Method for producing optical film, optical film, polarizing plate and liquid crystal display device

Abstract

[Problem] The problem of the present invention is to provide a method for manufacturing a wide optical film, an optical film, a polarizing plate, and a liquid crystal display device, which uses a plant-derived resin and has small retardation values ​​in the in-plane direction and thickness direction, and also suppresses non-uniformity in display caused by environmental fluctuations of the display device. [Solution] The method for manufacturing an optical film according to the present invention comprises a process of forming a dopro long film containing a cellulose ester resin having a total acetyl group substitution degree of 2.30 to 2.60 and a sugar ester having a furanose structure or a pyranose structure, and a process of stretching the long film, wherein the retardation value Ro is 0 to 10 nm and Rt is -10 to 10 nm, and the process of stretching the long film comprises a first process of obtaining a first stretched film and a second process of further stretching the first stretched film to obtain a second stretched film in this order, and further characterized in that the stretching temperature of the second process is within the range of 190 to 220 ℃.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an optical film, an optical film, a polarizing plate, and a liquid crystal display device. More specifically, the invention relates to a method for manufacturing a wide optical film using a plant-derived resin, which has small retardation values ​​in the in-plane direction and thickness direction, and also suppresses non-uniformity in display caused by environmental fluctuations of the display device, and to the optical film, etc. Background Technology

[0002] Among cellulose ester resins, it is known that cellulose acetate can be applied to optical films with a wide range of retardation by varying the degree of acetyl group substitution. Generally, triacetylcellulose with a high degree of acetyl group substitution has a low retardation value, so it is preferably used as a protective film for polarizers mounted on IPS mode liquid crystal display devices. However, when used as an optical compensation film for various liquid crystal modes such as VA mode or TN mode, stretching operations alone are insufficient to produce retardation, so a technique for adding a retardation enhancing agent is required (see, for example, Patent Document 1).

[0003] Meanwhile, various technical studies are being conducted on diacetylcellulose with a low degree of acetyl group substitution, as it is possible to perform high-magnification stretching operations and has high retardation expression, so it can be expected to be used as an optical compensation film without adding the aforementioned retardation enhancer (see, for example, Patent Document 2).

[0004] In addition, since the above-mentioned diacetylcellulose allows for high-magnification stretching operations and is advantageous for widening optical films, conversely, it is also being considered to appropriately select and adjust additives or manufacturing methods so that it has a low retardation value even when stretched at high magnification (see, for example, Patent Document 3).

[0005] However, cellulose acetate with a low degree of acetyl group substitution was considered difficult to use as an optical film as is, as its resistance to environmental variations, such as dimensional stability and deviations in optical properties, was slightly inferior due to its excessively high hydrophilicity, which resulted in a high water content of the film.

[0006] However, due to the recent demand for reducing environmental burden, there is a growing demand for optical films using plant-derived resins. Additionally, with the recent increase in the size of display devices such as televisions and monitors, there is a strong demand for wider optical films and higher performance display capabilities. Specifically, there is a strong demand for optical films that reduce the occurrence of non-uniformity in screen display caused by changes in the surrounding environment, even when widened. Prior art literature

[0007] European Patent Publication No. 911656 Specification International Patent Publication No. 2011 / 135980 Japanese Patent Publication No. 2014-149325 The problem to be solved

[0008] The present invention is made in consideration of the above problems and situations, and the problem to be solved is to provide a method for manufacturing a wide optical film, an optical film, a polarizing plate, and a liquid crystal display device, which uses a plant-derived resin and has small retardation values ​​in the in-plane direction and thickness direction, and also suppresses non-uniformity in screen display caused by environmental fluctuations of the display device. means of solving the problem

[0009] In order to solve the above problem, the inventors, while examining the cause of the problem, etc., discovered that by a method for manufacturing an optical film in which a dope containing a specific cellulose ester resin and a specific compound is prepared, a flexible film is formed to produce a long film, and further stretching is performed under specific conditions to control the retardation value, a method for manufacturing a wide optical film is obtained using a plant-derived resin, which has a small retardation value in the in-plane direction and thickness direction, and also suppresses non-uniformity in screen display caused by environmental fluctuations of the display device.

[0010] That is, the above problem related to the present invention is solved by the following means.

[0011] 1. A method for manufacturing an optical film containing at least a cellulose ester resin, wherein

[0012] A process for forming a long film by flexiblely applying a dope containing at least a cellulose ester resin and a sugar ester onto a support, and

[0013] The method includes a process of stretching the long film formed above, and

[0014] The above cellulose ester resin has a total degree of acetyl group substitution within the range of 2.30 to 2.60, and

[0015] The above sugar ester is a compound in which all or part of the hydroxyl groups in a compound (A) having one furanose structure or pyranose structure, or in a compound (B) in which at least 2 to 12 of at least one type of furanose structure or pyranose structure are bonded, are esterified by an aliphatic acyl group, and

[0016] The above optical film has a retardation value R defined by the following equation (i). o α is within the range of 0 to 10 nm, and the retardation value R is defined by the following equation (ii). t α is within the range of -10 to 10 nm, and

[0017] A method for manufacturing an optical film, characterized in that the process of stretching the long film formed above comprises, in this order, a first process of obtaining a first stretched long film and a second process of further stretching the first stretched long film to obtain a second stretched film, and further, the stretching temperature of the second process is within the range of 190 to 220 ℃.

[0018] Equation (i) R o = (n x - n y ) × d

[0019] Equation (ii) R t ={(n x + n y ) / 2 - n z}× d

[0020] (during food, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n z θ represents the refractive index in the thickness direction of the film (refractive index measured at a wavelength of 590 nm under conditions of 23 ℃ and 55 %RH), and d represents the film thickness (nm).

[0021] 2. A method for manufacturing an optical film as described in claim 1, characterized in that the content of the sugar ester is within the range of 10 to 25 mass%.

[0022] 3. A method for manufacturing an optical film as described in claim 1, characterized in that the above dope additionally contains polyester.

[0023] 4. A method for manufacturing an optical film as described in claim 3, characterized in that the content of the polyester is within the range of 5 to 15 mass%.

[0024] 5. A method for manufacturing an optical film according to claim 1 or 2, characterized in that the process of stretching the long film formed above has a precipitation inhibition zone after the second process, and the temperature of the precipitation inhibition zone is within the range of -100 to -50 ℃ compared to the stretching temperature of the second process.

[0025] 6. A method for manufacturing an optical film according to claim 1 or 2, characterized in that the stretching temperature of the second process is within the range of +60 to +100 ℃ compared to the stretching temperature of the first process.

[0026] 7. The difference ΔR in retardation values ​​when the above optical film is measured in the same way after being left for 24 hours in environments of 23 ℃·20 %RH and 23 ℃·80 %RH o and ΔR t A method for manufacturing an optical film as described in claim 1 or 2, characterized in that the absolute values ​​of all are 5 nm or less.

[0027] 8. Of the optical film above 13 A method for manufacturing an optical film according to claim 1 or 2, characterized in that the longitudinal relaxation time T1 measured by C-NMR is within the range of 50 to 80 seconds.

[0028] 9. An optical film containing at least a cellulose ester resin,

[0029] The above cellulose ester resin has a total degree of acetyl group substitution within the range of 2.30 to 2.60, and

[0030] Additionally, it contains sugar esters,

[0031] The above sugar ester is a compound in which all or part of the hydroxyl groups in a compound (A) having one furanose structure or pyranose structure, or in a compound (B) in which at least 2 to 12 of at least one type of furanose structure or pyranose structure are bonded, are esterified by an aliphatic acyl group, and

[0032] The above optical film has a retardation value R defined by the following equation (i). o α is within the range of 0 to 10 nm, and the retardation value R is defined by the following equation (ii). t α is within the range of -10 to 10 nm, and

[0033] The difference ΔR in retardation values ​​when the above optical film is measured in the same way after being left for 24 hours in environments of 23°C·20%RH and 23°C·80%RH o and ΔR t The absolute values ​​of are all 5 nm or less, and

[0034] In addition, the optical film 13 An optical film characterized by a longitudinal relaxation time T1 measured by C-NMR being within the range of 50 to 80 seconds.

[0035] Equation (i) R o = (n x - n y ) × d

[0036] Equation (ii) R t ={(n x + n y ) / 2 - n z}× d

[0037] (during food, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n z θ represents the refractive index in the thickness direction of the film (refractive index measured at a wavelength of 590 nm under conditions of 23 ℃ and 55 %RH), and d represents the film thickness (nm).

[0038] 10. An optical film according to claim 9, characterized in that the content of the above sugar ester is within the range of 10 to 25 mass%.

[0039] 11. A polarizing plate characterized by having the optical film described in claim 9 or 10 laminated to at least one surface of a polarizer.

[0040] 12. A liquid crystal display device characterized by using the polarizing plate described in claim 11 on at least one surface of a liquid crystal cell.

[0041] 13. A liquid crystal display device as described in claim 12, characterized as being an IPS mode type liquid crystal display device. Effects of the invention

[0042] It is possible to provide a method for manufacturing a wide optical film, an optical film, a polarizer, and a liquid crystal display device using a plant-derived resin, which has small retardation values ​​in the in-plane direction and thickness direction, and also suppresses non-uniformity in screen display caused by environmental fluctuations of the display device.

[0043] Although the mechanism of manifestation or mechanism of action of the present invention is not clearly defined, it is inferred as follows.

[0044] Generally, by stretching at a temperature higher than the glass transition point of the film, it is possible to reduce the stretching stress associated with the film (also referred to as "low-stress stretching" in the present invention), so it is believed that an optical film with a small retardation value can be obtained while suppressing the rise in haze or the deterioration of brittleness that is prone to occur due to stress.

[0045] It was discovered that cellulose acetate, a plant-derived resin, becomes ordered due to its three-dimensional structure resulting from intermolecular interactions, and thus stress is generated even when stretched at temperatures higher than the glass transition temperature; however, by adjusting the degree of substitution of the pyranose ring at the 6th position, the ordering of the resin can be suppressed, thereby enabling low-stress stretching at high temperatures. Furthermore, by combining it with a specific additive (a sugar ester in the present invention) and stretching it at high temperatures, the additive becomes more easily inserted between the cellulose molecules, randomizing the orientation of the cellulose to reduce stress and thereby minimizing the phase difference. Additionally, due to the strong interaction between the cellulose backbone and the additive, changes in orientation do not easily occur in response to changes in ambient temperature and humidity, and consequently, it is inferred that a film with small phase difference fluctuations accompanying environmental variations is obtained.

[0046] Focusing on the degree of substitution of the pyranose ring at the 6 positions mentioned above, for example, triacetylcellulose has the property that, when treated at high temperature, nearby acetyl groups become crosslinking points, causing ordering and the polymer chains to become bundled; therefore, the stretching ratio is limited to about 40%, and at stretching beyond that, the polymer chains break and the film fractures. In the case of diacetylcellulose, since there are no nearby acetyl groups that can become crosslinking points even when treated at high temperature, the above ordering does not occur, and therefore, the stretching ratio can be up to about 200% by low-stress stretching, so it can be said to be a resin that is advantageous for widening optical films while suppressing the occurrence of retardation by combining it with appropriate additives. Brief explanation of the drawing

[0047] FIG. 1 shows an optical film containing a cellulose ester resin, 13 Schematic diagram showing the measurement locations of the cellulose backbone when measuring the longitudinal relaxation time T1 using C-NMR FIG. 2 is a schematic drawing showing an example of an apparatus and flow for a dope preparation process, a flexibility process, a stretching process, and a drying process of a solution flexible film forming method. Specific details for implementing the invention

[0048] The method for manufacturing an optical film according to the present invention comprises, wherein the method comprises: a process of forming a long film by spreading a dope containing at least a cellulose ester resin and a sugar ester on a support; and a process of stretching the long film formed above, wherein the cellulose ester resin has a total acetyl group substitution degree within the range of 2.30 to 2.60, and the sugar ester is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or a pyranose structure, or a hydroxyl group in a compound (B) having at least two or twelve of the furanose structure or a pyranose structure bonded together, is esterified by an aliphatic acyl group, and the optical film has a retardation value R defined by formula (i). o α is within the range of 0 to 10 nm, and the retardation value R defined by the above equation (ii) t The length is within the range of -10 to 10 nm, and the process of stretching the formed long film comprises, in this order, a first process of obtaining a first stretched long film and a second process of further stretching the first stretched long film to obtain a second stretched film, and further, the stretching temperature of the second process is within the range of 190 to 220 ℃. This feature is a technical feature common to or corresponding to the following embodiments.

[0049] In an embodiment of the present invention, for the sake of expressing the effects of the present invention, it is preferable that the content of the sugar ester in the film be in the range of 10 to 25 mass%.

