JP2020098351A - Laminated front panel and method for manufacturing the same - Google Patents

Abstract

To provide a novel laminated front panel used to be disposed on a viewing side in a liquid crystal display device having a polarizing plate on the viewing side, the laminated front panel being capable of configuring a liquid crystal display device capable of ensuring visibility of the device even when the device is observed by wearing polarizing sunglasses.SOLUTION: In a liquid crystal display device including a liquid crystal cell A, a polarizing plate B disposed on a viewing side of the liquid crystal cell A, and a backlight light source C having a continuous emission spectrum, a laminated front panel is disposed on a viewing side of the polarizing plate B and is used. In the laminated front panel, a retardation film E is arranged, where the retardation film is directly joined to a rear surface side of an injection molding layer D and has an in-plane retardation ReE satisfying 3000 nm<ReE≤100000 nm, the retardation film is arranged so that an angle between a slow axis of the retardation film and an absorption axis of the polarizing plate B is 35° to 55°, and a retardation ReH of the laminated front panel in an image display region satisfies 3000 nm≤ReH.SELECTED DRAWING: Figure 3

Description

The present invention is a display device mounted on an automobile, an aircraft, a ship, etc., a smartphone, a tablet terminal, a mobile game device, a mobile device such as a digital camera, a public space, a digital signage installed in a store of a commercial facility, or the like. The present invention relates to a liquid crystal display device used as an image display device for other devices, and in particular, in a liquid crystal display device including a polarizing plate, the laminated front panel used on the viewing side of the polarizing plate, and a method for manufacturing the same.

In recent years, the liquid crystal display devices are increasingly used outdoors. For example, display devices installed in automobiles, aircrafts, ships, mobile devices such as smartphones, tablet terminals, digital cameras for portable game devices, digital signage installed in public spaces, stores of commercial facilities, and the like can be mentioned.
Many liquid crystal display devices used outdoors are provided with a cover material (also referred to as “front plate” or “front panel”) on the visible surface for the purpose of preventing scratches and damages.

As a material for such a cover material, a glass material such as tempered glass has been conventionally used, but in recent years, a plastic material has been used because of advantages such as weight reduction and no breakage.
For example, Patent Document 1 discloses a resin laminate in which a hard coat layer is laminated on a laminate obtained by coextruding a polycarbonate resin and an acrylic resin.
Further, in Patent Document 2, as a laminated extruded resin plate for a touch panel which is hard to be scratched on the surface and is relatively easy to manufacture, an acrylic resin layer is formed by coextrusion molding on at least the surface of the polycarbonate resin layer on the touched side. Disclosed is a laminated extruded resin plate for a touch panel, which is laminated.

As described above, since the number of liquid crystal display devices used outdoors is increasing, the chances of wearing polarized sunglasses and visually recognizing the display screen of the liquid crystal display device are increasing.
Most liquid crystal display devices are provided with a linear polarizing plate on the viewing side. In such a liquid crystal display device, the observer sees the linearly polarized light emitted from the polarizing plate. When the display screen is mounted and the display screen is observed, various problems may occur due to the positional relationship between the absorption axis of the polarizing plate on the viewing side of the liquid crystal display device and the absorption axis of the sunglasses. For example, if there is no member having a phase difference between the viewing-side polarizing plate of the liquid crystal display device and the observer's polarized sunglasses, it is completely determined that the absorption axes of these polarizing plates and the polarized sunglasses are orthogonal to each other. You will not be able to see it. In addition, if a member having a phase difference is interposed between the two polarization axes, the screen may become dark, undesired coloring may occur, or interference colors may be visible, so that an accurate display can be recognized. There were times when it disappeared.

In order to provide a liquid crystal display device capable of ensuring highly favorable visibility regardless of the observation angle when observing a screen through a polarizing plate such as sunglasses when a member having a phase difference is not present, Patent Document 4 (JP 2012-230390A) discloses a white light emitting diode as a backlight light source in a liquid crystal display device including at least a backlight light source, a liquid crystal cell, and a polarizing plate disposed on the viewing side of the liquid crystal cell. And a polymer film having a retardation of 3000 to 30,000 nm on the viewing side of the polarizing plate forms an angle of about 45 degrees between the absorption axis of the polarizing plate and the slow axis of the polymer film. There has been proposed a method of improving visibility of a liquid crystal display device, which is characterized by being arranged and used as described above.

Furthermore, plastic cover materials made by injection molding can be easily manufactured even with special shapes such as curved shapes, shapes with openings, curved ends, non-rectangular shapes such as heart shape, etc. Therefore, it is preferably used as a cover material for the above-described liquid crystal display device. However, when this kind of plastic cover material is injection-molded, orientation occurs in the flow direction of the molding resin, and a phase difference having an optical axis in the flow direction of the resin occurs. Further, since the flow of resin in the molding die is not uniform, the orientation angle and the phase difference of various values often occur depending on the location in the injection molding member. In particular, when the cover material has portions with different thicknesses, has a curved surface shape or a 3D shape, or has an opening portion, etc., in the vicinity of the gate, the peripheral portion with different thickness or shape, etc. A large variation in phase difference occurs, and the visibility when wearing polarized sunglasses is significantly deteriorated.

Therefore, when a cover material having a phase difference is interposed, even when observing through a polarizing plate such as polarized sunglasses, a display device capable of preventing display variations such as coloring and unevenness of light and shade depending on places is disclosed in Patent Document 3 (Patent Document 3). No. 2005-157082), a display element having a polarizing plate on the forefront, a translucent cover arranged in front of the display element and having a phase difference in the plane, the polarizing plate and the translucent light. And a light-transmitting optical element having a phase difference in the plane, which is arranged between the light-transmitting cover and the light-transmitting cover and reduces the influence of the phase difference of the light-transmitting cover on human visual recognition. ..

