Cellulose ester film, method for producing the same, polarizing plate, and liquid crystal display device

Abstract

This invention relates to the field of optical film technology, specifically to cellulose ester films and their preparation methods, polarizing plates, and liquid crystal display devices. The raw materials for preparation include at least: cellulose resin with an acyl substitution degree of 2.50-3.00, sucrose derivatives of formula (1) with a total average substitution degree of 4.5-8.0, microparticles, additives, and solvents. In formula (1), R is a hydrogen atom, a straight-chain or branched aliphatic group with a substituent, a substituted or unsubstituted cycloalkyl group, and a substituted or unsubstituted aromatic group. R may be the same or different. By optimizing the cotton glue composition system, cellulose ester films with reduced adhesion during overlapping are prepared. When winding thinner, wider, or lower elastic modulus films, appearance defects such as pits, wrinkles, and adhesion marks are avoided, ensuring the subsequent polarizing plates and liquid crystal displays, and meeting the development needs of thinner and larger products.

Description

Technical Field

[0001] This invention relates to the field of optical film technology, specifically to cellulose ester films and their preparation methods, polarizing plates, and liquid crystal display devices. Background Technology

[0002] Cellulose ester films are widely used as optical films such as protective films for polarizers, retardation films, anti-reflective films, and transparent conductive films. Cellulose ester films are generally produced using solution casting methods. A cellulose ester adhesive solution is continuously cast onto the surface of a support through a casting die to form a strip-shaped film. After being peeled off from the support and dried, the elongated film is wound onto a core and stored in rolls. During the winding process, overlapping portions may sometimes stick together, or excessive pressure may cause the film to collapse and wrinkle. After unwinding, the product may have adhesion marks and creases, affecting its appearance and ultimately impacting the polarizer and liquid crystal display. Chinese patent application (publication number CN117126503A) discloses a film roll, its manufacturing method, a polarizer, and a display device. It primarily provides a film roll without residual tape transfer marks and without chain-like film deformation caused by air leakage during long-term storage by making the inter-film gap layer at the periphery of the roll core thicker than the gap layer at the outer periphery of the roll without knurling. However, in actual production, with the trend towards thinner and larger products, when winding thinner, wider films or films with lower elastic modulus, the overlapping portions of the films are more likely to stick together. Summary of the Invention

[0003] To address the aforementioned issues, this invention optimizes the cotton adhesive composition system to prepare cellulose ester films that reduce adhesion during overlapping. When winding thinner, wider, or lower elastic modulus films, it avoids appearance defects such as pits, wrinkles, and adhesion marks, ensuring the subsequent polarizing plates and liquid crystal displays meet the development needs of thinner and larger products.

[0004] This invention provides a cellulose ester film, the raw materials for which include at least: a cellulose resin with an acyl substitution degree of 2.50-3.00, a sucrose derivative of formula (1) with a total average substitution degree of 4.5-8.0, microparticles, additives, and a solvent.

[0005] Equation (1), Where R is a hydrogen atom, a straight-chain or branched aliphatic group with substituents, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted aromatic group.

[0006] When R is an aliphatic group or a cycloalkyl group, specific examples include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, and dodecyl. Substituents for these aliphatic groups or cycloalkyl groups include hydroxyl, alkoxy, mercapto, thioether, halogen atoms (fluorine, chlorine, bromine, iodine), cyano, sulfonyl, carboxyl, ester, nitro, isohydroxamic acid, sulfinyl, hydrazine, and imino.

[0007] When R is an aromatic group, it is selected from aromatic hydrocarbon groups or aromatic heterocyclic groups, and more preferably aromatic hydrocarbon groups.

[0008] The aromatic hydrocarbon group preferably has 6-24 carbon atoms, more preferably 6-12 carbon atoms. Specific examples of aromatic hydrocarbon groups include benzene, naphthalene, anthracene, biphenyl, terphenyl, with roximately naphthalene, naphthalene, and biphenyl being preferred.