[0050] It is desirable that the above dope additionally contain polyester, as this has the effect of lowering the Tg of the optical film and, from the perspective of controlling the stretching temperature to reduce energy costs. In addition, it is desirable that the content of the polyester be in the range of 5 to 15 mass% in the film.

[0051] In the view of obtaining a high-quality optical film, the process of stretching the long film formed above has a precipitation suppression zone after the second process, and the temperature of the precipitation suppression zone is within the range of -100 to -50 ℃ compared to the stretching temperature of the second process.

[0052] In addition, it is preferable that the stretching temperature of the second process be within the range of +60 to +100 ℃ compared to the stretching temperature of the first process, in order to enable stretching at a high magnification while maintaining a low retardation value.

[0053] The difference ΔR in retardation values ​​when the above optical film is measured in the same way after being left for 24 hours in environments of 23°C·20%RH and 23°C·80%RH o and ΔR t It is desirable that the absolute values ​​of all are 5 nm or less, from the perspective of suppressing the occurrence of non-uniformity in screen display caused by environmental variations of the display device.

[0054] In addition, the optical film 13 It is preferable that the longitudinal relaxation time T1 measured by C-NMR is within the range of 50 to 80 seconds, from the perspective of specifying the resin structure that solves the problem of the present invention.

[0055] FIG. 1 shows an optical film containing a cellulose ester resin, 13This is a schematic diagram showing the measurement locations of the cellulose backbone when measuring the longitudinal relaxation time T1 using C-NMR. In the figure, the longitudinal relaxation time originating from the point labeled [Ring 1] is measured. In the figure, Ac represents an acetyl group, and R represents a substituent.

[0056] In the present invention, in the examples (reference examples) described below, triacetylcellulose (TAC), cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP), and diacetylcellulose (DAC) were dried without stretching the flexible web. Optical films No. 27 to No. 32 were produced, and the longitudinal relaxation time T1 in [ring 1] of the cellulose backbone was measured (for the composition and evaluation of the optical films, see Tables II and III).

[0057] As a result, in the case of no sugar ester addition, it was found that diacetylcellulose (DAC) had a shorter longitudinal relaxation time (higher motility) compared to triacetylcellulose (TAC) (comparison of No. 31 and No. 32).

[0058] However, in the case of sugar ester addition, a phenomenon is observed where the longitudinal relaxation time of [Ring 1] of the cellulose backbone is significantly prolonged; in this case, compared to triacetylcellulose (TAC) (comparison of No. 27 and No. 31), diacetylcellulose (DAC) has a longer longitudinal relaxation time (comparison of No. 30 and No. 32). This indicates that the interaction between diacetylcellulose (DAC) and the sugar ester is strong, and as this interaction becomes stronger, the influence of environmental fluctuations (retardation fluctuation: ΔR o and ΔR t It is thought that the value of can be suppressed.

[0059] The optical film of the present invention is an optical film containing at least a cellulose ester resin, wherein the cellulose ester resin has a total degree of acetyl group substitution in the range of 2.30 to 2.60, and additionally contains a sugar ester, wherein the sugar ester is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or a pyranose structure, or a hydroxyl group in a compound (B) having at least 2 to 12 of the furanose structure or a pyranose structure bonded together, is esterified by an aliphatic acyl group, and the optical film has a retardation value R defined by formula (i). o α is within the range of 0 to 10 nm, and the retardation value R defined by the above equation (ii) t The difference ΔR in retardation values ​​when the optical film is within the range of -10 to 10 nm and is measured in the same way after being left for 24 hours in environments of 23 ℃·20 %RH and 23 ℃·80 %RH. o and ΔR t The absolute values ​​of are all 5 nm or less, and furthermore, the optical film 13 It is characterized by the longitudinal relaxation time T1 measured by C-NMR being within the range of 50 to 80 seconds.

[0060] The polarizing plate of the present invention is characterized by laminating the optical film of the present invention to at least one surface of a polarizer, and the liquid crystal display device of the present invention is characterized by using the polarizing plate on at least one surface of a liquid crystal cell. Preferably, the liquid crystal display device is an IPS mode type liquid crystal display device.

[0061] Hereinafter, the present invention, its components, and forms and modes for carrying out the present invention will be described in detail. Additionally, in this invention, "∼" is used to mean including the numerical values ​​described before and after it as lower and upper limits.

[0062] ≪Overview of the Method for Manufacturing the Optical Film of the Present Invention≫

[0063] The method for manufacturing an optical film according to the present invention comprises, wherein the method comprises: a process of forming a long film by spreading a dope containing at least a cellulose ester resin and a sugar ester on a support; and a process of stretching the long film formed above, wherein the cellulose ester resin has a total acetyl group substitution degree within the range of 2.30 to 2.60, and the sugar ester is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or a pyranose structure, or a hydroxyl group in a compound (B) having at least two or twelve of the furanose structure or a pyranose structure bonded together, is esterified by an aliphatic acyl group, and the optical film has a retardation value R defined by formula (i). o α is within the range of 0 to 10 nm, and the retardation value R defined by the above equation (ii) t The process of stretching the formed long film is within the range of -10 to 10 nm, and the process of stretching the long film comprises, in this order, a first process of obtaining a first stretched long film and a second process of further stretching the first stretched long film to obtain a second stretched film, and further, the stretching temperature of the second process is within the range of 190 to 220 ℃.

[0064] First, the measurement method for various parameters related to the manufacturing method of the optical film of the present invention will be explained.

[0065] <Retardation Value>

[0066] The in-plane retardation value R of the optical film o , and retardation value R in the thickness direction t It can be obtained using the following equations (i) and (ii).

[0067] Equation (i) Ro = (n x - n y ) × d

[0068] Equation (ii) R t ={(n x + n y ) / 2 - n z}× d

[0069] During the meal, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n z θ represents the refractive index in the thickness direction of the film, and d represents the thickness of the film (nm).

[0070] The above refractive index and film thickness are determined by measuring the average refractive index of randomly sampled optical films using an Abbe refractive index meter (4T). Additionally, the average thickness of the film is measured using a commercially available micrometer.

[0071] The retardation of the optical film is measured using an automatic birefringent KOBRA-21ADH (manufactured by Oji Measuring Instruments Co., Ltd.) for a film left for 24 hours in an environment of 23°C and 55%RH, and the retardation of the film at a wavelength of 590 nm is measured under the same environment.

[0072] In addition, the difference ΔR in retardation values ​​when the above optical film is measured in the same way after being left for 24 hours under environments of 23°C·20%RH and 23°C·80%RH o and ΔR t Calculate the absolute value of and use it as an indicator of the deviation of the retardation value during environmental changes.

[0073] ΔR o (nm) = |R o (23 ℃·20 %RH) - R o (23 ℃·80 %RH)|

[0074] ΔR t (nm) = |R t (23 ℃·20 %RH) - R t (23 ℃·80 %RH)|

[0075] < 13 Longitudinal relaxation time T1 by C-NMR

[0076] optical film 13 The longitudinal relaxation time T1 by C-NMR is measured as follows.

[0077] A 50 mg film sample was measured and taken, and using the JNM-ECA400W manufactured by JEOL RESONANCE, by CP / MAS 13 C-NMR measurements were performed, and the longitudinal relaxation time T1 originating from the [ring 1] region of the cellulose backbone in Figure 1 was calculated by the Torchia method.

[0078] In addition, the measurement conditions were set to 23 ℃, relaxation delay 3 seconds, number of integration cycles 512, and resonance frequency 100 MHz.

[0079] Hereinafter, the method for manufacturing the optical film of the present invention and, subsequently, the material used in the optical film of the present invention will be described in detail.

[0080] [1] Method for manufacturing an optical film

[0081] (Method for manufacturing optical film)

[0082] First, the method for manufacturing the optical film of the present invention will be described.

[0083] A method for manufacturing an optical film according to the present invention comprises a process of forming a long film by spreading a dope containing at least a cellulose ester resin and a sugar ester on a support, and a process of stretching the formed long film, wherein the cellulose ester resin and the sugar ester are specific compounds described below, and the optical film has a retardation value R defined by formula (i). o α is within the range of 0 to 10 nm, and the retardation value R defined by the above equation (ii) tThe process of stretching the long film so that the length is within the range of -10 to 10 nm comprises, in this order, a first process of obtaining a first stretched long film and a second process of further stretching the first stretched long film to obtain a second stretched film, and further, the stretching temperature of the second process is within the range of 190 to 220 ℃.

[0084] Accordingly, the method for manufacturing an optical film of the present invention relates to a method for manufacturing an optical film by a solution oscillation method.

[0085] The manufacturing process of the optical film of the present invention is described in flowchart by the following steps: preparing a dope by dissolving a cellulose ester resin and an additive in a solvent; spreading the dope onto an infinitely extendable metal support; drying the spread dope as a web; peeling the web from the metal support to obtain a film; stretching or maintaining the width of the film; adjusting the temperature of the film by means of a precipitation prevention zone; additionally drying the film; and subsequently, winding the finished film.

[0086] Among these, the process of stretching the film comprises, in this order, a first process of obtaining a long first stretched film and a second process of further stretching the long first stretched film to obtain a second stretched film, and is also characterized in that the stretching temperature of the second process is within the range of 190 to 220°C. Hereinafter, "the first process" may be referred to as "the first stretching process" and "the second process" as "the second stretching process."

[0087] 1) Dissolution process

[0088] The process of preparing the dope is described. A higher concentration of cellulose ester in the dope is preferable as it can reduce the drying load after being plied onto a metal support, but if the concentration of cellulose ester is excessively high, the load during filtration increases, and the filtration precision deteriorates. A concentration that is compatible with these is preferably 10 to 35 mass%, and more preferably 15 to 25 mass%.

[0089] The solvent used in the dope related to the present invention may be used alone or in combination of two or more types, but it is preferable to use a mixture of a solvent and a solvent for the cellulose ester in terms of production efficiency, and it is preferable to have a larger amount of solvent in terms of the solubility of the cellulose ester. The preferred range for the mixing ratio of the solvent and the solvent is 70 to 98 mass% for the solvent and 2 to 30 mass% for the solvent. The solvent and solvent are defined as a solvent that dissolves the cellulose ester used alone, and a solvent that swells or does not dissolve the cellulose ester used alone. For this reason, depending on the average degree of acetization (degree of acetyl group substitution) of the cellulose ester, the solvents change between good and bad solvents. For example, when acetone is used as a solvent, the acetic acid ester of the cellulose ester (degree of acetyl group substitution 2.4) and cellulose acetate propionate become good solvents, while the acetic acid ester of the cellulose (degree of acetyl group substitution 2.8) becomes a bad solvent.

[0090] The solvents used in the present invention are not particularly limited, but may include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. Particularly preferably, methylene chloride or methyl acetate may be used.

[0091] In addition, the solvent used in the present invention is not particularly limited, but, for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. In addition, it is preferable that the dope contains 0.01 to 2 mass% of water. In addition, the solvent used for dissolving the cellulose ester is the solvent removed from the film by drying during the film forming process, which is recovered and reused. Although the recovered solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., it can preferably be reused even if these are contained, and if necessary, it can be purified and reused.

[0092] When preparing the dope described above, a general method can be used for dissolving the cellulose ester. By combining heating and pressurization, heating can be achieved above the boiling point at atmospheric pressure. It is desirable to stir and dissolve the solvent while heating it above its boiling point at atmospheric pressure and at a temperature within a range where the solvent does not boil under pressure, as this prevents the formation of bulky undissolved products known as gels or dough lumps. Additionally, a method is also preferably used in which the cellulose ester is mixed with a solvent to wet or swell it, and then an additional solvent is added to dissolve it.

[0093] Pressurization may be performed by injecting an inert gas such as nitrogen gas, or by increasing the vapor pressure of the solvent through heating. It is preferable to perform heating from the outside, and, for example, a jacket type is preferred as it facilitates temperature control.

[0094] A higher heating temperature for adding the solvent is preferable from the perspective of the solubility of the cellulose ester, but if the heating temperature is excessively high, the required pressure increases, leading to poor productivity. The preferred heating temperature is 45 to 120°C, 60 to 110°C is more preferable, and 70 to 105°C is even more preferable. In addition, the pressure is adjusted so that the solvent does not boil at the set temperature.

[0095] Alternatively, a cooling dissolution method is also preferably used, thereby allowing the cellulose ester to be dissolved in a solvent such as methyl acetate.

[0096] Next, this cellulose ester solution is filtered using a suitable filter material such as filter paper. Regarding the filter material, it is preferable to have a small absolute filtration precision to remove insoluble matter, but if the absolute filtration precision is excessively small, there is a problem that clogging of the filter material is likely to occur. For this reason, a filter material with an absolute filtration precision of 0.008 mm or less is preferred, a filter material with a precision of 0.001 to 0.008 mm is more preferred, and a filter material with a precision of 0.003 to 0.006 mm is even more preferred.

