention, the ultraviolet absorber is cellulose such as methylene chloride, methyl acetate, dioxolane and the like. Dope by dissolving in a good solvent for ester or mixed solvent of good solvent and poor solvent such as lower aliphatic alcohol (methanol, ethanol, propanol, butanol, etc.) and adding to cellulose ester solution as UV absorber solution Is preferred. In this case, it is preferable to make the dope solvent composition and the solvent composition of the ultraviolet absorber solution the same or as close as possible. The content of the ultraviolet absorber is 0.01 to 5% by mass, particularly 0.5 to 3% by mass.

(Antioxidant)
As the antioxidant, hindered phenol compounds are preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3 , 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 1,3 , 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanate Examples include nurate. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.

(Matting agent)
In the present invention, in addition to a preferred domain forming material, fine particles can be further contained in the polarizing plate protective film as a matting agent. Thereby, conveyance and winding can be facilitated.

  The particle size of the matting agent is preferably primary particles or secondary particles of 10 nm to 0.1 μm. A substantially spherical matting agent having a primary particle aspect ratio of 1.1 or less is preferably used.

  As the fine particles, those containing silicon are preferable, and silicon dioxide is particularly preferable. Examples of preferable silicon dioxide fine particles for the present invention include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (manufactured by Nippon Aerosil Co., Ltd.) manufactured by Nippon Aerosil Co., Ltd. A commercially available product name can be mentioned, and Aerosil 200V, R972, R972V, R974, R202, R812 can be preferably used. Examples of polymer fine particles include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. Examples include Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.). I can do it.

  The fine particles of silicon dioxide preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more. The average diameter of the primary particles is more preferably 5 to 16 nm, further preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / L or more, and more preferably 100 to 200 g / L or more. Higher apparent specific gravity makes it possible to produce a high-concentration fine particle dispersion, which is preferable because no haze or aggregates are generated.

The addition amount of the matting agent in the present invention is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and still more preferably 0.08 to 0.16 g per 1 m ^{2 of} the polarizing plate protective film.

(Surfactant)
The dope or fine particle dispersion used in the present invention preferably contains a surfactant, and is not particularly limited to phosphoric acid, sulfonic acid, carboxylic acid, nonionic, cationic and the like. These are described in, for example, JP-A-61-243837. The addition amount of the surfactant is preferably 0.002 to 2% by mass and more preferably 0.01 to 1% by mass with respect to the cellulose ester. If the addition amount is less than 0.001% by mass, the effect of addition cannot be exhibited sufficiently, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.

  Nonionic surfactants include surfactants having nonionic hydrophilic groups such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyglycidyl and sorbitan, and specifically include polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Oxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, fatty acid diethanolamide, triethanolamine Examples include fatty acid partial esters.

  Examples of the anionic surfactant include carboxylate, sulfate, sulfonate, and phosphate ester salt. Representative examples include fatty acid salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfonate, α-olefin sulfonate, dialkylsulfosuccinate, α-sulfonated fatty acid salt, N-methyl-N oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated oil, polyoxyethylene alkyl ether sulfate, Examples thereof include polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, and naphthalene sulfonate formaldehyde condensate.

  Examples of cationic surfactants include amine salts, quaternary ammonium salts, pyridium salts, etc., and primary to tertiary fatty amine salts, quaternary ammonium salts (tetraalkyl ammonium salts, trialkylbenzyl ammonium salts, Alkyl pyridium salt, alkyl imidazolium salt, etc.). Examples of amphoteric surfactants include carboxybetaine and sulfobetaine, such as N-trialkyl-N-carboxymethylammonium betaine and N-trialkyl-N-sulfoalkyleneammonium betaine.

The fluorosurfactant is a surfactant having a fluorocarbon chain as a hydrophobic group. Examples of the fluorine-containing _{surfactant, C 8 F 17 CH 2 CH} 2 O- (CH 2 CH 2 O) 10 -OSO 3 Na, C 8 F 17 SO 2 N (C 3 H 7) (CH 2 CH 2 O _{) 16 -H, C 8 F 17} SO 2 N (C 3 H 7) CH 2 COOK, C 7 F 15 COONH 4, C 8 F 17 SO 2 N (C 3 H 7) (CH 2 CH 2 O) 4 _{- (CH 2) 4 -SO 3} Na, C 8 F 17 SO 2 N (C 3 H 7) (CH 2) 3 -N + (CH 3) 3 · I -, C 8 F 17 SO 2 N (C _{3 H 7) CH 2 CH 2} CH 2 N + (CH 3) 2 -CH 2 COO -, C 8 F 17 CH 2 CH 2 O (CH 2 CH 2 O) 16 -H, C 8 F 17 CH 2 CH ₂ O (CH ₂ ) ₃ —N ⁺ (CH ₃ ) ₃ .I ⁻ , H (CF ₂ ) ₈ —CH ₂ CH ₂ OCOCH ₂ CH (SO ₃ ) COOCH ₂ CH ₂ CH ₂ CH ₂ (CF ₂ ) _{8 -H, H (CF 2) 6} CH 2 _{CH 2 O (CH 2 CH 2} O) 16 -H, H (CF 2) 8 CH 2 CH 2 O (CH 2) 3 -N + (CH 3) 3 · I -, H (CF 2) 8 CH 2 _{CH 2 OCOCH 2 CH (SO 3} ) COOCH 2 H 2 CH 2 CH 2 C 8 F 17, C 9 F 17 -C 6 H 4 -SO 2 N (C 3 H 7) (CH 2 CH 2 O) 16 - H, C ₉ F ₁₇ —C ₆ H ₄ —CSO ₂ N (C ₃ H ₇ ) (CH ₂ ) ₃ —N ⁺ (CH ₃ ) ₃ · I ^−, etc. Absent.

(Peeling accelerator)
Furthermore, a peeling accelerator for reducing the load during peeling may be added to the dope. Of these, surfactants are effective, and phosphoric acid-based, sulfonic acid-based, carboxylic acid-based, nonionic-based, cationic-based and the like are not particularly limited thereto. These peeling accelerators are described in, for example, JP-A-61-243837. Japanese Patent Application Laid-Open No. 57-500833 discloses a polyethoxylated phosphate ester as a peeling accelerator. JP-A-61-69845 discloses that a mono- or di-phosphoric acid alkyl ester in which a non-esterified hydroxy group is in the form of a free acid can be rapidly removed by adding to the cellulose ester. JP-A-1-299847 discloses that the peeling load can be reduced by adding a phosphate ester compound containing a non-esterified hydroxyl group and a propylene oxide chain and inorganic particles.

  Moreover, it is preferable that the compound represented by following formula (2) or (3) is contained.

_{(2) (R 1 -B 1} -O) n1 -P (= O) - (OM 1) n2
(3) R ₂ -B ₂ -X
In the formula, R ₁ and R ₂ are each a substituted or unsubstituted alkyl group, alkenyl group, aralkyl group or aryl group having 4 to 40 carbon atoms; M ₁ is an alkali metal, ammonia, or a lower alkyl amine. Yes; B ₁ and B ₂ are each a divalent linking group; X is a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, or a sulfate ester or a salt thereof; n1 is 1 or 2; Yes; and n2 is 3-n1.

The cellulose acylate film contains at least one release agent represented by the formula (2) or (3). Hereinafter, these release agents will be described. Preferred examples of R ₁ and R ₂ include substituted and unsubstituted alkyl groups having 4 to 40 carbon atoms (for example, butyl, hexyl, octyl, 2-ethylhexyl, nonyl, dodecyl, hexadecyl, octadecyl, eicosanyl, docosanyl, myricyl). , Etc.), substituted with 4 to 40 carbon atoms, unsubstituted alkenyl groups (for example, 2-hexenyl, 9-decenyl, oleyl, etc.), substituted with 4 to 40 carbon atoms, unsubstituted aryl groups (for example, phenyl, Naphthyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, propylphenyl, diisopropylphenyl, triisopropylphenyl, t-butylphenyl, di-t-butylphenyl, tri-t-butylphenyl, isopentylphenyl, octylphenyl, Isooctylphenyl, isononyl phen Nyl, diisononylphenyl, dodecylphenyl, isopentadecylphenyl).

  Of these, more preferred are alkyl as hexyl, octyl, 2-ethylhexyl, nonyl, dodecyl, hexadecyl, octadecyl, docosanyl, alkenyl as alkenyl, aryl as phenyl, naphthyl, trimethylphenyl, diisopropylphenyl, triisopropyl. Isopropylphenyl, di-t-butylphenyl, tri-t-butylphenyl, isooctylphenyl, isononylphenyl, diisononylphenyl, dodecylisopentadecylphenyl.

Next, the divalent linking group of B ₁ and B ₂ will be described. C1-10 alkylene, poly (degree of polymerization 1-50) oxyethylene, poly (degree of polymerization 1-50) oxypropylene, poly (degree of polymerization 1-50) oxyglycerin, and a mixture thereof. . Preferred linking groups among these are methylene, ethylene, propylene, butylene, poly (degree of polymerization 1-25) oxyethylene, poly (degree of polymerization 1-25) oxypropylene, and poly (degree of polymerization 1-15) oxyglycerin.

  X is carboxylic acid (or salt), sulfonic acid (or salt), sulfate ester (or salt), and particularly preferably sulfonic acid (or salt) or sulfate ester (or salt). Preferred salts are Na, K, ammonium, trimethylamine and triethanolamine. Specific examples of preferred compounds of the present invention are described below.

