Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
SURFACE LAYER OF INTERIOR ARTICLE
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to a surface
layer of an interior article examples of which are the
instrument panel, front and rear doors on both sides and
the roof of an automobile.
2. Description of the Prior Art:
In a conventional interior material such as
the instrument panel of an automobile, as shown in
Fig. 5, a buffer layer 22 formed by a foam for example
is bonded to the outer surface of a frame member 21, and
a surface layer 23 formed of polyvinyl chloride resin
and having a suitable hardness is bonded to the outer
surface of the buffer layer 22. Further, on the surface
of the surface layer 23 is formed a wrinkle pattern as
an uneven pattern 24 expressing artificial leather cloth
for imparting a soft feeling to the said surface.
In order to form the uneven pattern 24 on the
surface of the surface layer 23, we have developed such
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a vacuum forming method as is disclosed in Japanese
Patent Laid-Open No. 104848/86 wherein the uneven
pattern 24 is formed simultaneously with a forming
operation using a pattern die having a sheet lap surface
formed with an uneven pattern corresponding to the
uneven pattern 24 and also having innumerable, fine,
continuous pores which are distributed uniformly
throughout the whole of the said sheet lap surface.
According to this method, a synthetic resin sheet with
the buffer layer 22 bonded thereto is softened by
heating at a high temperature beforehand onto the back
of the surface layer 23, then the surface of the surface
layer 23 is brought into close contact by suction with
the pattern die positioned just thereabove to effect
forming, whereby the uneven pattern 24 of the pattern
die, e.g. a wrinkle pattern, is transferred onto the
surface of the surface layer 23.
However, a portion of the surface layer 23,
e.g. a bent portion, which is drawn out largely during
the forming operation may be broken, or the uneven
pattern 24 may become unclear due to variations in
heating temperature for the synthetic resin sheet or due
to drop in temperature of the synthetic resin sheet or
variations in the said temperature drop during forming
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using the pattern die after the heating. And this
tendency is more conspicuous in the drawn-out portion.
SUMMARY OF THE INVENTION
The present invention has been accomplished
for solving the above-mentioned problems and it is the
object thereof to prevent the surface layer from being
broken during the forming operation and form an uneven
pattern on the surface of the surface layer clearly and
positively while maintaining the hardness of the same
layer.
According to technical means adopted by the
present invention for solving the foregoing problems,
the surface of a surface layer body formed of a
synthetic resin and endowed with high extensibility is
coated with a surface skin having a softening
temperature which is lower to an appropriate degree than
that of the surface layer body, and an uneven pattern is
formed on the surface skin.
According to the above means, since the
surface layer body maintains the hardness of the surface
layer and possesses high extensibility, the strength of
the surface layer is maintained even at its portion
which is drawn out during the forming operation;
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further, since the softening temperature of the surface
skin formed on the outer surface of the surface layer
body is lower to an appropriate degree than that of the
surface layer body, the surface skin is held in a softer
condition during, thereby permitting a positive transfer
of a clear uneven pattern onto the surface layer.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partially omitted perspective view
of an interior article;
Fig. 2 is an enlarged sectional view thereof;
Fig. 3 is a sectional view of a synthetic
resin sheet;
Fig. 4 is a sectional view of a formed part;
and
Fig. 5 is a sectional view showing a
conventional example.
DESCRIPTION OF A PREFERRED EMBODIMENT
An embodiment of the present invention will be
described hereinunder with reference to the accompanying
drawings.
Fig. 1 shows an automobile instrument panel as
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an example of an interior article A. The interior
article A comprises a frame member 4, a buffer layer 5
bonded to the outer surface of the frame member 4, and a
surface layer, a, bonded to the outer surface of the
buffer layer 5. The surface layer, a, is composed of
two layers which are a surface layer body 1 and a
surface skin 2. A complicated uneven pattern, b, such
as a wrinkle pattern is clearly formed throughout the
whole surface of the surface skin 2.
In the present invention, the uneven pattern,
b, can be formed on the surface of the surface layer, a,
simultaneously with forming of the interior article A by
a vacuum forming method using a pattern die (not shown),
the pattern die having a sheet lap surface of the same
shape as the outer surface shape of the surface skin 2
and formed with an uneven pattern corresponding to the
uneven pattern, b, and also having innumerable, fine,
continuous pores distributed uniformly throughout the
whole surface of the sheet lap surface, as explained
above in the description of the prior art.
