阅读说明：本技术 具有低双折射的人机界面显示器外壳 (Human-machine interface display housing with low birefringence ) 是由 马库斯·大卫·谢尔比 罗伯特·埃利斯·麦克拉里 托马斯·约瑟夫·佩科里尼 迈克尔·盖奇·阿姆斯 于 2020-03-25 设计创作，主要内容包括：提供了一种用于人机界面(HMI)触摸面板显示器的光学透明保护外壳板,其中该外壳板由包含高熔体流动聚碳酸酯的热塑性聚合物形成。聚碳酸酯的特征在于熔体流动速率(MFR)或熔体流动指数(MFI)在约60和约80g/10min之间(ASTM D-1238,300℃/1.2kg)。(An optically transparent protective skin plate for a Human Machine Interface (HMI) touch panel display is provided, wherein the skin plate is formed from a thermoplastic polymer comprising a high melt flow polycarbonate. The polycarbonates are characterized by a Melt Flow Rate (MFR) or Melt Flow Index (MFI) of between about 60 and about 80g/10min (ASTM D-1238, 300 ℃/1.2 kg).)

1. A human-machine interface shell in the form of a sheet having a thickness of about 2mm to about 5mm, comprising a thermoplastic polymer comprising:

(i) polycarbonate or

(ii) A polycarbonate having blended therein up to about 40 weight percent of a copolyester,

wherein the thermoplastic polymer has a melt flow rate of about 60 to about 80g/10 minutes as determined according to ASTM D-1238(300 ℃/1.2 kg).

2. The human-machine interface housing of claim 1, wherein the housing has a total optical delay range span of 160nm or less as measured by a difference between a maximum delay value and a minimum delay value over the viewable area of the HMI faceplate.

3. The human-machine interface housing of claim 1, wherein the housing has a total optical delay range span of 100nm or less as measured by a difference between a maximum delay value and a minimum delay value over the viewable area of the HMI faceplate.

4. The human-machine interface housing of any one of claims 1 to 3, further comprising one or more compensation film layers.

5. The human-machine interface housing of any one of claims 1 to 4 having a total optical retardation in the range:

(i) -from 100 to 100nm,

(ii)100 to 300nm, or

(iii) -100 to-300 nm.

6. The human-machine interface housing of claim 5, wherein the housing exhibits a total optical retardation in the range of-80 nm to 80 nm.

7. The human-machine interface housing of claim 5, wherein the housing exhibits a total optical retardation of from 100nm to 260nm or from-100 nm to-260 nm.

8. The human-machine interface housing of any one of claims 1-7, wherein the thermoplastic polymer is polycarbonate.

9. The human-machine interface housing of any one of claims 1 to 7, wherein the thermoplastic polymer is a blend of polycarbonate and copolyester.

10. The human-machine interface housing of any one of claims 1-7 or 9, wherein the copolyester is miscible with the polycarbonate.

11. The human-machine interface housing of claim 10, wherein the copolyester comprises: a diol component comprising CHDM residues and an acid component comprising TPA residues.

12. The human-computer interface housing of claim 11, wherein the copolyester is selected from PCTG, PCCD, or mixtures thereof.

13. The human-machine interface housing of any one of claims 1 to 12, wherein the housing further comprises a hard coating.

14. The human-computer interface housing of claim 13, wherein the hard coating is selected from a silicone based hard coating, a (poly) siloxane based hard coating, a urethane based hard coating, or an acrylic based hard coating.

15. A method for manufacturing a human-machine interface housing according to any one of claims 1 to 14, comprising the steps of:

(a) providing a mold configured for injection molding, the mold comprising a gate at one end of the mold, the gate having an opening configured to introduce molten thermoplastic polymer into the mold, and a mold width of at least 150mm at the gate end of the mold, wherein the gate opening has a width of at least 50% of the mold width; and

(b) injection molding the housing at a barrel temperature of at least the thermoplastic polymer Tg (° C) +170 ℃.

16. The method of claim 15, wherein the gate opening has a width that is at least 60% of the mold width.

17. The method of claim 15 or 16, wherein the barrel temperature is at least the thermoplastic polymer Tg (° c) +190 ℃.

18. The method of any one of claims 15-17, further comprising injection molding the housing at an injection speed of at least 1.3 cm/s.

19. The method of claim 18, wherein the injection speed is at least 3.0 cm/s.

Technical Field

The present invention relates generally to human-machine interface touch displays; in particular, the present invention relates to certain plastic touch panel housings.

Background

Human-machine interface (HMI) displays are becoming more common in automobiles because they provide passengers with more control over the interior through a single interface. For example, entertainment systems, air conditioning, lighting, etc. may be controlled by the single touch panel display through multiple selection options. HMI displays typically include some sort of optical module (e.g., a Liquid Crystal Display (LCD) panel, an Organic Light Emitting Diode (OLED), etc.) and a protective, optically transparent "touch panel" on a surface. Touch panels need to be both scratch resistant (allowing for frequent physical contact) and have very low optical birefringence to minimize optical shadowing.

Glass meets these criteria and is currently the material of choice, but is still considered to be inadequate because it adds additional weight and has poor impact resistance (which can lead to the risk of injury in a collision). Automobile manufacturers also desire greater design flexibility in automobile interiors, including larger and higher degree of curvature/definition HMI faceplates. This design is completely impractical for glass and therefore requires other options.

It has been desired to replace glass with plastic because it can be more easily molded into different shapes while still providing better impact strength. However, molded plastics tend to have residual orientation and stress that leads to optical birefringence in the panel. This birefringence in turn can lead to undesirable optical defects, most notably "shadowing". For example, shadows can occur whenever the driver looks at the HMI display wearing polarized sunglasses. The polarized lenses impart additional color and/or intensity gradations in the panel, making the panel look "mottled". The only way to eliminate this shadowing today is to use a very low birefringence material, such as glass, as the touch panel material.

It is also important to maintain low birefringence and optical clarity without sacrificing impact strength. Some polymers, such as acrylics, such as poly (methyl methacrylate) (PMMA), can be molded with sufficiently low birefringence, but these materials are inherently brittle and therefore unacceptable from a safety or reliability standpoint.

