JPWO2008056568A1 - Polarizing plate and liquid crystal display device - Google Patents

Abstract

The present invention provides a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, a polarizing plate in which a change in tint when a viewing angle is changed, and a liquid crystal display device using the same. The polarizing plate substantially includes at least a first protective film, a first polarizing film, a second protective film containing a specific cellulose ester as a main component, and a surface of the polarizing film or the second protective film. A retardation film in which the orientation of a vertically aligned rod-like liquid crystal is fixed in this order, is a polarizing plate, each retardation of the second protective film and the retardation layer, the second protective film And the retardation and wavelength dispersion characteristics in a state where the phase difference layer is laminated and within a specific range, and the absolute angle formed by the transmission axis of the polarizing film and the in-plane slow axis of the second protective film The value is in the range of 0 to 1 °.

Description

  The present invention relates to a polarizing plate and a liquid crystal display device, and more particularly to a polarizing plate suitable for a transverse electric field switching mode type liquid crystal display device, a polarizing plate with reduced color change when the viewing angle is changed, and a liquid crystal using the same The present invention relates to a display device.

  The transverse electric field switching mode type liquid crystal display device is excellent in color, contrast, viewing angle and the like in the liquid crystal mode of other liquid crystal display devices, for example, the TN mode, and in the vertical alignment mode (VA, MVA, PVA, etc.). On the other hand, it is excellent in display performance such as viewing angle, and also has excellent effects such as less luminance change due to viewing angle and less drop in response speed in halftone, so-called IPS (In Plane Switching) mode type liquid crystal display device As it came to be actively offered to the market. Examples of the IPS mode type liquid crystal display device include an FFS (fringe field switching) mode and an FLC (ferroelectric liquid crystal) mode in addition to the so-called IPS mode.

  Conventionally, the IPS system has a feature that a liquid crystal cell itself does not need to be compensated, and a wide viewing angle can be obtained without a compensation film (see, for example, Patent Document 1).

  However, when the polarizing plate used in the liquid crystal display device changes the viewing angle in the crossed Nicols state in the direction of 45 ° with respect to the absorption axis, light leakage occurs, thereby reducing the peripheral contrast of the liquid crystal display device. Is happening.

  Therefore, for example, a method has been proposed in which optical films as described in Patent Document 2 and Patent Document 3 are stacked on a polarizing plate to suppress light leakage of the polarizing plate. However, these methods are difficult to make into a polarizing plate by roll-to-roll, and a plurality of films are bonded through an adhesive layer or an adhesive layer. The problem of increasing the film thickness occurs.

Further, as described in Patent Document 4, a method of providing a layer in which a rod-like liquid crystal is vertically aligned and hardened on a support containing a retardation increasing agent, and as disclosed in Patent Document 5, the normal direction of the disk-shaped liquid crystal Has been proposed in which the film is oriented so as to be parallel to the film surface. These have achieved the above-mentioned orientation by providing a special layer for the orientation treatment and further performing a rubbing treatment or the like, and the contrast viewing angle is widened. However, the films produced by these methods have a problem in wavelength dispersion characteristics. As a result, when these films are used in liquid crystal display devices, the color changes when the viewing angle deviates from the front, It turns out that a big problem occurs.
JP 2000-131700 A JP 2006-126770 A Japanese Patent Laying-Open No. 2005-31626 JP 2005-265889 A JP 2005-309379 A

  Accordingly, an object of the present invention is to provide a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, and to provide a polarizing plate with reduced color change when the viewing angle is changed, and a liquid crystal display device using the same. It is in.

  The above object of the present invention is achieved by the following configurations.

1. A polarizing plate in which at least a first protective film, a first polarizing film, and a laminated retardation layer are arranged in this order, and the laminated retardation layer contains a cellulose ester satisfying the following formula 1 as a main component: And a retardation layer in which the orientation of the rod-like liquid crystal substantially perpendicularly aligned with the surface of the polarizing film or the second protective film is fixed, and the second protective film and the second protective film are stacked. Retardation Ro and Rt represented by the following formulas 3 and 4 at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH of the retardation layer,
Second protective film: Ro: 30 to 115 nm
Rt: 100 to 250 nm
Rt / Ro: 1.6 to 4.4
Retardation layer: Ro: 0 to 10 nm
Rt: −100 to −400 nm,
The laminated retardation layer has an in-plane optical axis, and the retardation at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH is Ro: 30 to 105 nm, Rt: −300 to 25 nm, and The chromatic dispersion characteristics defined by Equations 5, 6, 7, and 8 are
D (Ro) 1: 0.9 to 1.0
D (Ro) 2: −9.5 to 0 nm
D (Rt) 1: 0.3 to 0.9
D (Rt) 2: −100 to −10 nm,
A polarizing plate, wherein an absolute value of an angle formed by a transmission axis of the polarizing film and an in-plane slow axis of the second protective film is in a range of 0 to 1 °.

Formula 1: 2.00 ≦ (X + Y) ≦ 2.60
(In the formula, as the substitution degree of the acyl group of the cellulose ester, X represents the substitution degree of acetyl group, and Y represents the substitution degree of propionyl group.)
Formula 3: Ro = (nx−ny) × d
Formula 4: Rt = [(nx + ny) / 2−nz] × d
(In the formula, the refractive index in the slow axis direction in the plane of the second protective film or retardation layer or the laminate of the second protective film and the retardation layer is nx, and in-plane is orthogonal to the slow axis. (The refractive index in the direction to ny is the refractive index in the thickness direction, nz is the refractive index in the thickness direction, and d represents the thickness (nm).)
Formula 5: D (Ro) 1 = Ro (630) / Ro (480)
Formula 6: D (Ro) 2 = Ro (630) -Ro (480)
Formula 7: D (Rt) 1 = | Rt (630) / Rt (480) |
Formula 8: D (Rt) 2 = Rt (480) -Rt (630)
(In the formula, Ro (480) and Ro (630) are retardation Ro values at 480 nm and 630 nm, respectively, in an environment of 23 ° C. and 55% RH, and Rt (480) and Rt (630) are retardation Rt at 480 nm and 630 nm, respectively. Represents the value.)
2. 2. The polarizing plate according to 1 above, wherein the cellulose ester satisfies the following formula 2.

Formula 2: 0.10 ≦ Y ≦ 1.00
3. The first surface of the second protective film faces the polarizing film, and the second surface of the second protective film facing the first surface is arranged to face the retardation layer. The polarizing plate according to 1 above.

  4). 2. The polarizing plate according to 1, wherein the retardation layer is disposed between the second protective film and the polarizing film.

  5. A liquid crystal cell in which liquid crystal molecules are aligned in a direction substantially parallel to the glass substrate during black display, and the alignment directions on both glass substrates are substantially parallel to each other; A protective film 3, a second polarizing film, and a polarizing plate composed of a fourth protective film, the in-plane slow axis of the second protective film of the polarizing plate according to 1, and a liquid crystal The alignment directions of the cells are substantially parallel, the third protective film is Ro: 0 to 5 nm, Rt: −10 to 10 nm, and the thickness of the third protective film is 20 to 45 μm. A liquid crystal display device characterized by the above.

  6). A liquid crystal cell in which liquid crystal molecules are aligned in a direction substantially parallel to the glass substrate during black display, and the alignment directions on both glass substrates are substantially parallel to each other; A protective film 3, a second polarizing film, and a polarizing plate composed of a fourth protective film, the in-plane slow axis of the second protective film of the polarizing plate according to 1, and a liquid crystal The orientation direction of the cells is substantially orthogonal, the third protective film is Ro: 0 to 5 nm, Rt: −10 to 10 nm, and the thickness of the third protective film is 20 to 45 μm. A liquid crystal display device.

  According to the present invention, it is possible to provide a polarizing plate suitable for a horizontal electric field switching mode type liquid crystal display device, in which a color change when a viewing angle is changed is reduced, and a liquid crystal display device using the polarizing plate.

It is a schematic diagram which shows the structure of the polarizing plate which concerns on a claim, and a liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st protective film 2 2nd protective film 3 3rd protective film 4 4th protective film 5 1st polarizing film 6 2nd protective film 7 Phase difference layer 8 Liquid crystal cell 9, 10 Glass substrate a Polarized light Polarization transmission axis of film b Slow axis of second protective film c Orientation direction of liquid crystal cell d Rubbing axis of glass substrate

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  As a result of intensive studies on the above problems, the inventors of the present invention control the wavelength dispersion characteristic of the retardation of the retardation plate, particularly the wavelength dispersion characteristic of the retardation in the film thickness direction, in the lateral electric field switching mode type liquid crystal display device. This has been confirmed to have a great influence on the color change when the viewing angle is changed, and further investigations have led to a means for controlling the color variation at a suitable point of the viewing angle.

