(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2004/0247918A1
`Hashimoto
`(43) Pub. Date:
`Dec. 9, 2004
`
`US 2004O247918A1
`
`(54) CELLULOSE ACYLATE-BASED DOPE,
`CELLULOSE ACYLATE FILM, AND
`METHOD OF PRODUCING ACELLULOSE
`ACYLATE FILM
`(75) Inventor: Kiyokazu Hashimoto,
`Minami-ashigara-shi (JP)
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 4, 2003 (JP)...................................... 2003-1592.73
`Jun. 4, 2003 (JP).
`... 2003-159982
`Nov. 4, 2003 (JP)...................................... 2003-374856
`Publication Classification
`
`
`
`(51) Int. Cl. ................................................ B32B 29/00
`Correspondence Address:
`BURNS DOANE SWECKER & MATHIS LLP (52) U.S. Cl. ......................................... 428/532; 525/329.5
`POST OFFICE BOX 1404
`ALEXANDRIA, VA 22313-1404 (US)
`(73) Assignee: Fuji Photo Film Co., Ltd., Minami-ashi
`gara-shi (JP)
`(21) Appl. No.:
`10/858,288
`(22) Filed:
`Jun. 2, 2004
`
`A cellulose acylate-based dope, which has an exothermic
`peak giving a calorific value of 1 to 10 J/g (inclusive),
`between 0 and 40 C.; and a cellulose acylate film produced
`by using the Same.
`
`(57)
`
`ABSTRACT
`
`Page 1 of 38
`
`Tianma Exhibit 1014
`
`

`

`US 2004/0247918 A1
`
`Dec. 9, 2004
`
`CELLULOSE ACYLATE-BASED DOPE,
`CELLULOSE ACYLATE FILM, AND METHOD OF
`PRODUCING A CELLULOSE ACYLATE FILM
`
`FIELD OF THE INVENTION
`0001. The present invention relates to a cellulose acylate
`film which is useful for a liquid crystal image display device,
`a Silver halide photographic photoSensitive material, or the
`like; a cellulose acylate-based dope Suitable for forming a
`cellulose acylate film; and a proceSS for producing the film.
`BACKGROUND OF THE INVENTION
`0002 Hitherto, a chlorine-containing hydrocarbon, such
`as dichloromethane, has been used as an organic Solvent of
`a cellulose acylate Solution used when forming a cellulose
`acylate film used in a Silver halide photographic photosen
`Sitive material or a liquid crystal image display device.
`Dichloromethane (boiling point, about 40° C.) has been
`conventionally used as a good Solvent for cellulose acylate.
`Dichloromethane is a preferable Solvent due to its advantage
`of easy drying in film-forming and drying Steps in the
`proceSS for producing an article as described above, because
`it has a low boiling point. In recent years, as to chlorine
`containing organic Solvents having a low boiling point,
`leakage thereof has been remarkably reduced in the Step of
`handling the Solvents, even in airtight facilities, from the
`Viewpoint of protecting the environment. For example, an
`exhaustive closed System to prevent leakage from the System
`has been developed. Even if the organic Solvent is leaked,
`the following method is adopted to prevent the hydrocarbon
`from being discharged outdoors: installing a gas-absorbing
`tower to absorb the organic Solvent, and treating the Solvent
`before discharge. This method also has been improved.
`Furthermore, before discharge, the chlorine-containing
`organic Solvent is decomposed by burning based on thermal
`power, or by action of electron beams. In this way, the
`organic Solvent has hardly been discharged outdoors. How
`ever, it is necessary to conduct further research to attain
`complete prevention of discharge.
`0.003 Attempts have been made to find solvents for
`cellulose acylate that are different from dichloromethane,
`which has been favorably used as a chlorine-containing
`organic Solvent. Examples of known organic Solvents in
`which cellulose acylate, in particular cellulose triester, can
`be dissolved include acetone (boiling point, 56°C.), methyl
`acetate (boiling point, 56. C.), tetrahydrofuran (boiling
`point, 65 C.), 1,3-dioxolane (boiling point, 75° C), and
`1,4-dioxane (boiling point, 101° C). Of these examples,
`methyl acetate is excellent in Solubility and film-forming
`property.