JP, 2006-103169, A JP, 2010-182263, A JP, 2005-157082, A JP, 2012-230390, A

However, as described above, the injection-molded member may have a large variation in the phase difference and various directions of the phase difference. Therefore, the liquid crystal including the panel material formed by injection molding on the viewing side of the polarizing plate. In a display device, it is often the case that the effect of improving visibility is not sufficient simply by disposing a polymer film having a retardation as disclosed in Patent Document 3 and the like. In particular, when the retardation of the retardation film is a value close to the lower limit, or when there is a portion where the optical axis of the retardation of the injection panel member is abruptly changed, the interference color is observed and visually recognized. The effect of improving sex is not sufficient.

Further, the patent document suggests that the retardation film and the injection-molded panel are individually prepared, and then laminated and arranged. If the lamination method is not fixed to the cover material via an adhesive or the like, the retardation film may be displaced or the retardation film may be deformed, resulting in poor visibility, which is a practical obstacle. Occurs. Further, also in the case of the laminating method in which the adhesive material or the adhesive material is used for fixing, the attachment may be difficult depending on the shape of the cover material. In particular, when the cover material has a curved surface, has another three-dimensional shape, or has an opening, a concave portion, or a convex portion, the bonding itself may not be possible.

Therefore, it is an object of the present invention to provide a laminated front panel that is arranged and used on the viewing side in a liquid crystal display device having a polarizing plate on the viewing side, and it is possible to ensure the visibility even when wearing and wearing polarized sunglasses. Another object of the present invention is to provide a new laminated front panel that can form a liquid crystal display device that can be manufactured, a method of manufacturing the same, and a liquid crystal display device that uses the laminated front panel.

The present invention provides a liquid crystal display including a liquid crystal cell (A), a polarizing plate (B) arranged on the viewing side of the liquid crystal cell (A), and a backlight light source (C) having a continuous emission spectrum. A laminated front panel, which is used by being arranged on the viewing side of a polarizing plate (B) in an apparatus,
It has an image display area when viewed from the viewing side,
A retardation film (E) having an in-plane retardation (ReE) satisfying the formula (1) below is disposed on the back surface side of the injection molding layer (D), and the injection molding layer (D) and the retardation film ( E) is directly bonded, and is arranged such that an angle formed by the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55°, and
A retardation (ReH) of the laminated front panel in the image display region satisfies the following expression (2), and a laminated front panel is proposed.
(1) 3000 nm<ReE≦100,000 nm
(2) 3000 nm≦ReH

The present invention also provides a liquid crystal comprising a liquid crystal cell (A), a polarizing plate (B) arranged on the viewing side of the liquid crystal cell (A), and a backlight light source (C) having a continuous emission spectrum. A laminated front panel, which is used by being arranged on the viewing side of a polarizing plate (B) in a display device,
It has an image display area when viewed from the viewing side,
A retardation film (E) having an in-plane retardation (ReE) satisfying the formula (1) below is disposed on the back surface side of the injection molding layer (D), and the injection molding layer (D) and the retardation film ( E) is bonded via the adhesive layer (F), and the angle between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55°. And then
A retardation (ReH) of the laminated front panel in the image display region satisfies the following expression (2), and a laminated front panel is proposed.
(1) 3000 nm<ReE≦100,000 nm
(2) 3000 nm≦ReH

The present invention also provides a laminated front having a constitution in which a retardation film (E) having an in-plane retardation (ReE) satisfying the formula (1) below is arranged on the back surface side of the injection molding layer (D). A method of manufacturing a panel,
The retardation film (E) is placed in a mold in advance so that the angle between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55°, and melted. The injection-molded layer (D) and the retardation film (E) are insert-molded by injecting the molded thermoplastic resin for forming an injection-molded layer into the mold to mold the injection-molded layer. The manufacturing method of is proposed.
(1) 3000 nm<ReE≦100,000 nm

The laminated front panel proposed by the present invention is arranged and used on the viewing side of the polarizing plate (B) in a liquid crystal display device, and when the polarized sunglasses are attached and observed, the laminated front panel has a crossed Nicols relationship. Not only the blackout phenomenon can be avoided, but also the visibility deterioration due to the phase difference of the injection molding layer (D) can be prevented.

FIG. 1 is a plan view of an example of a liquid crystal display device according to an example of the present invention viewed from a viewer side. It is a side sectional view showing an example of a lamination front panel concerning an example of the present invention. FIG. 3 is a side sectional view showing an example of a liquid crystal display device incorporating the laminated front panel of FIG. 2 in an exploded state. FIG. 3 is a side sectional view showing an example of a laminated front panel different from the laminated front panel of FIG. 2. FIG. 5 is a side sectional view showing an example of a liquid crystal display device incorporating the laminated front panel of FIG. 4 in an exploded state. It is the figure which showed an example of the injection molding layer which comprises the liquid crystal display device of this invention, (a) is the sectional side view, (b) is a perspective view when it sees from a visual recognition side. It is a top view of the laminated front panel produced in the example. It is a graph showing the relationship between the distance from the gate and the phase difference when molded at a cylinder temperature of 300°C.

Next, the present invention will be described based on the embodiments. However, the present invention is not limited to the embodiment described below.

<Main laminated front panel>
As shown in FIG. 1, the laminated front panel according to the present embodiment includes an image display area and an image non-display area when viewed from the viewer side, and as shown in FIG. , A liquid crystal display device provided with a polarizing plate (B) arranged on the viewing side of the liquid crystal cell (A) and a backlight light source (C) having a continuous emission spectrum (hereinafter referred to as “present liquid crystal display device”). (3) is a laminated front panel used on the viewing side of the polarizing plate (B), the retardation having an in-plane retardation (ReE) within a predetermined range on the back side of the injection molding layer (D). The film (E) is arranged.

Here, the image display area is an area where the image of the liquid crystal display device is displayed, and the image non-display area is an area where the image of the liquid crystal display device is not displayed (printed area or the like).
However, the present liquid crystal display device and the present laminated front panel do not have to have image non-display areas on all four sides as shown in FIG. 1, and one side such as a so-called frameless display, or There may be a plurality of sides, and a part having substantially no image non-display area.

