JP5772680B2 - Cellulose acylate laminated film, production method thereof, polarizing plate and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a cellulose acylate laminated film, a method for producing the same, a polarizing plate using the same, and a liquid crystal display device.

  In recent years, liquid crystal display devices have been used for TVs, and with the increase in screen size, higher image quality and lower prices are increasingly required. In particular, VA mode liquid crystal display devices are the most common liquid crystal display devices for TVs because of their high contrast and relatively high production yield.

  The high image quality of this liquid crystal display device means the performance of "high contrast", "good viewing angle characteristics", and "small display unevenness on the screen". It is necessary to make the film thinner.

In other words, the properties of the retardation film can be said to satisfy the following three requirements:
1. Low internal haze;
2. Has reverse wavelength dispersion;
3. It is a thin film.

  It is well known that contrast is generally correlated with low internal haze. The lower the internal haze of the retardation film, the more the black display performance does not deteriorate and the high contrast can be achieved because polarized light does not depolarize due to scattering when passing through the retardation film.

  The viewing angle characteristics deteriorate due to a phenomenon (so-called color shift) in which the liquid crystal display device is colored blue or red when the screen during black display is observed from an oblique direction. It is well known that the color shift can be improved by improving the wavelength dispersion characteristics of the retardation film. In particular, the retardation film exhibiting a wavelength dispersion characteristic (reverse wavelength dispersion) having a larger birefringence as the wavelength is longer is advantageous for improving the color shift.

  The display unevenness of the screen is a problem caused by light leakage at a corner portion or an end portion of the screen when the black display screen of the liquid crystal display device is observed. This is because the cellulose acylate which is a general constituent material of the retardation film is easily affected by moisture, and the glass of the liquid crystal display device is curled when the retardation film is curled due to the moisture. In particular, when the screen size of the liquid crystal display device is increased, the curl is increased. As a result, the stress applied to the corner portion and the screen end portion is increased, and light leakage is likely to occur. Therefore, if the thickness of the retardation film is reduced, the generation of stress due to the curling of the retardation film is reduced, and even when the screen size of the liquid crystal display device is increased, the curling of the film is less likely to occur. Reducing the thickness of the retardation film is advantageous.

  Among cellulose esters, it is known that cellulose acylate can be applied to optical films having a wide retardation by changing the acyl group substitution degree. And so-called diacetyl cellulose (DAC) having a small substitution degree of acetyl group of 2.0 to 2.55 has high retardation and exhibits reverse wavelength dispersibility, so that no retardation increasing agent is added. However, it is expected that the function as an optical compensation film (viewing angle widening film) can be exhibited.

  However, when the total acyl group substitution degree of cellulose acylate is reduced as in the case of DAC, another problem arises as the hydrophilicity increases. For example, when a film is formed by the solution casting method, since the affinity between the support composed of a drum or an endless belt and the film surface is strong, the peeling force for peeling the film becomes large, and the step is May cause unevenness. Further, since the saponification resistance is lowered, there is also a problem that the surface of the film elutes into the saponification solution in the saponification process at the time of producing the polarizing plate, thereby contaminating the alkali saponification process.

  In order to solve these problems, a technique for adding a sugar ester compound to a cellulose acylate film using DAC has been proposed (see Patent Document 1). According to Patent Document 1, it is said that such a configuration can prevent the occurrence of problems due to the increase in hydrophilicity of cellulose acylate while suppressing the increase in internal haze of the film.

JP 2011-118339 A

  By the way, the reverse wavelength dispersibility of the cellulose acylate film shows a superior value as the cellulose acylate concentration in the film is higher (in other words, as the additive concentration is lower). Conventionally, various additives such as a plasticizer and a phase difference increasing agent are generally added to a cellulose acylate film which is supposed to be used as a retardation film. For this reason, addition of a further additive as in the technique described in Patent Document 1 leads to deterioration of the reverse wavelength dispersion of the film, and as a result, the viewing angle characteristic (color shift prevention performance) is lowered. .

  The present invention has been made in view of the above-mentioned circumstances in the prior art, and in a cellulose acylate film mainly composed of a low-substituted cellulose acylate such as DAC, the internal haze and the reverse wavelength dispersion are reduced. An object of the present invention is to provide means capable of exhibiting high phase difference expression while minimizing the above.

  The present inventors have intensively studied to solve the above problems. In the process, an attempt was made to make a predetermined sugar ester compound unevenly distributed in the surface layer portion of the cellulose acylate film. And it discovered that the said subject could be solved by such a structure, and came to complete this invention.

  That is, the said subject is solved by the following means.

  1. A cellulose acylate laminated film having a three-layer structure in which a core layer (B) containing cellulose acylate (B) is sandwiched by a pair of skin layers (A) containing cellulose acylate (A), Both of the pair of skin layers (A) have the following general formula (I):

In the formula, G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m represents a hydroxyl group directly bonded to the monosaccharide or disaccharide residue. The sum of the numbers, l is the sum of the number of — (O—C (═O) —R ² ) groups directly attached to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 Yes, l ≠ 0,
And the content of the sugar ester compound in the pair of skin layers (A) is larger than the content of the sugar ester compound in the core layer (B). A cellulose acylate laminated film in which the total acyl group substitution degree (DS (A)) of the rate (A) and the total acyl group substitution degree (DS (B)) of the cellulose acylate (B) satisfy the following formula (1) ;

2. The cellulose acylate laminated film according to 1 above, wherein the core layer (B) does not contain the sugar ester compound;
3. The cellulose acylate laminated film according to 1 or 2 above, wherein the in-plane direction retardation Re (630) at a wavelength of 630 nm and the in-plane direction retardation Re (450) at a wavelength of 450 nm satisfy the following formula (2);

  4). The in-plane phase difference Re (589) at a wavelength of 589 nm satisfies the following formula (3), and the thickness direction retardation Rth (589) at a wavelength of 589 nm satisfies the following formula (4): The cellulose acylate laminated film according to any one of the above;

5. Cellulose acylate laminated film of any one of said 1-4 whose internal haze is 0.04 or less;
6). The cellulose acylate laminated film according to any one of 1 to 5, wherein the core layer (B) contains a retardation increasing agent;
7). The cellulose acylate laminated film according to any one of 1 to 6 above, wherein the acyl substituent in the cellulose acylate (A) and the cellulose acylate (B) has 2 to 4 carbon atoms;
8). The cellulose acylate laminated film according to 7 above, wherein both the cellulose acylate (A) and the cellulose acylate (B) are cellulose acetates;
9. The average thickness of the core layer (B) is 20 to 50 μm, and the average thickness of at least one of the skin layers (A) is 0.6% or more and less than 5% of the average thickness of the core layer (B). The cellulose acylate laminated film according to any one of 1 to 8 above,
10. Cellulose acylate (A) and the following general formula (I):

In the formula, G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m represents a hydroxyl group directly bonded to the monosaccharide or disaccharide residue. The sum of the numbers, l is the sum of the number of — (O—C (═O) —R ² ) groups directly attached to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 Yes, l ≠ 0,
Preparing a dope (A) containing a sugar ester compound represented by: and a dope (B) containing cellulose acylate (B) and containing less sugar ester compound than the dope (A); The prepared dope (A) and dope (B) are cast on a support so that the dope (A) becomes a skin layer (A) and the dope (B) becomes a core layer (B) to form a web. A method for producing a cellulose acylate laminated film, comprising the steps of: and a step of peeling and stretching the formed web from the support;
11. The manufacturing method according to 10 above, further comprising a step of further performing at least one stretching treatment after drying the web subjected to at least one stretching treatment;
12 The production method according to 10 or 11 above, wherein casting is performed by simultaneous co-casting;
13. The polarizing plate which has at least 1 the cellulose acylate laminated film of any one of said 1-9, or the cellulose acylate laminated film manufactured by the manufacturing method of any one of said 10-12. ;
14 14. A liquid crystal display device comprising the polarizing plate as described in 13 above.

  According to the present invention, in a cellulose acylate film mainly composed of a low-substituted cellulose acylate such as DAC, high retardation development is achieved while minimizing deterioration of internal haze and reverse wavelength dispersion. Means that can be exerted can be provided.

It is the schematic which shows an example when casting the cellulose acylate laminated film of a 3 layer structure by simultaneous co-casting using a co-casting die. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. It is a schematic sectional drawing of an example of the liquid crystal display device of this invention.

  Hereinafter, the cellulose acylate laminated film of the present invention, the production method thereof, the additive used therein, and the like will be described in detail.

  The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In addition, a numerical range expressed using “to” in this specification means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. Furthermore, in the present specification, when the terms “Re” and “Rth” are used without particular notice, these represent values at a wavelength of 590 nm, respectively.

≪Cellulose acylate laminated film≫
One embodiment of the present invention relates to a cellulose acylate laminated film. More specifically, a cellulose acylate laminate having a three-layer structure in which a core layer (B) containing cellulose acylate (B) is sandwiched between a pair of skin layers (A) containing cellulose acylate (A). Related to film. However, the cellulose acylate laminated film according to the present embodiment is not limited to the above-mentioned “consisting only” of the three-layer structure, and other layers may be arranged above and below the three-layer structure or between the respective layers. Moreover, in this specification, the cellulose acylate contained in the skin layer (A) is also referred to as “cellulose acylate (A)”, and the cellulose acylate contained in the core layer (B) is referred to as “cellulose acylate (B)”. Also called. Moreover, although the structure of the cellulose acylate (A) contained in each of a pair of skin layers (A) may mutually be the same or different, it is preferable that it is the same.

And the cellulose acylate laminated film which concerns on this form has the following characteristics:
-A pair of skin layer (A) contains the sugar ester compound represented by general formula (I);
-Both content of the said sugar ester compound in a pair of skin layers (A) is larger than content of the said sugar ester compound in a core layer (B);
The total acyl group substitution degree (DS (A)) of cellulose acylate (A) and the total acyl group substitution degree (DS (B)) of cellulose acylate (B) satisfy the following formula (1):

<Cellulose acylate>
In the cellulose acylate laminated film according to this embodiment, both the skin layer (A) and the core layer (B) contain cellulose acylate as a main component (cellulose acylate (A) and cellulose acylate (B), respectively). ).

  In cellulose acylate, some or all of the hydrogen atoms of hydroxyl groups (—OH) at the 2nd, 3rd and 6th positions in the β-1,4-bonded glucose units constituting cellulose are substituted with acyl groups. Refers to a cellulose derivative.

