JP2001337222A - Optical retardation plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide band optical retardation plate which is manufactured with a simple process and at a low cost and which further gives nearly uniform phase difference characteristics with respect to incident light over the entire visible ray region. SOLUTION: The optical retardation plate is made by imparting alignment to a film comprising a polymer blend containing at least a kind of polymer with positive intrinsic birefringence value and at least a kind of polymer with negative intrinsic birefringence value. Preferably the optical retardation plate utilizes a norbornene resin and a styrene type resin as the polymers with the positive and negative intrinsic birefringence values respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which can be used as a display device in various fields, such as a personal computer, an AV device, a portable information communication device, a game and a simulation device, and a navigation system for a vehicle. The present invention relates to a retardation plate suitable for the invention.

[0002]

2. Description of the Related Art Retardation (Re) is 1/4 of wavelength.
Is used for reflection type liquid crystal display devices, optical disk pickups and anti-glare films, etc.
Has various uses. On the other hand, a half-wave plate whose Re is １ ／ of the wavelength is also used for a liquid crystal projector.
Has various uses. It is desired that the １ ／ wavelength plate and the 望 ま wavelength plate fully exhibit their functions with respect to all incident light in the visible light region in various applications. The film made of cellulose diacetate has the properties of a broadband retardation plate that can sufficiently exhibit its function with respect to the incident light in the entire visible light range, but has high water absorption and dimensional stability. Inferior, there is a practical problem. Therefore, the broadband retardation plate is not a single-layer film, but is disclosed in, for example, JP-A-5-27118 and JP-A-5-27118.
No. 100114, JP-A-10-68816,
As described in JP-A-10-90521 and the like,
A laminated film composed of two polymer films having mutually different optical anisotropy has been proposed.

[0003] However, in the case of the retardation plate composed of the laminated film, two kinds of chips obtained by cutting a stretched birefringent film stretched in one direction in directions different from each other with respect to the stretching direction are required for the production. It is necessary to bond the chips with an adhesive and laminate them. In a retardation plate such as a quarter-wave plate, the optical anisotropy (tilt of the optical axis and slow axis) of each polymer film is determined by the angle at which the chip is cut with respect to the stretching direction of the stretched film. Therefore, precise cutting technology is required. Also, 2
When laminating two chips, it is necessary to apply an adhesive or to perform precise alignment, and the manufacturing process is complicated.
In other words, it is necessary to carry out processes such as adhesive processing, chipping, bonding, and other cost-increase factors, which have an adverse effect on actual performance such as contamination of processing chips due to chipping, and variations in phase difference due to errors in bonding angles. Have a problem. A phase difference plate that gives uniform phase difference characteristics to incident light in the entire visible light range,
At present, a technique for forming a single layer instead of a stacked layer has not been provided yet.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, can be manufactured at a low cost by a simple process, and has a substantially uniform position with respect to incident light in the entire visible light region. It is an object of the present invention to provide a wide-band retarder that provides retardation characteristics.

[0005]

Means for solving the above problems are as follows. <1> A retardation plate obtained by imparting orientation to a film made of a polymer blend containing at least one kind of polymer having a positive intrinsic birefringence value and at least one kind of polymer having a negative intrinsic birefringence value. <2> Wavelength 450 nm, 550 nm, and 650 nm
At Re (450) and Re, respectively.
(550) and Re (650), Re (4
50) <Re (550) <Satisfies Re (650) <
1>. <3> Let the retardation value at wavelength λ be Re (λ)
When the wavelength is 450 nm or more and 650 nm or less, the retardation plate according to <1> or <2>, which satisfies the following relational expression. 0.20 ≦ Re (λ) /λ≦0.30 <4> The retardation value at the wavelength λ is represented by Re (λ).
When the wavelength is 450 nm or more and 650 nm or less, the retardation plate according to <1> or <2>, which satisfies the following relational expression. 0.40 ≦ Re (λ) /λ≦0.60

<5> The retardation plate according to any one of <1> to <4>, wherein the polymer having a positive intrinsic birefringence value is a norbornene resin. <6> The retardation plate according to any one of <1> to <5>, wherein the polymer having a negative intrinsic birefringence value is a styrene-based polymer. <7> The retardation plate according to <6>, wherein the styrene-based polymer is a copolymer of styrene and maleic anhydride.

