JP2021162622A - Reflection polarizing plate - Google Patents

Abstract

To provide a reflection polarizing plate obtained by extending, in a uniaxial direction, a repetition part composed of a laminate in which a high refractive index layer and a low refractive index layer are alternately and repeatedly laminated, the reflection polarizing plate exhibiting excellent heat resistance and capable of maintaining the refractive index of the low refractive index layer in a uniaxial direction almost constant before and after extension along the uniaxial direction.SOLUTION: The reflection polarizing plate pertaining to the present invention is obtained by extending, in a uniaxial direction, a laminate composed of a high refractive index layer 31 and a low refractive index layer 32 that are alternately and repeatedly laminated. A glass transition point Tg1 of main material of the high refractive index layer 31 and a glass transition point Tg2 of main material of the low refractive index layer 32 are Tg1≥Tg2≥105°C. The absolute value of double refraction ΔNxy of the low refractive index layer 32 at a wavelength of 589 nm when the low refractive index layer 32 is extended two-fold in a uniaxial direction at a temperature 10°C higher than the glass transition point Tg1 is less than 0.15.SELECTED DRAWING: Figure 2

Description

The present invention relates to a reflective polarizing plate.

In recent years, a transparent cover member made of resin as a cover film provided in a display device such as a liquid crystal display, a lens provided in eyewear such as sunglasses and eyeglasses, and a window member provided in a means of transportation such as a motorcycle or a car. It is known that a polarizing plate is used as the translucent cover member.

Further, when this translucent cover member is applied to, for example, an in-vehicle display device or an eyewear for sports, it is excellent assuming that it will be used under harsh conditions. It is required to have heat resistance.

Then, as a polarizing plate applied to this translucent cover member, in recent years, a uniaxially stretched multilayer layer that selectively reflects a certain polarization component and selectively transmits this polarization component and the polarization component in the direction perpendicular to the polarization light as polarized light. Laminated films, or reflective polarizing plates, have been proposed (see, for example, Patent Document 1).

In this reflective polarizing plate, that is, a uniaxially stretched multilayer laminated film, a repeating portion composed of a laminated body in which a high refractive index layer having a high refractive index and a low refractive index layer having a low refractive index are alternately and repeatedly laminated is uniaxially formed. By stretching along the direction, the refractive index of the high refractive index layer in the uniaxial direction is higher than the refractive index of the low refractive index layer in the uniaxial direction, and the refractive index in the orthogonal direction orthogonal to the uniaxial direction of the high refractive index layer. Is set to be substantially equal to the refractive index of the low refractive index layer in the orthogonal direction, whereby as a reflective polarizing plate that transmits only a specific polarizing component as polarized light and reflects other components along the orthogonal direction. Demonstrate the function of.

In the uniaxially stretched multilayer laminated film having such a structure, when the repeating portion (laminated body) is stretched along the uniaxial direction, the high refractive index layer has a high refractive index in the uniaxial direction, and the low refractive index layer has a high refractive index. Is required to maintain the refractive index in the uniaxial direction. However, there is a problem that the refractive index in the uniaxial direction cannot be maintained especially in the low refractive index layer during the stretching along the uniaxial direction.

Special Table 2013-533510

An object of the present invention is a reflective polarizing plate obtained by stretching a repeating portion composed of a laminated body in which high refractive index layers and low refractive index layers are alternately and repeatedly laminated along a uniaxial direction. It is an object of the present invention to provide a reflective polarizing plate which exhibits excellent heat resistance and can maintain the refractive index in the uniaxial direction in a low refractive index layer substantially constant before and after stretching along the uniaxial direction. ..

Such an object is achieved by the present invention described in the following (1) to (5).
(1) A reflective polarizing plate obtained by stretching a laminated body in which high refractive index layers and low refractive index layers are alternately and repeatedly laminated in the uniaxial direction.
The high refractive index layer has a higher refractive index in the uniaxial direction than the refractive index of the low refractive index layer in the uniaxial direction.
When the glass transition point of the main material constituting the high refractive index layer is Tg1 and the glass transition point of the main material constituting the low refractive index layer is Tg2, Tg1 ≧ Tg2 ≧ 105 ° C.
The low refractive index layer has an absolute value _{of birefringence ΔN xy} at a wavelength of 589 nm when the low refractive index layer is stretched twice in the uniaxial direction at a temperature 10 ° C. higher than the glass transition point Tg1. A reflective polarizing plate, characterized in that it is less than.