The polarizing plate for a lateral electric field switching mode type liquid crystal display device of the present invention includes at least a first protective film, a first polarizing film, and a second protective film mainly composed of cellulose ester satisfying the following formulas 1 and 2. And a retardation layer in which the orientation of the rod-like liquid crystal substantially perpendicularly aligned with the surface of the polarizing film or the second protective film is fixed in this order, and the second protective film Retardations Ro and Rt represented by Formulas 3 and 4 at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH of the film and the retardation layer,
Second protective film: Ro: 30 to 115 nm
Rt: 100 to 250 nm
Rt / Ro: 1.6 to 4.4
Retardation layer: Ro: 0 to 10 nm
Rt: -100 to -400 nm
In the state where the second protective film and the retardation layer are laminated, the retardation at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH is Ro: 30 to 105 nm, Rt: −300 to 25 nm. The laminated films have an optical axis in the same plane, and the wavelength dispersion characteristics defined by the following formulas 5, 6, 7, and 8 are:
D (Ro) 1: 0.9 to 1.0
D (Ro) 2: −9.5 to 0 nm
D (Rt) 1: 0.3 to 0.9
D (Rt) 2: −100 to −10 nm
The absolute value of the angle formed by the transmission axis of the polarizing film and the in-plane slow axis of the second protective film is in the range of 0 to 1 °.

Formula 1: 2.00 ≦ (X + Y) ≦ 2.60
Formula 2: 0.10 ≦ Y ≦ 1.00
(In the formula, as the substitution degree of the acyl group of the cellulose ester, X represents the substitution degree of acetyl group, and Y represents the substitution degree of propionyl group.)
Formula 3: Ro = (nx−ny) × d
Formula 4: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the slow axis direction in the plane of the second protective film or retardation layer or the laminate of the second protective film and the retardation layer is nx, and in-plane is orthogonal to the slow axis. (The refractive index in the direction to ny is the refractive index in the thickness direction, nz is the refractive index in the thickness direction, and d represents the thickness (nm).)
Formula 5: D (Ro) 1 = Ro (630) / Ro (480)
Formula 6: D (Ro) 2 = Ro (630) -Ro (480)
Formula 7: D (Rt) 1 = | Rt (630) / Rt (480) |
Formula 8: D (Rt) 2 = Rt (480) -Rt (630)
(In the formula, Ro (480) and Ro (630) are retardation Ro values at 480 nm and 630 nm, respectively, in an environment of 23 ° C. and 55% RH, and Rt (480) and Rt (630) are retardation Rt at 480 nm and 630 nm, respectively. Represents the value.)
In order to make the second protective film within the above numerical range, the second protective film is preferably stretched in a state where the film is heat-treated. Further, when the cellulose ester is stretched by heat treatment, in order to reduce the residual strain as much as possible, in the range of about 1.1 to 1.5 times in the range of glass transition point ± 10 ° C., the conveying direction 1.1 to 1.7 times in the direction orthogonal to the transport direction, with the residual solvent amount remaining about 2 to 100% by mass in a film stretched in a direction perpendicular to the film or by solution casting. It is preferable to stretch to the extent. In order to make the retardation layer in the above range, it is preferable to control the thickness of the retardation layer, the temperature during UV curing, the tilt angle control, and the control of the pretilt angle at the interface between the support and the air. . In particular, the film thickness control and the curing temperature have a great influence on the phase difference control. In some cases, a vertical alignment film is used for alignment of the liquid crystal. However, in the present invention, since the pretilt angle between the liquid crystal material and the air interface reaches the substrate side, no special alignment film is required.

  In order to set the retardation of the laminated retardation layer obtained by laminating the second protective film and the retardation layer within the above numerical range, the Ro of the second protective film is controlled by the above means, and This can be achieved by controlling the retardation of the second protective film and the retardation layer as viewed from the oblique directions. The phase difference in the oblique direction of the second protective film is preferably controlled by the stretching conditions when producing the second protective film. Reducing the phase difference based on the in-plane fast axis of the second protective film can be achieved by increasing the stretching ratio or decreasing the stretching temperature. The retardation in the oblique direction of the retardation layer is preferably controlled by the thickness of the retardation layer or the temperature during curing. Reducing the phase difference in the oblique direction can be achieved by reducing the film thickness or raising the temperature during curing. Rt can be calculated from the sum of the phase differences in the oblique direction with respect to these fast axes and the in-plane phase difference.

  Further, as means for controlling the wavelength dispersion, it is preferable that D (Ro) 1 and D (Ro) 2 are appropriately selected from the material and manufacturing method of the second protective film. Regarding the material, these values can be achieved by changing the substituent (type / substitution degree) of the cellulose ester material. In the case of only an acetyl group, the value increases as the degree of substitution decreases, and tends to decrease as the propionyl group increases. It also varies depending on the additive. In the case of the retardation increasing agent described in Patent Document 3 and the like, it tends to increase. D (Rt) 1 and D (Rt) 2 can be achieved by controlling the respective retardations of the second protective film and the retardation layer. Specifically, it becomes a small value by relatively increasing the phase difference of the second protective film.

  In the present invention, the absolute value of the angle formed by the transmission axis of the first polarizing film and the in-plane slow axis of the second protective film is in the range of 0 to 1 °. Can be achieved by setting the in-plane slow axis of the second protective film in the direction perpendicular to the transport direction and controlling in-plane unevenness. For this purpose, it is preferable to precisely control the balance between the stretching temperature and the stretching ratio and to independently control the stretched portion (such as a tenter clip) on both sides of the protective film. This can be achieved by adjusting the stretching temperature and the stretching ratio with respect to the clip position and the stress of the clip.

In the liquid crystal display device of the present invention, the polarizing plate of the present invention and the liquid crystal molecules are aligned in a direction substantially parallel to the glass substrate during the black display characteristic of the IPS mode type liquid crystal cell. A liquid crystal cell in which the alignment direction on the substrate side is substantially parallel; and a polarizing plate composed of a third protective film, a second polarizing film, and a fourth protective film. The in-plane slow axis of the second protective film of the polarizing plate according to Item 1 and the alignment direction of the liquid crystal cell are substantially parallel or orthogonal, and the third protective film is Ro: 0 to 5 nm, Rt The lateral electric field switching mode type liquid crystal display device is characterized in that the thickness is −10 to 10 nm and the thickness of the third protective film is 20 to 45 μm.

  That is, the retardation of the second protective film and the retardation layer is controlled within a specific range, and the retardation Ro and Rt of the third protective film are further reduced to reduce the thickness, thereby reducing the field of view of the lateral electric field switching mode type liquid crystal ideographic device. In addition to the effect of widening the corner, the change in color can be greatly suppressed. Conventionally, the change in color during black display has been remarkable, but this has been greatly reduced.

  In order to set the retardation of the third protective film within the above numerical range, if the third protective film is a cellulose ester, it is manufactured by melt film formation or glass transition in the middle by solution film formation. It is preferable to hold at a temperature above the point for 15 seconds or more, or to add an additive having a birefringence developing property opposite to that of the cellulose ester. Moreover, if it is a cycloolefin type film, it is preferable to use the film manufactured by melt | dissolution or solution casting as it is, without performing a extending | stretching process.

  Hereinafter, the present invention will be described in detail for each element.

(Measurement of retardation)
As an example, the retardation measurement according to the present invention can be performed in an environment of 23 ° C. and 55% RH using KOBRA 21ADH manufactured by Oji Scientific Instruments. Moreover, when calculating the retardation in the thickness direction, a value obtained by measuring the refractive index of the corresponding wavelength of each layer using an Abbe refractometer is used. Moreover, in the case of a laminated body, the average value of the refractive index of each layer shall be used.

  In the sample in which the retardation in the thickness direction of the laminate in the present invention is a negative value, when calculating the retardation, the in-plane fast axis of the laminate is set as the tilt axis, and the retardation when tilted by 40 degrees is calculated. It was decided to measure and use for calculation.

(Configuration of polarizing plate and liquid crystal display device)
The configuration of the polarizing plate and the liquid crystal display device of the present invention will be described with reference to the drawings.

  FIG. 1A shows a configuration of a polarizing plate and a liquid crystal display device according to claim 5.

  A viewing-side polarizing plate is constituted by the first protective film 1, the first polarizing film 5, the second protective film 2, and the retardation layer 7 in which the orientation of the rod-like liquid crystal is fixed from the viewing side. It is bonded to the liquid crystal cell 8 sandwiched between the glass substrates 9 and 10. Further, a polarizing plate constituted by the third protective film 3, the second polarizing film 6, and the fourth protective film 4 is disposed on the surface opposite to the liquid crystal cell 8.

  The in-plane slow axis b of the second protective film and the alignment direction c of the liquid crystal cell are parallel. The polarizing transmission axis a of the polarizing film and the rubbing axis d of the glass substrate are in the directions shown in the figure. In the drawing, the retardation layer 7 may be disposed between the first polarizing film 5 and the second protective film 2.

  FIG. 1B shows the configuration of the polarizing plate and the liquid crystal display device according to claim 6.

  A polarizing plate is constituted by the fourth protective film 4, the second polarizing film 6 and the third protective film 3 from the viewing side, and the polarizing plate is bonded to the liquid crystal cell 8 sandwiched between the glass substrates 9 and 10. The Further, on the surface opposite to the liquid crystal cell 8, a phase difference layer 7 in which the orientation of the rod-like liquid crystal is fixed, the second protective film 2, the first polarizing film 5, and the first protective film 1 are formed. A polarizing plate is disposed.

  The in-plane slow axis b of the second protective film and the alignment direction c of the liquid crystal cell are orthogonal. The polarizing transmission axis a of the polarizing film and the rubbing axis d of the glass substrate are in the directions shown in the figure. In the drawing, the retardation layer 7 may be disposed between the first polarizing film 5 and the second protective film 2.

