WO2011093216A1 - 位相差フィルム用セルロースジアセテート - Google Patents
位相差フィルム用セルロースジアセテート Download PDFInfo
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- WO2011093216A1 WO2011093216A1 PCT/JP2011/051058 JP2011051058W WO2011093216A1 WO 2011093216 A1 WO2011093216 A1 WO 2011093216A1 JP 2011051058 W JP2011051058 W JP 2011051058W WO 2011093216 A1 WO2011093216 A1 WO 2011093216A1
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- cellulose
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- acetylation
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B3/00—Preparation of cellulose esters of organic acids
- C08B3/06—Cellulose acetate, e.g. mono-acetate, di-acetate or tri-acetate
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
- C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
- C08L1/08—Cellulose derivatives
- C08L1/10—Esters of organic acids, i.e. acylates
- C08L1/12—Cellulose acetate
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3083—Birefringent or phase retarding elements
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/08—Cellulose derivatives
- C08J2301/10—Esters of organic acids
- C08J2301/12—Cellulose acetate
Definitions
- the present invention relates to a cellulose ester film, an optical film, particularly a cellulose diacetate used for a retardation film, which has excellent optical characteristics, allows easy control of retardation values, particularly R th , and has uniform retardation characteristics.
- a polarizing plate is necessary for display.
- a PVA film containing iodine is used as a polarizing plate. Since this polarizing plate is brittle, a polarizing plate protective film is used to protect it.
- a triacetyl cellulose film is widely used as a polarizing plate protective film.
- a retardation film is also used to control the retardation of polarized light.
- the retardation film used in such a liquid crystal display device is used to solve problems such as color compensation and viewing angle expansion by using Rth in combination with a polarizing plate.
- cage also sometimes has a function of converting the linearly polarized light circularly polarized light in the opposite or convert linearly polarized light into circularly polarized light using the R e with respect to the wavelength of visible light range.
- the purpose of the polarizing plate protective film is to protect the polarizing plate, and in order to protect the polarizing plate made of PVA containing water, it is most suitable to use a film made of cellulose acetate in consideration of the manufacturing process of the polarizing plate. Is preferred.
- materials other than cellulose acetate have been used for the retardation film in order to exhibit optical performance. That is, conventionally, examples of the material for the retardation film include polycarbonate, polysulfone, polyethersulfone, and amorphous polyolefin. These polymer films have the property that the retardation decreases as the wavelength increases, and it has been difficult to impart ideal retardation characteristics to all wavelengths in the visible light region.
- phase difference is preferably ⁇ / 4 at the wavelength ( ⁇ ).
- a retardation film can be used, for example, in a reflective liquid crystal display device having a configuration in which only one retardation film having a retardation of ⁇ / 4 and a polarizing plate is used and the back electrode is also used as a reflective electrode. Can be obtained.
- this retardation film is used on the back side, or circularly polarized light of a reflective polarizing plate composed of cholesteric liquid crystal that reflects only one of the left and right circularly polarized light It is used in the same manner as an element that converts the light into linearly polarized light.
- the polarizing plate protective film and the retardation film can be used together, and the retardation film composed of a plurality of retardation films is omitted. This is useful because it can improve the total light transmittance of the optical film in the liquid crystal display device.
- Patent Document 1 proposes to use an oriented film of cellulose acetate having a total substitution degree (acetylation degree) of 2.5 to 2.8 as a retardation film. According to this method, the longer the wavelength, the larger the phase difference, and ideal phase difference characteristics can be obtained for all wavelengths in the visible light region. That is, Patent Document 1 provides a phase difference plate in which the phase difference becomes smaller as the measurement wavelength is shorter in one film.
- a retardation film comprising a polymer oriented film having a larger birefringence ⁇ n at a wavelength of 400 to 700 nm as a longer wavelength, and the polymer oriented film is an oriented film of a polymer film having a larger average refractive index at the wavelength as a shorter wavelength
- a technique for orienting cellulose acetate having a degree of acetylation of 2.5 to 2.8 by stretching is disclosed.
- a film was produced by a solvent casting method from a solution obtained by dissolving 100 parts by weight of this polymer and 3 parts by weight of dibutyl phthalate as a plasticizer in 700 parts by weight of a mixed solvent of methylene chloride / methanol (weight ratio 9/1). Furthermore, it is disclosed that the film was uniaxially stretched 1.5 times at a temperature of 170 ° C. That is, in Example 1 of Patent Document 1, it is assumed that a retardation film having the wavelength characteristics (wavelength dispersion characteristics) as described above was obtained by stretching. It is disclosed that by adjusting the Re value, ⁇ / 4 or other retardation films can be obtained.
- Example 4 of Patent Document 1 cellulose acetate having a degree of acetylation of 2.421 is obtained.
- the film thickness is about 100 ⁇ m and (50 ⁇ 150 ⁇ m), R e when the suitable film thickness as free-standing film is insufficient.
- the film thickness is as thick as about 200 ⁇ m, a suitable R e of about 80 to 150 nm is given, but the R th at that time is excessively over 350 nm and functions as a ⁇ / 4 retardation film. Did not function as a viewing angle widening film and was not sufficient.
- the molecular weight distribution of the obtained cellulose acetate is not described, and there is no description or suggestion about controlling the molecular weight distribution to control the retardation characteristics.
- Patent Document 2 it has a uniform phase difference function, in addition, it has excellent surface quality (pushing failure and small film thickness deviation), and the retardation value R0 can be easily controlled, providing uniform phase difference characteristics. It is an object of the present invention to provide a cellulose ester film, a long retardation film, an optical film and a production method thereof that can produce an optical film having good productivity, and to provide a polarizing plate and a display device that are excellent in display quality using these films.
- the acyl group having 2 to 4 carbon atoms as a substituent, the total of the substitution degree of the 2-position, 3-position and 6-position in the glucose residue is less than 2.67, and 6
- the present invention discloses a cellulose ester film characterized by containing a cellulose ester having a degree of acyl group substitution of less than 0.87 (summary).
- 16 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride and 420 parts by mass of acetic acid were added to 100 parts by mass of cellulose, and the mixture was stirred from room temperature to 60 ° C. over 60 minutes.
- the ratio Mn / Mw of the number average molecular weight (Mn) to the weight average molecular weight (Mw) is described as being 2.0 (Example 1) to 3.0 (Example 2) (Mw / Mn it is conceivable that).
- Patent Document 3 for the purpose of providing a cellulose ester film excellent in optical characteristics, dimensional stability, transparency, flatness, frame-like whiteout failure resistance, a production method thereof, and a polarizing plate using the same, It contains a UV absorber and two or more plasticizers, one of the plasticizers is a polyhydric alcohol ester plasticizer, and the other is a plasticizer selected from other than phosphate ester plasticizers.
- a dope containing a cellulose ester having a molecular weight Mw / number average molecular weight Mn of 1.8 to 3.0 is cast on a belt support by a solution casting film forming method, and a residual solvent amount in the web is 40 mass.
- stretching in TD direction when the amount of residual solvents is less than 40 mass% is disclosed.
- Patent Document 4 for the purpose of obtaining a cellulose acylate solution having excellent stability over time and low viscosity in a practical dope concentration range, the total degree of acyl substitution at the 2nd and 3rd positions is 1.70 or more and 1 It is described that cellulose acylate having a substitution degree of .90 or less and an acyl substitution at the 6-position of 0.88 or more, that is, a total substitution degree of 2.58 to 2.78 is used. In Example 1 of Patent Document 4, cellulose acetate having 1.88 at the 2nd and 3rd positions and 0.89 at the 6th position, that is, a total substitution degree of 2.77 is disclosed.
- Patent Document 5 discloses that an optical film composed of a cellulose ester film useful as a protective film for a polarizing film used in a liquid crystal display device has a high longitudinal and lateral elastic modulus, thereby suppressing the contraction of the polarizing film. And providing an optical film that can prevent the polarizing film from peeling from the liquid crystal cell due to shrinkage of the polarizing film, a method for producing the same, and a polarizing film. And it describes that an optical film made of a cellulose ester film is produced by a solution casting film forming method.
- a cellulose ester having a molecular weight distribution in which the weight average molecular weight (Mw) is gradually reduced by the number average molecular weight (Mn): Mw / Mn of 1.4 to 3.0 is used, and the cellulose ester solution is placed on the support.
- Mw weight average molecular weight
- Mn number average molecular weight
- MD direction film transport direction
- TD direction direction perpendicular to the film transport direction
- a cellulose ester film suitable as a protective film for a polarizing plate in a liquid crystal display (LCD) has a good orientation angle distribution in the width direction of the cellulose ester film, and the film is peeled off from the support.
- Low-cost cellulose that is high quality, stable and easy to peel without causing so-called horizontal step failure (horizontal step thickness unevenness), and is very advantageous in terms of cost Providing an ester film is described.
- the cellulose ester film produced by the solution casting film forming method and containing a plurality of types of cellulose esters is a wood whose molecular weight distribution: Mw / Mn is 1.8 to 3.0 among the cellulose esters constituting the film.
- Patent Document 7 describes a cellulose ester film characterized in that Mw / Mn is 1.0 to 5.0 (Claim 5), and the cellulose ester is substantially cellulose triacetate. Preferred (paragraph 0056). In Examples 6 and 9 of Patent Document 7, a film containing cellulose triacetate having Mw / Mn of 3.5 is described, but Rth and the like have not been studied.
- Patent Document 8 there is a retardation film with little change in retardation characteristics due to long-term use or environmental fluctuations even when the film is thinned, and a manufacturing method thereof, and a wide viewing angle when used in a liquid crystal image display device.
- a retardation film capable of obtaining an excellent viewing angle is disclosed.
- the total substitution degree of acyl groups is 2.40 to 2.80, and the 6th position.
