JP6886761B2 - Laminated front panel and its manufacturing method - Google Patents

Description

The present invention relates to a display device mounted on an automobile, an aircraft, a ship, etc., a mobile device such as a smartphone, a tablet terminal, a portable game device, a digital camera, and a digital signage installed in a public space, a storefront of a commercial facility, or the like. The present invention relates to a laminated front panel and a method for manufacturing the same, in a liquid crystal display device used as an image display device of another device, particularly a liquid crystal display device provided with a polarizing plate, which is arranged and used on the visible side of the polarizing plate.

In recent years, more and more liquid crystal display devices are used outdoors. For example, display devices mounted on automobiles, aircraft, ships, etc., mobile devices such as smartphones, tablet terminals, mobile game devices, digital cameras, and 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 a "front panel" or "front panel") on the visible surface for the purpose of preventing scratches and damage.

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 non-breakability.
For example, Patent Document 1 discloses a resin laminate obtained by laminating a hard coat layer on a laminate obtained by co-extruding a polycarbonate resin and an acrylic resin.
Further, in Patent Document 2, as a laminated extruded resin plate for a touch panel whose surface is not easily scratched and which is relatively easy to manufacture, an acrylic resin layer is coextruded on at least the surface of the polycarbonate resin layer on the touched side. A laminated extruded resin plate for a touch panel, characterized in that it is laminated, is disclosed.

As described above, since the number of liquid crystal display devices used outdoors is increasing, the chances of wearing polarized sunglasses to visually recognize the display screen of the liquid crystal display device are also increasing.
Many liquid crystal display devices are provided with a linear polarizing plate on the visual side, and in such a liquid crystal display device, the observer sees the linearly polarized light emitted from the polarizing plate, so that the observer sees polarized sunglasses. When observing the display screen with the LCD display device attached, various problems may occur due to the positional relationship between the absorption axis of the polarizing plate on the visual side of the liquid crystal display device and the absorption axis of the sunglasses. For example, if a member having a phase difference does not intervene between the polarizing plate on the visual side of the liquid crystal display device and the polarized sunglasses of the observer, it is completely assumed that the absorption axes of these polarizing plates and the polarized sunglasses are orthogonal to each other. It becomes invisible. Further, if a member having a phase difference is interposed between them, the screen may be darkened, undesired coloring may occur, interference colors may be seen, or the like, and an accurate display can be recognized depending on the positional relationship between the two polarizing axes. Sometimes it disappeared.

In order to provide a liquid crystal display device capable of ensuring highly good visibility regardless of the observation angle when the screen is observed through a polarizing plate such as a polarizing plate when a member having a phase difference does not intervene. Patent Document 4 (Japanese Unexamined Patent Publication No. 2012-230390) describes a white light emitting diode as a backlight light source in a liquid crystal display device having at least a backlight light source, a liquid crystal cell, and a polarizing plate arranged on the visible side of the liquid crystal cell. The angle between the absorption axis of the polarizing plate and the slow axis of the polymer film of a polymer film having a phase difference of 3000 to 30,000 nm on the visible side of the polarizing plate is approximately 45 degrees. A method for improving the visibility of a liquid crystal display device, which is characterized in that it is arranged and used in such a manner, has been proposed.

Furthermore, the plastic cover material made by injection molding can be easily manufactured even if it has a special shape such as a curved shape, a shape with an opening, a shape with a curved end, a circular shape, or a non-rectangular shape such as a heart shape. Therefore, it is suitably used as a cover material for the liquid crystal display device as described above. However, when this type of plastic cover material is injection-molded, orientation occurs in the flow direction of the molding resin, and a phase difference having an optic axis in the flow direction of the resin occurs. Further, since the flow of the resin in the molding die is not uniform, it often has various orientation angles and phase differences of various values depending on the location in the injection molding member. In particular, when the cover material has parts with different thicknesses, curved surfaces, 3D shapes, openings, etc., in the vicinity of the gate, peripheral parts with different thicknesses and shapes, etc. Large phase difference variations occur, and visibility when wearing polarized sunglasses is significantly impaired.

Therefore, as a display device capable of preventing variations in display such as coloration and unevenness of shading depending on the location even when observing through a polarizing plate such as polarized sunglasses when a cover material having a phase difference is interposed, Patent Document 3 (Special Open 2005-157082), a display element having a polarizing plate on the foremost surface, 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. A display device having a translucent optical element having an in-plane phase difference, which is arranged between the translucent cover and reducing the influence of the phase difference of the translucent cover on human visibility, has been proposed. ..

