KR20210006970A - Polarizing plate and display device using same - Google Patents

Abstract

A polarizing plate having a hard coat layer on one side and an adhesive layer on the other side is provided, and the polarizer of the polarizing plate contains at least one dichroic dye, and the polarizing plate is measured for light in a wavelength range of 380 nm to 780 nm. The luminous sensitivity corrected single transmittance (Ys) is 45% or more and 60% or less, and the polarization degree (Py) is 50% or more and 95% or less, and a*s is -3 or more +3 in the color of the L*a*b* color system. And b*s is -3 or more and +3 or less, and a*p is -3 or more and +3 or less and b*p is -3 or more in hue when two polarizing films are used and the polarization axis is a parallel position It is less than +3.

Description

Polarizing plate and display device using same

The present disclosure relates to a polarizing plate and a display device using the same.

In recent years, a mirror display in which a mirror (mirror) and a display (image display device) are combined to be integrated has been widely used. In particular, when the rearview mirror (rearview mirror) of a vehicle is used as a mirror display, the rear view can be illuminated with a camera provided outside the rear of the vehicle to compensate for the blind spots obscured by the rear seats or the pillars of the vehicle. , More safe driving becomes possible.

The mirror display is typically known as a half-mirror system, and is a display device that includes a display device under the half-mirror, and displays an image to be exposed in a mirror, or can switch between a mirror state and an image display state. .

On the other hand, a mirror display provided with a shutter mechanism for switching between a display mode and a mirror mode on the front surface of a display device has been proposed (hereinafter referred to as a liquid crystal shutter system). In this method, a liquid crystal cell including an absorption type polarizing plate and a reflection type polarizing plate is provided on the front surface of the display unit, and the image display mode and the mirror mode can be switched by driving the liquid crystal cell. Thereby, in the liquid crystal shutter system, since double reflection (a phenomenon in which an image display image and a reflection image are visible at the same time), which was a problem in the half mirror system, is reduced, it is particularly preferable as a rearview mirror for automobiles.

As the absorption type polarizing plate used for the viewing side of such a mirror display, a polarizing plate provided with a polarizer formed by dyeing and stretching a dichroic dye such as iodine or dye in polyvinyl alcohol is used. . At this time, a polarizing plate having a high transmittance and high polarization degree may be used from the image display properties of the mirror display and the reflection characteristics during the mirror display. Therefore, an iodine-based polarizing plate, which has superior optical properties over a dye-based polarizing plate, is used, and the single transmittance of the polarizing plate is 42 to 45% and the polarization degree is 96.6 to 99.5% when both polarization characteristics and display contrast are combined. have. Accordingly, linearly polarized light from the image display unit can be emitted with high transmission.

Since the high polarization iodine polarizing plate generally has a low transmittance characteristic on the short wavelength side (near 420 nm), if the polarizing plate is used as a polarizing member for a shutter of the mirror display, it is displayed in a display mode or a mirror mode. There is a problem in that the image turns yellow, and it is not as good as a mirror made of conventional glass plate and metallic luster. Waveform balance and hue of a polarizing plate are generally performed by adjusting the mixing conditions of a dichroic dye or dyeing conditions of a polarizing film, but in a polarizing plate using only an iodine dye, it is not easy to adjust the polarizing plate to a neutral hue. not.

Further, in order to improve the function as a mirror, the reflectance in the mirror mode can be improved by increasing the transmittance of the polarizing plate. In this case, with an iodine polarizing plate, high transmittance can be achieved by reducing the amount of dyeing of iodine in the polarizing film. However, a polarizing plate including a polarizing film that has been highly permeable by reducing the amount of iodine has a remarkable decrease in optical durability against high temperature and high temperature and high humidity. Therefore, it does not correspond as a member requiring high durability of automobiles or the like.

From the above point of view, since the use of an iodine-based polarizing plate for the absorption type polarizing plate of the liquid crystal shutter cannot satisfy the above requirements, a polarizing plate having characteristics corresponding to the method is required. In addition, since the mirror member is constituted by laminating films such as a polarizing plate, if the smoothness of the film is poor or has a distortion (curvature), vibration will occur on the display. Therefore, in the mirror display of this system, it is necessary to maintain a display quality comparable to that of a conventional mirror using a smooth glass surface.

An object of the present disclosure is to provide a polarizing member excellent in optical properties, durability, and display quality as an absorption type polarizing plate of the shutter portion in a liquid crystal shutter type mirror display. That is, one aspect of the present disclosure includes a polarizing plate having a hard coat layer on one side and an adhesive layer on the other side, and the polarizer of the polarizing plate contains at least one dichroic dye, and the polarizing plate is 380 nm or more. The luminous sensitivity corrected single transmittance (Ys) measured for light in the wavelength range of 780 nm or less is 45% or more and 60% or less and the polarization degree (Py) is 50% or more and 95% or less, and the polarizing plate, In the hue of the simple L*a*b* color system, when a*s is -3 or more and +3 or less and b*s is -3 or more and +3 or less, and the polarization axis is set to a parallel position with two polarizing plates In the hue of, a*p is -3 or more and +3 or less, and b*p is -3 or more and +3 or less.

Here, the adhesive layer may have a bending degree of 7 or less, and the polarizing member may have a bending degree of 15 or less.

Further, the dichroic dye may contain a water-soluble disazo compound represented by the general formula (1) or a copper complex compound thereof.

[Formula 1]

(However, X represents a hydrogen atom, a methyl group, a methoxy group or an ethoxy group, and Y represents a methoxy group or an ethoxy group. R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, -C ₂ H ₄ OH group, a substituted or unsubstituted phenyl group, a phenyl group substituted with a carboxyl group, a phenyl group substituted with a sulfone group.)