(2) The reflective polarizing plate according to (1) above, wherein the glass transition point Tg1 and the glass transition point Tg2 satisfy the relationship of Tg1-Tg2 <60 ° C.

(3) The reflective polarizing plate according to (2) above, wherein the glass transition point Tg1 is 110 ° C. or higher and 250 ° C. or lower.

(4) The low refractive index layer according to any one of (1) to (3) above, wherein the low refractive index layer has a refractive index of 1.49 or more and 1.67 or less at a wavelength of 589 nm in the stretching direction of the laminated body. Reflective polarizing plate.

(5) The above-mentioned (1) to (4), wherein the high refractive index layer has a refractive index of 1.59 or more and 1.85 or less at a wavelength of 589 nm in the stretching direction of the laminated body. Reflective polarizing plate.

According to the present invention, a reflective polarizing plate obtained by stretching a repeating portion composed of a laminated body in which high refractive index layers and low refractive index layers are alternately and repeatedly laminated along a uniaxial direction can be obtained. Further, it can be assumed that the refractive index in the uniaxial direction of the low refractive index layer included in the reflective polarizing plate is maintained substantially constant before and after stretching along the uniaxial direction.

It is a vertical cross-sectional view which shows the embodiment of the translucent cover member provided with the reflective polarizing plate of this invention. FIG. 5 is an enlarged cross-sectional view of a part of the reflective polarizing plate included in the translucent cover member located in the region [B] surrounded by the alternate long and short dash line in FIG.

Hereinafter, the reflective polarizing plate of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

In the following, a case where the reflective polarizing plate of the present invention is applied to a translucent cover member will be described as an example.

<Translucent cover member>
FIG. 1 is a vertical cross-sectional view showing an embodiment of a translucent cover member including the reflective polarizing plate of the present invention, and FIG. It is an enlarged sectional view of a part of the reflective polarizing plate included in the property cover member. In the following, for convenience of explanation, the upper side in FIGS. 1 and 2 is referred to as "upper" or "upper", and the lower side is referred to as "lower" or "lower". Further, in FIGS. 1 and 2, the left-right direction of the paper surface in the drawing is the X-axis direction, the front-back direction of the paper surface is the Y-axis direction, and the vertical direction of the paper surface is the Z-axis direction, and these directions are orthogonal to each other. Further, in FIGS. 1 and 2, in order to facilitate understanding, the translucent cover member is shown in a flat state, and the thickness direction is exaggerated and schematically shown.

In the present embodiment, the translucent cover member 1 has a polarizing layer 3 that selectively reflects a constant polarization component and selectively transmits the polarization component in the direction perpendicular to the polarization component, as shown in FIG. It is composed of a laminated plate including a hard coat layer 5 laminated on both the upper surface and the lower surface (one surface and the other surface) of the polarizing layer 3.

In the translucent cover member 1, the polarizing layer 3 included in the transparent cover member 1 is composed of the reflective polarizing plate of the present invention. Hereinafter, each layer constituting the translucent cover member 1 will be described.

The polarizing layer 3 is an intermediate layer located at the center of the translucent cover member 1 in the thickness direction, selectively reflects a constant polarizing component, and selectively transmits the polarizing component and the polarizing component in the vertical direction. Is what you do. More specifically, in the present embodiment, the polarization component in the X-axis direction, which is the uniaxial direction, is selectively reflected, and the polarization component in the Y-axis direction orthogonal to the uniaxial direction is selectively transmitted. Yes, the polarizing layer 3 is composed of the reflective polarizing plate of the present invention.

As shown in FIG. 2, the polarizing layer 3 includes a repeating portion 33 composed of a laminated body in which a high refractive index layer 31 having a high refractive index and a low refractive index layer 32 having a low refractive index are alternately and repeatedly laminated. This is a so-called uniaxially stretched multilayer laminated film that is stretched along the uniaxial direction while being heated. That is, the polarizing layer 3 is formed by stretching a laminated body in which a plurality of repeating portions 33 are laminated along the uniaxial direction, so that one high refractive index layer 31 is sandwiched between two low refractive index layers 32. It has a structure that is repeated.