Japanese Unexamined Patent Publication No. 2006-103169 Japanese Unexamined Patent Publication No. 2010-182263 Japanese Unexamined Patent Publication No. 2005-157082 Japanese Unexamined Patent Publication No. 2012-230390

However, as described above, since the injection-molded member may have a large variation in phase difference and various directions of the phase difference, a liquid crystal having a panel material formed by injection molding on the visible side of the polarizing plate. In a display device, the effect of improving visibility is often not sufficient simply by arranging a polymer film having a phase difference as disclosed in Patent Document 3 and the like. In particular, when the phase difference of the retardation film is close to the lower limit, or when the optical axis of the phase difference of the injection panel member has a portion where the optical axis changes rapidly, the interference color is observed and visually recognized. The sexual improvement effect 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 laminating method is not fixed to the cover material via an adhesive or the like, the retardation film may shift or the retardation film may be deformed, resulting in deterioration of visibility, which is a practical problem. Occurs. Further, even in the case of the laminating method of fixing via an adhesive or an adhesive, it may be difficult to bond the cover material depending on the shape of the cover material. In particular, when the cover material has a curved surface, another three-dimensional shape, or an opening, a concave portion, or a convex portion, it may not be possible to bond the cover material itself.

Therefore, an object of the present invention is to ensure visibility of a laminated front panel used by arranging it on the viewing side in a liquid crystal display device having a polarizing plate on the viewing side, even when observing with polarized sunglasses worn. It is an object of the present invention to provide a new laminated front panel capable of forming a capable liquid crystal display device, a method for manufacturing the same, and a liquid crystal display device for arranging and using 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 visual side of the liquid crystal cell (A), and a backlight light source (C) having a continuous emission spectrum. A laminated front panel that is arranged and used on the visible side of the polarizing plate (B) in the apparatus.
It has an image display area when viewed from the visual side,
On the back surface side of the injection-molded layer (D), a retardation film (E) having an in-plane retardation (ReE) satisfying the following formula (1) is arranged, and the injection-molded layer (D) and the retardation film (D) E) is directly bonded and arranged so that the angle formed by the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55 °.
We propose a laminated front panel characterized in that the phase difference (ReH) of the laminated front panel in the image display area satisfies the following equation (2).
(1) 3000 nm <ReE ≤ 100,000 nm
(2) 3000 nm ≤ ReH

The present invention also includes a liquid crystal cell (A), a polarizing plate (B) arranged on the visual side of the liquid crystal cell (A), and a backlight light source (C) having a continuous emission spectrum. A laminated front panel used by arranging it on the visual side of the polarizing plate (B) in a display device.
It has an image display area when viewed from the visual side,
On the back surface side of the injection-molded layer (D), a retardation film (E) having an in-plane retardation (ReE) satisfying the following formula (1) is arranged, and the injection-molded layer (D) and the retardation film (D) It is bonded to E) via an adhesive layer (F), and the 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
We propose a laminated front panel characterized in that the phase difference (ReH) of the laminated front panel in the image display area satisfies the following equation (2).
(1) 3000 nm <ReE ≤ 100,000 nm
(2) 3000 nm ≤ ReH

The present invention also has a laminated front having a configuration in which a retardation film (E) having an in-plane retardation (ReE) satisfying the following formula (1) is arranged on the back surface side of the injection molded layer (D). It ’s a panel manufacturing method.
The retardation film (E) is placed in a mold in advance so that the 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 melted. A laminated front panel characterized in that the injection molding layer (D) and the retardation film (E) are insert-molded by injecting the molded thermoplastic resin for forming an injection molding layer into the mold and molding the resin. Propose a manufacturing method for.
(1) 3000 nm <ReE ≤ 100,000 nm

The laminated front panel proposed by the present invention occurs when the laminated front panel is arranged and used on the visual side of the polarizing plate (B) in the liquid crystal display device, and is in an orthogonal Nicol relationship when observed with polarized sunglasses worn. Not only can the blackout phenomenon be avoided, but visibility deterioration due to the phase difference of the injection molded layer (D) can be prevented.