Further, as the polarizing member, it may be used for a mirror display of a liquid crystal shutter system.

Another aspect of the present disclosure is a liquid crystal shutter type mirror display, wherein the polarizing member, the shutter liquid crystal cell, the reflective polarizing plate, and the image display device are arranged in this order from the viewing side.

According to the present disclosure, it is possible to provide a polarizing member that suppresses coloration of a display image or a reflective image, is highly durable, and does not shake the display while maintaining an emission luminance equivalent to an iodine polarizing plate having a high polarization degree. Thereby, it is possible to realize a mirror display of a liquid crystal shutter system that displays high-quality images or reflective images.

1 is a schematic cross-sectional view showing a configuration of a polarizing member in an embodiment of the present disclosure.
2 is a diagram showing a measurement result of linearly polarized light transmittance with respect to wavelength in Example 1 and Comparative Example 1. FIG.

As shown in the cross-sectional schematic diagram of FIG. 1, the polarizing member 100 in the embodiment of the present disclosure is the adhesive layer 10, the first support film 12a, the polarizing film 14, and the second support film ( 12b) and a hard coat layer 16. Fig. 1 is a schematic diagram only, and the actual film thickness of each layer is not the same as in the drawing.

The polarizing member 100 can be used as a member of a liquid crystal shutter type mirror display, and is provided, for example, on the viewing side of a mirror display mounted on a rear view mirror of an automobile. The mirror display may include a display device on the entire surface, the mirror and the display image may be switched on the entire surface or partially, and at least one display device is provided on a part of the front surface, and the location is partially The mirror and the display image may be switched. In addition, the display image is information displayed by the display device unit, and refers to a color display such as an image or a moving picture, or a simple display using dots or segments such as alphanumeric characters.

In a liquid crystal shutter type mirror display, an absorption type polarizing plate, a liquid crystal cell, and a reflective polarizing plate are provided as shutter members on the front surface of a liquid crystal display device in this order from the viewer side, and the state of the mirror and the image display state are determined. It is a switchable display device.

Light emitted from the display device is linearly polarized light. In the case of the display mode of the display (an image is monitored by the display device), the transmission axes of the polarizing plate, the reflective polarizing plate, and the absorbing polarizing plate on the front surface of the display device are in a parallel relationship. That is, this method can suppress a decrease in the amount of light from the display device compared to the half mirror method. At this time, since the absorption axis of the absorption type polarizing plate is orthogonal to the transmission axis of the reflection type polarizing plate, the reflected light (reflected polarized light) of the reflection type polarizing plate is absorbed by the absorption type polarizing plate. Thereby, double reflection in the display mode is reduced.

In the case of the mirror mode, the transmission axes of the reflective polarizing plate and the absorbing polarizing plate have an orthogonal relationship. In this case, reflection of external light (natural light) is transmitted from the absorption type polarizing plate (it becomes linearly polarized light), then is reflected by the reflection type polarizing plate, and again passes through the absorption type polarizing plate. therefore. In order to obtain a higher reflectance, the absorption type polarizing plate is preferably made to have a higher transmittance, and thereby becomes a mirror with high visibility.

The liquid cell is a liquid crystal layer sandwiched by a transparent electrode. Specifically, a state in which the polarization axis is changed when the incident linearly polarized light is transmitted, and a state in which the polarization axis is not changed is used for electrical conversion. It is an element having a structure that can be selected by Thereby, the relationship between the polarization axis of the absorption type polarizing plate and the reflection type polarizing plate is switched, and the state of the mirror and the state of image display can be switched. As a liquid crystal cell, a TN (twisted nematic) type liquid crystal is typically used.

The reflective polarizing plate includes a polarizer having a function of transmitting polarized light parallel to the transmission axis and reflecting polarized light orthogonal to the transmission axis, and serves as a mirror in the mirror display according to the present embodiment. As the polarizing plate, for example, a birefringent reflective polarizing film in which a plurality of layers of different birefringent polymer films are alternately laminated can be used, and as a commercially available reflective polarizing film, the DBEF series manufactured by 3M is mentioned. As another reflective polarizing film, a film having a configuration in which a phase difference layer of 1/4 wavelength is disposed on the outside and inside of the cholesteric liquid crystal layer can be mentioned. Further, a wire grid type inorganic polarizing plate can be used as a reflective polarizing plate. Such a film is used by bonding to a liquid crystal cell through an adhesive layer or an adhesive layer. In addition, between the display device unit and the liquid crystal shutter unit, that is, between the reflective polarizing plate, in order to reduce internal reflection, for example, an optical adhesive layer may be provided and laminated, or an antireflection layer may be provided on both surfaces. do.

The polarizing plate (absorption type polarizing plate) according to the present disclosure will be described below.

[Polarizer]

The polarizing plate has a configuration in which the support film 12 (in FIG. 1, the first support film 12a and the second support film 12b) are bonded to each other on one or both surfaces of the polarizing film 14 having a polarizer. Have. Although only the polarizing film 14 may be used, it is preferable to use both sides of the polarizing film 14 as a polarizing plate sandwiched between the first support film 12a and the second support film 12b. Because, in general, the polarizing film 14 is a polyvinyl alcohol-based resin (PVA) film dyed with a dichroic dye uniaxially stretched, and has a thin film shape, so that the first support film 12a and the first 2 This is because, in the state not being pinched by the support film 12b, it is easily deformed by heat or moisture, and further, there is a fear that the polarization characteristic may be impaired.

