JP2022062028A - Circular polarizing plate and image display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circular polarizing plate that has a neutral reflective hue.

SOLUTION: A circular polarizing plate of the present invention includes a polarizer, a phase difference layer, and an adhesive layer, wherein the angle formed by an absorption axis of the polarizer and a slow axis of the phase difference layer is 39° to 51°, and at least one of the polarizer, phase difference layer, and adhesive layer contains a dye compound present in a wavelength area where the maximum absorption wavelength of an absorption spectrum is 650 nm or more.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a circular polarizing plate and an image display device.

In recent years, with the spread of thin displays, organic EL display devices equipped with organic EL panels have been proposed. The organic EL panel has a highly reflective metal layer, and tends to cause problems such as external light reflection and background reflection. Therefore, it is known to prevent these problems by providing a circular polarizing plate on the visual recognition side. Further, it is known that the viewing angle is improved by providing a circular polarizing plate on the visual recognition side of the liquid crystal display panel. However, the conventional circularly polarizing plate has a problem that an undesired coloring may occur in the reflected hue.

Japanese Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a circular polarizing plate having a neutral reflected hue and an image display device including such a circular polarizing plate. It is in.

The circular polarizing plate of the present invention includes a polarizing element, a retardation layer, and an adhesive layer, and the angle formed by the absorption axis of the polarizing element and the slow axis of the retardation layer is 39 ° to 51 °. And at least one of the above-mentioned polarizing element, the above-mentioned retardation layer, and the above-mentioned pressure-sensitive adhesive layer contains a dye compound present in a wavelength region where the maximum absorption wavelength of the absorption spectrum is 650 nm or more.
In one embodiment, the in-plane retardation of the retardation layer satisfies Re (450) / Re (550)> 1.
In one embodiment, the in-plane retardation of the retardation layer satisfies 1.1> Re (450) / Re (550)> 1.
In one embodiment, the in-plane retardation of the retardation layer satisfies 115 nm ≦ Re (550) ≦ 135 nm.
In one embodiment, the pressure-sensitive adhesive layer comprises the dye compound.
In one embodiment, the retardation layer is made of a retardation film having an alicyclic structure.
According to another aspect of the present invention, an image display device is provided. This image display device includes the circular polarizing plate.

According to the present invention, in a circular polarizing plate including a polarizing element, a retardation layer, and a pressure-sensitive adhesive layer, at least one of the substituent, the retardation layer, and the pressure-sensitive adhesive layer has the maximum absorption wavelength of the absorption spectrum. By including the dye compound present in the wavelength region of 650 nm or more, it is possible to realize a circular polarizing plate having a neutral reflected hue.

It is the schematic sectional drawing of the circular polarizing plate by one Embodiment of this invention. It is a schematic plan view explaining the whole structure of an example of a stretching apparatus which can be used for manufacturing a retardation film. FIG. 2 is a schematic plan view of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 2, and shows a state where the clip pitch is the minimum. FIG. 2 is a schematic plan view of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 2, and shows a state in which the clip pitch is maximum. It is a schematic diagram explaining one embodiment of diagonal stretching in the manufacture of a retardation film. It is a graph which shows the relationship between each zone of the stretching apparatus and a clip pitch at the time of diagonal stretching shown in FIG. It is a graph which shows the relationship between each zone of the stretching apparatus and a clip pitch at the time of diagonal stretching of another embodiment. It is a schematic diagram explaining another embodiment of diagonal stretching in the manufacture of a retardation film. It is a graph which shows the relationship between each zone of the stretching apparatus and a clip pitch at the time of diagonal stretching shown in FIG. It is a schematic diagram explaining the relationship between the diagonal stretching and the formula (1) in the manufacture of a retardation film. It is a schematic diagram explaining the clip moving speed and the formula (1) for each of the left and right in one embodiment of diagonal stretching in the manufacture of a retardation film. It is a schematic diagram explaining the clip moving speed and the formula (1) for each of the left and right in another embodiment of diagonal stretching in the manufacture of a retardation film.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
"Nx" is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the direction of the slow phase axis), and "ny" is the direction orthogonal to the slow phase axis in the plane (that is, the direction of the phase advance axis). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of the layer (film).

A. Circular polarizing plate FIG. 1 is a schematic cross-sectional view of a circularly polarizing plate according to one embodiment of the present invention. The circular polarizing plate 100 includes a polarizing element 10, a retardation layer 20, and an adhesive layer 30. The angle formed by the absorption axis of the polarizing element 10 and the slow axis of the retardation layer 20 is 39 ° to 51 °. At least one of the polarizing element 10, the retardation layer 20, and the pressure-sensitive adhesive layer 30 contains a dye compound present in a wavelength region where the maximum absorption wavelength of the absorption spectrum is 650 nm or more. This makes it possible to bring the reflected hue of the circularly polarizing plate closer to neutral. In the example shown in FIG. 1, the polarizing element 10, the retardation layer 20, and the pressure-sensitive adhesive layer 30 are laminated in this order, but the configuration of the circular polarizing plate 100 is not limited to the configuration of the illustrated example. For example, the circularly polarizing plate 100 may have a protective layer for the polarizing element 10 and / or another retardation layer other than the retardation layer 20. Further, the circularly polarizing plate 100 may have a plurality of pressure-sensitive adhesive layers, and the pressure-sensitive adhesive layer may be arranged at an arbitrary appropriate position. In one embodiment, at least one of the pressure-sensitive adhesive layers of the circularly polarizing plate 100 contains a dye compound. The in-plane retardation of the retardation layer 20 preferably satisfies 115 nm ≦ Re (550) ≦ 135 nm. In one embodiment, the retardation layer 20 is made of a retardation film having an alicyclic structure.

The in-plane retardation of the retardation layer preferably satisfies the relationship of Re (450) / Re (550)> 1. That is, the retardation layer has a positive wavelength dispersion characteristic in which the in-plane retardation value is smaller as the wavelength of the measurement light is larger, or a flat wavelength dispersion characteristic in which the in-plane retardation value hardly changes regardless of the wavelength of the measurement light. show. The in-plane retardation of the retardation layer more preferably satisfies the relationship of 1.1> Re (450) / Re (550)> 1. That is, the retardation layer exhibits flat wavelength dispersion characteristics. The retardation layer exhibiting a positive wavelength dispersion characteristic or a flat wavelength dispersion characteristic can be made thinner for obtaining a desired in-plane retardation value than the retardation layer exhibiting a reverse wavelength dispersion characteristic. Here, since the bending elasticity of the circularly polarizing plate is inversely proportional to the cube of the thickness of the circularly polarizing plate, the thinner the thickness of the circularly polarizing plate, the better the bending resistance. Therefore, a circularly polarizing plate using a retardation layer exhibiting a positive wavelength dispersion characteristic or a flat wavelength dispersion characteristic is thin and has excellent bending resistance. Such a circular polarizing plate can be suitably used for a bendable image display device. Further, in general, a retardation layer exhibiting a positive wavelength dispersion characteristic or a flat wavelength dispersion characteristic may have an undesired coloring in the reflected hue as compared with a retardation layer exhibiting a reverse wavelength dispersion characteristic. As described above, by having the dye compound in any of the layers constituting the circular polarizing plate, the reflected hue can be brought closer to neutral. Therefore, the circularly polarizing plate of the present embodiment has excellent bending resistance and can realize a neutral reflected hue.

