TWI843713B - Circularly polarizing plate and optical display device - Google Patents

Abstract

This invention provides a circularly polarizing plate suppressing the coloring of the reflection light. Also provided is an optical display device having such circularly polarizing plate and capable of realizing good image displaying.

This invention provides a circularly polarizing plate containing a polarizer layer, a retardation layer and a light-absorbing layer, wherein, as the in-plane phase retardation of the retardation layer for the light having a wavelength of λnm is set as Re(λ), the retardation layer satisfies the following functions (1) and (2); the light absorbing layer has a substrate layer and pigment dispersed in the substrate layer; and the pigment has a maximum absorbing wavelength in the wavelength band of 390 to 430nm.

0.80<Re(450)/Re(550)<1.00…(1)

1.00<Re(650)/Re(550)<1.30…(2)

Description

Circular polarizer and optical display device

The present invention relates to a circular polarizer and an optical display device.

In the past, circular polarizers were used as optical films for suppressing external light reflection in display devices (for example, see Patent Document 1). Such optical films are commonly known as anti-reflection films. Circular polarizers have: a polarizer disposed on the light incident side, and a phase difference layer (λ/4 plate) disposed on the side opposite to the light incident side relative to the polarizer.

The circular polarizing plate suppresses the reflection of external light as described below.

First, the external light incident on the circular polarizer is converted into linear polarization by the polarizer and then converted into circular polarization by the phase difference layer. After reaching the display device equipped with the circular polarizer, the circular polarization is reflected by the fixed end on the surface of the display device with a phase shift of λ/2.

Afterwards, the reflected circularly polarized light is incident on the phase difference layer again and converted into linearly polarized light. At this time, the linearly polarized light converted by the fixed-end reflection of the circularly polarized light is orthogonal to the linearly polarized light converted by the external light that previously passed through the polarizer in the vibration plane. As a result, the external light reflected on the surface of the display device cannot pass through the polarizer, so it will not be emitted to the outside, but will be absorbed or reflected by the polarizer. In this way, the circularly polarizing plate suppresses the reflection of external light.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2014-170221

The phase difference value of the phase difference layer varies according to the wavelength of light. Therefore, even if it is the same phase difference layer, the performance of the phase difference layer varies with the wavelength of light. For example, a phase difference layer that can well convert linear polarization with a wavelength near green into circular polarization will not be able to well convert linear polarization with a wavelength near red or blue into circular polarization.

Circular polarizing plates, which are mainly designed to suppress external light reflection, often use a phase difference layer that can convert light near green, which has high visual sensitivity, into ideal circularly polarized light. Circular polarizing plates designed in this way can easily reduce the glare of external light. However, on the other hand, such circular polarizing plates will easily make the reflection suppression of light with wavelengths near red or blue insufficient, making the reflected light easily colored.

Therefore, if a conventional circular polarizing plate is used as an anti-reflection plate as described above, the image quality will be reduced due to the colored reflected light. Therefore, a circular polarizing plate that can suppress the coloring of reflected light is sought.

In view of such a situation, the present invention aims to provide a circular polarizer that suppresses the coloring of reflected light. In addition, it also aims to provide an optical display device that has such a circular polarizer and can achieve good image display.

In order to solve the above problem, one aspect of the present invention is a circular polarizing plate having a polarizing element layer, a phase difference layer, and a light absorption layer; wherein, when the in-plane phase difference value of the phase difference layer relative to light of wavelength λnm is Re(λ), the phase difference layer satisfies the following equations (1) and (2); the light absorption layer has a substrate layer and a pigment dispersed in the substrate layer; the pigment has a maximum absorption wavelength in the wavelength band of 390 to 430nm.

0.80<Re(450)/Re(550)<1.00…(1)

1.00<Re(650)/Re(550)<1.30…(2)

In one embodiment of the present invention, the structure may be such that the transmittance Ta(λ) of the circular polarizer relative to light of wavelength λnm satisfies the following equations (3) to (5).

Ta(390)<4%…(3)

Ta(410)<38%…(4)

Ta(430)<42%…(5)

In one aspect of the present invention, the structure may be: the aforementioned substrate layer is an adhesive layer or a bonding agent layer.

In one embodiment of the present invention, the structure may be: the transmittance Tb(λ) of the aforementioned light absorption layer relative to light of wavelength λnm satisfies the following formulas (i) to (iii).

Tb(390)≦85%…(i)

Tb(410)≦98%…(ii)

Tb(430)≦99%…(iii)

Furthermore, one aspect of the present invention is to provide an optical display device, which comprises: an optical display panel, and the circular polarizer bonded to the display surface of the optical display panel.

In one aspect of the present invention, the structure may be: the circular polarizing plate is arranged so that the polarizing layer is on the opposite side of the optical display panel relative to the phase difference layer, and a front panel is provided on the polarizing layer side of the circular polarizing plate.

In one aspect of the present invention, the structure may be: a touch sensor is provided between the display surface and the circular polarizer.

According to the present invention, a circular polarizing plate that suppresses coloring of reflected light can be provided. Furthermore, an optical display device having such a circular polarizing plate and capable of achieving good image display can be provided.

1: Polarizing plate

2‧‧‧Polarizing layer

3‧‧‧Phase difference layer

5.6‧‧‧Protective film

7‧‧‧Light absorption layer

8‧‧‧Adhesive layer

10.100‧‧‧Optical display devices

20‧‧‧Optical display panel

30‧‧‧Circular polarizing plate

31‧‧‧Transparent substrate

32‧‧‧Hard coating

35‧‧‧Front panel (window film)

40‧‧‧Touch sensor

41‧‧‧Base material

42‧‧‧Lower electrode

43‧‧‧Upper electrode

42a, 43a‧‧‧Multiple small electrodes

44‧‧‧Insulating layer

FIG. 1 is a cross-sectional view showing the structure of an optical display device 10 having a circular polarizer 1 and an optical display panel 20.

Figure 2 is an explanatory diagram for explaining the design concept of the phase difference layer 3.

Figure 3 is an explanatory diagram showing a variation of the optical display device.

The circular polarizer of this embodiment is described below with reference to the drawings. In addition, in all the following drawings, the size or ratio of each component has been appropriately adjusted to make the drawings easier to read.

[Definition of terms and symbols]

The definitions of terms and symbols in this manual are as follows.

(1) Refractive index (nx, ny, nz)

"nx" is the refractive index in the direction where the refractive index in the plane is the largest (i.e., the slow axis direction).

"ny" is the refractive index in the direction orthogonal to the slow axis within the plane.

"nz" is the refractive index in the thickness direction.

(2) Phase difference within the plane

The in-plane phase difference value (Re(λ)) refers to the in-plane phase difference value of the film at 23°C and wavelength λ(nm). When the thickness of the film is set to d(nm), Re(λ) is obtained by Re(λ)=(nx-ny)×d.

Here, nx, ny, and nz used in the calculation of Re(λ) are values measured at 23℃ using light of wavelength λ(nm). d is a value measured at 23℃.

In the following description, the in-plane phase difference value is sometimes referred to as "in-plane phase difference value".