RZ-1 C ₈ H ₁₇ O—P (═O) — (OH) ₂
RZ-2 C ₁₂ H ₂₅ O—P (═O) — (OK) ₂
RZ-3 C ₁₂ H ₂₅ OCH ₂ CH ₂ O—P (═O) — (OK) ₂
RZ-4 C ₁₅ H ₃₁ (OCH ₂ CH ₂ ) ₅ O—P (═O) — (OK) _{2
RZ-5 {C 12 H 25} O (CH 2 CH 2 O) 5} 2 -P (= O) -OH
_{RZ-6 {C 18 H 35} (OCH 2 CH 2) 8 O} 2 -P (= O) -ONH 4
_{RZ-7 (t-C 4} H 9) 3 -C 6 H 2 -OCH 2 CH 2 O-P (= O) - (OK) 2
_{RZ-8 iso-C 9 H} 19 -C 6 H 4 -O- (CH 2 CH 2 O) 5 -P (= O) - (OK) (OH)
RZ-9 C ₁₂ H ₂₅ SO ₃ Na
RZ-10 C ₁₂ H ₂₅ OS ₃ Na
RZ-11 C ₁₇ H ₃₃ COOH
RZ-12 C ₁₇ H ₃₃ COOH · N (CH ₂ CH ₂ OH) _{3
RZ-13 iso-C 8 H} 17 -C 6 H 4 -O- (CH 2 CH 2 O) 3 - (CH 2) 2 SO 3 Na
_{RZ-14 (iso-C 9} H 19) 2 -C 6 H 3 -O- (CH 2 CH 2 O) 3 - (CH 2) 4 SO 3 Na
RZ-15 sodium triisopropyl naphthalene sulfonate RZ-16 sodium tri-t-butyl naphthalene sulfonate RZ-17 C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ CH ₂ SO ₃ Na
RZ-18 C ₁₂ H ₂₅ -C ₆ H ₄ SO ₃ .NH ₄
The amount of these compounds used is preferably 0.002 to 2% by mass in the dope. More preferably, it is 0.005-1 mass%, More preferably, it is 0.01-0.5 mass%. The addition method is not particularly limited, but it may be liquid or solid as it is and added together with other materials before dissolution, or may be added later to a cellulose ester solution prepared in advance. By containing these, it becomes easy to align the domains.

(Other additives)
In addition, thermal stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. Furthermore, an antistatic agent, a flame retardant, a lubricant, an oil agent, etc. may be added.

[Solution casting film forming method]
The polarizing plate protective film of the present invention is preferably formed by a solution casting film forming method. Here, the solution casting film forming method will be described with reference to FIG.

  FIG. 4 is a diagram showing an example of a process schematically showing a dope preparation process, a casting process, and a drying process of the solution casting film forming method according to the present invention.

(1) Cellulose ester solution preparation process In this invention, dope is prepared by mixing the polymer, polymer nanoparticle or liquid crystalline polymer which is a domain forming material prepared in advance, a solvent and a cellulose ester. Specifically, it is preferable to add and mix or disperse a part of the solvent and the domain forming material in the dissolution vessel, and then add and dissolve the remaining solvent and cellulose ester with stirring. Additives such as plasticizers can be added later or added to the dissolution vessel.

  Alternatively, an additive such as cellulose ester or a plasticizer may be added to the solvent in the dissolution vessel while stirring, and the domain forming material may be further added during dissolution of the cellulose ester. Alternatively, a solvent and an additive such as a cellulose ester and a plasticizer can be mixed to obtain a cellulose ester solution, and the domain-forming material mixed or dispersed in the solvent can be added thereto while stirring.

  The method for preparing the cellulose ester solution will be described in more detail.

  An additive such as cellulose ester and plasticizer is dissolved in an organic solvent mainly composed of a good solvent for the cellulose ester with stirring. For dissolution, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a high-temperature dissolution method performed by pressurization above the boiling point of the main solvent, a cooling dissolution method performed by cooling and a high-pressure dissolution method performed at a considerably high pressure However, in the present invention, the high temperature dissolution method is preferably used.

  The cellulose ester solution obtained by mixing the domain-forming material, cellulose ester, and solvent in the dissolution vessel is dissolved in the cellulose ester and then sent to a filter by a pump and filtered.

  Filtration is preferably carried out using the cellulose ester solution with an appropriate filter medium such as filter paper for filter press. As the filter medium in the present invention, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matter, etc., but if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged, and absolute filtration Filter media with an accuracy of 8 μm or less are preferred, filter media in the range of 1-8 μm are more preferred, and filter media in the range of 3-6 μm are even more preferred. Examples of filter paper include No. of Azumi Filter Paper Co., Ltd., a commercially available product. 244, 277, etc. can be mentioned and used preferably.

  There are no particular restrictions on the material of the filter medium for filtration, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark) and metal filter media such as stainless steel do not lose fibers. preferable. The filter medium is preferably a metal, particularly stainless steel, from the viewpoint of durability. From the viewpoint of clogging, it is preferable to have a porosity of 60 to 80%. Most preferably, filtration is performed with a metal filter medium having an absolute filtration accuracy of 30 to 60 μm and a porosity of 60 to 80%, so that coarse foreign matters can be reliably removed over a long period of time. preferable. Examples of metal filter media having an absolute filtration accuracy of 30 to 60 μm and a porosity of 60 to 80% include, for example, NF-10, NF-12, and NF-13 of Fine pore NF series manufactured by Nippon Seisen Co., Ltd. Can be mentioned.

  Filtration can be performed by a normal method, but the method of filtering while heating or keeping the temperature at a temperature in a range not lower than the boiling point of the organic solvent used under normal pressure and in a range where the organic solvent does not boil is a filter medium. The increase in differential pressure before and after (hereinafter sometimes referred to as filtration pressure) is small and preferable. The preferred temperature range depends on the organic solvent used, but is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C. The filtration pressure is preferably as small as possible, preferably 0.3 to 1.6 MPa, more preferably 0.3 to 1.2 MPa, and still more preferably 0.3 to 1.0 MPa.

  The dope thus obtained is stored in a stock tank, defoamed and then used for casting.

(2) In-line addition process When a dope is prepared by previously mixing a domain-forming material, a cellulose ester, and a solvent in a melting pot, it is usually unnecessary to add the domain-forming material in-line. However, if necessary, all or part of the domain forming material can be mixed in-line. The in-line addition process will be described with reference to FIG. 4. A cellulose ester solution (sometimes referred to as a dope stock solution) and a domain-forming material solution are respectively transferred by liquid feed pumps 5 and 14 and filtered by filter units 6 and 15. 8 and 16 are transferred, and both liquids are merged by the merge pipe 20. Since the combined liquids are transported in layers in the conduit, they are difficult to mix as they are. Therefore, the two liquids are merged and then transferred to the next step while being sufficiently mixed by the mixer 21 such as an in-line mixer. As the in-line mixer that can be used in the present invention, for example, a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer, manufactured by Toray Engineering) is preferable. Further, a filter is disposed immediately before the merging pipe 20, and for example, lump and large foreign matter generated from the path due to exchange of the filter medium or the like is removed from the domain forming material solution or the dope stock solution being fed. I can do it. Here, a metal filter having solvent resistance is preferably used.

  In the present invention, the film is stretched in any of the drying steps described later, and the birefringence of the stretched film is measured, and the content of the domain forming material contained in the dope can be adjusted according to the measurement result of the birefringence. preferable. That is, when it is confirmed that the measurement result of birefringence deviates from the desired birefringence value, it is insufficient when the cause is considered to be the low content of the domain forming material. In order to compensate for this, it is preferable to add a domain forming material to the dope stock solution. An in-line addition process is preferably used as a method of adding the domain forming material to the dope stock solution. Specifically, there is a method of adjusting the content of the domain forming material having birefringence in the dope by adding the domain forming material to the dope in-line. Specifically, it can be added by a method using the in-line mixer. The domain-forming material solution prepared by the above-described method can be used as it is as the domain-forming material solution added in-line (this may be referred to as an in-line additive solution). Or the liquid which adjusted the domain formation material density | concentration and the cellulose-ester density | concentration by adding a solvent, a cellulose-ester solution, another additive etc. further can be used as an in-line additive liquid. The in-line additive solution preferably contains the domain forming material at a concentration 1.1 to 50 times the concentration of the domain forming material in the dope used for casting.

  In the dope prepared by the step (2), the solid content concentration in the dope is preferably adjusted to 15% by mass or more, particularly preferably 18 to 30% by mass. If the solid content concentration in the dope is too high, the viscosity of the dope becomes too high, and sharkskin or the like may occur during casting to deteriorate the film flatness. Therefore, it is preferably 30% by mass or less.

(3) Casting process On the metal support 31 such as an endless metal support 31, for example, a stainless steel belt or a rotating metal drum, the dope prepared up to the previous process is fed to the die 30 and transferred infinitely. This is a step of casting the dope from the die 30 at the casting position. The surface of the metal support 31 is a mirror surface. A die 30 (for example, a pressure die) is preferable because the slit shape of the die portion can be adjusted and the film thickness can be easily made uniform. The die 30 includes a coat hanger die and a T die, and any of them is preferably used. In order to increase the film-forming speed, two or more dies may be provided on the metal support 31, and the dope amount may be divided and stacked.

  The surface temperature of the metal support for casting is 10 to 55 ° C., the temperature of the dope is 25 to 60 ° C., and the temperature of the solution is preferably equal to or higher than the temperature of the support. More preferably, the temperature is set to a temperature of

  The higher the solution temperature and the support temperature, the higher the drying speed of the solvent, which is preferable. However, if the temperature is too high, foaming or flatness may be deteriorated.

  Although the more preferable range of the temperature of a support body is dependent on the organic solvent to be used, it is 20-55 degreeC, and the more preferable range of solution temperature is 35-45 degreeC.