(Retardation layer)
The polarizing plate of the present invention is obtained by applying liquid crystal (or a liquid crystal solution) to a substrate, drying and heat treatment (also referred to as alignment treatment), fixing liquid crystal alignment by ultraviolet curing or thermal polymerization, and the like. It is characterized by having a retardation layer made of vertically aligned rod-like liquid crystals. The retardation layer is formed on the first polarizing film or the second protective film as a base material, and preferably formed on the second protective film.

  The term “vertical alignment” as used herein refers to black when a liquid crystal alignment layer is sandwiched between crossed Nicol polarizers when evaluated using a polarizing microscope in order to evaluate the optical phase difference of the obtained liquid crystal alignment layer. It is defined as a vertically aligned material that transmits light when the liquid crystal alignment layer is tilted between the crossed Nicol polarizers.

  When forming the liquid crystal alignment layer, a so-called vertical alignment film may be used, and the vertical alignment film is not particularly limited. However, when the liquid crystal material itself is vertically aligned at the air interface, the alignment regulating force is the air interface. The alignment film is not particularly necessary when it extends to the interface opposite to that, and it is preferable from the viewpoint of simplifying the configuration. When using a vertical alignment film, it is also preferable to use an alignment film made of a cross-linked product of a block polymer composition containing a (meth) acrylic block polymer described in JP-A-2005-148473.

  The retardation layer according to the present invention is a retardation layer composed of substantially vertically aligned rod-like liquid crystals having retardation Ro in the range of 0 to 10 nm and Rt in the range of −100 to −400 nm. Further, Ro is more preferably in the range of 0 to 5 nm. In order to make the retardation layer in the above range, it is preferable to control the thickness of the retardation layer, the temperature during ultraviolet curing, the tilt angle control, and the control of the pretilt angle at the support / air interface.

  The retardation layer is formed by curing a liquid crystal material capable of forming a liquid crystal phase at a predetermined temperature with a predetermined liquid crystal regularity. The upper limit of the temperature showing the liquid crystal phase is not particularly limited as long as the transparent resin film of the base material is not damaged, for example. Specifically, a temperature of 120 ° C. or lower is preferable from the viewpoint of easy control of process temperature and maintenance of dimensional accuracy, and a liquid crystal material that becomes a liquid crystal phase at a temperature of 100 ° C. or lower is preferably used. On the other hand, the lower limit of the temperature showing the liquid crystal phase can be said to be a temperature at which the liquid crystal material can maintain the alignment state when used as a phase difference plate.

  As the liquid crystal material used as the retardation plate according to the present invention, a polymerizable liquid crystal material is preferably used. The polymerizable liquid crystal material can be used by being polymerized by irradiating with predetermined actinic radiation. Since the alignment state is fixed in the polymerized state, the liquid crystal phase is used when the polymerizable liquid crystal material is used. The lower limit of the temperature is not particularly limited.

  As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and they can also be mixed with each other. Since the polymerizable liquid crystal material can fix the alignment state, the alignment of the liquid crystal can be easily performed at a low temperature, and the alignment state is fixed at the time of use. Can be used regardless of the usage conditions.

  Of the above, a polymerizable liquid crystal monomer is particularly preferably used as the polymerizable liquid crystal material. This is because the polymerizable liquid crystal monomer can be aligned at a lower temperature than the polymerizable liquid crystal oligomer and the polymerizable liquid crystal polymer and has high sensitivity at the time of alignment, so that it can be easily aligned.

  Specific examples of the polymerizable liquid crystal monomer include a rod-like liquid crystal compound (I) represented by the following general formula (1) and a rod-like liquid crystal compound (II) represented by the following general formula (2). be able to. As the rod-like liquid crystalline compound (I), two or more compounds included in the general formula (1) can be mixed and used. Similarly, as the rod-like liquid crystalline compound (II), the general formula (II) A mixture of two or more of the compounds included in 2) can also be used. Moreover, 1 or more types of rod-shaped liquid crystalline compounds (I) and 1 or more types of rod-shaped liquid crystalline compounds (II) can also be mixed and used.

In the general formula (1) representing the rod-like liquid crystal compound (I), R ¹ and R ² each represent a hydrogen atom or a methyl group, but both R ¹ and R ² are hydrogen due to the wide temperature range showing the liquid crystal phase. An atom is preferred. X may be any of a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is a chlorine atom or a methyl group. It is preferable. Further, a and b indicating the chain lengths of the (meth) acryloyloxy groups at both ends of the molecular chain of the rod-like liquid crystalline compound (I) and the alkylene group which is a spacer with the aromatic ring are each independently in the range of 2 to 12 However, it is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. The compound of the general formula (1) in which a = b = 0 is poor in stability, easily subjected to hydrolysis, and the compound itself has high crystallinity. In addition, the compound of the general formula (1) in which a and b are each 13 or more has a low isotropic transition temperature (TI). For this reason, both of these compounds are not preferred because the temperature range showing liquid crystallinity is narrow.

  The rod-like liquid crystal compound (I) can be synthesized by any method. For example, the rod-like liquid crystalline compound (I) in which X is a methyl group can be obtained by an esterification reaction of 1 equivalent of methylhydroquinone and 2 equivalents of 4- (m- (meth) acryloyloxyalkoxy) benzoic acid. it can. In the esterification reaction, the benzoic acid is usually activated with an acid chloride or a sulfonic anhydride, and this is reacted with methylhydroquinone. In addition, a carboxylic acid unit and methylhydroquinone can be reacted directly using a condensing agent such as DCC (dicyclohexylcarbodiimide). As other methods, esterification reaction of 1 equivalent of methylhydroquinone and 2 equivalents of 4- (m-benzyloxyalkoxy) benzoic acid is first performed, and then the resulting ester is debenzylated by hydrogenation reaction or the like. Then, the rod-like liquid crystalline compound (I) can also be synthesized by a method in which the molecular terminal is acryloylated after conversion. When performing esterification reaction of methylhydroquinone and 4- (m-benzyloxyalkoxy) benzoic acid, methylhydroquinone is introduced into diacetate and then reacted with the above benzoic acid in a molten state to obtain an ester directly. It is also possible. The rod-like liquid crystalline compound (I) in the case where X in the general formula (1) is not a methyl group can also be obtained by performing the same reaction as above using hydroquinone having a corresponding substituent instead of methylhydroquinone. it can.

In the general formula (2) representing the rod-like liquid crystal compound (II), R ³ represents a hydrogen atom or a methyl group, but R ³ is preferably hydrogen because of the wide temperature range showing the liquid crystal phase. Speaking of c indicating the chain length of the alkylene group, the rod-like liquid crystal compound (II) having this value of 2 to 12 does not exhibit liquid crystallinity. However, in consideration of compatibility with the rod-like liquid crystal compound (I) having liquid crystallinity, c is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. The rod-like liquid crystalline compound (II) can also be synthesized by an arbitrary method. For example, esterification reaction of 1 equivalent of 4-cyanophenol and 1 equivalent of 4- (n- (meth) acryloyloxyalkoxy) benzoic acid. Thus, the rod-like liquid crystalline compound (II) can be synthesized. As in the case of synthesizing the rod-like liquid crystalline compound (I), this esterification reaction is generally performed by activating the benzoic acid with an acid chloride or sulfonic anhydride, and reacting it with 4-cyanophenol. It is. Moreover, you may make the said benzoic acid and 4-cyanophenol react using condensing agents, such as DCC (dicyclohexyl carbodiimide).

  In addition to the above, in the present invention, a polymerizable liquid crystal oligomer, a polymerizable liquid crystal polymer, or the like can be used. As such a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, those conventionally proposed can be appropriately selected and used.

  In the present invention, a photopolymerization initiator may be used as necessary in addition to the polymerizable liquid crystal material. When polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary. However, in the case of curing by, for example, ultraviolet (UV) irradiation, which is generally used, photopolymerization is usually performed. This is because the initiator is used for promoting the polymerization.

  Photopolymerization initiators include benzyl (also called bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, benzyl methyl ketal, dimethylamino Methylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4 -(Methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2- Droxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2- Examples include methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, or 1-chloro-4-propoxythioxanthone. it can. In general, the addition amount of the photopolymerization initiator is preferably 0.01% to 20%, more preferably 0.1% to 10%, and still more preferably 0.5% to 5%. Can be added to the polymerizable liquid crystal material of the present invention. In addition to the photopolymerization initiator, a sensitizer can be added as long as the object of the present invention is not impaired.

  The film thickness of the liquid crystal layer in the present invention is preferably in the range of 0.1 μm to 20 μm, and more preferably in the range of 0.2 to 10 μm. When the liquid crystal layer according to the present invention is thicker than the above range, an optical anisotropy more than necessary occurs, and when it is thinner than the above range, a predetermined optical anisotropy may not be obtained. Therefore, the film thickness of the liquid crystal layer may be determined according to the required optical anisotropy.

  A polymerizable liquid crystal material is prepared by using a composition for forming a liquid crystal layer by blending a photopolymerization initiator, a sensitizer, etc., if necessary, and coating on a substrate to form a liquid crystal layer forming layer. To do. As a method for forming a liquid crystal layer forming layer, for example, a method of laminating a liquid film layer forming layer on a substrate by previously forming a dry film or the like, or melting a liquid crystal layer forming composition However, in the present invention, the composition for forming a liquid crystal layer is a coating composition in which other components are dissolved by adding a solvent. It is preferable to form the liquid crystal layer forming layer by coating on the alignment film and removing the solvent. This is simple in terms of process as compared with other methods.