[0097] There are no specific restrictions on the material of the filter, and conventional filter materials may be used; however, plastic filter materials such as polypropylene or Teflon (registered trademark), or metal filter materials such as stainless steel, are preferred as they prevent fiber shedding. It is desirable to remove or reduce impurities contained in the raw material, the cellulose ester, particularly white spot foreign substances, through filtration.

[0098] A bright spot foreign substance refers to a spot (foreign substance) that is visible when light leaks out from the opposite side and is observed from the other side of a polarizing plate after light is shone from one side of an optical film placed between two polarizing plates arranged in a cross-Nicole state and light is shone from the other side of the polarizing plate. It is preferable that the number of bright spots with a diameter of 0.01 mm or more be 200 or fewer per cm². More preferably, it is 100 or fewer per cm², even more preferably 50 or fewer per m², and even more preferably 0 to 10 or fewer per cm². In addition, it is preferable that the number of bright spots of 0.01 mm or less is also low.

[0099] Although the filtration of the dope can be performed by conventional methods, a method of filtration while heating at a temperature above the boiling point of the solvent at atmospheric pressure and in a range where the solvent does not boil under pressure is preferred because the increase in the difference in pressure before and after filtration (called differential pressure) is small. The preferred temperature is 45 to 120°C, 45 to 70°C is more preferred, and 45 to 55°C is even more preferred.

[0100] It is preferable for the pressure to be low. It is preferable for the pressure to be 1.6 MPa or less, more preferable for 1.2 MPa or less, and even more preferable for 1.0 MPa or less.

[0101] Here, we explain Dope's flexibility.

[0102] 2) Flexible Process

[0103] In the casting process, it is preferable that the metal support has a mirror-finished surface, and as the metal support, a stainless steel belt or a drum with a plated surface cast is preferably used. The width of the cast can be 1 to 4 m. The surface temperature of the metal support in the casting process is -50°C to a temperature below the boiling point of the solvent; a higher temperature is preferable because it can accelerate the drying speed of the web (the dope film formed by casting the dope onto the support for casting is called the "web"), but if it is too high, the web may foam or its flatness may deteriorate. The preferred support temperature is 0 to 40°C, and 5 to 30°C is more preferable. Alternatively, it is also a preferred method to gel the web by cooling and peel it off from the drum while it contains a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, but there are methods such as spraying hot or cold air or bringing hot water into contact with the other side of the metal support. Using hot water is preferable because heat transfer is more efficient, resulting in a shorter time for the metal support to reach a constant temperature. When using hot air, the air may be at a temperature higher than the target temperature.

[0104] 3) Solvent Evaporation Process

[0105] It is a process of heating the web on a flexible support to evaporate the solvent.

[0106] To evaporate the solvent, methods such as blowing air from the web side, transferring heat with a liquid from the back side of the support, or transferring heat from the front and back sides by radiant heat are available, but the back-side liquid heat transfer method is preferred because it has good drying efficiency. In addition, a combination of these methods is also preferably used. It is preferable to dry the web on the support after flexibility on the support under an atmosphere of 40 to 100°C. To maintain an atmosphere of 40 to 100°C, it is preferable to blow hot air at this temperature onto the upper surface of the web or to heat it by means such as infrared rays.

[0107] In terms of cotton quality, moisture permeability, and peelability, it is desirable to peel the web from the support within 30 to 120 seconds.

[0108] 4) Peeling process

[0109] This is a process of peeling off the web, from which the solvent has evaporated on a metal support, at the peeling location. The peeled web is sent to the next process.

[0110] The temperature at the peeling location on the metal support is preferably in the range of 10 to 40 ℃, and more preferably in the range of 11 to 30 ℃.

[0111] In addition, the amount of residual solvent at the time of peeling the web on the metal support is preferably in the range of 50 to 120 mass% depending on the strength of the drying conditions, the length of the metal support, etc. However, if peeling is performed at a time when the amount of residual solvent is greater, the web becomes excessively soft, which damages the flatness during peeling and makes it easy for cracks or longitudinal lines to occur due to peeling tension, so the amount of residual solvent at the time of peeling can be determined in a balance of economical speed and quality.

[0112] The residual solvent amount of the web is defined by the following formula.

[0113] Residual solvent amount (%) = (Mass of web before heat treatment - Mass of web after heat treatment) / (Mass of web after heat treatment) × 100

[0114] In addition, the heat treatment when measuring the residual solvent amount refers to performing a heat treatment at 140°C for 1 hour.

[0115] The peeling tension when peeling the metal support and the film is typically in the range of 50 to 245 N / m, but if wrinkles are likely to occur during peeling, it is preferable to peel with a tension of 190 N / m or less.

[0116] In the present invention, it is preferable to set the temperature at the peeling location on the metal support to a range of -50 to 40 ℃, more preferable to a range of 10 to 40 ℃, and most preferable to a range of 15 to 30 ℃.

[0117] In order for the optical film to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150 mass%, more preferably 20 to 40 mass% or 60 to 130 mass%, and particularly preferably 20 to 30 mass% or 70 to 120 mass%.

[0118] 5) Stretching and drying process

[0119] (Stretching operation, refractive index control)

[0120] The process of stretching the optical film of the present invention comprises, in this order, a first process of obtaining a long first stretched film and a second process of further stretching the long first stretched film to obtain a second stretched film, and is further characterized in that the stretching temperature of the second process is within the range of 190 to 220 ℃.

[0121] The first process above is a process of volatilizing residual solvent in the optical film to some extent and securing the flatness of the film. The second process above is a process of reducing the phase difference by relaxing the orientation of the cellulose ester resin by high-temperature treatment and obtaining a wide optical film by high-magnification stretching.

[0122] In other words, cellulose acetate, a plant-derived resin, becomes ordered due to its three-dimensional structure resulting from intermolecular interactions during high-temperature stretching, and stress is generated even when stretched at temperatures higher than the glass transition temperature. However, by adjusting the degree of substitution of the pyranose ring at the 6th position, the ordering of the resin is suppressed, making low-stress stretching at high temperatures possible. Furthermore, by combining it with a sugar ester related to the present invention and stretching it at high temperatures, the additive becomes easier to penetrate between the cellulose molecules, randomizing the orientation of the cellulose to reduce stress and minimize the phase difference. Additionally, due to the strong interaction between the cellulose backbone and the additive, changes in orientation do not easily occur in response to changes in ambient temperature and humidity, and as a result, a film with small phase difference fluctuations accompanying environmental variations is obtained.

[0123] Therefore, by adjusting the degree of substitution at the 6th position of the pyranose ring or using appropriate additives, fracture or deterioration of physical properties can be minimized even when stretched at high magnification at high temperatures. In addition, if high-temperature treatment is suddenly performed in the first process, foaming or curl deformation caused by residual solvent occurs, making it easy for the physical properties or optical characteristics of the optical film to deteriorate; thus, the first process and the second process following it are required.

[0124] The optical film of the present invention has a retardation value R represented by the above formula. o ga is in the range of 0 to 10 nm, R t It is characterized by having a range of -10 to 10 nm.

[0125] Also, the retardation value R ois in the range of 0 to 5 nm, and also R t It is more preferable that the range is -5 to 5 nm for enhancing the effect of the present invention.

[0126] The above retardation value R o , R t To obtain this, it is preferable that the optical film takes the composition of the present invention and additionally control the refractive index by stretching operations related to the present invention.

[0127] Generally, stretching operations can be performed sequentially or simultaneously with respect to the length direction of the film (film formation direction) and the direction orthogonal to it within the film plane, i.e., the width direction. However, in the present invention, the process of stretching the film comprises, in this order, a first process of obtaining a long first stretched film and a second process of further stretching the long first stretched film to obtain a second stretched film, and furthermore, the stretching temperature of the second process is within the range of 190 to 220°C. That is, it is necessary to perform sequential stretching.

[0128] The stretching temperature of the first process for obtaining the first stretched film is preferably in the temperature range of (Tg + 10) to (Tg + 50) ℃, where Tg is the glass transition temperature of the film. At temperatures below (Tg + 10) ℃, retardation is prone to appear, and haze increases as stretching stress increases. If stretching is performed at a temperature exceeding (Tg + 50) ℃, breakage due to film foaming occurs, flatness deteriorates, or furthermore, the discoloration of the film itself becomes strong. The stretching temperature is preferably in the range of (Tg + 15) to (Tg + 40) ℃.

[0129] In addition, the glass transition temperature Tg mentioned here is the midpoint glass transition temperature (Tmg) obtained according to JIS K7121 (1987) by measuring at a heating rate of 20 ℃ / min using a commercially available differential scanning calorimeter.

[0130] The method for measuring the glass transition temperature Tg of a specific optical film is to use a differential scanning calorimeter DSC220 manufactured by Seiko Instool Co., Ltd. in accordance with JIS K7121 (1987).

[0131] An optical film sample of about 10 mg is set, and under conditions of a nitrogen flow rate of 50 ml / min, the temperature is raised from room temperature to 250 ℃ at a rate of 20 ℃ / min and maintained for 10 minutes (1st scan), then lowered to 30 ℃ at a rate of 20 ℃ / min and maintained for 10 minutes (2nd scan), and then raised again to 250 ℃ at a rate of 20 ℃ / min (3rd scan) to create a DSC curve, and the glass transition temperature Tg can be obtained from the DSC curve of the 3rd scan.

[0132] In the present invention, it is preferable to fabricate an optical film experimentally in advance using a material constituting the optical film, and to stretch it within the above temperature range with respect to the measured Tg of the optical film.

[0133] The stretching temperature of the second process for obtaining the second stretched film is preferably +60 to +100 ℃ higher than the stretching temperature of the first process for obtaining the first stretched film, and also, since lower stress stretching is possible as the stretching temperature of the second process increases, it is preferably 200 ℃ or higher, and more preferably in the range of 205 to 215 ℃.

[0134] In addition to the first and second stretching processes, the stretching operation may be performed in multiple stages, or biaxial stretching may be performed in the flexibility direction and the width direction. Furthermore, when performing biaxial stretching, simultaneous biaxial stretching may be performed, or it may be performed in stages. The stretching ratio, combining the flexibility direction and the width direction, is preferably within the range of 1.1 to 4 times, and preferably 1.2 to 3 times, relative to the original width of the film.

[0135] In this case, "step-by-step" means, for example, that it is possible to sequentially perform stretching in different directions, divide stretching in the same direction into multiple stages, and also apply stretching in different directions at any of those stages. That is, for example, the following stretching steps are also possible.

[0136] Stretch in the flexibility direction → Stretch in the width direction → Stretch in the flexibility direction → Stretch in the flexibility direction

[0137] Stretch in width direction → Stretch in width direction → Stretch in flexibility direction → Stretch in flexibility direction

[0138] The preferred stretching ratio is in the range of 1.1 to 2.5 times the original width in both the width and length directions. Particularly preferably, from the perspective of reducing the retardation value, stretching in the width direction is preferred within a range of 1.1 to 2.5 times the original film width, and more preferably within a range of 1.5 to 2.1 times. In addition, stretching in the length direction is preferred within a range of 1.1 to 2.0 times, and stretching in the width direction is preferred within a range of 1.2 to 1.5 times.

[0139] There are no specific limitations on the method of stretching the web. For example, methods include applying a difference in peripheral speed to multiple rolls and stretching in the longitudinal direction using the difference in roll peripheral speed between them, fixing both ends of the web with clips or pins and stretching in the longitudinal direction by widening the spacing between the clips or pins in the direction of travel, stretching in the transverse direction by widening in the same way, or stretching in both transverse and longitudinal directions by widening simultaneously. Of course, these methods may be used in combination. Furthermore, in the case of the so-called tenter method, it is preferable to drive the clip portion using a linear drive system so that smooth stretching can be performed and the risk of breakage can be reduced.

[0140] It is preferable that the width maintenance or transverse stretching of these film-forming processes be performed by a tenter, and it may be a pin tenter or a clip tenter.

[0141] After stretching, the long film is cooled in a precipitation suppression zone to relieve stretching stress. It is preferable that the temperature of the precipitation suppression zone be within the range of -100 to -50°C, which is higher than the temperature of the second stretching process, in order to maintain and improve the flatness and optical properties of the film. More preferably, it is within the range of -70 to -50°C. The time spent passing through the precipitation suppression zone is appropriately adjusted while monitoring the temperature of the film.

[0142] Next, the optical film is dried using a drying device that alternately passes it through multiple rollers arranged within the drying device.

[0143] In the drying process of the optical film, it is preferable to keep the residual solvent amount of the film at 1 mass% or less, more preferably 0.1 mass% or less, and particularly preferably 0 to 0.01 mass% or less.

[0144] There are no particular restrictions on the means for drying the film, and it can generally be done using hot air, infrared rays, heated rollers, microwaves, etc., but from the perspective of convenience, it is preferable to use hot air.

[0145] In the drying process of the film, it is desirable to gradually increase the drying temperature from 40 to 200°C, and it is even more desirable to perform it in the range of 50 to 140°C because it ensures good dimensional stability.

