JP4920734B2 - Production method of retardation plate - Google Patents

Description

  The present invention relates to a method of manufacturing a retardation plate, and more specifically, can be used for display devices in various fields such as personal computers, AV equipment, portable information communication equipment, games and simulation equipment, and in-vehicle navigation systems. The present invention also relates to a method of manufacturing a retardation plate.

  A quarter-wave plate having a retardation (Re) of ¼ of the wavelength has various uses such as a reflection type liquid crystal display device, a pickup for an optical disk, and an anti-glare film. On the other hand, a half-wave plate whose Re is ½ of the wavelength also has various uses such as being used in a liquid crystal projector. The quarter-wave plate and the half-wave plate are desired to exhibit their functions sufficiently for all incident light in the visible light region in various applications. As a broadband retardation plate capable of sufficiently exhibiting the function with respect to incident light in the entire visible light region, for example, JP-A-5-27118, JP-A-5-100114, JP-A-10-68816 And those obtained by laminating two polymer films having different optical anisotropies, such as JP-A-10-90521.

  However, in the conventional laminated phase difference plate, for production thereof, two kinds of chips are formed by cutting a stretched birefringent film stretched in one direction in directions that make different angles with respect to the stretch direction, This chip needs to be bonded and laminated with an adhesive material. In addition, when bonding two chips, not only the cost increase due to adhesive material coating, chip formation, and bonding, but also the effect on performance, such as the performance degradation due to the angle shift accompanying chip bonding It cannot be ignored. Moreover, in the multilayered phase difference plate formed by chip bonding, performance degradation due to an increase in thickness may be a problem.

  The present invention has been made in view of the above-mentioned problems, and is capable of manufacturing a retardation plate capable of manufacturing a broadband retardation plate that gives uniform retardation characteristics to incident light in the entire visible light region by a simple process. It aims to provide a method.

Means for solving the above problems are as follows. That is,
<1> A resin having a positive intrinsic birefringence value and a resin having a negative intrinsic birefringence value are coextruded, a first layer made of a resin having a positive intrinsic birefringence value and having birefringence, Forming a laminate having a second layer made of a negative resin and having birefringence,
Provided after the step of producing the laminate, and by stretching the laminate, the slow axis of the first layer and the slow axis of the second layer are orthogonal to each other, and the wavelengths are 450 nm and 550 nm. And the step of adjusting the retardation so that Re (450) <Re (550) <Re (650) where Re (450), Re (550) and Re (650) are the retardation values at 650 nm and 650 nm, respectively. When,
It is a manufacturing method of the phase difference plate which has these.

<2> The method for producing a retardation plate according to <1>, wherein the resin having a positive intrinsic birefringence value is a norbornene-based polymer.
<3> The method for producing a retardation plate according to <1> or <2>, wherein the resin having a negative intrinsic birefringence value is polystyrene or a polystyrene-based polymer.
<4> The retardation plate according to <3>, wherein the polystyrene-based polymer is a copolymer of styrene and / or a styrene derivative and at least one selected from acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. It is a manufacturing method.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the phase difference plate which can manufacture the broadband phase difference plate which gives a uniform phase difference characteristic with respect to the incident light of the visible light whole region by a simple process can be provided.

It is a schematic sectional drawing of one Embodiment of the phase difference plate of this invention. It is a graph which shows the measurement result of the wavelength dispersion characteristic of Re value in the visible light region of the manufactured phase difference plate. It is a graph which shows the measurement result of the wavelength dependence of the (Re / wavelength) value in the visible light region of the manufactured circularly-polarizing plate. It is the schematic of the extrusion apparatus used in the Example. It is sectional drawing of the die | dye of the extrusion apparatus used in the Example. 2 is a graph showing the wavelength dispersion of retardation of 19% stretched film and 39% stretched film prepared in Example 1. FIG. 3 is a schematic cross-sectional view of a stretched film produced in Example 2. FIG. 6 is a graph showing the wavelength dispersion of retardation of a stretched film produced in Example 2. It is a graph which shows the wavelength dispersion of the retardation of the stretched film produced in Comparative Examples 7 and 8.

(Phase difference plate)
The retardation plate manufactured according to the present invention includes a material having a positive intrinsic birefringence value (hereinafter, simply referred to as “positive material”) and a material having a negative value (hereinafter simply referred to as “negative material”). And at least one other component, and other components appropriately selected as necessary. The retardation plate manufactured according to the present invention includes a form in which the material having a positive intrinsic birefringence value and the material having a negative intrinsic birefringence value are contained in different layers. In the phase difference plate manufactured according to the present invention, incident light is given phase difference characteristics by a multilayer containing materials whose intrinsic birefringence values are positive and negative. The material with positive intrinsic birefringence and the material with negative intrinsic birefringence are the result of offsetting the characteristics of each retardation because the slow axes are orthogonal when the orientation direction of the molecules becomes equal due to stretching operation, etc. Retardation as a composite of In the present invention, the wavelength dispersion of the retardation to be expressed is controlled by various combinations of the positive material and the negative material and / or by adjusting the production conditions such as stretching conditions, and visible light It is possible to provide a phase difference plate that gives a phase difference characteristic with substantially uniform Re / λ to incident light in the entire area.

  First, a material having a positive intrinsic birefringence value and a material having a negative value used for the retardation plate manufactured according to the present invention will be described.

-Materials with positive intrinsic birefringence values-
In the present invention, “a material having a positive intrinsic birefringence value” refers to a material having a characteristic of optically uniaxiality when molecules are oriented in a uniaxial order. For example, when the positive material is a resin, when light is incident on a layer in which molecules have a uniaxial orientation, the refractive index of the light in the orientation direction is perpendicular to the orientation direction. A resin that is larger than the refractive index of light. Examples of the positive material include various materials such as a resin, a rod-like liquid crystal, and a rod-like liquid crystal polymer. These may be used individually by 1 type and may use 2 or more types together. In these, resin is preferable among these in this invention.

