JP2019150952A - Cover panel and its manufacturing method - Google Patents

Abstract

To provide a cover panel capable of securing a good visibility which prevents occurrence of blackout and iridescent unevenness even when a liquid crystal display panel is observed through a polarizing panel such as polarizing sunglasses.SOLUTION: A transparent cover panel is used for protecting a front face of a liquid crystal display panel mounted on a vehicle and has a substrate layer and a surface layer, and both the substrate layer and the surface layer are made of polycarbonate resin, the thickness of the substrate layer is 0.5-10 mm and the thickness of the surface layer is 0.1-2 mm, a retardation value of the surface layer is 1500 nm or more and a retardation value of the whole cover panel is 2000 nm or more, and the cover panel is formed by directly bonding the substrate layer to the surface layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transparent cover panel that protects the front surface of a liquid crystal display panel mounted on an automobile. The present invention also relates to a method for manufacturing the cover panel.

  Liquid crystal displays (LCDs) are widely used for monitors of car navigation systems. A liquid crystal display panel used for an LCD has a configuration in which a liquid crystal cell composed of a color filter substrate, a liquid crystal layer, an array substrate, and the like is sandwiched between two polarizing filters. Therefore, when you look at the LCD with polarized sunglasses, the screen may appear dark depending on the angle (a phenomenon called “blackout”), or uneven color (also called “interference fringes” or “rainbow unevenness”). ) May be visible.

  For such problems, Patent Document 1 proposes a visibility improvement method. This method uses 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 disposed on the viewing side of the liquid crystal cell, and on the viewing side of the polarizing plate. , A polymer film having a retardation of 3000 to 30000 nm is used with an angle formed between the absorption axis of the polarizing plate and the slow axis of the polymer film being about 45 degrees. According to this method, even when the liquid crystal display screen is observed through a polarizing plate such as sunglasses, good visibility can be ensured regardless of the observation angle.

  In order to suppress the occurrence of blackout and interference fringes using a high retardation polymer film according to the visibility improving method described in Patent Document 1, the polymer film is used by pasting it on the surface of the component. It will be. However, this method requires a step of attaching a polymer film to the surface of the component, and there is a possibility that foreign matter is mixed between the component and the polymer film.

JP2011-107198A

  The present invention has been made to solve the above problems, and even when the liquid crystal display panel is viewed through a polarizing plate such as polarized sunglasses, the occurrence of blackout and rainbow unevenness is suppressed and good visibility is achieved. An object of the present invention is to provide a cover panel that can be secured.

  The above-described problem is a transparent cover panel that protects the front surface of a liquid crystal display panel mounted on an automobile; the cover panel has a base material layer and a surface layer, and the base material layer and the surface layer are both The cover panel is made of a polycarbonate resin, the substrate layer has a thickness of 0.5 to 10 mm, the surface layer has a thickness of 0.1 to 2 mm, and the surface layer has a retardation value of 1500 nm or more. This is solved by providing a cover panel having an overall retardation value of 2000 nm or more and having the base material layer and the surface layer directly bonded to each other.

  At this time, it is preferable that a scratch-resistant layer is further formed on the surface opposite to the surface layer. The cover panel is preferably curved or bent.

  The above-mentioned problem is a method for producing the above cover panel; a first step of mounting a polycarbonate film having a thickness of 0.1 to 2 mm and a retardation value of 1500 nm or more in the mold; It is also solved by providing a method for manufacturing a cover panel comprising a second step of injecting and filling a polycarbonate resin and a third step of taking out a molded product from the mold.

  At this time, it is preferable that the polycarbonate film is preliminarily thermoformed so as to match the shape of the mold and then mounted in the mold. In the first step, it is also preferable that the scratch-resistant film is mounted in a mold facing the mold.

  A preferred embodiment of the present invention is a liquid crystal display device in which the cover panel covers the front surface of the liquid crystal display panel and the surface layer of the cover panel is arranged in a direction facing the liquid crystal display panel.

  When the cover panel of the present invention is used, even when the liquid crystal display panel is viewed through a polarizing plate such as polarized sunglasses, the occurrence of blackout and rainbow unevenness can be suppressed and good visibility can be ensured.