(4) Solvent evaporation step Web 32 can be peeled from metal support 31 by heating web 32 (referred to as dope film after casting dope on metal support as web) 32 on metal support 31 This is a step of evaporating the solvent until. In order to evaporate the solvent, there are a method of blowing air from the web 32 side and / or a method of transferring heat from the back surface of the metal support 31 by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. This method is preferable because of good drying efficiency. A method of combining them is also preferable. In the case of backside liquid heat transfer, it is preferable to heat at or below the boiling point of the main solvent of the organic solvent used in the dope or the organic solvent having the lowest boiling point.

(5) Peeling step In this step, the web 32 having the solvent evaporated on the metal support 31 is peeled off at the peeling position 33. The peeled web 32 is sent to the next process. If the residual solvent amount of the web 32 (explained later) at the time of peeling is too large, peeling is difficult, or conversely, if the film is sufficiently dried on the metal support 31 and then peeled off, a part of the web 32 is halfway. May come off. In the present invention, when peeling the thin web from the metal support, it is preferable to peel the thin web with a force within 170 N / m from the minimum tension that can be peeled as the peeling tension in order to prevent the flatness from being deteriorated and hung. A force within 140 N / m is more preferred.

  There is a gel casting method (gel casting) as a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible). For example, a poor solvent for the cellulose ester is added to the dope, and the dope is cast and then gelled, and the temperature of the metal support is lowered to gel. By gelling on the metal support 31 and increasing the strength of the film at the time of peeling, peeling can be accelerated and the film forming speed can be increased. The web 32 on the metal support 31 can be peeled in the range of 5 to 150% by mass depending on the strength of the condition, the length of the metal support 31, etc., but peels off when the amount of residual solvent is larger. In this case, if the web 32 is too soft, the flatness at the time of peeling tends to be lost, or a slip or vertical stripe due to the peeling tension is likely to occur, and the residual solvent amount at the time of peeling is determined in consideration of the economic speed and quality. Therefore, in the present invention, the temperature at the peeling position on the metal support 31 is 10 to 40 ° C., preferably 15 to 30 ° C., and the residual solvent amount of the web 32 at the peeling position is 10 to 120% by mass. It is preferable to do.

  In order to maintain good flatness of the polarizing plate protective film during production, the amount of residual solvent when peeling from the metal support is preferably 10 to 150% by mass, more preferably 70 to 150% by mass. More preferably, it is 100-130 mass%. The proportion of the good solvent contained in the residual solvent is preferably 50 to 90%, more preferably 60 to 90%, and particularly preferably 70 to 80%.

  In the present invention, the residual solvent amount can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is a mass at an arbitrary time point of the web, and is a mass measured by the following gas chromatography. N is a mass when the M is dried at 110 ° C. for 3 hours. The measurement is performed by gas chromatography connected to a headspace sampler. In the present invention, gas chromatography 5890 type SERISII and headspace sampler HP7694 type manufactured by Hewlett-Packard Company were used and the measurement was performed under the following measurement conditions.

Headspace sampler heating conditions: 120 ° C, 20 minutes GC introduction temperature: 150 ° C
Temperature rise: 40 ° C, hold for 5 minutes → 100 ° C (8 ° C / min)
Column: J-W DB-WAX (inner diameter 0.32 mm, length 30 m).

(6) Drying step After peeling, generally, the web 32 is dried using a roll drying device 35 that alternately conveys the web 32 through a plurality of rolls and a tenter device 34 that grips and conveys both ends of the web 32. . In FIG. 4, the roll drying device 35 is arranged after the tenter device 34, but is not limited to this arrangement. As a drying means, hot air is generally blown on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Throughout, the drying temperature is usually in the range of 40 to 250 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used. 37 is winding of the completed polarizing plate protective film. In the step of drying the polarizing plate protective film, the residual solvent amount is preferably 0.5% by mass or less, more preferably 0.1% by mass or less.

  The polarizing plate protective film according to the present invention is formed into a film by a casting process after preparing a dope to which a domain forming material is added. As a method for orienting the added domain forming material, the film is formed by TD or A method of stretching in the MD direction or a method of making a dope flow during casting and orienting the domain forming material along the flow can be used. Further, the orientation of the domain forming material can be promoted by an electric field or a magnetic field.

  Hereinafter, a specific method for aligning the domains will be described.

  In this invention, MD represents the film-forming direction of a polarizing plate protective film, and TD represents the direction orthogonal to the film-forming direction within the plane of a polarizing plate protective film. Therefore, in the case of a roll-shaped polarizing plate protective film, MD is the film longitudinal direction and TD represents the film width direction.

(How to arrange domains in TD direction)
The polarizing plate protective film of the present invention can be produced by the following production method.

  (A) A method for producing a polarizing plate protective film containing a domain by a solution casting method, wherein a domain forming material, a cellulose ester and a dope containing a solvent are extruded from a nozzle onto a casting support. A method for producing a polarizing plate protective film, comprising casting the dope on a casting support while moving the nozzle in a direction not parallel to the moving direction of the casting support.

In this case, it is preferable that the plurality of nozzles are arranged in the width direction (FIG. 6A).
Therefore, the dope is pushed out to the casting support while reciprocating or vibrating the coater in which the nozzle is arranged in a direction perpendicular to the moving direction of the casting support (FIG. 6 (b)). Orient the forming material.

  Using a coater provided with the nozzle or a normal die, the dope is cast by overlapping the casting by casting the cover layer by successive casting to smooth the dope film on the casting support. preferable.

Also,
(B) A method for producing a polarizing plate protective film containing domains by a solution casting method, which is used when a domain forming material, a cellulose ester and a dope containing a solvent are extruded from a die onto a casting support. A method for producing a polarizing plate protective film, wherein the die has a structure in which the dope flows in a direction that is not parallel to the moving direction of the casting support in the die.

  For example, a die in which a dope supply unit and a dope discharge unit are arranged in a direction not parallel to the moving direction of the casting support is used (FIG. 7).

  Preferably, the dope supply unit and the dope discharge unit are arranged in a direction substantially orthogonal to the moving direction of the casting support in the die. Thus, the dope flows in a direction that is not parallel to the moving direction of the casting support, and a part of the flow is discharged from the die onto the casting support. Preferably, the dope once discharged from the dope discharging unit is circulated and returned to the dope supplying unit again. As a result, the domain forming material in the dope discharged onto the casting support can be oriented.

  This can also be smoothed by casting another dope by using another coater (cover layer). In this case, it is desirable that the structure of the coater for casting the cover layer is symmetrical with respect to the MD direction with respect to the coater that has been cast previously. Thereby, the alignment can be made uniform.

  Moreover, you may provide a groove | channel in the direction which is not parallel with the moving direction of a casting support body inside the slit of die | dye (FIG. 8 (a)). As a result, the dope in a state where the domain forming material is oriented in the TD direction is cast by allowing flow along the groove during casting in the die. Also in this case, it is preferable that the dope is cast by successive casting (cover layer) by using another die having grooves in the slit in the opposite direction to make the orientation uniform and smooth (FIG. 8). (B)).

  (C) A method for producing a polarizing plate protective film containing a domain by a solution casting method, wherein a domain forming material, a cellulose ester and a dope containing a solvent are cast on a casting support, A method for producing a polarizing plate protective film, characterized by rubbing in a direction not parallel to the moving direction (that is, pressing a member for determining the direction of the layer).

  The member to be rubbed is not limited, but includes, for example, a gravure roll having a hatched line described later, an orientation belt provided separately, and the like. This imparts a shearing force to the dope, thereby orienting the domain forming material.

Then, as this one aspect,
(D) A method for producing a polarizing plate protective film containing a domain by a solution casting method, and casting a dope containing a domain forming material, a cellulose ester and a solvent on a casting support, A method for producing a polarizing plate protective film, characterized by using a gravure roll to cast the dope so that the dope is rubbed (pressed) in a direction not parallel to the moving direction of the casting support.

  In this method, gravure rolls with diagonal lines are used. In FIG. 9, the dotted line indicates the hatched groove on the gravure roll.

  The dope cast on the support is cast so that a gravure is formed in a lateral direction or an oblique direction by a gravure roll. Specifically, the rotational speed of the casting support and the gravure roll is controlled by using a slanted gravure roll as shown in the figure so that the gravure is noticed in the lateral direction or in the oblique direction.

  If it is 1: 1 with the web (rotary speed of gravure roll and web conveyance speed are in a state where there is no difference in circumferential speed), the gravure roll will be a diagonal line, but make a difference in circumferential speed. Since the angle of the slanted line changes, the rotation speed of the casting support and the gravure roll can be adjusted so that the gravure can be seen sideways.

  The gravure roll may be provided in a direction orthogonal to the film forming direction or may be provided at an angle.

  (E) A method for producing a polarizing plate protective film containing a domain by a solution casting method, wherein a domain forming material, a cellulose ester and a dope containing a solvent are cast on a casting support using a die. A method for producing a polarizing plate protective film comprising pressing a dope on a casting support with a member that moves in a direction not parallel to the direction of movement of the casting support.

  The member that moves in a direction that is not parallel to the moving direction of the casting support is an orientation belt.

  This is shown in FIG. 10, and the surface of the cast web is rubbed with an orientation belt as an example of the member. It is preferable that the surface of the alignment belt has a structure that promotes alignment by forming grooves like the gravure roll. The groove of the alignment belt is cut obliquely with respect to the moving direction of the alignment belt (FIG. 10A). In this case, as in the case of the gravure roll, the orientation can be adjusted horizontally by adjusting the moving speed of the alignment belt and the casting speed of the dope (that is, the moving speed of the casting support).

  In addition, the grooves of the alignment belt may be cut along the belt rotation direction. In this case, the alignment belt should be arranged at an angle so that the rotation direction of the alignment belt is not parallel to the web conveyance direction. Thus, the same effect can be obtained (FIG. 10B).