  The solvent is not particularly limited as long as it is a solvent capable of dissolving the above-described polymerizable liquid crystal material and the like and does not deteriorate the properties of the transparent resin film. Specifically, benzene Hydrocarbons such as toluene, xylene, n-butylbenzene, diethylbenzene, tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene, diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or 2,4 -Ketones such as pentanedione; ethyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, or γ-butyrolactone Ters; Amide solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, or dimethylacetamide; chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, or orthodichlorobenzene Halogen solvents such as t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve, or butyl cellosolve; phenols, One or more of phenols such as parachlorophenol can be used.

  If only a single kind of solvent is used, the solubility of the polymerizable liquid crystal material or the like is insufficient, and the substrate may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents. Of the above-mentioned solvents, preferred as a single solvent are a hydrocarbon solvent and a glycol monoether acetate solvent, and a preferred mixed solvent is a mixed system of ethers or ketones and glycols. It is. The concentration of the solution depends on the solubility of the polymerizable liquid crystal material or the like and the film thickness of the liquid crystal layer to be produced, but cannot be defined unconditionally, but is usually preferably 1% to 60%, more preferably 3% to It is adjusted within the range of 40%.

  Compounds other than those described above can be added to the composition for forming a liquid crystal layer used in the present invention within a range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amine epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like (meth) Ak Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting le acid, or a photopolymerizable liquid crystal compound, and the like having an acrylic group or methacrylic group. The amount of these compounds added to the composition for forming a liquid crystal layer of the present invention is selected within a range that does not impair the purpose of the present invention, and is generally 40% or less of the composition for forming a liquid crystal layer of the present invention. Preferably, it is 20% or less. Addition of these compounds improves the curability of the liquid crystal material in the present invention, increases the mechanical strength of the resulting liquid crystal layer, and improves its stability.

  In addition, a surfactant or the like can be added to the composition for forming a liquid crystal layer containing a solvent in order to facilitate coating. Examples of surfactants that can be added include cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides and polyamine derivatives; polyoxyethylene-polyoxypropylene condensates, primary or secondary Alcohol ethoxylates, alkylphenol ethoxylates, polyethylene glycol and esters thereof, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonates, alkyl phosphates, aliphatic or aromatic sulfonic acid formalin condensates, etc. Anionic surfactants; amphoteric surfactants such as laurylamidopropylbetaine and laurylaminoacetic acid betaine; nonionics such as polyethylene glycol fatty acid esters and polyoxyethylene alkylamine Surfactant: Perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl trimethyl ammonium salt, perfluoroalkyl group / hydrophilic group-containing oligomer, perfluoroalkyl / lipophilic group Fluorosurfactants such as containing oligomer perfluoroalkyl group-containing urethanes. The amount of surfactant added depends on the type of surfactant, the type of liquid crystal material, the type of solvent, and the type of alignment film on which the solution is applied. 10 ppm to 10% is preferable, more preferably 100 ppm to 5%, and still more preferably 0.1 to 1%.

  As a method for coating the composition for forming a liquid crystal layer, a spin coating method, a roll coating method, a printing method, a dip pulling method, a die coating method, a casting method, a bar coating method, a blade coating method, a spray coating method, a gravure coating method , Reverse coating method or extrusion coating method. The method for removing the solvent after coating the composition for forming a liquid crystal layer is performed, for example, by air drying, heat removal, or removal under reduced pressure, or a combination thereof. By removing the solvent, a liquid crystal layer forming layer is formed.

  In the step of curing the polymerizable liquid crystal material, energy for curing the polymerizable liquid crystal material is given, and thermal energy may be used, but it is usually performed by irradiation with ionizing radiation capable of causing polymerization. If necessary, a polymerization initiator may be contained in the polymerizable liquid crystal material. The ionizing radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus, and the wavelength. Is preferably from 150 to 500 nm, more preferably from 250 to 450 nm, and even more preferably from 300 to 400 nm.

  In the present invention, a method of performing radical polymerization by irradiating ultraviolet rays (UV) as actinic radiation and generating radicals from the polymerization initiator with ultraviolet rays is preferable. This is because the method using UV as the actinic radiation is an established technique, and therefore it is easy to apply to the present invention including the polymerization initiator to be used.

  As a light source for irradiating ultraviolet rays, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), or a short arc discharge lamp (ultra-high-pressure mercury lamp, xenon) Lamp, mercury xenon lamp) and the like. In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity may be appropriately adjusted depending on the composition of the polymerizable liquid crystal material forming the liquid crystal layer and the photopolymerization initiator.

  The alignment fixing step by irradiation with actinic radiation may be performed at the processing temperature in the step of forming the liquid crystal layer forming layer described above, that is, the temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, It may be performed at a lower temperature. The polymerizable liquid crystal material once in a liquid crystal phase does not suddenly disturb the alignment state even if the temperature is lowered thereafter.

(Base material)
In this invention, as a base material used for the 1st-4th protective film, it is preferable that manufacture is easy and it is optically transparent, and it is especially preferable that it is a transparent resin film.

  The term “transparent” as used in the present invention means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  Although it will not specifically limit if it has said property, For example, cellulose ester-type films, such as a cellulose diacetate film, a cellulose triacetate film, a cellulose acetate propionate film, a cellulose acetate butyrate film, a polyester-type film, a polycarbonate Film, polyarylate film, polysulfone (including polyethersulfone) film, polyester film such as polyethylene terephthalate and polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol Film, syndiotactic polystyrene film, polycarbonate film, nor Runen resin film, a polymethylpentene film, a polyether ketone film, polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, polymethyl methacrylate film, acrylic film or a glass plate or the like. Of these, norbornene resin films and cellulose ester films are preferred.

  The norbornene-based resin film preferably used in the present invention is an amorphous polyolefin film having a norbornene structure. For example, APO manufactured by Mitsui Petrochemical Co., Ltd., ZEONEX manufactured by Nippon Zeon Co., Ltd., manufactured by JSR Co., Ltd. ARTON etc.

  Among these, in the first to fourth protective films according to the present invention, it is preferable to use a cellulose ester film, and in particular, the base material of the second protective film is cellulose mainly composed of a specific cellulose ester described later. It is an ester film. As the cellulose ester, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are preferable, and among these, cellulose acetate and cellulose acetate propionate are preferably used. Commercially available cellulose ester films include, for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4FR, KC8UY-HA, KC8UY-HA, KC8UY Etc. are preferably used from the viewpoints of production, cost, transparency, adhesion and the like. These films may be films produced by melt casting film formation or films produced by solution casting film formation.

<Cellulose ester>
The cellulose ester used for the second protective film according to the present invention will be described in detail.

  The cellulose ester used in the second protective film according to the present invention is an aliphatic carboxylic acid ester having 2 to 22 carbon atoms, an aromatic carboxylic acid ester, or a mixed ester of an aliphatic carboxylic acid ester and an aromatic carboxylic acid ester. It is preferably used, and particularly preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. Specifically, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate phthalate, etc., JP-A Nos. 10-45804, 8-231761, U.S. Pat. No. 2,319,052, etc. And mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate. Among the above descriptions, the lower fatty acid ester of cellulose particularly preferably used is cellulose acetate propionate.

  The cellulose ester has an acyl group having 2 to 22 carbon atoms as a substituent, a cellulose that simultaneously satisfies the following formulas 1 and 2 when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group is Y: Ester.

Formula 1 2.00 ≦ X + Y ≦ 2.60
Formula 2 0.10 ≦ Y ≦ 1.00
Among them, 2.30 ≦ X + Y ≦ 2.55 is preferable, and 2.40 ≦ X + Y ≦ 2.55 is more preferable. Further, 0.50 ≦ Y ≦ 0.90 is preferable, and 0.70 ≦ Y ≦ 0.90 is more preferable.

  The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods. Moreover, these acyl group substitution degrees can be measured according to the method prescribed | regulated to ASTM-D817-96.

  As the cellulose ester, a cellulose ester synthesized using cotton linter, wood pulp, kenaf or the like as a raw material can be used alone or in combination. In particular, it is preferable to use a cotton linter (hereinafter sometimes simply referred to as a linter) or a cellulose ester synthesized from wood pulp alone or in combination.

  Moreover, the cellulose ester obtained from these can be mixed and used in arbitrary ratios, respectively. These cellulose esters are prepared by using an organic acid such as acetic acid or an organic solvent such as methylene chloride when sulfuric acid is used as the acylating agent (acetic anhydride, propionic anhydride, butyric anhydride). It can obtain by making it react by a conventional method using a protic catalyst like.

  In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds at the same time, and the polymer chain is broken and the acetyl group is decomposed, resulting in undesirable results. Therefore, it is necessary to set the reaction time within a certain range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions are various and greatly change depending on the reaction apparatus, equipment and other conditions. As the decomposition of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. That is, in the process of acetylation of cellulose triacetate, the weight average molecular weight is used as one index of the reaction degree for allowing the acetylation reaction to be carried out for a sufficient time for acetylation without being too long and being decomposed too much. The value of (Mw) / number average molecular weight (Mn) can be used.