In the polarizing layer 3, the high refraction layer 31 contains a resin material having a high positive stress optical coefficient, that is, a resin material in which double refraction is likely to occur, and the low refraction layer 32 is a resin having a low positive stress optical coefficient. By forming a structure containing a material, that is, a resin material in which double refraction is unlikely to occur, the refractive index of the high refractive index layer 31 is double-refracted by stretching along the X-axis direction, which is the uniaxial direction, to obtain anisotropy. To increase the difference in refraction between the layers with the low refraction layer 32 in the stretching direction in the layer plane, that is, in the X-axis direction, while increasing the refraction coefficient difference between the layers in the stretching direction in the layer plane, that is, in the direction orthogonal to the stretching direction in the layer plane, that is, in the Y-axis direction. The difference in refraction between the two layers can be reduced. As a result, the polarizing layer 3 can be provided with a function as a uniaxially stretched multilayer laminated film, that is, a reflective polarizing plate, which transmits only a specific polarizing component as polarized light and reflects other components.

In other words, in the polarizing layer 3, when polarized light polarized along the X-axis direction, which is the stretching direction, is incident on the polarizing layer 3 as incident light, the polarized light is transmitted at the maximum block, that is, at the minimum. On the other hand, when polarized light polarized along the Y-axis direction is incident on the polarizing layer 3 as incident light, the polarized light exerts a function as a minimum blocking, that is, a reflective polarizing plate that is transmitted at the maximum. do.

Therefore, when the translucent cover member 1 provided with the polarizing layer 3 is applied to, for example, a cover member included in a display unit included in an in-vehicle display device, external light emitted from the outside of the display device, that is, When sunlight (natural light) passes through the translucent cover member 1, light in a predetermined polarization direction is absorbed by the translucent cover member 1, and the remaining light, that is, attenuated light is inside the display unit. Will be reached. As a result, the intrusion of sunlight into the display unit is suppressed, and thus the inside of the display unit can be prevented from deteriorating over time due to sunlight (particularly ultraviolet rays and heat) as much as possible. Further, when the translucent cover member 1 is applied to, for example, a lens provided in eyewear for sports, external light emitted from the outside of the eyewear, that is, direct sunlight or reflected light thereof. Is transmitted through the translucent cover member 1, the light in a predetermined polarization direction is absorbed by the translucent cover member 1, and the remaining light, that is, the attenuated light reaches the eyes of the wearer of the eyewear. Will be done. As a result, the direct light of sunlight and the reflected light from entering the eye are suppressed, so that the wearer can recognize the object in the field of view relatively easily. As described above, the translucent cover member 1 exhibits a function as a polarizing plate.

Here, as described above, when the translucent cover member 1 is applied to an in-vehicle display device or an eyewear for sports, it is assumed that the translucent cover member 1 will be used under harsh conditions. The polarizing layer 3 included in the optical cover member 1 is required to have excellent heat resistance. Therefore, in the present invention, the glass transition point of the resin material having a high positive stress optical coefficient contained in the high refractive index layer 31 is set to Tg1, and the glass of the resin material contained in the low refractive index layer 32 having a low positive stress optical coefficient is set to Tg1. When the transition point is Tg2, the one that satisfies the relationship of Tg1 ≧ Tg2 ≧ 105 ° C. is selected. By using a material that satisfies the relationship between the glass transition point Tg1 and the glass transition point Tg2 as a constituent material of the high refractive index layer 31 and the low refractive index layer 32, excellent heat resistance is imparted to the polarizing layer 3. be able to.

Further, the polarizing layer 3 (uniaxially stretched multilayer laminated film), which is required to have excellent heat resistance, is a repeating portion in which a high refractive index layer 31 and a low refractive index layer 32 are alternately and repeatedly laminated as described above. After obtaining 33 (laminated body), it is obtained by stretching the repeating portion 33 along the uniaxial direction (X-axis direction) while heating, and more specifically, it can be manufactured as follows. ..

That is, first, as the resin composition for forming the high refractive index layer 31 and the low refractive index layer 32, a resin material having a high positive stress optical coefficient and a resin material having a low positive stress optical coefficient are mainly used. By preparing what is contained as a material and alternately laminating them, a repeating portion 33 (laminated body) in which the high refractive index layer 31 and the low refractive index layer 32 are alternately and repeatedly laminated is obtained (lamination step). ).