B. Dye compound As described above, the dye compound exists in the wavelength region where the maximum absorption wavelength of the absorption spectrum is 650 nm or more. The maximum absorption wavelength of the absorption spectrum of the dye compound preferably exists in the wavelength region of 650 nm to 750 nm, and more preferably exists in the wavelength region of 670 nm to 730 nm. By using such a dye compound, it is possible to bring the reflected hue of the circularly polarizing plate closer to neutral while suppressing the decrease in the visible light transmittance of the circularly polarizing plate. By suppressing the decrease in the visible light transmittance of the circularly polarizing plate, it is possible to suppress the decrease in the white brightness when used in an image display device.

The absorption half width of the dye compound is preferably 120 nm or less, and more preferably 5 nm to 110 nm. The absorption half width of the dye compound can be measured from the permeation absorption spectrum of the solution of the dye compound under the following measurement conditions using an ultraviolet-visible spectrophotometer (U-4100, manufactured by Hitachi High-Tech Science Co., Ltd.). Typically, from the spectroscopic spectrum measured by adjusting the concentration so that the absorbance of the maximum absorption wavelength becomes 1.0, the wavelength interval (half width at half maximum) between two points that becomes 50% of the peak value is the dye compound. The absorption half width of.
(Measurement condition)
Solvent: Toluene or chloroform Cell: Quartz cell Optical path length: 10 mm

The dye compound may be any compound as long as the maximum absorption wavelength of the absorption spectrum exists in the above wavelength region, and its structure and the like are not particularly limited. Examples of the dye compound include an organic dye compound and an inorganic dye compound, and among these, an organic dye compound is preferable from the viewpoint of maintaining dispersibility and transparency. The dye compound may be used alone or in combination of two or more.

Examples of the dye compound include imonium-based, nickeldithiol-based, phthalocyanine-based, cyanine-based, azo-based, quinophthalone-based, indigo-based, and porphyrin-based.

As the dye compound, a commercially available compound can be preferably used. Specifically, as the phthalocyanine compound, FDR-003 (manufactured by Yamada Chemical Co., Ltd.) and FDR-004 (Yamada Chemical Co., Ltd.) can be used. Made) can be mentioned. Details of the dye compound are described in, for example, Japanese Patent Application Laid-Open No. 2016-188357, and the description is incorporated herein by reference.

When the pressure-sensitive adhesive layer contains the above-mentioned dye compound, the content of the dye compound in the pressure-sensitive adhesive layer is preferably 0.01 part by weight to 10 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer. , More preferably about 0.05 parts by weight to 5 parts by weight. By setting the addition amount of the dye compound within the above range, it is possible to bring the reflected hue of the circularly polarizing plate closer to neutral while suppressing the decrease in the visible light transmittance of the circularly polarizing plate.

C. Phase difference layer As described above, the in-plane phase difference of the phase difference layer preferably satisfies the relationship of Re (450) / Re (550)> 1, and more preferably 1.1> Re (450) / Re. (550)> 1 is satisfied.

The in-plane retardation of the retardation layer preferably satisfies 115 nm ≦ Re (550) ≦ 135 nm. The Re (550) of the retardation layer is more preferably 118 nm to 132 nm, still more preferably 120 nm to 130 nm.

The thickness of the retardation layer is preferably 1 μm to 50 μm, more preferably 2 μm to 40 μm, and further preferably 3 μm to 30 μm.

The retardation layer is typically composed of a retardation film that satisfies the above characteristics. The retardation film can be formed by stretching any suitable resin film. In one embodiment, the resin forming the retardation film has an alicyclic structure. Examples of the resin forming the retardation film include polycarbonate resin, cyclic olefin resin, cellulose resin, polyester resin, polyvinyl alcohol resin, polyamide resin, polyimide resin, polyether resin, and polystyrene resin. , Acrylic resin, polyester carbonate resin and the like. Among these, a polycarbonate-based resin or a cyclic olefin-based resin can be preferably used.

As the polycarbonate-based resin, any suitable polycarbonate resin can be used as long as the effects of the present invention can be obtained. Preferably, the polycarbonate resin is selected from the group consisting of structural units derived from isosorbide dihydroxy compounds and alicyclic diols, alicyclic dimethanol, di, tri or polyethylene glycol, and alkylene glycols or spiroglycols. Includes structural units derived from at least one dihydroxy compound. More preferably, the polycarbonate resin contains a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol and / or a structural unit derived from di, tri or polyethylene glycol. The polycarbonate resin may contain structural units derived from other dihydroxy compounds, if necessary. Details of a method for producing a polycarbonate resin and a retardation film that can be suitably used in the present invention are described in, for example, International Publication No. 2011/062239, and the description is incorporated herein by reference. To.

The cyclic olefin resin is a general term for resins polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A No. 1-240517, JP-A-3-14882, JP-A-3-122137, and the like. The resin used is mentioned. Specific examples include a ring-opening (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and an α-olefin such as ethylene and propylene (typically, a random copolymer). , And a grafted polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene-based monomers. Examples of the norbornene-based monomer include the monomers described in JP-A-2015-210459. Various products of the cyclic olefin resin are commercially available. Specific examples include Zeon Corporation's product names "Zeonex" and "Zeonoa", JSR's product name "Arton", TICONA's product name "Topus", and Mitsui Chemicals' product name. "APEL" can be mentioned.

As a method for producing the retardation film, any suitable method including a stretching step of the resin film can be adopted. Examples of the stretching method include horizontal uniaxial stretching (fixed end biaxial stretching), sequential biaxial stretching, and diagonal stretching. The stretching temperature is preferably 125 to 160 ° C, more preferably 130 to 150 ° C.

In one embodiment, the retardation film is made by uniaxially stretching or fixed end uniaxially stretching the resin film. Specific examples of the fixed-end uniaxial stretching include a method of stretching the resin film in the width direction (lateral direction) while running the resin film in the longitudinal direction. The draw ratio is preferably 1.1 times to 3.5 times.

In another embodiment, the retardation film is produced by continuously obliquely stretching a long resin film in a direction of an angle θ with respect to a longitudinal direction. By adopting diagonal stretching, a long stretched film having an orientation angle of an angle θ with respect to the longitudinal direction of the film (a slow axis in the direction of the angle θ) can be obtained. Roll-to-roll is possible and the manufacturing process can be simplified.

Examples of the stretching machine used for diagonal stretching include a tenter type stretching machine capable of applying a feeding force, a pulling force, or a pulling force at different speeds in the lateral and / or vertical directions. The tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but any suitable stretching machine can be used as long as the long resin film can be continuously and diagonally stretched.

The method for manufacturing a retardation film by diagonal stretching is to grip the left and right edges of the film with variable pitch type left and right clips whose clip pitch in the vertical direction changes (grip step); preheating the film. (Preheating step); The film is stretched diagonally by increasing the clip pitch of one clip and decreasing the clip pitch of the other clip while increasing the distance between the left and right clips (first). Diagonal stretching step); While increasing the distance between the left and right clips, the clip pitch of one clip is maintained or reduced so that the clip pitches of the left and right clips are equal, and the clip of the other clip is maintained or reduced. Increasing the pitch may include diagonally stretching the film (second diagonal stretching step); and releasing the clip that grips the film (release step). Hereinafter, each step will be described in detail.