  The cellulose acylate is not particularly limited. For example, an aliphatic group having 2 to 20 carbon atoms such as a hydrogen atom in a hydroxyl group of cellulose having an acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, pivaloyl group, hexanoyl group, octanoyl group, lauroyl group, stearoyl group, etc. Examples include cellulose acylate substituted with an acyl group. Among these, those having an acyl group having 2 to 4 carbon atoms are preferable, and an acetyl group, a propionyl group, and a butanoyl group are more preferable. The acyl group in cellulose acylate may be a single species or a combination of a plurality of acyl groups.

  Specific examples of the cellulose acylate include cellulose acylates such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. In the present invention, cellulose acetate is preferable.

  Cellulose as a raw material for cellulose acylate is not particularly limited, and examples thereof include cotton linter, wood pulp (derived from coniferous tree, derived from broadleaf tree), kenaf and the like. Moreover, the cellulose acylate obtained from them can be mixed and used at an arbitrary ratio.

  The cellulose acylate according to this embodiment can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, the three hydroxyl groups of the glucose unit are substituted with an acyl group of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose acylate such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, cellulose acylate having a desired degree of acyl substitution is synthesized by hydrolyzing cellulose triester. Thereafter, cellulose acylate is obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  Specifically, cellulose acylate can be synthesized with reference to the methods described in JP-A-10-45804, JP-A-2005-281645, JP-A-2003-270442, and the like.

  Commercially available products include Daicel Corporation L20, L30, L40, L50, Eastman Chemical Co. Ca398-3, Ca398-6, Ca398-10, Ca398-30, Ca394-60S, and the like.

  In the cellulose acylate laminated film according to the present embodiment, the total acyl group substitution degree (DS (A)) of the cellulose acylate (A) contained in the skin layer (A) and the total acyl group substitution of the cellulose acylate (B) It is indispensable that the degree (DS (B)) satisfies the following formula (1) from the viewpoint of expressing the effect of the present invention. Further, DS (A) is preferably larger than DS (B). By setting it as such a structure, the advantage that the peelability of the film from the support body at the time of film-forming a film is improved is also acquired.

  The cellulose acylate laminated film according to the present embodiment has a pair of (that is, two) skin layers (A), but the total of the cellulose acylates (A) contained in the respective skin layers (A). Both the acyl group substitution degrees (DS (A)) must satisfy the above formula (1). As long as both the total acyl group substitution degrees (DS (A)) satisfy the above formula (1), the values of the total acyl group substitution degrees (DS (A)) may be different from each other. . Further, from the viewpoint of more remarkably expressing the effect of the present invention, it is more preferable that DS (A) and DS (B) satisfy the following formula (5).

  The most common method for determining the total acyl group substitution degree of cellulose acylate is a method for measuring the degree of acetylation in ASTM-D-817-91 (testing method for cellulose acetate and the like).

  The weight average molecular weight (Mw) of cellulose acylate is preferably 100,000 to 250,000, and more preferably 150,000 to 200,000. If the weight average molecular weight (Mw) is 100,000 or more, the elongation at break is sufficiently high. On the other hand, when the weight average molecular weight (Mw) is 250,000 or less, an increase in viscosity is suppressed and good filterability is obtained. The weight average molecular weight (Mw) of cellulose acylate is measured by gel permeation chromatography (GPC). The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (3 used by Showa Denko Co., Ltd. connected)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  It is preferable that the total amount (mass ppm) of calcium and magnesium and the amount of acetic acid (mass ppm) contained in the cellulose acylate laminated film according to this embodiment satisfy the following formula (6).

  Calcium and magnesium are contained in the cellulose acylate that is the raw material of the film, but are used to neutralize and stabilize the acid catalyst (especially sulfuric acid) added to the cellulose acylate production process. , And may be added as a metal salt (inorganic acid salt, organic acid salt). Moreover, you may add as a metal oxide, a metal hydroxide, and a metal salt (inorganic acid salt, organic acid salt) at the time of film forming. The “total amount of calcium and magnesium (mass ppm)” in the present invention refers to the total amount thereof.

  In the production process of cellulose acylate, acetic anhydride and acetic acid are used as a reaction solvent and an esterifying agent. Unreacted acetic anhydride is hydrolyzed by a reaction stopper (water, alcohol, acetic acid, etc.) to produce acetic acid. The “acetic acid amount (mass ppm)” according to this embodiment refers to the total amount of residual acetic acid and free acetic acid.

  As shown in the above formula (6), the total amount of acetic acid (mass ppm) / calcium and magnesium (mass ppm) is 1 or more and 30 or less. When the value of this ratio is 1 or more, it means that the amount of acetic acid is more than the total amount of calcium and magnesium. In this case, the occurrence of light scattering due to calcium and magnesium metal salts is suppressed, and the decrease in contrast is prevented. Can be done. In addition, when the value of this ratio is 30 or less, it means that acetic acid is not excessive with respect to the total amount of calcium and magnesium. In this case, the polarizer with acetic acid after the cellulose acylate is bonded to the polarizer Is preferable because deterioration of the is suppressed.

  In addition, the total amount (absolute value) of calcium and magnesium contained in the cellulose acylate laminated film according to this embodiment is preferably 5 to 130 ppm by mass, more preferably 5 to 80 ppm by mass, and even more preferably 5 to 5 ppm by mass. 50 ppm by mass. Moreover, the amount of acetic acid contained in the cellulose acylate laminated film is preferably 20 to 500 ppm by mass, more preferably 25 to 250 ppm by mass, and further preferably 30 to 150 ppm by mass. Here, a known method can be used to measure the total amount of calcium and magnesium contained in the film. For example, after the dried film is completely burned, a pretreatment in which ash is dissolved in hydrochloric acid is performed. The above can be measured by atomic absorption. The measured value is obtained in units of ppm by mass as the total content of calcium and magnesium in 1 g of an absolutely dry film. Moreover, although a well-known method can be used also for the measurement of the amount of acetic acid contained in a film, for example, a film is melt | dissolved in a methylene chloride and methanol is added and reprecipitation is performed. The amount of acetic acid can be obtained in units of mass ppm by filtering the supernatant and measuring the supernatant with gas chromatography.

<Sugar ester compound>
As described above, in the cellulose acylate laminated film according to this embodiment, the pair of skin layers (A) both contain the sugar ester compound represented by the general formula (I).

  Since the skin layer (A) contains such a sugar ester compound, hydrolysis of the cellulose acylate is prevented, so that the water resistance of the film can be improved. In addition, the film surface is saponified at the time of bonding with a polarizer when constituting a polarizing plate, but hydrolysis of cellulose acylate during the saponification treatment and accompanying elution into an alkaline saponification solution can also be prevented. .

In the general formula (I), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. 1 is the total number of — (O—C (═O) —R ² ) groups directly bonded to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 and l ≠ 0.

The compound having the structure represented by the general formula (I) is a single kind of compound in which the number of hydroxyl groups (m) and the number of-(O—C (═O) —R ² ) groups (1) are fixed. It is difficult to isolate, and it is known that a compound in which several different components of m and l in the formula are mixed is obtained. Therefore, the number of hydroxyl groups (m), - (O- C (= O) -R 2) The number of group (l) is important performance as each variation mixture, when the cellulose acylate film of the present invention A compound having a structure represented by the general formula (I) with respect to haze characteristics and a mixing ratio of a component of m = 0 and a component of m> 0 is 45:55 to 0: 100. More preferably, in terms of performance and cost, the mixing ratio of the component m = 0 and the component m> 0 is in the range of 10:90 to 0.1: 99.9. In addition, the component of said m = 0 and the component of m> 0 can be measured by a high performance liquid chromatography by a conventional method.

  In the above general formula (I), G represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, and the like.

  Although the structural example of the compound which has a monosaccharide residue represented with general formula (I) below is shown, this invention is not limited to these specific examples.

  Specific examples of the disaccharide include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and isotrehalose.

  Although the structural example of the compound which has a disaccharide residue represented with general formula (I) below is shown, this invention is not limited to these specific examples.

In the general formula (I), R ² represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

In general formula (I), m is the total number of hydroxyl groups directly bonded to the monosaccharide or disaccharide residue, and l is directly bonded to the monosaccharide or disaccharide residue. The total number of — (O—C (═O) —R ² ) groups. And it is necessary that 3 ≦ m + 1 ≦ 8, and it is preferable that 4 ≦ m + 1 ≦ 8. Also, l ≠ 0. In addition, when l is 2 or more, the — (O—C (═O) —R ² ) groups may be the same or different.

The aliphatic group in the definition of R ² may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms. Those of ˜15 are particularly preferred. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Examples include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

The aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include benzene, naphthalene, anthracene, biphenyl, terphenyl and the like. As the aromatic hydrocarbon group, benzene, naphthalene, and biphenyl are particularly preferable. As the aromatic heterocyclic group, those containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom are preferable. Specific examples of the heterocyclic ring include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Examples include isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, and tetrazaindene. As the aromatic heterocyclic group, pyridine, triazine, and quinoline are particularly preferable.

  Next, although the preferable example of a compound represented by general formula (I) is shown below, this invention is not limited to these specific examples.

  (Synthesis Example: Synthesis Example of Compound Represented by General Formula (I))

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas inlet tube was charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass. A part of the obtained mixture was purified by silica gel column chromatography to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively.

  One of the characteristics of the cellulose acylate laminated film according to this embodiment is that the content of the predetermined sugar ester compound in the pair of skin layers (A) is larger than the content of the sugar ester compound in the core layer (B). It is in that point. Specifically, the content of the sugar ester compound represented by the general formula (I) in the core layer (B) is preferably 80% or less with respect to the content of the sugar ester compound in the skin layer (A). More preferably, it is 50% or less, more preferably 20% or less, still more preferably 10% or less, particularly preferably 5% or less, and most preferably 0%. That is, it is preferable that the core layer (B) does not contain the sugar ester compound represented by the general formula (I).

<Other additives>
The cellulose acylate laminated film according to this embodiment may contain various additives other than those described above. Some of them will be described below, but the present invention is not limited to these.

(Matting agent (fine particles))
In the cellulose acylate laminated film according to this embodiment, the skin layer (A) and / or the core layer (B) may contain a matting agent. In particular, the skin layer (A) preferably contains a matting agent (fine particles). The “mat agent” is also called “fine particles” and is added for the purpose of imparting slipperiness to the film.