The method for obtaining the repeating portion 33 is not particularly limited, but for example, a feed block method in which the resin material as a raw material is melt-extruded by several extruders, a coextrusion T-die method such as a multi-manifold method, and the like. Air-cooled or water-cooled coextrusion inflation methods can be mentioned, and the coextrusion T-die method is particularly preferable. The coextrusion T-die method is preferably used because it is excellent in controlling the thickness of each layer to be formed.

Next, the obtained repeating portion 33 (laminated body) is stretched along the uniaxial direction (X-axis direction) while heating (stretching step).

By stretching along the X-axis direction, which is the uniaxial direction of the repeating portion 33, the refractive index of the high refractive index layer 31 is birefringent to give anisotropy. On the other hand, the low refractive index layer 32 maintains the magnitude of the refractive index in the X-axis direction and the Y-axis direction. As a result, the difference in refractive index between the high refractive index layer 31 and the low refractive index layer 32 in the X-axis direction is increased, and the layer between the high refractive index layer 31 and the low refractive index layer 32 in the Y-axis direction is increased. The difference in refractive index can be reduced.

Next, the repeating portion 33 (laminated body) stretched along the uniaxial direction (X-axis direction) is cooled, dried and solidified (cooling step). As a result, a polarizing layer 3 that functions as a uniaxially stretched multilayer laminated film (reflecting polarizing plate) that transmits only a specific polarizing component along the Y-axis direction as polarized light and reflects other components can be obtained.

By going through the above steps, the polarizing layer 3 (uniaxially stretched multilayer laminated film) can be obtained. In the stretching step, when the repeating portion 33 is stretched along the X-axis direction, the repeating portion 33 is heated. The temperature is usually set in order to make the refractive index of the high refractive index layer 31 birefringent, that is, a resin material having a high positive stress optical coefficient contained as a main material in the high refractive index layer 31 is used along the X-axis direction. When the glass transition point of the resin material having a high positive stress optical coefficient is Tg1, it is usually set to about (Tg1 + 10) ° C.

At this time, in order to prevent the refractive index of the low refractive index layer 32 from being double-refracted, that is, the resin material having a low positive stress optical coefficient contained as the main material in the low refractive index layer 32 is in the X-axis direction. Various studies have been conducted to prevent the refractive index from changing due to orientation along the above. For example, when the glass transition point of a resin material having a low positive stress optical coefficient is Tg2, the glass transition point It is being studied to select one having a large difference between Tg1 and the glass transition point Tg2, specifically, one satisfying the relationship of Tg1-Tg2 ≥ 60 ° C.

However, when a material satisfying such a relationship is selected as a resin material having a low positive stress optical coefficient, a resin material having a low positive stress optical coefficient, that is, a material that can be used as a main material constituting the low refractive index layer 32. There was a problem that the range of choices was narrowed.

On the other hand, in the present invention, the low refractive index layer 32 is stretched twice in the uniaxial direction (X-axis direction) at a temperature 10 ° C. higher than the glass transition point Tg1 of the main material constituting the high refractive index layer 31. _{A material that can satisfy that the absolute value of the birefringence ΔN xy} at a wavelength of 589 nm is less than 0.15 is used as a constituent material of the low refractive index layer 32.

By satisfying such a relationship, a low refractive index layer even if the difference between the glass transition point Tg1 and the glass transition point Tg2 is small, specifically, even if the relationship of Tg1-Tg2 <60 ° C. is satisfied. Since it can be used as a constituent material of 32, that is, a resin material having a low positive stress optical coefficient, the range of selection of a material that can be used as a resin material having a low positive stress optical coefficient is widened.

As described above, the main material of the high refractive index layer 31, that is, the resin material having a high positive stress optical coefficient, was stretched along the uniaxial direction (X-axis direction) while being heated at a heating temperature of about (Tg1 + 10) ° C. As a material that can be oriented along the uniaxial direction (requirement A), and as a main material of the low refractive index layer 32, that is, a resin material having a low positive stress optical coefficient, the birefringence ΔN of the low refractive index layer 32 _{Any material can be used as long as the absolute value of xy} can be set to less than 0.15 (requirement B), but a non-crystalline polycarbonate resin, a polystyrene resin, and a crystal, respectively, can be used. It is preferably at least one of a polyester resin and an acrylic resin having properties, and more preferably at least one of a polycarbonate resin and a polyester resin. By appropriately selecting the main materials of the high refractive index layer 31 and the low refractive index layer 32 from these, the high refractive index layer 31 and the low refractive index layer 32 can be relatively easily selected from the requirements A and the above, respectively. Requirement B may be satisfied.