C-1. Gripping Step First, with reference to FIGS. 2 to 4, a stretching device that can be used in a method for manufacturing a retardation film including this step will be described. FIG. 2 is a schematic plan view illustrating an overall configuration of an example of a stretching device that can be used in a method for manufacturing a retardation film. 3 and 4 are schematic plan views of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 2, respectively, FIG. 3 shows a state where the clip pitch is the minimum, and FIG. 4 shows a state where the clip pitch is the minimum. Indicates the maximum clip pitch. The stretching device 100 has an endless loop 10L and an endless loop 10R having a large number of clips 20 for gripping the film on both the left and right sides symmetrically in a plan view. In the present specification, the endless loop on the left side when viewed from the inlet side of the film is referred to as the endless loop 10L on the left side, and the endless loop on the right side is referred to as the endless loop 10R on the right side. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 70 and circulate in a loop shape, respectively. The endless loop 10R on the left side circulates in the counterclockwise direction, and the endless loop 10R on the right side circulates in the clockwise direction. In the stretching device, a gripping zone A, a preheating zone B, a first diagonal stretching zone C, a second diagonal stretching zone D, and a release zone E are provided in this order from the inlet side to the outlet side of the sheet. .. It should be noted that each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, first diagonally stretched, second diagonally stretched and released, and is mechanically and structurally independent. It does not mean a parcel. Also note that the length ratio of each zone in the stretching device of FIG. 2 is different from the actual length ratio.

In the gripping zone A and the preheating zone B, the left and right endless loops 10R and 10L are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the first diagonally stretched zone C and the second diagonally stretched zone D, the separation distances of the left and right endless loops 10R and 10L correspond to the width of the film after stretching from the side of the preheating zone B toward the release zone E. It is said that it will gradually expand to. In the release zone E, the left and right endless loops 10R and 10L are configured to be substantially parallel to each other at a separation distance corresponding to the stretched width of the film.

The clip (clip on the left side) of the endless loop 10L on the left side and the clip (clip on the right side) 20 of the endless loop 10R on the right side can be cyclically moved independently. For example, the drive sprockets 11 and 12 of the endless loop 10L on the left side are rotationally driven in the counterclockwise direction by the electric motors 13 and 14, and the drive sprockets 11 and 12 of the endless loop 10R on the right side are clocked by the electric motors 13 and 14. It is driven to rotate in the clockwise direction. As a result, a running force is applied to the clip-supporting member 30 of the drive roller (not shown) engaged with the drive sprockets 11 and 12. As a result, the endless loop 10L on the left side circulates in the counterclockwise direction, and the endless loop 10R on the right side circulates in the clockwise direction. By driving the electric motor on the left side and the electric motor on the right side independently, the endless loop 10L on the left side and the endless loop 10R on the right side can be patrolled independently.

Further, the clip (clip on the left side) of the endless loop 10L on the left side and the clip (clip on the right side) 20 of the endless loop 10R on the right side are each of a variable pitch type. That is, the left and right clips 20 and 20 can independently change the clip pitch (distance between clips) in the vertical direction (MD) with movement. The variable pitch type can be realized by any suitable configuration. Hereinafter, the link mechanism (pantograph mechanism) will be described as an example.

As shown in FIGS. 3 and 4, a clip supporting member 30 having an elongated rectangular shape in the horizontal direction in a plan view is provided to individually support the clips 20. Although not shown, the clip-supporting member 30 is formed into a strong frame structure having a closed cross section by an upper beam, a lower beam, a front wall (a wall on the clip side), and a rear wall (a wall on the opposite side of the clip). The clip-supporting member 30 is provided so as to roll on the traveling road surfaces 81 and 82 by the traveling wheels 38 at both ends thereof. In addition, in FIGS. 3 and 4, the traveling wheel on the front wall side (the traveling wheel rolling on the traveling road surface 81) is not shown. The traveling road surfaces 81 and 82 are parallel to the reference rail 70 over the entire area. A long hole 31 is formed on the rear side (opposite side of the clip) of the upper beam and the lower beam of the clip supporting member 30 along the longitudinal direction of the clip supporting member, and the slider 32 can slide in the longitudinal direction of the elongated hole 31. Is engaged in. In the vicinity of the clip 20 side end of the clip supporting member 30, one first shaft member 33 is vertically provided so as to penetrate the upper beam and the lower beam. On the other hand, the slider 32 of the clip-supporting member 30 is provided with a second shaft member 34 vertically penetrating. One end of the main link member 35 is pivotally connected to the first shaft member 33 of each clip-supporting member 30. The other end of the main link member 35 is pivotally connected to the second shaft member 34 of the adjacent clip-supporting member 30. In addition to the main link member 35, one end of the sub-link member 36 is pivotally connected to the first shaft member 33 of each clip-supporting member 30. The other end of the sub-link member 36 is pivotally connected to the intermediate portion of the main link member 35 by a pivot 37. As shown in FIG. 3, the more the slider 32 moves to the rear side (opposite side of the clip side) of the clip supporting member 30, the more the clip supporting members 30 move to each other due to the link mechanism by the main link member 35 and the sub link member 36. The pitch in the vertical direction (hereinafter, simply referred to as clip pitch) becomes smaller, and as shown in FIG. 4, the clip pitch becomes larger as the slider 32 moves to the front side (clip side) of the clip supporting member 30. .. Positioning of the slider 32 is performed by the pitch setting rail 90. As shown in FIGS. 3 and 4, the larger the clip pitch, the smaller the separation distance between the reference rail 70 and the pitch setting rail 90. Since the link mechanism is well known in the art, a more detailed description thereof will be omitted.

By diagonally stretching the film using the stretching device as described above, a retardation film having a slow phase axis in the diagonal direction (for example, a direction of 45 ° with respect to the vertical direction) can be produced. First, in the gripping zone A (the entrance of the film take-in of the stretching device 100), the left and right endless loops 10R and 10L clips 20 grip the both edges of the film to be stretched at a constant clip pitch equal to each other, and the left and right edges are gripped. The film is fed to the preheating zone B by the movement of the endless loops 10R and 10L (substantially, the movement of each clip supporting member 30 guided by the reference rail 70).

C-2. Preheating step In the preheating zone (preheating step) B, the left and right endless loops 10R and 10L are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched as described above. Basically, neither lateral stretching nor longitudinal stretching is performed, and the film is heated. However, the distance between the left and right clips (distance in the width direction) may be slightly increased in order to avoid problems such as the film bending due to preheating and contact with the nozzle in the oven.

In the preheating step, the film is heated to a temperature of T1 (° C.). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably Tg + 2 ° C. or higher, still more preferably Tg + 5 ° C. or higher. On the other hand, the heating temperature T1 is preferably Tg + 40 ° C. or lower, more preferably Tg + 30 ° C. or lower. Although it depends on the film used, the temperature T1 is, for example, 70 ° C. to 190 ° C., preferably 80 ° C. to 180 ° C.

The temperature raising time up to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent materials of the film and the manufacturing conditions (for example, the transport speed of the film). These temperature rise time and holding time can be controlled by adjusting the moving speed of the clip 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

C-3. First Diagonal Stretching Step In the first diagonal stretching zone (first diagonal stretching step) C, the distance between the left and right clips (more specifically, the separation distance between the left and right endless loops 10R and 10L) is expanded. While increasing the clip pitch of one clip and decreasing the clip pitch of the other clip, the film is stretched diagonally. By changing the clip pitch in this way, the left and right clips are moved at different speeds, whereby one side edge of the film is elongated in the longitudinal direction and the other side edge is contracted in the longitudinal direction. However, diagonal stretching can be performed. As a result, a slow axis can be developed with high uniaxial and in-plane orientation in a desired direction (eg, 45 ° with respect to the longitudinal direction).