`0004 Generally, a film is produced by a method in which
`a dope (a concentrated polymer Solution) using the afore
`mentioned organic Solvents is cast on a band and peeled
`from the band, followed by drying with conveying. Methods
`for producing a film from a dope prepared with methyl
`acetate are described in JP-A-2002-192541, JP-A-2002
`160242, and JP-A-2003-55476. These methods are prima
`rily directed at improving the Solubility of a polymer, which
`results in improvements in each of long-term continuous
`productivity of the film, Storage Stability of the dope, and
`ease of peeling from the band.
`0005. However, in each of these methods, optical
`unevenness (i.e., unevenness of retardation (Rth) in the thick
`
`direction; the term “retardation in the thick direction” means
`the value of the difference in an average refractive indices in
`the casting direction (MD) and the width direction (TD) and
`the refractive index in thick direction (TH); multiplied by
`the thickness of the film) is large. Further, uneven thermal
`expansion are apt to arise.
`0006. In addition, in each of these methods, a formed film
`of the dope is low in elastic modulus at the time of peeling,
`and Stretch is easily caused by tension during conveyance of
`the formed film after peeling. From these defects, optical
`unevenness (i.e., unevenness of retardation (Re) in the face;
`the term “retardation in the face” means the value of the
`difference in refractive indices of the film between the
`casting direction (MD) and the width direction (TD), mul
`tiplied by the thickness of the film) and uneven thermal
`Shrinkage are apt to arise.
`0007. The production of cellulose acylate films by a cast
`method is classified into a method called "drum casting
`which comprises Steps of casting the prepared cellulose
`acylate Solution onto a chilled drum, cooling it to a tem
`perature ranging from 15 C. to -100° C., for gelling, and
`then peeling the gelled cellulose acylate, followed by drying
`the peeled film; and a method called “band casting” which
`comprises Steps of casting the prepared cellulose acylate
`Solution onto a band heated at a temperature ranging from
`15° C. to 50 C., for drying, and then peeling the dried film.
`However, the aforementioned problems have been remark
`able in drum casting.
`0008. When Rth unevenness is large, in case that a
`cellulose acylate film is used for a large-size liquid crystal
`display plate, irregularity (unevenness) of display resulting
`from the uneven Rth is easy to occur. In particular, when the
`large-size liquid crystal display plate is Seen from the
`oblique direction thereof, this problem is remarkable. In
`addition, if the uneven thermal expansion is Severe, uneven
`StreSS to the expansion occurs on account that the heat
`expansion owing to thermal generated from light Sources is
`locally different, which easily leads to occurrence of optical
`unevenneSS Owing to photo-elasticity. Therefore, improve
`ment on these defects has been desired.
`0009. When a cellulose acylate film is used for a large
`Size liquid crystal display plate, irregularity (unevenness) of
`display resulting from uneven Re easily occurs. In addition,
`if uneven thermal shrinkage is Severe, uneven StreSS to the
`Shrinkage occurs, because the thermal shrinkage owing to
`heat generated from light Sources is locally different, which
`easily leads to occurrence of optical unevenneSS Owing to
`photoelasticity.
`0010 Further, when a cellulose acylate film is used for a
`Silver halide photosensitive material, Such uneven thermal
`expansion or uneven thermal shrinkage easily causes image
`distortion during long-term preservation. In other words, a
`major cause for these problems is a shortage of Strength
`when a dope is cast. Therefore, improvement on these
`defects has been desired.
`SUMMARY OF THE INVENTION
`0011. The present invention resides in a cellulose acylate
`based dope, which has an exothermic peak giving a calorific
`value of 1 to 10 J/g (inclusive), between 0 and 40° C.