In the present invention, by using a film made of a polymer blend in which polymers having different intrinsic birefringence values are blended, the wavelength dispersion characteristics of retardation exhibited by each polymer are alleviated to each other, and the entire range of visible light is reduced. It is possible to give a uniform phase difference characteristic to incident light. As a result, a wide-band retardation plate can be manufactured in a single-layer structure, and complicated steps such as chip cutting and bonding are not required, and a phase difference plate can be manufactured with a simple process and at low cost. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The retardation film of the present invention is a film comprising a polymer blend containing at least one polymer having a positive intrinsic birefringence value and at least one polymer having a negative intrinsic birefringence value. It is provided with orientation.

The “polymer having a positive intrinsic birefringence value” (hereinafter sometimes simply referred to as a “positive polymer”) is defined as a case where light is incident on a layer in which molecules are oriented uniaxially. A polymer in which the refractive index of light in the alignment direction is larger than the refractive index of light in a direction orthogonal to the alignment direction.
On the other hand, the “polymer having a negative intrinsic birefringence value” (hereinafter, may be simply referred to as “negative polymer”) means that when light is incident on a layer in which molecules have a uniaxial orientation,
A polymer in which the refractive index of light in the alignment direction is smaller than the refractive index of light in a direction orthogonal to the alignment direction.

It is preferable that the positive polymer and the negative polymer are used in combination of those having different wavelength dispersions of intrinsic birefringence values. For example, the ratio of the intrinsic birefringence values at a wavelength of 450 nm and a wavelength of 550 nm, Δn (450) / Δ (550), of the stretched film of the positive polymer alone and the stretched film of the negative polymer alone, respectively, is 0.02 in absolute value. Preferably, there is a difference of at least 0.05,
More preferably, there is a difference as described above.

It is preferable that the positive polymer and the negative polymer are used in combination with each other.
In the case of using a combination of incompatibilities, a third component such as a compatibilizing agent can be added for compatibility.
As a combination compatible without adding the third component, a norbornene-based resin having a positive intrinsic birefringence value (JSR
A combination of "Arton") and a random copolymer of styrene and maleic anhydride having a negative intrinsic birefringence,
A norbornene resin having a positive intrinsic birefringence value (manufactured by JSR Corporation;
"Arton") and polystyrene with a negative intrinsic birefringence value and a relatively small molecular weight, and polyphenylether with a positive intrinsic birefringence value and polystyrene with a negative intrinsic birefringence value show heat resistance, dimensional It can be preferably used from the viewpoint of degree stability, transparency and the like. Among them, a combination of a norbornene-based resin and a styrene-based polymer (including a copolymer) is most preferable.

The norbornene resin has a norbornene skeleton as a repeating unit. As the norbornene-based resin, transparency, low water absorption, high heat resistance,
A thermoplastic norbornene-based resin is preferable in that it is suitable for optical use. Examples of the thermoplastic norbornene-based resin include JP-A-60-168708 and JP-A-62-2.
No. 52406, JP-A-62-252407,
JP-A-2-133413, JP-A-63-1453
No. 24, JP-A-63-264626, JP-A-1-240517, and JP-B-57-8815 can be suitably used, but the invention is not limited thereto. These may be used alone or in combination of two or more.

Among the thermoplastic norbornene resins, those having a repeating unit represented by any of the following structural formulas (I) to (IV) are preferred.

[0014]

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In the above structural formulas (I) to (IV), A, B, C
And D each independently represent a hydrogen atom or a monovalent organic group.

Further, among the thermoplastic norbornene resins, at least one of tetracyclododecene represented by the following structural formula (V) and an unsaturated cyclic compound copolymerizable therewith are subjected to metathesis polymerization. A hydrogenated polymer obtained by hydrogenating the obtained polymer is also preferable.

[0017]

Embedded image

In the above structural formula, A, B, C and D each independently represent a hydrogen atom or a monovalent organic group.