The polarizing film 14 is a film having a function of converting natural light into linearly polarized light, and a dichroic dye may be adsorbed and oriented in a PVA film. Examples of the dichroic dye include an azo compound, an anthraquinone compound, or a tetragine type. In particular, when a dichroic dye of an azo compound is used, the optical properties of the azo compound are obtained under high temperature conditions or high temperature and high humidity conditions. Excellent durability and easy color adjustment. Therefore, in the case of using a dichroic dye, even if the polarizing film 14 is superimposed on the display device, the influence of yellow coloring can be suppressed compared to the iodine polarizing film.

As the dichroic dye used for the polarizing film 14, from the viewpoint of optical properties and durability, an azo compound-based dye is preferable. For example, CIDirect Yellow 12, CIDirect Yellow 28, CIDirect Yellow 44, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 107, CIDirect Red 2, CIDirect Red 31, CIDirect Red 79, the dye described in Japanese Unexamined Patent Application Publication No. 2003-215338, the dye described in WO2007/138980 Can be lifted.

Commercially available dyes include Kayafect Violet P Liquid (manufactured by Nihon Kayaku Corporation), Kayafect Yellow Y and Kayafect Orange G, Kayafect Blue KW, Kayafect Blue Liquid 400, and the like.

Further, in order to obtain the color of the achromatic polarizing plate described in WO2015/186681, WO2014/162634, etc., an optimized dichroic dye may be used.

At this time, it is preferable to make a neutral gray color by mixing two or three or more of these dyes and dyeing them on the PVA so as to complement the polarization characteristics at each wavelength in the visible region. For example, in the case of mixing three or more types of dyes containing blue-based dichroic dyes, in particular, by adjusting the blending amount of blue-based dichroic dyes, the polarizing film 14 is superimposed on the display device. The degree of coloration of yellow can be optimized or matched to coloration from blue. In addition, by using a dichroic dye optimized to obtain an achromatic color, it is possible to more easily adjust the neutral gray color. As the commercially available dye-based polarizing plate, the "Achromatic" series manufactured by Polar Techno Co., Ltd. is mentioned, for example.

As the azo compound, it is particularly preferable from the viewpoint of durability that the water-soluble disazo compound represented by the general formula (2) or the copper complex compound is included.

[Formula 2]

Here, X represents a hydrogen atom, a methyl group, a methoxy group or an ethoxy group, and Y represents a methoxy group or an ethoxy group. R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, a -C ₂ H ₄ OH group, a substituted or unsubstituted phenyl group, a phenyl group substituted with a carboxyl group, a phenyl group substituted with a sulfone group.

As the compound, a commercially available one may be used, and it can be produced by a known manufacturing method, for example, a manufacturing method described in Japanese Unexamined Patent Application Publication No. 59-145255.

Further, as the azo compound, it is preferable to contain a water-soluble compound represented by the general formula (3) or a copper complex salt compound thereof.

[Formula 3]

Here, A represents a phenyl group or a naphthyl group substituted with a methyl group, and R represents an amino group, a methylamino group, an ethylamino group or a phenylamino group.

As the compound, a commercially available one may be used, and it can be produced by a known production method, for example, a production method described in Japanese Unexamined Patent Application Publication No. Hei 3-12606.

When a dichroic dye is used as the dichroic dye, the durability of the optical properties under high temperature conditions or high temperature and high humidity conditions is superior to that of iodine, and the color change during molding is also less than that of iodine. Therefore, while the color adjustment in the polarizing film 14 is easy, yellow can be made low compared with the case where iodine is used as a dichroic dye.

The polarizing film 14 or polarizing plate suitable for the polarizing member 100 has a luminous sensitivity corrected single transmittance (Ys) of 45% or more and 60% or less, measured for light in a wavelength range of 380 nm or more and 780 nm or less, and a polarization degree ( It is preferable that Py) is 50% or more and 95% or less. However, the relationship between the optical properties of the single transmittance (Ys) and the polarization degree (Py) is the case of a polarizing film using a general dichroic dye. There is a possibility that the optical properties can be improved by increasing the performance of individual dichroic dyes or improving orientation. In that case, with respect to the range of Ys, Py may exceed the range upward.

When the single transmittance (Ys) is less than 45%, the polarization degree (Py) exceeds 95%. The transmittance of linearly polarized light in this case is about 85% or less. Therefore, a display luminance equivalent to an iodine polarizing plate (single transmittance (Ys): 43%, linearly polarized transmittance: about 86%) cannot be obtained, and coloration on the display cannot be improved.

In the case of a polarizing plate having a single transmittance (Ys) of more than 60%, the degree of polarization (Py) is less than 50%, and since sufficient polarization characteristics are not obtained, there is a fear that the shutter function of the mirror display may not sufficiently function.

Therefore, the preferable optical property of the polarizing film 14 is a single transmittance (Ys) of 45% or more and 60% or less, particularly 50% or more and 55% or less. Thereby, the linearly polarized light transmittance becomes 87% or more, and display luminance equal to or equal to or higher than the iodine polarizing plate can be obtained. In this case, coloration of a display image can be suppressed than that of an iodine polarizing plate. Further, since the polarizing plate has a higher transmittance, the reflectance of natural light is improved, and the visibility of the mirror mode is improved.

Since the polarizing plate is disposed on the front surface of the display device, it is preferable that the polarizing plate has a neutral hue without coloring in order to prevent the image display image or the reflective image from being colored in yellow or the like. Specifically, in the color of the L*a*b* color system, the values of a* and b* of the polarizing plate are all 0 or close to 0, but from the viewpoint of processing the polarizing plate and the characteristics of various dyes, It is not easy to manufacture a polarizing plate having such a color value. Therefore, when applied to a mirror display, it is preferable to set it as a color value that is difficult to visually recognize coloring. In the case of the polarizing plate alone (s), it is preferable that a*s is -3 or more and +3 or less, and b*s is -3 or more and +3 or less. Thereby, coloring on the image display from the information device can be suppressed. Further, in the case of a color value when two polarizing plates are used and the polarization axis is a parallel position (p), it is preferable that a*p is -3 or more and +3 or less and b*p is -3 or more and +3 or less. As a result, coloring can be suppressed on the reflection of the mirror.