It is a figure which shows an example of a molded article. It is a cross-sectional schematic diagram of a molded product. It is a figure which shows arrangement | positioning of a liquid crystal monitor, a molded article, and the polarizing plate for observation. 2 is a photograph of the appearance of a molded article taken at the time of evaluation in Example 1. FIG. 4 is a photograph of the appearance of a molded article taken at the time of evaluation in Example 4. 2 is a photograph of the appearance of a molded article taken during evaluation of Comparative Example 1. FIG. 2 is a photograph of the appearance of a molded article taken during evaluation of Reference Example 1. 6 is an external appearance photograph of a molded article taken at the time of evaluation in Reference Example 2.

  The present invention relates to a transparent cover panel that protects the front surface of a liquid crystal display panel mounted on an automobile. The cover panel of the present invention has a base material layer and a surface layer. The greatest feature of the present invention is that both the base material layer and the surface layer are made of polycarbonate resin, and the retardation value (hereinafter referred to as Re value) of the entire cover panel is 2000 nm or more. When the Re value is 2000 nm or more, even when the liquid crystal display panel is viewed through a polarizing plate such as polarized sunglasses, the occurrence of blackout and rainbow unevenness is suppressed and good visibility can be ensured.

  When manufacturing a cover panel, after forming a base material layer previously, the method of sticking a highly retardation polycarbonate film on the surface of the said base material layer with an adhesive agent can be considered. However, this method requires a step of attaching a polycarbonate film to the surface of the base material layer after the base material layer is formed, so that productivity is lowered. In addition, the adhesive layer may cause retardation unevenness and rainbow unevenness. Furthermore, there is a possibility that foreign substances are mixed between the base material layer and the surface layer, and when the cover panel is used under high temperature and high humidity, the base material layer and the surface layer may be peeled off.

  On the other hand, as a method for producing a cover panel, there is a method in which a polycarbonate film is mounted in a mold and then a polycarbonate resin is injected and filled into the mold to obtain a molded product. In this case, it was expected that when the molten high-temperature polycarbonate resin was in direct contact with the oriented polycarbonate film having a high retardation, the surface of the film was melted and the orientation was greatly relaxed. Therefore, even when an oriented polycarbonate film having a high Re value was used, it was considered that the Re value was greatly reduced. However, when insert molding was actually performed using an oriented polycarbonate film, it was surprisingly found that a practical Re value can be maintained by devising molding conditions.

  The base material layer in this invention consists of polycarbonate resin. The kind of polycarbonate resin is not particularly limited, and examples thereof include those obtained by interfacial polycondensation of dihydroxyaryl and phosgene in the presence of an alkali catalyst. Among them, a polycarbonate obtained by the reaction of bisphenol A and phosgene (bisphenol A type polycarbonate) is preferable.

  The polycarbonate resin may contain additives and the like as long as transparency and mechanical properties are not impaired. The Re value of the base material layer in the present invention is usually 500 nm or less.

  In the present invention, the base material layer has a thickness of 0.5 to 10 mm. When the thickness of the base material layer is less than 0.5 mm, the rigidity required as a component mounted on an automobile cannot be satisfied. The thickness of the base material layer is preferably 1 mm or more. On the other hand, when the thickness of the base material layer exceeds 10 mm, the production cost may increase. Moreover, it is not preferable also from a viewpoint of weight reduction of a motor vehicle. The thickness of the base material layer is preferably 6 mm or less, and more preferably 4 mm or less.

  The surface layer in the present invention is made of a polycarbonate resin. The polycarbonate resin described above can be used. The surface layer has a Re value of 1500 nm or more. When the Re value is less than 1500 nm, a cover panel that can suppress the occurrence of blackout and rainbow unevenness cannot be obtained. The Re value of the surface layer is preferably 2000 nm or more, and more preferably 3000 nm or more. On the other hand, the Re value of the surface layer is usually 10000 nm or less.

  In the present invention, the thickness of the surface layer is 0.1 to 2 mm. When the thickness of the surface layer is less than 0.1 mm, the Re value of the entire cover panel may not be 2000 nm or more. The thickness of the surface layer is preferably 0.2 mm or more, and more preferably 0.25 mm or more. On the other hand, when the thickness of the surface layer exceeds 2 mm, the production cost may increase. Moreover, it is not preferable also from a viewpoint of weight reduction of a motor vehicle. The thickness of the surface layer is preferably 1 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. The surface layer in the present invention is thinner than the substrate layer.

