JP7613241B2 - Display device - Google Patents

Description

This disclosure relates to a display device mounted on a vehicle, etc.

A head-up display is mounted on a vehicle and projects various information, such as information necessary for the driver to drive, onto a projection target such as the windshield, allowing the user to visually recognize a virtual image. Today, with the increase in the amount of information and the diversification of the types of information, the display formats of images provided to users are also diversifying. For example, Patent Document 1 discloses a head-up display device that reflects the light of a display unit onto a black ceramic-painted area provided between the glass of the windshield.

JP 2013-047021 A

Various locations on a vehicle can be used to display information, but display locations are not necessarily suitable for projecting and reflecting display light. For example, when the black ceramic painted area described above faces the light source, this painted area has a rough surface and diffusely reflects the display light, making it unsuitable as a projection destination. Furthermore, when the windshield glass faces the light source, there is a risk of multiple reflections on the windshield, which is made up of multiple layers, causing double images, making it unsuitable as a projection destination. In particular, when a user wears polarized sunglasses that block S-polarized light, visibility is improved by increasing the reflectance of P-polarized light on the reflective surface. However, when the windshield has a low reflectance for P-polarized light, in addition to the factors described above, it is also unsuitable as a projection destination.

This disclosure has been made in consideration of these circumstances, and aims to provide a display device that can improve the visibility of the displayed image.

In order to solve the above-mentioned problems, the display device of the present disclosure is a display device including a display unit that emits display light related to an image to be viewed by a viewer, and a projection unit having a projection surface onto which the display light is projected and a fixed surface fixed to an arrangement location, and reflects the projected display light to be viewed by a user, wherein the projection unit has a reflective polarizer layer having a higher reflectivity for P-polarized light than for S-polarized light, a light-shielding layer that is arranged closer to the fixed surface than the reflective polarizer layer, and a fixed layer that is fixed to the arrangement location, and at least a portion of the outer edge of the light-shielding layer is formed with a gradation so that it changes from light-shielding to light-transmitting.

The display device disclosed herein can improve the visibility of the displayed image.

FIG. 1 is an explanatory diagram showing a display device mounted on an automobile according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view illustrating the structure of a display unit of the display device. FIG. 4 is a cross-sectional view of the windshield and the projection unit fixed to the windshield taken along a substantially vertical direction. FIG. 4 is an explanatory diagram showing the windshield and the projection unit fixed to the windshield as viewed from the rear. FIG. 13 is an explanatory diagram showing an example of gradation of the projection portion, as viewed from the rear, of the projection portion and the windshield.

An embodiment of the display device of the present disclosure will be described with reference to the attached drawings. The display device of the present disclosure can be applied to a display device mounted on a vehicle such as an automobile or motorcycle, a ship, an agricultural machine, or a construction machine. The display device has, for example, a light source side disposed in the instrument panel of the vehicle on which it is mounted, and a projection/reflection side disposed in the windshield, and displays a virtual image which is visible to the viewer. In this embodiment, an example will be described in which the display unit of the display device is disposed in the instrument panel of the automobile on which it is mounted, and the projection unit is disposed on the inside of the windshield.

Figure 1 is an explanatory diagram showing an embodiment of the display device 1 of the present disclosure, the display device 1 being mounted on an automobile.

Figure 2 is a cross-sectional view illustrating the structure of the display unit 7 of the display device 1.

Figure 3 is a cross-sectional view of the windshield 3 and the projection unit 8 fixed to the windshield 3 taken along the generally vertical direction.

Figure 4 is an explanatory diagram of the windshield 3 and the projection unit 8 fixed to the windshield 3, viewed from the rear (towards the driver 4).

The display device 1 is a so-called head-up display (HUD), which projects display light 2 onto a projection unit 8 that is primarily fixed to the light-blocking area 3a of the windshield 3, and reflects it in the direction of the driver 4 (viewer) of the vehicle. The display device 1 particularly projects and reflects the display light 2 onto the light-blocking area 3a formed on the windshield 3, allowing the driver 4 to view it.