As the main material of the high refractive index layer 31, the glass transition point Tg1 may satisfy the relationship of Tg1 ≧ Tg2 ≧ 105 ° C., but preferably 110 ° C. or higher and 250 ° C. or lower, more preferably 150 ° C. or higher and 200 ° C. The temperature or lower is selected, and specifically, it is preferable to use at least one of polyethylene naphthalate (PEN), polycarbonate (PC) and polyarylate (PAR).

Further, when a material having a glass transition point Tg1 of 110 ° C. or higher and 250 ° C. or lower is selected as the main material of the high refractive index layer 31 as the main material of the low refractive index layer 32, specifically, polycarbonate (PC) is used. , Polyethylene terephthalate (PET), polyester resin such as polyethylene naphthalate (PEN), acrylic resin such as polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene copolymer (AS) It is preferable to use at least one of.

When such a resin material is used, the combination of the main materials contained in the high refractive index layer 31 and the low refractive index layer 32 is specifically polycarbonate (PC) and polymethyl methacrylate (PMMA). Combination with, combination of polycarbonate (PC) and acrylonitrile-styrene copolymer (AS), combination of polyarylate (PAR) and polycarbonate (PC), combination of polyethylene naphthalate (PEN) and polycarbonate (PC) , A combination of polycarbonate (PC) and polymethyl methacrylate (PMMA) and the like. According to such a combination, the magnitude of the absolute value of the birefringence ΔNxy can be surely set to less than 0.15 while satisfying the relationship of Tg1-Tg2 <60 ° C. and Tg1 ≧ Tg2 ≧ 105 ° C. can.

The high refractive index layer 31 and the low refractive index layer 32 may each contain an additive such as a filler in addition to the main material. Thereby, the high refractive index layer 31 and the low refractive index layer 32 can more easily satisfy the requirement A and the requirement B, respectively.

The filler is not particularly limited, but is, for example, an inorganic filler such as silica, alumina, calcium carbonate, strontium carbonate, calcium phosphate, kaolin, talc, smectite, crosslinked polystyrene, and a styrene-divinylbenzene copolymer. Calcium fillers such as strontium carbonate and smectite are preferably at least one of strontium carbonate and smectite, and strontium carbonate can be used in combination. More preferably. It can be said that strontium carbonate is a filler having a particularly excellent negative birefringence. Therefore, for example, by adding it to a resin having positive birefringence such as polycarbonate, it is possible to surely reduce the occurrence of birefringence in the low refractive index layer 32 containing these.

Further, the filler may be in any shape of particles such as spherical and flat, granules, pellets and scales, but is preferably contained in particles.

In the high refractive index layer 31 and the low refractive index layer 32 obtained by the combination of the resin materials as described above, the high refractive index layer 31 has a refractive index at a wavelength of 589 nm in the uniaxial direction (X-axis direction). The refractive index of the low refractive index layer 32 is preferably 59 or more and 1.85 or less, and the refractive index of the low refractive index layer 32 at a wavelength of 589 nm in the uniaxial direction (X-axis direction) is preferably 1.49 or more and 1.67 or less. As a result, the polarized light component in the X-axis direction, which is the uniaxial direction, can be selectively reflected.

_{Further, in the low refractive index layer 32, the absolute value of the birefringence ΔN xy} at a wavelength of 589 nm when the layer 32 is stretched twice in the uniaxial direction (X-axis direction) may be less than 0.15, but 0. It is preferably 10 or less, and more preferably 0.05 or less. As a result, it can be said that the refractive index in the X-axis direction, which is the uniaxial direction, is more reliably maintained.

The average thickness of the high refractive index layer 31 and the low refractive index layer 32 is preferably 50 nm or more and 300 nm or less, and more preferably 100 nm or more and 200 nm or less.

Further, the repeating portion 33 in which the high refractive index layer 31 and the low refractive index layer 32 are laminated is preferably 10 or more and 3000 or less, and more preferably 100 or more and 1500 or less.

By setting the average thickness of the high refractive index layer 31 and the low refractive index layer 32 and the number of repeating portions 33 in which the high refractive index layer 31 and the low refractive index layer 32 are laminated within the above range, one axis is formed. The polarization component in the X-axis direction, which is the direction, can be more reliably reflected.