(3) Phase difference in thickness direction

The in-plane phase difference value (Rth(λ)) refers to the phase difference value in the thickness direction of the film at 23°C and at a wavelength of λ(nm). When the thickness of the film is set to d(nm), Rth(λ) is obtained by Rth(λ)=((nx+ny)/2-nz)×d.

Here, nx, ny, and nz used in the calculation of Rth(λ) are values measured at 23℃ using light of wavelength λ(nm). d is a value measured at 23℃.

(4) Nz coefficient

The Nz coefficient is the value obtained by Nz coefficient = Rth(λ)/Re(λ)+0.5.

[Circular polarizer, optical display device]

Figure 1 is a cross-sectional view showing the structure of an optical display device 10 having a circular polarizing plate 1 and an optical display panel 20 according to this embodiment.

As shown in FIG. 1 , the circular polarizing plate 1 includes a polarizing layer 2 and a phase difference layer 3 disposed on one side of the polarizing layer 2. Furthermore, protective films 5 and 6 are disposed on both sides of the polarizing layer 2, respectively.

On one side of the polarizer layer 2, a phase difference layer 3 is laminated via a light absorption layer 7. On the surface of the phase difference layer 3 opposite to the polarizer layer 2, an adhesive layer 8 is arranged for lamination on the optical display panel 20 described later. In addition, a peeling film not shown is attached to the surface of the adhesive layer 8 until before use. In addition, the adhesive layer 8 is formed of, for example, an acrylic adhesive.

(Polarizing layer)

The polarizer layer 2 allows linearly polarized light with a polarization plane in a specific direction to pass through. The light passing through the polarizer layer 2 becomes linearly polarized light vibrating in the transmission axis direction of the polarizer. The thickness of the polarizer layer 2 is, for example, about 1μm to 80μm.

For the polarizer layer 2, for example, hydrophilic polymer films such as polyvinyl alcohol films, partially formaldehyde-treated polyvinyl alcohol films, and partially saponified films of ethylene-vinyl acetate copolymers can be used, which are dyed and stretched with dichroic substances such as iodine or dichroic dyes. In addition, for the polarizer layer 2, polyene-based alignment films such as dehydrated polyvinyl alcohol films or dehydrogenated polyvinyl chloride films can be used. Among these, the polarizer layer 2 obtained by dyeing the polyvinyl alcohol film with iodine and stretching it in one axis is excellent in optical properties and is therefore preferred.

Dyeing with iodine is performed, for example, by immersing the polyvinyl alcohol film in an iodine aqueous solution. The stretching ratio of one axis stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or at the same time as dyeing. Furthermore, dyeing can also be performed after stretching.

For the polyvinyl alcohol film, swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc. are carried out as needed. For example, before dyeing, by immersing the polyvinyl alcohol film in water and washing it, not only can the stains and anti-caking agents on the surface of the polyvinyl alcohol film be washed, but the polyvinyl alcohol film can also be swollen to prevent uneven dyeing.

As for the polarizer layer 2, as described in Japanese Patent Publication No. 2016-170368, for example, a dichroic dye can be used in a cured film formed by polymerization of a liquid crystal compound. As for the dichroic dye, one that absorbs in the wavelength range of 380 to 800 nm can be used, and it is preferred to use an organic dye. As for the dichroic dye, for example, azo compounds can be listed. The liquid crystal compound is a liquid crystal compound that can be polymerized in an aligned state, and its molecule can have a polymerizable group.

The visual sensitivity compensation polarization degree of the polarizer layer 2 is preferably above 95%, and more preferably above 97%. In addition, it can be above 99%, and can also be above 99.9%. The visual sensitivity compensation polarization degree of the polarizer layer 2 can be below 99.995%, and can also be below 99.99%.

Here, the "sensitivity-compensated polarization degree" of the polarizer layer 2 refers to the value after the polarization degree of the polarizer layer 2 relative to the light of wavelength λnm is corrected by the sensitivity of the light of wavelength λnm. Hereinafter, the "sensitivity-compensated polarization degree" is sometimes simply referred to as "compensated polarization degree".

The polarization compensation can be calculated by using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and correcting the polarization obtained according to the 2-degree field of view (C light source) of "JIS Z 8701" for visual sensitivity.

When the degree of positive polarization of polarizer layer 2 does not reach 95%, it may not be able to function as an anti-reflection film.

The transmittance of the sensitivity correction monomer of the polarizer layer 2 is preferably 40% or more, and more preferably 42% or more. In addition, the transmittance of the sensitivity correction monomer of the polarizer layer 2 is preferably 50% or less, and more preferably 45% or less. The circular polarizer with a high transmittance polarizer layer can easily identify the coloring of the reflected light as the subject of this case. Therefore, compared with the circular polarizer with a high transmittance polarizer layer but not applicable to the invention of this case, the circular polarizer with a high transmittance polarizer layer and applicable to the invention of this case can become a high-quality circular polarizer that suppresses the coloring of the reflected light.

Here, the "sensitivity-corrected single unit transmittance" of the object refers to the value after the transmittance of the object relative to light of wavelength λnm is corrected by the sensitivity of light of wavelength λnm. Hereinafter, the "sensitivity-corrected single unit transmittance" is sometimes simply referred to as the "corrected transmittance".

The corrected transmittance can be calculated by using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and correcting the obtained transmittance for the 2-degree field of view (C light source) of JIS Z 8701.

The polarizer layer 2 with a corrected transmittance of more than 50% is sometimes unable to function as an anti-reflection film because the polarization degree is too low.

(Phase difference layer)

The phase difference layer 3 may be a positive A plate that functions as a 1/4 wavelength plate (λ/4 plate).

In the phase difference layer 3, when the refractive index in the slow axis direction in the plane is set to nx, the refractive index in the fast axis direction in the plane is set to ny, and the refractive index in the thickness direction is set to nz, the relationship nx>ny is satisfied. The phase difference layer 3 as a λ/4 plate has the function of converting linear polarization of a specific wavelength into circular polarization, or converting circular polarization into linear polarization.

As long as the phase difference layer 3 satisfies the relationship of nx>ny, any appropriate refractive index ellipse can be displayed. Preferably, the refractive index ellipse of the phase difference layer 3 displays the relationship of nx>ny≧nz. The Nz coefficient of the phase difference layer 3 is preferably 1 to 2, more preferably 1 to 1.5, and even more preferably 1 to 1.3.

Furthermore, the phase difference layer 3 exhibits reverse wavelength dispersion characteristics.

In a conventional resin film, when the ratio of the in-plane retardation value Rg relative to green light to the in-plane retardation value Rb relative to blue light is set to Rb/Rg, and the ratio of the in-plane retardation value Rg to the in-plane retardation value Rr relative to red light is set to Rr/Rg, Rr/Rg becomes smaller than Rb/Rg. Hereinafter, such wavelength dispersion is sometimes referred to as "positive" wavelength dispersion.

In contrast, in the phase difference layer 3, Rr/Rg becomes larger than Rb/Rg. For such phase difference layer characteristics, since the magnitude relationship of the ratio of the in-plane phase difference values is reversed with respect to the optical characteristics of the ordinary resin film, it is called "reverse" wavelength dispersion.