  The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester used in the present invention is preferably 1.4 to 3.0. In the present invention, the cellulose ester film may contain, as a material, a cellulose ester having a Mw / Mn value of 1.4 to 3.0, but the cellulose ester contained in the film (preferably cellulose triacetate). Or the value of Mw / Mn of cellulose acetate propionate) is more preferably in the range of 1.4 to 3.0. In the process of synthesizing cellulose ester, it is difficult to make it less than 1.4, and cellulose ester having a uniform molecular weight can be obtained by fractionation by gel filtration or the like. However, this method is very expensive. Moreover, it is preferable that it is 3.0 or less because the flatness is easily maintained. In addition, More preferably, it is 1.7-2.2.

  The molecular weight of the cellulose ester used in the present invention is preferably a number average molecular weight (Mn) of 80,000 to 200,000. More preferred are 100,000 to 200,000, particularly preferably 150,000 to 200,000.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

The measurement conditions are as follows.
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 samples are used. It is preferable to obtain 13 samples at approximately equal intervals.

  The method for producing cellulose ester can be obtained by the method described in JP-A-10-45804.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. Coordination compounds with ligands, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma optical emission spectrometry).

  The cellulose ester film used in the present invention preferably has a refractive index of 1.45 to 1.60 at 550 nm. As a method for measuring the refractive index of the film, an Abbe refractometer is used, and measurement is performed based on Japanese Industrial Standard JIS K 7105.

<Additive>
The cellulose ester film can contain additives such as a plasticizer, an ultraviolet absorber, an antioxidant, and a matting agent.

  As described above, the cellulose ester film used in the third protective film according to the present invention preferably has a retardation in the range of 0 to 5 nm and Rt in the range of -10 to 10 nm. In order to obtain the above numerical range, if the third protective film is a cellulose ester, it is manufactured by melt film formation, or it is kept in solution film formation at a temperature above the glass transition point for 15 seconds or longer. It is preferable to add an additive having birefringence that is opposite to that of cellulose ester. Especially, in order to adjust retardation within the said range, it is preferable to contain the following acrylic polymer.

<Acrylic polymer>
The cellulose ester film used for the third protective film according to the present invention preferably contains an acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less that exhibits negative orientation birefringence with respect to the stretching direction, The acrylic polymer is preferably an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain.

  By controlling the composition of the polymer so that the weight average molecular weight of the polymer is 500 or more and 30000 or less, the compatibility between the cellulose ester and the polymer can be improved.

  In particular, for an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or an acrylic polymer having a cyclohexyl group in the side chain, if the weight average molecular weight is preferably 500 or more and 10,000 or less, in addition to the above, The cellulose ester film has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like. The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, the acrylic polymer refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring.

  The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl) and the like can be mentioned, but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  Among acrylic polymers having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. % Is preferable. The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

  In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and preferably 50 to 80% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  A polymer obtained by polymerizing the above ethylenically unsaturated monomer, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, and an acrylic polymer having a cyclohexyl group in the side chain are all excellent in compatibility with the cellulose resin.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in the acrylic polymer in an amount of 2 to 20% by mass.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. Examples include those substituted with methacrylic acid, preferably 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, low moisture permeability, and polarized light. It is particularly excellent in adhesiveness with a polarizer as a plate protective film, and has the effect of improving the durability of the polarizing plate.

  The method of having a hydroxyl group at at least one terminal of the main chain of the acrylic polymer is not particularly limited as long as it has a hydroxyl group at the terminal of the main chain, but azobis (2-hydroxyethylbutyrate) A method using a radical polymerization initiator having such a hydroxyl group, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and terminating a hydroxyl group by living ion polymerization. A compound having one thiol group and a secondary hydroxyl group as disclosed in JP 2000-128911 A or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination The method described in the above publication is particularly preferred.

  The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  Furthermore, a polymer using styrene as an ethylenically unsaturated monomer exhibiting negative orientation birefringence with respect to the stretching direction is preferred in order to develop negative refraction. Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, and vinyl benzoic acid methyl ester. Although it is mentioned, it is not a thing limited to these.

  It may be copolymerized with the exemplified monomers listed as the unsaturated ethylenic monomer, or may be used by being dissolved in a cellulose ester using two or more of the above polymers for the purpose of controlling birefringence.

  Further, the cellulose ester film used in the present invention is composed of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated group having no hydrophilic ring and having a hydrophilic group in the molecule. A weight average molecular weight of 500 or more obtained by polymerizing a polymer X having a weight average molecular weight of 5000 or more and 30000 or less obtained by copolymerization with the monomer Xb, and more preferably an ethylenically unsaturated monomer Ya having no aromatic ring. It is preferable to contain 3000 or less polymer Y.

(Polymer X, Polymer Y)
The polymer X used in the present invention includes an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule, and an ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group. Is a polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization of Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-(Xa) _m- (Xb) _n- (Xc) _p-
More preferably, it is a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m - [CH 2 -C (-R3) (- CO 2 R4-OH) -] n - [Xc] p -
(In the formula, R 1, R ₃ and R 5 represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms and a cycloalkyl group. R 4 and R 6 represent —CH ₂ — and —C ₂ H ₄ —. Or -C ₃ H _6- , Xc represents a monomer unit that can be polymerized to Xa and Xb, m, n, and p represent molar composition ratios, provided that m ≠ 0, n ≠ 0, k ≠ 0. M + n + p = 100.)
Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-ethoxyethyl) ) Or the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

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

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio (m: n) of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high. Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  As for the molecular weight of the polymer X, the weight average molecular weight is preferably 5000 or more and 30000 or less, and more preferably 8000 or more and 25000 or less.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because the cellulose ester film has advantages such as less dimensional change under high temperature and high humidity and less curling as a polarizing plate protective film. When the weight average molecular weight is 30000 or less, the compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity, and further haze generation immediately after film formation is suppressed.

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

  The measuring method of a weight average molecular weight can be based on the following method.

(Weight average molecular weight measurement method)
The weight average molecular weight Mw is measured using gel permeation chromatography.

  The measurement conditions are as follows.

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

  The polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring.

  A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance.

  Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
− (Ya) _k − (Yb) _q −
More preferably, it is a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k - [Yb] q -
(Wherein, R5 is, .Yb .R6 representing H or CH ₃ is representing an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms, .k and q represents the Ya and copolymerizable monomer units, This represents the molar composition ratio, where k ≠ 0 and k + q = 100.)
Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. It is preferred.

  In this case, the terminal of the polymer X and the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. By this terminal residue, the compatibility between the polymers X and Y and the cellulose ester can be adjusted.

  The hydroxyl value of the polymers X and Y is preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C.

  After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained.

  The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimensional stability. Are better.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y act sufficiently to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<Other additives>
The cellulose ester film that is the first to fourth protective films of the present invention may contain an additive that can be added to a normal cellulose ester film.

  Examples of these additives include plasticizers, ultraviolet absorbers, and fine particles.

  The present invention preferably contains the following plasticizer. Examples of plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, glycolate plasticizers, citrate ester plasticizers, and polyesters. A plasticizer, a polyhydric alcohol ester plasticizer, and the like can be preferably used.

For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy For trimellitic acid plasticizers such as ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, diphenyl phthalate, dicyclohexyl phthalate, tributyl trimellitate, triphenyl trimellitate, triethyl For pyromellitic acid ester plasticizers such as trimellitate, tetrabutylpyromellitate, In the case of glycolate plasticizers such as lupyromelitate and tetraethylpyromellitate, triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate, etc. Citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate and the like can be preferably used. Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters.

  As the polyester plasticizer, a copolymer of a dibasic acid and a glycol such as an aliphatic dibasic acid, an alicyclic dibasic acid, or an aromatic dibasic acid can be used. The aliphatic dibasic acid is not particularly limited, and adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid, and the like can be used. As glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like can be used. These dibasic acids and glycols may be used alone or in combination of two or more.

The polyhydric alcohol ester plasticizer comprises an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid. Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, 2-n-butyl-2-ethyl-1,3- Propanediol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, and the like can be raised. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable. There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto. As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid. Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid can be raised. Examples of preferable alicyclic monocarboxylic acid include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. Aromatic monocarboxylic acids or derivatives thereof can be raised. Particularly preferred is benzoic acid. The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

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

  These plasticizers are preferably used alone or in combination.

  The amount of these plasticizers used is preferably from 1 to 20% by mass, particularly preferably from 3 to 13% by mass, based on the cellulose ester, in terms of film performance, processability and the like.

  The ultraviolet absorber that can be used in the present invention aims to improve durability by absorbing ultraviolet rays of 400 nm or less, and preferably has a transmittance of 10% or less at a wavelength of 370 nm. More preferably, it is 5% or less, and further preferably 2% or less.

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

  It is preferable to use fine particles for the cellulose ester film used in the present invention. As the fine particles, both inorganic compounds and organic compounds can be used. Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate And calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably 5 to 50 nm, and more preferably 7 to 20 nm. These are preferably contained mainly as secondary aggregates having a particle size of 0.05 to 0.3 μm. The content of the fine particles in the cellulose ester film is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.5% by mass. In the case of a cellulose ester film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.). Can do.

  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.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (above, manufactured by Toshiba Silicone Co., Ltd.) It is commercially available under the trade name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the cellulose ester film low.