Examples of the resin include olefin polymers (eg, polyethylene, polypropylene, norbornene polymers, cycloolefin polymers, etc.), polyester polymers (eg, polyethylene terephthalate, polybutylene terephthalate, etc.), polyarylene sulfide polymers (eg, polyphenylene). Sulfides, etc.), polyvinyl alcohol polymers, polycarbonate polymers, polyarylate polymers, cellulose ester polymers (some of which have negative intrinsic birefringence values), polyethersulfone polymers, polysulfone polymers, polyallylsulfides Examples include phonic polymers, polyvinyl chloride polymers, and multi-component (binary, ternary, etc.) copolymer polymers thereof. These may be used individually by 1 type and may use 2 or more types together.
In the present invention, among these, olefin polymers are preferable, and among olefin polymers, norbornene polymers are particularly preferable from the viewpoints of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, and the like. As the olefin polymer, “Art So” made by Nippon Synthetic Rubber, “Zeonex” and “Zeonor” made by Nippon Zeon, “APO” made by Mitsui Petrochemical, etc. are preferably used.

  The norbornene-based polymer has a norbornene skeleton as a repeating unit, and specific examples thereof include JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403, JP-A-5-43663, JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, JP-A-9 Although it can utilize suitably what was described in 241484 gazette etc., it is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together.

  In the present invention, among the norbornene-based polymers, those having a repeating unit represented by any of the following structural formulas (I) to (IV) are preferable.

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

  Among the norbornene-based polymers, a polymer obtained by metathesis polymerization of at least one compound represented by the following structural formula (V) or (VI) and an unsaturated cyclic compound copolymerizable therewith. A hydrogenated polymer obtained by hydrogenating is also preferred.

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

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

-Material with negative intrinsic birefringence value-
In the present invention, “a material having a negative intrinsic birefringence value” refers to a material having a characteristic that exhibits optically negative uniaxiality when molecules are oriented in a uniaxial order. For example, when the negative material is a resin, when light is incident on a layer in which molecules have a uniaxial orientation, light in a direction in which the refractive index of light in the orientation direction is orthogonal to the orientation direction A resin having a refractive index lower than that of the resin. Examples of the negative material include various materials such as resin, discotic liquid crystal, and discotic liquid crystal polymer. These may be used individually by 1 type and may use 2 or more types together. In the present invention, among these, a polymer is preferable.

Examples of the polymer include polystyrene, a polystyrene-based polymer (a copolymer of styrene and / or a styrene derivative and another monomer), a polyacrylonitrile-based polymer, a polymethyl methacrylate-based polymer, and a cellulose ester-based polymer (the intrinsic birefringence value is Some of them are positive), or their multiple (binary, ternary, etc.) copolymer. These may be used individually by 1 type and may use 2 or more types together. The polystyrene polymer is preferably a copolymer of styrene and / or a styrene derivative and at least one selected from acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. In the present invention, among these, at least one selected from polystyrene, polystyrene-based polymers, polyacrylonitrile-based polymers, and polymethylmethacrylate-based polymers is preferable, and among these, from the viewpoint of high birefringence expression. Polystyrene and polystyrene-based polymers are more preferable, and a copolymer of styrene and / or a styrene derivative and maleic anhydride is particularly preferable in terms of high heat resistance.
In addition, when utilizing the phase difference plate of this invention for an optical use (display element etc.), it is preferable to use the polymer whose glass transition point is 110 degreeC or more (more preferably 120 degreeC or more).

-Preferred combination of positive and negative materials-
In the present invention, the material having a positive intrinsic birefringence value and the material having a negative value are preferably combined as an index that satisfies the following conditions.
When the absolute value of the retardation (Re) value at a wavelength of 450 nm and a wavelength of 550 nm is Re (450) and Re (550), respectively, the value of (Re (450) / Re (550)) of the positive material, A combination in which the values of (Re (450) / Re (550)) of the negative material are not equal (that is, one is smaller or larger than the other) is preferable. More specifically, a combination where the difference between the two values is 0.03 or more is preferable, and a combination where 0.05 or more is more preferable.

  Furthermore, when the value of (Re (450) / Re (550)) of the positive material is larger than the value of (Re (450) / Re (550)) of the negative material, the positive material The value of Re (550) of the negative material is smaller than the value of Re (550) of the negative material, and the value of (Re (450) / Re (550)) of the positive material is Is smaller than the value of (Re (450) / Re (550)), the value of Re (550) of the positive material is larger than the value of Re (550) of the negative material. A combination satisfying the above is preferable.

Next, a preferable combination when the positive material and the negative material are each a resin will be described.
When a resin having a large wavelength dispersion of intrinsic refraction value (Δn) is used as a negative material, a resin having a small wavelength dispersion of Δn is preferably used as a positive material. In addition, when a resin having a small wavelength dispersion of intrinsic refraction value (Δn) is used as a negative material, it is preferable to use a resin having a large wavelength dispersion of Δn as a positive material. For example, when a norbornene polymer is used as the positive material, it is preferable that the negative material has a large wavelength dispersion of its intrinsic birefringence value, specifically, an intrinsic complex having a wavelength of 450 nm and a wavelength of 550 nm. When the refraction value (Δn) is Δn (450) and Δn (550), respectively, it is preferably selected from resins satisfying the following relational expression.
| Δn (450) / Δn (550) | ≧ 1.02
Furthermore, it is more preferable that the resin is selected from resins that satisfy the following relational expression.
| Δn (450) / Δn (550) | ≧ 1.05
The larger value of | Δn (450) / Δn (550) | is preferable, but in the case of resin, it is generally 2.0 or less.