It is a top view which saw an example of the liquid crystal display device which concerns on one example of this invention from the visual side. It is a side sectional view which showed an example of the laminated front panel which concerns on one example of this invention. It is a side sectional view which showed an example of the liquid crystal display device which incorporated the laminated front panel of FIG. 2 in the disassembled state. It is a side sectional view which showed an example of the laminated front panel different from the laminated front panel of FIG. 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 a figure which showed an example of the injection molding layer which comprises the liquid crystal display device of this invention, (a) is the side sectional view, (b) is the perspective view when viewed from the visual side. It is a top view of the laminated front panel produced in an Example. It is a graph which showed the relationship between the distance from a gate and a phase difference at the time of molding at a cylinder temperature of 300 degreeC.

Next, the present invention will be described based on examples of embodiments. However, the present invention is not limited to the embodiments 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 visual side, and as shown in FIG. 3, the liquid crystal cell (A) and the laminated front panel. , A liquid crystal display device (referred to as "the present liquid crystal display device") including a polarizing plate (B) arranged on the visual side of the liquid crystal cell (A) and a backlight light source (C) having a continuous emission spectrum. ), The laminated front panel is arranged and used on the visible side of the polarizing plate (B), and has an in-plane phase difference (ReE) in a predetermined range on the back surface side of the injection molding layer (D). A film (E) is arranged.

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

<Phase difference film (E)>
The material and structure of the retardation film (E) constituting the laminated front panel are not limited as long as the in-plane retardation (ReE) is larger than 3000 nm and 100,000 nm or less.

When a member having a phase difference is placed between two polarizing plates having an orthogonal Nicol relationship and white light is observed, it 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 exists in a large number of wavelength regions, so that the observer can recognize it as white light. On the other hand, a material having an in-plane phase difference (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 larger than 3000 nm and less than 100,000 nm. It is more preferably 4000 nm or more or 50,000 nm or less, and more preferably 5000 nm or more or 20000 nm or less in consideration of the production surface of the retardation film (E).
The in-plane retardation (ReE) of the retardation film (E) is an average value obtained by measuring in-plane retardations at any plurality of locations, for example, five locations, which are different from each other in the orthogonal direction in the slow axis direction. Is preferably the in-plane phase difference (ReE).

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

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

As the polycarbonate, aromatic polycarbonate mainly composed of bisphenol A, and as the polyester, polyethylene terephthalate, polyethylene naphthalate, polycyclohexylene methylene terephthalate and the like can be mentioned as particularly preferable base resins. Further, as the polyamide, semi-aromatic polyamides such as PA6T and PA9T, which have a relatively high Tg and can maintain transparency even when oriented and crystallized, are particularly suitable.

The retardation film (E) is an alignment film obtained by stretching a substantially non-oriented sheet obtained by an appropriate method such as a melt extrusion method or a casting method from the base resin exemplified above in a specific direction. Is preferable.
For example, in the case of an oriented polycarbonate film, a non-oriented sheet obtained by melting polycarbonate and extruding it into a sheet is stretched in one direction or, if necessary, in two directions at a temperature equal to or higher than the glass transition temperature. An oriented polycarbonate film having a phase difference of can be used.
On the other hand, in the case of an oriented polyester film or an oriented polyamide film, it is obtained by melting a resin and stretching and heat-treating an unaligned sheet extruded into a sheet at a temperature equal to or higher than the glass transition temperature in at least one direction. Orientation film can be used.

Examples of the method for adjusting the retardation of the retardation film (E) include a method for 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 draw ratio is preferably 2.5 to 6.0 times, and more preferably 3.0 times or more or 5.5 times or less in the case of lateral uniaxial stretching. If the draw ratio is too high, the mechanical strength of the obtained film, particularly the problem of being easily torn in the stretching direction, is likely to occur. On the other hand, if the draw ratio is too low, the birefringence of the obtained film becomes small and the phase difference 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, the stretching temperature is preferably 150 to 180 ° C., particularly 155 ° C. or higher or 170 ° C. or lower. Is preferable. The draw 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 ensuring adhesiveness and a decorative layer printed on the above-mentioned non-image area on the adhesive surface with the injection molding layer described later. On the opposite surface thereof, for the purpose of improving the adhesiveness, water resistance, chemical resistance, etc. with the layers formed on the film such as the pressure-sensitive adhesive layer, the antireflection layer, and the antistatic layer. The surface of the film may be surface-treated by a known method, that is, a corona discharge treatment or an easy-adhesion treatment may be performed. In this case, the phase difference of the retardation film (E) of the present invention means the phase difference of the laminated film including the adhesive layer and the like.