  In the cover panel of the present invention, the base material layer and the surface layer are directly bonded, and the base material layer and the surface layer are not bonded via an adhesive. The problems in the case of bonding via an adhesive are as described above. Such a problem does not occur because the base material layer and the surface layer are directly bonded, and a cover panel having excellent visibility can be manufactured with high productivity.

  The cover panel of this invention has the said base material layer and the said surface layer. Here, in the present invention, it is important that the Re value of the entire cover panel is 2000 nm or more. When the Re value is less than 2000 nm, blackout or rainbow unevenness occurs when the liquid crystal display panel is viewed with polarized sunglasses. The Re value is preferably 2300 nm or more, more preferably 2600 nm or more, still more preferably 3000 nm or more, and particularly preferably 3500 nm or more. On the other hand, the upper limit of the Re value is not particularly limited, but is usually 10,000 nm or less and preferably 8000 nm or less. Here, the Re value is a value obtained by measuring the Re value of the entire cover panel and calculating the average value.

  Since the cover panel of the present invention is provided on the front surface of a liquid crystal display panel mounted on an automobile, if the scratch resistance is insufficient, the user's switch operation may cause scratches and maintain a good appearance. There are cases where it is not possible. Therefore, it is preferable that a scratch-resistant layer is further formed on the surface opposite to the surface layer. From the viewpoint of high pencil hardness and excellent scratch resistance, the scratch-resistant layer is preferably made of an acrylic resin.

  At this time, the method for forming the scratch-resistant layer on the surface opposite to the surface layer is not particularly limited. For example, a scratch-resistant layer can be formed on the surface by sticking a film having scratch resistance performance using an adhesive. However, as will be described later, a method of forming a scratch-resistant layer by mounting a scratch-resistant film on a mold and injecting a polycarbonate resin into the mold is preferable. According to this method, the process of attaching the scratch-resistant film becomes unnecessary, and foreign substances can be prevented from being mixed between the base material layer and the scratch-resistant layer.

  In addition to the scratch-resistant layer, a layer having another function may be further formed on the surface opposite to the surface layer. Examples of the other layers include an antireflection layer (antiglare and antireflection layer) and a fingerprint adhesion prevention layer (antifinger layer). In addition, when the base material layer itself has scratch resistance, it may not be necessary to form the scratch resistance layer.

  The cover panel of the present invention is transparent and protects the front surface of a liquid crystal display panel mounted on an automobile. Here, the term “transparent” means that the display content of the liquid crystal display panel is transparent enough to be visually recognized. The cover panel of the present invention only needs to be able to visually recognize the display content of the liquid crystal display panel, and other portions (such as the edge of the cover panel) may be printed, painted, plated, or the like. Absent.

  In the present invention, the cover panel is preferably curved or bent. In recent years, a panel of a car navigation system mounted on an automobile has many curved surfaces from the viewpoint of design and operability. When the cover panel is curved or bent, the degree of freedom in designing the panel is increased and the design is improved.

  A preferred method for producing the cover panel of the present invention includes a first step of mounting a polycarbonate film having a thickness of 0.1 to 2 mm and a Re value of 1500 nm or more in a mold, and a polycarbonate resin in the mold. A second step of injecting and filling and a third step of taking out the molded product from the mold.

  In the first step, a polycarbonate film having a thickness of 0.1 to 2 mm and an Re value of 1500 nm or more is mounted in the mold. The surface shape of the mold used at this time may be flat, or may be curved or bent. The polycarbonate film used at this time is a stretched film and has an orientation axis in a specific direction. In addition, let the axis | shaft which shows a large refractive index among orientation axes be a slow axis.

  When the thickness of the polycarbonate film is less than 0.1 mm, the retardation value of the entire cover panel may not be 2000 nm or more. The thickness of the polycarbonate film is preferably 0.2 mm or more, and more preferably 0.25 mm or more. On the other hand, when the thickness of the polycarbonate film exceeds 2 mm, the production cost may increase. Moreover, it is not preferable also from a viewpoint of weight reduction of a motor vehicle. The thickness of the polycarbonate film is preferably 1 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less.