- a retardation film is disclosed that is formed using a cellulose ester having a hydroxyl group unsubstituted degree of 0.15 to 0.42.
- the molecular weight distribution Mw / Mn of cellulose ester is not examined, and in the examples, only a retardation Rt in the thickness direction of 155 nm or less is obtained.
- Patent Document 9 describes that a 6-position highly acetylated cellulose diacetate useful as a raw material for cellulose mixed acylates having excellent optical properties and high acyl group total substitution that can be used as photographic materials and optical materials is described. ing.
- the 6-position highly acetylated cellulose diacetate satisfies the following relational expressions (1) and (2) when the total acetyl substitution degree is DSt and the 6-position acetyl substitution degree is DS6, and the viscosity is 6%.
- Cellulose diacetate is described wherein 2.0 ⁇ DSt ⁇ 2.6 and 0.400 ⁇ DS6 / DSt ⁇ 0.531 ⁇ 0.088 ⁇ DSt when the pressure is 40 to 600 mPa ⁇ s .
- This document aims to provide a cellulose acetate having a high degree of acetyl substitution at the 6-position, a low degree of total acetyl substitution, room for introduction of acyl groups other than acetyl groups to some extent, and a relatively high molecular weight. .
- the cellulose was reacted with an acetylating agent in the presence of a catalyst in a solvent to synthesize a cellulose triacetate having a total degree of acetyl substitution of 2.6 or more, and obtained in the above step
- Cellulose triacetate in acetic acid in the presence of 0.56 to 8.44 parts by weight of an acetylation catalyst with respect to 100 parts by weight of cellulose triacetate and 22 to 50 mol% of water with respect to acetic acid
- a process of hydrolyzing at a temperature of 40 to 90 ° C. to obtain cellulose diacetate having a high 6-acetyl substitution degree is disclosed.
- the half-value width of the maximum peak of the intermolecular substitution degree distribution curve or acetylation degree distribution curve of cellulose diacetate can be used as an index.
- the half-value width of the maximum peak of the intermolecular substitution degree distribution curve of cellulose diacetate is preferably 0.150 or less, more preferably 0.140 or less, and particularly preferably 0.130 or less. .
- Cited Document 9 in order to impart stretchability by introducing a substituent having a larger number of carbon atoms than the acetyl group of cellulose acetate, the total degree of acetyl substitution is not so high. It aims at supplying the cellulose acetate raw material which has the room which can introduce acyl groups other than to some extent. Cited Document 9 does not disclose the weight average molecular weight Mw / number average molecular weight Mn, and there is a description or suggestion about obtaining high stretchability by optimizing the weight average molecular weight Mw / number average molecular weight Mn. Absent.
- Non-patent document 1 describes the basic principle of the cellulose acetate synthesis method.
- a typical synthesis method is a liquid phase acetylation method using acetic anhydride (acetyl group donor) -acetic acid (solvent) -sulfuric acid (catalyst).
- acetic anhydride acetyl group donor
- solvent solvent
- catalyst acetic acid
- a cellulose raw material such as wood pulp is pretreated with an appropriate amount of acetic acid, and then put into a precooled acetylated mixed solution to be acetic acid ester to synthesize cellulose acetate.
- the acetylated mixed solution generally contains acetic acid as a solvent, acetic anhydride as an acetyl group donor (esterifying agent), and sulfuric acid as a catalyst.
- Acetic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system.
- a neutralizing agent for example, sodium, potassium, calcium, magnesium, iron, etc.
- An aqueous solution of aluminum, zinc or ammonium carbonate, acetate or oxide is added.
- the obtained cellulose acetate is aged by maintaining it at 50 to 90 ° C.
- acetylation reaction catalyst generally, remaining sulfuric acid
- desired degree of acetyl substitution and degree of polymerization The cellulose acetate is changed.
- the catalyst remaining in the system is completely neutralized with the neutralizing agent as described above, or water or Cellulose acetate solution was put into acetic acid (or water or dilute acetic acid was put into cellulose acetate solution) to separate cellulose acetate, and cellulose acetate was obtained by washing and stabilization treatment.
- cellulose is treated with an acetylated solvent (solvent for the acetylation step) to activate the cellulose.
- acetylation solvent acetic acid is usually used, but a solvent other than acetic acid (such as methylene chloride) or a mixed solvent of acetic acid and a solvent other than acetic acid (such as methylene chloride) can also be used.
- a solvent other than acetic acid such as methylene chloride
- a mixed solvent of acetic acid and a solvent other than acetic acid such as methylene chloride
- a strong acid such as sulfuric acid
- the amount of strong acid (sulfuric acid) added in the pretreatment step is about 0.1 to 0.5 parts by weight with respect to 100 parts by weight of the raw material cellulose.
- Non-patent Document 2 it is known that when a strong acid (sulfuric acid) is used in an amount of 0.5 parts by weight or more per 100 parts by weight of the raw material cellulose, the molecular weight of the raw material cellulose is lowered (Non-patent Document 2).
- the activation process time is, for example, 10 to 180 minutes, preferably 20 to 120 minutes.
- the acetylation time (total acetylation time) in the acetylation step varies depending on the reaction temperature and the like, but is, for example, in the range of 20 minutes to 36 hours, preferably 30 minutes to 20 hours.
- the reaction is carried out at a temperature of at least 30 to 50 ° C. for about 30 to 180 minutes (preferably about 50 to 150 minutes).
- it is not recognized that the time for stopping the acetylation reaction has a great influence on the properties of the cellulose acetate to be obtained. In many cases, it was decided by restrictions such as supply amount.
- the uniform chemical composition means that the chemical composition becomes uniform by sufficiently reacting in the cellulose esterification and hydrolysis of the produced cellulose ester. Therefore, in order to obtain cellulose diacetate having a uniform chemical composition, it is necessary to perform esterification and hydrolysis of cellulose acetate in as long a time as possible. Therefore, in the synthesis of cellulose acetate, uniform chemical composition and non-uniform molecular weight distribution are contradictory requirements and could not be realized.
- the object of the present invention is that the stretchability for adjusting the retardation is good, the filterability for obtaining an optical film is excellent, and the content of cellulose ester with a low degree of substitution that causes bright spot foreign matter and the like is included.
- the object is to obtain a cellulose diacetate for a retardation film, which is small and has a relatively high Rth even if it is not stretched, and is effective in developing retardation when stretched.
- the inventors of the present invention have a chemical composition when synthesizing cellulose diacetate having a total substitution degree (average substitution degree) of 2.27 to 2.56.
- the present inventors have found that stretchability and filterability can be improved by using cellulose diacetate having a high molecular weight while maintaining a uniform molecular weight.
- the non-uniformity of the molecular weight distribution of cellulose diacetate is effective in improving stretchability, but further reducing unreacted substances and low acetylation components in cellulose diacetate. It has been found that the stretchability is also improved. This is because unreacted substances and low acetylation components in cellulose diacetate are not completely removed even in the filtration step performed in the cellulose ester film forming step, and at least a part remains, so at the time of synthesis It is thought that extensibility is improved by not including these unreacted substances and low acetylation component.
- the present invention is a cellulose diacetate having a total acetyl group substitution degree of 2.27 to 2.56, a dispersity Mw / Mn of more than 3.0 and 7.5 or less, and a 6-position substitution degree of 0.
- a cellulose diacetate for a retardation film characterized in that the half-value width of acetylation distribution is 1.0 to 2.3 and the viscosity average polymerization degree is 182 or more and 213 or less.
- the cellulose diacetate for retardation film of the present invention preferably has a 6% viscosity of 120 to 230 mPa ⁇ s, and preferably has a weight average molecular weight Mw of 205,000 or more and 235,000 or less.
- the cellulose diacetate for retardation film of the present invention it is possible to achieve both stretchability and retardation development property when stretched, filterability, and a small amount of optical foreign matter such as bright spot foreign matter.
- the contradictory required properties of a uniform chemical composition and a non-uniform molecular weight distribution were realized.
- the cellulose diacetate for retardation film of the present invention is a cellulose diacetate having a total acetyl group substitution degree of 2.27 to 2.56, a dispersity Mw / Mn of more than 3.0 and not more than 7.5, and The 6-position substitution degree is 0.65 to 0.85, the acetylation degree distribution half width is 1.0 to 2.3, and the viscosity average degree of polymerization is 182 or more and 213 or less.
- the 6% viscosity is preferably 120 to 230 mPa ⁇ s.
- the weight average molecular weight Mw is 205,000 or more and 235,000 or less.
- the cellulose diacetate for retardation film of the present invention has an acetyl group total substitution degree (average substitution degree) of 2.27 to 2.56, that is, an acetylation degree of 52.9 to 57.0.
- the R th retardation films for example, cellulose diacetate retardation film capable of a 200 ⁇ 400 nm is provided.
- the total substitution degree of cellulose diacetate is 2.27, that is, the acetylation degree is less than 52.9, the retardation (R e ) in the surface direction becomes too high.
- the total substitution degree of cellulose diacetate is 2.56, that is, when the acetylation degree exceeds 57.0, the retardation (R th ) in the thickness direction cannot be sufficiently increased.
- the most common method for determining the average degree of substitution of cellulose acetate is a method for measuring the degree of acetylation in ASTM-D-817-91 (testing method for cellulose acetate and the like).
- the degree of acetylation (the amount of bound acetic acid) determined according to ASTM may be converted to the degree of substitution by the following formula (1).
- DS 162 ⁇ AV ⁇ 0.01 / (60-42 ⁇ AV ⁇ 0.01) (1)
- DS is the total degree of acetyl substitution
- AV the degree of acetylation (%).
- the value of the degree of substitution obtained by conversion corresponds to 52.9 to 57.0 when applied to the total degree of substitution (average degree of substitution) of 2.27 to 2.56. There is usually some error between the NMR measurements.
