JP7214412B2 - Display device using polarizing layer - Google Patents

Description

The present invention relates to a display device using a polarizing layer.

A dye-based polarizing layer that uses a dichroic azo dye or the like has higher durability in high-temperature, high-humidity and heat environments than an iodine-based polarizing layer that uses iodine, and can be used for a long time in such an environment. It is suitable for providing a display device in which deterioration of display hardly occurs over a long period of time. In particular, the dye-based polarizing layer is suitable for display devices for automobiles and outdoor use, which are used in harsh environments.

In recent years, along with the improvement in the optical performance of dichroic dyes, the optical properties of dye-based polarizing layers have also been improved, and display properties such as contrast in display devices such as liquid crystal display devices are also being improved.

Japanese Patent No. 6054588

By the way, in the dye-based polarizing layer, a plurality of dyes are blended and used in order to obtain desired polarizing properties in the visible light region. Individual dyes generally have a wavelength range (primary absorption region) exhibiting main polarization characteristics in the visible light region and a wavelength range (secondary absorption region) that does not contribute to polarization characteristics. When a plurality of dyes are blended, the secondary absorption region of one dye overlaps with the main absorption region of another dye, which causes the overall polarization characteristics of the dye-based polarizing layer to deteriorate.

For example, in order to ensure the brightness of white display in a display device, there is a case where a dye is blended so as to increase the single transmittance of the dye-based polarizing layer in the entire visible light region. However, when a dye is blended so as to increase the single transmittance of the entire visible light region, the transmittance at the orthogonal position (orthogonal transmittance) also increases in parallel, especially the orthogonal transmittance in the wavelength range of 700 nm or more is the iodine-based It may become larger than in the case of the polarizing layer. Specifically, for example, in order to increase the single transmittance in the wavelength range of 380 nm to 700 nm, if the type of dye that has a sub-absorption region in that wavelength range is reduced, 700 nm to 780 nm included in the main absorption region of the dye , the light absorption in the wavelength range may decrease, and the orthogonal transmittance in the wavelength range may increase.

In addition, the optical properties of the polarizing layer are generally evaluated based on the CIE1931 colorimetric system with values obtained using a light source with natural light (sunlight) as standard light. On the other hand, backlights used as light sources for display devices are generally white LEDs, which have emission luminance characteristics different from those of natural light. Therefore, when a display device attached with a dye-based polarizing layer having the above characteristics is evaluated based on the above method, no correlation is obtained between the obtained optical characteristic values and visual evaluation, and the dye-based polarized light having the above characteristics is not obtained. At the same time, an optical design has been demanded for the layer to impart polarization characteristics on the long wavelength side. In addition, since the iodine-based polarizing layer conventionally used for display devices has a wide range of polarization characteristics in the visible light region of 380 nm to 780 nm, the light emission characteristics of the backlight are considered with respect to the polarization characteristics of the polarizing layer. However, the optical design of the display device has not been carried out.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a display device in which desired optical characteristics can be obtained as a whole device including a dye-based polarizing layer and a backlight in consideration of the polarization characteristics of the dye-based polarizing layer.

One aspect of the present invention is a display device comprising a dye-based polarizing layer and a backlight, wherein the dye-based polarizing layer has a cross transmittance (Tc) of 1 in the visible light region of 380 nm or more and 780 nm or less. % or more, and the backlight has an emission intensity normalized by the maximum emission intensity in the visible light region of 380 nm or more and 780 nm or less in the orthogonal transmission wavelength range of 0.03 or less. A display device characterized by

Here, the dye-based polarizing layer preferably has the orthogonal transmission wavelength range in which the orthogonal transmittance (Tc) is 1% or more over the entire wavelength range of 700 nm or more and less than 750 nm.

In addition, the dye-based polarizing layer has a single transmittance (Ts) of 33% or more over the entire wavelength range of the visible light region of 420 nm or more and 780 nm or less, and a cross transmittance corrected for visibility in the wavelength range of 400 nm or more and 700 nm. (Yc) is preferably 0.01% or less.

Moreover, it is preferable to provide a liquid crystal layer.

According to the present invention, desired optical properties can be obtained in a display device using a dye-based polarizing layer.

It is a figure which shows the structure of the display apparatus in embodiment of this invention. It is a figure which shows the structure of the polarizing layer in embodiment of this invention. FIG. 4 is a diagram showing an example of light emission characteristics of a light source; It is a figure which shows the single transmittance|permeability of a polarizing layer. FIG. 4 is a diagram showing orthogonal transmittance of a polarizing layer; It is a schematic diagram which shows the structure at the time of performing an optical design simulation.

A display device 100 according to the embodiment of the present invention includes a polarizing layer 10, a first substrate 12, a color filter 14, a counter electrode 16, an alignment film 18, a liquid crystal layer 20, and an alignment film, as shown in the schematic cross-sectional view of FIG. 22 , a display electrode 24 , an interlayer insulating film 26 , a second substrate 28 , a polarizing layer 30 and a backlight 32 . The display device 100 functions as a device that receives light from the backlight 32 and outputs the light transmitted through the color filter 14 from the polarizing layer 10 side as indicated by an arrow to display an image. Note that FIG. 1 is a schematic diagram, and the size and thickness of each component do not reflect actual values.

In this embodiment, a liquid crystal display device will be described as an example of the display device 100, but the present invention can be applied to any display device that uses a combination of a polarizing layer and a backlight. be able to.

In the present embodiment, an active matrix liquid crystal display device will be described as an example of the display device 100. However, the scope of application of the present invention is not limited to this, and a display using a combination of a polarizing layer and a backlight can be used. The present invention can be applied to any display device as long as it is a device.

The first substrate 12 is a transparent substrate such as glass. The first substrate 12 is used to mechanically support the display device 100 and transmit light to display an image. The first substrate 12 may be a flexible substrate made of resin such as epoxy resin, polyimide resin, acrylic resin, polycarbonate resin, or the like.