[0009] The aromatic heterocyclic group preferably contains at least one of an oxygen atom, a nitrogen atom, and a sulfur atom. Specific examples of aromatic heterocyclic groups include furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline, phthalazine, naphthidine, quinoxaline, quinazoline, porphyrin, pteridine, acridine, phenanthroline, phenazine, tetrazolium, benzimidazole, benzoxazole, benzothiazole, benzotriazole, and tetrazanaphthalene, preferably pyridine, triazine, and quinoline.

[0010] Preferably, examples of R include lactose, sucrose, fructotetraose, fructopentose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose, 1-fructotriose, gentiobiose, gentiotriose, gentiotetraose, xylitol, galactosylsucrose, preferably one of sucrose, fructopentose, and stachyose, more preferably sucrose.

[0011] An example of the preparation method of the sucrose derivative is as follows:

[0012] Take 34.2g of sucrose, 100g of pyridine, and 300mL of ethyl acetate in a 1000mL three-necked flask, keep the temperature at 35℃, and add ethyl acetate solution containing 90g of N-methylglycyl chloride dropwise over 40 minutes. After the addition is complete, continue heating for 10 minutes to obtain sucrose benzoate with a degree of substitution of 6.8.

[0013] As a preferred technical solution, the amount of sucrose derivative added, based on the mass of cellulose resin, is 2-20 wt%, preferably 4-15 wt%, more preferably 6-12 wt%, and most preferably 6-10 wt%.

[0014] As a preferred technical solution, the total average degree of substitution of the sucrose derivative is 5.5-8.0.

[0015] As a preferred technical solution, the sucrose derivative is selected from at least one of sucrose benzoate, sucrose isobutyrate, sucrose octaacetate, and sucrose hexaacetate.

[0016] As a preferred technical solution, the degree of acyl substitution of the cellulose resin is 2.70-2.96. The degree of acyl substitution of cellulose can be tested according to ASTM D-817-96 test method or nuclear magnetic resonance method.

[0017] As a preferred technical solution, the average degree of polymerization of the cellulose resin is 180–700, preferably 180–400, and particularly preferably 180–350. The average degree of polymerization can be determined using the intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of the Textile Society, Vol. 18, No. 1, pp. 105–120, 1962). The specific test method is as follows:

[0018] Weigh 0.2 g of the dried sample (accurate to 0.0001 g) into a 150 ml Erlenmeyer flask with a stopper. Add 50 ml to 70 ml of a mixed solvent of dichloromethane and methanol [(92+8) V / V]. Shake and let stand for 8 to 10 hours until completely dissolved. Then transfer the solution to a 100 ml volumetric flask and place it in a constant temperature water bath at (25±0.1) °C for 1 hour. Simultaneously... The Orthophile viscometer is placed vertically in a water bath for later use.

[0019] Dilute the sample solution to the mark using a mixed solvent, and pipette 10 ml into the bottom bulb of the viscometer. After the air bubbles disappear (10 minutes), use a suction bulb to fill the two upper bulbs of the viscometer with the sample solution. Then allow the sample solution to flow naturally through the capillary tube. Use a stopwatch to record the time it takes for the solution to flow through the marks at both ends of the second bulb. Repeat the measurement several times and take the average of the two closest measurements as t.

[0020] Simultaneously perform a blank test, taking the average of two similar measurements in the blank test as t0. The blank measurement should be performed before the sample measurement, that is, first measure the viscosity of the blank, then dry the viscometer, and then measure the viscosity of the sample.

[0021] The average degree of polymerization (DP) is calculated using the following formula:

[0022]

[0023] In the formula:

[0024] t — the average time (s) it takes for the sample solution to flow through the two markings.

[0025] t0 — the average time (in seconds) for the blank solution to flow through the two markings.

[0026] c — Sample concentration (g / L)

[0027] 2.303 / (6×10 -4 — A constant in the calculation formula.