As shown in FIG. 3, the windshield 3 has two pieces of light-transmitting glass 9a and a shielding layer 9b formed on at least a part of the periphery. The shielding layer 9b is a portion that forms a light-shielding color such as black, made of black ceramics or the like. The shielding layer 9b is formed on the outer edge of the windshield 3. The shielding layer 9b is formed for the purpose of preventing deterioration of the adhesive that fixes the windshield 3 to the automobile due to sunlight, concealing the adhesive, and improving the design. In the windshield 3, the portion where the shielding layer 9b is formed becomes the light-shielding region 3a, and the portion other than the light-shielding region 3a becomes the light-transmitting region 3b. The shielding layer 9b may be formed between the two pieces of glass 9a that form the windshield 3, or may be formed on the inside surface of the glass 9a on the inside of the vehicle.

The display device 1 has a display unit 7 and a projection unit 8.

The display unit 7 emits display light 2 related to an image to be viewed by the viewer. The display unit 7 has a case 10, a protective cover 20, and a display section 30.

The case 10 supports and houses the display unit 7. The case 10 is made of, for example, a synthetic resin having light-shielding properties (for example, black polypropylene). The case 10 has an opening 11 that allows the display light 2 to pass through in the portion facing the light-shielding area 3a. The case 10 also has an attachment structure (not shown) for being placed in a space provided within the instrument panel 5.

The protective cover 20 is a plate-shaped member made of a translucent synthetic resin (e.g., inorganic glass, polycarbonate resin, PMMA resin). The protective cover 20 covers the opening 11 of the case 10, thereby protecting the display unit 30 inside the case 10 from moisture, dust, etc.

The display unit 30 has a display panel 31 and a backlight unit 32.

The display panel 31 is disposed on the front side of the display unit 30. The display panel 31 is, for example, a TFT (Thin Film Transistor) type liquid crystal display panel. The display panel 31 has a pair of glass substrates that encapsulate a liquid crystal layer. Transparent electrodes are formed on the pair of glass substrates using ITO (Indium Tin Oxide) or the like. The display panel 31 also has a pair of polarizing plates (polarizing filters) that are disposed to sandwich the pair of glass substrates.

The display panel 31 is connected to a circuit board (not shown) provided separately from the display unit 7 via an FPC (Flexible Printed Circuits, not shown). The display panel 31 is controlled by a control unit such as a graphics controller on the circuit board, and a driving voltage is applied to the liquid crystal layer via the transparent electrodes. The liquid crystal layer changes the transmittance of each pixel by controlling the orientation of the liquid crystal molecules. The display panel 31 is fixed to the protective cover 20 via an optical bonding layer 36. The optical bonding layer 36 is made of a transparent synthetic resin (e.g., a silicone-based, urethane-based, or acrylic-based resin).

The backlight unit 32 is disposed behind the display panel 31. The backlight unit 32 has a light source board 33 and an optical sheet 34. The light source board 33 has a plurality of LEDs (Light Emitting Diodes) 35. The light source board 33 is connected to the above-mentioned circuit board via an FPC. The LEDs 35 emit light when a drive current is supplied. The optical sheet 34 is, for example, a prism sheet that diffuses light. The light emitted from the LEDs 35 illuminates the display panel 31 through the optical sheet 34. As a result, the display unit 30 emits display light 2 related to an image to be viewed by the viewer.

The projection unit 8 is a film-like member in which multiple films are laminated, and functions as a projection unit 8 paired with the display unit 7 by being attached to an area that overlaps the light-shielding area 3a when viewed from the driver 4. The projection unit 8 reflects the projected display light 2 and allows the user (driver 4) to view it. As shown in FIG. 3, the projection unit 8 has a projection surface 8a and a fixed surface 8b. The projection surface 8a is a surface that faces the display unit 7 and is a surface on which the display light 2 is reflected and projected. The fixed surface 8b is a surface opposite to the projection surface 8a and is fixed to an arrangement location (described later). The projection unit 8 has a fixed layer 41, a light-shielding layer 42, a reflective polarizer layer 43, and a transparent protective layer 44 from the fixed surface 8b to the projection surface 8a.