<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose ester film used for this invention is demonstrated.

  The cellulose ester film used in the present invention is preferably a cellulose ester film produced by a solution casting method or melt casting.

  The cellulose ester film used in the present invention was produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support, and casting the dope. The step of drying the dope as a web, the step of peeling from the metal support, the step of stretching or maintaining the width, the step of further drying, and the step of winding up the finished film are performed.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and does not boil under pressure, in order to prevent the formation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

The bright spot foreign matter was placed in a crossed Nicols state with two polarizing plates, a rolled cellulose ester was placed between them, and light was applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) that light from the opposite side appears to leak sometimes, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable.

  Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the film-like cellulose ester to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. %, Particularly preferably 20 to 30% by mass or 70 to 120% by mass.

  Further, in the drying step of the film-like cellulose ester, the web is peeled off from the metal support, and further dried, so that the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. Particularly preferably, it is 0 to 0.01% by mass or less.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

  In order to produce a cellulose ester film used for the second protective film according to the present invention, the web immediately after peeling from the metal support, stretched in the transport direction (= long direction) where the amount of residual solvent is large, Furthermore, it is preferable to stretch in the width direction by a tenter method in which both ends of the web are gripped by clips or the like.

  The stretching operation may be performed in multiple stages, and biaxial stretching is preferably performed in the casting direction and the width direction. Also, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

  A preferable draw ratio is 1.05 to 2 times, preferably 1.1 to 1.5 times. In the case of simultaneous biaxial stretching, the film may be contracted in the longitudinal direction, or may be contracted so as to be 0.8 to 0.99, preferably 0.9 to 0.99. Preferably, the area is preferably 1.12 times to 1.44 times, more preferably 1.15 times to 1.32 times, due to transverse stretching and longitudinal stretching or shrinkage. This can be determined by the draw ratio in the longitudinal direction × the draw ratio in the transverse direction.

  In addition, the “stretch direction” in the present invention is usually used to mean a direction in which a stretching stress is directly applied when performing a stretching operation. In some cases, it is used in the sense of the one having a higher draw ratio (that is, the direction usually serving as the slow axis).

  In the cellulose ester film used for the second protective film according to the present invention, the retardation represented by the following formulas 3 and 4 is such that Ro is 30 to 115 nm, Rt is 100 to 250 nm, and Rt / Ro is 1 The range is from 6 to 4.4. Further, Ro is in the range of 45 to 95 nm, Rt is in the range of 110 to 200 nm, and Rt / Ro is preferably in the range of 2.0 to 3.5. The retardation is measured at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH.

  In particular, a film produced by stretching in the direction orthogonal to the conveying direction by about 1.1 to 1.5 times in the range of glass transition point ± 10 ° C. or by solution casting has a residual solvent amount of 2 By extending about 1.1 to 1.7 times in a direction perpendicular to the transport direction while about ~ 100% by mass remains, the retardation can be kept within the above range.

  The retardation in the state where the second protective film and the retardation layer according to the present invention are laminated has a range of Ro of 30 to 105 nm and Rt of −300 to 25 nm. Further, Ro is 45 to 95 nm, Rt is -100 to 25 nm, and Rt is particularly preferably -60 to 20 nm.

Furthermore, in the state where the second protective film according to the present invention and the retardation layer are laminated, the laminated film has an optical axis in the same plane, and is defined by the following formulas 5, 6, 7, and 8. Chromatic dispersion characteristics
D (Ro) 1: 0.9 to 1.0
D (Ro) 2: −9.5 to 0 nm
D (Rt) 1: 0.3 to 0.9
D (Rt) 2: −100 to −10 nm
The absolute value of the angle formed by the transmission axis of the first polarizing film and the in-plane slow axis of the second protective film is in the range of 0 to 1 °.

  In particular, D (Ro) 1 is preferably in the range of 0.93 to 0.98, and D (Rt) 1 is preferably in the range of 0.4 to 0.8, and preferably in the range of 0.45 to 0.65.

  In order for the absolute value of the angle formed between the transmission axis of the first polarizing film and the in-plane slow axis of the second protective film to be in the range of 0 to 1 °, the in-plane retardation of the second protective film is used. This can be achieved by setting the phase axis in the direction perpendicular to the conveying direction and controlling in-plane unevenness. For this purpose, it is preferable to precisely control the balance between the stretching temperature and the stretching ratio and to independently control the stretched portion (such as a tenter clip) on both sides of the protective film. This can be achieved by adjusting the stretching temperature and the stretching ratio with respect to the clip position and the stress of the clip.

Formula 3: Ro = (nx−ny) × d
Formula 4: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the slow axis direction in the plane of the second protective film or retardation layer or the laminate of the second protective film and the retardation layer is nx, and in-plane is orthogonal to the slow axis. (The refractive index in the direction to ny is the refractive index in the thickness direction, nz is the refractive index in the thickness direction, and d represents the thickness (nm).)
Formula 5: D (Ro) 1 = Ro (630) / Ro (480)
Formula 6: D (Ro) 2 = Ro (630) -Ro (480)
Formula 7: D (Rt) 1 = | Rt (630) / Rt (480) |
Formula 8: D (Rt) 2 = Rt (480) -Rt (630)
(In the formula, Ro (480) and Ro (630) are retardation Ro values at 480 nm and 630 nm, respectively, in an environment of 23 ° C. and 55% RH, and Rt (480) and Rt (630) are retardation Rt at 480 nm and 630 nm, respectively. Represents the value.)
As means for controlling the wavelength dispersion, D (Ro) 1 and D (Ro) 2 can be achieved by appropriately selecting the material and manufacturing method of the second protective film. Regarding the material, it is preferable to change the substituent (type and degree of substitution) with a cellulose ester-based material. In the case of only an acetyl group, the value increases as the degree of substitution decreases, and tends to decrease as the propionyl group increases. It also varies depending on the additive. Generally, in the case of a retardation increasing agent or the like, it tends to be large. It is preferable that D (Rt) 1 and D (Rt) 2 control the respective retardations of the second protective film and the retardation layer. Specifically, the value becomes smaller by relatively increasing the phase difference of the second protective film.

  The retardation of the first protective film and the fourth protective film used in the polarizing plate of the present invention is not particularly limited, and the retardation Ro in the in-plane direction is preferably in the range of 30 nm to 1000 nm, and more preferably Is in the range of 30 nm to 500 nm, particularly preferably in the range of 30 nm to 150 nm, and most preferably in the range of 30 nm to 75 nm.

  Moreover, as retardation Rt of the thickness direction, the range of 30 nm-1000 nm is preferable, More preferably, it is the range of 30 nm-500 nm, Most preferably, it is the range of 30 nm-250 nm.

  As for the cellulose-ester film used for the 1st-4th protective film which concerns on this invention, it is preferable that the film thickness is the range of 20-200 micrometers, It is more preferable that it is 20-100 micrometers, It is 20-80 micrometers. More preferably. In particular, the cellulose ester film used for the third protective film is preferably 20 to 45 μm for obtaining the effects of the present invention.

(Polarizer)
The polarizing plate can be produced by a general method. A fully saponified polyvinyl alcohol is formed on at least one surface of a polarizing film prepared by subjecting the back side of the cellulose ester film used in the first to fourth protective films of the present invention to an alkali saponification treatment and immersion drawing in an iodine solution. It is preferable to bond using an aqueous solution. The film may be used on the other surface, or another polarizing plate protective film may be used. Commercially available cellulose ester films (for example, Konica Minoltap KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4FR (also Konica Minolta Opto Co., Ltd., preferably used)).

  A polarizing film, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film currently known is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound.

(Display device)
By incorporating the polarizing plate of the present invention into a liquid crystal display device, the liquid crystal display device of the present invention having excellent visibility can be produced. The polarizing plate of the present invention is preferably used in an IPS mode type LCD, and particularly preferably used in an IPS mode type liquid crystal display device adopting the configuration defined in claim 5 or claim 6. It is done. In particular, even a large-screen liquid crystal display device with a screen of 30 or more types, particularly 30 to 54 types, has a high contrast, and in particular, has the effect of suppressing color change due to viewing angle and preventing eye fatigue even during long-time viewing. .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<< Measurement of retardation and chromatic dispersion >>
In the examples, retardation measurement was performed in an environment of 23 ° C. and 55% RH using KOBRA 21ADH manufactured by Oji Scientific Instruments. Further, when calculating retardation in the thickness direction, a value obtained by measuring the refractive index of the corresponding wavelength of each layer using an Abbe refractometer was used. In the case of a laminate, the average refractive index of each layer was used. Retardation was calculated using the following formulas 3 and 4.

  When the retardation in the thickness direction of the laminate in the present invention is a negative value, when calculating the retardation, the retardation is obtained when the in-plane fast axis of the laminate is the tilt axis and tilted by 40 degrees. Was used for calculation.

Formula 3: Ro = (nx−ny) × d
Formula 4: Rt = ((nx + ny) / 2−nz) × d
(In the formula, the refractive index in the slow axis direction in the plane of the second protective film or retardation layer or the laminate of the second protective film and the retardation layer is nx, and in-plane is orthogonal to the slow axis. (The refractive index in the direction to ny is the refractive index in the thickness direction, nz is the refractive index in the thickness direction, and d represents the thickness (nm).)
Moreover, the wavelength dispersion characteristic was calculated | required according to Formula 5-8.