The norbornene resin has a weight average molecular weight of about 5,000 to 1,000,000, preferably 8,000 to 200,000.

The polymer having a negative intrinsic birefringence value is
One kind of polymer having the above properties may be used alone, or two or more kinds may be used in combination when two or more kinds are blended to show the above properties. As the negative polymer, a polymer having a large wavelength dispersion of an intrinsic birefringence value is preferable. Specifically, a wavelength of 450 nm and a wavelength of 5
The intrinsic birefringence value (Δn) of 50 nm is calculated as Δn (45
0) and Δn (550), it is preferable to select from resins satisfying the following relational expression. | Δn (450) / Δn (550) | ≧ 1.02 Further, it is more preferable to select from resins satisfying the following relational expression. | Δn (450) / Δn (550) | ≧ 1.05 The negative polymer includes | Δn (450) / Δn
The value of (550) | is preferably larger, but is generally 2.0 or less in the case of a polymer.

Examples of the negative polymer include polystyrene-based polymers, polyacrylonitrile-based polymers, polymethyl methacrylate-based polymers, cellulose ester-based polymers (excluding those having a positive intrinsic birefringence value),
Alternatively, a multi-component (binary, ternary, etc.) copolymer may be used. These may be used alone or in combination of two or more. In the present invention,
Among these, polystyrene-based polymers such as polystyrene, a copolymer of styrene and acrylonitrile, a copolymer of styrene and maleic anhydride, and a copolymer of styrene and methyl methacrylate are preferred, and particularly, styrene and maleic anhydride. Is preferred.

In the polymer blend composed of the positive polymer and the negative polymer, the mixing ratio of the negative polymer to the positive polymer is determined by the magnitude of the absolute value of the intrinsic birefringence of the two or the birefringence at the molding temperature. It depends on the expression of etc., and cannot be specified unconditionally, but when a norbornene resin is used as a positive polymer,
5: 5 by mass ratio (norbornene resin: negative polymer)
~ 9: 1 is preferable, and 7: 3 ~ 8: 2 is preferable. When another material is used as the positive polymer, the preferable range of the mass ratio is generally the same.

The polymer blend may contain other components in addition to the positive polymer and the negative polymer. The component is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected depending on the purpose.
For example, a compatibilizer and the like are preferably mentioned. The compatibilizer can be suitably used, for example, when phase separation does not occur when the positive polymer and the negative polymer are mixed, and by using the compatibilizer, the positive The mixed state of the polymer and the negative polymer can be improved.

The retardation plate of the present invention is obtained by imparting an orientation to a film comprising the polymer blend. The orientation can be imparted by forming a film comprising the polymer blend and then stretching the film.
There is no particular limitation on the method for forming the film, and the polymer blend is dissolved in a predetermined organic solvent to prepare a coating solution, and the solution is formed by applying the coating solution to form a film. It may be a melt film formation in which the blend is heated and melted to form a film using the same. The method of stretching the film is not particularly limited, and a longitudinal uniaxial stretching, a horizontal uniaxial stretching (tenter stretching), an unbalanced biaxial stretching method, or the like can be used.

In the retardation plate of the present invention, since a polymer blend having a different intrinsic birefringence value is used, a film made of the polymer blend is stretched so that the orientation directions of the positive polymer and the negative polymer coincide with each other. Then, the slow axes derived from the intrinsic birefringence values of the respective polymer chains are orthogonal to each other. As a result, each polymer chain cancels each other's birefringence, but because the wavelength dispersion characteristics of each other's intrinsic birefringence are different,
The degree of cancellation has wavelength dependence. The degree of cancellation of the retardation can be adjusted by selecting the blend ratio of the polymer blend and the stretching conditions, that is, the respective values Re (450), Re (550) and Re (650) of the retardation at wavelengths of 450 nm, 550 nm and 650 nm. ) Is Re (450) <Re (55)
0) <Re (650) The retardation can be adjusted to satisfy the relational expression.