<Retardation film (E)>
The retardation film (E) constituting the present laminated front panel is not limited in its material and structure as long as it has a in-plane retardation (ReE) of more than 3000 nm and 100,000 nm or less.

When white light is observed by arranging a member having a phase difference between two polarizing plates having a crossed Nicols relationship, white light is canceled by interference at a certain wavelength and transmitted at a certain wavelength. If the in-plane retardation (ReE) of the retardation film (E) is sufficiently large, transmitted light will exist in many wavelength regions, so that an observer can recognize it as white light. On the other hand, a material having an in-plane retardation (ReE) of more than 100,000 nm cannot be applied as a member of a liquid crystal display device because it is extremely difficult to manufacture a plastic material or the thickness becomes too thick.

From this point of view, when the light source of the liquid crystal display device used in the present invention has a continuous emission spectrum, the in-plane retardation (ReE) of the retardation film (E) is preferably more than 3000 nm and 100,000 nm or less, and above all, It is 4000 nm or more or 50,000 nm or less, and among them, 5000 nm or more or 20,000 nm or less is more preferable in view of the production of the retardation film (E).
The in-plane retardation (ReE) of the retardation film (E) is an average value obtained by measuring in-plane retardation at arbitrary plural points, for example, 5 points, which are different with respect to the direction orthogonal to the slow axis direction. Is preferably the in-plane retardation (ReE).

The material of the retardation film (E) is not particularly limited. For example, a transparent film having a base resin of one kind or a mixture of two or more kinds selected from the group consisting of polycarbonate, polyester, polystyrene, polyarylate and polyamide can be mentioned. Further, polycarbonate, polyester, polystyrene, and polyamide include copolymers with different types of monomers.

Among them, a film having a base resin selected from the group consisting of polycarbonate, polyester and polyamide is preferable as a material which is transparent, has excellent heat resistance and mechanical properties, and easily causes a phase difference by stretching orientation.

As the polycarbonate, an aromatic polycarbonate mainly containing bisphenol A, and as the polyester, polyethylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate and the like can be mentioned as particularly preferable base resins. Further, as the polyamide, a semi-aromatic polyamide such as PA6T or PA9T, which has a relatively high Tg and can maintain the transparency even when oriented and crystallized, is particularly suitable.

The retardation film (E) is an oriented film obtained by stretching a substantially non-oriented sheet obtained by a suitable method such as a melt extrusion method or a casting method using the above-illustrated base resin in a specific direction. Is preferred.
For example, in the case of an oriented polycarbonate film, it is obtained by melting a polycarbonate and stretching an unoriented sheet extruded into a sheet at a temperature not lower than the glass transition temperature in one direction, and optionally in two directions. An oriented polycarbonate film having a retardation of can be used.
On the other hand, in the case of an oriented polyester film or oriented polyamide film, it is obtained by melting a resin and subjecting a non-oriented sheet extruded into a sheet shape to stretching and heat treatment in at least one direction at a temperature not lower than the glass transition temperature. Oriented film that can be used.

Examples of the method of adjusting the retardation of the retardation film (E) include a method of adjusting the stretching ratio, the stretching temperature, the thickness of the film, and the like. However, it is not limited to these.
For example, when the base resin of the retardation film (E) is polyethylene terephthalate, the stretching temperature is preferably 80 to 130°C, and more preferably 85°C or higher or 120°C or lower. The stretching ratio is preferably 2.5 to 6.0 times in the case of lateral uniaxial stretching, and more preferably 3.0 times or more or 5.5 times or less. If the stretching ratio is too high, the mechanical strength of the obtained film, particularly the problem of easy tearing in the stretching direction, tends to occur. On the other hand, if the stretching ratio is too low, the birefringence of the obtained film becomes small and the retardation becomes small, which is not preferable.

On the other hand, when the base resin of the retardation film (E) is an aromatic polycarbonate containing bisphenol A as a constituent component, the stretching temperature is preferably 150 to 180°C, and above all 155°C or 170°C. Is preferred. The stretching ratio is preferably 3.0 to 5.0 times in the case of longitudinal uniaxial stretching.

The retardation film (E) has an adhesive layer for securing adhesiveness and a decorative layer printed in the image non-display area described above on the adhesive surface with the injection molding layer described later. May be, on the opposite surface, an adhesive layer, an antireflection layer, an adhesive property with a layer formed on the film such as an antistatic layer, water resistance, for the purpose of improving chemical resistance, The surface of the film may be subjected to surface treatment by a known method, that is, corona discharge treatment or easy adhesion treatment. In this case, the retardation of the retardation film (E) of the present invention means the retardation of the laminated film including the adhesive layer and the like.

Regarding the thickness of the retardation film (E), if it is thin, it becomes difficult to increase the retardation, so it is preferable that the retardation film (E) be thick to have a high retardation, but excessive stress is required for stretching, There is a possibility that it will be difficult to set the mold in the mold during insert molding, and further the temperature of the retardation film (D) will rise excessively, and the retardation will disappear.
From such a viewpoint, the thickness of the retardation film (E) is preferably 25 μm to 500 μm, and particularly preferably 50 μm or more or 350 μm or less.

Further, regarding the thickness of the retardation film (E), depending on the material, due to the fact that the intrinsic birefringence is different depending on the base resin, the expression state of the retardation is different, the mechanical strength of the resulting oriented film is different, etc. It is particularly preferable to set the thickness of the phase difference development. For example, when the base resin of the retardation film (E) is polycarbonate, the thickness is preferably 80 μm to 500 μm, and particularly preferably 100 μm or more or 350 μm or less. On the other hand, when the base resin of the retardation film (E) is polyethylene terephthalate, it is preferably 25 μm to 350 μm, and particularly preferably 40 μm or more or 250 μm or less.

<Injection molding layer (D)>
The injection-molded layer (D) includes a member having a sheet shape or a plate shape, a curved surface shape, another three-dimensional shape, an opening portion, a convex portion, a concave portion, or the like. Here, the three-dimensional shape means a shape having a Z axis (height, standing wall).