Regarding the thickness of the retardation film (E), if it is thin, it is difficult to increase the retardation. Therefore, it is preferable that the retardation film (E) is thick in order to have a high retardation. At the time of insert molding, there is a possibility that the setting on the mold becomes difficult, the temperature of the retardation film (D) rises excessively, and the retardation disappears, and there is a limit to the thickness.
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), the intrinsic birefringence differs depending on the base resin, the expression state of the retardation difference differs, and the mechanical strength of the obtained alignment film differs depending on the material. It is particularly preferable to set the thickness of the occurrence of the phase difference. For example, when the base resin of the retardation film (E) is polycarbonate, it 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 molded layer (D)>
The injection-molded layer (D) includes a member having a curved surface shape, another three-dimensional shape, an opening, a convex shape portion, a concave shape portion, and the like, in addition to a sheet shape or a plate shape. Here, the three-dimensional shape is intended to have a shape having a Z axis (height, standing wall).

In general, injection-molded members often show phase differences of various values depending on the location, and may have various orientation axes depending on the shape. Therefore, the phase difference of the injection-molded layer (D) depends on the shape of the molded panel and the injection conditions, and it is possible to set the shape and the injection conditions so that the phase difference hardly occurs in the display region. However, there are many inconveniences such as impairing the degree of freedom in panel design and having to set unfavorable injection conditions.

Regions where the phase difference tends to be high or variations in the orientation direction are likely to occur include the vicinity of the gate, the region around the opening, the vicinity of parts having different thicknesses such as concave portions and convex portions, and non-rectangular regions such as circular and heart-shaped. Examples include the end of a molded panel for a liquid crystal panel having a shape. In such a region, in general, the phase difference is often 350 nm or more, which causes remarkable coloring due to interference when observing orthogonal Nicols, and it is necessary to consider the panel design so that the region is not used as 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 thermal deterioration of the resin, sink marks, short shots, weld lines, etc. may occur. To avoid these, a great deal of effort is required to review the mold design and set the injection conditions. Needed.

The present invention can avoid such inconveniences. For example, by expanding the display area of the liquid crystal display device, the degree of freedom in design can be increased, and the injection conditions can also be applied. You can enjoy the benefit of being able to expand the scope.

The resin material constituting the injection molding layer (D) is not particularly limited as long as it is a transparent thermoplastic resin. For example, exemplify a material whose base resin is 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. Can be done. Among them, polycarbonate, acrylic resin, polyester and the like can be preferably exemplified from the viewpoint of transparency and ease of molding. Above all, in the front panel used for the touch panel display for in-vehicle devices, a material using polycarbonate as a base resin is preferable from the viewpoint of anti-scattering property.

As the polyester resin, a low crystallinity polyester resin is preferable from the viewpoint of transparency, moldability, etc., for example, a copolymer in which a part of the acid component of polyethylene terephthalate is replaced with isophthalic acid or the like, or a glycol component. A copolymer or the like in which a part of the above is replaced with 1.4-cyclohexanedimethanol or the like is suitable.

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

Since the injection-molded layer (D) is formed by injection-molding, it is possible to take a form having a special shape as described above, and for example, in order to impart an antiglare effect, an image display is performed. It is also possible to form fine irregularities on the surface.
Further, as shown in FIG. 6, a display surface portion D1 having fine irregularities for imparting an antiglare effect corresponding to the image display area 1 of the liquid crystal display device and a high-class feeling corresponding to the image non-display area 2 are provided. It is also possible to provide a peripheral portion D2 having a smooth surface for holding the panel on the surface on the viewing side of the panel.

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 emitted light from the liquid crystal cell is excessively scattered. , There is no problem such as blurring of the image. From this point of view, 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 that impart antiglare properties are also useful in improving the visibility of the present invention. In particular, if there is a portion having a sudden phase difference change in the image display region 1 of the injection molded layer (D), a thin boundary line may be observed, although it does not affect the visibility. In such a case, the fine unevenness has the effect of diffusing the light emitted from the liquid crystal cell, and therefore has the effect of making the boundary line inconspicuous.
The arithmetic surface roughness (Ra) is an arithmetic mean 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 in order to give 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 an on-reflection angle of 60 ° and a mirror glossiness of 85% or more, and more preferably 90% or more.