The frame member 4 may be bonded to the buffer
layer 5 simultaneously with forming of the buffer layer
and the surface layer, a. Or, as shown in Fig. 3, a
synthetic resin sheet, c, comprising the buffer layer 5
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and the surface layer, a, which have been bonded
together may be formed into a predetermined shape
together with the uneven pattern, b, separately from the
frame member 4 to constitute a formed part, c', (see
Fig. 4), and thereafter the frame member 4 may be bonded
to the formed part, c', in another step. There may be
adopted any other suitable method.
The frame member 4, having a layer which
serves as a core of the interior article A, is formed
into a predetermined shape using a material having
appropriate strength and hardness such as ABS resin,
rigid polyurethane resin, or polypropylene. To the
outer surface of the frame member 4 is bonded the buffer
layer 5 using an adhesive such as a hot-melt adhesive.
The buffer layer 5, which serves as a cushion,
is obtained by foaming such a material as polypropylene
or polyurethane resin at a suitable expansion ratio. To
the outer surface of the buffer layer 5 is bonded the
surface layer, a, using a suitable adhesive.
The surface layer, a, as noted previously, is
composed of two layers which are the surface layer body
1 having a suitable hardness and the surface skin 2
formed on the outer surface of the surface layer body 1
and having the uneven pattern, b, formed using such a
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pattern die as referred to above.
The surface layer body 1 maintains the surface
layer, a, at a predetermined hardness and it is endowed
with high extensibility thereby permitting the surface
layer, a, to be drawn out easily during the forming
operation. The surface skin 2 is of a thin layer
structure for forming an uneven pattern, b, of say 100 ~
or so in depth on the outer surface of the surface layer,
a, and it has a softening temperature lower than that of
the surface layer body 1.
In the combination of the surface layer body 1
and the surface skin 2, when both 1 and 2 mainly
comprise the same chemical substance and this chemical
substance is a polymer of a single compound, the polymer
is prepared so that the degree of polymerization thereof
is smaller in the surface skin 2 than in the surface
layer body 1, whereby the softening temperature of the
surface skin 2 is made smaller than that of the surface
layer body 1.
For example, where both the surface layer body
1 and the surface skin 2 mainly comprise polyvinyl
chloride, a polyvinyl chloride of a high polymerization
degree of about 2,500 may be used for the surface layer
body 1, while using a polyvinyl chloride of a low
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polymerization degree of about 800 for the surface skin
2. In this case, the amount of a plasticizer to be
incorporated in the surface layer body 1 is suitably
increased on the basis of a relatively high
polymerization degree of a resin material to lower the
softening temperature for making the surface layer body
highly extensible while maintaining the required
hardness. To assist maintaining the hardness and
strength of the surface layer body 1, a synthetic resin,
e.g. ABS resin, may be incorporated therein at a
suitable proportion.
The following is an explanation about the
method of forming the uneven pattern, b, on the surface
skin 2 of the surface layer, a, using the material
mentioned above.
The synthetic resin sheet, c, shown in Fig. 3
is suspended horizontally and heat-softened at
approximately 185C. The thus-softened sheet, c, is
placed, with the surface layer, a, facing upwards, just
under the sheet lap surface at the lower end of the
foregoing pattern die (not shown) followed by vacuum
suction to let the sheet, c, adhere strongly to the
pattern die through the surface skin side 2. In this
case, in order to improve the adhesion, a pressure die
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which is in a corresponding relation to the pattern die
may be pressed against the sheet, c, from below the
sheet. Upon release of the synthetic resin sheet, c,
there is obtained a formed part, c', having a clear and
complicated uneven pattern, b, such as buffalo wrinkles
which pattern was formed simultaneously with the forming
operation.
The temperature of the synthetic resin sheet,
c, which has been heated to approximately 185C lowers
to 160C or so at the time of vacuum forming using the
pattern die and further lowers to 70 - 80C at the time
of release. The said temperature (approx. 160C) in the
vacuum forming operation is a material shaping
temperature, at which temperature the surface layer body
1 is in a softened condition insufficient to form the
uneven pattern, b, on it. However, since the surface
skin 2 is in a sufficiently softened condition, a clear
uneven pattern, b, can be formed positively on the
surface of the surface layer, a.
The surface layer body 1 and the buffer layer
5 also play the role of preventing the synthetic resin
sheet, c, from being softened too much and hanging down
during heating of the sheet.