  The average primary particle size of the matting agent (fine particles) is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm. The matting agent (fine particles) is preferably contained in the film by forming secondary particles having a particle size of 0.1 to 5 μm, and a preferable average secondary particle size is 0.1 to 2 μm, and more preferably 0.8. 2 to 0.6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

  The average primary particle size of the matting agent (fine particles) is measured by observing the particles with a transmission electron microscope (magnification 500,000 to 2,000,000 times), observing 100 particles, measuring the particle size, and measuring the average. The value is taken as the average primary particle size.

  The apparent specific gravity of the matting agent (fine particles) is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  Silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen burned in air at 1000 to 1200 ° C. Can be obtained. For example, Aerosil 200V, Aerosil R972, Aerosil R972V (above, manufactured by Nippon Aerosil Co., Ltd.) are commercially available, and these can be used.

  The apparent specific gravity described above is calculated according to the following formula (7) by measuring a weight of silicon dioxide fine particles in a graduated cylinder and measuring the weight.

  Examples of the method for preparing the dispersion of the matting agent (fine particles) used in the present invention include the following three types.

<< Preparation Method A >>
After stirring and mixing the solvent and fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

<< Preparation Method B >>
After stirring and mixing the solvent and fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose acylate is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

<< Preparation Method C >>
Add a small amount of cellulose acylate to the solvent and stir to dissolve. Fine particles are added to this and dispersed by a disperser. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  Preparation method A is excellent in dispersibility of silicon dioxide fine particles, and preparation method C is excellent in that silicon dioxide fine particles are difficult to re-aggregate. Among them, the preparation method B described above is a preferable preparation method that is excellent in both dispersibility of the silicon dioxide fine particles and difficulty in reaggregation of the silicon dioxide fine particles.

《Distribution method》
The concentration of silicon dioxide when the silicon dioxide fine particles are mixed with a solvent and dispersed is preferably 5% by mass to 30% by mass, more preferably 10% by mass to 25% by mass, and most preferably 15% by mass to 20% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate.

  When the matting agent (fine particles) is contained in the skin layer (A), the amount added is preferably 0.01 to 100 parts by mass of the cellulose acylate (A) contained in each skin layer (A). 5.0 parts by mass, more preferably 0.05 to 1.0 parts by mass, and still more preferably 0.1 to 0.5 parts by mass. When the addition amount is large, the coefficient of dynamic friction is excellent, and when the addition amount is small, aggregates are reduced. The content of the matting agent (fine particles) in the core layer (B) is preferably 0 to 0.1 parts by mass with respect to 100 parts by mass of the cellulose acylate (B) contained in the core layer (B). More preferably, it is 0-0.05 mass part, Most preferably, it is 0 mass part.

  A normal disperser can be used as the disperser. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersion of silicon dioxide fine particles, a medialess disperser is preferable because of excellent haze reduction performance. Examples of the media disperser include a ball mill, a sand mill, and a dyno mill.

  Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. A high-pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

  When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more, and more preferably 19.613 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable.

  Examples of the high-pressure dispersing device include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer. UHN-01 manufactured by Sanwa Machinery Co., Ltd.

  In addition, when a film is produced by casting, casting a dope containing a matting agent (fine particles) so as to be in direct contact with the casting support results in a film having high slipperiness and low internal haze. preferable.

(Plasticizer)
The cellulose acylate laminated film according to this embodiment may include a plasticizer. As the plasticizer, many compounds known as cellulose acylate plasticizers can be suitably used. Examples of the plasticizer include the following general formula (II):

A preferred example is a polyester compound represented by the formula:

  In the general formula (II), B represents a linear or branched alkylene group or cycloalkylene group having 2 to 6 carbon atoms, and A represents an aromatic ring having 6 to 14 carbon atoms or a C 2 to 6 carbon atoms. A linear or branched alkylene group or a cycloalkylene group is represented, X represents a monocarboxylic acid residue containing a hydrogen atom or an aromatic ring having 6 to 14 carbon atoms, and n represents a natural number of 1 or more.

  The polyester compound represented by the general formula (II) includes a dicarboxylic acid having an aromatic ring (having 6 to 14 carbon atoms) or a linear or branched alkylene group or cycloalkylene group (both having 2 to 6 carbon atoms) and a carbon number. It is an alternating copolymer obtained by alternating copolymerization with 2-6 linear or branched alkylene diols or cycloalkylene diols. The aromatic dicarboxylic acid and the dicarboxylic acid having a linear or branched alkylene group or cycloalkylene group may be used alone or as a mixture, but the main component constituting the polarizing plate protective film may be used. In view of compatibility with a resin (for example, a cellulose ester resin), it is preferable that at least 10% of an aromatic dicarboxylic acid is contained. Moreover, you may seal both ends with the monocarboxylic acid which has an aromatic ring (C6-C14).

  Examples of the dicarboxylic acid having an aromatic ring (6 to 14 carbon atoms), that is, an aromatic dicarboxylic acid having 8 to 16 carbon atoms include, for example, phthalic acid, isophthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2,2′-biphenyldicarboxylic acid, 4,4 '-Biphenyldicarboxylic acid, and the like. Among these, terephthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid are preferable.

  Examples of the dicarboxylic acid having a linear or branched alkylene group or cycloalkylene group (2 to 6 carbon atoms) include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and 1,2-cyclohexane. Examples thereof include dicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Of these, succinic acid, adipic acid, and 1,4-cyclohexanedicarboxylic acid are preferable.

  Examples of the linear or branched alkylene diol or cycloalkylene diol having 2 to 6 carbon atoms include ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6- Examples include hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Among these, ethanediol (ethylene glycol), 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol are preferable.

  Among these, A is preferably a benzene ring, naphthalene ring or biphenyl ring which may have a substituent, from the viewpoint of excellent plasticity imparting performance. Here, the “substituent” that the benzene ring, naphthalene ring or biphenyl ring may have is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. is there.

  Examples of the monocarboxylic acid having an aromatic ring (having 6 to 14 carbon atoms) that seals both ends of the polyester compound include benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, p-tert-butylbenzoic acid, and dimethylbenzoic acid. Examples include acids and paramethoxybenzoic acid. Of these, benzoic acid, p-toluic acid and p-tert-butylbenzoic acid are preferred.

  Aromatic polyester compounds can be prepared by the conventional methods, such as the above-mentioned hot-melt condensation method by the polyesterification reaction or transesterification reaction between the dicarboxylic acid and alkylene diol or cycloalkylene diol, or the interfacial condensation method between acid chlorides of these acids and glycols. It can be easily synthesized by either method. Furthermore, by adding the above-described aromatic monocarboxylic acid, a polyester compound in which both ends are sealed can be synthesized.

  Below, the aromatic polyester compound which can be used in this invention is illustrated.

  Although it does not specifically limit as plasticizers other than the polyester compound represented by general formula (II), Preferably, polyhydric carboxylic acid ester plasticizer, glycolate plasticizer, phthalate ester plasticizer, fatty acid ester type It is selected from plasticizers and polyhydric alcohol ester plasticizers, ester plasticizers, acrylic plasticizers and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

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

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

(In the formula, R ¹¹ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxy group (hydroxyl group).

  Examples of preferred polyhydric alcohols include, but are not limited to, the following.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

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

  Examples of preferred monocarboxylic acids include the following, but are not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. The inclusion of acetic acid is preferred because the compatibility with cellulose acetate increases, and it is also preferred to use a mixture of acetic acid and other monocarboxylic acids.

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

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

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

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

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

In the formula, R ¹² represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxy group, and an OH group represents an alcoholic or phenolic hydroxy group.

  Examples of preferred polyvalent carboxylic acids include, but are not limited to, the following.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxy group (hydroxyl group) of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound 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 larger one is preferable in terms of improving the retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose resin.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxy group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, 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, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  There is no restriction | limiting in particular about the quantity of the plasticizer contained in the skin layer (A) or core layer (B) of the cellulose acylate laminated film which concerns on this form, According to a desired plastic action, it can determine suitably. However, it is preferable that content of the plasticizer in both skin layers (A) is 1-20 mass parts with respect to 100 mass parts of cellulose acylates (A) contained in each skin layer (A). Moreover, it is preferable that content of the plasticizer in a core layer (B) is 1-20 mass parts with respect to 100 mass parts of cellulose acylates (B) contained in a core layer (B).

(Acrylic compound)
The cellulose acylate laminated film according to this embodiment may contain an acrylic compound (hereinafter also referred to as “acrylic polymer”). The acrylic compound can function as a phase difference adjusting agent. Such an acrylic compound (acrylic polymer) preferably has a weight average molecular weight of 500 or more and 30000 or less from the viewpoint of an increase in haze during stretching and stability of retardation. Obtained by inter alia copolymerizing an ethylenically unsaturated monomer X _b having an ethylenically unsaturated monomer X _a have no aromatic ring in the intramolecular hydrophilic group having no aromatic ring and a hydrophilic group in the molecule was weight average molecular weight of 5,000 to 30,000 of the polymer X, more preferably, an ethylenically unsaturated monomer X _a hydrophilic group having no aromatic ring in a molecule having no aromatic ring and a hydrophilic group in the molecule ethylenically unsaturated monomer X _b and copolymerizing the polymer 30,000 weight average molecular weight of 5000 or more obtained in X, the weight average obtained by polymerizing no ethylenically unsaturated monomer Y _a aromatic ring having It is preferable to contain a polymer Y having a molecular weight of 500 or more and 3000 or less.

(Polymer X)
Polymer X is copolymerized with ethylenically unsaturated monomer X _b having a hydrophilic group does not have an aromatic ring in the ethylenically unsaturated monomer X _a and the molecule having no aromatic ring and a hydrophilic group in the molecule The obtained polymer has a weight average molecular weight of 5,000 to 30,000.

Preferably, _Xa is a (meth) acrylic monomer having no aromatic ring and no hydrophilic group in the molecule, and _Xb is a (meth) acrylic monomer having no aromatic ring in the molecule and having a hydrophilic group. .

  The polymer X is represented by the following general formula (X).

In the general formula (X), X _a represents an ethylenically unsaturated monomer having no aromatic ring and a hydrophilic group in the molecule, an ethylenically X _b has a hydrophilic group having no aromatic ring in the molecule not refers to a saturated monomers, _{X c} represents a _X a, _{X b} and copolymerizable monomer units. m, n, and p represent a molar composition ratio. However, m ≠ 0, n ≠ 0, and m + n + p = 100.