[0028] As a preferred technical solution, the mass-average molecular weight (Mw) of the cellulose resin is 100,000-400,000, more preferably 150,000-370,000, more preferably 50,000-250,000, and even more preferably 70,000-200,000.

[0029] As a preferred technical solution, the dispersion index Mw / Mn (Mw is the mass-average molecular weight, Mn is the number-average molecular weight) of the cellulose resin is 1.0 to 4.0, more preferably 1.3 to 3.7, and most preferably 1.6 to 3.4.

[0030] The mass-average molecular weight and number-average molecular weight of cellulose resins can be measured by gel permeation chromatography.

[0031] As a preferred technical solution, the cellulose resin is cellulose acetate, preferably cellulose triacetate.

[0032] The raw material cellulose for cellulose acetate is not particularly limited; examples include cotton lint, wood pulp (from coniferous trees, broadleaf trees, kenaf, etc.), and cellulose acetate obtained by mixing these materials in any proportion. The cellulose acetate of the present invention can be manufactured by known methods. Specifically, it can be synthesized according to the method described in Japanese Patent Application Publication No. 10-45804.

[0033] The hydroxyl groups substituted in cellulose are any of acyl aliphatic or aromatic groups having 2 to 22 carbon atoms. Cellulose acylates substituted with these groups include cellulose alkyl carbonyl esters, cellulose alkenyl carbonyl esters, cellulose aromatic carbonyl esters, and cellulose aromatic alkyl carbonyl esters, each of which may further have substituents.

[0034] Preferred acyl groups include acetyl, propionyl, butyryl, heptayl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecayl, tetradecanoyl, hexadecanoyl, octadecanoyl, isobutyryl, tert-butyryl, cyclohexanecarbonyl, oleoyl, benzoyl, naphthylcarbonyl, and cinnamoyl. More preferably, acetyl, propionyl, butyryl, dodecanoyl, octadecanoyl, tert-butyryl, oleoyl, benzoyl, naphthylcarbonyl, and cinnamoyl are used. Acetyl, propionyl, and butyryl are preferred from the viewpoints of ease of synthesis, cost, and ease of controlling substituent distribution. Acetyl and propionyl are particularly preferred, especially acetyl. Furthermore, when two or more acyl groups are substituted, acetyl and propionyl are preferred.

[0035] Commercially available examples of the cellulose resins include: Daicel's LT-100, LT-35, LT-55, and LT-75; Eastman Chemical Company's VM-138, VM-160, and VM-149; and Sichuan Pushi's H1 and H11 cellulose.

[0036] In the cellulose ester film prepared by the present invention, by introducing a sucrose derivative of formula (1) with a total average degree of substitution of 4.5-8.0 and a cellulose resin with an acyl substitution degree of 2.50-3.00, the mechanical properties and durability of the cellulose ester film are effectively improved while meeting the requirements of the casting process. This enables the preparation of thin products with high elastic modulus and high pressure resistance, thus better meeting the needs of the invention.

[0037] Furthermore, by controlling the total average degree of substitution of the sucrose derivative shown in formula (1) to be 5.5-7.6, and by controlling the amount added, the cellulose film is endowed with excellent optical properties. The haze of the prepared cellulose ester film is <0.25%, while promoting the aggregation of microparticles in the system within a certain range, increasing the protrusion of microparticles in the film, and distributing them on the film surface at a height of more than 0.05 μm, further solving the problem of film adhesion.

[0038] As a preferred technical solution, the amount of the microparticles added is 0.03-0.5 wt% based on the mass of the cellulose resin, more preferably 0.05-0.3 wt%.

[0039] As a preferred technical solution, the microparticles are selected from at least one of silicon dioxide, 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, preferably silicon dioxide.

[0040] As a preferred technical solution, the average primary particle size of the microparticles is ≤20nm, and the apparent specific gravity is ≥70g / L.

[0041] Preferably, the average primary particle size of the microparticles is 5-16 nm, and the apparent specific gravity is 100-200 g / L.