Disclosure of Invention

In one aspect, the present invention relates to an optically transparent protective cover or skin plate for a Human Machine Interface (HMI) touch panel display, wherein the skin plate is formed from a polymer resin composition comprising a high melt flow Polycarbonate (PC). In the examples, the polycarbonates are characterized by a Melt Flow Rate (MFR) or Melt Flow Index (MFI) of between about 60 and about 80g/10min (ASTM D-1238, 300 ℃/1.2 kg). In embodiments, the polymeric resin composition is selected from "standard" bisphenol-a polycarbonate or polycarbonate-copolymer blends, such as copolyesters and polycarbonate blends. In embodiments, the blend may comprise up to about 40 weight percent copolyester.

It has been found that high melt flow polycarbonate (as described herein) can have sufficiently low and controllable birefringence when processed, for example, by injection or compression molding, or by thermoforming, and can be processed into HMI skin plates having commercially acceptable impact strength and substantially no optical shadows. In an embodiment, the outer shell plate can further comprise one or more compensation layers to provide an outer shell plate assembly, wherein the compensation layer(s) can provide the outer shell plate assembly with a total optical retardation that falls within an acceptable range for HMI shell applications. In an embodiment, the closure plate assembly exhibits a total optical retardation in a range selected from: (i) from-100 to 100nm, (ii) from 100 to 300nm, or (iii) from-100 to-300 nm; alternatively, the absolute value of the delay is 0 to 100 or 100 to 300. In other embodiments, the closure panel assembly exhibits a total optical retardation in a range selected from: (i) from-80 to 80nm, (ii) from 100 to 260nm, or (iii) from-100 to-260 nm; alternatively, the absolute value of the delay is 0 to 80 or 100 to 260. In another embodiment, the closure panel assembly exhibits a total optical retardation in a range selected from: (i) from-50 to 50nm, (ii) from 130 to 230nm, or (iii) from-130 to-230 nm; alternatively, the absolute value of the delay is 0 to 50 or 130 to 230. In an embodiment, the closure plate assembly exhibits an overall optical delay (as described above) over at least the visible portion of the HMI display.

Drawings

FIG. 1 is a typical cross-polarizer setup for measuring birefringence.

Fig. 2 is a close-up of the horizontal and vertical components of the waveform diagram delay and phase shift.

Fig. 3 depicts the effect of tilt angle on effective refractive index.

Fig. 4 depicts a schematic diagram of a typical LCD structure.

Fig. 5 is a schematic diagram of an LCD configuration assuming a polarized sunglasses is worn by an observer.

FIG. 6 is a schematic diagram of an LCD configuration assuming the addition of a compensation layer on the HMI touch screen.

FIG. 7 is a depiction of an injection mold containing a lap gate with an associated polymer flow front.

FIG. 8 is a depiction of an injection mold containing a fan gate with an associated polymer flow front.

Detailed Description

Shadow is an optical defect that occurs when a passenger views the HMI display while wearing polarized sunglasses. It produces a brightness change from grey to white which has the effect that the display appears distorted and/or mottled. This distortion is caused by local variations in birefringence. Whereas birefringence refers to the difference in refractive index of a given transparent substrate in different directions, which is caused by stress and/or molecular orientation. This shading usually consists of a change in grey coloration, but when the optical birefringence is sufficiently large, it can even lead to a color shift in the display, starting with yellow and then orange, red, violet, up to the entire color spectrum. It is desirable that no color change occurs and the display maintains a uniform color, e.g. black or grey, but white is also acceptable.

The birefringence of a substrate is expressed as Δ, and is defined as the difference in refractive index n between any two mutually perpendicular directions. Typically, these directions will be related to, for example, the Machine Direction (MD), the Transverse Direction (TD), and the thickness direction (thick). If these directions are indicated by subscripts a, b, and c, three different values of birefringence can be calculated.

Only two of the three are independent and the choice of which is best used depends on the application. Birefringence is a parameter that takes a vector by refractive index reflection. The refractive index, in turn, is an inverse measure of the speed of light in the medium, assuming that the light wave is polarized in that particular direction. Higher value of n means lower speed, so if n is_a＞n_bThis means that light waves polarized in the a-direction will propagate slower than light waves polarized in the b-direction. Thus, given a sufficient distance, the light wave along a will lag further behind b and become increasingly out of phase.

FIG. 1 shows the birefringence of a sample in a typical crossed polarizer configuration. The light source 1 provides random unpolarized light 2 to a first polarizer 10 having a polarization axis at +45 degrees from the vertical. The resulting polarized light 3 is then incident on a sample 20 of thickness L, the principal axes of which are aligned with the vertical and horizontal directions and each having a refractive index n_aAnd n_b。

For simplicity, the incident light wave 3 can be vectorially decomposed into electric field components along the vertical and horizontal axes and perpendicular to the propagation direction. Given the different refractive indices, each of these components will then propagate at a different velocity in the sample. Due to this difference in velocity, the emergent wavefronts 5 and 6 will be phase separated by a distance 8 (FIG. 2), which is denoted as the optical retardation. Retardation is expressed in nanometers, or as a fraction of the wavelength λ in the medium. For plastics, a white light source is assumed, with a wavelength of approximately 570 nm. Thus, a "quarter wave" retardation is a sample with a retardation of about 142nm (or one-fourth of 570 nm).

When the two components 5 and 6 reach the second polarizer 30, the waves are effectively recombined to produce an output wave 7 seen by the viewer 90. If the delay is zero, the waves remain in phase and add back to their original amplitude and direction. Since the combined wave is now oriented at 90 degrees to the second polarizer, it will be completely blocked and there will be a black or zero state with no light transmission. This is the same black state that would be observed through two crossed polarizers in the absence of the sample.

Conversely, if the two components are out of phase, vector addition will result in a portion of the wave being aligned with the second polarizer, thereby causing it to be transmitted. This "light leakage" will vary with the level of retardation and will reach a maximum as the retardation increases and will eventually return to near zero at integer multiples of the wavelength of the hypothetical monochromatic light. If the delay is equal to λ, it is denoted as the first order extinction point. Likewise, additional extinction occurs at 2 λ,3 λ, etc., denoted as second and third order extinction points, respectively.