- the degree of dispersion of the cellulose diacetate for retardation film of the present invention (molecular weight distribution Mw / Mn obtained by dividing weight average molecular weight Mw by number average molecular weight Mn) is more than 3.0 and 7.5 or less.
- the degree of dispersion Mw / Mn is 3.0 or less, the molecular sizes are too physically aligned, so that the elongation at break is low.
- the degree of dispersion Mw / Mn is greater than 7.5, there are many unreacted substances, and the elongation at break becomes low.
- the dispersity Mw / Mn is preferably 4.0 to 7.5, and particularly preferably 4.5 to 7.3.
- the cellulose diacetate for retardation film of the present invention may be a mixture of a plurality of cellulose diacetates having different average molecular weights and dispersities, as long as the average molecular weight and dispersity of the mixture are in the above ranges.
- the weight average molecular weight Mw of the cellulose diacetate for retardation film of the present invention is preferably from 205,000 to 235,000, more preferably from 210,000 to 233,000.
- the weight average molecular weight Mw is less than 205,000, the viscosity tends to be low and the elongation at break tends to be low. If the weight average molecular weight Mw exceeds 235,000, the filterability tends to deteriorate.
- the number average molecular weight (Mn), weight average molecular weight (Mw) and dispersity (Mw / Mn) of the cellulose ester can be determined by a known method using high performance liquid chromatography.
- the 6-position substitution degree of the cellulose diacetate for retardation film of the present invention is 0.65 to 0.85.
- the substitution degree at the 6-position is lower than 0.65, the reaction becomes non-uniform, filterability is poor, and elongation at break is low.
- the substitution degree at the 6-position is higher than 0.85, the hydrogen bond due to the hydroxyl group at the 6-position is reduced, so that the breaking elongation is lowered.
- the substitution degree at the 6-position is preferably 0.68 to 0.85, particularly preferably 0.70 to 0.85.
- the degree of acetyl substitution at the 2,3,6 position of the glucose ring of the cellulose diacetate of the present invention can be measured by the NMR method according to the method of Tezuka (Carbondr. Res. 273, 83 (1995)). That is, the free hydroxyl group of a cellulose diacetate sample is propionylated with propionic anhydride in pyridine. The obtained sample is dissolved in deuterated chloroform and the 13 C-NMR spectrum is measured.
- the carbon signal of the acetyl group appears in the order of 2, 3, 6 from the high magnetic field in the region of 169 ppm to 171 ppm, and the signal of the carbonyl carbon of the propionyl group appears in the same order in the region of 172 ppm to 174 ppm. From the abundance ratio of acetyl groups and propionyl groups at the corresponding positions, the degree of acetyl substitution at the 2, 3, and 6 positions of the glucose ring in the original cellulose diacetate can be determined. The degree of acetyl substitution can be analyzed by 1 H-NMR in addition to 13 C-NMR.
- the half width of the acetylation degree distribution of the cellulose diacetate for retardation film of the present invention is 1.0 to 2.3.
- the half-value width of the acetylation distribution is less than 1.0, and when the half-value width of the acetylation distribution is greater than 2.3, the elongation at break becomes low.
- the half-value width of the acetylation degree distribution is preferably 1.5 to 2.3, particularly preferably 1.9 to 2.3.
- the cellulose diacetate of the present invention is preferably cellulose diacetate having a uniform degree of acetyl total substitution.
- the half-value width of the maximum peak of the intermolecular substitution degree distribution curve or acetylation degree distribution curve of cellulose diacetate can be used as an index.
- the “half width” is the peak of the chart when the degree of acetylation (degree of substitution) is on the horizontal axis (x-axis) and the amount of acetylation (degree of substitution) is on the vertical axis (y-axis). This is the width of the chart at half the height of, and is an index representing the standard of variation in distribution.
- the half-value width of the substitution degree distribution can be determined by high performance liquid chromatography (HPLC) analysis.
- HPLC analysis was performed using a plurality of cellulose esters having different substitution degrees as standard samples with a predetermined measuring apparatus and measurement conditions, and a calibration curve prepared using the analytical values of these standard samples [abundance of cellulose ester And a curve showing the relationship between the degree of substitution (degree of acetylation), usually a quadratic curve (particularly a parabola)], the composition distribution half-value width of the cellulose ester of the present invention can be determined.
- the half value width of the substitution degree distribution is calculated by converting the horizontal axis (elution time) of the cellulose ester elution curve in HPLC (reverse phase HPLC) measured under the prescribed processing conditions into the substitution degree (0 to 3). Can be obtained.
- the method described in JP-A-2003-201301 can be used as a method for converting the elution time into the degree of substitution.
- the conversion formula conversion formula which calculates
- a calibration curve function [usually, the following quadratic expression (2)] is obtained by the least square method.
- DS aT 2 + bT + c (2) (Where DS is the degree of ester substitution, T is the elution time, and a, b and c are coefficients of the conversion equation)
- the substitution degree distribution half width is obtained as follows. That is, the base (A) on the low substitution degree side of the peak (E) and the base line (AB) in contact with the base (B) on the high substitution degree side are drawn, and the maximum peak (E ) To the horizontal axis. An intersection (C) between the perpendicular and the base line (AB) is determined, and an intermediate point (D) between the maximum peak (E) and the intersection (C) is obtained.
- a straight line parallel to the base line (AB) is drawn through the intermediate point (D) to obtain two intersection points (A ′, B ′) with the intermolecular substitution degree distribution curve.
- a perpendicular line is drawn from the two intersections (A ′, B ′) to the horizontal axis, and the width between the two intersections on the horizontal axis is defined as the half-value width of the maximum peak.
- the half-value width of the substitution degree distribution depends on the retention time (retention) of the cellulose ester molecular chain in the sample, depending on the degree of esterification of the hydroxyl group of each glucose chain constituting the polymer chain. (Also called time). Therefore, ideally, the holding time width indicates the width of the composition distribution (in units of substitution degree).
- a high-performance liquid chromatograph has a pipe portion (such as a guide column for protecting the column) that does not contribute to distribution. Therefore, depending on the configuration of the measurement apparatus, the width of the holding time that is not caused by the width of the composition distribution is often included as an error. As described above, this error is affected by the length and inner diameter of the column, the length from the column to the detector, the handling, and the like, and varies depending on the apparatus configuration.
- the substitution degree distribution half-value width of the cellulose ester can be usually obtained as a correction value Z based on a correction formula represented by the following formula (3).
- a more accurate substitution degree distribution half-value width can be obtained as the same (substantially the same) value even if the measurement apparatus (and measurement conditions) are different.
- Z (X 2 ⁇ Y 2 ) 1/2 (3)
- X is a substitution degree distribution half-value width (uncorrected value) obtained with a predetermined measuring apparatus and measurement conditions
- Y is a cellulose ester having a total substitution degree of 3 obtained with the same measuring apparatus and measurement conditions as X.
- the half-value width of the substitution degree distribution is shown.
- cellulose ester having a total degree of substitution of 3 means a cellulose ester in which all of the hydroxyl groups of cellulose are esterified (for example, cellulose triacetate having an acetylation degree of 62.5% in cellulose triacetate). Is equivalent to the non-deacylated fully substituted product obtained after aging and before aging, and does not actually (or ideally) have a half-value width of substitution degree distribution (ie substitution degree) It is a cellulose ester having a distribution half-value width of 0.
- the intermolecular substitution degree distribution curve of cellulose diacetate was obtained by obtaining the elution curve of cellulose diacetate in reverse phase HPLC, and the horizontal axis (elution time) of the elution curve was expressed as the total degree of acetyl substitution (0 to 3). It can be obtained by conversion.
- an acetylation degree distribution curve can also be obtained from an elution curve of cellulose diacetate in reversed-phase HPLC, and from this, the acetylation degree distribution half width can be obtained in the same manner as the substitution degree distribution half width.
- the viscosity average polymerization degree of the cellulose diacetate for retardation film of the present invention is 182 or more and 213 or less.
- the range is preferably 185 to 210, more preferably 187 to 206.
- the viscosity average polymerization degree is smaller than 182, the elongation at break becomes low.
- the viscosity average degree of polymerization exceeds 213, the filterability is deteriorated.
- the viscosity average degree of polymerization can be measured by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pp. 105-120, 1962).
- the 6% viscosity of the cellulose diacetate for retardation film of the present invention is, for example, from 120 mPa ⁇ s to 230 mPa ⁇ s, preferably from 125 mPa ⁇ s to 210 mPa ⁇ s, more preferably from 130 mPa ⁇ s to 200 mPa ⁇ s, particularly preferably 135 mPa ⁇ s. ⁇ From s to 160 mPa ⁇ s. If the 6% viscosity is high, the filterability may deteriorate, and it will be difficult to maintain a high molecular weight distribution.
- the cellulose diacetate of the present invention may be stretched to break.
- the viscometer coefficient was measured using the standard solution for viscometer calibration [made by Showa Oil Co., Ltd., trade name “JS-200” (based on JIS Z 8809)] in the same manner as described above, and the following formula ( 8).
- Viscometer coefficient ⁇ standard solution absolute viscosity (mPa ⁇ s) ⁇ solution density (0.827 g / cm 3 ) ⁇ / ⁇ standard solution density (g / cm 3 ) ⁇ standard solution flow-down seconds (s) ⁇ (8)
- the filtration degree (Kw) of the cellulose diacetate for retardation film of the present invention is preferably in the range of 50 to 200.
- the filtration degree (Kw) is less than 50, the viscosity may be too low, and the breaking elongation tends to be low, which is not preferable.