`0012 Further, the present invention resides in a process
`for producing a cellulose acylate based dope, comprising the
`Steps of
`
`Page 2 of 38
`
`

`

`US 2004/0247918 A1
`
`Dec. 9, 2004
`
`0013 (1) adding collected wastes of cellulose acy
`late, which are obtained by collecting and crushing a
`cellulose acylate film edge trimmed when raw mate
`rial of the film is cast, again when the dope is
`produced, and
`0014) (2) cooling the cellulose acylate, and heating
`the cellulose acylate Stepwise, to dissolve the cellu
`lose acylate.
`Further, the present invention resides in a cellulose
`0.015
`acylate-Series dope having a diffraction peak (A) whose full
`width at half maximum is from 0.1 degrees to 2 degrees in
`the range from 20=20 degrees to 20=25 degrees, when
`measured according to X-ray diffraction while cooling at
`-50° C.
`0016 Further, the present invention resides in a process
`for producing a cellulose acylate-based dope, comprising the
`Steps of:
`0017 (1) using a recovery solvent;
`0018 (2) Swelling a cellulose acylate before disso
`lution; and
`0019 (3) multistage-cooling the cellulose acylate
`during cooling/heat-up dissolution.
`0020. Other and further features and advantages of the
`invention will appear more fully from the following descrip
`tion.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0021 According to the present invention, there are pro
`vided the following means:
`0022 (1) A cellulose acylate-based dope, which has an
`exothermic peak giving a calorific value of 1 to 10 J/g
`(inclusive), between 0 and 40° C.
`0023 (2) The cellulose acylate-based dope according to
`the above item (1), wherein the absorbance (A40) of the
`dope to a wavelength of 550 nm at 40 C. is 0.02 to 3
`(inclusive) higher than the minimum absorbance (Am)
`thereof to a wavelength of 550 nm at temperatures ranging
`from 0 to -40° C.
`0024 (3) The cellulose acylate-based dope according to
`the above item (1), wherein the infrared spectrum intensity
`ratio of the dope before the addition of boric acid (A1=a
`value obtained by dividing the absorbance of the dope to a
`wave number of 3552 cm by the absorbance thereof to a
`wave number of 3475 cm, or A2=a value obtained by
`dividing the absorbance of the dope to a wave number of
`3629 cm by the absorbance thereof to a wave number of
`3475 cm), and the infrared spectrum intensity ratio when
`1.5%, by mass, of boric acid is added to the dope (B1=a
`value obtained by dividing the absorbance of the dope to a
`wave number of 3552 cm by the absorbance thereof to a
`wave number of 3475 cm, or B2=a value obtained by
`dividing the absorbance of the dope to a wave number of
`3629 cm by the absorbance thereof to a wave number of
`3475 cm), satisfy the following expressions (A) and (B):
`Expression (A)
`3.02B1A121.2
`Expression (B)
`3.02B2A221.2
`
`0025 (4) The cellulose acylate-based dope according to
`any one of the above items (1) to (3), wherein the cellulose
`acylate is made of one, or a mixture of two or more, Selected
`from cellulose acylates wherein the Substitution degree of
`cellulose to a hydroxy group Satisfies all of the following
`expressions (i) to (iii):
`(i)
`2.6SSA+SBs3.0
`(ii)
`2.OSSAs 3.0
`(iii)
`OscSBSO.8
`0026 wherein, SA and SB represent degrees of
`Substitution of acyl groups for hydroxyl groups of
`cellulose, and more Specifically SA is the degree of
`acetyl substitution and SB is the degree of acyl
`Substitution having 3 to 22 carbon atoms.
`0027 (5) The cellulose acylate-based dope according to
`the above item (4), wherein at least one chlorine-free organic
`solvent is used, which is selected from ethers having 3 to 12
`carbon atoms, ketones having 3 to 12 carbon atoms, and
`esters having 3 to 12 carbon atoms.
`0028 (6) A process for producing a cellulose acylate
`based dope, comprising the Steps of:
`0029 (i) adding collected wastes of cellulose acy
`late, which are obtained by collecting and crushing a
`cellulose acylate film edge trimmed when raw mate
`rial of the film is cast, again when the dope is
`produced, and
`0030 (ii) cooling the cellulose acylate, and heating
`the cellulose acylate Stepwise to dissolve the cellu
`lose acylate.