For white or polychromatic light, each color corresponds to a different wavelength and, assuming constant retardation of the portion, each color will experience a different degree of extinction. For example, blue and violet are much shorter in wavelength than red, so as the retardation level increases they will experience more relative phase shift (e.g. if λ is 400nm, a 100nm retardation shift will be equivalent to a quarter-wave shift, but for a 600nm wavelength will only be a λ/6 shift). As the intensities of the various colors undergo different shifts, the color of the transmitted light also changes. At zero retardation, no light is transmitted and the color appears black. With increasing retardation, the color changes from black to dark gray and then to white at about 100 nm. White color is maintained between about 100nm and 300nm, and a shift towards yellow begins at 300 nm. From yellow to orange, then red and finally to violet at the first extinction point of 570 nm. Above 570nm, the color cycle is essentially repeated, although with some slightly different color shifts. However, in the case of HMI housing plates, retardation levels in excess of 570nm are unacceptably high from a shading perspective.

The retardation change from about-100 nm to +100nm typically appears black to gray with minimal shading. Also, retardation variation in the range of 100 to 300nm (or-100 to-300) provides a nearly uniform white appearance, and shows minimal shading. Thus, both are delay targets of the present invention.

The delay in any two directions (i, j) can be easily calculated from the thickness of the part L as follows:

(2)R_ij＝LΔ_ij

as with birefringence, there are multiple retardation values depending on the direction selected. For shading purposes, two values are of particular importance, denoted Re and Rth. They are defined as follows:

(3)Re＝R_MD-TD＝L(n_MD-n_TD)

(4)

this assumes that the a, b and c directions correspond to the MD, TD and thickness of the part, respectively. Re and Rth are important for shading for different reasons. Re represents the retardation and phase lag of a light wave propagating perpendicular to the surface, as shown in fig. 1. Note that Re is not bound by n_thickBecause the normal incident wave is polarized only in the plane direction (MD/TD).

However, for off-axis or oblique viewing, n must be taken into account_thickThus, Rth is required. This is illustrated in fig. 3, where light waves parallel to the page 65 are incident on the sample at an angle (the vector represents the direction and magnitude of the electric field component perpendicular to the direction of propagation). After refraction, the direction of this light component changes slightly to 66. Assuming the sample to be anisotropicA refractive index ellipsoid 60 in which the refractive index in the thickness direction 62 is smaller than the refractive index in the plane direction 61. This is typical of most films or molded parts having in-plane orientation.

It is known that the refractive index varies between principal axes with an elliptical shape. For normal incidence, the polarization direction will correspond to the horizontal/planar refractive index 61. But as the angle increases, the effective index corresponds to the point on the ellipsoid where the polarization vectors intersect. The effective index approaches the thickness value 62 as the tilt angle increases. It should be noted that if the thickness and the in-plane refractive index are the same, as described below, then 60 will take the shape of a sphere rather than an ellipsoid, and thus the effective refractive index will not change with tilt angle. Ideally, we would like to have very small Rth and Re in the display housing to minimize any shading. It is also preferable that the value of Rth be equal to or close to Re so that no noticeable shading occurs when the viewing angle is changed.

It is important to note that shadowing and retardation occur only in the presence of an optical polarizer. In practice, shadowing occurs only when a retardation shift occurs between two polarizers (e.g., 10 and 30 in fig. 1). The effect of the polarizer pair is to first isolate a certain polarization direction, then allow the relative phase shift or retardation of the wave components, and then to recombine the polarization components vectorially so that constructive and destructive interference occurs. Without these polarizers, this interference does not occur. As such, unless the viewer wears polarized sunglasses, no shadows appear.

Although the display module itself has a pair of polarizers, the (HMI) touch panel is not between these polarizers and therefore no additional optical interference occurs. However, when wearing sunglasses, the situation changes because the touch panel is now located between the second polarizer of the LCD module and the polarized sunglasses. Sunglasses essentially incorporate a third polarizer, and hence a second polarizer pair, and all that is between these polarizers must now be taken into account when attempting to reduce shading. The following description of an example HMI faceplate is provided for further explanation.

Examples of LCD structures

A typical structure of an LCD-based HMI panel is shown in fig. 4. The only elements included are those optically relevant to the system, and other layers, such as those used for electrical switching and sensing, are not included in the figures. It should also be noted that there are many other design elements and structures that may be included in an LCD module (e.g., light diffusers, brightness enhancement films, color filters, etc.), but these are not critical to explaining optical shading or the present invention and are therefore not shown. It should be noted that these elements are typically present in the module in one of many possible forms, and that these variations may be included in embodiments of the invention.

The LCD module is very similar to the arrangement in fig. 1, except now the "sample" is replaced with a liquid crystal module 50. As previously described, first and second polarizer stacks 10, 30 and some sort of backlight 1 are present to provide illumination. The first polarizer has a polarization axis phi with respect to a reference perpendicular direction, and the second polarizer is typically rotated 90 degrees with respect to this direction. Typically, the angle φ is 45 degrees, but this is not required.

The polarizer typically also includes a protective or "compensation" film that sandwiches the active polarizing elements (13 and 33). They are denoted 11 and 12 for the first polarizer and 31 and 32 for the second polarizer. Layers 11 and 32 are typically made of solvent cast cellulose triacetate films or cycloolefins. Because they are "external" to the polarizer pair, they generally do not affect retardation, and thus their retardation is generally not critical. In contrast, layers 12 and 31 are between the polarizers, so their retardation affects the visual quality. For conventional LCD applications, these films are typically designed with specific specified Re and Rth in order to counteract any residual retardation in the liquid crystal module. By properly designing these compensation films, the viewing angle and contrast of the display are significantly increased.

The retardation effect discussed above with respect to fig. 1 is also applicable to liquid crystal displays, except that the liquid crystal module 50 is a material whose birefringence changes dynamically (as opposed to the static birefringence of the sample 20). There are different types of liquid crystal cells on the market, but regardless of the type, the liquid crystal molecules change direction and alignment in response to an applied voltage. By changing this arrangement and thus the birefringence, the brightness of light passing through can be modulated from dark to light using the principles previously described, thereby turning a given pixel on or off. By passing the light through a color filter, various colors can be obtained.

Upon exiting the second polarizer, the light will pass through the display housing 70. In most applications, such as a conventional LCD television, light will pass through the protective housing and reach the viewer. Since there is no other polarizer behind the housing, its retardation has no effect on the visual quality.