[0146] The dried optical film is wound in an optical film winding device (39) to become an optical film roll.

[0147] The film thickness of the optical film is not particularly limited, but is used to be 10 to 200 μm. In particular, it is particularly preferable that the film thickness be 10 to 100 μm. More preferably, it is 20 to 60 μm.

[0148] The optical film of the present invention is used with a width of 1 to 4 m. In particular, a width of 1.4 to 4 m is preferably used, and particularly preferably, from the perspective of obtaining an optical film of light, the width is 1.6 to 3 m.

[0149] FIG. 2 is a schematic diagram showing an example of an apparatus used in the dope preparation process, the flexibility process, the stretching process, and the drying process of a solution flexible film forming method preferred by the present invention.

[0150] Various additive liquids are transferred from the input furnace (41) to the filter (44) to remove large aggregates and then to the stock furnace (42). After that, various additive liquids are added from the stock furnace (42) to the main paste melting furnace (1). The prepared main paste is filtered, then plied from the pressure die (30) onto a metal belt (support) (31), dried to become a web, peeled at the peeling position (33), then dried while being conveyed by a plurality of conveying rollers, and then stretched to a desired retardation value by the stretching device (34) of the first stretching process and the stretching device (35) of the second stretching process. After that, it is cooled in the precipitation suppression zone (36) to relieve the film temperature and then dried in the drying device (37). After that, it is dried while being conveyed in a drying device (37) having a plurality of conveying rollers (38), and wound in an optical film winding device (39) to become an optical film roll (40).

[0151] [2] Materials constituting optical film

[0152] <Cellulose Ester Resin>

[0153] The optical film of the present invention comprises a cellulose ester resin (hereinafter referred to as "cellulose ester") having a total acetyl group substitution degree within the range of 2.30 to 2.60. By employing a cellulose ester with such a low total acetyl group substitution degree, a wide film is obtained by stretching at a high stretching ratio, and low phase difference value expression is achieved by enabling low-stress stretching. Furthermore, failures such as breakage can be avoided. In the case of a cellulose ester with an acetyl group substitution degree exceeding 2.60, ordering of the cellulose ester occurs, making it difficult to achieve a high stretching ratio.

[0154] Here, the cellulose molecule is composed of multiple glucose units connected together, and each glucose unit has three hydroxyl groups. The number of acetyl groups induced on these three hydroxyl groups is called the degree of acetyl substitution. For example, in diacetylcellulose (DAC), acetyl groups are bonded to an average of 2 to 2.5 hydroxyl groups out of the three hydroxyl groups of the glucose units.

[0155] Examples of cellulose esters used in the present invention include carboxylic acid esters having about 2 to 22 carbon atoms, and may be esters of aromatic carboxylic acids, but it is particularly preferable that they be lower fatty acid esters of cellulose. In the context of lower fatty acid esters of cellulose, a lower fatty acid refers to a fatty acid having 6 or fewer carbon atoms. The acetyl group bonded to the hydroxyl group may be a straight chain, branched, or form a ring. Additionally, other substituents may be substituted. Regarding the number of carbon atoms, it is preferable to select from acetyl groups having 2 to 6 carbon atoms. It is preferable that the number of carbon atoms of the acetyl group be 2 to 4, and more preferable that the number of carbon atoms be 2 to 3. That is, in the present invention, using diacetylcellulose is a cellulose ester resin essential for exhibiting the effects of the present invention.

[0156] The degree of acetyl group substitution of cellulose esters can be measured in accordance with ASTM D-817-91, and the preferred degree of acetyl group substitution is 2.30 to 2.45.

[0157] If the degree of acetyl group substitution of the cellulose ester is below 2.30, the absorbency and moisture permeability of the film increase, and there is a concern that the protective function of the polarizer becomes insufficient.

[0158] The weight-average molecular weight Mw of the cellulose ester is preferably 120,000 or higher, and while there is no specific upper limit, it is more preferable to be within the range of 120,000 to 190,000. If it is within the above range, the dope viscosity during solution flexibility does not become excessively high, and appearance defects such as die streaks during flexibility do not occur easily. In addition, since the weight-average molecular weight Mw is within the above range, physical properties such as mechanical strength as an optical film are also excellent.

[0159] The number average molecular weight (Mn) of the cellulose ester is preferably in the range of 30,000 to 300,000, as this results in a strong mechanical strength of the obtained cellulose ester film. Additionally, a cellulose ester with a number average molecular weight of 40,000 to 100,000 is preferably used.

[0160] It is preferable that the value of the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester be 1.4 to 3.0.

[0161] The number average molecular weight (Mn) and weight average molecular weight (Mw) of cellulose esters are measured using gel permeation chromatography (GPC).

[0162] The measurement conditions are as follows.

[0163] Solvent: Methylene chloride

[0164] Column: Shodex K806, K805, K803G (Manufactured by Showa Electric Co., Ltd.; use 3 units connected together)

[0165] Column temperature: 25 ℃

[0166] Sample concentration: 0.1 mass%

[0167] Detector: RI Model 504 (Manufactured by GL Science)

[0168] Pump: L6000 (Manufactured by Hitachi, Ltd.)

[0169] Flow rate: 1.0 ml / min

[0170] Calibration Curve: Use a calibration curve based on 13 samples of standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.) with Mw = 1,000,000 to 500. The 13 samples are used at approximately equal intervals.

[0171] The cellulose ester used in the present invention can be synthesized by known methods. Specifically, it can be synthesized by referring to the method described in Japanese Patent Publication No. Hei 10-45804.

[0172] There are no particular limitations on the cellulose used as a raw material for cellulose esters, but examples include cotton lint, wood pulp (derived from conifers, derived from hardwoods), kenaf, etc. In addition, cellulose esters obtained from these sources may be used by mixing them in any proportion.

[0173] Meanwhile, commercially available cellulose esters may be used. Examples of commercially available cellulose esters include Daicel’s L20, L30, L40, and L50, and Eastman Chemical’s Ca398-3, Ca398-6, Ca398-10, Ca398-30, and Ca394-60S.

[0174] Hereinafter, a method for synthesizing cellulose acetate preferred in the present invention will be described.

[0175] Synthesis of Cellulose Acetate

[0176] (Synthesized Example 1)

[0177] Kraft method dissolved pulp (α-cellulose content 93%) was dissolved in water, then dried by substitution with acetone. For every 100 parts by mass of this pulp, 500 parts by mass of acetic acid was uniformly dispersed and mixed at 40°C for 30 minutes to perform pretreatment activation.

[0178] Meanwhile, a mixture of 250 parts by mass of acetic anhydride and 4.0 parts by mass of sulfuric acid was added, and esterification was carried out by a conventional method. The contents were heated by the reaction of water accompanied by raw pulp with acetic anhydride and the reaction of cellulose with acetic anhydride, but the reaction was controlled by external cooling, then 125 parts by mass of an organic solvent was added, and the acetization reaction was carried out again while maintaining the temperature.

[0179] Next, after removing the organic solvent, which is the reaction solution, by heat, 35 parts by mass of a 20% aqueous calcium acetate solution was added and mixed to completely neutralize the sulfuric acid in the system and also add an excess of calcium acetate (1.09 times the equivalent amount of sulfuric acid).

[0180] After maintaining the completely neutralized reaction mixture at 150°C for 50 minutes, the reaction mixture was heated to 100°C under atmospheric conditions. Under stirring, a dilute aqueous acetic acid solution was added to the reaction mixture, separated into flake-like cellulose acetate, thoroughly washed with water, removed, and dried. The obtained flake-like cellulose acetate A had an acetyl group substitution degree of 2.4, a number average molecular weight of 47,500, and a weight average molecular weight of 166,000.

[0181] (Synthesized Example 2)

[0182] In Synthesis Example 1, the 35 parts by mass 20% calcium acetate aqueous solution was replaced with 29 parts by mass 20% magnesium acetate aqueous solution (1.00 times the equivalent amount of sulfuric acid).

[0183] (Synthesized Example 3)

[0184] In Synthesis Example 1, the amount of 20% aqueous calcium acetate solution added was changed to 39 parts by mass (1.21 times the equivalent amount with respect to sulfuric acid).

[0185] (Synthesized Example 4)

[0186] In Synthesis Example 2, the amount of 20% aqueous magnesium acetate solution added was changed to 37 parts by mass (1.28 times the amount of sulfuric acid).

[0187] (Synthesized Example 5)

[0188] In Synthesis Example 1, the amount of 20% aqueous calcium acetate solution added was changed to 28 parts by weight (0.98 times the equivalent amount with respect to sulfuric acid).

[0189] <Sugar ester having a furanose structure or pyranose structure related to the present invention>

[0190] The optical film of the present invention is characterized by comprising a so-called "sugar ester," which is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or pyranose structure, or a compound (B) in which at least two to twelve of at least one type of furanose structure or pyranose structure are bonded, is esterified by an aliphatic acyl group.

[0191] Examples of preferred compounds (A) and compounds (B) include the compounds shown below, but the present invention is not limited to these.

[0192] Examples of compounds (A) include glucose, galactose, mannose, fructose, xylose, arabinose, etc.

[0193] In addition, examples of compound (B) include lactose, sucrose, cellobiose, maltose, cellotriose, maltotriose, raffinose, kestose, etc. Among these compounds (A) and (B), it is particularly desirable to have both a furanose structure and a pyranose structure. An example is sucrose.

[0194] There are no particular limitations on the monocarboxylic acid used when synthesizing a compound in which all or part of the hydroxyl groups in compounds (A) and (B) related to the present invention are esterified; the sugar ester used in the present invention can be synthesized by esterifying using known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, etc. The carboxylic acid used may be of one type or may be a mixture of two or more types.

[0195] Desirable aliphatic monocarboxylic acids include, for example, saturated fatty acids such as acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enantic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanic acid, arachnic acid, behenic acid, lignoceric acid, cerotic acid, heptacosonic acid, montanic acid, melisic acid, laceric acid, unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, and octene acid.

[0196] Examples of desirable cyclocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, or derivatives thereof.

[0197] Details of the method for manufacturing these compounds are described in Japanese Patent Publication No. Hei 8-245678.

[0198] In addition to the esterified compounds of the above compounds (A) and (B), the esterified compound of the oligosaccharide can be applied as a compound having 3 to 12 bonds of at least one type of furanose structure or pyranose structure related to the present invention.

[0199] Oligosaccharides are produced by acting on starch, sucrose, etc. with enzymes such as amylase. Examples of oligosaccharides applicable to the present invention include malto-oligosaccharide, isomalto-oligosaccharide, fructo-oligosaccharide, galacto-oligosaccharide, and xylooligosaccharide. Oligosaccharides can also be acetylated in the same way as compounds (A) and (B) above.

[0200] Next, an example of the preparation of a sugar ester compound is described.

[0201] Acetic anhydride (200 ml) was added dropwise to a solution of glucose (29.8 g, 166 mmol) and pyridine (100 ml), and the mixture was reacted for 24 hours. Afterward, the solution was concentrated using an evaporator and added to ice water. After standing for 1 hour, the mixture was filtered through a glass filter to separate the solid from the water. The solid on the glass filter was dissolved in chloroform and separated with cold water until it became neutral. After separating the organic layer, it was dried with sodium anhydride sulfate. After removing the sodium anhydride sulfate by filtration, the chloroform was removed using an evaporator, and the mixture was further dried under reduced pressure to obtain glucose pentaacetate (58.8 g, 150 mmol, 90.9%). Additionally, the monocarboxylic acid described above may be used instead of the acetic anhydride.

[0202] Specific examples of sugar ester compounds related to the present invention are given below, but the present invention is not limited thereto.

[0203] [Chemical Formula 1]

[0204]

[0205] [Chemical Formula 2]

[0206]

[0207] [Chemical Formula 3]

[0208]

[0209] [Chemical Formula 4]

[0210]

[0211] [Chemical Formula 5]

[0212]

[0213] [Chemical Formula 6]

[0214]

[0215] [Chemical Formula 7]

[0216]

[0217] In order to suppress humidity fluctuations in phase difference values ​​and stabilize display quality, the optical film of the present invention preferably contains, in the range of 1 to 35 mass%, particularly 10 to 25 mass%, a sugar ester in which all or part of the hydroxyl groups in a compound (A) having one furanose structure or pyranose structure, or 2 to 12 hydroxyl groups in a compound (B) having at least one type of furanose structure or pyranose structure bonded together, is esterified with aliphatic acyl groups. Within this range, it is desirable to exhibit the excellent effects of the present invention and to prevent bleed-out during storage of the original material. Among these, it is preferable to use a sugar ester in which all hydroxyl groups are esterified and a sugar ester in which one or more hydroxyl groups remain. This is desirable because, compared to the case where all hydroxyl groups are esterified, there is even less bleed-out and less fluctuation in viewing angle.

