JP2003126768A - Drying method for optical thin film, method for manufacturing the same and optical thin film obtained from these methods - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drying method for an optical thin film uniform in film thickness distribution, free of defects such as irregular color and cissing and having high quality and good transportability and to provide a method for manufacturing the same and an optical thin film obtained from these methods. SOLUTION: In the drying method for an optical thin film obtained by coating and drying on a support, the surface of a coating film of the optical thin film having 1-50% solid concentration is dried at 0.2-1 m/sec velocity of air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical thin film, and more particularly to a method for drying an optical thin film which is excellent in flatness and film thickness distribution and has no trouble such as color unevenness, a method for producing the same and an optical thin film obtained by these methods.

[0002]

2. Description of the Related Art In recent years, along with the widespread use of liquid crystal display devices, their upsizing, and their outdoor use, durability has been required under the use conditions of optical thin films, and resistance to reflected light. The demand for optical thin films for use in liquid crystal display devices has been growing significantly since functional thin films have been produced.

Generally, the visibility of a liquid crystal display device is reduced by the reflection of a scene due to the surface reflection of external light, and a method of providing an optical thin film for antireflection on the outermost surface is generally performed.

However, since the optical thin film for antireflection is provided on the outermost surface in order to realize its function, it inevitably suffers from many issues of high quality from the viewpoint of toughness with respect to the performance of the optical thin film. ing. For example, it is possible to reduce the reflectance to the limit, the appearance such as color unevenness, the scratch resistance, the prevention of adhesion of fingerprints and oils and fats, and the ease of removal.

As the antireflection thin film, a transparent thin film of a metal oxide such as magnesium fluoride or silicon dioxide having a wide wavelength range / low reflectance, which has the ability to cover the entire wavelength range of visible light, is laminated by a method such as vapor deposition. Multilayer films have been used. A method such as vapor deposition is very expensive because it requires a number of operations to control the film thickness with high accuracy according to the relationship between the refractive index and the film thickness of each layer that is optimally designed in advance. In addition, it is very difficult to obtain a film having a large area, and the suitability for mass production is poor.

On the other hand, although an optical thin film by a coating method has been developed, how to lower the refractive index of the uppermost layer (air side interface) of the film, and to improve the appearance such as color unevenness and the physical characteristics of the film. There is a problem in strengthening. These antireflection technologies have a small refractive index difference with the base material and have an insufficient antireflection effect, and in addition, the film becomes brittle and is easily cracked when an antireflection function is imparted to a flexible film, and the handleability is low. There were problems such as becoming difficult.

Further, when heat treatment is carried out to sufficiently advance the curing reaction for the purpose of improving the physical properties of the film, the plastic support is deformed and good flatness cannot be maintained, and an optical thin film having uniform optical performance is obtained. I can't. When a thin optical material such as an antireflection film is produced by coating and drying, the optical function is impaired due to uneven thickness of several nm.

In particular, the low refractive index layer is provided on the surface side of the multilayer optical thin film. Therefore, if slight thickness unevenness occurs in the low refractive index layer, color unevenness of reflected light will occur. In the coating, stepwise coating unevenness and a wind ripple during drying are likely to occur, and it is difficult to form a low refractive index layer having a uniform thickness.

Therefore, there is a demand for a method of drying and a method of manufacturing an optical thin film (antireflection optical thin film) which has a uniform film thickness without drying unevenness and repellency and has good transportability when continuously processed by a web method. It was being done.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for drying an optical thin film which has a uniform film thickness distribution, is free from defects such as color unevenness and repellency, and has good transportability. It is to provide a manufacturing method and an optical thin film obtained by these methods.

[0011]

The above object of the present invention can be achieved by the following constitutions.

1. In the method for drying an optical thin film obtained by coating and drying on a support, the air velocity of the coating film surface of the optical thin film having a solid content concentration of 1 to 50% is 0.2 to 1 m / sec. A method for drying an optical thin film, which comprises:

2. 2. The method for drying an optical thin film as described in 1 above, wherein the airflow temperature in the drying chamber is 40 to 130 ° C.

3. 3. The method for drying an optical thin film as described in 1 or 2 above, which comprises drying with infrared rays.

4. In a method for drying an optical thin film obtained by coating and drying on a support, a roller and a base material which are in contact with the back surface of the coating film of the optical thin film until the solid content concentration of the coating film of the optical thin film becomes 10 to 98%. The method for drying an optical thin film is characterized in that the temperature difference from the temperature is 0 to 15 ° C.

5. In a method for drying an optical thin film obtained by coating and drying on a support, the back side of the coating film of the optical thin film is not brought into contact with a roller until the solid content concentration of the coating film of the optical thin film becomes 10 to 98%. A method for drying an optical thin film, which comprises transporting.

6. Any one of the above 1 to 3, characterized in that the back surface of the coating film of the optical thin film is supported by a non-contact floater.
Item 5. A method for drying an optical thin film according to item.

7. Immediately after coating the optical thin film, the film thickness is 3 to 10
7. The method for drying an optical thin film as described in any one of 1 to 6 above, wherein the method is dry.

8. In the method for drying an optical thin film obtained by coating and drying on a support, the coating temperature for drying the optical thin film coating film has a solid content concentration of 10 to 98%. And a method for drying an optical thin film.

9. In the method for drying an optical thin film obtained by coating and drying on a support, when the solid content concentration of the coating film of the optical thin film is 10 to 98% and the coating film of the optical thin film is dried, it is represented by the above h × ΔT. Drying speed is 400 ~ 15
A method for drying an optical thin film, wherein the method is 00 w / m ² .

10. A method for producing an optical thin film, which is produced using the drying method according to any one of 1 to 9 above.

11. An optical thin film obtained by using the drying method according to any one of 1 to 9 above.

12. 12. The optical thin film as described in 11 above, wherein the optical thin film is an antireflection optical thin film.

13. 11. The method for producing an optical thin film as described in 10 above, wherein the optical thin film is an antireflection optical thin film.

The present invention will be described in more detail below. The drying method and manufacturing method of the optical thin film of the present invention will be described.

The solid content concentration of the coating film of the present invention is determined by the following formula. Solid content concentration (%) = (mass of solid content / total mass) × 100 In the invention of claim 1, the solid content concentration of the coating film of the optical thin film is 1 to 50% of the coating film surface of the optical thin film. It is characterized by drying at a wind speed of 0.2 to 1 m / sec.

The air velocity on the surface of the coating film of the optical thin film during this drying is 0.2 to 1.0 m / sec, preferably 0.2 to 0.5 m / sec. This is because when a solvent having a very high drying rate is used, the coating film is disturbed by a slight wind and the drying locally progresses, resulting in uneven drying.

The airflow temperature in the drying chamber is preferably 40 to 130 ° C, more preferably 40 to 110 ° C, and further preferably 55 to 110 ° C.

If the airflow temperature in the drying chamber is lower than 40 ° C., the drying speed will be reduced, which will affect the productivity and, at the same time, a repellant failure will occur and a uniform film will not be formed. Also, the temperature is 13
If the temperature exceeds 0 ° C, the drying speed becomes too fast, and the drying locally progresses, which causes unevenness in drying.

The method for drying the optical thin film of the present invention is preferably drying with infrared rays. For infrared rays, it is preferable to use a medium to long wave infrared heater and set the distance to the optical thin film to be conveyed to 3 to 5 cm, and the infrared temperature at this distance is 200.
It is preferable to set the temperature to 300 ° C to 300 ° C.