Formula 5: D (Ro) 1 = Ro (630) / Ro (480)
Formula 6: D (Ro) 2 = Ro (630) -Ro (480)
Formula 7: D (Rt) 1 = | Rt (630) / Rt (480) |
Formula 8: D (Rt) 2 = Rt (480) -Rt (630)
(In the formula, Ro (480) and Ro (630) are retardation Ro values at 480 nm and 630 nm in an environment of 23 ° C. and 55% RH, respectively, and Rt (480) and Rt (630) are retardations at 480 nm and 630 nm, respectively. Rt value is represented.)
<< Production of Protective Films A to L with Retardation Layer >>
(Silicon dioxide dispersion)
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 12 parts by mass (average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter)
88 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with a Manton Gorin disperser. The liquid turbidity after dispersion was 200 ppm. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion.

(Dope solution)
Cellulose ester (acetyl group substitution degree 2.50, propionyl group substitution degree 0.10, total acyl group substitution degree 2.60) 100 parts by mass Trimethylolpropane tribenzoate 5 parts by mass Ethylphthalylethyl glycolate 5 parts by mass Silicon dioxide Dispersion diluent 10 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 1.2 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 0.8 parts by weight Methylene chloride 430 parts by weight Ethanol 40 parts by weight The above dope composition The product was put into a sealed container, heated to 70 ° C., and while stirring, the cellulose ester was completely dissolved to obtain a dope solution. Next, after the dope solution was filtered, the dope solution whose temperature was adjusted to 33 ° C. was fed to the die and uniformly cast with a width of 2.5 m from the die slit onto the stainless steel belt. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film on the metal support (which is called a web after casting on the stainless steel belt) is dried by applying hot air of 44 ° C., and the residual solvent in the peeling is peeled off at 120 mass%. Then, the web was stretched so that the longitudinal stretching ratio was 1.1 times, and then the end of the web was gripped with a tenter at a residual solvent amount of 24% and a temperature of 135 ° C., and 1.2 times in the width direction. It extended | stretched so that it might become the draw ratio of. After stretching, the film was held for several seconds while maintaining its width, then the tension in the width direction was relaxed, and the film was dried at 120 ° C. after releasing the width. A cellulose ester film having a thickness of 30 μm, a width of 2.65 m, and a length of 7500 m produced as described above was wound around a core.

  As for the retardation of this cellulose ester film, Ro was 30 nm, Rt was 130 nm, and Rt / Ro was 4.3.

  Next, the following retardation layer was provided on the obtained cellulose ester film.

  45% by mass of the compound of the following formula (a)

  45% by mass of the compound of the following formula (b)

  10% by mass of the compound of the following formula (d)

A polymerizable liquid crystal composition (H) comprising: The polymerizable liquid crystal composition (H) had a nematic-isotropic liquid phase transition temperature of 73 ° C. Polymerizability obtained by adding 0.2% of photopolymerization initiator Lucillin TPO (manufactured by Basf) and 0.1% of hindered amine LS-765 (manufactured by Sankyo Lifetech Co., Ltd.) to 99.7% of the polymerizable liquid crystal composition (H). A liquid crystal composition (H1) was prepared. Next, a xylene solution containing 33% of the polymerizable liquid crystal composition (H1) was prepared. This xylene solution was applied to a cellulose ester film with a thickness of 5 μm by a die coater. The coated film was irradiated with UV light of 250 mJ / mm for 80 seconds at an oxygen concentration of 0.2% and a temperature of 38 ° C. to cure the polymerizable liquid crystal composition (H1) to obtain a protective film A with a retardation layer. .

  When the retardation of this cured film was measured, Ro was 0.5 nm, Rt was -288 nm, and Ro of the protective film A with retardation layer laminated was 30.5 nm, and Rt was -105 nm.

  Further, D (Ro) 1 defined by the above formula was 0.9, D (Ro) 2 was -3.09 nm, D (Rt) 1 was 0.70, and D (Rt) 2 was -36 nm. .

  Subsequently, as the second protective film, the cellulose ester of the type described in Table 1 and Table 2, the stretching conditions and film thickness described in Table 3, and the formulas (a), (b), and (d). A protective film with a retardation layer is produced in the same manner as in the production of the protective film A with a retardation layer, except that the retardation layer shown in Tables 1 and 2 in which the retardation is changed by changing the composition ratio of the compound is used. B to L were produced.

<< Preparation of protective films M and N with retardation layers >>
Protective film M with retardation layer in the same manner as protective film A with retardation layer, except that cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.75) was used as the cellulose ester. N was produced.

<< Preparation of protective films O and P with retardation layer >>
A cellulose ester film as a second protective film was produced according to the following.

(Preparation of dope solution B)
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 9.5 parts by weight Ethyl phthalyl ethyl glycolate 2.2 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above is put into a closed container, heated and stirred, completely dissolved, and Azumi filter paper Azumi filter paper No. 24, and the dope liquid B was prepared. The dope solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. (A part of the dope solution B was also used for preparing the following in-line additive solution B.)
(Silicon dioxide dispersion B)
Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass (average diameter of primary particles 12 nm, apparent specific gravity 100 g / liter)
18 parts by mass or more of ethanol was stirred and mixed with a dissolver for 30 minutes, and then dispersed with a Manton Gorin disperser. The liquid turbidity after dispersion was 100 ppm. 18 parts by mass of methylene chloride was added to the silicon dioxide dispersion with stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare silicon dioxide dispersion dilution B.

(Preparation of inline additive solution B)
Methylene chloride 100 parts by mass Dope solution B 34 parts by mass Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 5 parts by mass Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by mass Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 3 parts by mass or more was put into a closed container, heated, stirred and completely dissolved and filtered.

  To this, 20 parts by mass of silicon dioxide dispersion diluent B was added with stirring, and the mixture was further stirred for 60 minutes, and then filtered with Advantech Toyo Co., Ltd. polypropylene wind cartridge filter TCW-PPS-1N. B was prepared.

  In-line additive solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the in-line additive solution line. Add 2.5 parts by weight of the filtered inline additive B to 100 parts by weight of the filtered dope liquid B, mix thoroughly with an inline mixer (Toray static in-pipe mixer Hi-Mixer, SWJ), and then belt Using a casting apparatus, casting was uniformly performed on a stainless steel band support at a temperature of 35 ° C. and a width of 2.5 m. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 35 ° C., and then dried at a drying temperature of 130 ° C. while being stretched 1.2 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 11%. After that, drying is completed while transporting the drying zone at 120 ° C. and 110 ° C. with a number of rolls, slitting to 2.6 m width, and knurling with a width of 15 mm and an average height of 10 μm is applied to both ends of the film. A cellulose ester film O, which is a second protective film having a thickness of 80 μm and a length of 7500 m, was wound around a core having an inner diameter of 6 inches with a tension of 220 N / m and a final tension of 110 N / m.

  Similarly, a cellulose ester film P as a second protective film having a thickness of 40 μm and a length of 7500 m was produced without stretching in the width direction.

  Next, using the produced cellulose ester films O and P, protective films O and P with a retardation layer were prepared in the same manner as the protective film A with a retardation layer.

<< Production of protective film Q with retardation layer (and third protective films Q, V to Z) >>
<Polymer synthesis>
(Synthesis of polymer X)
Polymer X was synthesized with reference to the method described in JP-A-2003-12859. That is, 40 g of a monomer mixture obtained by mixing methyl methacrylate (MMA): 2-hydroxyethyl methacrylate (HEMA) in a ratio of 80:20 to a glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer. Then, 3.0 g of the chain transfer agent mercaptopropionic acid and 30 g of toluene were charged, and the temperature was raised to 90 ° C. Thereafter, 60 g of the monomer mixture was dropped from one dropping funnel over 3 hours, and 0.6 g of azobisisobutyronitrile dissolved in 14 g of toluene was dropped from the other funnel over 3 hours. Thereafter, 0.6 g of azobisisobutyronitrile dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain polymer X. The weight average molecular weight was 8000.

(Synthesis of polymer Y)
Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-344823. That is, the contents were heated to 70 ° C. while introducing the following methyl methacrylate and ruthenocene into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser. Next, half of the following β-mercaptopropionic acid which had been sufficiently purged with nitrogen gas was added to the flask under stirring. After the addition of β-mercaptopropionic acid, the contents in the stirring flask were maintained at 70 ° C. and polymerization was carried out for 2 hours. Further, after adding the other half of β-mercaptopropionic acid substituted with nitrogen gas, the temperature of the content being stirred was maintained at 70 ° C., and polymerization was carried out for 4 hours. The temperature of the reaction product was returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added to the reaction product to stop the polymerization. While gradually heating the polymer to 80 ° C. under reduced pressure with an evaporator, tetrahydrofuran, residual monomer and residual thiol compound were removed to obtain polymer Y. The weight average molecular weight was 1000.

Methyl methacrylate 100 parts by mass Ruthenocene (metal catalyst) 0.05 parts by mass β-mercaptopropionic acid 12 parts by mass A method for measuring the weight average molecular weight is shown below.

(Weight average molecular weight measurement method)
The weight average molecular weight Mw was measured using gel permeation chromatography.

  The measurement conditions are as follows.

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

  Using the polymers X and Y, as shown below, a protective film Q with a retardation layer and third protective films Q and V to Z having no retardation layer were prepared.