  The grooves cut in the gravure rolls are spaced in the range of 25 to 250 lines / inch (2.54 mm), preferably 50 to 150 lines / inch, and the engraving depth is 30 to 500 μm for effective orientation. The engraving angle is preferably in the range of 45 ° ± 15 °.

  The same applies to a groove cut in the slit of the die or a groove cut on the orientation belt.

  (F) A method for producing a polarizing plate protective film, wherein a cellulose ester solution containing a domain is cast on a support, the web is stretched in a state containing a solvent, and then dried.

  After the web containing the solvent is peeled off, a film in which the domains are oriented can be obtained by transverse stretching. Further, for example, a resin casting support may be used, and the web containing the solvent may be stretched together with the support.

  However, this method is preferably used in combination with the above method because the orientation may not be sufficient only by stretching.

  A polarizing plate protective film having polarization scattering anisotropy can be produced by orienting the domains in the TD direction by the method as described above.

  Next, a method for arranging domains in the MD direction will be described.

(How to arrange domains in the MD direction)
(G) A method for producing a polarizing plate protective film containing a domain by a solution casting method, wherein a domain forming material, a cellulose ester and a dope containing a solvent are extruded from a die onto a casting support. A method for producing a polarizing plate protective film, comprising: casting a dope extruded in a laminar flow in a direction parallel to a moving direction of the support on the cast support.

Laminar flow and turbulent flow are defined by Reynolds (Re) number. The Reynolds number is the typical length of an object in the flow, D, velocity U, density ρ, viscosity η,
Re = DUρ / η
Is defined by a dimensionless number.

  Generally, when Re <2300, it is called laminar flow, 2300 <Re <3000 is called a transition region, and when Re> 3000, it is called turbulent flow. In the present invention, the domain size, casting speed, dope density, etc. are adjusted so that the Reynolds number is 2300 or less.

  For example, FIG. 11 shows a cross-sectional view of a die used for casting. For example, by slightly narrowing the slit interval (usually 400 to 1000 μm), for example, 350 μm or less, and making the slit length longer than usual (10 to 30 mm), For example, when the slit width is set to 35 mm or more, the domain forming material in the dope can be oriented using a portion that becomes a laminar flow inside the die. Further, although not shown in the figure, it is preferable to apply shear force to the dope by aligning the slit interval in multiple stages inside the die, thereby orienting the domain forming material.

  (H) A method for producing a polarizing plate protective film containing a domain by a solution casting method, wherein a domain forming material, a cellulose ester and a solvent-containing dope are extruded from a die onto a casting support. A method for producing a polarizing plate protective film, characterized in that a dope ribbon extruded in a laminar flow in a direction parallel to the moving direction of the support is cast so as to be pulled by the support.

  This is shown in FIG. In the figure, the ribbon is stretched by pulling the ribbon in the MD direction based on the difference between the dope discharge speed and the conveyance speed of the support (belt).

  Similarly to (F), the orientation can be obtained in the same manner by stretching the web in the MD direction while containing a solvent. However, in this method, since sufficient alignment may not be obtained, it is preferable to use in combination with other methods.

  Next, the stretching process in the present invention will be described.

(7) Stretching process (also called tenter process)
The polarizing plate protective film of the present invention can adjust birefringence by stretching. A film containing a solvent can be stretched during the production of the solution casting method, or a film in a state where the solvent is dried can be stretched. The stretching temperature is preferably performed at a glass transition temperature of the film from −20 ° C. to a temperature at which it flows. Here, the glass transition temperature of the film can be measured by a known method. Stretching can be performed in the film forming direction or the width direction, but in the present invention, it is preferable to stretch at least in the width direction or the longitudinal direction. By stretching, the ratio of domains oriented in the stretching direction can be increased.

  The stretching process will be described in more detail. The draw ratio at the time of producing the polarizing plate protective film of the present invention is 1.01 to 3 times, preferably 1.5 to 3 times, with respect to the film forming direction or the width direction. 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.

  Thereby, while being able to obtain preferably the polarizing plate protective film which has the polarization scattering anisotropy of this invention, the flatness favorable polarizing plate protective film can be obtained. It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter.

  An example of a stretching process (also referred to as a tenter process) for producing the polarizing plate protective film according to the present invention will be described with reference to FIG.

  In FIG. 13, step A is a step of gripping the film transported from the film transport step D0 (not shown), and in the next step B, the film is stretched in the width direction (at a stretching angle as shown in FIG. In the process C, the stretching is finished and the film is conveyed while being held.

  It is preferable to provide a slitter for cutting off the end in the film width direction after the film is peeled off and before the start of the process B and / or immediately after the process C. In particular, it is preferable to provide a slitter that cuts off the film edge immediately before the start of the step A. When the same stretching is performed in the width direction, particularly when the film edge is cut off before the start of step B and the condition in which the film edge is not cut is compared, the former is more optically retarded in the width direction of the film. The effect of improving the axial distribution (hereinafter referred to as orientation angle distribution) can be obtained.

  This is considered to be an effect of suppressing unintended stretching in the longitudinal direction from the peeling with a relatively large amount of residual solvent to the width stretching step B.

  In the tenter process, it is also preferable to intentionally create compartments with different temperatures in order to improve the orientation angle distribution. It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  In addition, extending | stretching operation may be divided | segmented and implemented in multiple steps, and it is preferable to implement biaxial stretching in a casting direction and a width direction. Also, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

  In addition, the stretching direction in the present invention is usually used in the sense of a direction in which stretching stress is directly applied when performing a stretching operation. It is used to mean the one with a higher draw ratio.

  It is well known that the orientation angle distribution is deteriorated when the polarizing plate protective film is stretched in the width direction. In order to carry out the widthwise stretching with a constant ratio of Rt and Ro and a good orientation angle distribution, there is a preferable film temperature relative relationship in steps A, B, and C. When the film temperatures at the end points of Steps A, B, and C are Ta ° C., Tb ° C., and Tc ° C., respectively, it is preferable that Ta ≦ Tb−10. Moreover, it is preferable that Tc ≦ Tb. More preferably, Ta ≦ Tb−10 and Tc ≦ Tb.

  The film heating rate in the step B is preferably in the range of 0.5 to 10 ° C./s in order to improve the orientation angle distribution.

  The stretching time in step B is preferably a short time in order to reduce the dimensional change rate under the conditions of 80 ° C. and 90% RH. However, the minimum required stretching time range is defined from the viewpoint of film uniformity. Specifically, the range is preferably 1 to 10 seconds, and more preferably 4 to 10 seconds. Moreover, the temperature of the process B is 40-180 degreeC, Preferably it is 100-160 degreeC.

In the tenter process, the heat transfer coefficient may be constant or changed. The heat transfer coefficient preferably has a heat transfer coefficient in the range of 41.9 to 419 × 10 ³ J / m ² · hr. More preferably, in the range of ^{41.9~209.5 × 10 3 J / m 2} · hr, and most preferably a range of ^{41.9~126 × 10 3 J / m 2} · hr.

  In order to improve the dimensional stability under the conditions of 80 ° C. and 90% RH, the stretching speed in the width direction in the step B may be constant or may be changed. The stretching speed is preferably 50 to 500% / min, more preferably 100 to 400% / min, and most preferably 200 to 300% / min.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C. is most preferable. By reducing the temperature distribution, it can be expected that the temperature distribution in the width of the film is also reduced.

  In step C, it is preferable to relax in the width direction in order to suppress dimensional changes. Specifically, it is preferable to adjust the film width so that it is in the range of 95 to 99.5% with respect to the film width of the previous step.

  After the treatment in the tenter process, it is preferable to further provide a post-drying process (hereinafter referred to as process D1). It is preferable to carry out at 50-160 degreeC. More preferably, it is the range of 80-150 degreeC, Most preferably, it is the range of 110-150 degreeC.

  In step D1, it is preferable that the atmospheric temperature distribution in the width direction of the film is small from the viewpoint of improving the uniformity of the film. Within ± 5 ° C is preferable, within ± 2 ° C is more preferable, and within ± 1 ° C is most preferable.

  The film transport tension in the step D1 is affected by the physical properties of the dope, the peeling and the residual solvent amount in the step D0, the temperature in the step D1, etc., but is preferably 120 to 200 N / m, and 140 to 200 N / m. Further preferred. 140 to 160 N / m is most preferable.

  In order to prevent the film from stretching in the transport direction in step D1, 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.

  In this invention, when a polarizing plate protective film is elongate, it is preferable that the slow axis of a polarizing plate protective film corresponds with a conveyance direction. This can form a slow axis in a conveyance direction by extending | stretching the polarizing plate protective film containing a domain formation material continuously in the width direction. The long PVA polarizer has an absorption axis in the longitudinal direction, and the slow axis of the polarizing plate protective film applied as the polarizing plate protective film is in the longitudinal direction, so that both can be directly bonded together. Become. This is a preferable configuration from the viewpoint of productivity of the polarizing plate.

(8) Winding step This is a step of winding the web after drying as a film. By setting the amount of residual solvent to finish drying to 0.5% by mass or less, preferably 0.1% by mass or less, a film having good dimensional stability can be obtained. The winding method may be a commonly used winder, and there are methods for controlling the tension such as the constant torque method, constant tension method, taper tension method, and program tension control method with constant internal stress. That's fine.

  The film thickness of the polarizing plate protective film of the present invention varies depending on the purpose of use, but from the viewpoint of thinning the liquid crystal display device, the finished film is preferably in the range of 10 to 150 μm, more preferably in the range of 30 to 100 μm, particularly The range of 40-80 micrometers is preferable. If it is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If it is too thick, the advantage of thinning the film over the conventional polarizing plate protective film is lost. In adjusting the film thickness, it is preferable to control the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the metal support and the like so as to obtain a desired thickness. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. .

  Next, the case where the polarizing plate protective film having polarization scattering anisotropy of the present invention is used for a liquid crystal display device will be described.