Further, in the retardation plate of the present invention, the ratio of retardation Re (λ) to wavelength λ, Re (λ) / λ, at wavelength λ is selected by selecting the blend ratio of the polymer blend and the stretching conditions. The retardation can be adjusted so as to have a substantially constant value over the entire visible light range. As a result, a substantially uniform phase difference characteristic is given to incident light in the entire visible light range.
Characteristics as a broadband half-wave plate can be imparted. When the retardation plate of the present invention is used as a broadband quarter-wave plate, Re (λ) / λ is preferably 0.20 to 0.30 in the wavelength range of 450 nm to 650 nm, and 0.23 to 0.30. More preferably ~ 0.27,
More preferably, it is 0.24 to 0.26. on the other hand,
When used as a broadband half-wave plate, a wavelength of 450
Re (λ) / λ is in the range of 0.3 nm to 650 nm.
40 to 0.60, preferably 0.46 to 0.5
2, more preferably 0.48 to 0.52.

The retardation plate of the present invention can adjust retardation by selecting a blend ratio of a positive polymer and a negative polymer, stretching conditions, and the like, and can be used for various applications. For example, a reflective liquid crystal display device that can be used as a display device in various fields such as a personal computer, an AV device, a portable information communication device, a game or a simulation device, and an in-vehicle navigation system; an optical disc pickup; Λ / 4
It can be suitably used as a plate. Further, it can be suitably used as a λ / 2 plate of a liquid crystal projector.

When the retardation plate of the present invention is used for a liquid crystal display device or the like, the thickness of the retardation plate is preferably from 10 μm to 200 μm, more preferably from 50 μm to 150 μm. When used by being bonded to another member in the display device, for example, a polarizing plate or the like, the retardation plate is preferably as thin as possible, but a certain thickness is required in consideration of handling properties and the like during the bonding process. However, if the difficulty in manufacturing is solved, it is preferable to use as a thin retardation plate of about several μm.

[0029]

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. Example 1 A polymer having a positive intrinsic birefringence value was 16 parts by mass of a norbornene-based resin (manufactured by JSR; "ARTON F"), and a copolymer of styrene and maleic anhydride was used as a polymer having a negative intrinsic birefringence value. 9 parts by mass of the combined product (manufactured by Sekisui Chemical Co., Ltd .; "Dilark 232") were dissolved in toluene to prepare a coating solution (25% by mass).

The coating solution was cast on a glass plate using a doctor blade and dried to form a transparent film having a thickness of 120 μm. 120 ° C
The film was uniaxially stretched by 27% to produce a retardation plate. About this retardation plate, a retardation measuring device (manufactured by Oji Scientific Co., Ltd .;
Using “KOBRA21DH”), the wavelength dispersion of the retardation was measured. The results are shown in FIG. As shown in FIG. 1, the retardation plate of the first embodiment has a wavelength of 450 nm and 550 nm.
The values of retardation (Re) at nm and 650 nm are Re (450), Re (550) and Re (6), respectively.
50), Re (450) <Re (550) <
Re (650) was satisfied, and it was found that the characteristics of a quarter-wave plate were exhibited over a wide band.

Comparative Example 1 The norbornene-based resin used in Example 1 was formed alone to obtain a transparent film (thickness: 105 μm). This transparent film is heated at 110 ° C for 2 hours.
A retardation plate was prepared in the same manner as in Example 1 except that the film was uniaxially stretched by 0%, and the retardation wavelength dispersion was examined in the same manner as in Example 1. The results are shown in FIG. As shown in FIG. 1, the retardation plate did not function as a broadband quarter-wave plate.

Comparative Example 2 The styrene / maleic anhydride copolymer used in Example 1 was formed alone to obtain a transparent film (thickness: 101 μm). A retardation plate was prepared in the same manner as in Example 1 except that the transparent film was uniaxially stretched at 110 ° C. for 20%, and retardation and wavelength dispersion were examined in the same manner as in Example 1. The results are shown in FIG.
As shown in FIG. 1, the retardation plate did not function as a broadband quarter-wave plate.

(Example 2) As a polymer having a positive intrinsic birefringence value, 16 parts by mass of a norbornene-based resin (manufactured by JSR; "ARTON F"), and a polymer having a negative intrinsic birefringence value of styrene / 9 parts by mass of the maleic anhydride copolymer was dissolved in toluene to prepare a coating solution (25% by mass).