The fixing layer 41 is a layer that is fixed to the windshield 3 as the placement location, and is made of, for example, the required adhesive material for fixing the projection unit 8.

The light-shielding layer 42 is disposed on the surface of the reflective polarizer layer 43 facing the fixed surface 8b. The light-shielding layer 42 is a printed layer formed by printing the reflective polarizer layer 43 with an ink having light-shielding properties (e.g., black ink). The light-shielding layer 42 is formed, for example, in a color similar to that of the light-shielding region 3a, so that the light-shielding region 3a and the light-shielding layer 42 can be integrated in appearance. The light-shielding layer 42 prevents the light passing through the reflective polarizer layer 43 from being multiple-reflected in the subsequent stage, thereby preventing the formation of a double image with the light reflected by the reflective polarizer layer 43.

The light-shielding layer 42 has a gradation formed in which the upper edge 8c (at least a part of the outer edge) of the projection unit 8, which is approximately parallel to the boundary of the light-shielding area 3a, gradually transitions from light-shielding to light-transmitting. Here, FIG. 5 is an explanatory diagram of the projection unit 8 and the windshield 3 seen from the rear to show an example of the gradation of the projection unit 8. At the boundary between the light-shielding area 3a and the light-transmitting area 3b of the windshield 3, dot-shaped gradation printing is applied to the upper edge 3c of the light-shielding area 3a so that the light-shielding area 3a gradually transitions to the light-transmitting area 3b. Similarly, in the projection unit 8, dot-shaped gradation printing is applied to the light-shielding layer 42 so that the light-shielding rate of the upper edge 8c gradually decreases. This, together with the gradation printing of the upper edge 3c of the light-shielding area 3a, makes the upper edge 3c of the projection unit 8 less noticeable.

The reflective polarizer layer 43 is a layer made of, for example, a polarization-controllable multilayer thin film that has a higher reflectance for P-polarized light than for S-polarized light. The reflective polarizer layer 43 is designed to have a reflectance of 20% or more for P-polarized light and a reflectance of 10% or less for S-polarized light when the incident angle of the display light 2, which is set by the arrangement of the display unit 7 and the windshield 3, is between 55 degrees and 60 degrees. This is to improve visibility by increasing the reflectance of P-polarized light at the projection unit 8 when the user is wearing polarized sunglasses that block S-polarized light.

The transparent protective layer 44 is made of a required material (e.g., PMMA) that can prevent the formation of scratches on the reflective polarizer layer 43 and prevent a decrease in the functionality of the reflective polarizer layer 43. In addition to preventing scratches, the transparent protective layer 44 preferably also has functions such as preventing surface reflection and preventing fogging.

The projection unit 8 may be disposed only in the light-shielding area 3a onto which the display light 2 is projected, or may include light-shielding areas 3a other than the projected area. For example, if the projection unit 8 is attached only to the light-shielding area 3a onto which the display light 2 is projected, it is only necessary to prepare the projection unit 8 for the required area, thereby reducing the manufacturing cost related to materials. In addition, a line can be formed by printing between the light-shielding layer 42 on the outer edge of the projection unit 8 and the reflective polarizer layer 43 with an ink of a color (e.g., white or gray) that is distinguishable (has contrast) with the color of the light-shielding layer 42, and the line can be formed by printing to surround the projection unit 8, thereby allowing the user to recognize the display area of the display device 1.

When the projection unit 8 is also attached to the light-shielding area 3a other than the area where the display light 2 is projected, the boundary between the light-shielding area 3a and the projection unit 8 will not be noticeable, and the appearance of the windshield 3 will not be impaired. Also, when heat lines for preventing fogging of the windshield 3 are arranged in the light-shielding area 3a so as to be visible to the user, the projection unit 8 can be arranged to cover the heat lines, thereby also having the effect of blocking the heat lines.