[0218] For example, a mixture of sucrose octaacetate, sucrose heptaacetate, and sucrose hexaacetate is preferred. The mixing ratio is not particularly limited, but examples include combinations such as 30:30:30, 40:30:30, 40:50:10, 50:30:20, 60:30:10, 80:10:10, 90:7:3, 95:5:0, etc. These may be controlled by adjusting the reaction time or the amount of monocarboxylic acid added to react with the sugar during the esterification of the sugar, or they may be mixed individually.

[0219] [3] Other additives

[0220] Polyester

[0221] In addition to the sugar ester, the optical film of the present invention preferably uses a polyester, and among them, it is preferable to use a polyester having a structure represented by the following general formula (I). In order to improve brittleness due to its plastic effect, the polyester is preferably contained in a range of 1 to 20 mass%, and more preferably in a range of 5 to 15 mass%.

[0222] General formula (I): B-(GA)nGB

[0223] (In the formula, B represents an aliphatic or aromatic monocarboxylic acid residue. G represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylenedicarboxylic acid residue having 4 to 12 carbon atoms or an aryldicarboxylic acid residue having 6 to 12 carbon atoms. n represents an integer of 1 or more.)

[0224] The polyester used in the present invention is a polyester containing repeating units obtained by reacting a dicarboxylic acid with a diol, where A represents a carboxylic acid residue in the ester and G represents an alcohol residue.

[0225] The dicarboxylic acid constituting the polyester is an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or a dicarboxylic acid, and preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be of one type or a mixture of two or more types.

[0226] The diol constituting the polyester is an aromatic diol, an aliphatic diol, or a diol alicyclic, preferably an aliphatic diol, and more preferably a diol having 1 to 4 carbon atoms. The diol may be of one type or a mixture of two or more types.

[0227] Among these, it is preferable to contain a repeating unit obtained by reacting a dicarboxylic acid containing at least an aromatic dicarboxylic acid with a diol having 1 to 8 carbon atoms, and it is more preferable to contain a repeating unit obtained by reacting a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid with a diol having 1 to 8 carbon atoms.

[0228] The two ends of the polyester molecule may or may not be encapsulated, but from the perspective of reducing the retardation variation of the optical film due to temperature and humidity fluctuations, it is preferable that they be encapsulated.

[0229] Specific examples of the alkylenedicarboxylic acid constituting A of general formula (I) include divalent groups derived from 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 1,4-butanedicarboxylic acid (adipic acid), 1,5-pentanedicarboxylic acid (pimelic acid), 1,8-octanedicarboxylic acid (sebakic acid), etc. Specific examples of the alkenylenedicarboxylic acid constituting A include maleic acid, fumaric acid, etc. Specific examples of the aryldicarboxylic acid constituting A include 1,2-benzenedicarboxylic acid (phthalic acid), 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, etc.

[0230] A may be of one type or a combination of two or more types. Among these, A is preferably a combination of an alkylenedicarboxylic acid having 4 to 12 carbon atoms and an aryldicarboxylic acid having 8 to 12 carbon atoms.

[0231] G in general formula (I) represents a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, a divalent group derived from an aryl glycol having 6 to 12 carbon atoms, or a divalent group derived from an oxyalkylene glycol having 4 to 12 carbon atoms.

[0232] Examples of divalent groups derived from alkylene glycols having 2 to 12 carbon atoms in G include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, It includes divalent groups derived from 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-octadecanediol, etc.

[0233] Examples of divalent groups derived from aryl glycols having 6 to 12 carbon atoms in G include divalent groups derived from 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), 1,4-dihydroxybenzene (hydroquinone), etc. Examples of divalent groups derived from oxyalkylene glycols having 4 to 12 carbon atoms in G include divalent groups derived from diethyleneglucol, triethyleneglycol, tetraethyleneglycol, dipropyleneglycol, tripropyleneglycol, etc.

[0234] G may be of one type or a combination of two or more types. Among these, G is preferably an alkylene glycol having 2 to 12 carbon atoms.

[0235] B of general formula (I) is a monovalent group derived from an aromatic ring-containing monocarboxylic acid or an aliphatic monocarboxylic acid.

[0236] The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid containing an aromatic ring within the molecule, and includes not only cases where the aromatic ring is directly bonded to the carboxyl group, but also cases where the aromatic ring is bonded to the carboxyl group via an alkylene group, etc. Examples of monovalent groups derived from the aromatic ring-containing monocarboxylic acid include monovalent groups derived from benzoic acid, para-tertiarybutylbenzoic acid, orthotoluic acid, metatoluic acid, paratoluic acid, dimethylbenzoic acid, ethylbenzoic acid, normalpropylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, phenylacetic acid, 3-phenylpropionic acid, etc.

[0237] Examples of monovalent groups derived from aliphatic monocarboxylic acids include monovalent groups derived from acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, etc. Among these, monovalent groups derived from alkyl monocarboxylic acids having 1 to 3 carbon atoms in the alkyl portion are preferred, and acetyl groups (monovalent groups derived from acetic acid) are more preferred.

[0238] The weight average molecular weight of the polyester related to the present invention is preferably in the range of 500 to 3000, and more preferably in the range of 600 to 2000. The weight average molecular weight can be measured by the gel permeation chromatography (GPC).

[0239] Specific examples of polyesters related to the present invention having a structure represented by general formula (I) are shown below, but are not limited thereto.

[0240] [Chemical Formula 8]

[0241]

[0242] [Chemical Formula 9]

[0243]

[0244] [Chemical Formula 10]

[0245]

[0246] Hereinafter, specific synthetic examples of polyester related to the present invention are described.

[0247] Polyester P1

[0248] 180 g of ethylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted ethylene glycol was removed by vacuum distillation at 200 °C to obtain polyester P1. It had an acid value of 0.20 and a number average molecular weight of 450.

[0249] Polyester P2

[0250] 251 g of 1,2-propylene glycol, 244 g of phthalic anhydride, 103 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was slowly increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted 1,2-propylene glycol was removed by vacuum distillation at 200 °C to obtain polyester P2. The acid value was 0.10 and the number average molecular weight was 450.

[0251] Polyester P3

[0252] 330 g of 1,4-butanediol, 244 g of phthalic anhydride, 103 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted 1,4-butanediol was removed by vacuum distillation at 200 °C to obtain polyester P3. It had an acid value of 0.50 and a number average molecular weight of 2000.

[0253] Polyester P4

[0254] 251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted 1,2-propylene glycol was removed by vacuum distillation at 200 °C to obtain polyester P4. The acid value was 0.10 and the number average molecular weight was 400.

[0255] Polyester P5

[0256] 251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 680 g of p-toluic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted 1,2-propylene glycol was removed by vacuum distillation at 200 °C to obtain polyester P5. It had an acid value of 0.30 and a number average molecular weight of 400.

[0257] Polyester P6

[0258] 180 g of 1,2-propylene glycol, 292 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 200 ℃. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted 1,2-propylene glycol was removed by vacuum distillation at 200 ℃ to obtain polyester P6. The acid value was 0.10 and the number average molecular weight was 400.

[0259] Polyester P7

[0260] 160 g of ethylene glycol, 292 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a condenser, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 200 ℃. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted ethylene glycol was removed by vacuum distillation at 200 ℃ to obtain <polyester P7>. The acid value was 0.10 and the number average molecular weight was 1000.

[0261] Polyester P8

[0262] 251 g of ethylene glycol, 244 g of phthalic anhydride, 200 g of sebacic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were added to a 2 L four-necked flask equipped with a thermometer, a stirrer, and a cooling tube, and the temperature was gradually increased while stirring under a nitrogen stream until it reached 230 °C. A dehydration condensation reaction was carried out while observing the degree of polymerization. After the reaction was completed, unreacted ethylene glycol was removed by vacuum distillation at 200 °C to obtain polyester P8. It had an acid value of 0.50 and a number average molecular weight of 2000.

[0263] The content of the polyester used in the optical film of the present invention is preferably in the range of 1 to 20 mass%, and more preferably in the range of 1.5 to 15 mass%. Within the above range, the effect of imparting plasticity can be expressed, and the effect of improving the brittleness of the optical film is obtained.

[0264] Plasticizer

[0265] In the optical film of the present invention, in addition to the sugar ester and polyester, a known plasticizer having a molecular weight of 10,000 or less may be used within a range that does not impede the effect. The plasticizer is not particularly limited, but preferably is selected from polycarboxylic acid ester-based plasticizers, glycolate-based plasticizers, phthalic acid ester-based plasticizers, fatty acid ester-based plasticizers, and polyalcohol ester-based plasticizers.

[0266] The polyhydric alcohol ester is an ester (alcohol ester) of a monocarboxylic acid and an aliphatic polyhydric alcohol with a valence of 2 or more, preferably an aliphatic polyhydric alcohol ester with a valence of 2 to 20. It is preferable that the polyhydric alcohol ester has an aromatic ring or a cycloalkyl ring within its molecule.

[0267] Preferred examples of aliphatic polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, trimethylolpropane, pentaerythritol, trimethylolethane, xylitol, etc. Among these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, xylitol, etc. are preferred.

[0268] Monocarboxylic acids are not particularly limited and may be aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, or aromatic monocarboxylic acids. In order to increase the moisture permeability of the film and also prevent volatilization, alicyclic monocarboxylic acids or aromatic monocarboxylic acids are preferred. Monocarboxylic acids may be of a single type or a mixture of two or more types. In addition, all OH groups contained in the aliphatic polyalcohol may be esterified, or some may be left as OH groups.

[0269] The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The number of carbon atoms of the aliphatic monocarboxylic acid is more preferably 1 to 20, and even more preferably 1 to 10. Examples of aliphatic monocarboxylic acids include saturated fatty acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethylhexanoic acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanic acid, arachnoid acid, behenic acid, lignoceric acid, cerotic acid, heptacosonic acid, montanic acid, melisic acid, and laceric acid; Unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid are included. Among these, acetic acid, or a mixture of acetic acid and other monocarboxylic acids, is preferred to increase compatibility with cellulose acetate.

[0270] Examples of alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, and cyclooctanecarboxylic acid.

[0271] Examples of aromatic monocarboxylic acids include benzoic acid; benzoic acid in which 1 to 3 alkyl groups or alkoxy groups (e.g., methoxy or ethoxy groups) are introduced into the benzene ring (e.g., toluic acid); and aromatic monocarboxylic acids having two or more benzene rings (e.g., biphenylcarboxylic acid, naphthalene carboxylic acid, tetraline carboxylic acid, etc.), and preferably benzoic acid.

[0272] The polycarboxylic acid ester is an ester of an alcohol and a polycarboxylic acid having 2 or more valence, preferably 2 to 20 valence. The polycarboxylic acid is preferably an aliphatic polycarboxylic acid having 2 to 20 valence, an aromatic polycarboxylic acid having 3 to 20 valence, or an alicyclic polycarboxylic acid having 3 to 20 valence.

[0273] Examples of polyvalent carboxylic acids include aromatic polyvalent carboxylic acids of trivalent or higher valence such as trimellitic acid, trimesic acid, and pyromellitic acid or their derivatives, aliphatic polyvalent carboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, and tetrahydrophthalic acid, oxypolyvalent carboxylic acids such as tartaric acid, tartronic acid, malic acid, and citric acid, and oxypolyvalent carboxylic acids are preferred to suppress volatilization from the film.

[0274] Examples of alcohols include aliphatic saturated alcohols having a straight chain or a side chain, aliphatic unsaturated alcohols having a straight chain or a side chain, alicyclic alcohols, or aromatic alcohols. The number of carbon atoms of aliphatic saturated alcohols or aliphatic unsaturated alcohols is preferably 1 to 32, more preferably 1 to 20, and even more preferably 1 to 10. Examples of alicyclic alcohols include cyclopentanol, cyclohexanol, etc. Examples of aromatic alcohols include benzyl alcohol, cinnamyl alcohol, etc.

[0275] The molecular weight of the polycarboxylic acid ester is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The molecular weight of the polycarboxylic acid ester-based plasticizer is preferably large from the perspective of suppressing bleed-out; and is preferably small from the perspective of moisture permeability or compatibility with cellulose acetate.

[0276] Examples of polyvalent carboxylic acid esters include triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, tributyl trimellitate, tetrabutyl pyromellitate, etc.

[0277] Polycarboxylic acid esters may be phthalic acid esters. Examples of phthalic acid esters include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, etc.