- the filtration degree (Kw) exceeds 200, the handleability tends to deteriorate. Kw can be improved by subjecting the mixed solution after the reaction to a fractionation process such as microfiltration using diatomaceous earth, for example.
- the cellulose diacetate for retardation film of the present invention includes, for example, (A) activation step (pretreatment step), (B) acetylation step, (C) acetylation reaction termination step, and (D) aging step (hydrolysis). (Decomposition step), (E) aging reaction termination step, and (F) fractionation step.
- cellulose As the raw material cellulose, various cellulose sources such as wood pulp (coniferous pulp, hardwood pulp), linter pulp (cotton linter pulp, etc.) can be used. These pulps usually contain foreign components such as hemicellulose. Therefore, in the present specification, the term “cellulose” is used in the sense that it also contains different components such as hemicellulose. As wood pulp, at least one selected from hardwood pulp and softwood pulp can be used, and hardwood pulp and softwood pulp may be used in combination. Also, linter pulp (such as refined cotton linter) and wood pulp may be used in combination. In the present invention, cellulose having a high degree of polymerization, such as linter pulp, particularly cotton linter pulp, can be used.
- cellulose it is preferable to use cellulose at least partially composed of linter pulp.
- Cellulose may usually contain some carboxyl groups in a state of being bound to cellulose molecules and / or hemicellulose molecules.
- cellulose is treated with an acetylated solvent (solvent for the acetylation step) to activate the cellulose.
- acetylation solvent acetic acid is usually used, but a solvent other than acetic acid (such as methylene chloride) or a mixed solvent of acetic acid and a solvent other than acetic acid (such as methylene chloride) can also be used.
- a solvent other than acetic acid such as methylene chloride
- a mixed solvent of acetic acid and a solvent other than acetic acid such as methylene chloride
- the time (treatment time) of the activation step of the present invention is, for example, at least 10 hr (600 minutes) or more, preferably 20 hr or more, more preferably 50 hr or more, and even more preferably about 60 hr.
- time of the activation process greatly exceeds 60 hours (for example, 100 hours), it becomes difficult to obtain a desired molecular weight (degree of polymerization), and production efficiency tends to decrease.
- the activation step is less than 10 hr, even if the next esterification step (acetylation step) is optimized, the molecular weight distribution is not increased and the elongation at break tends to decrease.
- the effect of reducing the polymerization degree (molecular weight) of the cellulose before an acetylation reaction is acquired by lengthening the time of pre-processing (activation process) (at least 10 hours).
- the time of pre-processing activation process
- cellulose having a low polymerization degree it is possible to shorten the acetylation time for making cellulose acetate the desired polymerization degree (viscosity).
- the degree of dispersion becomes narrower with the progress of uniform depolymerization in the acetylation reaction. Therefore, cellulose acetate having the desired degree of polymerization (viscosity) is prepared in a short acetylation reaction time using cellulose with a long pretreatment time as a raw material. By doing so, cellulose acetate having a wider degree of dispersion than the usual method can be obtained.
- the amount of the acetylated solvent used in the activation step is, for example, about 10 to 100 parts by weight, preferably about 15 to 60 parts by weight per 100 parts by weight of the raw material cellulose.
- the temperature in the activation step is, for example, in the range of 10 to 40 ° C., preferably 15 to 35 ° C.
- cellulose activated by the activation treatment cellulose acetate (particularly, cellulose triacetate) acetylated with an acetylating agent in the presence of an acetylation catalyst in an acetylation solvent can be produced.
- the activated cellulose subjected to the acetylation step may be a mixture obtained by blending pulps having different pretreatment conditions. By using the mixture, the dispersity of the finally obtained cellulose diacetate can be widened, and a film having a high elongation can be obtained.
- acetylation catalyst a strong acid, particularly sulfuric acid can be used.
- the amount of acetylation catalyst (especially sulfuric acid) used in the acetylation step is about 1 to 20 parts by weight with respect to 100 parts by weight of the raw material cellulose, including the amount of acetylation catalyst used in the activation step.
- the acetylation catalyst is sulfuric acid, it is about 7 to 15 parts by weight (for example, 7 to 14 parts by weight, preferably 8 to 14 parts by weight, more preferably 9 to 14 parts by weight).
- the acetylating agent may be an acetic acid halide such as acetic acid chloride, but acetic anhydride is usually used.
- the amount of the acetylating agent used in the acetylation step is, for example, about 1.1 to 4 equivalents, preferably 1.1 to 2 equivalents, more preferably about 1.3 to 1.8 equivalents based on the hydroxyl group of cellulose. is there.
- the amount of the acetylating agent used is, for example, 200 to 400 parts by weight, preferably 230 to 350 parts by weight per 100 parts by weight of the raw material cellulose.
- acetic acid, methylene chloride and the like are used as the acetylation solvent.
- Two or more solvents may be mixed and used.
- the amount of the acetylated solvent used is, for example, about 50 to 700 parts by weight, preferably 100 to 600 parts by weight, and more preferably about 200 to 500 parts by weight with respect to 100 parts by weight of cellulose.
- the amount of acetic acid used as an acetylation solvent in the acetylation step is 30 to 500 parts by weight, preferably 80 to 450 parts by weight, more preferably 100 parts by weight of cellulose.
- About 150 to 400 parts by weight for example, 250 to 380 parts by weight).
- the acetylation reaction can be carried out under conventional conditions, for example, a temperature of about 0 to 55 ° C., preferably 20 to 50 ° C., more preferably about 30 to 50 ° C.
- the acetylation reaction may be initially performed at a relatively low temperature [eg, 10 ° C. or lower (eg, 0 to 10 ° C.)].
- the reaction time at such a low temperature may be, for example, 30 minutes or more (for example, 40 minutes to 5 hours, preferably about 60 to 300 minutes) from the start of the acetylation reaction.
- the acetylation time total acetylation time
- the reaction is preferably carried out at a temperature of at least 30 to 50 ° C. for about 30 to 95 minutes.
- the acetylation time is important, and when the acetylation time is 95 minutes or less, the 6% viscosity, that is, the degree of polymerization of the obtained cellulose acetate does not decrease, which is particularly preferable.
- the completion (or end point) of the acetylation reaction is also the start (or start point) of the hydrolysis reaction or alcohol decomposition reaction.
- reaction terminator is added to the reaction system in order to deactivate the acetylating agent remaining in the reaction system.
- acetylating agent especially acid anhydride
- the reaction terminator need only be capable of deactivating the acetylating agent, and usually contains at least water.
- the reaction terminator may be composed of, for example, water and at least one selected from an acetylated solvent (such as acetic acid), an alcohol, and a neutralizing agent. More specifically, examples of the reaction terminator include, for example, water alone, a mixture of water and acetic acid, a mixture of water and alcohol, a mixture of water and neutralizing agent, and a mixture of water, acetic acid and neutralizing agent. Examples thereof include a mixture of water, acetic acid, alcohol and a neutralizing agent.
- the neutralizing agent examples include basic substances such as alkali metal compounds (for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; sodium hydrogen carbonate and the like).
- Alkaline earth metal carbonates such as alkaline earth metal hydroxides, magnesium carbonate and calcium carbonate; Alkaline earth metal carboxylates such as magnesium acetate and calcium acetate; Alkaline earth metal alkoxides such as magnesium ethoxide) Can be used.
- alkaline earth metal compounds particularly magnesium compounds such as magnesium acetate are preferred.
- the neutralizing agents can be used alone or in combination of two or more. A part of the acetylation catalyst (such as sulfuric acid) is neutralized by the neutralizing agent.
- the stop time of the acetylation reaction is preferably at least less than 10 minutes, and more preferably less than 5 minutes.
- the time for stopping the acetylation reaction is long, the degree of substitution at the 6-position tends to increase. In this case, intermolecular hydrogen bonding due to the hydroxyl group bonded to the glucose ring decreases, so the elongation at break tends to decrease, It becomes difficult to cause a phase difference.
- cellulose acetate (cellulose triacylate) is ripened [hydrolyzed (deacetylated)] using the residual acetylation catalyst (particularly sulfuric acid) as a ripening catalyst.
- the residual acetylation catalyst particularly sulfuric acid
- a solvent or the like acetic acid, methylene chloride, water, alcohol, etc.
- the neutralizing agent those exemplified in the step of stopping the acetylation reaction can be preferably used.
- cellulose triacetate is added in an amount of 0.56 to 8.44 parts by weight of an acetylation catalyst (aging catalyst; particularly sulfuric acid) with respect to 100 parts by weight of the cellulose triacetate in acetic acid.
- acetylation catalyst particularly sulfuric acid
- the hydrolysis is preferably performed in a temperature range of 40 to 90 ° C.
- the amount of water in the aging step can be, for example, 50 mol% or more and less than 65 mol% with respect to acetic acid.
- the presence of 50 mol% or more and less than 65 mol% of water with respect to acetic acid is preferable because cellulose diacetate having a high 6-acetyl substitution degree can be produced.
- the amount of water present is 65 mol% or more, the filtration degree of the cellulose diacetate obtained tends to decrease.
- sulfuric acid is preferred.
- the amount of the acetylation catalyst and the amount of water are based on the amount at the start of the ripening reaction in the case of a batch reaction, and are based on the amount charged in the case of a continuous reaction.
- the amount of acetic acid in the aging step is preferably 56 to 1125 parts by weight, more preferably 112 to 844 parts by weight, and still more preferably about 169 to 563 parts by weight with respect to 100 parts by weight of cellulose triacetate.
- the amount of acetic acid in the ripening step is preferably 100 to 2000 parts by weight, more preferably 200 to 1500 parts by weight, still more preferably 300 to 1000 parts by weight based on 100 parts by weight of cellulose used as a raw material in the acetylation reaction. About parts by weight.