Further, the translucent cover member 1 may satisfy the relationship that the glass transition point Tg1 and the glass transition point Tg2 described above have Tg1 ≧ Tg2 ≧ 105 ° C., but satisfy the relationship that Tg1 ≧ Tg2> 110 ° C. It is more preferable to satisfy the relationship of Tg1 ≧ Tg2 ≧ 115 ° C., and it is particularly preferable to satisfy the relationship of Tg1 ≧ Tg2 ≧ 130 ° C. Thereby, it can be said that the translucent cover member 1 exhibits more excellent heat resistance.

As shown in FIG. 1, the hard coat layer 5 is formed on both the upper surface and the lower surface of the polarizing layer 3 and is made of an ultraviolet curable resin. By protecting the polarizing layer 3, the hard coat layer 5 is translucent. It is provided to impart excellent weather resistance, durability, scratch resistance, and thermoforming property to the cover member 1. The translucent cover member 1 provided with the hard coat layer 5 can be attached to, for example, a window portion provided in the storage body in a curved state.

Examples of the ultraviolet curable resin constituting the hard coat layer 5 include an ultraviolet curable resin containing an acrylic compound as a main component, a urethane acrylate oligomer or a polyester urethane acrylate oligomer as a main component, and an epoxy resin. , An ultraviolet curable resin containing at least one of vinyl phenolic resins and the like as a main component can be mentioned. Among these, an ultraviolet curable resin containing an acrylic compound as a main component is preferable. As a result, the adhesion to the polarizing layer 3 can be improved.

The average thickness of the hard coat layer 5 is not particularly limited, and is preferably 2.0 μm or more and 20 μm or less, and more preferably 3.0 μm or more and 15 μm or less. As a result, the function as a coat layer that protects the polarizing layer 3 can be reliably imparted.

The refractive index of the hard coat layer 5 is not particularly limited, and is preferably 1.40 or more and 1.60 or less, and more preferably 1.450 or more and 1.595 or less.

The hard coat layer 5 is formed by, for example, applying a varnish-like ultraviolet curable resin composition on the polarizing layer 3 to form a liquid film, and irradiating the liquid film with ultraviolet rays to cure the liquid film. It is formed.

The translucent cover member 1 may omit the formation of the hard coat layer 5.

The total thickness of the translucent cover member 1 having the above configuration is preferably, for example, 4 μm or more and 150 μm or less, and more preferably 10 μm or more and 100 μm or less. As a result, the translucent cover member 1 can be made as thin as possible, and can be made rigid enough to withstand normal use as the translucent cover member 1.

The translucent cover member 1 has a rectangular shape in a plan view, and is preferably 50 mm or more and 200 mm or less in length, more preferably 60 mm or more and 190 mm or less, and 100 mm or more and 400 mm or less in width. It is preferably 130 mm or more and 380 mm or less.

The reflective polarizing plate of the present invention has been described above, but the present invention is not limited to this, and each layer constituting the translucent cover member 1 provided with the reflective polarizing plate can exhibit the same function. It can be replaced with any configuration.

Further, in the above-described embodiment, the case where the reflective polarizing plate of the present invention is applied to the translucent cover member 1 provided as the polarizing layer 3 (polarizing plate) has been described. It can be applied as a cover film for display devices such as liquid crystal displays and head-up displays, lenses for eyewear such as sunglasses and eyewear, and window members for transportation means such as motorcycles and cars. The reflective polarizing plate of the present invention can be used as a brightness improving film or cold mirror provided in a light source of a head-up display, a polarizing plate of an in-vehicle sensor such as an infrared sensor, a polarizing plate of a transparent display that reflects a visible light laser, and the like. Can be applied. As described above, the reflective polarizing plate of the present invention satisfies Tg1 ≧ Tg2 ≧ 105 ° C. and exhibits excellent heat resistance, and therefore can be suitably used as such a polarizing plate.

Hereinafter, the present invention will be described in more detail based on Examples. The present invention is not limited to these examples.

1. 1. Preparation of raw materials <Polycarbonate (PC1)>
As polycarbonate (PC1), Iupiron E2000 (manufactured by Mitsubishi Engineering Plastics) was prepared.

<Polymethyl methacrylate (heat resistant PMMA1)>
As polymethyl methacrylate (heat resistant PMMA1), Delpet PM120N (manufactured by Asahi Kasei Corporation) was prepared.