Hereinafter, one embodiment of the first diagonal stretching will be specifically described with reference to FIGS. 5 and 6. _First , in the preheating zone B, the left and right clip pitches are both set to P1. P ₁ is the clip pitch when the film is gripped. Next, as soon as the film enters the first diagonally stretched zone C, the clip pitch of one clip (on the right side in the illustrated example) starts to increase, and the clip pitch of the other clip (on the left side in the illustrated example) begins to increase. Start decreasing. _In the _first diagonally stretched zone C, the clip pitch of the right clip is increased to P2 and the clip pitch of the left clip is decreased to P3. Therefore, at the end of the first diagonally stretched zone C (the start of the _second diagonally stretched zone D), the left clip moves at the clip pitch _P3 and the right clip moves at the clip pitch P2. ing. The clip pitch ratio can roughly correspond to the clip moving speed ratio. Therefore, the ratio of the clip pitches of the left and right clips can roughly correspond to the ratio of the draw ratios of the right side edge portion and the left side edge portion of the film in the MD direction.

In FIGS. 5 and 6, the position where the clip pitch of the right clip starts to increase and the position where the clip pitch of the left clip starts to decrease are both set as the start portions of the first diagonally stretched zone C, but unlike the illustrated example, they are different from the illustrated examples. The clip pitch of the left clip may begin to decrease after the clip pitch of the right clip begins to increase (eg, Figure 7), or the clip pitch of the right clip may begin to increase after the clip pitch of the left clip begins to decrease. Good (not shown). In one preferred embodiment, the clip pitch of the clip on one side begins to increase and then the clip pitch of the clip on the other side begins to decrease. According to such an embodiment, since the film has already been stretched to a certain extent (preferably about 1.2 to 2.0 times) in the width direction, even if the clip pitch on the other side is greatly reduced. Wrinkles are less likely to occur. Therefore, it is possible to stretch diagonally at an acute angle, and a retardation film having high uniaxial and in-plane orientation can be preferably obtained.

Similarly, in FIGS. 5 and 6, the clip pitch of the right clip continues to increase and the clip pitch of the left clip continues to decrease until the end of the first oblique extension zone C (the start of the second oblique extension zone D). However, unlike the illustrated example, either the increase or decrease of the clip pitch ends before the end of the first diagonally stretched zone C, and clips to the end of the first diagonally stretched zone C. The pitch may be maintained as it is.

The rate of change in the increased clip pitch (P ₂ / P ₁ ) is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, and even more preferably 1.35 to 1.65. .. The rate of change in clip pitch (P ₃ / P ₁ ) that decreases is, for example, 0.50 or more and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, and even more preferably. It is 0.55 to 0.85. When the rate of change of the clip pitch is within such a range, the slow axis can be developed with high uniaxial and in-plane orientation in the direction of approximately 45 degrees with respect to the longitudinal direction of the film.

As described above, the clip pitch can be adjusted by adjusting the separation distance between the pitch setting rail of the stretching device and the reference rail to position the slider.

The stretching ratio (W ₂ / W ₁ ) in the width direction of the film in the first diagonal stretching step is preferably 1.1 times to 3.0 times, more preferably 1.2 times to 2.5 times, still more preferable. Is 1.25 to 2.0 times. If the draw ratio is less than 1.1 times, galvanized iron-like wrinkles may occur on the side edge portion on the contracted side. Further, if the draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film becomes high, and the viewing angle characteristics may deteriorate when applied to a circular polarizing plate or the like.

In one embodiment, in the first diagonal stretching, the product of the rate of change in the clip pitch of one clip and the rate of change in the clip pitch of the other clip is preferably 0.7 to 1.5, more preferably 0.7. It is carried out so as to be 0.8 to 1.45, more preferably 0.85 to 1.40. If the product of the rate of change is within such a range, a retardation film having high uniaxial and in-plane orientation can be obtained.

The first diagonal stretching can typically be done at temperature T2. The temperature T2 is preferably Tg-20 ° C. to Tg + 30 ° C., more preferably Tg-10 ° C. to Tg + 20 ° C., and particularly preferably about Tg, with respect to the glass transition temperature (Tg) of the resin film. Although it depends on the resin film used, the temperature T2 is, for example, 70 ° C. to 180 ° C., preferably 80 ° C. to 170 ° C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ± 2 ° C. or higher, more preferably ± 5 ° C. or higher. In one embodiment, T1> T2, so the film heated to temperature T1 in the preheating step can be cooled to temperature T2.

C-4. Second diagonal stretching step In the second diagonal stretching zone (second diagonal stretching step) D, the distance between the left and right clips (more specifically, the separation distance between the left and right endless loops 10R and 10L) is expanded. While maintaining or decreasing the clip pitch of the clip on one side so that the clip pitches of the left and right clips are equal, and increasing the clip pitch of the clip on the other side, the film is stretched diagonally. By diagonally stretching while reducing the difference between the left and right clip pitches in this way, it is possible to sufficiently stretch in the diagonal direction while relaxing the excess stress. Further, since the film can be subjected to the release process in a state where the moving speeds of the left and right clips are equal, it is difficult for the film transfer speed and the like to vary when the left and right clips are released, and the subsequent winding of the film is preferable. Can be done in.

Hereinafter, one embodiment of the second diagonal stretching will be specifically described with reference to FIGS. 5 and 6. First, as soon as the film enters the second diagonally stretched zone D, it begins to increase the clip pitch of the left clip. In the _second diagonally stretched zone D, the clip pitch of the left clip is increased to P2. On the other hand, the clip pitch of the right clip is maintained at P2 in the _second diagonally stretched zone D. Therefore, at the end of the second diagonally stretched zone D (the start of the release zone E), _both the left clip and the right clip are supposed to move at the clip pitch P2.

The rate of change in the increased clip pitch (P ₂ / P ₃ ) in the above embodiment is not limited as long as a retardation film having desired optical characteristics can be obtained. The rate of change (P ₂ / P ₃ ) is, for example, 1.3 to 4.0, preferably 1.5 to 3.0.

Next, another embodiment of the second diagonal stretching will be specifically described with reference to FIGS. 8 and 9. First, as soon as the film enters the second diagonally stretched zone D, the clip pitch of the right clip starts to decrease, and the clip pitch of the left clip starts to increase. _In the _second diagonally stretched zone D, the clip pitch of the right clip is reduced to P4 and the clip pitch of the left clip is increased to P4. Therefore, at the end of the second diagonally stretched zone D (the start of the release zone E), both the left clip and the right clip are supposed to move at the clip pitch _P4 . In the illustrated example, for the sake of simplicity, both the clip pitch decrease start position of the right clip and the clip pitch increase start position of the left clip are set as the start portions of the second diagonal extension zone D, but these positions are different. It may be a position. Similarly, the clip pitch decrease end position of the right side clip and the clip pitch increase end position of the left side clip may be different positions.