- the amount of the acetylation catalyst is, for example, 0.56 to 8.44 parts by weight, more preferably 0.56 to 5.63 parts by weight with respect to 100 parts by weight of cellulose triacetate. Parts, more preferably 0.56 to 2.81 parts by weight, particularly preferably 1.69 to 2.81 parts by weight.
- the amount of cellulose used as a raw material in the acetylation reaction is preferably 1 to 15 parts by weight, more preferably 1 to 10 parts by weight, still more preferably 1 to 5 parts by weight, particularly preferably 3 to 5 parts by weight.
- the amount of the acetylation catalyst (aging catalyst) When the amount of the acetylation catalyst (aging catalyst) is small, the hydrolysis time becomes too long, which may cause a decrease in the molecular weight of cellulose acetate.
- the amount of the acetylation catalyst (ripening catalyst) is too large, the degree of change in the depolymerization rate with respect to the ripening temperature increases, and the depolymerization rate increases even if the ripening temperature is somewhat low, and the cellulose diacetate has a large molecular weight. Is difficult to obtain.
- the above reaction stopper is added to the reaction solution after completion of acetylation, and a neutralizing agent is further added to form an acetylation catalyst.
- a part of the acetylation catalyst may be neutralized, and the remaining acetylation catalyst may be used as a hydrolysis catalyst in the aging step, and a predetermined amount of water may be added to perform the aging step.
- the amount of the acetylation catalyst, acetic acid and water with respect to 100 parts by weight of the above cellulose triacetate it is assumed that the raw material cellulose is all converted into fully trisubstituted cellulose triacetate at the stage where the acetylation step is completed. It is a written numerical value.
- the amount of acetylation catalyst, acetic acid and water per 100 parts by weight of cellulose triacetate is preferably calculated based on the raw material cellulose at the start of the acetylation process. It is a numerical value (parts by weight) obtained by multiplying the amount of acetylation catalyst, acetic acid and water per 100 parts by weight by 1.777.
- the amount of acetylation catalyst used for aging is 1 gram of acetylation catalyst after subtracting the chemical equivalent of the acetylation catalyst added to the reaction system from the chemical equivalent of the neutralizing agent added to the reaction system.
- a value obtained by multiplying the equivalent value by 1.777 as described above is the amount (weight basis) of the acetylation catalyst based on the raw material cellulose.
- the amount of water multiplied by 1.777 to the amount of water added to the reaction system up to the aging step such as water added to the reaction system at the end of the acetylation step, water added at the start of ripening, etc.
- the numerical value is the amount of water (weight basis) based on the raw material cellulose.
- acetic acid add the amount of acetic acid generated by hydrolysis of acetic anhydride to the amount of acetic acid added to the reaction system in the pretreatment (activation step), acetylation step, and aging step, A numerical value obtained by multiplying 1.777 is the amount of acetic acid (weight basis) based on the raw material cellulose.
- the aging temperature is, for example, 40 to 90 ° C., preferably 50 to 90 ° C., more preferably 60 to 90 ° C. (for example, 65 to 90 ° C.). If the aging temperature is too high, although depending on the amount of the acetylation catalyst, the depolymerization rate tends to be high, and the molecular weight of cellulose acetate tends to decrease. On the other hand, when the ripening temperature is too low, the reaction rate of the hydrolysis reaction tends to decrease and the productivity tends to be hindered.
- the aging reaction After producing the predetermined cellulose diacetate, the aging reaction is stopped. That is, after the aging (hydrolysis reaction, deacetylation), the neutralizing agent (preferably the alkaline earth metal compound, particularly a calcium compound such as calcium hydroxide) may be added as necessary. Even if the reaction product (dope containing cellulose diacetate) is put into a precipitation solvent (water, aqueous acetic acid solution, etc.) to separate the produced cellulose diacetate, the free metal component or sulfuric acid component is removed by washing with water. Good. In addition, the said neutralizing agent can also be used in the case of washing with water.
- the neutralizing agent preferably the alkaline earth metal compound, particularly a calcium compound such as calcium hydroxide
- the cellulose diacetate obtained in the above step may be separated and purified.
- the half-value width of the acetylation degree distribution can be made narrower by fractionation.
- the separation method the method described in JP-A-09-77801 can be used. In principle, it is dissolved in a good solvent of cellulose acetate having a high acetylation degree (for example, methylene chloride), and a gel-like precipitate is obtained by centrifugation. This is a good solvent for cellulose acetate having a low acetylation degree (for example, methyl alcohol). )
- cellulose acetate is subjected to precipitation fractionation or dissolution fractionation in a solvent system in which each of the high acetylation degree component and the low acetylation degree component is selective.
- the solvent having high selective solubility for the high acetylation component include methylene chloride such as dichloromethane and chloroform.
- the solvent having high selective solubility for the low acetylation component include methanol, acetone / methanol (2/8, weight ratio), and the like.
- Cellulose diacetate can be dissolved in a suitable solvent such as methylene chloride or methanol to prepare a dope for film formation.
- the film can be peeled from the substrate by casting and drying the dope on a substrate such as a glass plate at a temperature of 25 ° C. (room temperature), for example, using a bar coater. Furthermore, you may dry the peeled film as needed.
- a film with a uniform surface is obtained by leveling after casting.
- a stretched film is obtained by stretching the film. Stretching can be performed by a known method.
- the film can contain a plasticizer as long as the effects of the present invention are not hindered.
- the plasticizer is not particularly limited, but polyvalent carboxylic acid ester plasticizer, glycolate plasticizer, phthalate ester plasticizer, fatty acid ester plasticizer and polyhydric alcohol ester plasticizer, polyester plasticizer, acrylic System plasticizers and the like.
- the retardation in the plane of the film represents R e, a retardation in the thickness direction R th.
- R e the in-plane longitudinal and lateral refractive index difference at a wavelength of 632.8 nm of the film is obtained.
- the in-plane retardation (R e ) is a value obtained by multiplying the obtained refractive index difference by the film thickness, and is obtained by the following formula (10).
- R e (n x ⁇ n y ) ⁇ d (10) Where nx is the refractive index in the transverse direction; ny is the refractive index in the longitudinal direction; and d is the thickness (nm) of the film.
- a smaller in-plane retardation (R e ) means higher optical isotropy in the in-plane direction (no optical anisotropy).
- the in-plane retardation (R e ) is preferably 0 to 300 nm, and the simplest method for adjusting the in-plane retardation (R e ) that can be freely set in accordance with the purpose is within this range. That is.
- the retardation (R th ) in the thickness direction of the film is a value obtained by calculating the birefringence in the thickness direction at a wavelength of 632.8 nm of the film and multiplying this by the film thickness, and is obtained by the following equation (11). It is done.
- R th ⁇ (n x + ny ) / 2 ⁇ n z ⁇ ⁇ d (11)
- nx is the refractive index in the transverse direction
- ny is the refractive index in the longitudinal direction
- nz is the refractive index in the thickness direction
- d is the thickness (nm) of the film.
- the retardation in the thickness direction (R th ) is defined by the following equation (12) following Patent Document 8, for example.
- the definition is different from R th in the following formula (12), and a notation method in which the sign is reversed from R th in the present application may be adopted.
- the following equation (12) is defined as described above.
- nx refractive index in the width direction of the film material
- ny refractive index in the longitudinal direction of the film material
- nz refractive index in the thickness direction of the film material
- d thickness of the film material (nm)
- the retardation in the thickness direction (R th ) is positive, and its absolute value is preferably 200 to 350 nm.
- its absolute value is preferably 200 to 350 nm.
- it is 200 nm or more and 350 nm or less, preferably 220 nm or more and 300 nm or less, more preferably 240 nm or more and 280 nm or less.
- a 150 nm R e is from 80nm to adjust the R e by stretching such film in the longitudinal direction, when R th was obtained 350nm plate from 200nm is lambda / 4 phase plate and the viewing A single angle expansion film can be obtained.
- the elongation at break is the elongation (%) at the time of rupture when the produced film is pulled, and is preferably 20% or more, for example. If it is less than 20%, the film strength is too low and it becomes difficult to use it as a retardation film.
- Example 1 A hardwood prehydrolyzed kraft pulp having an ⁇ -cellulose content of 98.4 wt% was pulverized into a cotton shape with a disc refiner. After 26.8 parts by weight of acetic acid was sprayed on 100 parts by weight of pulverized pulp (water content 8%) and stirred well, the mixture was allowed to stand for 60 hours and activated as a pretreatment (activation step). The activated pulp is added to a mixture consisting of 323 parts by weight acetic acid, 245 parts by weight acetic anhydride, 13.1 parts by weight sulfuric acid and adjusted to a maximum temperature of 5 ° C to 40 ° C in 40 minutes, Vinegared for 90 minutes.
- a neutralizing agent (24% magnesium acetate aqueous solution) was added over 3 minutes so that the amount of sulfuric acid (aged sulfuric acid amount) was adjusted to 2.5 parts by weight. Furthermore, after raising the temperature of the reaction bath to 75 ° C., water was added to make the reaction bath moisture (ripening moisture) a concentration of 52 mol%. The aging water concentration was expressed in mol% by multiplying the ratio of the reaction bath water to acetic acid expressed in molar ratio by 100. Thereafter, aging was carried out at 85 ° C. for 100 minutes, and aging was stopped by neutralizing sulfuric acid with magnesium acetate to obtain a reaction mixture containing cellulose diacetate. A dilute aqueous acetic acid solution was added to the obtained reaction mixture to separate cellulose diacetate, and then washed with water, dried, and stabilized with calcium hydroxide to obtain cellulose diacetate.
- Table 1 shows the conditions for preparing cellulose acetate.
- Cellulose diacetate was obtained in the same manner as in Example 1 under the conditions shown in Table 1.
