JP2001324614A - Laminated polarizing element and liquid crystal display device having the same - Google Patents

Abstract

(57) Abstract: Provided is a laminated polarizing element exhibiting a high front contrast ratio and having a wide viewing angle characteristic, and a liquid crystal display device including the same. A polarizing film obtained by stretching a dichroic substance-containing polyvinyl alcohol film or a polarizing film having a stretch-oriented polyene structure and a polarizing element having a dichroic substance oriented by flow orientation are laminated. The polarizing element in which the dichroic substance is oriented by the flow alignment is preferably a polarizing element fixed by flow alignment from the lyotropic liquid crystal phase of the dichroic dye or a polarizing element made of a dichroic substance exhibiting lyotropic liquid crystallinity. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polarizing element having a wide viewing angle, high contrast and high uniform display performance, and a liquid crystal display device having the same.

[0002]

2. Description of the Related Art LCDs are used in personal computers and the like, and have been rapidly increasing in recent years. The use of LCDs is expanding, and in recent years, LCDs are also being used for monitors. In general, a polarizing plate used in this LCD is prepared by dyeing a PVA film with iodine or a dye having dichroism and then crosslinking the film with boric acid or borax. In addition, uniaxial stretching is performed in the dyeing step and the crosslinking step. This stretching may be performed during the step, or may be performed before or after the step. After the dyeing step and the cross-linking step, it is usually dried using a drier or the like, and bonded to a protective layer such as a triacetyl cellulose (TAC) film using an adhesive.

In recent years, LCDs have become larger and have higher contrasts, and higher quality polarizing plates have been demanded. By optically compensating for the birefringence anisotropy of the liquid crystal, higher accuracy is achieved. Improvements in liquid crystal panels are required.
In particular, twisted nematic mode, vertical alignment mode,
In the horizontal alignment mode and the like, studies using an optical compensation film have been studied to increase the viewing angle.

[0004] Conventionally, an optical compensation film is intended to optically compensate birefringence of a liquid crystal. But,
What affects the viewing angle of the liquid crystal panel is the viewing angle characteristic of the polarizing element itself. As for viewing angle compensation of a polarizing film, as disclosed in Japanese Patent No. 2844331, it has been proposed to increase the viewing angle by using a retardation film.

However, this is to compensate for the rotation of the polarization axis due to the viewing angle and the birefringence of the protective layer of the polarizing film, but it may be insufficient depending on the mode of the panel.

A polarizing element formed by flow alignment from a lyotropic liquid crystal phase of a dichroic dye disclosed in WO97 / 39380 and JP-A-8-511109 is known to have high contrast over a wide viewing angle. Has been confirmed.

However, when compared with a polarizing film of a stretched polyvinyl alcohol film in which iodine or a dichroic dye is adsorbed or dispersed, the front contrast ratio (parallel transmittance / orthogonal transmittance) is low, and this is insufficient for some panels. It is.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention provides a laminated polarizing element having a wide viewing angle, high contrast and high uniform display performance, and a liquid crystal display having the same. It is intended to provide a device.

[0009]

In order to achieve the above-mentioned object, a laminated polarizing element of the present invention comprises a polarizing film formed by stretching a dichroic substance-containing polyvinyl alcohol film or a polarizing film having a stretch-oriented polyene structure. When,
It is characterized in that polarizing elements in which dichroic substances are oriented by flow orientation are laminated.

In the above, the polarizing element in which the dichroic substance is oriented by the flow orientation comprises a polarizing element which is flow-aligned and fixed from the lyotropic liquid crystal phase of the dichroic dye or a dichroic substance exhibiting lyotropic liquid crystallinity. It is preferably a polarizing element.

In the above, the azimuth of the absorption axis is 0.
°, 0 ° parallel transmittance (A), 0 ° and 90 °
Is preferably 10 or more when inclined at an inclination angle of 60 ° in an azimuth angle of 45 °, and the front contrast ratio is 55 or more.

In the present invention, it is preferable that a pressure-sensitive adhesive is further formed on at least one surface of any one of the above-mentioned laminated polarizing elements.

In the present invention, it is preferable that a film having a birefringence compensation function having optical anisotropy is further laminated on any one of the above-mentioned laminated polarizing elements.

Next, a liquid crystal display device according to the present invention is characterized in that any one of the above-mentioned laminated polarizing elements is provided on at least one side of a liquid crystal display panel.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a high-performance film by laminating a polarizing film in which a dichroic substance-containing polyvinyl alcohol film is stretched and oriented and a polarizing element in which a dichroic dye is oriented from a lyotropic liquid crystal phase in a flow orientation. An object of the present invention is to provide a laminated polarizing element which shows a front contrast ratio and can maintain a contrast ratio at a wide viewing angle.

The polyvinyl alcohol-based polarizing film containing a dichroic substance used in the present invention is not particularly limited to a dichroic substance. In general, a polarizing film obtained by dyeing or dispersing iodine or a dichroic dye on a polyvinyl alcohol film and stretching it about 2 to 10 times in an aqueous solution of boric acid or the like can be used. The stretch-oriented polyene structure can be formed by a dehydration reaction of polyvinyl alcohol.

