EP4100939B1

EP4100939B1 - Hidden until lit display panel and a display assembly comprising thereof

Info

Publication number: EP4100939B1
Application number: EP20711350.7A
Authority: EP
Inventors: Katarzyna MAJDIUK; Justyna KRZYZYK; Krystian JAGODA; Marek Wozniak; Konrad STANEK; Wojciech SYREK
Original assignee: Merit Automotive Electronics Systems SL
Current assignee: Merit Automotive Electronics Systems SL
Priority date: 2020-02-04
Filing date: 2020-02-04
Publication date: 2024-04-10
Anticipated expiration: 2040-02-04
Also published as: EP4100939A1; WO2021158133A1

Description

The present invention relates to a display panel, in particular for use in an automotive vehicle, having a layered construction having a front side to present displayed symbol to a user and a back side apt to be illuminated by a light source. The present invention relates also to a display assembly comprising such a display panel.

Background of the invention

Display panels of this kind are commonly used in various consumer devices to illuminate given symbol in a form of a mark, sign, picture, letter, word, or other when required. The hidden until lit feature ensures that this symbol is visible only when illuminated from the back side of the panel. Since the energization of the light source is the only condition required to present the displayed symbol to the user, display panels of this kind have an advantage over the full-area 2-dimensional displays which are controlled by computer systems. Since no computer system can be made entirely hang or freeze-proof, malfunction of the computer system may lead to the malfunction of the display.
Display panels of this kind should provide sufficient brightness and homogeneity of the displayed symbol with substantially constant directivity or wide angle of visibility. Furthermore the light illuminating a given symbol on the panel should not propagate through the panel to illuminate other inactive (unlit) symbols of the panel, which adverse effect is commonly known as cross talk.
Publication GB 2558941 discloses an interior car part with a lighting element lying in a recess in a substrate and covered by a translucent layer and next a stencil layer, covered in turn by a top, translucent layer. From the front a visible effect of light through the stencil layer is seen and when the lighting element is switched off the presence of the element and the stencil is largely or completely hidden. The part 10 may include an intermediate layer in line with the lighting element. The top translucent layer and intermediate layer may be layers of lacquer. The lighting element may comprise and electroluminescent device or one or more LEDs. The top translucent layer and/or intermediate translucent layer may be tinted.
Publication US 2005/0074681 discloses a display panel including a transparent image recording sheet having electrophotographically formed thereon at least a background portion, wherein space factor of pinholes per unit area of the background portion is no greater than 1×10^-2%. The background portion has a transparent optical density of 3.0 or greater and an image portion has a transparent optical density of 1.0 or less, and preferably 0.1 to 1.
Publication US 2012/0281423 discloses an illuminated indicator display apparatus for use in an automotive vehicle display or dashboard. The illuminated indicator includes a light source, at least one baffle disposed adjacent the light source, a first panel disposed opposite the light source and connected to the at least one baffle, and a second panel spaced apart at a predetermined distance and positioned parallel to the first panel. The first panel or the second panel further includes printed or painted graphics viewable to the operator of an automotive vehicle. The baffle is made of an opaque material operable to block light from the light source. The second panel is tinted dark operable only to allow a portion of the light from a light source to pass through the second panel thereby further dimming the light able to pass through the second pane Document KR101977221B1 is considered the closest prior art for the present invention.
It has been the object of the present invention to provide a compact, cost efficient and simple to manufacture hidden until lit display panel featuring uniform brightness with substantially constant directivity and homogeneity of displayed symbols, which would be devoid of cross talk between separate symbols.
Another object of the present invention has been to provide a display assembly comprising such a display panel.