The peripheral portion D2 may be formed with the peripheral edge portion as a curved surface, or may have a portion having a different thickness such as a stepped shape or a taber shape. Further, it is also possible to optionally 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 checkered pattern and a zigzag pattern can be added to appropriate places, and the back surface can be printed for decorative purposes.

<Manufacturing method of laminated front panel>
This laminated front panel is composed of the above-mentioned retardation film (E) and injection molding layer (D), and one of the features is that both layers are adhered at the time of injection molding. Specifically, in this laminated front panel, an injection molding layer is formed by arranging a retardation film (E) in a mold and injecting a molten thermoplastic resin into the mold to mold the laminated front panel. A laminated front panel having a structure in which (D) and a retardation film (E) are joined can be manufactured. The retardation film (E) arranged in the mold may be preformed according to the shape of the laminated front panel. Further, the injection molding may be normal injection molding, injection compression molding in which the resin is supplied and then molded by molding, or H & C molding in which the mold temperature is controlled for molding. May be good. However, the manufacturing method of the laminated front panel is not limited to such a manufacturing method.

(Laminated front panel 1)
As one of the embodiments of the present invention (referred to as a laminated front panel 1), an embodiment in which the injection molded layer (D) and the retardation film (E) are directly bonded to each other without an adhesive layer or the like can be mentioned. 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 material of the injection molded layer (D) and the retardation film (E) are the same material, but different materials may be used as long as the interface is sufficiently adhered. 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, the material of the retardation film (E) is preferably a composition mainly composed of an amorphous polymer.

From this point of view, the retardation film (E) is particularly preferably a resin based on polycarbonate, polystyrene, or amorphous polyester, and the resin forming the injection molding layer is adhered 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 in which the same polycarbonate is used as the base resin. This combination not only provides strong adhesiveness at the interface, but also has the advantage that the reflection loss at the interface is eliminated because the refractive indexes of both layers are the same. The polycarbonate referred to here is exemplified by an aromatic polycarbonate having bisphenol A as a constituent unit, but is not limited thereto.
When the materials of the injection-molded layer (D) and the retardation film (E) are a combination using the same polycarbonate as the base resin, when the vertical cross section of the laminated front panel is observed under a microscope, the injection-molded layer (D) and the retardation film (D) and the retardation film are observed. The feature that the interface with (E) is not observed can be mentioned.

(Laminated front panel 2)
The laminated front panel (referred to as “the main laminated front panel 2”) according to another example of the present embodiment is provided with an appropriate adhesive layer on the surface of the retardation film (E) in contact with the injection molded layer (D). There is also a form 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 film through 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 to facilitate adhesion.

The method for forming the adhesive layer is not particularly limited, and a known method may be used. Specifically, a layer that functions as an adhesive layer is formed by coextrusion or extrusion laminating, or is formed by coating a film before stretching, and then stretched to obtain a retardation film (E). The method can be given. 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 print layer in advance on an image non-display area or the like. In this case, it is also possible to provide an adhesive layer in the printing process.

Since the injection-molded layer (D) and the retardation film (E) are bonded to each other via the adhesive layer (F) in the laminated front panel 2, the injection-molded layer (D) and the position are different from those of the laminated front panel 1. There are few restrictions on the selection of the base resin for the retardation film (E), and the materials can be freely designed for each. Therefore, as the retardation film (E), a film using crystalline polyester as a base resin, which is thin and easily obtains a high retardation, can be selected, and the injection molding layer is heat-resistant and transparent. A material using polycarbonate having excellent properties and impact resistance as a base resin can be selected as a preferable example.

(Laminated front panels 1 and 2)
As described above, the laminated front panels 1 and 2 are molded by injecting a molten resin into a retardation film (E) previously arranged in a mold. At this time, the retardation film (E) includes the absorption axis of the visible side polarizing plate (B) of the liquid crystal cell in which the laminated front panels 1 and 2 are put into practical use and the slow axis of the retardation film (E). It is necessary to arrange it in the mold so that the angle between the two is within a limited range.