The rate of change in the decreasing clip pitch (P ₄ / P ₂ ) and the rate of change in the increasing clip pitch (P ₄ / P ₃ ) in the above embodiment are not limited as long as the effects of the present invention are not impaired. The rate of change (P ₄ / P ₂ ) is, for example, 0.4 or more and less than 1.0, preferably 0.6 to 0.95. The rate of change (P ₄ / P ₃ ) is, for example, more than 1.0 and 2.0 or less, preferably 1.2 to 1.8. Preferably, P ₄ is P ₁ or higher. If P ₄ <P ₁ , problems such as wrinkles on the side edges and high biaxiality may occur.

The stretching ratio (W ₃ / W ₂ ) in the width direction of the film in the second diagonal stretching step is preferably 1.1 times to 3.0 times, more preferably 1.2 times to 2.5 times, still more preferable. Is 1.25 to 2.0 times. If the draw ratio is less than 1.1 times, galvanized iron-like wrinkles may occur on the side edge portion on the contracted side. Further, if the draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film becomes high, and the viewing angle characteristics may deteriorate when applied to a circular polarizing plate or the like. Further, the stretching ratio (W ₃ / W ₁ ) in the width direction in the first diagonal stretching step and the second diagonal stretching step is preferably 1.2 times to 4.0 times from the same viewpoint as above. , More preferably 1.4 to 3.0 times.

In one embodiment, the first diagonal stretch and the second diagonal stretch have a diagonal stretch ratio obtained from the following formula (1), preferably 2.0 or more, more preferably 2.0 to 4.0. , More preferably 2.5 to 3.5. If the diagonal draw ratio is less than 2.0, the biaxiality may be high or the in-plane orientation may be low.

（式中、
Ｗ_１は、第１の斜め延伸前のフィルム幅、
Ｗ_３は、第２の斜め延伸後のフィルム幅、
ｖ_３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチに変化した際のクリップ移動速度、
t_３は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップが、予熱ゾーンに入ってから、第２の斜め延伸工程が終了するまでの時間、
t_３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが、予熱ゾーンに入ってから、第２の斜め延伸工程が終了するまでの時間
を表す。）

(During the ceremony,
W ₁ is the film width before the first diagonal stretching,
W ₃ is the film width after the second diagonal stretching,
v _3'is the clip moving speed when the clip pitch of the clip is changed to a predetermined clip pitch in the second diagonal stretching step with respect to the clip whose clip pitch is increased in the first diagonal stretching step.
t3 is the time from when the clip whose clip pitch is reduced in the _first diagonal stretching step enters the preheating zone to the end of the second diagonal stretching step.
t _3'represents the time from when the clip whose clip pitch is increased in the first diagonal stretching step enters the preheating zone to the end of the second diagonal stretching step. )

With respect to the above v ₃ ', the predetermined clip pitch means the clip pitch after the clip pitch whose increase has been completed in the first diagonal stretching step is maintained or decreased in the second diagonal stretching step, and the above C-3. Corresponds to P ₂ or P ₄ in the description of the section. Further, with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip corresponds to a predetermined clip pitch in the _first diagonal stretching step (P2 in the above description of item C-3). ), If the moving speed of the clip is v ₂ ',
When v ₂ '= v ₃ ', the above t ₃ is expressed by the following equation (2), and the above t'3 is expressed by the following equation ( ₃ ).
In the case of v ₂ '> v ₃ ', the above t ₃ is represented by the following formula (4), and the above _t'3 is represented by the following formula (5).

Hereinafter, equations (2) to (4) will be described. In the explanation of each symbol in the formula, FIGS. 10 to 12 can be referred to. The asterisk mark (*) in the equations (1) to (5) is a multiplication symbol. The unit of film width is m, the unit of speed is m / sec, the unit of distance is m, and the unit of time is sec.

（式中、
ａ１＝（ｖ２－ｖ３）／（Ｌ２－Ｌ３）、
ｂ１＝ｖ３－ａ１＊Ｌ３、
ａ＝（ｖ１－ｖ２）／（Ｌ１－Ｌ２）、
ｂ＝ｖ２－ａ＊Ｌ２であり、
ｖ１は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_３に対応する）に減少した際のクリップ移動速度、
ｖ３は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_２またはＰ_４に対応する）に増大した際のクリップ移動速度であり、
Ｌ１は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを減少し始めるまでの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを増大し始める箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第２の斜め延伸ゾーン出口までの距離）
である。）

(During the ceremony,
a1 = (v2-v3) / (L2-L3),
b1 = v3-a1 * L3,
a = (v1-v2) / (L1-L2),
b = v2-a * L2,
v1 is the clip moving speed when the clip whose clip pitch is reduced in the first diagonal stretching step passes through the preheating zone.
In v2, with respect to the clip whose clip pitch is reduced in the first diagonal stretching step, the clip pitch of the clip corresponds to a predetermined clip pitch in the first diagonal stretching step (P3 in the description of the above item C- ₃ ). Clip movement speed when reduced to),
In v3, with respect to the clip whose clip pitch is reduced in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the _second diagonal stretching step (P2 or P in the above description of item C-3). It is the clip movement speed when it is increased to (corresponding to ₄ ).
L1 is the distance from the preheating zone inlet to the clip whose clip pitch is reduced in the first diagonal stretching step starts to reduce the clip pitch (in one embodiment, from the preheating zone inlet to the preheating zone outlet). distance),
L2 is the distance from the preheating zone inlet to the point where the clip that reduces the clip pitch in the first diagonal stretching step begins to increase the clip pitch (in one embodiment, the first diagonal from the preheating zone inlet). Distance to the extension zone exit),
L3 is the distance from the preheating zone inlet to the point where the clip that reduces the clip pitch in the first diagonal stretching step finishes increasing the clip pitch (in one embodiment, the second diagonal from the preheating zone inlet). Distance to the extension zone exit)
Is. )

（式中、
ａ’＝（ｖ１’－ｖ２’）／（Ｌ１’－Ｌ２’）、
ｂ’＝ｖ３’－ａ’＊Ｌ２’であり、
ｖ１’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_２に対応する）に増大した際のクリップ移動速度
ｖ３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップが第２の斜め延伸ゾーンを通過する際のクリップ移動速度であり、
Ｌ１’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し始めるまでの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３’は、予熱ゾーン入口から、第２の斜め延伸ゾーン出口までの距離
である。）

(During the ceremony,
a'= (v1'-v2') / (L1'-L2'),
b'= v3'-a'* L2',
v1'is the clip moving speed when the clip that increases the clip pitch in the first diagonal stretching step passes through the preheating zone.
In v2', with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the first diagonal stretching step (in P2 in the above description of item C- ₃ ). The clip movement speed v3'when increased to (corresponding) is the clip movement speed when the clip passes through the second diagonal stretching zone with respect to the clip whose clip pitch is increased in the first diagonal stretching step. can be,
L1'is the distance from the preheating zone inlet to the clip whose clip pitch is increased in the first diagonal stretching step starts to increase the clip pitch (in one embodiment, from the preheating zone inlet to the preheating zone outlet). Distance),
L2'is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first diagonal stretching step finishes increasing the clip pitch (in one embodiment, the first from the preheating zone inlet). Distance to the exit of the diagonal extension zone),
L3'is the distance from the entrance of the preheating zone to the exit of the second diagonal extension zone. )

（式中、ａ１、ｂ１、ａ、ｂ、ｖ１、ｖ２、ｖ３、Ｌ１、Ｌ２およびＬ３は、式（２）に関して定義したとおりである。）

(In the formula, a1, b1, a, b, v1, v2, v3, L1, L2 and L3 are as defined with respect to the formula (2).)