The location where the projection unit 8 is placed may include the light-transmitting area 3b near the light-shielding area 3a. Specifically, (at least a part of) the upper edge 8c of the projection unit 8 may be located closer to the light-transmitting area 3b than the boundary between the light-transmitting area 3b and the light-shielding area 3a. If the upper edge 8c of the projection unit 8 is located in the light-shielding area 3a, the upper edge 8c is visible on the light-shielding area 3a, and the upper edge 3c of the light-shielding area 3a and the upper edge 8c of the projection unit 8 form a double line, which may impair the appearance. On the other hand, if the upper edge 8c of the projection unit 8 is located closer to the light-transmitting area 3b than the upper edge 3c of the light-shielding area 3a, the upper edge 3c of the light-shielding area 3a is covered by the projection unit 8 and is not visible, so the appearance can be maintained.

In addition, when a gradation is formed on the upper edge 8c of the light-shielding layer 42 by dot printing, the other layers other than the light-shielding layer 42 (fixing layer 41, reflective polarizer layer 43, transparent protective layer 44) also form the upper edge 8c along the shape of the dots, so that the upper edge 8c of the projection section 8 is not noticeable in the light-transmitting area 3b.

By having a projection unit 8 with a polarization-controllable reflective polarizer layer 43 and a light-shielding layer 42 arranged behind it, such a display device 1 can improve the visibility of the display image compared to when the display light 2 is directly projected and reflected onto the windshield 3. In other words, by having the projection unit 8, the display light 2 can be made visible to the user regardless of the user's condition (whether or not the user is wearing polarized sunglasses) or the condition of the windshield 3 (the material and condition of the surface onto which the display light 2 is projected). In addition, by having the light-shielding layer 42, it is possible to suppress reflection of the display light 2 that has passed through the reflective polarizer layer 43 on the subsequent layers or the windshield 3.

In addition, when attaching the projection unit 8 to an existing windshield 3, there is a risk that the outer edge of the projection unit 8 will be visible and the appearance will be reduced, but by forming a gradation in the light-shielding layer 42 on the upper edge 8c and by considering the relative positions of the light-transmitting area 3b and the light-shielding area 3a and the projection unit 8, the appearance can be maintained.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

For example, in order to eliminate the step in thickness of the projection unit 8 relative to the windshield 3, a recess equivalent to the thickness of the projection unit 8 may be provided in the windshield 3 corresponding to the location of the projection unit 8, and the light-transmitting area 3b of the windshield 3 and the projection surface 8a of the projection unit 8 may be formed to be flush with each other.

Reference Signs List 1 Display device 2 Display light 3 Windshield 3a Light-shielding area 3b Light-transmitting area 3c Upper edge 4 Driver 5 Instrument panel 7 Display unit 8 Projection section 8a Projection surface 8b Fixation surface 8c Upper edge 9a Glass 9b Shielding layer 10 Case 11 Opening 20 Protective cover 30 Display section 31 Display panel 32 Backlight unit 33 Light source substrate 34 Optical sheet 35 LED
36 Optical bonding layer 41 Fixing layer 42 Light shielding layer 43 Reflective polarizer layer 44 Transparent protective layer

Claims (5)

a display unit that emits display light related to an image to be viewed by a viewer;
A display device including: a projection unit having a projection surface onto which the display light is projected and a fixed surface fixed to an arrangement location, the projection unit reflecting the projected display light and allowing a user to view the display light;
The projection unit is
a reflective polarizer layer having a higher reflectivity for P-polarized light than for S-polarized light;
a light-shielding layer disposed on the fixed surface side of the reflective polarizer layer;
A fixing layer fixed to the placement location ,
A display device in which at least a part of an outer edge of the light-shielding layer is formed with a gradation so as to change from light-shielding to light-transmitting . The display device according to claim 1, wherein the placement location includes a light-shielding area of a vehicle windshield having a light-transmitting area and a light-shielding area formed on at least a portion of the periphery. The display device according to claim 2, wherein at least a portion of the outer edge of the projection section is located closer to the light-transmitting region than the boundary between the light-transmitting region and the light-shielding region. The display of claim 1 , wherein the pinning layer and the reflective polarizer layer form an upper edge along the gradation . 2. The display device according to claim 1, wherein the reflective polarizer layer has a reflectance of the P-polarized light of 20% or more and a reflectance of the S-polarized light of 10% or less when the incident angle of the display light is from 55 degrees to 60 degrees.

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