- Example 7 Purification of cellulose diacetate 100 parts by weight of the mixture containing cellulose diacetate obtained in Example 2 was dispersed in 1,000 parts by weight of methylene chloride at room temperature (about 22 ° C.), and 8,000 rpm for 30 minutes at 15 ° C. Centrifugation was performed under the conditions described above to obtain a gel-like sediment. The gel-like sediment was dispersed in 2,000 parts by weight of methanol and centrifuged under the conditions described above to obtain a sediment. This washing with methanol was performed twice. Furthermore, it washed twice using 50 weight% of acetone aqueous solution instead of methanol. Thereafter, it was further washed twice with 1,000 parts by weight of water and dried under reduced pressure at 40 ° C. until a constant weight was obtained, to obtain 61 parts by weight of purified cellulose diacetate.
- Example 10 A 1: 1 ratio by weight mixture of cellulose diacetates with different viscosities obtained in Comparative Example 2 and Example 4 was prepared.
- Comparative Example 10 A mixture of cellulose diacetates having different viscosities obtained in Comparative Example 1 and Comparative Example 4 was prepared at a weight ratio of 1: 1.
- Blend of pulps with different pretreatment conditions (Pretreatment condition 1) Hardwood prehydrolyzed kraft pulp having an ⁇ -cellulose content of 98.4% (by weight) was pulverized into cotton with a disc refiner. After 26.8 parts by weight of acetic acid was sprayed on 100 parts by weight of pulverized pulp (water content 8%), the mixture was well stirred, and then allowed to stand for 60 hours for pretreatment. (Pretreatment condition 2) A hardwood prehydrolyzed kraft pulp having an ⁇ -cellulose content of 98.4% (by weight) was pulverized into a cotton shape with a disc refiner.
- acetic acid 15.9 parts by weight of acetic acid is sprayed on 100 parts by weight of pulverized pulp (water content 8%), and after stirring well, 48.9 parts by weight of a sulfuric acid / acetic acid mixture (sulfuric acid concentration 3% by weight) is sprayed. Stir for 180 minutes.
- the pretreated pulp activated in the pretreatment condition 1 and the pretreatment condition 2 was mixed at 1: 1 (weight ratio). This activated pulp mixture was subjected to acetylation and aging reaction in the same manner as in Example 1 to prepare cellulose diacetate.
- ⁇ 6% viscosity> 3.00 g of a dried sample of cellulose diacetate obtained in Examples and Comparative Examples and 39.90 g of 95% acetone aqueous solution were placed in an Erlenmeyer flask, sealed, and stirred for about 1.5 hours. Then, it was completely dissolved by shaking for about 1 hour with a rotary shaker. The obtained 6 wt / vol% solution was transferred to a predetermined Ostwald viscometer mark and temperature-controlled at 25 ⁇ 1 ° C. for about 15 minutes. The flow-down time between the time gauges was measured, and the 6% viscosity was calculated from the above equation (7). 6% viscosity (mPa ⁇ s) flowing time (s) ⁇ viscosity coefficient (7)
- ⁇ 6-position substitution degree> The free hydroxyl group of cellulose diacetate obtained in Examples and Comparative Examples was propionylated with propionic anhydride in pyridine, and the resulting sample was dissolved in deuterated chloroform, and the 13 C-NMR spectrum was measured. From the abundance ratio of the acetyl group and propionyl group at, the degree of acetyl substitution at the 2, 3, and 6 positions of the glucose ring in the original cellulose diacetate was determined.
- Kw degree of filtration
- the predetermined filter cloth is obtained by sandwiching a single-sided flannel (product number 9A) manufactured by Yamanishi Denko Co., Ltd. between two sheets (product number 6570) manufactured by Toyobo Co., Ltd.
- the film was then supported on a stainless steel frame and dried for 20 minutes with a hot air dryer at 100 ° C. to obtain a film (unstretched film).
- the film thickness of this unstretched film was 80 ⁇ m.
- the breaking elongation and retardation of the obtained film were measured as follows.
- R th is large, the elongation at break is large film was obtained.
- Comparative Examples 1 to 3 the viscosity was low and the elongation at break was low.
- Comparative Example 4 unreacted cellulose increased and Kw (filterability) was poor.
- unreacted cellulose was not uniformly dissolved in the solvent for film preparation dope, and the break elongation was also lowered.
- Comparative Example 5 the reaction was non-uniform because there was too much water in the aging bath and the system was on the side where cellulose diacetate was likely to precipitate. Moreover, Kw was bad and the elongation at break was low.
- Comparative Example 6 hydrogen bonds due to the 6-position hydroxyl group were reduced, and the elongation at break was low.
- Comparative Example 7 the half width of acetylation distribution was wide and the elongation at break was low.
- Comparative Example 8 was a blend of cellulose acetates having different degrees of substitution, but the acetylation degree distribution had a wide half-value width and a low elongation at break.
- Comparative Example 10 was a blend of cellulose acetates having different viscosities (60 mPa ⁇ s and 240 mPa ⁇ s), but the elongation at break was low due to unreacted substances.