The transmittance (unit:%) and polarization degree (unit:%) in this embodiment are values measured by V-7100 manufactured by Nippon Spectroscopy Corporation or U-4100 manufactured by Hitachi Corporation. Specifically, a polarizing plate is prepared, and the transmittance when one sheet of the polarizing plate is used is the single transmittance (Ys), and the transmittance when the two polarizing plates are stacked so that the absorption axis direction is the same is the parallel position transmittance (Yp). , The transmittance when the two polarizing plates are stacked so that their absorption axes are orthogonal is taken as the orthogonal position transmittance (Yc). Each transmittance is calculated by calculating the spectral transmittance τλ at a predetermined wavelength interval dλ (here 5 nm) in a wavelength range of 380 to 780 nm, and is calculated by Equation (1). In Equation (1), Pλ represents the spectral distribution of the standard light (C light source), yλ represents the 2-degree field isochromic function, and τλ represents the spectral transmittance.

[Equation 1]

Further, the degree of polarization Py is obtained from the parallel position transmittance Yp and the orthogonal position transmittance Yc by the equation (2).

[Equation 2]

The transmittance of linearly polarized light is a transmittance obtained by injecting absolute polarized light into a polarizing plate and measuring the vibration direction of the absolute polarized light and the absorption axis direction of the polarizing plate so as to be orthogonal, and is expressed as an absolute parallel transmittance (Ky). Here, the absolute parallel transmittance (Ky) can be obtained by substituting the single transmittance (Ys) and the orthogonal position transmittance (Yc) obtained above into Equation (3). In addition, the absolute parallel transmittance (Ky) may be determined only for the transmittance of a predetermined wavelength at each wavelength of 380 nm or more and 780 nm or less, depending on the design of the display device or the waveform characteristics of the polarizing plate, and is within a predetermined wavelength range. You may express it as an average value.

[Equation 3]

When using the support film 12 as a polarizing plate, the support film 12 is pasted on one side or both sides of the polarizing film 14 via an adhesive layer. As the support film 12 (the first support film 12a, the second support film 12b), a cycloolefin resin film, a polyester resin film, an acrylic resin film, a polycarbonate resin film, a polysulfone resin Films, alicyclic polyimide resin films, acetyl cellulose resin films, and the like can be applied. From the viewpoint of easily adhering to a polarizing film to obtain a polarizing plate, it is preferable to use an acetyl cellulose resin, more preferably triacetyl cellulose (TAC).

Further, depending on the type of UV absorber or the like added to the support film, the transmittance on the short wavelength side (around 420 nm) decreases, and as a result, b*s as a polarizing plate affects the increase. The degree of this increase is proportional to the thickness of the support film. Therefore, the thickness of the support film is preferably 100 µm or less, more preferably 40 to 80 µm, and a polarizing plate configuration in which the influence of coloring is suppressed is preferable.

When drivers of automobiles wear polarized sunglasses, there is a concern that the polarization axis of the polarizing film 18 of the polarizing member 100 and the polarizing sunglasses coincide, so that the displayed image cannot be visually recognized or used as a mirror. have. Therefore, by providing a retardation film on the viewing side of the polarizing member 100, that is, on the viewing side of the polarizing plate, the problem of visibility can be solved. In this embodiment, you may bond to the visual recognition side of a polarizing plate via an adhesive or adhesive layer, and you may use it as the supporting film 12b of a polarizing plate. In this case, it is preferable to provide a hard coat layer on the surface which becomes the visible side of the retardation film.

The retardation film is a film-shaped optical member made of a birefringent material. The thickness of the retardation film may be 5 µm or more and 200 µm or less, or 10 µm or more and 150 µm or less. When the thickness of the retardation film is less than 5 µm, the handleability as an industrial material decreases. In addition, when the film thickness is more than 200 µm, distortion or curvature due to film formation tends to occur, and there is a concern that the display quality of the mirror display may be impaired.

The material of the retardation film is, for example, a stretched film containing a polycarbonate-based resin, a polyester-based resin, or a cycloolefin-based resin as a main component, or a UV-curable polymer liquid is coated on a transparent film and oriented. You can choose one.

The retardation of the retardation film may be in a range of 100 nm or more and 30000 nm or less. As a retardation film, a lambda /4 retardation film, a lambda /2 retardation film, and other high-order retardation films which have super birefringence are mentioned, for example.

In the retardation film, it is preferable that the relationship between the angle formed by the slow axis and the absorption axis of the polarizing plate 100 is greater than 0° and less than 90°. That is, it is preferable to exclude the case where the slow axis of the retardation film and the absorption axis of the polarizing plate 100 coincide (the relation angle is 0°) and the case where they are orthogonal (the relation angle is 90°), and in one aspect, 40 It is preferable to laminate the retardation film and the polarizing plate 100 so as to be -50 degrees, more preferably 45 degrees. In this relationship, since the polarized light emitted or reflected from the mirror display is not absorbed by the absorption axis of the polarized sunglasses, display information of the device can be visually recognized even when wearing polarized sunglasses.