In the present invention, by suitably
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combining conditions such as the polymerization degrees
of the components of the surface layer body 1 and the
surface skin 2, the difference between both
polymerization degrees and heating temperature for the
synthetic resin sheet, c, the uneven pattern, b, can be
formed on the surface of the surface layer, a, clearly
and positively.
The interior article A is formed by a method
wherein the frame member 4 preformed as shown in Fig. 1
is bonded to the formed part, c', which has been
obtained in the manner described previously, using a
suitable adhesive in a separate step, or by a method
wherein, in vacuum forming, the frame member 4 is fixed
the foregoing pressure die (not shown) and is bonded to
the synthetic resin sheet, c, during forming of the
sheet, or by a method wherein the frame member 4 is
formed by urethane foam on the back of the buffer layer
5 of the formed part, c'.
Where polyurethane is used in place of the
polyvinyl chloride as a component of the surface layer,
a, the kind and the degree of polymerization of
isocyanate and polyol components of the polyurethane in
the surface skin 2 and surface layer body 1, whereby the
softening temperature of the surface skin 2 is made
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lower to an appropriate extent than that of the surface
layer body 1.
In the combination of the surface layer body 1
and the surface skin 2, when both 1 and 2 mainly
comprise the same chemical substance and this chemical
substance is a copolymer of two or more kinds of monomer
units, the proportions of the monomer units in the
surface layer body 1 and that of the monomer units in
the surface skin 2 are made different from each other,
or the copolymer is prepared so as to be lower in
molecular weight in the surface skin 2 than in the
surface layer body 1, whereby the softening temperature
of the surface skin 2 is made lower than that of the
surface layer body 1. For example, a thermoplastic
elastomer prepared by copolymerizing polypropylene as a
base component with another compound is used and the
proportion of monomer units of the polypropylene and
that of the another compound are changed suitably
between both 1 and 2, the said elastomer in the surface
skin is made lower in molecular weight than the
elastomer in the surface layer body 1, whereby the
softening temperature of the surface skin 2 can be made
lower than that of the surface layer body 1.
In the present invention, moreover, the
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surface layer body 1 and the surface skin 2 may be
formed of different chemical substances to thereby
render the softening temperature of the surface skin 2
lower than that of the surface layer body 1. Examples
of the "different chemical substances" include the cases
where the chemical substance as a main component is a
polymer of a single monomer unit, a copolymer of plural
monomer units, and a mixture of both, wherein the kind
of monomer units and the number of such kind are made
different from each other. For example, there may be
adopted a combination of a polyvinyl chloride resin as
the surface layer body 1 and a urethane-based
thermoplastic elastomer as the surface skin 2.
Examples of the resin material which
constitutes the surface layer, a, used in the present
invention include polymers and copolymers of a
crosslinked structure.
- The chemical substances which may be used to
constitute the surface skin and the surface layer body
are not limited to those described in the above
embodiment. Suitable combinations may be adopted. And
the temperature and other forming conditions may be
suitably selected accordingly.
In the present invention, the method of
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forming the uneven pattern on the surface skin is not
limited to the one described in the above embodiment.
The interior article is not limited to the one shown in
Fig. 1. It may be the one shown in Fig. 4, or may be
constituted by only the surface layer, a, comprising the
surface layer body and the surface skin formed thereon.
Further, it is not always necessary that the
interior article be of a three-dimensional structure
having a bent portion. It may be of a flat shape like
sheet. Moreover, the outer surface of the surface skin
2 may be surface-finished using a urethane resin or an
acrylic resin.
The following are concrete working examples of
the present invention and the results of evaluation of
the resulting baffalo wrinkles-like uneven patterns.
The evaluation of the uneven patterns will be made in
comparison with the case where an uneven pattern is
formed on a conventional material (comparative example).