[0278] Examples of glycolates include alkylphthalylalkyl glycolates. Examples of alkylphthalylalkyl glycolates include methylphthalylmethylglycolate, ethylphthalylethylglycolate, propylphthalylpropylglycolate, butylphthalylbutylglycolate, octylphthalyloctylglycolate, methylphthalylethylglycolate, ethylphthalylmethylglycolate, ethylphthalylpropylglycolate, methylphthalylbutylglycolate, ethylphthalylbutylglycolate, butylphthalylmethylglycolate, butylphthalylethylglycolate, propylphthalylbutylglycolate, butylphthalylpropylglycolate, methylphthalyloctylglycolate, ethylphthalyloctylglycolate, octylphthalylmethylglycolate, octylphthalylethylglycolate, etc., and preferably ethylphthalylethylglycolate.

[0279] Ester-based plasticizers include fatty acid esters, citric acid esters, and phosphate esters.

[0280] Examples of fatty acid esters include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate. Examples of citric acid esters include acetyltrimethyl citrate, acetyltriethyl citrate, and acetyltribuyl citrate. Examples of phosphate esters include triphenyl phosphate, tricrezyl phosphate, crezyl diphenyl phosphate, octyl diphenyl phosphate, biphenyl diphenyl phosphate, trioctyl phosphate, and tributyl phosphate, and preferably triphenyl phosphate.

[0281] The content of the plasticizer is preferably in the range of 1 to 20 mass% with respect to the cellulose ester, and more preferably in the range of 1.5 to 15 mass%. If the content of the plasticizer is within the above range, the effect of imparting plasticity can be exhibited, and the resistance of the plasticizer to seeping out from the optical film is also excellent.

[0282] UV absorber

[0283] When the optical film of the present invention is used as an optical film placed on the surface side (visibility side) of a liquid crystal display device, it is preferable to contain an ultraviolet absorber from the perspective of improving lightfastness. The ultraviolet absorber is intended to improve lightfastness by absorbing ultraviolet rays of 400 nm or less, and in particular, it is preferable that the transmittance at a wavelength of 370 nm is 10% or less, more preferably 5% or less, and even more preferably 2% or less.

[0284] The ultraviolet absorbers preferably used in the present invention are benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers, and particularly preferably benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers.

[0285] For example, there are 5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole, (2-2H-benzotriazole-2-yl)-6-(straight-chain and side-chain dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and there are also Tinuvin series such as Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, and Tinuvin 928, all of which can be preferably used as commercially available products manufactured by BASF Japan. Among these, it is preferable that they be halogen-free.

[0286] In addition, disc-shaped compounds, such as compounds having a 1,3,5-triazine ring, are also preferably used as ultraviolet absorbers.

[0287] The optical film of the present invention preferably contains two or more types of ultraviolet absorbers.

[0288] In addition, as an ultraviolet absorber, a polymeric ultraviolet absorber may also be preferably used, and in particular, a polymeric ultraviolet absorber described in Japanese Patent Publication No. Hei 6-148430 is preferably used.

[0289] The method of adding a UV absorber may be to dissolve the UV absorber in an alcohol such as methanol, ethanol, or butanol, or in an organic solvent such as methylene chloride, methyl acetate, acetone, or dioxolane, or in a mixture of these solvents, and then add it to the dope, or to add it directly into the dope composition.

[0290] Inorganic powders that are not soluble in organic solvents are dispersed in an organic solvent and cellulose ester using a dissolver or sand mill, and then added to the dope.

[0291] The amount of UV absorber used is not constant depending on the type of UV absorber, usage conditions, etc., but when the dry film thickness of the optical film is 15 to 50 μm, a range of 0.5 to 10 mass% with respect to the optical film is preferred, and a range of 0.6 to 4 mass% is more preferred.

[0292] <Antioxidant>

[0293] Antioxidants are also called degradation inhibitors. If a liquid crystal display device or similar equipment is placed in a high-humidity, high-temperature environment, degradation of the optical film may occur.

[0294] It is desirable to include an antioxidant in the optical film because it plays a role in slowing down or preventing the decomposition of the optical film caused by, for example, halogens in the residual solvent amount in the optical film or phosphoric acid of phosphate-based plasticizers.

[0295] As such antioxidants, hindered phenol-based compounds are preferably used, for example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], Examples include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N´-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, and tris(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate.

[0296] In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] are preferred. In addition, hydrazine-based metal inerts such as N,N´-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine or phosphorus-based processing stabilizers such as tris(2,4-di-t-butylphenyl)phosphite may be used in combination.

[0297] The amount of these compounds added is preferably in the range of 1 ppm to 1.0% by mass ratio with respect to the cellulose ester, and more preferably in the range of 10 to 1000 ppm.

[0298] <Microparticles (Matte)>

[0299] The optical film may additionally contain fine particles (matting agents) as needed to increase the slipperiness of the surface.

[0300] The fine particles may be inorganic fine particles or organic fine particles. Examples of inorganic fine particles include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Among these, silicon dioxide or zirconium oxide is preferred, and silicon dioxide is more preferably used to minimize the increase in haze of the resulting film.

[0301] Examples of silicon dioxide fine particles include Aerozil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (all manufactured by Nihon Aerozil Co., Ltd.), Seahorstar KE-P10, KE-P30, KE-P50, KE-P100 (all manufactured by Nippon Catalytic Co., Ltd.), etc. Among these, Aerozil R972V, NAX50, Seahorstar KE-P30, etc. are particularly preferred to reduce the friction coefficient while maintaining low turbidity of the resulting film.

[0302] The primary particle size of the fine particles is preferably in the range of 5 to 50 nm, and more preferably in the range of 7 to 20 nm. While a larger primary particle size has a greater effect in increasing the slipperiness of the resulting film, it tends to reduce transparency. Therefore, the fine particles may be contained as secondary aggregates with a particle size in the range of 0.05 to 0.3 μm. The size of the primary particles or the secondary aggregates of the fine particles can be determined by observing the primary particles or secondary aggregates with a transmission electron microscope at a magnification of 50 to 2 million times and obtaining the average value of the particle sizes of 100 primary particles or secondary aggregates.

[0303] The content of fine particles is preferably in the range of 0.05 to 1.0 mass% with respect to the cellulose ester resin, and more preferably in the range of 0.1 to 0.8 mass%.

[0304] [4] Polarizing plate and liquid crystal display device

[0305] A polarizing plate to which the optical film of the present invention is applied, and a liquid crystal display device of the present invention using the same will be described.

[0306] The polarizing plate of the present invention is characterized by being a polarizing plate formed by clamping at least one surface of a polarizer by the polarizing plate protection film of the present invention. The liquid crystal display device of the present invention is characterized by having a polarizing plate related to the present invention laminated to at least one liquid crystal cell surface with an adhesive layer interposed therebetween.

[0307] The polarizing plate of the present invention can be manufactured by a general method. It is preferable to laminate at least one surface of a polarizing plate manufactured by alkali saponifying the polarizer side of the polarizing plate protective film of the present invention and immersing and stretching it in an iodine solution using a fully saponifiable type aqueous polyvinyl alcohol solution. For the other surface, the polarizing plate protective film may be used, or another polarizing plate protective film may be used. A commercially available cellulose ester film (e.g., Konica Minolta TAC KC4UY: manufactured by Konica Minolta Inc.) is also preferably used.

[0308] With respect to the polarizer protective film of the present invention, the polarizer protective film used on the polarizer on the opposite side via a liquid crystal cell has an in-plane retardation R measured at a wavelength of 590 nm. o g 150 ∼ 350 nm, R t It is preferable that the phase difference be -100 to 100 nm. These can be manufactured, for example, by the methods described in Japanese Patent Publication No. 2005-196149 and Japanese Patent Publication No. 2005-275104. Alternatively, it is also preferable to use a polarizer protection film that serves as an optical compensation film, having an optical anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, an optical anisotropic layer can be formed by the method described in Japanese Patent Publication No. 2005-275083. By using the above phase difference film in combination with the polarizer protection film of the present invention, a liquid crystal display device having a stable viewing angle expansion effect can be obtained.

[0309] A polarizer, which is a main component of a polarizing plate, is a device that transmits only light of a polarization plane in a specific direction. A representative polarizer currently known is a polyvinyl alcohol-based polarizing film, which includes polyvinyl alcohol-based films dyed with iodine and films dyed with dichroic dyes. The polarizer is used by forming a film of an aqueous polyvinyl alcohol solution, stretching it uniaxially and dyeing it, or stretching it uniaxially after dyeing and then preferably performing a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, and particularly preferably 10 to 20 μm.

[0310] In addition, ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000, and a degree of saponification of 99.0 to 99.99 mol% as described in Japanese Patent Publication No. 2003-248123, Japanese Patent Publication No. 2003-342322, etc. is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73°C is preferably used. Furthermore, it is more preferable for reducing color stains that the difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the film is 1°C or less, and it is even more preferable for reducing color stains that the difference in hot water cutting temperature between two points 1 cm apart in the TD direction of the film is 0.5°C or less.

[0311] Polarizers using this ethylene-modified polyvinyl alcohol film have excellent polarization performance and durability, and have low color staining, making them particularly suitable for use in large liquid crystal displays.

[0312] The polarizer obtained as described above is typically used as a polarizing plate with a protective film laminated onto both or one side thereof. Examples of adhesives used for lamination include PVA-based adhesives and urethane-based adhesives, but among these, PVA-based adhesives are preferably used.

[0313] (IPS mode liquid crystal display)

[0314] By inserting the polarizing plate of the present invention into a commercially available IPS (In Plane Switching) mode liquid crystal display device, a liquid crystal display device of the present invention with excellent visibility and an expanded viewing angle can be manufactured.

[0315] The IPS modes related to the present invention also include a Fringe-Field Switching (FFS) mode. By incorporating the polarizer of the present invention, a liquid crystal display device of the present invention having the same effect can be manufactured.

[0316] When installing the polarizing plate protection film of the present invention on a liquid crystal display device, typically a viewing-side polarizer and a backlight-side polarizer are configured on both sides of the liquid crystal cell. However, it is preferable to install at least one polarizing plate protection film between the liquid crystal cell and the viewing-side polarizer or between the liquid crystal cell and the backlight-side polarizer, such that the polarizing plate protection film of the present invention is on the liquid crystal cell side.

[0317] [Example]

[0318] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Additionally, in the examples, the notations "parts" or "%" are used, but unless otherwise specifically stated, "parts by mass" or "mass%" are indicated.

[0319] [Example 1]

[0320] (Cellulose ester resin)

[0321] Diacetylcellulose 1: Acetyl substitution degree 2.45, number average molecular weight 70,000 (listed as DAC1 in the table)

[0322] Diacetylcellulose 2: Acetyl substitution degree 2.30, number average molecular weight 70,000 (listed as DAC2 in the table)

[0323] Diacetylcellulose 3: Acetyl substitution degree 2.60, number average molecular weight 70,000 (listed as DAC3 in the table)

[0324] Triacetylcellulose: Degree of acetyl substitution 2.93, number average molecular weight 70,000 (listed as TAC in the table)

[0325] Cellulose acetate butyrate: Degree of acetyl substitution 1.29, degree of butyryl substitution 1.66, degree of polymerization 230, number average molecular weight 70,000 (listed as CAB in the table)

[0326] Cellulose acetate propionate: Degree of acetyl substitution 0.32, degree of propionyl substitution 2.60, degree of polymerization 250, number average molecular weight 70,000 (listed as CAP in the table)

[0327] (sugar ester)

[0328] Sugar ester 1: Sucrose octaacetate of the following structure (Ac represents an acetyl group.)

[0329] [Chemical Formula 11]

[0330]

[0331] Sugar ester 2:

[0332] In the sugar ester used in Table 2, No. 7 of Japanese Patent Publication No. 2014-149325 Paragraph No.

[0265] , the sugar ester was synthesized by changing the type and number of substituents of the aliphatic alkyl group (AL) and the aromatic alkyl group (AR) to 6 acetyl groups and 2 benzoyl groups, respectively, and the sugar ester was made into sugar ester 2.

[0333] In addition, in the table, “(number of substituents of AL + AR / total number of OH groups)” represents the total number of aliphatic alkyl groups (AL) and aromatic alkyl groups (AR) substituents for the total OH groups that are substituents of the sugar ester, and for example, “6 / 8” indicates that 6 of the 8 substituents are substituents of AL and / or AR.

[0334] Sugar ester 3:

[0335] In paragraph

[0048] [Formula 5] of International Publication No. 2011 / 135980, a sugar ester compound represented by compound name a3 was used as sugar ester 3. The sugar ester 3 was synthesized by changing the type and number of substituents of the aliphatic alkyl group (AL) and aromatic alkyl group (AR) to 6 benzoyl groups and 2 acetyl groups, respectively.

[0336] (Polyester 1)

[0337] A mixture of compounds represented by the following structures was used as polyester 1. The number average molecular weight of the mixture is 450, and n = 1.5401.

[0338] [Chemical Formula 12]

[0339]

[0340] <Production of Optical Film 1>

[0341] (Judov's Jose)

[0342] A main paste of the following composition was prepared. First, methylene chloride and ethanol were added to a pressurized dissolution tank. Diacetylcellulose 1 was added to the pressurized dissolution tank containing the solvent while stirring, and the mixture was heated and completely dissolved while stirring.