When the in-plane phase difference value of the phase difference layer 3 relative to light of wavelength λnm is set to Re(λ), the phase difference layer 3 satisfies the following (1) and (2).

0.80<Re(450)/Re(550)<1.00…(1)

1.00<Re(650)/Re(550)<1.30…(2)

In formula (1), Re(450)/Re(550) is a value exceeding 0.80, preferably exceeding 0.82. Furthermore, Re(450)/Re(550) is preferably less than 1.00 and less than 0.95, more preferably less than 0.92, and particularly preferably less than 0.90. Re(450)/Re(550) is preferably greater than 0.80 and less than 0.95, more preferably greater than 0.80 and less than 0.92, even more preferably greater than 0.82 and less than 0.92, and may also exceed 0.80 and less than 0.90.

In formula (2), Re(650)/Re(550) is preferably less than 1.30 and less than 1.20, and more preferably less than 1.10. Re(650)/Re(550) is preferably greater than 1.00 and less than 1.20, and more preferably greater than 1.00 and less than 1.10.

The thickness of the phase difference layer 3 is not particularly limited, preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm. In addition, the thickness of the phase difference layer 3 is obtained by measuring the thickness of any five points on the surface and taking the arithmetic average thereof.

The wavelength dispersion characteristics of such a phase difference layer are caused by the wavelength dispersion characteristics of the liquid crystal compound used as the raw material of the phase difference layer. The wavelength dispersion characteristics of the phase difference layer showing the reverse wavelength dispersion characteristics can be appropriately adjusted by controlling the mixing ratio of the "wavelength dispersion liquid crystal compound showing positive wavelength dispersion" and the "wavelength dispersion liquid crystal compound showing reverse wavelength dispersion" and the thickness of the phase difference layer.

The phase difference layer of the implementation form of Japanese Patent Publication No. 2017-167517 adjusts the balance between the wavelength dispersion characteristics on the short wavelength side and the wavelength dispersion characteristics on the long wavelength side based on 550nm.

By adjusting in this way, the wavelength dispersion characteristics of the phase difference layer 3 become close to the ideal state on the long wavelength side (red side), which can suppress the reflected light from being colored red. In addition, "ideal state" refers to the phase difference state of the phase difference layer in an ideal state where light of any wavelength can be converted into ideal circularly polarized light.

On the other hand, through the above-mentioned adjustment, the wavelength dispersion characteristics of the phase difference layer 3 deviate from the ideal state on the short wavelength side (blue side), so the reflected light becomes more likely to be colored blue.

In the circular polarizer of this embodiment, the coloring of the reflected light generated in this way can be reduced by the function of the light absorption layer described later.

The phase difference layer 3 can be made using a known method.

For example, after synthesizing polymerizable reverse wavelength dispersion liquid crystal by a known method, the reverse wavelength dispersion liquid crystal can be coated on the alignment film formed on the substrate to align it in one direction, and the reverse wavelength dispersion liquid crystal can be polymerized to produce a phase difference layer 3 with reverse wavelength dispersion characteristics.

(Protective film)

The protective films 5 and 6 function as protective layers for protecting the polarizer layer 2. In the figure, the protective films 5 and 6 are arranged on both sides of the polarizer layer 2, but the protective film 6 can be omitted in the structure, and only the protective film 5 is arranged on the outer side of the polarizer layer 2 (the side opposite to the side facing the phase difference layer 3). In addition, the protective film 6 can also be arranged on the inner side of the polarizer layer 2 (the side facing the phase difference layer 3).

As for the material of the protective films 5 and 6, for example, a light-transmitting thermoplastic resin can be used. The protective films 5 and 6 can be formed of, for example, chain polyolefin resins such as polypropylene resins, cyclic polyolefin resins such as polyolefin resins, cellulose ester resins such as cellulose triacetate and cellulose diacetate, polyester resins, polycarbonate resins, (meth) acrylic resins, polystyrene resins, etc. As for cyclic polyolefin resins, exemplified are norbornene resins. These materials can also be used as mixtures, copolymers, etc.

In addition, the protective films 5 and 6 can be protective films having optical functions such as phase difference layers or brightness enhancement films. For example, a phase difference layer with an arbitrary phase difference value can be produced by stretching the film composed of the above-mentioned thermoplastic resin in one axis or two axes, or forming a liquid crystal layer on the film.

At this time, the above-mentioned phase difference layer 3 can also serve as a protective film 6.

The total thickness of the protective films 5 and 6 is preferably 5μm to 200μm, more preferably 5μm to 100μm, and even more preferably 10μm to 95μm. The total in-plane phase difference value Re(550) of the protective films 5 and 6 is, for example, 0nm to 10nm or 70nm to 140nm, and the total phase difference value Rth(550) in the thickness direction is, for example, -80nm to +80nm.

For the protective film 5, the surface opposite to the side facing the polarizer layer 2 can be subjected to surface treatments such as hard coating, anti-reflection, anti-sticking, and anti-glare as needed. The thickness of the surface treatment layer is less than 500μm, preferably less than 150μm, more preferably 1μm to 20μm, and even more preferably 2μm to 10μm.

In addition, when the circularly polarizing plate 1 of this embodiment is arranged on the display surface of a passive stereoscopic display device using circularly polarized light, a λ/4 plate may be provided on the surface of the protective film 5 on the opposite side to the side facing the polarizer layer 2 in the circularly polarizing plate 1.

The protective film 6 is preferably optically isotropic. That is, this "optical isotropy" means that the in-plane phase difference value Re(550) is 0nm to 10nm, and the phase difference value Rth(550) in the thickness direction is -10nm to +10nm. At this time, the thickness of the protective film 6 is preferably 2μm to 200μm, and more preferably 5μm to 100μm.

(Light absorbing layer)

The light absorbing layer 7 has a substrate layer and a pigment dispersed in the substrate layer.

The base layer can be formed of "active energy ray-curable adhesive containing a curable compound that is cured by irradiation with active energy rays" or "a water-based adhesive formed by dissolving or dispersing adhesive components such as polyvinyl alcohol resins in water". In this case, the light absorbing layer 7 functions as an adhesive layer.

The active energy that starts the curing reaction of the active energy ray-curing adhesive can be, for example, ultraviolet rays, visible light, electron beams, and X-rays. The active energy ray-curing adhesive is preferably an ultraviolet ray-curing adhesive.

Since it exhibits good adhesion, the active energy ray-curable adhesive is preferably an active energy ray-curable adhesive composition containing either or both of "cationically polymerizable curable compounds" and "free radically polymerizable curable compounds". The active energy ray-curable adhesive may further contain either or both of a cationic polymerization initiator and a free radical polymerization initiator for initiating the curing reaction.

As for the cationically polymerizable curable compounds, for example, there are epoxy compounds having one or more epoxy groups in the molecule, and oxetane compounds having one or more oxetane rings in the molecule.

As for the free radical polymerizable curable compounds, for example, there can be mentioned: (meth)acrylic acid compounds having one or more (meth)acryloyloxy groups in the molecule, or other vinyl compounds having free radical polymerizable double bonds.