（式中、
ａ’＝（ｖ１’－ｖ２’）／（Ｌ１’－Ｌ２’）、
ｂ’＝ｖ２’－ａ’＊Ｌ２’、
ａ’’＝（ｖ２’－ｖ３’）／（Ｌ２’－Ｌ３’）、
ｂ’’＝ｖ３’－ａ’’＊Ｌ３’であり、
ｖ１’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_２に対応する）に増大した際のクリップ移動速度、
ｖ３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_４に対応する）に減少した際のクリップ移動速度であり、
Ｌ１’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し始める箇所までの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが第２の斜め延伸工程でクリップピッチを所定のクリップピッチ（上記Ｃ－３項の説明におけるＰ_４に対応する）に減少し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第２の斜め延伸ゾーン出口までの距離）である。）

(During the ceremony,
a'= (v1'-v2') / (L1'-L2'),
b'= v2'-a' * L2',
a'' = (v2'-v3') / (L2'-L3'),
b''= v3'-a'' * L3',
v1'is the clip moving speed when the clip that increases the clip pitch in the first diagonal stretching step passes through the preheating zone.
In v2', with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the first diagonal stretching step (in P2 in the above description of item C- ₃ ). Clip movement speed when increased to (corresponding),
In v3', with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip becomes a predetermined clip pitch in the second diagonal stretching step (in P4 in the above description of item C- ₃ ). It is the clip movement speed when it is reduced to (corresponding).
L1'is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first diagonal stretching step starts to increase the clip pitch (in one embodiment, from the preheating zone inlet to the preheating zone outlet). Distance to),
L2'is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first diagonal stretching step finishes increasing the clip pitch (in one embodiment, the first from the preheating zone inlet). Distance to the exit of the diagonal extension zone),
In L3', the clip whose clip pitch is increased in the first diagonal stretching step from the preheating zone inlet has a predetermined clip pitch in the second diagonal stretching step (P4 in the above description of item C- ₃ ). The distance to the point where the decrease ends (in one embodiment, the distance from the inlet of the preheating zone to the exit of the second oblique extension zone). )

The second diagonal stretching can typically be done at temperature T3. The temperature T3 can be equivalent to the temperature T2.

C-5. Release Step Finally, the clip holding the film is released to obtain a retardation film. If necessary, the film is heat treated to fix the stretched state and cooled before releasing the clip.

The heat treatment can typically be performed at temperature T4. The temperature T4 depends on the film to be stretched, and may be T3 ≧ T4 or T3 <T4. Generally, when the film is an amorphous material, T3 ≧ T4, and when the film is a crystalline material, the crystallization treatment may be performed by setting T3 <T4. When T3 ≧ T4, the difference between the temperatures T3 and T4 (T3-T4) is preferably 0 ° C to 50 ° C. The heat treatment time is typically 10 seconds to 10 minutes.

The heat-fixed film is usually cooled to Tg or less, and after releasing the clips, the clip gripping portions at both ends of the film are cut and wound up.

D. Adhesive Layer The adhesive layer is formed of any suitable adhesive. Examples of such adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, and polyacrylamide adhesives. Examples thereof include adhesives and cellulose-based adhesives. Among these, an acrylic pressure-sensitive adhesive containing a (meth) acrylic polymer is preferably used as the base polymer. In one embodiment, the pressure-sensitive adhesive layer comprises a dye compound, as described above.

The (meth) acrylic polymer contains an alkyl (meth) acrylate as a main component as a monomer unit. Examples of the alkyl (meth) acrylate include those having a linear or branched alkyl group having 1 to 24 carbon atoms at the ester terminal. The alkyl (meth) acrylate may be used alone or in combination of two or more. The "alkyl (meth) acrylate" refers to an alkyl acrylate and / or an alkyl methacrylate.

The alkyl (meth) acrylate having an alkyl group having 1 to 24 carbon atoms at the ester terminal is preferably 40% by weight or more based on the total amount of the monofunctional monomer component forming the (meth) acrylic polymer, and is preferably 50. By weight% or more is more preferable, and 60% by weight or more is further preferable.

The monomer component may contain a copolymerization monomer other than the alkyl (meth) acrylate as the monofunctional monomer component. The copolymerizable monomer can be used as the remainder of the alkyl (meth) acrylate in the monomer component. The copolymerization monomer may include, for example, a cyclic nitrogen-containing monomer. As the cyclic nitrogen-containing monomer, a monomer having a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group and having a cyclic nitrogen structure can be used without particular limitation. The cyclic nitrogen structure preferably has a nitrogen atom in the cyclic structure. The content of the cyclic nitrogen-containing monomer is preferably 0.5 to 50% by weight, more preferably 0.5 to 40% by weight, based on the total amount of the monofunctional monomer components forming the (meth) acrylic polymer. %, More preferably 0.5 to 30% by weight.

The monomer component forming the (meth) acrylic polymer may contain other functional group-containing monomers, if necessary. Examples of such a monomer include a carboxyl group-containing monomer, a monomer having a cyclic ether group, and a hydroxyl group-containing monomer.

As the (meth) acrylic polymer, one having a weight average molecular weight in the range of 500,000 to 3,000,000 is usually used. Considering durability, particularly heat resistance, it is preferable to use one having a weight average molecular weight of 700,000 to 2.7 million. Further, it is preferably 800,000 to 2.5 million. If the weight average molecular weight is less than 500,000, it is not preferable in terms of heat resistance. Further, when the weight average molecular weight is larger than 3 million, a large amount of diluting solvent is required to adjust the viscosity to be suitable for coating, which is not preferable because it increases the cost. The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

As a method for producing the (meth) acrylic polymer, any appropriate method such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, bulk polymerization, and various radical polymerization such as emulsion polymerization can be adopted. Further, the obtained (meth) acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

E. Polarizer As the splitter, any suitable splitter can be adopted. For example, the resin film forming the polarizing element may be a single-layer resin film or a laminated body having two or more layers.

Specific examples of the polarizing element composed of a single-layer resin film include a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples thereof include those which have been dyed and stretched with a bicolor substance such as iodine and a bicolor dye, and polyene-based oriented films such as a dehydrated product of PVA and a dehydrogenated product of polyvinyl chloride. Preferably, since the PVA-based film is excellent in optical properties, a polarizing element obtained by dyeing a PVA-based film with iodine and uniaxially stretching it is used.

The dyeing with iodine is performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed while dyeing. Further, it may be dyed after being stretched. If necessary, the PVA-based film is subjected to a swelling treatment, a crosslinking treatment, a cleaning treatment, a drying treatment and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible not only to clean the dirt and blocking inhibitor on the surface of the PVA-based film, but also to swell the PVA-based film to prevent uneven dyeing. Can be prevented.

Specific examples of the polarizing element obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a resin base material and the resin. Examples thereof include a polarizing element obtained by using a laminate with a PVA-based resin layer coated and formed on a base material. The polarizing element obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying it. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer a stator. obtain. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching may further comprise, if necessary, stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in boric acid aqueous solution. The obtained resin base material / polarizing element laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizing element), and the resin base material is peeled off from the resin base material / polarizing element laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. Details of the method for producing such a polarizing element are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

The thickness of the splitter is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the stator is preferably 1 μm to 25 μm, more preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the splitter is in such a range, curling during heating can be satisfactorily suppressed, and good appearance durability during heating can be obtained.