  The polarizing plate protective film having polarization scattering anisotropy of the present invention has an advantage that a conventional polarizing plate manufacturing process can be utilized because the resin constituting the polarizing plate protective film is a cellulose resin, and is particularly commonly used. Since the polarizing plate protective film according to the present invention can be directly bonded with a water-soluble adhesive material such as water paste, to a light-absorbing polarizer utilizing a dichroic dye by drawing a polyvinyl alcohol derivative It is excellent in thinning and productivity.

  Moreover, since the polarizing plate protective film according to the present invention has characteristics as a polarizing plate protective film composed of cellulose ester, the production process of the polarizing plate in a roll shape as a long film having a brightness enhancement function Therefore, the roll-shaped film also has an advantage that it is not necessary to use a protective sheet for preventing scratches and dust adhesion.

  The polarizing plate of the present invention preferably has a configuration of polarizing plate protective film / polarizer / polarizing plate protective film B having polarization scattering anisotropy.

  In the present invention, it is preferable that the polarizing plate protective film, the polarizer, and the polarizing plate protective film B having polarization scattering anisotropy are all long films, and for laminating each, roll-to-roll is performed. It is preferable.

  FIG. 15 is a schematic view showing a method for producing a polarizing plate preferable for the present invention.

  By roll-to-roll from both sides to a light-absorbing polarizer using water paste or the like, using a polarizing film protective film 1 having a long roll-shaped polarization scattering anisotropy and similarly a polarizing film protective film 2 in a roll shape. Paste.

  When used in a liquid crystal display device, it is preferable that a polarizing plate protective film having polarization scattering anisotropy is disposed on the most backlight side among polarizing plates in a transmissive liquid crystal display device.

  For the polarizing plate protective film having polarization scattering anisotropy, the polarizing plate protective film B positioned opposite to the polarizer may be a TAC film represented by a general cellulose acetate resin. The film B may be a polarizing plate protective film having a function of a viewing angle widening film or a retardation film. Moreover, when using as a polarizing plate, you may install the functional film or functional layer for improving display quality with respect to a contrast or a hue on the polarizing plate protective film B through an adhesion layer or an adhesive layer.

  The polarizing plate protective film B used for the polarizing plate of the present invention may be a cellulose ester film or a polarizing plate protective film other than the cellulose ester film. Further, the present invention, regardless of the properties of the polarizing plate protective film B, in the drying process of polarizing plate production using water paste or the like, the polarizing plate protective film of the present invention preferably has moisture permeability, In this case, there is an advantage that moisture contained in the production of the polarizing plate can be removed in the drying process.

Accordingly, in the present invention, the moisture permeability of the polarizing plate protective film having polarization scattering anisotropy of the present invention is preferably 50 g / m ² / day or more, and preferably 100 g / m ² / day or more. It is preferable at the point which reduces the drying load at the time of manufacture. On the other hand, the upper limit of the moisture permeability of the polarizing plate protective film having scattering anisotropy of the present invention is preferably 1500 g / m ² / day or less from the viewpoint of maintaining the polarizing ability of the polarizer, more preferably 1200 g / m ² / day or less.

  The polarizing plate protective film is saponified with an alkali solution to increase the wettability with respect to water, which leads to adhesion with a polyvinyl alcohol-based paste typified by the aforementioned water paste. In the polarizing plate protective film of the present invention, at least one surface has a contact angle with water before saponification treatment of 60 ° or more and 80 ° or less, and a contact angle with water after saponification treatment of 15 ° or more and 40 ° or less. It is a feature. The contact angle with respect to water before saponification treatment is 60 ° or more and 80 ° or less is that when the polarizing plate protective film before polarizing plate processing is stored in a long and roll shape, the humidity is high when the protective film is This is in order to avoid sticking to each other. Before polarizing plate processing, it is required to have a low wettability with respect to water, that is, a high contact angle with respect to water in order to stably store in a roll shape. On the other hand, in order to realize high adhesion between films after saponification treatment, high wettability, that is, low contact angle with water is required. The wettability satisfying both is within the range specified above.

  Therefore, the polarizing plate protective film having polarization scattering anisotropy of the present invention preferably has a contact angle with water after saponification treatment of 40 ° or less, more preferably 35 ° or less. When the contact angle with respect to water is a value higher than 40 °, the polarizing plate protective film having the polarization scattering anisotropy of the present invention is stretched with a polyvinyl alcohol derivative by using the water glue, and an absorption type utilizing a dichroic dye It becomes difficult to adhere to the polarizer. Even if the above-mentioned adhesion is achieved, the polarizing plate protective film is peeled off by being exposed to high temperature and high humidity for a long time, or the display quality required for the polarizing plate is deteriorated.

  Examples of the polarizer preferably used for the polarizing plate of the present invention 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. One side of the polarizing plate protective film of the present invention is bonded to the surface of the polarizer to form a polarizing plate.

  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 thickness of the polarizing plate protective film 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 polarizing plate protective film is thinned, it is particularly important to suppress the stretching rate in the casting direction. . Since the polarizing plate protective film of this invention is excellent in dimensional stability, it is used suitably as such a polarizing plate protective film.

  Next, the polarizing plate protective film B preferable in the present invention will be described.

  A preferred polarizing plate protective film B in the present invention is the other polarizing plate protective film disposed with a liquid crystal cell sandwiched between the polarizing plate protective films having polarization scattering anisotropy according to the present invention.

  The polarizing plate protective film B is not particularly limited. For example, a polyester film such as polyethylene terephthalate or polyethylene naphthalate, a polyethylene film, a polypropylene film, a polycycloolefin film, cellophane, a cellulose acetate film, a cellulose acetate butyrate film, Cellulose acetate phthalate film, cellulose acetate propionate film, cellulose triacetate, cellulose ester film such as cellulose nitrate or derivatives thereof, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene series Film, polycarbonate film, cycloolefin Rimmer film (for example, ARTON (manufactured by JSR), ZEONEX, ZEONOR (manufactured by ZEON Corporation)), polymethylpentene film, polyetherketone film, polyethersulfone film, polysulfone film, polyetherketoneimide film, polyamide film And acrylic film or polyacrylate film.

  In the present invention, a cellulose ester film such as a cellulose acetate propionate film or a cellulose triacetate film (TAC film) (for example, Konica Minolta Op Co., Ltd. Konica Minolta Tack KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA, etc. are preferably used), cycloolefin polymer film, polycarbonate film, polyester film or polyacrylic film are preferable in terms of transparency, mechanical properties, and lack of optical anisotropy. An ester film and a cycloolefin polymer film are preferred. From the viewpoint of producing a polarizing plate by roll-to-roll as described above, a cellulose ester having excellent saponification suitability. A stealth film is most preferred. These resin films may be films formed by a melt casting method or a solution casting method.

  The polarizing plate protective film B used in the present invention preferably has a retardation value Ro defined by the following formula of 0 to 300 nm and a retardation value Rt of -600 to 600 nm. Further, a more preferable range is a range where the Ro value is 0 to 120 nm and an Rt value is −400 to 400 nm, and a particularly preferable range is a range where the Ro value is 0 to 100 nm and the Rt value is −300 to 300 nm.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
In the formula, nx, ny, and nz are the refractive index nx (maximum in-plane refractive index of the film, also referred to as the refractive index in the slow axis direction) at 23 ° C. RH and 590 nm, and ny (the slow axis in the film plane). ) (Refractive index in the direction perpendicular to), nz (refractive index of the film in the thickness direction), and d is the thickness (nm) of the film.

  When the polarizing plate protective film B of the present invention is used as an optical compensation film for a VA liquid crystal display device having a VA mode liquid crystal cell, the Ro value is preferably 20 to 150 nm and the Rt value is preferably 70 to 400 nm. . The Ro value is more preferably 30 to 100 nm. When two optical compensation films are used in the VA liquid crystal display device, the Rt value of the film is preferably 70 to 250 nm. When one optical compensation film is used for the VA liquid crystal display device, the Rt value of the film is preferably 150 to 400 nm.

  Hereinafter, the properties of the polarizing plate protective film having polarizing scattering anisotropy and the polarizing plate protective film B according to the present invention are summarized below.

(Transmissivity of polarizing plate protective film)
As a member of an LCD display device, high transmittance is required, and the 500 nm transmittance of the manufactured polarizing plate protective film is preferably 85 to 100%, more preferably 90 to 100%, by adding the above-mentioned additives in combination. Preferably, 92 to 100% is most preferable. The 400 nm transmittance is preferably 40 to 100%, more preferably 50 to 100%, and most preferably 60 to 100%. Moreover, ultraviolet absorption performance may be calculated | required, In that case, 0 to 10% is preferable, as for 380 nm transmittance | permeability, 0 to 5% is still more preferable, and 0 to 3% is the most preferable.

(Thickness distribution in the width direction of the polarizing plate protective film)
The polarizing plate protective film of the present invention preferably has a thickness distribution R (%) in the width direction of 0 ≦ R (%) ≦ 5%, more preferably 0 ≦ R (%) ≦ 3%. Particularly preferably, 0 ≦ R (%) ≦ 1%.

(Haze value of polarizing plate protective film)
The polarizing plate protective film of the present invention preferably has a haze value of 2% or less, more preferably 1.5%, and most preferably 1% or less.

(Elastic modulus of polarizing plate protective film)
The elastic modulus is preferably in the range of 1.5 to 5 GPa, more preferably in the range of 1.8 to 4 GPa, and particularly preferably in the range of 1.9 to 3 GPa.

  Further, the stress at break is preferably in the range of 50 to 200 MPa, more preferably in the range of 70 to 150 MPa, and most preferably in the range of 80 to 100 MPa.

  The elongation at break at 23 ° C. and 55% RH is preferably in the range of 20 to 80%, more preferably in the range of 30 to 60%, and most preferably in the range of 40 to 50%. .