The injection-molded member generally exhibits a phase difference of various values depending on the place, and has a characteristic that it may have various orientation axes depending on the shape. Therefore, the phase difference of the injection molding layer (D) depends on the shape of the molding panel and the injection condition, and it is possible to set the shape and the injection condition such that the phase difference hardly occurs in the display area. However, there are many inconveniences such as impairing the degree of freedom in the design of the panel and having to set unfavorable injection conditions.

Areas where the phase difference is likely to be high or orientation variations are likely to occur include areas near the gate, areas around openings, areas with different thicknesses such as recesses and projections, and non-rectangular shapes such as circles and heart shapes. For example, the end portion of the shaped molded panel for a liquid crystal panel may be mentioned. In such a region, in general, the phase difference is often 350 nm or more, which causes remarkable coloring due to interference during orthogonal Nicols observation, and it is necessary to consider the panel design so that the region is not the display region.

Further, in order to reduce the phase difference that appears, it is necessary to adjust various injection conditions such as gate shape and position, injection temperature, injection speed, mold temperature, and holding pressure. However, in some cases, other problems such as heat deterioration of resin, sink marks, short shots, weld lines, etc. may occur, so in order to avoid these, a great deal of effort such as reviewing the mold design and setting injection conditions is required. Needed.

The present invention is capable of avoiding such inconvenience. For example, the display area of the liquid crystal display device can be expanded, so that the degree of freedom in design can be increased and the injection condition can be applied. You can enjoy the benefit of being able to extend the range.

The resin material forming the injection molding layer (D) is not particularly limited as long as it is a transparent thermoplastic resin. For example, a material having one or a mixture of two or more selected from the group consisting of polycarbonate, acrylic resin, polyester, polyethylene, polypropylene, cyclic olefin resin, styrene resin and vinyl chloride resin as a base resin is exemplified. You can Among them, polycarbonate, acrylic resin, polyester and the like can be preferably exemplified from the viewpoints of transparency and ease of molding. Above all, in the front panel used for the touch panel display for in-vehicle equipment, a material using polycarbonate as a base resin is preferable from the viewpoint of scattering prevention.

From the viewpoint of transparency and moldability, the polyester resin is preferably a low crystalline polyester resin, for example, a copolymer in which a part of the acid component of polyethylene terephthalate is replaced with isophthalic acid, or a glycol component. A copolymer in which a part of the above is replaced with 1.4-cyclohexanedimethanol is suitable.

As the polycarbonate, for example, an aromatic polycarbonate, an aliphatic polycarbonate, or an aromatic-aliphatic polycarbonate can be used, and is not limited to a general polycarbonate containing bisphenol A as a main raw material. For example, the diol component also includes a polycarbonate whose main component is an ether diol such as isosorbite.

Since the injection-molded layer (D) is formed by injection molding, it can have a form having the above-mentioned special shape, and, for example, in order to impart an antiglare effect, an image display is provided. It is also possible to form fine irregularities on the surface.
Further, as shown in FIG. 6, a display surface portion D1 having fine unevenness for imparting an antiglare effect corresponding to the image display area 1 of the present liquid crystal display device and a sense of luxury corresponding to the image non-display area 2 are provided. It is also possible to adopt a configuration in which the peripheral portion D2 having a smooth surface for holding is provided on the panel viewing side surface.

If the arithmetic surface roughness (Ra) of the surface of the display surface portion D1 is 0.1 μm or more, the antiglare effect can be obtained, and if it is 0.7 μm or less, the light emitted from the liquid crystal cell is excessively scattered. , No problem such as blurring of the image. From this viewpoint, the arithmetic surface roughness (Ra) of the surface of the display surface portion D1 is preferably 0.1 μm to 0.7 μm, and more preferably 0.2 μm or more or 0.5 μm or less.

The fine irregularities imparting the antiglare property are also useful in improving the visibility of the present invention. In particular, if there is a portion having a rapid phase difference change in the image display region 1 of the injection molding layer (D), a thin boundary line may be recognized although it does not affect the visibility. In such a case, since the fine unevenness has an effect of diffusing the light emitted from the liquid crystal cell, it has an effect of making the boundary line inconspicuous.
The arithmetic surface roughness (Ra) is an arithmetic average roughness defined in JIS B 0601-2013, and is measured by, for example, a surface roughness measuring machine, a shape measuring machine, a tool microscope, a laser microscope, or other equipment. be able to.

On the other hand, the peripheral portion D2 is preferably a smooth surface for imparting a high-class feeling, and particularly preferably a mirror surface showing gloss.
From the above viewpoint, the surface of the peripheral portion D2 preferably has a specular gloss of 85% or more, and more preferably 90% or more, according to JIS Z8741 at an incident reflection angle of 60°.

The peripheral portion D2 may have the peripheral edge portion formed as a curved surface, or may have a stepped portion, a taber portion, or the like having different thicknesses. Further, it is also possible to arbitrarily provide an opening such as a through hole, a concave portion, a convex portion, a rib, or the like at an appropriate portion of the peripheral portion D2. Further, various patterns such as a lattice pattern and a zigzag pattern can be provided at appropriate places, and printing can be performed on the back surface for decoration purposes.

<Method for manufacturing laminated front panel>
This laminated front panel is composed of the retardation film (E) and the injection molding layer (D) described above, and one of the features is that both layers are adhered at the time of injection molding. Specifically, the laminated front panel has an injection molding layer in which the retardation film (E) is placed in a mold and the melted thermoplastic resin is injected into the mold for molding. It is possible to manufacture a laminated front panel having a structure in which (D) and the retardation film (E) are joined. The retardation film (E) arranged in this mold may be preshaped according to the shape of the laminated front panel. The injection molding may be ordinary injection molding, injection compression molding in which the resin is supplied and then the mold is clamped, or H&C molding in which the mold temperature is controlled. Good. However, the manufacturing method of the present laminated front panel is not limited to such a manufacturing method.