The feature of infrared drying is that it is possible to proceed with the drying without generating a wind flow, and to obtain a uniform optical thin film with no uneven drying.

According to a fourth aspect of the present invention, the temperature of the roller and the substrate which come into contact with the back surface of the coating film of the optical thin film is maintained until the solid content concentration of the coating film of the optical thin film reaches 10 to 98%. The difference is 0 to 15 ° C., and the preferable temperature difference is 0 to 10 ° C.

When the roller temperature from the back surface of the optical thin film is high, the temperature of the film surface rises due to the abrupt movement of heat, and the drying locally progresses, resulting in uneven drying. The heat transfer coefficient from the roller is extremely high compared to the air flow, and is also affected by the slight difference in the contact area of the support. In particular, when the support is apt to cause a crack, vertical uneven drying is remarkable due to the difference in contact area of the width. Therefore, when the roller temperature is sufficiently low, heat does not move and unevenness does not occur. However, when the solid content concentration is less than 10%, the drying does not become uneven.

According to a fifth aspect of the present invention, the optical thin film coating film has a solid content concentration of 10 to 98% and the optical thin film coating film is dried until the drying is completed. The feature is that the back side is conveyed without contacting the roller.

In the sixth aspect of the present invention, when the optical thin film is dried, it is preferable that the back surface of the coating film of the optical thin film is supported by a non-contact floater.

In the method of drying an optical thin film of the present invention, it is preferable that the thickness of the coating film of the optical thin film immediately after coating is 3 to 10 μm.

If the film thickness immediately after coating is less than 3 μm, it is difficult to form a uniform coating film, the distance to the end of drying is short, and it is possible to create a situation in which the back surface cannot be brought into contact relatively easily in terms of equipment. If it exceeds 10 μm, the drying period becomes long, and the optical thin film cannot be supported until the coating and drying are completed, which is not preferable from the viewpoint of transport stability. As a method for solving this problem, an optical thin film having good quality with no transport unevenness and no drying unevenness can be obtained by supporting the optical thin film from the back surface with a non-contact floater by an air flow. The difference between the airflow temperature of the non-contact floater and the surface temperature of the coating film is preferably 0 to 15 ° C., like the back surface of the coating film and the roller. If there is no such temperature difference, various disturbances are likely to be received, and it becomes difficult to solve uneven drying and the like.

According to the eighth aspect of the present invention, in the method for drying an optical thin film, the solid concentration of the coating film of the optical thin film is 10 to 98%.
The coating temperature for drying the coating film of the optical thin film is 25
The coating temperature is preferably 30 to 50 ° C. If the coating temperature is less than 25 ° C., a repellant failure will occur and a uniform film will not be formed. On the other hand, if the coating temperature exceeds 55 ° C., the drying speed becomes too fast and the drying locally progresses, which causes unevenness in drying.

In the method for drying an optical thin film according to a ninth aspect of the present invention, the solid content concentration of the coating film of the optical thin film is 10 to 98%.
When drying the coating film of the optical thin film, the following h × ΔT
Is characterized by a drying rate of 400 to 1500 w / m ² .

Drying rate: h × ΔT (w / m ² ) h (heat transfer coefficient): (w / (m ² K)) ΔT: Temperature difference between air flow and substrate (K) The above drying rate is preferably , 600-1000 w / m ²
Is. If the drying speed is less than 400, a repellency failure will occur and a uniform film will not be formed. Further, if the drying speed exceeds 1500, the drying locally progresses, which causes unevenness in drying.

The method for producing an optical thin film of the present invention is characterized in that the optical thin film is obtained through the drying step of any one of the above-mentioned optical thin films.

The optical thin film of the present invention is characterized by being obtained through the above-mentioned manufacturing method, and in the present invention, the optical thin film is preferably an antireflection optical thin film.

A feature of the antireflection optical thin film in the present invention is a laminated body of optical interference layers in which a high refractive layer and a low refractive layer are laminated in that order from the support side on at least one surface of the support (in some cases, other It is possible to add layers of.

With respect to the light of wavelength λ, the optical film thickness of the high-refractive layer and the low-refractive layer is set to λ / 4, and the antireflection laminate is produced. The optical film thickness is a quantity defined by the product of the layer refraction n and the film thickness d. The high or low of the refractive index is almost determined by the metal or compound contained therein, and for example,
Ti is high, Si is low, and compounds containing F are even lower, and such a combination sets the refractive index. The refractive index and the film thickness are calculated and calculated by measuring the spectral reflectance.

When a solution containing a metal compound is applied to a support to obtain a film, the antireflection optical characteristics are determined only by the physical film thickness as described above.

In particular, the color of the reflected light near 550 nm changes between red purple and blue purple when the film thickness deviates by only a few nm. This color unevenness is hardly noticeable when the amount of light transmitted from the display is large, but when the amount of light is small or when the display is turned off, color unevenness is noticeable and the quality deteriorates.

When the deviation of the film thickness is large, 400
The reflectance at ˜700 nm cannot be lowered, and it becomes difficult to obtain desired antireflection characteristics.

[Support] The support used in the present invention is not particularly limited, and examples thereof include a polyester film, a cellulose ester film, a polycarbonate film, a polyether sulfone film, and a norbornene resin film. Of these, a cellulose ester film is preferable in the present invention, and a cellulose ester film stretched in at least one direction is particularly preferable.

Stretching is 1.02 in the machine direction (machine direction).
~ 1.50 times, or 1.02 in the lateral direction (width direction)
It is preferably performed 1.520 times, and more preferably biaxially stretched in the longitudinal and transverse directions.

The stretching method is not particularly limited as long as it can be stretched. For example, a method of passing the web through several tight rolls, a method of gripping both ends of the web with a clip or the like and stretching in the width direction, and a method of clipping There is a method of gripping the sheet and widening the clip interval in the traveling direction, and the like, and any of them can be preferably used. The stretching not only increases the strength of the support, but also has the effect of improving the flatness and can improve the uniformity of the reflectance over the entire area of the support as an antireflection optical thin film.

The cellulose as a raw material of the cellulose ester preferably used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, kenaf and the like. The cellulose esters obtained from them can be used alone or as a mixture at an arbitrary ratio, but it is preferable to use 50% by mass or more of cotton linter.

In the cellulose ester, the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride,
Butyric anhydride), the reaction is carried out using an organic acid such as acetic acid or an organic solvent such as methylene chloride and a protic catalyst such as sulfuric acid. The acylating agent is an acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ C
In the case of OCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, JP-A-10
It can be synthesized by the method described in JP-A-45804. In the cellulose ester, the acyl group reacts with the hydroxyl group of the cellulose molecule. The cellulose molecule is composed of a large number of glucose units linked together, and each glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution.

For example, cellulose triacetate has an acetyl group bonded to all three hydroxyl groups of the glucose unit.

The cellulose ester that can be used in the cellulose ester film is not particularly limited, but the total degree of substitution of acyl groups is preferably 2.40 to 2.98, and the degree of substitution of acetyl groups among acyl groups is preferable. Is 1.4
The above is more preferably used.

The method of measuring the substitution degree of the acyl group is ASTM-
It can be measured according to D817-96.

Cellulose ester includes cellulose acetate such as cellulose triacetate and cellulose diacetate, acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate, as well as propionate group or butyrate group. It is preferably a cellulose ester in which is bonded. Note that butyrate includes iso-in addition to n-. Cellulose acetate propionate having a large degree of substitution of propionate groups has excellent water resistance.