A polarizing layer 10 is formed on the display surface side of the first substrate 12 . A polarizing layer 10 is formed to cover the substrate surface of the first substrate 12 . The polarizing layer 10 includes a dyed polarizing element obtained by dyeing a PVA (polyvinyl alcohol) resin with a dichroic dye. The polarizing layer 10 is generally laminated on the surface of the first substrate 12 via an adhesive layer.

A normal polarizing element is an iodine-based polarizing element formed of a resin dyed with iodine or an iodine compound. However, iodine and iodine compounds are weak against heat, and are deteriorated by heating at about 100°C. On the other hand, polarizing elements using dyes (dichroic dyes) are relatively resistant to heat. In addition, it has good resistance to aging when used at high temperatures.

A color filter 14 is formed on the first substrate 12 . The color filters 14 are arranged in a matrix in the in-plane direction of the first substrate 12 for each pixel. The color filter 14 receives light from a backlight 32, which will be described later, and transmits only light within a specific wavelength range. Specifically, a color filter 14 that transmits any one of red (R), green (G), and blue (B) light is provided for each pixel.

A counter electrode 16 is formed on the color filter 14 . The counter electrode 16 is a transparent electrode made of, for example, ITO (indium-tin-oxide).

An alignment film 18 is formed on the counter electrode 16 . The alignment film 18 is made of a resin material such as polyimide. For the alignment film 18, for example, a 5 wt % solution of N-methyl-2-pyrrolidinone, which is a polyimide resin, is printed on the counter electrode 16, cured by heating at about 110° C. to 280° C., and then rubbed with a rubbing cloth. It can be formed by performing an orientation treatment. The orientation direction of the orientation film 18 is perpendicular to the orientation direction of the orientation film 22, which will be described later.

Next, the configuration and manufacturing method of the second substrate 28 will be described. The second substrate 28 is used to mechanically support the display device 100 and transmit light from the backlight 32 to enter the color filter 14 and the like. The second substrate 28 can be a transparent substrate such as glass. Also, the second substrate 28 may be a flexible substrate made of resin such as epoxy resin, polyimide resin, acrylic resin, polycarbonate resin, or the like.

A polarizing layer 30 is formed on the second substrate 28 . The polarizing layer 30 preferably includes a dyed polarizing element obtained by dyeing a PVA (polyvinyl alcohol) resin with a dichroic dye. For example, the dye-based material preferably contains an azo compound and/or its salt. The polarizing layer 30 is generally laminated to the surface of the second substrate 28 via an adhesive layer.

As described above, polarizing elements using dyes (dichroic dyes) are relatively heat resistant. In addition, it has good resistance to aging when used at high temperatures.

A backlight 32 is provided on the polarizing layer 30 . The backlight 32 includes a light source that outputs light. The light source is preferably a white LED, for example.

A switching element such as a TFT can be arranged on the second substrate 28 for each pixel. In FIG. 1, two TFTs are shown. A gate electrode 28a connected to a gate line is arranged below (on the substrate) in the approximate middle of the TFT. A gate insulating film 28b is formed to cover the gate electrode 28a, and a semiconductor layer 28c is formed to cover the gate insulating film 28b. The gate insulating film 28b is made of an insulator such as SiO ₂ . The semiconductor layer 28c is made of amorphous silicon or polysilicon, the portion immediately above the gate electrode 28a is a channel region with almost no impurities, and the both sides are a source region and a drain region to which conductivity is imparted by impurity doping. be done. A contact hole is formed over the drain region of the TFT, a metal (e.g., aluminum) drain electrode is arranged (electrically connected) there, and a contact hole is formed over the source region, where the metal A source electrode (eg, aluminum) is deposited (electrically connected). The drain electrode is connected to a data line supplied with a data voltage.

A display electrode 24 is provided via an interlayer insulating film 26 on the surface of the second substrate 28 on which the TFTs are formed. The display electrodes 24 are individual electrodes separated for each pixel, and are transparent electrodes made of, for example, ITO (indium tin oxide). The display electrodes 24 are connected to source electrodes formed on the second substrate 28 .

An alignment film 22 is formed covering the display electrodes 24 . The alignment film 22 is made of a resin material such as polyimide. For the alignment film 22, for example, a 5 wt % solution of N-methyl-2-pyrrolidinone, which is a polyimide resin, is printed on the display electrodes 24, cured by heating at about 180° C. to 280° C., and then rubbed with a rubbing cloth. It can be formed by performing an orientation treatment.

Furthermore, the liquid crystal layer 20 is sealed between the alignment films 18 and 22 so that the alignment films 18 and 22 face each other. A spacer (not shown) is inserted between the alignment films 18 and 22, liquid crystal is injected between the alignment films 18 and 22, and the periphery is sealed with a sealing material (not shown). Thus, the liquid crystal layer 20 is formed.

The alignment of the liquid crystal layer 20 is controlled by the alignment films 18 and 22 , and the initial alignment state of the liquid crystal in the liquid crystal layer 20 (when no electric field is applied) is determined by the alignment films 18 and 22 . By applying a voltage between the display electrode 24 and the counter electrode 16, an electric field is generated between the display electrode 24 and the counter electrode 16, and the orientation of the liquid crystal layer 20 is controlled to control the transmission/non-transmission of light. is controlled.

The relationship between the polarizing layers 10 and 30 and the backlight 32 in the display device 100 will be described below. Moreover, the configurations of the polarizing layer 10 and the polarizing layer 30 and the numerical values of the wavelength ranges described below are not limited to these.

As described above, the polarizing layer 10 and the polarizing layer 30, which are dye-based polarizing layers, use a combination of multiple dyes to obtain desired polarizing properties in the visible light region. That is, the dye-based polarizing layer generally has polarization characteristics broadly in the visible light region by blending a plurality of dichroic dyes of different hues so as to obtain polarization characteristics and waveform bands that extend to the iodine-based polarizing plate. Become.