(Laminate front panel 1)
As one of the embodiments of the present invention (referred to as a laminated front panel 1), there may be mentioned a mode in which the injection molding layer (D) and the retardation film (E) are directly bonded without an adhesive layer or the like. In this case, when the resin to be injection-molded comes into contact with the retardation film in a molten state, it is necessary to ensure sufficient adhesiveness, so that the injection-molded layer (D) and the retardation film (E) can be applied. The combination of materials is limited. Generally, it is preferable that the injection molding layer (D) and the retardation film (E) are made of the same material, but different materials may be used as long as the adhesion at the interface is sufficient. However, when the material of the retardation film (E) is a crystalline resin such as polyester or polyamide, sufficient adhesiveness may not be obtained even if the material of the injection molding layer (D) is the same resin. Therefore, when the laminated front panel is formed without an adhesive layer or the like, it is preferable that the retardation film (E) is composed mainly of an amorphous polymer.

From this viewpoint, the retardation film (E) is particularly preferably a resin based on polycarbonate, polystyrene, or amorphous polyester, and the resin forming the injection-molded layer is bonded to the material of the retardation film (E). A resin composition having good properties may be selected. Among these, it is particularly preferable that the materials of the injection molding layer (D) and the retardation film (E) are a combination of the same polycarbonate as the base resin. This combination is considered to have an advantage that not only strong adhesiveness at the interface can be obtained, but also the reflection loss at the interface is eliminated because both layers have the same refractive index. Examples of the polycarbonate mentioned here include aromatic polycarbonates having bisphenol A as a constituent unit, but the polycarbonate is not limited thereto.
When the material of the injection molding layer (D) and the retardation film (E) is a combination of the same polycarbonate as the base resin, the injection molding layer (D) and the retardation film are observed by observing the longitudinal section of the laminated front panel with a microscope. The feature is that no interface is observed with (E).

(Laminate front panel 2)
A laminated front panel according to another example of the present embodiment (referred to as "main laminated front panel 2") has an appropriate adhesive layer provided on the surface of the retardation film (E) in contact with the injection molding layer (D). Another example is a mode in which the injection molding layer (D) is adhered. In particular, when the retardation film (E) is a crystalline resin such as polyester or polyamide, it is preferable to bond the retardation film (E) via a copolymer layer or an amorphous layer having low crystallinity as an adhesive layer. However, even if the retardation film (E) is formed of an amorphous polymer, an adhesive layer may be interposed in order to facilitate the adhesion.

The method for forming the adhesive layer is not particularly limited, and a known method may be used. Specifically, a layer functioning as an adhesive layer is formed by coextrusion or extrusion lamination, or is formed by coating a film before stretching, and then stretched to obtain a retardation film (E). There is a method. Further, a method of forming an adhesive layer by a method such as coating or laminating after obtaining the retardation film (E) may be used. Further, the retardation film (E) can be provided with a decorative layer such as a printing layer in advance in the image non-display area or the like. In this case, it is possible to provide an adhesive layer in the printing process.

Since the main laminate front panel 2 joins the injection molding layer (D) and the retardation film (E) via the adhesive layer (F), the injection molding layer (D) and the position are similar to those of the main laminate front panel 1. There are few restrictions on the selection of the base resin of the retardation film (E), and the materials can be freely designed. Therefore, as the retardation film (E), it is possible to select a thin film having a crystalline polyester as a base resin, which easily obtains a high retardation. Polycarbonate having excellent properties and impact resistance as a base resin can be selected as a preferable example.

(Laminate front panels 1, 2)
As described above, the laminated front panels 1 and 2 are formed by injecting a molten resin into the retardation film (E) which is previously placed in the mold. At this time, the retardation film (E) has an absorption axis of the viewing side polarizing plate (B) and a slow axis of the retardation film (E) of the liquid crystal cell in which the laminated front panels 1 and 2 are practically used. It is necessary to arrange them in the mold so that the angle formed by them is within a limited range.

Generally, when a member having a phase difference is inserted between orthogonal Nicols to transmit white light, when the angle between the absorption axis of the polarizing plate and the slow axis of the member having a phase difference is 45°, the transmitted light is Maximum strength. When the present laminated front panels 1 and 2 are incorporated into the present liquid crystal display device, the angle formed between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) of the present laminated front panel is 45°. Further, it is most preferable to position and laminate the retardation film (E), and practically it is preferable to position and laminate the retardation film (E) so as to be 35 to 55°. By thus disposing the retardation film (E) in the mold, it is possible to secure a practically sufficient transmitted light intensity when wearing sunglasses.
From this viewpoint, the angle is preferably 35 to 55°, and more preferably 40° or more or 50° or less.

Further, the retardation film (E) and the injection molding layer (D) have an angle between the slow axis of the retardation film (E) and the slow axis of the injection molding layer (D) in the image display area. It is preferable to consider so as to be within 45°.

The value of the retardation of the injection-molded layer (D) greatly differs depending on its shape and molding conditions. For example, when the injection-molded layer (D) is molded under the condition that a large retardation is developed, the retardation of the laminated front panels 1 and 2 may be different depending on the angle formed by the retardation film (E). The value may be smaller than the retardation of the retardation film (E) before molding. Generally, when two members having a phase difference are laminated, the phase difference as the laminated member has an additive relationship when the angle formed by the slow axis is 45° as a boundary and is 45° or more. Then, it becomes a reduction relation. Therefore, the injection-molded layer (D) of the laminated front panels 1 and 2 may be injection-molded such that the slow axis thereof forms an angle of 45° or less with the slow axis of the retardation film. preferable. If this relationship can be maintained, the laminated front panel of the present invention can ensure good visibility in observation when wearing polarized sunglasses.