[0042] Commercially available examples of silica microparticles include: Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Aerosil Corporation of Japan), and Evonik R972, R974, and R812. Commercially available examples of zirconia microparticles include: Aerosil R976 and R811 (manufactured by Aerosil Corporation of Japan).

[0043] As a preferred technical solution, the solvent includes a combination of a main solvent and a co-solvent.

[0044] Preferably, the mass ratio of the main solvent to the co-solvent is (70-97):(3-30), and more preferably (85-97):(3-15).

[0045] Preferably, the main solvent is selected from at least one of dichloromethane, trichloromethane, and acetone.

[0046] Preferably, the co-solvent is a lower alcohol, which is selected from at least one of methanol, ethanol, propanol, isopropanol, and butanol.

[0047] As a preferred technical solution, the additive is selected from at least one of plasticizers, ultraviolet absorbers, anti-deterioration agents, stripping agents, infrared absorbers, wavelength dispersion modifiers, antioxidants, peroxide decomposers, free radical inhibitors, metal passivators, and acid scavengers.

[0048] Preferably, the additive includes an ultraviolet absorber.

[0049] The amount of the ultraviolet absorber added is 0.05 to 4 wt%, more preferably 0.07 to 3.0 wt%, based on the total mass of the cellulose resin.

[0050] Another aspect of the present invention provides a method for preparing a cellulose ester film, comprising at least the following steps: dissolving cellulose resin, sucrose derivative, and additives in a solvent to prepare a cotton swab solution; stirring and dispersing microparticles into the remaining solvent and cotton swab solution to prepare a microparticle pre-dispersion; redispersing the microparticle pre-dispersion to obtain a microparticle redispersion; mixing the microparticle redispersion with the remaining cotton swab solution to obtain a raw material solution; and casting and film formation of the raw material solution to obtain a cellulose ester film.

[0051] As a preferred technical solution, the redispersion method includes at least one of ultrasonic dispersion, grinding dispersion, and high-pressure dispersion, with grinding dispersion being the preferred method.

[0052] As a preferred technical solution, the mass concentration of particles in the pre-dispersion liquid is 0.05-0.5 wt%, preferably 0.1-0.35 wt%, and most preferably 0.2-0.3 wt%.

[0053] Preferably, the mass ratio of the remaining solvent to the cotton swab pus in the microparticle predispersant is (5-15):(0-5), more preferably (5-15):(2-4), and even more preferably (8-12):3.

[0054] As a preferred technical solution, the microparticle predispersant contains microparticle aggregates with a secondary particle size ≥ 0.7 μm, and the number of microparticle aggregates with a secondary particle size ≥ 0.7 μm accounts for at least 30% of the total number of microparticles in the microparticle predispersant.

[0055] As a preferred technical solution, the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0056] a. D50 is 0.153-0.704μm;

[0057] b. D90 is 0.424-1.669 μm;

[0058] c. D97 is 1.017-1.980μm.

[0059] Preferably, the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0060] a. D50 is 0.507-0.704μm;

[0061] b. D90 is 1.407-1.669 μm;

[0062] c. D97 is 1.877-1.980μm

[0063] As a preferred technical solution, the stirring and dispersing speed is 200-250 r / min, and the time is 2-3 h.

[0064] As a preferred technical solution, the grinding and dispersing speed is 70-90 r / min and the time is 2-3 h.

[0065] Furthermore, this invention, by preferentially adding silica microparticles with an average primary particle size of 5-16 nm and an apparent specific gravity of 100-200 g / L, and controlling the pre-dispersion (stirring dispersion) and redispersion processes, ensures that the number of silica microparticle aggregates with a secondary particle size ≥0.7 μm in the prepared cellulose ester film accounts for at least 30% of the total number of microparticles. This effectively increases the number of protrusions in the cellulose ester film, solving the adhesion problem when the film overlaps while ensuring the haze level of the film. In addition, through the optimization of the pre-dispersion (stirring dispersion) and redispersion processes, the film's sliding properties are further improved, the relative friction between the film and the guide shaft is reduced, scratches are reduced, the integrity of the film is improved, light leakage from the polarizer is reduced, and the yield rate is increased.