Each dye has a wavelength range (main absorption region) exhibiting main polarization characteristics and a wavelength range (secondary absorption region) that does not contribute to polarization characteristics in the visible light region of 380 nm or more and 780 nm or less. Therefore, by mixing a plurality of dyes, the sub-absorbing region overlaps with the main absorbing region of another dye, and this becomes a factor of deteriorating the polarization characteristics of the dye-based polarizing layer as a whole. In particular, if the design emphasizes the polarization characteristics at a wavelength of 550 nm, which has high visibility, it is not easy to achieve a waveform band equivalent to that of the iodine-based polarizing plate. Therefore, by making the wavelength range having the polarization characteristics of the dye-based polarizing layer narrower than 380 to 780 nm, the types of dichroic dyes that can be selected for optical design are expanded, and the performance can be easily improved by blending. can be For example, it is preferably designed as a polarizing layer having polarizing properties covering at least a wavelength range of 400 to 700 nm, and more preferably covering a band having luminance in the emission spectrum of the backlight 32, which will be described later.

The preparation of the polarizing layers 10 and 30, which are dye-based polarizing layers, will be described. It can have a configuration in which a support film 42 (in FIG. 2, a first support film 42a and a second support film 42b on both sides, respectively) is adhered to one side or both sides of a polarizing film that functions as a polarizing element. Although only the polarizing film 40 can be used, it is preferable to use the polarizing film 40 as a polarizing plate sandwiched between the first support film 42a and the second support film 42b on both sides. This is because the polarizing film 40 is generally made by uniaxially stretching a polyvinyl alcohol-based resin (PVA) film dyed with a dichroic dye, and is a thin film. This is because, if it is not sandwiched by the 2 support films 42b, it may be easily deformed by heat or moisture, and furthermore, the polarization characteristics may be impaired.

The polarizing film 40 is a film having a function of converting natural light into linearly polarized light, and is preferably a PVA film having a dichroic dye adsorbed and oriented. When dichroic dyes such as azo-based compounds, anthraquinone-based compounds, or tetrazine-based dichroic dyes are used as dichroic dyes, they have excellent durability of optical properties under high temperature conditions, high temperature and high humidity conditions, and hue adjustment. becomes easier.

As the dichroic dye used for the polarizing film 40, an azo compound dye is preferable from the viewpoint of optical properties and durability. The following dyes can be exemplified as azo compound dyes.

（式中、Ｒ_１は水素原子、低級アルキル基、低級アルコキシル基、ヒドロキシル基、スルホン酸基、又はカルボキシル基を示し、Ｒ_２～Ｒ_５は各々独立に、水素原子、低級アルキル基、低級アルコキシル基、又はアセチルアミノ基を示し、Ｘは置換基を有してもよいベンゾイルアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、又は置換基を有してもよいナフトトリアゾール基であり、ｍは１又は２、ｎは０又は１を示す。） (1) An azo compound or a salt thereof represented by the chemical formula (1) disclosed in republished patent WO2009/057676 (A1).

(wherein R ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a hydroxyl group, a sulfonic acid group, or a carboxyl group; R ₂ to R ₅ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxyl or an acetylamino group, and X is a benzoylamino group optionally having a substituent, a phenylamino group optionally having a substituent, a phenylazo group optionally having a substituent, or a substituent It is a naphthotriazole group that may have, m is 1 or 2, n is 0 or 1.)

（式中、Ａは、置換基を有するフェニル基又は１～３のスルホン酸基を有するナフチル基を示し、Ｘは、－Ｎ＝Ｎ－又は－ＮＨＣＯ－を示す。Ｒ_１～Ｒ_４は各々独立に水素原子、低級アルキル基又は低級アルコキシル基を示し、ｍ＝１～３、ｎ＝０または１を示す。） (2) an azo compound or a salt thereof represented by the chemical formula (2) disclosed in republished patent WO2007/145210 (A1);

(In the formula, A represents a substituted phenyl group or a naphthyl group having 1 to 3 sulfonic acid groups, X represents -N=N- or -NHCO-. R ₁ to R ₄ each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxyl group, and m=1 to 3 and n=0 or 1.)

（式中、Ｒ_１はスルホン酸基、カルボキシル基又は低級アルコキシ基を表し、Ｒ_２は、スルホン酸基、カルボキシル基、低級アルキル基又は低級アルコキシ基を表す。但し、Ｒ_１、Ｒ_２がともにスルホン酸基の場合を除く。Ｒ_３～Ｒ_６は各々独立に水素原子、低級アルキル基又は低級アルコキシル基、Ｒ_７、Ｒ_８は各々独立に水素原子、アミノ基、水酸基、スルホン酸基又はカルボキシル基を表す。） (3) A trisazo dye represented by the chemical formula (3) disclosed in republished WO2006/057214 (A1).

(wherein R ₁ represents a sulfonic acid group, a carboxyl group or a lower alkoxy group, and R ₂ represents a sulfonic acid group, a carboxyl group, a lower alkyl group or a lower alkoxy group, provided that both R ₁ and R ₂ Except for sulfonic acid groups, each of R ₃ to R ₆ is independently a hydrogen atom, a lower alkyl group or a lower alkoxyl group, and each of R ₇ and R ₈ is independently a hydrogen atom, an amino group, a hydroxyl group, a sulfonic acid group or a carboxyl group. represents a group.)

（式中、Ｍは銅、ニッケル、亜鉛及び鉄から選ばれる遷移金属を表し；Ａ^１は置換されていてもよいフェニル又は置換されていてもよいナフチルを表し；Ｂ^１は置換されていてもよい１－又は２－ナフトール残基を表し、そのナフトールの水酸基はアゾ基の隣接位にあって、Ｍで表される遷移金属と錯結合しており；Ｒ^１及びＲ^２はそれぞれ独立に、水素、低級アルキル、低級アルコキシ、カルボキシル、スルホ、スルファモイル、Ｎ－アルキルスルファモイル、アミノ、アシルアミノ、ニトロ又はハロゲンを表す。） (4) A metal-containing disazo compound represented by the chemical formula (4) disclosed in JP-A-2004-251963 or a salt thereof.