Number average molecular weight Mn of cellulose ester
(The measuring method is described below) is 70,000 to 250,000.
In the range of 00, the mechanical strength of the obtained film is high,
In addition, the dope viscosity is appropriate, which is preferable. Further 80,00
0 to 150,000 is preferable. Further, a cellulose ester having a ratio (MW / Mn) to the weight average molecular weight Mw of 1.0 to 5.0 is preferably used, and more preferably 1.5.
~ 4.5.

<< Measurement of Number Average Molecular Weight of Cellulose Ester >> It is measured by high performance liquid chromatography under the following conditions.

Solvent: Acetone column: MPW × 1 (manufactured by Tosoh Corporation) Sample concentration: 0.2 (mass / volume)% Flow rate: 1.0 mL / min Sample injection amount: 300 μL Standard sample: Polymethylmethacrylate (weight Average molecular weight 188,200) Temperature: 23 ° C.

Further, it is preferable that the amount of metal in the cellulose ester used during the production of the cellulose ester during production or mixed in the used material in a small amount is as small as possible, and the total content of metals such as Ca, Mg, Fe and Na is contained. Quantity is 10
0 ppm or less is preferable.

[Organic Solvent] As a useful organic solvent for dissolving a cellulose ester to form a cellulose ester solution or dope, methylene chloride (methylene chloride), which is a chlorine-based organic solvent, can be mentioned. Dissolution of a cellulose ester, particularly cellulose triacetate Suitable for As the non-chlorine organic solvent, for example, methyl acetate,
Ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1- Propanol, 1,3-difluoro-2-propanol,
1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3 Examples thereof include 3-pentafluoro-1-propanol and nitroethane.

When these organic solvents are used for cellulose triacetate, a dissolving method at room temperature can be used, but by using a dissolving method such as a high temperature dissolving method, a cooling dissolving method and a high pressure dissolving method. Insoluble matter can be reduced, which is preferable.

For cellulose esters other than cellulose triacetate, methylene chloride can be used, but methyl acetate, ethyl acetate and acetone can be preferably used without using methylene chloride. Methyl acetate is particularly preferable. In the present invention, an organic solvent having good solubility in the above-mentioned cellulose ester is referred to as a good solvent, and also exhibits a main effect on dissolution, in which a large amount of organic solvent is the main (organic) solvent or the main ( Organic) solvent.

In the dope, in addition to the above organic solvent, 1 to 4
It is preferable to contain 0% by mass of an alcohol having 1 to 4 carbon atoms. These are used as a gelling solvent that makes the web gel when the dope is cast on a metal support and the solvent begins to evaporate and the ratio of alcohol increases, and makes the web tough and easy to peel from the metal support. When these proportions are small, it also has a role of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent.

As the alcohol having 1 to 4 carbon atoms,
Methanol, ethanol, n-propanol, iso-
Propanol, n-butanol, sec-butanol,
Mention may be made of tert-butanol.

Of these, ethanol is preferred because it is excellent in stability of the dope, has a relatively low boiling point, has good drying property, and has no toxicity. These organic solvents alone are not soluble in cellulose ester and are therefore called poor solvents.

[Production of Cellulose Ester Film by Solution Casting Method] A method for forming a cellulose ester film used as a support will be described. The cellulose ester film is produced by a solution casting film forming method.

Dissolving step: a step of dissolving the cellulose ester, the polymer and additives in an organic solvent mainly containing a good solvent for the cellulose ester (flakes) while stirring to form a dope, or the cellulose ester This is a step of forming a dope by mixing a polymer solution and an additive solution with the solution. To dissolve the cellulose ester, a method carried out under normal pressure, a method carried out below the boiling point of the main solvent,
Method of pressurizing above the boiling point of the main solvent, JP-A-9-95
544, 9-95557 or 9-95538.
Japanese Patent Laid-Open Publication No. 11-1999
Although various dissolution methods such as a high pressure method described in JP-A-21379 can be used, in the present invention, a method of pressurizing above the boiling point of the main solvent is particularly preferable.

The concentration of cellulose ester in the dope is 1
0 to 35 mass% is preferable. An additive is added to the dope during or after the dissolution to dissolve and disperse it, and the dope is filtered through a filter medium, defoamed, and sent to the next step by a liquid sending pump.

Casting step: An endless metal belt, such as a stainless steel belt, or a rotating metal drum, which feeds the dope to a pressure die through a liquid feed pump (for example, a pressure-type metering gear pump) and transfers it indefinitely. This is a step of casting the dope from the pressure die slit at the casting position on the support. It is preferable to use a pressure die that can adjust the slit shape of the die die and facilitates uniform film thickness. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film formation speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided to form multiple layers.

Solvent evaporation step: The web (the dope film is called the web after casting the dope on the metal support) is heated on the metal support until the web can be peeled from the metal support. This is a step of evaporating the solvent. To evaporate the solvent, a method of blowing a wind from the web side and / or
Alternatively, there are a method of transferring heat from the back surface of the metal support by a liquid, a method of transferring heat from the front and back sides by radiant heat, and the like, and the back surface liquid heat transfer method is preferable because of good drying efficiency. A method of combining them is also preferable. In the case of rear surface liquid heat transfer, it is preferable to heat at a temperature not higher than the boiling point of the main solvent of the organic solvent used for the dope or the organic solvent having the lowest boiling point.

Peeling step: This is a step of peeling the web having the solvent evaporated on the metal support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount of the web at the time of peeling (the following formula) is too large, it is difficult to peel, or conversely if you peel it after drying it sufficiently on the metal support, part of the web may peel off in the middle .

As a method of increasing the film forming speed (the film forming speed can be increased by peeling while the residual solvent amount is as large as possible), there is a gel casting method (gel casting).

In the method for drying and producing the optical thin film of the present invention, a cellulose ester film produced by the solution casting film forming method is used as a support, but the solution casting film forming method itself is not particularly limited. , Methods commonly used in the art, eg, US Pat. No. 2,492,97.
No. 8, No. 2,739,070, No. 2,739,0
No. 69, No. 2,492,977, No. 2,336.
No. 310, No. 2,367,603, No. 2,60
7,704, British Patents 64,071, 73
No. 5,892, Japanese Patent Publication No. 45-9074, No. 49-45.
No. 54, No. 49-5614, No. 60-27562,
The methods described in No. 61-39890, No. 62-4208, etc. can be referred to.

The solvent used in the preparation of the dope solution of the cellulose ester used in the solution casting film formation method may be used alone or in combination of two or more kinds, but a good solvent of the cellulose ester and a poor solvent are mixed. It is preferable to use it in terms of production efficiency, and it is preferable that the amount of the good solvent is large in terms of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass of the good solvent,
The poor solvent is 30 to 2 mass%.

The good solvent and the poor solvent are defined as those in which the cellulose ester used alone is dissolved, and those in which the cellulose ester swells or does not dissolve alone are defined as the poor solvent. Therefore, depending on the average degree of acetylation of the cellulose ester, the target of good solvent and poor solvent changes. For example, when acetone is used as a solvent, the amount of bound acetic acid in the cellulose ester of 55% is a good solvent, and the amount of bound acetic acid is 60. %
Then it becomes a poor solvent.

The good solvent used in the present invention is not particularly limited. For example, in the case of cellulose triacetate, an organic halogen compound such as methylene chloride, dioxolanes, methyl acetate, or cellulose acetate propionate is used. , Methylene chloride, acetone, methyl acetate and the like.

The poor solvent used in the present invention is not particularly limited, but for example, methanol, ethanol, i-propyl alcohol, n-butanol, cyclohexane, acetone, cyclohexanone and the like are preferably used.