As for the polarizing member 100 provided with the retardation film, it is preferable to select a material or manufacturing method in the above-described retardation film, adhesive or adhesive layer, hard coat layer, etc. so that the degree of curvature as defined below is 15 or less. In particular, when using an adhesive layer in lamination of a polarizing plate and a retardation film, it is preferable to use an adhesive layer in which the occurrence of "curvature" described later is suppressed. Thereby, also in the polarizing member 100 provided with the retardation film, the mirror display which has a high-quality mirror surface with little distortion can be obtained.

[Adhesive layer (10)]

The adhesive layer 10 is provided as a layer used when bonding the polarizing member 100 to another member. The adhesive layer 10 is provided on the surface opposite to the polarizing film 14 in the first support film 12a. The pressure-sensitive adhesive layer 10 is formed by applying a pressure-sensitive adhesive obtained by diluting a solid component of an acrylic or polyester-based pressure-sensitive adhesive with a solvent such as toluene or methyl ethyl ketone (MEK) on a release film and drying it. The pressure-sensitive adhesive is not particularly limited as long as it is an acrylic type or a polyester type, and an adhesive other than these may be further used. In addition, additives such as a curing agent or a silane coupling agent may be blended in the pressure-sensitive adhesive to adjust the adhesion to the adherend, or to have a characteristic in which the occurrence of peeling or foaming is suppressed in terms of durability. Here, the dilution rate of the solid component by the solvent may be 5 times or less. Thereby, it can be set as the adhesive layer which suppressed the generation|occurrence|production of "currency" mentioned later.

Next, the blended pressure-sensitive adhesive is applied to a release film, and the solvent is volatilized in the drying step. In the drying process, the solvent may be volatilized from the release film to which the pressure-sensitive adhesive has been applied using a plurality of drying furnaces set in a temperature range of 40°C to 100°C, respectively.

At this time, the coating amount is adjusted so that the thickness of the pressure-sensitive adhesive after drying is 1 µm or more and 30 µm or less, and more preferably 5 µm or more and 25 µm or less. After that, the pressure-sensitive adhesive side is bonded toward the first support film 12a.

[Hard coat layer (16)]

The hard coat layer 16 is a layer for protecting the surface of the polarizing member 100. The hard coat layer 16 is provided on the surface of the second support film 12b on the opposite side of the polarizing film 14. The hard coat layer 16 can be obtained, for example, by applying an ultraviolet curable resin to the surface of the second support film 12b and curing it by irradiating with ultraviolet rays. Specifically, for example, a paint was prepared by mixing with methyl ethyl ketone as a solvent with one or more polyfunctional (meth)acrylates, a polymerization initiator, and a surface modifier, and applied to one side of the TAC film. The hard coat layer 16 may be formed by drying the solvent at -80°C and then curing by irradiating with ultraviolet rays using a high-pressure mercury lamp. The film thickness of the hard coat layer 16 may be 1 µm or more and 20 µm or less from the viewpoint of the hardness and curing after curing. When the film thickness is 20 μm or more, high hardness is obtained, but the film is severely bent, and thus it cannot be easily bonded to the polarizing film, and there is a risk of cracks in the hard coat layer due to bending during processing. , It may cause peeling in the durability test. Therefore, the film thickness may be 2 µm or more and 10 µm or less, and a hard coat layer having both hardness and workability can be obtained. In addition, a solvent in which nano-level colloidal silica is dispersed (for example, organo silica sol manufactured by Nissan Chemical Industries, Ltd.) may be blended to improve hardness or reduce warpage.

At this time, by using a dilute solvent that has an erosive effect on the support film, the interface between the formed hard coat layer and the support film is mixed with each other, and the thin film interference of the reflected light between the hard coat layer and the support film (interference pattern ) Can be suppressed.

Further, by performing ultraviolet irradiation in a nitrogen atmosphere, scratch resistance can be improved. The scratch resistance is evaluated by, for example, a scratch test with steel wool (#0000, 250 g load, 10 to 100 reciprocations), and it is preferable that the hard coat surface is not scratched by the test.

The hardness of the hard coat layer is evaluated by a pencil hardness test (scratch hardness (pencil method)) based on JIS5600-5-4. For example, when the supporting film on which the hard coat layer is formed is a TAC film (40 to 80 μ), the hardness is generally preferably 750 g load 2H or more in the evaluation method, more preferably By having a 750 g load of 4H or more, it is determined to have a hard coat layer of high hardness. However, since the hardness according to the evaluation method depends not only on the film thickness of the hard coat layer, but also on physical properties such as the thickness of the supporting film used as the base and the pressing hardness (easily crushed), it is limited to the above index. no.

The hard coat layer 16 may contain a surface modifier. Thereby, leveling of the applied coating liquid is urged to form a smooth surface, and a surface having an excellent surface feel as a member for a mirror display can be formed. Further, by using a silicone-based or fluorine-based surface modifier, it is possible to impart antifouling properties and anti-fingerprint functions to the hard coat layer 16.

[About the curvature]

When the supporting film 12 or other membranes, especially resin diluted with a solvent, are formed by the cast method, the resin and the solvent convection in the process of concentration concentration due to removal of the solvent during film formation. There is a case that the vibration caused by the film remains even after film formation. In addition, there may be cases where shaking occurs due to the influence of wind during air drying. The "curvature" refers to a state of such a distribution of fluctuations in film thickness and a non-uniform distribution of phase difference.

When the support film 12 or the adhesive layer 10 of the polarizing member 100 has a curvature, it becomes a cause of distortion of a display image in a liquid crystal display to which the polarizing member 100 is applied. Therefore, it is preferable that the member used for the polarizing member 100 has as low a degree of curvature as possible.

The degree of curvature is an evaluation value for numerically evaluating the quality of a displayed image on a mirror display. The bending degree of the support film 12, the polarizing plate, the adhesive layer 10, etc. can be measured using a polarizing plate bending inspection apparatus manufactured by Fusion Corporation.