  The polymer X is preferably represented by the following general formula (X-1).

In the formula, R ₁ and R ₃ represent a hydrogen atom or a methyl group, R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms, and R ₄ represents —CH ₂ —, -C ₂ H ₄ - or _-C 3 _{H 6} - represents a. X _{c represents} an X a, _{X b} and copolymerizable monomer units. m, n, and p represent a molar composition ratio. However, m ≠ 0, n ≠ 0, and m + n + p = 100.

  In the polymer X, the “hydrophilic group” refers to a group having a hydroxyl group and a polyoxyalkylene chain (for example, a polyoxyethylene chain).

Aromatic ring and a hydrophilic group ethylenically unsaturated monomer X _a no in the molecule, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i -, S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n -, I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxy Ethyl), acrylic acid (2-ethoxyethyl) and the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Of these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

The ethylenically unsaturated monomer _Xb having no hydrophilic ring in the molecule and having a hydrophilic group is preferably a (meth) acrylic acid ester as a monomer unit having a hydroxyl group, for example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Preferred are (meth) acrylic acid (2-hydroxyethyl), (meth) acrylic acid (2-hydroxypropyl), and (meth) acrylic acid (3-hydroxypropyl).

X _c is not particularly limited as long as it is an ethylenically unsaturated monomer other than X _a and X _b and can be copolymerized, but preferably does not have an aromatic ring.

The molar composition ratio of X _a and _{X b} (m: n) is 99: 1-65: is preferably in the range of 35, more preferably 95: 5 to 75: in the range of 25. If the value of the molar ratio is within this range of X _a and X _b, it is possible to suppress the while ensuring the compatibility with cellulose acylate retardation value Rt in the thickness direction of the film becomes too large. Moreover, _if the molar composition ratio of _Xb is a value within this range, the expression of haze during film formation can also be suppressed. In addition, the molar composition ratio (p) of _Xc is 0-10. _Xc may be a plurality of monomer units.

  As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000. By setting the weight average molecular weight of the polymer X to 5000 or more, the dimensional change of the layer to which the polymer X is added (skin layer (A) and / or core layer (B)) under high temperature and high humidity is reduced, and the phase difference When used as a film, it is preferable because of advantages such as less curling. When the weight average molecular weight is 30000 or less, compatibility with cellulose acylate is further improved, bleeding out under high temperature and high humidity is prevented, and generation of haze during stretching is also suppressed.

  The weight average molecular weight (Mw) of the polymer X can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C. The molecular weight can be adjusted by adjusting this temperature or the polymerization reaction time.

  In addition, the weight average molecular weight (Mw) of the polymer X is measured by gel permeation chromatography (GPC). The measurement conditions are as described above as the measurement conditions for the weight average molecular weight (Mw) of cellulose acylate.

(Polymer Y)
The polymer Y is _a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferred because the residual monomer in the polymer decreases. Further, when the weight average molecular weight is 3000 or less, the performance of reducing the retardation Rth in the film thickness direction can be maintained. Y _a is preferably _a (meth) acrylic monomer having no aromatic ring. The polymer Y is represented by the following general formula (Y).

In the general formula (Y), Y _a represents an ethylenically unsaturated monomer having no aromatic ring, Yb represents Ya and copolymerizable monomer units. k and q represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

  The polymer Y is preferably one represented by the following general formula (Y-1).

In General Formula (Y-1), R ⁵ represents a hydrogen atom or a methyl group, and R ⁶ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms. Further, _{Y b} represents _{Y a} copolymerizable monomer units. k and q represent a molar composition ratio. However, k ≠ 0 and k + q = 100.

Y _b is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Y _a . Y _b may be plural. q is preferably 0-30.

Ethylenically unsaturated monomer Y _a constituting the polymer Y obtained by polymerization of ethylenically unsaturated monomers having no aromatic ring, include acrylic acid esters, e.g., methyl acrylate, ethyl acrylate, propyl acrylate (i -, N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), acrylic acid Heptyl (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2 -Ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypro ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl); a methacrylic acid ester in which the acrylic acid ester is changed to a methacrylic acid ester; an unsaturated acid such as acrylic acid, methacrylic acid Examples thereof include acid, maleic anhydride, crotonic acid, itaconic acid and the like.

Y _b is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Y _a , but examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and capron. Vinyl acetate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate, etc. . Y _b may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and JP-A No. 2000-128911 or JP-A No. 2000-344823. And a method of bulk polymerization using a compound having one thiol group and a secondary hydroxyl group as described above, or a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, polymer Y uses a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. Polymerization process is preferred. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. By this terminal residue, the compatibility between Y and cellulose acylate can be adjusted.

  Both the hydroxyl values of the polymer X and the polymer Y are preferably 30 to 150 [mgKOH / g]. The hydroxyl value of these polymers is measured according to JIS K 0070 (1992). Specifically, this hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 mL of an acetylating reagent (a solution obtained by adding pyridine to 20 mL of acetic anhydride to 400 mL) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, and 1 mL of purified water is added from an air cooling tube to decompose acetic anhydride into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula (8).

  In the formula, B is the amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test, C is the amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for titration, f is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11.

  There is no restriction | limiting in particular about the quantity of the acryl-type compound (acrylic polymer) contained in the skin layer (A) and core layer (B) of the cellulose acylate laminated film which concerns on this form, It determines suitably according to the desired phase difference adjustment effect. Can be done. However, from the viewpoint of reducing the internal haze of the laminated film and improving the durability of the cellulose acylate laminated film, the content of the acrylic compound (acrylic polymer) in both the skin layers (A) is different for each skin. It is preferable that it is 5-15 mass parts with respect to 100 mass parts of cellulose acylates (A) contained in a layer (A). Moreover, it is preferable that content of the acrylic compound (acrylic polymer) in a core layer (B) is 5-20 mass parts with respect to 100 mass parts of cellulose acylates (B) contained in a core layer (B). .

(Phase difference increasing agent)
The cellulose acylate laminated film according to this embodiment may contain a retardation increasing agent. Examples of the retardation increasing agent include those made of a rod-like compound and those made of a compound having a cyclic structure such as a cycloalkane or an aromatic ring. As the compound having a cyclic structure, a discotic compound is preferable. As the rod-like compound or discotic compound, a compound having at least two aromatic rings is preferable.

  There is no restriction | limiting in particular about the quantity of the phase difference raising agent contained in the skin layer (A) or core layer (B) of the cellulose acylate laminated film which concerns on this form, According to a desired phase difference raising effect | action, it can determine suitably. However, the content of the retardation increasing agent in both the skin layers (A) is 0 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate (A) contained in each skin layer (A). preferable. Moreover, it is preferable that content of the phase difference increasing agent in a core layer (B) is 0-10 mass parts with respect to 100 mass parts of cellulose acylates (B) contained in a core layer (B). Especially, in the cellulose acylate laminated film which concerns on this form, it is preferable that a core layer (B) contains a phase difference increasing agent from a viewpoint of film thinning. Further, when the core layer (B) contains a retardation increasing agent, the content of the discotic compound contained in the retardation increasing agent contained in the core layer (B) is the cellulose acid contained in the core layer (B). From the viewpoint of lowering internal haze, it is particularly preferred that the rate (B) is less than 5 parts by mass with respect to 100 parts by mass.

(Peeling accelerator)
The cellulose acylate laminated film according to this embodiment preferably contains a release accelerator from the viewpoint of further improving the releasability. As the peeling accelerator, known ones can be adopted, and organic and inorganic acidic compounds, surfactants, chelating agents and the like can be used. Of these, polyvalent carboxylic acids and esters thereof are effective, and in particular, ethyl esters of citric acid can be used effectively.

  There is no restriction | limiting in particular about the quantity of the peeling accelerator contained in the skin layer (A) or core layer (B) of the cellulose acylate laminated film which concerns on this form, According to the desired peeling acceleration | stimulation effect | action, it can determine suitably. However, the content of the peeling accelerator in both skin layers (A) is 0.001 to 1 part by mass with respect to 100 parts by mass of cellulose acylate (A) contained in each skin layer (A). Is preferably 0.005 to 0.5 parts by mass, and more preferably 0.01 to 0.3 parts by mass. If content of a peeling accelerator is a value more than the lower limit mentioned above, the desired peeling acceleration effect can be exhibited. Moreover, if the content is a value equal to or less than the above-described upper limit value, it is preferable because separation of the peeling accelerator from the film hardly occurs. Moreover, it is the same as that of the above also about content of the peeling promoter in a core layer (B). However, in the cellulose acylate laminated film according to this embodiment, the skin layer (A) on the side in contact with the casting belt (so-called B surface side) at the time of production of the film essentially contains the peeling accelerator with the above-described content. It is preferable.

(UV absorber)
The cellulose acylate laminated film according to this embodiment can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by BASF Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The cellulose acylate laminated film according to this embodiment preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol, butanol, an organic solvent such as methylene chloride, methyl acetate, acetone, dioxolane, or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acylate to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the cellulose acylate laminated film. 6-4 mass parts is more preferable.

(Antioxidant)
The cellulose acylate laminated film according to this embodiment can also contain an antioxidant. Antioxidants are additives that are also referred to as “deterioration inhibitors”, and are additives having a function of preventing film deterioration that occurs when a liquid crystal image display device or the like is placed in a high-humidity and high-temperature state.

  As an antioxidant, for example, it has a role of delaying or preventing the film from being decomposed by halogen contained in a residual solvent in the film or phosphoric acid of a phosphoric acid plasticizer. Can also be preferably added.

  As the antioxidant, hindered phenol compounds are preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3 , 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3 (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3 , 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanate Examples include nurate.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The content of these antioxidants is preferably 0.0001 to 1.0 mass%, more preferably 0.001 to 0.1 mass%, with respect to 100 mass parts of the total amount of the cellulose acylate laminated film.

<Physical properties of cellulose acylate laminated film>
(Film thickness)
There is no restriction | limiting in particular about the film thickness of a cellulose acylate laminated film, and it can set suitably in consideration of the request | requirement with respect to thin film formation, the physical property which can endure it, etc. As an example, the average film thickness of the core layer (B) is preferably 20 to 50 μm, more preferably 30 to 40 μm. The average film thickness of at least one of the skin layers (A) is preferably 0.6% or more and less than 5%, more preferably 1 to 3% of the average film thickness of the core layer (B). If this ratio is 0.6% or more, sufficient peelability is ensured, streaky unevenness, non-uniform film thickness, non-uniform optical properties, etc. are suppressed, and if it is less than 5%, the core layer (B) Thus, the laminated film can obtain sufficient optical characteristics. The film thickness (absolute value) of the skin layer (A) is preferably 1 to 10 μm, more preferably 1 to 5 μm.