A polarizing element in which a dichroic dye is oriented in a flow orientation from a lyotropic liquid crystal phase is described in WO 9/39380.
POLARIZE manufactured by (OPTIVA) Co., Ltd. as shown in the specification and Japanese Patent Publication No. Hei 8-511109.
R (product name) is preferably used.

Particularly, the lyotropic liquid crystalline dichroic dye includes, for example, a compound represented by the formula: (chromogen) (SO ₃
M) _n is a water-soluble organic dye represented by _{n. The} chromogen is composed of an azo or polycyclic compound to give liquid crystallinity, and the sulfonic acid or its salt gives water solubility to give a whole. Shows lyotropic liquid crystallinity as
No. 11109).

Specific examples of the above-mentioned dichroic dyes include compounds represented by the following formulas (1) to (7).

[0020]

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In the above formula (1), R1 is hydrogen or chlorine, and R is hydrogen, an alkyl group, ArNH or Ar
CONH. As the alkyl group, one having 1 to 4 carbon atoms, particularly, a methyl group or an ethyl group is preferable, and as the aryl group (Ar), a substituted or unsubstituted phenyl group, particularly, a phenyl group in which the 4-position is substituted with chlorine is preferable. . M is a cation, a hydrogen ion, Li or Na, K or C
Preferred are ions of a Group 1 metal such as s, ammonium ions and the like (the same applies hereinafter).

[0022]

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[0023]

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[0024]

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In the above formulas (2) to (4), A is represented by the formula (a) or (b), wherein R2 is hydrogen, an alkyl group, a halogen or an alkoxy group, and A is substituted or unsubstituted. A substituted aryl group, n is 2 or 3. The alkyl group has 1 to 4 carbon atoms, particularly a methyl group or an ethyl group, and the halogen is preferably bromine or chlorine. The alkoxy group is preferably one having 1 or 2 carbon atoms, particularly a methoxy group, and the aryl group is a substituted or unsubstituted phenyl group, particularly an unsubstituted or 4-position methoxy group, an ethoxy group, a chlorine or butyl group, Alternatively, a phenyl group in which the 3-position is substituted with a methyl group is preferable.

[0026]

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In the above formula (5), n is preferably 3 to 5.

[0028]

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[0029]

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The organic dye represented by the above formula: (chromogen) (SO ₃ M) _n shows a stable liquid crystal phase in the chromogen, and is dissolved in a water-soluble organic solvent such as water, acetone, alcohol and dioxane. Then, a solution in which one or two or more of the dyes are dissolved, for example, having a solid content concentration of 1 to 20% by weight is applied by an appropriate coating method such as a doctor blade method in which a shearing force acts, thereby orienting. Can be processed, and the alignment fixed layer exhibits a dichroic polarization function.

The adhesive for laminating the polarizing film composed of a polyvinyl alcohol film and the flow-oriented polarizer is not particularly limited, but an ultraviolet curable or thermosetting transparent resin is used. When the protective layer is formed, there is no particular limitation, and examples thereof include a cellulose-based film, an acrylic-based film, a norbornene-based film, an olefin-based, a polyester-based, a polycarbonate-based, a maleimide-based, and a modified version thereof. The protective layer is
These films are stretched, oriented, etc.
A liquid crystal composition, a birefringent fine particle, or the like may be applied, impregnated, and oriented.

Further, a compensation film (retardation film)
Can be added to realize a higher quality panel. Examples of the retardation film include a film obtained by stretching and orienting a polymer film. The polymer film used for the retardation film is not particularly limited, but a film which is optically transparent and has little alignment unevenness is preferably used. For example, polycarbonate, polyarylate, polysulfone, polyolefin, polyester typified by polyethylene terephthalate and polyethylene naphthalate, norbornene,
Acrylic-based, polystyrene-based, cellulose-based, maleimide-based and modified ones thereof can be used. Furthermore, these films are subjected to treatments such as stretching and orientation, liquid crystal compositions such as nematic liquid crystal, discotic liquid crystal, and cholesteric liquid crystal, birefringent fine particles such as inorganic layered compounds and inorganic needle-shaped compounds, and fluorescent brighteners. It may be one that is coated with, impregnated with, and oriented with a fluorescent substance. As the orientation, there are methods such as uniaxial stretching, biaxial stretching, rubbing treatment, and polarized ultraviolet treatment.

The pressure-sensitive adhesive used for the pressure-sensitive adhesive polarizing element is not particularly limited, but an acrylic adhesive is preferably used.

In laminating the polarizing film and the retardation film, the relation between the transmission axis and the fast axis is not particularly limited. In general, STN-type LCDs are often stacked at different angles, and TN-type LCDs are generally parallel or substantially orthogonal.

In order to compensate with higher precision, a plurality of retardation films may be used. In this case, the same type of retardation film may be combined, or a different type of retardation film may be combined.

[0036]

The present invention will be described more specifically with reference to the following examples.