[0066] In this invention, the primary and secondary particle sizes are determined by observing the particles in the membrane with a scanning electron microscope and measuring the diameter of the circle of the outer particle. 200 particles are observed at different positions, and the average value is taken as the average particle size.

[0067] As a preferred technical solution, the mixing method is as follows: the microparticle redispersible liquid is added online and mixed with the remaining cotton glue pus through a static mixer to obtain the raw material pus.

[0068] As a preferred technical solution, the casting process includes: extruding raw pus through a casting nozzle and casting it onto a continuously running stainless steel belt to form a liquid film with a thickness of 10-80 μm, more preferably 20-60 μm.

[0069] As a preferred technical solution, the film formation includes: peeling the liquid film from the front drum, stretching and shrinking it through the intermediate cover at a stretching temperature not exceeding 130°C, further drying it at a drying temperature not exceeding 110°C, trimming the edges, embossing, and winding it up to obtain the cellulose ester film provided by the present invention.

[0070] A third aspect of the present invention provides a polarizing plate containing a cellulose ester film.

[0071] The polarizing plate of the present invention has the above-mentioned cellulose ester film, and the polarizing plate contains a polarizer and two polarizing protective films for protecting both sides thereon, wherein the cellulose ester film serves as at least one polarizing protective film.

[0072] A polarizing film is fabricated by adsorbing iodine-containing compound molecules onto a thin film made of polyvinyl alcohol (PVA) and orienting the PVA and iodine-containing compound molecules. A PVA-based adhesive is used to bond the cellulose ester film and the polarizing film. However, the polarizing film is not limited to this; any film commonly used as a polarizing film can be used. Furthermore, in this invention, the structure of bonding the cellulose ester film to both sides of the polarizing film to form a polarizing plate is not limited to this. For example, the cellulose ester film can be bonded only to one side of the polarizing film, or a protective film layer (including PET) can be formed on the outermost surface of the cellulose ester film bonded to both sides of the polarizing film.

[0073] A fourth aspect of the present invention provides a liquid crystal display device, comprising a polarizing plate containing a cellulose ester film.

[0074] The liquid crystal display device of the present invention includes a polarizing plate having the cellulose ester film of the present invention. Specifically, the polarizing plate (including the cellulose ester film of the present invention) is disposed on at least one layer of liquid crystal cells, and the film on the liquid crystal cell side of the polarizing plate is the cellulose ester film of the present invention.

[0075] In the liquid crystal display device of the present invention, preferably, the polarizing plate is attached to one or both sides of the liquid crystal cell via an adhesive layer.

[0076] In addition to an anti-glare layer or a transparent hard coating, the polarizing plate protective film used on the surface side of the liquid crystal display device of the present invention preferably also has an anti-reflective layer, an anti-static layer, an anti-fouling layer and a back coating.

[0077] The cellulose ester film provided by the present invention has excellent stiffness and optical properties. Even when it is made thinner, it can maintain excellent elastic modulus and is not prone to collapse or deformation. Polarizing plates and liquid crystal display devices using the cellulose ester film have excellent dimensional stability and a good visual experience.

[0078] The cellulose ester film provided by this invention, when used as a protective film for a polarizing plate, can improve the appearance and optical properties of the film and the polarizing plate, as well as improve the dimensional stability of the polarizing plate, prevent the polarizing plate from deteriorating, and further improve the service life of the liquid crystal display.

[0079] Beneficial effects

[0080] 1. This invention prepares cellulose ester films with reduced adhesion during overlapping by optimizing the cotton adhesive composition system. When winding thinner, wider, or lower elastic modulus films, it avoids appearance defects such as pits, wrinkles, and adhesion marks, ensuring the subsequent polarizing plates and liquid crystal displays, and meeting the development needs of thinner and larger products.

