TWI657919B - Circular polarizing film, circular polarizing film with adhesive layer, and image display device - Google Patents

Abstract

The present invention relates to a circularly polarizing film, which comprises a polarizing element, a retardation film disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. The retardation film has The function of converting linearly polarized light into circularly polarized light or elliptical polarized light. The thickness is less than 35 μm, and the two sides of the retardation film have different initial damage loads in the scratch test. The side where the initial damage load is higher is set. When it is the first surface and the lower side is the second surface, the polarizing element is bonded to the first surface of the retardation film. The circular polarizing film of the present invention is excellent in impact resistance or repeatability, and can suppress curl.

Description

Circular polarizing film, circular polarizing film with adhesive layer, and image display device

The invention relates to a circular polarizing film. The present invention also relates to a circularly polarizing film using the above-mentioned circularly polarizing film with an adhesive layer. Furthermore, the present invention relates to an image display device using the above-mentioned circularly polarizing film or a circularly polarizing film with an adhesive layer. The circularly polarizing film of the present invention can be favorably used in an image display device, and can be particularly favorably used in an image display device that visually displays a display screen through a polarizing lens such as polarized sunglasses.

In recent years, such as mobile phones, smart phones, tablet personal computers (PC, Personal Computer), car navigation systems, digital signage, window displays, etc., the chances of image display devices being used under strong outer light have increased . When the image display device is used outdoors in this way, when the viewer wears polarized sunglasses to view the image display device, the transmission axis direction of the polarized sunglasses and the image display device are based on the angle viewed by the viewer. The direction of the transmission axis on the exit side becomes orthogonally polarized. As a result, the screen may become black and the display image may not be visually recognized. In order to solve such a problem, a technology has been proposed in which a circularly polarizing film (a polarizing film for polarizing sunglasses) is disposed on the viewing side surface of an image display device (Patent Document 1). In addition, the image display device described above is susceptible to external impact such as dropping or impact, and the circular polarizing film is also required to have impact resistance.

In addition, when an optical film such as a circular polarizing film is bonded to a liquid crystal cell, the optical film may be peeled from the liquid crystal panel and the liquid crystal cell may be peeled off from the liquid crystal panel when the bonding position is wrong or a foreign object is sandwiched on the bonding surface. In the case of reuse. In this peeling step, re-peelability (repeating processability) is required in which the entire optical film can be peeled from the liquid crystal panel without a paste residue.

The above-mentioned circularly polarizing film may use a retardation film having a circularly polarizing function or an elliptically polarizing function as a protective film provided on one side of the polarizing element. As this retardation film, a stretched polycarbonate film or a stretched olefin polymer film is known. However, the polycarbonate film or olefin polymer film has low moisture permeability. Although the dimensional stability in a humid environment is high and good, the use of a polycarbonate film may cause a large amount of light. A major problem of unevenness of the in-plane retardation Re caused by the elastic coefficient. In addition, in the case where the lower side of the optical unit (for example, the liquid crystal cell) is viewed (and further more than the polarized element is viewed side), the olefin film is used as the retardation film, which has the following major problems: # 158665; The olefin-based film is cracked or dissolved due to the solvent contained in the interlayer resin when the sebum or lotion is adhered or the above-mentioned circular polarizing film is fully laminated.

On the other hand, as the retardation film of the circularly polarizing film, a cellulose ester film such as a cellulose acetate film or a cellulose acetate propionate film can be used. The cellulose ester-based film has a small photoelastic coefficient, so it does not easily cause unevenness of the in-plane retardation Re. Furthermore, it can suppress the generation or dissolution of cracks even when it comes into contact with sebum, lotions, or solvents (Patent Document 2). In addition, a retardation film obtained by extending a cellulose ester film is often used for TV (Television) applications, and its thickness is usually 40 μm or more. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2014-16425 [Patent Document 2] Japanese Patent Laid-Open Publication No. 2016-177165

[Problems to be solved by the invention]

In addition, thinning of image display devices in recent years is required, and thinning of the retardation films is also required. Moreover, since the said retardation film can be obtained by extending | stretching process, curl is easy to generate | occur | produce, and from the viewpoint of suppressing curl, thickness reduction is also requested | required. However, a circularly polarizing film obtained by bonding a retardation film obtained by extending a cellulose ester-based film to a polarizing element is caused by the bonding of the retardation film and the polarizing element during external impact or secondary processing. The problem of peeling near the surface.

An object of the present invention is to provide a circularly polarizing film having a polarizing element, a retardation film disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. It has excellent processability and can suppress curl.

Another object of the present invention is to provide a circularly polarizing film using the above-mentioned circularly polarizing film with an adhesive layer, and further provide an image display device using the above-mentioned circularly polarizing film or a circularly polarizing film with an adhesive layer. [Technical means to solve the problem]

The inventors of the present invention and others worked hard and found that the above-mentioned problems can be solved by the following circular polarizing film and the like, thereby completing the present invention.

That is, the present invention relates to a circularly polarizing film, which is characterized by comprising a polarizing element, a retardation film disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. It has the function of converting linear polarized light into circular polarized light or elliptical polarized light. The thickness is less than 35 μm, and the two sides of the retardation film have different initial damage loads in the scratch test. When it is set to the first surface and the lower side is set to the second surface, the polarizing element is bonded to the first surface of the retardation film.

In the above-mentioned circularly polarizing film, it is preferable that the initial load of the first surface of the retardation film is 55 mN or more.

In the circular polarizing film, a surface functional layer may be provided on the second surface of the retardation film.

In the circular polarizing film, it is preferable that an angle formed by the absorption axis of the polarizing element and the retardation axis of the retardation film is 35 ° to 55 °. In the case where the circularly polarizing film is elongated, it is preferable that the angle formed by the late phase axis and the longitudinal direction of the retardation film is 35 ° to 55 °.

In the above-mentioned circularly polarizing film, it is preferable that the retardation film is an extension of a resin film formed on a casting body by a solution casting method, and the side of the casting body side of the resin film is the above First side.

In the circularly polarizing film, a cellulose ester film can be used as the retardation film.