In the image display area, in order to make the angle between the slow axis of the retardation film (E) and the slow axis generated during injection molding of the injection molding layer (D) 45° or less, It is necessary to pay attention to the panel shape design, mold design, gate position and shape, etc. Since the optical axis of the phase difference that appears during the injection molding of the injection molding layer (D) substantially coincides with the flow direction, the flow of the molding resin in the mold may be particularly taken into consideration. Specifically, when the resin forming the injection-molded layer (D) is a material that exhibits positive birefringence, the resin is made to flow in a direction parallel to the slow axis of the retardation film (E). You can do this. When the resin forming the injection-molded layer (D) is a material exhibiting negative birefringence, the resin may be made to flow in the direction of the fast axis of the retardation film (E). Further, in the image display area, since it is necessary to align the flow directions, it is preferable to use the film gate method in which the resin flows uniformly.
At this time, the magnitude of the retardation and the direction of the slow axis of the injection-molded layer (D) can be obtained from the obtained measured values of the laminated front panels 1 and 2 by a known method.

Since the laminated front panels 1 and 2 have the characteristic of being bonded to the retardation film (E) arranged in the mold during injection molding, they are not preferable for the retardation of the retardation film (E) during injection molding. It is necessary to set the conditions so that the deterioration does not occur. At the same time, it is necessary to take measures to prevent harmful effects on the front panel, such as film deformation and haze increase. Specifically, conditions such as the injection molding temperature, the injection molding speed, the structure of the mold, the set temperature of the mold, and the position of the gate can be mentioned, but from the viewpoint of reducing the retardation of the retardation film (E). Of particular concern is the mold temperature.

The temperature of the mold during injection resin is preferably set lower than the glass transition temperature (Tg) of the retardation film (E) as the insert film. If the temperature is higher than the glass transition temperature (Tg) of the retardation film (E), the retardation may be reduced if the retardation film (E) is an amorphous resin, which is not preferable. Further, in the case of a crystalline resin, an unfavorable phenomenon such as crystallization progressing to increase haze or shrinkage to deform the film may occur. However, in the case of performing heat & cool molding in which injection molding is performed by controlling the mold temperature by heating and cooling, if the heating time and the like are sufficiently controlled, the mold temperature is the glass transition of the retardation film (E). In some cases, even if the temperature (Tg) is exceeded, it can be carried out.
With such consideration, if the phase difference (ReH) of the obtained laminated front panels 1 and 2 satisfies the following expression (2), the effect of the present invention can be enjoyed.
(2) 3000 nm≦ReH

<Thickness of this laminated front panel>
The average thickness of the laminated front panel varies depending on its application, but is preferably about 0.5 mm to 5 mm. If the thickness is 0.5 mm or less, deformation and warpage during removal from the mold are likely to occur, and injection molding becomes difficult. On the other hand, if the thickness is 5 mm or more, the thickness of the entire liquid crystal display device becomes too thick, which is not practical.
Therefore, the average thickness of the laminated front panel is preferably 0.5 mm to 5 mm, more preferably 1 mm or more or 3 mm or less, and further preferably 1.5 mm or more or 2.5 mm or less.

Further, within the thickness range of the retardation film (E) and the thickness range of the laminated front panel, the ratio of the thickness of the retardation film (E) to the average thickness of the laminated front panel is 2 to 20%. It is preferable to set it so that it is 5% or more or 15% or less. By setting the thickness ratio of the retardation film (E) to the above lower limit value or more, it is possible to facilitate installation in a mold and prevent deformation of the film during injection molding. Further, by controlling the ratio within the above range, the risk that the cooling from the wall surface of the mold becomes insufficient and the phase difference decreases may be suppressed.

<Other>
Since the present laminated front panel only needs to have the above configuration, it may be provided with another member or another functional coat layer on the viewing side or the back side thereof. Examples of other members include, but are not limited to, hard coat films, antireflection films, antifouling coat films, touch sensors, and louver films. The member may be formed by insert molding at the time of injection molding, or may be a laminated front panel by being pasted with an adhesive or an adhesive after injection molding.

Other functional coat layers include hard coat, antireflection coat, antistatic coat, antifouling coat, etc., if necessary. Examples of the method for forming the coat layer include a dip coat method, a spray coat method, and a coat method using an inkjet, a silk screen, a gravure roll, or the like. However, it is not limited to these.

Examples of the coat resin composition include an ultraviolet (UV) curable resin composition, a solvent dry curable resin composition, and a thermosetting resin composition. Among them, those having high transparency after forming the coat layer are preferable.

<Using this laminated front panel>
As shown in FIGS. 3 and 5, this laminated front panel includes a liquid crystal cell (A), a polarizing plate (B) arranged on the viewing side of the liquid crystal cell (A), and a back light having a continuous emission spectrum. In the present liquid crystal display device including the light source (C), the angle formed between the absorption axis of the polarizing plate (B) and the slow axis of the laminated front panel is 45 in advance on the viewing side of the polarizing plate (B). It is preferable to stack and arrange the main laminated front panel made to have an angle of 0°.

<This liquid crystal display device>
The liquid crystal cell (A) is not limited to the configuration of the liquid crystal cell (A) itself as long as the polarizing plate (B) is arranged at least on the viewing side. As an example, a liquid crystal cell using a driving method such as TN type, VA type, IPS type, etc., which is an active matrix driving method which is widely used at present, can be mentioned.

The polarizing plate (B) is a linear polarizing plate arranged on the viewing side of the liquid crystal cell (A).
The material and configuration of the polarizing plate (B) are arbitrary. For example, a stretched polyvinyl alcohol film using iodine as an alignment dye and a TAC (triacetyl cellulose) film laminated as a protective film are widely put into practical use as a polarizing plate of this type.
Further, the polarizing plate (B) may have a layer structure having a hard coat having substantially no phase difference, an antiglare property, a low reflection property, an antistatic function, etc. on the surface.

The backlight light source (C) preferably has a continuous emission spectrum from the viewpoint of enjoying the effects of the present invention.
When the backlight light source (C) is a set of monochromatic light with a narrow half width, such as a cold cathode fluorescent lamp, even if the phase difference of the retardation film (E) is sufficiently large, the transmitted light remains biased. However, it is difficult to enjoy the effect of the present invention because the interference color does not disappear. On the other hand, in the case of continuous light having a continuous emission spectrum such as a white LED, if the retardation of the retardation film (E) is sufficiently large, a good image without interference color can be visually recognized. Therefore, the effect of the present invention can be effectively enjoyed.