Active energy ray-curable adhesives may contain additives such as cationic polymerization accelerators, ion scavengers, antioxidants, chain transfer agents, adhesive agents, thermoplastic resins, fillers, flow regulators, plasticizers, defoamers, antistatic agents, leveling agents, solvents, etc., as needed.

The pigment dispersed in the substrate layer of the light absorbing layer 7 has a maximum absorption wavelength in the wavelength band of 390 to 430 nm, which belongs to the short wavelength band of visible light. Here, in this embodiment, "visible light" refers to the wavelength included in the range of 390 nm to 830 nm.

Examples of such pigments include KEMISORB 111, KEMISORB 73 (all manufactured by CHEMIPRO Chemicals Co., Ltd.), and SUMISORB 300 (manufactured by Sumika Chemitex Co., Ltd.).

In addition, compounds having a maximum absorption wavelength in the wavelength band of 390 to 430 nm can be synthesized using known methods and used as the pigment of this embodiment. Such a pigment can be, for example, a compound known as a photoselective absorption compound described in Japanese Patent Application Laid-Open No. 2017-120430.

When the light absorbing layer 7 functions as a bonding agent layer, the thickness of the light absorbing layer 7 is preferably 0.5 to 5 μm, and more preferably 0.5 to 3 μm.

In such a light absorbing layer 7, the pigment dispersed in the base material layer absorbs blue light. Therefore, the blue light level of the light emitted through the circular polarizing plate 1 can be reduced.

In addition, in the base material layer, "an adhesive that exhibits adhesion to a degree that does not peel off in a high temperature environment, a humid and hot environment, or an environment where high and low temperatures are repeated, to which the polarizing plate is exposed" can be appropriately selected as a forming material. At this time, the light absorbing layer 7 functions as an adhesive layer.

The materials for forming the substrate layer include commonly known acrylic adhesives, silicone adhesives, rubber adhesives, etc. Among them, acrylic adhesives are particularly preferred due to their transparency, high weather resistance, excellent heat resistance, and ease of processing.

In the adhesive, various additives such as adhesive agents, plasticizers, glass fibers, glass beads, metal powders, other inorganic powders, fillers, pigments, colorants, fillers, antioxidants, ultraviolet absorbers, antistatic agents, silane coupling agents, etc. can be appropriately formulated as needed.

The light absorbing layer 7 as an adhesive layer is usually formed by applying an adhesive solution on a release sheet and drying it. The so-called application on the release sheet can be, for example, reverse coating, gravure coating, roller coating, spin coating, screen printing, injection coating, dipping, spraying, etc. The release sheet provided with the adhesive layer can be used by a transfer method, etc.

The thickness of the light absorbing layer 7 as an adhesive layer is usually about 3 to 100 μm, preferably 5 to 50 μm.

The amount of blue light absorbed by the light absorbing layer 7 can be controlled by adjusting the type of pigment, the amount of pigment contained in the light absorbing layer 7, and the thickness of the light absorbing layer 7. If the amount of pigment contained in the light absorbing layer 7 is increased, the amount of blue light absorbed by the light absorbing layer 7 tends to increase. In addition, if the thickness of the light absorbing layer 7 is increased, the amount of blue light absorbed by the light absorbing layer 7 tends to increase.

In the light absorbing layer 7, the transmittance Tb(λ) preferably satisfies the following (i) to (iii).

Tb(390)≦85%…(i)

Tb(410)≦98%…(ii)

Tb(430)≦99%…(iii)

Tb(390) is preferably less than 40%, and more preferably less than 1%.

Tb(410) is preferably less than 50%, and more preferably less than 10%.

Tb(430) is preferably below 90%, and more preferably below 88%.

In this embodiment, the transmittance of the light absorbing layer 7 is a value measured by the following method.

One side of the light absorbing layer was bonded to an alkali-free glass (Corning, trade name "EagleXG"), and a 23μm thick cycloolefin film (ZEON, Japan, trade name "ZF-14-23") was bonded to the other side of the light absorbing layer. Next, a spectrophotometer with an integrating sphere (V7100, JASCO Corporation) was used to measure the transmittance of the obtained multilayer at 390nm, 410nm, and 430nm, and the obtained values were used as the required transmittances Tb(390), Tb(410), and Tb(430). In addition, the measured values exclude the influence of interface reflection.

(Circular polarizing plate)

In such a circular polarizing plate 1, the transmittance Ta(λ) preferably satisfies the following (3) to (5).

Ta(390)<4%…(3)

Ta(410)<38%…(4)

Ta(430)<42%…(5)

In this embodiment, the transmittance of the circular polarizer 1 is measured using the following method.

The circular polarizing plate was bonded to the alkali-free glass (Corning, EagleXG) via a 25μm thick acrylic adhesive (LINTEC, trade name "P-3132"), and the obtained laminate was measured using an ultraviolet-visible near-infrared spectrophotometer (JASCO Corporation, trade name "V-7100") to obtain the value as the transmittance of the circular polarizing plate 1.

As described above, in the circular polarizing plate 1, a reverse wavelength dispersion type phase difference layer with adjusted optical characteristics is used as the phase difference layer 3. Therefore, in the circular polarizing plate 1, the leakage of red light is reduced, and the leakage of blue light is increased. That is, if the structure of the phase difference layer 3 is taken into consideration, the circular polarizing plate 1 becomes a structure that easily causes the reflected light to be colored blue.

Here, the circular polarizer 1 is configured to absorb blue light well in the light absorbing layer 7.

Therefore, in the circular polarizing plate 1, the light absorbing layer 7 can absorb the blue light contained in the reflected light well and suppress the coloring of the reflected light.

(Optical display panel)

The optical display panel 20 may be, for example, a liquid crystal display device or an organic EL panel. The liquid crystal display device or the organic EL panel may use a commonly known structure.

As shown in FIG. 1, the circular polarizing plate 1 is attached to the display surface of the optical display panel 20 to form an optical display device 10. In the optical display device 10, by providing the circular polarizing plate 1 on the display surface, the reflection of external light and the coloring of reflected light are suppressed.

The circular polarizing plate 1 with the above structure becomes a circular polarizing plate that suppresses the coloring of reflected light.

Furthermore, the optical display device 10 constructed as above can achieve good image display.

In addition, although the circular polarizing plate 1 of this embodiment has a phase difference layer 3 as a positive A plate, a positive C plate can also be used in combination.

Positive C plate satisfies the relationship of nz>nx≧ny. The difference between the value of nx and the value of ny is preferably within 0.5% of the value of ny, and is even better within 0.3%. If it is within 0.5%, it can be regarded as nx=ny in essence.

In the positive C plate, the phase difference value Rth(λ) in the thickness direction at the wavelength λnm is preferably satisfied with the relationship of -300nm≦Rth(550)≦-20nm, and is more preferably satisfied with the relationship of -150nm≦Rth(550)≦-20nm.

Such a positive C plate can be disposed between the polarizer layer 2 and the optical display panel 20.

Furthermore, in this embodiment, a pigment is dispersed in the adhesive layer or the adhesive layer that integrates the polarizer layer 2 and the phase difference layer 3 and is made to function as the light absorption layer 7, but it is not limited to this.