More specifically, when the negative material is polymethyl methacrylate or the like having a small value of (Re (450) / Re (550)), the positive material combined therewith is a polyethylene terephthalate polymer. Polyphenylene sulfide polymers, polycarbonate polymers, polyarylate polymers, polyethersulfone polymers, polysulfone polymers, polyallylsulfone polymers, polyvinyl chloride polymers, and the like are preferable.
In addition, when the negative material is a polystyrene or a polystyrene-based polymer having a large value of (Re (450) / Re (550)), the positive material combined therewith is an olefin polymer or a cycloolefin. Polymers such as polyethylene, polypropylene, norbornene polymers, cellulose ester polymers, and the like are preferable. Among these, a combination of polystyrene and / or polystyrene-based polymer as a negative material and a norbornene-based polymer among olefin-based polymers as a positive material is particularly preferable.

-Other ingredients-
The other components are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately selected according to the purpose. Examples thereof include a compatibilizing agent. The compatibilizing agent can be suitably used in a retardation plate having a layer containing a mixture of the positive material and the negative material, when the mixture causes phase separation, etc. By using a solubilizer, the mixed state of the material having a positive intrinsic birefringence value and the material having a negative value can be improved.

Hereinafter, embodiments of the retardation plate of the present invention will be described.
As a reference form of the retardation film, a film or sheet made of a polymer blend of a resin having a positive intrinsic birefringence value and a negative resin can be mentioned. Re (450) <Re (550) <Re (650) where Re (450), Re (550) and Re (650) are retardation values at wavelengths of 450 nm, 550 nm and 650 nm of the film or sheet, respectively. The relationship is established.

  The retardation plate of this reference embodiment can be produced by various methods. For example, a positive material and a negative material are appropriately selected according to the index, a blending ratio is determined, the compatibilizer is added as necessary, and these are blended. And after that, this compound is dissolved in an arbitrary organic solvent to prepare a coating solution, and the coating solution is coated on a support (or temporary support) and dried to form a film. (Solution casting method). Alternatively, the blend can be pelletized, melt extruded, and formed into a film (extrusion method).

  A retardation plate satisfying the relationship of Re (450) <Re (550) <Re (650) can be obtained by subjecting the film or the like produced by the above method to stretching treatment. Suitable examples of the stretching include longitudinal uniaxial stretching that stretches in the mechanical flow direction and transverse uniaxial stretching that stretches in the direction orthogonal to the mechanical flow direction (for example, tenter stretching). Axial stretching may be used. Details of the adjustment of the retardation by stretching are the same as the method of adjusting the retardation in the retardation plate having a laminated structure described later. In addition, when the film-like or sheet-like retardation plate produced by the above-described method already exhibits a desired range of retardation, it can be used as it is without being subjected to stretching treatment.

  When the retardation plate of the present embodiment is used for a circularly polarizing plate (λ / 4 plate), in a wide range of wavelengths from 450 nm to 650 nm, at least at wavelengths of 450 nm, 550 nm, and 650 nm, (retardation (Re) / The wavelength) is 0.2 to 0.3, in other words, the retardation (Re) value at the wavelength 550 nm is 110 nm to 165 nm, and it is necessary to have a positive correlation with the wavelength length. It is. More preferably, at least at wavelengths of 450 nm, 550 nm and 650 nm, the value of (retardation (Re) / wavelength) is 0.23 to 0.27, and more preferably 0.24 to 0.26.

  When the retardation plate of the present embodiment is used for a λ / 2 plate, (retardation (Re) / wavelength) of at least wavelengths of 450 nm, 550 nm and 650 nm in a wide range from wavelengths of 450 nm to 650 nm. It is necessary that the value is 0.40 to 0.60, in other words, the retardation (Re) value at a wavelength of 550 nm is 220 nm to 330 nm, and has a positive correlation with the length of the wavelength. More preferably, at least at wavelengths of 450 nm, 550 nm and 650 nm, the value of (retardation (Re) / wavelength) is 0.46 to 0.54, and more preferably 0.48 to 0.52.

  In the retardation plate of this reference embodiment, the layers made of a mixture of the positive material and the negative material (a polymer blend when the material is a resin) have the same molecular orientation of each material. . When the molecular orientations of the positive material and the negative material are matched, the slow axis is perpendicular to each other, and the wavelength dispersion of the retardation of each material is reduced with respect to the incident light in the entire visible light range. In addition, it is possible to provide a retardation plate that provides substantially uniform retardation characteristics. Therefore, the retardation plate of the present invention can provide uniform retardation characteristics for broadband (visible light) light, and does not require a lamination process for production, and is made of a single material at low cost. It can be formed.

One embodiment of the retardation plate of the present invention is shown in FIG.
The phase difference plate 10 has a configuration in which a layer 12 made of a resin having a positive intrinsic birefringence value and a layer 14 made of a resin having a negative intrinsic birefringence value are laminated. The layers 12 and 14 have birefringence and are laminated with their slow axes orthogonal to each other. That is, the orientation direction of the positive resin molecules contained in the layer 12 and the orientation direction of the negative resin contained in the layer 14 are the same. Since the retardation of the retardation plate 10 is the sum of the retardations of the layers 12 and 14, the short wavelength of the retardation plate 10 is obtained by laminating the layers 12 and 14 with their slow axes orthogonal to each other. The retardation on the side is small and the retardation on the long wavelength side can be increased. As a result, the ratio Re (λ) / λ of the retardation Re (λ) to the wavelength λ of the retardation plate 10 can be made substantially constant over the entire visible light range.

In the retardation plate of the present embodiment, when the retardation (Re) values at wavelengths of 450 nm, 550 nm, and 650 nm are Re (450), Re (550), and Re (650), respectively, It is preferable to satisfy.
Re (450) <Re (550) <Re (650)
In order to satisfy the above relational expression, a material having a small wavelength dispersion of its intrinsic refraction value is selected as a resin having a positive intrinsic birefringence value, and a wavelength of its intrinsic birefringence value is chosen as a resin having a negative intrinsic birefringence value. Select and combine materials with large dispersion, and select a material with a large intrinsic birefringence value as a resin with a positive intrinsic birefringence value and a resin with a negative intrinsic birefringence value as a resin with a negative intrinsic birefringence value. It is preferable to select and combine materials having a small birefringence wavelength dispersion. Specific examples of preferable combinations of materials are as described above.