`0031 (7) A cellulose acylate film, produced by use of the
`cellulose acylate-based dope according to any one of the
`above items (1) to (5).
`0032 (8) The cellulose acylate film according to the
`above item (7), which is for a polarizing plate, for an
`optically compensating film, or for a low reflecting film.
`0033 (9) The cellulose acylate film according to the
`above item (7), which is for a liquid crystal display element.
`0034 (10) A polarizing plate, wherein at least one layer
`made of the cellulose acylate film according to the above
`item (7) is laminated, as a light-polarizing layer.
`0035 (11) The polarizing plate according to the above
`item (10), wherein the light-polarizing layer is drawn by use
`of a tenter in the State that the absorption axis of the layer is
`inclined at an angle of 45 to 90 degrees to the carrying
`direction of the layer.
`0036 (12) An optically compensating film for a liquid
`crystal display plate, wherein the cellulose acylate film
`according to the above item (7) is used as a Substrate.
`0037 (13) An antireflection film, wherein the cellulose
`acylate film according to the above item (7) is used as a
`Substrate.
`0038 (14) A silver halide photographic photosensitive
`film, wherein the cellulose acylate film according to the
`above item (7) is used as a Substrate.
`0039 (Hereinafter, a first embodiment of the present
`invention means to include the cellulose acylate-based dopes
`described in the items (1) to (5) above, the producing
`
`Page 3 of 38
`
`

`

`US 2004/0247918 A1
`
`Dec. 9, 2004
`
`process described in the item (6) above, the cellulose acylate
`films described in the items (7) to (9) above, the polarizing
`plates described in the items (10) to (11) above, the optically
`compensating film described in the item (12) above, the
`antireflection film described in the item (13) above, and the
`Silver halide photographic photosensitive film described in
`the item (14) above.)
`0040 (15) A cellulose acylate-based dope having a dif
`fraction peak (A) whose half width is from 0.1 degrees to 2
`degrees in the range from 20=20 degrees to 20=25 degrees,
`when measured according to X-ray diffraction while cooling
`at -50 C.
`0041 (16) The cellulose acylate-based dope according to
`the above item (15), wherein the relative intensity of the
`diffraction peak (A) is in the range from 0.05 to 2.
`0.042 (17) The cellulose acylate-based dope according to
`the above item (15) or (16), further having a diffraction peak
`(B) whose full width at half maximum is from 3 degrees to
`20 degrees in the range from 20=15 degrees to 20=28
`degrees.
`0043 (18) The cellulose acylate-based dope according to
`any one of the above items (15) to (17), wherein the ratio of
`the diffraction peak (A) to the diffraction peak (B) is from
`0.05 to 1 in terms of peak intensity.
`0044) (19) The cellulose acylate-based dope according to
`the above item (15), wherein an absorbance of 550 nm at
`-50° C. (A-50) is higher, by a range from 0.01 to 3, than a
`minimum absorbance of 550 nm in the range from O C. to
`–40° C. (Am).
`0045 (20) The cellulose acylate-based dope according to
`the above item (15), wherein a property that a temperature
`at which tano (a value of G" (Viscous Modulus) divided by
`G' (Elastic Modulus)) of not more than 1 is obtained, when
`measured in a closed System, is in the range from -80 C. to
`15° C.
`0046 (21) The cellulose acylate-based dope according to
`the above item (20), wherein G' at the temperature giving
`tanö of 1, when measured in a closed System, is in the range
`from 400 Pa to 4,000 Pa.
`0047 (22) The cellulose acylate-based dope according to
`the above item (15), wherein two or more peaks exist in a
`distribution curve of diffusion constant at -50 C., in which
`the difference in the natural logarithm of the diffusion
`constant between the highest peak and the Second highest
`peak of these peaks is in the range from 0.5 to 8 in terms of
`absolute value (AlogD).