  Moreover, the sum total of the average film thickness of a pair of core layer (A) and skin layer (B) in a cellulose acylate laminated film becomes like this. Preferably it is 10-70 micrometers, More preferably, it is 30-60 micrometers. The average film thickness of the core layer (A) and the average film thickness of the skin layer (B) are measured as five or more points using a film thickness meter and calculated as an arithmetic average value of these measured values. Is the value to be

(Internal haze)
The internal haze of the cellulose acylate laminated film is preferably 0.05 or less, more preferably 0.03 or less. Conventionally, in order to improve CR (contrast), it has been said that it is necessary to reduce the internal haze of the film. However, when the haze is separated into a film inside and a surface, the improvement effect is internal. It has become clear that things are bigger. The internal haze is a haze generated by a scattering factor inside the film, and the internal is a portion of 0.1 μm or more from the film surface. The internal haze is measured with a haze meter by dropping a solvent having a refractive index of film refractive index ± 0.05 on the film interface so that the haze on the film surface can be ignored as much as possible. A haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.) is used as an internal haze measuring device, a 5V9W halogen bulb is used as a light source, and a silicon photocell (specific luminous efficiency) is used as a light receiving part. With filter). Moreover, a measurement shall be performed by the method as described in the Example mentioned later based on JISK-7136.

  Moreover, when the cellulose acylate laminate film is stretched, it prevents the occurrence of problems such as phase separation and interface breakage at the minute interface between the skin layer (A) and the core layer (B), and lowers the internal haze. From the viewpoint that the glass transition temperature (Tg (A)) of at least one of the skin layer (A) can be reduced to the glass transition temperature (Tg (B)) of the core layer (B), It is preferable to satisfy (9), and it is more preferable to satisfy the following formula (10).

  In addition, as a value of each glass transition temperature of a skin layer (A) and a core layer (B), the value of Tg (glass transition temperature) of the single layer film of a skin layer (A) or a core layer (B), Using the following measuring device, heat is applied to the film (film thickness 50 μm) at a temperature increase rate of 15 ° C./s from room temperature, and the temperature is measured as the temperature at which the surface begins to soften. Here, in order to measure the accurate surface softening temperature of the sample, a calibration curve is first created, and then the sample is measured. As calibration samples, polycaprolactone (surface softening temperature: 55 ° C.), polymethyl methacrylate (PMMA, surface softening temperature: 131.5 ° C.), polyethylene terephthalate (PET, surface softening temperature: 235 ° C.) Is used. The measurement position is changed and measured twice or three times, and the average value is defined as the surface softening temperature.

Apparatus: Nanoscale Thermal Analysis system nano-TA2 (model name and model number, manufactured by Anasys Instruments)
Measurement mode: Close contact mode (5 μm square, scan speed: 1 Hz)
Cantilever: AN2-200 (manufactured by Anasys Instruments).

  The cellulose acylate laminated film is preferably one having a width of 1 to 4 m from the viewpoint of productivity and easy conveyance. More preferably, those having a width of 1.4 to 4 m are used, and particularly preferably 1.6 to 3 m.

Moisture permeability of the cellulose acylate laminate film, 40 ° C., preferably 300~1800g ^/ m 2 · 24h at 90% RH, preferably more ^{400~1500g / m 2 · 24h, 40~1300g} / m 2 · 24h is particularly preferable. The moisture permeability can be measured according to the method described in JIS-Z-0208.

  The breaking elongation of the cellulose acylate laminated film is preferably 5 to 80%, more preferably 10 to 50%.

  The visible light transmittance of the cellulose acylate laminated film is preferably 90% or more, and more preferably 93% or more.

  Regarding the retardation of the cellulose acylate laminated film, the in-plane direction retardation Re (630) at a wavelength of 630 nm and the in-plane direction retardation Re (450) at a wavelength of 450 nm satisfy the following formula (2). preferable. This means that the cellulose acylate laminated film has reverse wavelength dispersion, and can contribute to the improvement of viewing angle characteristics by preventing the occurrence of color shift.

  Further, the in-plane phase difference Re (589) at a wavelength of 589 nm preferably satisfies the following formula (3). Moreover, it is preferable that phase difference Rth (589) in the film thickness direction at a wavelength of 589 nm satisfies the following formula (4). Thus, a film that can be suitably applied to a liquid crystal display device (particularly, a VA mode liquid crystal display device and / or a large liquid crystal display device) is obtained.

  Further, the thickness direction retardation Rth (630) at a wavelength of 630 nm and the thickness direction retardation Rth (450) at a wavelength of 450 nm preferably satisfy the following formula (11). This means that the cellulose acylate laminated film has reverse wavelength dispersion, and can contribute to the improvement of viewing angle characteristics by preventing the occurrence of color shift.

  Further, the variation of Rth and the width of distribution are preferably less than ± 50%, preferably less than ± 30%, and more preferably less than ± 20%. It is more preferably less than ± 15%, even more preferably less than ± 10%, still more preferably less than ± 5%, and particularly preferably less than ± 1%. Most preferably, there is no fluctuation of Rth.

  The phase difference values Re and Rth can be obtained by the following formula (12) and the following formula (13).

  In Expressions (12) and (13), d represents the film thickness (nm), nx represents the maximum refractive index in the plane of the film (also referred to as the refractive index in the slow axis direction), and ny represents The refractive index in the direction perpendicular to the slow axis in the film plane is represented, and nz represents the refractive index of the film in the thickness direction of the film. The phase difference values Re and Rth can be measured using an automatic birefringence meter. For example, it can be obtained at a desired measurement wavelength (for example, 450 nm, 589 nm, and 630 nm) in an environment of 23 ° C. and 55% RH using KOBRA-21ADH (Oji Scientific Instruments).

  The cellulose acylate laminated film according to this embodiment is preferably one that has not been subjected to surface activation treatment such as saponification treatment on the surface thereof.

≪Method for producing cellulose acylate laminated film≫
There is no restriction | limiting in particular about the manufacturing method of the cellulose acylate laminated film of the form mentioned above. For example, a dope A for forming the skin layer (A) and a dope B for forming the core layer (B) are respectively prepared, and these are cast using a casting technique such as a solution casting method or a melt casting method. Thus, the cellulose acylate laminated film can be produced by sequentially forming a film or simultaneously forming (co-casting) simultaneously. A preferred production method in the present invention includes the following steps:
A dope (A) containing cellulose acylate (A) and the above sugar ester compound, and a dope (B) containing cellulose acylate (B) and containing less sugar ester compound than the dope (A) Preparing step;
Cast the dope (A) and dope (B) prepared above onto a support so that the dope (A) becomes the skin layer (A) and the dope (B) becomes the core layer (B). Forming a web by; and
A step of peeling the formed web from the support and stretching.

  Here, the cellulose acylate (A) and the cellulose acylate (B) are the same as described above. That is, the total acyl group substitution degree (DS (A)) of cellulose acylate (A) and the total acyl group substitution degree (DS (B)) of cellulose acylate (B) satisfy the following formula (1):

  Below, the case where such a manufacturing method is implemented by a solution casting method is mentioned as an example, and the manufacturing method of a cellulose acylate laminated film is demonstrated concretely, However, It is not restrict | limited only to such a form.

<Preparation of dope>
First, a cellulose acylate, an additive, and an organic solvent are dissolved while stirring in a dissolution vessel to prepare a dope. The dissolution method is not particularly limited, and various methods such as a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, a method performed using the cooling dissolution method, a method performed at high pressure, etc. A dissolution method can be employed.

  In the manufacturing method of the present embodiment, at least two types of dopes (A) and dope (B) are prepared. The dope (A) essentially contains the cellulose acylate (A) and the sugar ester compound represented by the general formula (I), and optionally contains other additives. On the other hand, the dope (B) essentially contains the cellulose acylate (B), and optionally contains other additives.

The dope (A) is for constituting the skin layer (A), and the dope (B) is for constituting the core layer (B). Film arrangement may be doped formulation which constitutes both the skin layer are the same as A / B / A, for example may have different doping formulation of both skin layers as A _{1 /} B _/ A _2.

  As a method for adding the additive into the dope (A) and the dope (B), the additive may be added to the melting pot, or the additive or additive is dissolved or dissolved between the melting pot and the co-casting die. You may add the disperse | distributed solution to dope in liquid feeding. In the latter case, it is preferable to provide a mixing means such as a static mixer in order to improve the mixing property.

Since cellulose acylate may contain impurities such as unacetylated substances, it is preferable to dissolve the cellulose acylate in an organic solvent as described above and then filter the dope with a filter medium. For example, it can be carried out by passing the dope from a coarse filter to a fine filter using a filter press type filtration device. The filtration operation may be repeated by circulating the dope. As the filter paper to be used, for example, No. made by Azumi filter paper is used. 142451, no. 244, no. A laminate of 260 grades of filter paper is preferred. A slower filtration flow rate is preferable because it prevents passage of gel and the like. Usually, it is preferably 5 L / m ² or less per minute. A smaller filtration pressure is preferable because it prevents passage of gel and the like. Usually, 2 MPa or less is preferable. A metal fiber type leaf disk type filter can also be preferably used. Examples thereof include NF-06D2 and NF12N manufactured by Nippon Seisen. A filter press and a leaf disk type filter may be used in combination.

  The filtered dope is sent to a dope tank, left to stand and degassed by a conventional method. For example, the dope can be degassed by standing at a temperature of 30 ° C. to the boiling point of the solvent for several hours.

<Casting>
Subsequently, the dope (A) and the dope (B) prepared above are successively applied onto the support so that the dope (A) becomes the skin layer (A) and the dope (B) becomes the core layer (B). Cast or co-cast. Thereby, a web is formed.

  Casting is preferably carried out by a solution casting method (solvent casting method). Examples of producing a cellulose acylate film using a solution casting method are described in US Pat. Nos. 2,336,310, 2,367,603, 2,492,078, and 2,492,977. Nos. 2,492,978, 2,607,704, 2,739,069 and 2,739,070, British Patent Nos. 640731 and 736892 And JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, JP-A-60-203430, JP-A-62-115035, and the like.