However, this situation can change if a 3 rd polarizer is introduced, for example, the viewer wears polarized sunglasses. This is indicated as 80 in fig. 5. These polarizers typically have vertically aligned polarization axes (0 degrees) because this may better reduce glare because most of the reflected light from the road and water surface is horizontally polarized. In this case, the layers 12, 31, 32, and 70 may all affect the retardation (except the liquid crystal module 50), and thus may affect the shading. Without sunglasses, only 12 and 31 have an effect on visual quality.

FIG. 6 illustrates another aspect of the present invention, including an additional optical compensation film, indicated at 71. As previously mentioned, films 12 and 31 are typically compensation films having the specified retardations Re and Rth and are designed to counteract some of the extraneous retardation from the liquid crystal module itself. By eliminating the unwanted delay in the module 50, panel manufacturers can significantly improve contrast and viewing angle performance.

In automobiles, these films (12 and 31) can also potentially affect shadows, so one option is to modify the retardation of these films even further to reduce the perception of shadows seen by passengers wearing polarized sunglasses. However, this option is not preferred because under normal conditions when sunglasses are not being worn, adjustment of the compensation films 12 and 31 can compromise visual performance. Instead, it may be preferable to add an additional compensation layer 71 to the touch panel itself, or to replace the location of or on top of layer 32. Films are easier to achieve a specified level of retardation than molded products, and this therefore provides an alternative way of increasing or decreasing the retardation as required. In embodiments, the film (shown on the touch surface) may also be applied to the surface as a protective layer having scratch resistance, hard coat, and the like. In an embodiment, such a film may also be applied to the underside of the panel (not shown), if desired. Application may be by direct adhesion, in-mold labeling/decoration, etc.

In embodiments, the HMI touch panel may be bonded to the liquid crystal display component/assembly with a Liquid Optically Clear Adhesive (LOCA) or Optically Clear Adhesive (OCA) film (or tape) (e.g., the touch panel may be bonded to a polarizer layer or a protective layer on a polarizer layer located between the liquid crystal module and the touch panel). Such adhesives may also be used to adhere a protective housing, such as a lens or hard coat, to a touch panel. In embodiments, the adhesive is cured with ultraviolet light (UV), heat, moisture, or a combination thereof, according to the manufacturer and specifications of the LOCA or OCA.

In embodiments, the LOCA or OCA may improve the optical performance of the display, for example by eliminating air gaps between the adhesive layers. In an embodiment, such optical coupling may improve contrast, and thus visibility, by reducing the amount of reflected light. Reflection from the touch panel screen or protective cover cap layer and the adhesive can reduce the visibility of the LCD. Reflection may be caused by an impedance mismatch between the air and the one or more layers. Reflection can make white brighter, but can dilute black and other colors, thereby reducing contrast. In certain embodiments, LOCA is selected to match the index of refraction of the HMI touch panel to minimize losses. In embodiments, the LCOA or OCA comprises acrylic-based and/or siloxane-based chemistry.

In an embodiment, the touch panel is molded with in-mold decoration (IMD) or in-mold label (IML) to provide indicia and/or passive tactile features. In embodiments, the IMD or IML is a thin film that transfers a decorated and/or UV-curable hardcoated surface to a plastic touch panel. The IML film has a coating against the mold. A molten thermoplastic (e.g., a cellulose ester thermoplastic) is injected such that it contacts the surface of the film facing the interior of the mold and has good adhesion to the thermoplastic. Once the molded part is released from the mold, the coating on the IML film will undergo a UV curing step that hardens the surface and can impart scratch and chemical resistance. Other functions that may be imparted to the outward facing surface (of the molded part) include anti-fingerprint (oleophobic properties), anti-glare, and/or anti-reflective properties. In an embodiment, the tag may be associated with a control function of the HMI unit. In embodiments, multicolor screen and offset printed graphics may be used to create the indicia or graphics. In certain embodiments, a second surface graphic is used in which the decoration is printed on the back side of a transparent backing film (e.g., a polycarbonate, acrylic, or cellulose film) and the plastic is contact-injected on the ink side of the film (e.g., during injection molding). This encapsulates the decoration between the film layer and the injected plastic so that the decoration does not wear out during use. In embodiments, a vision system may be used to ensure accurate label positioning and may verify label correctness. In embodiments, printing can be performed by any known method, such as digital printing (e.g., inkjet or xerography), spraying, transfer, flexographic printing, gravure printing, and the like.

In embodiments, the thickness of a touch panel module constructed using IMD or IML is relatively thinner than a similar touch panel constructed using a printed layer bonded by LOCA or OCA. In embodiments, IMD technology may be used to provide hardcoat and/or ink transfer marks.

HMI display production

In one embodiment, the HMI touch panel is prepared by injection molding or Compression Injection Molding (CIM). Both techniques have been used to manufacture optical discs. A third option is to use thermoforming, in particular to make larger panels. Thermoforming requires extruding and forming a heated sheet into a mold. This has the advantage that larger size parts can be manufactured, but has the disadvantages of high scrap rates, possibly high stress levels, and difficulty in moulding lugs and attachment points.

One key aspect of any production technique is minimizing birefringence. There are two main types of birefringence, namely, orientation birefringence and "glassy" or stress-dependent birefringence. The former is caused by residual chain orientation left in the part after molding, while the latter is caused by thermal stresses formed during cooling of the part. For each production method, both parts will be changed independently.

Polycarbonate (PC) is at a disadvantage in terms of birefringence over PMMA, as small changes in residual stress (or residual orientation) will cause large changes in birefringence. This sensitivity is usually quantified by the Stress Optical Coefficient (SOC), which is the birefringence change that occurs when the unit stress changes.

(5)Δ_ij＝SOC*(σ_i-σ_j)

Where σ i is the stress in the i direction. A given material has two SOC values, one for stresses above the glass transition temperature in the rubbery State (SOC)_R) And the other for the stress in the glassy State (SOC)_G). The former involves oriented birefringence, the latter is the more traditional stress-dependent birefringence. For PC, both SOC values are typically much higher than acrylic, which makes low birefringence molding more difficult.

During injection molding, the mold geometry and gate effects are very important with respect to stress and birefringence. Fig. 7 shows a simple plaque mold 101 with an overlapping gate 102, and a flow front of polymer entering the mold 105. The polymer entering through the runner 100 has undergone orientation and alignment and continues as it enters the mold.