Here, the term "continuous emission spectrum" means light that does not separate into individual line spectra when viewed with a spectroscope and produces a spectrum that continuously spreads with respect to wavelength, preferably visible light wavelength. It is a spectrum that includes all light of any wavelength in the range. For example, an emission spectrum of a light emitting diode (LED), an electroluminescence panel or the like is a continuous emission spectrum, whereas an emission spectrum of a cold cathode tube or a hot cathode is not a continuous emission spectrum.

The method and configuration of arranging the backlight light source (C) may be the same as those of the conventional liquid crystal display device, and any configuration can be adopted. For example, in the case of an edge light source, light is guided to the liquid crystal cell via a backlight unit including a reflection sheet, a light guide plate, a diffusion plate, a prism sheet, a brightness enhancement film and the like.

If necessary, other constituent members may be arranged between the laminated front panel and the polarizing plate (B) on the viewing side of the liquid crystal cell (A), but a member having a phase difference of a certain value or more may be used. It is not preferable to place it between them. When a member having a phase difference is present, good visibility can be obtained when the polarized sunglasses are in a crossed Nicols relationship with the polarizing plate (B), but at other angles, the phase difference of the intervening member is reduced. Depending on the color, the visibility may deteriorate. From this viewpoint, when the present laminated front panel constitutes a liquid crystal display device, it is preferable that no member having a phase difference of 600 nm or more is interposed between the present laminated front panel and the polarizing plate (B). Above all, it is more preferable that no member having a phase difference of 400 nm or more is present.

Here, as an example of the member having no phase difference, a transparent pressure-sensitive adhesive or adhesive for fixing the laminated front panel to the liquid crystal display device can be mentioned.
As a method of fixing the laminated front panel, there is a method of fixing with screws or a double-sided tape in the non-image display part, but as a means for reducing the interface reflection of the image display part, the entire display part is transparent without phase difference. There is a method of sticking with an adhesive or an adhesive.

At this time, the pressure-sensitive adhesive or adhesive composition forming the transparent pressure-sensitive adhesive or adhesive layer is not particularly limited. It may be in the form of liquid, gel or film. Further, it may have a hot melt property or may not have a hot melt property. Further, it may be one that is further crosslinked and cured by irradiation with ultraviolet rays or the like.
Further, as another example, a touch panel sensor formed of a glass or plastic substrate having no phase difference, an antireflection film using a base material having no phase difference, and the like can be given.

<Explanation of terms>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “preferably larger than X” or “preferably Y” is used together with “meaning X or more and Y or less” unless otherwise specified. It also means "less than".
When expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it is preferably "greater than X" or "less than Y". It also includes intent.

Further, in the present specification, the "base resin" means a resin having the highest content of the resins constituting the resin composition, and usually 50% by mass or more of the resin constituting the resin composition, Above all, it is 80% by mass or more, and among them, 90% by mass or more (including 100% by mass) resin. However, when the resin composition contains two types of base resins, the total amount is the above-mentioned mass ratio.

Further, in the present specification, the “viewing side” is the side on which display light is emitted from the display screen, and means the side on which the display on the front panel is observed.
The “back surface side” means the side opposite to the “viewing side”, and means the side on which the display light from the display screen enters.
The term "transparent" is not limited to colorless and transparent, and includes colored and transparent.

Hereinafter, the present invention will be described in more detail based on the following examples and comparative examples.

<Production of retardation film>
Polycarbonate (polycarbonate derived from bisphenol A, Tg 145° C.) is melted at 260° C., and a sheet having a predetermined thickness obtained by a melt extrusion method is stretched uniaxially at a temperature of 160° C. by a roll stretching method to obtain an original sheet thickness. And the stretching ratio are adjusted, and the thickness is 300 μm, the polycarbonate retardation film 1 having an in-plane retardation of 5500 nm, the thickness 125 μm, the polycarbonate retardation film 2 having an in-plane retardation of 3260 nm, the thickness 80 μm, the in-plane retardation. A polycarbonate retardation film 3 having a wavelength of 2750 nm was obtained.

<Production of laminated front panel>
The polycarbonate retardation films 1, 2 and 3 as insert films are arranged on the cavity surface in the mold so that the slow axis thereof coincides with the long side direction of the laminated front panel as an insert molded product, Injection molding resin was filled into the mold from the gate, and injection molding was carried out.

Polycarbonate (polycarbonate derived from bisphenol A, Tg 145° C.) is used as the injection molding resin, and an injection molding machine with a mold clamping pressure of 50 t is used to form a plate-like laminate having an outer diameter of 104 mm×64 mm and an average thickness of 2.0 mm as shown in FIG. 7. A front panel was made.
The cylinder temperature was 280° C. or 300° C., and the mold temperature was fixed at 80° C., and insert molding was performed. The gate was provided on the short side and was set so that the flow direction of the resin and the slow axis of the retardation film were substantially in the same direction.

In Example 1, the polycarbonate retardation film 1 having an in-plane retardation of 5500 nm was used as an insert film, and the cylinder temperature was set to 280° C. to produce an insert molded product, that is, a laminated front panel.
In Example 2, the polycarbonate retardation film 1 having an in-plane retardation of 5500 nm was used as an insert film, and the cylinder temperature was set to 300° C. to produce an insert molded product, that is, a laminated front panel.
In Example 3, the polycarbonate retardation film 2 having an in-plane retardation of 3260 nm was used as an insert film, and the cylinder temperature was set to 280° C. to produce an insert molded product, that is, a laminated front panel.
In Example 4, the polycarbonate retardation film 2 having an in-plane retardation of 3260 nm was used as an insert film, and the cylinder temperature was set to 300° C. to produce an insert molded product, that is, a laminated front panel.

As a result of observing a cross section of each of the laminated front panels obtained in Examples 1 to 4 with an optical microscope, it is found that there is no clear bonding interface between the transparent panel, that is, the injection-molded resin portion and the retardation film. confirmed.