<Polymethyl methacrylate (PMMA1)>
Sumipex MM (manufactured by Sumitomo Chemical Co., Ltd.) was prepared as polymethyl methacrylate (PMMA1).

<Polyethylene terephthalate (heat resistant PETG1)>
As a heat-resistant amorphous polyethylene terephthalate (heat-resistant PETG1), Tritan TX2001 (Glycol-modified polyethylene terephthalate manufactured by Eastman Chemical Company) was prepared.

<Polyethylene terephthalate (PETG2)>
Skygreen K2012 (manufactured by SK Chemical Corp.) was prepared as an amorphous polyethylene terephthalate copolymer (PETG2).

<Polyarylate (PAR1)>
As a polyarylate (PAR1), U polymer P-5001 (manufactured by Unitika Ltd.) was prepared.

<Polyarylate (PAR2)>
U polymer U-100 (manufactured by Unitika Ltd.) was prepared as a polyarylate (PAR2).

<Polyethylene naphthalate (PEN1)>
As polyethylene naphthalate (PEN1), Theonex TN8065S (manufactured by Teijin Limited) was prepared.

<Polyethylene terephthalate (APET1)>
As polyethylene terephthalate (APET1), Novapex GM700Z (manufactured by Mitsubishi Chemical Corporation, crystalline polyethylene terephthalate) was prepared.

<Strontium carbonate (SrCO ₃ )>
Strontium carbonate (SrCO ₃ ) was prepared as a particle having negative birefringence.

<Acrylonitrile-styrene copolymer (AS1)>
Denka AS-XGS (manufactured by Denka Co., Ltd.) was prepared as an acrylonitrile-styrene copolymer (AS1).

<Styrene-N-Phenylmaleimide-Maleic anhydride copolymer (IP1)>
Denka IP-ND (manufactured by Denka Co., Ltd.) was prepared as a styrene-N-phenylmaleimide-maleic anhydride copolymer (IP1).

<(PCTG1)>
Skygreen J2003 (manufactured by SK Chemical Corp.) was prepared as a polyethylene terephthalate / cyclohexanedimethanol-modified copolymer (PCTG1).

<Polystyrene (heat resistant PS1)>
As a heat-resistant PS copolymer (heat-resistant PS1), TF4000 (manufactured by Toyo Styrene Co., Ltd.) was prepared.

2. Production of Reflective Polarizing Plate (Example 1)
[1] First, polycarbonate (PC1) is prepared as a resin material for forming the high refractive index layer 31, and polymethylmethacrylate (heat-resistant PMMA1) is prepared as a resin material for forming the low refractive index layer 32, respectively. bottom.

[2] Next, polycarbonate (PC1) and polymethyl methacrylate (heat-resistant PMMA1) are each melted at 270 ° C. by an extruder (manufactured by Sun NT Co., Ltd., “SNT40-28”) and fed. A film was formed by coextrusion using a block and a die, and then cooled to form a film, whereby the high refractive index layer 31 and the low refractive index layer 32 were alternately and repeatedly laminated, for a total of 1023 layers. The body was made. Here, the discharge amount was adjusted so that the laminated thickness ratio was high refractive index layer 31: low refractive index layer 32 = 1: 1.

In the obtained laminate, the refractive index of the low refractive index layer 32 at a wavelength of 589 nm was measured using an Appe refractive index meter (manufactured by ATAGO, “model number NA-1T SOLID”) and found to be 1.510. rice field. Further, the refractive index of the high refractive index layer 31 at a wavelength of 589 nm was measured using an Appe refractive index meter (manufactured by ATAGO, “model number NA-1T SOLID”) and found to be 1.585.

[3] Next, the laminated body was stretched twice along the uniaxial direction (X-axis direction) while being heated at 160 ° C. to obtain a reflective polarizing plate of Example 1.

In the obtained reflective polarizing plate, the refractive index of the low refractive index layer 32 at a wavelength of 589 nm was determined by using Axoscan (manufactured by AXOMETRICS) in the stretching direction (X-axis direction) and the non-stretching direction (Y-axis direction). When measured, they were 1.509 and 1.5100, respectively, and the birefringence ΔN _xy obtained from them was −0.0001. Further, the refractive index of the high refractive index layer 31 at a wavelength of 589 nm was measured in the stretching direction (X-axis direction) and the non-stretching direction (Y-axis direction) using Axoscan (manufactured by AXOMETRICS). It was 652 and 1.552.