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Example ~
(1) Surface Skin
part by weight
Composition: Polyvinyl chloride resin lO0
(polymerization degree: 800)
Trimellitic acid-based 64
plasticizer
Epoxy-based stabilizer 8
Heat- and light-resisting 4
stabilizer
Pigment 5
Thickness: 0.2 mm
Bonding with surface layer body: heat fusion
(2) Surface Layer Body
part by weight
Composition: Polyvinyl chloride resin 70
(polymerization degree: 2,500)
High temp. elongation 30
modifying resin
Trimellitic acid-based 54
plasticizer
Epoxy-based stabilizer 6
Heat- and light-resisting 4
stabilizer
Pigment 5
Thickness: 0.6 mm
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Bonding with buffer layer:
a solvent type urethane-based adhesive
(3) Buffer Layer
Material:
an electron beam-crosslinked polypropylene foam
(expansion: 18X)
Thickness: 4 mm
Comparative Example
(1) Surface Layer Body
part by weight
Composition: Polyvinyl chloride resin 75
(polymerization degree: 1,200)
High temp. elongation 25
modifying resin
Trimellitic acid-based 28
plasticizer
Epoxy-based stabilizer 7
Heat- and light-resisting 4
stabilizer
Thickness: 0.6 mm
Bonding with buffer layer:
a solvent type urethane-based adhesive
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(2) Buffer Layer
Material:
an electron beam-crosslinked polyurethane foam
(expansion: 18X)
Thickness: 4 mm
Example ~
(1) Surface Skin
part by weight
Composition: Olefinic thermoplastic 100
elastomer
(M~R = 20, Shore A = 63)
Heat- and light-resisting 0.5
stabilizer
Pigment 5
(Note) MFR 230C, 10 kg, g/10 min, JISK72010
Thickness: 0.1 mm
Bonding with surface layer body: heat fusion
(2) Surface Layer Body
part by weight
Composition: Olefinic thermoplastic 70
elastomer
(MFR = 2, Shore A ~ 95)
Polypropylene 30
Heat- and light-resisting 0.5
stabilizer
Pigment 5
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Thickness: 0.2 mm
Bonding with buffer layer: heat fusion
(3) Buffer Layer
Material:
an electron beam-crosslinked polyethylene foam
(expansion: 30X)
Thickness: 2.5 mm
Example ~
(1) Surface Skin
part by weight
Composition: Polyether-based urethane 100
thermoplastic elastomer
(JIS hardness A = 80)
Lubricant (polyethylene wax)
Pigment 2
Thickness: 0.2 mm
Bonding with surface layer body: heat fusion
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2) Surface Layer Body
part by weight
Composition: Polyvinyl chloride resin 70
(polymerization degree: 2,500)
High temp. elongation 30
modifying resin
Trimellitic acid-based 54
plasticizer
Epoxy-based stabilizer 6
Heat- and light-resisting 4
stabilizer
Pigment 5
Thickness: 0.6 mm
Bonding with buffer layer:
a solvent type urethane-based adhesive
(3) Buffer Layer
Material:
an electron beam-crosslinked polypropylene foam
(expansion: 18X)
Thickness: 4 mm
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Results of evaluation of uneven pattern transferability
Sheet Transferability
Surface Sheet Sample of Uneven
Temp. (*l) Pattern (*2)
Example
Example
185C
Example
Comparative
Example O
Example
Example
175C
Example
Comparative
Example O
Example ~ O
Example ~ O
165C
Example ~ O
Comparative
Example
Example ~ O
Example ~ O
155C
Example ~ O
Comparative Q
Example
*1. Sheet Surface Temp.:
Surface temperature just after heating of sheet
*2. Transferability of Uneven Pattern:
Visual comparison about the depth and clearness
of uneven pattern
(Superior) ~ > O > ~ (Inferior)
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The above Examples ~ - ~ correspond to
Claims 2, 3 and 4, respectively.
From the results obtained above it can be said
that all of the products ( ~ - ~ ) obtained according
to the present invention are superior in the
transferability of uneven pattern even in a low sheet
surface temperature region as compared with the
conventional products (Comparative Example).
Moreover, in the products according to the
present invention, their uneven patterns are maintained
over a long period and thus superior in shape retaining
property.
According to our experiment there was obtained
a result such that the surface layer body itself endowed
with high extensibility according to the present
invention was superior in the transferability of uneven
pattern to the conventional surface layer body.
According to the present invention, as set
forth hereinabove, since the basic structure of the
surface layer is constituted by the surface layer body
endowed with high extensibility, the surface layer can
be prevented from being broken even at its portion to be
drawn out at the time of forming operation; besides,
since the softening temperature of the surface skin
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formed on the surface layer body is lower than that of
the surface layer body, the surface skin is held in a
softer condition during the forming operation, thereby
permitting a clear uneven pattern to be transferred
positively onto the surface skin.
Consequently, not only the surface layer can
be prevented from being broken during the forming
operation but also the transferability of uneven pattern
on the surface of the surface layer can be improved by
the surface skin thereby permitting an uneven pattern
superior in shape retaining property to be formed on the
surface of the surface layer clearly and positively
while maintaining the conventional surface layer
hardness. Thus, the desired object of the present
invention can be attained.
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