  The solution casting method is a method of uniformly extruding the prepared dope from a pressure die onto a metal support, and a method using a doctor blade for adjusting the film thickness of the dope once cast on the metal support with a blade. Although there is a method using a reverse roll coater that adjusts with a reverse rotating roll, a method using a pressure die is preferred. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods mentioned here, it can be carried out by various methods known in the art for casting a cellulose acylate solution.

  In the manufacturing method according to the present embodiment, the distribution in the width direction of the laminated film and the lamination are such that the viscosity of the dope (B) at 25 ° C. is 1.1 times or more compared with the viscosity of the dope (A) at 25 ° C. It is preferable from the viewpoint of film production suitability.

(Co-casting)
There is no particular limitation on the casting method, and it is preferable to use a lamination casting method such as a co-casting method, a sequential casting method, and a coating method. In particular, the simultaneous co-casting method is used for stable production and production cost reduction From the viewpoint of the above, it is particularly preferable.

  In the co-casting method (multi-layer simultaneous casting), the casting dope of each layer (which may be three layers or more) is simultaneously pressed from another slit or the like on a casting support (band or drum). This is a casting method in which a web is formed by extruding from a casting giusa to be cast, casting each layer simultaneously, peeling off from a support at an appropriate time, and drying. FIG. 1 is a schematic view showing an example when a cellulose acylate laminated film having a three-layer structure is cast by simultaneous co-casting using a co-casting die. In FIG. 1, a dope (A) 1 for a skin layer (A) and a dope (B) 2 for a core layer (B) are formed on a support 4 for casting using a co-casting giesser 3. A state in which three layers are extruded simultaneously and cast by the simultaneous co-casting method is shown as a cross-sectional view.

  In the sequential casting method, a casting dope for a first layer (for example, one skin layer (A)) is first extruded from a casting giusa on a casting support, cast, dried, or dried. Without drying, a casting dope for the second layer (for example, the core layer (B)) is extruded from the casting giusa and cast, and if necessary, the third layer (for example, the other layer) This is a casting method in which the dope is successively cast and laminated to the skin layer (A)) or more, peeled off from the support at an appropriate time, and dried to form a film.

  In the coating method, generally, a film of the core layer (B) is formed by a solution casting method. Then, a coating solution for the skin layer (A) is prepared, and a film having a laminated structure is formed as a web by applying and drying one side or both sides simultaneously on both sides of the obtained film using an appropriate coating machine. Form.

  Examples of the support used in the manufacturing method according to this embodiment include an endless metal belt (band) that moves indefinitely or a metal drum that rotates. The surface of the casting support is preferably a mirror surface. Both end portions (portions that do not become products) when the cast film is grounded are preferably roughened to facilitate peeling of the web from the support. The co-casting die is not limited as long as the co-casting structure is possible, and for example, a coat hanger die or a T die can be preferably used. A multi-manifold type die or a feed block type die may be used. One die or two or more die may be installed above the support. Preferably 1 or 2 groups. When two or more are installed, the dope amount to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps at each ratio. The temperature of the dope used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all solution temperatures in the process may be the same or may be different in each part of the process. If they are different, the temperature may be a desired temperature just before casting.

  After casting, the web (dope film after casting the dope on the support) is preferably heated on the support to evaporate the solvent until the web can be peeled from the support. For this purpose, there are a method of blowing wind from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. It is preferable from the viewpoint of efficiency. A method of combining them is also preferable.

<Peeling / Drying / Drawing>
(Peeling)
Subsequently, the web formed as described above is peeled off from the support. At this time, if the amount of residual solvent in the web at the time of peeling is too large, there is a possibility that peeling will be difficult. On the other hand, if it peels after fully drying on a support body, there is also a possibility that a part of web may tear on the way.

  As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) capable of peeling even if the amount of residual solvent is large. As this method, there are a method of adding a poor solvent for cellulose acylate into the dope and casting the dope and then gelling, a method of reducing the temperature of the support and gelling. There is also a method of adding a metal salt in the dope. By making the web stronger by gelling on the support, it is possible to accelerate the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, or slipping and vertical stripes due to peeling tension will be likely to occur, so economic speed and quality Therefore, the amount of residual solvent at the time of peeling is determined.

  Although there is no restriction | limiting in particular about the web temperature at the time of peeling a web from a support body, Preferably it is 10-40 degreeC, More preferably, it is 11-30 degreeC. Moreover, it is preferable to peel the web when the residual solvent amount of the web at the peeling position is 10 to 120% by mass. In order to set the residual solvent amount at the time of peeling of the web within this range, there is a method of controlling the surface temperature of the support after casting so that the organic solvent can be efficiently evaporated from the web. It can be preferably used. In order to control the support temperature, it is preferable to use a heat transfer method with good heat transfer efficiency. For example, a back surface heat transfer method using a liquid is preferable. In the belt (support) machine, the belt temperature can be adjusted with a gentle wind for temperature control at the point where the belt to be transferred comes to the lower side. The temperature of the support can be partially changed by dividing the heating means, and can be set to different temperatures such as a casting position, a drying part, and a peeling position of the casting support.

(Dry)
The web peeled from the support as described above is dried by a drier or the like as necessary until a desired residual solvent amount is obtained. The drying method can be carried out, for example, using a drying apparatus that alternately conveys the web through rolls arranged in a staggered manner, or a tenter apparatus that clips and conveys both ends of the web with clips. These may be used in combination.

  As a drying means, hot air is generally blown on both sides of the web, but there is also a means of heating by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.

  In the drying process after peeling from the support surface, the web tends to shrink in the width direction by evaporation of the solvent. Shrinkage increases as the drying temperature increases rapidly. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point of view, for example, a method of drying the entire drying process or a part of the process as disclosed in JP-A-62-46625 while holding both ends of the web with clips in the width direction (tenter method) Is preferred. Then, if necessary, the width | variety both ends of a web are cut off with a slitter, and it introduce | transduces into an extending process.

(Stretching)
The web is then stretched. With respect to the stretching method and conditions, for example, refer to JP-A-62-115035, JP-A-4-152125, 4-284221, 4-298310, and 11-48271. can do.

  In the production method according to this embodiment, it is preferable to stretch the peeled web obtained above in a state where the residual solvent amount is 5% by mass or more. Preferably, the web is stretched in a state where the residual solvent amount is 10 to 70 mass%, more preferably 12 to 35 mass%. When a plurality of stretching processes are performed, it is sufficient that at least one (for example, the first) stretching process satisfies this condition, but more preferably, all stretching processes are performed so as to satisfy this condition. As described above, the cellulose acylate laminated film according to the present invention preferably has wavelength dispersion characteristics, but it is possible to impart such optical performance by a stretching treatment, and further the cellulose acylate laminated film. A desired retardation (retardation) can be imparted to the film. The stretching direction of the web is preferably a film conveyance direction (longitudinal direction; MD direction) and a direction (width direction; TD direction) orthogonal to the conveyance direction, but is a direction orthogonal to the film conveyance direction (width direction). Is particularly preferable from the viewpoint of a subsequent polarizing plate processing process using the film.

  Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, JP-A-2842211, JP-A-298310, and JP-A-11-48271. Yes. On the other hand, in the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying the film while holding it with a tenter and gradually widening the tenter. After the film is dried, it may be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine).

  In the manufacturing method according to the present embodiment, there is no particular limitation on the temperature at which the web is stretched (stretching temperature). However, it is preferable to perform stretching at a stretching temperature of “Tg-30 of core layer” ° C. or higher. By stretching at such a stretching temperature, an effect of reducing internal haze can be obtained. The stretching temperature is preferably “Tg-20 of the core layer” or higher, and more preferably “Tg-10 of the core layer” or higher. When a plurality of stretching processes are performed, it is sufficient that at least one (for example, the first) stretching process satisfies this condition.

  The draw ratio is preferably 5 to 200%, more preferably 10 to 100%, and particularly preferably 20 to 50%. When a plurality of stretching processes are performed, it is sufficient that at least one (for example, the first) stretching process satisfies this condition, but more preferably, all stretching processes are performed so as to satisfy this condition.

  When the produced cellulose acylate laminated film is used as a protective film for a polarizer, the transmission axis of the polarizer and the surface of the cellulose acylate laminated film are used in order to suppress light leakage when the polarizing plate is viewed obliquely. It is necessary to arrange the slow axis in parallel. Since the transmission axis of the roll film-like polarizer produced continuously is generally parallel to the width direction of the roll film, it is composed of the roll film-like polarizer and the roll film-like cellulose acylate laminated film. In order to continuously bond the protective film, the in-plane slow axis of the roll film-shaped protective film (cellulose acylate laminated film according to the present invention) needs to be parallel to the width direction of the film. Become. Therefore, it is preferable to extend more in the width direction from such a viewpoint. In addition, the stretching treatment may be performed in the middle of the film forming process, or the raw film that has been formed and wound may be stretched. However, in the manufacturing method according to the present embodiment, the residual solvent amount is a predetermined value or more. In order to stretch in the state, it is preferable to stretch in the middle of the film forming process.

(Drying / Re-stretching)
In a preferred embodiment of the manufacturing method according to this embodiment, after the web subjected to at least one stretching process is dried, at least one stretching process is further performed. Under the present circumstances, it is preferable that the extending | stretching temperature of the extending | stretching process performed later is "Tg-10 of core layer" degree C or more, More preferably, it is "Tg-5 of core layer" degree C or more. By setting it as such a structure, the phase difference expression property of the cellulose acylate laminated | multilayer film obtained can be improved further. Since the drying method and conditions are as described above, detailed description is omitted here.

  About the film thickness of the film obtained and the film thickness of each layer (skin layer (A) and core layer (B)) constituting the film, the solid content concentration of the dope, the die The slit gap of the die, the extrusion pressure from the die, the support speed, etc. may be adjusted.

(Take-up)
The cellulose acylate laminated film obtained as described above is preferably wound on a roll so that the length per roll is 100 to 10,000 m, more preferably 500 to 7000 m, and still more preferably. 1000 to 6000 m. When winding, it is preferable to give a knurling to at least one end, and the width of the knurling is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm. The height of the knurling is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. This may be a single push or a double push.