With such a small lap gate, a radially progressive flow similar to balloon expansion occurs. The polymer is stretched radially and circumferentially, which results in principal stresses σ r and σ in the radial and circumferential directions (108)_Θ. As shown in the above equation (5), birefringence increases with an increase in the relative stress difference, and the stress difference near the gate tends to be very high. Due to this radial stress mode, the orientation and birefringence curves will have similar radial geometry, which is used to magnify the shadow, since there will be more angular dependence. Thus, in embodiments, it is preferable to employ a wider fan or film gate that provides a more uniform flow front through the part. This is shown in FIG. 8, where the flow from 106 is now more uniform and the molecular orientation is throughout the entire sectionAnd also more consistent. This will reduce the angular dependence of the shadowing, as the stress difference 108 will be more consistent.

Compression injection molding is an alternative to standard injection molding in that the mold is initially kept partially open during filling to reduce flow stresses, but then closed to produce the final part. For thinner articles, such as optical discs, this can reduce birefringence more than conventional injection molding alone.

In one embodiment, the component thickness of the HMI display ranges from about 1mm to about 10mm, or 1mm to 8mm, or 1mm to 5mm, or about 2mm to about 10mm, or 2mm to 8mm, or 2mm to 5mm, or greater than 2m to 5mm, or 2mm to 4mm, or from 2mm to 3 mm. Thickness has a significant effect on birefringence and retardation because, as previously mentioned, retardation is equal to birefringence multiplied by thickness. Thus, the thicker portion will have a higher delay, all things being equal. However, it has been found that thicker parts may have reduced filling pressure and therefore reduced levels of oriented birefringence. Therefore, even with higher thicknesses, the average birefringence across the entire part may be lower, and thus the overall retardation may sometimes be reduced. Thicker parts are preferred from the point of view of impact resistance and crashworthiness, but not too thick, as this adds additional weight. In an embodiment, the thickness is about 2 to 3 mm.

It has been found that higher polymer melt temperature molding can also help reduce birefringence by reducing viscosity, reducing overall stress and orientation formation. There is often a practical upper limit to molding of most materials before excessive degradation and/or flashing becomes a problem.

The mold temperature may also be increased to reduce stress, although this would result in longer cycle times (due to longer cooling cycles). The mold temperature has a particularly strong influence on the residual stress and the birefringence caused by the stress resulting from cooling. To help further reduce this, the part may also be annealed after molding at a temperature near the glass transition temperature Tg. This can minimize the stress component of birefringence, but generally does not affect oriented birefringence. Moreover, this is less desirable because it significantly increases cycle time and cost.

Other processing parameters, such as injection rate/pressure, can affect the formation of birefringence, and the fill rate can be plotted to optimize birefringence. It has been found that by operating at higher injection fill rates and/or mold fill pressures, particularly at the end of filling, birefringence can be reduced, particularly in the gate area. Likewise, the holding pressure should be kept high, but low enough to prevent flashing. If the filling rate is too low, the cooling effect during filling is considered too strong, which increases the orientation birefringence, since the material has to flow through the more viscous skin layers.

Reducing the molecular weight of the polymer can reduce the viscosity and orientation that occurs during molding. This approach has been used to reduce birefringence in polycarbonate optical discs, but at the expense of reduced impact strength. Molecular weight can be quantified in different ways, but is usually expressed indirectly by Melt Flow Rate (MFR) in grams of flow per 10 minutes at 300 ℃ and 1.2kg load. The permissible MFR is sometimes reported as being measured at 250 ℃ rather than 300 ℃, for the purposes of this application the MFR is measured at 300 ℃ (as described above). Molecular weight can also be quantified by Melt Volume Rate (MVR) instead of MFR, where the flow volume in cubic centimeters is measured instead of mass under the same conditions. To convert from MVR to MFR, the MVR value was multiplied by the melt density, and the melt density of PC was 1.08 g/cc.

It has been found that conventional lower MFR PC grades (for molded articles) produce excessive birefringence and are not practical for HMI housing plates. In contrast, it has been found that higher MFR grades of PC will result in lower birefringence, but impact strength will generally be reduced.

Surprisingly, it has been found that certain MFR grades of polycarbonate can be used to produce HMI display panels that exhibit adequate shadow elimination and adequate toughness.

Accordingly, in a first aspect, the present invention provides a Human Machine Interface (HMI) housing in the form of a sheet having a thickness of from about 2mm to about 5mm, comprising a thermoplastic polymer comprising (i) a polycarbonate or (ii) a polycarbonate having blended therein up to about 40 wt% copolyester, wherein the thermoplastic polymer has a melt flow rate of from about 60 to about 80g/10 minutes, as determined according to ASTM D-1238(300 ℃/1.2 kg). In another embodiment, the human-machine interface housing of the invention further comprises one or more compensation layers and has a total optical retardation in the range

(i) -from 100 to 100nm,

(ii)100 to 300nm, or

(iii) -100 to-300 nm.

In other embodiments, the human-machine interface housing of the present invention further comprises one or more compensation layers having a total optical retardation in the range of-80 to 80nm, 100nm to 260nm, or-100 nm to-260 nm.

The polycarbonate may be a bisphenol a polycarbonate or a polycarbonate-copolyester blend. In embodiments, the blend may contain up to about 40 wt% of the copolyester. It has been found that when the material is processed, for example by injection moulding, compression moulding or thermoforming, the material may have a sufficiently low and controllable birefringence. It has been found that such materials can be processed into HMI housing plates having commercially acceptable impact strength and substantially no optical shadows.

In an embodiment, the polycarbonate may be a standard bisphenol a type polycarbonate. In other embodiments, other modified copolymers and polycarbonates may also be used. For example, copolymers of copolyesters and polycarbonates are also contemplated herein. In one embodiment, the Melt Flow Rate (MFR) or Melt Flow Index (MFI) is between about 60 to about 80g/10min as determined by ASTM D-1238(300 ℃/1.2 kg). As described herein, conventional stabilizers, catalysts, impact modifiers, flame retardants, reinforcing agents, and the like, well known in the polycarbonate and polyester arts, may be used, provided the type and/or amount of such additives does not result in an outer shell having unacceptable optical or strength properties. Examples of additives contemplated for use include those available from BASFAndantioxidants, and obtainable from basfAndlight stabilizers.