[0343] Diacetylcellulose 1 100 parts by mass

[0344] Sugar ester 1 7 parts by mass

[0345] Matte: 1.4 parts by mass of 12% ethanol dispersion of R812 (manufactured by Nihon Aerosil Co., Ltd.)

[0346] 430 parts by mass of methylene chloride

[0347] 40 parts by mass of ethanol

[0348] The above additive components were placed in a sealed container and dissolved while stirring, and the mixture was filtered using Azumi Filter Paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. to prepare a main sauce.

[0349] (Preparation of optical film 1)

[0350] The above-described main tube was uniformly stretched onto a stainless steel band support at a temperature of 22°C and a width of 1.8 m using a belt stretching device. The stretching film thickness was 46.3 μm before the stretching treatment, and the solvent was evaporated from the stainless steel band support until the residual solvent amount was 75%, and the tube was peeled off from the stainless steel band support with a peeling tension of 180 N / m.

[0351] Next, the web of the peeled main pipe 1 was subjected to solvent evaporation at 35°C, and then, in the first stretching process, it was stretched in the width direction relative to the original width by a stretching ratio of 1.12 times (12%) using a tenter stretching device at a temperature of 140°C ("TD stretching"). The solvent was evaporated until the residual solvent amount was 3% or less. At that time, when the glass transition temperature of the optical film was denoted as Tg, Tg was 155°C.

[0352] The above glass transition temperature was determined by reading the glass transition temperature (Tg) from the endothermic peak when the film sample was heated using a DSC (differential scanning calorimetry) in a temperature range of -30 to 200 ℃ at a heating rate of 10 (℃ / min).

[0353] Next, in the second stretching process, the original width was stretched 1.88 times (88%) in the width direction at a temperature of 215°C by a tenter stretching device. At this time, the amount of residual solvent when stretching by the tenter was started was 0.5%. Therefore, the total stretching ratio in the first and second stretching processes is 2 times (100%) the original width.

[0354] Subsequently, the sequentially stretched optical film was cooled in a precipitation suppression zone at a zone temperature of 150°C, and then the drying was completed by conveying it to a plurality of rollers at a temperature of 120°C in a drying zone. The obtained optical film was cut to a total length of 150 mm at both ends and slit to a width of 2500 mm. In addition, knurling with a width of 10 mm and a height of 2.5 μm was performed on both ends of the optical film, and then wound onto a core to produce the optical film 1 of the present invention. The film thickness was 30 μm, and the winding length was 6000 m.

[0355] <Production of Optical Film 2>

[0356] (Judov's Jose)

[0357] In the production of optical film 1, polyester was added to the base paste to prepare a base paste of the following composition. First, methylene chloride and ethanol were added to a pressurized melting tank. Diacetylcellulose 2 was added to the pressurized melting tank containing the solvent while stirring, and the mixture was heated and completely dissolved while stirring.

[0358] Diacetylcellulose 2 100 parts by mass

[0359] Sugar ester 1 7 parts by mass

[0360] Polyester 1 4 parts by mass

[0361] Matte: 1.4 parts by mass of 12% ethanol dispersion of R812 (manufactured by Nihon Aerosil Co., Ltd.)

[0362] 430 parts by mass of methylene chloride

[0363] 40 parts by mass of ethanol

[0364] Next, the film was formed in the same manner as the production of optical film 1, and sequential stretching treatment by TD stretching was performed while passing through a first stretching process, a second stretching process, a precipitation inhibition zone, and a drying zone under the conditions listed in Table I, thereby obtaining an optical film 2 with a product width of 2500 mm after slitting.

[0365] <Production of Optical Film 3>

[0366] In the production of optical film 1, polyester was added to the base paste to prepare a base paste of the following composition. First, methylene chloride and ethanol were added to a pressurized melting tank. Diacetylcellulose 3 was added to the pressurized melting tank containing the solvent while stirring, and the mixture was heated and completely dissolved while stirring.

[0367] Diacetylcellulose 3 100 parts by mass

[0368] Sugar ester 1 7 parts by mass

[0369] Polyester 1 4 parts by mass

[0370] Matte: 1.4 parts by mass of 12% ethanol dispersion of R812 (manufactured by Nihon Aerosil Co., Ltd.)

[0371] 430 parts by mass of methylene chloride

[0372] 40 parts by mass of ethanol

[0373] Next, the film was formed in the same manner as the production of optical film 1, and sequential stretching treatment by MD stretching and TD stretching was performed while passing through a first stretching process, a second stretching process, a precipitation inhibition zone, and a drying zone under the conditions listed in Table I, and an optical film 3 with a product width of 2500 mm after slitting was obtained.

[0374] <Production of Optical Films 4–18>

[0375] In the production of optical film 1, optical films 4 to 18 were produced by varying the addition and amount of polyester, the type and amount of sugar ester, the temperature and stretching ratio of the first stretching process, the temperature and stretching ratio of the second stretching process, the temperature of the precipitation inhibition zone, the product width after slitting, and the product film thickness, respectively, as described in Table I. In addition, optical films No. 12 to 18 were produced for the following purposes.

[0376] Optical film 12 reduced the total stretching magnification and narrowed the slit width.

[0377] Optical film 13 increased the total stretching ratio to make the product film thickness thin.

[0378] Optical film 14 increased the stretching ratio in the first stretching process.

[0379] Optical film 15 was subjected to three sequential stretching treatments by dividing the second stretching process into two.

[0380] In the first stretching process, the optical film 16 is stretched (MD stretching) in the longitudinal direction at a stretching ratio of 1.12 times (12%) at a temperature of 140°C using a roller peripheral speed difference between them, and then in the second stretching process, it is stretched in the width direction at a temperature of 215°C by a tenter stretching device by 1.88 times (88%) relative to the original width.

[0381] Optical film 17 was subjected to a precipitation inhibition zone temperature of 100°C, and the temperature of the optical film stretched in the second stretching process was rapidly cooled.

[0382] Optical film 18 was made by stretching a main pipe onto a stainless steel band support of a belt flexibleing device so that the flexible film thickness was 11.2 μm before stretching treatment, and then stretching it at a low magnification (12% each for both the first and second) to produce an optical film with a film thickness of 10 μm.

[0383] <Production of Optical Films 19–21: Comparative Example>

[0384] In the production of optical film 1, the triacetylcellulose, cellulose acetate butyrate, and cellulose acetate propionate were used instead of the cellulose ester resin diacetylcellulose 1, and the film formation and stretching were performed in the same manner. As a result, as described in Table II, the film broke and could not be stretched, and the film dissolved and could not be stretched, respectively, and an optical film could not be obtained.

[0385] <Production of Optical Film 22: Comparative Example>

[0386] In the production of optical film 1, the main paste was prepared without adding sugar ester 1 and the film was formed, and as a result, the glass transition temperature Tg of the optical film increased, and "the film broke and could not be stretched."

[0387] <Production of Optical Film 23: Comparative Example>

[0388] In the production of optical film 1, a main paste was prepared in the same manner as in the production of optical film 1, except that sugar ester 1 was replaced with sugar ester 3, and the film formation and stretching treatments described in Table II were performed to produce optical film 23.

[0389] <Production of Optical Films 24, 25: Comparative Example>

[0390] In the production of optical film 10, the film formation and stretching treatments described in Table II were performed in the same manner except that the temperature of the second stretching process was changed to 185°C, and an optical film 24 was produced.

[0391] Likewise, in the production of optical film 10, the film formation and stretching treatment described in Table II were performed in the same manner except that the temperature of the second stretching process was changed to 230°C, and as a result of producing optical film 25, "the film melted and could not be stretched."

[0392] <Production of Optical Film 26: Comparative Example>

[0393] In the production of the optical film (10), as an online stretching process, the first stretching process was performed under the temperature conditions of the second stretching process, and as a result of not performing sequential stretching by the second stretching process, the film was broken and could not be stretched, and the optical film could not be obtained.

[0394] <Production of Optical Films 27–32: Reference Example>

[0395] In the production of optical film 1, a dope prepared by varying the type of cellulose ester resin and the presence or absence of sugar ester addition was flexible to produce a web, and in the first stretching process, only drying was performed at 140°C without stretching treatment to obtain unstretched optical films 27 to 32, which are reference examples.

[0396] ≪Evaluation≫

[0397] Unless otherwise noted, the evaluation was performed by humidifying the optical film for 24 hours at 23 ℃ and 55 %RH, and then measuring it under the same environment.

[0398] <Retardation Value>

[0399] The in-plane retardation value R of the optical film o , and retardation value R in the thickness direction t It was calculated using the following equations (i) and (ii).

[0400] Equation (i) R o = (n x - n y ) × d

[0401] Equation (ii) R t ={(n x + n y ) / 2 - n z}× d

[0402] During the meal, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n zθ represents the refractive index in the thickness direction of the film, and d represents the thickness of the film (nm).

[0403] The above refractive index and film thickness were measured by using an Abbe refractive index meter (4T) to measure the average refractive index of randomly sampled optical films. In addition, the average thickness of the film was measured using a commercially available micrometer.

[0404] The retardation of the optical film was measured using an automatic birefringent KOBRA-21ADH (manufactured by Oji Measuring Instruments Co., Ltd.) on a film left for 24 hours in an environment of 23°C and 55%RH, at a wavelength of 590 nm under the same environment.

[0405] The evaluation rank is as follows. R o and R t When the value of (nm) is expressed as an absolute value,

[0406] ◎ : 0 ∼ 2 (nm)

[0407] ○ : 3 ∼ 5 (nm)

[0408] △ : 6 ∼ 10 (nm)

[0409] × : 11 (nm) or more

[0410] ◎, ○, and △ are considered to be of no practical use.

[0411] <Humidity variation of retardation value: ΔR o / R t >

[0412] The difference ΔR in retardation values ​​when the above optical film is measured in the same way after being left for 24 hours in environments of 23°C·20%RH and 23°C·80%RH o and ΔR t The absolute value of was calculated and used as an indicator of the deviation of the retardation value during environmental changes.

[0413] ΔR o (nm) = |R o (23 ℃·20 %RH) - R o (23 ℃·80 %RH)|

[0414] ΔR t (nm) = |R t (23 ℃·20 %RH) - R t (23 ℃·80 %RH)|

[0415] The evaluation ranks are as follows.

[0416] ◎ : 0 ∼ 1 (nm)

[0417] ○ : 2 ∼ 3 (nm)

[0418] △ : 3 ∼ 5 (nm)

[0419] × : 6 (nm) or more

[0420] ◎, ○, and △ are considered to be of no practical use.

[0421] <Measurement of Elastic Modulus>

[0422] The measurement conditions for the elastic modulus of an optical film (also called tensile elastic modulus) are set as follows, and the elastic modulus is obtained by linear regression between a deformation of 0.05 to 0.25%.

[0423] For the MD direction, the tensile modulus was measured in accordance with JIS K7127 (1999) using the following method.

[0424] 1) Cut the optical film to a size of 100 mm (MD direction) × 10 mm (TD direction) and use it as a test specimen.

[0425] 2) Using a Tensilon RTC-1225A manufactured by Orientech, the test specimen was stretched in the longitudinal direction (MD direction) at a tensile speed of 50 mm / min with a chuck distance of 50 mm, and the tensile modulus in the MD direction was measured. The measurement was performed under 23 ℃ and 55 %RH.

[0426] <YI : Yellow Index Value>

[0427] The yellow index value was determined according to the film's YI (Yellow Index: index of yellowness) specified in JIS K7103. As a method for measuring the yellow index value, a sample of the optical film was prepared, and using the spectrophotometer U-3300 of Hitachi High Technologies Co., Ltd. and the attached chroma calculation program, the three stimulus values ​​X, Y, and Z of the light source color specified in JIS Z 8701 were obtained, and the yellow index value was calculated according to the definition of the following formula.

[0428] Yellow Index Value (YI Value) = 100(1.28X - 1.06Z) / Y

[0429] The evaluation ranks are as follows.

[0430] ◎ : 0 ∼ 0.8

[0431] ○ : 0.9 ∼ 1.2

[0432] △ : 1.3 ∼ 1.8

[0433] × : 1.9 or higher

[0434] ◎, ○, and △ are considered to be of no practical use.

[0435] <Heize>

[0436] Haze (total haze) was measured using a haze meter (NDH-2000 (manufactured by Nippon Denkaku Kogyo Co., Ltd.)) in accordance with JIS K-7136.

[0437] The evaluation ranks are as follows.

[0438] ◎ : 0 ∼ 0.7

[0439] ○ : 0.8 ∼ 1.0

[0440] △ : 1.1 ∼ 1.5

[0441] × : 1.6 or more

[0442] ◎, ○, and △ are considered to be of no practical use.