  In general, a large screen display device has a noticeable decrease in contrast and coloration in an oblique direction. Therefore, the cellulose acylate laminated film according to the present invention is particularly suitable for use in a large screen liquid crystal display device. When used as a retardation film for a large-screen liquid crystal display device, for example, the film width is preferably 1470 mm or more. In addition, the film of the present invention is not only in the form of a film piece cut to a size that can be incorporated into a liquid crystal display device as it is, but also is produced in a long shape by continuous production and wound into a roll. Also included are films with different shapes. The retardation film having the latter shape is stored and transported in that state, and is cut into a desired size and used when it is actually incorporated into a liquid crystal display device or bonded to a polarizer or the like. Similarly, after being bonded to a polarizer or the like made of a polyvinyl alcohol film or the like that has been made into a long shape, it is cut into a desired size when actually incorporated into a liquid crystal display device. It is done. As one form of the retardation film wound up into a roll, a form wound up into a roll having a roll length of 2500 m or more can be mentioned.

  In addition, after being drawn up into a roll after stretching, a functional thin film such as a hard coat layer or an antireflection layer may be provided. Until processing and shipment, packaging is usually performed in order to protect the product from dirt and electrostatic dust adhering.

  The packaging material is not particularly limited as long as the above purpose can be achieved, but a material that does not hinder volatilization of the residual solvent from the film is preferable. Specific examples include polyethylene, polyester, polypropylene, nylon, polystyrene, paper, various non-woven fabrics, and the like. Those in which the fibers are mesh cloth are more preferably used.

≪Polarizing plate≫
Moreover, according to the other form of this invention, the polarizing plate which has at least 1 film of this invention is also provided.

  The polarizing plate which concerns on this form has a polarizer and the cellulose acylate laminated film which concerns on this invention arrange | positioned at the single side | surface of the said polarizer. By setting it as such a structure, the cellulose acylate laminated film which concerns on this invention functions as a protective film for protecting a polarizer in a polarizing plate.

  In the same manner as described above for the cellulose acylate laminated film according to the present invention, the polarizing plate in the form of a film piece cut into a size that can be incorporated into a liquid crystal display device as it is also in the shape of the polarizing plate according to this embodiment. In addition, a polarizing plate having a shape (for example, a roll length of 2500 m or more or 3900 m or more) that is produced in a long shape by continuous production and rolled up is also included. In order to use for a large-screen liquid crystal display device, as described above, the width of the polarizing plate is preferably 1470 mm or more.

  The specific configuration of the polarizing plate is not particularly limited and a known configuration can be adopted. For example, the configuration shown in FIG. 6 of Japanese Patent Application Laid-Open No. 2008-262161 can be adopted. Hereinafter, an example of the configuration of the polarizing plate will be briefly described.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which includes polyvinyl alcohol. There are a film in which iodine is dyed on an alcohol film and a film in which a dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol 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. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability performance and has few color spots, and is particularly preferably used for a large-screen liquid crystal display device.

  When producing a polarizing plate, the cellulose acylate laminated film of the present invention is applied to a polarizer produced by immersing and stretching in an iodine solution with a completely saponified polyvinyl alcohol aqueous solution (so-called water paste). It is preferable to bond them together.

  Under the present circumstances, when the value of a pure water contact angle differs between two main surfaces of the cellulose acylate laminated film which concerns on this invention (preferably, when these differences are 20-40 degrees), the said pure It is preferable that the main surface having a smaller water contact angle (that is, higher hydrophilicity) is bonded to one main surface of the polarizer. By setting it as such a structure, when bonding a polarizer and a polarizing plate protective film using a water paste, the saponification process with respect to the surface of a film can be abbreviate | omitted.

  As described above, the cellulose acylate laminated film according to the present invention is disposed (bonded) on one surface of the polarizer constituting the polarizing plate. The cellulose acylate laminated film according to the invention may be used, and it is also preferable to bond another optical film. Such other optical films include, for example, commercially available cellulose acylate films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-X KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, manufactured by Konica Minolta Opto Co., Ltd.) are preferably used. In the case of other polarizing plate protective films, it is necessary to perform surface activation treatment such as saponification treatment in advance.

  Bonding of the polarizer, the cellulose acylate laminated film according to the present invention and, if necessary, another optical film is usually performed using an adhesive. Examples of the adhesive that can be used in this case include a PVA-based adhesive and a urethane-based adhesive. Among them, a PVA-based adhesive is preferably used.

  The film placed on the viewing side of the polarizing plate used on the surface side of the display device has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer in addition to the antiglare layer or the clear hard coat layer. Is preferred.

≪Liquid crystal display device≫
The polarizing plate provided by the said form can be used for a liquid crystal display device. Since the liquid crystal display device according to this embodiment uses the polarizing plate provided with the cellulose acylate laminated film having excellent durability provided by the present invention, the liquid crystal display device is similarly excellent in durability.

  The pasting of the exposed surface of the polarizing plate protective film in the polarizing plate and at least one surface of the liquid crystal cell can be performed by a conventionally known method. Depending on the case, it may be bonded through an adhesive layer.

  There are no particular restrictions on the mode (driving method) of the liquid crystal display device, and liquid crystal display devices in various modes (driving methods) such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, and OCB can be used. . A VA (MVA, PVA) type liquid crystal display device is preferable. By using the polarizing plate provided by the present invention for these liquid crystal display devices, there is little environmental fluctuation, and excellent visibility such as color unevenness and front contrast, even with a large-screen liquid crystal display device of 30 type or more. A liquid crystal display device can be obtained.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the technical scope of the present invention is not limited to the following specific examples.

≪Production of film≫
(Preparation of cellulose acylate)
Cellulose acylate was synthesized by the method described in JP-A-10-45804 and 08-231761, and the degree of substitution was measured. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(Preparation of cellulose acylate solution for skin layer (dope (A)))
Each component was dissolved by putting the following composition into a mixing tank and stirring to prepare a cellulose acylate solution for skin layer (dope (A)) for producing the film 101.
Cellulose acetate (substitution degree 2.00; Mw = 19000) 100.0 parts by mass Sugar ester compound (1) 10.0 parts by mass Silica fine particles R972 (manufactured by Nippon Aerosil Co., Ltd.) 0.15 parts by mass Methylene chloride 395. 0 parts by mass / ethanol 59.0 parts by mass In addition, in the sugar ester compound (1), R ¹ in the disaccharide residue B-2 described above is a benzoyl group (substitution degree 6.5) and a hydrogen atom (substitution degree 1. The compound substituted in 5).

For skin layers for producing films 102 to 109, 123 and 125 to 127 in the same manner as described above except that the substitution degree of cellulose acylate and the types and amounts of additives were changed as shown in Table 1 below. A cellulose acylate solution (dope (A)) was prepared (the film 124 was a single layer composed of the core layer (B), and the skin layer (A) was not formed). In addition, in the sugar ester compounds (2) to (4) used in the preparation of the dope (A), R ¹ in the disaccharide residue B-2 described above is an acetyl group (substitution degree 5) and a hydrogen atom (substitution). Compound substituted with degree 3) (sugar ester compound (2)), and R ¹ in monosaccharide residue A-1 described above was substituted with a phenylacetyl group (degree of substitution 3) and a hydrogen atom (degree of substitution 2) Compound (sugar ester compound (3)), and compound (sugar) in which R ¹ in disaccharide residue B-2 described above is substituted with a benzoyl group (substitution degree 5.5) and a hydrogen atom (substitution degree 2.5) Ester compound (4)). The polyester compound (1) is a terephthalic acid / succinic acid / propylene glycol / ethylene glycol copolymer (copolymerization ratio [mol%] = 27.5 / 22.5 / 25/25, Mw: 1100, Mn : 900, Mw / Mn = 1.2).

(Preparation of cellulose acylate solution for core layer (dope (B)))
Each component was dissolved by putting the following composition into a mixing tank and stirring to prepare a core layer cellulose acylate solution (dope (B)) for producing the film 101.
Cellulose acetate (substitution degree 2.00; Mw = 19000) 100.0 parts by mass Polyester compound (1) 15.0 parts by mass Methylene chloride 365.5 parts by mass Ethanol 54.6 parts by mass As shown above, the cellulose acylate solution for core layer (dope () for producing films 102 to 109 and 123 to 127 was prepared in the same manner as above except that the substitution degree of cellulose acylate and the kind and amount of additives were changed. B)) was prepared. The retardation increasing agents (1) and (2) used in the preparation of the dope (B) are compounds having the following chemical formulas.

(Production of cellulose acylate laminated film)
The cellulose acylate solution for the skin layer prepared above (the dope (A)) so that it becomes the skin layer (A) having the film thickness described in Table 1 above, and the cellulose acylate solution for the core layer prepared above. On the endless stainless steel belt that moves indefinitely using a co-casting die as shown in FIG. 1 so that the (dope (B)) becomes the core layer (B) having the thickness described in Table 1 above. Simultaneous co-casting. The obtained web was peeled from the belt and sandwiched between clips, and when the residual solvent amount of the web was 20 to 5%, the first transverse stretching was performed using a tenter under the conditions shown in Table 3 below. . Then, after removing the clip from the film and drying at 130 ° C. for 20 minutes, the film was further subjected to a second transverse stretching using a tenter under the conditions shown in Table 3 below. The film 124 was not subjected to the second transverse stretching.

  The residual solvent amount was determined according to the following formula (14).

  Here, M is the mass of the web at an arbitrary point, and N is the mass when the web of which M is measured is dried at 120 ° C. for 2 hours.

≪Film evaluation≫
The following measurements and evaluations were carried out on the properties of the respective films obtained in the examples and comparative examples. The results are shown in Table 4 below.

(Phase difference)
The retardation values Re and Rth of the film produced above were determined by the following formula (12) and the following formula (13).

  In Expressions (12) and (13), d represents the film thickness (nm), nx represents the maximum refractive index in the plane of the film (also referred to as the refractive index in the slow axis direction), and ny represents The refractive index in the direction perpendicular to the slow axis in the film plane is represented, and nz represents the refractive index of the film in the thickness direction of the film. The phase difference values Re and Rth are measured at 450 nm, 589 nm, and 630 nm in an environment of 23 ° C. and 55% RH using KOBRA-21ADH (Oji Scientific Instruments) as an automatic birefringence meter. did.

  Based on these measurement results, Table 4 below shows the values of Re (589) and Rth (589), and the value of Re (450) / Re (630) as an index of inverse wavelength dispersion.

(Internal haze)
The film prepared above was conditioned for 5 hours or more in an environment of 23 ° C. and 55% RH, and then the internal haze was evaluated by the following method.

  First, the blank haze 1 of a measuring instrument other than a film is measured.

  1. Drip a drop (0.05 mL) of glycerin on a cleaned glass slide. At this time, care is taken so that bubbles do not enter the droplet. Glass must be washed with a detergent (see Fig. 2).