As long as it does not harm the effect of the invention, the blue light absorbing pigment can also be dispersed in other layers. For example, if the above-mentioned pigment is mixed into the adhesive layer 8, the adhesive layer 8 will become the light absorbing layer of the present invention.

Furthermore, pigments can be dispersed in the protective films 5 and 6 to function as light absorbing layers.

At this time, the base layer of the light absorbing layer can be a film formed by forming a thermoplastic resin. The light absorbing layer having such a base layer can be any film arranged on the identification side of the display element like a protective film.

As for the light absorbing layer, it is preferable to use "an adhesive layer or a bonding agent layer that can be produced under relatively mild conditions" as a base layer and to disperse pigments in the base layer.

The light absorbing layer may be only one layer or may be provided with two or more layers.

Figure 3 is an explanatory diagram showing a variation of the optical display device.

The optical display device 100 includes: a circular polarizer 30 with a front panel, a touch sensor 40, and an optical display panel 20. As shown in the figure, in the optical display device 100, the circular polarizer 30 with a front panel, the touch sensor 40, and the optical display panel 20 can be stacked on each other.

In the optical display device 100, the circular polarizer 1 is arranged so that the polarizer layer 2 is on the outside (i.e., the side opposite to the optical display panel 20), and the phase difference layer 3 is on the side of the optical display panel 20. In other words, in the optical display device 100, the circular polarizer 1 is arranged so that the phase difference layer 3 is located between the polarizer layer 2 and the optical display panel 20.

The circular polarizing plate 30 with a front panel has the circular polarizing plate 1 and a front panel (window film) 35 connected to the protective film 5 of the circular polarizing plate 1. That is, the circular polarizing plate 30 with a front panel is composed of the front panel (window film) 35 and the polarizing plate 1 stacked together. The polarizing plate 30 with a front panel has the front panel 35 on the side of the polarizing element layer 2 constituting the polarizing plate 1.

(Front panel)

The front panel 35 has a transparent substrate 31 and a hard coating layer 32 formed on at least one side of the transparent substrate 31. The front panel 35 has the function of protecting the optical display panel 20 or other components of the optical display device 10 from internal stress caused by external impact and temperature/humidity changes. The front panel 35 is shown in the figure in such a way that the side of the transparent substrate 31 is connected to the protective film 5.

If the transparent substrate 31 is a flexible resin film with light transmittance, various types can be used. In addition, in this specification, the so-called "transparent" means that the transmittance of visible light is more than 70% or more than 80%.

As for the transparent substrate 31, unstretched films, uniaxially stretched films or biaxially stretched films of various transparent resins can be used. The transparent resin constituting the transparent substrate 31 can be used only one type or a mixture of two or more types.

As for such a transparent substrate 31, polyamide imide film, polyimide film, stretched polyester film, cycloolefin derivative film, polymethyl methacrylate film, cellulose triacetate or isobutyl cellulose film is preferred.

The thickness of the transparent substrate 31 is preferably 5 μm to 200 μm, more preferably 20 μm to 100 μm.

The hard coating layer 32 has the function of improving the surface hardness of the transparent substrate 31. In addition, the hard coating layer 32 has light transmittance and flexibility.

The hard coating layer 32 can be formed by hardening a hard coating composition containing a photocurable (meth)acrylate monomer or oligomer, a photocurable epoxy monomer or oligomer, etc. as a forming material.

In addition to the above-mentioned monomers or oligomers, the hard coating composition may contain solvents and initiators as needed. In addition, the hard coating composition may contain additives such as inorganic fillers, leveling agents, stabilizers, antioxidants, UV absorbers, surfactants, lubricants, and antifouling agents within the scope that does not impair the effects of the invention.

The hard coating layer 32 can be formed by applying the above-mentioned hard coating composition on at least one side of the transparent substrate 31 and curing it.

The thickness of the hard coating layer 32 is not particularly limited, but preferably 5 μm to 100 μm. When the thickness of the hard coating layer 32 is 5 μm or more, sufficient impact resistance can be ensured. In addition, when the thickness of the hard coating layer 32 is 100 μm or less, the hard coating layer 32 becomes sufficiently flexible for practical use. In addition, when the hard coating layer 32 is formed, curling due to the curing and shrinkage of the hard coating composition is not easy to occur.

(Touch sensor)

The optical display device 100 shown in FIG. 3 has a touch sensor 40 between the display surface of the optical display panel 20 and the circular polarizer 1. The touch sensor 40 has: a substrate 41, a lower electrode 42 disposed on the substrate 41, an upper electrode 43 facing the lower electrode 42, and an insulating layer 44 sandwiched between the lower electrode 42 and the upper electrode 43. The touch sensor 40 shown in the figure is a so-called projection type capacitive touch sensor.

The touch sensor 40 shown in the figure is sandwiched between the circular polarizer 30 with the front panel and the optical display panel 20, with the substrate 41 facing the optical display panel 20 and the upper electrode 43 facing the circular polarizer 30 with the front panel.

As long as the substrate 41 is a flexible resin film with light transmittance, various types can be used. For example, as for the substrate 41, the film exemplified as the material of the transparent substrate 31 mentioned above can be used.

The lower electrode 42 is, for example, a plurality of small electrodes having a square shape in a plane view. The plurality of small electrodes 42a are arranged in a matrix shape.

Furthermore, a plurality of small electrodes 42a are connected to each other in the diagonal direction of one side of the small electrode 42a to form a plurality of electrode rows. The plurality of electrode rows are connected to each other at the ends, and the capacitance between the adjacent electrode rows can be detected.

The upper electrode 43 is, for example, a plurality of small electrodes having a square shape in a planar view. The plurality of small electrodes 43a are arranged in a matrix in a complementary manner at positions where the lower electrode 42 is not arranged in a planar view. That is, the upper electrode 43 and the lower electrode 42 are arranged without a gap in a planar view.

Furthermore, a plurality of small electrodes 43a are connected to each other in the diagonal direction of the other side of the small electrode 43a to form a plurality of electrode rows. The plurality of electrode rows are connected to each other at the ends, and the capacitance between the adjacent electrode rows can be detected.

The insulating layer 44 insulates the lower electrode 42 from the upper electrode 43. The insulating layer 44 can be formed of a material commonly known as an insulating layer of a touch panel.

In addition, in this embodiment, the touch sensor 40 is described as a so-called projection type electrostatic capacitance type touch sensor, but other types of touch sensors such as film resistance type can also be used within the scope of not impairing the effect of the invention.

Each layer (front panel, circular polarizer, touch sensor) of the aforementioned optical display device can be formed by lamination with adhesive. As for adhesive, water-based adhesive, organic solvent-based adhesive, solvent-free adhesive, solid adhesive, solvent-volatile adhesive, moisture-hardening adhesive, heat-hardening adhesive, anaerobic-hardening adhesive, active energy ray-hardening adhesive, hardener-mixed adhesive, hot melt adhesive, pressure-sensitive adhesive (adhesive), rewetting adhesive, etc. are widely used. Among them, water-based solvent-volatile adhesive, active energy ray-hardening adhesive, and adhesive are commonly used. The thickness of the adhesive layer can be adjusted appropriately according to the required bonding force, etc., and is 0.01μm to 500μm, preferably 0.1μm to 300μm. There are multiple laminates used in the above-mentioned flexible image display device, and the thickness of each type can be the same or different.