(wherein M represents a transition metal selected from copper, nickel, zinc and iron; A ¹ represents optionally substituted phenyl or optionally substituted naphthyl; B ¹ represents optionally substituted represents a good 1- or 2-naphthol residue, the hydroxyl group of which naphthol is adjacent to the azo group and is complexed with the transition metal represented by M; R ¹ and R ² are each independently represents hydrogen, lower alkyl, lower alkoxy, carboxyl, sulfo, sulfamoyl, N-alkylsulfamoyl, amino, acylamino, nitro or halogen.)

（式中、Ａ^２及びＢ^２はそれぞれ独立に、置換されていてもよいフェニル又は置換されていてもよいナフチルを表し；Ｒ^３及びＲ^４はそれぞれ独立に、水素、低級アルキル、低級アルコキシ、カルボキシル、スルホ、スルファモイル、Ｎ－アルキルスルファモイル、アミノ、アシルアミノ、ニトロ又はハロゲンを表し；ｍは０又は１を表す。） (5) A trisazo compound represented by the chemical formula (5).

(wherein A ² and B ² each independently represent optionally substituted phenyl or optionally substituted naphthyl; R ³ and R ⁴ each independently represent hydrogen, lower alkyl, lower alkoxy, carboxyl, sulfo, sulfamoyl, N-alkylsulfamoyl, amino, acylamino, nitro or halogen; m represents 0 or 1.)

（式中、Ａはメチル基で置換されたフェニル基又はナフチル基を表し、Ｒはアミノ基、メチルアミノ基、エチルアミノ基又はフェニルアミノ基を表す。） (6) A water-soluble compound represented by the chemical formula (6) disclosed in JP-A-3-12606 or a copper complex salt thereof.

(In the formula, A represents a phenyl group or naphthyl group substituted with a methyl group, and R represents an amino group, methylamino group, ethylamino group or phenylamino group.)

(7) A water-soluble disazo compound represented by the chemical formula (7) disclosed in JP-A-2-61988 or a copper complex salt thereof.

(8) Others, such as C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 28, C.I. I. Direct Yellow 44, C.I. I. Direct Yellow 142, C.I. I. Direct Orange 26, C.I. I. Direct Orange 39, C.I. I. Direct Orange 71, C.I. I. Direct Orange 107, C.I. I. Direct Red 2, C.I. I. Direct Red 31, C.I. I. Direct Red 79, C.I. I. Direct Red 81, C.I. I. Direct Red 117, C.I. I. Direct Red 247, C.I. I. Direct Green 80, C.I. I. Direct Green 59, C.I. I. Direct Blue 71, C.I. I. Direct Blue 78, C.I. I. Direct Blue 168, C.I. I. Direct Blue 202, C.I. I. Direct Violet 9, C.I. I. Direct Violet 51, C.I. I. Direct Brown 106, C.I. I. Direct Brown 223 and the like. In addition, it is preferable to dye PVA with two or more of these dyes so as to compensate for the polarization characteristics at each wavelength in the visible region, thereby providing a hue exhibiting a neutral gray. Thereby, a liquid crystal display device having high contrast and excellent displayability can be obtained. Furthermore, when three or more dyes containing a blue dichroic dye are blended, in particular, by adjusting the blending amount of the blue dichroic dye, the yellow color when the polarizing film is attached to the display device By optimizing the degree of tint of the tint and by using dichroic dyes for achromatic polarizers, the neutral gray color can be more easily adjusted.

Examples of commercially available dyes include Kayafect Violet P Liquid (manufactured by Nippon Kayaku Co., Ltd.), Kayafect Yellow Y and Kayafect Orange G, Kayafect Blue KW and Kayafect Blue Liquid 400.

Furthermore, by obtaining a polarizing layer that uniformly has a single transmittance of 33% or more in the wavelength range of 400 to 700 nm and a cross transmittance of 0.01% or less, a display device with excellent contrast is obtained. can be done. The dye used in the polarizing layer has, for example, a maximum absorption wavelength (principal absorption) and high dichroism in any of the wavelength regions of (1) 400 to 500 nm, (2) 500 to 590 nm, and (3) 590 to 660 nm. and have optical properties of no (or little) secondary absorption in a wavelength range other than the wavelength range having the maximum absorption wavelength, and it is preferable to combine dyes having these properties by blending.

Examples of the dye having the property (1) above include the following orange dyes.

（式中Ｒ１、Ｒ２は各々独立に水素原子、炭素数１～４のアルキル基、又は炭素数１～４のアルコキシ基を示し、ｎは１又は２を示す。） An azo compound or a salt of an azo compound represented by the chemical formula (8) disclosed in International Publication WO2007/138980.

(In the formula, R1 and R2 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and n represents 1 or 2.)

Examples of the dye having the property (2) include the following red dyes.

（式中、Ａは水素原子、ヒドロキシ基、スルホ基を有する炭素数１～５のアルコキシ基及び／又はスルホ基を有するナフチル基であり、Ｒ１～Ｒ４の少なくとも１つは各々独立にスルホ基を有する炭素数１～４のアルキル基又は炭素数１～４のアルコキシ基である。） An azo compound or a salt thereof represented by the chemical formula (9) disclosed in International Publication WO2016/186196.

(In the formula, A is a hydrogen atom, a hydroxy group, an alkoxy group having 1 to 5 carbon atoms having a sulfo group and/or a naphthyl group having a sulfo group, and at least one of R1 to R4 each independently represents a sulfo group. is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.)

Examples of dyes having the properties related to (3) above include the following blue dyes.