  2. Place the cover glass on top of it. Glycerin spreads without pressing the cover glass.

  3. Set on a haze meter and measure blank haze 1.

  Next, the haze 2 including the sample is measured by the following procedure.

  4). Glycerin (0.05 mL) is dripped on a slide glass (refer FIG. 2).

  5. A sample film to be measured is placed thereon so that air bubbles do not enter (see FIG. 3).

  6). Glycerin (0.05 mL) is dropped onto the sample film (see FIG. 4).

  7). A cover glass is placed thereon (see FIG. 5).

  8). The laminate prepared as described above (from above, cover glass / glycerin / sample film / glycerin / slide glass) is set on a haze meter and haze 2 is measured.

  9. (Haze 2) − (Haze 1) = (Internal haze of film) is calculated.

  In addition, the glass and glycerol used in said measurement are as follows.

Glass: MICRO SLIDE GLASS S9213 MATUNAMI
Glycerin: Deer special grade (Purity> 99.0%) manufactured by Kanto Chemical Co., Ltd. Refractive index 1.47

≪Preparation of polarizing plate≫
The surface of the cellulose acylate laminated film of each Example and Comparative Example prepared above was subjected to alkali saponification treatment. Specifically, it was immersed in a 1.5N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and neutralized with 0.1N sulfuric acid at 30 ° C. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm. Polyvinyl alcohol (Kuraray PVA-117H) 3% by weight aqueous solution as an adhesive, the cellulose acylate laminated films of the examples and comparative examples subjected to the alkali saponification treatment as described above, and the same alkali saponification-treated Konica Minoltack KC8UX (Konica) Prepared by Minolta Opto Co., Ltd., and the saponified surfaces thereof are bonded to each other with the polarizer in between so that the saponified surface is on the polarizer side, and the cellulose acylate laminated films and polarizers of each Example and Comparative Example , KC8UX were obtained in this order to obtain polarizing plates. Under the present circumstances, it bonded so that the MD direction of each cellulose acylate laminated film and the slow axis of KC8UX might become parallel to the absorption axis of a polarizer.

≪Production of liquid crystal display device≫
Using the polarizing plates of the Examples and Comparative Examples prepared above, the polarizing plates prepared above were laminated to the viewing side of the liquid crystal cell as shown in FIG. The film 12 was bonded using an adhesive so that the film 12 was disposed on the liquid crystal cell 13 side. On the other hand, on the opposite side of the liquid crystal cell, an optically anisotropic film ("Fujitac TD80UL" manufactured by Fuji Film) 14, a polarizer 15, a polarizer protective film ("Konica Minoltak KC8UX" manufactured by Konica Minolta Opto) The polarizing plate which consists of 16 3 layers was bonded together with the adhesive so that Fujitac TD80UL might be arrange | positioned at the liquid crystal cell 13 side. At this time, they were bonded so that the absorption axes of the upper and lower polarizing plates were orthogonal to each other.

<< Evaluation of Liquid Crystal Display >>
Various characteristics evaluation was performed about the VA mode liquid crystal display device produced above. The results are shown in Table 5 below.

<Evaluation of panel viewing angle>
As an evaluation of the color viewing angle of the panel, a backlight is installed on the side of the polarizer 11 in FIG. 6, and for each, using a measuring machine (EZ-Contrast XL88, manufactured by ELDIM), black display and white display in a dark room The luminance and chromaticity at the time were measured, and the front contrast ratio (CR) and color shift in black display were calculated.

(Front contrast ratio (CR))
The measurement result of the front contrast ratio (CR) was evaluated according to the following criteria:
A: CR is 3000 or more, which is preferable for practical use;
○: CR is 2000 or more and less than 3000, and there is no practical problem;
Δ: CR is 1500 or more and less than 2000, but can withstand practical use;
X: CR is less than 1500, which is problematic in practical use.

(Viewing angle (polar color shift))
During black display, changes in chromaticity Δxθ and Δyθ when the viewing angle is tilted from the normal direction of the liquid crystal cell to the center line direction of the transmission axis of the pair of polarizing plates (azimuth angle 45 degrees) are polar angles 0 to 80. Measured between degrees. Here, [Delta] x [theta] = x [theta] -x [theta] 0, [Delta] y [theta] = y [theta] -y [theta] 0, (x [theta] 0, y [theta] 0) is the chromaticity measured in the normal direction of the liquid crystal cell in black display, and (x [theta], y [theta]) is the liquid crystal cell in black display. It is chromaticity measured in a direction in which the viewing angle is tilted from the normal direction to the polar angle θ degree in the center line direction of the transmission axis of the pair of polarizing plates.

The color shift measurement results were evaluated according to the following criteria:
A: Δxθ and Δyθ are both 0.02 or less;
○: Δxθ and Δyθ are both 0.03 or less;
Δ: Δxθ and Δyθ are both 0.05 or less;
X: Both Δxθ and Δyθ are larger than 0.1.

  In addition, it is preferable that the polar color shift always satisfies the following expressions (15) and (16).

  From the results shown in Tables 4 and 5, the cellulose acylate laminated films of the examples of the present invention all had low internal haze, reverse wavelength dispersibility, and good retardation development even in a thin film. Also, due to this, both the front contrast ratio (CR) and viewing angle characteristics were excellent.

  On the other hand, in the films 123 and 127 in which the substitution degree of the cellulose acylate in the skin layer (A) is larger than the range of the present invention, the cellulose acylate in the skin layer (A) is mixed into the core layer (B), resulting in poor compatibility. As a result, the internal haze increased, and as a result, the front CR deteriorated. Further, in the film 124 composed of a single layer of the core layer (B), the dispersion of the retardation increasing agent and the sugar ester compound throughout the film results in a decrease in reverse wavelength dispersion and a deterioration in viewing angle characteristics. became. Furthermore, in the film 125 in which the substitution degree of the cellulose acylate in the skin layer (A) and the core layer (B) are both larger than the range of the present invention, a sufficient retardation was not obtained, so that the front CR and viewing angle characteristics were obtained. Neither showed sufficient properties. Further, since the film 126 did not contain a sugar ester compound, the saponification resistance was insufficient, and both the front CR and viewing angle characteristics were deteriorated.

  As described above, by adopting the configuration of the present invention, even in a cellulose acylate film mainly composed of a low-substituted cellulose acylate such as DAC, the decrease in internal haze and reverse wavelength dispersibility is minimized. It was shown that a high phase difference can be expressed.

1 Dope (A)
2 Dope (B)
3 Co-casting Giesa 4 Support 10 Polarizer Protective Film (Konica Minoltack KC8UX)
DESCRIPTION OF SYMBOLS 11 Polarizer 12 Cellulose acylate laminated film of each Example and Comparative Example 13 Liquid crystal cell 14 Optical anisotropic film (Fujitac TD80UL)
15 Polarizer 16 Polarizer Protective Film (Konica Minoltack KC8UX)

Claims (14)

A cellulose acylate laminated film having a three-layer structure in which a core layer (B) containing cellulose acylate (B) is sandwiched by a pair of skin layers (A) containing cellulose acylate (A),
Both of the pair of skin layers (A) are represented by the following general formula (I):
In the formula, G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m represents a hydroxyl group directly bonded to the monosaccharide or disaccharide residue. The sum of the numbers, l is the sum of the number of — (O—C (═O) —R ² ) groups directly attached to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 Yes, l ≠ 0,
Containing a sugar ester compound represented by
Both the content of the sugar ester compound in the pair of skin layers (A) is greater than the content of the sugar ester compound in the core layer (B),
The cellulose acylate wherein the total acyl group substitution degree (DS (A)) of the cellulose acylate (A) and the total acyl group substitution degree (DS (B)) of the cellulose acylate (B) satisfy the following formula (1): Rate laminated film.
  The cellulose acylate laminated film according to claim 1, wherein the core layer (B) does not contain the sugar ester compound. The cellulose acylate laminated film according to claim 1 or 2, wherein the in-plane direction retardation Re (630) at a wavelength of 630 nm and the in-plane direction retardation Re (450) at a wavelength of 450 nm satisfy the following formula (2): .
The in-plane phase difference Re (589) at a wavelength of 589 nm satisfies the following formula (3), and the thickness direction retardation Rth (589) at a wavelength of 589 nm satisfies the following formula (4): 4. The cellulose acylate laminated film according to any one of 3 above.
  The cellulose acylate laminated film according to any one of claims 1 to 4, wherein the internal haze is 0.04 or less.   The cellulose acylate laminated film according to any one of claims 1 to 5, wherein the core layer (B) contains a retardation increasing agent.   The cellulose acylate laminated film according to any one of claims 1 to 6, wherein an acyl substituent in the cellulose acylate (A) and the cellulose acylate (B) has 2 to 4 carbon atoms.   The cellulose acylate laminated film according to claim 7, wherein both the cellulose acylate (A) and the cellulose acylate (B) are cellulose acetate.   The average thickness of the core layer (B) is 20 to 50 μm, and the average thickness of at least one of the skin layers (A) is 0.6% or more and less than 5% of the average thickness of the core layer (B). The cellulose acylate laminated film according to any one of claims 1 to 8, wherein Cellulose acylate (A) and the following general formula (I):
In the formula, G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m represents a hydroxyl group directly bonded to the monosaccharide or disaccharide residue. The sum of the numbers, l is the sum of the number of — (O—C (═O) —R ² ) groups directly attached to the monosaccharide or disaccharide residue, and 3 ≦ m + l ≦ 8 Yes, l ≠ 0,
Preparing a dope (A) containing a sugar ester compound represented by: and a dope (B) containing cellulose acylate (B) and containing less sugar ester compound than the dope (A);
The prepared dope (A) and dope (B) are cast on a support so that the dope (A) becomes a skin layer (A) and the dope (B) becomes a core layer (B) to form a web. And a process of
Peeling the formed web from the support and stretching,
A method for producing a cellulose acylate laminated film, comprising:   The manufacturing method according to claim 10, further comprising a step of further performing at least one stretching treatment after drying the web subjected to at least one stretching treatment.   The manufacturing method according to claim 10 or 11, wherein the casting is performed by simultaneous co-casting.   It has at least 1 the cellulose acylate laminated film of any one of Claims 1-9, or the cellulose acylate laminated film manufactured by the manufacturing method of any one of Claims 10-12, Polarizer.   A liquid crystal display device comprising the polarizing plate according to claim 13.