[0443] < 13 Measurement of Longitudinal Relaxation Time T1 by C-NMR

[0444] optical film 13 The longitudinal relaxation time T1 by C-NMR was measured as follows.

[0445] A 50 mg film sample was measured and taken, and using the JNM-ECA400W manufactured by JEOL RESONANCE, by CCP / MAS 13 C-NMR measurements were performed, and the longitudinal relaxation time T1 originating from the [ring 1] region of the cellulose backbone of Figure 1 was calculated by the Torcia method.

[0446] In addition, the measurement conditions were set to 23 ℃, relaxation delay 3 seconds, number of integration cycles 512, and resonance frequency 100 MHz.

[0447] The composition of the optical film and the evaluation results are shown in Tables I, II, and III.

[0448] [Table I]

[0449]

[0450] [Table II]

[0451]

[0452] [Table III]

[0453]

[0454] From Tables I, II, and III, it can be seen that optical films 1 to 18 related to the composition of the present invention have excellent wide-width suitability compared to comparative examples, in that they have excellent performance such as elastic modulus, YI value, and haze even when stretched to a very wide width, and also have excellent retardation performance and resistance to environmental variations of retardation.

[0455] [Example 2]

[0456] (1) Fabrication of a polarizing plate

[0457] <Fabrication of Polarizing Plates 1 to 18>

[0458] Polarizing plates 1 to 18 were fabricated using the optical films 1 to 18 produced above.

[0459] (Fabrication of a polarizer)

[0460] A polyvinyl alcohol film with a thickness of 45 μm was swollen with water at 35°C. The obtained film was immersed for 60 seconds in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and further immersed in an aqueous solution at 45°C consisting of 3 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. The obtained film was uniaxially stretched under conditions of a stretching temperature of 55°C and a stretching ratio of 5x. After washing the uniaxially stretched film with water, it was dried to obtain a polarizer with a thickness of 15 μm.

[0461] (Preparation of active energy beam curable adhesive solution: cation polymerization type)

[0462] After mixing each of the following components and degassing, an active energy beam curable adhesive solution was prepared. In addition, triarylsulfonium hexafluorophosphate was incorporated as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate is indicated below.

[0463] 3,4-Epoxycyclohexylmethyl-3,4-Epoxycyclohexanecarboxylate 45 parts by mass

[0464] Eporide GT-301 (cycloaliphatic epoxy resin manufactured by Daicel Chemical Co., Ltd.) 40 parts by mass

[0465] 1,4-butanediol diglycidyl ether 15 parts by mass

[0466] 2.3 parts by mass of triarylsulfonium hexafluorophosphate

[0467] 9,10-dibutoxycyanthracene 0.1 parts by mass

[0468] 2.0 parts by mass of 1,4-diethoxynaphthalene

[0469] (Fabrication of polarizing plates)

[0470] A polarizing plate was manufactured according to the following method.

[0471] First, as protective film 1, a KC6UA film (manufactured by Konica Minolta Inc.) was prepared, and the above-prepared active energy beam curable adhesive solution was coated to a thickness of 5 μm using a micro-gravure coater (gravure roller: #300, rotation speed 140% / line speed) to form an active energy beam curable adhesive layer a.

[0472] Next, the prepared active energy beam curable adhesive liquid was coated onto the optical film 1 prepared above, in the same manner as above, to a thickness of 5 μm, and an active energy beam curable adhesive layer b was formed.

[0473] A polyvinyl alcohol-iodine-based polarizer fabricated above was placed between the active energy beam curable adhesive layers a and b, and laminated using a roller machine to obtain a laminate in which a protective film 1 / active energy beam curable adhesive layer / polarizer / active energy beam curable adhesive layer / optical film 1 is laminated. At that time, the lamination was performed using a roller machine such that the ground axis of the optical film and the absorption axis of the polarizer were orthogonal to each other.

[0474] Polarizer 1 was fabricated by irradiating electron beams from both sides of this laminate.

[0475] The line speed was set to 20 m / min, the acceleration voltage to 250 kV, and the irradiation dose to 20 kGy.

[0476] Polarizers 2 to 18 were produced in the same manner, except that optical films 2 to 18 were used instead of optical film 1. In addition, comparative polarizers 23 and 24 were produced in the same manner, using optical films 23 and 24 of the comparative example.

[0477] (2) Fabrication of liquid crystal display devices

[0478] On both sides of an IPS mode type liquid crystal cell, the polarizing plates manufactured above were attached so that the optical film of the present invention came into contact with the liquid crystal cell. The two polarizing plates were attached in a cross-Nicole arrangement to obtain a liquid crystal display device. In addition, the optical films of the two polarizing plates used had the same number.

[0479] ≪Evaluation≫

[0480] <Polarizing Plate Durability>

[0481] For the above-mentioned fabricated polarizers, samples conditioned for 24 hours under an atmosphere of 23°C and 55%RH were first subjected to parallel transmittance and orthogonal transmittance under the same conditions, and the degree of polarization was calculated according to the following formula. Subsequently, each polarizer was subjected to forced degradation for 1000 hours under conditions of 60°C and 90%RH, after which the parallel transmittance and orthogonal transmittance were measured again, and the degree of polarization was calculated according to the following formula. The amount of change in the degree of polarization was obtained using the following formula.

[0482] Degree of polarization P = ((H0 - H90) / (H0 + H90))0.5 × 100

[0483] Change in polarization degree = P0 - P1000

[0484] H0: Parallel transmittance

[0485] H90: Orthogonal transmittance

[0486] P0: Polarization degree before forced degradation

[0487] P1000: Polarization degree after 1,000 hours of forced degradation

[0488] (metewand)

[0489] ○ : Rate of change in polarization degree less than 10%

[0490] △ : Rate of change in polarization degree 10% or more and less than 25%

[0491] × : Change rate of polarization degree 25% or more

[0492] If the rate of change in polarization degree is 25% or more, when a polarizing plate is inserted into a display device, non-uniformity in display due to environmental fluctuations can be visually confirmed, and it is judged to be a defective product.

[0493] <Evaluation of Front Contrast of Display Device>

[0494] The front contrast of the above-described IPS mode liquid crystal display device was evaluated by the following method.

[0495] The liquid crystal display device manufactured above was placed on a schaucasten set up in a bright room such that the substrate on which the electrode is formed among the substrates constituting the liquid crystal cell faces the schaucasten. Then, using a luminance meter (spectral radiance meter CS-1000: manufactured by Konica Minolta Inc.) installed 1 m away in the normal direction of the liquid crystal cell, the luminance when white is displayed and the luminance when black is displayed were measured, respectively. Based on this, the ratio of luminance (luminance when white is displayed / luminance when black is displayed) was calculated and set as the contrast ratio.

[0496] And, frontal contrast was evaluated based on the following criteria.

[0497] ◎ : Contrast ratio of 400 or higher

[0498] ○ : Contrast ratio is 360 or higher and less than 400

[0499] △ : Contrast ratio of 320 or more and less than 360

[0500] × : Contrast ratio less than 320

[0501] The evaluation results of the above polarizer and liquid crystal display device are shown in Table IV.

[0502] [Table IV]

[0503]

[0504] Polarizers 1 to 18 using optical films 1 to 18 of the examples had polarizer durability in the range of △ to ○, whereas polarizers 23 and 24 using optical films 23 and 24 of the comparative examples had polarizer durability of ×, which was inferior, and it was clearly evident that the optical films of the examples had excellent resistance to environmental fluctuations. Therefore, it can be seen that by mounting a polarizer using the optical film of the present invention on an IPS mode liquid crystal display device, a display device is obtained in which the occurrence of non-uniformity in screen display is suppressed even due to environmental fluctuations.

[0505] In addition, it was confirmed that the liquid crystal display devices 1 to 18, which incorporate polarizing plates 1 to 18 using optical films 1 to 18 of the examples, have superior front contrast compared to the comparative examples. Explanation of the symbols

[0506] 1 : Melting furnace 3, 6, 12, 15: Filter 4, 13: Stock kiln 2, 5, 14: Fluid delivery pumps 8, 16: Conduit 10: Kiln for inserting UV absorber 20: Confluence pipe 21 : Mixer 30: Pressurized die 31 : Metal belt (support) 32: Web or long film 33: Detachment location 34: Stretching device of the first stretching process 35: Stretching device of the second stretching process 36: Precipitation inhibition zone 37: Drying device 38: Return roller 39: Optical film winding device 40: Optical film rolls 41 : Input kiln 42 : Stock kiln 43 : Pump 44 : Filter

Claims

Claim 1 A method for manufacturing an optical film containing at least a cellulose ester resin comprises the steps of: forming a long film by spreading a dope containing at least a cellulose ester resin and a sugar ester on a support; and stretching the formed long film, wherein the cellulose ester resin has a total acetyl group substitution degree within the range of 2.30 to 2.60, and the sugar ester is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or a pyranose structure, or a hydroxyl group in a compound (B) having at least two but no more than twelve of the furanose structure or a pyranose structure bonded together, is esterified by an aliphatic acyl group, and the optical film has a retardation value R defined by the following formula (i). o α is within the range of 0 to 10 nm, and the retardation value R is defined by the following equation (ii). t A method for manufacturing an optical film, wherein the length is within the range of -10 to 10 nm, and the process of stretching the formed long film comprises, in this order, a first process of obtaining a first stretched long film and a second process of further stretching the first stretched long film to obtain a second stretched film, wherein the stretching temperature of the second process is within the range of 190 to 220 ℃, and the process of stretching the formed long film comprises, after the second process, a precipitation inhibition zone, and the temperature of the precipitation inhibition zone is within the range of -100 to -50 ℃ compared to the stretching temperature of the second process. Formula (i) R o = (n x - n y ) × d (ii) R t ={(n x + n y ) / 2 - n z }× d(formula, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n z θ represents the refractive index in the thickness direction of the film (refractive index measured at a wavelength of 590 nm under conditions of 23 ℃ and 55 %RH), and d represents the film thickness (nm). Claim 2 A method for manufacturing an optical film according to claim 1, characterized in that the content of the sugar ester is within the range of 10 to 25 mass%. Claim 3 A method for manufacturing an optical film according to claim 1, characterized in that the dope further contains polyester. Claim 4 A method for manufacturing an optical film according to claim 3, characterized in that the content of the polyester is within the range of 5 to 15 mass%. Claim 5 delete Claim 6 A method for manufacturing an optical film according to claim 1 or 2, characterized in that the stretching temperature of the second process is within the range of +60 to +100 ℃ compared to the stretching temperature of the first process. Claim 7 In claim 1 or 2, the difference ΔR in retardation values ​​when the optical film is measured in the same way after being left for 24 hours in environments of 23°C·20%RH and 23°C·80%RH. o and ΔR t A method for manufacturing an optical film characterized in that the absolute values ​​are all 5 nm or less. Claim 8 In claim 1 or 2, the optical film 13 A method for manufacturing an optical film characterized by a longitudinal relaxation time T1 measured by C-NMR being within the range of 50 to 80 seconds. Claim 9 An optical film comprising at least a cellulose ester resin, wherein the cellulose ester resin has a total degree of acetyl group substitution in the range of 2.30 to 2.60, and additionally contains a sugar ester, wherein the sugar ester is a compound in which all or part of a hydroxyl group in a compound (A) having one furanose structure or pyranose structure, or a compound (B) in which at least 2 to 12 of at least one type of furanose structure or pyranose structure are bonded, is esterified by an aliphatic acyl group, and the optical film has a retardation value R defined by the following formula (i). o α is within the range of 0 to 10 nm, and the retardation value R is defined by the following equation (ii). t The difference ΔR in retardation values ​​when the optical film is within the range of -10 to 10 nm and is measured in the same way after being left for 24 hours under environments of 23 ℃·20 %RH and 23 ℃·80 %RH. o and ΔR t The absolute values ​​of are all 5 nm or less, and furthermore, the optical film 13 An optical film characterized by a longitudinal relaxation time T1 measured by C-NMR being within the range of 50 to 80 seconds. Formula (i) R o = (n x - n y ) × d (ii) R t ={(n x + n y ) / 2 - n z }× d(formula, n x is the refractive index in the direction of the ground axis within the film plane, n y is the refractive index in the direction of the true image axis within the film plane, n z θ represents the refractive index in the thickness direction of the film (refractive index measured at a wavelength of 590 nm under conditions of 23 ℃ and 55 %RH), and d represents the film thickness (nm). Claim 10 An optical film according to claim 9, characterized in that the content of the sugar ester is within the range of 10 to 25 mass%. Claim 11 A polarizing plate characterized by having the optical film described in claim 9 or 10 laminated to at least one surface of a polarizer. Claim 12 A liquid crystal display device characterized by using the polarizing plate described in claim 11 on at least one surface of a liquid crystal cell. Claim 13 A liquid crystal display device characterized by being an IPS mode type liquid crystal display device in claim 12.

Images