In embodiments, the thermoplastic polymer may contain up to about 40 wt% copolyester, but the polycarbonate/copolyester blend should maintain a blend Tg of 105 ℃ or greater, or 110 ℃ or greater, to withstand thermal stresses in the interior of an automobile. Due to suitability and processability requirements, in embodiments, the Tg of the blend may range from 105 ℃ to 160 ℃, 105 ℃ to 150 ℃, 110 ℃ to 160 ℃, or 120 ℃ to 150 ℃. In embodiments, the thermoplastic polymer may be a polycarbonate or a blend of a polycarbonate and a copolyester, comprising 0 wt% to 40 wt% of a copolyester, or 0 wt% to 30 wt% of a copolyester, or 0 wt% to 25 wt% of a copolyester, or 0 wt% to 20 wt% of a copolyester, or 0 wt% to 10 wt% of a copolyester, or 0 wt% to 5 wt% of a copolyester, or 0 wt% to less than 5 wt% of a copolyester, or more than 0 wt% to 40 wt% of a copolyester, or 1 wt% to 40 wt% of a copolyester, or 5 wt% to 40 wt% of a copolyester, or 10 wt% to 40 wt% of a copolyester, or 20 wt% to 40 wt% of a copolyester, or 30 wt% to 40 wt% of a copolyester.

In embodiments, the copolyester is miscible with the polycarbonate. In embodiments, the copolyester may be prepared from one or more diols selected from Cyclohexanedimethanol (CHDM), Tetramethylcyclobutanediol (TMCD), butanediol, and/or ethylene glycol, and one or more diacids selected from terephthalic acid, isophthalic acid, and/or cyclohexanedicarboxylic acid (CHDA).

In an embodiment, the copolyester comprises: a diol component comprising CHDM residues and a diacid component comprising CHDA residues, wherein the copolyester has excellent miscibility with polycarbonate and provides a blend having reduced oriented birefringence as compared to polycarbonate itself. In another embodiment, the copolyester comprises: a diol component comprising residues of CHDM, TMCD, and/or EG, and a diacid component comprising residues of terephthalic acid and optionally isophthalic acid. In one embodiment, the copolyester is selected from PCTG or poly (1, 4-cyclohexanedicarboxylate 1, 4-cyclohexanedimethanol ester) (PCCD).

In one embodiment, the polyester used in the present invention may comprise the following levels of diol residues: 15 to 40 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 60 to 85 mole% 1, 4-cyclohexanedimethanol; 20 to 40 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 60 to 80 mole% 1, 4-cyclohexanedimethanol; 20 mol% -35 mol% -2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 65 mol% -80 mol% of 1, 4-cyclohexanedimethanol; 20 to 30 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 70 to 80 mole% 1, 4-cyclohexanedimethanol; 30 to 40 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 60 to 70 mole% 1, 4-cyclohexanedimethanol; 20 to 25 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 75 to 80 mole% 1, 4-cyclohexanedimethanol; and 30 mole% to 35 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 65 mole% to 70 mole% 1, 4-cyclohexanedimethanol. In one embodiment of the invention, the polyester used in the present invention may comprise diacid residues in an amount of from 70 mole% to 100 mole%, or from 80 mole% to 100 mole%, or from 90 mole% to 100 mole%, of terephthalic acid, isophthalic acid, or esters thereof, or mixtures thereof.

In one embodiment, the polyester for use in the present invention may comprise ethylene glycol residues in an amount of 10 mole% to 27 mole% 2,2,4, 4-tetramethyl-1, 3-cyclobutanediol and 73 mole% to 90 mole% ethylene glycol; in one embodiment of the invention, the polyester used in the present invention may comprise diacid residues in an amount of from 70 mole% to 100 mole%, or from 80 mole% to 100 mole%, or from 90 mole% to 100 mole%, of terephthalic acid, isophthalic acid, or esters thereof, or mixtures thereof.

In one embodiment, the polyester used in the present invention may comprise from 80 mole% to 100 mole% 1, 4-cyclohexanedimethanol; or diol residues in an amount of 90 mole% to 100 mole% 1, 4-cyclohexanedimethanol. In this embodiment of the invention, the polyester used in the invention may comprise diacid residues in an amount of 70 mole% to 100 mole%, or 80 mole% to 100 mole%, or 90 mole% to 100 mole% of dimethyl cyclohexanedicarboxylate (DMCD), i.e., hydrogenated DMT. Any isomer of DMCD may be present in any amount; in one embodiment, the trans isomer may be present in a majority, i.e., greater than 50 mol%, or greater than 60 mol%, or greater than 70 mol%, greater than 80 mol%, or greater than 90 mol% of trans DMCD.

In one embodiment, the polyester used in the present invention may comprise the following amounts of diol residues: 50 mol% -100 mol% of 1, 4-cyclohexanedimethanol and 0 mol% -50 mol% of ethylene glycol; 50 mol% -95 mol% of 1, 4-cyclohexane dimethanol and 5 mol% -50 mol% of ethylene glycol; 50 mol% -90 mol% of 1, 4-cyclohexanedimethanol and 10 mol% -50 mol% of ethylene glycol; 50 mol% -80 mol% of 1, 4-cyclohexanedimethanol and 20 mol% -50 mol% of ethylene glycol; 50 to 70 mol% of 1, 4-cyclohexanedimethanol and 30 to 50 mol% of ethylene glycol. In one embodiment of the invention, the polyester used in the present invention may comprise diacid residues in an amount of from 70 mole% to 100 mole%, or from 80 mole% to 100 mole%, or from 90 mole% to 100 mole%, of terephthalic acid, isophthalic acid, or esters thereof, or mixtures thereof.

For the polyesters described herein, the total mole percent of the glycol component is equal to 100 mole percent and the total mole percent of the acid component is equal to 100 mole percent.

Examples of commercially available blends of polycarbonates and copolyesters suitable for use in the manufacture of HMI shells according to the invention include XYLEX which meet the ultimate desired properties of the HMI shell^TMResins (available from sauter basic industries, inc (SABIC)) as described herein.