  Moreover, when the Re value of the polycarbonate film is less than 1500 nm, it is not possible to obtain a cover panel that can suppress the occurrence of blackout and rainbow unevenness. The Re value of the polycarbonate film is more preferably 2500 nm or more, further preferably 3000 nm or more, and particularly preferably 3500 nm or more. On the other hand, the Re value of the polycarbonate film is usually 10000 nm or less and preferably 8000 nm or less.

  Here, as described above, the polycarbonate film used in the first step has a slow axis. However, when the polycarbonate film is mounted in a mold, the direction of the slow axis is not particularly limited. However, it is preferable to mount the polycarbonate film so that the angle formed by the slow axis with respect to the direction of the absorption axis of the polarizing filter provided on the viewing side (front side) of the liquid crystal monitor to be protected is appropriate. . The blackout occurs when the angle formed by the absorption axis of the polarizing filter used on the viewing side of the liquid crystal monitor and the absorption axis of the polarized sunglasses becomes a right angle. Therefore, when the liquid crystal monitor is protected by the cover panel, the polycarbonate film is placed in the mold so that the angle formed by the absorption axis of the polarizing plate (viewing side) of the liquid crystal monitor and the slow axis of the polycarbonate film is 45 °. It is preferable to attach to.

  In the second step, a polycarbonate resin is injected and filled into the mold. The surface shape of the mold used at this time may be flat, or may be curved or bent. The molding conditions at the time of injection molding are not particularly limited, but the resin temperature at the time of injection is preferably 200 to 350 ° C. The mold temperature is preferably 150 ° C. or lower. When the mold temperature exceeds 150 ° C., excessive heat is transferred to the polycarbonate film by the melted polycarbonate resin, the orientation of the polycarbonate film is greatly relaxed, and the Re value may be greatly reduced. The mold temperature is more preferably 100 ° C. or less, further preferably 80 ° C. or less, particularly preferably 60 ° C. or less, and most preferably 50 ° C. or less. On the other hand, the mold temperature is usually 0 ° C. or higher. In a subsequent third step, the molded product is taken out from the mold.

  In the said manufacturing method, it is preferable to mount | wear an abrasion-resistant film in the metal mold | die facing the said metal mold | die in a 1st process. The scratch-resistant film used at this time may be a single layer or a multilayer. The layer structure in the case of a multilayer is not particularly limited, but from the viewpoint of adhesiveness and scratch resistance of the resin as the base material, it is composed of a layer made of polycarbonate resin (PC layer) / acrylic resin (PMMA layer) 2 It is preferable that it is a layer, and it is preferable to mount it in the mold so that the base resin and the PC layer are in contact with each other. In this case, the acrylic resin layer forms a scratch-resistant layer.

  In the manufacturing method, it is preferable that the polycarbonate film is pre-thermoformed so as to match the shape of the mold and then mounted in the mold. By doing so, the polycarbonate film can be accurately mounted in the mold and can be stably held in the mold. The thermoforming method is not particularly limited, and examples thereof include a vacuum / pressure forming method using a mold. The mold temperature in this case is usually 80 to 150 ° C., and the polycarbonate film is preheated before vacuum / pressure forming.

  In the above manufacturing method, after the polycarbonate resin is injected and filled in the mold (after the second step), one mold is changed to another mold, and a two-color molding method in which the resin is further injected It can also be adopted. In this case, it is possible to integrally form a cover panel that is further excellent in design.

  The kind of liquid crystal display panel protected by the cover panel of the present invention is not particularly limited. A liquid crystal display panel usually has a configuration in which a liquid crystal cell is sandwiched between two polarizing filters. The driving method of the liquid crystal cell is not particularly limited. For example, TN (Twisted Nematic), IPS (In-Plane Switching), VA (Vertically Alignment), STN (Super Twisted Nematic), HAN (Hybrid Aligned Nematic) ), ECB (Electrically Controlled Birefringence), OCB (Optically Compensated Bend), and CPA (Continuous Pinwheel Alignment).