  Further, the hygroscopic expansion coefficient is preferably in the range of −1 to 1%, more preferably in the range of −0.5 to 0.5%, and most preferably 0 to 0.2% or less.

Further, the bright spot foreign matter is preferably 0 to 80 pieces / cm ² , more preferably 0 to 60 pieces / cm ² , and most preferably 0 to 30 pieces / cm ^2. .

(Center line average roughness of polarizing plate protective film (Ra))
When using a polarizing plate protective film as a member for LCD, high flatness is required to reduce light leakage of the film. The center line average roughness (Ra) is a numerical value defined in JIS B 0601, and examples of the measuring method include a stylus method or an optical method.

  As centerline average roughness (Ra) of the polarizing plate protective film of this invention, 20 nm or less is preferable, More preferably, it is 10 nm or less, Especially preferably, it is 4 nm or less.

(Polarizer)
The polarizing plate of the present invention and the liquid crystal display device of the present invention using the polarizing plate will be described.

  The polarizing plate can be produced by a general method. The polarizing plate protective film having polarization-scattering anisotropy of the present invention, which has been subjected to alkali saponification treatment, is a completely saponified polyvinyl alcohol aqueous solution on at least one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution. It is preferable to stick together. It is preferable to paste the polarizing plate protective film B on the other surface.

  The polarizing plate according to the present invention is a laminate in which the transmission axis of the dichroic polarizing film and the transmission axis of the polarizing plate protective film having polarization scattering anisotropy are in a parallel relationship.

  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 other 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 using the polarizing plate of the present invention as a liquid crystal display device bonded to at least one surface of a liquid crystal cell, the luminance can be improved and the liquid crystal display device of the present invention excellent in visibility can be manufactured. The polarizing plate protective film of the present invention is a reflective, transmissive, transflective LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type LCD etc. Are preferably used. In particular, a large-screen display device with a 30-inch screen or more has the effect that there is little unevenness in color and undulation, and eyes are not tired even during long-time viewing.

  The arrangement position of the polarizing plate in the liquid crystal display device is not particularly limited and can be arranged on the viewing side. However, the polarization on the light source side of the liquid crystal panel is avoided from the viewpoint of avoiding the visual hindrance based on the back scattering by the scattering polarizing plate. It is preferable to arrange as a plate.

  Although FIG. 16 shows a configuration example of a liquid crystal display device preferable for the present invention, it is not limited to this.

  The liquid crystal display device of the present invention includes a polarizing plate 60 (polarizing plate protective film 61 having polarization scattering anisotropy) adjacent to the light reflecting plate 64, the backlight 67, the light guide plate 65, and the light diffusing plate 66. / Configuration of dichroic polarizing film 62 / polarizing plate protective film B63 utilizing light absorption action by dichroic substance), liquid crystal cell 68, and viewing side polarizing plate 69 are preferably laminated in this order.

  As a specific example of the light guide plate, a light source such as a light source such as a light source such as a linear light source such as a cathode tube (light-emitting diode) or an EL is disposed on the side surface of a transparent resin plate, and light transmitted through the plate to the resin plate. Can be emitted to one side of the plate by diffusion, reflection, diffraction, interference, or the like. When forming a laminated polarizing plate including a light guide plate, a prism array layer composed of a prism sheet or the like for controlling the light emission direction, a light diffusion plate for obtaining uniform light emission, and light emitted from a linear light source are guided. Auxiliary means such as a light source holder for guiding the light plate to the side surface of the light plate can be arranged in an appropriate combination by arranging one layer or two or more layers at predetermined positions such as the upper and lower surfaces and the side surface of the light guide plate.

  The backlight of the liquid crystal display device is preferably a direct backlight type. Specific examples of the direct backlight system include backlights described in JP-A-2001-215497, JP-A-2001-305535, JP-A-2003-215585, JP-A-2004-29091, JP-A-2004-102119, and the like. Light is used effectively.

  In particular, the liquid crystal display device using the polarizing plate of the present invention is effective for a thin liquid crystal display device having a size of 15 or more and having a large influence of heat with a short distance between the light source and the polarizing plate.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
(Preparation of cellulose ester film 101)
<Preparation of Dope 1>
Cellulose acetate propionate (acetyl substitution degree 1.01, propionyl group substitution degree 1.50, total acyl group substitution degree 2.51, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3.1) 100 mass Part Methylene chloride 350 parts by mass Ethanol 60 parts by mass Liquid crystal polymer represented by the following formula (glass transition temperature 80 ° C., nematic liquid crystallizing temperature 100 to 290 ° C.) 50 parts by mass Plasticizer: Trimethylolpropane tribenzoate 10 parts by mass Tinuvin 109 (Ciba Specialty Chemicals Co., Ltd.) 0.5 parts by mass Tinuvin 171 (Ciba Specialty Chemicals Co., Ltd.) 0.5 parts by weight Matting agent: R972V (Nippon Aerosil Co., Ltd.) 0.2 parts by mass

  The above composition was put into a container and completely dissolved to obtain a dope 1.

  The dope 1 was kept at 40 ° C. and uniformly cast on a stainless steel belt kept at 40 ° C. The slit length of the die used for casting was 20 mm, and the slit interval was 500 μm.

  After the residual solvent amount was dried to 80%, it was peeled off from the stainless steel belt and then stretched 1.05 times in the TD (width) direction with a tenter. Furthermore, it dried at 120 degreeC, making it convey with many rolls, and obtained the cellulose-ester film 101 of 80 micrometers and width 1.3m. By making the winding speed higher than the peeling speed, the film was stretched 1.5 times in the MD (film formation) direction during conveyance.

<Evaluation of domain aspect ratio, azimuth, and average azimuth>
The domain aspect ratio, azimuth angle, and average azimuth angle were evaluated according to the following procedures.

  The produced film was photographed at a magnification of 20,000 with a transmission electron microscope, and the image was read in 300 dpi monochrome 256 gradation using a scanner Canon Scan FB 636U manufactured by Canon Inc.

  The read image was taken into the image processing software WinROOF Ver3.60 (manufactured by Mitani Corp.) installed in the Endeavor Pro720L (CPU: Athlon-1 GHz, memory: 512 MB) which is a personal computer manufactured by Epson Direct.

  With this image processing software, the aspect ratio, absolute maximum length, and azimuth angle can be obtained for each domain.

  As an image pre-processing for the captured image, a field range of 2 × 2 μm was extracted (automatic binarization of the image) to extract a domain image. Confirm that 90% or more of the domain has been extracted on the screen after extracting the domain image. If the extraction is not sufficient, manually adjust the detection level so that 90% or more of the domain is detected and extracted. Adjustments were made.

  When the number of domains in the observation range was less than 1000, the same operation was performed for another 2 × 2 μm field of view until the total number of domains reached 1000 or more.

  The azimuth angle and aspect ratio were measured for each domain of the image data extracted in this way. The aspect ratio can be obtained by the following formula. The absolute maximum length corresponds to the length of the long axis of the domain.

Aspect Ratio = Absolute Maximum Length / Diagonal Width Diagonal width refers to the shortest distance between two straight lines when an image of a domain projected by two straight lines parallel to the absolute maximum length is sandwiched.

  A domain having an aspect ratio of less than 2 such as a foreign substance or a broken domain becomes noise, and is excluded from the calculation of the average azimuth, and each domain having an aspect ratio of 2 or more is obtained.

  The angle with the reference axis when taking the absolute maximum length of the domain is taken as the azimuth angle. The reference axis can be set arbitrarily, but can be set, for example, in the width direction of the film. The azimuth angle of each domain was determined, and the average value was taken as the average azimuth angle.

  In addition, with the average azimuth angle direction as the reference axis, the difference between the azimuth angle of each domain and the average azimuth angle direction was determined for each domain, and the average of absolute values was determined. This is [the average value H of the absolute value of the angle formed by the direction of the average azimuth and the azimuth of each domain].

  Table 1 shows the aspect ratio, azimuth angle, and average azimuth value of the obtained domain. The cellulose ester film 1 has an absolute maximum length of a domain of 70 nm, an aspect ratio of 2, an average azimuth angle parallel to the MD direction of the film, and an absolute angle formed by the direction of the average azimuth angle and the azimuth angle of each domain. The average value of the values was H = 4 °.

<Evaluation of refractive index of cellulose ester film and domain>
The refractive index here is a value at a temperature of 20 ° C. based on the D line (589 nm). The method of measuring the refractive index was performed as follows. A cross section of the sample parallel to the above TD or MD direction was cut to 1 mm thickness and observed with a polarizing microscope. Using a method of immersing a sample in liquids having different refractive indexes, a Abbe refractometer-4T is used to remove a liquid in which the interface between the major axis direction of domains existing in the MD direction and the liquid for refractive index measurement is unclear. The refractive index in the major axis direction of the domain was determined by measurement. Similarly, the refractive index in the minor axis direction of the domain is measured by measuring the refractive index of the liquid in which the interface between the minor axis direction of the domain existing in the TD direction and the liquid for refractive index measurement is unclear with the Abbe refractometer-4T. It was determined.

  On the other hand, the refractive index of the resin phase of the cellulose ester film was performed as follows. Using a method of immersing a sample in a liquid having a different refractive index, the refractive index of a liquid in which the interface between the resin phase other than the domain in the MD direction and the liquid for refractive index measurement is unclear is measured with an Abbe refractometer-4T. Then, the refractive index in the MD direction of the resin phase was determined. Using a method of immersing a sample in a liquid with a different refractive index, measure the refractive index of the liquid in which the interface between the resin phase other than the domain in the TD direction and the liquid for refractive index measurement is unclear with the Abbe refractometer -4T. Thus, the refractive index in the TD direction of the resin phase was determined.