`0.048 (23) The cellulose acylate-based dope according to
`the above item (15), wherein the cellulose acylate-Series
`dope is prepared with a cellulose acylate having a property
`that, in terms of the ratio in height of a peak in the
`neighborhood of 1056 cm', to a peak in the neighborhood
`of 1753 cm, measured according to infrared spectropho
`tometry (IR), a value of the ratio measured at -50° C.
`(I(-50)) is larger, by a range from 0.1 to 1.5, than a value of
`the ratio measured at 25 C. (I(25)).
`0049 (24) The cellulose acylate-based dope according to
`any one of the items (15) to (23), wherein the cellulose
`acylate is made of one, or a mixture of two or more, Selected
`
`from cellulose acylates wherein the Substitution degree of
`cellulose to a hydroxy group Satisfies all of the following
`expressions (I) to (III):
`(I)
`2.6SSA+SBs3.0
`(II)
`2.OSSAs 3.0
`(III)
`OscSBSO.8
`0050 wherein, SA and SB represent degrees of
`Substitution of acyl groups for hydroxyl groups of
`cellulose, and more Specifically SA is the degree of
`acetyl substitution and SB is the degree of acyl
`Substitution having 3 to 22 carbon atoms.
`0051 (25) The cellulose acylate-series dope according to
`any one of the above items (15) to (24), wherein the sum
`total (S6) of a degree of Substitution of SA and SB in the
`6-position of said cellulose acylate satisfies formula (IV)
`described below:
`
`O.8 s.S.6s 1
`(IV)
`0.052 (26) The cellulose acylate-based dope according to
`the above item (24) or (25), wherein at least one chlorine
`free organic Solvent is used, which is Selected from ethers
`having 3 to 12 carbon atoms, ketones having 3 to 12 carbon
`atoms, and esters having 3 to 12 carbon atoms.
`0053 (27) A process for producing a cellulose acylate
`based dope, comprising the Steps of:
`0.054
`(i) using a recovery solvent;
`0055 (ii) Swelling a cellulose acylate before disso
`lution; and
`0056 (iii) multistage-cooling the cellulose acylate
`during cooling/heat-up dissolution.
`0057 (28) A cellulose acylate film, produced by use of
`the cellulose acylate-based dope according to any one of the
`above items (15) to (26).
`0.058 (29) The cellulose acylate-series dope described in
`the above item (19) or (20), wherein the increasing ratio
`(AG) of G' at a temperature of from 10° C. to -35° C.
`measured in a closed system is in the range from 5 Pa/ C.
`to 300 Pa/ C.
`0059 (30) The cellulose acylate film according to the
`above item (28), which is for a polarizing plate, for an
`optically compensating film, or for a low reflecting film.
`0060 (31) The cellulose acylate film according to the
`above item (28), which is for a liquid crystal display
`element.
`0061 (32) A polarizing plate, wherein at least one layer
`made of the cellulose acylate film according to the above
`item (28) is laminated, as a light-polarizing layer.
`0062 (33) The polarizing plate according to the above
`item (32), wherein the light-polarizing layer is drawn by use
`of a tenter in the State that the absorption axis of the layer is
`inclined at an angle of 45 to 90 degrees to the carrying
`direction of the layer.
`0063 (34) An optically compensating film for a liquid
`crystal display plate, wherein the cellulose acylate film
`according to the above item (28) is used as a Substrate.
`
`Page 4 of 38
`
`

`

`US 2004/0247918 A1
`
`Dec. 9, 2004
`
`0064 (35) An antireflection film, wherein the cellulose
`acylate film according to the above item (28) is used as a
`Substrate.
`0065 (36) A silver halide photographic photosensitive
`film, wherein the cellulose acylate film according to the
`above item (28) is used as a Substrate.
`0.066
`(Hereinafter, a second embodiment of the present
`invention means to include the cellulose acylate-based dopes
`described in the items (15) to (26), and (29) above, the
`producing process described in the item (27) above, the
`cellulose acylate films described in the items (28), (30) and
`(31) above, the polarizing plates described in the items (32)
`to (33) above, the optically compensating film described in
`the item (34) above, the antireflection film described in the
`item (35) above, and the Silver halide photographic photo
`sensitive film described in the item (36) above.)