The measurement of the bending degree will be described. Dot patterns at equal intervals are displayed on a monitor display of 4K resolution, and a monitor image of a dot pattern reflected in the mirror portion is photographed with a camera through a smoothing mirror installed at an angle of 45 degrees. This is taken as blank measurement. Next, an object to be measured, such as a support film 12, a polarizing plate, and an adhesive layer 10, is placed between the mirror and the camera, and the image of the dot pattern when the object to be measured is transmitted is measured with the camera. In this case, the object to be measured is bonded to a smooth glass plate using an adhesive. By image analysis of the captured dot pattern, the standard deviation (Total?) of the shift of the dot pattern is obtained, and the value is taken as the curvature.

The degree of curvature is about 5 at the time of blanking. That is, as the degree of curvature is closer to 5, there is almost no curvature, and as the degree of curvature is greater than 5, the optical distortion is inherent in the object to be measured.

The degree of curvature of a general polarizing member (including a polarizing plate and an adhesive layer) applied to a liquid crystal display is 20 or more and 23 or less. When such a polarizing member is used as a member of a mirror display, a curvature is more likely to be recognized compared to a case where a liquid crystal display is viewed directly. The reason for this is that in a mirror display, it is often used in a mirror state without image display, and since the reflected image is observed, the surface shape becomes important. Therefore, if there is a curvature of the polarizing member 100 serving as a mirror surface, a landscape image reflected as a reflective image is distorted, and a sufficient function as a mirror display cannot be performed.

Therefore, the degree of curvature of the polarizing member 100 suitable for a mirror display is preferably 15 or less, and more preferably 8 or less. By setting it as such a curvature, in a mirror display using the polarizing member 100, a high-quality mirror surface with little distortion can be obtained.

In order to realize such a degree of curvature of the polarizing member 100, the support film 12 may be formed with a small degree of curvature. The support film 12 may have a degree of curvature of 12 or less, more preferably 7 or less. The degree of curvature in this case is a value when measured using an adhesive layer with a degree of curvature of 6 or less (there is little contribution of the adhesive layer). Since the degree of curvature of the support film 12 depends on its thickness, the thickness of the support film 12 may be 200 µm or less, more preferably 80 µm or less, and more preferably 40 to 60 µm.

In addition, the adhesive layer 10 may have a degree of curvature of 7 or less of the adhesive layer.

[About durability]

A member used for interior of an automobile is required to have high durability. For example, a display device such as a liquid crystal display is required to satisfy the reliability of 1000 hours or more in a dry heat test of 95°C and 1000 hours or more in a wet heat test of 65°C and 93%. This is based on the durability of a member such as a TFT liquid crystal display device used in the display device portion. It is preferable that the polarizing member used for the display device has the same or equivalent reliability. As for the durability in that case, for example, the dry heat test is 1000 hours or more at 105 degreeC, and the wet heat test is 240 hours or more at 85 degreeC and 85%. Therefore, it is preferable to use a dye-based polarizing film containing a dichroic dye as the polarizing member. In addition, as an evaluation item of the durability of a polarizing member, it is a change in optical characteristics, and changes in appearance, such as discoloration, peeling, and distortion, for example.

[Example 1]

[Production of the polarizing film 14]

After swelling a polyvinyl alcohol resin film (VF-PS (75 μm) manufactured by Kuraray Co., Ltd.) in water at 30°C for 5 minutes, a dyeing solution at 30°C (1000 parts by weight of water, 0.3 parts by weight of sodium tripolyphosphate, 0.11 parts by weight of C-I direct orange 39, 0.11 parts by weight of C-I direct red 81, 0.10 parts by weight of blue dye obtained from the method described in Japanese Unexamined Patent Application Publication No. Hei 3-12606, Japan A green-based dye obtained from the method described in Korean Patent Application Laid-Open No. 59-145255 is immersed in 0.11 parts by weight for 5 minutes, followed by dyeing treatment with the dye, and then stretched by 5.5 times in a 3 wt% boric acid aqueous solution at 50° C. After the stretching treatment, the stretched film was immersed in a 5% by weight boric acid aqueous solution at 50°C for 2 minutes, and after washing with water, it was dried in air at 30 to 80°C to obtain the polarizing film 14 of the present disclosure. The thickness of the polarizing film 14 was 30 µm.

[Manufacture of hard coat layer]

As a polyfunctional (meth)acrylate, 40 parts by weight of pentaerythritol triacrylate (manufactured by Nihon Kayaku Co., Ltd., KAYARADPET-30), 60 parts by weight of methyl ethyl ketone as a solvent, 0.2 parts by weight of an acrylic polymer leveling agent Part and 2 parts by weight of Irgacure 184 (manufactured by Chiba Specialty Chemical) as a polymerization initiator were mixed to prepare a coating material, and applied to one side of a 60 μ thick TAC film with a microgravure coater. Thereafter, the solvent was dried at 40 to 80° C. for 2 minutes to remove, and then the coating film was irradiated with ultraviolet rays with a high pressure mercury lamp in a nitrogen atmosphere, and the coating film was cured to form a hard coat layer on the TAC film. The film thickness of the obtained hard coat layer was about 5 mu. The pencil hardness of this hard coat layer was 2H under 750 g load.