Generally, when a member having a phase difference is inserted between orthogonal Nicols to transmit white light, the transmitted light is transmitted when the angle between the absorption axis of the polarizing plate and the slow axis of the member having the phase difference is 45 °. Maximum strength. When the laminated front panels 1 and 2 are incorporated into the liquid crystal display device, the angle between the slow axis of the retardation film (E) of the laminated front panel and the absorption axis of the polarizing plate (B) is 45 °. Most preferably, the retardation film (E) is positioned and laminated, and practically, the retardation film (E) is preferably positioned and laminated so as to have a temperature of 35 to 55 °. By arranging the retardation film (E) in the mold in this way, it is possible to secure a practically sufficient transmitted light intensity when wearing sunglasses.
From this point of view, 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-molded layer (D) have an angle formed by the slow axis of the retardation film (E) and the slow-phase axis of the injection-molded layer (D) in the image display region. It is preferable to take care so that it is within 45 °.

The value of the phase difference of the injection-molded layer (D) varies greatly depending on its shape and molding conditions. For example, when the injection-molded layer (D) is molded under conditions that cause a large retardation, the phase difference between the laminated front panels 1 and 2 is ejected depending on the angle formed with the retardation film (E). The value may be smaller than the phase difference of the retardation film (E) before molding. Generally, when members having two phase differences are laminated, the phase difference as the laminated member has an additive relationship when the angle formed by the slow phase axis is 45 ° or less, and is 45 ° or more. Then, it becomes a mutual decrease relationship. Therefore, the injection-molded layers (D) of the laminated front panels 1 and 2 may be injection-molded so that the slow-phase axis thereof forms an angle of 45 ° or less with the slow-phase axis of the retardation film. preferable. If this relationship can be maintained, the laminated front panel of the present invention can ensure good visibility when observing while 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, the front It is necessary to pay attention to the panel shape design, mold design, gate position and shape, etc. Since the optical axes of the phase difference developed during injection molding of the injection molding layer (D) substantially coincide with the flow direction, the flow of the molding resin in the mold may be particularly considered. Specifically, when the resin forming the injection molded layer (D) is a material that exhibits positive birefringence, the resin is allowed to flow in a direction parallel to the slow axis of the retardation film (E). It should be. When the resin forming the injection-molded layer (D) is a material that exhibits negative birefringence, the resin may be allowed to flow in the direction of the phase-advancing axis of the retardation film (E). Further, since it is necessary to align the flow directions in the image display region, the film gate method in which the flow of the resin becomes uniform is preferable.
At this time, the magnitude of the phase difference of the injection-molded layer (D) and the direction of the slow-phase axis can also be obtained by a known method from the measured values of the obtained laminated front panels 1 and 2.

Since the laminated front panels 1 and 2 have a feature of adhering 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 decrease does not occur. At the same time, consideration must be given to prevent harmful effects on the front panel such as deformation of the film and increase in haze. Specifically, conditions such as injection molding temperature, injection molding speed, mold structure, mold set temperature, and gate position can be set, but from the viewpoint of reducing the phase difference of the retardation film (E). It is the temperature of the mold that needs special attention.

The temperature of the mold at the time of the injection resin is preferably set to be 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), if the retardation film (E) is an amorphous resin, the retardation may be reduced, which is not preferable. Further, in the case of a crystalline resin, unfavorable phenomena such as crystallization progressing to increase the haze or shrinkage causing deformation of the film may occur. However, in the case of heat & cool molding in which injection molding is performed by controlling the heating and cooling of the mold temperature, the mold temperature shifts to the glass of the retardation film (E) if the heating time is sufficiently controlled. Even if the temperature (Tg) is exceeded, it may be feasible.
With such consideration, the effect of the present invention can be enjoyed if the phase difference (ReH) of the obtained laminated front panels 1 and 2 satisfies the following equation (2).
(2) 3000 nm ≤ ReH

<Thickness of this laminated front panel>
The average thickness of the laminated front panel varies depending on the application, but is preferably about 0.5 mm to 5 mm. If it is 0.5 mm or less, deformation and warpage when taken out 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 more 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 as to be, and more preferably 5% or more or 15% or less. By setting the ratio of the thickness of the retardation film (E) to the above lower limit value or more, it is possible to facilitate the installation in the mold and prevent the film from being deformed during injection molding. Further, by suppressing the ratio within the above range, the cooling from the mold wall surface becomes insufficient, and the risk of causing a decrease in the phase difference is suppressed.