(Dope solution)
Cellulose triacetate (degree of acetylation: 61.5%, Mn: 110000, Mw / Mn = 2.0) 100 parts by weight Polymer X 10 parts by weight Polymer Y 5 parts by weight Methylene chloride 430 parts by weight Ethanol 40 parts by weight The above dope composition Was put in a sealed container, heated to 70 ° C., and while stirring, cellulose triacetate (TAC) was completely dissolved to obtain a dope. The time required for dissolution was 4 hours. Next, after the dope composition was filtered, the cellulose ester solution whose temperature was adjusted to 33 ° C. was fed to a die and uniformly cast on a stainless steel belt from a die slit to a width of 2.5 m. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film on the metal support (which is called a web after casting on the stainless steel belt) is dried by applying hot air of 44 ° C., and the residual solvent in the peeling is peeled off at 120 mass%. The film was stretched so as to have a longitudinal stretching ratio of 1.1 times with a tension of 1. Then, the residual solvent amount was adjusted to 4% by mass and the temperature was adjusted to 123 ° C., the web end was gripped with a tenter, The film was stretched so as to have a draw ratio of 1.1 times in the direction. After stretching, the film was held for several seconds while maintaining its width, and after the tension in the width direction was relaxed, the width was released and dried at 120 ° C. A cellulose ester film as a second protective film having a film thickness of 41 μm, a width of 2.65 m, and a length of 7500 m produced as described above was wound around a core.

  Next, in the same manner as the protective film A with a retardation layer, a retardation layer was provided to produce a protective film Q with a retardation layer.

  Moreover, the said cellulose-ester film was used as the 3rd protective film Q, without providing a phase difference layer. Regarding the retardation of the third protective film Q, Ro was 0.8 nm and Rt was 1 nm.

  Furthermore, the ratio of the polymer X and the polymer Y was changed, and the 3rd protective films VZ which have the retardation and film thickness of Table 1, Table 2 were produced.

<< Preparation of protective films R to U with retardation layer >>
Protective films R to U with retardation layers were produced in the same manner as the production of protective film A with retardation layers, except that the substitution degree of cellulose ester was changed as shown in Table 1.

  As described above, protective films A to U with a retardation layer and third protective films Q and V to Z without a retardation layer were produced.

<Production of polarizing plate>
The prepared protective films A to U with the retardation layer and the third protective films Q and V to Z having no retardation layer are alkali-treated with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, It was washed with water for 3 minutes and saponified to obtain an alkali-treated film.

  Next, a 120 μm-thick polyvinyl alcohol film 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 of 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 polarizing film.

  Next, the prepared polarizing film and a commercially available polarizing plate protective film, Konica Minolta-Tac, KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) were saponified by the above method, and a fully saponified polyvinyl alcohol 5% aqueous solution was adhered. As the agent, a polarizing plate on the viewing side was prepared by laminating protective films A to U with a retardation layer, a polarizing film, and KC4UY (first protective film) in this order. Similarly, a polarizing plate on the backlight side (BL side) was produced by laminating the third protective films Q, V to Z, a polarizing film, and KC4UY (fourth protective film) without providing a retardation layer in this order. .

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plate previously bonded to Hitachi liquid crystal television Wooo W17-LC50, which is an IPS mode type liquid crystal display device, is peeled off, and the thus-prepared viewing side and BL side polarizing plates are shown in FIG. The IPS mode type liquid crystal display devices 1 to 26 were prepared by bonding to the glass surface of the liquid crystal cell with the structure of The in-plane slow axis of the second protective film of the polarizing plate and the alignment direction of the liquid crystal cell were substantially parallel.

<Evaluation of liquid crystal display device>
(Viewing angle)
The viewing angle of the produced liquid crystal display device was measured by EZ-contrast manufactured by ELDIM. As the viewing angle, the contrast between the white display and the black display of the liquid crystal cell was calculated, and the angle at which the contrast was 100 in the oblique direction was defined as the viewing angle.

(Color)
Color measurement at the time of black display was performed with Topcon SR-3A.

Tint measurement was performed between the front and an inclination angle of 60 ° (azimuth angle 45 °) (front reference), and ((x−x ′) ² + (y−y ′) ² ) ^1/2 was evaluated. .

  * In the formula, front: (x, y), diagonal: (x ′, y ′).

  Table 4 shows the obtained results.

  As is clear from the results shown in Table 4, the liquid crystal display devices 1 to 16 of the present invention have a viewing angle (contrast of 100 or more) exceeding 50 degrees and smaller than 0.09 of the color change. It turns out that it is superior to.

Example 2
A polarizing plate was produced in the same manner as in Example 1 using the protective films A to U with retardation layer prepared in Example 1 and the third protective films Q and V to Z without the retardation layer. An IPS mode type liquid crystal display device having the configuration shown in 1 (B) was manufactured. In this case, the in-plane slow axis of the second protective film of the polarizing plate and the alignment direction of the liquid crystal cell are substantially orthogonal.

  Using the produced IPS mode type liquid crystal display device, the viewing angle and the hue were evaluated in the same manner as in Example 1. As a result, the liquid crystal display device of the present invention was reproduced with excellent contrast and color. It turns out that it has.

Claims (6)

A polarizing plate in which at least a first protective film, a first polarizing film, and a laminated retardation layer are arranged in this order, and the laminated retardation layer contains a cellulose ester satisfying the following formula 1 as a main component: And a retardation layer in which the orientation of the rod-like liquid crystal substantially perpendicularly aligned with the surface of the polarizing film or the second protective film is fixed, and the second protective film and the second protective film are stacked. Retardation Ro and Rt represented by the following formulas 3 and 4 at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH of the retardation layer,
Second protective film: Ro: 30 to 115 nm
Rt: 100 to 250 nm
Rt / Ro: 1.6 to 4.4
Retardation layer: Ro: 0 to 10 nm
Rt: −100 to −400 nm,
The laminated retardation layer has an in-plane optical axis, and the retardation at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH is Ro: 30 to 105 nm, Rt: −300 to 25 nm, and The chromatic dispersion characteristics defined by Equations 5, 6, 7, and 8 are
D (Ro) 1: 0.9 to 1.0
D (Ro) 2: −9.5 to 0 nm
D (Rt) 1: 0.3 to 0.9
D (Rt) 2: −100 to −10 nm,
A polarizing plate, wherein an absolute value of an angle formed by a transmission axis of the polarizing film and an in-plane slow axis of the second protective film is in a range of 0 to 1 °.
Formula 1: 2.00 ≦ (X + Y) ≦ 2.60
(In the formula, as the substitution degree of the acyl group of the cellulose ester, X represents the substitution degree of acetyl group, and Y represents the substitution degree of propionyl group.)
Formula 3: Ro = (nx−ny) × d
Formula 4: Rt = [(nx + ny) / 2−nz] × d
(In the formula, the refractive index in the slow axis direction in the plane of the second protective film or retardation layer or the laminate of the second protective film and the retardation layer is nx, and in-plane is orthogonal to the slow axis. (The refractive index in the direction to ny is the refractive index in the thickness direction, nz is the refractive index in the thickness direction, and d represents the thickness (nm).)
Formula 5: D (Ro) 1 = Ro (630) / Ro (480)
Formula 6: D (Ro) 2 = Ro (630) -Ro (480)
Formula 7: D (Rt) 1 = | Rt (630) / Rt (480) |
Formula 8: D (Rt) 2 = Rt (480) -Rt (630)
(In the formula, Ro (480) and Ro (630) are retardation Ro values at 480 nm and 630 nm, respectively, in an environment of 23 ° C. and 55% RH, and Rt (480) and Rt (630) are retardation Rt at 480 nm and 630 nm, respectively. Represents the value.) The polarizing plate according to claim 1, wherein the cellulose ester satisfies the following formula 2.
Formula 2: 0.10 ≦ Y ≦ 1.00   The first surface of the second protective film faces the polarizing film, and the second surface of the second protective film facing the first surface is arranged to face the retardation layer. The polarizing plate according to claim 1.   The polarizing plate according to claim 1, wherein the retardation layer is disposed between the second protective film and the polarizing film.   The polarizing plate according to claim 1 and a liquid crystal in which liquid crystal molecules are aligned in a direction substantially parallel to the glass substrate during black display, and the alignment directions on both glass substrates are substantially parallel. A polarizing plate composed of a cell, a third protective film, a second polarizing film, and a fourth protective film; and the second protective film of the polarizing plate according to claim 1 The in-plane slow axis and the alignment direction of the liquid crystal cell are substantially parallel, and the third protective film is Ro: 0 to 5 nm, Rt: −10 to 10 nm. A liquid crystal display device having a thickness of 20 to 45 μm.   The polarizing plate according to claim 1 and a liquid crystal in which liquid crystal molecules are aligned in a direction substantially parallel to the glass substrate during black display, and the alignment directions on both glass substrates are substantially parallel. A polarizing plate composed of a cell, a third protective film, a second polarizing film, and a fourth protective film; and the second protective film of the polarizing plate according to claim 1 The in-plane slow axis and the alignment direction of the liquid crystal cell are substantially orthogonal, the third protective film is Ro: 0 to 5 nm, Rt: −10 to 10 nm, and the film of the third protective film A liquid crystal display device having a thickness of 20 to 45 μm.