JP2005350492A - Coated film having coated layer by using cellulose ester film as supporting body, protective film for polarized plate, combination of productive film for polarized plate and polarized plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated film having a coated layer by using a cellulose ester film improved with its physical characteristics, as a supporting body, capable of suppressing an appearance disorder such as a spot like malfunction of the polarized film in preparing the polarized film of a liquid crystal-displaying device (LCD), a protective film for a polarized film, a combination of the protective film for the polarized film and the polarized film by using the protective film for the polarized film. <P>SOLUTION: This coated film having the coated layer by using the cellulose ester film as the supporting body is provided by using heat irradiation conditions of 80°C temperature, 90%RH humidity and 50 hr irradiation on performing the heat irradiation for changing the film dimension, and exhibiting ≥0% and ≤0.60% rate of dimensional change in parallel direction (lengthwise direction) to the film-forming direction, and ≥0% and ≤0.30% rate of the dimensional change in vertical direction (widthwise direction) to the film-forming direction of the coated film. Also, the protective film of the polarized plate is constituted such coated films. The combination of the protective films for the polarized plate is constituted by the protective film for the polarized plate consisting of the cellulose ester film with the protective film for the polarized plate consisting of the coated film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is useful as a protective film for a polarizing plate of a liquid crystal display device (LCD) and has a coating layer using a cellulose ester film having improved physical properties as a support, and the coating film The protective film for polarizing plates which consists of these, The combination of the protective film for polarizing plates, and the polarizing plate using the protective film for polarizing plates.

  In recent years, liquid crystal display devices (LCD) are more space-saving and energy-saving than conventional CRT display devices, and therefore, the use of liquid crystal displays for TVs, personal computers, mobile phones, and the like is increasing. In particular, liquid crystal displays are required to have higher quality due to the progress of larger screens and higher image quality of TVs as well as the expansion of use places and generalization and diversification.

  It has been found that the quality of a liquid crystal display depends on the physical characteristics of a polarizing plate which is one of the constituent members of the liquid crystal display.

  As a protective film for a polarizing plate of a liquid crystal display device, a cellulose ester film is often used at present because of its low birefringence, and among them, a cellulose triacetate film (also called a TAC film) is mainly used. It was done.

  On the other hand, with the expansion of the use place of liquid crystal display devices, generalization, and diversification, further improvement in display function and visual recognition function is required, and multi-functionalization of polarizing plates and protective films for polarizing plates is progressing. . Then, a new optical coating film has been developed by coating an optical functional layer using a TAC film as a support, and various multifunctionalizations of this coating film are also progressing. The load on the physical properties of such a TAC film or coating film is increased, and these are required to have higher physical properties.

  Taking cellulose triacetate as an example of a protective film for a polarizing plate, cellulose triacetate as a protective film is formed on one or both sides of a polarizing film made of a polyvinyl alcohol film uniaxially stretched by saponifying the surface of the film with iodine. In addition, it is used by being bonded through an adhesive such as polyvinyl alcohol.

  Here, a cellulose triacetate film (so-called raw TAC film) and a coating film having a coating layer on a cellulose triacetate film as a support are used as protective films for polarizing plates to create a polarizing plate. As a result, an appearance abnormality may occur in the obtained polarizing plate.

  Here, the planar appearance abnormality such as a spot failure of the polarizing plate is caused by a difference in physical properties between the protective films for polarizing plates to be bonded to both sides of the polarizer, particularly a difference in dimensional change. Had guessed.

By the way, the improvement of the physical properties of the cellulose ester film used for the protective film for polarizing plates has been studied for a long time, especially the dimensional stability of the film. There is.
JP, 10-151706, A The invention of patent documents 1 is a support of a magnetic recording medium excellent in abrasion resistance and handling nature in film formation and processing, and excellent in electromagnetic conversion characteristics, dropout characteristics, and repetitive running characteristics. The present invention relates to the development of a material (laminated film) that can be used.

The invention of the laminated film of Patent Document 1 has an average particle diameter dB of 5 to 100 nm and a volume shape factor of 0.1 to 0.524 (at least on one side of the thermoplastic resin layer A containing no inert particles). A laminated film provided with a coating layer B made of a water-soluble resin containing inert particles B, which is π / 6), the dimensions in the vertical and horizontal directions when the environmental temperature is changed from 80 ° C. to 20 ° C. The difference in displacement was 8 × 10 ⁻⁴ % or less.
The invention described in Japanese Patent Application Laid-Open No. 11-65025 relates to a photographic support and a method for producing the photographic support, and a photographic support having good dimensional change after heat development and having good flatness. A preparation method is provided.

The invention of the photographic support described in Patent Document 2 is a biaxially stretched photographic support mainly composed of polyester, and changes in thermal dimensions when heated at a temperature of 120 ° C. for 30 seconds. The ratio is 0.001% or more and 0.04% or less. Specifically, an undercoat layer is provided on one side of a photographic support mainly comprising polyester, and a back layer is provided on the opposite side. It is what has been.
JP, 2001-66734, A In addition, the present applicant has previously described a photographic support having optimum thermal dimensional stability and heat treatment dimensional shift suppression for a heat-developable photographic photosensitive material, a method for producing the same, and photographic photosensitive. A material invention was proposed.

  In the invention of the method for producing a photographic support described in Patent Document 3, a biaxially stretched polyester film in which the difference in orientation angle between the central portion and the end portion in the width direction after film formation is 30 degrees or more is obtained at both ends. The heat treatment is performed after cutting into two or more so that the difference in orientation angle is 25 degrees or less. Then, after the heat treatment is cut into two or more, the heat treatment is performed before applying the photographic constituent layer including the photosensitive layer, and the heat treatment is performed after applying the undercoat layer (undercoat layer).

  Further, the invention of the photographic support described in Patent Document 3 is a biaxially stretched polyester film in which the difference in orientation angle between the central portion and the end portion in the width direction after film formation is 30 degrees or more. The film is characterized by being cut into two or more so that the difference in orientation angle between both ends is 25 degrees or less and having the following thermal dimensional stability.

[Thermal dimensional stability] In any part in the film forming width direction, the absolute value of the dimensional change rate is 0.001 to 0.08% in the longitudinal direction (MD direction) even at a temperature of 120 ° C. and a heat treatment of 30 seconds. The width direction (TD direction) is within a range of 0.001 to 0.04%.
JP, 2003-344657, A The invention of patent documents 4 is a biaxial which can form a liquid crystal display device etc. which is excellent in optical compensation performance, enabling thinning of a phase contrast plate, a lamination polarizing plate, a liquid crystal display device, etc. A birefringent film is provided.

  In the invention described in Patent Document 4, a solution obtained by dissolving at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide in a solvent is applied to a substrate. In the step of forming a film after drying, a birefringent film formed using a base material that changes in dimensions, and its birefringence is in the range of 0.0005 to 0.5. When the substrate made of the protective film material is dried, the maximum dimensional change rate is 1% or more.

  However, even if any film whose dimensional change is improved by the conventional inventions described in Patent Documents 1 to 4 above, the appearance abnormality when the polarizing plate is produced cannot be improved.

  The object of the present invention is to solve the above-mentioned problems of the prior art and to support a cellulose ester film with improved physical properties, which can suppress abnormal appearance such as a polarizing plate spot failure when a polarizing plate is produced. To provide a coated film having a coating layer as a body, a protective film for a polarizing plate comprising a coated film, a combination of protective films for a polarizing plate, and a polarizing plate using the protective film for a polarizing plate is there.

  As a result of intensive studies in view of the above points, the inventor is subjected to heat irradiation on a coating film having a cellulose ester film as a support and having a coating layer, and changes in dimensions when the dimensions of the film change. If the difference in rate is as small as possible, it is found that when a polarizing plate is produced using a protective film for a polarizing plate made of a coating film, appearance abnormality such as a polarizing plate spot failure can be suppressed, and the present invention is achieved. Has been reached.

  In order to achieve the above object, the invention of a coating film having a coating layer with the cellulose ester film according to claim 1 of the present invention as a support has a coating layer with the cellulose ester film as a support. When the coated film is irradiated with heat and the dimensions of the film change, the heat irradiation conditions are a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, and a direction parallel to the film forming direction of the coated film (longitudinal) The direction change ratio is 0% or more and 0.60% or less.

  Moreover, the invention of the coating film which has a coating layer by using the cellulose ester film according to claim 2 of the present invention as a support, the coating film having a coating layer by using a cellulose ester film as a support, is irradiated with heat. When the dimensions of the film change, the heat irradiation conditions are temperature 80 ° C., humidity 90% RH, and irradiation for 50 hours, and the dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the coated film is 0% or more and 0.30% or less.

  The invention of the coating film according to claim 3 of the present invention is the coating film according to claim 1 or 2, wherein the coating film having a coating layer with the cellulose ester film as a support is applied before coating. It is produced by providing a coating layer on a cellulose ester film which has been treated for 3 hours or more in an environment having a temperature of 50 ° C. or higher.

  Moreover, invention of the protective film for polarizing plates of Claim 4 of this invention is comprised by the coating film as described in any one of Claims 1-3, It is characterized by the above-mentioned.

  The invention of a polarizing plate according to claim 5 of the present invention is characterized in that a protective film for polarizing plate constituted by the coating film according to claim 4 is bonded to at least one surface of a polarizer.

  Invention of the combination of the protective film for polarizing plates of Claim 6 of this invention consists of the protective film for polarizing plates which consists of a cellulose-ester film, and the coating film which has a coating layer by using a cellulose-ester film as a support body. Dimensional change rate (B) of the protective film for a polarizing plate made of a cellulose ester film, when both films are irradiated with heat under the same conditions and the dimensions of these films change. The ratio (A / B) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film with respect to is 100% or more and 140% or less.

  The invention of the combination of the protective films for polarizing plates according to claim 7 of the present invention is that when the heat irradiation conditions according to claim 6 are irradiated at a temperature of 80 ° C., a humidity of 90% RH, and 50 hours of irradiation, The dimensional change rate in the parallel direction (longitudinal direction) to the film forming direction of the protective film for polarizing plate is 0% or more and 0.60% or less, and the dimensional change rate of the protective film for polarizing plate made of a cellulose ester film (B The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plate made of a coating film to 100) is 100% or more and 140% or less.

  The invention of the combination of the protective films for polarizing plates according to claim 8 of the present invention is that the heat irradiation conditions according to claim 6 are applied when the temperature is 80 ° C., the humidity is 90% RH, and the irradiation time is 50 hours. The dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the polarizing plate protective film is 0% or more and 0.30% or less, and the dimensional change rate of the polarizing plate protective film made of a cellulose ester film (B The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plate made of a coating film to 100) is 100% or more and 140% or less.

  Invention of Claim 9 of this invention is a combination of the protective film for polarizing plates as described in any one of Claims 6-8, Comprising: The protective film for polarizing plates which consists of a coating film is coating. It is produced by providing a coating layer on a cellulose ester film that has been treated for 3 hours or more in an environment at a temperature of 50 ° C. or more before construction.

  The invention of a polarizing plate according to claim 10 of the present invention is a polarizing plate protective film comprising the cellulose ester film according to any one of claims 6 to 9 and a polarizing plate protective film comprising a coating film. Among the protective films for polarizing plates constituted by the combination with the polarizing plate, the protective film for polarizing plates made of one coating film is on one side of the polarizer, and the protective film for polarizing plates made of the other cellulose ester film is the polarizer It is characterized by being bonded to the other surface.

  As described above, the invention of the coating film having the coating layer with the cellulose ester film according to claim 1 of the present invention as the support is applied to the coating film having the coating layer with the cellulose ester film as the support. When heat irradiation is performed and the dimensions of the film change, the heat irradiation conditions are a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, and the dimensions in the direction parallel to the film forming direction of the coated film (longitudinal direction). The rate of change is 0% or more and 0.60% or less. According to the invention of the coated film according to claim 1, the so-called longitudinal dimensional change rate of the film is small, and the physical characteristics Since it has been improved, it contributes to suppressing the dimensional change rate after coating, and when producing a polarizing plate, it has the effect of suppressing abnormal appearance such as a polarizing plate spot failure. .

  Moreover, the invention of the coating film having a coating layer with the cellulose ester film according to claim 2 of the present invention as a support is a coating having a coating layer with the cellulose ester film as a support as described above. When the film is irradiated with heat and the dimensions of the film change, the heat irradiation conditions are a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, and the direction perpendicular to the film-forming direction of the coated film (lateral direction) The dimensional change rate of the film is 0% or more and 0.30% or less. According to the invention of the coated film according to claim 2, the so-called lateral change rate of the film is small, Because it has improved physical properties, it contributes to reducing the rate of dimensional change after coating, and when polarizing plates are produced, it is possible to suppress abnormal appearance such as polarizing plate spot failure Unlikely to.

  As described above, the invention of the coating film according to claim 3 of the present invention is the coating film according to claim 1 or 2, wherein the coating film has a coating layer using the cellulose ester film as a support. Is produced by providing a coating layer on a cellulose ester film that has been treated for 3 hours or more in an environment at a temperature of 50 ° C. or more before coating. According to the invention of a coating film, it contributes to suppressing the dimensional change rate after coating, and when producing a polarizing plate, there is an effect that an appearance abnormality such as a polarizing plate spot failure can be suppressed.

  The invention of a protective film for a polarizing plate according to claim 4 of the present invention is constituted by the coating film according to any one of claims 1 to 3, and is characterized by claim 4. According to the invention of the protective film for polarizing plate, when the polarizing plate is produced using this, there is an effect that appearance abnormality such as a polarizing plate spot failure can be suppressed.

  The invention of the polarizing plate according to claim 5 of the present invention is characterized in that the protective film for polarizing plate constituted by the coating film according to claim 4 is bonded to at least one surface of the polarizer. According to the invention of the polarizing plate according to claim 5, since the protective film for polarizing plate made of a coating film having excellent physical properties is laminated on at least one surface of the polarizer, the physical properties of the polarizing plate and Appearance can be improved, and further, the visibility of a liquid crystal display with a polarizing plate bonded to a liquid crystal cell can be improved, and a liquid crystal display that can maintain stable display performance over a long period of time can be produced. There is an effect that is possible.

  The invention of the combination of the protective films for polarizing plates according to claim 6 of the present invention, as described above, has a protective film for polarizing plates made of a cellulose ester film and a coating layer using the cellulose ester film as a support. It is comprised with the protective film for polarizing plates which consists of a coating film, and when heat irradiation of the same conditions is made to each of both films and the dimension of these films changes, the dimension of the protective film for polarizing plates which consists of a cellulose-ester film The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plate made of a coating film to the change rate (B) is 100% or more and 140% or less, and is characterized in that: According to the invention of the combination of protective film for polarizing plate described, the difference in the dimensional change rate of the film is small, the physical properties are improved Because, when producing a polarizing plate, an effect that it is possible to suppress abnormal appearance such as a polarizing plate spot failure.

  In the invention of the combination of the protective films for polarizing plates according to claim 7 of the present invention, as described above, when the heat irradiation condition according to claim 6 is temperature 80 ° C., humidity 90% RH, and irradiation for 50 hours, The dimensional change rate in the parallel direction (longitudinal direction) with respect to the film-forming direction of the protective film for polarizing plate made of a coating film is 0% or more and 0.60% or less, and the protective film for polarizing plate made of a cellulose ester film The ratio (A / B) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film to the dimensional change rate (B) is 100% or more and 140% or less. According to invention of the combination of the protective film for polarizing plates of claim | item 7, there is little difference of the dimensional change rate of what is called the vertical direction of the protective film for polarizing plates consisting of a coating film, and the physical characteristic is improved. For painting Contributes to suppress the dimensional change rate after, when producing a polarizing plate, an effect that it is possible to suppress abnormal appearance such as a polarizing plate spot failure.

  In the invention of the combination of the protective films for polarizing plates according to claim 8 of the present invention, as described above, when the heat irradiation conditions according to claim 6 are the temperature of 80 ° C., the humidity of 90% RH, and the irradiation of 50 hours. The dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the protective film for polarizing plate made of a coating film is 0% or more and 0.30% or less, and the protective film for polarizing plate made of a cellulose ester film The ratio (A / B) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film to the dimensional change rate (B) is 100% or more and 140% or less. According to the invention of the protective film for polarizing plate according to item 8, there is little difference in the so-called lateral dimensional change rate of the protective film for polarizing plate made of a coating film, and physical properties are improved. For painting Contributes to suppress the dimensional change rate after, when producing a polarizing plate, an effect that it is possible to suppress abnormal appearance such as a polarizing plate spot failure.

  Invention of Claim 9 of this invention is a combination of the protective film for polarizing plates as described in any one of Claims 6-8 as above-mentioned, Comprising: For polarizing plates which consist of a coating film The protective film is produced by providing a coating layer on a cellulose ester film that has been treated for 3 hours or more in an environment at a temperature of 50 ° C or higher before coating, and is characterized in that: According to the invention of the combination of the protective films for polarizing plates described, because the physical properties are improved, it contributes to reducing the dimensional change rate after coating, An effect that appearance abnormality such as a plate spot failure can be suppressed is achieved.

  Invention of Claim 10 of this invention consists of the protective film for polarizing plates which consists of a cellulose-ester film as described in any one of Claims 6-9 as mentioned above, and a coating film. Among the protective films for polarizing plates constituted by the combination with the protective film for polarizing plates, the protective film for polarizing plates made of one coating film is on one side of the polarizer, and for the polarizing plate made of the other cellulose ester film. The protective film is produced by being bonded to the other surface of the polarizer. According to the polarizing plate of claim 10, the coated film having excellent physical properties is a polarizer. Since the other cellulose ester film is laminated on the other side of the polarizer on at least one side of the polarizing plate, the physical properties and appearance of the polarizing plate can be improved. Improved visibility of the liquid crystal display by bonding the liquid crystal cell are possible, there is an effect that it is possible to produce a liquid crystal display which can maintain a stable display performance over a long period of time.

  Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.

  Invention of the coating film which has a coating layer by using the cellulose ester film according to claim 1 of the present invention as a support, the coating film having a coating layer by using a cellulose ester film as a support is subjected to heat irradiation, When the film dimensions change, the heat irradiation conditions are a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, and the dimensional change rate in the parallel direction (longitudinal direction) to the film forming direction of the coating film is 0. % Or more and 0.60% or less.

  Here, when the dimensional change rate in the parallel direction (longitudinal direction) with respect to the film forming direction of the coating film exceeds 0.60%, the dimensional change is large and the film is deformed. A polarizing plate using this film Then, since the distortion of a polarizing plate will generate | occur | produce, it is not preferable.

  In addition, the dimensional change rate as used in the field of this invention is a characteristic value showing the dimensional change of the film vertical direction and a horizontal direction in the conditions where temperature and humidity conditions are severe. Specifically, the longitudinal and lateral dimensional changes after the film is placed under heating conditions, humidification conditions, and hot humidity conditions and subjected to forced deterioration treatment are measured.

  For example, a film sample to be measured is cut into a size of 150 mm in the width direction and 120 mm in the length direction, and the film surface is crossed with two sharp edges such as a razor at 100 mm intervals in the width direction and the length direction. Mark the mold. The film is conditioned for 24 hours or more in an environment of 23 ° C. and 55% RH, and the distance between marks L1 in the width direction and the longitudinal direction before processing is measured with a microscope.

  Next, the sample is subjected to a high-temperature and high-humidity treatment (condition: left at 50 ° C. and 90% RH for 50 hours) in an electric thermostat. Again, the sample was conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and the distance L2 between the marks in the width direction and the longitudinal direction after processing was measured with a microscope. The rate of change before and after this processing is obtained by the following equation.

Dimensional change rate (%) = {(L2−L1) / L1} × 100
In the formula, L1 represents a distance between marks before processing, and L2 represents a distance between marks after processing.

  That is, a desired dimensional change rate measurement can be performed by attaching the mark positions in the longitudinal direction (longitudinal direction or film forming direction) and lateral direction (width direction) of the film.

  In order to achieve the dimensional change rate of the present invention, there is no particular technical limitation. For example, the temperature in each step during the production of a cellulose ester film is optimized, or the type and amount of plasticizer described later Can be appropriately adjusted. The plasticizer to be used preferably has a vapor pressure at 200 ° C. of 1333 Pa or less, and particularly preferably a phosphate ester plasticizer.

  Moreover, the invention of the coating film which has a coating layer by using the cellulose ester film according to claim 2 of the present invention as a support, the coating film having a coating layer by using a cellulose ester film as a support, is irradiated with heat. When the dimensions of the film change, the heat irradiation conditions are temperature 80 ° C., humidity 90% RH, and irradiation for 50 hours, and the dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the coated film is 0% or more and 0.30% or less.

  Here, when the dimensional change rate in the vertical direction (transverse direction) with respect to the film forming direction of the coated film exceeds 0.30%, the dimensional change is large and the film is deformed. A polarizing plate using this film Then, since the distortion of a polarizing plate will generate | occur | produce, it is not preferable.

  The invention of the coating film according to claim 3 of the present invention is the coating film according to claim 1 or 2, wherein the coating film having a coating layer with the cellulose ester film as a support is applied before coating. It was prepared by providing a coating layer on a cellulose ester film that was treated for 3 hours or more in an environment at a temperature of 50 ° C. or higher.

  In this way, the cellulose ester film before coating is treated for 3 hours or more in an environment of a temperature of 50 ° C. or higher to make the dimensional stability of the cellulose ester film excellent, and then a coating layer is provided. The dimensional change rate with respect to the film forming direction of the coating film is as small as possible.

  Moreover, invention of the protective film for polarizing plates of Claim 4 of this invention is comprised by the coating film as described in any one of Claims 1-3, It is characterized by the above-mentioned.

  In the invention of the polarizing plate according to claim 5 of the present invention, the protective film for polarizing plate constituted by the coating film according to claim 4 is bonded to at least one surface of the polarizer.

  Invention of the combination of the protective film for polarizing plates of Claim 6 of this invention consists of the protective film for polarizing plates which consists of a cellulose-ester film, and the coating film which has a coating layer by using a cellulose-ester film as a support body. Dimensional change rate (B) of the protective film for a polarizing plate made of a cellulose ester film, when both films are irradiated with heat under the same conditions and the dimensions of these films change. The ratio (A / B) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film with respect to is 100% or more and 140% or less.

  Here, the ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plates made of a coating film to the dimensional change rate (B) of the protective film for polarizing plates made of a cellulose ester film is 140%. If it exceeds, the difference in dimensional change between the protective film for polarizing plate made of cellulose ester film and the protective film for polarizing plate made of coating film will be large, and when the dimensional change occurs as a polarizing plate, Since the stabilization balance at the time is lost, the polarizing plate is distorted.

  Furthermore, the invention of the combination of the protective films for polarizing plates according to claim 7 of the present invention is that the heat irradiation conditions according to claim 6 are applied when the temperature is 80 ° C., the humidity is 90% RH, and the irradiation is for 50 hours. The dimensional change rate in the parallel direction (longitudinal direction) of the protective film for a polarizing plate made of a film is 0% or more and 0.60% or less, and the dimensional change rate of the protective film for a polarizing plate made of a cellulose ester film The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plate made of a coating film with respect to (B) is 100% or more and 140% or less.

  Here, when the dimensional change rate in the parallel direction (longitudinal direction) with respect to the film forming direction of the protective film for polarizing plate made of a coating film exceeds 0.60%, deformation of the film occurs due to large dimensional change, A polarizing plate using this film is not preferable because the polarizing plate is distorted. Moreover, ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plates consisting of a coating film with respect to the dimensional change rate (B) of the protective film for polarizing plates consisting of a cellulose ester film exceeds 140%. And the difference in dimensional change between the protective film for polarizing plate made of cellulose ester film and the protective film for polarizing plate made of coating film is large, and when the dimensional change occurs as a polarizing plate, Therefore, the polarizing plate is distorted.

  The invention of the combination of the protective films for polarizing plates according to claim 8 of the present invention is that the heat irradiation conditions according to claim 6 are applied when the temperature is 80 ° C., the humidity is 90% RH, and the irradiation time is 50 hours. The dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the polarizing plate protective film is 0% or more and 0.30% or less, and the dimensional change rate of the polarizing plate protective film made of a cellulose ester film (B The ratio (A / B) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film is 100% or more and 140% or less.

  Here, when the dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the protective film for polarizing plate made of a coating film exceeds 0.30%, the deformation of the film occurs due to the large dimensional change, A polarizing plate using this film is not preferable because the polarizing plate is distorted. Further, the ratio (A /) of the dimensional change rate (A) of the protective film for a polarizing plate made of a coating film using the cellulose ester film as a support to the dimensional change rate (B) of the protective film for a polarizing plate made of a cellulose ester film. If B) exceeds 140%, the difference in dimensional change between the protective film for polarizing plate made of cellulose ester film and the protective film for polarizing plate made of coating film will be large, resulting in a dimensional change as a polarizing plate. At this time, since the stabilization balance on both sides of the polarizing plate is lost, the polarizing plate is distorted.

  Invention of Claim 9 of this invention is a combination of the protective film for polarizing plates as described in any one of Claims 6-8, Comprising: The protective film for polarizing plates which consists of a coating film is coating. It is produced by providing a coating layer on a cellulose ester film that has been treated for 3 hours or more in an environment at a temperature of 50 ° C. or more before construction.

  In this way, the cellulose ester film before coating is treated for 3 hours or more in an environment of a temperature of 50 ° C. or higher to make the dimensional stability of the cellulose ester film excellent, and then a coating layer is provided. The dimensional change rate with respect to the film forming direction of the polarizing plate protective film made of a coating film is as small as possible.

  The invention of a polarizing plate according to claim 10 of the present invention is a polarizing plate protective film comprising the cellulose ester film according to any one of claims 6 to 9 and a polarizing plate protective film comprising a coating film. Among the protective films for polarizing plates constituted by the combination with the polarizing plate, the protective film for polarizing plates made of one coating film is on one side of the polarizer, and the protective film for polarizing plates made of the other cellulose ester film is the polarizer It was produced by being bonded to the other surface.

  The present invention will be specifically described below.