`0067. Herein, the present invention means to include all
`of the above first and Second embodiments, unless otherwise
`Specified.
`0068 According to the first embodiment of the present
`invention, in a band flow casting manner of casting a dope
`onto a band at ambient temperature, and then Stripping off
`the dope while drying the dope, the Strength of the dope on
`the band is made high, thereby Solving the above-mentioned
`problems. That is, the cast dope undergoes Volume shrinkage
`as the dope is dried on the band. However, the dope does not
`Shrink easily in its in-plane direction, because of frictional
`force between the band and the dope. Thus, shrinkage of the
`dope advances Selectively only in its thickneSS direction. AS
`a result, molecules in the dope are easily oriented in the
`thickness direction, such that the Rth of the dope is liable to
`rise. When the Rth becomes large in this way, variation in
`the Rth is liable to become large.
`0069. When the strength of the dope is low, the dope is
`easily drawn by tensile StreSS when the dope is Striped.
`Orientation in the in-plane direction of the dope advances
`accordingly. As a result, the Rth is easily exhibited. When
`the dope Strength is low at this time, StreSS unevenneSS is
`easily generated when the dope is drawn. Thus, unevenneSS
`of the Rth is easily made larger.
`0070 AS to film in which Rth unevenness is generated
`and uneven orientation of the molecules is generated in the
`in-plane direction, the distribution of the thermal expansion
`coefficient thereof is also liable to become large. The thermal
`expansion coefficient of molecules is liable to be larger as
`the thermal motion of the molecules is less restricted.
`Therefore, if an area where the in-plane direction orientation
`advances locally is present as described above, an area
`where the thermal expansion coefficient is locally Small is
`generated. Thus, thermal expansion unevenneSS is easily
`generated.
`0071. In the first embodiment of the present invention,
`therefore, it is the chief aim that, in the range of ambient
`temperatures, which is a temperature band for casting a dope
`in the band manner, the Strength of the dope is improved;
`that is, the Viscosity or the elasticity of the dope is made
`high. As a result of eager research for the aim, the following
`has been found out for the first embodiment of the present
`invention: To improve the Strength of a dope, it is important
`to Strengthen the hydrogen bonds between cellulose acylate
`molecules. That is, cellulose acylate is Synthesized by acy
`
`lating three hydroxyl groups in each unit of a cellulose
`molecule, but all of the hydroxyl groups in the cellulose
`molecule cannot be acylated. Thus, unreacted hydroxyl
`groups remain. By forming hydrogen bonds between the
`remaining hydroxyl groups of the cellulose acylate mol
`ecules, a network is formed in the dope made of the
`molecules, and the Strength of the dope can be improved.
`0072. It has been found out for the first embodiment of
`the present invention that when the dope is Scanned in the
`range of from 40 to 0° C. with a differential scanning
`calorimeter (DSC), an exothermic peak, on which the num
`ber of such hydrogen bonds is reflected, is exhibited in the
`Step of the cooling. The calorific value in this case is
`preferably from 1 to 10J/g (inclusive), more preferably from
`2 to 9 J/g (inclusive), and even more preferably from 3 to 8
`J/g (inclusive). In this way, calories are generated in either
`of the Step of cooling the dope and the Step of heating the
`dope.
`0073 Such hydrogen bonds can be made more intense by
`causing phase Separation. In other words, phase Separation is
`followed by the appearance of concentration fluctuation in
`the dope (i.e. the appearance of high-concentration areas and
`low-concentration areas, in cycles of Several nanometers to
`Several millimeters, based on phase Separation Such as
`Spinodal decomposition orbinodal decomposition); thus, the
`hydroxyl groups between cellulose acylate molecules easily
`come close to each other in the high-concentration phase, So
`that hydrogen bonds are easily caused. Preferably Such
`phase Separation is caused at the temperature when the dope
`is cast. The phase Separation can be analyzed or estimated by
`measuring the absorbance of the dope, for example, at 40
`C. The Separated phases are converted to a homogeneous
`phase by a change in the temperature of the System. There
`fore, the phase Separation can be estimated by the rise ratio
`of the absorbance at 40 C. to the absorbance attemperatures
`ranging from 0 to -40 C., at which cellulose acylate turns
`into a homogeneous phase. In the first embodiment of the
`present invention, cellulose acylate is dissolved in a Solvent.