Summary of the invention

The invention provides a display panel according to claim 1, as mentioned in the outset, characterized in that, it has a layered arrangement comprising a translucent solid base layer; an opaque stencil layer adjoining the front side of said translucent base layer and including voids representing symbols displayable at the front side of the panel when illuminated from the back side of the panel; an opaque crosstalk reduction layer adjoining the back side of said translucent base layer and including voids corresponding to said voids of said stencil layer or to the symbols defined by said voids of said stencil layer; and a semi-opaque layer adjoining the front side of said stencil layer.
The term "translucent layer" as used in the context of the present invention denotes a layer which allows light to pass through but on the macroscopic scale does not follow Snell's law providing diffuse reflection of light characterized by omni-directional reflection angles within the volume thereof (not following Snell's law), featuring an absorbance, defined as the logarithm with base 10 of the ratio of the incident optical power to the transmitted optical power (i.e. inverse of transmittance), of 0.4 or less (i.e. more than about 40% of the incident optical power is transmitted through the translucent layer).
The term "opaque layer" or "stencil layer " as used in the context of the present invention denotes a layer providing lightsealing ability (i.e. an ability to prevent light from transmitted therethrough) featuring an absorbance of 1.3 or more (i.e. up to 5% of the incident optical power is transmitted through the opaque layer).
The term "semi-opaque layer or "hidden until lit layer" as used in the context of the present invention denotes a layer which is substantially opaque, but mainly due to its relatively low thickness, becomes non-opaque when illuminated by the light source from the back side of the panel, featuring an absorbance within the range of 0.4 to 1 (i.e. about 10 to 40% of the incident optical power is transmitted through the semi-opaque layer).
Said layered arrangement further comprises a tinted layer adjoining the front side of said hidden until lit layer.
The term "tinted layer" as used in the context of the present invention denotes a layer which is either transparent or translucent for the light within a predefined wavelength range of a light source used for backlighting the panel of the present invention featuring an absorbance for the light within a predefined wavelength range of 0.4 or less. This layer is responsible for the external appearance of the display panel but not for the hidden until lit functionality.
Said translucent base layer is made of plastic and has a thickness within the range of 0.2 to 1.5 mm (millimetre).
Said stencil layer, said opaque crosstalk reduction layer, said semi-opaque layer and/or said tinted layer is/are made of foil, paint, ink or lacquer and has/have a thickness within the range of 5 to 20 µm (micrometre).
Preferably said translucent base layer, said stencil layer, said opaque crosstalk reduction layer, said semi-opaque layer and/or said tinted layer is/are composed of more than one sublayer.
Preferably the display panel further comprises an adhesive layer adjoining the back side of said crosstalk reduction layer, made of glued tape or glue coating and having a thickness within the range of 10 to 100 µm.
The display panel according to the invention is easy and cost efficient to manufacture, in particular in embodiments in which all the layers but the carrier base layer are made by subsequent coating the base layer with paint, ink or lacquer. Due to relatively low thickness of the optic layers and elasticity of the base layer the panel is flexible and resistant to cracking and delamination.
The invention also provides display assembly comprising a housing having a number of chambers opening at the front face of the housing, and at least one light source disposed in at least one of said chambers, characterized in that, it further comprises a display panel as defined above and fixed to said front face of said housing.
Preferably said light source has a form of a light-emitting diode.

Brief description of drawings

The invention shall be described and explained below in connection with the attached drawings in which:

Fig. 1 is a schematic axonometric view of an embodiment of a display assembly comprising an embodiment of a display panel according to the present invention;
Fig. 2 is a schematic cross-sectional view of the embodiment of a display assembly shown in Fig. 1;
Hg. 3 is a schematic cross-sectional view of an embodiment of a display panel; and
Fig. 4 is a schematic axonometric, exploded view of a display panel shown in Fig. 3.