The coating solution was cast on a glass plate using a doctor blade and dried to form a transparent film having a thickness of 240 μm. 120 ° C
The film was uniaxially stretched by 30% to produce a retardation plate. About this retardation plate, a retardation measuring device (manufactured by Oji Scientific Co., Ltd .;
Using “KOBRA21DH”), the wavelength dispersion of the retardation was measured. The results are shown in FIG. As shown in FIG. 1, the retardation plate of the first embodiment has a wavelength of 450 nm and 550 nm.
The values of retardation (Re) at nm and 650 nm are Re (450), Re (550) and Re (6), respectively.
50), Re (450) <Re (550) <
Re (650) was satisfied, and it was found that the characteristics of a half-wave plate were exhibited over a wide band.

Comparative Example 3 The norbornene-based resin used in Example 2 was formed alone to obtain a transparent film (210 μm in thickness). This transparent film is heated at 120 ° C for 3 hours.
A retardation plate was prepared in the same manner as in Example 2 except that the film was uniaxially stretched by 3%, and the retardation wavelength dispersion was examined in the same manner as in Example 2. The results are shown in FIG. As shown in FIG. 2, the retardation plate did not function as a broadband half-wave plate.

Comparative Example 4 The styrene / maleic anhydride copolymer used in Example 2 was formed into a single film to obtain a transparent film (thickness: 180 μm). A retardation plate was prepared in the same manner as in Example 2 except that this transparent film was uniaxially stretched at 115 ° C. by 28%, and retardation and wavelength dispersion were examined in the same manner as in Example 2. The results are shown in FIG.
As shown in FIG. 2, the retardation plate did not function as a broadband half-wave plate.

[0037]

According to the present invention, there is provided a wide-band retardation plate which can be manufactured at a low cost by a simple process and which gives substantially uniform retardation characteristics to incident light in the entire visible light region. can do.

[Brief description of the drawings]

FIG. 1 is a graph showing the wavelength dispersion characteristics of retardation in the visible light region of the retardation films manufactured in Example 1, Comparative Examples 1 and 2.

FIG. 2 is a graph showing the wavelength dispersion characteristics of retardation in the visible light region of the retardation films manufactured in Example 2, Comparative Examples 3 and 4.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13363 G02F 1/13363 F-term (Reference) 2H049 BA06 BA07 BA42 BB50 BC03 BC22 2H091 FA11X FA11Z FB02 KA01 KA02 LA12 LA16 4F071 AA22 AA22X AA36X AA39 AF31 AF31Y AF35Y BC01 4J002 BC03X BC04X BC06X BC07X BG06X BG10X BK00W

Claims (7)

[Claims] 1. A retardation plate obtained by imparting orientation to a film made of a polymer blend containing at least one polymer having a positive intrinsic birefringence value and at least one polymer having a negative intrinsic birefringence value. 2. Wavelengths of 450 nm, 550 nm and 65 nm.
Retardation values at 0 nm are each represented by Re (45
0), Re (550) and Re (650), Re (450) <Re (550) <Re (650)
The retardation plate according to claim 1, wherein the following conditions are satisfied. 3. The retardation value at a wavelength λ is represented by Re
3. When (λ) is satisfied, the following relational expression is satisfied at a wavelength of 450 nm or more and 650 nm or less.
2. The retardation plate according to 1. 0.20 ≦ Re (λ) /λ≦0.30 4. The retardation value at a wavelength λ is represented by Re
3. When (λ) is satisfied, the following relational expression is satisfied at a wavelength of 450 nm or more and 650 nm or less.
2. The retardation plate according to 1. 0.40 ≦ Re (λ) /λ≦0.60 5. The retardation plate according to claim 1, wherein the polymer having a positive intrinsic birefringence value is a norbornene resin. 6. The retardation plate according to claim 1, wherein the polymer having a negative intrinsic birefringence value is a styrene-based polymer. 7. The retardation plate according to claim 6, wherein the styrene-based polymer is a copolymer of styrene and maleic anhydride.