As a method for dissolving the cellulose ester when preparing the above dope solution, a general method can be used, but in a range above the boiling point of the solvent under normal pressure and under which the solvent does not boil under pressure. The method of heating at the temperature of 1 and dissolving with stirring is more preferable because it can prevent the generation of undissolved lumps called gel or mamako.

A method in which the cellulose ester is mixed with a poor solvent, moistened or swollen, and then mixed with a good solvent to dissolve the cellulose ester is also preferably used.

The type of the pressure vessel is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition to the pressure gauge,
Appropriately install thermometers and other instruments. The pressurization may be carried out by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

The heating temperature after the addition of the solvent is preferably higher than the boiling point of the solvent used at normal pressure and within the range where the solvent does not boil from the viewpoint of the solubility of the cellulose ester, but the heating temperature is too high. Therefore, the required pressure increases and the productivity deteriorates. The preferred heating temperature is 45 to 120.
℃, more preferably 60 ~ 110 ℃, 70 ℃ ~ 1
The range of 05 ° C is more preferable. Also, the pressure is the set temperature,
The solvent is adjusted so that it does not boil.

In addition to the cellulose ester and the solvent, necessary additives such as a plasticizer and an ultraviolet absorber are mixed with the solvent in advance and dissolved or dispersed, and then added to the solvent before the dissolution of the cellulose ester. It may be added to the dope after dissolution.

After the dissolution, the product is taken out from the container while being cooled, or is taken out from the container by a pump or the like and cooled by a heat exchanger and the like, and is used for film formation. At this time, the cooling temperature is cooled to room temperature. However, it is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced. The method for measuring the degree of substitution of the acetyl group is ASTM-817-96.
It can be measured according to the regulations of.

These cellulose esters are manufactured (film formation) by a method generally called a solution casting film formation method as described later. This method is used for endless metal belts (eg stainless steel belts) or rotating metal drums (eg cast iron chrome-plated drums) that can be transferred indefinitely.
A dope (a cellulose ester solution) is cast from a pressure die onto a casting metal support (hereinafter, also simply referred to as a metal support), and a web (metal casting) on the metal support is cast. The doped film) from the metal support,
It is manufactured by drying.

From the viewpoint of preventing deterioration when the cellulose ester film is placed outdoors as an image display device, it is preferable to contain the ultraviolet absorber described below.

As the ultraviolet absorber, those which are excellent in absorption of ultraviolet rays having a wavelength of 370 nm or less and have little absorption of visible light having a wavelength of 400 nm or more can be preferably used. For example, oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds,
Examples thereof include nickel complex salt compounds, but the present invention is not limited thereto.

In the present invention, the thickness of the cellulose ester film is preferably 10 to 500 μm, and particularly preferably 10 to 80 μm.

The thickness of the optical thin film of the present invention is from 1 to 1
000 nm is preferred. In the present invention, when the optical thin film of the present invention is provided on the support surface as described above, it can be provided so that the film thickness deviation with respect to the average film thickness is ± 8%, more preferably within ± 5%. It is possible to form a thin film uniformly within ± 1%.

By laminating multiple thin films by the drying method and manufacturing method of the present invention, it is possible to obtain a uniform optical thin film without unevenness of each layer.

As described above, according to the present invention, it is possible to provide an optical thin film formed with a thin film having various functions.

In the present invention, as the antistatic layer or the conductive layer, a layer having a film thickness of 0.1 to 2 μm coated with conductive resin fine particles such as metal oxide fine particles and crosslinked cationic polymers may be provided.

The optical thin film obtained by the method for drying an optical thin film of the present invention is particularly useful as a polarizing plate protective film, and a polarizing plate can be produced by a known method using this. Since these optical thin films have high uniformity of thin films, they can be preferably used in various display devices and can obtain excellent display performance.

In the optical thin film of the present invention, if necessary, a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, a conductive layer, a light diffusion layer, an easy adhesion layer, an antifouling layer, an easy adhesion layer, Alignment layer,
A liquid crystal layer, an optically anisotropic layer and the like can be provided alone or in combination.

In a liquid crystal display device, it is usually preferable to dispose a substrate containing a liquid crystal between two polarizing plates. In particular, a polarizing plate protective film on the outermost surface of the liquid crystal display device on the display side has a hard coat layer and an antiglare layer. Since a layer, an antireflection layer and the like are provided, it is particularly preferable to use the polarizing plate in this portion.

The optical thin film of the present invention can be easily transported and wound by incorporating a matting agent into a cellulose ester film (support) described later.

The matting agent is preferably as fine particles as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, and silica. Inorganic fine particles such as aluminum oxide, magnesium silicate, and calcium phosphate, polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder,
Silicon-based resin powder, polystyrene-based resin powder, polycarbonate resin powder, benzoguanamine-based resin powder, melamine-based resin powder, polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, or polyfluorinated ethylene-based powder Resin powder and the like can be mentioned, but crosslinked polymer fine particles are particularly preferable. The present invention is not limited to these.

Of the above, silicon dioxide is particularly preferable for adjusting the dynamic friction coefficient, and is preferable because it can reduce the haze of the film. The average particle diameter of the primary particles or secondary particles of the fine particles is in the range of 0.01 to 5.0 μm, and the content thereof is 0.005 to 0.
5 mass% is preferable.

Fine particles such as silicon dioxide are often surface-treated with an organic substance, but such particles are preferable because they can reduce the haze of the film.

Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like. The larger the average particle size of the fine particles, the greater the slippery effect, and the smaller the average particle size, the more excellent the transparency.
It is preferably 0 nm or less, preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

In the cellulose ester film, these fine particles have 0.0% on the surface of the cellulose ester film.
It is preferable to generate unevenness of 1 to 1.0 μm.

Fine particles of silicon dioxide include Aerosil 200 and 2 manufactured by Nippon Aerosil Co., Ltd.
00V, 300, R972, R972V, R974, R
202, R812, OX50, TT600 and the like, preferably Aerosil 200V, R972,
R972V, R974, R202 and R812. Two or more kinds of these fine particles may be used in combination. When two or more kinds are used in combination, they can be mixed and used at an arbitrary ratio. In this case, fine particles having different average particle diameters and different materials, for example, Aerosil 200V and R972V in a mass ratio of 0.1: 9.
It can be used in the range of 9.9 to 99.9 to 0.1. As zirconium oxide, for example, Aerosil R976 or R
Commercially available products such as 811 (manufactured by Nippon Aerosil Co., Ltd.) can also be used.

As organic fine particles, for example, silicone resin, Tospearl 103, 105, 108, 12
0,145,3120,240 (Toshiba Silicone Co., Ltd.)
Commercially available products such as manufactured products can also be used.

The primary average particle diameter of the fine particles preferably used in the present invention is measured by a transmission electron microscope (magnification: 500,000 to
The particles were observed at a magnification of 2,000,000), 100 particles were observed, and the average value was taken as the primary average particle diameter.

The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200.
g / liter, particularly preferably 100 to 200
g / liter. The larger the apparent specific gravity is, the higher the concentration of the dispersion liquid can be made, and the haze and the agglomerates are improved, which is preferable, and when the dope having a high solid content concentration is prepared as in the present invention. , Particularly preferably used.

The silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / L or more are, for example, 1000 obtained by mixing vaporized silicon tetrachloride and hydrogen.
It can be obtained by burning in air at ~ 1200 ° C. In the present invention, the apparent specific gravity described above was calculated by the following formula by taking a certain amount of silicon dioxide fine particles in a graduated cylinder and measuring the weight at this time.