<Others>
Since the laminated front panel may have the above configuration, another member or another functional coat layer may be provided on the visible side or the back side thereof. Examples of other members include, but are not limited to, a hard coat film, an antireflection film, an antifouling coat film, a touch sensor, and a louver film. The member may be formed by insert molding at the time of injection molding, or may be formed as a laminated front panel by bonding with an adhesive or an adhesive after injection molding.

Further, examples of the other functional coat layer include a hard coat, an antireflection coat, an antistatic coat, and an antifouling coat, if necessary. Examples of the coating layer forming method include a coating method using an inkjet, a silk screen, a gravure roll, or the like, in addition to a dip coating and a spray coating. However, it is not limited to these.

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

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

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

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

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 source (C) is a set of monochromatic light having a narrow half-value 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. Since the interference color does not disappear, it is difficult to enjoy the effect of the present invention. On the other hand, in the case of continuous light having a continuous emission spectrum such as a white LED, if the phase difference 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 "continuous emission spectrum" means light that does not separate into individual line spectra when viewed with a spectroscope, and produces a spectrum that is continuously expanded with respect to wavelength, and is preferably a visible light wavelength. It is a spectrum that includes all light of any wavelength in the range. For example, the emission spectrum of a light emitting diode (LED), an electroluminescence panel, or the like is a continuous emission spectrum, while the emission spectrum of a cold cathode tube, a hot cathode, or the like is not a continuous emission spectrum.

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

If necessary, other constituent members can be arranged between the laminated front panel and the polarizing plate (B) on the visual side of the liquid crystal cell (A), but a member having a phase difference of a certain level or more can be arranged. It is not preferable to arrange it between them. When a member having a phase difference intervenes, good visibility can be obtained when the polarized sunglasses have an orthogonal Nicol relationship with the polarizing plate (B), but at other angles, the phase difference of the intervening member Corresponding coloring may be seen and visibility may deteriorate. From this point of view, when the laminated front panel constitutes a liquid crystal display device, it is preferable that a member having a phase difference of 600 nm or more does not intervene between the laminated front panel and the polarizing plate (B). Above all, it is more preferable that a member having a phase difference of 400 nm or more does not intervene.

Here, as an example of a member having no phase difference, a transparent adhesive or an 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 also a method of fixing with screws or double-sided tape in the non-image display part, but as a means of reducing the interfacial reflection of the image display part, the entire surface of the display part is transparent without a 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 liquid, gel-like, or film-like. Further, it may have a hot melt property or may not have a hot melt property. Further, it may be further crosslinked and cured by irradiation with ultraviolet rays or the like.
Further, as another example, a touch panel sensor made 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 mentioned.

<Explanation of words>
When expressed as "X to Y" (X and Y are arbitrary numbers) in the present specification, unless otherwise specified, they mean "X or more and Y or less" and "preferably larger than X" or "preferably Y". It also includes the meaning of "smaller".
Further, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it means "preferably larger than X" or "preferably less than Y". Intention is also included.

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

Further, in the present specification, the "visual recognition side" means a side on which display light is emitted from the display screen and a side for observing the display on the front panel.
The "back side" means the side opposite to the "visual side", and means the side on which the display light from the display screen enters.
"Transparent" is not limited to colorless and transparent, but also includes colored transparent.

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

<Manufacturing 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 160 ° C. by a roll stretching method to obtain the thickness of the original sheet. Adjusting the draw ratio, the thickness 300 μm, in-plane retardation 5500 nm polycarbonate retardation film 1, thickness 125 μm, in-plane retardation 3260 nm polycarbonate retardation film 2, thickness 80 μm, in-plane retardation A 2750 nm polycarbonate retardation film 3 was obtained.

<Manufacturing of laminated front panel>
Polycarbonate retardation films 1, 2 and 3 as insert films are arranged on the cavity surface in the mold so that their slow axes coincide with the long side direction of the laminated front panel as an insert molded product. The 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 a plate-shaped laminate having an outer diameter of 104 mm × 64 mm and an average thickness of 2.0 mm is shown in FIG. The front panel was made.
Further, insert molding was carried out with the cylinder temperature fixed at 280 ° C. or 300 ° C. and the mold temperature fixed at 80 ° C. 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 the same direction.

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

As a result of observing the 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 the 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 an insert molded product, that is, a laminated front panel was manufactured by setting the cylinder temperature to 300 ° C.