  A preferred embodiment of the present invention is a liquid crystal display device in which the cover panel covers the front surface of the liquid crystal display panel, and the surface layer of the cover panel is disposed in a direction facing the liquid crystal display panel. At this time, it is preferable that the angle formed by the slow axis of the surface layer and the absorption axis of the polarizing filter provided on the viewing side (surface side) of the liquid crystal monitor is 45 °.

  Hereinafter, the present invention will be described more specifically with reference to examples. Here, regarding the angles in this embodiment, the positive direction of the y-axis is 0 °, and the positive direction of the x-axis is 90 °.

(Resin type)
・ Polycarbonate resin: bisphenol A type polycarbonate resin "Iupilon H3000UR (clear)" manufactured by Mitsubishi Engineering Plastics Co., Ltd.

(Type of film)
・ Film 1: Polycarbonate resin sheet “Iupilon sheet NF2000F” manufactured by Mitsubishi Gas Chemical Company, Inc.
The film 1 has a thickness of 0.32 mm and a retardation value (average value) of 4500 nm. This film 1 is a stretched film and has an orientation axis in a specific direction. Of these orientation axes, the axis showing a large refractive index is the slow axis.

・ Film 2: Scratch resistant film “Iupilon Film DF02PU” manufactured by Mitsubishi Gas Chemical Company, Inc.
The film 2 has a thickness of 0.5 mm. Further, the layer structure of the film 2 is a two-layer structure composed of a layer made of polycarbonate resin (PC layer) / acrylic resin (PMMA layer).

Example 1
(Thermoforming)
A mold is attached to a vacuum / pneumatic molding machine (“FKS” manufactured by Asano Laboratories Co., Ltd.). 120 ° C., upper air pressure time 1.0 seconds, upper air pressure delay 1.5 seconds), and thermoformed so as to match the shape of the mold in the “injection molding” step to be described later to obtain a thermoformed film 1. Next, unnecessary portions of the thermoformed film 1 were cut using a trimming machine.

(injection molding)
The mold was attached to an injection molding machine (“FANAC ROBOSHOT α-S300iA” manufactured by FANUC CORPORATION). Then, the thermoformed film 1 was mounted in this mold so that the direction of the slow axis of the thermoformed film 1 was 45 °. Next, after the film 2 is mounted in a mold facing the mold, a polycarbonate resin is placed on the mold at a mold temperature of 40 ° C., a resin temperature of 290 ° C., an injection speed of 30 mm / second, and a holding pressure of 100 MPa × 7 seconds. Injected and filled. Next, after cooling the mold for 30 seconds, the molded product was taken out from the mold, and a curved molded product as shown in FIG. 1 was obtained. The thickness of the molded product thus obtained was 2.16 to 3.66 mm. Table 1 shows the molding conditions. Moreover, the cross-sectional schematic diagram of a molded article is shown in FIG. As shown in FIG. 2, the molded article has a scratch-resistant layer, a base material layer, and a surface layer laminated in this order. And the following evaluation was performed using the obtained molded article.

[Evaluation]
(Measurement of retardation value)
Using a photonic lattice wide-range two-dimensional birefringence meter (WPA-100L-PR0-002), the retardation value of the entire region where the surface layer was formed in the molded product was measured. And the average value was calculated. The results are shown in Table 1.

(Observation of interference fringes)
The liquid crystal monitor shown below was prepared.
-LCD monitor 1: LCD monitor of Dell laptop computer "XPS 13 9360" The driving method of the liquid crystal cell of this LCD monitor is IPS (In-Plane-Switching). When this liquid crystal monitor was visually recognized through the polarizing plate, the screen became dark when the absorption axis of the polarizing plate was in the horizontal direction (90 °). The absorption axis of the polarizing filter provided on the viewing side (front side) of this liquid crystal monitor is considered to be in the vertical direction (0 °).

-LCD monitor 2: LCD monitor of Toshiba's notebook computer "dynabook R731 / C" The driving method of the liquid crystal cell of this LCD monitor is TN (Twisted Nematic). When the liquid crystal monitor was viewed through the polarizing plate, the screen became dark when the absorption axis of the polarizing plate was 45 °. The absorption axis of the polarizing filter provided on the viewing side (front side) of the liquid crystal monitor is considered to be 135 °.