[0081] 2. In the cellulose ester film prepared by the present invention, by introducing the sucrose derivative of formula (1) with a total average degree of substitution of 4.5-8.0 and the cellulose resin with an acyl substitution degree of 2.50-3.00, the mechanical properties and durability of the cellulose ester film are effectively improved while meeting the requirements of the casting process. It can realize the preparation of thin products with high elastic modulus and high pressure resistance, and better meet the needs of discovery.

[0082] 3. By controlling the total average degree of substitution of the sucrose derivative shown in formula (1) to 5.5-8.0 and controlling the amount added, the present invention imparts excellent optical properties to the cellulose film. The haze of the prepared cellulose ester film is <0.25%. At the same time, it promotes the aggregation of microparticles in the system within a certain range, increases the protrusion of microparticles in the film, and distributes them on the film surface at a height of more than 0.05 μm, further solving the problem of film adhesion.

[0083] 4. This invention, by preferentially adding silica microparticles with an average primary particle size of 5-16 nm and an apparent specific gravity of 100-200 g / L, and by controlling the pre-dispersion (stirring dispersion) and redispersion processes, ensures that the number of silica microparticle aggregates with a secondary particle size ≥ 0.7 μm in the prepared cellulose ester film accounts for at least 30% of the total number of microparticles. This can effectively increase the number of protrusions in the cellulose ester film, solve the adhesion problem when the film overlaps, and ensure the haze level of the film.

[0084] 5. The cellulose ester film provided by the present invention has excellent stiffness and optical properties. Even when it is made thinner, it can maintain excellent elastic modulus and is not prone to collapse or deformation. Polarizing plates and liquid crystal display devices using the cellulose ester film have excellent dimensional stability and a good visual experience. Attached Figure Description

[0085] Figure 1 This is a schematic diagram of the preparation method of the photovoltaic enhancement film of cellulose ester film provided in Embodiment 1 of the present invention. In the figure, 1-cotton glue preparation vessel; 2-microparticle pre-dispersion stirring tank; 3-microparticle pre-dispersion tank; 4-filter; 5-static mixer; 6-casting nozzle; 7-stainless steel strip; 8-stretching machine; 9-edge trimming; 10-drying oven; 11-winding. Detailed Implementation

[0086] Example 1

[0087] Example 1 of the present invention provides a cellulose ester film, the raw materials for which are prepared by weight are shown in Table 1.

[0088] Table 1

[0089]

[0090] See Figure 1In another aspect, Embodiment 1 of the present invention provides a method for preparing a cellulose ester film, comprising the following steps:

[0091] A cotton swab solution was prepared by dissolving cellulose resin, sucrose derivatives, and additives in 300 parts of solvent. The microparticles were stirred and dispersed into the remaining solvent and 15 parts by weight of cotton swab solution to prepare a microparticle pre-dispersion. The microparticle pre-dispersion was redispersed to obtain a microparticle redispersion. The microparticle redispersion was mixed with the remaining cotton swab solution to obtain a raw material solution. The raw material solution was cast and film-formed to obtain a cellulose ester film.

[0092] The redispersion method is grinding dispersion.

[0093] The particle size of the particles in the pre-dispersion liquid meets the following condition:

[0094] a. D50 is 0.507μm;

[0095] b. D90 is 1.632μm;

[0096] c. D97 is 1.877 μm.

[0097] The stirring and dispersion was carried out at a speed of 200 r / min for 2 h.

[0098] The grinding and dispersing process was carried out at a speed of 80 r / min for 2 hours.

[0099] The mixing method is as follows: the microparticle redispersible liquid is added online and mixed with the remaining cotton glue pus liquid through a static mixer to obtain the raw material pus liquid.

[0100] The casting process includes: extruding raw pus through a casting nozzle and casting it onto a continuously running stainless steel belt to form a liquid film with a thickness of 60 μm.

[0101] The film formation process includes: peeling the liquid film from the front drum, stretching and shrinking it through the intermediate cover at a stretching temperature of 120°C, further drying it at a drying temperature of 100°C, trimming the edges, embossing, and winding it up to obtain the cellulose ester film provided by the present invention.