The splitter preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the substituent is 35.0% to 46.0%, preferably 37.0% to 46.0%. The degree of polarization of the polarizing element is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

F. Protective layer The protective layer is formed of any suitable protective film that can be used as a film to protect the polarizing element. Specific examples of the material that is the main component of the protective film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone. Examples thereof include transparent resins such as polyester-based, polystyrene-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, and acetate-based. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

The thickness of the protective film is preferably 10 μm to 100 μm. The protective film may be laminated on the polarizing element via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be laminated in close contact with the polarizing element (without interposing an adhesive layer). good. If necessary, a surface treatment layer such as a hard coat layer, an antiglare layer and an antireflection layer may be formed on the protective film arranged on the outermost surface of the circularly polarizing plate.

G. Image display device The circularly polarizing plate according to the above items A to F can be used in an image display device. Therefore, the present invention also includes an image display device using such an optical laminate. Typical examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to the embodiment of the present invention includes the circular polarizing plate according to the above items A to F.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method and evaluation method for each characteristic are as follows.
(1) Thickness Measured using a digital gauge (manufactured by Ozaki Seisakusho Co., Ltd., product name "DG-205 type pds-2").
(2) In-plane phase difference With respect to the retardation film used in Examples and Comparative Examples, the in-plane retardation was measured using Axoscan (manufactured by Axometrics). The measurement temperature was 23 ° C., and the measurement wavelengths were 450 nm and 550 nm.
(3) Reflectance and Reflective Hue A black image is displayed on the organic EL panel obtained in Examples and Comparative Examples, and the front reflectance and the reflected hue are measured using a spectrophotometer CM-2600d manufactured by Konica Minolta. bottom.
Further, for the reflected hue u'v' obtained by the measurement, the distance from the neutral point ((u', v') = (0.210, 0.471)) on the chromaticity diagram is calculated and obtained. The value was set to Δu'v'.
(4) Luminance A white image was displayed on the organic EL panels obtained in Examples and Comparative Examples, and the front luminance was measured using a spectroradiometer (trade name “SR-UL1R”) manufactured by TOPCON.
(5) Flexibility The circularly polarizing plates obtained in Examples and Comparative Examples were cut into a size of 150 mm in length × 20 mm in width and used as an evaluation sample.
The evaluation sample is hung on a horizontally arranged mandrel having a diameter of 12 mm with a protective film on the outside, and a metal ball having a diameter of 1 mm is sandwiched between the evaluation sample and the mandrel for evaluation. The sample was held for 10 seconds with a total load of 300 g applied to both ends. Then, the bending resistance of the circularly polarizing plate was evaluated according to the following criteria.
◯ ・ ・ ・ No abnormality was found in the circularly polarizing plate.
× ... The protective film was cracked.

[Example 1]
1. 1. Preparation of polarizing plate While uniaxially stretching a long roll of a polyvinyl alcohol film (manufactured by Kuraray, product name "PE6000") with a thickness of 60 μm in the long direction so as to be 5.9 times in the long direction with a roll stretching machine. At the same time, swelling, dyeing, cross-linking, and washing treatment were performed, and finally a drying treatment was performed to prepare a polarizing element having a thickness of 22 μm.
Specifically, the swelling treatment was carried out by stretching 2.2 times while treating with pure water at 20 ° C. Next, the dyeing treatment was carried out in an aqueous solution at 30 ° C. in which the weight ratio of iodine and potassium iodide was adjusted so that the transmittance of the produced polarizing film was 43.0% and the weight ratio was 1: 7. However, it was stretched 1.4 times. Further, the cross-linking treatment adopted a two-step cross-linking treatment, and the first-step cross-linking treatment was carried out 1.2 times while being treated with an aqueous solution in which boric acid and potassium iodide were dissolved at 40 ° C. The boric acid content of the aqueous solution of the first-step crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. The second-step cross-linking treatment was carried out by stretching 1.6 times while treating with an aqueous solution in which boric acid and potassium iodide were dissolved at 65 ° C. The boric acid content of the aqueous solution of the second-step crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. The washing treatment was carried out with an aqueous potassium iodide solution at 20 ° C. The potassium iodide content of the aqueous solution of the washing treatment was set to 2.6% by weight. Finally, the drying treatment was carried out at 70 ° C. for 5 minutes to obtain a stator.
A low-reflection TAC film (thickness: 72 μm, large) having a hard coat (HC) layer formed on one side of the TAC film by a low-reflection hard coat treatment on one side of the obtained polarizing element via a polyvinyl alcohol-based adhesive. A product name "DSG-03HL" manufactured by Nippon Printing Co., Ltd.) was bonded to obtain a long polarizing plate having a protective film / polarizing element configuration.
2. 2. Preparation of adhesive In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 94.9 parts of butyl acrylate, 5 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, and dibenzoyl 0.3 part of peroxide was added to 100 parts of the monomer (solid content) together with ethyl acetate and reacted at 60 ° C. for 7 hours under a nitrogen gas stream, and then ethyl acetate was added to the reaction solution and weight averaged. A solution containing an acrylic polymer having a molecular weight of 2.2 million (solid content concentration: 30% by weight) was obtained. 0.6 parts of trimethylolpropane tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L") and 0.075 parts of γ-glycidoxypropylmethoxy per 100 parts of the solid content of the acrylic polymer solution. Silane (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name "KBM-403") and 1 part by weight of FDR-003 (manufactured by Yamada Chemical Co., Ltd., maximum absorption wavelength of absorption spectrum: 702 nm, half-price range of absorption: 100 nm) and stirred to obtain a dye compound-containing pressure-sensitive adhesive.
The above dye compound-containing pressure-sensitive adhesive was applied to a separator made of a polyester film surface-treated with a silicone-based release agent and heat-treated at 155 ° C. for 3 minutes to obtain a pressure-sensitive adhesive layer having a thickness of 20 μm.
3. 3. Preparation of retardation film 47.19 parts by mass of tricyclodecanedimethanol, 175.1 parts by mass of diphenyl carbonate, and 0.979 parts by mass of 0.2% by mass aqueous solution of cesium carbonate as a catalyst with respect to 81.98 parts by mass of isosorbide. The part was put into a reaction vessel, and in a nitrogen atmosphere, as the first step of the reaction, the heating tank temperature was heated to 150 ° C., and the raw material was dissolved while stirring as necessary (about 15). Minutes).
Next, the generated phenol was extracted from the reaction vessel while the pressure was changed from normal pressure to 13.3 kPa and the heating tank temperature was raised to 190 ° C. in 1 hour. After holding the entire reaction vessel at 190 ° C. for 15 minutes, as the second step, the pressure inside the reaction vessel is set to 6.67 kPa, the heating tank temperature is raised to 230 ° C. in 15 minutes, and the generated phenol is generated. It was taken out of the reaction vessel. Since the stirring torque of the stirrer increased, the temperature was raised to 250 ° C. in 8 minutes, and the pressure in the reaction vessel was brought to 0.200 kPa or less in order to remove the generated phenol. After reaching a predetermined stirring torque, the reaction was terminated, and the produced reactant was extruded into water to obtain pellets of a polycarbonate copolymer.
This polycarbonate resin is used for a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220 ° C), T-die (width 300 mm, set temperature: 220 ° C), chill roll (set temperature: 120 to 130 ° C). A polycarbonate resin film having a thickness of 60 μm was obtained by using a film forming apparatus equipped with a temperature) and a winder.
The polycarbonate resin film was obliquely stretched using the stretching device shown in FIG. 2 to obtain a retardation film. The preheating temperature and the stretching temperature were 140.5 ° C., and the diagonal stretching ratio represented by the formula (1) was 3.0 times. The stretching direction was 45 ° with respect to the longitudinal direction of the film. Then, in the release zone, the film was held at 125 ° C. for 60 seconds for heat fixation. After cooling the heat-fixed film to 100 ° C., the left and right clips were released. The thickness of the obtained retardation film was 20 μm, Re (550) was 125 nm, and Re (450) / Re (550) was 1.02.
4. Fabrication of Circular Polarizer and Organic EL Panel The surface of the retardation film is obtained by applying an easy-adhesive composition prepared by using a modified polyolefin resin and a PVA-based resin to one surface of the retardation film and drying it. An easy-adhesion layer (thickness: 500 nm) was formed on the surface.
A circular polarizing plate was obtained by adhering the surface on the polarizing element side of the polarizing plate to the easily adhesive layer forming surface of the retardation film via a water-soluble adhesive containing a PVA-based resin as a main component. The polarizing plate and the retardation film were bonded together so that the angle formed by the absorption axis of the polarizing element and the slow axis of the retardation film was 45 °.
The pressure-sensitive adhesive layer was bonded to the surface of the circular polarizing plate on the retardation film side. Next, the organic EL panel of Example 1 is attached by attaching the circular polarizing plate to the visible side of the organic EL panel of the organic EL display device (manufactured by LG Display, product name "55C7P") via the pressure-sensitive adhesive layer. Got
The obtained circular polarizing plate was subjected to the evaluation of (5) above. Moreover, the obtained organic EL panel was subjected to the evaluation of the above (3) and (4). The results are shown in Table 1.