  As shown in FIG. 3, the molded product was placed in front of the liquid crystal monitor. As described above, since the thermoformed film 1 is mounted in the mold so that the direction of the slow axis is 45 °, the direction of the slow axis of the thermoformed film 1 layer in the molded product is 45 °. (The direction of the slow axis in FIG. 3 is 45 °). And as shown in FIG. 2, the liquid crystal monitor was observed through the polarizing plate for observation from the direction of the arrow. At this time, the polarizing plate for observation was rotated, the direction of the absorption axis of the polarizing plate for observation was set to 0 °, 45 °, and 90 °, and the liquid crystal monitor was observed and evaluated according to the following criteria. The results are shown in Table 1.

(Evaluation criteria)
A: Interference fringes (rainbow irregularities) are hardly visible B: Interference fringes (rainbow irregularities) are slightly visible C: Interference fringes (rainbow irregularities) are visible D: Interference fringes (rainbow irregularities) are noticeable E: One part of the screen The part became dark

Examples 2-7
Except for changing the molding conditions as shown in Table 1, molded products were produced in the same manner as in Example 1, and the molded products were evaluated. The results are shown in Table 1.

Example 8
The thermoformed film 1 is mounted in a mold so that the direction of the slow axis of the thermoformed film 1 is 0 ° to obtain a molded product (“the direction of the slow axis” in FIG. 3 is 0 °). Evaluation was conducted in the same manner as in Example 1 except that the liquid crystal monitor 2 was used. The results are shown in Table 1.

Comparative Example 1
A molded product was produced in the same manner as in Example 1 except that the molding conditions were changed as shown in Table 1 without mounting the thermoformed film 1 in the mold, and the molded product was evaluated. The results are shown in Table 1.

Comparative Example 2
A molded product was produced in the same manner as in Example 1 except that the molding conditions were changed as shown in Table 1 without mounting the thermoformed film 1 and film 2 in the mold, and the molded product was evaluated. . The results are shown in Table 1.

Reference example 1
Except for changing the molding conditions as shown in Table 1, molded products were produced in the same manner as in Example 1, and the molded products were evaluated. The results are shown in Table 1.

Reference example 2
Evaluation was performed in the same manner as in Example 1 except that the molding conditions were changed as shown in Table 1 to obtain a molded product, and the molded product was evaluated using the liquid crystal monitor 2. The results are shown in Table 1.

  In Reference Examples 1 and 2, even if a molded product was produced using the thermoformed film 1, the angle formed by the absorption axis of the polarizing plate of the liquid crystal monitor and the slow axis of the thermoformed film 1 is not 45 °. This indicates that the occurrence of blackout cannot be suppressed.

Claims (7)

A transparent cover panel that protects the front of a liquid crystal display panel mounted in an automobile;
The cover panel has a base material layer and a surface layer,
Both the base material layer and the surface layer are made of polycarbonate resin,
The thickness of the base material layer is 0.5 to 10 mm, the thickness of the surface layer is 0.1 to 2 mm,
The cover panel is characterized in that the retardation value of the surface layer is 1500 nm or more, the retardation value of the entire cover panel is 2000 nm or more, and the base material layer and the surface layer are directly bonded. .   The cover panel according to claim 1, wherein a scratch-resistant layer is further formed on the surface opposite to the surface layer.   The cover panel according to claim 1, wherein the cover panel is curved or bent. It is a manufacturing method of the cover panel in any one of Claims 1-3,
A first step of mounting a polycarbonate film having a thickness of 0.1 to 2 mm and a retardation value of 1500 nm or more in a mold;
A second step of injecting and filling polycarbonate resin into the mold;
And a third step of taking out the molded product from the mold.   The manufacturing method according to claim 4, wherein the polycarbonate film is preliminarily thermoformed so as to match the shape of the mold and then mounted in the mold.   The manufacturing method according to claim 4 or 5, wherein, in the first step, a scratch-resistant film is mounted in a mold facing the mold.   A liquid crystal display device, wherein the cover panel according to any one of claims 1 to 3 covers a front surface of the liquid crystal display panel, and the surface layer of the cover panel is arranged in a direction facing the liquid crystal display panel.