In embodiments, in addition to having a Tg of at least 100 ℃, the display panel must also meet certain impact requirements. In an embodiment, a skin plate made from a cellulose ester composition having a thickness of 1mm to 10mm, or 1mm to 8mm, or 1mm to 5mm, or 2mm to 10mm, or 2mm to 8mm, or 2mm to 5mm is capable of withstanding impact from a height of 20 inches (50.8cm) with a 1.05kg steel ball at both room temperature and-30 ℃ without breaking. The height represents an impact energy of 5.2 joules. Due to the variety of available panel geometries, the panel was supported by a 4 inch (10.2cm) diameter tube, receiving an impact at the center of the panel or tile.

In order for the HMI display panel to be shadow-free, it is important that the total retardation of all "optically active layers" fall within one of two ranges:

the first is from-100 nm to 100nm, or-80 nm to 80nm, since this constitutes the "grey" area on the Michel-Levy diagram for light transmission through crossed polarizers using a uniform white light source. The display within this delay range will always be black or grey, so the shading is minimal.

The second is 100nm to 300nm or-100 nm to-300 nm, or 100nm to 260nm or-100 nm to-260 nm, since this constitutes the "white" part of the light transmission. Although the panel will appear uniformly white rather than gray, the shading here will also be minimal.

The reason for targeting one of these two regions is that the color change is very small for a given change in retardation. In contrast, for retardations in the range of greater than 260nm or greater than 300nm (or less than-260 nm or less than-300 nm), the effective color changes rapidly through non-gray values (initially yellow) as the retardation increases. Therefore, even a slight change in retardation will produce a noticeable color shift. It should also be noted that if one portion of the panel is in a gray area and another portion is in a "white" area, then an unacceptably noticeable shadow will appear. The entire viewing area (or in one embodiment, the entire panel) should be in one or the other area, but not both. Again, these ranges listed are considered acceptable minima, but even lower variation ranges around 0nm or about 180nm (or-180 nm) are preferred.

With the above acceptable range, generally spanning a 160nm delay, it is desirable that the difference between the maximum and minimum delay of the polycarbonate component (at least over the viewable area of the HMI enclosure) be less than or equal to about 160 nm. In an embodiment, the maximum variation in retardation that a component can have across the entire viewable area and still be acceptable is 160 nm. However, if the average retardation of the component is not within the target range, it can be offset by adding an optically active compensation layer to the housing plate.

For example, a component with an average retardation of 100nm (150 nm maximum and 50nm minimum) would have unacceptable shading if used alone, since part of the retardation is in the gray area and part is in the white area. However, since the retardation range (max-min) is only 100nm, the average value can be shifted down using a-100 nm optically active compensation layer. This shifts the average to 0nm, the minimum to-50 nm, and the maximum to 50 nm. All spots are now within the-80 to +80nm grey region, so shading is minimized. Alternatively, the average value may be moved upward so that the entire range falls within the white area.

The "optically active layer" constitutes all layers between the second polarizer of the display 33 and the polarizing sunglasses 80. Thus, the outer protective layer 32 of the second polarizer, the HMI display 70, and any protective/compensation layers applied to the display 71 (or alternatively applied between 32 and 70) may be considered optically active layers. The sum of the in-plane retardance should be substantially within one of the two ranges. It is acceptable that if areas around or on the edges of the gate are hidden (e.g., outside the viewable area of the HMI housing) and/or removed as part of the installation, these areas may be outside of an acceptable range.

In an embodiment, the display panel has a thickness of 2 to 5mm, or 2 to 4mm, or 2 to 3mm, and will withstand an impact of dropping from a height of 20 inches (50.8cm) at room temperature and-30 ℃ using a 1.05kg steel ball without cracking. In an embodiment, the HMI display housing is larger than a typical molded optical disk and is asymmetric in geometry, both of which make it more difficult to meet low birefringence requirements (as described herein).

In embodiments, the HMI enclosure panel is produced by injection molding, compression injection molding, or thermoforming, and may optionally be annealed to further reduce birefringence. In an embodiment, the housing is injection molded and the gate is at least 50% or more, or at least 60%, or at least 70%, or at least 80% of the width of the housing at the inlet side of the mold, in order to reduce the angular dependence of the retardation.

In one aspect, a method for fabricating a human interface housing is provided, comprising the steps of:

(a) providing a mold configured for injection molding, the mold comprising a gate at one end of the mold, the gate having an opening configured to introduce molten thermoplastic polymer into the mold, and a mold width at the gate end of the mold of at least 150mm, wherein the gate opening has a width of at least 50% of the mold width; and

(b) the housing is injection molded at a barrel temperature of at least the thermoplastic polymer Tg (° C) +170 ℃.

In an embodiment, the gate opening has a width of at least 60% of the mold width. In embodiments, the barrel temperature is at least the thermoplastic polymer Tg (° c) +190 ℃, in embodiments, the thermoplastic polymer is a polycarbonate having an MFR (as discussed herein) of 60 to 80g/10min, and the housing is made by injection molding at the following barrel temperatures: at least 310 ℃, or at least 315 ℃, or at least 320 ℃, or at least 325 ℃, or at least 330 ℃, or at least 335 ℃, or at least 340 ℃, or at least 345 ℃; or in the range of 310 ℃ to 360 ℃, or 320 ℃ to 360 ℃, or 330 ℃ to 360 ℃, or 340 ℃ to 360 ℃, or 310 ℃ to 355 ℃, or 320 ℃ to 355 ℃, or 330 ℃ to 355 ℃, or 340 ℃ to 355 ℃, or 310 ℃ to 350 ℃, or 320 ℃ to 350 ℃, or 330 ℃ to 350 ℃, or 340 ℃ to 350 ℃.

In embodiments, the method further comprises injection molding the housing at an injection speed of at least 1.3cm/s, or at least 2.0cm/s, or at least 3.0cm/s, or at least 4.0 cm/s.

The optically active layer can be prepared by a variety of methods including solvent casting, extrusion, stretching, and the like. In embodiments, the compensation layer may be made of one or more cellulose esters. In another embodiment, the compensation layer may be made of oriented polycarbonate, for example in the case of a normal quarter-wave plate film. Additional layers may also be added to improve scratch resistance, glare, etc. For example, these "hard coat" layers may be applied to a compensation film and then adhered to a polycarbonate display panel using in-mold labeling techniques, direct adhesion, coating, or other methods known in the art. In an embodiment, the hard coating is selected from a silicone based hard coating, a (poly) siloxane based hard coating, a urethane based hard coating, or an acrylic based hard coating.