- the cellulose diacetate for retardation film of the present invention it is possible to achieve both stretchability and retardation development property when stretched, filterability, and a small amount of optical foreign matter such as bright spot foreign matter, and is thin and lightweight. It is possible to provide a protective film for a polarizing plate, which is used in a display device such as a liquid crystal display device such as a notebook personal computer, in response to the demand for thin film and high performance.
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Abstract
Description
本発明の位相差フィルム用セルロースジアセテートは、好ましくは6%粘度が120~230mPa・sであり、また好ましくは、重量平均分子量Mwが205,000以上235,000以下である。
本発明の位相差フィルム用セルロースジアセテートは、アセチル基総置換度(平均置換度)が2.27~2.56、すなわち、酢化度が52.9~57.0である。本発明では、位相差フィルムのRthを、例えば、200~400nmとできる位相差フィルム用セルロースジアセテートが提供される。セルロースジアセテートの総置換度が2.27、すなわち、酢化度が52.9を下回る場合には、面方向のリターデーション(Re)が高くなりすぎる。セルロースジアセテートの総置換度が2.56、すなわち、酢化度が57.0を上回る場合には、厚み方向のリターデーション(Rth)を十分に高くすることができない。
DS=162×AV×0.01/(60-42×AV×0.01) (1)
上記式において、DSはアセチル総置換度であり、AVは酢化度(%)である。なお、換算して得られる置換度の値は、上記の総置換度(平均置換度)の2.27から2.56に当てはめた場合には52.9から57.0に相当する。前記のNMR測定値との間に若干の誤差が生じることが普通である。
本発明の位相差フィルム用セルロースジアセテートの分散度(重量平均分子量Mwを数平均分子量Mnで除した分子量分布Mw/Mn)は3.0超7.5以下である。分散度Mw/Mnが3.0以下の場合には、分子の大きさが物理的に揃いすぎ、このため、破断伸度が低くなる。分散度Mw/Mnが7.5より大きい場合には未反応物が多く存在し、このため、破断伸度が低くなる。さらに、分散度Mw/Mnは、4.0~7.5が好ましく、4.5~7.3が特に好ましい。本発明の位相差フィルム用セルロースジアセテートは、異なる平均分子量と分散度を有するセルロースジアセテートを複数混合したものでもよく、混合物の平均分子量と分散度が前記範囲に有ればよい。
本発明の位相差フィルム用セルロースジアセテートの6位置換度は0.65~0.85である。6位置換度が0.65より低い場合には、反応が不均一となり、濾過性が悪く、破断伸度が低くなる。6位置換度が0.85より高い場合には、6位水酸基による水素結合が少なくなるため、破断伸度が低くなる。さらに、6位置換度は、0.68~0.85が好ましく、0.70~0.85が特に好ましい。
本発明の位相差フィルム用セルロースジアセテートの酢化度分布半価幅は1.0~2.3である。酢化度分布半価幅が1.0より小さい場合、また、酢化度分布半価幅が2.3より大きい場合には、破断伸度が低くなる。さらに、酢化度分布半価幅は1.5~2.3が好ましく、1.9~2.3が特に好ましい。
DS=aT2+bT+c (2)
(式中、DSはエステル置換度であり、Tは溶出時間であり、a、bおよびcは変換式の
係数である)
Z=(X2-Y2)1/2 (3)
(式中、Xは所定の測定装置および測定条件で求めた置換度分布半価幅(未補正値)、Yは前記Xと同じ測定装置および測定条件で求めた総置換度3のセルロースエステルの置換度分布半価幅を示す。)
本発明の位相差フィルム用セルロースジアセテートの粘度平均重合度は182以上213以下である。好ましくは185~210、さらに好ましくは187~206の範囲が好ましい。粘度平均重合度が182より小さいと、破断伸度が低くなる。粘度平均重合度が213を超えると、濾過性が悪くなる。
ηrel=t/t0 (4)
[η]=(lnηrel)/c (5)
DP=[η]/(6×10-4) (6)
(式中、tは溶液の通過時間(秒)、t0は溶媒の通過時間(秒)、cは溶液のセルロースジアセテート濃度(g/L)、ηrelは相対粘度、[η]は極限粘度、DPは平均重合度を示す)
本発明の位相差フィルム用セルロースジアセテートの6%粘度は、例えば120mPa・sから230mPa・s、好ましくは125mPa・sから210mPa・s、より好ましくは130mPa・sから200mPa・s、特に好ましくは135mPa・sから160mPa・sである。6%粘度が高いと濾過性が悪くなる場合があり、また分子量分布を高く維持することが難しくなる。また6%粘度が低い場合には、本発明のセルロースジアセテートを延伸した場合に破断することがある。なお、6%粘度の異なるセルロースジアセテートをブレンドして、上記範囲の6%粘度を有するセルロースジアセテートとしてもよい。
三角フラスコに乾燥試料3.00g、95%アセトン水溶液を39.90g入れ、密栓して約1.5時間攪拌する。その後、回転振盪機で約1時間振盪して完溶させる。得られた6wt/vol%の溶液を所定のオストワルド粘度計の標線まで移し、25±1℃で約15分間整温する。計時標線間の流下時間を測定し、次式(7)により6%粘度を算出する。
6%粘度(mPa・s)=流下時間(s)×粘度計係数 (7)
粘度計係数
={標準液絶対粘度(mPa・s)×溶液の密度(0.827g/cm3)}/{標準液の密度(g/cm3)×標準液の流下秒数(s)} (8)
濾過度(Kw)は、溶液の濾過度の高さを表す指標であり、濾過定数をkとするとき、Kw=k×10000(すなわち、kの一万倍)で表される。そして、濾過定数kは、時間t1経過時における濾過量P1と、時間t2(≠t1)経過時における濾過量P2とから、下記式(9)により求めることができる。
k={2-(P2/P1)}/2(P1+P2) (9)
本発明の位相差フィルム用セルロースジアセテートは、例えば、(A)活性化工程(前処理工程)、(B)アセチル化工程、(C)アセチル化反応の停止工程、(D)熟成工程(加水分解工程)、(E)熟成反応の停止工程、及び(F)分別工程により製造できる。
原料セルロースとしては、木材パルプ(針葉樹パルプ、広葉樹パルプ)、リンターパルプ(コットンリンターパルプなど)などの種々のセルロース源を用いることができる。これらのパルプは、通常、ヘミセルロースなどの異成分を含有している。従って、本明細書において、用語「セルロース」は、ヘミセルロースなどの異成分も含有する意味で用いる。木材パルプとしては、広葉樹パルプ及び針葉樹パルプから選択された少なくとも一種が使用でき、広葉樹パルプと針葉樹パルプとを併用してもよい。また、リンターパルプ(精製綿リンターなど)と木材パルプとを併用してもよい。本発明では重合度の高いセルロース、例えば、リンターパルプ、特にコットンリンターパルプが使用でき、セルロースとしては、少なくとも一部はリンターパルプで構成されたセルロースを使用するのが好ましい。セルロースの結晶化度の指標となるα-セルロース含有量(重量基準)は、98%以上(例えば、98.5~100%、好ましくは99~100%、さらに好ましくは99.5~100%程度)である。セルロースは、通常、セルロース分子及び/又はヘミセルロース分子に結合した状態などで多少のカルボキシル基を含有しているものであってもよい。
活性化工程(又は前処理工程)では、セルロースをアセチル化溶媒(アセチル化工程の溶媒)で処理し、セルロースを活性化させる。アセチル化溶媒としては、通常酢酸が用いられるが、酢酸以外の溶媒(塩化メチレンなど)を用いたり、酢酸と酢酸以外の溶媒(塩化メチレンなど)の混合溶媒を用いることもできる。通常、原料セルロースはシート状の形態で供給される場合が多いため、セルロースを乾式で解砕処理し、活性化処理(又は前処理)する。
前記活性化処理により活性化されたセルロースを用いて、アセチル化溶媒中、アセチル化触媒の存在下、アセチル化剤でアセチル化されたセルロースアセテート(特に、セルローストリアセテート)を生成することができる。なお、アセチル化工程に付す活性化されたセルロースは、前処理条件の異なるパルプをブレンドした混合物であってもよい。混合物を用いることにより、最終的に得られるセルロースジアセテートの分散度を広くすることができ、伸度の高いフィルムを得ることができる。
アセチル化反応の終了後、反応系に残存するアセチル化剤を失活(クエンチ)させるため、反応系に反応停止剤を添加する。この操作により、少なくとも前記アセチル化剤(特に酸無水物)が失活させられる。前記反応停止剤は、アセチル化剤を失活可能であればよく、通常、少なくとも水を含んでいる場合が多い。
前記アセチル化反応を停止した後、生成したセルロースアセテート[セルローストリアセテート;アセチル総置換度が2.6以上(2.6~3.0)のセルロースアセテート]を酢酸中で熟成[加水分解(脱アセチル化)]することにより、アセチル総置換度及び置換度分布を調整したセルロースジアセテートを得ることができる。この反応において、アセチル化に利用したアセチル化触媒(特に硫酸)の一部を中和し、残存するアセチル化触媒(特に硫酸)を熟成触媒として利用してもよく、中和することなく残存した全てのアセチル化触媒(特に硫酸)を熟成触媒として利用してもよい。好ましい態様では、残存アセチル化触媒(特に硫酸)を熟成触媒として利用してセルロースアセテート(セルローストリアシレート)を熟成[加水分解(脱アセチル化)]する。なお、熟成において、必要に応じて新たに溶媒等(酢酸、塩化メチレン、水、アルコールなど)を添加してもよい。中和剤としては、アセチル化反応の停止工程で例示のものが好ましく使用できる。
所定のセルロースジアセテートを生成させた後、熟成反応を停止させる。すなわち、前記熟成(加水分解反応、脱アセチル化)の後、必要により前記中和剤(好ましくは前記アルカリ土類金属化合物、特に、水酸化カルシウム等のカルシウム化合物)を添加してもよい。反応生成物(セルロースジアセテートを含むドープ)を析出溶媒(水、酢酸水溶液など)に投入して生成したセルロースジアセテートを分離し、水洗などにより遊離の金属成分や硫酸成分などを除去してもよい。なお、水洗の際に前記中和剤を使用することもできる。このような方法により、セルロースジアセテートの重合度の低下を抑制しつつ、不溶物又は低溶解性成分(未反応セルロース、低アセチル化セルロースなど)の生成を低減できる。
上記の工程で得られたセルロースジアセテートは、分別して精製してもよい。分別により酢化度分布半価幅をより狭いものとすることができる。分別の方法については、特開平09-77801号公報に記載されている方法が利用できる。原理としては高酢化度のセルロースアセテートの良溶媒(例えば塩化メチレン)に溶解して、遠心分離でゲル状の沈降物を得る、これを低酢化度のセルロースアセテートの良溶媒(例えばメチルアルコール)にて洗浄して、セルロースジアセテート成分のみを精製する。遠心分離と共に、又は遠心分離に代えて、珪藻土等を用いて精密濾過をして精製してもよい。
セルロースジアセテートを、塩化メチレン、メタノール等の適当な溶媒に溶解し、フィルム作成用のドープを調製できる。このドープをガラス板等の基板上に、例えばバーコーターを用いて、例えば温度25℃(室温)で流延、乾燥することにより、基板からフィルムを剥離することができる。さらに、必要に応じて剥離したフィルムを乾燥してもよい。なお、流延後、レベリングすることで表面の均一なフィルム(未延伸フィルム)が得られる。さらに、このフィルムを延伸することにより、延伸フィルムが得られる。延伸は公知の方法で行うことができる。
フィルムの面内のリターデーションをRe、厚さ方向のリターデーションをRthで表す。面内のリターデーション(Re)の測定では、フィルムの波長632.8nmにおける面内の縦横の屈折率差を求める。面内のリターデーション(Re)は、得られた屈折率差にフィルム膜厚さを乗じた値であり、下記の式(10)で求められる。
Re=(nx-ny)×d (10)