As for the aforementioned water-based solvent volatile adhesive, water-soluble polymers such as polyvinyl alcohol polymers, starch, ethylene-vinyl acetate emulsions, styrene-butadiene emulsions, etc. can be used as the main polymer. In addition to water and the aforementioned main polymer, crosslinking agents, silane compounds, ionic compounds, crosslinking catalysts, antioxidants, dyes, pigments, inorganic fillers, organic solvents, etc. can also be formulated.

When bonding with the aforementioned water-based solvent volatile adhesive, the aforementioned water-based solvent volatile adhesive can be injected between the bonded layers and the bonded layers can be bonded, and then dried to impart adhesion. When using the aforementioned water-based solvent volatile adhesive, the thickness of the adhesive layer can be 0.01 to 10μm, preferably 0.1μm to 1μm. When using multiple layers of the aforementioned water-based solvent volatile adhesive, the thickness of each layer can be the same or different.

The aforementioned active energy ray-curable adhesive includes a reactive material that forms an adhesive layer by irradiating active energy rays. When the aforementioned active energy ray-curable adhesive is used, the adhesive layer can be formed by curing the active energy ray-curable composition. The aforementioned active energy ray-curable composition can contain at least one polymer of the same free radical polymerizable compound and cationic polymerizable compound as the hard coating composition. The aforementioned free radical polymerizable compound can be the same type as the hard coating composition. As for the free radical polymerizable compound used in the adhesive layer, it is preferably a compound having an acryl group. As for the adhesive composition, in order to reduce the viscosity, the aforementioned active energy ray-curable adhesive preferably also contains a monofunctional compound.

The cationic polymerizable compound mentioned above can be the same type as the hard coating composition. The cationic polymerizable compound used in the active energy ray curing composition is particularly preferably an epoxy compound. As for the adhesive composition, in order to reduce the viscosity, the cationic polymerizable compound mentioned above preferably also contains a monofunctional compound as a reactive diluent.

The active energy ray-curable composition may further contain a polymerization initiator. As for the polymerization initiator, free radical polymerization initiators, cationic polymerization initiators, free radical and cationic polymerization initiators, etc. may be appropriately selected. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating, and generate free radicals or cations to perform free radical polymerization and cationic polymerization. The polymerization initiator may be the initiator used in the active energy ray-curable adhesive shown in the above description of the light absorbing layer.

The aforementioned active energy ray curing composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, and a solvent. By using the aforementioned active energy ray curing adhesive During bonding, the aforementioned active energy ray curing composition may be applied to one or both of the bonded layers and then bonded, and the bonded layer or the two bonded layers may be irradiated with active energy rays and cured.

When using the aforementioned active energy ray-curing adhesive, the thickness of the adhesive layer can be 0.01μm to 20μm, preferably 0.1μm to 10μm. When using multiple layers of the aforementioned active energy ray-curing adhesive, the thickness of each layer can be the same or different.

The aforementioned pressure-sensitive adhesive (adhesive) can be classified into any of acrylic adhesive, polyurethane adhesive, rubber adhesive, silicone adhesive, etc. according to the main agent polymer. In the adhesive, in addition to the main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, an adhesive imparting agent, a plasticizer, a dye, a pigment, an inorganic filler, etc. can also be formulated. The components constituting the aforementioned adhesive are dissolved/dispersed in a solvent to obtain an adhesive composition, which is applied to a substrate and dried to form an adhesive layer (adhesive layer). The adhesive layer can be formed directly or transferred from another layer formed on the substrate. In order to cover the adhesive surface before bonding, it is also preferred to use a release film.

When the aforementioned pressure-sensitive adhesive (adhesive) is used, the thickness of the adhesive layer (adhesive layer) can be 0.1μm to 500μm, preferably 1μm to 300μm. When multiple layers of the aforementioned adhesive are used, the thickness of each layer can be the same or different.

If the optical display device 100 has the above structure, the coloring of reflected light can be suppressed to achieve good image display.

The above is an explanation of the appropriate implementation example of the present invention with reference to the attached drawings, but it goes without saying that the present invention is not limited to the above examples. The various shapes or combinations of the components shown in the above examples are only examples, and various changes can be made according to design requirements within the scope of the present invention.

[Implementation example]

The present invention is described below by way of examples, but the present invention is not limited to such examples.

(Implementation Example 1)

(Production of polarizers)

A 30μm thick polyvinyl alcohol film (average degree of polymerization of about 2400, saponification degree of more than 99.9 mol%) was stretched to about 5 times in one axis by dry stretching, and then immersed in pure water at 60°C for 1 minute while maintaining tension, and then immersed in a 28°C aqueous solution with a mass ratio of iodine/potassium iodide/water of 0.05/5/100 for 60 seconds.

Secondly, immerse in a 72°C aqueous solution with a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100 for 300 seconds.

Then, after washing with pure water at 26°C for 20 seconds and drying at 65°C, a polarizer with a thickness of 12μm was obtained.

The polarizer produced is a polyvinyl alcohol film with iodine adsorbed and aligned.

(Preparation of water-based adhesives)

3 parts by mass of carboxyl-modified polyvinyl alcohol (Kuraray Co., Ltd., trade name "KL-318") was dissolved in 100 parts of water, and 1.5 parts by mass of polyamide epoxy additive (Taoka Chemical Co., Ltd., trade name "Sumirez resin 650 (30)"), a 30% solids aqueous solution, was added to the obtained aqueous solution to prepare a water-based adhesive.

(Production of polarizing plates)

The above-mentioned water-based adhesive was applied to one side of the obtained polarizer, and a norbornene resin film with a hard coating layer (manufactured by Nippon Paper Industries, Ltd., trade name "COP25ST-HC", hereinafter also referred to as HC-COP) was attached.

The HC-COP used is a film of "3μm thick hard coating resin" formed on "a stretched film composed of 25μm thick cycloolefin resin".

The above-mentioned water-based adhesive is applied to the other side of the polarizer, and a 20μm thick cellulose triacetate resin film (manufactured by Fuji Film Co., Ltd., trade name "ZRG20SL", hereinafter also referred to as TAC) is laminated to produce a polarizing plate.

The obtained polarizing plate has a positive transmittance of 45%.

(Production of phase difference layer)

(Production of reverse wavelength dispersion liquid crystal)

5 parts by mass of the photo-alignment material represented by the following formula (11) (mass average molecular weight: 30,000) and 95 parts by mass of cyclopentanone as a solvent were mixed, and the obtained mixture was stirred at 80°C for 1 hour to obtain a composition for forming an alignment film.

In addition, a mixture was prepared by mixing the polymerizable liquid crystal compound A represented by the following formula (12) and the polymerizable liquid crystal compound B represented by the following formula (13) at a mass ratio of 90:10.

The polymerizable liquid crystal compound A is produced by the method described in Japanese Patent Publication No. 2010-31223. In addition, the polymerizable liquid crystal compound B is produced by the method described in Japanese Patent Publication No. 2009-173893.