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

The in-plane phase difference is the refractive index Nx in the slow-phase axial direction in the test piece (the direction showing the maximum refractive index in the film plane) and the in-plane phase-advancing axial direction (direction orthogonal to the slow-phase axial direction). It is a value indicated by (Nx−Ny) × d using the refractive index Ny of and the film thickness d (nm). Nx-Ny is shown as the birefringence value Δn.
The in-plane phase difference described later was also measured in the same manner.

<Liquid crystal display device for evaluation>
As shown in FIG. 2, as described above, a liquid crystal cell having a pseudo-white backlight source (C) in which a blue LED and a yellow phosphor are combined and having a polarizing plate (B) on the viewing side is on the viewing side. The laminated front panel created in 1 was laminated to form an evaluation liquid crystal device.
Since the absorption axis of the viewing side polarizing plate (B) of the liquid crystal cell is tilted 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 are formed. The angle is 45 °, which is a positional relationship in which the highest transmitted light intensity can be obtained when observing with an orthogonal Nicol.

(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 relationship of orthogonal Nicol with the polarizing plate on the visual side of the liquid crystal display device. Further, the angle of the polarizing plate was changed from the relationship of orthogonal Nicols to the relationship of parallel Nicols, and the display state of the image was observed in the same manner. The evaluation site was set to the range shown in FIG. 7 (center portion of the molded product 90 mm × 50 mm) in order to avoid the influence of irregular resin flow in the vicinity of the gate and the end portion of the molded product. The judgment was based on the presence or absence of interference colors within this range, the brightness of the screen, and the presence or absence of color changes. A combination in which no interference color, which is harmful to the visibility of the image, was visible and the brightness did not change significantly even when the angle of the polarizing plate was changed was judged as "○ good". On the other hand, when an interference color occurs, it is determined as "x". Table 1 shows the determination results in each Example / Comparative Example.

At the same time, injection molding was performed under the same conditions without arranging the retardation film, and the tendency of the retardation generated during injection molding was confirmed. As a result, in the region of the evaluation site, a 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 not observed. Therefore, in the evaluation region, it was confirmed that the phase difference generated in the injection molded layer (D) does not have a positional relationship that reduces the phase difference of the retardation film (E).

Further, as shown in FIG. 7, the phase difference was measured along the central portion of the laminated front panel. The slow-phase axis generally coincided with the direction of the retard-phase axis of the retardation film (E), and the value decreased as the distance from the gate increased.
FIG. 8 shows the distance dependence from the gate when molding is performed at a cylinder temperature of 300 ° C. The phase difference at a position sufficiently distant from the gate is an extremely small value as compared with the phase difference of the retardation film (E), and is a numerical value that has almost no effect on the phase difference value of the laminated front panel (F). It is believed that there is.

In the examples and comparative examples of the present invention, as shown in FIG. 7, the numerical value at the lower end of the evaluation region (the part farthest from the gate) was used as the phase difference 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 is used as an evaluation index.

From the results shown in Table 1, the examples satisfy the constituent requirements of the present invention 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 phase difference after insert molding is also insufficient. The result was inferior to that.

Claims (4)

A method for manufacturing a laminated front panel having a configuration in which a retardation film (E) having an in-plane retardation (ReE) satisfying the following formula (1) is arranged on the back surface side of the injection molding layer (D). There,
The retardation film (E) is placed in a mold in advance so that the angle formed by the slow axis of the retardation film (E) and the absorption axis of the polarizing plate (B) is 35 to 55 °.
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 phase difference of the injection molding layer (D) generated during injection molding of the injection molding layer (D) is 45 °. The injection molding layer (D) and the retardation film (E) are insert-molded by injecting the molten thermoplastic resin for forming an injection molding layer into the mold so as to be within the range. A method for manufacturing a laminated front panel characterized by.
(1) 3000 nm <ReE ≤ 100,000 nm The method for manufacturing a laminated front panel according to claim 1.
A method for manufacturing a laminated front panel, which comprises directly joining an injection-molded layer (D) and a retardation film (E). The method for manufacturing a laminated front panel according to claim 1.
A method for manufacturing a laminated front panel, which comprises joining an injection-molded layer (D) and a retardation film (E) via an adhesive layer (F). The method for manufacturing a laminated front panel according to any one of claims 1 to 3, wherein the mold temperature at the time of injection molding is set to a temperature lower than Tg of the retardation film (E).

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