When the retardation plate of this embodiment is used for a circularly polarizing plate (λ / 4 plate), in a wide range of wavelengths from 450 nm to 650 nm, at least at wavelengths of 450 nm, 550 nm, and 650 nm, (retardation (Re) / The value of (wavelength) is preferably 0.2 to 0.3. More preferably, at least at wavelengths of 450 nm, 550 nm and 650 nm, the value of (retardation (Re) / wavelength) is 0.23 to 0.27, and more preferably 0.24 to 0.26. In addition, when the retardation plate of the present embodiment is used for a λ / 2 plate, the (retardation (Re) / wavelength) is at least at wavelengths of 450 nm, 550 nm, and 650 nm in a wide range of wavelengths from 450 nm to 650 nm. The value is preferably 0.40 to 0.60. More preferably, at least at wavelengths of 450 nm, 550 nm and 650 nm, the value of (retardation (Re) / wavelength) is 0.46 to 0.54, and more preferably 0.48 to 0.52.
In the present embodiment, the wavelength dispersion can be adjusted by stretching conditions such as stretching temperature and stretching ratio.

  In the present embodiment, the retardation plate having a structure having one layer each made of a resin having a positive or negative intrinsic birefringence value is shown. However, the retardation plate of the present invention is not limited to this, and the third and second retardation plates are not limited thereto. A structure having four layers may be used. It may be a structure having third and fourth layers. Forming the third and fourth layers is preferable because the physical characteristics of the retardation plate are improved. In particular, in the present invention, it is preferable to have a third layer having birefringence so that the cross section of the retardation plate has symmetry. When the third layer is made of a resin having a positive intrinsic birefringence value, an embodiment in which layers made of resins having positive, negative, and positive intrinsic birefringence values are sequentially laminated is preferable. When the third layer is made of a resin having a negative intrinsic birefringence value, an embodiment in which layers made of resins having a negative intrinsic birefringence value of negative, positive, and negative are sequentially laminated is preferable. In the three-layer structure, it is preferable that the layers made of the resin having the same intrinsic birefringence value are laminated so that their slow axes coincide with each other. Further, it is preferable that the resins having the same sign of the intrinsic birefringence value are the same material.

  Further, between the layer made of a resin having a positive intrinsic birefringence value and the layer made of a resin having a negative intrinsic birefringence value, a layer for improving the adhesion of both layers (hereinafter referred to as “adhesive layer”) May be arranged). A material having an affinity for both the positive resin and the negative resin can be used for the layer. For example, when a norbornene-based polymer is used as the resin having a positive intrinsic birefringence value and polystyrene (or polystyrene-based polymer) is used as the negative resin, the adhesive layer includes an olefin-based polymer and polystyrene (or styrene-based). Polymer) and a layer made of a polymer whose glass transition point is 5 ° C. or lower (more preferably 10 ° C. or lower) lower than the glass transition point of the positive resin and the negative resin. Preferably there is. However, it is not limited to this. The product of birefringence and thickness of the adhesive layer is preferably small.

  The retardation plate of the present embodiment is produced using coextrusion. If it manufactures with the manufacturing method of this invention using the co-extrusion demonstrated below, while being able to simplify a manufacturing process, manufacturing cost can be reduced.

  The method for producing a retardation plate of the present invention includes a resin having a positive intrinsic birefringence value (hereinafter sometimes simply referred to as “positive resin”) and a resin having a negative intrinsic birefringence value (hereinafter simply referred to as “negative resin”). And a second layer made of a resin having a negative intrinsic birefringence value and a second layer made of a resin having a negative intrinsic birefringence value are laminated. And a step of stretching the laminate and adjusting the retardation.

In the step of forming the laminate, for example, in the extruder, each of the positive resin and the negative resin is stored, heated and pressurized, and each is in a fluid state, and each is continuously extruded from the die, Make a laminate. Subsequently, the laminate may be continuously inserted through the nip portion of the nip roll and pressed.
In the case of producing the retardation plate of the aspect having the third layer, in the step of forming the laminate, the positive or negative resin constituting the third layer is stored in an extruder, A laminate having a three-layer structure is formed by coextrusion. For example, in the case of producing a retardation plate having a layer for improving the adhesiveness of both layers between a layer made of a positive resin and a layer made of a negative resin, the laminate is formed. In order to improve the adhesion between the layer made of a positive resin and the layer made of a negative resin by separately storing a resin for improving the adhesion in an extruder and co-extrusion The laminated body of the structure which has arrange | positioned this layer is formed. Also, a plurality of flow paths are provided between the location where the resin in the extruder is stored and the extrusion die, for example, positive resin / third layer resin / negative resin / third layer resin / positive It is possible to form a laminate having a five-layer structure made of three types of resins having the same structure.

The step of stretching the laminate to adjust the retardation can be carried out using various stretching machines. For example, longitudinal uniaxial stretching that stretches in the mechanical flow direction and tenter stretching that stretches in the direction perpendicular to the mechanical flow direction can be suitably used, and biaxiality can also be imparted for thickness direction control. is there. Here, the stretching temperature is set to (Tg _min −20) ° C. to (Tg _min ) ° C., where Tg _min is the minimum glass transition temperature of the basic materials (positive resin and negative resin) constituting the layer. Is preferred.