(Examples 2 to 10, Comparative Examples 1 to 4)
In the step [1], the resin materials shown in Table 1 are prepared as the resin materials for forming the high refractive index layer 31 and the low refractive index layer 32, respectively, and in the step [3], the laminate is further prepared. Reflective polarizing plates of Examples 2 to 10 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the stretching temperature at the time of stretching while heating was changed as shown in Table 1.

3. 3. Evaluation The reflective polarizing plates of each Example and each Comparative Example were evaluated by the following methods.

<1A> Measurement of transmittance (%) in the X-axis direction and the Y-axis direction of the reflective polarizing plate First, the reflective polarizing plates of each Example and each Comparative Example are provided with a light source that emits light of 589 nm and a light receiving portion. The angle between the upper surface of the reflective polarizing plate and the straight line connecting the light source and the light receiving portion is 90 °.

Then, the emitted light (transmitted light) emitted from the light source transmitted through the reflective polarizing plate was received by the light receiving unit, and the transmittance (%) of the transmitted light in the X-axis direction and the Y-axis direction was measured, respectively.

<2A> Presence or absence of heat resistance of the reflective polarizing plate First, each of the reflective polarizing plates of each example and each comparative example having a size of 10 cm in length × 10 cm in width is stored in an oven at 100 ° C. for one week. After that, the dimensional change amount (%) of the length in the MD direction was obtained, and the evaluation was made as follows based on the magnitude of the dimensional change amount (%).

[Evaluation criteria]
⊚: No change was observed.
〇: A slight amount of change was observed, but the amount of dimensional change was less than 1%.
Δ: The magnitude of the amount of dimensional change is 1% or more and less than 5%.
X: The magnitude of the amount of dimensional change is 5% or more.

The evaluation results of the reflective polarizing plates of each of the Examples and Comparative Examples obtained as described above are shown in Table 1 below.

As shown in Table 1, the reflective polarizing plate in each example has heat resistance because the glass transition point Tg1 and the glass transition point Tg2 satisfy the relationship of Tg1 ≧ Tg2 ≧ 105 ° C. The result can be said to be. _{Further, since the absolute value of the birefringence ΔN xy} at the wavelength of 589 nm of the low refractive index layer is satisfied to be less than 0.15, the transmittance (%) in the X-axis direction is 10% or less and , Satisfied that the transmittance (%) in the Y-axis direction was 30% or more, and showed the result that it can be used as a polarizing plate.

On the other hand, the reflective polarizing plate in each comparative example does not satisfy either the _{relationship of Tg1 ≧ Tg2 ≧ 105 ° C. and the absolute value of the birefringence ΔN xy being less than 0.15.} As a result, those having no heat resistance or not having a sufficient function as a polarizing plate were obtained.

1 Translucent cover member 3 Polarizing layer 5 Hard coat layer 31 High refractive index layer 32 Low refractive index layer 33 Repeating part

Claims (5)

A reflective polarizing plate obtained by stretching a laminated body in which high refractive index layers and low refractive index layers are alternately and repeatedly laminated in the uniaxial direction.
The high refractive index layer has a higher refractive index in the uniaxial direction than the refractive index of the low refractive index layer in the uniaxial direction.
When the glass transition point of the main material constituting the high refractive index layer is Tg1 and the glass transition point of the main material constituting the low refractive index layer is Tg2, Tg1 ≧ Tg2 ≧ 105 ° C.
The low refractive index layer has an absolute value _{of birefringence ΔN xy} at a wavelength of 589 nm when the low refractive index layer is stretched twice in the uniaxial direction at a temperature 10 ° C. higher than the glass transition point Tg1. A reflective polarizing plate, characterized in that it is less than. The reflective polarizing plate according to claim 1, wherein the glass transition point Tg1 and the glass transition point Tg2 satisfy the relationship of Tg1-Tg2 <60 ° C. The reflective polarizing plate according to claim 2, wherein the glass transition point Tg1 is 110 ° C. or higher and 250 ° C. or lower. The reflective polarizing plate according to any one of claims 1 to 3, wherein the low refractive index layer has a refractive index of 1.49 or more and 1.67 or less at a wavelength of 589 nm in the stretching direction of the laminated body. The reflective polarizing plate according to any one of claims 1 to 4, wherein the high refractive index layer has a refractive index of 1.59 or more and 1.85 or less at a wavelength of 589 nm in the stretching direction of the laminated body.

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