Apparent specific gravity (g / L) = mass of silicon dioxide (g) / volume of silicon dioxide (L) As a method for preparing a dispersion of fine particles useful in the present invention and a method for adding it to a dope, For example, the following three methods can be mentioned.

<< Preparation Method A >> An organic solvent and fine particles are mixed by stirring, and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. The fine particle dispersion liquid is added to the dope liquid and stirred.

<< Preparation Method B >> The organic solvent and the fine particles are mixed by stirring, and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. Separately, a small amount of cellulose ester is added to an organic solvent and stirred and dissolved, and the fine particle dispersion is added and stirred. This is used as a fine particle added liquid, and is thoroughly mixed with the dope liquid by an in-line mixer. Here, after the addition of the following fine particle additive liquid,
An ultraviolet absorber may be added.

<< Preparation Method C >> A small amount of cellulose ester is added to an organic solvent and dissolved by stirring. Fine particles are added to this and dispersed by a disperser. This is used as a fine particle addition liquid. The fine particle added liquid is thoroughly mixed with the dope liquid by 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 less likely to reaggregate. Above all, the above-mentioned preparation method B is a preferable preparation method which is excellent in both the dispersibility of the silicon dioxide fine particles and the difficulty of re-aggregation of the silicon dioxide fine particles.

<< Dispersion Method >> When the silicon dioxide fine particles are mixed and dispersed with an organic solvent or the like, the concentration of silicon dioxide is 5 to 5.
30 mass% is preferable, 10 to 25 mass% is more preferable, and 15 to 20 mass% is the most preferable.

The amount of the silicon dioxide fine particles added to the cellulose ester is preferably 0.01 to 0.5 parts by weight, more preferably 0.05 to 0.2 parts by weight, based on 100 parts by weight of the cellulose ester. , 0.0
Most preferably, it is 8 to 0.12 parts by mass. The larger the amount added, the better the dynamic friction coefficient of the cellulose ester film,
The smaller the added amount is, the better the haze is and the less agglomerates are.

The organic solvent used in the dispersion is preferably lower alcohols, and examples of the lower alcohols include methanol, ethanol, propyl alcohol, isopropyl alcohol, butanol and the like. The organic solvent other than the lower alcohol is not particularly limited, but the organic solvent used when preparing the dope is preferable.

As the disperser, an ordinary disperser can be used. Dispersers are roughly divided into media dispersers and medialess dispersers. The latter is preferable for dispersing the silicon dioxide fine particles, since the haze is low. Examples of the media disperser include a ball mill, a sand mill and a dyno mill. Further, as the medialess disperser, there are an ultrasonic type, a centrifugal type, a high pressure type and the like. In the present invention, the high pressure type is preferable, and the high pressure dispersing device is preferable. The high-pressure dispersion device is a device that creates a special condition such as high shear or high-pressure state by passing a composition obtained by mixing fine particles and an organic solvent at high speed through a thin tube. In the case of processing with a high-pressure dispersion device, for example, the maximum pressure condition inside the device is preferably 9.8 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. More preferably, it is 19.6 MPa or more. At that time, it is preferable that the maximum reaching speed is 100 m / sec or more and the heat transfer speed is 420 kJ / hour or more.

The high-pressure dispersing device as described above has a Micro
There is an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by fluidics Corporation or a nanomizer manufactured by Nanomizer. In addition, there is a Manton-Gaulin type high-pressure disperser, for example, a homogenizer manufactured by Izumi Food Machinery, a UHN- manufactured by Sanwa Machinery Co., Ltd. There is 01 etc.

In the present invention, when the above fine particles are contained, it is preferable that they are uniformly distributed in the thickness direction of the cellulose ester film, but it is more preferable that they are mainly distributed near the surface, for example, It is preferable that two or more kinds of dope are simultaneously cast from one die by a co-casting method, and the dope containing fine particles is arranged on the surface layer side. By doing so, the haze can be reduced and the dynamic friction coefficient can be lowered. More preferably, it is desirable to use three types of dopes to arrange the dope containing fine particles in one surface layer or both surface layers.

In order to adjust the dynamic friction coefficient of the support, a back coat layer containing fine particles may be provided on the back surface side. The coefficient of dynamic friction can be adjusted by the size and amount of the fine particles to be added, the material, and the like.

As the plasticizer preferably used in the present invention, a non-phosphate ester plasticizer is preferably used.

Examples of the non-phosphoric acid ester plasticizer include phthalic acid ester, citric acid ester, glycolic acid ester, fatty acid ester, pyromellitic acid ester and trimellitic acid ester.

Specific examples include, for example, dibenzyl phthalate, dibenzyl isophthalate, dibenzyl terephthalate, diphenyl phthalate, diphenyl isophthalate, diphenyl terephthalate, dicyclohexyl phthalate, dicyclohexyl isophthalate, dicyclohexyl terephthalate, phenyl cyclohexyl isophthalate, phenyl cyclohexyl. Examples thereof include phthalic acid-based esters such as terephthalate, phenylcyclohexyl phthalate, benzyl cyclohexyl phthalate, benzyl cyclohexyl terephthalate, and benzyl cyclohexyl isophthalate, but the present invention is not limited thereto.

Abietic acid, dehydroabietic acid, parastophosphoric acid, KE-604 (manufactured by Arakawa Kagaku), KE-8
5 (manufactured by Arakawa Chemical), Araldide EPN1139 (manufactured by Asahi Chiba Co., Ltd.), Araldide GY260 (Asahi Chiba Co., Ltd.)
(Made by Hitachi Chemical Co., Ltd.), Hirac 110H (made by Hitachi Chemical Co., Ltd.), Hirac 111 (made by Hitachi Chemical Co., Ltd.)
Ketone resins and the like are also preferably used.

JP-A-11-124445 and 11-9.
2574, 11-246704, 11-635.
No. 60, a non-phosphate ester plasticizer described in JP 2001-48840 A can also be used. These are preferably used alone or in combination.

The ultraviolet absorber preferably used in the present invention will be described. Specific examples of the ultraviolet absorber include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, and the like. However, other UV absorbers may also be used.

Specific examples include the following compounds. UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-
tert-Butylphenyl) benzotriazole UV-3: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-
tert-Butylphenyl) -5-chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ",
4 ", 5", 6 "-tetrahydrophthalimidomethyl)
-5'-Methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3)
3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) UV-7: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2,4-dihydroxybenzophenone UV-9: 2,2'-dihydroxy-4-methoxybenzophenone UV-10: 2-hydroxy-4-methoxy -5-Sulfobenzophenone UV-11: Bis (2-methoxy-4-hydroxy-5)
-Benzoylphenylmethane) As the ultraviolet absorber, those having excellent absorption of ultraviolet rays having a wavelength of 370 nm or less and little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display property. The ultraviolet absorption capacity of the optical thin film of the present invention is preferably 10% or less, more preferably less than 6%, particularly preferably less than 6%, with respect to light having a wavelength of 380 nm. Is less than.

The content of the ultraviolet absorber used in the optical thin film is an appropriate addition amount according to the setting of the transmittance of light having a wavelength of 380 nm.

The optical thin film and antireflection thin film in the present invention preferably have a high refractive index layer, a medium refractive index layer and a low refractive index layer.

Titanium compounds used in the high refractive index layer and the medium refractive index layer include organic titanium compounds, titanium hydrogen compounds, titanium halides, and the like, and organic titanium compounds include triethyl titanium, trimethyl titanium, and triisopropyl titanium. , Tributyl titanium, tetraethyl titanium, tetraisopropyl titanium, tetrabutyl titanium,
Triethoxy titanium, trimethoxy titanium, triisopropoxy titanium, tributoxy titanium, tetraethoxy titanium, tetraisopropoxy titanium, methyldimethoxy titanium, ethyl triethoxy titanium, methyl triisopropoxy titanium, tetradimethylamino titanium, dimethyl titanium diacetate Acetonate, ethyltitanium triacetoacetonate, etc., examples of titanium hydrogen compounds include monotitanium hydrogen compounds, dititanium hydrogen compounds, etc., and examples of titanium halides include titanium trichloride, titanium tetrachloride, etc. Can be preferably used in.

The silicon compound used for the low refractive index layer may be an organic silicon compound, a silicon hydrogen compound, a silicon halide compound, or the like, and the organic silicon compound may be tetraethylsilane, tetramethylsilane or tetramethylsilane. Isopropylsilane, tetrabutylsilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diethylsilanediacetoacetonate, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane As the silicon hydrogen compound, tetrahydrogenated silane, hexahydrogenated disilane and the like can be mentioned, and any of them can be preferably used in the present invention.

The preferred antireflection optical thin film of the present invention may have the metal oxide layer formed directly on the support, but may also have the other layer provided thereon at least one layer. In the present invention, examples of the other layer include a hard coat layer and the like, and these layers are preferably actinic ray curable resin layers that are cured by actinic rays such as ultraviolet rays. By forming a metal oxide layer on such a resin layer cured by ultraviolet rays, an antireflection optical thin film having excellent scratch resistance can be obtained.

The actinic radiation curable resin layer such as the hard coat layer is
The resin layer is preferably formed by polymerizing a component containing an ethylenically unsaturated monomer.

Here, the actinic ray curable resin layer means a layer containing as a main component a resin which is cured through a crosslinking reaction or the like by irradiation with actinic rays such as ultraviolet rays and electron beams.

Typical examples of the actinic ray curable resin include an ultraviolet curable resin and an electron beam curable resin. However, a resin which is cured by irradiation with an actinic ray other than an ultraviolet ray or an electron beam may be used. As the ultraviolet curable resin, for example,
Examples thereof include UV-curable acrylic urethane-based resin, UV-curable polyester acrylate-based resin, UV-curable epoxy acrylate-based resin, UV-curable polyol acrylate-based resin, and UV-curable epoxy resin.

The UV-curable acrylic urethane resin is
In general, a product obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer further includes 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate (hereinafter, when it is described as acrylate, methacrylate is included), 2 −
It can be easily obtained by reacting an acrylate-based monomer having a hydroxyl group such as hydroxypropyl acrylate (for example, JP-A-59-15111).
(See No. 0).

The UV-curable polyester acrylate resin can generally be easily obtained by reacting a polyester polyol with a 2-hydroxyethyl acrylate or a 2-hydroxy acrylate monomer (for example, JP-A-59-151112). (See the description of).

Specific examples of the ultraviolet-curable epoxy acrylate resin include epoxy acrylate as an oligomer, to which a reactive diluent and a photoreaction initiator are added and reacted (for example, Kaihei 1
-105738). As the photoreaction initiator, one or more selected from benzoin derivatives, oxime ketone derivatives, benzophenone derivatives, thioxanthone derivatives and the like can be used.

Specific examples of the UV-curable polyol acrylate resin include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and alkyl-modified dipenta. Examples thereof include erythritol pentaacrylate.

These resins are usually used together with known photosensitizers. The above photoreaction initiator can also be used as a photosensitizer. Specifically, acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone,
Examples thereof include α-amyloxime ester, thioxanthone, and derivatives thereof. When using an epoxy acrylate-based photoreactive agent, n-butylamine,
Sensitizers such as triethylamine and tri-n-butylphosphine can be used. The photoreaction initiator or photosensitizer contained in the ultraviolet curable resin composition excluding the solvent component which volatilizes after coating and drying can be added in an amount of usually 1 to 10% by mass of the composition, and 2.5 to 6 can be added. Mass% is preferred.

The actinic radiation curable resin layer preferably used in the present invention can be applied by a known method.

As the light source for forming the cured film layer by the photo-curing reaction of the actinic ray curable resin, any light source which emits ultraviolet rays can be used.

For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, a super high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, etc. can be used. The irradiation conditions vary depending on individual lamps, but the amount of light irradiated may if 20~10000mJ / cm ^2, preferably from 50~2000mJ / cm ^2. It can be used by using a sensitizer having an absorption maximum in the near-ultraviolet region to the visible light region.

As the solvent for applying the actinic radiation curable resin layer, for example, hydrocarbons, alcohols, ketones,
It can be appropriately selected from esters, glycol ethers and other solvents, or can be used by mixing them.
Preferably, propylene glycol mono (having 1 to 4 carbon atoms
Alkyl group) alkyl ether of propylene glycol mono (alkyl group having 1 to 4 carbon atoms) alkyl ether ester is 5% by mass or more, more preferably 5 to 8%.
A solvent containing 0% by mass or more is used.

As a method for applying the ultraviolet curable resin composition coating solution, known methods such as a gravure coater, a spinner coater, a wire bar coater, a roll coater, a reverse coater, an extrusion coater and an air doctor coater can be used. The coating amount is usually 0.1 to 30 μm in terms of wet film thickness, preferably 0.5 to 1
It is 5 μm. The coating speed is preferably 10 to 60 m / min.

The UV-curable resin composition is coated and dried, and then irradiated with UV rays from a light source. The irradiation time is preferably 0.5 seconds to 5 minutes. Seconds to 2 minutes are more preferable.

Inorganic or organic fine particles are preferably added to the thus obtained cured film layer in order to prevent blocking and enhance scratch resistance.

For example, as the inorganic fine particles, silicon oxide,
Examples thereof include titanium oxide, aluminum oxide, tin oxide, zinc oxide, calcium carbonate, barium sulfate, talc, kaolin, calcium sulfate, and the like, and as the organic fine particles, polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin Powder, polymethylmethacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin Powders, polyfluorinated ethylene-based resin powders and the like can be mentioned, which can be added to the ultraviolet curable resin composition. The average particle size of these fine particle powders is preferably 0.005 to 1 μm, and 0.0
Particularly preferably, it is 1 to 0.1 μm.

The ratio of the ultraviolet curable resin composition to the fine particle powder is 0.1 to 10 relative to 100 parts by mass of the resin composition.
It is desirable to mix them in such an amount that they will be part by mass.

In the present invention, when the optical thin film of the present invention is provided on the surface of the support as described above, it is preferable to provide it so that the deviation of the average film thickness is ± 10%.
It is more preferably within ± 5%, and most preferably ± 1.
It is preferable to provide it so as to be within%.

As the antioxidant, hindered phenol type compounds are preferably used.
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], 1,
6-hexanediol-bis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3
5-triazine, 2,2-thio-diethylenebis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], 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)- Isocyanurate and the like can be mentioned. 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, N, N'-bis [3- (3,3
5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and other hydrazine-based metal deactivators and tris (2,4-di-t-butylphenyl) phosphite and other phosphorus-based processing stabilizers You may. The addition amount of these compounds is preferably 1 ppm to 1.0% by mass ratio with respect to the cellulose ester, and is 10 to 1000 p.
pm is more preferred.