Detailed description of preferred embodiments

Figs. 1 and 2 show an embodiment of a display assembly 1 according to the present invention comprising a display panel 3 and a housing 2 containing energizable light sources 4. As shown in Fig. 2 the housing 2 is made of opaque plastic and comprises a number of chambers 21 opening at the front face 22 of the housing. Light sources 4 in the form of a LED diodes are disposed at the bottoms of the chambers 21 and electrically connected with a separate control unit (not shown) through an interface socket 23 of the housing 2. When energised, light sources 4 emit light in a narrow wavelength range (such as 495 to 570 nm for green or 625 to 740 nm for red) dispersed around a certain dominant wavelength, that to the human eye appears as a pure colour.
The display panel 3 that shall be explained below is glued to the front face 21 of the housing 2. In this embodiment the panel may display symbols 5 in a form of Latin letters 5a, words 5b and icons 5c, such as low fuel indicator, battery status, etc.
The display panel 3 shown in Fig. 3 and 4 has a layered construction and in this embodiment comprises a translucent solid base layer 31 made of translucent plastic such as polycarbonate (PC), poly(methyl methacrylate) (PMMA), or polyamide (PA) having a thickness of about 0.7 mm. The base layer 31 provides support for the remaining layers of the panel 3 as well as diffuse reflection of light emitted by the light sources 4 characterized by omni-directional reflection angles within the volume of the base layer 31.
An opaque stencil layer 32 adjoins the base layer 31 at the front side thereof. The stencil layer 32 is made of opaque foil or paint or ink coating and has a thickness of about 12 µm. The stencil layer 32 includes voids 321 representing symbols 5a, 5b, 5c. Each symbol 5 can be viewed separately at the front side of the panel 3 when the light source 4 disposed in a given chamber 21 of the housing 2 is energised.
The stencil layer 32 and parts of the base layer 31 exposed by the voids 321 of the stencil layer 32 are coated at the front side thereof with a semi-opaque or hidden until lit layer 34 made of lacquer and having a thickness of about 10 µm. The semi-opaque layer 34 is substantially opaque for the ambient light shining on it from the front side of the panel 3 but, mainly due to its relatively low thickness, becomes transparent when illuminated by the light source 4 from the back side of the panel 3,
An opaque crosstalk reduction layer 33 adjoins the base layer 31 at the back side thereof. The crosstalk reduction layer 33 is mads of opaque paint which is opaque when illuminated by the light source 4 from the back side of the panel 3 and has a thickness of about 7 µm. The crosstalk reduction layer 33 also includes voids 331 corresponding to the groups of voids 321 of the stencil layer 32 defining particular symbols 5, which are larger than voids 321 of the stencil layer 32.
The crosstalk reduction layer 33 absorbs photons emitted from the translucent base layer 31 that could otherwise be reflected back toward the front side of the panel 3 and pass through the voids 321 of the stencil layer 32 representing other inactive (or not directly illuminated by the light sources 4 located in a separate chambers 21) symbols 5 of the panel 3 producing an adverse cross talk effect.
The hidden until lit layer 34 is coated at the front side with a tinted layer 35 made of paint and having a thickness of about 10 µm. The transparency range of the tinted layer 35 corresponds to wavelength range of the light sources 4. The tinted layer 35 provides an appropriate colour and lusterlessness of the front surface of the panel 3 and has a class of surface finish according to the iSO 1302 standard of at least N4,
In this embodiment an adhesive layer 36 made of glued tape or glue coating and having a thickness of about 90 µm adjoins the crosstalk reduction layer 33 at the back side thereof. The adhesive layer 36 also includes voids 361 substantially corresponding to the voids 331 of the crosstalk reduction layer 33.

List of reference numerals

1.: display assembly
2.: housing
21. chamber
22. front face
23, interface socket
3.: display panel
31. translucent base layer
32. opaque stencil layer
321. voids
33: opaque crosstalk reduction layer
331, voids
34.: semi-opaque layer
35.: tinted layer
36.: adhesive layer
361. voids
4.: light source (light emitting diode)
5.: displayed symbol

Claims

A display panel (3), for use in an automotive vehicle, having a front side to present displayed symbol (5) to a user and a back side apt to be illuminated by a light source (4),
having a layered arrangement comprising a translucent solid base layer (31), featuring absorbance of 0.4 or less, made of plastic that does not follow Snell's law, providing diffuse reflection of light emitted by the light source (4) with omni-directional reflection angles within the volume of said translucent solid base layer (31), and having a thickness within the range of 0.2 to 1.5 mm;

an opaque stencil layer (32) adjoining the front side of said translucent base layer (31), featuring absorbance of 1.3 or more, and including voids (321) representing symbols (5) displayable at the front side of the panel (3) when illuminated from the back side of the panel (3);

an opaque crosstalk reduction layer (33) adjoining the back side of said translucent base layer (31), featuring absorbance of 1.3 or more, and including voids (331) corresponding to said voids (321) of said stencil layer (32) or to the symbols (5) defined by said voids (321) of said stencil layer;

a semi-opaque layer (34) adjoining the front side of said stencil layer (32), featuring absorbance within the range of 0.4 to 1; and

a tinted layer (35) adjoining the front side of said semi-opaque layer (34), transparent or translucent for the light within a predefined wavelength range of light emitted by the light source (4), and featuring absorbance for this light within a predefined wavelength range of 0.4 or less, wherein

said stencil layer (32), said opaque crosstalk reduction layer (33), said semi-opaque layer (34) and/or said tinted layer (35) is/are made of foil, paint, ink or lacquer and has/have a thickness within the range of 5 to 20 µm.
The display panel according to Claim 1, characterized in that said translucent base layer (31), said stencil layer (32), said opaque crosstalk reduction layer (33), said semi-opaque layer (34) and/or said tinted layer (35) is/are composed of more than one sublayer.
The display panel according to Claim 1 or 2, characterized in that it further comprises an adhesive layer (36) adjoining the back side of said crosstalk reduction layer (33), made of glued tape or glue coating and having a thickness within the range of 10 to 100 µm.
A display assembly (1) comprising a housing (2) having a number of chambers (21) opening at the front face (22) of the housing, at least one light source (4) disposed in at least one of said chambers (21), characterized in that it further comprises a display panel (3) as defined in any of the Claims 1 to 3 and fixed to said front face (21) of said housing (2).
The display assembly according to Claim 4, characterized in that said light source (4) has a form of a light emitting diode.