In the circular polarizing film, the polarizing element, the retardation film, and the protective layer may be bonded together via an adhesive layer.

In addition, the present invention relates to a circular polarizing film with an adhesive layer, which is characterized by having the above-mentioned circular polarizing film and an adhesive layer.

Furthermore, the present invention relates to an image display device, characterized in that a circular polarizing film or a circular polarizing film with an adhesive layer is provided on the viewing side of the optical unit, and the retardation film is disposed on the viewing side than the polarizing element. . [Effect of the invention]

Polycarbonate film or olefin polymer film is generally formed by a melt extrusion method, and there is no difference in physical properties on both sides of the film obtained by the film formation method. On the other hand, a cellulose-ester-based film is generally formed by a film-forming method using a solution casting method. In the solution casting method, a resin solution (sticky substance) is poured into and adhered to a smooth surface drum (casting drum) or a stainless steel smooth belt, and the solvent is evaporated by a step of heating the film to make the film forming. In this solution casting method, the solvent is rapidly removed on the side (air side) that is not in contact with the belt or the drum surface. Therefore, especially in the case of forming a thin film, the air side and the contact belt or drum The side of the face is easier to harden (those with fur-like edges on the surface). As a result, it was found that the physical properties of both sides of the film obtained by the solution casting method were different. Moreover, when the film obtained by the solution casting method is bonded to another film, it can also be seen that the said air side is bonded for the point.

The retardation film for a circularly polarizing film can be obtained by performing an oblique stretching process so that the angle formed by the width direction and the in-plane retardation axis is within a specific range. Therefore, it can be seen that when a film with two different physical properties on both sides is stretched at a high magnification as described above, the mechanical characteristics of the air side of the obtained retardation film are weak compared with the opposite side. Especially in the case of a thin film, the mechanical properties on the air side are weak. As a result, it is estimated that when a thin retardation film is bonded to a polarizing element, peeling occurs during impact or during secondary processing.

According to the above findings, in the case of the circularly polarizing film of the present invention, when the retardation film (having a function of converting linearly polarized light to circularly polarized light or elliptical polarized light) having different physical properties is disposed on both sides of the polarizing element, the retardation film is used The side with stronger mechanical properties, that is, the side with the initial damage load in the scratch test as an index, and the side with the higher initial damage load is attached to the polarizing element. The thickness of the film is not good in terms of impact resistance or reproducibility. However, in the present invention, by adopting such a structure, a circularly polarizing film can be provided, which is also used to reduce the thickness to 35 μm or less. In the case of a thin retardation film, it is not easy to cause cohesion and destruction near the bonding surface of the retardation film and the polarizing element during impact or secondary processing, and it is excellent in impact resistance and repeatability. In the present invention, curl can be suppressed by using a thickness of 35 μm or less as the retardation film.

(Definition of terms and symbols) Definitions of terms and symbols in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the refractive index in the plane becomes the largest (that is, the direction of the late phase axis), and "ny" is in the plane that is orthogonal to the late phase axis The refractive index in the direction (that is, the direction of the advancing axis), "nz" is the refractive index in the thickness direction. (2) In-plane retardation (Re) "Re (λ)" is the in-plane retardation of a film measured at 23 ° C using light having a wavelength of λ nm. For example, "Re (450)" is the in-plane retardation of a film measured at 23 ° C using light with a wavelength of 450 nm. Re (λ) is determined by using the formula: Re = (nx-ny) × d when the thickness of the film is d (nm). (3) Phase difference (Rth) in the thickness direction "Rth (λ)" is a phase difference in the thickness direction of the film measured at 23 ° C with light having a wavelength of 550 nm. For example, "Rth (450)" is the phase difference in the thickness direction of the film measured at 23 ° C using light with a wavelength of 450 nm. When Rth (λ) is a film thickness of d (nm), Rth (λ) is obtained by the formula: Rth = (nx-nz) × d. (4) Nz coefficient The Nz coefficient is obtained from Nz = Rth / Re. (5) Substantially orthogonal or parallel expressions of "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by the two directions is 90 ° ± 10 °, preferably 90 ° ± 7 °, and further It is preferably 90 ° ± 5 °. The expressions "substantially parallel" and "substantially parallel" include the case where the angle formed by the two directions is 0 ° ± 10 °, preferably 0 ° ± 7 °, and further preferably 0 ° ± 5 °. Furthermore, in this specification, when it is only referred to as "orthogonal" or "parallel", it may include a state of being substantially orthogonal or substantially parallel. (6) Angle When referring to angles in this specification, unless otherwise specified, the angle includes the angles in two directions, clockwise and counterclockwise. (7) Long strip The "long strip" means an elongated shape having a length sufficiently longer than the width, and includes, for example, an elongated shape having a length that is 10 times or more, preferably 20 times or more, relative to the width.

<Overall Structure of Polarizing Film> FIG. 1 is a schematic cross-sectional view showing an example of a structural cross section of a circular polarizing film of the present invention. The circularly polarizing film F in FIG. 1 includes a polarizing element 1, a retardation film 2 disposed on one side of the polarizing element 1, and a protective layer 3 disposed on the other side of the polarizing element 1. The retardation film 2 has a function of converting linearly polarized light into circularly polarized light or elliptically polarized light. Therefore, the circularly polarizing film of the present invention means a circularly polarizing film or a circularly polarizing film. The circularly polarizing film F is typically arranged on the viewing side of the image display device. In this case, it arrange | positions so that the retardation film 2 may become a viewing side. With the configuration described above, even when the display screen is viewed through a polarizing lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, the circularly polarizing film F can also be suitably used for an image display device that can be used outdoors.

The retardation film 2 uses a different initial damage load in a scratch test on both sides. In the retardation film 2 described above, the side having a higher breaking initiation load is referred to as a first surface 2a, and the lower side is referred to as a second surface 2b. As shown in FIG. 1, the polarizing element 1 is bonded to the side of the first surface 2 a of the retardation film 2.