[Example 2]
A norbornene-based resin film (manufactured by Nippon Zeon Corporation, product name "ZF-14") is stretched using a lab stretcher (manufactured by Bruckner, KARO IV) at a stretching temperature of 137 ° C and a stretching ratio of 2.0 times. It was uniaxially stretched to obtain a retardation film.
The thickness of the obtained retardation film was 20 μm, the in-plane retardation Re (550) was 125 nm, and Re (450) / Re (550) was 1.01.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that this retardation film was used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 3]
A retardation film was obtained in the same manner as in Example 1 except that the polycarbonate resin film having a thickness of 60 μm was stretched by setting the preheating temperature and the stretching temperature to 140 ° C. The thickness of the obtained retardation film was 20 μm, Re (550) was 130 nm, and Re (450) / Re (550) was 1.02.
Further, the same as in Example 1 except that 0.5 parts by weight of FDR-004 (manufactured by Yamada Chemical Co., Ltd., maximum absorption wavelength of absorption spectrum: 712 nm, absorption half width: 36 nm) was blended as a dye compound. , A pressure-sensitive adhesive layer was obtained.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained retardation film and the pressure-sensitive adhesive layer were used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 4]
A retardation film was obtained in the same manner as in Example 1 except that the polycarbonate resin film having a thickness of 75 μm was stretched by setting the preheating temperature and the stretching temperature to 144.5 ° C. The thickness of the obtained retardation film was 25 μm, Re (550) was 125 nm, and Re (450) / Re (550) was 1.02.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained retardation film was used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 5]
A retardation film was obtained in the same manner as in Example 1 except that the polycarbonate resin film having a thickness of 60 μm was stretched by setting the preheating temperature and the stretching temperature to 141.2 ° C. The thickness of the obtained retardation film was 20 μm, Re (550) was 120 nm, and Re (450) / Re (550) was 1.02.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained retardation film was used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100 ° C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane (Compound 3) 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 parts by mass Parts (0.139 mol), DPC 63.77 parts by mass (0.298 mol) and calcium acetate monohydrate 1.19 × ^10-2 parts by mass (6.78 × ^10-5 mol) were charged as a catalyst. After substituting nitrogen under reduced pressure in the reactor, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was brought to 220 ° C. 40 minutes after the start of the temperature rise, and the depressurization was started at the same time as controlling to maintain this temperature, and the temperature was 13.3 kPa 90 minutes after reaching 220 ° C. The phenol vapor produced by the polymerization reaction was guided to a reflux condenser at 100 ° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was guided to a condenser at 45 ° C. for recovery. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature rise and depressurization in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until the stirring power became a predetermined value. When the predetermined power was reached, nitrogen was introduced into the reactor to repressurize, the produced polyester carbonate was extruded into water, and the strands were cut to obtain pellets.
After vacuum-drying the obtained polycarbonate resin at 80 ° C. for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 300 mm, set temperature: 250 ° C.), chill roll ( A resin film having a thickness of 135 μm was produced using a film-forming device equipped with a set temperature (120 to 130 ° C.) and a winder.
The polycarbonate resin film was obliquely stretched using the stretching device shown in FIG. 2 to obtain a retardation film. The preheating temperature was 145 ° C., the stretching temperature was 138 ° C., and the diagonal stretching ratio represented by the formula (1) was 2.94 times. The stretching direction was 45 ° with respect to the longitudinal direction of the film. Then, in the release zone, the film was held at 125 ° C. for 60 seconds for heat fixation. After cooling the heat-fixed film to 100 ° C., the left and right clips were released. The thickness of the obtained retardation film was 58 μm, Re (550) was 144 nm, and Re (450) / Re (550) was 0.855.
Further, a pressure-sensitive adhesive layer was obtained in the same manner as in Example 1 except that the dye compound was not blended in the pressure-sensitive adhesive composition.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained retardation film and the pressure-sensitive adhesive layer were used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A pressure-sensitive adhesive layer was obtained in the same manner as in Example 1 except that the dye compound was not blended in the pressure-sensitive adhesive composition.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive layer was used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
Adhesive in the same manner as in Example 1 except that 0.3 parts by weight of FDG-007 (manufactured by Yamada Chemical Co., Ltd., maximum absorption wavelength of absorption spectrum: 592 nm, absorption half width: 29 nm) was blended as a dye compound. An agent layer was obtained.
A circularly polarizing plate and an organic EL panel were produced in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive layer was used. The obtained circularly polarizing plate and the organic EL panel were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

The circularly polarizing plate of the comparative example had low bending resistance or had an undesired coloring in the reflected hue. On the other hand, the circularly polarizing plate of the example was excellent in bending resistance and the reflected hue was close to neutral. Further, according to the circular polarizing plate of the example, the above-mentioned excellent characteristics are obtained without significantly reducing the white brightness of the organic EL panel as compared with the circular polarizing plates of Comparative Examples 1 and 2 containing no dye compound. I was able to realize it.

The circularly polarizing plate of the present invention can be suitably used for an image display device such as an organic EL display device.

10 Polarizing plate 20 Phase difference layer 30 Adhesive layer 100 Circular polarizing plate

Claims (1)

Includes a polarizing element, a retardation layer, and an adhesive layer.
The angle formed by the absorption axis of the polarizing element and the slow axis of the retardation layer is 39 ° to 51 °.
A circular polarizing plate comprising a dye compound in which at least one of the polarizing element, the retardation layer, and the pressure-sensitive adhesive layer is present in a wavelength region in which the maximum absorption wavelength of the absorption spectrum is 650 nm or more.

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