These antioxidants are also called deterioration inhibitors, and when the liquid crystal image display device is placed in a high-humidity and high-temperature state, the cellulose ester film may be deteriorated. Since the cellulose ester film has a role of delaying or preventing decomposition due to the residual solvent amount of halogen, phosphoric acid of a phosphoric acid plasticizer, or the like, it is preferably contained in the cellulose ester film.

[0151]

EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1 << Preparation of Dope Liquid >> (Preparation of Silicon Oxide Dispersion Liquid) Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 1 kg Ethanol 9 kg After stirring and mixing the above materials with a dissolver for 30 minutes, Manton-Gaulin type high pressure dispersion Dispersion was performed using the device.

(Preparation of Additive Liquid A) Cellulose acetate propionate (acetyl substitution degree: 1.9, propionyl group substitution degree: 0.7) 4 kg Methylene chloride 76 kg Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 3 kg Tinuvin 109 (Ciba) Specialty Chemicals Co., Ltd.) 4 kg Tinuvin 171 (Ciba Specialty Chemicals Co., Ltd.) 4 kg The above materials are placed in a closed container, heated and stirred,
It was completely dissolved and filtered. To this, 9 kg of the above silicon oxide dispersion was added with stirring, and the mixture was further stirred for 30 minutes and then filtered to prepare an addition liquid A.

(Preparation of Dope A) Compound 1 18 kg Methylene chloride 320 kg Ethanol 60 kg Cellulose acetate propionate (acetyl substitution degree: 1.9, propionyl group substitution degree: 0.7) 110 kg A closed container while stirring the above materials in order. It was put into a vessel and completely dissolved and mixed while heating and stirring. The dope was cooled to a temperature at which it was cast, allowed to stand overnight, and subjected to a defoaming operation. Then, the solution was added to Azumi Filter Paper No. Filtered using 244. Furthermore, the additive solution A per 100 kg of the solution
Was added at a rate of 2 kg, thoroughly mixed with an in-line mixer (Toray static type in-tube mixer Hi-Mixer, SWJ), and filtered to prepare a dope (A).

[0155]

[Chemical 1]

<< Preparation of Transparent Support >> After filtering the dope solution A, a dope temperature of 35 ° C. and a temperature of 30 ° C.
It was evenly cast on the stainless steel band support. After drying on the support for 90 seconds, the web formed on the stainless band support was peeled off.

After the web was peeled from the stainless band support and dried while being conveyed by a roll in a drying zone of 80 ° C., when the residual solvent amount in the web was 20% by mass or less, a biaxial stretching tenter was used. 1.07 times in TD direction (width direction) and 1.01 in MD direction (film formation direction)
After being double-stretched and dried at 90 ° C., the width grip was released, and further drying was completed in a drying zone at 120 ° C. while being conveyed by rolls to prepare a transparent support having a film thickness of 60 μm.

The film width was 1300 mm and the winding length was 2000 m. The amount of residual solvent in the film after winding was less than 0.1% by mass.

Here, the MD direction indicates the film forming direction of the film during the casting film formation, and the TD direction indicates the width direction of the film during the casting film formation.

The following hard coat layer composition was applied on one surface of the transparent support to the following hard coat layer composition (1) so that the dry film thickness was 3.5 μm, and dried at 80 ° C. for 5 minutes. . Next, an 80 W / cm high-pressure mercury lamp was irradiated from a distance of 12 cm for 4 seconds to be cured to prepare a transparent support having a hard coat layer. The refractive index of the hard coat layer was 1.50.

[0161]   <Hard coat layer composition (1)>   Dipentaerythritol hexaacrylate monomer 60 parts by mass   Dipentaerythritol hexaacrylate dimer 20 parts by mass   Dipentaerythritol hexaacrylate trimer or more components                                                           20 parts by mass   2 parts by weight of diethoxybenzophenone (UV photoinitiator)   Aerosil R-972V (manufactured by Nippon Aerosil Co., Ltd.) 1 part by mass   Methyl ethyl ketone 50 parts by mass   50 parts by mass of ethyl acetate   Isopropyl alcohol 50 parts by mass The above composition was ultrasonically dispersed while stirring.

<< Preparation of Multi-Layer Antireflection Optical Thin Film >><Coating Liquid for Medium Refractive Index Layer> Tetra (n) butoxytitanium 250 parts by mass Terminal reactive dimethyl silicone oil (L-9000 manufactured by Nippon Unicar Co., Ltd.) 0.48 parts by mass Aminopropyltrimethoxysilane (KBE903 manufactured by Shin-Etsu Chemical Co., Ltd.) 22 parts by mass UV curable epoxy resin (KR500 manufactured by Asahi Denka Co., Ltd.) 21 parts by mass Propylene glycol monomethyl ether 4900 parts by mass Isopropyl alcohol 4840 parts by mass <Coating liquid for high refractive index layer > Tetra (n) butoxy titanium 310 mass parts Terminal reactive dimethyl silicone oil (L-9000 manufactured by Nippon Unicar Co., Ltd.) 0.4 mass part Aminopropyltrimethoxysilane (KBE903 manufactured by Shin-Etsu Chemical Co., Ltd.) 4.8 mass parts UV curability Epoxy resin (KR500 manufactured by Asahi Denka Co., Ltd.) 4.6 parts by mass Propylene glycol monomethyl ether 4900 parts by mass Isopropyl alcohol 4800 parts by mass <Coating liquid for low refractive index layer> Tetraethoxysilane hydrolyzate A 1020 parts by mass Terminal reactive dimethyl silicone oil (L-9000 manufactured by Unicar Japan) ) 0.42 parts by mass propylene glycol monomethyl ether 2700 parts by mass isopropyl alcohol 6300 parts by mass On the transparent support having the hard coat layer, the medium refractive index layer coating solution is applied using a bar coater, and 120
After drying at ℃, cure the coating layer by UV irradiation,
A medium refractive index layer (thickness: 0.081 μm) was formed.

The coating liquid for a high refractive index layer was applied onto the medium refractive index layer using a bar coater, dried at 120 ° C., and then the coating layer was cured by irradiation with ultraviolet rays to give a high refractive index layer (thickness). : 0.060 μm) was formed.

The coating liquid for low refractive index was applied onto the high refractive index layer using a bar coater and dried at 120 ° C.,
The coating layer was cured by UV irradiation to form a low refractive index layer (thickness: 0.090 μm), and a multilayer antireflection thin film was produced. The refractive index of each of the completed layers was a medium refractive index layer 1.65, a high refractive index layer 1.90, and a low refractive index layer 1.45.

The refractive index, the film thickness and the degree of acyl group substitution of cellulose ester were determined by the following methods.

(Refractive Index, Film Thickness) The refractive index and film thickness of each refractive index layer are obtained from the measurement results of the spectral reflectance of a spectrophotometer for a sample in which each layer is applied alone. A spectrophotometer of U-4000 type (manufactured by Hitachi, Ltd.) is used to roughen the back surface of the sample on the measurement side and then perform light absorption processing with a black spray to prevent reflection of light on the back surface. Then, the reflectance in the visible light region (400 to 700 nm) is measured under the condition of regular reflection of 5 degrees.

(Substitution degree of acyl group of cellulose ester)
It is performed according to the method specified in ASTM-D817-96.

(Number average molecular weight of cellulose ester) Solvent to be measured by high performance liquid chromatography under the following conditions: Acetone column: MPW × 1 (manufactured by Tosoh Corporation) Sample concentration: 0.2 mass / volume% Flow rate: 1. 0 ml / min Sample injection rate: 300 μl Standard sample: polymethylmethacrylate (MW = 188,2
00) Temperature: 23 ° C. Detector: Differential refractometer.