  In the present invention, examples of the cellulose ester used include cellulose triacetate (TAC), cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate (CAP). In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a base strength having a bound acetic acid amount of 58 to 62.5% is strong and more preferable. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. It is preferred that the cellulose ester is substantially cellulose triacetate.

  In the present invention, the solvent used for dissolving the cellulose ester may be used alone or in combination, but it is preferable to use a mixture of a good solvent and a poor solvent from the viewpoint of increasing production efficiency. This is preferable in terms of the solubility of the film and the amount of film foreign matter due to minute insoluble matter. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by weight for the good solvent and 30 to 2% by weight for the poor solvent.

  Here, the good solvent and the poor solvent used in the present invention define a good solvent that dissolves the cellulose ester used alone, and a poor solvent that swells or does not dissolve alone.

  The good solvent used in the present invention is not particularly limited. For example, in the case of cellulose triacetate (TAC), an organic halogen compound such as methylene chloride (DCM), dioxolanes, and cellulose acetate propionate (CAP). Examples include methylene chloride (DCM), acetone, and methyl acetate (MA). The poor solvent is not particularly limited, but for example, methanol, ethanol (EtOH), i-propyl alcohol, n-butanol, cyclohexane, acetone, cyclohexanone and the like are preferably used.

  Examples of the non-chlorine organic solvent for cellulose ester include acetone, methyl acetate (MA), cyclohexanone, ethyl formate, 1,3-dioxolane, 2,2,2-trifluoroethanol, 2,2,3,3- Tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3 Examples include 3-hexafluoro-2-propanol and 2,2,3,3,3-pentafluoro-1-propanol. These solvents may be used alone or in combination of two or more.

  Among these, methyl acetate (MA) and acetone are most preferable as the non-chlorine organic solvent. Methyl acetate and acetone can obtain a film having good solubility and excellent transparency.

  In the present invention, when the cellulose ester is dissolved in a non-chlorine organic solvent to prepare a cellulose ester solution, the blending weight ratio of the non-chlorine organic solvent to the cellulose ester is 2 or more and 5 or less. The blending weight ratio of the non-chlorine organic solvent to the cellulose ester is preferably 2.5 or more and 4.5 or less, and more preferably 3 or more and 4 or less.

  In the present invention, the cellulose ester solution contains a lower alcohol having 1 to 6 carbon atoms for the purpose of improving the solubility, adjusting the viscosity, adjusting the drying speed, and promoting gelation when the solution is cast. You may make it contain. Examples of these lower alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, isobutyl alcohol, 2-butanol, t-butyl alcohol, and cyclohexanol. Of these, methanol, ethanol, and 1-butanol are preferable. These lower alcohols are preferably contained in an amount of 2 to 20% by weight based on the total organic solvent. A cellulose ester solution containing a lower alcohol having 1 to 6 carbon atoms has a strong film strength even when it contains a large amount of residual solvent during casting, and is a casting support used for casting. It becomes easy to peel off from the belt or drum.

  The cellulose ester solution may be prepared by an ordinary method, and is obtained by putting the cellulose ester and the solvent in a container and stirring and mixing at room temperature or under a temperature condition where the solvent does not boil. It is preferable that the stirring and mixing be performed by an apparatus and a system in which no liquid film remains inside the container. Further, the inside of the container may be filled with an inert gas such as nitrogen gas to suppress decomposition. If necessary, a pressurized container or the like may be used and stirred and mixed under pressure.

  The cellulose ester concentration in the solution is preferably as high as possible from the viewpoint of drying efficiency during film formation. On the other hand, when the concentration is too high, the viscosity of the solution is too large, and the flatness of the obtained film may deteriorate. Considering these points, the cellulose ester concentration of a preferable solution is in the range of 15% by weight to 40% by weight. Furthermore, the range of 20% by weight to 35% by weight is preferable.

  The viscosity of the cellulose ester solution may be in a range that allows casting during film formation, and is usually preferably adjusted to a range of 5 P (poise) to 500 P (poise).

  The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, it is taken out from the container while cooling, or extracted from the container with a pump or the like and cooled with a heat exchanger or the like, and used for film formation.

  In the present invention, the cellulose ester film contains additives such as a plasticizer and an ultraviolet absorber in addition to the cellulose ester and the solvent.

  These additives such as plasticizers and ultraviolet absorbers may be mixed with a solvent in advance and dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester, or may be added to the dope after dissolving the cellulose ester. .

  Although it does not specifically limit as a plasticizer which can be used by this invention, In a phosphate ester type | system | group, a triphenyl phosphate (TPP), a biphenyl diphenyl phosphate (BDP), a tricresyl phosphate, a cresyl diphenyl phosphate, an octyl diphenyl phosphate, For phthalate esters such as trioctyl phosphate and tributyl phosphate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate (EPEG), methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate and the like can be used.

  The above plasticizers may be used in combination of two or more as required. By containing these plasticizers, a film having excellent dimensional stability and water resistance can be obtained, which is particularly preferable.

  In the present invention, in order to make the water absorption rate and the moisture content within a specific range, the preferable addition amount of the plasticizer is 12% by weight or less with respect to the cellulose ester. When two or more kinds of plasticizers are used in combination, the total amount of these plasticizers may be 12% by weight or less.

  Next, the ultraviolet absorber that can be used in the present invention is not particularly limited, but is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal, and has a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties. Those that absorb as little visible light as possible are preferably used.

  Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  The fine particles added as a matting agent for the purpose of improving the slipperiness and preventing blocking after winding of the cellulose ester film of the present invention may be added to the main dope. Is preferable. Add to additive solution and add to film. Moreover, although it may be contained in the main dope, any fine particles can be used.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated calcium silicate. Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used. Among these, fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. Examples of these are those commercially available under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.). Can do. Furthermore, the silicon dioxide fine particles are preferably silicon dioxide fine particles having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Examples of the silicon dioxide fine particles that satisfy these requirements include Aerosil 200V and Aerosil R972V, which are particularly preferable because they have a great effect of reducing the friction coefficient while keeping the turbidity of the film low.

  In the present invention, the fine particles are used by adding 0.04 to 0.4% by weight to the cellulose ester. Preferably, it is 0.05 to 0.3% by weight, more preferably 0.05 to 0.2% by weight.

  In the present invention, a dope obtained by dissolving cellulose ester is cast on a casting support (casting process), and then heated to remove a part of the solvent (drying process on casting support). Then, the film is peeled from the casting support, and the peeled film is dried (film drying process) to obtain a cellulose ester film.

  As the casting support in the casting step, a casting support obtained by mirror-finishing belt-shaped or drum-shaped stainless steel is used. The casting support in the casting step can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent, but is cast on a casting support at 5 to 30 ° C. Since the dope is gelled to increase the separation limit time, it is preferable to cast the dope on a support for casting at 5 to 15 ° C.

  In the drying process on the casting support, the dope is cast, once gelled, and when the time from casting to peeling is 100%, the dope temperature is 40 ° C. to within 30% from casting. By setting the temperature to 70 ° C., the evaporation of the solvent is promoted, and it can be peeled off from the casting support as soon as possible. Further, since the peeling strength is increased, the dope temperature is preferably within 55% to 70 ° C. More preferably. This temperature is preferably maintained at 20% or more, more preferably 40% or more.

  It is preferable that the drying on the casting support is peeled from the casting support with a residual solvent amount of 60% to 150% because the peeling strength from the casting support is small, and 80 to 120% is preferable. More preferred. The temperature of the dope at the time of peeling is preferably 0 ° C. to 30 ° C., because it can increase the strength of the casting support at the time of peeling and can prevent the casting support from being broken at the time of peeling. 20 ° C. is more preferable.

  In the film drying step, the film peeled off from the casting support is further dried, and the residual solvent amount is 3% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less. It is preferable for obtaining a film having good stability. In the film drying process, generally, a roll suspension system, a pin tenter system, or a clip tenter system is used for drying while transporting the film. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve the dimensional stability.

  The means for drying the film is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and divided into 3 to 5 stages, and it is preferable to increase the temperature step by step, more preferably in the range of 80 ° C. to 140 ° C. in order to improve dimensional stability. . These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

  In the present invention, the winder for producing the cellulose ester film may be one generally used, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. It can be wound up by a take-up method.

  In the present invention, the thickness of the cellulose ester film is not particularly limited, but since it is used for a protective film for a liquid crystal display element used in a liquid crystal display device, that is, a polarizing plate, it is usually preferably 100 μm or less. Among these, a cellulose ester film having a thickness of 20 to 80 μm is preferable.

  In this invention, after winding up the cellulose ester film obtained at the above film forming processes once, or without winding up, a coating layer can be provided continuously.

  The layer configuration and the manufacturing process of the coating film are described in, for example, JP-A-2001-83327, JP-A-2003-39014, JP-A-2003-337202, and JP-A-2003-240922. ing.