[Polymerizable liquid crystal compound A]

[Polymerizable liquid crystal compound B]

To the obtained mixture, 1.0 parts by mass of a leveling agent (manufactured by DIC Corporation, trade name "F-556") and 6 parts by mass of 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butane-1-one (manufactured by BASF JAPAN Corporation, trade name "Irgacure (registered trademark) 369 (Irg369)") as a polymerization initiator were added.

Furthermore, N-methyl-2-pyrrolidone (NMP) was added so that the solid concentration became 13 mass %, and the mixture was stirred at 80°C for 1 hour to obtain a composition for forming a liquid crystal cured film.

Prepare a 50μm thick cycloolefin film (produced by ZEON Co., Ltd., Japan, trade name "ZF-14-50") as a substrate.

After the substrate was subjected to corona treatment, the composition for forming an alignment film was applied to the surface subjected to corona treatment by a rod coater, dried at 80°C for 1 minute, and polarized UV irradiation device (manufactured by USHIO Electric Co., Ltd., trade name "SPOT CURE SP-9") was used to perform polarized UV exposure at an axial angle of 45° with a cumulative light dose of 100 mJ/ ^cm2 at a wavelength of 313 nm to form an alignment film.

Next, a bar coater was used to apply the liquid crystal cured film forming composition to the alignment film and dried at 120°C for 1 minute.

Thereafter, the coating of the liquid crystal cured film forming composition was irradiated with ultraviolet light using a high-pressure mercury lamp (manufactured by USHIO Electric Co., Ltd., trade name: "Yunikyua VB-15201BY-A"). The ultraviolet light irradiation conditions were a nitrogen atmosphere and a cumulative light amount of 500 mJ/ ^cm2 at a wavelength of 365 nm.

In this way, a liquid crystal curing film is formed, and a laminated body formed by laminating the substrate, the alignment film and the liquid crystal curing film is obtained. The laminated body of the alignment film and the liquid crystal curing film is equivalent to the "phase difference layer" in the present invention.

The laminate produced by the above method is bonded to glass via an adhesive layer. The surface in contact with the adhesive layer is a liquid crystal cured film. The cycloolefin film as a substrate is peeled off from the laminate to obtain a sample for phase difference measurement.

The obtained in-plane phase difference value Re(λ) of the phase difference layer was measured by a measuring machine (manufactured by Oji Testing Instruments Co., Ltd., product name "KOBRA-WPR").

The measured results of the phase difference Re(λ) at each wavelength are Re(450)=121nm, Re(550)=142nm, Re(650)=146nm. Re(450)/Re(550)=0.85, Re(650)/Re(550)=1.03.

Figure 2 is a graph showing the ratio of the "phase difference of light of other wavelengths" to the "phase difference of light of wavelength 550nm" in the phase difference layer. In Figure 2, the horizontal axis represents the wavelength (unit: nm), and the vertical axis represents the ratio of the phase difference of light of other wavelengths to the phase difference of light of wavelength 550nm (unit: dimensionless). In addition, in the figure, the line indicated by symbol S1 is a line showing the "phase difference of the phase difference layer in the ideal state where light of any wavelength is converted into ideal circularly polarized light." Such a line is called an "ideal curve."

(Preparation of adhesive composition mixed with pigment)

(Preparation of acrylic resin)

In a reaction container equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer, a mixed solution of 81.8 parts by mass of ethyl acetate as a solvent, 70.4 parts by mass of butyl acrylate as a monomer, 20.0 parts by mass of methyl acrylate, 8.0 parts by mass of 2-phenoxyethyl acrylate, 1.0 parts by mass of 2-hydroxyethyl acrylate, and 0.6 parts by mass of acrylic acid was added.

Replace the reaction container with a nitrogen gas environment and raise the internal temperature of the reaction container to 55°C. In addition, prepare a solution of 0.14 parts by mass of azobisisobutyronitrile dissolved in 10 parts by mass of ethyl acetate as a polymerization initiator, and add the entire amount of the polymerization initiator solution to the reaction container at an internal temperature of 55°C. After adding the initiator, maintain the temperature for 1 hour.

Secondly, while maintaining the internal temperature at 54 to 56°C, ethyl acetate was continuously added to the reaction vessel at an addition rate of 17.3 parts by mass/hr. The addition of ethyl acetate was stopped when the concentration of the obtained polymer reached 35% by mass.

After 12 hours from the start of adding ethyl acetate, the temperature was kept at 54 to 56°C, and ethyl acetate was added to adjust the polymer concentration to 20% by mass to obtain the desired acrylic resin.

(Synthesis of pigments)

A 100 mL four-necked flask equipped with a Dimroth condenser and a thermometer was placed in a nitrogen gas environment, and the compound represented by the following formula (14) (hereinafter also referred to as compound (14)) was synthesized with reference to the synthesis example of Japanese Patent Publication No. 2017-120430.

2.0 g of the obtained powder of compound (14), 1.2 g of triethylene glycol monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), 20 mg of N,N-dimethyl-4-aminopyridine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 8 g of chloroform were added to a reaction container, stirred with a magnetic stirring bar, and cooled in an ice bath to an internal temperature of 0°C.

Prepare a solution by dissolving 1.4 g of 1-ethyl-3-(3-dimethylaminopropyl)carboxylimide hydrochloride (produced by Tokyo Chemical Industry Co., Ltd.) in 2.0 g of chloroform. Use a dropping funnel to drop the prepared solution into the above reaction container maintained at an internal temperature of 0°C over 12 hours. After the dropwise addition is completed, keep the temperature at 0°C for another 6 hours.

After the reaction is completed, use an evaporator to remove chloroform. Dissolve the obtained oil in ethyl acetate, wash it with 10% dilute sulfuric acid, and then wash the ethyl acetate solution with pure water until the pH of the water layer is >6.

The washed organic layer is dried with mirabilite. After removing the mirabilite, the ethyl acetate is removed by an evaporator to obtain the pigment represented by the following formula (15) (hereinafter also referred to as compound (15)).

(Preparation of adhesive composition mixed with pigment)

0.5 parts by mass of a crosslinking agent (manufactured by Tosoh Co., Ltd., trade name "Coronate"), 0.5 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403"), and 3.5 parts by mass of compound (15) were mixed with 100 parts by mass of the solid content of the synthetic acrylic resin. 2-Butanone was further added so that the solid content concentration was 14% by mass.

The obtained composition was stirred and mixed at 300 rpm for 30 minutes using a stirrer (manufactured by YAMATO Science Co., Ltd., trade name "three-one motor") to prepare an adhesive composition containing a pigment (compound (15)).

(Production of pigmented adhesive sheets)

The above adhesive was applied to the release-treated surface of the polyethylene terephthalate film (manufactured by LINTEC Co., Ltd., trade name "SP-PLR382050") using an applicator so that the thickness of the adhesive layer after drying would be 20μm. Drying was performed at 100°C for 1 minute to prepare an adhesive sheet formulated with a pigment.