  According to the above method, in the cellulose ester film 101, the refractive index of the resin phase in the direction corresponding to the average major axis direction of the domain is 1.48, and the refractive index of the resin phase in the direction corresponding to the average minor axis direction of the domain. Was 1.48. The refractive index in the major axis direction of the domain was 1.67, and the refractive index in the minor axis direction of the domain was 1.49.

<Measurement of contact angle with water before and after saponification treatment>
Preparation of a film sample cut to 5 cm × 10 cm, soaking the cellulose ester film after saponification treatment after saponification treatment and after immersing in 40 ° C., 2N-KOH for 90 seconds, washing with running water for 90 seconds, and drying overnight The contact angle with water was measured. The contact angle was measured using a DCA-VZ type automatic / dynamic contact angle meter manufactured by FACE, and evaluated by a contact angle 0.1 seconds after dropping a water droplet.

  Table 1 shows the values of contact angles with water before and after the saponification treatment of the obtained film. The contact angle with the pure water before the saponification treatment of the cellulose ester film 1 was 71 °, and the contact angle with the pure water after the saponification treatment was 38 °.

(Cellulose ester films 102-115)
Cellulose ester films 102 to 115 were produced in the same manner except that the cellulose ester film 101 was changed in the type (substitution degree) of cellulose ester and the aspect ratio of the liquid crystal polymer as a domain as shown in Table 1.

  In the same manner as described above, evaluation of the domain aspect ratio, azimuth angle, and average azimuth angle, and contact angle measurement with water before and after saponification treatment were performed, and the results are shown in Table 1.

  The evaluation results of the refractive indexes of the films and domains of the cellulose ester films 102 to 115 were the same as those of the cellulose ester film 101.

(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.

  Next, polarizing plates 101 to 115 were produced according to steps 1 to 5.

Process 1
As the polarizing plate protective film, the produced cellulose ester film 101 produced in Example 1 was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water, dried and bonded to a polarizer. Saponified side.

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

Process 2
The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Process 3
The excess adhesive adhered to the polarizer in Step 2 is gently wiped off, and this is placed on the saponified surface of the cellulose ester film 101 treated in Step 1 and further treated in Step 1 as a polarizing plate protective film on the opposite side. The obtained cellulose ester film KC8UCR-5 was laminated in the same manner as shown in FIG. 15 so that the saponified surface was in contact with the polarizer, and a polarizing plate 101 was obtained.

Process 4
The polarizing plate obtained by laminating the cellulose ester film and the polarizer in Step 3 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 in step 4 was dried for 2 minutes in a dryer at 80 ° C.

  Similarly, polarizing plates 102 to 115 were produced using cellulose ester films 102 to 115.

  Further, a commercially available cellulose ester film KC8UY (manufactured by Konica Minolta Opto Co., Ltd .: normal TAC film) is bonded to the surface of the polarizer on which the cellulose ester film 101 is bonded, and a commercially available adhesive is used thereon. Except that the cellulose ester film 101 was bonded, the polarizing plate 116 of the present invention but having a configuration outside the scope of claim 2 was produced in the same manner as the polarizing plate 101.

(Evaluation of polarizing plate)
The following evaluation was implemented using the produced said polarizing plates 101-116.

<Durability of polarizing plate winding shape>
The produced polarizing plate was stored at 80 ° C. and 90% RH for 1000 hours, and the winding shape was evaluated according to the following criteria.

◎: No change such as wrinkles or deformation is observed on the roll surface ○: Slight wrinkles are observed on the roll surface, but no deformation is observed △: Weak wrinkles are observed on the roll surface, and some Deformation is also observed x: Strong wrinkles on the surface of the roll to the inside, strong deformation on the surface, deformation to the inside <Polarizer adhesion>
The adhesion of the produced polarizing plate was evaluated according to the following criteria.

  Each polarizing plate was cut into a size of 5 cm × 7 cm. The obtained cut pieces are each temporarily attached to the center of a 6 cm × 8 cm glass plate with an acrylic adhesive, and then pressed to completely remove bubbles between the pieces and the glass plate. Sticked to a glass plate.

  The test pieces thus prepared were placed vertically in a constant temperature and humidity oven set at 80 ° C. and 95% RH so as not to overlap each other and fixed to the support frame for 1000 hours, and then the polarizer and the protective film were bonded to each piece. The sex was measured.

  Evaluation of adhesion between polarizer and protective film: After high-temperature and high-humidity treatment, visual observation was performed to evaluate the peeled state between the polarizer and the protective film.

◎: The film lifted part is not found at all. ○: The film lifted part is recognized, but the periphery is 1 mm or less. △: The film lifted part is in the range of 1 to 5 mm in the periphery. X: The film lifted part is 5 mm or more in the periphery. (Production of liquid crystal display device)
A liquid crystal panel for evaluating visibility was produced as follows.

  The polarizing plate on the backlight side of the 15-inch liquid crystal display VL-1530S manufactured by Fujitsu was previously peeled off, and the produced polarizing plates 101 to 116 were each bonded to the glass surface of the liquid crystal cell.

  At that time, the direction of bonding of the polarizing plate is absorbed so that the surfaces of the cellulose ester films 101 to 116 of the polarizing plate are on the backlight side and in the same direction as the polarizing plate previously bonded. The liquid crystal display devices 101 to 116 were respectively produced so that the axes were directed.

<Evaluation of brightness of liquid crystal display device>
The front luminance of each manufactured liquid crystal display device was evaluated.

For luminance, luminance (cd / m ² ) was determined using luminance measured with a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing).

A commercially available cellulose ester film KC8UY was used on both sides of the polarizer, and a polarizing plate for comparing the luminance was prepared in the same manner as the polarizing plate 101 except for the above. The polarizing plate for comparing this brightness | luminance was bonded so that the absorption axis might face in the same direction as the polarizing plate previously bonded to the backlight side. At this time, white display was performed so that the front luminance was 200 cd / m ² .

  The liquid crystal display devices 101 to 115 are excellent when the front luminance measured under the same white display conditions shows a higher value than the front luminance of a comparative liquid crystal display device using a polarizing plate for comparing the luminance. It can be said.

A: 1.20 times or more of the front luminance of the comparative liquid crystal display device B: 1.10 times or more and less than 1.20 times of the front luminance of the comparative liquid crystal display device Δ: It is 1.05 times or more and less than 1.10 times the front luminance of the comparative liquid crystal display device. X: Less than 1.05 times the front luminance of the comparative liquid crystal display device. Evaluation of durability>
[Contrast unevenness]
The liquid crystal display panel was subjected to forced deterioration (durability test) under the conditions of 40 ° C. and 80%, and each liquid crystal display panel was treated for 500 hours.

  Evaluation of the viewing angle characteristics of the liquid crystal display device was performed by using EZ-contrast manufactured by ELDIM and measuring the amount of emitted light during black display and white display. The viewing angle was evaluated by calculating contrast = (transmitted light amount during white display) / (transmitted light amount during black display) and evaluated according to the following criteria.

  The viewing angle was evaluated using the angle indicating the viewing angle of contrast 10 as an index.

  Compared with the viewing angle at which the liquid crystal display panel was not subjected to forced deterioration (endurance test), the difference in viewing angle was defined as the contrast unevenness of the liquid crystal display device.

A: Contrast unevenness before and after forced deterioration is 5 ° or less with respect to all directions. ○: There is a portion where the contrast unevenness before and after forced deterioration is 5 ° or more and less than 10 ° with respect to the direction. Δ: There is a portion where the contrast unevenness before and after the forced deterioration is 10 ° or more and less than 15 ° with respect to some orientation, and the display image is uneven ×: The contrast unevenness before and after the forced deterioration is in some orientation On the other hand, the evaluation results are shown in Table 2 below.

  From the above table, the polarizing plates using the cellulose ester films 101 to 109 of the present invention and the liquid crystal display devices 101 to 109 are superior to the comparative examples in winding durability, adhesion, brightness, and contrast unevenness. I understand.

Example 2
(Preparation of cellulose ester film 201)
<Preparation of dope 2>
Cellulose acetate propionate (acetyl substitution degree 1.01, propionyl group substitution degree 1.50, total acyl group substitution degree 2.51, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3.1) 100 mass Part Methylene chloride 380 parts by mass Ethanol 70 parts by mass Polymer A-1 50 parts by mass Plasticizer: Trimethylolpropane tribenzoate 10 parts by mass Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.5 part by mass Tinuvin 171 (Ciba Specialty) Chemicals Co., Ltd.) 0.5 parts by mass Matting agent: R972V (Nippon Aerosil Co., Ltd.) 0.2 parts by mass <Synthesis of Polymer A-1>
A water-cooled reflux condenser and a stirrer were attached to a 200-liter reaction kettle, 60 kg of toluene was added, and nitrogen gas was sent into the system for replacement. A mixture of 18 kg of styrene monomer, 2 kg of ethyl acrylate monomer and 300 g of 2-2′azobisisobutyronitrile (polymerization initiator) was added and heated to 70 ° C. for solution polymerization.

  After heating for 2 hours, the mixture was further reacted for 1 hour at the reflux temperature of toluene, and then recovered while volatilizing toluene, and the reaction mixture was concentrated. 80 kg of ethyl alcohol was added to the reaction kettle contained in the reaction mixture allowed to cool to room temperature, and the reaction mixture was washed with stirring for 2 hours. The solvent was filtered off, the solid was separated, and the solvent was removed by drying under reduced pressure to obtain a white solid.

  As a result of testing the polymer A-1 by the birefringence test method, it was confirmed that all of the polymers were materials showing negative birefringence in the stretching direction.