[0102] Example 2

[0103] Example 2 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative is replaced with 6 parts by weight of sucrose octaacetic acid ester, with a molecular weight of 678.59, from Zhejiang Hetang Technology Co., Ltd.; the grinding and dispersion speed is 70 r / min, and the time is 2 h; the particle size of the particles in the microparticle pre-dispersion solution meets the following conditions:

[0104] a. D50 is 0.704μm;

[0105] b. D90 is 1.669 μm;

[0106] c. D97 is 1.978 μm.

[0107] Example 3

[0108] Example 3 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative is replaced by 8 parts by weight of sucrose benzoate ester with a degree of substitution of 6.8-7.0, which is from Zhejiang Hetang Technology Co., Ltd.; the stirring and dispersion speed is 250 r / min for 2 h, the grinding and dispersion speed is 90 r / min for 3 h, and the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0109] a. D50 is 0.264μm;

[0110] b. D90 is 0.545μm;

[0111] c. D97 is 1.116μm.

[0112] Example 4

[0113] Example 4 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative is replaced with 7.5 parts by weight of sucrose hexaacetate, which is from Hubei Henglvyuan Technology Co., Ltd.; the stirring and dispersion speed is 200 r / min and the time is 3 h; and the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0114] a. D50 is 0.552μm;

[0115] b. D90 is 1.407 μm;

[0116] c. D97 is 1.953 μm.

[0117] Example 5

[0118] Example 5 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative is replaced by 15 parts by weight of sucrose benzoate ester with a degree of substitution of 7.2-7.4, which is from Zhejiang Hetang Technology Co., Ltd.; the stirring and dispersion speed is 250 r / min for 3 h, the grinding and dispersion speed is 80 r / min for 2.5 h, and the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0119] a. D50 is 0.153μm;

[0120] b. D90 is 0.424μm;

[0121] c. D97 is 1.017μm.

[0122] Example 6

[0123] Example 6 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative is replaced by 10 parts by weight of sucrose benzoate ester with a degree of substitution of 7.6-7.8, which is from Hubei Henglvyuan Technology Co., Ltd.; the grinding and dispersion speed is 70 r / min and the time is 3 h, and the particle size of the particles in the microparticle pre-dispersion solution meets the following conditions:

[0124] a. D50 is 0.641 μm;

[0125] b. D90 is 1.627 μm;

[0126] c. D97 is 1.417μm.

[0127] Comparative Example 1

[0128] Comparative Example 1 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative replaces 8 parts by weight of 1,2-dipropylene glycol dibenzoate, which is from Foshan Jinjia New Material Technology Co., Ltd.; the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0129] a. D50 is 0.641 μm;

[0130] b. D90 is 1.627 μm;

[0131] c. D97 is 1.417μm.

[0132] Comparative Example 2

[0133] Comparative Example 2 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative replaces 8 parts by weight of diethylene glycol dibenzoate, which is from Foshan Jinjia New Material Technology Co., Ltd.; the stirring and dispersion speed is 250 r / min for 2 h, the grinding and dispersion speed is 80 r / min for 3 h, and the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0134] a. D50 is 0.244μm;

[0135] b. D90 is 0.669μm;

[0136] c. D97 is 1.078μm.

[0137] Comparative Example 3

[0138] Comparative Example 3 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative replaces 8.8 parts by weight of triphenyl phosphate and is obtained from Dijie Chemical Co., Ltd.; the stirring and dispersion speed is 220 r / min for 2 h, the grinding and dispersion speed is 90 r / min for 2 h, and the particle size of the particles in the microparticle pre-dispersion liquid meets the following conditions:

[0139] a. D50 is 0.162μm;

[0140] b. D90 is 0.389μm;

[0141] c. D97 is 1.014μm.