A coating film was prepared by changing the wind speed on the surface of the coating film when the solid content concentration of the coating film was 1 to 50%.

A black acrylic plate was attached to the back of each antireflection multilayer optical thin film, and unevenness in drying and repellency were visually observed.
Graded.

(Dry unevenness) Evaluation Criteria ◯: No unevenness Δ: There is unevenness, but there is no problem in practical use ×: There is unevenness and cannot be used in practice (repelling: film thickness) Evaluation Criteria ◯: 5 pieces / m less than 50 μm ² or less Δ: 5 to less than 50 to 100 μm / m ² or less ×: 5 to 100 μm or more / m ² or more

[0172]

[Table 1]

As is clear from the above results, the surface wind velocity immediately after coating the antireflection multilayer optical thin film was 0.2 to 1.0 m.
It can be seen that by controlling the value of the present invention so that it is / sec, a high-quality antireflection multilayer optical thin film free from repellency and drying unevenness can be obtained.

Example 2 In the same manner as in Example 1, an antireflection multilayer optical thin film was applied. The air velocity on the surface of the coating film is kept constant at 0.5 m / sec,
An antireflection multilayer optical thin film was prepared in the same manner as in Example 1 except that the airflow temperature was changed to 30 to 160 ° C., and repellency and unevenness of drying were evaluated.

[0175]

[Table 2]

As is clear from the above results, the temperature of the air flow in the vicinity of the optical coating film immediately after coating the coating film is 40 to 130.
It can be seen that by controlling to the value of the present invention so as to be ℃, it is possible to obtain a high-quality antireflection multilayer optical thin film free from repellency and drying unevenness.

Example 3 An antireflection multilayer optical thin film obtained by drying by changing the temperature of the roller by using a drying device in which a back surface of the antireflection multilayer optical thin film coated with a die on a coating line is supported by a roller. In the same manner as in Example 1, the uneven dryness and repellency were evaluated. The temperature difference at this time was (roller temperature)-(base material temperature).

[0178]

[Table 3]

As is clear from the above table, by setting the temperature difference between the roller and the substrate to be 0 to 15 ° C. (temperature difference of the present invention) as described above, it is possible to obtain high quality without unevenness in drying and repelling. It can be seen that an antireflection multilayer optical thin film is obtained.

Example 4 In Example 1, an antireflection multilayer optical thin film sample was prepared by changing the film surface temperature and the drying speed of the coating film in which the solid content concentration of the antireflection multilayer optical thin film was 10%. In the same manner as in 1, the unevenness of dryness and the repellency were evaluated.

[0181]

[Table 4]

[0182]

[Table 5]

As is clear from the results in the table, by controlling the film surface temperature and the drying rate of the antireflection multilayer optical thin film to the values of the present invention, a high quality antireflection multilayer optical thin film free from unevenness in drying and repellency can be obtained. You can see that you can get it.

Example 5 The antireflection multilayer optical thin film of Example 1 was dried after coating using a drying device (FIG. 1) equipped with an infrared heater on the coating line. For infrared rays, a medium- and long-wave infrared heater made by Heraeus Germany is used and the distance to the film to be conveyed is 5
It was set to cm. The temperature in the vicinity of the optical film surface after coating at this distance was 120 ° C.

The coated antireflection multilayer optical thin film of Example 1 was dried using a drying device (FIG. 2) equipped with a non-contact floater. As the non-contact floater, a horizontal floater type air tumbler manufactured by Belle Mattique was used. Static pressure in the floater is 9.8 kPa, approx. 2 mm
The width was evenly floated and conveyed.

<< Evaluation of Transportability >> Evaluation criteria ◯: Support meander width less than 5 mm △: less than 5 to 7 mm ×: 7 mm or more

[0187]

[Table 6]

From the above results, it is understood that the infrared drying can proceed the drying without generating the flow of the wind, and the uniform antireflection multilayer optical thin film without the uneven drying can be obtained.

Further, it can be seen that by using the non-contact floater, unevenness in drying and transportability are excellent.

[0190]

As demonstrated in the examples, the method for drying an optical thin film according to the present invention, the method for producing the same, and the optical thin film obtained by these methods have a uniform film thickness distribution and are free from color unevenness and repellency failure. It has a high quality and an excellent effect of good transportability.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a drying device used in a drying method of the present invention.

FIG. 2 is a schematic view showing another example of a drying device used in the drying method of the present invention.

[Explanation of symbols]

1 tank 2 coaters 3 backup roll 4 Optical thin film 5 rollers 6 infrared heater 7 Non-contact rotor P pump

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02B 1/10 A F term (reference) 2H091 FA48X FB02 FB12 FC08 FC09 FD14 GA02 GA06 GA16 LA02 LA03 LA07 LA12 2K009 AA06 AA15 BB28 CC03 CC06 CC09 CC21 CC42 DD02 DD06 3L113 AA03 AB06 AC10 AC32 AC35 BA01 DA24 4D075 AC72 AC78 AC80 AC93 AC96 BB24Z BB37Z BB92Z BB93YBA38EB22 EB38 EB32 EB32 EB32 EB32 DB24 DB24 DB24 DB31 DB33 DB24 DB24 DB31 DB33 DB24 DB24 DB24

Claims (13)

[Claims] 1. A method for drying an optical thin film obtained by coating and drying it on a support, wherein the air velocity on the surface of the coating of the optical thin film is 1 to 50%.
A method for drying an optical thin film, which comprises drying at 2-1 m / sec. 2. The method for drying an optical thin film according to claim 1, wherein the air temperature in the drying chamber is 40 to 130 ° C. 3. The method for drying an optical thin film according to claim 1, wherein the method is drying with infrared rays. 4. A method of drying an optical thin film obtained by coating and drying on a support, wherein the back side of the optical thin film is contacted until the solid content concentration of the optical thin film becomes 10 to 98%. The method for drying an optical thin film, wherein the temperature difference between the roller and the substrate is 0 to 15 ° C. 5. A method for drying an optical thin film obtained by coating and drying on a support, wherein a roller is provided on the back surface of the optical thin film until the solid content concentration of the optical thin film reaches 10 to 98%. A method for drying an optical thin film, characterized in that the optical thin film is conveyed without being brought into contact with the substrate. 6. The back surface of the coating film of the optical thin film is supported by a non-contact floater.
Item 5. A method for drying an optical thin film according to item. 7. The film thickness immediately after coating the optical thin film is 3 to 10 μm.
The method for drying an optical thin film according to any one of claims 1 to 6, wherein m is m. 8. A method for drying an optical thin film obtained by coating and drying on a support, wherein the coating temperature for drying the optical thin film coating film has a solid content concentration of 10 to 98%. Is from 25 to 55 ° C., a method for drying an optical thin film. 9. A method for drying an optical thin film obtained by coating and drying on a support, wherein when the optical thin film coating film has a solid content concentration of 10 to 98%,
The drying rate represented by the following h × ΔT is 400 to 1500
A method for drying an optical thin film, wherein the method is w / m ² . Drying rate: h × ΔT (w / m ² ) h (heat transfer coefficient): w / (m ² K) ΔT: Temperature difference (K) between air flow and substrate 10. A method for producing an optical thin film, which is produced by using the drying method according to claim 1. 11. An optical thin film obtained by using the drying method according to any one of claims 1 to 9. 12. The optical thin film according to claim 11, wherein the optical thin film is an antireflection optical thin film. 13. The method for producing an optical thin film according to claim 10, wherein the optical thin film is an antireflection optical thin film.