（式中、Ａは置換基を有してもよいフェニル基を示し、Ｒ１～Ｒ６は各々独立に、水素原子、炭素数１～５のアルキル基、炭素数１～５のアルコキシ基、又はスルホ基を有する炭素数１～５のアルコキシ基、置換基を有してもよいベンゾイルアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、又は置換基を有してもナフトトリアゾール基を示す。） An azo compound represented by the chemical formula (10) disclosed in International Publication WO2012/108169 and/or a salt thereof.

(Wherein, A represents a phenyl group which may have a substituent, and R1 to R6 are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a sulfo an alkoxy group having 1 to 5 carbon atoms having a group, a benzoylamino group optionally having a substituent, a phenylamino group optionally having a substituent, a phenylazo group optionally having a substituent, or a substituent indicates a naphthotriazole group.)

When the support film 42 is used as the polarizing plate, the support film 42 is attached to one side or both sides of the polarizing film 40 via an adhesive layer. As the support film 42 (first support film 42a, second support film 42b), cycloolefin resin film, polyester resin film, acrylic resin film, polycarbonate resin film, polysulfone resin film, alicyclic polyimide film A resin film, an acetylcellulose-based resin film, or 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 acetylcellulose-based resin, more preferably triacetylcellulose (TAC).

Furthermore, a retardation layer and a viewing angle compensation layer may be provided on the surface opposite to the adhesive surface of the support film via an adhesive or the like, or these may be directly used as the support film. Moreover, an appropriate surface functional layer 44 such as an antiglare layer, an antireflection layer, a hard coat layer, or the like may be provided on the surface of the support film on the viewing side of the display device.

The adhesive layer 46 is provided as a layer used when bonding the polarizing layer to the first substrate 12 or the second substrate 28 of the display device. The adhesive layer 46 is provided on the surface of the first support film 42 a opposite to the polarizing film 40 . The adhesive layer 46 is formed by, for example, applying an adhesive obtained by diluting a solid component of an acrylic or polyester adhesive with a solvent such as toluene or methyl ethyl ketone (MEK) to a release film and drying it. The adhesive is not particularly limited as long as it is acrylic or polyester, and adhesives other than these may be used. In addition, additives such as curing agents and silane coupling agents are added to the adhesive to adjust the adhesion to the adherend and to reduce the occurrence of peeling and foaming in terms of durability. can be done.

Next, the blended pressure-sensitive adhesive is applied to a release film, and the solvent is volatilized in a drying process. In the drying step, it is preferable to volatilize the solvent from the release film coated with the pressure-sensitive adhesive using a plurality of drying ovens each set to a temperature range of 40°C to 100°C.

At this time, the coating amount is adjusted so that the thickness of the adhesive after drying is 1 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less. After that, they are laminated with the adhesive side facing the first support film 42a.

In general, the optical properties of the polarizing layer are evaluated by measuring the transmittance of each wavelength in the wavelength range of 380 to 780 nm at intervals of 5 nm or 10 nm using a spectrophotometer. At this time, values such as transmittance in the visible light region are represented by values corrected for visibility based on JIS Z8719 (CIE1931 color system). The transmittance of the single polarizing layer (Ys, hereinafter also referred to as single transmittance; unit: %) is obtained from the following formula (1). At this time, S is the standard light, y is the 2-degree visual field color matching function, and t is the transmittance of each wavelength. Formula (1) is usually automatically calculated by a program installed in a commercially available spectrophotometer. The standard light S is obtained by transmitting or irradiating natural light such as a C light source or a D65 light source having a spectrum close to that of sunlight.

Other methods for evaluating the optical properties of the polarizing layer will be described. Contrast (C) is the transmittance (Yp, hereinafter also referred to as parallel transmittance, unit: %) when the polarizing axes of the two sets of polarizing layers are parallel to each other, and the contrast (C) when the polarizing axes of the two sets of polarizing layers are perpendicular to each other. It is represented by a ratio of transmittance (Yc, hereinafter also referred to as orthogonal transmittance, unit: %) (formula (2)), and each transmittance is obtained using formula (1). C is an index for estimating the display characteristics when the polarizing layer is applied to a liquid crystal display device, Yp corresponds to white display in the display device, and Yc corresponds to black display in the display device.

The degree of polarization P (unit: %) that indicates the polarization properties of the polarizing layer can be obtained from Equation (3). In this case, since Py is a value that depends on the transmittance of the polarizing layer, the lower the transmittance, the higher the degree of polarization.

なお、ＫｙとＫｚは、ＹｓとＹｃを用いてそれぞれ数式（７）及び数式（８）より求めることができる。

Also, the dichroic ratio Rd can be used to evaluate the orientation of the dye in the polarizing layer and the polarizing performance. Absolute parallel transmittance Kz obtained by making absolutely polarized light incident on the polarizing layer so that it is parallel to the absorption axis of the polarizing plate, and absolute orthogonal transmittance Ky obtained by making it orthogonal to the absorption axis of the polarizing plate The absorbance is calculated from each of the above, and expressed by the ratio (formula (4)). Here, A ₀ is determined by Equation (5), and A ₉₀ is determined by Equation (6). Generally, the dichroic ratio Rd of the iodine-based polarizing plate is 50 to 60 or more, and the dichroic ratio Rd of the dye-based polarizing plate is 30 to 40 or more.

Ky and Kz can be obtained from equations (7) and (8) using Ys and Yc, respectively.

Further, calculation may be performed in a wavelength range of 400 to 700 nm, for example, as in Equation (9). In general, the human eye can hardly perceive colors and light in the wavelength range of 400 nm or less and 700 nm or more. This is the case of using a photometer or the case of simple evaluation that does not require accuracy.

LED backlights used in liquid crystal display devices and the like are generally so-called pseudo-white light-emitting elements in which blue light-emitting elements are coated with a fluorescent agent that emits yellow, and have almost no luminance in the wavelength range of 700 nm or more. is adopted. Therefore, in the evaluation of display brightness and display contrast when the polarizing plate is actually attached to the display device, it is considered that there is almost no brightness in the wavelength range of 700 nm or more. For example, when the visibility correction calculation based on the formula (1) is performed for the optical characteristics of the dye-based polarizing layer that does not have effective polarization characteristics in the wavelength range of 700 nm or more, the value of the optical characteristics obtained by the calculation, A difference may occur between the optical evaluation when the polarizing layer is actually attached to the display device. In this case, by narrowing the range of the visibility correction calculation to, for example, a wavelength range of 380 nm or more and 700 nm or less, or 400 nm or more and 700 nm or less, the difference can be eliminated conveniently.

Note that the y component (color matching function) in Equation (1) is treated as a value of substantially 0 with respect to a wavelength of 555 nm in the wavelength range of 750 nm to 780 nm. Therefore, in the optical design of the dye-based polarizing layer of the present invention, it is not necessary to consider the presence or absence of polarizing properties at wavelengths of 750 nm or more.

Furthermore, it is preferable to use the waveform band of the actually used backlight 32 as standard light for the visibility correction calculation in evaluating the optical characteristics of the dye-based polarizing layer and the liquid crystal display device to which it is attached. As a result, it is possible to obtain an evaluation result that is comparable to the optical properties of the film alone and the structure actually attached to the display device. In this case, a value obtained by normalizing the emission spectrum of the actually used backlight may be used for S in Equation (1). In addition, with the above expedient solution for narrowing the calculation range, there is a risk that the obtained values such as hue may be inaccurate. Obtainable. The above S is a value obtained by normalizing the wavelength of the maximum luminance (maximum emission intensity) in the wavelength range of 380 to 780 nm in the emission spectrum of the backlight as 1.

The luminance band of the backlight 32 used in the liquid crystal display device attached with the dye-based polarizing plate having excellent polarization characteristics in the visible region is white light having luminance in the visible light region and luminance in the wavelength range of 700 nm or more. preferably not. Specifically, the maximum luminance in the wavelength range of 700 to 780 nm is preferably 0.03 or less, more preferably 0.01 or less.

FIG. 3 shows normalized emission luminance waveforms in the wavelength range of 380 nm or more and 780 nm or less for the backlight 32 as the white LED and the C light source (indicated by the dotted line in the figure) as the standard light. Here, the backlight 32b (indicated by a dashed line in the figure) is NS2W364G manufactured by Nichia Corporation, and is an example of the emission spectrum of a white LED for general liquid crystal display devices. The backlight 32a (indicated by the solid line in the drawing) is NS2W364G-HG manufactured by Nichia Corporation, and is an example of the emission spectrum of a white LED that provides high color rendering properties. Table 1 shows normalized emission luminance values on the long wavelength side (660 nm or more and 740 nm or less) of the backlights 32a and 32b.

In addition, high color rendering in a liquid crystal display device means that the spectrum of each RGB color filter and the emission spectrum of the backlight correspond to each other, and by improving the transmission efficiency of each color filter, the color reproducibility in the display is enriched. It is.

As shown in FIG. 3, the standard light has emission intensity over the entire wavelength range of visible light, but the backlight 32 has almost no emission intensity on the longer wavelength side. Further, as shown in Table 1, in the wavelength range of 680 to 740 nm, the luminance value of the backlight 32a is about 1/10 of the luminance value of the backlight 32b. The light 32a has sufficiently low luminance. As described above, the backlight 32 in the present embodiment preferably has a normalized luminance value of 0.03 or less in the wavelength range of 700 nm or more and 780 nm or less, and more preferably 0.01 or less. , backlight 32a is preferably used. In particular, by using a backlight having a luminance of 0.01 or less at a wavelength of 700 nm or more and 780 nm or less, even a dye-based polarizing plate that does not have polarization characteristics at a wavelength of 700 nm or more can prevent whitening and coloring even in black display. A high-contrast liquid crystal display device can be obtained.

(Example 1)
[Preparation of polarizing plate]
After swelling a polyvinyl alcohol resin film (VF-PE (60 μm thick) manufactured by Kuraray Co., Ltd.) in water at 30 ° C. for 5 minutes, the dye described in Example 1 in International Publication WO2007/138980 was added at 30 ° C. Dyeing treatment was performed by immersing it in a dyeing solution (0.1 to 0.3 parts by weight per 1000 parts by weight of water and 1 part by weight of sodium tripolyphosphate) for 5 minutes. Then, the dyed film was stretched 4 to 6 times in a 3% by weight boric acid aqueous solution at 50° C. so as to maximize the polarizing properties to obtain a stretched film. After the stretching treatment, the stretched film was immersed in a 5% by weight boric acid aqueous solution at 50° C. for 2 minutes, washed with water, and dried in the air at 30 to 80° C. to obtain an orange polarizing film. The thickness of the obtained polarizing film was 20 μm. The resulting polarizing film was laminated with a saponified TAC film (60 μm thick, containing an ultraviolet absorber) on both sides of the polarizing film using a water-based adhesive containing polyvinyl alcohol (PVA). Then, the polarizing layer A was obtained by drying at 70° C. for 5 minutes.

A red polarizing film was obtained in the same manner as in Example 1 using the dye of Example 1 in International Publication WO2016/186196. The thickness of the obtained polarizing film was 20 μm. Thereafter, a TAC film was attached to obtain a polarizing layer B in the same manner as described above.

A blue polarizing film was obtained in the same manner as in Example 1 using the dye of Example 36 in International Publication WO2012/108169. The thickness of the obtained polarizing film was 20 μm. Thereafter, a TAC film was attached to obtain a polarizing layer C in the same manner as described above.

For the polarizing layers A, B, and C, a spectrophotometer (Hitachi U-4100) was used to measure the single transmittance (Ts) and parallel transmittance (Tp ), and the cross transmittance (Tc) was measured. Table 2 shows the results of the measurements at the maximum absorption wavelength (λmax) and the dichroic ratio (Rd).

The optical properties of the dye-based polarizing layer having features of the present invention were obtained by the following methods. Using the monochromatic spectroscopic measurement results of the polarizing layers A, B, and C, calculation was performed using a computer based on the following waveform synthesis method, and optical design of a polarizing film with a neutral gray color was performed by simulation. By optimizing the waveform contribution of the polarizing layers A, B, and C, a dye-based polarizing layer D having high polarizing properties over the visible light region with a wavelength of 400 to 700 nm was obtained.

4 and 5 show waveforms of single transmittance and orthogonal transmittance of the polarizing layer D, respectively. Table 3 shows the optical properties of the polarizing layer D. In the actual production of the polarizing layer D, a dyeing solution is prepared by optimally blending the dyes used above so that the wavy shape of the polarizing layer D can be obtained, and then PVA is dyed and stretched. , a polarizing layer equivalent to the polarizing layer D can be obtained directly.

The polarizing layer D has a cross transmission wavelength range in which the cross transmittance (Tc) is 1% or more in the visible light region of 380 nm or more and 780 nm or less. Moreover, the polarizing layer D has the orthogonal transmission wavelength range in which the orthogonal transmittance (Tc) is 1% or more over the entire wavelength range of 700 nm or more and 740 nm or less. In addition, the polarizing layer D has a single transmittance (Ts) of 33% or more in the entire wavelength range of the visible light region from 420 nm to 780 nm, and a cross transmittance (Yc ) was 0.01% or less.

[Waveform synthesis method]
(1) From the transmittance (Ts, Tp, Tc) at each wavelength, the absolute orthogonal transmittance Ky obtained so as to be orthogonal to the absorption axis of the polarizing plate at each wavelength and the absorption axis of the polarizing plate Absolute parallel transmittance Kz obtained by
(2) Assuming that the contribution of the surface and internal reflectance of the polarizing layer is about 4% each, find the product of 0.96 ⁻² for each of Ky and Kz.
(3) Ky and Kz obtained in (2) are converted into absorbance, and further multiplied by an arbitrary concentration value.
(4) The above (1) to (3) are performed on the polarizing layers A to C, and the sum of the respective values is the combined absorbance of the polarizing layer D. By adjusting the arbitrary density value in (3), the waveform balance of the polarizing layer D can be optimized. Here, processing was performed so as to maximize the dichroic ratio in the wavelength range of 400 to 700 nm.
(5) Convert the absorbance of the polarizing layer D obtained in (4) into Ky and Kz. Further, based on ( ² ), each of Ky and Kz is multiplied by 0.962.
(6) Calculate the transmittance (Ts, Tp, Tc) of the polarizing layer D from (5). Further, the transmittance (Ys, Yc) and the degree of polarization Py of the polarizing layer alone are obtained based on the above equations.

[Evaluation of Luminance Characteristics in Black Display]
Using an optical design simulation software (LCD master manufactured by Shintech Co., Ltd.), a simulation of front luminance in a dark state (luminance of black display) was performed. FIG. 6 shows a schematic diagram of a configuration for simulating this evaluation. A polarizing layer 50 (front side), a liquid crystal cell 52, and a polarizing layer 54 (rear side) are arranged in this order. The relationship of the polarization axes of 54 was orthogonal. Further, the liquid crystal cell 52 was set so that the liquid crystal 52 was horizontally aligned in the plane. As the material of the liquid crystal 52, Merck's ZLI-4792 selected from the software database was applied. The luminance was calculated using the orthogonal transmittance waveform obtained above and the normalized emission intensity waveform of the backlight 32a shown in FIG. 3 (NS2W364G-HG manufactured by Nichia Corporation) as the standard light. Table 4 shows the evaluation results.

(Example 2)
The contents were the same as those described in Example 1, except that the normalized emission spectrum of NS2W364G (backlight 32a) manufactured by Nichia Corporation was used as the standard light LED backlight. The evaluation results are shown in Table 4.

(Comparative example 1)
The contents were the same as those described in Example 1, except that optical data obtained from spectroscopic measurement of a commercially available high-contrast dye-based polarizing plate SHC-13U (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

(Comparative example 2)
The contents were the same as those described in Example 2, except that optical data obtained from spectroscopic measurement of a commercially available high-contrast dye-based polarizing plate SHC-13U (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

(Comparative Example 3)
The contents were the same as those described in Example 1, except that optical data obtained from spectroscopic measurement of a commercially available high-contrast dye-based polarizing plate VHC-128U (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

(Comparative Example 4)
The contents were the same as those described in Example 2, except that the optical data obtained from the spectroscopic measurement of a commercially available high-contrast dye-based polarizing plate VHC-128U (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

(Comparative Example 5)
The contents are the same as those described in Example 1, except that the optical data obtained from the spectroscopic measurement of the commercially available iodine-based polarizing plate SKN-18243T (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

(Comparative Example 6)
The contents are the same as those described in Example 2, except that the optical data obtained from the spectroscopic measurement of the commercially available iodine-based polarizing plate SKN-18243T (manufactured by Polatechno Co., Ltd.) was used. The evaluation results are shown in Table 4.

The results in Table 3 will be explained. The polarizing layer D is used when the calculated wavelength range is 380 to 780 nm (Case 1) and when the calculated wavelength range is 400 to 700 nm (Case 2). However, there is a difference in the calculation results. This difference is particularly manifested in the value of the transmittance Yc, which can also be seen from the fact that the ratio (Case 1/Case 2) is larger than that of the other polarizing layers. As a result, the values of the obtained dichroic ratio Rd were also different. The reason for this is that in the calculation method using light source C (natural light) as standard light, the polarizing layer D has almost no polarizing properties at wavelengths of 700 nm or more, so it cannot block light with wavelengths of 700 nm or more in standard light. be. On the contrary, according to the calculation results of Case 2, the polarizing layer D exhibited optical properties superior to those of the conventional dye-based polarizing layer. This suggests that in the structure of the orthogonal transmission waveforms of the polarizing layer D, it is necessary to consider the waveform characteristics of the light source luminance. Therefore, in the actual design of a display device using the polarizing layer D, by using a light source that has almost no luminance at wavelengths of 700 nm or more, high display performance can be achieved even with the use of the dye-based polarizing layer.