In order to satisfy the characteristics of Re (450) <Re (550) <Re (650), the resin is controlled by adjusting the weight ratio, the stretching temperature, the stretching ratio, etc., for a resin having a negative intrinsic birefringence value and a positive resin. it can.
For example, an example of an adjustment method when using norbornene-based polymer as a resin having a positive intrinsic birefringence value and using polystyrene as a resin having a negative intrinsic birefringence value is shown. The melt softening temperatures of polystyrene and norbornene polymers are Ts and Tn, respectively. Since Ts <Tn, when a laminate of a norbornene polymer layer and a polystyrene layer is stretched at a temperature close to Tn, the relaxation of the orientation of polystyrene molecules is fast, and the molecules of the polystyrene layer are mostly oriented. The layer made of polystyrene does not have birefringence. As a result, a laminated film obtained by laminating a layer made of norbornene-based polymer and a layer made of polystyrene is almost equal to the wavelength dispersion exhibited by the layer made of norbornene-based polymer. As the stretching temperature is lowered, polystyrene molecules become oriented and the layer made of polystyrene has birefringence. Since the retardation of the layer made of polystyrene is negative, the positive retardation of the layer made of norbornene-based polymer is reduced. The retardation reduction ratio is due to the wavelength dispersion of polystyrene, and the retardation is greatly reduced on the short wavelength side. As a result, the characteristics of Re (450) <Re (550) <Re (650) are obtained. By controlling the stretching temperature, Re (λ) / λ can be made constant over the entire visible light wavelength range, and a phase difference plate that exhibits uniform phase difference characteristics over a wide band can be obtained. In addition, by adjusting the draw ratio, it is possible to obtain wideband 1/4 wavelength and 1/2 wavelength characteristics.

  When forming a retardation plate having the adhesive layer between a layer made of a positive resin and a layer made of a negative resin, the resin constituting the adhesive layer is melted at a temperature lower than the stretching temperature. It is preferable to use a resin having a softening temperature. Specifically, it is preferable to use a resin having a low glass transition point, which has a glass transition temperature lower by 5 ° C. or more than a resin having a positive intrinsic birefringence value and a resin having a negative intrinsic birefringence value. More preferably, a resin is used. It is 20 ° C or higher.

  In this embodiment, by laminating two layers composed of resins having positive and negative intrinsic birefringence with the slow axes orthogonal to each other, the wavelength dispersion of the retardation that each layer independently shows is reduced, and visible It is possible to provide a phase difference plate that gives substantially uniform phase difference characteristics to incident light in the entire light range. Further, in order to laminate two layers made of resins having intrinsic birefringence values of positive and negative with the slow axes orthogonal to each other, it is only necessary to match the stretching directions of the respective layers. Etc. can be omitted. That is, since the retardation plate of the present invention is a laminate of layers each using two types of resins having different intrinsic birefringence values, if the stretching directions of the two layers are matched, the retardation of the two layers is delayed. The phase axes can be inevitably perpendicular to each other, for example, by using the above-described coextrusion, at the time of chip cutting or chip pasting of a stretched film, which was necessary for the production of a conventional laminated retardation plate Manufacture by a simple process is possible without going through operations such as delicate and complicated angle adjustment. That is, the retardation plate of the present embodiment can provide a uniform retardation characteristic to light in a wide band (visible light range), and is a laminate by using coextrusion or the like during production. Nevertheless, it can be formed at a low cost by a simple process. Further, this embodiment is preferable in that it is not necessary to consider the compatibility of materials when selecting materials, and the range of selection of materials is widened. For example, the material can be selected in consideration of the glass transition point. Further, it is advantageous in that the cost of the extrusion device is low, and is an optimal mode.

  The retardation plate of the present invention (including both a single-layer structure and a laminated structure; hereinafter the same) can be a broadband quarter-wave plate by adjusting Re (λ) / λ. It can be used as a reflective liquid crystal display device used as a display device in various fields such as personal computers, AV equipment, portable information communication equipment, games and simulation equipment, and in-vehicle navigation systems. In addition, the retardation plate of the present invention can be a wideband half-wave plate by adjusting Re (λ) / λ, and can be used for a projector PBS or the like.

  The phase difference plate of the present invention preferably has a photoelastic modulus of 20 Bleuster or less, more preferably 10 Bleuster or less, and even more preferably 5 Bleuster or less. Generally, the retardation film is bonded to another member (for example, a polarizing plate) when used as a member of a display element. The stress applied at the time of bonding is uneven, and a larger stress is applied at the end compared to the center. As a result, there is a difference in retardation, and the end portion is whitish and light is lost, and display characteristics may be deteriorated in the display element. If the photoelastic modulus of the retardation plate is within the above range, even if there is a bias in stress at the time of pasting, it is possible to suppress partial differences in retardation, and it is more useful as a member such as a display element. It is.

Next, a circularly polarizing plate and a λ / 2 plate using the retardation plate of the present invention will be described.
In addition, the phase difference plate of the present invention used for the following uses includes the phase difference plate of both the single layer structure and the laminated structure.
(Circularly polarizing plate and λ / 2 plate)
The circularly polarizing plate of the present invention is formed by laminating a polarizing plate and the retardation plate of the present invention. The retardation plate preferably has a (retardation (Re) / wavelength) value of 0.2 to 0.3 over a wide range of wavelengths from 450 nm to 650 nm and at least at wavelengths of 450 nm, 550 nm and 650 nm. More preferably, it is 0.23 to 0.27 at least at the three wavelengths, and more preferably 0.24 to 0.26 at least at the three wavelengths. The λ / 2 plate of the present invention is formed by laminating a polarizing plate and the retardation plate of the present invention. The retardation plate preferably has a (retardation (Re) / wavelength) value of 0.40 to 0.60 in a wide range of wavelengths from 450 nm to 650 nm and at least at wavelengths of 450 nm, 550 nm and 650 nm. More preferably, it is 0.46 to 0.54 at least at the three wavelengths, and further preferably 0.48 to 0.52 at least at the three wavelengths.

-Polarizing plate-
There is no restriction | limiting in particular as said polarizing plate, A conventionally well-known thing can be used conveniently, For example, an iodine type polarizing plate, a dye type polarizing plate using a dichroic dye, a polyene type polarizing plate etc. are suitable. Can be mentioned.
Among these polarizing plates, the iodine polarizing plate and the dye polarizing plate can be produced by generally stretching a polyvinyl alcohol film and adsorbing iodine or a dichroic dye thereto. In this case, the polarizing axis of the polarizing plate is a direction perpendicular to the stretching direction of the film.

The polarizing plate may have a protective layer.
The protective layer is preferably made of a material having high optical isotropy. As such a material, for example, cellulose swell, particularly triacetyl cellulose is preferable.