  Here, in this invention, the coating layer provided in a cellulose-ester film is a layer provided in order to provide various functions to a cellulose-ester film, for example, an antiblocking layer, an anti-glare layer, an antireflection layer, clear hard A layer, an antistatic layer, an anti-curl layer, an easy adhesion layer, an alignment layer, a liquid crystal layer, an optical anisotropic layer, an optical compensation layer, and the like. An organic solvent is preferably used for the coating solution used for imparting these various functions. At this time, it is preferable to use a solvent having a property of dissolving or swelling the resin film because it is excellent in adhesion between the coated layer and the resin film, but on the other hand, it can be obtained by using such a solvent. There exists a problem that the planarity of a cellulose-ester film will fall remarkably.

  In the present invention, the organic solvent used as the coating solution includes alcohols such as methanol, ethanol, propanol, n-butanol, 2-butanol, tert-butanol, and cyclohexanol, and ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetone. , Esters such as ethyl acetate, methyl acetate, ethyl lactate, isopropyl acetate, amyl acetate, ethyl butyrate, glycol ethers (propylene glycol mono (C1-C4) alkyl ethers (specifically, propylene glycol monomethyl ether (PGME), Propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, etc.), Propylene glycol mono (C1 -C4) alkyl ester (propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate)), toluene, benzene, cyclohexane, and other solvents hydrocarbons such as n- hexane. Although not particularly limited to these, a solvent in which these are appropriately mixed is preferably used.

  In the present invention, the method of applying the coating liquid is doctor coating, extrusion coating, slide coating, roll coating, gravure coating, wire bar coating, reverse coating, curtain coating, extrusion coating, or US Pat. No. 2,681,294. It can apply | coat by the extrusion coating method etc. which use the hopper as described in a specification.

  In addition, among these various functional layers, the planarity may be deteriorated particularly in a layer formed by irradiating and curing an active ray. Therefore, as a result of intensive studies to solve this problem, a coating liquid containing an actinic radiation curable substance is applied and dried on a resin film, and the rotating casting support having a diameter larger than the width of the resin film is applied. By irradiating the actinic radiation while winding, a cellulose ester film having an actinic radiation cured layer having excellent flatness can be obtained.

  As another embodiment, it was confirmed that the planarity was also improved by applying a coating solution containing an actinic ray curable substance on a resin film and irradiating actinic rays while gripping the width. More preferably, a coating solution containing an actinic radiation curable substance is applied on a resin film, wound on a rotating casting support having a diameter equal to or larger than the width of the resin film, and irradiated with actinic radiation while gripping the width. Thereby, the cellulose-ester film which has the active ray hardened layer excellent in planarity is obtained.

  In the present invention, examples of the layer structure of a coating film having a coating layer using a cellulose ester film as a support include the following examples, but are not particularly limited thereto. Among these, the clear hard coat layer, the antiglare layer, the middle refractive index layer, the high refractive index layer, and the low refractive index layer are cured by being irradiated with ultraviolet rays after coating and drying.

Back coat layer / resin film / clear hard coat layer / high refractive index layer / low refractive index layer Back coat layer / resin film / clear hard coat layer / medium refractive index layer / high refractive index layer / low refractive index layer Antistatic layer / Resin film / Clear hard coat layer / Medium refractive index layer / High refractive index layer / Low refractive index layer Back coat layer / Resin film / Anti-glare layer / High refractive index layer / Low refractive index layer Back coat layer / Resin film / Antiglare layer / Medium refractive index layer / High refractive index layer / Low refractive index layer Antistatic layer / Resin film / Antiglare layer / Medium refractive index layer / High refractive index layer / Low refractive index layer Further, in the present invention, cellulose An example of an actinic radiation curable resin layer, which is a coating layer provided using an ester film as a support, will be described.

  Here, the actinic radiation curable resin layer refers to a layer mainly composed of a resin that is cured through a crosslinking reaction by irradiation with actinic rays such as ultraviolet rays and electron beams. Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but a resin that is cured by irradiation with an actinic ray other than ultraviolet rays or an electron beam may be used. Examples of the ultraviolet curable resin include an ultraviolet curable acrylic urethane resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, and an ultraviolet curable epoxy resin. be able to.

  Next, in the present invention, the case where the coating film having a coating layer using a cellulose ester film as a support is an antireflection film will be described.

  When the coating film is an antireflection film, the metal oxide layer may be directly formed on the cellulose ester film, but at least one other coating layer is provided and formed on the cellulose ester film having an uneven surface. May be. As the other coating layer, a cured resin layer having a center line average surface roughness (Ra) defined by JIS B0601 of 0.01 to 1 μm is preferable. These are preferably actinic radiation curable resin layers that are cured by actinic radiation such as ultraviolet rays. An antireflection film excellent in scratch resistance can be obtained by forming the metal oxide layer according to the present invention on such a resin layer cured with ultraviolet rays.

  The metal oxide layer is preferably used as at least one of a high refractive index layer, a medium refractive index layer, and a low refractive index layer.

  In the present invention, the method for providing the metal oxide layer is not particularly limited, and it can be formed by coating, CVD, sputtering, or vapor deposition, but it is preferably formed by plasma CVD even during coating or CVD.

  Next, a method for forming a metal oxide layer by coating will be described. The basic structure of the antireflection film of the present invention will be described. For example, a preferred antireflection film has a layer structure in the order of a transparent support, a hard coat layer, a medium refractive index layer, a high refractive index layer, and a low refractive index layer. The transparent support, the middle refractive index layer, the high refractive index layer, and the low refractive index layer have a refractive index that satisfies the following relationship.

  The refractive index of the low refractive index layer <the refractive index of the transparent support <the refractive index of the medium refractive index layer <the refractive index of the high refractive index layer.

  In the antireflection film having a medium refractive index layer, a high refractive index layer, and a low refractive index layer, as described in, for example, JP-A-59-50401, the medium refractive index layer has the following formula (1). When the high refractive index layer satisfies the following mathematical formula (2) and the low refractive index layer satisfies the following mathematical formula (3), it is possible to further reduce the average reflectance as an antireflection film.

(Hλ / 4) × 0.7 <n ₃ d ₃ <(hλ / 4) × 1.3 (1)
In Formula (1), h is a positive integer (generally 1, 2 or 3), n ₃ is the refractive index of the medium refractive index layer, and d ₃ is the film thickness (nm) of the medium refractive index layer. It is. Further, λ is a wavelength, which is a value in the range of 350 to 800 (nm).

(Jλ / 4) × 0.7 <n ₄ d ₄ <(jλ / 4) × 1.3 (2)
In formula (2), j is a positive integer (generally 1, 2 or 3), n ₄ is the refractive index of the high refractive index layer, and d ₄ is the film thickness (nm) of the high refractive index layer. It is. Further, λ is a wavelength, which is a value in the range of 350 to 800 (nm).

(Kλ / 4) × 0.7 <n ₅ d ₅ <(kλ / 4) × 1.3 (3)
In Equation (3), k is a positive odd number (generally 1), n ₅ is the refractive index of the low refractive index layer, and d 5 is the film thickness (nm) of the low refractive index layer. Further, λ is a wavelength, which is a value in the range of 350 to 800 (nm).

  In the present invention, it is also preferable to provide an antiglare antireflection film by providing irregularities on the hard coat layer or the high refractive index layer.

  In addition, a layer structure in the order of a transparent support, a hard coat layer (antiglare layer), a high refractive index layer, a low refractive index layer, a high refractive index layer, and a low refractive index layer is also a preferable configuration. It is preferable to impart an antiglare property to the low refractive index layer on the surface, and an antiglare layer may be provided on the surface.

  Next, the back coat layer will be described.

<Protrusion of back coat layer using cellulose ester film as support>
In the present invention, when a coating film having a coating layer with a cellulose ester film as a support is a low-reflection film, the low-reflection film has an uneven layer, a reflection layer on one surface of the support of the cellulose ester film. It has a prevention layer or the like, but the other surface (also referred to as the back surface) preferably has 10 to 500/100 μm ² protrusions having a height from the surface of 0.1 μm or more, more preferably 50 to 500 pieces / 100 μm ² , particularly preferably 100 pieces to 450 pieces / 100 μm ² .

  Here, the number of protrusions on the film surface can be measured using an optical interference type surface roughness meter (for example, RST PLUS manufactured by WYKO) to count the number of protrusions having a height of 0.1 μm or more from the film surface. .

  Such a protrusion on the back side can be formed by a method in which fine particles are added to the film in advance, or a method in which a coating liquid containing fine particles is applied to provide a backcoat layer. The number and size of the protrusions can be controlled by controlling the amount of fine particles added and the dispersion state.

This not only prevents the occurrence of blocking even if it is wound into a roll once during the application of each optical interference layer, but can also significantly reduce coating unevenness when the next optical interference layer is applied. . Although the cause of coating unevenness is not completely clarified, it is presumed that as one of the causes, peeling electrification at the time of feeding a film wound up in a roll shape to the coating process is related. By adding fine particles to the base film, it is possible to have 10 to 500/100 μm ² protrusions having a height of 0.1 μm to 10 μm on the back surface. At this time, the base film can be formed into a multilayer structure, and fine particles can be included only in the surface layer.

  By adjusting the protrusions on the back surface within the above range, there is an effect in improving the storage stability of the long roll-shaped low reflection film.

  In the present invention, when the coating film having a coating layer with a cellulose ester film as a support is a low-reflection film, the low-reflection film comprises a medium-refractive index layer, a high-refractive index layer, and a low-refractive index layer of the antireflection layer When applying each coating composition of the rate layer, it is preferable to control the amount of moisture in the air in the coating part (coater part) or in the drying zone. The moisture content control in the air at the time of application is easy to adjust with the dew point, and the dew point is preferably 5 ° C. or higher and 16 ° C. or lower, and particularly preferably 9 ° C. or higher and 12 ° C. or lower. When the dew point is 5 ° C. or less, the applied film is fragile and easily damaged, which is not preferable. If the dew point is too high, brushing occurs and the coating layer becomes cloudy. It was found that moisture in the air at the time of application increased the hardness of the coating and improved the high temperature durability of the low reflection film. By controlling the dew point at the time of coating, not only a low reflection film having a surface roughness Ra of 0.08 μm to 0.5 μm but also a low reflection film having a surface roughness of 0.01 μm to less than 0.08 nm can obtain the same effect. .

  Moreover, it is preferable that a low reflection film processes each coating composition of the middle refractive index layer of a reflection prevention layer, a high refractive index layer, and a low refractive index layer on the conditions of high temperature or high temperature / humidity after application | coating. In the case of high temperature treatment after coating, it is 30 ° C. or higher and below the temperature at which the support is deformed, specifically 30 ° C. or higher and 120 ° C. or lower, preferably 40 ° C. or higher and 110 ° C. or lower, more preferably 50 ° C. ~ 100 ° C. In the case of high temperature and high humidity, the temperature is preferably 40 ° C. or higher and 90 ° C. or lower and the relative humidity is 40% to 90% or lower. The treatment time varies depending on the temperature, relative humidity, and winding shape, but higher temperatures are preferable because the treatment time is shorter. It was also found that when the humidity is high, the same performance tends to be obtained even when the processing temperature is lowered. When this treatment is performed, the storage durability of the low-reflection film is improved, and microcracks are hardly formed, and a high quality state can be maintained for a long time. Although the mechanism is unknown, it is presumed that high temperature durability is improved because bonding of unreacted parts and adhesion between layers are promoted by heat and moisture. Preferred treatment conditions of the present invention are different depending on the form of the sample (winding length and packaging), but for 3 to 7 days at a temperature of 40 ° C. and a relative humidity of 80%, at 50 ° C. and a relative humidity of 80%. The conditions are 1 to 3 days, 90 ° C., relative humidity 10% for several hours to 2 days, 90 ° C., relative humidity 90% for several hours to 1 day, and the like. Furthermore, this effect can be applied not only to an antiglare low reflection film but also to a low reflection film that does not have an antiglare property.

  Next, in the present invention, a general method may be used as a method for producing a polarizing plate. Hereinafter, the polarizing plate of the present invention and a liquid crystal display device using the same will be described.

  A conventionally well-known thing can be used as a polarizer used for the polarizing plate of this invention. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as vinyl chloride is treated and oriented. The polarizer thus obtained is laminated with the protective film for polarizing plate according to the present invention.

  That is, the invention of the protective film for a polarizing plate of the present invention is constituted by the coating film according to any one of claims 1 to 3 described above, and for the polarizing plate constituted by the coating film. A protective film is bonded to at least one surface of the polarizer. When the protective film for polarizing plate composed of a coating film is bonded only on one side of the polarizer, a cellulose ester film support or other transparent support or cellulose triacetate (not coated with a liquid crystal layer on the other side) TAC) film may be used.

  Moreover, the polarizing plate by this invention is a group of the protective film for polarizing plates which consists of a cellulose-ester film as described in any one of Claims 6-9 mentioned above, and the protective film for polarizing plates which consists of a coating film. Among the protective films for polarizing plates formed by combining, the protective film for polarizing plates made of one coating film is on one side of the polarizer, and the protective film for polarizing plates made of the other cellulose ester film is the other side of the polarizer It was produced by pasting together.

  Thus, the obtained polarizing plate may be provided in the cell side surface of a liquid crystal cell, and may be provided in both surfaces side. When provided on one side, a liquid crystal display device can be obtained by attaching an optical compensation film made of a cellulose ester film to the polarizer closer to the liquid crystal cell.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Examples 1-3
<Preparation of cellulose acetate solution (dope)>
Cellulose acetate 100 parts by weight (acetyl substitution degree 2.85, number average molecular weight 150,000)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 0.3 part by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.4 part by weight Tinuvin 171 ( Ciba Specialty Chemicals Co., Ltd.) 0.4 parts by weight AEROSIL R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by weight Methylene chloride 475 parts by weight Ethanol 25 parts by weight After raising the internal temperature to 60 ° C., the mixture was stirred at 60 ° C. and completely dissolved. Thereafter, the stirring was stopped, the temperature of the solution was lowered to 43 ° C., a dope was prepared, and the solution was immediately sent to a filtration step described later via a connected pipe, and filtered using a filter paper having an absolute filtration accuracy of 0.005 mm. It was.

<Production of cellulose acetate film>
Using a solution casting film forming apparatus (not shown) having a tenter drying apparatus, the cellulose acetate dope prepared above was cast and dried to prepare a cellulose acetate film.

  Specifically, the dope solution prepared above is cast on a stainless steel belt support through a casting die, the temperature of the stainless steel belt is controlled at 25 ° C., and 45 ° C. from the film-side drying step. From the drying process on the stainless steel belt side, the film is dried by applying the wind at an angle of 10 m / sec and drying the film at a speed of 10 m / sec, and the residual solvent amount in the film becomes 70% by weight. After evaporating the solvent, it was peeled off with a peeling roll.

  Next, the film is introduced into a tenter drying apparatus and a roll drying apparatus, dried at 90 ° C. while maintaining the width with the tenter drying apparatus, and subsequently dried at 120 ° C. with a roll drying apparatus arranged in a staggered manner. Then, the film was wound up by a winder of the winder, and finally cooled to 20 ° C. to produce a cellulose acetate film 1 having a width of 1.3 m and a thickness of 50 μm. In addition, it was set to 196 N / width as tension | tensile_strength at the time of conveyance of a film through the said whole process. Both ends of the width were wound by providing a knurling having a width of 10 mm and a height of 8 μm.

  Thus, three types of cellulose acetate films having different dimensional change rates (dimensional shrinkage rates) were produced. About these three types of cellulose acetate films, the dimensional shrinkage rate (dimensional change rate) (B) in the vertical direction of the film was measured by the method described above, and the obtained results are shown in Table 1 below.

  In addition, in order to achieve the dimensional change rate of three different types of cellulose acetate films, it can be obtained by appropriately adjusting the peeling tension conditions, stretching conditions, conveying tension conditions, etc. at the time of forming the cellulose acetate film. It is.

<Preparation of antireflection film>
Using the three types of cellulose acetate films prepared as described above as a support, an antiglare layer was formed on the film by the following method. The cellulose acetate film support was heat-treated at 70 ° C. for 3 hours before coating.

<Formation of antiglare layer>
On one surface of the cellulose acetate film produced as described above, an antiglare layer (ultraviolet curable resin layer) was formed according to the following.

Antiglare layer UV curable acrylic urethane resin 100 parts by weight (Unidec 17-806, manufactured by Dainippon Ink Co., Ltd.)
5 parts by weight of spherical crosslinked polystyrene fine particles having an average particle diameter of 3.5 μm 7 parts by weight of synthetic silica fine particles having an average particle diameter of 16 nm 1 part by weight of a polyisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.)
Photopolymerization initiator (Irgacure 184, manufactured by Ciba Geigy) 3 parts by weight The above materials were mixed with a solvent (ethyl acetate) by a homogenizer to prepare a homogeneous dispersion having a volatile concentration of 50% by weight.

This was die-coated on the above film, dried at 90 ° C. for 2 minutes, and then cured by irradiating with 110 mJ / cm ² of ultraviolet rays to form an antiglare layer having a thickness of 3 μm. This was immersed in a 2 mol / L NaOH aqueous solution at 50 ° C. for 90 seconds, subjected to alkali treatment (saponification), then washed with water and dried.

  Next, a metal oxide layer (antireflection layer) was formed on the antiglare layer by the following procedure to obtain an antireflection film.

<Formation of metal oxide layer (antireflection layer)>
(Preparation of titanium dioxide dispersion)
30 parts by weight of titanium dioxide (weight average particle size of primary particles: 50 nm, refractive index: 2.70), 4.5 parts by weight of anionic diacrylate monomer (PM21, Nippon Kayaku Co., Ltd.), cationic methacrylate monomer (DMAEA) (Manufactured by Kojin Co., Ltd.) 0.3 parts by weight and 65.2 parts by weight of methyl ethyl ketone were dispersed by a sand grinder to prepare a titanium dioxide dispersion.

<Preparation of medium refractive index layer coating solution>
In 151.9 g of cyclohexanone and 37.0 g of methyl ethyl ketone, 0.14 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) and 0.04 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were dissolved. Further, 6.1 g of the above titanium dioxide dispersion and 2.4 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.) were added, and the mixture was stirred at room temperature for 30 minutes. The solution was filtered through a 0.4 μm polypropylene filter to prepare a coating solution for a medium refractive index layer.

<Preparation of coating solution for high refractive index layer>
In 1152.8 g of cyclohexanone and 37.2 g of methyl ethyl ketone, 0.06 g of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) and 0.02 g of a photosensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) were dissolved. Furthermore, the titanium dioxide dispersion and a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.) were adjusted so that the refractive index of the high refractive index layer was 1.95. The mixture was stirred at room temperature for 30 minutes and then filtered through a polypropylene filter having a pore size of 0.4 μm to prepare a coating solution for a high refractive index layer.

<Preparation of coating solution for low refractive index layer>
210 g of thermally crosslinkable fluorine-containing polymer having a refractive index of 1.40 (JN-7223, solid concentration 6 wt%, manufactured by JSR Corporation) and silica sol (MIBK-ST, average particle size 10-20 nm, solid concentration 30 wt%) (Nissan Chemical) 15.2 g and methyl isobutyl ketone 174 g were added, and after stirring, the mixture was filtered through a polypropylene filter having a pore size of 1 μm to prepare a coating solution for a low refractive index layer.

(Preparation of antireflection film)
The above-mentioned coating solution for the medium refractive index layer is applied on the alkali-glare layer provided on the cellulose acetate film using a bar coater, dried at 60 ° C., and then irradiated with ultraviolet rays to cure the coating layer. Thus, a middle refractive index layer (refractive index 1.72) was formed. On top of this, the coating solution for the high refractive index layer is applied using a bar coater, dried at 60 ° C., then irradiated with ultraviolet rays to cure the coating layer, and a high refractive index layer (refractive index 1.95). Formed. Furthermore, the antireflective film was produced by apply | coating the said coating liquid for low-refractive-index layers using a bar coater, and drying and hardening at 120 degreeC for 10 minutes.

  Thus, three types of antireflection films (coating films) having different dimensional change rates (dimensional shrinkage rates) from each other were produced. And about these three types of antireflection films (coating films), the dimension shrinkage rate (dimensional change rate) (B) of the antireflection film (coating film) in the vertical direction was measured by the method described above, and obtained. The results obtained are shown in Table 1 below.

  Moreover, the dimensional change rate of the protective film for polarizing plates which consists of an antireflection film (coating film) with respect to the dimensional change rate (B) of the protective film for polarizing plates which consists of said three types of cellulose acetate films ( The ratio (A / B) of A) was calculated, and the obtained results are shown in Table 1 below.

<Creation of polarizing plate>
A coated film was bonded to one side of the polarizer, and a cellulose acetate film was bonded to the other side to form a polarizing plate.

  According to the following method, the polarizing plate of this invention was produced using the low-reflection film (coating film) and one each of the cellulose acetate film used as a support body for this film as a protective film for polarizing plates.

(A) Production of Polarizing Film A long polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a long polarizing film.

(B) Production of Polarizing Plate Next, according to the following steps 1 to 5, the polarizing film and the polarizing plate protective film were bonded together to produce a polarizing plate.

  Step 1: A long cellulose acetate film and a low reflection film were immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried. A surface of the low reflection film provided with the antireflection layer was previously protected with a peelable protective film (PET).

  Similarly, a long cellulose acetate film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried.

  Process 2: The above-mentioned long polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and it was sandwiched between a cellulose acetate film and a low reflection film that had been subjected to alkali treatment in Step 1, and laminated.

  Step 4: The two rotating rollers were bonded together at a pressure of 20 to 30 N / cm 2 and a speed of about 2 m / min. At this time, care was taken so that no bubbles would enter.

  Step 5: The sample prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare three types of polarizing plates of the present invention.

<Creation of liquid crystal display>
The polarizing plates of Examples 1 to 3 according to the present invention in which the polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display MultiSync LCD1525J: model name LA-1529HM) was carefully peeled off and the polarization direction was adjusted thereto were used. Pasted.

(Evaluation of liquid crystal display visibility)
The liquid crystal panel obtained as described above was placed on a desk 80 cm high from the floor, and a daylight direct fluorescent lamp (FLR40S • D / MX, Matsushita Electric Industrial Co., Ltd.) was placed on the ceiling 3 m high from the floor. Sangyo Co., Ltd.) 40W × 2 were used as one set, and 10 sets were arranged at 1.5 m intervals. At this time, when the evaluator is in front of the display surface of the liquid crystal panel, the fluorescent lamp is arranged so that the fluorescent lamp comes to the ceiling from the evaluator's overhead to the rear. The liquid crystal panel was tilted by 25 ° from the vertical direction with respect to the desk, and a fluorescent lamp was reflected so that the visibility of the screen (visibility) was evaluated as follows.

  ◎: Cannot read from the closest fluorescent light, and can clearly read characters with a font size of 8 or less.

  ○: Reflection of a nearby fluorescent lamp is a little annoying, but I don't care about the distance, and I can manage to read characters with a font size of 8 or less.

  Δ: It is difficult to read characters with a font size of 8 or less due to the reflection of distant fluorescent lights.

  X: The reflection of the fluorescent lamp is quite worrisome, and the portion of the reflection cannot read characters with a font size of 8 or less.

  The evaluation results of the visibility of the obtained liquid crystal display are shown in Table 1 below.

(Measurement of spot failure)
Next, spot-like failures were measured for the polarizing plates obtained in Examples 1 to 3 of the present invention, and the obtained results are shown in Table 1 below.

The spot failure of the polarizing plate was measured by visually observing the prepared polarizing plate and performing grade evaluation based on the number of spots that can be distinguished per 400 cm ^{2 of} the polarizing plate.

  A: 0, o: 1-4, Δ: 5-9, x: 10 or more.

Comparative Examples 1-3
For comparison, a cellulose acetate film and an antireflection film (coating film) are prepared in the same manner as in Examples 1 to 3, but as shown in Table 1 below, Comparative Examples 1 to 3 are prepared. Then, the dimensional change rate (dimensional shrinkage rate) (B) in the vertical direction is outside the range of the present invention, or the antireflection film (B) for the dimensional change rate (B) of the protective film for polarizing plate made of a cellulose acetate film ( The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plate made of a coating film was outside the scope of the present invention.

  And about the cellulose acetate film and antireflection film (coating film) of these comparative examples 1-3, it is the same as the case of the said Examples 1-3, a reflection film (coating film), and a support body to this film The polarizing plates of Comparative Examples 1 to 3 were prepared using one cellulose acetate film each as a polarizing plate protective film.

  Subsequently, the polarizing plates of Comparative Examples 1 to 3 having the same polarization direction were attached to the outermost surface of a commercially available liquid crystal display panel in the same manner as in Examples 1 to 3 above. With respect to the liquid crystal panels of Comparative Examples 1 to 3 thus obtained, the visibility was evaluated in the same manner as in Examples 1 to 3, and the obtained results are shown in Table 1 below.

In addition, about the polarizing plate obtained in Comparative Examples 1-3, a spot-like failure was measured like the case of the said Examples 1-3, and the obtained result was combined with following Table 1, and was shown.

  As is clear from the results in Table 1 above, a polarizing plate comprising an antireflection film (coating film) with respect to the dimensional change rate (B) of the protective film for polarizing plate comprising the cellulose acetate film of Examples 1 to 3 according to the present invention. The ratio (A / B) of the dimensional change rate (A) of the protective film for a film is within the scope of the present invention, and the protective film for a polarizing plate made of one coating film is on one side of the polarizer, According to each polarizing plate of Examples 1 to 3, which was prepared by laminating a protective film for a polarizing plate made of a cellulose ester film on the other surface of the polarizer, no spot failure occurred in the polarizing plate. Moreover, the visibility of the image obtained with the liquid crystal display produced using each polarizing plate of Examples 1-3 is favorable, and also the protective film for polarizing plates which consists of a cellulose acetate film, and antireflection film (coating film) It can be seen that the polarizing property of the protective film for polarizing plate made of is improved.