`The phenomenon that, at this time, domains (phase) where
`the concentration of the cellulose acylate is high, and
`domains (phase) where it is low, are produced, is referred to
`as “phase Separation.”
`0074 The absorbance of the dope to a wavelength of 550
`nm at 40°C. (A40) is preferably 0.02 to 3 (inclusive), more
`preferably 0.02 to 2 (inclusive), even more preferably 0.02
`to 1 (inclusive) higher than the minimum absorbance thereof
`to the wavelength of 550 nm at temperatures ranging from
`0 to -40° C. (Am). The Am is preferably from 0 to 0.3
`(inclusive), more preferably from 0.01 to 0.25 (inclusive),
`even more preferably from 0.02 to 0.2 (inclusive).
`0075. The ease of formation of Such hydrogen bonds is
`controlled by the activity of the hydroxyl groups. That is, as
`the activity is higher, hydrogen bonds between cellulose
`acylate molecules are more easily formed, So that the
`Strength of the dope rises more easily. A dope having low
`activity is one in which the hydrogen bonds are formed in
`the individual molecules of the cellulose acylate, and hydro
`gen bonds are not easily formed between the molecules.
`0076. The activity of the hydroxyl groups can be esti
`mated by infrared spectroscopy (IR). That is, O-H
`Stretches make their appearance in the wave number range
`from 3400 to 3600 cm. Of these stretches, those having
`
`Page 5 of 38
`
`

`

`US 2004/0247918 A1
`
`Dec. 9, 2004
`
`low wave numbers result from hydrogen bonds between the
`molecules, and those having high wave numbers result from
`free hydroxyl groups, which undergo no hydrogen bonds.
`0077. Addition of boric acid, which interacts with
`hydroxyl groups, to the dope enables knowing the State of
`hydrogen bonds in the dope. That is, when boric acid is
`added to the hydroxyl groups that form hydrogen bonds
`firmly in the individual molecules, the hydroxyl groups do
`not interact with boric acid, Such that the Signal intensity of
`these hydroxyl groupS does not change. In contrast, the
`hydroxyl groups that form hydrogen bonds weakly in the
`individual molecules interact easily with boric acid, Such
`that the hydrogen bonds in the molecules are cut. This fact
`enables knowing the intensity of the hydrogen bonds in the
`molecules. With greater intensity, hydrogen bonds between
`the molecules are less easily generated.
`0078 (i) The infrared spectrum intensity ratio of a dope
`before the addition of boric acid, i.e., A1 (=a value obtained
`by dividing the absorbance of the dope to a wave number of
`3552 cm by the absorbance thereof to a wave number of
`3475 cm), or A2 (=a value obtained by dividing the
`absorbance of the dope to a wave number of 3629 cm by
`the absorbance thereof to a wave number of 3475 cm), is
`calculated.
`0079 (ii) The infrared spectrum intensity ratios when
`1.5%, by mass, of boric acid is added to the dope, i.e., B1
`(=a value obtained by dividing the absorbance of the dope to
`a wave number of 3552 cm (corresponding to free
`hydroxyl groups) by the absorbance thereof to a wave
`number of 3475 cm (corresponding to hydroxyl groups
`subjected to hydrogen bonds in individual molecules), or B2
`(=a value obtained by dividing the absorbance of the dope to
`a wave number of 3629 cm (corresponding to free
`hydroxyl groups) by the absorbance thereof to a wave
`number of 3475 cm), are calculated.