式中、nxは、横方向の屈折率であり;nyは、縦方向の屈折率であり;そして、dは、フィルムの厚さ(nm)である。面内のリターデーション(Re)が小さいほど、面内方向の光学的等方性が高い(光学異方性がない)ことを意味する。面内のリターデーション(Re)は、0乃至300nmであることが好ましく、この範囲内で目的に応じて自由に設定できる最も簡便な面内のリターデーション(Re)の調整方法は延伸することである。
Rth={(nx+ny)/2-nz}× d (11)
式中、nxは、横方向の屈折率;nyは、縦方向の屈折率;nzは、厚さ方向の屈折率であり;そして、dは、フィルムの厚さ(nm)である。
Rth={(nx+ny)/2-nz}× d (12)
nx: フィルム材料の幅方向の屈折率
ny: フィルム材料の長手方向の屈折率
nz: フィルム材料の厚さ方向の屈折率
d: フィルム材料の厚さ(nm)
破断伸度は、上記作成したフィルムを引っ張った場合の破断するときの伸度(%)であり、例えば20%以上が好ましい。20%より小さい場合には、フィルム強度が低すぎて、位相差用フィルムとして使用しにくくなる。
αセルロース含量98.4wt%の広葉樹前加水分解クラフトパルプをディスクリファイナーで綿状に解砕した。100重量部の解砕パルプ(含水率8%)に26.8重量部の酢酸を噴霧し、良くかき混ぜた後、前処理として60時間静置し活性化した(活性化工程)。活性化したパルプを、323重量部の酢酸、245重量部の無水酢酸、13.1重量部の硫酸からなる混合物に加え、40分を要して5℃から40℃の最高温度に調整し、90分間酢化した。中和剤(24%酢酸マグネシウム水溶液)を、硫酸量(熟成硫酸量)が2.5重量部に調整されるように3分間かけて添加した。さらに、反応浴を75℃に昇温した後、水を添加し、反応浴水分(熟成水分)を52mol%濃度とした。なお、熟成水分濃度は、反応浴水分の酢酸に対する割合をモル比で表わしたものに100を乗じてmol%で示した。その後、85℃で100分間熟成を行ない、酢酸マグネシウムで硫酸を中和することで熟成を停止し、セルロースジアセテートを含む反応混合物を得た。得られた反応混合物に希酢酸水溶液を加え、セルロースジアセテートを分離した後、水洗・乾燥・水酸化カルシウムによる安定化をしてセルロースジアセテートを得た。
表1に、セルロースアセテートの調製条件を示す。表1に示す条件で、実施例1と同様にしてセルロースジアセテートを得た。
セルロースジアセテートの精製
実施例2で得られたセルロースジアセテートを含む混合物100重量部を1,000重量部の塩化メチレンに室温(約22℃)で分散し、15℃で8,000rpm-30分の条件で遠心分離を行い、ゲル状の沈降物を得た。ゲル状の沈降物は、2,000重量部のメタノールに分散し、前述の条件で遠心分離し、沈降物を得た。このメタノールによる洗浄を2回行なった。さらに、メタノールに代えて50重量%のアセトン水溶液を用いて、2回洗浄を行なった。その後さらに、1,000重量部の水で2回洗浄を行ない、40℃で恒量となるまで減圧乾燥し、61重量部の精製セルロースジアセテートを得た。
比較例2と実施例4で得られた粘度の異なるセルロースジアセテートの、重量比1:1の混合物を調製した。
表1に示すように、熟成時間のみを130分と70分とに異ならせて合成した2種類のセルロースアセテートの、重量比1:1の混合物を調製した。これらの2種類のセルロースアセテートは、酢化度がそれぞれ52.8%(熟成時間130分)、57.8%(熟成時間70分)であった。
比較例1と比較例4で得られた粘度の異なるセルロースジアセテートの、重量比1:1の混合物を調製した。
前処理条件の異なるパルプのブレンド
(前処理条件1)αセルロース含量98.4%(重量基準)の広葉樹前加水分解クラフトパルプをディスクリファイナーで綿状に解砕した。100重量部の解砕パルプ(含水率8%)に26.8重量部の酢酸を噴霧し、良くかき混ぜた後、60時間静置し前処理とした。
(前処理条件2)αセルロース含量98.4%(重量基準)の広葉樹前加水分解クラフトパルプをディスクリファイナーで綿状に解砕した。100重量部の解砕パルプ(含水率8%)に15.9重量部の酢酸を噴霧し、良くかき混ぜた後、48.9重量部の硫酸/酢酸混合物(硫酸濃度3重量%)を噴霧し、180分かき混ぜた。
上記前処理条件1及び前処理条件2でそれぞれ活性化した前処理済パルプを1:1(重量比)で混合した。この活性化パルプの混合物を、実施例1と同様の方法で酢化・熟成反応させ、セルロースジアセテートを調製した。
実施例、比較例で得られたセルロースジアセテートの酢化度を、ASTM-D-817-91(セルロースアセテートなどの試験方法)における酢化度の測定方法により求めた。本願の酢化度測定で用いた高速液体クロマトグラフィー分析条件を以下に示す。
高速液体クロマトグラフィー条件:
溶離液:アセトン/水/メタノール(4/3/1、容量比)から15分間を要して、アセトンへグラジェント
カラム:ハミルトン社製 PRP-1(4.1×150mm)
温度:35℃
流速:0.8mL/min
試料溶液:0.2% アセトン溶液
注入量:10μL
検出器:VAREX社 MK111(エバポレイティブ・チューブ温度105℃,窒素流量2.4L/min)
実施例、比較例で得られたセルロースジアセテートの乾燥試料3.00gと、95%アセトン水溶液39.90gを三角フラスコに入れ、密栓して約1.5時間攪拌した。その後、回転振盪機で約1時間振盪して完溶させた。得られた6wt/vol%の溶液を所定のオストワルド粘度計の標線まで移し、25±1℃で約15分間整温した。計時標線間の流下時間を測定し、前記の式(7)により6%粘度を算出した。
6%粘度(mPa・s)=流下時間(s)×粘度計係数 (7)
粘度計係数
={標準液絶対粘度(mPa・s)×溶液の密度(0.827g/cm3)}/{標準液の密度(g/cm3)×標準液の流下秒数(s)} (8)
実施例、比較例で得られたセルロースジアセテートを、メチレンクロライド/メタノール=9/1(重量比)の混合溶液に溶解し、所定の濃度c(2.00g/L)の溶液を調製し、この溶液をオストワルド粘度計に注入し、25℃で粘度計の刻線間を溶液が通過する時間t(秒)を測定した。一方、前記混合溶媒単独についても上記と同様にして通過時間t0(秒)を測定し、前記の式(4)~(6)に従って、粘度平均重合度を算出した。
ηrel=t/t0 (4)
[η]=(lnηrel)/c (5)
DP=[η]/(6×10-4) (6)
(式中、tは溶液の通過時間(秒)、t0は溶媒の通過時間(秒)、cは溶液のセルロースジアセテート濃度(g/L)、ηrelは相対粘度、[η]は極限粘度、DPは平均重合度である)
実施例、比較例で得られたセルロースジアセテートの遊離水酸基をピリジン中で無水プロピオン酸によりプロピオニル化し、得られた試料を重クロロホルムに溶解したものの13C-NMRスペクトルを測定し、それぞれ対応する位置でのアセチル基とプロピオニル基の存在比から、元のセルロースジアセテートにおけるグルコース環の2,3,6位の各アセチル置換度を求めた。
実施例、比較例で得られたセルロースジアセテートの酢化度分布半価幅(%)は、上記酢化度分析において得られた溶出曲線の半価幅から求めた。すなわち、あらかじめ平均酢化度50%、52%、55%、60%程度の酢酸セルロースを用い溶出ピーク時間対平均酢化度の関係について、時間に関する2次関数で検量線を作成した。試料の溶出曲線から、ピーク高さに対して1/2の高さを与える2点の溶出時間をもとめ、検量線から2点の溶出時間に相当する酢化度を算出した。得られた酢化度の差の絶対値を酢化度分布半価幅とした。
次の条件でGPC分析を行い、Mw及びMnを測定した。これらの値から、Mw/Mnを決定した。
溶媒: アセトン
カラム: GMHxl(東ソー)2本、同ガードカラム
流速: 0.8mL/min
温度: 29℃
試料濃度:0.25%(wt/vol)
注入量: 100μL
検出: RI
標準物質:PMMA(分子量1890、6820、27600、79500、207400、518900、772000)
Kw(濾過度)は以下の方法で測定した。
セルロースジアセテートを20重量%になるように95容量%アセトン水溶液に溶解した溶液を30℃で所定の濾布により濾過した場合において、0.196MPaの圧力下で濾過量を測定し、下記式(13)から濾過度(Kw)を算出した。所定の濾布とは、東洋紡績(株)製(品番6570)2枚の間に、山西染工(株)製の片面ネル(品番9号A)を挟んだものである。
Kw=(2-P2/P1)・10000/(P1+P2) (13)
P1:濾過開始から20分間の濾過量(g)
P2:濾過開始から20分から60分までの40分間の濾過量(g)
実施例、比較例で得られたセルロースジアセテート15重量部、塩化メチレン72重量部、およびメタノール13重量部を密閉容器に入れ、混合物をゆっくり撹拌しながら24時間かけて溶解した。このドープを加圧ろ過した後、さらに24時間静置し、ドープ中の泡を除いた。
上記ドープを、ガラス板上にバーコーターを用いてドープ温度25℃(室温)で流延した。流延したガラス板を密閉し、表面を均一にする(レベリングする)ために2分間静置した。レベリング後、40℃の温風乾燥機で8分間乾燥させた後、ガラス板からフィルムを剥離した。次いでフィルムをステンレス製の枠に支持し、100℃の温風乾燥機で20分間乾燥させてフィルム(未延伸フィルム)を得た。この未延伸フィルムの膜厚は80μmであった。
得られたフィルムの破断伸度とリターデーションは以下のように測定した。
メチレンクロライド:メタノール=9:1(重量比)の混合溶媒に、15wt%固形分濃度になるように試料を溶解した。この溶液をバーコーターを用いてガラス板上に流延し、厚さ75~85μmのフィルムを得た。このフィルムを、引張り試験機(オリエンテック(株)製、「UCT-5T」)および環境ユニット(オリエンテック(株)製、「TLF-U3」)を用いて、室温(約22℃)で、5cm/分の速度で引っ張り、破断するときの伸度(%)を求めた。結果を表2に示す。
上記フィルム(未延伸フィルム)を、引張り試験機(オリエンテック(株)製、「UCT-5T」)および環境ユニット(オリエンテック(株)製、「TLF-U3」)を用いて、フィルム試料の流延方向に、室温(約22℃)で、破断伸度に0.9を乗じた伸度に延伸を行った。延伸後のフィルムの膜厚は65μmであった。
上記で得られた未延伸フィルムのRth、及び延伸のフィルムのReを、エリプソメーター(偏光解析計AEP-100 商品名:島津製作所(株)製)を用いて測定した。結果を表2に示す。
Claims (3)
- アセチル基総置換度が2.27~2.56であるセルロースジアセテートであって、分散度Mw/Mnが3.0超7.5以下、かつ6位置換度が0.65~0.85、かつ酢化度分布半価幅が1.0~2.3、且つ粘度平均重合度が182以上213以下であることを特徴とする位相差フィルム用セルロースジアセテート。
- 6%粘度が120~230mPa・sである請求項1記載の位相差フィルム用セルロースジアセテート。
- 重量平均分子量Mwが205,000以上235,000以下である請求項1又は2記載の位相差フィルム用セルロースジアセテート。
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US13/395,731 US8846900B2 (en) | 2010-01-29 | 2011-01-21 | Cellulose diacetate for retardation film |
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KR1020117015491A KR101118879B1 (ko) | 2010-01-29 | 2011-01-21 | 위상차 필름용 셀룰로오스 디아세테이트 |
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EP2472296A4 (en) | 2013-01-16 |
US8846900B2 (en) | 2014-09-30 |
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US20120172585A1 (en) | 2012-07-05 |
KR101118879B1 (ko) | 2012-03-20 |
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TW201137013A (en) | 2011-11-01 |
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