The circularly polarizing film F may further include a surface functional layer 4 on the second surface 2b (opposite to the polarizing element 1) of the retardation film 2 as necessary. Furthermore, the circularly polarizing film F may be provided with another retardation film (not shown). The number, arrangement position, optical characteristics (such as refractive index ellipsoid, in-plane phase difference, thickness direction phase difference, wavelength dispersion characteristic), and mechanical characteristics of another retardation film can be appropriately set according to the purpose.

The polarizing element 1 and the retardation film 2 are laminated so that the absorption axis of the polarizing element 1 and the retardation axis of the retardation film 2 become a specific angle. The angle formed by the absorption axis of the polarizing element 1 and the late phase axis of the retardation film 2 is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, and even more preferably 40 ° to 50 °, and particularly preferably 42 ° ~ 48 °, especially around 45 °. By disposing the retardation film 2 on the viewing side with respect to the polarizing element 1 with such an axial relationship, even when the display screen is viewed through a polarizing lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, the polarizing film according to the embodiment of the present invention can be suitably used for an image display device that can be used outdoors.

The circularly polarizing film F may be a single sheet or a long sheet (for example, a roll). In the case where the circularly polarizing film F is elongated, the absorption axis direction of the elongated polarizing element may be the length direction or the width direction. The absorption axis direction of the polarizing element is preferably a length direction. This is because the polarizing element is easy to manufacture, and as a result, the circular polarizing film has excellent manufacturing efficiency. In the case where the circularly polarizing film is long, the angle θ formed by the retardation film 2 and the length direction of the retardation film 2 is preferably 35 ° to 55 °, more preferably 38 ° to 52 °, and even more preferably 40 ° ~ 50 °, especially preferred is 42 ° ~ 48 °, particularly preferred is around 45 °. As described below, by forming the retardation film constituting the retardation film by obliquely extending, a long retardation film (retardation film) having a retardation axis in the oblique direction can be formed. As a result, a long Strip-shaped circular polarizing film. Such a long circular polarizing film can be produced by roll-to-roll, and therefore it is very excellent in productivity.

The overall thickness of the circular polarizing film is typically 40 μm to 300 μm, preferably 40 μm to 160 μm, more preferably 50 μm to 140 μm, and still more preferably 60 μm to 120 μm. According to the embodiment of the present invention, a circularly polarizing film having a very thin thickness as described above but excellent curl suppression can be obtained. The overall thickness of the circular polarizing film refers to the total thickness of the surface functional layer and the adhesive layer for laminating the polarizing element, the retardation film, and the protective layer.

Hereinafter, each layer constituting the circularly polarizing film according to the embodiment of the present invention will be described.

<Polarizing Element> As the polarizing element 1, any appropriate polarizing element can be used. For example, the resin film forming the polarizing element may be a single-layer resin film or a laminated body of two or more layers.

Specific examples of the polarizing element composed of a single-layer resin film include a polyvinyl alcohol (PVA, Polyvinyl Alcohol) -based resin film, a partially formalized PVA-based resin film, and an ethylene-vinyl acetate copolymer-based portion. Saponified membrane and other hydrophilic polymer membranes are obtained by dyeing and extending treatment of dichroic substances such as iodine or dichroic dyes; polyene-based alignments such as dehydrated products of PVA or dehydrochlorinated products of polyvinyl chloride Film, etc. In terms of excellent optical characteristics, it is preferred to use a polarizing element obtained by dyeing a PVA-based resin film with iodine and uniaxially stretching it.

The above dyeing with iodine is performed, for example, by immersing a PVA-based resin film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after the dyeing treatment, or it can be performed while dyeing. It is also possible to perform dyeing after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, and the like. For example, by immersing the PVA-based resin film in water and washing with water before dyeing, not only the dirt or anti-blocking agent on the surface of the PVA-based resin film can be cleaned, but also the PVA-based resin film can be swelled to prevent uneven dyeing.

Specific examples of the polarizing element obtained by using the laminated body include a laminated body using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and coated on A polarizing element obtained from a laminate of a PVA-based resin layer formed from this resin substrate. A polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying it. A PVA-based resin layer is formed on a resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is extended and dyed to form a PVA-based resin layer as a polarizing element. In this embodiment, extending | stretching typically includes immersing a laminated body in a boric-acid aqueous solution, and extending. Further, if necessary, the stretching may further include: performing air stretching at a high temperature (for example, 95 ° C. or higher) of the laminate before stretching in a boric acid aqueous solution. The obtained resin substrate / polarizing element laminated body can be directly used (that is, the resin substrate can also be used as a protective layer of the polarizing element), and the resin substrate can also be peeled from the resin substrate / polarizing element laminated body, An appropriate protective layer is formed on the peeling area according to the purpose. The details of the method of manufacturing such a polarizing element are described in, for example, Japanese Patent Laid-Open No. 2012-73580. This publication is incorporated by reference in its entirety into this specification.

The thickness of the polarizing element is preferably 15 μm or less, more preferably 13 μm or less, even more preferably 10 μm, and even more preferably 8 μm or less. The lower limit of the thickness of the polarizing element is 2 μm in one embodiment and 3 μm in another embodiment. According to the embodiment of the present invention, although the thickness of the polarizing element is extremely thin as described above, it is also possible to satisfactorily suppress curl when heating the polarizing film.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing element is preferably 42.0% to 45.5%, and more preferably 42.5% to 45.0%. According to the present invention, it is possible to realize a polarizing film that is very thin and suppresses curl, and further, such a polarizing film can achieve excellent monomer transmittance as described above.

As described above, the polarization degree of the polarizing element is 98% or more, preferably 98.5% or more, and further preferably 99% or more. According to the present invention, a very thin polarizing film with suppressed curl can be realized, and further, such a polarizing film can achieve excellent polarization as described above.

<Phase retardation film> As described above, the retardation film 2 has a function of converting linearly polarized light into circularly polarized light or elliptical polarized light. That is, typically, the refractive index characteristics of the retardation film 2 show a relationship of nx> ny. The in-plane retardation Re (550) of the retardation film is preferably 80 nm ~ 160 nm, and more preferably 90 nm ~ 120 nm. If the in-plane retardation is within this range, a retardation film having suitable elliptical polarization performance can be obtained with excellent productivity and proper cost. As a result, it is possible to obtain a polarizing film that can ensure good visibility even when the display screen is viewed through a polarizing lens such as polarized sunglasses with excellent productivity and proper cost.