[Manufacture of polarizing plate]

Using a water-based adhesive containing polyvinyl alcohol (PVA), a TAC film having a thickness of 60 μm was laminated on both surfaces of the polarizing film obtained by the above method. Then, it dried at 70 degreeC for 5 minutes, and obtained the polarizing plate. At this time, on one side to be laminated, a TAC film having a hard coat layer obtained by the above method is used as the second support film 12b, and a TAC film without a hard coat layer is adhered to the polarizing film as the first support film 12a. did. Table 1 shows the results of measuring the optical properties of the obtained polarizing plate using a spectrophotometer U-4100 manufactured by Hitachi. At this time, the single transmittance (Ys) of the polarizing plate was 50.1%, and the polarization degree (Py) was 73.7%. Further, linearly polarized light transmittance was measured using V-7100 made by Japan Spectroscopy, and the transmittance waveform of the polarizing plate in the visible region is shown in FIG. 1.

[Production of adhesive layer 10]

According to a known document (Japanese Patent Application Laid-Open No. 2016-206468), an acrylic pressure-sensitive adhesive was applied onto a release film and dried to prepare the pressure-sensitive adhesive layer 10. The adhesive layer 10 was provided to the polarizing member 100 by bonding the obtained coating surface toward the 1st support film 12a. After that, in order to accelerate the crosslinking reaction of the curing agent in the adhesive layer 10, it was held at 35°C for 3 days or more to obtain the polarizing member 100 in this example.

The film thickness of the obtained adhesive layer 10 was 20 µm. Only this adhesive layer 10 was bonded on a glass plate, and the degree of bending was 6.6 as measured by a polarizing plate bending inspection apparatus manufactured by Fusion Corporation. In addition, the TAC film having a thickness of 60 μm measured in the same manner was 6.5 and the degree of curvature of the polarizing member 100 was 7.4.

[Example 2]

After swelling a polyvinyl alcohol resin film (VF-PS (75 μm) manufactured by Kuraray Co., Ltd.) in water at 30°C for 5 minutes, a dyeing solution at 30°C (1000 parts by weight of water, 0.3 parts by weight of sodium tripolyphosphate, 0.0.10 parts by weight of C-I direct orange 39, 0.10 parts by weight of C-I direct red 81, and 0.13 parts by weight of blue dye obtained by the method described in Japanese Unexamined Patent Application Publication No. Hei 3-12606 , The green dye obtained from the method described in Japanese Unexamined Patent Application Publication No. 59-145255 is immersed in 0.10 parts by weight for 5 minutes, followed by dyeing treatment with the dye, followed by stretching by 5.5 times in a 3% boric acid aqueous solution at 50°C. After the stretching treatment, the stretched film was immersed in a 5% by weight boric acid aqueous solution at 50°C for 2 minutes, and after washing with water, it was dried in air at 30 to 80°C to obtain the polarizing film 14 of the present disclosure. The thickness of (14) was 30 µm. The optical properties of the obtained polarizing film were measured using a spectrophotometer U-4100 manufactured by Hitachi, and the single transmittance (Ys) was 50.1% and the polarization degree (Py) was 73.8%. In addition, since the ratio of the blue dye was increased in the dye formulation, the color could be shifted to blue color rather than the color of Example 1.

Production of a polarizing plate and production of a polarizing member were the same as those described in Example 1.

[Comparative Example]

An iodine polarizing plate SKN-18243T-HC (manufactured by Polar Techno) having a hard coat as a commercially available polarizing member was used. The thickness of the product (not including the protective film and the release film) is 220 µm, specifically, the film thickness of the hard coat layer is 5 µm, the support film is a 80 µm thick TAC film, and the adhesive layer is 25 µm. When the optical properties of the polarizing member were determined, the single transmittance (Ys) was 42.8% and the polarization degree (Py) was 99.9%. Further, linearly polarized light transmittance was measured using V-7100 made by Japan Spectroscopy, and the transmittance waveform of the polarizing plate in the visible region is shown in FIG. 1.

In the same manner as in Example 1, the polarizing member was bonded on a glass plate to measure the degree of bending, and the degree of bending was 22.2.

[Evaluation of optical properties]

The polarizing members of Example 1 and Comparative Example 1 were bonded to one side of a white plate glass having a thickness of 1.1 mm, and a reflective polarizing plate made by 3M DBEF was bonded to the opposite side of the glass plate using the aforementioned adhesive layer, and selected as a liquid crystal shutter. An evaluation sample was produced. At this time, the relationship between the polarization axis of the polarizing member and the transmission axis of the reflective polarizing plate was produced to be orthogonal and parallel, respectively. The case of the orthogonal relationship corresponds to the mode of the mirror mode in the mirror display, and the total light reflectance of the polarizing plate member surface of the sample at this time was measured to calculate the reflection hue (a*r, b*r). The total light reflectance (Yr) (unit:%) was measured using a spectrophotometer U-4100 manufactured by Hitachi Corporation, and the polarizing member surface of the evaluation sample was placed toward the integrating sphere side at the location of the white plate of the integrating sphere and measured. In the same manner as in the calculation method of Formula (1), the total light reflectance (Yr) was calculated.

In addition, the case of a parallel relationship corresponds to an aspect of a display mode in a mirror display. The transmittance of the sample at this time was measured and its hue was calculated. Table 2 shows the measurement results.

[Durability test]

The polarizing member obtained above was cut into a size of 45 x 40 mm (the absorption axis was parallel to the long side) and bonded on a white plate glass (thickness 1.1 mm) to be a sample for durability test. Thereafter, the sample was put into an autoclave, and pressure treatment was performed for 15 minutes under an atmospheric pressure of 0.5 MPa and a temperature of 60° C. to sufficiently adhere the adhesive layer of the polarizing member and the glass.

The conditions of the durability test were 105°C as a dry heat test and 85°C and 85% humidity as a wet heat test, and samples were put in each condition. In the evaluation of the durability performance, the optical properties of the sample before and after the insertion of the durability tester are measured using a spectrophotometer U-4100, and the amount of change in transmittance (Ys) and hue (a*s, b*s) before and after injection It was carried out by obtaining (after injection-before injection).