In Comparative Example 1, a polycarbonate retardation film 3 having an in-plane retardation of 2750 nm was used as an insert film, and a cylinder temperature was set to 280° C. to produce an insert molded product, that is, a laminated front panel.
In Comparative Example 2, a polycarbonate retardation film 3 having an in-plane retardation of 2750 nm was used as an insert film, and a cylinder temperature was set to 300° C. to produce an insert molded product, that is, a laminated front panel.

(Phase difference measurement method)
The in-plane retardation was measured using a retardation measuring device KOBRA-WR (manufactured by Oji Scientific Instruments).
The test piece is set in the cutting device, the phase difference measurement software KOBRA-RE is started, the measurement method is set to high phase difference, and the measurement is performed with light having a wavelength of 446.1 nm to 749.2 nm, and light having a wavelength of 586.4 nm is used. The measured value was defined as the in-plane retardation.

The in-plane retardation is the refractive index Nx in the slow axis direction (direction showing the maximum refractive index in the film plane) in the plane of the test piece, the fast axis direction in the same plane (direction orthogonal to the slow axis direction). It is a value represented by (Nx-Ny)*d using the refractive index Ny of and the film thickness d (nm). Nx-Ny is shown as a birefringence value Δn.
The in-plane retardation described below was measured in the same manner.

<Liquid crystal display device for evaluation>
As shown in FIG. 2, a liquid crystal cell having a pseudo white backlight light source (C) in which a blue LED and a yellow phosphor are combined and a polarizing plate (B) on the viewer side is provided on the viewer side as described above. The laminated front panel prepared in Example 1 was laminated to obtain a liquid crystal device for evaluation.
Since the absorption axis of the viewing side polarizing plate (B) of the liquid crystal cell is inclined by 45° from the vertical direction of the screen, the absorption axis of the polarizing plate and the slow axis of the retardation film of the laminated front panel form The angle is 45°, which is the positional relationship in which the highest transmitted light intensity is obtained during observation with crossed Nicols.

(Effect judgment method)
With the liquid crystal cell emitting white light, the display state of the image was observed at a position where the polarizing plate regarded as polarized sunglasses was in a crossed Nicols relationship with the polarizing plate on the viewing side of the liquid crystal display device. Further, the angle of the polarizing plate was changed from the crossed Nicols relation to the parallel Nicols relation, and the image display state was observed in the same manner. In order to avoid the influence of irregular resin flow in the vicinity of the gate and the end of the molded product, the evaluation site was within the range shown in FIG. 7 (90 mm×50 mm in the central part of the molded product). The judgment was based on the presence/absence of interference colors, the brightness of the screen, and the presence/absence of color changes within this range. A combination in which no interference color, which is harmful to the visibility of the image, is visible and the brightness does not significantly change even when the angle of the polarizing plate is changed was determined to be “good”. On the other hand, when an interference color was generated, it was determined as “x”. Table 1 shows the determination results in each of the examples and comparative examples.

At the same time, injection molding was carried out under the same conditions without the retardation film being arranged, and the tendency of the appearance of the retardation generated during injection molding was confirmed. As a result, in the region of the above-mentioned evaluation site, no portion where the angle formed by the slow axis of the retardation generated during injection molding and the slow axis of the retardation film (E) exceeds 45° was observed. Therefore, it was confirmed that the retardation generated in the injection-molded layer (D) was not in the positional relationship of reducing the retardation of the retardation film (E) within the evaluation region.

Further, as shown in FIG. 7, the phase difference was measured along the central portion of the laminated front panel. The slow axis generally coincided with the direction of the slow axis of the retardation film (E), and the value thereof decreased as the distance from the gate increased.
FIG. 8 shows the distance dependence from the gate in the case of molding at a cylinder temperature of 300° C. The retardation at a position sufficiently distant from the gate is an extremely small value as compared with the retardation of the retardation film (E), and is a numerical value that hardly affects the retardation value of the laminated front panel (F). It is believed that there is.

In Examples and Comparative Examples of the present invention, as shown in FIG. 7, the numerical value of the lower end portion (the portion farthest from the gate) of the evaluation region was used as the retardation value of the sample. In this example and the comparative example, the numerical value of this portion is the minimum value of the laminated front panel, and this value was used as the evaluation index.

From the results of Table 1, the examples satisfy the constituent requirements of the invention of the present application and show excellent characteristics in improving the visibility of the liquid crystal display device when wearing polarized sunglasses. On the other hand, in each of the comparative examples, the retardation value of the retardation film (E) is insufficient, and the retardation after insert molding is also insufficient. It is inferior to the result.

Claims (5)

A method for producing a laminated front panel, comprising a structure in which a retardation film (E) having an in-plane retardation (ReE) satisfying the formula (1) below is arranged on the back surface side of the injection-molded layer (D). There
The retardation film (E) is placed in a mold in advance so that the angle between the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55°, and melted. The injection-molded layer (D) and the retardation film (E) are insert-molded by injecting the molded thermoplastic resin for forming an injection-molded layer into the mold to mold the injection-molded layer. Manufacturing method.
(1) 3000 nm<ReE≦100,000 nm A method of manufacturing a laminated front panel according to claim 1,
A method for manufacturing a laminated front panel, which comprises directly bonding the injection-molded layer (D) and the retardation film (E). A method of manufacturing a laminated front panel according to claim 1,
A method for manufacturing a laminated front panel, comprising bonding an injection molding layer (D) and a retardation film (E) via an adhesive layer (F). The method for producing a laminated front panel according to claim 1, wherein a mold temperature during injection molding is set to a temperature lower than Tg of the retardation film (E). At least in the image display region, the angle formed by the slow axis of the retardation film (E) and the slow axis of the retardation of the injection molding layer (D) generated during injection molding of the injection molding layer (D) is 45°. The method for producing a laminated front panel according to any one of claims 1 to 4, wherein the thermoplastic resin for forming an injection-molded layer is injected into the mold so as to be within the range.

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