Example 1 A polarizing film made of a polyvinyl alcohol film containing a dichroic substance (F5225DU manufactured by Nitto Denko Corporation) was applied to a lyotropic liquid crystal aqueous solution containing a dichroic dye (manufactured by Optiva, LC polarizer, solid content). Concentration of 16.7% by weight) with a wire bar (N
o. After coating using 5) so as to be coaxial with the absorption axis of the polarizing film, it was dried at 40 ° C. to form a polarizing element having a thickness of 1.8 μm, thereby obtaining a laminated polarizer.

Example 2 As a polyvinyl alcohol film containing a dichroic substance, HEG5 manufactured by Nitto Denko Corporation was used.
A laminated polarizer was obtained in the same manner as in Example 1 except that 425 DU was used.

(Comparative Example 1) A lyotropic liquid crystal aqueous solution containing dichroic dyes (LC Polarizer, manufactured by Optiva, solid content concentration: 16.7% by weight) was mixed with a triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd., TD-80U).
After coating with a wire bar (No. 7),
After drying at 40 ° C., a polarizing element having a thickness of 2.6 μm was obtained.

(Comparative Example 2) F1225DU manufactured by Nitto Denko Corporation
Only a polarizing film was used.

(Comparative Example 3) HEG1425 manufactured by Nitto Denko Corporation
A polarizing film consisting of only DU was used.

(Evaluation Method and Results) The viewing angle characteristics of the contrast ratio between the parallel transmittance and the orthogonal transmittance were determined by ELDIM.
Measured using EZContrast. The viewing angle characteristic of the contrast ratio was calculated by setting the viewing angle characteristic of the parallel transmittance to the ON state and the viewing angle characteristic of the orthogonal transmittance to the OFF state.

At this time, the parallel transmittance is determined by the azimuth of the absorption axis.
At 0 ° and 0 °, the orthogonal transmittance is 0 ° for the azimuth of the absorption axis.
And installed at 90 °. In particular, the measurements of Examples 1 and 2 and Comparative Example 1 were carried out by forming a pressure-sensitive adhesive on the surface coated with the LC polarizer and bonding them to both surfaces of a glass plate. Comparative Examples 2 and 3 were also measured by bonding to both sides of a glass plate. Table 1 shows the results.

[0044]

[Table 1]

From Table 1, it can be seen that Examples 1 and 2 have higher front contrast and higher contrast when tilted at 45 ° azimuth than Comparative Examples 1 to 3, and therefore have high contrast polarization having a wide viewing angle characteristic. It was a film.

On the other hand, Comparative Example 1 was a low-contrast polarizing film because it had a wide viewing angle characteristic but had low front contrast.

Comparative Examples 2 and 3 were conventional polarizing plates having a narrow viewing angle.

[0048]

As described above, according to the present invention,
By laminating a dichroic substance-containing polyvinyl alcohol film-based polarizing film or a polarizing film having a stretch-oriented polyene structure and a polarizing element in which a dichroic dye is oriented in a flow orientation, it shows a high front contrast ratio and A laminated polarizing element having a wide viewing angle characteristic and a liquid crystal display device having the same can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuichi Nishikoji 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Tomoaki Masuda 1-1-1-2 Shimohozumi, Ibaraki-shi, Osaka No. Nitto Denko F-term (reference) 2H049 BA02 BA06 BA25 BA27 BA47 BB03 BB23 BB27 BB28 BB33 BB43 BB44 BB46 BB47 BB48 BB49 BB51 BC03 BC14 BC22 2H091 FA08Y FA11X FD06 FD15 LA17 LA19

Claims (6)

[Claims] 1. A polarizing film formed by stretching a dichroic substance-containing polyvinyl alcohol film or a polarizing film having a stretch-oriented polyene structure, and a polarizing element in which a dichroic substance is oriented by flow orientation. A laminated polarizing element characterized by the above-mentioned. 2. A polarizing element in which a dichroic substance is oriented by flow alignment, wherein the polarizing element is flow-aligned and fixed from a lyotropic liquid crystal phase of a dichroic dye, or a polarizing element comprising a dichroic substance exhibiting lyotropic liquid crystallinity. The laminated polarizing element according to claim 1, wherein 3. The contrast ratio between the parallel transmittance (A) when the azimuth of the absorption axis is 0 ° and 0 ° and the orthogonal transmittance (B) when the azimuth of the absorption axis is 0 ° and 90 ° is an inclination angle in the azimuth angle of 45 °. 3. The laminated polarizing element according to claim 1, wherein the angle of inclination is 60 or more, and the contrast ratio of the front surface is 55 or more. 4. A laminated polarizing element according to claim 1, wherein a pressure-sensitive adhesive is further formed on at least one surface of the laminated polarizing element according to claim 1. 5. A laminated polarizing element comprising a laminated polarizing element according to claim 1 and a film having an optical anisotropy and a birefringence compensation function laminated thereon. 6. A liquid crystal display device comprising the laminated polarizing element according to claim 1 on at least one side of a liquid crystal display panel.