`0080 (iii) The change in the intensity ratio before and
`after the addition of boric acid (i.e. the ratio between the
`absorbance to 3552 cm and that to 3475 cm, or the ratio
`between the absorbance to 3629 cm and that to 3475 cm)
`is calculated from expressions described below. The added
`amount of boric acid is preferably 1.5% by mass of the
`cellulose acylate in the dope. This means that the mol
`number of boric acid is about 2-10 times larger than that of
`the hydroxyl groups in the cellulose acylate. That is, the
`amount of boric acid is necessary and Sufficient for that of
`the hydroxide groups.
`0081. The infrared spectrum intensity ratio in the first
`embodiment of the present invention preferably satisfies the
`following expressions (A) and (B).
`Expression (A)
`3.02B1A121.2
`Expression (B)
`3.02B2A221.2
`0082 The intensity ratio more preferably satisfies the
`following expressions (A) and (B).
`Expression (A')
`2.92B1A121.25
`Expression (B')
`2.92 B2A221.25
`0.083. The intensity ratio even more preferably satisfies
`the following expressions (A") and (B").
`2.82B1A121.3
`2.82B2A221.3
`
`Expression (A")
`Expression (B")
`
`In the dope having large ratios B1/A1 and B2/A2,
`0084.
`that is, the dope wherein a lot of free hydroxyl groups are
`generated by the addition of boric acid, the activity of the
`hydroxyl groups in the dope is high So that hydrogen bonds
`are easily formed between the cellulose acylate molecules in
`the dope. In Such a dope, the intensity thereof is easily raised
`by the hydrogen bonds between the molecules.
`0085 To form such hydrogen bonds between cellulose
`acylate molecules, it is important that the molecules be
`dissolved in a spreading manner Such that the cellulose
`acylate molecules do not form hydrogen bonds between the
`molecules in the dope So as not to be a shrink Structure. In
`this case, the hydroxyl groups are directed to the outside of
`the molecules. This enables the hydroxyl group of one
`molecule of cellulose acylate to combine with the hydroxyl
`group of another molecule thereof to form a hydrogen bond.
`0086) Such a dope can be prepared as follows:
`0.087
`(1) Collected Wastes of Cellulose Acylate are
`Added.
`0088 Collected wastes are wastes obtained by collecting
`and crushing a cellulose acylate film edge trimmed when
`raw material of the film is cast. The collected wastes are
`again added to a dope-producing System when a dope is
`produced. The added amount thereof is preferably from 5 to
`60% (inclusive), more preferably from 10 to 55% (inclu
`sive), and even more preferably from 15 to 50% (inclusive)
`by weight of the whole of the cellulose acylate.
`0089. The reason adding the collected wastes causes an
`improvement in the Solubility of the cellulose acylate can be
`presumed to be as follows. Since the collected wastes once
`receive large shearing StreSS in a kneader, the molecular
`weight of the cellulose acylate of the collected wastes is
`lowered, So that cellulose acylate molecules wherein acetyl
`groups are hydrolyzed are partially present in all of the
`cellulose acylate; these cellulose acylate molecules, which
`are of lower molecular weight, which makes their polarity
`high, act as a Surfactant to disentangle shrunken molecules
`of the cellulose acylate, thereby improving the solubility of
`the cellulose acylate.
`0090 (2) The Cellulose Acylate is Cooled, and is Heated,
`Stepwise, to Dissolve the Cellulose Acylate.
`0091. It is known that the dissolution of cellulose acylate
`is advanced by cooling it once and Subsequently heating it.
`A known method to attain this industrially and continuously
`is that of kneading and mixing cellulose acylate at a low
`temperature in a Screw-shaped kneading extruder, the
`periphery of which is covered with a coolant, as described
`in JP-A-10-324774. The present invention has discovered
`that heating cellulose acylate Stepwise improves the Solu
`bility thereof dramatically in the range of ambient tempera
`tures (band casting temperature range). The multi-step heat
`ing is preferably performed at 2 to 10 Steps, more preferably
`at 2 to 6 steps, even more preferably at 2 to 4 Steps. About
`the temperatures for the heating, the temperature of the
`downstream Side (outlet Side) of each of the Steps is made
`higher than that of the upstream side (inlet Side) thereof
`preferably by 5 to 30° C. (inclusive), more preferably