  The dope 2 was uniformly cast on a stainless steel belt kept at 40 ° C. The die used for casting is of the type shown in FIG. 8, and the dope is supplied from one side with a slit length of 30 mm and a slit interval of 0.8 mm. The depth is 0.5 mm in the slit in the direction opposite to the supply side. Were provided at an angle of 45 ° with respect to the slit width direction at intervals of 1 mm. By passing the dope through the slit, the polymer was oriented in the TD direction at the slit exit of the die.

  After the residual solvent amount was dried to 80%, it was peeled off from the stainless steel belt. Thereafter, the film was stretched 1.4 times in the TD direction with a tenter. Furthermore, it dried at 120 degreeC, making it convey with many rolls, and obtained the cellulose-ester film 201 of 80 micrometers and width 1.3m.

  Table 3 shows the aspect ratio, azimuth angle, and average azimuth value of the obtained domain, and the contact angle value with respect to pure water before and after the saponification treatment. The cellulose ester film 201 has an absolute maximum domain length of 90 nm, an aspect ratio of 2, an average azimuth angle parallel to the TD direction of the film, and an absolute angle between the direction of the average azimuth angle and the azimuth angle of each domain. The average value of the values was H = 4 °.

  Subsequently, with respect to the cellulose ester film 201, the cellulose ester films 202 to 202 were similarly formed except that the type (substitution degree) of the cellulose ester and the aspect ratio of the polymer A-1 as the domain were changed as shown in Table 3. 215 was produced.

<Evaluation of refractive index of cellulose ester film and domain>
In the cellulose ester film 201, the refractive index of the resin phase in the direction corresponding to the average major axis direction of the domain is 1.48, and the refractive index of the resin phase in the direction corresponding to the average minor axis direction of the domain is 1. 48. The refractive index in the major axis direction of the domain was 1.49, and the refractive index in the minor axis direction of the domain was 1.67. The cellulose ester films 202 to 214 were the same.

  Polarizers 201 to 215 and liquid crystal display devices 201 to 215 were produced using cellulose ester films 201 to 215 in the same manner as in Example 1. Further, in the same manner as in Example 1, durability of polarizing plate winding and polarization Evaluation of child adhesion, luminance of the liquid crystal display device, and contrast unevenness of the liquid crystal display device were performed. The results are shown in Table 4 below.

  From the above table, the polarizing plate using the cellulose ester films 201 to 209 of the present invention and the liquid crystal display devices 201 to 209 are excellent in winding shape durability, adhesion, luminance, and contrast unevenness compared to the comparative example. I understand.

Example 3
(Preparation of cellulose ester film 301)
As cellulose ester, cellulose acetate propionate (acetyl group substitution degree 1.01, propionyl group substitution degree 1.5, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3.1) 90 parts by mass, Examples 50 parts by mass of the liquid crystal polymer (glass transition temperature 80 ° C., nematic liquid crystallizing temperature 100 to 290 ° C.) used in No. 1, 0.2 parts by mass of Ciba Specialty Chemicals Tinuvin 144 as a heat stabilizer, epoxidized tall oil 0.1 Part by mass, 0.2 part by mass of para-tert-butylphenol and 0.02 part by mass of strontium naphthoate were mixed uniformly. After dissolving the obtained mixture, it was dried and the solvent was distilled off to form pellets.

  After mixing 8 parts by mass of trimethylolpropane tribenzoate as a plasticizer and 1.0 part by mass of Tinuvin 360 (manufactured by Ciba Specialty Chemicals) as an ultraviolet absorber, the pellets were fed to a twin screw extruder. The screw rotation speed was 100 rpm, the temperature in the barrel (melting temperature) was set to 240 ° C., the material was melted, and the fluidized cellulose ester composition was cast on a cooling drum maintained at 130 ° C. The cellulose ester film 301 was peeled and stretched 1.5 times in the MD direction and 1.05 in the TD direction to obtain a cellulose ester film 301 having a width of 80 μm and a width of 1.3 m.

  Table 5 shows the values of the aspect ratio, azimuth angle, and average azimuth angle of the domains in the obtained film. The cellulose ester film 301 has a domain aspect ratio of 2, an average azimuth angle parallel to the MD direction of the film, and an average absolute value H = the angle formed by the average azimuth angle direction and the azimuth angle of each domain. It was 4 °.

  Next, cellulose ester films 302 to 305 were produced in the same manner except that the type of cellulose ester and the aspect ratio of the liquid crystal polymer were changed.

(Preparation of cellulose ester film 306)
As cellulose ester, cellulose acetate propionate (acetyl group substitution degree 1.01, propionyl group substitution degree 1.5, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3.1) 90 parts by mass, Examples 50 parts by weight of polymer A-1 used in No. 2, 0.2 parts by weight of Tinuvin 144 manufactured by Ciba Specialty Chemicals as a heat stabilizer, 0.1 parts by weight of epoxidized tall oil, 0.2 parts by weight of para-tert-butylphenol, 0.02 part by mass of strontium naphthoate was uniformly mixed. After dissolving the obtained mixture, it was dried and the solvent was distilled off to form pellets.

After mixing 8 parts by mass of trimethylolpropane tribenzoate as a plasticizer and 1.0 part by mass of tinuvin 360 (manufactured by Ciba Specialty Chemicals) as an ultraviolet absorber, the pellets were fed to a twin screw extruder. The screw rotation speed was 100 rpm, the temperature in the barrel (melting temperature) was set to 240 ° C., the material was melted, and the fluidized cellulose ester composition was cast on a cooling drum maintained at 130 ° C. The film was peeled and stretched 1.05 times in the MD direction and 1.50 in the TD direction to obtain a cellulose ester film 306 having a width of 80 μm and a width of 1.3 m. Aspect ratio and azimuth angle of domains in the obtained film The average azimuth values are shown in Table 5. The cellulose ester film 306 has a domain aspect ratio of 2, the average azimuth angle is parallel to the TD direction of the film, and the average absolute value of the angle formed by the average azimuth angle direction and the azimuth angle of each domain H = It was 3 °.

  Next, cellulose ester films 307 to 310 were produced in the same manner except that the type of cellulose ester and the aspect ratio of the polymer A-1 were changed.

  Using the cellulose ester films 301 to 310 of the present invention, polarizing plates 301 to 310 and liquid crystal display devices 301 to 310 were prepared in the same manner as in Example 1, and polarizing plate winding shape durability, polarizer adhesion, and liquid crystal When the luminance of the display device and the contrast unevenness of the liquid crystal display device were evaluated, the same excellent effects as those of Examples 1 and 2 were reproduced.

It is a schematic diagram of the polarizing plate protective film which has the polarization scattering anisotropy containing the optical continuous phase and domain which mainly have the cellulose ester which concerns on this invention. It is a figure which shows the azimuth angle of a domain. It is a figure which shows the angle which each domain makes with respect to the direction of an average azimuth. It is the figure which showed typically the dope preparation process of the solution casting film forming method concerning this invention, a casting process, and a drying process. It is the figure which showed typically the apparatus which measures absolute filtration accuracy. It is a figure which shows the example of the dice | dies with which the some nozzle is arrange | positioned in the width direction. It is a figure which shows an example of the die | dye by which the liquid supply part and the liquid discharge part are arrange | positioned in the direction which is not parallel with respect to the moving direction of a casting support body within a die | dye. It is a figure which shows an example of the die | dye which provided the groove | channel in the direction which is not parallel with respect to the moving direction of a casting support body inside die | dye. It is a figure which shows an example of the method using a diagonal gravure roll. It is a figure which shows an example of the method using an orientation belt. An example of a die having a long slit length for laminar flow is shown. It is a figure which shows an example of the method of pulling dope by conveyance of a belt and performing substantial extending | stretching during casting. It is the schematic which shows an example of the tenter process used for this invention. It is a figure explaining the extending | stretching angle in an extending | stretching process. It is a schematic diagram of polarizing plate manufacture by the roll to roll preferable for this invention. It is the schematic which shows the structure of the liquid crystal display device preferable for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Melting pot 3,6,12,15 Filter 4,13 Stock tank 5,14 Liquid feed pump 8,16 Conduit 20 Junction pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll drying apparatus A Filter medium sample B Filtered liquid C Filtration M Manometer P Low pressure vacuum pump S Stirrer V valve 60 Polarizing plate 61 Polarizing plate protective film 62 Dichroic polarizer 63 Polarizing plate protective film B
64 Light reflector 65 Light guide plate 66 Light diffuser plate 67 Backlight 68 Liquid crystal cell 69 Viewing side polarizing plate

Claims (3)

A polarizing plate protective film having polarization scattering anisotropy comprising at least an optical continuous phase mainly composed of cellulose ester and a domain having an optical anisotropy having an aspect ratio of 2 or more defined by the following formula:
The average azimuth angle of the domain having optical anisotropy is perpendicular or parallel to the film forming direction of the polarizing plate protective film, and the absolute value of the angle formed by the average azimuth angle and each domain The average value H is within 20 °, and at least one surface of the polarizing plate protective film having polarization scattering anisotropy has a contact angle with water before saponification treatment of 60 ° or more and 80 ° or less, and saponification treatment. A polarizing plate protective film having polarization scattering anisotropy, characterized in that the subsequent contact angle with water is 15 ° or more and 40 ° or less.
Expression Aspect ratio = absolute maximum length / diagonal width (here, the diagonal width is the shortest distance between two straight lines when sandwiching the image of the domain projected by two straight lines parallel to the absolute maximum length) .) A polarizing plate integrated in the order of a polarizing plate protective film having polarization scattering anisotropy according to claim 1 / a dichroic polarizing film / polarizing plate protective film B utilizing a light absorption action by a dichroic substance. A polarizing plate, wherein the absorption axis of the dichroic polarizing film is in the longitudinal direction of the film. A liquid crystal display device using the polarizing plate according to claim 2, wherein the polarizing plate protective film having polarization scattering anisotropy is disposed on a light source side.

Images