Tables 1 to 4 and Fig. 2 show measurement results for each Example and Comparative Example 1.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

As shown in Table 1, the color values of the polarizing plates obtained from Examples 1 and 2 were smaller than that of Comparative Example 1 using an iodine-based polarizing plate. As shown in the spectral waveform of Fig. 2, the transmittance on the short wavelength side was improved than that of Comparative Example 1, and a flat waveform was formed in the entire visible light region, so that a more neutral hue than that of Comparative Example 1 could be achieved. Further, by setting the single transmittance (Ys) to 50.1%, a linearly polarized light transmittance equivalent to that of Comparative Example 1 could be obtained. Therefore, since the amount of light from the display device is inferior to the case of using an iodine-based polarizing plate of high polarization, the same display luminance can be obtained.

Table 2 shows the evaluation results of the optical properties of the evaluation samples selected as the liquid crystal shutter unit. The reflectance of the mirror mode was higher than that of the polarizing member in Comparative Example 1 using an iodine-based polarizing plate. That is, in the polarizing member 100 according to the first embodiment, the visibility in the mirror state can be improved. In addition, the value of b*r of the polarizing member 100 in Example 1 was lower than that of Comparative Example 1. That is, coloration of the mirror can be suppressed by using the polarizing member 100 in Example 1. In addition, in the display mode, the polarization member 100 in Example 1 had a small hue value of Comparative Example 1. Therefore, similarly to the mirror mode, a display image with small coloring can be obtained.

The durability test results are shown in Tables 3 and 4. In the dry heat test (shown in Table 3), in Examples 1 and 2, the change in b*s was smaller than in Comparative Example 1. In other words, even when exposed to high temperatures for a long period of time, the degree to which the display turns yellow is small. In addition, in the moist heat test (shown in Table 4), in Examples 1 and 2, the amount of change in transmittance was small, so that the polarization performance was maintained, but in Comparative Example 1, the polarization degree (Py) was significantly lowered, and the polarization performance was lost. It is in the state.

Therefore, Examples 1 and 2, which are dye-based polarizing plates, have excellent optical durability under both high temperature and high humidity conditions.

As described above, according to the polarizing member 100 according to the present embodiment, since it is a polarizing member having a low degree of curvature, it is possible to suppress shaking of a display image or a reflection image. In addition, by using the polarizing member 100, in a liquid crystal shutter type mirror display used as a rear view mirror for automobiles, a high reflectance is provided in the mirror mode, and also in the display mode, the effect of coloring by the polarizing plate is reduced. I can do less. Further, it is possible to provide a dye-based polarizing plate for a mirror display having excellent durability in long-term use, and a mirror display using the same.

Claims (11)

As a polarizing member,
A polarizing plate having a hard coat layer on one side and an adhesive layer on the other side is provided,
The polarizer of the polarizing plate contains at least one dichroic dye,
The polarizing plate has a luminous sensitivity-corrected single transmittance (Ys) of 45% or more and 60% or less, and a polarization degree (Py) of 50% or more and 95% or less, measured for light in a wavelength range of 380 nm to 780 nm,
The polarizing plate is, in the hue of the single L*a*b* color system, a*s is -3 or more and +3 or less and b*s is -3 or more and +3 or less, and the polarization axis is parallel to two polarizing plates. A polarizing member in which a*p is -3 or more and +3 or less and b*p is -3 or more and +3 or less in hue when the position is set. The method of claim 1,
The adhesive layer has a degree of curvature of 7 or less,
The polarizing member has a degree of curvature of 15 or less. The method of claim 1,
The said dichroic dye is a polarizing member containing a water-soluble disazo compound represented by Formula (1) or its copper complex salt compound.
[Formula 1]

(However, X represents a hydrogen atom, a methyl group, a methoxy group or an ethoxy group, and Y represents a methoxy group or an ethoxy group. R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, -C ₂ H ₄ OH group, a substituted or unsubstituted phenyl group, a phenyl group substituted with a carboxyl group, a phenyl group substituted with a sulfone group.) The method of claim 2,
The said dichroic dye is a polarizing member containing a water-soluble disazo compound represented by Formula (2) or its copper complex salt compound.
[Formula 2]

(However, X represents a hydrogen atom, a methyl group, a methoxy group or an ethoxy group, and Y represents a methoxy group or an ethoxy group. R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, -C ₂ H ₄ OH group, a substituted or unsubstituted phenyl group, a phenyl group substituted with a carboxyl group, a phenyl group substituted with a sulfone group.) The method of claim 1,
A polarizing member used in a liquid crystal shutter type mirror display. The method of claim 2,
A polarizing member used in a liquid crystal shutter type mirror display. The method of claim 3,
A polarizing member used in a liquid crystal shutter type mirror display. The polarizing member according to claim 1,
A liquid crystal shutter type mirror display, characterized in that a shutter liquid crystal cell, a reflective polarizing plate, and an image display device are arranged in this order from the viewing side. The polarizing member according to claim 2, and
A liquid crystal shutter type mirror display, characterized in that a shutter liquid crystal cell, a reflective polarizing plate, and an image display device are arranged in this order from the viewing side. The polarizing member according to claim 3, and
A liquid crystal shutter type mirror display, characterized in that a shutter liquid crystal cell, a reflective polarizing plate, and an image display device are arranged in this order from the viewing side. The polarizing member according to claim 4, and
A liquid crystal shutter type mirror display, characterized in that a shutter liquid crystal cell, a reflective polarizing plate, and an image display device are arranged in this order from the viewing side.

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