-Lamination-
The polarizing plate and the retardation plate are laminated so that the polarization transmission axis of the polarizing plate and the slow axis (maximum refractive index direction) of the retardation plate intersect, and the angle of the intersection is 30 to 60 ° is preferable, 40 to 50 ° is more preferable, and 43 to 47 ° is particularly preferable.

-Application-
The circularly polarizing plate of the present invention has a simple structure, is easy to manufacture, functions as a broadband λ / 4 plate and can be used in various fields, and is particularly preferably used for the reflective liquid crystal display device of the present invention described later. be able to. The λ / 2 plate of the present invention functions as a broadband λ / 2 plate, can be used in various fields, and is suitable for a projector PBS or the like.

(Reflective liquid crystal display)
The reflective liquid crystal display device of the present invention is formed by laminating a reflective plate, a liquid crystal cell, and a polarizing plate in this order, and has the retardation plate of the present invention between the reflective plate and the polarizing plate. As a preferable example of the reflective liquid crystal display device, a structure in which a reflective plate, a liquid crystal cell, the retardation plate of the present invention and a polarizing plate are laminated in this order, or a reflective plate, and the present invention are provided. And a structure in which a retardation plate, a liquid crystal cell, and a polarizing plate are laminated in this order. As the retardation plate, a retardation plate having a λ / 4 characteristic can be used. The preferred range of Re / λ is the same as the preferred range of the retardation plate used in the circularly polarizing plate described above. It is. The reflective liquid crystal display device of the present invention may further include other members as necessary.
In the reflective liquid crystal display device, when the retardation plate and the polarizing plate are laminated, the laminate corresponds to the circularly polarizing plate of the invention.

-Reflector-
There is no restriction | limiting in particular as said reflecting plate, A conventionally well-known thing can be used conveniently.
The reflecting plate is generally disposed outside a transparent substrate on the back side of a liquid crystal cell described later.

-Liquid crystal cell-
There is no restriction | limiting in particular as said liquid crystal cell, A conventionally well-known thing can be used conveniently, for example, it is comprised by filling the TN type | mold liquid crystal layer between the front side transparent substrate and the back side transparent substrate. A thing is mentioned suitably. In this case, an electrode layer made of a conductive film of ITO (indium tin oxide) is formed on the inside of the front transparent substrate and the inside of the back transparent substrate. In the present invention, not only the TN liquid crystal layer but also an STN liquid crystal layer may be employed as the liquid crystal layer.

  The liquid crystal cell may be driven by a matrix drive or a segment drive. In the case of the matrix drive, a simple matrix drive method or an active matrix drive method may be used.

-Polarizing plate-
There is no restriction | limiting in particular as said polarizing plate, A conventionally well-known thing can be used conveniently, What was mentioned above is mentioned.
The polarizing plate is generally disposed outside the front transparent substrate of the liquid crystal cell together with the retardation plate of the present invention.

  The above reflective liquid crystal display device is for monochrome display. In the present invention, a color filter layer is further disposed between the front transparent substrate and the retardation plate of the present invention, and the front transparent A color filter layer may be formed on the substrate to be used for color display.

The monochrome display function of the reflective liquid crystal display device of the present invention will be described below.
In a state where no voltage is applied to the electrode layer (white display), when light is incident on the polarizing plate, the incident light becomes linearly polarized light in the polarization axis direction by the polarizing plate. This linearly polarized light is converted into circularly polarized light by the retardation plate of the present invention and is incident on the liquid crystal cell. The circularly polarized light reaches the reflecting plate as linearly polarized light parallel to the polarization axis by the liquid crystal molecules of the liquid crystal layer, is reflected by the reflecting plate, and enters the liquid crystal cell again. The incident linearly polarized light becomes circularly polarized light again by the liquid crystal layer, is converted again to linearly polarized light parallel to the polarization axis through the retardation plate, passes through the polarizing plate, and becomes white display.

  Next, in a state where a voltage higher than the liquid crystal saturation voltage is applied to the electrode layer (black display), the linearly polarized light transmitted through the polarizing plate is converted into circularly polarized light by the retardation plate of the present invention. The circularly polarized light is reflected as it is by the reflecting plate, passes through the liquid crystal cell as it is, and passes through the retardation plate of the present invention. In other words, the linearly polarized light is transmitted twice through the retardation plate of the present invention with the reflection plate interposed between the linearly polarized light and the retardation of the linearly polarized light. The reflected light does not pass through the polarizing plate and is displayed in black.

  In the reflective liquid crystal display device of the present invention, linearly polarized light in almost the entire visible light region is converted into circularly polarized light by the broadband retardation plate of the present invention. As a result, coloring and a decrease in contrast due to wavelength dispersion of light incident on the liquid crystal cell are reduced, and high-contrast display is possible.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Reference Example 1)
As the material having a negative intrinsic birefringence value, polystyrene (manufactured by Nippon Steel Chemical Co., Ltd., HRM2211L) is used. As the material having a positive intrinsic birefringence value, norbornene resin (manufactured by JSR Corporation, Arton) is used. The mixture was blended at a weight ratio of 23:77 (polystyrene: norbornene resin) and dissolved in a methylene chloride solution to prepare a coating solution.

  When the absolute values of retardation (Re) at wavelengths of 450 nm and 550 nm are Re (450) and Re (550), respectively, the value of (Re (450) / Re (550)) of the norbornene resin is 1. 01, the value of (Re (450) / Re (550)) of polystyrene is 1.05, both values are not the same, and the difference is 0.04.

The coating solution had a viscosity of 9.8 Pa · s (98 poise), and this coating solution was cast on a glass plate using a doctor blade and dried to form a transparent film having a thickness of 107 μm. This transparent film was uniaxially stretched 13% at 150 ° C. to obtain a birefringent film. About this birefringent film, the wavelength dispersion of the Re value was measured using the retardation measuring device (the Oji Scientific company make, KOBRA21DH). The results are shown in FIG.
As shown in FIG. 2, the birefringent film is a retardation plate having a Re value of approximately 0.25 in the entire visible light range (Re / wavelength) and a ¼ wavelength plate characteristic in a wide band. It was. Moreover, it was 13 blue star when the photoelastic modulus of this phase difference plate was measured using "M-150" by JASCO Corporation.