The retardation film 2 only needs to have a relationship of nx> ny, and can display any suitable refractive index ellipsoid. It is preferable that the refractive index ellipsoid of the retardation film shows a relationship of nx> ny ≧ nz. The Nz coefficient of the retardation film is preferably 1 to 2, more preferably 1 to 1.5, and even more preferably 1 to 1.3.

The retardation film 2 includes any appropriate retardation film that can satisfy the optical characteristics as described above. In addition, the retardation film 2 may be different from the initial load of failure in the scratch test on both sides. As described above, in the retardation film 2, the side with a higher breaking initiation load is set as the first surface 2 a, and the lower side is set as the second surface 2 b. The first breaking surface load 2a is preferably 55 mN or more. When the above-mentioned failure initial load satisfies 55 mN or more, it is not easy to cause cohesive failure near the surface of the first surface 2a, and meets the impact resistance or repetitive processability of the circular polarizing film obtained by attaching the polarizing element. It ’s better. The first breaking surface load 2a is more preferably 58 mN or more, more preferably 60 mN or more, and even more preferably 70 mN or more.

As a resin for forming a retardation film, a cellulose ester resin (henceforth a cellulose ester) is mentioned typically.

Specific examples of the cellulose ester include (di and tri) cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, Cellulose phthalate. Preferred are cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. The cellulose ester may be used alone or in combination.

Cellulose ester is a part of free hydroxyl groups at positions 2, 3, and 6 in the glucose unit of cellulose using β-1,4-glycosidic bonds through fluorenyl groups such as ethenyl and propionyl. Or all esterified polymers. Here, the "degree of substitution with a fluorenyl group" refers to the total of the ratio of hydroxyl esterification to the 2-, 3-, and 6-positions of glucose in repeating units. Specifically, when the hydroxyl groups at the 2nd, 3rd, and 6th positions of cellulose were 100% esterified, the degree of substitution was 1 respectively. Therefore, in the case where the 2nd, 3rd, and 6th positions of cellulose are all 100% esterified, the degree of substitution becomes the third highest. The "average fluorenyl substitution degree" refers to a fluorenyl substitution degree in which the fluorenyl substitution degree of a plurality of glucose units constituting the cellulose ester resin is represented by the average value of each unit. The degree of fluorenyl substitution can be measured in accordance with ASTM-D817-96.

Examples of the fluorenyl group include an ethyl fluorenyl group, a propyl fluorenyl group, a butyl fluorenyl group, a heptyl fluorenyl group, a hexamethylene group, an octyl fluorenyl group, a decyl fluorenyl group, a dodecyl fluorenyl group, a tridecyl fluorenyl group, a tetradecyl fluorenyl group, Hexadecanyl, octadecyl, isobutylfluorenyl, tertiary butylfluorenyl, cyclohexanecarbonyl, oleyl, benzamidine, naphthylcarbonyl, cinnamyl.

In one embodiment, when the degree of substitution of ethyl acetate of the cellulose ester resin is X and the degree of substitution of propionyl is Y, X and Y preferably satisfy the following formulae (1) and (2) . Formula (1): 2.0 ≦ (X + Y) ≦ 2.8 Formula (2): 0 ≦ Y ≦ 1.0 More preferably, the cellulose ester resin satisfying the above formula (1) and formula (2) contains a formula (1a) ) And a cellulose ester resin with the above formula (2), and a cellulose ester resin satisfying the following formula (1b). Formula (1a): 2.0 ≦ (X + Y) <2.5 Formula (1b): 2.5 ≦ (X + Y) ≦ 2.8 Further, “degree of substitution of ethylamyl” and “degree of substitution of propanyl” are the above-mentioned fluorenyl groups A more specific indicator of the degree of substitution is the so-called "degree of substitution of ethyl", which refers to the total of the ratios of the 2, 3, and 6 positions of the repeating unit of glucose and the esterification of the hydroxyl group with ethyl. The "degree of substitution" refers to the total of the ratios of the hydroxyl groups to ethyl esters at the 2-, 3-, and 6-positions of the repeating units of glucose.

The molecular weight distribution (weight average molecular weight Mw / number average molecular weight mN) of the cellulose ester resin is preferably 1.5 to 5.5, more preferably 2.0 to 5.0, even more preferably 2.5 to 5.0, and even more preferably 3.0 to 5.0.

As the cellulose used as a raw material of the cellulose ester resin, any suitable cellulose can be used. Specific examples include cotton wool, wood pulp, and kenaf. A cellulose ester resin obtained from different raw materials can also be used in combination.

The cellulose ester resin can be produced by any suitable method. As a representative example, a method including the following procedures can be mentioned: a raw material cellulose, a specific organic acid (for example, acetic acid, propionic acid), an acid anhydride (for example, acetic anhydride, propionic anhydride), and a catalyst (for example, sulfuric acid) are mixed and mixed The cellulose is esterified and reacted until a cellulose triester is obtained. In cellulose triesters, the three hydroxyl groups of the glucose unit are replaced by amidino acids of organic acids. When two organic acids are used at the same time, a mixed ester type cellulose ester (for example, cellulose acetate propionate, cellulose acetate butyrate) can be produced. Then, the cellulose triester is hydrolyzed to synthesize a cellulose ester having a desired degree of substitution of a fluorenyl group. Thereafter, the cellulose ester resin can be obtained through steps such as filtration, precipitation, water washing, dehydration, and drying.

The retardation film 2 (retardation film) is typically produced by extending a resin film formed of a resin as described above in at least one direction.

As a method for forming the resin film, any appropriate method can be adopted. Examples include melt extrusion (for example, T-die forming), casting coating (for example, casting), calendering, hot pressing, coextrusion, cofusion, multilayer extrusion, and inflation. Forming method, etc. The T-die forming method, the casting method, and the inflation forming method are preferably used.