The invention may be further illustrated by the following examples of specific embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

Experimental part

The following experimental methods were used to characterize the molded articles of the present invention.

Melt flow rate or Melt Flow Index (MFI) was measured at 300 ℃ under a load of 1.2kg according to ASTM D-1238.

Optical birefringence in the plane (Re) is characterized by one of two methods. The first is by using Streinoptics^TMPS-100SF polarimeter. Testing in "plane polarization" mode, using the rotation analyser method or using Streinoptics^TMThe LWC-100 wedge compensator is optimized quantitatively. Measurements are taken at multiple points throughout the part and the maximum and minimum points are also recorded.

When Re and Rth values are desired, Woolam is used^TMThe ellipsometer performs the test. The ellipsometer makes a series of measurements at different tilt angles and then extrapolates the retardation results to a full 90 degree tilt to determine Rth.

The impact strength was measured at room temperature and-30 ℃. The impact was performed by dropping 1.05kg of steel balls from a height of 4 inches (10cm) and 20 inches (50.8 cm). The panels were supported by 4 inch (10.2cm) diameter tubes. This height represents a maximum impact energy of 5.2 joules, and the sample must withstand the impact without cracking or breaking to pass the test.

Examples 1 to 24 Effect of processing conditions

Rectangular plaques were injection molded on a Toyo Plastar TM-200G2 molding machine having a 50mm screw and an injection capacity of 397 cc. Design experiments were performed using various processing conditions and resins. Rectangular plaques of dimensions 10.2cm by 15.2cm and a thickness of 2.5mm were prepared. The mold was filled with film gates along the entire 10.2cm short side of the plaque.

Molded plaques were prepared using three different polycarbonate resins as follows: makrolon^TM2458(19MVR or 20MFR), Makrolon^TM2207(35MVR or 38MFR) and Tarflon^TMLC1500(65MVR or 70 MFR). Makrolon resin is supplied by Bayer (Bayer) (Covestro), and Tarlon resin is supplied by Idemitsu Kosan. In addition to the polycarbonate samples, the PMMA polymer Acrylite was tested^TMH12 (winning Industries) was used as a control.

The mold temperature for the PMMA sample was fixed at 82 ℃ and the mold temperature for the polycarbonate sample at 88 ℃. Both barrel temperature and injection speed were varied to determine optimal conditions. The retardation value (Re) was then measured at the center of the plaque and 1cm from the gate end of the plaque. Maxima and minima were also recorded throughout the part, but excluding the 2cm region near the gate. Although it is believed that the level of delay near the gate area will be higher, it is assumed that such high delay can be incorporated into a larger gate area that will be removed and/or hidden upon final assembly of the panel. The molding conditions and test results are listed in table 1.

Review of table 1 shows that only sample 18 falls within the desired target retardation range (-100 to 100nm) and/or has a retardation change of less than 160 nm. This was produced using a 65MVR (70MFR) sample operating at a hotter barrel temperature and a fast injection rate. Samples 14 and 17 were close to the target and could be made acceptable by simply using a larger gate/manifold area. Other processing conditions do not produce sufficiently low delay variability and can produce unacceptable shadowing. Also, the samples with lower MVR did not even approach the desired retardation target.

The acrylic samples (examples 1 to 6) also had low retardation profiles, but were not usable due to their low impact strength.

Examples 25 to 28

In these examples, additional plaques were molded for impact testing using the same materials and equipment as described above. The thickness of the decorative plate is 2.5 mm. The results are shown in Table 2. A review of Table 2 shows that the PMMA sample failed the impact test. The low MVR PC sample was expected to pass, but surprisingly, the high MVR PC (example 26) also passed the impact test.

EXAMPLE 29 HMI faceplates with optically active Compensation layers

In this example, a 2mm thick HMI faceplate was molded using the 65MVR PC previously described. The panel was 160mm wide at the gate end and expanded to 200mm at the distal end. The length of the faceplate is 150mm, with the components slightly curved to reflect the likely HMI touch shell shape. A fan gate of approximately 65% of the part width was used. The panels were molded using a rapid injection rate at a cylinder temperature of 315 ℃. The maximum retardation was measured to be 171nm and the minimum retardation was about 50 nm. With an average value of about 110 nm.

When viewed through crossed polarizers, the part appears predominantly white, but some slight gray "spots" appear in some areas because the retardation spans the gray and white areas. To correct this, the average value of the retardation is shifted up 60nm using the compensation layer. The compensation layer was prepared by uniaxially stretching a Cellulose Acetate Propionate (CAP) film made from Eastman (Eastman) CAP 482-20 polymer 2-fold at 150 ℃ using a Brueckner laboratory film stretcher. The film was added in line with the panel so that the retardation added together, moving the average to 170nm (near the center of the "white" area). The resulting composite structure has a more uniform white appearance with minimal shading.

Prophetic example 30-PC/polyester blend

In this prophetic example, 30 wt% PCCD polyester (e.g., PCCD commercially available from Istman chemical company) was blended with the aforementioned 65MVR polycarbonate. It is known that polymers are miscible and that the Tg of the blend is nominally 120 ℃, which is lower than the Tg of PC itself, but still sufficient for applications. The display panel was molded at a barrel temperature of 300 ℃ and using a fast injection rate in a manner similar to example 1. Since PCCD has lower intrinsic birefringence than PC, even lower retardation is expected than in the previous examples. Similarly, PCCD is a tough polymer that can operate at higher Molecular Weights (MW) while maintaining low birefringence. The toughness of the molded parts is also expected to be good.

TABLE 1 plaque injection Molding data

TABLE 2 plaque impact data (1.05kg steel ball)

Sample (I)	Description of the invention	10cm/23℃	10cm/-30℃	50cm/23℃	50cm/-30℃
						25	PMMA	Failed through	Failed through	Failed through	Failed through
26	PC,70MFR	By passing	By passing	By passing	By passing
						27	PC,38MFR	By passing	By passing	By passing	By passing
28	PC,20MFR	By passing	By passing	By passing	By passing