On the other hand, in the conventional dye-based polarizing layers (SHC-13U and VHC-128U) and the iodine-based polarizing layer (SKN-18243T), in each of the calculations for Case 1 and Case 2, the calculated values for both compared with the polarizing layer D are Almost no difference in optical properties occurred. In particular, in the case of SHC-13U, there was almost no difference in values between cases 1 and 2. This is due to the fact that the orthogonal transmittance at a wavelength of 700 nm or longer is the lowest among all dye-based polarizing layers. Therefore, in the optical design of the dye-based polarizing layer, it is possible to provide a polarizing band comparable to that of the iodine-based polarizing layer by having such a structure of orthogonal transmission waveforms.

Next, the results of Table 4 will be explained. The black luminance values of Examples 1 and 2 were lower than those of conventional dye-based polarizing layers (Comparative Examples 1 to 4) and iodine-based polarizing layers (Comparative Examples 5 and 6). That is, in the display device using the LED light source of the backlight 32a or the backlight 32b, the polarizing layer D was able to realize a black display comparable to that of the iodine-based polarizing layer. In addition, it is desirable to handle the calculation result of Case 2 in Table 3 as the optical properties of the polarizing layer D. In addition, from the results of using the backlight 32a of Example 1, the normalized emission luminance at a wavelength of 700 nm or more is 0.01 or less, and in the combination of the polarizing layer D, the black luminance is 36% higher than that of the backlight 32b. % could be reduced. That is, it was possible to improve the displayability of black in the display device.

On the other hand, in Comparative Examples 1 to 6, the black luminance value when the backlight 32a is used is only improved by 2 to 17% compared to the case when the backlight 32b is used. However, there was almost no effect of improving the displayability of black.

From the above results, according to the present embodiment, in order to improve the display characteristics of a display device using a dye-based polarizing layer, not only the dye formulation for optimizing the optical characteristics but also the display device By focusing on the emission spectrum of the backlight used for the display, display performance comparable to the case of using an iodine-based polarizing layer can be obtained. That is, even if the dye-based polarizing layer has a orthogonal transmittance (Tc) of 1.0% or more in the wavelength range of 700 nm or more, the normalized emission luminance of the backlight in the wavelength range of 700 nm or more is 0.03. By combining with a backlight having a luminance of 0.01 or less, it is possible to lower the luminance during black display and improve the display contrast.

In addition, in the optical design of the dye-based polarizing layer according to the present embodiment, it is not necessary to impart polarizing properties in the wavelength range of 700 nm or more, so the types of dyes to be blended can be reduced compared to conventional methods. As a result, in the wavelength range of 400 nm or more and 700 nm or less, the influence of the dye-specific secondary absorption can be reduced, and a single transmittance higher than that of the conventional dye-based polarizing layer can be realized. Therefore, in the present embodiment, it is possible not only to improve the black display, but also to improve the luminance during the white display and further improve the display contrast of the display device.

(Modification)
In the structure of the display device according to the embodiment of the present invention, any layer from the emission side of the backlight 32 to the polarizing layer 10 contains a material that absorbs light with a wavelength of 700 nm or more, or absorbs light in the wavelength range. By adding an absorbing layer, the light emitted from the backlight 32 with a wavelength of 700 nm or more can be cut. As a result, even if a dye-based polarizing layer such as the polarizing layer D is used, a liquid crystal display device with excellent display characteristics can be obtained regardless of the light emission characteristics of the backlight 32 .

For example, it is possible to apply a commercially available "optical filter" that transmits only light having a predetermined property among incident light and does not transmit other light. More specifically, it is preferable to use a short-pass filter that transmits only wavelengths shorter than a certain wavelength. In the present embodiment, for example, a short-pass filter having wavelength selectivity in the wavelength range around 650 to 700 nm may be used.

As another example, a cyanine-based dye having a maximum absorption wavelength in the range of 700 nm to 780 nm may be used. In the case of the material, it may be contained in the adhesive layer of the polarizing layer 10 or may be provided in any layer from the emission side of the backlight 32 to the polarizing layer 10 by a method such as coating.

10 polarizing layer 12 first substrate 14 color filter 14 polarizing film 16 counter electrode 18 alignment film 20 liquid crystal layer 22 alignment film 24 display electrode 26 interlayer insulating film 28 second substrate 28a gate electrode , 28b Gate insulating film 28c Semiconductor layer 30 Polarizing layer 32 (32a, 32b) Backlight 40 Polarizing film 42 (42a, 42b) Supporting film 44 Surface functional layer 46 Adhesive layer 50 Polarizing layer 52 liquid crystal, 54 polarizing layer, 100 display device.

Claims (2)

A dye having a maximum absorption wavelength and dichroism in each wavelength range of 400 to 500 nm, 500 to 590 nm, and 590 to 660 nm, and having a wavelength range that does not contribute to polarization characteristics excluding the wavelength range having the maximum absorption wavelength. A display device comprising a compounded dye-based polarizing layer and a backlight,
The dye-based polarizing layer has an orthogonal transmission wavelength range in which the orthogonal transmittance (Tc) is 1% or more in the visible light region of 700 nm or more and 780 nm or less, and the entire wavelength range of the visible light region of 420 nm or more and 780 nm or less. , the single transmittance (Ts) is 33% or more, and the orthogonal transmittance (Yc) corrected for visibility in the wavelength range of 400 nm to 700 nm is 0.01% or less,
A display device, wherein the backlight has an emission intensity normalized by a maximum emission intensity in a visible light region of 700 nm or more and 780 nm or less in the orthogonal transmission wavelength range of 0.03 or less. 2. A display device according to claim 1 , comprising a liquid crystal layer.

Images