One side of the obtained adhesive sheet was bonded to alkali-free glass (Corning, trade name "EagleXG"), and a 23μm thick cycloolefin film (ZEON, Japan, trade name "ZF-14-23") was bonded to the other side of the adhesive sheet. Next, a spectrophotometer with an integrating sphere (V7100, JASCO Corporation) was used to measure the transmittance of the obtained laminate at 390nm, 410nm, and 430nm.

Regarding the obtained layered structure, its transmittance excluding the influence of interface reflection is as follows.

Tb(390)≦0.001%

Tb(410)≦0.8%

Tb(430)≦83.0%

(Production of circular polarizing plates)

The above adhesive sheet is attached to the protective film made of cellulose triacetate resin of the polarizing plate.

Next, the polyethylene terephthalate film is peeled off from the adhesive sheet, and the liquid crystal cured film surface of the phase difference layer is bonded to the exposed adhesive layer. The obtained adhesive layer is equivalent to the "light absorption layer" of the present invention.

Next, the cycloolefin film stacked with the phase difference layer was peeled off, and a 25μm thick acrylic adhesive (manufactured by LINTEC Co., Ltd., trade name "P-3132") was adhered to the exposed surface to obtain a circularly polarizing plate.

The circular polarizing plate is composed of HC-COP, polarizer, TAC, adhesive layer (light absorption layer), liquid crystal curing film, alignment film, and adhesive layer.

[Measurement of penetration rate]

The circular polarizing plate was attached to the alkali-free glass (manufactured by Corning, trade name "EagleXG") through the adhesive layer. The transmittance at 390nm, 410nm, and 430nm was measured with an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, trade name "V-7100").

The transmittance is measured in the absorption axis direction and the transmission axis direction of the polarizer, and the transmittance at each wavelength λnm is obtained from the following formula (A).

T(λ)=((transmittance in the absorption axis direction)+(transmittance in the transmission axis direction))/2...(A)

The transmittance Ta(λ) of the manufactured circular polarizer is Ta(390)=0.12%, Ta(410)=4.53%, Ta(430)=39.40%.

[Measurement of reflectance hue]

The circular polarizing plate was attached to the display surface of an OLED display element (Samsung Electronics Co., Ltd., trade name "Galaxy-Tab S8.4") through an adhesive layer. The reflection hue b* was measured using a spectrophotometer (Konica Minolta Co., Ltd., trade name "CM-2600d") in a non-lit state.

[Visual evaluation of appearance]

The appearance of the samples prepared for the measurement of reflected hue was visually observed. The evaluation criteria are as follows. Samples evaluated as "◎" and "○" were judged as good products, and samples evaluated as "×" were judged as defective products.

(Evaluation criteria)

◎: Black

○: Slightly bluish but still black

×: blue

(Example 2)

When preparing the adhesive composition, a circular polarizing plate was prepared in the same manner as in Example 1 except that the amount of compound (15) added was changed to 2.5 parts by weight. The transmittance of the adhesive layer measured in the same manner as in Example 1 is as follows.

Tb(390)≦0.001%

Tb(410)≦3.2%

Tb(430)≦86.9%

(Implementation Example 3)

When preparing the adhesive composition, a circular polarizing plate was prepared in the same manner as in Example 1 except that the amount of compound (15) added was changed to 1.0 parts by weight. The transmittance of the adhesive layer measured in the same manner as in Example 1 is as follows.

Tb(390)≦0.01%

Tb(410)≦3.2%

Tb(430)≦95.0%

(Implementation Example 4)

When preparing the adhesive composition, a circular polarizing plate was prepared in the same manner as in Example 1 except that the amount of compound (15) added was changed to 0.02 parts by weight. The transmittance of the adhesive layer measured in the same manner as in Example 1 is as follows.

Tb(390)≦81.9%

Tb(410)≦97.2%

Tb(430)≦99.0%

(Example 5)

When preparing the adhesive composition, a circular polarizing plate was prepared in the same manner as in Example 1 except that the amount of compound (15) added was changed to 0.035 parts by weight. The transmittance of the adhesive layer measured in the same manner as in Example 1 is as follows.

Tb(390)≦70.5%

Tb(410)≦95.2%

Tb(430)≦98.0%

(Comparison Example 1)

A circular polarizing plate was prepared in the same manner as in Example 1 except that the light selective absorbing adhesive sheet was replaced with a 5 μm thick acrylic adhesive (manufactured by LINTEC Co., Ltd., trade name "#L2"). The acrylic adhesive used did not contain a pigment (compound (15)).

One side of a 5μm thick acrylic adhesive (manufactured by LINTEC Co., Ltd., trade name "#L2") was bonded to an alkali-free glass (manufactured by Corning, trade name "EagleXG") adhesive, and a 23μm thick cycloolefin film (manufactured by ZEON Co., Ltd., Japan, trade name "ZF-14-23") was bonded to the other side of the acrylic adhesive. Using a spectrophotometer with an integrating sphere, the transmittance of the obtained laminate at 390nm, 410nm, and 430nm was measured in the same manner as in the embodiment. The transmittance of the acrylic adhesive is as follows.

Tb(390)≦99.9%

Tb(410)≦99.9%

Tb(430)≦99.9%

The evaluation results are shown in Table 1.

As for the evaluation results, it can be seen that compared with the circular polarizing plate of Comparative Example 1, the circular polarizing plates of Examples 1 to 5 have a reflection hue b* close to 0, and the bluish feeling is reduced.

From the above, it can be seen that the present invention is useful.

Claims (7)

A circular polarizing plate comprises: a polarizing element layer, a phase difference layer, and a light absorbing layer, wherein when the in-plane phase difference value of the phase difference layer relative to light of wavelength λ nm is Re(λ), the phase difference layer satisfies the following equations (1) and (2); the light absorbing layer comprises a substrate layer and a pigment dispersed in the substrate layer; the pigment has a maximum absorption wavelength in a wavelength band of 390 to 430 nm, and the transmittance Ta( λ ) of the circular polarizing plate relative to light of wavelength λ nm satisfies the following equations (3) to (5); 0.80<Re(450)/Re(550)<0.90…(1) 1.00<Re(650)/Re(550)<1.30…(2) Ta(390)<0.22%…(3) Ta(410)<4.92%…(4) Ta(430)<40.08%…(5). As described in Item 1 of the patent application scope, the aforementioned substrate layer is an adhesive layer or a bonding agent layer. A circular polarizing plate as described in item 1 or 2 of the patent application, wherein the transmittance Tb(λ) of the aforementioned light absorption layer relative to light of wavelength λnm satisfies the following formulas (i) to (iii), Tb(390)≦85%…(i) Tb(410)≦98%…(ii) Tb(430)≦99%…(iii). The circular polarizing plate as described in item 1 or 2 of the patent application, wherein the Re(550) of the phase difference layer is 142nm. An optical display device comprises: an optical display panel, and a circular polarizer as described in any one of items 1 to 4 of the patent application scope bonded to the display surface of the optical display panel. As described in item 5 of the patent application scope, the circular polarizer is configured so that the polarizer layer is on the opposite side of the optical display panel relative to the phase difference layer, and a front panel is provided on the side of the circular polarizer layer. An optical display device as described in Item 6 of the patent application, wherein a touch sensor is provided between the display surface and the circular polarizer.

Images