[0142] Comparative Example 4

[0143] Comparative Example 4 of the present invention provides a cellulose ester film and its preparation method, the specific implementation of which is the same as that of Example 1, except that the sucrose derivative replaces 6 parts by weight of triethyl acetyl citrate, and is sourced from Kaiyin Chemical; the particle size of the particles in the microparticle pre-dispersion solution meets the following conditions:

[0144] a. D50 is 0.652μm;

[0145] b. D90 is 1.407 μm;

[0146] c. D97 is 1.799μm.

[0147] Performance testing

[0148] 1. Adhesion: Three A4 samples prepared according to this invention were stacked together (steel strip side facing air), pressed together with two frames, and placed in a constant temperature and humidity chamber at 40℃ and 85% humidity for 2 hours. After removing the samples, the A4 sample in the middle position was placed on an A4 graph paper (A4 graph paper has 9 columns and 12 rows, and each grid is 2*2cm). The adhesion of the coordinate area was counted. Grids showing moisture absorption were counted cumulatively (the number of adhered grids was recorded as the test result). The test results are shown in Table 2.

[0149] 2. Referring to GB / T 25273, two 30mm×50mm samples of the cellulose ester film provided in the examples and comparative examples were taken and tested using a WGT / S transmittance haze meter. The test results are shown in Table 2.

[0150] 3. Referring to GB / T 12683, the cellulose ester films provided in the examples and comparative examples were cut into rectangular samples (10 parallel samples) of 250mm (MD direction) × 15mm (TD direction). The test results were taken as average values, as shown in Table 2.

[0151] Table 2

[0152]

Claims

1. A cellulose ester film characterized by, The raw materials for its preparation include at least: cellulose resin with an acyl substitution degree of 2.50-3.00, sucrose derivatives of formula (1) with a total average substitution degree of 4.5-8.0, microparticles, additives, and solvents. Formula (1), wherein R is a hydrogen atom, a straight chain or branched aliphatic group having a substituent, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aromatic group.

2. The cellulose ester film according to claim 1, characterized in that, The amount of sucrose derivative added is 2-20 wt% based on the mass of cellulose resin, and the total average degree of substitution of the sucrose derivative is 5.5-7.

6.

3. The cellulose ester film according to claim 1, characterized in that, The amount of the microparticles added is 0.03-0.5 wt% based on the mass of the cellulose resin, and the microparticles are selected from at least one of silicon dioxide, 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.

4. The cellulose ester film according to claim 3, characterized in that, The average primary particle size of the particles is ≤20nm, and the apparent specific gravity is ≥70g / L.

5. A process for the production of a cellulose ester film according to any one of claims 1 to 4, characterized in that, At least the following steps are included: A cotton swab solution was prepared by dissolving cellulose resin, sucrose derivatives, and additives in a solvent; a pre-dispersion of the particles was prepared by stirring and dispersing the particles in the remaining solvent and cotton swab solution. The pre-dispersed microparticle liquid is redispersed to obtain a redispersed microparticle liquid; The raw material pus solution is obtained by mixing the microparticle redispersible liquid with the remaining cotton glue pus solution. The raw material pus solution is then cast and film-formed to obtain a cellulose ester film.

6. The method for preparing the cellulose ester film according to claim 5, characterized in that, The microparticle predispersant contains microparticle aggregates with a secondary particle size ≥ 0.7 μm, and the number of microparticle aggregates with a secondary particle size ≥ 0.7 μm accounts for at least 30% of the total number of microparticles in the microparticle predispersant.

7. The method for preparing the cellulose ester film according to claim 6, characterized in that, The particle size of the particles in the pre-dispersion liquid meets the following condition: a. D50 is 0.153-0.704μm; b. D90 is 0.424-1.669 μm; c. D97 is 1.017-1.980μm.

8. The cellulose ester film according to claim 6, characterized in that, The stirring and dispersion is carried out at a speed of 200-250 r / min for 2-3 h.

9. A polarizing plate comprising a cellulose ester film according to any one of claims 1-8.

10. A liquid crystal display device comprising the polarizing plate of claim 9.

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