(Comparative Example 1)
A birefringent film was prepared in the same manner as in Reference Example 1 except that no norbornene resin was used in Reference Example 1, the viscosity of the coating solution was 8.9 Pa · s, and the transparent film was uniaxially stretched at 140 ° C. for 5%. Then, similarly to Reference Example 1, the chromatic dispersion of the Re value was measured. The results are shown in FIG.
As shown in FIG. 2, the birefringent film had a (Re / wavelength) value outside the range of 0.2 to 0.3.

(Comparative Example 2)
In Reference Example 1, a birefringent film was produced in the same manner as in Reference Example 1 except that polystyrene was not used, the viscosity of the coating solution was 13.2 Pa · s, and the transparent film was uniaxially stretched at 155 ° C. by 25%. As in Reference Example 1, the chromatic dispersion of the Re value was measured. The results are shown in FIG.
As shown in FIG. 2, the birefringent film had a (Re / wavelength) value outside the range of 0.2 to 0.3.

(Reference Example 2)
The retardation plate obtained in Reference Example 1 and the polarizing plate were bonded so that the slow axis of the retardation plate and the transmission axis of the polarizing plate intersected at an intersection angle of 45 °. About this bonding body, the wavelength dispersion of the Re value was measured using the retardation measuring device (the Oji Scientific company make, KOBRA21DH). The results are shown in FIG.
As shown in FIG. 3, the bonded body was a circularly polarizing plate having a Re value of approximately 0.25 in the entire visible light range (Re / wavelength) and a quarter wavelength characteristic in a wide band. Moreover, the bonding body showed a substantially uniform Re value at the center and at the end, and no whitening or the like occurred at the end.

(Comparative Example 3)
Reference Example 2 was the same as Reference Example 2, except that the retardation plate was replaced with the birefringent film prepared in Comparative Example 1.
As shown in FIG. 3, the birefringent film had a (Re / wavelength) value outside the range of 0.2 to 0.3.

(Comparative Example 4)
Reference Example 2 was the same as Reference Example 2 except that the retardation plate was replaced with the birefringent film prepared in Comparative Example 2.
As shown in FIG. 3, the birefringent film had a (Re / wavelength) value outside the range of 0.2 to 0.3.

(Reference Example 3)
The “Game Boy Color” manufactured by Nintendo Co., Ltd. was disassembled, the polarizing plate and retardation plate on the observer side were removed, and the circularly polarizing plate of Reference Example 2 was attached in place of this to produce a reflective liquid crystal display device. . As a result, in this reflection type liquid crystal display device, a clear white display was obtained. Further, the white display was uniform and clear from the entire area from the end to the center.

(Comparative Example 5)
Reference Example 3 was the same as Reference Example 3 except that the retardation plate was replaced with the birefringent film prepared in Comparative Example 2. As a result, in this reflective liquid crystal display device, the white display was yellowish and the black display was also light leaking, and the display state was not good in both contrast and color.

(Comparative Example 6)
Reference Example 3 was the same as Reference Example 3 except that the retardation plate was replaced with the birefringent film prepared in Comparative Example 3. As a result, in this reflective liquid crystal display device, the white display was yellowish and the black display was also light leaking, and the display state was not good in both contrast and color.

Example 1
As a resin having a positive intrinsic birefringence value, cycloolefin-based norbornene resin (trade name “ZEONOR 1420R”; manufactured by ZEON Corporation), and as a resin having a negative intrinsic birefringence value, polystyrene (trade name “HF-77”; And Mstyrene Co., Ltd.) was used. These resins were dried in advance under a nitrogen purge to reduce the water content.
When the absolute values of retardation (Re) at a wavelength of 450 nm and a wavelength of 550 nm are Re (450) and Re (550), respectively, (Re (450) / Re (550)) of the cycloolefin-based norbornene resin. The value is 1.005, the value of (Re (450) / Re (550)) of the polystyrene is 1.080, both values are not the same, and the difference is 0.075.

  The apparatus 20 having the configuration shown in FIG. 4 was used. The apparatus was “LABO PLASTOMILI” manufactured by Toyo Seiki, and the dice 22 had a width of 250 mm. Two units of extruders 24 and 26 are attached to the die 22, and the resin hopper stored in the extruder 24 and the extruder 26 has a structure in which the die 22 is joined. The extruder 26 has two openings. Inside the die 22, the resin hopper 2 extruded from the two openings of the extruder 26 centered on the resin hopper 1 extruded from the extruder 24 is the resin hopper 1. It has a structure that merges from both sides. The internal structure of the die 22 is shown in FIG. In addition, rolls 28, 30, and 32 are disposed below the die 22, and the thickness of the three-layer structure film 34 extruded from the die 22 can be adjusted.

The polystyrene hopper was stored in the extruder 24 and the norbornene resin hopper was stored in the extruder 26, and a melt-formed film 34 having a three-layer structure made of norbornene resin / polystyrene / norbornene resin was produced. Regarding the thickness of the laminated film 34, adjustment was attempted by controlling the peripheral speed of the rolls 28, 30, and 32. When the peripheral speed of the rolls 18, 20, and 22 was determined with a final thickness of 100 μm as a target, a laminated film having an actual thickness of 102 μm was obtained.
The molding conditions are shown in Table 1 below. The meanings of symbols in Table 1 below are shown below.
C1-C3: Extruder cylinder temperature (under C1 hopper)
D: Die (lip) temperature

  The obtained laminated film was subjected to stretching treatment of 19% and 39% in an atmosphere at 95 ° C. to obtain stretched films, respectively. With respect to the obtained 19% stretched film and 39% stretched film, the wavelength dependency of Re was measured by “KOBRA 21DH” manufactured by Oji Scientific. The results are shown in FIG. From the results shown in FIG. 6, it was found that the 19% stretched film has a broadband quarter-wave plate characteristic in which Re represents ¼ of the wavelength over the entire visible light range. Further, from the results shown in FIG. 6, it was found that the 39% stretched film has a broadband ½ wavelength plate characteristic in which Re represents ½ of the wavelength over the entire visible light region. Moreover, when the photoelastic modulus was measured about each obtained laminated film using "M-150" by JASCO Corporation, all were 8 blue star.