As the resin film used for the retardation film (different initiation load in the two-sided scratch test) used in the present invention, one obtained by a solution casting method can be used favorably. In the solution casting method, a resin solution (sticky substance) is poured into and adhered to a cast body (casting drum or stainless steel smooth belt) having a smooth surface, and the solvent is evaporated by a step of heating the casted body to thereby make Film forming. In this solution casting method, the solvent is rapidly removed on the side (air side) not in contact with the cast body, so that the air side is smaller than the cast body side with respect to the initial load of failure of the obtained resin film. In the retardation film obtained by extending the resin film obtained by the solution casting method, the surface on the cast body side of the resin film becomes the first surface.

The thickness of the thickness of the resin film (unstretched film) can be set to any appropriate value according to the required optical characteristics, the following stretching conditions, and the like. It is preferably 50 μm to 250 μm, and more preferably 80 μm to 200 μm.

Any suitable stretching method and stretching conditions (such as stretching temperature, stretching ratio, and stretching direction) can be adopted for the stretching. Specifically, various extension methods such as free-end extension, fixed-end extension / free-end contraction, and fixed-end contraction can be used alone, or they can be used simultaneously or sequentially. The extending direction can be performed in various directions or dimensions such as a horizontal direction, a vertical direction, a thickness direction, and a diagonal direction. The stretching temperature is preferably in the range of glass transition temperature (Tg) ± 20 ° C of the resin film.

A retardation film (the result is a retardation film) having the above-mentioned required optical characteristics (for example, refractive index ellipsoid, in-plane retardation, Nz coefficient) can be obtained by appropriately selecting the above-mentioned extension method and extension conditions.

In one embodiment, the retardation film 2 is produced by uniaxially stretching a resin film or uniaxially stretching a fixed end. As a specific example of uniaxial stretching, a method of extending the resin film in the longitudinal direction (longitudinal direction) while moving the resin film in the longitudinal direction can be mentioned. As another specific example of uniaxial stretching, a method of stretching in the lateral direction using a tenter can be cited. The stretching ratio is preferably 10% to 500%.

In another embodiment, the retardation film 2 is produced by continuously extending an oblong resin film obliquely in a direction at an angle θ with respect to the longitudinal direction. By using oblique extension, a strip-shaped stretched film having an alignment angle of angle θ with respect to the length direction of the film can be obtained. For example, roll-to-roll can be realized when laminated with a polarizing element, and the manufacturing steps can be simplified. The angle θ is as described above.

As the stretcher used for oblique stretching, for example, a tenter type stretcher that can apply a feed force, a tensile force, or a traction force at different speeds in the horizontal and / or vertical directions can be mentioned. Tenter-type stretching machines include horizontal uniaxial stretching machines and simultaneous biaxial stretching machines, but any suitable stretching machine can be used as long as the long resin film can be continuously stretched diagonally.

Examples of the method of oblique extension include: Japanese Patent Laid-Open No. Sho 50-83482, Japanese Patent Laid-Open No. 2-113920, Japanese Patent Laid-Open No. 3-182701, and Japanese Patent Laid-Open No. 2000-9912. The methods described in Gazette, Japanese Patent Laid-Open No. 2002-86554, Japanese Patent Laid-Open No. 2002-22944, and the like.

The thickness of the retardation film (for example, the above-mentioned stretched film) is 35 μm or less. When the thickness is increased, the shrinkage and swelling tends to increase. When the thickness exceeds 40 μm, the amount of warpage (curl) of the panel under heating and humidity reliability increases. The thickness is preferably 38 μm or less, and more preferably 35 μm or less. On the other hand, if the thickness is reduced, the load on the surface (first surface) with a large initial breaking load is reduced and the peeling force is reduced. Therefore, the thickness is preferably 15 μm or more, and more preferably 20 μm. the above.

As the retardation film constituting the retardation film 2, as long as it satisfies the necessary conditions of the present invention, a commercially available film may be used directly, or a commercially available film may be subjected to secondary processing (for example, extension treatment, surface Processing).

The surface of the polarizing element 1 side of the retardation film 2 may be surface-treated. Examples of the surface treatment include a corona treatment, a plasma treatment, a flame treatment, a primer coating treatment, and a saponification treatment. Examples of the corona treatment include a method of performing a discharge in a normal pressure air by a corona processor. Examples of the plasma treatment include a method in which a plasma discharger performs discharge in normal pressure air. Examples of the flame treatment include a method in which a flame directly contacts the film surface. Examples of the primer coating treatment include a method of diluting an isocyanate compound, a silane coupling agent, and the like with a solvent, and applying the thin solution thinly. Examples of the saponification treatment include immersion in an aqueous sodium hydroxide solution. Corona treatment and plasma treatment are preferred.

<Protective layer> The protective layer 3 may be formed of any appropriate film that can be used as a protective layer of a polarizing element. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), and polyesters such as polyethylene terephthalate and polyethylene naphthalate. System, polyvinyl alcohol system, polycarbonate system, nylon or aromatic polyamide, polyamidine, polyimide, polyether, polyfluorene, polystyrene, poly drop &# 158665 Transparent resins such as polyolefins, ring systems, or cyclic olefins, (meth) acrylic, and acetate based resins, such as olefins and ethylene-propylene copolymers. In addition, thermosetting resins such as (meth) acrylic, urethane, urethane, (meth) acrylic, epoxy, and polysiloxane, or ultraviolet curable can also be mentioned. Resin, etc. Further, for example, a glassy polymer such as a siloxane polymer may be mentioned.

As the (meth) acrylic resin, Tg (glass transition temperature) is preferably 115 ° C or higher, more preferably 120 ° C or higher, even more preferably 125 ° C or higher, and even more preferably 130 ° C or higher. The reason is that the durability can be made excellent. The upper limit of the Tg of the (meth) acrylic resin is not particularly limited, but it is preferably 170 ° C. or lower in terms of moldability and the like.

As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be used as long as the effect of the present invention is not impaired. Examples include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic copolymer, methyl methacrylate- (meth) acrylate copolymer, and methyl Methyl acrylate-acrylate- (meth) acrylic acid copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymers having alicyclic hydrocarbon groups (e.g. methyl methacrylate-methyl Cyclohexyl acrylate copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, etc.). Preferably, a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylate is used. More preferred examples include methyl methacrylate resins containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

Specific examples of the (meth) acrylic resin include, for example, ACRYPET VH or ACRYPET VRL20A manufactured by MITSUBISHI RAYON, and (Methyl) having a ring structure in the molecule described in Japanese Patent Laid-Open No. 2004-70296. Acrylic resin, high Tg (meth) acrylic resin obtained by intramolecular crosslinking or intramolecular cyclization reaction.

As the (meth) acrylic resin, the (meth) acrylic resin having a lactone ring structure is particularly preferable in terms of high heat resistance, high transparency, and high mechanical strength. .

Examples of the (meth) acrylic resin having a lactone ring structure include Japanese Patent Laid-Open No. 2000-230016, Japanese Patent Laid-Open No. 2001-151814, Japanese Patent Laid-Open No. 2002-120326, and Japan The (meth) acrylic resin having a lactone ring structure described in Japanese Patent Application Laid-Open No. 2002-254544 and Japanese Patent Laid-Open No. 2005-146084.

The mass average molecular weight (sometimes referred to as the weight average molecular weight) of the (meth) acrylic resin having a lactone ring structure is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and even more preferably 10,000 to 500,000. Particularly preferred is 50,000 to 500,000.

The Tg (glass transition temperature) of the (meth) acrylic resin having a lactone ring structure is preferably 115 ° C or higher, more preferably 125 ° C or higher, even more preferably 130 ° C or higher, particularly preferably 135 ° C. It is preferably above 140 ° C. The reason is that the durability can be made excellent. The upper limit value of Tg of the (meth) acrylic resin having a lactone ring structure is not particularly limited, but it is preferably 170 ° C. or lower in terms of moldability and the like.

In addition, in this specification, "(meth) acrylic type" means an acrylic type and / or a methacrylic type.

The protective layer 3 is preferably optically isotropic. In this specification, "optical isotropy" means that the in-plane phase difference Re (550) is 0 nm to 10 nm, and the phase difference Rth (550) in the thickness direction is -10 nm to +10 nm.

The thickness of the protective layer is preferably 5 μm to 60 μm, and more preferably 10 μm to 40 μm.

<Surface functional layer> A surface functional layer 4 may be provided on the second surface of the retardation film 2 described above. Examples of the surface functional layer include a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, and an anti-glare layer. In addition, the functional layers such as the hard coating layer, the anti-reflection layer, the anti-adhesion layer, the diffusion layer, or the anti-glare layer may be provided in addition to the retardation film itself, and may also be provided as separate entities different from the retardation film. .

As the surface functional layer, for example, a hard coat layer can be favorably applied. The hard coat layer has the function of imparting chemical resistance, scratch resistance and surface smoothness to the circular polarizing film, and improving the dimensional stability under high temperature and high humidity. As the hard coat layer, any suitable structure can be adopted. The hard coat layer is, for example, a hardened layer of any suitable ultraviolet hardening resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amido resins, and epoxy resins. The glass transition temperature of the resin constituting the hard coat layer is preferably 120 ° C to 300 ° C, and more preferably 130 ° C to 250 ° C. Within this range, a polarizing film having excellent dimensional stability at high temperatures can be obtained. The hard coat layer may also include any suitable additives as needed. Examples of the additive include inorganic fine particles and / or organic fine particles.

The details of the hard coat layer are described in, for example, Japanese Patent Laid-Open No. 2007-171943, and the description is incorporated herein by reference.

The thickness of the surface functional layer 4 is preferably 10 μm or less, more preferably 1 μm to 8 μm, and still more preferably 2 μm to 7 μm.

<Adhesive Layer> Any appropriate adhesive layer (not shown) is used for bonding the respective layers constituting the circular polarizing film according to the embodiment of the present invention. The adhesive layer may be an adhesive layer or an adhesive layer. The adhesive layer is formed of an adhesive. The type of the adhesive is not particularly limited, and various types can be used. The above-mentioned adhesive layer is not particularly limited as long as it is optically transparent. As the adhesive, various forms such as water-based, solvent-based, hot-melt, and active energy ray hardening types may be used. An aqueous adhesive or active energy ray is preferred. Hardening type adhesive.

Typically, the polarizing element 1 is bonded to the retardation film 2 and the protective layer 3 with an aqueous adhesive. As the water-based adhesive, any suitable water-based adhesive can be used. It is preferable to use a water-based adhesive containing a PVA-based resin. In terms of adhesiveness, the average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably about 100 to 5,500, and more preferably 1,000 to 4500. In terms of adhesion, the average saponification degree is preferably about 85 mol% to 100 mol%, and more preferably 90 mol% to 100 mol%.

The PVA-based resin contained in the water-based adhesive preferably contains an ethylamidine group. This is because the polarizer and the retardation film and the protective layer can have excellent adhesion and excellent durability. The acetamidine-containing PVA-based resin can be obtained, for example, by reacting a PVA-based resin with diketene by any method. The degree of modification of acetamidine in a PVA-based resin containing acetamidine is typically 0.1 mol% or more, preferably 0.1 mol% to 40 mol%, and more preferably 1 mol. Ear% ~ 20 mole%, especially preferably 1 mole% ~ 7 mole%. It should be noted that the degree of modification of acetamidine is a value measured by NMR (Nuclear Magnetic Resonance, nuclear magnetic resonance).

The solid content concentration of the water-based adhesive is preferably 6% by weight or less, more preferably 0.1% to 6% by weight, and still more preferably 0.5% to 6% by weight. If the solid component concentration is within this range, there is an advantage that the size control ratio of the polarizing plate can be easily controlled. If the solid component concentration is too low, the moisture content of the obtained polarizing film increases, and the dimensional change may increase depending on the drying conditions. If the concentration of the solid component is too high, the viscosity of the adhesive is increased, and the productivity of the polarizing film may be insufficient.

The thickness of the adhesive layer is preferably 0.01 μm to 7 μm, more preferably 0.05 μm to 5 μm, still more preferably 0.05 μm to 2 μm, and even more preferably 0.1 μm to 1 μm. If the thickness of the adhesive layer is too thin, the cohesive force of the adhesive itself may not be obtained, and the adhesive strength may not be obtained. If the thickness of the adhesive layer is too thick, the circular polarizing film may not satisfy the durability.

An adhesive layer (not shown) may be provided on one or both sides of the circular polarizing film F. For example, it can be easily bonded to other optical components (such as a liquid crystal cell or an organic EL (Electroluminescence) panel) by providing an adhesive layer in advance on the protective layer 3 side of the circular polarizing film F. Moreover, it is preferable to stick a release film on the surface of this adhesive layer until it is used before use. On the other hand, the adhesive layer on the visual recognition side (the retardation film 2 side) can be used, for example, in input devices such as a touch panel and the like in a visual recognition application of an image display device, or in a transparent substrate such as cover glass or a plastic cover.

<Manufacturing method of circularly polarizing film> With respect to an example of the manufacturing method of the circularly polarizing film according to the embodiment of the present invention, only the characteristic portions will be briefly described. The manufacturing method includes: fabricating a laminated body having a polarizing element 1, a retardation film 2 disposed on one side of the polarizing element 1, and a protective layer 3 disposed on the other side of the polarizing element 1. Heating is performed at a temperature of 85 ° C or higher (hereinafter, sometimes referred to as high-temperature heating). The heating temperature for high-temperature heating is preferably 86 ° C or higher. The upper limit of the heating temperature for high-temperature heating is, for example, 100 ° C. The heating time for high temperature heating is preferably 3 minutes to 10 minutes, and more preferably 3 minutes to 6 minutes. It is also possible to heat the laminate at a temperature below 85 ° C (low temperature heating) before and / or after high temperature heating. The heating temperature and heating time for the low-temperature heating can be appropriately set according to the purpose and the required characteristics of the obtained polarizing film. High-temperature heating and / or low-temperature heating can also be used as a drying treatment for the adhesive when laminating a polarizing element, a retardation film (a retardation film), and a protective layer (a protective film). The method for forming the polarizing element, the retardation film (phase retardation film), and the protective layer (protective film) is as described above, or any appropriate method may be adopted. In addition, any appropriate method may be adopted as the lamination method of the polarizing element, the retardation film (retardation film), and the protective layer (protective film).

<Image display device> The image display device according to the embodiment of the present invention includes a circularly polarizing film on the viewing side of the optical unit. The circularly polarizing film is arranged such that the retardation film is closer to the viewing side than the polarizing element. Typical examples of the image display device including an optical unit include a liquid crystal display device and an organic electroluminescence (EL) display device. Since such an image display device is provided with the above-mentioned polarizing film on the viewing side, even when the display screen is viewed through a polarizing lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, such an image display device can also be used well outdoors. [Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited to these examples. The evaluation items in the examples are as follows.

<Initial Failure Load> As a measuring device for the initial failure load, a nano scratch tester manufactured by CSM Instruments SA was used. The first surface or the second surface of each retardation film (sample) was attached to a slide glass with the other surface (the second surface or the first surface) facing upward, and fixed to the stage of the measurement device. In a measurement environment of 23 ° C and 50% RH, a cantilever ST-150 equipped with a conical diamond indenter (the radius of curvature of the front end is 10 μm) was used. In the continuous load mode of the above-mentioned device, a self-supporting Scratch test with 0 mN increased load (scratch load) to 300 mN with friction in one direction. For the sample subjected to the scratch test described above, the surface of the scratch was observed with an objective lens 20 times using an optical microscope (manufactured by Nikon) provided with the apparatus. In addition, the initial part where the upper and back layers of the scratch are peeled off in the scratch direction by more than 2 μm is set as the damage starting point, and the center of the length (breaking length) of the damage starting point in the scratch direction is set. The corresponding scratch load is set as the breaking initial load. FIG. 2 is an image showing scratches before the initiation of destruction (non-destructive portion), and FIG. 3 is an image showing scratches at the initiation of destruction. As a result of measuring the above-mentioned samples, the surface having the larger initial breaking load was set as the first surface, and the smaller surface was set as the second surface. The results are shown in Table 1.

(Production of polarizing element) While immersing a polyvinyl alcohol film with a polymerization degree of 2400, a saponification degree of 99.9 mol%, and a thickness of 30 μm in warm water at 30 ° C to swell, the length of the polyvinyl alcohol film became the original length. Uniaxial extension was performed in a 2.0x manner. Next, immerse it in a 0.3% by weight aqueous solution (dyeing bath) of a mixture of iodine and potassium iodide (weight ratio of 0.5: 8), and extend uniaxially so that the length of the polyvinyl alcohol film becomes 3.0 times the original length. Stained. After that, it was immersed in an aqueous solution (crosslinking bath 1) of 5% by weight of boric acid and 3% by weight of potassium iodide, and extended so that the length of the polyvinyl alcohol film became 3.7 times the original length, and then boric acid 4 at 60 ° C In an aqueous solution (crosslinking bath 2) with a weight% and 5 weight% potassium iodide, the length of the polyvinyl alcohol film is extended to 6 times the original length. Thereafter, an iodine ion impregnation treatment was performed using a 3% by weight potassium iodide aqueous solution (iodine impregnation bath), and then dried in an oven at 60 ° C. for 4 minutes to obtain a long (roll) polarizer. The thickness of the obtained polarizing element was 12 μm. The absorption axis of the polarizing element is parallel to the longitudinal direction.

(Phase-Difference Film) A film obtained by obliquely extending a long triacetyl cellulose (TAC) film obtained by a solution casting method is used. The thickness of the stretched film (the extension of the TAC film) is 35 μm, 32 μm, 28 μm, 25 μm, 20 μm, 40 μm. A hard coat layer having a thickness of 5 μm is provided on the first surface or the second surface (the surface not bonded to the polarizing element) of each stretched film (an extension of the TAC film). Each stretched film (an extension of the TAC film) is adjusted separately so that the in-plane retardation Re (550) becomes 105 nm, and the angle formed by the late phase axis and the length direction is 45 °.

(Protective layer: Protective film) A long cyclic olefin (COP) film (thickness: 13 μm, trade name: ZF14-013, manufactured by Japan Zeon Corporation) was used.

(Preparation of water-based adhesive) A polyvinyl alcohol-based resin containing an acetamidine group (average degree of polymerization: 1200, saponification degree: 98.5 mole%, acetamidine degree: 5 mole%) It was dissolved in pure water at a temperature of ℃ and adjusted to a solid content concentration of 4% to obtain an aqueous adhesive.

Example 1 (Production of a circularly polarizing film) As a retardation film, a hard coating was provided on the second surface of a 35 μm-thick stretched film (an extension of a TAC film). The water-based adhesive was applied on the first surface of the retardation film so that the thickness of the dried adhesive layer became 80 nm. Similarly, the water-based adhesive was applied to the protective film so that the thickness of the dried adhesive layer became 80 nm. Then, at a temperature of 23 ° C, the phase difference film and the protective film of the above-mentioned adhesive were bonded to both sides of the polarizing element by a roller press, and then dried at 55 ° C for 4 minutes and at 86 ° C for 4 minutes. Minutes to produce a circular polarizing film. The above-mentioned bonding of the polarizing element, the retardation film with an adhesive, and the protective film is performed so that the polarizing element is in contact with the adhesive layer of the protective film. In the obtained circular polarizing film, the direction of the absorption axis of the polarizing element is parallel to the length direction, and the angle formed by the retardation axis of the retardation film and the length direction is 45 °.

Examples 2 to 5, Comparative Examples 1 to 7 In Example 1, the thickness of the stretched film used for the retardation film and the surface of the retardation film attached to the polarizing element were changed as shown in Table 1, except that Other than that, a circularly polarizing film was obtained in the same manner as in Example 1. In addition, the retardation films of the same thickness used in Examples 1 to 5 and Comparative Examples 1 to 5 are the same retardation films, and only the surfaces attached to the polarizing elements are different. In addition, the retardation films of the same thickness used in Comparative Example 6 and Comparative Example 7 are the same retardation films, and only the surfaces bonded to the polarizing elements are different.

The following evaluations of the circular polarizing films obtained in the above examples and comparative examples are shown in Table 1.

<Peeling force measurement method> About the obtained circular polarizing film, the peeling force was measured by the following method. The circularly polarizing film was cut to a size parallel to the extension direction of the polarizing element of 200 mm and an orthogonal direction of 15 mm. A slit was used to cut a cut between the retardation film and the polarizing element, and the phase difference film of the circularly polarizing film was cut. The side is attached to the glass plate. The protective film and the polarizing element were peeled by Tensilon at a peeling speed of 3000 mm / min in a direction of 90 degrees, and the peeling strength (N / 15 mm) was measured. Regarding the peeled surface after peeling, the infrared absorption spectrum was measured by the ATR (Attenuated Total Reflectance) method, and it was confirmed that the retardation film was agglomerated and broken (film broken). The peeling force is preferably 0.8 N / 15 mm or more, more preferably 1 N / 15 mm or more, and even more preferably 1.5 N / 15 mm or more. In Table 1, the case where the peeling force is 0.8 N / 15 mm or more is designated as "", and the case where the peeling force is less than 0.8 N / 15 mm is designated as "×". When the initial load of the phase difference film attached to the surface of the polarizing element is 55 mN or more, the peeling force from the polarizing element can be 0.8 N / 15 mm.

<Length in the Curl Direction> The obtained circular polarizing film was cut to a length of 112 mm × 65 mm (5 inches) so that the direction of the absorption axis of the polarizing element became the long side. With the orientation of the hard coating layer as the upper surface, the cut circular polarizing film was placed on a horizontal plane and the height of the end of the sample curled from the plane was measured. The maximum floating height (maximum floating height) is 3 mm or less, and the maximum floating height exceeds 3 mm is ×.

[Table 1]

1‧‧‧ polarizing element

2‧‧‧ retardation film

2a‧‧‧First side of retardation film

2b‧2nd side of retardation film

3‧‧‧ protective layer

4‧‧‧ surface functional layer

F‧‧‧ circular polarizing film

FIG. 1 is a schematic cross-sectional view showing an example of a structural cross section of a circular polarizing film of the present invention. FIG. 2 is an image showing scratches before the initiation of failure (non-destructive portion) in the measurement of the initiation failure load. FIG. 3 is an image showing a scratch at a failure initiation point in the measurement of the failure initiation load.

Claims (10)

A circular polarizing film, comprising: a polarizing element, a retardation film disposed on one side of the polarizing element, and a protective layer disposed on the other side of the polarizing element. The retardation film has a function of converting linearly polarized light into The function of circular polarized light or elliptically polarized light is 35 μm or less, and the two sides of the retardation film have different initial damage loads in the scratch test. Set the side with the higher initial damage load as the first surface, When the lower side is the second surface, the polarizing element is bonded to the first surface of the retardation film. For example, the circularly polarizing film of claim 1, wherein the first load on the first side of the retardation film is 55mN or more. For example, the circularly polarizing film of claim 1 has a surface functional layer on the second surface of the retardation film. For example, the circular polarizing film of claim 1, wherein the angle formed by the absorption axis of the polarizing element and the retardation axis of the retardation film is 35 ° to 55 °. For example, the circularly polarizing film of claim 1 is elongated, and the angle formed by the retardation axis and the length direction of the retardation film is 35 ° to 55 °. For example, the circularly polarizing film of claim 1, wherein the retardation film is an extension of a resin film formed on a casting body by a solution casting method, and the side of the casting body side of the resin film is the first surface described above. . The circularly polarizing film according to claim 1, wherein the retardation film is a cellulose ester film. The circular polarizing film according to any one of claims 1 to 7, wherein the polarizing element is bonded to the retardation film and the protective layer through an adhesive layer. A circularly polarizing film with an adhesive layer is characterized in that it has a circularly polarizing film according to any one of claims 1 to 8 and an adhesive layer. An image display device characterized in that a circularly polarizing film according to any one of claims 1 to 8 or a circularly polarizing film with an adhesive layer according to claim 9 is provided on the visual side of the optical unit, and the phase difference is as described above. The film is disposed closer to the viewing side than the polarizing element.