  On the other hand, in the cellulose ester film of Comparative Example 1, the longitudinal dimensional change rate (dimensional shrinkage rate) (B) is out of the scope of the present invention, and the polarization is made of the cellulose acetate film of Comparative Examples 1 to 3. The ratio (A / B) of the dimensional change rate (A) of the protective film for polarizing plates made of an antireflection film (coating film) to the dimensional change rate (B) of the protective film for plates is outside the scope of the present invention. Therefore, according to each polarizing plate of Comparative Examples 1 to 3, spot-like failure occurred in each polarizing plate. Moreover, in the polarizing plate of Comparative Examples 1-3, it turns out that the visibility of the image obtained with a liquid crystal display is deteriorated.

Examples 4-6
In the same manner as in Examples 1 to 3, a cellulose acetate film and an antireflection film (coated film) were produced. And about these three types of antireflection film (coating film), the dimension shrinkage rate (dimensional change rate) (B) of the antireflection film (coating film) in the horizontal direction is measured and obtained by the method described above. The results obtained are shown in Table 2 below.

  Also, the lateral dimensional change rate of the polarizing plate protective film made of the antireflection film (coating film) relative to the lateral dimensional change rate (B) of the polarizing plate protective film made of the above three types of cellulose acetate films ( The ratio (A / B) of A) was calculated, and the obtained results are shown in Table 2 below.

<Creation of polarizing plate>
In the same manner as in Examples 1 to 3, the low-reflection film (coating film) of Examples 4 to 6 and one cellulose acetate film each used as a support for the film are protected for polarizing plates. The polarizing plate of this invention was produced using it as a film.

  And about the cellulose acetate film and antireflection film (coating film) of these Examples 4-6, it is the same as that of the said Examples 1-3, and a reflection film (coating film) and a support body to this film The polarizing plates of Examples 4 to 6 were produced using one cellulose acetate film used as a polarizing plate protective film.

  Next, the polarizing plates of Examples 4 to 6 having the same polarization direction were attached to the outermost surface of a commercially available liquid crystal display panel in the same manner as in Examples 1 to 3 above. With respect to the liquid crystal panels of Examples 4 to 6 thus obtained, the visibility was evaluated in the same manner as in Examples 1 to 3, and the obtained results are shown in Table 2 below.

  In addition, about the polarizing plate obtained in Examples 4-6, the spot-like failure was measured like the case of the said Examples 1-3, and the obtained result was combined with following Table 2, and was shown.

Comparative Examples 4-6
For comparison, a cellulose acetate film and an antireflection film (coating film) are produced in the same manner as in Examples 1 to 3, but as shown in Table 2 below, Comparative Examples 4 to 6 are prepared. Then, the dimensional change rate (dimensional shrinkage rate) (B) in the lateral direction is outside the range of the present invention, or the reflection with respect to the dimensional change rate (B) in the lateral direction of the protective film for polarizing plate made of a cellulose acetate film. The ratio (A / B) of the dimensional change rate (A) in the lateral direction of the protective film for polarizing plate made of a prevention film (coating film) was outside the scope of the present invention.

  And about the cellulose acetate film and antireflection film (coating film) of these comparative examples 4-6, it carries out similarly to the case of the said Examples 4-6, and a support body to this film. The polarizing plates of Comparative Examples 1 to 3 were prepared using one cellulose acetate film each as a polarizing plate protective film.

  Subsequently, the polarizing plates of Comparative Examples 4 to 6 having the same polarization direction were attached to the outermost surface of a commercially available liquid crystal display panel in the same manner as in Examples 4 to 6. With respect to the liquid crystal panels of Comparative Examples 4 to 6 thus obtained, the visibility was evaluated in the same manner as in Examples 4 to 6, and the obtained results are shown in Table 2 below.

In addition, about the polarizing plate obtained in Comparative Examples 4-6, the spot-like failure was measured like the case of the said Examples 4-6, and the obtained result was combined with following Table 2, and was shown.

  As is clear from the results in Table 2 above, a polarizing plate comprising an antireflection film (coating film) with respect to the dimensional change rate (B) of the protective film for polarizing plate comprising the cellulose acetate film of Examples 4 to 6 according to the present invention. The ratio (A / B) of the dimensional change rate (A) of the protective film for a film is within the scope of the present invention, and the protective film for a polarizing plate made of one coating film is on one side of the polarizer, According to each polarizing plate of Examples 4-6 produced by bonding a protective film for a polarizing plate made of a cellulose ester film to the other surface of the polarizer, no spot-like failure occurred in the polarizing plate. Moreover, the visibility of the image obtained with the liquid crystal display produced using each polarizing plate of Examples 4-6 is favorable, and by extension, the protective film for polarizing plates which consists of a cellulose acetate film, and an antireflection film (coating film) It can be seen that the polarizing property of the protective film for polarizing plate made of

  On the other hand, the dimensional change rate (A) of the protective film for polarizing plates made of the antireflection film (coating film) relative to the dimensional change rate (B) of the protective film for polarizing plates made of the cellulose acetate film of Comparative Examples 4 to 6 Since the ratio (A / B) is outside the range of the present invention, according to each of the polarizing plates of Comparative Examples 4 to 6, spot failure occurred in the polarizing plate. Moreover, in the polarizing plate of Comparative Examples 4-6, it turns out that the visibility of the image obtained with a liquid crystal display is deteriorated.

  For comparison, an antireflection film (coating film) produced without heat treatment before coating has a dimensional shrinkage of the coated film exceeding 0.60% in the vertical direction and 0 in the horizontal direction. It exceeded 30%, and the effect of the present invention was not obtained.

Claims (10)

  When a coating film having a coating layer with a cellulose ester film as a support is subjected to heat irradiation, and the dimensions of the film change, the heat irradiation conditions are temperature 80 ° C., humidity 90% RH, and irradiation for 50 hours. The dimensional change rate in the parallel direction (longitudinal direction) with respect to the film forming direction of the coating film is 0% or more and 0.60% or less, and has a coating layer with a cellulose ester film as a support. Coating film.   When a coating film having a coating layer with a cellulose ester film as a support is subjected to heat irradiation, and the dimensions of the film change, the heat irradiation conditions are temperature 80 ° C., humidity 90% RH, and irradiation for 50 hours. The dimensional change rate in the vertical direction (lateral direction) with respect to the film forming direction of the coating film is 0% or more and 0.30% or less, and has a coating layer with a cellulose ester film as a support. Coating film.   A coating film having a coating layer using a cellulose ester film as a support was produced by providing a coating layer on a cellulose ester film that had been treated for 3 hours or more in an environment at a temperature of 50 ° C. or more before coating. The coated film according to claim 1, wherein the coated film is a product.   A protective film for a polarizing plate, comprising the coating film according to claim 1.   A polarizing plate, wherein a protective film for a polarizing plate composed of the coating film according to claim 4 is bonded to at least one surface of a polarizer.   It is comprised by the protective film for polarizing plates which consists of a cellulose-ester film, and the protective film for polarizing plates which consists of a coating film which has a coating layer by using a cellulose-ester film as a support body, and heat irradiation of the same conditions on each of both films When the dimensions of these films change, the ratio of the dimensional change amount (A) of the protective film for polarizing plates made of a coating film to the dimensional change amount (B) of the protective film for polarizing plates made of a cellulose ester film A combination of protective films for polarizing plates, wherein (A / B) is 100% or more and 140% or less.   When the heat irradiation condition according to claim 6 is a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, the dimensional change in the parallel direction (longitudinal direction) with respect to the film forming direction of the protective film for polarizing plate made of a coating film The rate is 0% or more and 0.60% or less, and the dimensional change amount (A) of the protective film for polarizing plates made of a coating film with respect to the dimensional change amount (B) of the protective film for polarizing plates made of a cellulose ester film A combination of protective films for polarizing plates, wherein the ratio (A / B) is 100% or more and 140% or less.   When the heat irradiation condition according to claim 6 is a temperature of 80 ° C., a humidity of 90% RH, and irradiation for 50 hours, the dimensional change in the vertical direction (lateral direction) with respect to the film forming direction of the protective film for polarizing plate made of a coating film The rate is 0% or more and 0.30% or less, and the dimensional change amount (A) of the protective film for polarizing plates made of a coating film with respect to the dimensional change amount (B) of the protective film for polarizing plates made of a cellulose ester film A combination of protective films for polarizing plates, wherein the ratio (A / B) is 100% or more and 140% or less.   A protective film for a polarizing plate comprising a coating film is produced by providing a coating layer on a cellulose ester film that has been treated for 3 hours or more in an environment at a temperature of 50 ° C or higher before coating. The combination of the protective film for polarizing plates as described in any one of 6-8.   A polarizing plate protective film comprising a combination of a polarizing plate protective film comprising a cellulose ester film according to any one of claims 6 to 9 and a polarizing plate protective film comprising a coating film. Among them, the protective film for polarizing plate made of one coating film was produced by bonding the protective film for polarizing plate made of the other cellulose ester film to one side of the polarizer and the other side of the polarizer. A polarizing plate.