(Example 2)
As a resin having a positive intrinsic birefringence value, a cycloolefin-based norbornene resin (trade name “ZEONOR 1420R”; manufactured by ZEON CORPORATION), and as a resin having a negative intrinsic birefringence value, a styrene-based maleic anhydride copolymer resin (Nova Chemical) Manufactured by "Dairaku D332"). These resins were dried in advance under a nitrogen purge to reduce the water content.
When the absolute values of retardation (Re) at a wavelength of 450 nm and a wavelength of 550 nm are Re (450) and Re (550), respectively, (Re (450) / Re (550)) of the cycloolefin-based norbornene resin. The value was 1.005, and the value of (Re (450) / Re (550)) of the styrene maleic anhydride copolymer resin was 1.069, both values were not the same, and the difference was 0.064. It is.

  The apparatus 20 having the configuration shown in FIG. 4 was used. The apparatus was “LABO PLASTOMILI” manufactured by Toyo Seiki, and the dice 22 had a width of 250 mm. Two units of extruders 24 and 26 are attached to the die 22, and the resin hopper stored in the extruder 24 and the extruder 26 has a structure in which the die 22 is joined. The extruder 26 has two openings. Inside the die 22, the resin hopper 2 extruded from the two openings of the extruder 26 centered on the resin hopper 1 extruded from the extruder 24 is the resin hopper 1. It has a structure that merges from both sides. The internal structure of the die 22 is shown in FIG. In addition, rolls 28, 30, and 32 are disposed below the die 22, and the thickness of the three-layer structure film 34 extruded from the die 22 can be adjusted.

  A hopper of the styrene maleic anhydride copolymer resin is stored in the extruder 24, and a hopper of the norbornene resin is stored in the extruder 26. A film 34 was produced. Regarding the thickness of the laminated film 34, adjustment was attempted by controlling the peripheral speed of the rolls 28, 30, and 32. When the peripheral speed of the rolls 18, 20, and 22 was determined with a final thickness of 150 μm as a target, an actual laminated film having a thickness of 102 μm was obtained.

  The obtained laminated film was subjected to a 65% stretching treatment in an atmosphere at 120 ° C. to obtain a stretched film having a three-layer structure. A schematic cross-sectional view of the obtained stretched film is shown in FIG. The obtained stretched film 50 had a structure in which a layer 54 made of a styrene maleic anhydride copolymer was sandwiched between two layers 52 made of norbornene resins. The thickness of the norbornene resin layer 52 / styrene maleic anhydride copolymer resin layer 54 / norbornene resin layer 52 was 36 μm / 39 μm / 38 μm. About the obtained stretched film, the wavelength dependence of Re was measured with “KOBRA 21DH” manufactured by Oji Scientific. The results are shown in FIG. From the results shown in FIG. 8, it was found that Re has a broadband quarter-wave plate characteristic in which Re represents ¼ of the wavelength over the entire visible light range. Moreover, it was 3 blue star when the photoelastic modulus was measured using "M-150" by JASCO Corporation about each obtained laminated | multilayer film.

(Comparative Example 7)
A single-layer film was produced in the same manner as in Example 1 using the cycloolefin-based norbornene used in Example 1 under the molding conditions shown in Table 1 above. The thickness of the obtained film was 103 μm.
The obtained single layer film was stretched 28% at 130 ° C. to obtain a stretched film. When the wavelength dependency of Re was measured in the same manner as in Example 1, the stretched film did not exhibit the characteristics of a broadband quarter-wave plate. The results are shown in FIG.
(Comparative Example 8)
A single layer film was produced in the same manner as in Example 1 using the polystyrene used in Example 1 under the molding conditions shown in Table 1 above. The thickness of the obtained film was 101 μm.
The obtained single layer film was stretched 18% under the condition of 100 ° C. to obtain a stretched film. When the wavelength dependency of Re was measured in the same manner as in Example 1, the stretched film did not exhibit the characteristics of a broadband quarter-wave plate. The results are shown in FIG.

DESCRIPTION OF SYMBOLS 10 Phase difference plate 12 Layer which consists of resin with positive intrinsic birefringence value 14 Layer which consists of resin with negative intrinsic birefringence value 20 Extrusion device 22 Dies 24, 26 Extruder 28, 30, 32 Roll 34 Three-layer laminated film

Claims (4)

A co-extrusion of a resin with a positive intrinsic birefringence value and a resin with a negative intrinsic birefringence value, a first layer made of a resin with a positive intrinsic birefringence value and having birefringence, and a negative intrinsic birefringence value A step of producing a laminate having a second layer made of a resin and having birefringence;
Provided after the step of producing the laminate, and by stretching the laminate, the slow axis of the first layer and the slow axis of the second layer are orthogonal to each other, and the wavelengths are 450 nm and 550 nm. And the step of adjusting the retardation so that Re (450) <Re (550) <Re (650) where Re (450), Re (550) and Re (650) are the retardation values at 650 nm and 650 nm, respectively. When,
The manufacturing method of the phase difference plate which has these.   The method for producing a retardation plate according to claim 1, wherein the resin having a positive intrinsic birefringence value is a norbornene-based polymer.   The method for producing a retardation plate according to claim 1, wherein the resin having a negative intrinsic birefringence value is polystyrene or a polystyrene-based polymer.   The method for producing a retardation plate according to claim 3, wherein the polystyrene polymer is a copolymer of styrene and / or a styrene derivative and at least one selected from acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene.